| 摘要 |
PROBLEM TO BE SOLVED: To accurately and surely detect an internal flaw in a welded part over the whole of a welded part cross section by means of a small number of ultrasonic probes in comparison with a conventional one in ultrasonic flaw detection in the welded steel pipe welded part. SOLUTION: On the outside face of the steel pipe on the lateral side of the welded part 2 in the welded steel pipe 1, an array type ultrasonic probe 3 having multiple ultrasonic oscillators 12 arranged on a convex face of a fan-shaped wedge 10 is arranged, and in the ultrasonic wave oscillator groups 11, a certain number of oscillator groups are excited simultaneously. After ultrasonic beams are transmitted/received by means of the oscillator groups, the oscillator groups are sequentially switched at a predetermined interval for performing scanning, and a vertical flaw 8 on the welded part overall cross section is detected by changing an incident angle of the ultrasonic wave beam. Just above the welded part 2, an ordinary type ultrasonic probe 4 is arranged, and a lateral flaw 9 in the welded part overall cross section is detected by transmitting/receiving ultrasonic wave beams in the welded part longitudinal direction.
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