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The Project Gutenberg eBook of The Working of Steel
This eBook is for the use of anyone anywhere in the United States and most other parts of the world at no
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Title: The Working of Steel
Author: Fred H. Colvin
K. A. Juthe
Release date: January 4, 2007 [eBook #20282]
Language: English
Other information and formats: www.gutenberg.org/ebooks/20282
Credits: Produced by Robert J. Hall
*** START OF THE PROJECT GUTENBERG EBOOK THE WORKING OF STEEL ***
THE
WORKING OF STEEL
ANNEALING, HEAT TREATING
AND
HARDENING OF CARBON AND ALLOY STEEL
BY
FRED H. COLVIN
Member American Society of Mechanical Engineers and Franklin Institute; Editor of the American Machinist,
Author of "Machine Shop Arithmetic," "Machine Shop Calculations," "American Machinists' Hand Book."
This eBook is for the use of anyone anywhere in the United States and most other parts of the world at no
cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms
of the Project Gutenberg License included with this eBook or online at www.gutenberg.org. If you are not
located in the United States, you will have to check the laws of the country where you are located before
using this eBook.
Title: The Working of Steel
Author: Fred H. Colvin
K. A. Juthe
Release date: January 4, 2007 [eBook #20282]
Language: English
Other information and formats: www.gutenberg.org/ebooks/20282
Credits: Produced by Robert J. Hall
*** START OF THE PROJECT GUTENBERG EBOOK THE WORKING OF STEEL ***
THE
WORKING OF STEEL
ANNEALING, HEAT TREATING
AND
HARDENING OF CARBON AND ALLOY STEEL
BY
FRED H. COLVIN
Member American Society of Mechanical Engineers and Franklin Institute; Editor of the American Machinist,
Author of "Machine Shop Arithmetic," "Machine Shop Calculations," "American Machinists' Hand Book."
Page 4
AND
K. A. JUTHE, M.E.
Chief Engineer, American Metallurgical Corp. Member American Society Mechanical Engineers, American
Society Testing Materials, Heat Treatment Association, Etc.
SECOND EDITION
THIRD IMPRESSION
McGRAW-HILL BOOK COMPANY, Inc.
NEW YORK: 370 SEVENTH AVENUE
LONDON: 6 & 8 BOUVERIE ST., E. C. 4
K. A. JUTHE, M.E.
Chief Engineer, American Metallurgical Corp. Member American Society Mechanical Engineers, American
Society Testing Materials, Heat Treatment Association, Etc.
SECOND EDITION
THIRD IMPRESSION
McGRAW-HILL BOOK COMPANY, Inc.
NEW YORK: 370 SEVENTH AVENUE
LONDON: 6 & 8 BOUVERIE ST., E. C. 4
Page 5
PREFACE TO SECOND EDITION
Advantage has been taken of a reprinting to revise, extensively, the portions of the book relating to the
modern science of metallography. Considerable of the matter relating to the influence of chemical
composition upon the properties of alloy steels has been rewritten. Furthermore, opportunity has been
taken to include some brief notes on methods of physical testing—whereby the metallurgist judges of the
excellence of his metal in advance of its actual performance in service.
NEW YORK, N. Y.,
August, 1922.
Advantage has been taken of a reprinting to revise, extensively, the portions of the book relating to the
modern science of metallography. Considerable of the matter relating to the influence of chemical
composition upon the properties of alloy steels has been rewritten. Furthermore, opportunity has been
taken to include some brief notes on methods of physical testing—whereby the metallurgist judges of the
excellence of his metal in advance of its actual performance in service.
NEW YORK, N. Y.,
August, 1922.
Page 6
PREFACE TO FIRST EDITION
The ever increasing uses of steel in all industries and the necessity of securing the best results with the
material used, make a knowledge of the proper working of steel more important than ever before. For it is
not alone the quality of the steel itself or the alloys used in its composition, but the proper working or
treatment of the steel which determines whether or not the best possible use has been made of it.
With this in mind, the authors have drawn, not only from their own experience but from the best sources
available, information as to the most approved methods of working the various kinds of steel now in
commercial use. These include low carbon, high carbon and alloy steels of various kinds, and from a
variety of industries. The automotive field has done much to develop not only new alloys but efficient
methods of working them and has been drawn on liberally so as to show the best practice. The practice in
government arsenals on steels used in fire arms is also given.
While not intended as a treatise on steel making or metallurgy in any sense, it has seemed best to include
a little information as to the making of different steels and to give considerable general information which
it is believed will be helpful to those who desire to become familiar with the most modern methods of
working steel.
It is with the hope that this volume, which has endeavored to give due credit to all sources of
information, may prove of value to its readers and through them to the industry at large.
July, 1921.
THE AUTHORS.
The ever increasing uses of steel in all industries and the necessity of securing the best results with the
material used, make a knowledge of the proper working of steel more important than ever before. For it is
not alone the quality of the steel itself or the alloys used in its composition, but the proper working or
treatment of the steel which determines whether or not the best possible use has been made of it.
With this in mind, the authors have drawn, not only from their own experience but from the best sources
available, information as to the most approved methods of working the various kinds of steel now in
commercial use. These include low carbon, high carbon and alloy steels of various kinds, and from a
variety of industries. The automotive field has done much to develop not only new alloys but efficient
methods of working them and has been drawn on liberally so as to show the best practice. The practice in
government arsenals on steels used in fire arms is also given.
While not intended as a treatise on steel making or metallurgy in any sense, it has seemed best to include
a little information as to the making of different steels and to give considerable general information which
it is believed will be helpful to those who desire to become familiar with the most modern methods of
working steel.
It is with the hope that this volume, which has endeavored to give due credit to all sources of
information, may prove of value to its readers and through them to the industry at large.
July, 1921.
THE AUTHORS.
Page 7
CONTENTS
PREFACE
INTRODUCTION
CHAPTER
I. STEEL MAKING
II. COMPOSITION AND PROPERTIES OF STEELS
III. ALLOYS AND THEIR EFFECT UPON STEEL
IV. APPLICATION OF LIBERTY ENGINE MATERIALS TO THE AUTOMOTIVE
INDUSTRY
V. THE FORGING OF STEEL
VI. ANNEALING
VII. CASE-HARDENING OR SURFACE-CARBURIZING
VIII. HEAT TREATMENT OF STEEL
IX. HARDENING CARBON STEEL FOR TOOLS
X. HIGH SPEED STEEL
XI. FURNACES
XII. PYROMETRY AND PYROMETERS
APPENDIX
INDEX
PREFACE
INTRODUCTION
CHAPTER
I. STEEL MAKING
II. COMPOSITION AND PROPERTIES OF STEELS
III. ALLOYS AND THEIR EFFECT UPON STEEL
IV. APPLICATION OF LIBERTY ENGINE MATERIALS TO THE AUTOMOTIVE
INDUSTRY
V. THE FORGING OF STEEL
VI. ANNEALING
VII. CASE-HARDENING OR SURFACE-CARBURIZING
VIII. HEAT TREATMENT OF STEEL
IX. HARDENING CARBON STEEL FOR TOOLS
X. HIGH SPEED STEEL
XI. FURNACES
XII. PYROMETRY AND PYROMETERS
APPENDIX
INDEX
Page 8
INTRODUCTION
THE ABC OF IRON AND STEEL
In spite of all that has been written about iron and steel there are many hazy notions in the minds of
many mechanics regarding them. It is not always clear as to just what makes the difference between iron
and steel. We know that high-carbon steel makes a better cutting tool than low-carbon steel. And yet
carbon alone does not make all the difference because we know that cast iron has more carbon than tool
steel and yet it does not make a good cutting tool.
Pig iron or cast iron has from 3 to 5 per cent carbon, while good tool steel rarely has more than 1¼ per
cent of carbon, yet one is soft and has a coarse grain, while the other has a fine grain and can be hardened
by heating and dipping in water. Most of the carbon in cast iron is in a form like graphite, which is almost
pure carbon, and is therefore called graphitic carbon. The resemblance can be seen by noting how cast-
iron borings blacken the hands just as does graphite, while steel turnings do not have the same effect. The
difference is due to the fact that the carbon in steel is not in a graphitic form as well as because it is
present in smaller quantities.
In making steel in the old way the cast iron was melted and the carbon and other impurities burned out of
it, the melted iron being stirred or "puddled," meanwhile. The resulting puddled iron, also known as
wrought iron, is very low in carbon; it is tough, and on being broken appears to be made up of a bundle of
long fibers. Then the iron was heated to redness for several days in material containing carbon (charcoal)
until it absorbed the desired amount, which made it steel, just as case-hardening iron or steel adds carbon
to the outer surface of the metal. The carbon absorbed by the iron does not take on a graphitic form,
however, as in the case of cast iron, but enters into a chemical compound with the iron, a hard brittle
substance called "cementite" by metallurgists. In fact, the difference between the hard, brittle cementite
and the soft, greasy graphite, accounts for many of the differences between steel and gray cast iron.
Wrought iron, which has very little carbon of any sort in it, is fairly soft and tough. The properties of
wrought iron are the properties of pure iron. As more and more carbon is introduced into the iron, it
combines with the iron and distributes itself throughout the metal in extremely small crystals of cementite,
and this brittle, hard substance lends more and more hardness and strength to the steel, at the expense of
the original toughness of the iron. As more and more carbon is contained in the alloy—for steel is a true
alloy—it begins to appear as graphite, and its properties counteract the remaining brittle cementite.
Eventually, in gray cast iron, we have properties which would be expected of wrought iron, whose tough
metallic texture was shot through with flakes of slippery, weak graphite.
But to return to the methods of making steel tools in use 100 years ago.
The iron bars, after heating in charcoal, were broken and the carbon content judged by the fracture.
Those which had been in the hottest part of the furnace would have the deepest "case" and highest carbon.
So when the steel was graded, and separated into different piles, a few bars of like kind were broken into
short lengths, melted in fire-clay crucibles at an intense white heat, cast carefully into iron molds, and the
resulting ingot forged into bars under a crude trip hammer. This melting practice is still in use for crucible
steel, and will be described further on page 4.
THE ABC OF IRON AND STEEL
In spite of all that has been written about iron and steel there are many hazy notions in the minds of
many mechanics regarding them. It is not always clear as to just what makes the difference between iron
and steel. We know that high-carbon steel makes a better cutting tool than low-carbon steel. And yet
carbon alone does not make all the difference because we know that cast iron has more carbon than tool
steel and yet it does not make a good cutting tool.
Pig iron or cast iron has from 3 to 5 per cent carbon, while good tool steel rarely has more than 1¼ per
cent of carbon, yet one is soft and has a coarse grain, while the other has a fine grain and can be hardened
by heating and dipping in water. Most of the carbon in cast iron is in a form like graphite, which is almost
pure carbon, and is therefore called graphitic carbon. The resemblance can be seen by noting how cast-
iron borings blacken the hands just as does graphite, while steel turnings do not have the same effect. The
difference is due to the fact that the carbon in steel is not in a graphitic form as well as because it is
present in smaller quantities.
In making steel in the old way the cast iron was melted and the carbon and other impurities burned out of
it, the melted iron being stirred or "puddled," meanwhile. The resulting puddled iron, also known as
wrought iron, is very low in carbon; it is tough, and on being broken appears to be made up of a bundle of
long fibers. Then the iron was heated to redness for several days in material containing carbon (charcoal)
until it absorbed the desired amount, which made it steel, just as case-hardening iron or steel adds carbon
to the outer surface of the metal. The carbon absorbed by the iron does not take on a graphitic form,
however, as in the case of cast iron, but enters into a chemical compound with the iron, a hard brittle
substance called "cementite" by metallurgists. In fact, the difference between the hard, brittle cementite
and the soft, greasy graphite, accounts for many of the differences between steel and gray cast iron.
Wrought iron, which has very little carbon of any sort in it, is fairly soft and tough. The properties of
wrought iron are the properties of pure iron. As more and more carbon is introduced into the iron, it
combines with the iron and distributes itself throughout the metal in extremely small crystals of cementite,
and this brittle, hard substance lends more and more hardness and strength to the steel, at the expense of
the original toughness of the iron. As more and more carbon is contained in the alloy—for steel is a true
alloy—it begins to appear as graphite, and its properties counteract the remaining brittle cementite.
Eventually, in gray cast iron, we have properties which would be expected of wrought iron, whose tough
metallic texture was shot through with flakes of slippery, weak graphite.
But to return to the methods of making steel tools in use 100 years ago.
The iron bars, after heating in charcoal, were broken and the carbon content judged by the fracture.
Those which had been in the hottest part of the furnace would have the deepest "case" and highest carbon.
So when the steel was graded, and separated into different piles, a few bars of like kind were broken into
short lengths, melted in fire-clay crucibles at an intense white heat, cast carefully into iron molds, and the
resulting ingot forged into bars under a crude trip hammer. This melting practice is still in use for crucible
steel, and will be described further on page 4.
Page 9
THE WORKING OF STEEL
ANNEALING, HEAT TREATING AND HARDENING
OF
CARBON AND ALLOY STEEL
ANNEALING, HEAT TREATING AND HARDENING
OF
CARBON AND ALLOY STEEL
Page 10
CHAPTER I
STEEL MAKING
There are four processes now used for the manufacture of steel. These are: The Bessemer, Open Hearth,
Crucible and Electric Furnace Methods.
BESSEMER PROCESS
The bessemer process consists of charging molten pig iron into a huge, brick-lined pot called the
bessemer converter, and then in blowing a current of air through holes in the bottom of the vessel into the
liquid metal.
The air blast burns the white hot metal, and the temperature increases. The action is exactly similar to
what happens in a fire box under forced draft. And in both cases some parts of the material burn easier and
more quickly than others. Thus it is that some of the impurities in the pig iron—including the carbon—
burn first, and if the blast is shut off when they are gone but little of the iron is destroyed. Unfortunately
sulphur, one of the most dangerous impurities, is not expelled in the process.
A bessemer converter is shown in Fig. 1, while Fig. 2 shows the details of its construction. This shows
how the air blast is forced in from one side, through the trunnion, and up through the metal. Where the
steel is finished the converter is tilted, or swung on its trunnions, the blast turned off, and the steel poured
out of the top.
OPEN HEARTH PROCESS
The open hearth furnace consists of a big brick room with a low arched roof. It is charged with pig iron
and scrap through doors in the side walls.
STEEL MAKING
There are four processes now used for the manufacture of steel. These are: The Bessemer, Open Hearth,
Crucible and Electric Furnace Methods.
BESSEMER PROCESS
The bessemer process consists of charging molten pig iron into a huge, brick-lined pot called the
bessemer converter, and then in blowing a current of air through holes in the bottom of the vessel into the
liquid metal.
The air blast burns the white hot metal, and the temperature increases. The action is exactly similar to
what happens in a fire box under forced draft. And in both cases some parts of the material burn easier and
more quickly than others. Thus it is that some of the impurities in the pig iron—including the carbon—
burn first, and if the blast is shut off when they are gone but little of the iron is destroyed. Unfortunately
sulphur, one of the most dangerous impurities, is not expelled in the process.
A bessemer converter is shown in Fig. 1, while Fig. 2 shows the details of its construction. This shows
how the air blast is forced in from one side, through the trunnion, and up through the metal. Where the
steel is finished the converter is tilted, or swung on its trunnions, the blast turned off, and the steel poured
out of the top.
OPEN HEARTH PROCESS
The open hearth furnace consists of a big brick room with a low arched roof. It is charged with pig iron
and scrap through doors in the side walls.
Page 11
FIG. 1.—A typical Bessemer converter.
Through openings at one end of the furnace come hot air and gas, which burn in the furnace, producing
sufficient heat to melt the charge and refine it of its impurities. Lime and other nonmetallic substances are
put in the furnace. These melt, forming a "slag" which floats on the metal and aids materially in the
refining operations.
In the bessemer process air is forced through the metal. In the open-hearth furnace the metal is protected
from the flaming gases by a slag covering. Therefore it is reasonable to suppose that the final product will
not contain so much gas.
FIG. 2.—Action of Bessemer converter.
Through openings at one end of the furnace come hot air and gas, which burn in the furnace, producing
sufficient heat to melt the charge and refine it of its impurities. Lime and other nonmetallic substances are
put in the furnace. These melt, forming a "slag" which floats on the metal and aids materially in the
refining operations.
In the bessemer process air is forced through the metal. In the open-hearth furnace the metal is protected
from the flaming gases by a slag covering. Therefore it is reasonable to suppose that the final product will
not contain so much gas.
FIG. 2.—Action of Bessemer converter.
Page 12
FIG. 3.—Regenerative open hearth furnace.
A diagram of a modern regenerative furnace is shown in Fig. 3. Air and gas enter the hearth through
chambers loosely packed with hot fire brick, burn, and exit to the chimney through another pair of
chambers, giving to them some of the heat which would otherwise waste. The direction is reversed about
every twenty minutes by changing the position of the dampers.
CRUCIBLE STEEL
Crucible steel is still made by melting material in a clay or graphite crucible. Each crucible contains
about 40 lb. of best puddled iron, 40 lb. of clean "mill scrap"—ends trimmed from tool steel bars—and
sufficient rich alloys and charcoal to make the mixture conform to the desired chemical analysis. The
crucible is covered, lowered into a melting hole (Fig. 4) and entirely surrounded by burning coke. In about
four hours the metal is converted into a quiet white hot liquid. Several crucibles are then pulled out of the
hole, and their contents carefully poured into a metal mold, forming an ingot.
FIG. 4.—Typical crucible furnace.
A diagram of a modern regenerative furnace is shown in Fig. 3. Air and gas enter the hearth through
chambers loosely packed with hot fire brick, burn, and exit to the chimney through another pair of
chambers, giving to them some of the heat which would otherwise waste. The direction is reversed about
every twenty minutes by changing the position of the dampers.
CRUCIBLE STEEL
Crucible steel is still made by melting material in a clay or graphite crucible. Each crucible contains
about 40 lb. of best puddled iron, 40 lb. of clean "mill scrap"—ends trimmed from tool steel bars—and
sufficient rich alloys and charcoal to make the mixture conform to the desired chemical analysis. The
crucible is covered, lowered into a melting hole (Fig. 4) and entirely surrounded by burning coke. In about
four hours the metal is converted into a quiet white hot liquid. Several crucibles are then pulled out of the
hole, and their contents carefully poured into a metal mold, forming an ingot.
FIG. 4.—Typical crucible furnace.
Page 13
If modern high-speed steel is being made, the ingots are taken out of the molds while still red hot and
placed in a furnace which keeps them at this temperature for some hours, an operation known as
annealing. After slow cooling any surface defects are ground out. Ingots are then reheated to forging
temperature, hammered down into "billets" of about one-quarter size, and 10 to 20 per cent of the length
cut from the top. After reheating the billets are hammered or rolled into bars of desired size. Finished bars
are packed with a little charcoal into large pipes, the ends sealed, and annealed for two or three days. After
careful inspection and testing the steel is ready for market.
THE ELECTRIC PROCESS
The fourth method of manufacturing steel is by the electric furnace. These furnaces are of various sizes
and designs; their size may be sufficient for only 100 lb. of metal—on the other hand electric furnaces for
making armor-plate steel will hold 40 tons of steel. Designs vary widely according to the electrical
principles used. A popular furnace is the 6-ton Heroult furnace illustrated in Fig. 5.
It is seen to be a squat kettle, made of heavy sheet steel, with a dished bottom and mounted so it can be
tilted forward slightly and completely drained. This kettle is lined with special fire brick which will
withstand most intense heat and resist the cutting action of hot metal and slag. For a roof, a low dome of
fire brick is provided. The shell and lining is pierced in front for a pouring spout, and on either side by
doors, through which the raw material is charged.
Two or three carbon "electrodes"—18-in. cylinders of specially prepared coke or graphite—extend
through holes in the roof. Electrical connections are made to the upper ends, and a very high current sent
through them. This causes tremendous arcs to form between the lower ends of the electrodes and the metal
below, and these electric arcs are the only source of heat in this style of furnace.
Electric furnaces can be used to do the same work as is done in crucible furnaces—that is to say, merely
melt a charge of carefully selected pure raw materials. On the other hand it can be used to produce very
high-grade steel from cheap and impure metal, when it acts more like an open-hearth furnace. It can push
the refining even further than the latter furnace does, for two reasons: first the bath is not swept
continuously by a flaming mass of gases; second, the temperature can be run up higher, enabling the
operator to make up slags which are difficult to melt but very useful to remove small traces of impurities
from the metal.
Electric furnaces are widely used, not only in the iron industry, but in brass, copper and aluminum
works. It is a useful melter of cold metal for making castings. It can be used to convert iron into steel or
vice versa. Its most useful sphere, however, is as a refiner of metal, wherein it takes either cold steel or
molten steel from open hearth or bessemer furnaces, and gives it the finishing touches.
placed in a furnace which keeps them at this temperature for some hours, an operation known as
annealing. After slow cooling any surface defects are ground out. Ingots are then reheated to forging
temperature, hammered down into "billets" of about one-quarter size, and 10 to 20 per cent of the length
cut from the top. After reheating the billets are hammered or rolled into bars of desired size. Finished bars
are packed with a little charcoal into large pipes, the ends sealed, and annealed for two or three days. After
careful inspection and testing the steel is ready for market.
THE ELECTRIC PROCESS
The fourth method of manufacturing steel is by the electric furnace. These furnaces are of various sizes
and designs; their size may be sufficient for only 100 lb. of metal—on the other hand electric furnaces for
making armor-plate steel will hold 40 tons of steel. Designs vary widely according to the electrical
principles used. A popular furnace is the 6-ton Heroult furnace illustrated in Fig. 5.
It is seen to be a squat kettle, made of heavy sheet steel, with a dished bottom and mounted so it can be
tilted forward slightly and completely drained. This kettle is lined with special fire brick which will
withstand most intense heat and resist the cutting action of hot metal and slag. For a roof, a low dome of
fire brick is provided. The shell and lining is pierced in front for a pouring spout, and on either side by
doors, through which the raw material is charged.
Two or three carbon "electrodes"—18-in. cylinders of specially prepared coke or graphite—extend
through holes in the roof. Electrical connections are made to the upper ends, and a very high current sent
through them. This causes tremendous arcs to form between the lower ends of the electrodes and the metal
below, and these electric arcs are the only source of heat in this style of furnace.
Electric furnaces can be used to do the same work as is done in crucible furnaces—that is to say, merely
melt a charge of carefully selected pure raw materials. On the other hand it can be used to produce very
high-grade steel from cheap and impure metal, when it acts more like an open-hearth furnace. It can push
the refining even further than the latter furnace does, for two reasons: first the bath is not swept
continuously by a flaming mass of gases; second, the temperature can be run up higher, enabling the
operator to make up slags which are difficult to melt but very useful to remove small traces of impurities
from the metal.
Electric furnaces are widely used, not only in the iron industry, but in brass, copper and aluminum
works. It is a useful melter of cold metal for making castings. It can be used to convert iron into steel or
vice versa. Its most useful sphere, however, is as a refiner of metal, wherein it takes either cold steel or
molten steel from open hearth or bessemer furnaces, and gives it the finishing touches.
Page 14
FIG. 5.—"Slagging off" an electric furnace.
FIG. 6.—Pouring the ingots.
As an illustration of the furnace reactions that take place the following schedule is given, showing the
various stages in the making of a heat of electric steel. The steel to be made was a high-carbon chrome
steel used for balls for ball bearings:
6-TON HEROULT FURNACE
11:50 A.M. —Material charged:
Boiler plate 5,980 lb.
Stampings 5,991 lb.
11,971 lb.
Limestone 700 lb.
12:29 P.M. —Completed charging (current switched on).
3:20 P.M. —Charge melted down.
Preliminary analysis under black slag.
Analysis:
Carbon Silicon Sulphur Phosphorus Manganese
0.06 0.014 0.032 0.009 0.08
Note the practical elimination of phosphorus.
FIG. 6.—Pouring the ingots.
As an illustration of the furnace reactions that take place the following schedule is given, showing the
various stages in the making of a heat of electric steel. The steel to be made was a high-carbon chrome
steel used for balls for ball bearings:
6-TON HEROULT FURNACE
11:50 A.M. —Material charged:
Boiler plate 5,980 lb.
Stampings 5,991 lb.
11,971 lb.
Limestone 700 lb.
12:29 P.M. —Completed charging (current switched on).
3:20 P.M. —Charge melted down.
Preliminary analysis under black slag.
Analysis:
Carbon Silicon Sulphur Phosphorus Manganese
0.06 0.014 0.032 0.009 0.08
Note the practical elimination of phosphorus.
Page 15
3:40 P.M. —The oxidizing (black) slag is now poured and skimmed off as clean as possible to prevent
rephosphorizing and to permit of adding carburizing materials. For this purpose carbon is
added in the form of powdered coke, ground electrodes or other forms of pure carbon.
The deoxidizing slag is now formed by additions of lime, coke and fluorspar (and for some analyses
ferrosilicon). The slag changes from black to white as the metallic oxides are reduced by these
deoxidizing additions and the reduced metals return to the bath. A good finishing slag is creamy white,
porous and viscous. After the slag becomes white, some time is necessary for the absorption of the sulphur
in the bath by the slag.
The white slag disintegrates to a powder when exposed to the atmosphere and has a pronounced odor of
acetylene when wet.
Further additions of recarburizing material are added as needed to meet the analysis. The further
reactions are shown by the following:
3:40 P.M. —Recarburizing material added:
130 lb. ground electrodes.
25 lb. ferromanganese.
Analysis:
Carbon Silicon Sulphur Phosphorus Manganese
0.76 0.011 0.030 0.008 0.26
To form white slag there was added:
225 lb. lime.
75 lb. powdered coke.
55 lb. fluorspar.
4:50 P.M. —
Analysis:
Carbon Silicon Sulphur Phosphorus Manganese
0.75 0.014 0.012 0.008 0.28
During the white-slag period the following alloying additions were made:
500 lb. pig iron.
80 lb. ferrosilicon.
9 lb. ferromanganese.
146 lb. 6 per cent carbon ferrochrome.
The furnace was rotated forward to an inclined position and the charge poured into the ladle, from which
in turn it was poured into molds.
5:40 P.M. —Heat poured.
Analysis:
Carbon Silicon Sulphur Phosphorus Manganese
0.97 0.25 0.013 0.33 0.70
Ingot weight poured 94.0 per cent
rephosphorizing and to permit of adding carburizing materials. For this purpose carbon is
added in the form of powdered coke, ground electrodes or other forms of pure carbon.
The deoxidizing slag is now formed by additions of lime, coke and fluorspar (and for some analyses
ferrosilicon). The slag changes from black to white as the metallic oxides are reduced by these
deoxidizing additions and the reduced metals return to the bath. A good finishing slag is creamy white,
porous and viscous. After the slag becomes white, some time is necessary for the absorption of the sulphur
in the bath by the slag.
The white slag disintegrates to a powder when exposed to the atmosphere and has a pronounced odor of
acetylene when wet.
Further additions of recarburizing material are added as needed to meet the analysis. The further
reactions are shown by the following:
3:40 P.M. —Recarburizing material added:
130 lb. ground electrodes.
25 lb. ferromanganese.
Analysis:
Carbon Silicon Sulphur Phosphorus Manganese
0.76 0.011 0.030 0.008 0.26
To form white slag there was added:
225 lb. lime.
75 lb. powdered coke.
55 lb. fluorspar.
4:50 P.M. —
Analysis:
Carbon Silicon Sulphur Phosphorus Manganese
0.75 0.014 0.012 0.008 0.28
During the white-slag period the following alloying additions were made:
500 lb. pig iron.
80 lb. ferrosilicon.
9 lb. ferromanganese.
146 lb. 6 per cent carbon ferrochrome.
The furnace was rotated forward to an inclined position and the charge poured into the ladle, from which
in turn it was poured into molds.
5:40 P.M. —Heat poured.
Analysis:
Carbon Silicon Sulphur Phosphorus Manganese
0.97 0.25 0.013 0.33 0.70
Ingot weight poured 94.0 per cent
Page 16
Scull 2.7 per cent
Loss 3.3 per cent
Total current consumption for the heat, 4,700 kW.-hr. or 710 kw.-hr. per ton.
Electric steel, in fact, all fine steel, should be cast in big-end-up molds with refractory hot tops to prevent
any possibility of pipage in the body of the ingot. In the further processing of the ingot, whether in the
rolling mill or forge, special precautions should be taken in the heating, in the reduction of the metal and
in the cooling.
No attempt is made to compare the relative merits of open hearth and electric steel; results in service,
day in and day out, have, however, thoroughly established the desirability of electric steel. Ten years of
experience indicate that electric steel is equal to crucible steel and superior to open hearth.
The rare purity of the heat derived from the electric are, combined with definite control of the slag in a
neutral atmosphere, explains in part the superiority of electric steel. Commenting on this recently Dr. H.
M. Howe stated that "in the open hearth process you have such atmosphere and slag conditions as you can
get, and in the electric you have such atmosphere and slag conditions as you desire."
Another type of electric furnace is shown in Figs. 7 and 8. This is the Ludlum furnace, the illustrations
showing a 10-ton size. Figure 7 shows it in normal, or melting position, while in Fig. 8 it is tilted for
pouring. In melting, the electrodes first rest on the charge of material in the furnace. After the current is
turned on they eat their way through, nearly to the bottom. By this time there is a pool of molten metal
beneath the electrode and the charge is melted from the bottom up so that the roof is not exposed to the
high temperature radiating from the open arc. The electrodes in this furnace are of graphite, 9 in. in
diameter and the current consumed is about 500 kw.-hr. per ton.
FIG. 7.—Ludlum electric furnace.
Loss 3.3 per cent
Total current consumption for the heat, 4,700 kW.-hr. or 710 kw.-hr. per ton.
Electric steel, in fact, all fine steel, should be cast in big-end-up molds with refractory hot tops to prevent
any possibility of pipage in the body of the ingot. In the further processing of the ingot, whether in the
rolling mill or forge, special precautions should be taken in the heating, in the reduction of the metal and
in the cooling.
No attempt is made to compare the relative merits of open hearth and electric steel; results in service,
day in and day out, have, however, thoroughly established the desirability of electric steel. Ten years of
experience indicate that electric steel is equal to crucible steel and superior to open hearth.
The rare purity of the heat derived from the electric are, combined with definite control of the slag in a
neutral atmosphere, explains in part the superiority of electric steel. Commenting on this recently Dr. H.
M. Howe stated that "in the open hearth process you have such atmosphere and slag conditions as you can
get, and in the electric you have such atmosphere and slag conditions as you desire."
Another type of electric furnace is shown in Figs. 7 and 8. This is the Ludlum furnace, the illustrations
showing a 10-ton size. Figure 7 shows it in normal, or melting position, while in Fig. 8 it is tilted for
pouring. In melting, the electrodes first rest on the charge of material in the furnace. After the current is
turned on they eat their way through, nearly to the bottom. By this time there is a pool of molten metal
beneath the electrode and the charge is melted from the bottom up so that the roof is not exposed to the
high temperature radiating from the open arc. The electrodes in this furnace are of graphite, 9 in. in
diameter and the current consumed is about 500 kw.-hr. per ton.
FIG. 7.—Ludlum electric furnace.
Page 17
FIG. 8.—The furnace tilted for pouring.
One of the things which sometimes confuse regarding the contents of steel is the fact that the percentage
of carbon and the other alloys are usually designated in different ways. Carbon is usually designated by
"points" and the other alloys by percentages. The point is one ten-thousandth while 1 per cent is one one-
hundredth of the whole. In other words, "one hundred point carbon" is steel containing 1 per cent carbon.
Twenty point carbon, such as is used for carbonizing purposes is 0.20 per cent. Tool steel varies from one
hundred to one hundred and fifty points carbon, or from 1.00 to 1.50 per cent.
Nickel, chromium, etc., are always given in per cent, as a 3.5 per cent nickel, which means exactly what
it says—3½ parts in 100. Bearing this difference in mind all confusion will be avoided.
CLASSIFICATIONS OF STEEL
Among makers and sellers, carbon tool-steels are classed by "grade" and "temper." The word grade is
qualified by many adjectives of more or less cryptic meaning, but in general they aim to denote the
process and care with which the steel is made.
Temper of a steel refers to the carbon content. This should preferably be noted by "points," as just
explained; but unfortunately, a 53-point steel (containing 0.53 per cent carbon) may locally be called
something like "No. 3 temper."
A widely used method of classifying steels was originated by the Society of Automotive Engineers. Each
specification is represented by a number of 4 digits, the first figure indicating the class, the second figure
the approximate percentage of predominant alloying element, and the last two the average carbon content
in points. Plain carbon steels are class 1, nickel steels are class 2, nickel-chromium steels are class 3,
chromium steels are class 5, chromium-vanadium steels are class 6, and silico-manganese steels are class
9. Thus by this system, steel 2340 would be a 3 per cent nickel steel with 0.40 per cent carbon; or steel
1025 would be a 0.25 plain carbon steel.
Steel makers have no uniform classification for the various kinds of steel or steels used for different
purposes. The following list shows the names used by some of the well-known makers:
Air-hardening steel Chrome-vanadium steel
Alloy steel Circular saw plates
Automobile steel Coal auger steel
Awl steel Coal mining pick or cutter steel
One of the things which sometimes confuse regarding the contents of steel is the fact that the percentage
of carbon and the other alloys are usually designated in different ways. Carbon is usually designated by
"points" and the other alloys by percentages. The point is one ten-thousandth while 1 per cent is one one-
hundredth of the whole. In other words, "one hundred point carbon" is steel containing 1 per cent carbon.
Twenty point carbon, such as is used for carbonizing purposes is 0.20 per cent. Tool steel varies from one
hundred to one hundred and fifty points carbon, or from 1.00 to 1.50 per cent.
Nickel, chromium, etc., are always given in per cent, as a 3.5 per cent nickel, which means exactly what
it says—3½ parts in 100. Bearing this difference in mind all confusion will be avoided.
CLASSIFICATIONS OF STEEL
Among makers and sellers, carbon tool-steels are classed by "grade" and "temper." The word grade is
qualified by many adjectives of more or less cryptic meaning, but in general they aim to denote the
process and care with which the steel is made.
Temper of a steel refers to the carbon content. This should preferably be noted by "points," as just
explained; but unfortunately, a 53-point steel (containing 0.53 per cent carbon) may locally be called
something like "No. 3 temper."
A widely used method of classifying steels was originated by the Society of Automotive Engineers. Each
specification is represented by a number of 4 digits, the first figure indicating the class, the second figure
the approximate percentage of predominant alloying element, and the last two the average carbon content
in points. Plain carbon steels are class 1, nickel steels are class 2, nickel-chromium steels are class 3,
chromium steels are class 5, chromium-vanadium steels are class 6, and silico-manganese steels are class
9. Thus by this system, steel 2340 would be a 3 per cent nickel steel with 0.40 per cent carbon; or steel
1025 would be a 0.25 plain carbon steel.
Steel makers have no uniform classification for the various kinds of steel or steels used for different
purposes. The following list shows the names used by some of the well-known makers:
Air-hardening steel Chrome-vanadium steel
Alloy steel Circular saw plates
Automobile steel Coal auger steel
Awl steel Coal mining pick or cutter steel
Page 18
Axe and hatchet steel Coal wedge steel
Band knife steel Cone steel
Band saw steel Crucible cast steel
Butcher saw steel Crucible machinery steel
Chisel steel Cutlery steel
Chrome-nickel steel Drawing die steel (Wortle)
Drill rod steel Patent, bush or hammer steel
Facing and welding steel Pick steel
Fork steel Pivot steel
Gin saw steel Plane bit steel
Granite wedge steel Quarry steel
Gun barrel steel Razor steel
Hack saw steel Roll turning steel
High-speed tool steel Saw steel
Hot-rolled sheet steel Scythe steel
Lathe spindle steel Shear knife steel
Lawn mower knife steel Silico-manganese steel
Machine knife steel Spindle steel
Magnet steel Spring steel
Mining drill steel Tool holder steel
Nail die shapes Vanadium tool steel
Nickel-chrome steel Vanadium-chrome steel
Paper knife steel Wortle steel
Passing to the tonnage specifications, the following table from Tiemann's excellent pocket book on "Iron
and Steel," will give an approximate idea of the ordinary designations now in use:
Approximate
Grades carbon range Common uses
Extra soft 0.08-0.18 Pipe, chain and other welding purposes; case-hardening
(dead soft) purposes; rivets; pressing and stamping purposes.
Structural (soft) 0.08-0.18 Structural plates, shapes and bars for bridges, buildings, cars,
(medium) locomotives; boiler (flange) steel; drop forgings; bolts.
Medium 0.20-0.35 Structural purposes (ships); shafting; automobile parts; drop
forgings.
Medium hard 0.35-0.60 Locomotive and similar large forgings; car axles; rails.
Hard 0.60-0.85 Wrought steel wheels for steam and electric railway service;
locomotive tires; rails; tools, such as sledges, hammers, pick
points, crowbars, etc.
Spring 0.85-1.05 Automobile and other vehicle springs; tools, such as hot and cold
chisels, rock drills and shear blades.
Spring 0.90-1.15 Railway springs; general machine shop tools.
Band knife steel Cone steel
Band saw steel Crucible cast steel
Butcher saw steel Crucible machinery steel
Chisel steel Cutlery steel
Chrome-nickel steel Drawing die steel (Wortle)
Drill rod steel Patent, bush or hammer steel
Facing and welding steel Pick steel
Fork steel Pivot steel
Gin saw steel Plane bit steel
Granite wedge steel Quarry steel
Gun barrel steel Razor steel
Hack saw steel Roll turning steel
High-speed tool steel Saw steel
Hot-rolled sheet steel Scythe steel
Lathe spindle steel Shear knife steel
Lawn mower knife steel Silico-manganese steel
Machine knife steel Spindle steel
Magnet steel Spring steel
Mining drill steel Tool holder steel
Nail die shapes Vanadium tool steel
Nickel-chrome steel Vanadium-chrome steel
Paper knife steel Wortle steel
Passing to the tonnage specifications, the following table from Tiemann's excellent pocket book on "Iron
and Steel," will give an approximate idea of the ordinary designations now in use:
Approximate
Grades carbon range Common uses
Extra soft 0.08-0.18 Pipe, chain and other welding purposes; case-hardening
(dead soft) purposes; rivets; pressing and stamping purposes.
Structural (soft) 0.08-0.18 Structural plates, shapes and bars for bridges, buildings, cars,
(medium) locomotives; boiler (flange) steel; drop forgings; bolts.
Medium 0.20-0.35 Structural purposes (ships); shafting; automobile parts; drop
forgings.
Medium hard 0.35-0.60 Locomotive and similar large forgings; car axles; rails.
Hard 0.60-0.85 Wrought steel wheels for steam and electric railway service;
locomotive tires; rails; tools, such as sledges, hammers, pick
points, crowbars, etc.
Spring 0.85-1.05 Automobile and other vehicle springs; tools, such as hot and cold
chisels, rock drills and shear blades.
Spring 0.90-1.15 Railway springs; general machine shop tools.
Page 19
CHAPTER II
COMPOSITION AND PROPERTIES OF STEEL
It is a remarkable fact that one can look through a dozen text books on metallurgy and not find a
definition of the word "steel." Some of them describe the properties of many other irons and then allow
you to guess that everything else is steel. If it was difficult a hundred years ago to give a good definition
of the term when the metal was made by only one or two processes, it is doubly difficult now, since the
introduction of so many new operations and furnaces.
We are in better shape to know what steel is than our forefathers. They went through certain operations
and they got a soft malleable, weldable metal which would not harden; this they called iron. Certain other
operations gave them something which looked very much like iron, but which would harden after
quenching from a red heat. This was steel. Not knowing the essential difference between the two, they
must distinguish by the process of manufacture. To-day we can make either variety by several methods,
and can convert either into the other at will, back and forth as often as we wish; so we are able to
distinguish between the two more logically.
We know that iron is a chemical element—the chemists write it Fe for short, after the Latin word
"ferrum," meaning iron—it is one of those substances which cannot be separated into anything else but
itself. It can be made to join with other elements; for instance, it joins with the oxygen in the air and forms
scale or rust, substances known to the chemist as iron oxide. But the same metal iron can be recovered
from that rust by abstracting the oxygen; having recovered the iron nothing else can be extracted but iron;
iron is elemental.
We can get relatively pure iron from various minerals and artificial substances, and when we get it we
always have a magnetic metal, almost infusible, ductile, fairly strong, tough, something which can be
hardened slightly by hammering but which cannot be hardened by quenching. It has certain chemical
properties, which need not be described, which allow a skilled chemist to distinguish it without difficulty
and unerringly from the other known elements—nearly 100 of them.
Carbon is another chemical element, written C for short, which is widely distributed through nature.
Carbon also readily combines with oxygen and other chemical elements, so that it is rarely found pure; its
most familiar form is soot, although the rarer graphite and most rare diamond are also forms of quite pure
carbon. It can also be readily separated from its multitude of compounds (vegetation, coal, limestone,
petroleum) by the chemist.
With the rise of knowledge of scientific chemistry, it was quickly found that the essential difference
between iron and steel was that the latter was iron plus carbon. Consequently it is an alloy, and the
definition which modern metallurgists accept is this:
"Steel is an iron-carbon alloy containing less than about 2 per cent carbon."
Of course there are other elements contained in commercial steel, and these elements are especially
important in modern "alloy steels," but carbon is the element which changes a soft metal into one which
may be hardened, and strengthened by quenching. In fact, carbon, of itself, without heat treatment,
COMPOSITION AND PROPERTIES OF STEEL
It is a remarkable fact that one can look through a dozen text books on metallurgy and not find a
definition of the word "steel." Some of them describe the properties of many other irons and then allow
you to guess that everything else is steel. If it was difficult a hundred years ago to give a good definition
of the term when the metal was made by only one or two processes, it is doubly difficult now, since the
introduction of so many new operations and furnaces.
We are in better shape to know what steel is than our forefathers. They went through certain operations
and they got a soft malleable, weldable metal which would not harden; this they called iron. Certain other
operations gave them something which looked very much like iron, but which would harden after
quenching from a red heat. This was steel. Not knowing the essential difference between the two, they
must distinguish by the process of manufacture. To-day we can make either variety by several methods,
and can convert either into the other at will, back and forth as often as we wish; so we are able to
distinguish between the two more logically.
We know that iron is a chemical element—the chemists write it Fe for short, after the Latin word
"ferrum," meaning iron—it is one of those substances which cannot be separated into anything else but
itself. It can be made to join with other elements; for instance, it joins with the oxygen in the air and forms
scale or rust, substances known to the chemist as iron oxide. But the same metal iron can be recovered
from that rust by abstracting the oxygen; having recovered the iron nothing else can be extracted but iron;
iron is elemental.
We can get relatively pure iron from various minerals and artificial substances, and when we get it we
always have a magnetic metal, almost infusible, ductile, fairly strong, tough, something which can be
hardened slightly by hammering but which cannot be hardened by quenching. It has certain chemical
properties, which need not be described, which allow a skilled chemist to distinguish it without difficulty
and unerringly from the other known elements—nearly 100 of them.
Carbon is another chemical element, written C for short, which is widely distributed through nature.
Carbon also readily combines with oxygen and other chemical elements, so that it is rarely found pure; its
most familiar form is soot, although the rarer graphite and most rare diamond are also forms of quite pure
carbon. It can also be readily separated from its multitude of compounds (vegetation, coal, limestone,
petroleum) by the chemist.
With the rise of knowledge of scientific chemistry, it was quickly found that the essential difference
between iron and steel was that the latter was iron plus carbon. Consequently it is an alloy, and the
definition which modern metallurgists accept is this:
"Steel is an iron-carbon alloy containing less than about 2 per cent carbon."
Of course there are other elements contained in commercial steel, and these elements are especially
important in modern "alloy steels," but carbon is the element which changes a soft metal into one which
may be hardened, and strengthened by quenching. In fact, carbon, of itself, without heat treatment,
Page 20
strengthens iron at the expense of ductility (as noted by the percentage elongation an 8-in. bar will stretch
before breaking). This is shown by the following table:
Elastic Ultimate
Percentage
Class by Per cent limit strength
Class by use. elongation
hardness. carbon. lb. per lb. per
in 8 inches.
sq. in. sq. in.
Boiler rivet steel Dead soft 0.08 to 0.15 25,000 50,000 30
Struc. rivet steel Soft 0.15 to 0.22 30,000 55,000 30
Boiler plate steel Soft 0.08 to 0.10 30,000 60,000 25
Structural steel Medium 0.18 to 0.30 35,000 65,000 25
Machinery steel Hard 0.35 to 0.60 40,000 75,000 20
Rail steel Hard 0.35 to 0.55 40,000 75,000 15
Spring steel High carbon 1.00 to 1.50 60,000 125,000 10
Tool steel High carbon 0.90 to 1.50 80,000 150,000 5
Just why a soft material like carbon (graphite), when added to another soft material like iron, should
make the iron harder, has been quite a mystery, and one which has caused a tremendous amount of study.
The mutual interactions of these two elements in various proportions and at various temperatures will be
discussed at greater length later, especially in Chap. VIII, p. 105. But we may anticipate by saying that
some of the iron unites with all the carbon to form a new substance, very hard, a carbide which has been
called "cementite." The compound always contains iron and carbon in the proportions of three atoms of
iron to one atom of carbon; chemists note this fact in shorthand by the symbol Fe3C (a definite chemical
compound of three atoms of iron to one of carbon). Many of the properties of steel, as they vary with
carbon content, can be linked up with the increasing amount of this hard carbide cementite, distributed in
very fine particles through the softer iron.
Sulphur is another element (symbol S) which is always found in steel in small quantities. Some sulphur
is contained in the ore from which the iron is smelted; more sulphur is introduced by the coke and fuel
used. Sulphur is very difficult to get rid of in steel making; in fact the resulting metal usually contains a
little more than the raw materials used. Only the electric furnace is able to produce the necessary heat and
slags required to eliminate sulphur, and as a matter of fact the sulphur does not go until several other
impurities have been eliminated. Consequently, an electric steel with extremely low sulphur (0.02 per
cent) is by that same token a well-made metal.
Sulphur is of most trouble to rolling and forging operations when conducted at a red heat. It makes steel
tender and brittle at that temperature—a condition known to the workmen as "red-short." It seems to have
little or no effect upon the physical properties of cold steel—at least as revealed by the ordinary testing
machines—consequently many specifications do not set any limit on sulphur, resting on the idea that if
sulphur is low enough not to cause trouble to the manufacturer during rolling, it will not cause the user
any trouble.
Tool steel and other fine steels should be very low in sulphur, preferably not higher than 0.03 per cent.
Higher sulphur steels (0.06 per cent, and even up to 0.10 per cent) have given very good service for
machine parts, but in general a high sulphur steel is a suspicious steel. Screw stock is purposely made with
up to 0.12 per cent sulphur and a like amount of phosphorus so it will cut freely.
Manganese counteracts the detrimental effect of sulphur when present in the steel to an amount at least
five times the sulphur content.
Phosphorus is an element (symbol P) which enters the metal from the ore. It remains in the steel when
made by the so-called acid process, but it can be easily eliminated down to 0.06 per cent in the basic
before breaking). This is shown by the following table:
Elastic Ultimate
Percentage
Class by Per cent limit strength
Class by use. elongation
hardness. carbon. lb. per lb. per
in 8 inches.
sq. in. sq. in.
Boiler rivet steel Dead soft 0.08 to 0.15 25,000 50,000 30
Struc. rivet steel Soft 0.15 to 0.22 30,000 55,000 30
Boiler plate steel Soft 0.08 to 0.10 30,000 60,000 25
Structural steel Medium 0.18 to 0.30 35,000 65,000 25
Machinery steel Hard 0.35 to 0.60 40,000 75,000 20
Rail steel Hard 0.35 to 0.55 40,000 75,000 15
Spring steel High carbon 1.00 to 1.50 60,000 125,000 10
Tool steel High carbon 0.90 to 1.50 80,000 150,000 5
Just why a soft material like carbon (graphite), when added to another soft material like iron, should
make the iron harder, has been quite a mystery, and one which has caused a tremendous amount of study.
The mutual interactions of these two elements in various proportions and at various temperatures will be
discussed at greater length later, especially in Chap. VIII, p. 105. But we may anticipate by saying that
some of the iron unites with all the carbon to form a new substance, very hard, a carbide which has been
called "cementite." The compound always contains iron and carbon in the proportions of three atoms of
iron to one atom of carbon; chemists note this fact in shorthand by the symbol Fe3C (a definite chemical
compound of three atoms of iron to one of carbon). Many of the properties of steel, as they vary with
carbon content, can be linked up with the increasing amount of this hard carbide cementite, distributed in
very fine particles through the softer iron.
Sulphur is another element (symbol S) which is always found in steel in small quantities. Some sulphur
is contained in the ore from which the iron is smelted; more sulphur is introduced by the coke and fuel
used. Sulphur is very difficult to get rid of in steel making; in fact the resulting metal usually contains a
little more than the raw materials used. Only the electric furnace is able to produce the necessary heat and
slags required to eliminate sulphur, and as a matter of fact the sulphur does not go until several other
impurities have been eliminated. Consequently, an electric steel with extremely low sulphur (0.02 per
cent) is by that same token a well-made metal.
Sulphur is of most trouble to rolling and forging operations when conducted at a red heat. It makes steel
tender and brittle at that temperature—a condition known to the workmen as "red-short." It seems to have
little or no effect upon the physical properties of cold steel—at least as revealed by the ordinary testing
machines—consequently many specifications do not set any limit on sulphur, resting on the idea that if
sulphur is low enough not to cause trouble to the manufacturer during rolling, it will not cause the user
any trouble.
Tool steel and other fine steels should be very low in sulphur, preferably not higher than 0.03 per cent.
Higher sulphur steels (0.06 per cent, and even up to 0.10 per cent) have given very good service for
machine parts, but in general a high sulphur steel is a suspicious steel. Screw stock is purposely made with
up to 0.12 per cent sulphur and a like amount of phosphorus so it will cut freely.
Manganese counteracts the detrimental effect of sulphur when present in the steel to an amount at least
five times the sulphur content.
Phosphorus is an element (symbol P) which enters the metal from the ore. It remains in the steel when
made by the so-called acid process, but it can be easily eliminated down to 0.06 per cent in the basic
Page 21
process. In fact the discovery of the basic process was necessary before the huge iron deposits of Belgium
and the Franco-German border could be used. These ores contain several per cent phosphorus, and made a
very brittle steel ("cold short") until basic furnaces were used. Basic furnaces allow the formation of a slag
high in lime, which takes practically all the phosphorus out of the metal. Not only is the resulting metal
usable, but the slag makes a very excellent fertilizer, and is in good demand.
Silicon is a very widespread element (symbol Si), being an essential constituent of nearly all the rocks of
the earth. It is similar to carbon in many of its chemical properties; for instance it burns very readily in
oxygen, and consequently native silicon is unknown—it is always found in combination with one or more
other elements. When it bums, each atom of silicon unites with two atoms of oxygen to form a compound
known to chemists as silica (SiO2), and to the small boy as "sand" and "agate."
Iron ore (an oxide of iron) contains more or less sand and dirt mixed in it when it is mined, and not only
the iron oxide but also some of the silicon oxide is robbed of its oxygen by the smelting process. Pig iron
—the product of the blast furnace—therefore contains from 1 to 3 per cent of silicon, and some silicon
remains in the metal after it has been purified and converted into steel.
However, silicon, as noted above, burns very readily in oxygen, and this property is of good use in steel
making. At the end of the steel-making process the metal contains more or less oxygen, which must be
removed. This is sometimes done (especially in the so-called acid process) by adding a small amount of
silicon to the hot metal just before it leaves the furnace, and stirring it in. It thereupon abstracts oxygen
from the metal wherever it finds it, changing to silica (SiO2) which rises and floats on the surface of the
cleaned metal. Most of the silicon remaining in the metal is an excess over that which is required to
remove the dangerous oxygen, and the final analysis of many steels show enough silicon (from 0.20 to
0.40) to make sure that this step in the manufacture has been properly done.
Manganese is a metal much like iron. Its chemical symbol is Mn. It is somewhat more active than iron
in many chemical changes—notably it has what is apparently a stronger attraction for oxygen and sulphur
than has iron. Therefore the metal is used (especially in the so-called basic process) to free the molten
steel of oxygen, acting in a manner similar to silicon, as explained above. The compound of manganese
and oxygen is readily eliminated from the metal. Sufficient excess of elemental manganese should remain
so that the purchaser may be sure that the iron has been properly "deoxidized," and to render harmless the
traces of sulphur present. No damage is done by the presence of a little manganese in steel, quite the
reverse. Consequently it is common to find steels containing from 0.3 to 1.5 per cent.
Alloying Elements.—Commercial steels of even the simplest types are therefore primarily alloys of iron
and carbon. Impurities and their "remedies" are always present: sulphur, phosphorus, silicon and
manganese—to say nothing of oxygen, nitrogen and carbon oxide gases, about which we know very little.
It has been found that other metals, if added to well-made steel, produce definite improvements in certain
directions, and these "alloy steels" have found much use in the last ten years. Alloy steels, in addition to
the above-mentioned elements, may commonly contain one or more of the following, in varying amounts:
Nickel (Ni), Chromium (Cr), Vanadium (Va), Tungsten (W), Molybdenum (Mo). These steels will be
discussed at more length in Chapters III and IV.
PROPERTIES OF STEEL
Steels are known by certain tests. Early tests were more or less crude, and depended upon the ability of
the workman to judge the "grain" exhibited by a freshly broken piece of steel. The cold-bend test was also
very useful—a small bar was bent flat upon itself, and the stretched fibers examined for any sign of break.
Harder stiff steels were supported at the ends and the amount of central load they would support before
fracture, or the amount of permanent set they would acquire at a given load noted. Files were also used to
test the hardness of very hard steel.
and the Franco-German border could be used. These ores contain several per cent phosphorus, and made a
very brittle steel ("cold short") until basic furnaces were used. Basic furnaces allow the formation of a slag
high in lime, which takes practically all the phosphorus out of the metal. Not only is the resulting metal
usable, but the slag makes a very excellent fertilizer, and is in good demand.
Silicon is a very widespread element (symbol Si), being an essential constituent of nearly all the rocks of
the earth. It is similar to carbon in many of its chemical properties; for instance it burns very readily in
oxygen, and consequently native silicon is unknown—it is always found in combination with one or more
other elements. When it bums, each atom of silicon unites with two atoms of oxygen to form a compound
known to chemists as silica (SiO2), and to the small boy as "sand" and "agate."
Iron ore (an oxide of iron) contains more or less sand and dirt mixed in it when it is mined, and not only
the iron oxide but also some of the silicon oxide is robbed of its oxygen by the smelting process. Pig iron
—the product of the blast furnace—therefore contains from 1 to 3 per cent of silicon, and some silicon
remains in the metal after it has been purified and converted into steel.
However, silicon, as noted above, burns very readily in oxygen, and this property is of good use in steel
making. At the end of the steel-making process the metal contains more or less oxygen, which must be
removed. This is sometimes done (especially in the so-called acid process) by adding a small amount of
silicon to the hot metal just before it leaves the furnace, and stirring it in. It thereupon abstracts oxygen
from the metal wherever it finds it, changing to silica (SiO2) which rises and floats on the surface of the
cleaned metal. Most of the silicon remaining in the metal is an excess over that which is required to
remove the dangerous oxygen, and the final analysis of many steels show enough silicon (from 0.20 to
0.40) to make sure that this step in the manufacture has been properly done.
Manganese is a metal much like iron. Its chemical symbol is Mn. It is somewhat more active than iron
in many chemical changes—notably it has what is apparently a stronger attraction for oxygen and sulphur
than has iron. Therefore the metal is used (especially in the so-called basic process) to free the molten
steel of oxygen, acting in a manner similar to silicon, as explained above. The compound of manganese
and oxygen is readily eliminated from the metal. Sufficient excess of elemental manganese should remain
so that the purchaser may be sure that the iron has been properly "deoxidized," and to render harmless the
traces of sulphur present. No damage is done by the presence of a little manganese in steel, quite the
reverse. Consequently it is common to find steels containing from 0.3 to 1.5 per cent.
Alloying Elements.—Commercial steels of even the simplest types are therefore primarily alloys of iron
and carbon. Impurities and their "remedies" are always present: sulphur, phosphorus, silicon and
manganese—to say nothing of oxygen, nitrogen and carbon oxide gases, about which we know very little.
It has been found that other metals, if added to well-made steel, produce definite improvements in certain
directions, and these "alloy steels" have found much use in the last ten years. Alloy steels, in addition to
the above-mentioned elements, may commonly contain one or more of the following, in varying amounts:
Nickel (Ni), Chromium (Cr), Vanadium (Va), Tungsten (W), Molybdenum (Mo). These steels will be
discussed at more length in Chapters III and IV.
PROPERTIES OF STEEL
Steels are known by certain tests. Early tests were more or less crude, and depended upon the ability of
the workman to judge the "grain" exhibited by a freshly broken piece of steel. The cold-bend test was also
very useful—a small bar was bent flat upon itself, and the stretched fibers examined for any sign of break.
Harder stiff steels were supported at the ends and the amount of central load they would support before
fracture, or the amount of permanent set they would acquire at a given load noted. Files were also used to
test the hardness of very hard steel.
Page 22
These tests are still used to a considerable extent, especially in works where the progress of an operation
can be kept under close watch in this way, the product being periodically examined by more precise
methods. The chief furnace-man, or "melter," in a steel plant, judges the course of the refining process by
casting small test ingots from time to time, breaking them and examining the fracture. Cutlery
manufacturers use the bend test to judge the temper of blades. File testing of case-hardened parts is very
common.
However there is need of standardized methods which depend less upon the individual skill of the
operator, and which will yield results comparable to others made by different men at different places and
on different steels. Hence has grown up the art of testing materials.
TENSILE PROPERTIES
Strength of a metal is usually expressed in the number of pounds a 1-in. bar will support just before
breaking, a term called the "ultimate strength." It has been found that the shape of the test bar and its
method of loading has some effect upon the results, so it is now usual to turn a rod 5½ in. long down to
0.505 in. in diameter for a central length of 2-3/8 in., ending the turn with 1/2-in. fillets. The area of the
bar equals 0.2 sq. in., so the load it bears at rupture multiplied by 5 will represent the "ultimate strength"
in pounds per square inch.
Such a test bar is stretched apart in a machine like that shown in Fig. 9. The upper end of the bar is held
in wedged jaws by the top cross-head, and the lower end grasped by the movable head. The latter is
moved up and down by three long screws, driven at the same speed, which pass through threads cut in the
corners of the cross-head. When the test piece is fixed in position the motor which drives the machine is
given a few turns, which by proper gearing pulls the cross-head down with a certain pull. This pull is
transmitted to the upper cross-head by the test bar, and can be weighed on the scale arm, acting through a
system of links and levers.
Thus the load may be increased as rapidly as desirable, always kept balanced by the weighing
mechanism, and the load at fracture may be read directly from the scale beam.
This same test piece may give other information. If light punch marks are made, 2 in. apart, before the
test is begun, the broken ends may be clamped together, and the distance between punch marks measured.
If it now measures 3 in. the stretch has been 1 in. in 2, or 50 per cent. This figure is known as the
elongation at fracture, or briefly, the "elongation," and is generally taken to be a measure of ductility.
When steel shows any elongation, it also contracts in area at the same time. Often this contraction is
sharply localized at the fracture; the piece is said to "neck." A figure for contraction in area is also of much
interest as an indication of toughness; the diameter at fracture is measured, a corresponding area taken out
from a table of circles, subtracted from the original area (0.200 sq. in.) and the difference divided by 0.2 to
get the percentage contraction.
can be kept under close watch in this way, the product being periodically examined by more precise
methods. The chief furnace-man, or "melter," in a steel plant, judges the course of the refining process by
casting small test ingots from time to time, breaking them and examining the fracture. Cutlery
manufacturers use the bend test to judge the temper of blades. File testing of case-hardened parts is very
common.
However there is need of standardized methods which depend less upon the individual skill of the
operator, and which will yield results comparable to others made by different men at different places and
on different steels. Hence has grown up the art of testing materials.
TENSILE PROPERTIES
Strength of a metal is usually expressed in the number of pounds a 1-in. bar will support just before
breaking, a term called the "ultimate strength." It has been found that the shape of the test bar and its
method of loading has some effect upon the results, so it is now usual to turn a rod 5½ in. long down to
0.505 in. in diameter for a central length of 2-3/8 in., ending the turn with 1/2-in. fillets. The area of the
bar equals 0.2 sq. in., so the load it bears at rupture multiplied by 5 will represent the "ultimate strength"
in pounds per square inch.
Such a test bar is stretched apart in a machine like that shown in Fig. 9. The upper end of the bar is held
in wedged jaws by the top cross-head, and the lower end grasped by the movable head. The latter is
moved up and down by three long screws, driven at the same speed, which pass through threads cut in the
corners of the cross-head. When the test piece is fixed in position the motor which drives the machine is
given a few turns, which by proper gearing pulls the cross-head down with a certain pull. This pull is
transmitted to the upper cross-head by the test bar, and can be weighed on the scale arm, acting through a
system of links and levers.
Thus the load may be increased as rapidly as desirable, always kept balanced by the weighing
mechanism, and the load at fracture may be read directly from the scale beam.
This same test piece may give other information. If light punch marks are made, 2 in. apart, before the
test is begun, the broken ends may be clamped together, and the distance between punch marks measured.
If it now measures 3 in. the stretch has been 1 in. in 2, or 50 per cent. This figure is known as the
elongation at fracture, or briefly, the "elongation," and is generally taken to be a measure of ductility.
When steel shows any elongation, it also contracts in area at the same time. Often this contraction is
sharply localized at the fracture; the piece is said to "neck." A figure for contraction in area is also of much
interest as an indication of toughness; the diameter at fracture is measured, a corresponding area taken out
from a table of circles, subtracted from the original area (0.200 sq. in.) and the difference divided by 0.2 to
get the percentage contraction.
Page 23
FIG. 9.—Olsen testing machine.
Quite often it is desired to discover the elastic limit of the steel, in fact this is of more use to the designer
than the ultimate strength. The elastic limit is usually very close to the load where the metal takes on a
permanent set. That is to say, if a delicate caliper ("extensometer," so called) be fixed to the side of the test
specimen, it would show the piece to be somewhat longer under load than when free. Furthermore, if the
load had not yet reached the yield point, and were released at any time, the piece would return to its
original length. However, if the load had been excessive, and then relieved, the extensometer would no
longer read exactly 2.0 in., but something more.
Soft steels "give" very quickly at the yield point. In fact, if the testing machine is running slowly, it takes
some time for the lower head to catch up with the stretching steel. Consequently at the yield point, the top
head is suddenly but only temporarily relieved of load, and the scale beam drops. In commercial practice,
the yield point is therefore determined by the "drop of the beam." For more precise work the calipers are
read at intervals of 500 or 1,000 lb. load, and a curve plotted from these results, a curve which runs
straight up to the elastic limit, but there bends off.
A tensile test therefore gives four properties of great usefulness: The yield point, the ultimate strength,
the elongation and the contraction. Compression tests are seldom made, since the action of metal in
compression and in tension is closely allied, and the designer is usually satisfied with the latter.
IMPACT TESTS
Impact tests are of considerable importance as an indication of how a metal will perform under shock.
Some engineers think that the tensile test, which is one made under slow loading, should therefore be
supplemented by another showing what will happen if the load is applied almost instantaneously. This
test, however, has not been standardized, and depends to a considerable extent upon the type of machine,
but more especially the size of the specimen and the way it is "nicked." The machine is generally a
swinging heavy pendulum. It falls a certain height, strikes the sample at the lowest point, and swings on
past. The difference between the downward and upward swing is a measure of the energy it took to break
the test piece.
FATIGUE TESTS
Quite often it is desired to discover the elastic limit of the steel, in fact this is of more use to the designer
than the ultimate strength. The elastic limit is usually very close to the load where the metal takes on a
permanent set. That is to say, if a delicate caliper ("extensometer," so called) be fixed to the side of the test
specimen, it would show the piece to be somewhat longer under load than when free. Furthermore, if the
load had not yet reached the yield point, and were released at any time, the piece would return to its
original length. However, if the load had been excessive, and then relieved, the extensometer would no
longer read exactly 2.0 in., but something more.
Soft steels "give" very quickly at the yield point. In fact, if the testing machine is running slowly, it takes
some time for the lower head to catch up with the stretching steel. Consequently at the yield point, the top
head is suddenly but only temporarily relieved of load, and the scale beam drops. In commercial practice,
the yield point is therefore determined by the "drop of the beam." For more precise work the calipers are
read at intervals of 500 or 1,000 lb. load, and a curve plotted from these results, a curve which runs
straight up to the elastic limit, but there bends off.
A tensile test therefore gives four properties of great usefulness: The yield point, the ultimate strength,
the elongation and the contraction. Compression tests are seldom made, since the action of metal in
compression and in tension is closely allied, and the designer is usually satisfied with the latter.
IMPACT TESTS
Impact tests are of considerable importance as an indication of how a metal will perform under shock.
Some engineers think that the tensile test, which is one made under slow loading, should therefore be
supplemented by another showing what will happen if the load is applied almost instantaneously. This
test, however, has not been standardized, and depends to a considerable extent upon the type of machine,
but more especially the size of the specimen and the way it is "nicked." The machine is generally a
swinging heavy pendulum. It falls a certain height, strikes the sample at the lowest point, and swings on
past. The difference between the downward and upward swing is a measure of the energy it took to break
the test piece.
FATIGUE TESTS
Page 24
It has been known for fifty years that a beam or rod would fail at a relatively low stress if only repeated
often enough. It has been found, however, that each material possesses a limiting stress, or endurance
limit, within which it is safe, no matter how often the loading occurs. That limiting stress for all steels so
far investigated causes fracture below 10 million reversals. In other words, a steel which will not break
before 10,000,000 reversals can confidently be expected to endure 100,000,000, and doubtless into the
billions.
About the only way to test one piece such a large number of times is to fashion it into a beam, load it,
and then turn the beam in its supports. Thus the stress in the outer fibers of the bar varies from a
maximum stretch through zero to a maximum compression, and back again. A simple machine of this sort
is shown in Fig. 10, where B and E are bearings, A the test piece, turned slightly down in the center, C and
D ball bearings supporting a load W. K is a pulley for driving the machine and N is a counter.
FIG. 10.—Sketch of rotating beam machine for measuring
endurance of metal.
HARDNESS TESTING
The word "hardness" is used to express various properties of metals, and is measured in as many
different ways.
"Scratch hardness" is used by the geologist, who has constructed "Moh's scale" as follows:
Talc has a hardness of 1
Rock Salt has a hardness of 2
Calcite has a hardness of 3
Fluorite has a hardness of 4
Apatite has a hardness of 5
Feldspar has a hardness of 6
Quartz has a hardness of 7
Topaz has a hardness of 8
Corundum has a hardness of 9
Diamond has a hardness of 10
A mineral will scratch all those above it in the series, and will be scratched by those below. A weighted
diamond cone drawn slowly over a surface will leave a path the width of which (measured by a
microscope) varies inversely as the scratch hardness.
"Cutting hardness" is measured by a standardized drilling machine, and has a limited application in
machine-shop practice.
often enough. It has been found, however, that each material possesses a limiting stress, or endurance
limit, within which it is safe, no matter how often the loading occurs. That limiting stress for all steels so
far investigated causes fracture below 10 million reversals. In other words, a steel which will not break
before 10,000,000 reversals can confidently be expected to endure 100,000,000, and doubtless into the
billions.
About the only way to test one piece such a large number of times is to fashion it into a beam, load it,
and then turn the beam in its supports. Thus the stress in the outer fibers of the bar varies from a
maximum stretch through zero to a maximum compression, and back again. A simple machine of this sort
is shown in Fig. 10, where B and E are bearings, A the test piece, turned slightly down in the center, C and
D ball bearings supporting a load W. K is a pulley for driving the machine and N is a counter.
FIG. 10.—Sketch of rotating beam machine for measuring
endurance of metal.
HARDNESS TESTING
The word "hardness" is used to express various properties of metals, and is measured in as many
different ways.
"Scratch hardness" is used by the geologist, who has constructed "Moh's scale" as follows:
Talc has a hardness of 1
Rock Salt has a hardness of 2
Calcite has a hardness of 3
Fluorite has a hardness of 4
Apatite has a hardness of 5
Feldspar has a hardness of 6
Quartz has a hardness of 7
Topaz has a hardness of 8
Corundum has a hardness of 9
Diamond has a hardness of 10
A mineral will scratch all those above it in the series, and will be scratched by those below. A weighted
diamond cone drawn slowly over a surface will leave a path the width of which (measured by a
microscope) varies inversely as the scratch hardness.
"Cutting hardness" is measured by a standardized drilling machine, and has a limited application in
machine-shop practice.
Page 25
"Rebounding hardness" is commonly measured by the Shore
scleroscope, illustrated in Fig. 11. A small steel hammer, ¼ in. in
diameter, ¾ in. in length, and weighing about 1/12 oz. is dropped a
distance of 10 in. upon the test piece. The height of rebound in arbitrary
units represents the hardness numeral.
Should the hammer have a hard flat surface and drop on steel so hard
that no impression were made, it would rebound about 90 per cent of
the fall. The point, however, consists of a slightly spherical, blunt
diamond nose 0.02 in. in diameter, which will indent the steel to a
certain extent. The work required to make the indentation is taken from
the energy of the falling body; the rebound will absorb the balance, and
the hammer will now rise from the same steel a distance equal to about
75 per cent of the fall. A permanent impression is left upon the test
piece because the impact will develop a force of several hundred
thousand pounds per square inch under the tiny diamond-pointed
hammer head, stressing the test piece at this point of contact much
beyond its ultimate strength. The rebound is thus dependent upon the
indentation hardness, for the reason that the less the indentation, the
more energy will reappear in the rebound; also, the less the indentation,
the harder the material. Consequently, the harder the material, the more
the rebound.
"Indentation hardness" is a measure of a material's resistance to
penetration and deformation. The standard testing machine is the
Brinell, Fig. 12. A hardened steel ball, 10 mm. in diameter, is forced FIG. 11.—Shore scleroscope.
into the test piece with a pressure of 3,000 kg. (3-1/3 tons). The
resulting indentation is then measured.
scleroscope, illustrated in Fig. 11. A small steel hammer, ¼ in. in
diameter, ¾ in. in length, and weighing about 1/12 oz. is dropped a
distance of 10 in. upon the test piece. The height of rebound in arbitrary
units represents the hardness numeral.
Should the hammer have a hard flat surface and drop on steel so hard
that no impression were made, it would rebound about 90 per cent of
the fall. The point, however, consists of a slightly spherical, blunt
diamond nose 0.02 in. in diameter, which will indent the steel to a
certain extent. The work required to make the indentation is taken from
the energy of the falling body; the rebound will absorb the balance, and
the hammer will now rise from the same steel a distance equal to about
75 per cent of the fall. A permanent impression is left upon the test
piece because the impact will develop a force of several hundred
thousand pounds per square inch under the tiny diamond-pointed
hammer head, stressing the test piece at this point of contact much
beyond its ultimate strength. The rebound is thus dependent upon the
indentation hardness, for the reason that the less the indentation, the
more energy will reappear in the rebound; also, the less the indentation,
the harder the material. Consequently, the harder the material, the more
the rebound.
"Indentation hardness" is a measure of a material's resistance to
penetration and deformation. The standard testing machine is the
Brinell, Fig. 12. A hardened steel ball, 10 mm. in diameter, is forced FIG. 11.—Shore scleroscope.
into the test piece with a pressure of 3,000 kg. (3-1/3 tons). The
resulting indentation is then measured.
Page 26
FIG. 12.—Hydraulic testing machine. (Brinell principle.)
While under load, the steel ball in a Brinell machine naturally flattens somewhat. The indentation left
behind in the test piece is a duplicate of the surface which made it, and is usually regarded as being the
segment of a sphere of somewhat larger radius than the ball. The radius of curvature of this spherical
indentation will vary slightly with the load and the depth of indentation. The Brinell hardness numeral is
the quotient found by dividing the test pressure in kilograms by the spherical area of the indentation. The
denominator, as before, will vary according to the size of the sphere, the hardness of the sphere and the
load. These items have been standardized, and the following table has been constructed so that if the
diameter of the identation produced by a load of 3,000 kg. be measured the hardness numeral is found
directly.
TABLE FOR BRINELL BALL TEST
Hardness Number Hardness Number
Diameter of Ball Diameter of Ball
for a Load of for a Load of
Impression, mm. Impression, mm.
3,000 kg. 3,000 kg.
2.0 946 4.5 179
2.1 857 4.6 170
2.2 782 47 163
2.3 713 4.8 156
2.4 652 4.9 149
2.5 600 5.0 143
2.6 555 5.1 137
2.7 512 5.2 131
While under load, the steel ball in a Brinell machine naturally flattens somewhat. The indentation left
behind in the test piece is a duplicate of the surface which made it, and is usually regarded as being the
segment of a sphere of somewhat larger radius than the ball. The radius of curvature of this spherical
indentation will vary slightly with the load and the depth of indentation. The Brinell hardness numeral is
the quotient found by dividing the test pressure in kilograms by the spherical area of the indentation. The
denominator, as before, will vary according to the size of the sphere, the hardness of the sphere and the
load. These items have been standardized, and the following table has been constructed so that if the
diameter of the identation produced by a load of 3,000 kg. be measured the hardness numeral is found
directly.
TABLE FOR BRINELL BALL TEST
Hardness Number Hardness Number
Diameter of Ball Diameter of Ball
for a Load of for a Load of
Impression, mm. Impression, mm.
3,000 kg. 3,000 kg.
2.0 946 4.5 179
2.1 857 4.6 170
2.2 782 47 163
2.3 713 4.8 156
2.4 652 4.9 149
2.5 600 5.0 143
2.6 555 5.1 137
2.7 512 5.2 131
Page 27
2.8 477 5.3 126
2.9 444 5.4 121
3.0 418 5.5 116
3.1 387 5.6 112
3.2 364 5.7 107
3.3 340 5.8 103
3.4 321 5.9 99
3.5 302 6.0 95
3.6 286 6.1 92
3.7 269 6.2 89
3.8 255 6.3 86
3.9 241 6.4 83
4.0 228 6.5 80
4.1 217 6.6 77
4.2 207 6.7 74
4.3 196 6.8 71.5
4.4 187 6.9 69
2.9 444 5.4 121
3.0 418 5.5 116
3.1 387 5.6 112
3.2 364 5.7 107
3.3 340 5.8 103
3.4 321 5.9 99
3.5 302 6.0 95
3.6 286 6.1 92
3.7 269 6.2 89
3.8 255 6.3 86
3.9 241 6.4 83
4.0 228 6.5 80
4.1 217 6.6 77
4.2 207 6.7 74
4.3 196 6.8 71.5
4.4 187 6.9 69
Page 28
CHAPTER III
ALLOYS AND THEIR EFFECT UPON STEEL
In view of the fact that alloy steels are coming into a great deal of prominence, it would be well for the
users of these steels to fully appreciate the effects of the alloys upon the various grades of steel. We have
endeavored to summarize the effect of these alloys so that the users can appreciate their effect, without
having to study a metallurgical treatise and then, perhaps, not get the crux of the matter.
NICKEL
Nickel may be considered as the toughest among the non-rare alloys now used in steel manufacture.
Originally nickel was added to give increased strength and toughness over that obtained with the ordinary
rolled structural steel and little attempt was made to utilize its great possibilities so far as heat treatment
was concerned.
The difficulties experienced have been a tendency towards laminated structure during manufacture and
great liability to seam, both arising from improper melting practice. When extra care is exercised in the
manufacture, particularly in the melting and rolling, many of these difficulties can be overcome.
The electric steel furnace, of modern construction, is a very important step forward in the melting of
nickel steel; neither the crucible process nor basic or acid open-hearth furnaces give such good results.
Great care must be exercised in reheating the billet for rolling so that the steel is correctly soaked. The
rolling must not be forced; too big reduction per pass should not be indulged in, as this sets up a tendency
towards seams.
Nickel steel has remarkably good mechanical qualities when suitably heat-treated, and it is preeminently
adapted for case-hardening. It is not difficult to machine low-nickel steel, consequently it is in great favor
where easy machining properties are of importance.
Nickel influences the strength and ductility of steel by being dissolved directly in the iron or ferrite; in
this respect differing from chromium, tungsten and vanadium. The addition of each 1 per cent nickel up to
5 per cent will cause an approximate increase of from 4,000 to 6,000 lb. per square inch in the tensile
strength and elastic limit over the corresponding steel and without any decrease in ductility. The static
strength of nickel steel is affected to some degree by the percentage of carbon; for instance, steel with
0.25 per cent carbon and 3.5 per cent nickel has a tensile strength, in its normal state, equal to a straight
carbon steel of 0.5 per cent with a proportionately greater elastic limit and retaining all the advantages of
the ductility of the lower carbon.
To bring out the full qualities of nickel it must be heat-treated, otherwise there is no object in using
nickel as an alloy with carbon steel as the additional cost is not justified by increased strength.
Nickel has a peculiar effect upon the critical ranges of steel, the critical range being lowered by the
percentage of nickel; in this respect it is similar to manganese.
ALLOYS AND THEIR EFFECT UPON STEEL
In view of the fact that alloy steels are coming into a great deal of prominence, it would be well for the
users of these steels to fully appreciate the effects of the alloys upon the various grades of steel. We have
endeavored to summarize the effect of these alloys so that the users can appreciate their effect, without
having to study a metallurgical treatise and then, perhaps, not get the crux of the matter.
NICKEL
Nickel may be considered as the toughest among the non-rare alloys now used in steel manufacture.
Originally nickel was added to give increased strength and toughness over that obtained with the ordinary
rolled structural steel and little attempt was made to utilize its great possibilities so far as heat treatment
was concerned.
The difficulties experienced have been a tendency towards laminated structure during manufacture and
great liability to seam, both arising from improper melting practice. When extra care is exercised in the
manufacture, particularly in the melting and rolling, many of these difficulties can be overcome.
The electric steel furnace, of modern construction, is a very important step forward in the melting of
nickel steel; neither the crucible process nor basic or acid open-hearth furnaces give such good results.
Great care must be exercised in reheating the billet for rolling so that the steel is correctly soaked. The
rolling must not be forced; too big reduction per pass should not be indulged in, as this sets up a tendency
towards seams.
Nickel steel has remarkably good mechanical qualities when suitably heat-treated, and it is preeminently
adapted for case-hardening. It is not difficult to machine low-nickel steel, consequently it is in great favor
where easy machining properties are of importance.
Nickel influences the strength and ductility of steel by being dissolved directly in the iron or ferrite; in
this respect differing from chromium, tungsten and vanadium. The addition of each 1 per cent nickel up to
5 per cent will cause an approximate increase of from 4,000 to 6,000 lb. per square inch in the tensile
strength and elastic limit over the corresponding steel and without any decrease in ductility. The static
strength of nickel steel is affected to some degree by the percentage of carbon; for instance, steel with
0.25 per cent carbon and 3.5 per cent nickel has a tensile strength, in its normal state, equal to a straight
carbon steel of 0.5 per cent with a proportionately greater elastic limit and retaining all the advantages of
the ductility of the lower carbon.
To bring out the full qualities of nickel it must be heat-treated, otherwise there is no object in using
nickel as an alloy with carbon steel as the additional cost is not justified by increased strength.
Nickel has a peculiar effect upon the critical ranges of steel, the critical range being lowered by the
percentage of nickel; in this respect it is similar to manganese.
Page 29
Nickel can be alloyed with steel in various percentages, each percentage having a very definite effect on
the microstructure. For instance, a steel with 0.2 per cent carbon and 2 per cent nickel has a pearlitic
structure but the grain is much finer than if the straight carbon were used. With the same carbon content
and say 5 per cent nickel, the structure would still be pearlitic, but much finer and denser, therefore
capable of withstanding shock, and having greater dynamic strength. With about 0.2 per cent carbon and 8
per cent nickel, the steel is nearing the stage between pearlite and martensite, and the structure is
extremely fine, the ferrite and pearlite having a very pronounced tendency to mimic a purely martensite
structure. Steel with 0.2 per cent carbon and 15 per cent nickel is entirely martensite. Higher percentages
of nickel change the martensitic structure to austenite, the steel then being non-magnetic. The higher
percentages, that is 30 to 35 per cent nickel, are used for valve seats, valve heads, and valve stems, as the
alloy is a poor conductor of heat and is particularly free from any tendency towards corrosion or pitting
from the action of waste gases of the internal-combustion engine.
Nickel steels having 3½ per cent nickel and 0.15 to 0.20 per cent carbon are excellent for case-hardening
purposes, giving hard surfaces and tough interiors.
To obtain the full effect of nickel as an alloy, it is essential that the correct percentage of carbon be used.
High nickel and low carbon will not be more efficient than lower nickel and higher carbon, but the cost
will be much greater. Generally speaking, heat-treated nickel alloy steels are about two to three times
stronger than the same steel annealed. This point is very important as many instances have been found
where nickel steel is incorrectly used, being employed when in the annealed or normal state.
CHROMIUM
Chromium when alloyed with steel, has the characteristic function of opposing the disintegration and
reconstruction of cementite. This is demonstrated by the changes in the critical ranges of this alloy steel
taking place slowly; in other words, it has a tendency to raise the Ac range (decalescent points) and lower
the Ar range (recalescent points). Chromium steels are therefore capable of great hardness, due to the
rapid cooling being able to retard the decomposition of the austenite.
The great hardness of chromium steels is also due to the formation of double carbides of chromium and
iron. This condition is not removed when the steel is slightly tempered or drawn. This additional hardness
is also obtained without causing undue brittleness such as would be obtained by any increase of carbon.
The degree of hardness of the lower-chrome steels is dependent upon the carbon content, as chromium
alone will not harden iron.
The toughness so noticeable in this steel is the result of the fineness of structure; in this instance, the
action is similar to that of nickel, and the tensile strength and elastic limit is therefore increased without
any loss of ductility. We then have the desirable condition of tough hardness, making chrome steels
extremely valuable for all purposes requiring great resistance to wear, and in higher-chrome contents
resistance to corrosion. All chromium-alloy steels offer great resistance to corrosion and erosion. In view
of this, it is surprising that chromium steels are not more largely used for structural steel work and for all
purposes where the steel has to withstand the corroding action of air and liquids. Bridges, ships, steel
building, etc., would offer greater resistance to deterioration through rust if the chromium-alloy steels
were employed.
Prolonged heating and high temperatures have a very bad effect upon chromium steels. In this respect
they differ from nickel steels, which are not so affected by prolonged heating, but chromium steels will
stand higher temperatures than nickel steels when the period is short.
Chromium steels, due to their admirable property of increased hardness, without the loss of ductility,
make very excellent chisels and impact tools of all types, although for die blocks they do not give such
good results as can be obtained from other alloy combinations.
the microstructure. For instance, a steel with 0.2 per cent carbon and 2 per cent nickel has a pearlitic
structure but the grain is much finer than if the straight carbon were used. With the same carbon content
and say 5 per cent nickel, the structure would still be pearlitic, but much finer and denser, therefore
capable of withstanding shock, and having greater dynamic strength. With about 0.2 per cent carbon and 8
per cent nickel, the steel is nearing the stage between pearlite and martensite, and the structure is
extremely fine, the ferrite and pearlite having a very pronounced tendency to mimic a purely martensite
structure. Steel with 0.2 per cent carbon and 15 per cent nickel is entirely martensite. Higher percentages
of nickel change the martensitic structure to austenite, the steel then being non-magnetic. The higher
percentages, that is 30 to 35 per cent nickel, are used for valve seats, valve heads, and valve stems, as the
alloy is a poor conductor of heat and is particularly free from any tendency towards corrosion or pitting
from the action of waste gases of the internal-combustion engine.
Nickel steels having 3½ per cent nickel and 0.15 to 0.20 per cent carbon are excellent for case-hardening
purposes, giving hard surfaces and tough interiors.
To obtain the full effect of nickel as an alloy, it is essential that the correct percentage of carbon be used.
High nickel and low carbon will not be more efficient than lower nickel and higher carbon, but the cost
will be much greater. Generally speaking, heat-treated nickel alloy steels are about two to three times
stronger than the same steel annealed. This point is very important as many instances have been found
where nickel steel is incorrectly used, being employed when in the annealed or normal state.
CHROMIUM
Chromium when alloyed with steel, has the characteristic function of opposing the disintegration and
reconstruction of cementite. This is demonstrated by the changes in the critical ranges of this alloy steel
taking place slowly; in other words, it has a tendency to raise the Ac range (decalescent points) and lower
the Ar range (recalescent points). Chromium steels are therefore capable of great hardness, due to the
rapid cooling being able to retard the decomposition of the austenite.
The great hardness of chromium steels is also due to the formation of double carbides of chromium and
iron. This condition is not removed when the steel is slightly tempered or drawn. This additional hardness
is also obtained without causing undue brittleness such as would be obtained by any increase of carbon.
The degree of hardness of the lower-chrome steels is dependent upon the carbon content, as chromium
alone will not harden iron.
The toughness so noticeable in this steel is the result of the fineness of structure; in this instance, the
action is similar to that of nickel, and the tensile strength and elastic limit is therefore increased without
any loss of ductility. We then have the desirable condition of tough hardness, making chrome steels
extremely valuable for all purposes requiring great resistance to wear, and in higher-chrome contents
resistance to corrosion. All chromium-alloy steels offer great resistance to corrosion and erosion. In view
of this, it is surprising that chromium steels are not more largely used for structural steel work and for all
purposes where the steel has to withstand the corroding action of air and liquids. Bridges, ships, steel
building, etc., would offer greater resistance to deterioration through rust if the chromium-alloy steels
were employed.
Prolonged heating and high temperatures have a very bad effect upon chromium steels. In this respect
they differ from nickel steels, which are not so affected by prolonged heating, but chromium steels will
stand higher temperatures than nickel steels when the period is short.
Chromium steels, due to their admirable property of increased hardness, without the loss of ductility,
make very excellent chisels and impact tools of all types, although for die blocks they do not give such
good results as can be obtained from other alloy combinations.
Page 30
For ball bearing steels, where intense hardness with great toughness and ready recovery from temporary
deflection is required, chromium as an alloy offers the best solution.
Two per cent chromium steels; due to their very hard tough surface, are largely used for armor-piercing
projectiles, cold rolls, crushers, drawing dies, etc.
The normal structure of chromium steels, with a very low carbon content is roughly pearlitic up to 7 per
cent, and martensitic from 8 to 20 per cent; therefore, the greatest application is in the pearlitic zone or the
lower percentages.
NICKEL-CHROMIUM
A combination of the characteristics of nickel and the characteristics of chromium, as described, should
obviously give a very excellent steel as the nickel particularly affects the ferrite of the steel and the
chromium the carbon. From this combination, we are able to get a very strong ferrite matrix and a very
hard tough cementite. The strength of a strictly pearlitic steel over a pure iron is due to the pearlitic being
a layer arrangement of cementite running parallel to that of a pure iron layer in each individual grain. The
ferrite i.e., the iron is increased in strength by the resistance offered by the cementite which is the simple
iron-carbon combination known to metallurgists as Fe3C. The cementite, although adding to the tensile
strength, is very brittle and the strength of the pearlite is the combination of the ferrite and cementite. In
the event of the cementite being strengthened, as in the case of strictly chromium steels, an increased
tensile strength is readily obtained without loss of ductility and if the ferrite is strengthened then the
tensile strength and ductility of the metal is still further improved.
Nickel-chromium alloy represents one of the best combinations available at the present time. The nickel
intensifies the physical characteristics of the chromium and the chromium has a similar effect on the
nickel.
For case-hardening, nickel-chromium steels seem to give very excellent results. The carbon is very
rapidly taken up in this combination, and for that reason is rather preferable to the straight nickel steel.
With the mutually intensifying action of chromium and nickel there is a most suitable ratio for these two
alloys, and it has been found that roughly 2½ parts of nickel to about 1 part of chromium gives the best
results. Therefore, we have the standard types of 3.5 per cent nickel with 1.5 per cent chromium to 1.5 per
cent nickel with 0.6 per cent chromium and the various intermediate types. This ratio, however, does not
give the whole story of nickel-chromium combinations, and many surprising results have been obtained
with these alloys when other percentage combinations have been employed.
VANADIUM
Vanadium has a very marked effect upon alloy steels rich in chromium, carbon, or manganese. Vanadium
itself, when combined with steel very low in carbon, is not so noticeably beneficial as in the same carbon
steel higher in manganese, but if a small quantity of chromium is added, then the vanadium has a very
marked effect in increasing the impact strength of the alloy. It would seem that vanadium has the effect of
intensifying the action of chromium and manganese, or that vanadium is intensified by the action of
chromium or manganese.
Vanadium has the peculiar property of readily entering into solution with ferrite. If vanadium contained
is considerable it also combines with the carbon, forming carbides. The ductility of carbon-vanadium
steels is therefore increased, likewise the ductility of chrome-vanadium steels.
The full effect of vanadium is not felt unless the temperatures to which the steel is heated for hardening
are raised considerably. It is therefore necessary that a certain amount of "soaking" takes place, so as to
deflection is required, chromium as an alloy offers the best solution.
Two per cent chromium steels; due to their very hard tough surface, are largely used for armor-piercing
projectiles, cold rolls, crushers, drawing dies, etc.
The normal structure of chromium steels, with a very low carbon content is roughly pearlitic up to 7 per
cent, and martensitic from 8 to 20 per cent; therefore, the greatest application is in the pearlitic zone or the
lower percentages.
NICKEL-CHROMIUM
A combination of the characteristics of nickel and the characteristics of chromium, as described, should
obviously give a very excellent steel as the nickel particularly affects the ferrite of the steel and the
chromium the carbon. From this combination, we are able to get a very strong ferrite matrix and a very
hard tough cementite. The strength of a strictly pearlitic steel over a pure iron is due to the pearlitic being
a layer arrangement of cementite running parallel to that of a pure iron layer in each individual grain. The
ferrite i.e., the iron is increased in strength by the resistance offered by the cementite which is the simple
iron-carbon combination known to metallurgists as Fe3C. The cementite, although adding to the tensile
strength, is very brittle and the strength of the pearlite is the combination of the ferrite and cementite. In
the event of the cementite being strengthened, as in the case of strictly chromium steels, an increased
tensile strength is readily obtained without loss of ductility and if the ferrite is strengthened then the
tensile strength and ductility of the metal is still further improved.
Nickel-chromium alloy represents one of the best combinations available at the present time. The nickel
intensifies the physical characteristics of the chromium and the chromium has a similar effect on the
nickel.
For case-hardening, nickel-chromium steels seem to give very excellent results. The carbon is very
rapidly taken up in this combination, and for that reason is rather preferable to the straight nickel steel.
With the mutually intensifying action of chromium and nickel there is a most suitable ratio for these two
alloys, and it has been found that roughly 2½ parts of nickel to about 1 part of chromium gives the best
results. Therefore, we have the standard types of 3.5 per cent nickel with 1.5 per cent chromium to 1.5 per
cent nickel with 0.6 per cent chromium and the various intermediate types. This ratio, however, does not
give the whole story of nickel-chromium combinations, and many surprising results have been obtained
with these alloys when other percentage combinations have been employed.
VANADIUM
Vanadium has a very marked effect upon alloy steels rich in chromium, carbon, or manganese. Vanadium
itself, when combined with steel very low in carbon, is not so noticeably beneficial as in the same carbon
steel higher in manganese, but if a small quantity of chromium is added, then the vanadium has a very
marked effect in increasing the impact strength of the alloy. It would seem that vanadium has the effect of
intensifying the action of chromium and manganese, or that vanadium is intensified by the action of
chromium or manganese.
Vanadium has the peculiar property of readily entering into solution with ferrite. If vanadium contained
is considerable it also combines with the carbon, forming carbides. The ductility of carbon-vanadium
steels is therefore increased, likewise the ductility of chrome-vanadium steels.
The full effect of vanadium is not felt unless the temperatures to which the steel is heated for hardening
are raised considerably. It is therefore necessary that a certain amount of "soaking" takes place, so as to
Page 31
get the necessary equalization. This is true of all alloys which contain complex carbides, i.e., compounds
of carbon, iron and one or more elements.
Chrome-vanadium steels also are highly favored for case hardening. When used under alternating
stresses it appears to have superior endurance. It would appear that the intensification of the properties due
to chromium and manganese in the alloy steel accounts for this peculiar phenomenon.
Vanadium is also a very excellent scavenger for either removing the harmful gases, or causing them to
enter into solution with the metal in such a way as to largely obviate their harmful effects. Chrome-
vanadium steels have been claimed, by many steel manufacturers and users, to be preferable to nickel-
chrome steels. While not wishing to pass judgment on this, it should be borne in mind that the chrome-
vanadium steel, which is tested, is generally compared with a very low nickel-chromium alloy steel (the
price factor entering into the situation), but equally good results can be obtained by nickel-chromium
steels of suitable analysis.
Where price is the leading factor, there are many cases where a stronger steel can be obtained from the
chrome and vanadium than the nickel-chrome. It will be safe to say that each of these two systems of
alloys have their own particular fields and chrome-vanadium steel should not be regarded as the sole
solution for all problems, neither should nickel-chromium.
