| LI Lei,KUANG Xian-ren,JI Rui,DING Han,FU An-qing,BAI Zhen-quan.Analysis on Failure Behavior and Reason of 316L/L360NB Mechanically Bimetallic Composite Pipes Used in an Oilfield[J],47(6):224-231 |
| Analysis on Failure Behavior and Reason of 316L/L360NB Mechanically Bimetallic Composite Pipes Used in an Oilfield |
| Received:December 16, 2017 Revised:June 20, 2018 |
| View Full Text View/Add Comment Download reader |
| DOI：10.16490/j.cnki.issn.1001-3660.2018.06.032 |
| KeyWord:bimetallic composite pipes sealing weld liner pipe perforation corrosion failure |
| Author | Institution |
| LI Lei |
1.CNPC Tubular Goods Research Institute, Xi'an , China;2.SKL for Performance and Structure Safety of Petroleum Tubular Goods and Equipment Materials, Xi'an , China |
| KUANG Xian-ren |
1.CNPC Tubular Goods Research Institute, Xi'an , China;2.SKL for Performance and Structure Safety of Petroleum Tubular Goods and Equipment Materials, Xi'an , China |
| JI Rui |
Xi'An Changqing Technology Engineering Co. Ltd, Xi'an , China |
| DING Han |
1.CNPC Tubular Goods Research Institute, Xi'an , China;2.SKL for Performance and Structure Safety of Petroleum Tubular Goods and Equipment Materials, Xi'an , China |
| FU An-qing |
1.CNPC Tubular Goods Research Institute, Xi'an , China;2.SKL for Performance and Structure Safety of Petroleum Tubular Goods and Equipment Materials, Xi'an , China |
| BAI Zhen-quan |
1.CNPC Tubular Goods Research Institute, Xi'an , China;2.SKL for Performance and Structure Safety of Petroleum Tubular Goods and Equipment Materials, Xi'an , China |
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| Abstract: |
| For perforation problem of 316L/L360NB mechanically bimetallic composite pipes used in an oilfield, the work aims to provide theoretical basis for failure control of these pipes by analyzing failure behavior and cause. Based on production standards and service conditions of the faulty pipes, the cause of perforation failure was comprehensively analyzed by means of visual inspection, nondestructive testing, chemical composition analysis, metallographic structure analysis, hardness analysis, scanning electron microscope and energy spectrum analysis while referring to welding process specification. Outer diameter, wall thickness, chemical composition and hardness of 316L liner pipe and L360NB base pipe of the faulty pipe were in conformity with relevant standards, and no abnormality was detected in metallographic structure. Sealing weld has penetrated to the liner pipe, microstructure was martensite, and no other welding defects were found. Pitting corrosion occurred in the sealing weld. Main chemical elements of corrosion products were C, O and Fe, and there was a small amount of Cl as well. No corrosion was found in the 316L liner pipe, and corrosion resistance of the sealing area was the worst. Failure behavior of the bimetallic composite pipes was local internal corrosion perforation. Failure cause was that improper sealing operation caused the sealing weld to penetrate into the liner pipe, which resulted in pitting corrosion of less corrosion-resistant sealing weld in high Cl− corrosion environment. The liner and base tube constitute galvanic corrosion after the sealing penetration, which lead to rapid corrosion perforation of less corrosion-resistant carbon steel base pipe. It is suggested that ends of mechanically bimetallic composite pipes be sealed with welding materials exhibiting better corrosion resistance, so as to prevent the failure effectively. |
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