电极极性和保护气体种类对TIG电弧辅助MIG焊引弧性能的影响

Effects of electrode polarity and shielding gas type on arc ignition of TIG arc-assisted MIG welding

通过电信号-高速摄像采集系统记录钨极惰性气体保护-熔化极惰性气体保护(TIG-MIG)复合焊引弧过程中的电压-电流信号和电弧图像,研究了TIG焊和MIG焊的电极极性接法、MIG焊保护气体种类对TIG电弧辅助MIG焊引弧性能的影响。试验结果表明:MIG焊采用直流反接是TIG电弧辅助MIG焊依靠细长放电通道实现非接触引弧的必要条件,TIG焊采用直流正接还是反接仅影响TIG电弧辅助MIG焊实现非接触引弧的容易度;MIG焊非接触引弧是由于TIG电弧外层的电子向MIG焊丝末端移动,在途中与周围的保护气体发生频繁碰撞并使之部分电离,产生大量正负带电粒子,导致间隙的电导率显著提高,以致间隙在低电压下发生了电击穿;相比Ar+1%O2(体积分数)和Ar+15%CO2(体积分数),MIG焊在纯Ar中实现非接触引弧更容易。

The voltage and current signals and arc images during arc ignition of tungsten inert gas-metal inert gas(TIG-MIG)hybrid welding were recorded using a data acquisition system and a high-speed camera.The data was used to study the effects of electrode polarity of the TIG welding and the MIG welding and the shielding gas type for the MIG welding on the arc ignition of TIG arc-assisted MIG welding.MIG welding with direct current electrode positive is necessary for TIG arc-assisted MIG welding to achieve non-contact arc ignition through an elongated discharge channel.TIG welding with direct current electrode negative or positive only affects the ease of non-contact arc ignition for TIG arc-assisted MIG welding.MIG welding achieves non-contact arc ignition because the electrons in the outer layer of the TIG arc move towards the end of the MIG welding wire where they collide with neutral particles in the surrounding shielding gas which ionizes some of them and generates many positively and negatively charged particles.The gap conductivity then significantly increases and the gap breaks down at low voltage.MIG welding with pure Ar shielding gas more easily achieves non-contact arc ignition than with Ar+1%O2(volume fraction)or Ar+15%CO2(volume fraction).