| Abstract Scope |
Copper plays a critical role in electric vehicle manufacturing, particularly in components like battery connectors, busbars, and electric motor windings. Laser welding is widely used for precision joining of intricate parts, and high-quality joints are essential to ensure the reliability and performance of copper components. However, achieving high-quality welds in copper is challenging due to its high thermal conductivity and reflectivity to near infrared laser, which result in poor laser absorption and high susceptibility to defects such as porosity and spatter. Hence, multiple laser process parameters need to be optimized to produce high-quality welds and reduce defect formation. Multi-physics simulations of the molten pool during laser welding are crucial to help understand the complex interactions between the laser beam and the material, predict molten pool behavior, and optimize welding parameters. A prerequisite for these simulations is an accurate description of the laser absorption by copper. However, there exists a large scatter in the laser absorptivity values reported in the literature which can alter the accuracy of simulations. Specifically, the laser absorption is highly non-linear due to its dependence on temperature and incident angle is currently not well understood.
Here, we present a 3D-transient heat transfer and fluid flow model that simulates keyhole-mode welding of copper with near-infrared lasers with varying beam distribution. The model incorporates relevant physics in a keyhole mode welding by utilizing electrical resistivity-based temperature- and angle-dependent copper absorptivity. The model is used to study how the beam distribution affects the critical parameters like nominal absorption, keyhole collapse, and their resultant effect on solidification time, bead profiles, and temperature distribution. The simulation results are further validated against experimental data, including in-situ high-speed images for melt pool size, cross-sectional analysis, and thermocouple measurements available in the literature. |