1993 Volume 33 Issue 11 Pages 1174-1181
Data obtained on a 70-ton UHP electric arc furnace have been used for studying the effects of the sponge iron proportion in the metallic charge on important technological parameters of the steelmaking operation. The results obtained show that an increase in the sponge iron proportion leads to an increase in the consumptions of electric power, graphite electrodes, furnace refractories, lime and deoxidizers. The metallic yield decreases, whereas the slag weight per ton of liquid steel, the total ferrous oxide in the slag and the oxygen content of the bath increase with increasing sponge iron in the charge. The effects of metallization of the direct reduced pellets on power consumption and metallic yield are the reverse of the effects of the sponge iron proportion. The levels of the residual metals Cu, Ni and Cr, and the concentrations of the impurities P and S decrease with increasing sponge iron in the furnace feed. The use of sponge iron also improves the segregation of C, S and N in the steel. The yield point and tensile strength of hot-rolled plain steel bars decrease slightly, whereas elongation increases with increasing sponge iron in the charge. The actual steelmaking time decreases when the sponge iron proportion grows.