| 摘要 |
PURPOSE:To form a square steel pipe having good quality by welding inexpensively by providing inserting rolls in a steel pipe to be welded, positioning said rolls to face the top rolls on the outside of the steel pipe and disposing pressing devices on the right and left side surfaces. CONSTITUTION:A steel pipe 4 to be welded is so positioned that welding surfaces 1, 2 face each other through a spacing 11. A core 5 having right and left upper rolls 8 at the top and right and left lower rolls 9 at the bottom are inserted into the pipe 4. The rolls 8 are positioned to face the pressing rolls 10 in the upper part on the outer side of the pipe 4 above and below. Lateral pressing dies 6, 7 are provided in right and left directions. The surfaces 1, 2 are corrected with the rolls 10 and the rolls 8 and the spacing 11 is welded; at the same time, the pipe is formed continuously to a aquare shape, whereby the square shape having high accuracy is formed. |
