FLAW DETECTION METHOD OF METALLIC MATERIAL

PURPOSE:To detect automatically and continuously flaws with high reliability, by disposing an electrode which is applied with voltage oppositely to a metallic material and detecting the electric discharge pulses generated between the metallic material and a power source. CONSTITUTION:One end of a traveling metallic wire rod 10 is grounded and a DC voltage E is applied from a DC power source 14 to an annular electrode 12 which encloses the wire rod 10 apart therefrom. If there is a flaw such as a projection or dent on the surface of the traveling wire rod 10, the electric field between the electrode 12 and the wire rod 10 increases in the vertex of the projection, the edge of the dent, etc.; therefore, a partial discharge is generated between the flaw part and the annular electrode. Then a pulse current flows to a capacitor 16 and a pulse voltage Ep is detected by a pulse detector 20. The presence or absence of the flaw in the wire rod 10 and the position thereof are detected from the traveling speed of the wire rod 10 by the pulse detector 20 in the above-mentioned way.