Optimization of open-die forging process design to ensure homogeneous grain size refinement of cast structures by three-dimensional rigid-plastic finite element analysis

Abstract

Focusing on the rough-forging stage of the hot open-die forging process, the influence of pass schedule on the equivalent plastic strain distribution at the surface of a forged billet has been numerically analysed using a three-dimensional rigid-plastic finite element method. By analysing the circumferential distribution of the strain obtained by one forging pass, it has been clarified that the distribution is strongly influenced by the cross-sectional shape of a workpiece. By utilizing the analytical results, a new method has been developed to predict the cross-sectional shape and the strain distribution without numerically analysing all passes. As a result, a new pass schedule has been proposed to ensure homogeneous grain size refinement of cast structures and the effect of the pass schedule was verified by a real hot open-die forging experiment.