The Development of Large Diameter and Thickness X80 HSAW Linepipe

For the requirement of 2^nd West-East Pipeline Project of China, X80 large diameter & thickness linepipe with helical seam submerged arc welded (HSAW) were developed, with 1219 mm OD and 18.4 mm WT. Acicular ferrite type and super-low carbon, high Niobium chemical composition pipeline steel was adopted for the base material. The very stringent requirements at −10 °C for toughness, i.e. 220J/170J for average/minimum for pipe body and 80J/60J for average/minimum for weld and HAZ were meet successfully. The yield strength loss due to Bauschinger effect was found lower than 20MPa, which benefited. The very low residual stress level was testified by cut-ring test which cuts a section pipe about exceed 100mm long, and then cut the section apart from welds 100mm along the longitudinal direction.