Fracture-toughness evaluations by different test methods for the Chinese Second West-East gas transmission X-80 pipeline steels

摘要

Fracture Resistance Determination was one of the most important aspects during the research and development of the Chinese 2nd West-East X-80 pipeline steels. More than 30 kinds of longitudinal submerged-arc-welded (LSAW) X-80 pipes were tested using the 2-mm striker Charpy V-notch (CVN) test, the 8-mm striker CVN test, and the instrumented drop-weight tear test (DWTT). It was found that the threshold energy was about 200 J for the 2-mm striker and 8-mm striker CVN tests. Below this threshold, the difference between the 2-mm striker CVN energy and the 8-mm striker CVN energy was small. Above the threshold, however, the difference between the 2-mm striker CVN energy and the 8-mm striker CVN energy increases as the CVN energy increases. It was also found that there is a linear relation between the DWTT energy and the 8-mm striker CVN energy when the latter is lower than 400 J/cm2. Otherwise, the DWTT energy trends to reach a plateau.