METHOD AND APPARATUS FOR DETECTING UNEVEN SURFACE DEFECT

摘要

A detection method for detecting a concavo-convex shape surface defect existing on a ferromagnetic metal comprises a step of sensing a signal attributed to strain of the concavo-convex shape surface defect having a size in a range of 0.5 to 6 µm. The signal is magnetic flux leaking from the ferromagnetic metal to which magnetic flux is applied. A detecting apparatus incorporates a magnetizer for magnetizing a ferromagnetic metal and a plurality of magnetic sensors arranged in the direction perpendicular to a traveling direction of the ferromagnetic metal to sense a signal attributed to strain of a concavo-convex shape surface defect having a size in a range of 0.5 to 6 µm. [Selected Drawing] FIG. 1