Structure and Properties of the Metal in the Laser Welding Joints of an Austenitic Steel Containing ~0.5% N in the As-Cast and Deformed States

The microstructure, the chemical and the phase compositions, and the mechanical properties of the welded-joint metal of sheet (hot-rolled) and as-cast austenitic 0.05% C–(21–23)% Cr–8% Ni–15% Mn–(1–2)% Mo–(0.2–0.5)% N steels butt welded with a laser beam have been studied. Welding is carried out without a welding additive using a fiber ytterbium laser developed by IPG IRE–Polus. It is shown that defect-free welds from 350 to 1200 μm wide without δ-ferrite and σ phase can be formed over the entire welding regime range. Laser welding is found to affect the manganese and nitrogen contents in the weld metal. The mechanical properties of the weld metal are estimated. In welding the hot-rolled and the as-cast steels, the ultimate strength of the weld metal is shown to be almost the same as that of the base metal, which correlates with the microhardness measured in the base metal and the weld metal, and to be higher than the ultimate strength of traditional corrosion-resistant nitrogen-free steels.