JP2019024039A - Wound iron core - Google Patents

Abstract

To provide a wound iron core having a low iron loss.SOLUTION: Disclosed is a wound iron core including a directional electromagnetic steel sheet for extending in a direction intersecting with a rolling direction and having a steel sheet surface on which a groove for anti-SRA magnetic domain control is formed, in which a groove depth direction becomes a thickness direction. The groove faces an outer winding side. A gap between center lines of the groove in the rolling direction is 2 mm or more and less than 5 mm. A radius of curvature of a bend processing part of the innermost peripheral part is 50 mm or less. When the groove is viewed in a groove longitudinal cross section including a groove extension direction and a plate thickness direction, an arithmetic average height Ra of roughness curve forming a contour of a groove bottom region of the groove is 1.1 μm or more and 2.7 μm or less. An average length RSm of a roughness curve element forming the contour of the groove bottom region is 50 μm or more and 150 μm or less.SELECTED DRAWING: Figure 11

Description

  The present disclosure relates to a wound iron core.

DESCRIPTION OF RELATED ART Conventionally, the grain-oriented electrical steel plate which exhibits the magnetic characteristic excellent in the specific direction is known as a steel plate for iron cores (core) of a transformer. This grain-oriented electrical steel sheet is a steel sheet whose crystal orientation is controlled by a combination of a cold rolling process and an annealing process so that the easy axis of crystal grains coincides with the rolling direction. It is desirable that the iron loss of the grain-oriented electrical steel sheet is as low as possible.
Iron loss is classified into eddy current loss and hysteresis loss. Furthermore, eddy current loss is classified into classical eddy current loss and abnormal eddy current loss.
In order to reduce classical eddy current loss, a grain-oriented electrical steel sheet in which an insulating film is formed on the surface of a steel sheet (ground iron) whose crystal orientation is controlled as described above is generally known.
On the other hand, as a method for reducing the abnormal eddy current loss, the strain extending in the direction intersecting the rolling direction is formed at predetermined intervals along the rolling direction, thereby narrowing the width of the 180 ° magnetic domain (180 ° magnetic domain). The magnetic domain control method is known.
This magnetic domain control method includes a non-destructive magnetic domain control method in which the above-described distortion is imparted to a steel sheet of a grain-oriented electrical steel sheet by a non-destructive means, and a destructive magnetic domain control method such as forming a groove on the surface of the steel sheet. being classified.

When manufacturing a wound iron core for a transformer using a grain-oriented electrical steel sheet, it is necessary to carry out a strain relief annealing process in order to remove the deformation strain caused by the grain-oriented electrical steel sheet being wound in a coil shape. is there.
When a wound core is manufactured using grain oriented electrical steel sheets that have been strained by the non-destructive magnetic domain control method, the strain disappears by performing strain relief annealing, so the magnetic domain refinement effect (ie, abnormal eddy current loss) Reduction effect) also disappears.
On the other hand, when producing a wound core using a grain-oriented electrical steel sheet provided with grooves by the destructive magnetic domain control method, since the grooves are not lost by carrying out strain relief annealing, the magnetic domain refinement effect can be maintained. .
Therefore, a destructive magnetic domain control method is generally employed for a wound core as a method for reducing abnormal eddy current loss.

  Patent Document 1 discloses a wound core using a unidirectional electrical steel sheet having linear grooves introduced at intervals of 5 mm in a direction perpendicular to the rolling direction.

  In Patent Document 2, a linear groove is formed on one surface with a groove width of 300 μm or less, a groove depth of 100 μm or less, an interval between groove centerlines in the rolling direction of 1 mm or more, and an angle of 30 ° or more with the rolling direction. A wound iron core formed by winding directional electromagnetic steel sheets is disclosed.

  Patent Document 3 discloses a grain-oriented electrical steel sheet in which grooves are formed in a steel sheet surface layer using a laser for magnetic domain control.

JP 61-15309 A Japanese Patent Publication No. 6-22179 International Publication No. 2016/171124

As a specification of the wound core, there is a case where the iron loss is deteriorated and the building factor (BF) is inferior in the wound core using the magnetically controlled steel plate.
The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a wound core with low iron loss.

