旁路等离子-MIG复合电弧及耦合熔池作用机理与数值分析

Numerical analysis and mechanism investigation of the bypass-current plasma-MIG hybrid arc and the molten pool

旁路等离子-MIG复合工艺是通过等离子焊枪的导电铜嘴与焊丝之间形成的分流弧、焊丝与母材之间的主路弧同轴耦合进行焊接的新型工艺,不但保持了MIG焊的高效性,还可以通过对旁路电流的调节实现焊接过程能量的精确控制.为了深入了解该工艺条件下复合电弧与耦合熔池的物理作用机制,通过建立流体动力学瞬态计算模型,并基于合理的试验验证,对旁路电流加载前后气液两相内部及界面处的传热传质行为进行了对比研究.结果表明,相比未加载旁路电流时,电弧的最高温度下降约1000 K,同时电弧与耦合熔池交界处的有效热通量整体下降;熔池内部液态金属回流速度明显下降,因此导致熔深和熔宽尺寸均有所减少;复合电弧和耦合熔池的最大电磁力方向没有改变,但数值均有所降低.

The bypass-current plasma-MIG hybrid welding is a new process by coaxial coupling of the shunt arc achieved between the conductive copper nozzle of the plasma torch and the welding wire and the main arc between the wire and the base material.This process not only maintains the high efficiency of MIG welding but also provides more schemes for precise control of the welding process energy through the regulation of the bypass current.In order to understand the physical mechanism of action of the hybrid arc and the molten pool under this process,a hydrodynamic transient model was developed and verified with a reasonable experiment to compare the heat and mass transfer behavior inside the gas and liquid phases,and at the interface between them before and after the bypass-current loading.The results show that the maximum temperature of the arc decreases by about 1000 K compared to that without the bypass current,and the effective heat flux at the interface of the hybrid arc and the molten pool decreases overall;the liquid metal flow rate inside the molten pool decreases significantly,and thus leading to a decrease in both dimensions of the penetration and the width;the maximum electromagnetic force direction of the hybrid arc and the molten pool remains unchanged,but the values are reduced.