Thermo-mechanical-metallurgical modeling and validation for ferritic steel weldments

This work explained the effects of solid-state phase transformation (SSPT) on welding residual stress (WRS) evolution in SA508 Gr.3 C1.1 (SA508) ferritic steel single-pass and multi-pass weldments. A thermo-mechanical-metallurgical (TMM) model incorporating thermo-elastic-plastic stains and SSPT-related strains was presented. The SSPT kinetics and transformation-induced plasticity (TRIP) models of SA508 steel were established by employing user-defined subroutines developed for ABAQUS. The simulated WRS distribution in the single-pass weldment was compared with previously published neutron diffraction measurement data, and a good agreement was achieved and thus validating the developed TMM model. The microstructural and WRS distribution characteristics of the multi-pass weldment were further investigated based on the validated TMM model. Numerical simulations illustrated how the transformation and heat transfer/cumulative behavior associated with different welding process conditions resulted in the generation of triaxial compressive and tensile stresses in the upper and underlying weld beads at the multi-pass welded joint, respectively. Moreover, an additional simulation model with SSPT but without TRIP was developed to reveal the potential effects of TRIP on WRS distribution. This study numerically provided valuable understanding of microstructure and WRS evolution in air cooling bainitic steel weldments under multiple thermal cycles and constituted a fundamental basis for developing new welding materials to minimize the formation of deleterious tensile WRS by simultaneously combining bainitic and martensitic transformations. (C) 2020 Elsevier Ltd. All rights reserved.