Test on the effect of fracture separation on the fracture resistance of X90 welded pipe

High-grade steel pipeline transportation is an inevitable development trend of natural gas pipeline in the world, and the resistance to the long-range propagation of cracks in X90 pipeline is one of the important research contents. In order to clarify the effect of fracture separation on fracture resistance of X90 welded pipe, the X90 welded pipe experimentally manufactured in a small scale in China was selected as the research object in this paper. After Charpy V-Notch Test (CVN Test) and Drop-Weight Tear Test (DWTT Test) were carried out, the energy relation between CVN and DWTT and the effect of fracture separation on DWTT fracture resistance were comparatively analyzed. It is shown that as for X90 welded pipe, when the energy density of CVN is lower than 450 J/cm², the energy density of DWTT is in a linear relation with that of CVN, and their increasing rates are the same; and when the energy density of CVN is higher than 450 J/cm², the energy density of DWTT increases slowly with the increase of that of CVN. Fracture separation mainly decreases the crack propagation work of the total DWTT energy, but has no significant effect on the fracture initiation work. Compared with the CVN sample, the full-thickness DWTT sample can reflect the reducing action of the fracture separation on the propagation resistance of cracks more accurately.