Papers by Keyword: Electrical Steel

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Authors: Shuang Hong Wang, Yong Feng Long, Shi Lu Zhao, Cheng Qiang An, Ke Ding
Abstract: The water-based paint had been examined to prepare a new chromate-free insulating coating on silicon steels. The structure of the insulating coating was characterized by scanning electron microscopy, energy dispersive spectroscopy and infrared spectroscopy. Adhesion, high temperature annealing, and surface insulating resistance were measured. Corrosion resistance was investigated by neutral salt spray test and electrochemical test. Results exhibited that the insulating coating had excellent comprehensive performance. The adhesive level was 5B degree; the high temperature annealing test showed no coating degradation after heat treatment of 2 h at 450 °C in air or at 750 °C in nitrogen; the salt spray test showed the corrosion area was less than 2 % after the 12 h salt spray; when the coating thickness was 1.0-1.2 μm, the surface insulating resistance value was 380-420 Ω/mm2.
Authors: K. Eloot, Annick De Paepe, J. Dilewijns, C. Standaert
Authors: Yvan Houbaert, T. Ros Yáñez, Marta Prado
Authors: Pornthep Chivavibul, Manabu Enoki, Shigeru Konda, Yasushi Inada, Tamotsu Tomizawa, Akira Toda
Abstract: A possibility to reduce core loss in non-oriented (NO) electrical steel by applying magnetic coating has been investigated. This technique involves electroless plating of magnetic coating onto the surface of electrical steel. The material system was NiCoP coatings with different thicknesses (1, 5, and 10 􀁐m) deposited onto the surface of commercially available Fe-3%Si NO electrical steel. Characterization of deposited NiCoP coating was carried out using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray (EDX) spectrometer. The deposited Ni-Co-P coatings were amorphous/nanocrystalline and composed of 56-59% Ni, 32-35% Co and 8-10% P by mass. Effect of coatings on core loss of the electrical steel was determined using a single sheet test. A core loss reduction was achieved with the NiCoP coating with a thickness of 1 􀁐m magnetized at a magnetic flux density of 0.3T.
Authors: Alina Agüero, F.A. Actis, H.R. Moyano, O. Casais
Authors: Enrique Díaz Barriga-Castro, Armando Salinas-Rodríguez, Enrique Nava-Vázquez
Abstract: The aim of the present work is to determine the austenite to ferrite transformation temperatures in a Si-Al non-oriented electrical steel. Critical transformation temperatures on heating and cooling are determined using an in-situ X-ray diffraction technique where the specimen is heated or cooled in a stepwise manner. The transformation temperatures are estimated from changes in the intensities of the (110)α and (111)γ peaks as a function of temperature. The time evolution of the microstructure resulting from isothermal heat treatments at temperatures between 800 and 1000 °C applied after cooling from 1050 °C is followed by quantitative metallography on samples quenched into water. The results show that, on cooling, formation of ferrite starts at about 950 °C and ends at 790 °C, indicating a strong effect of Si and Al on the austenite to ferrite and eutectoid transformations. These results suggest that the low tensile ductility exhibited by this material at temperatures near 1000 °C can be attributed to strain localization in strain-induced ferrite formed at temperatures as high as 1025 °C.
