| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method of pipe-shaped processed goods having better surface roughness and high strength at low costs and capable of simplifying a manufacturing process. SOLUTION: In a method forging a serration portion on an outer peripheral surface of a bottom portion of a pipe-shaped stock by retaining the metal pipe- shaped stock by a lower die 12 in a standing state and also descending an upper die 11 against the lower die 12, the lower die 12 comprises a die set portion 15 formed a serration-shaped projected and recessed portions 23a on an inner peripheral surface of a through hole 22 capable of insert through a bottom portion of the pipe-shaped stock, and a guide pin 18 arranged on a part of the through hole 22 corresponding with the serration-shaped projected and recessed portion 23a. A circular gap is formed between the guide pin 18 and the serration-shaped projected and recessed portion 23a. According to descending of the upper die 11, the bottom portion of the pipe-shaped stock 5 is guided through the circular gap, a serration portion is forged on the outer peripheral surface of the bottom portion of the pipe-shaped stock 5.
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