Abstract: In order to reduce the content of harmful sulfur elements in steel, KR desulfurization method is widely used in steel enterprises to produce low sulfur steel, and the influence of desulfurizer on the desulfurization efficiency is especially critical. In this paper, the effect of components on liquidus temperature, sulfur capacity, desulfurizer consumption, melting point, viscosity and desulfurization rate of CaO-Al₂O₃-SiO₂-CaF₂-MgO slag system were analyzed, based on simplex lattice method, FactSage 8.1 thermodynamic software, hemispherical melting point meter, rotating viscometer and slag-metal experiment. It was concluded that, the liquidus temperature of desulfurizer increased with CaO addition, and decreased with CaF₂ addition, while the sulfur capacity of desulfurizer increased with CaO and decreased with Al₂O₃ and CaF₂ enhancement. Meanwhile, with CaF₂ and Al₂O₃ addition, the desulfurizer consumption and melting point changed little in slag with low content of SiO₂, while the consumption increased greatly and the melting point decreased obviously in slag with high content of SiO₂. The desulfurization efficiency of desulfurizer with melting point of 1 400-1 424 ℃, w(SiO₂) of 0-10 %, w(Al₂O₃) and w(CaF₂) of 5 % -15 %, w(MgO) of 6 % was better than that of desulfurizer used in an enterprise, and the comprehensive desulfurization ability of CaF₂was stronger than that of Al₂O₃. Combined with the high temperature viscosity, the desulfurization efficiency and the subsequent slagging-off process, No.2 desulfurizer was the best choice for KR desulfurization.

Key words: KR desulfurizer, FactSage thermodynamic calculation, melting temperature, desulfurization efficiency