Improvements relating to the Tempering and Toughening of Ordnance and to Apparatus therefor.
Year: 1888

page_text: Date of Application, 20th Sept., 1888
Complete Specification Left, 20th June, 1889-Accepted, 17th Aug., 1889
PROVISIONAL
SPECIFICATION.
Improvements relating to the Tempering and Toughening of
Ordnance and to Apparatus therefor.
I, HIRAM STEVENS MAXIM of 57° Hatton Garden in the County of Middlesex,
Mechanical Engineer, do hereby declare the nature of this invention to be as
follows:-
My invention relates to the tempering and toughening of ordnance and to apparatus
therefor, and is designed to provide for imparting great hardness to the interior
surface or bore of a gun-barrel whilst greatly toughening the mass of metal around
the bore.
My said invention comprises an improved method of tempering and toughening a
gun-barrel by first heating the same to a suitable temperature and then rapidly or
suddenly and forcibly applying a large quantity of cold oil or other cooling inedium
to the inner surface thereof.
My said invention also comprises a method of hardening the skin or surface of the
interior of the barrel by causing a current of hydrocarbon gas or vapor to pass
through the same whilst subjected externally to heat in the furnace.
To provide for the rapid or sudden and forcible application of oil or other cooling
medium to the interior of the barrel, I employ a tank or reservoir which is filled
partly with the oil or other liquid and partly with compressed air. This tank or
reservoir is connected with the bore of the gun after the latter is placed in the
furnace, so that the oil or other liquid can be forced by the expansion of the com-
pressed air, into and through the barrel. Or I provide other suitable means for
obtaining the required pressure for forcing the oil or other liquid into, and through,
the barrel.
When the
I provide in the furnace suitable means for supporting the barrel in a vertical
position and for rotating the said barrel upon or about its axis. The barrel when
placed in the furnace is, as above mentioned, connected in any convenient manner
with the aforesaid tank or reservoir and communication between the latter and the
barrel is prevented by a suitable cock, which is kept closed until the barrel is
properly heated.
The barrel is rotated while subjected to heat in the furnace, so
that the temperature of the same throughout will be uniformly increased.
temperature is raised to the required degree, the said cock, which should be of
large size, is opened, thus allowing the oil to be forced suddenly, and with great
violence, into and through the heated harrel by the expansion of the compressed
air. In this manner I ensure the rapid cooling of the interior of the barrel, while
its exterior is subjected to heat. As the pressure in the tank diminishes, the current
of oil through the barrel is maintained at a slower rate by means of a pump,
whereby the hot oil from the barrel is forced through a condenser and back into
the said tank or reservoir, whence it is forced, or flows, into the barrel at the upper
end thereof.
To prevent oxidation of the interior of the barrel during the heating of the same
and to form a hard skin or surface thereon, I introduce hydrocarbon gas or vapor
into the said barrel and cause it to pass through the same.
For this purpose
I sometimes use ordinary coal-gas; I find it more efficacious, however, to employ
coal-gas enriched by mixing therewith petroleum vapor. When this mixture is used
it has the effect of case-hardening the bore of the gun. In some instances I
introduce carbonized bones, bone-dust, leather or other suitable material into the
barrel for the purpose of case-hardening the bore.
Dated this 20th day of September 1888

page_text: COMPLETE SPECIFICATION.
Improvements relating to the Tempering and Toughening of
Ordnance and to Apparatus therefor.
I, HIRAM STEVENS MAXIM, of Crayford Works, Crayford, in the County of Kent
and 53 Parliament Street, in the City of Westminster, Mechanical Engineer, 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 the tempering and toughening of ordnance and to apparatus
therefor, and is designed to provide for imparting great hardness to the interior
surface or bore of a gun whilst greatly toughening the mass of metal around
the bore.
My said invention comprises an improved method or process of tempering and
toughening a gun-barrel by first heating the same to a suitable temperature and then
rapidly or suddenly and forcibly applying a large quantity of oil or other cooling
medium to the interior surface or hore of the said barrel whilst its exterior is subjected
to heat.
If the oil used in tempering a gun-barrel is introduced and forced slowly through
the same in a comparatively small volume, the oil brought into contact with the inner
surface or bore of the gun while in a highly heated state is heated to such a
temperature as to cause its decomposition. In tempering large gun-barrels, a great
quantity of oil is thus decomposed, and the tempering process is therefore very
costly.
