Numerical and experimental validation of gas metal arc welding on AISI 441 ferritic stainless steel through mechanical and microstructural analysis

Residual stresses and strains, distortions, heat-affected zone (HAZ), grain size changes and hardness variation during gas metal arc welding (GMAW), are fundamental aspects to study and control during welding processes. For this reason, numerical simulations of the welding processes represent the more frequently used tool to better analyse the several aspects characterizing this joining process with the aim to reduce lead time and production costs. In the present study, an uncoupled 3D thermo-mechanical analysis was carried out by two commercial finite element method (FEM) software to model an experimental single bead GMAW of AISI 441 at different processes set-up. The experimental HAZ and measured temperatures were used to calibrate the heat source of both the used numerical codes, then a validation phase was done to test the robustness of the two developed analytical procedures. One software was used to predict the residual stresses and strains and the distortions of the welded components, while in the second software, a user routine was implemented, including a physical based model and the Hall-Petch (H-P) equation, to predict grain size change and hardness evolution, respectively. The results demonstrate that the predicted mechanical and microstructural aspects agree with those experimentally found showing the reliability of the two codes in predicting the thermal phenomena characterizing the HAZ during the analysed welding process.