Measurement of beam energy absorption in CO2 laser beam welding

Abstract

Rate of absorption of CO2 laser beam energy during bead-on-plate welding of SM400 mild steel plate was measured. A 10 kW industrial CO2 laser welding equipment was used in this study. In the first part of the experiments, bead-on-plate welding was made on a water-cooled steel plate placed in a welding jig made of acrylic plastics. The surface of the steel plate was machine-finished. The laser beam energy absorbed into the steel plate was calculated from the measurements of the inlet and the outlet water temperatures, the water flow rate and the beam-on time. Rate of absorption was calculated as the ratio of the absorbed beam energy to the total beam power. In the second part, bead-on-plate welding was carried out on either a machine-finished, a paint-coated on machine-finished or a ground-finished steel plate. Absorption met also evaluated. In the third part, heat conduction loss to the acrylic welding jig was evaluated and found to be approximately 5%. The results of measurements and calculation were reported and discussed. It was estimated in this study that absorption of CO2 laser beam energy during bead-on-plate welding of a mild steel plate at a laser power of 10 kW was in the range from 30 to 50%.