薄带连铸无取向6.5 wt.% Si钢力学行为与织构调控研究

To solve the problem of the low magnetic induction of the brittle non-oriented 6.5 wt.% Si steel, which is attributed to the instability of the {001} texture that is hard to intensify and the hereditary effect of the hard-magnetization {111} texture, this project specifically designs a processing route involving strip casting, hot rolling, two-stage warm rolling and annealing stages, which fully utilizes the advantage of strip casting technology characterized by near-net shape. Based on the clarification of the mechanical behavior of the as-cast strip, the processing route is specifically designed to decrease the stored energy of deformed {111} grains and facilitate the nucleation of {001} nuclei by strain induced boundary migration. The impacts of the solidification microstructure and texture of the as-cast strip together with the processing parameters of the hot rolling, two-stage warm rolling, the intermediate normalizing and the final annealing on the {001} and {111} textural evolutions are systematically investigated, which is conductive to clarify the correlation between the critical processing parameters and the textural evolution processes. Finally, the formation and evolution mechanisms of the {001} and {111} annealing textures are further disclosed. The implementation of this project will lay a theoretical and practical foundation for the development of high magnetic-induction non-oriented 6.5 wt.% Si steel that processes our own intellectual-property rights, which is to enrich the textural regulating and controlling theory of the strip casting technology and accelerate the application of non-oriented 6.5 wt.% Si steel in electric power, electric-vehicle and high-frequency telecommunication industries.

针对脆性无取向6.5 wt.% Si钢亚稳{001}面织构不易强化，且难磁化{111}面织构易于遗传所导致的低磁感问题，本项目基于薄带连铸法的近终形技术特点，在明确无取向6.5 wt.% Si钢铸带力学行为的前提下，针对性设计薄带连铸、热轧、两阶段温轧和退火工艺方案，以降低{111}变形晶粒的变形储能，并促进{001}晶核的形变诱导晶界迁移形核机制。系统研究初始铸带凝固组织、织构、热轧、两阶段温轧、中间常化和退火工艺对{001}和{111}面织构演化行为的影响，明确关键工艺参数与织构演化进程的相关性，揭示{001}和{111}再结晶织构的形成机制以及对应退火织构的演化机理。本项目的实施将为开发具有自主知识产权的高磁感无取向6.5 wt.% Si钢提供理论与实践基础，对丰富薄带连铸工艺的织构调控理论，加速普及无取向6.5 wt.% Si钢在电力、电动汽车乃至高频电讯等领域的应用具有推动作用。

无取向6.5%Si钢具备优异的高频软磁性能，如低的高频铁损、高磁导率和近乎于零的饱和磁致伸缩，用于制做发电机和电动机的转子铁芯，可实现节能降噪。然而，其高Si含量所致高脆性和难加工等技术难题严重制约其产业化和商用。薄带连铸技术可以将钢液通过旋转结晶辊直接凝固为2~3mm厚的金属薄板，具备短流程与近终形的技术特点，适用于脆性金属材料的加工成形。本项目利用该技术特点，探索了薄带连铸在无取向6.5%Si钢加工成型、组织、织构调控方面的技术可行性。主要研究内容包括无取向6.5%Si钢的稀土微合金化增塑、薄带连铸全流程组织演变、织构调控及磁性能优化研究。研究结果澄清了无取向6.5%Si钢的稀土增塑机制，解决了中温脆性和轧制开裂问题，在脆性无取向6.5%Si钢的加工成型方面取得了一定的技术突破。明确了易磁化织构的控制机理，弱化了{111}难磁化织构的遗传效应，优化了成品板的综合磁性能，丰富了无取向6.5%Si钢的组织、织构和磁性能调控手段，建立了以织构和磁性能为导向的薄带连铸技术路线，推动了无取向6.5%Si钢的产业化和商用。