| 摘要 |
PURPOSE:To reduce the boundary face echo without reducing the flaw detection sensitivity, by making a probe eccentric to make an ultrasonic beam incident obliquely in the direction of the tube circumference and inclining the probe in a plane parallel with the tube axis including the direction of incidence. CONSTITUTION:A probe 3 is made eccentric to make an ultrasonic beam U incident obliquely in the direction of the tube circumference, and the probe 3 is inclined at an angle alpha in the plane parallel with the tube axis including the direction of incidence to reduce the boundary face echo without reducing the flaw detection sensitivity for a welded part. Simultaneously, a frequency (f) of the probe and the spread and the frequency band width of the ultrasonic beam are selected to prevent the occurrence of a grass, and the attenuation of the ultrasonic beam is reduced to detect flaws. For example, the inclination angle alpha of the probe and an angle theta of refraction are defined as 3-12 deg. and 30-50 deg. respectively, and a broad band probe where the frequency (f) is 2MHz-5MHz and the ultrasonic beam is converged and a frequency band width W is 50-75% is applied. |
