Improvements in the Manufacture of Compound Ingots.
Year: 1899

page_text: Date of Application, 12th Dec., 1899-Accepted, 27th Jan.,
1900
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Compound Ingots.
I, SYLVESTER ALPHONSE COSGRAVE, Manufacturer, residing at Edgewood Park,
County of Allegheny, State of Pennsylvania, 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:
The invention described herein relates to certain improvements in the manu-
facture of compound ingots or billets, i.e. those consisting of two grades or kinds
of metal as hard and soft steel. The method now in general use consists in
dividing the ingot or billet mold by a thin sheet metal partition and pouring
the two kinds or grades of metal on opposite sides of the partition. By contact
with the hot metal the partition is either melted, and so becomes incorporated
with the molten metals and permits the two bodies of metal to come together and
unite; or the partition becomes heated to a welding heat and the two bodies of
metal unite with the surfaces of the partition. This method will produce a
close union between the two bodies of metal, but not a welding or intimate
knitting of the two metals. This failure to weld is believed to be due to a change
in the metals in contact with the cold or comparatively cold partition.
And further two metals have been united by applying a flux to the surface of
one metal, heating such metal to a high temperature, and then pouring the other
metal on the prepared surface. In this method the flux does not penetrate below
the surface of the first metal, but simply acts to remove the surface oxide which
would prevent the adherence of the two metals.
It is characteristic of the methods above described that the two metals simply
adhere together, and that neither in any way affects the chemical or physical
characteristics of the other, but that each, even at the plane of adherence, has
the same chemical and physical characteristics as at points distant from the plane
of adherence.
It has also been attempted to produce compound ingots by casting one of the
metals in a suitable mold, then immediately exposing or uncovering one surface'
thereof and casting the other metal thereon. Although the metal first cast may
appear to be still molten, there will be formed thereon a thin skin which will
prevent the complete welding of the two metals.
While either of these methods will produce an adhesion of the two metals,
which will be sufficient where the articles are not subjected to excessive strains,
they will not produce such a union or homogeneity of the two metals as is
necessary to preclude the possibility of one metal being removed from the other
under violent shocks.
It is characteristic of the methods heretofore employed that there is a sharp
line of demarkation between the two grades of metal, so that a plane of cleavage

page_text: or separation exists. It is characteristic of armor plates having their exposed
faces hardened by recarburizing or otherwise, that the hardened portions will
not break off even when subjected to the severest shocks. This characteristic is,
I believe, due to the fact that there is a gradual change from one kind or grade
of metal to the other so that no plane or line of cleavage is formed.
The object of the present invention is to prevent the elemental change produced
in the portions of the bodies of metal in contact with the partition whereby a
union of the adjacent portions of the two bodies is prevented in the practice of
the old methods; or in case such elemental change is produced, to provide for
the re-conversion of the changed portions.
It is a further object of the invention to bring the two metals together under
such conditions that the chemical and physical characteristics of both metals at
and adjacent to the plane of mixture or union will be changed, the characteristics
of one metal being modified or changed by the other. The invention is herein-
after more fully described and claimed.
In the accompanying drawings forming a part of this specification, Fig. 1 is
a sectional elevation of an ingot mold having a core in position and showing one
kind or grade of metal cast around the core; Fig. 2 is a horizontal section of the
same; Figs. 3 and 4 are views respectively similar to Figs. 1 and 2, showing the
core removed and the space occupied by the core filled with another kind or
grade of metal; Fig. 5 is a sectional elevation of a mold constructed to permit
of the casting of the metal through the bottom of the mold, and Fig. 6 is a similar
view showing the core partially withdrawn, and the space so formed filled with
metal.
