| 摘要 |
PURPOSE:To reduce the incidence of defect by deviating the range of welding heat input added to a butting part by specific % up and down with respect to the welding heat input of a welding flash starting point to control it between the maximum and minimum heat inputs. CONSTITUTION:A beltlike steel sheet 1 is heated with a heating furnace 2 and afterward, is formed tubularly on forming stands 3 and welded by high-frequency seam welding device 4 and reheated and afterward, finished to a product by a drawing machine 13. The welding heat gain is calculated via a voltage and current measurement part 8 and the arithmetic part 6 of the device 4 and the welding heat gain is maintained and controlled within the range of the maximum and minimum heat gains of + or -10% of the precalculated heat gain of the welding flash starting point. Since the occupation area of a residual oxide of a welded zone is maintained to the minimum by the regulation of the heat gain range, the incidence of defect due to a weld flaw is reduced.
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