Activity of Silica in the Slag of an Electric Arc Furnace Using Direct Reduced Iron for Steelmaking

Abstract

Test charges consisting of DRI and scrap were melted in a 70t UHP electric arc furnace. Slag samples were collected and used to estimate the activity coefficient and activity of silica in the slag and to investigate the influences of basicity, temperature and optical basicity on both of them. A relationship between the activity coefficient and temperature was obtained which shows that the relative partial molar enthalpy of solution of SiO₂ in the slag is 70.0 kJ/mol. A simple linear equation has been obtained for the variation of the activity of silica with its concentration in the slag. Metal samples containing from 0.01 to 0.03 wt% of silicon show that the mean activity coefficient of silicon dissolved in the bath is 0.991.