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Title: A few secrets of the metallurgist simply told
Author: Gerald W. Hinkley
Release date: February 9, 2025 [eBook #75326]
Language: English
Original publication: Dunkirk: Atlas Crucible Steel Co, 1918
Credits: deaurider, Richard Scheibel and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive)
*** START OF THE PROJECT GUTENBERG EBOOK A FEW SECRETS OF THE METALLURGIST SIMPLY TOLD ***
TRANSCRIBER’S NOTE
Some minor misspellings in the text are silently corrected.
Enclosed small caps in ≈double tilde≈,
enclosed italics font in _underscores_,
bold text in =equal sign=.
The numbering of the drawings does not correspond to their marked
number. However, they have been left as they are, as the author has
entered them by hand in the drawings.
In the table on the color of the oxide layer of tempered steel in the
tempering section, the first column has been set without trailing
commas, as the author has handled this inconsistently.
The new original cover art included with this eBook is granted to the
public domain.
A FEW SECRETS OF THE
METALLURGIST
SIMPLY TOLD
ATLAS CRUCIBLE STEEL CO.
PUBLISHERS
DUNKIRK, N. Y.
A FEW SECRETS OF THE
METALLURGIST
SIMPLY TOLD
BY
GERALD W. HINKLEY, M. E.
CORNELL UNIVERSITY
ORDNANCE ENGINEER
AND ASSISTANT TO PRESIDENT
ATLAS CRUCIBLE STEEL CO.
DUNKIRK, N. Y.
FIRST EDITION
COPYRIGHTED 1918
BY
PRESS OF DUNKIRK PRINTING COMPANY
PREFACE.
This is not and is not intended to be a thoroughly complete explanation
or discussion of the allotropic theory of iron and steel, but rather a
brief outline of a few of the great principles of metallurgy written
primarily for the layman. If without leading him astray from the real
scientific understanding of the subject we have succeeded in briefly
but satisfactorily answering the old familiar question, “Why do steels
harden?”, we will in a large measure, have accomplished our purpose.
Besides the personal observations which the writer has made from time
to time in the metallurgical laboratory, he has availed himself freely
of the works of many and eminent authors dealing with this subject and
where disputable conditions have arisen in regard to certain theories,
uses, etc., has attempted to adopt the most logical consensus of
opinion.
G. W. H.
CONTENTS.
A FEW SECRETS OF THE
METALLURGIST
SIMPLY TOLD.
Page
INTRODUCTION 17
CHAPTER I.
≈A Slight Test of the Imagination≈ 19
CHAPTER II.
≈Comparison Between Conditions
Which Exist in the Iron and
Steel Family to Those Which
Exist with More Familiar Elements≈ 22
CHAPTER III.
≈An Experiment Performed with
a Piece of Pearlitic Steel≈ 29
CHAPTER IV.
≈High Speed Steel≈ 51
CHAPTER V.
≈The General Effect of the More
Important Elements in Tool
Steels≈ 61
≈Carbon Steels≈ 61
≈Alloy Steels≈ 63
≈High Speed Steels≈ 64
≈Elements Which Occur in all
Steels≈ 66
≈Iron≈ 66
≈Carbon≈ 67
≈Manganese≈ 67
≈Silicon≈ 68
≈Phosphorus≈ 69
≈Sulphur≈ 70
≈Elements Which Have Become
Especially Associated with
Special Alloy Steels≈ 70
≈Chromium≈ 70
≈Tungsten≈ 72
≈Molybdenum≈ 73
≈Vanadium≈ 73
≈Cobalt≈ 74
≈Uranium, Titanium and Aluminum≈ 75
≈Impurities≈ 75
≈Heat Treatment≈ 76
≈Hardening≈ 77
≈Annealing≈ 79
≈Tempering≈ 81
≈Conclusion≈ 84
CHAPTER VI.
≈What Tool Steel Is Doing Towards
Winning the War≈ 85
APPENDIX.
≈Analysis, Uses and Heat Treatment
of Various Grades of
Tool Steels≈ 92
≈High Speed Steels≈ 93
≈Die Steel for Hot Work≈ 94
≈Special Alloy Steel≈ 95
≈Semi-High Speed Steel≈ 96
≈Simple Carbon Tool Steel≈ 97
≈Non-Shrinking Oil Hardening
Steel≈ 98
≈Special Hot Work Alloy Steel≈ 99
A FEW SECRETS OF THE
METALLURGIST
SIMPLY TOLD
INTRODUCTION.
When as a student at a Technical College of one of our great
Universities, I came to the study of Differential and Integral
Calculus, I remember that I was seized with a kind of mental paralysis
at the thought of the great unknown that lay before me. Fortunately,
however, a little book was brought to my attention, under the
encouraging title “Calculus Made Easy”. As a matter of fact the little
volume did not attempt to take its readers through all the intricacies
of the entire subject, but it did succeed in giving a certain start on
the long journey which has to be undergone by a student of the
Calculus. Its opening sentence was encouraging, which I have always
remembered, and which read something as follows:
“What one fool can accomplish, another fool can do, therefore take
courage”. This same thought applies to the subject which is now before
us.
CHAPTER I.
A SLIGHT TEST OF THE IMAGINATION.
We live in a world in which certain conditions of the atmosphere and
the so-called elements surrounding our daily existence, are entirely
familiar to us. From force of habit we are likely to forget that had
Nature, for instance, been planned under a different range of livable
temperatures, all the familiar objects of our daily existence would
have existed under entirely different form.
For instance, if the normal temperature had been about 2700 degrees
Fahrenheit instead of about 60 degrees Fahrenheit, and we had been
constructed so that we could comfortably endure that degree of
temperature, we could have gone sailing on a sea of molten iron, in
boats built of plumbago crucibles, and oars made of silica brick. Under
these delightful conditions we could place frozen lumps of our sea of
iron in our ice boxes for refrigeration. Flat irons and stove lids
would therefore have been the product of the ice man. The water with
which we are now familiar, of course, could not exist in its liquid
form, or even as steam, but instead as a highly gaseous state, which we
would probably have been called upon to breathe. Certain other
substances with which we are perfectly familiar in our daily life, such
as the common stick sulphur, for instance, would exist in an entirely
different =physical= state, although their =chemical= properties would
be entirely unchanged, and we would be given to understand that an
“allotropic” transformation had taken place.
If we can now imagine ourselves as existing under the relative
conditions described above, which are undoubtedly the “natural”
conditions of some other world, it will then be easy for us to
understand quite clearly some of the other “allotropic” forms of iron
and steel than those with which we are at present familiar.
CHAPTER II.
COMPARISON BETWEEN CONDITIONS WHICH EXIST IN THE IRON AND STEEL FAMILY
TO THOSE WHICH EXIST WITH MORE FAMILIAR ELEMENTS.
One of the first physical changes which we would discover would be that
when we desired to “freeze” a “crucible” pailful of our iron water, we
could do so much more easily if the same were in its absolutely pure
state than we could if it were mixed with some other element, such as
carbon. Of course, we have long known that this is the case with water
and salt, and just as it becomes harder and harder to freeze water with
greater and greater percentages of salt mixed with it, so the freezing
of iron with greater and greater percentages of carbon mixed with it,
would also occur at lower and lower temperatures.
