An Improved Method of and Apparatus for Manufacturing Armour Plates.
Year: 1893

page_text: Date of Application, 6th Oct., 1893
Complete Specification Left, 6th July, 1894-Accepted, 6th Oct., 1894
PROVISIONAL SPECIFICATION.
An Improved Method of and Apparatus for Manufacturing
Armour Plates.
I, BENJAMIN HOWARTH THWAITE, of 95 and 97 Finsbury Pavement, in the
City of London, Civil Engineer, do hereby declare the nature of this invention to
be as follows
My invention relates to an improved method of and apparatus for manufacturing
armour plates, whereby many important advantages are obtained. The said
invention consists chiefly in subjecting the metal in a molten condition to the action
of gas or vapour containing carbon, and also in a peculiar method of insuring a
decremental and stratified condition of the carburized plate. It also consists in
improved apparatus for use in such manufacture.
The metal, i.e. fluid steel or ferro-carbon metal from an open hearth steel furnace,
or from a Bessemer or any other apparatus for producing ferro-carbon, is run into a
specially devised ladle which has a multiple number of outlet nozzles provided with
suitable stoppers, these nozzles being properly arranged to allow the molten metal
to flow freely and equally from the ladle into all parts of a mould or casting
chamber as hereinafter described.
For controlling the flow of the metal from the said ladle I provide the following
devices, that is to say :-The stoppers are connected by vertical rods with a cross-
piece which, through the medium of worm-wheel or other suitable gearing, is
connected with a hand-wheel or other means whereby the said stoppers can all be
operated simultaneously to open or close the nozzles. Therefore the said stoppers
can be instantly lowered to close the nozzles or can be raised therefrom to permit
the flow of metal from the ladle into the mould so that at any predetermined
time the metallic flow can be started, retarded arrested, or restarted, to allow an
intervening period for a specific action of carburization to be effected as herein-
after described. The vertical ends should be protected by fire clay or the like.
The said rods have weights fixed at their upper ends and so arranged that the
weights of each rod can act independently thereon to close the nozzle.
The aforesaid mould is constructed of refractory bricks or the like lined with
silicious, calcareous or other suitable material which can be raised to a high
temperature in situ. The temperature being, by the combustion of fuel well
distributed under the surface and along the sides of the mould, elevated to the
melting point of steel if necessary. The mould is provided with a refractory and
portable or movable arched cover arranged in combination with an overhead
traveller or the like which cover can be rapidly raised and moved away from the
mould so that the armour plate after being cast in the mould and solidified can be
readily removed therefrom. The refractory arched cover over the mould or casting
chamber drops into a specially formed iron groove or chaunel in such a manner that
by the application of fine sand, carbon, or water or other liquid a sufficiently tight
joint can be secured. After the arch frame is dropped into its place and the joints
made tight as described, the multiple-stoppered ladle with its molten contents is
moved over the mould to such a position that the nozzles are brought immediately
over nozzles or tubes which extend through the arched cover and permit the metal
to flow in evenly distributed streams into the mould.
Assuming that the metal of an armour plate 12 inches thick may be required to
have four layers or strata of different and decremental or increasing percentages of
carbon, say, for example, the series of 0.10, 0.25, 0.50, and 0.75, the metal is run
into the mould until a metallic depth of 3 inches is obtained, then the flow of metal
is instantly arrested by dropping the stoppers. During the flow of the metal into

page_text: the mould the atmosphere therein is distinctly deoxidising but when the flow of
metal is arrested a highly carburizing atmosphere must exist in the casting chamber
over the metal. I produce this condition either by the introduction of a rich hydro-
carbon gas generated from petroleum or from bituminous coal or from any other
source, or by an evenly-distributed injection into the casting chamber over the
metal of very finely-divided pure carbon. Stoppers in the arched cover nozzles
can be arranged to allow the supply of the carburizing medium to be so controlled
that any desired pressure can be produced upon the surface of the metal, and by
such action the metal is consequently recarburized.
When the desired degree of carburization is produced in the first layer or
stratum of molten metal, the metal is allowed to flow until a depth of 6 inches or an
additional 3 inches is attained. The process is then continued ab initio. It is
obvious that instead of the specific metallic strata of varying carbon percentages,
the proportion of carbon can be regularly or uninterruptedly increased through the
mass that is to say in such a degree that it could be graphically expressed or
represented by a continuous line or curve from the minimum to the maximum
allowable percentage of carbon. During the metallic flow, a high temperature is
maintained both around and under the mould, the bottom of the casting or armour
plate being allowed to gradually solidify primarily, the direction of solidification
being preferably an ascensional one, but the manner of solidification may vary
according to the character of plate required.
If desired the lower part of the plate next to the bottom of the mould can be the
most highly carburized, the proportion of carbon added being gradually reduced as
the metal is being fed to the mould so that the last layer of metal is the mildest.
