IMPROVEMENTS IN THE METHODS AND APPARATUS EMPLOYED IN THE FUSION OF METALS AND METALLIC ALLOYS AND IN FOUNDING OR CASTING THE SAME
Year: 1869

page_text: LETTERS PATENT to Henry Bessemer, of Queen Street Place, Cannon
Street, in the City of London, for the Invention of "IMPROVEMENTS
IN THE METHODS AND APPARATUS EMPLOYED IN THE FUSION OF METALS AND
METALLIC ALLOYS AND IN FOUNDING OR CASTING THE SAME."
Sealed the 26th October 1869, and dated the 10th August 1869.
PROVISIONAL SPECIFICATION left by the said Henry Bessemer at the
Office of the Commissioners of Patents, with his Petition, on the
10th August 1869.
I, HENRY BESSEMER, of Queen Street Place, Cannon Street, in the
City of London, do hereby declare the nature of the said Invention'
for "IMPROVEMENTS IN THE METHODS AND APPARATUS EMPLOYED IN THE FUSION
OF METALS AND METALLIC ALLOYS AND IN FOUNDING OR CASTING THE SAME," to
be as follows;-
These improvements relate to the fusion and founding of various
articles in any description of pig or cast iron, wrought or malleable iron
and steel, and also to the fusion and founding of the more refractory
metals, such as platina, cobalt, and nickel, and to the more fusible

page_text: metals, copper, zinc, tin, and to the alloys of all or any of such
metals, by subjecting them to pressure during the fusing and founding
operations.
In a Patent granted to me and bearing date the 10th day of November
1868, No. 3419, I have described a means of fusing malleable iron and
steel by the employment of combustible gases and atmospheric air in a
close or high-pressure furnace, the products of combustion being therein
retained under a pressure considerably more than that of the external
atmosphere, and thereby rendering it necessary to employ powerful force
pumps for the injection of the combustible gases into such furnaces.
Now the first part of my present improvements relates to the supply
of combustible gases or vapours to high-pressure furnaces in such a
manner that the employment of forcing pumps and engine power is no
longer rendered necessary for such purpose. Thus when petroleum,
creosote, coal oil, naptha, or other liquid hydrocarbons are to be used, I
construct a boiler or vessel in which these fluids are vaporized and
retained under such pressure as will cause them to enter the high-
pressure furnace by means of their own expansive force, although the
gaseous products of such furnace be retained at a pressure equal to
several atmospheres in excess of the external atmospheric pressure. In
like manner when the combustible gas is to be produced by the destruc-
tive distillation of solid carbonaceous matter, such as coal or bitumen
shale, I employ metal retorts, and generate pressure in them sufficient
to cause the gases so formed to enter the high-pressure furnace without
the aid of force pumps; the retort employed for this purpose I prefer to
be cast steel or of wrought iron. Any of the gases or vapours so generated
under pressure may be supplied to the furnace by simple jets or tuyeres,
or in lieu thereof compound jets of air and gas may be employed, the
orifices being formed of fire-clay or other refractory substances, or they
may be made of platina or wrought iron and cooled by a flow of water
through them as in ordinary water tuyeres. I also in some cases cool
the exterior shell of such furnaces by employing a jacket in which
cold water circulates, and whereby I am enabled without injury to
the shell of the furnace by overheating it to line it with a thin
coating of ganister or other refractory material; the heat from this
thin lining being conducted into the water will prevent the rapid
destruction of the lining. Excessively high temperatures may be
obtained by the employment of gases and air at a pressure of several
atmospheres; this may be increased by heating the gas and air before

