Precise control on inclusions is of great importance for improving steel quality. In secondary refining, three types of inclusion are generally observed in Al-killed steel: Al₂O₃, MgO·Al₂O₃ spinel, and CaO–Al₂O₃ type. Many researchers have reported on inclusions transformed in the routine of Al₂O₃ → MgO·Al₂O₃ spinel → CaO–Al₂O₃ during secondary refining in Al-killed steel. The deoxidizer of Al is intentionally added to the steel, and Al₂O₃ inclusions are formed as a deoxidation product. However, MgO·Al₂O₃ spinel and CaO–Al₂O₃-type inclusions have been observed even without any intentional Mg or Ca addition. Therefore, it is important to clarify the source of Mg and Ca causing MA spinel and CaO–Al₂O₃-type inclusions formation, in order to control the compositions of the inclusions. Regarding to this phenomenon, a good review was published by Park and Todoroki in 2010. Several studies have since been conducted. This paper summarized the research activities on the composition changes of inclusions during secondary refining from the aspect of thermodynamics and kinetics.

精确控制夹杂物对于改善钢质至关重要。在二次精炼中，一般在Al镇静钢中观察到三种夹杂物：Al ₂ O ₃，MgO·Al ₂ O ₃尖晶石和CaO–Al ₂ O ₃型。许多研究人员报道了在Al镇静钢的二次精炼过程中，Al ₂ O ₃ →MgO·Al ₂ O ₃尖晶石→CaO–Al ₂ O _3的转变过程中的夹杂物。有意将Al的脱氧剂添加到钢中，并将Al ₂ O ₃夹杂物作为脱氧产物形成。然而，即使没有故意添加Mg或Ca，也观察到MgO·Al ₂ O ₃尖晶石和CaO–Al ₂ O ₃型夹杂物。因此，重要的是要弄清楚引起MA尖晶石和CaO–Al ₂ O ₃型夹杂物形成的Mg和Ca的来源，以便控制夹杂物的成分。关于这种现象，Park和Todoroki在2010年发表了一篇很好的评论。此后进行了一些研究。本文从热力学和动力学的角度总结了二次精炼过程中夹杂物组成变化的研究活动。