IRONING DIE, IRONING PUNCH AND IRONING APPARATUS USING THEM

摘要

PROBLEM TO BE SOLVED: To solve a problem where ironing die composed of an inner cylinder with an inner circumference coming in contact with the outer circumference of a workpiece W and an outer cylinder into which the inner cylinder is fit is cracked sometimes when ironing is repeated. SOLUTION: The ironing die 4 is composed of the inner cylinder 2 and the outer cylinder 3 into which the inner cylinder 2 is fit. The inner cylinder 2 is made from silicon nitride sintered compact and the ironing die 4 therefore has high tensile strength and rigidity and is hardly cracked even when high tensile stress is applied to the inner cylinder 2 by the ironing and also the outer cylinder is hardly cracked since the outer cylinder 3 is hardly expanded radially. Te outer cylinder 3 is made from an alloyed tool steel of the level of SKD 60th stipulated by JIS G 4404, consequently the outer cylinder has high tensile strength and the outer cylinder 3 is hardly cracked even when high tensile stress is applied from the inner cylinder 2 to the outer cylinder 3 by ironing and the life of the ironing die 4 is prolonged. COPYRIGHT: (C)2008,JPO&INPIT