Viscosity and surface tension of CaF2–CaO–Al2O3-based slag with varying SiO2and B2O3contents for ESR of rotor steel

The effect of SiO2and B2O3on viscosity and surface tension of CaF2–CaO–Al2O3–MgO–SiO2–B2O3slag designed for electroslag remelting of rotor steel was investigated. The viscosity of the slag melts increases with increasing the SiO2content from 0.37 to 8.03 mass%, and the viscous activation energy increases from 54.21 to 58.49 kJ/mol. Increasing B2O3content of the slag from 0 to 3.62 mass% exhibits a similar effect on the viscosity, and the activation energy increases from 47.30 to 55.71 kJ/mol. The increase in the viscosity and activation energy for viscous flow of slag is attributed to the enhanced polymerization degree of slag melts network with increasing either SiO2or B2O3content. The surface tension of slag melts decreases with increasing temperature. The surface tension of slag melts decreases with increasing either SiO2or B2O3content, which is originated from the increase in the polymerization degree and the decrease in the CaO content of the slag.