AN IMPROVED. PROCESS FOR CARBONIZING AND HARDENING WROUGHT IRON
Year: 1869

page_text: PROVISIONAL SPECIFICATION left by Leonard Wray at the
Office of the Commissioners of Patents, with his Petition, on the
3rd February 1869.
I, LEONARD WRAY, of Ramsgate, in the County of Kent, Gentleman,
do hereby declare the nature of the said Invention for "AN IMPROVED.
PROCESS FOR CARBONIZING AND HARDENING WROUGHT IRON," to be as follows:-
My Invention of "An Improved Process for Carbonizing and
Hardening Wrought Iron" has for its object to impart to the surface
of wrought-iron railway or other bars or rails, shafting, and other parts
of machinery, wrought or rolled iron armour and other plates, wrought-
iron tubing, and other similar articles a very hard or steely character
without destroying or materially affecting the tough or fibrous character
of the interior of the article.
It is well known that wrought iron contains but a very small per-.
centage of carbon, and that it is owing to this quality that it is
capable of being hammered, rolled, and wrought, so as to convert it into
a tough fibrous substance, whereas cast iron, which contains a much
higher per-centage of carbon, is harder but of a brittle nature and

page_text: crystalline structure, and consequently cannot be hammered or rolled.
It is further known that an intermediate per-centage of carbon will
produce an alloy of iron and carbon which is capable of being hardened
and also of being hammered or wrought. This alloy is known under
the name of steel and can be produced either by the addition of a given
per-centage of carbon to wrought iron, as in the ordinary cementing or
cementation process, or by decarbonizing cast iron until it contains
only the proper per-centage of carbon. It has also been proposed to
produce a strong hard metal by mixing wrought iron or steel scrap with
molten cast iron, and thus incorporating or mixing the two substances
so as to produce what is called or known as "homogeneous metal."
Wrought-iron articles have also been hardened on their surface by
heating them in any convenient reheating furnace, and then plunging
them for a certain time in a mass of fused cyanide of potassium, or in a
strong solution of the same. It is probable that the change produced in
the iron by this and analogous processes is due to the fact that the
metal while in a heated state has taken up some of the carbon contained
in the liquid mass.
In carrying out my Invention and applying the same, say, for
instance, to railway bars, wrought-iron plates or shafting, or wrought-
iron tubes for steam boilers and other purposes, I heat the articles in
a rcheating furnace, and while thus heated I plunge them into a bath
of molten cast iron. The length of time they are to remain in the
molten cast-iron bath will depend upon the nature of the article
to be operated upon and the effect it is desired to produce; for
instance, railway bars or rails will require a much longer time
than articles not subject to such rough and severe wear and tear.
Again iron shafting will only be liable to wear at its journals, whereas
armour plates are, as is well known, intended to resist enormous con.
cussive force without cracking or splitting up. When the wrought-
iron articles are taken out of the bath of molten cast iron they are
cooled by plunging them in water, in which may be dissolved salt or
other chemical or metallic substances which will facilitate the hardening
of the iron surface.
It is of great importance that the cast-iron bath should be kept in a
fluid state and not be exposed to oxidation from the atmosphere. This
may be done by constructing a vessel or chamber in the form of a
trough (to contain the cast iron) in the hearth or floor of the reheating

page_text: furnace, so that the cast iron may be kept in a molten state by the heat
in the furnace. The molten cast iron may from time to time be run
from a cupola or other melting furnace into this trough or vessel, into
which the wrought-iron articles are to be placed for the space of time
required to produce the change, as already described. The same object
may be effected by melting the cast iron in a reverberatory furnace
somewhat resembling in form and construction an ordinary puddling
furnace, except that the hearth or chamber in which the iron is melted
should be long enough and deep enough to receive the wrought-iron
articles it is intended to operate upon. By the side or at the end of this
melting chamber, as may be found most convenient, may be formed a
raised bridge or platform on which may be placed the wrought-iron
articles, so that they may be heated by the waste heat passing from the
melting furnace,
It is well known that as molten cast iron loses its carbon it requires
an increasing temperature to keep it in a fluid state, and that after the
decarbonization has proceeded beyond a certain point it would be
difficult if not impracticable to maintain it in such a state of fluidity as
is required for the purposes of my Invention. When therefore the cast
iron has become so far decarbonized by the action of the wrought iron
thereon as to be no longer effective for the purposes of the first part of
my Invention, it may be tapped off into ingots or moulds, or run into
a puddling furnace, Bessemer vessel, or other suitable converting vessel,
and be converted into steel or into wrought iron, and thus become a
highly valuable product, thereby giving a compound character to this
Invention.
If found more convenient the trough or vessel to contain the molten
cast iron may be constructed separately from the reheating or melting
furnace, and may be heated by the waste heat arising therefrom, or from
any other convenient furnace.