| 摘要 |
PURPOSE:To shroten a scanning distance in rough detection and to enable reduction of the time for flaw detection by a method wherein flaw detection sensitivity is set to be higher than a reference value while a scanning pitch is made a value enabling detection of a minimum defect length, on the occasion of the rough detection, and the flaw detection sensitivity is restored to the reference value on the occasion of precise detection. CONSTITUTION:First and second attenuators 23 and 24 are provided for an ultrasonic flaw detector 15 and thereby flaw detection sensitivity can be lowered by -6dB. An ultrasonic probe 11 is made to conduct square scanning along the surface of a body 12 to be inspected, by a scanning mechanism 14, and echo detection is executed by the probe 15. On the occasion, rough detection in which a scanning pitch P1 is large is executed and a defect position is stored 18. Then, the probe is returned to the stored defect position and precise detection in which a detecting scanning pitch P2 is small is executed. On the occasion of the rough detection, the flaw detection sensitivity is set to be higher by 6dB than a reference value and the pitch 1 is set at an added approximate value of a minimum defect length and an effective beam width of the minimum width of a far sound field in an ultrasonic beam, at 7mm, for instance. According to this constitution, the number of scans in the rough detection can be lessened and shortening of the time for flaw detection and, in its turn, an improvement in a working efficiency can be attained. |