Now in my process I introduce the oil into the heated gun-barrel in a large volume
and under a very high pressure and thus obtain a much more rapid flow of the oil into
and through the barrel than is practicable by hydrostatic pressure or by a pump. The
quantity of oil thus introduced into the barrel in a given time is, therefore, much
greater than has hitherto been practicable; consequently none, or but a very small
quantity of the oil is heated to a temperature sufficiently high to decompose it, and
great economy is effected in respect of the quantity of oil wasted in the tempering
process.
1 find it advantageous to effect this sudden and forcible application of a large
quantity of the cooling medium by means of compressed air which is contained in a
suitable chamber or accumulator connected (by a pipe provided with a suitable stop
cock or valve) with the furnace in which the gun-barrel is to be tempered. The flow
or circulation of the cooling medium through the barrel, after the pressure in the said
chamber or accumulator has greatly diminished, is maintained by means of a force-
pump or otherwise. As the bore of the gun is somewhat cooled by the large influx of
oil into the same under the pressure of the air, the subsequent flow may take place
more slowly without risk of decomposition of the oil.
I combine, with the furnace and the means for forcing the oil through the barrel, an
apparatus for cooling the oil after its passage through the said barrel so that it can be
again used; a continuous circulation of the oil being maintained through the p pump,
the gun-barrel and the cooler.
To more effectually ensure uniformity in the heating and cooling of the barrel,
I provide for rotating the same about its longitudinal axis whilst it is being subjected
to heat in the furnace and during the application of the cooling inedium to its
interior.
To prevent oxidation and still further harden the skin or surface of the interior or
bore of the barrel, I pass through the said barrel, whilst the latter is subjected
externally to heat in the furnace, a current of hydrocarbon gas or vapour or other
material which will readily give up or part with the carbon contained in it, a portion
whereof will combine with the steel of which the barrel is composed and thus improve
its quality.
My said invention, moreover, comprises improved apparatus hereinafter described.

page_text: In the accompanying drawings I have shown how my said invention may be
conveniently and advantageously carried into practice.
Figure 1 is a vertical central section of a furnace constructed according to my said
invention, showing also a gun-barrel suspended in position in the said furnace, ready
for being hardened or tempered and toughened by my improved process.
Figure 2 is a front elevation of the said furnace.
Figure 3 is a vertical central section on the line a, a, Figure 1, drawn to an
enlarged scale.
Figure 4 is a horizontal section on the line y, y, Figure 3, the turning gear
hereinafter described being shown in dotted lines.
Figure 5 is a vertical central section on the line a¹, 21, Figure 3, some of the parts
being shown in side elevation.
Figure 6 is a vertical central section of an accumulator forming part of my
improved apparatus.
Figure 7 is a horizontal section on the line y, y¹, Figure 6.
Figure 8 is a vertical central section of a cooler hereinafter described, and
Figure 9 is a horizontal section on the line y², y², Figure 8.
Like letters indicate corresponding parts throughout the drawings.
A is the furnace which is constructed in lengths or sections A¹ arranged one above
another on a metal base or foundation A*. The said furnace is made with an outer
casing of iron or other suitable metal and with a lining of fire-bricks or other
refractory material, ashes or other non-conducting substances being introduced
between the said casing and lining. Any desired number of lengths or sections A¹
may be removed from, or added to, the furnace to alter the height of the same
according to the length of the gun to be tempered; the said furnace is thus adapted
for operating upon guns of different length. The said sections A' are secured
together by bolts passed through lugs A2 formed on the exterior of each section, or
in any other convenient manner. Each section is provided with a door A³ which
extends throughout the height of the said section. These doors are connected by
hinge-joints to the sections A¹ alternately at either side of the furnace, so that they
must be moved alternately in either direction to open them. The whole of one side of
the furnace may thus be thrown open to permit the insertion or withdrawal of a
gun-barrel. A', A are the fire-bars; A is the ash-pit; A is a cover or casing for
protecting the turning-mechanism hereinafter described and preventing the falling of
ashes thereon. The sections A¹ are provided with studs or projections A7 which
extend between guides composed of angle-irons A8 firmly attached to vertical pillars
or columns A at the sides and rear of the furnace. One of the angle-irons of each
of the pairs at the sides of the furnace, is cut away at suitable intervals to facilitate
the introduction of the said sections into the places one above another, and their
removal therefrom.
