微量Ce对EH36船板钢夹杂物、组织和耐腐蚀性能的影响

发布时间：2018-12-18 08:12

【摘要】：近年来,随着船舶逐渐向大型化、轻型化、环保化以及海洋工程的深海化方向发展,对船板钢的强度、低温韧性、焊接性能和耐腐蚀性能提出了更高的要求。普通船板钢已经不能满足船体结构的要求,高强度的船板钢在船舶制造业中的使用比例在不断提高。此外,受全球金融危机的影响,船舶市场急剧萎缩,船舶制造业用钢市场形势严峻,船板钢生产企业同质化竞争越来越激烈。鉴于我国船板钢质量水平和国外水平还有一定差距,开发高强度及超高强度船板钢,改善船板钢的韧性、焊接性能以及耐腐蚀性能不仅可以提高钢铁企业的经济效益,减小同质化竞争的压力,同时也符合国家海洋发展战略的方向要求。本研究以应用广泛的EH36高强度船板钢作为研究对象,旨在开发低成本、高性能的船板钢生产关键技术。通过向钢中添加不同[Ce]含量后,利用扫描电子显微镜、光学金相显微镜、电化学工作站等检测设备分析、研究了[Ce]含量对EH36船板钢夹杂物、组织和耐腐蚀性能的影响,并探讨了添加Ce后钢中Al_2O_3夹杂物的演变机理以及含Ce夹杂物诱发晶内针状铁素体形核的机制。通过本研究所观察到的实验结果和相关机理的分析,为稀土元素在船板钢的实际生产应用提供技术数据支撑。通过相关计算以及对实验数据的分析和讨论,本实验得出以下结论:(1)EH36船板钢中的夹杂物主要是Al_2O_3和Mn S,形状不规则,尺寸均大于5μm。经过Ce处理后,夹杂物逐渐转变为Al_2O_3和Ce_2O_2S以及Mn S和Ce_2O_2S的复合夹杂物,当[Ce]含量达到0.026%时,夹杂物完全转变为小尺寸的Ce_2O_2S夹杂物。(2)随着[Ce]含量的增加,小尺寸夹杂物(2μm)所占的比例先增加后减小,当[Ce]含量为0.026%时,尺寸小于2μm的夹杂物所占的比例最大,达到87%,此时夹杂物最为细小,且弥散分布,当[Ce]达到0.034%时,大于5μm的夹杂物所占比例有所增加。(3)向钢中添加Ce,可以细化钢的显微组织,随着[Ce]的增加,晶内针状铁素体先增多后减少,当钢中[Ce]含量为0.026%时,晶内针状铁素体含量达到最大值。(4)向钢中添加Ce,可以显著提高船板钢的自腐蚀电位和极化电阻,从而提高EH36船板钢的耐腐蚀性能,当[Ce]含量为0.026%时,EH36船板钢的耐腐蚀性能最好。(5)相关热力学计算表明,在本实验条件下,Ce_2O_2S生成吉布斯自由能最负,因此,向钢中添加Ce,优先析出Ce_2O_2S。动力学分析表明,夹杂物的演变过程主要受Ce~(3+)和Al~(3+)在夹杂物和反应生成的中间层的扩散速率控制。经过计算,Ce_2O_2S与α-Fe相之间的错配度只有1.2%,因而具有较好的形核能力,是理想的异质形核点。
[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 伪-Fe is only 1. 2%, so it has better nucleation ability and is an ideal heterogeneous nucleation point.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TF76

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