碱洗塔出口法兰与管线焊缝热影响区产生裂纹原因

Analysis on the Reason of Crack in the HAZ of Weld Connecting Flange and Pipe of Outlet Line in Alkaline Tower

对某厂碱洗塔出口管线的法兰与管线焊缝热影响区产生裂纹的原因进行了分析。对已经发生裂纹的碱洗塔出口管线的法兰与管线的材质作了一次全面的检验、分析和研究后认为该材质的化学成分、机械性能均符合国家标准,母材及焊缝的金相组织均正常,法兰与管线内表面的腐蚀产物主要为Fe3O4,结合表面裂纹形貌判定该裂纹为应力腐蚀裂纹。对应力腐蚀裂纹产生的原因进行了分析,并提出了应对措施。

The cause why the crack occurred in the HAZ of the weld connecting flange and pipe of outlet line was analyzed. The material of flange and pipe occurring crack was tested and analyzed thoroughly, the result shows that the chemical component and mechanical performance of the flange are all coincided with GB9948-88, the microstructure of base material and weld is normal, the corrosion products in the inner faces of flange and pipe mainly is Fe3O4, the crack is considered as stress corrosion crack by its surface shape. The cause of its formation was analyzed and countermeasure was proposed too.