摘要：目前能源需求日益增加，海洋資源的開發(fā)變得尤為重要。對(duì)海洋的利用和通過鉆井平臺(tái)對(duì)石油的開采正逐步加大。淺海和環(huán)境條件較好地區(qū)的石油和天然氣資源正逐漸枯竭，這迫使石油和天然氣的開采逐漸向更具有挑戰(zhàn)的深海和嚴(yán)酷海洋環(huán)境的地區(qū)發(fā)展。相對(duì)于一般的結(jié)構(gòu)鋼，使用在深海和嚴(yán)酷海洋環(huán)境下的海洋平臺(tái)結(jié)構(gòu)鋼需要具有更好的機(jī)械性能，它必須有較高的強(qiáng)度、韌性、焊接性能，低溫加工性能，并且抗疲勞、抗層狀撕裂和較好的耐腐蝕性能。因此具有高強(qiáng)度和韌性的新型低碳貝氏體鋼正逐步取代原有的鐵素體和珠光體結(jié)構(gòu)的鋼種應(yīng)用于海洋平臺(tái)等結(jié)構(gòu)。目前，690MPa級(jí)高強(qiáng)鋼是應(yīng)用于海洋平臺(tái)結(jié)構(gòu)中強(qiáng)度級(jí)別最高的低碳貝氏體結(jié)構(gòu)鋼，然而這種結(jié)構(gòu)鋼在嚴(yán)酷海洋環(huán)境下很有可能發(fā)生腐蝕和應(yīng)力腐蝕開裂等問題，制約海洋工程的發(fā)展。

　　在海洋工程中，腐蝕，尤其是應(yīng)力腐蝕開裂是導(dǎo)致海洋平臺(tái)和其它鋼結(jié)構(gòu)失效的重要問題之一。在較難發(fā)現(xiàn)和評(píng)估的情況下，應(yīng)力腐蝕開裂會(huì)造成海洋平臺(tái)極大的安全問題，引起脆性斷裂和失穩(wěn)破壞，造成大量的人員傷亡，以及嚴(yán)重環(huán)境污染和巨大的經(jīng)濟(jì)損失。但是目前對(duì)海洋環(huán)境中高強(qiáng)度的低碳貝氏體鋼的應(yīng)力腐蝕行為并沒有清楚的認(rèn)識(shí)，對(duì)其應(yīng)力腐蝕開裂的機(jī)理也沒有深入的研究。

　　本研究利用電化學(xué)測(cè)量技術(shù)及建立模擬海洋干濕交替環(huán)境下的恒載荷應(yīng)力腐蝕試驗(yàn)方法，對(duì)模擬海洋干濕交替環(huán)境中E690高強(qiáng)鋼的電化學(xué)腐蝕行為及應(yīng)力腐蝕敏感性、機(jī)理及裂紋擴(kuò)展方式進(jìn)行研究。結(jié)果表明：模擬海洋干濕交替環(huán)境下，隨試驗(yàn)周期增加，E690高強(qiáng)鋼的陽(yáng)極電流密度逐漸減小，陰極電流密度有逐漸增加的趨勢(shì)，腐蝕電流密度先增加后減小，耐腐蝕性能先減小后略有增大；其腐蝕較為嚴(yán)重，120h后表面已被腐蝕產(chǎn)物所覆蓋，隨時(shí)間的延長(zhǎng)，腐蝕產(chǎn)物逐漸增多；海洋干濕交替環(huán)境下，E690高強(qiáng)鋼具有應(yīng)力腐蝕敏感性，應(yīng)力腐蝕機(jī)理為陽(yáng)極溶解和氫脆的混合控制機(jī)制，裂紋擴(kuò)展模式為典型的穿晶擴(kuò)展模式；腐蝕產(chǎn)物以Fe3O4為主，并伴有α-FeOOH、β-FeOOH、γ-FeOOH、FeOCl等。銹層的結(jié)構(gòu)和種類，對(duì)E690高強(qiáng)鋼的應(yīng)力腐蝕敏感性有較大的影響，Cl-富集在腐蝕產(chǎn)物內(nèi)層，對(duì)應(yīng)力腐蝕開裂有促進(jìn)作用，Cr促進(jìn)了銹層的致密化，降低了材料均勻腐蝕。

　　關(guān)鍵詞：干濕交替，高強(qiáng)鋼，應(yīng)力腐蝕，電化學(xué)，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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