凝固两相区溶质富集与夹杂物析出对钢液多元体系溶质分配系数的影响

Solute partition coefficient is an important parameter for accurate studies on solute segregation in molten steel during solidification. Each solute partition coefficient is affected by its own concentration and the other solutes’ concentration in the multi-component molten steel system. Solutes enrichment and inclusions precipitation in mushy zone would cause changes of solute concentrations during solidification, thus indirectly affecting all the solute partition coefficients in molten steel. In the project, solutes enrichment characteristic and the influence rule of inclusions precipitation on solute concentrations in the solidification mushy zone during steel continuous casting will be studied. The interaction mechanism among solutes in multi-component molten steel system is to be explored, the quantitative influence relation between solute concentrations and solute partition coefficients will be determined, and a model for solute partition coefficients in molten steel considering multi-component interactions will be established. On this basis, the influence mechanism of solutes enrichment and inclusions precipitation in mushy zone on the solute partition coefficients of multi-component molten steel will be investigated and mastered. And the relationship of solute partition coefficients with solute concentrations, inclusions precipitation and solid fraction in mushy zone will be clearly defined. The results will provide fundamental basis and scientific basis for further study and effectively control of solutes segregation in molten steel during solidification.

合理的溶质分配系数是准确研究与调控钢液凝固偏析的重要参数保证。钢液多元体系中各组元之间存在着相互作用，各溶质分配系数都受到其本身及其它组元浓度的影响。凝固过程中两相区的溶质富集与夹杂物析出均会引起溶质浓度场的变化，间接影响钢液各溶质分配系数。本项目拟研究钢液连铸凝固过程中两相区的溶质富集特征以及夹杂物析出对溶质浓度场的耗变规律；探讨多元钢液体系中各组元之间的相互作用机制，确立各溶质分配系数与组元浓度之间的定量影响关系，并建立基于钢液多组元相互作用的溶质分配系数模型及相关算法；在此基础上，研究掌握凝固两相区溶质富集及夹杂物析出对钢液多元体系各溶质分配系数的影响机理，明确各溶质分配系数与凝固两相区的溶质浓度场、夹杂物析出、固相分率之间的内在关系，为钢液凝固偏析的深化研究与有效调控提供理论基础和科学依据。

偏析是钢液连铸的常见缺陷之一，严重的中心偏析对铸坯探伤合格率及钢产品的寿命与使用性能有重要的影响。溶质分配系数决定了钢液凝固溶质偏析属性，准确的溶质分配系数是研究与调控钢液凝固偏析的重要参数保证。凝固过程中，两相区溶质偏析富集及夹杂物析出均对钢液多元体系溶质分配系数有着不可忽视的影响。本基金课题建立了钢液多组元相互作用的溶质分配系数模型，研究讨论了钢液凝固各组元间的相互影响作用机制，明确了各组元浓度、凝固相变路径和温度对溶质分配系数(ki)的定量影响关系；并揭示了凝固过程中夹杂物析出对溶质浓度场的耗变规律及对溶质分配系数的影响机理。基于V-B模型及夹杂物析出热力学理论，采用考虑钢液组元成分、凝固路径和温度影响的溶质分配系数，建立了钢液凝固微观偏析-夹杂物析出耦合模型，深入研究了钢液凝固溶质分配系数、夹杂物析出及凝固相变路径对溶质微观偏析的定量影响规律。此外，针对钢液连铸过程，建立了板坯连铸钢液流动、传热凝固以及溶质传输三维溶质宏观偏析模型，实时耦合计算考虑凝固过程中夹杂物的析出，研究钢液连铸凝固过程中两相区溶质富集及夹杂物析出对溶质浓度场的耗变规律，探讨了溶质富集、夹杂物析出与宏观偏析的相互影响作用。本基金课题研究结果为先进钢铁材料凝固偏析的深入研究与有效调控提供了理论基础和科学依据。