Method and apparatus for the ultrasonic testing of steel tubes

摘要

The present invention relates to a method and an apparatus of ultrasonic inspection for inspecting a planar defect, existing in a plane including a radial direction and an axial direction in a welded part of a steel pipe, using angle probes attached to the outer peripheral surface of the steel pipe, characterized in that an inspection refractive angle of an ultrasonic wave entered into the steel pipe from the angle probes is set to an angle at which the ultrasonic wave enters the planar defect perpendicularly based on the ratio of the thickness to the outer diameter of the steel pipe. In the case where the steel pipe has acoustical anisotropy, it is preferable to measure and store refractive angle dependency of the sonic velocity in advance for each steel type and rolling condition, automatically calculate an incident angle corresponding to a refractive angle used in the inspection using the stored data, and select angle probes having the calculated incident angle. By this invention, it is possible to inspect planar defects with a high defect-detection capability and to easily and accurately to inspect them even for a steel pipe having acoustical anisotropy.