CaO-Al2O3-SiO2-B2O3基连铸保护渣的热力学研究

B2O3 has been widely applied in new type mould fluxes such as fluoride free mould fluxes and high aluminum steel mould fluxes. The lack of research on reaction between mould fluxes containing B2O3 is an obstacle for application of mould fluxes containing B2O3 in continuous casting. There is an urgent need of thermodynamic data of mould fluxes containing B2O3 for optimization of mould fluxes composition to control the reaction between mould fluxes and steel. The present project would measure the thermodynamic data of CaO-Al2O3-SiO2-B2O3 based mould fluxes. This includes: measurement of thermodynamic data of basic system CaO-Al2O3-SiO2-B2O3; measurement of the activity data of components in fluoride free mould fluxes and high aluminum steel mould fluxes; measurement of structural information of CaO-Al2O3-SiO2-B2O3 based mould fluxes to establish the relationship between structural data and thermodynamic data; calculating the equilibrium between steel and mould fluxes in terms of thermodynamic data measured and verifying the calculated equilibrium through steel-flux equilibrium; adjusting the composition of mould fluxes to control the reaction between mould fluxes and steel. The present project would enrich the fundamental thermodynamic data for slag systems and provide references for controlling the reaction between mould fluxes and steel during casting.

B2O3常用于无氟连铸保护渣和高铝钢连铸保护渣等新型连铸保护渣中。目前缺乏含B2O3连铸保护渣与钢液反应的研究，阻碍了其在实际连铸生产中的应用。优化含B2O3连铸保护渣以控制连铸保护渣与钢液的反应，亟需含B2O3连铸保护渣的热力学数据。本项目将对CaO-Al2O3-SiO2-B2O3基连铸保护渣的热力学进行研究。包括测定基本体系CaO-Al2O3-SiO2-B2O3中组元的活度；测定含B2O3无氟连铸保护渣和高铝钢连铸保护渣中组元的活度。测定CaO-Al2O3-SiO2-B2O3基连铸保护渣的结构以建立结构与热力学性质的关联。根据测定的保护渣活度计算保护渣与钢液的平衡并利用平衡实验进行验证。对含B2O3连铸保护渣成分进行调节，最终达到对含B2O3连铸保护渣和钢液反应的热力学控制。本项目将丰富基础炉渣体系的热力学数据，并将为控制浇铸中高铝钢连铸保护渣和无氟连铸保护渣与钢液反应提供热力学参考。

CaO-Al2O3-SiO2-B2O3基连铸保护渣是最有希望商业化应用的无氟高铝钢连铸保护渣之一。对其结构和热力学的认识目前仍然不够，阻碍了其在实际连铸生产中的应用。优化含B2O3连铸保护渣以控制连铸保护渣与钢液的反应和提高其控制传热和润滑等性能，亟需含B2O3连铸保护渣的结构和热力学数据。本项目对CaO-Al2O3-SiO2-B2O3基连铸保护渣的热力学和结构进行了研究，包括了：利用淬冷法精确测定了1773K下CaO-Al2O3 -B2O3三元系和四元系的等温截面图。利用渣-金平衡法测定了CaO-Al2O3-B2O3-SiO2体系的SiO2的活度，研究了CaO/Al2O3 和SiO2含量等因素对SiO2的活度和活度系数的影响。研究了Li2O和Na2O对CaO-Al2O3 -B2O3-5%SiO2的SiO2的活度和活度系数的影响。利用多种先进分析手段（魔角自旋核磁共振谱、拉曼光谱、同步辐射高能X射线衍射、X射线光电子能谱）测定了CaO-Al2O3-B2O3-SiO2和CaO-Al2O3-B2O3-BaO等体系的结构。测定了CaO-Al2O3-B2O3-SiO2和CaO-Al2O3-B2O3-BaO等体系的高温粘度值，并与炉渣的结构建立了关联。。本项目丰富了基础炉渣体系的结构和热力学数据，并为控制浇铸钢液和保护渣反应和提高保护渣性能提供理论参考。