Rolled iron core and method for manufacturing the same

Abstract

To provide a winding iron core that is formed by a method of laminating bent steel plates to form a winding iron core, the winding iron core being highly efficient by localizing bent regions more than before.SOLUTION: A winding iron core 10 includes: directional electromagnetic steel plates 1 laminated in a plate thickness direction; and a winding iron core body substantially rectangular in a side view. A flat surface part and a bent surface part alternately continue to each other in a longer direction. Also, when the maximum value of a difference between a distance from a center of curvature of the bent surface part and a curvature radius r for a curve representing an inner surface of the bent part is Hmax, a plate thickness of the directional electromagnetic steel plates 1 at a point of Hmax is tm, and a plate thickness of the directional electromagnetic steel plates 1 is t in a side view of at least one bent surface part of an arbitrary one of the laminated directional electromagnetic steel plates 1, Hmax / t≥0.10 (1) and tm / t≤0.98 (2) are satisfied.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a wound core and a method for manufacturing the wound core.

Background Art

[0002] A grain-oriented electrical steel sheet contains 7 mass% or less of Si and has a secondary recrystallized texture in which secondary recrystallized grains are aggregated in the {110}<001> orientation (Goss orientation). The magnetic properties of the grain-oriented electrical steel sheet are greatly affected by the degree of aggregation in the {110}<001> orientation. In recent years, in the grain-oriented electrical steel sheets that are in practical use, the angle between the <001> direction of the crystal and the rolling direction is controlled to be within a range of about 5°, and for example, by sophisticated orientation control techniques such as those described in Patent Documents 1 to 3, a high magnetic flux density and low iron loss, which are the main magnetic properties, are ensured.

[0003] The grain-oriented electrical steel sheets are laminated and used for cores of transformers, etc. Conventionally, for the manufacture of a wound core, for example, as described in Patent Document 4, after winding a steel sheet into a cylindrical shape, the cylindrical laminate is formed into a rectangle by pressing and annealed to remove strain and maintain the shape. This method is widely known.

[0004] On the other hand, as another method for manufacturing a wound core, a technique as described in Patent Documents 5 to 8 is disclosed, in which a portion of the steel sheet that becomes a corner portion of the wound core is pre-bent so that a relatively small bending region having a curvature radius of 3 mm or less is formed, and the bent steel sheets are laminated to form a wound core. According to this manufacturing method, a large-scale pressing process as in the conventional method is unnecessary, the steel sheet is precisely bent and the core shape is maintained, and the processing strain is concentrated only in the bent portion (corner portion), so that the omission of the strain removal by the annealing process is also possible, and the industrial merit is large and the application is progressing.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] The inventors of the present application have studied further reduction of iron loss in a transformer core manufactured by a method in which a steel plate is pre-bent so that a relatively small bending region having a curvature radius of 5 mm or less is formed, and the bent steel plates are laminated to form a wound core. One of the merits of this core is that the deformation region is limited to a very narrow bent portion with respect to the entire core, and good core efficiency can be exhibited without performing stress relief annealing after core formation (after bending). However, there are few studies on how much the deformation region should be localized.

[0007] The inventor has studied the limit of localization of the deformation region. As a result, it has been found that by forming a stress concentration possible site in advance in the bending region, the deformation region can be further localized and the deterioration of iron loss due to bending can be suppressed.

[0008] In the conventional processing method, due to the elastic deformation (springback) of the steel plate, even if a die with a small bending radius, for example, a die with a curvature radius of zero, is used, the deformation region spreads. For this reason, it has been difficult to make the curvature radius less than 1 mm. Therefore, the present inventors considered concentrating the deformation stress by forming a deformation starting point on the steel sheet before processing and localizing the deformed region after bending. As a result, it was confirmed that by providing minute recesses on the steel sheet surface and bending the portion, the iron loss deterioration due to bending can be reduced, and it is reasonable to consider that the cause is the localization of the deformed region.

[0009] From this perspective, various processing conditions and the like were examined, and it was found that by forming an appropriate recess shape serving as a stress concentration starting point before bending, the iron loss deterioration due to bending can be reduced and good transformer iron loss can be obtained, and the present inventors succeeded in specifying the characteristics of the appropriate recess shape and the bent portion shape after bending.

[0010] The present invention has been made in view of the above problems, and in a wound core manufactured by a method of pre-bending a steel sheet so that a bent region is formed and laminating the bent steel sheets to form a wound core, an object is to provide a wound core and a method for manufacturing a wound core in which deterioration of iron loss is reduced by locally concentrating strain that was conventionally uniformly distributed throughout the bent region.

Means for Solving the Problems

[0011] To achieve the above object, the gist of the present invention employs the following means. (1) A wound core according to an embodiment of the present invention is a wound core in which grain-oriented electrical steel sheets are laminated in the plate thickness direction and are substantially rectangular in side view, the grain-oriented electrical steel sheets have a flat portion and a bent portion continuously alternating in the longitudinal direction, the grain-oriented electrical steel sheets by mass, Si: 2.0 to 7.0%, contain, and the balance consists of Fe and impurities, having a chemical composition, have an aggregate structure oriented in the Goss orientation, and in side view of at least one bent portion of any of the laminated grain-oriented electrical steel sheets, Regarding the curve representing the inner surface of the bent portion, the maximum value of the difference between the distance from the center of curvature of the bent portion and the radius of curvature r is Hmax, the thickness of the grain-oriented electrical steel sheet at the point where Hmax is obtained is tm, and when t is the thickness of the grain-oriented electrical steel sheet, Hmax / t ≥ 0.10 ·····(1) tm / t ≤ 0.98 ·····(2) It is characterized by satisfying the above conditions. (2) In the above (1), the following configuration may be adopted: Let the center of curvature be point A, extend a straight line perpendicular to the outer surface from each boundary between the flat portions on both sides sandwiching the bent portion and the bent portion on the outer surface of the bent portion, and let the intersection points with the curve representing the inner surface be point E' and point D' respectively. Let the point on the curve representing the inner surface where Hmax is obtained be point I, the angle between line segment AD' and line segment AI be θ'(°), the angle between line segment AD' and line segment AE' be Φ(°), and when AR = 1 / 2 - |θ' / Φ - 1 / 2|, AR is greater than 0.25 and less than or equal to 0.50. (3) In the above (2), the following configuration may be adopted: When the shape of the bent portion is measured at a plurality of cross-sections at equal intervals along the width direction of the grain-oriented electrical steel sheet, if the total number of cross-sections to be measured is Nt and the number of cross-sections in which AR is in the range of 0.25 to 0.50 in each cross-section is Nc, then Nc / Nt > 0.50. (4) In any one of the above (1) to (3), the following configuration may be adopted: The inner surface radius of curvature r in the side view of the bent portion is 5 mm or less. (5) In any one of the above (1) to (4), the following configuration may be adopted: There is a concave portion on the inner surface that is recessed in the direction away from the center of curvature, The point where Hmax is obtained is the bottom of the concave portion, The radius of curvature r is the radius of curvature of the inner surface when it is assumed that there is no such concave portion in the side view. (6) The method for manufacturing a wound iron core according to an embodiment of the present invention is A method for manufacturing a wound iron core using a grain-oriented electrical steel sheet as a material, When bending the material, after identifying the bending portion, a concave portion having a width smaller than the bending radius of curvature is formed on the inner surface of the planned bending portion, and then the region including the concave portion forming portion is bent The method for manufacturing a wound core according to any one of (1) to (5) above, characterized in that.

