Effects of Joint-Edge Preparation on Weld Quality and Mechanical Properties of Thin AISI 304 Stainless Steel Sheets Under Autogenous and Filler-Wire Laser Beam Welding Conditions

Laser beam welding (LBW) offers low thermal distortion for thin austenitic stainless steel sheets but is sensitive to butt-joint fit-up and edge quality. This study compared machined and sheared joint edges under selected autogenous and ER308L filler-wire LBW conditions. Bead geometry, defects, microstructure, microhardness, tensile properties, and fracture behavior were characterized using conventional microscopy, EBSD-KAM, and three-dimensional digital image correlation (3D-DIC). The machined-edge autogenous condition (LBW-A-M) produced a stable bead with 0.04 mm top underfill and only a small number of internal discontinuities, while its tensile properties remained close to those of the base metal and fracture occurred in the base metal. In contrast, the sheared-edge autogenous condition (LBW-A-S) exhibited 0.24 mm top underfill, 0.18 mm misalignment, multiple pores, and localized strain near the weld, with tensile strength and elongation of 682.31 MPa and 44.04%, respectively. Under the selected filler-wire conditions, no measurable top underfill was observed, although pores remained. Because the autogenous and filler-wire modes used different process parameters and heat inputs, cross-mode differences are condition-specific rather than isolated filler-wire effects. Overall, joint-edge preparation and fit-up control remained important for thin-sheet LBW.