ULTRASONIC FLAW DETECTING METHOD, MANUFACTURING METHOD FOR WELDED STEEL PIPE, AND ULTRASONIC FLAW DETECTING APPARATUS

摘要

Provided is an ultrasonic flaw detecting method, in which an angle probe is arranged on the outer face of a welded steel pipe, such that the propagation direction of a transverse-wave ultrasonic beam in the welded steel pipe may be substantially perpendicular to the longitudinal direction of a weld beam and such that the transverse ultrasonic beam having a deflection angle of 40 degrees or more and less than 55 degrees may propagate to that one of the two toes of the weld beam in the inner face of the welded steel pipe, which is less distant from the angle probe. The flaw of the welded steel pipe is detected by the angle probe arranged, so that it is decided on the basis of the flaw detection result whether or not the toes of the inner face extending from the toes to the inside of the mother material and inclined in the radial direction of the welded steel pipe to the side opposite to the weld bead are cracked. As a result, it is possible to improve the detecting performance of that cracking of the inner face toes, which occurs at the toes of the weld bead on the inner face of the welded steel pipe.