Improvements in the Manufacture or Treatment of Armour Plates and in Apparatus Employed therein."
Year: 1897

page_text: Date of Application, 3rd Apr., 1897
Complete Specification Left, 31st Aug., 1897-Accepted, 24th Dec., 1897
Improvements in the Manufacture or Treatment of Armour Plates
and in Apparatus Employed therein."
I, BENTON KNOTT JAMISON of 441 Chestnut Street, Philadelphia, Pennsylvania,
United States of America, Manufacturer, do hereby declare the nature of this
invention to be as follows:-
This invention has reference to the manufacture or treatment of armour plates
and more particularly of armour plates of low grade or mild open-hearth steel
containing say from 20 to 50 per cent of carbon and alloyed or not with a small
percentage say from 1 to 5 per cent of nickel.
The invention chiefly consists of an improved and economical method of harden-
ing the face of the plates to any required depth so as to increase their resisting
power and at the same time render them more tenacious and less liable to fracture.
According to my invention I take a steel plate which is preferably of low grade
or mild open-hearth steel and heat it slowly and gradually until it attains a bright
red heat and then with as little delay as practicable immerse it to a depth corre
sponding with the depth to which it is required to harden it in a cold bath of
hardening liquid such as is hereinafter described of such character that the contact
of the heated metal and liquid bath will generate hydro carbon gases which will
be absorbed or taken up by the metal. The time occupied in slowly beating the
plate to a bright red as above described will depend upon the thickness of the plate;
for a plate 6 inches thick the time will be from to 4 hours. I leave the plate in
this bath for a sufficient length of time to effect the hardening process, viz until
hydro carbon gases cease to be generated from the bath and to be absorbed by the
plate, the time depending upon the depth to which the hardening is to extend,
say 30 to 40 minutes for a depth of 3 inches and I maintain the hath as nearly
as practicable at a uniform temperature during the whole time, so that the chemical
properties of the liquid will be retained and the plate be gradually cooled. This
temperature should be about 108° to 120° Fahrenheit to which temperature the
bath will be raised by the heat of the plate when the plate is first introduced. I
have found that a temperature of 1100 gives the best results. The maintenance
of a practically uniform temperature may be best effected by admitting more cold
hardening liquid through a regulated outlet to the lower part of the bath, pre-
viding the bath at the same time with an over-flow orifice so that the level of the
liquid in the bath and therefore the depth of immersion of the plate shall be kept
uniform.
The effect of the above treatment is that the portion of the plate which is im-
mersed in the hardening liquid undergoes a molecular change from a granular to
a fibrous condition blending with the softer or untreated hack nortion of the plate
but leaving this backing or untreated portion in its original condition.
While the desired portion of the plate is being treated and hardened as above
described I preferably place upon the non-submerged part or back of the plate, a
hot plate or several hot plates in succession according to the thickness of the plate

page_text: under treatment; the hot plate or plates should be heated to a greater heat than
the plate under treatment preferably to a bright red heat which is a greater heat
than that of the plate under treatment at the time the hot plate or plates are
applied thereto, the said plate under treatment being then at a black heat; they
have the effect of drawing a portion of the carbon from the back part of the plate
and of annealing this portion thereby rendering it exceeding tenacious and ductile
and counteracting the tendency of the front portion of the plate to crack when it
receives the impact of a heavy projectile. I have found that in dealing with an
armour plate of 6 inch thickness a good result is obtained by applying the first
hot plate about 4 minutes after the armour plate has been put in the bath, leaving
it for about 11 minutes, then applying another hot plate and leaving this about
16 minutes.
The front or hardened portion of the plate may if desired be subsequently
surface tempered by immersion in water and in this case I obtain an armour plate
of three different grades of steel viz:-the tempered surface, the portion hardened
by the action of the bath, and the remainder either in its original condition or
more or less annealed by the application of a hot plate or hot plates to the back
as above described.
