Properties Of Non-oriented Electrical Steels Research Articles

Effects of Lanthanum and Boron on the Microstructure and Magnetic Properties of Non-oriented Electrical Steels

AbstractThe effects of lanthanum and boron on the inclusion size distribution, microstructure, texture and magnetic properties of three non-oriented electrical steels have been studied. After final annealing, lanthanum effectively inhibited the precipitation of MnS precipitates and promoted the growth of grains, an addition of 0.0041 wt.% boron led to the precipitation of Fe2B particles and inhibited grain growth. On the other hand, steel containing 0.0055 wt.% lanthanum had the strongest {100} and {111} fiber texture and the weakest {112}〈110〉 texture among the steels. Compared to steel without lanthanum and boron, steel with 0.0050 wt.% lanthanum and 0.0041 wt.% boron obtained slightly stronger intensities of {100} and {111} fiber texture, and a little weaker intensity of {112}〈110〉 texture. Steel containing 0.0055 wt.% lanthanum achieved the best magnetic properties, whose core loss and magnetic flux density were 4.268 W/kg and 1.768 T, respectively.

Effect of lanthanum content on microstructure and magnetic properties of non-oriented electrical steels

The effect of lanthanum content in the range of 0–0.011 wt.%, on the inclusion size distribution, microstructure, texture and magnetic properties of three non-oriented electrical steels was studied. After final annealing, lanthanum effectively inhibited the precipitation of MnS precipitates in steel, the formations of La2O2S and LaS inclusions not only acted as nuclei of AlN precipitates, but also combined with Al2O3 and formed composite inclusions with larger size. Grain size firstly increased and then decreased with lanthanum content increasing. Steel containing 0.0066 wt.% lanthanum obtained the largest grain size, the strongest {110}<110> texture and the weakest {112}<110> texture among all the tested steels. Magnetic flux density firstly increased and then decreased, core loss firstly dramatically decreased and then slightly decreased with lanthanum content increasing. Among the three tested steels, steel with 0.0066 wt.% lanthanum demonstrated the best comprehensive magnetic properties mainly through the development of favorable texture and appropriate final grain size.

Metallurgical, Mechanical and Magnetic Properties of Electrical Steel Sheets in TIG and PLASMA Welding

The influence of Tungsten Insert Gas (TIG) and Plasma welding on the microstructure, mechanical and magnetic properties of non-oriented electrical steels is presented and evaluated. Samples of sizes of 5.5 cm x 5.5cm x 2.0 mm were prepared from stock plate, installed on the welding table and welded at welding speeds and pulsed currents following a predesigned protocol. The samples microstructure was studied using SEM after standard mechanical grinding and polishing procedures. The characterization of the samples is concluded with microhardness tests and magnetic measurement (Barkhausen Noise) on TIG and Plasma welded joints in order to investigate the influence of welding on the magnetizing behavior of a high Si-alloyed grade of non-oriented electrical steel.

Magnetic properties and domain structure of nonoriented electrical steel under stress

AbstractThe influence of stresses on the magnetic properties of nonoriented electrical steels was studied. The dependence of iron loss on compressive stress was affected by grain size. The magnetic polarization J in strong magnetic fields such as 5000 and 10,000 A/m increased due to compressive stresses and decreased due to tensile stresses in samples with low Si content. Using Kerr‐effect domain observation, it was found that the reduction in J caused by tensile stresses was attributable to residual striped domains. Magnetostriction measurements in strong magnetic fields indicated that the increase in J under compressive stresses originated from the Villari effect (inverse magnetostrictive effect) due to negative magnetostriction in low‐Si materials. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 182(4): 10–18, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22320

Nonoriented Electrical Steels

The physical origins of the magnetic properties of nonoriented electrical steels; its relations to microstructural features like grain size, nonmetallic inclusions, dislocation density distribution, crystallographic texture, and residual stresses; and its processing by cold rolling and annealing are overviewed, using quantitative relations whenever available.

