Toward process optimization in pulsed Nd: YAG laser seam welding of zinc coated steel

The study investigates the feasibility of pulsed laser seam welding of zinc coated steel sheets in lap configuration using Lumonics JK 701 Nd : YAG laser. This is a useful and beneficial joining technique for the automotive industry in the assembly lines. Laser seam welds were produced in 0.7 mm thick electro-galvanized steel sheets in the lap-joint configuration with rectangular power pulses. A wide range of process parameters is identified. These includes average peak power density (APPD), mean laser power, traverse speeds, and pulse duration, etc. To optimize the welding process, the effects of these parameters on weld quality are thus systematically investigated. The experimental study suggests that APPD is the most critical factor in governing pulsed laser seam welding application. It is followed by average power and travel speed. As such, the processing map for APPD effects is developed as a guide for effective control and execution of welding application. Accordingly, the pulsed Nd : YAG laser seam welding process can be further optimised by proper choices of APPDs, mean powers, and traverse speeds for producing the best quality welds. That is, welds with no porosity inside the fusion zone.