Characterization of Submerged-Arc and Gas-Metal-Arc Weldments in HY-100 Steel

摘要

Unsatisfactory weld toughness in submerged arc welded (SAW) HY-100 steel weldments precludes this process from large scale HY-100 shipbuilding production efforts. The gas metal arc welding (GMAW) process produces acceptable weldments in HY-100 steel. Optical, scanning electron and transmission electron microscopy were utilized to characterize and compare the microstructure in the last pass in each weldment for each process. The SAW weldment contains a coarse-upper bainitic microstructure and the GMAW weldment contains a martensitic structure. The cooling rate in the SAW was 42% slower than in GMAW. The SAW contained 25% more weld metal conducted and the profiles reflect significantly lower microhardness in the untempered last pass weld metal of SAW weldment, but the tempered weld metal microhardness in both weldments was measured at 250 HV. Charpy impact tests were conducted and impact transition curves were developed revealing that the SAW weldments ductile-to-brittle transition temperature was 50 deg C higher than the GMAW weldment. (Author)