MANGANESE
Manganese adds considerably to the tensile strength of steel, but this is dependent on the carbon content.
High carbon materially adds to the brittleness, whereas low-carbon, pearlitic-manganese steels are very
tough and ductile and are not at all brittle, providing the heat-treating is correct. Manganese steel is very
susceptible to high temperatures and prolonged heating.
In low-carbon pearlitic steels, manganese is more effective in increasing ultimate strength than is nickel;
that is to say, a 0.45 carbon steel with 1.25 per cent manganese is as strong as a 0.45 carbon steel with 1.5
per cent nickel. The former steel is much used for rifle barrels, and in the heat-treated condition will give
80,000 to 90,000 lb. per square inch elastic limit, 115,000 to 125,000 lb. per square inch tensile strength,
23 per cent elongation, and 55 per cent reduction in area.
Manganese when added to steel has the effect of lowering the critical range; 1 per cent manganese will
lower the upper critical point 60°F. The action of manganese is very similar to that of nickel in this
respect, only twice as powerful. As an instance, 1 per cent nickel would have the effect of lowering the
upper critical range from 25 to 30°F.
Low-carbon pearlitic-manganese steel, heat-treated, will give dynamic strength which cannot be equaled
by low-priced and necessarily low-content nickel steels. In many instances, it is preferable to use high-
grade manganese steel, rather than low-content nickel steel.
High-manganese steels or austenite manganese steels are used for a variety of purposes where great
resistance to abrasion is required, the percentage of manganese being from 11 to 14 per cent, and carbon 1
to 1.5 per cent. This steel is practically valueless unless heat-treated; that is, heated to about yellow red
and quenched in ice water. The structure is then austenite and the air-cooled structure of this steel is
martensite. Therefore this steel has to be heated and very rapidly cooled to obtain the ductile austenite
structure.
Manganese between 2 and 7 per cent is a very brittle material when the carbon is about 1 per cent or
higher and is, therefore, quite valueless. Below 2 per cent manganese steel low in carbon is very ductile
and tough steel.
of carbon, iron and one or more elements.
Chrome-vanadium steels also are highly favored for case hardening. When used under alternating
stresses it appears to have superior endurance. It would appear that the intensification of the properties due
to chromium and manganese in the alloy steel accounts for this peculiar phenomenon.
Vanadium is also a very excellent scavenger for either removing the harmful gases, or causing them to
enter into solution with the metal in such a way as to largely obviate their harmful effects. Chrome-
vanadium steels have been claimed, by many steel manufacturers and users, to be preferable to nickel-
chrome steels. While not wishing to pass judgment on this, it should be borne in mind that the chrome-
vanadium steel, which is tested, is generally compared with a very low nickel-chromium alloy steel (the
price factor entering into the situation), but equally good results can be obtained by nickel-chromium
steels of suitable analysis.
Where price is the leading factor, there are many cases where a stronger steel can be obtained from the
chrome and vanadium than the nickel-chrome. It will be safe to say that each of these two systems of
alloys have their own particular fields and chrome-vanadium steel should not be regarded as the sole
solution for all problems, neither should nickel-chromium.
MANGANESE
Manganese adds considerably to the tensile strength of steel, but this is dependent on the carbon content.
High carbon materially adds to the brittleness, whereas low-carbon, pearlitic-manganese steels are very
tough and ductile and are not at all brittle, providing the heat-treating is correct. Manganese steel is very
susceptible to high temperatures and prolonged heating.
In low-carbon pearlitic steels, manganese is more effective in increasing ultimate strength than is nickel;
that is to say, a 0.45 carbon steel with 1.25 per cent manganese is as strong as a 0.45 carbon steel with 1.5
per cent nickel. The former steel is much used for rifle barrels, and in the heat-treated condition will give
80,000 to 90,000 lb. per square inch elastic limit, 115,000 to 125,000 lb. per square inch tensile strength,
23 per cent elongation, and 55 per cent reduction in area.
Manganese when added to steel has the effect of lowering the critical range; 1 per cent manganese will
lower the upper critical point 60°F. The action of manganese is very similar to that of nickel in this
respect, only twice as powerful. As an instance, 1 per cent nickel would have the effect of lowering the
upper critical range from 25 to 30°F.
Low-carbon pearlitic-manganese steel, heat-treated, will give dynamic strength which cannot be equaled
by low-priced and necessarily low-content nickel steels. In many instances, it is preferable to use high-
grade manganese steel, rather than low-content nickel steel.
High-manganese steels or austenite manganese steels are used for a variety of purposes where great
resistance to abrasion is required, the percentage of manganese being from 11 to 14 per cent, and carbon 1
to 1.5 per cent. This steel is practically valueless unless heat-treated; that is, heated to about yellow red
and quenched in ice water. The structure is then austenite and the air-cooled structure of this steel is
martensite. Therefore this steel has to be heated and very rapidly cooled to obtain the ductile austenite
structure.
Manganese between 2 and 7 per cent is a very brittle material when the carbon is about 1 per cent or
higher and is, therefore, quite valueless. Below 2 per cent manganese steel low in carbon is very ductile
and tough steel.
Page 32
The high-content manganese steels are known as the "Hadfield manganese steels," having been
developed by Sir Robert Hadfield. Small additions of chrome up to 1 per cent increase the elastic limit of
low-carbon pearlitic-manganese steels without affecting the steel in its resistance to shock, but materially
decrease the percentage of elongation.
Vanadium added to low-carbon pearlitic manganese steel has a very marked effect, increasing greatly the
dynamic strength and changing slightly the susceptibility of this steel to heat treatments, giving a greater
margin for the hardening temperature. Manganese steel with added vanadium is most efficient when heat-
treated.
TUNGSTEN
Tungsten, as an alloy in steel, has been known and used for a long time. The celebrated and ancient
damascus steel being a form of tungsten-alloy steel. Tungsten and its effects, however, did not become
generally realized until Robert Mushet experimented and developed his famous mushet steel and the many
improvement made since that date go to prove how little Mushet himself understood the peculiar effects
of tungsten as an alloy.
Tungsten acts on steel in a similar manner to carbon, that is, it increases its hardness, but is much less
effective than carbon in this respect. If the percentage of tungsten and manganese is high, the steel will be
hard after cooling in the air. This is impossible in a carbon steel. It was this combination that Mushet used
in his well-known "air-hardening" steel.
The principal use of tungsten is in high-speed tool steel, but here a high percentage of manganese is
distinctly detrimental, making the steel liable to fire crack, very brittle and weak in the body, less easily
forged and annealed. Manganese should be kept low and a high percentage of chromium used instead.
Tools of tungsten-chromium steels, when hardened, retain their hardness, even when heated to a dark
cherry red by the friction of the cutting or the heat arising from the chips. This characteristic led to the
term "red-hardness," and it is this property that has made possible the use of very high cutting speeds in
tools made of the tungsten-chromium alloy, that is, "high-speed" steel.
Tungsten steels containing up to 6 per cent do not have the property of red hardness any more than does
carbon tool steel, providing the manganese or chromium is low.
When chromium is alloyed with tungsten, a very definite red-hardness is noticed with a great increase of
cutting efficiency. The maximum red-hardness seems to be had with steels containing 18 per cent
tungsten, 5.5 per cent chromium and 0.70 per cent carbon.
Very little is known of the actual function of tungsten, although a vast amount of experimental work has
been done. It is possible that when the effect of tungsten with iron-carbon alloys is better known, a greater
improvement can be expected from these steels. Tungsten has been tried and is still used by some steel
manufacturers for making punches, chisels, and other impact tools. It has also been used for springs, and
has given very good results, although other less expensive alloys give equally good results, and are in
some instances, better.
Tungsten is largely used in permanent magnets. In this, its action is not well understood. In fact, the
reason why steel becomes a permanent magnet is not at all understood. Theories have been evolved, but
all are open to serious questioning. The principal effect of tungsten, as conceded by leading authorities, is
that it distinctly retards separation of the iron-carbon solution, removing the lowest recalescent point down
to atmospheric temperature.
developed by Sir Robert Hadfield. Small additions of chrome up to 1 per cent increase the elastic limit of
low-carbon pearlitic-manganese steels without affecting the steel in its resistance to shock, but materially
decrease the percentage of elongation.
Vanadium added to low-carbon pearlitic manganese steel has a very marked effect, increasing greatly the
dynamic strength and changing slightly the susceptibility of this steel to heat treatments, giving a greater
margin for the hardening temperature. Manganese steel with added vanadium is most efficient when heat-
treated.
TUNGSTEN
Tungsten, as an alloy in steel, has been known and used for a long time. The celebrated and ancient
damascus steel being a form of tungsten-alloy steel. Tungsten and its effects, however, did not become
generally realized until Robert Mushet experimented and developed his famous mushet steel and the many
improvement made since that date go to prove how little Mushet himself understood the peculiar effects
of tungsten as an alloy.
Tungsten acts on steel in a similar manner to carbon, that is, it increases its hardness, but is much less
effective than carbon in this respect. If the percentage of tungsten and manganese is high, the steel will be
hard after cooling in the air. This is impossible in a carbon steel. It was this combination that Mushet used
in his well-known "air-hardening" steel.
The principal use of tungsten is in high-speed tool steel, but here a high percentage of manganese is
distinctly detrimental, making the steel liable to fire crack, very brittle and weak in the body, less easily
forged and annealed. Manganese should be kept low and a high percentage of chromium used instead.
Tools of tungsten-chromium steels, when hardened, retain their hardness, even when heated to a dark
cherry red by the friction of the cutting or the heat arising from the chips. This characteristic led to the
term "red-hardness," and it is this property that has made possible the use of very high cutting speeds in
tools made of the tungsten-chromium alloy, that is, "high-speed" steel.
Tungsten steels containing up to 6 per cent do not have the property of red hardness any more than does
carbon tool steel, providing the manganese or chromium is low.
When chromium is alloyed with tungsten, a very definite red-hardness is noticed with a great increase of
cutting efficiency. The maximum red-hardness seems to be had with steels containing 18 per cent
tungsten, 5.5 per cent chromium and 0.70 per cent carbon.
Very little is known of the actual function of tungsten, although a vast amount of experimental work has
been done. It is possible that when the effect of tungsten with iron-carbon alloys is better known, a greater
improvement can be expected from these steels. Tungsten has been tried and is still used by some steel
manufacturers for making punches, chisels, and other impact tools. It has also been used for springs, and
has given very good results, although other less expensive alloys give equally good results, and are in
some instances, better.
Tungsten is largely used in permanent magnets. In this, its action is not well understood. In fact, the
reason why steel becomes a permanent magnet is not at all understood. Theories have been evolved, but
all are open to serious questioning. The principal effect of tungsten, as conceded by leading authorities, is
that it distinctly retards separation of the iron-carbon solution, removing the lowest recalescent point down
to atmospheric temperature.
Page 33
A peculiar property of tungsten steels is that if a heating temperature of 1,750°F. is not exceeded, the
cooling curves indicate but one critical point at about 1,350°F. But when the heating temperature is raised
above 1,850°F., this critical point is nearly if not quite suppressed, while a lower critical point appears and
grows enormously in intensity at a temperature between 660 and 750°F.
The change in the critical ranges, which is produced by heating tungsten steels to over 1,850°F., is the
real cause of the red-hard properties of these alloys. Its real nature is not understood, and there is no direct
evidence to show what actually happens at these high temperatures.
It may readily be understood that an alloy containing four essential elements, namely: iron, carbon,
tungsten and chromium, is one whose study presents problems of extreme complexity. It is possible that
complex carbides may be formed, as in chromium steels, and that compounds between iron and tungsten
exist. Behavior of these combinations on heating and cooling must be better known before we are able to
explain many peculiarities of tungsten steels.
MOLYBDENUM
Molybdenum steels have been made commercially for twenty-five years, but they have not been widely
exploited until since the war. Very large resources of molybdenum have been developed in America, and
the mining companies who are equipped to produce the metal are very active in advertising the advantages
of molybdenum steels.
It was early found that 1 part molybdenum was the equivalent of from 2 to 2½ parts of tungsten in tool
steels, and magnet steels. It fell into disrepute as an alloy for high-speed tool steel, however, because it
was found that the molybdenum was driven out of the surface of the tool during forging and heat treating.
Within the last few years it has been found that the presence of less than 1 per cent of molybdenum
greatly enhances certain properties of heat-treated carbon and alloy steels used for automobiles and high-
grade machinery.
In general, molybdenum when added to an alloy steel, increases the figure for reduction of area, which is
considered a good measure of "toughness." Molybdenum steels are also relatively insensible to variations
in heat treatment; that is to say, a chromium-nickel-molybdenum steel after quenching in oil from 1,450°F.
may be drawn at any temperature between 900 and 1,100°F. with substantially the same result (static
tensile properties and hardness).
SILICON
Silicon prevents, to a large extent, defects such as gas bubbles or blow holes forming while steel is
solidifying. In fact, steel after it has been melted and before it has been refined, is "wild" and "gassy." That
is to say, if it would be cast into molds it would froth up, and boil all over the floor. A judicious amount of
silicon added to the metal just before pouring, prevents this action—in the words of the steel maker,
silicon "kills" the steel. If about 1.75 per cent metallic silicon remains in a 0.65 carbon steel, it makes
excellent springs.
PHOSPHORUS
Phosphorus is one of the impurities in steel, and it has been the object of steel makers for years to
eliminate it. On cheap grades of steel, not subject to any abnormal strain or stress, 0.1 per cent phosphorus
is not objectionable. High phosphorus makes steel "cold short," i.e., brittle when cold or moderately
warm.
SULPHUR
cooling curves indicate but one critical point at about 1,350°F. But when the heating temperature is raised
above 1,850°F., this critical point is nearly if not quite suppressed, while a lower critical point appears and
grows enormously in intensity at a temperature between 660 and 750°F.
The change in the critical ranges, which is produced by heating tungsten steels to over 1,850°F., is the
real cause of the red-hard properties of these alloys. Its real nature is not understood, and there is no direct
evidence to show what actually happens at these high temperatures.
It may readily be understood that an alloy containing four essential elements, namely: iron, carbon,
tungsten and chromium, is one whose study presents problems of extreme complexity. It is possible that
complex carbides may be formed, as in chromium steels, and that compounds between iron and tungsten
exist. Behavior of these combinations on heating and cooling must be better known before we are able to
explain many peculiarities of tungsten steels.
MOLYBDENUM
Molybdenum steels have been made commercially for twenty-five years, but they have not been widely
exploited until since the war. Very large resources of molybdenum have been developed in America, and
the mining companies who are equipped to produce the metal are very active in advertising the advantages
of molybdenum steels.
It was early found that 1 part molybdenum was the equivalent of from 2 to 2½ parts of tungsten in tool
steels, and magnet steels. It fell into disrepute as an alloy for high-speed tool steel, however, because it
was found that the molybdenum was driven out of the surface of the tool during forging and heat treating.
Within the last few years it has been found that the presence of less than 1 per cent of molybdenum
greatly enhances certain properties of heat-treated carbon and alloy steels used for automobiles and high-
grade machinery.
In general, molybdenum when added to an alloy steel, increases the figure for reduction of area, which is
considered a good measure of "toughness." Molybdenum steels are also relatively insensible to variations
in heat treatment; that is to say, a chromium-nickel-molybdenum steel after quenching in oil from 1,450°F.
may be drawn at any temperature between 900 and 1,100°F. with substantially the same result (static
tensile properties and hardness).
SILICON
Silicon prevents, to a large extent, defects such as gas bubbles or blow holes forming while steel is
solidifying. In fact, steel after it has been melted and before it has been refined, is "wild" and "gassy." That
is to say, if it would be cast into molds it would froth up, and boil all over the floor. A judicious amount of
silicon added to the metal just before pouring, prevents this action—in the words of the steel maker,
silicon "kills" the steel. If about 1.75 per cent metallic silicon remains in a 0.65 carbon steel, it makes
excellent springs.
PHOSPHORUS
Phosphorus is one of the impurities in steel, and it has been the object of steel makers for years to
eliminate it. On cheap grades of steel, not subject to any abnormal strain or stress, 0.1 per cent phosphorus
is not objectionable. High phosphorus makes steel "cold short," i.e., brittle when cold or moderately
warm.
SULPHUR
Page 34
Sulphur is another impurity and high sulphur is even a greater detriment to steel than phosphorus. High
sulphur up to 0.09 per cent helps machining properties, but has a tendency to make the steel "hot short,"
i.e., subject to opening up cracks and seams at forging or rolling heats. Sulphur should never exceed 0.06
per cent nor phosphorus 0.08 per cent.
Steel used for tool purposes should have as low phosphorus and sulphur contents as possible, not over
0.02 per cent.
We can sum up the various factors something as follows for ready reference.
The ingredient Its effect
Iron The basis of steel
Carbon The determinative
Sulphur A strength sapper
Phosphorus The weak link
Oxygen A strength destroyer
Manganese For strength
Nickel For strength and toughness
Tungsten Hardener and heat resister
Chromium For resisting shocks
Vanadium Purifier and fatigue resister
Silicon Impurity and hardener
Titanium Removes nitrogen and oxygen
Molybdenum Hardener and heat resister
Aluminum Kills or deoxidizes steel
PROPERTIES OF ALLOY STEELS
The following table shows the percentages of carbon, manganese, nickel, chromium and vanadium in
typical steel alloys for engineering purposes. It also gives the elastic limit, tensile strength, elongation and
reduction of area of the various alloys, all being given the same heat treatment with a drawing temperature
of 1,100°F. (600°C.). The specimens were one inch rounds machined after heat treatment.
Tungsten is not shown in the table because it is seldom used in engineering construction steels and then
usually in combination with chromium. Tungsten is used principally for the magnets of magnetos, to some
extent in the manufacture of hacksaws, and for special tool steels.
TABLE I.—PROPERTIES OF ALLOY STEELS
Elastic Tensile
Nickel, Elongation Reduction
Carbon, Manganese, Chromium, Vanadium, limit, Strength,
per in 2 in., of area,
per cent per cent per cent per cent lb. per lb. per
cent per cent per cent
sq. in. sq. in.
0.27 0.55 49,000 80,000 30 65
0.27 0.47 0.26 66,000 98,000 25 52
0.36 0.42 58,000 90,000 27 60
0.34 0.87 0.13 82,500 103,000 22 57
0.45 0.50 65,000 96,000 22 52
0.43 0.60 0.32 96,000 122,000 21 52
0.47 0.90 0.15 102,000 127,500 23 58
sulphur up to 0.09 per cent helps machining properties, but has a tendency to make the steel "hot short,"
i.e., subject to opening up cracks and seams at forging or rolling heats. Sulphur should never exceed 0.06
per cent nor phosphorus 0.08 per cent.
Steel used for tool purposes should have as low phosphorus and sulphur contents as possible, not over
0.02 per cent.
We can sum up the various factors something as follows for ready reference.
The ingredient Its effect
Iron The basis of steel
Carbon The determinative
Sulphur A strength sapper
Phosphorus The weak link
Oxygen A strength destroyer
Manganese For strength
Nickel For strength and toughness
Tungsten Hardener and heat resister
Chromium For resisting shocks
Vanadium Purifier and fatigue resister
Silicon Impurity and hardener
Titanium Removes nitrogen and oxygen
Molybdenum Hardener and heat resister
Aluminum Kills or deoxidizes steel
PROPERTIES OF ALLOY STEELS
The following table shows the percentages of carbon, manganese, nickel, chromium and vanadium in
typical steel alloys for engineering purposes. It also gives the elastic limit, tensile strength, elongation and
reduction of area of the various alloys, all being given the same heat treatment with a drawing temperature
of 1,100°F. (600°C.). The specimens were one inch rounds machined after heat treatment.
Tungsten is not shown in the table because it is seldom used in engineering construction steels and then
usually in combination with chromium. Tungsten is used principally for the magnets of magnetos, to some
extent in the manufacture of hacksaws, and for special tool steels.
TABLE I.—PROPERTIES OF ALLOY STEELS
Elastic Tensile
Nickel, Elongation Reduction
Carbon, Manganese, Chromium, Vanadium, limit, Strength,
per in 2 in., of area,
per cent per cent per cent per cent lb. per lb. per
cent per cent per cent
sq. in. sq. in.
0.27 0.55 49,000 80,000 30 65
0.27 0.47 0.26 66,000 98,000 25 52
0.36 0.42 58,000 90,000 27 60
0.34 0.87 0.13 82,500 103,000 22 57
0.45 0.50 65,000 96,000 22 52
0.43 0.60 0.32 96,000 122,000 21 52
0.47 0.90 0.15 102,000 127,500 23 58
Page 35
0.30 0.60 3.40 75,000 105,000 25 67
0.33 0.63 3.60 0.25 118,000 142,000 17 57
0.30 0.49 3.60 1.70 119,000 149,500 21 60
0.25 0.47 3.47 1.60 0.15 139,000 170,000 18 53
0.25 0.50 2.00 1.00 102,000 124,000 25 70
0.38 0.30 2.08 1.16 120,000 134,000 20 57
0.42 0.22 2.14 1.27 0.26 145,000 161,500 16 53
0.36 0.61 1.46 0.64 117,600 132,500 16 58
0.36 0.50 1.30 0.75 0.16 140,000 157,500 17 54
0.30 0.50 0.80 90,000 105,000 20 50
0.23 0.58 0.82 0.17 106,000 124,000 21 66
0.26 0.48 0.92 0.20 112,000 137,000 20 61
0.35 0.64 1.03 0.22 132,500 149,500 16 54
0.50 0.92 1.02 0.20 170,000 186,000 15 45
NON-SHRINKING, OIL-HARDENING STEELS
Certain steels have a very low rate of expansion and contraction in hardening and are very desirable for
test plugs, gages, punches and dies, for milling cutters, taps, reamers, hard steel bushings and similar
work.
It is recommended that for forging these steels it be heated slowly and uniformly to a bright red, but not
in a direct flame or blast. Harden at a dull red heat, about 1,300°F. A clean coal or coke fire, or a good
muffle-gas furnace will give best results. Fish oil is good for quenching although in some cases warm
water will give excellent results. The steel should be kept moving in the bath until perfectly cold. Heated
and cooled in this way the steel is very tough, takes a good cutting edge and has very little expansion or
contraction which makes it desirable for long taps where the accuracy of lead is important.
The composition of these steels is as follows:
Per cent
Manganese 1.40 to 1.60
Carbon 0.80 to 0.90
Vanadium 0.20 to 0.25
0.33 0.63 3.60 0.25 118,000 142,000 17 57
0.30 0.49 3.60 1.70 119,000 149,500 21 60
0.25 0.47 3.47 1.60 0.15 139,000 170,000 18 53
0.25 0.50 2.00 1.00 102,000 124,000 25 70
0.38 0.30 2.08 1.16 120,000 134,000 20 57
0.42 0.22 2.14 1.27 0.26 145,000 161,500 16 53
0.36 0.61 1.46 0.64 117,600 132,500 16 58
0.36 0.50 1.30 0.75 0.16 140,000 157,500 17 54
0.30 0.50 0.80 90,000 105,000 20 50
0.23 0.58 0.82 0.17 106,000 124,000 21 66
0.26 0.48 0.92 0.20 112,000 137,000 20 61
0.35 0.64 1.03 0.22 132,500 149,500 16 54
0.50 0.92 1.02 0.20 170,000 186,000 15 45
NON-SHRINKING, OIL-HARDENING STEELS
Certain steels have a very low rate of expansion and contraction in hardening and are very desirable for
test plugs, gages, punches and dies, for milling cutters, taps, reamers, hard steel bushings and similar
work.
It is recommended that for forging these steels it be heated slowly and uniformly to a bright red, but not
in a direct flame or blast. Harden at a dull red heat, about 1,300°F. A clean coal or coke fire, or a good
muffle-gas furnace will give best results. Fish oil is good for quenching although in some cases warm
water will give excellent results. The steel should be kept moving in the bath until perfectly cold. Heated
and cooled in this way the steel is very tough, takes a good cutting edge and has very little expansion or
contraction which makes it desirable for long taps where the accuracy of lead is important.
The composition of these steels is as follows:
Per cent
Manganese 1.40 to 1.60
Carbon 0.80 to 0.90
Vanadium 0.20 to 0.25
Page 36
FIG. 13.—Effect of copper in steel.
EFFECT OF A SMALL AMOUNT OF COPPER IN MEDIUM-CARBON STEEL
This shows the result of tests by C. R. Hayward and A. B. Johnston on two types of steel: one containing
0.30 per cent carbon, 0.012 per cent phosphorus, and 0.860 per cent copper, and the other 0.365 per cent
carbon, 0.053 per cent phosphorus, and 0.030 per cent copper. The accompanying chart in Fig. 13 shows
that high-copper steel has decided superiority in tensile strength, yield point and ultimate strength, while
the ductility is practically the same. Hardness tests by both methods show high-copper steel to be harder
than low-copper, and the Charpy shock tests show high-copper steel also superior to low-copper. The tests
confirm those made by Stead, showing that the behavior of copper steel resembles that of nickel steel. The
high-copper steels show finer grain than the low-copper. The quenched and drawn specimens of high-
copper steel were found to be slightly more martensitic.
HIGH-CHROMIUM OR RUST-PROOF STEEL
High-chromium, or what is called stainless steel containing from 11 to 14 per cent chromium, was
originally developed for cutlery purposes, but has in the past few years been used to a considerable extent
for exhaust valves in airplane engines because of its resistance to scaling at high temperatures.
Percentage
Carbon 0.20 to 0.40
Manganese, not to exceed 0.50
Phosphorus, not to exceed 0.035
Sulphur, not to exceed 0.035
Chromium 11.50 to 14.00
Silicon, not to exceed 0.30
The steel should be heated slowly and forged at a temperature above 1,750°F. preferably between 1,800
and 2,200°F. If forged at temperatures between 1,650 and 1,750°F. there is considerable danger of
rupturing the steel because of its hardness at red heat. Owing to the air-hardening property of the steel, the
drop-forgings should be trimmed while hot. Thin forgings should be reheated to redness before trimming,
as otherwise they are liable to crack.
EFFECT OF A SMALL AMOUNT OF COPPER IN MEDIUM-CARBON STEEL
This shows the result of tests by C. R. Hayward and A. B. Johnston on two types of steel: one containing
0.30 per cent carbon, 0.012 per cent phosphorus, and 0.860 per cent copper, and the other 0.365 per cent
carbon, 0.053 per cent phosphorus, and 0.030 per cent copper. The accompanying chart in Fig. 13 shows
that high-copper steel has decided superiority in tensile strength, yield point and ultimate strength, while
the ductility is practically the same. Hardness tests by both methods show high-copper steel to be harder
than low-copper, and the Charpy shock tests show high-copper steel also superior to low-copper. The tests
confirm those made by Stead, showing that the behavior of copper steel resembles that of nickel steel. The
high-copper steels show finer grain than the low-copper. The quenched and drawn specimens of high-
copper steel were found to be slightly more martensitic.
HIGH-CHROMIUM OR RUST-PROOF STEEL
High-chromium, or what is called stainless steel containing from 11 to 14 per cent chromium, was
originally developed for cutlery purposes, but has in the past few years been used to a considerable extent
for exhaust valves in airplane engines because of its resistance to scaling at high temperatures.
Percentage
Carbon 0.20 to 0.40
Manganese, not to exceed 0.50
Phosphorus, not to exceed 0.035
Sulphur, not to exceed 0.035
Chromium 11.50 to 14.00
Silicon, not to exceed 0.30
The steel should be heated slowly and forged at a temperature above 1,750°F. preferably between 1,800
and 2,200°F. If forged at temperatures between 1,650 and 1,750°F. there is considerable danger of
rupturing the steel because of its hardness at red heat. Owing to the air-hardening property of the steel, the
drop-forgings should be trimmed while hot. Thin forgings should be reheated to redness before trimming,
as otherwise they are liable to crack.
Page 37
The forgings will be hard if they are allowed to cool in air. This hardness varies over a range of from 250
to 500 Brinell, depending on the original forging temperature.
Annealing can be done by heating to temperatures ranging from 1,290 to 1,380°F. and cooling in air or
quenching in water or oil. After this treatment the forgings will have a hardness of about 200 Brinell and a
tensile strength of 100,000 to 112,000 lb. per square inch. If softer forgings are desired they can be heated
to a temperature of from 1,560 to 1,650°F. and cooled very slowly. Although softer the forgings will not
machine as smoothly as when annealed at the lower temperature.
Hardening.—The forgings can be hardened by cooling in still air or quenching in oil or water from a
temperature between 1,650 and 1,750°F.
The physical properties do not vary greatly when the carbon is within the range of composition given, or
when the steel is hardened and tempered in air, oil, or water.
When used for valves the following specification of physical properties have been used:
Yield point, pounds per square inch 70,000
Tensile strength, pounds per square inch 90,000
Elongation in 2 in., per cent 18
Reduction of area, per cent 50
The usual heat treatment is to quench in oil from 1,650°F. and temper or draw at 1,100 to 1,200°F. One
valve manufacturer stated that valves of this steel are hardened by heating the previously annealed valves
to 1,650°F. and cooling in still air. This treatment gives a scleroscope hardness of about 50.
In addition to use in valves this steel should prove very satisfactory for shafting for water-pumps and
other automobile parts subject to objectionable corrosion.
TABLE 2.—COMPARISON OF PHYSICAL PROPERTIES FOR HIGH-
CHROMIUM STEELS OF DIFFERENT CARBON CONTENT
C 0.20 C 0.27
C 0.50
Mn 0.45 Mn 0.50
Cr 14.84
Cr 12.56 Cr 12.24
Quenched in oil from degrees Fahrenheit 1,600 1,600 1,650
Tempered at degrees Fahrenheit 1,160 1,080 1,100
Yield point, pounds per square inch 78,300 75,000 91,616
Tensile strength, pounds per square inch 104,600 104,250 123,648
Elongation in 2 in., per cent 25.0 23.5 14.5
Reduction of area, per cent 52.5 51.4 33.5
TABLE 3.—COMPARISON OF PHYSICAL PROPERTIES BETWEEN AIR, OIL AND WATER-
HARDENED STEEL HAVING CHEMICAL ANALYSIS IN PERCENTAGE OF
Carbon 0.24
Manganese 0.30
Phosphorus 0.035
Sulphur 0.035
Chromium 12.85
Silicon 0.20
to 500 Brinell, depending on the original forging temperature.
Annealing can be done by heating to temperatures ranging from 1,290 to 1,380°F. and cooling in air or
quenching in water or oil. After this treatment the forgings will have a hardness of about 200 Brinell and a
tensile strength of 100,000 to 112,000 lb. per square inch. If softer forgings are desired they can be heated
to a temperature of from 1,560 to 1,650°F. and cooled very slowly. Although softer the forgings will not
machine as smoothly as when annealed at the lower temperature.
Hardening.—The forgings can be hardened by cooling in still air or quenching in oil or water from a
temperature between 1,650 and 1,750°F.
The physical properties do not vary greatly when the carbon is within the range of composition given, or
when the steel is hardened and tempered in air, oil, or water.
When used for valves the following specification of physical properties have been used:
Yield point, pounds per square inch 70,000
Tensile strength, pounds per square inch 90,000
Elongation in 2 in., per cent 18
Reduction of area, per cent 50
The usual heat treatment is to quench in oil from 1,650°F. and temper or draw at 1,100 to 1,200°F. One
valve manufacturer stated that valves of this steel are hardened by heating the previously annealed valves
to 1,650°F. and cooling in still air. This treatment gives a scleroscope hardness of about 50.
In addition to use in valves this steel should prove very satisfactory for shafting for water-pumps and
other automobile parts subject to objectionable corrosion.
TABLE 2.—COMPARISON OF PHYSICAL PROPERTIES FOR HIGH-
CHROMIUM STEELS OF DIFFERENT CARBON CONTENT
C 0.20 C 0.27
C 0.50
Mn 0.45 Mn 0.50
Cr 14.84
Cr 12.56 Cr 12.24
Quenched in oil from degrees Fahrenheit 1,600 1,600 1,650
Tempered at degrees Fahrenheit 1,160 1,080 1,100
Yield point, pounds per square inch 78,300 75,000 91,616
Tensile strength, pounds per square inch 104,600 104,250 123,648
Elongation in 2 in., per cent 25.0 23.5 14.5
Reduction of area, per cent 52.5 51.4 33.5
TABLE 3.—COMPARISON OF PHYSICAL PROPERTIES BETWEEN AIR, OIL AND WATER-
HARDENED STEEL HAVING CHEMICAL ANALYSIS IN PERCENTAGE OF
Carbon 0.24
Manganese 0.30
Phosphorus 0.035
Sulphur 0.035
Chromium 12.85
Silicon 0.20
Page 38
Hardened Tempered at, Elastic Tensile Reduction of
Hardening Elongation in
from, degrees degrees limit, per strength, lb. area, per
medium 2 in. per cent
Fahrenheit Fahrenheit lb. sq. in. per sq. in. cent
930 158,815 192,415 13.0 40.5
1,100 99,680 120,065 21.0 59.2
Air 1,650 1,300 70,785 101,250 26.0 64.6
1,380 66,080 98,335 28.0 63.6
1,470 70,785 96,990 27.0 64.7
930 163,070 202,720 8.0 18.2
1,100 88,255 116,480 20.0 56.9
Oil 1,650
1,300 77,950 105,505 25.5 63.8
1,380 88,255 98,785 27.0 66.3
930 158,815 202,050 12.0 34.2
1,100 90,270 120,735 22.0 59.8
Water 1,650
1,300 66,080 102,590 25.8 64.8
1,380 67,200 97,890 27.0 65.2
This steel can be drawn into wire, rolled into sheets and strips and drawn into seamless tubes.
Corrosion.—This steel like any other steel when distorted by cold working is more sensitive to
corrosion and will rust. Rough cut surfaces will rust. Surfaces finished with a fine cut are less liable to
rust. Ground and polished surfaces are practically immune to rust.
When chromium content is increased to 16 to 18 per cent and silicon is added, from 2 to 4 per cent, this
steel becomes rust proof in its raw state, as soon as the outside surface is removed. It does not need to be
heat-treated in any way. These compositions are both patented.
S. A. E. STANDARD STEELS
The following steel specifications are considered standard by the Society of Automotive Engineers and
represents automobile practice in this country. These tables give the S. A. E. number, the composition of
the steel and the heat treatment. These are referred to by letter—the heat treatments being given in detail
on pages 134 to 137 in Chap. 8. It should be noted that the percentage of the different ingredients desired
is the mean, or halfway between the minimum and maximum.
TABLE 4.—CARBON STEELS
Carbon Manganese
S. A. E. (minimum (minimum Phosphorus Sulphur
Heat treatment
Specification no. and and (maximum) (maximum)
maximum) maximum)
1,010 0.05 to 0.15 0.30 to 0.60 0.045 0.05 Quench at 1,500
1,020 0.15 to 0.25 0.30 to 0.60 0.045 0.05 A or B
1,025 0.20 to 0.30 0.50 to 0.80 0.045 0.05 H
1,035 0.30 to 0.40 0.50 to 0.80 0.045 0.05 H, D or E
1,045 0.40 to 0.50 0.50 to 0.80 0.045 0.05 H, D or E
1,095 0.90 to 1.05 0.25 to 0.50 0.040 0.05 F
TABLE 5.—SCREW STOCK
Hardening Elongation in
from, degrees degrees limit, per strength, lb. area, per
medium 2 in. per cent
Fahrenheit Fahrenheit lb. sq. in. per sq. in. cent
930 158,815 192,415 13.0 40.5
1,100 99,680 120,065 21.0 59.2
Air 1,650 1,300 70,785 101,250 26.0 64.6
1,380 66,080 98,335 28.0 63.6
1,470 70,785 96,990 27.0 64.7
930 163,070 202,720 8.0 18.2
1,100 88,255 116,480 20.0 56.9
Oil 1,650
1,300 77,950 105,505 25.5 63.8
1,380 88,255 98,785 27.0 66.3
930 158,815 202,050 12.0 34.2
1,100 90,270 120,735 22.0 59.8
Water 1,650
1,300 66,080 102,590 25.8 64.8
1,380 67,200 97,890 27.0 65.2
This steel can be drawn into wire, rolled into sheets and strips and drawn into seamless tubes.
Corrosion.—This steel like any other steel when distorted by cold working is more sensitive to
corrosion and will rust. Rough cut surfaces will rust. Surfaces finished with a fine cut are less liable to
rust. Ground and polished surfaces are practically immune to rust.
When chromium content is increased to 16 to 18 per cent and silicon is added, from 2 to 4 per cent, this
steel becomes rust proof in its raw state, as soon as the outside surface is removed. It does not need to be
heat-treated in any way. These compositions are both patented.
S. A. E. STANDARD STEELS
The following steel specifications are considered standard by the Society of Automotive Engineers and
represents automobile practice in this country. These tables give the S. A. E. number, the composition of
the steel and the heat treatment. These are referred to by letter—the heat treatments being given in detail
on pages 134 to 137 in Chap. 8. It should be noted that the percentage of the different ingredients desired
is the mean, or halfway between the minimum and maximum.
TABLE 4.—CARBON STEELS
Carbon Manganese
S. A. E. (minimum (minimum Phosphorus Sulphur
Heat treatment
Specification no. and and (maximum) (maximum)
maximum) maximum)
1,010 0.05 to 0.15 0.30 to 0.60 0.045 0.05 Quench at 1,500
1,020 0.15 to 0.25 0.30 to 0.60 0.045 0.05 A or B
1,025 0.20 to 0.30 0.50 to 0.80 0.045 0.05 H
1,035 0.30 to 0.40 0.50 to 0.80 0.045 0.05 H, D or E
1,045 0.40 to 0.50 0.50 to 0.80 0.045 0.05 H, D or E
1,095 0.90 to 1.05 0.25 to 0.50 0.040 0.05 F
TABLE 5.—SCREW STOCK
Page 39
S. A. E. Phosphorus
Carbon Manganese Sulphur
Specification no. (maximum)
1,114 0.08 to 0.20 0.30 to 0.80 0.12 0.06 to 0.12
TABLE 6.—NICKEL STEELS
Carbon Manganese Nickel
S. A. E.
(minimum (minimum Phosphorus Sulphur (minimum Heat
Specification
and and (maximum) (maximum) and treatment
no.
maximum) maximum) maximum)
2,315 0.10 to 0.20 0.50 to 0.80 0.04 0.045 3.25 to 3.75 G, H or K
2,320 0.15 to 0.25 0.50 to 0.80 0.04 0.045 3.25 to 3.75 G, H or K
2,330 0.25 to 0.35 0.50 to 0.80 0.04 0.045 3.25 to 3.75 H or K
2,335 0.30 to 0.40 0.50 to 0.80 0.04 0.045 3.25 to 3.75 H or K
2,340 0.35 to 0.45 0.50 to 0.80 0.04 0.045 3.25 to 3.75 H or K
2,345 0.40 to 0.50 0.50 to 0.80 0.04 0.045 3.25 to 3.75 H or K
TABLE 7.—NICKEL-CHROMIUM STEELS
Carbon Manganese Nickel Chromium
S. A. E.
(minimum (minimum Phosphorus Sulphur (minimum (minimum Heat
Specification
and and (maximum) (maximum) and and treatment
no.
maximum) maximum) maximum) maximum)
3,120 0.15 to 0.25 0.50 to 0.80 0.04 0.045 1.00 to 1.50 0.45 to 0.75* G, H or D
3,125 0.20 to 0.30 0.50 to 0.80 0.04 0.045 1.00 to 1.50 0.45 to 0.75* H, D or E
3,130 0.25 to 0.35 0.50 to 0.80 0.04 0.045 1.00 to 1.50 0.45 to 0.75* H, D or E
3,135 0.30 to 0.40 0.50 to 0 80 0.04 0.045 1.00 to 1.50 0.45 to 0 75* H, D or E
3,140 0.35 to 0.45 0.50 to 0.80 0.04 0.045 1.00 to 1.50 0.45 to 0.75* H, D or E
3,220 0.15 to 0.25 0.30 to 0.60 0.04 0.040 1.50 to 2.00 0.90 to 1.25 G, H or D
3,230 0.25 to 0.35 0.30 to 0.60 0.04 0.040 1.50 to 2.00 0.90 to 1.25 H or D
3,240 0.35 to 0.45 0.30 to 0.60 0.04 0.040 1.50 to 2.00 0.90 to 1.25 H or D
3,250 0.45 to 0.55 0.30 to 0.60 0.04 0.040 1.50 to 2.00 0.90 to 1.25 M or Q
X3,315 0.10 to 0.20 0.45 to 0.75 0.04 0.040 2.75 to 3.25 0.60 to 0.95 G
X3,335 0.30 to 0.40 0.45 to 0.75 0.04 0.040 2.75 to 3.25 0.60 to 0.95 P or R
X3,350 0.45 to 0.55 0.45 to 0.75 0.04 0.040 2.75 to 3.25 0.60 to 0.95 P or R
3,320 0.15 to 0.25 0.30 to 0.60 0.04 0.040 3.25 to 3.75 1.25 to 1.75 L
3,330 0.25 to 0.35 0.30 to 0.60 0.04 0.040 3.25 to 3.75 1.25 to 1.75 P or R
3,340 0.35 to 0.45 0.30 to 0.60 0.04 0.040 3.25 to 3.75 1.25 to 1.75 P or R
* Another grade of this type of steel is available with chromium content of 0.15 per cent to 45 per cent. It
has somewhat lower physical properties.
TABLE 8.—CHROMIUM STEELS
S. A. E. Carbon Manganese Phosphorus Sulphur Chromium Heat
Specification (minimum (minimum (maximum) (maximum) (minimum treatment
no.
Carbon Manganese Sulphur
Specification no. (maximum)
1,114 0.08 to 0.20 0.30 to 0.80 0.12 0.06 to 0.12
TABLE 6.—NICKEL STEELS
Carbon Manganese Nickel
S. A. E.
(minimum (minimum Phosphorus Sulphur (minimum Heat
Specification
and and (maximum) (maximum) and treatment
no.
maximum) maximum) maximum)
2,315 0.10 to 0.20 0.50 to 0.80 0.04 0.045 3.25 to 3.75 G, H or K
2,320 0.15 to 0.25 0.50 to 0.80 0.04 0.045 3.25 to 3.75 G, H or K
2,330 0.25 to 0.35 0.50 to 0.80 0.04 0.045 3.25 to 3.75 H or K
2,335 0.30 to 0.40 0.50 to 0.80 0.04 0.045 3.25 to 3.75 H or K
2,340 0.35 to 0.45 0.50 to 0.80 0.04 0.045 3.25 to 3.75 H or K
2,345 0.40 to 0.50 0.50 to 0.80 0.04 0.045 3.25 to 3.75 H or K
TABLE 7.—NICKEL-CHROMIUM STEELS
Carbon Manganese Nickel Chromium
S. A. E.
(minimum (minimum Phosphorus Sulphur (minimum (minimum Heat
Specification
and and (maximum) (maximum) and and treatment
no.
maximum) maximum) maximum) maximum)
3,120 0.15 to 0.25 0.50 to 0.80 0.04 0.045 1.00 to 1.50 0.45 to 0.75* G, H or D
3,125 0.20 to 0.30 0.50 to 0.80 0.04 0.045 1.00 to 1.50 0.45 to 0.75* H, D or E
3,130 0.25 to 0.35 0.50 to 0.80 0.04 0.045 1.00 to 1.50 0.45 to 0.75* H, D or E
3,135 0.30 to 0.40 0.50 to 0 80 0.04 0.045 1.00 to 1.50 0.45 to 0 75* H, D or E
3,140 0.35 to 0.45 0.50 to 0.80 0.04 0.045 1.00 to 1.50 0.45 to 0.75* H, D or E
3,220 0.15 to 0.25 0.30 to 0.60 0.04 0.040 1.50 to 2.00 0.90 to 1.25 G, H or D
3,230 0.25 to 0.35 0.30 to 0.60 0.04 0.040 1.50 to 2.00 0.90 to 1.25 H or D
3,240 0.35 to 0.45 0.30 to 0.60 0.04 0.040 1.50 to 2.00 0.90 to 1.25 H or D
3,250 0.45 to 0.55 0.30 to 0.60 0.04 0.040 1.50 to 2.00 0.90 to 1.25 M or Q
X3,315 0.10 to 0.20 0.45 to 0.75 0.04 0.040 2.75 to 3.25 0.60 to 0.95 G
X3,335 0.30 to 0.40 0.45 to 0.75 0.04 0.040 2.75 to 3.25 0.60 to 0.95 P or R
X3,350 0.45 to 0.55 0.45 to 0.75 0.04 0.040 2.75 to 3.25 0.60 to 0.95 P or R
3,320 0.15 to 0.25 0.30 to 0.60 0.04 0.040 3.25 to 3.75 1.25 to 1.75 L
3,330 0.25 to 0.35 0.30 to 0.60 0.04 0.040 3.25 to 3.75 1.25 to 1.75 P or R
3,340 0.35 to 0.45 0.30 to 0.60 0.04 0.040 3.25 to 3.75 1.25 to 1.75 P or R
* Another grade of this type of steel is available with chromium content of 0.15 per cent to 45 per cent. It
has somewhat lower physical properties.
TABLE 8.—CHROMIUM STEELS
S. A. E. Carbon Manganese Phosphorus Sulphur Chromium Heat
Specification (minimum (minimum (maximum) (maximum) (minimum treatment
no.
Page 40
and and and
maximum) maximum) maximum)
5,120 0.15 to 0.25 * 0.04 0.045 0.65 to 0.85 B
5,140 0.35 to 0.45 * 0.04 0.045 0.65 to 0.85 H or D
5,165 0.60 to 0.70 * 0.04 0.045 0.65 to 0.85 H or D
5,195 0.90 to 1.05 0.20 to 0.45 0.03 0.03 0.90 to 1.10 M, P or R
51,120 1.10 to 1.30 0.20 to 0.45 0.03 0.03 0.90 to 1.10 M, P or R
5,295 0.90 to 1.05 0.20 to 0.45 0.03 0.03 1.10 to 1.30 M, P or R
52,120 1.10 to 1.30 0.20 to 0.45 0.03 0.03 1.10 to 1.30 M, P or R
—Two types of steel are available in this class, one with manganese 0.25 to 0.50 per cent (0.35 per cent
desired), and silicon not over 0.20 per cent; the other with manganese 0.60 to 0.80 per cent (0.70 per cent
desired), and silicon 0.15 to 0.50 per cent.
TABLE 9.—CHROMIUM-VANADIUM STEELS
Carbon Manganese Chromium Vanadium
S. A. E.
(minimum (minimum Phosphorus Sulphur (minimum (minimum Heat
Specification
and and (maximum) (maximum) and and treatment
no.
maximum) maximum) maximum) maximum)
6,120 0.15 to 0.25 0.50 to 0.80 0.04 0.04 0.80 to 1.10 0.15 S
6,125 0.20 to 0.30 0.50 to 0.80 0.04 0.04 0.80 to 1.10 0.15 S or T
6,130 0.25 to 0.35 0.50 to 0.80 0.04 0.04 0.80 to 1.10 0.15 T or U
6,135 0.30 to 0.40 0.50 to 0.80 0.04 0.04 0.80 to 1.10 0.15 T or U
6,140 0.35 to 0.45 0.50 to 0.80 0.04 0.04 0.80 to 1.10 0.15 T or U
6,145 0.40 to 0.50 0.50 to 0.80 0.04 0.04 0.80 to 1.10 0.15 U
6,150 0.45 to 0.55 0.50 to 0.80 0.04 0.04 0.80 to 1.10 0.15 U
6,195 0.90 to 1.05 0.20 to 0.45 0.03 0.03 0.80 to 1.10 0.15 U
TABLE 10.—SILICO-MANGANESE STEELS
Carbon Manganese Silicon
S. A. E.
(minimum (minimum Phosphorus Sulphur (minimum Heat
Specification
and and (maximum) (maximum) and treatment
no.
maximum) maximum) maximum)
9,250 0.45 to 0.55 0.60 to 0.80 0.045* 0.045 1.80 to 2.10 V
9,260 0.55 to 0.65 0.50 to 0.70 0.045* 0.045 1.50 to 1.80 V
* Steel made by the acid process may contain maximum 0.05 phosphorus.
LIBERTY MOTOR CONNECTING RODS
The requirements for materials for the Liberty motor connecting rods are so severe that the methods of
securing the desired qualities will be of value in other lines. The original specifications called for chrome-
nickel but the losses due to the difficulty of handling caused the Lincoln Motor Company to suggest the
substitution of chrome-vanadium steel, and this was accepted by the Signal Corps. The rods were
accordingly made from chromium-vanadium steel, containing carbon, 0.30 to 0.40 per cent; manganese,
0.50 to 0.80 per cent; phosphorus, not over 0.04 per cent; sulphur, not over 0.04 per cent; chromium, 0.80
to 1.10 per cent; vanadium, not less than 0.15 per cent. This steel is ordinarily known in the trade as 0.35
carbon steel, S. A. E., specification 6,135, which provides a first-rate quality steel for structural parts that
are to be heat-treated. The fatigue resisting or endurance qualities of this material are excellent. It has a
maximum) maximum) maximum)
5,120 0.15 to 0.25 * 0.04 0.045 0.65 to 0.85 B
5,140 0.35 to 0.45 * 0.04 0.045 0.65 to 0.85 H or D
5,165 0.60 to 0.70 * 0.04 0.045 0.65 to 0.85 H or D
5,195 0.90 to 1.05 0.20 to 0.45 0.03 0.03 0.90 to 1.10 M, P or R
51,120 1.10 to 1.30 0.20 to 0.45 0.03 0.03 0.90 to 1.10 M, P or R
5,295 0.90 to 1.05 0.20 to 0.45 0.03 0.03 1.10 to 1.30 M, P or R
52,120 1.10 to 1.30 0.20 to 0.45 0.03 0.03 1.10 to 1.30 M, P or R
—Two types of steel are available in this class, one with manganese 0.25 to 0.50 per cent (0.35 per cent
desired), and silicon not over 0.20 per cent; the other with manganese 0.60 to 0.80 per cent (0.70 per cent
desired), and silicon 0.15 to 0.50 per cent.
TABLE 9.—CHROMIUM-VANADIUM STEELS
Carbon Manganese Chromium Vanadium
S. A. E.
(minimum (minimum Phosphorus Sulphur (minimum (minimum Heat
Specification
and and (maximum) (maximum) and and treatment
no.
maximum) maximum) maximum) maximum)
6,120 0.15 to 0.25 0.50 to 0.80 0.04 0.04 0.80 to 1.10 0.15 S
6,125 0.20 to 0.30 0.50 to 0.80 0.04 0.04 0.80 to 1.10 0.15 S or T
6,130 0.25 to 0.35 0.50 to 0.80 0.04 0.04 0.80 to 1.10 0.15 T or U
6,135 0.30 to 0.40 0.50 to 0.80 0.04 0.04 0.80 to 1.10 0.15 T or U
6,140 0.35 to 0.45 0.50 to 0.80 0.04 0.04 0.80 to 1.10 0.15 T or U
6,145 0.40 to 0.50 0.50 to 0.80 0.04 0.04 0.80 to 1.10 0.15 U
6,150 0.45 to 0.55 0.50 to 0.80 0.04 0.04 0.80 to 1.10 0.15 U
6,195 0.90 to 1.05 0.20 to 0.45 0.03 0.03 0.80 to 1.10 0.15 U
TABLE 10.—SILICO-MANGANESE STEELS
Carbon Manganese Silicon
S. A. E.
(minimum (minimum Phosphorus Sulphur (minimum Heat
Specification
and and (maximum) (maximum) and treatment
no.
maximum) maximum) maximum)
9,250 0.45 to 0.55 0.60 to 0.80 0.045* 0.045 1.80 to 2.10 V
9,260 0.55 to 0.65 0.50 to 0.70 0.045* 0.045 1.50 to 1.80 V
* Steel made by the acid process may contain maximum 0.05 phosphorus.
LIBERTY MOTOR CONNECTING RODS
The requirements for materials for the Liberty motor connecting rods are so severe that the methods of
securing the desired qualities will be of value in other lines. The original specifications called for chrome-
nickel but the losses due to the difficulty of handling caused the Lincoln Motor Company to suggest the
substitution of chrome-vanadium steel, and this was accepted by the Signal Corps. The rods were
accordingly made from chromium-vanadium steel, containing carbon, 0.30 to 0.40 per cent; manganese,
0.50 to 0.80 per cent; phosphorus, not over 0.04 per cent; sulphur, not over 0.04 per cent; chromium, 0.80
to 1.10 per cent; vanadium, not less than 0.15 per cent. This steel is ordinarily known in the trade as 0.35
carbon steel, S. A. E., specification 6,135, which provides a first-rate quality steel for structural parts that
are to be heat-treated. The fatigue resisting or endurance qualities of this material are excellent. It has a
Page 41
tensile strength of 150,000 lb. minimum per square inch; elastic limit, 115,000 lb. minimum per square
inch; elongation, 5 per cent minimum in 2 in.; and minimum reduction in area, 25 per cent.
The original production system as outlined for the manufacturers had called for a heat treatment in the
rough-forged state for the connecting rods, and then semi-machining the rod forgings before giving them
the final treatment. The Lincoln Motor Company insisted from the first that the proper method would be a
complete heat treatment of the forging in the rough state, and machining the rod after the heat treatment.
After a number of trial lots, the Signal Corps acceded to the request and production was immediately
increased and quality benefited by the change. This method was later included in a revised specification
issued to all producers.
The original system was one that required a great deal of labor per unit output. The Lincoln organization
developed a method of handling connecting rods whereby five workmen accomplished the same result
that would have required about 30 or 32 by the original method. Even after revising the specification so as
to allow complete heat treatments in the rough-forged state, the ordinary methods employed in heat-
treating would have required 12 to 15 men. With the fixtures employed, five men could handle 1,300
connecting rods, half of which are plain and half, forked, in a working period of little over 7 hr.
Fig. 14.—Rack for holding rods.
inch; elongation, 5 per cent minimum in 2 in.; and minimum reduction in area, 25 per cent.
The original production system as outlined for the manufacturers had called for a heat treatment in the
rough-forged state for the connecting rods, and then semi-machining the rod forgings before giving them
the final treatment. The Lincoln Motor Company insisted from the first that the proper method would be a
complete heat treatment of the forging in the rough state, and machining the rod after the heat treatment.
After a number of trial lots, the Signal Corps acceded to the request and production was immediately
increased and quality benefited by the change. This method was later included in a revised specification
issued to all producers.
The original system was one that required a great deal of labor per unit output. The Lincoln organization
developed a method of handling connecting rods whereby five workmen accomplished the same result
that would have required about 30 or 32 by the original method. Even after revising the specification so as
to allow complete heat treatments in the rough-forged state, the ordinary methods employed in heat-
treating would have required 12 to 15 men. With the fixtures employed, five men could handle 1,300
connecting rods, half of which are plain and half, forked, in a working period of little over 7 hr.
Fig. 14.—Rack for holding rods.
Page 42
Fig. 15.—Sliding rods into tank.
The increase in production was gained by devising fixtures which enabled fewer men to handle a greater
quantity of parts with less effort and in less time.
In heat-treating the forgings were laid on a rack or loop A, Fig. 14, made of 1¼-in. double extra-heavy
pipe, bent up with parallel sides about 9 in. apart, one end being bent straight across and the other end
being bent upward so as to afford an easy grasp for the hook. Fifteen rods were laid on each loop, there
being four loops of rods charged into a furnace with a hearth area of 36 by 66 in. The rods were charged at
a temperature of approximately 900°F. They were heated for refining over a period of 3 hr. to 1,625°F.,
soaked 15 min, at this degree of heat and quenched in soluble quenching oil.
In pulling the heat to quench the rods, the furnace door was raised and the operator pulls one of the loops
A, Fig. 15 forward to the shelf of the furnace, supporting the straight end of the loop by means of the
porter bar B. They swung the loop of rods around from the furnace shelf and set the straight end of the
loop on the edge of the quenching tank, then raise the curved end C, by means of their hook D so that all
the rods on the loop slide into the oil bath.
Before the rods cooled entirely, the baskets in the quenching tank were raised and the oil allowed to
partly drain off the forgings, and they were stacked on curved-end loops or racks and charged into the
furnace for the second or hardening heat. The temperature of the furnace was raised in 1½ hr. to 1,550°F.,
the rods soaked for 15 min. at this degree of heat and quenched in the same manner as above.
They were again drained while yet warm, placed on loops and charged into the furnace for the third or
tempering heat. The temperature of the furnace was brought to 1,100°F. in 1 hr., and the rods soaked at
this degree of heat for 1 hr. They were then removed from the furnace the same as for quenching, but were
dumped onto steel platforms instead of into the quenching oil, and allowed to cool on these steel platforms
down to the room temperature.
PICKLING THE FORGINGS
The increase in production was gained by devising fixtures which enabled fewer men to handle a greater
quantity of parts with less effort and in less time.
In heat-treating the forgings were laid on a rack or loop A, Fig. 14, made of 1¼-in. double extra-heavy
pipe, bent up with parallel sides about 9 in. apart, one end being bent straight across and the other end
being bent upward so as to afford an easy grasp for the hook. Fifteen rods were laid on each loop, there
being four loops of rods charged into a furnace with a hearth area of 36 by 66 in. The rods were charged at
a temperature of approximately 900°F. They were heated for refining over a period of 3 hr. to 1,625°F.,
soaked 15 min, at this degree of heat and quenched in soluble quenching oil.
In pulling the heat to quench the rods, the furnace door was raised and the operator pulls one of the loops
A, Fig. 15 forward to the shelf of the furnace, supporting the straight end of the loop by means of the
porter bar B. They swung the loop of rods around from the furnace shelf and set the straight end of the
loop on the edge of the quenching tank, then raise the curved end C, by means of their hook D so that all
the rods on the loop slide into the oil bath.
Before the rods cooled entirely, the baskets in the quenching tank were raised and the oil allowed to
partly drain off the forgings, and they were stacked on curved-end loops or racks and charged into the
furnace for the second or hardening heat. The temperature of the furnace was raised in 1½ hr. to 1,550°F.,
the rods soaked for 15 min. at this degree of heat and quenched in the same manner as above.
They were again drained while yet warm, placed on loops and charged into the furnace for the third or
tempering heat. The temperature of the furnace was brought to 1,100°F. in 1 hr., and the rods soaked at
this degree of heat for 1 hr. They were then removed from the furnace the same as for quenching, but were
dumped onto steel platforms instead of into the quenching oil, and allowed to cool on these steel platforms
down to the room temperature.
PICKLING THE FORGINGS
Page 43
The forgings were then pickled in a hot solution of either niter cake or sulphuric acid and water at a
temperature of 170°F., and using a solution of about 25 per cent. The solution was maintained at a
constant point by taking hydrometer readings two or three times a day, maintaining a reading of about
1.175. Sixty forked or one hundred single rods were placed in wooden racks and immersed in a lead-lined
vat 30 by 30 by 5 ft. long. The rack was lowered or lifted by means of an air hoist and the rods were
allowed to stay in solution from 1/2 to 1 hr., depending on the amount of scale. The rods were then swung
and lowered in the rack into running hot water until all trace of the acid was removed.
The rod was finally subjected to Brinell test. This shows whether or not the rod has been heat-treated to
the proper hardness. If the rods did not read between 241 and 277, they were re-treated until the proper
hardness is obtained.
temperature of 170°F., and using a solution of about 25 per cent. The solution was maintained at a
constant point by taking hydrometer readings two or three times a day, maintaining a reading of about
1.175. Sixty forked or one hundred single rods were placed in wooden racks and immersed in a lead-lined
vat 30 by 30 by 5 ft. long. The rack was lowered or lifted by means of an air hoist and the rods were
allowed to stay in solution from 1/2 to 1 hr., depending on the amount of scale. The rods were then swung
and lowered in the rack into running hot water until all trace of the acid was removed.
The rod was finally subjected to Brinell test. This shows whether or not the rod has been heat-treated to
the proper hardness. If the rods did not read between 241 and 277, they were re-treated until the proper
hardness is obtained.
Page 44
CHAPTER IV
APPLICATION OF LIBERTY ENGINE MATERIALS TO THE AUTOMOTIVE
INDUSTRY[1]
[Footnote 1: Paper presented at the summer meeting of the S. A. E. at Ottawa Beach in June, 1919.]
The success of the Liberty engine program was an engineering achievement in which the science of
metallurgy played an important part. The reasons for the use of certain materials and certain treatments for
each part are given with recommendations for their application to the problems of automotive industry.
The most important items to be taken into consideration in the selection of material for parts of this type
are uniformity and machineability. It has been demonstrated many times that the ordinary grades of
bessemer screw stock are unsatisfactory for aviation purposes, due to the presence of excessive amounts
of unevenly distributed phosphorus and sulphide segregations. For this reason, material finished by the
basic open hearth process was selected, in accordance with the following specifications: Carbon, 0.150 to
0.250 per cent; manganese, 0.500 to 0.800 per cent; phosphorus, 0.045 maximum per cent; sulphur, 0.060
to 0.090 per cent.
This material in the cold-drawn condition will show: Elastic limit, 50,000 lb. per square inch, elongation
in 2 in., 10 per cent, reduction of area, 35 per cent.
This material gave as uniform physical properties as S. A. E. No. 1020 steel and at the same time was
sufficiently free cutting to produce a smooth thread and enable the screw-machine manufacturers to
produce, to the same thread limits, approximately 75 per cent as many parts as from bessemer screw
stock.
There are but seven carbon-steel carbonized parts on the Liberty engine. The most important are the
camshaft, the camshaft rocker lever roller and the tappet. The material used for parts of this type was S. A.
E. No. 1,020 steel, which is of the following chemical analysis: Carbon 0.150 to 0.250 per cent;
manganese, 0.300 to 0.600 per cent; phosphorus, 0.045 maximum per cent; sulphur, 0.050 maximum per
cent.
The heat treatment consisted in carbonizing at a temperature of from 1,650 to 1,700°F. for a sufficient
length of time to secure the proper depth of case, cool slowly or quench; then reheat to a temperature of
1,380 to 1,430°F. to refine the grain of the case, and quench in water. The only thing that should limit the
rate of cooling from the carbonizing heat is distortion. Camshaft rocker lever rollers and tappets, as well
as gear pins, were quenched directly from the carbonizing heat in water and then case-refined and
rehardened by quenching in water from a temperature of from 1,380 to 1,430°F.
The advantage of direct quenching from the carbonizing heat is doubtless one of economy, and in many
cases will save the cost of a reheating. Specifications for case hardening, issued by the Society of
Automotive Engineers, have lately been revised; whereas they formerly called for a slow cooling, they
now permit a quenching from the pot. Doubtless this is a step in advance. Warpage caused by quenching
can be reduced to a minimum by thoroughly annealing the stock before any machine work is done on it.
APPLICATION OF LIBERTY ENGINE MATERIALS TO THE AUTOMOTIVE
INDUSTRY[1]
[Footnote 1: Paper presented at the summer meeting of the S. A. E. at Ottawa Beach in June, 1919.]
The success of the Liberty engine program was an engineering achievement in which the science of
metallurgy played an important part. The reasons for the use of certain materials and certain treatments for
each part are given with recommendations for their application to the problems of automotive industry.
The most important items to be taken into consideration in the selection of material for parts of this type
are uniformity and machineability. It has been demonstrated many times that the ordinary grades of
bessemer screw stock are unsatisfactory for aviation purposes, due to the presence of excessive amounts
of unevenly distributed phosphorus and sulphide segregations. For this reason, material finished by the
basic open hearth process was selected, in accordance with the following specifications: Carbon, 0.150 to
0.250 per cent; manganese, 0.500 to 0.800 per cent; phosphorus, 0.045 maximum per cent; sulphur, 0.060
to 0.090 per cent.
This material in the cold-drawn condition will show: Elastic limit, 50,000 lb. per square inch, elongation
in 2 in., 10 per cent, reduction of area, 35 per cent.
This material gave as uniform physical properties as S. A. E. No. 1020 steel and at the same time was
sufficiently free cutting to produce a smooth thread and enable the screw-machine manufacturers to
produce, to the same thread limits, approximately 75 per cent as many parts as from bessemer screw
stock.
There are but seven carbon-steel carbonized parts on the Liberty engine. The most important are the
camshaft, the camshaft rocker lever roller and the tappet. The material used for parts of this type was S. A.
E. No. 1,020 steel, which is of the following chemical analysis: Carbon 0.150 to 0.250 per cent;
manganese, 0.300 to 0.600 per cent; phosphorus, 0.045 maximum per cent; sulphur, 0.050 maximum per
cent.
The heat treatment consisted in carbonizing at a temperature of from 1,650 to 1,700°F. for a sufficient
length of time to secure the proper depth of case, cool slowly or quench; then reheat to a temperature of
1,380 to 1,430°F. to refine the grain of the case, and quench in water. The only thing that should limit the
rate of cooling from the carbonizing heat is distortion. Camshaft rocker lever rollers and tappets, as well
as gear pins, were quenched directly from the carbonizing heat in water and then case-refined and
rehardened by quenching in water from a temperature of from 1,380 to 1,430°F.
The advantage of direct quenching from the carbonizing heat is doubtless one of economy, and in many
cases will save the cost of a reheating. Specifications for case hardening, issued by the Society of
Automotive Engineers, have lately been revised; whereas they formerly called for a slow cooling, they
now permit a quenching from the pot. Doubtless this is a step in advance. Warpage caused by quenching
can be reduced to a minimum by thoroughly annealing the stock before any machine work is done on it.
Page 45
Another advantage obtained from rapid cooling from the carbonizing heat is the retaining of the majority
of the excess cementite in solution which produces a less brittle case and by so doing reduces the liability
of grinding checks and chipping of the case in actual service.
In the case of the camshaft, it is not possible to quench directly from the carbonizing heat because of
distortion and therefore excessive breakage during straightening operations. All Liberty camshafts were
cooled slowly from carbonizing heat and hardened by a single reheating to a temperature of from 1,380 to
1,430°F. and quenching in water.
Considerable trouble has always been experienced in obtaining uniform hardness on finished camshafts.
This is caused by insufficient water circulation in the quenching tank, which allows the formation of
steam pockets to take place, or by decarbonization of the case during heating by the use of an
overoxidizing flame. Another cause, which is very often overlooked, is due to the case being ground off
one side of cam more than the other and is caused by the roughing master cam being slightly different
from the finishing master cam. Great care should be taken to see that this condition does not occur,
especially when the depth of case is between 1/32 and 3/64 in.
CARBON-STEEL FORGINGS
Low-stressed, carbon-steel forgings include such parts as carbureter control levers, etc. The important
criterion for parts of this type is ease of fabrication and freedom from over-heated and burned forgings.
The material used for such parts was S. A. E. No. 1,030 steel, which is of the following chemical
composition: Carbon, 0.250 to 0.350 per cent; manganese, 0.500 to 0.800 per cent; phosphorus, 0.045
maximum per cent; sulphur, 0.050 maximum per cent.
To obtain good machineability, all forgings produced from this steel were heated to a temperature of
from 1,575 to 1,625°F. to refine the grain of the steel thoroughly and quenched in water and then tempered
to obtain proper machineability by heating to a temperature of from 1,000 to 1,100°F. and cooled slowly
or quenched.
Forgings subjected to this heat treatment are free from hard spots and will show a Brinell hardness of
177 to 217, which is proper for all ordinary machining operations. Great care should be taken not to use
steel for parts of this type containing less than 0.25 per cent carbon, because the lower the carbon the
greater the liability of hard spots, and the more difficult it becomes to eliminate them. The only
satisfactory method so far in commercial use for the elimination of hard spots is to give forgings a very
severe quench from a high temperature followed by a proper tempering heat to secure good machine
ability as outlined above.
The important carbon-steel forgings consisted of the cylinders, the propeller-hubs, the propeller-hub
flange, etc. The material used for parts of this type was S. A. E. No. 1,045 steel, which is of the following
chemical composition: Carbon, 0.400 to 0.500 per cent; manganese, 0.500 to 0.800 per cent; phosphorus,
0.045 maximum per cent; sulphur, 0.050 maximum per cent.
All forgings made from this material must show, after heat treatment, the following minimum physical
properties: Elastic limit, 70,000; lb. per square inch, elongation in 2 in., 18 per cent, reduction of area, 45;
per cent, Brinell hardness, 217 to 255.
To obtain these physical properties, the forgings were quenched in water from a temperature of 1,500 to
1,550°F., followed by tempering to meet proper Brinell requirements by heating to a temperature of 1,150
to 1,200°F. and cooled slowly or quenched. No trouble of any kind was ever experienced with parts of this
type.
of the excess cementite in solution which produces a less brittle case and by so doing reduces the liability
of grinding checks and chipping of the case in actual service.
In the case of the camshaft, it is not possible to quench directly from the carbonizing heat because of
distortion and therefore excessive breakage during straightening operations. All Liberty camshafts were
cooled slowly from carbonizing heat and hardened by a single reheating to a temperature of from 1,380 to
1,430°F. and quenching in water.
Considerable trouble has always been experienced in obtaining uniform hardness on finished camshafts.
This is caused by insufficient water circulation in the quenching tank, which allows the formation of
steam pockets to take place, or by decarbonization of the case during heating by the use of an
overoxidizing flame. Another cause, which is very often overlooked, is due to the case being ground off
one side of cam more than the other and is caused by the roughing master cam being slightly different
from the finishing master cam. Great care should be taken to see that this condition does not occur,
especially when the depth of case is between 1/32 and 3/64 in.
CARBON-STEEL FORGINGS
Low-stressed, carbon-steel forgings include such parts as carbureter control levers, etc. The important
criterion for parts of this type is ease of fabrication and freedom from over-heated and burned forgings.
The material used for such parts was S. A. E. No. 1,030 steel, which is of the following chemical
composition: Carbon, 0.250 to 0.350 per cent; manganese, 0.500 to 0.800 per cent; phosphorus, 0.045
maximum per cent; sulphur, 0.050 maximum per cent.
To obtain good machineability, all forgings produced from this steel were heated to a temperature of
from 1,575 to 1,625°F. to refine the grain of the steel thoroughly and quenched in water and then tempered
to obtain proper machineability by heating to a temperature of from 1,000 to 1,100°F. and cooled slowly
or quenched.
Forgings subjected to this heat treatment are free from hard spots and will show a Brinell hardness of
177 to 217, which is proper for all ordinary machining operations. Great care should be taken not to use
steel for parts of this type containing less than 0.25 per cent carbon, because the lower the carbon the
greater the liability of hard spots, and the more difficult it becomes to eliminate them. The only
satisfactory method so far in commercial use for the elimination of hard spots is to give forgings a very
severe quench from a high temperature followed by a proper tempering heat to secure good machine
ability as outlined above.
The important carbon-steel forgings consisted of the cylinders, the propeller-hubs, the propeller-hub
flange, etc. The material used for parts of this type was S. A. E. No. 1,045 steel, which is of the following
chemical composition: Carbon, 0.400 to 0.500 per cent; manganese, 0.500 to 0.800 per cent; phosphorus,
0.045 maximum per cent; sulphur, 0.050 maximum per cent.
All forgings made from this material must show, after heat treatment, the following minimum physical
properties: Elastic limit, 70,000; lb. per square inch, elongation in 2 in., 18 per cent, reduction of area, 45;
per cent, Brinell hardness, 217 to 255.
To obtain these physical properties, the forgings were quenched in water from a temperature of 1,500 to
1,550°F., followed by tempering to meet proper Brinell requirements by heating to a temperature of 1,150
to 1,200°F. and cooled slowly or quenched. No trouble of any kind was ever experienced with parts of this
type.
Page 46
The principal carbon-steel pressed parts used on the Liberty engine were the water jackets and the
exhaust manifolds. The material used for parts of this type was S. A. E. No. 1,010 steel, which is of the
following chemical composition: Carbon, 0.05 to 0.15 per cent; manganese, 0.30 to 0.60 per cent;
phosphorus, 0.045 maximum per cent; sulphur, 0.045 maximum per cent.
No trouble was experienced in the production of any parts from this material with the exception of the
water jacket. Due to the particular design of the Liberty cylinder assembly, many failures occurred in the
early days, due to the top of the jacket cracking with a brittle fracture. It was found that these failures were
caused primarily from the use of jackets which showed small scratches or die marks at this joint and
secondarily by improper annealing of the jackets themselves between the different forming operations. By
a careful inspection for die marks and by giving the jackets 1,400°F. annealing before the last forming
operation, it was possible to completely eliminate the trouble encountered.
HIGHLY STRESSED PARTS
The highly stressed parts on the Liberty engine consisted of the connecting-rod bolt, the main-bearing
bolt, the propeller-hub key, etc. The material used for parts of this type was selected at the option of the
manufacturer from standard S. A. E. steels, the composition of which are given in Table 11.
TABLE 11.—COMPOSITION OF S. A. E. STEELS Nos. 2,330, 3,135 AND 6,130
Steel No 2,330 3,135 6,130
Carbon, minimum 0.250 0.300 0.250
Carbon, maximum 0.350 0.400 0.450
Manganese, minimum 0.500 0.500 0.500
Manganese, maximum 0.800 0.800 0.800
Phosphorus, maximum 0.045 0.040 0.040
Sulphur, maximum 0.045 0.045 0.045
Nickel, minimum 3.250 1.000
Nickel, maximum 3.750 1.500
Chromium, minimum 0.450 0.800
Chromium, maximum 0.750 1.100
Vanadium, minimum 0.150
All highly stressed parts on the Liberty engine must show, after heat treatment, the following minimum
physical properties: Elastic limit, 100,000 lb. per square inch; elongation in 2 in., 16 per cent; reduction of
area, 45 per cent; scleroscope hardness, 40 to 50.
The heat treatment employed to obtain these physical properties consisted in quenching from a
temperature of 1,525 to 1,575°F., in oil, followed by tempering at a temperature of from 925 to 975°F.
Due to the extremely fine limits used on all threaded parts for the Liberty engine, a large percentage of
rejection was due to warpage and scaling of parts. To eliminate this objection, many of the Liberty engine
builders adopted the use of heat-treated and cold-drawn alloy steel for their highly stressed parts. On all
sizes up to and including 3/8 in. in diameter, the physical properties were secured by merely normalizing
the hot-rolled bars by heating to a temperature of from 1,525 to 1,575°F., and cooling in air, followed by
the usual cold-drawing reductions. For parts requiring stock over 3/8 in. in diameter, the physical
properties desired were obtained by quenching and tempering the hot-rolled bars before cold-drawing. It is
the opinion that the use of heat-treated and cold-drawn bars is very good practice, provided proper
inspection is made to guarantee the uniformity of heat treatment and, therefore, the uniformity of the
physical properties of the finished parts.
exhaust manifolds. The material used for parts of this type was S. A. E. No. 1,010 steel, which is of the
following chemical composition: Carbon, 0.05 to 0.15 per cent; manganese, 0.30 to 0.60 per cent;
phosphorus, 0.045 maximum per cent; sulphur, 0.045 maximum per cent.
No trouble was experienced in the production of any parts from this material with the exception of the
water jacket. Due to the particular design of the Liberty cylinder assembly, many failures occurred in the
early days, due to the top of the jacket cracking with a brittle fracture. It was found that these failures were
caused primarily from the use of jackets which showed small scratches or die marks at this joint and
secondarily by improper annealing of the jackets themselves between the different forming operations. By
a careful inspection for die marks and by giving the jackets 1,400°F. annealing before the last forming
operation, it was possible to completely eliminate the trouble encountered.
HIGHLY STRESSED PARTS
The highly stressed parts on the Liberty engine consisted of the connecting-rod bolt, the main-bearing
bolt, the propeller-hub key, etc. The material used for parts of this type was selected at the option of the
manufacturer from standard S. A. E. steels, the composition of which are given in Table 11.
TABLE 11.—COMPOSITION OF S. A. E. STEELS Nos. 2,330, 3,135 AND 6,130
Steel No 2,330 3,135 6,130
Carbon, minimum 0.250 0.300 0.250
Carbon, maximum 0.350 0.400 0.450
Manganese, minimum 0.500 0.500 0.500
Manganese, maximum 0.800 0.800 0.800
Phosphorus, maximum 0.045 0.040 0.040
Sulphur, maximum 0.045 0.045 0.045
Nickel, minimum 3.250 1.000
Nickel, maximum 3.750 1.500
Chromium, minimum 0.450 0.800
Chromium, maximum 0.750 1.100
Vanadium, minimum 0.150
All highly stressed parts on the Liberty engine must show, after heat treatment, the following minimum
physical properties: Elastic limit, 100,000 lb. per square inch; elongation in 2 in., 16 per cent; reduction of
area, 45 per cent; scleroscope hardness, 40 to 50.
The heat treatment employed to obtain these physical properties consisted in quenching from a
temperature of 1,525 to 1,575°F., in oil, followed by tempering at a temperature of from 925 to 975°F.
Due to the extremely fine limits used on all threaded parts for the Liberty engine, a large percentage of
rejection was due to warpage and scaling of parts. To eliminate this objection, many of the Liberty engine
builders adopted the use of heat-treated and cold-drawn alloy steel for their highly stressed parts. On all
sizes up to and including 3/8 in. in diameter, the physical properties were secured by merely normalizing
the hot-rolled bars by heating to a temperature of from 1,525 to 1,575°F., and cooling in air, followed by
the usual cold-drawing reductions. For parts requiring stock over 3/8 in. in diameter, the physical
properties desired were obtained by quenching and tempering the hot-rolled bars before cold-drawing. It is
the opinion that the use of heat-treated and cold-drawn bars is very good practice, provided proper
inspection is made to guarantee the uniformity of heat treatment and, therefore, the uniformity of the
physical properties of the finished parts.
Page 47
The question has been asked many times by different manufacturers, as to which alloy steel offers the
best machineability when heat-treated to a given Brinell hardness. The general consensus of opinion
among the screw-machine manufacturers is that S. A. E. No. 6,130 steel gives the best machineability and
that S. A. E. No. 2,330 steel would receive second choice of the three specified.
In the finishing of highly stressed parts for aviation engines, extreme care must be taken to see that all
tool marks are eliminated, unless they are parallel to the axis of strain, and that proper radii are maintained
at all changes of section. This is of the utmost importance to give proper fatigue resistance to the part in
question.
GEARS
The material used for all gears on the Liberty engine was selected at the option of the manufacturer from
the following standard S. A. E. steels, the composition of which are given in Table 12,
TABLE 12.—COMPOSITION OF STEELS NOS. X-3,340 AND 6,140
Steel No X-3,340 6,140
Carbon, minimum 0.350 0.350
Carbon, maximum 0.450 0.450
Manganese, minimum 0.450 0.500
Manganese, maximum 0.750 0.800
Phosphorus, maximum 0.040 0.040
Sulphur, maximum 0.045 0.045
Nickel, minimum 2.750
Nickel, maximum 3.250
Chromium, minimum 0.700 0.800
Chromium, maximum 0.950 1.100
Vanadium, minimum 0.150
All gears were heat-treated to a scleroscope hardness of from 55 to 55. The heat treatment used to secure
this hardness consisted in quenching the forgings from a temperature of 1,550 to 1,600°F. in oil and
annealing for good machineability at a temperature of from 1,300 to 1,350°F. Forgings treated in this
manner showed a Brinell hardness of from 177 to 217.
RATE OF COOLING
At the option of the manufacturer, the above treatment of gear forgings could be substituted by
normalizing the forgings at a temperature of from 1,550 to 1,600°F. The most important criterion for
proper normalizing, consisted in allowing the forgings to cool through the critical temperature of the steel,
at a rate not to exceed 50°F. per hour. For the two standard steels used, this consisted in cooling from the
normalizing temperature down to a temperature of 1,100°F., at the rate indicated. Forgings normalized in
this manner will show a Brinell hardness of from 177 to 217. The question has been repeatedly asked as to
which treatment will produce the higher quality finished part. In answer to this I will state that on simple
forgings of comparatively small section, the normalizing treatment will produce a finished part which is of
equal quality to that of the quenched and annealed forgings. However, in the case of complex forgings, or
those of large section, more uniform physical properties of the finished part will be obtained by quenching
and annealing the forgings in the place of normalizing.
The heat treatment of the finished gears consisted of quenching in oil from a temperature of from 1,420
to 1,440°F. for the No. X-3,340 steel, or from a temperature of from 1,500 to 1,540°F. for No. 6,140 steel,
followed by tempering in saltpeter or in an electric furnace at a temperature of from 650 to 700°F.
best machineability when heat-treated to a given Brinell hardness. The general consensus of opinion
among the screw-machine manufacturers is that S. A. E. No. 6,130 steel gives the best machineability and
that S. A. E. No. 2,330 steel would receive second choice of the three specified.
In the finishing of highly stressed parts for aviation engines, extreme care must be taken to see that all
tool marks are eliminated, unless they are parallel to the axis of strain, and that proper radii are maintained
at all changes of section. This is of the utmost importance to give proper fatigue resistance to the part in
question.
GEARS
The material used for all gears on the Liberty engine was selected at the option of the manufacturer from
the following standard S. A. E. steels, the composition of which are given in Table 12,
TABLE 12.—COMPOSITION OF STEELS NOS. X-3,340 AND 6,140
Steel No X-3,340 6,140
Carbon, minimum 0.350 0.350
Carbon, maximum 0.450 0.450
Manganese, minimum 0.450 0.500
Manganese, maximum 0.750 0.800
Phosphorus, maximum 0.040 0.040
Sulphur, maximum 0.045 0.045
Nickel, minimum 2.750
Nickel, maximum 3.250
Chromium, minimum 0.700 0.800
Chromium, maximum 0.950 1.100
Vanadium, minimum 0.150
All gears were heat-treated to a scleroscope hardness of from 55 to 55. The heat treatment used to secure
this hardness consisted in quenching the forgings from a temperature of 1,550 to 1,600°F. in oil and
annealing for good machineability at a temperature of from 1,300 to 1,350°F. Forgings treated in this
manner showed a Brinell hardness of from 177 to 217.
RATE OF COOLING
At the option of the manufacturer, the above treatment of gear forgings could be substituted by
normalizing the forgings at a temperature of from 1,550 to 1,600°F. The most important criterion for
proper normalizing, consisted in allowing the forgings to cool through the critical temperature of the steel,
at a rate not to exceed 50°F. per hour. For the two standard steels used, this consisted in cooling from the
normalizing temperature down to a temperature of 1,100°F., at the rate indicated. Forgings normalized in
this manner will show a Brinell hardness of from 177 to 217. The question has been repeatedly asked as to
which treatment will produce the higher quality finished part. In answer to this I will state that on simple
forgings of comparatively small section, the normalizing treatment will produce a finished part which is of
equal quality to that of the quenched and annealed forgings. However, in the case of complex forgings, or
those of large section, more uniform physical properties of the finished part will be obtained by quenching
and annealing the forgings in the place of normalizing.
The heat treatment of the finished gears consisted of quenching in oil from a temperature of from 1,420
to 1,440°F. for the No. X-3,340 steel, or from a temperature of from 1,500 to 1,540°F. for No. 6,140 steel,
followed by tempering in saltpeter or in an electric furnace at a temperature of from 650 to 700°F.
Page 48
The question has been asked by many engineers, why is the comparatively low scleroscope hardness
specified for gears? The reason for this is that at best the life of an aviation engine is short, as compared
with that of an automobile, truck or tractor, and that shock resistance is of vital importance. A sclerescope
hardness of from 55 to 65 will give sufficient resistance to wear to prevent replacements during the life of
an aviation engine, while at the same time this hardness produces approximately 50 per cent greater
shock-resisting properties to the gear. In the case of the automobile, truck or tractor, resistance to wear is
the main criterion and for that reason the higher hardness is specified.
Great care should be taken in the design of an aviation engine gear to eliminate sharp corners at the
bottom of teeth as well as in keyways. Any change of section in any stressed part of an aviation engine
must have a radius of at least 1/32 in. to give proper shock and fatigue resistance. This fact has been
demonstrated many times during the Liberty engine program.
CONNECTING RODS
The material used for all connecting rods on the Liberty engine was selected at the option of the
manufacturer from one of two standard S. A. E. steels, the composition of which are given in Table 13.
TABLE 13.—COMPOSITION OF STEELS NOS. X-3,335 AND 6,135
Steel No. X-3,335 6,135
Carbon, minimum 0.300 0.300
Carbon, maximum 0.400 0.400
Manganese, minimum 0.450 0.500
Manganese, maximum 0.750 0.800
Phosphorus, maximum 0.040 0.040
Sulphur, maximum 0.045 0.045
Nickel, minimum 2.750
Nickel, maximum 3.250
Chromium, minimum 0.700 0.800
Chromium, maximum 0.950 1.100
Vanadium minimum 0.150
All connecting rods were heat-treated to show the following minimum physical properties; Elastic limit,
105,000 lb. per square inch: elongation in 2 in., 17.5; per cent, reduction of area 50.0; per cent., Brinell
hardness, 241 to 277.
The heat treatment used to secure these physical properties consisted in normalizing the forgings at a
temperature of from 1,550 to 1,600°F., followed by cooling in the furnace or in air. The forgings were then
quenched in oil from a temperature of from 1,420 to 1,440°F. for the No. X-3,335 steel, or from a
temperature of from 1,500 to 1,525°F. for No. 6,135 steel, followed by tempering at a temperature of from
1,075 to 1,150°F. At the option of the manufacturer, the normalizing treatment could be substituted by
quenching the forgings from a temperature of from 1,550 to 1,600°F., in oil, and annealing for the best
machineability at a temperature of from 1,300 to 1,350°F. The double quench, however, did not prove
satisfactory on No. X-3,335 steel, due to the fact that it was necessary to remove forgings from the
quenching bath while still at a temperature of from 300 to 500°F. to eliminate any possibility of cracking.
In view of the fact that this practice is difficult to carry out in the average heat-treating plant, considerable
trouble was experienced.
The most important criterion in the production of aviation engine connecting rods is the elimination of
burned or severely overheated forgings. Due to the particular design of the forked rod, considerable
specified for gears? The reason for this is that at best the life of an aviation engine is short, as compared
with that of an automobile, truck or tractor, and that shock resistance is of vital importance. A sclerescope
hardness of from 55 to 65 will give sufficient resistance to wear to prevent replacements during the life of
an aviation engine, while at the same time this hardness produces approximately 50 per cent greater
shock-resisting properties to the gear. In the case of the automobile, truck or tractor, resistance to wear is
the main criterion and for that reason the higher hardness is specified.
Great care should be taken in the design of an aviation engine gear to eliminate sharp corners at the
bottom of teeth as well as in keyways. Any change of section in any stressed part of an aviation engine
must have a radius of at least 1/32 in. to give proper shock and fatigue resistance. This fact has been
demonstrated many times during the Liberty engine program.
CONNECTING RODS
The material used for all connecting rods on the Liberty engine was selected at the option of the
manufacturer from one of two standard S. A. E. steels, the composition of which are given in Table 13.
TABLE 13.—COMPOSITION OF STEELS NOS. X-3,335 AND 6,135
Steel No. X-3,335 6,135
Carbon, minimum 0.300 0.300
Carbon, maximum 0.400 0.400
Manganese, minimum 0.450 0.500
Manganese, maximum 0.750 0.800
Phosphorus, maximum 0.040 0.040
Sulphur, maximum 0.045 0.045
Nickel, minimum 2.750
Nickel, maximum 3.250
Chromium, minimum 0.700 0.800
Chromium, maximum 0.950 1.100
Vanadium minimum 0.150
All connecting rods were heat-treated to show the following minimum physical properties; Elastic limit,
105,000 lb. per square inch: elongation in 2 in., 17.5; per cent, reduction of area 50.0; per cent., Brinell
hardness, 241 to 277.
The heat treatment used to secure these physical properties consisted in normalizing the forgings at a
temperature of from 1,550 to 1,600°F., followed by cooling in the furnace or in air. The forgings were then
quenched in oil from a temperature of from 1,420 to 1,440°F. for the No. X-3,335 steel, or from a
temperature of from 1,500 to 1,525°F. for No. 6,135 steel, followed by tempering at a temperature of from
1,075 to 1,150°F. At the option of the manufacturer, the normalizing treatment could be substituted by
quenching the forgings from a temperature of from 1,550 to 1,600°F., in oil, and annealing for the best
machineability at a temperature of from 1,300 to 1,350°F. The double quench, however, did not prove
satisfactory on No. X-3,335 steel, due to the fact that it was necessary to remove forgings from the
quenching bath while still at a temperature of from 300 to 500°F. to eliminate any possibility of cracking.
In view of the fact that this practice is difficult to carry out in the average heat-treating plant, considerable
trouble was experienced.
The most important criterion in the production of aviation engine connecting rods is the elimination of
burned or severely overheated forgings. Due to the particular design of the forked rod, considerable
Page 49
trouble was experienced in this respect because of the necessity of reheating the forgings before they are
completely forged. As a means of elimination of burned forgings, test lugs were forged on the channel
section as well as on the top end of fork. After the finish heat treatment, these test lugs were nicked and
broken and the fracture of the steel carefully examined. This precaution made it possible to eliminate
burned forgings as the test lugs were placed on sections which would be most likely to become burned.
There is a great difference of opinion among engineers as to what physical properties an aviation engine
connecting rod should have. Many of the most prominent engineers contend that a connecting rod should
be as stiff as possible. To produce rods in this manner in any quantity, it is necessary for the final heat
treatment to be made on the semi-machined rod. This practice would make it necessary for a larger
percentage of the semi-machined rods to be cold-straightened after the finish heat treatment. The cold-
straightening operation on a part having important functions to perform as a connecting rod is extremely
dangerous.
In view of the fact that a connecting rod functions as a strut, it is considered that this part should be only
stiff enough to prevent any whipping action during the running of the engine. The greater the fatigue-
resisting property that one can put into the rod after this stiffness is reached, the longer the life of the rod
will be. This is the reason for the Brinell limits mentioned being specified.
In connection with the connecting rod, emphasis must be laid on the importance of proper radii at all
changes of section. The connecting rods for the first few Liberty engines were machined with sharp
corners at the point where the connecting-rod bolt-head fits on assembly. On the first long endurance test
of a Liberty engine equipped with rods of this type, failure resulted from fatigue starting at this point. It is
interesting to note that every rod on the engine which did not completely fail at this point had started to
crack. The adoption of a 1/32-in. radius at this point completely eliminated fatigue failures on Liberty
rods.
CRANKSHAFT
The crankshaft was the most highly stressed part of the entire Liberty engine, and, therefore, every
metallurgical precaution was taken to guarantee the quality of this part. The material used for the greater
portion of the Liberty crankshafts produced was nickel-chromium steel of the following chemical
composition: Carbon, 0.350 to 0.450 per cent; manganese, 0.300 to 0.600 per cent; phosphorus, 0.040
maximum per cent; sulphur, 0.045 maximum per cent; nickel, 1.750 to 2.250 per cent; chromium, 0.700 to
0.900 per cent.
Each crankshaft was heat-treated to show the following minimum physical properties: Elastic limit,
116,000 lb. per square inch; elongation in 2 in., 16 per cent, reduction of area, 50 per cent, Izod impact, 34
ft.-lb.; Brinell hardness, 266 to 321.
For every increase of 4,000 lb. per square inch in the elastic limit above 116,000 lb. per square inch, the
minimum Izod impact required was reduced 1 ft.-lb.
The heat treatment used to produce these physical properties consisted in normalizing the forgings at a
temperature of from 1,550 to 1,600°F., followed by quenching in water at a temperature of from 1,475 to
1,525°F. and tempering at a temperature of from 1,000 to 1,100°F. It is absolutely necessary that the
crankshafts be removed from the quenching tank before being allowed to cool below a temperature of
500°F., and immediately placed in the tempering furnace to eliminate the possibility of quenching cracks.
A prolongation of not less than the diameter of the forging bearing was forged on one end of each
crankshaft. This was removed from the shaft after the finish heat treatment, and physical tests were made
on test specimens which were cut from it at a point half way between the center and the surface. One
tensile test and one impact test were made on each crankshaft, and the results obtained were recorded
completely forged. As a means of elimination of burned forgings, test lugs were forged on the channel
section as well as on the top end of fork. After the finish heat treatment, these test lugs were nicked and
broken and the fracture of the steel carefully examined. This precaution made it possible to eliminate
burned forgings as the test lugs were placed on sections which would be most likely to become burned.
There is a great difference of opinion among engineers as to what physical properties an aviation engine
connecting rod should have. Many of the most prominent engineers contend that a connecting rod should
be as stiff as possible. To produce rods in this manner in any quantity, it is necessary for the final heat
treatment to be made on the semi-machined rod. This practice would make it necessary for a larger
percentage of the semi-machined rods to be cold-straightened after the finish heat treatment. The cold-
straightening operation on a part having important functions to perform as a connecting rod is extremely
dangerous.
In view of the fact that a connecting rod functions as a strut, it is considered that this part should be only
stiff enough to prevent any whipping action during the running of the engine. The greater the fatigue-
resisting property that one can put into the rod after this stiffness is reached, the longer the life of the rod
will be. This is the reason for the Brinell limits mentioned being specified.
In connection with the connecting rod, emphasis must be laid on the importance of proper radii at all
changes of section. The connecting rods for the first few Liberty engines were machined with sharp
corners at the point where the connecting-rod bolt-head fits on assembly. On the first long endurance test
of a Liberty engine equipped with rods of this type, failure resulted from fatigue starting at this point. It is
interesting to note that every rod on the engine which did not completely fail at this point had started to
crack. The adoption of a 1/32-in. radius at this point completely eliminated fatigue failures on Liberty
rods.
