The effect of hot rolling temperature 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 show that being hot rolled at 1 152 °C and 1 227 °C respectively, the effect of hot rolling temperature on microstructures of hot rolled and normalized sheets is little, and there is only a small difference in grain size between the samples. Secondary recrystallization is difficult to occur in the medium temperature sample due to the lack of sufficient inhibitors in the sample. The major deformed texture component in center region of hot rolled sheets is {114} which has obviously heredity, and it is more sharp in low temperature sample

C. J. Wang

Q. Guo

Y. Y. Shao

English

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216  METALURGIJA 60 (2021) 3-4, 216-218C. J. WANG, Q. GUO, Y. Y. SHAOEFFECT OF HOT ROLLING TEMPERATURE  ON MICROSTRUCTURES AND TEXTURES  OF GRAIN ORIENTED SILICON STEELReceived – Primljeno: 2021-02-12Accepted – Prihvaćeno: 2021-04-10Original Scientific Paper – Izvorni znanstveni radC. J. Wang, Y. Y. Shao: College of Applied Technology, University of Science and Technology Liaoning, Anshan, Liaoning, ChinaQ. Guo: Cold Rolling Silicon Plant, Ansteel Co. Ltd., Anshan, Liaon-ing, ChinaCorresponding author: Y. Y. Shao (Email address: shaoyy1980@163.com) The effect of hot rolling temperature 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 show that being hot rolled at 1 152 °C and 1 227 °C respectively, the effect of hot rolling temperature on microstructures of hot rolled and normalized sheets is little, and there is only a small difference in grain size between the samples. Secondary recrystallization is difficult to occur in the medium tem-perature sample due to the lack of sufficient inhibitors in the sample. The major deformed texture component in center region of hot rolled sheets is {114}<481> which has obviously heredity, and it is more sharp in low tempera-ture sample.Keywords: grain oriented silicon steel, hot rolling, sheet, texture; microstructureINTRODUCTIONGrain oriented silicon steel is an important soft mag-netic alloy material used as transformer core. Its mag-netic induction intensity is determined by the orientation and sharpness of {110}<001> texture. It is reported that the type, size and number of inhibitor have an important effect on the formation of sharp {110}<001> texture dur-ing the secondary recrystallization  [1,2]. The production process of grain oriented silicon steel is divided into high heating temperature technology and low heating temper-ature technology according to the type of inhibitor [3,4]. At present, the development trends of the grain oriented silicon steel is to reduce heating temperature [5,6]. Con-sequently, it is important to produce grain oriented silicon steel with low heating temperature that research the evo-lution of microstructure and texture of grain oriented sili-con steel at different temperature. In this paper, the effect of hot rolling temperature on microstructure and texture of grain oriented silicon steel was studied.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, of which the main inhibitor was AlN. Continuous cast slab was hot rolled to 2,3 mm thick after heating at ISSN 0543-5846METABK 60(3-4) 216-218 (2021)UDC – UDK 669.15.782:621.771-536.45:621-41.002.61:620.18=1111 152 °C and 1 227 °C respectively, and then the hot rolled sheets were designated as low temperature sam-ple (L-sample) and medium temperature sample (M-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 hot rolling temperature on micro-structures and textures of grain oriented silicon steel. The microstructure was observed by using optical mi-croscopy technique. The crystallographic orientation measurement was carried out on the lateral section of the samples using electron backscattered diffraction 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 (SEM).MICROSTRUCTURE ANALYSISFigure 1 shows the microstructures of the hot rolled sheets. It can be recognized that the microstructure is composed of ferrite and pearlite, and dynamic recrystal-lization grains can be found in the surface layer and the center layer of the samples. According to the statistical results, the average surface and center grain size of the L-sample is 16,63 μm and 11,73 μm respectively, while that of the M-sample is 24,47 μm and 21,87 μm respec-tively. And the reason is that the high rolling temperature leads to the grain coarsening. Taking grain size less than or equal to 10 μm as the statistical standard of recrystal-lized grain, the recrystallized grain size ratio of L-sample is 36 – 42 %, while that of M-sample is 18 – 42 %. It 217C. J. WANG et al.: EFFECT OF HOT ROLLING TEMPERATURE ON MICROSTRUCTURES AND TEXTURES...METALURGIJA 60 (2021) 3-4, 216-218shows that more dynamic recrystallization grains can be obtained at the low hot rolling temperature.Figure 2 indicates the microstructures of the normal-ized sheets. It can be seen that the surface layer is con-sisted of coarse recrystallized grains, and the center layer is consisted of the recovered and recrystallized grains. According to the statistical results, the average surface and center grain size of the L-sample is 40,57 μm and 10,79 μm respectively, while that of the M-sam-ple is 49,62 μm and 16,86 μm respectively. It is shown that surface grains are coarsened obviously, while