The wound core of the present disclosure includes a grain-oriented electrical steel sheet having a steel sheet surface extending in a direction intersecting the rolling direction and having a groove for SRA magnetic domain control in which the groove depth direction is the sheet thickness direction. A wound iron core,
The groove faces the outer winding side,
The interval between the center lines of the grooves in the rolling direction is 2 mm or more and less than 5 mm,
The radius of curvature of the bent portion of the innermost peripheral portion is 50 mm or less,
When the groove is viewed in the groove longitudinal section including the groove extending direction and the plate thickness direction, the arithmetic average height Ra of the roughness curve defining the groove bottom region of the groove is 1.1 μm or more and 2.7 μm. And
The average length RSm of the roughness curve element forming the contour of the groove bottom region is 50 μm or more and 150 μm or less.

  In the wound iron core of the present disclosure, the Ra may be 1.3 μm or more and 2.5 μm or less, and the RSm may be 60 μm or more and 130 μm or less.

  In the wound iron core of the present disclosure, the angle of the direction intersecting the rolling direction of the groove may be 0 <θ <30 ° with respect to the rolling direction.

  In the wound iron core of the present disclosure, the radius of curvature of the bent portion of the innermost peripheral portion may be 3 mm or more and less than 10 mm.

  According to the present disclosure, it is possible to provide a wound core with low iron loss.

1 is a plan view of a grain-oriented electrical steel sheet 1 according to an embodiment of the present disclosure. It is arrow sectional drawing in the AA line of FIG. 1 (The figure which looked at the groove | channel 5 in the cross section containing a groove extension direction). It is arrow sectional drawing in the BB line of FIG. 1 (The figure which looked at the groove | channel 5 in the cross section orthogonal to a groove extension direction). FIG. 6 is a first explanatory diagram regarding the definition of a groove reference line BL of the groove 5. 12 is a second explanatory diagram regarding the definition of the groove reference line BL of the groove 5. FIG. FIG. 10 is a third explanatory diagram regarding the definition of the groove reference line BL of the groove 5. FIG. 10 is a fourth explanatory diagram regarding the definition of the groove reference line BL of the groove 5. FIG. 8 is a cross-sectional view taken along the line CC in FIG. 7 and is an explanatory diagram relating to the definition of the groove bottom region 5 a of the groove 5. It is a schematic diagram which shows the roughness curve RC which comprises the outline of the groove bottom area | region 5a. It is arrow sectional drawing in the EE line | wire of FIG. 7, and is explanatory drawing regarding the definition of the groove area | region 5b and the steel plate area | region 2b. It is a mimetic diagram showing one embodiment of a wound iron core concerning this indication.

The wound core of the present disclosure includes a grain-oriented electrical steel sheet having a steel sheet surface extending in a direction intersecting the rolling direction and having a groove for SRA magnetic domain control in which the groove depth direction is the sheet thickness direction. A wound iron core,
The groove faces the outer winding side,
The interval between the center lines of the grooves in the rolling direction is 2 mm or more and less than 5 mm,
The radius of curvature of the bent portion of the innermost peripheral portion is 50 mm or less,
When the groove is viewed in the groove longitudinal section including the groove extending direction and the plate thickness direction, the arithmetic average height Ra of the roughness curve defining the groove bottom region of the groove is 1.1 μm or more and 2.7 μm. And
The average length RSm of the roughness curve element forming the contour of the groove bottom region is 50 μm or more and 150 μm or less.

Hereinafter, the wound core according to the present disclosure will be described in detail.
As used in this specification, the shape and geometric conditions and their degree are specified. For example, terms such as “parallel”, “vertical”, “same”, length and angle values, etc. are strictly Without being bound by meaning, it should be interpreted including the extent to which similar functions can be expected.

The researchers found that the cause of the iron loss deterioration in the above-mentioned wound core is that the compressive force is generated around the groove and twins are generated by processing the groove surface of the material to be on the inner surface layer of the iron core. I found out that it was because I invited you.
In addition, the present inventors have found that even when the groove surface is arranged on the outside, the iron loss may deteriorate and the building factor (BF) may deteriorate very unstablely.
And in order to suppress the said iron loss deterioration, these researchers process the groove | channel formed in the steel plate so that it may become the outer side of an iron core, and control the shape (Ra and RSm) of a groove bottom. It was experimentally clarified that this is extremely important.

