Strain-based design, to be used in Northern Pipeline applications, will likely call for the strength of the girth welds to over-match the longitudinal strength of the pipes. As well, a minimum level of weld metal fracture toughness, as measured by Charpy V-Notch (CVN), Crack-Tip Opening Displacement (CTOD) as well as Wide-Plate tests, will be required. The development work done to date, on Submerged Arc Welds (SAW) used to double joint pipes, has resulted in the production of girth welds for large diameter X80 pipes with minimum yield strength above 100,000 psi (690 MPa), Charpy-V-Notch absorbed energy more than 74 ft-lb (100 Joules) at −4 F (−20 C), CTOD greater than 0.006” (0.15 mm) at −4 F (−20 C) and Wide Plate remote strain greater than 4%, at −4 F (−20 C). This presentation will describe the metallurgical approach adopted for promoting high toughness and achieving over-matching yield strength, for strain-based design application.

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