MAGNETIC SENSOR, AND MAGNETIC FLAW DETECTION METHOD AND APPARATUS USING THE MAGNETIC SENSOR

摘要

A magnetic sensor for magnetic leakage flaw detection with high accurracy without much reducing lift-off, and a method and an apparatus for magnetic flaw detection using the magnetic sensor. The magnetic sensor (50) detects a magnetic flux generated due to a flaw in an object which is magnetized, and includes a ferromagnetic E-shaped core (51) having poles (51a, 51b, 51c) disposed in the proximity of a steel sheet (13) under inspection, and a search coil (52) for detecting the magnetic flux, wound on a center pole (51b) of the E-shaped core. External magnetic fields around this E-shaped magnetic sensor (50) pass through the magnetic poles (51a, 51c) on both sides of the E-shaped core but do not cross the center magnetic pole (51b) of the E-shaped core. Therefore, a voltage due to the external magnetic fields is not induced in the search coil (52), and only the magnetic flux resulting from the flaw is detected. Therefore, directivity to the external magnetic fields can be improved, the occurrence of the noise due to external magnetic fields can be restricted, and an S/N ratio can be improved at the time of flaw detection.