If we started to add salt to a pail of water we, of course, would have
different degrees of brine. Just so with the addition of carbon to a
crucible of pure iron, we would likewise have different degrees of the
resulting mixture. In adding the salt to the pailful of water, we would
arrive at a point where the water had absorbed all of the salt which it
was capable of holding at room temperature. If we had added a little
less salt we would have had free water in excess of salt, and if we had
added a little more salt it would have been impossible for the water to
have dissolved it, and we would, therefore, have had salt in excess of
water.
For convenience we will call the mixture above mentioned, at which the
water had become thoroughly saturated with the salt, “cementite”,
because this is the name which our friends, the metallurgists, have
given to a similar mixture of iron and carbon. They call the water,
“ferrite”; the salt, “carbide” and the resulting mixture of brine,
“cementite”. This mixture of iron and carbon always exists in exactly
the same ratio, namely, 93.4% iron and 6.6% carbon, and is expressed
chemically by the symbol Fe3C, which means, in other words, that three
“atoms” of iron have united with one “_atom_” of carbon to form the
“chemical compound”, “iron carbide”, which the metallurgists, as above
mentioned, desire to term “Cementite”.
Now let us go back to the brine solution with which we are already
familiar, and suppose that we added a little more salt than the water
could absorb, and which therefore would exist in a “solid solution”,
and then bring this “mechanical mixture” to such a low temperature that
it would actually “freeze”. For convenience, and in order to agree with
the metallurgists again, let us call the resulting structure
“pearlite”. That is the name which they have given to a corresponding
“mechanical mixture” of cementite and ferrite.
This new constituent “pearlite” contains approximately O.9% carbon and
consists of inter-stratified layers or bands of ferrite and cementite.
It is regarded as a separate and distinct constituent of steel, and
takes its name from the fact that it has a mother of pearl-like
appearance under the microscope. It always occurs at a definite range
of temperature and always contains the above mentioned definite
percentage of carbon.
From the above it may be suspected that a steel containing O.9% carbon,
consisting entirely of pearlite, forms rather a special and particular
class of steels, which the metallurgists have decided to dignify with
the title “Eutectoid Steels”. Having done this much to properly impress
the unsuspecting probers of their secrets, they decided to call steels
containing less than this Eutectoid ratio of carbon (0.9% C)
“Hypo-eutectoid Steels”. These steels, of course, contain certain
definite amounts of pearlite with other amounts of free or excess
ferrite. Likewise, if the carbon content is greater than O.9% there
will be an excess of cementite over the ferrite and we will then have a
structure of pearlite plus free cementite. And these steels are spoken
of as “hyper-eutectoid” steels.
[Illustration: Hypo-eutectoid Steel. Carbon .11%. Structure:
Light—Ferrite; Dark—Pearlite. Mag. 500x]
[Illustration: Hypo-eutectoid Steel. Carbon .37%. Structure:
Light—Ferrite; Dark—Pearlite. Mag. 500x]
[Illustration: Eutectoid Steel. Carbon .90%. Structure: Fine uniform
Pearlitic condition. Mag. 500x]
[Illustration: Hyper-eutectoid Steel. Carbon 1.20%. Structure:
Dark—Pearlitic; White boundaries—Cementite. Mag. 500x]
CHAPTER III.
AN EXPERIMENT PERFORMED WITH A PIECE OF PEARLITIC STEEL.
However, let us not trouble ourselves with too many definitions at one
time, but instead amuse ourselves for a while by running through a
little experiment with a piece of carbon tool steel similar to that
which we have just been discussing. For our investigation we will also
need a special kind of thermometer for measuring high temperatures.
Such an instrument is known as a “pyrometer”. Now we will drill a
little hole in the test piece of carbon steel and after inserting the
“couple” of the pyrometer into it, place the same in the electric
furnace.
As the current is turned on, the test piece begins to grow warm and
then hotter and hotter, gradually up through a range of temperatures
which are continually recorded by the needle of the pyrometer. 800,
900, 1000, 1200 degrees Fahrenheit are uniformly reached, and the
temperature of our test piece continues to rise, as the absorption of
heat progresses. Suddenly, however, the test piece assumes a bright
glow and the needle of the pyrometer ceases to advance, and we note
that it is pausing at about 1350 degrees Fahrenheit. Then after its
pause, the advance is again resumed until the piece has become almost
ready to melt. By plotting the uniform periods of time at which we read
the different temperatures recorded by the needle of the pyrometer,
against the temperatures as read, we would have a picture of our
phenomenon something as follows:
[Illustration: Graph showing the course of the temperature curve as a
function of the heating time of the metal sample.]
Now let us begin to let our test piece cool off gradually. The
temperature of the furnace is lowered and the uniform range of cooling
temperatures is recorded by the ever sensitive needle of the pyrometer.
Suddenly as before, the test piece assumes the brilliant glow noted
previously, and again the needle comes to rest, but this time we note
that the recorded temperature is about 1250 degrees Fahrenheit instead
of 1350 degrees Fahrenheit as before. Evidently there has been a
certain tardiness or “lag” which has caused the phenomenon to take
place a little too high going up and a little too low coming down, and
in fact the metallurgists tell us that such is exactly the case, and
that the real point in which we are interested lies just half way
between the two points indicated, as we shall presently see. If we
again represent the results of our latest experiment graphically, we
would have a picture something as Fig. 2.
[Illustration: Graph of the cooling curve of the metal sample
over time]
Now placing the second curve so obtained on the first, we are able to
study the following interesting relationship. Fig. 3.
[Illustration: Graph combining the heating- and cooling-curves from
before and demonstrating the critical range]
It is natural to suspect that both of the parallel sections of our
curves have something to do with the same thing, and for convenience
since we noticed that mysterious glow of the test piece just as the
needle came to rest, we might call the particular point which lies just
half way between the temperatures under discussion, the point of glow,
or as the metallurgists call it, the “point of recalescence” and the
range between these two temperatures the “critical range”.
I suppose it would be difficult to explain this phenomenon of the test
piece unless we imagine that as the critical range is reached some
internal reaction of the steel causes it to spontaneously take on heat
at the same temperature in the first place and give off the stored heat
at the same temperature as the piece was being cooled down, and this
heat caused it to glow as was noticed. Now if we were to experiment
further with our piece while at the critical range, we would find
certain other remarkable changes, one of the most noticeable of which
is the loss of magnetism at and above the critical range.
Irons and steels are usually the most magnetic materials, but the
attraction of the magnet is completely lost at or above the critical
range.
We can easily satisfy ourselves in this respect by noting the
attraction of a simple horse shoe magnet when our piece of test steel
is brought into its magnetic field. As the pyrometer needle passes on
up through the range of temperatures noted above, the magnetic
attraction is perfectly evident when suddenly the recalescence point is
reached, the spell is broken and the magnet and the test piece fall
apart. But let us just consider this phenomenon a moment. We are told
by the physicists that magnetism is induced in a piece of iron or steel
by a “rearrangement of the internal molecular structure, in which the
positive ions face one direction and the negative ions in the opposite
direction”. Therefore, if magnetism suddenly ceases to exist it would
seem as if something had happened to the “internal molecular structure”
of the test piece. Thus when the recalescence point is reached we may
conclude that something more than a mere absorption of heat units has
taken place. In fact we may really believe that an actual internal
molecular revolution has occurred and that some of the natural laws
which formerly had governed all of these little molecules which go to
make up the whole piece of steel, have been overthrown and that the
molecules are more or less free to set up a new form of government for
themselves, and that, therefore, when a piece of steel is brought to
the recalescence point it is really in a very sensitive condition. In
fact, if we should care to investigate further we should find that
certain other great changes take place at this critical point, such,
for instance, as partial failure of the test piece to conduct an
electric current, which formerly, of course, it did with great ease.
