Grain-oriented Silicon Steel Sheets Research Articles

Measurement and analysis of magnetic fields on the surface of grain-oriented silicon steel sheet

Grain oriented, 3% silicon steel sheet is used in motors and transformer cores where an accurate knowledge of its magnetic properties is needed for design calculations. The magnetic field distribution on the sheet surface is of fundamental importance in assessing its overall magnetic properties. The magnetisation often is not always along the rolling direction and the field H and flux density B need not be co-linear leading to errors in measurement of field calculations. The angle between B and H varies with sheet width which may be attributed to demagnetising factors which are not taken into account in magnetic anisotropy modelling for FEM applications. This paper reports results of an investigation of the effect of strip width, peak flux density and direction of magnetic field on the locus of flux density throughout the magnetising cycle. The flux density varies in direction considerably during the cycle and it is shown that this can be related to the corresponding variation of demagnetising field. The paper attempts to identify the influence of the demagnetisation factor so that the results can be related to local magnetisation conditions in the limbs and corners of a transformer.

Analysis of the phenomena of non-Fourier heat conduction in switch-Q laser processing for reducing the core loss of grain-oriented silicon steel

In a previous study, it was found that the core loss of grain-oriented silicon steel sheets can prominently be reduced substantially by means of switch-Q laser processing: however, their coating is inevitably damaged. The experimental studies in the present paper were conducted to observe and analyse the effect of switch-Q laser processing on the domain structure, the metallographic structure and the core loss of the sheet. Two phenomena have been discovered that are difficult to explain: (i) the coating is more easily damaged; and (ii) the depth of the dislocation is much greater than predicted by means of conventional Fourier heat conduction. The two problems have been analyzed and explained by the non-Fourier heat conduction approximation.

Local Two-Dimensional Magnetic Properties of Grain-Oriented Sheets

Magnetic properties of electrical steel sheets are usually measured by using a single-sheet tester or Epstein‘s tester. The permeability is measured as a scalar value, that is, the relationship between the magnetic flux density B and the magnetic field intensity H in only the rolling direction, and the measured value represents an average for the specimens. However, it is well known that the local distributions of B and H are not uniform in a grain-oriented silicon steel sheet. The reasons for this are closely related to not only the magnetic properties, but also the local loss distributions. Thus it is necessary to measure the local B and H as vector variables and to estimate the local iron losses with those vector relations in constructed cores. In this paper, the relationship between the grain form and the local iron loss distribution is investigated in detail by using a grain-oriented 3% silicon steel sheet without insulator coating.

Strain-Magnetization Properties and Domain Structures of Silicon Steel Sheets with Stress Applied to Plastic Deformation Regions

The effects of tensile stress and strain on magnetization and magnetic domains in grain-oriented silicon steel sheets were investigated. The strain-magnetization properties of plastic deformation regions under stress showed peculiar characteristics. The magnetization increased with decreasing strain and, after reaching a peak value, decreased with decreasing strain. We observed Lancet domains in a sample after removing stress applied to a plastic deformation region. This phenomenon can be explained by changes in the domain structures, which were partly observed. The results obtained in this investigation can be applied to the nondestructive detection of fatigue in metallic magnetic materials.

Decreasing the core loss of grain-oriented silicon steel by laser processing

Both experimental investigation into the lowering of the core loss of grain-oriented silicon steel sheets and theoretical analyses of heat conduction and elastoplastic stress have been conducted in this paper. The investigation indicates that either pulse laser or continuous-wave laser processing is able to reduce the core loss by more than 5% without damage to the coating and bending of sheet caused by unreasonable technical conditions. As a result, the theoretical analyses reveal that a reasonable heating time should be determined, within about 10 −8 and 10 −8 s, in order to prevent damage to the coating and bending of the sheet.

