对25Cr2Ni2MoV低压转子钢焊接模拟件进行低周疲劳性能试验，测得焊接接头应变与疲劳寿命关系式，对比分析接头不同区域低周疲劳性能，确定热影响区是接头低周疲劳性能的薄弱环节。进行焊接接头硬度分布测定、疲劳裂纹扩展路径金相分析以及热影响区原奥氏体晶界元素偏聚行为俄歇分析等一系列试验。结果表明，焊接接头热影响区存在大硬度梯度的软硬界面，在疲劳载荷作用下形成应变集中，导致焊接构件低周疲劳性能弱化；在热影响区扩展过程中，疲劳裂纹遇到原奥氏体晶界往往会沿着晶界发生偏折，并在晶界上形成一定程度的割裂；俄歇分析表明热影响区原奥氏体晶界存在明显的杂质元素S和合金元素Cr的偏聚，其共同作用致使该区抗疲劳裂纹扩展性能弱化，从而降低整个焊接构件的低周疲劳性能。

A low-cycle fatigue property test is conducted on the test piece of welded rotor made by 25Cr2Ni2MoV material. The relation of strain and fatigue life is measured and the low-cycle fatigue properties of different joint zones are contrastingly researched. The heat affected zone is the relatively weak part of welded joint on low-cycle fatigue property. Researches of matrix hardness distribution of welded joint, fatigue crack propagation path and auger electron component analysis of element segregation at original austenite grain boundary of heat affected zone are conducted. The results show that soft zone and interface of hard and soft appear in the heat affected zone, which makes it suffer big strain concentration and reduced low-cycle fatigue property under fatigue load. In heat affected zone, the fatigue crack propagation path is likely to deflect along the original austenite grain boundary and separate the boundary to some extent. Through AES analysis, obvious element segregation of S and Cr are found at the original austenite grain boundary of heat affected zone, which weakens the resistance of fatigue crack propagation of this zone and degrades the low-cycle fatigue property of the whole weldment.