| 摘要 |
PURPOSE:To aim at improvement in power efficiency for heating by constituting an inductor with a main conductor to be opposed to a slit of the conveyed metal pipe, an extension conductor being unitized with this main conductor and set up inside the slit and the core attached to the main conductor. CONSTITUTION:A medium-frequency current is made to flow into a main conductor 5 and an extension conductor 7 of an inductor while conveying a metal pipe 2 in the longitudinal direction, and this extension conductor 7 is set up in a slit 4. If so, two circulating passages by an induced current (i) flowing in an edge 2a are formed in both inner circumferential and outer circumferential surfaces of the metal pipe 2, whereby the edge 2a, where the induced current (i) concentratedly flows, is heated. Thus, the induced current (i) flows as being divided into the inner circumferential surface and the outer circumferential surface of the metal pipe 2 at parts other than the edge part and as being extensively dispersed over the whole circumference so that a temperature rise in both inner and outer circumferential surfaces other than the edge 2a is thus checked. With this constitution, heating efficiency in the heating power is conspicuously improved.
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