海上气田井口管线双相不锈钢焊接接头泄漏失效分析

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Abstract： Failure analysis was carried out for the leakage problem caused by cracks in the welding joint of duplex stainlesstee te in the wellhead pipeline of ofshore gas fields.The failure causes were comprehensively analyzed from macroscopic and microscopic fracture morphology，crack propagation path， microstructural characteristics， phase proportion and hardnessof the welding joint.Theresults show that the crack initiates from the weld toe of the welding joint on the inner wallof the pipeline，passes through theheat affected zoneandextends to thebase metal， leading to pipeline leakage.The main failure reasons are the stress concentration caused by poor weld formation of the welding joint on the inner wallof the pipeline and the corrosion environment，which induces stress corrosion cracking.A large number of secondary austenite are formed in the weld metal structure，resulting in the increase of austenite content and the ferrite content isonly 20% ，which reduces the resistance of the weld metal to stress corosioncracking.Alarge numberof blocky sigma（o）phase intermetalic compounds distributed along thegrain appear in the base metal structure，leading to britlenessof the base metal，accelerating crack propagationand increasing the risk of local corrosion leakage.

Keywords：duplex stainless steel;welded joint;crack;stress corrosion

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随着海上气田开发不断向深水、超高温高压方向发展，井口管线面临极端服役环境。（剩余4895字）