Ultrasonic inspection of austenitic weldments

An outline is given of how the microstructure of austenitic weld metal and HAZ gives rise to problems in ultrasonic examination, and suitable methods of inspection are outlined. Experimental investigations are reported on fatigue cracks of 2-8 mm depth in types 316 and 347 stainless steel plates welded with 316 Staintrode and 347 Micrex electrodes respectively. The test parameters (beam angle, frequency, mode and scanning position) were evaluated and optimised. Particular aspects covered were tests of cracks of known depths under compressive stress, and tests on 50 mm thick single V preparation butt welds in type 316 using longitudinal waves. Problems in defining a reference calibration standard for crack-like defects are discussed. (author)