Physical mechanism of polar zone phenomena in cross-coupling arc welding

Abstract

As a new-type welding heat source, cross-coupling arc (CCA) is able to realize the decoupling control of heat transfer, force transfer and mass transfer in welding process. However, the physical mechanism of CCA still remains unclear, restricting the application and optimization of CCA welding technology. In order to explore the laws and causes of polar zone phenomena (PZP) in CCA welding and based on the electromagnetic field effect of the inter-wire arc (IWA) itself, the novel methods of an electrified tungsten rod crossing a free burning arc and an electrified parallel plate capacitor applied to both sides of a burning arc were designed to decouple the electromagnetic coupling field generated by the IWA. The arc shape during the experiments was recorded by a high-speed camera system in real time. The results show that the laws of PZP in CCA welding were supplemented and summarized. When the main arc polarity is direct current electrode negative, the main arc deflects to the IWA cathode, and when the main arc polarity is direct current electrode positive, the main arc deflects to the IWA anode. More importantly, the causes of PZP were found. The magnetic field generated by the IWA and the limitation in bottom area and position of the main arc tungsten electrode are the causes of PZP. The direction control of PZP could be achieved by adjusting the polarities of the IWA or the main arc and the PZP effect could be reduced by changing the current direction in the IWA.