GCr15轴承钢EAF-LF-VD-CC流程非金属夹杂物的演变

Evolution of non-metallic inclusions in EAF-LF-VD-CC process of GCr15bearing steel

为研究GCr15轴承钢中非金属夹杂物的演变,对某钢厂EAF-LF-VD-CC流程生产的GCr15轴承钢进行全流程取样,利用可进行大面积自动检测分析的ASPEX扫描电镜结合普通扫描电镜(SEM-EDS),系统分析了各工序中夹杂物的演变行为。结果表明,GCr15轴承钢精炼过程中夹杂物主要类型为MgO-Al2O3-CaO类复合夹杂物与MnS,少量SiO2-Al2O3,90%以上夹杂物尺寸为1~8μm。随着精炼的进行,夹杂物数量逐渐减少,在VD软吹阶段后期夹杂物数量及总面积降到最低。精炼期间,夹杂物成分在最初的高Al2O3(w([Al2O3])>80%)的区域逐渐向MgO、CaO含量升高的区域转移,VD破真空后MgO(w([MgO])>20%)、CaO(w([CaO])>30%)达到最高,之后向Al2O3含量升高的区域移动,最终在中间包浇注时停留在高Al2O3(w([Al2O3])>65%)的区域。钢中Ds类夹杂物主要为MgO-Al2O3-CaO类复合夹杂物,Ds类夹杂物的生成及去除随机性强,VD对Ds类夹杂物有较强去除作用。

To study the evolution of non-metallic inclusions in GCr15bearing steel.The GCr15bearing steel produced by EAF-LF-VD-CC process was sampled in various stages in a steel factory.The evolution behavior of inclusions in various processes was systematically analyzed by scanning electron microscopy(SEM-EDS)and ASPEX inclusion quick analysis equipment,which can scan large areas.The result indicates that the main types of inclusions in the refining process of GCr15bearing steel are MgO-Al2O3-CaO compound inclusions,MnS inclusions and a small amount of SiO2-Al2O3 inclusions,more than 90% of the inclusions distribute in 1-8μm.With the progress of refining,the number of inclusions decreases gradually,and the number and total area of inclusions decrease to the lowest at the VD soft blowing process.During the refining,the inclusions were gradually transferred to the areas with elevated MgO and CaO content from the initial high Al2O3(w([Al2O3])>80%)region.After the vacuum condition breaking,the MgO(w([MgO])>20%)and CaO(w([CaO])>30%)reached the highest.It then moves to the area where the Al2O3content is elevated,and finally stays in the high Al2O3(w([Al2O3])>65%)region in the tundish.The main Ds inclusions in steel are MgO-Al2O3-CaO composite inclusions.The formation and removal of Ds inclusions are random.The VD process has a strong removal effect on Ds inclusions.