电厂磨煤机40Cr高强螺栓失效分析

Failure Analysis on 40Cr High Strength Bolt for Coal Pulverizer in Power Plant

某电厂磨煤机运行过程中40Cr高强螺栓发生断裂。通过化学成分、硬度和金相检测对螺栓进行了失效分析,并采用扫描电子显微镜对断口形貌进行了观察。结果表明,螺栓断裂属于疲劳断裂,裂纹起源于螺栓头杆结合的R处;螺栓中Cr元素的含量和螺栓硬度均低于标准要求;金相组织中铁素体含量偏高,且螺栓心部的铁素体含量明显多于边缘,说明螺栓的原始热处理未达到要求。

40Cr high strength bolts for coal pulverizer in a power plant broke down in the work process. The failureanalysis of bolts was carried out through chemical composition, hardness and metallographic detection. The fracture surfb.cewas observed by scanning electron microscopy （SEM）. The results show that the bolt fracture belongs to fatigue fracture, andthe crack originates from the R place of bolt head; the Cr content and hardness of bolts are lower than the standardrequirements; the content of ferrite in microstructure is high, and ferrite content near the edge is higher than that in the core,which illustrates that the original heat treatment of the bolts does not meet the requirements.