Full Gas Burst Test for HFW Linepipe at Low Temperature

A full gas burst test at low temperature below −40°C was performed using a high frequency welded (HFW) linepipe with high-quality weld seam, “MightySeam®,” [1–4] in order to verify the applicability of the Drop Weight Tear Test (DWTT). Residual stress exists in the pipe body of HFW linepipe because the manufacturing method includes a sizing process. Therefore, it is necessary to clarify the difference between the arrestability in the DWTT without residual stress in the specimen and that in the full gas burst test with residual stress in the pipe body. The full gas burst test is performed using a test pipe specimen in which a notch is introduced into the base material by an explosive cutter. In addition, a test pipe specimen with a notch introduced into the weld seam was used in this study because the developed HFW linepipe, “MightySeam®,” has excellent low-temperature toughness as a result of control of the morphology and distribution of oxides generated in the welding process by temperature and deformation distribution control. The Charpy transition temperature of “Mighty Seam®” was much lower than −45 °C. Ductile cracks were initiated from the initial explosive notch, and these cracks were arrested after ductile crack propagation of about 1 m in base material on both sides. The fracture behavior was similar in appearance in the DWTT without residual stress and the full gas burst test with residual stress.