【作者】 易献勋；

【导师】 李亚伟；

【作者基本信息】 武汉科技大学 ， 材料学， 2011， 博士

【摘要】 滑板是炼钢连铸生产过程中直接用于控制钢水流量和流速、稳定钢水液面的关键部件,是滑动水口系统中最重要的部分。铝锆碳质滑板是目前钢厂大中型钢包和中间包普遍采用的材质。随着高效连铸技术的发展以及钢种的增加,滑板的使用条件愈发苛刻,因此进一步提升铝锆碳滑板的综合性能显得尤为重要。金属Al、单质Si是铝锆碳滑板常用的添加剂,在热处理过程中它们与原料中的碳或周围气氛中的CO、N₂发生的一系列化学反应,生成Al₄C₃、SiC、AlN或Si3N4等陶瓷增强相,赋予了铝锆碳滑板良好的性能。Al-Si-SiO₂三元体系在氮气气氛且有碳存在条件下的热力学分析表明,该体系中反应特性更为丰富,反应产物均具有优良的理化性能,这为进一步通过材料的组分裁剪、微结构设计来提升材料的综合性能提供了可能。到目前为止,还未见到系统研究金属Al、单质Si、SiO₂微粉含量及工艺制度对铝锆碳滑板微结构及力学性能的影响报道。因此,系统研究金属Al、单质Si和SiO₂微粉含量、引入形式以及热处理制度对提升铝锆碳滑板材料综合性能和降低滑板的生产成本具有重要的现实意义。本论文针对目前主流使用的铝锆碳滑板,首先对不同温度下金属Al、单质Si、SiO₂微粉与碳反应进行热力学模拟和微结构表征,在此基础上系统研究了Al/Si比以及SiO₂微粉的引入量、引入形式及烧成气氛对Al₂O₃-ZrO₂-C滑板材料微结构与性能的影响,借助压汞仪和扫描电镜等检测手段分析了材料力学行为与微结构之间的关系,最后基于实验室的研究成果研制出新一代铝锆碳滑板,并进行了规模化生产及工业试验,得到以下主要结论:（1）碳复合耐火材料中添加剂（金属Al、单质Si、SiO₂微粉中的一种或一种以上复合）和鳞片石墨及炭黑的混合物反应生成的物相,与碳的反应热力学模拟结果完全一致。物相生成温度和形貌与添加剂种类、组合方式及烧成温度和气氛密切相关。同时碳素原料也显著影响材料中陶瓷相的形貌。（2）通过Al/Si比对Al₂O₃-ZrO₂-C滑板微结构与性能的影响研究发现,Al、Si加入比例显著影响Al₂O₃-ZrO₂-C材料的力学性能。经800和1000℃煅烧后,试样的抗折强度、弹性模量和韧性均随铝粉加入量的增加而增大,而经1 300和1 400℃煅烧后,试样的抗折强度、弹性模量和韧性均随铝粉加入量的增加而减小。试样的平均孔径呈现出与力学性能相反的变化规律。试样强度的变化主要与试样的微观结构密切相关。不同Al/Si加入比例的试样可以通过选择合理处理温度,优化材料的微观结构,获得最佳力学性能。（3）SiO₂微粉加入量、加入形式以及烧成气氛对不同Al/Si复合Al₂O₃-ZrO₂-C滑板的微结构均有影响,并使材料表现出不同的力学行为。SiO₂微/纳米粉的引入,还可以改善含金属Al的滑板抗水化性能,并避免高温烧成时强度的急剧下降,降低了滑板材料对烧成温度的敏感性。在氮气保护条件下烧成,铝锆碳滑板材料获得更佳的性能。（4）在上述工作基础上,选取基质中添加2%金属铝、3%单质硅和1%硅微粉的配方A21进行规模化工业生产。在工业生产线上经过1200℃烧成后的新型滑板具有晶须细小且均匀分布的结构特征,获得了优良的物理性能;并在不同的钢厂大中型钢包上取得一致良好的使用效果。更多还原

【Abstract】 Sliding gate plate is the key component to directly control molten steel flux and flowing speed,and stabilize the liquid level as it is the most important part in whole sliding gate system. Currently, Al₂O₃-ZrO₂-C sliding gate plates are widely used on medium or large size ladles and tundish in steel-making industries all over the world. With the development of the continuous casting technology with higher efficiency and steel grades, the field conditions for sliding gate plates are becoming harsher. Therefore, it is very important to continuously improve the properties of Al₂O₃-ZrO₂-C sliding gate plates. Metal aluminum and silicon powder are usually added into Al₂O₃-ZrO₂-C refractories to form ceramic phases such as Al₄C₃、SiC、AlN or Si3N4,etc, due to in-situ reaction with carbon in the matrix or the CO、N2 in surrounding atmosphere, which contributes to the excellent properties. From the thermodynamic analysis of Al-Si-SiO₂ ternary system with carbon under nitrogen atmosphere, quite a lot of reactions present, and all related resulting products have excellent physical and chemical properties, which provide different approaches to improve the refractories properties by the materials selection and microstructure design. Up to now, there are very few reports about the influence of Al, Si, SiO₂ content and manufacturing process on microstructure and mechanical properties Al₂O₃-ZrO₂-C refractories. Therefore, it is of great importance to have the whole research about the influence of amount and types of metal Al, Si, SiO₂, and firing atmospheres on Al₂O₃-ZrO₂-C refractories properties.In this thesis, focusing on Al₂O₃-ZrO₂-C refractories, the thermodynamic simulation of reactions among carbon and Al, Si under different temperatures and their micro-structure characterization were carried out. The influence of ratio of Al/Si, additional amount and types of SiO₂ powder and firing atmospheres on Al₂O₃-ZrO₂-C refractories microstructure and properties were studied. The relationship between material microstructure and mechanical properties were characterized by means of mercury analyzer and scanning electron microscopy. A new generation of aluminum zirconium carbon sliding gate material was developed, and the large-scale production and field trials were carried out. The main results are as follows:（1）. The new phases from the reactions among metal Al, Si and SiO₂ powder with the mixture of graphite and carbon black are in line with those results from the thermodynamic simulation. The formation temperatures and morphology of new phases depend on the types of additions, additional ratios, and firing temperatures and atmospheres. Another remarkable influence of new ceramic phases on the morphology is from the carbon source.（2）. The additional ratios of metal Al and Si play a main role on the microstructure and properties of Al₂O₃-ZrO₂-C refractories. From 800℃to 1000℃, the CCS, CMOR, elastic moduls, and toughness of samples increase as the metal Al content increases, but when firing temperature is 1300 or 1400℃, those mechnical properties show the dropping as the metal Al content increases. The average pore sizes present opposite trends against the mechanical properties. The strength change of samples depends on their microstructure. The mechnical properties of Al₂O₃-ZrO₂-C refractories can be optimized by the additional ratio of metal Al and Si under reasonable firing temperature.（3）. The different mechanical properties of Al₂O₃-ZrO₂-C refractories are contributed to the addition, types of micro/nano size SiO₂ powder and atmosphere. Addition of micro / nano size SiO₂ powder in the matrixes is beneficial for the improvement of hydration resistance, and less strength sensitivity on firing temperature for those sliding gate refractories containing metal Al. Compared with coke-bed atmosphere, samples fired under nitrogen atmosphere present better properties.（4）. Based on the work above, code A21 formulation with 2% Al, 3% Si and 1% SiO₂ powder was chose to run the industrial production. Those new sliding gate plates present good microstructure with finer and well distributed whiskers after fired under 1200℃in industrial production line, showed excellent physical properties, and achieved good field performance on large/medium size ladles.更多还原