连铸结晶器无氟保护渣的基础研究

As a major fluxing agent, fluoride has been widely used in the mold flux system during the process of continuous casting. However, fluorine tends to evaporate easily during the high temperature atmosphere, and introduces the environmental pollution, speeding of the corrosion of equipment, and the damage of the human health. Therefore, it is urgent to develop the fluorine free mold flux system for the green continuous casting process. This proposal will focus on the molten structure, physiochemical properties, interfacial phenomena of the designed fluorine free mold fluxes, and develop the overall method to evaluate the performance that the mold fluxes play in the mold. The proposal will first study the molten structure of the deigned fluorine free mold fluxes by using FTIR/Raman Spectrometer and NMR Spectrometer, etc. Then combine with Hot Thermocouple Technology and Infrared Emitter Technology to study the variation of their properties with the change of the major components, and establish the relationship between the molten structure and properties. The interfacial properties between the molten slag and steel will also be conducted based on the Sessile Drop method. Finally, the dynamic crystallization and heat transfer behavior of mold flux as well as the initial solidification of molten steel in the mold will be studied through numeric and high temperature physical simulation. This proposal will elucidate the mutual relationship of the molten structure/properties, slag/steel interfacial behavior, mold flux dynamic crystallization and heat transfer as well as their effects on the molten steel initial solidification. The outcome of this proposal will develop the guideline for the design of environmental friendly mold fluxes for the continuous casting steels.

钢铁连铸过程中，氟作为主要熔剂常被添加到结晶器保护渣中。由于氟在高温环境中易挥发，会导致环境污染和设备腐蚀，且会损害人体健康；因此发展环保型无氟保护渣对于绿色连铸工艺来说具有重要的意义。本项目围绕保护渣无氟化后的熔体结构、理化性能、界面属性，以及其性能的科学评价方法而展开系统研究。首先利用Raman/FTIR光谱和NMR波谱等先进检测手段研究无氟保护渣熔体结构的演变规律；然后结合热电偶技术、红外发射热流技术等研究方法，研究主要组分对保护渣理化性能的影响机理；接着利用卧滴法等对无氟保护渣与钢坯界面特性开展研究；最后利用数值建模和高温物理模拟等方法建立起保护渣的动态结晶、传热与钢液初始凝固行为的科学评价体系。通过本项目的研究，将揭示无氟保护渣熔体结构/理化性能、渣/钢界面特性、保护渣动态结晶/传热及其与铸坯质量的相互影响关系；为环保型连铸结晶器保护渣体系的设计提供理论基础。

氟在保护渣中具有降低熔点和粘度、促进枪晶石晶相析出控制传热等重要的作用。然而，氟在高温连铸过程容易挥发导致环境的污染和设备的腐蚀。为此，本项目基于绿色冶金开发无氟保护渣过程中的科学问题，开展无氟保护渣的基础研究，并设计新型含硼保护渣系，从根源上解决钢铁连铸过程中氟污染问题。.首先，项目团队建立了以硼硅酸盐结构为基础的含硼无氟渣系，揭示了无氟渣系中硼硅酸盐结构的解聚与聚合的演变规律，这为明确保护渣性能变化的内在机理提供了理论支撑。其次，明确了组分对无氟渣系性能的调控作用，并建立了无氟保护渣系熔体结构与性能、以及熔化-粘度-结晶-传热等性能之间的相互关系，这为如何调控无氟渣系理化性能以适应不同的钢种和工艺参数提供了理论指导。接着，探明了含硼无氟渣系与传统含氟渣系的钢渣界面属性差异、以及含硼无氟渣系组分对其界面属性的影响，并建立了含硼无氟渣系的钢渣界面计算模型和钢渣界面对夹杂物去除和结晶器卷渣的关系；最后，本项目设计了一种含钛钢连铸用5mass% B2O3含量的无氟保护渣，对比评估了其与传统含氟渣的综合理化性能，利用连铸热模拟试验建立了保护渣结晶相变-渣膜传热-钢液初始凝固-铸坯质量的关系。最终，基于以上基础研究，本项目设计开发的无氟保护渣在含钛钢连铸生产试验中取得了成功。.本项目形成了‘含硼无氟保护渣从熔体结构-组分设计-理化性能-钢液初始凝固-铸坯质量’一套完整的保护渣基础理论和开发技术体系。项目相关研究成果已在Journal of Cleaner Production、Journal of the American Ceramic Society、Ceramics International、Metallurgical and Materials Transactions B等冶金环境国际权威期刊发表SCI论文46篇；相关保护渣及其研究技术已申请国家发明专利23项，已授权20项；相关技术获得了TMS（国际矿物、金属、材料学会）- Champion H. Mathewson Award、ASM International（美国金属学会）- Marcus Grossmann Young Author Award等国际学术奖4项，以及中国钢铁工业协会的冶金科学技术奖等行业科技奖励2项。此外，项目团队成员应邀在冶金国际会议及学术交流上担任分会主席或作相关报告共计10余次。