Future treatment of weld acceptance: The significance of incomplete fusiondiscontinuities in low structural transition temperature gas metal are weldments

The welding acceptance standards for naval ships and submarine pressure hul ls indicates that the presence of any incomplete fusion discontinuity in th e welds is cause for rejection. In this paper, it is suggested that dependi ng upon thp size and location of the discontinuity and the weldment structu ral transition performance, certain amounts of incomplete fusion are accept able. In short, weldmetal tearing resistance often overrides the weld disco ntinuity's influence on weldment failure. In our study, six explosion bulge panels were welded to have severe in comp lete fusion discontinuities in weldments which otherwise exhibited low stru ctural transition temperature performance; two panels had root discontinuit ies and the other four had cap discontinuities. Explosion bulge tests were performed to determine if the welds could resist crack extension beyond the limits of the bulge apex. Prior to explosion testing, the welds were examined with manual and compute r aided ultrasonics. They were also radiographed at plus and minus twenty d egrees to normal (standard radiography would be shot at normal). The nondes tructive resting (NDT) was conducted to relate performance back to NDT (as opposed to just discontinuity size, nature and location). Following explosion testing, the welds were sectioned and opened to determi ne the true discontinuity nature, size and the degree and nature of extensi on under explosive loading. Sectioning showed that extension was always by a ductile mechanism for these low structural transition weldments. Based on this work, discontinuity size and location was found to be less of a determining factor in the quality of the weld than the structural transi tion performance of the weld and steel. It was found that acceptance criter ia should be based on whether the structural transition performance is belo w, within or above the operational envelope as well as, and not merely, on the size and location of discontinuities.