Improvements in the Manufacture or Treatment of Iron or Steel.
Year: 1892

page_text: Date of Application, 2nd Feb., 1892-Accepted, 5th Mar., 1892
COMPLETE SPECIFICATION.
Improvements in the Manufacture or Treatment of Iron or Steel.
I, DOUGLAS DYRENFORTH, Lawyer, of 225 Dearborn Street Chicago, County
of Cook, State of Illinois, United States of America, do hereby declare the nature
of this invention and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement :-
My invention relates to a process of treating iron, and more particularly to a
process by which iron which has been decarburized, or which is not thoroughly
saturated with carbon, may be supplied with the desired proportion of carbon and
otherwise improved without the introduction of foreign impurities, or other agents,
such as manganese or silicon.
In the production of cast-iron for foundry use it is usually desirable to provide
a pig iron as thoroughly saturated with graphitic carbon as it is possible to secure
under the conditions of smelting in a blast furnace, but on remelting in a cupola
for the purpose of casting it is found that there is a decrease in the amount of
carbon, silicon and manganese and an increase in the amount of sulphur contained
in the metal. Of these changes the decrease in the amount of manganese tends to
the formation of grey iron, but its action is quite feeble and is much more than
overpowered by the other changes, all of which favor the formation of white iron,
so that as a final result there is a strong tendency towards the formation of white
iron and the production of castings hard and brittle and of a tensile strength
approximately less than the original character of the pig iron would justify. "A
second and third remelt of such a casting increases its brittle character, so that iron
thus subjected to the remelt is classed as scrap iron and is of slight value except
for the commoner kind of casting.
My invention has for its object, therefore, to increase the percentage of carbon
and even
saturate iron, when in an incompletely saturated condition, or when
decarburized, with carbon in such a manner as to increase the tensile strength and
density of the iron, and at the same time to counteract the tendency to hardening
which usually goes with an increased tensile strength, and even to reduce its normal
hardness. Incidentally, I seek, by my process, to provide a mode of casting iron
in metallic molds without chilling.
I have ascertained that iron when in a molten condition and at a temperature at
which it runs freely, viz., a temperature of about 3000° F., or upward, when
brought into contact with carbonaceous material in a pulverulent condition acts to
dissolve the carbon, which becomes incorporated into the iron; and that if a
sufficient quantity of pulverized carbon is acted upon, a distinct and material change
in the character of the iron takes place throughout, contributing a material
increase in its tensile strength, causing a material increase in the softness of the
iron, and a density or fineness of grain of the product very noticeable on mere
inspection. Other changes also take place in the metal, the exact nature of which
I have not yet been able to ascertain; but I believe that the finely divided
carbon exerts a reducing action upon the slag and oxides entangled in the iron and
causes their removal.
In carrying out my process, I find it best to introduce the pulverized carbon, in
the form of graphite, plumbago, or the like, and in as fine a state of division as can
practically be obtained, into metallic molds, by coating the interior of the mold with
a paste composed of pulverized carbon and water, with or without gum arabic or
an analogous substance, to insure its adhering to the wall of the mold, thereupon
to subject the mold to heat for the purpose of evaporating the water, and finally
while the mold is still hot, say at a temperature of 200° F., or thereabout, to
introduce molten iron having a temperature of not less than about 3000° F., and
preferably approaching the highest temperature obtainable in the cupola

page_text: to wit, 4000° F., or upward. The iron is then allowed to cool in the ordinary
manner, and the casting is found to present the characteristics of increased tensile
strength, softness and density before mentioned.
Another mode under which I have successfully effected the operation on iron
remelted in a cupola has been to prepare ingot-pans each capable of holding an
ingot of say 100 pounds, by coating such pans with pulverized carbonaceous
material (graphite or plumbago) combined into a paste with water, and sometimes
with and sometimes without a small amount of gum arabic or other analogous
substance, heating the pans and thereupon introducing the iron in a molten con-
dition and at a high temperature. The ingot thus produced is thoroughly saturated
with carbon and may be remelted in the cupola for re-casting.
