Multiphase and multi-physical simulation of open keyhole plasma arc welding

Plasma arc welding (PAW) is an important technique in the manufacturing industry. To improve the welding efficiency, the special keyhole mode has attracted considerable attention because it has the potential to achieve full penetration without a groove. However, rigorous process con-ditions are required to maintain a stable keyhole mode. For better and more widespread appli-cation in industry, a multiphase and multi-physical model is established to reveal the complicated electro-magneto-thermo-hydro-mechanical phenomena and gas-liquid-solid interactions in the keyhole PAW process. Arc backward reflection and deviation of the heating center occur because of the relative movement in the system, and molten liquid metal is pushed backward and upward to form a salient metal layer at the rear. The maximum height reaches 1.45 mm. Outflow phe-nomenon occurs through the open keyhole, and the outflow temperature and velocity are approximately 6000 K and 60 m/s by the calculation, respectively. The predicted weld pool and keyhole basically coincide with measured results. This study provides a comprehensive understanding of the multiphase and multi-physical interactions in the PAW process, which may help improve the associated techniques.