| 摘要 |
A leakage flux flaw detection apparatus in which an object material is magnetized and leakage fluxes derived from a flaw are detected to thereby search for a flaw of the object material in a predetermined flaw-detection direction. The apparatus has a pair of magnet poles for magnetizing the object material in a direction different from the flaw-detection direction, another pair of magnet poles for magnetizing the object material in a direction different from the magnetization direction and flaw-detection direction of the first pair of magnet poles at a predetermined distance in the flaw-detection direction from the magnetization area of the two magnet poles, and two leakage sensors each of which is interposed between each of the two pairs of magnet poles. The leakage flux sensor which detects leakage fluxes from a flaw of the magnetized object material through two flux-sensing parts arranged in opposed relation to the object material and in predetermined spaced relation with each other along the flaw-detection direction includes two flux-sensing parts having the center distance d thereof not more than 4 mm, the length L of not less than 0.5 mm in the direction perpendicular to the flaw-detection direction, and the value d/L of nor less than 1. The leakage flux sensor includes two concentrically-arranged flux-sensing parts having circular cross sections with different cross sectional areas.
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