通过钢液与夹杂物之间的热力学平衡计算，讨论了20CrMnTiH1精炼钢水中Al2O3夹杂物钙处理后可能变性的程度及CaS夹杂生成的条件。计算结果表明对硫的质量分数为0.020％～0.035%，铝的质量分数0.02％～0.04%的钢水进行钙处理时易生成稳定的CaS并难以使铝脱氧产生的Al2O3夹杂完全变性成低熔点C12A7钙铝酸盐。通过对炼钢厂生产的20CrMnTiH1齿轮钢材中夹杂物的检验，以及对连铸过程中水口堵塞物的扫描电镜能谱分析，发现钢材中含有许多CaS及变性不完全的钙铝酸盐CA，同时水口堵塞物也主要由CaS和变性不完全的钙铝酸盐CA组成。
20CrMnTiH1 is a aluminumdeoxidized resulphurized steel. Normally calcium is added in the last stage of refining process to modify oxides and sulphides to improve the product quality. Based on the thermodynamic equilibrium, the conditions of Al2O3 modification and CaS formation for Ca treated 20CrMnTiH1 steel were discussed in detail. The calculated results show that in the steel melt containing 0.02%0.03%［S］, 0.02%0.04%［Al］ treated by calcium, CaS is easily formed and it is difficult modify Al2O3 into low melting point C12A7. With analysis of the steel sample and blocked nozzle by SEMEDS, it was found that there were CaS and not fully modified calciumaluminate in the steel. Inclusions which caused nozzle blockage during casting were mainly of CaS and CA. The calculation agreed well with the SEM observation. Counter measures to avoid nozzle blockage are proposed.
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