| 摘要 |
PURPOSE:To prevent infiltration of wafer into the inner surface of a steel pipe, by implementing a lamination flaw detection of a beveled part of a steel pipe admitting an ultrasonic wave from the outer surface of the steel pipe to enable the identification in the equipment with an ultrasonic flaw detector mechanism section at a part other than the beveled part of the steel pipe. CONSTITUTION:An ultrasonic wave is made incident into the outer surface 3 of a steel pipe from outside the steel pipe 1 and the position of a probe 5 is so set as to meet an angle thetaof refraction by a transverse wave. An ultrasonic beam 7 from the probe 5 is made incident into the outer surface 3 of the steel pipe at an angle gamma of incidence and reflection to generate an surface echo S. Thereafter, the beam 7 propagates through the steel pipe 1 at an angle thetaof refraction of a transverse wave is reflected on a defect 8 at an angle of incidence and reflection and reflected again on the surface of a bevel-worked part 2 of the steel pipe vertically. In the case of a lamination defect, the reflecting surface of which 8 is parallel with the inner and outer surfaces of the steel pipe, the beam 7 is received by the probe 5 in the same path as the incident direction therefor 7 to obtain a defect echo (F). When no defect exists, the beam 7 is reflected on the inner surface 4 at an angle beta of incidence and reflection to obtain an inner surface echo S1, and later, reflected on the surface of the bevel-worked part 2 to obtain a bottom surface echo (B).
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