B indicates the gun-barrel to he tempered; the said barrel is suspended or
supported in an upright or vertical position in the furnace with the breech downward,
in such a manner that it can be rotated while subjected to heat in the furnace. For
instance, the said barrel may be supported at its upper end by a travelling crab and at
its lower end on a turntable as hereinafter described, that is to say :-The muzzle end
of the barrel B is secured, by means of screw-threads as shown, or otherwise, in a
socket B which is screwed into a tube B'. This tube is formed with an annular
groove or recess near its upper end, into which fit the two parts of a cross-bar or
clip B³, these parts being firmly connected by bolts or otherwise in such a manner
that the said cross-bar or clip will support the tube B2 whilst permitting rotation
of the same within it. The cross-bar or clip B³ is suspended by chains B from
another cross-bar B³ connected, by means of a shackle B, to a chain attached to, and
wound upon the drum or chain-barrel of an ordinary crab (not shown in the drawing)
arranged to run upon rails B' suitably supported by means of girders B³ on the
vertical pillars or columns A°. By the means above described, the gun-barrel may be
conveniently introduced into and removed from the furnace. Each end of the cross-bar
or clip B³ engages with one of the guide-bars or angle-irons A³ so that rotation of the

page_text: said cross-bar or clip with the gun-barrel is prevented. I provide a series or set of
interchangeable sockets B' so that gun-barrels of different sizes can be connected with
the tube B²
To provide for the rotation of the gun-barrel while subjected to heat in the furnace,
the said barrel is screwed at its lower end upon a hollow vertical spindle C firmly
secured to a hollow turntable D. This turntable is formed with an extension Di,
which is fitted in a socket or base mounted upon girders E¹, and which forms the
central pivot of the turntable. The said turntable is, moreover, supported upon the
said base E by means of a ring of balls E2 or other rollers, and has fixed upon it a
worm-wheel D² with which is geared a worm F fixed upon a shaft F. This shaft is
supported in suitable bearings on the girders E' and is arranged to be driven by a
steam-engine or other motor. I provide a series or set of interchangeable spindles C
so that gun-barrels of different sizes may be connected with the turntable D.
By rotating the barrel while it is subjected to heat in the furnace, I ensure the equal
or uniform heating of the said barrel on all sides thereof, thus effectually preventing
warping or twisting of the said barrel in the tempering thereof.
G is a pipe for the introduction into the barrel of the oil or other cooling medium
from an accumulator hereinafter described. This pipe extends through a stuffing-
box G in the lower end of the extension D1 of the turntable D, as more clearly shown
in Figure 3. A pipe H (Figures 1 and 2) is provided at the upper end of the
furnace A for the flow or discharge of oil therefrom. This pipe extends through a
stuffing-box H in the upper end of the tube B2 and is provided with a collar H2 fitting
the said tube so that the said pipe, whilst securely retained in the tube B², is capable
of sliding longitudinally therein and in the stuffing-box H', thus forming a telescopic
joint. The pipe H is, moreover, provided with a cross-head H³ (Figure 2) through
which are passed two long screw-bolts H coupled or pivoted to the cross-bar or clip B³
and provided with nuts H³ whereby the said pipe H may be raised or lowered and
may be firmly secured in any desired position. The said pipe H is connected by a
bent pipe J with a branch K of a vertical pipe K communicating with a cooler
hereinafter described. This vertical pipe K is provided with any desired number of
branches Kat intervals corresponding with the length of the sections A¹ of
the furnace, so that the pipe J may be connected with one or other of the said
branches according to the length of the barrel to be tempered. The branches which
are not, for the time being, in use, are closed by blank flanges. By raising or lowering
the pipe H in the tube B, the pipe J can be adjusted so that its flange accurately
coincides with that of the adjacent branch K' of the pipe K.
To provide for the rapid or sudden and forcible introduction of a large quantity of
the oil or other cooling medium into the barrel, I employ a tank or accumulator L,
Figures 6 and 7, constructed preferably of boiler-plates and supported on suitable
standards L. This tank or accumulator is connected by the pipe G with the hollow
extension D¹ of the turntable D, it is, moreover connected by an inlet or feed pipe M
with a force-pump (not shown in the drawing), for the purposes hereinafter specified.
The pipe G is provided with a branch-pipe G for draining or drawing off the oil from
the accumulator L when necessary. This branch-pipe should be provided with a
suitable stop-cock or valve. N is a safety-valve applied to the inlet-pipe M. for the
purpose of preventing excessive pressure in the accumulator. The said safety-valve is
provided with an overflow-pipe N1 which conducts the oil passing through the said valve
back to the cooler hereinafter described, whence the said force-pump draws its supply.
0,0 are glass gauges for showing the high and low levels of the oil in the accumu-
lator P is a pressure-gauge.
