| 摘要 |
PURPOSE:To obtain a welded joint having high reliability by joining unit pipes to each other, and welding the same while passing cooling liquid in the pipe in the region before or after the weld zone as a center and cooling the same in such a way. CONSTITUTION:Unit pipes 1, 1 are set by pressing a welded joint part 2 opposite to each other on support rolls 7, 7- and while valves 16, 16 are held closed, sealing plugs 8, 8 are inserted in proximity to the weld heat affected zone. Driving motors 6, 6- are started to rotate the pipes 1, 1 at a set speed via the rolls 7, 7-; at the same time, the weld beam for the 1st layer is deposited in the groove of the joint part 2 by a torch 20. Valves 17, 17 are opened to feed compressed air to the cavities 12, 12 of the plugs 8, 8 and to bulge sealing rubber 11, 11 thereby bringing the same into press contact with the inside surface of the pipes 1, 1. The valves 16, 16 are then opened to fill the cooling liquid in the pipes 1, 1 and to discharge the same from the other and the welding for the 2nd and succeeding layers is accomplished while the heat affected zone is forcibly cooled. |
