Spot Weld Strength Modeling and Processing Maps for Hot-Stamping Steels

This research focuses on developing a novel methodology for modeling the link between nugget size and strength, as well as resistance spot welding (RSW) parameters and expulsion, in commercial hot-stamping Usibor® 1500 and Ductibor® 500.The RSW process was simulated for more than 250 different sets of welding time, current, and electrode force, resulting in the creation of 3D processing maps for both materials.The predictions were evaluated by measurements, and 3D nonlinear regression methods were used to explain the variations in strength as the function of welding parameters.A substantial amount of effort was devoted to taking the effect of expulsion into the numerical models so that the shear-tension strength of the spot welds would be predictable based on the occurrence and extent of expulsion during RSW.The results indicated that the occurrence of expulsion may decrease the strength of the spot weld up to 10 kN (2248 lbf) in Usibor (45%) and leads to 4 kN (899 lbf) strength loss (23%) in Ductibor.The models can estimate the strength of the spot weld with ± 1 kN (224 lbf) error.