MOLDING METHOD BY FORGING AND MOLDING METHOD FOR CASE

摘要

A molding method by forging, wherein, a material (1) manufactured by punching out a plate-like member is molded, in an upsetting step, in a first intermediate molded product (2) by molding its peripheral edge part in an annular thin-walled part (21), molding the inside of the annular thin-walled part (21) in a thick-walled part (22) thicker in wall thickness than the annular thin-walled part (21), and forming a recessed part (22A) at the center part of the thick-walled part (22). A gear or a cup-like case with an inner boss is manufactured by using the first intermediate molded product (2). When the cup-like case with the inner boss is manufactured, the first intermediate molded product (2) is molded into a second intermediate molded product (3), in a drawing with ironing step, by molding its thick-walled part (22) in a bottom part (32) and pressing/molding the annular thin-walled part (21) in a peripheral wall part (31) integrally extended from the bottom part (32). The second intermediate molded product (3) is extruded forward and backward to extrude an inner boss (43) on the inside of the bottom part (42) and an outer boss (44) on the outside of the bottom part (42), and an outward flange part (41A) is formed at the outer end edge part of a peripheral wall part (41).