摘要：目前能源需求日益增加，海洋资源的开发变得尤为重要。对海洋的利用和通过钻井平台对石油的开采正逐步加大。浅海和环境条件较好地区的石油和天然气资源正逐渐枯竭，这迫使石油和天然气的开采逐渐向更具有挑战的深海和严酷海洋环境的地区发展。相对于一般的结构钢，使用在深海和严酷海洋环境下的海洋平台结构钢需要具有更好的机械性能，它必须有较高的强度、韧性、焊接性能，低温加工性能，并且抗疲劳、抗层状撕裂和较好的耐腐蚀性能。因此具有高强度和韧性的新型低碳贝氏体钢正逐步取代原有的铁素体和珠光体结构的钢种应用于海洋平台等结构。目前，690MPa级高强钢是应用于海洋平台结构中强度级别最高的低碳贝氏体结构钢，然而这种结构钢在严酷海洋环境下很有可能发生腐蚀和应力腐蚀开裂等问题，制约海洋工程的发展。

　　在海洋工程中，腐蚀，尤其是应力腐蚀开裂是导致海洋平台和其它钢结构失效的重要问题之一。在较难发现和评估的情况下，应力腐蚀开裂会造成海洋平台极大的安全问题，引起脆性断裂和失稳破坏，造成大量的人员伤亡，以及严重环境污染和巨大的经济损失。但是目前对海洋环境中高强度的低碳贝氏体钢的应力腐蚀行为并没有清楚的认识，对其应力腐蚀开裂的机理也没有深入的研究。

　　本研究利用电化学测量技术及建立模拟海洋干湿交替环境下的恒载荷应力腐蚀试验方法，对模拟海洋干湿交替环境中E690高强钢的电化学腐蚀行为及应力腐蚀敏感性、机理及裂纹扩展方式进行研究。结果表明：模拟海洋干湿交替环境下，随试验周期增加，E690高强钢的阳极电流密度逐渐减小，阴极电流密度有逐渐增加的趋势，腐蚀电流密度先增加后减小，耐腐蚀性能先减小后略有增大；其腐蚀较为严重，120h后表面已被腐蚀产物所覆盖，随时间的延长，腐蚀产物逐渐增多；海洋干湿交替环境下，E690高强钢具有应力腐蚀敏感性，应力腐蚀机理为阳极溶解和氢脆的混合控制机制，裂纹扩展模式为典型的穿晶扩展模式；腐蚀产物以Fe3O4为主，并伴有α-FeOOH、β-FeOOH、γ-FeOOH、FeOCl等。锈层的结构和种类，对E690高强钢的应力腐蚀敏感性有较大的影响，Cl-富集在腐蚀产物内层，对应力腐蚀开裂有促进作用，Cr促进了锈层的致密化，降低了材料均匀腐蚀。

　　关键词：干湿交替，高强钢，应力腐蚀，电化学，海洋

 Stress Corrosion Cracking Of E690 High Strength Steel In Alterating Wet-Dry Environments
Hao Wenkui，Liu Zhiyong，Li Xiaogang²⁾，Du Cuiwei，Wu Wei，Qian Hongchang
( China Corrosion and Protection Center，University of Science and Technology Beijing，Beijing 100083)

　　Abstract:The exploitation of natural resource mostly deposited in the ocean had played an important role in the many nations recently. Marine resource utilization was popular in these years and underneath oil was available through off-shore platforms. In recent years, the oil and natural gas in shallow waters and reasonably benign environments have been largely depleted, and the oil and gas industries have been compelled to move into more challenging environments such as deeper waters and harsher metocean conditions. Steels used in deep sea applications or harsh marine environment for constructing offshore platform need to have mechanical properties that exceed those commonly used in construction. It is necessary to enhance strength, toughness, anti-fatigue, anti-lamellar tearing, weldability, cold formability, and corrosion resistance for development of these steels. Currently, the low carbon bainite steel is a new kind of multi-use steel with high strength and toughness, So it is gradually taking place of ferrite and pearlite as the offshore platform steel. At present, 690MPa high strength steel grade is the highest strength grade of low carbon bainite steels by applied off-shore platforms. However, the low carbon bainite steel may corrode and stress corrosion cracking （SCC） in the harsher metocean conditions, restricts the development of ocean engineering.

　　The corrosion and especially SCC problems are considered to be the most important factors leading to structural degradation of off-shore platforms and many other types of steel structures. The SCC has a harmful consequence from the point of view of safety and can lead to brittle fracture and unstable failure, with little or no warning. These failures can imply a risk of loss of human lives, a risk of polluting the environment and huge economic losses. But the SCC behavior and mechanism for the low carbon bainite steel with high strength has not been adequately investigated.

　　In the present paper, Electrochemical corrosion behavior and the sensitivity, mechanism and the mode of crack propagation of stress corrosion cracking of E690 high strength steel in marine alternating wet-dry environments was investigated by electrochemical technologies and the set up by oneself of constant load test method. Results show that the extension of the time not only enhanced the cathode current density and reduced the anode current density, but also influenced resistance of corrosion in alternating wet-dry environments. E690 high strength steel in alternating wet-dry environments was serious corrosion and sensitivite to stress corrosion cracking. The SCC mechanism was a mixture of anodic dissolution and hydrogen-induced cracking （HIC） in terms of transgranular fracture. Fe3O4 was the main corrosion product and α-FeOOH、β-FeOOH、γ-FeOOH、FeOCl was also produced of E690 high strength steel in alternating wet-dry environments. The electrochemical corrosion behavior and stress corrosion cracking of E690 high strength steel in alternating wet-dry environments was influenced by the structure and species of the rust layer. The stress corrosion cracking of E690 steel were promoted by the enrichment of Cl- in the inner corrosion products. Cr contributed to the formation of a dense rust layer, reduced the uniform corrosion.

　　Key words:alternating wet-dry,high strength steel,stress corrosion cracking,electrochemistry <javascript:void（0）；>,ocean

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