Rapid annealing effects on microstructure, texture, and magnetic properties of non-oriented electrical steel

This paper presents a classic process-structure-properties approach for optimizing the magnetic properties of electrical steels. Cold-rolled non-oriented electrical steel (Fe; 0.001 wt% C; 0.2 wt.% Mn; 1.3 wt% Si) was subjected to extremely short 3–30 seconds annealing cycles in a range from 880 °C to 980 °C with a heating rate varying from 15 °C to 300 °C/sec. The resulting microstructure was studied by means of optical microscopy and X-ray orientation distribution function analysis. Recrystallized grains were refined with increased heating rate, caused by the nucleation rate increase, which is faster than the growth rate due to rapid heating. The optimal grain size of 60 to 80 mm in terms of magnetic properties was obtained by increasing the annealing temperature range to 920 °C to 940 °C with a higher heating rate of 300 °C/sec and an annealing time of 6 to 9 seconds. With the heating rate increase, the characteristic {111} recrystallization fiber of cold-rolled steel was depressed, but the beneficial {110}〈001〉 Goss texture component was significantly strengthened. The recrystallized grain size and texture were enhanced by rapid annealing, and, as a result, the magnetic properties of non-oriented electrical steel improved.

Texture Change during Grain Growth in Non-Oriented Electrical Steel

Grain size and texture are very important for controlling the magnetic properties in non-oriented electrical steel. Grain size and texture are closely related because the texture usually changes during grain growth. In this study, texture changes with grain growth in non-oriented electrical steel are investigated. Two kinds of materials, Sample A and Sample B, were prepared in order to study the differences of the texture. Sample A, Fe-0.5wt%Si, is not annealed before cold rolling. Sample B, the same chemical composition as Sample A, is annealed before cold rolling. In Sample A, the {111} texture component increases markedly during grain growth. By contrast, in Sample B, the increase in {111} is less pronounced. The recrystallized orientations in both Samples are analyzed, and computer simulation is used to attempt to explain the texture changes during grain growth. In the case of Sample A, the simulations reproduce the experimental result well; for Sample B, however, the simulations do not agree as well. The microstructures before annealing exhibit strong alignment of the orientations, which will require a new approach to building the digital microstructures for instantiation of the simulations.

Modeling the Magnetic Properties of Non-Oriented Electrical Steels Based on Microstructural Parameters

Magnetic properties of electrical steels such as magnetization behavior and electrical losses are mainly related to chemical composition, crystallographic orientation and microstructure. By now, several models have been proposed to empirically correlate magnetic properties and affecting parameters. A quantitative model based on physical understanding of the interaction between the magnetic field variables (e.g. domain structure) and local microstructural variables (e.g. grain orientation and misorientation, grain boundary plane inclination) is still missing. To obtain a better understanding of the interaction between grain boundaries and domain walls, the magnitude of free pole density at grain boundaries was taken into account. Experimental results from 3-dimentional EBSD experiments were employed to measure the grain boundary orientation for several samples with different chemical composition and grain size. The free pole density was calculated using the relative misorientation between adjacent grains, and was included in a model together with grain size, magnetocrystalline anisotropy energy and silicon equivalent. By comparison with the experimental results of the magnetic induction measured at low, medium and high magnetic fields, is shown that the magnetization behavior can be more accurately predicted when the above mentioned phenomena are taken into account.

Effect of initial grain size on texture evolution and magnetic properties in nonoriented electrical steels

The magnetic properties of nonoriented electrical steels are influenced by the grain size and crystallographic texture. The technologies used to control the grain size in nonoriented electrical steels are approaching their limits. However, there is still some room for improvement of the magnetic properties through texture control. Hot-band annealing is known to be one of the most effective processing stages for texture modification. In this study, two types of initial grain sizes prior to cold rolling are obtained by different hot-band annealing. The effect of initial grain size on texture evolution and magnetic properties in nonoriented electrical steels containing 2% Si is examined. The specimens having different initial grain sizes have significantly different textures in the cold-rolled state and the annealed state. During the recrystallization stage, new grains formed in the coarse-grained specimens have stronger Goss but weaker γ-fibre texture than those in the fine-grained specimens. During the grain growth after complete recrystallization, the coarse-grained specimens still have weaker γ-fibre texture than the fine-grained specimens. The magnetic induction of the coarse-grained specimens is always higher at the same temperature than that of the fine-grained specimens. The core loss of the coarse-grained specimens is lower at the same temperature than that of fine-grained specimens. However, the improvement of the core loss becomes less pronounced as the annealing temperature increases.

