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某电厂600 MW亚临界机组12Cr1Mo V钢末级再热器管运行51 020 h后发生爆裂。采用光学显微镜、扫描电镜等设备,从宏观检查、氧化层检测、组织分析和能谱分析方面对失效管样进行研究。结果显示,爆口呈长期过热开裂宏观特征。管样向火侧氧化层过厚,组织球化严重。爆口处向火侧管壁存在明显的蠕变孔洞和沿晶裂纹,裂纹沿着晶界发展并充满氧化物。能谱分析结果显示,末级再热器管向火侧管壁在长期服役过程中,基体出现固溶合金元素贫化,导致组织劣化。综上,12Cr1Mo V钢末级再热器管失效是由长期过热引起管件向火侧组织劣化、蠕变开裂造成的。
A power plant 600 MW subcritical 12Cr1Mo V steel last stage reheater tube running after 5120 h burst. Using optical microscopy, scanning electron microscopy and other equipment, from the macroscopic examination, oxide layer detection, tissue analysis and energy spectrum analysis of failed tube samples. The results show that the explosion has long-term overheating crack macroeconomic characteristics. Pipe-like to the fire side of the oxide layer is too thick, serious tissue spheroidization. There are obvious creep holes and intergranular cracks to the fire side wall at the crack mouth, and the crack develops along the grain boundary and is filled with oxide. The results of energy spectrum analysis showed that during the long service life of the reheater tube to the fire side, the solid solution alloyed element was depleted in the matrix, resulting in the deterioration of the microstructure. In summary, 12Cr1Mo V steel end-stage reheater tube failure is caused by the long-term overheating caused by the pipe to the fire side of tissue deterioration, caused by creep cracking.