Abstract: An inductive heating device for uniformly heating a workpiece at rest has a plurality of heating coil units disposed so as to surround the workpiece. The heating coil units are connected in parallel to a power source, and a transformer is used to vary the voltage across the terminals of the outermost units to increase the current flowing through these outermost units. The device, therefore, has a very short insufficient heating temperature zone attributable to an end magnetic flux effect.

Abstract: An inductive heating device for heating a workpiece made of carbon has a heating coil disposed so as to surround the carbon workpiece. A first and second heat insulating layer is interposed between the workpiece and the heating coil, with the first layer being made of a carbon powder and the second layer being made of a carbon and silica powder mixture. A high frequency electrical source is used to drive the heating coil, which causes an eddy current to be induced in the workpiece, thus heating the workpiece. The first and second heat insulating layers prevent the surface of the workpiece from oxidizing and minimize heat loss from the workpiece during the heating thereof.