Effect of the Invention

[0012] According to the present invention, in a wound core manufactured by a method of pre-bending a steel sheet so that a bending region is formed and laminating the bent steel sheets to form a wound core, by localizing the bending region more than before, good core efficiency can be obtained.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0014] Hereinafter, the wound core according to the present invention will be described in detail in order. However, the present invention is not limited only to the configurations disclosed in the present embodiment, and various modifications are possible without departing from the spirit of the present invention. In addition, the lower limit value and the upper limit value are included in the numerical limitation range described below. Numerical values indicated as "more than" or "less than" are not included in the numerical range. Further, "%" regarding the chemical composition means "mass%" unless otherwise specified. In addition, with regard to terms used in this specification for specifying shapes, geometric conditions, and their degrees, such as terms like "parallel", "perpendicular", "identical", "right angle", and values of lengths and angles, they are not bound by a strict meaning, and are to be interpreted to include a range where similar functions can be expected. In addition, in this specification, the "grain-oriented electrical steel sheet" may be simply described as "steel sheet" or "electrical steel sheet", and the "wound core" may be simply described as "core".

[0015] (1) The wound core according to the present embodiment is a wound core in which grain-oriented electrical steel sheets are laminated in the plate thickness direction and are substantially rectangular in side view, In the grain-oriented electrical steel sheet, a flat portion and a bent portion are continuously alternated in the longitudinal direction, and the grain-oriented electrical steel sheet by mass, Si: 2.0 to 7.0%, contains, and the balance consists of Fe and impurities, having a chemical composition, has an aggregate structure oriented in the Goss orientation, and moreover In a side view of at least one bent portion of any arbitrarily oriented laminated electromagnetic steel sheet, Regarding the curve representing the inner surface of the bent portion, when the maximum value of the difference between the distance from the center of curvature of the bent portion and the radius of curvature r is Hmax, the thickness of the oriented electromagnetic steel sheet at the point where Hmax is obtained is tm, and t is the thickness of the oriented electromagnetic steel sheet, Hmax / t ≥ 0.10 ·····(1) tm / t ≤ 0.98 ·····(2) It is characterized by satisfying the above conditions. (2) In the above (1), the following configuration may be adopted: Taking the center of curvature as point A, extending perpendicular lines from the boundaries between the flat portions on both sides sandwiching the bent portion and the bent portion on the outer surface of the bent portion to the outer surface, and designating the intersection points with the curve representing the inner surface as point E' and point D' respectively, taking the point on the curve representing the inner surface where Hmax is obtained as point I, taking the angle between line segment AD' and line segment AI as θ'(°), taking the angle between line segment AD' and line segment AE' as Φ(°), and when AR = 1 / 2 - |θ' / Φ - 1 / 2|, AR is greater than 0.25 and less than or equal to 0.50. (3) In the above (2), the following configuration may be adopted: When the shape of the bent portion is measured at a plurality of cross-sections at equal intervals along the width direction of the oriented electromagnetic steel sheet, taking the total number of cross-sections to be measured as Nt and the number of cross-sections in which AR is in the range of 0.25 to 0.50 at each cross-section as Nc, then Nc / Nt > 0.50. (4) In any one of the above (1) to (3), the following configuration may be adopted: Furthermore, the inner surface radius of curvature r in the side view of the bent portion is 5 mm or less. (5) In any one of the above (1) to (4), the following configuration may be adopted: There is a concave portion on the inner surface that is recessed in the direction away from the center of curvature, The point where Hmax is obtained is the bottom of the concave portion, The radius of curvature r is the radius of curvature of the inner surface when it is assumed that there is no concave portion in the side view. (6) The manufacturing method of the wound core according to an embodiment of the present invention is a method for manufacturing a wound core using a grain-oriented electrical steel sheet as a material, when bending the material, after identifying the bending portion, a concave portion having a width smaller than the radius of curvature of the bending is formed on the inner surface of the bending of the planned bending portion, and then, the region including the concave portion forming portion is bent which is the manufacturing method of the wound core according to any one of the above (1) to (5).

[0016] 1. Shapes of the wound core and the grain-oriented electrical steel sheet First, the shape of the wound core according to this embodiment will be described. The shapes of the wound core and the grain-oriented electrical steel sheet themselves described here are not particularly novel. For example, they conform to the known shapes of the wound core and the grain-oriented electrical steel sheet introduced as Patent Documents 5 to 8 in the background art. FIG. 1 is a perspective view schematically showing an embodiment of the wound core. FIG. 2 is a side view of the wound core shown in the embodiment of FIG. 1. Further, FIG. 3 is a side view schematically showing another embodiment of the wound core. In this embodiment, the side view means viewing in the width direction of the grain-oriented electrical steel sheet constituting the wound core (the Y-axis direction in FIG. 1, hereinafter may be described as the "width direction"), and the side view is a view showing the shape visually recognized by the side view (the view in the Y-axis direction of FIG. 1, that is, corresponding to FIG. 2). Also, in this embodiment, the shape of the bent portion is measured and determined in the "side view", but the "side view" in this measurement and determination means a "cross section parallel to the side surface of the wound core". And the regulation of this embodiment is determined by the data measured at a plurality of locations in the width direction of the grain-oriented electrical steel sheet. This is because the shape of the bent portion of the long grain-oriented electrical steel sheet constituting the wound core targeted by this embodiment may not necessarily be the same over the entire width of the steel sheet, and it is for specifying the characteristic representing the shape of the bent portion.

[0017] The wound core according to this embodiment includes a wound core body that is substantially rectangular in side view. The wound core body has a laminated structure in which oriented electromagnetic steel sheets are stacked in the plate thickness direction and are substantially rectangular in side view. The wound core body may be used as a wound core as it is, or may be provided with a known fastener such as a binding band or the like in order to fix the wound core as necessary.

[0018] In this embodiment, there is no particular limitation on the core length of the wound core body. However, even if the core length changes in the core, since the volume of the bent portion is constant, the iron loss generated in the bent portion is constant. Since the volume ratio of the bent portion becomes smaller when the core length is longer, it is preferably 1.5 m or more, and more preferably 1.7 m or more because the influence on the deterioration of iron loss is small. In this embodiment, the core length of the wound core body refers to the perimeter at the center point in the stacking direction of the wound core body in side view.

