Electrical Conductivity, Viscosity and Structure of CaO–Al2O3-Based Mold Slags for Continuous Casting of High-Al Steels

The four-electrode method was employed to examine the electrical conductivity and viscosity of CaO–Al 2 O 3 -based mold slags designed especially for continuous casting of high-Al steels. The effect of equal mass substitutions of SiO 2 by Al 2 O 3 and CaO by BaO on the electrical conductivity and viscosity of the mold slags was investigated in combination with the microstructure analysis using Raman spectroscopy. The equal mass substitutions of SiO 2 by Al 2 O 3 and CaO by BaO in the molten slags caused the electrical conductivity to decrease and the viscosity to increase, which was attributed to the increased polymerization degree of the melts and the depletion of the cations. The polymerization degree of the melts increased with Al 2 O 3 replacing SiO 2 because of the generation of Al-related networks by the charge compensation effect of Al 3+ . The equal mass substitution of CaO by BaO decreased the number of available network modifiers and accelerated the structural complexity of the [SiO 4 ] tetrahedra. Meanwhile, Ba 2+ would preferentially promote the [AlO 4 ] tetrahedra configuration because it has a stronger ability of charge compensation than Ca 2+ . So the polymerization degree of slag melts increased with BaO replacing CaO. Nonlinear equations between the electrical conductivity and the polymerization degree of the molten slags were obtained to accurately predict the electrical conductivity of the melts at different temperatures in the current slag compositions range.