| 摘要 |
PROBLEM TO BE SOLVED: To inspect a whole area conveniently and efficiently eliminating the effect of magnetic inhomogeneity on a ferromagnetic metal tube with a non- magnetic metal layer formed therein, particularly on a hot-dip aluminum-plated carbon steel tube. SOLUTION: In this inspecting method, an unused tube and a plurality of tubes at different damage stages are tested for flaws by an insertion probe type eddy current flaw detector, and on the basis of the information therefrom a reference graphic is formed. By likewise forming a graphic about a metal tube being inspected and by comparing it with the reference graphic, a damage stage of the metal tube being inspected is determined. Also, a permanent magnet 202 with a weak magnetic force is arranged on both sides of a test coil 201 in a probe 200.
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