[0019] The wound core according to this embodiment can be suitably used for any conventionally known applications.

[0020] As shown in FIGS. 1 and 2, the wound core body 10 includes a portion where the flat portions 4 and the corner portions 3 are alternately continuous in the longitudinal direction, and the oriented electromagnetic steel sheets 1 in which the angle formed by two adjacent flat portions 4 at each corner portion 3 is 90° are stacked in the plate thickness direction, and has a laminated structure 2 that is substantially rectangular (substantially polygonal) in side view. In other words, the wound core body 10 has an octagonal laminated structure 2. In this embodiment, the wound core body 10 has an octagonal laminated structure. However, the present invention is not limited to this. The wound core body 10 may have a laminated structure in which a plurality of polygonal annular oriented electromagnetic steel sheets 1 are stacked in the plate thickness direction, as long as the flat portions 4 and the bent portions 5 are alternately continuous in the longitudinal direction (circumferential direction) of the oriented electromagnetic steel sheet 1.

[0021] Hereinafter, the wound core body 10 will be described as being substantially rectangular with four corner portions 3. Each corner portion 3 has two bent portions 5 having a curved shape in a side view of the oriented electromagnetic steel sheet 1, has a second flat portion 4a between adjacent bent portions 5, 5, and the sum of the bending angles of the two bent portions 5, 5 existing in one corner portion 3 is 90°. Also, as shown in FIG. 3, each corner portion 3 has three bent portions 5 having a curved shape in a side view of the oriented electromagnetic steel sheet 1, has a second flat portion 4a between adjacent bent portions 5, 5, and the sum of the bending angles of the three bent portions 5, 5, 5 existing in one corner portion 3 is 90°.

[0022] Also, each corner portion 3 may have four or more bent portions. In this case as well, there is a second flat portion 4a between adjacent bent portions 5, 5, and the sum of the bending angles of the four or more bent portions 5 existing in one corner portion 3 is 90°. That is, each corner portion 3 is disposed between two adjacent first flat portions 4, 4 arranged at a right angle, and has two or more bent portions 5 and one or more second flat portions 4a. Also, in the wound core body 10 shown in FIG. 2, the bent portion 5 is disposed between the first flat portion 4 and the second flat portion 4a, but in the wound core body 10 shown in FIG. 3, the bent portion 5 is disposed between the first flat portion 4 and the second flat portion 4a and between two second flat portions 4a, 4a. That is, the second flat portion 4a may be disposed between two adjacent second flat portions 4a, 4a.

[0023] Furthermore, in the wound core body 10 shown in FIGS. 2 and 3, the length of the first flat portion 4 in the longitudinal direction (circumferential direction of the wound core body 10) is longer than that of the second flat portion 4a, but the lengths of the first flat portion 4 and the second flat portion 4a may be equal. In the present specification, the "first flat portion" and the "second flat portion" may sometimes be simply described as "flat portion", respectively. Each corner portion 3 of the directional electromagnetic steel sheet 1 has two or more bent portions 5 having a curved shape in a side view, and the sum of the bending angles of the bent portions 5, 5 existing in one corner portion 3 is 90°. The corner portion 3 has a second flat portion 4a between adjacent bent portions 5, 5. Therefore, the corner portion 3 has a configuration including two or more bent portions 5 and one or more second flat portions 4a. The embodiment of FIG. 2 has two bent portions 5, 5 in one corner portion 3. The embodiment of FIG. 3 has three bent portions 5, 5, 5 in one corner portion 3.

[0024] As shown in these examples, in the present embodiment, one corner portion 3 can be constituted by two or more bent portions 5. However, from the viewpoint of suppressing the generation of strain due to deformation during processing and suppressing iron loss, the bending angle φ (φ1, φ2, φ3) of the bent portion 5 is preferably 60° or less, and more preferably 45° or less. In the embodiment of FIG. 2 having two bent portions 5, 5 in one corner portion 3, from the viewpoint of reducing iron loss, for example, φ1 = 60° and φ2 = 30°, or φ1 = 45° and φ2 = 45°, etc. can be set. Also, in the embodiment of FIG. 3 having three bent portions 5, 5, 5 in one corner portion 3, from the viewpoint of reducing iron loss, for example, φ1 = 30°, φ2 = 30° and φ3 = 30°, etc. can be set. Further, from the viewpoint of production efficiency, it is preferable that the bending angles are equal. Therefore, when one corner portion 3 has two bent portions 5, 5, it is preferable to set φ1 = 45° and φ2 = 45°. Also, in the embodiment of FIG. 3 having three bent portions 5, 5, 5 in one corner portion 3, from the viewpoint of reducing iron loss, for example, it is preferable to set φ1 = 30°, φ2 = 30° and φ3 = 30°.

[0025] With reference to FIG. 4, the bent portion 5 will be described in more detail. FIG. 4 is a diagram schematically showing an example of one bent portion (curved portion) 5 of the grain-oriented electromagnetic steel sheet. FIG. 4 is a side view of the grain-oriented electromagnetic steel sheet 1. However, as described above, this figure is not limited to the "side surface" exposed to the outside of the wound iron core, but also includes a cross section parallel to this side surface (a cross section perpendicular to the Y-axis direction in FIG. 1). Hereinafter, regarding the shape of the bent portion 5, it will simply be described as "side view", which shall include a "cross-sectional view at a specific position in the steel sheet width direction" considering the cross section perpendicular to the Y-axis direction in FIG. 1 as the side surface. The bending angle of the bent portion 5 means the angular difference generated between the straight portion on the rear side in the bending direction and the straight portion on the front side in the bent portion 5 of the grain-oriented electromagnetic steel sheet 1, and is represented as the supplementary angle φ of the angle formed by two virtual lines Lb-elongation1 and Lb-elongation2 obtained by extending the straight line portions on the surfaces of the flat portions 4 on both sides sandwiching the bent portion 5 on the outer surface of the grain-oriented electromagnetic steel sheet 1. At this time, the point where the extended straight line detaches from the steel sheet surface is the boundary between the flat portion 4 and the bent portion 5 on the surface on the outer side of the steel sheet, which are points F and G in FIG. 4.