Also when the critical range is reached, a peculiar contraction of size
interrupts the gradual expansion which had been developing as the test
piece absorbed heat units, and therefore these several observations
give us reason to believe that our conclusions as noted above must be
more or less correct.
Now if all steels acted exactly like the little test piece which we
have been observing above as they were placed in the hardening furnace,
it would not take us very much longer to finish our preliminary
investigations. You remember the piece of steel which we have been
investigating was a piece of simple carbon tool steel, containing about
0.90% carbon. But all steels do not contain just this same percentage
of carbon, and may also contain various elements other than carbon, all
of which produce many and varied results during the process of heating,
treating and hardening.
In order to better visualize the investigation which we are making, let
us picture graphically each step which we take. If therefore, we let
the vertical lines represent the different carbon contents which steel
might have, and the horizontal lines the different degrees of
temperatures through which we might desire to heat the steel under
discussion and then plotted the phenomenon described above we would
have a picture something as follows:
[Illustration: Graph showing the point of recalescence]
Now all that picture means is that as we heated up a piece of simple
carbon tool steel containing O.9% C, we discovered a certain very
noticeable reaction which occurred just about half way between 1250
degrees and 1350 degrees Fahrenheit, which we decided to call the point
of recalescence, and then on further heating of the piece no other such
phenomenon was noticed.
Now let us go through the same experiment with a piece of steel
containing .45% C. Yes, just as before, as the temperature 1250 degrees
Fahrenheit is reached we note all the strange symptoms which are
characteristic of the point of recalescence and then, just as we are
about to decide that it is hardly necessary to go further we notice
that the pyrometer needle has again come to rest, but that this time it
is registering 1390 degrees Fahrenheit. Therefore, it would seem as if
this piece had two critical ranges instead of one and we are now quite
ready to again proceed with our heating to see if anything else occurs.
However, as nothing does happen we turn to our picture and plot the two
points just observed, together with the one point found on our first
investigation, and the drawing then looks something as follows:
[Illustration: Graph additional shows the recalescence of a
second sample containing a different rate of carbon]
Now let us take a piece of carbon steel as before, but this time
containing .15% carbon, and again proceed with our observations. Again
the needle of the pyrometer records the point of recalescence and also
the point designating the second range of critical temperature, but
this time strange to say, as the test piece continues to absorb heat, a
third critical range is registered, all of which when added to our
former picture gives a result something as follows:
[Illustration: Graph showing different behavior of
samples containing different rates of carbon]
By repeating the operations as outlined above, with pieces of steel
containing various percentages of carbon from zero to 1.25% and by
plotting the different critical temperatures so obtained, we finally
obtain a chart which graphically expresses the critical ranges of iron
and steels due to the variation of the carbon content. With very low
carbon steel it is interesting to note that the first critical point
would not occur until 1395 degrees Fahrenheit was reached.
Metallurgists have long designated the lines so obtained by letters,
“r”, standing for, “refroidissement”, which is the French word meaning
“cooling”, the suffixes 1-2-3 simply standing for the lines in the
order drawn.
From the completed chart it is further evident that our first piece
containing 0.9% carbon in one way is the most interesting of all since
it is the only case where only one point of critical temperature
occurs.
It will be noticed from the chart that steels containing less than .10%
carbon have no point Ar1 and it is therefore undoubtedly due to the
carbon content that this, the point of recalescence, occurs. From tests
which we made with the magnet we would also find that the temperatures
at which loss of magnetism occurs are those designated by the line Ar2,
whereas the loss of ability to conduct an electric current occurs at
the point designated Ar3. In steels containing .45% carbon to .75%
carbon loss of magnetism and loss of ability to conduct an electric
current occur at the same points designated on our chart by the line
Ar3-2; whereas in the steel containing .90% carbon—all these changes
take place at the same time.
Now, as we concluded before, it is evident that some internal change
must have taken place in the steel itself, and as we know that the
chemical content does not vary, it is further evident that the change
must be of a physical nature, or as in the language of the
Metallurgist, an “allotropic change”. Therefore, another conclusion
which we can draw at this point is that a very much more thorough
investigation is required for the proper handling of steel at high
temperatures than a mere knowledge of the chemical analysis of the
same.
There is one very fortunate circumstance connected with the passing
from one of these allotropic changes to another, and that is that the
effecting of one of these changes takes =time=. It does not take a very
long time, however, for in some instances the change is affected in a
very small fraction of a second, while rarely more than one or two
seconds are required. The higher the temperature the quicker the
change.
Would it not be interesting if we had been so constructed as outlined
in the beginning of this little volume; that we could have withstood
the high temperatures in which some of these very interesting changes
occur, because we could then handle the steel, examine it and
experiment with it at our leisure. However, such not being the case, we
will have to derive some other means for “catching” the steel while it
is in one of these interesting conditions, and then bringing it in its
entrapped condition down to room temperature. How shall we do it? Well,
we remember that we said it took =time= to effect the changes under
discussion and furthermore we remember that the changes can only take
place when the steel is within the proper critical range. Therefore, if
we could do something to lower the temperature of a piece of steel
while in one of the critical ranges before the steel had time to effect
the usual allotropic change of form, we might be able to catch a piece
of steel while in one of these unusual conditions, before it had really
had time to get back to normal.
Therefore, let us place a piece of .9% carbon tool steel in the heating
furnace and bring it up to and beyond the point of recalescence. Now,
grasping the piece firmly in a pair of tongs with all possible speed we
plunge it into a nearby pail of ice water, keeping the steel
constantly in motion. Almost instantly the steel becomes black and
within a few seconds is actually brought down to room temperature.
Now let us take the steel out and examine it. The act of tapping it on
the anvil in order to knock off the surplus water gives us a hint that
our test piece has undergone some sort of a change. For now it rings
with a bell-like clearness and gives the hammer with which we strike it
a quick snapping rebound which in itself indicates great hardness.
Next, we test the piece with a hardened steel file with which we could
easily have made a deep ridge before we attempted the heating operation
and to our surprise the file has as little effect as if it had been
made of wood. And to our surprise on closer examination, we actually
find that our test piece has scratched the file—surely it must be very
hard. We are convinced that some marked change must have taken place.
What can it be? Why it must be that due to the rapid cooling in the
pail of ice water we brought the temperature of the test piece down
below the critical range =before= the abnormal condition at which it
existed while at and above the critical range had found =time= to
change back to its former condition. And we remember that if one of
these allotropic changes is going to take place at all, nature says it
=must= do so while the steel is within the critical range and therefore
having forced the steel through that critical range which separates one
allotropic condition from another, before it had found =time= to effect
its desired change, we managed to entrap the abnormal condition so that
we could see it and feel it and get familiar with it at room
temperature.
If we so desire we can now make other hardness tests on our piece of
steel at our leisure. For these scientists have invented several
machines. One of the most common is called the scleroscope in which a
hardened steel ball is allowed to drop from a given height on to the
piece of steel to be tested. Then the rebound of the ball is carefully
noted. The higher the rebound, the harder the piece. That is natural
isn’t it? We know that if the ball were allowed to drop on butter, it
wouldn’t rebound at all, because the butter is so soft. A piece of wood
would possibly record a very tiny rebound, while a piece of hardened
tool steel would effect a very material action of the scleroscope ball,
thus indicating extreme hardness.
