Effect of surface-machining and butt-welding on residual stress and hardness of type 316L stainless steel pipes

Asano, Wataru*; Katsuyama, Jinya  ; Onizawa, Kunio ; Mochizuki, Masahito*; Toyoda, Masao*

Stress corrosion cracking near welding zone of core internals and/or recirculation pipes of Type 316L stainless steel are initiated and grown at inner surface due to tensile residual stress and hardening. Surface-machining is conducted before and after piping butt-welding to match the ID of pipes and to provide a smooth surface finish, respectively. In present work, simulation evaluated residual stress by surface-machining before welding by using full scale FEM analysis was compared with experimental measurements. Piping-butt welding simulation was conducted after the surface-machining to evaluate redistribution behavior of residual stress by welding. Estimation of Vickers hardness distribution by surface-machining was carried out based on strained region map observed by FE-SEM equipped with EBSD and compared with experimental measurements. The effect of surface-machining before/after welding on distribution of residual stress and hardening are presented.