METHOD OF EDDY CURRENT FLAW DETECTION FOR CONTINUOUSLY-CAST PIECE

• Main Authors: SAKAMOTO TAKAHIDE, TAKAHASHI AKIO, HIROSHIMA TATSUO, TAGUCHI KATSUMI, ONO TOMIAKI
• Format: Patent
• Language: English
• Published: 23.08.1985
• Subjects: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIRCHEMICAL OR PHYSICAL PROPERTIES; MEASURING; PHYSICS; TESTING

PURPOSE:To enable the detection of a flaw without being affected by a noise signal caused by an oscillation mark signal, by a method wherein probe coils electrified with currents of two frequencies are moved for scanning in the prescribed direction and detection signal components are rotated on a vector plane to discriminate a flaw signal from the noise signal. CONSTITUTION:Probe coils 105a and 105b electrified with currents of frequencies f1 and f2 are moved in reciprocation for scanning in the direction oblique to the direction of the movement of a continuously-cast piece 1. Detection outputs of the frequencies f1 and f2 by detectors 110 and 111 are turned into necessary and unnecessary signals A1' and B1', and A2' and B2', by phasers 112 and 113, and these signals are rotated in phase by a phaser 114 and turned thereby into necessary and unnecessary signals A and B which are perpendicular to each other on another vector plane. Then, the signal A corresponding to a presence/absence component of a flaw is disciminated excellently from the signal B corresponding to a noise component, and the flaw of the continuously-cast piece is detected by an eddy current test from the ratio between the respective differences between the maximum and minimum values of the flaw component and the noise component without being affected by the noise caused by an oscillation mark signal.