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某电厂锅炉投产后首次大修水压试验过程中,低温再热器至高温再热器过渡段管子发现多处漏点,漏点都在管子与防磨罩的焊接处,扩大性检查发现存在大范围该种现象。对照规程及设计参数,对母管及防磨罩材质和焊条材质进行材质分析,同时对现场存在裂纹的管子进行焊接工艺分析,发现普遍存在收弧点弧坑现象。分析结果认为导致裂纹产生的主要原因为防磨罩与管子焊缝较长,导致不同材质间膨胀产生的应力过大,同时焊接收弧点存在弧坑致使裂纹扩展到母材,及焊材选择不符合规程要求。
During the first overhaul of hydrostatic test after the commissioning of a boiler in a power plant, multiple leaks were found in the pipe of the transition section between the low temperature reheater and the high temperature reheater. The leak points were all at the welding place of the pipe and the wear protection cover. Range of this phenomenon. According to the rules and design parameters, the material analysis of the material of the parent pipe and the wear-resistant cover and the material of the welding rod are conducted. Meanwhile, the welding process analysis of the pipe with the crack in the scene is found. The analysis shows that the main reason of the crack is that the wear-resistant cover and pipe weld longer, resulting in the stress caused by the expansion of different materials is too large. At the same time, there is a crater in the welding arc spot to expand the crack to the base metal, Does not meet the rules and requirements.