Optimizing Weld Geometry for High-Speed Wire-Fed Laser Welding of Thin-Gauge Press-Hardened Steel

Abstract

As the automotive industry continues to prioritize fuel efficiency and performance, the demand for stronger, lighter materials, such as press-hardened steel (PHS) increases in vehicle design. This research examines the impact of high-speed wire-fed laser welding parameters on the final weld bead geometry for thin-gauge Al-Si coated PHS sheets used as tailor welded blanks. The primary objective is to determine the optimal laser welding parameters that consistently produce defect-free welds, with reinforcement and undercut values not exceeding 10% of the material thickness, while achieving the highest possible travel speeds. A comparative analysis is conducted on key welding parameters including laser spot diameter size, laser power, wire feed speed, travel speed, and sheet gap size to establish best practices for laser welding in thin-gauge press-hardened steels. To identify the individual contribution of each laser welding parameter on the final weld geometry, a variety of welding conditions are tested such that the individual influence of each specific welding parameter is isolated and compared against macroscopic weld cross-sectional measurements, primarily focusing on the degree of excess reinforcement and undercut. It is shown for welding 1 mm thick Al-Si coated PHS blanks that utilizing a laser spot diameter size of 0.6 mm, a laser power of 4500 W, a wire feed speed of 2.75 m/min, a travel speed of 8 m/min and a sheet gap size of 0.04 mm consistently produced welds with geometry not varying by more than 10% of the base materials thickness for undercut and excess reinforcement. These findings provide a better understanding of laser welding parameters required for welding Usibor®1500 at higher welding speeds.