Evaluation of Mechanical Property for Welded Austenitic Stainless Steel 304 by Following Post Weld Heat Treatment

Austenitic stainless steels have excellent mechanical property and corrosion resistance, and are for these reasons used in demanding applications such as power plant, nuclear reactor and off-shore plant. Especially, austenitic stainless steel 304 (STS304) is mainly used as a pipe material in nuclear power plants. Submerged arc welding (SAW) is a commonly used method of welded steel pipes. This method has some problems of microstructure and mechanical properties such as heterogeneous microstructure, ductility decreases, brittleness of a weld region after SAW process. Especially, delta ferrite and dendrite structure is happened in the weld metal after welding process, which affects the decrease of toughness and ductility. Therefore, it requires the post weld heat treatment (PWHT) in order to solve these problems. In this study, welded STS304 was investigate the microstructure and mechanical properties after SAW process. In order to improve the toughness and ductility of weld region, PWHT was performed by controlling the delta-ferrite and dendrite structure. It was found that the mechanical property of the weld region were increased due to the decrease of the delta-ferrite and the recrystallization of the austenite structure after PWHT.