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某发电公司1 000 MW燃煤发电机组在运行中,Q235B钢循环水母管发生断裂。通过宏观检验、化学成分分析、力学性能测试、金相检验、扫描电镜及能谱分析等方法,对循环水母管的断裂原因进行了分析。结果表明:循环水母管焊缝部位存在未焊透现象及焊渣、焊瘤等夹杂物,焊接质量低、显微组织异常导致焊缝处承载能力差;在腐蚀环境存在的情况下,裂纹在焊渣处形成并快速扩展,导致循环水母管断裂失效。
During the operation of a 1 000 MW coal-fired generating unit of a power generation company, the Q235B steel circulation jelly tube fractured. Through the macroscopical inspection, the chemical composition analysis, the mechanical property test, the metallographic examination, the scanning electron microscope and the energy spectrum analysis and so on, has analyzed the reason of the rupture of the circulation jellyfish tube. The results show that there is the phenomenon of incomplete penetration and the inclusions such as welding slag and welding torch in the welded joints of the circulating jelly tube. The welding quality is low and the microstructure is abnormal, resulting in poor bearing capacity. In the presence of corrosive environment, Spatter at the formation and rapid expansion, resulting in failure of circulation mast rupture.