improvements in or relating to the Manufacture of Armour Plates.
Year: 1896

page_text: PROVISIONAL SPECIFICATION.
improvements in or relating to the Manufacture of Armour
Plates.
We, JosЕPп HENRY DICKINSON of 13 Montague Place, Russell Square,
London, Engineer and EDWIN MARSHALL Fox of 34 Victoria Street,
Westminster, Esquire, do hereby declare the nature of this invention to be as
follows:-
Hitherto it has been practically impossible to plane or drill armour plates which
have been previously "Harveyized' or otherwise decrementally treated or face
hardened and chilled, owing to the intense hardness acquired by the steel.
Various attempts have been made to obtain a means of drilling and planing the
hardened surface of such plates. Holes have been bored in the plates prior to the
completion of the Harveying process, the holes being then filled up with non-
carbonaceous material, so that after the Harveying process is complete the
holes have merely to be unplugged. This, however, has not proved altogether
satisfactory, because the plates warp and undergo some change of form during
the chilling operation. Other attempts have been made to bore the necessary.
holes by means of an electric current and subsequent boring, but the plant required
for this is very expensive.
In their efforts to accomplish the result which we have obtained all experimenters
have hitherto proceeded upon the theory that it was necessary to heat the plate
locally with an intense heat, in other words to get the plate as hot as possible
short of the melting point and some indeed have gone so far as to melt the plate
locally, then they have reduced the heat gradually so as to anneal the plate locally.
We have found by experiment that the theory upon which these attempts have been
based is wrong.
Our invention consists in doing what is practically the reverse that is to say, we
beat the plate locally up to a comparatively low temperature such as from 600°
to 900° Fahrenheit then at once remove the source of heat, letting the plate cool
naturally which it does with great rapidity in a very few seconds owing to the mass
of the metal which rapidly carries the heat away;
As is well known to steel manufacturers, steel at a temperature that gives the
dark blue color incident to a temperature between 60° and 900° Fahrenheit will
not harden so as to become untoolable when suddenly chilled no matter how the
chilling may be effected, whereas above that temperature steel will always harden.
when chilled, the degree of hardness depending upon the amount of carbon in the
steel and the temperature at which the chilling is effected.
Now it is obvious from the above explanation why experimenters have hitherto
failed, inasmuch as having heated the steel locally to an intense heat, sometimes
red heat sometimes a cherry heat or even a white heat unless they accidentally
cool the steel locally back again by annealing or gradual removal of the source
of heat or its diminution and then allow it to chill it would be as hard as ever.
Electricity has been the principal means hitherto employed to accomplish this
result and inventors in this method have always described the necessity of
gradually cooling down after the local heating because they found that with the

page_text: intense heat they obtained locally by the current that if they took off the
current suddenly the plate chilled so rapidly it remained as hard as before and
was untoolable.
According to our invention we take an armour plate completely Harveyized
or otherwise decrementally treated and face hardened and chilled and we locally
heat the place where the hole is to be made or where the plate is to be planed
or chipped by means of the oxyhydrogen flame taking care to remove the source
of heat when the dark blue color is reached and easily observable which we find
to be in from 2 to 5 minutes. The place thus heated is then found locally soft
and toolable.
If the heating of the spot is carried to the extent above indicated to which we
attach great importance, it is possible to drill the hole at the first attempt
whereas if the heating is carried too far or not far enough it is desirable to
reheat.
Accordingly we also find it desirable to effect the softening by two or even more
heats that is to say first we heat by the flame the part to be softened, then bore
or plane as the case may be to a short depth say or of an inch, then when
the toul commences to meet great resistance in cutting, take it away and heat as
before.
Sometimes the softening may be fully accomplished with one heating.
It will be understood that in lieu of the oxyhydrogen flame we may employ the
flame of any other suitable gas or gases, such for instance as acetylene, or producer
gas, mixed with oxygen in suitable proportions, or we may locally heat the plate
by means of electricity or otherwise care being taken not to allow the spot to be
heated too intensely.
In cases where it is desired to construct Harveyed plates with port holes or the
like, the same process is carried out. We bore out a series of holes arranged in a
circle (or other form that the aperture is to take) so that the intermediate part
may be removed, leaving the aperture as may be designed.
Dated this 18th day of March 1896.
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London, Chartered Patent Agents.
Improvements in or relating to the Manufacture of Armour
Plates.
We, JOSEPH HENRY DICKINSON, of 13 Montague Place, Russell Square,
London, Engineer, and EDWIN MARSHALL Fox, of 34 Victoria Street,
Westminster, Esquire, 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 relates to armour plates which are "Harveyed" or decrementally
carburized or face hardened and chilled. By reason of the intense surface hardness
of such plates it has been heretofore practically impossible to drill, plane or other-
wise cut them for making the apertures holes or recesses necessary for various
purposes in ships armour. Various methods of providing for this necessity have
been adopted; for example the apertures, or recesses have been made in the plates
prior to the completion of the "Harveying" process, and have been plugged or
filled up with non-carbonaceous material, so that subsequently to such process they
have merely to be unplugged. This method, however, has not proved altogether
eatisfactory, chiefly because the plates are liable to warping or change of form

