Effect of slag composition on titanium distribution ratio between ferrosilicon melt and CaO-SiO2-Al2O3 slag at 1773 K

Because the environmental problems are occurred by greenhouse gases such as CO2, the industries have tried to increase electric motor efficiency to reduce CO2 emissions. A core material of electric motor is high-silicon electrical steel. The ferrosilicon (FeSi) alloy, a raw material for the production of electrical steel, affects the electric properties of silicon steel. The main impurities such as Ca, Al and Ti make inclusions or precipitates that causes core loss. The slag treatment has been widely used to remove impurity elements. Thermodynamic principles for the refining of several impurities, specifically Ca and Al, have been investigated, whereas thermodynamic behaviour of Ti has not been fully understood yet. Therefore, in the present study, the titanium distribution ratio (𝐿􀯍􀯜) between ferrosilicon and CaO-SiO2-Al2O3 slag system at 1773 K was investigated. The results show that 𝐿􀯍􀯜 is influenced by both the basicity and stability of titanium ion in the slag. Specifically, 𝐿􀯍􀯜 exhibits a minimum value at about C/S=0.7 indicating a shift in the titanate structure unit from [TiO5]-square pyramid to [TiO4]-tetrahedron because of lack of Ca2+ ions in a C/S<0.8 region, contributing to an increase in titanate capacity and 𝐿􀯍􀯜.