ULTRASONIC FLAW DETECTION METHOD AND DEVICE THEREOF

PROBLEM TO BE SOLVED: To improve the accuracy of flaw detection in internal flow detection of an angular billet using a volume focus flaw detection method.SOLUTION: A device according to this invention uses a volume focus flaw detection method, in which a plurality of oscillators 1...1 of each of array probes 10 are arranged along one side of a rectangle presented by a test material m about one of the array probes 10 and along one of sides adjacent to the one side about another array probe 10 in a cross-sectional view of the test material m. Exciting means makes ultrasonic wave incident on each of the array probes with respective sides with corresponding arrays going therealong as an incident side by a vertical flaw detection method and an angle beam method from each position of the incident side to the inside of the test material by one oscillation of a plurality of oscillators, makes the ultrasonic wave made incident by the vertical flaw detection method reach an opposite side facing the incident side, and makes the ultrasonic wave made incident by the angle beam method reach one of adjacent sides adjacent to the incident side, and an actual focal point of the ultrasonic wave is not set inside of the test material.