A Study on the Weldability of Cylindrical Secondary Battery Material using Green Laser

Abstract

This study investigates a green laser welding on a nickel-coated copper-mild steel material used in an electric vehicle battery. The laser power and scan speed were varied, and through optical microscopy, it was demonstrated that excessive heat input led to increased weld penetration depth and bead width. Regarding defects, excessive heat input caused the formation of oxide, spatter on the bead surface, as well as porosity and cracks inside the weld penetration depth. The mechanical properties were evaluated through shear stress and microhardness measurements, indicating that as the heat input increased, the mechanical properties improved for the sample welded under the 2 kW condition. Considering the fire risk (occur at weld penetration depth over 50%) and joining aspects (start at weld penetration depth higher 20%), the optimal conditions were set as 1.6 kW and 300 mm/s. This optimized condition was set as the reference for monitoring. Based on the optimized condition, the results shown that an increase in heat input led to increased plasma and temperature signals, and an increase in scanning speed resulted in an increase in reflected light signal.