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Article

Microstructure and Texture Evolution of High Permeability Grain-Oriented Silicon Steel

by
Yujie Fu
and
Lifeng Fan
*
School of Materials Science and Engineering, Inner Mongolia University of Technology, Hohhot 010051, China
*
Author to whom correspondence should be addressed.
Metals 2025, 15(3), 268; https://doi.org/10.3390/met15030268
Submission received: 3 February 2025 / Revised: 21 February 2025 / Accepted: 27 February 2025 / Published: 28 February 2025
(This article belongs to the Special Issue Transformation Texture and Its Prediction in Cubic and Hexagonal Metals)
Browse Figures
Figure 1
<p>Test steel phase diagram.</p> "> Figure 2
<p>The standard ODF map (ϕ<sub>2</sub> = 45°).</p> "> Figure 3
<p>Microstructure of hot rolled plate. (<b>a</b>) Rolling direction; (<b>b</b>) transverse direction.</p> "> Figure 4
<p>Microstructure of normalized plate. (<b>a</b>) Rolling direction; (<b>b</b>) transverse direction.</p> "> Figure 5
<p>Microstructure of cold-rolled sheet (Red circles represent the shear bands).</p> "> Figure 6
<p>Microstructure of decarburized nitriding sheet.</p> "> Figure 7
<p>Macrostructure of finished product.</p> "> Figure 8
<p>Texture and orientation line at ϕ<sub>2</sub> = 45° section of hot rolled plate. Microstructure texture: (<b>a</b>) surface layer; (<b>b</b>) 1/4 layer; (<b>c</b>) center layer orientation line; (<b>d</b>) {110}; (<b>e</b>) ϕ<sub>1</sub> = 90°; (<b>f</b>) α-fiber.</p> "> Figure 9
<p>Texture and orientation line at ϕ<sub>2</sub> = 45° section of normalized plate orientation: (<b>a</b>) Surface layer; (<b>b</b>) 1/4 layer; (<b>c</b>) 1/2 layer orientation linel (<b>d</b>) {110}; (<b>e</b>) λ-fiber; (<b>f</b>) α-fiber.</p> "> Figure 10
<p>Texture at ϕ<sub>2</sub> = 45° section of cold sheet. (<b>a</b>) ODF map; (<b>b</b>) grain orientation map; (<b>c</b>) α-fiber line.</p> "> Figure 11
<p>Textures of decarburized nitriding sheet and finished product: (<b>a</b>) decarburized nitriding sheet; (<b>b</b>) finished product.</p> ">
Versions Notes

Abstract

:
Industrialization trial production of high permeability (Hi-B) steel was carried out by “one cold rolled + decarburization and nitridation technologies”. The finished product reached the level of 23Q100 with an average grain size of 5.47 cm, magnetic flux density B8 of 1.902T, and the iron loss P1.7/50 of 0.975 W/Kg. The evolution law of the microstructure and texture under different processes was analyzed with the help of OM, EBSD, and XRD. The results showed that the microstructure of the hot rolled plate was equiaxed crystals in the surface layer, a mixture of recrystallization grains and banded fiber in the quarter of the thickness layer, and banded fiber in the center layer. The texture gradient of the hot rolled plate from the surface layer to the center layer was {112}<111> + {110}<114> → {441}<014> → {001}~{111}<110>. The texture of the normalized plate was in major {110}<113> in the surface layer, diffuse α-fiber texture and {441}<014> in the quarter of the thickness layer, and sharp α texture {001}~{111}<110> in the center layer. The texture of the cold-rolled sheet was concentrated in {001}~{332}<110>. The average grain size of the decarburizing and nitriding sheet was 26.4 μm, and the texture of the first recrystallization is sharp α*-fiber and weak {111}<112>. The finished product has a sharp single Goss texture. For Hi-B steel, the Goss secondary nucleus originated from the surface layer to 1/4 layer of the hot rolled plate and reached the highest content of 11.5% in the quarter of the thickness. The content of the Goss texture decreased with the subsequent normalization and cold rolling, then the Goss grains nucleated again during the decarburization annealing and high temperature annealing processes.

