RU2814178C1 - Strip core - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: strip core has a main portion obtained by laminating a plurality of polygonal annular anisotropic electrical steel sheets in a side view, wherein the anisotropic electrical steel sheet has flat portions and curved portions that alternate continuously in the longitudinal direction, wherein at least one curved portion has a crystalline grain size Dpx in the anisotropic electrical steel sheet of 2W or less, where W is the width of the curved portion in the side view (mm).

EFFECT: minimized deterioration in efficiency due to the combination of the shape of the metal core in the steel sheet used.

3 cl, 5 tbl, 8 ex

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. 2020-179266, filed on 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 sheet are significantly affected by the degree of concentration in the {110}<001> orientation. In recent years, anisotropic electrical steel sheets that have been put into practical use are controlled so that the angle between the <001> crystal direction and the rolling direction is in the range of approximately 5°.

[0003]

Anisotropic electrical steel sheets are laminated (stacked) and used in transformer cores, 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]

In addition, the effect of crystal grain size in an anisotropic electrical steel sheet is well known, and Patent Documents 4 to 7 disclose a technique for improving properties by controlling the crystal grain size.

[0005]

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 the corner portion has a constant curvature, giving it is essentially rectangular in shape and then annealed to relieve stress and maintain shape.

[0006]

On the other hand, as another method for manufacturing the strip core, methods such as those described in Patent Documents 9 to 11 can be used, in which those portions of the steel sheets that become the corner portions of the strip core are bent in advance so as to form a relatively small bending area with a radius of curvature of 3 mm or less, and bent steel sheets are laminated to form a strip core. According to this production method, the usual large-scale pressing process is not required, the steel sheet is precisely bent to maintain the core shape, and the processing load is concentrated only in the bent part (corner), so that the stress removal according to the above annealing process can be eliminated, so it The industrial benefits are great and its applications are expanding.

BIBLIOGRAPHY

PATENT DOCUMENTS

[0007]

[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 3]

Japanese Unexamined Patent Application, First Publication No. H6-89805

[Patent Document 5]

Japanese Unexamined Patent Application, First Publication No. H8-134660

[Patent Document 6]

Japanese Unexamined Patent Application, First Publication No. H10-183313

[Patent Document 7]

WO 2019/131974

[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

[0008]

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 region having a radius of curvature of 5 mm or less is formed, and laminating the bent steel sheets to form a strip core, thereby minimizing the degradation in efficiency due to the combination the shape of the metal core and the steel sheet used.

REMEDIES FOR SOLVING THE PROBLEM

[0009]

The inventors of the present invention have studied in detail the effectiveness of a transformer metal core produced by a method of bending a steel sheet 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, they discovered that even when the material used is steel sheets with essentially the same crystal orientation control and essentially the same magnetic flux density and magnetic loss measured for a single sheet, there is a difference in the efficiency of the metal core.

[0010]

After investigating the cause, it was found that the difference in efficiency that is the problem is caused by the influence of the crystal grain size of the material. In addition to this, it has been found that the extent of this phenomenon (ie differences in core efficiency) also varies depending on the sizes and shapes of the core. In addition, when this phenomenon was studied in detail, it was particularly suggested that the cause was a difference in the degree of degradation of magnetic losses due to bending.

In this regard, various production conditions of steel sheet and metal core shape were studied, and their effects on the efficiency of the metal core were classified. As a result, it was found that if steel sheets produced under specific production conditions are used as metal core materials having specific sizes and shapes, then the efficiency of the metal core can be controlled to become the optimum efficiency according to the magnetic properties of the steel sheet material .

[0011]

The essence of the present invention, which was created to solve the above-described problem, is as follows.

The strip core according to one embodiment of the present invention is a strip core having a strip core body obtained by laminating a plurality of polygonal annular anisotropic electrical steel sheets in a sheet thickness direction in a side view,

wherein the anisotropic electrical steel sheet has flat parts and curved parts that continuously alternate in the longitudinal direction,

the curved portion in the side view has an inner radius r of curvature of 1 mm or more and 5 mm or less,

anisotropic electrical steel sheet has a chemical composition containing,

in mass percent:

Si: from 2.0 to 7.0%, with the remainder of Fe and impurities, and

has a texture oriented in Goss orientation, and

at least in one of the curved parts, the crystal grain size Dpx (mm) of the laminated anisotropic electrical steel sheet is 2W or less.

Here Dpx represents the average value of Dp according to the following Formula (1),

Dc (mm) is the average crystal grain size in the direction in which the boundary line extends (hereinafter referred to as "boundary direction") at the respective boundaries between the curved part and the two flat parts between which the curved part is placed,

Dl (mm) is the average crystal grain size at the boundary in the direction perpendicular to the boundary direction, and

W (mm) is the width of the curved part in the side view.

In addition, the average Dp value is the average of the Dp on the inside and the Dp on the outside of one flat portion between two flat portions and the Dp on the inside and Dp on the outside of the other flat portion.

Dp=√(Dc×Dl/π) (1)

[0012]

Moreover, the strip core according to another embodiment of the present invention is a strip core having a strip core body obtained by laminating a plurality of polygonal annular anisotropic electrical steel sheets in a sheet thickness direction in a side view,

wherein the anisotropic electrical steel sheet has flat parts and curved parts that continuously alternate in the longitudinal direction,

the curved portion in the side view has an inner radius r of curvature of 1 mm or more and 5 mm or less,

anisotropic electrical steel sheet has a chemical composition containing,

in mass percent:

Si: from 2.0 to 7.0%, with the remainder of Fe and impurities, and

has a texture oriented in Goss orientation,

at least in one of the curved parts, the crystal grain size Dpy (mm) of the laminated anisotropic electrical steel sheet is 2W or less,

where Dpy is the average value of Dl,

Dl (mm) is the average crystal grain size in the direction perpendicular to the boundary direction at the respective boundaries between the curved portion and the two flat portions between which the curved portion is placed, and

W (mm) is the width of the curved part in the side view.

In addition, the average Dl value is the average of the Dl on the inside and the Dl on the outside of one flat portion between two flat portions and the Dl on the inside and Dl on the outside of the other flat portion.

[0013]

In addition, another embodiment of the present invention provides a strip core having a strip core body obtained by laminating a plurality of polygonal annular anisotropic electrical steel sheets in a sheet thickness direction in a side view,

wherein the anisotropic electrical steel sheet has flat parts and curved parts that continuously alternate in the longitudinal direction,

the curved portion in the side view has an inner radius r of curvature of 1 mm or more and 5 mm or less,

anisotropic electrical steel sheet has a chemical composition containing,

in mass percent:

Si: from 2.0 to 7.0%, with the remainder of Fe and impurities, and

has a texture oriented in Goss orientation,

at least in one of the curved parts, the crystal grain size Dpz (mm) of the laminated anisotropic electrical steel sheet is 2W or less.

