Fracture behaviour of overmatched girth welds

The fracture behaviour of overmatched girth welds produced by shielded metal arc welding (SMAW) in API 5L Grade X 70 pipeline steel has been studied. Weld metal specimens exhibit a significant scattering, with the values at the 12 o'clock position clearly lower than those recorded at the two other positions. Scanning electron microscope examination revealed the existence of weld defects in this zone which could justify the observed differences. Charpy V notch impact testing was performed at three different temperatures showing a decrease in toughness as the testing temperature diminishes. CTOD tests were carried out on specimens notched at the weld metal. Once again a large scatter in the results is observed having been associated with weld defects that were present in some specimens.