page_text: it enters the furnace. A still higher degree of heat may be obtained by
the employment of oxygen gas alone or mixed with atmospheric air as
a supporter of combustion, so that the mass of refractory substances
may be fused or vaporized by such means.
The second part of my said Invention relates to the founding or
casting under pressure of any description of pig or cast iron, wrought or
malléable iron and steel, or mixtures or alloys thereof, and also the
casting or founding of articles composed of copper, zinc, tin, or other
metals or any alloys thereof where great soundness or tenacity is
desirable.
In a Patent granted to me bearing date the 31st day of May 1856,
No. 1292, I have shown how pressure may be applied to malleable iron
or steel in moulds by the forcing in of a ram or plunger actuated by
hydrostatic pressure, and I have also described in the said Patent a
means of subjecting the metal to gaseous pressure in a close vessel by
the employment of powerful force pumps, by means of which air or
gases are stored in a receiver under great pressure, and are afterwards
let into the chamber or vessel in which the casting is placed. When
employing a plunger to consolidate the article cast its effects can only
remain uniform while the metal retains its fluidity, whereas it is most
desirable to apply this pressure while the shrinking of the partially or
wholly solidified mass is going on, but when employing gaseous pressure
an ordinary mould may be used suitable to the metal under operation,
and the pressure will in this case be equal on all the exterior surface
of the article cast; but it has been found that metals like iron or steel
require several tons pressure on the square inch to fully develope their
strength and tenacity, and it not only requires most powerful and expen-
sive machinery to force air up to these pressures, but the heat developed
by such compression is a source of great inconvenience and trouble.
Now, therefore, the object sought to be obtained in this second
part of my improvements is to entirely dispense with the hydrostatic
press and plunger, and also to entirely dispense with the air force pumps
and engine power necessary for forcing in the air ar gases, as described
in my former Patent of the 31st of May 1856, and in lieu thereof to
generate gases of extremely high pressure by the combustion of in-
flammable matter or by the vaporization of fluids either in the chamber
containing the casting or in a chamber or vessel in connection there-
with

page_text: In carrying this part of my Invention into operation I construct a
pressure vessel of great strength of cylindrical or other form specially
suited for the articles to be cast. When the vessel is made of cast iron
I prefer to hoop it with wrought iron or steel hoops, or the whole vessel
may be cast in steel or be built up of coils or hoops in a similar manner
to built up guns. The pressure vessel is to be of an internal capacity
sufficient to hold the mould in which castings under pressure are to be
made; it must have its upper end moveable or otherwise be made to open
so as to admit the mould and be capable of being closed securely so as
to resist the great internal pressure to which it is to be exposed. The
cover may be slightly oval so as to be put in in a manner similar to
the man-hole plates of boilers, or the cover may be bolted on or be
formed into a large screw plug like a gun breach. The pressure vessel
should be lined with a slow conductor of heat so as to prevent the vessel
from becoming too much heated, and the mould should have in it
sufficient metal to absorb a large portion of the heat of the casting. In
some cases the interstices between the mould and the vessel may be
filled with pieces of cold iron in order to lessen the vacant space, and
also to absorb the heat of the casting, the heat may also be absorbed by
a circulation of cold water or by its injection upon the mould or the
surrounding pieces of metal. An opening is provided in the cover or.
top of the pressure vessel capable of being closed air-tight when desired.
The moulds for casting in may be made of cast iron, and lined with fire-
clay or other bad conductor of heat, or of iron alone in some cases, and
generally of such materials and in such manner as would be suitable for
each kind of metal if cast in the open air. A small chamber or generator
is constructed so as to be attached to the pressure vessel and removed at
will by simply unscrewing it. This generator may be made somewhat
like an elongated rifle shell, and is to be charged with the combustible
matter employed to generate gas within the pressure vessel; it is also
provided with a means of igniting the combustible matters when required
as practised in discharging ordnance. The combustible material may
be "meal powder" alone, or mixed with some inert matter to render its
combustion more slow. I, however, prefer to employ cheaper materials,
such as anthracite coal, nitrate of soda, and sulphur reduced to powder
and well mixed, and so apportioned in their respective quantities as to
burn quickly but not explode; or in lieu thereof vegetable matters heated
with nitric acid and possessing feebly the property of gun cotton may
be employed.