Different irons require, for the best results from the treatment, the employment
of different proportions of pulverized carbon, but it may be stated as a general rule,
that the treatment with graphite in a proportion of upward of one-thirty-second
of one per cent., but ordinarily not exceeding two or two and one-half per cent.,
may be used with full benefit. In the treatment of scrap iron usually bought in
open market and varying very materially in its character, the process has been
very successfully carried on with about one-tenth of one per cent. of pulverized
carbon by weight. In the treatment of certain pigs, such as Bay View pig, when
one-fourth of one per cent. of pulverized graphite was introduced in the mold it was
found that the entire quantity was not taken up by the iron, the calculation, made
under difficulties, indicating that perhaps one-twelfth of one per cent. had been
taken up, leaving the rest in the form of a deposit on the sides of the mold. It is
apparent, therefore, that by increasing the thickness of the pulverulent lining to
provide a quantity of carbon in excess of the amount which the iron will take,
successive castings under the process may be made in the same mold after one
application of carbon thereto.
As before stated, any kind of pig or scrap iron can be effectively treated and
improved so as to have an increased tensile strength, softness and density, but the
proportion of improvement varies in inverse ratio to the quality of the original
metal. A low grade of pig is improved to a much greater degree than a high
grade of pig.
While the best, surest, and, under most conditions the quickest, mode of intro-
ducing the carbon, is, as stated, to apply it in a coating to the interior of the mold
or ingot-pan or ladle, it may be introduced in bulk, preferably not in a single mass
but in subdivided masses in different parts of the ladle or pan. Under all circum-
stances I find it necessary that the carbon shall be finely divided, not exceeding in
granular dimension fairly fine sand; and under the conditions of heat possible in
carrying on the process at the cupola it is desirable that the carbon shall be reduced
to the finest practicable state of division, as before mentioned.
Certain of the test samples made to demonstrate the operativeness of this process
were made from No. Bay View pig, remelted, and, at a temperature of
about 3500° F., introduced into a metal (cast iron) mold, holding about six pounds,
into which had been previously introduced about one-fifth of one per cent. by
weight, say ninety-six grains, of carbon (plumbago) in a finely pulverized condition.
The carbon was mixed with water into a paste, to which was added a very small
proportion of gum abrabic, and while in this condition was applied to the mold
with a brush, thus being spread uniformly throughout the mold. The latter was
thereupon heated to about 150° F. and the Bay View iron, at the temperature
named, was introduced into the mold. The two samples of castings one treated
and the other not treated, were taken from the same ladle and the conditions of
pouring were identical to both.
The untreated casting shows, on analysis, the following composition :

page_text: Tensile strength (average two samples) 28,622 pounds per square inch. One
sample showed a tensile strength of 28,722 and the other 28,522. There is an
increase in tensile strength of the iron of 10,087.5 pounds, or about fifty-five
per cent., while the treated iron is softer than the untreated as the results of this
process. It may be stated that a mixture of scrap and pig iron subjected to this
treatment showed an increase of about fifty per cent. in tensile strength, accompanied
by an increase in softness and density.
The process herein described is to be carefully distinguished from the process in
common use, by which the exterior of a casting has been given a smoother surface
by dusting a small portion of powdered graphite on the interior of the mold.
