Non-destructive inspections of weld metals in carbon steel and stainless steel pipes must become more important if high reliability of power plants are to be maintained. Flaws in the weld metals, i.e. porosities or cracks, may be produced by a change in welding conditions and then continue to grow during thermal stress repetitions. If non-destructive inspection of flaw sizing and recognition in the welds of pipes are possible, reliability evaluation and residual life estimation of pipes can be improved. Based on this background, the authors applied an acoustical holographic method to weld metal inspections. In the present work, flaw sizing and recognition capabilities of the acoustical holographic inspections were examined. The ultrasonic inspections with normal and 45 and 70 degree angled longitudinal waves were done to inspect flaws in weld metals of SGV410 carbon steel and SUS316 stainless steel. The capabilities of the acoustical holographic method, based on results of the systematic experimental investigations in comparison with other traditional non-destructive techniques, are as follows.(1) For porosities having a diameter of 0.3 - 1.5 mm in 25 mm thick weld metals. The holographic method with a normal beam could detect and represent the flaws as spherical images, although sizings were overestimated with an error of 1.7 mm against those of radiographic testing.
(2) For cracks having a depth of 1-6 mm in 25 mm thick weld metals, the sizing errors in the holographic method with 45 and 70 degree angled beams were less than 0.9 mm.
These experimental investigations have been carried out, as a part of JAPEIC's SUN project.
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