Numerical investigation of thermal and mechanical deviations in a hot forging process of 16MnCr5 and 42CrMo4 steel

The development of tools in bulk metal forming for the production of steel components consists of an iterative development process and requires a large number of test tools, resulting in high costs as well as increased production time. The simulation of process steps on the basis of the finite element method is an established technique for tool design and provides a significant contribution to the optimization of processes in the development phase. Thermally and mechanically induced deviations from the desired component geometry occur due the forging process. The approximation of the actual to the target geometry of the component must be worked out in several iteration loops by adapting the process conditions, or by modifying the forming tools. A newly developed process-accompanying compensation strategy helps to reduce the deviations by modifying the forming tool and process conditions within the virtual product development phase. In that regard, the numerical investigation of a forging process has been carried out in this study. The influence of different process conditions and their influence on the workpiece deviation are investigated. For this purpose, first of all the material data such as flow curves and coefficients of thermal expansion are determined in experimental tests. The coefficients for an analytical flow curve approach called GMT, which is implemented in the commercial software simufact.forming are computed for the investigated steel grades 16MnCr5 and 42CrMo4. Finally, the flow curve approach was validated by comparing numerical and experimental results of a uniaxial compression test. Also the numerical results of the forging process with different initial forging temperatures are compared with each other and the deviations of the workpiece are discussed.