While any suitable bath liquid may be utilized for the treatment of plates in
accordance with my invention, I prefer that the bath liquid shall be composed of
the following ingredients in approximately the proportions named: —
Spirits of Nitre
Aqua Ammonia
Chloride of Ammonium
Sulphate of Zinc
Sulphate of Alumina and Ammonia
Glycerine
3 oz.
3 oz.
4 oz.
3 oz.
3 oz.
6 oz.
1 gal.
Water
Or I may use merely a mixture of glycerine and water in the proportions of 6 oz.
of glycerine and 1 gal of water, but while this last named bath answers well and is
found to be entirely practical, it has also been found by experiment that the first
named ingredients and proportions are better adapted for the purpose.
It should be stated that either of the baths above described gives substantially
the same results in the treatment of armour plates of low grade steel, and in
practice this process (which should be understood as being distinguished from the
process of tempering steel in oil) changes the nature, the physical structure and
molecular construction of the steel, whereas the tempering of steel in oil simply
tempers the steel more slowly than is done by tempering in water and other agents,
And further, the changes caused by the oil tempering process are merel temporary,
leaving the steel less hard but somewhat tougher than water tempered material.
and do not change the physical and granular structure of the metal, and such
changes of the metal caused thereby can be readily neutralized by re-heating and
allowing the metal to cool. The plates treated according to my invention as above
described can be re-heated, forged and re-forged without changing their nature
physical structure or molecular construction.
The treatment of a plate when at proper temperature by this liquid, causes that
portion thereof which is subjected to the bath to absorb a large quantity of hydro-
carhon gas, which has a strong affinity for the metal when the latter is in a heated
state, thus facilitating this absorption, which has been shown to greatly improve
the quality of the steel in its tensile strength and elasticity, and vet not deteriorate
it in its capacity or ductility.
By many tests this process has been found to be especially adapted for the
treatment of armour plates since when such a plate is composed entirely of low
grade nickel steel, it may be converted to a high grade steel through a certain
portion thereof, while the remainder is left in its original condition,
and when the portion which is treated consists of a face of the
plate, and the treatment is permitted to extend a considerable distance below the

page_text: surface thereof, a plate will be produced, the face of which will have a greater
resisting power than the highest grade nickel steel when untreated, while the
back, being low grade nickel steel, will prevent the cracking or shivering of the
plate, as is well known in composite armour plates.
To produce such a plate by my improvement it is only necessary to form it from
low grade or mild open hearth steel with say from 20 to 50 per cent carbon, and
an alloy of from 1 to 5 per cent of nickei, bringing the same to the required
temperature for the proper treatment of the plate, and immersing a portion thereof
in the bath above described to the depth required to face-harden the same in the
manner herein before set forth.
Although I have mentioned that the percentage of nickel may be from 1 to 5,
my experiments have shown the best results when the percentage of nickel has
been 34. If no nickel be employed the percentage of carbon should be .55 to .65,
I may also employ with or without nickel a proportion of manganese say .60 to
.75 per cent, and the metal should contain as little silicon sulphur and phosphorus
as practicable.
The mode herein before described of annealing the back portion of an armour
plate by placing a hot plate or plates thereon is also applicable to armour plates
(such for example as Harveyized Plates) the front portion of which has been
hardened by other means than those hereinbefore described. In this case the
armour plate should be heated to a suitable heat say a bright red and the plate or
plates to be placed on the back of same should be heated to a greater heat say a
white heat. These hot plates when placed on the back of the heated armour plate
will draw a portion of the carbon from the back part of the armour plate and will
thereby anneal this back part.
My invention includes a special construction of apparatus for carrying out
the mode of manufacture above, described. In this apparatus I place in a con-
venient position relatively to a furnace for heating the plates and as close thereto
as practicable, a bath tank to and from which the plates may be conveyed by a
travelling crane.. In the bath tank there may be supports for an armour plate
and this tank has leading therefrom an over flow pipe in which is a valve for regu-
lating the level of the liquid within the tank, as will be readily understood; and
for convenience in determining the level of the liquid within the bath tank a
graduated scale may be provided.
