Improvements in the Manufacture of Armour Plates.
Year: 1893

page_text: Date of Application, 23rd Jan., 1893
Complete Specification Left, 17th Oct., 1893-Accepted, 18th Nov., 1893
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Armour Plates.
I TOLMIE JOHN TRESIDDER, Captain late of Her Majesty's Royal Engineers
now of The Atlas Steel and Iron Works Sheffield in the County of York do hereby
declare the nature of my invention to be as follows:-
-
Hitherto in the process of cementation or conversion to supercarburise one side
of a plate to constitute an armour plate the carburising material has always been in
contact at least with the whole surface of the side to be supercarburised and
commonly has in addition been carried more or less down the edges at the parts
contiguous to that side. In the first case the supercarburisation is carried quite to
the edges of the plate and in the second case the supercarburisation is not only
carried to the edges but is there considerably intensified. In the first case when
the plate is chilled its hardness at the corners will exceed that at the edges and
that at the edges will exceed that at the surface generally for the reason that
while the carburisation is uniform the corners can part with their heat to the
chilling medium in three directions and the edges in two directions but the surface
of the side, only in one direction whilst in the second case this applies not only to
the chilling but also to the carburisation which precedes it and which enters the
corners from three directions, the edges from two directions and the surface from
one direction only. Hence armour plates hitherto manufactured on any method
involving supercarburisation on one side followed by chilling have necessarily had
their hardest parts at their corners and edges. This is most undesirable for armour
plates since it must inevitably tend to facilitate the cracking and breaking thereof
and it is a serious drawback from the manufacturer's point of view since the very
parts where a greater or less final trimming and correction of shape are likely to be
required are unmachineable.
With a view to removing these objections my invention consists in so arranging
the carburising material, whatever it may be, that its contact with the surface of
the plate ceases some distance from the edges and corners. This distance is so
arranged that the surface of the plate shall be supercarburised up to about say for
example half an inch from its final finished outline but rather more from the
corners. The extreme edges therefore not being supercarburised are not susceptible
of hardening by chilling and can be machined as freely after the plate has been
chilled as before although the general surface is of the requisite hardness. The
unhardened portion also forms a sort of tough hoop or frame all round the plate
and thereby lessens its liability to cracking or breaking.
To overcome the objection armour plates are sometimes open to, namely that
they cannot be operated upon, for instance by drilling for the attachment of fittings
when in place on ship or fort I insert when required in the carburising medium (of
whatever kind) a piece or patch or pieces or patches of non-carburising material of
such size and form and in such positions as to cover the part or parts of the plate
which it is desired to drill or otherwise operate upon so that the said part or parts
will not be supercarburised and so will remain in a condition to be operated upon
by steel tools after the plate has been chilled..
The plate is of course protected from the fire by non-carbonaceous material at
places not covered by the super-carburising matter.
Dated this 23rd day of January 1893.
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, W.C., Agents.

page_text: COMPLETE SPECIFICATION.
Improvements in the Manufacture of Armour Plates.
I, TOLMIE JOHN TRESIDDER, Captain late of Her Majesty's Royal Engineers,
now of The Atlas Steel and Iron Works, Sheffield, in the County of York, 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 :-
Hitherto, in the process of cementation, or conversion, to supercarburize one side
of an iron or a low grade steel plate to constitute an armour plate the carburizing
material has always been in contact at least with the whole surface of the side to
be supercarburized as illustrated by Figure 1 of the accompanying diagrams where
(and also in all the other figures) A is the armour plate, B is the carburizing
material, and C is the non-carburizing material, and more generally the said
carburizing material has in addition been carried more or less down the edges at
the parts contiguous to that side as illustrated by Figure 2. In the first case the
supercarburization is carried quite to the edges of the plate and in the second case
the supercarburization is not only carried to the edges but is there considerably
intensified. In the first case when the plate is chilled its hardness at the corners
will exceed that at the edges and that at the edges will exceed that at the surface
generally for the reason that while the supercarburization is uniform the corners
can part with their heat to the chilling medium in three directions and the edges in
two directions but the surface can part with its heat only in one direction whilst in
the second case this applies not only to the chilling but also to the supercarburiza-
tion which precedes it, as the carbon enters the corners from three directions the
edges from two directions, but the surface from one direction only.
Hence armour plates, hitherto manufactured on any method involving super-
carburization on one side followed by chilling, have necessarily had their hardest
parts at their corners and edges. This is most undesirable for armour plates since
it must inevitably tend to facilitate the cracking and breaking thereof under the
impact of projectiles and it is a serious drawback from the manufacturers point of
view since the very parts where a greater, or lesser final trimming, and correction
of shape are likely to be required are the most unmachineable.
With a view to removing these objections my invention consists in so applying
the carburizing material (whatever it may be) that its contact with the surface of
the plate ceases some distance from the edges and corners, as illustrated in cross
section in Figure 3 and in the plan of a plate in Figure 4, the nou-carbonaceous
matter C being omitted from Figure 4 for the sake of clearness. This distance
is so arranged that the surface of the plate shall be supercarburized to the required
extent only; for instance, in cases where the plate has been cut to its finished
dimensions before supercarburization, the carbonaceous matter may be in contact
with the surface of the plate up to about say within one half of an inch from the
edges so as to lose the bulk of its effect at about one eighth of an inch from the
edges and so allow a little final trimming of those edges with steel tools, or
the carbonaceous matter may be in contact with the surface of the plate up to say
one, two, or three inches or more from its edges so as to leave a margin or frame
of tough, or unhardened, metal of any desired width round the whole or part of
the plate or, if the plate is to be cut to its finished dimensions after the super-
carburizing process, it may be supercarburized to within say one eighth of an inch
from the edge plus the width of the portion to be cut off, or plus that width together
with any desired width of tough unhardened margin or frame. The width at the
corners of the un-supercarburized portion should, in either case, be rather more
than its width at the sides, as shewn clearly by the plan Figure 4. The extreme
edges at a and the corners therefore, not being supercarburized, are not susceptible
of hardening by the subsequent chilling and can be machined as freely after the
plate has been chilled as before, although the general surface of the plate is of the

