基于二步形核理论的钢液凝固过程中夹杂物细化控制基础研究

控制钢中形成大量弥散分布的细小夹杂物对提高钢的力学性能有重要作用，是炼钢领域的重要课题。目前，以经典形核理论为基础建立的夹杂物生成规律及凝固工艺参数与夹杂物数量及尺寸的关系，因不涉及临界核形成之前的物相（中间体）对夹杂物形核长大的影响，用于细化控制时存在一定偏差。本项目基于二步形核理论提出了“中间体和临界核性质耦合作用的夹杂物二步形核率模型”，认识钢液凝固过程中夹杂物生成规律。项目拟采用电化学检测、第一性原理和分子动力学方法，研究形核过程中间体和临界核的组成、结构及性质，揭示夹杂物形核长大途径；通过高温激光共聚焦显微镜实验，考察熔体组成和各种凝固工艺参数对夹杂物数量及尺寸的影响；在此基础上，建立熔体组成和凝固参数与形核参数之间的关系；基于二步形核率模型、扩散长大及Ostwald熟化机制，定量描述夹杂物形核长大规律。研究成果对揭示钢中夹杂物形成机理及其尺寸细化控制具有重要意义。

Controlling a large number of non-metallic inclusions with small size and dispersive distribution in steel is very important to improve the mechanical properties of steels. It is a key project in steelmaking. There is a certain deviation for controlling inclusions size refinement because the regularity of inclusion formation and the relationship between solidification parameters and the number and size of inclusions based on the classical nucleation theory, cannot reveal the influence of the phase (intermediate) before nucleation to inclusion nucleating and growth. In this project, “a two-step nucleation rate model of inclusions based on the coupling of properties of intermediates and critical nucleus” will be constructed based on the two-step nucleation mechanism and used to study the formation of inclusions in solidification process of liquid steel. The electrochemical method, first principle and molecular dynamics methods will be applied to study the composition, structure and properties of the intermediate and critical nucleus. Thus, the pathway of nucleation and growth of inclusions will be revealed. The influence of melt composition and solidification process parameters to the number and size of inclusions will be investigated by the design experiments based on the Confocal Laser Scanning Microscope (CLSM). On the basis of the above study, the relationship between the melt composition and solidification parameters and the nucleation parameters will be established. The quantitative description on nucleation and growth of inclusions will be studied based on the two-step nucleation rate model, diffusion growth and Ostwald ripening mechanisms. The project has great significance to understand the formation mechanism of inclusions and their size refinement control in steels.