Now let us take our test piece to the grind stone and grind it down to
the shape of a cutting tool. It is necessary to resort to the grind
stone, in order to get the desired shape, because of course, our test
piece is far too hard to cut with any other metal. After having
produced a tool of the desired shape and size, let us fasten the same
securely into the carriage of a lathe, and then upon applying the
cutting edge to a revolving piece of cast iron, or soft steel, or even
to a piece of the very same grade of steel out of which the tool was
made, only while it is still in the softened or annealed condition, we
find that it is capable of easily and quickly cutting out a good sized
ribbon of chips from the metal which is to be machined.
However, we are soon confronted with a new difficulty, for as the cut
progresses, our tool runs into a rough spot which causes it to tremble
and chatter and then suddenly our tool cracks in two in the middle and
is at once completely ruined.
It is evident that as we are able to increase the desirable element of
hardness in a piece of tool steel, we also automatically increase the
undesirable element of brittleness, and therefore some new method must
be devised which will allow a sufficient degree of hardness to allow
the tool to cut other metals and at the same time not cause so much
brittleness that it will crack in two at the first rough spot which it
encounters.
One method of assisting the toughening of a piece of hardened tool
steel is accomplished by the process of “drawing”. This simply means
heating the piece of hardened tool steel up to some fairly warm
temperature, which of course must be kept well below the critical range
(at which the steel would jump at the chance to quickly change back
into one of its softer allotropic forms) and then keeping the steel at
this drawing temperature for a while until the unusual strains and
stress caused by the rapid cooling have had an opportunity to have
become somewhat relieved. Therefore, the process of “drawing” is quite
as important as is the first act of hardening itself, and great care
must be exercised in undertaking the same.
CHAPTER IV.
HIGH SPEED STEELS.
After the processes of hardening and drawing our sample of simple
carbon tool steel have become thoroughly mastered, it might seem that
all which was desired had been accomplished and that we could go on
indefinitely making and using our simple carbon steel tools. However,
when the extraordinary demands of modern industry required faster and
faster cutting speeds, and deeper and deeper cuts, we commenced to
realize that our familiar carbon tool steels would not fill the bill.
This was due to the fact that as the tools became pressed with the
faster speeds and deeper cuts, they could not do their work without
becoming over-heated by the friction caused by the work of upsetting
the chip and therefore the critical temperature was rapidly approached.
Of course we know that if this temperature should be reached the steel
would quickly lose its hardness and its cutting edge would therefore be
completely ruined.
Therefore, it was necessary to develop a new kind of steel to meet a
new and severe condition and accordingly the mother of experiment and
invention gave birth to the now famous “High Speed” Steel.
The general principles applying to the hardening and drawing of High
Speed Steel are in many ways the same as described above for the simple
carbon steel, except that as we begin to add various elements other
than carbon to the melt, the resulting alloy becomes more and more
complex in its form and reactions and therefore its heat treatment
causes greater and greater study and skill in its successful
undertaking.
It is generally known among tool hardeners that it is necessary to heat
the tool to a higher degree of temperature in order to secure proper
hardness when using High Speed Steel than it is when a simple Carbon
Tool Steel is employed. We are told that the introduction of certain
elements into the melt of a simple Carbon Tool Steel has the tendency
to change the critical range. Of course, the formulas used in the
manufacture of any high grade High Speed Steel contain very appreciable
amounts of various elements other than Carbon which materially effect
the property which the steel will have when hard. The effect which
these elements appear to produce in the period of critical range can be
seen from figure 7.
[Illustration: ≈HEATING AND COOLING OF HIGH SPEED STEEL SHOWN IN FIG.
12.≈]
In this case an experiment was made with a piece of High Tungsten High
Speed Steel similar to the experiment which was described in detail
above with the test piece of simple Carbon Tool Steel. The readings of
the pyrometer were carefully recorded and when plotted on the graph
sheet produced the picture under discussion.
Here it will be noticed that the vivid reaction, which we might have
expected would occur as the temperature indicating the first critical
range was reached, was materially reduced. This might lead us to
suspect that the desired allotropic change had not completely taken
place at this point. In fact we noticed that the pyrometer needle did
not record a vivid critical point until a very much higher temperature
was reached. All of these observations serve as a possible explanation
or indication of why it is necessary to employ very much higher
temperatures in the hardening of High Speed Steel than it is in the
hardening of a piece of simple Carbon Tool Steel.
In a later chapter of this little volume we define Carbon Steels as
those which do =not= contain enough of any element other than carbon to
materially affect the physical properties which the steel will have
when hard. High Speed Steels which are one of a very important group of
special alloy steels, are those steels to which some element =other=
than carbon has been added in sufficient amount to materially effect
the physical properties which the steel will have when hard.
The element which stands out alone as the most vital and important one
as affecting the wonderful and highly desirable features looked for in
High Speed Steels is Tungsten. We will discuss the various effects
which the different elements give to the different alloy steels in a
later chapter, but for the present we will confine ourselves to a brief
discussion of the heat treatment of the now famous modern High Speed
Steel.
[Illustration: High Speed Steel. Carbon .58%. Structure: Very fine
pearlitic condition, with particles of free carbide. Mag. 500x]
As previously suggested the pressing demand of modern industry for
quicker work, greater efficiency and enormously increased out-put of
product, gave rise to the necessity of producing far more remarkable
tools than was possible with the old fashioned carbon tool steel.
Therefore it became necessary to produce a steel which could be
rendered sufficiently hard to cut deep furrows in the various metals
which have to be machined and, which could be made sufficiently tough
to stand the enormous cutting strains and chatter and vibration of the
machine, and at the same time maintain all these characteristics when
the work done by upsetting the chip of the machined member actually
rendered the cutting edge of the tool red hot.
After the seemingly impossible task of producing a steel to meet these
terrific conditions had been successfully accomplished, the next
question which arose was to produce a machine which was sufficiently
powerful to stand the work done by the tool, and so fast has been the
progress made by the tool steel producer, that many of our modern
manufacturing industries of today are constantly having to introduce
new and heavier machinery into their various machine shop and tool
rooms in order to keep pace with the possibilities of the tool made
from the modern High Speed Steel.
Now, if we were to run an experiment with a test piece made from High
Speed Steel similar to the one which we ran on the simple Carbon Tool
Steel, we would find that many of the same phenomena previously noticed
would again be recorded.
Probably the most important difference would be the fact that instead
of having to quench the same in water it would be desirable to use a
bath of oil. In fact, water would cause the High Speed Steel to cool
off far too quickly so that it would be likely to crack and be rendered
useless.
A peculiar action of the various elements in High Speed Steel is very
likely to materially retard the change of one allotropic form into
another. In fact, the change is so slow that after a piece of High
Speed Steel has been heated above the critical temperature, it will
actually retain its hardened or austenitic condition even if allowed to
cool in the air, and it would only be possible to get it back into its
softened condition by the lengthy process of annealing.
Annealing is the process of undoing exactly what the act of hardening
accomplished. Long tubes are filled with the tool steel bars and sealed
from the air and then placed into the annealing furnaces, wherein the
annealing temperature is maintained for a sufficient number of hours,
until the steel has had an opportunity to become thoroughly softened.
As before stated “drawing” or “tempering” means the careful re-heating
of the steel to 400 degrees Fahr. to 600 degrees Fahr., thus allowing a
slight “slipping” of enough of the higher allotropic solution to a
lower form, which it is always eager to accomplish at temperatures near
the point of recalescence. This, of course, relieves the excess
brittleness of the hardened steel.
