Effects of welding and constraint conditions on the welding residual stress and hardness of Type 316 stainless steel pipe

溶接条件と拘束条件によるSUS316ステンレス鋼管の溶接残留応力及び硬さに及ぼす影響評価

Li, S.  ; 山口 義仁 ; 勝山 仁哉  ; Li, Y. 

Li, S.; Yamaguchi, Yoshihito; Katsuyama, Jinya; Li, Y.

Flaws due to stress corrosion cracking (SCC) were recently detected in welded joints of austenitic stainless steel piping lines in pressurized water reactors. Welding-induced high hardness and tensile residual stress are known as one of the main factors affecting SCC. In this work, thermal-elastic-plastic coupled three-dimensional finite element analyses were performed to investigate the distributions of welding residual stress and hardness in butt-welded joints of Type 316 stainless steel. Different heat inputs were applied to the pipe welds, including normal heat input, high heat input and very high heat input. Two different constraint conditions were considered for the welded joints, i.e., both ends free or clamped, the latter indicating that the welded joint is constrained by the surrounding piping system. Simulation results were compared with experimental data such as welding thermal cycle, axial shrinkage and residual stress for validation. The effects of heat input and constraint condition on the welding residual stress and hardness at different sections of the welded joints including the weld start/end location were discussed in detail.