pa1778data.pdf

U.S. STEEL DUQUESNE WORKS
HAER No. PA-115
(Page 17 8)
or when a sample of the molten metal indicated that its
composition met the requirements of the heat, the power was
turned off and the final deoxidation additions, such as aluminum,
were made. At this point, the furnace was tilted forward on its
rockers and its tap hole was opened. Due to the elevation of the
tap hole, the molten metal flowed out of the furnace before the
slag. It was tapped into a 40 or 80-ton teeming ladle, which was
spotted under the tapping spout by an E.O.T. crane. After the
steel was tapped, the slag was dumped into a cinder pot and the
ladle was conveyed across the pouring aisle to the platform where
the steel was teemed into ingot moulds. The moulds were prepared
for teeming at the southern end of the platform.
If the solidified ingots were slated to be rolled into bars,
the moulds were delivered by rail to the work's primary mill
where the ingots were stripped and charged into soaking pits. If
the ingots were slated to be forged into armor plate, they were
delivered to the forging plant at the Homestead Works. 2
Significant changes to the steelmaking process at the
electric furnace facility were made shortly after the war and
continued until the mid 1970s. Among the earliest of these
changes was the use of iron ore and gaseous oxygen in the
production of stainless steel. By adding these elements to the
process, the men who operated the facility were able to produce a
lower cost, quality product at a faster pace. Iron ore was added
to the furnace with the initial charge because it was beneficial
in starting the oxidation of the silicon and manganese during the
early stages of melt down and because it provided a cheap source
of iron. When approximately 75 percent of the charge had been
melted, an oxygen lance, which was connected to the work's dri-ox
piping system, was inserted into the slag-metal interface of the
bath through the wicket holes on the charging door. The plastic
refractory coated lances delivered 10,000 to 12,000 cubic feet of
oxygen per hour to the bath under a pressure of 110 psi.
Subsequent to the beginning of the oxygen blow, the electrodes
were often raised and the melting was completed with the
exothermic heat of the oxygen reaction, significantly saving
power costs. The reaction of the oxygen with the silicon in the
bath, moreover, quickly raised its temperature above that
required to reduce the carbon content, even though unmelted scrap
remained around the banks of the furnace. As a result,
elimination of the carbon had proceeded so far by the time the
charge was completely melted that the additional time necessary
to reduce the carbon content to the requirements of the heat was
greatly decreased.
The use of oxygen in electric furnace steelmaking also
provided a measure of flexibility to the system. If, for