轴承钢中D类夹杂物的形成与控制

轴承钢对钢中非金属夹杂物, 尤其是对D类夹杂物的要求非常严格.为了分析国内某钢厂GCr15轴承钢棒材试样探伤不合的D类夹杂物形成原因并提出有效控制措施, 采用ASPEX自动扫描电镜对GCr15轴承钢生产工艺优化前后全流程夹杂物的演变进行观察.研究结果表明, 原工艺下轴承钢中D类钙铝酸盐夹杂物生成的主要原因包括两个方面, 一是精炼渣碱度过高导致渣中Ca O活度很大;二是在真空脱气 (VD) 精炼过程中, 强烈搅拌给钢-渣反应提供了良好的动力学条件.本文从精炼渣碱度和VD真空度两方面对轴承钢生产工艺进行了优化.优化后能够在保持高洁净度情况下, 使钢中夹杂物由钙铝酸盐类转变为镁铝尖晶石类, 减少了轴承钢中D类夹杂物的生成.

Formation and controlling of Type-D inclusions in bearing steel

There are strict requirements for non-metallic inclusions in bearing steel, especially for Type-D inclusions.To analyze the formation mechanism of Type-D inclusions in high-frequency detection defects of GCr15 bearing steel bar sample in domestic steel plant and give the effective controlling measure, the inclusion evolution in bearing steel production process before and after optimization was investigated by ASPEX automatic scanning electron microscope.The results show that, the main formation mechanism of calcium aluminate Type-D inclusions present in the original process includes two aspects:one is the high basicity of refining slag, resulting in the high Ca O activity in slag.The other is the strong stirring in vacuum degassing (VD) process, providing good kinetic conditions for slag-steel reactions.The bearing steel production process is optimized from the basicity of refining slag and the vacuum degree of VD process.After optimization, the inclusions change from calcium aluminate to spinel type, and the formation of Type-D inclusions in bearing steel is reduced.Meanwhile, the high cleanliness of bearing steel is maintained.