薄规格取向硅钢二次再结晶过程中Goss织构演变的Monte Carlo模拟

通过EBSD实验获取了薄规格取向硅钢(0.18mm厚)初次再结晶样品表面晶粒组织的取向数据,并以此构建模拟的初始组织。采用Potts模型Monte Carlo方法对薄规格取向硅钢初次再结晶样品的二次再结晶过程进行了模拟仿真,研究了表面能对Goss织构演变的影响。模拟结果表明:Goss取向晶粒与相邻晶粒的表面能差是Goss取向晶粒异常长大的重要驱动力;表面能差存在一个临界值(约12%),只有当表面能差大于此临界值时才会发生表面能驱动Goss取向晶粒的异常长大。     

薄规格取向硅钢中晶粒取向和尺寸对Goss晶粒异常长大的影响

利用EBSD技术统计了薄规格取向硅钢片中初次再结晶和二次再结晶前期组织中{411}〈148〉、{111}〈112〉、{100}〈025〉取向晶粒尺寸分布,分析了三种不同取向的晶粒对Goss晶粒异常长大的影响。结果表明:初次再结晶组织中不同的取向晶粒对应的平均晶粒尺寸(d)存在差异,{411}〈148〉取向晶粒的平均尺寸最大,其次为{100}〈025〉取向晶粒,{111}〈112〉取向晶粒的平均尺寸最小。Goss取向晶粒异常长大的过程中优先吞噬{111}〈112〉取向晶粒,其次是{411}〈148〉取向晶粒,最后是近{100}〈025〉取向晶粒和近黄铜取向晶粒。{111}〈112〉、{411}〈148〉取向晶粒对Goss取向晶粒异常长大的影响主要体现在二次再结晶的前期。因此,可以推断取向硅钢中最终残留的"岛晶"可能来源于近黄铜取向晶粒或近{100}〈025〉取向晶粒。     

升温速率对冷轧超薄取向硅钢再结晶行为的影响

利用EBSD技术对比分析了升温速率对冷轧超薄取向硅钢再结晶行为的影响.结果表明,冷轧超薄带中再结晶形核位置、再结晶织构类型受升温速率的影响不大,主要取决于形变组织;剪切带、{111}〈112〉取向晶粒晶界、形变带和形变不均匀区均为再结晶的形核位置,剪切带的再结晶形核优势更为明显;再结晶晶粒取向以Goss({110}〈001〉)取向为主,同时存在{210}〈001〉、{310}〈001〉以及一定比例的杂乱取向.然而,升温速率显著影响Goss织构的强度及退火样品的组织均匀性;慢速升温条件下,Goss织构比例和锋锐度降低,说明回复导致不同织构的形变组织储存能差异减小,降低了Goss取向的形核优势;快速升温条件下,剪切带内的Goss晶核具有更大的形核优势,吞并临近的形变组织完成再结晶,形成更强和锋锐的Goss织构.此外,快速升温可提高再结晶完成后的组织均匀性、降低平均晶粒尺寸.     

初次再结晶组织和渗氮量对低温渗氮取向硅钢二次再结晶行为的影响

通过控制初次再结晶工艺获得尺寸不同的低温渗氮取向硅钢初次再结晶组织,研究初次晶粒尺寸对二次再结晶行为和磁性能的影响,探索初次晶粒尺寸过大条件下合适的渗氮量,并分析初次再结晶组织中{411}〈148〉织构对二次再结晶行为的影响。结果表明:随着初次晶粒尺寸由10μm升高至15μm,二次再结晶温度升高,Goss织构更加锋锐,成品磁性能提高,当初次晶粒尺寸为28μm时,合适的渗氮量约为6×10-4。初次再结晶组织中{411}〈148〉取向晶粒生长能力更强,极易粗化,阻碍二次晶粒的异常长大,同时{411}〈148〉与黄铜晶粒之间为大于45°的低迁移率晶界,对黄铜晶粒异常长大的阻碍作用更为显著。     

