Low Transformation Temperature Welding Consumables for Residual Stress Management: A Numerical Model for the Prediction of Phase TransformationInduced Compressive Residual Stresses

Harmful tensile residual stresses are observed in structural steel weld joints as a result of the thermal strains between the solidified weld metal and surrounding base material. These harmful stresses, superimposed on external stresses, make the welded joints more prone to fatigue failures. Thus, the presence of compressive residual stresses, instead of the typical tensile residual stresses, improves the fatigue resistance of the structural welded joint. In this research work, numerical analysis of gas metal arc welding (GMAW) with developed low transformation temperature welding (LTTW) wires was performed using Sysweld. Simulation of all-around fillet welds on a structural steel plate clearly estimated the effects of the different 
experimentally developed LTTW wires on residual stress generation and welding distortion control. Alloys with higher chromium equivalent promoted greater control on out-of-plane distortion. Their effect on compressive residual stress generation around the weld toes was not as evident and deserves further investigation. Simulation results agreed reasonably well with the experimentally determined results. The weld made using the higher chromium equivalent welding wire showed the maximum induced compressive residual stress in and around the weld joint (at the order of 600 MPa) with relatively low transverse distortion values compared to the other welds. Stress evolution with time plots from Sysweld simulation were able to show the interaction between thermal contraction and phase transformation induced expansion, and also the amount of martensite required to promote overall residual compressive stresses in the fillet weld joint.