Influence of Current Pulsing on Mechanical Properties and Microstructure of Tungsten Inert Gas (TIG) Welded AISI 304L Austenite Stainless Steel Joints

The Austenitic Stainless Steels (ASS) are probably the most widely used materials in stainless steels, category AISI 304L is an important grade of the ASS, which is commonly used in many of important industries such as containers of transporting chemicals, oil refinery, nuclear reactor tanks, dairy industries, and textile industries. Currently, 304L Austenitic stainless steel sheets are used as fuel tanks in Armour Fighting Vehicle (AFV). These tanks are fabricated by conventional Tungsten Inert Gas (TIG) welding process. In conventional welding, fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification. This often results in inferior weld mechanical properties. Interpulse Tungsten Inert Gas (IPTIG) welding is a new variant of conventional Tungsten Inert Gas (TIG) welding process. This process offers many advantages over conventional TIG welding process such as narrow heat affected zone, deeper penetration compared to Constant Current TIG (CCTIG) and Pulsed Current TIG (PCTIG) welding processes. The present investigation was carried out to understand the effect of arc pulsing technique on cross sectional weld bead profile, micro hardness, microstructure and the tensile properties of welded joints. It is found that IPTIG welded joints showed superior mechanical properties compared to CCTIG and PCTIG joints, and this is mainly due to formation of finer grains in the fusion zone, caused by the combined effect of arc constriction and pulsating action.