The casting chamber may be connected with a steam-jet exhauster so that a
slight vacuum can be established in the casting chamber to facilitate the removal of
added or occluded gases.
During any intervening period of the arrest of the flow of the metal an alloy of
nickel, chromium, or any other metal, can be allowed to flow through the aforesaid
or other nozzles in such a manner as to be uniformly distributed throughout the
molten mass.
Rapid cooling of the metal in the intervening period of the arrest of the metallic
flow, or after the plate has been cast, can be effected by the introduction of
ammoniacal or other refrigerating vapour or gas either under the mould or over the
metal, and under such pressure as may be found desirable.
To facilitate its removal I cast lugs on the sides of the plate for the attachment
of lifting shackles thereto.
The said plate can be taken from the mould whilst sufficiently hot to ensure the
full effect of the chilling operation to which the plate is subsequently subjected.
But if desirable or necessary the plate may be reheated in a special furnace before
chilling.
Dated this 4th dow of Ontabor 1803
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.
COMPLETE SPECIFICATION.
An Improved Method of and Apparatus for Manufacturing
Armour Plates.
I, BENJAMIN HOWARTH THWAITE, of 95 and 97 Finsbury Pavement, in the
City of London, Civil Engineer, do hereby declare the nature of this invention,
and in what manner the same is to be performed, to be particularly described and 5
ascertained, in and by the following statement:-
My invention relates to an improved method of and apparatus for manufacturing
armour-plates whereby many important advantages are obtained. The said

page_text: invention consists chiefly in subjecting the metal in a molten condition to the action
of gas or vapour containing carbon, and also in a peculiar method of insuring a
decremental and stratified condition of the carburized plate. It also consists in
improved apparatus for use in such manufacture.
In practising my invention I take fluid steel or ferro-carbon metal from an open
bearth steel-furnace or from a Bessemer converter or other apparatus for producing
ferro-carbon, and conduct the same into a mould or casting chamber. I use for
this purpose a specially devised ladle which has outlet nozzles provided with
suitable stoppers, these nozzles being properly arranged to allow the molten metal
to flow freely and equally from the ladle into all parts of the mould or casting
chamber as hereinafter described. After the plate has been cast and carburized
and solidified in the said mould it is removed therefrom and it is then chilled by
spraying or otherwise to harden or temper its carburized surface.
If desired the said plate after carburization and previous to the chilling may be
rolled, hammered or pressed.
In the accompanying drawings I have shewn the apparatus which I have devised
for casting and carburizing the metal of an armour-plate according to my invention.
Figure 1 is a vertical longitudinal section and
Figure 2 is a vertical transverse section of the said apparatus.
Figures 3 and 4 are similar sections showing slight modifications of the said
apparatus.
Figure 5 is partly a horizontal section and partly a plan of a mould or casting
chamber such as that shewn in Figures 3 and 4.
Like letters indicate the same parts throughout the drawings.
A is the aforesaid mould constructed of refractory bricks or the like and lined
at A' with silicious, calcareous or other suitable material which can be raised to a
high temperature in situ. This mould or chamber is so constructed that by the
combustion of fuel well distributed under the surface or along the sides of the
mould, or both under and at the sides of the mould, the temperature can be elevated
to the melting point of steel if necessary. The drawing shews combustion
chambers Pat the sides only. QQ are pipes for the admission of the carburizing
gas. The mould has a refractory and portable or movable arched cover B which
in the apparatus shewn in Figures 1 and 2 is provided with nozzles or tubes B¹
through which the molten metal is supplied from the ladle to the mould, the said
nozzles being arranged in such positions as to permit a uniform distribution of the
metal in the mould as hereinafter described.
The arch-cover is constructed as follows, that is to say: D' is a steel rectangular
frame furnished with inside angle-irons D' which carry skew-back blocks d as
shown and from which springs the arch constructed of refractory blocks. The
upper surface of the arch is covered with sand filled up level with the top of the
steel frame D' but with openings for the introduction of the metal into the nozzle B¹
built into the arch. This arch when in position over the casting chamber rests on
a rebated block of fire-brick d'. The arch is smaller than the containing cast
iron frame D and a channel is thus provided between the arch and the frame.
This channel is filled with sand carbon or water or other liquid to prevent the
escape of gases. The said cover is arranged in combination with an overhead
traveller C or the like running on joists or girders above the mould and connected
by lifting shackles and screws to the cover so that the cover can be readily raised
and moved away from the mould, and the armour plate after being cast in the
mould and solidified can be removed therefrom with facility.
