發(fā)布時間：2018-01-19 05:35

  本文關(guān)鍵詞： 高強度鋼 點蝕 浪花飛濺區(qū) 銹層 干濕交替　出處：《中國科學(xué)院研究生院(海洋研究所)》2016年博士論文　論文類型：學(xué)位論文

【摘要】：低合金高強度鋼通常是指含碳量為0.2%-0.45%質(zhì)量分數(shù)、配以適當合金元素,并經(jīng)淬火、回火等工藝處理的低合金鋼。為了應(yīng)對海洋環(huán)境的強耐蝕性,海洋用低合金高強度鋼常會采用Cr、Ni、Mo、Cu、P、Si等元素進行合金化處理。隨著海洋用新材料研究工作的不斷深入,高強度鋼的性能不斷提高,其在整個海洋環(huán)境的使用將成為可能,海洋用低合金高強度鋼代表著一種趨勢,在我國海洋開發(fā)和利用中有廣闊的應(yīng)用前景。海洋環(huán)境中鋼鐵材料的局部腐蝕,尤其是點蝕(也稱小孔腐蝕),是影響鋼鐵材料強度和壽命的重要原因。在浪濺區(qū),鋼結(jié)構(gòu)表面幾乎連續(xù)不斷地被充分而又不斷更新的海水所潤濕,具有干燥時間短、水膜停留時間長、干濕交替頻率高、海鹽粒子量大等特點。由于波浪和海水飛濺,海水與空氣充分接觸,海水含氧量達到最大程度,浪濺區(qū)海水的沖擊也加劇材料的破壞。材料表面被銹層覆蓋后,其腐蝕過程不再是簡單的金屬陽極溶解和氧的陰極還原,而是一種十分復(fù)雜的多種物質(zhì)參與的氧化還原過程。鋼的腐蝕行為與鋼材表面銹層的多孔性、導(dǎo)電性、離子選擇性和還原性等性質(zhì)關(guān)系很大。目前,對于浪濺區(qū)鋼鐵材料的局部腐蝕機理研究相對較少,而浪濺區(qū)的腐蝕是海洋環(huán)境各區(qū)帶中最嚴重的,銹層結(jié)構(gòu)也與其它區(qū)帶不同,因此,針對高強度鋼浪濺區(qū)銹層覆蓋下的點蝕破壞規(guī)律及機制進行深入研究對于促進高強度鋼在海洋環(huán)境中的應(yīng)用推廣及安全評估有重要意義�；谝陨媳尘�,本文以低合金高強度鋼AISI 4135鋼為研究對象,對浪花飛濺區(qū)低合金高強度鋼表面銹層發(fā)生、發(fā)展過程進行了觀察,包括實海掛片實驗和實驗室模擬實驗兩部分。在實海實驗的不同階段,通過分析銹層的組成分析了主要的腐蝕環(huán)境因子。根據(jù)這些結(jié)果對銹層和鋼材界面的狀態(tài)進行模擬,為用電化學(xué)方法研究銹層底部的點蝕機制創(chuàng)造了條件。實驗室模擬實驗主要通過調(diào)整浪花飛濺區(qū)溫度和干濕交替變化研究其對點蝕發(fā)展規(guī)律及機制的影響。本論文的主要研究結(jié)果如下:1.AISI 4135鋼經(jīng)過合適的熱處理能提高鋼的強度并改善力學(xué)性能,但當海水液膜的溫度升高,所有熱處理試樣的開路電位降低,腐蝕速率增加。熱處理影響試驗材料的力學(xué)性能,但在相同溫度海水液膜下的腐蝕行為沒有顯著影響。2.浪花飛濺區(qū)實海暴露實驗的結(jié)果表明,暴露初期的溫度對AISI 4135鋼的腐蝕影響很大,暴露初期溫度越高,腐蝕速率越大。經(jīng)過一年四季溫度的更替后,暴露初期溫度高的試樣比暴露初期溫度低的試樣腐蝕要嚴重的多。另外,AISI4135鋼在浪花飛濺區(qū)實海暴露兩年后出現(xiàn)點蝕穿孔現(xiàn)象。3.在不同溫度海水液膜下,循環(huán)陽極極化曲線的滯后環(huán)的面積在低溫下大于其在高溫下的面積,表明點蝕在低溫下更容易發(fā)生。鈍化膜或者是氧化物膜在低溫下存在,但當溫度升高時會變的不穩(wěn)定或完全消失。4.溫度和濕度的日際和年際變化以及環(huán)境的濕-干-濕循環(huán)對海洋飛濺區(qū)銹層的結(jié)構(gòu)和性質(zhì)都有影響。當AISI 4135鋼暴露于飛濺區(qū)一年后,產(chǎn)生了能夠從飛濺和冷凝水中吸收海水的裂縫和空洞,這些裂縫為電解質(zhì)和O2提供了侵入內(nèi)銹層、接觸銹底層的通道。5.暴露于飛濺區(qū)的AISI 4135鋼含有裂縫的外銹層中有γ-FeOOH存在,γ-FeOOH是能加速裂縫腐蝕的電化學(xué)活性物質(zhì)。其次,AISI 4135鋼暴露于飛濺區(qū)一年后,其內(nèi)銹層中含有高濃度的氯化物,所產(chǎn)生的低pH可促進β-FeOOH的生成。β-FeOOH易被還原,能夠促進海洋飛濺區(qū)環(huán)境下的腐蝕過程。6.銹層覆蓋下的AISI 4135鋼在浪花飛濺區(qū)的干濕循環(huán)的干燥過程pH有最小值。在狹窄的陽極通道內(nèi),與鋼表面接觸的強酸性條件會導(dǎo)致腐蝕速率增大,加速裂縫和空洞處的局部腐蝕。
[Abstract]:High strength low alloy steel usually refers to the carbon content of 0.2%-0.45% mass fraction, with appropriate alloying elements, and after quenching, tempering process of low-alloy steel. In order to cope with the strong corrosion resistance of the marine environment, marine high strength low alloy steel is often used by Cr, Ni, Mo, Cu, P. Si and other alloying elements such as the oceans. The use of new materials and the deepening of the research work, the properties of high strength steel continues to improve, it will become possible in the use of the marine environment, marine high strength low alloy steel represents a trend, and has broad application prospects in the marine development and utilization in China local corrosion of steel in marine environment, especially pitting (also known as pitting corrosion), is an important factor affecting the steel material strength and life. In the splash zone, the surface of the steel structure is almost continuously being fully and continuously updated with water wetting. Short drying time, water retention time long, alternate high frequency characteristics of large amount of sea salt particles. Due to wave and seawater splash, full contact with seawater and air, oxygen levels in the water to reach the maximum level, the impact area of seawater splash also increased the damage of materials. The surface of the material being covered in rust layer after the corrosion process is no longer the cathodic reduction of anodic dissolution of metal oxygen and simple, but a variety of complex substances involved in the redox process. The porosity and corrosion behavior of the steel surface rust layer steel electrical conductivity, large ion selectivity and reductive properties. At present, the study on the local corrosion mechanism of steel splash zone the material is relatively small, and the splash zone corrosion is the most