The effect of hot rolling reduction on microstructures and textures of grain oriented silicon steel was studied by optical microscopy (OM), zeiss ultra 55 Scanning electron microscope (SEM) and Electron backscatter diffraction (EBSD) technique respectively. The results indicate that the effect of hot rolling reduction on grain size of hot rolled and normalized sheets in surface layer is great, while the effect on grain size of primary recrystallized grain is little. The shear zone thickens with the finishing reduction decreases, moreover strong {111} and {110} textures can be obtained in hot rolled sheets. Combined with the previous research conclusions, it can be found that the rolling process of oriented silicon steel is contributed to the formation of texture, while the recrystallization process reduces the sharpness of the texture

Guo, Q.

Jia, Z. W.

Shao, Y. Y.

English

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697METALURGIJA 61 (2022) 3-4, 697-699Y. Y. SHAO, Z. W. JIA, Q. GUOEFFECT OF HOT ROLLING REDUCTION ON MICROSTRUCTURES AND TEXTURES OF GRAIN ORIENTED SILICON STEELReceived – Primljeno: 2022-01-24Accepted – Prihvaćeno: 2022-03-10Original Scientific Paper – Izvorni znanstveni radThe effect of hot rolling reduction on microstructures and textures of grain oriented silicon steel was studied by optical microscopy (OM), zeiss ultra 55 Scanning electron microscope (SEM) and Electron backscatter diffraction (EBSD) technique respectively. The results indicate that the effect of hot rolling reduction on grain size of hot rolled and normalized sheets in surface layer is great, while the effect on grain size of primary recrystallized grain is little. The shear zone thickens with the finishing reduction decreases, moreover strong {111}<112> and {110}<001> tex-tures can be obtained in hot rolled sheets. Combined with the previous research conclusions, it can be found that the rolling process of oriented silicon steel is contributed to the formation of texture, while the recrystallization process reduces the sharpness of the texture.Keywords: grain oriented silicon steel; hot rolling; reduction; microstructure; textureISSN 0543-5846METABK 61(3-4) 697-699 (2022)UDC – UDK 669.15.782:621.771-536.45:539.373:620-18.002.3:620.18=111INTRODUCTIONGrain oriented silicon steel is an important soft mag-netic alloy material which is widely used in electric power and electron industry. The typical texture is {110}<001> texture which is beneficial to improve the magnetic induction of grain oriented silicon steel. Therefore, the purpose of preparing oriented silicon steel is to obtain sharp {110}<001> texture mainly through hot rolling, normalizing, cold rolling and an-nealing processes[1-3]. At present, a large number of studies on grain oriented silicon steel has focused on cold rolling and recrystallization in order to clarify the growth mechanism of {110}<001> oriented grains dur-ing secondary recrystallization, while the research on hot rolling is less[4-6]. Consequently, it is very impor-tant to develop new grade grain oriented silicon steel that clarify the evolution of microstructure and texture under different hot rolling processes. The effect of hot rolling temperature on microstructures and textures was studied in previous research[7], and the effect of hot re-duction was studied in this paper.EXPERIMENTAL MATERIALS AND METHODSGrain oriented silicon steel was selected as the ex-perimental material with main components of 0,053 % C, 3,18 % Si, 0,115 % Mn, 0,028 % Alsol and 0,05 % Sn. Continuous cast slab was rolled to 50 mm and 40 mm thickness on roughing mill espectively, and then the intermediate billets were rolled to 2,3 mm thickness on the finishing mill. Then the hot rolled sheets were designated as low 50-sample and 40-sample separately. Subsequently, the hot rolled sheets were cooled at the same cooling rate of 35 °C/s in order to study the effect of finishiing reduction on microstructures and textures of grain oriented silicon steel. The microstructure was observed by using optical microscopy technique. The crystallographic orientation measurement was carried out on the lateral section of the samples using an HKL-EBSD system, and the image field was the region of 1/2 thickness beneath the surface of hot rolled and normalized sheets. The precipitates in hot rolled sheets were observed by zeiss ultra 55 Scanning electron mi-croscope.MICROSTRUCTURE ANALYSISFigure 1 shows the microstructures of the hot rolled sheets. It can be recognized that the grain size of the surface layer decreases, while the grain size of the cen-ter layer changes little with the decrease of the finishing reduction. The reason is that the surface layer micro-structure of hot rolled sheets is significantly affected by reduction. The decrease of the reduction reduces defor-mation energy storage of the sheet surface, and leads to the lower driving force of recovery and recrystalliza-tion, which resulting in smaller dynamic recrystalliza-tion grains in the surface layer of hot rolled sheets. Tak-ing grain size less than or equal to 10 μm as the statisti-cal standard of recrystallized grain, the recrystallized 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)698  METALURGIJA 61 (2022) 3-4, 697-699Y. Y. SHAO et al.: EFFECT OF HOT ROLLING REDUCTION ON MICROSTRUCTUREs AND TEXTUREs…grain size ratio of 50-sample is 35 – 44 %, while that of 40-sample is 32 – 34 %. It shows that more dynamic recrystallization grains can be obtained under the large finishing reduction.ple is 40,48 μm and 19,68 μm respectively. It is shown that center grains are coarsened obviously, while the surface grains size has no distinct change with the de-crease of the finishing reduction after