高钢级管线钢自保护药芯焊丝环焊接头韧性影响因素研究

Influencing Factors on Welding Toughness of Self Shielded Flux Cored Wire Girth Welding Joint of High-grade Pipeline Steel

针对高钢级管道自保护药芯焊丝半自动焊接环焊缝韧性离散性较大的问题,结合国内某X80天然气长输管道项目自保护药芯焊丝环焊接头实际分析结果,运用扫描电镜、透射电镜、气体元素分析、化学萃取相分析以及夏比冲击韧性测试等检测手段,对焊缝韧性影响因素进行了综合分析。结果显示,焊缝中夹杂物的平均颗粒尺寸为0.4μm,在解理面或准解理面的起裂位置均未发现夹杂物;自保护药芯焊丝环焊缝中存在一定数量的间隙固溶氮;自保护药芯焊丝中大量Al的加入促进了室温下大量M/A组元的生成。研究表明,夹杂物并不是导致环焊缝韧性离散分布的主要原因,而焊缝中存在的间隙固溶氮和大量M/A组元是导致自保护药芯焊丝环焊缝韧性离散分布的主要原因。

Aiming at the problem of large discreteness of toughness of semi-automatic welding girth weld with self-shielded flux cored wire for high-grade pipeline,combined with the actual analysis results of self-shielded flux cored wire girth weld joint of a X80 natural gas long-distance pipeline project in China,scanning electron microscope,transmission electron microscope,gas element analysis,chemical extraction phase analysis and Charpy impact toughness test are used to analyze the influencing factors of weld toughness.The results show that the average size of inclusions in the weld is 0.4μm and no inclusions are found at the crack initiation position of cleavage surface or quasi cleavage surface.There is a certain amount of interstitial solid solution nitrogen in the girth weld of self-shielded flux cored wire.The addition of a large amount of Al in self-shielded flux cored wire promotes the formation of a large number of M/A components at room temperature.The results show that the inclusion is not the main reason for the discrete distribution of toughness in the girth weld,and the interstitial solid solution nitrogen and a large number of M/A components in the weld are the main reasons for the discrete distribution of toughness in the girth weld of self-shielded flux cored wire.