Optimum Weld-Metal Strength for High-Strength Steel Structures.

Abstract : This report provides data and analysis to support the acceptance of undermatched welds in high-strength steel in shipbuilding. Wide-plate tensile tests made from HSLA-l00 steel plate (690 MPa minimum yield strength) with transverse groove welds demonstrated that moderately-undermatched joints (actual weld yield strength up to 12 percent less than actual base-plate yield strength) can achieve strength and ductility as high as overmatched welds. Welds undermatched between 18 and 28 percent exhibited full strength but minimal ductility. Relatively coarse-mesh elastoplastic finite-element analysis adequately reproduced the behavior observed in the experiments. Wide-plate specimens were prepared with various controlled intentional defects in both moderately-undermatched and overmatched welds. These defect specimens exhibited remarkable performance and there was no consistent difference between the results of the moderately-undermatched welds and the overmatched welds. When loaded in shear, groove welds undermatched up to 28 percent developed the required minimum shear strength of the MSLA-100 plate and had excellent ductility. Guidelines and commentary for design, finite-element analysis, selection of weld filler metal and welding procedure for various types of joints are given to facilitate the use of high-strength steel with optimum weld metal properties. (MM)