Process characteristics of fibre-laser-assisted plasma arc welding

Experimental and theoretical investigations on fibre -laser assisted plasma arc welding (LAPW) have been per formed . Welding experim ents were carried out on alumin ium and steel sheets. In case of a highly focused laser beam and a separate arrangement of plasma torch and laser beam, h igh -speed video recordings of the plasma arc and corresponding mea surements of th e time -dependent arc vol tage revealed dif ferences in the process behavio ur for bo th materials. In case of alumin ium welding, a sharp decline in arc voltage and stabiliz ation and guiding of the anodic arc root was observed whereas in steel welding the arc v ol tage was slightly in creased after the laser beam was switched on. However, significant improv ement of the melting efficiency with the combined action of plasma arc and laser beam was achieved for both types of material . Theoretical results of additional numerical simulations of the arc behavio ur suggest that the properties of the arc plasma are mainly influenced not by a d irect interaction with the laser radiation but by the laser induced evaporation of metal. Arc stabil ization with increased current dens ities is predicted for moderate rates of evaporated metal only whereas metal vapo ur rates above a certain threshold causes a destabilization of the arc and reduced current densities along the arc axis.

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