Hot Press Forming of Tailor Welded Blank: Experiments and FE modeling

Abstract

Hot Press Forming (HPF) of Tailor Welded Blank (TWB) was investigated with particular focus on the formability and phase transformation of the constituent base materials. Dilatometric analyses were conducted to study strength differentials for various cooling rates after heat treatment. U-draw bending tests were performed to evaluate the influence of a number of process parameters, namely, blank and tool temperatures, and cooling time, on the mechanical properties of the product. Formability at elevated temperature was assessed using forming limit diagrams for each monolithic material under realistic hot press forming conditions. Lab-scaled forming tests of a newly designed B-pillar were carried out to evaluate the formability of TWB under an actual hot press forming process. Finally, coupled thermomechanical finite element simulations, which utilize flow stresses and forming limit diagrams determined under realistic HPF conditions, were carried out. In particular, finite element simulation results for the weld-line displacement and thinning of the TWB were compared to experimental data for validation purpose. © 2012 ISIJ.