Improvements in the Manufacture of Steel.
Year: 1888

page_text: COMPLETE SPECIFICATION.
Improvements in the Manufacture of Steel.
I, MATTHEW GRAFF, of Pittsburgh, in the County of Allegheny, State of
Pennsylvania, United States of America, Manufacturer of Steel, do hereby declare the
nature of my said invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
In the attempts heretofore made to manufacture steel direct from the ore, the
carbonaceous material and the ore were crushed or broken up and after being thoroughly
mingled, were placed in a suitable furnace and subjected to a reducing heat. This
method, however, has proved practically unsuccessful, on account of the rapid com-
bustion of the carbonaceous material, which would be entirely consumed before thorough
deoxidation could be effected. And further the heat generated in the combustion of
the carbonaceous material would fuse the metallic iron which would then convert the
phosphoric acid to its elemental condition and then absorb it. And it has been the
usual practice to form the metallic sponge produced by deoxidation of the ore, into
bars or billets by squeezing, rolling or hammering, thereby forcing out not only the
slag and cinder but also a large percentage of the metallic iron. Such method also
allows of considerable oxidation of the sponge.
"
The object of the invention herein is during the deoxidizing operation, to so retard
or lessen the combustion of the carbonaceous material as to afford opportunity for the
combination of the carbon with the oxygen of the ore, and to prevent the generation of
such a heat as will fuse the metallic iron, which in its molten condition will readily
combine with the phosphorus. And it is a further object of my invention to provide
for a separation of the phosphorus from the sponge without rolling or hammering the
same, thereby avoiding the loss of metallic iron incident to such rolling or hammering.
In the practice of my invention, I take any suitable form of carbonaceous
material, such as hard coal or coke produced in the usual manner or by the com-
bustion of fluids or by the distillation of oils such as petroleum. The carbonaceous
material is then broken up into small lumps and then ground up or reduced to
about the size of coarse sand, preparatory to mixing it with iron ore similarly
prepared. These small lumps or particles of carbonaceous material are then coated
or covered with a thin lime or loam wash, which may be applied in any suitable
manner, as for example, pouring the wash over the carbonaceous material or by
immersing the latter in a bath of the wash. The carbonaceous material thus protected
or coated is mixed with the broken or disintegrated ore in suitable proportions, about
25 to 33 per cent., more or less, by weight of the ore. The mixed ore and carbonaceous
material are then charged into a suitable reverberatory furnace and there subjected to
a sufficient degree of heat to liberate the oxygen from the ore, and also to melt the

page_text: matrix in which the iron is held. The bottom of the reducing furnace is formed first
of a layer of comparatively large lumps of carbonaceous material and then with a
layer of smaller lumps and finally with a layer of fine material which will fill the
interstices between the lumps and form a smooth bed. The material forming this bed
is either coated with a wash of lime or loam prior to being placed in the furnace, or
else a quantity of the wash is poured over the bed after being formed. In lieu of
forming the bottom of carbonaceous material protected as above stated, unwashed
graphite may be employed if desired. The coating or wash will protect the
carbonaceous material to such an extent as to prevent a rapid combustion thereof,
and hence there will be a slower generation of carbonic oxide. On account of this
slow generation the carbonic oxide will be enabled to form a chemical union with the
oxygen of the ore, thereby forming carbonic acid, whereas if the carbonaceous material
were unprotected, the oxygen would not be given off with sufficient rapidity to combine
in proper proportions with the large volumes of carbonic oxide rapidly evolved from
the carbonaceous material. The charge is heated to about a cherry red heat and
maintained thereat until the gangue is melted into a fluid slag and until the oxygen
has been entirely removed or practically so and the metallic iron brought into an
adhesive state. Care should, however, be taken that the charge is not raised to such
a temperature that the metallic iron will unite with the phosphoric acid of
the slag.
Any. suitable material which will retard or lessen the combustion of the car-
bonaceous material may be employed in lieu of the lime or loam to form the
wash.
In some cases it is preferred to mingle the carbonaceous material and the ore, and
to charge them into the furnace before the wash or coating has become dry, thereby
preventing any loss of the ore and carbonaceous material in the form of dust.
The fluid slag removes or takes up from the sponge a great part of the impurities
held therein including the phosphoric acid. When the charge has been brought to
this state, which can be determined by testing whether the mass of iron can be rolled up
into a sheet or ball, the iron sponge is worked up into masses of a suitable size and
removed from the furnace, the larger part of the slag with its contained impurities
remaining in the reverberatory furnace, and being tapped off from the same after-
wards. The masses of iron sponge are thrown directly into an open hearth furnace,
containing a bath of melted iron or steel. I prefer to use an amount of metal in the
bath equal to about 33 1-3 per cent, by weight of the entire charge placed in
the open hearth furnace. The heat is applied in the open hearth furnace, until the iron
sponge is melted and unites with the melted metal of the bath. A sufficient quantity
of spiegel or ferro-manganese is then added to the melted metal to recarbonize it, and
this is thoroughly mixed and stirred with the charge, the heat being maintained meanwhile.
Before the steel is tapped off from the open hearth furnace, the liquid slag which
has risen to the top of the charge, may be drawn off through any suitable aperture,
or this slag may be left on the top of the charge. In the latter case portions of the
slag will flow on to the top of the steel in the ladle, and may then be removed, or
the steel may be poured into the ingot mould, leaving the slag in the ladle.
It will be seen that in my improved process, the iron sponge is taken from the
reducing furnace, and is thrown directly into the open hearth furnace, without being
allowed to cool, and without being subjected to any intermediate squeezing, rolling
or hammering to remove the slag. This secures a saving in time, labor and
metal.
The slag which adheres to the balls or masses of iron sponge when they are
removed from the reducing furnace, and which is introduced into the open hearth
furnace with the iron sponge, rises quickly to the top of the charge in the open hearth
furnace, carying with it the phosphoric acid and other impurities. The phosphoric
acid is thus removed from contact with the greater part of the mass of metal, before
it is melted or before it is brought into such a condition as to readily absorb or unite
with the acid, converting same into a phosphide of iron. My process will not entirely
remove the phosphoric acid from the sponge or phosphorus from the steel, but will

