DIE SET FOR FULL ENCLOSED DIE FORGING AND FULL ENCLOSED DIE FORGING METHOD

PROBLEM TO BE SOLVED: To prevent the development of shrinkage hole and underfill in the corner part of a tooth form, in the case of forming a large scaled gear, etc. SOLUTION: In a die set for full enclosed die forging, in which a cavity 2a is closed between an upper die 1 fitted to a slide side 6 and a lower die 2 set at a bolster 17 side, and an annular work 7 in the cavity 2a is pressurized and fluidly filled with an upper counter punch 8 and a lower counter punch 24 arranged in the upper die 1 and the lower die 2 to closely forge the annular work 7, the upper die 1 and the lower die 2 are closed to the upper part of the upper counter punch 8 and also, the upper counter punch 8 is pressurized from the upper part and the annular work 7 in the cavity 2a is fluidly filled to the outer peripheral side of the cavity 2a. Further, in this die set, a pressurizing means 11 fluidly filling the annular work 7 in the cavity 2a between the upper counter punch 8 and the lower counter punch 24 by releasing the pressurized force near a slide bottom dead center, is arranged, and even in the case of forging the large scaled gear, etc., since a blank is fluidly filled to the corner part of the tooth form, the formed product without developing the shrinkage hole and the underfill is obtained.