Multi-physics coupling model-based numerical analysis of the effect of electric current path on large cross-section electroslag fusion welding

This study investigates the effect of different electric current path configurations on electroslag fusion welding (ESFW) process through a coupled multiphysics model, which integrates finite-element and finite-volume methods. ESFW experiments were carried out using a thick steel plate with dimensions of 1090 × 100 × 600 mm under the electrical parameters of 45 V/3000 A and an initial slag thickness of 100 mm, and the accuracy of the model was verified by the experimental data. The analysis focuses on the impacts of electrode-top, electrode-side, and electrode-bottom electric current paths on various physical quantity, including current density distribution, Joule heat generation, temperature field, liquid-phase volume fraction, slag pool flow dynamics, Lorentz force and slag pool morphology. Key results reveal: The skin effect led to high current density and Joule heat density near the electrode in an inverted triangular distribution. The side scheme exhibited a more uniform current density in the slag pool compared to the top and bottom schemes. At 0.5 m welding height, horizontal melt depths were 46.8 mm (−9.8%), 58.7 mm (+13.1%) and 51.9 mm for top, side and bottom schemes, respectively. Slag pool depths measured 32.2 mm (top), 27.1 mm (side) and 29.5 mm (bottom), with Lorentz force-driven circulation enhancing heat transfer in side/bottom schemes. Electrode-top configuration optimised stability, requiring slag replenishment at 542 mm versus 353 mm (side) and 435 mm (bottom). The electrode-top path achieves balanced efficiency, morphology and safety, making it optimal for large-section ESFW.