1. Introduction

Power grid is the lifeblood of a national energy transmission. Transformers with high energy efficiency, safety, and environmental protection are required to develop a new energy transmission pattern, which is the extra-high voltage power grid as the main channel and high energy efficiency distribution network as the end. Hi-B steel widely used in transformers is not only a landmark for the high-quality development of the steel industry but also has gradually become a business card leading the green and low-carbon transformation of the manufacturing industry. Hi-B steel production technology is currently mastered by only a few enterprises such as Baowu Group and Shougang Group in China, Nippon Steel and JFE Steel in Japan, and Posco in South Korea.
The core manufacturing technology for Hi-B steel is to form the accurate {110}<001> texture by secondary recrystallization. Inokuti Y [1] found that the {110}<001> secondary recrystallization nuclei were inherited from the original hot rolled texture. Bottcher A [2] proposed that the “texture inheritance” of the surface layer of the hot rolled plate was present at the whole process. D. Dorner [3] found that Goss texture was formed in shear bands and deformed bands with reduction ratios more than 70%. Therefore, the texture and microstructure of a hot rolled plate are critical to obtain a strong Goss texture. Yu Chun ming et al. [4] found that the {110}<001> grain content on the surface increased and {112}<111> texture in the central layer changed into {110}<001> texture after being normalized. Fu Bing et al. [5] found that the texture type did not change after being normalized, but {001}<100>, α, γ, {112}<111> texture weakened and {110}<001>, {110}<112> enhanced. Duan Yanghui et al. [6] found that the sharpness of the texture reduced after being normalized. Yin-Ping Wang [7] found that the microstructure of the cold-rolled sheet was smooth, and the angles between the deformation bands and the rolling direction gradually decreased from 40° to 5° with the increased cold rolling reduction ratio. Tang Shunqi [8] found that the decarburized sheet texture of the Hi-B steel is mainly composed of {111}<112> and {111}<110>. Mengqi Yan [9] found that the texture of the decarburized sheet was a component of {001}<120> and γ-fiber. Therefore, texture types and the strong point texture of Hi-B steel in each process are still not completely consistent and texture evolution law in the whole process remains unclear, which is mainly because most of the data are mainly laboratory studies and the process parameters are different.
This study focused on the industrial production of Hi-B steel; the microstructure and texture of the whole processing were analyzed, and the evolution characteristics and transformation law were clarified, which provides theoretical guidance for production process optimization and magnetic performance improvement.

2. Materials and Methods

All samples were taken from the industrial field. The industrialization process of Hi-B steel was blast furnace ironmaking, hot metal pre-treatment, converter smelting, RH (Ruhstahl hausen Process) refining, 220 mm thick slab continuous casting, low temperature heating at 1150 °C, hot rolling, normalizing, pickling, cold rolling, decarburizing annealing and nitriding, MgO coating, high temperature annealing, tension leveling, and insulation coating. The chemical composition of the hot rolled plate was determined by chemical method (According to the standard GB/T20123-2006) which is shown in Table 1. The phase diagram of the test steel is shown in Figure 1.
The hot rolled, normalized, cold-rolled, decarburized and nitrided, and high temperature annealed samples were, respectively, cut into a size of 10 mm (rolling direction, RD) × 8 mm (Normal Direction, ND), polished, and then etched by a 4% nitric acid alcohol solution for about 15 s~20 s. The microstructure was observed by Olympus GX51 F inverted metallographic microscope. The average grain size was calculated from 5 to 8 photos by the intercept method.
EI QUANTA 650 FEGfield emission scanning (FEI, brno, Czech) electron microscope equipped with electron backscatter diffraction (EBSD) technology was used to detect and collect the micro-orientation characteristics of the samples. The scanned * .cpr data were analyzed and processed by HKL Channel 5 software (Oxford instruments, Oxford, UK) to obtain ODF maps. The maximum deviation angle of grain orientation was set to 15°. Figure 2 is the standard ODF (Orientation distribution function) map [10]. The macro-texture of the finished product was measured by PANalytical B.V. X’Pert PRO MPDx-ray diffractometer, the three incomplete pole figures of {110}, {200}, and {211} of each sample were measured, and the orientation distribution function and the main texture content were calculated. The magnetic flux density B8 and the core losses P1.7/50 were measured by the single sheet tester method (500 × 500 mm, rolling direction × transverse direction).

