稀土作用效果不稳定和浇注工艺不顺行是长期以来制约稀土钢发展的两大瓶颈问题，单纯通过钢液内部洁净度控制无法解决上述问题。鉴于冶金渣系对钢中稀土赋存状态控制和稀土夹杂物去除的重要影响，而传统的精炼渣、覆盖剂和保护渣无法满足稀土钢需求，项目提出了稀土钢新型冶金渣系的设计理念，并以CaO-Al2O3-Ce2O3渣系为基础，开展多元渣系物理化学性质研究。基于CALPHAD原理和平衡实验法，绘制CaO-Al2O3-Ce2O3基渣系相图和活度场分布图，揭示其相平衡关系和活度变化规律；在此基础上，系统解析新型渣系的微观结构和宏观性能，探索揭示渣金界面反应机理、稀土夹杂物的溶解吸收机理及其对渣系结构性能的影响机理，进而构建渣系结构性能稳定化控制的理论与方法、多相复杂反应体系中稀土赋存状态的综合调控理论与方法；最终设计出稀土钢新型冶金渣系。研究工作极具创新性，将为解决稀土钢发展面临的瓶颈问题提供重要理论依据。

Unsteady effect of the rare earth (RE) elements and the tight pouring process are the bottleneck of the RE steel development. The above problems cannot be solved effectively by controlling the steel cleanliness. Considering the effect of the metallurgical slag system on the existence of RE elements and the removal of RE-containing inclusions, several matched metallurgical slag systems are demanded to make up the deficiency for the RE steel development. Since the traditional fluxes, including refining slag, tundish flux and mold flux, are insufficient for the production of the RE steel, this project aims at designing a series of new metallurgical slag systems for the RE steel production and investigating the physicochemical properties of the multi-slag system on the basis of CaO-Al2O3-Ce2O3. In this project, the CALPHAD principle and the equilibrium experiments will be employed to depict the phase diagrams and the activity distribution diagrams of CaO-Al2O3-Ce2O3-based slag systems. The phase equilibrium relations and component activities of the new slag systems will be revealed. The microstructure and macro-property of the new slag systems will be then analyzed to illuminate some key problems during the RE steel production, including the mechanism of the slag-metal interfacial reaction, the dissolution and absorption of RE-containing inclusions and its influence on the microstructure and macro-property of the slag system. On that basis, the methods and theories of stabilizing control of the structure and property and adjusting of the RE existence in multi-phase reaction system will be built. Ultimately, a series of new metallurgical slag systems for the RE steel will be designed. This innovative research would provide significant theoretical foundation for relieving the bottleneck of the RE steel development.