Research on the Optimization of Oscillation for the Joint Quality of Laser Welded Joints in Automobile Seat Frames

Abstract

The increasing adoption of high-strength steel in automotive manufacturing has made laser welding a preferred technique due to its ability to reduce thermal deformation and facilitate single-sided welding. Despite these advantages, challenges persist, particularly in achieving precise welds at the edges of seat frame assemblies. This study explores the application of laser weaving techniques to improve joint strength and penetration depth. The critical variables evaluated include defocusing distance and weaving parameters, which were assessed for their impact on penetration depth, effective joint width, and edge weld quality in a three-sheet stack of dual-phase (DP) steel. Results indicate that increasing the defocusing distance from 5 mm to 20 mm at a fixed oscillation frequency of 20 Hz leads to a corresponding increase in surface bead width. A significant correlation was found between the effective joint width and maximum tensile shear strength, with the highest strength of 34.6 kN observed at an 8 mm defocusing distance. Additionally, the use of oscillation in the welding process improved tensile shear strength by approximately 9 kN compared to line welding without oscillation. Oscillation also enhanced microstructural properties, demonstrating that optimal welding conditions can be achieved even with off-position welding. These improvements are attributed to minimized heat-affected zone (HAZ) effects, which contributed to increased joint strength and hardness.