3. Results and Discussions

3.1. Microstructure Evolution

The microstructure of the Hi-B steel hot rolled plate is shown in Figure 3, which is inhomogeneous in the thickness direction. The surface layer is recrystallized ferrites and pearlites, with an average grain size of 26.7 μm, accounting for 5.75% of the whole plate thickness. The quarter of the thickness layer is composed of a recrystallized structure and banded fiber structure, accounting for 47.89% of the whole plate thickness. The center layer is fibrous tissue. RD means the rolling direction, TD means the transverse direction, and ND means the Normal Direction. The reheating temperature of the slab is 1150 °C, and the finish rolling temperature is 950 °C. It can be seen from Figure 1 that the maximum amount of austenite (35%) was obtained at 1150 °C, and the rest are ferrites. Finish rolling temperature is controlled at 950 °C while a little austenite still exists (13%). Therefore, the phase transition occurred during the hot rolling process, and the austenite content decreases as the temperature decreases. The α-phase does not recrystallize during hot rolling, which maintains a banded structure along the rolling direction after low temperature coiling. The γ-phase is prone to dynamic recrystallization during high temperature deformation, and the recrystallized γ-phase is transformed into fine equiaxed ferrite and pearlite after low temperature coiling [11,12]. Temperature drop of Hi-B is very small (<80 °C) during the finishing rolling stage; therefore, the cooling water in the hot rolling process is basically closed. Moreover, the rolling speed reaches 16~18 m/s. Therefore, the friction between the roll and the hot rolled plate increases the surface temperature of the strip steel. However, due to the low thermal conductivity of Hi-B steel, the surface temperature rise cannot be transmitted to the central layer, and a temperature gradient is formed in the hot rolled plate. Therefore, there are more recrystallized microstructures on the surface of the hot rolled plate. The central layer is almost unaffected by the frictional heat, which is characterized by the elongated ferrite. The literature [13] demonstrates similar conclusions.
Figure 4 shows the microstructure of the normalized plate. Contributed to the high temperature and diminished the pinning effect by re-dissolution of part of the second phase particles (AlN) during normalization, the grain boundaries migrate more easily and the grains grow up more easily compared with the hot rolled plate [11]. The decarburization layer is more obvious in the normalized plate than that in hot rolled plate. Polygon grains on the surface and long strip grains on the center showed that the microstructure of the normalized plate is still uneven, which is conducive to the formation of the microstructure of the final Goss texture [14].
Affected by temperature and deformation, the microstructures of both the hot rolled plate and the normalized plate are inhomogeneous in the thickness direction. The surface is subjected to the maximum shear stress resulting from the friction between the roll and the hot rolled plate. The high stored energy and large nucleation driving force make fine recrystallization grains begin to form on the surface. Due to the temperature gradient in the thickness direction during the hot rolling process, only partial recrystallization occurred in the quarter of the thickness layer, and the ribbon fiber structure in the center layer was subjected to the compressive stress. The surface of the normalized plate is prone to recrystallization due to the inheritance influence of the hot rolled plate. The central layer is only partially recrystallized for the reason that the deformation energy storage is too small to generate enough recrystallization nucleation force. Tang Gang et al. [15] reported that, compared to structure of samples without normalizing process, the normalizing treatment could decrease primary recrystallizing grian size, increase the percentage of Σ9 grain boundaries and high angle grain boundaries, and improve the content of {111}<112> and Goss texture, which could enhance the magnetic flux density and decrease the iron loss. Huang Rusheng et al. [16] reported that the grain size of primary recrystallization without normalizing treatment was 1.15 times that of the normalizing treatment. Compared with the hot rolled plate, the microstructure of the normalized plate is much more uniform, and the amount and size of the recrystallization grain increases, which is conducive to enhance the magnetic properties of the finished product.
Figure 5 displays the microstructure of the Hi-B steel cold-rolled sheet. Two kinds of morphology exist along the rolling direction after being cold-rolled with a 90% reduction ratio, one is slender and deeply etched ribbon fiber, the other is shear bands (regions delineated in red) of 22–36° with the rolling direction. The etching degree is related to the deformation energy storage during cold rolling. Park J T et al. [17] believed that shear bands are easy to be formed in the ferritic steel with coarse grain size and high interstitial carbon or nitrogen content during cold rolling. Sebastiao et al. [18] considered that the 35° shear bands with the rolling direction is the nucleation point of the recrystallized grains, and new grains would be distributed along the shear bands. Kohsaku et al. [19] also found that a wide 35° shear band and a narrow 17° shear band with the rolling direction were observed in a {111}<112> single crystal cold-rolled plate, with recrystallization grains mainly nucleated at the shear band and growing into the surrounding matrix. The grains with a minor deviation angle from the standard Goss grains are preferentially formed in the 35° shear zone. According to the Taylor formula [20] of plastic deformation ( M = σ χ τ = d γ d ε χ , where M is the directional factor, σx is the normal stress, τ is the shear stress, γ is the shear strain, and εx is the normal strain), the lower the value of M is, the more easily deformation occurs. Yuanxiang Zhang et al. [21] considered that 25°~40° shear bands are composed of low M-oriented textures such as Goss and Cube, which have small deformation resistance. These low M-oriented grains changed from “soft orientation” to “hard orientation” with the increase in deformation to ensure the continuity of plastic deformation. Therefore, 22°~36° shear bands in the cold-rolled plate is conducive to the nucleation of accurate Goss grain.
Figure 6 displays the microstructure of the decarburized and nitrided sheet. Complete recrystallization occurred after the decarburizing and nitriding treatment. The most suitable primary grain size for secondary recrystallization in Hi-B steel is reported to be 8~29 μm [22,23,24,25,26,27]. The average size of the primary recrystallization grain in this experiment is 26.4 μm, which is conducive to the development of secondary recrystallization.
Figure 7 displays the macrostructure of the finished product. The average grain size of the finished product was 5.47 cm, and the maximum grain size reached 8.793 cm. The magnetic flux density B8 is 1.902T, and the iron loss P1.7/50 is 0.975 W/Kg, achieving a level of 23Q100 grade.

