某管道阀门用304不锈钢螺栓在服役过程中发生断裂, 采用宏观分析、化学成分分析、硬度测试、断口分析、能谱分析、金相检验以及晶间腐蚀试验等方法对螺栓断裂的性质及原因进行了分析。结果表明: 螺栓断裂为在硫、氯等腐蚀性介质以及工作应力与残余应力共同作用下的沿晶应力腐蚀断裂; 螺栓化学成分不合格, 碳含量偏高、铬含量偏低导致晶界贫铬, 增加了螺栓发生应力腐蚀断裂的敏感性。

Fracture of 304 stainless steel valve bolts occurred during the service process, and means such as macro examination, chemical compositions analysis, hardness test, fracture analysis, energy spectrum analysis, metallographic examination and intergranular corrosion test were used to analyse the fracture property and reasons of the bolts. The results show that the fracture of the bolts was intergranular stress corrosion fracture under the coactions of sulfur and chloride corrosive medium, working stress and residual stress. The chemical compositions of the bolts were unqualified with the carbon content being higher than the standard value and chromium content being lower than the standard value resulted in grain boundary poor chromium, which increased the sensitivity of the bolts to stress corrosion fracture.