Control of forming behavior by inhomogeneous heating of semi-finished products during cross-wedge rolling

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The present research proposal deals with the control of the forming behavior with the aid of locally variable flow stresses through inhomogeneous heating of the semi-finished product during cross wedge rolling. By heating the semi-finished product inhomogeneously, e.g. in half-warm and warm areas, the flow properties of the material can be adapted to the cross wedge rolling die. This should increase process stability and prevent rolling defects. During the cross-wedge rolling process, different rolling defects can occur that influence the component quality along the process chain. For example, voids, internal cracks along the longitudinal axis of the semi-finished product, internal wrinkles, surface defects, insufficient impressions, fishmouth effects or overrolling can occur during cross wedge rolling. One cause of rolling defects is insufficient process stability due to, for example, slippage or uneven torsion of the semi-finished product during the cross-wedge rolling process. Slippage or torsion results from the locally different flow paths during the cross wedge rolling process. The material in the area of the wedge flows significantly more than in the area outside the wedge. This results in different torsions, for example. Currently, serrations are introduced into the cross wedge rolling tool, for example to reduce slippage. However, the large number of serrations leave surface defects during the cross wedge rolling process and can only be used in areas without functional surfaces. Inhomogeneous heating can reduce the surface defects, by reducing the number of serrations in the die and additionally reduce die costs. In addition, inhomogeneous heating also leads to a local reduction in scaling of the semi-finished product and improves surface quality. The heating strategy of inhomogeneous heating of semi-finished products for cross wedge rolling has not yet been the subject of research. From the preliminary investigations carried out, the working hypothesis of this research project is that inhomogeneous heating of semi-finished products leads to a more process-stable and quality-assured cross wedge rolling process. The aim of this research project is to determine the influence of inhomogeneous semi-finished product heating on the cross wedge rolling process in order to increase rolling quality and process stability. Different flow stresses in specifically inhomogeneously heated semi-finished products are to be used to specifically influence the forming behavior and thus increase the rolling quality. The rolling quality is assessed in terms of fishmouth depth, surface defects, internal defect probabilities and torsion. Process stability is assessed by looking at the slippage of the semi-finished product.