[0026] Furthermore, extend straight lines perpendicular to the outer surface of the steel sheet from points F and G respectively, and let the intersection points with the surface on the inner side of the steel sheet be points E and D respectively. These points E and D are the boundaries between the flat portion 4 and the bent portion 5 on the surface on the inner side of the steel sheet. And in this embodiment, the bent portion 5 is the portion of the grain-oriented electromagnetic steel sheet 1 surrounded by the above points D, E, F, and G in the side view of the grain-oriented electromagnetic steel sheet 1. In FIG. 4, the steel sheet surface including points D and E, that is, the inner surface of the bent portion 5 is shown as La, and the steel sheet surface including points F and G, that is, the outer surface of the bent portion 5 is shown as Lb. In addition, in the present embodiment, when strain concentrates in the minimum region within the bent portion 5, it is conceivable that the surfaces of the steel plates on both sides of the minimum region are pressed against each other and come into contact with each other by bending. That is, a situation is conceivable where a part of the surface of the steel plate having the minute recesses is not the surface exposed in the space where the bent steel plate is placed. Even in such a case, a line La is defined as the line following the surface of the steel plate having the minute recesses. Hereinafter, this line may be described as "curve La".

[0027] Also, in the present embodiment, the radius of curvature of the bent portion 5 is defined in a side view of the bent portion 5. Taking FIG. 4 as an example, a method for determining the radius of curvature of the bent portion 5 will be specifically described. First, on each of the flat portions 4 on both sides sandwiching the bent portion 5, a straight line that is in contact with the straight portion that is the surface of the flat portion 4 over at least 1 mm or more is determined. These are respectively defined as virtual lines Lb-elongation1 and Lb-elongation2, and the intersection point of these is defined as point B. Ideally, the lengths of line segment BF and line segment BG are the same, but in reality, due to variations in the processing situation and inevitable fluctuations, etc., some differences may occur. Even in such a case, in order to enable a proper evaluation of the effects of the present embodiment, points F' and G' are determined from points B, F, and G. That is, the longer distance between line segment BF and line segment BG is defined as LL (for example, assuming that line segment BG is longer than line segment BF). A point that is at a distance LL from point B toward point F on virtual line Lb-elongation1 is defined as point F', and a point that is at a distance LL from point B toward point G on virtual line Lb-elongation2 is defined as point G'. At this time, either point F' or point G' will coincide with the original point F or point G respectively (for example, when line segment BG is longer than line segment BF, point G' coincides with the original point G). Note that when the lengths of line segment BF and line segment BG are equal, in FIG. 4, point F' coincides with the original point F, and accordingly, point E' described below coincides with the original point E. Then, a straight line perpendicular to the outer surface of the steel plate is extended from each of point F' and point G', and the intersection point is defined as the center of curvature A. The intersection points of line segment AF' and line segment AG' with curve La are defined as point E' and point D', respectively. At this time, a circle passing through point E' and point D' with point A as the center is the curved surface approximating the bent portion 5 in the present embodiment, and the length of line segment AE' (which is equal to the length of line segment AD') is the radius of curvature in the present embodiment.

[0028] In the wound core according to the present embodiment, the radius of curvature at each bent portion 5 of each oriented electrical steel sheet 1 laminated in the plate thickness direction may have a certain degree of variation. This variation may be due to the forming accuracy, or it is also conceivable that unintentional variations occur during handling during lamination. Such unintentional errors can be suppressed to about 0.3 mm or less in current normal industrial manufacturing. When such variations are large, the radius of curvature can be measured for a sufficiently large number of steel sheets and averaged to obtain a representative value. Also, for some reason, it is conceivable to intentionally change the radius of curvature of the bent portion 5 at a specific part within the core, but the present embodiment does not exclude such a form. In addition, in the present embodiment, as described above, it is assumed that the lengths of line segment BF and line segment BG are different and the bending process is asymmetric. In such a situation, it is considered that strain is more locally concentrated in the region on the side where the length of the line segment is shorter, and the effect of the present embodiment is considered to be more effectively exerted on the side where the length of the line segment is shorter.

[0029] Note that there is no particular limitation on the method for measuring the form of the bent portion 5. For example, it can be measured by observing at 200 times magnification using a commercially available microscope (Nikon ECLIPSE LV150). In the present embodiment, by controlling the form of the bent portion 5 described below within a specific range, it has become possible to improve the efficiency of the wound core.

[0030] FIG. 5 and FIG. 6 are diagrams schematically showing an example of the grain-oriented electromagnetic steel sheet 1 for one layer in the wound core body 10. As shown in the examples of FIG. 5 and FIG. 6, the grain-oriented electromagnetic steel sheet 1 used in the present embodiment is bent, has a corner portion 3 composed of two or more bent portions 5 and a flat portion 4, and forms a substantially rectangular ring in side view through a joint portion 6 on the widthwise end surface of one or more grain-oriented electromagnetic steel sheets 1. In the present embodiment, it is only necessary that the wound core body 10 has a laminated structure that is substantially rectangular in side view as a whole. As shown in the example of FIG. 5, one grain-oriented electromagnetic steel sheet 1 may constitute one layer of the wound core body 10 through one joint portion 6. Also, as shown in the example of FIG. 6, one grain-oriented electromagnetic steel sheet 1 may constitute about half a circumference of the wound core 10, and two grain-oriented electromagnetic steel sheets 1 may constitute one layer of the wound core body 10 through two joint portions 6. Also, although the iron loss of the transformer usually increases as the number of joint portions increases, since the effect of the present invention exists in the bent portion, there may be three or more joint portions.

[0031] The plate thickness t of the grain-oriented electromagnetic steel sheet 1 used in the present embodiment is not particularly limited and may be appropriately selected according to the application or the like. Usually, it is in the range of 0.10 mm to 0.35 mm, preferably in the range of 0.15 mm to 0.23 mm.

[0032] 2. Form of the bent portion Here, the characteristics of the form of the bent portion 5 of the grain-oriented electromagnetic steel sheet 1 constituting the wound core body 10, which is one of the present embodiments, will be described. In the following description, the characteristic values defined in this embodiment and the characteristic points, lines, etc. necessary to determine those characteristic values will be described for one "side view". However, in this embodiment, the above measurement is performed on each cross-section (each side view) obtained by equally dividing the width direction of the directional electromagnetic steel sheet 1 into 21 parts, that is, a total of 20 cross-sections (side views), and this embodiment is defined by the average value thereof. That is, for the sake of simplicity of explanation, the measurement method will be described using "one side view", but the characteristic values obtained from each side view are not directly used for the definition of this embodiment. Instead, the average value of the above 20 data will be used as the definition of this embodiment. This is because, as described above, it is intended to evaluate the effect of this embodiment assuming that the shape of the bent portion 5 is not the same over the entire width direction of the directional electromagnetic steel sheet 1. In addition, when it is considered that there may be a bias in the 20 data and the above measurement method cannot represent the overall characteristics (for example, when the bent portion satisfies the present invention outside the cross-sections equally divided into 21 parts), the number of measurements may be increased to 20 or more to eliminate the suspected bias.

