Abstract
One 530mm X80 pipeline weld failed infrequently in service process. This paper gives a systematic analysis in consideration of both material quality and loading condition. Inspection was performed on chemical composition, mechanical performance, metallograghy and micro-morphology. The result shows that weld joint’s leakage failure accident is fatigue failure. Under the effect of tensile- tensile stress fatigue stress, fatigue crack originated from weld fusion line near the pipe body and developed along the weld. Porosity defect in the weld reduced its bearing capacity, and promoted the formation and development of the fatigue crack. Fatigue strength and fatigue life of the weld has great relationship with the size and distribution of porosity. The greater the porosity, the more close to surface, the decrease of fatigue life is more obvious.
Highlights
X80 pipeline steel with excellent service performance was widely applied in offshore oil and gas drilling and transportation field in recent years
The mechanical properties were conducted according to ASTM standards, and hardness in various regions around fracture was made using a testing system (HV)
X80 pipeline and the flange joint was welded by the way of TIG welding
Summary
X80 pipeline steel with excellent service performance was widely applied in offshore oil and gas drilling and transportation field in recent years. Weld is the most weak part of pipeline system, and it is prone to failure. In 2013, one weld leakage failure accident of. X80 pipeline occurred in our country infrequentely. In order to analyze failure reason of the weld, we took part of the failed pipeline system and carried out experiment study
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