Measurement/inspection of weld interior

The inspection of the interior of weld beads or base materials requires the use of ultrasonic waves or radiation.
This page introduces welding-related internal measurements and inspections.

Ultrasonic testing (UT)

Ultrasonic waves are effective for the detection of defects such as insufficient penetration, insufficient fusion, and internal cracking. Ultrasonic testing (UT) uses a tool called a probe. A probe contains an oscillator that generates and receives ultrasonic waves. When the probe touches a weld and emits an ultrasonic wave, the wave propagates inside the weld. When there are no cavities or foreign matter, the ultrasonic wave reflects on the bottom (echo) and returns to the probe. If there is a cavity or foreign matter in the middle, the echo reflects on the cavity or foreign matter and returns to the probe more quickly. These echoes are identified as peaks on the display and used for detection and position measurement of defects.

Radiographic testing (RT)

Interior inspection using radiation is effective for detecting defects such as blow holes and slag inclusion. One major method is radiographic testing (RT) which is the same technique as X-ray examination used for human health diagnosis. Just like with an X-ray, a beam of radiation is applied to the weld. The beam passes more easily through defects than through other parts. When the result is exposed on film, defects are shown in black and can be detected.