Solid-state phase transformation and strain hardening on the residual stresses in S355 steel weldments

•The mechanism of the strain hardening recovery induced by solid-state phase transformation is clarified in detail.•The influence of the strain hardening recovery induced by solid-state phase transformation on welding residual stresses is investigated by methods of both experimental method and numerical simulation.•The effect of strain hardening model on welding residual stresses in S355 steel weldments is studied systematically. A series of numerical simulations were performed to examine the variability in welding residual stresses (WRS) for different material models. An experiment was carried out to measure thermal cycles and WRS in the ferritic steel S355 weldment for validation. Since solid-state phase transformation (SSPT) affects the dislocation density and thereby also the strain hardening, strain hardening recovery caused by SSPT should be considered for the accurate prediction of WRS, especially in single-pass welds. The mixed hardening model provides the more accurate prediction of WRS. It is recommended to consider SSPT regardless of strain hardening in numerical simulation of WRS for simplification but still with acceptable accuracy.