3.2. Texture Evolution

Figure 8 shows the texture of the surface layer, the quarter of the thickness layer, and the center layer of the hot rolled plate. The first image of Figure 8a is the ODF (Orientation distribution function), and the right color legend is the orientation density, which represents the low and high orientation density with the color from blue to red.
It can be seen from Figure 8a,d,e that the main texture of the surface layer is concentrated in {110}<114>, {112}<111>, and Goss texture {110}<001>, with texture contents of 9.68%, 14%, and 6.75%, and an orientation density of 6.22, 5.0, and 5.0, respectively. These three textures are typical shear textures, indicating the strong shear effect on the surface. As shown in Figure 8b,d,f, the texture of the quarter of the thickness layer is mainly concentrated in the {441}<014> texture with a content of 27%, which is close to Goss texture. Moreover, the {110}<114> and {112}<111> textures disappeared, which shows that the shear effect is reduced at the quarter of the thickness layer of the hot rolled plate. As shown in Figure 8c,e,f, the texture of the central layer of the hot rolled plate is concentrated in {001}<110> with a texture content of 61.6%, and the orientation density reached to 24.2. There is only the sharp rolling deformation texture in the central layer, indicating that it was only affected by compressive stress.
The texture of the surface layer is mainly subjected to shear deformation during hot rolling, while the central layer is mainly subjected to compression deformation. Such differences in the deformation mode greatly impact texture formation, causing a texture component from the surface layer to the center layer to change from shear texture to rolling texture [28,29]. Goss-oriented grains nucleate firstly under a low shear force and then rotate around the TD and ND axes to form a copper texture and brass texture with the increase in shear force [30]. The copper-type texture turns to a rotating cubic {100}<011> orientation during cold rolling, which has little influence on the formation of the Goss texture. However, the grain boundary mobility of {110}<112> at low temperatures is higher than the Goss grains, which is not conducive to the abnormal growth of Goss grains [31].
The surface layer of the hot rolled plate contains significant copper and brass texture (Figure 8a), indicating that the surface layer is subjected to the largest shear force. Because of the reduction of the temperature gradient and shear stress gradient in the thickness direction, the quarter layer retains a large number of Goss texture (Figure 8b). The center layer of the hot rolled plate is dominated by deformed grains, which have low energy storage. The texture in the center layer is characterized as a rolling texture, which gathers on the α orientation line [32], as shown in Figure 8c. Therefore, the main texture gradient distribution from the surface layer to the center layer of the hot rolled plate is ({112}<111> copper texture + {110}<114> brass texture) → {441}<014> (partial Goss texture) → {001}~{111}<110> texture.
Figure 9 shows textures of the surface layer, the quarter of the thickness layer, and the center layer of the normalized plate. It can be seen from Figure 9a,d,e that the main texture of the surface layer is concentrated in {110}<113>, with a content of 13.4% and orientation density of 6.15. There is also the weak {112}<111> and cubic texture {100}<001>, whose orientation densities were only 2.0. The shear texture on the surface layer of the normalized plate is more diffuse than that of the hot rolled plate (Figure 8a). As shown in Figure 9b,d–f, the texture in the quarter of the thickness layer of the normalized plate is mainly {441}<014> with a content of 22.4%, and the orientation density reached to 4.37. There are also weak α-fibers concentrated in the {116}<110> and {001} plane textures concentrated in {001}<120>. The texture in the center layer is mainly composed of {001}~{111}<110>αfiber, and the strong point is concentrated in {001}<110> with a content of 29.5%, and the orientation density reached to 19.3, as shown in Figure 9c,f. Because of recrystallization without deformation in the normalizing treatment, the texture characteristics in the surface layer of the normalizing plate are basically inherited from the hot rolled plate, the quarter of the thickness layer is mainly composed of diffuse α-fiber texture and partial Goss texture, and the center layer is dominated by an α-fiber rolling texture. Compared with the hot rolled plate (Figure 8), the orientation density of the normalized plate is reduced and the rolling deformation alleviated.
As shown in Figure 10, the cold-rolled sheet shows a sharp α-fiber texture with the strong point at {001}<110> and a content of 12.9%. It can be seen from Figure 10b that the {114}<481> grains appears in the {001}<110> deformation grains, indicating that the {114}<481> grains can nucleate in the α-fiber grains.
Figure 11a shows the texture of the decarburized annealing sheet. The microstructure of the decarburized annealed plate is fine recrystallized grains, and the texture is mainly the α* fiber texture with strong {114} <481>, and there are also the weak {115} <120>, {223} <231>, and {111} <112> textures. Figure 11b shows that the finished product is a single Goss texture.