CRANKSHAFT
The crankshaft was the most highly stressed part of the entire Liberty engine, and, therefore, every
metallurgical precaution was taken to guarantee the quality of this part. The material used for the greater
portion of the Liberty crankshafts produced was nickel-chromium steel of the following chemical
composition: Carbon, 0.350 to 0.450 per cent; manganese, 0.300 to 0.600 per cent; phosphorus, 0.040
maximum per cent; sulphur, 0.045 maximum per cent; nickel, 1.750 to 2.250 per cent; chromium, 0.700 to
0.900 per cent.
Each crankshaft was heat-treated to show the following minimum physical properties: Elastic limit,
116,000 lb. per square inch; elongation in 2 in., 16 per cent, reduction of area, 50 per cent, Izod impact, 34
ft.-lb.; Brinell hardness, 266 to 321.
For every increase of 4,000 lb. per square inch in the elastic limit above 116,000 lb. per square inch, the
minimum Izod impact required was reduced 1 ft.-lb.
The heat treatment used to produce these physical properties consisted in normalizing the forgings at a
temperature of from 1,550 to 1,600°F., followed by quenching in water at a temperature of from 1,475 to
1,525°F. and tempering at a temperature of from 1,000 to 1,100°F. It is absolutely necessary that the
crankshafts be removed from the quenching tank before being allowed to cool below a temperature of
500°F., and immediately placed in the tempering furnace to eliminate the possibility of quenching cracks.
A prolongation of not less than the diameter of the forging bearing was forged on one end of each
crankshaft. This was removed from the shaft after the finish heat treatment, and physical tests were made
on test specimens which were cut from it at a point half way between the center and the surface. One
tensile test and one impact test were made on each crankshaft, and the results obtained were recorded
Page 50
against the serial number of the shaft in question. This serial number was carried through all machining
operations and stamped on the cheek of the finished shaft. In addition to the above tensile and impact
tests, at least two Brinell hardness determinations were made on each shaft.
All straightening operations on the Liberty crankshaft which were performed below a temperature of
500°F. were followed by retempering at a temperature of approximately 200°F. below the original
tempering temperature.
Another illustration of the importance of proper radii at all changes of section is given in the case of the
Liberty crankshaft. The presence of tool marks or under cuts must be completely eliminated from an
aviation engine crankshaft to secure proper service. During the duration of the Liberty program, four
crankshafts failed from fatigue, failures starting from sharp corners at bottom of propeller-hub keyway.
Two of the shafts that failed showed torsional spirals running more than completely around the shaft. As
soon as this difficulty was removed no further trouble was experienced.
One of the most important difficulties encountered in connection with the production of Liberty
crankshafts was hair-line seams. The question of hair-line seams has been discussed to greater length by
engineers and metallurgists during the war than any other single question. Hair-line seams are caused by
small non-metallic inclusions in the steel. There is every reason to believe that these inclusions are in the
greater majority of cases manganese sulphide. There is a great difference of opinion as to the exact effect
of hair-line seams on the service of an aviation engine crankshaft. It is the opinion of many that hair-line
seams do not in any way affect the endurance of a crankshaft in service, provided they are parallel to the
grain of the steel and do not occur on a fillet. Of the 20,000 Liberty engines produced, fully 50 per cent of
the crankshafts used contain hair-line seams but not at the locations mentioned. There has never been a
failure of a Liberty crankshaft which could in any way be traced to hair-line seams.
It was found that hair-line seams occur generally on high nickel-chromium steels. One of the main
reasons why the comparatively mild analysis nickel-chromium steel was used was due to the very few
hair-line seams present in it. It was also determined that the hair lines will in general be found near the
surface of the forgings. For that reason, as much finish as possible was allowed for machining. A number
of tests have been made on forging bars to determine the depths at which hair-line seams are found, and
many cases came up in which hair-line seams were found 3/8 in. from the surface of the bar. This means
that in case a crankshaft does not show hair-line seams on the ground surface this is no indication that it is
free from such a defect.
One important peculiarity of nickel-chromium steel was brought out from the results obtained on impact
tests. This peculiarity is known as "blue brittleness." Just what the effect of this is on the service of a
finished part depends entirely upon the design of the particular part in question. There have been no
failures of any nickel-chromium steel parts in the automotive industry which could in any way be traced to
this phenomena.
Whether or not nickel-chromium-steel forgings will show "blue brittleness" depends entirely upon the
temperature at which they are tempered and their rate of cooling from this temperature. The danger range
for tempering nickel-chromium steels is between a temperature of from 400 to 1,100°F. From the data so
far gathered on this phenomena, it is necessary that the nickel-chromium steel to show "blue brittleness"
be made by the acid process. There has never come to my attention a single instance in which basic open
hearth steel has shown this phenomena. Just why the acid open hearth steel should be sensitive to "blue
brittleness" is not known.
All that is necessary to eliminate the presence of "blue brittleness" is to quench all nickel-chromium-
steel forgings in water from their tempering temperature. The last 20,000 Liberty crankshafts that were
made were quenched in this manner.
operations and stamped on the cheek of the finished shaft. In addition to the above tensile and impact
tests, at least two Brinell hardness determinations were made on each shaft.
All straightening operations on the Liberty crankshaft which were performed below a temperature of
500°F. were followed by retempering at a temperature of approximately 200°F. below the original
tempering temperature.
Another illustration of the importance of proper radii at all changes of section is given in the case of the
Liberty crankshaft. The presence of tool marks or under cuts must be completely eliminated from an
aviation engine crankshaft to secure proper service. During the duration of the Liberty program, four
crankshafts failed from fatigue, failures starting from sharp corners at bottom of propeller-hub keyway.
Two of the shafts that failed showed torsional spirals running more than completely around the shaft. As
soon as this difficulty was removed no further trouble was experienced.
One of the most important difficulties encountered in connection with the production of Liberty
crankshafts was hair-line seams. The question of hair-line seams has been discussed to greater length by
engineers and metallurgists during the war than any other single question. Hair-line seams are caused by
small non-metallic inclusions in the steel. There is every reason to believe that these inclusions are in the
greater majority of cases manganese sulphide. There is a great difference of opinion as to the exact effect
of hair-line seams on the service of an aviation engine crankshaft. It is the opinion of many that hair-line
seams do not in any way affect the endurance of a crankshaft in service, provided they are parallel to the
grain of the steel and do not occur on a fillet. Of the 20,000 Liberty engines produced, fully 50 per cent of
the crankshafts used contain hair-line seams but not at the locations mentioned. There has never been a
failure of a Liberty crankshaft which could in any way be traced to hair-line seams.
It was found that hair-line seams occur generally on high nickel-chromium steels. One of the main
reasons why the comparatively mild analysis nickel-chromium steel was used was due to the very few
hair-line seams present in it. It was also determined that the hair lines will in general be found near the
surface of the forgings. For that reason, as much finish as possible was allowed for machining. A number
of tests have been made on forging bars to determine the depths at which hair-line seams are found, and
many cases came up in which hair-line seams were found 3/8 in. from the surface of the bar. This means
that in case a crankshaft does not show hair-line seams on the ground surface this is no indication that it is
free from such a defect.
One important peculiarity of nickel-chromium steel was brought out from the results obtained on impact
tests. This peculiarity is known as "blue brittleness." Just what the effect of this is on the service of a
finished part depends entirely upon the design of the particular part in question. There have been no
failures of any nickel-chromium steel parts in the automotive industry which could in any way be traced to
this phenomena.
Whether or not nickel-chromium-steel forgings will show "blue brittleness" depends entirely upon the
temperature at which they are tempered and their rate of cooling from this temperature. The danger range
for tempering nickel-chromium steels is between a temperature of from 400 to 1,100°F. From the data so
far gathered on this phenomena, it is necessary that the nickel-chromium steel to show "blue brittleness"
be made by the acid process. There has never come to my attention a single instance in which basic open
hearth steel has shown this phenomena. Just why the acid open hearth steel should be sensitive to "blue
brittleness" is not known.
All that is necessary to eliminate the presence of "blue brittleness" is to quench all nickel-chromium-
steel forgings in water from their tempering temperature. The last 20,000 Liberty crankshafts that were
made were quenched in this manner.
Page 51
PISTON PIN
The piston pin on an aviation engine must possess maximum resistance to wear and to fatigue. For this
reason, the piston pin is considered, from a metallurgical standpoint, the most important part on the engine
to produce in quantities and still possess the above characteristics. The material used for the Liberty
engine piston pin was S. A. E. No. 2315 steel, which is of the following chemical composition: Carbon,
0.100 to 0.200 per cent; manganese, 0.500 to 0.800 per cent; phosphorus, 0.040 maximum per cent;
sulphur, 0.045 maximum per cent; nickel, 3.250 to 3.750 per cent.
Each finished piston pin, after heat treatment, must show a minimum scleroscope hardness of the case of
70, a scleroscope hardness of the core of from 35 to 55 and a minimum crushing strength when supported
as a beam and the load applied at the center of 35,000 lb. The heat treatment used to obtain the above
physical properties consisted in carburizing at a temperature not to exceed 1,675°F., for a sufficient length
of time to secure a case of from 0.02 to 0.04 in. deep. The pins are then allowed to cool slowly from the
carbonizing heat, after which the hole is finish-machined and the pin cut to length. The finish heat
treatment of the piston pin consisted in quenching in oil from a temperature of from 1,525 to 1,575°F. to
refine the grain of core properly and then quenching in oil at a temperature of from 1,340 to 1,380°F. to
refine and harden the grain of the case properly, as well as to secure proper hardness of core. After this
quenching, all piston pins are tempered in oil at a temperature of from 375 to 400°F. A 100 per cent
inspection for scleroscope hardness of the case and the core was made, and no failures were ever recorded
when the above material and heat treatment was used.
APPLICATION TO THE AUTOMOTIVE INDUSTRY
The information given on the various parts of the Liberty engine applies with equal force to the
corresponding parts in the construction of an automobile, truck or tractor. We recommend as first choice
for carbon-steel screw-machine parts material produced by the basic open hearth process and having the
following chemical composition; Carbon, 0.150 to 0.250 per cent; manganese, 0.500 to 0.800 per cent;
phosphorus, 0.045 maximum per cent; sulphur, 0.075 to 0.150 per cent.
This material is very uniform and is nearly as free cutting as bessemer screw stock. It is sufficiently
uniform to be used for unimportant carburized parts, as well as for non-heat-treated screw-machine parts.
A number of the large automobile manufacturers are now specifying this material in preference to the
regular bessemer grades.
As second choice for carbon-steel screw-machine parts we recommend ordinary bessemer screw stock,
purchased in accordance with S. A. E. specification No. 1114. The advantage of using No. 1114 steel lies
in the fact that the majority of warehouses carry standard sizes of this material in stock at all times. The
disadvantage of using this material is due to its lack of uniformity.
The important criterion for transmission gears is resistance to wear. To secure proper resistance to wear a
Brinell hardness of from 512 to 560 must be obtained. The material selected to obtain this hardness should
be one which can be made most nearly uniform, will undergo forging operations the easiest, will be the
hardest to overheat or burn, will machine best and will respond to a good commercial range of heat
treatment.
It is a well-known fact that the element chromium, when in the form of chromium carbide in alloy steel,
offers the greatest resistance to wear of any combination yet developed. It is also a well-known fact that
the element nickel in steel gives excellent shock-resisting properties as well as resistance to wear but not
nearly as great a resistance to wear as chromium. It has been standard practice for a number of years for
many manufacturers to use a high nickel-chromium steel for transmission gears. A typical nickel-
chromium gear specification is as follows: Carbon, 0.470 to 0.520 per cent; manganese, 0.500 to 0.800 per
The piston pin on an aviation engine must possess maximum resistance to wear and to fatigue. For this
reason, the piston pin is considered, from a metallurgical standpoint, the most important part on the engine
to produce in quantities and still possess the above characteristics. The material used for the Liberty
engine piston pin was S. A. E. No. 2315 steel, which is of the following chemical composition: Carbon,
0.100 to 0.200 per cent; manganese, 0.500 to 0.800 per cent; phosphorus, 0.040 maximum per cent;
sulphur, 0.045 maximum per cent; nickel, 3.250 to 3.750 per cent.
Each finished piston pin, after heat treatment, must show a minimum scleroscope hardness of the case of
70, a scleroscope hardness of the core of from 35 to 55 and a minimum crushing strength when supported
as a beam and the load applied at the center of 35,000 lb. The heat treatment used to obtain the above
physical properties consisted in carburizing at a temperature not to exceed 1,675°F., for a sufficient length
of time to secure a case of from 0.02 to 0.04 in. deep. The pins are then allowed to cool slowly from the
carbonizing heat, after which the hole is finish-machined and the pin cut to length. The finish heat
treatment of the piston pin consisted in quenching in oil from a temperature of from 1,525 to 1,575°F. to
refine the grain of core properly and then quenching in oil at a temperature of from 1,340 to 1,380°F. to
refine and harden the grain of the case properly, as well as to secure proper hardness of core. After this
quenching, all piston pins are tempered in oil at a temperature of from 375 to 400°F. A 100 per cent
inspection for scleroscope hardness of the case and the core was made, and no failures were ever recorded
when the above material and heat treatment was used.
APPLICATION TO THE AUTOMOTIVE INDUSTRY
The information given on the various parts of the Liberty engine applies with equal force to the
corresponding parts in the construction of an automobile, truck or tractor. We recommend as first choice
for carbon-steel screw-machine parts material produced by the basic open hearth process and having the
following chemical composition; Carbon, 0.150 to 0.250 per cent; manganese, 0.500 to 0.800 per cent;
phosphorus, 0.045 maximum per cent; sulphur, 0.075 to 0.150 per cent.
This material is very uniform and is nearly as free cutting as bessemer screw stock. It is sufficiently
uniform to be used for unimportant carburized parts, as well as for non-heat-treated screw-machine parts.
A number of the large automobile manufacturers are now specifying this material in preference to the
regular bessemer grades.
As second choice for carbon-steel screw-machine parts we recommend ordinary bessemer screw stock,
purchased in accordance with S. A. E. specification No. 1114. The advantage of using No. 1114 steel lies
in the fact that the majority of warehouses carry standard sizes of this material in stock at all times. The
disadvantage of using this material is due to its lack of uniformity.
The important criterion for transmission gears is resistance to wear. To secure proper resistance to wear a
Brinell hardness of from 512 to 560 must be obtained. The material selected to obtain this hardness should
be one which can be made most nearly uniform, will undergo forging operations the easiest, will be the
hardest to overheat or burn, will machine best and will respond to a good commercial range of heat
treatment.
It is a well-known fact that the element chromium, when in the form of chromium carbide in alloy steel,
offers the greatest resistance to wear of any combination yet developed. It is also a well-known fact that
the element nickel in steel gives excellent shock-resisting properties as well as resistance to wear but not
nearly as great a resistance to wear as chromium. It has been standard practice for a number of years for
many manufacturers to use a high nickel-chromium steel for transmission gears. A typical nickel-
chromium gear specification is as follows: Carbon, 0.470 to 0.520 per cent; manganese, 0.500 to 0.800 per
Page 52
cent; phosphorus, 0.040 maximum per cent; sulphur, 0.045 maximum per cent; chromium, 0.700 to 0.950
per cent.
There is no question but that a gear made from material of such an analysis will give excellent service.
However, it is possible to obtain the same quality of service and at the same time appreciably reduce the
cost of the finished part. The gear steel specified is of the air-hardening type. It is extremely sensitive to
secondary pipe, as well as seams, and is extremely difficult to forge and very easy to overheat. The heat-
treatment range is very wide, but the danger from quenching cracks is very great. In regard to the
machineability, this material is the hardest to machine of any alloy steel known.
COMPOSITION OF TRANSMISSION-GEAR STEEL
If the nickel content of this steel is eliminated, and the percentage of chromium raised slightly, an ideal
transmission-gear material is obtained. This would, therefore, be of the following composition: Carbon,
0.470 to 0.520 per cent; manganese, 0.500 to 0.800 per cent; phosphorus, 0.040 maximum per cent;
sulphur, 0.045 maximum per cent; chromium, 0.800 to 1.100 per cent.
The important criterion in connection with the use of this material is that the steel be properly
deoxidized, either through the use of ferrovanadium or its equivalent. Approximately 2,500 sets of
transmission gears are being made daily from material of this analysis and are giving entirely satisfactory
results in service. The heat treatment of the above material for transmission gears is as follows:
"Normalize forgings at a temperature of from 1,5.50 to 1,600°F. Cool from this temperature to a
temperature of 1,100°F. at the rate of 50° per hour. Cool from 1,100°F., either in air or quench in water."
Forgings so treated will show a Brinell hardness of from 177 to 217, which is the proper range for the
best machineability. The heat treatment of the finished gears consists of quenching in oil from a
temperature of 1,500 to 1,540°F., followed by tempering in oil at a temperature of from 375 to 425°F.
Gears so treated will show a Brinell hardness of from 512 to 560, or a scleroscope hardness of from 72 to
80. One tractor builder has placed in service 20,000 sets of gears of this type of material and has never had
to replace a gear. Taking into consideration the fact that a tractor transmission is subjected to the worst
possible service conditions, and that it is under high stress 90 per cent of the time, it seems inconceivable
that any appreciable transmission trouble would be experienced when material of this type is used on an
automobile, where the full load is applied not over 1 per cent of the time, or on trucks where the full load
is applied not over 50 per cent of the time.
The gear hardness specified is necessary to reduce to a minimum the pitting or surface fatigue of the
teeth. If gears having a Brinell hardness of over 560 are used, danger is encountered, due to low shock-
resisting properties. If the Brinell hardness is under 512, trouble is experienced due to wear and surface
fatigue of the teeth.
For ring gears and pinions material of the following chemical composition is recommended: Carbon,
0.100 to 0.200 per cent; manganese, 0.350 to 0.650 per cent; phosphorus, 0.040 maximum per cent;
sulphur, 0.045 maximum per cent; chromium, 0.550 to 0.750 per cent; nickel, 0.400 to 0.600 per cent.
Care should be taken to see that this material is properly deoxidized either by the use of ferrovanadium
or its equivalent. The advantage of using a material of the above type lies in the fact that it will produce a
satisfactory finished part with a very simple treatment. The heat treatment of ring gears and pinions is as
follows: "Carburize at a temperature of from 1,650 to 1,700°F. for a sufficient length of time to secure a
depth of case of from 1/32 to 3/64 in., and quench directly from carburizing heat in oil. Reheat to a
temperature of from 1,430 to 1,460°F. and quench in oil. Temper in oil at a temperature of from 375 to
425°F. The final quenching operation on a ring gear should be made on a fixture similar to the Gleason
press to reduce distortion to a minimum."
per cent.
There is no question but that a gear made from material of such an analysis will give excellent service.
However, it is possible to obtain the same quality of service and at the same time appreciably reduce the
cost of the finished part. The gear steel specified is of the air-hardening type. It is extremely sensitive to
secondary pipe, as well as seams, and is extremely difficult to forge and very easy to overheat. The heat-
treatment range is very wide, but the danger from quenching cracks is very great. In regard to the
machineability, this material is the hardest to machine of any alloy steel known.
COMPOSITION OF TRANSMISSION-GEAR STEEL
If the nickel content of this steel is eliminated, and the percentage of chromium raised slightly, an ideal
transmission-gear material is obtained. This would, therefore, be of the following composition: Carbon,
0.470 to 0.520 per cent; manganese, 0.500 to 0.800 per cent; phosphorus, 0.040 maximum per cent;
sulphur, 0.045 maximum per cent; chromium, 0.800 to 1.100 per cent.
The important criterion in connection with the use of this material is that the steel be properly
deoxidized, either through the use of ferrovanadium or its equivalent. Approximately 2,500 sets of
transmission gears are being made daily from material of this analysis and are giving entirely satisfactory
results in service. The heat treatment of the above material for transmission gears is as follows:
"Normalize forgings at a temperature of from 1,5.50 to 1,600°F. Cool from this temperature to a
temperature of 1,100°F. at the rate of 50° per hour. Cool from 1,100°F., either in air or quench in water."
Forgings so treated will show a Brinell hardness of from 177 to 217, which is the proper range for the
best machineability. The heat treatment of the finished gears consists of quenching in oil from a
temperature of 1,500 to 1,540°F., followed by tempering in oil at a temperature of from 375 to 425°F.
Gears so treated will show a Brinell hardness of from 512 to 560, or a scleroscope hardness of from 72 to
80. One tractor builder has placed in service 20,000 sets of gears of this type of material and has never had
to replace a gear. Taking into consideration the fact that a tractor transmission is subjected to the worst
possible service conditions, and that it is under high stress 90 per cent of the time, it seems inconceivable
that any appreciable transmission trouble would be experienced when material of this type is used on an
automobile, where the full load is applied not over 1 per cent of the time, or on trucks where the full load
is applied not over 50 per cent of the time.
The gear hardness specified is necessary to reduce to a minimum the pitting or surface fatigue of the
teeth. If gears having a Brinell hardness of over 560 are used, danger is encountered, due to low shock-
resisting properties. If the Brinell hardness is under 512, trouble is experienced due to wear and surface
fatigue of the teeth.
For ring gears and pinions material of the following chemical composition is recommended: Carbon,
0.100 to 0.200 per cent; manganese, 0.350 to 0.650 per cent; phosphorus, 0.040 maximum per cent;
sulphur, 0.045 maximum per cent; chromium, 0.550 to 0.750 per cent; nickel, 0.400 to 0.600 per cent.
Care should be taken to see that this material is properly deoxidized either by the use of ferrovanadium
or its equivalent. The advantage of using a material of the above type lies in the fact that it will produce a
satisfactory finished part with a very simple treatment. The heat treatment of ring gears and pinions is as
follows: "Carburize at a temperature of from 1,650 to 1,700°F. for a sufficient length of time to secure a
depth of case of from 1/32 to 3/64 in., and quench directly from carburizing heat in oil. Reheat to a
temperature of from 1,430 to 1,460°F. and quench in oil. Temper in oil at a temperature of from 375 to
425°F. The final quenching operation on a ring gear should be made on a fixture similar to the Gleason
press to reduce distortion to a minimum."
Page 53
One of the largest producers of ring gears and pinions in the automotive industry has been using this
material and treatment for the last 2 years, and is of the opinion that he is now producing the highest
quality product ever turned out by that plant.
On some designs of automobiles a large amount of trouble is experienced with the driving pinion. If the
material and heat treatment specified will not give satisfaction, rather than to change the design it is
possible to use the following analysis material, which will raise the cost of the finished part but will give
excellent service: Carbon, 0.100 to 0.200 per cent; manganese, 0.350 to 0.650 per cent; phosphorus, 0.040
maximum per cent; sulphur, 0.045 maximum per cent; nickel, 4.750 to 5.250 per cent.
The heat treatment of pinions produced from this material consists in carburizing at a temperature of
from 1,600 to 1,650°F. for a sufficient length of time to secure a depth of case from 1/32 to 3/64 in. The
pinions are then quenched in oil from a temperature of 1,500 to 1,525°F. to refine the grain of the core and
quenched in oil from a temperature of from 1,340 to 1,360°F. To refine and harden the case. The use of
this material however, is recommended only in an emergency, as high-nickel steel is very susceptible to
seams, secondary pipe and laminations.
The main criterion on rear-axle and pinion shafts, steering knuckles and arms and parts of this general
type is resistance to fatigue and torsion. The material recommended for parts of this character is either S.
A. E. No. 6135 or No. 3135 steel, which have the chemical composition given in Tables 9 and 7.
HEAT TREATMENT OF AXLES
Parts of this general type should be heat-treated to show the following minimum physical properties:
Elastic limit, 115,000 lb. per square inch; elongation in 2 in., 16 per cent; reduction of area, 50 per cent;
Brinell hardness, 277 to 321.
The heat treatment used to secure these physical properties consists in quenching from a temperature of
from 1,520 to 1,540°F. in water and tempering at a temperature of from 975 to 1,025°F. Where the axle
shaft is a forging, and in the case of steering knuckles and arms, this heat treatment should be preceded by
normalizing the forgings at a temperature of from 1,550 to 1,600°F. It will be noted that these physical
properties correspond to those worked out for an ideal aviation engine crankshaft. If parts of this type are
designed with proper sections, so that this range of physical properties can be used, the part in question
will give maximum service.
One of the most important developments during the Liberty engine program was the fact that it is not
necessary to use a high-analysis alloy steel to secure a finished part which will give proper service. This
fact should save the automotive industry millions of dollars on future production.
If the proper authority be given the metallurgical engineer to govern the handling of the steel from the
time it is purchased until it is assembled into finished product, mild-analysis steels can be used and the
quality of the finished product guaranteed. It was only through the careful adherence to these fundamental
principles that it was possible to produce 20,000 Liberty engines, which are considered to be the most
highly stressed mechanism ever produced, without the failure of a single engine from defective material or
heat treatment.
MAKING STEEL BALLS
Steel balls are made from rods or coils according to size, stock less than 9/16-in. comes in coils. Stock
5/8-in. and larger comes in rods. Ball stock is designated in thousandths so that 5/8-in. rods are known as
0.625-in. stock.
Steel for making balls of average size is made up of:
material and treatment for the last 2 years, and is of the opinion that he is now producing the highest
quality product ever turned out by that plant.
On some designs of automobiles a large amount of trouble is experienced with the driving pinion. If the
material and heat treatment specified will not give satisfaction, rather than to change the design it is
possible to use the following analysis material, which will raise the cost of the finished part but will give
excellent service: Carbon, 0.100 to 0.200 per cent; manganese, 0.350 to 0.650 per cent; phosphorus, 0.040
maximum per cent; sulphur, 0.045 maximum per cent; nickel, 4.750 to 5.250 per cent.
The heat treatment of pinions produced from this material consists in carburizing at a temperature of
from 1,600 to 1,650°F. for a sufficient length of time to secure a depth of case from 1/32 to 3/64 in. The
pinions are then quenched in oil from a temperature of 1,500 to 1,525°F. to refine the grain of the core and
quenched in oil from a temperature of from 1,340 to 1,360°F. To refine and harden the case. The use of
this material however, is recommended only in an emergency, as high-nickel steel is very susceptible to
seams, secondary pipe and laminations.
The main criterion on rear-axle and pinion shafts, steering knuckles and arms and parts of this general
type is resistance to fatigue and torsion. The material recommended for parts of this character is either S.
A. E. No. 6135 or No. 3135 steel, which have the chemical composition given in Tables 9 and 7.
HEAT TREATMENT OF AXLES
Parts of this general type should be heat-treated to show the following minimum physical properties:
Elastic limit, 115,000 lb. per square inch; elongation in 2 in., 16 per cent; reduction of area, 50 per cent;
Brinell hardness, 277 to 321.
The heat treatment used to secure these physical properties consists in quenching from a temperature of
from 1,520 to 1,540°F. in water and tempering at a temperature of from 975 to 1,025°F. Where the axle
shaft is a forging, and in the case of steering knuckles and arms, this heat treatment should be preceded by
normalizing the forgings at a temperature of from 1,550 to 1,600°F. It will be noted that these physical
properties correspond to those worked out for an ideal aviation engine crankshaft. If parts of this type are
designed with proper sections, so that this range of physical properties can be used, the part in question
will give maximum service.
One of the most important developments during the Liberty engine program was the fact that it is not
necessary to use a high-analysis alloy steel to secure a finished part which will give proper service. This
fact should save the automotive industry millions of dollars on future production.
If the proper authority be given the metallurgical engineer to govern the handling of the steel from the
time it is purchased until it is assembled into finished product, mild-analysis steels can be used and the
quality of the finished product guaranteed. It was only through the careful adherence to these fundamental
principles that it was possible to produce 20,000 Liberty engines, which are considered to be the most
highly stressed mechanism ever produced, without the failure of a single engine from defective material or
heat treatment.
MAKING STEEL BALLS
Steel balls are made from rods or coils according to size, stock less than 9/16-in. comes in coils. Stock
5/8-in. and larger comes in rods. Ball stock is designated in thousandths so that 5/8-in. rods are known as
0.625-in. stock.
Steel for making balls of average size is made up of:
Page 54
Carbon 0.95 to 1.05 per cent
Silicon 0.20 to 0.35 per cent
Manganese 0.30 to 0.45 per cent
Chromium 0.35 to 0.45 per cent
Sulphur and phosphorus not to exceed 0.025 per cent
For the larger sizes a typical analysis is:
Carbon 1.02 per cent
Silicon 0.21 per cent
Manganese 0.40 per cent
Chromium 0.65 per cent
Sulphur 0.026 per cent
Phosphorus 0.014 per cent
Balls 5/8 in. and below are formed cold on upsetting or heading machines, the stock use is as follows:
TABLE 14.—SIZES OF STOCK FOR FORMING
BALLS ON HEADER
Diameter of Diameter of Diameter of Diameter of
ball, inch stock inch ball, inch stock inch
1/8 0.100 5/16 0.235
5/32 0.120 3/8 0.275
3/16 0.145 7/16 0.320
7/32 0.170 1/2 0.365
1/4 0.190 9/16 0.395
9/32 0.220 5/8 0.440
For larger balls the blanks are hot-forged from straight bars. They are usually forged in multiples of four
under a spring hammer and then separated by a suitable punching or shearing die in a press adjoining the
hammer. The dimensions are:
Diameter of ball, Diameter of die, Diameter of stock,
inch inch inch
3/4 0.775 0.625
7/8 0.905 0.729
1 1.035 0.823
Before hardening, the balls are annealed to relieve the stresses of forging and grinding, this being done
by passing them through a revolving retort made of nichrome or other heat-resisting substance. The
annealing temperature is 1,300°F.
The hardening temperature is from 1,425 to 1,475°F. according to size and composition of steel. Small
balls, 5/16 and under, are quenched in oil, the larger sizes in water. In some special cases brine is used.
Quenching small balls in water is too great a shock as the small volume is cooled clear through almost
instantly. The larger balls have metal enough to cool more slowly.
Balls which are cooled in either water or brine are boiled in water for 2 hr. to relieve internal stresses,
after which the balls are finished by dry-grinding and oil-grinding.
Silicon 0.20 to 0.35 per cent
Manganese 0.30 to 0.45 per cent
Chromium 0.35 to 0.45 per cent
Sulphur and phosphorus not to exceed 0.025 per cent
For the larger sizes a typical analysis is:
Carbon 1.02 per cent
Silicon 0.21 per cent
Manganese 0.40 per cent
Chromium 0.65 per cent
Sulphur 0.026 per cent
Phosphorus 0.014 per cent
Balls 5/8 in. and below are formed cold on upsetting or heading machines, the stock use is as follows:
TABLE 14.—SIZES OF STOCK FOR FORMING
BALLS ON HEADER
Diameter of Diameter of Diameter of Diameter of
ball, inch stock inch ball, inch stock inch
1/8 0.100 5/16 0.235
5/32 0.120 3/8 0.275
3/16 0.145 7/16 0.320
7/32 0.170 1/2 0.365
1/4 0.190 9/16 0.395
9/32 0.220 5/8 0.440
For larger balls the blanks are hot-forged from straight bars. They are usually forged in multiples of four
under a spring hammer and then separated by a suitable punching or shearing die in a press adjoining the
hammer. The dimensions are:
Diameter of ball, Diameter of die, Diameter of stock,
inch inch inch
3/4 0.775 0.625
7/8 0.905 0.729
1 1.035 0.823
Before hardening, the balls are annealed to relieve the stresses of forging and grinding, this being done
by passing them through a revolving retort made of nichrome or other heat-resisting substance. The
annealing temperature is 1,300°F.
The hardening temperature is from 1,425 to 1,475°F. according to size and composition of steel. Small
balls, 5/16 and under, are quenched in oil, the larger sizes in water. In some special cases brine is used.
Quenching small balls in water is too great a shock as the small volume is cooled clear through almost
instantly. The larger balls have metal enough to cool more slowly.
Balls which are cooled in either water or brine are boiled in water for 2 hr. to relieve internal stresses,
after which the balls are finished by dry-grinding and oil-grinding.
Page 55
The ball makers have an interesting method of testing stock for seams which do not show in the rod or
wire. The Hoover Steel Ball Company cut off pieces of rod or wire 7/16 in. long and subject them to an
end pressure of from 20,000 to 50,000 lb. A pressure of 20,000 lb. compresses the piece to 3/16 in. and the
50,000 lb. pressure to 3/32 in. This opens any seam which may exist but a solid bar shows no seam.
Another method which has proved very successful is to pass the bar or rod to be tested through a
solenoid electro-magnet. With suitable instruments it is claimed that this is an almost infallible test as the
instruments show at once when a seam or flaw is present in the bar.
wire. The Hoover Steel Ball Company cut off pieces of rod or wire 7/16 in. long and subject them to an
end pressure of from 20,000 to 50,000 lb. A pressure of 20,000 lb. compresses the piece to 3/16 in. and the
50,000 lb. pressure to 3/32 in. This opens any seam which may exist but a solid bar shows no seam.
Another method which has proved very successful is to pass the bar or rod to be tested through a
solenoid electro-magnet. With suitable instruments it is claimed that this is an almost infallible test as the
instruments show at once when a seam or flaw is present in the bar.
Page 56
CHAPTER V
THE FORGING OF STEEL
So much depends upon the forging of steel that this operation must be carefully supervised. This is
especially true because of the tendency to place unskilled and ignorant men as furnace-tenders and
hammer men. The main points to be supervised are the slow and careful heating to the proper temperature;
forging must be continued at a proper rate to the correct temperature. The bar of stock from which a
forging was made may have had a fairly good structure, but if the details of the working are not carefully
watched, a seamy, split article of no value may easily result.
Heating.—Although it is possible to work steels cold, to an extent depending upon their ductility, and
although such operations are commonly performed, "forging" usually means working heated steel.
Heating is therefore a vital part of the process.
Heating should be done slowly in a soaking heat. A soft "lazy" flame with excess carbon is necessary to
avoid burning the corners of the bar or billet, and heavily scaling the surface. If the temperature is not
raised slowly, the outer part of the metal may be at welding heat while the inner part is several hundred
degrees colder and comparatively hard and brittle.
The above refers to muffle furnaces. If the heating is done in a small blacksmith's forge, the fire should
be kept clean, and remade at intervals of about two hours. Ashes and cinders should be cleaned from the
center down to the tuyere and oily waste and wood used to start a new fire. As this kindles a layer of coke
from the old fire is put on top, and another layer of green coal (screened and dampened blacksmiths' coal)
as a cover. When the green coal on top has been coked the fire is ready for use. As the fuel burns out in the
center, the coke forming around the edge is pushed inward, and its place taken by more green coal. Thus
the fire is made up of three parts; the center where coke is burning and the iron heating; a zone where coke
is forming, and the outside bank of green coal.
Steel Worked in Austenitic State.—As a general rule steel should be worked when it is in the austenitic
state. (See page 108.) It is then soft and ductile.
As the steel is heated above the critical temperature the size of the austenite crystals tends to grow
rapidly. When forging starts, however, these grains are broken up. The growth is continually destroyed by
the hammering, which should consequently be continued down to the upper critical temperature when the
austenite crystals break up into ferrite and cementite. The size of the final grains will be much smaller and
hence a more uniform structure will result if the "mother" austenite was also fine grained. A final steel will
be composed of pearlite; ferrite and pearlite; or cementite and pearlite, according to the carbon content.
The ultimate object is to secure a fine, uniform grain throughout the piece and this can be secured by
uniform heating and by thoroughly rolling it or working it at a temperature just down to its critical point.
If this is correctly done the fracture will be fine and silky. Steel which has been overheated slightly and
the forging stopped at too high a temperature will show a "granular" fracture. A badly overheated or
"burned" steel will have iridescent colors on a fresh fracture, it will be brittle both hot and cold, and
absolutely ruined.
THE FORGING OF STEEL
So much depends upon the forging of steel that this operation must be carefully supervised. This is
especially true because of the tendency to place unskilled and ignorant men as furnace-tenders and
hammer men. The main points to be supervised are the slow and careful heating to the proper temperature;
forging must be continued at a proper rate to the correct temperature. The bar of stock from which a
forging was made may have had a fairly good structure, but if the details of the working are not carefully
watched, a seamy, split article of no value may easily result.
Heating.—Although it is possible to work steels cold, to an extent depending upon their ductility, and
although such operations are commonly performed, "forging" usually means working heated steel.
Heating is therefore a vital part of the process.
Heating should be done slowly in a soaking heat. A soft "lazy" flame with excess carbon is necessary to
avoid burning the corners of the bar or billet, and heavily scaling the surface. If the temperature is not
raised slowly, the outer part of the metal may be at welding heat while the inner part is several hundred
degrees colder and comparatively hard and brittle.
The above refers to muffle furnaces. If the heating is done in a small blacksmith's forge, the fire should
be kept clean, and remade at intervals of about two hours. Ashes and cinders should be cleaned from the
center down to the tuyere and oily waste and wood used to start a new fire. As this kindles a layer of coke
from the old fire is put on top, and another layer of green coal (screened and dampened blacksmiths' coal)
as a cover. When the green coal on top has been coked the fire is ready for use. As the fuel burns out in the
center, the coke forming around the edge is pushed inward, and its place taken by more green coal. Thus
the fire is made up of three parts; the center where coke is burning and the iron heating; a zone where coke
is forming, and the outside bank of green coal.
Steel Worked in Austenitic State.—As a general rule steel should be worked when it is in the austenitic
state. (See page 108.) It is then soft and ductile.
As the steel is heated above the critical temperature the size of the austenite crystals tends to grow
rapidly. When forging starts, however, these grains are broken up. The growth is continually destroyed by
the hammering, which should consequently be continued down to the upper critical temperature when the
austenite crystals break up into ferrite and cementite. The size of the final grains will be much smaller and
hence a more uniform structure will result if the "mother" austenite was also fine grained. A final steel will
be composed of pearlite; ferrite and pearlite; or cementite and pearlite, according to the carbon content.
The ultimate object is to secure a fine, uniform grain throughout the piece and this can be secured by
uniform heating and by thoroughly rolling it or working it at a temperature just down to its critical point.
If this is correctly done the fracture will be fine and silky. Steel which has been overheated slightly and
the forging stopped at too high a temperature will show a "granular" fracture. A badly overheated or
"burned" steel will have iridescent colors on a fresh fracture, it will be brittle both hot and cold, and
absolutely ruined.
Page 57
FIG. 16.—A sound forging.
FIG. 17.—Burst from improper forging.
For making an occasional forging of a given size, a smaller hammer may be used than if we are
manufacturing this same piece in large quantities. If we have a 6-in. piece to forge, such as a pinion
or a short shaft, a hammer of about 1,100-lb. capacity would answer very nicely. But should the
general work be as large as this, it would be very much better to use a 1,500-lb. hammer. If, on the
other hand, we wish to forge 6-in. axles economically, it would be necessary to use a 7,000- or
8,000-lb. hammer. The following table will be found convenient for reference for the proper size of
hammer to be used on different classes of general blacksmith work, although it will be understood
that it is necessary to modify these to suit conditions, as has already been indicated.
FIG. 17.—Burst from improper forging.
For making an occasional forging of a given size, a smaller hammer may be used than if we are
manufacturing this same piece in large quantities. If we have a 6-in. piece to forge, such as a pinion
or a short shaft, a hammer of about 1,100-lb. capacity would answer very nicely. But should the
general work be as large as this, it would be very much better to use a 1,500-lb. hammer. If, on the
other hand, we wish to forge 6-in. axles economically, it would be necessary to use a 7,000- or
8,000-lb. hammer. The following table will be found convenient for reference for the proper size of
hammer to be used on different classes of general blacksmith work, although it will be understood
that it is necessary to modify these to suit conditions, as has already been indicated.
Page 58
FIG. 18.—Burst from a piped center.
FIG. 19.—Result of using too light a hammer.
Diameter of stock Size of hammer
3½ in. 250 to 350 lb.
4 in. 350 to 600 lb.
4½ in. 600 to 800 lb.
5 in. 800 to 1,000 lb.
6 in. 1,100 to 1,500 lb.
Steam hammers are always rated by the weight of the ram, and the attached parts, which include
the piston and rod, nothing being added on account of the steam pressure behind the piston. This
makes it a little difficult to compare them with plain drop or tilting hammers, which are also rated in
the same way.
FIG. 19.—Result of using too light a hammer.
Diameter of stock Size of hammer
3½ in. 250 to 350 lb.
4 in. 350 to 600 lb.
4½ in. 600 to 800 lb.
5 in. 800 to 1,000 lb.
6 in. 1,100 to 1,500 lb.
Steam hammers are always rated by the weight of the ram, and the attached parts, which include
the piston and rod, nothing being added on account of the steam pressure behind the piston. This
makes it a little difficult to compare them with plain drop or tilting hammers, which are also rated in
the same way.
Page 59
FIG. 20.—Good and bad ingots.
Steam hammers are usually operated at pressures varying from 75 to 100 lb. of steam per square
inch, and may also be operated by compressed air at about the same pressures. It is cheaper,
however, in the case of compressed air to use pressures from 60 to 80 lb. instead of going higher.
Forgings must, however, be made from sound billets if satisfactory results are to be secured.
Figure 20 shows three cross-sections of which A is sound, B is badly piped and C is worthless.
PLANT FOR FORGING RIFLE BARRELS
The forging of rifle barrels in large quantities and heat-treating them to meet the specifications
demanded by some of the foreign governments led Wheelock, Lovejoy & Company to establish a
complete plant for this purpose in connection with their warehouse in Cambridge, Mass. This plant,
designed and constructed by their chief engineer, K. A. Juthe, had many interesting features. Many
features of this plant can be modified for other classes of work.
FIG. 21.—Cutting up barrels.
Steam hammers are usually operated at pressures varying from 75 to 100 lb. of steam per square
inch, and may also be operated by compressed air at about the same pressures. It is cheaper,
however, in the case of compressed air to use pressures from 60 to 80 lb. instead of going higher.
Forgings must, however, be made from sound billets if satisfactory results are to be secured.
Figure 20 shows three cross-sections of which A is sound, B is badly piped and C is worthless.
PLANT FOR FORGING RIFLE BARRELS
The forging of rifle barrels in large quantities and heat-treating them to meet the specifications
demanded by some of the foreign governments led Wheelock, Lovejoy & Company to establish a
complete plant for this purpose in connection with their warehouse in Cambridge, Mass. This plant,
designed and constructed by their chief engineer, K. A. Juthe, had many interesting features. Many
features of this plant can be modified for other classes of work.
FIG. 21.—Cutting up barrels.
Page 60
FIG.
22.—Upsetting the ends.
The stock, which came in bars of mill length, was cut off so as to make a barrel with the proper
allowances for trimming (Fig. 21). They then pass to the forging or upsetting press in the adjoining
room. This press, which is shown in more detail in Fig. 22, handled the barrels from all the heating
furnaces shown. The men changed work at frequent intervals, to avoid excessive fatigue.
FIG. 23.—Continuous heating furnace.
Then the barrels were reheated in the continuous furnace, shown in Fig. 23, and straightened
before being tested.
The barrels were next tested for straightness. After the heat-treating, the ends are ground, a spot
ground on the enlarged end and each barrel tested on a Brinell machine. The pressure used is 3,000
kg., or 6,614 lb., on a 10-millimeter ball, which is standard. Hardness of 240 was desired.
22.—Upsetting the ends.
The stock, which came in bars of mill length, was cut off so as to make a barrel with the proper
allowances for trimming (Fig. 21). They then pass to the forging or upsetting press in the adjoining
room. This press, which is shown in more detail in Fig. 22, handled the barrels from all the heating
furnaces shown. The men changed work at frequent intervals, to avoid excessive fatigue.
FIG. 23.—Continuous heating furnace.
Then the barrels were reheated in the continuous furnace, shown in Fig. 23, and straightened
before being tested.
The barrels were next tested for straightness. After the heat-treating, the ends are ground, a spot
ground on the enlarged end and each barrel tested on a Brinell machine. The pressure used is 3,000
kg., or 6,614 lb., on a 10-millimeter ball, which is standard. Hardness of 240 was desired.
Page 61
The heat-treating of the rifle blanks covered four separate operations: (1) Heating and soaking the
steel above the critical temperature and quenching in oil to harden the steel through to the center;
(2) reheating for drawing of temper for the purpose of meeting the physical specifications; (3)
reheating to meet the machine ability test for production purposes; and (4) reheating to straighten
the blanks while hot.
A short explanation of the necessity for the many heats may be interesting. For the first heat, the
blanks were slowly brought to the required heat, which is about 150°F. above the critical
temperature. They are then soaked at a high heat for about 1 hr. before quenching. The purpose of
this treatment is to eliminate any rolling or heat stresses that might be in the bars from mill
operations; also to insure a thorough even heat through a cross-section of the steel. This heat also
causes blanks with seams or slight flaws to open up in quenching, making detection of defective
blanks very easy.
The quenching oil was kept at a constant temperature of 100°F., to avoid subjecting the steel to
shocks, thereby causing surface cracks. The drawing of temper was the most critical operation and
was kept within a 10° fluctuation. The degree of heat necessary depends entirely on the analysis of
the steel, there being a certain variation in the different heats of steel as received from the mill.
MACHINEABILITY
Reheating for machine ability was done at 100° less than the drawing temperature, but the time of
soaking is more than double. After both drawing and reheating, the blanks were buried in lime
where they remain, out of contact with the air, until their temperature had dropped to that of the
workroom.
For straightening, the barrels were heated to from 900 to 1,000°F. in an automatic furnace 25 ft.
long, this operation taking about 2 hr. The purpose of hot straightening was to prevent any stresses
being put into the blanks, so that after rough-turning, drilling or rifling operations they would not
have a tendency to spring back to shape as left by the quenching bath.
A method that produces an even better machining rifle blank, which practically stays straight
through the different machining operations, was to rough-turn the blanks, then subject them to a
heat of practically 1,0000 for 4 hr. Production throughout the different operations is materially
increased, with practically no straightening required after drilling, reaming, finish-turning or rifling
operations.
steel above the critical temperature and quenching in oil to harden the steel through to the center;
(2) reheating for drawing of temper for the purpose of meeting the physical specifications; (3)
reheating to meet the machine ability test for production purposes; and (4) reheating to straighten
the blanks while hot.
A short explanation of the necessity for the many heats may be interesting. For the first heat, the
blanks were slowly brought to the required heat, which is about 150°F. above the critical
temperature. They are then soaked at a high heat for about 1 hr. before quenching. The purpose of
this treatment is to eliminate any rolling or heat stresses that might be in the bars from mill
operations; also to insure a thorough even heat through a cross-section of the steel. This heat also
causes blanks with seams or slight flaws to open up in quenching, making detection of defective
blanks very easy.
The quenching oil was kept at a constant temperature of 100°F., to avoid subjecting the steel to
shocks, thereby causing surface cracks. The drawing of temper was the most critical operation and
was kept within a 10° fluctuation. The degree of heat necessary depends entirely on the analysis of
the steel, there being a certain variation in the different heats of steel as received from the mill.
MACHINEABILITY
Reheating for machine ability was done at 100° less than the drawing temperature, but the time of
soaking is more than double. After both drawing and reheating, the blanks were buried in lime
where they remain, out of contact with the air, until their temperature had dropped to that of the
workroom.
For straightening, the barrels were heated to from 900 to 1,000°F. in an automatic furnace 25 ft.
long, this operation taking about 2 hr. The purpose of hot straightening was to prevent any stresses
being put into the blanks, so that after rough-turning, drilling or rifling operations they would not
have a tendency to spring back to shape as left by the quenching bath.
A method that produces an even better machining rifle blank, which practically stays straight
through the different machining operations, was to rough-turn the blanks, then subject them to a
heat of practically 1,0000 for 4 hr. Production throughout the different operations is materially
increased, with practically no straightening required after drilling, reaming, finish-turning or rifling
operations.
Page 62
FIG. 24.
FIG. 25.
FIGS. 24 and 25.—Roof system of cooling quenching oil.
This method was tested out by one of the largest manufacturers and proved to be the best way to
eliminate a very expensive finished gun-barrel straightening process.
FIG. 25.
FIGS. 24 and 25.—Roof system of cooling quenching oil.
This method was tested out by one of the largest manufacturers and proved to be the best way to
eliminate a very expensive finished gun-barrel straightening process.
Page 63
FIG. 26.—Details of the cooler.
The heat-treating required a large amount of cooling oil, and the problem of keeping this at the
proper temperature required considerable study. The result was the cooling plant on the roof, as
shown in Figs. 24, 25 and 26. The first two illustrations show the plant as it appeared complete.
Figure 26 shows how the oil was handled in what is sometimes called the ebulator system. The oil
was pumped up from the cooling tanks through the pipe A to the tank B. From here it ran down onto
the breakers or separators C, which break the oil up into fine particles that are caught by the fans D.
The spray is blown up into the cooling tower E, which contains banks of cooling pipes, as can be
seen, as well as baffies F. The spray collects on the cool pipes and forms drops, which fall on the
curved plates G and run back to the oil-storage tank below ground.
The water for this cooling was pumped from 10 artesian wells at the rate of 60 gal. per minute and
cooled 90 gal. of oil per minute, lowering the temperature from 130 or 140 to 100°F. The water as it
came from the wells averaged around 52°F. The motor was of a 7½-hp. variable-speed type with a
range of from 700 to 1,200 r.p.m., which could be varied to suit the amount of oil to be cooled. The
plant handled 300 gal. of oil per minute.
The heat-treating required a large amount of cooling oil, and the problem of keeping this at the
proper temperature required considerable study. The result was the cooling plant on the roof, as
shown in Figs. 24, 25 and 26. The first two illustrations show the plant as it appeared complete.
Figure 26 shows how the oil was handled in what is sometimes called the ebulator system. The oil
was pumped up from the cooling tanks through the pipe A to the tank B. From here it ran down onto
the breakers or separators C, which break the oil up into fine particles that are caught by the fans D.
The spray is blown up into the cooling tower E, which contains banks of cooling pipes, as can be
seen, as well as baffies F. The spray collects on the cool pipes and forms drops, which fall on the
curved plates G and run back to the oil-storage tank below ground.
The water for this cooling was pumped from 10 artesian wells at the rate of 60 gal. per minute and
cooled 90 gal. of oil per minute, lowering the temperature from 130 or 140 to 100°F. The water as it
came from the wells averaged around 52°F. The motor was of a 7½-hp. variable-speed type with a
range of from 700 to 1,200 r.p.m., which could be varied to suit the amount of oil to be cooled. The
plant handled 300 gal. of oil per minute.
Page 64
CHAPTER VI
ANNEALING
There is no mystery or secret about the proper annealing of different steels, but in order to secure
the best results it is absolutely necessary for the operator to know the kind of steel which is to be
annealed. The annealing of steel is primarily done for one of three specific purposes: To soften for
machining purposes; to change the physical properties, largely to increase ductility; or to release
strains caused by rolling or forging.
Proper annealing means the heating of the steel slowly and uniformly to the right temperature, the
holding of the temperature for a given period and the gradual cooling to normal temperature. The
proper temperature depends on the kind of steel, and the suggestions of the maker of the special
steel being used should be carefully followed. For carbon steel the temperatures recommended for
annealing vary from 1,450 to 1,600°F. This temperature need not be long continued. The steel
should be cooled in hot sand, lime or ashes. If heated in the open forge the steel should be buried in
the cooling material as quickly as possible, not allowing it to remain in the open air any longer than
absolutely necessary. Best results, however, are secured when the fire does not come in direct
contact with the steel.
Good results are obtained by packing the steel in iron boxes or tubes, much as for case-hardening
or carbonizing, using the same materials. Pieces do not require to be entirely surrounded by carbon
for annealing, however. Do not remove from boxes until cold.
Steel to be annealed may be classified into four different groups, each of which must be treated
according to the elements contained in its particular analysis. Different methods are therefore
necessary to bring about the desired result. The classifications are as follows: High-speed steel,
alloy steel, tool or crucible steel, and high-carbon machinery steel.
ANNEALING OF HIGH-SPEED STEEL
For annealing high-speed steel, some makers recommend using ground mica, charcoal, lime, fine
dry ashes or lake sand as a packing in the annealing boxes. Mixtures of one part charcoal, one part
lime and three parts of sand are also suggested, or two parts of ashes may be substituted for the one
part of lime.
To bring about the softest structure or machine ability of high-speed steel, it should be packed in
charcoal in boxes or pipes, carefully sealed at all points, so that no gases will escape or air be
admitted. It should be heated slowly to not less than 1,450°F. and the steel must not be removed
from its packing until it is cool. Slow heating means that the high heat must have penetrated to the
very core of the steel.
ANNEALING
There is no mystery or secret about the proper annealing of different steels, but in order to secure
the best results it is absolutely necessary for the operator to know the kind of steel which is to be
annealed. The annealing of steel is primarily done for one of three specific purposes: To soften for
machining purposes; to change the physical properties, largely to increase ductility; or to release
strains caused by rolling or forging.
Proper annealing means the heating of the steel slowly and uniformly to the right temperature, the
holding of the temperature for a given period and the gradual cooling to normal temperature. The
proper temperature depends on the kind of steel, and the suggestions of the maker of the special
steel being used should be carefully followed. For carbon steel the temperatures recommended for
annealing vary from 1,450 to 1,600°F. This temperature need not be long continued. The steel
should be cooled in hot sand, lime or ashes. If heated in the open forge the steel should be buried in
the cooling material as quickly as possible, not allowing it to remain in the open air any longer than
absolutely necessary. Best results, however, are secured when the fire does not come in direct
contact with the steel.
Good results are obtained by packing the steel in iron boxes or tubes, much as for case-hardening
or carbonizing, using the same materials. Pieces do not require to be entirely surrounded by carbon
for annealing, however. Do not remove from boxes until cold.
Steel to be annealed may be classified into four different groups, each of which must be treated
according to the elements contained in its particular analysis. Different methods are therefore
necessary to bring about the desired result. The classifications are as follows: High-speed steel,
alloy steel, tool or crucible steel, and high-carbon machinery steel.
ANNEALING OF HIGH-SPEED STEEL
For annealing high-speed steel, some makers recommend using ground mica, charcoal, lime, fine
dry ashes or lake sand as a packing in the annealing boxes. Mixtures of one part charcoal, one part
lime and three parts of sand are also suggested, or two parts of ashes may be substituted for the one
part of lime.
To bring about the softest structure or machine ability of high-speed steel, it should be packed in
charcoal in boxes or pipes, carefully sealed at all points, so that no gases will escape or air be
admitted. It should be heated slowly to not less than 1,450°F. and the steel must not be removed
from its packing until it is cool. Slow heating means that the high heat must have penetrated to the
very core of the steel.
Page 65
When the steel is heated clear through it has been in the furnace long enough. If the steel can
remain in the furnace and cool down with it, there will be no danger of air blasts or sudden or
uneven cooling. If not, remove the box and cover quickly with dry ashes, sand or lime until it
becomes cold.
Too high a heat or maintaining the heat for too long a period, produces a harsh, coarse grain and
greatly increases the liability to crack in hardening. It also reduces the strength and toughness of the
steel.
Steel which is to be used for making tools with teeth, such as taps, reamers and milling cutters,
should not be annealed too much. When the steel is too soft it is more apt to tear in cutting and
makes it more difficult to cut a smooth thread or other surface. Moderate annealing is found best for
tools of this kind.
TOOL OR CRUCIBLE STEEL
Crucible steel can be annealed either in muffled furnace or by being packed. Packing is by far the
most satisfactory method as it prevents scaling, local hard spots, uneven annealing, or violent
changes in shape. It should be brought up slowly to just above its calescent or hardening
temperature. The operator must know before setting his heats the temperature at which the different
carbon content steels are hardened. The higher the carbon contents the lower is the hardening heat,
but this should in no case be less than 1,450°F.
ANNEALING ALLOY STEEL
The term alloy steel, from the steel maker's point of view, refers largely to nickel and chromium
steel or a combination of both. These steels are manufactured very largely by the open-hearth
process, although chromium steels are also a crucible product. It is next to impossible to give proper
directions for the proper annealing of alloy steel unless the composition is known to the operator.
Nickel steels may be annealed at lower temperatures than carbon steels, depending upon their
alloy content. For instance, if a pearlitic carbon steel may be annealed at 1,450°C., the same
analysis containing 2½ per cent nickel may be annealed at 1,360°C. and a 5 per cent nickel steel at
1,270°.
In order that high chromium steels may be readily machined, they must be heated at or slightly
above the critical for a very long time, and cooled through the critical at an extremely slow rate. For
a steel containing 0.9 to 1.1 per cent carbon, under 0.50 per cent manganese, and about 1.0 per cent
chromium, Bullens recommends the following anneal:
1. Heat to 1,700 or 1,750°F.
2. Air cool to about 800°F.
3. Soak at 1,425 to 1,450°F.
4. Cool slowly in furnace.
HIGH-CARBON MACHINERY STEEL
remain in the furnace and cool down with it, there will be no danger of air blasts or sudden or
uneven cooling. If not, remove the box and cover quickly with dry ashes, sand or lime until it
becomes cold.
Too high a heat or maintaining the heat for too long a period, produces a harsh, coarse grain and
greatly increases the liability to crack in hardening. It also reduces the strength and toughness of the
steel.
Steel which is to be used for making tools with teeth, such as taps, reamers and milling cutters,
should not be annealed too much. When the steel is too soft it is more apt to tear in cutting and
makes it more difficult to cut a smooth thread or other surface. Moderate annealing is found best for
tools of this kind.
TOOL OR CRUCIBLE STEEL
Crucible steel can be annealed either in muffled furnace or by being packed. Packing is by far the
most satisfactory method as it prevents scaling, local hard spots, uneven annealing, or violent
changes in shape. It should be brought up slowly to just above its calescent or hardening
temperature. The operator must know before setting his heats the temperature at which the different
carbon content steels are hardened. The higher the carbon contents the lower is the hardening heat,
but this should in no case be less than 1,450°F.
ANNEALING ALLOY STEEL
The term alloy steel, from the steel maker's point of view, refers largely to nickel and chromium
steel or a combination of both. These steels are manufactured very largely by the open-hearth
process, although chromium steels are also a crucible product. It is next to impossible to give proper
directions for the proper annealing of alloy steel unless the composition is known to the operator.
Nickel steels may be annealed at lower temperatures than carbon steels, depending upon their
alloy content. For instance, if a pearlitic carbon steel may be annealed at 1,450°C., the same
analysis containing 2½ per cent nickel may be annealed at 1,360°C. and a 5 per cent nickel steel at
1,270°.
In order that high chromium steels may be readily machined, they must be heated at or slightly
above the critical for a very long time, and cooled through the critical at an extremely slow rate. For
a steel containing 0.9 to 1.1 per cent carbon, under 0.50 per cent manganese, and about 1.0 per cent
chromium, Bullens recommends the following anneal:
1. Heat to 1,700 or 1,750°F.
2. Air cool to about 800°F.
3. Soak at 1,425 to 1,450°F.
4. Cool slowly in furnace.
HIGH-CARBON MACHINERY STEEL
Page 66
The carbon content of this steel is above 30 points and is hardly ever above 60 points or 0.60 per
cent. Annealing such steel is generally in quantity production and does not require the care that the
other steels need because it is very largely a much cheaper product and a great deal of material is
generally removed from the outside surface.
The purpose for which this steel is annealed is a deciding factor as to what heat to give it. If it is
for machineability only, the steel requires to be brought up slowly to just below the critical and then
slowly cooled in the furnace or ash pit. It must be thoroughly covered so that there will be no access
of cool air. If the annealing is to increase ductility to the maximum extent it should be slowly heated
to slightly over the upper critical temperature and kept at this heat for a length of time necessary for
a thorough penetration to the core, after which it can be cooled to about 1,200°F., then reheated to
about 1,360°F., when it can be removed and put in an ash pit or covered with lime. If the annealing
is just to relieve strains, slow heating is not necessary, but the steel must be brought up to a
temperature not much less than a forging or rolling heat and gradually cooled. Covering in this case
is only necessary in steel of a carbon content of more than 40 points.
ANNEALING IN BONE
Steel and cast iron may both be annealed in granulated bone. Pack the work the same as for case-
hardening except that it is not necessary to keep the pieces away from each other. Pack with bone
that has been used until it is nearly white. Heat as hot as necessary for the steel and let the furnace
cool down. If the boxes are removed from furnace while still warm, cover boxes and all in warm
ashes or sand, air slaked lime or old, burned bone to retain heat as long as possible. Do not remove
work from boxes until cold.
ANNEALING OF RIFLE COMPONENTS AT SPRINGFIELD ARMORY
In general, all forgings of the components of the arms manufactured at the Armory and all forgings
for other ordnance establishments are packed in charcoal, lime or suitable material and annealed
before being transferred from the forge shop.
Except in special cases, all annealing will be done in annealing pots of appropriate size. One fire
end of a thermo-couple is inserted in the center of the annealing pot nearest the middle of the
furnace and another in the furnace outside of but near the annealing pots.
The temperatures used in annealing carbon steel components of the various classes used at the
Armory vary from 800°C. To 880°C. or 1,475 to 1,615°F.
The fuel is shut off from the annealing furnace gradually as the temperature of the pot approaches
the prescribed annealing temperature so as to prevent heating beyond that temperature.
The forgings of the rifle barrel and the pistol barrel are exceptions to the above general rule. These
forgings will be packed in lime and allowed to cool slowly from the residual heat after forging.
cent. Annealing such steel is generally in quantity production and does not require the care that the
other steels need because it is very largely a much cheaper product and a great deal of material is
generally removed from the outside surface.
The purpose for which this steel is annealed is a deciding factor as to what heat to give it. If it is
for machineability only, the steel requires to be brought up slowly to just below the critical and then
slowly cooled in the furnace or ash pit. It must be thoroughly covered so that there will be no access
of cool air. If the annealing is to increase ductility to the maximum extent it should be slowly heated
to slightly over the upper critical temperature and kept at this heat for a length of time necessary for
a thorough penetration to the core, after which it can be cooled to about 1,200°F., then reheated to
about 1,360°F., when it can be removed and put in an ash pit or covered with lime. If the annealing
is just to relieve strains, slow heating is not necessary, but the steel must be brought up to a
temperature not much less than a forging or rolling heat and gradually cooled. Covering in this case
is only necessary in steel of a carbon content of more than 40 points.
ANNEALING IN BONE
Steel and cast iron may both be annealed in granulated bone. Pack the work the same as for case-
hardening except that it is not necessary to keep the pieces away from each other. Pack with bone
that has been used until it is nearly white. Heat as hot as necessary for the steel and let the furnace
cool down. If the boxes are removed from furnace while still warm, cover boxes and all in warm
ashes or sand, air slaked lime or old, burned bone to retain heat as long as possible. Do not remove
work from boxes until cold.
ANNEALING OF RIFLE COMPONENTS AT SPRINGFIELD ARMORY
In general, all forgings of the components of the arms manufactured at the Armory and all forgings
for other ordnance establishments are packed in charcoal, lime or suitable material and annealed
before being transferred from the forge shop.
Except in special cases, all annealing will be done in annealing pots of appropriate size. One fire
end of a thermo-couple is inserted in the center of the annealing pot nearest the middle of the
furnace and another in the furnace outside of but near the annealing pots.
The temperatures used in annealing carbon steel components of the various classes used at the
Armory vary from 800°C. To 880°C. or 1,475 to 1,615°F.
The fuel is shut off from the annealing furnace gradually as the temperature of the pot approaches
the prescribed annealing temperature so as to prevent heating beyond that temperature.
The forgings of the rifle barrel and the pistol barrel are exceptions to the above general rule. These
forgings will be packed in lime and allowed to cool slowly from the residual heat after forging.
Page 67
CHAPTER VII
CASE-HARDENING OR SURFACE-CARBURIZING
Carburizing, commonly called case-hardening, is the art of producing a high-carbon surface, or
case, upon a low carbon steel article. Wrenches, locomotive link motions, gun mechanisms, balls
and ball races, automobile gears and many other devices are thereby given a high-carbon case
capable of assuming extreme hardness, while the interior body of metal, the core, remains soft and
tough.
The simplest method is to heat the piece to be hardened to a bright red, dip it in cyanide of
potassium (or cover it by sprinkling the cyanide over it), keep it hot until the melted cyanide covers
it thoroughly, and quench in water. Carbon and nitrogen enter the outer skin of the steel and harden
this skin but leave the center soft. The hard surface or "case" varies in thickness according to the
size of the piece, the materials used and the length of time which the piece remains at the
carburizing temperature. Cyanide case-hardening is used only where a light or thin skin is
sufficient. It gives a thickness of about 0.002 in.
In some cases of cyanide carburizing, the piece is heated in cyanide to the desired temperature and
then quenched. For a thicker case the steel is packed in carbon materials of various kinds such as
burnt leather scraps, charcoal, granulated bone or some of the many carbonizing compounds.
Machined or forged steel parts are packed with case-hardening material in metal boxes and
subjected to a red heat. Under such conditions, carbon is absorbed by the steel surfaces, and a
carburized case is produced capable of responding to ordinary hardening and tempering operations,
the core meanwhile retaining its original softness and toughness.
Such case-hardened parts are stronger, cheaper, and more serviceable than similar parts made of
tool steel. The tough core resists breakage by shock. The hardened case resists wear from friction.
The low cost of material, the ease of manufacture, and the lessened breakage in quenching all serve
to promote cheap production.
For successful carburizing, the following points should be carefully observed:
The utmost care should be used in the selection of pots for carburizing; they should be as free as
possible from both scaling and warping. These two requirements eliminate the cast iron pot,
although many are used, thus leaving us to select from malleable castings, wrought iron, cast steel,
and special alloys, such as nichrome or silchrome. If first cost is not important, it will prove cheaper
in the end to use pots of some special alloy.
CASE-HARDENING OR SURFACE-CARBURIZING
Carburizing, commonly called case-hardening, is the art of producing a high-carbon surface, or
case, upon a low carbon steel article. Wrenches, locomotive link motions, gun mechanisms, balls
and ball races, automobile gears and many other devices are thereby given a high-carbon case
capable of assuming extreme hardness, while the interior body of metal, the core, remains soft and
tough.
The simplest method is to heat the piece to be hardened to a bright red, dip it in cyanide of
potassium (or cover it by sprinkling the cyanide over it), keep it hot until the melted cyanide covers
it thoroughly, and quench in water. Carbon and nitrogen enter the outer skin of the steel and harden
this skin but leave the center soft. The hard surface or "case" varies in thickness according to the
size of the piece, the materials used and the length of time which the piece remains at the
carburizing temperature. Cyanide case-hardening is used only where a light or thin skin is
sufficient. It gives a thickness of about 0.002 in.
In some cases of cyanide carburizing, the piece is heated in cyanide to the desired temperature and
then quenched. For a thicker case the steel is packed in carbon materials of various kinds such as
burnt leather scraps, charcoal, granulated bone or some of the many carbonizing compounds.
Machined or forged steel parts are packed with case-hardening material in metal boxes and
subjected to a red heat. Under such conditions, carbon is absorbed by the steel surfaces, and a
carburized case is produced capable of responding to ordinary hardening and tempering operations,
the core meanwhile retaining its original softness and toughness.
Such case-hardened parts are stronger, cheaper, and more serviceable than similar parts made of
tool steel. The tough core resists breakage by shock. The hardened case resists wear from friction.
The low cost of material, the ease of manufacture, and the lessened breakage in quenching all serve
to promote cheap production.
For successful carburizing, the following points should be carefully observed:
The utmost care should be used in the selection of pots for carburizing; they should be as free as
possible from both scaling and warping. These two requirements eliminate the cast iron pot,
although many are used, thus leaving us to select from malleable castings, wrought iron, cast steel,
and special alloys, such as nichrome or silchrome. If first cost is not important, it will prove cheaper
in the end to use pots of some special alloy.
Page 68
FIGS. 27 to 30.—Case-hardening or carburizing boxes.
FIG. 31.—A lid that is easily luted.
The pots should be standardized to suit the product. Pots should be made as small as possible in
width, and space gained by increasing the height; for it takes about 1½ hr. to heat the average small
pot of 4 in. in width, between 3 and 4 hr. to heat to the center of an 8-in. box, and 5 to 6 hr. to heat
to the center of a 12-in. box; and the longer the time required to heat to the center, the more uneven
the carburizing.
The work is packed in the box surrounded by materials which will give up carbon when heated. It
must be packed so that each piece is separate from the others and does not touch the box, with a
sufficient amount of carburizing material surrounding each. Figures 27 to 31 show the kind of
boxes used and the way the work should be packed. Figure 31 shows a later type of box in which
the edges can be easily luted. Figure 30 shows test wires broken periodically to determine the depth
of case. Figure 28 shows the minimum clearance which should be used in packing and Fig. 29 the
way in which the outer pieces receive the heat first and likewise take up the carbon before those in
the center. This is why a slow, soaking heat is necessary in handling large quantities of work, so as
to allow the heat and carbon to soak in equally.
While it has been claimed that iron below its critical temperature will absorb some carbon, Giolitti
has shown that this absorption is very slow. In order to produce quick and intense carburization the
iron should preferably be above its upper critical temperature or 1,600°F.,—therefore the carbon
absorbed immediately goes into austenite, or solid solution. It is also certain that the higher the
temperature the quicker will carbon be absorbed, and the deeper it will penetrate into the steel, that
FIG. 31.—A lid that is easily luted.
The pots should be standardized to suit the product. Pots should be made as small as possible in
width, and space gained by increasing the height; for it takes about 1½ hr. to heat the average small
pot of 4 in. in width, between 3 and 4 hr. to heat to the center of an 8-in. box, and 5 to 6 hr. to heat
to the center of a 12-in. box; and the longer the time required to heat to the center, the more uneven
the carburizing.
The work is packed in the box surrounded by materials which will give up carbon when heated. It
must be packed so that each piece is separate from the others and does not touch the box, with a
sufficient amount of carburizing material surrounding each. Figures 27 to 31 show the kind of
boxes used and the way the work should be packed. Figure 31 shows a later type of box in which
the edges can be easily luted. Figure 30 shows test wires broken periodically to determine the depth
of case. Figure 28 shows the minimum clearance which should be used in packing and Fig. 29 the
way in which the outer pieces receive the heat first and likewise take up the carbon before those in
the center. This is why a slow, soaking heat is necessary in handling large quantities of work, so as
to allow the heat and carbon to soak in equally.
While it has been claimed that iron below its critical temperature will absorb some carbon, Giolitti
has shown that this absorption is very slow. In order to produce quick and intense carburization the
iron should preferably be above its upper critical temperature or 1,600°F.,—therefore the carbon
absorbed immediately goes into austenite, or solid solution. It is also certain that the higher the
temperature the quicker will carbon be absorbed, and the deeper it will penetrate into the steel, that
Page 69
is, the deeper the "case." At Sheffield, England, where wrought iron is packed in charcoal and
heated for days to convert it into "blister steel," the temperatures are from 1,750 to 1,830°F.
Charcoal by itself carburizes slowly, consequently commercial compounds also contain certain
"energizers" which give rapid penetration at lower temperatures.
The most important thing in carburizing is the human element. Most careful vigilance should be
kept when packing and unpacking, and the operator should be instructed in the necessity for clean
compound free from scale, moisture, fire clay, sand, floor sweepings, etc. From just such causes,
many a good carburizer has been unjustly condemned. It is essential with most carburizers to use
about 25 to 50 per cent of used material, in order to prevent undue shrinking during heating;
therefore the necessity of properly screening used material and carefully inspecting it for foreign
substances before it is used again. It is right here that the greatest carelessness is generally
encountered.
Don't pack the work to be carburized too closely; leave at least 1 in. from the bottom, ¾ in. from
the sides, and 1 in. from the top of pots, and for a 6-hr. run, have the pieces at least 1/2 in. apart.
This gives the heat a chance to thoroughly permeate the pot, and the carburizing material a chance
to shrink without allowing carburized pieces to touch and cause soft spots.
Good case-hardening pots and annealing tubes can be made from the desired size of wrought iron
pipe. The ends are capped or welded, and a slot is cut in the side of the pot, equal to one quarter of
its circumference, and about 7/8 of its length. Another piece of the same diameter pipe cut
lengthwise into thirds forms a cover for this pot. We then have a cheap, substantial pot, non-
warping, with a minimum tendency to scale, but the pot is difficult to seal tightly. This idea is
especially adaptable when long, narrow pots are desired.
When pots are packed and the carburizer thoroughly tamped down, the covers of the pot are put on
and sealed with fire clay which has a little salt mixed into it. The more perfect the seal the more we
can get out of the carburizer. The rates of penetration depend on temperature and the presence of
proper gas in the required volume. Any pressure we can cause will, of course, have a tendency to
increase the rate of penetration.
If you have a wide furnace, do not load it full at one time. Put one-half your load in first, in the
center of the furnace, and heat until pots show a low red, about 1,325 to 1,350°F. Then fill the
furnace by putting the cold pots on the outside or, the section nearest the source of heat. This will
give the work in the slowest portion of the furnace a chance to come to heat at the same time as the
pots that are nearest the sources of heat.
To obtain an even heating of the pots and lessen their tendency to warp and scale, and to cause the
contents of the furnace to heat up evenly, we should use a reducing fire and fill the heating chamber
with flame. This can be accomplished by partially closing the waste gas vents and reducing slightly
the amount of air used by the burners. A short flame will then be noticed issuing from the partially
closed vents. Thus, while maintaining the temperature of the heating chamber, we will have a lower
temperature in the combustion chamber, which will naturally increase its longevity.
Sometimes it is advisable to cool the work in the pots. This saves compound, and causes a more
gradual diffusion of the carbon between the case and the core, and is very desirable condition,
inasmuch as abrupt cases are inclined to chip out.
heated for days to convert it into "blister steel," the temperatures are from 1,750 to 1,830°F.
Charcoal by itself carburizes slowly, consequently commercial compounds also contain certain
"energizers" which give rapid penetration at lower temperatures.
The most important thing in carburizing is the human element. Most careful vigilance should be
kept when packing and unpacking, and the operator should be instructed in the necessity for clean
compound free from scale, moisture, fire clay, sand, floor sweepings, etc. From just such causes,
many a good carburizer has been unjustly condemned. It is essential with most carburizers to use
about 25 to 50 per cent of used material, in order to prevent undue shrinking during heating;
therefore the necessity of properly screening used material and carefully inspecting it for foreign
substances before it is used again. It is right here that the greatest carelessness is generally
encountered.
Don't pack the work to be carburized too closely; leave at least 1 in. from the bottom, ¾ in. from
the sides, and 1 in. from the top of pots, and for a 6-hr. run, have the pieces at least 1/2 in. apart.
This gives the heat a chance to thoroughly permeate the pot, and the carburizing material a chance
to shrink without allowing carburized pieces to touch and cause soft spots.
Good case-hardening pots and annealing tubes can be made from the desired size of wrought iron
pipe. The ends are capped or welded, and a slot is cut in the side of the pot, equal to one quarter of
its circumference, and about 7/8 of its length. Another piece of the same diameter pipe cut
lengthwise into thirds forms a cover for this pot. We then have a cheap, substantial pot, non-
warping, with a minimum tendency to scale, but the pot is difficult to seal tightly. This idea is
especially adaptable when long, narrow pots are desired.
When pots are packed and the carburizer thoroughly tamped down, the covers of the pot are put on
and sealed with fire clay which has a little salt mixed into it. The more perfect the seal the more we
can get out of the carburizer. The rates of penetration depend on temperature and the presence of
proper gas in the required volume. Any pressure we can cause will, of course, have a tendency to
increase the rate of penetration.
If you have a wide furnace, do not load it full at one time. Put one-half your load in first, in the
center of the furnace, and heat until pots show a low red, about 1,325 to 1,350°F. Then fill the
furnace by putting the cold pots on the outside or, the section nearest the source of heat. This will
give the work in the slowest portion of the furnace a chance to come to heat at the same time as the
pots that are nearest the sources of heat.
To obtain an even heating of the pots and lessen their tendency to warp and scale, and to cause the
contents of the furnace to heat up evenly, we should use a reducing fire and fill the heating chamber
with flame. This can be accomplished by partially closing the waste gas vents and reducing slightly
the amount of air used by the burners. A short flame will then be noticed issuing from the partially
closed vents. Thus, while maintaining the temperature of the heating chamber, we will have a lower
temperature in the combustion chamber, which will naturally increase its longevity.
Sometimes it is advisable to cool the work in the pots. This saves compound, and causes a more
gradual diffusion of the carbon between the case and the core, and is very desirable condition,
inasmuch as abrupt cases are inclined to chip out.
Page 70
The most satisfactory steel to carburize contains between 0.10 and 0.20 per cent carbon, less than
0.35 per cent manganese, less than 0.04 per cent phosphorus and sulphur, and low silicon. But steel
of this composition does not seem to satisfy our progressive engineers, and many alloy steels are
now on the market, these, although more or less difficult to machine, give when carburized the
various qualities demanded, such as a very hard case, very tough core, or very hard case and tough
core. However, the additional elements also have a great effect both on the rate of penetration
during the carburizing operation, and on the final treatment, consequently such alloy steels require
very careful supervision during the entire heat treating operations.
RATE OF ABSORPTION
According to Guillet, the absorption of carbon is favored by those special elements which exist as
double carbides in steel. For example, manganese exists as manganese carbide in combination with
the iron carbide. The elements that favor the absorption of carbon are: manganese, tungsten,
chromium and molybdenum those opposing it, nickel, silicon, and aluminum. Guillet has worked
out the effect of the different elements on the rate of penetration in comparison with steel that
absorbed carbon at a given temperature, at an average rate of 0.035 in. per hour.
His tables show that the following elements require an increased time of exposure to the
carburizing material in order to obtain the same depth of penetration as with simple steel:
When steel contains Increased time of exposure
2.0 per cent nickel 28 per cent
7.0 per cent nickel 30 per cent
1.0 per cent titanium 12 per cent
2.0 per cent titanium 28 per cent
0.5 per cent silicon 50 per cent
1.0 per cent silicon 80 per cent
2.0 per cent silicon 122 per cent
5.0 per cent silicon No penetration
1.0 per cent aluminum 122 per cent
2.0 per cent aluminum 350 per cent
The following elements seem to assist the rate of penetration of carbon, and the carburizing time
may therefore be reduced as follows:
When steel contains Increased time of exposure
0.5 per cent manganese 18 per cent
1.0 per cent manganese 25 per cent
1.0 per cent chromium 10 per cent
2.0 per cent chromium 18 per cent
0.5 per cent tungsten 0
1.0 per cent tungsten 0
2.0 per cent tungsten 25 per cent
1.0 per cent molybdenum 0
2.0 per cent molybdenum 18 per cent
0.35 per cent manganese, less than 0.04 per cent phosphorus and sulphur, and low silicon. But steel
of this composition does not seem to satisfy our progressive engineers, and many alloy steels are
now on the market, these, although more or less difficult to machine, give when carburized the
various qualities demanded, such as a very hard case, very tough core, or very hard case and tough
core. However, the additional elements also have a great effect both on the rate of penetration
during the carburizing operation, and on the final treatment, consequently such alloy steels require
very careful supervision during the entire heat treating operations.
RATE OF ABSORPTION
According to Guillet, the absorption of carbon is favored by those special elements which exist as
double carbides in steel. For example, manganese exists as manganese carbide in combination with
the iron carbide. The elements that favor the absorption of carbon are: manganese, tungsten,
chromium and molybdenum those opposing it, nickel, silicon, and aluminum. Guillet has worked
out the effect of the different elements on the rate of penetration in comparison with steel that
absorbed carbon at a given temperature, at an average rate of 0.035 in. per hour.
His tables show that the following elements require an increased time of exposure to the
carburizing material in order to obtain the same depth of penetration as with simple steel:
When steel contains Increased time of exposure
2.0 per cent nickel 28 per cent
7.0 per cent nickel 30 per cent
1.0 per cent titanium 12 per cent
2.0 per cent titanium 28 per cent
0.5 per cent silicon 50 per cent
1.0 per cent silicon 80 per cent
2.0 per cent silicon 122 per cent
5.0 per cent silicon No penetration
1.0 per cent aluminum 122 per cent
2.0 per cent aluminum 350 per cent
The following elements seem to assist the rate of penetration of carbon, and the carburizing time
may therefore be reduced as follows:
When steel contains Increased time of exposure
0.5 per cent manganese 18 per cent
1.0 per cent manganese 25 per cent
1.0 per cent chromium 10 per cent
2.0 per cent chromium 18 per cent
0.5 per cent tungsten 0
1.0 per cent tungsten 0
2.0 per cent tungsten 25 per cent
1.0 per cent molybdenum 0
2.0 per cent molybdenum 18 per cent
Page 71
The temperature at which carburization is accomplished is a very important factor. Hence the
necessity for a reliable pyrometer, located so as to give the temperature just below the tops of the
pots. It must be remembered, however, that the pyrometer gives the temperature of only one spot,
and is therefore only an aid to the operator, who must use his eyes for successful results.
The carbon content of the case generally is governed by the temperature of the carburization. It
generally proves advisable to have the case contain between 0.90 per cent and 1.10 carbon; more
carbon than this gives rise to excess free cementite or carbide of iron, which is detrimental, causing
the case to be brittle and apt to chip.
T. G. Selleck gives a very useful table of temperatures and the relative carbon contents of the case
of steels carburized between 4 and 6 hrs. using a good charcoal carburizer. This data is as follows:
TABLE 15.—CARBON CONTENT OBTAINED AT
VARIOUS TEMPERATURES
At 1,500°F., the surface carbon content will be 0.90 per cent
At 1,600°F., the surface carbon content will be 1.00 per cent
At 1,650°F., the surface carbon content will be 1.10 per cent
At 1,700°F., the surface carbon content will be 1.25 per cent
At 1,750°F., the surface carbon content will be 1.40 per cent
At 1,800°F., the surface carbon content will be 1.75 per cent
To this very valuable table, it seems best to add the following data, which we have used for a
number of years. We do not know the name of its author, but it has proved very valuable, and seems
to complete the above information. The table is self-explanatory, giving depth of penetration of the
carbon of the case at different temperatures for different lengths of time:
Temperature
Penetration
1,550 1,650 1,800
Penetration after 1/2 hr. 0.008 0.012 0.030
Penetration after 1 hr. 0.018 0.026 0.045
Penetration after 2 hr. 0.035 0.048 0.060
Penetration after 3 hr. 0.045 0.055 0.075
Penetration after 4 hr. 0.052 0.061 0.092
Penetration after 6 hr. 0.056 0.075 0.110
Penetration after 8 hr. 0.062 0.083 0.130
From the tables given, we may calculate with a fair degree of certainty the amount of carbon in the
case, and its penetration. These figures vary widely with different carburizers, and as pointed out
immediately above, with different alloy steels.
CARBURIZING MATERIAL
The simplest carburizing substance is charcoal. It is also the slowest, but is often used mixed with
something that will evolve large volumes of carbon monoxide or hydrocarbon gas on being heated.
A great variety of materials is used, a few of them being charcoal (both wood and bone), charred
leather, crushed bone, horn, mixtures of charcoal and barium carbonate, coke and heavy oils, coke
treated with alkaline carbonates, peat, charcoal mixed with common salt, saltpeter, resin, flour,
necessity for a reliable pyrometer, located so as to give the temperature just below the tops of the
pots. It must be remembered, however, that the pyrometer gives the temperature of only one spot,
and is therefore only an aid to the operator, who must use his eyes for successful results.
The carbon content of the case generally is governed by the temperature of the carburization. It
generally proves advisable to have the case contain between 0.90 per cent and 1.10 carbon; more
carbon than this gives rise to excess free cementite or carbide of iron, which is detrimental, causing
the case to be brittle and apt to chip.
T. G. Selleck gives a very useful table of temperatures and the relative carbon contents of the case
of steels carburized between 4 and 6 hrs. using a good charcoal carburizer. This data is as follows:
TABLE 15.—CARBON CONTENT OBTAINED AT
VARIOUS TEMPERATURES
At 1,500°F., the surface carbon content will be 0.90 per cent
At 1,600°F., the surface carbon content will be 1.00 per cent
At 1,650°F., the surface carbon content will be 1.10 per cent
At 1,700°F., the surface carbon content will be 1.25 per cent
At 1,750°F., the surface carbon content will be 1.40 per cent
At 1,800°F., the surface carbon content will be 1.75 per cent
To this very valuable table, it seems best to add the following data, which we have used for a
number of years. We do not know the name of its author, but it has proved very valuable, and seems
to complete the above information. The table is self-explanatory, giving depth of penetration of the
carbon of the case at different temperatures for different lengths of time:
Temperature
Penetration
1,550 1,650 1,800
Penetration after 1/2 hr. 0.008 0.012 0.030
Penetration after 1 hr. 0.018 0.026 0.045
Penetration after 2 hr. 0.035 0.048 0.060
Penetration after 3 hr. 0.045 0.055 0.075
Penetration after 4 hr. 0.052 0.061 0.092
Penetration after 6 hr. 0.056 0.075 0.110
Penetration after 8 hr. 0.062 0.083 0.130
From the tables given, we may calculate with a fair degree of certainty the amount of carbon in the
case, and its penetration. These figures vary widely with different carburizers, and as pointed out
immediately above, with different alloy steels.
CARBURIZING MATERIAL
The simplest carburizing substance is charcoal. It is also the slowest, but is often used mixed with
something that will evolve large volumes of carbon monoxide or hydrocarbon gas on being heated.
A great variety of materials is used, a few of them being charcoal (both wood and bone), charred
leather, crushed bone, horn, mixtures of charcoal and barium carbonate, coke and heavy oils, coke
treated with alkaline carbonates, peat, charcoal mixed with common salt, saltpeter, resin, flour,
Page 72
potassium bichromate, vegetable fibre, limestone, various seed husks, etc. In general, it is well to
avoid complex mixtures.
H. L. Heathcote, on analyzing seventeen different carburizers, found that they contained the
following ingredients:
Per cent
Moisture 2.68 to 26.17
Oil 0.17 to 20.76
Carbon (organic) 6.70 to 54.19
Calcium phosphate 0.32 to 74.75
Calcium carbonate 1.20 to 11.57
Barium carbonate nil to 42.00
Zinc oxide nil to 14.50
Silica nil to 8.14
Sulphates (SO3) trace to 3.45
Sodium chloride nil to 7.88
Sodium carbonate nil to 40.00
Sulphides (S) nil to 2.80
Carburizing mixtures, though bought by weight, are used by volume, and the weight per cubic foot
is a big factor in making a selection. A good mixture should be porous, so that the evolved gases,
which should be generated at the proper temperature, may move freely around the steel objects
being carburized; should be a good conductor of heat; should possess minimum shrinkage when
used; and should be capable of being tamped down.
Many "secret mixtures" are sold, falsely claimed to be able to convert inferior metal into crucible
tool steel grade. They are generally nothing more than mixtures of carbonaceous and cyanogen
compounds possessing the well-known carburizing properties of those substances.
QUENCHING
It is considered good practice to quench alloy steels from the pot, especially if the case is of any
appreciable depth. The texture of carbon steel will be weakened by the prolonged high heat of
carburizing, so that if we need a tough core, we must reheat it above its critical range, which is
about 1,600°F. for soft steel, but lower for manganese and nickel steels. Quenching is done in either
water, oil, or air, depending upon the results desired. The steel is then very carefully reheated to
refine the case, the temperature varying from 1,350 to 1,450°F., depending on whether the material
is an alloy or a simple steel, and quenched in either water or oil.
avoid complex mixtures.
H. L. Heathcote, on analyzing seventeen different carburizers, found that they contained the
following ingredients:
Per cent
Moisture 2.68 to 26.17
Oil 0.17 to 20.76
Carbon (organic) 6.70 to 54.19
Calcium phosphate 0.32 to 74.75
Calcium carbonate 1.20 to 11.57
Barium carbonate nil to 42.00
Zinc oxide nil to 14.50
Silica nil to 8.14
Sulphates (SO3) trace to 3.45
Sodium chloride nil to 7.88
Sodium carbonate nil to 40.00
Sulphides (S) nil to 2.80
Carburizing mixtures, though bought by weight, are used by volume, and the weight per cubic foot
is a big factor in making a selection. A good mixture should be porous, so that the evolved gases,
which should be generated at the proper temperature, may move freely around the steel objects
being carburized; should be a good conductor of heat; should possess minimum shrinkage when
used; and should be capable of being tamped down.
Many "secret mixtures" are sold, falsely claimed to be able to convert inferior metal into crucible
tool steel grade. They are generally nothing more than mixtures of carbonaceous and cyanogen
compounds possessing the well-known carburizing properties of those substances.
QUENCHING
It is considered good practice to quench alloy steels from the pot, especially if the case is of any
appreciable depth. The texture of carbon steel will be weakened by the prolonged high heat of
carburizing, so that if we need a tough core, we must reheat it above its critical range, which is
about 1,600°F. for soft steel, but lower for manganese and nickel steels. Quenching is done in either
water, oil, or air, depending upon the results desired. The steel is then very carefully reheated to
refine the case, the temperature varying from 1,350 to 1,450°F., depending on whether the material
is an alloy or a simple steel, and quenched in either water or oil.
Page 73
FIG. 32.—Case-hardening depths.
There are many possibilities yet to be developed with the carburizing of alloy steels, which can
produce a very tough, tenacious austenitic case which becomes hard on cooling in air, and still
retains a soft, pearlitic core. An austenitic case is not necessarily file hard, but has a very great
resistance to abrasive wear.
The more carbon a steel has to begin with the more slowly will it absorb carbon and the lower the
temperature required. Low-carbon steel of from 15 to 20 points is generally used and the carbon
brought up to 80 or 85 points. Tool steels may be carbonized as high as 250 points.
In addition to the carburizing materials given, a mixture of 40 per cent of barium carbonate and 60
per cent charcoal gives much faster penetration than charcoal, bone or leather. The penetration of
this mixture on ordinary low-carbon steel is shown in Fig. 32, over a range of from 2 to 12 hr.
EFFECT OF DIFFERENT CARBURIZING MATERIAL
FIGS. 33 to 37.
Each of these different packing materials has a different effect upon the work in which it is heated.
Charcoal by itself will give a rather light case. Mixed with raw bone it will carburize more rapidly,
and still more so if mixed with burnt bone. Raw bone and burnt bone, as may be inferred, are both
quicker carbonizers than charcoal, but raw bone must never be used where the breakage of
hardened edges is to be avoided, as it contains phosphorus and tends to make the piece brittle.
Charred leather mixed with charcoal is a still faster material, and horns and hoofs exceed even this
in speed; but these two compounds are restricted by their cost to use with high-grade articles,
usually of tool or high-carbon steel, that are to be hardened locally—that is, "pack-hardened."
There are many possibilities yet to be developed with the carburizing of alloy steels, which can
produce a very tough, tenacious austenitic case which becomes hard on cooling in air, and still
retains a soft, pearlitic core. An austenitic case is not necessarily file hard, but has a very great
resistance to abrasive wear.
The more carbon a steel has to begin with the more slowly will it absorb carbon and the lower the
temperature required. Low-carbon steel of from 15 to 20 points is generally used and the carbon
brought up to 80 or 85 points. Tool steels may be carbonized as high as 250 points.
In addition to the carburizing materials given, a mixture of 40 per cent of barium carbonate and 60
per cent charcoal gives much faster penetration than charcoal, bone or leather. The penetration of
this mixture on ordinary low-carbon steel is shown in Fig. 32, over a range of from 2 to 12 hr.
EFFECT OF DIFFERENT CARBURIZING MATERIAL
FIGS. 33 to 37.
Each of these different packing materials has a different effect upon the work in which it is heated.
Charcoal by itself will give a rather light case. Mixed with raw bone it will carburize more rapidly,
and still more so if mixed with burnt bone. Raw bone and burnt bone, as may be inferred, are both
quicker carbonizers than charcoal, but raw bone must never be used where the breakage of
hardened edges is to be avoided, as it contains phosphorus and tends to make the piece brittle.
Charred leather mixed with charcoal is a still faster material, and horns and hoofs exceed even this
in speed; but these two compounds are restricted by their cost to use with high-grade articles,
usually of tool or high-carbon steel, that are to be hardened locally—that is, "pack-hardened."
Page 74
Cyanide of potassium or prussiate of potash are also included in the list of carbonizing materials;
but outside of carburizing by dipping into melted baths of this material, their use is largely confined
to local hardening of small surfaces, such as holes in dies and the like.
Dr. Federico Giolitti has proven that when carbonizing with charcoal, or charcoal plus barium
carbonate, the active agent which introduces carbon into the steel is a gas, carbon monoxide (CO),
derived by combustion of the charcoal in the air trapped in the box, or by decomposition of the
carbonate. This gas diffuses in and out of the hot steel, transporting carbon from the charcoal to the
outer portions of the metal:
If energizers like tar, peat, and vegetable fiber are used, they produce hydrocarbon gases on being
heated—gases principally composed of hydrogen and carbon. These gases are unstable in the
presence of hot iron: it seems to decompose them and sooty carbon is deposited on the surface of
the metal. This diffuses into the metal a little, but it acts principally by being a ready source of
carbon, highly active and waiting to be carried into the metal by the carbon monoxide—which as
before, is the principal transfer agent.
