| 摘要 |
PURPOSE:To improve thermal efficiency and improve quality of products by applying high frequency current directly on opposite edge faces of an open pipe made by forming a strip to nearly cylindrical shape by a multi-stage roll, clamping by a squeeze roll and welding. CONSTITUTION:Contact pieces 7a, 7b for supplying high freqyency current are brought into direct contact on opposite edge faces of the open pipe 1 made by forming the strip to nearly cylindrical shape by the multi-stage roll. High frequency current is impressed through the two contact pieces 7a, 7b for supplying high frequency current, and at the same time, clamped by the squeeze roll and welded. At this time, heating current supplied from contact position of the edge faces and contact pieces 7a, 7b flows uniformly over whole edge faces and goes to the weld point 5.
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