Numerical Investigation of Heat Transfer During Submerged Arc Welding Phenomena by Coupled DEM-ISPH Simulation

•Heat source distributions of arc with 600 a were simulated by a grid-based method.•Penetration depth obtained by coupled DEM-ISPH simulation agreed with experiment.•Welding flux initially heated the metal and was subsequently heated by the metal.•The slag covering the metal maintained the metal surface temperature. Two-dimensional axisymmetric heat source distributions of the arc plasma were obtained by a grid-based simulation. These distributions and a particle-based method that couples the discrete element method (DEM) and incompressible smoothed particle hydrodynamics (ISPH) were then applied to verify the mechanisms of slag and weld pool formation and the thermal effects of flux and slag on the base metal, weld pool and weld bead. The slag and weld pool were simulated together, and their formation and resolidification mechanisms were verified. The velocity fields in the weld pool showed that the transport of high-temperature molten metal from the weld pool surface behind the center of the heat source to the bottom of the weld pool heated the bottom of the weld, leading to deep penetration. It was found that the heat on the metal surface near the heat source was temporarily absorbed by the flux, and the heat was transferred back to the metal surface after the heat source passed. The temperature decrease of the metal surface was also limited by the slag covering the metal surface, leading to a higher surface temperature in submerged arc welding than in gas metal arc welding.