3.3. Discussion

The texture of the normalized plate basically inherits the characteristics of the hot rolled plate. The α-fiber texture of the center layers of both the hot rolled plate and the normalized plate are mainly concentrated in {001}~{111}<110>. The texture density of the normalized plate is weaker than that of the hot rolled plate, indicating that the normalizing treatment makes the structure of the hot rolled plate more uniform. The rotated cube {001}<110> texture is relatively stable and cannot rotate easily in the subsequent cold rolling [33], and needs to be reduced for the development of {110}<001>.
It was found that that cube oriented grains were distributed in shear bands, which tilted toward the {113}<361> orientation during cold rolling, and finally stabilized at {112}<110>~{111}<110> [21]. Related literature [34] also proved that the texture of {115}<120> (class {114}<481>) rotated toward {113}<110> after cold rolling with the reduction ratio increasing from 55% to 72%. The Goss texture in the hot rolled plate rotates along the following path during cold rolling: {110}<001>→{554}<225>→{111}<112>→{111}<110>→{223}<110> [35]. The stable rotating cube texture {001}<110> is inherited from the hot rolled plate and continues to grow during cold rolling [36]. With a 90% reduction ratio, the texture rotation path from the normalized to the cold-rolled plate was as follows: the cubic texture of the surface and sub-surface on the normalized plate first rotated to α*, and finally stabilized at {001}~{332}<110>; the Goss texture of the surface layer and the quarter of the thickness layer first rotated to {111}<110>, then finally concentrated in {001}~{332}<110>. Oyarzabal et al. [37] found that α deformed fiber grains split under an excessive cold rolling reduction ratio, and part of the deformed α-fiber grains formed the {114}<481> substructure, becoming a recrystallization nucleus of α* fiber grains in the subsequent annealing and recrystallization process. It was found that {114} <481> oriented grains are recrystallized near the grain boundary of {001}<110>~{112}<110> deformed α-fiber grains in the late recrystallization period; {114}<481> grains could grow up rapidly by relying on large angle grain boundaries with α-fiber grains [38,39]. However, the γ-oriented grains have high energy storage and many nucleation points, which can only grow slowly due to the oriented pinning effect. According to the literature, {114}<481> orientated grains can nucleate at one site like the grain boundary and deformation bands of {114}~{112}<110> oriented grains, or at another kind of position like the grain boundary of {111}<112> oriented grains. In the initial stage of recrystallization, {111}<112> oriented grains grow at the fastest rate and have advantages in size, quantity, and texture strength. In the intermediate stage of recrystallization, the growth rate of {114}<481> oriented grains gradually exceeds that of {111}<112> oriented grains, and become the dominant texture. In the later stage of recrystallization, {114}<481> oriented grains swallow {111}<112> oriented grains and become the dominant texture [10].
In this study, the cold-rolled sheet with a reduction ratio of 90% showed sharp α texture. The α-fiber texture would converge toward {115}<120> (class {114}<481>) during the decarburization annealing process, and {001}<110> grains would first rotate to {112}<110> and then to {111}<112>. Moreover, {111}<110> texture in the cold-rolled sheet would also form the {111}<112> recrystallization texture during the decarburization annealing process. Therefore, the decarburizing and nitriding sheet is mainly a sharp α* fiber texture and a weak {111}<112> texture. It can be concluded that there are two rotate paths of the texture from cold rolling to decarburizing and nitriding process in this experiment, one is α → {115}<120>, another is {001}<110> → {112}<110> → {111}<112>, {111}<110> → {111} <112>.
