Improvements in Casting Ingots.
Year: 1898

page_text: Date of Application, 23rd Aug., 1898-Accepted, 8th Oct., 1898
COMPLETE SPECIFICATION.
Improvements in Casting Ingots.
I, ROBERT ALEXANDER MCDONALD, Superintendent, residing at Aspinwall,
County of Allegheny, State of Pennsylvania, and United States of America, do here-
by 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;-
*
"
As is well known to steel workers, ingots of all sizes are subject to what is
known as piping or the formation of a conical cavity of greater or less depth
at the upper end of the ingot during cooling and solidification. It is thought that
this piping is caused by the sinking of the metal in the upper portion of the ingot
to compensate for the contraction due to solidification in the interior lower portions
of the ingot. When the ingot is cast, an external shell is formed throughout the
entire length of the ingot by contact of the molten metal with the cool walls of the
mold. This shell is formed while the interior portion of the ingot is in a molten
condition and as the solidification proceeds, it is thought, from the bottom and sides
towards the top and interior of the ingot, the metal will settle or be drawn down,
forming a conical cavity at the upper end. It is also characteristic of this manner
of cooling and solidification that gases which are generated in the metal or caught
therein during the teeming will tend to rise towards the upper end of the ingot
or be forced up by the contraction of the cooling metal, but will be prevented
from escaping by the solidification of the metal and the thin skin or hardened
shell formed across the upper end.
It has been attempted to avoid this piping and the collection of the gases at the
upper end of the ingot by opening or moving outward one side of the mold as soon,
as the external shell has been formed, placing a bar or rod against the exposed
side and then forcing such bar or rod into the body of the ingot by pushing in the
removed side of the mold. The purpose of such operation is to displace the molten
metal in the interior of the ingot with the idea that such displaced metal will fill
up or prevent the formation of the "pipe" or cavity. This method is wholly
ineffective for the reason that displacement occurs simultaneously throughout the
entire length of the ingot, with the result of simply elongating the ingot. If a
cavity had been formed prior to the squeezing operation, as above described, the
pressure which is exerted at the upper end simultaneously with the pressure on
the other portions, will simply force together the sides of the cavity without pro-
ducing any welding thereof. If, on the other hand, the squeezing was effected
before any material "piping" had occurred, the ingot would be elongated and the
cooling and solidification subsequent to such elongation would produce a pipe" or
cavity.
04
The object of the present invention is to provide for the gradual upward forcing
or displacement of the interior molten portions of the ingot towards the upper end
as the cooling and solidification proceed, and thereby prevent the formation of the
pipe or cavity or ensure the filling up of the formed pipe or cavity by the metal so
forced upwardly from the lower portions of the interior of the ingot.

page_text: In the accompanying drawings forming a part of this specification, Figure 1 is
a top plan view of a form of rolls or apparatus applicable for use in the practice
of my invention; Fig. 2 is a similar view of a modified form or construction of
apparatus; Fig. 3 shows in sectional plan view an untreated ingot and one after
it has been treated or operated upon, the plane of section being through the upper
portion of the ingot, and Fig. 4 shows similar views of an ingot before and after
it has been subjected to the mechanism shown in Fig. 2.
"
In the practice of my invention the metal is teemed into an ingot mold in the
usual manner, and as soon as an external shell or skin of sufficient thickness or
rigidity to permit of the handling of the ingot has been formed, it is removed
from the mold and fed in a vertical position between the reducing rolls 2. As
shown in Fig. 1, these rolls are provided with collars 3 of such size or shape as
compared with the expected piping of the ingot, that they will displace by forcing
inwardly opposite sides of the shell a sufficient quantity of metal to compensate for
the expected contraction. These rolls are mounted in suitable housing or supports
in such manner as to permit of the feeding of the ingot with its lower end fore-
most into the bite of the rolls and preferably while in a vertical position, so as to
prevent the bleeding or escape of molten metal from the interior of the ingot. As
it is desired to effect in this operation, only a displacement of the interior molten
metal in a direction of the axis of the ingot, retaining rolls 4 are arranged in such
relation, to the displacing rolls as to prevent any material cross-sectional enlarge-
ment of the ingot while passing between the rolls 2. If desired, these rolls 4
may be constructed to effect a portion of the displacement of the interior molten
portion of the ingot. In some instances, it may be desirable to effect what might
be termed a graduated displacement, i.e., a displacement which would gradually
decrease from the lower towards the upper end of the ingot. This graduated
displacement can be produced by employing rolls whose operative perimeter will
be practically equal to the length of the ingot operated on and by forming the collar
eccentric. Or the same effect can be produced by changing the position of its rolls
with relation to each other, i.e., gradually separating them as the ingot passes
between them.
It will be readily understood by those skilled in the art that as the lower end of
the ingot enters the bite of the rolls, thereby forcing in portions of one or more side
walls, the molten metal in line with such forced in portions will be forced or
pressed towards the opposite end of the ingot. As this forcing in proceeds more
and more metal will be pushed up towards the upper end of the ingot, thereby
filling in from its lower end the pipe or cavity. If desired, the speed of the rolls
may be so adjusted that the displacement will occur with approximately the
same rapidity as the solidification, thereby compensating at each point in the
length of the ingot for the contraction and consequent solidification.
In addition to this filling in of the cavity or compensation for contraction, this
progressive squeezing will also effect an upward displacement of gases caught by
or generated within the metal in the mold, thereby eliminating blow-holes from
the ingot, or forcing them to and out of the extreme upper end of the ingot.
In lieu of forcing portions of one or more of the sides of the ingot in beyond the
general plane of such sides, as above described, the ingot may be cast with portions
of one or more of its sides projecting beyond the general planes of such sides,
as clearly shown at a in Fig. 4. These projecting portions, which may extend
from the lower end towards or to the upper end of the ingot, are so proportioned
as to cross-sectional dimensions, that when forced inwardly to the general plane
of the sides of the ingot, the amount of metal in the interior of the ingot displaced
thereby, will compensate for the expected contraction and consequent piping.
When the ingot is formed with these projecting portions along one or more of its
sides, the squeezing or reducing rolls have their operative faces plain as shown
at 2 in Fig. 2. In order to effect what has heretofore been termed a graduated
displacement, the projecting portions of the sides of the ingot, are made larger at
the lower end thereof and gradually diminish in width and projection towards the

page_text: upper end where such projecting portions may merge into the general wall or sides
of the ingot.
While the form of apparatus shown, i.e., reducing rolls, seems at present to be
the most convenient and practical manner for the practice of my invention, I
desire to include as a part of this invention any form or construction of apparatus
whereby a progressive displacement of the metal in the interior of the ingot may
be effected, such displacement proceeding from the lower towards the upper end of
the ingot.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:-
1. As an improvement in the art of treating ingots, the method herein described,
which consists in progressively displacing in a longitudinal direction from the
lower towards the upper end of the ingot the molten interior portions of the ingot
by pressure applied to the exterior of the ingot, substantially as set forth.
2. As an improvement in the art of treating ingots, the method herein described,
which consists in removing the ingot from the mold while the interior portions
are in a plastic condition, and then forcing inwardly a portion of one or more sides
of the ingot progressively from its lower towards its upper end, substantially as
set forth.
3. As an improvement in the art of treating ingots, the method herein described,
which consists in forcing inwardly a portion of one or more sides of the ingot while
the metal of the interior is plastic, such inward movement being progressive and
graduated from the lower towards the upper end of the ingot, substantially as set
forth.
day o
1050T
Witnesses:
DARWIN S. WOLCOTT,
BAYARD H. CHRISTY.
ROBERT ALEXANDER MCDONALD.