40CrNiMo钢轴开裂原因分析

Cause analysis of cracking of 40CrNiMo steel shaft

通过对40CrNiMo钢轴取样进行化学成分分析、硬度检测和金相高低倍观察,结合钢轴断口形貌检验,分析讨论了钢轴产生开裂的原因,并针对原因提出了改进措施。结果表明:芯部存在较严重的带状组织偏析是导致钢轴开裂的主要原因,调质热处理过程中形成的上贝氏体进一步降低了材料性能,促进了裂纹形成和扩展。

The causes of cracking of 40CrNiMo steel shaft was analyzed and discussed based on chemical composition analysis,hardness testing and metallographic structure inspection as well as fracture morphology observation. Moreover,the improvement measures were proposed. The results showed that the serious segregation of banded structure in the center of the steel shaft was the main reason for the cracking. The upper bainite formed in quenched-tempered heat treatment process further reduced the properties of material,which accelerated the formation and propagation of cracks.