高速摄像技术中TIG焊接过程的熔池和电极研究

TIG焊接过程中，熔池液体的流动和阴极表面的变化直接影响焊接质量和电弧稳定性的好坏。本采用高速摄像机配合光学窄带滤光片，很好地解决焊接过程熔池液体流动和电极现象的观察困难的问题，研究焊接过程中液面的流动和电极表面的变化情况。研究结果表明：焊接电弧的辐射由一些不连续波长的峰组成，选择950—960nm波长的红外窄带滤光片有选择地降低等离子体电弧的亮度，清晰地观察焊接过程中熔池表面的变化和电极表面的变化。熔池液体的对流的原因是由于温度差别造成的液体表面张力和密度不同、电弧等离子体的压力以及电弧电流的电磁力，液体流动的平均速度为0．12m／s，最高瞬间速度可达0．7m／s。在焊接过程中，电弧上方的电极表面形成钨枝晶和氧化钍富集区，是下一次使用时电弧的起弧点，电弧起弧的稳定性取决于电极尖端氧化钍的含量。

Observation of Melting Pool and Electrode during TIG Arc Welding from High Speed Video Image

Understanding the influence of convection flow of liquid metal dur ing arc welding is very important to improve weld metal characteristics. In this paper, the wavelength distribution of welding plasma arc was studied and the me lting pool and electrode surface were observed using high-speed video camera. Ex periment results show that it was easy to observe the welding pool motion the su rface of cathode when a 950-960 nm interferential optical band pass filter was u sed to reduce the arc brightness to an appropriate value. Main forces to influen ce the fluid flow are surface tension, buoyancy, plasma gas flow and electro-mag netic field by arc current. The average rate of the fluid flow was about 0.12m/s , and sometimes the maximum rate reached up to 0.7m/s. Tungsten dendrite rim and thoria concentration were formed on the surface of tungsten cathode during arci ng operation. The next arc ignition occurred on the regions of Tungsten dendrite rim or thoria concentration. Thoria in the tip of cathode served stable arc ign ition.