Laser beam welding of copper under vacuum to extend the process limits

Abstract This study explores challenges and innovations in laser beam welding of copper, focusing on infrared lasers, beam shaping and laser welding under vacuum (LaVa). Using a Trumpf TruFiber 2000 P and a Trumpf TruDisc 6000 with BrightLine technology, the research examines copper welding under reduced ambient pressure to improve process stability and seam quality. Single-mode welding shows improved stability with reduced melt ejection and minimal to no porosity. High-speed camera observations show unique behaviour for the analysed parameters, such as a smaller molten pool (2.4 to 4.0 times smaller) and capillary expansion (1.7 to 2.7 times larger) under vacuum conditions. BrightLine technology similarly shows a smaller molten pool (2.0 to 3.3 times smaller) and increased stability. While single-mode welding does not significantly increase penetration depth, multimode welding achieves greater penetration depth (up to 34%) at lower welding velocities (50 mm/s) under vacuum. Comparisons between atmospheric and vacuum welding highlight the benefits of the latter, emphasising uniformity and minimal melt ejection. Process stability correlates with weld quality, demonstrating the benefits of vacuum conditions. The combination of vacuum and established welding techniques extends process boundaries, achieving higher stability and seam quality with both types of lasers. The results indicate that vacuum conditions combined with proven welding approaches enhance copper laser welding. The potential for greater stability and improved weld quality under vacuum, particularly in single-mode welding, enables lower welding velocities down to 8.3 mm/s. Lower velocities, associated with higher energy per unit length, enable greater penetration depths.