| 摘要 |
PURPOSE:To make the production of materials cut beforehand to finish sizes possible by working the opposite edges of a small gap so as to expand toward a groove at a gentle curve in such a way that the small gap makes point contact necessary for high frequency resistance welding successively from one terminal of the steel materials which are cut to a specified length. CONSTITUTION:A small gap 9 which expands from a constant small gap part 11 to a small opening gap 2 and becomes largest in an opening end part is provided at one terminal of a steel material 4. The opposite lines 1, 1 thereof assume a gentle curve. Thereupon, opposite flanges 3, 3 are held in place between rolls 5 and 7, and the lines 1, 1 are brought into point contact successively in a longitudinal direction, whereby the lines are subjected to high frequency resistance welding. Thus the closed tubular steel material of a specified length is obtained from the steel material beforehand cut to the finish specified length. |