Spatial distribution of the gap-stray fields and it influence on domain structure and magnetization processes of laminated grain-oriented silicon steel sheets

The spatial distribution of the magnetic stray field Hs, arising at the air gap, was investigated. The longitudinal component Hxs was studied in detail. Near the air gaps both the regions ΔX1, where Hxs coincides (Hxs+) with the direction of external field He and the regions ΔX2, where it counteracts (Hxs−) with the field He have been detected. It was shown that the longitudinal stray field component Hxs exerts substantial and main influence on magnetization processes and domain structure behavior of laminated silicon steel sheets.

Domain Structures Due to Stress in Grain-Oriented Silicon Steel Sheets

The effects of tensile stress on magnetization and magnetic domains in grain-oriented silicon steel sheets were investigated. Magnetization properties due to tension were different among samples cut at various declining angles from the rolling direction. In samples with angles of less than 55°, the magnetization simply decreased with increasing tensions. In samples with angles of more than 55°, however, the magnetization increased for low tensions and decreased for high tensions. This phenomenon can be explained by changes in the domain structures, which were partly observed, and partly inferred from the magnetostatic energy and magnetoelastic energy.

Reduction of iron loss in thin grain-oriented silicon steel sheets

We investigated the effect of the intermediate annealing conditions on the grain textures and the magnetic properties in thin grain-oriented silicon steel sheets produced by the three-stage rolling method. It was found that the lower the intermediate annealing temperature is, the better the [001] orientation is achieved. In addition, the reduction of the intermediate annealing temperatures improves dc magnetic properties (B/sub 8/, H/sub c/) and enables to reduce the iron loss in thin silicon steels. The measured iron loss W13/50 under the applied tensile strength of 2 kg/mm/sup 2/ was 0.28 W/kg, which is less than that of the conventional (300 /spl mu/m) grain-oriented silicon steels by about 50%.

Ultrathick glassless high-permeability, grain-oriented silicon steel sheets with high workability

A high-permeability, grain-oriented silicon steel sheet of ultrathick gauge 0.50 nm with better punchability, realized by the formation of an extremely thin glass film formed in the surface region, has been developed. The new product has almost the same core loss as conventional grain-oriented steel sheet of 0.35 mm gauge, when used in the iron cores of large rotary machines.

Two-dimensional magnetic properties of a three-phase amorphous transformer core

The distribution of the rotational magnetic flux density and the rotational field strength in a three-phase amorphous transformer model core is investigated using a special sensor. The differences at various locations of the three-phase amorphous core can be compared with the results for a grain-oriented silicon steel sheet.

けい素鋼板の２次元磁気ひずみ特性 Ｉ． 交番磁束下の任意方向の磁気ひずみ

This paper describes the rotational dynamic megnetostriction of non-oriented and grain-oriented silicon steel sheets. The magnetostriction of arbitrary direction under a rotating magnetic flux measured by a two-dimensional magnetic measurement method. The rotational magnetostriction was larger than alternating magnetostriction, and increased with the axis ratio of the rotating magnetic flux. In the case of non-oriented silicon steel sheets, it reached a peak value in a direction 135 degrees from the rolling direction. In the case of grain-oriented silicon steel sheets, it reached a peak value in a direction 90 degrees from the rolling direction.

けい素鋼板の２次元磁気ひずみ特性 ＩＩ． 回転磁束下の任意方向の磁気ひずみ

This paper describes the rotational dynamic megnetostriction of non-oriented and grain-oriented silicon steel sheets. The magnetostriction of arbitrary direction under a rotating magnetic flux measured by a two-dimensional magnetic measurement method. The rotational magnetostriction was larger than alternating magnetostriction, and increased with the axis ratio of the rotating magnetic flux. In the case of non-oriented silicon steel sheets, it reached a peak value in a direction 135 degrees from the rolling direction. In the case of grain-oriented silicon steel sheets, it reached a peak value in a direction 90 degrees from the rolling direction.

