Effect of Filler Si content on the Microstructure and Properties of Underwater Hyperbaric Welded Duplex stainless steel

Two flux-cored wires with 0.36% Si and 0.63% Si respectively were employed for this study. Welding using a type of wire with low Si content need one more weld pass than using the other type of wire with high Si content to fill the groove at a pressure of 0.45 MPa. The microstructures and mechanical properties of the welded metals were studied. The average austenite content was higher in the welded metal with low Si content than that in the welded metal with high Si content. More and larger inclusions were another important factor for the higher austenite content in the welded metal with low Si content. The excessive inclusions in the welded metal with low Si content decreased the grain sizes of ferrite and austenite and induced a greater number of special ferrite-austenite boundaries. Compared with the welded metal with high Si content, the welded metal with low Si content had more inclusions and a less pronounced solid strengthening effect, which deteriorated its mechanical performance. The hardness, yield strength, tensile strength elongation and impact toughness of the welded metal with high Si content were all higher than those of the welded metal with low Si content. Wire with more Si content could guarantee preferable microstructure, less inclusions and better comprehensive mechanical properties of the welded metal.