某汽轮机蒸汽调节阀杆在拆机检测时发生断裂，通过宏观观察、化学成分分析、力学性能试验、断口分析、能谱分析、显微组织观察和硬度试验等方法，分析了阀杆断裂的原因。结果表明：阀杆在蒸汽输入口处早已存在腐蚀坑与应力腐蚀裂纹，根据阀杆的使用环境与实际使用情况判断，认为阀杆是在停机检测时发生了一次性脆性断裂。

The steam control valve stem in a turbine was broken during disassembling and inspection. The reason for the break of valve stem was analyzed by macroscopic observation, chemical composition analysis, mechanical performance test, fracture analysis, energy spectrum analysis, microstructure observation and hardness test. The results showed that valve stem had corrosion pits and stress corrosion cracks at steam inlet. According to the use environment and actual use of valve stem, it was considered that valve stem was a one-time fracture during stoppage test.