Effect of magnetic properties of non-oriented electrical steel on torque characteristics of interior-permanent-magnet synchronous motor

The torque characteristics of interior-permanent-magnet synchronous motor (IPMSM), in which core materials were our conventional non-oriented electrical steel 35SX250 and our developed steels 35SXH, 27SXH with high permeability, were measured by a pulse wave modulation (PWM) inverter control. The torque characteristics of the motor with developed steels were superior to that of conventional steel. The advantage of developed steels was remarkable in the high-toque region. Experimental torque separation using current phase control showed that reluctance torque was strongly affected by the magnetic properties of core materials. And we did magnetic field analysis of the motors by finite element method (FEM). The flux density in the teeth of the stator core was higher in the high permeability steels than that in the conventional steel under the same current condition. The developed steels are expected to be suited to the stator material of IPMSM used as drive motors for electric vehicles and compressor motors for air conditioner.

Influence of grain size and additions of Al and Mn on the magnetic properties of non-oriented electrical steels with 3 wt. (%) Si

The influence of hot-band grain size and additions of aluminum and manganese on the magnetic properties of non-oriented grain (NOG) low-carbon electrical steel with about 3 wt. (%) Si were investigated using optical microscopy and X ray diffraction. The addition of manganese resulted in larger grains after final annealing. Coarse grains in the hot-band and addition of Mn led to a Goss orientation component after final annealing, which resulted in an increase in the magnetic permeability.

Effect of Cerium Content on the Magnetic Properties of Non-oriented Electrical Steels

The effects of cerium content in the range of 0–0.022 wt%, on the microstructure, texture and magnetic properties of four non-oriented electrical steels have been studied. After final annealing, grain size increased with increasing cerium content and reached a maximum value in the steel with 0.011 wt% cerium. Furthermore, steel containing 0.003 wt% cerium had the strongest (110)‹001› texture among the steels. In the steel with the same cerium content, the intensity of (111)‹uvw› fiber texture decreased with decreasing hot finishing rolling temperature and increasing hot band annealing temperature. Under the same processing conditions, flux density slightly increased with increasing cerium and reached a maximum value in the steel with 0.003 wt% cerium. For steel with the same cerium content, flux density increased with increasing hot band annealing temperature and decreasing hot finishing rolling temperature. Conversely, core loss decreased with increasing cerium content and reached a minimum value in the steels containing 0.003 wt% cerium. For steel with the same cerium content, core loss decreased with increasing hot band annealing temperature and decreasing hot finishing rolling temperature. Steel with 0.003 wt% cerium obtained the best magnetic properties, predominantly through the development of favorable texture and optimum grain size.

無方向性電磁鋼板における磁気特性方向依存性の検討

This paper discusses the direction dependence of the magnetic properties of non-oriented electrical steels (NO). The direction dependences are due to magnetic anisotropy induced by grain boundaries, steel edges and manufacturing stresses. NO sheets are easy to magnetize in the rolling direction (RD), because of the RD magnetization orientation induced by grain boundaries. Therefore, NO sheets have uniaxial direction dependence at lower magnetic flux densities. However, the direction dependence at higher densities is affected by the {110} steel surface which is present to a small extent in NO, although NO has generally {111} sheet surface texture that hardly affects the direction dependences.

Recrystallisation, Grain Growth and Texture Evolution in Nonoriented Electrical Steels

The magnetic properties of nonoriented electrical steels are influenced by grain size and texture of final products. The key technology in the commercial production of nonoriented electrical steels is to grow grains with {hk0}&lt;001&gt; texture up to the optimum size in the final annealing process. The problems related to grain size control have been extensively investigated, while texture control has received much less attention. Therefore, there is enough room to improve the magnetic properties through the control of texture. In this study, systematic investigations on the texture evolution during both recrystallization and grain growth have been made. The formation of recrystallization texture is explained by oriented nucleation. This is supported by the fact that the area fraction of nuclei or recrystallized grains with specific orientation to all new grains remains almost constant during the progress of recrystallization. Most nuclei have a high misorientation angle of 25∼55° with the surrounding deformed matrices. During the progress of grain growth, the Goss texture component continues to decrease because the Goss grains have a high percentage of low angle, low mobility grain boundaries. The grains of Goss orientation have a smaller grain size than those of random orientation.