Animal refuse when used to speed up the action of clean charcoal acts somewhat in the same
manner, but in addition the gases given off by the hot substance contain nitrogen compounds.
Nitrogen and cyanides (compounds of carbon and nitrogen) have long been known to give a very
hard thin case very rapidly. It has been discovered only recently that this is due to the steel
absorbing nitrogen as well as carbon, and that nitrogen hardens steel and makes it brittle just like
carbon does. In fact it is very difficult to distinguish between these two hardening agents when
examining a carburized steel under the microscope.
One of the advantages of hardening by carburizing is the fact that you can arrange to leave part of
the work soft and thus retain the toughness and strength of the original material. Figures 33 to 37
show ways of doing this. The inside of the cup in Fig. 34 is locally hardened, as illustrated in Fig.
34, "spent" or used bone being packed around the surfaces that are to be left soft, while cyanide of
potassium is put around those which are desired hard. The threads of the nut in Fig. 35 are kept soft
by carburizing the nut while upon a stud. The profile gage, Fig. 36, is made of high-carbon steel and
is hardened on the inside by packing with charred leather, but kept soft on the outside by
surrounding it with fireclay. The rivet stud shown in Fig. 37 is carburized while of its full diameter
and then turned down to the size of the rivet end, thus cutting away the carburized surface.
After packing the work carefully in the boxes the lids are sealed or luted with fireclay to keep out
any gases from the fire. The size of box should be proportioned to the work. The box should not be
too large especially for light work that is run on a short heat. If it can be just large enough to allow
the proper amount of material around it, the work is apt to be more satisfactory in every way.
Pieces of this kind are of course not quenched and hardened in the carburizing heat, but are left in
the box to cool, just as in box annealing, being reheated and quenched as a second operation. In
fact, this is a good scheme to use for the majority of carburizing work of small and moderate size.
Material is on the market with which one side of the steel can be treated; or copper-plating one side
of it will answer the same purpose and prevent that side becoming carburized.
QUENCHING THE WORK
In some operations case-hardened work is quenched from the box by dumping the whole contents
into the quenching tank. It is common practice to leave a sieve or wire basket to catch the work,
but outside of carburizing by dipping into melted baths of this material, their use is largely confined
to local hardening of small surfaces, such as holes in dies and the like.
Dr. Federico Giolitti has proven that when carbonizing with charcoal, or charcoal plus barium
carbonate, the active agent which introduces carbon into the steel is a gas, carbon monoxide (CO),
derived by combustion of the charcoal in the air trapped in the box, or by decomposition of the
carbonate. This gas diffuses in and out of the hot steel, transporting carbon from the charcoal to the
outer portions of the metal:
If energizers like tar, peat, and vegetable fiber are used, they produce hydrocarbon gases on being
heated—gases principally composed of hydrogen and carbon. These gases are unstable in the
presence of hot iron: it seems to decompose them and sooty carbon is deposited on the surface of
the metal. This diffuses into the metal a little, but it acts principally by being a ready source of
carbon, highly active and waiting to be carried into the metal by the carbon monoxide—which as
before, is the principal transfer agent.
Animal refuse when used to speed up the action of clean charcoal acts somewhat in the same
manner, but in addition the gases given off by the hot substance contain nitrogen compounds.
Nitrogen and cyanides (compounds of carbon and nitrogen) have long been known to give a very
hard thin case very rapidly. It has been discovered only recently that this is due to the steel
absorbing nitrogen as well as carbon, and that nitrogen hardens steel and makes it brittle just like
carbon does. In fact it is very difficult to distinguish between these two hardening agents when
examining a carburized steel under the microscope.
One of the advantages of hardening by carburizing is the fact that you can arrange to leave part of
the work soft and thus retain the toughness and strength of the original material. Figures 33 to 37
show ways of doing this. The inside of the cup in Fig. 34 is locally hardened, as illustrated in Fig.
34, "spent" or used bone being packed around the surfaces that are to be left soft, while cyanide of
potassium is put around those which are desired hard. The threads of the nut in Fig. 35 are kept soft
by carburizing the nut while upon a stud. The profile gage, Fig. 36, is made of high-carbon steel and
is hardened on the inside by packing with charred leather, but kept soft on the outside by
surrounding it with fireclay. The rivet stud shown in Fig. 37 is carburized while of its full diameter
and then turned down to the size of the rivet end, thus cutting away the carburized surface.
After packing the work carefully in the boxes the lids are sealed or luted with fireclay to keep out
any gases from the fire. The size of box should be proportioned to the work. The box should not be
too large especially for light work that is run on a short heat. If it can be just large enough to allow
the proper amount of material around it, the work is apt to be more satisfactory in every way.
Pieces of this kind are of course not quenched and hardened in the carburizing heat, but are left in
the box to cool, just as in box annealing, being reheated and quenched as a second operation. In
fact, this is a good scheme to use for the majority of carburizing work of small and moderate size.
Material is on the market with which one side of the steel can be treated; or copper-plating one side
of it will answer the same purpose and prevent that side becoming carburized.
QUENCHING THE WORK
In some operations case-hardened work is quenched from the box by dumping the whole contents
into the quenching tank. It is common practice to leave a sieve or wire basket to catch the work,
Page 75
allowing the carburizing material to fall to the bottom of the tank where it can be recovered later
and used again as a part of a new mixture. For best results, however, the steel is allowed to cool
down slowly in the box after which it is removed and hardened by heating and quenching the same
as carbon steel of the same grade. It has absorbed sufficient carbon so that, in the outer portions at
least, it is a high-carbon steel.
THE QUENCHING TANK
The quenching tank is an important feature of apparatus in case-hardening—possibly more so than
in ordinary tempering. One reason for this is because of the large quantities of pieces usually
dumped into the tank at a time. One cannot take time to separate the articles themselves from the
case-hardening mixture, and the whole content of the box is droped into the bath in short order, as
exposure to air of the heated work is fatal to results. Unless it is split up, it is likely to go to the
bottom as a solid mass, in which case very few of the pieces are properly hardened.
FIG. 38.—Combination cooling tank for case-hardening.
A combination cooling tank is shown in Fig. 38. Water inlet and outlet pipes are shown and also a
drain plug that enables the tank to be emptied when it is desired to clean out the spent carburizing
material from the bottom. A wire-bottomed tray, framed with angle iron, is arranged to slide into
this tank from the top and rests upon angle irons screwed to the tank sides. Its function is to catch
the pieces and prevent them from settling to the tank bottom, and it also makes it easy to remove a
batch of work. A bottomless box of sheet steel is shown at C. This fits into the wire-bottomed tray
and has a number of rods or wires running across it, their purpose being to break up the mass of
material as it comes from the carbonizing box.
Below the wire-bottomed tray is a perforated cross-pipe that is connected with a compressed-air
line. This is used when case-hardening for colors. The shop that has no air compressor may rig up a
satisfactory equivalent in the shape of a low-pressure hand-operated air pump and a receiver tank,
for it is not necessary to use high-pressure air for this purpose. When colors are desired on case-
hardened work, the treatment in quenching is exactly the same as that previously described except
and used again as a part of a new mixture. For best results, however, the steel is allowed to cool
down slowly in the box after which it is removed and hardened by heating and quenching the same
as carbon steel of the same grade. It has absorbed sufficient carbon so that, in the outer portions at
least, it is a high-carbon steel.
THE QUENCHING TANK
The quenching tank is an important feature of apparatus in case-hardening—possibly more so than
in ordinary tempering. One reason for this is because of the large quantities of pieces usually
dumped into the tank at a time. One cannot take time to separate the articles themselves from the
case-hardening mixture, and the whole content of the box is droped into the bath in short order, as
exposure to air of the heated work is fatal to results. Unless it is split up, it is likely to go to the
bottom as a solid mass, in which case very few of the pieces are properly hardened.
FIG. 38.—Combination cooling tank for case-hardening.
A combination cooling tank is shown in Fig. 38. Water inlet and outlet pipes are shown and also a
drain plug that enables the tank to be emptied when it is desired to clean out the spent carburizing
material from the bottom. A wire-bottomed tray, framed with angle iron, is arranged to slide into
this tank from the top and rests upon angle irons screwed to the tank sides. Its function is to catch
the pieces and prevent them from settling to the tank bottom, and it also makes it easy to remove a
batch of work. A bottomless box of sheet steel is shown at C. This fits into the wire-bottomed tray
and has a number of rods or wires running across it, their purpose being to break up the mass of
material as it comes from the carbonizing box.
Below the wire-bottomed tray is a perforated cross-pipe that is connected with a compressed-air
line. This is used when case-hardening for colors. The shop that has no air compressor may rig up a
satisfactory equivalent in the shape of a low-pressure hand-operated air pump and a receiver tank,
for it is not necessary to use high-pressure air for this purpose. When colors are desired on case-
hardened work, the treatment in quenching is exactly the same as that previously described except
Page 76
that air is pumped through this pipe and keeps the water agitated. The addition of a slight amount of
powdered cyanide of potassium to the packing material used for carburizing will produce stronger
colors, and where this is the sole object, it is best to maintain the box at a dull-red heat.
The old way of case-hardening was to dump the contents of the box at
the end of the carburizing heat. Later study in the structure of steel thus
treated has caused a change in this procedure, the use of automobiles
and alloy steels probably hastening this result. The diagrams reproduced
in Fig. 39 show why the heat treatment of case-hardened work is
necessary. Starting at A with a close-grained and tough stock, such as
ordinary machinery steel containing from 15 to 20 points of carbon, if
such work is quenched on a carbonizing heat the result will be as shown
at B. This gives a core that is coarse-grained and brittle and an outer
case that is fine-grained and hard, but is likely to flake off, owing to the
great difference in structure between it and the core. Reheating this
work beyond the critical temperature of the core refines this core, closes
the grain and makes it tough, but leaves the case very brittle; in fact,
more so than it was before.
REFINING THE GRAIN
This is remedied by reheating the piece to a temperature slightly above
the critical temperature of the case, this temperature corresponding
ordinarily to that of steel having a carbon content of 85 points, When
this is again quenched, the temperature, which has not been high enough
FIG. 39.—Why heat treatment of
to disturb the refined core, will have closed the grain of the case and case-hardened work is necessary.
toughened it. So, instead of but one heat and one quenching for this
class of work, we have three of each, although it is quite possible and often profitable to omit the
quenching after carburizing and allow the piece or pieces and the case-carburizing box to cool
together, as in annealing. Sometimes another heat treatment is added to the foregoing, for the
purpose of letting down the hardness of the case and giving it additional toughness by heating to a
temperature between 300° and 500°. Usually this is done in an oil bath. After this the piece is
allowed to cool.
It is possible to harden the surface of tool steel extremely hard and yet leave its inner core soft and
tough for strength, by a process similar to case-hardening and known as "pack-hardening." It
consists in using tool steel of carbon contents ranging from 60 to 80 points, packing this in a box
with charred leather mixed with wood charcoal and heating at a low-red heat for 2 or 3 hr., thus
raising the carbon content of the exterior of the piece. The article when quenched in an oil bath will
have an extremely hard exterior and tough core. It is a good scheme for tools that must be hard and
yet strong enough to stand abuse. Raw bone is never used as a packing for this class of work, as it
makes the cutting edges brittle.
CASE-HARDENING TREATMENTS FOR VARIOUS STEELS
Plain water, salt water and linseed oil are the three most common quenching materials for case-
hardening. Water is used for ordinary work, salt water for work which must be extremely hard on
the surface, and oil for work in which toughness is the main consideration. The higher the carbon of
the case, the less sudden need the quenching action take hold of the piece; in fact, experience in
powdered cyanide of potassium to the packing material used for carburizing will produce stronger
colors, and where this is the sole object, it is best to maintain the box at a dull-red heat.
The old way of case-hardening was to dump the contents of the box at
the end of the carburizing heat. Later study in the structure of steel thus
treated has caused a change in this procedure, the use of automobiles
and alloy steels probably hastening this result. The diagrams reproduced
in Fig. 39 show why the heat treatment of case-hardened work is
necessary. Starting at A with a close-grained and tough stock, such as
ordinary machinery steel containing from 15 to 20 points of carbon, if
such work is quenched on a carbonizing heat the result will be as shown
at B. This gives a core that is coarse-grained and brittle and an outer
case that is fine-grained and hard, but is likely to flake off, owing to the
great difference in structure between it and the core. Reheating this
work beyond the critical temperature of the core refines this core, closes
the grain and makes it tough, but leaves the case very brittle; in fact,
more so than it was before.
REFINING THE GRAIN
This is remedied by reheating the piece to a temperature slightly above
the critical temperature of the case, this temperature corresponding
ordinarily to that of steel having a carbon content of 85 points, When
this is again quenched, the temperature, which has not been high enough
FIG. 39.—Why heat treatment of
to disturb the refined core, will have closed the grain of the case and case-hardened work is necessary.
toughened it. So, instead of but one heat and one quenching for this
class of work, we have three of each, although it is quite possible and often profitable to omit the
quenching after carburizing and allow the piece or pieces and the case-carburizing box to cool
together, as in annealing. Sometimes another heat treatment is added to the foregoing, for the
purpose of letting down the hardness of the case and giving it additional toughness by heating to a
temperature between 300° and 500°. Usually this is done in an oil bath. After this the piece is
allowed to cool.
It is possible to harden the surface of tool steel extremely hard and yet leave its inner core soft and
tough for strength, by a process similar to case-hardening and known as "pack-hardening." It
consists in using tool steel of carbon contents ranging from 60 to 80 points, packing this in a box
with charred leather mixed with wood charcoal and heating at a low-red heat for 2 or 3 hr., thus
raising the carbon content of the exterior of the piece. The article when quenched in an oil bath will
have an extremely hard exterior and tough core. It is a good scheme for tools that must be hard and
yet strong enough to stand abuse. Raw bone is never used as a packing for this class of work, as it
makes the cutting edges brittle.
CASE-HARDENING TREATMENTS FOR VARIOUS STEELS
Plain water, salt water and linseed oil are the three most common quenching materials for case-
hardening. Water is used for ordinary work, salt water for work which must be extremely hard on
the surface, and oil for work in which toughness is the main consideration. The higher the carbon of
the case, the less sudden need the quenching action take hold of the piece; in fact, experience in
Page 77
case-hardening work gives a great many combinations of quenching baths of these three materials,
depending on their temperatures. Thin work, highly carbonized, which would fly to pieces under the
slightest blow if quenched in water or brine, is made strong and tough by properly quenching in
slightly heated oil. It is impossible to give any rules for the temperature of this work, so much
depending on the size and design of the piece; but it is not a difficult matter to try three or four
pieces by different methods and determine what is needed for best results.
The alloy steels are all susceptible of case-hardening treatment; in fact, this is one of the most
important heat treatments for such steels in the automobile industry. Nickel steel carburizes more
slowly than common steel, the nickel seeming to have the effect of slowing down the rate of
penetration. There is no cloud without its silver lining, however, and to offset this retardation, a
single treatment is often sufficient for nickel steel; for the core is not coarsened as much as low-
carbon machinery steel and thus ordinary work may be quenched on the carburizing heat. Steel
containing from 3 to 3.5 per cent of nickel is carburized between 1,650 and 1,750°F. Nickel steel
containing less than 25 points of carbon, with this same percentage of nickel, may be slightly
hardened by cooling in air instead of quenching.
Chrome-nickel steel may be case-hardened similarly to the method just described for nickel steel,
but double treatment gives better results and is used for high-grade work. The carburizing
temperature is the same, between 1,650 and 1,750°F., the second treatment consisting of reheating
to 1,400° and then quenching in boiling salt water, which gives a hard surface and at the same time
prevents distortion of the piece. The core of chrome-nickel case-hardened steel, like that of nickel
steel, is not coarsened excessively by the first heat treatment, and therefore a single heating and
quenching will suffice.
CARBURIZING BY GAS
The process of carburizing by gas, briefly mentioned on page 88, consists of having a slowly
revolving, properly heated, cylindrical retort into which illuminating gas (a mixture of various
hydrocarbons) is continuously injected under pressure. The spent gases are vented to insure the
greatest speed in carbonizing. The work is constantly and uniformly exposed to a clean carbonizing
atmosphere instead of partially spent carbonaceous solids which may give off very complex
compounds of phosphorus, sulphur, carbon and nitrogen.
Originally this process was thought to require a gas generator but it has been discovered that city
gas works all right. The gas consists of vapors derived from petroleum or bituminous coal.
Sometimes the gas supply is diluted by air, to reduce the speed of carburization and increase the
depth.
PREVENTING CARBURIZING BY COPPER-PLATING
Copper-plating has been found effective and must have a thickness of 0.0005 in. Less than this
does not give a continuous coating. The plating bath used has a temperature of 170°F. A voltage of
4.1 is to be maintained across the terminals. Regions which are to be hardened can be kept free
from copper by coating them with paraffin before they enter the plating tank. The operation is as
follows:
Operation
No. Contents of bath Purpose
depending on their temperatures. Thin work, highly carbonized, which would fly to pieces under the
slightest blow if quenched in water or brine, is made strong and tough by properly quenching in
slightly heated oil. It is impossible to give any rules for the temperature of this work, so much
depending on the size and design of the piece; but it is not a difficult matter to try three or four
pieces by different methods and determine what is needed for best results.
The alloy steels are all susceptible of case-hardening treatment; in fact, this is one of the most
important heat treatments for such steels in the automobile industry. Nickel steel carburizes more
slowly than common steel, the nickel seeming to have the effect of slowing down the rate of
penetration. There is no cloud without its silver lining, however, and to offset this retardation, a
single treatment is often sufficient for nickel steel; for the core is not coarsened as much as low-
carbon machinery steel and thus ordinary work may be quenched on the carburizing heat. Steel
containing from 3 to 3.5 per cent of nickel is carburized between 1,650 and 1,750°F. Nickel steel
containing less than 25 points of carbon, with this same percentage of nickel, may be slightly
hardened by cooling in air instead of quenching.
Chrome-nickel steel may be case-hardened similarly to the method just described for nickel steel,
but double treatment gives better results and is used for high-grade work. The carburizing
temperature is the same, between 1,650 and 1,750°F., the second treatment consisting of reheating
to 1,400° and then quenching in boiling salt water, which gives a hard surface and at the same time
prevents distortion of the piece. The core of chrome-nickel case-hardened steel, like that of nickel
steel, is not coarsened excessively by the first heat treatment, and therefore a single heating and
quenching will suffice.
CARBURIZING BY GAS
The process of carburizing by gas, briefly mentioned on page 88, consists of having a slowly
revolving, properly heated, cylindrical retort into which illuminating gas (a mixture of various
hydrocarbons) is continuously injected under pressure. The spent gases are vented to insure the
greatest speed in carbonizing. The work is constantly and uniformly exposed to a clean carbonizing
atmosphere instead of partially spent carbonaceous solids which may give off very complex
compounds of phosphorus, sulphur, carbon and nitrogen.
Originally this process was thought to require a gas generator but it has been discovered that city
gas works all right. The gas consists of vapors derived from petroleum or bituminous coal.
Sometimes the gas supply is diluted by air, to reduce the speed of carburization and increase the
depth.
PREVENTING CARBURIZING BY COPPER-PLATING
Copper-plating has been found effective and must have a thickness of 0.0005 in. Less than this
does not give a continuous coating. The plating bath used has a temperature of 170°F. A voltage of
4.1 is to be maintained across the terminals. Regions which are to be hardened can be kept free
from copper by coating them with paraffin before they enter the plating tank. The operation is as
follows:
Operation
No. Contents of bath Purpose
Page 78
1 Gasoline To remove grease
2 Sawdust To dry
3 Warm potassium hydroxide solution To remove grease and dirt
4 Warm water To wash
5 Warm sulphuric acid solution To acid clean
6 Warm water To wash
7 Cold water Additional wash
8 Cold potassium cyanide solution Cleanser
9 Cold water To wash
10 Electric cleaner, warm sodium hydroxide case-iron Cleanser to give good
anode plating surface
11 Copper plating bath of copper sulphate and potassium Plating bath
cyanide solution warm
There are also other methods of preventing case-hardening, one being to paint the surface with a
special compound prepared for this purpose. In some cases a coating of plastic asbestos is used
while in others thin sheet asbestos is wired around the part to be kept soft.
PREPARING PARTS FOR LOCAL CASE-HARDENING
At the works of the Dayton Engineering Laboratories Company, Dayton, Ohio, they have a large
quantity of small shafts, Fig. 40, that are to be case-hardened at A while the ends B and C are to be
left soft. Formerly, the part A was brush-coated with melted paraffin but, as there were many shafts,
this was tedious and great care was necessary to avoid getting paraffin where it was not wanted.
FIG. 40.—Shaft to be coated with paraffin.
To insure uniform coating the device shown in Fig. 41 was made. Melted paraffin is poured in the
well A and kept liquid by setting the device on a hot plate, the paraffin being kept high enough to
touch the bottoms of the rollers. The shaft to be coated is laid between the rollers with one end
against the gage B, when a turn or two of the crank C will cause it to be evenly coated.
2 Sawdust To dry
3 Warm potassium hydroxide solution To remove grease and dirt
4 Warm water To wash
5 Warm sulphuric acid solution To acid clean
6 Warm water To wash
7 Cold water Additional wash
8 Cold potassium cyanide solution Cleanser
9 Cold water To wash
10 Electric cleaner, warm sodium hydroxide case-iron Cleanser to give good
anode plating surface
11 Copper plating bath of copper sulphate and potassium Plating bath
cyanide solution warm
There are also other methods of preventing case-hardening, one being to paint the surface with a
special compound prepared for this purpose. In some cases a coating of plastic asbestos is used
while in others thin sheet asbestos is wired around the part to be kept soft.
PREPARING PARTS FOR LOCAL CASE-HARDENING
At the works of the Dayton Engineering Laboratories Company, Dayton, Ohio, they have a large
quantity of small shafts, Fig. 40, that are to be case-hardened at A while the ends B and C are to be
left soft. Formerly, the part A was brush-coated with melted paraffin but, as there were many shafts,
this was tedious and great care was necessary to avoid getting paraffin where it was not wanted.
FIG. 40.—Shaft to be coated with paraffin.
To insure uniform coating the device shown in Fig. 41 was made. Melted paraffin is poured in the
well A and kept liquid by setting the device on a hot plate, the paraffin being kept high enough to
touch the bottoms of the rollers. The shaft to be coated is laid between the rollers with one end
against the gage B, when a turn or two of the crank C will cause it to be evenly coated.
Page 79
FIG. 41.—Device for coating the shaft.
THE PENETRATION OF CARBON
Carburized mild steel is used to a great extent in the manufacture of automobile and other parts
which are likely to be subjected to rough usage. The strength and ability to withstand hard knocks
depend to a very considerable degree on the thoroughness with which the carburizing process is
conducted.
Many automobile manufacturers have at one time or another passed through a period of
unfortunate breakages, or have found that for a certain period the parts turned out of their hardening
shops were not sufficiently hard to enable the rubbing surfaces to stand up against the pressure to
which they were subjected.
So many factors govern the success of hardening that often this succession of bad work has been
actually overcome without those interested realizing what was the weak point in their system of
treatment. As the question is one that can create a bad reputation for the product of any firm it is
well to study the influential factors minutely.
INTRODUCTION OF CARBON
The matter to which these notes are primarily directed is the introduction of carbon into the case
of the article to be hardened. In the first place the chances of success are increased by selecting as
few brands of steel as practicable to cover the requirements of each component of the mechanism.
The hardener is then able to become accustomed to the characteristics of that particular material,
and after determining the most suitable treatment for it no further experimenting beyond the usual
check-test pieces is necessary.
THE PENETRATION OF CARBON
Carburized mild steel is used to a great extent in the manufacture of automobile and other parts
which are likely to be subjected to rough usage. The strength and ability to withstand hard knocks
depend to a very considerable degree on the thoroughness with which the carburizing process is
conducted.
Many automobile manufacturers have at one time or another passed through a period of
unfortunate breakages, or have found that for a certain period the parts turned out of their hardening
shops were not sufficiently hard to enable the rubbing surfaces to stand up against the pressure to
which they were subjected.
So many factors govern the success of hardening that often this succession of bad work has been
actually overcome without those interested realizing what was the weak point in their system of
treatment. As the question is one that can create a bad reputation for the product of any firm it is
well to study the influential factors minutely.
INTRODUCTION OF CARBON
The matter to which these notes are primarily directed is the introduction of carbon into the case
of the article to be hardened. In the first place the chances of success are increased by selecting as
few brands of steel as practicable to cover the requirements of each component of the mechanism.
The hardener is then able to become accustomed to the characteristics of that particular material,
and after determining the most suitable treatment for it no further experimenting beyond the usual
check-test pieces is necessary.
Page 80
Although a certain make of material may vary in composition from time to time the products of a
manufacturer of good steel can be generally relied upon, and it is better to deal directly with him
than with others.
In most cases the case-hardening steels can be chosen from the following: (1) Case-hardening
mild steel of 0.20 per cent carbon; (2) case-hardening 3½ per cent nickel steel; (3) case-hardening
nickel-chromium steel; (4) case-hardening chromium vanadium. After having chosen a suitable
steel it is best to have the sample analyzed by reliable chemists and also to have test pieces
machined and pulled.
To prepare samples for analysis place a sheet of paper on the table of a drilling machine, and with
a 3/8-in. diameter drill, machine a few holes about 3/8 in. deep in various parts of the sample bar,
collecting about 3 oz. of fine drillings free from dust. This can be placed in a bottle and dispatched
to the laboratory with instructions to search for carbon, silicon, manganese, sulphur, phosphorus
and alloys. The results of the different tests should be carefully tabulated, and as there would most
probably be some variation an average should be made as a fair basis of each element present, and
the following tables may be used with confidence when deciding if the material is reliable enough
to be used.
TABLE 16.—CASE-HARDENING MILD STEEL OF 0.20 PER CENT CARBON
Carbon 0.15 to 0.25 per cent
Silicon Not over 0.20 per cent
Manganese 0.30 to 0.60 per cent
Sulphur Not over 0.04 per cent
Phosphorus Not over 0.04 per cent
A tension test should register at least 60,000 lb. per square inch.
TABLE 17.—CASE-HARDENING 3½ PER CENT NICKEL STEEL
Carbon 0.12 to 0.20 per cent
Manganese 0.65 per cent
Sulphur Not over 0.045 per cent
Phosphorus Not over 0.04 per cent
Nickel 3.25 to 3.75 per cent
TABLE 18.—CASE-HARDENING NICKEL CHROMIUM STEEL
Carbon 0.15 to 0.25 per cent
Manganese 0.50 to 0.80 per cent
Sulphur Not over 0.045 per cent
Phosphorus Not over 0.04 per cent
Nickel 1 to 1.5 per cent
Chromium 0.45 to 0.75 per cent
TABLE 19.—CASE-HARDENING CHROMIUM VANADIUM STEEL
Carbon Not over 0.25 per cent
Manganese 0.50 to 0.85 per cent
manufacturer of good steel can be generally relied upon, and it is better to deal directly with him
than with others.
In most cases the case-hardening steels can be chosen from the following: (1) Case-hardening
mild steel of 0.20 per cent carbon; (2) case-hardening 3½ per cent nickel steel; (3) case-hardening
nickel-chromium steel; (4) case-hardening chromium vanadium. After having chosen a suitable
steel it is best to have the sample analyzed by reliable chemists and also to have test pieces
machined and pulled.
To prepare samples for analysis place a sheet of paper on the table of a drilling machine, and with
a 3/8-in. diameter drill, machine a few holes about 3/8 in. deep in various parts of the sample bar,
collecting about 3 oz. of fine drillings free from dust. This can be placed in a bottle and dispatched
to the laboratory with instructions to search for carbon, silicon, manganese, sulphur, phosphorus
and alloys. The results of the different tests should be carefully tabulated, and as there would most
probably be some variation an average should be made as a fair basis of each element present, and
the following tables may be used with confidence when deciding if the material is reliable enough
to be used.
TABLE 16.—CASE-HARDENING MILD STEEL OF 0.20 PER CENT CARBON
Carbon 0.15 to 0.25 per cent
Silicon Not over 0.20 per cent
Manganese 0.30 to 0.60 per cent
Sulphur Not over 0.04 per cent
Phosphorus Not over 0.04 per cent
A tension test should register at least 60,000 lb. per square inch.
TABLE 17.—CASE-HARDENING 3½ PER CENT NICKEL STEEL
Carbon 0.12 to 0.20 per cent
Manganese 0.65 per cent
Sulphur Not over 0.045 per cent
Phosphorus Not over 0.04 per cent
Nickel 3.25 to 3.75 per cent
TABLE 18.—CASE-HARDENING NICKEL CHROMIUM STEEL
Carbon 0.15 to 0.25 per cent
Manganese 0.50 to 0.80 per cent
Sulphur Not over 0.045 per cent
Phosphorus Not over 0.04 per cent
Nickel 1 to 1.5 per cent
Chromium 0.45 to 0.75 per cent
TABLE 19.—CASE-HARDENING CHROMIUM VANADIUM STEEL
Carbon Not over 0.25 per cent
Manganese 0.50 to 0.85 per cent
Page 81
Sulphur Not over 0.04 per cent
Phosphorus Not over 0.04 per cent
Chromium 0.80 to 1.10 per cent
Vanadium Not less than 0.15 per cent
Having determined what is required we now proceed to inquire into the question of carburizing,
which is of vital importance.
USING ILLUMINATING GAS
The choice of a carburizing furnace depends greatly on the facilities available in the locality where
the shop is situated and the nature and quantity of the work to be done. The furnaces can be heated
with producer gas in most cases, but when space is of value illuminating gas from a separate source
of supply has some compensations. When the latter is used it is well to install a governor if the
pressure is likely to fluctuate, particularly where the shop is at a high altitude or at a long distance
from the gas supply.
Many furnaces are coal-fired, and although greater care is required in maintaining a uniform
temperature good results have been obtained. The use of electricity as a means of reaching the
requisite temperature is receiving some attention, and no doubt it would make the control of
temperature comparatively simple. However, the cost when applied to large quantities of work will,
for the present at least, prevent this method from becoming popular. It is believed that the results
obtainable \with the electric furnace would surpass any others; but the apparatus is expensive, and
unless handled with intelligence would not last long.
The most elementary medium of carburization is pure carbon, but the rate of carburization induced
by this material is very low, and other components are necessary to accelerate the process. Many
mixtures have been marketed, each possessing its individual merits, and as the prices vary
considerably it is difficult to decide which is the most advantageous.
Absorption from actual contact with solid carbon is decidedly slow, and it is necessary to employ a
compound from which gases are liberated, and the steel will absorb the carbon from the gases much
more readily.
Both bone and leather charcoal give off more carburizing gases than wood charcoal, and although
the high sulphur content of the leather is objectionable as being injurious to the steel, as also is the
high phosphorus content of the bone charcoal, they are both preferable to the wood charcoal.
By mixing bone charcoal with barium carbonate in the proportions of 60 per cent of the former to
40 per cent of the latter a very reliable compound is obtained.
The temperature to which this compound is subjected causes the liberation of carbon monoxide
when in contact with hot charcoal.
Many more elaborate explanations may be given of the actions and reactions taking place, but the
above is a satisfactory guide to indicate that it is not the actual compound which causes
carburization, but the gases released from the compound.
Phosphorus Not over 0.04 per cent
Chromium 0.80 to 1.10 per cent
Vanadium Not less than 0.15 per cent
Having determined what is required we now proceed to inquire into the question of carburizing,
which is of vital importance.
USING ILLUMINATING GAS
The choice of a carburizing furnace depends greatly on the facilities available in the locality where
the shop is situated and the nature and quantity of the work to be done. The furnaces can be heated
with producer gas in most cases, but when space is of value illuminating gas from a separate source
of supply has some compensations. When the latter is used it is well to install a governor if the
pressure is likely to fluctuate, particularly where the shop is at a high altitude or at a long distance
from the gas supply.
Many furnaces are coal-fired, and although greater care is required in maintaining a uniform
temperature good results have been obtained. The use of electricity as a means of reaching the
requisite temperature is receiving some attention, and no doubt it would make the control of
temperature comparatively simple. However, the cost when applied to large quantities of work will,
for the present at least, prevent this method from becoming popular. It is believed that the results
obtainable \with the electric furnace would surpass any others; but the apparatus is expensive, and
unless handled with intelligence would not last long.
The most elementary medium of carburization is pure carbon, but the rate of carburization induced
by this material is very low, and other components are necessary to accelerate the process. Many
mixtures have been marketed, each possessing its individual merits, and as the prices vary
considerably it is difficult to decide which is the most advantageous.
Absorption from actual contact with solid carbon is decidedly slow, and it is necessary to employ a
compound from which gases are liberated, and the steel will absorb the carbon from the gases much
more readily.
Both bone and leather charcoal give off more carburizing gases than wood charcoal, and although
the high sulphur content of the leather is objectionable as being injurious to the steel, as also is the
high phosphorus content of the bone charcoal, they are both preferable to the wood charcoal.
By mixing bone charcoal with barium carbonate in the proportions of 60 per cent of the former to
40 per cent of the latter a very reliable compound is obtained.
The temperature to which this compound is subjected causes the liberation of carbon monoxide
when in contact with hot charcoal.
Many more elaborate explanations may be given of the actions and reactions taking place, but the
above is a satisfactory guide to indicate that it is not the actual compound which causes
carburization, but the gases released from the compound.
Page 82
Until the temperature of the muffle reaches about 1,300°F. carburization does not take place to any
useful extent, and consequently it is advisable to avoid the use of any compound from which the
carburizing gases are liberated much before that temperature is reached. In the case of steel
containing nickel slightly higher temperatures may be used and are really necessary if the same rate
of carbon penetration is to be obtained, as the presence of nickel resists the penetration.
At higher temperatures the rate of penetration is higher, but not exactly in proportion to the
temperature, and the rate is also influenced by the nature of the material and the efficiency of the
compound employed.
The so-called saturation point of mild steel is reached when the case contains 0.90 per cent of
carbon, but this amount is frequently exceeded. Should it be required to ascertain the amount of
carbon in a sample at varying depths below the skin this can be done by turning off a small amount
after carburizing and analyzing the turnings. This can be repeated several times, and it will probably
be found that the proportion of carbon decreases as the test piece is reduced in diameter unless
decarburization has taken place.
FIG. 42.—Chart showing penetration of carbon.
The chart, Fig. 42, is also a good guide.
In order to use the chart it is necessary to harden the sample we desire to test as we would harden
a piece of tool steel, and then test by scleroscope. By locating on the chart the point on the
horizontal axis which represents the hardness of the sample the curve enables one to determine the
approximate amount of carbon present in the case.
Should the hardness lack uniformity the soft places can be identified by etching. To accomplish
this the sample should be polished after quenching and then washed with a weak solution of nitric
acid in alcohol, whereupon the harder points will show up darker than the softer areas.
The selection of suitable boxes for carburizing is worthy of a little consideration, and there can be
no doubt that in certain cases results are spoiled and considerable expense caused by using
unsuitable containers.
useful extent, and consequently it is advisable to avoid the use of any compound from which the
carburizing gases are liberated much before that temperature is reached. In the case of steel
containing nickel slightly higher temperatures may be used and are really necessary if the same rate
of carbon penetration is to be obtained, as the presence of nickel resists the penetration.
At higher temperatures the rate of penetration is higher, but not exactly in proportion to the
temperature, and the rate is also influenced by the nature of the material and the efficiency of the
compound employed.
The so-called saturation point of mild steel is reached when the case contains 0.90 per cent of
carbon, but this amount is frequently exceeded. Should it be required to ascertain the amount of
carbon in a sample at varying depths below the skin this can be done by turning off a small amount
after carburizing and analyzing the turnings. This can be repeated several times, and it will probably
be found that the proportion of carbon decreases as the test piece is reduced in diameter unless
decarburization has taken place.
FIG. 42.—Chart showing penetration of carbon.
The chart, Fig. 42, is also a good guide.
In order to use the chart it is necessary to harden the sample we desire to test as we would harden
a piece of tool steel, and then test by scleroscope. By locating on the chart the point on the
horizontal axis which represents the hardness of the sample the curve enables one to determine the
approximate amount of carbon present in the case.
Should the hardness lack uniformity the soft places can be identified by etching. To accomplish
this the sample should be polished after quenching and then washed with a weak solution of nitric
acid in alcohol, whereupon the harder points will show up darker than the softer areas.
The selection of suitable boxes for carburizing is worthy of a little consideration, and there can be
no doubt that in certain cases results are spoiled and considerable expense caused by using
unsuitable containers.
Page 83
As far as initial expense goes cast-iron boxes are probably the most expedient, but although they
will withstand the necessary temperatures they are liable to split and crack, and when they get out
of shape there is much difficulty in straightening them.
The most suitable material in most cases is steel boiler plate 3/8 or 1/2 in. thick, which can be
made with welded joints and will last well.
The sizes of the boxes employed depend to a great extent on the nature of the work being done,
but care should be exercised to avoid putting too much in one box, as smaller ones permit the heat
to penetrate more quickly, and one test piece is sufficient to give a good indication of what has
taken place. If it should be necessary to use larger boxes it is advisable to put in three or four test
pieces in different positions to ascertain if the penetration of carbon has been satisfactory in all parts
of the box, as it is quite possible that the temperature of the muffle is not the same at all points, and
a record shown by one test piece would not then be applicable to all the parts contained in the box.
It has been found that the rate of carbon penetration increases with the gas pressure around the
articles being carburized, and it is therefore necessary to be careful in sealing up the boxes after
packing. When the articles are placed within and each entirely surrounded by compound so that the
compound reaches to within 1 in. of the top of the box a layer of clay should be run around the
inside of the box on top of the compound. The lid, which should be a good fit in the box, is then to
be pressed on top of this, and another layer of clay run just below the rim of the box on top of the
cover.
A SATISFACTORY LUTING MIXTURE
A mixture of fireclay and sand will be found very satisfactory for closing up the boxes, and by
observing the appearance of the work when taken out we can gage the suitability of the methods
employed, for unless the boxes are carefully sealed the work is generally covered with dark scales,
while if properly done the articles will be of a light gray.
By observing the above recommendations reliable results can be obtained, and we can expect
uniform results after quenching.
GAS CONSUMPTION FOR CARBURIZING
Although the advantages offered by the gas-fired furnace for carburizing have been generally
recognized in the past from points of view as close temperature regulation, decreased attendance,
and greater convenience, very little information has been published regarding the consumption of
gas for this process. It has therefore been a matter of great difficulty to obtain authentic information
upon this point, either from makers or users of such furnaces.
In view of this, the details of actual consumption of gas on a regular customer's order job will be
of interest. The "Revergen" furnace, manufactured by the Davis Furnace Company, Luton, Bedford,
England, was used on this job, and is provided with regenerators and fired with illuminating gas at
ordinary pressure, the air being introduced to the furnace at a slight pressure of 3 to 4 in. water
gage. The material was charged into a cold furnace, raised to 1,652°F., and maintained at that
temperature for 8 hr. to give the necessary depth of case. The work consisted of automobile gears
packed in six boxes, the total weight being 713 lb. The required temperature of 1,652°F. was
obtained in 70 min. from lighting up, and a summary of the data is shown in the following table:
will withstand the necessary temperatures they are liable to split and crack, and when they get out
of shape there is much difficulty in straightening them.
The most suitable material in most cases is steel boiler plate 3/8 or 1/2 in. thick, which can be
made with welded joints and will last well.
The sizes of the boxes employed depend to a great extent on the nature of the work being done,
but care should be exercised to avoid putting too much in one box, as smaller ones permit the heat
to penetrate more quickly, and one test piece is sufficient to give a good indication of what has
taken place. If it should be necessary to use larger boxes it is advisable to put in three or four test
pieces in different positions to ascertain if the penetration of carbon has been satisfactory in all parts
of the box, as it is quite possible that the temperature of the muffle is not the same at all points, and
a record shown by one test piece would not then be applicable to all the parts contained in the box.
It has been found that the rate of carbon penetration increases with the gas pressure around the
articles being carburized, and it is therefore necessary to be careful in sealing up the boxes after
packing. When the articles are placed within and each entirely surrounded by compound so that the
compound reaches to within 1 in. of the top of the box a layer of clay should be run around the
inside of the box on top of the compound. The lid, which should be a good fit in the box, is then to
be pressed on top of this, and another layer of clay run just below the rim of the box on top of the
cover.
A SATISFACTORY LUTING MIXTURE
A mixture of fireclay and sand will be found very satisfactory for closing up the boxes, and by
observing the appearance of the work when taken out we can gage the suitability of the methods
employed, for unless the boxes are carefully sealed the work is generally covered with dark scales,
while if properly done the articles will be of a light gray.
By observing the above recommendations reliable results can be obtained, and we can expect
uniform results after quenching.
GAS CONSUMPTION FOR CARBURIZING
Although the advantages offered by the gas-fired furnace for carburizing have been generally
recognized in the past from points of view as close temperature regulation, decreased attendance,
and greater convenience, very little information has been published regarding the consumption of
gas for this process. It has therefore been a matter of great difficulty to obtain authentic information
upon this point, either from makers or users of such furnaces.
In view of this, the details of actual consumption of gas on a regular customer's order job will be
of interest. The "Revergen" furnace, manufactured by the Davis Furnace Company, Luton, Bedford,
England, was used on this job, and is provided with regenerators and fired with illuminating gas at
ordinary pressure, the air being introduced to the furnace at a slight pressure of 3 to 4 in. water
gage. The material was charged into a cold furnace, raised to 1,652°F., and maintained at that
temperature for 8 hr. to give the necessary depth of case. The work consisted of automobile gears
packed in six boxes, the total weight being 713 lb. The required temperature of 1,652°F. was
obtained in 70 min. from lighting up, and a summary of the data is shown in the following table:
Page 84
Cubic Foot Total
Per Pound Number of
of Load Cubic Foot
Gas to raise furnace and charge from cold to 1,652°F., 70 min. 1.29 925
Gas to maintain 1,652°F. for 1st hour 0.38 275
Gas to maintain 1,652°F. for 2nd hour 0.42 300
Gas to maintain 1,652°F. for 3rd hour 0.38 275
Gas to maintain 1,652°F. for 4th hour 0.42 300
Gas to maintain 1,652°F. for 5th hour 0.49 350
Gas to maintain 1,652°F. for 6th hour 0.49 350
Gas to maintain 1,652°F. for 7th hour 0.45 325
Gas to maintain 1,652°F. for 8th hour 0.45 325
The overall gas consumption for this run of 9 hr. 10 min. was only 4.8 cu. ft. per pound of load.
THE CARE OF CARBURIZING COMPOUNDS
Of all the opportunities for practicing economy in the heat-treatment department, there is none that
offers greater possibilities for profitable returns than the systematic cleaning, blending and
reworking of artificial carburizers, or compounds.
The question of whether or not it is practical to take up the work depends upon the nature of the
output. If the sole product of the hardening department consists of a 1.10 carbon case or harder,
requiring a strong highly energized material of deep penetrative power such as that used in the
carburizing of ball races, hub-bearings and the like, it would be best to dispose of the used material
to some concern whose product requires a case with from 0.70 to 0.90 carbon, but where there is a
large variety of work the compound may be so handled that there will be practically no waste.
This is accomplished with one of the most widely known artificial carburizers by giving all the
compound in the plant three distinct classifications: "New," being direct from the maker; "half and
half," being one part of new and one part first run; and "2 to 1," which consists of two parts of old
and one part new.
SEPARATING THE WORK FROM THE COMPOUND
During the pulling of the heat, the pots are dumped upon a cast-iron screen which forms a table or
apron for the furnace. Directly beneath this table is located one of the steel conveyor carts, shown in
Fig. 43, which is provided with two wheels at the rear and a dolly clevis at the front, which allows it
to be hauled away from beneath the furnace apron while filled with red-hot compound. A steel
cover is provided for each box, and the material is allowed to cool without losing much of the
evolved gases which are still being thrown off by the compound.
Per Pound Number of
of Load Cubic Foot
Gas to raise furnace and charge from cold to 1,652°F., 70 min. 1.29 925
Gas to maintain 1,652°F. for 1st hour 0.38 275
Gas to maintain 1,652°F. for 2nd hour 0.42 300
Gas to maintain 1,652°F. for 3rd hour 0.38 275
Gas to maintain 1,652°F. for 4th hour 0.42 300
Gas to maintain 1,652°F. for 5th hour 0.49 350
Gas to maintain 1,652°F. for 6th hour 0.49 350
Gas to maintain 1,652°F. for 7th hour 0.45 325
Gas to maintain 1,652°F. for 8th hour 0.45 325
The overall gas consumption for this run of 9 hr. 10 min. was only 4.8 cu. ft. per pound of load.
THE CARE OF CARBURIZING COMPOUNDS
Of all the opportunities for practicing economy in the heat-treatment department, there is none that
offers greater possibilities for profitable returns than the systematic cleaning, blending and
reworking of artificial carburizers, or compounds.
The question of whether or not it is practical to take up the work depends upon the nature of the
output. If the sole product of the hardening department consists of a 1.10 carbon case or harder,
requiring a strong highly energized material of deep penetrative power such as that used in the
carburizing of ball races, hub-bearings and the like, it would be best to dispose of the used material
to some concern whose product requires a case with from 0.70 to 0.90 carbon, but where there is a
large variety of work the compound may be so handled that there will be practically no waste.
This is accomplished with one of the most widely known artificial carburizers by giving all the
compound in the plant three distinct classifications: "New," being direct from the maker; "half and
half," being one part of new and one part first run; and "2 to 1," which consists of two parts of old
and one part new.
SEPARATING THE WORK FROM THE COMPOUND
During the pulling of the heat, the pots are dumped upon a cast-iron screen which forms a table or
apron for the furnace. Directly beneath this table is located one of the steel conveyor carts, shown in
Fig. 43, which is provided with two wheels at the rear and a dolly clevis at the front, which allows it
to be hauled away from beneath the furnace apron while filled with red-hot compound. A steel
cover is provided for each box, and the material is allowed to cool without losing much of the
evolved gases which are still being thrown off by the compound.
Page 85
FIG. 43.—The cooling carts.
FIG. 44.—Machine for blending the mixture.
As this compound comes from the carburizing pots it contains bits of fireclay which represent a
part of the luting used for sealing, and there may be small parts of work or bits of fused material in
it as well. After cooling, the compound is very dusty and disagreeable to handle, and, before it can
be used again, must be sifted, cleaned and blended.
Some time ago the writer was confronted with this proposition for one of the largest consumers of
carburizing compound in the world, and the problem was handled in the following manner: The
cooled compound was dumped from the cooling cars and sprinkled with a low-grade oil which
served the dual purposes of settling the dust and adding a certain percentage of valuable
FIG. 44.—Machine for blending the mixture.
As this compound comes from the carburizing pots it contains bits of fireclay which represent a
part of the luting used for sealing, and there may be small parts of work or bits of fused material in
it as well. After cooling, the compound is very dusty and disagreeable to handle, and, before it can
be used again, must be sifted, cleaned and blended.
Some time ago the writer was confronted with this proposition for one of the largest consumers of
carburizing compound in the world, and the problem was handled in the following manner: The
cooled compound was dumped from the cooling cars and sprinkled with a low-grade oil which
served the dual purposes of settling the dust and adding a certain percentage of valuable
Page 86
hydrocarbon to the compound. In Fig. 44 is shown the machine that was designed to do the cleaning
and blending.
BLENDING THE COMPOUND
Essentially, this consists of the sturdy, power-driven separator and fanning mill which separates
the foreign matter from the compound and elevates it into a large settling basin which is formed by
the top of the steel housing that incloses the apparatus. After reaching the settling basin, the
compound falls by gravity into a power-driven rotary mixing tub which is directly beneath the
settling basin. Here the blending is done by mixing the proper amount of various grades of material
together. After blending the compound, it is ready to be stored in labeled containers and delivered to
the packing room.
It will be seen that by this simple system there is the least possible loss of energy from the
compound. The saving commences the moment the cooling cart is covered and preserves the
valuable dust which is saved by the oiling and the settling basin of the blending machine.
Then, too, there is the added convenience of the packers who have a thoroughly cleaned, dustless,
and standardized product to work with. Of course, this also tends to insure uniformity in the case-
hardening operation.
With this outfit, one man cleans and blends as much compound in one hour as he formerly did in
ten.
and blending.
BLENDING THE COMPOUND
Essentially, this consists of the sturdy, power-driven separator and fanning mill which separates
the foreign matter from the compound and elevates it into a large settling basin which is formed by
the top of the steel housing that incloses the apparatus. After reaching the settling basin, the
compound falls by gravity into a power-driven rotary mixing tub which is directly beneath the
settling basin. Here the blending is done by mixing the proper amount of various grades of material
together. After blending the compound, it is ready to be stored in labeled containers and delivered to
the packing room.
It will be seen that by this simple system there is the least possible loss of energy from the
compound. The saving commences the moment the cooling cart is covered and preserves the
valuable dust which is saved by the oiling and the settling basin of the blending machine.
Then, too, there is the added convenience of the packers who have a thoroughly cleaned, dustless,
and standardized product to work with. Of course, this also tends to insure uniformity in the case-
hardening operation.
With this outfit, one man cleans and blends as much compound in one hour as he formerly did in
ten.
Page 87
CHAPTER VII
HEAT TREATMENT OF STEEL
Heat treatment consists in heating and cooling metal at definite rates in order to change its
physical condition. Many objects may be attained by correct heat treatment, but nothing much can
be expected unless the man who directs the operations knows what is the essential difference in a
piece of steel at room temperature and at a red heat, other than the obvious fact that it is hot. The
science of metallography has been developed in the past 25 years, and aided by precise methods of
measuring temperature, has done much to systematize the information which we possess on
metallic alloys, and steel in particular.
CRITICAL POINTS
One of the most important means of investigating the properties of pure metals and their alloys is
by an examination of their heating and cooling curves. Such curves are constructed by taking a
small piece and observing and recording the temperature of the mass at uniform intervals of time
during a uniform heating or cooling. These observations, when plotted in the form of a curve will
show whether the temperature of the mass rises or falls uniformly.
The heat which a body absorbs serves either to raise the temperature of the mass or change its
physical condition. That portion of the heat which results in an increase in temperature of the body
is called "sensible heat," inasmuch as such a gain in heat is apparent to the physical senses of the
observer. If heat were supplied to the body at a uniform rate, the temperature would rise
continuously, and if the temperature were plotted against time, a smooth rising curve would result.
Or, if sensible heat were abstracted from the body at a uniform rate, a time-temperature curve would
again be a smooth falling curve. Such a curve is called a "cooling curve."
However, we find that when a body is melting, vaporizing, or otherwise suffering an abrupt
change in physical properties, a quantity of heat is absorbed which disappears without changing the
temperature of the body. This heat absorbed during a change of state is called "latent heat," because
it is transformed into the work necessary to change the configuration and disposition of the
molecules in the body; but it is again liberated in equal amount when the reverse change takes
place.
From these considerations it would seem that should the cooling curve be continuous and smooth,
following closely a regular course, all the heat abstracted during cooling is furnished at the expense
of a fall in temperature of the body; that is to say, it disappears as "sensible heat." These curves,
however, frequently show horizontal portions or "arrests" which denote that at that temperature all
of the heat constantly radiating is being supplied by internal changes in the alloy itself; that is, it is
being supplied by the evolution of a certain amount of "latent heat."
HEAT TREATMENT OF STEEL
Heat treatment consists in heating and cooling metal at definite rates in order to change its
physical condition. Many objects may be attained by correct heat treatment, but nothing much can
be expected unless the man who directs the operations knows what is the essential difference in a
piece of steel at room temperature and at a red heat, other than the obvious fact that it is hot. The
science of metallography has been developed in the past 25 years, and aided by precise methods of
measuring temperature, has done much to systematize the information which we possess on
metallic alloys, and steel in particular.
CRITICAL POINTS
One of the most important means of investigating the properties of pure metals and their alloys is
by an examination of their heating and cooling curves. Such curves are constructed by taking a
small piece and observing and recording the temperature of the mass at uniform intervals of time
during a uniform heating or cooling. These observations, when plotted in the form of a curve will
show whether the temperature of the mass rises or falls uniformly.
The heat which a body absorbs serves either to raise the temperature of the mass or change its
physical condition. That portion of the heat which results in an increase in temperature of the body
is called "sensible heat," inasmuch as such a gain in heat is apparent to the physical senses of the
observer. If heat were supplied to the body at a uniform rate, the temperature would rise
continuously, and if the temperature were plotted against time, a smooth rising curve would result.
Or, if sensible heat were abstracted from the body at a uniform rate, a time-temperature curve would
again be a smooth falling curve. Such a curve is called a "cooling curve."
However, we find that when a body is melting, vaporizing, or otherwise suffering an abrupt
change in physical properties, a quantity of heat is absorbed which disappears without changing the
temperature of the body. This heat absorbed during a change of state is called "latent heat," because
it is transformed into the work necessary to change the configuration and disposition of the
molecules in the body; but it is again liberated in equal amount when the reverse change takes
place.
From these considerations it would seem that should the cooling curve be continuous and smooth,
following closely a regular course, all the heat abstracted during cooling is furnished at the expense
of a fall in temperature of the body; that is to say, it disappears as "sensible heat." These curves,
however, frequently show horizontal portions or "arrests" which denote that at that temperature all
of the heat constantly radiating is being supplied by internal changes in the alloy itself; that is, it is
being supplied by the evolution of a certain amount of "latent heat."
Page 88
In addition to the large amount of heat liberated when a metal solidifies, there are other changes
indicated by the thermal analysis of many alloys which occur after the body has become entirely
solidified. These so-called transformation points or ranges may be caused by chemical reactions
taking place within the solid, substances being precipitated from a "solid solution," or a sudden
change in some physical property of the components, such as in magnetism, hardness, or specific
gravity.
It may be difficult to comprehend that such changes can occur in a body after it has become
entirely solidified, owing to the usual conception that the particles are then rigidly fixed. However,
this rigidity is only comparative. The molecules in the solid state have not the large mobility they
possess as a liquid, but even so, they are still moving in circumscribed orbits, and have the power,
under proper conditions, to rearrange their position or internal configuration. In general, such
rearrangement is accompanied by a sudden change in some physical property and in the total energy
of the molecule, which is evidenced by a spontaneous evolution or absorption of latent heat.
Cooling curves of the purest iron show at least two well-defined discontinuities at temperatures
more than 1,000°F., below its freezing-point. It seems that the soft, magnetic metal so familiar as
wrought iron, and called "alpha iron" or "ferrite" by the metallurgist, becomes unstable at about
1,400°F. and changes into the so-called "beta" modification, becoming suddenly harder, and losing
its magnetism. This state in turn persists no higher than 1,706°C., when a softer, non-magnetic
"gamma" iron is the stable modification up to the actual melting-point of the metal. These various
changes occur in electrolytic iron, and therefore cannot be attributed to any chemical reaction or
solution; they are entirely due to the existence of "allotropic modifications" of the iron in its solid
state.
indicated by the thermal analysis of many alloys which occur after the body has become entirely
solidified. These so-called transformation points or ranges may be caused by chemical reactions
taking place within the solid, substances being precipitated from a "solid solution," or a sudden
change in some physical property of the components, such as in magnetism, hardness, or specific
gravity.
It may be difficult to comprehend that such changes can occur in a body after it has become
entirely solidified, owing to the usual conception that the particles are then rigidly fixed. However,
this rigidity is only comparative. The molecules in the solid state have not the large mobility they
possess as a liquid, but even so, they are still moving in circumscribed orbits, and have the power,
under proper conditions, to rearrange their position or internal configuration. In general, such
rearrangement is accompanied by a sudden change in some physical property and in the total energy
of the molecule, which is evidenced by a spontaneous evolution or absorption of latent heat.
Cooling curves of the purest iron show at least two well-defined discontinuities at temperatures
more than 1,000°F., below its freezing-point. It seems that the soft, magnetic metal so familiar as
wrought iron, and called "alpha iron" or "ferrite" by the metallurgist, becomes unstable at about
1,400°F. and changes into the so-called "beta" modification, becoming suddenly harder, and losing
its magnetism. This state in turn persists no higher than 1,706°C., when a softer, non-magnetic
"gamma" iron is the stable modification up to the actual melting-point of the metal. These various
changes occur in electrolytic iron, and therefore cannot be attributed to any chemical reaction or
solution; they are entirely due to the existence of "allotropic modifications" of the iron in its solid
state.
Page 89
FIG. 45.—Inverse Rate Cooling Curve of 0.38 C Steel.
Steels, or iron containing a certain amount of carbon, develop somewhat different cooling curves
from those produced by pure iron. Figure 45 shows, for instance, some data observed on a cooling
piece of 0.38 per cent carbon steel, and the curve constructed therefrom. It will be noted that the
time was noted when the needle on the pyrometer passed each dial marking. If the metal were not
changing in its physical condition, the time between each reading would be nearly constant; in fact
for a time it required about 50 sec. to cool each unit. When the dial read about 32.5 (corresponding
in this instrument to a temperature of 775°C. or 1,427°F.) the cooling rate shortened materially, 55
sec. then 65, then 100, then 100; showing that some change inside the metal was furnishing some of
the steadily radiating heat. This temperature is the so-called "upper critical" for this steel. Further
down, the "lower critical" is shown by a large heat evolution at 695°C. or 1,283°F.
Just the reverse effects take place upon heating, except that the temperatures shown are somewhat
higher—there seems to be a lag in the reactions taking place in the steel. This is an important point
to remember, because if it was desired to anneal a piece of 0.38 carbon steel, it is necessary to heat
it up to and beyond 1,476° F. (1,427°F. plus this lag, which may be as much as 50°).
It may be said immediately that above the upper critical the carbon exists in the iron as a "solid
solution," called "austenite" by metallographers. That is to say, it is uniformly distributed as atoms
throughout the iron; the atoms of carbon are not present in any fixed combination, in fact any
Steels, or iron containing a certain amount of carbon, develop somewhat different cooling curves
from those produced by pure iron. Figure 45 shows, for instance, some data observed on a cooling
piece of 0.38 per cent carbon steel, and the curve constructed therefrom. It will be noted that the
time was noted when the needle on the pyrometer passed each dial marking. If the metal were not
changing in its physical condition, the time between each reading would be nearly constant; in fact
for a time it required about 50 sec. to cool each unit. When the dial read about 32.5 (corresponding
in this instrument to a temperature of 775°C. or 1,427°F.) the cooling rate shortened materially, 55
sec. then 65, then 100, then 100; showing that some change inside the metal was furnishing some of
the steadily radiating heat. This temperature is the so-called "upper critical" for this steel. Further
down, the "lower critical" is shown by a large heat evolution at 695°C. or 1,283°F.
Just the reverse effects take place upon heating, except that the temperatures shown are somewhat
higher—there seems to be a lag in the reactions taking place in the steel. This is an important point
to remember, because if it was desired to anneal a piece of 0.38 carbon steel, it is necessary to heat
it up to and beyond 1,476° F. (1,427°F. plus this lag, which may be as much as 50°).
It may be said immediately that above the upper critical the carbon exists in the iron as a "solid
solution," called "austenite" by metallographers. That is to say, it is uniformly distributed as atoms
throughout the iron; the atoms of carbon are not present in any fixed combination, in fact any
Page 90
amount of carbon from zero to 1.7 per cent can enter into solid solution above the upper critical.
However, upon cooling this steel, the carbon again enters into combination with a definite
proportion of iron (the carbide "cementite," Fe3C), and accumulates into small crystals which can
be seen under a good microscope. Formation of all the cementite has been completed by the time
the temperature has fallen to the lower critical, and below that temperature the steel exists as a
complex substance of pure iron and the iron carbide.
It is important to note that the critical points or critical range of a plain steel varies with its carbon
content. The following table gives some average figures:
Carbon Content. Upper Critical. Lower Critical.
0.00 1,706°F. 1,330°F.
0.20 1,600°F. 1,330°F.
0.40 1,480°F. 1,330°F.
0.60 1,400°F. 1,330°F.
0.80 1,350°F. 1,330°F.
0.90 1,330°F. 1,330°F.
1.00 1,470°F. 1,330°F.
1.20 1,650°F. 1,330°F.
1.40 1,830°F. 1,330°F.
1.60 2,000°F. 1,330°F.
It is immediately noted that the critical range narrows with increasing carbon content until all the
heat seems to be liberated at one temperature in a steel of 0.90 per cent carbon. Beyond that
composition the critical range widens rapidly. Note also that the lower critical is constant in plain
carbon steels containing no alloying elements.
This steel of 0.90 carbon content is an important one. It is
called "eutectoid" steel. Under the microscope a properly
polished and etched sample shows the structure to consist of thin
sheets of two different substances (Fig. 46). One of these is pure
iron, and the other is pure cementite. This structure of thin sheets
has received the name "pearlite," because of its pearly
appearance under sunlight. Pearlite is a constituent found in all
annealed carbon steels. Pure iron, having no carbon, naturally
would show no pearlite when examined under a microscope;
only abutting granules of iron are delicately traced. The
metallographist calls this pure iron "ferrite." As soon as a little
carbon enters the alloy and a soft steel is formed, small angular
areas of pearlite appear at the boundaries of the ferrite crystals FIG. 46.—Microphotograph of steel used in
(Fig. 47). With increasing carbon in the steel the volume of iron S. K. F. bearings, polished and etched with
crystals becomes less and less, and the relative amount of nitric acid and magnified 1,000 times. Made
by H. O. Walp.
pearlite increases, until arriving at 0.90 per cent carbon, the large
ferrite crystals have been suppressed and the structure is all
pearlite. Higher carbon steels show films of cementite outlining grains of pearlite (Fig. 48).
However, upon cooling this steel, the carbon again enters into combination with a definite
proportion of iron (the carbide "cementite," Fe3C), and accumulates into small crystals which can
be seen under a good microscope. Formation of all the cementite has been completed by the time
the temperature has fallen to the lower critical, and below that temperature the steel exists as a
complex substance of pure iron and the iron carbide.
It is important to note that the critical points or critical range of a plain steel varies with its carbon
content. The following table gives some average figures:
Carbon Content. Upper Critical. Lower Critical.
0.00 1,706°F. 1,330°F.
0.20 1,600°F. 1,330°F.
0.40 1,480°F. 1,330°F.
0.60 1,400°F. 1,330°F.
0.80 1,350°F. 1,330°F.
0.90 1,330°F. 1,330°F.
1.00 1,470°F. 1,330°F.
1.20 1,650°F. 1,330°F.
1.40 1,830°F. 1,330°F.
1.60 2,000°F. 1,330°F.
It is immediately noted that the critical range narrows with increasing carbon content until all the
heat seems to be liberated at one temperature in a steel of 0.90 per cent carbon. Beyond that
composition the critical range widens rapidly. Note also that the lower critical is constant in plain
carbon steels containing no alloying elements.
This steel of 0.90 carbon content is an important one. It is
called "eutectoid" steel. Under the microscope a properly
polished and etched sample shows the structure to consist of thin
sheets of two different substances (Fig. 46). One of these is pure
iron, and the other is pure cementite. This structure of thin sheets
has received the name "pearlite," because of its pearly
appearance under sunlight. Pearlite is a constituent found in all
annealed carbon steels. Pure iron, having no carbon, naturally
would show no pearlite when examined under a microscope;
only abutting granules of iron are delicately traced. The
metallographist calls this pure iron "ferrite." As soon as a little
carbon enters the alloy and a soft steel is formed, small angular
areas of pearlite appear at the boundaries of the ferrite crystals FIG. 46.—Microphotograph of steel used in
(Fig. 47). With increasing carbon in the steel the volume of iron S. K. F. bearings, polished and etched with
crystals becomes less and less, and the relative amount of nitric acid and magnified 1,000 times. Made
by H. O. Walp.
pearlite increases, until arriving at 0.90 per cent carbon, the large
ferrite crystals have been suppressed and the structure is all
pearlite. Higher carbon steels show films of cementite outlining grains of pearlite (Fig. 48).
Page 91
This represents the structure of annealed, slowly cooled steels. It is possible to change the relative
sizes of the ferrite and cementite crystals by heat treatment. Large grains are associated with
brittleness. Consequently one must avoid heat treatments which produce coarse grains.
FIG. 47.—Structure of low carbon steel, polished, etched
and viewed under 100 magnifications. Tiny white granules
of pure iron (ferrite) have small accumulations of dark-
etching pearlite interspersed between them. Photograph by
H. S. Rawdon.
FIG. 48.—Slowly cooled high-carbon steel, polished,
etched and viewed at 100 magnifications. The dark grains
are pearlite, separated by white films of iron carbide
(cementite). Photograph by H. S. Rawdon.
In general it may be said that the previous crystalline structure of a steel is entirely obliterated
when it passes just through the critical range. At that moment, in fact, the ferrite, cementite or
pearlite which previously existed has lost its identity by everything going into the solid solution
called austenite. If sufficient time is given, the chemical elements comprising a good steel distribute
themselves uniformly through the mass. If the steel be then cooled, the austenite breaks up into new
crystals of ferrite, cementite and pearlite; and in general if the temperature has not gone far above
the critical, and cooling is not excessively slow, a very fine texture will result. This is called
"refining" the grain; or in shop parlance "closing" the grain. However, if the heating has gone above
the critical very far, the austenite crystals start to grow; a very short time at an extreme temperature
will cause a large grain growth. Subsequent cooling gives a coarse texture, or an arrangement of
ferrite, cementite and pearlite grains which is greatly coarsened, reflecting the condition of the
austenite crystals from which they were born.
sizes of the ferrite and cementite crystals by heat treatment. Large grains are associated with
brittleness. Consequently one must avoid heat treatments which produce coarse grains.
FIG. 47.—Structure of low carbon steel, polished, etched
and viewed under 100 magnifications. Tiny white granules
of pure iron (ferrite) have small accumulations of dark-
etching pearlite interspersed between them. Photograph by
H. S. Rawdon.
FIG. 48.—Slowly cooled high-carbon steel, polished,
etched and viewed at 100 magnifications. The dark grains
are pearlite, separated by white films of iron carbide
(cementite). Photograph by H. S. Rawdon.
In general it may be said that the previous crystalline structure of a steel is entirely obliterated
when it passes just through the critical range. At that moment, in fact, the ferrite, cementite or
pearlite which previously existed has lost its identity by everything going into the solid solution
called austenite. If sufficient time is given, the chemical elements comprising a good steel distribute
themselves uniformly through the mass. If the steel be then cooled, the austenite breaks up into new
crystals of ferrite, cementite and pearlite; and in general if the temperature has not gone far above
the critical, and cooling is not excessively slow, a very fine texture will result. This is called
"refining" the grain; or in shop parlance "closing" the grain. However, if the heating has gone above
the critical very far, the austenite crystals start to grow; a very short time at an extreme temperature
will cause a large grain growth. Subsequent cooling gives a coarse texture, or an arrangement of
ferrite, cementite and pearlite grains which is greatly coarsened, reflecting the condition of the
austenite crystals from which they were born.
Page 92
It maybe noted in passing that the coarse crystals of cast metal cannot generally be refined by heat
treatment unless some forging or rolling has been done in the meantime. Heat treatment alone does
not seem to be able to break up the crystals of an ingot structure.
HARDENING
Steel is hardened by quenching from above the upper critical. Apparently the quick cooling
prevents the normal change back to definite and sizeable crystals of ferrite and cementite. Hardness
is associated with this suppressed change. If the change is allowed to continue by a moderate
reheating, like a tempering, the hardness decreases.
If a piece of steel could be cooled instantly, doubtless austenite could be preserved and examined.
In the ordinary practice of hardening steels, the quenching is not so drastic, and the transformation
of austenite back to ferrite and cementite is more or less completely effected, giving rise to certain
transitory forms which are known as "martensite," "troostite," "sorbite," and finally, pearlite.
Austenite has been defined as a solid solution of cementite (Fe3C) in gamma iron. It is stable at
various temperatures dependent upon its carbon content, which may be any amount up to the
saturated solution containing 1.7 per cent. Austenite is not nearly as hard as martensite, owing to its
content of the soft gamma iron. Fig. 49 shows austenite to possess the typical appearance of any
pure, crystallized substance.
In the most quickly quenched high carbon steels, austenite commonly forms the ground mass
which is interspersed with martensite, a large field of which is illustrated in Fig. 50. Martensite is
usually considered to be a solid solution of cementite in beta iron. It represents an unstable
condition in which the metal is caught during rapid cooling. It is very hard, and is the chief
constituent of hardened high-carbon steels, and of medium-carbon nickel-steel and manganese-
steel.
Troostite is of doubtful composition, but possibly is an unstable mixture of untransformed
martensite with sorbite. It contains more or less untransformed material, as it is too hard to be
composed entirely of the soft alpha modification, and it can also be tempered more or less without
changing in appearance. Its normal appearance as rounded grains is given in Fig. 51; larger patches
show practically no relief in their structure, and a photograph merely shows a dark, structureless
area.
Sorbite is believed to be an early stage in the formation of pearlite, when the iron and iron carbide
originally constituting the solid solution (austenite) have had an opportunity to separate from each
other, and the iron has entirely passed into the alpha modification, but the particles are yet too small
to be distinguishable under the microscope. It also, possibly, contains some incompletely
transformed matter. Sorbite is softer and tougher than troostite, and is habitually associated with
pearlite. Its components are tending to coagulate into pearlite, and will do so in a fairly short time at
temperatures near the lower critical, which heat will furnish the necessary molecular freedom. The
normal appearance, however, is the cloudy mass shown in Fig. 52.
Pearlite is a definite conglomerate of ferrite and cementite containing about six parts of the former
to one of the latter. When pure, it has a carbon content of about 0.95 per cent. It represents the
complete transformation of the eutectoid austenite accomplished by slow-cooling of an iron-carbon
alloy through the transformation range. (See Fig. 46.)
treatment unless some forging or rolling has been done in the meantime. Heat treatment alone does
not seem to be able to break up the crystals of an ingot structure.
HARDENING
Steel is hardened by quenching from above the upper critical. Apparently the quick cooling
prevents the normal change back to definite and sizeable crystals of ferrite and cementite. Hardness
is associated with this suppressed change. If the change is allowed to continue by a moderate
reheating, like a tempering, the hardness decreases.
If a piece of steel could be cooled instantly, doubtless austenite could be preserved and examined.
In the ordinary practice of hardening steels, the quenching is not so drastic, and the transformation
of austenite back to ferrite and cementite is more or less completely effected, giving rise to certain
transitory forms which are known as "martensite," "troostite," "sorbite," and finally, pearlite.
Austenite has been defined as a solid solution of cementite (Fe3C) in gamma iron. It is stable at
various temperatures dependent upon its carbon content, which may be any amount up to the
saturated solution containing 1.7 per cent. Austenite is not nearly as hard as martensite, owing to its
content of the soft gamma iron. Fig. 49 shows austenite to possess the typical appearance of any
pure, crystallized substance.
In the most quickly quenched high carbon steels, austenite commonly forms the ground mass
which is interspersed with martensite, a large field of which is illustrated in Fig. 50. Martensite is
usually considered to be a solid solution of cementite in beta iron. It represents an unstable
condition in which the metal is caught during rapid cooling. It is very hard, and is the chief
constituent of hardened high-carbon steels, and of medium-carbon nickel-steel and manganese-
steel.
Troostite is of doubtful composition, but possibly is an unstable mixture of untransformed
martensite with sorbite. It contains more or less untransformed material, as it is too hard to be
composed entirely of the soft alpha modification, and it can also be tempered more or less without
changing in appearance. Its normal appearance as rounded grains is given in Fig. 51; larger patches
show practically no relief in their structure, and a photograph merely shows a dark, structureless
area.
Sorbite is believed to be an early stage in the formation of pearlite, when the iron and iron carbide
originally constituting the solid solution (austenite) have had an opportunity to separate from each
other, and the iron has entirely passed into the alpha modification, but the particles are yet too small
to be distinguishable under the microscope. It also, possibly, contains some incompletely
transformed matter. Sorbite is softer and tougher than troostite, and is habitually associated with
pearlite. Its components are tending to coagulate into pearlite, and will do so in a fairly short time at
temperatures near the lower critical, which heat will furnish the necessary molecular freedom. The
normal appearance, however, is the cloudy mass shown in Fig. 52.
Pearlite is a definite conglomerate of ferrite and cementite containing about six parts of the former
to one of the latter. When pure, it has a carbon content of about 0.95 per cent. It represents the
complete transformation of the eutectoid austenite accomplished by slow-cooling of an iron-carbon
alloy through the transformation range. (See Fig. 46.)
Page 93
FIG. 49.—Coarse-grained martensite,
polished and etched with nitric acid and
magnified 50 times. Made by Prof. Chas. Y.
Clayton.
FIG. 50.—Quenched high-carbon steel, polished, etched and
viewed at 100 magnifications. This structure is called
martensite and is desired when maximum hardness is
essential. Photograph by H. S. Rawdon.
FIG. 51.—Martensite (light FIG. 52.—Sorbite (dark patches)
needles) passing into troosite passing into pearlite (wavy
polished and etched with nitric acid and
magnified 50 times. Made by Prof. Chas. Y.
Clayton.
FIG. 50.—Quenched high-carbon steel, polished, etched and
viewed at 100 magnifications. This structure is called
martensite and is desired when maximum hardness is
essential. Photograph by H. S. Rawdon.
FIG. 51.—Martensite (light FIG. 52.—Sorbite (dark patches)
needles) passing into troosite passing into pearlite (wavy
Page 94
(dark patches). 130 X. From a striations). Light Areas are Patches
piece of eutectoid steel of Ferrite. 220 X. From a piece of
electrically welded. hypo-eutectoid steel electrically
welded.
These observations are competent to explain annealing and toughening practice. A quickly
quenched carbon steel is mostly martensitic which, as noted, is a solid solution of beta iron and
cementite, hard and brittle. Moderate reheating or annealing changes this structure largely into
troostite, which is a partly transformed martensite, possessing much of the hardness of martensite,
but with a largely increased toughness and shock resistance. This toughness is the chief
characteristic of the next material in the transformation series, sorbite, which is merely martensite
wholly transformed into a mixture of ultramicroscopic crystals of ferrite (alpha iron) and cementite
(Fe3C).
"Tempering" or "drawing" should be restricted to mean moderate reheating, up to about 350° C.,
forming troostitic steel. "Toughening" represents the practice of reheating hardened carbon steels
from 350° C. up to just below the lower critical, and forms sorbitic steel; while "annealing" refers to
a heating for grain size at or above the transformation ranges, followed by a slow cooling. Any of
these operations not only allows the transformations from austenite to pearlite to proceed, but also
relieves internal stresses in the steel.
Normalizing is a heating like annealing, followed by a moderately rapid quench.
JUDGING THE HEAT OF STEEL
While the use of a pyrometer is of course the only way to have accurate knowledge as to the heat
being used in either forging or hardening steels, a color chart will be of considerable assistance if
carefully studied. These have been prepared by several of the steel companies as a guide, but it must
be remembered that the colors and temperatures given are only approximate, and can be nothing
else.
FIG. 53.—Finding hardening heats with a magnet.
The Magnet Test.—The critical point can also be determined by an ordinary horse-shoe magnet.
Touch the steel with a magnet during the heating and when it reaches the temperature at which steel
fails to attract the magnet, or in other words, loses its magnetism, the critical point has been
reached.
Figures 53 and 54 show how these are used in practice.
piece of eutectoid steel of Ferrite. 220 X. From a piece of
electrically welded. hypo-eutectoid steel electrically
welded.
These observations are competent to explain annealing and toughening practice. A quickly
quenched carbon steel is mostly martensitic which, as noted, is a solid solution of beta iron and
cementite, hard and brittle. Moderate reheating or annealing changes this structure largely into
troostite, which is a partly transformed martensite, possessing much of the hardness of martensite,
but with a largely increased toughness and shock resistance. This toughness is the chief
characteristic of the next material in the transformation series, sorbite, which is merely martensite
wholly transformed into a mixture of ultramicroscopic crystals of ferrite (alpha iron) and cementite
(Fe3C).
"Tempering" or "drawing" should be restricted to mean moderate reheating, up to about 350° C.,
forming troostitic steel. "Toughening" represents the practice of reheating hardened carbon steels
from 350° C. up to just below the lower critical, and forms sorbitic steel; while "annealing" refers to
a heating for grain size at or above the transformation ranges, followed by a slow cooling. Any of
these operations not only allows the transformations from austenite to pearlite to proceed, but also
relieves internal stresses in the steel.
Normalizing is a heating like annealing, followed by a moderately rapid quench.
JUDGING THE HEAT OF STEEL
While the use of a pyrometer is of course the only way to have accurate knowledge as to the heat
being used in either forging or hardening steels, a color chart will be of considerable assistance if
carefully studied. These have been prepared by several of the steel companies as a guide, but it must
be remembered that the colors and temperatures given are only approximate, and can be nothing
else.
FIG. 53.—Finding hardening heats with a magnet.
The Magnet Test.—The critical point can also be determined by an ordinary horse-shoe magnet.
Touch the steel with a magnet during the heating and when it reaches the temperature at which steel
fails to attract the magnet, or in other words, loses its magnetism, the critical point has been
reached.
Figures 53 and 54 show how these are used in practice.
Page 95
The first (Fig. 53) shows the use of a permanent horse-shoe magnet and the second (Fig. 54) an
electro-magnet consisting of an iron rod with a coil or spool magnet at the outer end. In either case
the magnet should not be allowed to become heated but should be applied quickly.
FIG. 54.—Using electro-magnet to determine heat.
The work is heated up slowly in the furnace and the magnet applied from time to time. The steel
being heated will attract the magnet until the heat reaches the critical point. The magnet is applied
frequently and when the magnet is no longer attracted, the piece is at the lowest temperature at
which it can be hardened properly. Quenching slightly above this point will give a tool of
satisfactory hardness. The method applies only to carbon steels and will not work for modern high-
speed steels.
HEAT TREATMENT OF GEAR BLANKS
This section is based on a paper read before the American Gear Manufacturers' Association at
White Sulphur Springs, W. Va., Apr. 18, 1918.
Great advancement has been made in the heat treating and hardening of gears. In this advancement
the chemical and metallurgical laboratory have played no small part. During this time, however, the
condition of the blanks as they come to the machine shop to be machined has not received its share
of attention.
There are two distinct types of gears, both types having their champions, namely, carburized and
heat-treated. The difference between the two in the matter of steel composition is entirely in the
carbon content, the carbon never running higher than 25-point in the carburizing type, while in the
heat-treated gears the carbon is seldom lower than 35-point. The difference in the final gear is the
hardness. The carburized gear is file hard on the surface, with a soft, tough and ductile core to
withstand shock, while the heat-treated gear has a surface that can be touched by a file with a core
of the same hardness as the outer surface.
Annealing Work.—With the exception of several of the higher types of alloy steels, where the
percentages of special elements run quite high, which causes a slight air-hardening action, the
carburizing steels are soft enough for machining when air cooled from any temperature, including
the finishing temperature at the hammer. This condition has led many drop-forge and manufacturing
concerns to consider annealing as an unnecessary operation and expense. In many cases the drop
forging has only been heated to a low temperature, often just until the piece showed color, to relieve
the so-called hammer strains. While this has been only a compromise it has been better than no
reheating at all, although it has not properly refined the grain, which is necessary for good
machining conditions.
Annealing is heating to a temperature slightly above the highest critical point and cooling slowly
either in the air or in the furnace. Annealing is done to accomplish two purposes: (1) to relieve
mechanical strains and (2) to soften and produce a maximum refinement of grain.
electro-magnet consisting of an iron rod with a coil or spool magnet at the outer end. In either case
the magnet should not be allowed to become heated but should be applied quickly.
FIG. 54.—Using electro-magnet to determine heat.
The work is heated up slowly in the furnace and the magnet applied from time to time. The steel
being heated will attract the magnet until the heat reaches the critical point. The magnet is applied
frequently and when the magnet is no longer attracted, the piece is at the lowest temperature at
which it can be hardened properly. Quenching slightly above this point will give a tool of
satisfactory hardness. The method applies only to carbon steels and will not work for modern high-
speed steels.
HEAT TREATMENT OF GEAR BLANKS
This section is based on a paper read before the American Gear Manufacturers' Association at
White Sulphur Springs, W. Va., Apr. 18, 1918.
Great advancement has been made in the heat treating and hardening of gears. In this advancement
the chemical and metallurgical laboratory have played no small part. During this time, however, the
condition of the blanks as they come to the machine shop to be machined has not received its share
of attention.
There are two distinct types of gears, both types having their champions, namely, carburized and
heat-treated. The difference between the two in the matter of steel composition is entirely in the
carbon content, the carbon never running higher than 25-point in the carburizing type, while in the
heat-treated gears the carbon is seldom lower than 35-point. The difference in the final gear is the
hardness. The carburized gear is file hard on the surface, with a soft, tough and ductile core to
withstand shock, while the heat-treated gear has a surface that can be touched by a file with a core
of the same hardness as the outer surface.
Annealing Work.—With the exception of several of the higher types of alloy steels, where the
percentages of special elements run quite high, which causes a slight air-hardening action, the
carburizing steels are soft enough for machining when air cooled from any temperature, including
the finishing temperature at the hammer. This condition has led many drop-forge and manufacturing
concerns to consider annealing as an unnecessary operation and expense. In many cases the drop
forging has only been heated to a low temperature, often just until the piece showed color, to relieve
the so-called hammer strains. While this has been only a compromise it has been better than no
reheating at all, although it has not properly refined the grain, which is necessary for good
machining conditions.
Annealing is heating to a temperature slightly above the highest critical point and cooling slowly
either in the air or in the furnace. Annealing is done to accomplish two purposes: (1) to relieve
mechanical strains and (2) to soften and produce a maximum refinement of grain.
Page 96
Process of Carburizing.—Carburizing imparts a shell of high-carbon content to a low-carbon
steel. This produces what might be termed a "dual" steel, allowing for an outer shell which when
hardened would withstand wear, and a soft ductile core to produce ductility and withstand shock.
The operation is carried out by packing the work to be carburized in boxes with a material rich in
carbon and maintaining the box so charged at a temperature in excess of the highest critical point
for a length of time to produce the desired depth of carburized zone. Generally maintaining the
temperature at 1,650 to 1,700° F. for 7 hr. will produce a carburized zone 1/32 in. deep.
Heating to a temperature slightly above the highest critical point and cooling suddenly in some
quenching medium, such as water or oil hardens the steel. This treatment produces a maximum
refinement with the maximum strength.
Drawing to a temperature below the highest critical point (the temperature being governed by the
results required) relieves the hardening strains set up by quenching, as well as the reducing of the
hardness and brittleness of hardened steel.
Effect of Proper Annealing.—Proper annealing of low-carbon steels causes a complete solution
or combination to take place between the ferrite and pearlite, producing a homogeneous mass of
small grains of each, the grains of the pearlite being surrounded by grains of ferrite. A steel of this
refinement will machine to good advantage, due to the fact that the cutting tool will at all times be
in contact with metal of uniform composition.
While the alternate bands of ferrite and pearlite are microscopically sized, it has been found that
with a Gleason or Fellows gear-cutting machine that rough cutting can be traced to poorly annealed
steels, having either a pronounced banded structure or a coarse granular structure.
Temperature for Annealing.—Theoretically, annealing should be accomplished at a temperature
at just slightly above the critical point. However, in practice the temperature is raised to a higher
point in order to allow for the solution of the carbon and iron to be produced more rapidly, as the
time required to produce complete solution is reduced as the temperature increases past the critical
point.
For annealing the simpler types of low-carbon steels the following temperatures have been found
to produce uniform machining conditions on account of producing uniform fine-grain pearlite
structure:
0.15 to 0.25 per cent carbon, straight carbon steel.—Heat to 1,650°F. Hold at this temperature until
the work is uniformly heated; pull from the furnace and cool in air.
0.15 to 0.25 per cent carbon, 1½ per cent nickel, 1/2 per cent chromium steel.—Heat to 1,600°F.
Hold at this temperature until the work is uniformly heated; pull from the furnace and cool in air.
0.15 to 0.25 per cent carbon, 3½ per cent nickel steel.—Heat to 1,575°F. Hold at this temperature
until the work is uniformly heated; pull from the furnace and cool in air.
Care in Annealing.—Not only will benefits in machining be found by careful annealing of
forgings but the subsequent troubles in the hardening plant will be greatly reduced. The advantages
in the hardening start with the carburizing operation, as a steel of uniform and fine grain size will
carburize more uniformly, producing a more even hardness and less chances for soft spots. The
holes in the gears will also "close in more uniformly," not causing some gears to require excessive
steel. This produces what might be termed a "dual" steel, allowing for an outer shell which when
hardened would withstand wear, and a soft ductile core to produce ductility and withstand shock.
The operation is carried out by packing the work to be carburized in boxes with a material rich in
carbon and maintaining the box so charged at a temperature in excess of the highest critical point
for a length of time to produce the desired depth of carburized zone. Generally maintaining the
temperature at 1,650 to 1,700° F. for 7 hr. will produce a carburized zone 1/32 in. deep.
Heating to a temperature slightly above the highest critical point and cooling suddenly in some
quenching medium, such as water or oil hardens the steel. This treatment produces a maximum
refinement with the maximum strength.
Drawing to a temperature below the highest critical point (the temperature being governed by the
results required) relieves the hardening strains set up by quenching, as well as the reducing of the
hardness and brittleness of hardened steel.
Effect of Proper Annealing.—Proper annealing of low-carbon steels causes a complete solution
or combination to take place between the ferrite and pearlite, producing a homogeneous mass of
small grains of each, the grains of the pearlite being surrounded by grains of ferrite. A steel of this
refinement will machine to good advantage, due to the fact that the cutting tool will at all times be
in contact with metal of uniform composition.
While the alternate bands of ferrite and pearlite are microscopically sized, it has been found that
with a Gleason or Fellows gear-cutting machine that rough cutting can be traced to poorly annealed
steels, having either a pronounced banded structure or a coarse granular structure.
Temperature for Annealing.—Theoretically, annealing should be accomplished at a temperature
at just slightly above the critical point. However, in practice the temperature is raised to a higher
point in order to allow for the solution of the carbon and iron to be produced more rapidly, as the
time required to produce complete solution is reduced as the temperature increases past the critical
point.
For annealing the simpler types of low-carbon steels the following temperatures have been found
to produce uniform machining conditions on account of producing uniform fine-grain pearlite
structure:
0.15 to 0.25 per cent carbon, straight carbon steel.—Heat to 1,650°F. Hold at this temperature until
the work is uniformly heated; pull from the furnace and cool in air.
0.15 to 0.25 per cent carbon, 1½ per cent nickel, 1/2 per cent chromium steel.—Heat to 1,600°F.
Hold at this temperature until the work is uniformly heated; pull from the furnace and cool in air.
0.15 to 0.25 per cent carbon, 3½ per cent nickel steel.—Heat to 1,575°F. Hold at this temperature
until the work is uniformly heated; pull from the furnace and cool in air.
Care in Annealing.—Not only will benefits in machining be found by careful annealing of
forgings but the subsequent troubles in the hardening plant will be greatly reduced. The advantages
in the hardening start with the carburizing operation, as a steel of uniform and fine grain size will
carburize more uniformly, producing a more even hardness and less chances for soft spots. The
holes in the gears will also "close in more uniformly," not causing some gears to require excessive
Page 97
grinding and others with just enough stock. Also all strains will have been removed from the
forging, eliminating to a great extent distortion and the noisy gears which are the result.
With the steels used, for the heat-treated gears, always of a higher carbon content, treatment after
forging is necessary for machining, as it would be impossible to get the required production from
untreated forgings, especially in the alloy steels. The treatment is more delicate, due to the higher
percentage of carbon and the natural increase in cementite together with complex carbides which
are present in some of the higher types of alloys.
Where poor machining conditions in heat-treated steels are present they are generally due to
incomplete solution of cementite rather than bands of free ferrite, as in the case of case-hardening
steels. This segregation of carbon, as it is sometimes referred to, causes hard spots which, in the
forming of the tooth, cause the cutter to ride over the hard metal, producing high spots on the face
of the tooth, which are as detrimental to satisfactory gear cutting as the drops or low spots produced
on the face of the teeth when the pearlite is coarse-grained or in a banded condition.
In the simpler carburized steels it is not necessary to test the forgings for hardness after annealing,
but with the high percentages of alloys in the carburizing steels and the heat-treated steels a
hardness test is essential.
To obtain the best results in machining, the microstructure of the metal should be determined and a
hardness range set that covers the variations in structure that produce good machining results. By
careful control of the heat-treating operation and with the aid of the Brinell hardness tester and the
microscope it is possible to continually give forgings that will machine uniformly and be soft
enough to give desired production. The following gives a few of the hardness numerals on steel
used in gear manufacture that produce good machining qualities:
0.20 per cent carbon, 3 per cent nickel, 1¼; per cent chromium—Brinell 156 to 170.
0.50 per cent carbon, 3 per cent nickel, 1 per cent chromium—Brinell 179 to 187.
0.50 per cent carbon chrome-vanadium—Brinell 170 to 179.
THE INFLUENCE OF SIZE
The size of the piece influences the physical properties obtained in steel by heat treatment. This
has been worked out by E. J. Janitzky, metallurgical engineer of the Illinois Steel Company, as
follows:
forging, eliminating to a great extent distortion and the noisy gears which are the result.
With the steels used, for the heat-treated gears, always of a higher carbon content, treatment after
forging is necessary for machining, as it would be impossible to get the required production from
untreated forgings, especially in the alloy steels. The treatment is more delicate, due to the higher
percentage of carbon and the natural increase in cementite together with complex carbides which
are present in some of the higher types of alloys.
Where poor machining conditions in heat-treated steels are present they are generally due to
incomplete solution of cementite rather than bands of free ferrite, as in the case of case-hardening
steels. This segregation of carbon, as it is sometimes referred to, causes hard spots which, in the
forming of the tooth, cause the cutter to ride over the hard metal, producing high spots on the face
of the tooth, which are as detrimental to satisfactory gear cutting as the drops or low spots produced
on the face of the teeth when the pearlite is coarse-grained or in a banded condition.
In the simpler carburized steels it is not necessary to test the forgings for hardness after annealing,
but with the high percentages of alloys in the carburizing steels and the heat-treated steels a
hardness test is essential.
To obtain the best results in machining, the microstructure of the metal should be determined and a
hardness range set that covers the variations in structure that produce good machining results. By
careful control of the heat-treating operation and with the aid of the Brinell hardness tester and the
microscope it is possible to continually give forgings that will machine uniformly and be soft
enough to give desired production. The following gives a few of the hardness numerals on steel
used in gear manufacture that produce good machining qualities:
0.20 per cent carbon, 3 per cent nickel, 1¼; per cent chromium—Brinell 156 to 170.
0.50 per cent carbon, 3 per cent nickel, 1 per cent chromium—Brinell 179 to 187.
0.50 per cent carbon chrome-vanadium—Brinell 170 to 179.
THE INFLUENCE OF SIZE
The size of the piece influences the physical properties obtained in steel by heat treatment. This
has been worked out by E. J. Janitzky, metallurgical engineer of the Illinois Steel Company, as
follows:
Page 98
FIG. 55.—Effect of size on heating.
"With an increase in the mass of steel there is a corresponding decrease in both the minimum
surface hardness and depth hardness, when quenched from the same temperature, under identical
conditions of the quenching medium. In other words, the physical properties obtained are a function
of the surface of the metal quenched for a given mass of steel. Keeping this primary assumption in
mind, it is possible to predict what physical properties may be developed in heat treating by
calculating the surface per unit mass for different shapes and sizes. It may be pointed out that the
figures and chart that follow are not results of actual tests, but are derived by calculation. They
indicate the mathematical relation, which, based on the fact that the physical properties of steel are
determined not alone by the rate which heat is lost per unit of surface, but by the rate which heat is
lost per unit of weight in relation to the surface exposed for that unit. The unit of weight has for the
different shaped bodies and their sizes a certain surface which determines their physical properties.
"For example, the surface corresponding to 1 lb. of steel has been computed for spheres, rounds
and flats. For the sphere with a unit weight of 1 lb. the portion is a cone with the apex at the center
of the sphere and the base the curved surface of the sphere (surface exposed to quenching). For
rounds, a unit weight of 1 lb. may be taken as a disk or cylinder, the base and top surfaces naturally
do not enter into calculation. For a flat, a prismatic or cylindrical volume may be taken to represent
the unit weight. The surfaces that are considered in this instance are the top and base of the section,
as these surfaces are the ones exposed to cooling."
The results of the calculations are as follows:
TABLE 20.—SPHERE
Diameter Surface per
of sphere pound of steel
X Y
"With an increase in the mass of steel there is a corresponding decrease in both the minimum
surface hardness and depth hardness, when quenched from the same temperature, under identical
conditions of the quenching medium. In other words, the physical properties obtained are a function
of the surface of the metal quenched for a given mass of steel. Keeping this primary assumption in
mind, it is possible to predict what physical properties may be developed in heat treating by
calculating the surface per unit mass for different shapes and sizes. It may be pointed out that the
figures and chart that follow are not results of actual tests, but are derived by calculation. They
indicate the mathematical relation, which, based on the fact that the physical properties of steel are
determined not alone by the rate which heat is lost per unit of surface, but by the rate which heat is
lost per unit of weight in relation to the surface exposed for that unit. The unit of weight has for the
different shaped bodies and their sizes a certain surface which determines their physical properties.
