Secondary Recrystallization Process Research Articles

Evolution of Microstructure and Texture in Grain-Oriented 6.5% Si Steel Processed by Rolling with Intrinsic Inhibitors and Additional Inhibitors.

A grain-oriented steel containing 6.5% Si, characterized by a notable Goss texture, was effectively manufactured through the rolling technique, incorporating both intrinsic inhibitors and additional inhibitors. This investigation focuses on tracking the development of texture and magnetic properties during the manufacturing process and delineates the mechanism underlying secondary recrystallization. The empirical findings clearly demonstrated the significant influence of nitriding duration and quantity on the secondary recrystallization process. In instances where additional nitrogen is absent, the intrinsic inhibitors alone do not lead to secondary recrystallization. However, when the nitriding duration is 90 s and the nitriding amount is 185 ppm, a complete secondary recrystallization structure with a strong Goss texture enables the finished products have excellent magnetic properties. The preferential growth of Goss grains is mainly governed by the enhanced mobility of high-energy (HE) grain boundaries. With the increase in annealing temperature, the occurrence of 20°-45° HE grain boundaries with Goss grains becomes more progressively frequent. At the secondary recrystallization temperature of 1000 °C, the frequency of 20°-45° HE grain boundaries with Goss grains reaches 62.7%, providing favorable conditions for the abnormal growth of Goss grains. This results in a secondary recrystallization structure predominantly characterized by a strong Goss texture. In light of these observations, the present study provides fundamental theoretical insights and serves as a valuable procedural guideline for the industrial manufacturing of 6.5% Si grain-oriented electrical steels.

Effect of Secondary Cold Rolling Reduction Rate on Secondary Recrystallization Behavior of CGO Steel

With the implementation of the “double carbon” policy in various countries in the world, the demand for grain-oriented electrical steel with low iron loss and high magnetic induction is increasing. Reducing the thickness of the steel sheets is an effective method to reduce the iron loss.The sheet thickness reduction means the increasing cold rolling reduction rate, especially the secondary cold rolling reduction rate, will directly affect the texture evolution of the secondary recrystallization process. In this paper, the secondary cold rolling reduction rate of commercial grain-oriented silicon steel was studied by means of X-Ray Diffraction, Electron Backscatter Diffraction. The results showed that Ultra-thin oriented silicon steel cannot be obtained by increasing the secondary cold rolling reduction rate alone; the optimum secondary cold rolling reduction rate was 59.2%. The grain size increased as the secondary cold rolling reduction rate increased and favorable texture content decreased, which was disadvantage to obtain a secondary recrystallization environment.

Свойства магнитотвердого порошкового сплава Fe – 30 Cr – 20 Co – Mo с повышенной пористостью

The purpose of this work is an experimental study of the influence of the sintering environment (vacuum and argon) on the structural and magnetic characteristics of the Fe – 30 Cr – 20 Co – Mo magnetically hard alloy with increased porosity. The material was synthesized by powder metallurgy. In the present work, studies were carried out on materials with a porosity of about 4 %. All porosity of the material was closed. Powders of pure elements were used to synthesize the alloy. The samples were sintered at a temperature of 1140 °C for 150 minutes in vacuum and argon. The experiments were carried out on materials in three states — after sintering, quenching material and material after heat treatment to obtain magnetic properties. Sintering in argon increases the density of samples by approximately 0.3 % compared to samples sintered in vacuum. Vacuum sintered material has slightly higher magnetic properties compared to argon sintered material, despite the lower density. Hardened samples have significantly higher plasticity compared to materials after sintering and after heat treatment. Such samples are deformed without fracture at a deformation of more than 60 %. Hardening simultaneously reduces the yield strength. Samples after sintering have the lowest plasticity (about 10 %), approximately three times less than after heat treatment. There is a good correlation between yield strength values and hardness data. For specimens with higher yield strengths, there are also higher hardness values. The grain size of the material sintered in vacuum is almost the same as the size of the material sintered in argon. Their size is about 30 µm. Irregularity is not observed, which indicates that the process of secondary recrystallization did not occur. Anisotropy is also not observed. Thus, it was experimentally established that the Fe – 30 Cr – 20 Co – Mo alloy can be sintered both in vacuum and in argon. In this case, the mechanical and magnetic properties are approximately at the same level acceptable for technical applications.

