Effect of Reeling on Fracture Toughness Behavior of Welded API5LX65 Line Pipe

Abstract

The effect of reeling on the fracture toughness (FT) behavior of welded pipe was investigated both in-air as well as in sour environment. The FT behavior of the reeled pipe in various notch locations parent pipe (PP), heat affected zone (HAZ), weld center line (WCL) did not exhibit any effect of reeling (i.e. the properties in the strained and aged condition was similar to the as-fabricated welds). Fracture toughness in sour environments is 4× to 6× lower than the In-Air values. The fracture toughness behavior of parent pipe in sour environments was affected by reeling at strains associated with 2.12%/cycle and 2.72%/cycle. WCL fracture toughness was not affected by reeling in sour environments. The intrados HAZ exhibited the lowest fracture toughness properties. Some of the sour service fracture toughness tests on parent pipe and HAZ strained to 2.72%/cycle on the intrados samples exhibited pop-in behavior possibly due to higher YS. Parent pipe strained to a lower level of 2.12%/cycle did not exhibit any evidence of pop-in’s. Reeling appears to decrease the parent pipe toughness in the extrados and intrados in sour service both at 2.12%/cycle and 2.72%/cycle. The extrados parent pipe and intrados HAZ showed the lowest fracture toughness values in sour environment.