Regarding the mechanism of reducing BF by setting Ra and RSm within the above predetermined ranges, the stress generated inside the groove due to the melting of iron is changed to a tension that suppresses the generation of the return magnetic domain by the stress generated in the bending portion. It is estimated that this is because it changes.
Therefore, in order to reduce the iron loss, it is important to set the radius of curvature of the bent portion of the wound core to a predetermined range.
That is, the radius of curvature of the bent portion of the wound core is set within a predetermined range, the shape of the groove bottom formed on the steel sheet surface layer is controlled, and the groove faces the outer winding side of the wound core. It is estimated that the iron loss of the wound core can be further reduced by the synergistic effect.

(1) Oriented electrical steel sheet Generally, a grain oriented electrical steel sheet is a steel sheet in which the orientation of crystal grains in the steel sheet is highly accumulated in the {110} <001> orientation and the easy axis of magnetization is aligned in the longitudinal direction. . Since the easy magnetization axes are aligned in the longitudinal direction, it refers to an electrical steel sheet having the characteristics of low iron loss and excellent magnetism.

In the present disclosure, the grain-oriented electrical steel sheet has at least a base steel plate, and may have a coating on the surface of the base steel plate as necessary. Examples of the film include a glass film and an insulating film.
The base steel plate is a steel plate in which the orientation of crystal grains in the base steel plate is highly accumulated in the {110} <001> orientation, and has excellent magnetic properties in the rolling direction.
In the present disclosure, the mother steel plate is not particularly limited, and can be appropriately selected from those known as grain-oriented electrical steel plates. Hereinafter, although an example of a preferable mother steel plate will be described, in the present disclosure, the mother steel plate is not limited to the following.

  The chemical composition of the mother steel plate is not particularly limited. For example, in mass%, Si: 0.8% to 7%, C: higher than 0% and 0.085% or less, acid-soluble Al: 0 % To 0.065%, N: 0% to 0.012%, Mn: 0% to 1%, Cr: 0% to 0.3%, Cu: 0% to 0.4%, P: 0% to 0.5%, Sn: 0% to 0.3%, Sb: 0% to 0.3%, Ni: 0% to 1%, S: 0% to 0.015%, Se: 0% to 0. It is preferable that 015% is contained and the balance consists of Fe and impurities. The chemical composition of the mother steel plate is a preferable chemical component for controlling the Goss texture in which the crystal orientation is accumulated in the {110} <001> orientation.

Of the elements in the mother steel plate, Si and C are basic elements, and acid-soluble Al, N, Mn, Cr, Cu, P, Sn, Sb, Ni, S, and Se are selective elements. Since these selective elements may be contained according to the purpose, there is no need to limit the lower limit value, and it may not be contained substantially. Moreover, even if these selective elements are contained as inevitable impurities, the effect of the present disclosure is not impaired. In the mother steel plate, the balance of the basic element and the selective element is composed of Fe and inevitable impurities.
In the present disclosure, “inevitable impurities” refers to elements that are inevitably mixed from ores, scraps, or production environments as raw materials when the mother steel plate is industrially produced.
In general, grain oriented electrical steel sheets undergo purification annealing during secondary recrystallization. In the purification annealing, the inhibitor forming elements are discharged out of the system. In particular, for N and S, the decrease in the concentration is remarkable, and it becomes 50 ppm or less. Under normal purification annealing conditions, 9 ppm or less, further 6 ppm or less. If the purification annealing is sufficiently performed, it reaches a level that cannot be detected by general analysis (1 ppm or less).

The chemical composition of the mother steel plate may be measured by a general steel analysis method. For example, the chemical composition of the mother steel plate 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 center position of the base steel plate after removal of the film, and is based on a calibration curve created in advance by ICPS-8100 manufactured by Shimadzu Corporation (measurement device). It can be specified by measuring. C and S may be measured using a combustion-infrared absorption method, and N may be measured using an inert gas melting-thermal conductivity method.
The chemical component of the base steel plate is a component obtained by analyzing a component of a steel plate obtained by removing a glass coating and an insulating coating containing phosphorus described later from a grain-oriented electrical steel plate by a method described below.