[0033] In this embodiment, the magnitude of the deviation between the curve represented by the curve La and the arc of the radius r (mm) that becomes the above curvature radius is defined. Hereinafter, the "arc of the radius r that becomes the curvature radius" will be simply described as the "curvature arc". As described above, the curvature arc is determined as an arc passing through points D' and E' with the center at point A. And in this embodiment, the value obtained by subtracting the curvature radius from the distance between point A and a point on the curve La (the curve representing the position of the inner surface side of the directional electromagnetic steel sheet 1) is defined as H (mm), and the maximum value of H is defined as Hmax (mm). And the average value of the above 20 Hmax satisfies the following formula (1). t is the plate thickness (mm) of the directional electromagnetic steel sheet 1. Hmax / t ≧ 0.10 ·····(1) Furthermore, in this embodiment, the plate thickness of the directional electromagnetic steel sheet 1 at point I where Hmax is obtained is defined as tm (mm). And the average value of the above 20 tm satisfies the following formula (2). tm / t ≦0.98···(2) Here, Hmax and tm are determined as the distances in the direction perpendicular to the curvature arc.

[0034] Since the bending process assumed in this embodiment is carried out by pressing against a mold having a specific radius, generally, the shape of the curve La is approximately an arc shape and does not deviate significantly from the curvature arc locally. In contrast, in this embodiment, the shape of the curve La deviates significantly from the curvature arc locally, and the steel plate thickness tm in this region becomes thinner than that in the peripheral region, resulting in a steep convex shape toward the outer surface side of the core. As described above, since the curvature arc (curvature radius r) is determined based on the flat region around the bent portion 5, when the bent portion 5 has a steep convex shape, although r itself does not change much, Hmax becomes a very large value locally. This embodiment sets Hmax to a value that cannot be achieved only by bending with a mold having a normal curvature.

[0035] The effect of this embodiment can be defined by the ratio of each of the above Hmax and the above tm to the plate thickness t of the directionally electromagnetic steel sheet 1. The value of Hmax / t is preferably 0.20 or more, more preferably 0.30 or more. Although no upper limit is particularly provided, when Hmax increases, it may lead to the absence of a substance (steel sheet) in the region along the inner peripheral portion and an increase in the gap, which may prevent the transmission of magnetic flux when the core is magnetized. Therefore, it is preferable to keep the value of Hmax / t at 0.50 or less. The value of tm / t is preferably 0.95 or less, more preferably 0.90 or less. Although no lower limit is particularly provided, when tm becomes excessively small, it may lead to the easy deformation of the bent portion 5 due to the action of an external force after bending, resulting in a decrease in the shape accuracy of the processed body of the directionally electromagnetic steel sheet 1 and may cause problems in handling the core. Therefore, it is preferable to keep the value of tm / t at 0.50 or more.

[0036] Moreover, the effect of this embodiment itself has "limiting deformation to a narrow region" as its basic mechanism. Therefore, in a situation where the entire deformation region is greatly expanded (the entire bent portion 5, that is, the curve La is long), the adverse effect of the wide deformation region becomes large, canceling out the merit of the local deformation brought about by this embodiment. From this, it is a preferable form to apply this embodiment after making the bent portion 5 itself smaller, that is, reducing the radius of curvature. Specifically, it is preferable that the radius of curvature is 5 mm or less, and further preferably 3 mm or less. Here, the "radius of curvature" defined as a preferable condition is the average value of the radius of curvature r obtained in each side view of the above 20 locations. Also, as described above, the shape of the bent portion 5 of this embodiment as viewed from the side is assumed to be asymmetric. However, for concentrating the strain due to bending processing in a narrow region, it is more convenient if the shape of the bent portion 5 is symmetric. That is, when the shape of the bent portion 5 is asymmetric, the region where the bending process is gentle, that is, the region corresponding to the line segment BG in the above example, has the strain spreading into a wide region. Concentrating the strain in this region into a narrower region is a preferable change for this embodiment, and this acts to make the shape of the bent portion 5 symmetric. Of course, in the example of FIG. 4, although the overall deformation region can also be narrowed by processing so that the region corresponding to the narrow line segment BF of the bent region becomes even narrower, the operation of further concentrating the strain at a site where the strain is already concentrated in a narrow region is not efficient. In this embodiment, the symmetry of the shape of the bent portion 5, that is, the degree of strain concentration, is defined by the position (angle θ (°)) on the central angle of the arc of the point indicating Hmax. As shown in Fig. 7, with the center at point A, in the arc formed by points D' and E', let the angle counterclockwise from line segment AD' be θ (°). Point D' located on curve La on line segment AD' is at θ = 0°, and point E' located on curve La on line segment AE' is at θ = Φ°. At this time, when the angle θ' formed by line segment AI and line segment AD' for point I on curve La where Hmax is obtained is considered, AR = 1 / 2 - |θ' / Φ - 1 / 2|. And it is preferable that the average value of the above 20 ARs is greater than 0.25 and less than or equal to 0.50. More preferably, AR is 0.33 to 0.50, and even more preferably 0.40 to 0.50. AR = 0.50 is the situation where Hmax exists at the center of the bent portion 5, which is the most preferable form.

[0037] The above-mentioned H and θ are measured at 20 cross-sections (side view) in the width direction of the directional electromagnetic steel sheet 1 as described above. And the effect of this embodiment is manifested if the average value of the above 20 data satisfies the above regulations. However, regarding the extending direction of the bent portion 5, that is, the width direction of the long directional electromagnetic steel sheet 1, it is preferable that the ratio of the region satisfying the condition regarding the above AR is large. In this embodiment, when the total number of cross-sections for measuring the shape of the bent portion 5 is Nt and the number of cross-sections where AR is in the range of 0.25 to 0.50 in each cross-section is Nc, it is preferable that Nc / Nt > 0.50. This indicates a preferable situation regarding the abundance of good sites that cannot be fully expressed simply by the average value of the characteristic values obtained at each cross-section. The value of Nc / Nt is preferably greater than 0.70, more preferably greater than 0.85, and most preferably 1.00.

[0038] Note that the above description is for one bent portion 5, but in this embodiment, as long as one of the multiple existing bent portions 5 satisfies the above conditions. This is because the effect is manifested as long as even one bent portion 5 satisfies the conditions of this embodiment. However, since normal cores rarely change the processing conditions for each bent portion 5, if even one bent portion 5 satisfies the conditions, the bent portions 5 at many sites in the core will also satisfy the conditions.

[0039] (1) Grain-oriented electrical steel sheet As described above, in the grain-oriented electrical steel sheet 1 used in this embodiment, the mother steel sheet is a steel sheet in which the orientations of crystal grains in the mother steel sheet are highly concentrated in the {110}<001> orientation, and has excellent magnetic properties in the rolling direction. In this embodiment, a known grain-oriented electrical steel sheet 1 can be used as the mother steel sheet. Hereinafter, an example of a preferable mother steel sheet will be described.