Here Dpz represents the average value of Dc,

Dc (mm) is the average crystal grain size in the boundary direction at the respective boundaries between the curved part and the two flat parts between which the curved part is placed,

W (mm) is the width of the curved part in the side view.

In addition, the average Dc value is the average of the Dc on the inside and the Dc on the outside of one flat portion between two flat portions and the Dc on the inside and Dp on the outside of the other flat portion.

USEFUL EFFECTS OF THE INVENTION

[0014]

According to the present invention, in a strip core formed by laminating curved anisotropic electrical steel sheets, performance degradation can be effectively minimized due to the combination of the shape of the core and the steel sheet used.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]

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

Fig. 4 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. 5 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. 6 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. 7 illustrates a method for measuring the crystal grain size of an anisotropic electrical steel sheet constituting a strip core according to the present invention, FIG. 7(a) is a schematic perspective view of the main parts, and FIG. 7(b) is a schematic cross-section of the main parts.

Fig. 8 is a schematic view showing the dimensional parameters of the strip cores produced in the examples and comparative examples.

OPTIONS FOR IMPLEMENTING THE INVENTION

[0016]

Next, a tape core in accordance with one embodiment of the present invention will be described in detail. However, the present invention is not limited only to the configuration disclosed in the present embodiment, but can be modified in various ways without departing from the spirit of the present invention. Here, the lower limit values and upper limit values are included in the numerical value limit ranges described below. Numeric values designated "greater than" or "less than" are not included in these numeric value ranges. In addition, unless expressly stated otherwise, "%" referring to chemical composition means "% by weight."

In addition, the terms "parallel", "perpendicular", "identical" and "right angle", as well as the values of length and angle used in this description to define shapes, geometric conditions and their degrees, are not strictly bound meaning and should be interpreted as including the extent to which similar functions can be expected.

In addition to this, in this specification, "anisotropic electrical steel sheet" may be simply described as "steel sheet" or "electrical steel sheet", and "tape core" may be simply described as "core".

[0017]

The strip core according to the present embodiment is a strip core having a strip core body obtained by laminating a plurality of polygonal annular anisotropic electrical steel sheets in a sheet thickness direction in a side view,

wherein the anisotropic electrical steel sheet has flat parts and curved parts that continuously alternate in the longitudinal direction,

the curved portion in the side view has an inner radius r of curvature of 1 mm or more and 5 mm or less,

anisotropic electrical steel sheet has a chemical composition containing,

in mass percent:

Si: from 2.0 to 7.0%, with the remainder of Fe and impurities, and

has a texture oriented in Goss orientation, and

at least in one of the curved parts, the crystal grain size Dpx (mm) of the laminated anisotropic electrical steel sheet is 2W or less.

Here Dpx (mm) is the average value of Dp (mm) according to the following Formula (1),

Dc (mm) is the average crystal grain size in the boundary direction at the respective boundaries between the curved part and the two flat parts between which the curved part is placed,

Dl (mm) is the average crystal grain size in the direction perpendicular to the boundary direction, and

W (mm) is the width of the curved part in the side view.

In addition, the average Dp value is the average of the Dp on the inside and the Dp on the outside of one flat portion between two flat portions and the Dp on the inside and Dp on the outside of the other flat portion.

Dp=√(Dc×Dl/π) (1)

[0018]

1. Shape of strip core and anisotropic electrical steel sheet

First, the shape of the band core of the present embodiment will be described. The shapes of the strip core and anisotropic electrical steel sheet described herein are not particularly new in themselves. For example, they 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 a strip core in accordance with one embodiment. 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.

Here, in the present embodiment, the side view is a view of the long-shaped anisotropic electrical steel sheet constituting the strip core in the width direction (in the Y-axis direction in FIG. 1). The side view shows the shape as seen from the side (view in the Y direction in Fig. 1).

[0019]

The strip core according to the present embodiment includes a strip core main body 10 in a side view, in which a plurality of annular polygonal (rectangular or polygonal) anisotropic electrical steel sheets 1 are laminated in the sheet thickness direction. The strip core main body 10 has a polygonal 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 the strip core without modification or may include, as needed, for example, a known lock such as a strapping strip for jointly securing a plurality of stacked anisotropic electrical steel sheets 1.

[0020]

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 portion 5 is constant, so that the magnetic loss occurring in the bent portion 5 remains constant. If the length of the metal core is longer, the volume ratio of the bent portion 5 to the main strip core portion 10 will be smaller, and the effect on magnetic loss degradation will also be small. Therefore, a longer length of the strip core body 10 is preferable. The length of the strip core body 10 is preferably 1.5 m or more, and more preferably 1.7 m or more. Here, in the present embodiment, the length of the strip core body 10 is the circumferential length at the center point in the laminating direction of the strip core body 10 in the side view.

[0021]

The tape core of the present embodiment can be suitably used for any conventionally known application. Particularly when it is applied to a power transformer where core efficiency is an issue, significant benefits can be achieved.

[0022]

As shown in FIG. 1 and 2, the strip core main body 10 includes a portion in which the anisotropic electrical steel sheets 1, in which the first flat portions 4 and the corner portions 3 alternate continuously in the longitudinal direction, and the angle formed by two adjacent first flat portions 4 in each of corner pieces 3, is 90°, are stacked in the direction of the sheet thickness, and has a substantially rectangular laminated structure 2 in side view. In addition to this, from another point of view, the strip core body 10 shown in FIG. 1 and 2 has an octagonal laminated structure 2. The strip core body 10 according to the present embodiment has an octagonal laminated structure, but the present invention is not limited to this, and in the strip core body in a side view there are a plurality of polygonal laminated anisotropic electrical steel annular sheets in the thickness direction of the sheet, and in anisotropic electrical steel sheets, flat parts and curved parts can be continuously alternated in the longitudinal direction (circumferential direction).

Next, the strip core main part 10 having a substantially rectangular shape including four corner parts 3 will be described.

Each corner portion 3 of the anisotropic electrical steel sheet 1 in a side view includes two or more curved portions 5 having a curved shape, and a second flat portion 4a between adjacent curved portions 5 and 5. Therefore, the corner portion 3 has a configuration including two or more curved parts 5 and one or more second flat parts 4a. In addition to this, the sum of the bending angles of the two curved parts 5 and 5 in one corner part 3 is 90°.

In addition to this, as shown in FIG. 3, each corner portion 3 of the anisotropic electrical steel sheet 1 in the side view includes three curved portions 5 having a curved shape, and a second flat portion 4a between adjacent curved portions 5 and 5, and the sum of the bending angles of the three curved portions 5, 5, and 5 in one corner part 3 is equal to 90°.

In addition, each corner portion 3 may include four or more curved portions. In this case also, a second flat portion 4a is provided between adjacent curved portions 5 and 5, and the sum of the bending angles of four or more curved portions 5 in one corner portion 3 is 90°. That is, the corner portions 3 according to the present embodiment are disposed between two adjacent first flat portions 4 and 4 at right angles, and include two or more curved portions 5 and one or more second flat portions 4a.

In addition to this, in the strip core body 10 shown in FIG. 2, the curved portion 5 is located between the first flat portion 4 and the second flat portion 4a, but in the main strip core portion 10 shown in FIG. 3, the curved part 5 is located between the first flat part 4 and the second flat part 4a, and also between the two second flat parts 4a and 4a. Thus, the second flat part 4a can be located between two adjacent second flat parts 4a and 4a.

In addition to this, in the strip core body 10 shown in FIG. 2 and Fig. 3, the first flat portion 4 has a longer length than the second flat portion 4a in the longitudinal direction (the circumferential direction of the core band body 10), but the first flat portion 4 and the second flat portion 4a may have the same length.

In this specification, the “first planar portion” and the “second planar portion” may be referred to simply as the “planar portion.”

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

The embodiment shown in FIG. 2 includes two curved portions 5 in one corner portion 3. The embodiment shown in FIG. 3 includes three curved parts 5 in one corner part 3.

[0023]

As shown in these examples, in the present embodiment, one corner portion may be formed with two or more curved portions, but in order to minimize the generation of distortion due to deformation during processing and minimize magnetic loss, the bending angle ϕ(ϕ1, ϕ2 , ϕ3) of the curved portion 5 is preferably 60° or less, and more preferably 45° or less.

In the embodiment of FIG. 2, including two curved parts in one corner part, in order to reduce magnetic loss, for example, ϕ1=60° and ϕ2=30°, and ϕ1=45° and ϕ2=45° can be set. In addition to this, in the embodiment of FIG. 3, including three curved parts in one corner part, in order to reduce magnetic loss, for example, ϕ1=30°, ϕ2=30° and ϕ3=30° can be set. In addition, in view of production efficiency, since it is preferable that the bending angles (bending angles) be equal, when one corner portion includes two curved portions, ϕ1=45° and ϕ2=45° are preferred. In addition to this, in the embodiment of FIG. 3, including three curved parts in one corner part, in order to reduce magnetic loss, for example, ϕ1=30°, ϕ2=30° and ϕ3=30° are preferred.

[0024]

The curved portion 5 will be described in more detail with reference to FIG. 6. Fig. 6 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 part is the angle difference occurring between the rear straight part and the front straight part in the bending direction on the bent part 5 of the anisotropic electrical steel sheet 1, and is expressed on the outer surface of the anisotropic electrical steel sheet 1 as an angle ϕ, which is a complementary angle to the angle formed by two virtual lines Lb-extent1 and Lb-extent2 obtained by extending the straight sections which are the surfaces of the flat parts 4 and 4a on both sides of the curved part 5. In this case, the point at which the extended straight line is separated from the surface of the steel sheet , is the boundary between the flat parts 4 and 4a and the curved part 5 on the outer surface of the steel sheet (points F and G in Fig. 6).

[0025]

In addition, straight lines perpendicular to the outer surface of the steel sheet extend from point F and point G, and their intersections with the inner surface of the steel sheet are point E and point D. Point E and point D are the boundaries between the flat parts 4 and 4a and a curved part 5 on the inner surface of the steel sheet.

Here, in the present embodiment, in the side view of the anisotropic electrical steel sheet 1, the curved part 5 is a part of the anisotropic electrical steel sheet 1 surrounded by point D, point E, point F and point 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.

[0026]

In addition to this, FIG. 6 shows the inner radius of curvature r (hereinafter simply referred to as the radius of curvature r) of the curved portion 5 in a side view. The radius of curvature r of the curved portion 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 greater curvature of the curved portion 5, and a larger radius of curvature r indicates less curvature of the curved portion 5.

In the strip core of the present embodiment, the radius of curvature r in each curved portion 5 of the anisotropic electrical steel sheets 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. If such variation is large, a representative value can be obtained by measuring the radii of curvature of a sufficiently large number of steel sheets and averaging them. In addition, it is possible to intentionally change for any reason, but the present embodiment does not exclude such a form.

[0027]

In addition, the method for measuring the inner radius of curvature r of the curved portion 5 is not particularly limited, and, for example, the inner radius of curvature r can be measured using a commercially available microscope (Nikon ECLIPSE LV150) with a magnification of 200x. Specifically, the center curvature point A, as shown in FIG. 6 is obtained from the observation result, and as a way to obtain it, for example, if the intersection of the straight line segment EF and the straight line segment DG, extended inward on the side opposite to point B, is determined as A, the value of the internal radius of curvature r corresponds to the length of the segment AC. Here, when point A and point B are connected by a straight line, the intersection on arc DE inside the curved part 5 is point C.

In the present embodiment, when the inner radius of curvature r of the curved portion 5 is in the range of 1 mm or more and 5 mm or less, and specific anisotropic electrical steel sheets with a controlled crystal grain size, which will be described below, are used to form the strip core, it is possible optimize the efficiency of the strip core according to the magnetic properties. The inner radius of curvature r of the curved portion 5 is preferably 3 mm or less. In this case, the effects of the present embodiment are more significant.

In addition, it is most preferable that all curved portions present in the metal core satisfy the inner radius of curvature r defined in the present embodiment. If there are bent portions that satisfy the inner radius of curvature r of the present embodiment and bent portions that do not satisfy the inner radius of curvature r in the strip core, it is desirable that at least half of the bent portions satisfy the inner radius of curvature r defined in the present embodiment .

[0028]

Fig. 4 and Fig. 5 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. 4 and Fig. 5, the anisotropic electrical steel sheet 1 used in the present embodiment is curved and includes a corner portion 3 composed of two or more curved portions 5 and a first flat portion 4, and forms a substantially rectangular ring in a side view through a connecting part 6, which is the end surface of one or more sheets 1 of anisotropic electrical steel in the longitudinal direction.

In the present embodiment, the entire strip core body 10 may have a substantially rectangular laminated structure 2 in a side view. As shown in the example in FIG. 4, one anisotropic electrical steel sheet 1 can form one layer of the strip core body 10 through one connecting part 6 (that is, one anisotropic electrical steel sheet 1 is connected through one connecting part 6 for each revolution), and as shown in the example in FIG. 5, one anisotropic electrical steel sheet 1 can form approximately half the circumference of the strip core, or two anisotropic electrical steel sheets 1 can form one layer of the strip core body 10 through two connecting parts 6 (that is, two anisotropic electrical steel sheets 1 are connected to each other via two connecting parts 6 for each revolution).

[0029]

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

[0030]

2. Configuration of anisotropic electrical steel sheet

Next, the configuration of the anisotropic electrical steel sheet 1 constituting the main part 10 of the strip core will be described. The present embodiment has features such as the crystal grain size of the flat portions 4 and 4a adjacent to the curved portion 5 of the anisotropic electrical steel sheets stacked on top of each other, and the position of the portion of the anisotropic electrical steel sheet with a controlled crystal grain size in core.

[0031]

(1) Crystal grain size of the flat part adjacent to the curved part

In the anisotropic electrical steel sheet 1 constituting the strip core of the present embodiment, at least in part of the corner portion, the crystal grain size of the laminated steel sheets is controlled so that it becomes smaller. If the crystal grain size near the curved portion 5 becomes coarse, the effect of preventing deterioration in the efficiency of the core in the present embodiment is not exhibited. In other words, when the crystal grain boundaries are located near the curved portion 5, it indicates that the degradation in efficiency can be easily minimized.

[0032]

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

In the metal core of the present embodiment, the macroscopic stress (strain) due to bending is limited to the curved portion 5, which is a very narrow region. However, when considering the crystal structure inside the steel sheet, it is believed that the dislocation formed in the bent portion 5 moves and propagates beyond the bent portion 5, that is, into the flat portions 4 and 4a. In this case, it is believed that in the anisotropic electrical steel sheets with a crystal grain size of several mm, which are used as the core material of the present embodiment, the crystal grain boundary acts as a strong obstacle to the movement of dislocation, and the movement of dislocation is confirmed within the single crystal grain, which can be considered like one single crystal. Thus, dislocations are not considered to form in adjacent crystal grains beyond crystal grain boundaries. It is well known that lattice defects such as dislocations significantly worsen magnetic losses. Therefore, when the crystal grain size near the bent portion becomes fine and the crystal grain boundary begins to function as an obstacle (dislocation elimination site) for the dislocation to move toward the flat portion, it is possible to keep the dislocation region very close to the bent portion 5. As a result, it is believed that it is possible minimize reduction in core efficiency. This operating mechanism of the present embodiment is considered to be a special phenomenon in the metal core having the specific shape of the present embodiment and has not been discussed much so far, but can be interpreted in accordance with the findings obtained by the inventors of the present invention.

[0033]

In the present embodiment, the crystal grain size is measured as follows.

When the laminated thickness of the steel sheets of the strip core main body 10 is T (which corresponds to "L3" in Fig. 8), a total of 5 anisotropic electrical steel sheets laminated at the positions of each T/4 including the innermost surface are removed from the innermost surface. the surface of the area including the corner portion of the main part 10 of the strip core. For each of the removed steel sheets, if the primary coating is made of oxide, etc. (glass coating and intermediate layer), insulating coating, etc. provided on the surface of the steel sheet, this coating is removed in a known manner, and then, as shown in FIG. 7(a), the crystalline structure of the inner surface and outer surface of the steel sheet is visually observed. Then, on the boundary line B between the curved portion and the flat portion, which is a substantially straight line on each surface, the particle size in the boundary direction (the direction in which the boundary line B extends (the direction perpendicular to the rolling direction of the anisotropic electrical steel sheet)) and the particle size in the direction perpendicular to the boundary direction (vertical boundary direction (rolling direction of the anisotropic electrical steel sheet)) is measured as follows.

The particle size Dc (mm) in the boundary direction is obtained, for example, as shown schematically in FIG. 7(a), according to the following Formula (2), when the length of the boundary line B (corresponding to the width of the anisotropic electrical steel sheet 1 constituting the core) is Lc, and the number of crystal grain boundaries intersecting the boundary line B is Nc.

Dc=Lc/(Nc+1) (2)

In addition to this, for particle size Dl (mm) in the vertical boundary direction (direction perpendicular to the boundary direction), in the direction of the extension of the boundary line B (boundary direction) at five positions excluding the end, among the positions obtained by dividing Lc by six , the distance from the boundary line B between one curved part 5 and the first flat part 4 as the starting point to the first intersection of a line running perpendicular to the boundary line B towards the region of the first flat part 4, the crystal grain boundaries are defined as Dl1 - Dl5 in the first flat part 4. In addition to this, the distances from the boundary line B between one curved part 5 and the second flat part (the flat part in the corner part) 4a as the starting point to the first intersection of a line running perpendicular to the boundary line B towards the area of the second flat part 4a , the boundary line B between the other adjacent curved portions 5 with the crystal grain boundary, or the second flat portion 4a between them are defined as Dl1 to Dl5 in the second flat portion. For the other curved part 5, Dl1 - Dl5 are obtained in the first flat part 4 and the second flat part 4a in a similar way. The particle size Dl in the vertical direction of the boundary is then obtained as the average distance for Dl1 - Dl5.

In addition to this, the crystal grain equivalent circle size Dp (mm) of the first flat portion 4 and the second flat portion 4a adjacent to the curved portion 5 is obtained by the following Formula (1).

Dp=√(Dc×Dl/π) (1)

In addition to this, as shown in FIG. 7(b), the suffix ii means the crystal grain size on the inside of the second flat part 4a, the suffix io means the crystal grain size on the outside thereof, the suffix oi means the crystal grain size on the inside of the first flat part 4, and the suffix oo means the crystal grain size grains on its outside. Thus, for one curved part 5, 12 crystal grain sizes are determined (Dcii, Dcio, Dcoi, Dcoo, Dlii, Dlio, Dloi, Dloo, Dpii, Dpio, Dpoi, Dpoo), i.e. (Dc, Dl, Dp) - (ii, io, oi, oo). Thus, for two or more curved portions 5 in each corner portion (for example, two curved portions in the tape core body 10 shown in FIG. 2 and three curved portions in the tape core body 10 shown in FIG. 3) , the above 12 crystal grain sizes are averaged, and for each corner portion, 12 crystal grain sizes are determined, i.e. (Dc, Dl, Dp) - (ii, io, oi, oo).

Here, generally, the anisotropic electrical steel sheet has a crystal grain size of several mm, which is very coarse compared with the thickness of the steel sheet. Therefore, in many cases, the single crystal grain penetrates from one surface of the steel sheet (for example, the inner side in the present embodiment) to another surface (for example, the outer side in the present embodiment) in a columnar form when observing the cross-section of the sheet along its thickness. Therefore, the crystal grain sizes measured on the inner side and the outer side as described above are the crystal grain sizes having essentially the same size, but in reality, fine crystal grains that do not penetrate through the thickness of the sheet may remain on surface layer, so that in the present embodiment, the crystal grain sizes are measured on both surfaces of the steel sheet, and their average value is used to determine the strip core of the present embodiment.

In the present embodiment, these crystal grain sizes are determined by comparison with the width W (mm) of the bent portion 5. In the present embodiment, the width W of the bent portion 5 is the average value of the inner surface length La of the bent portion 5 (length in the bending direction) (see FIG. 6) and the length of the outer surface of the curved part 5 Lb (length in the bending direction) (see Fig. 6).

[0034]

In one embodiment, at least one corner portion 3 fulfills the condition Dpx≤2W, where Dpx (mm) is the average value of Dp-(ii, io, oi, oo). This expression corresponds to the main feature of the mechanism described above. When this expression is satisfied, the crystal grain boundary can function as an obstacle to the movement of dislocations generated in the curved portion 5 to the first flat portion 4 and the second flat portion 4a, and as a result, the effects of the present embodiment are manifested. The reason why the upper limit of Dpx is twice W is that the dislocations generated in the bent part 5 move a distance of no more than twice the deformation region, and even if Dpx exceeds 2W, it is unlikely to become an obstacle to the movement of dislocations. Preferably, Dpx ≤ W. In addition, it goes without saying that it is preferable that the condition Dpx ≤ 2W be satisfied in all four corner portions existing in the strip core body 10.

[0035]

As another embodiment, in at least one corner portion 3 the condition Dpy ≤ 2W is satisfied, where Dpy (mm) is the average value of Dl-(ii, io, oi, oo). In view of the mechanism described above, this expression particularly corresponds to the feature in which crystal grain boundaries that intersect the direction towards the first flat part 4 and the second flat part 4a (the direction perpendicular to the boundary direction in the curved part 5) more easily act as obstacles to move dislocations in the direction of each flat part than the crystal grain boundaries that are parallel to the direction to the first flat part 4 and the second flat part 4a (the direction perpendicular to the boundary of the curved part). When this expression is satisfied, the movement of dislocations towards the flat portion region can be sufficiently minimized. Preferably, Dpy ≤ W. In addition, it goes without saying that it is preferable that the condition Dpy ≤ 2W be satisfied in all four corner portions existing in the strip core body 10.

[0036]

As another embodiment, in at least one corner portion 3 Dpz ≤ 2W, where Dpz (mm) is the average value of Dc-(ii, io, oi, oo). This expression corresponds to the feature in which the crystal grain boundaries parallel to the direction to the first flat part 4 and the second flat part 4a (the direction perpendicular to the boundary of the curved part) also easily act as dislocation elimination sites that move to the first flat part 4 and the second flat part 4a. When this expression is satisfied, the movement of dislocations towards the flat portion region can be sufficiently minimized. Preferably, Dpz ≤ W. In addition, it goes without saying that it is preferable that the condition Dpz ≤ 2W be satisfied in all four corner portions existing in the strip core body 10.

[0037]

(2) Anisotropic electrical steel sheet

As described above, in the anisotropic electrical steel sheet 1 used in the present embodiment, the main steel sheet is a steel sheet in which the crystal grain orientations in the main steel sheet 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.

[0038]

The main steel sheet has the following chemical composition, in wt.%: Si: 2.0-6.0%, with the remainder of Fe and impurities. This chemistry allows the crystal orientation to be controlled to a Goss texture concentrated in the {110}<001> orientation and provides favorable magnetic properties. Other elements are not particularly limited, and in the present embodiment, in addition to Si, Fe and impurities, such elements may be contained as long as the effects of the present invention are not impaired. For example, the following elements may be contained in the following ranges instead of some Fe. Ranges for the number of representative optional 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 effects of the present embodiment are not impaired. In addition, since it is difficult to make the C content 0% in a practical steel sheet during production, the C content may exceed 0%. In addition to this, impurities refer to elements that are unintentionally contained and mean elements that inevitably enter the steel from ore, scrap, industrial environment, etc. in the industrial production of basic steel sheet. The upper limit of the total impurity content may be, for example, 5%.

[0039]

The chemical component of the base steel sheet can be measured using a conventional analytical method for steel. For example, the chemical component of a base steel sheet can be measured using inductively coupled plasma atomic emission spectrometry (ICP-AES). Specifically, for example, a 35 mm square test piece is taken from the center position of the base steel sheet after removing the coating, and can be analyzed by performing a measurement under conditions based on a previously created calibration curve using an ICPS-8100 measuring instrument, etc. . (commercially available from Shimadzu Corporation). Here, 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.

[0040]

Here, the above-mentioned chemical composition is the composition of the anisotropic electrical steel sheet 1 as the base steel sheet. When the anisotropic electrical steel sheet 1 used as a measurement sample has a primary oxide coating or the like on its surface. (glass coating and intermediate layer) and insulating coating, etc., the chemical composition is measured after removing this coating, etc. by known methods.

[0041]

(3) Method for producing anisotropic electrical steel sheet

The production method of the anisotropic electrical steel sheet is not particularly limited, and as will be described below, when the production conditions are precisely controlled, the crystal grain size of the steel sheet can be taken into account. When anisotropic electrical steel sheets having such a desired crystal grain size are used and the strip core is produced under suitable processing conditions, which will be described below, it is possible to obtain a strip core capable of minimizing the degradation in efficiency. As a preferred specific example of the production method, for example, first, a slab containing 0.04 to 0.1 mass% C with the remainder being the chemical composition of an anisotropic electrical steel sheet is heated to 1000°C or higher and hot rolled, and then unwinds at 400-850°C. Hot annealing is performed as necessary. The hot annealing conditions are not particularly limited, and in view of controlling the formation of precipitates, the annealing heating temperature may be 800-1200°C and the annealing duration may be 10-1000 seconds. The cold rolled steel sheet is then obtained by cold rolling one, two or more times with intermediate annealing. The cold rolling reduction rate in this case can be 80-99%, taking into account texture control. The cold-rolled steel sheet is heated, for example, in a humid atmosphere of hydrogen and inert gas at 700-900°C, decarburized and annealed, and subjected to nitriding annealing as necessary. Then, after the annealing separator is applied to the steel sheet after annealing, final annealing is performed at a maximum temperature of 1000-1200°C for 40-90 hours, and the insulating coating is formed at a temperature of approximately 900°C. Among the above conditions, in particular, decarburization annealing and final annealing affect the crystal grain size of the steel sheet. Therefore, when producing the strip core, it is preferable to use an anisotropic electrical steel sheet produced within the above ranges of conditions.

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

[0042]

As stated above, the crystal grain size, which is a feature of the anisotropic electrical steel sheet 1 used in the present embodiment, is preferably controlled depending on, for example, the maximum temperature and final annealing time. When the average crystal grain size of the entire steel sheet is reduced in this way, and each crystal grain size is set to 2W or less, even if the bent portion 5 is formed at an arbitrary position in the production of the strip core, the above-mentioned Dpx values and the like are expected. will be equal to 2W or less. In addition to this, in order to produce a strip core in which grains with a small crystal grain size are located near the bent portion 5, it is also effective to control the bending position of the steel sheet so that the area with a small crystal grain size is located near the bent portion 5. In this method, a steel sheet is produced in which the growth of secondary recrystallization grains is locally minimized according to a known method such as locally changing the state of an annealing separator, and bending can be performed by selecting the position at which fine grains are generated.

[0043]

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 the strip core according to the present embodiment can be produced, and, for example, the method according to the known strip core described in Patent Documents 9 to 11 in the foregoing can be applied. level of technology. In particular, it may be mentioned that a method using the UNICORE production device (commercially available from AEM UNICORE) ( https://www.aemcores.com.au/technology/Unicore/ ) is optimal.

In addition, in order to accurately control the above-mentioned Dpx, Dpy and Dpz, it is preferable to control the shapes of the punch and die used during processing, as well as the amount of temperature increase of the steel sheet due to the heat generated during processing. Specifically, when the radius of curvature of the punch used is r _p (mm) and the radius of curvature of the die is r _d (mm), the value of r _p /r _d is preferably in the range of 2.0 to 10.0. In addition, when the amount of temperature increase of the steel sheet due to heat generated during processing is ΔT, ΔT is preferably reduced to 4.8°C or less. If ΔT is excessively large, even if a steel sheet having a crystal grain size in a suitable range is used as the material, the crystal grain size may become coarse and the efficiency of the strip core may be reduced. The cooling method is not particularly limited, but, for example, the temperature of the steel sheet can be adjusted by spraying a coolant such as liquid nitrogen during processing or immediately after processing.

[0044]

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

[0045]

The present embodiment is not limited to the above-described embodiment. The above-described embodiment is merely an example, and any embodiment having substantially the same configuration and showing an effect similar to the technical idea described in the claims of the present invention also falls within the scope of the present invention.

[Examples]

[0046]

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 demonstrate the feasibility and effects of the present invention, and the present invention is not limited to these example conditions. In addition, the present invention may use various conditions without departing from the spirit of the present invention as long as the object of the present invention is achieved.

[0047]

(Anisotropic Electrical Steel Sheet)

Using a slab having the chemical composition (in mass%, with Fe residue) shown in Table 1 as a material, a final product (product sheet) was produced with the chemical composition (in mass%, with Fe remainder) shown in Table 2. The width of the resulting steel sheet was 1200 mm.

In Table 1 and Table 2, “-” means that the item was not controlled or produced with awareness of the content, and its content was not measured. In addition, “<0.002” and “<0.004” mean that the item was controlled and produced with awareness of the content, the content was measured, but sufficient measurement values were not obtained with confidence in the accuracy (detection limit or less).

[0048]

[Table 1] Steel type Slab C Si Mn S Al N Cu Bi Nb A 0.070 3.26 0.07 0.025 0.026 0.008 0.07 - - B 0.070 3.26 0.07 0.025 0.026 0.008 0.07 - 0.007 C 0.070 3.26 0.07 0.025 0.025 0.008 0.07 0.002 - D 0.060 3.45 0.10 0.006 0.027 0.008 0.20 - 0.005

[0049]

[Table 2] Steel type Product Sheet C Si Mn S Al N Cu Bi Nb A 0.001 3.15 0.07 <0.002 <0.004 <0.002 0.07 - - B 0.001 3.15 0.07 <0.002 <0.004 <0.002 0.07 - 0.005 C 0.001 3.15 0.07 <0.002 <0.004 <0.002 0.07 0.002 - D 0.001 3.34 0.10 <0.002 <0.004 <0.002 0.20 - -

[0050]

Here Table 3 shows the details and conditions of the steel sheet production process.

Specifically, hot rolling, hot annealing, and cold rolling were performed. In part of the cold-rolled steel sheet after decarburization annealing, nitriding treatment (nitriding annealing) was performed in a mixed atmosphere containing hydrogen, nitrogen and ammonia.

In addition, an annealing separator consisting mainly of MgO was applied and final annealing was performed. An insulating coating solution containing chromium and consisting mainly of phosphate and colloidal silica was applied to a primary coating formed on the surface of a final annealed steel sheet and heated to form an insulating coating.

[0051]

In this case, the cold rolling reduction ratio or the final annealing time was controlled, and thus steel sheets with a controlled crystal grain size were produced. Table 3 shows the details of the steel sheets produced.

[0052]

[Table 3] Steel Sheet No. Steel type Hot rolling Hot annealing Cold rolling Decarburizing annealing Nitriding Final annealing Magnetic domain management Properties Heating temperature Finish temperature Rewinding temperature Sheet thickness Temperature Time Sheet thickness Cold rolling reduction ratio Temperature Time Temperature Time B8 Magnetic losses Crystal grain size °C °C °C mm °C With mm % °C With °C hour Tl W/kg mm A1 A 1150 900 540 3.0 1100 180 0.35 88.3 830 180 Yes 1100 45 Etching control 1.91 1.01 6 A2 A 1150 900 540 3.1 1100 180 0.35 88.7 830 180 1100 50 1.91 0.95 8 A3 A 1150 900 540 3.2 1100 180 0.35 89.1 830 180 1100 55 1.92 0.93 13 A4 A 1150 900 540 3.3 1100 180 0.35 89.4 830 180 1100 60 1.91 0.94 18 B1 B 1150 880 650 2.2 1150 180 0.23 89.5 850 180 Yes 1100 45 Mechanical stress management 1.90 0.77 7 B2 B 1150 880 650 2.3 1150 180 0.23 90.0 850 180 1100 50 1.91 0.77 eleven B3 B 1150 880 650 2.4 1150 180 0.23 90.4 850 180 1100 55 1.92 0.72 18 B4 B 1150 880 650 2.5 1150 180 0.23 90.8 850 180 1100 60 1.92 0.78 21 C1 C 1150 900 750 2.5 1100 120 0.26 89.6 860 180 Yes 1150 55 Laser control 1.90 0.81 6 C2 C 1150 900 750 2.6 1100 120 0.26 90.0 860 180 1150 60 1.92 0.79 9 C3 C 1150 900 750 2.7 1100 120 0.26 90.4 860 180 1150 65 1.94 0.77 14 C4 C 1150 900 750 2.8 1100 120 0.26 90.7 860 180 1150 70 1.93 0.83 18 D1 D 1350 930 540 2.5 1050 180 0.26 89.6 860 180 No 1100 65 Electron beam control 1.91 0.80 5 D2 D 1350 930 540 2.6 1050 180 0.26 90.0 860 180 1100 70 1.92 0.72 8 D3 D 1350 930 540 2.7 1050 180 0.26 90.4 860 180 1100 75 1.94 0.70 12 D4 D 1350 930 540 2.8 1050 180 0.26 90.7 860 180 1100 80 1.93 0.73 16

[0053]

(Metal core)

Cores a - f having the shapes shown in Table 4 and FIG. 8, have been produced using appropriate steel sheets as materials. Here, L1 is parallel to the X-axis direction and is the distance between the parallel sheets 1 of the anisotropic electrical steel at the innermost periphery of the strip core in a flat cross-section including the center CL (the distance between the inner flat parts), L2 is parallel to the Z-axis direction and is the distance between the parallel sheets 1 anisotropic electrical steel 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 thickness of the laminated strip core in the flat cross section including the center CL (thickness in the fusion direction) , L4 is parallel to the X-axis direction and is the width of the laminated steel sheets of the strip core in a flat cross section including the center CL, and L5 is the distance between the flat parts adjacent to each other in the innermost part of the strip core and forming a right angle with each other (the distance between curved parts). In other words, L5 is the shortest length of the flat portion 4a in the longitudinal direction among the flat portions 4 and 4a of the anisotropic electrical steel sheets at the innermost periphery. r is the radius of curvature (mm) 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 metal cores a - f have a structure in which a flat portion of length L1 is separated approximately at the center of distance L1, and two cores having a substantially U-shape are connected together.

Here, the core f is traditionally used as an ordinary strip core and is a so-called main core produced by winding a steel sheet into a cylindrical shape, and then pressing the cylindrical laminated body without modification so that the corner portion has a constant curvature, forming it into a substantially rectangular shape. shape, and then perform annealing and maintain that shape. Therefore, the radius of curvature of the curved part changes significantly depending on the fusion position of the steel sheet. In addition to this, in Table 4, the radius of curvature r (mm) of the core f increases in the outward direction, and is 6 mm at the innermost part of the periphery and approximately 85 mm at the outermost part of the periphery (marked with a “-” in Table 4).

[0054]

[Table 4] Core No. Core shape L1 L2 L3 L4 L5 r φ mm mm mm mm mm mm ° a 197 66 45 150 16 1 45 b 197 66 45 150 18 3 45 c 197 66 45 150 20 5 45 d 197 66 55 150 20 2 thirty e 197 66 55 150 22 6 45 f 197 66 55 150 - thirty 90

[0055]

(Evaluation method)

(1) Magnetic properties of anisotropic electrical steel sheet

The magnetic properties of anisotropic electrical steel sheet 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 with a current density of 800 A/m and the magnetic loss of the steel sheet at an alternating current frequency of 50 Hz with an excitation magnetic flux density of 1.7 T were measured.

(2) Particle size in the metal core

The 12 crystal grain sizes (Dcii, Dcio, Dcoi, Dcoo, Dlii, Dlio, Dloi, Dloo, Dpii, Dpio, Dpoi, and Dpoo) were determined by observing both surfaces of the steel sheet removed from the core as described above.

(3) Core efficiency

The density factor (BF) was obtained by calculating the no-load loss for the core formed from each steel sheet as a material and taking the relationship with the magnetic properties of the steel sheet obtained in step (1). Here, BF is a value obtained by dividing the magnetic loss value of the strip core by the magnetic loss value of the anisotropic electrical steel sheet, which is the strip core material. A lower BF value indicates lower magnetic losses of the strip core relative to the steel sheet. In this example, when the BF was 1.15 or less, it was considered that the degradation of magnetic loss efficiency was minimized.

[0056]

The efficiency was evaluated for different metal cores produced using different steel sheets with different magnetic domain widths. The results are shown in Table 5. Here in Table 5, “r _p /r _d ” represents the ratio of the radius of curvature r _p (mm) of the punch and the radius of curvature r _d (mm) of the die used in core processing, and “ΔT” represents the amount of temperature increase in the steel sheet (°C) due to the heat generated during processing.

It can be understood that core efficiency can be improved by appropriately controlling the crystal grain size, even if the same type of steel is used.

[0057]

[Table 5] Test No. Steel Sheet No. Core No. Processing conditions Properties of the metal core Note r _p / r _d ΔT (°C) W Dpx Dpy Dpy Density Factor (BF) mm mm mm mm 1-1 A1 a 6.3 0.7 0.98 0.97 1.72 1.65 1.08 Example of the present invention 1-2 A2 a 5.2 1.0 0.98 1.15 1.82 2.04 1.11 Example of the present invention 1-3 A3 a 1.4 6.7 0.98 2.30 4.05 3.71 1.17 Comparative example 1-4 A4 a 1.7 5.7 0.98 3.18 4.53 4.91 1.18 Comparative example 1-5 B1 a 4.6 1.3 0.98 0.95 1.57 1.41 1.08 Example of the present invention 1-6 B2 a 10.0 0.8 0.98 1.55 2.45 2.88 1.14 Example of the present invention 1-7 B3 a 1.2 5.2 0.98 3.08 4.82 4.96 1.18 Comparative example 1-8 B4 a 0.7 6.1 0.98 3.41 5.44 5.69 1.19 Comparative example 1-9 C1 a 2.0 2.2 0.98 1.03 1.72 1.64 1.09 Example of the present invention 1-10 C2 a 3.4 1.7 0.98 1.38 2.41 1.95 1.10 Example of the present invention 1-11 C3 a 0.8 6.7 0.98 2.10 3.87 3.46 1.18 Comparative example 1-12 C4 a 1.3 7.8 0.98 2.87 5.27 4.61 1.19 Comparative example 1-13 D1 a 8.6 4.8 0.98 0.73 1.15 1.21 1.07 Example of the present invention 1-14 D2 a 6.7 0.3 0.98 1.10 2.08 1.61 1.11 Example of the present invention 1-15 D3 a 9.3 1.6 0.98 1.93 3.05 3.35 1.13 Example of the present invention 1-16 D4 a 1.7 5.5 0.98 2.91 4.68 4.20 1.18 Comparative example 1-17 A1 b 8.4 2.0 1.76 0.98 1.53 1.74 1.07 Example of the present invention 1-18 A4 b 6.7 0.3 1.76 3.22 4.67 5.26 1.15 Example of the present invention 1-19 B1 b 9.3 1.6 1.76 0.94 1.66 1.39 1.06 Example of the present invention 1-20 B4 b 6.7 1.9 1.76 3.55 5.37 6.34 1.19 Comparative example 1-21 C1 c 2.0 2.2 2.61 1.15 1.89 1.64 1.05 Example of the present invention 1-22 C4 c 3.4 1.7 2.61 3.13 5.04 5.45 1.11 Example of the present invention 1-23 D1 d 2.0 0.6 1.21 0.87 1.49 1.24 1.08 Example of the present invention 1-24 D4 d 1.5 5.0 1.21 2.58 4.13 5.01 1.18 Comparative example 1-25 C1 e 2.0 2.2 3.32 1.01 1.74 1.80 1.18 Comparative example 1-26 C3 e 3.4 1.7 3.32 2.13 3.71 3.82 1.17 Comparative example 1-27 D1 e 0.8 6.7 3.32 0.83 1.37 1.29 1.18 Comparative example 1-28 D3 e 1.3 7.8 3.32 1.92 3.31 3.12 1.16 Comparative example 1-29 A1 f 8.6 2.0 47.33 1.06 1.81 1.72 1.16 Comparative example 1-30 A3 f 6.7 0.3 47.33 2.20 4.12 3.88 1.16 Comparative example 1-31 B1 f 9.3 1.6 47.33 0.88 1.55 1.43 1.17 Comparative example 1-32 B3 f 6.7 0.3 47.33 2.66 4.68 4.83 1.18 Comparative example

[0058]

Based on the above results, it can be clearly seen that in the strip core of the present invention, each of the crystal grain sizes Dpx, Dpy and Dpz of the laminated anisotropic electrical steel sheet was 2W or less, so that the strip core had low magnetic loss properties.

INDUSTRIAL APPLICABILITY

[0059]

According to the present invention, in a strip core formed by laminating curved steel sheets, deterioration in the efficiency of the core can be effectively minimized.

BRIEF DESCRIPTION OF REFERENCE SYMBOLS

[0060]

1 - sheet of anisotropic electrical steel

2 - laminated structure

3 - corner part

4 - first flat part (flat part)

4a - second flat part (flat part)

5 - curved part

6 - connecting part

10 - main part of the strip core

Claims (38)

1. A strip core having a strip core body obtained by laminating a plurality of polygonal annular anisotropic electrical steel sheets in a sheet thickness direction in a side view, wherein the anisotropic electrical steel sheet has flat parts and curved parts that continuously alternate in the longitudinal direction, wherein the curved portion in the side view has an inner radius of curvature r of 1 mm or more and 5 mm or less, wherein the sheets of anisotropic electrical steel have a chemical composition containing in mass percent: Si: from 2.0 to 7.0% with the balance of Fe and impurities, and have a texture oriented in Goss orientation, and at least in one of the curved parts, the crystal grain size Dpx (mm) of the laminated anisotropic electrical steel sheet is 2W or less, where Dpx (mm) is the average value of Dp (mm) according to the following formula (1), Dc (mm) is the average crystal grain size in the direction in which the boundary line extends at the respective boundaries between the curved part and the two flat parts between which the curved part is placed, Dl (mm) is the average crystal grain size at the boundary in the direction perpendicular to the direction in which the boundary line at the boundary runs, W (mm) is the width of the curved part in the side view, and The average Dp is the average of the Dp on the inside and the Dp on the outside of one flat part between two flat parts and the Dp on the inside and Dp on the outside of the other flat part: Dp=√(Dc×Dl/π) (1). 2. A strip core having a strip core body obtained by laminating a plurality of polygonal annular anisotropic electrical steel sheets in a sheet thickness direction in a side view, wherein the anisotropic electrical steel sheet has flat parts and curved parts that continuously alternate in the longitudinal direction, wherein the curved portion in the side view has an inner radius of curvature r of 1 mm or more and 5 mm or less, in which the anisotropic electrical steel sheets have a chemical composition containing in mass percent: Si: from 2.0 to 7.0% with the balance of Fe and impurities, and have a texture oriented in Goss orientation, and at least in one of the curved parts, the crystal grain size Dpy (mm) of the laminated anisotropic electrical steel sheet is 2W or less, where Dpy is the average value of Dl, Dl (mm) is the average crystal grain size in the direction perpendicular to the direction in which the boundary line extends at the respective boundaries between the curved part and the two flat parts between which the curved part is placed, W (mm) is the width of the curved part in the side view, and the average Dl is the average of the Dl on the inside and the Dl on the outside of one flat part between two flat parts and the Dl on the inside and Dl on the outside of the other flat part. 3. A strip core having a strip core body obtained by laminating a plurality of polygonal annular anisotropic electrical steel sheets in a sheet thickness direction in a side view, wherein the anisotropic electrical steel sheet has flat parts and curved parts that continuously alternate in the longitudinal direction, wherein the curved portion in the side view has an inner radius of curvature r of 1 mm or more and 5 mm or less, in which the anisotropic electrical steel sheets have a chemical composition containing in mass percent: Si: from 2.0 to 7.0% with the balance of Fe and impurities, and have a texture oriented in Goss orientation, and at least in one of the curved parts, the crystal grain size Dpz (mm) of the laminated anisotropic electrical steel sheet is 2W or less, where Dpz is the average value of Dc, Dc (mm) is the average crystal grain size in the direction in which the boundary line extends at the respective boundaries between the curved part and the two flat parts between which the curved part is placed, W (mm) is the width of the curved part in the side view, and the average Dc is the average of Dc on the inside and Dc on the outside of one flat part between two flat parts and Dc on the inside and Dp on the outside of the other flat part.