Influence of base metal geometry on heat dissipation, molten pool dynamics, and solidification behavior in GMAW bead formation

The geometrical configuration of the base metal can alter heat dissipation and molten pool behavior during gas metal arc welding (GMAW), even when the same nominal welding parameters are applied. This study investigated the effect of base metal width on heat dissipation, bead morphology, and solidification behavior using bead-on-plate experiments and three-dimensional computational fluid dynamics (CFD) simulations. SS400 base metals with widths of 150, 40, and 8 mm were welded using ER70S-6 filler wire under the same nominal welding parameters. As the base metal width decreased, the molten pool length increased from 29.3 to 38.2 mm in the experiment and from 28.5 to 41.4 mm in the simulation, whereas the centerline penetration depth decreased from 3.18 to 2.30 mm. In the 8 mm base metal, the high-temperature and molten regions extended markedly toward the rear and lateral edges owing to the restricted transverse heat-dissipation path and direct edge interaction. The numerical model predicted corresponding changes in the instantaneous flow field and solidification-front evolution, while the thermal history showed slower post-arc cooling in the 8 mm case. These results demonstrate that lateral base-metal geometry strongly influences molten-pool evolution, penetration profile, and solidification behavior under the investigated GMAW conditions. The findings provide fundamental insight into GMAW bead formation on narrow and geometrically constrained base metals.