Annealing is the complete release of the higher allotropic form of the
solution and the “trapped” carbon which allows of their return to the
normal condition of pearlite and alpha iron. Therefore, it is necessary
to heat the steel above the point of recalescence and cool more or less
slowly. Different speeds of cooling give different grain, size,
structure and physical property.
This explanation of hardening, which is known as the “allotropic
theory” is not universally accepted, although it is difficult to find a
better or more complete explanation of the remarkable phenomena
involved. However, the fact remains that the great accomplishments
which have been made by the men of science and understanding have
caused remarkable results to have taken place in the manufacturing
world of today and the fine and obscure lines which these patient and
careful laborers are continually drawing upon the map of knowledge are
doing much to make the world a better and safer and more wonderful
place in which to live.
CHAPTER V.
THE GENERAL EFFECT OF THE MORE IMPORTANT ELEMENTS IN TOOL STEELS.
We know that all metals of engineering nature are crystalline in
character, that is, the crystals form when the metal solidifies. If
these crystals were free it would be easy to determine definitely just
what properties the metal would have. However, the crystals are not
free, but exist in the steel in combination with many other types of
crystals. This results in many complicated and complex possibilities in
the finished product, and will bring us presently to the subject of
“Alloy Steels”.
CARBON STEELS.
Carbon Steels are those which do =not= contain enough of any element
=other= than carbon to materially affect the physical properties which
the steel will have when hard. Carbon is one element used above all
others by manufacturers in getting required physical properties. An
increase of one hundredth of one per cent (.01%) gives a tensile
strength of about one thousand pounds per square inch, but even this
amount of carbon also regularly decreases the ductility of the finished
product. When steel is heated red hot and plunged into water, the
carbon in the metal unites with the iron in some peculiar way so that
it produces a compound of extreme hardness. If the steel contains
nine-tenths of one per cent (.90%) of carbon, a sharp point so quenched
will almost scratch glass. With one per cent (1.00%) of carbon it
reaches nearly its limit of hardness. Now carbon steels with this
percentage carbon can be used for some of the harder tools, which do
not require much ductility or toughness, but with higher carbon
contents than this percentage, the brittleness increases so fast that
the usefulness of the metal is decidedly limited.
Therefore, when the steel must meet requirements other than just that
of hardness, such as, strength, ductility, toughness, resistance to
repeated shock, “red hardness”, etc., then it is necessary to resort to
other means and combinations for obtaining the required needs. It is to
be remembered that such methods and combinations will materially
increase the cost of the final product.
ALLOY STEELS.
What is an alloy steel? The general definition of an alloy steel is, “a
solidified solution of two or more metallic substances”. The
International Committee upon the nomenclature of iron and steel defines
alloy steels as “those steels which owe their properties chiefly to the
presence of an element (or elements) =other= than carbon”.
This latter definition more nearly applies to our case, but it must be
born in mind that the distinction between an element added merely to
produce a slight benefit to ordinary carbon steel, and the very same
element added to produce an alloy steel itself, is sometimes a very
delicate one. For example: Manganese is added in amounts usually less
than 1.50% to all Bessemer and Open-Hearth Steels, for the purpose of
getting rid of oxygen, and neutralizing the effect of the sulphur. But
this does not produce an Alloy Steel. When we make “manganese steel”
containing 10 to 20% manganese, the material then has properties quite
different from the same steel without the manganese, and we then have a
Manganese Alloy Steel.
Thus, for our purpose, we may consider an alloy steel as being one to
which some element =other= than carbon has been added in sufficient
amount to materially affect the physical properties which the steel
will have when hard.
HIGH SPEED STEELS.
High Speed Steels are perhaps the most important of alloy steels, and
derive their name from the fact that they can be used as cutting tools
when the cut on the machined member is being made at a high speed.
This, of course, subjects the tool to severe operating conditions,
which simple carbon steels could not stand. These steels have other
notable characteristics, among which is that of “self-hardening” or
“air-hardening”, as it is sometimes called. This means, when the steel
cools naturally in the air, from a red heat or above, it is not soft
like ordinary steel, but is hard and capable of cutting other metals.
Another striking characteristic of high speed steels is their ability
to maintain a sharp cutting edge while heated to a temperature far
above that which would at once destroy the cutting ability of a simple
tool steel. Because of this property, a tool made of high speed steel
can be made to cut continuously at speeds three to five times as great
as that practicable with other tools. The result of the friction of the
chip on the tool may cause the tool to become red hot at the point on
top where the chip rubs hardest, and the chip may, itself, by its
friction on the tool, and the internal work done on it, by upsetting
it, be heated to a blue heat, or even hotter.
ELEMENTS WHICH OCCUR IN ALL STEELS.
There are certain elements which are practically always found in =any=
kind of steel. These elements are capable of producing many varied
effects on the finished product. They are Iron, Carbon, Manganese,
Silicon, Phosphorous and Sulphur.
IRON.
The base of all steels is Iron. It goes without saying that this
element should be obtained in the best and purest state possible.
Probably the best “base” iron comes largely from Sweden, which country
seems to have produced the highest quality of iron on the market today.
CARBON.
Carbon has already been discussed under Carbon Steels, although, of
course, its importance in Alloy Steels must not be under-estimated. The
proportion of carbon aimed at in high speed tool steels is about 0.65%,
which in simple steel would not be enough to give the maximum hardness,
even if the steel were heated above the critical point and quenched in
water, and still less so when the steel is cooled as slowly as these
steels are in their treatment. This shows that the carbon element acts
in a different way from what it does in simple carbon steels as
previously discussed.
MANGANESE.
Manganese Steel is a typical self-hardening steel and so, obviously, is
any steel which is in the austenitic condition at atmospheric
temperatures, that is to say, whose critical temperature is below
atmospheric temperature. Thus, self-hardening steels are non-magnetic.
Because of its low-yield point, manganese steel does not give
satisfaction in many lines, for which otherwise it might be eminently
fitted.
Manganese used in =small= quantities (.30% to 1.50%) will produce
certain desired effects. Under these conditions it acts as a purifier.
And when added in the form of Ferro Manganese to a heat of steel it
unites with the oxygen and transforms it to slag as oxide of manganese.
There is also good reason for believing that manganese prevents the
coarse crystallization, which impurities such as Phosphorus and Sulphur
would otherwise produce. Five per cent to 14% manganese renders the
steel non-magnetic as well as a poor conductor of electricity.
SILICON.
The dividing line between silicon-treated steels and silicon-alloy
steels is not clearly defined, but the latter are used for several
important purposes.
Such steel has been used in springs of the leaf type for automobiles
and other vehicles, the silicon being considered to add slightly to the
toughness of the springs. However, the most important use of steels of
this type is probably in the manufacture of electrical machinery. It is
possible to produce a silicon-alloy steel which has not only a greater
magnetic permeability than the purest iron, but also, a high electrical
resistance. Its hysteresis is, of course, low, this property always
accompanying a high permeability. It therefore is a very valuable
material for use in electro-magnets, and in electric generating
machinery, is the most efficient material known.
In silicon-treated steels, the silicon is used somewhat as a scavenger,
although it also produces results somewhat similar to manganese.
PHOSPHORUS.
Phosphorus has little effect upon the hot properties, but in the cold
state makes the steel brittle and is of course highly undesirable
although some writers have claimed that it adds to the tensile strength
in about the same degree as carbon.