Table 2 shows the Goss texture content of each process. It is considered [3,40] that shear bands in the cold-rolled sheet are the nucleation point of the Goss-oriented grains. Goss grains located in the sub-surface layer will transform into {111}<112> orientation under a large shear force during cold rolling, and a small amount of substructures will remain in the deformation band [41,42]. In the recovery stage, the dislocation rearrangement forms substructures consisting of small-angle grain boundaries. These Goss orientation substructures preferentially transform into the recrystallization nucleus, and Goss grains can be re-transformed from {111}<112> grains during recrystallization due to the advantage of the orientation relationship between the Goss and {111}<112> grains. Therefore, the secondary nucleus of {110}<001> after decarburizing annealing of Hi-B steel is formed by sub-grain aggregation, which is located at the {111} <112> deformed bands [43].
It can be seen from Table 2 that the normalization and cold rolling processes lead to a decrease in the content of Goss grains, and the Goss content of the decarbonized annealing sheet was only 0.0615%. For Hi-B steel, only a small amount and accurate Goss orientation grains can lower the secondary recrystallization nucleation rate and make the Goss texture fully grow.
The purpose of the whole process control of the oriented silicon steel is to obtain a sharp {110}<001> texture. The Goss texture was formed in the surface layer and quarter layer during hot rolling, and the {110}<001> oriented grains are coarsened after normalizing. After cold rolling, the {110}<001> texture exists in the shear bands of the cold-rolled plates. The Goss sub-grains in the cold-rolled plates gather to grow up to become the secondary core of the Goss grains during the decarburizing annealing stage. The texture of the decarburizing annealing plate is mainly concentrated in {114}<481> and {111}<112>, which are, respectively, 39.4°and 35.4° for the Goss grains, close to the Σ9 grain boundary (38.9°).
In the process of high temperature annealing, the Goss grains have no size advantage at the beginning, but they maintain the fastest grain boundary mobility due to the high-energy grain boundary relationship with {114}<481> and {111}<112>, and then their earlier escape from the pinning of the precipitate. Relying on a low surface energy advantage, the Goss-oriented grains continue to swallow other oriented grains and grow in the later stage of high temperature annealing, and finally form a single sharp Goss texture [42].

4. Conclusions

(1)
The hot-rolled plate of the experimental steel displays a gradient both in the microstructure and texture in the thickness direction. The surface layer is composed of recrystallized grains, the center layer is elongated fibrous tissue, and the quarter of thickness layer is a mixed structure. The main texture from the surface to the center layer is as follows: ({112}<111> copper texture + {110}<114> brass texture) → {441}<014> → {001}~{111}<110>.
(2)
The surface of the normalized plate is mainly the {110}<113> texture, the quarter of the thickness layer is mainly composed of diffuse α-fiber texture, and partial Goss texture. The center layer is characterized by a sharp α-fiber texture.
(3)
The cold-rolled plate is composed of fibrous tissue and a shear band of 22°~36° with the rolling direction. The texture of the cold-rolled sheet is typically sharp α-fiber.
(4)
The average grain size of the primary recrystallization is 26.4 μm, and the texture of the decarburized nitriding sheet is composed of sharp α* and weak γ-fibers.
(5)
The finished product has a sharp single Goss texture with an average grain size of 5.47 cm.

Author Contributions

Conceptualization, Y.F. and L.F.; methodology, Y.F.; software, Y.F.; validation, L.F.; formal analysis, Y.F.; investigation, Y.F. and L.F.; resources, Y.F.; data curation, Y.F.; writing—original draft preparation, L.F. and Y.F.; writing—review and editing, L.F.; visualization, Y.F.; supervision, L.F.; project administration, Y.F.; funding acquisition, L.F. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported by the National Natural Science Foundation of China (52361025), the Inner Mongolia Science and Technology Project (2022YFHH0079, 2022ZY0001), and the Scientific and Technical Young Talents of the Inner Mongolia Autonomous Region (NJYT23116, JY20240063).

