Improvements in the Manufacture of Armour Plates.
Year: 1891

page_text: COMPLETE SPECIFICATION.
Improvements in the Manufacture of Armour Plates.
I, TOLMIE JOHN TRESIDDER, Captain, late of H. M. Royal Engineers, now of
the Atlas Steel 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:-
This invention is founded on that described in my Specification No. 5551" which
consists mainly in submitting the armour plate whilst in a heated state to the
equable chilling of one or both of its faces by very numerous small jets of water or
other fluid projected at high pressure and simultaneously against the whole area of
the face or faces of the plate.
My method of procedure is the following
(1.) If the plate to be treated is a compound plate (steel face and iron back) to
finish approximately flat, (as belt plates), I make it and machine it in the usual
way except that I use faise templates to which to bend it. These false templates
are constructed from the designer's templates as will be described further on.
When the plate is finished as far as regards all machine work to the steel portion,
all holes (if there be any, such as those tapped in the top edges of belt plates for
the deck attachment,) in the steel, are plugged with flush wrought iron screw plugs
arranged so as to be withdrawn with facility, similarly any keyways in the edges,
if in the steel portion, are fitted with temporary keys. The plate is then carefully
heated in a furnace to a "hardening heat" which will of course vary with the
When hot enough
nature of the steel; ordinarily a moderate red heat will suffice.
it is taken from the furnace and deposited steel side up on four supports in a large
flat tray (see Figure 2) in such a way that the edge of the tray is everywhere a
little higher than the bottom of the plate. An apparatus, which I call a douche,
consisting of a system of pipes, perforated with a large number of small holes, in
connection with a water supply (Figures 1 and 2), is then brought up and supported
a little above the plate, and the water is turned on. At first the water quenches
the steel side only, but in a few moments the tray becomes full and forms a bath to
the lower iron side. The object of this is to reduce the warping of the plate,
which it does by about one half; it also tends to assist the chilling action of the
douche above, but the soft iron on which it acts is not affected. If the utmost
possible degree of hardness is desired the douching is continued till the plate is
cold, but I sometimes stop the water after all redness has disappeared, throw on
the plate some scraps of soft alloy, and turn on the water again as soon as these
scraps show signs of melting. In this way, by using alloys of suitable melting
points, the plate can be tempered with great nicety to any required degree. When
the plate is cold it will be found to have its proper finished shape if the false
templates have been correctly made and worked to. The temporary plugs and
keys (if any) can then be withdrawn and the bolt holes drilled and tapped in the
back to complete the plate. No correction whatever of the edges should be
required, but if a little proves necessary I employ an emery wheel mounted in the

page_text: In
tool box of a planing machine, and independently driven, as a planing tool.
order to prevent too great rapidity of cooling at the corners of the plate I some-
times attach thereto iron shoes (Figure 4) which modify the chilling action of the
water at those parts. In special cases the edges of the plate also may be protected
in a similar manner (Figure 5) even to the extent of keeping them soft enough to
be machined.
(2.) If the plate to be finished is a compound plate (steel face and iron back) to
be finished with considerable curvature (as a turret or conning tower plate &c.) !
proceed exactly as described above except that instead of a tray I use a second
douching apparatus to cool the under side of the plate (Figure 3). This acts
upwards, but it must be remembered in all cases that the douche which is to harden
the plate is at its best advantage when acting directly downwards.
(3.) If the plate to be treated is a compound steel plate in which the back is of
so mild a nature as to undergo water quenching without losing toughness, the
double douche as described for a curved compound plate may be used; but if it is
undesirable to quench the back then the downward douche on the face only, without
any tray to hold the water up against the back, is to be preferred. In this last
case the false templates will require to be differently designed as described further
Another method is to use the double douche with water above the plate, and
air or wet air below.
on.
(4.) If the plate to be treated is a homogeneous steel plate requiring toughness
throughout rather than a hard face, either the double douche or the single douche
with tray will be efficient, and false templates are not very important in such a case
since the plate can be "set" after treatment without heating. But in a case of this
kind prefer to use a double douche of wet air applied in the same way as the
water. The air is wetted by passing through a chamber into which tiny jets of
water are allowed to play or by the method described in my Patent 12347 of 1887.
and it then passes into a box one side of which is full of perforations or into the
same douche as described for use with water or other fluid.
Repeated experiments have shown that the warping produced by quenching a
straight plate 9 or 10 inches thick from one side only is of a uniform convexity
towards the quenched side, and that the amount of convexity is about inch in a
distance of 4 feet; also that the warping of a steel faced compound plate of the
same thickness quenched from both sides is similar in nature but less in extent
being at the rate of about 4 inch in a distance of four feet. Homogeneous steel
plates equally quenched from both sides after being uniformly heated have no
tendency to warp. Experiment has also shown that by bending a flat plate till
it is concave on the side to be hardened to an extent determined in the manner
above specified, its flatness will be restored by the warp due to quenching.
Thus plates to be treated by this process must be originally bent with less
convexity on the hard side than ultimately required, and the proper form for
the false templates previously alluded to can be arrived at approximately by
applying one of the corrections given above and with accuracy after a few
trials with the particular kind of plate to be treated. Thin plates warp more
than thick ones.
A plate 4 inches thick shows a convexity of inch in four feet
when hardened on one side only.
As regards the water pressure to be used I prefer a high pressure, say 80 lbs.
to the square inch, but this depends greatly upon the area of the surface to be
treated in any case there must be sufficient volume of water to cause a brisk
flow from all the apertures of the douching apparatus. For the air or wet air
quenching a pressure of about 10 lbs. to the inch will suffice.
In cases where it is not desirable to let the water run to waste, or where
the douching apparatus is employed with special fluids which are of value,
arrangements can easily be made for catching the fluid as it falls from the plate and
conveying it to a tank to be pumped and used over again.
The action of the water douche on high carbon steels is, as might be expected,
to produce intense hardness. As the carbon is lower the hardening becomes less