the center grains size has no distinct change after normali-zation. This is due to that the center recovered struc-tures of the hot rolled samples are difficult to recrystal-lize during normalization. The effect of hot rolling tem-perature on microstructures of hot rolled and normal-ized grain oriented silicon steel sheets is little at the medium and low hot rolling temperature in conclusion. Figure 3 shows the macrostructures of finished products. Secondary recrystallized structures can be seen in L-sample, while a large number of fine grain structures can be seen in M-sample. It is due to that the number of inhibitors is little in M-sample, as shown in Figure 4. The reason is that a large number of AlN par-ticles dissolve in M-sample during hot rolling, whereas the peak temperature of AlN particle precipitation is lower than the finishing temperature, which cause that the more dissolved AlN particles are too late to precipi-tate in the M-samples.TEXTURE ANALYSISFigure 5 shows the EBSD orientation maps of the hot rolled sheets. The texture components of hot rolled sheets are mainly {110}<001>, {110}<112>, {111}<110>, {111}<112>, {114}<481> and {100}<011>. The shear surface region of the M-sample is thicker, while the deformed center region of the L-sample is thicker. More {110}<001> oriented grains can be found in surface layer of M-sample, and more {114}<481> oriented grains can be found in center lay-er of L-sample.Figure 6 indicates the EBSD orientation maps of the normalized sheets. It can be seen that the texture char-acteristic of normalized sheets is similar to that of hot rolled sheets, and it is merely that the intensity of the α-fiber <110> texture is slightly reduced. The {114}<481> texture in the L-sample is sharper and the magnetic property is better than that in M-sample. The Figure 1  Microstructures of hot rolled sheets (a) L-sample; (b) M-sampleFigure 2  Microstructures of normalized sheets  (a) L-sample; (b) M-sampleFigure 3  Macrostructures of finished products (a) L-sample; (b) M-sampleFigure 4  Precipitation of hot rolled sheets (a) L-sample; (b) M-sampleFigure 5  EBSD orientation maps of hot rolled sheets (a) L-sample; (b) M-sample218C. J. WANG et al.: EFFECT OF HOT ROLLING TEMPERATURE ON MICROSTRUCTURES AND TEXTURES... METALURGIJA 60 (2021) 3-4, 216-218shear region is thicker and the intensity of {110}<001> texture is reduced in M-sample.Finally, the EBSD orientation maps of the decar-burized strips are shown in Figure 7. The texture com-ponents of decarburized annealed strips are mainly {100}<021>, {114}<481> and γ-fiber texture. This texture feature shows obvious inheritance from center region textures of hot rolled sheets. It can be seen that the texture components of the samples are similar, but the intensity and relative quantity are different. The difference of the samples is mainly the grain size, of which the M-sample is larger. Therefore, the hot roll-ing temperature mainly affects the grain size of decar-burized strips, but has little effect on the texture com-ponents.CONCLUSIONSThe grain oriented silicon steel is hot rolled at 1 152 °C and 1 227 °C respectively, and the conclusions are as follows:The effect of hot rolling temperature on microstruc-tures of hot rolled and normalized sheets is little, and there is only a small difference in grain size between the samples.Secondary recrystallization is difficult to occur in the M-sample due to the lack of sufficient inhibitors in the sample.The major deformed texture component in center re-gion of hot rolled sheets is {114}<481> which has obvi-ously heredity, and it is more sharp in L-sample. AcknowledgementsThis work is completed under the guidance of teach-er Y. Y. Shao. This work is financially supported by University Student Innovation and Entrepreneurship Training Pro-ject Fund of China, No. S202010146045.REFERENCES[1] P. Horký, P. Pácl. Effective grain growth  inhibition in sili-con steel [J]. Journal of Magnetism and Magnetic Materi-als 41(1984)1-3, 14-16.[2] Z. Z. He, X. F. Sun, R. J. Shuai. Behaviour of secondary recrystallization in oriented Si steel containing various in-hibitors [J]. Acta metallurgica sinica 21(1985)2, A126-130. [3]  S. T. Qiu, B. Fu, L. Xiang, et al. Recent research trends and developments of production process and technology for high magnetic induction grain-oriented silicon steel [J]. Iron and Steel 48(2013)3, 1-8.[4]  Takeshi Kubota, Masahiro Fujikura, Yoshiyuki Ushigami. Recent Progress and Future Trend on Grain-Oriented Sili-con Steel [J]. Journal of Magnetism and Magnetic Materi-als 215-216(2000)1, 69-73.[5]  J. Li, Y. Sun, Y. Zhao, et al. Development of low tempera-ture slab reheating technique for grain-oriented silicon steel[J]. Iron and Steel 42(2007)10, 72-75.[6]  A. F. Dong, P. F. Hou, W. K. Zhang. Investigation on pro-cess and magnetic properties of low-temperature heating common grain-oriented silicon steel slab [J]. Special Steel 40(2019)5, 31-36.Note:  The responsible translator for English is Yuan Yuan Shao, Univer-sity of Science and Technology Liaoning, Anshan, ChinaFigure 6  EBSD orientation maps of normalized sheets (a) L-sample; (b) M-sample Figure 7  EBSD orientation maps of decarburized strips (a) L-sample; (b) M-sample 

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

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