Experimental characterization of the heat transfer coefficient under different close loop controlled pressures and die temperatures

Abstract

The prediction of the final microstructure on press hardening processes strongly depends on the heat transfer kinetics that cools down the blank and governs its martensitic transformation. The main objective of the work is to rigorously and in a systematic manner analyse the influence of the contact pressure and die temperature on the heat transfer coefficient (HTC) for press hardening applications.The columnar experimental set-up used in this work is presented and the efficient analytical/numerical methodology developed for the surface temperature, heat flux and therefore HTC identification are shown. From the present analysis it is concluded that the HTC critically varies during the cooling process. In the same way the strong dependency of the results on the contact pressure and their weak dependency on the die temperature are shown. An analytical model to represent the HTC evolution on press hardening simulation is presented.This work presents a valuable set of experimental data regarding the HTC characterization.