Use of different flow stresses for forming inhomogeneously heated billets

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The goal of the research project is to determine the effect of an inhomogeneous induction heating of billets on subsequent steps of a forging process chain. Therefore the different flow stresses in the inhomogeneously heated billet shall be used to influence the forming behavior. Different processes with homogeneous and inhomogeneous heating of billets shall be designed and evaluated considering various assessment criteria (flash, folds, forming force) to determine the potentials. In addition, the process limits of an inhomogeneous heating are to be determined. In differentiation to the industrially established partial heating in which only sections of the billets are heated and formed, the entire billet shall be inhomogeneously heated and formed in this research project. The research results will help to make manufacturing processes in bulk forming more efficient regarding use of materials and energy consumption. For this research goal, the following three sub-goals can be derived.The first sub-goal is the simulation and experimental study of the adjustability of an inhomogeneous temperature field in cylindrical billets by induction. In order to evaluate scaling effects, billets with very different dimensions in the range of customary dimensions shall be examined. The primary criterion of the adjustability is the temperature compensation as a function of time. A FEA-model shall be built and verified by practical heating experiments.The focus of the second sub-goal is the investigation of the effect of inhomogeneous heating of billets to forging process chains with preforming and finish forging steps using FEA-simulations. For this purpose various process chains with inhomogeneous heated billets shall be designed and evaluated. Reference processes with homogeneous heated billets shall be designed and evaluated for comparison purpose. Finally a suitable process window for experimental testing shall be determined for all process chains.The third sub-goal is the experimental study of the effect of inhomogeneously heated billets to a forging process chain. Therefore the processes chains designed by simulations in the second sub-goal shall be replicated in experimental tests. Subsequently, a comparative evaluation of the various process chains considering the established assessment criteria (e.g.: flash, folds, forming forces) has to be done to determine the potential of an inhomogeneous heating of billets. In order to make statements about the parts quality, all parts have to be analyzed with regard to their dimensional accuracy and by a structural analysis.