Pipelines for transport of oil and gas in Arctic areas are subjected to some extreme challenges; among these being low temperatures. Thus, the steel behaviour with respect to the ductile to brittle transition will be important. Moreover, when the design temperature falls down to -50 to -60°C, the toughness of the weld metal may become a critical factor. In the present investigation, submerged arc welding was performed using two different wires (Wires 1 and 2), using 23.7 mm base plate corresponding to API X80 quality. The test programme included tensile and notched tensile testing, Charpy V notch testing, and finally, SENB05 (bending with a/W = 0.5) and SENT02 (tension with a/W = 0.2). The tensile test results confirmed that the base metal and weld metal yield and ultimate strength increases with falling temperature. The Charpy V results showed high values for Wire A with all individual values above 50 J. The fusion line (FL), FL+2 mm and FL+5 mm had even higher toughness than the weld metal. The CTOD testing confirmed the trend from Charpy V. Wire A gave good weld metal results (SENB05 > 0.3 mm), while wire B possessed low toughness (≤ 0.11 mm). Constraint effects are evident by comparing the results obtained from SENB05 and SENT02 weld metal testing.

This content is only available via PDF.
You can access this article if you purchase or spend a download.