Analysis of Sensitization in Austenitic Stainless Steel-Welded Joint

Abstract

The main aim of this paper is to study the mechanical properties of the weld also the microstructure of the weld joints were analyzed. The effects of sensitization of gas tungsten arc (GTA) welded 304L stainless steel (SS) joints were observed. 304L stainless steel was heated to 450–950 °C, soaked for 0.5–2 h, and was observed. The three heat groups were chosen from the operative window of tungsten inert gas welding; these heat groups are low heat -2200 J/mm, medium heat–3320 J/mm, and high heat 3800 J/mm. Using these heat groups, weld joints were made which were normalized at 750 °C, 850 °C, and 1000 °C for 0.5 h, 1 h, and 2 h, respectively. These specimens were used to perform tensile test, impact strength test, microstructure, and microhardness for welded joint. The effect of sensitization was observed for these joints for stated mechanical properties. The outcomes of this study indicate that the tensile strength is maximum at weld joints normalized at 750 °C but remarkably decreased as the temperature was increased while the yield strength did not notably change with increasing of the temperature. The Charpy impact energy and micro-harness showed higher value at weld joints normalized at 750 °C but remarkably decreased as the temperature was increased. The major reason for Charpy impact energy decrease was compound of manganese–silicon–Sulfur formed in the weld pool during solidification. The microstructures of sensitized samples have been observed by optical microscope. The sensitization was found to be more for heat-treated welded joints and parent metal as compared to unprocessed weld joints and parent metal. Precisely, welded joints were normalized at 850 °C with soaking time 2 h and allowed to cool in a furnace was observed to be more sensitized.