L51738 Weld Metal Yield Strength Testing of Girth Welds

The present trend towards higher strength line-pipe steels makes weld metal yield strength a consideration as the girth weld deposit can be the weakest region of the weld. Weld metal yield strength is also a key element in girth weld defect engineering critical assessments. The development of a reliable test procedure for determining the actual transverse weld metal yield strength in both under-matching and overmatching welds is therefore needed. The objective of the present investigation was to develop a testing procedure which could be used to measure the weld metal yield strength in the transverse direction and which would have technical advantages over any commonly used test for measuring weld metal yield strength. The objective has been achieved by conducting an extensive series of tensile and hardness tests on base/pipe metal (initial studies) and on SMAW girth welds. The plate metal specimens for the initial studies have been taken from a 12,5 mm (0,5 inch) thick Grade X70 plate. The pipe metal, all-weld metal and side notched transverse weld tensile test specimens have been taken from three girth welds in a 40 inch diameter Grade X70 pipe with a 14,7 mm (0,579 inch) wall thickness.