TWI Industrial Member Report Summary 333/1987
By I M Norris
During laser welding, a plasma cloud often forms above the weld pool and interacts with the laser beam. At high laser powers, and low welding speeds, the plasma cloud can significantly reduce the power reaching the workpiece in the form of a focused beam, and therefore limit the weld penetration achieved. A number of techniques have been developed with the aim of reducing the effect of the plasma cloud and hence improving the welding performance of the laser. One such technique employs a mechanical beam chopper to give a pulsed laser output with a pulse duration that is shorter than the time taken to form a significantly absorbing plasma cloud above the weld. In the work reported here, trials have been conducted to determine whether switching of the high voltage electrical supply to a 500W fast axial flow CO2 laser can be used to pulse the laser output in a similar manner, and limit plasma formation when welding Type 316 austenitic stainless steel sheet material.