【摘要】：近年來,隨著船舶逐漸向大型化、輕型化、環(huán)�；约昂Ｑ蠊こ痰纳詈；较虬l(fā)展,對船板鋼的強度、低溫韌性、焊接性能和耐腐蝕性能提出了更高的要求。普通船板鋼已經(jīng)不能滿足船體結(jié)構(gòu)的要求,高強度的船板鋼在船舶制造業(yè)中的使用比例在不斷提高。此外,受全球金融危機的影響,船舶市場急劇萎縮,船舶制造業(yè)用鋼市場形勢嚴峻,船板鋼生產(chǎn)企業(yè)同質(zhì)化競爭越來越激烈。鑒于我國船板鋼質(zhì)量水平和國外水平還有一定差距,開發(fā)高強度及超高強度船板鋼,改善船板鋼的韌性、焊接性能以及耐腐蝕性能不僅可以提高鋼鐵企業(yè)的經(jīng)濟效益,減小同質(zhì)化競爭的壓力,同時也符合國家海洋發(fā)展戰(zhàn)略的方向要求。本研究以應用廣泛的EH36高強度船板鋼作為研究對象,旨在開發(fā)低成本、高性能的船板鋼生產(chǎn)關(guān)鍵技術(shù)。通過向鋼中添加不同[Ce]含量后,利用掃描電子顯微鏡、光學金相顯微鏡、電化學工作站等檢測設備分析、研究了[Ce]含量對EH36船板鋼夾雜物、組織和耐腐蝕性能的影響,并探討了添加Ce后鋼中Al_2O_3夾雜物的演變機理以及含Ce夾雜物誘發(fā)晶內(nèi)針狀鐵素體形核的機制。通過本研究所觀察到的實驗結(jié)果和相關(guān)機理的分析,為稀土元素在船板鋼的實際生產(chǎn)應用提供技術(shù)數(shù)據(jù)支撐。通過相關(guān)計算以及對實驗數(shù)據(jù)的分析和討論,本實驗得出以下結(jié)論:(1)EH36船板鋼中的夾雜物主要是Al_2O_3和Mn S,形狀不規(guī)則,尺寸均大于5μm。經(jīng)過Ce處理后,夾雜物逐漸轉(zhuǎn)變?yōu)锳l_2O_3和Ce_2O_2S以及Mn S和Ce_2O_2S的復合夾雜物,當[Ce]含量達到0.026%時,夾雜物完全轉(zhuǎn)變?yōu)樾〕叽绲腃e_2O_2S夾雜物。(2)隨著[Ce]含量的增加,小尺寸夾雜物(2μm)所占的比例先增加后減小,當[Ce]含量為0.026%時,尺寸小于2μm的夾雜物所占的比例最大,達到87%,此時夾雜物最為細小,且彌散分布,當[Ce]達到0.034%時,大于5μm的夾雜物所占比例有所增加。(3)向鋼中添加Ce,可以細化鋼的顯微組織,隨著[Ce]的增加,晶內(nèi)針狀鐵素體先增多后減少,當鋼中[Ce]含量為0.026%時,晶內(nèi)針狀鐵素體含量達到最大值。(4)向鋼中添加Ce,可以顯著提高船板鋼的自腐蝕電位和極化電阻,從而提高EH36船板鋼的耐腐蝕性能,當[Ce]含量為0.026%時,EH36船板鋼的耐腐蝕性能最好。(5)相關(guān)熱力學計算表明,在本實驗條件下,Ce_2O_2S生成吉布斯自由能最負,因此,向鋼中添加Ce,優(yōu)先析出Ce_2O_2S。動力學分析表明,夾雜物的演變過程主要受Ce~(3+)和Al~(3+)在夾雜物和反應生成的中間層的擴散速率控制。經(jīng)過計算,Ce_2O_2S與α-Fe相之間的錯配度只有1.2%,因而具有較好的形核能力,是理想的異質(zhì)形核點。
[Abstract]:In recent years, with the development of ship gradually towards the direction of large-scale, light, environmental protection and deep-sea engineering, the strength, low temperature toughness, welding performance and corrosion resistance of ship plate steel have been put forward higher requirements. Ordinary ship plate steel can not meet the requirements of hull structure, and the proportion of high strength steel used in shipbuilding industry is increasing. In addition, under the influence of the global financial crisis, the ship market shrinks sharply, the steel market of ship manufacturing industry is severe, and the homogeneous competition of shipboard steel manufacturing enterprises is becoming more and more fierce. In view of the fact that there is still a certain gap between the quality level of shipboard steel in our country and that in foreign countries, the development of high strength and ultra high strength shipboard steel, the improvement of toughness, welding property and corrosion resistance of shipboard steel can not only improve the economic benefit of iron and steel enterprises. Reduce the pressure of homogeneous competition, but also meet the direction of the national marine development strategy. The purpose of this study is to develop the key technology of low cost and high performance shipboard steel. The effect of [Ce] content on the inclusion, microstructure and corrosion resistance of EH36 steel was studied by means of scanning electron microscope, optical metallography microscope and electrochemical workstation after adding different [Ce] content to the steel, and by means of scanning electron microscope, optical microscope and electrochemical workstation, the effect of [Ce] content on the inclusion, microstructure and corrosion resistance of EH36 steel was studied. The evolution mechanism of Al_2O_3 inclusions in steel after adding Ce and the mechanism of acicular ferrite nucleation induced by Ce inclusions were discussed. Through the experimental results and the analysis of the related mechanism, the technical data support is provided for the practical application of rare earth elements in the production of shipboard steel. The conclusions are as follows: (1) the inclusions in EH36 steel are mainly Al_2O_3 and Mn S with irregular shape and size larger than 5 渭 m. After Ce treatment, the inclusions gradually changed into Al_2O_3 and Ce_2O_2S and Mn S and Ce_2O_2S composite inclusions. When the content of [Ce] reached 0.026, The inclusion completely changed into small size Ce_2O_2S inclusion. (2) with the increase of [Ce] content, the proportion of small size inclusion (2 渭 m) increased first and then decreased, when the [Ce] content was 0.026, The proportion of inclusions with size less than 2 渭 m is the largest, reaching 87. The inclusions are the smallest and dispersed. When [Ce] reaches 0.034, the proportion of inclusions larger than 5 渭 m increases. (3) adding Ce, to steel. The microstructure of the steel can be refined. With the increase of [Ce], the acicular ferrite in the crystal increases first and then decreases. When the content of [Ce] in the steel is 0.026, the content of acicular ferrite in the crystal reaches the maximum. (4) Ce, is added to the steel. The corrosion resistance of EH36 steel can be improved by increasing the corrosion potential and polarization resistance. When the content of [Ce] is 0.026, the corrosion resistance of EH36 steel is the best. (5) the thermodynamic calculation shows that the corrosion resistance of EH36 steel is the best when the content of [Ce] is 0.026. Under the experimental conditions, the Gibbs free energy generated by Ce_2O_2S is the most negative, so adding Ce, to the steel preferentially precipitates Ce_2O_2S.. The kinetic analysis shows that the evolution of inclusions is mainly controlled by the diffusion rate of Ce~ (3) and Al~ (3) in the interlayer of inclusion and reaction. It is calculated that the mismatch between Ce_2O_2S and 偽-Fe is only 1. 2%, so it has better nucleation ability and is an ideal heterogeneous nucleation point.
【學位授予單位】：太原理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TF76

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