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某超临界参数直流锅炉高温过热器出口三通在累计运行近5?104h后发生泄漏。对该失效三通进行解体,采用宏观检验与微观组织观察、力学性能检验、有限元蠕变应力分析等方法,开展裂纹观察分析、材质性能评价,并结合厚壁三通的生产工艺进行原因分析。研究结果表明:三通本体、主裂纹附近及相邻管均未出现明显的长时蠕变空洞、组织严重老化等特征,无明显因运行导致的组织过热特征,强度校核满足设计要求。主裂纹直管肩部过渡区内壁内凹带处启裂,并向外壁扩展。该裂纹在三通热挤压成型过程中形成,在服役过程中进一步扩展直至断裂失效。
A supercritical parameters of the boiler after the high temperature superheater exports tee in the cumulative run nearly 5? 104h after the leak. The disintegration of the failed tee was carried out, and the crack analysis and material property evaluation were carried out by macroscopic examination, microstructure observation, mechanical property test and finite element creep stress analysis, and the reasons were analyzed in combination with the production process of thick-walled tee . The results show that there are no long-term creep voids and serious aging in the tee body, the main crack and the adjacent tubes. There is no obvious overheating of the tissue due to the operation, and the strength checking meets the design requirements. The crack in the inner wall of the transitional zone of the straight crack of the straight crack in the main crack is cracked and expanded to the outer wall. The crack formed during the tee extrusion process and further expanded during service until fracture failure.