page_text: The apparatus thus arranged may be used as follows for casting an
article in steel:-A massive cast-iron mould may be used, the interior
being coated with a mixture of burned fire-clay ground up and mixed
with a small quantity of plastic clay and water; when dry this mould
is placed in the pressure vessel, the cover of which is then put on, fluid
steel is then poured through an opening made in the cover for that
purpose, the opening is then quickly closed with a cone or screw plug,
and one of the small generators is screwed on to an orifice in the
pressure vessel and ignited; the rapid production of gaseous matter will
produce great pressure within the pressure vessel, which acting on the
metal while fluid and continuing to press upon it uniformly as it
shrinks and solidifies will not only prevent the formation of bubbles
within the casting, but will so force the particles of metal together as to
increase the tenacity of the metal and confer on it the general properties
of forged steel. The pressure employed may be from 1 to 20 tons to
the square inch, depending on the nature of the metal and uses for
which it is intended; thus castings in mild steel or malleable homo-
geneous iron may be made for crank axles, anchors, guns, or parts of
guns, projectiles, shafts, and other articles usually forged into shape
from ingots. Some metals and alloys if formed into ingots under great
pressure will be found much better suited for rolling or hammering
than if cast in the open air.
It will be understood that in lieu of the generator herein-before
described the pressure may be obtained by injecting into the pressure
vessel water or other fluid or matter capable of being by heat connected
with an elastic vapour; in either case a small loaded valve on the vessel
should be employed, in order to allow an escape of gases if too much
pressure is.generated, this valve also allowing the escape of gas previous
to opening the vessel and removing the mould and casting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Tenth day of August, in the year of
our Lord One thousand eight hundred and sixty-nine, in the thirty-
third year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Henry Bessemer, Her special licence that
I, the said Henry Bessemer, my executors, administrators, and assigns,
or such others as I, the said Henry Bessemer, my executors, adminis-
trators, and assigns, should at any time agree with, and no others, from
time to time and at all times thereafter during the term therein expressed,
should and lawfully might make, use, exercise, and vend, within the
United Kingdom of Great Britain and Ireland, the Channel Islands, and
Isle of Man, an Invention for "IMPROVEMENTS IN THE METHODS AND APPA-
RATUS EMPLOYED IN THE FUSION OF METALS AND METALLIC ALLOYS AND IN
FOUNDING OR CASTING THE SAME,, upon the condition (amongst others) that
I, the said Henry Bessemer, my executors or administrators, by an
instrument in writing under my, or their, or one of their hands and
seals, should particularly describe and ascertain the nature of the said
Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Seal Patent Office within six
calendar months next and immediately after the date of the said Letters
NOW KNOW YE, that I, the said Henry Bessemer. do hereby declare
the nature of the said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by the
following statement thereof, that is to say:-
These improvements relate to the fusion and founding. of various
articles in any description of pig or cast iron, wrought or malleable
iron and steel, and also to the fusion and founding of the more refractory
metals, such as platina, cobalt, and nickel, and to the founding of the
more fusible metals, copper, zinc, tin, and to the alloys of such
metals, by subjecting them to pressure during the fusing and founding
'operations.
In a Patent granted to me, and bearing date the 10th day of November
1868, No. 3419, I have described a means of fusing malleable iron and
steel by the employment of combustible gases and atmospheric air
in a close or high-pressure furnace, the products of combustion being
therein retained under a pressure considerably more than that of the

page_text: external atmosphere, and powerful force pumps were employed for the
injection of the combustible gases into such furnaces.
Now the first part of my present improvements relates to the supply
of combustible gases or vapours to high-pressure furnaces in such a
manner that the employment of forcing pumps and engine power is no
longer rendered necessary for such purpose. I use the vapour or gas
obtained from petroleum, creosote, coal oil, naptha, or other liquid
hydrocarbons, and I construct a boiler or vessel in which these fluids are
vapourized and retained under such pressure as will cause them w
enter the high-pressure furnace by means of their own expansive force,
although the gaseous products of such furnace be retained at a pressure
equal to several atmospheres in excess of the external atmospheric
pressure.
And in order that the mode of generating and employing such gas or
vapour under pressure may be fully understood I have shown at Figure 1
on the annexed Sheet of Drawings a vertical longitudinal section of a
boiler or generator adapted for this purpose.
a is a strong rivetted cylindrical iron boiler with hemispherical ends
set in brickwork in a manner similar to that employed in setting steam
boilers; b, the fire-grate, over which is formed an arch of brickwork c,
which extends as far as the fire-bridge d, beyond which the flame and
heated matters from the fire pass under and in contact with the boiler
until they arrive at the entrance e of the side flues, shown by dots;
these flues unite at e*, and pass upward through the flue f into the
chimney g. When however the generation of vapour goes on too rapidly
the damper slide h may be pushed in a short distance, which will allow
a portion of the flame and heated gases of the furnace to pass up the
flue into the chimney g without traversing over the surface of the
boiler, and so in like manner when the supply of combustible vapours
from the boiler is for any short time not required. The damper h may
be pushed in as far as it will slide, thus entirely closing the flue f, and
opening the flue i, so that all circulation of flame beneath the boiler
ceases; the fire, however, will be thus kept up, and immediately on its
becoming necessary that the boiler should again yield a supply of com-
bustible vapour or gas the pulling out of the damper h will reverse the
current of flame and heated matters in the flues, and put the boiler at
once into active operation. I prefer to fix the boiler or generator in an
inclined position, as shown, to favour the running out of sediment and

