Through laboratory experiments and thermodynamic calculation, the chemical composition and morphology of inclusion and grain size in the cast melt are comprehensively characterized herein. The results show the evolution of Al₂O₃ inclusion formed by Al deoxidation in the gear steel 20CrNiMo follows the route of Al₂O₃ → CeAlO₃ → Ce₂O₂S → Ce₂O₂S + CeS, and thus the nucleation core of complex CemnS sulfides changes from CeAlO inclusion to CeOS inclusion with the increase in Ce addition. Moreover, grain size of gear steel 20CrNiMo treated by Ce addition decreases from 491.4 to 164.0 μm, because both the Ce₂O₂S and CeS form with Ce addition and have potential to be effective heterogeneous nucleation agents for the primary δ‐ferrite during the solidification process of gear steel 20CrNiMo. And statistical results show that the percentage of small inclusion with a diameter less than 3 μm are, respectively, 64.4%, 86.5%, 96.4%, 93.6%, and 75.6% in the steel samples with Ce content of 0, 13, 31, 77, and 203 ppm. Thus, the recommended Ce content to achieve fine inclusions and solidification structure of gear steel 20CrNiMo is 31 ppm.

中文翻译：

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铈对20CrNiMo齿轮钢中夹杂物和晶粒组织的影响

通过实验室实验和热力学计算，本文全面表征了熔铸物中夹杂物的化学组成和形态以及晶粒尺寸。结果表明，齿轮钢20CrNiMo中Al脱氧形成的Al ₂ O ₃夹杂物的演化遵循Al ₂ O ₃  →CeAlO ₃  →Ce ₂ O ₂ S→Ce ₂ O ₂ S + CeS的路径，从而形核的复杂的Ce核心米ñ 选自Ce小号硫化物变化铝 Ò列入铈 Ò 随着Ce添加量的增加，S夹杂物也增加。此外，通过添加铈处理的20CrNiMo齿轮钢的晶粒尺寸从491.4减小到164.0μm，这是因为Ce ₂ O ₂ S和CeS都通过添加Ce形成，并且有可能在初级δ铁素体中成为有效的异质成核剂齿轮钢20CrNiMo的凝固过程。统计结果表明，在Ce含量为0、13、31， 77和203 ppm。因此，为实现齿轮钢20CrNiMo的细微夹杂物和凝固组织的推荐Ce含量为31 ppm。