What is the primary use of ultrasonic testing in weld inspection?

Ultrasonic testing is primarily utilized in weld inspection for identifying sub-surface discontinuities. This method employs high-frequency sound waves that are transmitted into the material being inspected. When these waves encounter a boundary, such as a flaw or a crack, they are reflected back to the surface. This capability allows ultrasonic testing to effectively detect internal defects, such as inclusions, voids, or lack of fusion within welds that are not visible through other testing methods.

The advantage of ultrasonic testing lies in its ability to provide a much deeper analysis of the weld integrity than surface inspection methods can achieve. It is particularly valuable for examining thick materials where surface defects may not fully represent the condition of the weld. Additionally, ultrasonic testing can provide quantitative measurements, such as the size and location of the discontinuities detected.

While other methods like radiographic testing are also employed to identify internal flaws, ultrasonic testing is favored in many situations for its precision and ability to analyze welds without the need for potentially hazardous materials like x-rays.