Abstract
The extend forging process is divided into the initial reduction, performing process (square process) and the finish forging process, and so on. High productivity and dimensional accuracy are desirable features in the finish forging process. In this paper, the relationship between forging conditions and dimensional accuracy was investigated in the finish forging process. The cross-section is deformed from square to octagon by a pair of flat dies, and from octagon to round by a pair of tap dies in the finish forging process. The equations for prediction of the width were developed using a numerical simulation, and a process design method in which the target size is achieved in 4 passes was developed in the octagon process. The width size of predictions using this method and the actual measurement width size were compared, and the accuracy was verified. As a result, it was clarified that the actual width size was predictable within 10 mm. The influence of the feed, the rotation angle, and the octagon size on dimensional accuracy was investigated in the spiral forging. The actual improved experimental conditions were decided on as a result of determining the improvement forging conditions using a numerical simulation. The results of the improved conditions were compared with the conventional ones. By using a numerical simulation, the optimum conditions for forging the octagon to the target round shape were calculated. Both satisfactory dimensional accuracy and productivity were achieved compared with the conventional conditions.