The invention consists in bringing together two bodies of molten metal on
opposite sides of a wall or diaphragm formed of metal of the same character as
one of the bodies, and being heated to such a temperature that it will not have
any material cooling action on either body, but will become molten almost instan-
taneously when inclosed by the two molten bodies. This method can be effected
by pouring one of the metals in a mold, as 1, having a removable core 3, as
shown in Fig. 2, or having a removable partition. As soon as the metal in contact
with the core or partition has solidified sufficiently to restrain the molten metal
in the interior portion, the core or partition is withdrawn and the other metal
poured into the mold. It is preferred, as shown in Fig. 5, to construct the mold
so that the second body of metal may enter through the bottom of the mold, so
that the metal will as nearly as practicable follow up the core or partition as
they are withdrawn, thereby avoiding to a great extent, any exposure of the
surface of the metal first cast, to atmospheric influences. As a general practice,
it is preferred to form the core or partition of, or to coat the same with, some
material which will either prevent such elemental changes of the metal in contact
therewith as would tend to prevent a union or mixture of the metals, or will, in case
such changes should occur, effect a reconversion or elimination of the portions
of metal so changed. These ends can be attained either by forming the core or
partition of, or coating them as at a, with a fluxing material, as silica, or, a
deoxidizing material, as carbon.
A desirable method of practicing the invention herein described consists in
casting one of the metals, as high carbon steel, in a suitable mold and then, while
still at a high temperature, the surface to which the other metal is to be united
is subjected to such treatment as will prevent such elemental changes, as the
formation of oxides, etc., which would interfere with an intimate union with the
other metal, or in case such changes have occurred, will reconvert the metal to
a homogeneous condition. As soon as the surface of the metal has been heated,
the other metal is cast thereon.
This treatment of the surface of the first body of metal should be effected while
the metal is in a molten condition, or while it is at such a high temperature as
to become molten when the other metal is poured thereon. A convenient manner

page_text: of practicing my invention consists in forming that wall of a mold forming the
matrix of the surface against which the other metal is to be poured, of some
suitable material, as carbon, which will prevent the formation of oxides, or will
reconvert such oxides to a metallic condition. The carbon should be in such
condition that it will be readily taken up by the metal in contact therewith, so
that each metal will have a considerable amount of graphitic or free carbon mixed
therewith. As soon as the metal in contact with the prepared wall has hardened
sufficiently to retain the interior metal, such metal being at such time in a
molten condition, the mold wall is removed and the other body of metal, as low
carbon steel, is poured into the mold. The thin metal retaining shell on the
surface of the body of metal first cast, will be again fused, as it is at the time of
pouring the second body of metal, at a temperature not greatly below its melting
point, and lies between two bodies of metal at a temperature considerably above
melting point. As the thin shell of metal and the molten metal of the body
first cast, adjacent to such shell, are saturated with carbon, it follows that when
the shell of wall becomes molten, there will be a thin strata of molten metal
between the two bodies containing a higher percentage of carbon than either of
these two bodies. As the metal of both bodies is molten, a condition most favor-
able to the diffusion of the carbon, the carbon in the saturated strata will gradually
diffuse, the low carbon steel taking up the greater proportion thereof. Although
the portion of the high carbon metal adjacent to the other body of metal may
have a little higher carbon than the remaining portions thereof, so that the ingot
will contain three strata of metal, each varying in carbon content, i.e., stratum
containing high percentage of carbon, a comparatively thin stratum containing
a still higher percentage of carbon, and a strata containing a low percentage of
carbon, it is still true that there will not be a sharp line of demarkation between
the several strata, but there will be a gradual change in carbon content from
one stratum to the other.
Another method of producing a homogeneous compound ingot, consists in
treating that surface of the body first cast, against the other metal to be cast,
with any suitable flux, such as silica, so that the exposed surface shall become
thoroughly fluxed and to such a depth that the other metal will, when poured on
the fluxed portions, become incorporated therewith. As soon as the exposed
portion of the body of metal has been thoroughly fluxed, the other metal is poured
thereon. It is preferred that an amount of flux in excess of that required to
cleanse and prepare the surface of metal first cast should be applied thereto,
so that the portion of the second metal in contact with the fluxed surface may
also be cleansed and liquefied, so as to promote or facilitate the amalgamation or
union of the two metals.