The outer end of the pipe empties into an over flow tank or reservoir, and this
tank is preferably of a size to act as a reservoir to store a sufficient quantity of
bath liquid for a continuous operation.
A pump is connected by a pipe with the oven flow tank, the object of which is
to force the bath liquid through a pipe to a cooling coil, which latter is arranged
within a casing having a spray nozzle at the upper portion thereof; which is fed
by a suitable water supply so as to reduce the temperature of this coil and the
liquid passing therethrough, and the water which accumulates within the casing
is drawn therefrom through the waste pipe; or the casing may be filled with ice.
From the coil leads a pipe to a flush tank, the latter being of sufficient capacity
to hold enough of the bath liquid to supply the bath tank with sufficient speed
to maintain the temperature within the bath tank when a hot plate has been
placed therein; and for the regulation of the down flow of the liquid from the
Hush tank, a valve is interposed in the pipe which leads from the flush tank to the
bath tank.
The operation of this apparatus will be obviously as follows:
The pump being set in operation, a portion of the liquid will be drawn from the
reservoir and overflow tank, and forced upward through the coil, when this tem-
perature will be reduced, and from thence it will be conveved to the flush tank
where it is stored for use when needed. Now when a plate to be treated has been
properly heated within the furnace, it is conveyed therefrom by the travelling
crane to the bath tank deposited upon the supports within said tank and immersed
to the depth that it is desired to harden the surface of said plate, and the proper

page_text: flow of bath liquid to the bath tank will be established by the manipulation of
the valve and the level of this liquid will be maintained at the desired point by
the adjustment of the valve in the overflow pipe.
When the plate is first introduced into the bath tank, it is obvious that the
intense heat thereof will tend to greatly increase the temperature of the bath,
but as it is essential that the temperature of this bath, should not be unduly
increased, as the chemical action thereof would be altered, the supply valve is so
manipulated at this stage of the process as to greatly increase the flow of the bath
liquid to the tank, but this increased flow will not alter the level of the liquid
within the tank, since the overflow is of a capacity sufficient to carry away this
increased supply; but the result of this increased supply will be to maintain the
temperature of the bath liquid within the tank at the proper degree, which may
be determined by a thermometer extending downward below the level of the bath.
In mild or small classes of work it may be found desirable to maintain the over-
flow or level of the bath liquid at a given point, and regulate the depth of the
plate therein by the movements of the supports. This may be provided for by
providing the supports with suitable guide-ways within the bath tank and sup
porting them upon a piston rod which passes through the bottom of the tank
and into a hydraulic cylinder where it is attached to a suitable piston; inlet and
outlet pipes being arranged for the operation of this piston. Thus the depth of the
plate within the bath may be regulated by the lowering and raising of the supports.
When plates with curved faces are to be treated, the upper surface of the supports
within the bath tank may have a similar curvature therein so that said plates
may be placed firmly against the supports thereby preventing a tendency to
warping.
Dated this 2.1
J
30 1007
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London. Chartered Patent Agents.
66
Improvements in the Manufacture or Treatment of Armour Plates
and in Apparatus Employed therein."
I, BENTON KNOTT JAMISON of 441 Chestnut Street, Philadelphia, Pennsylvania,
United States of America, Manufacturer, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:—
This invention has reference to the manufacture or treatment of armour plates
and more particularly of armour plates of low grade or mild open-hearth steel
containing say from 20 to 50 per cent of carbon and alloyed or not with a small
percentage say from 1 to 5 per cent of nickel.
This invention chiefly consists of an improved and economical method of harden-
ing the face of the plates to any required depth so as to increase their resisting
power and at the same time render them more tenacious and less liable to fracture.