低温薄规格取向硅钢初次再结晶组织对二次再结晶行为的影响

取向硅钢成品带材具有锋锐的Goss织构,其前提是需要保证在高温退火过程中能发生完善的二次再结晶,而合适的初次再结晶组织是发生二次再结晶的关键要点之一,探索初次再结晶组织对二次再结晶行为的影响具有重要的研究意义。分析了低温薄规格取向硅钢在不同脱碳退火时间条件下的初次再结晶组织,并研究了初次再结晶组织对二次再结晶行为的影响规律。结果表明:在脱碳退火温度880℃条件下,最佳退火时间约为3 min,此时高温退火可发生完全二次再结晶。延长脱碳退火时间,初次再结晶组织平均晶粒尺寸增大,导致二次再结晶不完善,高温退火后出现"细晶"组织。二次再结晶不稳定很大程度是初次再结晶组织中心层的{100}〈025〉取向晶粒长大所致,最终未发生二次再结晶的"细晶"组织也多为{100}〈025〉取向。     

取向电工钢中Goss晶粒生长的取向环境

将以MnS为主要抑制剂的普通取向电工钢作为实验材料,检测并分析脱碳样品的宏观织构及脱碳和随后加热至925℃时样品的微观织构,统计分析了Goss与周围晶粒的取向差分布。根据取向差原理计算了脱碳样品主要织构组分内各取向晶粒的取向差环境。结果表明,取向电工钢脱碳退火后Goss晶粒与周围晶粒的取向差分布呈现大角度特征,主要取向差分布范围为30°-45°,而非Goss晶粒与周围晶粒的取向差分布则呈现更多小角度特征。二次再结晶后,Goss晶粒与周围晶粒的取向差分布仍然以大角度特征为主。     

0.20mm CGO硅钢高温退火Goss晶粒起源及异常长大行为研究

利用X射线衍射织构分析技术和电子背散射衍射微织构分析技术,对0.20mm CGO硅钢薄板在高温退火缓慢升温过程中表层和次表层的织构演变规律进行了研究。结果表明:0.20mm CGO硅钢在高温退火过程中经历了低温回复、初次再结晶、初次再结晶晶粒长大和二次再结晶形成最终锋锐Goss织构的演变过程。Goss取向晶粒最初起源于变形回复基体中残存于{111}〈112〉形变带上少量的Goss晶粒亚结构,600℃保温2h后,Goss取向晶粒率先从变形基体中转变形核,在随后的升温过程中逐渐发生再结晶,Goss取向晶粒在此过程中并不具有尺寸优势,700℃时初次再结晶完成,基体中以γ纤维织构和{112}〈110〉织构为主;随着退火温度的升高,Goss晶粒的含量和平均晶粒尺寸逐渐增加,在900~1000℃之间,Goss取向晶粒迅速"吞噬"其他取向晶粒形成锋锐的Goss织构,1000℃时已经发生了二次再结晶。     

残余碳对取向硅钢初次和二次再结晶的影响

研究了脱碳退火样品中的残余碳对取向硅钢初次和二次再结晶的组织和磁性能的影响。结果表明：随着脱碳退火样品中残余碳含量的提高,初次再结晶的平均晶粒尺寸减小,表层和中心层的晶粒尺寸差增大;初次再结晶的强{111}<110>或{111}<112>织构向强{112}<110>织构转变,部分1/4层的Goss晶粒或{111}<112>晶粒转变为其他取向的晶粒;残余碳含量超过0.0200%后,高温退火样品二次再结晶不完善,磁性能较差。相变是导致上述现象的主要原因。     

脉冲磁场下冷轧取向硅钢的初次再结晶研究

研究了脉冲磁场对冷轧取向硅钢热处理过程中初次再结晶组织形成规律的影响。通过分析冷轧硅钢在不同热处理条件下初次再结晶晶粒长大的动力学可知,施加脉冲磁场能够抑制晶粒的再结晶及正常晶粒长大,而且沿法向施加脉冲磁场抑制晶粒长大的作用最大。脉冲磁场作用下可用异速生长幂函数建立基体晶粒的生长动力学模型。     

