METHOD AND APPARATUS FOR ULTRASONICALLY DETECTING FLAW OF WELDED PORTION

摘要

Provided are an ultrasonic flaw detecting method and an apparatus for detecting a flaw existing in a welded portion of an object under examination, such as a welded pipe with high accuracy irrespective of the position of the flaw.  The ultrasonic flaw detecting apparatus (100) equipped with n vibrators (11) (n=2) arranged in the direction perpendicular to the weld line of the welded portion (P1) of the object (P) includes an ultrasonic probe (1) placed oppositely to the welded portion and a transmission/reception control means (2) for selecting m vibrators (n>m=1) out of the n vibrators, transmitting an ultrasonic wave from the selected vibrators to the welded portion while sequentially changing over the selected vibrators.  The transmission/reception control means sequentially changes over the selected vibrators so that the ranges of the beam widths of the selected vibrators effective for the flaw to be detected overlap with one another.  The sensitivity of the detection of the transmission/reception control means is previously adjusted for each of the selected vibrators so that the maximum intensities of the echoes from the flaw to be detected received by the selected vibrators are approximately equal.