[0040] The chemical composition of the mother steel sheet contains Si: 2.0% to 7.0% by mass, and the balance is Fe. This chemical composition is to control the crystal orientation into a Goss texture in which the {110}<001> orientation is concentrated, and to ensure good magnetic properties. Regarding other elements, they are not particularly limited, and it is allowed to contain known elements within a known range in place of Fe. The typical content ranges of typical elements are as follows. C: 0 to 0.0050%, Mn: 0 to 1.0%, S: 0 to 0.0150%, Se: 0 to 0.0150%, Al: 0 to 0.0650%, N: 0 to 0.0050%, Cu: 0 to 0.40%, Bi: 0 to 0.010%, B: 0 to 0.080%, P: 0 to 0.50%, Ti: 0 to 0.0150%, Sn: 0 to 0.10%, Sb: 0 to 0.10%, Cr: 0 to 0.30%, Ni: 0 to 1.0%, Nb: 0 to 0.030%, V: 0 to 0.030%, Mo: 0 to 0.030%, Ta: 0 to 0.030%, W: 0 to 0.030%, These selected elements may be included according to their purpose, so there is no need to limit the lower limit value, and they may not be substantially included. Even if these selected elements are included as impurities, the effects of this embodiment will not be impaired. Note that impurities refer to elements that are contained unintentionally, and mean elements that are mixed in from ores, scraps, or manufacturing environments as raw materials when industrially manufacturing the mother steel sheet.

[0041] The chemical composition of the mother steel sheet may be measured by a general analysis method for steel. For example, the chemical composition of the mother steel sheet may be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Specifically, for example, a 35 mm square test piece is obtained from the central position of the mother steel sheet after removing the coating, and it can be specified by measuring under conditions based on a calibration curve prepared in advance using an ICPS-8100 (measurement device) manufactured by Shimadzu Corporation or the like. Note that C and S may be measured using the combustion-infrared absorption method, and N may be measured using the inert gas fusion-thermal conductivity method.

[0042] Note that the above chemical composition is that of the grain-oriented electrical steel sheet 1. When the grain-oriented electrical steel sheet 1 serving as the measurement sample has a primary coating (glass coating, intermediate layer), insulating coating, etc. made of oxides or the like on its surface, these are removed by the following method and then the chemical composition is measured.

[0043] (2) Manufacturing method of grain-oriented electrical steel sheet The manufacturing method of the mother steel plate is not particularly limited, and a conventionally known manufacturing method of the grain-oriented electrical steel sheet 1 can be appropriately selected. As a preferable specific example of the manufacturing method, for example, after heating a slab having a C content of 0.04 to 0.1% by mass and having the chemical composition of the above mother steel plate to 1000 °C or higher and performing hot rolling, hot-rolled plate annealing is performed as necessary, and then cold rolling is performed by one or more cold rollings sandwiching an intermediate annealing to obtain a cold-rolled steel plate. The cold-rolled steel plate is heated to 700 to 900 °C in, for example, a wet hydrogen-inert gas atmosphere for decarburization annealing, and further nitriding annealing is performed as necessary. After applying an annealing separating agent, finish annealing is performed at about 1000 °C, and an insulating film is formed at about 900 °C. Further, after that, painting or the like for adjusting the friction coefficient may be performed. In addition, even a steel plate obtained by performing a process generally called "magnetic domain control" in a known method in the manufacturing process of the steel plate can enjoy the effects of the present embodiment.

[0044] 3. Manufacturing method of wound core The basic manufacturing method of the wound core 10 according to the present embodiment is not particularly limited as long as the wound core 10 according to the present embodiment can be manufactured. For example, a method according to a known wound core 10 introduced as Patent Documents 8 to 10 in the background art may be applied. In particular, the method using the UNICORE (https: / / www.aemcores.com.au / technology / unicore / ) manufacturing apparatus of AEM UNICORE can be said to be optimal.

[0045] In the manufacturing method of the wound core 10 according to the present embodiment, when bending a material, after specifying a bending portion, a concave portion having a width smaller than the bending radius is formed on the inner surface of the bending planned portion of the bending planned portion, and then the region including the concave portion forming portion is bent. As a preferable specific example of the manufacturing method of the wound core 10 according to the present embodiment, for example, as shown in FIG. 8(a), by forming minute concave portions 7 on the surface of the steel plate at the bending planned site where the bent portion 5 is formed, the surface shape of the bent portion 5 after bending can be appropriately controlled.

[0046] The means (device) for forming the minute recesses 7 on the surface of the steel sheet is not particularly limited. For example, it is possible to mechanically scratch the surface of the steel sheet with a sharp die like a scribing tool, perform cutting with a sharp tool, or form the recesses by pressing a sharp convex die. Further, it is conceivable to form minute grooves by chemical reaction such as irradiation with high energy rays like a laser or etching. Considering the simplicity and cost of the device, scribing or laser irradiation is a preferable form.

[0047] These minute recesses 7 may be formed anywhere as long as it is in the region where stress is generated by bending. However, considering the concentration of deformation, it is preferable that the center of the bending and the recess coincide. That is, as shown in Fig. 8(a), in the steel sheet (directional electromagnetic steel sheet) 1a before bending, that is, before forming the bent portion 5, minute recesses 7 are formed at a position (center portion) approximately equidistant from both ends 5a, 5a of the portion 5b that will become the bent portion 5, or the existing recesses are processed so that they become the center of the bending. In this case, it may be formed on at least one of the outer surface side and the inner surface side of the steel sheet before bending. However, considering the effect, simplicity of the device and cost, an embodiment of forming only on the inner surface side of the steel sheet is preferable. Then, for example, a recess 7 having a V-shaped cross section is formed on the inner surface side or the outer surface side of the bent portion of the steel sheet 1a before forming the bent portion 5, and then the bent portion 5 is formed by bending. In Fig. 8(a), the recess 7 is formed on the inner surface side of the bent portion. Note that the shape of the recess 7 is not limited to a V-shaped cross section, and may be, for example, a rectangular cross section or an arc-shaped cross section.

[0048] The shape of the recess 7 formed as described above is not particularly limited as long as it causes concentration of deformation in bending. However, the depth h (μm) of the recess 7 is preferably about 5 μm or more. Of course, since the steel plate will be broken when h = t, h is less than t. Also, since the main deformation during bending is borne by the remaining plate thickness portion excluding the recess 7, from the perspective of concentrating the deformation, it is preferable to make the remaining plate thickness, that is, t - h, as small as possible. However, if the remaining plate thickness becomes excessively thin, there is a concern that unintended deformation may occur during the handling of the steel plate. Therefore, h is preferably 0.8t or less, more preferably 0.6t or less, and preferably 0.4t or less. As shown in FIG. 8(b), the recess 7 formed on the inner surface side during bending is deformed so that the opening width w decreases as the bending progresses.

