省煤器联箱接管座与管排焊接接头泄漏原因分析

通过宏观分析、化学组成分析、金相分析、扫描电镜分析等方法,对省煤器联箱接管座与管排焊接接头泄漏原因进行了分析。结果表明,焊接管化学成分、换算强度均符合GB5310—2008标准要求。熔合区、过热区晶粒组织粗大,甚至形成魏氏组织,使这一区域性能弱化。省煤器联箱接管座与管排焊接接头穿孔是因应力作用下在熔合区、过热区薄弱处首先产生微裂纹,启裂后虽未形成贯穿裂纹,但微裂纹导致缝隙腐蚀,缝隙腐蚀加速裂纹由内向外深化和扩展直至穿孔,产生泄漏。

Analysis of Leakage Reasons for Joint of Tube of Header and Weld Joints of Coil Tube on Coal Economizer

Through macro-analysis,chemical composition analysis,metallographic observation,and SEM,the leakage reasons for joint of tube of header and coil tube of coal economizer was analyzed.The results show that the alloy element compositions of welded tubes and conversion strength both met the standard of GB 5310—2008.The grains at fusion zone and overheated zone were coarse and even formed widmanstaten structure which made the performance of the zone weaken.Leakage from the joint of tube of header and coil tube of coal economizer resulted in the micro cracks in the weakened region of fusion and overheated zone under the thermal stress.Though through-wall crack was not formed after micro cracks initiation,micro cracks resulted in crevice corrosion and the crevice corrosion accelerated crack propagation from the inside outwords,and eventually caused the leakage.