:
In Figures 8 and 9, Q is a cooler, which is supported on standards Q' and is
constructed with numerous small tubes Q2 fixed in tube-plates Q³. The said tube-
plates divide the cooler into three compartments, communication being established
between the upper and lower compartments by means of the said tubes Q². The
middle compartiment is provided with an inlet-pipe Q and with an outlet-pipe Q³ for
the circulation of water or other cooling medium through the said compartment and
around the tubes Q through which the oil flows. The upper compartment is connected

page_text: with the pipe K for the return of the oil from the gun-barrel, and the lower com-
partment is connected by a pipe R with the suction side of the aforesaid pump, so that
a complete circuit is formed and a continuous circulation of the oil may be maintained
through the pump, the gun-barrel and the cooler. The heated oil or other medium
which has been employed in cooling the gun-barrel will return by the pipe K and,
entering the upper compartment of the cooler, will pass through the tubes Q2 into
the lower compartment thereof which serves as the suction-well of the pump. In
passing through the said tubes, the oil is cooled by contact with the interior surface
thereof.
To prevent oxidation of the interior surface or bore of the gun-barrel during the
heating of the same, and to form a hard skin or surface thereon, I introduce hydro-
carbon gas or vapour into the said barrel and cause it to pass through the same
during the heating of the said barrel in the furnace. For this purpose I sometimes
use ordinary coal-gas; 1 find it more efficacious, however, to employ coal-gas enriched
by mixing therewith petroleum vapour.
To provide for the admission of the hydrocarbon gas or vapour to the interior of
the barrel, the pipe G for the introduction of the oil, is connected by a small pipe S
(Figure 3) with a gas-holder or main, the said pipe S being provided with a
suitable cock S¹ for regulating or controlling the flow of the gas. A cock T is,
moreover, provided at or near the upper end of the pipe K (Figure 1) to permit
the escape of the gas or vapour after its passage through the barrel. The gas
escaping through the said cock T may, if desired, be utilized for lighting or heating
purposes.
Suitable cocks or valves are also provided, where necessary, in the various pipes for
the circulation of the oil or other cooling medium.
The tempering and toughening of a gun-barrel by my improved method or process is
effected by means of the above described apparatus as follows, viz. :-The tankor accu-
mulator being filled with air at atmospheric pressure, oil is forced into it by means
of the aforesaid pump until the air is compressed to a pressure of about from one
hundred and fifty to two hundred and fifty pounds (150 lbs. to 250 lbs.) per square
inch. I find it advantageous to compress the air to two hundred pounds per
square inch, the level of the oil being then at about the height indicated in
Figure 6. The barrel is placed in its proper position in the furnace, in which it
is heated to the required temperature, the said barrel being rotated by the worm-
gearing above described while the heat is applied, in order to ensure uniformity of
temperature throughout its mass. The cock for controlling the communication
between the said tank or reservoir and the gun-barrel is kept closed until the
gun is properly heated. During the heating of the barrel, moreover, the cocks S, T
are opened, so that carburetted hydrogen gas enters through the pipe G and passing
through the said barrel, not only keeps the air away from the interior surface thereof,
but also hardens the said surface, a portion of the carbon becoming separated from the
hydrogen and combining with the steel, thus converting the latter into a higher grade
of steel. The gas, after it has passed through the barrel, escapes through the cock T.
When the barrel has been heated to the required temperature, the cocks S, T are
closed; the cock or valve for the admission of the oil is then opened, the rotation of
the barrel and the heating of the exterior of the same being continued. By reason of
the sudden expansion of the compressed air in the accumulator L, the oil from the
said accumulator is forced suddenly and with great violence into and through the
heated gun-barrel, and the oil flows through the barrel very rapidly at first and then
more slowly as the pressure in the accumulator diminishes, until a balance, or an
approximate balance is established between the pressure in the accumulator and that
due to the head of liquid in the gun-barrel and its connections; the subsequent flow
of the oil or other cooling medium is maintained entirely by the action of the aforesaid
force-pump which is set to work at the moment when, or immediately after, the cock
for the admission of the oil to the gun-barrel is opened.
In this manner, I effect the rapid cooling of the interior of the gun-barrel while
its exterior is subjected to heat, and thus harden or temper the interior surface or

page_text: bore of the said barrel. Moreover, by reason of the cooling of the barrel internally
whilst it is subjected to heat externally, the outer layers or portions of the barrel
will, in cooling, shrink upon the interior layers or portions thereof with great force,
setting up practically the same stresses in the mass that are set up by the various
rings or hoops in a built-up gun, the exterior of the mass being in a state of tension
while the interior thereof is in a high state of compression.
