无取向硅钢凝固CET转变过程{100}晶粒的形成机理及调控机制

Due to having two easy magnetization <001> axis, {100}<uvw> texture has been considered as a key to achieve high efficiency non-oriented silicon steel. For the purpose of promoting the effective inheritance of initial solidification {100} texture and reducing the corrugated defects of products, the formation and control mechanism of {100} grain during CET process in non-oriented silicon steel will be researched. Firstly, the evolution rule of solid-liquid interface morphology and crystal orientation during CET process will be studied, the interaction of boundaries on the {100} <uvw> orientation and other orientation is to be explored, which will reveal the nucleation and grain boundary migration behavior of {100} equiaxed crystal. Secondly, the geometry, orientation and typical solute accumulation characteristics of dendrite before and after CET process will be discussed, which could reveal the influence mechanism of heat and mass transfer behavior on the formation of {100} equiaxed crystal. Lastly, based on the above achievements, the three-dimensional CAFE model which combines both macro heat and mass transfer and micro nucleation and growth of {100} grain, and related algorithms will be established, which will define the relationship of nucleation mechanism of {100} equiaxed crystal and solute concentration field, temperature field and nucleating agents in solid-liquid two-phase zone. The results will provide fundamental basis and scientific basis for further study and effectively control of {100} equiaxed crystal in non-oriented silicon steel.

{100}<uvw>织构因具有两个易磁化<001>轴，一直被视为是实现无取向硅钢高效化的关键。本项目以促进初始凝固{100}织构的有效遗传和减轻成品瓦楞状缺陷为目的，开展无取向硅钢CET转变过程{100}晶粒的形成机理及调控机制研究。首先考察CET转变过程固-液界面特征和晶体取向的演变规律以及晶界对{100}<uvw>和其他取向的交互作用，阐述{100}等轴晶的形核机制及长大过程的晶界迁移行为；其次对CET转变前后枝晶的几何、取向和典型溶质富集含量进行表征，揭示CET转变过程的传热、传质行为对{100}等轴晶形成的影响机制；最后基于以上结论建立宏观传热、传质与微观形核、生长相结合的三维CAFE模型及相关算法，明晰{100}等轴晶形核机制与凝固两相区溶质浓度场、温度场和形核剂之间的内在关系。该项目研究成果将为无取向硅钢{100}等轴晶凝固组织的深化研究与有效调控奠定理论基础和技术指导。

{100}<uvw>织构因具有两个易磁化<001>轴，一直被视为是实现无取向硅钢高效化的关键。本项目以促进初始凝固{100}织构的有效遗传和减轻成品瓦楞状缺陷为目的，开展无取向硅钢CET转变过程{100}晶粒的形成机理及调控机制研究。采用Bridgman区域熔炼定向凝固装置、Gleeble 3500热模拟试验机、FactSage热力学软件以及金相显微镜、场发射扫描电镜、电子探针分析仪、电子背散射衍射分析技术等检测手段系统研究了凝固速率对0.73%~4.57%Si-0.14%~0.51%Al无取向硅钢凝固过程组织转变、硅、铝原子富集特征、Fe-Si相、AlN析出特性以及晶体取向的影响规律，得出其凝固过程发生CET转变的冷速在0.098 ℃/s~0.343 ℃/s之间；硅原子在固液界面的偏析加剧会进一步促进凝固过程{100}等轴晶的形核；高硅含量（>4.57%）、低凝固速率（<10µm/s）有利于其凝固过程{100}<001>等轴晶形核及长大，高铝含量（>0.28%）、高凝固速率（>80µm/s）有利于其凝固过程高斯柱状晶形核及长大等研究成果，为高效无取向硅钢{100}等轴晶凝固组织的有效调控提供了明确改进方向。对4.53%Si-0.31%Al无取向硅钢典型{100}晶面或<100>晶向铸态组织热轧过程的遗传特性及取向转变规律进行了模拟研究，得出4.53%Si-0.31%Al无取向硅钢铸锭边部高斯晶粒经热轧后发生明显二次再结晶并转变为{001}<100>和{001}<110>取向；四分之一、中心处{001}<100>取向晶粒经热轧后得到有效遗传，少量发生二次再结晶并转变为{111}<uvw>取向，该研究成果可为高硅、高铝高效无取向硅钢热加工及热处理后的{001}<uvw>织构调控提供可靠的理论基础和技术指导。