The sulphide capacities of CaO-Al₂-Al₃, CaO-Al₂O₃-MgO and CaO-Al₂O₃-SiO₂ slags were studied at 1823 to 1923 K to estimate the sulphur distribtion ratio between secondary steelmaking slag and liquid steel.
From the obtained results, it was confirmed that substitution of MgO or SiO₂ for CaO at a given N_Al2O3 decreased the sulphide capacities in both systems of CaO=Al₂O₃-MgO and CaO-Al₂O₃-SiO₂. The evaluated maximum values of sulphide distribution ratio for both slags were higher than 1000 at 1873 K on the condition of CaO-saturation if the dissolved aluminium content in steel was assumed to be 0.01 mass%.