Abstract: In order to effectively reduce and control the non-metallic inclusions in a GCr15 bearing steel produced by BOF→LF→VD→CC process and improve its product quality， the characteristics and evolution mechanism of inclusions in bearing steel produced by the whole process were analyzed firstly by methods of systematic sampling， automatic analysis and scanning of inclusions and thermodynamic calculation in the present study. The results show that the inclusions in molten steel are mainly MgO-Al₂O₃ and Al₂O₃ after the slag melting during LF stage， and they are transformed into CaO-MgO-Al₂O₃ and CaO-Al₂O₃ with the size of 1-5 μm in the end of the LF stage. The type of inclusions remains unchanged after VD soft blowing. However， the inclusion density decreases from 16.53 pcs/mm² in the end of the LF stage to 14.02 pcs/mm²， resulting in an inclusion removal rate of approximately 15.2%. The number density of inclusions in the tundish increases to 16.39 pcs/mm². The types of inclusions are still mainly CaO-MgO-Al₂O₃ and CaO-Al₂O₃， of which 1-2 μm and ＞ 2-5 μm size accounted for 62.8% and 35.6%， respectively. The number of CaS-containing compound inclusions in the billet increases significantly. Thermodynamic calculation explains the evolution causes of the above inclusions. It is found that when the w［Al］_s is at 0.02%， the stable existence of MgO-Al₂O₃ is associated with a significant variation in Mg content， ranging from 0.000 3% to 0.01%， which facilitates the formation of MgO-Al₂O₃ or CaO-MgO-Al₂O₃ type inclusions during the production of GCr15 bearing steel. The T.Ca/T.O ratios of the molten steel in LF ending， VD soft blowing process， and tundish were observed to be 0.39， 1.0， and 0.62， respectively； these values align with the theoretical （T.Ca）/（T.O） ratio range （0.13 to 1.25） conducive to the formation of five distinct types of calcium aluminate. As a result， a substantial quantity of calcium aluminate inclusions was detected. During the cooling process of the molten steel， a transformation of inclusions occurs. The liquid calcium aluminate inclusions diminishes， while the quantities of MgO·Al2O3 and CaS inclusions markedly increases.

Key words: GCr15 Bearing Steel, Non-metallic Inclusions, Thermodynamics, Solidification, Evolution

摘要： 为进一步降低和控制某钢厂由BOF→LF→VD→CC工艺流程生产的GCr15轴承钢中的非金属夹杂物，提高产品质量，首先通过全流程系统取样、夹杂物自动分析扫描以及热力学计算等方法对该工艺生产的轴承钢中夹杂物的特性和演变规律进行了研究。结果表明，LF化渣时夹杂物主要为MgO-Al₂O₃和Al₂O₃，LF出站时演变为CaO-MgO-Al₂O₃和CaO-Al₂O₃，尺寸主要分布在1~5 μm；VD软吹后夹杂物主要类型不变，但数密度由LF出站时的16.53 个/mm²降低至14.02 个/mm²，夹杂物去除率约15.2%；中间包中夹杂物数密度又上升至16.39 个/mm²，夹杂物类型仍主要为CaO-MgO-Al₂O₃和CaO-Al₂O₃，其中1~2 μm和＞2~5 μm占比分别为62.8%和35.6%。铸坯中CaS复合型夹杂物明显增多。热力学计算解释了以上夹杂物的产生原因，表明，当w［Al］_s为0.02%时，MgO-Al₂O₃稳定存在对应的Mg含量变化区间较大，为0.000 3%～0.01%，因而，GCr15轴承钢生产过程中容易生成MgO-Al₂O₃或CaO-MgO-Al₂O₃类夹杂物。LF出站、VD软吹后、中间包钢水的（T.Ca）/（T.O）分别为0.39、1.0、0.62，位于生成五类钙铝酸盐的理论钙氧比范围（0.13~1.25），因此，检测到大量的钙铝酸盐夹杂物。钢液冷却过程中夹杂物发生了转变，液态钙铝酸盐夹杂消失，而MgO·Al₂O₃和CaS夹杂明显增多。

关键词: GCr15轴承钢, 非金属夹杂物, 热力学, 凝固, 演变