IMPROVEMENTS IN THE TREATMENT OF IRON AND STEEL FOR CLEANSING AND ANNEALING, COATING WITH OTHER METALS, WELDING, AND CASE HARDENING
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by William Ireland at the Office of the
Commissioners of Patents on the 15th August 1876. Partly a communication
from abroad by Eduard Blass, of Cleve, Prussia.
WILLIAM IRELAND, of Beech Lane, Macclesfield, in the County of Chester.
"IMPROVEMENTS IN THE TREATMENT OF IRON AND STEEL FOR CLEANSING AND
ANNEALING, COATING WITH OTHER METALS, WELDING, AND CASE HARDENING."
This Invention consists mainly in the use of a bath of molten salt for the treat-
ment of iron and steel, so that these metals can be annealed, cleansed from oxide
and other surface impurities, fitted to receive a coating of other metal, such as
copper, or to be welded or case hardened, according to the mode in which the said
bath is applied.
For the purpose of cleansing and brightening the surface of iron or steel in wire
or other forms it is only necessary to pass it through a bath of molten salt, which
has also the effect of annealing the metal without discolouring or scaling the surface,
as in ordinary annealing processes. When the surface of the metal is rusty it should
be left in the bath for some time, according to the extent or depth of the oxidation.
It is also advantageous to mix borax with the salt. The metal cleansed in this
manner is at once fitted to receive a coating of other metal, such as copper, zinc, tin,
silver, nickel silver, or alloys thereof, fused either in a bath separate from the salt
bath, or under the salt in the same bath with it, so that wire or other pieces of iron
or steel can be passed through the fused salt and subsequently through the molten
metal, so as to become coated therewith. For iron in the spongy or pulverulent
condition, as it is produced by reduction of ore, the cleansing by means of the bath
of fused salt is of great advantage in facilitating the union of the particles of metal
by welding.
In order to apply the salt bath to metal in this form the salt is melted in an
ordinary or rotating puddling furnace, and the iron sponge, mixed with a small
quantity of quicklime or other suitable flux in the proper proportion, is added in
such successive portions that the salt is not too much cooled by any one charge.
The iron is left in the bath until the flux combining with the impurities of the
sponge melts these out, whereupon the iron can be balled and taken out to bo
shingled or compressed. During this process the iron being completely covered by
CD 9.77

page_text: the salt is protected from oxidation, while the fluxes form a slag with the impurities
of the sponge.
For case hardening iron the process is conducted in the following manner:-The
salt is melted in any suitable vessel, and the articles to be case hardened are
immersed in this bath, and small quantities of dehydrated yellow prussiate of potass
are added from time to time to the extent of 1 to 2 lbs. for every hundredweight
of iron treated. The pieces to be hardened are retained in the bath from five
minutes to half an hour, according to the thickness of skin to be hardened, and are
then immersed in a bath consisting of water 100 parts, with about 1 part of
hydrochloric acid, about 5 parts of common vinegar, and about 1 part of salt. If
the articles are required to present a silvery surface they are afterwards immersed
for a few minutes in a mixture of common vinegar and hydrochloric acid in about
the proportion of 3 parts of the former to 1 part of the latter.