page_text: marked, but an appreciable hardening or stiffening effect is produced with steels
containing as little as two-tenths of one per cent. of carbon. In such a case the
effect of the treatment resembles that obtained by hardening a steel of somewhat
higher carbon in oil at say 1600° F. and then annealing at say 900° F. The wet
air has a milder action (on large masses) about that of oil hardening at 1300° F.
and annealing at 1200° F. Dry air, especially hot dry air, has the mildest effect
of all, but the uniform distribution of the cooling action peculiar to this invention
always results in improving the steel.
In the drawings annexed
Figure 1 is a plan of the douche apparatus.
a a aa are four inch quarter bends with flanges.
c is a four inch pipe with two four inch flanged paps. d
from water service. ee are four inch pipes cast with
screw connections.
is a four inch straight pipe.
d are four inch connections
numerous paps for one inch
are one inch cross pipes. g g are long unions for cross
pipes. These pipes are full of inch perforations on under side drilled at various
angles to spread the flow of water. Several douches of different sizes are to be
provided. Some flat as above, and others more or less curved.
Figure 2 is a side elevation of single douche, armour plate and tray for flat
plates or plates of slight curvature.
a a² is the douche. 2 is the armour plate bent concave to finish flat. c c² c² is
the tray to hold water up against back of plate. d² d³ are supports on which plate
rests (cast iron pyramids). e²e water overflowing edges of tray and running to
waste. × one of the water inlets.
If the water or other cooling medium is not to be wasted an overflow pipe to this
tray would be provided. The level of this overflow would depend on whether the
cooling medium was required to touch back of plate or not.
Figure 3 is an end elevation of curved plate and double douche,
a³ a³ is the upper douche for hardening. ³ ³ is the lower douche for moderating
the warp.
ecce are the water inlets. ³ ³ is the curved armour plate to finish
to quicker curvature as dotted. The full line shows the curve of the false template
and the dotted line that of the designer's template. ese are the keyways in edges
temporarily filled up..
attach to
The top
Figure 4 shows a shoe with clamping screw, to
corners of plate when
required, to prevent too rapid cooling of corners.
rests on top of plate
and the clamping screw bites on under surface. It is cast iron about 1 inch thick
and bevelled to inch at edge, which is curved as shown.
Figure 5 shows an edge guard with clamping screws to attach to edges of plates,
when required to check chilling of edges. This will be straight or curved as
required. The upper flange rests on top of plate and the clamping screws bite on
the under surface.
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 use of a spray or douche applied in
the manner described for hardening the faces of the plates, in combination with a
tray or bath collecting the liquid flowing from the plate and applying it to the
under surface thereof.
2. In the manufacture of armour plates the use of a spray or douche applied in
the manner described for hardening the faces of the plates, in combination with a
tray or bath collecting the liquid flowing from the plate and with pumping apparatus
returning the liquid so collected to again form a spray or douche.
3. In the hardening of armour plates the protection of the bolt holes and key-
ways from exposure to fire and water by filling them with plugs of wrought iron or
other suitable material.
4. In the hardening of armour plates the protection of the corners or edges or

page_text: both from the active influence of the cooling medium by the use of shoes or guards
substantially as described.
5. In the manufacture of armour plates the method of false templates herein
described that is to say the giving such initial curvature to the plate as shall in
conjunction with the curvature induced by quenching result finally in the desired
curvature or flatness.
6. In the manufacture of armour plates the method substantially as described of
tempering the plate consisting in the application of the douche until redness has
disappeared, then applying scraps of soft alloy and again turning on the water as
the scraps show signs of melting.
Dated this 17th day of December 1891
T. J. TRESIDDER.