Optimizing the toughness of high strength steel weld metal

ended

For many steel constructions, high toughness of welds is a critical parameter to meet with current safety standards. For some high strength steel grades, HSS, the required weld metal toughness can be hard to reach due to non-uniform metallurgy achieved by means of standard welding techniques. Heterogeneous distribution of alloy elements of the wire filler metal into the weld seam, together high dilution levels, can lead to poor toughness in conventional welded HSS. For conventional laser arc hybrid welding, LAHW, of thick HSS plates, in addition, the narrow laser welding gaps associated to narrow-and-deep penetration hybrid welds limit the penetration of the elements added by the filler wire and, thus, the attainment of homogenous element distribution along the hybrid weld. As a consequence, scattering of the toughness data is obtained when testing at low temperature, down to -60º C. In the OptoSteel proposal, a novel experimental and simulation-based approach, combined with extensive toughness testing and a detailed metallurgical characterization of welds, will allow defining the new welding strategies and procedures, including filler metal development, aimed at ensuring homogeneous filler material distribution across the weld metal. This will lead to optimized weld metal toughness, enabled by using advanced laser welding techniques and methods, which are non-conventional LAHW and narrow gap multi-layer laser welding with wire addition, NGMLW.