NM450/ZG30SiMn构件双丝窄间隙GMAW焊缝成形及组织与性能

Formation of weld,microstructure and performance of NM450/ZG30SiMn components by double wire narrow gap GMAW

采用双丝GMAW进行了50 mm厚NM450与ZG30SiMn异种钢材的窄间隙焊接。在模拟窄间隙坡口内进行了焊丝角度与焊接模式的探索,发现当焊丝夹角为6°、2个焊机的焊接模式均为恒压时,能够得到成形良好、无宏观缺陷的焊接接头。在进行厚板焊接时,2个电弧能够在侧壁稳定燃烧,并且熔体能够充分流动并润湿侧壁使得焊缝呈凹面形态。由于2根焊丝之间呈一定角度,侧壁未熔合缺陷得到有效抑制,并且在未预热的条件下也未出现宏观裂纹。焊缝组织主要为大量针状铁素体与少量块状铁素体,盖面层存在有较多的块状铁素体,而且块体比较大,而打底层与填充层块状铁素体数量较少,而且块体比较小,这也导致打底层焊缝的显微硬度大于填充层焊缝的显微硬度大于盖面层焊缝的显微硬度。

Narrow gap welding of 50 mm thick NM450 and ZG30SiMn dissimilar steels was carried out with double wire GMAW.Angle of welding wire and welding mode were explored in simulated narrow gap groove.It was found that when angle of welding wire was 6°and welding mode of two welders was constant pressure,well-formed welded joints without macroscopic defects could be obtained.In thick plate welding,two arcs could burn stably on sidewall,and melt could flow sufficiently and wet sidewall to make weld appear concave.Due to presence of angle between two wires,incomplete fusion of sidewall was effectively suppressed,and no macroscopic cracks appeared under the condition of no preheating.Microstructure of weld mainly consisted of a large amount of acicular ferrite and a small amount of massive ferrite.There was more massive ferrite in covering layer,and massive ferrite was relatively large,while number of massive ferrite in backing layer and filling layer was small,and massive ferrite was relatively small.Consequently,microhardness of backing layer was greater than that of filling layer and microhardness of filling layer was greater than that of covering layer.