Effect of flattening reduction rate of primary recrystallization microstructure and rare earth in copper-containing grain-oriented silicon steel on secondary recrystallization

The results show that the content of rare earth and the flattening reduction rate after the initial recrystallization annealing have significant effects on the secondary recrystallization process and grain growth behavior in the copper oriented silicon steel produced by the first cold rolling method. After the initial recrystallization of the oriented silicon steel containing copper, the flattening with a reduction ratio of about 9%, relatively coarse recrystallized grains are obtained after high temperature annealing. About 8 ppm of lanthanum and 3 ppm of cerium were added to the oriented silicon steel containing copper, the temperature at which the secondary recrystallization abnormally grew during the high temperature annealing was increased by 30 °C ∼50 °C . After the primary recrystallization annealing, the secondary recrystallized structure of copper-oriented silicon steel containing rare earth is relatively coarse after being flattened.

Investigation on the primary and secondary recrystallization textures of rare earth micro-alloyed grain-oriented silicon steel

The primary and secondary recrystallization textures of rare earth micro-alloyed grain-oriented electrical steel was examined by using electron backscattered diffraction (EBSD) techniques. The results show that the primary recrystallization texture comprises {111} < 112 >, {111}<110 >, {411}<148>, and {012} < 001> components. The benefiting texture components of primary recrystallization increase with increasing rare earth addition after decarburizing annealing. During secondary recrystallization, the proportion of Σ9 boundaries are reduced. The sample containing 5ppm rare earth starts secondary recrystallization at 900°C, and the sample containing of 17ppm rare earth starts secondary recrystallization at 950°. The addition of rare earth can delay the process of secondary recrystallization.

Sharp secondary recrystallization and large magnetostriction in Fe81Ga19 sheet induced by composite nanometer-sized inhibitors

Abstract Strong Goss texture ({1 1 0}〈0 0 1〉) in Fe81Ga19 thin sheet is successfully produced by secondary recrystallization process based on the precise control of inhibitor and primary recrystallization texture. Nanometer-sized sulfides of MnS and Cu2S are dispersedly precipitated during hot rolling as inhibitors for secondary recrystallization. Primary recrystallization texture is characteristic of weak Goss and strong γ textures distributed through sheet thickness by appropriate rolling and annealing schedule. The composite nanometer-sized inhibitors accompanied with the primary recrystallization texture can provide a well-matched pinning effect on normal grain growth of matrix grains and induce abnormal grain growth of exact Goss grains in final annealing process. The magnetostriction coefficient as high as 285 ppm is obtained in Fe81Ga19 sheet after complete secondary recrystallization. Thus, an efficient method is proposed for developing sharp Goss texture and upgrading magnetostriction coefficient in Fe-Ga sheet.

Microstructural Evolution of Mechanically Deformed Polycrystalline Silicon for Kerfless Photovoltaics

Silicon wafers for photovoltaics could be produced without kerf loss by rolling, provided sufficient control of defects such as dislocations can be achieved. A study using mainly high resolution electron backscatter diffraction (HR‐EBSD) of the microstructural evolution of Siemens polycrystalline silicon feedstock during a series of processes designed to mimic high temperature rolling is reported here. The starting material is heavily textured and annealing at 1400 °C results in 90% recrystallization and a reduction in average geometrically necessary dislocation (GND) density from &gt;1014 to 1013 m−2. Subsequent compression at 1150 °C – analogous to rolling – produce sub‐grain boundaries seen as continuous curved high GND content linear features spanning grain interiors. Post‐deformation annealing at 1400 °C facilitates a secondary recrystallization process, resulting in large grains typically of 100 μm diameter. HR‐EBSD gives the final average GND density in as 3.2 × 1012 m−2. This value is considerably higher than the dislocation density of 5 × 1010 m−2 from etch pit counting, so the discrepancy is investigated by direct comparison of GND maps and etch pit patterns. The GND map from HR‐EBSD gives erroneously high values at the method's noise floor (≈1012 m−2) in regions with low dislocation densities.