"For example, the surface corresponding to 1 lb. of steel has been computed for spheres, rounds
and flats. For the sphere with a unit weight of 1 lb. the portion is a cone with the apex at the center
of the sphere and the base the curved surface of the sphere (surface exposed to quenching). For
rounds, a unit weight of 1 lb. may be taken as a disk or cylinder, the base and top surfaces naturally
do not enter into calculation. For a flat, a prismatic or cylindrical volume may be taken to represent
the unit weight. The surfaces that are considered in this instance are the top and base of the section,
as these surfaces are the ones exposed to cooling."
The results of the calculations are as follows:
TABLE 20.—SPHERE
Diameter Surface per
of sphere pound of steel
X Y
Page 99
8 in. 2.648 sq. in.
6 in. 3.531 sq. in.
4 in. 5.294 sq. in.
3 in. 7.062 sq. in.
2 in. 10.61 sq. in.
XY = 21.185.
TABLE 21.—ROUND
Diameter Surface per
of round pound of steel
X Y
8.0 in. 1.765 sq. in.
6.0 in. 2.354 sq. in.
5.0 in. 2.829 sq. in.
4.0 in. 3.531 sq. in.
3.0 in. 4.708 sq. in.
2.0 in. 7.062 sq. in.
1.0 in. 14.125 sq. in.
0.5 in. 28.25 sq. in.
0.25 in. 56.5 sq. in.
XY = 14.124.
TABLE 22.—FLAT
Diameter Surface per
of flat pound of steel
X Y
8.0 in. 0.8828 sq. in.
6.0 in. 1.177 sq. in.
5.0 in. 1.412 sq. in.
4.0 in. 1.765 sq. in.
3.0 in. 2.345 sq. in.
2.0 in. 3.531 sq. in.
1.0 in. 7.062 sq. in.
0.5 in. 14.124 sq. in.
0.25 in. 28.248 sq. in.
XY = 7.062.
Having once determined the physical qualities of a certain specimen, and found its position on the
curve we have the means to predict the decrease of physical qualities on larger specimens which
receive the same heat treatment.
When the surfaces of the unit weight as outlined in the foregoing tables are plotted as ordinates
and the corresponding diameters as abscissæ, the resulting curve is a hyperbola and follows the law
XY = C. In making these calculations the radii or one-half of the thickness need only to be taken
6 in. 3.531 sq. in.
4 in. 5.294 sq. in.
3 in. 7.062 sq. in.
2 in. 10.61 sq. in.
XY = 21.185.
TABLE 21.—ROUND
Diameter Surface per
of round pound of steel
X Y
8.0 in. 1.765 sq. in.
6.0 in. 2.354 sq. in.
5.0 in. 2.829 sq. in.
4.0 in. 3.531 sq. in.
3.0 in. 4.708 sq. in.
2.0 in. 7.062 sq. in.
1.0 in. 14.125 sq. in.
0.5 in. 28.25 sq. in.
0.25 in. 56.5 sq. in.
XY = 14.124.
TABLE 22.—FLAT
Diameter Surface per
of flat pound of steel
X Y
8.0 in. 0.8828 sq. in.
6.0 in. 1.177 sq. in.
5.0 in. 1.412 sq. in.
4.0 in. 1.765 sq. in.
3.0 in. 2.345 sq. in.
2.0 in. 3.531 sq. in.
1.0 in. 7.062 sq. in.
0.5 in. 14.124 sq. in.
0.25 in. 28.248 sq. in.
XY = 7.062.
Having once determined the physical qualities of a certain specimen, and found its position on the
curve we have the means to predict the decrease of physical qualities on larger specimens which
receive the same heat treatment.
When the surfaces of the unit weight as outlined in the foregoing tables are plotted as ordinates
and the corresponding diameters as abscissæ, the resulting curve is a hyperbola and follows the law
XY = C. In making these calculations the radii or one-half of the thickness need only to be taken
Page 100
into consideration as the heat is conducted from the center of the body to the surface, following the
shortest path.
The equations for the different shapes are as follows:
For flats XY = 7.062
For rounds XY = 14.124
For spheres XY = 21.185
It will be noted that the constants increase in a ratio of 1, 2, and 3, and the three bodies in question
will increase in hardness on being quenched in the same ratio, it being understood that the diameter
of the sphere and round and thickness of the flat are equal.
Relative to shape, it is interesting to note that rounds, squares, octagons and other three axial
bodies, with two of their axes equal, have the same surface for the unit weight.
For example:
Size Length Surface Weight Surface for 1 lb.
2 in. Sq. 12 in. 96.0 sq. in. 13.60 lb. 7.06 sq. in.
2 in. Round 12 in. 75.4 sq. in. 10.68 lb. 7.06 sq. in.
Although this discussion is at present based upon mathematical analysis, it is hoped that it will
open up a new field of investigation in which but little work has been done, and may assist in
settling the as yet unsolved question of the effect of size and shape in the heat treatment of steel.
HEAT-TREATING EQUIPMENT AND METHODS FOR MASS PRODUCTION
The heat-treating department of the Brown-Lipe-Chapin Company, Syracuse, N. Y., runs day and
night, and besides handling all the hardening of tools, parts of jigs, fixtures, special machines and
appliances, carburizes and heat-treats every month between 150,000 and 200,000 gears, pinions,
crosses and other components entering into the construction of differentials for automobiles.
The treatment of the steel really begins in the mill, where the steel is made to conform to a specific
formula. On the arrival of the rough forgings at the Brown-Lipe-Chapin factory, the first of a long
series of inspections begins.
Annealing Method.—Forgings which are too hard to machine are put in pots with a little charcoal
to cause a reducing atmosphere and to prevent scale. The covers are then luted on and the pots
placed in the furnace. Carbon steel from 15 to 25 points is annealed at 1,600°F. Nickel steel of the
same carbon and containing in addition 3½ per cent nickel is annealed at 1,450°F. When the pots
are heated through, they are rolled to the yard and allowed to cool. This method of annealing gives
the best hardness for quick machining.
The requirements in the machine operations are very rigid and, in spite of great care and probably
the finest equipment of special machines in the world, a small percentage of the product fails to
pass inspection during or at the completion of the machine operations. These pieces, however, are
not a loss, for they play an important part in the hardening process, indicating as they do the exact
depth of penetration of the carburizing material and the condition of both case and core.
shortest path.
The equations for the different shapes are as follows:
For flats XY = 7.062
For rounds XY = 14.124
For spheres XY = 21.185
It will be noted that the constants increase in a ratio of 1, 2, and 3, and the three bodies in question
will increase in hardness on being quenched in the same ratio, it being understood that the diameter
of the sphere and round and thickness of the flat are equal.
Relative to shape, it is interesting to note that rounds, squares, octagons and other three axial
bodies, with two of their axes equal, have the same surface for the unit weight.
For example:
Size Length Surface Weight Surface for 1 lb.
2 in. Sq. 12 in. 96.0 sq. in. 13.60 lb. 7.06 sq. in.
2 in. Round 12 in. 75.4 sq. in. 10.68 lb. 7.06 sq. in.
Although this discussion is at present based upon mathematical analysis, it is hoped that it will
open up a new field of investigation in which but little work has been done, and may assist in
settling the as yet unsolved question of the effect of size and shape in the heat treatment of steel.
HEAT-TREATING EQUIPMENT AND METHODS FOR MASS PRODUCTION
The heat-treating department of the Brown-Lipe-Chapin Company, Syracuse, N. Y., runs day and
night, and besides handling all the hardening of tools, parts of jigs, fixtures, special machines and
appliances, carburizes and heat-treats every month between 150,000 and 200,000 gears, pinions,
crosses and other components entering into the construction of differentials for automobiles.
The treatment of the steel really begins in the mill, where the steel is made to conform to a specific
formula. On the arrival of the rough forgings at the Brown-Lipe-Chapin factory, the first of a long
series of inspections begins.
Annealing Method.—Forgings which are too hard to machine are put in pots with a little charcoal
to cause a reducing atmosphere and to prevent scale. The covers are then luted on and the pots
placed in the furnace. Carbon steel from 15 to 25 points is annealed at 1,600°F. Nickel steel of the
same carbon and containing in addition 3½ per cent nickel is annealed at 1,450°F. When the pots
are heated through, they are rolled to the yard and allowed to cool. This method of annealing gives
the best hardness for quick machining.
The requirements in the machine operations are very rigid and, in spite of great care and probably
the finest equipment of special machines in the world, a small percentage of the product fails to
pass inspection during or at the completion of the machine operations. These pieces, however, are
not a loss, for they play an important part in the hardening process, indicating as they do the exact
depth of penetration of the carburizing material and the condition of both case and core.
Page 101
Heat-treating Department.—The heat-treating department occupies an L-shaped building. The
design is very practical, with the furnace and the floor on the same level so that there is no lifting of
heavy pots. Fuel oil is used in all the furnaces and gives highly satisfactory results. The
consumption of fuel oil is about 2 gal. per hour per furnace.
The work is packed in the pots in a room at the entrance to the heat-treatment building. Before
packing, each gear is stamped with a number which is a key to the records of the analysis and
complete heat treatment of that particular gear. Should a question at any time arise regarding the
treatment of a certain gear, all the necessary information is available if the number on the gear is
legible. For instance, date of treatment, furnace, carburizing material, position of the pot in the
furnace, position of gear in pot, temperature of furnace and duration of treatment are all tabulated
and filed for reference.
After marking, all holes and parts which are to remain uncarburized are plugged or luted with a
mixture of kaolin and Mellville gravel clay, and the gear is packed in the carburizing material.
Bohnite, a commercial carburizing compound is used exclusively at this plant. This does excellent
work and is economical. Broadly speaking, the economy of a carburizing compound depends on its
lightness. The space not occupied by work must be filled with compound; therefore) other things
being equal, a compound weighing 25 lb. would be worth more than twice as much as one weighing
60 lb. per cubic foot. It has been claimed that certain compounds can be used over and over again,
but this is only true in a limited way, if good work is required. There is, of course, some carbon in
the compound after the first use, but for first-class work, new compound must be used each time.
The Packing Department.—In Fig. 56 is shown the packing pots where the work is packed.
These are of malleable cast iron, with an internal vertical flange around the hole A. This fits in a bell
on the end of the cast-iron pipe B, which is luted in position with fireclay before the packing begins.
At C is shown a pot ready for packing. The crown gears average 10 to 12 in. in diameter and weigh
about 11 lb. each. When placed in the pots, they surround the central tube, which allows the heat to
circulate. Each pot contains five gears. Two complete scrap gears are in each furnace (i.e., gears
which fail to pass machining inspection), and at the top of front pot are two or more short segments
of scrap gear, used as test pieces to gage depth of case.
FIG. 56.—Packing department and special pots.
After filling to the top with compound, the lid D is luted on. Ten pots are then placed in a furnace.
It will be noted that the pots to the right are numbered 1, 2, 3, 4, indicating the position they are to
occupy in the furnace.
design is very practical, with the furnace and the floor on the same level so that there is no lifting of
heavy pots. Fuel oil is used in all the furnaces and gives highly satisfactory results. The
consumption of fuel oil is about 2 gal. per hour per furnace.
The work is packed in the pots in a room at the entrance to the heat-treatment building. Before
packing, each gear is stamped with a number which is a key to the records of the analysis and
complete heat treatment of that particular gear. Should a question at any time arise regarding the
treatment of a certain gear, all the necessary information is available if the number on the gear is
legible. For instance, date of treatment, furnace, carburizing material, position of the pot in the
furnace, position of gear in pot, temperature of furnace and duration of treatment are all tabulated
and filed for reference.
After marking, all holes and parts which are to remain uncarburized are plugged or luted with a
mixture of kaolin and Mellville gravel clay, and the gear is packed in the carburizing material.
Bohnite, a commercial carburizing compound is used exclusively at this plant. This does excellent
work and is economical. Broadly speaking, the economy of a carburizing compound depends on its
lightness. The space not occupied by work must be filled with compound; therefore) other things
being equal, a compound weighing 25 lb. would be worth more than twice as much as one weighing
60 lb. per cubic foot. It has been claimed that certain compounds can be used over and over again,
but this is only true in a limited way, if good work is required. There is, of course, some carbon in
the compound after the first use, but for first-class work, new compound must be used each time.
The Packing Department.—In Fig. 56 is shown the packing pots where the work is packed.
These are of malleable cast iron, with an internal vertical flange around the hole A. This fits in a bell
on the end of the cast-iron pipe B, which is luted in position with fireclay before the packing begins.
At C is shown a pot ready for packing. The crown gears average 10 to 12 in. in diameter and weigh
about 11 lb. each. When placed in the pots, they surround the central tube, which allows the heat to
circulate. Each pot contains five gears. Two complete scrap gears are in each furnace (i.e., gears
which fail to pass machining inspection), and at the top of front pot are two or more short segments
of scrap gear, used as test pieces to gage depth of case.
FIG. 56.—Packing department and special pots.
After filling to the top with compound, the lid D is luted on. Ten pots are then placed in a furnace.
It will be noted that the pots to the right are numbered 1, 2, 3, 4, indicating the position they are to
occupy in the furnace.
Page 102
The cast-iron ball shown at E is small enough to drop through the pipe B, but will not pass through
the hole A in the bottom of the pot. It is used as a valve to plug the bottom of the pot to prevent the
carburizing compound from dropping through when removing the carburized gears to the
quenching bath.
Without detracting from the high quality of the work, the metallurgist in this plant has succeeded
in cutting out one entire operation and reducing the time in the hardening room by about 24 hr.
Formerly, the work was carburized at about 1,700°F. for 9 hr. The pots were then run out into the
yard and allowed to cool slowly. When cool, the work was taken out of the pots, reheated and
quenched at 1,600°F. to refine the core. It was again reheated to 1,425°F. and quenched to refine the
case. Finally, it was drawn to the proper temper.
Short Method of Treatment.—In the new method, the packed pots are run into the case-
hardening furnaces, which are heated to 1,600°F. On the insertion of the cold pots, the temperature
naturally falls. The amount of this fall is dependent upon a number of variables, but it averages
nearly 500°F. as shown in the pyrometer chart, Fig. 61. The work and furnace must be brought to
1,600°F. Within 2½ hr.; otherwise, a longer time will be necessary to obtain the desired depth of
case. On this work, the depth of case required is designated in thousandths, and on crown gears, the
depth in 0.028 in. Having brought the work to a temperature of 1,600°F. the depth of case
mentioned can be obtained in about 5½ hr. by maintaining this temperature.
As stated before, at the top of each pot are several test pieces consisting of a whole scrap gear and
several sections. After the pots have been heated at 1,600°F. for about 5¼ hr., they are removed, and
a scrap-section test-piece is quenched direct from the pot in mineral oil at not more than 100°F. The
end of a tooth of this is then ground and etched to ascertain the depth of case. As these test pieces
are of exactly the same cross-section as the gears themselves, the carburizing action is similar.
When the depth of case has been found from the etched test pieces to be satisfactory, the pots are
removed. The iron ball then is dropped into the tube to seal the hole in the bottom of the pot; the
cover and the tube are removed, and the gears quenched direct from the pot in mineral oil, which is
kept at a temperature not higher than 100°F.
The Effect.—The heating at 1,600°F. gives the first heat treatment which refines the core, which
under the former high heat (1,700°F.) was rendered coarsely crystalline. All the gears, including the
scrap gears, are quenched direct from the pot in this manner.
The gears then go to the reheating furnaces, situated in front of a battery of Gleason quenching
machines. These furnaces accommodate from 12 to 16 crown gears. The carbon-steel gears are
heated in a reducing atmosphere to about 1,425°F. (depending on the carbon content) placed in the
dies in the Gleason quenching machine, and quenched between dies in mineral oil at less than
100°F. The test gear receives exactly the same treatment as the others and is then broken, giving a
record of the condition of both case and core.
Affinity of Nickel Steel for Carbon.—The carbon- and nickel-steel gears are carburized
separately owing to the difference in time necessary for their carburization. Practically all printed
information on the subject is to the effect that nickel steel takes longer to carburize than plain
carbon steel. This is directly opposed to the conditions found at this plant. For the same depth of
case, other conditions being equal, a nickel-steel gear would require from 20 to 30 min. less than a
low carbon-steel gear.
the hole A in the bottom of the pot. It is used as a valve to plug the bottom of the pot to prevent the
carburizing compound from dropping through when removing the carburized gears to the
quenching bath.
Without detracting from the high quality of the work, the metallurgist in this plant has succeeded
in cutting out one entire operation and reducing the time in the hardening room by about 24 hr.
Formerly, the work was carburized at about 1,700°F. for 9 hr. The pots were then run out into the
yard and allowed to cool slowly. When cool, the work was taken out of the pots, reheated and
quenched at 1,600°F. to refine the core. It was again reheated to 1,425°F. and quenched to refine the
case. Finally, it was drawn to the proper temper.
Short Method of Treatment.—In the new method, the packed pots are run into the case-
hardening furnaces, which are heated to 1,600°F. On the insertion of the cold pots, the temperature
naturally falls. The amount of this fall is dependent upon a number of variables, but it averages
nearly 500°F. as shown in the pyrometer chart, Fig. 61. The work and furnace must be brought to
1,600°F. Within 2½ hr.; otherwise, a longer time will be necessary to obtain the desired depth of
case. On this work, the depth of case required is designated in thousandths, and on crown gears, the
depth in 0.028 in. Having brought the work to a temperature of 1,600°F. the depth of case
mentioned can be obtained in about 5½ hr. by maintaining this temperature.
As stated before, at the top of each pot are several test pieces consisting of a whole scrap gear and
several sections. After the pots have been heated at 1,600°F. for about 5¼ hr., they are removed, and
a scrap-section test-piece is quenched direct from the pot in mineral oil at not more than 100°F. The
end of a tooth of this is then ground and etched to ascertain the depth of case. As these test pieces
are of exactly the same cross-section as the gears themselves, the carburizing action is similar.
When the depth of case has been found from the etched test pieces to be satisfactory, the pots are
removed. The iron ball then is dropped into the tube to seal the hole in the bottom of the pot; the
cover and the tube are removed, and the gears quenched direct from the pot in mineral oil, which is
kept at a temperature not higher than 100°F.
The Effect.—The heating at 1,600°F. gives the first heat treatment which refines the core, which
under the former high heat (1,700°F.) was rendered coarsely crystalline. All the gears, including the
scrap gears, are quenched direct from the pot in this manner.
The gears then go to the reheating furnaces, situated in front of a battery of Gleason quenching
machines. These furnaces accommodate from 12 to 16 crown gears. The carbon-steel gears are
heated in a reducing atmosphere to about 1,425°F. (depending on the carbon content) placed in the
dies in the Gleason quenching machine, and quenched between dies in mineral oil at less than
100°F. The test gear receives exactly the same treatment as the others and is then broken, giving a
record of the condition of both case and core.
Affinity of Nickel Steel for Carbon.—The carbon- and nickel-steel gears are carburized
separately owing to the difference in time necessary for their carburization. Practically all printed
information on the subject is to the effect that nickel steel takes longer to carburize than plain
carbon steel. This is directly opposed to the conditions found at this plant. For the same depth of
case, other conditions being equal, a nickel-steel gear would require from 20 to 30 min. less than a
low carbon-steel gear.
Page 103
From the quenching machines, the gears go to the sand-blasting machines, situated in the wing of
the heat-treating building, where they are cleaned. From here they are taken to the testing
department. The tests are simple and at the same time most thorough.
Testing and Inspection of Heat Treatment.—The hard parts of the gear must be so hard that a
new mill file does not bite in the least. Having passed this file test at several points, the gears go to
the center-punch test. The inspector is equipped with a wooden trough secured to the top of the
bench to support the gear, a number of center punches (made of ¾-in. hex-steel having points
sharpened to an angle of 120 deg.) and a hammer weighing about 4 oz. With these simple tools,
supplemented by his skill, the inspector can feel the depth and quality of the case and the condition
of the core. The gears are each tested in this way at several points on the teeth and elsewhere, the
scrap gear being also subjected to the test. Finally, the scrap gear is securely clamped in the
straightening press shown in Fig. 57. With a 3½-lb. hammer and a suitable hollow-ended drift
manipulated by one of Sandow's understudies, teeth are broken out of the scrap gear at various
points. These give a record confirming the center-punch tests, which, if the angle of the center
punch is kept at 120 deg. and the weight of the hammer and blow are uniform, is very accurate.
After passing the center-punch test the ends of the teeth are peened lightly with a hammer. If they
are too hard, small particles fly off. Such gears are drawn in oil at a temperature of from 300 to
350°F., depending on their hardness. Some builders prefer to have the extreme outer ends of the
teeth drawn somewhat lower than the rest. This drawing is done on gas-heated red-hot plates, as
shown at A in Fig. 58.
FIG. 57.—Press for holding test gears for breaking.
Nickel steel, in addition to all the tests given to carbon steel, is subjected to a Brinell test. For each
steel, the temperature and the period of treatment are specific. For some unknown reason,
apparently like material with like treatment will, in isolated cases, not produce like results. It then
remains for the treatment to be repeated or modified, but the results obtained during inspection form
a valuable aid to the metallurgist in determining further treatment.
the heat-treating building, where they are cleaned. From here they are taken to the testing
department. The tests are simple and at the same time most thorough.
Testing and Inspection of Heat Treatment.—The hard parts of the gear must be so hard that a
new mill file does not bite in the least. Having passed this file test at several points, the gears go to
the center-punch test. The inspector is equipped with a wooden trough secured to the top of the
bench to support the gear, a number of center punches (made of ¾-in. hex-steel having points
sharpened to an angle of 120 deg.) and a hammer weighing about 4 oz. With these simple tools,
supplemented by his skill, the inspector can feel the depth and quality of the case and the condition
of the core. The gears are each tested in this way at several points on the teeth and elsewhere, the
scrap gear being also subjected to the test. Finally, the scrap gear is securely clamped in the
straightening press shown in Fig. 57. With a 3½-lb. hammer and a suitable hollow-ended drift
manipulated by one of Sandow's understudies, teeth are broken out of the scrap gear at various
points. These give a record confirming the center-punch tests, which, if the angle of the center
punch is kept at 120 deg. and the weight of the hammer and blow are uniform, is very accurate.
After passing the center-punch test the ends of the teeth are peened lightly with a hammer. If they
are too hard, small particles fly off. Such gears are drawn in oil at a temperature of from 300 to
350°F., depending on their hardness. Some builders prefer to have the extreme outer ends of the
teeth drawn somewhat lower than the rest. This drawing is done on gas-heated red-hot plates, as
shown at A in Fig. 58.
FIG. 57.—Press for holding test gears for breaking.
Nickel steel, in addition to all the tests given to carbon steel, is subjected to a Brinell test. For each
steel, the temperature and the period of treatment are specific. For some unknown reason,
apparently like material with like treatment will, in isolated cases, not produce like results. It then
remains for the treatment to be repeated or modified, but the results obtained during inspection form
a valuable aid to the metallurgist in determining further treatment.
Page 104
Temperature Recording and Regulation.—Each furnace is equipped with pyrometers, but the
reading and recording of all temperatures are in the hands of one man, who occupies a room with an
opening into the end of the hardening department. The opening is about 15 ft. above the floor level.
On each side of it, easily legible from all of the furnaces, is a board with the numbers of the various
furnaces, as shown in Figs. 59 and 60. Opposite each furnace number is a series of hooks whereon
are hung metal numbers representing the pyrometer readings of the temperature in that particular
furnace. Within the room, as shown in Fig. 60, the indicating instrument is to the right, and to the
left is a switchboard to connect it with the thermo-couples in the various furnaces. The boards
shown to the right and the left swing into the room, which enables the attendant easily to change the
numbers to conform to the pyrometer readings. Readings of the temperatures of the carburizing
furnaces are taken and tabulated every ten minutes. These, numbered 1 to 10, are shown on the
board to the right in Fig. 59. The card shown in Fig. 61 gives such a record. These records are filed
away for possible future reference.
FIG. 58.—Gas heated drawing plate for tooth ends.
The temperatures of the reheating furnaces, numbered from 1 to 26 and shown on the board to the
left in Fig. 59, are taken every 5 min.
Each furnace has a large metal sign on which is marked the temperature at which the furnace
regulator is required to keep his heat. As soon as any variation from this is posted on the board
outside the pyrometer room, the attendant sees it and adjusts the burners to compensate.
reading and recording of all temperatures are in the hands of one man, who occupies a room with an
opening into the end of the hardening department. The opening is about 15 ft. above the floor level.
On each side of it, easily legible from all of the furnaces, is a board with the numbers of the various
furnaces, as shown in Figs. 59 and 60. Opposite each furnace number is a series of hooks whereon
are hung metal numbers representing the pyrometer readings of the temperature in that particular
furnace. Within the room, as shown in Fig. 60, the indicating instrument is to the right, and to the
left is a switchboard to connect it with the thermo-couples in the various furnaces. The boards
shown to the right and the left swing into the room, which enables the attendant easily to change the
numbers to conform to the pyrometer readings. Readings of the temperatures of the carburizing
furnaces are taken and tabulated every ten minutes. These, numbered 1 to 10, are shown on the
board to the right in Fig. 59. The card shown in Fig. 61 gives such a record. These records are filed
away for possible future reference.
FIG. 58.—Gas heated drawing plate for tooth ends.
The temperatures of the reheating furnaces, numbered from 1 to 26 and shown on the board to the
left in Fig. 59, are taken every 5 min.
Each furnace has a large metal sign on which is marked the temperature at which the furnace
regulator is required to keep his heat. As soon as any variation from this is posted on the board
outside the pyrometer room, the attendant sees it and adjusts the burners to compensate.
Page 105
FIG. 59.—Pyrometer recording room.
FIG. 60.—Inside of Pyrometer switch room.
Dies for Gleason Tempering Machines.—In Fig. 62 is shown a set of dies for the Gleason
tempering machine. These accurately made dies fit and hold the gear true during quenching, thus
preventing distortion.
FIG. 60.—Inside of Pyrometer switch room.
Dies for Gleason Tempering Machines.—In Fig. 62 is shown a set of dies for the Gleason
tempering machine. These accurately made dies fit and hold the gear true during quenching, thus
preventing distortion.
Page 106
FIG. 61.—Carburizing furnace record.
Referring to Fig. 62, the die A has a surface B which fits the face of the teeth of the gear C. This
surface is perforated by a large number of holes which permit the quenching oil to circulate freely.
The die A is set in the upper end of the plunger A of the tempering machine, shown in Fig. 63, a few
inches above the surface of the quenching oil in the tank N. Inside the die A are the centering jaws
D, Fig. 62, which are an easy fit for the bore of the gear C. The inner surface of the centering jaws
is in the shape of a female cone. The upper die is shown at E. In the center (separate from it, but a
snug sliding fit in it) is the expander G, which, during quenching, enters the taper in the centering
jaws D, expanding them against the bore of the gear C. The faces F of the upper die E fit two angles
at the back of the gear and are grooved for the passage of the quenching oil. The upper die E is
secured to the die carrier B, shown in Fig. 9, and inside the die is the expander G, which is backed
up by compression springs.
Referring to Fig. 62, the die A has a surface B which fits the face of the teeth of the gear C. This
surface is perforated by a large number of holes which permit the quenching oil to circulate freely.
The die A is set in the upper end of the plunger A of the tempering machine, shown in Fig. 63, a few
inches above the surface of the quenching oil in the tank N. Inside the die A are the centering jaws
D, Fig. 62, which are an easy fit for the bore of the gear C. The inner surface of the centering jaws
is in the shape of a female cone. The upper die is shown at E. In the center (separate from it, but a
snug sliding fit in it) is the expander G, which, during quenching, enters the taper in the centering
jaws D, expanding them against the bore of the gear C. The faces F of the upper die E fit two angles
at the back of the gear and are grooved for the passage of the quenching oil. The upper die E is
secured to the die carrier B, shown in Fig. 9, and inside the die is the expander G, which is backed
up by compression springs.
Page 107
FIG. 62.—Dies for Gleason gear-hardening machine.
Hardening Operation.—Hardening a gear is
accomplished as follows: The gear is taken from the
furnace by the furnaceman and placed in the lower die,
surrounding the centering jaws, as shown at H in Fig. 62
and C in Fig. 63. Air is then turned into the cylinder D,
and the piston rod E, the die carrier B, the top die F and
the expander G descend. The pilot H enters a hole in the
center of the lower die, and the expander G enters the
centering jaws I, causing them to expand and center the
gear C in the lower die. On further advance of the piston
rod E, the expander G is forced upward against the
pressure of the springs J and the upper die F comes in
contact with the upper surface of the gear. Further
downward movement of the dies, which now clamp the
work securely, overcomes the resistance of the pressure
weight K (which normally keeps up the plunger A), and
the gear is submerged in the oil. The quenching oil is
circulated through a cooling system outside the building
and enters the tempering machine through the inlet pipe
L. When the machine is in the position shown, the oil
passes out through the ports M in the lower plunger to
the outer reservoir N, passing to the cooling system by
way of the overflow O. When the lower plunger A is
forced downward, the ports M are automatically closed
and the cool quenching oil from the inlet pipe L, having
no other means of escape, passes through the holes in
the lower die and the grooves in the upper, circulating in
contact with the surfaces of the gear and passes to the
overflow. When the air pressure is released, the
counterweights return the parts to the positions shown
in Fig. 63, and the operator removes the gear.
The gear comes out uniformly hard all over and of the
same degree of hardness as when tempered in an open FIG. 63.—Gleason tempering machine.
tank. The output of the machine depends on the amount
Hardening Operation.—Hardening a gear is
accomplished as follows: The gear is taken from the
furnace by the furnaceman and placed in the lower die,
surrounding the centering jaws, as shown at H in Fig. 62
and C in Fig. 63. Air is then turned into the cylinder D,
and the piston rod E, the die carrier B, the top die F and
the expander G descend. The pilot H enters a hole in the
center of the lower die, and the expander G enters the
centering jaws I, causing them to expand and center the
gear C in the lower die. On further advance of the piston
rod E, the expander G is forced upward against the
pressure of the springs J and the upper die F comes in
contact with the upper surface of the gear. Further
downward movement of the dies, which now clamp the
work securely, overcomes the resistance of the pressure
weight K (which normally keeps up the plunger A), and
the gear is submerged in the oil. The quenching oil is
circulated through a cooling system outside the building
and enters the tempering machine through the inlet pipe
L. When the machine is in the position shown, the oil
passes out through the ports M in the lower plunger to
the outer reservoir N, passing to the cooling system by
way of the overflow O. When the lower plunger A is
forced downward, the ports M are automatically closed
and the cool quenching oil from the inlet pipe L, having
no other means of escape, passes through the holes in
the lower die and the grooves in the upper, circulating in
contact with the surfaces of the gear and passes to the
overflow. When the air pressure is released, the
counterweights return the parts to the positions shown
in Fig. 63, and the operator removes the gear.
The gear comes out uniformly hard all over and of the
same degree of hardness as when tempered in an open FIG. 63.—Gleason tempering machine.
tank. The output of the machine depends on the amount
Page 108
of metal to be cooled, but will average from 8 to 16 per hour. Each machine is served by one man,
two furnaces being required to heat the work. A slight excess of oil is used in the firing of the
furnaces to give a reducing atmosphere and to avoid scale.
two furnaces being required to heat the work. A slight excess of oil is used in the firing of the
furnaces to give a reducing atmosphere and to avoid scale.
Page 109
FIG. 64.—Hardening and shrinking sleeves.
Carburizing Low-carbon Sleeves.—Low-carbon sleeves are carburized and pushed on malleable-iron
differential-case hubs. Formerly, these sleeves were given two treatments after carburization in order to refine the
case and the core, and then sent to the grinding department, where they were ground to a push fit for the hubs.
After this they were pushed on the hubs. By the method now employed, the first treatment refines the core, and on
the second treatment, the sleeves are pushed on the hub and at the same time hardened. This method cuts out the
internal grinding time, pressing on hubs, and haulage from one department to another. Also, less work is lost
through splitting of the sleeves.
The machine for pushing the sleeves on is shown in Fig. 64. At A is the stem on which the hot sleeve B is to be
pushed. The carburized sleeves are heated in an automatic furnace, which takes them cold at the back and feeds
them through to the front, by which time they are at the correct temperature. The loose mandrel C is provided with
a spigot on the lower end, which fits the hole in the differential-case hub. The upper end is tapered as shown and
acts as a pilot for the ram D. The action of pushing on and quenching is similar to the action of the Gleason
tempering machine, with the exception that water instead of oil is used as a quenching medium. The speed of
operation depends on a number of variables, but from 350 to 500 can be heated and pressed on in 11 hr.
Cyanide Bath for Tool Steels.—All high-carbon tool steels are heated in a cyanide bath. With this bath, the heat
can be controlled within 3 deg. The steel is evenly heated without exposure to the air, resulting in work which is
not warped and on which there is no scale. The cyanide bath is, of course, not available for high-speed steel
because of the very high temperatures necessary.
DROP FORGING DIES
The kind of steel used in the die of course influences the heat treatment it is to receive, but this also depends on
the kind of work the die is to perform. If the die is for a forging which is machined all over and does not have to be
especially close to size, where a variation of 1/16 in. is not considered excessive, a low grade steel will be perfectly
satisfactory.
In cases of fine work, however, where the variation cannot be over 0.005 to 0.01 in. we must use a fine steel and
prevent its going out of shape in the heating and quenching. A high quality crucible steel is suggested with about
the following analysis: Carbon 0.75 per cent, manganese 0.25 per cent, silicon 0.15 per cent, sulphur 0.015 per
cent, and phosphorus 0.015 per cent. Such a steel will have a decalescent point in the neighborhood of 1,355°F.
and for the size used, probably in a die of approximately 8 in., it will harden around 1,450°F.
To secure best results care must be taken at every step. The block should be heated slowly to about 1,400°F., the
furnace closed tight and allowed to cool slowly in the furnace itself. It should not soak at the high temperature.
Carburizing Low-carbon Sleeves.—Low-carbon sleeves are carburized and pushed on malleable-iron
differential-case hubs. Formerly, these sleeves were given two treatments after carburization in order to refine the
case and the core, and then sent to the grinding department, where they were ground to a push fit for the hubs.
After this they were pushed on the hubs. By the method now employed, the first treatment refines the core, and on
the second treatment, the sleeves are pushed on the hub and at the same time hardened. This method cuts out the
internal grinding time, pressing on hubs, and haulage from one department to another. Also, less work is lost
through splitting of the sleeves.
The machine for pushing the sleeves on is shown in Fig. 64. At A is the stem on which the hot sleeve B is to be
pushed. The carburized sleeves are heated in an automatic furnace, which takes them cold at the back and feeds
them through to the front, by which time they are at the correct temperature. The loose mandrel C is provided with
a spigot on the lower end, which fits the hole in the differential-case hub. The upper end is tapered as shown and
acts as a pilot for the ram D. The action of pushing on and quenching is similar to the action of the Gleason
tempering machine, with the exception that water instead of oil is used as a quenching medium. The speed of
operation depends on a number of variables, but from 350 to 500 can be heated and pressed on in 11 hr.
Cyanide Bath for Tool Steels.—All high-carbon tool steels are heated in a cyanide bath. With this bath, the heat
can be controlled within 3 deg. The steel is evenly heated without exposure to the air, resulting in work which is
not warped and on which there is no scale. The cyanide bath is, of course, not available for high-speed steel
because of the very high temperatures necessary.
DROP FORGING DIES
The kind of steel used in the die of course influences the heat treatment it is to receive, but this also depends on
the kind of work the die is to perform. If the die is for a forging which is machined all over and does not have to be
especially close to size, where a variation of 1/16 in. is not considered excessive, a low grade steel will be perfectly
satisfactory.
In cases of fine work, however, where the variation cannot be over 0.005 to 0.01 in. we must use a fine steel and
prevent its going out of shape in the heating and quenching. A high quality crucible steel is suggested with about
the following analysis: Carbon 0.75 per cent, manganese 0.25 per cent, silicon 0.15 per cent, sulphur 0.015 per
cent, and phosphorus 0.015 per cent. Such a steel will have a decalescent point in the neighborhood of 1,355°F.
and for the size used, probably in a die of approximately 8 in., it will harden around 1,450°F.
To secure best results care must be taken at every step. The block should be heated slowly to about 1,400°F., the
furnace closed tight and allowed to cool slowly in the furnace itself. It should not soak at the high temperature.
Page 110
After machining, and before it is put in the furnace for hardening, it should be slowly preheated to 800 or 900°F.
This can be done in several ways, some putting the die block in front of the open door of a hardening furnace and
keeping the furnace at about 1,000°F. The main thing is to heat the die block very slowly and evenly.
The hardening heat should be very slow, 7 hr. being none too long for such a block, bringing the die up gradually
to the quenching temperature of 1,450°. This should be held for 1/2 hr. or even a little more, when the die can be
taken out and quenched. There should be no guess work about the heating, a good pyrometer being the only safe
way of knowing the correct temperature.
The quenching tank should be of good size and have a spray or stream of water coming up near the surface. Dip
the die block about 3 in. deep and let the stream of water get at the face so as to play on the forms. By leaving the
rest of the die out of the water, moving the die up and down a trifle to prevent a crack at the line of immersion, the
back of the block is left tough while the face is very hard. To overcome the tendency to warp the face it is a good
plan to pour a little water on the back of the die as this tends to even up the cooling. The depth to which the die is
dipped can be easily regulated by placing bars across the tank at the proper depth.
After the scleroscope shows the die to be properly hardened, which means from 98 to 101, the temper should be
drawn as soon as convenient. A lead pot in which the back of the die can be suspended so as to heat the back side,
makes a good method. Or the die block can be placed back to the open door of a furnace. On a die of this size it
may take several hours to draw it to the desired temper. This can be tested while warm by the scleroscope method,
bearing in mind that the reading will not be the same as when cold. If the test shows from 76 to 78 while warm, the
hardness when cold will be about 83, which is about right for this work.
S. A. E. HEAT TREATMENTS
The Society of Automotive Engineers have adopted certain heat treatments to suit different steels and varying
conditions. These have already been referred to on pages 39 to 41 in connection with the different steels used in
automobile practice. These treatments are designated by letter and correspond with the designations in the table.
HEAT TREATMENTS
Heat Treatment A
After forging or machining:
1. Carbonize at a temperature between 1,600°F. and 1,750°F. (1,650-1,700°F. desired.)
2. Cool slowly or quench.
3. Reheat to 1,450-1,500°F. and quench.
Heat Treatment B
After forging or machining:
1. Carbonize between 1,600°F. and 1,750°F. (1,650-1,700°F. Desired.)
2. Cool slowly in the carbonizing mixture.
3. Reheat to 1,550-1,625°F.
4. Quench.
5. Reheat to 1,400-1,450°F.
6. Quench.
7. Draw in hot oil at 300 to 450°F., depending upon the degree of hardness desired.
Heat Treatment D
After forging or machining:
1. Heat to 1,500-1,600°F.
2. Quench.
3. Reheat to 1,450-1,500°F.
This can be done in several ways, some putting the die block in front of the open door of a hardening furnace and
keeping the furnace at about 1,000°F. The main thing is to heat the die block very slowly and evenly.
The hardening heat should be very slow, 7 hr. being none too long for such a block, bringing the die up gradually
to the quenching temperature of 1,450°. This should be held for 1/2 hr. or even a little more, when the die can be
taken out and quenched. There should be no guess work about the heating, a good pyrometer being the only safe
way of knowing the correct temperature.
The quenching tank should be of good size and have a spray or stream of water coming up near the surface. Dip
the die block about 3 in. deep and let the stream of water get at the face so as to play on the forms. By leaving the
rest of the die out of the water, moving the die up and down a trifle to prevent a crack at the line of immersion, the
back of the block is left tough while the face is very hard. To overcome the tendency to warp the face it is a good
plan to pour a little water on the back of the die as this tends to even up the cooling. The depth to which the die is
dipped can be easily regulated by placing bars across the tank at the proper depth.
After the scleroscope shows the die to be properly hardened, which means from 98 to 101, the temper should be
drawn as soon as convenient. A lead pot in which the back of the die can be suspended so as to heat the back side,
makes a good method. Or the die block can be placed back to the open door of a furnace. On a die of this size it
may take several hours to draw it to the desired temper. This can be tested while warm by the scleroscope method,
bearing in mind that the reading will not be the same as when cold. If the test shows from 76 to 78 while warm, the
hardness when cold will be about 83, which is about right for this work.
S. A. E. HEAT TREATMENTS
The Society of Automotive Engineers have adopted certain heat treatments to suit different steels and varying
conditions. These have already been referred to on pages 39 to 41 in connection with the different steels used in
automobile practice. These treatments are designated by letter and correspond with the designations in the table.
HEAT TREATMENTS
Heat Treatment A
After forging or machining:
1. Carbonize at a temperature between 1,600°F. and 1,750°F. (1,650-1,700°F. desired.)
2. Cool slowly or quench.
3. Reheat to 1,450-1,500°F. and quench.
Heat Treatment B
After forging or machining:
1. Carbonize between 1,600°F. and 1,750°F. (1,650-1,700°F. Desired.)
2. Cool slowly in the carbonizing mixture.
3. Reheat to 1,550-1,625°F.
4. Quench.
5. Reheat to 1,400-1,450°F.
6. Quench.
7. Draw in hot oil at 300 to 450°F., depending upon the degree of hardness desired.
Heat Treatment D
After forging or machining:
1. Heat to 1,500-1,600°F.
2. Quench.
3. Reheat to 1,450-1,500°F.
Page 111
4. Quench.
5. Reheat to 600-1,200°F. and cool slowly.
Heat Treatment E
After forging or machining:
1. Heat to 1,500-1,550°F.
2. Cool slowly.
3. Reheat to 1,450-1,500°F.
4. Quench.
5. Reheat to 600-1,200°F. and cool slowly.
Heat Treatment F
After shaping or coiling:
1. Heat to 1,425-1,475°F.
2. Quench in oil.
3. Reheat to 400-900°F., in accordance with temper desired and cool slowly.
Heat Treatment G
After forging or machining:
1. Carbonize at a temperature between 1,600°F. and 1,750°F. (1,650-1,700°F. desired).
2. Cool slowly in the carbonizing mixture.
3. Reheat to 1,500-1,550°F.
4. Quench.
5. Reheat to 1,300-1,400°F.
6. Quench.
7. Reheat to 250-500°F. (in accordance with the necessities of the case) and cool slowly.
Heat Treatment H
After forging or machining:
1. Heat to 1,500-1,600°F.
2. Quench.
3. Reheat to 600-1,200°F. and cool slowly.
Heat Treatment K
After forging or machining:
1. Heat to 1,500-1,550°F.
2. Quench.
3. Reheat to 1,300-1,400°F.
4. Quench.
5. Reheat to 600-1,200°F. and cool slowly.
Heat Treatment L
After forging or machining:
1. Carbonize between 1,600°F. and 1,750°F. (1,650-1,700°F. desired).
2. Cool slowly in the carbonizing mixture.
3. Reheat to 1,400-1,500°F.
5. Reheat to 600-1,200°F. and cool slowly.
Heat Treatment E
After forging or machining:
1. Heat to 1,500-1,550°F.
2. Cool slowly.
3. Reheat to 1,450-1,500°F.
4. Quench.
5. Reheat to 600-1,200°F. and cool slowly.
Heat Treatment F
After shaping or coiling:
1. Heat to 1,425-1,475°F.
2. Quench in oil.
3. Reheat to 400-900°F., in accordance with temper desired and cool slowly.
Heat Treatment G
After forging or machining:
1. Carbonize at a temperature between 1,600°F. and 1,750°F. (1,650-1,700°F. desired).
2. Cool slowly in the carbonizing mixture.
3. Reheat to 1,500-1,550°F.
4. Quench.
5. Reheat to 1,300-1,400°F.
6. Quench.
7. Reheat to 250-500°F. (in accordance with the necessities of the case) and cool slowly.
Heat Treatment H
After forging or machining:
1. Heat to 1,500-1,600°F.
2. Quench.
3. Reheat to 600-1,200°F. and cool slowly.
Heat Treatment K
After forging or machining:
1. Heat to 1,500-1,550°F.
2. Quench.
3. Reheat to 1,300-1,400°F.
4. Quench.
5. Reheat to 600-1,200°F. and cool slowly.
Heat Treatment L
After forging or machining:
1. Carbonize between 1,600°F. and 1,750°F. (1,650-1,700°F. desired).
2. Cool slowly in the carbonizing mixture.
3. Reheat to 1,400-1,500°F.
Page 112
4. Quench.
5. Reheat to 1,300-1,400°F.
6. Quench.
7. Reheat to 250-500°F. and cool slowly.
Heat Treatment M
After forging or machining:
1. Heat to 1,450-1,500°F.
2. Quench.
3. Reheat to 500-1.250°F. and cool slowly.
Heat Treatment P
After forging or machining:
1. Heat to 1,450-1,500°F.
2. Quench.
3. Reheat to 1,375-1,450°F. slowly.
4. Quench.
5. Reheat to 500-1,250°F. and cool slowly.
Heat Treatment Q
After forging:
1. Heat to 1,475-1,525°F. (Hold at this temperature one-half hour, to insure thorough heating.)
2. Cool slowly.
3. Machine.
4. Reheat to 1,375-1,425°F.
5. Quench.
6. Reheat to 250-550°F. and cool slowly.
Heat Treatment R
After forging:
1. Heat to 1,500-1,550°F.
2. Quench in oil.
3. Reheat to 1,200-1,300°F. (Hold at this temperature three hours.)
4. Cool slowly.
5. Machine.
6. Reheat to 1,350-1,450°F.
7. Quench in oil.
8. Reheat to 250-500°F. and cool slowly.
Heat Treatment S
After forging or machining:
1. Carbonize at a temperature between 1,600 and 1,750°F. (1,650-1,700°F. Desired.)
2. Cool slowly in the carbonizing mixture.
3. Reheat to 1,650-1,750°F.
4. Quench.
5. Reheat to 1,475-1,550°F.
6. Quench.
7. Reheat to 250-550°F. and cool slowly.
5. Reheat to 1,300-1,400°F.
6. Quench.
7. Reheat to 250-500°F. and cool slowly.
Heat Treatment M
After forging or machining:
1. Heat to 1,450-1,500°F.
2. Quench.
3. Reheat to 500-1.250°F. and cool slowly.
Heat Treatment P
After forging or machining:
1. Heat to 1,450-1,500°F.
2. Quench.
3. Reheat to 1,375-1,450°F. slowly.
4. Quench.
5. Reheat to 500-1,250°F. and cool slowly.
Heat Treatment Q
After forging:
1. Heat to 1,475-1,525°F. (Hold at this temperature one-half hour, to insure thorough heating.)
2. Cool slowly.
3. Machine.
4. Reheat to 1,375-1,425°F.
5. Quench.
6. Reheat to 250-550°F. and cool slowly.
Heat Treatment R
After forging:
1. Heat to 1,500-1,550°F.
2. Quench in oil.
3. Reheat to 1,200-1,300°F. (Hold at this temperature three hours.)
4. Cool slowly.
5. Machine.
6. Reheat to 1,350-1,450°F.
7. Quench in oil.
8. Reheat to 250-500°F. and cool slowly.
Heat Treatment S
After forging or machining:
1. Carbonize at a temperature between 1,600 and 1,750°F. (1,650-1,700°F. Desired.)
2. Cool slowly in the carbonizing mixture.
3. Reheat to 1,650-1,750°F.
4. Quench.
5. Reheat to 1,475-1,550°F.
6. Quench.
7. Reheat to 250-550°F. and cool slowly.
Page 113
Heat Treatment T
After forging or machining:
1. Heat to 1,650-1,750°F.
2. Quench.
3. Reheat to 500-1,300°F. and cool slowly.
Heat Treatment U
After forging:
1. Heat to 1,525-1,600°F. (Hold for about one-half hour.)
2. Cool slowly.
3. Machine.
4. Reheat to 1,650-1,700°F.
5. Quench.
6. Reheat to 350-550°F. and cool slowly.
Heat Treatment V
After forging or machining:
1. Heat to 1,650-1,750°F.
2. Quench.
3. Reheat to 400-1,200°F. and cool slowly.
RESTORING OVERHEATED STEEL
FIG. 65.—Chart of changes due to heating and cooling.
The effect of heat treatment on overheated steel is shown graphically in Fig. 65 to the series of illustrations on
pages 137 to 144. This was prepared by Thos. Firth & Sons, Ltd., Sheffield, England.
After forging or machining:
1. Heat to 1,650-1,750°F.
2. Quench.
3. Reheat to 500-1,300°F. and cool slowly.
Heat Treatment U
After forging:
1. Heat to 1,525-1,600°F. (Hold for about one-half hour.)
2. Cool slowly.
3. Machine.
4. Reheat to 1,650-1,700°F.
5. Quench.
6. Reheat to 350-550°F. and cool slowly.
Heat Treatment V
After forging or machining:
1. Heat to 1,650-1,750°F.
2. Quench.
3. Reheat to 400-1,200°F. and cool slowly.
RESTORING OVERHEATED STEEL
FIG. 65.—Chart of changes due to heating and cooling.
The effect of heat treatment on overheated steel is shown graphically in Fig. 65 to the series of illustrations on
pages 137 to 144. This was prepared by Thos. Firth & Sons, Ltd., Sheffield, England.
Page 114
FIG. 66.—The structure of overheated mild steel from which
all the pegs were made (magnified 25 diameters). The pegs
withdrawn at 720°C., or earlier, had this structure and were
quite soft.
FIG. 67.—Peg withdrawn at 750°C. (magnified 25
diameters). The structure is apparently unaltered, but the peg
was hard and, unlike the earlier ones, would not bend double.
FIG. 68.—A portion of 66 magnified 200 diameters to show
that the dark (pearlite) areas are laminated.
all the pegs were made (magnified 25 diameters). The pegs
withdrawn at 720°C., or earlier, had this structure and were
quite soft.
FIG. 67.—Peg withdrawn at 750°C. (magnified 25
diameters). The structure is apparently unaltered, but the peg
was hard and, unlike the earlier ones, would not bend double.
FIG. 68.—A portion of 66 magnified 200 diameters to show
that the dark (pearlite) areas are laminated.
Page 115
FIG. 69.—A portion of 67 magnified 200 diameters,
showing that pearlite areas are no longer laminated and
providing reason for observed hardness
FIG. 70.—Peg withdrawn at 780°C. (magnified 25
diameters), showing inter-diffusion of transformed pearlite
and ferrite areas.
FIG. 71.—Peg withdrawn at 800°C. (magnified 25
diameters), showing inter-diffusion so far advanced that the
original outline of the crystals is now only faintly
suggested.
showing that pearlite areas are no longer laminated and
providing reason for observed hardness
FIG. 70.—Peg withdrawn at 780°C. (magnified 25
diameters), showing inter-diffusion of transformed pearlite
and ferrite areas.
FIG. 71.—Peg withdrawn at 800°C. (magnified 25
diameters), showing inter-diffusion so far advanced that the
original outline of the crystals is now only faintly
suggested.
Page 116
FIG. 72.—Peg withdrawn at 850°C. (magnified 100
diameters) after inter-diffusion was completed. Note the
regular outlines and the small size of the crystals as
compared with 67.
FIG. 73.—To facilitate comparison 67 was enlarged to the same
magnification as 62, and the one superimposed on the other. The
single large crystal occupied as much space as 8,000 of the smaller
ones.
FIG. 74.—The peg withdrawn on cooling at 800°C.
(magnified 100 diameters) shows the first reappearance of
diameters) after inter-diffusion was completed. Note the
regular outlines and the small size of the crystals as
compared with 67.
FIG. 73.—To facilitate comparison 67 was enlarged to the same
magnification as 62, and the one superimposed on the other. The
single large crystal occupied as much space as 8,000 of the smaller
ones.
FIG. 74.—The peg withdrawn on cooling at 800°C.
(magnified 100 diameters) shows the first reappearance of
Page 117
free ferrite. All pegs withdrawn at higher temperatures
were like Fig. 72.
FIG. 75.—Peg withdrawn after cooling to 760°C. The
increased amount of free ferrite arranges itself about the
crystals as envelopes.
FIG. 76.-Peg withdrawn after cooling to 740°C.
were like Fig. 72.
FIG. 75.—Peg withdrawn after cooling to 760°C. The
increased amount of free ferrite arranges itself about the
crystals as envelopes.
FIG. 76.-Peg withdrawn after cooling to 740°C.
Page 118
FIG. 77.—Peg withdrawn after cooling to 670°C. (magnified
800 diameters). Just at this moment the lamination of pearlite,
which now occupied its original area, was taking place. In
some parts the lamination was perfect, in other parts the iron
and iron-carbide were still dissolved in each other.
The center piece Fig. 65 represents a block of steel weighing about 25 lb. The central hole accommodated a
thermo-couple which was attached to an autographic recorder. The curve is a copy of the temperature record
during heating and cooling. Into the holes in the side of the block small pegs of overheated mild steel were
inserted. One peg was withdrawn and quenched at each of the temperatures indicated by the numbered arrows, and
after suitable preparation these pegs were photographed in order to show the changes in structure taking place
during heating and cooling operations. The illustrations here reproduced are selected from those photographs with
the object of presenting pictorially the changes involved in the refining of overheated steel or steel castings.
Figures 66 to 79 with their captions show much that is of value to steel users.
FIG. 78.—Any peg withdrawn after 670°C. on cooling
(magnified 100 diameters).
800 diameters). Just at this moment the lamination of pearlite,
which now occupied its original area, was taking place. In
some parts the lamination was perfect, in other parts the iron
and iron-carbide were still dissolved in each other.
The center piece Fig. 65 represents a block of steel weighing about 25 lb. The central hole accommodated a
thermo-couple which was attached to an autographic recorder. The curve is a copy of the temperature record
during heating and cooling. Into the holes in the side of the block small pegs of overheated mild steel were
inserted. One peg was withdrawn and quenched at each of the temperatures indicated by the numbered arrows, and
after suitable preparation these pegs were photographed in order to show the changes in structure taking place
during heating and cooling operations. The illustrations here reproduced are selected from those photographs with
the object of presenting pictorially the changes involved in the refining of overheated steel or steel castings.
Figures 66 to 79 with their captions show much that is of value to steel users.
FIG. 78.—Any peg withdrawn after 670°C. on cooling
(magnified 100 diameters).
Page 119
FIG. 79.—Structure of overheated steel before (left) and after refining
(right).
(right).
Page 120
CHAPTER IX
HARDENING CARBON STEEL FOR TOOLS
For years the toolmaker had full sway in regard to make of steel wanted for shop tools, he generally made his
own designs, hardened, tempered, ground and usually set up the machine where it was to be used and tested it.
Most of us remember the toolmaker during the sewing machine period when interchangeable tools were
beginning to find their way; rather cautiously at first. The bicycle era was the real beginning of tool making from a
manufacturing standpoint, when interchangeable tools for rapid production were called for and toolmakers were in
great demand. Even then, jigs, and fixtures were of the toolmaker's own design, who practically built every part of
it from start to finish.
The old way, however, had to be changed. Instead of the toolmaker starting his work from cutting off the stock in
the old hack saw, a place for cutting off stock was provided. If, for instance, a forming tool was wanted, the
toolmaker was given the master tool to make while an apprentice roughed out the cutter. The toolmaker, however,
reserved the hardening process for himself. That was one of the particular operations that the old toolmaker refused
to give up. It seemed preposterous to think for a minute that any one else could possibly do that particular job
without spoiling the tools, or at least warp it out of shape (most of us did not grind holes in cutters 15 to 20 years
ago); or a hundred or more things might happen unless the toolmaker did his own hardening and tempering.
That so many remarkably good tools were made at that time is still a wonder to many, when we consider that the
large shop had from 30 to 40 different men, all using their own secret compounds, heating to suit eyesight, no
matter if the day was bright or dark, and then tempering to color. But the day of the old toolmaker has changed.
Now a tool is designed by a tool designer, O.K.'d, and then a print goes to the foreman of the tool department, who
specifies the size and gets the steel from the cutting-off department. After finishing the machine work it goes to the
hardening room, and this is the problem we shall now take up in detail.
The Modern Hardening Room.—A hardening room of today means a very different place from the dirty, dark
smithshop in the corner with the open coal forge. There, when we wanted to be somewhat particular, we
sometimes shoveled the coal cinders to one side and piled a great pile of charcoal on the forge. We now have a
complete equipment; a gas- or oil-heating furnace, good running water, several sizes of lead pots, and an oil tank
large enough to hold a barrel of oil. By running water, we mean a large tank with overflow pipes giving a constant
supply. The ordinary hardening room equipment should consist of:
Gas or oil muffle furnace for hardening.
Gas or oil forge furnace.
A good size gas or oil furnace for annealing and case-hardening.
A gas or oil furnace to hold lead pots.
Oil tempering tank, gas- or oil-heated.
Pressure blower.
Large oil tank to hold at least a barrel of oil.
Big water tank with screen trays connected with large pipe from bottom with overflow.
Straightening press.
The furnace should be connected with pyrometers and tempering tank with a thermometer.
Beside all this you need a good man. It does not make much difference how completely the hardening department
is fitted up, if you expect good work, a small percentage of loss and to be able to tackle anything that comes along,
you must have a good man, one who understands the difference between low- and high-carbon steel, who knows
HARDENING CARBON STEEL FOR TOOLS
For years the toolmaker had full sway in regard to make of steel wanted for shop tools, he generally made his
own designs, hardened, tempered, ground and usually set up the machine where it was to be used and tested it.
Most of us remember the toolmaker during the sewing machine period when interchangeable tools were
beginning to find their way; rather cautiously at first. The bicycle era was the real beginning of tool making from a
manufacturing standpoint, when interchangeable tools for rapid production were called for and toolmakers were in
great demand. Even then, jigs, and fixtures were of the toolmaker's own design, who practically built every part of
it from start to finish.
The old way, however, had to be changed. Instead of the toolmaker starting his work from cutting off the stock in
the old hack saw, a place for cutting off stock was provided. If, for instance, a forming tool was wanted, the
toolmaker was given the master tool to make while an apprentice roughed out the cutter. The toolmaker, however,
reserved the hardening process for himself. That was one of the particular operations that the old toolmaker refused
to give up. It seemed preposterous to think for a minute that any one else could possibly do that particular job
without spoiling the tools, or at least warp it out of shape (most of us did not grind holes in cutters 15 to 20 years
ago); or a hundred or more things might happen unless the toolmaker did his own hardening and tempering.
That so many remarkably good tools were made at that time is still a wonder to many, when we consider that the
large shop had from 30 to 40 different men, all using their own secret compounds, heating to suit eyesight, no
matter if the day was bright or dark, and then tempering to color. But the day of the old toolmaker has changed.
Now a tool is designed by a tool designer, O.K.'d, and then a print goes to the foreman of the tool department, who
specifies the size and gets the steel from the cutting-off department. After finishing the machine work it goes to the
hardening room, and this is the problem we shall now take up in detail.
The Modern Hardening Room.—A hardening room of today means a very different place from the dirty, dark
smithshop in the corner with the open coal forge. There, when we wanted to be somewhat particular, we
sometimes shoveled the coal cinders to one side and piled a great pile of charcoal on the forge. We now have a
complete equipment; a gas- or oil-heating furnace, good running water, several sizes of lead pots, and an oil tank
large enough to hold a barrel of oil. By running water, we mean a large tank with overflow pipes giving a constant
supply. The ordinary hardening room equipment should consist of:
Gas or oil muffle furnace for hardening.
Gas or oil forge furnace.
A good size gas or oil furnace for annealing and case-hardening.
A gas or oil furnace to hold lead pots.
Oil tempering tank, gas- or oil-heated.
Pressure blower.
Large oil tank to hold at least a barrel of oil.
Big water tank with screen trays connected with large pipe from bottom with overflow.
Straightening press.
The furnace should be connected with pyrometers and tempering tank with a thermometer.
Beside all this you need a good man. It does not make much difference how completely the hardening department
is fitted up, if you expect good work, a small percentage of loss and to be able to tackle anything that comes along,
you must have a good man, one who understands the difference between low- and high-carbon steel, who knows
Page 121
when particular care must be exercised on particular work. In other words, a man who knows how his work should
be done, and has the intelligence to follow directions on treatments of steel on which he has had no experience.
Jewelers' tools, especially for silversmith's work, probably have to stand the greatest punishment of any all-steel
tools and to make a spoon die so hard that it will not sink under a blow from an 1,800-lb. hammer with a 4-ft. drop,
and still not crack, demands careful treatment.
To harden such dies, first cover the impression on the die with paste made from bone dust or lampblack and oil.
Place face down in an iron box partly filled with crushed charcoal, leaving back of die uncovered so that the heat
can be seen at all times. Heat slowly in furnace to a good cherry red. The heat depends on the quality and the
analysis of steel and the recommended actions of the steel maker should be carefully followed. When withdrawn
from the fire the die should be quenched as shown in Fig. 80 with the face of die down and the back a short
distance out of the water. When the back is black, immerse all over.
FIG. 80.—Quenching a die, face down.
If such a tank is not at hand, it would pay to rig one up at once, although a barrel of brine may be used, or the
back of the die may be first immersed to a depth of about 1/2 in. When the piece is immersed, hold die on an angle
as in Fig. 81.
FIG. 81.—Hold die at angle to quench.
This is for the purpose of expelling all steam bubbles as they form in contact with hot steel. We are aware of the
fact that a great many toolmakers in jewelry shops still cling to the overhead bath, as in Fig. 82, but more broken
pieces and more dies with soft spots are due to this method than to all the others combined, as the water strikes one
spot in force, contracting the surface so much faster than the rest of the die that the results are the same as if an
uneven heating had been given the steel.
Take Time for Hardening.—Uneven heating and poor quenching has caused loss of many very valuable dies,
and it certainly seems that when a firm spends from $75 to $450 in cutting a die that a few hours could be spared
be done, and has the intelligence to follow directions on treatments of steel on which he has had no experience.
Jewelers' tools, especially for silversmith's work, probably have to stand the greatest punishment of any all-steel
tools and to make a spoon die so hard that it will not sink under a blow from an 1,800-lb. hammer with a 4-ft. drop,
and still not crack, demands careful treatment.
To harden such dies, first cover the impression on the die with paste made from bone dust or lampblack and oil.
Place face down in an iron box partly filled with crushed charcoal, leaving back of die uncovered so that the heat
can be seen at all times. Heat slowly in furnace to a good cherry red. The heat depends on the quality and the
analysis of steel and the recommended actions of the steel maker should be carefully followed. When withdrawn
from the fire the die should be quenched as shown in Fig. 80 with the face of die down and the back a short
distance out of the water. When the back is black, immerse all over.
FIG. 80.—Quenching a die, face down.
If such a tank is not at hand, it would pay to rig one up at once, although a barrel of brine may be used, or the
back of the die may be first immersed to a depth of about 1/2 in. When the piece is immersed, hold die on an angle
as in Fig. 81.
FIG. 81.—Hold die at angle to quench.
This is for the purpose of expelling all steam bubbles as they form in contact with hot steel. We are aware of the
fact that a great many toolmakers in jewelry shops still cling to the overhead bath, as in Fig. 82, but more broken
pieces and more dies with soft spots are due to this method than to all the others combined, as the water strikes one
spot in force, contracting the surface so much faster than the rest of the die that the results are the same as if an
uneven heating had been given the steel.
Take Time for Hardening.—Uneven heating and poor quenching has caused loss of many very valuable dies,
and it certainly seems that when a firm spends from $75 to $450 in cutting a die that a few hours could be spared
Page 122
for proper hardening. But the usual feeling is that a tool must be hurried as soon as the hardener gets it, and if a
burst die is the result from either uneven or overheated steel and quenching same without judgment, the steel gets
the blame.
FIG. 82.—An obsolete method.
Give the steel a chance to heat properly, mix a little common sense with "your 30 years experience on the other
fellows steel." Remember that high-carbon steel hardens at a lower heat than low-carbon steel, and quench when at
the right heat in the two above ways, and 99 per cent of the trouble will vanish.
When a die flies to pieces in quenching, don't rush to the superintendent with a "poor-steel" story, but find out
first why it broke so that the salesman who sold it will not be able to harden piece after piece from the same bar
satisfactorily. If you find a "cold short," commonly called "a pipe," you can lay the blame on the steelmaker. If it is
a case of overheating and quenching when too hot, you will find a coarse grain with many bright spots like crystals
to the hardening depth. If uneven heating is the cause, you will find a wider margin of hardening depth on one side
than on the other, or find the coarse grain from over-heating on one side while on the other you will find a close
grain, which may be just right. If you find any other faults than a "pipe," or are not able to harden deep enough,
then take the blame like a man and send for information. The different steel salesmen are good fellows and most of
them know a thing or two about their own business.
For much work a cooling bath at from 50 to 75°F. is very good both for small hobs, dies, cutter plates or
plungers. Some work will harden best in a barrel of brine, but in running cold water, splendid results will be
obtained. Cutter plates should always be dipped corner first and if any have stripper holes, they should first be
plugged with asbestos or fire clay cement.
In general it may be said that the best hardening temperature for carbon steel is the lowest temperature at which it
will harden properly.
CARBON IN TOOL STEEL
Carbon tool steel, or "tool steel" as it is commonly called, usually contains from 80 to 125 points (or from 0.80 to
1.25 per cent) of carbon, and none of the alloys which go to make up the high speed steels. This was formerly
known also as crucible or "cast" steel, or crucible cast steel, from the way in which it was made. This was before
the days of steel castings. The advent of these caused so much confusion that the term was soon dropped. When we
say "tool steel," we nearly always refer to carbon-tool steel, high-speed steel being usually designated by that
name.
For many purposes carbon-steel cutters are still found best, although where a large amount of material is to be
removed at a rapid rate, it has given way to high-speed steels.
CARBON STEELS FOR DIFFERENT TOOLS
burst die is the result from either uneven or overheated steel and quenching same without judgment, the steel gets
the blame.
FIG. 82.—An obsolete method.
Give the steel a chance to heat properly, mix a little common sense with "your 30 years experience on the other
fellows steel." Remember that high-carbon steel hardens at a lower heat than low-carbon steel, and quench when at
the right heat in the two above ways, and 99 per cent of the trouble will vanish.
When a die flies to pieces in quenching, don't rush to the superintendent with a "poor-steel" story, but find out
first why it broke so that the salesman who sold it will not be able to harden piece after piece from the same bar
satisfactorily. If you find a "cold short," commonly called "a pipe," you can lay the blame on the steelmaker. If it is
a case of overheating and quenching when too hot, you will find a coarse grain with many bright spots like crystals
to the hardening depth. If uneven heating is the cause, you will find a wider margin of hardening depth on one side
than on the other, or find the coarse grain from over-heating on one side while on the other you will find a close
grain, which may be just right. If you find any other faults than a "pipe," or are not able to harden deep enough,
then take the blame like a man and send for information. The different steel salesmen are good fellows and most of
them know a thing or two about their own business.
For much work a cooling bath at from 50 to 75°F. is very good both for small hobs, dies, cutter plates or
plungers. Some work will harden best in a barrel of brine, but in running cold water, splendid results will be
obtained. Cutter plates should always be dipped corner first and if any have stripper holes, they should first be
plugged with asbestos or fire clay cement.
In general it may be said that the best hardening temperature for carbon steel is the lowest temperature at which it
will harden properly.
CARBON IN TOOL STEEL
Carbon tool steel, or "tool steel" as it is commonly called, usually contains from 80 to 125 points (or from 0.80 to
1.25 per cent) of carbon, and none of the alloys which go to make up the high speed steels. This was formerly
known also as crucible or "cast" steel, or crucible cast steel, from the way in which it was made. This was before
the days of steel castings. The advent of these caused so much confusion that the term was soon dropped. When we
say "tool steel," we nearly always refer to carbon-tool steel, high-speed steel being usually designated by that
name.
For many purposes carbon-steel cutters are still found best, although where a large amount of material is to be
removed at a rapid rate, it has given way to high-speed steels.
CARBON STEELS FOR DIFFERENT TOOLS
Page 123
All users of tool steels should carefully study the different qualities of the steels they handle. Different uses
requires different kinds of steel for best results, and for the purpose of designating different steels some makers
have adopted the two terms "temper," and "quality," to distinguish between them.
In this case temper refers to the amount of carbon which is combined with the iron to make the metal into a steel.
The quality means the absence of phosphorous, sulphur and other impurities, these depending on the ores and the
methods of treatment.
Steel makers have various ways of designating carbon steels for different purposes. Some of these systems
involve the use of numbers, that of the Latrobe Steel Company being given herewith. It will be noted that the
numbers are based on 20 points of carbon per unit. The names given the different tempers are also of interest.
Other makers use different numbers.
The temper list follows:
LATROBE TEMPER LIST OF CARBON
TOOL STEELS
No. 3 temper 0.60 to 0.69 per cent carbon
No. 3½ temper 0.70 to 0.79 per cent carbon
No. 4 temper 0.80 to 0.89 per cent carbon
No. 4½ temper 0.90 to 0.99 pet cent carbon
No. 5 temper 1.00 to 1.09 per cent carbon
No. 5½ temper 1.10 to 1.19 per cent carbon
No. 6 temper 1.20 to 1.29 per cent carbon
No. 6½ temper 1.30 to 1.39 per cent carbon
No. 7 temper 1.40 to 1.49 per cent carbon
USES OF THE VARIOUS TEMPERS OF CARBON TOOL STEEL
Die Temper.—No. 3: All kinds of dies for deep stamping, pressing and drop forgings. Mining drills to harden
only. Easily weldable.
Smiths' Tool Temper.—No. 3½: Large punches, minting and rivet dies, nailmakers' tools, hammers, hot and cold
sets, snaps and boilermakers' tools, various smiths' tools, large shear blades, double-handed chisels, caulking tools,
heading dies, masons' tools and tools for general welding purposes.
Shear Blade Temper.—No. 4: Punches, large taps, screwing dies, shear blades, table cutlery, circular and long
saws, heading dies. Weldable.
General Purpose Temper.—No. 4½: Taps, small punches, screwing dies, sawwebs, needles, etc., and for all
general purposes. Weldable.
Axe Temper.—No. 5: Axes, chisels, small taps, miners' drills and jumpers to harden and temper, plane irons.
Weldable with care.
Cutlery Temper.—No. 5½: Large milling cutters, reamers, pocket cutlery, wood tools, short saws, granite drills,
paper and tobacco knives. Weldable with very great care.
Tool Temper.—No. 6: Turning, planing, slotting, and shaping tools, twist drills, mill picks, scythes, circular
cutters, engravers' tools, surgical cutlery, circular saws for cutting metals, bevel and other sections for turret lathes.
Not weldable.
Hard Tool Temper.—No. 6½: Small twist drills, razors, small and intricate engravers' tools, surgical instruments,
knives. Not weldable.
Razor Temper.—No. 7: Razors, barrel boring bits, special lathe tools for turning chilled rolls. Not weldable.
requires different kinds of steel for best results, and for the purpose of designating different steels some makers
have adopted the two terms "temper," and "quality," to distinguish between them.
In this case temper refers to the amount of carbon which is combined with the iron to make the metal into a steel.
The quality means the absence of phosphorous, sulphur and other impurities, these depending on the ores and the
methods of treatment.
Steel makers have various ways of designating carbon steels for different purposes. Some of these systems
involve the use of numbers, that of the Latrobe Steel Company being given herewith. It will be noted that the
numbers are based on 20 points of carbon per unit. The names given the different tempers are also of interest.
Other makers use different numbers.
The temper list follows:
LATROBE TEMPER LIST OF CARBON
TOOL STEELS
No. 3 temper 0.60 to 0.69 per cent carbon
No. 3½ temper 0.70 to 0.79 per cent carbon
No. 4 temper 0.80 to 0.89 per cent carbon
No. 4½ temper 0.90 to 0.99 pet cent carbon
No. 5 temper 1.00 to 1.09 per cent carbon
No. 5½ temper 1.10 to 1.19 per cent carbon
No. 6 temper 1.20 to 1.29 per cent carbon
No. 6½ temper 1.30 to 1.39 per cent carbon
No. 7 temper 1.40 to 1.49 per cent carbon
USES OF THE VARIOUS TEMPERS OF CARBON TOOL STEEL
Die Temper.—No. 3: All kinds of dies for deep stamping, pressing and drop forgings. Mining drills to harden
only. Easily weldable.
Smiths' Tool Temper.—No. 3½: Large punches, minting and rivet dies, nailmakers' tools, hammers, hot and cold
sets, snaps and boilermakers' tools, various smiths' tools, large shear blades, double-handed chisels, caulking tools,
heading dies, masons' tools and tools for general welding purposes.
Shear Blade Temper.—No. 4: Punches, large taps, screwing dies, shear blades, table cutlery, circular and long
saws, heading dies. Weldable.
General Purpose Temper.—No. 4½: Taps, small punches, screwing dies, sawwebs, needles, etc., and for all
general purposes. Weldable.
Axe Temper.—No. 5: Axes, chisels, small taps, miners' drills and jumpers to harden and temper, plane irons.
Weldable with care.
Cutlery Temper.—No. 5½: Large milling cutters, reamers, pocket cutlery, wood tools, short saws, granite drills,
paper and tobacco knives. Weldable with very great care.
Tool Temper.—No. 6: Turning, planing, slotting, and shaping tools, twist drills, mill picks, scythes, circular
cutters, engravers' tools, surgical cutlery, circular saws for cutting metals, bevel and other sections for turret lathes.
Not weldable.
Hard Tool Temper.—No. 6½: Small twist drills, razors, small and intricate engravers' tools, surgical instruments,
knives. Not weldable.
Razor Temper.—No. 7: Razors, barrel boring bits, special lathe tools for turning chilled rolls. Not weldable.
Page 124
STEEL FOR CHISELS AND PUNCHES
The highest grades of carbon or tempering steels are to be recommended for tools which have to withstand
shocks, such as for cold chisels or punches. These steels are, however, particularly useful where it is necessary to
cut tempered or heat-treated steel which is more than ordinarily hard, for cutting chilled iron, etc. They are useful
for boring, for rifle-barrel drilling, for fine finishing cuts, for drawing dies for brass and copper, for blanking dies
for hard materials, for formed cutters on automatic screw machines and for roll-turning tools.
Steel of this kind, being very dense in structure, should be given more time in heating for forging and for
hardening, than carbon steels of a lower grade. For forging it should be heated slowly and uniformly to a bright red
and only light blows used as the heat dies out. Do not hammer at all at a black heat. Reheat slowly to a dark red for
hardening and quench in warm water. Grind on a wet grindstone.
Where tools have to withstand shocks and vibration, as in pneumatic hammer work, in severe punching duty, hot
or cold upsetting or similar work, tool steels containing vanadium or chrome-vanadium give excellent results.
These are made particularly for work of this kind.
CHISELS-SHAPES AND HEAT TREATMENT[1]
[Footnote 1: Abstract of paper by HENRY FOWLER, chief mechanical engineer of the Midland Ry., England, before the Institution of Mechanical
Engineers.]
In the chief mechanical engineer's department of the Midland Ry., after considerable experimenting, it was
decided to order chisel steel to the following specifications: carbon, 0.75 to 0.85 per cent, the other constituents
being normal. This gives a complete analysis as follows: carbon, 0.75 to 0.85; manganese, 0.30; silicon, 0.10;
sulphur, 0.025; phosphorus, 0.025.
The analysis of a chisel which had given excellent service was as follows: carbon, 0.75; manganese, 0.38; silicon,
0.16; sulphur, 0.028; phosphorus, 0.026. The heat treatment is unknown.
The highest grades of carbon or tempering steels are to be recommended for tools which have to withstand
shocks, such as for cold chisels or punches. These steels are, however, particularly useful where it is necessary to
cut tempered or heat-treated steel which is more than ordinarily hard, for cutting chilled iron, etc. They are useful
for boring, for rifle-barrel drilling, for fine finishing cuts, for drawing dies for brass and copper, for blanking dies
for hard materials, for formed cutters on automatic screw machines and for roll-turning tools.
Steel of this kind, being very dense in structure, should be given more time in heating for forging and for
hardening, than carbon steels of a lower grade. For forging it should be heated slowly and uniformly to a bright red
and only light blows used as the heat dies out. Do not hammer at all at a black heat. Reheat slowly to a dark red for
hardening and quench in warm water. Grind on a wet grindstone.
Where tools have to withstand shocks and vibration, as in pneumatic hammer work, in severe punching duty, hot
or cold upsetting or similar work, tool steels containing vanadium or chrome-vanadium give excellent results.
These are made particularly for work of this kind.
CHISELS-SHAPES AND HEAT TREATMENT[1]
[Footnote 1: Abstract of paper by HENRY FOWLER, chief mechanical engineer of the Midland Ry., England, before the Institution of Mechanical
Engineers.]
In the chief mechanical engineer's department of the Midland Ry., after considerable experimenting, it was
decided to order chisel steel to the following specifications: carbon, 0.75 to 0.85 per cent, the other constituents
being normal. This gives a complete analysis as follows: carbon, 0.75 to 0.85; manganese, 0.30; silicon, 0.10;
sulphur, 0.025; phosphorus, 0.025.
The analysis of a chisel which had given excellent service was as follows: carbon, 0.75; manganese, 0.38; silicon,
0.16; sulphur, 0.028; phosphorus, 0.026. The heat treatment is unknown.
Page 125
FIG. 83.—Forms of chisels standardized for the locomotive shops of the
Midland Ry., England.
At the same time that chisel steel was standardized, the form of the chisels themselves was revised, and a
standard chart of these as used in the locomotive shops was drawn up. Figure 83 shows the most important forms,
which are made to stock orders in the smithy and forwarded to the heat-treatment room where the hardening and
tempering is carried out on batches of fifty. A standard system of treatment is employed, which to a very large
extent does away with the personal element. Since the chemical composition is more or less constant, the chief
variant is the section which causes the temperatures to be varied slightly. The chisels are carefully heated in a gas-
fired furnace to a temperature of from 730 to 740°C. (1,340 to 1,364°F.) according to section. In practice, the first
chisel, is heated to 730°C.; and the second to 735°C. (1,355°F.); and a 1 in. half round chisel to 740°C., because of
their varying increasing thickness of section at the points. Upon attaining this steady temperature, the chisels are
quenched to a depth of 3/8 to 1/2 in. from the point in water, and then the whole chisel is immersed and cooled off
in a tank containing linseed oil.
The oil-tank is cooled by being immersed in a cold-water tank through which water is constantly circulated. After
this treatment, the chisels have a dead hard point and a tough or sorbitic shaft. They are then tempered or the point
"let down." This is done by immersing them in another oil-bath which has been raised to about 215°C. (419°F).
The first result is, of course, to drop the temperature of the oil, which is gradually raised to its initial point. On
approaching this temperature the chisels are taken out about every 2°C. rise and tested with a file, and at a point
between 215 and 220°C. (428°F.), when it is found that the desired temper has been reached, the chisels are
removed, cleaned in sawdust, and allowed to cool in an iron tray.
No comparative tests of these chisels with those bought and treated by the old rule-of-thumb methods have been
made, as no exact method of carrying out such tests mechanically, other than trying the hardness by the Brinell or
scleroscope method, are known; any ordinary test depends so largely upon the dexterity of the operator. The
universal opinion of foremen and those using the chisels as to the advantages of the ones receiving the standard
treatment described is that a substantial improvement has been made. The chisels were not "normalized." Tests of
chisels normalized at about 900°C. (1,652°F.) showed that they possessed no advantage.
Midland Ry., England.
At the same time that chisel steel was standardized, the form of the chisels themselves was revised, and a
standard chart of these as used in the locomotive shops was drawn up. Figure 83 shows the most important forms,
which are made to stock orders in the smithy and forwarded to the heat-treatment room where the hardening and
tempering is carried out on batches of fifty. A standard system of treatment is employed, which to a very large
extent does away with the personal element. Since the chemical composition is more or less constant, the chief
variant is the section which causes the temperatures to be varied slightly. The chisels are carefully heated in a gas-
fired furnace to a temperature of from 730 to 740°C. (1,340 to 1,364°F.) according to section. In practice, the first
chisel, is heated to 730°C.; and the second to 735°C. (1,355°F.); and a 1 in. half round chisel to 740°C., because of
their varying increasing thickness of section at the points. Upon attaining this steady temperature, the chisels are
quenched to a depth of 3/8 to 1/2 in. from the point in water, and then the whole chisel is immersed and cooled off
in a tank containing linseed oil.
The oil-tank is cooled by being immersed in a cold-water tank through which water is constantly circulated. After
this treatment, the chisels have a dead hard point and a tough or sorbitic shaft. They are then tempered or the point
"let down." This is done by immersing them in another oil-bath which has been raised to about 215°C. (419°F).
The first result is, of course, to drop the temperature of the oil, which is gradually raised to its initial point. On
approaching this temperature the chisels are taken out about every 2°C. rise and tested with a file, and at a point
between 215 and 220°C. (428°F.), when it is found that the desired temper has been reached, the chisels are
removed, cleaned in sawdust, and allowed to cool in an iron tray.
No comparative tests of these chisels with those bought and treated by the old rule-of-thumb methods have been
made, as no exact method of carrying out such tests mechanically, other than trying the hardness by the Brinell or
scleroscope method, are known; any ordinary test depends so largely upon the dexterity of the operator. The
universal opinion of foremen and those using the chisels as to the advantages of the ones receiving the standard
treatment described is that a substantial improvement has been made. The chisels were not "normalized." Tests of
chisels normalized at about 900°C. (1,652°F.) showed that they possessed no advantage.
Page 126
Tools or pieces which have holes or deep depressions should be filled before heating unless it is necessary to
have the holes hard on the inside. In that case the filling would keep the water away from the surface and no
hardening would take place. Where filling is to be done, various materials are used by different hardeners. Fireclay
and common putty seem to be favored by many.
Every mechanic who has had anything to do with the hardening of tools knows how necessary it is to take a cut
from the surface of the bar that is to be hardened. The reason is that in the process of making the steel its outer
surface has become decarbonized. This change makes it low-carbon steel, which will of course not harden. It is
necessary to remove from 1/16 to ¼ in. of diameter on bars ranging from 1/2 to 4 in.
This same decarbonization occurs if the steel is placed in the forge in such a way that unburned oxygen from the
blast can get at it. The carbon is oxidized, or burned out, converting the outside of the steel into low-carbon steel.
The way to avoid this is to use a deep fire. Lack of this precaution is the cause of much spoiled work, not only
because of decarbonization of the outer surface of the metal, but because the cold blast striking the hot steel acts
like boiling hot water poured into an ice-cold glass tumbler. The contraction sets up stresses that result in cracks
when the piece is quenched.
PREVENTING DECARBONIZATION OF TOOL STEEL
It is especially important to prevent decarbonization in such tools as taps and form cutters, which must keep their
shape after hardening and which cannot be ground away on the profile. For this reason it is well to put taps,
reamers and the like into pieces of pipe in heating them. The pipe need be closed on one end only, as the air will
not circulate readily unless there is an opening at both ends.
Even if used in connection with a blacksmith's forge the lead bath has an advantage for heating tools of
complicated shapes, since it is easier to heat them uniformly and they are submerged and away from the air. The
lead must be stirred frequently or the heat is not uniform in all parts of the lead bath. Covering the lead with
powdered charcoal will largely prevent oxidization and waste of lead.
Such a bath is good for temperatures between 620 and 1,150°F. At higher temperatures there is much waste of
lead.
ANNEALING TO RELIEVE INTERNAL STRESSES
Work quenched from a high temperature and not afterward tempered will, if complex in shape, contain many
internal stresses which may later cause it to break. They may be eased off by slight heating without materially
lessening the hardness of the piece. One way to do this is to hold the piece over a fire and test it with a moistened
finger. Another way is to dip the piece in boiling water after it has first been quenched in a cold bath. Such steps
are not necessary with articles which will afterward be tempered and in which the strains are thus reduced.
In annealing steels the operation is similar to hardening, as far as heating is concerned. The critical temperatures
are the proper ones for annealing as well as hardening. From this point on there is a difference, for annealing
consists in cooling as slowly as possible. The slower the cooling the softer will be the steel.
Annealing may be done in the open air, in furnaces, in hot ashes or lime, in powdered charcoal, in burnt bone, in
charred leather and in water. Open-air annealing will do as a crude measure in cases where it is desired to take the
internal stresses out of a piece. Care must be taken in using this method that the piece is not exposed to drafts or
placed on some cold substance that will chill it. Furnace annealing is much better and consists in heating the piece
in a furnace to the critical temperature and then allowing the work and the furnace to cool together.
When lime or ashes are used as materials to keep air away from the steel and retain the heat, they should be first
heated to make sure that they are dry. Powdered charcoal is used for high-grade annealing, the piece being packed
in this substance in an iron box and both the work and the box raised to the critical temperature and then allowed
to cool slowly. Machinery steel may be annealed in spent ground-bone that has been used in casehardening; but
tool steel must never be annealed in this way, as it will be injured by the phosphorus contained in the bone.
Charred leather is the best annealing material for high-carbon steel, because it prevents decarbonizing taking place.
have the holes hard on the inside. In that case the filling would keep the water away from the surface and no
hardening would take place. Where filling is to be done, various materials are used by different hardeners. Fireclay
and common putty seem to be favored by many.
Every mechanic who has had anything to do with the hardening of tools knows how necessary it is to take a cut
from the surface of the bar that is to be hardened. The reason is that in the process of making the steel its outer
surface has become decarbonized. This change makes it low-carbon steel, which will of course not harden. It is
necessary to remove from 1/16 to ¼ in. of diameter on bars ranging from 1/2 to 4 in.
This same decarbonization occurs if the steel is placed in the forge in such a way that unburned oxygen from the
blast can get at it. The carbon is oxidized, or burned out, converting the outside of the steel into low-carbon steel.
The way to avoid this is to use a deep fire. Lack of this precaution is the cause of much spoiled work, not only
because of decarbonization of the outer surface of the metal, but because the cold blast striking the hot steel acts
like boiling hot water poured into an ice-cold glass tumbler. The contraction sets up stresses that result in cracks
when the piece is quenched.
PREVENTING DECARBONIZATION OF TOOL STEEL
It is especially important to prevent decarbonization in such tools as taps and form cutters, which must keep their
shape after hardening and which cannot be ground away on the profile. For this reason it is well to put taps,
reamers and the like into pieces of pipe in heating them. The pipe need be closed on one end only, as the air will
not circulate readily unless there is an opening at both ends.
Even if used in connection with a blacksmith's forge the lead bath has an advantage for heating tools of
complicated shapes, since it is easier to heat them uniformly and they are submerged and away from the air. The
lead must be stirred frequently or the heat is not uniform in all parts of the lead bath. Covering the lead with
powdered charcoal will largely prevent oxidization and waste of lead.
Such a bath is good for temperatures between 620 and 1,150°F. At higher temperatures there is much waste of
lead.
ANNEALING TO RELIEVE INTERNAL STRESSES
Work quenched from a high temperature and not afterward tempered will, if complex in shape, contain many
internal stresses which may later cause it to break. They may be eased off by slight heating without materially
lessening the hardness of the piece. One way to do this is to hold the piece over a fire and test it with a moistened
finger. Another way is to dip the piece in boiling water after it has first been quenched in a cold bath. Such steps
are not necessary with articles which will afterward be tempered and in which the strains are thus reduced.
In annealing steels the operation is similar to hardening, as far as heating is concerned. The critical temperatures
are the proper ones for annealing as well as hardening. From this point on there is a difference, for annealing
consists in cooling as slowly as possible. The slower the cooling the softer will be the steel.
Annealing may be done in the open air, in furnaces, in hot ashes or lime, in powdered charcoal, in burnt bone, in
charred leather and in water. Open-air annealing will do as a crude measure in cases where it is desired to take the
internal stresses out of a piece. Care must be taken in using this method that the piece is not exposed to drafts or
placed on some cold substance that will chill it. Furnace annealing is much better and consists in heating the piece
in a furnace to the critical temperature and then allowing the work and the furnace to cool together.
When lime or ashes are used as materials to keep air away from the steel and retain the heat, they should be first
heated to make sure that they are dry. Powdered charcoal is used for high-grade annealing, the piece being packed
in this substance in an iron box and both the work and the box raised to the critical temperature and then allowed
to cool slowly. Machinery steel may be annealed in spent ground-bone that has been used in casehardening; but
tool steel must never be annealed in this way, as it will be injured by the phosphorus contained in the bone.
Charred leather is the best annealing material for high-carbon steel, because it prevents decarbonizing taking place.
Page 127
DOUBLE ANNEALING
Water annealing consists in heating the piece, allowing it to cool in air until it loses its red heat and becomes
black and then immediately quenching it in water. This plan works well for very low-carbon steel; but for high-
carbon steel what is known as the "double annealing treatment" must be given, provided results are wanted
quickly. The process consists in heating the steel quickly to 200° or more above the upper critical, cooling in air
down through the recalescence point, then reheating it to just above the critical point and again cooling slowly
through the recalescence, then quenching in oil. This process retains in the steel a fine-grained structure combined
with softness.
QUENCHING TOOL STEEL
To secure proper hardness, the cooling of quenching of steel is as important as its heating. Quenching baths vary
in nature, there being a large number of ways to cool a piece of steel in contrast to the comparatively few ways of
heating it.
Plain water, brine and oil are the three most common quenching materials. Of these three the brine will give the
most hardness, and plain water and oil come next. The colder that any of these baths is when the piece is put into it
the harder will be the steel; but this does not mean that it is a good plan to dip the heated steel into a tank of ice
water, for the shock would be so great that the bar would probably fly to pieces. In fact, the quenching bath must
be sometimes heated a bit to take off the edge of the shock.
Brine solutions will work uniformly, or give the same degree of hardness, until they reach a temperature of
150°F. above which their grip relaxes and the metals quenched in them become softer. Plain water holds its grip up
to a temperature of approximately 100°F.; but oil baths, which are used to secure a slower rate of cooling, may be
used up to 500° or more. A compromise is sometimes effected by using a bath consisting of an inch or two of oil
floating on the surface of water. As the hot steel passes through the oil, the shock is not as severe as if it were to be
thrust directly into the water; and in addition, oil adheres to the tool and keeps the water from direct contact with
the metal.
The old idea that mercury will harden steel more than any other quenching material has been exploded. A bath
consisting of melted cyanide of potassium is useful for heating fine engraved dies and other articles that are
required to come out free from scale. One must always be careful to provide a hood or exhaust system to get rid of
the deadly fumes coming from the cyanide pot.
The one main thing to remember in hardening tool steel is to quench on a rising heat. This does not mean a rapid
heating as a slow increase in temperature is much better in every way.
The Theory of Tempering.—Steel that has been hardened is generally harder and more brittle than is necessary,
and in order to bring it to the condition that meets our requirements a treatment called tempering is used. This
increases the toughness of the steel, i.e., decrease the brittleness at the expense of a slight decrease in hardness.
There are several theories to explain this reaction, but generally it is only necessary to remember that in
hardening we quench steel from the austenite phase, and, due to this rapid cooling, the normal change from
austenite to the eutectoid composition does not have time to take place, and as a consequence the steel exists in a
partially transformed, unstable and very hard condition at atmospheric temperatures. But owing to the internal
rigidity which exists in cold metal the steel is unable to change into its more stable phase until atoms can rearrange
themselves by the application of heat. The higher the heat, the greater the transformation into the softer phases. As
the transformation takes place, a certain amount of heat of reaction, which under slow cooling would have been
released in the critical range, is now released and helps to cause a further slight reaction.
If a piece of steel is heated to a certain temperature and held there, the tempering color, instead of remaining
unchanged at this temperature, will advance in the tempering-color scale as it would with increasing temperature.
This means that the tempering colors do not absolutely correspond to the temperatures of steels, but the variations
are so slight that we can use them in actual practice. (See Table 23, page 158.)
Water annealing consists in heating the piece, allowing it to cool in air until it loses its red heat and becomes
black and then immediately quenching it in water. This plan works well for very low-carbon steel; but for high-
carbon steel what is known as the "double annealing treatment" must be given, provided results are wanted
quickly. The process consists in heating the steel quickly to 200° or more above the upper critical, cooling in air
down through the recalescence point, then reheating it to just above the critical point and again cooling slowly
through the recalescence, then quenching in oil. This process retains in the steel a fine-grained structure combined
with softness.
QUENCHING TOOL STEEL
To secure proper hardness, the cooling of quenching of steel is as important as its heating. Quenching baths vary
in nature, there being a large number of ways to cool a piece of steel in contrast to the comparatively few ways of
heating it.
Plain water, brine and oil are the three most common quenching materials. Of these three the brine will give the
most hardness, and plain water and oil come next. The colder that any of these baths is when the piece is put into it
the harder will be the steel; but this does not mean that it is a good plan to dip the heated steel into a tank of ice
water, for the shock would be so great that the bar would probably fly to pieces. In fact, the quenching bath must
be sometimes heated a bit to take off the edge of the shock.
Brine solutions will work uniformly, or give the same degree of hardness, until they reach a temperature of
150°F. above which their grip relaxes and the metals quenched in them become softer. Plain water holds its grip up
to a temperature of approximately 100°F.; but oil baths, which are used to secure a slower rate of cooling, may be
used up to 500° or more. A compromise is sometimes effected by using a bath consisting of an inch or two of oil
floating on the surface of water. As the hot steel passes through the oil, the shock is not as severe as if it were to be
thrust directly into the water; and in addition, oil adheres to the tool and keeps the water from direct contact with
the metal.
