Development of laser beam welding of advanced high-strength steels

Abstract

Advanced high-strength steels have been extensively used in automobile construction, although a more complete understanding of their weld microstructure and mechanical behavior is needed. This work aims to contribute to the understanding of these basic features as well as propose the fiber laser processing conditions. Similar and dissimilar welds of dual-phase or transformation-induced plasticity (TRIP) steels present similarities in terms of microstructure features with the presence of martensite, proeutectoid ferrite, and bainite in the fusion zone and in the heat-affected zone. However, the more important microconstituent is bainite under regular and coalesced morphologies. The tensile behavior could be considered acceptable as most of the welded coupons broke in the base material and far from the weld. Fatigue curves presented a limit at approximately 350 MPa for dual-phase steels and 450 MPa for the TRIP steel.