管线钢焊接接头韧性影响因素及评价方法

Research Status of Influencing Factors and Evaluation Methods for Toughness of Pipeline Steel Joints

长输管道环焊缝的部分失效是由于焊缝韧性不足导致断裂,这对长输管道的韧性提出了更高的要求。首先详细分析了焊条电弧焊、半自动焊和全自动焊在管线钢焊接中的应用情况及其优缺点。其次总结了影响焊接接头韧性的主要因素:管线钢合金成分、微量元素、焊接接头组织、残余应力、晶体学特征及强度匹配。最后介绍焊接接头韧性的主要评价方法:夏比冲击实验、落锤撕裂实验(DWTT)和裂纹尖端张开位移(CTOD)实验。并指出强度匹配的概念有待进一步明确,不同强度匹配接头的韧性断裂机理有待进一步探究。由于坡度的影响,焊缝两侧热影响区不对称,建议在山区条件下焊接工艺评定时热影响区的冲击、落锤撕裂和CTOD实验区分上下坡口。

Partial failure of girth welds in long-distance pipelines is due to fracture due to insufficient weld toughness,which puts forward higher requirements for the toughness of long-distance pipelines.Firstly,the application and advantages and disadvantages of electrode arc welding,semi-automatic welding and fully automatic welding in pipeline steel welding are analyzed in detail.Secondly,the main factors affecting the toughness of welded joints are summarized:pipeline steel alloy composition,trace elements,microstructure of welded joints,residual stress,crystallographic characteristics and strength matching.Finally,the main evaluation methods for the toughness of welded joints:Charpy impact test,drop weight tear test(DWTT)and crack tip opening displacement(CTOD)test.It is also pointed out that the concept of strength matching needs to be further clarified,and the ductile fracture mechanism of joints with different strength matching needs to be further explored.Due to the influence of the slope,the heat-affected zones on both sides of the weld are asymmetrical.It is suggested that the impact,drop weight tear and CTOD experiments of the heat-affected zone in the welding process evaluation under mountainous conditions should be distinguished from the upper and lower grooves.