Optimization of Endpoint Control for Low Carbon and Phosphorus Steel Produced by Converter Single Slag Process

Abstract

Through field test and thermodynamic calculation of decarbonization, this paper studies the effect of endpoint control of low-carbon and phosphorus steels produced with single-slag in basic oxygen furnace (BOF) on furnace lining erosion. The study reveals that practicing step control of C% till steel tapping in lieu of the thoroughgoing blowing method can effectively reduce the tapping temperature and FeO% in final slags, thereby mitigating the effect of heat and mass transfer on the compact slag layer of furnace lining and lowering the rate of furnace lining erosion. One key point is to control the endpoint C% somewhere above the critical C% value (C_t) of C–Fe selective oxidation in the final phase of blowing, which can be accomplished effectively by shortening the press-lance time to 40 s–70 s. Another key point is to raise the control range of endpoint carbon C₂ to 0.040%–0.050%. The tapping requirement for low-carbon and phosphorus steels can be satisfied through static stirring operation such that the carbon value at steel tapping C₃ < 0.038%.