The metal is supplied to the mould from the afore-aid peculiarly constructed
ladle E. This ladle is provided with stoppered nozzles E' and in the apparatus
shewn in Figures 1 and 2 is so arranged that alter the arch frame B is dropped
into its place and the joint made tight as described, the said ladle containing the
molten metal can be moved over the mould to such a position that the said nozzles
will be immediately over the nozzles or tubes B₁ which extend through the arched
cover.

page_text: For controlling the flow of the metal from the said ladle I provide the following
devices, that is to say, the nozzle-stoppers E' are connected by vertical rods E³
with a cross-piece E which is suspended from a bridge E' and which through the
medium of worm-wheel or other suitable gearing, is connected with a hand-wheel
or chain wheel E° or other means whereby the said stoppers can all be operated
simultaneously to open or close the nozzles E'. Therefore the said stoppers can
all be instantly adjusted to permit or prevent the flow of metal from the ladle E
into the mould A so that at any predetermined tine the metallic flow can be started,
retarded arrested or restarted to allow an intervening period for a specific action
of carburization to be effected as hereinafter described. The vertical ends of the
mould should be protected by fireclay or the like.
The rods E3 are loaded at their upper ends by weights E' and are so arranged
that the weights of each rod can act independently thereon to close the nozzle.
A sheet iron or other tube S having suitable terminals S' has one end arranged
to fit in a lute frame S' on the casting chamber and the other end arranged to
enter a similar frame communicating with the chimney or with the heating
chamber V surrounding the casting mould. The gases in the mould can escape
by the tube S. A disc valve T is provided to enable the pressure in the chamber
to be regulated. In order to establish uniformity of heating effect in the heating
chamber or flues around the mould or casting chamber I provide a series of stop
valves W which regulate the gas escape from the gas main W. The combustion
occurring in the chamber V extends into the flue or combustion chamber P aforesaid
that surrounds the casting chamber. The heat thus generated prevents rapid
radiation of the heat from the said chamber.
In the apparatus shewn in Figures 3 and 4 1 provide one two or more feeding
channels or "gits" F which are built outside the armour plate mould A and
through which the metal is poured from the ladle into the mould, the nozzles of
the said ladle being in this case arranged to discharge the metal into the outer
ends of the feeding "gits." The channel-frame is constructed with detachable or
movable parts where the "gits are situated so that the metal or header therein
shall not obstruct the removal of the armour-plate from the mould. I provide
arrangements to enable the header either to be broken from the armour plate or to
be removed with it.
"
The refractory arched cover B is preferably constructed with an outer casing of
steel and strengthened by means of angle pieces and ties. The sides of the arch
when placed in situ over the combustion chamber rest in a cast iron channel D'
which is filled with sand or other suitable material to prevent the escape of gas.
The ends of the cover B are provided with connections to the gas inlets and
outlets as shown at G, H in Figures 3 and 4. The parts G, H', of these
connections dip into a hydraulic or sand seal-frame G, H, arranged over the gas
and outlet mains so that when the cover is dropped into position over the mould
or casting chamber immediate connection is made between the interior of the
casting chamber and the gas supply and chimney outlets.
The gas-supply and chimney connections may be formed of sheet steel with
firebrick inner linings. R is a flexible air-supply pipe.
Similar apparatus to that above described with reference to Figures 1 and 2
may be used for lifting the cover of the mould and for removing the armour plate
from the mould. The removal of the lining of the mould at certain well
distributed points will allow a lifting hook to be placed under the armour plate.
And to facilitate the removal of the plate I cast lugs on its sides for the attachment
of the shackles thereto.
Assuming that the metal of an armour plate 12 inches thick may be required to
have four layers or strata of different and decremental or increasing percentages of
carbon, say, for example the series of 0-10, 0.2, 0.50 and 0.75, the metal is run
into the mould until a depth of about 3 inches thereof is obtained; then the flow of
metal is arrested. During the flow of the metal into the mould or casting chamber
a deoxidizing or very slightly carburizing atmosphere exists therein but when the

page_text: flow of metal is arrested a highly carburizing atmosphere must exist in the casting
chamber over the metal. produce this condition either by the introduction of a
rich hydrocarbon gas generated from petroleum or from bituminous coal or from
any other source, or by an evenly distributed injection, into the casting chamber
over the metal, of very finely divided pure carbon. Stoppers can be arranged in
the arched cover nozzles or other passages to allow the supply of the carburizing
medium to be so controlled that any desired pressure can be produced upon the
surface of the metal. When the desired degree of carburization is produced in the
first layer or stratum of molten metal, the metal is again allowed to flow until a
depth of 6 inches, i.e. an additional three inches, is attained this being carburized
and the process continued till sufficient metal to produce the required thickness of
the plate has been run into the mould and carburized. It is obvious that instead of
the specific metallic strata of varying carbou percentages the proportion of carbon
could be regularly or uninterruptedly increased or decreased through the mass that
is to say it could be graphically expressed or represented by a continuous line or
curve. During the metallic flow, a high temperature may be maintained both
around and under the mould, the lower surface of the casting or armour plate
being first allowed to gradually solidify and the direction of solidification being
preferably an ascensional one, but the manner of solidification may vary
according to the required character or condition of the plate.
