某电厂锅炉主给水管道上的电动闸阀阀杆在服役过程中发生断裂，阀杆材料为38CrMoAlA钢。采用化学成分分析、力学性能试验、金相检验、断口分析以及能谱分析等方法，对阀杆断裂原因进行了分析。结果表明：阀杆断裂主要是由于阀杆材料热处理不当，导致材料硬度偏高、冲击韧度严重偏低，从而使阀杆在开启过程中于应力集中的退刀槽处发生脆性断裂。

The electric gate valve stem with material of 38CrMoAlA steel and on the main water supply pipe of a power plant fractured during service. Means such as chemical composition analysis, mechanical property test, metallographic test, fracture analysis and energy spectrum analysis were used to analyze the fracture causes of the valve stem. The results show that the fracture of the valve stem was mainly due to improper heat treatment of the valve stem material which resulted in high hardness and seriously low impact toughness of the material, thus brittle fracture of the valve stem occured at the groove to withdrawal the cutting tool as stress concentration location during the opening process.