Effects of shielding gas composition and activating flux on GTAW weldments

This study investigated the effects of shielding gas composition and activating flux on weld morphology, angular distortion, retained delta-ferrite content, mechanical properties and hot cracking susceptibility. An autogenous gas tungsten arc welding process was used on austenitic stainless steel to produce a bead-on-plate weld. The nitrogen content in the argon-based shielding gas was in the range of 2.5-10 vol.% Activating flux materials consisted of a manganese oxide powder and zinc oxide powder mixture. The results showed that the penetration and cross-sectional area of the weld increased with the increase of nitrogen added to the argon-base shielding gas. An increase in shielding gas nitrogen content had markedly reduced the angular distortion of the weldment. Increasing the nitrogen increased the tensile strength and hardness but reduced the retained delta-ferrite. The hot cracking susceptibility of the austenitic stainless steel welds increased as the nitrogen content increased. Activating flux plays a major role than nitrogen added in argon shielding gas, which influenced the various properties of austenitic stainless steel TIG welds. (c) 2008 Elsevier Ltd. All rights reserved.