Control of nitrogen content and porosity in gas tungsten arc welding of high nitrogen steel

Abstract

In welding of high nitrogen steel (HNS), it is essential to control the nitrogen content and porosity in the weld metal. In this paper, the influence of shielding gas composition and heat input on the nitrogen content and porosity in the weld metal of HNS was investigated by gas tungsten arc welding. The experimental results indicate that the weld nitrogen content increases as N₂ in the shielding gas is increased in the same heat input of welding. The weld nitrogen content decreases with increasing the heat input for pure argon used as a shielding gas, whereas it increases with increasing the heat input for the shielding gas including some nitrogen. The nitrogen pore can be avoided when the nitrogen content in the shielding gas is <4% in the heat input range of 528–2340 J mm^–1.