Magnetic field-induced arc coupling and process stabilization in KTIG-MIG hybrid welding: Mechanism, optimization, and performance enhancement

Abstract

A hybrid welding process (KTIG-MIG) that combines keyhole tungsten inert gas (KTIG) welding and metal inert gas (MIG) welding under the external magnetic field was proposed. It effectively solved the instability and poor quality issues of stainless steel welding under pure argon, and overcame arc repulsion and coupling problems. The arc morphology, droplet transfer, electrical signals, probability density distribution, weld formation and microstructure evolution in KTIG-MIG hybrid welding were studied. The results indicated that the magnetic field had spatially optimized and reconstructed the hybrid arcs. Transverse magnetic fields (0–1.8 mT) enabled dynamic equilibrium between Lorentz forces and arc repulsion, achieving optimal coupling at 1.0 mT with KTIG/MIG currents of 300/220 A. This configuration reduced current/voltage fluctuations by 14.6 %/13.7 % and suppressed peak currents below 450 A (50 A reduction vs. non-magnetic conditions). Magnetic confinement transformed droplet behavior from irregular globular to stable jet transfer. The period and fluctuation of electrical signals decreased. In addition, the average current of the MIG was lower than the set value of 220 A, indicating the existence of a shunt channel between arcs. Electromagnetic stirring generated equiaxed grains (9.6–192.2 μm vs. 12.8–316.3 μm baseline), elevating weld hardness to 234 HV through δ-ferrite redistribution.