Under this process no change in the constitution of the iron was sought or
effected, neither of the essential conditions of heat nor quantity apparently being
present. The purpose was different and the quantity of graphite was too slight
to exert any noticeable effect in the line of improvement which forms the subject
of this invention. My invention is also to be carefully distinguished from any
process in which the carbon is rendered hard and slaty by the association with it
of oil, clay, or other substance, since it is essential for success with my process
that the carbon be in a finely divided state and the particles easily surrounded and
absorbed by the metal. I am aware of a process by which a coating essentially
solid in its character and of a thickness of a half inch, or thereabout, has been
provided on the interior of molds to serve for heat non-conducting purposes in the
process of casting, but, as will be apparent, such a procedure is foreign to my
invention and is not to be included therein. It is probable that the non-conductive
character of plumbago contributes an advantage in the practice of my process to
the extent that it assists in preventing the chill of the iron at the surface adjacent
to the mold; but this effect, if obtained, is a minor feature of my invention. By
none of the processes above named as existing before my invention or any other
process heretofore practiced with which I am familiar, has the very marked
improvement above mentioned been obtained; and the importance of the invention
arises, not only from the remarkable character of the product, but from the fact
that the practicing of the process, under ordinary circumstances, involves an
insignificant additional expense to the ordinary cost of treatment. It will be
remembered that the commercial value of iron is largely governed by its tensile
strength and the ease with which it may be manipulated in the foundry and machine
shop. The loss, due to the treatment by my process, is so slight that it may be
disregarded.
The essential result of my aforesaid treatment is iron having the peculiarities of
exceptional tensile strength and softness, which have led me to adopt for my
product the significant appellation "Fortimolite" metal, which implies strong and
-soft.
The readiness and thoroughness with which the carbon when my process is
followed, becomes associated with the iron, has been utilized by me in the recar-
burization of steel after the same has been decarburized in any of the usual ways.
It is a common practice to pass the molten iron from the decarburizing apparatus
through coke or other form of carbon in lumps, and also to inject the carbon in
other ways.
I have demonstrated, however, and this forms an important feature of
my invention, that if pulverulent carbon in introduced into a vessel and the molten

page_text: metal then introduced into the same vessel above the carbon, the carbon becomes
immediately taken up by the iron, serving to saturate the iron to the desired point
with carbon for the production of steel. The carbon is, of course, to be retained
in the vessel in the form of a powder of greater or less fineness, but it may, if
desired, be mixed with other matter, such as manganese, which it is also desired to
incorporate with the iron.. Instead of being in the form of a layer or coating, the
carbon may be held in bulk in the vessel, or in a readily dissolved or destroyed
receptacle, such as one of paper.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is
1-The process of treating iron which consists in introducing pulverulent
carbonaceous material into a vessel, raising the temperature of the iron to a point
at which it will flow freely and while in this condition bringing the same in contact
with the carbonaceous material, and thereupon permitting the carbonaceous
material to act upon the iron, substantially as described.
2-The process of treating iron which has been cast and permitted to solidify,
which consists in remelting the iron and raising its temperature to a point at which
it will flow freely, introducing pulverulent carbonaceous material into a vessel.
bringing the iron while in the condition named into contact with the carbonaceous
material and thereupon permitting the carbonaceous material to act upon the iron,
substantially as described.
3-The process of treating iron which consists in introducing pulverulent
carbonaceous material into a receptacle, raising the temperature of the iron to a
point at which it will flow freely and while in this condition conveying it to the
receptacle containing carbonaceous material, permitting the carbon to act upon the
iron and allowing the iron to solidify, and thereupon removing and remelting
the iron, substantially as described.
4 The process of treating iron which consists in coating a metallic receptacle
with pulverized carbonaceous material in substantially the proportion named, there-
upon introducing into said receptacle molten iron at a temperature at which it will
flow freely and allowing the same to solidify without removal, substantially as
described.
5-The process of producing castings which consists in introducing pulverulent
carbonaceous material into a vessel and introducing molten iron into said vessel at
a temperature at which it will flow freely, permitting the carbonaceous material to
act upon the iron, and permitting the iron to solidify, thereupon remelting the iron
and introducing the same into a metallic mold having an interior coating of
pulverulent carbonaceous material, substantially as described.
6-As a new article of manufacture, the metal herein described as resulting
from my aforesaid process, whereby its qualities of density, tensile strength and
sottness are increased.
7-As a new article of manufacture, iron to which, while in a molten condition,
has been added by absorption pulverulent carbonaceous material, thereby giving
to the metal the distinguishing qualities of increased density, tensile strength and
softness.
Dated this 2nd day of February 1892
W. P. THOMPSON & BOULT,
Agents for the Applicant.