Microstructure and properties of S30432 steel tube after long-term service at high temperature

doi:10.13251/j.issn.0254-6051.2024.05.003

Abstract

Abstract: Microstructure and mechanical properties of the S30432 steel tube after high temperature service for 79 000 h in ultra supercritical units were studied by means of room temperature tensile and impact test, hardness test, high temperature tensile test, metallographic microscope, scanning electron microscope and energy dispersive spectrometer. The results show that the room temperature hardness and tensile strength of the 79 000 h long-term serviced S30432 steel tube increase, while the plasticity and toughness significantly decrease, the elongation is lower than the standard requirement. The tensile strength and plasticity at high temperature significantly decrease, and the tensile strength at 670 ℃ is lower than the standard extrapolation value. The microstructure of the tube material is seriously aged, and the twins disappear. Except for carbides such as NbC and M₂₃C₆, σ phases precipitate to varying degrees in the grain or at the grain boundary, which is the main reason for the significant decrease in plasticity, toughness and high temperature tensile strength.

Key words: S30432 steel, high temperature long-term service, microstructure, σ phase, mechanical properties

CLC Number:

TG142.1

Yang Xirui, Jiang Baoshi, Hu Fengtao, Li Yanjun, Sheng Chaojie, Wang Chen. Microstructure and properties of S30432 steel tube after long-term service at high temperature[J]. Heat Treatment of Metals, 2024, 49(5): 17-21.

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