Effect of annealing models on the welding-induced residual stress and plastic strain in Type 316 stainless steel welded joints

Li, S.  ; Yamaguchi, Yoshihito ; Katsuyama, Jinya  ; Sun, W.*; Deng, D.*; Li, Y. 

Many flaws due to stress corrosion cracking (SCC) have been reported in the heat affected zone of austenitic stainless steel welded joints in nuclear power plants. High tensile residual stresses and hardness induced by the welding process may affect the initiation and propagation of SCC. During the welding thermal cycles, the accumulated strain hardening can be reduced or eliminated below the melting point due to the dynamic recovery, recrystallization, and grain growth of the material, which is known as the annealing effect. Different annealing models were proposed including the single-stage and two-stage annealing models, which are temperature dependent models to eliminate the accumulated strain hardening in one or two steps, and dynamic annealing models, in which the time-temperature dependent annealing effect can be considered. In this study, numerical investigations were carried out to evaluate the effect of different annealing models on the distributions of welding residual stress and accumulated plastic strain. Two butt-welded joints of Type 316 stainless steel were fabricated. The welding residual stresses of the two welded joints were measured using the neutron diffraction method and sectioning method, respectively. Two-dimensional finite element analysis was performed based on Abaqus platform. Chaboche combined isotropic-kinematic strain hardening model was used. The simulation results of welding residual stresses were compared with measurements. The results obtained have shown that the annealing effect can significantly influence the formation of the accumulated plastic strain and residual stresses in Type 316 stainless steel welded joints. The residual stresses will be overestimated if the annealing effect is neglected, or a relatively high value of the annealing temperature is used. The annealing model plays a major role in determining the magnitude of the accumulated plastic strain in the welding simulation.