IMPROVEMENTS IN TREATING IRON ORES, AND IN PROCESSES AND APPARATUS FOR THE PRODUCTION OF CAST STEEL AND MALLEABLE IRON
Year: 1870

page_text: PROVISIONAL SPECIFICATION left by William Hackney at the Office
of the Commissioners of Patents, with his Petition, on the 30th
November 1870.
I, WILLIAM HACKNEY, of Landore, Swansea, in the County of
Glamorgan, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN TREATING IRON ORES, AND IN PROCESSES AND APPARATUS
FOR THE PRODUCTION OF CAST STEEL AND MALLEABLE IRON," to be as follows:-
In making cast steel directly from iron ore in an open hearth steel
melting furnace, the ore has heretofore been first reduced to the
condition of spongy or pulverulent metallic iron, which is then melted
or dissolved either at once or in successive charges in a bath of liquid pig
iron or steel in the melting furnace. The reduction of the ore to the
condition of spongy metallic iron is a matter of comparatively little
difficulty, and may be effected in many different ways, but owing to the
porosity of the spongy reduced iron, and the great extent of surface it
exposes, great difficulty has hitherto been experienced in melting or
dissolving it in the bath of pig iron without turning it again either
wholly or in great part to oxide before it could be either melted in the

page_text: pig iron or got under the surface of the bath of liquid metal and so
protected from further oxidation.
In the Specification to certain Letters Patent granted to C. W. Siemens,
dated 28th February 1870, No. 594, a process was described for obviating
these difficulties wherein the iron ore was first wholly or partially
reduced and converted into solid masses by a separate process, which
solid masses were then introduced into the bath in the steel melting
furnace.
Now according to one part of my present Invention consolidated
masses of wholly reduced ore are produced by first converting the ore
by any known means into the form of wholly reduced spongy or pul-
verulent iron, and then consolidating such spongy iron by subjecting it
to powerful pressure under either a press, steam hammer, or other suitable
known compressing apparatus before charging it into the bath of liquid
metal in the melting furnace. The reduced iron may be compressed at
a welding beat if this is found desirable, but I prefer to effect the
compression at a heat below welding, as I find that spongy iron reduced
from moderately pure ores at a heat below welding, such as, for instance,
a moderate red heat, and not cohering together in the least, may be
compressed at a red heat by a moderate blow from a steam hammer, or
by a dead pressure of about two or three tons per square inch into very
hard solid and heavy blocks of reduced iron which may then be melted
in the bath of the melting furnace (whether a Siemens' regenerative
gas furnace or other suitable open hearth furnace) with little or no loss
from oxidation. To enable the spongy iron to cohere in this way into
a solid block at a temperature below the welding point, it must be
throughly reduced and the surfaces must be quite clean, that is, it must
not be reoxidized or tarnished at all on the surface. To ensure this, I
prefer to enclose the compressing apparatus in a casing or chamber filled
with reducing (or at least non-oxidizing) gases, and to prevent all
contact of the reduced iron with the air until after it has been compressed
into solid blocks. Spongy iron may be compressed into tolerably solid
blocks even in a cold state, provided that the surfaces of the particles
of metal are perfectly clean and free from oxide, but I prefer to effect
the compression at a red heat as above described both to ensure the
formation of more solid blocks and to save the time that would be
required to cool down the sponge in closed vessels before compressing
it.

page_text: As the compressing apparatus (which may be of any suitable known
construction) is required to work on hot material, it may be found
desirable to cool the working parts by means of currents of air or
water circulating through passages formed therein. Fluxing materials,
such as lime or silica, as the case may be, depending on the nature of the
impurities in the ore or other substances, such as excess of reducing
agents, manganese or compounds of manganese, tungsten, or its com-
pounds, &c. may be mixed with the ore either before or after its reduction,
and thus incorporated in the blocks of reduced metal; but I do not
consider the addition of such substances essential, and the formation
of such mixtures forms in itself and apart from the compression of the
reduced sponge no part of my present Invention. Instead of expressly
adding lime or silica to the ore as a fluxing material siliceous ores, such
as haematites may be advantageously worked in admixture with other
ores, such as spathic carbonates rich in lime, each class of ore thus
supplying a flux to the other.
-
Another part of my Invention consists in the employment of such
consolidated masses of reduced iron prepared as above described for the
manufacture of malleable iron, for which purpose these blocks (if the
ore of which they are made is sufficiently pure) may be reheated and
rolled off at once into bars of malleable iron, or they may be worked up
in any other suitable known manner into a marketable form.
Another part of my Invention relates to the treatment of the bath of
liquid metal formed in the open hearth steel melting furnace by melting
or dissolving either blocks of reduced iron formed as above described, or
reduced iron or ore in any other form or scrap iron or steel in the bath
of pig iron in the melting furnace. In using in the melting furnace
materials of any kind containing much earthy matter, and especially in
working with ore in any form, the layer of slag on the surface of the metal
frequently becomes so thick as seriously to impede the working of the
charge on account of the metal being thereby kept comparatively cold,
and so rendering it liable to set on the bottom and making the melting
slow and tedious notwithstanding that a keen heat is maintained in the
upper part of the furnace above the slag. It is difficult to skim off this
slag with rakes or rabbles, as is done in other metallurgical processes, on
account of the intense heat of the furnace, which soon causes the rabble
to bend, so that it dips into the metal instead of skimming over it, and
the slag is frequently too stiff to flow out readily without skimming.

page_text: it
Now by my Invention instead of skimming off the slag it is blown
towards one side of the furnace by a blast of combustible gas or air
employed either together or separately. One or more such jets may be
introduced at the same time into the furnace, their directions being so
adjusted as to blow all the slag towards one side of the bath from which
may be readily withdrawn. Jets either of air or of combustible gas
(such as the gas ordinarily used in the Siemens' gas furnace). may be
employed to blow off the slag, but to avoid any cooling of the furnace.
or oxidation of the metal in the bath, I prefer to employ jets of flame,
that is of air and gas thrown in together in a jet similar in principle to
that of an argand gas burner rather than to use either air or gas alone,
the difference between such jets of flame and the ordinary flame of the
furnace being that they are introduced under pressure as a blast and in
such a manner as to blow the slag to one side of the furnace in order
that it may readily be either raked out or be caused to flow out of
itself.