pa1778data.pdf

U.S. STEEL DUQUESNE WORKS
HAER No. PA-115
(Page 166)
hearth process involved the burning of a mixture of gas and air
over a charge of limestone, iron ore, scrap steel, and molten pig
iron contained within a rectangular, magnesite refractory brick-
lined regenerative furnace. The oxygen content of the air, the
limestone and the iron ore transformed the iron into steel by
eliminating carbon, silicon, manganese, sulphur, and phosphorus
from the molten bath by means of oxidation.
The use of the open hearth process had several advantages
over the acid Bessemer process. Because the process used iron
ore as a oxidizing agent and because heat was applied externally,
the temperature of the bath was made independent of the purifying
reactions and the impurities were eliminated gradually so that
the temperature and composition of the molten bath was under much
better control. For the same reasons, a greater variety of raw
materials could be utilized, particularly scrap which was not
readily consumable in the Bessemer converter, and a greater
variety of products could be made. This was particularly
significant at Duquesne which became an important producer of
alloy steel bars for the eastern market in the United States.
Another important advantage of the basic open hearth process was
the increased yield of finished steel from a given quantity of
pig iron, because of lower inherent iron losses and because of
the recovery of the iron content of the ore used for oxidation.
Finally, the greatest advantage of the open hearth over the
Bessemer process was its ability to eliminate phosphorus and
sulphur from the bath. This opened up vast quantities of
American iron ore deposits high in phosphorus content for use in
steelmaking. 1
Open Hearth Number One was located on the present site of
the basic oxygen steelmaking facility. Like the Bessemer plant,
its structures and equipment were laid out in such a manner as to
permit a smooth and easy flow of materials. Open Hearth Number
One initially consisted of a stockyard, a furnace building, a
cinder yard, a skull cracker, and a mould conditioning building.
The furnace building, which was the center of activity, had split
level floors with the floor of the charging aisle located 9 f -0"
above the floor of the pouring aisle. Twelve 50-ton capacity
stationary open hearth furnaces, laid out linearly, divided the
building between the charging and pouring aisles. Along the
wall of the pouring aisle, opposite the furnaces, stood the
teeming platform.
The process began with the proportioned loading of scrap and
raw materials boxes set upon flat rail cars in the stockyard
which adjoined the furnace building. The proportions of scrap
and raw materials used depended upon the desired grade of steel.
When loading was complete, the cars were run along a narrow gauge