Microstructure, Performance and Remaining Life Assessment of 12Cr1MoVG Steel Pipe of Final Reheater after Long Service

Using optical microscope, scanning electron microscope, energy spectrometer, Vickers hardness tester and other equipment, the microstructure analysis, performance test and remaining life assessment of the 12Cr1MoVG steel pipe of final reheater of a thermal power unit after 1×10⁵ h service were carried out. The results showed that chemical compositions and mechanical properties of steel pipe met standard requirements, and steel pipe were in a stress safe state. Steel pipe pearlite spheroidization level was 3-4, the alloying elements had produced obvious redistribution phenomenon, and the solid solution alloying elements are obviously depleted. No creep holes were observed, and the creep was in a stable second stage, the equivalent temperature of pipe wall calculated based on oxide scale thickness exceeded the rated steam temperature. There was an over-temperature phenomenon, but it did not exceed the maximum service temperature of 12Cr1MoVG steel. The remaining service life of steel pipe estimated based on oxide film thickness exceeded 100 000 h.