page_text: of such portions of the fluids acted upon as do not evaporate readily; and
for this purpose I employ the valve m opening outwards, so as to dis-
charge the matter into the tank k. A rod n passes up through the
boiler, terminating in a screw working through a stuffing box at p, and
having a wheel and handle o, by means of which the valve m can be
opened or shut when desired. q is a man-hole plate for the purpose
of giving access to the boiler or generator. A stop valver with a screw
and wheel is also provided for the purpose of controlling the supply.
of vapour or gas to the furnaces in which it is consumed, and s is a second
valve, consisting of a ball s ground into a spherical seating; from
this ball a weight t is suspended, so that in case the pressure of the
combustible gases or air in the furnace working under pressure should
at any time by an accidental cause exceed the pressure of the vapours
or gases in the boiler or generator, then the valve s will close and
prevent the entry of such air or products of combustion into the boiler
or generator. A safety valve and glass gauge, such as is generally
employed in steam boilers should also be used, the former to prevent
an undue amount of pressure in the boiler or generator, and the latter
to indicate the level of the fluid within it. A small force pump is also
employed for the purpose of supplying the requisite quantity of the
fluid matters to be evaporated.
Having thus described the kind of apparatus which I prefer to employ
for generating the gases or vapours and passing them into high-pressure
furnaces, I desire it to be understood that I lay no claim to the pro-
duction of gases or vapours from fluid hydrocarbons in a boiler or
generator; nor do I claim the supply of such gases or vapours to
ordinary furnaces, as the same has been before known and practised.
Sometimes I produce the combustible gases or vapours for the pur-
poses of my Invention by the destructive distillation of solid carbon-
aceous matter, such as coal or bitumen or shale. I employ metal retorts,
and generate pressure in them sufficient to cause the gases so formed to
enter the high-pressure furnace without the aid of force pumps. The
retorts employed for this purpose I prefer to be of cast steel or of
wrought iron. Any of the gases or vapours so generated under pressure
may be supplied to the furnace by simple jets or tuyeres, or in lieu
thereof compound jets of air and gas may be employed, the orifices
being formed of fire-clay or other refractory substances, or they may be
made of platina or wrought iron, and cooled by a flow of water through

page_text: them, as in ordinary water tuyeres. I also in some cases cool the
exterior shell of such furnaces by employing a jacket in which cold
water circulates, and whereby I am enabled without injury to the shell
of the furnace by overheating it to employ only a thin coating of ganister
or other refractory material. The heat from this thin lining being con-
ducted into the water will prevent the rapid destruction of the lining,
which it would be difficult to avoid were its thickness great. Exces-
sively high temperatures may be obtained by the employment of gases
and air at a pressure of several atmospheres; this may be increased by
heating the gas and air before it enters the furnace. A still higher
degree of heat may be obtained by the employment of oxygen gas alone
or mixed with atmospheric air, as a supporter of combustion, so that
the most refractory substances may be fused or vaporized by such
means.
And in order that the method which I prefer to employ for the
fusion of the more refractory metals, such as platina, cobalt, nickel, and
malleable iron and steel may be fully understood, I have shown at
Figure 2 on the Sheet of Drawings hereunto annexed a vertical section
through the centre of a circular furnace to be employed for such
purposes.
A is the outer shell or casing of the furnace formed of stout steel
or iron plates domed or worked up to the form shown; the upper and
lower parts are bolted together by the flanges A' which rest on the
columns W. A second shell or jacket B envelopes the greater part of
the furnace, and between it and the shell A water is allowed to cir-
culate; the water is admitted by a pipe from an elevated reservoir to the
lowest part of the jacket, and escapes by another pipe from the highest
point (these pipes are not shown). A thin lining C consisting of a
mixture of plumbago and fire-clay (such as is employed for making
plumbago crucibles) or ganister or other refractory substance well
rammed into its place with the least amount of moisture which will make
it adhere defends the metal shell of the furnace from the direct action
of the heat generated within it, while the water circulating in the
jacket not only absorbs heat from the metal shell A but also from the
lining C, which is forced into close contact with the metal shell by the
great internal pressure of the gases employed. Thus I am enabled to
employ a very thin lining and to absorb heat from its outer surface
with sufficient rapidity to prevent its interior surface from becoming

