| 摘要 |
PROBLEM TO BE SOLVED: To reduce a working load and to secure the uniformity of a thickness of a material to be worked after working by upsetting a thickness of a center part with the tool having an area smaller than the material to be worked and upsetting a thickness of the part of the surrounding of the center part with the tool having an area larger than the above tool. SOLUTION: A material 3 to be worked, in which a metal material is formed to a disk of a prescribed thickness, is placed on a die and upset with a tool of a punch, etc., to be compressed to a desired thickness. At this time, by using the tool having an area smaller than the material 3 to be worked, the thickness of the center part 6a of the material 3 to be worked is upset, the material of this compressed part is moved to the outer peripheral part not compressed. The material 3a to be worked, in which the thickness of the center part 6a is upset, is upset by the tool having an area larger than when the center part 6a is upset. The material 3b to be worked, in which the center part 6b of this large area is upset, is gradually upset with using successive tools of larger area, a flat material 3c to be worked not having unevenness in thickness is easily obtained.
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