If desired the lower part of the plate i.e. the surface next to the bottom of the
mould may be the most highly carburized, the proportion of carbon added being
gradually reduced while the metal is entering the mould so that the last layer of
metal is the mildest or least carburized part of the plate.
The casting chamber may be connected with a steam-jet exhauster so that a
slight vacuum can be established in the said chamber to facilitate the removal of
added or occluded gases.
During any intervening period of the arrest of the flow of the metal an
alloy of nickel, chromium, or other suitable metal, can be allowed to flow
into the mould in such a manner as to be uniformly distributed throughout the
molten mass.
Rapid cooling of the metal in the intervening period of the arrest of the
metallic flow or after the plate has been cast, can be effected by the introduction
of ammoniacal or other refrigerating vapour or gas either under the mould or over
the metal and under such pressure as may be found desirable.
The said plate can be taken from the mould whilst sufficiently hot to ensure
the full effect of the chilling operation to which the plate is subsequently
subjected. But if the plate is rolled or otherwise worked after the carburization
or if otherwise desirable or necessary, the plate may be reheated in a special furnace
before being chilled.
For obtaining gas suitable for my purpose I prefer to employ an iron cased
firebrick lined vessel filled with checker brickwork. This being heated to a high
state of incandescence, I inject petroleum or other hydrocarbon oil by means of a
jet of steam, or force the oil into the highly heated vessel by means of a pressure
pump. The supply of oil is continued as long as the heat is sufficiently high to
volatilise it; after this temperature has fallen below that necessary for volatilisa-
tion the oil-flow is directed into a second vessel which has been raised to a high
temperature by the combustion of gaseous fuel within it.
The oil gas thus produced may be conducted directly to the casting chamber A
or into a small gas holder, weighted to produce suitable pressure of carburising gas
in the casting chamber.
The partial and carbon depositing combustion of the oil-gas is effected in the
mould in the following manner, i.e. the oil-gas is directed into the gas flues or pipes
under suitable pressure, and is conducted to a burner apparatus in which the
required volume of air under a slight pressure is introduced.
The combustion ensuing being only partially completed is consequently of a very
smoky character and such as to cover the walls of the mould or chamber A. and the

page_text: metal as it is run into the mould with a film of carbon. The quantity of carbon
deposited will be proportionate to the incompleteness of the combustion and this
can be controlled by the regulation of the supply of oil-gas and of air. The metal
being gradually supplied to the mould the carburizing effect can be regulated in a
pari passu degree.
Independently of the deposition of carbon by partial combustion of the oil-gas I
sometimes inject atomised carbon by means of a jet of steam or of carbon monoxide
or other gas at such a pressure as to enable powdered carbon to be ejected into the
casting chamber. For the injection of the carbon I arrange uniformly distributed
apertures around the chamber walls or through the arch or the channel frame of
the mould. I sometimes cover the bottom of the mould with a layer of finely
powdered carbon to increase or accelerate the carburizing effect in the mould.
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 is :-
:-
1. In the manufacture, of armour-plates the carburization of the molten metal as
herein described during the casting of the same in a mould, for the purposes
specified.
2. In the manufacture of armour-plates, the above described method or manner
of decrementally adding carbon to the metal in the mould, for the purpose
specified.
3. The manufacture of an armour-plate by casting and at the same time
carburizing the metal in the mould and then, either before the plate has cooled or
after rolling or otherwise compressing and reheating the plate, chilling it by spraying
or otherwise, for the purposes specified.
4. The mould or casting chamber constructed as shewn, and provided with the
arched removable cover and with means for making a tight joint around the same
when in place on the mould, and for connecting the inlet and outlet apertures
or passages through the cover with the gas and air mains and chimney while
ensuring tight joints around such connections, substantially as set forth.
5. The ladle provided with nozzles and the means for simultaneously opening or
closing the nozzles, substantially as, and for the purposes, set forth.
6. The cover provided with tubes or nozzles which connect or coincide in
position with the nozzles in the ladle when the latter is placed above the mould,
for feeding the same, substantially as and for the purpose specified.
7. The combination with the said mould of apparatus for removing and
replacing the cover and removing the armour-plate, substantially as set forth.
8. The apparatus comprising the aforesaid mould or casting chamber and its
removable cover arranged in combination with suitable gas generating and gas
and air-supplying apparatus, substantially as, and for the purpose, specified.
9. A decrementally carburized and hardened or tempered armour-plate manu-
factured by the method hereinabove described.
Dated this 6th day of July 1894.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.