Influence of Nitrogen and Heat Input on Weld Metal of Gas Tungsten Arc Welded High Nitrogen Steel

High nitrogen stainless steel (HNS) which generally contains over 0.4wt% nitrogen is considered to be a high strength, high ductility and high toughness material. In order to study the nitrogen behavior in welding of high nitrogen steel, the steel 1Cr22Mn16N was welded by gas tungsten arc welding, and the influence of the shielding gas composition and heat input on the N-content and porosity of the weld metal was investigated. The experimental results indicate that the N-content of the weld metal increases as the nitrogen in the shielding gas containing Ar and N2 is increased under the same heat input of welding. The N-content of the weld metal decreases with the increase of the heat input when pure Ar is used as the shielding gas, whereas that of the weld metal is improved with the increase of the heat input when some nitrogen is added to the shielding gas. The nitrogen pore can be avoided when the N-content of the shielding gas is lower than a critical value. When N-content exceeds the value, the tendency of porosity in the weld metal increases with the increase of the N-content of the shielding gas. The microstructure in the weld metal consists of austenite and δ-ferrite. The amount and size of δ-ferrite is reduced with the increase of nitrogen in the shielding gas composition.