Thermodynamic Activity of B2O3 in CaO-SiO2-Al2O3-B2O3-MnO-MgO Molten Slags at 1723 K

This study aimed to investigate the thermodynamic characteristics of the reaction between Al and B2O3 in the continuous casting process of high-aluminum steel. The activity coefficient of B2O3 in molten slag of (31.1 to 58.4) pct CaO-(0.2 to 16.7) pct SiO2-(14.7 to 49.2) pct Al2O3-(0 to 30.3) pct B2O3-(0 to 10.5) pct CaF2-(2.1 to 4.7) pct MgO-(0 to 1.8) pct MnO slags was measured at 1450 & DEG;C using B equilibrium experiments between liquid copper and molten slag in a graphite crucible under the mixed gas atmosphere of CO and Ar. The effects of B2O3, Al2O3, SiO2, and CaF2 and the basicity (B = mass pct CaO/(mass pct SiO2+mass pct Al2O3) on the activity coefficient of B2O3 in molten slag were discussed. Regression analysis was used to investigate the quadratic relationship between the activity coefficient of B2O3 and the concentrations of components in the slag. The results indicated that (a) the activity coefficient of B2O3 increased with an increase in B2O3 when B2O3 > 7 pct and B < 1, but decreased when B2O3 > 7 pct and B > 1. (b) When B > 0.9 and Al2O3 > 26 pct, the activity coefficient of B2O3 went up with the increase of Al2O3, but decreased when B < 0.9. (c) When B = 0.93 to 0.97, B2O3 = 9.1 to 9.5 pct, and CaF2 < 11 pct, the activity coefficient of B2O3 decreased with an increase in CaF2. (d) When B = 0.8 to 1.3, the activity coefficient of B2O3 increased with the increase of the basicity B. These findings provide insight into the factors affecting the activity coefficient of B2O3 in the molten slag and contribute to the optimization of the continuous casting process of high-aluminum steel.