The old idea that mercury will harden steel more than any other quenching material has been exploded. A bath
consisting of melted cyanide of potassium is useful for heating fine engraved dies and other articles that are
required to come out free from scale. One must always be careful to provide a hood or exhaust system to get rid of
the deadly fumes coming from the cyanide pot.
The one main thing to remember in hardening tool steel is to quench on a rising heat. This does not mean a rapid
heating as a slow increase in temperature is much better in every way.
The Theory of Tempering.—Steel that has been hardened is generally harder and more brittle than is necessary,
and in order to bring it to the condition that meets our requirements a treatment called tempering is used. This
increases the toughness of the steel, i.e., decrease the brittleness at the expense of a slight decrease in hardness.
There are several theories to explain this reaction, but generally it is only necessary to remember that in
hardening we quench steel from the austenite phase, and, due to this rapid cooling, the normal change from
austenite to the eutectoid composition does not have time to take place, and as a consequence the steel exists in a
partially transformed, unstable and very hard condition at atmospheric temperatures. But owing to the internal
rigidity which exists in cold metal the steel is unable to change into its more stable phase until atoms can rearrange
themselves by the application of heat. The higher the heat, the greater the transformation into the softer phases. As
the transformation takes place, a certain amount of heat of reaction, which under slow cooling would have been
released in the critical range, is now released and helps to cause a further slight reaction.
If a piece of steel is heated to a certain temperature and held there, the tempering color, instead of remaining
unchanged at this temperature, will advance in the tempering-color scale as it would with increasing temperature.
This means that the tempering colors do not absolutely correspond to the temperatures of steels, but the variations
are so slight that we can use them in actual practice. (See Table 23, page 158.)
Page 128
Temperatures to Use.—As soon as the temperature of the steel reaches 100°C. (212°F.) the transformation
begins, increasing in intensity as the temperature is raised, until finally when the lower critical range is reached,
the steel has been all changed into the ordinary constituents of unhardened steels.
If a piece of polished steel is heated in an ordinary furnace, a thin film of oxides will form on its surface. The
colors of this film change with temperature, and so, in tempering, they are generally used as an indication of the
temperature of the steel. The steel should have at least one polished face so that this film of oxides may be seen.
An alternative method to the determination of temper by color is to temper by heating in an oil or salt bath. Oil
baths can be used up to temperatures of 500°F.; above this, fused-salt baths are required. The article to be tempered
is put into the bath, brought up to and held at the required temperature for a certain length of time, and then cooled,
either rapidly or slowly. This takes longer than the color method, but with low temperatures the results are more
satisfactory, because the temperature of the bath can be controlled with a pyrometer. The tempering temperatures
given in the following table are taken from a handbook issued by the Midvale Steel Company.
TABLE 23.—TEMPERING TEMPERATURES FOR STEELS
Temperature Temperature
for 1 hr. Color for 8 min. Uses
Deg. F. Deg. C. Deg. F. Deg. C.
370 188 Faint yellow 460 238 Scrapers, brass-turning tools, reamers, taps, milling cutters, saw
teeth.
390 199 Light straw 510 265 Twist drills, lathe tools, planer tools, finishing tools
410 210 Dark straw 560 293 Stone tools, hammer faces, chisels for hard work, boring cutters.
430 221 Brown 610 321 Trephining tools, stamps.
450 232 Purple 640 337 Cold chisels for ordinary work, carpenters' tools, picks, cold
punches, shear blades, slicing tools, slotter tools.
490 254 Dark blue 660 343 Hot chisels, tools for hot work, springs.
510 265 Light blue 710 376 Springs, screw drivers.
It will be noted that two sets of temperatures are shown, one being specified for a time interval of 8 min. and the
other for 1 hr. For the finest work the longer time is preferable, while for ordinary rough work 8 min. is sufficient,
after the steel has reached the specified temperature.
The rate of cooling after tempering seems to be immaterial, and the piece can be cooled at any rate, providing
that in large pieces it is sufficiently slow to prevent strains.
Knowing What Takes Place.—How are we to know if we have given a piece of steel the very best possible
treatment?
The best method is by microscopic examination of polished and etched sections, but this requires a certain
expense for laboratory equipment and upkeep, which may prevent an ordinary commercial plant from attempting
such a refinement. It is highly recommended that any firm that has any large amount of heat treatment to do, install
such an equipment, which can be purchased for from $250 to $500. Its intelligent use will save its cost in a very
short time.
The other method is by examination of fractures of small test bars. Steel heated to its correct temperatures will
show the finest possible grain, whereas underheated steel has not had its grain structure refined sufficiently, and so
will not be at its best. On the other hand, overheated steel will have a coarser structure, depending on the extent of
overheating.
To determine the proper quenching temperature of any particular grade of steel it is only necessary to heat pieces
to various temperatures not more than 20°C. (36°F.) apart, quench in water, break them, and examine the fractures.
The temperature producing the finest grain should be used for annealing and hardening.
Similarly, to determine tempering temperatures, several pieces should be hardened, then tempered to various
degrees, and cooled in air. Samples, say six, reheated to temperatures varying by 100° from 300 to 800°C. will
begins, increasing in intensity as the temperature is raised, until finally when the lower critical range is reached,
the steel has been all changed into the ordinary constituents of unhardened steels.
If a piece of polished steel is heated in an ordinary furnace, a thin film of oxides will form on its surface. The
colors of this film change with temperature, and so, in tempering, they are generally used as an indication of the
temperature of the steel. The steel should have at least one polished face so that this film of oxides may be seen.
An alternative method to the determination of temper by color is to temper by heating in an oil or salt bath. Oil
baths can be used up to temperatures of 500°F.; above this, fused-salt baths are required. The article to be tempered
is put into the bath, brought up to and held at the required temperature for a certain length of time, and then cooled,
either rapidly or slowly. This takes longer than the color method, but with low temperatures the results are more
satisfactory, because the temperature of the bath can be controlled with a pyrometer. The tempering temperatures
given in the following table are taken from a handbook issued by the Midvale Steel Company.
TABLE 23.—TEMPERING TEMPERATURES FOR STEELS
Temperature Temperature
for 1 hr. Color for 8 min. Uses
Deg. F. Deg. C. Deg. F. Deg. C.
370 188 Faint yellow 460 238 Scrapers, brass-turning tools, reamers, taps, milling cutters, saw
teeth.
390 199 Light straw 510 265 Twist drills, lathe tools, planer tools, finishing tools
410 210 Dark straw 560 293 Stone tools, hammer faces, chisels for hard work, boring cutters.
430 221 Brown 610 321 Trephining tools, stamps.
450 232 Purple 640 337 Cold chisels for ordinary work, carpenters' tools, picks, cold
punches, shear blades, slicing tools, slotter tools.
490 254 Dark blue 660 343 Hot chisels, tools for hot work, springs.
510 265 Light blue 710 376 Springs, screw drivers.
It will be noted that two sets of temperatures are shown, one being specified for a time interval of 8 min. and the
other for 1 hr. For the finest work the longer time is preferable, while for ordinary rough work 8 min. is sufficient,
after the steel has reached the specified temperature.
The rate of cooling after tempering seems to be immaterial, and the piece can be cooled at any rate, providing
that in large pieces it is sufficiently slow to prevent strains.
Knowing What Takes Place.—How are we to know if we have given a piece of steel the very best possible
treatment?
The best method is by microscopic examination of polished and etched sections, but this requires a certain
expense for laboratory equipment and upkeep, which may prevent an ordinary commercial plant from attempting
such a refinement. It is highly recommended that any firm that has any large amount of heat treatment to do, install
such an equipment, which can be purchased for from $250 to $500. Its intelligent use will save its cost in a very
short time.
The other method is by examination of fractures of small test bars. Steel heated to its correct temperatures will
show the finest possible grain, whereas underheated steel has not had its grain structure refined sufficiently, and so
will not be at its best. On the other hand, overheated steel will have a coarser structure, depending on the extent of
overheating.
To determine the proper quenching temperature of any particular grade of steel it is only necessary to heat pieces
to various temperatures not more than 20°C. (36°F.) apart, quench in water, break them, and examine the fractures.
The temperature producing the finest grain should be used for annealing and hardening.
Similarly, to determine tempering temperatures, several pieces should be hardened, then tempered to various
degrees, and cooled in air. Samples, say six, reheated to temperatures varying by 100° from 300 to 800°C. will
Page 129
show a considerable range of properties, and the drawing temperature of the piece giving the desired results can be
used.
For drawing tempers up to 500°F. oil baths of fresh cotton seed oil can be safely and satisfactorily used. For
higher temperature a bath of some kind of fused salt is recommended.
HINTS FOR TOOL STEEL USERS
Do not hesitate to ask for information from the maker as to the best steel to use for a given purpose, mentioning
in as much detail as possible the use for which it is intended.
Do not heat the steel to a higher degree than that fixed in the description of each class. Never heat the steel to
more than a cherry red without forging it or giving it a definite heat treatment. Heating steel at even moderate
temperature is liable to coarsen the grain which can only be restored by forging or by heat treating.
Let the forging begin as soon as the steel is hot enough and never let tool steel soak in the fire. Continue the
hammering vigorously and constantly, using lighter blows as it cools off, and stopping when the heat becomes a
very dull red or a faint brown.
Should welding be necessary care should be taken not to overheat in order to make an easy weld. Keep it below
the sparkling point as this indicates that the steel is burnt.
Begin to forge as soon as the welds are put together, taking care to use gentle strokes at first increasing them as
the higher heat falls, but not overdoing the hammering when the steel cools. The hammering should be extended
beyond the welding point and should continue until the dull red or brown heat is reached.
PREVENTING CRACKS IN HARDENING
The blacksmith in the small shop, where equipment is usually very limited, often consisting of a forge, a small
open hard-coal furnace, a barrel of water and a can of oil must have skill and experience. With this equipment the
smith is expected to, and usually can, produce good results if proper care is taken.
In hardening carbon tool steel in water, too much cannot be said in favor of slow, careful heating, nor against
overheating if cracks are to be avoided.
It is not wise to take the work from the hardening bath and leave it exposed to the air if there is any heat left in it,
because it is more liable to crack than if left in the bath until cold. In heating, plenty of time is taken for the work
to heat evenly clear through, thus avoiding strains caused by quick and improper heating, In quenching in water,
contraction is much more rapid than was the expansion while heating, and strains begin the moment the work
touches the water. If the piece has any considerable size and is taken from the bath before it is cold and allowed to
come to the air, expansion starts again from the inside so rapidly that the chilled hardened surface cracks before the
strains can be relieved.
Many are most successful with the hardening bath about blood warm. When the work that is being hardened is
nearly cold, it is taken from the water and instantly put into a can of oil, where it is allowed to finish cooling. The
heat in the body of the tool will come to the surface more slowly, thus relieving the strain and overcoming much of
the danger of cracking.
Some contend that the temper should be drawn as soon as possible after hardening: but that if this cannot be done
for some hours, the work should be left in the oil until the tempering can be done. It is claimed that forming dies
and punch-press dies that are difficult to harden will seldom crack if treated in this way.
Small tools or pieces that are very troublesome because of peculiar shape should be made of steel which has been
thoroughly annealed. It is often well to mill or turn off the outer skin of the bar, to remove metal which has been
cold-worked. Then heat slowly just through the critical range and cool in the furnace, in order to produce a very
fine grain. Tools machined from such stock, and hardened with the utmost care, will have the best chance to
survive without warping, growth or cracking.
used.
For drawing tempers up to 500°F. oil baths of fresh cotton seed oil can be safely and satisfactorily used. For
higher temperature a bath of some kind of fused salt is recommended.
HINTS FOR TOOL STEEL USERS
Do not hesitate to ask for information from the maker as to the best steel to use for a given purpose, mentioning
in as much detail as possible the use for which it is intended.
Do not heat the steel to a higher degree than that fixed in the description of each class. Never heat the steel to
more than a cherry red without forging it or giving it a definite heat treatment. Heating steel at even moderate
temperature is liable to coarsen the grain which can only be restored by forging or by heat treating.
Let the forging begin as soon as the steel is hot enough and never let tool steel soak in the fire. Continue the
hammering vigorously and constantly, using lighter blows as it cools off, and stopping when the heat becomes a
very dull red or a faint brown.
Should welding be necessary care should be taken not to overheat in order to make an easy weld. Keep it below
the sparkling point as this indicates that the steel is burnt.
Begin to forge as soon as the welds are put together, taking care to use gentle strokes at first increasing them as
the higher heat falls, but not overdoing the hammering when the steel cools. The hammering should be extended
beyond the welding point and should continue until the dull red or brown heat is reached.
PREVENTING CRACKS IN HARDENING
The blacksmith in the small shop, where equipment is usually very limited, often consisting of a forge, a small
open hard-coal furnace, a barrel of water and a can of oil must have skill and experience. With this equipment the
smith is expected to, and usually can, produce good results if proper care is taken.
In hardening carbon tool steel in water, too much cannot be said in favor of slow, careful heating, nor against
overheating if cracks are to be avoided.
It is not wise to take the work from the hardening bath and leave it exposed to the air if there is any heat left in it,
because it is more liable to crack than if left in the bath until cold. In heating, plenty of time is taken for the work
to heat evenly clear through, thus avoiding strains caused by quick and improper heating, In quenching in water,
contraction is much more rapid than was the expansion while heating, and strains begin the moment the work
touches the water. If the piece has any considerable size and is taken from the bath before it is cold and allowed to
come to the air, expansion starts again from the inside so rapidly that the chilled hardened surface cracks before the
strains can be relieved.
Many are most successful with the hardening bath about blood warm. When the work that is being hardened is
nearly cold, it is taken from the water and instantly put into a can of oil, where it is allowed to finish cooling. The
heat in the body of the tool will come to the surface more slowly, thus relieving the strain and overcoming much of
the danger of cracking.
Some contend that the temper should be drawn as soon as possible after hardening: but that if this cannot be done
for some hours, the work should be left in the oil until the tempering can be done. It is claimed that forming dies
and punch-press dies that are difficult to harden will seldom crack if treated in this way.
Small tools or pieces that are very troublesome because of peculiar shape should be made of steel which has been
thoroughly annealed. It is often well to mill or turn off the outer skin of the bar, to remove metal which has been
cold-worked. Then heat slowly just through the critical range and cool in the furnace, in order to produce a very
fine grain. Tools machined from such stock, and hardened with the utmost care, will have the best chance to
survive without warping, growth or cracking.
Page 130
SHRINKING AND ENLARGING WORK
Steel can be shrunk or enlarged by proper heating and cooling. Pins for forced fits can be enlarged several
thousandths of an inch by rapid heating to a dull red and quenching in water. The theory is that the metal is
expanded in heating and that the sudden cooling sets the outer portion before the core can contract. In dipping the
piece is not held under water till cold but is dipped, held a moment and removed. Then dipped again and again
until cold.
Rings and drawing dies are also shrunk in a similar way. The rings are slowly heated to a cherry red, slipped on a
rod and rolled in a shallow pan of water which cools only the outer edge. This holds the outside while the inner
heated portion is forced inward, reducing the hole. This operation can be repeated a number of times with
considerable success.
TEMPERING ROUND DIES
A number of circular dies of carbon tool steel for use in tool holders of turret lathes were required. No proper
tempering oven was available, so the following method was adopted and proved quite successful.
After the dies had been hardened dead hard in water, they were cleaned up bright. A pair of ordinary smiths' tongs
was made with jaws of heavy material and to fit nicely all around the outside of the die, leaving a 3/32-in. space
when the jaws were closed around the die. The dies being all ready, the tongs were heated red hot, and the dies
were picked up and held by the tongs. This tempered them from the outside in, left the teeth the temper required
and the outside slightly softer. The dies held up the work successfully and were better than when tempered in the
same bath.
THE EFFECT OF TEMPERING ON WATER-QUENCHED GAGES
The following information has been supplied by Automatic and Electric Furnaces, Ltd., 6, Queenstreet, London,
S. W.:
Two gages of ¾ in. diameter, 12 threads per inch, were heated in a Wild-Barfield furnace, using the pyroscopic
detector, and were quenched in cold water. They were subsequently tempered in a salt bath at various increasing
temperatures, the effective diameter of each thread and the scleroscope hardness being measured at each stage. The
figures are in 10,000ths of an inch, and indicate the change + or - with reference to the original effective diameter
of the gages. The results for the two gages have been averaged.
TABLE 24.—CHANGES DUE TO QUENCHING
After Tempering temperature, degrees Centigrade
Thread
quenching 220 260 300 340 380 420
1 +25 +19 +17 +15 +13 +11 +11
2 +18 +12 +11 + 9 + 6 + 5 + 5
3 +12 + 6 + 5 + 3 0 0 0
4 +10 + 4 + 4 + 2 ... 0 - 1
5 + 9 + 4 + 4 + 2 0 0 0
6 + 9 + 4 + 3 + 2 0 0 0
7 +10 + 5 + 5 + 3 + 2 + 1 +2
8 + 8 + 4 + 3 + 2 0 0 + 1
9 + 9 + 4 + 3 + 2 + 1 +1 + 1
10 + 9 + 5 + 5 + 3 + 2 + 2 + 2
11 +7 +4 +4 +2 +1 +1 +1
12 + 9 + 5 + 5 + 5 + 4 + 4 + 3
Scleroscope 80 70 70 62 56 53 52
Had these gages been formed with a plain cylindrical end projecting in front of the screw, the first two threads
would have been prevented from increasing more than the rest. The gages would then have been fairly easily
Steel can be shrunk or enlarged by proper heating and cooling. Pins for forced fits can be enlarged several
thousandths of an inch by rapid heating to a dull red and quenching in water. The theory is that the metal is
expanded in heating and that the sudden cooling sets the outer portion before the core can contract. In dipping the
piece is not held under water till cold but is dipped, held a moment and removed. Then dipped again and again
until cold.
Rings and drawing dies are also shrunk in a similar way. The rings are slowly heated to a cherry red, slipped on a
rod and rolled in a shallow pan of water which cools only the outer edge. This holds the outside while the inner
heated portion is forced inward, reducing the hole. This operation can be repeated a number of times with
considerable success.
TEMPERING ROUND DIES
A number of circular dies of carbon tool steel for use in tool holders of turret lathes were required. No proper
tempering oven was available, so the following method was adopted and proved quite successful.
After the dies had been hardened dead hard in water, they were cleaned up bright. A pair of ordinary smiths' tongs
was made with jaws of heavy material and to fit nicely all around the outside of the die, leaving a 3/32-in. space
when the jaws were closed around the die. The dies being all ready, the tongs were heated red hot, and the dies
were picked up and held by the tongs. This tempered them from the outside in, left the teeth the temper required
and the outside slightly softer. The dies held up the work successfully and were better than when tempered in the
same bath.
THE EFFECT OF TEMPERING ON WATER-QUENCHED GAGES
The following information has been supplied by Automatic and Electric Furnaces, Ltd., 6, Queenstreet, London,
S. W.:
Two gages of ¾ in. diameter, 12 threads per inch, were heated in a Wild-Barfield furnace, using the pyroscopic
detector, and were quenched in cold water. They were subsequently tempered in a salt bath at various increasing
temperatures, the effective diameter of each thread and the scleroscope hardness being measured at each stage. The
figures are in 10,000ths of an inch, and indicate the change + or - with reference to the original effective diameter
of the gages. The results for the two gages have been averaged.
TABLE 24.—CHANGES DUE TO QUENCHING
After Tempering temperature, degrees Centigrade
Thread
quenching 220 260 300 340 380 420
1 +25 +19 +17 +15 +13 +11 +11
2 +18 +12 +11 + 9 + 6 + 5 + 5
3 +12 + 6 + 5 + 3 0 0 0
4 +10 + 4 + 4 + 2 ... 0 - 1
5 + 9 + 4 + 4 + 2 0 0 0
6 + 9 + 4 + 3 + 2 0 0 0
7 +10 + 5 + 5 + 3 + 2 + 1 +2
8 + 8 + 4 + 3 + 2 0 0 + 1
9 + 9 + 4 + 3 + 2 + 1 +1 + 1
10 + 9 + 5 + 5 + 3 + 2 + 2 + 2
11 +7 +4 +4 +2 +1 +1 +1
12 + 9 + 5 + 5 + 5 + 4 + 4 + 3
Scleroscope 80 70 70 62 56 53 52
Had these gages been formed with a plain cylindrical end projecting in front of the screw, the first two threads
would have been prevented from increasing more than the rest. The gages would then have been fairly easily
Page 131
corrected by lapping after tempering at 220°C. Practically no lapping would be required if they were tempered at
340°C. There seems to be no advantage in going to a higher temperature than this. The same degree of hardness
could have been obtained with considerably less distortion by quenching directly in fused salt. It is interesting to
note that when the swelling after water quenching does not exceed 0.0012 in., practically the whole of it may be
recovered by tempering at a sufficiently high temperature, but when the swelling exceeds this amount the steel
assumes a permanently strained condition, and at the most only 0.0014 in. can be recovered by tempering.
TEMPERING COLORS ON CARBON STEELS
Opinions differ as to the temperature which is indicated by the various colors, or oxides, which appear on steel in
tempering.
The figures shown are from five different sources and while the variations are not great, it is safer to take the
average temperature shown in the last column.
TABLE 25.—COLORS, TEMPERATURES,
DEGREES FAHRENHEIT
A B C D E Average
Faint yellow 430 430 430 430 430 430
Light straw 475 460 450 ... 450 458
Dark straw 500 500 470 450 470 478
Purple (reddish) 525 530 520 530 510 523
Purple (bluish) ... 555 550 550 550 551
Blue 575 585 560 580 560 572
Gray blue ... 600 ... 600 610 603
Greenish blue ... 625 ... ... 630 627
TABLE 26.—ANOTHER COLOR TABLE
Degrees
High temperatures judged by color
Fahrenheit
430 Very pale yellow
460 Straw-yellow
480 Dark yellow
500 Brown-yellow
Visible in full daylight
520 Brown-purple
540 Full purple
560 Full blue
600 Very dark blue
752 Red heat, visible in the dark
885 Red heat, visible in the twilight
975 Red heat, visible in the daylight
1,292 Dark red
1,652 Cherry-red
1,832 Bright cherry-red
2,012 Orange-red
2,192 Orange-yellow
2,372 Yellow-white
2,552 White welding heat
2,732 Brilliant white
2,912 Dazzling white (bluish-white)
These differences might easily be due to the difference in the light at the time the colors were observed. It must
also be remembered that even a thin coating of oil will make quite a difference and cause confusion. It is these
possible sources of error, coupled with the ever present chance of human error, that makes it advisable to draw the
340°C. There seems to be no advantage in going to a higher temperature than this. The same degree of hardness
could have been obtained with considerably less distortion by quenching directly in fused salt. It is interesting to
note that when the swelling after water quenching does not exceed 0.0012 in., practically the whole of it may be
recovered by tempering at a sufficiently high temperature, but when the swelling exceeds this amount the steel
assumes a permanently strained condition, and at the most only 0.0014 in. can be recovered by tempering.
TEMPERING COLORS ON CARBON STEELS
Opinions differ as to the temperature which is indicated by the various colors, or oxides, which appear on steel in
tempering.
The figures shown are from five different sources and while the variations are not great, it is safer to take the
average temperature shown in the last column.
TABLE 25.—COLORS, TEMPERATURES,
DEGREES FAHRENHEIT
A B C D E Average
Faint yellow 430 430 430 430 430 430
Light straw 475 460 450 ... 450 458
Dark straw 500 500 470 450 470 478
Purple (reddish) 525 530 520 530 510 523
Purple (bluish) ... 555 550 550 550 551
Blue 575 585 560 580 560 572
Gray blue ... 600 ... 600 610 603
Greenish blue ... 625 ... ... 630 627
TABLE 26.—ANOTHER COLOR TABLE
Degrees
High temperatures judged by color
Fahrenheit
430 Very pale yellow
460 Straw-yellow
480 Dark yellow
500 Brown-yellow
Visible in full daylight
520 Brown-purple
540 Full purple
560 Full blue
600 Very dark blue
752 Red heat, visible in the dark
885 Red heat, visible in the twilight
975 Red heat, visible in the daylight
1,292 Dark red
1,652 Cherry-red
1,832 Bright cherry-red
2,012 Orange-red
2,192 Orange-yellow
2,372 Yellow-white
2,552 White welding heat
2,732 Brilliant white
2,912 Dazzling white (bluish-white)
These differences might easily be due to the difference in the light at the time the colors were observed. It must
also be remembered that even a thin coating of oil will make quite a difference and cause confusion. It is these
possible sources of error, coupled with the ever present chance of human error, that makes it advisable to draw the
Page 132
temper of tools in an oil bath heated to the proper temperature as shown by an accurate high-temperature
thermometer.
Another table, by Gilbert and Barker, runs to much higher temperatures. Beyond 2,200°, however, the eye is very
uncertain.
TABLE 26.—COLORS FOR TEMPERING TOOLS
Approximate
color and Kind of tool
temperature
Yellow Thread chasers, hollow mills (solid type) twist drills centering tools, forming tools, cut-off tools,
430 to 450°F. profile cutters, milling cutters, reamers, dies, etc.
Straw-yellow Thread rolling dies, counterbores, countersinks. Shear blades, boring tools, engraving tools, etc.
460°F.
Brown- Taps, Thread dies, cutters, reamers, etc.
yellow
500°F.
Light purple Taps, dies, rock drills, knives, punches, gages, etc.
530°F.
Dark purple Circular saws for metal, augers, dental and surgical instruments, cold chisels, axes.
550°F.
Pale blue Bone saws, chisels, needles, cutters, etc.
580°F.
Blue Hack saws, wood saws, springs, etc.
600°F.
thermometer.
Another table, by Gilbert and Barker, runs to much higher temperatures. Beyond 2,200°, however, the eye is very
uncertain.
TABLE 26.—COLORS FOR TEMPERING TOOLS
Approximate
color and Kind of tool
temperature
Yellow Thread chasers, hollow mills (solid type) twist drills centering tools, forming tools, cut-off tools,
430 to 450°F. profile cutters, milling cutters, reamers, dies, etc.
Straw-yellow Thread rolling dies, counterbores, countersinks. Shear blades, boring tools, engraving tools, etc.
460°F.
Brown- Taps, Thread dies, cutters, reamers, etc.
yellow
500°F.
Light purple Taps, dies, rock drills, knives, punches, gages, etc.
530°F.
Dark purple Circular saws for metal, augers, dental and surgical instruments, cold chisels, axes.
550°F.
Pale blue Bone saws, chisels, needles, cutters, etc.
580°F.
Blue Hack saws, wood saws, springs, etc.
600°F.
Page 133
CHAPTER X
HIGH-SPEED STEEL
For centuries the secret art of making tool steel was handed down from father to son. The manufacture of tool
steel is still an art which, by the aid of science, has lost much of its secrecy; yet tool steel is today made by
practical men skilled as melters, hammer-men, and rollers, each knowing his art. These practical men willingly
accept guidance from the chemist and metallurgists.
A knowledge of conditions existing today in the manufacture of high-speed steel is essential to steel treaters. It is
well for the manufacturer to have steel treaters understand some of his troubles and difficulties, so that they will
better comprehend the necessity of certain trade customs and practices, and, realizing the manufacturer's desire to
cooperate with them, will reciprocate.
The manufacturer of high-speed steel knows and appreciates the troubles and difficulties that may sometimes
arise in the heat-treating of his product. His aim is to make a uniform steel that will best meet the requirements of
the average machine shop on general work, and at the same time allow the widest variation in heat treatment to
give desired results.
High speed steel is one of the most complex alloys known. A representative steel contains approximately 24 per
cent of alloying metals, namely, tungsten, chromium, vanadium, silicon, manganese, and in addition there is often
found cobalt, molybdenum, uranium, nickel, tin, copper and arsenic.
STANDARD ANALYSIS
The selection of a standard analysis by the manufacturer is the result of a series of compromises between various
properties imparted to the steel by the addition of different elements and there is a wide range of chemical analyses
of various brands. The steel, to be within the range of generally accepted analysis, should contain over 16 per cent
and under 20 per cent tungsten; if of lower tungsten content it should carry proportionately more chromium and
vanadium.
The combined action of tungsten and chromium in steel gives to it the remarkable property of maintaining its
cutting edge at relatively high temperature. This property is commonly spoken of as "red-hardness." The
percentages of tungsten and chromium present should bear a definite relationship to each other. Chromium imparts
to steel a hardening property similar to that given by carbon, although to a less degree. The hardness imparted to
steel by chromium is accompanied by brittleness. The chromium content should be between 3.5 and 5 per cent.
Vanadium was first introduced in high-speed steel as a "scavenger," thereby producing a more homogeneous
product, of greater density and physical strength. It soon became evident that vanadium used in larger quantities
than necessary as a scavenger imparted to the steel a much greater cutting efficiency. Recently, no less an authority
than Prof. J. O. Arnold, of the University of Sheffield, England, stated that "high-speed steels containing vanadium
have a mean efficiency of 108.9, as against a mean efficiency of 61.9 obtained from those without vanadium
content." A wide range of vanadium content in steel, from 0.5 to 1.5 per cent, is permissible.
An ideal analysis for high-speed steel containing 18 per cent tungsten is a chromium content of approximately
3.85 per cent; vanadium, 0.85 to 1.10 per cent, and carbon, between 0.62 and 0.77 per cent.
Detrimental Elements.—Sulphur and phosphorus are two elements known to be detrimental to all steels.
Sulphur causes "red-shortness" and phosphorus causes "cold-shortness." The detrimental effects of these two
elements counteract each other to some extent but the content should be not over 0.02 sulphur and 0.025
HIGH-SPEED STEEL
For centuries the secret art of making tool steel was handed down from father to son. The manufacture of tool
steel is still an art which, by the aid of science, has lost much of its secrecy; yet tool steel is today made by
practical men skilled as melters, hammer-men, and rollers, each knowing his art. These practical men willingly
accept guidance from the chemist and metallurgists.
A knowledge of conditions existing today in the manufacture of high-speed steel is essential to steel treaters. It is
well for the manufacturer to have steel treaters understand some of his troubles and difficulties, so that they will
better comprehend the necessity of certain trade customs and practices, and, realizing the manufacturer's desire to
cooperate with them, will reciprocate.
The manufacturer of high-speed steel knows and appreciates the troubles and difficulties that may sometimes
arise in the heat-treating of his product. His aim is to make a uniform steel that will best meet the requirements of
the average machine shop on general work, and at the same time allow the widest variation in heat treatment to
give desired results.
High speed steel is one of the most complex alloys known. A representative steel contains approximately 24 per
cent of alloying metals, namely, tungsten, chromium, vanadium, silicon, manganese, and in addition there is often
found cobalt, molybdenum, uranium, nickel, tin, copper and arsenic.
STANDARD ANALYSIS
The selection of a standard analysis by the manufacturer is the result of a series of compromises between various
properties imparted to the steel by the addition of different elements and there is a wide range of chemical analyses
of various brands. The steel, to be within the range of generally accepted analysis, should contain over 16 per cent
and under 20 per cent tungsten; if of lower tungsten content it should carry proportionately more chromium and
vanadium.
The combined action of tungsten and chromium in steel gives to it the remarkable property of maintaining its
cutting edge at relatively high temperature. This property is commonly spoken of as "red-hardness." The
percentages of tungsten and chromium present should bear a definite relationship to each other. Chromium imparts
to steel a hardening property similar to that given by carbon, although to a less degree. The hardness imparted to
steel by chromium is accompanied by brittleness. The chromium content should be between 3.5 and 5 per cent.
Vanadium was first introduced in high-speed steel as a "scavenger," thereby producing a more homogeneous
product, of greater density and physical strength. It soon became evident that vanadium used in larger quantities
than necessary as a scavenger imparted to the steel a much greater cutting efficiency. Recently, no less an authority
than Prof. J. O. Arnold, of the University of Sheffield, England, stated that "high-speed steels containing vanadium
have a mean efficiency of 108.9, as against a mean efficiency of 61.9 obtained from those without vanadium
content." A wide range of vanadium content in steel, from 0.5 to 1.5 per cent, is permissible.
An ideal analysis for high-speed steel containing 18 per cent tungsten is a chromium content of approximately
3.85 per cent; vanadium, 0.85 to 1.10 per cent, and carbon, between 0.62 and 0.77 per cent.
Detrimental Elements.—Sulphur and phosphorus are two elements known to be detrimental to all steels.
Sulphur causes "red-shortness" and phosphorus causes "cold-shortness." The detrimental effects of these two
elements counteract each other to some extent but the content should be not over 0.02 sulphur and 0.025
Page 134
phosphorus. The serious detrimental effect of small quantities of sulphur and phosphorus is due to their not being
uniformly distributed, owing to their tendency to segregate.
The manganese and silicon contents are relatively unimportant in the percentages usually found in high-speed
steel.
The detrimental effects of tin, copper and arsenic are not generally realized by the trade. Small quantities of these
impurities are exceedingly harmful. These elements are very seldom determined in customers' chemical
laboratories and it is somewhat difficult for public chemists to analyze for them.
In justice to the manufacturer, attention should be called to the variations in chemical analyses among the best of
laboratories. Generally speaking, a steel works' laboratory will obtain results more nearly true and accurate than is
possible with a customer's laboratory, or by a public chemist. This can reasonably be expected, for the steel works'
chemist is a specialist, analyzing the same material for the same elements day in and day out.
The importance of the chemical laboratory to a tool-steel plant cannot be over-estimated. Every heat of steel is
analyzed for each element, and check analyses obtained; also, every substance used in the mix is analyzed for all
impurities. The importance of using pure base materials is known to all manufacturers despite chemical evidence
that certain detrimental elements are removed in the process of manufacture.
The manufacture of high-speed steel represents the highest art in the making of steel by tool-steel practice. Some
may say, on account of our increased knowledge of chemistry and metallurgy, that the making of such steel has
ceased to be an art, but has become a science. It is, in fact an art; aided by science. The human element in its
manufacture is a decided factor, as will be brought in the following remarks:
The heat treatment of steel in its broad aspect may be said to commence with the melting furnace and end with
the hardening and tempering of the finished product. High-speed steel is melted by two general types of furnace,
known as crucible and electric. Steel treaters, however, are more vitally interested in the changes that take place in
the steel during the various processes of manufacture rather than a detailed description of those processes, which
are more or less familiar to all.
In order that good high-speed steel may be furnished in finished bars, it must be of correct chemical analysis,
properly melted and cast into solid ingots, free from blow-holes and surface defects. Sudden changes of
temperature are to be guarded against at every stage of its manufacture and subsequent treatment. The ingots are
relatively weak, and the tendency to crack due to cooling strains is great. For this reason the hot ingots are not
allowed to cool quickly, but are placed in furnaces which are of about the same temperature and are allowed to
cool gradually before being placed in stock. Good steel can be made only from good ingots.
Steel treaters should be more vitally interested in the important changes which take place in high-speed steel
during the hammering operations than that of any other working the steel receives in the course of its manufacture.
QUALITY AND STRUCTURE
The quality of high-speed steel is dependent to a very great extent upon its structure. The making of the structure
begins under the hammer, and the beneficial effects produced in this stage persist through the subsequent
operations, provided they are properly carried out. The massive carbides and tungstides present in the ingot are
broken down and uniformly distributed throughout the billet.
To accomplish this the reduction in area must be sufficient and the hammer blows should be heavy, so as to carry
the compression into the center of the billet; otherwise, undesirable characteristics such as coarse structure and
carbide envelopes will exist and cause the steel treater much trouble. Surface defects invisible in the ingot may be
opened up under the hammering operation, in which event they are chipped from the hot billet.
Ingots are first hammered into billets. These billets are carefully inspected and all surface defects ground or
chipped. The hammered billets are again slowly heated and receive a second hammering, known as "cogging." The
billet resulting therefrom is known as a "cogged" billet and is of the proper size for the rolling mill or for the
finishing hammer.
uniformly distributed, owing to their tendency to segregate.
The manganese and silicon contents are relatively unimportant in the percentages usually found in high-speed
steel.
The detrimental effects of tin, copper and arsenic are not generally realized by the trade. Small quantities of these
impurities are exceedingly harmful. These elements are very seldom determined in customers' chemical
laboratories and it is somewhat difficult for public chemists to analyze for them.
In justice to the manufacturer, attention should be called to the variations in chemical analyses among the best of
laboratories. Generally speaking, a steel works' laboratory will obtain results more nearly true and accurate than is
possible with a customer's laboratory, or by a public chemist. This can reasonably be expected, for the steel works'
chemist is a specialist, analyzing the same material for the same elements day in and day out.
The importance of the chemical laboratory to a tool-steel plant cannot be over-estimated. Every heat of steel is
analyzed for each element, and check analyses obtained; also, every substance used in the mix is analyzed for all
impurities. The importance of using pure base materials is known to all manufacturers despite chemical evidence
that certain detrimental elements are removed in the process of manufacture.
The manufacture of high-speed steel represents the highest art in the making of steel by tool-steel practice. Some
may say, on account of our increased knowledge of chemistry and metallurgy, that the making of such steel has
ceased to be an art, but has become a science. It is, in fact an art; aided by science. The human element in its
manufacture is a decided factor, as will be brought in the following remarks:
The heat treatment of steel in its broad aspect may be said to commence with the melting furnace and end with
the hardening and tempering of the finished product. High-speed steel is melted by two general types of furnace,
known as crucible and electric. Steel treaters, however, are more vitally interested in the changes that take place in
the steel during the various processes of manufacture rather than a detailed description of those processes, which
are more or less familiar to all.
In order that good high-speed steel may be furnished in finished bars, it must be of correct chemical analysis,
properly melted and cast into solid ingots, free from blow-holes and surface defects. Sudden changes of
temperature are to be guarded against at every stage of its manufacture and subsequent treatment. The ingots are
relatively weak, and the tendency to crack due to cooling strains is great. For this reason the hot ingots are not
allowed to cool quickly, but are placed in furnaces which are of about the same temperature and are allowed to
cool gradually before being placed in stock. Good steel can be made only from good ingots.
Steel treaters should be more vitally interested in the important changes which take place in high-speed steel
during the hammering operations than that of any other working the steel receives in the course of its manufacture.
QUALITY AND STRUCTURE
The quality of high-speed steel is dependent to a very great extent upon its structure. The making of the structure
begins under the hammer, and the beneficial effects produced in this stage persist through the subsequent
operations, provided they are properly carried out. The massive carbides and tungstides present in the ingot are
broken down and uniformly distributed throughout the billet.
To accomplish this the reduction in area must be sufficient and the hammer blows should be heavy, so as to carry
the compression into the center of the billet; otherwise, undesirable characteristics such as coarse structure and
carbide envelopes will exist and cause the steel treater much trouble. Surface defects invisible in the ingot may be
opened up under the hammering operation, in which event they are chipped from the hot billet.
Ingots are first hammered into billets. These billets are carefully inspected and all surface defects ground or
chipped. The hammered billets are again slowly heated and receive a second hammering, known as "cogging." The
billet resulting therefrom is known as a "cogged" billet and is of the proper size for the rolling mill or for the
finishing hammer.
Page 135
Although it is not considered good mill practice, some manufacturers who have a large rolling mill perform the
very important cogging operation in the rolling mill instead of under the hammer. Cogging in a rolling mill does
not break up and distribute the carbides and tungstides as efficiently as cogging under the hammer; another
objection to cogging in the rolling mill is that there is no opportunity to chip surface defects developed as they can
be under the trained eye of a hammer-man, thereby eliminating such defects in the finished billet.
The rolling of high-speed steel is an art known to very few. The various factors governing the proper rolling are
so numerous that it is necessary for each individual rolling mill to work out a practice that gives the best results
upon the particular analysis of steel it makes. Important elements entering into the rolling are the heating and
finishing temperatures, draft, and speed of the mill. In all of these the element of time must be considered.
High-speed steel should be delivered from the rolling mill to the annealing department free from scale, for scale
promotes the formation of a decarbonized surface. In preparation of bars for annealing, they are packed in tubes
with a mixture of charcoal, lime, and other material. The tubes are sealed and placed in the annealing furnace and
the temperature is gradually raised to about 1,650°F., and held there for a sufficient length of time, depending upon
the size of the bars. After very slow cooling the bars are removed from the tubes. They should then show a Brinnell
number of between 235 and 275.
The inspection department ranks with the chemical and metallurgical departments in safeguarding the quality of
the product. It inspects all finished material from the standpoint of surface defects, hardness, size and fracture. It
rejects such steel as is judged not to meet the manufacturer's standard. The inspection and metallurgical
departments work hand in hand, and if any department is not functioning properly it will soon become evident to
the inspectors, enabling the management to remedy the trouble.
The successful manufacture of high-speed steel can only be obtained by those companies who have become
specialists. The art and skill necessary in the successful working of such steel can be attained only by a man of
natural ability in his chosen trade, and trained under the supervision of experts. To become an expert operator in
any department of its manufacture, it is necessary that the operator work almost exclusively in the production of
such steel.
As to the heat treatment, it is customary for the manufacturer to recommend to the user a procedure that will give
to his steel a high degree of cutting efficiency. The recommendations of the manufacturer should be conservative,
embracing fairly wide limits, as the tendency of the user is to adhere very closely to the manufacturer's
recommendations. Unless one of the manufacturer's expert service men has made a detailed study of the customer's
problem, the manufacturer is not justified in laying down set rules, for if the customer does a little experimenting
he can probably modify the practice so as to produce results that are particularly well adapted to his line of work.
The purpose of heat-treating is to produce a tool that will cut so as to give maximum productive efficiency. This
cutting efficiency depends upon the thermal stability of the complex hardenites existing in the hardened and
tempered steel. The writer finds it extremely difficult to convey the meaning of the word "hardenite" to those that
do not have a clear conception of the term. The complex hardenites in high-speed steel may be described as that
form of solid solution which gives to it its cutting efficiency. The complex hardenites are produced by heating the
steel to a very high temperature, near the melting point, which throws into solution carbides and tungstides,
provided they have been properly broken up in the hammering process and uniformly distributed throughout the
steel. By quenching the steel at correct temperature this solid solution is retained at atmospheric temperature.
It is not the intention to make any definite recommendations as to heat-treating of high-speed steel by the users. It
is recognized that such steel can be heat-treated to give satisfactory results by different methods. It is, however,
believed that the American practice of hardening and tempering is becoming more uniform. This is due largely to
the exchange of opinions in meetings and elsewhere. The trend of American practice for hardening is toward the
following:
First, slowly and carefully preheat the tool to a temperature of approximately 1,500°F., taking care to prevent the
formation of excessive scale.
Second, transfer to a furnace, the temperature of which is approximately 2,250 to 2,400°F., and allow to remain in
the furnace until the tool is heated uniformly to the above temperature.
very important cogging operation in the rolling mill instead of under the hammer. Cogging in a rolling mill does
not break up and distribute the carbides and tungstides as efficiently as cogging under the hammer; another
objection to cogging in the rolling mill is that there is no opportunity to chip surface defects developed as they can
be under the trained eye of a hammer-man, thereby eliminating such defects in the finished billet.
The rolling of high-speed steel is an art known to very few. The various factors governing the proper rolling are
so numerous that it is necessary for each individual rolling mill to work out a practice that gives the best results
upon the particular analysis of steel it makes. Important elements entering into the rolling are the heating and
finishing temperatures, draft, and speed of the mill. In all of these the element of time must be considered.
High-speed steel should be delivered from the rolling mill to the annealing department free from scale, for scale
promotes the formation of a decarbonized surface. In preparation of bars for annealing, they are packed in tubes
with a mixture of charcoal, lime, and other material. The tubes are sealed and placed in the annealing furnace and
the temperature is gradually raised to about 1,650°F., and held there for a sufficient length of time, depending upon
the size of the bars. After very slow cooling the bars are removed from the tubes. They should then show a Brinnell
number of between 235 and 275.
The inspection department ranks with the chemical and metallurgical departments in safeguarding the quality of
the product. It inspects all finished material from the standpoint of surface defects, hardness, size and fracture. It
rejects such steel as is judged not to meet the manufacturer's standard. The inspection and metallurgical
departments work hand in hand, and if any department is not functioning properly it will soon become evident to
the inspectors, enabling the management to remedy the trouble.
The successful manufacture of high-speed steel can only be obtained by those companies who have become
specialists. The art and skill necessary in the successful working of such steel can be attained only by a man of
natural ability in his chosen trade, and trained under the supervision of experts. To become an expert operator in
any department of its manufacture, it is necessary that the operator work almost exclusively in the production of
such steel.
As to the heat treatment, it is customary for the manufacturer to recommend to the user a procedure that will give
to his steel a high degree of cutting efficiency. The recommendations of the manufacturer should be conservative,
embracing fairly wide limits, as the tendency of the user is to adhere very closely to the manufacturer's
recommendations. Unless one of the manufacturer's expert service men has made a detailed study of the customer's
problem, the manufacturer is not justified in laying down set rules, for if the customer does a little experimenting
he can probably modify the practice so as to produce results that are particularly well adapted to his line of work.
The purpose of heat-treating is to produce a tool that will cut so as to give maximum productive efficiency. This
cutting efficiency depends upon the thermal stability of the complex hardenites existing in the hardened and
tempered steel. The writer finds it extremely difficult to convey the meaning of the word "hardenite" to those that
do not have a clear conception of the term. The complex hardenites in high-speed steel may be described as that
form of solid solution which gives to it its cutting efficiency. The complex hardenites are produced by heating the
steel to a very high temperature, near the melting point, which throws into solution carbides and tungstides,
provided they have been properly broken up in the hammering process and uniformly distributed throughout the
steel. By quenching the steel at correct temperature this solid solution is retained at atmospheric temperature.
It is not the intention to make any definite recommendations as to heat-treating of high-speed steel by the users. It
is recognized that such steel can be heat-treated to give satisfactory results by different methods. It is, however,
believed that the American practice of hardening and tempering is becoming more uniform. This is due largely to
the exchange of opinions in meetings and elsewhere. The trend of American practice for hardening is toward the
following:
First, slowly and carefully preheat the tool to a temperature of approximately 1,500°F., taking care to prevent the
formation of excessive scale.
Second, transfer to a furnace, the temperature of which is approximately 2,250 to 2,400°F., and allow to remain in
the furnace until the tool is heated uniformly to the above temperature.
Page 136
Third, cool rapidly in oil, dry air blast, or lead bath.
Fourth, draw back to a temperature to meet the physical requirements of the tool, and allow to cool in air.
It was not very long ago that the desirability of drawing hardened high-speed steel to a temperature of 1,100° was
pointed out, and it is indeed encouraging to learn that comparatively few treaters have failed to make use of this
fact. Many treaters at first contended that the steel would be soft after drawing to this temperature and it is only
recently, since numerous actual tests have demonstrated its value, that the old prejudice has been eliminated.
High-speed steel should be delivered only in the annealed condition because annealing relieves the internal
strains inevitable in the manufacture and puts it in vastly improved physical condition. The manufacturer's
inspection after annealing also discloses defects not visible in the unannealed state.
The only true test for a brand of high-speed steel is the service that it gives by continued performance month in
and month out under actual shop conditions. The average buyer is not justified in conducting a test, but can well
continue to purchase his requirements from a reputable manufacturer of a brand that is nationally known. The
manufacturer is always willing to cooperate with the trade in the conducting of a test and is much interested in the
information received from a well conducted test. A test, to be valuable, should be conducted in a manner as nearly
approaching actual working conditions in the plant in which the test is made as is practical. In conducting a test a
few reputable brands should be allowed to enter. All tools entered should be of exactly the same size and shape.
There is much difference of opinion as to the best practical method of conducting a test, and the decision as to how
the test should be conducted should be left to the customer, who should cooperate with the manufacturers in
devising a test which would give the best basis for conclusions as to how the particular brands would perform
under actual shop conditions.
The value of the file test depends upon the quality of the file and the intelligence and experience of the person
using it. The file test is not reliable, but in the hands of an experienced operator, gives some valuable information.
Almost every steel treater knows of numerous instances where a lathe tool which could be touched with a file has
shown wonderful results as to cutting efficiency.
Modern tool-steel practice has changed from that of the past, not by the use of labor-saving machinery, but by the
use of scientific devices which aid and guide the skilled craftsman in producing a steel of higher quality and
greater uniformity. It is upon the intelligence, experience, and skill of the individual that quality of tool steel
depends.
HARDENING HIGH-SPEED STEELS
We will now take up the matter of hardening high-speed steels. The most ordinary tools used are for lathes and
planers. The forging should be done at carbon-steel heat. Rough-grind while still hot and preheat to about carbon-
steel hardening heat, then heat quickly in high-speed furnace to white heat, and quench in oil. If a very hard
substance is to be cut, the point of tool may be quenched in kerosene or water and when nearly black, finish
cooling in oil. Tempering must be done to suit the material to be cut. For cutting cast iron, brass castings, or hard
steel, tempering should be done merely to take strains out of steel.
On ordinary machinery steel or nickel steel the temper can be drawn to a dark blue or up to 900°F. If the tool is of
a special form or character, the risk of melting or scaling the point cannot be taken. In these cases the tool should
be packed, but if there is no packing equipment, a tool can be heated to as high heat as is safe without risk to
cutting edges, and cyanide or prussiate of potash can be sprinkled over the face and then quenched in oil.
Some very adverse criticism may be heard on this point, but experience has proved that such tools will stand up
very nicely and be perfectly free from scales or pipes. Where packing cannot be done, milling cutters, and tools to
be hardened all over, can be placed in muffled furnace, brought to 2,220° and quenched in oil. All such tools,
however, must be preheated slowly to 1,400 to 1,500° then placed in a high-speed furnace and brought up quickly.
Do not soak high-speed steel at high heats. Quench in oil.
We must bear in mind that the heating furnace is likely to expand tools, therefore provision must be made to
leave extra stock to take care of such expansion. Tools with shanks such as counter bores, taps, reamers, drills, etc.,
Fourth, draw back to a temperature to meet the physical requirements of the tool, and allow to cool in air.
It was not very long ago that the desirability of drawing hardened high-speed steel to a temperature of 1,100° was
pointed out, and it is indeed encouraging to learn that comparatively few treaters have failed to make use of this
fact. Many treaters at first contended that the steel would be soft after drawing to this temperature and it is only
recently, since numerous actual tests have demonstrated its value, that the old prejudice has been eliminated.
High-speed steel should be delivered only in the annealed condition because annealing relieves the internal
strains inevitable in the manufacture and puts it in vastly improved physical condition. The manufacturer's
inspection after annealing also discloses defects not visible in the unannealed state.
The only true test for a brand of high-speed steel is the service that it gives by continued performance month in
and month out under actual shop conditions. The average buyer is not justified in conducting a test, but can well
continue to purchase his requirements from a reputable manufacturer of a brand that is nationally known. The
manufacturer is always willing to cooperate with the trade in the conducting of a test and is much interested in the
information received from a well conducted test. A test, to be valuable, should be conducted in a manner as nearly
approaching actual working conditions in the plant in which the test is made as is practical. In conducting a test a
few reputable brands should be allowed to enter. All tools entered should be of exactly the same size and shape.
There is much difference of opinion as to the best practical method of conducting a test, and the decision as to how
the test should be conducted should be left to the customer, who should cooperate with the manufacturers in
devising a test which would give the best basis for conclusions as to how the particular brands would perform
under actual shop conditions.
The value of the file test depends upon the quality of the file and the intelligence and experience of the person
using it. The file test is not reliable, but in the hands of an experienced operator, gives some valuable information.
Almost every steel treater knows of numerous instances where a lathe tool which could be touched with a file has
shown wonderful results as to cutting efficiency.
Modern tool-steel practice has changed from that of the past, not by the use of labor-saving machinery, but by the
use of scientific devices which aid and guide the skilled craftsman in producing a steel of higher quality and
greater uniformity. It is upon the intelligence, experience, and skill of the individual that quality of tool steel
depends.
HARDENING HIGH-SPEED STEELS
We will now take up the matter of hardening high-speed steels. The most ordinary tools used are for lathes and
planers. The forging should be done at carbon-steel heat. Rough-grind while still hot and preheat to about carbon-
steel hardening heat, then heat quickly in high-speed furnace to white heat, and quench in oil. If a very hard
substance is to be cut, the point of tool may be quenched in kerosene or water and when nearly black, finish
cooling in oil. Tempering must be done to suit the material to be cut. For cutting cast iron, brass castings, or hard
steel, tempering should be done merely to take strains out of steel.
On ordinary machinery steel or nickel steel the temper can be drawn to a dark blue or up to 900°F. If the tool is of
a special form or character, the risk of melting or scaling the point cannot be taken. In these cases the tool should
be packed, but if there is no packing equipment, a tool can be heated to as high heat as is safe without risk to
cutting edges, and cyanide or prussiate of potash can be sprinkled over the face and then quenched in oil.
Some very adverse criticism may be heard on this point, but experience has proved that such tools will stand up
very nicely and be perfectly free from scales or pipes. Where packing cannot be done, milling cutters, and tools to
be hardened all over, can be placed in muffled furnace, brought to 2,220° and quenched in oil. All such tools,
however, must be preheated slowly to 1,400 to 1,500° then placed in a high-speed furnace and brought up quickly.
Do not soak high-speed steel at high heats. Quench in oil.
We must bear in mind that the heating furnace is likely to expand tools, therefore provision must be made to
leave extra stock to take care of such expansion. Tools with shanks such as counter bores, taps, reamers, drills, etc.,
Page 137
should be heated no further than they are wanted hard, and quench in oil. If a forge is not at hand and heating must
be done, use a muffle furnace and cover small shanks with a paste from fire clay or ground asbestos. Hollow mills,
spring threading dies, and large cutting tools with small shanks should have the holes thoroughly packed or
covered with asbestos cement as far as they are wanted soft.
CUTTING-OFF STEEL FROM BAR
To cut a piece from an annealed bar, cut off with a hack saw, milling cutter or circular saw. Cut clear through the
bar; do not nick or break. To cut a piece from an unannealed bar, cut right off with an abrasive saw; do not nick or
break. If of large cross-section, cut off hot with a chisel by first slowly and uniformly heating the bar, at the point
to be cut, to a good lemon heat, 1,800 to 1,850°F. and cut right off while hot; do not nick or break. Allow the tool
length and bar to cool before reheating for forging.
LATHE AND PLANER TOOLS
Forging.—Gently warm the steel to remove any chill, is particularly desirable in the winter, then heat slowly and
carefully to a scaling heat, that is a lemon heat (1,800 to 2,000°F.), and forge uniformly. Reheat the tool for further
forging directly the steel begins to stiffen under the hammer. Under no circumstances forge the steel when the
temperature falls below a dark lemon to an orange color about 1,700°F. Reheat as often as is necessary to finish
forging the tool to shape. Allow the tool to cool after forging by burying the tool in dry ashes or lime. Do not place
on the damp ground or in a draught of air.
The heating for forging should be done preferably in a pipe or muffle furnace but if this is not convenient use a
good clean fire with plenty of fuel between the blast pipe and the tool. Never allow the tool to soak after the
desired forging heat has been reached. Do not heat the tool further back than is necessary to shape the tool, but
give the tool sufficient heat. See that the back of the tool is flatly dressed to provide proper support under the nose
of the tool.
Hardening High-speed Steel.—Slowly reheat the cutting edge of the tool to a cherry red, 1,400°F., then force
the blast so as to raise the temperature quickly to a full white heat, 2,200 to 2,250°F., that is, until the tool starts to
sweat at the cutting face. Cool the point of the tool in a dry air blast or preferably in oil, further cool in oil keeping
the tool moving until the tool has become black hot.
To remove hardening strains reheat the tool to from 500 to 1,100°F. Cool in oil or atmosphere. This second heat
treatment adds to the toughness of the tool and therefore to its life.
Grinding Tools.—Grind tools to remove all scale. Use a quick-cutting, dry, abrasive wheel. If using a wet wheel,
be sure to use plenty of water. Do not under any circumstances force the tool against the wheel so as to draw the
color, as this is likely to set up checks on the surface of the tool to its detriment.
FOR MILLING CUTTERS AND FORMED TOOLS
Forging—Forge as before.—Annealing.—Place the steel in a pipe, box or muffle. Arrange the steel so as to
allow at least 1 in. of packing, consisting of dry powder ashes, powdered charcoal, mica, etc., between the pieces
and the walls of the box or pipe. If using a pipe close the ends. Heat slowly and uniformly to a cherry red, 1,375 to
1,450°F. according to size. Hold the steel at this temperature until the heat has thoroughly saturated through the
metal, then allow the muffle box and tools to cool very slowly in a dying furnace or remove the muffle with its
charge and bury in hot ashes or lime. The slower the cooling the softer the steel.
The heating requires from 2 to 10 hr. depending upon the size of the piece.
Hardening and Tempering.—It is preferable to use two furnaces when hardening milling cutters and special
shape tools. One furnace should be maintained at a uniform temperature from 1,375 to 1,450°F. while the other
should be maintained at about 2,250°F. Keep the tool to be hardened in the low temperature furnace until the tool
has attained the full heat of this furnace. A short time should be allowed so as to be assured that the center of the
tool is as hot as the outside. Then quickly remove the tool from this preheating furnace to the full heat furnace.
Keep the tool in this furnace only as long as is necessary for the tool to attain the full temperature of this furnace.
be done, use a muffle furnace and cover small shanks with a paste from fire clay or ground asbestos. Hollow mills,
spring threading dies, and large cutting tools with small shanks should have the holes thoroughly packed or
covered with asbestos cement as far as they are wanted soft.
CUTTING-OFF STEEL FROM BAR
To cut a piece from an annealed bar, cut off with a hack saw, milling cutter or circular saw. Cut clear through the
bar; do not nick or break. To cut a piece from an unannealed bar, cut right off with an abrasive saw; do not nick or
break. If of large cross-section, cut off hot with a chisel by first slowly and uniformly heating the bar, at the point
to be cut, to a good lemon heat, 1,800 to 1,850°F. and cut right off while hot; do not nick or break. Allow the tool
length and bar to cool before reheating for forging.
LATHE AND PLANER TOOLS
Forging.—Gently warm the steel to remove any chill, is particularly desirable in the winter, then heat slowly and
carefully to a scaling heat, that is a lemon heat (1,800 to 2,000°F.), and forge uniformly. Reheat the tool for further
forging directly the steel begins to stiffen under the hammer. Under no circumstances forge the steel when the
temperature falls below a dark lemon to an orange color about 1,700°F. Reheat as often as is necessary to finish
forging the tool to shape. Allow the tool to cool after forging by burying the tool in dry ashes or lime. Do not place
on the damp ground or in a draught of air.
The heating for forging should be done preferably in a pipe or muffle furnace but if this is not convenient use a
good clean fire with plenty of fuel between the blast pipe and the tool. Never allow the tool to soak after the
desired forging heat has been reached. Do not heat the tool further back than is necessary to shape the tool, but
give the tool sufficient heat. See that the back of the tool is flatly dressed to provide proper support under the nose
of the tool.
Hardening High-speed Steel.—Slowly reheat the cutting edge of the tool to a cherry red, 1,400°F., then force
the blast so as to raise the temperature quickly to a full white heat, 2,200 to 2,250°F., that is, until the tool starts to
sweat at the cutting face. Cool the point of the tool in a dry air blast or preferably in oil, further cool in oil keeping
the tool moving until the tool has become black hot.
To remove hardening strains reheat the tool to from 500 to 1,100°F. Cool in oil or atmosphere. This second heat
treatment adds to the toughness of the tool and therefore to its life.
Grinding Tools.—Grind tools to remove all scale. Use a quick-cutting, dry, abrasive wheel. If using a wet wheel,
be sure to use plenty of water. Do not under any circumstances force the tool against the wheel so as to draw the
color, as this is likely to set up checks on the surface of the tool to its detriment.
FOR MILLING CUTTERS AND FORMED TOOLS
Forging—Forge as before.—Annealing.—Place the steel in a pipe, box or muffle. Arrange the steel so as to
allow at least 1 in. of packing, consisting of dry powder ashes, powdered charcoal, mica, etc., between the pieces
and the walls of the box or pipe. If using a pipe close the ends. Heat slowly and uniformly to a cherry red, 1,375 to
1,450°F. according to size. Hold the steel at this temperature until the heat has thoroughly saturated through the
metal, then allow the muffle box and tools to cool very slowly in a dying furnace or remove the muffle with its
charge and bury in hot ashes or lime. The slower the cooling the softer the steel.
The heating requires from 2 to 10 hr. depending upon the size of the piece.
Hardening and Tempering.—It is preferable to use two furnaces when hardening milling cutters and special
shape tools. One furnace should be maintained at a uniform temperature from 1,375 to 1,450°F. while the other
should be maintained at about 2,250°F. Keep the tool to be hardened in the low temperature furnace until the tool
has attained the full heat of this furnace. A short time should be allowed so as to be assured that the center of the
tool is as hot as the outside. Then quickly remove the tool from this preheating furnace to the full heat furnace.
Keep the tool in this furnace only as long as is necessary for the tool to attain the full temperature of this furnace.
Page 138
Then quickly remove and quench in oil or in a dry air blast. Remove before the tool is entirely cold and draw the
temper in an oil bath by raising the temperature of the oil to from 500 to 750°F. and allow this tool to remain, at
this temperature, in the bath for at least 30 min., insuring uniformity of temper; then cool in the bath, atmosphere
or oil.
If higher drawing temperatures are desired than those possible with oil, a salt bath can be used. A very excellent
bath is made by mixing two parts by weight of crude potassium nitrate and three parts crude sodium nitrate. These
will melt at about 450°F. and can be used up to 1,000°F. Before heating the steel in the salt bath, slowly preheat,
preferably in oil. Reheating the hardened high-speed steel to 1,000°F. will materially increase the life of lathe
tools, but milling and form cutters, taps, dies, etc., should not be reheated higher than 500 to 650°F., unless
extreme hardness is required, when 1,100 to 1,000°F., will give the hardest edge.
INSTRUCTIONS FOR WORKING HIGH-SPEED STEEL
Owing to the wide variations in the composition of high-speed steels by various makers, it is always advisable to
follow the directions of each when using his brand of steel. In the absence of specific directions the following
general suggestions from several makers will be found helpful.
The Ludlum Steel Company recommend the following:
Cutting-off.—To cut a piece from an annealed bar, cut off with a hack saw, milling cutter or circular saw. Cut
clear through the bar; do not nick or break. To cut a piece from an unannealed bar, cut right off with an abrasive
saw; do not nick or break. If of large cross-section, cut off hot with a chisel by first slowly and uniformly heating
the bar, at the point to be cut, to a good lemon heat, 1,800°-1,850°F. and cut right off while hot; do not nick or
break. Allow the tool length and bar to cool before reheating for forging.
LATHE AND PLANER TOOLS
To Forge.—Gently warm the steel to remove any chill is particularly desirable in the winter. Then heat slowly
and carefully to a scaling heat, that is a lemon heat (1,800°-2,000°F.), and forge uniformly. Reheat the tool for
further forging directly the steel begins to stiffen under the hammer. Under no circumstances forge the steel when
the temperature falls below a dark lemon to an orange color: about 1,700°F. Reheat as often as is necessary to
finish forging the tool to shape. Allow the tool to cool after forging by burying the tool in dry ashes or lime. Do not
place on the damp ground or in a draught of air.
The heating for forging should be done preferably in a pipe or muffle furnace, but if this is not convenient use a
good clean fire with plenty of fuel between the blast pipe and the tool. Never allow the tool to soak after the
desired forging heat has been reached. Do not heat the tool further back than is necessary to shape the tool, but
give the tool sufficient heat. See that the back of the tool is flatly dressed to provide proper support under the nose
of the tool.
Hardening.—Slowly reheat the cutting edge of the tool to a cherry red, 1,400°F., then force the blast so as to
raise the temperature quickly to a full white heat, 2,200°-2,250°F., that is, until the tool starts to sweat at the
cutting face. Cool the point of the tool in a dry air blast or preferably in oil; further cool in oil, keeping the tool
moving until the tool has become black hot.
To remove hardening strains reheat the tool to from 500° to 1,100°F. Cool in oil or atmosphere. This second heat
treatment adds to the toughness of the tool and therefore to its life.
Grinding.—Grind tools to remove all scale. Use a quick cutting, dry, abrasive wheel. If using a wet wheel, be
sure to use plenty of water. Do not under any circumstances force the tool against the wheel so as to draw the
color, as this is likely to set up checks on the surface of the tool to its detriment.
The Firth-Sterling Steel Company say:
Instead of printing any rules on the hardening and tempering of Firth-Sterling Steels we wish to say to our
customers: Trust the steel to the skill and the judgement of your Toolsmith and Tool Temperer.
temper in an oil bath by raising the temperature of the oil to from 500 to 750°F. and allow this tool to remain, at
this temperature, in the bath for at least 30 min., insuring uniformity of temper; then cool in the bath, atmosphere
or oil.
If higher drawing temperatures are desired than those possible with oil, a salt bath can be used. A very excellent
bath is made by mixing two parts by weight of crude potassium nitrate and three parts crude sodium nitrate. These
will melt at about 450°F. and can be used up to 1,000°F. Before heating the steel in the salt bath, slowly preheat,
preferably in oil. Reheating the hardened high-speed steel to 1,000°F. will materially increase the life of lathe
tools, but milling and form cutters, taps, dies, etc., should not be reheated higher than 500 to 650°F., unless
extreme hardness is required, when 1,100 to 1,000°F., will give the hardest edge.
INSTRUCTIONS FOR WORKING HIGH-SPEED STEEL
Owing to the wide variations in the composition of high-speed steels by various makers, it is always advisable to
follow the directions of each when using his brand of steel. In the absence of specific directions the following
general suggestions from several makers will be found helpful.
The Ludlum Steel Company recommend the following:
Cutting-off.—To cut a piece from an annealed bar, cut off with a hack saw, milling cutter or circular saw. Cut
clear through the bar; do not nick or break. To cut a piece from an unannealed bar, cut right off with an abrasive
saw; do not nick or break. If of large cross-section, cut off hot with a chisel by first slowly and uniformly heating
the bar, at the point to be cut, to a good lemon heat, 1,800°-1,850°F. and cut right off while hot; do not nick or
break. Allow the tool length and bar to cool before reheating for forging.
LATHE AND PLANER TOOLS
To Forge.—Gently warm the steel to remove any chill is particularly desirable in the winter. Then heat slowly
and carefully to a scaling heat, that is a lemon heat (1,800°-2,000°F.), and forge uniformly. Reheat the tool for
further forging directly the steel begins to stiffen under the hammer. Under no circumstances forge the steel when
the temperature falls below a dark lemon to an orange color: about 1,700°F. Reheat as often as is necessary to
finish forging the tool to shape. Allow the tool to cool after forging by burying the tool in dry ashes or lime. Do not
place on the damp ground or in a draught of air.
The heating for forging should be done preferably in a pipe or muffle furnace, but if this is not convenient use a
good clean fire with plenty of fuel between the blast pipe and the tool. Never allow the tool to soak after the
desired forging heat has been reached. Do not heat the tool further back than is necessary to shape the tool, but
give the tool sufficient heat. See that the back of the tool is flatly dressed to provide proper support under the nose
of the tool.
Hardening.—Slowly reheat the cutting edge of the tool to a cherry red, 1,400°F., then force the blast so as to
raise the temperature quickly to a full white heat, 2,200°-2,250°F., that is, until the tool starts to sweat at the
cutting face. Cool the point of the tool in a dry air blast or preferably in oil; further cool in oil, keeping the tool
moving until the tool has become black hot.
To remove hardening strains reheat the tool to from 500° to 1,100°F. Cool in oil or atmosphere. This second heat
treatment adds to the toughness of the tool and therefore to its life.
Grinding.—Grind tools to remove all scale. Use a quick cutting, dry, abrasive wheel. If using a wet wheel, be
sure to use plenty of water. Do not under any circumstances force the tool against the wheel so as to draw the
color, as this is likely to set up checks on the surface of the tool to its detriment.
The Firth-Sterling Steel Company say:
Instead of printing any rules on the hardening and tempering of Firth-Sterling Steels we wish to say to our
customers: Trust the steel to the skill and the judgement of your Toolsmith and Tool Temperer.
Page 139
The steel workers of today know by personal experience and by inheritance all the standard rules and theories on
forging, hardening and tempering of all fine tool steels. They know the importance of slow, uniform heating, and
the danger of overheating some steels, and underheating others.
The tempering of tools and dies is a science taught by heat, muscle and brains.
The tool temperer is the man to hold responsible for results. The tempering of tools has been his life work. He
may find suggestions on the following pages interesting, but we are always ready to trust the treatment of our
steels to the experienced man at the fire.
HEAT TREATMENT OF LATHE, PLANER AND SIMILAR TOOLS
Fire.—For these tools a good fire is one made of hard foundry coke, broken in small pieces, in an ordinary
blacksmith forge with a few bricks laid over the top to form a hollow fire. The bricks should be thoroughly heated
before tools are heated. Hard coal may be used very successfully in place of hard coke and will give a higher heat.
It is very easy to give Blue Chip the proper heat if care is used in making up the fire.
Forging.—Heat slowly and uniformly to a good forging heat. Do not hammer the steel after it cools below a
bright red. Avoid as much as possible heating the body of the tool, so as to retain the natural toughness in the neck
of the tool.
Hardening.—Heat the point of the tool to an extreme white heat (about 2,200°F.) until the flux runs. This heat
should be the highest possible short of melting the point. Care should be taken to confine the heat as near to the
point as possible so as to leave the annealing and consequent toughness in the neck of the tool and where the tool
is held in the tool post.
Cool in an air blast, the open air or in oil, depending upon the tools or the work they are to do.
For roughing tools temper need not be drawn except for work where the edge tends to crumble on account of
being too hard.
For finishing tools draw the temper to suit the purpose for which they are to be used.
Grind thoroughly on dry wheel (or wet wheel if care is used to prevent checking).
HEAT TREATMENT OF MILLING CUTTERS, DRILLS, REAMERS, ETC.
The Fire.—Gas and electric furnaces designed for high heats are now made for treating high-speed steels. We
recommend them for treating all kinds of Blue Chip tools and particularly the above class. After tools reach a
yellow heat in the forge fire they must not be allowed to touch the fuel or come in contact with the blast or
surrounding air.
Heating.—Tools of this kind should be heated to a mellow white heat, or as hot as possible without injuring the
cutting edges (2,000 to 2,200°F.). For most work the higher the heat the better the tool. Where furnaces are used,
we recommend preheating the tools to a red heat in one furnace before putting them in a white hot furnace.
Cooling.—We recommend quenching all of the above tools in oil when taken from the fire. We have found fish
oil, cottonseed oil, Houghton's No. 2 soluble oil and linseed oil satisfactory. The high heat is the important thing in
hardening Blue Chip tools. If a white hot tool is allowed to cool in the open air it will be hard, but the air scales the
tool.
Drawing the Temper.—Tools of this class should be drawn considerably more than water-hardening steel for the
same purpose.
HEAT TREATMENT OF PUNCHES AND DIES, SHEARS, TAPS, ETC.
Heating.—The degree to which tools of the above classes should be heated depends upon the shape, size and use
for which they are intended. Generally, they should not be heated to quite as high a heat as lathe tools or milling
forging, hardening and tempering of all fine tool steels. They know the importance of slow, uniform heating, and
the danger of overheating some steels, and underheating others.
The tempering of tools and dies is a science taught by heat, muscle and brains.
The tool temperer is the man to hold responsible for results. The tempering of tools has been his life work. He
may find suggestions on the following pages interesting, but we are always ready to trust the treatment of our
steels to the experienced man at the fire.
HEAT TREATMENT OF LATHE, PLANER AND SIMILAR TOOLS
Fire.—For these tools a good fire is one made of hard foundry coke, broken in small pieces, in an ordinary
blacksmith forge with a few bricks laid over the top to form a hollow fire. The bricks should be thoroughly heated
before tools are heated. Hard coal may be used very successfully in place of hard coke and will give a higher heat.
It is very easy to give Blue Chip the proper heat if care is used in making up the fire.
Forging.—Heat slowly and uniformly to a good forging heat. Do not hammer the steel after it cools below a
bright red. Avoid as much as possible heating the body of the tool, so as to retain the natural toughness in the neck
of the tool.
Hardening.—Heat the point of the tool to an extreme white heat (about 2,200°F.) until the flux runs. This heat
should be the highest possible short of melting the point. Care should be taken to confine the heat as near to the
point as possible so as to leave the annealing and consequent toughness in the neck of the tool and where the tool
is held in the tool post.
Cool in an air blast, the open air or in oil, depending upon the tools or the work they are to do.
For roughing tools temper need not be drawn except for work where the edge tends to crumble on account of
being too hard.
For finishing tools draw the temper to suit the purpose for which they are to be used.
Grind thoroughly on dry wheel (or wet wheel if care is used to prevent checking).
HEAT TREATMENT OF MILLING CUTTERS, DRILLS, REAMERS, ETC.
The Fire.—Gas and electric furnaces designed for high heats are now made for treating high-speed steels. We
recommend them for treating all kinds of Blue Chip tools and particularly the above class. After tools reach a
yellow heat in the forge fire they must not be allowed to touch the fuel or come in contact with the blast or
surrounding air.
Heating.—Tools of this kind should be heated to a mellow white heat, or as hot as possible without injuring the
cutting edges (2,000 to 2,200°F.). For most work the higher the heat the better the tool. Where furnaces are used,
we recommend preheating the tools to a red heat in one furnace before putting them in a white hot furnace.
Cooling.—We recommend quenching all of the above tools in oil when taken from the fire. We have found fish
oil, cottonseed oil, Houghton's No. 2 soluble oil and linseed oil satisfactory. The high heat is the important thing in
hardening Blue Chip tools. If a white hot tool is allowed to cool in the open air it will be hard, but the air scales the
tool.
Drawing the Temper.—Tools of this class should be drawn considerably more than water-hardening steel for the
same purpose.
HEAT TREATMENT OF PUNCHES AND DIES, SHEARS, TAPS, ETC.
Heating.—The degree to which tools of the above classes should be heated depends upon the shape, size and use
for which they are intended. Generally, they should not be heated to quite as high a heat as lathe tools or milling
Page 140
cutters. They should have a high heat, but not enough to make the flux run on the steel (by pyrometer 1,900 to
2,100°F.).
Cooling.—Depending on the tools, some should be dipped in oil all over, some only part way, and others allowed
to cool down in the air naturally, or under air blast. In cooling, the toughness is retained by allowing some parts to
cool slowly and quenching parts that should be hard.
Drawing the Temper.—As in cooling, some parts of these tools will require more drawing than others, but, on
the whole, they must be drawn more than water hardening tools for the same purpose or to about 500°F. all over,
so that a good file will just "touch" the cutting or working parts.
Barium Chloride Process.—This is a process developed for treating certain classes of tools, such as taps,
forming tools, etc. It is being successfully used in many large plants. Briefly the treatment is as follows:
In this treatment the tools are first preheated to a red heat, but small tools may be immersed without preheating.
The barium chloride bath is kept at a temperature of from 2,000 to 2,100°F., and tools are held in it long enough to
reach the same temperature. They are then dipped in oil. The barium chloride which adheres to the tools is brushed
off, leaving the tools as dean as before heating.
A CHROMIUM-COBALT STEEL
The Latrobe Steel Company make a high-speed steel without tungsten, its red-hardness properties depending on
chromium and cobalt instead of tungsten. It is known as P. R. K-33 steel. It does not require the high temperature
of the tungsten steels, hardening at 1,830 to 1,850°F. instead of 2,200° or even higher, as with the tungsten.
This steel is forged at 1,900 to 2,000°F. and must not be worked at a lower temperature than 1,600°F. It requires
soaking in the fire more than the tungsten steels. It can be normalized by heating slowly and thoroughly to
1,475°F., holding this for from 10 to 20 min. according to the size of the piece and cooling in the open air,
protected from drafts.
A peculiarity of this steel is that it becomes non-magnetic at or above 1,960°F. and the magnetic quality is not
restored by cooling. Normalizing as above, however, restores the magnetic qualities. This enables the user to detect
any tools which have been overheated, with a horseshoe magnet.
It is sometimes advantageous to dip tools, before heating for hardening, in ordinary fuel or quenching oil. The oil
leaves a thin film of carbon which tends to prevent decarbonization, giving a very hard surface.
For other makes of high-speed steel used in lathe and planer tools the makers recommend that the tools be cut
from the bar with a hack saw or else heated and cut with a chisel. The heating should be very slow until the steel
reaches a red after which it can be heated more rapidly and should only be forged at a high heat. It can be forged at
very high heats but care should be taken not to forge at a low heat. The heating should be uniform and penetrate
clear to the center of the bar before forging is begun. Reheat as often as necessary to forge at the proper heat.
After forging cool in lime before attempting to harden. Do not attempt to harden with the forging heat as was
sometimes done with the carbon tools.
For hardening forged tools, heat slowly up to a bright red and then rapidly until the point of the tool is almost at a
melting heat. Cool in a blast of cold, dry air. For large sizes of steel, cool in linseed oil or in fish oil as is most
convenient. If the tools are to be used for finishing cuts heat to a bright yellow and quench in oil. Grind for use on
a sand wheel or grindstone in preference to an emery or an artificial abrasive wheel.
For hardening milling and similar cutters, preheat to a bright red, place the cutter on a round bar of suitable size,
and revolve it quickly over a very hot fire. Heat as high as possible without melting the points of the teeth and cool
in a cold blast of dry air or in fish oil.
Light fragile cutters, twist drills, taps and formed cutters may be heated almost white and then dipped in fish oil
for hardening. Where possible it is better to give an even higher heat and cool in the blast of cold, dry air as
previously recommended.
2,100°F.).
Cooling.—Depending on the tools, some should be dipped in oil all over, some only part way, and others allowed
to cool down in the air naturally, or under air blast. In cooling, the toughness is retained by allowing some parts to
cool slowly and quenching parts that should be hard.
Drawing the Temper.—As in cooling, some parts of these tools will require more drawing than others, but, on
the whole, they must be drawn more than water hardening tools for the same purpose or to about 500°F. all over,
so that a good file will just "touch" the cutting or working parts.
Barium Chloride Process.—This is a process developed for treating certain classes of tools, such as taps,
forming tools, etc. It is being successfully used in many large plants. Briefly the treatment is as follows:
In this treatment the tools are first preheated to a red heat, but small tools may be immersed without preheating.
The barium chloride bath is kept at a temperature of from 2,000 to 2,100°F., and tools are held in it long enough to
reach the same temperature. They are then dipped in oil. The barium chloride which adheres to the tools is brushed
off, leaving the tools as dean as before heating.
A CHROMIUM-COBALT STEEL
The Latrobe Steel Company make a high-speed steel without tungsten, its red-hardness properties depending on
chromium and cobalt instead of tungsten. It is known as P. R. K-33 steel. It does not require the high temperature
of the tungsten steels, hardening at 1,830 to 1,850°F. instead of 2,200° or even higher, as with the tungsten.
This steel is forged at 1,900 to 2,000°F. and must not be worked at a lower temperature than 1,600°F. It requires
soaking in the fire more than the tungsten steels. It can be normalized by heating slowly and thoroughly to
1,475°F., holding this for from 10 to 20 min. according to the size of the piece and cooling in the open air,
protected from drafts.
A peculiarity of this steel is that it becomes non-magnetic at or above 1,960°F. and the magnetic quality is not
restored by cooling. Normalizing as above, however, restores the magnetic qualities. This enables the user to detect
any tools which have been overheated, with a horseshoe magnet.
It is sometimes advantageous to dip tools, before heating for hardening, in ordinary fuel or quenching oil. The oil
leaves a thin film of carbon which tends to prevent decarbonization, giving a very hard surface.
For other makes of high-speed steel used in lathe and planer tools the makers recommend that the tools be cut
from the bar with a hack saw or else heated and cut with a chisel. The heating should be very slow until the steel
reaches a red after which it can be heated more rapidly and should only be forged at a high heat. It can be forged at
very high heats but care should be taken not to forge at a low heat. The heating should be uniform and penetrate
clear to the center of the bar before forging is begun. Reheat as often as necessary to forge at the proper heat.
After forging cool in lime before attempting to harden. Do not attempt to harden with the forging heat as was
sometimes done with the carbon tools.
For hardening forged tools, heat slowly up to a bright red and then rapidly until the point of the tool is almost at a
melting heat. Cool in a blast of cold, dry air. For large sizes of steel, cool in linseed oil or in fish oil as is most
convenient. If the tools are to be used for finishing cuts heat to a bright yellow and quench in oil. Grind for use on
a sand wheel or grindstone in preference to an emery or an artificial abrasive wheel.
For hardening milling and similar cutters, preheat to a bright red, place the cutter on a round bar of suitable size,
and revolve it quickly over a very hot fire. Heat as high as possible without melting the points of the teeth and cool
in a cold blast of dry air or in fish oil.
Light fragile cutters, twist drills, taps and formed cutters may be heated almost white and then dipped in fish oil
for hardening. Where possible it is better to give an even higher heat and cool in the blast of cold, dry air as
previously recommended.
Page 141
SUGGESTIONS FOR HANDLING HIGH-SPEED STEELS
The following suggestions for handling high-speed steels are given by a maker whose steel is probably typical of
a number of different makes, so that they will be found useful in other cases as well. These include hints as to
forging as well as hardening, together with a list of "dont's" which are often very useful. This applies to forging,
hardening of lathe, slotting, planing and all similar tools.
FIG. 84.—All-steel, 5/8 in. square, 1/2 × 1 in., and larger is usually mild
finished, and can be cut in a hack saw. If cut off hot, be sure to heat the butt
end slowly and thoroughly in a clean fire. Rapid and insufficient heating
invariably cracks the steel. If you want to stamp the end with the name of the
steel, it is necessary that this is done at a good high orange color heat, as it is
otherwise apt to split the steel. (Take your time, do not hurry.)
HARDENING HIGH-SPEED STEEL
In forging use coke for fuel in the forge. Heat steel slowly and thoroughly to a lemon heat. Do not forge at a
lower heat. Do not let the steel cool below a bright cherry red while forging. After the tool is dressed, reheat to
forging heat to remove the forging strain, and lay on the floor until cold. Then have the tool rough ground on a dry
emery wheel.
FIG. 85.—Be sure to have a full yellow heat at the dotted line. Remember this
is a boring mill tool and will stand out in the tool-post, and if you do not have a
high thorough lemon heat, your tool will snap off at the dotted line. (Ninety-
five per cent of all tools which break, have been forged at too low a heat or at a
heat not thorough to the center.)
FIG. 86.—Keep your high lemon forging heat up. If you forge under a steam
hammer, take light blows. Do not jam your tool into shape. Put frequently back
into the fire. Never let the high lemon color go down and beyond the dotted
line.
For built-up and bent tools special care should be taken that the forging heat does not go below a bright cherry.
For tools ¾ by 1½ or larger where there is a big strain in forging, such as bending at angles of about 45 deg. and
building the tools up, they should be heated to at least 1,700°F. Slowly and without much blast. For a ¾ by 1½ tool
it should take about 10 min. with the correct blast in a coke fire. Larger tools in proportion. They can then be bent
readily, but no attempt should be made to forge the steel further without reheating to maintain the bright cherry
red. This is essential, as otherwise the tools crack in hardening or while in use.
The following suggestions for handling high-speed steels are given by a maker whose steel is probably typical of
a number of different makes, so that they will be found useful in other cases as well. These include hints as to
forging as well as hardening, together with a list of "dont's" which are often very useful. This applies to forging,
hardening of lathe, slotting, planing and all similar tools.
FIG. 84.—All-steel, 5/8 in. square, 1/2 × 1 in., and larger is usually mild
finished, and can be cut in a hack saw. If cut off hot, be sure to heat the butt
end slowly and thoroughly in a clean fire. Rapid and insufficient heating
invariably cracks the steel. If you want to stamp the end with the name of the
steel, it is necessary that this is done at a good high orange color heat, as it is
otherwise apt to split the steel. (Take your time, do not hurry.)
HARDENING HIGH-SPEED STEEL
In forging use coke for fuel in the forge. Heat steel slowly and thoroughly to a lemon heat. Do not forge at a
lower heat. Do not let the steel cool below a bright cherry red while forging. After the tool is dressed, reheat to
forging heat to remove the forging strain, and lay on the floor until cold. Then have the tool rough ground on a dry
emery wheel.
FIG. 85.—Be sure to have a full yellow heat at the dotted line. Remember this
is a boring mill tool and will stand out in the tool-post, and if you do not have a
high thorough lemon heat, your tool will snap off at the dotted line. (Ninety-
five per cent of all tools which break, have been forged at too low a heat or at a
heat not thorough to the center.)
FIG. 86.—Keep your high lemon forging heat up. If you forge under a steam
hammer, take light blows. Do not jam your tool into shape. Put frequently back
into the fire. Never let the high lemon color go down and beyond the dotted
line.
For built-up and bent tools special care should be taken that the forging heat does not go below a bright cherry.
For tools ¾ by 1½ or larger where there is a big strain in forging, such as bending at angles of about 45 deg. and
building the tools up, they should be heated to at least 1,700°F. Slowly and without much blast. For a ¾ by 1½ tool
it should take about 10 min. with the correct blast in a coke fire. Larger tools in proportion. They can then be bent
readily, but no attempt should be made to forge the steel further without reheating to maintain the bright cherry
red. This is essential, as otherwise the tools crack in hardening or while in use.
Page 142
FIG. 87.—Be sure that the tool is absolutely straight at the bottom, so as to lie
flat in the tool-post.
FIG. 88.—This is the finished forged tool, and let this grow cold by itself, the
slower the better. It is well to cool the tool slowly in hot ashes, to remove all
forging strain. You can now grind the tool dry on a sharp emery wheel. The
more you now finish the tool in grinding, the less there is to come off after
hardening.
In hardening place the tool in a coke fire (hollow fire if possible) with a slow blast and heat gradually up to a
white welding heat on the nose of the tool. Then dip the white hot part only into thin oil or hold in a strong cold air
blast. When hardening in oil do not hold the tool in one place but keep it moving so that it cools as quickly as
possible. It is not necessary to draw the temper after hardening these tools.
FIG. 89.—This tool is ground, ready for hardening. Never harden from the
forging heat.
FIG. 90.—Heat the nose of the tool only up to dotted line, very slowly and
thoroughly to an absolutely white welding heat, so that it shows a trifle fused
around the edges, and be very sure that this fusing has gone thoroughly through
the nose, otherwise the fusing effect will be taken off after the second grinding.
Note the difference of the nose between this and Fig. 86.
flat in the tool-post.
FIG. 88.—This is the finished forged tool, and let this grow cold by itself, the
slower the better. It is well to cool the tool slowly in hot ashes, to remove all
forging strain. You can now grind the tool dry on a sharp emery wheel. The
more you now finish the tool in grinding, the less there is to come off after
hardening.
In hardening place the tool in a coke fire (hollow fire if possible) with a slow blast and heat gradually up to a
white welding heat on the nose of the tool. Then dip the white hot part only into thin oil or hold in a strong cold air
blast. When hardening in oil do not hold the tool in one place but keep it moving so that it cools as quickly as
possible. It is not necessary to draw the temper after hardening these tools.
FIG. 89.—This tool is ground, ready for hardening. Never harden from the
forging heat.
FIG. 90.—Heat the nose of the tool only up to dotted line, very slowly and
thoroughly to an absolutely white welding heat, so that it shows a trifle fused
around the edges, and be very sure that this fusing has gone thoroughly through
the nose, otherwise the fusing effect will be taken off after the second grinding.
Note the difference of the nose between this and Fig. 86.
Page 143
FIG. 91.—Shows unnecessary roasting and drossing. Such hardening requires a
great amount of grinding and is not good. After hardening grind carefully on a
wet emery wheel, and be sure that the wheel is sharp with a plentiful supply of
water. Do not force the grinding, otherwise the cold water striking the steel
heated up by friction, will crack the nose. Be sure that the grinding wheel is
sharp.
In grinding all tools should be ground as lightly as possible on a soft wet sandstone or on a wet emery wheel, and
care should be taken not to create any surface cracks, which are invariably the result of grinding too forcibly. The
foregoing illustrations, Figs. 84 to 91, with their captions, will be found helpful.
Special points of caution to be observed when hardening high-speed steel.
Don't use a green coal fire; use coke, or build a hollow fire.
Don't have the bed of the fire free from coal.
Don't hurry the heating for forging. The heating has to be done very slowly and the forging heat has to be kept
very high (a full lemon color) heat and the tool has to be continually brought back into the fire to keep the high
heat up. When customers complain about seams and cracks, in 9 cases out of 10, this has been caused by too low a
forging heat, and when the blacksmith complains about tools cracking, it is necessary to read this paragraph to
him.
Don't try to jam the tool into shape under a steam hammer with one or two blows; take easy blows and keep the
heat high.
Don't have the tool curved at the bottom; it must lie perfectly flat in the tool post.
Don't harden from your forging heat; let the tool grow cold or fairly cold. After forging you can rough grind the
tool dry, but not too forcibly.
Don't, for hardening, get more than the nose white hot.
Don't get the white heat on the surface only.
Don't hurry your heating for hardening; let the heat soak thoroughly through the nose of the tool.
Don't melt the nose of the tool.
Don't, as a rule, dip the nose into water; this should be done only for extremely hard material. It is dangerous to
put the nose into water for fear of cracking and when you do put the nose into water put just 1/2 in. only of the
extreme white hot part into the water and don't keep it too long in the water; just a few seconds, and then harden in
oil. We do not recommend water hardening.
Don't grind too forcibly.
Don't grind dry after hardening.
great amount of grinding and is not good. After hardening grind carefully on a
wet emery wheel, and be sure that the wheel is sharp with a plentiful supply of
water. Do not force the grinding, otherwise the cold water striking the steel
heated up by friction, will crack the nose. Be sure that the grinding wheel is
sharp.
In grinding all tools should be ground as lightly as possible on a soft wet sandstone or on a wet emery wheel, and
care should be taken not to create any surface cracks, which are invariably the result of grinding too forcibly. The
foregoing illustrations, Figs. 84 to 91, with their captions, will be found helpful.
Special points of caution to be observed when hardening high-speed steel.
Don't use a green coal fire; use coke, or build a hollow fire.
Don't have the bed of the fire free from coal.
Don't hurry the heating for forging. The heating has to be done very slowly and the forging heat has to be kept
very high (a full lemon color) heat and the tool has to be continually brought back into the fire to keep the high
heat up. When customers complain about seams and cracks, in 9 cases out of 10, this has been caused by too low a
forging heat, and when the blacksmith complains about tools cracking, it is necessary to read this paragraph to
him.
Don't try to jam the tool into shape under a steam hammer with one or two blows; take easy blows and keep the
heat high.
Don't have the tool curved at the bottom; it must lie perfectly flat in the tool post.
Don't harden from your forging heat; let the tool grow cold or fairly cold. After forging you can rough grind the
tool dry, but not too forcibly.
Don't, for hardening, get more than the nose white hot.
Don't get the white heat on the surface only.
Don't hurry your heating for hardening; let the heat soak thoroughly through the nose of the tool.
Don't melt the nose of the tool.
Don't, as a rule, dip the nose into water; this should be done only for extremely hard material. It is dangerous to
put the nose into water for fear of cracking and when you do put the nose into water put just 1/2 in. only of the
extreme white hot part into the water and don't keep it too long in the water; just a few seconds, and then harden in
oil. We do not recommend water hardening.
Don't grind too forcibly.
Don't grind dry after hardening.
Page 144
Don't discolor the steel in grinding.
Don't give too much clearance on tools for cutting cast iron.
Don't start on cast iron with a razor edge on the tool. Take an oil stone and wipe three or four times over the
razor edge.
Don't use tool holder steel from bars without hardening the nose of each individual tool bit.
Air-hardening Steels.—These steels are recommended for boring, turning and planing where the cost of high-
speed seems excessive. They are also recommended for hard wood knives, for roughing and finishing bronze and
brass, and for hot bolt forging dies. This steel cannot be cut or punched cold but can be shaped and ground on
abrasive wheels of various kinds.
It should be heated slowly and evenly for forging and kept as evenly heated at a bright red as possible. It should
not be forged after it cools to a dark red.
After the tool is made, heat it again to a bright red and lay it down to cool in a dry place or it can be cooled in a
cold, dry air blast. Water must be kept away from it while it is hot.
Don't give too much clearance on tools for cutting cast iron.
Don't start on cast iron with a razor edge on the tool. Take an oil stone and wipe three or four times over the
razor edge.
Don't use tool holder steel from bars without hardening the nose of each individual tool bit.
Air-hardening Steels.—These steels are recommended for boring, turning and planing where the cost of high-
speed seems excessive. They are also recommended for hard wood knives, for roughing and finishing bronze and
brass, and for hot bolt forging dies. This steel cannot be cut or punched cold but can be shaped and ground on
abrasive wheels of various kinds.
It should be heated slowly and evenly for forging and kept as evenly heated at a bright red as possible. It should
not be forged after it cools to a dark red.
After the tool is made, heat it again to a bright red and lay it down to cool in a dry place or it can be cooled in a
cold, dry air blast. Water must be kept away from it while it is hot.
Page 145
CHAPTER XI
FURNACES
There are so many standard furnaces now on the market that it is not necessary to go into details of their design
and construction and only a few will be illustrated. Oil, gas and coal or coke are most common but there is a steady
growth of the use of electric furnaces.
