高品质轴承钢LF--VD过程非金属夹杂物演变规律

对国内一钢厂EAF→LF→VD→CC工艺生产的高品质GCr15轴承钢进行系统取样,针对DS类非金属夹杂物随机性强的特点,利用能够进行大面积试样检测的ASPEX自动扫描电镜分析统计钢中非金属夹杂物的成分、尺寸、数量等信息。研究发现：GCr15轴承钢冶炼过程中非金属夹杂物主要为MgO- Al2 O3- CaO复合夹杂物和MnS,同时有少量的SiO2- Al2 O3和MgO-Al2 O3复合夹杂物；夹杂物尺寸主要集中在3~8μm,并有少量DS类夹杂物出现且尺寸范围波动很大,最大可以达70μm以上,形貌为圆形或近似圆形；VD有较强的去除夹杂物功能,经过VD真空精炼,夹杂物中CaO含量有增加趋势；吊包至铸坯过程,夹杂物成分向Al2 O3含量增多的区域移动,最终轴承钢铸坯中夹杂物成分位于高Al2 O3含量(≥80%),少量MgO (<20%)和低CaO(<5%)的区域；DS夹杂物的生成和去除具有较强的随机性。

Evolution rules of inclusions in high quality bearing steel produced by LF--VD process

High quality GCr15 steel produced by EAF-LF-VD-CC process was systematically studied by sampling in various sta-ges for a domestic factory. For the random characteristics of DS inclusions, the evolution rules of inclusions in bearing steel smelting process were investigated by ASPEX inclusion quick analysis equipment, which can scan the specimen surface in large enough area. The results indicate that the main inclusions are MgO-Al2 O3-CaO and MnS, and there are also a small quantity of SiO2- Al2 O3 and MgO- Al2 O3 . The size of the majority of inclusions is 3-8μm, few DS inclusions have a large size range, the biggest one can be more than 70μm, and the morphologies of the inclusions are round or nearly circular. Inclusions will be significantly removed by VD process and the content of CaO in inclusions increases after VD process. The content of Al2 O3 in inclusions increases during the tundish to continuous casting process. Finally, the content of Al2 O3 in inclusions is more than 80%, the content of MgO is less than 20%, and the content of CaO is less than 5% in the ternary system of MgO-Al2 O3-CaO. The formation and removal behaviors of DS inclusions in bearing steel are of higher degree randomness.