Effect of CaO/SiO₂ and CaO/Al₂O₃ in CaO-Al₂O₃-SiO₂ particles on desulfurization of molten steel studied by confocal scanning laser microscopy

The instantaneous desulfurization of CaO-Al₂O₃-SiO₂ slag particles in the molten steel was in situ observed using a high-temperature confocal scanning laser microscope. The desulfurization effect of CaO-Al₂O₃-SiO₂ slags with different compositions was discussed. The influence of CaO/Al₂O₃ and CaO/SiO₂ on the desulfurization effect was analyzed. It was shown that in the liquid phase range, the higher CaO/SiO₂ and CaO/Al₂O₃ can significantly improve the desulfurization effect of the slag. A dimensionless desulfurization index S_index was introduced to evaluate the desulfurization ability of CaO-Al₂O₃-SiO₂ slags quantitatively. The S_index values of CaO-Al₂O₃-SiO₂ with different compositions at 1550 °C were calculated. It was suggested to use (65%-75%)CaO-(0-20%)SiO₂-(20%-40%)Al₂O₃ slags to improve the molten steel desulfurization.