Investigation and Optimization of Variables in Hot Forming through FEA Simulations

Automotive manufacturers around the world are pushing towards the goal of better safety from their vehicles without compromising on the fuel economy. One of the very successful efforts in this direction is the hot forming technique that has been around for 30 years since Saab used it for the first time in 1986. Finite element simulations for this technique are of paramount importance to identify and optimize the process; as the steels used in hot stamping are sensitive to certain variables when heated that would otherwise cause very few disturbances in a normal cold forming process. The major contributor to the high strength of the stamped part is the phase transformation that it undergoes during the hot forming process. This paper investigates and identifies critical parameters through Finite Element Analysis (FEA) simulations. In an effort to match industry standards, values collected from various hot stamping suppliers such as for temperature, time etc. are used for these simulations. This paper investigates a simple geometry and a complex geometry, both of which are hot stamping industry parts - that are modelled and used for the simulations. The quality of a hot stamping part is determined by its tensile strength and hardness values that are in turn dependent on the Martensite and Bainite phase fractions of the component after it’s stamped. The results are compared and discussed to capture the most critical inputs parameters and the intensity of their influence on the part quality. The FE code- AutoForm R6 is used for the simulations. Apart from the influence of the process parameters, the influences of the geometry on the final quality of the part is also discussed. Further investigation is needed in the future to capture other factors such as exact tool contact and cyclic temperature increase of dies.