Structures and Properties of X80 Pipeline Girth Welds for Different Welding Procedures

Abstract

The X80 girth welds were produced by solid-wire gas metal arc welding (GMAW) and shield metal arc welding (SMAW) using two welding consumables respectively, which contained different mass fraction of C, Mo and Ni. The tensile properties, notch toughness, hardness, and microstructures of welded joints were evaluated. The results indicate that high strength and good toughness of welded joints can be achieved. But the tensile properties of all weld metal of GMAW and SMAW process were evidently different because of the difference of mass fraction of C, Mo, Ni. The strength reduced slightly in softening zone of HAZ. Using welding consumable which contain higher Mo additions, the microstructure in weld seam and fusion zones were IAF+GB and GB+M respectively. Furthermore, the mechanical properties of X80 pipeline welded by single wire welding and double wire welding respectively have been compared. The double wire welds exhibited lower yield strength but higher toughness compared to the corresponding single wire welds.