SULPHUR.
Sulphur has just the opposite effect of Phosphorus, and makes the steel
crack while it is being hot worked, although after the metal is cold it
seems to have no particular effect upon the physical properties.
ELEMENTS WHICH HAVE BECOME
ESPECIALLY ASSOCIATED
WITH SPECIAL
ALLOY STEELS.
Such elements are:—Chromium, Tungsten, Molybdenum, Vanadium, Cobalt,
Uranium, Titanium, Aluminum, etc.
CHROMIUM.
Chromium is an indispensable constituent in modern high speed steel,
and does not make a poor high speed steel, even when used alone. The
chief effect which chromium produces in high speed steels is
undoubtedly that of “hardening”. However, chromium, like carbon, will
produce brittleness, if added in too large quantities, although if kept
down to between 2 to 5% it seems to allow the lowering of the carbon
element, while at the same time maintaining the desired hardening
effect, without causing undue brittleness. The great hardness in the
face of an armor plate, and the great toughness in the back of the
plate, also the superb properties in the projectile which attempts to
pierce the plate, can all be induced in chromium steels to a degree
unattainable by the use of any other single element.
As a simple chromium steel the product may be used in five-ply plates
for the manufacture of safes. These plates are made of five alternate
layers, two of chrome steel and three of soft steel, and after having
been hardened, offer resistance to the drilling tools employed by
burglars. Hardened chromium rolls are manufactured for use in
cold-rolling metals. Files, ball and roller-bearings are other noted
products of this type of steel. It is the essential constituent of
those steels which neither rust nor tarnish.
TUNGSTEN.
It was soon found that the composition of “self-hardening” steels was
not the best one for high speed steels. Tungsten was discovered as an
element which gave the steel properties of hardness and toughness at a
red heat. After the peculiar heat treatment had been learned, and the
presence of manganese or chromium in addition to the tungsten was shown
to be unnecessary in appreciable amounts, it was found that more
durable qualities could be obtained by increasing the percentage of
tungsten, while at the same time the carbon element was greatly
reduced.
The best grade of High Speed Steel ought to have a tungsten content of
about 18.00% and a carbon content of about 0.65%. Thus whenever a steel
is needed which must operate under especially severe conditions, this
would be the steel to use. Such conditions are usually met in the case
of rapid turning, boring, planing, slotting and shaping tools, also
with twist drills and all forms of milling cutters, gear cutters, taps,
reamers, special dies, etc.
MOLYBDENUM.
Molybdenum was once thought of as being somewhat in a class with
tungsten, but its use in high speed tool steels is being generally
discontinued. The reason for this is that it was found that in rapid
steels this element caused irregular performance, such as large
variations in the cutting speeds which they would stand. This element
is also likely to make the steels seamy and contain physical
imperfections. Molybdenum steels were also found to crack on quenching,
and possess decided variations in internal structure.
VANADIUM.
Vanadium steels are still in their infancy. Therefore, the true value
of this element in rapid steels must probably be held as not yet fully
determined. With the single exception of carbon, no element has such a
powerful effect upon steel as vanadium, for it is only necessary to use
from 0.10 to 0.15% in order to obtain very noticeable results. In
addition to acting as a very great strengthener of steel, especially
against dynamic strains, vanadium also serves as a scavenger in getting
rid of oxygen and possibly nitrogen. It is also said to decrease
segregation, which we may readily believe, as most of the elements
which quiet the steel have this effect.
“Vanadium Steels” demand a somewhat higher price than do those steels
which do not contain this element in appreciable amounts. It is, of
course, especially useful for all purposes where strength and lightness
are desired, such as springs, axles, frames and other parts of railroad
rolling stock, and automobiles.
COBALT.
The valuable effect of cobalt is claimed to be that it increases the
red hardness of high speed tool steel, enabling the steel to cut at a
higher speed. However, this element much resembles nickel, which has
been largely condemned as not being a desirable ingredient for high
speed tool steels, because it has the effect of making the edge of the
finished tool soft or “leady”.
URANIUM, TITANIUM AND ALUMINUM.
These elements are generally classed as scavengers, although recently
important claims have been advanced for their effect upon the physical
properties of steel. This is especially true for the first two. In
present practice, however, they are used almost entirely as deoxidizers
or cleansers, and are added to the metal for this purpose only.
IMPURITIES.
Phosphorus, Sulphur and Copper are the most noted impurities which
occur in steel. The first two are practically always present in greater
or smaller amounts as the case may be. The best processes of tool steel
manufacture are capable of producing steels with no copper. While
Aluminum is not generally classed as an impurity, it nevertheless
sometimes shows up in the finished product when its presence is not
desired, and therefore, might be considered an impurity.
Combinations of iron with some or all of the above elements in the form
of slags and oxides are other well known impurities.
From the forgoing pages it must be evident that producing a steel with
exactly the correct chemical content is only =one= step towards
securing a satisfactory product. However, it might be well if we were
to briefly sum up a few of the more important features of our
discussion on this interesting subject.
HEAT TREATMENT.
The heat treatment of tool steels is of the utmost importance. Tool
makers of the old school proved their ability to accomplish certain
desired results in the art of heat treatment without really fully
understanding exactly how or why they were able to do so. Today,
however, progressive manufacturers are using the results of research
and such thorough scientific investigation that the process has become
far more complicated and complex, and the results obtained are
correspondingly more remarkable.
Chemically perfect steel may be easily and completely ruined during the
process of melting, cogging, rolling, hammering, annealing, heat
treating and tempering. It is the business of the steel manufacturer to
carefully guard his product up through the process of annealing, but it
usually falls to the tool maker to undertake the delicate operations of
heat treatment and tempering.
HARDENING.
The application of heat alone to steel can very materially affect the
condition of the structure of the metal, either with or without
simultaneous mechanical treatment. Depending upon the degree of heat,
the rate of heating and cooling and the duration of such treatment,
this application may be decidedly beneficial or harmful as the case may
be.
We now know that when steel is heated above the critical point, and is
then allowed to rapidly cool, a very marked hardness in the metal is
produced. The degree of hardness so attained will, in general, vary
directly with (1) the percentage of carbon, (2) the rate of cooling,
(3) and the temperature above the critical point from which the cooling
takes place. When the steel comes from the rolling mill and from the
finishing hammers it is in this hardened condition. Therefore, in order
to render it soft and ductile enough to cut and work up into certain
desired shapes, sizes and tools, it is necessary to subject the steel
to the process of annealing. This operation is usually undertaken by
the steel producer, under which circumstances he is able to control his
product through this delicate procedure, and deliver the same to his
customers in the best possible condition for their use.
ANNEALING.
Annealing has for its object: (1) Completely undoing the effect of
hardening, leaving the steel soft and ductile (2) refining the grain,
in which case the crystals are allowed to re-arrange and re-adjust
themselves, usually growing to a rather large size (3) and removing
strains and stresses caused by too rapid cooling. Such cooling strains
are particularly likely to exist where the rate of cooling is different
in different parts of the bar, but the process of annealing ought to
remedy any such condition, leaving the steel soft, ductile and of
refined and uniform crystalline structure throughout.
The process of annealing is easier to explain than it is to actually
put into practice. The steel is first packed in lime, charcoal, fine
dry ashes or sand, and then sealed in long air-tight tubes or boxes.
The whole receptacle is next slowly brought up to a dull red heat, of
about 1500 degrees Fahrenheit.
