连铸中间包微孔镁质耐火材料与过滤器的制备及其对钢液的净化机理

The present work aims to investigate the preparation of nano-submicron micropores containing MgO refractories used as the lining etc. in continuous casting tundish, and utilize the new mechanisms of the interaction between the micropores MgO refractories and molten slag or liquid steel to improve the ability of refractories to resist corrosion and absorb the inclusions. In order to clarify the strengthening and toughening mechanism of porous ceramics with micropores, we want to use the micropores MgO as bones of the inclusions filter with multi-scale pores structures and explore the effects of bones thickness, pore structure and the additives on the mechanical strength and thermal shock resistance of the filter. After that, we would apply the functional oxides coatings on the bones of micropores MgO filter and study the wetting behavior between the micropores MgO filter coated with the functional oxides and liquid steel as well as the reactions between the inclusions and filter. To explore the motion behavior of inclusions under specific flow conditions and adhesion mechanism of inclusions on the surface of the filter material under the flow of liquid steel, the movement of molten steel and inclusions in the complex three-dimensional porous structure would be investigated. Lastly, the theoretical foundation of the interaction between the porous ceramic filter and liquid steel would be demonstrated, and filtration mechanisms for the distinct types of inclusions with different size distribution and purification mechanisms of liquid steel with porous MgO ceramics coated with functional oxides coating would be revealed. This research would provide the theoretical reference for microstructural design and application of long-lived functional refractories as well as design of purification and filtration system for removing inclusions of molten steel in tundish.

研究制备含纳米-亚微米复合微孔的MgO中间包内衬等耐火材料，探索利用微孔耐火材料与渣、钢间作用的新机制提高耐材耐蚀性、吸附钢中夹杂物的新功能；利用微孔MgO制备多重孔结构的过滤器骨架，研究骨架厚度、孔结构、添加剂等因素对过滤器强度和热震稳定性影响，探明多孔陶瓷的增强增韧机理；在微孔MgO过滤器上施加功能氧化物涂层，研究带功能氧化物涂层的多孔MgO复合陶瓷与钢液的润湿行为、与夹杂物的反应或吸附作用；研究复杂三维多孔结构中钢液与夹杂物的运动，解析夹杂物在特定流动条件下的运动规律，探究钢液流动状态下夹杂物在过滤材料表面的附着机理。奠定多孔陶瓷过滤器与钢液的相互作用理论基础，揭示带功能氧化物涂层的MgO多孔陶瓷对钢液中不同种类和粒径分布的夹杂物的过滤及净化机制；为长寿功能化的耐火材料微结构设计与应用以及中间包钢液中去除夹杂物的净化过滤系统的设计提供理论指导。

为满足中间包钢液洁净度控制需求，本项目提出利用微孔镁质耐材与钢液之间相互作用的新机制净化钢液，通过耐火材料微结构设计制备了具备保温、长寿和钢液净化功能的中间包用微孔镁质耐火材料和过滤器。. 揭示了多孔氧化镁骨料微孔形成机制以及孔结构和性能的演变规律，并发展了氧化镁渣蚀行为的数学模型。通过引入纳米ZrO2与菱镁矿内CaO杂质反应形成晶间CaZrO3，提高了晶粒结合程度，抗渣渗透性能增强，纳米ZrO2最佳添加量为0.75 wt%。相比传统镁质耐火材料，微孔氧化镁与熔渣接触角更大，抗渣侵蚀性能更好。微孔耐材可以通过物理吸附和化学烧结捕获钢中Al2O3、SiO2和TiO2夹杂，其在与钢液的作用时能形成更为连续致密的冶金隔离层，更有利于钢液成分和洁净度的控制。在此基础上，开发制备了长寿化节能型微孔镁质浇注料。. 深入阐释了MgO-Al2O3质多孔原料的合成与成孔机理。相比于氧化气氛，还原气氛对菱镁矿的烧结起一定的抑制作用，且菱镁矿的杂质类型及含量决定了高温烧成条件，进而决定了多孔尖晶石材料的结构与性能，这为充分利用我国丰富的菱镁矿资源奠定了基础。采用一次挂浆后直接烧成工艺制备了氧化镁过滤器，由于多孔氧化镁细粉粗糙的表面结构，用其制备的多孔氧化镁过滤器骨架气孔率、耐压强度及热震性能更加优异。α-Al2O3微粉可促进颗粒之间的烧结，当α-Al2O3微粉含量为20wt%可获得优异的强度和气孔率。多孔氧化镁过滤器对钢中夹杂物的去除效果更好，处理后钢液总氧含量更低，表现出更高的洁净度，且涂覆CeAlO3和CA6涂层能发挥出更好的净化钢液的效果。. 发展了带过滤器的中间包内钢液流动和夹杂物运动的数学模型，并通过物理模型进行了验证。过滤器的使用促进了中间包死区钢液的流动，钢液平均停留时间增长，过滤器的形状对于夹杂物的去除有着重要的影响，长径比的增加可以提高夹杂物的去除率，此外，螺旋形孔道可以使夹杂物产生旋转运动，也可以增大夹杂物的吸附率。为中间包过滤器的结构设计及其在中间包内的布置提供了技术依据。