wound core

Abstract

The wound core is a wound core having a substantially rectangular wound core body in a side view, in the wound core body, a first planar portion and a corner portion are alternately continuous, and in at least one corner portion, with respect to at least one of 2 or more bending portions, the following (1) to (3) are satisfied. Tave ≤ 40 nm (1), (To - Tu) / Tave ≤ 0.50 (2), Tave (To - Tu) ≤ 240 nm 2 (3).

Description

Technical Field

[0001] This invention relates to wound iron cores. This application claims priority based on Japanese Patent Application No. 2020-178900, filed on October 26, 2020, the contents of which are incorporated herein by reference. Background Technology

[0002] Directional electromagnetic steel sheet contains less than 7% by mass of Si and has secondary recrystallized grains concentrated in {110}. <001> Steel sheet with a secondary recrystallization texture of orientation (Goss orientation). The magnetic properties of directional electromagnetic steel sheet are affected by the {110} direction. <001> The concentration of orientation has a significant impact. In recent years, in practical directional electromagnetic steel sheets, according to the principle of making the crystal... <001> The angle between the direction of rolling and the rolling direction was controlled to fall within a range of about 5°.

[0003] Directional electromagnetic steel sheets are laminated and used in transformer cores, etc., but the main magnetic properties required are high magnetic flux density and low iron loss. It is known that crystal orientation is strongly correlated with these properties, and for example, precise orientation control techniques such as those disclosed in Patent Documents 1-3 have been disclosed.

[0004] To reduce iron loss, a film is formed on the surface of the steel plate. In addition to reducing iron loss as a single steel plate by applying tension to the steel plate, this film also aims to reduce iron loss as a core when steel plates are stacked together by ensuring electrical insulation between the steel plates.

[0005] As a directional electromagnetic steel sheet with a film formed on the surface of a steel sheet, for example, there is a directional electromagnetic steel sheet with an intermediate layer (primary coating) formed on the surface of a mother steel sheet, which is mainly composed of magnesium olivine (Mg2SiO4), and an insulating film formed on the surface of the intermediate layer.

[0006] This tightness is mainly ensured by the anchoring effect generated by the unevenness of the interface between the mother steel plate and the intermediate layer. However, the unevenness of this interface also becomes an obstacle to the movement of magnetic domain walls when the electromagnet is magnetized, thus hindering the reduction of iron loss. Therefore, in order to reduce iron loss without the presence of a finished annealed film, patent documents 4-7 have disclosed techniques such as those described above: in a state where the interface is smoothed, a special intermediate layer of several nm to several tens of nm formed of SiO2 or TiN is used to ensure the tightness of the insulating film.

[0007] In addition, the manufacturing of wound iron cores has been widely known in the past, for example, by methods described in Patent Document 8: after the steel plate is rolled into a cylindrical shape, the corners are pressed in a manner that forms a certain curvature in the state of a cylindrical laminate, and after forming a roughly rectangular shape, stress is relieved and the shape is maintained by annealing.

[0008] On the other hand, as another manufacturing method for wound iron cores, patent documents 9-11 disclose a technique where the steel plate at the corner of the wound iron core is pre-bent to form a relatively small bending area with a radius of curvature of 3 mm or less, and the bent steel plate is then stacked to form the wound iron core. According to this manufacturing method, the large-scale pressing process as in the past is unnecessary; the steel plate is precisely bent to maintain the shape of the iron core, and the processing strain is concentrated only in the bending portion (corner). Therefore, the strain removal process performed using the aforementioned annealing step can be omitted, resulting in significant industrial advantages and progress in application.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2001-192785

[0012] Patent Document 2: Japanese Patent Application Publication No. 2005-240079

[0013] Patent Document 3: Japanese Patent Application Publication No. 2012-052229

[0014] Patent Document 4: Japanese Patent No. 4025514

[0015] Patent Document 5: Japanese Patent Application Publication No. 2002-322566

[0016] Patent Document 6: Japanese Patent Application Publication No. 2019-019360

[0017] Patent Document 7: Japanese Patent Application Publication No. 2005-264236

[0018] Patent Document 8: Japanese Patent Application Publication No. 2005-286169

[0019] Patent Document 9: Japanese Patent No. 6224468

[0020] Patent Document 10: Japanese Patent Application Publication No. 2018-148036

[0021] Patent Document 11: Australian Patent Application Publication No. 2012337260 Summary of the Invention

[0022] The problem that the invention aims to solve

[0023] The inventors of this invention conducted a detailed study on the efficiency of transformer cores manufactured by a method in which steel plates are pre-bent to form relatively small bending regions with a radius of curvature of less than 5 mm, and the bent steel plates are stacked to form a wound core. The results showed that even when using steel plates with approximately the same crystal orientation control and approximately the same magnetic flux density and iron loss measured on a single plate as raw materials, differences in core efficiency can still occur.

[0024] The causes were investigated, and it was found that the difference in efficiency, which is the problem, varies in degree depending on the size and shape of the iron core. Comparing the efficiency differences caused by different steel grades confirmed the influence of the type of intermediate layer, particularly its thickness and shape. Further detailed investigation suggests that the shape of the intermediate layer, in particular, alters the degree of resistance to magnetization caused by bending at the bend, thus affecting the degree of iron loss degradation in the steel plate containing the bend.

[0025] From this perspective, we studied various steel plate manufacturing conditions and core shapes, and categorized their effects on core efficiency. The result is that by optimally controlling the morphology of the intermediate layer of the raw material, it is possible to control the core efficiency in a way that matches the magnetic properties of the steel plate raw material.

[0026] The present invention was made in view of the above-mentioned problems, and the object is to provide a wound core in which the efficiency is improved in a way that suppresses unintentional deterioration in a wound core manufactured by the following method: a steel plate is pre-bent in such a way that a relatively small bending area with a radius of curvature of less than 5 mm is formed, and the bent steel plate is stacked to form a wound core.

[0027] Methods for solving problems

[0028] To achieve the above objectives, the present invention is characterized by having a wound core body that is substantially rectangular in shape when viewed from the side.

