from the conferences organized by TANGER Ltd.
In numerical process design, the heat transfer coefficient (HTC) is used to calculate the intensity of heat transfer at an interface, for example between dies and workpiece. In most finite element calculations for bulk metal forging, a constant HTC is currently assumed, as there is no complete understanding of the relationship between the heat transfer coefficient and its influencing variables (e.g. contact pressure or temperature), which leads to inaccuracies in the simulation results. However, specifically set temperature profiles are necessary, particularly in the compound forging of aluminum and steel, in order to adjust the forming properties of the dissimilar semi-finished products. Setting the incorrect boundary conditions in the compound forging processcan lead to temperature profiles that cause the aluminum semi-finished product to melt or to insufficient formability of the steel. Due to the required temperature difference in the compound forging process of dissimilar materials, the accurate modelling of the heat transfer coefficient is of particular importance in the process design. However, the investigation of the HTC in forging processes represents a major challenge from an experimental point of view due to the very short pressure contact times and the high heating rates that occur. According to the current state of the art, there is no method for determining the prevailing HTC within a compound forging process as a function of relevant effective variables such as pressure, temperature or lubrication with reasonable effort. This paper presents a new test setup for recording HTC for the compound forging of aluminum and steel. In addition to the first prototype of the test setup, the test materials EN AW-6082 and S235JR were investigated with regard to their plastic behaviour and their thermally induced elongation. These material properties are used to define process windows for compound forging as well as for joint heating.
Keywords: Heat transfer coefficient, compound forging, process design, EN AW-6082, S235JR© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.