Preventing Rephosphorization during Tapping in BOF Steelmaking

摘要

In this study,an attempt was made to establish a technique to prevent rephosphorization during tapping when producing high carbon low phosphorus steel.Slag samples of several heats after the blowing end were taken and the compositions of several phases of slag were analyzed by EPMA.The phosphorus distributions apparently attained pseudo equilibrium among molten steel,liquid slag and 2CaO · SiO2-3CaO · P2Os solid solution (C2 S-C3 P s.s.),although the oxygen potential of slag differs from that of high carbon molten steel.The results indicated the possibility of preventing rephosphorization by controlling the phosphorus distribution ratio to high.To obtain a higher ratio of phosphorus distribution,the slag temperature was lowered by the addition of lime into molten slag after the blowing end.By adopting this technique to the commercial operation,rephosphorization during tapping becomes 1.0 x10-3 mass％ [P] smaller than the conventional method without lime addition.