Precision Forging of Cast Preforms

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In die forging practice, intricate shaped components are progressively forged in multiple steps starting from simple semi-finished workpieces that are constant in cross sectional area. This presents the challenge of designing a process sequence with appropriate preform geometries which mainly depends on the part geometry, the available forming equipment and certain process parameters. All these aspects set measures to the design flexibility of the process. A restricted process design may have many consequences including but not limited to low material utilisation, defective products, longer run-up times, increased tooling costs and redundant labour. The technology of forging cast preforms (casting/forging) appears as a promising alternative to the conventional die forging to handle such problems in a simple but effective manner. Despite a few casting/forging examples for aluminium processing, a technological gap exists in terms of steel processing. Moreover, precision (net or near-net shape) forging principles have never been incorporated into such process technology. The main objective of this research proposal is to gain basic insights into the evolution of the mechanical and microstructural properties of the cast preforms under deformation processing and to identify the proper processing conditions. To this end, a two phase work programme is planned. In the first phase, the influence of deformation processing on the cast structure will be studied thoroughly utilizing cylinder upsetting process. The microstructural treatment and the deformation history will be related by means of extensive characterisation tests. In the second phase, processing of an intricate shaped demonstrator by casting/net-shape forging will be implemented relying on the findings of the first phase. A basic understanding of the casting/forging technology will be gained and the literature will be enriched which at its current state lacks information especially on steel processing. It is expected that the research findings will also give rise to new innovative concepts.