[0029] In the aforementioned wound core body, the directional electromagnetic steel plate, in which the first planar portion and the corner portion alternately continue in the length direction, and the angle formed by two adjacent first planar portions of each corner portion is 90°, includes overlapping portions in the thickness direction, and has a generally rectangular stacked structure when viewed from the side.

[0030] Each of the aforementioned corner portions, viewed from the side by the aforementioned directional electromagnetic steel plate, has two or more curved portions with a curved shape, and a second flat portion is provided between adjacent curved portions. The total curvature angle of each curved portion present at a corner portion is 90°.

[0031] In a side view of the curved portion, the radius of curvature r on the inner surface side is 1 mm to 5 mm,

[0032] The grain-oriented electrical steel sheet has the following chemical composition:

[0033] In terms of mass%:

[0034] Si: 2.0 to 7.0%,

[0035] the balance comprises Fe and impurities,

[0036] the grain-oriented electrical steel sheet has a texture oriented along the Goss orientation, and

[0037] in at least one corner portion, for at least one of the two or more curved portions present, the following formulas (1) to (3) are satisfied.

[0038] Tave≤40nm (1)

[0039] (To-Tu) / Tave≤0.50 (2)

[0040] Tave(To-Tu)≤240nm 2 (3)

[0041] wherein, the thickness T (nm) of the intermediate layer provided on the surface of the base steel sheet of the grain-oriented electrical steel sheet is measured at a plurality of positions in the first and second flat surface regions adjacent to the curved portion, the average thickness of the thickness T (nm) of the intermediate layer is defined as Tave (nm), the maximum thickness is defined as Tmax (nm), the minimum thickness is defined as Tmin (nm), the average value of data with T>Tave is defined as To (nm), and the average value of data with T<Tave is defined as Tu (nm).

[0042] Furthermore, in the above configuration of the present invention, in at least one corner portion, for at least one of the two or more curved portions present, the following formula (4) may also be satisfied.

[0043] N(To-Tu)≤24nm (4)

[0044] wherein, in the thickness distribution of the intermediate layer obtained along the direction of the steel sheet surface, a region where continuous measured values satisfy T>Tave is counted as one region, and the number of regions in all measurement regions is defined as N.

[0045] Furthermore, in the above configuration of the present invention, in at least one corner portion, for at least one of the two or more curved portions present, the following formula (5) may also be satisfied.

[0046] N≥2 (5)

[0047] Furthermore, in the above configuration of the present invention, in at least one corner portion, with regard to the existence of at least one of two or more curved portions, the following equation (6) can also be satisfied.

[0048] (Tmax-Tmin) <Tave (6)

[0049] Invention Effects

[0050] According to the present invention, in a wound iron core formed by stacking bent steel plates, unintentional efficiency degradation can be effectively suppressed. Attached Figure Description

[0051] Figure 1 This is a perspective view schematically illustrating one embodiment of the wound iron core of the present invention.

[0052] Figure 2 yes Figure 1 The side view of the wound iron core shown in the embodiment.

[0053] Figure 3 This is a side view schematically illustrating another embodiment of the wound iron core of the present invention.

[0054] Figure 4 This is a side view schematically showing an example of a curved portion of the directional electromagnetic steel sheet constituting the wound core of the present invention.

[0055] Figure 5 This is a side view schematically showing an example of a single layer of directional electromagnetic steel sheet constituting the wound core of the present invention.

[0056] Figure 6 This is a side view schematically showing another example of a single layer of directional electromagnetic steel sheet constituting the wound core of the present invention.

[0057] Figure 7 This is a schematic diagram illustrating a method for measuring the thickness of the intermediate layer of the directional electromagnetic steel plate constituting the wound core of the present invention.

[0058] Figure 8 This is a schematic diagram showing the dimensions of the wound iron core manufactured in the embodiments and comparative examples.

[0059] Figure 9 The diagram shows a schematic configuration of the three-phase wound iron core manufactured in the embodiments and comparative examples. (a) is a front view, and (b) is a cross-sectional view of line AA in (a). Detailed Implementation

[0060] The wound iron core of the present invention will now be described in detail. However, the present invention is not limited to the configuration disclosed in this embodiment, and various modifications can be made without departing from the spirit of the invention. It should be noted that the lower and upper limits of the numerical ranges described below are included within the range. Values ​​expressed as "more than" or "less than" are not included in the numerical range. Furthermore, the "%" in chemical composition refers to "mass %" unless otherwise specified.

[0061] Furthermore, the terms used in this specification that specifically describe shape, geometric conditions, and their degree, such as "parallel," "perpendicular," "identical," "right angle," etc., as well as the values ​​of length and angle, are not strictly defined and are interpreted to include the extent to which the same function can be expected.

[0062] In addition, in this specification, "directional electromagnetic steel plate" is sometimes simply referred to as "steel plate" or "electromagnetic steel plate", and "wound iron core" is simply referred to as "iron core".

[0063] The wound core of this embodiment is characterized in that it is a wound core having a generally rectangular core body when viewed from the side.

[0064] In the aforementioned wound core body, the directional electromagnetic steel plate, in which the first planar portion and the corner portion alternately continue in the length direction, and the angle formed by two adjacent first planar portions of each corner portion is 90°, includes overlapping portions in the thickness direction, and has a generally rectangular stacked structure when viewed from the side.

[0065] Each of the aforementioned corner portions, viewed from the side by the aforementioned directional electromagnetic steel plate, has two or more curved portions with a curved shape, and a second flat portion is provided between adjacent curved portions. The total curvature angle of each curved portion present at a corner portion is 90°.

[0066] The radius of curvature r of the inner surface of the aforementioned curved portion, viewed from the side, is 1 mm to 5 mm.

[0067] The aforementioned directional electromagnetic steel sheet has a chemical composition containing 2.0 to 7.0% Si by mass, with the remainder being Fe and impurities, has a texture oriented along a Gaussian orientation, and in at least one corner, with regard to at least one of two or more bends, satisfies the following equations (1) to (3).

