Simulation Of Phase Transformation In Hot Forging Dies During A Precision Forging Process By Means Of Finite- Element-Analysis

The Finite-Element-Analysis (FEA) is of major importance for the design and improvement of forging processes. In this field, FEA is traditionally used to predict die fill, residual stresses and forming forces. The intention of the work presented in this paper is the development of an advanced simulation model for the description of phase transformation processes in forging dies based on FEA. This simulation model enables the prediction of die wear, since the hardness of the surface layer could be predicted. Due to the mechanical and thermal interactions with the work piece, the temperature in certain regions of the die surface layer exceeds the austenitizing (Ac1b) temperature. After the lubrication, following the forging cycle, a fast cooling of the die surfaces takes place, so that martensite is generated in the surface layer. Below this layer, the temperature is higher than the annealing one, but lower than the Ac1b temperature of the forging die steel, which leads to soft annealing of this region. A precision forging process will be simulated to predcit this change of microstructure. The FEA includes the modelling of mechanical and thermal interactions between the work piece and the dies and the cooling through a lubrication medium. Finally, in order to calculate the microstructure, specific developed subroutines are implemented in a commercial FE-code.