| The equilibrium phosphorus distribution ratios, L_P between CaO-CaF₂ and CaO-BaO-CaF₂ slags and Fe-C_(sat·)-P melt were measured at 1400℃. The effect of BaO addition on L_P was determined at various CaO/CaF₂ ratios in slag. The addition of BaO up to 30 wt% in CaO-80%CaF₂ slag decreases L_P since BaO lowers the activity of CaO in liquid slag. BaO lowers the melting point of CaO-CaF₂ slags. As the CaO/CaF₂ratio increases in slag, where the slag is saturated with CaO on BaO addition, the decrease in L_P is not observed. At a BaO content higher than 30 wt%, however, L_P increases drastically due to the increase in BaO activity. The SEM-EDS analysis on a quenched CaO-40%BaO-CaF₂ slag containing 4% P indicates that the phosphate ions are dissolved in liquid phase and primarily associated with BaO in slag. Correlation between the phosphate capacities and the optical basicities of slags was also examined. The theoretical optical basicity of slags containing various components is not an universal standard of refining capability of slags. The thermodynamic activity of basic oxide in slag is one of main factors in determining the dephosphorization capability of slags. |
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