Experimental investigation on heat transfer of different phase in variable polarity plasma arc welding

Abstract

The heat-transfer properties of variable polarity plasma arc (VPPA) during the electrode negative (EN) phase and electrode positive (EP) phase in the real-time process are the key factors for the stability control and optimization of the welding process. In this paper, the heat transfer of different phase in the variable polarity plasma arc was investigated by measuring the real-time temperature of the heat capacity medium in the workpiece. Based on the heat transfer mechanism of VPPA in the phase of EN and EP, the influence rule of current on heat transfer characteristics and the correlation mechanism of heat transfer during EN and EP phases were studied. The experimental results show that with the same current increase in both phases, the heat transfer of arc has a more increase in EN phase. However, the heat transfer efficiency of the arc has a more decrease in EP phase due to its special arc behavior. Furthermore, the effect of thermal inertia between positive and negative polarity on the next phase of heat transfer could be ignored. That is to say, the positive and negative polarity currents have great influence on the heat transfer characteristics of each polarity, and this influence will not save to the next phase.