[0068] Tave≤40nm (1)

[0069] (To-Tu) / Tave≤0.50 (2)

[0070] Tave(To-Tu)≤240nm2 (3)

[0071] Wherein, the thickness T (nm) of the intermediate layer disposed on the surface of the base steel sheet of the grain-oriented electrical steel sheet is measured at a plurality of positions in the first and second planar region adjacent to the curved portion, the average thickness Tave (nm) is obtained from the thickness T (nm) of the intermediate layer, the maximum thickness is denoted as Tmax (nm), the minimum thickness is denoted as Tmin (nm), the average value of data satisfying T>Tave is denoted as To (nm), and the average value of data satisfying T<Tave is denoted as Tu (nm).

[0072] 1. Shapes of wound iron core and grain-oriented electrical steel sheet

[0073] First, the shape of the wound iron core according to the present embodiment will be described. The shapes of the wound iron core and the grain-oriented electrical steel sheet described herein are not particularly novel per se. For example, the wound iron core and the grain-oriented electrical steel sheet are merely those conforming to the known shapes of wound iron cores and grain-oriented electrical steel sheets introduced as patent documents 9 to 11 in the background art.

[0074] Figure 1 is a schematic perspective view showing one embodiment of a wound iron core. Figure 2 is Figure 1 a side view of the wound iron core shown in the embodiment. In addition, Figure 3 is a schematic side view showing another embodiment of a wound iron core.

[0075] It should be noted that the so-called side view in the present embodiment refers to observing along the width direction of the elongated grain-oriented electrical steel sheet constituting the wound iron core ( Figure 1 the Y-axis direction in). A side view is a drawing showing the shape recognized by side view ( Figure 1 a drawing in the Y-axis direction in).

[0076] The wound iron core of the present embodiment has a substantially rectangular (substantially polygonal) wound iron core body 10 in side view. The wound iron core body 10 has a laminated structure 2 with a substantially rectangular shape in side view, which is formed by overlapping grain-oriented electrical steel sheets 1 in the sheet thickness direction. The wound iron core body 10 can be directly used as a wound iron core, and if necessary, known fastening tools such as binding straps can be provided for integrally fixing the plurality of overlapping grain-oriented electrical steel sheets 1.

[0077] In this embodiment, there is no particular limitation on the core length of the wound core body 10. Even if the core length changes, the volume of the bend 5 remains constant, therefore the iron loss generated at the bend 5 is constant. When the core length is longer, the volume fraction of the bend 5 relative to the wound core body 10 decreases, thus its impact on iron loss degradation is also smaller. Therefore, the core length of the wound core body 10 is preferably longer. The core length of the wound core body 10 is preferably 1.5 m or more, more preferably 1.7 m or more. It should be noted that in this embodiment, the core length of the wound core body 10 refers to the circumference at the center point of the stacking direction of the wound core body 10 in a side view.

[0078] The wound core of this embodiment can also be suitably used for any of the conventionally known applications.

[0079] like Figure 1 and 2 As shown, in the wound core body 10, the directional electromagnetic steel plate 1, in which the first flat portion 4 and the corner portion 3 alternately continue in the length direction, and the angle formed by the two adjacent first flat portions 4 at each corner portion 3 is 90°, includes the overlapping portion in the thickness direction, and has a generally rectangular stacked structure 2 in side view. It should be noted that in this specification, the "first flat portion" and the "second flat portion" are sometimes simply referred to as "flat portion".

[0080] Each corner portion 3 of the directional electromagnetic steel plate 1 has two or more curved portions 5 in a side view, and the total bending angle of each curved portion 5 at a corner portion 3 is 90°. A second flat portion 4a is provided between adjacent curved portions 5. Therefore, the corner portion 3 is configured to have two or more curved portions 5 and one or more second flat portions 4a.

[0081] Figure 2 One implementation is that there are two curved portions 5 in one corner portion 3. Figure 3 One implementation is that there are three curved sections 5 in one corner section 3.

[0082] As shown in these examples, in this embodiment, one corner portion may be composed of two or more bend portions, but from the perspective of suppressing strain caused by deformation during processing and thus suppressing iron loss, the bending angle φ (φ1, φ2, φ3, etc.) of the bend portion 5 is preferably 60° or less, more preferably 45° or less.

[0083] It has two bends at one corner. Figure 2In this embodiment, from the perspective of reducing iron loss, for example, φ1 = 60° and φ2 = 30° can be set, or φ1 = 45° and φ2 = 45° can be set, etc. Furthermore, it has three bends at one corner. Figure 3 In this implementation, from the perspective of reducing iron loss, φ1 = 30°, φ2 = 30°, and φ3 = 30° can be set, for example. Furthermore, from the perspective of production efficiency, it is preferable that the bending angles are equal. Therefore, in the case where there are two bends at one corner, it is preferable to set φ1 = 45° and φ2 = 45°. Moreover, in the case where there are three bends at one corner... Figure 3 In the implementation of the method, from the perspective of reducing iron loss, it is preferred to set φ1 = 30°, φ2 = 30° and φ3 = 30°.

[0084] Reference Figure 4 The curved portion 5 will be described in more detail. Figure 4 This diagram schematically illustrates an example of a curved portion (curved section) of a directional electromagnetic steel sheet. The bending angle of the curved portion 5 refers to the angle difference between the straight section on the rear side and the straight section on the front side of the curved portion 5 in the bending direction. It is expressed as the supplementary angle φ formed by extending the straight sections of the two imaginary lines Lb extensions 1 and 2 obtained by extending the straight sections of the plane portions 4 and 4a on both sides of the curved portion 5 at the outer surface of the directional electromagnetic steel sheet 1. At this point, the point where the extended straight line detaches from the steel sheet surface is the boundary between the plane portion and the curved portion at the outer surface of the steel sheet. Figure 6 In the middle, points F and G are points F and G respectively.

[0085] Furthermore, straight lines perpendicular to the outer surface of the steel plate are extended from points F and G respectively, and their intersections with the inner surface of the steel plate are designated as points E and D. Points E and D represent the boundaries between the planar portion and the curved portion on the inner surface of the steel plate.

