The welding of thin sheets of various metals with a continuous CO₂ laser and a variety of shielding gases investigated by means of an integrated mathematical model Available to Purchase

An integrated mathematical model previously presented for the laser welding of thin metal sheets under a variety of laser material processing conditions is extended to consider the processing of different materials and shielding gases. Full account is taken of the interaction of the laser generated keyhole with the weld pool. An analytical solution of the heat conduction equation is obtained in the metal, subject to appropriate boundary conditions and is used to calculate weld pool shapes. The absorption of laser energy in the keyhole per unit depth is the sum of the energy absorbed in the plasma per unit depth due to inverse bremsstrahlung absorption processes and that due to Fresnel absorption processes on the boundary of the keyhole. The heat conduction equation is solved in the keyhole using the finite difference method taking full account of the variation of the properties of the plasma with temperature. The total power absorbed per unit depth is matched to the power absorbed per unit depth going into the metal. The keyhole radius together with its shape as a function of depth is computed for different shielding gases and the set of fundamental equations is solved iteratively. A predictive mathematical model of the laser welding process using continuous lasers is thus produced based only on fundamental physical principles. The mathematically computed weld pool shapes are then compared with experimentally determined weld pool shapes with the experimental data characterised by the weld pool length as a sensitive parameter. The mathematically computed power absorbed is then compared with the corresponding experimentally based value. Very good agreement is found in all cases between the mathematical theory and the results of experiment.