This study investigates the effect of welding speed on the microstructure and mechanical properties of pulsed laser lap-welded 0.2 mm 316L stainless steel sheets, commonly used in fuel cell bipolar plates. Welding speeds ranging from 6 to 26 mm/s were tested while other laser parameters remained constant. Results show that increasing welding speed reduces heat input, overlap factor, and weld dimensions. A transition from full to partial penetration occurs beyond 6 mm/s, with no visible heat-affected zone. The weld microstructure features columnar ferrite near fusion boundaries and globular ferrite in the center. Tensile–shear tests reveal that welds maintain higher strength than the base metal up to 22 mm/s, with all fractures occurring in the base material. An optimal speed range of 10–14 mm/s ensures defect-free joints with improved mechanical performance. These findings provide practical guidance for thin-gauge stainless steel welding in fuel cell applications.

This study investigated the effect of magnet working distance on the external magnetic-field distribution, weld-nugget geometry, and mechanical response of GMW2/H1000 dissimilar steel joints produced by magnetic-field-assisted resistance spot welding (MA-RSW). Three-dimensional magnetostatic simulations were performed for working distances of 34, 28, and 22 mm, together with experimental characterization of weld morphology, tensile–shear behavior, microstructure, and microhardness. The simulated magnetic flux density at the geometric weld center increased from 23.88 mT at $H = 34$ mm to 41.63 mT at $H = 28$ mm and 82.39 mT at $H = 22$ mm. The mean nugget diameter increased from $5.14 \pm 0.14$ mm for conventional RSW to $5.67 \pm 0.14$ mm at $H = 22$ mm, while the mean peak tensile–shear load increased from $5738.6 \pm 177.5$ N to $6604.1 \pm 211.1$ N, corresponding to a 15.1% increase. A first-order geometrical analysis showed that the equivalent fusion area increased by approximately 21.7%, indicating that nugget enlargement is an important contributor to the improved load-bearing capacity. Optical microscopy revealed a finer and less directionally developed dendritic morphology under MA-RSW. The results are consistent with an additional electromagnetic influence, although molten-metal flow was not directly resolved by the present magnetostatic model.