Effect of Al Content on Magnetic Properties of Non-Oriented Electrical Steel by Simulated CSP Process

Abstract In this work, non-oriented electrical steels are prepared by a simulated compact strip production (CSP) line in the laboratory. Effect of Al content on magnetic properties of non-oriented electrical steels was studied by means of optical microscope, SEM, TEM and energy spectrum analysis. The outcome from the simulated production line is quite consistent with findings from the industrial CSP production of non-oriented electrical steels: When Als content is in the dangerous range of 0.005∼0.15%, A1N precipitate is fine, grain growth is inhibited and core lose is increased.

Influence of Heat Treatment on Magnetic Properties of Non-Oriented Electrical Steel Prepared by CSP Process Simulated

Abstract Non-oriented electrical steel was prepared by simulated compact strip production process (CSP) in the laboratory. The primary results are obtained by observing the influence of heat treatment, especially normalizing and annealing, on magnetic properties of non-oriented electrical steel. The results show that magnetic properties can be improved by normalizing as well as higher temperature annealing.

Influence of shearing process on domain structure and magnetic properties of non-oriented electrical steel

The influence of shearing on the magnetic properties and domain structure of 0.5 mm thick non-oriented electrical steel was studied. In the region from 1 to 1.4 mm from the sheared edge, a striped domain pattern that indicated the existence of elastic strain was observed. From the degradation tendency of flux density with respect to shearing width, the width of the degraded region near the edge increased as the magnetic field decreased. These results suggested that the change in the flux density at high magnetic fields over 300 A/m were mainly dependent on the characteristics of the edge vicinity where the domain pattern was influenced by shearing.

Effect of mechanical and Nd:YAG laser cutting on magnetic flux distribution near the cut edge of non-oriented steels

Previous reports of the effect of laser cutting on magnetic properties of non-oriented electrical steels and how it compares to mechanical (guillotining, punching) reveal some seemingly conflicting findings. Measurements reported here confirm that it is possible to minimize the effect on magnetic properties by selecting an appropriate laser cutting process.

Magnetic properties of Fe–Si steel depending on compressive and tensile stresses under sinusoidal and distorted excitations

In this article, the magnetic properties of nonoriented electrical steel under sinusoidal and distorted excitations are investigated for the whole range of unidirectional mechanical stresses. The distorted flux obtained from the tooth tip of 3 kW induction machine at no-load test was put into the measurement system. The total losses increase for compressive stress both under sinusoidal and distorted excitations. For tensile elastic stresses, the total losses first decrease and then increase in a very similar way for both excitations. In contrast, the difference between total losses under sinusoidal and distorted magnetic fluxes becomes smaller with increase of the plastic strain. This work is a serious step toward complete characterization of the magnetic properties of electrical steel in the teeth area of induction machines. A deeper insight of that problem can improve the design of induction machines and other electromagnetic devices.

Effect of Heating Rate on the Development of Annealing Texture in Nonoriented Electrical Steels

The magnetic properties of nonoriented electrical steels are influenced by grain size and texture. During the final annealing process, heating rate, annealing temperature and time, and cooling rate are the main factors which can influence the formation of annealing texture. Among these parameters, heating rate is more effective in controlling texture development through changes in the recovery and recrystallization processes. Therefore, it can provide the means to decrease core loss and increase permeability. In nonoriented electrical steels with different initial grain sizes, the effect of heating rate on texture development during final annealing is examined, and the reasons for texture changes are discussed. The average grain size decreases with the increase in heating rate both in the coarse-grained and in the fine-grained specimens. In the coarse-grained specimen, the Goss texture is significantly strengthened but the {111}‹112› texture component is slightly weakened as heating rate increases. On the other hand, in the fine-grained specimen, the {111}‹112› intensity is greatly decreased but the Goss intensity is slightly increased as the heating rate increases. The heating rate up to the annealing temperature affects texture formation differently depending on the initial grain size prior to cold rolling. These differences are mainly related to the difference in the number of shear bands formed during cold rolling in grains having different sizes.