The influence of arc transfer mode in hybrid laser-mig welding

In the recently developed welding process, a Laser beam and an electric arc are coupled in order to combine the positive aspects of each technology: high speed, low thermal load and high seam depth, all typical features of the Laser; low cost and ability to withstand poor edge preparation, typical of GMAW arc welding. In particular hybrid Laser Nd:Yag-GMAW welding has been widely studied for thin sheet welding in the automotive industry. On the other hand hybrid Laser CO2-GMAW welding, which is nowadays one of the most promising solutions for optimum power/cost ratio, has significant advantages over Nd:Yag-GMAW in the welding of thick sheets, where high power sources are required. This paper investigates the stability condition of a hybrid Laser CO2-GMAW welding process by analyzing the influence of several process parameters. A first set of experiments was carried out in order to determine the optimal position of the two sources. A second set of trials made it possible to investigate the importance of the filler metal transfer mode on the stability of the whole process. The obtained specimens are I-butt joints of AISI 304 stainless steel sheet 8 mm thick. The depths, widths and reinforcements of the weld beads were measured, related to the controlled process parameters and analyzed by means of a statistical approach.