Method for producing a pipe and apparatus for the same

Abstract

According to the present invention, in the first process, a pipe end of a long pipe is bent with a radius of curvature which is larger than a minimum radius of curvature to form a large R portion. That is to say, bending with a large radius of curvature (R) is performed to form a large R portion in a region in which cracking or excessive reduction of plate thickness of the bend outer-side portion, or buckling of the bend inner-side portion does not occur. Subsequently, in the second process, the pipe is bent with a small radius of curvature form a small R portion by pressing a pipe-end portion of the pipe from a pipe-end direction while fixedly holding the bend side wall of the pipe. In this way, it is possible to obtain an R-minimum elbow configuration irrespective of magnitude of an amount of elongation of material and further without special equipment or mechanisms, by minor modification of present equipment.

Dependencies are inferred from the claim text.