pa1778data.pdf
pa1778data.pdf
pa1778data.pdf
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U.S. STEEL DUQUESNE WORKS<br />
HAER No. PA-115<br />
(Page 68)<br />
furnace, lime combined with the minerals which had been separated<br />
from the ore such as silica, aluminum, and part of the manganese<br />
to form slag. From this point the slag and the liquified iron<br />
trickled down through the interstices of the coke at the<br />
combustion zone of the furnace to the hearth. Both substances<br />
attracted the sulphur and ash of the coke to them during their<br />
downward flow. Due to its lighter weight, the slag formed a<br />
molten layer on top of the iron. As the hearth continued to<br />
fill, the slag, because of its chemical composition, attracted<br />
part of the sulphur in the molten iron to it.<br />
After an interval of several hours, the hearth became full<br />
and the furnace was ready to be tapped. Iron was taken from the<br />
furnace through a tap hole called the iron notch. Located on the<br />
furnace at the level of the cast house floor, the iron notch was<br />
opened by means of an pneumatic air drill. Upon opening, molten<br />
iron, at a temperature of approximately 2600 degrees F., rushed<br />
out of the furnace into a series of clay runners embedded in the<br />
cast house floor before making its way to sand molds located on<br />
the floor or to waiting ladle cars which were located on standard<br />
gauge tracks below the cast house at the end of the runners.<br />
After 1898, molten iron flowed exclusively to the ladle cars.<br />
Shortly after the iron had been tapped, the slag was withdrawn<br />
from the furnace through the slag notch or "monkey." Located 90<br />
degrees from the iron notch on the furnace at a slightly higher<br />
elevation, the "monkey," which was opened by removing a short<br />
iron rod called the bott, allowed the slag to flow from the<br />
furnace into a series of clay runners also embedded in the cast<br />
house floor. The runners led to either a slag pit, or to waiting<br />
cinder pot rail cars, either of which were located below and<br />
outside of the cast house. After tapping, the iron notch was<br />
plugged up by means of a mechanical clay gun and the bott was<br />
reinserted in the "monkey."<br />
Ladle cars filled with molten iron were either taken to a<br />
pig casting machine (after 1898) where it was cast into molds to<br />
be sold on the merchant iron market or to the steelmaking plant<br />
where it was converted into steel by a number of different<br />
steelmaking processes — including the Bessemer, open hearth, or<br />
basic oxygen processes. In either case, the iron had to be<br />
desulphurized because the presence of too much sulphur in<br />
merchant iron caused excessive shrinkage in castings and because<br />
its presence in steel caused cracking across the ingot surface<br />
during rolling. Historically, desulphurization took place<br />
internally within the Bessemer converter or open hearth furnace<br />
itself or externally by adding soda ash or calcium carbide to the<br />
ladle so as to create a slag which could attract the remaining<br />
sulphur to it. 1