薄带连铸流程基于热轧孪生行为的取向硅钢组织织构调控机理

In the strip casting process, the coarse λ grains are likely inherited from the solidification microstructure to the primary recrystallization matrix, leading to the imperfect secondary recrystallization and deteriorated magnetic properties. In order to solve this bottleneck problem, the low-temperature hot rolling is introduced as a new method in this project to induce the occurrence of twinning deformation of grain-oriented silicon steel. The present study will focus on the key controlling mechanism of microstructure, texture and inhibitor evolution. The formation mechanism of deformation twins under the condition of low-temperature hot rolling in the grain-oriented silicon steel will be revealed. The effects of hot rolling on the deformation twins with different features and the controlling methods will also be clarified. The recrystallization behavior of deformation twins during the normalizing annealing and its effects on the microstructure, texture and inhibitor evolution will be investigated. The mechanism of breaking the inheritance of coarse λ grains based on the hot rolling twinning behavior will be revealed. The relationships between the hot rolling twinning behavior, primary recrystallization microstructure and texture, secondary recrystallization behavior and magnetic properties will be established. Based on the optimization of the manufacturing route and processing, the theoretical points of microstructure, texture and inhibitor to manufacture the grain-oriented silicon steel based on the hot rolling twinning behavior will be obtained. In addition, the grain-oriented silicon steel will be produced by one-stage cold rolling process. This study can contribute to the enrichment and development of manufacturing theories of grain-oriented silicon steel. Besides, the research results of this project would provide the technical support for the industrialization of strip casting grain-oriented silicon steel.

薄带连铸流程下，取向硅钢凝固组织中粗大λ晶粒容易“遗传”至初次再结晶基体而导致二次再结晶不完善，严重恶化磁性能。对此，本项目拟利用低温热轧促使取向硅钢发生孪生变形作为解决该瓶颈问题的新手段，围绕关键的组织、织构及抑制剂调控开展研究。揭示低温热轧条件下取向硅钢形变孪晶的产生机理，阐明热轧工艺对不同特征形变孪晶的影响规律和控制方法。阐明形变孪晶的再结晶行为，揭示其对组织、织构和抑制剂的影响机理。通过分析全流程下的组织、织构演化，揭示利用热轧孪生行为解决粗大λ晶粒“遗传”导致磁性能恶化瓶颈问题的机理，建立热轧孪生行为-初次再结晶组织与织构-二次再结晶行为-磁性能的关系。据此开展技术路线和工艺优化，掌握薄带连铸流程基于热轧孪生行为制备取向硅钢的组织、织构、性能控制要点，以一步冷轧法制备出取向硅钢原型钢。本研究有助于丰富和发展取向硅钢的制备理论，为促进薄带连铸取向硅钢的产业化提供技术支持。

薄带连铸流程下，取向硅钢往往形成粗大的凝固组织和强烈λ纤维织构（<001>//ND），这些粗大λ晶粒容易“遗传”至初次再结晶基体，通过阻碍Goss晶粒的异常长大而严重恶化磁性能。对此，本项目利用低温热轧促使取向硅钢发生孪生变形作为解决该问题的新手段，主要研究了取向硅钢热轧形变孪晶的产生机理及控制方法，研究了热轧形变孪晶的再结晶行为及其对组织、织构演化的影响规律，研究了取向硅钢二次再结晶过程中Goss晶粒的异常长大行为。结果表明，粗大的凝固组织是促使取向硅钢在650℃发生孪生变形的主要因素，在650℃热轧的复杂应力状态及轧辊急冷作用下，取向硅钢大部分晶粒内均可形成高密度的{112}<111>孪晶，表现出弱取向依赖性。由于变形储能较高，孪晶界/孪晶界及孪晶界/晶界的交叉点成为常化退火时再结晶晶粒的优先形核位置，在经过常化退火后形成取向漫散且尺寸较小的常化退火组织。冷轧过程中，在变形晶粒内形成大量的变形带、剪切带等亚结构，从而在初次再结晶退火后形成均匀、细小的等轴晶组织，消除了有害的粗大λ晶粒，并在高温退火后形成完善的二次再结晶组织。针对Goss晶粒异常长大行为的研究表明，微织构对二次再结晶有重要影响，凝固组织粗大的情况下需有效细化常化组织才可基于一步冷轧工艺获得完善的二次再结晶组织，这是对现有二次再结晶机理的补充，也为凝固组织粗大的情况下调控组织提供了参考。通过本项目的研究，揭示了利用热轧孪生行为解决粗大λ晶粒“遗传”导致磁性能恶化的机理，找到了关键的工艺控制窗口，综合调整热轧、冷轧及退火工艺，获得完善的二次再结晶组织，成功制备出取向硅钢原型钢，建立了热轧孪生行为-初次再结晶组织与织构-二次再结晶行为的关系。本研究为取向硅钢在较高温度下发生孪生变形提供了新的理解，也有助于丰富和发展取向硅钢的制备理论，为促进薄带连铸取向硅钢的产业化提供技术支持。