| 摘要 |
PURPOSE:To execute an automatic welding by only placing a backing material, and to manufacture easily an excellent square steel pipe with a high yield, by executing in advance a suitable edge preparation to an edge part of a prescribed length of a rear end part of a pipe. CONSTITUTION:A rear end off-seam part is brought in advance to an edge preparation in a V-shaped before an electric welding. At the time of an electric welding, a groove part 12 is left by preventing metting due to heating by a proximity effect of an edge part, and thereafter, a backing material 11 is placed, and welding is executed by an automatic welding machine. In this way, a square steel pipe having a sound weld zone is manufactured easily. |
