Effect of Reel-Laying Simulation on Mechanical Performance of Flowlines

In this work, major efforts were devoted to a full understanding of the effect of the plastic deformation pattern which is typical of reeling on the in-service mechanical performance of quenched and tempered (Q&T) seamless pipes. This was performed by both laboratory multiple plastic straining cycle (MPSC) tests and full-scale reeling (FSR) trials. Different steel grades were investigated with and without aging after single deformation and MPSC/FSR. All materials showed similar deformation behavior. In MPSC tests and FSR trials, the direction of the last deformation step influenced the mechanical behaviour. Finishing with compression gave a slight reduction in YS, whereas subsequent aging gave a YS value similar to that in the as-received condition. Leaving the last step in tension, an increase in YS was observed and subsequent aging gave a further increase to a level similar to that of conventional tensile straining plus artificial aging. In terms of toughness properties (CVN energy, 50%FATT, CTOD) there was no significant effect of reeling plus aging process. Also girth welds were tested: no significant effect of reeling plus aging process was pointed out with respect to the as-received situation for both HAZ and weld metal. The behavior of deformed and aged material was explained in terms of work-hardening, Bauschinger and bake-hardening effects.