| 摘要 |
PURPOSE:To easily obtain the square steel pipe which is free from deformation by thermal strains by disposing nozzles so as to face the respective groove parts formed at the four ridge angles on the outer side of assembled steel plates formed by assembling 4 sheets of long-sized steel plates, at the same height, and continuously welding the groove parts by an automatic welding device, thereby forming the square steel pipe. CONSTITUTION:The automatic welding device A is previously lowered and a holder B which holds the assembled steel plates 1 formed by assembling the long-sized steel plates 1a to the square cylindrical shape is raised at the time of producing the square steel pipe C. The steel plates 1 are positioned vertically and the four nozzles 3 of welders 4 can face the respective four groove parts 2. While the automatic welding device A is risen, the groove parts 2 of the assembled steel plates 1 are continuously welded. Since the groove parts 2 are welded upward from below in this case, the flow-down of molten welding materials is obviated and the groove parts 2 are correctly and continuously built up. Since the same height parts of the long-sized steel plates are simultaneously and uniformly heated in this way, the square steel pipe which is not deformed by the thermal strains is easily obtd. |
