A study on annealing temperature in FEM simulation of residual stress in SUS316 weld

Abstract

This study investigates the recrystallization phenomenon of strain hardening during welding process in austenitic stainless steel (SUS316), and a suitable annealing temperature for finite element method (FEM) simulation was proposed. The electron backscatter diffraction (EBSD) analysis results of a 1-pass weld with prior surface machining proved that the annealing effect can be introduced owing to the recrystallization phenomenon caused by welding thermal cycle. Therefore, it was necessary to introduce a suitable annealing temperature into the FEM simulation to simulate this phenomenon. To establish a propriate annealing temperature, the 20 % and 30 % pre-strained cold-rolled specimens were subjected to peak temperatures ranging from 800 °C to 1300 °C, held at the peak temperature for 1 s, and their corresponding hardness was measured. The results showed that when the annealing temperature is approximately 1050 °C, the resulting hardness aligns with that of solution-treated specimens. To verify the accuracy of the proposed annealing temperature in the FEM simulation, this determined annealing temperature (1050 °C) was then applied in the FEM model to estimate the residual stress after 7-layer welding, with the results validated through measurements. The good agreement between the simulated residual stress and the measured results follows that the proposed annealing temperature of 1050 °C in FEM simulation is reasonable and effective. Therefore, the annealing temperature of 1050 °C should be included in the FEM simulation of SUS316 welding in the future.