Method of or Process for Increasing the Toughness and Hardness of Armour Plates and other Articles Made of Steel or of Mixtures of Steel capable of being Hardened.
Year: 1895

page_text: Date of Application, 26th Apr., 1895-Accepted, 1st June, 1895
Method of or Process for Increasing the Toughness and Hardness of
Armour Plates and other Articles Made of Steel or of Mixtures
of Steel capable of being Hardened.
I, AUGUST REICHWALD of 9 New Broad Street, in the City of London, Steel,
Iron, Metal, and 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 forming the subject of the present invention is particularly suitable
for the treatment of armour plates and other articles made of such kinds of steel
which are capable of being heated up to a considerable temperature and of being
suddenly cooled down, without acquiring hardness properly so-called, but which, as
a consequence of such sudden cooling, acquire a very considerable increase of their
toughness, with a simultaneous increase in (tensile) strength. Furthermore the
sudden cooling does also actually produce a certain increase in the hardness of the
steel, so that such steel can be designated as being both tough and hard, whilst
however no hardening, as popularly understood, takes place.
Now in order to impart to articles made of such kinds of steel, this combined
toughness and hardness which is in many cases desirable, the said articles are
treated in the following manner :-
The said articles are first heated' to an uniform and very high glow heat
whereby their molecules acquire a capability, of easily rearranging themselves.
They are suddenly cooled, by dipping or immersion in a hardening liquid, or by
being sprayed or played on (as with a hose) with the hardening liquid. The said
articles not only become very hard, but also undergo an improvement in the quality
of their material, by reason of such material acquiring (as is well known) the
extreme fineness of grain or texture which renders it capable of subsequently
acquiring a high degree of toughness.
These steel articles having thus been improved in quality, are then heated a
second time, to a temperature from which they can still be cooled down, without
acquiring hardness properly so-called, whereupon they are then cooled down afresh.
The articles have now acquired the desired extremely high toughness combined with
increased strength, and allow of their being machined, and shaped by bending.
As the heating necessary for effecting the bending of the plates &c. frequently
deteriorates the quality of the material, it is always advisable, after the articles
have had their proper shape imparted to them, to let the second beating combined
with sudden cooling, be followed by an exactly similar third heating, together with
a sudden cooling.
The articles may however have their proper shape imparted to them before the
first and highest heating. This is however only advisable when any change of
shape that may be caused by the said heating is not of any importance. In such
a case, in addition to the first high heating and corresponding sudden cooling, there
is merely necessary a second lower heating with a renewed sudden cooling which
does not cause any hardening properly so-called.
Also, the machining and shaping of the articles may be effected after the first
sudden cooling, if they be then rendered suitable for such operations by being
heated to a certain temperature of temper, and by being allowed to cool slowly down
from said temperature.

page_text: The great toughness is then imparted to said articles in a similar manner to that
above stated, by heating them to a temperature such that they will not be hardened
by sudden cooling, and then suddenly cooling them for the second time.
The second special heating with sudden cooling or slow cooling may be dispensed
with in certain cases if the bending of the plates be effected after the first sudden
cooling, because then the plates, in consequence of the heating for the purpose of
bending, and of the slow cooling in the course of said bending operation, are
adapted to be machined, without the necessity of a special heating and subsequent
sudden cooling or slow cooling.
In many cases it will be of considerable importance that not all the parts of the
articles subjected to the process herein described shall acquire their greatest
toughness, but certain parts, instead, shall acquire the greatest possible degree of
hardness. This can be effected without altering the process by making the parts
to be hardened of a different chemical composition of material (such as compound
plates, cemented plates &c.) to the other parts which are to be very tough, suid
different chemical composition being made such that the sudden cooling following
on to the last heating shall produce the greatest possible hardness.
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 :-
A method of or process for increasing the toughness of articles made of steel or
mixtures of steel capable of being hardened, or for increasing the toughness of
parts of said articles, and the hardness of the other parts of the said articles, said
process consisting in subjecting the articles to two heating operations, each of
which is followed by a sudden cooling, the first heating operation being carried to a
temperature that produces a capability of an easy rearrangement of their molecules,
whilst the second heating operation is carried to a temperature such that the
subsequent sudden cooling will not yet produce any hardening of those parts (of
the articles) which are to be rendered tough.
Dated this 26th day of April 1895.