The effect of finishing rolling reduction on microstructures and textures of grain oriented silicon steel was researched by optical microscopy, zeiss ultra 55 Scanning Electron Microscope (SEM) and Electron Backscatter Diffraction (EBSD) technique severally. The results show that the grain size of hot rolled sheets and decarburized strips decreases, while the center grain size of the normalized sheet increases with the increase of the finishing rolling reduction. The pearlite content increases with the increase of the finishing rolling reduction after normalization. Compare with the previous research, the effect of finishing rolling reduction on the grain size of primary recrystallization is greater than that of roughing rolling reduction, and large rolling reduction is beneficial to the formation of {110} texture

Guo, Q.

Jia, Z. W.

Shao, Y. Y.

English

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209METALURGIJA 63 (2024) 2, 209-211Y. Y. SHAO, Z. W. JIA, Q. GUOEFFECT OF FINISHING ROLLING REDUCTION  ON MICROSTRUCTURES AND TEXTURES  OF GRAIN ORIENTED SILICON STEELReceived – Primljeno: 2023-08-22Accepted – Prihvaćeno: 2023-11-20Original Scientific Paper – Izvorni znanstveni radThe effect of finishing rolling reduction on microstructures and textures of grain oriented silicon steel was re-searched by optical microscopy, zeiss ultra 55 Scanning Electron Microscope (SEM) and Electron Backscatter Diffrac-tion (EBSD) technique severally. The results show that the grain size of hot rolled sheets and decarburized strips decreases, while the center grain size of the normalized sheet increases with the increase of the finishing rolling reduction. The pearlite content increases with the increase of the finishing rolling reduction after normalization. Compare with the previous research, the effect of finishing rolling reduction on the grain size of primary recrystal-lization is greater than that of roughing rolling reduction, and large rolling reduction is beneficial to the formation of {110}<001> texture.Key words: grain oriented silicon steel; finishing rolling reduction; SEM; EBSD; microstructureISSN 0543-5846METABK 63(2) 209-211 (2024)UDC – UDK 669.15.782:621.771-539.373:620-18.002.3:620.18=111INTRODUCTIONGrain oriented silicon steel which is known as cold rolled transformer steel is an important ferrosilicon al-loy used in transformer manufacturing industry. The purpose of preparing oriented silicon steel is to obtain sharp {110}<001> texture during secondary recrystal-lization. Some research shows that the {110}<001> tex-ture is a typical shear texture formed during the hot roll-ing process, and it has obvious heritability[1-4]. It can be indicated that hot rolling texture has significant in-fluence on the secondary recrystallization texture. Con-sequently, it is very important to improve the magnetic performance of the grain oriented silicon steel that clar-ify the effect of hot rolling process on the microstruc-tures and the textures of it. As in the previous studies, the effect of hot rolling temperature and roughing roll-ing reduction on microstructures and textures of the grain oriented silicon steel was studied respectively[5, 6]. In this paper, the effect of finishing rolling reduction on microstructures and textures of the grain oriented silicon steel will be researched.EXPERIMENTAL MATERIALS AND METHODSGrain oriented silicon steel was selected as the ex-perimental material with main components of 0,053 % Y. Y. Shao: College of Applied Technology, University of Science and Technology Liaoning, Anshan, Liaoning, ChinaZ. W. Jia: Iron and Steel Research Institutes , Ansteel Co. Ltd., Anshan, Liaoning, ChinaQ. Guo: Cold Rolling Silicon Plant, Ansteel Co. Ltd., Anshan, Liaon-ing, ChinaCorresponding author: Y. Y. Shao (Email address: shaoyy1980@163.com)C, 3,18 % Si, 0,115 % Mn, 0,028 %. Continuous cast slab was rolled to 2,3 mm and 2,0 mm thickness during the hot rolling process respectively. Then the hot rolled sheets were designated as 2,3-sample and 2,0-sample separately. Subsequently, the microstructure was ob-served by using optical microscopy technique. The crystallographic orientation measurement was carried out on the lateral section of the samples using an HKL (Hough Kikuchi Laue) -EBSD system, and the image field was the region of 1/2 thickness beneath the surface of hot rolled and normalized sheets.MICROSTRUCTURE ANALYSISFigure 1 shows the microstructures of the hot rolled sheets with different final rolling thickness. It can be (a) - surface(a) - center(b) - surface(b) - centerFigure 1 Microstructures of hot rolled sheets(a) 2,0-sample; (b) 2,3-sample210  METALURGIJA 63 (2024) 2, 209-211Y. Y. SHAO et al.: EFFECT OF FINISHING ROLLING REDUCTION ON MICROSTRUCTURES AND TEXTURES…seen that the grain size of the hot rolled sheets decreases with the final rolling thickness thinning. The reason is that the deformation energy storage of the strip steel is large with the increase of finishing rolling reduction, which leads to the increase of recovery and recrystalli-zation driving force, and thus the number of dynamic recrystallized grains increases. According to the results of statistics, the recrystallized grain size ratio of 2,3-sample is 15 – 60 %, while that of 2, 0-sample is 14 – 63 %.Figure 2 illustrates the microstructures of the nor-malized sheets with different final rolling thickness. Ac-cording to the statistical results, the surface grain size of the normalized sheet decreases, while the center grain size of the normalized sheet increases with the final rolling thickness thinning. However, the change of the center grain size is not obvious. The main reason for this result is that the pearlite content in the