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The basic idea of this paper is developing process models which are online capable, i.e. which combine data from online measurements and simplified plastomechanical interrelations for the forecast of equivalent strain, equivalent strain rate and the temperature in the core of the part being forged. These models deliver the numerical basis for the forecast of the microstructures obtained. In combination with optimization methods a numerical assistant for the forging press operator can be implemented. At the Institute of Metal Forming of the RWTH Aachen University, models for the core fibre of a forged block were developed. The development of the models was based on reference solutions which were derived from FEM‐calculations. The equivalent strain and equivalent strain rate are thereby determined by the change of the geometry of the workpiece (i.e. change in length or change in height). For the determination of the temperature distribution along the core fibre an explicit Finite Difference model is used. This model considers the loss of temperature at the surface due to radiation and convection, and also the dissipation in the core fibre. For the subsequent prediction of the microstructure the module STRUCSIM, which was developed at the Institute of Metal Forming, is used. The results of the models show good agreements with the FEM‐solutions.

To provide a high quality of forged products, a homogeneous distribution of material properties has to be achieved inside the ingot. As the properties are not visible from the outside, an online monitoring during the forging process is required. By using modern measuring equipment and fast calculation models, the equivalent strain, temperature and average grain size in the core fibre of a forging ingot can be calculated parallel to the process. Software implementing the fast calculation models has been established and connected to the measuring system of two different open die forging presses. Two experimental forging processes with ten passes have been performed (20 ton steel ingot, 750 kg Ni-base alloy ingot). Parallel to the process, the current strain, temperature and average grain size in the centre of the ingot are visualised in the graphic user interface and recorded by the process monitor. It was shown that the calculation speed is high enough to allow online capability. After finishing the process, the developed software can further be used to analyse in detail the impact of every single stroke or pass on the whole process. Additionally, information like minimum or maximum grain size or recrystallized fraction is calculated and can be used to get insight into the process and optimize its design. Comparing the metallographically measured average grain size from experiment with the grain size estimated by the process monitor, the average deviation of three measured points is less than 13 %.

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