Evaluation of the mechanical properties of the X52 high frequency electric resistance welding pipes

The intensity assessment of the line pipe does not include the strength and the impact toughness, but also include the fatigue performance. In this paper, the tensile strength and the impact toughness of both the pipe body and the weld joint of X52 high frequency electric resistance welding (HF-ERW) pipes were measured. The amounts of fatigue for these specimens with and without surface finishing were investigated with a MTS servo-hydraulic universal testing machine at various maximum cycle stresses. The results showed that both the pipe bodies and the weld joints of the X52 HF-ERW pipes had an excellent balance of strength and impact toughness. The cyclic stress of the weld joints decreased more than the pipe bodies, and the resistance to fatigue was greatly affected by the surface defects. The effects of the surface defects on fatigue properties must be considered for the intensity assessment of line pipes.