Setting an ultrafine grain at forged preforms by using cross wedge rolling

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Preforms produced by cross wedge rolling are used for a variety of parts by the forging industry. They are characterized by a low amount of surplus material. Compared with ECAE cross wedge rolling is implemented and established in industry. In comparison, an ultrafine grain has better mechanical properties as a higher yield strength and notch impact strength than materials with a coarse grain. Therefore parts with ultrafine grain can be constructed more light-weighted which lowers the material consumption. The material that is saved through this lowers the energy consumption during the production and regarding moving parts, e.g. in combustion engines while usage, too. With the combination of cross wedge rolling and the improved mechanical properties of parts with ultrafine grain the design of processes and material efficiency can be both improved dramatically. The aim of this research project therefore is to develop a cross wedge rolling process that can be used to adjust an ultrafine gain for forging preforms and can be implemented in industry. The target grain size is the same as those producible with processes that are used only in research projects like ECAE. In the end the mechanical properties of the grain like the average grain diameter should be associated with geometry and process parameters at cross wedge rolling. The first of three sub-aims is to develop a suitable cross wedge rolling process that can successfully form cylindrical parts. The tools should be able to be varied systematically. Within the second sub-aim a dependency of the cross wedge rolling process from process parameters like forming velocity and billet temperature has to be investigated. Within the third sub-aim a dependency from cooling conditions after the cross wedge rolling should be examined. The cooling conditions determine the final grain size based on the nuclei grown at cross wedge rolling. Therefore different cooling velocities and fluid have to be investigated.