利用光学显微镜、扫描电镜、能谱仪、拉伸及冲击试验机等对服役15 a的制氢转化炉中HP40Nb钢炉管的显微组织和力学性能进行了研究,依据高温持久试验结果估算了炉管剩余寿命.结果表明:长期高温服役后,炉管钢组织中晶界粗化并有G相析出,晶内二次碳化物析出明显,近内壁、近外壁和基体中均出现蠕变孔洞,近内壁和近外壁发生氧化和贫铬,外壁形成脱碳层;与原始铸态炉管相比,长期高温服役后炉管的室温抗拉强度降幅超30%,高温抗拉强度降幅约18%,室温冲击功下降明显,剩余寿命不足1 a.
The microstructure and mechanical properties of HP40Nb steel furnace tube in a hydrogen reformer after 15-year service were studied by optical microscope, scanning electron microscope, energy dispersive spectrometer, tensile and impact testers.Based on the high-temperature creep rupture testing results, the remnant life of the furnace tube was evaluated.The results show that after the long-term high-temperature service, in the microstructure of furnace tube steel, the grain boundaries coarsened with the G phase precipitation;secondary carbides precipitated in grains obviously;creep voids were observed near inner and outer wall and in matrix;oxidation and chromium depletion were observed near inner and outer wall;decarburization layer was formed on the outer wall.Compared with the as-cast steel furnace tube, the tensile strength of the furnace tube after the long-term high-temperature service reduced by 30% and 18% at room and high temperature, respectively, the impact energy at room temperature decreased significantly, and the remnant life was less than 1 a.
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