| 摘要 |
PROBLEM TO BE SOLVED: To perform flaw detection of the while section of a material having a distribution wherein the crystal grain size is relatively small in a surface layer part and relatively large in an internal part. SOLUTION: A probe 1 for the surface layer part and a probe 2 for the internal part are provided on the surface Ma of a billet M to be rolled, and the probe 2 for the surface layer part is equipped with a transmission vibrator 21 and a reception vibrator 22, and the transmission vibrator 21 and the reception vibrator 22 are arranged so that each of mutual ultrasonic beam axes crosses each other in the surface layer part. The probe 1 for the internal part is equipped with a transmission/reception vibrator 11, and ultrasonic beams therefrom are focused in the internal part. COPYRIGHT: (C)2008,JPO&INPIT
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