【作者】 张正贵；

【导师】 王福；

【作者基本信息】 东北大学 ， 材料学， 2008， 博士

【摘要】 无取向硅钢是电力、电子工业广泛应用的软磁材料,其中高牌号无取向硅钢主要用于制造容量较大的大、中型电机以及发电机的铁芯。由于这些设备能耗大,且大多处于连续、长周期运行状态之中,其工作效率的稍许提高即可节省大量能源,产生明显的经济效益和社会效益。因此,从节能的观点出发,提高磁感、降低铁损一直是硅钢研究领域的重要课题。由于硅钢生产技术的保密性,其研究成果鲜有公开、系统的发表。目前,我国仅武钢和太钢具备生产高牌号无取向硅钢的能力,‘远远满足不了我国经济发展的需求,每年仍需大量进口高牌号无取向硅钢。影响无取向硅钢磁性的因素很多,原料的化学成分及纯净度、板坯的铸造组织、热轧工艺、冷轧和热处理工艺都是影响硅钢最终质量的重要因素。因此弄清各生产工艺过程的组织、织构状态及织构演变过程,研发新的轧制和退火技术以有效控制与优化织构的发展,具有重要的理论和实际意义。本论文选用某钢铁公司提供的无取向硅钢热轧及常化板材,在不同形变量及不同速比下,采用异步轧制方法对无取向硅钢进行轧制。同时采用同步轧制方法,在不同形变量下进行轧制,以便进行对比研究,然后在气氛保护条件下对冷轧样品进行再结晶退火。利用X射线衍射技术测定各样品的织构,借助ODF分析方法系统考察了热轧板织构、同步和异步轧制的无取向硅钢薄板的冷轧织构和再结晶织构,利用光学显微镜进行金相组织观察,利用单板磁性测试仪测定铁损及磁感应强度,并利用无取向硅钢织构数据,根据磁性理论进行模拟计算,探寻加工制造无取向硅钢生产的技术原型。热轧对硅钢的磁性能具有遗传性影响,但由于热轧无取向硅钢板制样等比较困难,研究工作相对比较少,本文对热轧无取向硅钢的研究结果表明：热轧板在距表面不同位置的织构组分是不同的,中心区域附近反高斯织构{001}<110>很强,而高斯织构{110}<001>只在表层附近存在。热轧板的织构与温度有很大的关系,同一板材的头部和尾部只是温度条件有差别,其它条件均相同,但头尾的织构组分差别却很大。在高硅条件下,尾部表层出现较高的反高斯织构。热轧板织构还与硅含量有关,高硅热轧板的反高斯织构{001}<110>和高斯织构{110}<001>组分均比低硅热轧板强度高。通过观察热轧板的显微组织发现无取向硅钢组织是不均匀的,在表层区域附近存在等轴晶组织,而中心区域附近为形变组织。等轴晶组织所占比例与硅含量有较大关系,在硅含量低的热轧板中等轴晶组织较多。另外温度对组织也有明显影响,热轧板头部等轴晶组织比较多,形变组织比较细小,热轧板尾部等轴晶组织较少,形变组织多而粗大。不同轧制工艺的研究结果表明：高牌号无取向硅钢在同步轧制和异步轧制过程中,随着形变量的增加,冷轧织构组分均逐渐向α织构和γ织构组分聚集,即冷轧织构由<110>//RD和<111>//ND织构组成,其中α织构以{100}-{111}<110>为主,Y织构则涵盖{111}<112>～<110>。但当压下率达到84%时,织构组分进一步变化,出现了较强的{001}<120>织构组分；在异步冷轧过程中高斯织构{110}<001>组分逐渐减少,直至消失,反高斯{001}<110>织构组分逐渐增强；常化板材沿厚度方向从表层到中心区域织构类型是不同的,中心区域反高斯织构较强,在异步冷轧后继续保持了这种状态,而表层和次表层高斯织构在冷轧后消失；异步轧制下沿厚度方向织构分布呈非对称状态,慢辊侧的反高斯织构强度明显高于快辊侧的强度,{111}<112>织构组分在表层附近的强度高于中心区域；不同速比下异步冷轧织构组分均含有反高斯织构以及α织构和γ织构,对于低牌号无取向硅钢,低速比异步轧制时的织构强度高于高速比异步轧制时的织构强度；在同步和异步轧制过程中,随着变形量的增加,晶粒逐渐被拉长,同时,晶粒也在发生复杂的转动,显微组织中存在形变孪晶组织。再结晶退火的研究结果表明：再结晶退火温度是控制高牌号无取向硅钢再结晶织构和组织的重要因素,改变温度可以显著影响再结晶组织和织构,进而改变磁性能,在800℃退火时的织构组分主要是{111}<112>,退火后的晶粒组织尺寸大小适中且大小比其他条件下的组织均匀,由于晶粒尺寸及其分布直接影响到无取向硅钢的性能,如果在最终产品中组织和织构的分布出现较大的不均匀性,必然会对产品的性能产生不利的影响；在异步轧制下,速比、温度和时间等因素共同影响着再结晶组织和织构,在一定的温度下,温度起主导作用,速比的影响不明显；以{110}和{113}织构为主的初始织构组分,异步冷轧后转变为较强的反高斯织构和α织构及γ织构,退火后,α织构明显降低,而γ织构变化不明显。退火后的{111}<110>织构组分减弱,{111}<112>织构组分增强。根据试验和理论计算,提出了无取向硅钢薄板在气氛保护条件下退火的主要技术参数选取原则,在800℃～900℃退火可以获得较好的磁性,磁性模拟计算的理论值与实测值吻合的较好。更多还原

【Abstract】 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.更多还原