[0086] Furthermore, in this embodiment, the so-called curved portion refers to the part of the directional electromagnetic steel plate 1 enclosed by the aforementioned points D, E, F, and G, viewed from the side. Figure 6 In the diagram, the inner surface of the steel plate between point D and point E, i.e., the curved part 5, is denoted as La, and the outer surface of the steel plate between point F and point G, i.e., the curved part 5, is denoted as Lb.

[0087] In addition, Figure 4 The diagram shows the radius of curvature r of the inner surface of the curved portion 5 in a side view. The radius of curvature r of the curved portion 5 is obtained by approximating La with an arc passing through points E and D. The smaller the radius of curvature r, the steeper the curve of the curved portion 5; the larger the radius of curvature r, the gentler the curve of the curved portion 5.

[0088] In the wound core of this embodiment, the radius of curvature r at each bend 5 of the directional electromagnetic steel plates 1 stacked along the thickness direction can vary to a certain extent. This variation may be due to variations in forming accuracy, or unintentional variations caused by operations during stacking. Such unintentional errors can be suppressed to about 0.2 mm or less in conventional industrial manufacturing. In cases of large variations, a representative value can be obtained by measuring the radius of curvature r of a sufficiently large number of steel plates and averaging them. Furthermore, intentional variations for some reason are also considered, but this embodiment does not exclude such variations.

[0089] Furthermore, there are no particular restrictions on the method for measuring the radius of curvature r of the inner surface of the curved portion 5, but it can be measured, for example, by observing it at 200x magnification using a commercially available microscope (Nikon ECLIPSE LV150). Specifically, the curvature center point A is determined from the observation results. For example, if the intersection point obtained by extending line segments EF and DG inwards to the opposite side of point B is defined as A, then the size of the radius of curvature r of the inner surface is equivalent to the length of line segment AC.

[0090] In this embodiment, by setting the radius of curvature r of the inner surface of the bent portion 5 to a range of 1 mm to 5 mm, and by optimally controlling the shape of the intermediate layer disposed on the surface of the mother steel plate of the directional electromagnetic steel plate 1 as described below, the efficiency of the iron core can be made to achieve the optimal efficiency that matches the magnetic characteristics. The effect of this embodiment is even more significant when the radius of curvature r of the inner surface of the bent portion 5 is preferably 3 mm or less.

[0091] Furthermore, it is most preferred that all the bends 5 existing within the iron core satisfy the inner surface curvature radius r specified in this embodiment. In the case where there are bends 5 that satisfy the inner surface curvature radius r of this embodiment and bends 5 that do not satisfy the inner surface curvature radius r of this embodiment, it is preferred that at least half of the bends 5 satisfy the inner surface curvature radius r specified in this embodiment.

[0092] Figure 5 and Figure 6 This is a schematic diagram illustrating an example of a directional electromagnetic steel sheet 1 wound in one layer within the core body 10. (See diagram below.) Figure 5 and Figure 6 As shown in the example, the directional electromagnetic steel plate 1 used in this embodiment is a bent steel plate with a corner portion 3 and a flat portion 4 formed by two or more bends 5. It forms a roughly rectangular ring in side view through one or more end faces in the longitudinal direction of the directional electromagnetic steel plate 1, i.e., joint portions 6 (gap).

[0093] In this embodiment, the wound core body 10 only needs to have a generally rectangular stacked structure 2 when viewed from the side as a whole. It can be as follows: Figure 5 As shown in the example, a single layer of directional electromagnetic steel sheet 1 is formed by a single joint 6 to form the core body 10 (each roll is connected by a single joint 6 to form a single directional electromagnetic steel sheet 1). Figure 6 As shown in the example, one directional electromagnetic steel plate 1 constitutes about half a turn of the core, and two directional electromagnetic steel plates 1 constitute one layer of the core body 10 through two joints 6 (each roll connects the two directional electromagnetic steel plates 1 to each other through two joints 6).

[0094] The thickness of the directional electromagnetic steel plate 1 used in this embodiment is not particularly limited. It can be appropriately selected according to the application, etc., but it is usually in the range of 0.15mm to 0.35mm, preferably in the range of 0.18mm to 0.23mm.

[0095] 2. Composition of directional electromagnetic steel plates

[0096] Next, the configuration of the directional electromagnetic steel plate 1 constituting the wound core body 10 will be described. In this embodiment, the intermediate layer shape near the bending portion 5 of the adjacently stacked electromagnetic steel plates and the arrangement position of the electromagnetic steel plates within the core that controls the intermediate layer shape are characterized.

[0097] (1) The intermediate layer morphology of the planar portion adjacent to the curved portion

[0098] In the directional electromagnetic steel plate 1 constituting the wound core of this embodiment, the intermediate layer near at least a portion of the bend 5 is controlled in a manner that makes the shape of the intermediate layer of the stacked steel plates thin and smooth. If the intermediate layer near the bend 5 is thick and the unevenness becomes severe, the efficiency degradation in the core having the core shape of this embodiment becomes significant.

[0099] The mechanism behind this phenomenon is not clear, but it can be considered as follows.

[0100] In this embodiment, the core is designed such that the magnetic properties of the steel sheet used as the raw material are fully reflected in terms of the core's characteristics. The planar portions 4 and 4a, which generate virtually no strain, are designed to be relatively very wide, and the strain (deformation) caused by bending is confined to a very narrow region near the bending portion 5. Therefore, the deterioration of the magnetic properties in the region near the bending portion 5 affects the overall characteristics of the core. It is believed that the deterioration of the magnetic properties at the bending portion 5 is primarily due to the introduction of lattice defects such as dislocation density and changes in the magnetic domain structure, including changes in crystal orientation resulting from these defects. Regarding the change in magnetic domain structure caused by strain under bending deformation of such a small radius as in this embodiment, practical control measures are not readily available. However, based on the understanding that forms the basis of this embodiment, a thin and smooth intermediate layer results in a smaller change in the magnetic domain structure and easier maintenance of good magnetic properties under the same strain. In simple terms, it is believed that if the intermediate layer, which is relatively harder than the parent steel plate, is thicker and has a complex interface morphology with the parent steel plate, complex strain will occur in the surface region of the parent steel plate (near the interface with the intermediate layer). This will complicate the magnetic domain structure and greatly degrade the magnetic properties. This mechanism of action in this embodiment is considered to be a special phenomenon in the specific shape of the iron core to which this embodiment is intended, and has not been considered until now, but can be explained in accordance with the insights gained by the inventors of this invention.

