DIN EN ISO 22825:2012-08

This document (EN ISO 22825:2012) has been prepared by Technical Committee CEN/TC 121 "Welding", the secretariat of which is held by DIN, in collaboration with Technical Committee ISO/TC 44 "Welding and allied processes".
The responsible German committee is Working Committee NA 062-08-23 AA "Ultraschallprüfung" ("Ultrasonic testing") at the Materials Testing Standards Committee (NMP) at DIN.
This standard differs from DIN EN ISO 22825:2006-10 as follows:
a) ISO 5577, ISO 17635 and ISO 17640 have been added to the normative references;
b) complete revision of content; editorial revision; c) the clauses have been restructured;
d) the explanatory figures have been revised;
e) a revised flowchart showing the development of a procedure has been included.
Welds in austenitic steel components and dissimilar metal welds are widely regarded as very difficult to inspect by ultrasound. The problems are mainly associated with unfavourable structure and grain size, as well as with different material properties which result in inhomogeneous and anisotropic mechanical and acoustic properties that contrast with the relatively homogeneous and isotropic behaviour in low-alloy steel welds. Austenitic weld metal and other coarse-grained, anisotropic materials can significantly affect ultrasound propagation. In addition, beam distortion, unexpected reflections and wave mode conversions on the fusion line and/or columnar grains can occur. Therefore it can be difficult and sometimes impossible for ultrasonic waves to penetrate the weld metal.
Ultrasonic testing of these metals may require techniques that differ from conventional techniques. These special techniques often include the use of dual-element probes designed for refracted compression (longitudinal) waves or creeping waves rather than for conventional shear waves.
In addition, it is necessary to produce representative reference blocks with welds in order to develop a testing procedure, set a preliminary sensitivity level, assess the procedure and demonstrate effectiveness before a definitive procedure is written. Material, weld preparation and welding procedure, as well as the geometry and surface condition of reference blocks are the same as for the component being tested.