Grain-oriented Silicon-iron Research Articles

Application of orientation distribution functions’ theory in the case of grain-oriented steels cut through classical and non-conventional technologies

Grain-oriented silicon iron alloys present an important magnetocrystalline anisotropy, which has a strong influence on the normal magnetization curve and the energy losses. The theory of Orientation Distribution Functions (ODF), applied in the case o

A semi-empirical approximation of static hysteresis for high flux densities in highly grain-oriented silicon iron

In calculations and simulations regarding magnetic materials, it is important to have a have an accurate model of the hysteresis loop. The major loop, in particular, is used in many simulations. However, it is generally not possible to measure the true major loop, and it must therefore be approximated using a minor loop. There are several methods available for approximating magnetization curves, but they are primarily designed for paramagnetic materials, and are poorly suited to the highly grain-oriented steels used in modern transformers. Therefore, we propose two expressions for approximating the magnetization curves of grain-oriented silicon-iron steels. Both methods give close agreement with measurements and can be extrapolated to in order to describe the major loop.

Dependence of Magnetization Near Saturation on Alloying Content in Ferromagnetic Steel

This paper shows that there is strong dependence of saturation magnetization on the alloying content in ferromagnetic steels. This dependence was used to determine the cross-sectional areas of the commercial non-oriented and grain-oriented silicon–iron steels. The relation between magnetization near saturation and the contents of silicon and aluminum for a large number of steel samples was experimentally obtained using an air-cored magnetizing system. The influence of the approach to magnetic saturation and its use in the determination of the cross-sectional area of electrical steel strips using the saturation magnetization method was estimated. Standard deviation (SD) of cross-sectional area obtained using the saturation magnetization method was on the order of 0.14%. SD for using conventional technique was also on the similar order of $\sim 0.11$ %.

Improvement of the Magnetic Properties of Silicon Iron Alloys through Laser Irradiation and Thermal Treatments

We report an investigation on the improvement of magnetic properties in crystalline silicon iron alloys. It was studied the influence of three thermal treatments on the energy losses of non-oriented silicon iron (NO FeSi) sheets, M800-65A industrial grade, at two peak magnetic polarizations 0.5 T and 1 T. First treatment was done at 200 °C for 60 minutes, the second treatment at 550 °C for 30 minutes and the third treatment at 700 °C for 10 minutes. In the case of grain-oriented silicon iron (GO FeSi) sheets, 30Z140 industrial grade, was analyzed the influence of laser scratching on the magnetic properties at peak magnetic polarization 0.25 T. In the case of both steel grades is presented the reduction of the hysteresis, classical and excess losses, that occur after the applied treatments, using the concept of energy loss separation.

Building Factor of Grain-Oriented Silicon Iron (3% SiFe) with Different Thickness on 100kVA Three Phase Distribution Transformer Core

The power loss in laminated transformer cores is always greater than the nominal loss of the electrical steel laminations, by a factor known as the building factor. This paper discussed result of an investigation towards the effect of using two different Grain-Oriented Silicon Iron (3%SiFe) materials to the 100kVA three phase distribution transformer. The thicknesses of the material that have been used in this research are 0.23mm and 0.27mm. The transformer core will be assembled with 60o T-joint with 5mm mitred corner overlap length. Power loss has been measured using no-load test with 29 layer of lamination while nominal loss measured using Epstein test frame. At the operation mode flux density, 1.5T, the building factor of the transformer model core material with 0.23mm thickness is 1.219 while with the building factor for 0.27mm thickness is 1.250. This shows that thinner transformer core lamination is better than the other one by 2.5% during operation mode.

Texture enhancement by inoculation during casting of ferritic stainless steel strip

Melt/substrate contacting experiments, designed to approximate conditions encountered during strip casting, were carried out to produce as-cast ferritic stainless steel strip. The results show that inoculation of the melt to produce TiN particles, together with casting onto a smooth substrate, results in the optimum conditions for nucleation and subsequent growth of an exceedingly high volume fraction of ferrite grains with 〈001〉 oriented within a few degrees of the normal direction (ND) of the strip surface. It is argued that, during casting, TiN particles either nucleate or deposit onto the substrate with 〈001〉 parallel to the ND, and since these particles exhibit crystallographic features similar to δ-ferrite, subsequent epitaxial growth inherits the initial particle orientation. Such oriented nucleation of ferrite from a smooth substrate results in the optimum heat-transfer conditions for further growth of dendrites with 〈001〉 perpendicular to the substrate, thus producing the intense through-thickness 〈001〉//ND fiber texture in the as-cast strip. The potential for producing grain-oriented silicon iron by direct strip casting is outlined.