normalization.Figure 3 shows the microstructures of decarburized strips. It can be recognized that the finishing reduction has little effect on grain size and homogeneity of pri-mary recrystallized grain. According to the statistical results, the grain size difference between the two sam-ples is about 0,2~0,8 μm, while the standard deviation difference is about 1μm.TEXTURE ANALYSISFigure 4 shows the EBSD orientation maps of the hot rolled sheets. It can be seen that shear textures such as {110}<001> and {110}<112> are the main texture components in surface layer of the samples, while the main texture components of center layer are deforma-tion textures such as α fibre texture <110>, {111}<112> and {114}<481>. Specifically, the shear surface region of the 40-sample is thicker, and more {110}<001> ori-ented grains can be found in surface layer. Moreover, the strong {100}<011> texture is formed in center layer of 40-sample due to the small finishing reduction.Figure 1  Microstructures of hot rolled sheets  (a) 50-sample; (b) 40-sampleFigure 2  Microstructures of normalized sheets  (a) 50-sample; (b) 40-sampleFigure 3  Microstructures of decarburized strips  (a) 50-sample; (b) 40-sampleFigure 2 indicates the microstructures of the normal-ized sheets. It is exhibited that the samples inherit the banded structure characteristic of hot rolled sheets and the thermally deformed structures recrystallize after normalizing. The recrystallization can be seen in sur-face layer obviously, while recovery and recrystalliza-tion as well as the grain growth can be found in center layer. According to the statistical results, the average surface and center grain size of the 50-sample is 40,58 μm and 15,96 μm respectively, while that of the 40-sam-Figure 4  EBSD orientation maps of hot rolled sheets  (a) 50-sample; (b) 40-sample   {111}<112>;  {110}<001>;  {114}<481>;  {100}<011>;  {110}<112> Figure 5 indicates the EBSD orientation maps of the normalized sheets. It can be seen that the surface layer is consisted of coarse recrystallized grains, and the cen-ter layer is consisted of the recovered and recrystallized grains. The texture components is basically in accor-dance with that of which the hot rolled sheets after nor-malizing, but the sharpness decrease significantly, fur-thermore the {114}<481> and {110}<001> are domi-nant textures. Compared with the 50-sample, more {110}<001> oriented grains can be seen in surface layer but less {114}<481> oriented grains can be seen in cen-ter layer of 40-sample.The EBSD orientation maps of the decarburized strips are shown in Figure 6. It is demonstrated that the recrystallized structure is fine and uniform after decar-burizing and nitriding. The grain size of primary recrys-tallized grains decreases from 21,73 μm in 50-sample to 20,30 μm in 40-sample with the decrease of the finish-ing reduction. It can be found that the texture compo-nents of decarburized annealed strips are mainly 699Y. Y. SHAO et al.: EFFECT OF HOT ROLLING REDUCTION ON MICROSTRUCTUREs AND TEXTUREs…METALURGIJA 61 (2022) 3-4, 697-699{114}<481> and γ fiber texture <112>. This texture fea-ture shows obvious inheritance from center region tex-tures of hot rolled sheets. The texture components of the samples are similar, but the intensity and relative quan-tity are different.CONCLUSIONSThe grain oriented silicon steel is hot rolled under different finishing reduction, and the conclusions are as follows:The effect of hot rolling reduction on grain size of hot rolled and normalized sheets in surface layer is Figure 5  EBSD orientation maps of normalized sheets  (a) 50-sample; (b) 40-sample   {111}<112>;  {110}<001>;  {114}<481>;  {100}<011>;  {110}<112>Figure 6  EBSD orientation maps of decarburized strips  (a) 50-sample; (b) 40-sample   {111}<112>;  {110}<001>;  {114}<481>;  {111}<110>;  {110}<112>great, while the effect on grain size of primary recrystal-lized grain is little.The texture component of normalized sheets is in accordance with that of the hot rolled sheets. The sharp-ness of texture is weak after hot rolling and normaliz-ing, but it is strong after cold rolling and decarburizing.The shear zone thickens with the finishing reduction decreases, moreover strong {111}<112> and {110} <001> textures can be obtained in hot rolled sheets.AcknowledgementsThis work is financially supported by Liaoning province Department of Education fund item, No. LJKZ0305.REFERENCES[1] H. Yashiki, T. Kaneko. Effects of Mn and S on the grain growth and texture in cold rolled 0,5 % Si steel[J]. ISIJ International, 30(1990)4, 325-330.[2] T. Kumano, T. Haratani, Y. Ushigami. The improvement of primary texture for sharp Goss orientation on grain orien-ted silicon steel[J]. ISIJ International, 43(2003)5, 736-745.[3]  N. H. Heo, S. B. Kim, Y. S. Choi, et al. Interfacial segrega-tion nucleation and texture development in 3% silicon steel[J]. Acta Materialia, 51(2003)17, 4953-4964.[4]  Y. Hayakawa, M. Kurosawa. Orientation relationship between primary and secondary recrystallized textured in electrical steel[J]. Acta Materialia, 20(2002)18, 4527-4534.[5]  H. Homma, B. Hutchinson. Orientation dependence of se-condary recrystallisation in silicon-iron[J]. Acta Materia-lia, 51(2003)13, 3795-3805.[6]  C. M. Yu, J. M. Zhang, B. Dang, et al. Grain boundary and texture evolution of a high magnetic grain-oriented silicon steel during rolling and heat treatment[J]. Heat Treatment of Metals, 46(2021)12, 204-208.[7]  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.Note:  The responsible translator for English is Yuan Yuan Shao, Univer-sity of Science and Technology Liaoning, Anshan, China

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

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