FORMING METHOD TO ATTAIN HIGH YIELD RATE OF FORGING MATERIAL

摘要

A high yield forming method of a forging workpiece is provided to improve quality of forgings by removing a surface defect layer that has been existed in the preform while performing a preliminary forging process with respect to an inside part of a preform. A high yield forming method of a forging workpiece comprises: forming a preform(M1) such that an inside part(Pi) and an outside part(Po) are mixed in the cross-sectional area of a finished forging; forging the preform by a preliminary forging mold having a larger cross-sectional forming area than the finished forging with respect to the inside part; forming a preliminary forging in which a surface defect layer existing in the inside part is positioned at inner and outer sides of a forming area of the preliminary forging mold; forging the preliminary forging by a main forging mold of which a cross-sectional forming area corresponds to that of the finished forging to remove the surface defect layer; and forging the outside part in the preliminary forging mold and main forging mold having the surface defect layer existing in the outside part positioned in forging areas thereof, thereby removing the surface defect layer to obtain a finished forging(M3).