Stress effects on the multidirectional magnetic behaviour of grain-oriented silicon iron sheets

The paper discusses effects of tensile and compressive stress on highly grain oriented SiFe sheets subject to rotational magnetisation which was simulated according to elliptical B -patterns of model transformer cores. Experimental results are given for all three H -patterns, losses and multidirectional magnetostriction. Interpretations are based on domain theory, and conclusions are presented with respect to transformer cores.

Statistical modeling of magnetic and magnetostrictive properties due to domain wall motion

Statistical mechanics is employed to derive magnetic and magnetostrictive bulk properties of soft magnetic materials dominated by domain wall motion. The material is divided into an ensemble of volumes with uniform magnetization, each one much smaller than a typical domain but much larger than one atom. The energy for such a volume element is assumed to consist of an internal energy: the interaction with the external magnetic field and a mean field interaction with the surrounding medium. The volume fractions of discrete mesoscopic magnetizations in the medium are derived from Boltzmann statistics. The bulk magnetization is the weighted average of the mesoscopic values. Magnetostriction is treated in a similar way. Calculations are compared with two-dimensional measurements on grain-oriented silicon–iron.

Magnetomechanical measurements and their application to soft magnetic materials

The use of magnetomechanical measurements in studying soft ferromagnets is surveyed. Suitable methods for measuring magnetostriction and the field-dependence of elastic moduli are described. The use of these measurements in conjunction with appropriate domain models is considered as a means of studying domain processes; in particular for distinguishing between magnetomechanically active processes (moment rotation and 90° wall motion) and magnetomechanically inactive processes (180° domain wall motion). Examples are drawn from amorphous ribbons and wires, nanocrystalline ribbons and grain-oriented silicon-iron.

On the metallurgical control of texture sharpness and related magnetic properties in grain-oriented silicon-iron

The final Goss texture sharpness and the related magnetic behaviour of a grain-oriented silicon-iron sheet is, in the end, controlled by its primary recrystallization texture at final thickness. In spite of the general idea that attributes the final Goss texture sharpness control to the precision of the Goss nuclei present at that stage, it is becoming clear that the main metallurgical role is played instead by the Goss nuclei surrounding texture. This texture selects the secondary recrystallization (SR) grains in a specific Goss-oriented spread range by a mechanism comparable, in principle, to the ‘lock-and-key’ enzymatic selective catalysis mechanism, well known in biochemistry. The microstructure and magnetic behaviour differences between conventional grain-oriented (CGO) and super-oriented (HiB) sheets, as well as between various final sheet thickness products, are explained in this framework.

Computation of magnetic field in Rogowski-Chattock potentiometer (RCP) compensated magnetic testers

The finite element technique was used to analyse an on-line power loss testing system based on the Rogowski- Chattock potentiometer (RCP) compensation method for use on grain-oriented electrical steel production lines. The main magnetisation and the compensation windings of the model were energised with the current values obtained from the practical model to produce a spatial magnetic flux density of 1.7 T in a 0.27 mm grain-oriented silicon iron steel sheet specimen (27M4). The computed and measured values of the magnetising force and the induced flux density in the sample showed good agreements. The model was solved for different magnetising and compensating current values, and the best magnetisation condition was achieved when the compensation current was twice that of the magnetising current.

Two-dimensional stress—magnetization effects of grain-oriented silicon steel sheets

Changes in the magnetization vector due to tensile stress under a constant magnetic field for grain-oriented silicon-iron sheet strip samples cut at various angles from the rolling direction have been investigated. In a low magnetic field, where the magnetization is less than 1.5 T, the magnetization vector lies in the direction of the sample length and the magnetization decreases with the application of tension. Beyond that magnetic field, the magnetization vector showed a two-dimensional hysteresis loop due to the application of tension. The maximum transverse magnetization change appeared in a 10° sample, where the rotation angle of the magnetization vector was 2.5°.

Domain structures and magnetic properties of advanced grain-oriented silicon steel

The dynamic behavior of surface closure domains governing the soft magnetic properties of grain-oriented 3% silicon-iron and the basic magnetic phenomena, such as domain wall pinning, are explained mainly through the observation of static and dynamic domain wall movements under a high-voltage scanning electron microscope. Techniques for manufacturing the latest grain-oriented silicon-iron, such as improvements in the alignment of the (110)[001] orientation, increases in the number of mobile domain walls and relaxation of domain wall pinning, are also described through the observation of domain patterns.

