中文摘要：

等离子电弧由于受机械压缩、热压缩和电磁压缩三种压缩效应,电位梯度高,当焊接参数不当时易出现双弧。在铝合金变极性等离子弧焊接反极性期间由于电弧相对正极性期间电弧发散,更易出现双弧。焊接电流与离子气流量的合理匹配、喷嘴孔径与电极内缩量的配合以及变极性等离子弧焊接电源结构等是影响变极性等离子弧双弧的主要因素。通过改进焊接电源的结构及控制方法,即在维弧电源主回路上串接MOSFET管,通过MOSFET管的开通与关断来实现对维弧电源主回路的通断控制,从而避免了铝合金变极性等离子弧焊接反极性期间维弧电源分流形成双弧。通过合理选择焊接参数有效解决了铝合金变极性等离子弧焊接时的双弧现象,在厚板铝合金变极性等离子弧焊接中获得了理想的焊接质量。

英文摘要：

It＇s considered that the electric potential gradient would raise,and it is apt to generate double-arc if inappropriate welding parameters are selected,all these two results are affected by three compressive effects：mechanical compression,heat compression,magnetic compression.Compared with positive polarity time,reverse polarity time in aluminum alloy variable polarity plasma arc welding（VPPAW） is easier to generate double-arc.The reasonable matching of welding current with plasma gas flow rate,orifice diameter with electrode neck-in,and the power source structure of VPPAW are the main factors that influence the double-arc of VPPA.By improving welding force configurations and controls,joining-up MOSFET tubes in main circuit of dimensional arc power supply which can be controlled with the switch of MOSFET tubes,the formation of double-arc is avoided.Furthermore,by reasonably selecting the welding parameters,the double-arc phenomenon in aluminum alloy VPPAW is solved,thus obtaining desirable welding quality.