Evaluating Mechanical Properties of Hybrid Laser Arc Girth Welds Available to Purchase

This paper presents the challenges and results associated with mechanical testing of overmatched X80 and X100 pipeline steel girth welds that were produced by Hybrid Laser Arc Welding (HLAW). The weld profile produced by this process is characterized as having a broad weld cap and a narrow leg, which traverses the through thickness direction. The development and testing of the HLAW process was conducted on NPS36 pipes of 10.4 mm and 14.3 mm thickness, respectively. The welds were deposited in the 5G welding position with all parameters and laser visual inspection data being collected for each weld pass. Subsequent sample extraction and testing of the hybrid laser arc welds were achieved by standard test practices for girth welds and modifications of these practices, where the latter was required to facilitate testing of the narrow HLAW geometry. Charpy results indicate that the fracture transition temperature, with the notch in either the weld metal or the heat-affected zone (HAZ), is higher at the 3 and 9 o’clock positions when compared to 9 and 12 o’clock positions. The likelihood of crack deviation influencing the results due to the non-conventional weld geometry needs to be examined in a further study. For crack tip opening displacement (CTOD) testing, shorter fatigue crack lengths were employed to reduce the possibility of fatigue crack deviation. The results show that this method does not influence the validity of the test outcomes.