关键词: 18CrNiMo74齿轮钢, 60t LF-VD精炼, 非金属夹杂物演变, 分析

Abstract: The metallurgical flowsheet for steel 18CrNiMo7-6 (/%: 0. 17C, 0. 57Mn, 0. 24Si, 0. 012P, 0. 003S, 1.70Cr, 1. 49Ni, 0. 28Mo) is 60t EAF-LF-VD-2.1t ingot. The variation of amount, size and ingredient of inclusions in steel after EAF aluminium pre-oxidation, LF aluminium shot and silicon-carbide mix deoxidant diffusion deoxidation (LF initial slag ingredient /%: 57 ~ 60CaO, 20. 5 ~ 22. 0Al₂O₃, 9. 9 ~ 11. 3SiO₂ , 8. 8 ~ 10. 6MgO, 0. 7 ~ 1. 1FeO, 0. 7 ~ 0.9MnO) , VD and soft blowing has been analyzed by sampling. Results show that during refining process the amount of  inclusions decreases by 16. 67% , the amount of >10μm inclusions decreases by 50% and the ≥30μm inclusions basically are removed from liquid ； during refining process the main formed-inclusions are magnesium-aluminium-calcium compound inclusions and CaS, MgS and MnS etc sulfide; the main inclusions in finished products are Mg-Al oxides and main sulfide is MgS with minor MnS and CaS etc sulfide. The further optimized steelmaking process is to control the formation of small and medium size inclusions.