Estimation of the heat transfer conditions in a die radius during hot stamping

摘要

The hot stamping process is a widely used technology in the automotive industry to produce high strength structural steel parts. This forming process consists in heating a blank until complete austenitization in a furnace. It is then transferred to the press where it is formed at a high temperature and subsequently quenched in the forming tools. Thus, an intense heat transfer takes place from the stamped part to the tools. The estimation of the temperature field in the tools can be useful for investigating the fatigue that occurs. On the other hand, the knowledge of the interface conditions in the die entry radius can present a high interest for improving the numerical simulations of this process. In this paper, an omega shape tool is instrumented with thermocouples in the die entry radius. A 2D inverse heat conduction problem is solved to estimate the surface heat flux along the die radius during the forming step. Moreover, it allows the estimation of the temperature field in the die entry radius including the surface temperature. In the semi thickness of the blank, thermocouples were welded. A finite element simulation is used to estimate their locations. Finally, the thermal contact resistance is estimated in front of each blank thermocouple.