Production of low phosphorous steel from low silicon high phosphorous hot metal in BOF

Production of low phosphorous (<= 0.015%) steel in Basic Oxygen Furnace (BOF) using high phosphorous (average 0.17%) and low silicon (<= 0.5%) hot metal with Si/P ratio <3 is a challenging task. In addition to temperature, slag basicity and FeO, the quantity of slag becomes important which is achieved by higher lime addition. However, how much lime is appropriate need to be understood. A detailed analysis of plant data indicated that a scope exists for lowering lime addition from existing level. Accordingly, systematic trials were conducted with reduction in lime which showed that lowering 12% lime had no effect while 19% reduction increased end blow (EB) P by 20 ppm. SEM-EDX studies of slag samples revealed chemical and morphological changes in trial heats. Lime addition pattern was also found to impact EB P. Addition of lime in a small batch during 10-25% of the oxygen blow resulted lower EB P.