Numerical analysis of the heat transfer and material flow during keyhole plasma arc welding using a fully coupled tungsten-plasma-anode model

A coupled tungsten plasma anode mathematical model is first proposed in this paper to analyze the heat transfer and fluid flow in stationary keyhole plasma arc welding (PAW). The calculated plasma arc pressure is validated by a water-cooled copper based arc pressure acquisition experiment. The plasma arc temperature calculated by spectrum experiment in radial direction is used to verify the arc temperature obtained by numerical simulation. The numerical results show that: the evolution of temperature and fluid flow behavior as well as the keyhole formation in the PAW process offers an invaluable insight into the understanding of the physical essence, revealing how the keyhole promotes the deep penetration welding. Besides, the driving forces are quantitatively analyzed to explain the material flow phenomenon in the molten pool. Moreover, the energy input, transformation, transfer, and dissipation due to different physical processes in the PAW process at 0.4 s after arc ignition are calculated and analyzed to understand the energy structure and flow in the system. The findings from the study provide guidance for engineers in designing plasma arc welding schedules to achieve quality welds. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.