The oil discharged from the gun-barrel through the pipe H, passes through the
pipes J and K to the cooler Q, it then passes to the pump, whereby it is forced
again through the barrel.
When a gun is to be used for firing a large number of steel-covered projectiles
such as are used in modern practice, it is necessary that the bore of the gun should
be very hard so that the rifling shall not be destroyed or injured, whilst the mass
of metal around the bore should be of tough steel. To obtain this result I some-
times introduce into the barrel, carbonized bones, bone-dust, leather or horn, which
is allowed to remain therein during the process of heating and which is driven out
afterwards by the flow of oil. I introduce the carbonized bones, bone-dust, leather
or other suitable material into the bore of the gun either alone or in addition to
the hydrocarbon gas or vapour for the purposes of case-hardening the interior of the
barrel.
It is obvious that I can modify the construction and arrangement of my apparatus
in some respects without departing from the nature of my invention. For instance
I can substitute for the compressed air accumulator, other means for obtaining the
required high pressure for forcing a large volume of oil or other liquid through the
barrel, as, and for the purpose, above specified. Moreover I can employ means other
than those above described for rotating the barrel about its longitudinal axis, or for
maintaining the flow of the oil or other liquid through the barrel after the pressure of
the air in the accumulator has become less than is necessary for forcing the oil through
the barrel.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I wish it understood that
I claim
First. In the hardening or tempering of a gun-barrel, the introduction of the oil or
other cooling medium into the heated barrel in a large volume and under very high
pressure, as, and for the purpose, above specified.
Second. The hardening or tempering of a gun-barrel by first heating the same and
then forcing into it by means of compressed air a large volume of oil or other liquid,
and maintaining the flow or circulation of the said liquid by means of a pump or
otherwise, substantially as, and for the purposes, set forth.
Third. The improved method or process of tempering and toughening a gun-barrel,
consisting in first heating the same whilst rotating it about its longitudinal axis, and
then suddenly and forcibly introducing by means of compressed air or otherwise a
large volume of oil or other liquid into the said barrel and maintaining the flow or
circulation of the said liquid through the barrel whilst the exterior of the same is
subjected to heat, substantially as hereinbefore described.
Fourth. The herein described method of preventing oxidation of, and hardening the
bore, of a gun by introducing into the same, whilst subjected to heat externally,
hydrocarbon gas or vapour or other substance which will readily part with carbon,
for the purpose specified.
Fifth. The improved method or procees of hardening or tempering and toughening
a gun-barrel, consisting in first heating the same and simultaneously subjecting it
internally to the action of hydrocarbon gas or vapour or similar substances, and then
cooling it internally whilst its exterior is subjected to heat, substantially as, and for
the purposes, set forth.
Sixth. The furnace and its adjuncts so constructed and arranged that the height of
the said furnace can be varied according to the length of the gun-barrel to be hardened
'or tempered.

page_text: Seventh. The above described improvements relating to the devices for supporting
the gun-barrel in the furnace, whereby I provide for interchangeability of the said
devices to suit barrels of different sizes.
Eighth. A furnace provided with a hollow turntable for supporting a gun-barrel
therein, and with a pipe connected with the said turntable for the circulation of oil or
other liquid through the said barrel, for the purposes above specified.
Ninth. The combination, with a furnace for tempering and toughening gun-barrels,
of a tank or accumulator suitably connected with the said furnace and designed to be
charged with oil or other liquid and with compressed air for forcing the said liquid
into and through the barrel, substantially as, and for the purpose, set forth.
Tenth. The combination, with a furnace for tempering and toughening gun-barrels,
of a compressed air chamber or accumulator, a pump or its equivalent and an
apparatus for cooling the oil or other liquid after its passage through the barrel, for
the purposes above specified.
Eleventh. The combination, with the furnace, of the improved means for supporting
the barrel therein and for facilitating the lifting of the said barrel into and out of the
said furnace, whilst permitting the rotation of the said barrel during the heating of
the same, substantially as, and for the purposes, set forth.
Twelfth. The improved furnace provided with the means for supporting and
rotating the gun-barrel and for permitting the circulation of oil or other liquid
through the said barrel, all constructed and arranged substantially as described with
reference to Figures 1 to 5 of the drawings, for the purposes above specified.
Dated this 20th day of June 1880
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.