| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of manufacturing steel pipes by a simple method of making a spiral pipe even when it is a thin small diameter pipe below 50 mmϕ. SOLUTION: When a steel strip is worked and formed into a spiral shape by making the steel strip pass through forming rolls and made into the spiral steel pipe by welding adjacent edges each other at weld points, one bar body having a circular cross section, which is extended in the axial direction of the pipe on the side of the inner surface of the pipe is used in place of an internal forming roll group composed of a plurality of forming rolls which are arranged inside a spiral-shaped formed pipe. It is made possible to remarkably reduce a formable diameter when making the pipe, which has been depended on the diameter of a roll supporting shaft with which the inner surface forming roll group has been mounted and held up to now. COPYRIGHT: (C)2011,JPO&INPIT |
