Method of or Process for Improving or Perfecting Steel Armour Plates and other Steel Articles.
Year: 1895

page_text: · Date of Application, 23rd Apr, 1895-Accepted, 8th June, 1895
J
Method of or Process for Improving or Perfecting Steel Armour
Plates and other Steel Articles.
I, AUGUST REICHWALD of 9 New Broad Street, in the City of Lonuuu,
Steel, Iron, Metal aud Mineral Merchant, do hereby declare the nature of this
invention (a communication to me from abroad by the Firm of Fried Krupp of
Essen in the Empire of Germany, Cast Steel Manufacturers) and in what manner
the same is to be performed to be particularly described and ascertained in and by
the following statement :-
The method or process forming the subject of the present invention has for
object the improvement of steel armour plates by imparting to the side thereof
which is exposed to projectiles the greatest suitable hardness, and to the other side
thereof the greatest toughness which the armour plate material can possibly
acquire. In this manner the plates acquire the greatest possible security against
cracking, and the highest possible degree of strength and resistance.
Steel armour plates of any composition can acquire extreme toughness by being
heated (after having been improved in quality by being suddenly cooled down
from a bigh temperature that renders the molecules capable of an easy rearrange-
ment) for a second time to a lower temperature, and by being allowed to cool
slowly down from said temperature. This suitable lower temperature which is
necessary for producing a particularly great degree of toughness, must be ascor-
tained specially by experiment for every composition of the material of the plates,
because such temperature is different for different kinds of steel. But if such
temperature be lower than that at which the particular kind of steel will acquire
hardness in consequence of sudden cooling therefrom, then by dipping the armour
plates (heated to such temperature) in hardening liquids or by spraying or playing
(as with a hose) upon them with such liquids, the greatest tougliness can be
produced with a highly fibrous grain or texture of the material. But if this
temperature on the contrary be increased to some extent before the sudden
cooling, the latter will increase the strength, but will at the same time diminish
the toughness to a certain extent, and the more so, the higher the heating was
carried up beyond the temperature aforesaid, until finally at a certain upper limit
of temperature, the sudden cooling down therefrom, produces the so-called "glass-
hardness," that is to say the greatest degree of hardness which that particular kind
of steel can possibly acquire.
But in order, in the case of armour plates, to combine the most favourable
hardness of one side with the greatest toughness of the other side, they are treated
in the following manner:-
:-They are first improved in quality by being heated to
the high temperature at which the molecules are rendered capable of easy
earrangement, and by suddenly cooling the entire plates from this temperature by
immersion in a hardening liquid or by spraying or playing (as with a hose) upon
the plates with such liquid. By this means the steel acquires, in addition to con-
siderable hardness, an extreme fineness of grain or texture which renders the steel
adapted to acquire subsequently the greatest toughness.
But as the hardness is now too great to allow of machining and bending the
plates, the latter are either tempered as a whole, and are theu bent during the
subsequent slow cooling of the same, or the plates are heated up to the temperature
at which hardening, properly so-called, is not produced by sudden cooling, and then
they are suddenly cooled. Then the plates can be shaped and machined in the cold

page_text: state. The plates having thus had their required shape imparted to them, their
face or front surface (viz. that exposed to gun fire) is heated to the temperature
adapted to produce the desired suitable hardness, whilst the back or rear surface is
on the contrary heated to a lower temperature that is to say to that temperature
which has been found by experiment adapted to produce the greatest degree of
toughness whereupon, if the less heated side of the plates does not acquire
hardness in consequence of the sudden cooling, the entire plates can be suddenly
cooled by immersion in a hardening liquid or by being sprayed or played upon (as
with a hose) with such liquid; but on the contrary the sudden cooling is limited to
the more intensely heated side only (that which is to be hardened) of the plates, if
it should be the case that the other side would become hardened by the sudden
cooling, or if the plates are so thin that the sudden cooling of the front or face
would also cause a rapid cooling of the back. The sudden cooling of the side
which is not to be hardened may also be omitted after the last heating of the
plates, if this side had already acquired its maximum toughness previously.
In this manner there are produced the desired hardness of one face or side, and
the maximum toughness of the other side, that is to say, the highest degree of
perfection of the plates.
The heating of the two sides is preferably effected for practical reasons, at one
and the same time, by bringing those parts which are to be more intensely heated,
rapidly to the said higher temperature, whilst those parts which are not to be
heated so intensely, are either embedded in sand or placed upon a rather cool
hearth and thus withdrawn from the direct or full action of the furnace; or they
may be placed on a hollow space and kept at the suitable lower temperature by
means of cooler gases introduced into the said hollow space. Or, what is less
practical, but is productive of the same result, the more intense heating of the
face to be hardened and the sudden cooling thereof, may be caused to follow on or
it may be to precede the heating of the other side to the lower temperature and
the sudden cooling or the slow cooling thereof.
It will be understood that this process is also suitable for improving other
articles of steel which have to fulfil requirements similar to those of armour plates,
and not only for articles of homogeneous steel and alloys of steel, such as chrome
steel, wolfram-steel, nickel-steel, chrome-nickel-steel, &c., but also for cemented,
compound, and other plates. In the case of cemented plates, the first special
heating may be dispensed with, because the heating necessary for the cementing
process may be utilized at the same time for the operation of improving the grain
or texture.
Moreover in cases in which the alteration of shape, produced by the first high
heating required for the improvement of the grain or texture, is not considered to
be material in the articles subjected to the process, the heating, which is otherwise
necessary for the bending and machining operations, and which is interposed
between the aforesaid first beating and the last heating (which first and last heats
are of different temperatures) may be dispensed with, because the shaping of the
articles may in such cases be effected previously thereto.
But if however this second heating has been effected, and if the operation has
been such as to impart already the maximum toughness to the back of the plate,
then in the subsequent third heating of the plate, any desired temperature may be
employed, so long as such temperature does not exceed the temperature of the
second heating.
be
In conclusion it may be stated that the hereindescribed operations which precede
the actually novel part of the process, that is to say, the first operation for the
purpose of improving the grain or texture of the material, and also the second
operation for facilitating the machining and shaping of the material, may
replaced by similar or equivalent treatments, without altering the essential nature
of the process.
For instance, the articles to be hardened on one side only, may
have imparted to them a suitable grain or structure by being rolled at a low
temperature, before their parts are differently heated.

page_text: Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The method of or process for imparting to plates and other articles of steel
or mixtures of steel capable of being hardened, special hardness at certain places,
and maximum toughness at other places, said process consisting in heating those
parts or places of the suitably prepared articles which it is desired to harden, to
the temperature corresponding to the degree of hardness desired, whilst heating the
other parts or places of the said articles only to a lower temperature that does not
produce hardening, and then suddenly cooling the articles down from their different
temperatures.
2. A mode of carrying out the process specified in Claim 1, in which only the
more highly heated parts are subjected to a sudden cooling.
3. A mode of carrying out the process specified in Claims 1 and 2, in which, for
the purpose of perfecting or improving the said process, the articles to be treated
are first or previously improved in quality by being heated to a high temperature
which allows of an easy capacity of rearrangement of their molecules, and then
subjected to sudden cooling following thereon.
4. A mode of carrying out the process specified in Claims 1 and 2, in which this
process is preceded, in addition to the operation for improvement in quality
(specified in Claim 3) of the articles to be treated, by another or second uniform
heating of the said articles up to a temperature that will not produce hardening,
with or without subsequent sudden cooling, with the object of facilitating the
machining and shaping of the articles after the improving operation.
BREWER & SON,
London and Leeds, Agents for Applicant.