IMPROVEMENTS IN REFINING PIG IRON
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by Charles Denton Abel at the Office
of the Commissioners of Patents on the 10th April 1878. A communication
from abroad by Thomas Schoenberger Blair, of Pittsburg, Pennsylvania, in the
United States of America.
CHARLES DENTON ABEL, of Southampton Buildings, in the County of Middlesex.
"IMPROVEMENTS IN REFINING PIG IRON." [A communication from abroad by
Thomas Schoenberger Blair, of Pittsburg, Pennsylvania, in the United States of
America.]
This Invention relates to the refining of pig iron by the removal from it of
impurities, such as silicon, sulphur, and phosphorus, and the addition to it of carbon
when required, to obtain fluidity in fusion, the object of the Invention being to
produce economically a refined pig iron available for the manufacture of wrought
iron and steel by known processes in which pig iron is employed.
For the purpose of refining, the pig iron is treated in a reverberatory furnace in a
molten state. It may be melted in the furnace itself, or melted in a cupola, and
run thence into the furnace, or it may be taken direct from the blast furnace.
The hearth of the refining furnace is made of siliceous sand, such as is commonly
employed for the open hearth steel melting furnace, or it may be made of any other
sufficiently refractory substance, which will not impart oxygen to the metallic
bath.
The furnace may be of any known form, stationary or rotative. The refining is
accomplished by means of oxide of iron introduced into the furnace before the pig
iron is charged, or thrown into the bath after the pig is melted.
The action of the oxide of iron so introduced is to remove the silicon, sulphur,
and phosphorus to a large extent before diminishing the carbon to any great degree,
and the charge of oxide is so regulated that its action is exhausted before it has 80
far reduced the proportion of carbon as to cause the metal to become pasty. The
metal thus refined is run off from the refining hearth, and either allowed to cool in
forms convenient for subsequent use, or it is conveyed in a molten state into other
furnaces or receptacles, as herein-after described, for further treatment.
If a single refining operation, as above described, is insufficient to eliminate the
silicon, sulphur, and phosphorus to the extent desired, the bath is prepared for a
fresh charge of oxide by first infusing into it a new supply of carbon. This is done

page_text: by mixing charcoal or other suitable carbonaceous matter, finely divided, with other
carbonaceous matter of a pasty or adhesive nature, such as coal tar, pitch, or the
like, so as to form a coherent mass.
It is advantageous to add a small quantity of prussiate of potash or other analogous
substance having the effect of accelerating the absorption of carbon by iron. This
mixture is made into balls having a core of refined metal from a previous charge
heavy enough to sink the ball well into the bath. The metal rapidly absorbing
carbon will thus be fitted to receive a second charge of oxide for eliminating the
impurities without its becoming pasty.
The refining may be carried so far that the metal will hardly run, provided it is:
still fluid enough to receive and envelope the carbonaceous balls.
When it is desired to produce refined metal having a low per-centage of carbon the
treatment is carried on as above described up to the tapping out of the metal, which
is then run into a vessel, wherein it is brought into contact with a further supply
of oxide of iron, either alone or with other oxidising agents, so that the proportion
of carbon is reduced. By this treatment the crude product of the blast furnace is
purified from nearly the whole of its silicon, sulphur, and phosphorus, while the
proportion of carbon may be varied as desired.
For treating large quantities it is of advantage to melt in a cupola, and supply
from it several refining hearths, and economy is secured by utilising the heat which
the pig carries with it out of the blast furnace, for which reason it is advantageous
to place the refining hearths near the blast furnace, and to run the metal into them
direct.
The refined metal obtained by the process above described may be used for the
manufacture of steel in the open hearth furnace, or in crucibles, as it supplies a 2
material more chemically pure than the puddled bar made from the same pig, the
impurities having been separated while both slag and metal were fluid.
As the refined metal may have a low per-centage of carbon it can be employed
with great advantage in the open hearth furnace, and with a higher proportion of
carbon, in crucible treatment, its ready fusibility is advantageous in hastening the 3
fusion of the rest of the charge.
For either open hearth or crucible operations it furnishes an excellent material
for working with iron sponge, as it furnishes the carbon requisito for fusing the
sponge in the best form as carbon already associated with iron.
For steel processes on the open hearth, in the crucible or in the converter, the g
refined metal, made rich is carbon, is valuable as a carburizer, which can be employed
to any desired extent without imparting manganese, dispensing with the use of
spiegel eisen or ferro-manganese.
It is also applicable in the Bessemer process when there is an excess of silicon in
the charge.
For puddling, the refined metal offers great facilities, especially when the puddling
is effected mechanically, as in a rotating furnace. In this case the pig iron is pre-
ferably melted in a cupola, run thence into the refining hearth, and after being
refined, while still fluid, run into the puddling chamber.
In the charcoal bloomery the refined metal can be treated with considerable 4
economy of fuel and superiority of product, and good castings can be made of the.
refined metal alone, or mixed with crude pig.
Besides oxides of iron other oxidising agents may be employed in the refining
process, but the use of oxide of iron presents the advantage that it gives to the
bath metallic iron in quantity sufficient to pay a considerable part of the expenses {
of the refining process.