SOME OF ELECTRICAL EFFECTS IN THE KEYHOLE PLASMA IN DEEP PENETRATION CW CO2-LASER WELDING

The process of laser welding of a material has been extensively studie d from an experimental point of view and considerable mathematical mod elling has been carried out on the cw aspects of the process as well. For a cw CO2 laser a partially ionised plasma is likely to exist in th e keyhole, emerging from it to produce a turbulent plume in which vari ations of electrical charge density have been observed. The presence o f large temperature gradients near the keyhole walls in conjunction wi th the Onsager/de Groot relations has the consequence that there must be an electrical potential gradient in the plasma and associated space -charge distribution, These effects are analysed and quantitative rela tions obtained for the case of a steel work piece.