Authors: Pablo Rodriguez-Calvillo, Juergen Schneider, Yvan Houbaert
Abstract: Steel containing a high Si-content is mainly used as electrical steel in flux carrying electrical machines. These materials are divided in the categories: grain oriented and non oriented electrical steels, mainly used in transformers and electrical motors, respectively. Their industrial production is normally limited to silicon contents lower than 3.5 m.-%, due to the generation of brittle ordered structures if the Si content is increased beyond this value. The paper reports on microstructure and texture evolution during processing by rolling of electrical steel in the high Si-range. The materials studied are two industrial electrical steels with a silicon content of 2.4 and 3.2 m.-%, their situation was as-received after hot rolling and industrial annealing. The different processing parameters, as rolling temperatures and cooling conditions have a strong influence on the final microstructures and textures. The importance of hot rolling and intermediate annealing processes is enhanced since above 2 m.-% Si these steels do not experience the usual α-γ-α phase transformation, because they present a bcc crystal structure over the entire solidus domain. Consequently, their microstructures and textures are strongly inherited from the earlier processing steps into the final product. The as-received materials were cold rolled with a nominal reduction of 75%. Their microstructures and textures were analysed by EBSD. The results obtained were compared with those of the industrial hot band. The textures were studied by the interpretation of the most important crystallographic fibre textures, extracted from the ODF’s of φ2 = 45o section of the Euler space. Special attention was given to the evolution of the most important magnetic textural components. Although in terms of grain shape, IQ, texture and normalised thickness position or ‘s’-parameter the microstructures obtained before and after cold rolling are totally different, the overall crystallographic textures seem not to differ very much.
Authors: I. Infante Danzo, Kim Verbeken, Yvan Houbaert
Abstract: In order to improve the magnetic properties of electrical steels, it may be desirable to increase the Si and/or Al content of the steel. A possible and alternative route to realize this is through the application of an Al-Si-rich coating on the steel substrate using a hot dipping process, followed by a diffusion annealing treatment. Previously, a series of compositions were used for dipping, namely: pure Al, Al + 10wt% Si (hypo-eutectic composition) and Al + 25wt% Si (hypereutectic composition). After these dipping experiments, and the subsequent evaluation of the coating and its formed intermetallic phases, the use of a hypo-eutectic Al-Si-bath was recommended for further investigation, because of certain advantages: i.e. hypo-eutectic concentrations allow lower dipping temperatures and reduce the formation of ordered Fe-Si-structures that cause brittleness in the coating and substrate. The present work reports on the results obtained on materials that were hot dipped in a hypo-eutectic Al-Si bath. An Al + 1wt%Si bath was used to coat electrical steel substrates with different silicon contents with dipping times, varying between 0 to 20 seconds, after a preheating of the samples to a temperature of 700°C. A thorough characterization of the formed intermetallics was made by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD). Three different compounds were identified as Fe2Al5, FeAl3 and a nearly pure Al phase.
Authors: José Barros, Tanya Ros-Yáñez, Yvan Houbaert
Abstract: The chemical and physical interaction between Fe-Si alloys in the range 0-3.8 Si wt% and a molten Al-(Si 25wt%) alloy at 800 °C has been studied for different reaction times (from 0.1 to 200s) by hot dipping tests. Several intermetallic phases have been identified, Fe2Al5, τ1-Al3Fe3Si2, τ2-Al12Fe6Si5, τ3- Al2FeSi and τ4- Al3FeSi2, which already were reported in the literature dealing with the interaction between iron and molten Al-Si alloys. In addition an ordered phase Fe3Si (D03) appears in contact with the Fe-Si substrate. Diffusion reaction and solidification phenomena appear to be involved in the developing of the coating. The growth kinetic has been studied and diffusion appears as the step controlling the intermetallic compounds growth. Special attention was paid to the effect of the microstructure of the dipped sheet on the interaction with the molten alloy. The higher deformed structures react faster; this effect can be explained by the faster diffusion through high diffusivity paths like grain boundaries and dislocations.
Authors: Polykseni Vourna, Aphrodite Ktena
Abstract: Results of an experimental study of electrical steel annealed at 500, 600, 700 °C and subsequently cooled via quenching or air, are presented. The samples have been characterized with respect to their magnetic properties using Magnetic Barkhausen Noise (MBN) and major and minor loop (B-H) measurements. MBN increases slightly with the annealing temperature especially in the quenched samples. The B-H loops suggest that the prevalent magnetization reversal mechanism in the air cooled samples is domain wall propagation, while in the quenched samples non 180o domain rotation seems to be significant approaching the high induction region. Scanning Electron Microscopy studies show a more homogeneous texture after annealing which in the case of the quenched samples is accompanied by not fully formed grain boundaries and orientation along he easy axis
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