Arc discharge and pressure characteristics in pulsed plasma gas of PAW

Abstract

This paper investigated the arc characteristics in pulsed plasma gas of plasma arc welding using a synchronous image- and electrical signal-acquisition system. The arc sizes (including the arc length L, the arc width on the water-cooling copper plate surface Wa, and the arc width under the nozzle Wc) and arc voltage changed regularly with the plasma gas periodically on/off. And the changing trends of arc sizes were affected by the plasma gas flow rate and the plasma gas switching frequency. The changing scale of arc voltage was proportional to the plasma gas flow rate and was inversely proportional to the plasma gas switching frequency. The average plasma arc welding (PAW) and plasma arc welding with pulsed plasma gas (PPG-PAW) arc voltages were equal when the plasma gas flow rate was the same. The arc pressure also presented cyclical changes during the plasma gas on/off, and the changing scale and the axial mean value were inversely proportional to the plasma gas switching frequency. The periodically oscillating arc and arc pressure would be beneficial to the refinement of grain structure during the welding process.