Mechanical properties of 30Cr2Ni4MoV low-pressure (LP) steam turbine rotor steel were investigated by microstructure analysis, room- and high-temperature tensile tests, room-temperature impact tests and fracture appearance transition temperature tests, so as to study the variation reasons of its strength and ductility. Results show that segregation of elements C, Cr, Ni and Mo exists in the central part of LP rotor at the generator end. The microstructure of LP rotor differs greatly at different locations and no obvious changes are observed in the quantity and size of carbides at high-temperature service locations. The room-temperature tensile properties are clearly different at different locations and no decreasing occurs in the tensile strength at high-temperature service locations. The impact ductility is almost the same for all locations close to the outer rim, which is obviously different for areas near the center hole. The difference of total impact energy is mainly from the crack propagation energy and the crack forming energy is almost the same for all locations. The fracture appearance transition temperature increases for locations enduring high service temperatures. The property non-uniformity is found to be caused by composition segregation and microstructure difference formed during manufacture of the LP rotor due to its too large size.%以1根长期服役的30Cr2Ni4MoV钢低压转子为例,通过显微组织分析、室温拉伸、高温拉伸和冲击以及韧脆性转变温度试验等方法研究了低压转子不同部位的显微组织和性能,并分析了低压转子强度和韧性变化的原因.结果表明:在低压转子电机端中心部位出现C、Cr、Ni和Mo等成分的偏析；转子不同部位的组织形态区别明显,服役时温度高的部位未发生明显的碳化物析出增多和颗粒粗化；转子不同部位的室温拉伸性能差别较大,服役时温度高的部位的拉伸强度未出现明显降低；转子外缘不同部位冲击韧性相同,但近中心孔不同部位的冲击韧性差别大；转子不同部位总冲击能量的区别主要表现为裂纹扩展能的差异,但裂纹形成能无明显区别；服役时转子高温部位的韧脆性转变温度升高；由于低压转子尺寸大,造成制造时不同部位的成分和显微组织的差别,这是导致不同部位性能差异的主要原因.
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