Effect of MgO content in slag on dephosphorisation in converter steelmaking

Abstract

In this study, the effect of MgO content in slag on the phosphorus distribution ratios, and the equilibrium solubility of MgO in slag during converter steelmaking were analysed using the modified Kozheurov regular solution model and the thermodynamic package FactSage. Thermodynamic analysis shows that the MgO content in the final slag should be greater than 5% to saturate the slag with MgO and minimise the chemical wear of the refractory lining. However, the phosphorus distribution ratio decreases dramatically with increasing MgO. Industrial tests were performed using an 80-t top-and-bottom combined blown converter showed that the average phosphorus distribution ratio reduces significantly from 120.7 to 75.7 when the average MgO content in the final slag increases from 7.0 to 9.8%, due to thermodynamics and kinetics reasons. By optimizing the MgO content between 6 and 8% dephosphorisation and refractory wear are optimised.