站场螺旋焊管环焊缝接头失效原因分析

Cracking Reason Analysis on Circumferential Welded Joints of Spiral Submerged Arc Welded Pipe

通过化学成分、微观组织、断口形貌分析等方法对某管线站场建设中螺旋焊管环焊接头裂纹产生的原因进行了研究。结果表明,裂纹出现于打底焊缝根焊区域,呈现出沿晶+穿晶的开裂形貌,属于焊接冷裂纹。打底焊单面焊双面成形根焊的焊瘤处附近存在未熔合缺陷是裂纹产生的直接原因,焊接工艺不当,中间焊接热输入量过大,导致粗大的粒状贝氏体形成是裂纹扩展的直接诱因。控制根焊焊缝成形,防止焊瘤产生,并且在中间施焊过程中控制焊接热输入量是防止该裂纹产生和扩展的主要途径。

The circumferential welded joints cracking reason of spiral submerged arc welded pipe in certain station was analyzed by chemical composition analysis, microstructure observation, fracture morphology analysis. The results showed that the crack appeared near butt weld toe of pipeline was the welding cold crack, which presents iutergranular and transgranular cracking morphology. The failed fusion defects near the welding beading of backing welding was the direct cause of the cracks. Improper welding process and excess intermediate welding heat input leaded to granular bainite coarse and resulted in crack extension. Excellent weld shape and smaller welding heat input should be the main way of preventing the crack generation and extension.