Investigation on metal flow and forming load of bi-metal gear hot forging process

Aiming at the lightweight of gears, this article presents the hot forging process of a bi-metal gear fabricated by two metals of steel (tooth ring material) and aluminum alloy (core material). The process was studied by the finite element (FE) simulation and forming experiment. The FE model of the bi-metal gear forging process was established based on the symmetry of the gear and the structure of forging die by using the software Deform-3D. The hot forging experiment of the bi-metal gear was carried out to verify the accuracy of the FE simulation by the comparison of the metal flow behavior. Metal flow of three stages, namely upsetting, gap and tooth filling, and corner filling was analyzed in the hot forging process. Effects of three aspects including the gap between the core and ring, the height difference between the core and ring, and the ring thickness on the metal flow and forming load were investigated. The results of numerical simulation showed that different gaps and different height differences between the core and ring influence the relative flow of two metals and different ring thicknesses significantly influence the structure of the bi-metal gear; large gap and small height difference between the core and ring and small ring thickness can reduce the forming load.