The amplitude of the ultrasonic echo is influenced by ultrasound scattering, phase-changes and mode-conversion in a characteristic way.

The spectrum of the ultrasonic pulse is distorted depending on the transfer characteristics of the columnar grained weld metal.

Ultrasonic grain boundary backscatter is measured as noise decreasing the signal-to-noise ratio during ultrasonic testing.

This paper describes the work carried out recently on this subject, and in particular gives the Round Robin Testing results of the Ultrasonic testing of the test pieces specially manufactured for this research programme.

Four groups of materials comprising the full scale of industrially relevant stainless steels were investigated: austenitic stainless Cr-Ni steels, fully austenitic stainless steels with increased Ni-content, Nickel-base-alloys, and Duplex steels (Ferritic-austenitic steels).

Test specimens with reference reflectors and realistic defects in the weld area, were prepared and inspected using various ultrasonic testing techniques.

Manual and automated inspections were carried out to assess and compare the intrinsic capability of different ultrasonic testing techniques currently used by the three industrial partners participating to this project.

Detection and sizing capability of the ultrasonic procedures was determined using the PISC (Programme for the Inspection of Steel Components) type A sharp notches, which were introduced in the weld area.

The Round Robin Test results demonstrate the importance of the transducer frequency on the weld inspectability.