SIMULATION OF STRESS INDUCED SENSITIZATION DURING ARC WELDING OF STAINLESS STEEL

Abstract

Austenitic stainless steels (ASS) are widely used in high performance pressure vessel, nuclear components and chemical industries due to its superior mechanical and excellent corrosion resistance properties. However ASS become prone to intergranular corrosion (IGC) and stress corrosion cracking (SCC) due to occurrence of sensitization at the heat affected zone (HAZ), when the region near to fusion line attain a temperature in the range of 500-850 OC during welding. During welding appreciable amount of strain generates in HAZ that introduces residual stresses in weld joint. The residual stresses also facilitate the precipitation of carbides at the grain boundary by encouraging the sensitization phenomena. Thus, it is inferred that during fusion welding the HAZ experiencing sensitization temperature in the range of 500-850 OC, along with simultaneous development of stresses collectively leads to enhanced formation of fine chromium rich carbides at the grain boundary. The regions of HAZ containing fine nucleated carbides may also attract early IGC/SCC attack through their growth by low temperature sensitization (LTS) during service, even at temperature as low as 350-400 OC. The primary objective of this work is to study about the stress-induced sensitization of HAZ of 304 LN stainless steel during its arc welding using the thermo-mechanical simulator. Thermo-mechanical simulator (Gleeble 3800) facilitates to simulate the HAZ under the thermal and stress effects. Three basic objectives of this topic are addressed in the present study. The first objective is considered as the simulation of sensitization in HAZ in case of single pass arc weld of 304LN stainless steel in thermo-mechanical simulator operated under different nature (tensile and compressive) and magnitude of stresses at 650 OC temperature. Rectangular sample of dimension 10 × 10 × 110 mm with thread was used to induce tensile and compressive stress during sensitization of HAZ at the simulation test.