WELDING EFFECTS ON THE MECHANICAL INTEGRITY OF A TRIP800 STEEL: A COMPARISON OF LASER CO2 AND GMAW PROCESSES

In this work a strip of a transformation induced plasticity (TRIP) steel was welded using gas metal arc welding (GMAW) and Laser CO2 welding (LBW) processes and the resultant strength and ductility of the welded joints evaluated. It was found that LBW lead to relatively high hardness in the fusion zone, FZ where the resultant microstructure was predominantly martensite. The relative volume fractions of phases developed in the welded regions were quantitatively measured using color metallography combined with X-ray diffraction analyses. It was found that the heat affected zone, HAZ developed the maximum amount of martensite (up to 32%) in the steel welded using LBW besides a mixture of bainite, retained austenite and ferrite phases. In contrast, a relatively low percent of martensite (10.8%) was found in the HAZ when the GMAW process was implemented.