| 摘要 |
PURPOSE:To prevent a buckling and to improve the material yield by upsetting with adjusting the gap between a mandrel and necking die. CONSTITUTION:The end part 2 of a tubular blank 1 in specific dimension is heated at the necessary forging temp. And a heating end part is drawn by using a die to form a necking part. The blank 1 is fitted to a press by inserting the mandrel 5 provided coaxially with the plunger punch 4 of a horizontal press and horizontally advancing and retreating into the inner hole of the blank 1 forming the necking part thereof. The outer periphery of the blank 1 is pinched by upper and lower necking dies to advance the pushing die 4, upsetting the mandrel 5 by gradually retreating it as well. The necking part is finally formed in the thick inclining necking part 7 thickening toward the end part.
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