海洋环境下E690低合金高强钢MAG焊接接头热影响区耐腐蚀性能研究

Study on the Corrosion Resistance of Heat-Affected Zone of E690 Low-Alloy High-Strength Steel MAG Welded Joints in Marine Environment

随着海洋石油开采技术的发展,高强度钢焊接接头的耐腐蚀性能成为关键问题。为研究E690低合金高强钢MAG焊接接头热影响区(HAZ)在模拟海洋环境下的腐蚀行为,并分析其腐蚀机理,并使用3.5%NaCl溶液作为腐蚀溶液进行浸泡试验。通过光学显微镜、扫描电镜和能谱分析等手段,观察和分析HAZ不同区域的微观组织、力学性能、腐蚀形貌和腐蚀产物成分。结果表明,HAZ不同区域的腐蚀程度由大到小依次为过热区(GRHAZ)>正火区(CHAZ)>混晶区(CGHAZ)。GRHAZ内的腐蚀产物最少且分布均匀,未产生大面积腐蚀,腐蚀产物主要以Fe_(3)O_(4)和Fe_(2)O_(3)两种化合物为主,结构表现为团状和柱状。CHAZ和CGHAZ的腐蚀产物相对较多,且分布不均匀,其中CHAZ的局部位置出现加重腐蚀现象。焊接接头设计时应充分考虑HAZ的腐蚀敏感性,并采取相应的防护措施,以保证海洋平台的安全性和可靠性。

With the development of marine oil exploitation technology,the corrosion resistance of high-strength steel welded joints has become a critical issue.This paper aims to study the corrosion behavior of the heat-affected zone(HAZ)of E690 low-alloy high-strength steel MAG welded joints in a simulated marine environment,and to analyze the corrosion mechanism.The study uses a 3.5%NaCl solution as the corrosive medium for immersion tests.Techniques such as optical microscopy,scanning electron microscopy,and energy-dispersive X-ray spectroscopy are employed to observe and analyze the microstructure,mechanical properties,corrosion morphology,and corrosion product composition in different regions of the HAZ.The results indicate that the corrosion degree of different regions in the HAZ decreases in the order of overheated zone(GRHAZ)>normalized zone(CHAZ)>mixed grain zone(CGHAZ).The GRHAZ has the least amount of corrosion products,which are evenly distributed,and no large-area corrosion occurs.The corrosion products are primarily composed of two compounds,Fe_(3)O_(4)and Fe_(2)O_(3),with a structure characterized by nodular and columnar shapes.The CHAZ and CGHAZ have relatively more corrosion products,which are unevenly distributed,and localized areas of enhanced corrosion are observed in the CHAZ.When designing welded joints,the corrosion sensitivity of the HAZ should be fully considered,and appropriate protective measures should be taken to ensure the safety and reliability of offshore platforms.With the devel‐opment of marine oil exploitation technology,the corrosion resistance of high-strength steel welded joints has become a criti‐cal issue.This paper aims to study the corrosion behavior of the heat-affected zone(HAZ)of E690 low-alloy high-strength steel MAG welded joints in a simulated marine environment,and to analyze the corrosion mechanism.The study uses a 3.5%NaCl solution as the corrosive medium for immersion tests.Techniques such as optical microscopy,scanning electron microscopy,and energy-dispersive X-ray spectroscopy are employed to observe and analyze the microstructure,mechanical properties,corrosion morphology,and corrosion product composition in different regions of the HAZ.The results indicate that the corrosion degree of different regions in the HAZ decreases in the order of overheated zone(GRHAZ)>normalized zone(CHAZ)>mixed grain zone(CGHAZ).The GRHAZ has the least amount of corrosion products,which are evenly dis‐tributed,and no large-area corrosion occurs.The corrosion products are primarily composed of two compounds,Fe_(3)O_(4)and Fe_(2)O_(3),with a structure characterized by nodular and columnar shapes.The CHAZ and CGHAZ have relatively more corro‐sion products,which are unevenly distributed,and localized areas of enhanced corrosion are observed in the CHAZ.When designing welded joints,the corrosion sensitivity of the HAZ should be fully considered,and appropriate protective mea‐sures should be taken to ensure the safety and reliability of offshore platforms.