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High ferrotitanium prepared directly by the thermite method has a disadvantageously high O content (≥ 10 wt％) because of the short slag-metal separation time.In this study,CaO and CaF2 are added to the melt to improve the basicity of the slag and melt separation under heat preservation is performed to strengthen slag-metal separation.The thermodynamics of the step-by-step reduction process of TiO2 in the Ti-Al-Fe-Si-O system whose composition is close to the alloy after melt separation were calculated.Samples of alloys and slags before and after melt separation were systematically analyzed.The result indicates that the reaction that TiO is reduced by Al to Ti is the limited step in the reduction process of TiO2.The O content of the alloys slightly decreases with temperature from 1873 to 2023 K,which agrees with the changes in the law of deoxidation limit.It is mainly attributed to the movement of chemical reactions in the alloy melt at different temperatures and slag-metal interfacial reaction.The addition of Al2O3-CaO-CaF2 slag and high temperature promote the removal of Al2O3 and titanium suboxides.The minimum contents of O and Al in the alloy reach 1.84 wt％ and 3.26 wt％,respectively.