Double slag practice for refining of steel in MgO-lined induction furnace

Abstract

The phosphorus in the steel ranges from 0.085 to 0.1 wt%, while sulfur is around 0.06–0.1 wt% forsteel being produced through the induction furnace route using DRI and cast iron ingot as feedmaterials. As per standard (IS 1786:2008), the phosphorus and sulfur content in any structuralsteel is within the ranges of 0.03–0.06 wt%. Therefore, controlling phosphorus and sulfur duringsteelmaking in the induction furnace is indispensable and poses a significant challenge due tothe use of acidic lining materials, the absence of basic slag, and other unfavourable conditions.To overcome problems, the double slag practice is employed - initially oxidising fordephosphorisation, then reducing slag for desulfurisation during steelmaking in the MgO linedinduction furnace with developed synthetic slag consisting of CaO: 50 wt%, SiO2: 20 wt%, MgO:6 wt%, FeO: 14 wt%, Al2O 3: 10 wt% for dephosphorisation and CaO: 58 wt%, SiO2 : 23 wt%,MgO: 7 wt%, Al 2O3: 12 wt% for desulfurisation. With double slag practice, the final phosphorusand sulfur in the treated steel are 0.025 and 0.0054 wt%, respectively. Hence, the developedsynthetic slag is suitable for reducing both sulfur and phosphorus in the steel in an inductionfurnace using double slag practice