DEFECT-DETECTING METHOD OF METAL BODY, AND SCANNING TYPE MAGNETIC DETECTOR

摘要

PROBLEM TO BE SOLVED: To sufficiently detect a defect of a magnetic metal body, using a magnetic impedance effect type sensor by a magnetic leakage flux testing method.;SOLUTION: Demagnetization or magnetization processing is applied so that the magnetization state of the metal body is made uniform. Then, a magnetic detector, having a coil for applying a magnetic field to the metal body and the magnetic impedance effect type sensor for detecting magnetic leakage flux at the defect part of the metal body, scans the surface of the metal body, while applying the magnetic field to it by the coil. Even if the metal body is distorted locally and magnetically, it will locally become magnetized by remanence, and the magnetic leakage flux noise occurs, the demagnetization or magnetic processing is applied to make the magnetization state uniform so that the magnetic impedance effect type sensor does not react to this, and the defect is detected using the magnetic impedance effect type sensor by the magnetic leakage flux testing method. Thus, the influence of magnetic leakage flux noise by the remanence is eliminated, and the defect parts of the metal body can be detected at original high sensitivity, based on the magnetic impedance effect.;COPYRIGHT: (C)2007,JPO&INPIT