page_text: produce a steel having a lower percentage of phosphorus than that produced by the
known processes, and will do this without the employment of any other reagents
beyond the carbon, thus greatly decreasing the cost of the steel while improving its
quality.
In my improved process all the iron contained in the ore is removed therefrom
and utilized, as no metal is lost by squeezing or rolling.
I am aware that it has been proposed to deposit the entire charge from the
reducing furnace direct into the bath in the open hearth furnace, but I consider
such practice as objectionable for the reason that all the impurities from the ore are
in that way introduced into the bath, thereby deteriorating the quality of the metal
produced or necessitating a longer working of the metal in the open hearth
furnace.
The spongy iron has also been balled up and then squeezed and rolled or hammered
into billets or bars which are subsequently charged into the bath of the open hearth
while cold or practically so. This method is objectionable for the reason that a
certain amount of slag containing phosphoric acid and other impurities is incorporated
in the billets or bars, which must be melted before the slag can be liberated, but
during this melting operation the phosphoric acid is converted by the continued heat to
which it is subjected to its original elements, which can be absorbed by the iron, and
cannot thereafter be removed.
In my method, however, the spongy iron being balled up and removed from the
reducing furnace, only a comparatively small amount of slag is incorporated therein,
and the ball being immediately charged while hot into the metal bath, the metallic
iron is so quickly dissolved, as it were, that the slag contained in the ball is liberated
and rises to the top of the bath so quickly as not to materially affect the metallic iron
while in direct contact therewith.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what
I claim is:
1. As a step in the art of manufacturing steel direct from ore, the herein described
process, which consists in intimately mixing the ore with a carbonaceous material
protected as against rapid combustion by a coating of suitable material, and then
subjecting the mixed ore and carbonaceous material to the action of a reducing
flame in a suitable furnace, substantially as set forth.
2. As a step in the art of manufacturing steel direct from ore, the herein described
process, which consists in intimately mixing the ore with a carbonaceous material
protected by a coating of lime as against rapid combustion, and then subjecting
the mixed ore and carbonaceous material to the action of the reducing flame in a
suitable furnace, substantially as set forth.
3. The herein described process of manufacturing steel direct from ore which
consists in intimately mixing the ore with a carbonaceous material protected by a
coating of suitable material as against rapid combustion, subjecting the mixed ore
and carbonaceous material to the action of a reducing flame in a suitable furnace,
balling the spongy iron so formed, thereby freeing the same from slag and other
impurities and finally charging the ball while hot into the metal bath of an open hearth
furnace, substantially as set forth.
Cint Didinhunch D
TTS A this Fifteenth day of October A.D) 1888
Witnesses,
DARWIN S. WOLCOTT.
R. H. WHITTLESEY.
MATTHEW GRAFF.