Study on Stress-Strain Behavior of X60 SSAW and ERW X52 Line Pipes

Tension tests under different temperatures were conducted for X60 SSAW and X52 ERW line pipes. The results indicate that the strength of both pipes increased as test temperature dropped, the plasticity dropped as test temperature decreased. The shape of stress-strain curves of both base metals was continuous yielding, while that of both welds was non-continuous yielding and presented apparent physical yielding. As to X60 SSAW pipes, the strength of base metal and weld was almost the same, but a big difference was found between the base metal and weld of X52 ERW pipes. During oil and gas pipeline design and safety assessment, emphasis should be put on stress-strain behavior of pipe metals under different temperatures and difference of stress and strain behavior between base metal and weld.