| 摘要 |
PURPOSE:To prevent a rejected article due to a short of thickness and to improve the yield by increasing the thickness at the side end of a strip steel by an upsetting roll and after making the angle between a side end face and tube outer side face in an acute angle as well, smoothing the side end face by a milling cut device. CONSTITUTION:The narrow width strip steel 1 slit in plural lines by a slitter is contracted by pressing it in the plate width direction by an upsetting roll 7, a thickness is increased on the side edge part and the angle made by the steel tube outer face and side end face becomes of an acute angle. The narrow width steel strip 1 is smoothly subjected to cutting by a milling cut device 9 and the angle made by the steel tube outer face and side end face is simultaneously aligned in an acute angle. It is then formed in a tubular shape via a breakdown roll 2, side roll 3 and fin pass roll 6, subjected to induction heating by a work coil 5 and joined by pressurizing by a squeezing roll 6. In the case of its thickness increase by rolling, no loss is caused because an angle can be formed. Also the edge end face is cut, so the groove suitable for welding can be formed.
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