单电源VPPA-GTA双面穿孔焊缺陷机理分析与工艺优化

Defect Mechanism Analysis and Process Optimization of Single-supplied VPPA-GTA Double-sided Keyhole Welding

针对铝合金传统单电源VPPA-GTA双面穿孔焊缝黑色氧化物夹渣问题,借助电信号传感、图像采集及图像处理手段对缺陷机理进行探究,获取焊接匙孔形成前后的电弧电压及电弧形态变化。分析发现匙孔形成后穿透电弧截面积明显变小,工件上阴极斑点大幅消失,造成工件反极性电压阶跃下降,阴极雾化作用减弱。为消除黑色氧化物夹渣缺陷,提出一种新型单电源VPPA-GTAW双态电弧穿孔焊接方法。通过优化变极性等离子弧电源DCEN段和DCEP段输出电流的流向,可在电源不同输出时间段形成等离子焊枪与工件间的正极性等离子电弧和等离子焊枪与TIG焊枪间的反极性穿透电弧。这两种电弧交替形成的双态电弧兼具变极性等离子弧的氧化膜清理作用和单电源穿孔电弧能量集中的优点,可获得良好的焊缝成形。

For the black oxide slag defects in the process of traditional single-supplied VPPA-GTAW double-sided keyhole welding of aluminum alloy, the defect mechanism was studied by using electrical signal sensing, image acquisition and image processing, and the current-voltage characteristics and arc shapes before and after the keyhole formation were obtained. The results show that the cross-sectional area of the penetrating arc after the keyhole formation decreases significantly, and the cathode spots on the workpiece disappear dramatically, which results in drop of reversed polarity voltage of workpiece and weak of cathode atomization effect. In order to eliminate the black slag defects, a new single-supplied VPPA-GTA dual-status arc welding method was proposed. By optimizing the output current direction of DCEN section and DCEP section of the variable polarity plasma arc power supply, the positive polarity plasma arc can be formed between plasma welding gun and workpiece, and the reverse polarity penetration arc can be formed between plasma welding gun and TIG welding gun. The dual-status arc owns the advantages of both the oxidation film cleaning effect of VPPA and the energy concentration of single power supply perforated arc, and good weld formation can be obtained.