Improvements in the Manufacture of Ordnance.
Year: 1891

page_text: Date of Application, 29th Sept., 1891-Accepted, 31st Oct., 1891
COMPLETE SPECIFICATION.
[Communicated from abroad by HAYWARD AUGUSTUS HARVEY, of 455, Main
Street, Orange, New Jersey, United States of America, Mechanical
Engineer.]
Improvements in the Manufacture of Ordnance.
I, HENRY HARRIS LAKE of the firm of Haseltine, Lake, & Co., Patent Agents,
45 Southampton Buildings, in the County of Middlesex, do hereby declare the
nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
The object of this invention is to produce a steel cannon or other piece of
ordnance, the barrel or tube of which, while in other respects homogeneous, presents
upon its interior a cylindrical stratum of steel which is excessively hard upon its
concave surface but which gradually diminishes in hardness as the depth from the
concave surface increases, and is adjoined by a cylindrical stratum of steel of any
desired thickness, which is of considerable toughness, and which is incapable of
being hardened so as to be brittle, but which is surrounded by an exterior
cylindrical stratum of steel of prescribed thickness, excessively hard upon its
convex surface, and also gradually diminishing in hardness from its exterior surface
to the place of its union with the tough and comparatively soft steel of which the
enclosed cylindrical stratum is composed.
The objects of this construction are as follows :-
Firstly, to provide an interior surface for the tube or barrel which is so hard that
it is incapable of being cut or scratched by the action upon it of the projectile when
the gun is fired.
Secondly, to provide a cylindrical stratum of steel which possesses tenacity and
toughness without the brittleness which is the unavoidable characteristic of
hardened steel.
Thirdly, to provide upon the exterior of the barrel a cylindrical stratum of steel
which is so hardened as to give it the quality of elasticity without excessive brittle-
ness, and which acts as an inextensible hoop, which completely surrounds the body
of softer steel and effectively prevents it from being permanently expanded by the
force of the explosion when the gun is fired. The cylindrical stratum of compara-
tively soft steel acts, as a buffer, to protect the exterior stratum of hard steel from
the immediate shock of the explosion, which, but for the interposition of the stratum
of comparatively soft steel might be sufficient to burst the exterior stratum of
hardened steel.
These results are accomplished by treating the barrel or tube of the gun, after
the same has been cast or forged and turned to the desired shape and dimensions,
by filling the gun to the muzzle with finely-powdered charcoal, and embedding the
barrel of the gun in an external body of finely-powdered charcoal contained in a
receptacle from which the air is excluded, and which is constructed of refractory
material, such as fire-brick, and which is contained within a furnace chamber in
which there is maintained a heat sufficient to melt cast iron for a period of such
duration as will suffice to cause those portions of the metal which are in contact
with the charcoal, to absorb prescribed percentages of carbon in addition to the
carbon originally contained in the steel from which the gun has been made.
This process of treatment is analogous to that described in Letters Patent of the
United States No. 376,194 issued to Hayward A. Harvey, Jan. 10, 1888.
The duration of the described treatment will of course vary according to the
size of the gun, and also according to the efficiency of the furnace, and the
character of the fuel employed. The necessary data for determining the duration
are ascertainable by observing the effects produced by the use, for an observed
..
1

page_text: period, of a given fuel in a given furnace. The longer the high heat is maintained,
the greater will be the depth of penetration of the added carbon, and the greater
will be the quantity of carbon absorbed by the strata of metal in contact with
charcoal.
In view of the multiplicity of furnaces, the variety of fuels, and the various
sizes of guns, no general prescription can be given which will be of universal
applicability.
For illustration, it may be stated that a prolongation of the heat for a period of
thirty hours after the furnace chamber has been brought up to a temperature high
enough to melt cast iron will usually be sufficient for the effective treatment of
guns of say four inches calibre.
By such treatment, a gun composed of steel originally containing say one quarter
of one per cent. of carbon will be super-carburized upon its interior and exterior
surfaces to such an extent that the surface strata of metal will each contain from
one and one-tenth per cent. of carbon; the next adjoining annular strata will contain
say nine-tenths per cent., the next seven-tenths per cent., the next five-tenths per cent.,
and next three-tenths per cent., until, at depths of say three-quarters of an inch from
the exterior and say half an inch from the interior surfaces, the metal will contain
only its original quarter per cent. of carbon.
"
Upon hardening the gun by removing it from the furnace, allowing it to cool
down to a dull red colour or other desired colour and then plunging it into water or
other tempering fluid the super-carburized strata will take the variable degrees of
temper incident to the variable distribution of carbon in them. The greatest
percentage of carbon being present in the strata of metal adjoining the surfaces
which have been in contact with the charcoal those surfaces will be so hard that
they cannot be cut or scratched by an ordinary cold chisel or file. The next
adjoining annular stratum will be slightly less hard; the next still less hard, and so
on. It will of course be understood that the expressions "stratum" and "strata
are herein used merely for convenience, and that in any super-carburized stratum
of given thickness there will be a regularly varying distribution of carbon, the
quantity present gradually diminishing from the side nearest the exposed surface
toward the side furthest therefrom. The resultant gradual diminution in the degree
of hardness in the metal as the distance from the exposed surfaces increases is a
feature of great importance, for if a stratum of excessive hardness, owing to the
presence in it of a large percentage of carbon, immediately adjoined a stratum
containing so little carbon as to be incapable of being hardened, the highly
carburized hard stratum would be liable to be chipped or cracked off by the force
of the explosion. It is desired that there shall be a comparatively shallow depth
of super-carburization of the metal upon the interior surface of the gun-barrel, the
object being to make the interior surface of the gun barrel capable of taking so
hard a temper that it will not be abraided by the contact with it of the projectile
when the gun is fired. For the strengthening effect the external super-carburized
stratum is mainly relied upon and as the external portion of the gun is that which
is most nearly exposed to the heat of the furnace chamber, there is no difficulty in
so regulating the duration of the treatment as to effect the desired greater depth of
super-carburization of such external portion.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed as communicated to me by
my foreign correspondent, I declare that what I claim is :-
First. The herein described gun composed of a mass of steel which, while other-
wise homogeneous, contains variably distributed percentages of carbon and the
barrel of which is composed of an annular stratum of metal containing a relatively
low-percentage of carbon enclosed between internal and external annular strata of
metal excessively hard upon their exposed surfaces and gradually diminishing in
hardness as the depths from their exposed surfaces increase, as and for the purpose
set forth.

page_text: Second. A steel gun the barrel of which is composed of a body of steel
homogeneously united to the exterior of an annular stratum of metal containing
variably distributed percentages of carbon and which is excessively hard upon its
exposed surface, but gradually diminishes in hardness as the depth from its exposed
concave surface increases, as and for the purpose set forth.
Third. A steel gun the barrel of which is composed of a body of steel
homogeneously united to the interior of an annular stratum of metal containing
variably distributed percentages of carbon and which is excessively hard upon its
exposed convex surface, but gradually diminishes in hardness as the depth from its
exposed convex surface increases, as and for the purpose set forth.
Dated this 29th day of September 1891.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.