| 摘要 |
PURPOSE:To correctly and easily perform a small radius bending without using the deformation preventing means of a core metal and guide body, by making the heating temp. at the pipe inner face side a higher temp. than that of the innerface side at the bending inner peripheral side and by making the heating temp. and heating width at the bending outer peripheral side lower and narrower than those of the bending inner peripheral side. CONSTITUTION:A pipe 11 is advanced by starting a heating and cooling after setting a high frequency inductor 22 at the prescribed position inside the pipe 11 and a cooling ring 28 at the prescribed position outside the pipe 11, by holding the tip of the metal pipe 11 to be bent with the clamp jig 16 of a bending arm 12. Since the high frequency inductor 22 is heated so that the pipe outer face side become lower than the pipe inner face side on the pipe wall at the bending inner peripheral side of the pipe 11 an irregular deformation can be avoided. At the bending outer peripheral side the heating temp. is kept lower and the heating width is made narrower within the allowable range compared to the inner peripheral side, so the pipe wall becomes difficult to be deformed, the thickness reduction amount is reduced, the flattening is reduced as well and the bend pipe having smooth thickness increasing part is obtainable.
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