The manufacturing method of a base steel plate is not specifically limited, The manufacturing method of a conventionally well-known grain-oriented electrical steel plate can be selected suitably. As a preferable specific example of the production method, for example, after C is 0.04 to 0.1% by mass, and the others are hot-rolled by heating a slab having the chemical composition of the base steel plate to 1000 ° C. or higher. Then, if necessary, hot-rolled sheet annealing is performed, and then cold-rolled steel sheet is formed by cold rolling at least once with intermediate or intermediate annealing, and the cold-rolled steel sheet is 700 in a wet hydrogen-inert gas atmosphere, for example. Examples include a method of heating to ˜900 ° C., decarburizing annealing, further nitriding annealing as necessary, and finish annealing at about 1000 ° C.
In the present disclosure, the thickness of the base steel plate is not particularly limited, but is preferably 0.1 mm or more and 0.5 mm or less, and more preferably 0.15 mm or more and 0.40 mm or less.

In the present disclosure, the grain-oriented electrical steel sheet may have a coating on the surface as long as the effects of the present disclosure are not impaired. Examples of such a film include a glass film and an insulating film formed on a mother steel plate.
The glass film includes, for example, one or more oxides selected from forsterite (Mg ₂ SiO ₄ ), spinel (MgAl ₂ O ₄ ), and cordierite (Mg ₂ Al ₄ Si ₅ O ₁₆ ). A film is mentioned.
The insulating film contains, for example, colloidal silica and phosphate, and plays a role of imparting not only electrical insulation properties but also tension, corrosion resistance, heat resistance, and the like to the steel sheet.

The method for forming the glass film is not particularly limited, and can be appropriately selected from known methods. For example, in a specific example of the manufacturing method of the base steel sheet, after the cold separator steel sheet is coated with an annealing separator containing one or more selected from magnesia (MgO) and alumina (Al ₂ O ₃ ), the finishing is performed. A method of annealing is mentioned. In addition, the said annealing separator has the effect which suppresses the sticking of the steel plates at the time of finish annealing. For example, when finish annealing is performed by applying the annealing separator containing magnesia, a glass coating containing forsterite (Mg ₂ SiO ₄ ) is formed on the surface of the base steel plate by reacting with silica contained in the base steel plate. The
In the present disclosure, the thickness of the glass film is not particularly limited, but is preferably 0.5 μm or more and 3 μm or less.

  The plate thickness of the grain-oriented electrical steel sheet used in the present disclosure is not particularly limited, and may be appropriately selected according to the use etc., but is usually within a range of 0.15 mm to 0.35 mm, preferably The range is from 0.18 mm to 0.23 mm.

(2) Groove The method for forming the groove on the surface of the grain-oriented electrical steel sheet is not particularly limited, and a conventionally known method can be adopted. For example, as a destructive magnetic domain control method, an electrolytic etching method (see Japanese Examined Patent Publication No. 62-54873) in which grooves are formed on the surface of a grain-oriented electrical steel sheet by electrolytic etching, and a gear is mechanically moved to the steel sheet surface of a grain-oriented electrical steel sheet. A gear pressing method (see Japanese Patent Publication No. Sho 62-53579) for forming grooves on the steel sheet surface by pressing, and a laser irradiation method for forming grooves on the steel sheet surface of the grain-oriented electrical steel sheet by laser irradiation (Japanese Patent Laid-Open No. Hei 6-1993). 57335, International Publication No. 2016/171124) and the like.
As the irradiation conditions in the case of the laser irradiation method, generally, the laser output is 200 to 2000 W, the focused spot diameter in the laser rolling direction (diameter including 86% of the laser output) is 10 to 1000 μm, and the laser It is preferable to set the focused spot diameter in the plate width direction to 10 to 1000 μm, the laser scanning speed to 5 to 100 m / s, and the laser scanning pitch (interval) to 2 to 10 mm. The desired groove shape can be obtained by appropriately adjusting these laser irradiation conditions within the above range.
In addition, as an example of conditions in which the characteristics when grooves were formed by laser irradiation in Examples described later, laser output: 200 W, focused spot diameter (86% diameter) in the laser rolling direction: 100 μm, laser The condensing spot diameter (86% diameter) in the plate width direction is 400 μm, the laser scanning speed is 16 m / s, and the laser scanning pitch is 4 mm.

