| 摘要 |
PURPOSE:To enable a stabilized outer face welding by obtaining an uniform back bead, by controlling the voltage between a base metal and backing copper plate to weld in case of the inner surface welding. CONSTITUTION:The bevelled steel plate is formed in an angular pipe body by a press 4 by performing the bevelling of both sides by a bevelling machine 3 with feeding a steel plate 1 by a feeding roller 2. The angular pipe body 5 having the butt part at the upper side is reversed in the upper and lower directions by a reversing machine 6 and the inner surface welding is performed at flat position by a forming roller 7 with the butt welding zone at the lower side. In this case, the back bead in uniform width is obtd. by controlling the power source to the electrode so as to keep it in the prescribed value by measuring the voltage. The angular pipe body 9 subjected to the inner surface welding is reversed by the reversing machine 6 and subjected to the outer surface welding at flat position by the outer surface welding machine 10 with the butt weld zone at the upper side. The angular steel pipe 11 subjected to the inner and outer surface welding is straightened in its cross section by a straightener 12 and in its bend by a large bend straightener 13, and finally cut in the prescribed length by a cutter 14.
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