| 摘要 |
A bending method for pipe material using a conventional device such as press device, wherein, in order to prevent wall thinning and cracks, one side of a cylindrical pipe material (1) is firmly held by a firs t clamp (2) with the other side loosely held by a second clamp (3). The clamp (2) is moved downward in the drawing with respect to the clamp (3) , with an axially pressing force applied to the pipe material (1) at the opposite ends thereof. The pipe material (1) is plastic-deformed by being guided by a 1/4 spherical surface (4a) of a core (4) and a 1/4 spherical surface (5a) of a core (5) to form linear portions at two bending portions and at an intermediate portion therebetween.
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