Analysis of microstructure properties of welded joint of high nitrogen steel by hybrid welding

In order to study microstructure and microhardness distributions of welded joint of high nitrogen steel at different heat inputs, high nitrogen austenitic stainless steel was welded by Nd:YAG-MAG hybrid welding technology. After theoretical analysis and experimental verification, microstructures and microhardness data of the welded joint were obtained under different heat inputs. The results show that, hybrid welding joint of high nitrogen steel cross-sectional is "goblet" shape. The upper is arc action area, and the lower is laser action area. The microstructure consists of austenite and a small amount of ferrite. With the increasing of heat input, the ferrite fraction increases, the ferrite branch crystal trunk grows longer and thicker, and the secondary dendrites is distributed on both sides of the branch crystal trunk. The microhardness distribution of welded joint is not uniform. The hardness of base metal zone is the highest and the value is between 330HV~370HV. The hardness of welding is the lowest, and the value is between 260HV~300HV. The hardness of welded joint decreases with the increasing of heat input. There is no soft zone in welded joint. The study provides a theoretical basis for the welding of high nitrogen steel under the certain heat input parameters.