High frequency whole inner peripheral surface heating coil for cylindrical work and high frequency whole inner peripheral surface heating method for cylindrical work

摘要

PURPOSE:To heat the whole inside circumferential surface of a cylindrical work to a uniform depth by installing a magnetic substance core in such a way as covering part or the whole of that outside surface area of the first lead conductor which mates with the second inside circumferential surface approximately. CONSTITUTION:A core 16 of a magnetic substance, for example ferrite, having a thickness (t) and a length L in the direction along the axis 29 is mounted in the lower part of the first lead conductor of a heater coil 10. The core is mounted on the lead conductor 11 in such a way that the top of the core 16 lies at a distance (d) from the boundary 28 between the first inside circumferential surface 23 and second inside circumferential surface 24 when the coil 10 is insered into a work 20 so that the coil 10 approaches and confronts the whole inside circumferential surface of the work 20. In the case the surface 25 of the work 20 is to be quenched by the coil 10, the density of the resultant magnetic flux intersecting the surface 24 becomes more than conventional because of provision of the core 16 on the lead conductor 11, and further because adjustments of the core angle theta, thickness (t), length L, and distance (d) have been conducted previously, the mean heating depth of the surface 24 becomes approx. the same as the surface 23, so that the heating depth of the surface 25 can be made approx. uniformly.