| 摘要 |
To provide an upsetting method capable of efficiently expanding a bar-shaped raw material at least two portions. A plurality of guides 31 and 32 each having an insertion hole 34 are prepared. The bar-shaped raw material 1 secured to a fixed die 20 is inserted and held in each insertion hole 34 of the plurality of guides 31 and 32 in order. Then, a first exposed portion 4 of the raw material 1 exposed between a first guide 31 located at the foremost side of the plurality of guides 31 and 32 and the fixed die 32 is expanded in diameter by moving the plurality of guides 31 and 32 in a direction opposite to a moving direction of the punch 50 R in a mutually adhering manner while pressurizing the raw material 1 in the axial direction with the punch 50 R. After completion of the movement of the first guide 31 , a second exposed portion of the raw material 1 exposed between both the guides 31 and 32 is expanded in diameter by relatively moving the second guide 32 located behind the first guide 31 among the plurality of guides 31 and 32 in a direction opposite to a moving direction of the punch 50 R.
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