| 摘要 |
PROBLEM TO BE SOLVED: To provide a method capable of producing a hollow metal part having double wall excellent in dimensional precision without leaving foreign matters into a gap between the inner and the outer wall parts constituted of the double wall. SOLUTION: A double metal tube blank composed of a metal-made inner tube 20 at the inside of a metal-made outer tube 10 is prepared. The double metal tube blank is set to a first forming die in the state of closing both end opening holes, and the double metal tube blank is bulged by acting fluid pressure into the inner part of the inner tube 20. In this way, the outer shape corresponding to the die shape of a first forming die, is given to both of the inner tube and the outer tube of the double metal tube blank (the first formation). Successively, the first formed product is set to a second forming dies (41, 42) in the state of closing both end opening holes and the outer tube portion 10 is bulged by acting the fluid pressure between the inner tube portion 20 and the outer tube portion 10 in the first formed product. In this way, the outer shape corresponding to the die shapes (41a, 42a) of a second forming dies is given to the outer tube portion 10 of the first formed product (the second formation). COPYRIGHT: (C)2005,JPO&NCIPI
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