Microstructure and mechanical properties of low-alloy high-strength steel for ship fabricated by wire-arc additive manufacturing

The multiple-pass multilayer steel wall was fabricated by wire-arc additive manufacturing (WAAM) technology using self-made low-alloy high-strength steel wire for ship. The microstructure and mechanical properties of the as-deposited and annealing heat treated samples were studied. The results showed that the low-alloy high-strength steel wall fabricated by WAAM had good forming quality and realized effective metallurgical combination between layers. The microstructure of the as-deposited sample was mainly composed of granular bainite and irregular polygonal ferrite, which had high strength, plasticity and good low temperature impact toughness. The martensite-austenite (M-A)components were continuously decomposed to form ferrite and many fine carbides after annealing at 400°C and 600°C, which reduced the number of granular bainite and increased the number of ferrite, resulting in strength reduction and plasticity and low temperature toughness improvement.