Properties of welded joint for narrow gap laser welding of austenitic stainless steels

Thick-section austenitic stainless steels are widely used in components and structures for nuclear power plant. Laser welding is being considered as a high-efficiency method instead of arc welding for some components, in order to improve production efficiency and reduce residual stresses of the heat-affected zone. In this paper, multi-passes narrow gap welding of 50mm thick SUS316L plates with 8 kW disk laser was investigated. The metallurgical and mechanical properties of the weld metal were discussed. It was found that the solidification crack, which usually occurs in the build-up metal for narrow gap laser welding, could be suppressed by controlling the chemical composition of the filler wire, so that the ferrite content of the weld metal could be controlled in an appropriate range. The mechanical properties and the welding residual stress of the narrow gap laser welded joint were evaluated. The maximal tensile residual stress and the range of the tensile stress of the laser welded joint were lower than those of the conventional gas tungsten arc welding (GTAW).