page_text: fused or rapidly destroyed by the intense heat to which it is subjected.
At the lowest part of the furnace the water jacket may be omitted and
a thicker lining used, as shown at C*, which forms a shallow cavity in
which the molten metal is received. In some cases the fused metal
may be allowed to solidify in the furnace, but I prefer to draw it off
by a tap-hole at the side or through the bottom. For this latter purpose
I insert a plumbago cone D into the lowest part of the furnace lining;
this cone of plumbago is moulded with a piece of iron projecting from it,
as shown, for the purpose of more easily withdrawing it by pincers from
its seat when the tapping takes place. The cone D is inserted with a
little clay cream around it and is then covered up with moist sand; the
plate E is then fastened on by cotters to keep the cone from falling out
When it is desired to tap the furnace the removal of this plate will
allow the sand to be easily raked out, when a casting ladle may be placed
beneath the furnace; the cone is then withdrawn and the metal run off.
When charging materials into the furnace the upper plate G is removed
and again cottered down; after the metal is put in, a small cone of
fire-clay H forms the restricted orifice, through which the products
of combustion issue with great force. Around the upper part of the
furnace are two channels K and L; the channel K is in connection with
the regulating vessel of a blast engine and conveys cold or heated
atmospheric air through several pipes and tuyeres M into the furnace;
the channel L is connected by a similar pipe to a boiler or generator (such
as shown in Figure 1), and conveys from thence the combustible vapours
or gases generated therein. The pipes and tuyeres P conduct the com-
bustible vapours or gases also into the furnace. The air jets and gas
jets are directed by preference at such an angle as to cross or intersect
each other at a point situated between the orifices from which they escape
and the material on to which they are directed, as shown in the annexed
Drawing. Sluice valves, such as are employed to regulate the admission
of steam from a boiler to a steam engine are employed to regulate the
supply of air and gas to such furnaces. Pressure gauges of the ordinary
kind should also be employed to indicate the pressure of the air and
combustible gases in order that their supply may be regulated so as to
insure the most complete combustion of the gas without employing such
an excess of air as would lower the temperature of the furnace; it is also
preferable to keep the supply of gas or vapour at a pressure greater than
that of the air supply, and thus prevent at any time the passage of air
into the gas supply pipes. The appearance of the issuing flame will be

page_text: a sufficient guide to the workman to enable him properly to regulate the
quantities of air and gas or vapour admitted.
In the form of furnace shown at Figure 2, and herein lastly described,
the powerful jets of air and combustible gases are projected downward
direct upon the materials from each of the several tuyeres situated
around the sides of the furnace, or the jets may be directed upon and
among any one or more crucibles occupying the central portion of the
furnace; and although I prefer and have herein shown separate jets of
air and combustible gases intersecting each other, it will nevertheless
be understood that compound jets may be employed if desired in lieu
thereof.
And here I would further state that I am aware that a circular
furnace arranged with gas jets around it has been described and
patented by Josiah Marshall Heath for the fusion of iron or steel, such
furnace allowing the products of combustion to expand freely and pass
off by a chimney. I therefore desire it to be understood that this is not
claimed by me, nor do I lay claim to the use of jets of combustible
vapours or gases, unless the gaseous products of combustion be retained
in the furnace at a pressure considerably in excess of the external
atmospheric pressure and unless the admission of the vapours or gases
to such high-pressure furnaces be caused by the expansive force of
the gases generated under pressure and without the employment of
pumps or other gas compressing machinery heretofore used for such
purpose.
And although I have herein shown and described a circular furnace
for the fusion of refractory metals by means of vapours or gases
generated and consumed under pressure, I desire it to be understood
that my present Invention of supplying combustible vapours or gases
to high-pressure furnaces without the employment of gas forcing
pumps is also applicable to reverberatory and other kinds of high-
pressure furnaces. The amount of pressure of the air and gases
employed will depend on the nature of the material to be fused and
on the rapidity of action desired by the manufacturer. A pressure
of less than three pounds per square inch in excess of atmospheric
pressure will produce so little advantage as not to compensate for the
trouble of employing a forced blast, but a pressure of 20 lbs. to 30 lbs.
per square inch gives a temperature which melts steel rapidly, but for

