Tests have been carried out on transverse butt welds containing various types of internal defects. Four tests were also carried out on specimens containing weld undercut,nFigure 25 contains a plot of F100,000vs. area reduction (based on radiographs of the welds) in which both the porosity and slag inclusion test results have been presented.nIt appears that one of the main causes for the low fatigue life of butt welded joints in the l-l/2 in. thick HY-80 steel is the existence of hot cracks which originate at high sulfide concentrations at the fusion line and then propagate into the weld metal. The application of a thermal stress relief heat treatment was effective in increasing the fatigue life.
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