[0049] The width w (μm) of the recess 7 may be appropriately determined in consideration of the depth h and the bending angle. If w is too small, the inner surface of the recess will contact during bending and the opening will close, and the deformation will proceed in a form where the recess area is strongly crushed, which will also increase the total amount of strain in the recess area, so this is not preferable. On the other hand, if the width w is too wide, the opening will not close even after the bending deformation is completed, causing a discontinuity in the material along the magnetization direction of the steel plate and significantly inhibiting the core efficiency. Considering such effects, as shown in FIG. 8(c), it is a preferable form to design such that the opening of the recess 7 closes almost simultaneously with the end of the bending deformation.

[0050] Another factor to be considered in the formation of the recess 7 is the relationship between the extending direction of the recess 7 and the extending direction of the bending portion (bending region) in the width direction of the grain-oriented electrical steel sheet 1. In the bending process targeted by this embodiment, the grain-oriented electrical steel sheet 1 is not bent in a spiral shape, but is bent so that the ends of the steel plate maintain the same height in a side view. That is, the bending region exists along the width direction of the grain-oriented electrical steel sheet 1 (i.e., along the Y-axis direction in FIG. 1). And in this specification, it is described on the premise that the continuous direction of the recess 7 coincides with the Y-axis direction in FIG. 1, that is, the recess 7 also exists along the width direction of the grain-oriented electrical steel sheet 1. Basically, this situation is assumed, and although it is the best form, practically, the existing state of the recess 7 in the width direction of the steel plate may not completely coincide with the Y-axis, and some deviation is allowed. If it is within 5°, a considerable effect can be obtained. In addition, in this specification, although the description is based on the premise that the recess 7 is formed continuously, it is also possible to obtain the effect even if the recesses are continuous in the form of circular dots or extend intermittently in a dashed line in the extending direction of the recess 7. Furthermore, the influence of the formation temperature of the recess 7 is also considered. Although the formation of the recess 7 is accompanied by the accumulation of a certain amount of strain, this strain increases the total amount of strain in the bent portion 5 and also becomes a factor for reducing the core efficiency. To avoid this, it is effective to form the recess 7 at a high temperature. Considering the working load and the like, processing within a temperature range up to about 400°C is also applicable in practice.

[0051] In this embodiment, the form and formation conditions of the above-mentioned recess 7 are not particularly limited. However, considering the shape of the curve La after bending, it is not very difficult for those skilled in the art to appropriately adjust from the above viewpoints.

[0052] Furthermore, according to a known method, heat treatment may be carried out as necessary. Considering that the main feature of the technology of this embodiment is "localization of processing strain", it may seem strange that the effectiveness of this embodiment extends until after the processing strain is removed by heat treatment. However, in reality, for the core bent by this embodiment, the improvement effect of the core efficiency can be confirmed not only in the state as processed but also in the state after the strain is removed by heat treatment. The reason for this is not clear, but it is considered that the flat portion expands due to the reduction of the bent region (regardless of the residual strain as a form), and thus the magnetic flux distribution in the core is in a favorable state.

[0053] In addition, the obtained wound core body 10 may be used as a wound core as it is, or it may be fixed using known fasteners such as binding bands as necessary to form a wound core.

[0054] The present invention is not limited to the above embodiment. The above embodiment is an example, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same operational effects is included in the technical scope of the present invention.

Example

[0055] Hereinafter, the technical content of the present invention will be further described by giving examples of the present invention. The conditions in the examples shown below are example conditions adopted for confirming the feasibility and effects of the present invention, and the present invention is not limited to these condition examples. Also, the present invention can adopt various conditions as long as it does not deviate from the gist of the present invention and achieves the object of the present invention.

[0056] Using the directionality electromagnetic steel sheet shown in Table 1, the iron core shown in Table 2 was fabricated, and the iron core characteristics were measured. The detailed manufacturing conditions and characteristics are shown in Tables 3A to 3F.

[0057]

Table 1

[0058]

Table 2

[0059]

Table 3A

[0060]

Table 3B

[0061]

Table 3C

[0062]

Table 3D

[0063]

Table 3E

[0064]

Table 3F

[0065] (Directional electromagnetic steel sheet) The magnetic properties of the directional electromagnetic steel sheet were measured based on the single-sheet magnetic property test method (Single Sheet Tester: SST) specified in JIS C 2556:2015. As magnetic properties, the magnetic flux density B8(T) in the rolling direction of the steel sheet when excited at 800 A / m and the iron loss at an AC frequency of 50 Hz and an excitation magnetic flux density of 1.7 T were measured. The magnetic properties are shown in Table 1 together with the chemical composition.

[0066] (Core) Using each steel plate as a raw material, core cores No. a to f having the shapes shown in Table 2 and Fig. 9 were manufactured. L1 is parallel to the X-axis direction and is the distance between mutually parallel oriented electromagnetic steel sheets 1 at the innermost circumference of the wound core in the flat cross-section in side view (distance between inner-plane portions). L2 is parallel to the Z-axis direction and is the distance between mutually parallel oriented electromagnetic steel sheets 1 at the innermost circumference of the wound core in the longitudinal cross-section in side view (distance between inner-plane portions). L3 is the stacking thickness of the wound core parallel to the X-axis direction (thickness in the stacking direction) (or parallel to the Z-axis direction). L4 is the width of the stacked steel plates of the wound core in the Y-axis direction. L5 is the distance between plane portions (distance between bent portions) that are adjacent to each other at the innermost part of the wound core and are arranged to form a right angle together. In other words, L5 is the longitudinal length of the plane portion 4a with the shortest length among the plane portions 4 and 4a of the innermost circumferential oriented electromagnetic steel sheet. r is the radius of curvature of the bent portion on the inner surface side of the wound core, and φ is the bending angle (°) of the bent portion of the wound core. The substantially rectangular core cores No. a to f have a plane portion with an inner-plane portion distance of L1 divided approximately in the center of the distance L1, and have a structure in which two cores having a "substantially U-shaped" shape are joined. Here, the core of core No. f is a core manufactured by a method in which a steel plate is wound into a cylindrical shape, and then the corner portion of the cylindrical laminate is pressed to have a constant curvature while remaining in the cylindrical laminate state, formed into a substantially rectangular shape, and then annealed to maintain the shape. For this reason, the radius of curvature r of the bent portion varies greatly depending on the stacking position of the steel plates. The r (mm) from Table 3A to Table 3F is the r at the innermost surface. r increases as it goes to the outside and is about 85 mm at the outermost peripheral portion.

