Improvements in the Process of Melting Iron.
Year: 1896

page_text: Date of Application, 21st Apr., 1896-Accepted, 23rd May, 1898
COMPLETE SPECIFICATION.
Improvements in the Process of Melting Iron.
We, THOMAS DOHERTY, of the Town of Sarnia, in the County of Lambton,
and Province of Ontario, Canada, Manufacturer, and PETER DUNCAN CRERAR,
of No. 1 Provident Chambers, Hughson Street South, in the City of Hamilton,
County of Wentworth, and said Province of Ontario, Barrister-at-Law, 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 following
statement:-
The object of this invention is to devise certain improvements in the process of
melting iron in foundries by the use of which an iron is produced much softer,
stronger and more workable than ordinary cast iron approaching in character to
mild steel, and it. consists, essentially, in the introduction into the cupola of a jet of
steam substantially as hereinafter more specifically described and thon definitely
claimed.
The drawing is a sectional elevation of the apparatus used in our process.
A, is a metal founders' cupola of ordinary construction.
B, is a blower operated from any convenient source of power. C. is a pipe
leading therefrom, which is connected by means of the brauch pipes D, with the
tuyeres E, which communicate with the interior of the furnace by means of the
tuyere holes F, as seen in the left-hand side in the figure.
G, is a steam pipe having branches H connecting with the tuyeres E, so that
steam jets may be introduced therein. These branches are preferably provided
with cut-off valves I, so thint the stenm supply may be properly regulated or cut off.
Better results are obtained if the steam is practically anhydrous, and therefore if
the source of steam is any considerable distance from the cupola, it should be
heated in any suitable apparatus, or may be super-heated if desired, in the cupula
by conducting it through a coil of pipe in the cupola linings at a point just above
the melting point over the tuyeres or the waste gases inay be utilized for the
purpose.
The manner of putting our process into practice is as follows:-
After placing the charge of coal or coke in the cupola, the fire is started in the
usual way and kept up until thoroughly going in the bed, when the tnyeres are
closed and the consumption of fuel delayed until the wind blast is turned on. The
temperature of the; furuace then rapidly rises, and when the iron commences to
melt, the steam jets are opened and the combined air and steam blown through the
fuel and iron. The amount of steam inust be regulated so as to produce the
hydrogen cast of flame, which can be seen at the charge hole of the cupola.
The combined air and steam produce an intense heat, and the decomposed steam
acts as a powerful deoxidizing agency, and that portion of the iron in the charge
which is oxidized or rusted, becomes deoxidized and re-smelted into metallic iron
of a more strict form.
By our process, the impurities usually found in iron are, to a large extent,
burned out or neutralized and the resulting cast iron is softer, stronger and more
workable, approaching to the character of mild steel, so that samples of it can be
upset or drawn out under a hammer to a limited degree, and castings made from it
are more easily machined and filed and are free from the hard skin usually formed
on castings made in the crdinary way. The castings also come out of the moulds
with a cleaner and finer surface and less sand-burnt than castings inade in tho

page_text: ordinary way and in addition are more uniform and homogeneous, being devoid of
hard spots and therefore free from uneven tension. Not only is a much superior
quality of casting produced by this process, but a much larger amount of cast-iron
is obtained from a given quantity of iron charged in the cupola than is produced
by methods in ordinary use. For example-It has been found experimentally that
with a charge consisting of seven thousand seven hundred and forty-five (7745)
pounds of scrap iron and two thousand and sixty-one (2061) pounds of pig iron
(making a total charge of 9806 pounds) there has been run out from a cupola nine
thousand five hundred and eighty-two (9582) pounds of castings, showing only a
loss of two hundred and twenty-four (224) pounds on the charge. After deducting
from that the loss caused by the slopping over from the Indles (which might be
fairly estimated at from thirty to forty pounds) the actual loss or shrinkage in the
process of melting where this process is used is under two per cent. of the total
charge put into the cupola; whereas in ordinary foundry practice, the loss where
the class of material used is of similar quality to that used in the said experiment,
will be not less than twenty to twenty-five per cent.
The superior results obtained by the use of this process are to be explained by
the chemical action of the injected steam and by the higher temperature obtained
from its use. That portion of the scrap iron which is oxidized or rusted becomes
de-oxidized and re-smelted into metallic iron of a purer form; whereas in the
ordinary process this oxide is carried off' in the slag, and lost.
It is further found that when this process is used it is not necessary to be
particular as to the quality of the coal or coke used, as is the case in ordinary
founders' practice, where great care must be used that the coal and coke shall bo
free frem sulphur. With this process it does not make any difference, as the use
of the steam prevents the sulphur from being absorbed by the metal.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. The herein described process of producing a cast iron approaching in quality
to malleable iron, or mild steel, but retaining some of the characteristics of cast
iron, which consists in charging a cupola with fuel and metal, raising the
temperature of the contents of the cupola to a high degree and admitting steam as
soon as the metal begins to liquify, continuing the injection in such a quantity as
will produce in the evolving gases the color of a hydrogen flame, substantially
as and for the purpose specified.
2. The herein described process of producing a cast iron approaching in quality
to malleable iron, or mild steel, but retaining some of the characteristics of cast
iron, which consists in charging a cupola with fuel and metal, raising the
temperature of the contents of the cupola to a high degree and liquifying the
metal with the aid of an air blast and admitting steam in connection with the air
blast as soon as the metal begins to liquify, continuing the injection in such a
quantity as will produce in the evolving gases the color of a hydrogen flame,
substantially as and for the purpose specified.
Dated this 21st day of Anril 1896
TONGUE & BIRKBECK,
Southampton Buildings, Chancery Lane, London, W.C.,
Agents for the Applicants.