20Mn钢套筒热处理质量不符合要求的原因及改进措施

Cause for Unqualified Heat Treatment Quality of 20Mn Steel Sleeves and Improvement

20Mn钢套筒表面硬度、硬化层深度和显微组织均不符合要求,且表层有白色异常组织。为此,对套筒进行了化学成分分析、硬度测定和金相检验及生产过程的复查。结果表明:套筒表面残留的切削液是导致套筒表面硬度偏低和硬化层深度不足且不均匀的原因。套筒热处理前增加滚筒式去油工序后,套筒的表面硬度、硬化层深度及表层显微组织均达到了技术要求。

Surface hardness,hardening depth and microstructure of 20Mn steel sleeves all did not meet the requirements,and a white abnormal structure appeared in the case.For this reason,the chemical composition analysis,hardness measurements,metallographic examination,and reinspection of production process were carried out on the sleeve.The results indicated that residual cutting liquid on the sleeve surface accounted for lower surface hardness,insufficient hardening depth and non-uniform hardened layer.After adding drum-type oil removal operation prior to heat treatment,the surface hardness,depth and microstructure of hardened layer all met the specification.