According to my invention I take a steel plate which is preferably of low grade
or mild open-hearth sttel and heat is slowly and gradually until it attains a bright
red heat and then with as little delay as practicable immerse it to a depth corre-
sponding with the depth to which it is required to harden it in a cold bath of
hardening liquid such as hereinafter described of such character that the contact
of the heated metal and liquid bath will generate hydro carbon gases which will
be absorbed or taken up by the metal. The time occupied in slowly heating the
plate to a bright red as above described will depend upon the thickness of the

page_text: plate; for a plate 6 inches thick the time will be from 3 to 4 hours. I leave
the plate in this bath for a sufficient length of time to effect the hardening process,
viz until hydro carbon gases cease to be generated from the bath and to be absorbed
by the plate, the time depending upon the depth to which the hardening is to
extend, say 30 to 40 minutes for a depth of 3 inches and I maintain the bath as
nearly as practicable at a uniform temperature during the whole time, so that the
chemical properties of the liquid will be retained and the plate be gradually
cooled. This temperature should be about 108° to 120° Fahrenheit to which
temperature the bath will be raised by the heat of the plate when the plate is first
introduced. I have found that a temperature of 110° gives the best results. The
maintenance of a practically uniform temperature may be best effected by admit-
ting more cold hardening liquid through a regulated outlet to the lower part of
the bath, providing the bath at the same time with an overflow orifice so that the
level of the liquid in the bath and therefore the depth of immersion of the plate
shall be kept uniform.
The effect of the above treatment is that the portion of the plate which is
immersed in the hardening liquid undergoes a molecular change from a granular
to a fibrous condition blending with the softer or untreated back portion of the
plate but leaving this backing or untreated portion in its original condition.
While the desired portion of the plate is being treated and hardened as above
described I preferably place upon the non-submerged part or back of the plate, a
hot plate or several hot plates in succession according to the thickness of the plate
under treatment; the hot plate or plates should be heated to a greater heat than
the plate under treatment preferably to a bright red heat which is a greater heat
than that of the plate under treatment at the time the hot plate or plates are
applied thereto, the said plate under treatment being then at a black heat; they
have the effect of drawing a portion of the carbon from the back part of the plate
and of annealing this portion thereby rendering it exceeding tenacious and ductile
and counteracting the tendency of the front portion of the plate to crack when it
receives the impact of a heavy projectile. I have found that in dealing with an
armour plate of 6 inch thickness a good result is obtained by applying the first hot
plate about 4 minutes after the armour plate has been out in the bath, leaving it
for about 11 minutes, then applying another hot plate and leaving this about 16
minutes.
The front or hardened portion of the plate may if desired be subsequently surface
tempered by immersion in water and in this case I obtain an armour plate of three
different grades of steel viz:-the tempered surface, the portion hardened by the
action of the bath, and the remainder either in its original condition or more or
less annealed by the application of a hot plate or hot plates to the back as above
described.
While any suitable bath liquid may be utilised for the treatment of plates in
accordance with my invention, I prefer that the bath liquid shall be composed
of the following ingredients in approximately the proportions named:-
Spirits of Nitre
Aqua Ammonia
Chloride of Ammonium
Sulphate of Zinc
Sulphate of Alumina and Ammonia
Glycerine
Water
3 oz.
3 0%.
4 oz.
3 oz.
3 oz.
6 oz.
1 gal.
Or I may use merely a mixture of glycerine and water in the proportions of 6 oz.
of glycerine and 1 gal. of water but while this last named bath answers well and is
found to be entirely practical, it has also been found by experiment that the first
named ingredients and proportions are better adapted for the purpose.
It should be stated that either of the baths above described gives substantially
the same results in the treatment of armour plates of low grade steel, and in
practice this process (which should be understood as being distinguished from the

page_text: process of tempering steel in oil) changes the nature, the physical structure, and
imolecular construction of the steel, whereas the tempering of steel in oil simply
tempers the steel more slowly than is done by tempering in water and other agents,
leaving the steel less hard but somewhat tougher than water tempered material.