While this fluxing of the surface of the metal first cast may be effected while
it is in a molten condition as stated, or after being heated to the required tem-
perature by any suitable means, it is preferred that the fluxing or preparation
of the metal is preferably effected at the time of casting of the first body of the
mold. This can be done by forming that portion of the mold serving as the
matrix of the surface to which the other metal is to be united, of a fluxing material
as sand, or coating such matrix portion with a fluxing material in lieu of the
deoxidizing material heretofore described. When the molten metal is poured into
such a mold, the metal in contact with the fluxing material will be so acted
on by the material that if the other metal be poured on such prepared surface
while the latter is at a welding temperature, the two metals will become
thoroughly intermingled or amalgamated.
This method is especially effective in uniting two grades of steel. as this metal
when sufficiently molten to cast, will penetrate a considerable depth into the
walls of the mold, so that the fluxing material becomes imbedded in the steel
and will therefore affect the latter to a greater depth than is practically possible
when the fluxing material is applied to the surface after the metal has been cast.
By this method, i.e. the incorporation of the fluxing material in the metal, a

page_text: perfect welding of two bodies of metal can be effected even if the body first cast
be allowed to cool below a welding temperature, provided it be raised to or
approximately to a welding temperature before the second body of metal is cast
thereon. The possibility of forming a perfect weld under such conditions is
due to the fact that the fluxing material forms a protective coating over the
surface, tending to prevent any material oxidation, or if oxidation should occur,
the presence of the flux will, when the body of metal is heated as described,
combine with the oxide or other surface, impurities forming a thin fluid slag,
which will float to the top of the ingot when the second body of metal is cast;
and also to the fact that flux penetrating as it does under such conditions, renders
the two metals so fluid and free from oxide for a considerable depth that the two
metals will be thoroughly intermingled, and the chemical and physical charac-
teristics of each will be greatly modified.
And further, this method ensures the presence of an amount of flux in excess
of that required to flux the surface of the first body of metal. This excess will,
as before stated, have a beneficial effect in promoting welding on the second
metal.
The character of the weld or connection thus formed is evidenced by the fact
that if the two metals are different in kind or quality, as high and low carbon
steel, the metal adjacent to the plane of weld will differ, as for example, in
carbon content, from both the metals united, thus showing an amalgamation of
the metals at the plane of weld, whereas, there is a sharp line of demarkation
when two bodies of metal are united under the old practice.
By way of more carefully setting forth the characteristic features of the present
invention, it may be stated, that in this branch of the art as heretofore practiced,
the aim of inventors has been to effect a perfect weld or the best attainable
weld or union along the meeting faces of the two bodies. This has been done,
or rather it has been aimed at, in two ways. In one way a solidified crust was
produced on one quality or body of metal, and the other quality or body of metal
was cast onto or against such crust, but the aim in all cases, so far as my know-
ledge goes, was to make such crust of the proper thickness whereby, on its being
fused or partially fused, the two qualities of metals should be welded together
along such plane of fusion or partial fusion, but in every case, so far as my
knowledge goes, the two bodies or qualities of metal were kept distinct from each
other, except as so welded, and any material or substantial inter-diffusion or
blending of the qualities of the two metals through each other, was either not
provided for or was studiously avoided, and in this latter respect, as will
presently be explained, the method involved in the present invention differs
substantially from the method above stated to be old.
In the other old method of uniting different qualities or bodies of metal in
a compound plate, it was customary to interpose between the two bodies a metallic
diaphragm of suitable material and the proper thickness, which diaphragm, under
the action of the heat of the metals cast thereon on its opposite sides, would
become fused, and thereby permitting the formation of a weld between the two
bodies, but as before, without any material or substantial inter-diffusion between
the different qualities of metal constituting the two bodies.
