Analysis of droplet transfer mode and forming process of weld bead in CO2 laser-MAG hybrid welding process

In this paper, CO2 laser-metal active gas (MAG) hybrid welding technique is used to weld high strength steel and the optimized process parameters are obtained. Using LD Pumped laser with an emission wavelength of 532 nm to overcome the strong interference from the welding arc, a computer-based system is developed to collect and visualize the waveforms of the electrical welding parameters and metal transfer processes in laser-MAC. The welding electric signals of hybrid welding processes are quantitatively described and analyzed using the ANALYSATOR HANNOVER. The effect of distance between laser and arc (D-LA) on weld bead geometry, forming process of weld shape, electric signals, arc characteristic and droplet transfer behavior is investigated. It is found that arc characteristic, droplet transfer mode and final weld bead geometry are strongly affected by the distance between laser and arc. The weld bead geometry is changed from "cocktail cup" to "cone-shaped" with the increasing D-LA. The droplet transfer mode is changed from globular transfer to projected transfer with the increasing D-LA. Projected transfer mode is an advantage for the stability of hybrid welding processes. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.