| 摘要 |
PROBLEM TO BE SOLVED: To provide an ultrasonic flaw detection method capable of certainly discriminating between a surface flaw of a steel material and an internal defect immediately below the surface.SOLUTION: Transversal wave beams B of ultrasonic wave are put into the cross section of a round-bar steel material M at a refraction angle &thetas; within a predetermined angle range. An intensity distribution is obtained in which the horizontal axis shows the scan positions of the transversal wave beams B in the circumferential direction of the round-bar steel material M and the vertical axis shows the time change in the reflected wave intensity of the ultrasonic wave at each scan position. Discrimination between a surface flaw M1 occurring in the round-bar steel material M and an internal defect M2 immediately below the surface is performed based on the size of the area of a region in which the reflected wave intensity in the intensity distribution is a certain value or more. |