18
It is a characteristic feature of the present invention that the formation of a
weld, as a weld, between two contiguous bodies the metal of different qualities
is carefully avoided. My own experience has been that where two qualities of
steel, characteristically different, are united by a weld in such way as to preserve
in each body its characteristic and distinctive qualities, and without any gradual
or decremental" merging of the qualities of one body into those of the other,
a practically homogeneous compound ingot or plate cannot be made. There will
always exist in such welded compound ingots or plates, a plane of cleavage or
breakage along which the cohesive properties of the metal will be materially less
than in any other part, and so much less that under severe use, the plate is
liable to be broken or destroyed.

page_text: In the present invention, on the other hand, I aim to avoid the formation of
a crust such as is liable to produce what previous inventors have aimed at and by
which they have produced a weld or a welded union; but I produce a crust so
thin that it will immediately disappear on the pouring in of the additional molten
metal, whereby two qualities or grades of molten metal are brought together
face to face, and in such condition that, before complete solidification takes place,
there will be an interchange of qualities from one to the other such as to result
in a gradual merging from the high carbon of the surface, to the low carbon of
the center, and without any definable or ascertainable plane of cleavage therein,
or any plane marked by a sudden or abrupt change in point of carbonization.
Employing a term commonly used in another branch of the art, the compound
plate or ingot which I thus produce may fairly be characterized as a plate or
ingot decrementally carbonized as distinguished from a compound plate formed
by welding together the adjacent surfaces.
The better to illustrate this, I have had a drawing. Fig. 4, showing in cross-
section one of the ingots as actually made by the present invention. The lines v-b
and de represent approximately the thickness of the hard metal portion; the
line b-d, represents approximately the thickness of the soft metal as cast, as
these parts were proportioned in that casting. As the exterior walls of the hard
metal portion became rapidly solidified, and as it is desirable that a thick wall
of hard metal should exist at the surface, I found that in the particular case
here illustrated, the interchange or inter-diffusion of the properties of the two
qualities of steel thus employed were found to exist substantially between the
points and y,-that is to say, in consequence of the inter-diffusion referred to,
the steel gradually changes or becomes reduced in carbonization, from about the
points and y toward the center of the plate as at c,-and this I have found to
be the case generally throughout the compound plate or ingot, that is through
other planes or sections. But in thus illustrating the peculiar features of the
present invention, I do not wish to limit myself to any specific depth or extent of
inter-diffusive action, provided only a hard outer surface or wall is preserved of the
desired thickness, and from the inside of such wall, to or approximately to the
center of the plate, there shall be a gradual and progressive change in the car-
bonization such as to exclude the presence of any well defined line or plane of
weld or cleavage. And such a plate, for the purpose of the present invention.
I would term a decrementally carbonized plate.
In the practice of my invention the ingot mold 1 is of the usual or any desired.
shape, with its walls preferably slightly inclined outwardly from the top down so
as to facilitate the removal of the mold from the ingot. This mold is supported
as is customary on the stool 2, and the core is arranged within the mold. It
will be understood that if a greater thickness of metal is desired on one side of
the core than on the other, the core can be placed eccentrically within the mold.
The method set forth in the application referred to can be effected by allowing
the metal first cast to solidify sufficiently to permit of the removal of the mold
and the forcing out of the core in any manner, then re-heating the hollow ingot.
placing it on a stool or plate and then casting the other metal into the heated
ingot. It is preferred to effect the removal of the core just as quick as a suffi-
ciently thick skin has formed around the core to retain the still molten metal
of the interior of the ingot and immediately casting the other metal into the
matrix thus formed. By this method the high heat of the two bodies separated
by the thin wall of solidified but still highly heated metal, will be melted, thereby
permitting an inter-diffusion of the characteristics of the two metals. In order
to effect a quick removal of the core 3, it is formed around a lifting rod 4, which
has a stripping plate 5 secured to its lower end. The core should be so formed
on the stripping plate as to entirely protect the latter from contact with the
molten metal first cast. This protection is preferably effected by making the
stripping plate slightly smaller than the core, as shown in Fig. 1, and providing
a socket 6 in the stool for the reception of the stripping plate. This socket is

page_text: made sufficiently deep to permit the edges of the core projecting outside of the
stripping plate to rest upon the stool.