page_text: during the chilling operation. Attempts have also been made to anneal the inetal
by means of an electric current after the plate has been hardened and provide the
necessary apertures or holes by subsequent boring, and we are aware of the method
adopted by the Thomson-Houston Electric Welding Company described in the
Specification of Patent No. 24569 of 1894 whereby a plate after being hardened is
locally reheated and then slowly cooled and annealed, but the apparatus required
for this process is expensive. Attempts have also been made to locally soften the
plate by means of the oxyhydrogen flame.
The attempts to accomplish the above purpose have hitherto been based upon
the theory that it is necessary to heat the hardened plate locally to an intense heat,
in other words to make the plate as hot as possible short of the melting point (and.
Bone indeed have gone so far as to melt the plate locally), and then reduce the
temperature gradually for the purpose of annealing the part thus heated. We,
have found however that this theory is incorrect.
It is well known that steel at a temperature indicated by a dark blue color.
i.e. a temperature between 550° and 700° Fahrenheit-will not, when chilled,
harden so as to become untoolable no matter how the chilling may be effected,,
whereas steel heated to a higher temperature than the above will, when chilled, be
too hard to be cut by any ordinary tools, the degree of hardness depending upon
the amount of carbou in the steel and the temperature at which the chilling is
effected. Therefore the reason of the failure of previous experiments is obvious
inasmuch as the steel having been heated locally to a very high temperature,
(sometimes even to a white heat) and the supply of heat having then been reduced,
the change of temperature due to the diminution of the supply of heat and to its
rapid dispersion by conduction has been sufficient to produce the effect of chilling
the metal so that it has remained as hard as before. Therefore the necessity of
the slow or gradual cooling of the metal after heating it to a high temperature has
been fully recognized and particularly when electricity has been employed for.
heating the same.
Now it follows that if a Harveyed plate after being chilled or hardened should
be locally reheated by the oxyhydrogen flame or otherwise to a high temperature
i.e.
temperature equal or approximate to that required in the original manu-"
facture of the plate the sudden stopping of the supply of heat would cause a great
and immediate change of temperature the effect of which upon the metal would be,
approximately similar to that of the application of water to its surface. Therefore.
the slow and gradual cooling of the metal is essential for the softening of the,
same.
But we have discovered that if a Harveyed plate be reheated locally to a,
temperature no higher than that indicated by a dark blue colour and the supply of
heat be then suddenly stopped the effect will be similar to that produced when
steel after being hardened is tempered or "let down" to this colour and then
plunged into a cold fluid; that is to say it will make and leave the metal sufficiently
soft to be cut by a drill or other like implement.
Therefore according to our invention instead of attempting to soften the
hardened metal by highly heating and gradually cooling and annealing it we
employ a process wherein the required result is obtained by tempering or "letting
down" the hard metal to a soft condition; and it is essential that in heating the
hardened plate locally we restrict it to a temperature much lower than that to
which it was raised when originally hardened; that is to say we raise the metal to
a temperature of about five hundred and fifty degrees (550°) to seven hundred
degrees (700°) Fahrenheit; then discontinue the supply of heat, letting the plate
cool naturally which it does with great rapidity owing chiefly to the conductivity
of the mass of metal contiguous to the locally heated part but the cooling down
from the above specified temperature to the lowest degree attainable under the
circumstance described will leave the locally treated part sufficiently soft for our
purpose.

page_text: In practising our invention we take an armour plate that has been "Harveyed"
or decrementally carburized and face-hardened and by means of the oxy-hydrogen
flame we locally heat the plate at the part where an aperture or recess is to be
made or where the plate is to be planed chipped or otherwise cut. In heating the
'plate we carefully watch the surface of the metal and when the dark blue color
appears, which we find to be in from 2 to 5 minutes, we immediately stop the
supply of heat. The part of the plate thus heated is found to be softened and
toolable.
If the limits of temperature above specified are carefully observed it will be
possible after once heating the metal to drill a hole in it of the required
diameter and depth. But if the part to be drilled is heated to a temperature
below or above these limits it may be necessary to reheat it. That is to say we
can in the latter case first heat the part to be softened then bore or otherwise cut
the metal to a depth say, of one eighth or one quarter of an inch, then when the
tool commences to meet great resistance in cutting, take it away and reheat the
metal to the same temperature as before and then complete the boring or other
cutting operation.
It will be understood that in lieu of the oxyhydrogen flame we may employ the
flame of any other suitable gas or gases, such for instance as acetylene, or producer
gas, mixed with oxygen in suitable proportions; or we may locally heat the plate
by means of electricity or otherwise, care being taken in all cases to avoid heating
the metal to a degree of temperature which will prevent the desired result as above
set forth.
In cases where it is desired to make "Harveyed" plates with embrasures or
port holes or the like, we can soften the metal along the circumference or outline
of the aperture and then plane a groove or drill a series of holes around the same
so that the part of the metal within the groove or series of holes may be
removed.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is
1. The berein described method or process of locally softening a hard steel plate
consisting in first heating the metal sufficiently to temper or let it down to a
condition indicated by a blue colour and then cooling it or allowing it to cool
quickly for the purpose specified.
2. A "Harvey "armour plate locally tempered or "let down" substantially as
described in one or more places in such manner as to permit the cutting of the
metal by ordinary drilling or other tools for the purpose specified.
Dated this 8th day of December 1806
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicants.