RU2814177C1 - Strip core - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: strip core includes a rectangular strip core body in a side view, in which the strip core body has a portion in which anisotropic electrical steel sheets, in which the first flat portions and the corner portions alternate continuously in the longitudinal direction, and an angle formed by the first two adjacent each other with each other flat parts, with each of the corner parts between them, is 90°, are stacked in a sheet thickness direction, and has a substantially rectangular laminated structure in side view, in which each of the corner portions has two or more curved portions having a curved shape in side view of the anisotropic electrical steel sheets, and the second flat portion between adjacent curved parts, and the sum of the bending angles of the curved parts in one corner part is 90°, in which each curved part in side view has an internal radius of curvature r equal to 1-5 mm. Sheets of anisotropic electrical steel have a chemical composition containing, wt.%, Si: C - up to 0.0050, not including 0, Si: 2.0-7.0, Fe and impurities are the rest and have a texture oriented in the Goss orientation, and in which at least one of the two or more curved parts present in at least one corner part satisfies the following equations (1 ) - (3): Tave≤ 40 nm (1), (To – Tu)/Tave≤ 0.5 (2), Tave (To – Tu)≤ 240 nm² (3), where the thickness T (nm) of the intermediate layer provided on the surface of the main steel sheet of the anisotropic electrical steel sheets is measured at a plurality of positions of the regions of the first and second flat parts adjacent to the curved parts, the average value of the thickness T (nm) the intermediate layer is denoted as Tave (nm), the maximum thickness is denoted as Tmax (nm), the minimum thickness is denoted as Tmin (nm), the average of the data where T>Tave is denoted as To (nm), and the average of the data where T <Tave, denoted by Tu, (nm).

EFFECT: strip core produced by bending steel sheets in advance so that a relatively small bending area with a radius of curvature of 5 mm or less is formed, and laminating the bent steel sheets to form the strip core, thereby minimizing unintended performance degradation.

4 cl, 5 tbl, 9 dwg

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

[0001]

The present invention relates to a strip core. Priority is claimed to Japanese Patent Application No. 2020-178900, filed October 26, 2020, the contents of which are incorporated herein by reference.

BACKGROUND OF THE ART

[0002]

The anisotropic (grain oriented) electrical steel sheet is a steel sheet containing 7 mass% or less of Si, and has a secondary recrystallization texture in which the secondary recrystallization grains are concentrated in the {110}<001> orientation (Goss orientation). The magnetic properties of anisotropic electrical steel sheets are significantly affected by the degree of concentration in the {110}<001> orientation. In recent years, in anisotropic electrical steel sheets that have been put into practical use, the angle between the crystal direction <001> and the rolling direction is controlled to be in the range of approximately 5°.

[0003]

Anisotropic electrical steel sheets are laminated (stacked) and used in transformer cores, etc., and require high magnetic flux density and low magnetic loss as their main magnetic properties. As is known, crystal orientation has a strong correlation with these properties, and, for example, Patent Documents 1-3 disclose techniques for precise control of orientation.

[0004]

A film is formed on the surface of the steel sheet to reduce magnetic losses. This film is used to reduce the magnetic loss of a single steel sheet by applying tension to the steel sheet, and also to reduce the magnetic loss of the core by guaranteeing the electrical insulating properties between the steel sheets when the steel sheets are laminated and used.

[0005]

As an anisotropic electrical steel sheet in which a film is formed on the surface of the steel sheet, for example, an anisotropic electrical steel sheet is known in which an intermediate layer (primary film) consisting mainly of forsterite (Mg ₂ SiO ₄ ) is formed on the surface of the main steel sheet, and an insulating coating is formed on the surface of the intermediate layer.

[0006]

Adhesion is achieved mainly through the anchoring effect due to the roughness of the interface between the base steel sheet and the intermediate layer. The boundary roughness interferes with the movement of the domain wall when the electrical steel sheet is magnetized, thereby preventing the magnetic loss reduction effect. In Patent Documents 4-7, techniques were disclosed in which adhesion of an insulating coating is ensured by using a special intermediate layer with a thickness of several nm to several tens of nm, consisting of SiO ₂ , TiN, etc. in a state in which the above-mentioned boundary is smoothed to reduce magnetic loss without the film being completely annealed.

[0007]

In addition, in the prior art for producing a strip core, as described, for example, in Patent Document 8, it is widely known to wind a steel sheet into a cylindrical shape and then press the cylindrical laminated body without modification so that its corner parts have a constant curvature , shaping it into a substantially rectangular shape and then annealing it to relieve stress and maintain its shape.

[0008]

On the other hand, as other methods for manufacturing a strip core, techniques such as those described in Patent Documents 9-11 have been disclosed, in which portions of the steel sheet that will be the corner portions of the strip core are bent in advance so as to form a relatively small bending area with a radius curvatures of 3 mm or less, and bent steel sheets are laminated to form a strip core. According to these production methods, the conventional large-scale pressing process is not required, the steel sheets are precisely bent to maintain the shape of the metal core, and the processing deformation is also concentrated only in the curved parts (corner parts). For this reason, it becomes possible to eliminate stress relief through the above-mentioned annealing process, the industrial benefits are great, and the application of this method is progressing.

BIBLIOGRAPHY

PATENT DOCUMENTS

[0009]

[Patent Document 1]

Japanese Unexamined Patent Application, First Publication No. 2001-192785

[Patent Document 2]

Japanese Unexamined Patent Application, First Publication No. 2005-240079

[Patent Document 3]

Japanese Unexamined Patent Application, First Publication No. 2012-052229

[Patent Document 4]

Japanese Patent No. 4025514

[Patent Document 5]

Japanese Unexamined Patent Application, First Publication No. 2002-322566

[Patent Document 6]

Japanese Unexamined Patent Application, First Publication No. 2019-019360

[Patent Document 7]

Japanese Unexamined Patent Application, First Publication No. 2005-264236

[Patent Document 8]

Japanese Unexamined Patent Application, First Publication No. 2005-286169

[Patent Document 9]

Japanese Patent No. 6224468

[Patent Document 10]

Japanese Unexamined Patent Application, First Publication No. 2018-148036

[Patent Document 11]

Australian Published Patent Application No. 2012337260

SUMMARY OF THE INVENTION

PROBLEMS SOLVED BY THE INVENTION

[0010]

The inventors of the present invention have studied in detail the effectiveness of a transformer metal core produced by a method of bending steel sheets in advance so that a relatively small bending region having a radius of curvature of 5 mm or less is formed, and laminating the bent steel sheets to form a strip core. As a result, it has been found that even when the material used is steel sheets with substantially the same crystal orientation control and substantially the same magnetic flux density and magnetic loss measured on a single sheet, there may be a difference in the efficiency of the metal cores.

[0011]

When investigating the cause of this problem, it was found that the extent of the problem of efficiency differences also varies depending on the sizes and shapes of the core. By comparing the difference in efficiency between steel types, the influence of the type of intermediate layer, especially the thickness and shape of the intermediate layer, can be confirmed. Taking a closer look at this phenomenon, the shape of the intermediate layer changes the degree of inhibition of bending magnetization in the bent parts, and therefore it is believed that this causes a difference in the degree of deterioration of magnetic loss of steel sheets including the bent parts.

In this regard, various steel sheet production conditions and core shapes were studied, and their effects on the efficiency of the cores were classified. As a result, it has been found that the shape of the intermediate layer of material can be controlled optimally to achieve core efficiency suitable for the magnetic properties of the steel sheet material.

[0012]

The present invention has been made in view of the above problem, and it is an object of the present invention to provide a strip core produced by a method of bending steel sheets in advance so that a relatively small bending area with a radius of curvature of 5 mm or less is formed, and laminating the bent steel sheets to form a strip core , thereby minimizing unintended performance degradation.

REMEDIES FOR SOLVING THE PROBLEM

[0013]

To solve this problem, the present invention provides a strip core having: a substantially rectangular strip core body in a side view, which has a portion in which anisotropic electrical steel sheets, in which first flat portions and corner portions alternate continuously in the longitudinal direction, and an angle between two first flat portions adjacent to each other, with each of the corner portions between them equal to 90°, stacked in a sheet thickness direction, and which has a substantially rectangular laminated structure in side view, each of the corner portions having two or more curved parts having a curved shape in the side view of the anisotropic electrical steel sheets, and a second flat part between adjacent curved parts, and the sum of the bending angles of the curved parts present in one corner part is 90°, each curved part in the side view has an inner radius of curvature r equal to 1-5 mm, the anisotropic electrical steel sheets have a chemical composition containing, in wt.%, Si: 2.0-7.0%, with the remainder of Fe and impurities, and have a texture oriented in the Goss orientation, and at least one of the two or more curved portions present in at least one corner portion satisfies Equations (1) to (3) below.

Tave ≤ 40 nm (1)

(To-Tu)/Tave ≤ 0.50 (2)

Tave (To-Tu) ≤ 240 nm ² (3)

Here, the thickness T (nm) of the intermediate layer provided on the surface of the main steel sheet of the anisotropic electrical steel sheets is measured at a plurality of positions of the regions of the first and second flat parts adjacent to the curved parts, the average value of the thickness T (nm) of the intermediate layer is denoted as Tave (nm ), the maximum thickness is denoted as Tmax (nm), the minimum thickness is denoted as Tmin (nm), the average of the data where T>Tave is denoted as To (nm), and the average of the data where T<Tave is denoted as Tu ( nm).

[0014]

In addition, in the configuration of the present invention, at least one of the two or more curved portions present in at least one corner portion may satisfy the following equation (4).

N (To-Tu) ≤ 24 nm (4)

Here, in the distribution of the thickness of the intermediate layer along the surface direction of steel sheets, the region in which the measurement values at T > Tave are continuous is considered as one region, and the number of these regions within the entire measurement region is denoted as N.

[0015]

In addition, in the configuration of the present invention, at least one of the two or more curved portions present in at least one corner portion may satisfy the following equation (5).

N ≥ 2 (5)

[0016]

In addition, in the configuration of the present invention, at least one of the two or more curved portions present in at least one corner portion may satisfy the following equation (6).

(Tmax-Tmin) < Tave (6)

USEFUL EFFECTS OF THE INVENTION

[0017]

According to the present invention, unintended performance degradation in a strip core formed by laminating curved steel sheets can be effectively minimized.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]

Fig. 1 is a perspective view schematically showing one embodiment of a strip core in accordance with the present invention.

Fig. 2 is a side view of the strip core shown in the embodiment of FIG. 1.

Fig. 3 is a side view schematically showing another embodiment of a strip core in accordance with the present invention.

Fig. 4 is a side view schematically showing one example of a curved portion of an anisotropic electrical steel sheet constituting a strip core according to the present invention.

Fig. 5 is a side view schematically showing one example of a single-layer anisotropic electrical steel sheet constituting a strip core according to the present invention.

Fig. 6 is a side view schematically showing another example of a single-layer anisotropic electrical steel sheet constituting a strip core according to the present invention.

Fig. 7 is a schematic view showing a method for measuring the thickness of the intermediate layer of an anisotropic electrical steel sheet constituting a strip core according to the present invention.

Fig. 8 is a schematic diagram showing the dimensions of the strip cores produced in the examples and comparative examples.

Fig. 9 shows schematic configurations of the three-phase strip core produced in the examples and comparative examples, in which (a) is a front view and (b) is a cross section along line A-A in view (a).

OPTIONS FOR IMPLEMENTING THE INVENTION

[0019]

Next, the tape cores in accordance with the present invention will be described in detail. However, the present invention is not limited to the configurations disclosed in these embodiments, and can be modified in various ways without departing from the spirit of the present invention. The lower limits and upper limits are included in the numerical limit ranges described below. Numerical values expressed using the phrases “greater than” or “less than” are not included in the specified ranges. In addition, "%" referring to chemical composition means "% by weight" unless otherwise expressly stated.

In addition, terms such as “parallel,” “perpendicular,” “identical,” and “right angle,” as well as length and angle values used herein to define shapes, geometric conditions, and degrees thereof, are not are bound by strict meaning and should be interpreted as including the extent to which similar functions can be expected.

In addition, in this specification, "anisotropic electrical steel sheet" is sometimes simply described as "steel sheet" or "electrical steel sheet", and "tape core" is sometimes simply described as "core".

[0020]

The strip core according to the present embodiment is a strip core having: a substantially rectangular strip core body in a side view, which has a portion in which anisotropic electrical steel sheets, in which first flat portions and corner portions alternate continuously in the longitudinal direction , and the angle between two first flat portions adjacent to each other, with each of the corner portions therebetween being 90°, are stacked in a sheet thickness direction, and which has a substantially rectangular laminated structure in side view, each of the corner portions having two or more curved portions having a curved shape in the side view of the anisotropic electrical steel sheets, and a second flat portion between adjacent curved portions, and the sum of the bending angles of the curved portions present in one corner portion is 90°, each curved portion in the side view has internal radius of curvature r equal to 1-5 mm, sheets of anisotropic electrical steel have a chemical composition containing, in wt.%, Si: 2.0-7.0%, with a remainder of Fe and impurities, and have a texture oriented in Goss orientation, and at least one of the two or more curved portions present in at least one corner portion satisfies Equations (1) to (3) below.

Tave ≤ 40 nm (1)

(To-Tu)/Tave ≤ 0.50 (2)

Tave (To-Tu) ≤ 240 nm ² (3)

Here, the thickness T (nm) of the intermediate layer provided on the surface of the main steel sheet of the anisotropic electrical steel sheets is measured at a plurality of positions of the regions of the first and second flat parts adjacent to the curved parts, the average thickness of the thickness T (nm) of the intermediate layer is denoted as Tave (nm ), the maximum thickness is denoted as Tmax (nm), the minimum thickness is denoted as Tmin (nm), the average of the data where T > Tave is denoted as To (nm), and the average of the data where T < Tave is denoted as Tu ( nm).

[0021]

1. Shapes of strip cores and sheets of anisotropic electrical steel

First, the shapes of the tape cores according to these embodiments will be described. The shapes of the anisotropic electrical steel strip cores and sheets described here are not particularly new. For example, these shapes simply correspond to the shapes of known anisotropic electrical steel strip cores and sheets described in prior art Patent Documents 9-11.

Fig. 1 is a perspective view schematically showing one embodiment of a strip core. Fig. 2 is a side view of the strip core shown in the embodiment of FIG. 1. In addition to this, FIG. 3 is a side view schematically showing another embodiment of a strip core.

The side view in these embodiments means a view of the long-shaped anisotropic electrical steel sheets constituting the strip core in the width direction (in the Y-axis direction in FIG. 1). The side view is a diagram (the diagram of Fig. 1 in the Y-axis direction) showing the shape as seen from the side.

[0022]

The strip core according to the present embodiment has a substantially rectangular (polygonal) strip core body 10 in a side view. The strip core body 10 has a substantially rectangular laminated structure 2 in a side view, in which the anisotropic electrical steel sheets 1 are stacked in the sheet thickness direction. The strip core body 10 may be used as a strip core without modification, or may optionally have known locks such as strapping tape for jointly securing a plurality of stacked anisotropic electrical steel sheets 1.

[0023]

In the present embodiment, the length of the metal core of the strip core body 10 is not particularly limited. Even if the length of the metal core changes, the volume of the bent parts 5 is constant, so that the magnetic loss occurring in the bent parts 5 remains constant. The longer the length of the metal core, the smaller the volume fraction of the curved portions 5 relative to the main strip core portion 10, and hence the lesser the impact on magnetic loss degradation. Accordingly, the length of the strip core body 10 is preferably long. The length of the strip core body 10 is preferably 1.5 m or more, and more preferably 1.7 m or more. In the present embodiment, the length of the strip core body 10 is the circumferential length of the strip core body at the center point in the laminating direction in the side view.

[0024]

The tape core of the present embodiment can be suitably used for any conventionally known applications.

[0025]

As shown in FIG. 1 and 2, the main body 10 of the strip core has a portion in which the anisotropic electrical steel sheets 1, in which the first flat parts 4 and the corner parts 3 alternate continuously in the longitudinal direction, and the angle formed by the two first flat parts 4 adjacent to each the corner portions 3 between them are 90°, are stacked in the sheet thickness direction, and have a substantially rectangular laminated structure 2 in side view. In this specification, the “first planar portion” and the “second planar portion” may be referred to simply as the “planar portion.”

Each of the corner portions 3 of the anisotropic electrical steel sheets 1 has two or more bent portions 5 having a curved shape in the side view of the anisotropic electrical steel sheets, and the sum of the bending angles of the bent portions 5 in one corner portion 3 is 90°. The corner portion 3 has a second flat portion 4a between adjacent curved portions 5. Accordingly, the corner portion 3 has a configuration including two or more curved portions 5 and one or more second flat portions 4a.

The embodiment in FIG. 2 is a case in which one corner portion 3 has two curved portions 5. The embodiment in FIG. 3 is a case in which one corner portion 3 has three curved portions 5.

[0026]

As shown in these examples, in the present embodiment, one corner portion may be formed with two or more curved portions, and the bending angle φ (such as φ1, φ2 and φ3) of the curved portion 5 is preferably 60° or less, and more preferably 45° or less in terms of minimizing magnetic losses by minimizing the generation of stresses caused by deformation during processing.

In the embodiment of FIG. 2, in which one corner part has two curved parts, it can be set, for example, φ1=60° and φ2=30° or φ1=45° and φ2=45° from the point of view of reducing magnetic loss. In addition to this, in the embodiment of FIG. 3, in which one corner part has three curved parts, it is possible to set, for example, φ1=30°, φ2=30° and φ3=30° from the viewpoint of reducing magnetic loss. In addition, from the point of view of production efficiency, it is preferable that the folding angles (bending angles) be equal. Therefore, it is preferable to set φ1=45° and φ2=45° in the case where one corner part has two curved parts, and it is preferable to set, for example, φ1=30°, φ2=30° and φ3=30° from the point of view of reduction magnetic losses in the embodiment of FIG. 3, in which one corner portion has three curved portions.

[0027]

The curved portion 5 will be described in more detail with reference to FIG. 4. Fig. 4 is a diagram schematically showing one example of a bent portion (curved portion) of an anisotropic electrical steel sheet. The bending angle of the bent portion 5 means the angular difference between the front straight portion and the rear straight portion in the bending direction on the bent portion 5 of the anisotropic electrical steel sheet 1, and is expressed as the angle φ, which is the complementary angle to the angle formed by the two virtual lines Lb-extent 1 and Lb-length2 obtained by extending the straight portions, which are the surfaces of the flat portions 4, 4a on both sides of the curved portion 5 on the outer surface of the anisotropic electrical steel sheet 1. Here, the point at which the extended straight line is separated from the surface of the steel sheet is the boundary between the flat part and the curved part on the outer surface of the steel sheet (points F and G in Fig. 6).

[0028]

In addition, straight lines perpendicular to the outer surface of the steel sheet respectively extend from points F and G, and their intersections with the inner surface of the steel sheet are point E and point D, respectively. Each of points E and D is the boundary between the flat part and the curved part on the inner surface of the steel sheet.

In the present embodiment, in the side view of the anisotropic electrical steel sheet 1, the bent portion is a part of the anisotropic electrical steel sheet 1 surrounded by the above-mentioned points D, E, F and G. In FIG. 6, the surface of the steel sheet between point D and point E, that is, the inner surface of the curved portion 5, is designated as La, and the surface of the steel sheet between points F and G, that is, the outer surface of the curved portion 5, is designated as Lb.

[0029]

In addition to this, the inner radius of curvature r in a side view of the curved portion 5 is shown in FIG. 4. The radius of curvature r of the curved part 5 is obtained by approximating the above La with an arc passing through point E and point D. A smaller radius of curvature r indicates a larger curvature of the curved part 5, and a larger radius of curvature r indicates a smaller curvature of the curved part 5.

In the strip core of the present embodiment, the radius of curvature r in each curved portion 5 of each anisotropic electrical steel sheet 1 laminated in the sheet thickness direction can be varied to some extent. This variation may be a variation due to molding precision, and it is possible that unintentional variation may occur due to handling during blending. Such unintentional error can be minimized to approximately 0.2 mm or less in current normal industrial production. In the case where such variations are large, a representative value can be obtained by measuring the radius of curvature r of a sufficiently large number of steel sheets and averaging them. In addition, it is possible to deliberately change the radius of curvature for some reasons, and the present embodiment does not exclude such a shape.

[0030]

The method for measuring the inner radius of curvature r of the curved portion 5 is not particularly limited, and the inner radius of curvature can be measured, for example, using a commercially available microscope (Nikon ECLIPSE LV150) with a magnification of 200x. In particular, the curvature center point A is obtained from the observation results. As a way to achieve this, for example, if the intersection of line segment EF and line segment DG extended inward on the side opposite point B is defined as A, the size of the inner radius of curvature r corresponds to the length of line segment AC.

In the present embodiment, the inner radius of curvature r of the curved portion 5 can be set within the range of 1-5 mm, and the shape of the intermediate layer provided on the surface of the main steel sheet of the anisotropic electrical steel sheet 1 described below can be optimally controlled to optimize the efficiency of the metal core, being suitable for magnetic properties. The effect of the present embodiment is more significant when the inner radius of curvature r of the curved portion 5 is preferably 3 mm or less.

In addition to this, it is most preferable that all the curved parts 5 in the core satisfy the inner radius of curvature of the side r defined in the present embodiment. In the case where there is a curved portion 5 satisfying the inner radius of curvature r of the present embodiment and a curved portion 5 not satisfying the inner radius of curvature r of the present embodiment, it is desirable that at least half of the curved portions 5 satisfy the inner radius of curvature r , defined in the present embodiment.

[0031]

Fig. 5 and 6 are diagrams schematically showing one example of a single-layer anisotropic electrical steel sheet 1 in the strip core body 10. As shown in the examples in FIGS. 5 and 6, the anisotropic electrical steel sheet 1 used in the present embodiment is curved, has a corner portion 3 composed of two or more curved portions 5, and a flat portion 4, and forms a substantially rectangular ring in a side view through the connecting portion. 6 (gap), which is the end surface of one or more sheets 1 of anisotropic electrical steel in the longitudinal direction.

In the present embodiment, it is sufficient that the strip core body 10 has a laminated structure 2 with a substantially rectangular overall shape in the side view. One anisotropic electrical steel sheet 1 can form one layer of the strip core body 10 through one connecting part 6, as shown in the example in FIG. 5 (one anisotropic electrical steel sheet 1 is connected by one connecting part 6 for each turn). Alternatively, one anisotropic electrical steel sheet 1 may constitute approximately half the circumference of the strip core, and two anisotropic electrical steel sheets 1 may form one layer of the strip core body 10 through two connecting parts 6, as shown in the example of FIG. 6 (two sheets 1 of anisotropic electrical steel are connected to each other by means of two connecting parts 6 for each turn).

[0032]

The thickness of the anisotropic electrical steel sheet 1 used in the present embodiment is not particularly limited and can be suitably selected depending on the application and the like, but is generally in the range of 0.15 mm to 0.35 mm, and is preferably in the range of 0.18 mm - 0.23 mm.

[0033]

2. Configuration of anisotropic electrical steel sheets

Next, the configuration of the anisotropic electrical steel sheets 1 constituting the main part 10 of the strip core will be described. The present embodiment has features such as the shape of the intermediate layer near the curved portions 5 of adjacent laminated electrical steel sheets and the positioning of the location of the electrical steel sheets in the core with the shape of the intermediate layer being controlled.

[0034]

(1) The shape of the intermediate layer in the flat part adjacent to the curved part

In the anisotropic electrical steel sheets 1 constituting the strip core of the present embodiment, the shape of the intermediate layer in the laminated steel sheets is controlled to be thin and smooth near at least a portion of the curved portions 5. If the shape of the intermediate layer near the curved portions 5 is thick and uneven, the efficiency of the core of the present embodiment is significantly deteriorated.

Although the mechanism by which this phenomenon occurs is unclear, it is believed to be as follows.

The target core of the present embodiment is designed so that the flat parts 4, 4a, which are practically not deformed, are relatively very wide, so that the magnetic properties of the steel sheets, which sufficiently reflect the properties of the core, as well as the stress (strain) due to bending were limited to very narrow regions near the curved parts 5. For this reason, deterioration of the magnetic properties in the regions near the curved parts 5 affects the properties of the entire core. It is believed that the deterioration of magnetic properties in the curved portions 5 is mainly caused by a change in the structure of the magnetic domains, including the amount of introduced lattice defects such as dislocation density and the resulting change in crystal orientation. There is almost no practical guidance for controlling the change in the structure of magnetic domains due to bending deformation with an extremely small diameter, which is the purpose of the present embodiment. However, in accordance with the knowledge that forms the basis of the present embodiment, it is believed that when the shape of the intermediate layer is thin and smooth, the change in the structure of the magnetic domains when the same voltage is applied is small, and favorable magnetic properties are more likely to be maintained. It is simply believed that if the intermediate layer, which is relatively harder than the main steel sheet, is thick and has a complex boundary shape with the main steel sheet, complex deformation occurs, especially in the area of the surface layer (near the boundary with the intermediate layer) of the main steel sheet , which complicates the structure of magnetic domains and significantly worsens magnetic properties. It is believed that this mechanism of action of the present embodiment is a special phenomenon in the core with a specific shape, which is the purpose of the present embodiment. Although this mechanism has hardly been considered until now, it can be interpreted that it is consistent with the information obtained by the authors of the present invention.

[0035]

In the specification of the present patent application, the term "intermediate layer" generally means a layered region (in the form of a film) located between the base steel sheet, which is an α-Fe phase, and the insulating coating imparting tension and insulation to the anisotropic electrical steel sheets 1 so as to guarantee adhesion to the base steel sheet and insulating coating. The material of the intermediate layer is not limited to forsterite, SiO ₂ , and TiN mentioned above in the Background Art section, and known substances for the above purpose are also contemplated. In addition, considering the mechanism of the effect of the present embodiment, a substance having a significant difference in deformability compared with the base steel sheet is targeted. In the present embodiment, it is defined as a compound. Thus, the target intermediate layer of the present embodiment consists of oxides, carbides and nitrides of metal elements and their composites. These are substances that are known to play an adhesion role when sandwiched between the base steel sheet and the insulating coating in the anisotropic electrical steel sheets 1.

In the case where the difference in deformability between the base steel sheet and the intermediate layer is small, the entire interface is deformed uniformly, regardless of the thickness or shape of the intermediate layer. Therefore, the effect of the present embodiment does not need to be applied, and at the same time, the effect of the present embodiment is not exhibited.

[0036]

In the present embodiment, the shape of the intermediate layer is measured as follows.

The anisotropic electrical steel sheets 1 taken from the core are observed in a cross section parallel to the side surface of the core. The observation method can be ordinary and does not require a special method. Since the thickness of the target intermediate layer of the present embodiment is very small, its cross section is observed using a transmission electron microscope (STEM) to measure the thickness of the intermediate layer.

[0037]

Specifically, in the first flat portions 4 and the second flat portions 4a of the regions adjacent to the curved portions 5 on the above-mentioned observed cross-section, quantitative analysis is performed at 101 positions (i.e., a 10 μm measurement area) defined at 0.1 μm intervals in direction (longitudinal direction) along the surface of the steel sheet at 1 nm intervals in the sheet thickness direction using energy dispersive X-ray spectroscopy (EDS) with an electron beam diameter of 10 nm. The region in which the total concentration of the constituent elements of the intermediate layer material (for example, the total concentration of Si and O if the intermediate layer is SiO ₂ or the total concentration of Ti and N if the intermediate layer is TiN) is 50 at.% or more, is considered as an intermediate layer and its thickness is determined.

In the present embodiment, with respect to the regions of the first flat portion 4 and the second flat portion 4a adjacent to the curved portion 5, the regions of the first flat portion 4 and the second flat portion 4a separated by more than twice the length of the curved portion 5 from the boundaries between the curved portion 5 and the first flat part 4 and between the curved part 5 and the second flat part 4a are set as the measuring area of the intermediate layer. Here, the reason why this region should be more than twice the length of the curved portion 5 is that the influence of the deformation of the intermediate layer due to bending can be avoided if the region is separated by such a distance from the curved portion 5. It should be noted that the effect of the present embodiment is initially expressed by an action mechanism according to the shape of the intermediate layer inside the curved portion 5 as described above, and is essentially evaluated by how the intermediate layer inside the curved portion 5 is deformed or how it affects the deformation of the main steel sheet. However, since the intermediate layer inside the curved portion 5 is deformed in a complex manner, and the structure of the main steel sheet is also changed in a complex manner according to its shape as described above, it is considered difficult to quantify the deformation and change as the definition of the present embodiment. For this reason, in the present embodiment, the quantitative value corresponding to the manifestation of the above action mechanism is determined by the state before applying the bending deformation, that is, the shape of the intermediate layer of the first flat portion 4 and the second flat portion 4a.

The area of the second flat part 4a is inside the corner part 3, and the area of the first flat part 4 is outside the corner part 3. The shape of the intermediate layer is determined by the second flat part 4a and/or the first flat part 4 in at least one curved part 5.

[0038]

In the present embodiment, characteristic values related to the shape of the intermediate layer are further determined as follows from 101 intermediate layer thickness measurement values that are obtained as described above.

For example, as shown in FIG. 7, first, the average thickness T (nm) of the intermediate layer at 101 positions (measuring positions) is determined as Tave (nm), the maximum thickness is determined as Tmax (nm), the minimum thickness is determined as Tmin (nm), the average value of the data, where T >Tave is defined as To (nm), and the average of the data, where T < Tave, is defined as Tu (nm). In addition, in the thickness distribution along the surface direction of steel sheets (longitudinal direction), the area in which the measurement values at T>Tave are continuous is considered as one area, and the number of these areas within the entire measurement area is defined as N. This N represents the number convex areas within the 10 µm measurement area. Thus, in a measurement region of 10 μm, when a continuous region thicker than Tave (the region protruding in the thickness direction) is considered as a convex region, N is the number of convex regions.

Here, the above-mentioned interlayer shape is measured on the outer side and inner side of the steel sheets, and the values obtained on the surfaces are averaged to determine Tave, Tmax, Tmin, To, Tu and N of the steel sheets. The outer side of the steel sheets is shown schematically in Fig. 7, and the thickness of the intermediate layer is exaggerated for ease of explanation. In addition, although an insulating coating is formed on the intermediate layer, it will not be illustrated.

[0039]

In the present embodiment, at least one of the two or more curved portions 5 present in at least one corner portion 3 satisfies the following Equations (1) to (3).

Tave ≤ 40 nm (1)

(To-Tu)/Tave ≤ 0.50 (2)

Tave (To-Tu) ≤ 240 nm ² (3)

The definition of Equation (1) is not special, but is a general definition corresponding to anisotropic electrical steel sheets 1 in which the intermediate layer boundary is mirror polished. The left side of Equation (1) is preferably 20 nm or less, and more preferably 10 nm or less.

It can be said that Equation (2) is one of the definitions indicating a characteristic feature of the present embodiment. Considering the above mechanism, this definition means that small variation (difference between the convex part and the concave part) in the thickness of the intermediate layer is a necessary condition. The left side of Equation (2) is preferably 0.3 or less, and more preferably 0.2 or less.

Equation (3) is one of the definitions indicating a characteristic feature of the present embodiment. This definition means that the thinner the intermediate layer, the more variation (the difference between the convex part and the concave part) in the thickness of the intermediate layer is allowed. This is considered to be a definition corresponding to an index for assessing the degree of influence on the base steel sheet when steel sheets coated with a harder coating than the base steel sheet are bent and deformed. The left side of Equation (3) is preferably 200 nm ² or less, and more preferably 180 nm ² or less.

If the above Equations (1) to (3) are satisfied, the magnetic domain structure of the curved parts 5 becomes a structure in which the influence of bending is minimized, and the effect of the present embodiment is exhibited. In addition to this, it goes without saying that in one corner portion 3, it is preferable that all curved portions 5 existing in that corner portion 3 satisfy the above Equations (1) to (3). Moreover, it goes without saying that it is preferable that all four corner portions 3 existing in the strip core satisfy the above Equations (1) to (3).

[0040]

In another embodiment, at least one of the two or more curved portions 5 present in at least one corner portion 3 satisfies Equation (4) below.

N (To-Tu)≤24 nm (4)

This definition means the degree of steepness of the variation of the thickness of the sheet of the intermediate layer, that is, the degree of change in the thickness of the sheet from the convex part to the concave part of the distribution of the sheet thickness in the region along the intermediate layer. If this value is large, the thickness of the sheet changes quickly in the local region of the intermediate layer, the main steel sheet in the curved parts 5 is deformed in a complex manner, and the structure of the magnetic domains becomes more complex. Consequently, the efficiency of the core decreases. In addition to this, it goes without saying that in one corner portion 3, it is preferable that all curved portions 5 existing in that corner portion 3 satisfy the above Equation (4). Moreover, it goes without saying that it is preferable that all four corner portions 3 existing in the strip core satisfy the above Equation (4).

[0041]

In yet another embodiment, at least one of the two or more curved portions 5 present in at least one corner portion 3 satisfies Equation (5) below.

N ≥ 2 (5)

From the point of view of Equation (4) above, the definition seems strange because it means that the degree of steepness increases. However, this means that when N exceeds a certain level, that is, when the variation interval of the sheet thickness from the convex part to the concave part, the sheet thickness distribution in the region along the intermediate layer becomes very narrow, even if the degree of steepness estimated by Equation (4) is high meaning, the complication of the structure of magnetic domains in the curved parts 5 is minimized. Although the reason for this is unclear, it is believed that there is a limit to the complexity and refinement of the structure of magnetic domains, even if the amount of variation in the shape of the boundary is reduced to some extent, and therefore the boundary acts as a flat boundary. According to the above Equation (5), if the sheet thickness variation interval (step) is 5 μm or less, the influence of the base steel sheet on the magnetic domain structure is interpreted as being closer to that of a flat surface. In addition to this, it goes without saying that in one corner portion 3, it is preferable that all curved portions 5 existing in that corner portion 3 satisfy the above Equation (5). Moreover, it goes without saying that it is preferable that all four corner portions existing in the strip core satisfy the above Equation (5).

[0042]

In yet another embodiment, at least one of the two or more curved portions 5 present in at least one corner portion 3 satisfies Equation (6) below.

(Tmax-Tmin)<Tave (6)

This definition is simply an index indicating the relative amount of variation in the thickness of the interlayer sheet. Intuitively, it can be understood that the smaller the value of Equation (6), the more preferable it is, but it has a special meaning in the present embodiment. In other words, since the target intermediate layer of the present embodiment is very thin, there is an inevitable concern that an abnormal portion may be produced due to variations in industrial production conditions. For example, there may be several areas where the intermediate layer is missing. The present embodiment specifies that it is preferable that such areas be minimized. In addition to this, it goes without saying that in one corner portion 3, it is preferable that all curved portions 5 existing in that corner portion 3 satisfy the above Equation (6). Moreover, it goes without saying that it is preferable that all four corner portions 3 existing in the strip core satisfy the above Equation (6).

[0043]

(2) Anisotropic electrical steel sheets

As described above, the base steel sheet of anisotropic electrical steel sheets 1 used in the present embodiment is a steel sheet in which the crystal grain orientations are highly concentrated in the {110}<001> orientation, and which has excellent magnetic properties in the rolling direction.

A known anisotropic electrical steel sheet can be used as the base steel sheet in the present embodiment. Next, one example of a preferred base steel sheet will be described.

[0044]

The base steel sheet has the following chemical composition, in wt.%: Si: from 2.0% to 6.0%, with the balance being Fe. This chemistry allows the crystal orientation to be controlled to a Goss texture concentrated in the {110}<001> orientation to provide favorable magnetic properties. Other elements are not particularly limited, and known elements may be contained in a known range instead of Fe. The content ranges of representative elements are as follows.

C: 0-0.0050%,

Mn: 0-1.0%,

S: 0-0.0150%,

Se: 0-0.0150%,

Al: 0-0.0650%,

N: 0-0.0050%,

Cu: 0-0.40%,

Bi: 0-0.010%,

B: 0-0.080%,

P: 0-0.50%,

Ti: 0-0.0150%,

Sn: 0-0.10%,

Sb: 0-0.10%,

Cr: 0-0.30%,

Ni: 0-1.0%,

Nb: 0-0.030%,

V: 0-0.030%,

Mo: 0-0.030%,

Ta: 0-0.030%,

W: 0-0.030%,

Since these optional elements may be contained depending on the specific purpose, there is no need to limit them to a lower limit, and therefore the optional elements may not be substantially contained. In addition to this, even if these optional elements are contained as impurities, the effect of the present embodiment is not deteriorated. Impurities refer to elements that are unintentionally contained and mean elements that enter the steel from ore, scrap metal, industrial environment, etc. in the industrial production of basic steel sheet.

[0045]

The chemical component of the base steel sheet can be measured using a conventional analytical method for steel. For example, the chemical composition of a base steel sheet can be measured using inductively coupled plasma atomic emission spectrometry (ICP-AES). Specifically, the chemical composition can be determined, for example, by taking a 35 mm square test piece from the center position of the base steel sheet after removing the coating and measuring with an ICPS-8100 measuring instrument manufactured by Shimadzu Corporation or the like. based on a calibration curve prepared in advance. The C and S contents can be measured by using an infrared flame absorption method, and the N content can be measured by using an inert gas melting thermal conductivity method.

[0046]

The above chemical composition is the composition of the base steel sheet. In the case where the anisotropic electrical steel sheet 1 used as a measurement sample has on its surface, for example, an insulating coating and a primary coating (such as a glass film or an intermediate layer) made from an oxide or the like, a chemical the composition is measured after removing this coating, etc. by known methods.

[0047]

(3) Method for producing anisotropic electrical steel sheet

The method for producing anisotropic electrical steel sheet 1 is not particularly limited, and the conventionally known method for producing anisotropic electrical steel sheet can be suitably selected. Preferable specific examples of the production method include a method in which a slab containing 0.04 to 0.1 mass% C and otherwise having the chemical composition of the above-mentioned anisotropic electrical steel sheet 1 is heated to 1000°C or higher to perform hot rolling, and then hot annealing as required, the cold rolled steel sheet is then obtained by cold rolling one, two or more times, including intermediate annealing, heated at 700°C - 900°C, for example, in a humid hydrogen atmosphere and inert gas, undergoes decarburization annealing, further undergoes nitriding annealing as necessary, and undergoes final annealing at approximately 1000°C after applying an annealing separator to the cold-rolled steel sheet to form an insulating coating at a temperature of approximately 900°C. Additionally, a coating can then be applied to adjust the dynamic coefficient of friction.

In addition to this, the effect of the present embodiment can be obtained even with a steel sheet that has been subjected to a treatment called "magnetic domain control" in the steel sheet manufacturing process in a known manner.

[0048]

The method for controlling the shape of the intermediate layer, which is a feature of the anisotropic electrical steel sheet 1 used in the present embodiment, is not particularly limited, but a known method can be used as appropriate. For example, various forms of intermediate layers can be formed by thermal oxidation after final annealing using an annealing separator consisting primarily of alumina (Al ₂ O ₃ ). Alternatively, after final annealing using an annealing separator consisting mainly of magnesium oxide (MgO), the forsterite formed on the surface of the steel sheet can be removed by etching or grinding, and then oxidation behavior during the baking temperature raising process to form an insulating coating can be manipulated to form different shapes of intermediate layers.

[0049]

3. Method for producing strip core

The method for producing a strip core according to the present embodiment is not particularly limited as long as it is capable of producing a strip core according to the present embodiment, and, for example, the methods for known strip cores described in Prior Art Patent Documents 9 to 11 can be applied. In particular, it can be mentioned that the optimal way is to use the UNICORE production device (https://www.aemcores.com.au/technology/unicore/) from AEM UNICORE.

[0050]

Moreover, heat treatment can be performed as necessary according to a known method. In addition, the resulting strip core body 10 can be used as a strip core without modification, or can be used as a strip core obtained by jointly fixing a plurality of stacked anisotropic electrical steel sheets 1 using a known lock as needed, such as like strapping tape.

[0051]

The present embodiment is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any shape which has substantially the same configuration and shows an effect similar to the technical idea described in the claims of the present invention is also within the scope of the present invention.

[Examples]

[0052]

In the following, the technical details of the present invention will be further described with reference to examples of the present invention. The conditions in the examples shown below are examples of conditions used to confirm the feasibility and effect of the present invention, and the present invention is not limited to these example conditions. In addition to this, the present invention may use various conditions as long as the object of the present invention is achieved without deviating from the spirit of the present invention.

[0053]

(Anisotropic electrical steel sheets)

A slab having the chemical composition shown in Table 1 (in wt.%, with the rest being Fe) was used as a material to produce a final product having the chemical composition (in wt.%, with the rest being Fe) shown in Table 2.

In Tables 1 and 2, “-” means that the item was not used, the item was not controlled, and thus its content was not measured.

[0054]

[Table 1]

Steel type Slab C Si Mn S Al N Cr Bi Nb A 0.060 3.36 0.10 0.007 0.028 0.008 0.11 - - B 0.060 3.41 0.11 0.006 0.029 0.008 0.12 - 0.007 C 0.060 3.37 0.11 0.006 0.028 0.008 0.11 0.002 - D 0.080 3.26 0.08 0.025 0.027 0.008 - - -

[0055]

[Table 2]

Steel type Final product C Si Mn S Al N Cr Bi Nb A 0.001 3.25 0.07 0.0007 0.011 0.0008 0.11 - - B 0.001 3.30 0.07 0.0008 0.010 0.001 0.12 - 0.005 C 0.001 3.27 0.07 0.0007 0.012 0.001 0.11 0.002 - D 0.001 3.17 0.10 0.0007 0.009 0.0008 - - -

[0056]

The production process corresponds to the production conditions for well-known anisotropic electrical steel sheets.

Hot rolling, hot annealing and cold rolling were performed. Some of the cold rolled steel sheets after decarburization annealing have been subjected to nitriding treatment (nitriding annealing) in a mixed atmosphere of hydrogen, nitrogen and ammonia.

In addition, the main component was magnesium oxide or alumina, and the annealing separator with different mixing ratios was applied and subjected to final annealing. An insulating coating solution containing chromium and consisting mainly of phosphate and colloidal silica was applied to primary films formed on the surfaces of final annealed steel sheets and heat treated to form an insulating coating. For some materials, the TiN coating was formed by ion metallization of the surface of the base steel sheet, which was obtained by peeling off the primary film during the final annealing of the steel sheets and performing a mirror finish, and then an insulating coating solution containing chromium and consisting of mainly from phosphate and colloidal silica, and was heat treated to form an insulating coating.

[0057]

In this way, a steel sheet was produced with an adjustable type and shape of the intermediate layer located between the main steel sheet and the insulating coating to ensure adhesion. The details of the produced steel sheet are shown in Table 3.

[0058]

[Table 3]

Steel Sheet No. Steel type Hot rolling Hot annealing Cold rolling Decarburization annealing Nitriding Annealing separator Final annealing Processing to form an intermediate layer Properties Heating temperature Finish temperature Rewinding temperature Sheet thickness Temperature Time Sheet thickness Cold rolling coefficient Temperature Time Magnesium oxide Alumina Additive Temperature Time B8 Magnetic losses °C °C °C mm °C With mm % °C With % % °C hour Tl W/kg A1 A 1150 900 540 2.7 1100 20 0.35 87% 800 180 Made 20 80 No 1200 20 Oxidative treatment at 800°C, PH2O/PH2=0.1 1.94 1.12 A2 A 1150 900 540 2.7 1100 20 0.35 87% 800 180 100 0 Titanium oxide 1200 20 No 1.93 1.13 A3 A 1150 900 540 2.7 1100 20 0.35 87% 800 180 100 0 Titanium oxide 1200 20 Cleaning and smoothing and then TiN coating 1.93 1.12 A4 A 1150 900 540 2.7 1100 20 0.35 87% 800 180 100 0 No 1200 20 No 1.93 1.13 B1 B 1150 880 650 2.3 1150 thirty 0.23 90% 820 120 Made 20 80 No 1200 20 Oxidative treatment at 800°C, PH2O/PH2=0.1 1.92 0.82 B2 B 1150 880 650 2.3 1150 thirty 0.23 90% 820 120 100 0 Titanium oxide 1200 20 No 1.92 0.83 B3 B 1150 880 650 2.3 1150 thirty 0.23 90% 820 120 100 0 Titanium oxide 1200 20 Cleaning and smoothing and then TiN coating 1.92 0.82 B4 B 1150 880 650 2.3 1150 thirty 0.23 90% 820 120 100 0 No 1200 20 No 1.92 0.84 C1 C 1150 900 750 2.6 1100 25 0.26 90% 850 150 Made 20 80 No 1200 20 Oxidative treatment at 800°C, PH2O/PH2=0.1 1.92 0.87 C2 C 1150 900 750 2.6 1100 25 0.26 90% 850 150 100 0 Titanium oxide 1200 20 No 1.93 0.88 C3 C 1150 900 750 2.6 1100 25 0.26 90% 850 150 100 0 Titanium oxide 1200 20 Cleaning and smoothing and then TiN coating 1.92 0.88 C4 C 1150 900 750 2.6 1100 25 0.26 90% 850 150 100 0 No 1200 20 No 1.92 0.87 D1 D 1350 1030 540 2.4 1100 20 0.26 89% 850 150 No 20 80 No 1200 20 Oxidative treatment at 800°C, PH2O/PH2=0.1 1.93 0.87 D2 D 1350 1030 540 2.4 1100 20 0.26 89% 850 150 100 0 Titanium oxide 1200 20 No 1.93 0.86 D3 D 1350 1030 540 2.4 1100 20 0.26 89% 850 150 100 0 Titanium oxide 1200 20 Cleaning and smoothing and then TiN coating 1.92 0.88 D4 D 1350 1030 540 2.4 1100 20 0.26 89% 850 150 100 0 No 1200 20 No 1.92 0.87

[0059]

(Metal core)

Cores a - h having the shapes shown in Table 4 and FIG. 8, were produced using each steel sheet as the material. Here, cores g and h were not used for testing as single cores, but three of each were prepared as single cores and arranged in an equilateral triangular cylindrical shape, as shown in Fig. 9, and a three-phase strip core (for example, the metal core shown in Japanese Unexamined Patent Application, First Publication No. 2005-333057) obtained by winding a coil around each leg (the part including the first flat part 4) was prepared. In addition to this, three single metal cores are arranged symmetrically around the axis of an equilateral triangular cylinder. Fig. 9(a) is a front view illustrating a schematic configuration of a three-phase strip core, and FIG. 9(b) is a cross section along line A-A in FIG. 9(a).

L1 is parallel to the X-axis direction and is the distance between the parallel anisotropic electrical steel sheets 1 at the innermost periphery of the strip core in the flat cross section including the center CL (distance between the inner flat parts). L2 is parallel to the Z-axis direction and is the distance between the parallel anisotropic electrical steel sheets 1 at the innermost periphery of the strip core in the vertical cross section including the center CL (the distance between the inner flat parts). L3 is parallel to the X-axis direction and is the lamination thickness (thickness in the lamination direction) of the strip core in a flat cross section including the center CL. L4 is the width of the laminated steel sheets of the strip core in a flat cross section parallel to the X-axis direction and including the center CL. L5 is the distance between flat parts (distance between curved parts) that are adjacent to each other in the innermost part of the strip core and together form a right angle. In other words, L5 is the shortest length of the flat portion 4a in the longitudinal direction between the flat portions 4, 4a of the anisotropic electrical steel sheet at the innermost periphery. r is the radius of curvature of the bent portion on the inner side of the strip core, and φ is the bending angle of the bent portion of the strip core. The substantially rectangular cores a to h, in which the flat portions having a distance L1 between the flat portions on the inner side are separated approximately at the center of the distance L1, have a structure in which two cores having a substantially U-shape are joined. Here, the core f is a core that is traditionally used as an ordinary strip core, and is produced by a method in which steel sheets are wound into a cylindrical shape, the corner portions 3 of the cylindrical laminated body are then compressed so that they have a constant curvature, and the cylindrical laminated body is formed essentially into a rectangular shape and then annealed to maintain that shape. For this reason, the radius of curvature r of the curved part 5 varies significantly depending on the position of the fusion of the steel sheets. r in Table 4 means r on the innermost surface. r increases outward and is approximately 90 mm at the outermost periphery.

[0060]

[Table 4]

Core No. Core shape L1 L2 L3 L4 L5 r φ mm mm mm mm mm mm ° a 300 180 60 150 25 1 45 b 300 180 60 150 25 3 45 c 300 180 60 150 25 6 45 d 300 180 60 150 25 5 thirty e 300 180 60 150 25 8 45 f 300 180 60 150 0 thirty 90 g 300 180 60 100 25 2 90 h 300 180 60 100 25 6 90

[0061]

(Evaluation method)

(1) Magnetic properties of anisotropic electrical steel sheet

The magnetic properties of anisotropic electrical steel sheet 1 were measured by the Single Sheet Tester (SST) method defined in JIS C 2556:2015.

As magnetic properties, the magnetic flux density B8 (T) of the steel sheet in the rolling direction under excitation current with a density of 800 A/m and magnetic losses at an alternating current frequency of 50 Hz and an excitation magnetic flux density of 1.7 T were measured.

(2) Shape of the intermediate layer

As described above, the shape of the intermediate layer was measured by observing the cross section of a steel sheet taken from the core.

(3) Core efficiency

The efficiency of the core was measured by measuring the power of a core made of steel sheets.

[0062]

The efficiency was evaluated in different metal cores produced using different steel sheets with different magnetic domain widths. The results are shown in Table 5. It can be observed that even when the same type of steel is used, the performance of the core can be improved by suitable control of the shape of the intermediate layer.

[0063]

[Table 5]

Test No. Steel Sheet No. Core No. Properties of the metal core Notes r
mm Tave
nm To
nm Tu
nm (To-Tu)/Tave Tave(To-Tu)
nm ² Tmax
nm Tmin
nm N Losses
W 1-1 A1 a 1 20 25 17 0.400 160 35 15 3 83.0 Example according to the invention 1-2 A2 a 1 3409 3943 2760 0.347 4032847 4524 2400 8 89.7 Comparative example 1-3 A3 a 1 19 23 17 0.316 114 33 15 3 83.5 Example according to the invention 1-4 A4 a 1 1867 2754 1588 0.625 2176922 2960 1456 7 88.7 Comparative example 1-5 B1 a 1 24 28 18 0.417 240 34 15 2 63.2 Example according to the invention 1-6 B2 a 1 3305 3694 2684 0.306 3338050 4432 2544 6 68.5 Comparative example 1-7 B3 a 1 22 26 19 0.318 154 34 15 3 63.8 Example according to the invention 1-8 B4 a 1 1798 2988 1654 0.742 2398532 3021 1455 5 67.8 Comparative example 1-9 C1 a 1 22 24 18 0.273 132 29 16 2 68.9 Example according to the invention 1-10 C2 a 1 3642 3988 3222 0.210 2789772 4021 3001 7 74.2 Comparative example 1-11 C3 a 1 21 25 17 0.381 168 29 14 2 68.4 Example according to the invention 1-12 C4 a 1 1877 2888 1540 0.718 2530196 3005 1336 8 72.3 Comparative example 1-13 D1 a 1 22 24 18 0.273 132 29 16 2 67.9 Example according to the invention 1-14 D2 a 1 3642 3988 3222 0.210 2789722 4021 3001 7 73.9 Comparative example 1-15 D3 a 1 21 25 17 0.381 168 29 14 2 68.7 Example according to the invention 1-16 D4 a 1 1877 2888 1540 0.718 2530196 3005 1336 8 73.1 Comparative example 1-17 A1 b 3 20 25 17 0.400 160 35 15 3 84.5 Example according to the invention 1-18 A2 b 3 3409 3943 2760 0.347 4032847 4524 2400 8 87.7 Comparative example 1-19 B1 b 3 24 28 18 0.417 240 34 15 2 64.4 Example according to the invention 1-20 B2 b 3 3305 3694 2684 0.306 3338050 4432 2544 6 68.2 Comparative example 1-21 C1 c 6 22 24 18 0.273 132 29 16 2 71.2 Comparative example 1-22 C3 c 6 21 25 17 0.381 168 29 14 2 70.9 Comparative example 1-23 D1 d 5 22 24 18 0.273 132 29 16 2 68.1 Example according to the invention 1-24 D3 d 5 21 25 17 0.381 168 29 14 2 68.4 Example according to the invention 1-25 A1 e 8 20 25 17 0.400 160 35 13 3 87.6 Comparative example 1-26 A3 e 8 19 23 17 0.316 114 33 13 3 88.0 Comparative example 1-27 B1 e 8 24 28 18 0.417 240 34 15 2 66.8 Comparative example 1-28 B3 e 8 22 26 19 0.318 154 34 15 3 66.5 Comparative example 1-29 C1 f thirty 22 24 18 0.273 132 29 16 2 73.6 Comparative example 1-30 C3 f thirty 21 25 17 0.381 168 29 14 2 74.1 Comparative example 1-31 D1 f thirty 22 24 18 0.273 132 29 16 2 73.6 Comparative example 1-32 D3 f thirty 21 25 17 0.381 168 29 14 2 73.8 Comparative example 1-33 A1 g 2 20 25 17 0.400 160 35 13 3 150.4 Example according to the invention 1-34 A3 g 2 19 23 17 0.316 114 33 13 3 154.5 Example according to the invention 1-35 B1 g 2 24 28 18 0.417 240 34 15 2 138.4 Example according to the invention 1-36 B3 g 2 22 26 19 0.318 154 34 15 3 139.6 Example according to the invention 1-37 A1 H 6 20 25 17 0.400 160 35 13 3 168.7 Comparative example 1-38 A3 h 6 19 23 17 0.316 114 33 13 3 170.4 Comparative example 1-39 B1 h 6 24 28 18 0.417 240 34 15 2 145.9 Comparative example 1-40 B3 h 6 22 26 19 0.318 154 34 15 3 154.1 Comparative example

[0064]

From the above results, it can be seen that the tape cores of the present invention are very effective because at least one of the two or more curved portions 5 present in at least one corner portion 3 satisfies the above Equations (1) to (3).

INDUSTRIAL APPLICABILITY

[0065]

According to the present invention, unintended performance degradation in a strip core formed by laminating curved steel sheets can be effectively minimized.

BRIEF DESCRIPTION OF REFERENCE SYMBOLS

[0066]

1 - sheet of anisotropic electrical steel

2 - laminated structure

3 - corner part

4 - first flat part

4a - second flat part

5 - curved part

6 - connecting part

10 - the main part of the strip core.

Claims (22)

1. A strip core containing a rectangular strip core body in a side view, wherein the main body of the strip core has a portion of anisotropic electrical steel sheets, in which the first flat portions and the corner portions alternate continuously in the longitudinal direction, and an angle formed by the two first flat portions adjacent to each other with each of the corner portions therebetween , is 90°, stacked in the direction of the sheet thickness, and has a substantially rectangular laminated structure in side view, wherein each of the corner portions has two or more curved portions having a curved shape in a side view of the anisotropic electrical steel sheets, and a second flat portion between adjacent curved portions, and the sum of the bending angles of the curved portions in one corner portion is 90°, in which each curved part in side view has an internal radius of curvature r equal to 1-5 mm, wherein the sheets of anisotropic electrical steel have a chemical composition containing, in mass percent: C: up to 0.0050, not including 0, Si: 2.0-7.0, with the remainder of Fe and impurities, and have a texture oriented in Goss orientation, and wherein at least one of the two or more curved portions present in at least one corner portion satisfies the following equations (1) to (3), where the thickness T (nm) of the intermediate layer provided on the surface of the main steel sheet of the anisotropic electrical steel sheets is measured at a plurality of positions of the regions of the first and second flat parts adjacent to the curved parts, the average value of the thickness T (nm) of the intermediate layer is denoted as Tave (nm ), the maximum thickness is denoted by Tmax (nm), the minimum thickness is denoted by Tmin (nm), the average of the data where T>Tave is denoted by To (nm), and the average of the data where T<Tave is denoted by Tu ( nm). 2. Tape core according to claim 1, wherein at least one of the two or more curved portions present in at least one corner portion satisfies equation (4) below, where in the distribution of the thickness of the intermediate layer along the surface direction of steel sheets, the region in which the measurement values at T>Tave are continuous is considered to be one region, and the number of these regions within the entire measurement region is denoted as N. 3. Tape core according to claim 2, wherein at least one of the two or more curved portions present in at least one corner portion satisfies the following equation (5) 4. Tape core according to claim 1, wherein at least one of the two or more curved portions present in at least one corner portion satisfies the following equation (6)