| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for precisely discriminating a porosity which is turned to be harmless when crimped in the process of product rolling from an intervening object which is turned to be harmful when left without being crimped. SOLUTION: Probes 21, 22, 23, and 24 are brought into contact with the side face of an angular billet 1 so that an ultrasonic pulse can be made incident, and surface echo and defective echo can be received from a metallic material, and amplified by amplifier 31, 32, 33, and 34, and displayed on monitor devices 41, 42, 43, and 44. Then, each beam 'path length is calculated based on the position of the displayed surface echo and defective echo on a time axis so that the position of a defect 5 can be decided, and a distance from the decided position of the defect 5 to the center of the angular bit 1 is calculated, and compared with a preliminarily decided threshold. When the distance is larger than the threshold, the defect is discriminated as an intervening object, and when the distance is smaller than the threshold, the absolute values of the maximum value and minimum value of the level of the received defective echo are compared with each other by deciding the order in which the probe 21 is the first. In the same way, the comparison processing is operated to the surface echo.
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