After the core has been placed in position, one kind or grade of metal, as high
carbon steel, is cast around the core. As soon as a sufficiently thick skin is formed
around the core to retain the interior metal, which is still molten, the core is
removed by pulling up on the rod 4, and the other metal immediately cast into
the space occupied by the core. While not necessary, it is preferred, to place a
tile 7 of fire-clay or other refractory material in the socket in the stool.
In order to prevent, as far as possible, any exposure to atmospheric influences
of the wall uncovered by the removal of the core, a pour gate 8 is connected to
a passage 9 through the stool of the mold, the outlet of each passage being located
so as to be covered by the core during the casting of the first metal. If the second
metal be poured into the gate 8 as the core is being withdrawn, there will not
be any material exposure of the surface uncovered by the removal of the core.
If the second metal be so poured as to closely follow the core as it is withdrawn,
the core may be withdrawn earlier, as the inflowing metal will support the shell
formed on the surface of the metal first cast.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:-
1. A homogeneous cast ingot having at the end of the casting operation, a
highly carburized face and a decrementally carburized interior from such face to
the centre or opposite side of the ingot, substantially as set forth.
2. The method herein described of making decrementally carbonized ingot for
armor plates which consists in bringing two bodies of metal of different kinds or
grades, while in the molten condition, against opposite sides of a comparatively
thin and easily fusible wall of metal of the same character as one of the bodies
to be united and thereby fusing such crust while a substantial portion of the
metal on either side is still in a state of fusion, whereby on the fusing of the crust,
an inter-diffusion of the peculiar properties of each body of metal will take place
as between the two bodies of molten metal, substantially as set forth.
3. The method herein described of forming compound ingots, which consists
in forming on the surface of a molten body of a wall or crust of metal free from
oxide or other substance which would tend to prevent welding, and then casting
nother body of metal against such wall, while the interior of the first body is
still molten, and the wall is at such a high temperature as to be melted when
enclosed by the two bodies of metal, whereby on fusing of the crust or wall an
inter-diffusion of the peculiar qualities of each body of metal will take place as
between the two bodies of metal, substantially as set forth.
4. The method herein described, which consists in casting a body of metal in
a mold having a movable wall, promptly removing said wall from the mold and
bringing another body of metal against the surface exposed by the withdrawal
of the wall progressively as such exposure occurs, substantially as set forth.
5. As an improvement in the art of manufacturing compound ingots, the
method herein described which consists in casting one of the metals against a
mold wall consisting of, or formed by, a deoxidizing material and then removing
the mold wall and casting the other metal on the exposed or uncovered surface,
while the latter is at a high temperature, substantially as set forth.
6. As an improvement in the art of manufacturing compound ingots, the
method herein described which consists in casting one of the metals against a
inold wall consisting of or formed in part by a fluxing material, and then removing
the mold wall and coating the other metal on the fluxed surface when the latter
is at a welding temperature, substantially as set forth.
7. The combination of a mold, a core, a stripping plate at one end of the core,
and means for forcing the stripping plate through the annular body of metal
formed around the core, substantially as set forth.

page_text: 8. The combination of a mold, a stripping plate, a pull rod attached to the
plate and a core formed around the rod and resting on the plate, substantially as
set forth.
9. The combination of an open-topped mold provided with an inlet at its
lower end, a core covering said inlet, and means for withdrawing said core,
thereby uncovering said inlet, substantially as set forth.
Dated at Pittsburg Pa ILSA this Third day of November An 1800
Witnesses:
DARWIN S. WALCOTT,
FRANCIS E. GAITHER.
SYLVESTER ALPHONSE COSGRAVE.