| 摘要 |
PURPOSE:To execute a flaw detection with a roughly uniform sensitivity with respect to the surface of the material, of a column or its similar shape to be inspected, by detecting an infrared-ray radiated from the surface of the material to be inspected, by plural pieces of infrared-ray detectors placed concentrically against the center of the material to be inspected. CONSTITUTION:A material to be inspected 1 whose surface is heated by a high frequency power source 2a and an induction heating coil 2b is carried and enters into the visual field of infrared ray detectors 3a1-3an. In this state, a current conducting to the surface of the material to be inspected 1 is usually concentrated in depth of <=1mm under the surface by a skin effect, therefore, in a surface defect part, its current path becomes longer than that of a part where there is no defect, the heating density increases and a temperature becomes high. On the other hand, before the material to be inspected 1 is carried and enters into the visual field of the infrared ray detectors 3a1-3an, the heat of the surface is diffused, but as for the surface defect part, the efficiency of heat conduction and heat radiation is worse than that of the part where there is no defect, therefore, a high temperature state is maintained. Accordingly, a defective part can be detected by being discriminated from the part where there is no defect.
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