Universal modelling of material and surface modifications for FEM simulation of drop forging of carbon steels

In this DFG-funded project, the influences of the scale layer on hot forging processes of steel materials are being investigated. While only carbon steels were considered in the first funding period, the alloy configuration is extended to include the element chromium in the second funding period. Other than existing literature, this project not only examines exemplary alloys, but also systematically investigates an entire steel grade. The focus is on the development of a holistic numerical representation of scale in the hot forging process chain. Within the thermomechanical simulation, the main attention is to be paid on real scale kinetics. These fundamentally influence the deformation processes in the forming zone. In the first funding period, the scale layer was modelled without a failure criterion during forming. However, in real hot forging processes critical stresses cause the scale layer to crack or slip. For a detailed representation of the local material temperature and the local friction conditions, which significantly influence the hot forging process, the failure of the scale layer during the process must therefore be taken into account in the numerical simulation. Moreover, for a holistic view of the hot forging process chain, the scale formation in the heating unit must be considered numerically. The results serve as input data for the forming simulation. The changes in the material properties of the base material as well as the scale layer are to be implemented in the commercial FE program Simufact Forming v16.0 by means of Fortran subroutines. Thus, a contribution for the process chain simulation in hot forging can be made under consideration of scale formation, microstructure transformation, tribology and scale damage depending on the relevant parameters such as temperature and alloying elements.