FIG. 92.—Standard lead pot furnace.
Typical Oil-fired Furnaces.—Several types of standard oil-fired furnaces are shown herewith. Figure 92 is a
lead pot furnace, Fig. 93 is a vertical furnace with a center column. This column reduces the cubical contents to be
heated and also supports the cover.
FURNACES
There are so many standard furnaces now on the market that it is not necessary to go into details of their design
and construction and only a few will be illustrated. Oil, gas and coal or coke are most common but there is a steady
growth of the use of electric furnaces.
FIG. 92.—Standard lead pot furnace.
Typical Oil-fired Furnaces.—Several types of standard oil-fired furnaces are shown herewith. Figure 92 is a
lead pot furnace, Fig. 93 is a vertical furnace with a center column. This column reduces the cubical contents to be
heated and also supports the cover.
Page 146
FIG. 93.—Furnace with center column.
A small tool furnace is shown in Fig. 94, which gives the construction and heat circulation. A larger furnace for
high-speed steel is given in Fig. 95. The steel is supported above the heat, the lower flame passing beneath the
support.
For hardening broaches and long reamers and taps, the furnace shown in Fig. 96 is used. Twelve jets are used,
these coming in radially to produce a whirling motion.
FIG. 94.—Furnace for cutting tools.
A small tool furnace is shown in Fig. 94, which gives the construction and heat circulation. A larger furnace for
high-speed steel is given in Fig. 95. The steel is supported above the heat, the lower flame passing beneath the
support.
For hardening broaches and long reamers and taps, the furnace shown in Fig. 96 is used. Twelve jets are used,
these coming in radially to produce a whirling motion.
FIG. 94.—Furnace for cutting tools.
Page 147
FIG. 95.—High-speed steel furnace.
Oil and gas furnaces may be divided into three types: the open heating chamber in which combustion takes place
in the chamber and directly over the stock; the semimuffle heating chamber in which combustion takes place
beneath the floor of the chamber from which the hot gases pass into the chamber through suitable openings; and
the muffle heating chamber in which the heat entirely surrounds the chamber but does not enter it. The open
furnace is used for forging, tool dressing and welding. The muffle furnace is used for hardening dies, taps, cutters
and similar tools of either carbon or high-speed steel. The muffle furnace is for spring hardening, enameling,
assaying and work where the gases of combustion may have an injurious effect on the material.
Oil and gas furnaces may be divided into three types: the open heating chamber in which combustion takes place
in the chamber and directly over the stock; the semimuffle heating chamber in which combustion takes place
beneath the floor of the chamber from which the hot gases pass into the chamber through suitable openings; and
the muffle heating chamber in which the heat entirely surrounds the chamber but does not enter it. The open
furnace is used for forging, tool dressing and welding. The muffle furnace is used for hardening dies, taps, cutters
and similar tools of either carbon or high-speed steel. The muffle furnace is for spring hardening, enameling,
assaying and work where the gases of combustion may have an injurious effect on the material.
Page 148
FIG. 96.—Furnace for hardening broaches.
FIG. 97.—Forging and welding furnace.
FIG. 97.—Forging and welding furnace.
Page 149
FIG. 98.—Semi-muffle furnace.
FIG. 99.—Muffle furnace.
Furnaces of these types of oil-burning furnaces are shown in Figs. 97, 98, and 99; these being made by the
Gilbert & Barker Manufacturing Company. The first has an air curtain formed by jets from the large pipe just
below the opening, to protect the operator from heat.
FIG. 99.—Muffle furnace.
Furnaces of these types of oil-burning furnaces are shown in Figs. 97, 98, and 99; these being made by the
Gilbert & Barker Manufacturing Company. The first has an air curtain formed by jets from the large pipe just
below the opening, to protect the operator from heat.
Page 150
FIG. 100.—Gas fired furnace.
FIG. 101.—Car door type of annealing furnace.
Oil furnaces are also made for both high- and low-pressure air, each having its advocates. The same people also
make gas-fired furnaces.
Several types of furnaces for various purposes are illustrated in Fig. 100 and 101. The first is a gas-fired
hardening furnace of the surface-combustion type.
A large gas-fired annealing furnace of the Maxon system is shown in Fig. 101. This is large enough for a flat car
to be run into as can be seen. It shows the arrangement of the burners, the track for the car and the way in which it
fits into the furnace. These are from the designs of the Industrial Furnace Corporation.
Before deciding upon the use of gas or oil, all sides of the problem should be considered. Gas is perhaps the
nearest ideal but is as a rule more expensive. The tables compiled by the Gilbert & Barker Manufacturing
Company and shown herewith, may help in deciding the question.
TABLE 27.—SHOWING COMPARISON OF OIL FUEL WITH VARIOUS GASEOUS FUELS
Heat units
per thousand
cubic feet
1,000,000
Natural gas 1,000,000
Air gas (gas machine) 20 cp 815,500
Public illuminating gas, average 650,000
Water gas (from bituminous coal) 377,000
FIG. 101.—Car door type of annealing furnace.
Oil furnaces are also made for both high- and low-pressure air, each having its advocates. The same people also
make gas-fired furnaces.
Several types of furnaces for various purposes are illustrated in Fig. 100 and 101. The first is a gas-fired
hardening furnace of the surface-combustion type.
A large gas-fired annealing furnace of the Maxon system is shown in Fig. 101. This is large enough for a flat car
to be run into as can be seen. It shows the arrangement of the burners, the track for the car and the way in which it
fits into the furnace. These are from the designs of the Industrial Furnace Corporation.
Before deciding upon the use of gas or oil, all sides of the problem should be considered. Gas is perhaps the
nearest ideal but is as a rule more expensive. The tables compiled by the Gilbert & Barker Manufacturing
Company and shown herewith, may help in deciding the question.
TABLE 27.—SHOWING COMPARISON OF OIL FUEL WITH VARIOUS GASEOUS FUELS
Heat units
per thousand
cubic feet
1,000,000
Natural gas 1,000,000
Air gas (gas machine) 20 cp 815,500
Public illuminating gas, average 650,000
Water gas (from bituminous coal) 377,000
Page 151
Water and producer gas, mixed 175,000
Producer gas 150,000
Since a gallon of fuel oil (7 lb.) contains 133,000 heat units, the following comparisons may evidently be made.
At 5 cts. a gallon, the equivalent heat units in oil would equal:
Heat units
per thousand
cubic feet
at $0.375
Natural gas at $0.375
Air gas, 20 cp at 0.307
Public illuminating gas, average at 0.244
Water gas (from bituminous coal) at 0.142
Water and producer gas, mixed at 0.065
Producer gas at 0.057
Comparing oil and coal is not always simple as it depends on the work to be done and the construction of the
furnaces. The variation rises from 75 to 200 gal. of oil to a ton of coal. For forging and similar work it is probably
safe to consider 100 gal. of oil as equivalent to a ton of coal.
Then there is the saving of labor in handling both coal and ashes, the waiting for fires to come up, the banking of
fires and the dirt and nuisance generally. The continuous operation possible with oil adds to the output.
When comparing oil and gas it is generally considered that 4½ gal. of fuel oil will give heat equivalent to 1,000
cu. ft. of coal gas.
The pressure of oil and air used varies with the system installed. The low-pressure system maintains a pressure of
about 8 oz. on the oil and draws in free air for combustion. Others use a pressure of several pounds, while gas
burners use an average of perhaps 1½ lb. of air to give best results.
The weights and volumes of solid fuels are: Anthracite coal, 55 to 65 lb. per cubic foot or 34 to 41 cubic feet per
ton; bituminous coal, 50 to 55 lb. per cubic foot or 41 to 45 cubic feet per ton; coke, 28 lb. per cubic foot or 80
cubic feet per ton—the ton being calculated as 2,240 lb. in each case.
A novel carburizing furnace that is being used by a number of people, is built after the plan of a fireless cooker.
The walls of the furnace are extra heavy, and the ports and flues are so arranged that when the load in the furnace
and the furnace is thoroughly heated, the burners are shut off and all openings are tightly sealed. The carburization
then goes on for several hours before the furnace is cooled below the effective carburizing range, securing an ideal
diffusion of carbon between the case and the core of the steel being carburized. This is particularly adaptable
where simple steel is used.
PROTECTIVE SCREENS FOR FURNACES
Workmen needlessly exposed to the flames, heat and glare from furnaces where high temperatures are maintained
suffer in health as well as in bodily discomfort. This shows several types of shields designed for the maximum
protection of the furnace worker.
Bad conditions are not necessary; in almost every case means of relief can be found by one earnestly seeking
them. The larger forge shops have adopted flame shields for the majority of their furnaces. Years ago the industrial
furnaces (particularly of the oil-burning variety) were without shields, but the later models are all shield-equipped.
These shields are adapted to all of the more modern, heat-treating furnaces, as well as to those furnaces in use for
working forges; and attention should be paid to their use on the former type since the heat-treating furnaces are
constantly becoming more numerous as manufacturers find need of them in the many phases of munitions making
or similar work.
Producer gas 150,000
Since a gallon of fuel oil (7 lb.) contains 133,000 heat units, the following comparisons may evidently be made.
At 5 cts. a gallon, the equivalent heat units in oil would equal:
Heat units
per thousand
cubic feet
at $0.375
Natural gas at $0.375
Air gas, 20 cp at 0.307
Public illuminating gas, average at 0.244
Water gas (from bituminous coal) at 0.142
Water and producer gas, mixed at 0.065
Producer gas at 0.057
Comparing oil and coal is not always simple as it depends on the work to be done and the construction of the
furnaces. The variation rises from 75 to 200 gal. of oil to a ton of coal. For forging and similar work it is probably
safe to consider 100 gal. of oil as equivalent to a ton of coal.
Then there is the saving of labor in handling both coal and ashes, the waiting for fires to come up, the banking of
fires and the dirt and nuisance generally. The continuous operation possible with oil adds to the output.
When comparing oil and gas it is generally considered that 4½ gal. of fuel oil will give heat equivalent to 1,000
cu. ft. of coal gas.
The pressure of oil and air used varies with the system installed. The low-pressure system maintains a pressure of
about 8 oz. on the oil and draws in free air for combustion. Others use a pressure of several pounds, while gas
burners use an average of perhaps 1½ lb. of air to give best results.
The weights and volumes of solid fuels are: Anthracite coal, 55 to 65 lb. per cubic foot or 34 to 41 cubic feet per
ton; bituminous coal, 50 to 55 lb. per cubic foot or 41 to 45 cubic feet per ton; coke, 28 lb. per cubic foot or 80
cubic feet per ton—the ton being calculated as 2,240 lb. in each case.
A novel carburizing furnace that is being used by a number of people, is built after the plan of a fireless cooker.
The walls of the furnace are extra heavy, and the ports and flues are so arranged that when the load in the furnace
and the furnace is thoroughly heated, the burners are shut off and all openings are tightly sealed. The carburization
then goes on for several hours before the furnace is cooled below the effective carburizing range, securing an ideal
diffusion of carbon between the case and the core of the steel being carburized. This is particularly adaptable
where simple steel is used.
PROTECTIVE SCREENS FOR FURNACES
Workmen needlessly exposed to the flames, heat and glare from furnaces where high temperatures are maintained
suffer in health as well as in bodily discomfort. This shows several types of shields designed for the maximum
protection of the furnace worker.
Bad conditions are not necessary; in almost every case means of relief can be found by one earnestly seeking
them. The larger forge shops have adopted flame shields for the majority of their furnaces. Years ago the industrial
furnaces (particularly of the oil-burning variety) were without shields, but the later models are all shield-equipped.
These shields are adapted to all of the more modern, heat-treating furnaces, as well as to those furnaces in use for
working forges; and attention should be paid to their use on the former type since the heat-treating furnaces are
constantly becoming more numerous as manufacturers find need of them in the many phases of munitions making
or similar work.
Page 152
The heat that the worker about these furnaces must face may be divided in general into two classes: there is first
that heat due to the flame and hot gases that the blast in the furnaces forces out onto a man's body and face. In the
majority of furnaces this is by far the most discomforting, and care must be taken to fend it and turn it behind a
suitable shield. The second class is the radiant heat, discharged as light from the glowing interior of the furnace.
This is the lesser of the two evils so far as general forging furnaces are concerned, but it becomes the
predominating feature in furnaces of large door area such as in the usual case-hardening furnaces. Here the amount
of heat discharged is often almost unbearable even for a moment. This heat can be taken care of by interposing
suitable, opaque shields that will temporarily absorb it without being destroyed by it, or becoming incandescent.
Should such shields be so constructed as to close off all of the heat, it might be impossible to work around the
furnace for the removal of its contents, but they can be made movable, and in such a manner as to shield the major
portion of the worker's body.
First taking up the question of flame shields, the illustration, Fig. 102, is a typical installation that shows the main
features for application to a forging machine or drop-hammer, oil-burning furnace, or for an arched-over, coal
furnace where the flame blows out the front. This shield consists of a frame covered with sheet metal and held by
brackets about 6 in. in front of the furnace. It will be noted that slotted holes make this frame adjustable for height,
and it should be lowered as far as possible when in use, so that the work may just pass under it and into the furnace
openings.
Immediately below the furnace openings, and close to the furnace frame will be noted a blast pipe carrying air
from the forge-shop fan. This has a row of small holes drilled in its upper side for the entire length, and these direct
a curtain of cold air vertically across the furnace openings, forcing all of the flame, or a greater portion of it, to rise
behind the shield. Since the shield extends above the furnace top there is no escape for this flame until it has
passed high enough to be of no further discomfort to the workman.
In this case fan-blast air is used for cooling, and this is cheaper and more satisfactory because a great volume may
be used. However, where high-pressure air is used for atomizing the oil at the burner, and nothing else is available,
this may be employed—though naturally a comparatively small pipe will be needed, in which minute holes are
drilled, else the volume of air used will be too great for the compressor economically to supply. Steam may also be
employed for like service.
FIGS. 102 to 108.—Protective devices for furnace fronts.
The latest shields of this type are all made double, as illustrated, with an inner sheet of metal an inch or two
inside of the front. In the illustration, A, Fig. 102, this inner sheet is smaller, but some are now built the same size
as the front and bolted to it with pipe spacers between. The advantage of the double sheet is that the inner one
that heat due to the flame and hot gases that the blast in the furnaces forces out onto a man's body and face. In the
majority of furnaces this is by far the most discomforting, and care must be taken to fend it and turn it behind a
suitable shield. The second class is the radiant heat, discharged as light from the glowing interior of the furnace.
This is the lesser of the two evils so far as general forging furnaces are concerned, but it becomes the
predominating feature in furnaces of large door area such as in the usual case-hardening furnaces. Here the amount
of heat discharged is often almost unbearable even for a moment. This heat can be taken care of by interposing
suitable, opaque shields that will temporarily absorb it without being destroyed by it, or becoming incandescent.
Should such shields be so constructed as to close off all of the heat, it might be impossible to work around the
furnace for the removal of its contents, but they can be made movable, and in such a manner as to shield the major
portion of the worker's body.
First taking up the question of flame shields, the illustration, Fig. 102, is a typical installation that shows the main
features for application to a forging machine or drop-hammer, oil-burning furnace, or for an arched-over, coal
furnace where the flame blows out the front. This shield consists of a frame covered with sheet metal and held by
brackets about 6 in. in front of the furnace. It will be noted that slotted holes make this frame adjustable for height,
and it should be lowered as far as possible when in use, so that the work may just pass under it and into the furnace
openings.
Immediately below the furnace openings, and close to the furnace frame will be noted a blast pipe carrying air
from the forge-shop fan. This has a row of small holes drilled in its upper side for the entire length, and these direct
a curtain of cold air vertically across the furnace openings, forcing all of the flame, or a greater portion of it, to rise
behind the shield. Since the shield extends above the furnace top there is no escape for this flame until it has
passed high enough to be of no further discomfort to the workman.
In this case fan-blast air is used for cooling, and this is cheaper and more satisfactory because a great volume may
be used. However, where high-pressure air is used for atomizing the oil at the burner, and nothing else is available,
this may be employed—though naturally a comparatively small pipe will be needed, in which minute holes are
drilled, else the volume of air used will be too great for the compressor economically to supply. Steam may also be
employed for like service.
FIGS. 102 to 108.—Protective devices for furnace fronts.
The latest shields of this type are all made double, as illustrated, with an inner sheet of metal an inch or two
inside of the front. In the illustration, A, Fig. 102, this inner sheet is smaller, but some are now built the same size
as the front and bolted to it with pipe spacers between. The advantage of the double sheet is that the inner one
Page 153
bears the brunt of the flame, and, if needs be, burns up before the outer; while, if due to a heavy fire it should be
heated red at any point, the outer sheet will still be much cooler and act as an additional shield to the furnace man.
Heavy Forging Practice.—In heavy forging practice where the metal is being worked at a welding heat, the
amount of flame that will issue from an open-front furnace is so great that a plain, sheet-steel front will neither
afford sufficient protection nor stand up in service. For such a place a water-cooled front is often used. The general
type of this front is illustrated in Fig. 103, and appears to have found considerable favor, for numbers of its kind
are scattered throughout the country.
In this case the shield is placed at a slight angle from the vertical, and along the top edge is a water pipe with a
row of small holes through which sprays of water are thrown against it. This water runs down in a thin sheet over
the shield, cooling it, and is collected in a trough connected with a run-off pipe at the bottom. The lower blast-pipe
arrangement is similar to the one first described.
There are several serious objections to this form of shield that should lead to its replacement by a better type; the
first is that with a very hot fire, portions in the center may become so rapidly heated that the steam generated will
part the sheet of water and cause it to flow from that point in an inverted V, and that section will then quickly
become red hot. Another feature is that after the water and fire are shut down for the night the heat of the furnace
can be great enough to cause serious warping of the surface of the shield so that the water will no longer cover it in
a thin, uniform sheet.
After rigging up a big furnace with a shield of this type several years ago, its most serious object was found in the
increase of the water bill of the plant. This was already of large proportions, but it had suddenly jumped to the
extent of several hundred dollars. Investigation soon disclosed the fact that this water shield was one of the main
causes of the added cost of water. A little estimating of the amount of water that can flow through a 1/2-in. pipe
under 30-lb. pressure, in the course of a day, will show that this amount at 10 cts. per 1,000 gal., can count up
rather rapidly.
Figure 103 is a section through a portion of the furnace front and shield showing all of the principal parts. This
shield consists essentially of a very thin tank, about 2½ in. between walls, and filled with water. Like other shields
it is fitted with an adjustment, that it may be raised and lowered as the work demands. The tank having an open
top, the water as it absorbs heat from the flame will simply boil away in steam; and only a small amount will have
to be added to make up for that which has evaporated. The water-feed pipe shown at F ends a short distance above
the top of the tank so that just how much water is running in may readily be seen.
An overflow pipe is provided at O which aids in maintaining the water at the proper height, as a sufficient
quantity can always be permitted to run in, to avoid any possibility of the shield ever boiling dry; at the same time
the small excess can run off without danger of an overflow. The shield illustrated in Fig. 104 has been in constant
use for over two years, giving greater satisfaction than any other of which the writer has known. It might also be
noted that this shield was made with riveted joints, the shop not having a gas-welding outfit. To flange over the
edges and then weld them with an acetylene torch would be a far more economical procedure, and would also
insure a tight and permanent joint.
The water-cooled front shown in Fig. 105 is an absurd effort to accomplish the design of a furnace that will
provide cool working conditions. This front was on a bolt-heating furnace using hard coal for fuel; and it may be
seen that it takes the place of all of the brickwork that should be on that side. Had this been nothing more than a
very narrow water-cooled frame, with brickwork below and supporting bricks above, put in like the tuyeres in a
foundry cupola, the case would have been somewhat different, for then it would have absorbed a smaller
proportion of the heat.
A blacksmith who knows how a piece of cold iron laid in a small welding furnace momentarily lowers the
temperature, will appreciate the enormous amount of extra heat that must be maintained in the central portion of
this furnace to make up for the constant chilling effect of the cold wall. Moreover, since there would have been
serious trouble had steam generated in this front, a steady stream of water had to be run through it constantly to
insure against an approach to the boiling point. This is illustrated because of its absurdity, and as a warning of
something to avoid.
heated red at any point, the outer sheet will still be much cooler and act as an additional shield to the furnace man.
Heavy Forging Practice.—In heavy forging practice where the metal is being worked at a welding heat, the
amount of flame that will issue from an open-front furnace is so great that a plain, sheet-steel front will neither
afford sufficient protection nor stand up in service. For such a place a water-cooled front is often used. The general
type of this front is illustrated in Fig. 103, and appears to have found considerable favor, for numbers of its kind
are scattered throughout the country.
In this case the shield is placed at a slight angle from the vertical, and along the top edge is a water pipe with a
row of small holes through which sprays of water are thrown against it. This water runs down in a thin sheet over
the shield, cooling it, and is collected in a trough connected with a run-off pipe at the bottom. The lower blast-pipe
arrangement is similar to the one first described.
There are several serious objections to this form of shield that should lead to its replacement by a better type; the
first is that with a very hot fire, portions in the center may become so rapidly heated that the steam generated will
part the sheet of water and cause it to flow from that point in an inverted V, and that section will then quickly
become red hot. Another feature is that after the water and fire are shut down for the night the heat of the furnace
can be great enough to cause serious warping of the surface of the shield so that the water will no longer cover it in
a thin, uniform sheet.
After rigging up a big furnace with a shield of this type several years ago, its most serious object was found in the
increase of the water bill of the plant. This was already of large proportions, but it had suddenly jumped to the
extent of several hundred dollars. Investigation soon disclosed the fact that this water shield was one of the main
causes of the added cost of water. A little estimating of the amount of water that can flow through a 1/2-in. pipe
under 30-lb. pressure, in the course of a day, will show that this amount at 10 cts. per 1,000 gal., can count up
rather rapidly.
Figure 103 is a section through a portion of the furnace front and shield showing all of the principal parts. This
shield consists essentially of a very thin tank, about 2½ in. between walls, and filled with water. Like other shields
it is fitted with an adjustment, that it may be raised and lowered as the work demands. The tank having an open
top, the water as it absorbs heat from the flame will simply boil away in steam; and only a small amount will have
to be added to make up for that which has evaporated. The water-feed pipe shown at F ends a short distance above
the top of the tank so that just how much water is running in may readily be seen.
An overflow pipe is provided at O which aids in maintaining the water at the proper height, as a sufficient
quantity can always be permitted to run in, to avoid any possibility of the shield ever boiling dry; at the same time
the small excess can run off without danger of an overflow. The shield illustrated in Fig. 104 has been in constant
use for over two years, giving greater satisfaction than any other of which the writer has known. It might also be
noted that this shield was made with riveted joints, the shop not having a gas-welding outfit. To flange over the
edges and then weld them with an acetylene torch would be a far more economical procedure, and would also
insure a tight and permanent joint.
The water-cooled front shown in Fig. 105 is an absurd effort to accomplish the design of a furnace that will
provide cool working conditions. This front was on a bolt-heating furnace using hard coal for fuel; and it may be
seen that it takes the place of all of the brickwork that should be on that side. Had this been nothing more than a
very narrow water-cooled frame, with brickwork below and supporting bricks above, put in like the tuyeres in a
foundry cupola, the case would have been somewhat different, for then it would have absorbed a smaller
proportion of the heat.
A blacksmith who knows how a piece of cold iron laid in a small welding furnace momentarily lowers the
temperature, will appreciate the enormous amount of extra heat that must be maintained in the central portion of
this furnace to make up for the constant chilling effect of the cold wall. Moreover, since there would have been
serious trouble had steam generated in this front, a steady stream of water had to be run through it constantly to
insure against an approach to the boiling point. This is illustrated because of its absurdity, and as a warning of
something to avoid.
Page 154
Water-cooled, tuyere openings, as mentioned above, which support brick side-walls of the furnace, have proved
successful for coal furnaces used for forging machine and drop-hammer heating, since they permit a great amount
of work to be handled through their openings without wearing away as would a brick arch. Great care should be
exercised properly to design them so that a minimum amount of the cold tuyere will be in contact with the interior
of the furnace, and all interior portions possible should be covered by the bricks. However, a discussion of these
points will hardly come in the flame-shield class, although they can be made to do a great deal toward relieving the
excessive heat to be borne by the furnace worker.
Flange Shields for Furnaces.—Such portable flame shields as the one illustrated in Fig. 106 may prove
serviceable before furnaces required for plate work, where the doors are often only opened for a moment at a time.
This shield can be placed far enough in front of the furnace, that it will be possible to work under it or around it, in
removing bulky work from the furnace, and yet it will afford the furnace tender some relief from the excessive
glare that will come out the wide-opened door. To have this shield of light weight so that it may be readily pushed
aside when not wanted, the frame may be made up of pipe and fittings, and a piece of thin sheet steel fastened in
the panel by rings about the frame.
About the most disagreeable task in a heat-treating shop is the removal of the pots from the case-hardening
furnaces; these must be handled at a bright red heat in order that their contents may be dumped into the quenching
tank with a minimum-time contact with the air, and before they have cooled sufficiently to require reheating.
Facing the heat before the large open doors of the majority of these furnaces, in a man-killing task even when the
weather is moderately cool. The boxes soon become more or less distorted, and then even the best of lifting
devices will not remove a hot pot without several minutes labor in front of the doors.
In Fig. 107 is shown a method of arranging a shield on one type of charging and removing truck. This shield
cannot afford more than a partial protection to the body of the furnace tender, because he must be able to see
around it, and in some cases even push it partly through the door of the furnace, but even small as it is it may still
afford some welcome protection. The great advantage in this case of having the shield on the truck instead of
stationary in front of the furnace, is that it still affords protection as long as the hot pot is being handled through
the shop on its way to the quenching tank.
It might be interesting to many engaged in the heat-treating or case hardening of steel parts, to make a special
note of the design of the truck that is illustrated in connection with the shield; the general form is shown although
the actual details for the construction of such a truck are lacking; these being simple, may be readily worked out by
anyone wishing to build one. This is considered to be one of the quickest and easiest operated devices for the
removal of this class of work from the furnace. To be sure it may only be used where the floor of the furnace has
been built level with the floor of the room, but many of the modern furnaces of this class are so designed.
The pack-hardening pots are cast with legs, from two to three inches high, to permit the circulation of the hot
gases, and so heat more quickly. Between these legs and under the body of the pot, the two forward prongs of the
truck are pushed, tilting the outer handle to make these prongs as low as possible. The handle is then lowered and,
as it has a good leverage, the pot is easily raised from the floor, and the truck and its load rolled out.
Heating of Manganese Steel.—Another form of heat-treating furnace is that which is used for the heating of
manganese and other alloy steels, which after having been brought to the proper heat are drawn from the furnace
into an immediate quenching tank. With manganese steel in particular, the parts are so fragile and easily damaged
while hot that it is frequent practice to have a sloping platform immediately in front of the furnace door down
which the castings may slide into a tank below the floor level. Such a furnace with a quenching tank in front of its
door is shown in Fig. 108.
These tanks are covered with plates while charging the furnace and the cold castings are placed in a moderately
cool furnace. Since some of these steels must not be charged into a furnace where the heat is extreme but should be
brought up to their final heat gradually, there is little discomfort during the charging process. When quenching,
however, from a temperature of 1,800° to 1,900°, it is extremely unpleasant in front of the doors. The swinging
shield is here adapted to give protection for this work. As will be noted it is hung a sufficient distance in front of
the doors, that it may not interfere with the castings as they come from the furnace, and slide down into the tank.
successful for coal furnaces used for forging machine and drop-hammer heating, since they permit a great amount
of work to be handled through their openings without wearing away as would a brick arch. Great care should be
exercised properly to design them so that a minimum amount of the cold tuyere will be in contact with the interior
of the furnace, and all interior portions possible should be covered by the bricks. However, a discussion of these
points will hardly come in the flame-shield class, although they can be made to do a great deal toward relieving the
excessive heat to be borne by the furnace worker.
Flange Shields for Furnaces.—Such portable flame shields as the one illustrated in Fig. 106 may prove
serviceable before furnaces required for plate work, where the doors are often only opened for a moment at a time.
This shield can be placed far enough in front of the furnace, that it will be possible to work under it or around it, in
removing bulky work from the furnace, and yet it will afford the furnace tender some relief from the excessive
glare that will come out the wide-opened door. To have this shield of light weight so that it may be readily pushed
aside when not wanted, the frame may be made up of pipe and fittings, and a piece of thin sheet steel fastened in
the panel by rings about the frame.
About the most disagreeable task in a heat-treating shop is the removal of the pots from the case-hardening
furnaces; these must be handled at a bright red heat in order that their contents may be dumped into the quenching
tank with a minimum-time contact with the air, and before they have cooled sufficiently to require reheating.
Facing the heat before the large open doors of the majority of these furnaces, in a man-killing task even when the
weather is moderately cool. The boxes soon become more or less distorted, and then even the best of lifting
devices will not remove a hot pot without several minutes labor in front of the doors.
In Fig. 107 is shown a method of arranging a shield on one type of charging and removing truck. This shield
cannot afford more than a partial protection to the body of the furnace tender, because he must be able to see
around it, and in some cases even push it partly through the door of the furnace, but even small as it is it may still
afford some welcome protection. The great advantage in this case of having the shield on the truck instead of
stationary in front of the furnace, is that it still affords protection as long as the hot pot is being handled through
the shop on its way to the quenching tank.
It might be interesting to many engaged in the heat-treating or case hardening of steel parts, to make a special
note of the design of the truck that is illustrated in connection with the shield; the general form is shown although
the actual details for the construction of such a truck are lacking; these being simple, may be readily worked out by
anyone wishing to build one. This is considered to be one of the quickest and easiest operated devices for the
removal of this class of work from the furnace. To be sure it may only be used where the floor of the furnace has
been built level with the floor of the room, but many of the modern furnaces of this class are so designed.
The pack-hardening pots are cast with legs, from two to three inches high, to permit the circulation of the hot
gases, and so heat more quickly. Between these legs and under the body of the pot, the two forward prongs of the
truck are pushed, tilting the outer handle to make these prongs as low as possible. The handle is then lowered and,
as it has a good leverage, the pot is easily raised from the floor, and the truck and its load rolled out.
Heating of Manganese Steel.—Another form of heat-treating furnace is that which is used for the heating of
manganese and other alloy steels, which after having been brought to the proper heat are drawn from the furnace
into an immediate quenching tank. With manganese steel in particular, the parts are so fragile and easily damaged
while hot that it is frequent practice to have a sloping platform immediately in front of the furnace door down
which the castings may slide into a tank below the floor level. Such a furnace with a quenching tank in front of its
door is shown in Fig. 108.
These tanks are covered with plates while charging the furnace and the cold castings are placed in a moderately
cool furnace. Since some of these steels must not be charged into a furnace where the heat is extreme but should be
brought up to their final heat gradually, there is little discomfort during the charging process. When quenching,
however, from a temperature of 1,800° to 1,900°, it is extremely unpleasant in front of the doors. The swinging
shield is here adapted to give protection for this work. As will be noted it is hung a sufficient distance in front of
the doors, that it may not interfere with the castings as they come from the furnace, and slide down into the tank.
Page 155
To facilitate the work, and avoid the necessity of working with the bars outside the edges of the shield, the slot-
like hole is cut in the center of the shield, and through this the bars or rakes for dragging out the castings are easily
inserted and manipulated. The advantage of such a swinging shield is that it may be readily moved from side to
side, or forward and back as occasion requires.
FURNACE DATA
In order to give definite information concerning furnaces, fuels etc., the following data is quoted from a paper by
Seth A. Moulton and W. H. Lyman before the Steel Heat Treaters Society in September, 1920.
This considers a factory producing 30,000 lb. of automobile gears per 24 hr. The transmission gears will be of
high-carbon steel and the differential of low-carbon steel, carburized. The heat-treating equipment required is:
1. Annealing furnaces 1,400 to 1,600°F.
2. Carburizing furnaces 1,700 to 1,800°F.
3. Hardening furnaces 1,450 to 1,550°F.
4. Drawing furnaces 350 to 950°F.
All of the forging blanks are annealed before machining, about three-quarters of the machined gears and parts are
carburized, all the carburized gears are given a double treatment for core and case, all gears and parts are hardened
and all parts are drawn.
The possible sources of heat supply and their values are as follows:—
1. Oil 140,000 B.t.u. per gallon
2. Natural gas 1,100 B.t.u. per cubic foot
3. City gas 650 B.t.u. per cubic foot
4. Water gas 300 B.t.u. per cubic foot
5. Producer gas 170 B.t.u. per cubic foot
6. Coal 12,000 B.t.u. per pound
7. Electric current 3,412 B.t.u. per kilowatt-hour
For the heat treatment specified only comparatively low temperatures are required. No difficulty will be
experienced in attaining the desired maximum temperature of 1,800°F. with any of the heating medium above
enumerated; but it should be noted that the producer gas with a B.t.u. content of 170 per cubic foot and the electric
current would require specially designed furnaces to obtain higher temperatures than 1800°F.
TABLE 28.—COMPARATTVE OPERATING COSTS
Assuming
Cost of oil- and gas-fired furnaces installed as $100.00 per square foot of hearth
Cost of coal-fired furnace installed as 150.00 per square foot of hearth
Cost of electric furnace 100 kw. capacity installed as 90.00 per kilowatt
Cost of electric furnace 150 kw. capacity installed as 70.00 per kilowatt
Output 3,000 lb. charge, 8 hr. heat carburizing, 2 hr. heating only. Annual service 7,200 hr. Fixed charges
including interest, depreciation, taxes, insurance and maintenance 15 per cent. Extra operating labor for coal-fired
furnace 60 cts. per hour, one man four furnaces.
COST OF VARIOUS TYPES OF FURNACES
Fuel per Unit fuel Installation Efficiency per Fixed Cost per
Class fuel
charge cost cost cent charges charge
1 2 3 4 5 6 7
Carburizing
1 Oil 52.0 gal. $0.15 gal. $2,400.00 12.6 $.40 $8.20
like hole is cut in the center of the shield, and through this the bars or rakes for dragging out the castings are easily
inserted and manipulated. The advantage of such a swinging shield is that it may be readily moved from side to
side, or forward and back as occasion requires.
FURNACE DATA
In order to give definite information concerning furnaces, fuels etc., the following data is quoted from a paper by
Seth A. Moulton and W. H. Lyman before the Steel Heat Treaters Society in September, 1920.
This considers a factory producing 30,000 lb. of automobile gears per 24 hr. The transmission gears will be of
high-carbon steel and the differential of low-carbon steel, carburized. The heat-treating equipment required is:
1. Annealing furnaces 1,400 to 1,600°F.
2. Carburizing furnaces 1,700 to 1,800°F.
3. Hardening furnaces 1,450 to 1,550°F.
4. Drawing furnaces 350 to 950°F.
All of the forging blanks are annealed before machining, about three-quarters of the machined gears and parts are
carburized, all the carburized gears are given a double treatment for core and case, all gears and parts are hardened
and all parts are drawn.
The possible sources of heat supply and their values are as follows:—
1. Oil 140,000 B.t.u. per gallon
2. Natural gas 1,100 B.t.u. per cubic foot
3. City gas 650 B.t.u. per cubic foot
4. Water gas 300 B.t.u. per cubic foot
5. Producer gas 170 B.t.u. per cubic foot
6. Coal 12,000 B.t.u. per pound
7. Electric current 3,412 B.t.u. per kilowatt-hour
For the heat treatment specified only comparatively low temperatures are required. No difficulty will be
experienced in attaining the desired maximum temperature of 1,800°F. with any of the heating medium above
enumerated; but it should be noted that the producer gas with a B.t.u. content of 170 per cubic foot and the electric
current would require specially designed furnaces to obtain higher temperatures than 1800°F.
TABLE 28.—COMPARATTVE OPERATING COSTS
Assuming
Cost of oil- and gas-fired furnaces installed as $100.00 per square foot of hearth
Cost of coal-fired furnace installed as 150.00 per square foot of hearth
Cost of electric furnace 100 kw. capacity installed as 90.00 per kilowatt
Cost of electric furnace 150 kw. capacity installed as 70.00 per kilowatt
Output 3,000 lb. charge, 8 hr. heat carburizing, 2 hr. heating only. Annual service 7,200 hr. Fixed charges
including interest, depreciation, taxes, insurance and maintenance 15 per cent. Extra operating labor for coal-fired
furnace 60 cts. per hour, one man four furnaces.
COST OF VARIOUS TYPES OF FURNACES
Fuel per Unit fuel Installation Efficiency per Fixed Cost per
Class fuel
charge cost cost cent charges charge
1 2 3 4 5 6 7
Carburizing
1 Oil 52.0 gal. $0.15 gal. $2,400.00 12.6 $.40 $8.20
Page 156
2 Natural gas 4.4 M 0.50 M 2,400.00 18.8 0.40 2.60
3 City gas 8.3 M 0.80 M 2,400.00 17.0 0.40 7.04
4 Water gas 18.7 M 0.40 2,400.00 16.4 0.40 7.88
5 Producer gas 37.3 M 0.10 M 2,400.00 14.5 0.40 4.13
6 Coal 814.0 lb. 6.00 ton 3,600.00 9.4 0.60 3.98
7 Electricity 500.0 kw-hr. 0.015 kw. 9,000.00 53.0 1.50 9.00
Heating
1 Oil 30.8 gal. 0.15 gal. 2,400.00 21.4 0.10 4.72
2 Natural gas 2.61 M 0.50 M 2,400.00 32.0 0.10 1.40
3 City gas 4.9 M 0.80 M 2,400.00 28.8 0.10 4.02
4 Water gas 11.1 M 0.40 M 2,400.00 27.6 0.10 4.54
5 Producer gas 22.1 M 0.10 M 2,400.00 24.6 0.10 2.31
6 Coal 348.0 lb. 6.00 ton 3,600.00 22.0 0.15 1.38
7 Electricity 329.0 kw-hr. 0.015 kw. 10,500.00 81.75 0.44 5.38
This shows but two of the operations and for a single furnace. The total costs for all operations on the 30,000 lb.
of gears per 24 hr. is shown in Table 29.
TABLE 29.—COMPARATIVE ANNUAL PRODUCTION COSTS FOR 30,000 POUNDS OUTPUT IN 24
HOURS
Annual operating expenses Cost
per
Installation
No. Equipment Fixed Total lb.
cost Heat Labor
charges metal,
cents
1 2 3 4 5 6 7 8
I Oil $179,000.00 $26,850.00 $156,000.00 $105,000.00 $287,850.00 $3.19
II Oil and electric 213,000.00 31,950.00 142,770.00 97,000.00 271,720.00 3.02
III Natural gas 117,000.00 17,550.00 44,250.00 97,000.00 158,800.00 1.78
IV (A) Natural gas containing furnaces 120,000.00 18,000.00 41,000.00 94,000.00 153,000.00 1.70
V Natural gas and electric 181,000.00 27,150.00 73,820.00 90,000.00 190,970.00 2.13
VI City gas 122,000.00 18,300.00 123,200.00 94,000.00 235,500.00 2.62
VII City gas and electric 182,000.00 27,300.00 128,820.00 90,000.00 246,020.00 2.74
VIII Water gas 214,000.00 18,600.00 104,000.00 94,000.00 216,600.00 2.41
IX Water gas and electric 238,000.00 27,450.00 117,420.00 90,000.00 234,870.00 2.62
X Producer gas 246,000.00 18,900.00 69,300.00 90,000.00 178,200.00 1.98
XI Producer gas and electric 255,000.00 27,750.00 92,520.00 90,000.00 210,270.00 2.34
XII Coal and electric 194,000.00 29,100.00 87,220.00 90,000.00 206,320.00 2.30
XIII Electric 257,000.00 38,550.00 135,000.00 84,000.00 257,550.00 2.86
NOTE.—Producer plant fixed charges are included in the cost of gas and are charged as "heat" in column 5, so
they are omitted from column 4.
3 City gas 8.3 M 0.80 M 2,400.00 17.0 0.40 7.04
4 Water gas 18.7 M 0.40 2,400.00 16.4 0.40 7.88
5 Producer gas 37.3 M 0.10 M 2,400.00 14.5 0.40 4.13
6 Coal 814.0 lb. 6.00 ton 3,600.00 9.4 0.60 3.98
7 Electricity 500.0 kw-hr. 0.015 kw. 9,000.00 53.0 1.50 9.00
Heating
1 Oil 30.8 gal. 0.15 gal. 2,400.00 21.4 0.10 4.72
2 Natural gas 2.61 M 0.50 M 2,400.00 32.0 0.10 1.40
3 City gas 4.9 M 0.80 M 2,400.00 28.8 0.10 4.02
4 Water gas 11.1 M 0.40 M 2,400.00 27.6 0.10 4.54
5 Producer gas 22.1 M 0.10 M 2,400.00 24.6 0.10 2.31
6 Coal 348.0 lb. 6.00 ton 3,600.00 22.0 0.15 1.38
7 Electricity 329.0 kw-hr. 0.015 kw. 10,500.00 81.75 0.44 5.38
This shows but two of the operations and for a single furnace. The total costs for all operations on the 30,000 lb.
of gears per 24 hr. is shown in Table 29.
TABLE 29.—COMPARATIVE ANNUAL PRODUCTION COSTS FOR 30,000 POUNDS OUTPUT IN 24
HOURS
Annual operating expenses Cost
per
Installation
No. Equipment Fixed Total lb.
cost Heat Labor
charges metal,
cents
1 2 3 4 5 6 7 8
I Oil $179,000.00 $26,850.00 $156,000.00 $105,000.00 $287,850.00 $3.19
II Oil and electric 213,000.00 31,950.00 142,770.00 97,000.00 271,720.00 3.02
III Natural gas 117,000.00 17,550.00 44,250.00 97,000.00 158,800.00 1.78
IV (A) Natural gas containing furnaces 120,000.00 18,000.00 41,000.00 94,000.00 153,000.00 1.70
V Natural gas and electric 181,000.00 27,150.00 73,820.00 90,000.00 190,970.00 2.13
VI City gas 122,000.00 18,300.00 123,200.00 94,000.00 235,500.00 2.62
VII City gas and electric 182,000.00 27,300.00 128,820.00 90,000.00 246,020.00 2.74
VIII Water gas 214,000.00 18,600.00 104,000.00 94,000.00 216,600.00 2.41
IX Water gas and electric 238,000.00 27,450.00 117,420.00 90,000.00 234,870.00 2.62
X Producer gas 246,000.00 18,900.00 69,300.00 90,000.00 178,200.00 1.98
XI Producer gas and electric 255,000.00 27,750.00 92,520.00 90,000.00 210,270.00 2.34
XII Coal and electric 194,000.00 29,100.00 87,220.00 90,000.00 206,320.00 2.30
XIII Electric 257,000.00 38,550.00 135,000.00 84,000.00 257,550.00 2.86
NOTE.—Producer plant fixed charges are included in the cost of gas and are charged as "heat" in column 5, so
they are omitted from column 4.
Page 157
CHAPTER XII
PYROMETRY AND PYROMETERS
A knowledge of the fundamental principles of pyrometry, or the measurement of temperatures, is quite necessary
for one engaged in the heat treatment of steel. It is only by careful measurement and control of the heating of steel
that the full benefit of a heat-treating operation is secured.
Before the advent of the thermo-couple, methods of temperature measurement were very crude. The blacksmith
depended on his eyes to tell him when the proper temperature was reached, and of course the "color" appeared
different on light or dark days. "Cherry" to one man was "orange" to another, and it was therefore almost
impossible to formulate any treatment which could be applied by several men to secure the same results.
One of the early methods of measuring temperatures was the "iron ball" method. In this method, an iron ball, to
which a wire was attached, was placed in the furnace and when it had reached the temperature of the furnace, it
was quickly removed by means of the wire, and suspended in a can containing a known quantity of water; the
volume of water being such that the heat would not cause it to boil. The rise in temperature of the water was
measured by a thermometer, and, knowing the heat capacity of the iron ball and that of the water, the temperature
of the ball, and therefore the furnace, could be calculated. Usually a set of tables was prepared to simplify the
calculations. The iron ball, however, scaled, and changed in weight with repeated use, making the determinations
less and less accurate. A copper ball was often used to decrease this change, but even that was subject to error. This
method is still sometimes used, but for uniform results, a platinum ball, which will not scale or change in weight,
is necessary, and the cost of this ball, together with the slowness of the method, have rendered the practice
obsolete, especially in view of modern developments in accurate pyrometry.
PYROMETERS
Armor plate makers sometimes use the copper ball or Siemens' water pyrometer because they can place a number
of the balls or weights on the plate in locations where it is difficult to use other pyrometers. One of these
pyrometers is shown in section in Fig. 109.
PYROMETRY AND PYROMETERS
A knowledge of the fundamental principles of pyrometry, or the measurement of temperatures, is quite necessary
for one engaged in the heat treatment of steel. It is only by careful measurement and control of the heating of steel
that the full benefit of a heat-treating operation is secured.
Before the advent of the thermo-couple, methods of temperature measurement were very crude. The blacksmith
depended on his eyes to tell him when the proper temperature was reached, and of course the "color" appeared
different on light or dark days. "Cherry" to one man was "orange" to another, and it was therefore almost
impossible to formulate any treatment which could be applied by several men to secure the same results.
One of the early methods of measuring temperatures was the "iron ball" method. In this method, an iron ball, to
which a wire was attached, was placed in the furnace and when it had reached the temperature of the furnace, it
was quickly removed by means of the wire, and suspended in a can containing a known quantity of water; the
volume of water being such that the heat would not cause it to boil. The rise in temperature of the water was
measured by a thermometer, and, knowing the heat capacity of the iron ball and that of the water, the temperature
of the ball, and therefore the furnace, could be calculated. Usually a set of tables was prepared to simplify the
calculations. The iron ball, however, scaled, and changed in weight with repeated use, making the determinations
less and less accurate. A copper ball was often used to decrease this change, but even that was subject to error. This
method is still sometimes used, but for uniform results, a platinum ball, which will not scale or change in weight,
is necessary, and the cost of this ball, together with the slowness of the method, have rendered the practice
obsolete, especially in view of modern developments in accurate pyrometry.
PYROMETERS
Armor plate makers sometimes use the copper ball or Siemens' water pyrometer because they can place a number
of the balls or weights on the plate in locations where it is difficult to use other pyrometers. One of these
pyrometers is shown in section in Fig. 109.
Page 158
Siemens' Water Pyrometer.—It consists of a
cylindrical copper vessel provided with a handle and
containing a second smaller copper vessel with double
walls. An air space a separates the two vessels, and a
layer of felt the two walls of the inner one, in order to
retard the exchange of temperature with the surroundings.
The capacity of the inner vessel is a little more than one
pint. A mercury thermometer b is fixed close to the wall
of the inner vessel, its lower part being protected by a
perforated brass tube, whilst the upper projects above the
vessel and is divided as usual on the stem into degrees,
Fahrenheit or Centigrade, as desired. At the side of the
thermometer there is a small brass scale c, which slides
up and down, and on which the high temperatures are
marked in the same degrees as those in which the
mercury thermometer is divided; on a level with the zero
division of the brass scale a small pointer is fixed, which
traverses the scale of the thermometer.
Short cylinders d, of either copper, iron or platinum, are
supplied with the pyrometer, which are so adjusted that
their heat capacity at ordinary temperature is equal to
one-fiftieth of that of the copper vessel filled with one
pint of water. As, however, the specific heat of metals
increases with the temperature, allowance is made on the FIG. 109.—Siemens' copper-ball
pyrometer.
brass sliding scales, which are divided according to the
metal used for the pyrometer cylinder d. It will therefore
be understood that a different sliding scale is required for the particular kind of
metal of which a cylinder is composed. In order to obtain accurate measurements,
each sliding scale must be used only in conjunction with its own thermometer, and
in case the latter breaks a new scale must be made and graduated for the new
thermometer.
The water pyrometer is used as follows:
Exactly one pint (0.568 liter) of clean water, perfectly distilled or rain water, is
poured into the copper vessel, and the pyrometer is left for a few minutes to allow
the thermometer to attain the temperature of the water.
The brass scale c is then set with its pointer opposite the temperature of the water
as shown by the thermometer. Meanwhile one of the metal cylinders has been
cylindrical copper vessel provided with a handle and
containing a second smaller copper vessel with double
walls. An air space a separates the two vessels, and a
layer of felt the two walls of the inner one, in order to
retard the exchange of temperature with the surroundings.
The capacity of the inner vessel is a little more than one
pint. A mercury thermometer b is fixed close to the wall
of the inner vessel, its lower part being protected by a
perforated brass tube, whilst the upper projects above the
vessel and is divided as usual on the stem into degrees,
Fahrenheit or Centigrade, as desired. At the side of the
thermometer there is a small brass scale c, which slides
up and down, and on which the high temperatures are
marked in the same degrees as those in which the
mercury thermometer is divided; on a level with the zero
division of the brass scale a small pointer is fixed, which
traverses the scale of the thermometer.
Short cylinders d, of either copper, iron or platinum, are
supplied with the pyrometer, which are so adjusted that
their heat capacity at ordinary temperature is equal to
one-fiftieth of that of the copper vessel filled with one
pint of water. As, however, the specific heat of metals
increases with the temperature, allowance is made on the FIG. 109.—Siemens' copper-ball
pyrometer.
brass sliding scales, which are divided according to the
metal used for the pyrometer cylinder d. It will therefore
be understood that a different sliding scale is required for the particular kind of
metal of which a cylinder is composed. In order to obtain accurate measurements,
each sliding scale must be used only in conjunction with its own thermometer, and
in case the latter breaks a new scale must be made and graduated for the new
thermometer.
The water pyrometer is used as follows:
Exactly one pint (0.568 liter) of clean water, perfectly distilled or rain water, is
poured into the copper vessel, and the pyrometer is left for a few minutes to allow
the thermometer to attain the temperature of the water.
The brass scale c is then set with its pointer opposite the temperature of the water
as shown by the thermometer. Meanwhile one of the metal cylinders has been
Page 159
exposed to the high temperature which is to be measured, and after allowing
sufficient time for it to acquire that temperature, it is rapidly removed and dropped
into the pyrometer vessel without splashing any of the water out.
The temperature of the water will rise until, after a little while, the mercury of the
thermometer has become stationary. When this is observed the degrees of the
thermometer are read off, as well as those on the brass scale c opposite the top of the
mercury. The sum of these two values together gives the temperature of the flue,
furnace or other heated space in which the metal cylinder had been placed. With
cylinders of copper and iron, temperatures up to 1,800°F. (1,000°C.) can be
measured, but with platinum cylinders the limit is 2,700°F. (1,500°C.).
For ordinary furnace work either copper or wrought-iron cylinders may be used.
Iron cylinders possess a higher melting point and have less tendency to scale than
those of copper, but the latter are much less affected by the corrosive action of the
furnace gases; platinum is, of course, not subject to any of these disadvantages.
The weight to which the different metal cylinders are adjusted is as follows:
Copper 137.0 grams
Wrought-iron 112.0 grams
Platinum 402.6 grams
In course of time the cylinders lose weight by scaling; but tables are provided
giving multipliers for the diminished weights, by which the reading on the brass
scale should be multiplied.
THE THERMO-COUPLE
With the application of the thermo-couple, the measurement of temperatures,
between, say, 700 and 2,500°F., was made more simple and precise. The theory of
the thermo-couple is simple; it is that if two bars, rods, or wires of different metals
are joined together at their ends, when heated so that one junction is hotter than the
other, an electromotive force is set up through the metals, which will increase with
the increase of the difference of temperature between the two junctions. This
electromotive force, or voltage, may be measured, and, from a chart previously
prepared, the temperature determined. In most pyrometers, of course, the
temperatures are inscribed directly on the voltmeter, but the fact remains that it is the
voltage of a small electric current, and not heat, that is actually measured.
There are two common types of thermo-couples, the first making use of common,
inexpensive metals, such as iron wire and nichrome wire. This is the so-called "base
sufficient time for it to acquire that temperature, it is rapidly removed and dropped
into the pyrometer vessel without splashing any of the water out.
The temperature of the water will rise until, after a little while, the mercury of the
thermometer has become stationary. When this is observed the degrees of the
thermometer are read off, as well as those on the brass scale c opposite the top of the
mercury. The sum of these two values together gives the temperature of the flue,
furnace or other heated space in which the metal cylinder had been placed. With
cylinders of copper and iron, temperatures up to 1,800°F. (1,000°C.) can be
measured, but with platinum cylinders the limit is 2,700°F. (1,500°C.).
For ordinary furnace work either copper or wrought-iron cylinders may be used.
Iron cylinders possess a higher melting point and have less tendency to scale than
those of copper, but the latter are much less affected by the corrosive action of the
furnace gases; platinum is, of course, not subject to any of these disadvantages.
The weight to which the different metal cylinders are adjusted is as follows:
Copper 137.0 grams
Wrought-iron 112.0 grams
Platinum 402.6 grams
In course of time the cylinders lose weight by scaling; but tables are provided
giving multipliers for the diminished weights, by which the reading on the brass
scale should be multiplied.
THE THERMO-COUPLE
With the application of the thermo-couple, the measurement of temperatures,
between, say, 700 and 2,500°F., was made more simple and precise. The theory of
the thermo-couple is simple; it is that if two bars, rods, or wires of different metals
are joined together at their ends, when heated so that one junction is hotter than the
other, an electromotive force is set up through the metals, which will increase with
the increase of the difference of temperature between the two junctions. This
electromotive force, or voltage, may be measured, and, from a chart previously
prepared, the temperature determined. In most pyrometers, of course, the
temperatures are inscribed directly on the voltmeter, but the fact remains that it is the
voltage of a small electric current, and not heat, that is actually measured.
There are two common types of thermo-couples, the first making use of common,
inexpensive metals, such as iron wire and nichrome wire. This is the so-called "base
Page 160
metal" couple. The other is composed of expensive metals such as platinum wire,
and a wire of an alloy of platinum with 10 per cent of rhodium or iridium. This is
called the "rare metal" couple, and because its component metals are less affected by
heat, it lasts longer, and varies less than the base metal couple.
The cold junction of a thermo-couple may be connected by means of copper wires
to the voltmeter, although in some installations of base metal couples, the wires
forming the couple are themselves extended to the voltmeter, making copper
connections unnecessary. From the foregoing, it may be seen that accurately to
measure the temperature of the hot end of a thermo-couple, we must know the
temperature of the cold end, as it is the difference in the temperatures that
determines the voltmeter readings. This is absolutely essential for precision, and its
importance cannot be over-emphasized.
When pyrometers are used in daily operation, they should be checked or calibrated
two or three times a month, or even every week. Where there are many in use, it is
good practice to have a master pyrometer of a rare metal couple, which is used only
for checking up the others. The master pyrometer, after calibrating against the
melting points of various substances, will have a calibration chart which should be
used in the checking operation.
It is customary now to send a rare metal couple to the Bureau of Standards at
Washington, where it is very carefully calibrated for a nominal charge, and returned
with the voltmeter readings of a series of temperatures covering practically the
whole range of the couple. This couple is then used only for checking those in daily
use.
Pyrometer couples are more or less expensive, and should be cared far when in
use. The wires of the couple should be insulated from each other by fireclay leads or
tubes, and it is well to encase them in a fireclay, porcelain, or quartz tube to keep out
the furnace gases, which in time destroy the hot junction. This tube of fireclay, or
porcelain, etc., should be protected against breakage by an iron or nichrome tube,
plugged or welded at the hot end. These simple precautions will prolong the life of a
couple and maintain its precision longer.
Sometimes erroneous temperatures are recorded because the "cold end" of the
couple is too near the furnace and gets hot. This always causes a temperature
reading lower than the actual, and should be guarded against. It is well to keep the
cold end cool with water, a wet cloth, or by placing it where coal air will circulate
around it. Best of all, is to have the cold junction in a box, together with a
thermometer, so that its temperature may definitely be known. If this temperature
should rise 20°F. on a hot day, a correction of 20°F. should be added to the
and a wire of an alloy of platinum with 10 per cent of rhodium or iridium. This is
called the "rare metal" couple, and because its component metals are less affected by
heat, it lasts longer, and varies less than the base metal couple.
The cold junction of a thermo-couple may be connected by means of copper wires
to the voltmeter, although in some installations of base metal couples, the wires
forming the couple are themselves extended to the voltmeter, making copper
connections unnecessary. From the foregoing, it may be seen that accurately to
measure the temperature of the hot end of a thermo-couple, we must know the
temperature of the cold end, as it is the difference in the temperatures that
determines the voltmeter readings. This is absolutely essential for precision, and its
importance cannot be over-emphasized.
When pyrometers are used in daily operation, they should be checked or calibrated
two or three times a month, or even every week. Where there are many in use, it is
good practice to have a master pyrometer of a rare metal couple, which is used only
for checking up the others. The master pyrometer, after calibrating against the
melting points of various substances, will have a calibration chart which should be
used in the checking operation.
It is customary now to send a rare metal couple to the Bureau of Standards at
Washington, where it is very carefully calibrated for a nominal charge, and returned
with the voltmeter readings of a series of temperatures covering practically the
whole range of the couple. This couple is then used only for checking those in daily
use.
Pyrometer couples are more or less expensive, and should be cared far when in
use. The wires of the couple should be insulated from each other by fireclay leads or
tubes, and it is well to encase them in a fireclay, porcelain, or quartz tube to keep out
the furnace gases, which in time destroy the hot junction. This tube of fireclay, or
porcelain, etc., should be protected against breakage by an iron or nichrome tube,
plugged or welded at the hot end. These simple precautions will prolong the life of a
couple and maintain its precision longer.
Sometimes erroneous temperatures are recorded because the "cold end" of the
couple is too near the furnace and gets hot. This always causes a temperature
reading lower than the actual, and should be guarded against. It is well to keep the
cold end cool with water, a wet cloth, or by placing it where coal air will circulate
around it. Best of all, is to have the cold junction in a box, together with a
thermometer, so that its temperature may definitely be known. If this temperature
should rise 20°F. on a hot day, a correction of 20°F. should be added to the
Page 161
pyrometer reading, and so on. In the most up-to-date installations, this cold junction
compensation is taken care of automatically, a fact which indicates its importance.
Optical pyrometers are often used where it is impracticable to use the thermo-
couple, either because the temperature is so high that it would destroy the couple, or
the heat to be measured is inaccessible to the couple of ordinary length. The
temperatures of slag or metal in furnaces or running through tap-holes or troughs are
often measured with optical pyrometers.
In one type of optical pyrometer, the observer focuses it on the metal or slag and
moves an adjustable dial or gage so as to get an exact comparison between the color
of the heat measured with the calor of a lamp or screen in the pyrometer itself. This,
of course, requires practice, and judgment, and brings in the personal equation. With
care, however, very reliable temperature measurements may be made. The
temperatures of rails, as they leave the finishing pass of a rolling mill, are measured
in this way.
Another type of optical pyrometer is focused on the body, the temperature of which
is to be measured. The rays converge in the telescope on metal cells, heating them,
and thereby generating a small electric current, the voltage of which is read an a
calibrated voltmeter similar to that used with the thermo-couple. The best precision
is obtained when an optical pyrometer is used each time under similar conditions of
light and the same observer.
Where it is impracticable to use either thermo-couples or optical pyrometers,
"sentinels" may be used. There are small cones or cylinders made of salts or other
substances of known melting points and covering a wide range of temperatures.
If six of these "sentinels," melting respectively at 1,300°, 1,350°, 1,400°, 1,450°,
1,500°, and 1,550°F., were placed in a row in a furnace, together with a piece of
steel to be treated, and the whole heated up uniformly, the sentinels would melt one
by one and the observer, by watching them through an opening in the furnace, could
tell when his furnace is at say 1,500° or between 1,500° and 1,550°, and regulate the
heat accordingly.
A very accurate type of pyrometer, but one not so commonly used as those
previously described, is the resistance pyrometer. In this type, the temperature is
determined by measuring the resistance to an electric current of a wire which is at
the heat to be measured. This wire is usually of platinum, wound around a quartz
tube, the whole being placed in the furnace. When the wire is at the temperature of
the furnace, it is connected by wires with a Wheatstone Bridge, a delicate device for
measuring electrical resistance, and an electric current is passed through the wire.
compensation is taken care of automatically, a fact which indicates its importance.
Optical pyrometers are often used where it is impracticable to use the thermo-
couple, either because the temperature is so high that it would destroy the couple, or
the heat to be measured is inaccessible to the couple of ordinary length. The
temperatures of slag or metal in furnaces or running through tap-holes or troughs are
often measured with optical pyrometers.
In one type of optical pyrometer, the observer focuses it on the metal or slag and
moves an adjustable dial or gage so as to get an exact comparison between the color
of the heat measured with the calor of a lamp or screen in the pyrometer itself. This,
of course, requires practice, and judgment, and brings in the personal equation. With
care, however, very reliable temperature measurements may be made. The
temperatures of rails, as they leave the finishing pass of a rolling mill, are measured
in this way.
Another type of optical pyrometer is focused on the body, the temperature of which
is to be measured. The rays converge in the telescope on metal cells, heating them,
and thereby generating a small electric current, the voltage of which is read an a
calibrated voltmeter similar to that used with the thermo-couple. The best precision
is obtained when an optical pyrometer is used each time under similar conditions of
light and the same observer.
Where it is impracticable to use either thermo-couples or optical pyrometers,
"sentinels" may be used. There are small cones or cylinders made of salts or other
substances of known melting points and covering a wide range of temperatures.
If six of these "sentinels," melting respectively at 1,300°, 1,350°, 1,400°, 1,450°,
1,500°, and 1,550°F., were placed in a row in a furnace, together with a piece of
steel to be treated, and the whole heated up uniformly, the sentinels would melt one
by one and the observer, by watching them through an opening in the furnace, could
tell when his furnace is at say 1,500° or between 1,500° and 1,550°, and regulate the
heat accordingly.
A very accurate type of pyrometer, but one not so commonly used as those
previously described, is the resistance pyrometer. In this type, the temperature is
determined by measuring the resistance to an electric current of a wire which is at
the heat to be measured. This wire is usually of platinum, wound around a quartz
tube, the whole being placed in the furnace. When the wire is at the temperature of
the furnace, it is connected by wires with a Wheatstone Bridge, a delicate device for
measuring electrical resistance, and an electric current is passed through the wire.
Page 162
This current is balanced by switching in resistances in the Wheatstone Bridge, until
a delicate electrical device shows that no current is flowing. The resistance of the
platinum wire at the heat to be measured is thus determined on the "Bridge," and the
temperature read off on a calibration chart, which shows the resistance at various
temperatures.
These are the common methods used to-day for measuring temperatures, but
whatever method is used, the observer should bear in mind that the greatest
precision is obtained, and hence the highest efficiency, by keeping the apparatus in
good working order, making sure that conditions are the same each time, and
calibrating or checking against a standard at regular intervals.
THE PYROMETER AND ITS USE
In the heat treatment of steel, it has become absolutely necessary that a measuring
instrument be used which will give the operator an exact reading of heat in furnace.
There are a number of instruments and devices manufactured for this purpose but
any instrument that will not give a direct reading without any guess work should
have no place in the heat-treating department.
A pyrometer installation is very simple and any of the leading makers will furnish
diagrams for the correct wiring and give detailed information as to the proper care
of, and how best to use their particular instrument. There are certain general
principles, however, that must be observed by the operators and it cannot be too
strongly impressed upon them that the human factor involved is always the deciding
factor in the heat treatment of steel.
A pyrometer is merely an aid in the performance of doing good work, and when
carefully observed will help in giving a uniformity of product and act as a check on
careless operators. The operator must bear in mind that although the reading on the
pyrometer scale gives a measure of the temperature where the junction of the two
metals is located, it will not give the temperature at the center of work in the
furnace, unless by previous tests, the heat for penetrating a certain bulk of material
has been decided on, and the time necessary for such penetration is known.
Each analysis of plain carbon or alloy steel is a problem in itself. Its critical
temperatures will be located at slightly different heats than for a steel which has a
different proportion of alloying elements. Furthermore, it takes time for metal to
acquire the heat of the furnace. Even the outer surface lags behind the temperature
of the furnace somewhat, and the center of the piece of steel lags still further. It is
apparent, therefore, that temperature, although important, does not tell the whole
story in heat treatment. Time is also a factor.
a delicate electrical device shows that no current is flowing. The resistance of the
platinum wire at the heat to be measured is thus determined on the "Bridge," and the
temperature read off on a calibration chart, which shows the resistance at various
temperatures.
These are the common methods used to-day for measuring temperatures, but
whatever method is used, the observer should bear in mind that the greatest
precision is obtained, and hence the highest efficiency, by keeping the apparatus in
good working order, making sure that conditions are the same each time, and
calibrating or checking against a standard at regular intervals.
THE PYROMETER AND ITS USE
In the heat treatment of steel, it has become absolutely necessary that a measuring
instrument be used which will give the operator an exact reading of heat in furnace.
There are a number of instruments and devices manufactured for this purpose but
any instrument that will not give a direct reading without any guess work should
have no place in the heat-treating department.
A pyrometer installation is very simple and any of the leading makers will furnish
diagrams for the correct wiring and give detailed information as to the proper care
of, and how best to use their particular instrument. There are certain general
principles, however, that must be observed by the operators and it cannot be too
strongly impressed upon them that the human factor involved is always the deciding
factor in the heat treatment of steel.
A pyrometer is merely an aid in the performance of doing good work, and when
carefully observed will help in giving a uniformity of product and act as a check on
careless operators. The operator must bear in mind that although the reading on the
pyrometer scale gives a measure of the temperature where the junction of the two
metals is located, it will not give the temperature at the center of work in the
furnace, unless by previous tests, the heat for penetrating a certain bulk of material
has been decided on, and the time necessary for such penetration is known.
Each analysis of plain carbon or alloy steel is a problem in itself. Its critical
temperatures will be located at slightly different heats than for a steel which has a
different proportion of alloying elements. Furthermore, it takes time for metal to
acquire the heat of the furnace. Even the outer surface lags behind the temperature
of the furnace somewhat, and the center of the piece of steel lags still further. It is
apparent, therefore, that temperature, although important, does not tell the whole
story in heat treatment. Time is also a factor.
Page 163
Time at temperature is also of great importance because it takes time, after the
temperature has been reached, for the various internal changes to take place. Hence
the necessity for "soaking," when annealing or normalizing. Therefore, a clock is as
necessary to the proper pyrometer equipment as the pyrometer itself.
For the purpose of general work where a wide range of steels or a variable
treatment is called for, it becomes necessary to have the pyrometer calibrated
constantly, and when no master instrument is kept for this purpose the following
method can be used to give the desired results:
CALIBRATION OF PYROMETER WITH COMMON SALT
An easy and convenient method for standardization and one which does not
necessitate the use of an expensive laboratory equipment is that based upon
determining the melting point of common table salt (sodium chloride). While
theoretically salt that is chemically pure should be used (and this is neither
expensive nor difficult to procure), commercial accuracy may be obtained by using
common table salt such as is sold by every grocer. The salt is melted in a clean
crucible of fireclay, iron or nickel, either in a furnace or over a forge-fire, and then
further heated until a temperature of about 1,600 to 1,650°F. is attained. It is
essential that this crucible be clean because a slight admixture of a foreign substance
might noticeably change the melting point.
The thermo-couple to be calibrated is then removed from its protecting tube and its
hot end is immersed in the salt bath. When this end has reached the temperature of
the bath, the crucible is removed from the source of heat and allowed to cool, and
cooling readings are then taken every 10 sec. on the milli-voltmeter or pyrometer. A
curve is then plotted by using time and temperature as coördinates, and the
temperature of the freezing point of salt, as indicated by this particular
thermocouple, is noted, i.e., at the point where the temperature of the bath remains
temporarily constant while the salt is freezing. The length of time during which the
temperature is stationary depends on the size of the bath and the rate of cooling, and
is not a factor in the calibration. The melting point of salt is 1,472°F., and the needed
correction for the instrument under observation can be readily applied.
It should not be understood from the above, however, that the salt-bath calibration
cannot be made without plotting a curve; in actual practice at least a hundred tests
are made without plotting any curve to one in which it is done. The observer, if
awake, may reasonably be expected to have sufficient appreciation of the lapse of
time definitely to observe the temperature at which the falling pointer of the
instrument halts. The gradual dropping of the pointer before freezing, unless there is
a large mass of salt, takes place rapidly enough for one to be sure that the
temperature has been reached, for the various internal changes to take place. Hence
the necessity for "soaking," when annealing or normalizing. Therefore, a clock is as
necessary to the proper pyrometer equipment as the pyrometer itself.
For the purpose of general work where a wide range of steels or a variable
treatment is called for, it becomes necessary to have the pyrometer calibrated
constantly, and when no master instrument is kept for this purpose the following
method can be used to give the desired results:
CALIBRATION OF PYROMETER WITH COMMON SALT
An easy and convenient method for standardization and one which does not
necessitate the use of an expensive laboratory equipment is that based upon
determining the melting point of common table salt (sodium chloride). While
theoretically salt that is chemically pure should be used (and this is neither
expensive nor difficult to procure), commercial accuracy may be obtained by using
common table salt such as is sold by every grocer. The salt is melted in a clean
crucible of fireclay, iron or nickel, either in a furnace or over a forge-fire, and then
further heated until a temperature of about 1,600 to 1,650°F. is attained. It is
essential that this crucible be clean because a slight admixture of a foreign substance
might noticeably change the melting point.
The thermo-couple to be calibrated is then removed from its protecting tube and its
hot end is immersed in the salt bath. When this end has reached the temperature of
the bath, the crucible is removed from the source of heat and allowed to cool, and
cooling readings are then taken every 10 sec. on the milli-voltmeter or pyrometer. A
curve is then plotted by using time and temperature as coördinates, and the
temperature of the freezing point of salt, as indicated by this particular
thermocouple, is noted, i.e., at the point where the temperature of the bath remains
temporarily constant while the salt is freezing. The length of time during which the
temperature is stationary depends on the size of the bath and the rate of cooling, and
is not a factor in the calibration. The melting point of salt is 1,472°F., and the needed
correction for the instrument under observation can be readily applied.
It should not be understood from the above, however, that the salt-bath calibration
cannot be made without plotting a curve; in actual practice at least a hundred tests
are made without plotting any curve to one in which it is done. The observer, if
awake, may reasonably be expected to have sufficient appreciation of the lapse of
time definitely to observe the temperature at which the falling pointer of the
instrument halts. The gradual dropping of the pointer before freezing, unless there is
a large mass of salt, takes place rapidly enough for one to be sure that the
Page 164
temperature is constantly falling, and the long period of rest during freezing is quite
definite. The procedure of detecting the solidification point of the salt by the
hesitation of the pointer without plotting any curve is suggested because of its
simplicity.
Complete Calibration of Pyrometers.—For the complete calibration of a thermo-
couple of unknown electromotive force, the new couple may be checked against a
standard instrument, placing the two bare couples side by side in a suitable tube and
taking frequent readings over the range of temperatures desired.
If only one instrument, such as a millivoltmeter, is available, and there is no
standard couple at hand, the new couple may be calibrated over a wide range of
temperatures by the use of the following standards:
Water, boiling point 212°F.
Tin, under charcoal, freezing point 450°F.
Lead, under charcoal, freezing point 621°F.
Zinc, under charcoal, freezing point 786°F.
Sulphur, boiling point 832°F.
Aluminum, under charcoal, freezing point 1,216°F.
Sodium chloride (salt), freezing point 1,474°F.
Potassium sulphate, freezing point 1,958°F.
A good practice is to make one pyrometer a standard; calibrate it frequently by the
melting-point-of-salt method, and each morning check up every pyrometer in the
works with the standard, making the necessary corrections to be used for the day's
work. By pursuing this course systematically, the improved quality of the product
will much more than compensate for the extra work.
The purity of the substance affects its freezing or melting point. The melting point
of common salt is given in one widely used handbook at 1,421°F., although
chemically pure sodium chloride melts at 1,474°F. as shown above. A sufficient
quantity for an extended period should be secured. Test the melting point with a
pyrometer of known accuracy. Knowing this temperature it will be easy to calibrate
other pyrometers.
Placing of Pyrometers.—When installing a pyrometer, care should be taken that it
reaches directly to the point desired to be measured, that the cold junction is kept
cold, and that the wires leading to the recording instrument are kept in good shape.
The length of these lead wires have an effect; the longer they are, the lower the
apparent temperature.
definite. The procedure of detecting the solidification point of the salt by the
hesitation of the pointer without plotting any curve is suggested because of its
simplicity.
Complete Calibration of Pyrometers.—For the complete calibration of a thermo-
couple of unknown electromotive force, the new couple may be checked against a
standard instrument, placing the two bare couples side by side in a suitable tube and
taking frequent readings over the range of temperatures desired.
If only one instrument, such as a millivoltmeter, is available, and there is no
standard couple at hand, the new couple may be calibrated over a wide range of
temperatures by the use of the following standards:
Water, boiling point 212°F.
Tin, under charcoal, freezing point 450°F.
Lead, under charcoal, freezing point 621°F.
Zinc, under charcoal, freezing point 786°F.
Sulphur, boiling point 832°F.
Aluminum, under charcoal, freezing point 1,216°F.
Sodium chloride (salt), freezing point 1,474°F.
Potassium sulphate, freezing point 1,958°F.
A good practice is to make one pyrometer a standard; calibrate it frequently by the
melting-point-of-salt method, and each morning check up every pyrometer in the
works with the standard, making the necessary corrections to be used for the day's
work. By pursuing this course systematically, the improved quality of the product
will much more than compensate for the extra work.
The purity of the substance affects its freezing or melting point. The melting point
of common salt is given in one widely used handbook at 1,421°F., although
chemically pure sodium chloride melts at 1,474°F. as shown above. A sufficient
quantity for an extended period should be secured. Test the melting point with a
pyrometer of known accuracy. Knowing this temperature it will be easy to calibrate
other pyrometers.
Placing of Pyrometers.—When installing a pyrometer, care should be taken that it
reaches directly to the point desired to be measured, that the cold junction is kept
cold, and that the wires leading to the recording instrument are kept in good shape.
The length of these lead wires have an effect; the longer they are, the lower the
apparent temperature.
Page 165
When pyrometers placed in a number of furnaces are connected up in series, and a
multiple switch is used for control, it becomes apparent that pyrometers could not be
interchanged between furnaces near and far from the instrument without affecting
the uniformity of product from each furnace.
Calibration can best be done without disturbing the working pyrometer, by
inserting the master instrument into each furnace separately, place it alongside the
hot junction of the working pyrometer, and compare the reading given on the
indicator connected with the multiple switch.
Protection tubes should be replaced when cracked, as it is important that no foreign
substance is allowed to freeze in the tube, so that the enclosed junction becomes a
part of a solid mass joined in electrical contact with the outside protecting tube.
Wires over the furnaces must be carefully inspected from time to time, as no true
reading can be had on an instrument, if insulation is burned off and short circuits
result.
If the standard calibrating instrument used contains a dry battery, it should be
examined from time to time to be sure it is in good condition.
THE LEEDS AND NORTHRUP POTENTIOMETER SYSTEM
The potentiometer pyrometer system is both flexible and substantial in that it is not
affected by the jar and vibration of the factory or the forge shop. Large or small
couples, long or short leads can be used without adjustment. The recording
instrument may be placed where it is most convenient, without regard to the distance
from the furnace.
Its Fundamental Principle.—The potentiometer is the electrical equivalent of the
chemical balance, or balance arm scales. Measurements are made with balance
scales by varying known weights until they equal the unknown weight. When the
two are equal the scales stand at zero, that is, in the position which they occupy
when there is no weight on either pan; the scales are then said to be balanced.
Measurements are made with the potentiometer by varying a known electromotive
force until it equals the unknown; when the two are equal the index of the
potentiometer, the galvanometer needle, stands motionless as it is alternately
connected and disconnected. The variable known weights are units separate from the
scales, but the potentiometer provides its own variable known electromotive force.
The potentiometer provides, first, a means of securing a known variable
electromotive force and, second, suitable electrical connections for bringing that
electromotive force to a point where it may be balanced against the unknown
multiple switch is used for control, it becomes apparent that pyrometers could not be
interchanged between furnaces near and far from the instrument without affecting
the uniformity of product from each furnace.
Calibration can best be done without disturbing the working pyrometer, by
inserting the master instrument into each furnace separately, place it alongside the
hot junction of the working pyrometer, and compare the reading given on the
indicator connected with the multiple switch.
Protection tubes should be replaced when cracked, as it is important that no foreign
substance is allowed to freeze in the tube, so that the enclosed junction becomes a
part of a solid mass joined in electrical contact with the outside protecting tube.
Wires over the furnaces must be carefully inspected from time to time, as no true
reading can be had on an instrument, if insulation is burned off and short circuits
result.
If the standard calibrating instrument used contains a dry battery, it should be
examined from time to time to be sure it is in good condition.
THE LEEDS AND NORTHRUP POTENTIOMETER SYSTEM
The potentiometer pyrometer system is both flexible and substantial in that it is not
affected by the jar and vibration of the factory or the forge shop. Large or small
couples, long or short leads can be used without adjustment. The recording
instrument may be placed where it is most convenient, without regard to the distance
from the furnace.
Its Fundamental Principle.—The potentiometer is the electrical equivalent of the
chemical balance, or balance arm scales. Measurements are made with balance
scales by varying known weights until they equal the unknown weight. When the
two are equal the scales stand at zero, that is, in the position which they occupy
when there is no weight on either pan; the scales are then said to be balanced.
Measurements are made with the potentiometer by varying a known electromotive
force until it equals the unknown; when the two are equal the index of the
potentiometer, the galvanometer needle, stands motionless as it is alternately
connected and disconnected. The variable known weights are units separate from the
scales, but the potentiometer provides its own variable known electromotive force.
The potentiometer provides, first, a means of securing a known variable
electromotive force and, second, suitable electrical connections for bringing that
electromotive force to a point where it may be balanced against the unknown
Page 166
electromotive force of the couple. The two are connected with opposite polarity, or
so that the two e.m.f.s oppose one another. So long as one is stronger than the other
a current will flow through the couple; when the two are equal no current will flow.
Figure 107 shows the wiring of the potentiometer in its simplest form. The thermo-
couple is at H, with its polarity as shown by the symbols + and -. It is connected
with the main circuit of the potentiometer at the fixed point D and the point G.
FIG. 110.—Simple potentiometer.
A current from the dry cell Ba is constantly flowing through the main, or so-called
potentiometer circuit, ABCDGEF. The section DGE of this circuit is a slide wire,
uniform in resistance throughout its length. The scale is fixed on this slide wire. The
current from the cell Ba as it flows through DGE, undergoes a fall in potential,
setting up a difference in voltage, that is, an electromotive force, between D and E.
There will also be electromotive force between D and all other points on the slide
wire. The polarity of this is in opposition to the polarity of the thermo-couple which
connects into the potentiometer at D and at G. By moving G along the slide wire a
point is found where the voltage between D and G in the slide wire is just equal to
the voltage between D and G generated by the thermo-couple. A galvanometer in the
thermo-couple circuit indicates when the balance point is reached, since at this point
the galvanometer needle will stand motionless when its circuit is opened and closed.
FIG. 111.—Standard cell potentiometer.
so that the two e.m.f.s oppose one another. So long as one is stronger than the other
a current will flow through the couple; when the two are equal no current will flow.
Figure 107 shows the wiring of the potentiometer in its simplest form. The thermo-
couple is at H, with its polarity as shown by the symbols + and -. It is connected
with the main circuit of the potentiometer at the fixed point D and the point G.
FIG. 110.—Simple potentiometer.
A current from the dry cell Ba is constantly flowing through the main, or so-called
potentiometer circuit, ABCDGEF. The section DGE of this circuit is a slide wire,
uniform in resistance throughout its length. The scale is fixed on this slide wire. The
current from the cell Ba as it flows through DGE, undergoes a fall in potential,
setting up a difference in voltage, that is, an electromotive force, between D and E.
There will also be electromotive force between D and all other points on the slide
wire. The polarity of this is in opposition to the polarity of the thermo-couple which
connects into the potentiometer at D and at G. By moving G along the slide wire a
point is found where the voltage between D and G in the slide wire is just equal to
the voltage between D and G generated by the thermo-couple. A galvanometer in the
thermo-couple circuit indicates when the balance point is reached, since at this point
the galvanometer needle will stand motionless when its circuit is opened and closed.
FIG. 111.—Standard cell potentiometer.
Page 167
The voltage in the slide wire will vary with the current flowing through it from the
cell Ba and a means of standardizing this is provided. SC, Fig. 111, is a cadmium
cell whose voltage is constant. It is connected at two points C and D to the
potentiometer circuit whenever the potentiometer current is to be standardized. At
this time the galvanometer is thrown in series with SC. The variable rheostat R is
then adjusted until the current flowing is such that as it flows through the standard
resistance CD, the fall in potential between C and D is just equal to the voltage of
the standard cell SC. At this time the galvanometer will indicate a balance in the
same way as when it was used with a thermo-couple. By this operation the current in
the slide wire DGE has been standardized.
FIG. 112.—Hand adjusted cold-end compensator.
Development of the Wiring Scheme of the Cold-end Compensator.—The net
voltage generated by a thermo-couple depends upon the temperature of the hot end
and the temperature of the cold end. Therefore, any method adopted for reading
temperature by means of thermo-couples must in some way provide a means of
correcting for the temperature of the cold end. The potentiometer may have either of
two very simple devices for this purpose. In one form the operator is required to set
a small index to a point on a scale corresponding to the known cold junction
temperature. In the other form an even more simple automatic compensator is
employed. The principle of each is described in the succeeding paragraphs, in which
the assumption is made that the reader already understands the potentiometer
principle as described above.
As previously explained the voltage of the thermo-couple is measured by balancing
it against the voltage drop DG in the potentiometer.
As shown in Fig. 111, the magnitude of the balancing voltage is controlled by the
position of G. Make D movable as shown in Fig. 112 and the magnitude of the
voltage DG may be varied either from the point D or the point G. This gives a means
of compensating for cold end changes by setting the slider D. As the cold end
temperature rises the net voltage generated by the couple decreases, assuming the
cell Ba and a means of standardizing this is provided. SC, Fig. 111, is a cadmium
cell whose voltage is constant. It is connected at two points C and D to the
potentiometer circuit whenever the potentiometer current is to be standardized. At
this time the galvanometer is thrown in series with SC. The variable rheostat R is
then adjusted until the current flowing is such that as it flows through the standard
resistance CD, the fall in potential between C and D is just equal to the voltage of
the standard cell SC. At this time the galvanometer will indicate a balance in the
same way as when it was used with a thermo-couple. By this operation the current in
the slide wire DGE has been standardized.
FIG. 112.—Hand adjusted cold-end compensator.
Development of the Wiring Scheme of the Cold-end Compensator.—The net
voltage generated by a thermo-couple depends upon the temperature of the hot end
and the temperature of the cold end. Therefore, any method adopted for reading
temperature by means of thermo-couples must in some way provide a means of
correcting for the temperature of the cold end. The potentiometer may have either of
two very simple devices for this purpose. In one form the operator is required to set
a small index to a point on a scale corresponding to the known cold junction
temperature. In the other form an even more simple automatic compensator is
employed. The principle of each is described in the succeeding paragraphs, in which
the assumption is made that the reader already understands the potentiometer
principle as described above.
As previously explained the voltage of the thermo-couple is measured by balancing
it against the voltage drop DG in the potentiometer.
As shown in Fig. 111, the magnitude of the balancing voltage is controlled by the
position of G. Make D movable as shown in Fig. 112 and the magnitude of the
voltage DG may be varied either from the point D or the point G. This gives a means
of compensating for cold end changes by setting the slider D. As the cold end
temperature rises the net voltage generated by the couple decreases, assuming the
Page 168
hot end temperature to be constant. To balance this decreased voltage the slider D is
moved along its scale to a new point nearer G. In other words, the slider D is moved
along its scale until it corresponds to the known temperature of the cold end and
then the potentiometer is balanced by moving the slider G. The readings of G will
then be direct.
FIG. 113.—Another type of compensator.
The same results will be obtained if a slide wire upon which D bears is in parallel
with the slide wire of G, as shown in Fig. 113.
Automatic Compensator.—It should be noted that the effect of moving the
contact D, Fig. 113, is to vary the ratio of the resistances on the two sides of the
point D in the secondary slide wire. In the recording pyrometers, an automatic
compensator is employed. This automatic compensator varies the ratio on the two
sides of the point D in the following manner:
The point D, Fig. 114, is mechanically fixed; on one side of D is the constant
resistance coil M, on the other the nickel coil N. N is placed at or near the cold end
of the thermo-couple (or couples). Nickel has a high temperature coefficient and the
electrical proportions of M and N are such that the resistance change of N, as it
varies with the temperature of the cold end, has the same effect upon the balancing
voltage between D and G that the movement of the point D, Fig. 114, has in the
hand-operated compensator.
Instruments embodying these principles are shown in Figs. 115 to 117. The
captions making their uses clear.
moved along its scale to a new point nearer G. In other words, the slider D is moved
along its scale until it corresponds to the known temperature of the cold end and
then the potentiometer is balanced by moving the slider G. The readings of G will
then be direct.
FIG. 113.—Another type of compensator.
The same results will be obtained if a slide wire upon which D bears is in parallel
with the slide wire of G, as shown in Fig. 113.
Automatic Compensator.—It should be noted that the effect of moving the
contact D, Fig. 113, is to vary the ratio of the resistances on the two sides of the
point D in the secondary slide wire. In the recording pyrometers, an automatic
compensator is employed. This automatic compensator varies the ratio on the two
sides of the point D in the following manner:
The point D, Fig. 114, is mechanically fixed; on one side of D is the constant
resistance coil M, on the other the nickel coil N. N is placed at or near the cold end
of the thermo-couple (or couples). Nickel has a high temperature coefficient and the
electrical proportions of M and N are such that the resistance change of N, as it
varies with the temperature of the cold end, has the same effect upon the balancing
voltage between D and G that the movement of the point D, Fig. 114, has in the
hand-operated compensator.
Instruments embodying these principles are shown in Figs. 115 to 117. The
captions making their uses clear.
Page 169
FIG. 114.—Automatic cold-end compensator.
PLACING THE THERMO-COUPLES
FIG. 115.—Potentiometer ready for use.
The following illustrations from the Taylor Instrument Company show different
applications of the thermo-couples to furnaces of various kinds. Figure 118 shows an
oil-fired furnace with a simple vertical installation. Figure 119 shows a method of
imbedding the thermo-couple in the floor of a furnace so as to require no space in
the heating chamber.
Various methods of applying a pyrometer to common heat-treatment furnaces are
shown in Figs. 120 to 122.
PLACING THE THERMO-COUPLES
FIG. 115.—Potentiometer ready for use.
The following illustrations from the Taylor Instrument Company show different
applications of the thermo-couples to furnaces of various kinds. Figure 118 shows an
oil-fired furnace with a simple vertical installation. Figure 119 shows a method of
imbedding the thermo-couple in the floor of a furnace so as to require no space in
the heating chamber.
Various methods of applying a pyrometer to common heat-treatment furnaces are
shown in Figs. 120 to 122.
Page 170
FIG. 116.—Eight-point recording pyrometer-Carpenter Steel Co.
LEEDS AND NORTHRUP OPTICAL PYROMETER
The principles of this very popular method of measuring temperature are sketched
in Fig. 123.
LEEDS AND NORTHRUP OPTICAL PYROMETER
The principles of this very popular method of measuring temperature are sketched
in Fig. 123.
Page 171
FIG. 117.—Multiple-point thermocouple recorder—Bethlehem Steel Co.
FIG. 118.—Tycos pyrometer in oil-fired furnace.
The instrument is light and portable, and can be sighted as easily as an opera glass.
The telescope, which is held in the hand, weighs only 25 oz.; and the case
FIG. 118.—Tycos pyrometer in oil-fired furnace.
The instrument is light and portable, and can be sighted as easily as an opera glass.
The telescope, which is held in the hand, weighs only 25 oz.; and the case
Page 172
containing the battery, rheostat and milliammeter, which is slung from the shoulder,
only 10 lb.
FIG. 119.—Thermocouple in floor of furnace.
FIG. 120.—Pyrometer in gas furnace.
A large surface to sight at is not required. So long as the image formed by the
objective is broader than the lamp filament, the temperature can be measured
accurately.
only 10 lb.
FIG. 119.—Thermocouple in floor of furnace.
FIG. 120.—Pyrometer in gas furnace.
A large surface to sight at is not required. So long as the image formed by the
objective is broader than the lamp filament, the temperature can be measured
accurately.
Page 173
FIG. 121.—Tycos multiple indicating pyrometer and recorder.
FIG. 122.—Pyrometer in galvanizing tank.
Distance does not matter, as the brightness of the image formed by the lens is
practically constant, regardless of the distance of the instrument from the hot object.
FIG. 122.—Pyrometer in galvanizing tank.
Distance does not matter, as the brightness of the image formed by the lens is
practically constant, regardless of the distance of the instrument from the hot object.
Page 174
FIG. 123.—Leeds & Northrup optical pyrometer.
The manipulation is simple and rapid, consisting merely in the turning of a knurled
knob. The setting is made with great precision, due to the rapid change in light
intensity with change in temperature and to the sensitiveness of the eye to
differences of light intensity. In the region of temperatures used for hardening steel,
for example, different observers using the instrument will agree within 3°C.
Only brightness, not color, of light is matched, as light of only one color reaches
the eye. Color blindness, therefore, is no hindrance to the use of this method. The
use of the instrument is shown in Fig. 127.
Optical System and Electrical Circuit of the Leeds & Northrup Optical
Pyrometer.—For extremely high temperature, the optical pyrometer is largely used.
This is a comparative method. By means of the rheostat the current through the lamp
is adjusted until the brightness of the filament is just equal to the brightness of the
image produced by the lens L, Fig. 123, whereupon the filament blends with or
becomes indistinguishable in the background formed by the image of the hot object.
This adjustment can be made with great accuracy and certainty, as the effect of
radiation upon the eye varies some twenty times faster than does the temperature at
1,600°F., and some fourteen times faster at 3,400°F. When a balance has been
obtained, the observer notes the reading of the milliammeter. The temperature
The manipulation is simple and rapid, consisting merely in the turning of a knurled
knob. The setting is made with great precision, due to the rapid change in light
intensity with change in temperature and to the sensitiveness of the eye to
differences of light intensity. In the region of temperatures used for hardening steel,
for example, different observers using the instrument will agree within 3°C.
Only brightness, not color, of light is matched, as light of only one color reaches
the eye. Color blindness, therefore, is no hindrance to the use of this method. The
use of the instrument is shown in Fig. 127.
Optical System and Electrical Circuit of the Leeds & Northrup Optical
Pyrometer.—For extremely high temperature, the optical pyrometer is largely used.
This is a comparative method. By means of the rheostat the current through the lamp
is adjusted until the brightness of the filament is just equal to the brightness of the
image produced by the lens L, Fig. 123, whereupon the filament blends with or
becomes indistinguishable in the background formed by the image of the hot object.
This adjustment can be made with great accuracy and certainty, as the effect of
radiation upon the eye varies some twenty times faster than does the temperature at
1,600°F., and some fourteen times faster at 3,400°F. When a balance has been
obtained, the observer notes the reading of the milliammeter. The temperature
Page 175
corresponding to the current is then read from a calibration curve supplied with the
instrument.
FIG. 127.—Using the optical pyrometer.
As the intensity of the light emitted at the higher temperatures becomes dazzling, it
is found desirable to introduce a piece of red glass in the eye piece at R. This also
eliminates any question of matching colors, or of the observer's ability to distinguish
colors. It is further of value in dealing with bodies which do not radiate light of the
same composition as that emitted by a black body, since nevertheless the intensity of
radiation of any one color from such bodies increases progressively in a definite
manner as the temperature rises. The intensity of this one color can therefore be used
as a measure of temperature for the body in question. Figures 124 to 126 show the
way it is read.
CORRECTION FOR COLD-JUNCTION ERRORS
The voltage generated by a thermo-couple of an electric pyrometer is dependent on
the difference in temperature between its hot junction, inside the furnace, and the
cold junction, or opposite end of the thermo-couple to which the copper wires are
connected. If the temperature or this cold junction rises and falls, the indications of
instrument.
FIG. 127.—Using the optical pyrometer.
As the intensity of the light emitted at the higher temperatures becomes dazzling, it
is found desirable to introduce a piece of red glass in the eye piece at R. This also
eliminates any question of matching colors, or of the observer's ability to distinguish
colors. It is further of value in dealing with bodies which do not radiate light of the
same composition as that emitted by a black body, since nevertheless the intensity of
radiation of any one color from such bodies increases progressively in a definite
manner as the temperature rises. The intensity of this one color can therefore be used
as a measure of temperature for the body in question. Figures 124 to 126 show the
way it is read.
CORRECTION FOR COLD-JUNCTION ERRORS
The voltage generated by a thermo-couple of an electric pyrometer is dependent on
the difference in temperature between its hot junction, inside the furnace, and the
cold junction, or opposite end of the thermo-couple to which the copper wires are
connected. If the temperature or this cold junction rises and falls, the indications of
Page 176
the instrument will vary, although the hot junction in the furnace may be at a
constant temperature.