In the wound core of the present disclosure, the groove formed on the surface of the grain-oriented electrical steel sheet faces the outer winding side.
It is estimated that when the groove faces the outer winding side, it is possible to suppress the generation of compressive force around the groove and to suppress the generation of twins, compared to the case where the groove faces the inner winding side. The

  In the wound iron core of the present disclosure, the interval between the center lines of the grooves in the rolling direction may be 2 mm or more and less than 5 mm, may be 2 mm or more and 4 mm or less, or 2 mm or more and 3 mm or less. If the distance is less than 2 mm, the gap between the grooves is too close, and the subdivision of the main magnetic domain for reducing the abnormal eddy current loss loses its effect, and it is rather widened by the introduction of the lancet type auxiliary magnetic domain. It is not preferable. Moreover, when the said space | interval is 5 mm or more, there exists a possibility that it may become difficult to obtain a desired magnetic domain subdivision effect.

In the wound iron core of the present disclosure, the radius of curvature of the bent portion of the innermost peripheral portion of the wound iron core may be 50 mm or less.
Further, from the viewpoint of reducing the iron loss of the wound iron core, the radius may be less than 30 mm, 20 mm or less, 10 mm or less, or 5 mm or less.
Furthermore, from the viewpoint of facilitating manufacture, the radius may be 2 mm or more, or 3 mm or more.
The radius of curvature of the bent portion of the innermost peripheral portion of the wound iron core can be appropriately adjusted using a conventionally known processing machine.

In the present disclosure, in the grain-oriented electrical steel sheet having a steel sheet surface formed with a groove extending in a direction intersecting with the rolling direction and having a groove depth direction being a plate thickness direction, the groove extending direction and the plate thickness When the groove is viewed in the groove longitudinal section including the direction, the arithmetic average height Ra of the roughness curve defining the groove bottom region of the groove is 1.1 μm or more and 2.7 μm or less, and the groove bottom The average length RSm of the roughness curve elements forming the contour of the region may be 50 μm or more and 150 μm or less.
Furthermore, for Ra and RSm, when Ra is 1.3 μm or more and 2.5 μm or less, and RSm is 60 μm or more and 130 μm or less, the iron loss reduction effect is increased.
When the surface roughness parameters (Ra, RSm) satisfy the above range, the groove bottom region becomes a certain degree of rough surface, and is generated inside the groove due to iron melting by appropriately changing the radius of curvature of the bent portion. It is presumed that the stress has the effect of tension that suppresses the generation of the return magnetic domain, and the iron loss of the wound core can be reduced.
Further, since the stress generated in the bent portion is involved in reducing the iron loss of the wound core, the radius of curvature of the bent portion of the innermost peripheral portion of the wound core is set to a size within the predetermined range, It is presumed that the iron loss of the wound core is further reduced by the synergistic effect that the surface roughness parameters (Ra, RSm) satisfy the above range and that the groove faces the outer winding side of the wound core.