退火温度对耐热型取向硅钢组织与磁性能的影响

采用OM和EBSD技术对两种耐热型取向硅钢的微观组织进行了检测分析，研究了不同退火温度下组织的变化规律及耐热机理。结果表明：齿状辊沟槽法是在带材表层形成小晶粒组织和“缝隙”,激光照射法是在带材表层形成“V”字型沟槽。激光照射法取向硅钢耐热温度约为850℃,齿状辊沟槽法取向硅钢耐热温度约为800℃,前者耐热性更为优异。随着退火温度的升高，两种带材的损耗逐渐升高。齿状辊沟槽法取向硅钢损耗升高主要是刻痕区与两侧的Goss晶粒取向差降低所致，而激光照射法取向硅钢损耗升高可能与沟槽附近处Goss晶粒取向的变化有关。     

Influence of primary annealing on Goss development in grain oriented silicon steels

Abstract

Two different primary annealing conditions (continuous heating and discontinuous heating) on conventional oriented silicon steel were employed, and the evolution of microstructure and Goss frequency, as well as orientations of Goss neighbourhood from recovery to secondary recrystallisation, was investigated by means of optical microscopy and advanced electron backscatter diffraction (EBSD) technique. It could be concluded that high Goss frequency before secondary recrystallisation possibly did not contribute to sharp Goss orientation, even excellent magnetic property and that no grains with less deviation from ideal Goss first began to grow. As for coincidence site lattice (CSL) grain boundary and high energy grain boundary theories, the latter can explain the development of Goss due to its high frequency compared with CSL boundary of low frequency.     

Analysis of Micro-texture during Secondary Recrystallization in a Hi-B Electrical Steel

The understanding of Goss texture in Hi-B electrical steels possesses significant industrial and academic value, thus attracts worldwide attention. The prevailing models for sharp Goss texture formation during secondary recrystallization are CSL (coincident site lattice) boundary theory and HE (high energy) boundary theory. These theories stress the key factor of preferred growth and the difference between them only lies in the specific selection manner. This work examined the texture gradient in primarily recrystallized sheet and demonstrated its possible influence on the formation of secondary grains, and then determined the micro- texture during different stages of secondary recrystallization using EBSD (electron back-scattered diffraction) technique, finally analyzed a special type of secondary grains with near Brass orientation, which were detected in the later stage of secondary recrystallization, and discussed its origin and effect in terms of surface energy effect. The results indicate that texture gradient in primarily recrystallized sheet will lead to a multi-stage formation of Goss texture, namely, early stage of secondary grains with various orientations in subsurface region, intermediate stage of preferred growth of Goss grains into center layer and re-grow back to the surface and the final stage of Goss grain growth by swallowing slowly the island grains with the help of H2 atmosphere.     

Texture evolution during inclined cold rolling of used non-oriented silicon steel

With the objective of optimizing the texture components and exploring a method to improve the magnetic properties of used silicon steel, the methods of one inclined rolling and two inclined rolling were applied. The result shows: the new Goss grains were nucleated except at {111} deformed grains, and also formed at the grain boundary between two deformed grains with {113} orientation, and at grains boundaries between {113} and {100} deformed grain. The grain size after one inclined rolling (57 %) was larger and more homogeneous than the grain size after the two inclined rolling. Although with different cold rolling methods (one and two inclined rolling), the resulted annealing textures all had similar features. The difference was the relative intensities between the main texture. A significant feature of one inclined rolling was the intensification of the η-fiber and the Goss texture component and the weakening of γ-fiber. At an inclination angle of 60°, a significantly strong Goss texture was produced, which was highest among all samples, and the maximum volume fraction of {110}+{100} texture can also be obtained. One inclined rolling can better improve the magnetic properties of used silicon steel (B₅₀), and the magnetic induction is between 1.712 T and 1.742 T. The highest magnetic induction of 1.742 T can be obtained by one inclined rolling (at an inclination angle of 60°).     

