Effect of Al2O3/SiO2 ratio on viscosity and structure of CaO–Al2O3–SiO2–CaF2–MgO slag

Abstract

Abstract The viscosity of Al2O3/SiO2 melts is important because it affects secondary steelmaking. In this study, the effect of the Al2O3/SiO2 ratio on the viscosity was investigated for a CaO–Al2O3–SiO2–CaF2–MgO slag system. Softening point determination, structural analysis, and thermodynamic analysis were carried to explain and confirm the viscosity results. The lowest viscosity of 19 mPa · s was observed for 14Al2O3-18SiO2. An increase in the Al2O3/SiO2 ratio to 27Al2O3-5SiO2 resulted in an increase in the viscosity to 83 mPa · s at 1 600 °C. In the case of 6Al2O3-26SiO2, the main structural unit was [SiO4]4 − (tetrahedral) stretching vibration bands, whereas for 14Al2O3-18SiO2, the dominant [SiO4]4 − (tetrahedral) stretching vibration bands decreased after Si–O–Al vibration bands became dominant. [AlO4]5– (octahedral) bands were observed with increasing Al2O3/SiO2 ratio in the CaO–Al2O3–SiO2–CaF2–MgO slag system.