Optimization of anvil design for ensuring dimensional precision of forged round billet without forging defects by three-dimensional rigid-plastic finite element analysis

Focusing upon finding an optimum anvil design of the spiral forging stage for manufacturing a round billet to good dimensional precision directly from an octagonal workpiece without forging defects, three-dimensional rigid-plastic finite element analyses have been carried out. By analysis and laboratory experiment, the mechanism through which overlapping defects are caused in spiral forging has been quantitatively clarified and a new parameter to predict overlapping defect generation proposed. By making use of the parameter, an anvil design of the entrance side has been proposed to prevent overlapping defects. Moreover, the whole geometry of the anvil has been optimized in order to ensure dimensional precision of the final round billet. As a result, a fundamental scheme to optimize anvil design for manufacturing a round billet directly from an octagonal workpiece has been established and the total number of passes was successfully reduced in the production line.