page_text: the more refractory metals, such as platina, a pressure of from 6 to 10
atmospheres may be employed with advantage.
I would further remark that in all cases I prefer that the air sup-
plied by a blast engine to support combustion in high-pressure
furnaces should be a few pounds per square inch less than the
the gases employed.
pressure
of
The second part of my said Invention relates to the founding or
casting under pressure of any description of pig or cast iron, wrought
or malleable iron and steel, or mixtures or alloys thereof, and also the
casting or founding of articles composed of copper, zinc, tin, or other
metals or alloys thereof where great soundness or tenacity is desirable.
In a Patent granted to me bearing date the 31st of May 1856,
No. 1292, I have shown how pressure may be applied to malleable iron
or steel in moulds by the forcing in of a ram or plunger actuated by
hydrostatic pressure, and I have also described in the said Patent a
means of subjecting the metal to gaseous pressure in a close vessel by
the employment of powerful force pumps, by means of which air or
gases are stored in a receiver under great pressure and are afterwards
let into the chamber or vessel in which the casting is placed. When
employing a plunger to consolidate the article cast, its effects can only
remain uniform while the metal retains its fluidity, whereas it is most
desirable to apply this pressure while the shrinking of the partially or
wholly solidified mass is going on, but when employing gaseous pressure
an ordinary mould may be used suitable to the metal under operation,
and the pressure will in that case be equal on all the exterior surface
of the article cast; but it has been found that metals like iron or steel
require several tons pressure on the square inch to fully develope their
strength and tenacity, and it not only requires most powerful and ex-
pensive machinery to force air up to these pressures, but the heat
developed by such compression is a source of great inconvenience and
trouble. Now therefore the object sought to be obtained in this second
part of my improvements is to entirely dispense with the hydrostatic
press and plunger, and also to entirely dispense with the air force pumps
and engine power necessary for forcing in the air or gases as described
in my former Patent of the 31st of May 1856, and in lieu thereof to
generate gases of extremely high pressure by the combustion of inflam
mable matter or by vaporization of fluids either in. the chamber con-
taining the casting or in a chamber or vessel in connection therewith

page_text: In carrying this part of my Invention into operation I construct a
pressure vessel of great strength of cylindrical or other form specially.
suited for the articles to be cast. When the vessel is made of cast
iron I prefer to hoop it with wrought iron or steel hoops, or the whole
vessel may be cast in steel or be built up of coils or hoops in a similar
manner to built-up guns. The pressure vessel is to be of an internal
capacity sufficient to hoid the mould in which castings under pressure are
to be made; it must have its upper end moveable or otherwise be made to
open so as to admit the mould and be capable of being closed securely
so as to resist the great internal pressure to which it is to be exposed.
The cover may be slightly oval so as to be put in in a manner similar
to the man-hole plates of boilers, or the cover may be bolted on or be
formed into a large screw plug like a gun breech.
The pressure
vessel should be lined with a slow conductor of heat so as to prevent the
vessel from becoming too much heated, and the mould should have in
it sufficient metal to absorb a large portion of the heat of the casting.
In some cases the interstices between the mould and the vessel may be
filled with pieces of cold iron in order to lessen. the vacant space and
also to absorb the heat of the casting; the heat may also be absorbed
by a circulation of cold water or by its injection upon the mould or the
surrounding pieces of metal. An opening is provided in the cover or
top of the pressure vessel capable of being closed air-tight when desired.
The moulds for casting in may be made of cast iron and lined with fire-
clay or other bad conductor of heat or of iron alone in some cases, and
generally of such materials and in such manner as would be suitable
for each kind of metal. If cast in the open air a small chamber or
generator is constructed so as to be attached to the pressure vessel and
removed at will by simply unscrewing it; this generator may be made
somewhat like an elongated rifle shell, and is to be charged with the
combustible matter employed to generate gas within the pressure vessel;
it is also provided with a means of igniting the combustible matters
when required, as practised in discharging ordnance. The combustible
material may be "meal powder" alone or mixed with some inert matter
to render its combustion more slow; i however prefer to employ cheaper
materials, such as anthracite coal, nitrate of soda, and sulphur reduced
to powder and well mixed and so apportioned in their respective
quantities as to burn quickly but not explode; or in lieu thereof vege-
table matter treated with nitric acid and possessing feebly the property
of gun cotton may be employed,

