Modification of electro gas weld metal microstructure reflecting mechanical property specifications in cruise vessel shipbuilding

To identify the microstructural factors effecting the electro gas welding (EGW) weld metal properties, this study investigated the influence of different prototype welding consumables and shielding gases on the microstructural composition and mechanical-technological properties. The aim was to adjust the weld metal properties as a trade-off between strength, ductility, and impact toughness to fulfill typical weld metal material specifications in cruise vessel shipbuilding under consideration of the manufacturing conditions at European shipyards. The microstructure is analyzed by quantitative metallography of the ferritic matrix, martensite-retained austenite (M/A) constituents, and non-metallic inclusions (NMI). The influence of the Ni content, the deoxidation concept by variation of Si and Ti contents, and different shielding gas activity by variation of the Ar proportions is discussed. The interaction of ferritic matrix with high acicular ferrite content of about 70 ± 10%, the existence of larger grain boundary ferrite formations, and the M/A morphology plus distribution are considered as the determining factors for the material properties.