[0101] In this application specification, the term "intermediate layer" refers to the layered (film-like) region between the base steel plate, which is essentially α-Fe phase, and the insulating film that imparts tension and insulation to the directional electromagnetic steel plate 1. It is not limited to magnesium olivine, SiO2, and TiN exemplified in the background art above, but can be any known material formed for the aforementioned purpose. Furthermore, considering the mechanism of action of this embodiment, materials with a significantly different deformability from the base steel plate are considered. In this embodiment, such materials are defined as compounds. That is, the intermediate layer in this embodiment is defined as a layer composed of oxides, carbides, nitrides of metallic elements, and compounds thereof. These are materials known to play a role in ensuring adhesion between the base steel plate and the insulating film in the directional electromagnetic steel plate 1.

[0102] When the difference in deformation capacity between the mother steel plate and the intermediate layer is small, regardless of the thickness and shape of the intermediate layer, the interface area deforms uniformly as a whole. Therefore, the effect of this embodiment is not required, and the effect of this embodiment will not be exhibited.

[0103] In this embodiment, the morphology of the intermediate layer is measured as follows.

[0104] The directional electromagnetic steel plate 1 extracted from the iron core is observed in a cross-section parallel to the side of the iron core. Any general observation method is acceptable; a special method is not necessary. However, since the thickness of the intermediate layer, which is the object of this embodiment, is very thin, the thickness of the intermediate layer is determined by observing the cross-section using STEM (scanning transmission electron microscopy).

[0105] Specifically, in the regions of the first planar portion 4 and the second planar portion 4a adjacent to the curved portion 5 in the aforementioned observation section, for 101 locations (i.e., measurement areas of 10 μm) determined at intervals of 0.1 μm along the direction (length direction) of the steel plate surface, quantitative analysis is performed at intervals of 1 nm along the plate thickness direction using energy-dispersive X-ray spectrometry (EDS) with an electron beam diameter set to 10 nm. Then, the region where the total concentration of the constituent elements of the material conceived as the intermediate layer (the total concentration of Si and O if the intermediate layer is SiO2, and the total concentration of Ti and N if the intermediate layer is TiN) is 50 atomic percent or more is defined as the intermediate layer, and its thickness is determined.

[0106] In this embodiment, the measurement area for the intermediate layer is defined as the region of the first plane portion 4 and the second plane portion 4a adjacent to the bending portion 5, which is at least twice the length of the boundary between the bending portion 5 and the first plane portion 4 and the second plane portion 4a. Here, it is set to at least twice the length because if the region is at this distance from the bending portion 5, the influence of deformation of the intermediate layer caused by bending can be avoided. It should be noted that, as described above, the effect of this embodiment is manifested through an action mechanism corresponding to the shape of the intermediate layer within the bending portion 5, and is essentially evaluated by how the intermediate layer within the bending portion 5 deforms and how it affects the deformation of the parent steel plate. However, since the intermediate layer within the bending portion 5 deforms in a complex manner corresponding to its shape, as described above, and the microstructure of the parent steel plate also changes in a complex manner, it is considered difficult to quantify it as a specification of this embodiment. Therefore, in this embodiment, a quantitative value corresponding to the performance of the above-described action mechanism is defined by assigning the state before bending deformation, i.e., the shape of the intermediate layer of the first plane portion 4 and the second plane portion 4a.

[0107] Furthermore, the second planar portion 4a is located inside the corner portion 3, and the first planar portion 4 is located outside the corner portion 3, but the shape of the intermediate layer is determined by the second planar portion 4a and / or the first planar portion 4 in at least one curved portion 5.

[0108] In this embodiment, based on the measured thickness of the intermediate layer at 101 points obtained as described above, characteristic values ​​regarding the morphology of the intermediate layer are further determined as follows.

[0109] For example, Figure 7 As shown in, first, let the average thickness of the thickness T (nm) of the intermediate layer at 101 positions (measurement positions) be Tave (nm), the maximum thickness be Tmax (nm), the minimum thickness be Tmin (nm), the average value of data where T>Tave be To (nm), and the average value of data where T<Tave be Tu (nm). Further, in the thickness distribution obtained along the steel plate surface direction (longitudinal direction), a continuous region of measurement values satisfying T>Tave is counted as one region, and the number within all measurement regions is defined as N. This N is the number of convex regions within the 10 μm measurement region. That is, when a region continuously thicker than Tave (a region protruding in the thickness direction) in the 10 μm measurement region is defined as a convex region, N is the number of convex regions.

[0110] Here, the measurement of the aforementioned intermediate layer morphology is performed on the outer surface side and the inner surface side of the steel plate respectively, and each value obtained on each surface is averaged to obtain Tave, Tmax, Tmin, To, Tu and N of the steel plate. It should be noted that, Figure 7 schematically shows the outer surface side of the steel plate, and the thickness of the intermediate layer is modified for convenience of description. In addition, an insulating coating is formed on the intermediate layer, but the illustration of this insulating coating is omitted.

[0111] In the present embodiment, the present invention is characterized in that, in at least one corner portion 3, for at least one of two or more bent portions 5, the following formulas (1) to (3) are satisfied.

[0112] Tave≤40nm (1)

[0113] (To-Tu) / Tave≤0.50 (2)

[0114] Tave(To-Tu)≤240nm 2 (3)

[0115] The stipulation of formula (1) is not a special one, and is a stipulation for grain-oriented electrical steel sheet 1 obtained by mirroring a general intermediate layer interface. The left side of formula (1) is preferably 20 nm or less, more preferably 10 nm or less.

[0116] Formula (2) can be said to be one of the stipulations representing the special features of the present embodiment. If the mechanism described above is considered, this stipulation indicates that small variation in the thickness of the intermediate layer (the difference between convex portions and concave portions) is a necessary condition. The left side of formula (2) is preferably 0.3 or less, more preferably 0.2 or less.

