The application of CS-technique to the ultrasonic examination of austenitic stainless steel welded pipe

The ultrasonic CS-technique has been proved to be applicable to the shear wave angle beam examination of the austenitic stainless steel longitudinally welded pipe. It enhances the signal-to-noise ratio especially in the axial scan flaw-detection of as-welded or as-annealed welds of thicker pipe where the previously recommended broad-band-transducer-technique did not give the sufficient signal-to-noise ratio. The CS-technique tends to be effective for the reflectors which convert the broad band incident beam into the narrow-band reflected beam. The allowable frequency range around the optimum value can be estimated for the individual critical flaw which shall be detected automatically by CS-technique. The definite number of frequencies, e.g. 1,2,3,4 and 5 MHz, may cover the allowable frequency ranges of the whole conceivable critical flaws. Thus, the newly developed Multi-Frequency Unit of CS-Transmitter will be utilized as the essential part of the automated CS-technique flaw-detecting system for pipe. (author)