ABSTRACT Cracking failure of butt-welded joint of 12Cr1MoV tube was comprehensively studied. Results show that both of initiation and propagation of the primary crack were circumferentially intergranular in the coarse-grained heat affect zone (CGHAZ). Many isolated and intergranular micro-cracks and cavities were observed near the primary crack．Neither oxide or corrosion products were observed in the isolated cavities or micro-cracks. According to the microstructure, location, propagation mode and morphology of the crack，the primary crack in butt-welded joint is concluded to be the intergranular reheating cracking (IRC). The crack failure is mainly due to poor welding quality, characterised by high residual stress and coarsened grain size. Mechanisms on the IRC based on previous laboratory research were studied on the failed tube sample, and results showed that the IRC is accumulation of high-stress induced creep damage, such as cavities along prior austenite grain boundaries (PAGBs). Neither segregation of alloys elements nor trace impurities were detected.

中文翻译：

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服役40000小时12Cr1MoV管对焊接头晶间再热裂纹机理

摘要 对12Cr1MoV管对焊接头的开裂失效进行了综合研究。结果表明，在粗晶热影响区（CGHAZ）中，初级裂纹的萌生和扩展都是沿周向晶间的。在初级裂纹附近观察到许多孤立的和晶间的微裂纹和空洞。在孤立的空洞和微裂纹中没有观察到氧化物或腐蚀产物。根据裂纹的显微组织、位置、扩展方式和形貌，对焊接头的主要裂纹为晶间再热裂纹（IRC）。裂纹失效主要是由于焊接质量差，其特点是残余应力高，晶粒粗化。基于先前实验室研究的 IRC 机制对失败的管样品进行了研究，结果表明，IRC 是高应力引起的蠕变损伤的积累，例如沿原奥氏体晶界 (PAGB) 的空腔。没有检测到合金元素的偏析和痕量杂质。