[0117] Equation (3) is a specification that represents a special feature of this embodiment. This specification indicates that the thinner the intermediate layer, the more tolerance is allowed for variations in the intermediate layer thickness (the difference between the convex and concave portions). This is believed to be equivalent to an indicator for evaluating the magnitude of the impact on the mother steel plate when the steel plate covered by a film harder than the mother steel plate is bent and deformed. The left side of equation (3) is preferably 200 nm. 2 The preferred option is 180nm. 2 the following.

[0118] By satisfying equations (1) to (3) above, the magnetic domain structure of the bent portion 5 becomes a structure that suppresses the effects caused by bending, thus demonstrating the effect of this embodiment. Furthermore, it is undoubtedly preferable that all bent portions 5 present in a corner portion 3 satisfy equations (1) to (3) above. Moreover, it is undoubtedly preferable that all four corner portions 3 present in the wound iron core satisfy equations (1) to (3) above.

[0119] As another embodiment, it is characterized in that, in at least one corner portion 3, with respect to at least one of two or more curved portions 5, the following equation (4) is satisfied.

[0120] N(To-Tu)≤24nm (4)

[0121] This specification indicates the steepness of the thickness variation in the intermediate layer, that is, the degree of thickness variation from the convex to the concave portion along the thickness distribution in the region of the intermediate layer. If this value is large, it will cause the thickness to change drastically in a local region of the intermediate layer, making the deformation of the mother steel plate in the bend 5 complex, complicating the magnetic domain structure, and thus reducing the core efficiency. Furthermore, it is undoubtedly preferable that the above formula (4) is satisfied for all bends 5 present in a corner 3. Moreover, it is undoubtedly preferable that the above formula (4) is satisfied for all four corners 3 present in the wound core.

[0122] As another embodiment, the feature is that, in at least one corner portion 3, with respect to at least one of two or more curved portions 5, the following equation (5) is satisfied.

[0123] N≥2 (5)

[0124] From the perspective of equation (4) above, this provision refers to increasing the steepness mentioned above, and is therefore considered strange. However, it is stated that if N reaches a certain number, that is, if the interval of the thickness variation from the convex to the concave portion along the thickness distribution in the region of the intermediate layer becomes very narrow, then even if the steepness evaluated by equation (4) is a certain high value, the complexity of the magnetic domain structure in the curved portion 5 can be suppressed. The reason is not clear, but it is believed to be because even if the size of the variation in the interface morphology is refined to a certain extent, the complexity and refinement of the magnetic domain structure are limited, and therefore, in a sense, it becomes as effective as a flat interface. According to equation (5) above, it can be interpreted that if the interval (spacing) of the thickness variation becomes less than 5 μm, then as an effect on the magnetic domain structure of the parent steel plate, it is close to a flat interface. Furthermore, it is undoubtedly desirable that all the curved portions 5 present in the corner portion 3 satisfy the above equation (5). Furthermore, it is beyond doubt that the above equation (5) is preferably satisfied in all four corner portions present in the wound iron core.

[0125] As another embodiment, the feature is that, in at least one corner portion 3, with respect to at least one of two or more curved portions 5, the following equation (6) is satisfied.

[0126] (Tmax-Tmin) <Tave (6)

[0127] This specification is simply an indicator of the absolute magnitude of the variation in the thickness of the intermediate layer. Intuitively, it can be understood that the smaller the value of equation (6), the better. However, in this embodiment, it has a special meaning. That is, since the intermediate layer of this embodiment is very thin, it is impossible to avoid the concern that abnormalities may occur due to variations in industrial manufacturing conditions. For example, there may be areas where the intermediate layer may slightly peel off. This embodiment specifies that it is preferable to suppress such areas. Furthermore, it is undoubtedly preferable that equation (6) is satisfied with all the bends 5 present in the corner 3. Moreover, it is undoubtedly preferable that equation (6) is satisfied with all four corners 3 present in the wound core.

[0128] (2) Directional electromagnetic steel sheet

[0129] As described above, in the directional electromagnetic steel plate 1 used in this embodiment, the mother steel plate is one in which the grain orientation is highly concentrated in {110}. <001> Oriented steel sheets have excellent magnetic properties in the rolling direction.

[0130] In this embodiment, the mother steel plate can be a known directional electromagnetic steel plate. Hereinafter, an example of a preferred mother steel plate will be described.

[0131] The chemical composition of the mother steel plate, by mass percent, contains 2.0%–6.0% Si, with the remainder being Fe. This chemical composition is designed to control the crystal orientation to be concentrated in {110}. <001> The oriented Gaussian texture ensures good magnetic properties. Regarding other elements, there are no particular restrictions; in place of Fe, known elements are permitted within a known range. Representative ranges for representative elements are as follows.

[0132] C: 0~0.0050%

[0133] Mn: 0~1.0%

[0134] S: 0~0.0150%

[0135] Se: 0~0.0150%

[0136] Al: 0~0.0650%

[0137] N: 0~0.0050%

[0138] Cu: 0–0.40%

[0139] Bi: 0~0.010%

[0140] B: 0~0.080%

[0141] P: 0–0.50%

[0142] Ti: 0~0.0150%

[0143] Sn: 0-0.10%

[0144] Sb: 0~0.10%

[0145] Cr: 0–0.30%

[0146] Ni: 0-1.0%

[0147] Nb: 0~0.030%

[0148] V: 0~0.030%

[0149] Mo: 0–0.030%

[0150] Ta: 0~0.030%

[0151] W: 0–0.030%.

[0152] These optional elements only need to be included according to their purpose, so there is no need to limit the lower limit value, and they can be substantially absent. Furthermore, even if these optional elements are included as impurities, it will not impair the effect of this embodiment. It should be noted that impurities refer to elements unintentionally present, meaning elements that are mixed in from the ore, waste, or manufacturing environment used as raw materials during the industrial manufacture of the master steel plate.

