Modelling the transient thermal behavior of the pressure die-casting process with the BEM

The pressure die-casting process involves the repeated injection of a molten metal into a die cavity. The temperatures within the die exhibit a cyclic variation with a period equal to the casting cycle time. This paper is concerned with the prediction of these transient temperatures when the operating conditions have stabilized. The temperature at any point in the die can be considered to be formed from two components, one a steady-state part and the other a time-dependent perturbation. The steady- state temperatures of the die are calculated by solving the potential problem and the pertubation temperation from the parabolic heat equation. This approach enables the transient temperatures to be calculated in an efficient way, since only the cavity surfaces are considered in the pertubation analysis. The other components of the die system, that is, cooling channels and the outer surfaces of the die, are sufficiently far from the cavity to be ignored in the pertubation analysis. The boundary element method (BEM) is used to predict the cavity temperatures. In die casting, only the temperatures on the cavity surfaces are of interest, since the surface quality of a component is related significantly to the temperature distribution over the cavity. Since only thin components are considered herein, it is not necessary to model the solidification process and discretize the cast. These factors make the BEM ideally suited for the work described in this paper. To verify the results, the predicted temperatures for two components are compared with experimental values measured by using thermocouples and a thermal imaging camera. It was found that there is good agreement between the two sets of results.