pa1778data.pdf

U.S. STEEL DUQUESNE WORKS
HAER No. PA-115
(Page 176)
slag mixture consisting of four parts lime and one part fluorspar
or clean sand was added. Several samples of the slag were taken
in the period after the mixture was added. As the heat
proceeded, the color of the slag samples taken varied between
shades of brown, and contained varying amounts of manganese
oxide, indicating the stage of deoxidation or levels of iron
oxide being reduced. A slag sample which was decidedly brown in
color meant that deoxidation was well under way. At this point a
second slag mixture consisting of proportioned amounts of lime,
fluorspar, sand, and coke dust was added to the bath. The
addition of this mixture made the slag less vitreous thereby
creating a tendency for it to slake or disintegrate. At the same
time the color of the slag began to fade. Deoxidation was judged
complete and preparations were made to finish the heat when a
sample of the slag disintegrated upon becoming cold, while the
color turned gray.
The heat was finished by adding whatever alloys were
required in the batch. In order to give these alloys time to
thoroughly mix with the steel, a period of approximately thirty
minutes was allowed to pass before the heat was tapped. After a
final sample was taken to determine if the condition of the slag
was satisfactory, the furnace was tapped. Tapping consisted of
tilting the furnace on its rockers toward a teeming ladle set in
a pit below the tapping spout on the pouring aisle of the
building. A special skimmer, attached to the pouring spout of
the furnace, separated the slag from the steel as it was being
poured into the ladle. Subsequent to tapping, the ladle was
carried over by a E.O.T. crane to the platform where the steel
was teemed into ingot moulds. 1
Full fledged use of the electric furnace process for melting
down steel scrap did not take place at Duquesne until World War
II when an alloy steel plant was built by the Defense Plant
Corporation (D.P.C.). The new facility, which was part of an
effort to increase production for war time needs, was designed to
work in conjunction with a newly constructed heavy forging plant
built by the D.P.C. at the nearby Homestead Works. Consisting
of electric furnace, heat treating, and steel conditioning
facilities, part of the plant was built on land occupied by the
city of Duquesne's First Ward, which had been located between the
upper and lower works. The electric furnace building originally
contained two side door charged 70-ton furnaces and one side door
35-ton capacity furnace. All of the furnaces contained a basic
(magnesite brick) lining.
Electric furnace alloy steelmaking at Duquesne followed the
precepts of the "cold melt process." The process employed the
direct arc method and was conducted in two stages. During the