[0153] The chemical composition of the base steel plate can be determined using general analytical methods for steel. For example, the chemical composition of the base steel plate can be determined using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Specifically, for example, it can be determined by taking a 35 mm square test piece from the center of the base steel plate after the coating has been removed, and measuring it using a Shimadzu ICPS-8100 or similar measuring device, based on pre-prepared calibration lines. Furthermore, C and S can be determined using the combustion-infrared absorption method, and N can be determined using the inert gas melting-thermal conductivity method.

[0154] It should be noted that the above-mentioned chemical composition refers to the composition of the mother steel plate. When the directional electromagnetic steel plate 1, which serves as the test sample, has a primary coating (glass coating, intermediate layer), insulating coating, etc., formed by oxides or the like on its surface, these are removed by known methods, and then the chemical composition is determined.

[0155] (3) Manufacturing method of directional electromagnetic steel sheet

[0156] The manufacturing method of the directional electromagnetic steel sheet 1 is not particularly limited, and conventionally known manufacturing methods for directional electromagnetic steel sheets can be appropriately selected. As a preferred specific example of the manufacturing method, the following method can be cited: A slab with C set to 0.04–0.1% by mass and other components having the chemical composition of the directional electromagnetic steel sheet 1 described above is heated to 1000°C or higher for hot rolling, followed by hot-rolled sheet annealing as needed. Then, a cold-rolled steel sheet is produced by one cold rolling or two or more cold rolling processes with intermediate annealing. This cold-rolled steel sheet is then heated to 700–900°C in a wet hydrogen-inert gas atmosphere for decarburization annealing, followed by nitriding annealing as needed. After applying an annealing separating agent, a finished product annealing is performed at approximately 1000°C, and an insulating film is formed at approximately 900°C. Furthermore, coating for adjusting the coefficient of kinetic friction can also be performed thereafter.

[0157] Furthermore, even steel sheets that have undergone a process known as "magnetic domain control" during the steel sheet manufacturing process can enjoy the effects of this embodiment.

[0158] The method for controlling the characteristics of the directional electromagnetic steel plate 1 used in this embodiment, i.e., the morphology of the intermediate layer, is not particularly limited, as long as a known method is appropriately used. For example, various morphologies of the intermediate layer can be formed by thermal oxidation after finished product annealing using an annealing separating agent with alumina (Al2O3) as the main component. Alternatively, after finished product annealing using an annealing separating agent with magnesium oxide (MgO) as the main component, the forsterite formed on the surface of the steel plate can be peeled off by pickling or grinding, and the oxidation behavior during the subsequent baking annealing process for forming the insulating film can be controlled to form various morphologies of the intermediate layer.

[0159] 3. Manufacturing method of wound iron core

[0160] The method for manufacturing the wound core in this embodiment is not particularly limited as long as it can manufacture the wound core of this embodiment described above. For example, the method for manufacturing a wound core according to known methods described in patent documents 9-11 in the background art can be used. In particular, the method using the UNICORE (https: / / www.aemcores.com.au / technology / unicore / ) manufacturing apparatus from AEM UNICORE Corporation is considered optimal.

[0161] Furthermore, heat treatment can be performed as needed using known methods. In addition, the resulting wound core body 10 can be used directly as a wound core, but it can also be further manufactured into a wound core by fixing multiple overlapping directional electromagnetic steel plates 1 together using known fastening tools such as cable ties, as needed.

[0162] This embodiment is not limited to the above-described embodiment. The above-described embodiment is illustrative, and any embodiment that has essentially the same structure and performs the same effect as the technical concept described in the claims of this invention, regardless of the method, is included within the technical scope of this invention.

[0163] Example

[0164] The technical content of the present invention will be further described below while listing embodiments of the invention. The conditions in the embodiments shown below are examples of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to these examples of conditions. Furthermore, various conditions can be adopted in the present invention as long as they do not depart from the spirit of the present invention and achieve the purpose of the present invention.

[0165] (Directional electromagnetic steel sheet)

[0166] Using slabs having the chemical composition shown in Table 1 (mass % and the remainder other than the displayed content being Fe) as raw materials, a final product having the chemical composition shown in Table 2 (mass % and the remainder other than the displayed content being Fe) is produced.

[0167] In Tables 1 and 2, “-” indicates elements for which no conscious control of content was carried out during manufacturing and for which no content determination was performed.

[0168] [Table 1]

[0169]

[0170] [Table 2]

[0171]

[0172] The manufacturing process follows the generally known manufacturing conditions for directional electromagnetic steel sheets.

[0173] Hot rolling, hot-rolled plate annealing, and cold rolling were performed. For some steel plates, and for cold-rolled steel plates after decarburization annealing, nitriding treatment (nitriding annealing) was performed in a mixed atmosphere of hydrogen, nitrogen, and ammonia.

[0174] Subsequently, the finished product was annealed by applying an annealing separating agent with magnesium oxide or aluminum oxide as the main components and varying their mixing ratio. On the primary coating formed on the surface of the finished annealed steel sheet, an insulating coating solution containing chromium and primarily composed of phosphate and colloidal silica was applied, followed by heat treatment to form an insulating coating. For some materials, after the primary coating was peeled off and mirror-finished on the surface of the mother steel sheet during the finished annealing process, a TiN coating was formed by ion plating, followed by an insulating coating solution containing chromium and primarily composed of phosphate and colloidal silica, and then heat treatment to form an insulating coating.

[0175] This process produces a steel sheet with a modified type and shape, which is positioned between the mother steel sheet and the insulating film to ensure a tight seal between the two. Details of the manufactured steel sheet are shown in Table 3.

[0176] [Table 3]

[0177]

[0178] (Iron core)

[0179] Using various steel plates as raw materials, manufacture products with the features shown in Table 4 and... Figure 8 The cores No. a to h are shown in the diagram. In this case, cores No. g and h are not tested as separate cores, but rather three are prepared as unit cores, and they are arranged as follows... Figure 9As shown, the three-phase wound iron cores are arranged in an equilateral triangular cylindrical shape, with coils wound on each of the individual columns (including the portion containing the first flat portion 4). (For example, the iron core shown in Japanese Patent Application Publication No. 2005-333057). Furthermore, the three unit iron cores are symmetrically arranged with the axis of the equilateral triangular cylinder as the center. Figure 9 (a) is a front view showing the schematic structure of a three-phase wound iron core. Figure 9 (b) is Figure 9 The cross-sectional view of line AA in (a).