And further, the changes caused by the oil tempering process are merely temporary,
and do not change the physical and granular structure of the metal, and such
changes of the metal caused thereby can be readily neutralised by re-heating and
allowing the metal to cool. The plates treated according to my invention as above
described can be re-heated, forged and re-forged without changing their nature,
physical structure or molecular construction.
The treatment of a plate when at proper temperature by this liquid causes that
portion thereof which is subjected to the bath to absorb a large quantity of hydro-
carbon gas, which has a strong affinity for the metal when the latter is in a heated
state, thus facilitating this absorption, which has been shown to greatly improve
the quality of the steel in its tensile strength and elasticity, and yet not deteriorate
it in its capacity or ductility.
By many tests this process has been found to be especially adapted for the
treatment of armour plates since when such a plate is composed entirely of low
grade nickel steel, it may be converted to a high grade steel through a certain
portion thereof, while the remainder is left in its original condition,
and when the portion which is treated consists of a face of the
plate, and the treatment is permitted to extend a considerable distance below the
surface thereof, a plate will be produced the face of which will have a greater
resisting power than the highest grade nickel steel when untreated, while the back,
being low grade nickel steel, will prevent the cracking or shivering of the plate,
as is well known in composite armour plates.
To produce such a plate by my improvement it is only necessary to form it from
low grade or mild open hearth steel with say from 20 to 50 per cent carbon, and
an alloy of from 1 to 5 per cent of nickel, bringing the same to the required
temperature for the proper treatment of the plate, and immersing a portion thereof
in the bath above described to the depth required to face-harden the same in the
manner herein before set forth.
Although I have mentioned that the percentage of nickel may be from 1 to 5,
my experiments have shown the best results when the percentage of nickel has
been 3. If no nickel be employed the percentage of carbon should be .55 to .65,
I may also employ with or without nickel a proportion of manganese say .60 to
.75 per cent, and the metal should contain as little silicon sulphur and phosphorus
as practicable.
The mode herein before described of annealing the back portion of an armour
plate by placing a hot plate or plates thereon is also applicable to armour plates
(such for example as Harveyized Plates) the front portion of which has been
hardened by other means than those herein before described. In this case the
armour plates should be heated to a suitable heat say a bright red
and the plate or plates to be placed on the back of same should
be heated to al greater heat say a white heat. These hot plates
when placed on the back of the heated armour plates will draw a portion
of the carbon from the back part of the armour plate and will thereby anneal this
back part.
My invention includes special constructions of apparatus for carrying out the
mode of manufacture above described. In this apparatus according to one modi-
fication which is shown in sectional elevation in Figure 1 of the drawings I place
in a convenient position relatively to a furnace A for heating the plates and as
close thereto as practicable, a bath tank D to and from which the plates may be
conveyed by a travelling crane B mounted on rails C. In the bath tank there
may be a support or supports E for an armour plate shown at F and this tank has
leading therefrom an overflow pipe G in which is a valve H for regulating the
level of the liquid within the tank, as will be readily understood; a handwheel I

page_text: being connected with the valve to operate the same, and for convenience in
determining the level of the liquid within the bath tank a graduated scale J may
be provided.
The outer end of the pipe G emipties into an overflow tank or reservoir K, and
this tank is preferably of a size to act as a reservoir to store a sufficient quantity
of bath liquid for a continuous operation.
A pump L is connected by a pipe M with the overflow tank K, the object of
which pump is to force the bath liquid through a pipe N, to a cooling coil 0, "which
latter is arranged within a casing P having a spray nozzle Q at the upper portion
thereof; which is fed by suitable water supply so as to reduce the temperature of
this coil and the liquid passing there through, and the water which accumulates
within the casing is drawn therefrom through the waste pipe R; or the casing may
be filled with ice.
