研究了12Cr1MoV钢主蒸汽管道在长时（26 a）服役后的显微组织以及室温与高温拉伸性能，并与未服役钢管的进行了对比。结果表明：长时服役后钢管的组织退化表现为珠光体明显球化、层状Fe₃C相明显碎化、铁素体中析出M₇C₃型碳化物以及晶粒明显长大；与未服役钢管相比，长时服役后钢管的室温屈服强度明显降低，但室温抗拉强度变化不大，高温屈服强度和抗拉强度则均明显降低；长时服役后钢管的室温拉伸断口存在典型的纤维区和撕裂区，为韧性断裂，高温拉伸时发生准解理断裂。

Microstructure and tensile properties at room temperature and elevated temperature of main steam piping of 12Cr1MoV steel after long-term (26 a) service were studied, and compared with those of the unused steel pipe. The results show that the structural degradation of the long-term served steel pipe was characterized by obvious spheroidization of pearlite, obvious fragmentation of layered Fe₃C phase, precipitation of M₇C₃ carbides in ferrite and significant growth of grains; Compared with those of the unused steel pipe, the yield strength at room temperature of the long-term served steel pipe decreased significantly, the tensile strength at room temperature changed little, and the yield strength and tensile strength at elevated temperature decreased greatly. The tensile fracture at room temperature of the long-term served steel pipe had typical fiber zone and tear zone, indicating a ductile fracture mode; while during tensile at elevated temperature, quasi-cleavage fracture occured.