紧固螺栓服役2年后发生成批断裂。采用宏观观察、化学成分分析、金相检验和扫描电镜与能谱分析等方法对失效螺栓进行了分析。结果表明，由于紧固螺栓长期浸在含有H2S介质的油料中，并在所承受的各种应力下又与腐蚀环境相互作用便产生了应力腐蚀，加上螺栓材质选用不当和硬度、显微组织不合理等其他因素，最终导致螺栓断裂。

The failure analysis of the bolts was made by macrostructure,chemical composieion,microstructure,fractography and EDS analysis. The results show that the stress corrosion,which is due to the interactions between the stresses and corrosion media ,make the bolts fracture. All of the fastening bolts fracture after used two years,as the bolts was long-term immcrsed in oil which contains the H2S. In addition,inproper material compositions,hardness,and microstructure also result in the fracture of the bolts.