page_text: The apparatus thus arranged may be used as follows:-For casting an
article in steel a massive cast-iron mould may be used, the interior
being coated with a mixture of burned fire-clay ground up and mixed
with a small quantity of plastic clay and water; when dry this mould is
placed in the pressure vessel, the cover of which is then put on, fluid steel
is then poured through an opening made in the cover for that purpose,
the opening is then quickly closed with a cone or screw plug, and one
of the small generators is screwed on to an orifice in the pressure vessel
and ignited. The rapid production of gaseous matter will produce
great pressure within the pressure vessel, which acting on the metal
while fluid and continuing to press upon it uniformly as it shrinks and
solidifies will not only prevent the formation of bubbles within the
casting, but will so force the particles of metal together as to increase
the tenacity of the metal, and confer on it the general properties of
forged steel or hammered metal of whatever kind it may be. The
pressure employed may be from 1 to 20 tons on the square inch
depending on the nature of the metal and uses for which it is intended,
but usually not exceeding six or eight tons; thus castings in mild steel or
malleable homogeneous iron may be made for crank axles, anchors,
guns, or parts of guns, projectiles, shafts, and other articles usually
forged into shape from ingots. Metals and alloys, such as gun metal,
copper, brass, and zinc, especially if formed into ingots under great
pressure, will be found much better suited for rolling or hammering
than if cast in the open air.
It will be understood that in lieu of the generator herein-before
described the pressure may be obtained by injecting into the pressure
vessel water or other fluid or matter capable of being by heat con-
verted into an elastic vapour; in either case a small loaded valve on
the vessel should be employed in order to allow an escape of gases if too
much pressure is generated, this valve will also allow the escape of gas
previous to opening the vessel and removing the mould and casting.
The pressure vessels in which articles of iron, steel, and other metals
are to be cast and retained under pressure while solidifying will neces-
sarily vary in size and form with the nature of the articles to be founded
therein; thus for casting guns entire in steel, cast iron, or gun metal a
long cylindrical vessel would be required, but in casting such objects
as railway carriage wheels or the bodies of steam pistons a shallow
pressure vessel would be best suited, therefore no exact rule can be laid

page_text: down for the size or shape of such vessels, but in all cases the moulds in
which the castings are made should occupy as near as conveniently
practicable the entire available space within the vessel, and when moulds
from their form do not so occupy the space I employ cast-iron filling up
pieces of such shapes as will fit in and nearly fill up the otherwise vacant
spaces within the vessel, or I fill up the spaces with granulated cast iron
or other matter, the object being in either case to diminish the space
occupied by air in the vessel and thereby reduce the quantity of material
employed to generate vapour of the required density within the pressure
vessel. The mode of constructing and closing these vessels may also be
greatly modified, because the amount of pressure necessary for producing
the desired effect differs considerably with different articles; thus when
casting ingots of steel or copper to be afterwards rolled a pressure of two
or three tons per square inch will prevent the formation of air bubbles
and confer on them sufficient tenacity to roll well without being ham-
mered as usual. But a pressure of from 5 to 8 tons per square inch would
be required to render a casting of steel as tough as a well executed forg-
ing of the same metal, while as low a pressure as one ton to the square
inch will considerably increase the tenacity and soundness of cast iron.
In order to obtain pressure within the vessel I sometimes inject in fine
sprays or jets water or other evaporable fluid matters on to the surface
of the dead head of the casting, or on the top of the ingot, or upon the
heated mould, or on the surrounding metal, and thus obtain an atmo-
sphere the density of which may be easily regulated by the loaded valve
and by the quantity or nature of the fluid injected; or water or other
liquid may be injected into a vessel containing heated material adjoining
and in communication with the pressure vessel, or the pressure vessel
may be put into communication with a vessel containing a very volatile
liquid, such as liquid carbonic acid, and such vessel being heated exter-
nally or otherwise. This mode is most suitable for the lower pressures
required in the system of founding under pressure.
An example of the mode of constructing pressure vessels to be
employed for casting a locomotive crank axle is shewn in vertical section
at Figure 3 of the annexed Sheet of Drawings.
a is the outer shell or vessel formed of cast iron or steel; it is
cylindrical in form, and around the upper end of it an enlarged band a' is
formed. A series of 16 to 20 rectangular grooves are formed vertically in
this raised band, and into them as many steel bolts 6 are fitted and held
in place by the stout steel hoop e which is shrunk on while hot; these

page_text: bolts
may be of about 4 inches in diameter, and be fitted with nuts d of
the same material. e is a cover of steel, through which each of the
bolts 6 pass and by means of which the cover is held in place, the joint
being secured by a hoop of lead or other metal circular in cross section,
and by preference of about half an inch in diameter; this hoop falls
partly into the grooves ƒ and g formed on the under side of the cover e
and on the upper surface of the vessel a. The tightening down of the
large screw nuts will compress the soft metal hoop and nearly or quite
fill up the grooves and g and form a sound joint. In the centre of the
cover a screw plug is fitted with a conical fitting for the purpose of
forming a close joint when screwed home; this plug has a capstan head
serving to tighten it up and also as a means of attaching it to a light
crane by which it may be removed or brought into place. For a like
purpose two ring bolts i, i, are screwed into the cover e.
The pressure
vessel may be lined with a slow conductor of heat to prevent it absorbing
too much heat from the castings formed within it when the process is
repeated at short intervals.
The composition used for generating gases under very high pressures
within the pressure vessel may be as before stated contained in a
separate chamber communicating with or attached to the pressure vessel,
but I prefer to form a deep cavity in the lower part of the vessel, as
shown at a²; over the mouth of this cavity a dish m is inverted having
numerous perforations around its rim for the escape of the gases
formed
in the cavity a. The dish m serves as a support for the cast-iron mould
or box n to rest upon. The mould is made of considerable weight in
order the better to absorb the heat of the metal casting. In it I have
shown a locomotive axle » moulded after the manner generally employed
in moulding articles to be cast in steel, care being taken to well
"ventilate " the mould by moulding numerous wires in the composition,
which are withdrawn before casting; numerous holes are also made in
the iron mould or box n at short distances apart all over its surface,
thus rendering every part of the mould as pervious to air as possible
without interfering with its necessary firmness and cohesion.
The composition employed for generating pressure in the vessel may
consist of "rocket composition" or meal powder, that is, coarse cannon
powder ground as fine as possible and mixed with about one-fifth its
weight of powdered charcoal, but as sulphur is one of the elements
employed in the production of gunpowder, and may injuriously affect

