IMPROVEMENTS IN THE MANUFACTURE OF STEEL, AND APPARATUS FOR THAT PURPOSE
Year: 1881

page_text: PROVISIONAL SPECIFICATION left by Charles William Siemens at the
Office of the Commissioners of Patents on the 17th June 1881.
CHARLES WILLIAM SIEMENS, of No. 12, Queen Anne's Gate, Westminster, in
the County of Middlesex. "IMPROVEMENTS IN THE MANUFACTURE OF STEEL,
AND APPARATUS FOR THAT PURPOSE."
In the manufacture of steel by the open hearth process, according to the method
hitherto practised, raw cast iron and scrap metal are charged in a regenerative gas
furnace, and the resulting metal is farther decarburised by addition of scrap or of
iron oxides, after which an alloy of iron carbon and manganese is added to the
chargo in the furnace, or when it is run into a ladle, as set forth in the Specifications
of Patents previously granted to mo. The metal is then discharged into moulds
for the production of steel ingots or castings.
According to my present Invention I employ an open earth regenerative gas
furnace, but in order to prevent or lessen the destructive action of scoria upon the
sides of the bed of the melting chamber, I add thereto pipes for circulating water
around the bed.
The furnace being heated and the bed or bottom being prepared in the usual
manner, I place thereon a charge of iron oxide, which may be a mixture of small
ore and roll scale, spread uniformly over the bed, followed by or mixed with scrap
metal or puddled bloom. The furnace doors are then closed and these materials
are raised as rapidly as possible to a white heat. Fluid cast iron is then poured
in, which may be taken direct from a blast furnace or from a cupola or other
melting furnace; but when a high class product is required, I prefer to take the
fluid cast iron from a special furnace, constructed and worked as hereafter
described. The cast iron, in uniting with the materials previously in the furnace,
becomes partially decarburised. In order farther to decarburise the metal under
treatment, ore, with or without addition of scrap and blooms, should be added
gradually in the manner now practised, or when the metal has attained the
desired point of conversion (which may be ascertained by taking samples from
time to time), in certain cases spiegeleisen or other alloy of metals may be added
in the usual manner. The contents of the furnace are then tapped into a ladle,
and as they run a small percentage of rich ferro-manganese, previously heated to
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page_text: redness and broken to the size of walnuts, may be thrown into the liquid stream.
From the ladle the fluid steel is discharged into moulds for the production of
ingots or castings.
The furnace above referred to, which I prefer to employ for melting and
purifying the cast iron for making steel, has a bed or floor steeply inclined and
terininating in a basin provided with a tapping hole. This bed should be of a
basic character, and either consist or have a lining or covering of a compound of
lime with alumina, or magnesia, or of bauxite. The flame ports are at the basin
or lower end of the bed, the passages to the chimney being at the higher ond.
The crown of the furnace consists of a double arch, the space between the
two arches forming a passage for the air destined to maintain the combustion.
This nir, in its passage through conduits interposed in the chimney flue and
through the channel in the furnace crown, becomes highly heated, and in this
condition meets at the flame ports gas supplied from a producer adjoining or near
to the furnace structure. In order to ensure a supply of gas rich in combustiblo
ingredients, a gas producer may be employed of the kind described in the
Specification of my Patent, No. 3374 of 1880. The inclined bed of the furnace being
covered with iron oxide on which the pig metal is charged, this metal in melting
and flowing down to the basin combines with or is reacted on by the iron oxide
and basic materials on the bed, finally presenting on the top of the molten metal
in the basin a basic slag containing a large proportion of the silicon, phosphorus,
and sulphur originally contained in the cast iron. The basic character of this slag
may be farther promoted by the addition of lime, manganese, or other suitable
substances, so as to prevent the re-incorporation of the impurities with the cast
iron under treatment.
One melting and purifying furnace of the kind described may be conveniently
placed opposite a row of four open hearth steel melting furnaces, and at such an
elevation that the metal will run through a removeable spout directly to one or
other of the steel melting furnaces which may be ready to receive a charge. This
method of working effects a saving of time and labour in the manufacture of steel
on the open hearth, the fluid cast iron coming in contact with scrap and blooms
and oxides in a highly heated condition, readily combining therewith, and forming
at once a liquid bath decarburised to a considerable extent.