RECESSED GROOVE FORMING METHOD OF METAL PIPE SURFACE, RECESSED GROOVE FORMING APPARATUS, AND METAL PIPE

摘要

PROBLEM TO BE SOLVED: To provide a recessed groove forming method of a metal pipe surface, a recessed groove forming apparatus, and a metal pipe, which are suitable for the production of a roof rail body of a roof rail for an automobile, which can prevent the wear or deterioration of a pattern thereby to maintain an initial pattern for a long period of time, and which intensify the strength of a metal pipe thereby to improve a lifetime.SOLUTION: A core grid 4 having a section substantially identical to that of a metal pipe 1 is inserted thereinto; a shaping roll 8 having one or more shaped salients 9 formed on a rotatable pressing face is rotated and moved in the axial direction of the metal pipe 1 so that the shaped salients are pressed onto the surface of the metal pipe thereby to form recesses 2.