| 摘要 |
PROBLEM TO BE SOLVED: To provide a flaw discriminating method for accurately discriminating whether the bad effect of flaw in a material to be inspected such as a square billet or the like is present by performing ultrasonic flaw detection with respect to the flaw generated in the material to be inspected. SOLUTION: The flaw echo reflected from the flaw in the square billet and the reflected echo transmitted through the flaw and reflected from the opposed surface are received and the flaws in the lattice blocks, which are formed by dividing the cross section of the square block, are detected. When the flaw is continuously recognized in the same block in the longitudinal direction of the billet, the flaw is recognized as one flaw and the length thereof is calculated and, when the length of the flaw is a prescribed value or more or the intensity of the flaw echo at every length position of the flaw is a prescribed value or more, the flaw is discriminated as a harmful flaw and, when the length of the flaw and the intensity of the flaw echo are below prescribed values, the phase of the flaw echo is compared with the phase of the reflected echo and, when the number of the phases discriminated to be the same is more than the number of the phases discriminated to be opposite, the flaw is discriminated as a harmful one and, in the case of opposite, the flaw is discriminated as a harmless one.
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