Effect of Initial Oriented Columnar Grains on the Texture Evolution and Magnetostriction in Fe–Ga Rolled Sheets

The effects of initial oriented columnar grains on the texture evolution and magnetostriction in (Fe83Ga17)99.9(NbC)0.1 rolled sheets were investigated. The recrystallization texture evolution exhibited the heredity of initial orientations, concerning the formation of cube and Goss textures in the primary recrystallized sheet for the columnar-grained sample. Moreover, the growth advantage of Goss grains was more obvious than that of cube grains during the secondary recrystallization process. Because of the combined effect of this and Nb-rich precipitates as inhibitors, a sharp Goss texture and very large Goss grains were achieved in the secondary recrystallized sheet for the columnar-grained sample. For comparison, the secondary recrystallization in the equiaxed-grained sample was not fully developed although there were Nb-rich precipitates as inhibitors. We think this could be ascribed to the large particle size and premature coarsening of precipitates. Magnetostriction of the secondary recrystallized columnar-grained sheet was up to 232 ppm owing to the ideal Goss texture and quite large grain size. As for the equiaxed-grained sample, the magnetostriction was only 163 ppm in the secondary recrystallized sheet.

{411}&lt;148&gt; Texture in Thin-Gauge Grain-Oriented Silicon Steel

The significant occupancy of {411}<148> texture exists in the thin-gauge grain-oriented silicon steel (TG-CRGO is defined that thickness of the sheet is <0.25 mm and the reduction in cold rolling is more than 90%) which has been considered to have obviously effects on the abnormal growth of Goss-oriented grains during the secondary recrystallization process. The microstructures of the TG-CRGO were investigated by X-ray diffraction and electron back-scattered diffraction in this study. It was found that {411}<148> texture mainly exists in the center layer of hot-rolled as well as normalized plates. With the increase in cold rolling reduction, {411}<148> orientation gradually rotates to α-fiber texture (<110>//RD). Finally, few {411}<148> would retain at the boundaries of deformed α-fiber grains (<110>//RD) as the reduction in cold rolling reaches 90%. After annealing treatment, a small amount of γ-fiber textures (<111>//ND) preferably nucleates and recrystallizes between the DBs (deformation bands) at first; then, the {411}<148> recrystallization texture occurs and mainly nucleates at the grains boundaries of the deformed α-fiber grains, and also quite a few {411}<148> orientation grains nucleate in the inner of {112}<110> grains. But this phenomenon was not observed in the {100}<011> deformation grains. With respect to the occurrence of {411}<148> recrystallization texture, it is mainly induced by strong α-fiber as well as weak γ-fiber textures formed during cold rolling other than originating from {411}<148> regions in hot bands.

Goss Texture Evolution of Grain Oriented Silicon Steel by High-Energy X-ray Diffraction

High energy synchrotron diffraction offers great potential to study the recrystallization kinetics of metallic materials. To study the formation of Goss texture ({110}〈001〉) of grain oriented (GO) silicon steel during secondary recrystallization process, an in situ experiment using high energy X-ray diffraction was designed. The results showed that the secondary recrystallization began when the heating temperature was 1,494 K, and the grains grew rapidly above this temperature. With an increase in annealing temperature, the large grains with γ orientation [〈111〉//normal direction] formed and gradually occupied the dominant position. As the annealing temperature increased even further, the grains with Goss orientation to a very large size by devouring the γ orientation grains that formed in the early annealing stage. A single crystal with a Goss orientation was observed in the GO silicon steel when the annealing temperature was 1,540 K.

On the use of copper-based substrates for YBCO coated conductors

It is well known that the recrystallization texture of heavily cold-rolled pure copperis almost completely cubic. However, one of the main drawbacks concerning the use of purecopper cube-textured substrates for YBCO coated conductor is the reduced secondaryrecrystallization temperature. The onset of secondary recrystallization (i.e., the occurrence ofabnormal grains with unpredictable orientation) in pure copper substrate was observed withinthe typical temperature range required for buffer layer and YBCO processing (600–850 °C). Toavoid the formation of abnormal grains the effect of both grain size adjustment (GSA) andrecrystallization annealing was analyzed. The combined use of a small initial grain size and arecrystallization two-step annealing (TSA) drastically reduced the presence of abnormal grainsin pure copper tapes.Another way to overcome the limitation imposed by the formation of abnormal grains is todeposit a buffer layer at temperatures where secondary recrystallization does not occur. Forexample, La2Zr2O7 (LZO) film with a high degree of epitaxy was grown by metal-organicdecomposition (MOD) at 1000 °C on pure copper substrate. In several samples the substrateunderwent secondary recrystallization. Our experiments indicate that the motion of grainboundaries occurring during secondary recrystallization process does not affect the quality ofLZO film.

