| 摘要 |
PURPOSE:To stably prevent the occurrence of the edge buckling by forming a coil plate by rolls and meeting both edges and heating or cooling the edges and moreover, monitoring a temperature or a meeting state of the edges to correct a heating or cooling condition of the edges. CONSTITUTION:The coil plate 1 is delivered and bent and formed by a group 2 of forming rolls ... and both edge parts 4 and 4 of the plate are met by a fin pass roll 3 and welded in a welding stage 5 to obtain a welded pipe. In this welded pipe producing method, a plate central part 6 other than the edge parts 4 of the plate 1 is heated and expanded at the position of the material inlet side from the welding stage 5 by a heating heater 10 to relax the compressive stress in the neighborhood of the above-mentioned edge parts 4. Moreover, a thremometer 11 of a 1st monitor and an image sensor 12 of a 2nd monitor are arranged in the rear from the above-mentioned position to measure the temperature and the meeting state of the plate 1. These measured values are inputted to a controller 13 and a heating source 14is controlled based on these values to correct the heating condition. In this way, the occurrence of the edge buckling is prevented easily and stably with high reliability.
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