[0067] (Recess) By laser control, mechanical (press method V-notch), mechanical (press method U-notch), mechanical (gear type), mechanical (disk rotation type), mechanical (scribing), and etching, recesses with changed h and w were formed. The extending shape of the recesses and the processing temperature are shown in Table 3A to Table 3F. Basically, the concave portion was formed at the center of the width of the bent portion, at the position where the AR is 0.50. In Tables 3A to 3F, those with θ: 20 to 25° correspond to this. Here, the center of the width is strictly θ = 22.5°, and processing aiming at this has been carried out. However, due to processing accuracy, the actual result is θ: 20 to 25°. Also, the concave portion was formed across the entire width of the steel plate. In Tables 3A to 3F, the test with "extended shape" being "continuous" and Nc / Nt = 1.00 corresponds to this. For some materials, Test Nos. 6a to 6e, 6k to 6m, 29a to 29e, 29k to 29m, the formation position of the concave portion with respect to the width of the bent portion was changed. Specifically, the concave portion was formed not at the center of the width of the bent portion but at a position where θ is less than 20° or more than 25°. Also, for some materials, Test Nos. 6f to 6m, 29f to 29m, the "extended shape" was changed. Specifically, the concave portion was made not in a continuous linear shape but in a dashed line shape. Considering avoiding bias and dispersing the concave portions within the length of the 150 mm width of the steel plate, the length of one concave portion in the width direction of the steel plate was set to 2 mm, and the interval in the width direction of the steel plate between each concave portion was changed according to the formation ratio of the concave portions. For example, in the case of "intermittent 90%", in the width direction of the steel plate, a 2 mm long concave portion and an unprocessed portion of 0.22 mm (interval between concave portions) were arranged. For example, in the case of "intermittent 70%", in the width direction of the steel plate, a 2 mm long concave portion and an unprocessed portion of 0.86 mm (interval between concave portions) were arranged. Regarding characteristic values other than Nc / Nt indicating the concave portion shape, the data obtained by measuring at 20 cross-sections where the width direction of the steel plate was equally divided into 21 parts were averaged. Nc / Nt was determined based on the above 20 measurement data.

[0068] (Efficiency of the core) For each core made of each steel plate, the no-load loss was obtained, and the building factor (BF) was obtained by taking the ratio with the magnetic characteristics of the material steel plate shown in Table 1. The results are shown in Tables 3A to 3F. In this example, those with BF of 1.12 or less were considered qualified.

[0069] From the results in Tables 3A to 3F, A wound core in which grain-oriented electromagnetic steel sheets are laminated in the plate thickness direction and which is substantially rectangular in side view, wherein the grain-oriented electromagnetic steel sheets have a flat portion and a bent portion continuously alternating in the longitudinal direction, the grain-oriented electromagnetic steel sheets contain, by mass%, Si: 2.0 to 7.0%, and the balance consists of Fe and impurities, have an aggregate structure oriented in the Goss orientation, and in a side view of at least one bent portion of the laminated grain-oriented electromagnetic steel sheets, for the curve representing the inner surface of the bent portion, the maximum value of the difference between the distance from the center of curvature of the bent portion and the radius of curvature r is Hmax, the plate thickness of the grain-oriented electromagnetic steel sheet at the point where Hmax is obtained is tm, and when t is the plate thickness of the grain-oriented electromagnetic steel sheet, Hmax / t ≧ 0.10 ·····(1) tm / t ≦ 0.98 ·····(2) It has been clarified that the wound core of this embodiment, which satisfies the above conditions, has characteristics of low iron loss. Also, it has been clarified that the wound core of this embodiment, in which the formation position of the recess is near the center of the width of the bent portion (AR ≧ 0.25) and the ratio in the extending direction of the bent portion of the region where the recess is formed near the center of the width of the bent portion is high (Nc / Nt > 0.50), has characteristics of low iron loss.

Explanation of Signs

[0070] 1 Grain-oriented electromagnetic steel sheet 1a Grain-oriented electromagnetic steel sheet before forming the bent portion 2 Laminated structure 3 Corner portion 4 Flat portion 5 Bent portion 6 Joint portion 7 Recess 10 Wound core body (wound core)

Claims

1. A wound core in which oriented electromagnetic steel sheets are laminated in the plate thickness direction and which is substantially rectangular in side view, wherein in the oriented electromagnetic steel sheet, a flat portion and a bent portion are alternately continuous in the longitudinal direction, the oriented electromagnetic steel sheet contains, in mass %, Si: 2.0 to 7.0%, has a chemical composition in which the balance consists of Fe and impurities, has an aggregate structure oriented in the Goss orientation, and in side view of at least one bent portion of the laminated oriented electromagnetic steel sheets, for a curve representing the inner surface of the bent portion, when the maximum value of the difference between the distance from the center of curvature of the bent portion and the radius of curvature r is Hmax, the plate thickness of the oriented electromagnetic steel sheet at the point where Hmax is obtained is tm, and t is the plate thickness of the oriented electromagnetic steel sheet, Hmax / t ≥ 0.10 ······ (1) tm / t ≤ 0.98 ······ (2) A wound core characterized by satisfying the above conditions.

2. Taking the center of curvature as point A, extending perpendicular lines from the boundaries between the flat portions and the bent portions on both sides sandwiching the bent portion on the outer surface of the bent portion to the outer surface, and designating the intersection points with the curve representing the inner surface as point E' and point D' respectively, taking the point where Hmax is obtained on the curve representing the inner surface as point I, taking the angle between line segment AD' and line segment AI as θ' (°), taking the angle between line segment AD' and line segment AE' as Φ (°), and when AR = 1 / 2 - |θ' / Φ - 1 / 2|, the wound core according to claim 1, characterized in that AR is greater than 0.25 and not more than 0.

50.

3. When the shape of the bent portion is measured at a plurality of cross-sections at equal intervals along the width direction of the oriented electromagnetic steel sheet, when the total number of cross-sections to be measured is Nt and the number of cross-sections in which AR is in the range of 0.25 to 0.50 in each cross-section is Nc, the wound core according to claim 2, characterized in that Nc / Nt > 0.

50.

4. The wound core according to any one of claims 1 to 3, characterized in that the inner radius of curvature r in side view of the bent portion is 5 mm or less.

5. The inner surface has a recess that is recessed in a direction away from the center of curvature. The point of Hmax is the bottom of the concave portion, The radius of curvature r is the radius of curvature of the inner surface when it is assumed that there is no concave portion in the side view. The wound core according to any one of claims 1 to 4.

6. A method for manufacturing a wound core made of a grain-oriented electrical steel sheet, When bending the material, after identifying the bending portion, A concave portion having a width smaller than the radius of curvature of the bending is formed on the inner surface to be bent of the planned bending portion, Then, the region including the concave portion forming portion is bent The method for manufacturing a wound core according to any one of claims 1 to 5, characterized by the above.

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