serious marine environment in each zone in the rust layer structure and other areas with different, therefore, to cover the splash zone of high strength steel rust pitting failure rules The law and mechanism of in-depth study has important significance for promoting the application and safety evaluation of high strength steel in marine environment. Based on the above background, this paper with high strength low alloy steel AISI 4135 steel as the research object, the splash zone of high strength low alloy stainless steel surface layer, the development process were observed. Including the real sea test and laboratory simulation experiment. The two part in different stages of real sea experiment, corrosion of main environmental factors were analyzed by analysis of the composition of the rust layer. According to the results of the rust layer and steel interface state simulation, to create the conditions for the research on the mechanism of pitting corrosion by electrochemical method of rust layer at the bottom. Simulation study on its influence on the law of development of pitting and mechanism mainly by adjusting the temperature and humidity in the splash zone alternating laboratory experiment. The main results are as follows: 1.AISI 4135 steel After proper heat treatment can improve the strength of steel and improve the mechanical properties, but when the water film temperature increases, all heat treated specimens of open circuit potential decreased, the corrosion rate increased. The effect of heat treatment on mechanical properties of test materials, but the corrosion behavior in seawater film under the same temperature did not significantly affect the.2. real splash zone the sea exposure experiment results indicated that the effects of exposure to the initial temperature corrosion of AISI 4135 steel, early exposure to higher temperature, higher corrosion rate. After a year after the change of temperature, exposure to high temperature samples than the initial samples exposed the initial corrosion of low temperature to be more serious. In addition, the real sea two years of exposure of AISI4135 steel in splash zone after pitting perforation phenomenon of.3. in seawater film under different temperature, hysteresis cyclic anodic polarization curves in the area is greater than that in the high temperature surface at low temperature That product, pitting more easily occur at low temperature. The passivation film or existing oxide film at low temperature, but when the effect of diurnal and annual variation of temperature will become unstable or disappear completely.4. temperature and humidity of the environment and the wet dry wet cycle of marine splash zone of rust layer the structure and properties of AISI 4135 steel. When exposed to the splash zone after one year, produced from splash and condensed water absorption water cracks and holes, these cracks as the electrolyte and O2 provide invade the inner rust layer, gamma -FeOOH outer rust layer contact the bottom of the rust channel.5. exposed to splash zone AISI 4135 steel containing cracks, gamma -FeOOH is electrochemically active substances can accelerate crack corrosion. Secondly, AISI 4135 steel exposed to splash zone after a year, containing a high concentration of chloride in the inner rust layer, caused by low pH can promote the formation of beta -FeOOH beta -FeOOH. Easy to be reduced, pH can promote the drying process of wet and dry cycle environment marine splash zone under the AISI corrosion process under the cover of.6. rust layer of 4135 steel in splash zone has a minimum value. In the anode channel narrow, strong acidic condition in contact with the steel surface will cause the corrosion rate increases, accelerate local corrosion and crack empty place.

【學(xué)位授予單位】：中國科學(xué)院研究生院(海洋研究所)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：P755.3

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