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Acknowledgments

Thanks to Zhu Yaxian for her support in the test analysis.

Conflicts of Interest

The authors have no relevant financial or non-financial interests to disclose.

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Figure 1. Test steel phase diagram.
Figure 1. Test steel phase diagram.
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Figure 2. The standard ODF map (ϕ2 = 45°).
Figure 2. The standard ODF map (ϕ2 = 45°).
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Figure 3. Microstructure of hot rolled plate. (a) Rolling direction; (b) transverse direction.
Figure 3. Microstructure of hot rolled plate. (a) Rolling direction; (b) transverse direction.
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Figure 4. Microstructure of normalized plate. (a) Rolling direction; (b) transverse direction.
Figure 4. Microstructure of normalized plate. (a) Rolling direction; (b) transverse direction.
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Figure 5. Microstructure of cold-rolled sheet (Red circles represent the shear bands).
Figure 5. Microstructure of cold-rolled sheet (Red circles represent the shear bands).
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Figure 6. Microstructure of decarburized nitriding sheet.
Figure 6. Microstructure of decarburized nitriding sheet.
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Figure 7. Macrostructure of finished product.
Figure 7. Macrostructure of finished product.
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Figure 8. Texture and orientation line at ϕ2 = 45° section of hot rolled plate. Microstructure texture: (a) surface layer; (b) 1/4 layer; (c) center layer orientation line; (d) {110}; (e) ϕ1 = 90°; (f) α-fiber.
Figure 8. Texture and orientation line at ϕ2 = 45° section of hot rolled plate. Microstructure texture: (a) surface layer; (b) 1/4 layer; (c) center layer orientation line; (d) {110}; (e) ϕ1 = 90°; (f) α-fiber.
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Figure 9. Texture and orientation line at ϕ2 = 45° section of normalized plate orientation: (a) Surface layer; (b) 1/4 layer; (c) 1/2 layer orientation linel (d) {110}; (e) λ-fiber; (f) α-fiber.
Figure 9. Texture and orientation line at ϕ2 = 45° section of normalized plate orientation: (a) Surface layer; (b) 1/4 layer; (c) 1/2 layer orientation linel (d) {110}; (e) λ-fiber; (f) α-fiber.
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Figure 10. Texture at ϕ2 = 45° section of cold sheet. (a) ODF map; (b) grain orientation map; (c) α-fiber line.
Figure 10. Texture at ϕ2 = 45° section of cold sheet. (a) ODF map; (b) grain orientation map; (c) α-fiber line.
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Figure 11. Textures of decarburized nitriding sheet and finished product: (a) decarburized nitriding sheet; (b) finished product.
Figure 11. Textures of decarburized nitriding sheet and finished product: (a) decarburized nitriding sheet; (b) finished product.
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Table 1. Chemical composition of experimental Hi-B steel (wt.%).
Table 1. Chemical composition of experimental Hi-B steel (wt.%).
ElementCSiMnSAlNCuFe
Content0.053.00.100.0050.020.0070.015Bal.
Table 2. Goss texture content in each process (%).
Table 2. Goss texture content in each process (%).
ProcessHot RollingNormalizingCold RollingDecarburing Annealing
Surface Layer1/4 Layer1/2 LayerSurface Layer1/4 Layer1/2 Layer
content/%6.7511.50.045.475.89000.0615
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Fu, Y.; Fan, L. Microstructure and Texture Evolution of High Permeability Grain-Oriented Silicon Steel. Metals 2025, 15, 268. https://doi.org/10.3390/met15030268

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Fu Y, Fan L. Microstructure and Texture Evolution of High Permeability Grain-Oriented Silicon Steel. Metals. 2025; 15(3):268. https://doi.org/10.3390/met15030268

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Fu, Yujie, and Lifeng Fan. 2025. "Microstructure and Texture Evolution of High Permeability Grain-Oriented Silicon Steel" Metals 15, no. 3: 268. https://doi.org/10.3390/met15030268

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Fu, Y., & Fan, L. (2025). Microstructure and Texture Evolution of High Permeability Grain-Oriented Silicon Steel. Metals, 15(3), 268. https://doi.org/10.3390/met15030268

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