Microstructure and properties of S30432 steel tube after long-term service at high temperature
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通过室温拉伸、室温冲击、硬度测试、高温拉伸、金相显微镜、扫描电镜和能谱仪等手段研究了超超临界锅炉服役79 000 h S30432钢管的组织和性能.结果表明,S30432钢管高温服役79 000 h后,室温硬度和抗拉强度升高,塑、韧性均显著降低,断后伸长率已低于标准要求;高温下抗拉强度和塑性显著降低,670℃抗拉强度已低于标准外推值;组织严重老化,孪晶消失,除NbC、M23C6等碳化物外,晶内、晶界均不同程度析出了硬脆的σ相,是导致塑、韧性及高温抗拉强度大幅下降的主要原因.
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 M23 C6,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.
S30432 steelhigh temperature long-term servicemicrostructureσ phasemechanical properties
NETL
NSTL
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