Optimisation of spiral forging process design for ensuring uniform quality of forged round billet by three-dimensional rigid-plastic finite element analysis

Focusing on the spiral forging stage of the hot open die forging process, which is the final stage of finishing round billets from ingots, the influence of operational conditions on the distribution of equivalent plastic strain has been numerically analysed using a three-dimensional rigid–plastic finite element method. The mechanism via which equivalent plastic strain is accumulated at the surface of the workpiece during spiral forging is clarified. The independent influence of each major operational parameter, i.e. rotational angle and feed, is revealed, and the optimum combination of these two parameters is clarified. The influence of the coefficient of friction is also discussed, and, as a result, a fundamental scheme to optimise spiral forging process design is suggested, taking account of not only uniformity of quality but also dimensional precision of the forged round billet.