The Energy Transfer Efficiency in Laser Welding Process

The process efficiency of laser beam welding was measured as a function of travel speed. Temperature measurements were carried out during the bead-on-plate laser welding of mild steel with a focused 2KW CO2 laser beam at various welding travel speeds. The laser welding process efficiency (power delivered to work/power in the beam) was calculated from the ratio of the heat content of the welded the specimen to the available laser beam energy (power × time). In the deep penetration welding region at intermediate travel speeds, the laser beam welding process efficiency (equal to the beam absorptance) was about 65%; but it was only about 28% in the shallow penetration region at high travel speeds. In deep penetration welding, multiple reflections within the penetration cavity enhance absorptance. A calculation based on four reflections within the cavity can account for the observed process efficiency.