采用宏观观察、化学成分分析、金相检验、力学性能测试、硬度测试等方法对某300 MW汽轮机主汽门门杆断裂原因进行了研究。结果表明:该门杆存在变截面结构、应力相对集中、内部存在夹杂物、材料硬度偏低等问题;在交变应力作用下,门杆受到很大的冲击力,超过其临界断裂强度,最终发生脆性断裂。

Macroscopic observation, chemical composition analysis, metallographic examination, mechanical property test and hardness test were used to study the fracture reason of main valve stem of a 300 MW steam turbine. The results show that there were problems with the door rod such as variable cross-section structure, relatively concentrated stress, inclusions in the interior, and low material hardness. Under the action of alternating stress, the door rod was subjected to great impact force, which exceeded its critical fracture strength, and finally brittle fracture occured.