Tri-Arc双丝焊“Γ”形电弧及其促进方法

"Γ"shaped arc and its promotion method in Tri-Arc dual wire welding

Tri-Arc双丝三电弧焊通过中间第3弧的M弧重新分配焊接热输入,实现高熔覆率低热输入焊接.M弧与主电弧耦合,在整个动态周期表现为“Γ”形和“μ”形及其镜像形态.该文研究“Γ”形电弧的形成机理和热输入调控机制,结果表明,“Γ”形态由“μ”形态转变而来,熔滴振荡引起焊丝末端间距的变化,从而促进耦合电弧“Γ”形态的形成,此时M弧不作用于母材,比“μ”形电弧焊接热输入更低.为提高Tri-Arc双丝焊接低热输入效果,在维持导电嘴末端到工件距离不变的前提下,提高焊枪枪体抬升距离从而改变焊丝末端间距.当导电嘴长度由30 mm增加至35 mm时,随着焊枪抬升,“Γ”形电弧作用时间逐渐增加,能更好地促进电弧热分配,降低Tri-Arc双丝焊接热输入,从而降低熔池最高温度,获得更小宽高比和更小熔深的焊缝.

The Tri-Arc dual wire welding achieves a high deposition rate and low heat input by redistributing the heat input through an intermediate third arc called M-Arc.The M-arc is coupled to the main arc and exhibits"Γ"and"μ"shapes and their mirror images throughout the dynamic cycle.In this paper,the formation mechanism of the"Γ"-shaped arc and the heat input regulation mechanism are investigated first.The results indicate that the"Γ"shape evolves from the"μ"shape,the oscillation of adhered molten droplets induces a variation in the distance between two wire ends,thereby facilitating the formation of"Γ"shape in the coupled arc.In this case,the M-arc does not touch the workpiece,rendering a lower heat input during welding than the"μ"-shaped arc.In order to enhance the low heat input effectiveness of the Tri-Arc dual wire welding,the alteration of the distance at two wire ends is achieved by elevating the welding torch.Simultaneously,the length of the conductive nozzle should be increased to maintaining a constant distance between the tip of the conductive nozzle and the workpiece.When the length of the conductive nozzle is increased from 30 mm to 35 mm,as the welding torch is elevated,the duration of the"Γ"shaped arc phase gradually extends.This extended duration effectively facilitates arc thermal distribution,consequently reducing the heat input during Tri-Arc dual wire welding.As a result,peak value of the highest temperature within the molten pool diminishes,thereby reduced the weld bead width-to-height ratios and weld penetration.