center layer of 2,0-sample with high reduction is more than that of 2,3-sample with low reduction after hot rolling. In addi-tion, the pearlite content increases with the increasing of finishing rolling reduction after normalization, which is related to the acceleration of the cooling rate caused by the thinning of the sheet thickness.size of primary recrystallized grain than roughing re-duction[6].TEXTURE ANALYSISFigure 4 shows the EBSD orientation maps of the hot rolled sheets. It can be seen that the surface layer of the hot rolled sheet is dominated by shear textures, such as sharp {111}<112> and {110}<001> texture. Moreo-ver, the center layer of the samples is dominated by de-formation textures, such as α fibre texture <110>. By comparison, the surface shear region of the 2,0-sample is thicker, and more {110}<001> oriented grains can be found. Furthermore, the strong {111}<112 > texture is formed in the center deformation region of the 2,0-sam-ple. The reason is that the friction and shear effects on the surface layer of the sample are larger, and the plane compression effect on the center layer is larger during the high reduction hot rolling.Figure 3 shows the microstructures of decarburized strips with different final rolling thickness. It can be found that the average size of primary recrystallized grain decreases with the increase of the final rolling re-duction. According to the result of statistics analysis, the grain size difference between the two samples is about 0,8~1,5 μm, while the standard deviation differ-ence is about 1,2 μm. It can be recognized that the fin-ishing reduction has a more obvious effect on the grain Figure 2 Microstructures of normalized sheets(a) 2,0-sample; (b) 2,3-sample(a) - surface(a) - center(b) - surface(b) - centerFigure 3 Microstructures of decarburized strips(a) 2,0-sample; (b) 2,3-sample(a) (b)Figure 4 EBSD orientation maps of hot rolled sheets(a) 2,0-sample; (b) 2,3-sample {110}<001>;  {114}<481>;  {111}<112>; {111}<110>;  {110}<112>Figure 5 indicates the EBSD orientation maps of the normalized sheets. As can be seen from the figure, the surface layer grain size of the normalized sheets de-creases, while the number of recovered and recrystal-lized grains of the center layer increases with the in-creasing of the finishing reduction. Compared with the hot rolled sheet, the texture components of the samples are basically similar, but the sharpness of the textures is decrease after normalizing. It can be seen by compari-son that the {110}<001> texture intensity of the 2,0-sample is higher than that of the 2,3-sample, while the {114}<481> texture intensity of the 2,0-sample is weaker than that of the 2,3-sample. Therefore, high re-duction rolling is beneficial to the formation of the Figure 5 EBSD orientation maps of normalized sheets(a) 2,0-sample; (b) 2,3-sample {110}<001>;  {114}<481>;  {111}<112>; {111}<110>;  {110}<112>211Y. Y. SHAO et al.: EFFECT OF FINISHING ROLLING REDUCTION ON MICROSTRUCTURES AND TEXTURES…METALURGIJA 63 (2024) 2, 209-211{110}<001> texture. The sharp {110}<001> texture obtained in the surface layer of the 2,0-sample indicates the heritability of the texture, while the sharp {110}<001> texture formed in the center layer shows the rotation of {111}<112> to {110}<001> texture.CONCLUSIONSThe grain oriented silicon steel is hot rolled under different finishing rolling reduction, and the conclu-sions are as follows:The grain size of hot rolled sheets and decarburized strips decreases, while the center grain size of the nor-malized sheet increases with the increase of the finish-ing rolling reduction.The pearlite content increases with the increase of the finishing rolling reduction after normalization, which is related to the acceleration of the cooling rate.The effect of finishing rolling reduction on the grain size of primary recrystallization is greater than that of roughing rolling reduction.Large rolling reduction is beneficial to the formation of {110}<001> texture. The {110}<001> texture of the surface layer indicates the heritability of the texture, while that of the center layer shows the rotation of {111}<112> to {110}<001> texture after normalization.AcknowledgementsThis work is financially supported by Liaoning province Department of Education fund item, No. LJKZ0305.REFERENCES[1] M. Munetsugu, S. Tomohiko, Y. Suga. Origin and deve-lopment of through the thickness variations of texture in the processing of grain-oriented silicon steel [J]. Metallur-gical Transactions A, 17(1986)8, 1313-1322.[2] I. Yukio, M. Chizuko, I. Yo, et al. Transmission Kossel stu-dy of origin of Goss texture in grain oriented silicon steel [J]. Transactions of the Iron and Steel Institute (1983)23, 440-446.[3] Y. Y. Shao, P. Yang, Y. J. Fu, et al. Texture evolution of columnar grains in electrical steel during hot rolling [J]. Journal of Iron and Steel Research, International 20(2013) 10, 99-106.[4] M. Q. Yan, H. Qian, P. Yang, et al. Behaviors of brass texture and its influence on Goss texture in grain oriented electrical steels [J]. Acta Metallurgica Sinica 48(2012)1, 16-22.[5] C. J. Wang, Q. Guo, Y. Y. Shao. Effect of hot rolling tem-perature on microstructures and textures of grain oriented silicon steel [J]. Metalurgija 60(2021)3-4, 216-218.[6] Y. Y. Shao Z. W. Jia, Q. Guo. Effect of hot rolling reduction on microstructures and textures of grain oriented silicon steel [J]. Metalurgija 61(2022)3-4, 697-699.Note:  The responsible translator for English is Yuan Yuan Shao, Univer-sity of Science and Technology Liaoning, Anshan, China

Effect of finishing rolling reduction on microstructures and textures of grain oriented silicon steel

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