From the coil leads a pipe S to a flush tank T, the latter being of sufficient
capacity to hold enough of the bath liquid to supply the bath tank D with sufficient
speed to maintain the temperature within the bath tank when the hot plate F
has been placed therein; and for the regulation of the down flow of the liquid
from the flush tank a valve U is interposed in the pipe V which leads from the
flush tank to the bath tank.
The operation of this apparatus will be obviously as follows:-
The pump L being set in operation, a portion of the liquid will be drawn from
the reservoir and overflow tank K, and forced upward through the coil O where
this temperature will be reduced, and from thence it will be conveyed to the flush
tank T where it is stored for use when needed. Now when a plate to be treated
has been properly heated within the furnace A, it is conveyed therefrom by the
travelling crane B to the bath tank D deposited upon the support E within said
tank and immersed to the depth that it is desired to harden the surface of said
plate and the proper flow of bath liquid to the bath tank will be established by the
manipulation of the valve U and the level of this liquid will be maintained at the
desired point by the adjustment of the valve H.
When the plate is first introduced into the bath tank it is obvious that the
intense heat thereof will tend to greatly increase the temperature of the bath, but
as it is essential that the temperature of this bath should not be unduly increased,
as the chemical action thereof would be altered the supply valve U is so manipu-
lated at this stage of the process as to greatly increase the flow of the bath liquid
to the tank, but this increased flow will not alter the level of the liquid within the
tank, since the overflow is of a capacity sufficient to carry away this increased
supply; but the result of this increased supply will be to maintain the tempera-
ture of the bath liquid within the tank at the proper degree, which may be
determined by a thermometer W extending downward below the level of the bath.
In mild or small classes of work it may be found desirable to maintain the over-
flow or level of the bath liquid at a given point, and regulate the depth of the
plate therein by the movement of the supports. This may be accomplished by
the modified construction shown in Figure 2 that is to say by providing the sup-
port a with suitable guide-ways within the bath tank b and supporting it upon
a piston rode which passes through the bottom of the tank and into a hydraulic
cylinder d where it is attached to a suitable piston: inlet and outlet pipes ee
being arranged for the operation of this piston. Thus the depth of the plate
within the bath may be regulated by the lowering and raising of the support
When plates with curved faces are to be treated, the upper surface of the supports
with the bath tank may have a similar curvature therein so that said plates mav
be placed firmly against the supports thereby preventing a tendency to warping.
Figures 3, 4 and 5 illustrate another construction of apparatus for carrying out
the mode of manufacture hereinbefore described, Figure 3 representing the bath
tank in plan, Figure 4 being a sectional elevation of the bath tank; and Figure 5
a diagrammatic plan of the general arrangement of the whole apparatus except
the furnace and crane. a is the bath tank, 6 the pump for circulating the liquid

page_text: e which
and the cooling tank. dd are ducts at two sides of the tank a; these ducts
are supplied with cool water from the cooling tank c by the main pipe
has two branches ff leading respectively to the two ducts dd. On the main
pipe e is a regulating valve g. hh are a series of horizontal pipes (not shown in
Figure 5) connected with, and supplied with cool liquid by the ducts dd. These
pipes are provided at their upper part with a number of nozzles ii adapted to
receive screw caps for closing them when required. The pipes are capable of
being rocked on their axes to the extent of about a quarter revolution; this rocking
may be imparted by any suitable means and has the effect of continually varying
the noints of issue of the cool liquid and thereby distributing it more or less
uniformly among the hot liquid in the tank and over the under surface of the
armour plate. The means shown in the Figures for imparting the rocking motion
to the pipes h h consist of a bar k to which the pipes are connected by lever arms 1,
the said bar being worked by a rod m bell crank m¹ and a rod 'n connected to
crank pin (Figure 5) on the engine that drives the pump b. In the other two
sides of the bath tank a are adjustable openings 99 (Figure 4) through which
the liquid in the tank flows into two wells rr (Figure 3) and at the same sides of
the tank are weirs ss over which the liquid flows into the same wells. From the
wells rr pipes tt lead to the pump band from the pump b pipe u leads to the cooling
tank c.