It is very important to heat the material uniformly all the way
through, and then hold it in this condition from three to eight hours.
Thus, allowing the slipping of one allotropic condition into another.
The receptacle must be cooled equally slowly, either allowing the
packed steel to cool slowly down with the furnace, or by placing the
same in a soaking or cooling pit, which also accomplishes the desired
result.
After the receptacle has become entirely cooled it is opened and the
steel unpacked and removed. The steel is then ready for its final
inspection before shipping to the tool maker.
TEMPERING.
The process of tempering usually has to be undertaken by the tool maker
or user after the annealed steel, which he received from the steel
mill, has been cut up and shaped into the desired form and size.
The main object of tempering steel is to re-harden the material to such
an extent that it will cut other metals, retaining its desired shape
size and cutting edge, while at the same time it must not possess too
much brittleness. The treatment varies materially with different brands
of steels.
For the average grade of the best High Speed Steel containing from 16%
to 18% tungsten, the tool should be brought very slowly up to a dull
cherry red. It is usually considered good practice to first place the
tool near or on top of the pre-heating furnace before actually placing
it in the pre-heater, in order that the heating might be effected just
as slowly as possible. The pre-heating operation should bring the tool
up to about 1600 to 1800 degrees Fahrenheit, after which the tool
should be placed in the high heating furnace and brought up to 2300 to
2400 degrees Fahrenheit, or a white sweating heat. Care should be taken
not to allow the tool to remain in this condition for more than an
instant, as it is then in a very critical condition and could be easily
burned or ruined.
Therefore, the tool should be immediately pulled from the furnace and
plunged into a good clean oil bath, keeping it constantly in motion.
As High Speed Steels are air-hardening steels, it is also the practice
to harden these steels by simply placing the cutting edge in an air
blast, which produces maximum hardness in the desired point and allows
the body of the tool to cool at a little slower rate, thus slightly
relieving the cooling strains and producing a little less brittleness
therein. Such cooling strains can be relieved throughout the whole tool
by drawing the same back to about 400 to 500 degrees Fahrenheit, and
sometimes as high as 1050 degrees Fahrenheit, depending upon the
particular tool and its use.
The treatment of Carbon Steels varies with each particular brand. Great
care must always be taken to heat the steel uniformly, as a material
which is heated unevenly will expand and contract unevenly and, in
consequence, will crack when quenched.
The steel should always be hardened on the rising heat, in general
bringing the same slowly up to a dull cherry red, or to about 1450
degrees Fahrenheit, and then quenching in clear cold water, keeping the
same in motion until the steel is cold. The temper should then be drawn
according to the purpose of the tool, which could only be discussed for
each particular case. The following range of temperatures are
interesting, as being approximately indicated by the thin film of oxide
tints which occur on the tool undergoing a tempering operation:
Pale Yellow 428 Degrees Fahrenheit
Golden Yellow 469 Degrees Fahrenheit
Purple 531 Degrees Fahrenheit
Bright Blue 550 Degrees Fahrenheit
Dark Blue 601 Degrees Fahrenheit
CONCLUSION.
The effects of annealing, rolling, hammering, treating and tempering
are best understood by those manufacturers who make a specialty of
supplying a high grade tool steel, and in general it would be well if
customers would consult freely with the producers of these steels,
before attempting the delicate undertaking of Heat Treatment.
CHAPTER VI.
WHAT TOOL STEEL IS DOING TOWARDS
WINNING THE WAR.
It hardly seems fitting that we should close these pages without giving
our readers some little idea of just what the tool steel industry is
doing for the successful conclusion of the great cause nearest our
hearts.
One of the first statements which we could make would be that every
metal worker in the world absolutely requires some form of tool steel
or special alloy steel in the manufacture of his product. Of course, a
very great many manufacturers other than the actual metal workers also
need this same supply of tool steel in order that their production
might not immediately cease. Volumes could be written on the vital
importance of tools to industry in general, from the drills which drill
out the hole in a hypodermic needle, to a twelve-ton drop-forge steam
hammer. But for the present we may confine ourselves to simply the
briefest mention of the vast number of iron and steel products actually
and vitally engaged in the prosecution of the war.
We are told that we need ships, yet the ship industry could not proceed
a day if its supply of necessary tools was cut off. The overwhelming
increase in the manufacturing operations of the world which has taken
place since the opening of the European War can better be imagined than
explained, it being only necessary for us to point out here that the
one absolute necessity which is common to all and required by all
branches of such vast manufacture is the proper supply of necessary
tools.
It has been the personal duty of the writer to make various visits to
different Government shops and Arsenals as well as to the plants and
shops of torpedo, shell and munition manufacturers and the vital part
which the tools of production are playing in the great undertaking has
been forcefully impressed upon his attention.
The metals which are destined to play an active part in actual warfare
are naturally required to meet the most severe conditions imaginable.
Thus we find the high manganese armor plate and the high
chrome-manganese armor piercing projectile. We find the new
specifications for steel forging, for hulls and engines now have rigid
chrome-vanadium and special nickle requirements, all of which means
that the tools that do the machining, planing, shaping, cutting,
drilling, boring, reaming, stamping and many other operations must be
made of a tougher and harder material than ever before.
We know that for every man who may fight on the battle field, at least
two men must labor in our shops and factories over mechanical
operations.
Those of us who have been in immediate touch with some of the vital
requirements of the War and Navy Departments in these strenuous days
realize the shocking absence of the complete preparedness, which we
must rapidly accomplish if we are to come anywhere near supplying our
own soldiers on the fighting front with the fighting machinery and
supplies of which they are in such urgent need. We realize that after
all these months of increased industrial preparedness, we are,
therefore, still unprepared in the full meaning of the word. The very
foundation of our structure shows a startling amount of unpreparedness.
We like to gaze upon the exterior towers and battlements of a castle of
preparedness, and these are wonderful and encouraging to look upon but
down below all these are certain neglected and unfinished pillars in
the unseen cellar of that foundation, which threaten the stability of
the entire mass. It is, therefore, some of these fundamental details
which have been neglected as we have beheld the vision of the
super-structure above. Pershing needs, 1,500,000 boys in khaki and over
the shoulder of each is his protection against the Hun. Everyone of
these rifles is a splendid monument of the accomplishment of tool steel
and special alloy steel.
Every day of our present existence it happens that over a million
shells scream over the miles of battle line in France. This curtain of
high explosive and shrapnel is another direct expression of the wonders
which the modern high speed and special alloy steel have accomplished.
We are told that a 3“ shrapnel shell contains seventy drilled holes or
a drilling of 19-1/4” in depth. That means that 1,600,000 feet or over
three hundred miles of drilled holes are shot away every twenty-four
hours on the battle fronts of Europe.
In a publication “Fighting Industry” published by one of our largest
twist drill companies in this country, we note that the drilled holes
in various implements of our militant harness are as follows:
8“ shrapnel shell 70
Springfield rifle 94
Torpedo 3466
Machine gun 350
Aeroplane 4089
3-ton auto truck 5946
Light ambulance 1500
3” field gun 1280
Gun caisson 594
Anti-air craft gun 1200
Self-binder 500
Thresher 420
Motorcycle 1160
Four million men must work with tools in order that two million men may
fight in France. These men can not, “just be given a tool and told to
use it.” It is necessary that they have years of careful training and
actual experience in order that they might effectively make use of the
intricate tools and machinery which the mother of modern industry is
striving to place in their hands. At present every tool steel mill in
America is straining its furnaces, hammers and rolling mills to their
maximum capacity. They are working days, nights and Sundays and still
the demand is far in excess of the supply. Conservative estimations
show that with all the added machinery and equipment which is in the
process of construction at this time, it will still take at least two
years and a half before the tool steel industry of America will come
any where near meeting the demand for its product.
