| 摘要 |
PURPOSE:To stably detect a flaw of a high temperature metallic material, by phase-detecting a flaw detecting signal with a detecting coil to a resistance portion and a reactance portion, and after that, executing each signal temperature compensation to said each signal by each temperature compensating signal. CONSTITUTION:The distribution of an eddy current generated on the surface layer part of a slab 100 by an AC magnetic field formed by an energizing coil 1 is detected by a detecting coil 2, the eddy current is varied by whether a flaw exists or not on the surface layer part, and an output signal SO of the coil is varied. A temperature detector 3 outputs a temperature detecting signal T corresponding to a temperature of the slab 100. The signal SO detected by the detecting coil 2 is resolved to a resistance portion RO and a reactance portion XO in phase- detecting circuits 41, 42. On the other hand, the temperature signal T is converted to a temperature compensating signal R2 against the resistance portion and a temperature compensating signal R2 against the reactance portion and a temperature compensating signal X2 against the reactance portion in function generators 51, 52. The signals R0, X0, and the signals R2, X2 are operated by adding circuits 61, 62, respectively, and a compensated signal, that is to say, a flaw detecting signal which has removed a portion influenced by a temperature is obtained, and this flaw detecting signal is sent to a succeeding signal processing part. By such a temperature compeansation, flaw detection of a high temperature metallic material is executed stably. |
