Composite Cold Forging of Cold Forged Semi-Finished Parts

Funding: German Research Foundation (DFG)
Project: 270149504
Contact: Robin Gitschel M. Sc.

Forward rod extrusion of composite billets consisting of a light metal core and a steel cup allow for the production of lightweight gear shafts while losing only small amounts of torsional and bending stiffness in comparison to a steel-only shaft.

The steel sheath of the composite billet is produced by backward can extrusion. To further increase the lightweight potential compared to aluminum cores, magnesium is used instead. To this end, C15 steel cups with three different wall thicknesses are produced, into which hot extruded round AZ 31 magnesium profiles with corresponding diameters are inserted. Subsequently, the hybrid billets are formed into composite shafts by forward rod extrusion (see Figure a). The high hydrostatic pressure during this forming process enables the magnesium to be formed at room temperature and up to large strains. The process is limited by the occurrence of chevron cracks when using low extrusion strains (see Figure b) and by upsetting of the shafts during ejection for high extrusion strains.

a) Process flow, b) Longitudinal cross section view of investigated specimens