The influence of pre-heating intensity on resistance spot welding performance was investigated through a combined experimental and finite element modeling approach. An axisymmetric electro-thermal-mechanical finite element model was developed to simulate the RSW of three-layered tailor-welded blanks (TWBs) comprising dissimilar steels: AISI 1035, IFHS, and ASTM A36. Pre-heating was modeled via varying contact resistance (CR) at the sheet interfaces, representing three conditions: no pre-heating (CR \(\sim\) 1000 μΩ), moderate pre-heating (CR \(\sim\) 100 μΩ), and intense pre-heating (CR \(\sim\) 0 μΩ). The simulations captured the spatial-temporal evolution of temperature and stress distributions during welding. Weld nugget geometry predicted by the model showed strong agreement with experimental results. Fractographic analysis revealed interfacial failure for non-pre-heated joints, pull-out failure in moderately pre-heated samples, and brittle fracture in the heat-affected zone under intense pre-heating. Electron backscatter diffraction analysis indicated a uniform dislocation density of (100–200) × 1012 m−2 at the weld nugget center and edge in moderately pre-heated samples, correlating with reduced residual stress. Consequently, these joints exhibited superior mechanical performance, with failure strength improvements of 11.8% and 35.7% over the non-pre-heated and intensely pre-heated samples, respectively. This study highlights the critical role of optimized pre-heating in enhancing weld quality and joint integrity in multi-material TWBs.
