Improvements in Working (Moulding and Welding) Metals.
Year: 1888

page_text: COMPLETE SPECIFICATION.
Improvements in Working (Moulding and Welding) Metals.
I WALTER, BURNHAM of Hyde Park, Cook County, State of Illinois, United
States of America, Gentleman, 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:-
This Invention relates to a method of moulding iron and steel by which the metal
is quickly given prescribed form and simultaneously is made to acquire increased
molecular cohesion and other superior physical qualities.
The invention consists in heating the object under treatment up to a temperature
short of the melting point, but at which the metal of which such object is composed
becomes highly viscous, and in then subjecting such object to continuously exerted
strong pressure while it is confined in a mould and while it is cooling down from the
temperature of viscosity to the temperature at which it may, without injury, be
relieved from pressure preparatory to its removal from the mould. By the term
"highly viscous" is meant a condition which exists only within a limited range of
temperature below the melting point, and in which the mass of metal is so affected
that its molecules will submit to rapid motion upon each other, and will quickly
cohere in their new relationships when such motion ceases.
The high temperatures at which iron and steel acquire the desired condition of
viscosity have heretofore been considered injurious, but by the confinement of the
viscous mass in a mould, and its subjection to continually exerted high pressure until
its temperature has fallen below the dangerous point, not only do no injurious effects
ensue, but the necessarily resulting increased density of the product is accompanied
with increased molecular cohesion, tensile strength, toughness and rigidity, and, in
the case of steel, with an increased capacity to take temper without the usual loss of
toughness.
Owing to the plastic condition of the mass, its substance flows readily when
subjected to pressure, and hence the mass acquires in reverse the shape of the mould
in which it is confined. Therefore the process may be effectively employed not only,
for example, upon an ingot of cast steel for the purpose of removing any piping or
blow-holes therefrom and welding it into a homogenous body of steel possessing the
useful properties accompanying the increased molecular cohesion which it thus

page_text: acquires, but it may also be employed to impart a prescribed shape to the mass, as for
example the finished shape of an axe, which has heretofore been usually imparted to
the axe blank by hammering or other forging. So employed. the process not only
takes the place of forging, but imparts to the material of which the finished axe is
composed, the improved qualities described.
In view of the character of the process, and to distinguish it from casting or
forging the term viscous moulding has been selected as a designation for it, especially
because it is applicable to all metals which have a high melting point, and which,
when they are subjected to strong pressure while in a condition of viscosity produced
by heating them up to high temperature short of their melting points, and are held
under such strong pressure until their temperatures have fallen below the heat,
which is injurious to them, acquire increased hardness, rigidity, and toughness.
The desired viscous condition must be produced by gradually raising the tem-
perature of the metal under treatment, and not by cooling it down from a molten
state. By the time the interior of a molten mass of metal has cooled down to the
temperature of viscosity, its exterior portion is liable to have cooled down below that
temperature. In the present process, pressure must be continuously exerted while
the metal is in the viscous state, and until it is cooled down to a low red heat. The
shaping of the object and the movement of the molecules of the metals of which the
object is composed is effected during the viscous state in order to secure the perfect
cohesion of the molecules, and it is essential that the pressure shall not be removed
during the period while the metal, in cooling down, has such a temperature that if
relieved from pressure it will open up, as it is called. At a red heat the danger
of opening up has ceased, and therefore at that heat the object under treatment may
be safely relieved from pressure, so far as the danger of opening up is concerned. It
is, however, also essential that the pressure shall be removed before the metal has
cooled below a low red heat, because when below low red heat the metal may be liable
to crack under pressure.
::
The process may be usefully employed, if desired, in effecting the perfect welding
to each other of several objects of blanks composed of the same metal, or composed
respectively of different metals. For example, the several pieces of iron and the piece
of steel of which an axe is composed may by this process be simultaneously united to
each other with a perfect weld, and with beneficial effects upon both the iron and
steel.
Heretofore it has been necessary to weld the iron pieces of an axe pile to each
other at one operation, and to weld the steel bit to the iron at another operation,
because the temperature required for welding iron is so high as to be injurious to the
steel.
By the present process no injury ensues during the simultaneous welding of all the
pieces to each other, because the pile is held under continuously-exerted strong
pressure until it is cooled below the dangerous heat; and, as has been explained, the
steel is especially improved by being made capable of taking the temper required for
it without acquiring the degree of brittleness which is the usual accompaniment of that
temper.
The process
of viscous moulding may also be usefully employed upon objects made
of cast-iron or of wrought-iron. In both cases the final shape is given to the object
treated, and the metal of which it is composed is rendered harder and tougher by
reason of the increased cohesión of the molecules, caused by their subjection to strong
pressure while the mass under treatment is in a viscous state.. A cast iron blank,
heated to viscosity, and subjected to pressure in dies, readily takes the shape of the
die; and the cast iron, after subjection to the process, exhibits in its fracture changes
similar to those exhibited by steel. Its crystals are smaller or finer, its strength is
ingreased so that it will bend further without breaking, and its surface capable of
taking a higher finish.
These results, which are remarkable in cast iron, because it, has heretofore been
supposed that cast iron could not be forged or changed in shape after it was cast, are
ao pro 'uced by subjecting wrought iron to the process of viscous moulding.