A cold-junction temperature of 75°F., or 25°C., is usually adopted in commercial
pyrometers, and the pointer on the pyrometer should stand at this point on the scale
when the hot junction is not heated. If the cold-junction temperature rises about
75°F., where base metal thermo-couples are used, the pyrometer will read
approximately 1° low for every 1° rise in temperature above 75°F. For example, if
the instrument is adjusted for a cold-junction temperature of 75°, and the actual
cold-junction temperature is 90°F., the pyrometer will read 15° low. If, however, the
cold-junction temperature falls below 75°F., the pyrometer will read high instead of
low, approximately 1° for every 1° drop in temperature below 75°F.
With platinum thermo-couples, the error is approximately 1/2° for 1° change in
temperature.
Correction by Zero Adjustment.—Many pyrometers are supplied with a zero
adjuster, by means of which the pointer can be set to any actual cold-junction
temperature. If the cold junction of the thermo-couple is in a temperature of 100°F.,
the pointer can be set to this point on the scale, and the readings of the instrument
will be correct.
Compensating Leads.—By the use of compensating leads, formed of the same
material as the thermo-couple, the cold junction can be removed from the head of
the thermo-couple to a point 10, 20 or 50 ft. distant from the furnace, where the
temperature is reasonably constant. Where greater accuracy is desired, a common
method is to drive a 2-in. pipe, with a pointed closed end, some 10 to 20 ft. into the
ground, as shown in Fig. 128. The compensating leads are joined to the copper
leads, and the junction forced down to the bottom of the pipe. The cold junction is
now in the ground, beneath the building, at a depth at which the temperature is very
constant, about 70°F., throughout the year. This method will usually control the
cold-junction temperature within 5°F.
Where the greatest accuracy is desired a compensating box will overcome cold-
junction errors entirely. It consists of a case enclosing a lamp and thermostat, which
can be adjusted to maintain any desired temperature, from 50 to 150°F. The
compensating leads enter the box and copper leads run from the compensating box
to the instrument, so that the cold junction is within the box. Figure 129 shows a
Brown compensating box.
constant temperature.
A cold-junction temperature of 75°F., or 25°C., is usually adopted in commercial
pyrometers, and the pointer on the pyrometer should stand at this point on the scale
when the hot junction is not heated. If the cold-junction temperature rises about
75°F., where base metal thermo-couples are used, the pyrometer will read
approximately 1° low for every 1° rise in temperature above 75°F. For example, if
the instrument is adjusted for a cold-junction temperature of 75°, and the actual
cold-junction temperature is 90°F., the pyrometer will read 15° low. If, however, the
cold-junction temperature falls below 75°F., the pyrometer will read high instead of
low, approximately 1° for every 1° drop in temperature below 75°F.
With platinum thermo-couples, the error is approximately 1/2° for 1° change in
temperature.
Correction by Zero Adjustment.—Many pyrometers are supplied with a zero
adjuster, by means of which the pointer can be set to any actual cold-junction
temperature. If the cold junction of the thermo-couple is in a temperature of 100°F.,
the pointer can be set to this point on the scale, and the readings of the instrument
will be correct.
Compensating Leads.—By the use of compensating leads, formed of the same
material as the thermo-couple, the cold junction can be removed from the head of
the thermo-couple to a point 10, 20 or 50 ft. distant from the furnace, where the
temperature is reasonably constant. Where greater accuracy is desired, a common
method is to drive a 2-in. pipe, with a pointed closed end, some 10 to 20 ft. into the
ground, as shown in Fig. 128. The compensating leads are joined to the copper
leads, and the junction forced down to the bottom of the pipe. The cold junction is
now in the ground, beneath the building, at a depth at which the temperature is very
constant, about 70°F., throughout the year. This method will usually control the
cold-junction temperature within 5°F.
Where the greatest accuracy is desired a compensating box will overcome cold-
junction errors entirely. It consists of a case enclosing a lamp and thermostat, which
can be adjusted to maintain any desired temperature, from 50 to 150°F. The
compensating leads enter the box and copper leads run from the compensating box
to the instrument, so that the cold junction is within the box. Figure 129 shows a
Brown compensating box.
Page 177
FIG. 128.—Correcting cold-junction error.
If it is desired to maintain the cold junction at 100°: the thermostat is set at this
point, and the lamp, being wired to the 110- or 220-volt lighting circuit, will light
and heat the box until 100° is reached, when the thermostat will open the circuit and
the light is extinguished. The box will now cool down to 98°, when the circuit is
again closed, the lamp lights, the box heats up, and the operation is repeated.
FIG. 129.—Compensating box.
BROWN AUTOMATIC SIGNALING PYROMETER
If it is desired to maintain the cold junction at 100°: the thermostat is set at this
point, and the lamp, being wired to the 110- or 220-volt lighting circuit, will light
and heat the box until 100° is reached, when the thermostat will open the circuit and
the light is extinguished. The box will now cool down to 98°, when the circuit is
again closed, the lamp lights, the box heats up, and the operation is repeated.
FIG. 129.—Compensating box.
BROWN AUTOMATIC SIGNALING PYROMETER
Page 178
In large heat-treating plants it has been customary to maintain an operator at a
central pyrometer, and by colored electric lights at the furnaces, signal whether the
temperatures are correct or not. It is common practice to locate three lights above
each furnace-red, white and green. The red light burns when the temperature is too
low, the white light when the temperature is within certain limits—for example,
20°F. of the correct temperature—and the green light when the temperature is too
high.
FIG. 130.—Brown automatic signaling pyrometer.
Instruments to operate the lights automatically have been devised and one made by
Brown is shown in Fig. 130. The same form of instrument is used for this purpose to
automatically control furnace temperatures, and the pointer is depressed at intervals
of every 10 sec. on contacts corresponding to the red, white and green lights.
central pyrometer, and by colored electric lights at the furnaces, signal whether the
temperatures are correct or not. It is common practice to locate three lights above
each furnace-red, white and green. The red light burns when the temperature is too
low, the white light when the temperature is within certain limits—for example,
20°F. of the correct temperature—and the green light when the temperature is too
high.
FIG. 130.—Brown automatic signaling pyrometer.
Instruments to operate the lights automatically have been devised and one made by
Brown is shown in Fig. 130. The same form of instrument is used for this purpose to
automatically control furnace temperatures, and the pointer is depressed at intervals
of every 10 sec. on contacts corresponding to the red, white and green lights.
Page 179
FIG. 131.—Automatic temperature control.
AN AUTOMATIC TEMPERATURE CONTROL PYROMETER
Automatic temperature control instruments are similar to the Brown indicating
high resistance pyrometer with the exception that the pointer is depressed at
intervals of every 10 sec. upon contact-making devices. No current passes through
the pointer which simply depresses the upper contact device tipped with platinum,
which in turn comes in contact with the lower contact device, platinum-tipped, and
the circuit is completed through these two contacts. The current is very small, about
1/10 amp., as it is only necessary to operate the relay which in turn operates the
switch or valve. A small motor is used to depress the pointer at regular intervals. The
contact-making device is adjustable throughout the scale range of the instrument,
and an index pointer indicates the point on the instrument at which the temperature
is being controlled. The space between the two contacts on the high and low side,
separated by insulating material, is equivalent to 1 per cent of the scale range. A
AN AUTOMATIC TEMPERATURE CONTROL PYROMETER
Automatic temperature control instruments are similar to the Brown indicating
high resistance pyrometer with the exception that the pointer is depressed at
intervals of every 10 sec. upon contact-making devices. No current passes through
the pointer which simply depresses the upper contact device tipped with platinum,
which in turn comes in contact with the lower contact device, platinum-tipped, and
the circuit is completed through these two contacts. The current is very small, about
1/10 amp., as it is only necessary to operate the relay which in turn operates the
switch or valve. A small motor is used to depress the pointer at regular intervals. The
contact-making device is adjustable throughout the scale range of the instrument,
and an index pointer indicates the point on the instrument at which the temperature
is being controlled. The space between the two contacts on the high and low side,
separated by insulating material, is equivalent to 1 per cent of the scale range. A
Page 180
control of temperature is therefore possible within 1 per cent of the total scale range.
Figure 131 shows this attached to a small furnace.
FIG. 132.—Portable thermocouple testing molten brass.
PYROMETERS FOR MOLTEN METAL
Pyrometers for molten metal are connected to portable thermocouples as in Fig.
132. Usually the pyrometer is portable, as shown in this case, which is a Brown.
Other methods of mounting for this kind of work arc shown in Figs. 133 and 134.
The bent mountings are designed for molten metal, such as brass or copper and are
supplied with either clay, graphite or carborundum tubes. Fifteen feet of connecting
wire is usually supplied.
The angle mountings, Fig. 134, are recommended for baths such as lead or
cyanide. The horizontal arm is usually about 14 in. long, and the whole mounting is
easily taken apart making replacements very easy. Details of the thermo-couple
shown in Fig. 132 are given in Fig. 135. This is a straight rod with a protector for the
hand of the operator. The lag in such couples is less than one minute. These are
Englehard mountings.
PROTECTORS FOR THERMO-COUPLES
Thermo-couples must be protected from the danger of mechanical injury. For this
purpose tubes of various refractory materials are made to act as protectors. These in
turn are usually protected by outside metal tubes. Pure wrought iron is largely used
Figure 131 shows this attached to a small furnace.
FIG. 132.—Portable thermocouple testing molten brass.
PYROMETERS FOR MOLTEN METAL
Pyrometers for molten metal are connected to portable thermocouples as in Fig.
132. Usually the pyrometer is portable, as shown in this case, which is a Brown.
Other methods of mounting for this kind of work arc shown in Figs. 133 and 134.
The bent mountings are designed for molten metal, such as brass or copper and are
supplied with either clay, graphite or carborundum tubes. Fifteen feet of connecting
wire is usually supplied.
The angle mountings, Fig. 134, are recommended for baths such as lead or
cyanide. The horizontal arm is usually about 14 in. long, and the whole mounting is
easily taken apart making replacements very easy. Details of the thermo-couple
shown in Fig. 132 are given in Fig. 135. This is a straight rod with a protector for the
hand of the operator. The lag in such couples is less than one minute. These are
Englehard mountings.
PROTECTORS FOR THERMO-COUPLES
Thermo-couples must be protected from the danger of mechanical injury. For this
purpose tubes of various refractory materials are made to act as protectors. These in
turn are usually protected by outside metal tubes. Pure wrought iron is largely used
Page 181
for this purpose as it scales and oxidizes very slowly. These tubes are usually made
from 2 to 4 in. shorter than the inner tubes. In lead baths the iron tubes often have
one end welded closed and are used in connection with an angle form of mounting.
FIG. 133.—Bent handle thermocouple with protector.
Where it is necessary for protecting tubes to project a considerable distance into
the furnace a tube made of nichrome is frequently used. This is a comparatively new
alloy which stands high temperatures without bending. It is more costly than iron
but also much more durable.
When used in portable work and for high temperatures, pure nickel tubes are
sometimes used. There is also a special metal tube made for use in cyanide. This
metal withstands the intense penetrating characteristics of cyanide. It lasts from six
to ten months as against a few days for the iron tube.
The inner tubes of refractory materials, also vary according to the purposes for
which they are to be used. They are as follows:
Marquardt mass tubes for temperatures up to 3,000°F., but they will not stand
sudden changes in temperature, such as in contact with intermittent flames, without
an extra outer covering of chamotte, fireclay or carborundum.
from 2 to 4 in. shorter than the inner tubes. In lead baths the iron tubes often have
one end welded closed and are used in connection with an angle form of mounting.
FIG. 133.—Bent handle thermocouple with protector.
Where it is necessary for protecting tubes to project a considerable distance into
the furnace a tube made of nichrome is frequently used. This is a comparatively new
alloy which stands high temperatures without bending. It is more costly than iron
but also much more durable.
When used in portable work and for high temperatures, pure nickel tubes are
sometimes used. There is also a special metal tube made for use in cyanide. This
metal withstands the intense penetrating characteristics of cyanide. It lasts from six
to ten months as against a few days for the iron tube.
The inner tubes of refractory materials, also vary according to the purposes for
which they are to be used. They are as follows:
Marquardt mass tubes for temperatures up to 3,000°F., but they will not stand
sudden changes in temperature, such as in contact with intermittent flames, without
an extra outer covering of chamotte, fireclay or carborundum.
Page 182
FIG. 134.—Other styles of bent mounting.
Fused silica tubes for continuous temperatures up to 1,800°F. and intermittently
up to 2,400°F. The expansion at various temperatures is very small, which makes
them of value for portable work. They also resist most acids.
Chamotte tubes are useful up to 2,800°F. and are mechanically strong. They have
a small expansion and resist temperature changes well, which makes them good as
outside protectors for more fragile tubes. They cannot be used in molten metals, or
baths of any kind nor in gases of an alkaline nature. They are used mainly to protect
a Marquardt mass or silica tube.
Carborundum tubes are also used as outside protection to other tubes. They stand
sudden changes of temperature well and resist all gases except chlorine, above
1,750°F. Especially useful in protecting other tubes against molten aluminum, brass,
copper and similar metals.
Fused silica tubes for continuous temperatures up to 1,800°F. and intermittently
up to 2,400°F. The expansion at various temperatures is very small, which makes
them of value for portable work. They also resist most acids.
Chamotte tubes are useful up to 2,800°F. and are mechanically strong. They have
a small expansion and resist temperature changes well, which makes them good as
outside protectors for more fragile tubes. They cannot be used in molten metals, or
baths of any kind nor in gases of an alkaline nature. They are used mainly to protect
a Marquardt mass or silica tube.
Carborundum tubes are also used as outside protection to other tubes. They stand
sudden changes of temperature well and resist all gases except chlorine, above
1,750°F. Especially useful in protecting other tubes against molten aluminum, brass,
copper and similar metals.
Page 183
Clay tubes are sometimes used in large annealing furnaces where they are
cemented into place, forming a sort of well for the insertion of the thermo-couple.
They are also used with portable thermo-couples for obtaining the temperatures of
molten iron and steel in ladles. Used in this way they are naturally short-lived, but
seem the best for this purpose.
FIG. 135.—Straight thermocouple and guard.
Corundite tubes are used as an outer protection for both the Marquardt mass and
the silica tubes for kilns and for glass furnaces. Graphite tubes are also used in some
cases for outer protections.
Calorized tubes are wrought-iron pipe treated with aluminum vapor which often
doubles or even triples the life of the tube at high temperature.
These tubes come in different sizes and lengths depending on the uses for which
they are intended. Heavy protecting outer tubes may be only 1 in. in inside diameter
and as much as 3 in. outside diameter, while the inner tubes, such as the Marquardt
mass and silica tubes are usually about ¾ in. outside and 3/8 in. inside diameter. The
length varies from 12 to 48 in. in most cases.
Special terminal heads are provided, with brass binding posts for electrical
connections, and with provisions for water cooling when necessary.
cemented into place, forming a sort of well for the insertion of the thermo-couple.
They are also used with portable thermo-couples for obtaining the temperatures of
molten iron and steel in ladles. Used in this way they are naturally short-lived, but
seem the best for this purpose.
FIG. 135.—Straight thermocouple and guard.
Corundite tubes are used as an outer protection for both the Marquardt mass and
the silica tubes for kilns and for glass furnaces. Graphite tubes are also used in some
cases for outer protections.
Calorized tubes are wrought-iron pipe treated with aluminum vapor which often
doubles or even triples the life of the tube at high temperature.
These tubes come in different sizes and lengths depending on the uses for which
they are intended. Heavy protecting outer tubes may be only 1 in. in inside diameter
and as much as 3 in. outside diameter, while the inner tubes, such as the Marquardt
mass and silica tubes are usually about ¾ in. outside and 3/8 in. inside diameter. The
length varies from 12 to 48 in. in most cases.
Special terminal heads are provided, with brass binding posts for electrical
connections, and with provisions for water cooling when necessary.
Page 184
APPENDIX
TABLE 32.—Temperature Conversion Tables.
TABLE 33.—Comparison Between Degrees Centigrade and Degrees Fahrenheit.
TABLE 34.—Weight of Round, Octagon and Square Carbon Tool Steel per Foot.
TABLE 35.—Weight of Round Carbon Tool Steel 12 In. in Diameter and Larger,
per Foot.
TABLE 36.—Decimal Equivalents of a foot.
TEMPERATURE CONVERSION TABLES
By ALBERT SAUVEUR
-459.4 to 0 0 to 100 100 to 1000
C. F. C. F. C. F. C. F. C. F.
-273 -459.4 -17.8 0 32 10.0 50 122.0 38 100 212 260 500 932
-268 -450 -17.2 1 33.8 10.6 51 123.8 43 110 230 266 510 950
-262 -440 -16.7 2 35.6 11.1 52 125.6 49 120 248 271 520 968
-257 -430 -16.1 3 37.4 11.7 53 127.4 54 130 266 277 530 986
-251 -420 -15.6 4 39.2 12.2 54 129.2 60 140 284 282 540 1004
-246 -410 -15.0 5 41.0 12.8 55 131.0 66 150 302 288 550 1022
-240 -400 -14.4 6 42.8 13.3 56 132.8 71 160 320 293 560 1040
-234 -390 -13.9 7 44.6 13.9 57 134.6 77 170 336 299 570 1058
-229 -380 -13.3 8 46.4 14.4 58 136.4 82 180 358 304 580 1076
-223 -370 -12.8 9 48.2 15.0 59 138.2 88 190 374 310 590 1094
-218 -360 -12.2 10 50.0 15.6 60 140.0 93 200 392 316 600 1112
-212 -350 -11.7 11 51.8 16.1 61 141.8 99 210 410 321 610 1130
-207 -340 -11.1 12 53.6 16.7 62 143.6 100 212 413 327 620 1148
-201 -330 -10.6 13 55.4 17.2 63 145.4 104 220 428 332 630 1166
-196 -320 -10.0 14 57.2 17.8 64 147.2 110 230 446 338 640 1184
TABLE 32.—Temperature Conversion Tables.
TABLE 33.—Comparison Between Degrees Centigrade and Degrees Fahrenheit.
TABLE 34.—Weight of Round, Octagon and Square Carbon Tool Steel per Foot.
TABLE 35.—Weight of Round Carbon Tool Steel 12 In. in Diameter and Larger,
per Foot.
TABLE 36.—Decimal Equivalents of a foot.
TEMPERATURE CONVERSION TABLES
By ALBERT SAUVEUR
-459.4 to 0 0 to 100 100 to 1000
C. F. C. F. C. F. C. F. C. F.
-273 -459.4 -17.8 0 32 10.0 50 122.0 38 100 212 260 500 932
-268 -450 -17.2 1 33.8 10.6 51 123.8 43 110 230 266 510 950
-262 -440 -16.7 2 35.6 11.1 52 125.6 49 120 248 271 520 968
-257 -430 -16.1 3 37.4 11.7 53 127.4 54 130 266 277 530 986
-251 -420 -15.6 4 39.2 12.2 54 129.2 60 140 284 282 540 1004
-246 -410 -15.0 5 41.0 12.8 55 131.0 66 150 302 288 550 1022
-240 -400 -14.4 6 42.8 13.3 56 132.8 71 160 320 293 560 1040
-234 -390 -13.9 7 44.6 13.9 57 134.6 77 170 336 299 570 1058
-229 -380 -13.3 8 46.4 14.4 58 136.4 82 180 358 304 580 1076
-223 -370 -12.8 9 48.2 15.0 59 138.2 88 190 374 310 590 1094
-218 -360 -12.2 10 50.0 15.6 60 140.0 93 200 392 316 600 1112
-212 -350 -11.7 11 51.8 16.1 61 141.8 99 210 410 321 610 1130
-207 -340 -11.1 12 53.6 16.7 62 143.6 100 212 413 327 620 1148
-201 -330 -10.6 13 55.4 17.2 63 145.4 104 220 428 332 630 1166
-196 -320 -10.0 14 57.2 17.8 64 147.2 110 230 446 338 640 1184
Page 185
-190 -310 -9.44 15 59.0 18.3 65 149.0 116 240 464 343 650 1202
-184 -300 -8.89 16 61.8 18.9 66 150.8 121 250 482 349 660 1220
-179 -290 -8.33 17 63.6 19.4 67 152.6 127 260 500 354 670 1238
-173 -280 -7.78 18 65.4 20.0 68 154.4 132 270 518 360 680 1256
-169 -273 -459.4 -7.22 19 67.2 20.6 69 156.2 138 280 536 366 690 1274
-168 -270 -454 -6.67 20 68.0 21.1 70 158.0 143 290 554 371 700 1292
-162 -260 -436 -6.11 21 69.8 21.7 71 159.8 149 300 572 377 710 1310
-157 -250 -418 -5.56 22 71.6 22.2 72 161.6 154 310 590 382 720 1328
-151 -240 -400 -5.00 23 73.4 22.8 73 163.4 160 320 608 388 730 1346
-146 -230 -382 -4.44 24 75.2 23.3 74 165.2 166 330 626 393 740 1364
-140 -220 -364 -3.89 25 77.0 23.9 75 167.0 171 340 644 399 750 1382
-134 -210 -346 -3.33 26 78.8 24.4 76 168.8 177 350 662 404 760 1400
-129 -200 -328 -2.78 27 80.6 25.0 77 170.6 182 360 680 410 770 1418
-123 -190 -310 -2.22 28 82.4 25.6 78 172.4 188 370 698 416 780 1436
-118 -180 -292 -1.67 29 84.2 26.1 79 174.2 193 380 716 421 790 1454
-112 -170 -274 -1.11 30 86.0 26.7 80 176.0 199 390 734 427 800 1472
-107 -160 -256 -0.56 31 87.8 27.2 81 177.8 204 400 752 432 810 1490
-101 -150 -238 0 32 89.6 27.8 82 179.6 210 410 770 438 820 1508
-95.6 -140 -220 0.56 33 91.4 28.3 83 181.4 216 420 788 443 830 1526
-90.0 -130 -202 1.11 34 93.2 28.9 84 183.2 221 430 806 449 840 1544
-84.4 -120 -184 1.67 35 95.0 29.4 85 185.0 227 440 824 454 850 1562
-78.9 -110 -166 2.22 36 96.8 30.0 86 186.8 232 450 842 460 860 1580
-73.3 -100 -148 2.78 37 98.6 30.6 87 188.6 238 460 860 466 870 1598
-67.8 -90 -130 3.33 38 100.4 31.1 88 190.4 243 470 878 471 880 1616
-62.2 -80 -112 3.89 39 102.2 31.7 89 192.2 249 480 896 477 890 1634
-56.7 -70 -94 4.44 40 104.0 32.2 90 194.0 254 490 914 482 900 1652
-51.1 -60 -76 5.00 41 105.8 32.8 91 195.8 488 910 1670
-45.6 -50 -58 5.56 42 107.6 33.3 92 197.6 493 920 1688
-40.0 -40 -40 6.11 43 109.4 33.9 93 199.4 499 930 1706
-34.4 -30 -22 6.67 44 111.2 34.4 94 201.2 504 940 1724
-28.9 -20 4 7.22 45 113.0 35.0 95 203.0 510 950 1742
-23.3 -10 14 7.78 46 114.8 35.6 96 204.8 516 960 1760
-17.8 0 32 8.33 47 116.6 36.1 97 206.6 521 970 1778
8.89 48 118.4 36.7 98 208.4 527 980 1796
9.44 49 120.2 37.2 99 210.2 532 990 1814
37.8 100 212.0 538 1000 1832
1000 to 2000 2000 to 3000
-184 -300 -8.89 16 61.8 18.9 66 150.8 121 250 482 349 660 1220
-179 -290 -8.33 17 63.6 19.4 67 152.6 127 260 500 354 670 1238
-173 -280 -7.78 18 65.4 20.0 68 154.4 132 270 518 360 680 1256
-169 -273 -459.4 -7.22 19 67.2 20.6 69 156.2 138 280 536 366 690 1274
-168 -270 -454 -6.67 20 68.0 21.1 70 158.0 143 290 554 371 700 1292
-162 -260 -436 -6.11 21 69.8 21.7 71 159.8 149 300 572 377 710 1310
-157 -250 -418 -5.56 22 71.6 22.2 72 161.6 154 310 590 382 720 1328
-151 -240 -400 -5.00 23 73.4 22.8 73 163.4 160 320 608 388 730 1346
-146 -230 -382 -4.44 24 75.2 23.3 74 165.2 166 330 626 393 740 1364
-140 -220 -364 -3.89 25 77.0 23.9 75 167.0 171 340 644 399 750 1382
-134 -210 -346 -3.33 26 78.8 24.4 76 168.8 177 350 662 404 760 1400
-129 -200 -328 -2.78 27 80.6 25.0 77 170.6 182 360 680 410 770 1418
-123 -190 -310 -2.22 28 82.4 25.6 78 172.4 188 370 698 416 780 1436
-118 -180 -292 -1.67 29 84.2 26.1 79 174.2 193 380 716 421 790 1454
-112 -170 -274 -1.11 30 86.0 26.7 80 176.0 199 390 734 427 800 1472
-107 -160 -256 -0.56 31 87.8 27.2 81 177.8 204 400 752 432 810 1490
-101 -150 -238 0 32 89.6 27.8 82 179.6 210 410 770 438 820 1508
-95.6 -140 -220 0.56 33 91.4 28.3 83 181.4 216 420 788 443 830 1526
-90.0 -130 -202 1.11 34 93.2 28.9 84 183.2 221 430 806 449 840 1544
-84.4 -120 -184 1.67 35 95.0 29.4 85 185.0 227 440 824 454 850 1562
-78.9 -110 -166 2.22 36 96.8 30.0 86 186.8 232 450 842 460 860 1580
-73.3 -100 -148 2.78 37 98.6 30.6 87 188.6 238 460 860 466 870 1598
-67.8 -90 -130 3.33 38 100.4 31.1 88 190.4 243 470 878 471 880 1616
-62.2 -80 -112 3.89 39 102.2 31.7 89 192.2 249 480 896 477 890 1634
-56.7 -70 -94 4.44 40 104.0 32.2 90 194.0 254 490 914 482 900 1652
-51.1 -60 -76 5.00 41 105.8 32.8 91 195.8 488 910 1670
-45.6 -50 -58 5.56 42 107.6 33.3 92 197.6 493 920 1688
-40.0 -40 -40 6.11 43 109.4 33.9 93 199.4 499 930 1706
-34.4 -30 -22 6.67 44 111.2 34.4 94 201.2 504 940 1724
-28.9 -20 4 7.22 45 113.0 35.0 95 203.0 510 950 1742
-23.3 -10 14 7.78 46 114.8 35.6 96 204.8 516 960 1760
-17.8 0 32 8.33 47 116.6 36.1 97 206.6 521 970 1778
8.89 48 118.4 36.7 98 208.4 527 980 1796
9.44 49 120.2 37.2 99 210.2 532 990 1814
37.8 100 212.0 538 1000 1832
1000 to 2000 2000 to 3000
Page 186
C. F. C. F. C. F. C. F.
538 1000 1832 816 1500 2732 1093 2000 3632 1371 2500 4534
543 1010 1850 821 1510 2750 1099 2010 3650 1377 2510 4552
549 1020 1868 827 1520 2768 1104 2020 3668 1382 2520 4560
554 1030 1886 832 1530 2786 1110 2030 3686 1388 2530 4588
560 1040 1904 838 1540 2804 1116 2040 3704 1393 2540 4606
566 1050 1922 843 1550 2822 1121 2050 3722 1399 2550 4622
571 1060 1940 849 1560 2840 1127 2060 3740 1404 2560 4640
577 1070 1958 854 1570 2858 1132 2070 3758 1410 2570 4658
582 1080 1976 860 1580 2876 1138 2080 3776 1416 2580 4676
588 1090 1994 866 1590 2894 1143 2090 3794 1421 2590 4694
593 1100 2012 871 1600 2912 1149 2100 3812 1427 2600 4712
599 1110 2030 877 1610 2930 1154 2110 3830 1432 2610 4730
604 1120 2048 882 1620 2948 1160 2120 3848 1438 2620 4748
610 1130 2066 888 1630 2966 1166 2130 3866 1443 2630 4766
616 1140 2084 893 1640 2984 1171 2140 3884 1449 2640 4784
621 1150 2102 899 1650 3002 1777 2150 3902 1454 2650 4802
627 1160 2120 904 1660 3020 1182 2160 3920 1460 2660 4820
632 1170 2138 910 1670 3038 1188 2170 3938 1466 2670 4838
638 1180 2156 916 1680 3056 1193 2180 3956 1471 2680 4854
643 1190 2174 921 1690 3074 1199 2190 3974 1477 2690 4876
649 1200 2192 927 1700 3092 1204 2200 3992 1482 2700 4892
654 1210 2210 932 1710 3110 1210 2210 4010 1488 2710 4910
660 1220 2228 938 1720 3128 1216 2220 4028 1493 2720 4928
666 1230 2246 943 1730 3146 1221 2230 4046 1499 2730 4946
671 1240 2264 949 1740 3164 1227 2240 4064 1504 2740 4964
677 1250 2282 954 1750 3182 1232 2250 4082 1510 2750 4982
682 1260 2300 960 1760 3200 1238 2260 4100 1516 2760 5000
688 1270 2318 966 1770 3218 1243 2270 4118 1521 2770 5018
693 1280 2336 971 1780 3236 1249 2280 4136 1527 2780 5036
699 1290 2354 977 1790 3254 1254 2290 4154 1532 2790 5054
704 1300 2372 982 1800 3272 1260 2300 4172 1538 2800 5072
710 1310 2390 988 1810 3290 1266 2310 4190 1543 2810 5090
716 1320 2408 993 1820 3308 1271 2320 4208 1549 2820 5108
721 1330 2426 999 1830 3326 1277 2330 4226 1554 2830 5126
727 1340 2444 1004 1840 3344 1282 2340 4244 1560 2840 5144
732 1350 2462 1010 1850 3362 1288 2350 4262 1566 2850 5162
738 1360 2480 1016 1860 3380 1293 2360 4280 1571 2860 5180
538 1000 1832 816 1500 2732 1093 2000 3632 1371 2500 4534
543 1010 1850 821 1510 2750 1099 2010 3650 1377 2510 4552
549 1020 1868 827 1520 2768 1104 2020 3668 1382 2520 4560
554 1030 1886 832 1530 2786 1110 2030 3686 1388 2530 4588
560 1040 1904 838 1540 2804 1116 2040 3704 1393 2540 4606
566 1050 1922 843 1550 2822 1121 2050 3722 1399 2550 4622
571 1060 1940 849 1560 2840 1127 2060 3740 1404 2560 4640
577 1070 1958 854 1570 2858 1132 2070 3758 1410 2570 4658
582 1080 1976 860 1580 2876 1138 2080 3776 1416 2580 4676
588 1090 1994 866 1590 2894 1143 2090 3794 1421 2590 4694
593 1100 2012 871 1600 2912 1149 2100 3812 1427 2600 4712
599 1110 2030 877 1610 2930 1154 2110 3830 1432 2610 4730
604 1120 2048 882 1620 2948 1160 2120 3848 1438 2620 4748
610 1130 2066 888 1630 2966 1166 2130 3866 1443 2630 4766
616 1140 2084 893 1640 2984 1171 2140 3884 1449 2640 4784
621 1150 2102 899 1650 3002 1777 2150 3902 1454 2650 4802
627 1160 2120 904 1660 3020 1182 2160 3920 1460 2660 4820
632 1170 2138 910 1670 3038 1188 2170 3938 1466 2670 4838
638 1180 2156 916 1680 3056 1193 2180 3956 1471 2680 4854
643 1190 2174 921 1690 3074 1199 2190 3974 1477 2690 4876
649 1200 2192 927 1700 3092 1204 2200 3992 1482 2700 4892
654 1210 2210 932 1710 3110 1210 2210 4010 1488 2710 4910
660 1220 2228 938 1720 3128 1216 2220 4028 1493 2720 4928
666 1230 2246 943 1730 3146 1221 2230 4046 1499 2730 4946
671 1240 2264 949 1740 3164 1227 2240 4064 1504 2740 4964
677 1250 2282 954 1750 3182 1232 2250 4082 1510 2750 4982
682 1260 2300 960 1760 3200 1238 2260 4100 1516 2760 5000
688 1270 2318 966 1770 3218 1243 2270 4118 1521 2770 5018
693 1280 2336 971 1780 3236 1249 2280 4136 1527 2780 5036
699 1290 2354 977 1790 3254 1254 2290 4154 1532 2790 5054
704 1300 2372 982 1800 3272 1260 2300 4172 1538 2800 5072
710 1310 2390 988 1810 3290 1266 2310 4190 1543 2810 5090
716 1320 2408 993 1820 3308 1271 2320 4208 1549 2820 5108
721 1330 2426 999 1830 3326 1277 2330 4226 1554 2830 5126
727 1340 2444 1004 1840 3344 1282 2340 4244 1560 2840 5144
732 1350 2462 1010 1850 3362 1288 2350 4262 1566 2850 5162
738 1360 2480 1016 1860 3380 1293 2360 4280 1571 2860 5180
Page 187
743 1370 2498 1021 1870 3398 1299 2370 4298 1577 2870 5198
749 1380 2516 1027 1880 3416 1304 2380 4316 1582 2880 5216
754 1390 2534 1032 1890 3434 1310 2390 4334 1588 2890 5234
760 1400 2552 1038 1900 3452 1316 2400 4352 1593 2900 5252
766 1410 2570 1043 1910 3470 1321 2410 4370 1599 2910 5270
771 1420 2588 1049 1920 3488 1327 2420 4388 1604 2920 5288
777 1430 2606 1054 1930 3506 1332 2430 4406 1610 2930 5306
782 1440 2624 1060 1940 3524 1338 2440 4424 1616 2940 5324
788 1450 2642 1066 1950 3542 1343 2450 4442 1621 2950 5342
793 1460 2660 1071 1960 3560 1349 2460 4460 1627 2960 5360
799 1470 2678 1077 1970 3578 1354 2470 4478 1632 2970 5378
804 1480 2696 1082 1980 3596 1360 2480 4496 1638 2980 5396
810 1490 2714 1088 1990 3614 1366 2490 4514 1643 2990 5414
1093 2000 3632 1649 3000 5432
NOTE.—The numbers in bold face type refer to the INTERPOLATION
temperature either in degrees Centigrade or Fahrenheit FACTORS
which it is desired to convert into the other scale. If C. F. C. F.
converting from Fahrenheit degrees to Centigrade 0.56 1 1.8 3.33 6 10.8
degrees the equivalent temperature will be found in the 1.11 2 3.6 3.89 7 12.6
left column, while if converting from degrees 1.67 3 5.4 4.44 8 14.4
Centigrade to degrees Fahrenheit, the answer will be 2.22 4 7.2 5.00 9 16.2
found in the column on the right. These tables are a
2.78 5 9.0 5.56 10 18.0
revision of those by Sauveur & Boylston, metallurgical
engineers, Cambridge, Mass. Copyright, 1920.
Those using pyrometers will find this and the preceding conversion table of great
convenience:
TABLE 33.—COMPARISON BETWEEN DEGREES CENTIGRADE AND
DEGREES FAHRENHEIT
Degrees Degrees Degrees Degrees Degrees Degrees Degrees
F. C. F. C. F. C. F. C. F. C. F. C. F. C.
-40 -40.0 3 -16.1 46 7.7 89 31.6 132 55.5 175 79.4 275 135.0
-39 -39.4 4 -15.5 47 8.3 90 32.2 133 56.1 176 80.0 300 148.8
-38 -38.8 5 -15.0 48 8.8 91 32.7 134 56.6 177 80.5 325 162.7
-37 -38.3 6 -14.4 49 9.3 92 33.3 135 57.2 178 81.1 350 176.6
-36 -37.7 7 -13.8 50 10.0 93 33.9 136 57.7 179 81.6 375 190.5
-35 -37.2 8 -13.3 51 10.5 94 34.4 137 58.3 180 82.2 400 204.4
749 1380 2516 1027 1880 3416 1304 2380 4316 1582 2880 5216
754 1390 2534 1032 1890 3434 1310 2390 4334 1588 2890 5234
760 1400 2552 1038 1900 3452 1316 2400 4352 1593 2900 5252
766 1410 2570 1043 1910 3470 1321 2410 4370 1599 2910 5270
771 1420 2588 1049 1920 3488 1327 2420 4388 1604 2920 5288
777 1430 2606 1054 1930 3506 1332 2430 4406 1610 2930 5306
782 1440 2624 1060 1940 3524 1338 2440 4424 1616 2940 5324
788 1450 2642 1066 1950 3542 1343 2450 4442 1621 2950 5342
793 1460 2660 1071 1960 3560 1349 2460 4460 1627 2960 5360
799 1470 2678 1077 1970 3578 1354 2470 4478 1632 2970 5378
804 1480 2696 1082 1980 3596 1360 2480 4496 1638 2980 5396
810 1490 2714 1088 1990 3614 1366 2490 4514 1643 2990 5414
1093 2000 3632 1649 3000 5432
NOTE.—The numbers in bold face type refer to the INTERPOLATION
temperature either in degrees Centigrade or Fahrenheit FACTORS
which it is desired to convert into the other scale. If C. F. C. F.
converting from Fahrenheit degrees to Centigrade 0.56 1 1.8 3.33 6 10.8
degrees the equivalent temperature will be found in the 1.11 2 3.6 3.89 7 12.6
left column, while if converting from degrees 1.67 3 5.4 4.44 8 14.4
Centigrade to degrees Fahrenheit, the answer will be 2.22 4 7.2 5.00 9 16.2
found in the column on the right. These tables are a
2.78 5 9.0 5.56 10 18.0
revision of those by Sauveur & Boylston, metallurgical
engineers, Cambridge, Mass. Copyright, 1920.
Those using pyrometers will find this and the preceding conversion table of great
convenience:
TABLE 33.—COMPARISON BETWEEN DEGREES CENTIGRADE AND
DEGREES FAHRENHEIT
Degrees Degrees Degrees Degrees Degrees Degrees Degrees
F. C. F. C. F. C. F. C. F. C. F. C. F. C.
-40 -40.0 3 -16.1 46 7.7 89 31.6 132 55.5 175 79.4 275 135.0
-39 -39.4 4 -15.5 47 8.3 90 32.2 133 56.1 176 80.0 300 148.8
-38 -38.8 5 -15.0 48 8.8 91 32.7 134 56.6 177 80.5 325 162.7
-37 -38.3 6 -14.4 49 9.3 92 33.3 135 57.2 178 81.1 350 176.6
-36 -37.7 7 -13.8 50 10.0 93 33.9 136 57.7 179 81.6 375 190.5
-35 -37.2 8 -13.3 51 10.5 94 34.4 137 58.3 180 82.2 400 204.4
Page 188
-34 -36.6 9 -12.7 52 11.1 95 35.0 138 58.8 181 82.7 425 218.3
-33 -36.1 10 -12.2 53 11.6 96 35.5 139 59.4 182 83.3 450 232.2
-32 -35.5 11 -11.6 54 12.2 97 36.1 140 60.0 183 83.8 475 246.1
-31 -35.0 12 -11.1 55 12.7 98 36.6 141 60.5 184 84.4 500 260.0
-30 -34.4 13 -10.5 56 13.3 99 37.2 142 61.1 185 85.0 525 273.8
-29 -33.9 14 -10.0 57 13.8 100 37.7 143 61.6 186 85.5 550 287.7
-28 -33.3 15 -9.3 58 14.4 101 38.3 144 62.2 187 86.1 575 301.6
-27 -32.7 16 -8.8 59 15.0 102 38.8 145 62.7 188 86.6 600 315.5
-26 -32.2 17 -8.3 60 15.5 103 39.4 146 63.3 189 87.2 625 329.4
-25 -31.6 18 -7.7 61 16.1 104 40.0 147 63.8 190 87.7 650 343.3
-24 -31.1 19 -7.2 62 16.6 105 40.5 148 64.4 191 88.3 675 357.2
-23 -30.5 20 -6.6 63 17.2 106 41.1 149 65.0 192 88.8 700 371.1
-22 -30.0 21 -6.1 64 17.7 107 41.6 150 65.5 193 89.4 725 385.0
-21 -29.4 22 -5.5 65 18.3 108 42.2 151 66.1 194 90.0 750 398.8
-20 -28.8 23 -5.0 66 18.8 109 42.7 152 66.6 195 90.5 775 412.7
-19 -28.3 24 -4.4 67 19.4 110 43.3 153 67.2 196 91.1 800 426.6
-18 -27.7 25 -3.8 68 20.0 111 43.8 154 67.7 197 91.6 825 440.5
-17 -27.2 26 -3.3 69 20.5 112 44.4 155 68.3 198 92.2 850 454.4
-16 -26.6 27 -2.7 70 21.1 113 45.0 156 68.8 199 92.7 875 468.3
-15 -26.1 28 -2.2 71 21.6 114 45.5 157 69.4 200 93.3 900 482.2
-14 -25.5 29 -1.6 72 22.2 115 46.1 158 70.0 201 93.8 925 496.1
-13 -25.0 30 -1.1 73 22.7 116 46.6 159 70.5 202 94.4 950 510.0
-12 -24.4 31 -0.5 74 23.3 117 47.2 160 71.1 203 95.0 975 523.8
-11 -23.8 32 -0.0 75 23.8 118 47.7 161 71.6 204 95.5 1,000 537.7
-10 -23.3 33 +0.5 76 24.4 119 48.3 162 72.2 205 96.1 1,100 593.3
-9 -22.7 34 1.1 77 25.0 120 48.8 163 72.7 206 96.6 1,200 648.8
-8 -22.2 35 1.6 78 25.5 121 49.4 164 73.3 207 97.2 1,300 704.4
-7 -21.6 36 2.2 79 26.1 122 50.0 165 73.8 208 97.7 1,400 760.0
-6 -21.1 37 2.7 80 26.6 123 50.5 166 74.4 209 98.3 1,500 815.5
-5 -20.5 38 3.3 81 27.2 124 51.1 167 75.0 210 98.8 1,600 871.1
-4 -20.0 39 3.8 82 27.7 125 51.6 168 75.5 211 99.4 1,700 926.6
-3 -19.4 40 4.4 83 28.3 126 52.2 169 76.1 212 100.0 1,800 982.2
-2 -18.8 41 5.0 84 28.8 127 52.7 170 76.6 213 100.5 1,900 1,037.7
-1 -18.3 42 5.5 85 29.4 128 53.3 171 77.2 214 101.1 2,000 1,093.3
0 -17.7 43 6.1 86 30.0 129 53.8 172 77.7 215 101.6 2,100 1,148.8
+1 -17.2 44 6.6 87 30.5 130 54.4 173 78.3 225 107.2 2,200 1,204.4
2 -16.6 45 7.2 88 31.1 131 55.0 174 78.8 250 121.1 2,300 1,260.0
-33 -36.1 10 -12.2 53 11.6 96 35.5 139 59.4 182 83.3 450 232.2
-32 -35.5 11 -11.6 54 12.2 97 36.1 140 60.0 183 83.8 475 246.1
-31 -35.0 12 -11.1 55 12.7 98 36.6 141 60.5 184 84.4 500 260.0
-30 -34.4 13 -10.5 56 13.3 99 37.2 142 61.1 185 85.0 525 273.8
-29 -33.9 14 -10.0 57 13.8 100 37.7 143 61.6 186 85.5 550 287.7
-28 -33.3 15 -9.3 58 14.4 101 38.3 144 62.2 187 86.1 575 301.6
-27 -32.7 16 -8.8 59 15.0 102 38.8 145 62.7 188 86.6 600 315.5
-26 -32.2 17 -8.3 60 15.5 103 39.4 146 63.3 189 87.2 625 329.4
-25 -31.6 18 -7.7 61 16.1 104 40.0 147 63.8 190 87.7 650 343.3
-24 -31.1 19 -7.2 62 16.6 105 40.5 148 64.4 191 88.3 675 357.2
-23 -30.5 20 -6.6 63 17.2 106 41.1 149 65.0 192 88.8 700 371.1
-22 -30.0 21 -6.1 64 17.7 107 41.6 150 65.5 193 89.4 725 385.0
-21 -29.4 22 -5.5 65 18.3 108 42.2 151 66.1 194 90.0 750 398.8
-20 -28.8 23 -5.0 66 18.8 109 42.7 152 66.6 195 90.5 775 412.7
-19 -28.3 24 -4.4 67 19.4 110 43.3 153 67.2 196 91.1 800 426.6
-18 -27.7 25 -3.8 68 20.0 111 43.8 154 67.7 197 91.6 825 440.5
-17 -27.2 26 -3.3 69 20.5 112 44.4 155 68.3 198 92.2 850 454.4
-16 -26.6 27 -2.7 70 21.1 113 45.0 156 68.8 199 92.7 875 468.3
-15 -26.1 28 -2.2 71 21.6 114 45.5 157 69.4 200 93.3 900 482.2
-14 -25.5 29 -1.6 72 22.2 115 46.1 158 70.0 201 93.8 925 496.1
-13 -25.0 30 -1.1 73 22.7 116 46.6 159 70.5 202 94.4 950 510.0
-12 -24.4 31 -0.5 74 23.3 117 47.2 160 71.1 203 95.0 975 523.8
-11 -23.8 32 -0.0 75 23.8 118 47.7 161 71.6 204 95.5 1,000 537.7
-10 -23.3 33 +0.5 76 24.4 119 48.3 162 72.2 205 96.1 1,100 593.3
-9 -22.7 34 1.1 77 25.0 120 48.8 163 72.7 206 96.6 1,200 648.8
-8 -22.2 35 1.6 78 25.5 121 49.4 164 73.3 207 97.2 1,300 704.4
-7 -21.6 36 2.2 79 26.1 122 50.0 165 73.8 208 97.7 1,400 760.0
-6 -21.1 37 2.7 80 26.6 123 50.5 166 74.4 209 98.3 1,500 815.5
-5 -20.5 38 3.3 81 27.2 124 51.1 167 75.0 210 98.8 1,600 871.1
-4 -20.0 39 3.8 82 27.7 125 51.6 168 75.5 211 99.4 1,700 926.6
-3 -19.4 40 4.4 83 28.3 126 52.2 169 76.1 212 100.0 1,800 982.2
-2 -18.8 41 5.0 84 28.8 127 52.7 170 76.6 213 100.5 1,900 1,037.7
-1 -18.3 42 5.5 85 29.4 128 53.3 171 77.2 214 101.1 2,000 1,093.3
0 -17.7 43 6.1 86 30.0 129 53.8 172 77.7 215 101.6 2,100 1,148.8
+1 -17.2 44 6.6 87 30.5 130 54.4 173 78.3 225 107.2 2,200 1,204.4
2 -16.6 45 7.2 88 31.1 131 55.0 174 78.8 250 121.1 2,300 1,260.0
Page 189
9 x degrees C.
Degrees Fahrenheit = + 32
5
5 x (degrees F. - 32)
Degrees Centigrade =
9
Three other useful tables are also given on the following pages.
TABLE 34.—WEIGHT OF ROUND, OCTAGON AND SQUARE
CARBON TOOL STEEL PER FOOT
Size Size
in Round Octagon Square in Round Octagon Square
inches inches
1/16 0.010 0.011 0.013 2-1/2 16.79 17.71 21.37
1/8 0.042 0.044 0.053 2-5/8 18.51 19.52 23.56
3/16 0.094 0.099 0.120 2-3/4 20.31 21.42 25.86
1/4 0.168 0.177 0.214 2-7/8 22.20 23.41 28.27
5/16 0.262 0.277 0.334 3 24.17 25.50 30.78
3/8 0.378 0.398 0.481 3-1/8 26.23 27.66 33.40
7/16 0.514 0.542 0.655 3-1/4 28.37 29.92 36.12
1/2 0.671 0.708 0.855 3-3/8 30.59 32.27 38.95
9/16 0.850 0.896 1.082 3-1/2 32.90 34.70 41.89
5/8 1.049 1.107 1.336 3-5/8 35.29 37.23 44.94
11/16 1.270 1.339 1.616 3-3/4 37.77 39.84 48.09
3/4 1.511 1.594 1.924 3-7/8 40.33 42.54 51.35
13/16 1.773 1.870 2.258 4 42.97 45.34 54.72
7/8 2.056 2.169 2.618 4-1/4 48.51 51.17 61.77
15/16 2.361 2.490 3.006 4-1/2 54.39 57.37 69.25
1 2.686 2.833 3.420 4-3/4 60.60 63.92 77.16
1-1/8 3.399 3.585 4.328 5 67.15 70.83 85.50
1-1/4 4.197 4.427 5.344 5-1/4 74.03 78.08 94.26
1-3/8 5.078 5.356 6.646 5-1/2 81.25 85.70 103.45
1-1/2 6.044 6.374 7.695 5-3/4 88.80 93.67 113.07
1-5/8 7.093 7.481 9.031 6 96.69 101.99 123.12
1-3/4 8.226 8.674 10.474 7 131.61 138.82 167.58
1-7/8 9.443 9.960 12.023 8 171.90 181.32 218.88
2 10.744 11.332 13.680 9 217.57 229.48 277.02
2-1/8 12.129 12.793 15.443 10 268.60 283.31 342.00
2-1/4 13.598 14.343 17.314 11 325.01 342.80 413.82
Degrees Fahrenheit = + 32
5
5 x (degrees F. - 32)
Degrees Centigrade =
9
Three other useful tables are also given on the following pages.
TABLE 34.—WEIGHT OF ROUND, OCTAGON AND SQUARE
CARBON TOOL STEEL PER FOOT
Size Size
in Round Octagon Square in Round Octagon Square
inches inches
1/16 0.010 0.011 0.013 2-1/2 16.79 17.71 21.37
1/8 0.042 0.044 0.053 2-5/8 18.51 19.52 23.56
3/16 0.094 0.099 0.120 2-3/4 20.31 21.42 25.86
1/4 0.168 0.177 0.214 2-7/8 22.20 23.41 28.27
5/16 0.262 0.277 0.334 3 24.17 25.50 30.78
3/8 0.378 0.398 0.481 3-1/8 26.23 27.66 33.40
7/16 0.514 0.542 0.655 3-1/4 28.37 29.92 36.12
1/2 0.671 0.708 0.855 3-3/8 30.59 32.27 38.95
9/16 0.850 0.896 1.082 3-1/2 32.90 34.70 41.89
5/8 1.049 1.107 1.336 3-5/8 35.29 37.23 44.94
11/16 1.270 1.339 1.616 3-3/4 37.77 39.84 48.09
3/4 1.511 1.594 1.924 3-7/8 40.33 42.54 51.35
13/16 1.773 1.870 2.258 4 42.97 45.34 54.72
7/8 2.056 2.169 2.618 4-1/4 48.51 51.17 61.77
15/16 2.361 2.490 3.006 4-1/2 54.39 57.37 69.25
1 2.686 2.833 3.420 4-3/4 60.60 63.92 77.16
1-1/8 3.399 3.585 4.328 5 67.15 70.83 85.50
1-1/4 4.197 4.427 5.344 5-1/4 74.03 78.08 94.26
1-3/8 5.078 5.356 6.646 5-1/2 81.25 85.70 103.45
1-1/2 6.044 6.374 7.695 5-3/4 88.80 93.67 113.07
1-5/8 7.093 7.481 9.031 6 96.69 101.99 123.12
1-3/4 8.226 8.674 10.474 7 131.61 138.82 167.58
1-7/8 9.443 9.960 12.023 8 171.90 181.32 218.88
2 10.744 11.332 13.680 9 217.57 229.48 277.02
2-1/8 12.129 12.793 15.443 10 268.60 283.31 342.00
2-1/4 13.598 14.343 17.314 11 325.01 342.80 413.82
Page 190
2-3/8 15.151 15.981 19.291 12 386.79 407.97 492.48
High-speed steel, being more dense than carbon steel, weighs from 10 to 11 per
cent more than carbon steel. This should be added to figures given in the table.
TABLE 35.—WEIGHT OF ROUND, CARBON TOOL STEEL
12 IN. IN DIAMETER AND LARGER, PER FOOT
Diameter, Weight Diameter, Weight Diameter, Weight
inches per foot inches per foot inches per foot
12 386.790 15-7/8 677.527 19-3/4 1,049.010
12-1/8 395.518 16 687.600 19-7/8 1,061.705
12-1/4 404.246 16-1/8 699.017 20 1,074.400
12-3/8 412.974 16-1/4 710.435 20-1/8 1,088.502
12-1/2 421.702 16-3/8 721.852 20-1/4 1,102.605
12-5/8 430.430 16-1/2 733.270 20-3/8 1,116.707
12-3/4 439.158 16-5/8 744.687 20-1/2 1,130.810
12-7/8 447.886 16-3/4 756.105 20-5/8 1,144.912
13 456.615 16-7/8 767.522 20-3/4 1,159.015
13-1/8 465.343 17 778.940 20-7/8 1,173.118
13-1/4 474.071 17-1/8 790.358 21 1,187.220
13-3/8 482.799 17-1/4 801.777 21-1/8 1,201.322
13-1/2 491.527 17-3/8 813.195 21-1/4 1,215.425
13-5/8 500.255 17-1/2 824.614 21-3/8 1,229.527
13-3/4 508.983 17-5/8 836.030 21-1/2 1,243.630
13-7/8 517.711 17-3/4 847.447 21-5/8 1,257.732
14 526.440 17-7/8 858.863 21-3/4 1,271.835
14-1/8 536.512 18 870.280 21-7/8 1,285.937
14-1/4 546.585 18-1/8 883.105 22 1,300.040
14-3/8 556.657 18-1/4 895.920 22-1/8 1,315.485
14-1/2 566.730 18-3/8 908.740 22-1/4 1,330.930
14-5/8 576.802 18-1/2 921.560 22-3/8 1,346.375
14-3/4 586.875 18-5/8 934.380 22-1/2 1,361.820
14-7/8 596.947 18-3/4 947.200 22-5/8 1,377.265
15 607.020 18-7/8 960.020 22-3/4 1,392.710
15-1/8 617.092 19 972.840 22-7/8 1,408.155
15-1/4 627.165 19-1/8 985.035 23 1,423.600
15-3/8 637.237 19-1/4 998.230 23-1/8 1,454.490
15-1/2 647.310 19-3/8 1,010.925 23-1/4 1,485.380
15-5/8 657.382 19-1/2 1,023.620 23-3/8 1,516.270
High-speed steel, being more dense than carbon steel, weighs from 10 to 11 per
cent more than carbon steel. This should be added to figures given in the table.
TABLE 35.—WEIGHT OF ROUND, CARBON TOOL STEEL
12 IN. IN DIAMETER AND LARGER, PER FOOT
Diameter, Weight Diameter, Weight Diameter, Weight
inches per foot inches per foot inches per foot
12 386.790 15-7/8 677.527 19-3/4 1,049.010
12-1/8 395.518 16 687.600 19-7/8 1,061.705
12-1/4 404.246 16-1/8 699.017 20 1,074.400
12-3/8 412.974 16-1/4 710.435 20-1/8 1,088.502
12-1/2 421.702 16-3/8 721.852 20-1/4 1,102.605
12-5/8 430.430 16-1/2 733.270 20-3/8 1,116.707
12-3/4 439.158 16-5/8 744.687 20-1/2 1,130.810
12-7/8 447.886 16-3/4 756.105 20-5/8 1,144.912
13 456.615 16-7/8 767.522 20-3/4 1,159.015
13-1/8 465.343 17 778.940 20-7/8 1,173.118
13-1/4 474.071 17-1/8 790.358 21 1,187.220
13-3/8 482.799 17-1/4 801.777 21-1/8 1,201.322
13-1/2 491.527 17-3/8 813.195 21-1/4 1,215.425
13-5/8 500.255 17-1/2 824.614 21-3/8 1,229.527
13-3/4 508.983 17-5/8 836.030 21-1/2 1,243.630
13-7/8 517.711 17-3/4 847.447 21-5/8 1,257.732
14 526.440 17-7/8 858.863 21-3/4 1,271.835
14-1/8 536.512 18 870.280 21-7/8 1,285.937
14-1/4 546.585 18-1/8 883.105 22 1,300.040
14-3/8 556.657 18-1/4 895.920 22-1/8 1,315.485
14-1/2 566.730 18-3/8 908.740 22-1/4 1,330.930
14-5/8 576.802 18-1/2 921.560 22-3/8 1,346.375
14-3/4 586.875 18-5/8 934.380 22-1/2 1,361.820
14-7/8 596.947 18-3/4 947.200 22-5/8 1,377.265
15 607.020 18-7/8 960.020 22-3/4 1,392.710
15-1/8 617.092 19 972.840 22-7/8 1,408.155
15-1/4 627.165 19-1/8 985.035 23 1,423.600
15-3/8 637.237 19-1/4 998.230 23-1/8 1,454.490
15-1/2 647.310 19-3/8 1,010.925 23-1/4 1,485.380
15-5/8 657.382 19-1/2 1,023.620 23-3/8 1,516.270
Page 191
15-3/4 667.455 19-5/8 1,036.315 24 1,547.160
To find the weight of discs made of carbon steel, in diameters up to and including
12 in., without any allowance for finishing multiply the per foot weight of round bar
steel, shown herewith by the decimal equivalent of a foot given in the following
table:
TABLE 36.—DECIMAL EQUIVALENTS OF A FOOT
In. 0 1/8 1/4 3/8 1/2 5/8 3/4 7/8
0 0.000 0.010 0.021 0.031 0.042 0.052 0.063 0.073
1 0.083 0.094 0.104 0.115 0.125 0.135 0.146 0.156
2 0.167 0.177 0.188 0.198 0.208 0.219 0.229 0.240
3 0.250 0.260 0.270 0.281 0.292 0.302 0.313 0.323
4 0.333 0.344 0.354 0.364 0.375 0.385 0.396 0.406
5 0.416 0.427 0.437 0.448 0.458 0.469 0.479 0.480
6 0.500 0.510 0.520 0.531 0.542 0.552 0.563 0.573
7 0.583 0.594 0.604 0.615 0.625 0.635 0.646 0.656
8 0.666 0.677 0.687 0.698 0.708 0.719 0.729 0.740
9 0.750 0.760 0.770 0.781 0.792 0.802 0.813 0.823
10 0.833 0.844 0.854 0.865 0.875 0.885 0.896 0.906
11 0.916 0.927 0.937 0.948 0.953 0.969 0.979 0.990
EXAMPLE.—If the weight of a carbon steel disc 7 in. diameter, 1-5/8 in. thick is
desired, turn to page 233, where the per foot weight of 7 in. round is given as 131.6
lb. Multiply this by the decimal equivalent of 1-5/8 in., or 0.135, as shown in the
above table, and the product will be the net weight of the disc.
131.61 lb. = the weight of 1 ft. of 7 in. round.
0.135 = the per foot decimal equivalent of 1-5/8 in:
65805
39483
13161
17.76735 lb. = weight of disc 7 in. diam. 1-5/8 in. thick without any
allowance for finishing.
To find the weight of discs made of carbon steel, in diameters up to and including
12 in., without any allowance for finishing multiply the per foot weight of round bar
steel, shown herewith by the decimal equivalent of a foot given in the following
table:
TABLE 36.—DECIMAL EQUIVALENTS OF A FOOT
In. 0 1/8 1/4 3/8 1/2 5/8 3/4 7/8
0 0.000 0.010 0.021 0.031 0.042 0.052 0.063 0.073
1 0.083 0.094 0.104 0.115 0.125 0.135 0.146 0.156
2 0.167 0.177 0.188 0.198 0.208 0.219 0.229 0.240
3 0.250 0.260 0.270 0.281 0.292 0.302 0.313 0.323
4 0.333 0.344 0.354 0.364 0.375 0.385 0.396 0.406
5 0.416 0.427 0.437 0.448 0.458 0.469 0.479 0.480
6 0.500 0.510 0.520 0.531 0.542 0.552 0.563 0.573
7 0.583 0.594 0.604 0.615 0.625 0.635 0.646 0.656
8 0.666 0.677 0.687 0.698 0.708 0.719 0.729 0.740
9 0.750 0.760 0.770 0.781 0.792 0.802 0.813 0.823
10 0.833 0.844 0.854 0.865 0.875 0.885 0.896 0.906
11 0.916 0.927 0.937 0.948 0.953 0.969 0.979 0.990
EXAMPLE.—If the weight of a carbon steel disc 7 in. diameter, 1-5/8 in. thick is
desired, turn to page 233, where the per foot weight of 7 in. round is given as 131.6
lb. Multiply this by the decimal equivalent of 1-5/8 in., or 0.135, as shown in the
above table, and the product will be the net weight of the disc.
131.61 lb. = the weight of 1 ft. of 7 in. round.
0.135 = the per foot decimal equivalent of 1-5/8 in:
65805
39483
13161
17.76735 lb. = weight of disc 7 in. diam. 1-5/8 in. thick without any
allowance for finishing.
Page 192
AUTHORITES QUOTED
A
ADDIS, W H., 102
AMERICAN MACHINISTS' HANDBOOK, 69
AMERICAN STEEL TREARERS' SOCIETY, 119
AMERICAN GEAR MFRS. ASSO., 115
AUTOMATIC AND ELECTRIC FURNACES LTD., 161
ARNOLD, PROF. J. O., 167
B
BURLEIGH, R. W.
BORDEN, B.
BOKER, HERMAN & Co.
BROWN INSTRUMENT Co., 224
BROWN-LIPE-CHAPLIN Co., 121
C
CAMPBELL, H. H.
CARHART, H. A., 42
CLAYTON, C. Y., 112
CURTIS AIRPLANE Co.
E
ENGLEHARD, CHARLES, 227
ENSAW, HOWARD, 79, 95
F
FIRTH-STERLING STEEL Co., 176
FIRTH, THOMAS & SONS, 137
FOWLER, HENRY, 151
G
GILBERT & BARKER, 164, 188
H
HAYWAHD, C. R., 35
HOWE, DR. H. M., 8, 108
HOOVER STEEL BALL CO., 61
HEATHCOTE, H. L., 85
A
ADDIS, W H., 102
AMERICAN MACHINISTS' HANDBOOK, 69
AMERICAN STEEL TREARERS' SOCIETY, 119
AMERICAN GEAR MFRS. ASSO., 115
AUTOMATIC AND ELECTRIC FURNACES LTD., 161
ARNOLD, PROF. J. O., 167
B
BURLEIGH, R. W.
BORDEN, B.
BOKER, HERMAN & Co.
BROWN INSTRUMENT Co., 224
BROWN-LIPE-CHAPLIN Co., 121
C
CAMPBELL, H. H.
CARHART, H. A., 42
CLAYTON, C. Y., 112
CURTIS AIRPLANE Co.
E
ENGLEHARD, CHARLES, 227
ENSAW, HOWARD, 79, 95
F
FIRTH-STERLING STEEL Co., 176
FIRTH, THOMAS & SONS, 137
FOWLER, HENRY, 151
G
GILBERT & BARKER, 164, 188
H
HAYWAHD, C. R., 35
HOWE, DR. H. M., 8, 108
HOOVER STEEL BALL CO., 61
HEATHCOTE, H. L., 85
Page 193
HARRIS, MATTHEW, 94
HUNTER, J. V., 192
J
JANITZKY, E. J., 119
JOHNSTON, A. B., 35
JUTHE, K. A., 1, 24, 65, 75, 79, 105, 145
L
LATROBE STEEL CO., 150, 178
LUDLUM STEEL CO., 175
LEEDS & NORTHRUP CO., 211
LYMAN, W. H., 199
M
MANSFIELD, C. A.
MIDVALE STEEL Co.
McKENNA, ROY C., 164
MOULTON, SETH A., 199
N
NILES, BEMENT, POND, 67
P
PARKER, S. W.
POOLE, C. R.
R
RAWDON, H. S., 110, 113
S
S. A. E. (SOCIETY AUTOMOTIVE ENGINEERS), 39, 46, 49, 134
SAUVEUR, ALBERT, 105, 232
SPRINGFIELD ARMORY, 78
SELLACK, T. G.
SMITH, A. J., 101
SHIRLEY, ALFRED J.
T
TAYLOR INSTRUMENT Co., 215
THUM, E. E., 12-23; 105-121.
TIEMANN, H. P., 11
U
U. S. BALL BEARING Co.
UNITED STEEL Co.
UNDERWOOD, CHARLES N.
V
HUNTER, J. V., 192
J
JANITZKY, E. J., 119
JOHNSTON, A. B., 35
JUTHE, K. A., 1, 24, 65, 75, 79, 105, 145
L
LATROBE STEEL CO., 150, 178
LUDLUM STEEL CO., 175
LEEDS & NORTHRUP CO., 211
LYMAN, W. H., 199
M
MANSFIELD, C. A.
MIDVALE STEEL Co.
McKENNA, ROY C., 164
MOULTON, SETH A., 199
N
NILES, BEMENT, POND, 67
P
PARKER, S. W.
POOLE, C. R.
R
RAWDON, H. S., 110, 113
S
S. A. E. (SOCIETY AUTOMOTIVE ENGINEERS), 39, 46, 49, 134
SAUVEUR, ALBERT, 105, 232
SPRINGFIELD ARMORY, 78
SELLACK, T. G.
SMITH, A. J., 101
SHIRLEY, ALFRED J.
T
TAYLOR INSTRUMENT Co., 215
THUM, E. E., 12-23; 105-121.
TIEMANN, H. P., 11
U
U. S. BALL BEARING Co.
UNITED STEEL Co.
UNDERWOOD, CHARLES N.
V
Page 194
VAN DE VENTER, JOHN H., 86
W
WALP, H. O., 109
WOOD, HAROLD F., 46
WHEELOCK, LOVEJOY & Co., 69
W
WALP, H. O., 109
WOOD, HAROLD F., 46
WHEELOCK, LOVEJOY & Co., 69
Page 195
INDEX
A
ABC of iron and steel, ix
Absorption of carbon, rate of, 83
Air hardening steels, 183
Analysis of high speed steel, 165
Allotropic modifications, 107
Alloy steel, annealing, 76
properties of, 34
Alloys and their effect, 16, 24
in high speed steel, 166
in steel, value of, 16, 24
upon steel, 24
Alpha iron, 106
Annealing, 113, 115
care in, 154, 155
furnace, 190
high-chromium steel, 36
high speed tools, 174
in bone, 77
methods, 122
proper, 117
rifle components, 78
rust-proof steel, 36
steels, 75
temperature, 119
Arrests, 106
Austentite, 108, 111
Automotive industry, application of Liberty engine materials to, 46
temperature control, 225
Axles, heat treatment of, 61
B
Balls, making steel, 61
Barium chloride process, 178
Baths for tempering, 157
Bessemer converter, 2
Beta iron, 106
Blending compounds, 103
Blister steel, 81
Blue brittleness, 56
Bone, annealing in, 77
Boxes for case hardening or carburizing, 80
Breaking test gears, 126
A
ABC of iron and steel, ix
Absorption of carbon, rate of, 83
Air hardening steels, 183
Analysis of high speed steel, 165
Allotropic modifications, 107
Alloy steel, annealing, 76
properties of, 34
Alloys and their effect, 16, 24
in high speed steel, 166
in steel, value of, 16, 24
upon steel, 24
Alpha iron, 106
Annealing, 113, 115
care in, 154, 155
furnace, 190
high-chromium steel, 36
high speed tools, 174
in bone, 77
methods, 122
proper, 117
rifle components, 78
rust-proof steel, 36
steels, 75
temperature, 119
Arrests, 106
Austentite, 108, 111
Automotive industry, application of Liberty engine materials to, 46
temperature control, 225
Axles, heat treatment of, 61
B
Balls, making steel, 61
Barium chloride process, 178
Baths for tempering, 157
Bessemer converter, 2
Beta iron, 106
Blending compounds, 103
Blister steel, 81
Blue brittleness, 56
Bone, annealing in, 77
Boxes for case hardening or carburizing, 80
Breaking test gears, 126
Page 196
Brinell hardness, 22
Broach hardening furnace, 188
Brown automatic pyrometer, 224
Burning, 65
C
Calorized tubes, 229
Carbon, 13
content at various temperatures, 84
content of case hardened work, 81
in cast iron, ix
in tool steel, 149-150
introduction of, 96
penetration of, 95
steel, 11
steel forgings, Liberty engine, 48
steel tools, 145
steels, S. A. E., 10, 39
steels, temper colors, 163
strengthens iron, 13
tool steel, forging, 65
Carbonizing, see Carburizing
Carborundum tubes, 229
Carburization, preventing, 93
Carburizing by gas, 88, 93
boxes, 80
compounds, 88, 102
gas consumption by, 101
local, 94
material, 85
nickel steel, 125
or case hardening, 79
pots for, 123
Carburizing, process of, ix, 83, 116
short method, 124
sleeves, 132
with charcoal, 81, 88
See Case hardening
Car door type of furnace, 190
Case, depth of, 86
Case hardening boxes, 80
cast iron, 89
local, 94
or surface carburizing, 79
treatments for various steels, 92
see Carburizing
Cast iron, carbon in, ix
case hardening, 89
Cementite, ix, 14
Center column furnace, 186
Centigrade table, 232-234
Chamotte tubes, 228
Chart of carbon penetration, 97
heat treatment, 151
shape, 151
Broach hardening furnace, 188
Brown automatic pyrometer, 224
Burning, 65
C
Calorized tubes, 229
Carbon, 13
content at various temperatures, 84
content of case hardened work, 81
in cast iron, ix
in tool steel, 149-150
introduction of, 96
penetration of, 95
steel, 11
steel forgings, Liberty engine, 48
steel tools, 145
steels, S. A. E., 10, 39
steels, temper colors, 163
strengthens iron, 13
tool steel, forging, 65
Carbonizing, see Carburizing
Carborundum tubes, 229
Carburization, preventing, 93
Carburizing by gas, 88, 93
boxes, 80
compounds, 88, 102
gas consumption by, 101
local, 94
material, 85
nickel steel, 125
or case hardening, 79
pots for, 123
Carburizing, process of, ix, 83, 116
short method, 124
sleeves, 132
with charcoal, 81, 88
See Case hardening
Car door type of furnace, 190
Case, depth of, 86
Case hardening boxes, 80
cast iron, 89
local, 94
or surface carburizing, 79
treatments for various steels, 92
see Carburizing
Cast iron, carbon in, ix
case hardening, 89
Cementite, ix, 14
Center column furnace, 186
Centigrade table, 232-234
Chamotte tubes, 228
Chart of carbon penetration, 97
heat treatment, 151
shape, 151
Page 197
Chrome steel, 26-27
Chrome-nickel steel, 27-28
steel, forging, 66
Chrome-vanadium steel, 28
Chromium, 26-27
steels, S. A. E., 41
Chromium-cobalt steel, 178
Chromium-vanadium steel, S. A. E., 41
Classification of steel, 10
Clay tubes, 229
Cold end compensator, 213
junction errors, 222
shortness, 15, 166
worked steel, 65
Color in tempering, 157
Colors on carbon steels, 163
Combination tank, 90
Comparison of fuels, 191
Compensating leads, 222
Compensator for cold ends, 214
automatic, 214
Composition of steel, 13
Compound, blending, 103
separating from work, 102
Compounds for carburizing, 102
Connecting rods, Liberty motor, 42, 52
Continuous heating furnace, 71
Converter, Bessemer, 2
Cooling curves, 106, 107
Cooling quenching oil, roof system, 74
rate of, for gear-forgings, 51
Copper, effect of, in medium carbon steel, 35
Copper-plating to prevent carburizing, 93
Corrosion of high-chromium steel, 38
of rust-proof steel, 38
Corundite tubes, 229
Cost of operating furnaces, 200
Cracks in hardening, preventing, 106
Crankshaft, Liberty motor, 54
Critical point, 105
Crucible or tool steel, x, 4
Cutting off high speed steel, 172
Cyanide bath for tool steel, 133
D
Decarbonizing of outer surface, 153
preventing, 154
Depth of case, 86
Detrimental elements in steel, 166
Dies, drop forging, 133
quenching, 147
soft spots in, 147
tempering round, 161
Drawing, 114
ends of gear teeth, 127
Chrome-nickel steel, 27-28
steel, forging, 66
Chrome-vanadium steel, 28
Chromium, 26-27
steels, S. A. E., 41
Chromium-cobalt steel, 178
Chromium-vanadium steel, S. A. E., 41
Classification of steel, 10
Clay tubes, 229
Cold end compensator, 213
junction errors, 222
shortness, 15, 166
worked steel, 65
Color in tempering, 157
Colors on carbon steels, 163
Combination tank, 90
Comparison of fuels, 191
Compensating leads, 222
Compensator for cold ends, 214
automatic, 214
Composition of steel, 13
Compound, blending, 103
separating from work, 102
Compounds for carburizing, 102
Connecting rods, Liberty motor, 42, 52
Continuous heating furnace, 71
Converter, Bessemer, 2
Cooling curves, 106, 107
Cooling quenching oil, roof system, 74
rate of, for gear-forgings, 51
Copper, effect of, in medium carbon steel, 35
Copper-plating to prevent carburizing, 93
Corrosion of high-chromium steel, 38
of rust-proof steel, 38
Corundite tubes, 229
Cost of operating furnaces, 200
Cracks in hardening, preventing, 106
Crankshaft, Liberty motor, 54
Critical point, 105
Crucible or tool steel, x, 4
Cutting off high speed steel, 172
Cyanide bath for tool steel, 133
D
Decarbonizing of outer surface, 153
preventing, 154
Depth of case, 86
Detrimental elements in steel, 166
Dies, drop forging, 133
quenching, 147
soft spots in, 147
tempering round, 161
Drawing, 114
ends of gear teeth, 127
Page 198
Drop forging dies, 133
Ductility, 13, 18
E
Effect of alloys, 24
of different carburizing material, 87
of size of piece, 89, 119
of copper in medium carbon steel, 35
Elastic limit, 18
Electric process of steel making, 5
Electrode, 5
Elements, chemical, 12
Elongation, 18
Endurance limit, 20
Energizer, 81, 88
Enlarging steel, 161
Equipment for heat treating, 121
Eutectoid, 109
F
Fahrenheit temperature table, 232
Fatigue test, 19
Ferrite, 106
File test, 16, 17
Flame shields, 193
Flange shields for furnaces, 197
Forging furnace, 189
high speed tools, 174
improper, 66
of steel, 64
practice, heavy, 195
rifle barrels, 69
Forgings, carbon steel Liberty engine, 48
Formed tools, high speed, 174
Fractures, examining by, 16, 159
Furnace, continuous heating, 71
crucible, 4
data, 199
electric, 5
Heroult, 6
open hearth, 3
records, 129
Furnaces, 185
annealing, 190
broach hardening, 188
car door type, 190
center column, 186
cost of operating, 200
data on, 199
forging, heavy, 195
fuels for, 199
gas fired, 190
high speed steel, 187
lead pot, 185
Ductility, 13, 18
E
Effect of alloys, 24
of different carburizing material, 87
of size of piece, 89, 119
of copper in medium carbon steel, 35
Elastic limit, 18
Electric process of steel making, 5
Electrode, 5
Elements, chemical, 12
Elongation, 18
Endurance limit, 20
Energizer, 81, 88
Enlarging steel, 161
Equipment for heat treating, 121
Eutectoid, 109
F
Fahrenheit temperature table, 232
Fatigue test, 19
Ferrite, 106
File test, 16, 17
Flame shields, 193
Flange shields for furnaces, 197
Forging furnace, 189
high speed tools, 174
improper, 66
of steel, 64
practice, heavy, 195
rifle barrels, 69
Forgings, carbon steel Liberty engine, 48
Formed tools, high speed, 174
Fractures, examining by, 16, 159
Furnace, continuous heating, 71
crucible, 4
data, 199
electric, 5
Heroult, 6
open hearth, 3
records, 129
Furnaces, 185
annealing, 190
broach hardening, 188
car door type, 190
center column, 186
cost of operating, 200
data on, 199
forging, heavy, 195
fuels for, 199
gas fired, 190
high speed steel, 187
lead pot, 185
Page 199
manganese steel, 198
muffle, 189
oil fired, 186
operating costs, 200
screens for, 192
tool, 187
Furnaces, water cooled fronts, 197
Fuels, comparison of, 191
for furnaces, 199
G
Gages, changes due to quenching, 162
tempering, 161
Gamma iron, 106
Gas, carburizing by, 93
consumption for carburizing, 101
fired furnace, 190
illuminating, for carburizing, 97
Gear blanks, heat treatment of, 115
forgings, rate of cooling for Liberty engine, 51
hardening machine, 130
steel, transmission, 59
teeth, drawing ends of, 127
Gears, Liberty engine, 50
Gleason tempering machine, 129
Grade of steel, 10
Grain, refining, 91, 110
size, 16
Graphitic carbon, ix
Grinding high speed steel, 176
H
Hair lines in forgings, 56
Hardening, 111
carbon steel for tools, 145
cracks, preventing, 160
dies, 146
gears, 130
high speed steel, 171
high speed tools, 177
of high-chromium steel, 37
of rust-proof steel, 37
room, modern, 146
Hardness tests, 20
Heating, effect of size, 119
for forging, 64
Heat, judging by color, 114
treating departments, 122
equipment, 121
forgings, 44
inspection of, 125
Liberty motor, 44
Heat treating, of axles, 61
of chisels, 151
muffle, 189
oil fired, 186
operating costs, 200
screens for, 192
tool, 187
Furnaces, water cooled fronts, 197
Fuels, comparison of, 191
for furnaces, 199
G
Gages, changes due to quenching, 162
tempering, 161
Gamma iron, 106
Gas, carburizing by, 93
consumption for carburizing, 101
fired furnace, 190
illuminating, for carburizing, 97
Gear blanks, heat treatment of, 115
forgings, rate of cooling for Liberty engine, 51
hardening machine, 130
steel, transmission, 59
teeth, drawing ends of, 127
Gears, Liberty engine, 50
Gleason tempering machine, 129
Grade of steel, 10
Grain, refining, 91, 110
size, 16
Graphitic carbon, ix
Grinding high speed steel, 176
H
Hair lines in forgings, 56
Hardening, 111
carbon steel for tools, 145
cracks, preventing, 160
dies, 146
gears, 130
high speed steel, 171
high speed tools, 177
of high-chromium steel, 37
of rust-proof steel, 37
room, modern, 146
Hardness tests, 20
Heating, effect of size, 119
for forging, 64
Heat, judging by color, 114
treating departments, 122
equipment, 121
forgings, 44
inspection of, 125
Liberty motor, 44
Heat treating, of axles, 61
of chisels, 151
Page 200
of gears, 131
of high speed steel, 170
of steel, 105
S. A. E., 134-137
Heat treatment, 105
Heroult furnace, 6
High-chromium steel, 36
annealing of, 36
corrosion of, 38
hardening of, 37
Highly stressed parts of Liberty engine, 49
High speed steel, analysis of, 166
annealing, 75
cutting off, 172
forging, 65
furnace, 187
hardening, 171
heat treatment of, 170
instructions for, 175, 180
manufacture, 166, 169
pack hardening, 172
structure of, 168
Hints for steel users, 159
I
Illuminating gas for carburizing, 97
Impact test, 19
Improper forging, 66
Influence of size on heating, 119
Inspection of heat treatment, 125
Internal stresses, relieving, 154
Introduction of carbon, 96
J
Jewelers' tools, 146
Judging heat of steel by color, 114
L
Latent heat, 105
Lathe and planer tools, 176
tools, high speed, 173
Latrobe temper list, 150
Lead bath, 154
pot furnace, 185
Leeds & Northrup potentiometer 211
optical pyrometer, 220
Liberty engine, highly stressed parts of, 49
Liberty engine materials, application to automotive industry, 46
motor connecting rods, 42, 52
motor, crankshaft, 54
motor piston pin, 57
Local case hardening, 94
Luting mixture, 100
of high speed steel, 170
of steel, 105
S. A. E., 134-137
Heat treatment, 105
Heroult furnace, 6
High-chromium steel, 36
annealing of, 36
corrosion of, 38
hardening of, 37
Highly stressed parts of Liberty engine, 49
High speed steel, analysis of, 166
annealing, 75
cutting off, 172
forging, 65
furnace, 187
hardening, 171
heat treatment of, 170
instructions for, 175, 180
manufacture, 166, 169
pack hardening, 172
structure of, 168
Hints for steel users, 159
I
Illuminating gas for carburizing, 97
Impact test, 19
Improper forging, 66
Influence of size on heating, 119
Inspection of heat treatment, 125
Internal stresses, relieving, 154
Introduction of carbon, 96
J
Jewelers' tools, 146
Judging heat of steel by color, 114
L
Latent heat, 105
Lathe and planer tools, 176
tools, high speed, 173
Latrobe temper list, 150
Lead bath, 154
pot furnace, 185
Leeds & Northrup potentiometer 211
optical pyrometer, 220
Liberty engine, highly stressed parts of, 49
Liberty engine materials, application to automotive industry, 46
motor connecting rods, 42, 52
motor, crankshaft, 54
motor piston pin, 57
Local case hardening, 94
Luting mixture, 100
Page 201
M
Machineability of steel, 72
Machinery steel, annealing, 77
Magnet test, 114
Making steel in electric furnace, 6
Manganese, 16, 33, 107
steel, 29-30
furnace, 198
Manufacture of high speed steel, 169
Marquardt mass tubes, 228
Martensite, 111
Medium carbon steel, effect of copper on, 35
Metallography, 105
Microphotographs, 109 e. s.
Microscopic examination, 158
Milling cutters, high speed, 174
Mixture for luting, 100
Modern hardening room, 146
Molten metal pyrometers, 226
Molybdenum, 32
Muffle furnace, 189
N
Nickel, 24
Nickel-chromium steel, 27-28
steels, S. A. E., 40
Nickel, influence of, on steel, 25
steel, 24-26
affinity for carbon, 125
steels, S. A. E., 39
Non-homogeneous melting, 24
Non-shrinking steels, 35
Normalizing, 114
O
Oil bath for tempering, 157
cooling on roof, 74
fired furnace, 186
hardening steel, forging, 66
steels, 35
temperature of quenching, 124
Open hearth furnace, 3
Operating costs of furnaces, 200
Outer surface decarbonizer, 153
Over-heated steel, restoring, 137
Overheating, 65
dies, 148
P
Pack-hardening, 87
high speed steel, 173
Packing work for carburizing, 123
Paste for hardening dies, 146
Machineability of steel, 72
Machinery steel, annealing, 77
Magnet test, 114
Making steel in electric furnace, 6
Manganese, 16, 33, 107
steel, 29-30
furnace, 198
Manufacture of high speed steel, 169
Marquardt mass tubes, 228
Martensite, 111
Medium carbon steel, effect of copper on, 35
Metallography, 105
Microphotographs, 109 e. s.
Microscopic examination, 158
Milling cutters, high speed, 174
Mixture for luting, 100
Modern hardening room, 146
Molten metal pyrometers, 226
Molybdenum, 32
Muffle furnace, 189
N
Nickel, 24
Nickel-chromium steel, 27-28
steels, S. A. E., 40
Nickel, influence of, on steel, 25
steel, 24-26
affinity for carbon, 125
steels, S. A. E., 39
Non-homogeneous melting, 24
Non-shrinking steels, 35
Normalizing, 114
O
Oil bath for tempering, 157
cooling on roof, 74
fired furnace, 186
hardening steel, forging, 66
steels, 35
temperature of quenching, 124
Open hearth furnace, 3
Operating costs of furnaces, 200
Outer surface decarbonizer, 153
Over-heated steel, restoring, 137
Overheating, 65
dies, 148
P
Pack-hardening, 87
high speed steel, 173
Packing work for carburizing, 123
Paste for hardening dies, 146
Page 202
Pearlite, 109, 112
Penetration of carbon, 95
carbon, chart of, 97
in case hardening, 83
Phosphorus, 15, 33
Pickling Liberty motor forgings, 44
Pig iron, ix
Piston pin, Liberty motor, 57
Placing pyrometers, 210
Planer tools, high speed, 173
"Points" of carbon in steel, 9
Potentiometer, Leeds & Northrup, 211
Pots for carburizing, 123
Press for testing gears, 126
Preventing carburization, 93
cracks in hardening, 160
Properties of alloy steels, 34
of alloy steels, table, 34
of steel, 12
Protective screens for furnaces, 192
Puddled iron, ix
Punches and chisels, steels for, 151
Pyrometers, 202
calibration, 208
copper ball, 202
indicating, 219
inspection, 208
iron ball, 202
molten metal, 226
optical, 206, 220
placing, 210
recording, 216
Siemens, 202
testing, 209
water, 203
Q
Quality and structure of high speed steel, 168
of steel, 149
Quenching,
after carburizing, 86-88
dies in tank, 147
obsolete method, 148
oil, temperature of, 124
tank, 89
tool steel, 156
R
Rate of absorption of carbon, 83
Recording temperatures, 127
Red shortness, 14, 166
Refining the grain, 91, 111
Regenerative open hearth furnace, 3
Restoring overheated steel, 137
Penetration of carbon, 95
carbon, chart of, 97
in case hardening, 83
Phosphorus, 15, 33
Pickling Liberty motor forgings, 44
Pig iron, ix
Piston pin, Liberty motor, 57
Placing pyrometers, 210
Planer tools, high speed, 173
"Points" of carbon in steel, 9
Potentiometer, Leeds & Northrup, 211
Pots for carburizing, 123
Press for testing gears, 126
Preventing carburization, 93
cracks in hardening, 160
Properties of alloy steels, 34
of alloy steels, table, 34
of steel, 12
Protective screens for furnaces, 192
Puddled iron, ix
Punches and chisels, steels for, 151
Pyrometers, 202
calibration, 208
copper ball, 202
indicating, 219
inspection, 208
iron ball, 202
molten metal, 226
optical, 206, 220
placing, 210
recording, 216
Siemens, 202
testing, 209
water, 203
Q
Quality and structure of high speed steel, 168
of steel, 149
Quenching,
after carburizing, 86-88
dies in tank, 147
obsolete method, 148
oil, temperature of, 124
tank, 89
tool steel, 156
R
Rate of absorption of carbon, 83
Recording temperatures, 127
Red shortness, 14, 166
Refining the grain, 91, 111
Regenerative open hearth furnace, 3
Restoring overheated steel, 137
Page 203
Rifle barrels, forging, 69
components, annealing, 78
Roof system of cooling oil, 74
Rust-proof steel, 36
annealing of, 36
corrosion of, 38
hardening of, 37
S
S. A. E. carbon steels, 10, 39
chromium steels, 41
chromium-vanadium, 41
heat treatments, 134-137
nickel-chromium steels, 40
nickel steels, 39
screw stock, 39
silico-manganese steel, 41
standard steels, 39
Salt bath for tempering, 157
Scleroscope test, 21
Scratch hardness, 20
Screens for furnaces, 192
Screw stock, S. A. E., 14, 39
Sensible heat, 105
Sentinels, melting of, 207
Separating work from compound, 102
Shields for furnace doors, 193
Shore Scleroscope, 21
Short method of carburizing, 124
Shrinking steel, 161
Silica tubes, 228
Silico-manganese steels, S. A. E., 41
Silicon, 15, 33, 107
Silversmiths' tools, 146
Size of piece, effect of, 89, 119
Slags, 7
Sleeves, carburizing, 132
hardening and shrinking, 132
shrinking, 132
Solid solution, 106
Sorbite, 112
Specimens, test, 17
Standard S. A. E. steels, 39
Steel,
balls, stock for, 62
bolts, making, 61
composition of, 12
deoxidation, 15
for chisels and punches, 151
forging of, 64
give it a chance, 148
heat treatment of, 105
high speed, 165
making, 1, 6, 15
Bessemer process, 1
components, annealing, 78
Roof system of cooling oil, 74
Rust-proof steel, 36
annealing of, 36
corrosion of, 38
hardening of, 37
S
S. A. E. carbon steels, 10, 39
chromium steels, 41
chromium-vanadium, 41
heat treatments, 134-137
nickel-chromium steels, 40
nickel steels, 39
screw stock, 39
silico-manganese steel, 41
standard steels, 39
Salt bath for tempering, 157
Scleroscope test, 21
Scratch hardness, 20
Screens for furnaces, 192
Screw stock, S. A. E., 14, 39
Sensible heat, 105
Sentinels, melting of, 207
Separating work from compound, 102
Shields for furnace doors, 193
Shore Scleroscope, 21
Short method of carburizing, 124
Shrinking steel, 161
Silica tubes, 228
Silico-manganese steels, S. A. E., 41
Silicon, 15, 33, 107
Silversmiths' tools, 146
Size of piece, effect of, 89, 119
Slags, 7
Sleeves, carburizing, 132
hardening and shrinking, 132
shrinking, 132
Solid solution, 106
Sorbite, 112
Specimens, test, 17
Standard S. A. E. steels, 39
Steel,
balls, stock for, 62
bolts, making, 61
composition of, 12
deoxidation, 15
for chisels and punches, 151
forging of, 64
give it a chance, 148
heat treatment of, 105
high speed, 165
making, 1, 6, 15
Bessemer process, 1
Page 204
crucible process, 4
electric furnace process, 5
open hearth, 1
tools, carbon, in, 149
users' hints, 159
Structure of high speed steel, 168
Sulphur, 14, 33
T
Tables, air, oil and water hardened steel, 38
alloy steels, properties of, 34
carbon content, 84
carbon steels, 39
case hardening, 97
changes due to quenching, 162
chromium steels, 41
chromium-vanadium steels, 41
colors and temperature, 163
composition of steels, 51, 52
cost of furnaces, 200
effect of size, 119
fuels, comparison of, 191
high-chromium steel, 37
nickel-chromium steels, 40
nickel steels, 39
operating cost of furnaces, 200
production cost of furnaces, 201
S. A. E. steels, 49
screw stock, 39
silico-manganese steels, 41
stock for balls, 62
temperature conversion, 232-234
tempering temperatures, 158
weight of steel, 235-237
Tank for quenching, 89
dies, 147
Taylor instruments, 215
Temper, colors of, 157
list, Latrobe, 150
of steel, 10, 149
Temperature recorders, 127
tables, 232-234
Temperatures for tempering, 158
Tempering colors on carbon steels, 163
gages, 161
high speed tools, 177
machine, Gleason, 129
round dies, 161
temperatures, 158
theory of, 114, 156
Tempers of carbon steel, 10, 150
Tensile test, 17
Testing heat treatment, 125
Tests of steel, 16
Test specimens, 17
electric furnace process, 5
open hearth, 1
tools, carbon, in, 149
users' hints, 159
Structure of high speed steel, 168
Sulphur, 14, 33
T
Tables, air, oil and water hardened steel, 38
alloy steels, properties of, 34
carbon content, 84
carbon steels, 39
case hardening, 97
changes due to quenching, 162
chromium steels, 41
chromium-vanadium steels, 41
colors and temperature, 163
composition of steels, 51, 52
cost of furnaces, 200
effect of size, 119
fuels, comparison of, 191
high-chromium steel, 37
nickel-chromium steels, 40
nickel steels, 39
operating cost of furnaces, 200
production cost of furnaces, 201
S. A. E. steels, 49
screw stock, 39
silico-manganese steels, 41
stock for balls, 62
temperature conversion, 232-234
tempering temperatures, 158
weight of steel, 235-237
Tank for quenching, 89
dies, 147
Taylor instruments, 215
Temper, colors of, 157
list, Latrobe, 150
of steel, 10, 149
Temperature recorders, 127
tables, 232-234
Temperatures for tempering, 158
Tempering colors on carbon steels, 163
gages, 161
high speed tools, 177
machine, Gleason, 129
round dies, 161
temperatures, 158
theory of, 114, 156
Tempers of carbon steel, 10, 150
Tensile test, 17
Testing heat treatment, 125
Tests of steel, 16
Test specimens, 17
Page 205
Theory of tempering, 114, 150
Thermocouple, 204
base metal, 205
cold end, 206
placing, 218
protectors, 227
rare metal, 205
Time for hardening, 148
Tool furnace, small, 187
Tool or crucible steel, annealing, 76
Tool steel, cyanide bath for, 133
quenching, 150
Tools, carbon in different, 149
carbon steel, 145
of high speed steel, 173
sulphur in, 14
tempers of various, 150
transformation points, 106
Transmission gear steel, 59
Treatments for various steels, 92
Troosite, 112
Tubes, calorized, 229
carborundum, 229
Chamotte, 228
clay, 229
Marquardt mass, 228
silica, 228
Tungsten steel, 30
U
Ultimate strength, 17
Users of steel, hints for, 159
V
Vanadium steel, 28
W
Water annealing, 155
cooled furnace fronts, 197
Weight of steel bars, 235-237
Working instructions for high speed steel, 175
Wrought iron, ix
Y
Yield Point, 19
Thermocouple, 204
base metal, 205
cold end, 206
placing, 218
protectors, 227
rare metal, 205
Time for hardening, 148
Tool furnace, small, 187
Tool or crucible steel, annealing, 76
Tool steel, cyanide bath for, 133
quenching, 150
Tools, carbon in different, 149
carbon steel, 145
of high speed steel, 173
sulphur in, 14
tempers of various, 150
transformation points, 106
Transmission gear steel, 59
Treatments for various steels, 92
Troosite, 112
Tubes, calorized, 229
carborundum, 229
Chamotte, 228
clay, 229
Marquardt mass, 228
silica, 228
Tungsten steel, 30
U
Ultimate strength, 17
Users of steel, hints for, 159
V
Vanadium steel, 28
W
Water annealing, 155
cooled furnace fronts, 197
Weight of steel bars, 235-237
Working instructions for high speed steel, 175
Wrought iron, ix
Y
Yield Point, 19
Page 206
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