Growth of structurally homogeneous CVD ZnSe plates

A model for the formation of the CVD ZnSe structure is proposed which takes into account the heat exchange between the surface of the growing crystal and the flow of gaseous reactants and the secondary recrystallization process at a varied substrate temperature. The calculation results are compared to experimental data. The time variation of the substrate temperature is optimized to achieve CVD of ZnSe with a homogeneous structure across the plate.

Effect of Hexagonal Crystal Structure Anisotropy on the Selective Grain Boundary Mobility during Texture Formation and Secondary Recrystallization in Zn

Texture formation during secondary recrystallization depends on the nature of secondary recrystallization process itself. So microstructure evolution and texture development during secondary recrystallization should be discussed concurrently. The main goal of the paper is studying of the effect of internal stresses on grain boundary motion or, more generally, the interaction of grain boundaries with stress fields and the effect of deformation inhomogeniety on grain boundary mobility during secondary recrystallization. Considering transformation from normal grain growth to secondary recrystallization, the attempt was made to characterize the microstructure and to relate it to the processes of nucleation and growth of new rains. The nucleation process is heterogeneous. The data allow us to assume that the nuclei are strain free grains.

Multifractal properties of grain structures in sodium niobate based binary ceramics with nonisostructural components

The process of grain structure formation and development in ferroelectric ceramics based on sodium noiobate are considered. Micrographs of the grain boundary regions are described in terms of multifractal parameters. Correlations between the multifractal and structural parameters of ferroelectric niobate ceramics are found. The process of secondary interrupted recrystallization has been studied. The results have been used for optimization of the technology of novel ferroelectric materials.

Observation of Secondary Recrystallization Process in 3% Si-Steel with EBSD

Observation of Secondary Recrystallization Process in 3% Si-Steel with EBSD

Effect of nitrogen on the size and distribution of ain precipitates in 3% silicon steel

Taguchi et al. first utilized AlN and MnS as grain growth inhibitors at the primary recrystallization stage and a nitrogen contained atmosphere at the secondary recrystallization stage to produce high quality grain oriented silicon steels with sharp {l_brace}110{r_brace} texture. Recently, further strengthening of the inhibition was realized by nitriding the final gauge steel sheet prior to the secondary recrystallization process. Though the beneficial effect of the nitrogen has been confirmed, there has not been sufficient understanding how the presence of the element changes the precipitate size and distribution. The authors investigated the size and distribution of AlN precipitates in 3% silicon steels under the influence of nitrogen in the matrix or annealing atmosphere. Final gauge steel sheets of 0.10 mm thickness were nitrided to have various nitrogen content in the matrix ([N]). They were, then, annealed under two different nitrogen partial pressures (100%H{sub 2}, 75%N{sub 2} + 25%H{sub 2}). Samples were taken prior to and at certain intervals during the annealing. Precipitates in the samples were inspected by analyzing the extraction replica images taken by transmission electron microscopy (TEM).

On the Use of Polycrystal and Individual Orientation Texture Analysis Methods for BCC Materials

The reliability of the harmonic method of the ODF calculation from X-ray pole figures was estimated for cubic symmetry materials. For this purpose simulated textures with a preset scattering value of the components were used. Some examples using the Roe method to the study of the secondary recrystallization process in the Fe-3% Si alloy are given. The capabilities of the etch-pits methods as the simplest discrete method used to determine the orientation density are discussed.

A general theory of secondary recrystallization in grain oriented Fe-Si: Metallurgical parameters controlling the microstructural evolution

The secondary recrystallization (SR) process and the related effects on the magnetic properties of silicon-iron are discussed in the framework of the general statistical theory of grain growth including texture and Zener drag influence. It has been shown that SR in silicon-iron is related to a selective growth process experienced by Goss grains due to specific grain boundary conditions generated by the surrounding grains (texture). In this paper some examples showing the specific role of various microstructural parameters influencing the selectivity of SR (such as Zener drag intensity and its drop rate, initial grain size, etc.), are discussed and related to the magnetic properties, which are mainly controlled by the final average grain size and orientation.

3mass%Si鋼の二次再結晶過程に及ぼすSn添加の影響

3mass%Si鋼の二次再結晶過程に及ぼすSn添加の影響

Interactions between the inhibitor phases, secondary grain growth and glass-film formation in HGO electrical steel

The heating period of box annealing is mainly responsible for the magnetic properties of HGO electrical steel sheet. The annealing atmosphere influences the behaviour of inhibitor phases, the process of secondary recrystallization and the formation of the forsteritic insulation layer. Different conditions before annealing may result in differences in magnetic quality.