Radiative emission in the laser welding of thin metal sheets

This paper calculates the infra-red, ultra-violet and weak X-ray emission that occur in the welding of thin metal sheets using a continous CO₂ laser. The various radiative contributions are evaluated on the basis of an integrated mathematical model for the laser welding of thin metal sheets that has been developed in a previous paper. That model furnishes, in essence, temperature contours in the weldpool as well as its shape and the temperature distribution in the laser generated keyhole as well as its radius. The infra-red and ultra-violet signals emitted in the laser welding are determined by integrating the temperature in the weldpool and of the keyhole respectively over the appropriate regions, using the Planck distribution. Visible and weak X-ray contributions are also evaluated. The mathematically calculated radiative contributions are compared with the results of experiments where possible and satisfactory agreement is found. This serves to validate further the mathematical model for the integrated keyhole and weldpool in the laser welding of thin sheets.