某电力公司风力发电机塔筒底座紧固用高强螺栓使用4 a(年)后, 在进行检修时发现个别断裂现象。通过对螺栓断口进行宏观检验以及扫描电镜分析, 并对螺栓材料进行化学成分分析、金相检验以及硬度测试, 查明了螺栓断裂原因。结果表明: 该螺栓断裂属于低应力高周疲劳断裂, 螺栓在调质处理过程中发生严重的表面脱碳, 导致螺栓表面硬度和强度降低, 于是在应力集中的螺纹根部萌生裂纹, 并疲劳扩展直至断裂。

In a routing inspection of a power company, the high-strength fastening bolts servicing for 4 years at the wind turbines pedestal were found fractured. After macrostructure inspection and scanning electron microscopy (SEM) analysis on the fracture, combining chemical compositions analysis, metallographic examination and hardness test to the bolt material, the fracture reason was discovered. The results show that the fracture was low stress and high cycle fatigue fracture. The severe surface decarburization produced during the quenching and tempering reduced surface hardness and strength of the bolt, accordingly, at the root of bolt where the stress concentrated, the cracks formed and constantly extended until fracture finally.