| Non-oriented silicon steels is widely used in electronic, electric power industry as soft magnetic materials. Among these, the high brand non-oriented silicon steel is mainly used to make high capacity, middle and large electric motor and the ferric core of the electric power generator. Because these equipments consume a lot of energy, and they are in a continuous and long-term working period, the slight improvement of working efficiency can save tremendous energy and have significant economic and social effect. Therefore, for the energy saving point of view, improving magnetic sensitivity and reducing ferromagnetic loss is always a major research task for silicon steel research field. Due to the confidential protection of silicon steel production technology, there are few systematic published research results. At present, only Wuhan steel company has the capability to manufacture high brand non-oriented silicon steel, but it is far below the demand of the economic development in our country. Therefore, large quantities of high brand silicon steel are imported every year. There are a lot of factors affecting the magnetic property of non-oriented silicon steel. The chemical composition of raw materials, impurities, texture of casting, hot-rolling, cold-rolling and heat treatment technology play important roles in controlling the final quality of the silicon steel. So there is a theoretical and realistic requirement to have a better understanding of the structure, texture and texture evolution for various process technologies, to develop new rolling and annealing technology and to efficiently control and optimize texture development.In this dissertation, non-oriented hot rolled and normal silicon steel provided by an iron and steel company was selected for cross-sear rolling under various deformation and speed ratio. Meanwhile, it was rolled synchronously under various deformations for a comparison study. The cold-rolled sample was annealed with gas protection. X-ray refraction technique was used to identify the macro-texture. ODF analysis method was used to systematically investigate the hot-rolled texture,synchronous and cross-shear rolling texture and recrystallization texture of non-oriented thin silicon steel plate.Optical microscopy was used to study the microstructure and single plate tester was used to measure ferromagnetic loss and the intensity of magnetic response. Based on the texture data of non-oriented silicon steel and with the help of magnetic theoretic model calculation, the technology protocol of manufacture of non-oriented silicon steel was studied.Hot-rolling has permanent effect on the magnetic property of silicon steel. There is little research of hot-rolling effect on magnetic property for non-oriented silicon steel due to the difficulty of sample preparation of hot-rolled non-oriented silicon steel plate. The results on hot-rolled non-oriented silicon steel show that the texture composition is different for hot-rolled plate with the varying depth from the surface. Anti-Gauss texture{111}<110> is very strong near the center, while the Gaussian texture{111}<110> exists near the top surface. The texture of hot-rolled plate is very sensitive to temperature.The same plate shows significantly different texture distribution for the front and end part due to the temperature difference with the other condition of the same. For high silicon steel, high level anti-Gauss texture appeared on the surface of tail part. The texture of hot-rolled plate is also dependent on silicon concentration. The anti-Gauss texture{111}<110> and Gaussian texture {111}<110> for high silicon steel shows higher intensity than that for low silicon steel. It was found that the structure of hot-rolled non-oriented silicon steel is not uniform. Isometric structure exists in the near surface region, while deformation structure exists in the central area. The concentration of isometric structure is dependent on the content of silicon; there is more isometric structure for hot-rolled low silicon steel plate. Apart from that, temperature also has a big effect on structure. There is more isometric structure at the front of the hot-rolled plate and deformation structure is finer. At the end of hot-rolled plate, isometric structure is less and deformation structure is coarse and big.The research results for different rolling technology show:that during the synchronous and cross shear rolling process for non-oriented high silicon steel, the texture converges to a and y texture with the increase of compressive deformation, i.e.,cold-rolled texture is <110>//RD and<111>//ND texture.αtexture is mainly{100}～{111}<110>, while y texture covers{111}<112>～<110>. strong texture of {001}<120> appeared when the compressive deformation reached 84%. During cross shear rolling process, the intensity of Gaussian texture{111}<110> gradually decreased until disappeared, and the anti-Gauss texture {111}<110> gradually increased. The texture type is different for normal plate in the depth direction from surface to center area. Anti-Gauss texture is stronger in the central area and it remains after cross shear rolling process, while Gaussian texture disappeared in the top surface and near top surface area after cold rolling process. Texture distribution is asymmetric in the thickness direction; anti-Gauss texture density along the slow speed roller side is more than that along the fast speed roller side. The intensity of{111}<112> texture is higher on the surface than that in the center area. Both anti-Gauss texture, a and y texture are found for cross shear rolling texture under different speed ratio.For non-oriented low silicon steel, texture intensity for cross shear rolling is higher under low speed ratio than under high speed ratio. For synchronous and cross shear rolling process, with the increase of deformation, grain is elongated and at the same time, grain is twisted. Therefore, deformed twin structure was found in the microstructure.The annealing recrystallization results indicate that:the annealing temperature plays an important role in controlling the recrystallization structure and texture for non-oriented high silicon steel. The change of annealing temperature can significantly affect recrystallization structure and texture, therefore, the magnetic property was also changed. At the annealing temperature of 800℃, the texture is mainly{111}<112>, the grain size is optimized after annealing and it is more uniform than other conditions. Since grain size and distribution can affect the property of non-oriented silicon steel, there will be adverse effect on the final product property if there is a big non-uniformity for the structure and texture distribution. Under cross shear rolling process, recrystallization structure and texture is dependent on rolling speed ratio, temperature and time. Under the testing condition used in this thesis, temperature plays a more important role and the effect of speed ratio is minor. The initial texture is mainly {110}and{113},after cross shear rolling, it changed to strong anti-Gauss texture and a and y texture. After annealing, a texture significantly decreased and no obvious change for y texture was found. Moreover, after annealing,{111}<110> texture weakened and{111}<112>texture enhanced. The main annealing technical parameter selection rule was proposed for non-oriented thin silicon steel sheet under atmosphere protection. Better magnetic property can be obtained after annealing at 800℃～900℃. A good match between theoretical simulation value and experimental results was obtained. |
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