Welding Journal Research Supplement

Abstract

Fe-10Ni is a high-strength, high-impact toughness steel developed for naval structural applications. Gas metal arc welding in spray transfer mode (GMAW-s) with a Fe-10Ni filler metal produces welds with complex, deep, finger-like penetration profiles. The GMAW-s process is preferred for its higher productivity, but multipass groove welds exhibit lower impact toughness than those made with gas tungsten arc welding (GTAW). This study developed a numerical simulation framework to analyze microstructure and hardness distribution in multipass Fe-10Ni groove welds produced by GMAW-s. The framework utilized finite element analysis (FEA) models of GMAW-s processes for groove and bead-on-plate welds, a heat-source model reproducing the fusion-zone profile in GMAW-s welds, and experimentally derived thermal history–hardness and thermal history microstructure relationships. The accuracy of the framework was confirmed by comparing FEA predictions with experimental results on heat affected zone thermal histories and the spatial distributions of hardness and microstructure in multipass weld metal. Fe-10Ni weld metal exhibited a weak response to tempering by short term subcritical reheats from multipass welding, resulting in a low weld metal hardness range, within 40  HV0.2 . However, the GMAW-s weld metal showed pronounced variation in the spatial distribution of as-solidified, reaustenitized, and tempered microstructures. As-solidified martensite, known to reduce impact toughness in Fe-10Ni welds, was found to occupy up to 0.43 fraction of the weld metal cross section. By linking thermal history to microstructure and properties, the proposed framework provides a pathway for computationally guided welding process optimization, aiming to reduce the regions of as-solidified martensitic microstructure and improve impact toughness in GMAW-s multipass Fe-10Ni welds.