Ｓｉ‐Ｆｅ単結晶における応力磁化特性

The effects of tensile and compressive stress on magnetization changes in a Si-Fe single crystal with a (110) surface and longitudinal directions declined from the [001] direction were investigated. This study investigates the mechanism whereby stress effects were obtained in grainoriented silicon steel sheets. In these sheets, the magnetization change due to stress consists of two effects: a reversible magnetization change (Ire) and an irreversible magnetization change (Iir) . We found a peculiar magnetization change, namely, a reversible magnetization change curve with two peak values, under a constant magnetic field. The appearance of a double peak in magnetization values is deeply connected with the appearance of an irreversible magnetization change. These double-peak characteristics appear in samples with angles smaller than 55° for the compressive stress, but with angles larger than 60° for the tensile stress. We also found a peculiar reversible magnetization change that appears in the 90° sample, in hich the resultant magnetization change shows a small value, although it shows a large value during the proces of the application and removal of tension.

Moving simulation of magnetic domain structure in grain-oriented silicon steel sheet

This paper describes a numerical analysis method of domain structure in a grain-oriented silicon steel sheet. The stable domain structure of silicon steel sheet in an external magnetic field is analyzed by an iterative method that minimizes its total domain energy. In this analysis, we have assumed that the total domain energy is sum of the magnetostatic energy, the anisotropy energy, the domain wall energy and the Zeeman energy. In particular, we applied the Biot-Savart formula and Gaussian quadrature formula on the surface integral for the calculation of the magnetostatic energy.

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°.

方向性ケイ素鋼板の圧縮力印加および除去による応力磁化特性

方向性ケイ素鋼板の圧縮力印加および除去による応力磁化特性

(110) [001] Grain Growth in Silicon Steel Sheets of 30 μm Thickness

Thin grain-oriented silicon steel sheets have the lowest iron loss at a thickness of 30 μm. We observed the recrystallization behavior and magnetic properties of 30 μm thick silicon steel sheets, and compared the results with those of 60 μm thick silicon steel sheets. The recrystallization processes in the two types of sheet were found to be different. The primary recrystallized 30 μm thick silicon steel sheets did not have a strong (110) [001] texture or other orientation; consequently secondary recrystallization did not occur. However, at annealing temperatures above 1050°C, (110) [001] grains grew selectively. Thus we were able to obtain very thin grain-oriented silicon steel sheets with a thickness of 30 μm.

方向性ケイ素鋼板の二次元応力磁化特性

The effects of tensile and compressive stress on the magnetization changes, under a constant magnetic field, of grain-oriented silicon steel sheets inclined from the rolling direction were investigated. Magnetization changes due to tension in a low magnetic field appeared only in the longitudinal direction of the sample, and the magnetization decreased. Beyond that magnetic field, the sample showed a two-dimensional hysteresis loop due to the application of tension. The appearance of the twodimensional hysteresis loop was due to the magnetization vector being forced to rotate in the rolling direction by the application of tension. The maximum transverse magnetization change appeared in the 10° sample. On the other hand, magnetization changes due to the compression under the same magnetic field did not show a two-dimensional hysteresis loop.

Very Thin Silicon Steel Tertiary Recrystallized by Continuous Annealing Method

It is well known that very thin grain-oriented silicon steel sheet has a very low iron loss. A continuous annealing method was used to obtain a long (over 1 m) thin grain-oriented silicon steel sheet. As a result, thin grain-oriented silicon steel sheet 40 ?m thick and 1 m long was obtained. The annealing temperature was 1423K and the sample speed was from 0.7 to 2.1 mm/s. The annealing time needed to complete the recrystallization of (110) [001] grains was only a few minutes. However, the grain size of the sample was not uniform. As a result, the magnetic properties depend on the position of the sample.

Grain Size and Domain Width of a Very Thin 3% Si-Fe Sheet

Very thin (less than 0.1 mm thick) grain-oriented silicon sheets are known to have lower iron losses than iron-based amorphous materials. It is possible to reduce the iron loss of very thin grain-oriented silicon steel further by applying new magnetic domain refining techniques. One method of domain refinement is through control of the grain size. We observed magnetic domains and measured the iron loss of very thin grain-oriented silicon steel sheets with small (less than 1 mm) grains. These experiments showed that the domains can be made narrower by decreasing the grain size, which reduces eddy current losses. On the other hand, materials with larger grain sizes have lower H c values and lower hysteresis losses.