A Study on ROLE OF NTROGEN IN 316 L STAINLESS STEEL WELDMENTS

Abstract

Nitrogen is increasingly becoming a popular alloying element in austenitic stainless steel. This is due to the remarkable improvements provided by nitrogen to austenitic stainless steel. Nitrogen increases the strength, toughness, corrosion resistance, and austenite stability. Nitrogen represents a good substitute for nickel, thereby, reducing alloying elements cost. This study was conducted to make use of these valuable effects of nitrogen in welding of 316L stainless steel. In addition, newly developed tungsten electrodes activated with rare

earth metals oxides were used to optimize the welding process.

Welding was done with autogenous automatic gas tungsten arc welding (GTAW) process using bead on plate technique. Nitrogen was introduced to the shielding gas with 10%, 5%, and .3.5% by volume. Pure argon was used for comparison. Ceriated, lanthanised, and yttriated tungsten electrodes were used in addition to the conventional thoriated tungsten electrode. The welding performance was evaluated by recording arc voltage and current, measuring the arc efficiency, and visual examination of surface appearance of the weldments. Properties of weld metal were examined by measuring weld metal area, weld metal hardness, nitrogen content of weld metal, ferrite content, and corrosion resistance. In addition, the hot cracking tendency was investigated.