As we gaze with belated pride upon the huge structure of our present
Preparedness, does it not seem strange to think that the most vital
pillar of its whole foundation should have been forgotten and neglected
so long and which is therefore now caused to endure such an abnormal
and terrific strain? We are at last forced to realize that tool steel
is the very essence of our whole existence.
Of course, the great importance of tool steel in this national
emergency does not stop with the actual weapons of warfare. Besides the
railroads, automobiles, tramways, elevators, bridges, buildings,
shoes, clothing and in fact, every branch of the intricate mass of
manufactured products so vital to our daily existence, nations are
crying for bread. Victory hangs on our food supply. Our threshing
machines, our reapers and our harvesting machinery are all working over
time. But before the threshing machines can thresh wheat and before the
reapers can reap and before the tractors and other farm machinery can
contribute their great service to humanity, it is necessary that the
American production of tool steel must pass its rigid inspection and
yield forth in full measure the great service which it is called upon
to give.
APPENDIX.
ANALYSIS, USES AND HEAT TREATMENT OF
VARIOUS GRADES OF TOOL STEELS.
Providing the many complications and difficulties which accompany the
melting, hammering, rolling, annealing, inspecting and finishing
operations, have been successfully accomplished, the chemical analysis
of the best grades of tool steel should come within the following
limits:
TYPICAL ANALYSIS OF HIGH
SPEED STEEL.
Carbon .66 %
Tungsten 18.01 %
Chromium 4.50 %
Vanadium .98 %
Phosphorus .023%
Sulphur .021%
Manganese .285%
Silicon .228%
Iron (by deduction) 75.293%
USES.
Turning, Boring, Planing, Slotting, Shaping Tools. Also Twist Drills,
Milling Cutters, Gear Cutters, Taps, Reamers, Special Dies, etc.
HEAT TREATMENT.
Heat slowly in pre-heater to 1700 degrees Fahrenheit. Then rapidly in
superheater to 2300 degrees Fahrenheit, taking care not to burn or
fuse delicate projections on special tools. Harden either in air blast,
or in good clean oil; keeping tool in motion. In all cases merely the
_end_ of the tool to white heat. Draw in oil from 400 degrees
Fahrenheit to 600 degrees Fahrenheit.
TYPICAL ANALYSIS OF DIE
STEEL FOR HOT WORK.
Carbon .39 %
Tungsten 8.41 %
Chromium 2.10 %
Phosphorus .019%
Sulphur .017%
Manganese .315%
Silicon .234%
Iron (by deduction) 88.515%
USES.
Hot shear blades, hot punches, header and gripper dies; used in bolt
and rivet making. Also excellent for compression sets and in general
for all hot work.
HEAT TREATMENT.
Will stand high hardening heats, similar to high speed steel, 1700
degrees Fahrenheit and then 2300 degrees Fahrenheit. Harden either in
air or oil. Keep away from water. Draw to 500 degrees Fahrenheit.
TYPICAL ANALYSIS OF SPECIAL
ALLOY STEEL.
Carbon .78 %
Vanadium .29 %
Phosphorus .014%
Sulphur .016%
Manganese .324%
Silicon .296%
Iron (by deduction) 98.28 %
USES.
Specially useful in tools subject to shock, such as hand and pneumatic
chisels, boilermakers caulking tools and rivet sets. Also for cold
upsetting dies, cold punches, shear blades and stamping dies. A special
grade of this steel makes excellent taps.
HEAT TREATMENT.
Heat slowly to a low red, about 1400 degrees Fahrenheit, or if low
carbon content to 1500 degrees Fahrenheit; being very careful not to
over-heat. Quench in good clean tempered water; keeping tool constantly
in motion. Draw from 250 degrees Fahrenheit to 400 degrees Fahrenheit.
TYPICAL ANALYSIS OF FAST FINISHING
SEMI-HIGH SPEED.
Carbon 1.28 %
Tungsten 3.56 %
Phosphorus .021%
Sulphur .019%
Manganese .316%
Silicon .271%
Iron (by deduction) 94.533%
USES.
Do not confuse the High Speed, although excellent for turning chilled
cast iron, clean finishing cuts. Especially adapted for taps and
reamers, as well as for tools for brass, bronze, aluminum, copper and
chilled roll turning.
HEAT TREATMENT.
Heat slowly to full bright red, 1425 degrees Fahrenheit to 1500 degrees
Fahrenheit. Quench in luke warm water. Keep tool constantly in motion.
Draw to not over 300 degrees Fahrenheit.
TYPICAL ANALYSIS OF SIMPLE
CARBON TOOL STEEL.
Carbon 1.12 %
Phosphorus .009%
Sulphur .011%
Manganese .254%
Silicon .213%
Iron (by deduction) 98.393%
USES.
General tool room usage _with moderate cutting speeds_. Excellent
lathe, planer, and shaper tools, drills, shear blades (for cold work
only) punches, chisels, files and mining tools.
HEAT TREATMENT.
Heat slowly to Low Red heat, approximately 1375 degrees Fahrenheit (the
higher the carbon the lower the heat). Care not to over-heat. Quench in
good clean luke warm water. Draw to not over 350 degrees Fahrenheit.
TYPICAL ANALYSIS OF NON-SHRINKING
OIL HARDENING
STEEL.
Carbon .91 %
Phosphorus .016%
Sulphur .019%
Manganese 1.62 %
Silicon .31 %
Iron (by deduction) 97.125%
USES.
Threading dies, chasers, taps, reamers, and all master tools. For
gauges, plugs, etc. Especially adapted for stamping, punching, trimming
dies and many other uses where it is necessary to overcome shrinking,
warping or change of shape.
HEAT TREATMENT.
Heat very slowly to pre-heating temperature of 1200 degrees Fahrenheit,
then to hardening temperature from 1360 degrees Fahrenheit to 1425
degrees Fahrenheit, depending upon size of piece being treated.
Harden in lard, linseed or cottonseed oil; preferably fish oil. Do not
quench in water.
Draw cutting tools, taps and reamers at 250 degrees to 300 degrees
Fahrenheit. Large tools such as blanking and stamping dies at 400
degrees to 450 degrees Fahrenheit.
TYPICAL ANALYSIS OF SPECIAL
HOT WORK ALLOY STEEL.
Carbon .86 %
Chromium 3.71 %
Phosphorus .023%
Sulphur .019%
Manganese .381%
Silicon .267%
Iron (by deduction) 94.740%
USES.
An excellent composition for hot work in service for grippers, headers,
hot punches, hot shear blades and similar tools. Especially valuable in
structural steel and boiler shop work. Rivet sets and bull dies made
from a steel of this composition ought to resist breaking and
battering.
HEAT TREATMENT.
Very flexible hardening in air, oil or water. If air is used heat to
1675 degrees to 1750 degrees Fahrenheit and place under dry air blast,
or stand in cool place. To harden in oil, heat to 1500 degrees to 1550
degrees Fahrenheit and quench in thin oil. To harden in water, heat to
1475 degrees Fahrenheit to 1525 degrees Fahrenheit and quench in cool
water. Draw from 250 degrees to 300 degrees Fahrenheit.
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