某减速机主轴曲柄预备二次服役, 在与主轴装配过程中发生断裂。采用化学成分分析、宏观分析、金相检验、力学性能测试、扫描电镜分析等手段, 对该曲柄断裂残体进行了检验和分析。结果表明: 断裂起源于曲柄内侧次表层, 该曲柄“内侧次表层”至“内表面”由2层不同的堆焊层组成, 曲柄断裂主要是由于其内侧补焊及补焊工艺不当所致;另曲柄制造工艺不良, 化学成分、力学性能及显微组织均不符合技术要求, 也加速了曲柄断裂失效。

The spindle crank of a reducer fractured when it was assembled with the spindle for secondary service, and the fractured crank was analyzed by means of chemical compositions analysis, macroscopic observation, metallographic examination, mechanical properties test and scanning electron microscope (SEM) analysis. The results show that the fracture originated form inner subsurface of the crank, and there were two layers of hardfacing layer between the matrix and the inner subsurface. The fracture of the crank was mainly caused by the inner side repair welding and the improper repair welding technology. At the same time, the bad processing technic and the unqualified chemical compositions, mechanical properties and microstructure also accelerated the fracture.