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某电站300MW机组汽轮机的多个GH901高温合金材质的高压调节阀阀杆相继发生断裂。为查找断裂原因,采用宏观形貌观察、化学分析、显微组织观察、力学性能试验以及析出相能谱分析等方法,对断裂阀杆进行研究。结果表明:由于阀杆材料热处理不当,组织异常,导致材料塑性差、脆性大、缺口敏感性差。在长期运行过程中,由于阀门调节频繁,阀芯处摆动大,引起下部阀杆圆弧过渡区受到较大的弯曲应力,造成阀杆在薄弱处被掰断。
A power plant steam turbine 300MW unit GH901 high-temperature alloy material high-pressure regulating valve stem fracture occurred one after another. In order to find out the reason of fracture, the fracture stem was studied by macroscopic morphology observation, chemical analysis, microstructure observation, mechanical property test and precipitation phase spectrum analysis. The results show that due to improper heat treatment of the valve rod material and abnormal structure, the material has poor plasticity, large brittleness and poor notch sensitivity. In the long run, due to the frequent valve adjustment, valve spool swing at large, causing the lower valve rod arc transition zone subject to greater bending stress, resulting in weakness at the valve stem is broken.