It will thus be understood that the pump continuously draws hot liquid
from the wells rr communicating with the tanks and pumps it into the cooling
from which it flows under pressure as cool liquid by the main pipe e,
branches ff pipes hh and nozzles ii to the bath tank a. The cooling water in
the tank c flows inside the tubes in the cooling tank entering at c¹ and leaving at c²
and extracts heat from the bath liquid which flows outside the same tubes; the
cooling tank c should have an air space at top.
tank c
vare a number of supports or stands (not shown in Figure 5) for the armour
plate in the bath tank a. The height of these supports is adjustable so as to
regulate the depth to which the plate is immersed in the bath liquid. The means
whereby the height of the supports can be adjusted consist of sprocket wheels w w
operated by an endless chain which is worked by a crank handle at y. The
wheels w have nuts z engaging with screw threads on the supports v so that as the
wheels w are caused to rotate by the chain a in the one direction or the other they
raise or lower all the supports simultaneously.
Although I have described and shown that the bath tank in Figures 3 and 4
has two ducts dd, two wells rr, and two weirs ss there may be only one duct,
one well and one weir, more particularly when the apparatus is constructed for
treating armour plates of comparatively small dimensions.
I do not in the present application for Patent make any specifie Claim to the
particular construction or arrangement of apparatus shown in Figures 3, 4 and 5
as such construction or arrangement constitutes the subject of a separate appli-
cation for Patent made by me on the 8th. June 1897 No. 14007.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I Claim is:-
1. The mode hereinbefore described of treating armour plates in order to harden
the face to any required depth which mode consists in slowly heating a steel
plate to a bright red heat, submerging it when at this heat in a bath of hardening
liquid such as is herein before described to a depth corresponding with the depth
to which it is required to harden the plate, keeping it in the bath for a sufficient
length of time to effect the hardening process, and maintaining the bath during
the process at as nearly as practicable a temperature of about 108° to 1200
Fahrenheit, substantially as set forth.
2. In the manufacture or treatment of armour plates, submitting a steel plate
to the treatment described in Claim 1 in order to harden the face to any required

page_text: depth and during the said treatment applying one or more hot plates to the non-
submerged part or back of the plate substantially as and for the purpose set forth.
3. In the manufacture or treatment of armour plates, submitting a steel plate
to the treatment described in Claim 1 in order to harden the face to any required
depth and then surface tempering the hardened portion whereby an armour plate
of three different grades of steel is obtained, substantially as set forth.
4. The manufacture of an armour plate face hardened to any required depth,
by slowly heating a plate or low grade or mild open hearth steel containing from
.20 to .50 per cent of carbon and alloyed with from 1 to 5 (preferably 3) per cent
of nickel, to a bright red heat, submerging it when at this heat for a sufficient
length of time to effect the hardening process in a bath of hardening liquid such
as is hereinbefore described to a depth corresponding with the depth to which it
is required to harden it, and maintaining the bath during the process at as nearly
as practicable to a temperature of about 108° to 120° F. substantially as set forth.
5. The mode herein before described of annealing the back portion of an armour
plate face hardened to any desired depth which mode consists in heating the plate
to a given heat, say a bright red, and placing upon the back of the plate when so
heated one or more plates heated to a greater heat, say a white heat, substantially
as set forth.
6. The special, construction of apparatus substantially as hereinbefore described
and shown in Figure 1 for employment in the manufacture or treatment of armour
plates in the manner set forth.
7. The modified construction of apparatus substantially as hereinbefore described
and shown in Figure 2 for the purpose set forth.
J. C. MEWBURN & ELLIS
55 and 56 Chancery Lane, London, Chartered Patent Agents.