Demands for cleanliness of high chromium steel have been increasing. In steel refining process, aluminum is usually added in molten steel as a deoxidizing agent. As a result, such inclusions as alumina (Al₂O₃) and spinel (MgO∙Al₂O₃) are formed, which cause fatigue failures and surface defects. Therefore, it is important to understand the conditions of the inclusions which form in high chromium steel, and to reduce their harmful effects on steel qualities. In this work, to begin with, thermodynamic conditions of MgO and MgO∙Al₂O₃ formation in Fe-17mass%Cr molten steel at 1873 K were investigated. The results showed that MgO is more stable in high chromium steel than in plain steel. The boundary of the stable condition of MgO and MgO∙Al₂O₃ shifts toward higher Al and lower Mg contents in high Cr steel. This cause is judged to be the effect of thermodynamic interaction between Cr and Mg. The interaction parameter of Cr on Mg was estimated to be 0.040 so that the boundary of stable condition of MgO and MgO∙Al₂O₃ can be explained. Moreover, phase stability diagram of Fe–Cr–Al–Ca–Mg–O system at 1873 K was developed to estimate the effect of chromium on the stable condition of MgO, MgO∙Al₂O₃ and CaO–MgO–Al₂O₃(l). Subsequently, the variations of inclusions which formed in Fe-17mass%Cr molten steel were also investigated at 1873 K. The variations of inclusions in molten Fe–Cr steel were reasonably explained by considering the stable conditions of MgO and MgO∙Al₂O₃ investigated in this work.

对高铬钢洁净度的要求一直在增加。在炼钢过程中，铝通常作为脱氧剂加入钢水中。结果，形成氧化铝（Al ₂ O ₃）和尖晶石（MgO∙Al ₂ O ₃）等夹杂物，导致疲劳失效和表面缺陷。因此，了解在高铬钢中形成的夹杂物的条件，并减少它们对钢质量的有害影响是很重要的。在这项工作中，首先，MgO 和 MgO∙Al ₂ O _{3 的}热力学条件研究了在 1873 K 的 Fe-17mass%Cr 钢水中的形成。结果表明MgO在高铬钢中比在普通钢中更稳定。在高铬钢中，MgO 和 MgO∙Al ₂ O ₃的稳定状态边界向较高的铝含量和较低的镁含量移动。该原因被判断为Cr和Mg之间的热力学相互作用的影响。Cr对Mg的相互作用参数估计为0.040，从而可以解释MgO和MgO∙Al ₂ O ₃稳定条件的边界。此外，还开发了 Fe-Cr-Al-Ca-Mg-O 系统在 1873 K 的相稳定性图来估计铬对 MgO、MgO∙Al ₂ O ₃和 CaO-MgO-Al稳定条件的影响₂ O ₃ (l)。随后，还研究了在 1873 K 时 Fe-17mass%Cr 钢水中形成的夹杂物的变化。通过考虑 MgO 和 MgO∙Al ₂ O ₃的稳定条件，合理解释了 Fe-Cr 钢中夹杂物的变化在这项工作中进行了调查。