FE thermo-mechanical simulation of welding residual stresses and distortion in Ti-containing TWIP steel through GTAW process

The effect of residual stresses can be beneficial or harmful depending on their magnitude, type and distribution. This research work applied the isotropic and kinematic hardening models with different strain rates (0.001-100 s(-1)) to simulate the non-linear mechanical behavior of Twinning Induced Plasticity (TWIP) steel microalloyed with titanium. A finite element (FE) thermo-mechanical model was employed to analyze the welding thermal cycle in the TWIP-Ti steel. The numerical prediction of residual stress was validated by X-ray diffraction (XRD) measurements in welding critical regions. Furthermore, a residual stress critical zone (SCZ) was defined as a function of the maximum tensile residual stress and hardness in the fusion zone (FZ) and heat affected zone (HAZ). The magnitude of residual stresses estimated in the SCZ was lower than the TWIP-Ti steel yield strength. The weld joint preparation and the mechanical constraint provided a control to mitigate both residual stress and distortion. Quantitatively, the results provided good weldability of the TWIP-Ti steel in higher plate thickness through the Gas Tungsten Arc Welding (GTAW) process at low heat input.