20鋼45°熱煨彎管失效分析

Investigation of Failure of 45°Hot-bend Elbow in St.G.20

摘要: 分析20鋼45°熱煨彎管在某油田服役48天后發(fā)生失效的原因。通過分析該熱煨彎管的化學(xué)成分、力學(xué)性能和金相組織以及爆裂區(qū)的能譜圖，發(fā)現(xiàn)沖刷腐蝕致管壁減薄是彎管爆裂的原因。輸送介質(zhì)中含H₂S、CO₂等腐蝕性介質(zhì)，加強(qiáng)了沖蝕的作用；沖蝕與腐蝕的交互作用會加速管壁的減薄；當(dāng)彎管管壁局部位置減薄到一定程度，在鋼管內(nèi)壓力作用下，造成彎管局部爆裂。

Abstract: The cause for failure of the 45°hot-bend elbow in St.G.20 as just having served in a certain oil field for 48 days is investigated.The chemical composition, the mechanical properties, the metallographic structure and the energy dispersive X-ray spectrum of the bursting area of the said elbow are analyzed.As a result, it is identified that the cause for the failure is that the erosion gets the elbow pipe wall thickness reduced, thus the burst happens.Corrosive medium like H₂S, and CO₂contained in the conveyed medium strengthens the erosion effect.And the interactions by erosion and corrosion speed up the reduction of the pipe wall thickness.Finally when some location of the wall thickness of the elbow is reduced to a certain extent, local burst will take place due to the internal pressure of the pipe.