Texture evolution and probability distribution of Goss orientation in magnetostrictive Fe–Ga alloy sheets

Texture evolution and the distribution of Goss orientation in polycrystalline Fe–Ga alloy were investigated as a series of rolling and subsequent annealing processes were used to develop highly textured rolled sheet. A dramatic change from the random nature of the as-rolled and primary recrystallized texture is observed when careful control of atmosphere and temperature during anneal leads to development of a sharp Goss orientation over up to 98 % of the surface of a sample during secondary recrystallization. In this work, grain boundary properties in local areas surrounding Goss grains are investigated and the evolution of Goss orientation is traced through the different stages of alloy processing using electron backscatter diffraction analysis. To evaluate the evolution of grains with Goss orientation, {011} grains are selected and separated from other texture components at each processing step and statistical analysis used to correlate the structural inheritance chain of Goss-oriented grains. The four processing stages considered are the alloy after hot rolling, the as-rolled alloy (i.e., after subsequent warm and cold rolling), the alloy after an initial anneal during which primary recrystallization occurs, and the alloy after final anneals in which secondary recrystallization with abnormal grain growth occurs. Analysis of Goss grain orientation probability distribution functions after primary and secondary recrystallization convincingly demonstrates that the orientation of the abnormally grown Goss texture that develops during secondary recrystallization is determined by the orientation of Goss components that develop during the primary recrystallization stage of alloy processing.     

冷轧压下率及初始高斯晶粒取向度对超薄取向硅钢织构演变与磁性能的影响

以不同高斯取向度的取向硅钢成品板为初始原料,采用一次冷轧法制备0.06~0.12mm厚的取向硅钢薄带。利用EBSD取向成像技术研究冷轧压下率以及初始高斯晶粒取向度对超薄取向硅钢织构演变与磁性能的影响。结果表明:随着冷轧压下率增大和厚度减小,退火后再结晶织构增强,当压下率为70%时,再结晶织构中RD∥〈001〉织构最锋锐,磁性能最佳;初始样品高斯取向度越高,制备的薄带样品磁性能越好;因此,生产高性能的取向硅钢薄带应选用初始高斯晶粒取向度较高的成品板。     

Mechanism of secondary recrystallization of Goss grains in grain-oriented electrical steel

Abstract

Since its invention by Goss in 1934, grain-oriented (GO) electrical steel has been widely used as a core material in transformers. GO exhibits a grain size of over several millimeters attained by secondary recrystallization during high-temperature final batch annealing. In addition to the unusually large grain size, the crystal direction in the rolling direction is aligned with <001>, which is the easy magnetization axis of α-iron. Secondary recrystallization is the phenomenon in which a certain very small number of {110}<001> (Goss) grains grow selectively (about one in 10⁶ primary grains) at the expense of many other primary recrystallized grains. The question of why the Goss orientation is exclusively selected during secondary recrystallization has long been a main research subject in this field. The general criterion for secondary recrystallization is a small and uniform primary grain size, which is achieved through the inhibition of normal grain growth by fine precipitates called inhibitors. This paper describes several conceivable mechanisms of secondary recrystallization of Goss grains mainly based on the selective growth model.     

3%Si电工钢铸坯中柱状晶的形变、再结晶行为及织构演变规律

利用电子背散射衍射(EBSD)技术和X射线衍射仪(XRD)研究3%(质量分数)Si电工钢铸坯中柱状晶的形变、再结晶行为及织构演变规律。结果表明:柱状晶长轴分别沿轧向、横向和法向放置,具有不同的初始织构。热轧后,表层形成的3种剪切取向中高斯取向较容易形成。中心区,RD样品中的α和γ线轧制取向,TD样品中的强γ线取向,ND样品中的强{100}取向以及各样品中的立方取向,均表现出明显的初始取向依赖性。冷轧后,RD,TD样品中的强{111}〈112〉取向来自热轧板中的高斯取向,ND样品中的强旋转立方取向遗传自初始{100}取向。受初始取向偏差及大晶粒尺寸影响,ND样品中的旋转立方取向晶粒内取向梯度较大。退火后,样品中心大尺寸的{100}取向晶粒是柱状晶初始取向遗传性的表现。