Analysis of spiral weld cracking at pipeline

The failure causes of spiral weld cracking were analyzed by means of macro inspection, tensile and impact testing, obsenation of microstructure and fracture surface, and fracture mechanics analysis. The effect of temperature on the spiral weld crocking and properties of the pipeline steel was also discussed. The results show that the cracking was initiated from the welding defects or cracko and propagated along heat affected zone, and belonded to the low stress brittle fracture. The decrease of fracture toughness of the pipeline steel at lower working temperature was also responsible for the brittle fracture.