[0180] It should be noted that L1 is the distance between the parallel directional electromagnetic steel plates 1 located at the innermost circumference of the wound core in a plane section parallel to the X-axis and including the center CL (distance between planar portions on the inner surface side). L2 is the distance between the parallel directional electromagnetic steel plates 1 located at the innermost circumference of the wound core in a longitudinal section parallel to the Z-axis and including the center CL (distance between planar portions on the inner surface side). L3 is the stacking thickness of the wound core in a plane section parallel to the X-axis and including the center CL (thickness in the stacking direction). L4 is the width of the stacked steel plates of the wound core in a plane section parallel to the X-axis and including the center CL. L5 is the distance between the innermost adjacent planar portions of the wound core, arranged in a manner that makes their sum right angle (distance between curved portions). In other words, L5 is the length in the longitudinal direction of the shortest planar portion 4a among the planar portions 4 and 4a of the innermost circumference directional electromagnetic steel plates. r is the radius of curvature of the curved portion on the inner surface side of the wound core, and φ is the bending angle of the curved portion of the wound core. The roughly rectangular cores No. a to h have the following structure: the planar portions with a distance of L1 between their inner surface side planes are divided at approximately the center of L1, and two cores with a roughly "U" shape are joined together. Core No. f is a core that has traditionally been used as a general wound core and is manufactured using the following method: after rolling a steel sheet into a cylindrical shape, the corner portion 3 is pressed in a cylindrical laminated state with a certain curvature to form a roughly rectangular shape, and then annealed to maintain its shape. Therefore, the radius of curvature r of the bent portion 5 varies considerably depending on the lamination position of the steel sheet. r in Table 4 is the r at the innermost surface. r increases as it becomes outermost, reaching approximately 90 mm at the outermost perimeter.

[0181] [Table 4]

[0182]

[0183] (Evaluation Method)

[0184] (1) Magnetic properties of directional electromagnetic steel sheets

[0185] The magnetic properties of the directional electromagnetic steel sheet 1 were determined based on the Single Sheet Tester (SST) method specified in JIS C 2556:2015.

[0186] As a magnetic property, the magnetic flux density B8(T) in the rolling direction of the steel plate was measured when it was excited at 800 A / m, and the iron loss was measured when the AC frequency was 50 Hz and the excitation magnetic flux density was 1.7 T.

[0187] (2) Morphology of the intermediate layer

[0188] The morphology of the intermediate layer is determined by observing the cross-section of the steel plate extracted from the core, as described above.

[0189] (3) Efficiency of the iron core

[0190] For iron cores made from various steel plates, the core efficiency is determined based on power meter measurements.

[0191] The efficiency of various cores manufactured using steel plates with different domain widths was evaluated. The results are shown in Table 5. It was found that even when using the same steel grade, the efficiency of the core can be improved by appropriately controlling the morphology of the intermediate layer.

[0192] [Table 5]

[0193]

[0194] The results above show that the wound core of the present invention has high efficiency because it satisfies the above-mentioned equations (1) to (3) in at least one of two or more bends 5 in at least one corner 3.

[0195] Industrial availability

[0196] According to the present invention, in a wound iron core formed by stacking bent steel plates, unintentional efficiency degradation can be effectively suppressed.

[0197] Explanation of symbols

[0198] 1 Directional Electromagnetic Steel Sheet

[0199] 2-layer structure

[0200] 3 corners

[0201] 4 First Plane Section

[0202] 4a Second Plane Part

[0203] 5. Bending section

[0204] 6 joints

[0205] 10-winding iron core body

Claims

1. A wound iron core, characterized in that, It is a wound core having a substantially rectangular wound core body in side view, In the wound core body, the grain-oriented electrical steel sheet, in which first flat portions and corner portions are alternately continuous in the length direction and an angle formed by two first flat portions adjacent to each other with each of the corner portions interposed therebetween is 90°, comprises portions overlapping in the plate thickness direction and has a substantially rectangular laminated structure in side view, Each of the corner portions, when viewed from the side of the grain-oriented electrical steel sheet, comprises two or more curved portions with a curved shape, a second flat portion is provided between adjacent curved portions, and the sum of the bending angles of each curved portion present at one corner portion is 90°, The radius of curvature r on the inner surface side of the curved portion in side view is 1 mm to 5 mm, The grain-oriented electrical steel sheet has the following chemical composition: In terms of mass%: Si: 2.0 to 7.0%, The remainder comprises Fe and impurities, The grain-oriented electrical steel sheet has a texture oriented along the Gauss orientation, and In at least one corner portion, for at least one of the two or more curved portions present, the following formulas (1) to (3) are satisfied, Tave≤40nm (1) (To-Tu) / Tave≤0.50 (2) You (To-You) ≤240nm 2 (3) Wherein, the thickness T of the intermediate layer arranged on the surface of the base steel sheet of the grain-oriented electrical steel sheet is measured at a plurality of positions in the first and second flat portion regions adjacent to the curved portion, the average thickness of the thickness T of the intermediate layer is defined as Tave, the maximum thickness is defined as Tmax, the minimum thickness is defined as Tmin, the average value of data with T>Tave is defined as To, and the average value of data with T<Tave is defined as Tu. The units of the above T, Tave, Tmax, Tmin, To and Tu are nm.

2. The wound iron core according to claim 1, characterized in that, In at least one corner portion, for at least one of the two or more curved portions present, the following formula (4) is satisfied, N(To-Tu)≤24nm (4) Wherein, in the thickness distribution of the intermediate layer obtained along the surface direction of the steel sheet, a region where continuous measured values satisfy T>Tave is counted as one region, and the number of all measurement regions is defined as N.

3. The wound iron core according to claim 2, characterized in that, In at least one corner portion, for at least one of the two or more curved portions present, the following formula (5) is satisfied, N≥2 (5)。 4. The wound iron core according to claim 1, characterized in that, In at least one corner portion, for at least one of the two or more curved portions present, the following formula (6) is satisfied, (Tmax-Tmin)<Tave (6).

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