page_text: requisite hardness. If a margin, or frame, of tough, or unhardened, metal be lef
round the finished plate, (or say in a "belt" plate along the top and bottom
edges,) the liability of the plate to cracking, or breaking, under the impact of
projectiles, will be lessened. Further, to overcome the objection very hard faced
armour plates are naturally open to, namely, that they cannot be operated upon,
for instance, by drilling for the attachment of fittings, such as torpedo booms for
a ship, or ring bolts for a fort, I insert where required in the carburizing medium
(of whatever kind) a piece, or patch, or pieces, or patches, of non-carburizing
material of such size and form and in such positions as to cover the part, or parts,
of the plate which it is desired to drill, or to otherwise operate upon, so that the
said part, or parts, will not be supercarburized and so will remain in a condition
to be operated upon by steel tools, for instance, after the plate has been chilled.
In Figures 5 and 6 I have repeated Figures 3 and 4 respectively with the additions
necessary to illustrate this modification D being the pieces or patches of the said
non-carbonaceous matter to protect the parts beneath them from supercarburization,
so that when the plate undergoes the final chilling process these parts will contain
too little carbon to allow of their becoming appreciably hardened.
The plate is, of course, in all cases protected from the fire by non-carbonaceous
material at places not covered by the carbonaceous ina tter as shewn, for instance,
at C in Figures 3 and 5. Also the necessary precautions for preventing access of
oxygen either to the plate or to the carbonaceous matter are to be taken as is usual
in cementation.
The carbonaceous material used may be of any ordinary, or suitable, kind, such,
for example, as granular, or powdered, carbon, with, or without, other substances
admixed therewith, or a molten bath of metal which gives up its carbon to the plate
may be used, when the non-carbonaceous material at C, will be built up around
the plate so as to properly retain the molten metal; or hydro-carbon gases may be
employed as super-carburizing agents, or any other known, or suitable, method of
super-carburizing may be adopted.
Although in the drawings I have shewn a single plate with carbonaceous material
on the top of it, the whole arrangement may be inverted so that the plate will be
on the top of the carbonaceous matter, or two or more plates (according to the
available height in the furnace) may be treated at the same time by piling them
on each other with a layer of carbonaceous material between each pair of the
faces which are to be super-carburized and non-carbonaceous matter in contact
with all the other parts.
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 i3:-
In the manufacture of armour plates by supercarburising and subsequently
chilling the face, or shot receiving, side thereof the arrangement in the converting
process of the carbonaceous and non-carbonaceous materials; (a) so that the edges
and corners of the face of the plate instead of being, as heretofore, its hardest
parts shall be unhardened, or soft enough to allow of the plate being cut to shape
after chilling, or of being finally corrected if necessary by steel tools; or (b) so
that the face of the finished plate shall be surrounded, or partly surrounded, by
tough and unhardened metal owing to a margin, or margins, having been protected
from the action of the carburizing medium and so kept soft; or, (c) so that the
attachment of fittings in predetermined parts of the face of the plate shall be
possible owing to the said predetermined parts having been protected from the
action of the carburizing medium and so kept soft; all substantially as herein
before described.
1000
J. H. JOHNSON & Co.,
Agents.