DIE FOR POWDER MOLDING

摘要

PROBLEM TO BE SOLVED: To provide a die for powder molding capable of suppressing degradation of the circularity of a powder compact.SOLUTION: In a pair of notch grooves 56 adjacent to a circumferential direction of a powder compact 50 in a view of a cross section orthogonal to an axial line X of the powder compact 50, a linear line bisecting one notch groove in the circumferential direction is made to be a first straight line C1, that bisecting the other notch groove in the same direction to be a second straight line C2, and that bisecting the angleθmade by the first and second straight lines C1 and C2 to be a third straight line. A point separating from the intersection of an inner peripheral face 3a of a first upper punch 3 and the first straight line C1 to a radial inside by the same length as the clearance Sbetween the first and second upper punches 3 and 4 is made to be a first end point P1, and a point separating from the intersection of the inner peripheral face 3a and the second straight line C2 to the radial inside by the same length as the clearance Sis made to be a second end point P2. When the intersection of the inner peripheral face 3a and the third straight line C3 is made to be an intermediate point P3, plural arc cylindrical parts 4a to 4c having the outer peripheral faces 4a1 to 4c1 formed on an arc locus from the first end point P1to the second end point P2through the intermediate point P3are formed in a peripheral direction to compose the lower end of the second upper punch 4.