An Improved Process for Hardening Steel
Year: 1898

page_text: Date of Application, 26th May, 1898-Accepted, 27th Aug., 1898
COMPLETE SPECIFICATION.
An Improved Process for Hardening Steel,
A communication by GUSTAV BEIR, of 1, Mozartstrasse, Cologne, and THEODOR
WALLFISCH, of 213, Breiter Weg, Magdeburg, both in the Empire of Ger-
many, Merchants.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for Foreign
Patent Solicitors, 6, Lord Street, Liverpool, & 6, Bank Street, Manchester, both
in the County of Lancaster, 118, New Street, Birmingham, in the County of
Warwick, & 322, High Holborn, in the County of Middlesex, 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 ascertained in and by the follow-
ing statement;.
-
In a process for hardening steel previously invented by me the steel before
being heated is coated with a substance composed of varnish and waste lime,
which forms a sort of protective casing for the article to be hardened and pre-
vents same warping.
In the coating of the steel with such a substance, which must not be confused
with the immersion in oil or tallow and subsequent burning off, a specially im-
portant phase of the hardening process is to be seen for the reasons previously
stated.
As the substance is not intended to burn off but to form during the heating
a protective crust, in place of waste lime any other suitable pulverulent or finely
granulated substance such as ground clay, white lead, zinc white or the like may
be employed, whilst the varnish which merely serves as a binding material may
be replaced by other suitable good adhesive oil, lacquer varnish or the like.
For large articles the substance composed of varnish and waste lime is found
to be sufficient.
In hardening finer articles the waste lime is preferably replaced by zine white
and into the mass there is mixed an addition of lead shavings or filings in order
on the subsequent heating to obtain by the melting of the lead with the substance
as solid a protective crust as possible.
If parts of machinery are to be hardened, this was hitherto done by sprinkling
cyanide of potassium or the like over the heated article and then allowing the
latter to cool.
In this process however the action of cyanide of potassium on the surface of the
article to be hardened and which is in itself well known, is a very incomplete
and unequal one so that thus the article after the hardening shows an uneven or
unequal superficial structure which facilitates cracking or breakage.
In the process forming the object of the present invention the article to be
hardened is first coated with above mentioned protective substance, then
sprinkled with cyanide of potassium, and then heated. During the heating coarse
salt and cyanide of potassium are further sprinkled, which then in consequence
of the protective casing acts evenly on the surface of the article to be hardened so

page_text: that the latter on cooling does not warp or crack and shows after the hardening
process a completely even superficial structure.
The protective crust cracks off of itself on cooling and is suitably removed sub-
sequently.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, as communicated to
me by my foreign correspondents I declare that what I claim is:-
A process for hardening steel characterised by the article to be hardened being
coated, before being heated, with a substance composed of waste lime, (or ground
clay, white lead, zinc white or the like), and a suitable binding material such as
varnish with the object of forming a protective casing for the article to be
hardened to which according to the nature of these articles lead shavings are
mixed with the substance, or the casing before the heating may be sprinkled with
cyanide of potassium or if desired during the heating with cyanide of potassium
and coarse salt or other similar acting substance,, substantially as herein before set
forth.