page_text: In all cases, the metal operated upon is made to approach to an amorphous
condition-there is a diminution in the size of its particles, or greater "fineness," as
it is called; an increase in its rigidity, toughness and tensile strength. In the case
of objects made of tool steel, this increase in toughness is especially valuable, because
while it is important that they should be capable of being tempered so that their
cutting edges may have the required hardness, it is a great advantage to avoid the
brittleness which usually accompanies such hardness.
In carrying out the process, it is preferred to use box or closed dies, adapted to
give in one operation, approximately the finished form to the object acted upon. The
operation of such dies must be by a continuously-exerted pressure which may be
secured by means of a hydraulic press. The desired result cannot be obtained by a
percussive blow, or blows.
The blank or object whatever it may be, which is to be operated upon, having been
heated up to the viscous state, is placed in the dies, and by their immediate operation
is quickly pressed into shape, the particles or molecules of metal being forced into
their ultimate relationship while they are in a viscous condition, so that they weld
perfectly to each other. By this process the shaping, or what would ordinarily be
called the forging, of the metal is to be completed by the time the metal has lost its
viscous condition. Therefore the operating motion of the dies must be rapid, because
the viscous condition is quickly lost, and the force with which they exert their
pressure must not be great enough to alter the shape, or in other words to forge the
metal, after it has lost its viscous condition. The force which the dies are to exert is
to be limited to that required for shaping or forging the metal in the viscous condition,
in order to avoid any alteration of the relative positions or mutual relationship which
the molecules or particles of metal have assumed or acquired during their viscous
state. Subsequent disturbance of the relationship of the particles would only be
possible by torsion or rupture, as in the ordinary process of forging, in which, after
rupture, no new cohesions are established, because of the absence of the viscous
condition which makes immediate cohesion possible.
The operating movement of the dies is intended to be arrested by the resistance
to their movement which the metal operated upon opposes when cooled down below
the prescribed viscous state. Therefore the dies are not to be permitted to acquire
contact with each other, but must continue to deliver their pressure upon the object
upon which they act, after it has cooled below the viscous temperature, and until it
has fallen to a heat at which it is no longer liable to open up, and therefore may be
safely relieved from pressure. It will be found that a force insufficient to rupture
metal which is at a forging heat will yet suffice to mould the metal into form, and
properly condense it, if exerted while the metal is in the prescribed viscous state.
Extreme powers, as for example, twenty tons to the inch of metal surface presented
at a right angle to the direction of the die motion, are only necessary when the
subject operated upon is composed of tool steel, and is to be compressed, say, in one
tenth of a second, to the thickness of, say, one eighth of an inch.
The object subjected to the process of viscous moulding having been heated,
moulded, condensed, held under pressure and released from the dies as described, is
subsequently treated as a completed casting or forging would be treated, as to final
tempering, grinding, and finishing.
Having now particularly described and ascertained the nature of this inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. In the art of iron and steel working, the process of viscous moulding, which
consists in heating the metallic object under treatment up to a temperature short of
the melting point, but at which the metal of which such object is composed acquires a
viscous condition, as described, and in then immediately confining such object in a
mould, and submitting it to a continuously-exerted strong pressure, while it is cooling
down from the temperature of viscosity to a temperature at which it may be safely
relieved from pressure preparatory to its removal from the mould.

page_text: 2. The process of welding by viscous moulding herein described, which consists in
heating up to a viscous state the several metallic objects which are to be welded
together, and in then immediately confining such objects in a mould, and subjecting
them to continuously-exerted strong pressure while they are cooling down from the
temperature of viscosity to a temperature at which they may be safely relieved from
pressure preparatory to removal from the mould.