In order to develop a forging process that enables effective closure and consolidation of voids in the centerline of a heavy ingot for ultralarge rotor shafts, optimization of the combination of die configuration and billet section geometry was performed using a 3-dimensional finite-element method and high-temperature modeling experiments on NiCrMoV-rotor steel. The results indicate that a pair of indenter flat dies with the initial die width-to-billet height ratio of 0.5 for a round billet is more efficient than the conventional broad dies and V-shaped dies because it is shown under the non excessive load requirement that good closure of voids at the center of the billet is achieved, and the amount of longitudinal elongation of the billet is smaller.