一方向性けい素鋼板の圧縮応力下における磁区構造変化

The effects of compressive stress on the magnetization in grain-oriented silicon iron sheets have been investigated. The magnetization changes due to compression are composed of two effects, reversible and irreversible magnetization changes. The magnetization changes due to compression for a sample cut at a declining angle of 35° from the rolling direction have peculiar characteristics. This sample shows two peaks of magnetization change due to compression. Changes in the domain structure due to compression were observed in order to determine the mechanism of magnetization change. A stripe domain pattern with 180° domain walls changes into a small perpendicular stripe pattern as a result of the application of both a magnetic field and compression, and the density of stripes changes as a result of compressive stress.

Effect of stress on tertiary recrystallized silicon iron

The effects of stress on the magnetization change for tertiary recrystallized silicon iron has been investigated. The processes of magnetization change due to tensile stress at various points on the hysteresis curve have been made clear. This material has an extremely small volume portion of 90° domains compared with high-grade commercial grain-oriented silicon iron sheet.

方向性薄けい素鋼の磁化過程とヒステリシス特性

Thin-gage grain-oriented silicon-iron sheet is expected as a low power loss core material in the future. With lowering thickness the hysteresis loss tends to increase while the eddy current loss decreases. It is important to suppress the increasing tendency of hysteresis loss to realize thin-gage silicon-iron with low power loss. In this paper the mechanism of the thickness dependence of hysteresis loss in (110)[001] oriented silicon-iron was discussed on the basis of the analysis of magnetization process and the experiments using single crystal specimens. It was revealed that the magnetization jump which occurs as a result of the magnetostatic interaction of surface free pole causes a great increase of hysteresis loss at lower thickness when the tilt angle of [001] axis out of the surface is large. The role of the surface closure domain on hysteresis loss was also studied.

Apparatus for measurement of velocity of domain boundaries in two dimensions in grain-oriented silicon iron

Disc samples of grain-oriented silicon iron have been subject to rotating magnetic flux, and domains observed by the Kerr effect. Moving patterns at 0.2 Hz were recorded on video tape and the images digitized. The co-ordinates of significant features were logged over several frames and velocities computed from knowledge of the frame count and frame rate.For some grains bar and zig-zag patterns alternate. The transition between these is a rapid sweep across the field of view, its velocity being around ten times that of the bar walls. Bar walls are also created and annihilated. Other grains display variants of this. The flux seems to take selective paths though the grains.Further work with this apparatus should provide data for a model of rotational power loss.

Geometrical factors affecting magnetic properties of wound toroidal cores

Although toroidal cores wound from grain-oriented silicon iron strip are basically simple devices used in many applications, their magnetic properties are known to vary in a complex manner with core dimensions. The theoretical effects of radial magnetic field and flux density variation, interlamina normal flux, and winding stress on the real and apparent power loss and the permeability of a range of toroids with typical commercial dimensions are discussed. Comparisons are made with actual performance. It is shown that the radial variation of flux densities has a very small effect on the power loss and permeability but the interlamina normal flux has an influential effect, particularly in small-diameter toroids. It is shown that to obtain low losses and magnetizing currents, toroids should be designed using wide strips having large internal diameter and low buildup. >

Measurement of power loss in stacked cores built with amorphous materials

The power loss was measured in several amorphous material and grain-oriented silicon-iron stacked cores built by employing butt and lap, and also 45° mitred overlap joints. Sandwich-cores using a combination of either Metglas 2605 SC or Metglas 2605 CO amorphous material and conventional M-OH grain-oriented silicon-iron were also built and tested. The results showed that the power loss in the sandwich-cores was higher than that in the cores built with only one type of material, either amorphous ribbon or grain-oriented silicon-iron.

Comparison of flux distribution in three-phase transformer cores assembled from amorphous material and grain oriented silicon iron

Model stacked three-phase transformer cores were assembled from amorphous material and from grain-oriented silicon iron, and both types were magnetized under sinusoidal flux density conditions. Small search coils were located at selected points on individual strips of material in both cores in order to monitor the localized flux density distribution from analysis of the voltages induced in the coils. The distribution of the fundamental and third- and fifth-harmonic flux density in the plane of the core was recorded at chosen instants in time, and the locus of the flux density at each measuring point was plotted. Three important differences were observed. First, the flux in the amorphous core tended to vary in direction as it proceeded around corners, whereas in the other core the flux density was directed along the rolling directions of the laminations almost everywhere. Second, there was a high degree of rotational flux in the T-joint of the amorphous core that did not occur in the core assembled from silicon iron. Third, the flux was more uniform in the amorphous core. On the basis of these results, the building factor of the amorphous core should be far less than that of the silicon iron core of the same geometry. >