ULTRASONIC INSPECTION OF AUSTENITIC STAINLESS STEEL WELDS.

While today the ultrasonic inspection of ferritic steels does not pose major problems since most have already been solved, no generally accepted standard procedure has been developed for austenitic steels, especially for great thicknesses. An austenitic structure in fact opposes the propagation of the ultrasonic beam by scattering, breaking up and absorbing it, with velocity variations and interferences: thus, both the selection of the control parameters and the interpretation of results in detecting and identifying defects of various kinds become problematic. A survey of certain experiments is at present underway to study such problems. The experimental program covers a number of tests made on different austenitic stainless steels welded with different procedures: the measure of velocity and alteration of the ultrasonic wave trains in the steels and welding seams under consideration, verification by extensimetric measurement of the elasticity modules, the measurement of angles of refraction, velocity profile vs transducer position and ultrasonic signal attenuation.