Papers by Keyword: Electrical Steel

Abstract: Now insulation films are often prepared by smooth rubberroll on the surface of non-oriented silicon steel sheet. Though the surface resistance is enough high to ensure the quality, it will dramatically decrease after stress relief annealing. In order to understand the related mechanism, the film’s microstructure was characterized by SEM. The results show that the main composition of semi-inorganic coating is Cr, Mg C and O, in which C come from the organic polymer. According to the composition, the insulation film can be divided into two parts, the outer one is organic polymer and the inner one is chromate. The main reason for the unstable surface resistance is that the coating in the thickness direction is not uniformity.

Abstract: The taper work roll of the 1700 mm tandem cold rolling mills had some problems in the course of using, and the taper roll contour was ground difficultly and the difference between the designed contour and grinding contour was very big, and the work roll and backup roll had very serious and non-uniform roll wearing and even often had roll spalling, and above those problems affected the stability of rolling process seriously. After analyzing the structure and contour of the taper work roll, it was found that the work roll contour was designed unreasonably and the straight line part and the edge drop control part of roll contours were not connected smoothly, and so it lead to the local stress concentration easily in the transition region and a bigger contacting pressure peak between work roll and backup roll appeared. On basis of decreasing the contacting pressure peak and taking the width of rolled strip and the grinding contour length change into consideration, the design method of the edge control contour part of the taper roll was put forward. The finite element model was built with the software ANASYS9.0 to analyze the mill shape adjusting characteristics, and the simulation result showed that the newly-designed taper roll contour could improve the mill shape adjusting ability. It was shown in the rolling trial that the strip edge drop average was decreased from 14.9μm to 7.5μm and the edge drop fluctuation of strip was restrained to some extent and controlled within ±3μm.

Abstract: Hot dipping is a coating technique used in industry for galvanizing machine elements and steel profiles for construction or automotive applications. However, an alternative use of this process might be to improve specific properties. For instance, in order to improve the magnetic properties of electrical steels, it may be desirable to increase the Si and/or Al content. A possible and alternative route to realize this is by the application of an Al-Si-rich coating on the steel substrate using a hot dipping process, followed by a diffusion annealing treatment in order to distribute the Al/Si more evenly in the steel. The obtained distribution depends on the annealing parameters and can be both beneficial and detrimental for the magnetic properties. In the present work, Fe-Si substrates were hot dipped in different Al-Si baths. Subsequently, the samples were annealed at 1100°C during 20 minutes and concentration profiles were measured with scanning electron microscope energy dispersive spectroscopy line scans. The experimental results were analyzed using a specifically designed simulation model in order to determine the Al and Si diffusion coefficients. This model uses an inverse algorithm to determine interdiffusion coefficients that arise in a macro ternary diffusion system.

Abstract: Magnetic annealing at 17T, 800°C, for 15 minutes was conducted to evaluate the effect of the field on the recrystallized microstructure of Fe-3.25%Si samples. According to X-ray results, the main texture components were found not to be affected by the field. The volume fraction of eta fiber was slightly increased and the gamma fiber, an unfavorable texture component for materials with magnetic application, was not decreased when compared to samples annealed without magnetic field.

Abstract: The effects of annealing prior to cold rolling on the microstructure and magnetic properties of a low-C grain non-oriented (GNO) electrical steel strip have been investigated. It is shown that annealing of the hot-rolled strips in the intercritical region, Ac₁3, causes rapid decarburization and development of large columnar ferrite grains. This microstructure leads, after cold-rolling and a fast annealing treatment at temperatures between 800 and 850 °C, to a polygonal ferrite grain microstructure with magnetic properties superior to those observed typically in the same steel in the industrial fully processed condition. The results are attributed to the {100}-fiber texture developed during the final annealing. Annealing at T<800 °C or T>850 °C results in formation of {111}-fiber texture components due to recristallization or transformation of deformed ferrite leading to a negative effect on the final magnetic properties. The results suggest that annealing prior to cold rolling offers an attractive alternative processing route for the manufacture of fully processed low-C, Si-Al GNO electrical steels strips.

Abstract: Effects of three heating rates, 5, 20/min., and 300°C/sec and decarburization temperature, 700-850°C in primary annealing on the microstructure and magnetic properties of a grain oriented electrical steel were investigated. It was found that the oxide layer thickness and grain size increased with increasing decarburization temperature. However, they decreased with increasing heating rate. On the other hand, injection nitrogen content into steel sheets decreased with increasing decarburization temperature. The percentage of abnormal grain growth obtained a peak value at 800°C in the specimens treated with heating rate less than 20°C per minute. But specimens with rapid heating rate, percentage of abnormal grain growth increased with increasing decarburization temperature. As percentage of abnormal growth increased, magnetic properties got better.

Abstract: An Fe-6.2wt%Si as-cast strip with equiaxed grains and obvious {001} fiber texture was produced by twin-roll strip casting process. The as-cast strip was successively performed by hot rolling, warm rolling and annealing. The microstructure and texture evolution at each process stage were investigated by using electron backscatter diffraction and x-ray diffraction. It was found that the finally annealed sheet was characterized by large grain size, mild γ-fiber texture and obvious {001} fiber texture. Therefore, a high magnetic induction and a low core loss were obtained in the sheet.

Abstract: The recrystallization (Rex) texture of cross-rolled 3.3% Si steel was similar to the deformation texture approximated by {100}. The deformation texture of cross-rolled 99.99% copper was approximated by major {110} plus minor {001}. Its Rex texture was approximated by major {110} plus minor {001}. The results have been discussed based on the strain-energy-release-maximization model.

Abstract: Non-oriented grain type electrical steels are used mainly in electrical rotating machines such as motors and compressors, in which the magnetization direction rotates 360 ° every cycle while remaining in the plane of the plate. The performance of these devices is affected by crystallographic texture of electrical steels due to strong anisotropy of magnetic properties. The electrical steel is supplied in the form of plates which are processed by cold rolling and subsequent annealing. Both, cold rolling and annealing directly influence the formation of crystallographic texture components. During annealing, recrystallization occurs, and this phenomenon gives rise to changes in texture that influences the quality of the final product and its application. Several works have been published in the study of the evolution of crystallographic texture and grain size in this type of electrical steel. In this work, samples have been taken in industrial conditions at various temperatures during the annealing in a coil box. Electrical steel samples cold rolled with reductions of 50% and 70% in thickness were removed during the process of annealing, and the evolution of texture with increasing temperature was studied. Aspects related to recrystallization, grain size and the evolution of texture and magnetic properties were discussed. Texture and recrystallization were studied by X-ray diffraction and electron backscatter diffraction (EBSD). The magnetic properties were measured in a vibrating sample magnetometer.

Abstract: To identify the relationship between grain orientation and precipitation of MnS/AlN particles during hot deformation, cylinder samples containing columnar grains in electrical steels were prepared with different angles between columnar grain axis and sample axis. They were heated at 1360°C and compressed at 1100°C for 50%. Grain orientations and the precipitation states are determined using XRD, EBSD, EDS and SEM. Results indicate a general behavior of less precipitates in <100> and more precipitates in <111> grains. In addition, more precipitates were observed in samples with grain boundaries perpendicular to compression axis.