Analysis of heat transfer and material flow in hybrid KPAW-GMAW process based on the novel three dimensional CFD simulation

In this study, a novel electrode-arc-droplet-weld pool model considering the complex interactive phenomena of arc, keyhole and weld pool is developed to investigate heat transfer and material flow in hybrid KPAW-GMAW process, in which the double-ellipse heat source models, arc pressure models, arc shear stress models and electromagnetic force models are adopted. The arc, droplet, keyhole and weld pool are observed by high speed video camera. The temperature of droplet and weld pool are measured by thermal camera. The numerical and experimental results show that: In the KPAW process, two convective eddies exist inside the weld pool. The maximum temperature of the weld pool is firstly increased, then is decreased, and finally becomes stable. In the KPAW-GMAW process, the Pull-Push flow pattern helps to transport the molten metals and energy from the region near the GMAW arc to the region near the KPAW arc, resulting in the temperature increase of the molten metals at the top surface of the rear keyhole. The Marangoni force and arc shear stress are proposed to be the dominant driven forces for the Pull-Push flow pattern on the top weld pool surface between the two arcs, while the droplet impingement has minor influence on it. (C) 2019 Elsevier Ltd. All rights reserved.