page_text: the quality of the metal in some cases, I prefer to employ charcoal and
nitrate of potash only; each is to be separately reduced to a very fine
powder, and then mixed in about the proportion of 25 lbs. of charcoal
to 75 to 100 lbs. of nitrate of potash. A less expensive material may be
made with nitrate of soda and anthracite coal reduced and mixed in a
similar manner. The powdered material I prefer to ram firmly into
stout paper or sheet-iron cases of cylindrical form having a hole
entirely through the central part. The composition employed should
in all cases be such as will not explode with violence, but will burn
quietly until the whole is consumed.
In order to regulate the pressure of the gaseous matters in the
vessel a small cone valve r is employed, to which the weights is
suspended by a rod t terminating in a loop, which embraces a projecting
piece a bolted on to the side of the vessel and pressing on the top of the
spindle of the valve r. The pressure vessel is strengthened by stout
hoops of iron or steel u shrunk on to it, as shown.
When employing this apparatus I proceed as follows:-An insulated
wire, shown at v, is passed through a small cavity in the bottom of the.
chamber a and a small quantity of meal powder is laid over it, the
cartridge or composition w is then put into the cavity a and the dish m
is inverted over it; the cast-iron mould or box n is then lowered down by
a crane into the pressure vessel and the cover e is also put on and bolted
securely down with its packing ring in the double grooves; the casting
ladle is then brought over the opening in the centre of the cover e and
the metal run in in the usual way; as soon as this is done the screw
plug his tightened up, and the charge of combustible composition is
ignited by passing a current of electricity through the wire v. The
spaces round about the mould being very small the pressure rapidly
increases, and before the metal has had time to solidify the pressure of
the accumulating gases may reach to ten or twelve thousand pounds
per square inch, pressing in at all points through the porous mould and
subjecting the metal as it solidifies to great pressure equally in all
directions and following up the surface as contraction takes place and
imparting to the casting the general properties and characteristics of
forged metal. When it is judged that the metal has cooled down to a
blood red heat the valve r may be raised and the confined gases allowed
to escape, after which the vessel may be opened and the casting taken
out

page_text: Having described my Invention, and the manner in which it may be
carried into practical operation, I desire it to be understood that I do
not confine myself to the precise modes herein-before described for that
purpose so long as the peculiar features of my said Invention be
retained; but what I do claim is,-
Firstly. The fusion of malleable iron and steel and other refractory
metals in high-pressure furnaces supplied with combustible gases or
vapours generated under pressure sufficient to cause them to enter such
furnaces by their own expansive force and without the employment of
force pumps or other gas forcing machinery.
Secondly. I claim casting or founding ingots and other masses or
articles in iron or steel or in other metals or alloys of metals in moulds
contained in close vessels in which great pressure is obtained by the
evolution of aeriform matters from combustible matters either in the
chamber containing the casting or in a chamber or vessel connected
therewith.
Thirdly. I claim casting or founding ingots and other masses or
articles in iron or steel or in other metals or alloys of metals in moulds
contained in close vessels in which great pressure is obtained by the
evolution of aeriform matters from liquids evaporated either in the
chamber containing the casting or in a chamber or vessel in connection
therewith.
Fourthly. I claim the application of gases or vapours under high
pressure generated in close vessels and acting by their expansive force on
metals or alloys of metals in the process of casting or founding articles
in such metals or alloys, substantially as herein described:
In witness whereof, I, the said Henry Bessemer, have hereunto set
my hand and seal, this Tenth day of February, in the year of our
Lord One thousand eight hundred and seventy.
HENRY BESSEMER. (L.S.)