俄制超临界机组再热蒸汽管道焊接接头裂纹解析

Analysis of Welded Joint Cracks in Steam Reheating Piping of a Russian Supercritical Unit

针对某火电厂俄制超临界机组运行7万h后,高温再热蒸汽管道(15x1M1φ)焊接接头裂纹并漏泄进行失效分析,通过宏观和微观组织研究发现,该焊接接头存在较大残余应力和应力集中,塑性储备不足、临界塑性变形能力εc低,为典型的耐热钢再热裂纹。管系结构、焊接和焊后热处理工艺不当是导致裂纹的主要原因,需对已经发现裂纹的焊接接头制定修复措施。同时,改善焊接及焊后热处理工艺,对其它暂未发现宏观裂纹的管道焊接接头进行UT、MT、PT等无损检验,以排除隐患。

Aiming at elucidating the steam leakage induced by the crack in the welded joints of high temperaturesteam reheating piping(15X1M1φ)in a Russian supercritical unit after70000hours,the failure analysis wasconducted.By the macroscopic and micro-structure observation,it is showed that the welded joints had large residual stress and stress concentration,a lack of plastic reserves and low critical plastic deformation capacityεc,therefore it is a typical reheat cracking of heat resistant steel.Pipeline structure,welding and post-weld heat treatment process is the main reasons leading to this crack.In order to eliminate it,it is necessary to take the repairing measures in the welding joints,improve the welding and post-weld heat treatment process,and develop thenon-destructive testing just like UT,MT,PT,etc for the other welded joints without the macroscopic cracks.