| 摘要 |
PROBLEM TO BE SOLVED: To form the disk parts from a barlike member with high precision and to extend the service life of a punch and a die by forming an annular portion on the outside of the center part using the another die after forming the center part by dividing a forming range into plural pieces with an axial core as the center, and further, correcting an erected corner in an unforming portion on the outside of the center part at the time of forming the center part. SOLUTION: In the formation of the first stage, a portion being the disk part of the bar-like blank is compressed in the center axial direction in the warm or hot condition to execute an upset formation. Successively, this formed material is transferred to another forming device, and the upset-formation is executed on the barlike blank 10 at the inside portion of the disk-like part with a punch 13 a lower die 14 at the second stage and the upset formation is executed on the unforming portion of the outside at the third stage. The inclining surface 13a of the punch 13 restricts the erected angleθto prevent the over lapping and this angle is adjusted to satisfy (90 deg.-θ)>=(200μ-20 deg.) (μis the coefficient of friction of the blank) by using the axial line of the unforming portion as a reference. In the formation of the third state, the upset-formation is executed on the outermost portion while preventing the concentration of the load into the center part.
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