The definitions of the arithmetic average height Ra of the roughness curve (RC) and the average length RSm of the roughness curve element conform to Japanese Industrial Standard JIS B0601 (2013).
Further, a laser type surface roughness measuring instrument (VK-9700 manufactured by Keyence Corporation) can be used for measuring the surface roughness parameters (Ra, RSm) indicating the surface roughness of the groove bottom region.
The length in the groove extending direction is not particularly limited, but may be 250 to 350 μm in order to preferably obtain the effect of magnetic domain fragmentation.
The groove depth D of the groove is not particularly limited, but may be 5 μm or more and 40 μm or less in order to obtain the effect of magnetic domain subdivision preferably.
The groove width W of the groove is not particularly limited, but may be 10 μm to 250 μm in order to obtain the effect of magnetic domain subdivision preferably.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a plan view of a grain-oriented electrical steel sheet 1 according to the present embodiment.
2 is a cross-sectional view taken along line AA in FIG.
3 is a cross-sectional view taken along line BB in FIG.
1 to 3, the rolling direction of the grain-oriented electrical steel sheet 1 is X, the sheet width direction of the grain-oriented electrical steel sheet 1 (direction perpendicular to the rolling direction in the same plane) is Y, and the grain-oriented electrical steel sheet 1 The thickness direction (direction orthogonal to the XY plane) is defined as Z.
As shown in FIGS. 1 to 3, in the grain-oriented electrical steel sheet 1, the crystal orientation was controlled by the combination of the cold rolling process and the annealing process so that the easy axis of crystal grains and the rolling direction X coincided with each other. A steel plate (ground iron) 2, a glass coating 3 formed on the surface of the steel plate 2 (steel plate surface 2 a), and an insulating coating 4 formed on the surface of the glass coating 3 are provided. As shown in FIG. 3, in this embodiment, the insulating film 4 may include iron-containing particles 6 having an equivalent circle diameter of 0.1 μm to 2 μm from the viewpoint of improving the strength.

As shown in FIG. 1, a plurality of grooves 5 extending in a direction intersecting the rolling direction X and having a groove depth direction coinciding with the sheet thickness direction Z are formed on the steel plate surface 2a for magnetic domain subdivision. It is formed at predetermined intervals along the rolling direction X.
That is, FIG. 2 is a view of one groove 5 as seen in a cross section including the groove extending direction and the plate thickness direction Z.
FIG. 3 is a view of one groove 5 as seen in a cross section orthogonal to the groove extending direction.
In addition, the groove | channel 5 should just be provided so that the rolling direction X may be crossed, and the groove extension direction and the rolling direction X do not necessarily need to be orthogonal.
In the wound iron core of the present disclosure, the angle in the direction in which the groove 5 intersects the rolling direction of the grain-oriented electrical steel sheet 1 may be 0 <θ ≦ 90 ° with respect to the rolling direction, and the reflux magnetic domain can be easily controlled. Therefore, 0 <θ ≦ 60 ° or 0 <θ <30 ° may be set with respect to the rolling direction.
However, in this embodiment, the case where the groove extending direction and the rolling direction X are orthogonal to each other is illustrated for convenience of explanation. Further, the groove 5 may have an arcuate shape when viewed from the plate thickness direction Z (when the groove 5 is viewed in plan). However, in this embodiment, the groove | channel 5 which has a linear shape is illustrated for convenience of explanation.

  Incidentally, as shown in FIG. 3, the depth of the groove 5 is not necessarily constant in the width direction of the groove 5. Therefore, it is necessary to clarify the groove bottom region 5a when the groove 5 is viewed in the longitudinal section of the groove. Below, an example of the identification method of the groove bottom area | region 5a at the time of seeing the groove | channel 5 in a groove longitudinal cross section is demonstrated.

As shown in FIG. 4, when the groove 5 is viewed from the plate thickness direction Z (when the groove 5 is viewed in plan), the observation range 50 is set to a part of the groove 5, and a plurality of grooves are provided along the groove extending direction. (N) virtual lines L <b> 1 to Ln are virtually set within the observation range 50.
The observation range 50 is desirably set in a region excluding an end in the extending direction of the groove 5 (that is, a region where the shape of the groove bottom is stable).
For example, the observation range 50 may be an observation region whose length in the groove extending direction is about 300 μm.
Next, when the surface roughness of the groove 5 is measured along the imaginary line L1 using a laser type surface roughness measuring instrument or the like, as shown in FIG. 5, a measurement cross section that forms a contour in the groove extending direction of the groove 5 is shown. A curve MCL1 is obtained along the virtual line L1.
After applying the low-pass filter (cut-off value λs) to the measured cross-sectional curve MCL1 obtained for the virtual line L1 as described above to obtain a cross-sectional curve, the band-pass filters (cut-off values λf and λc) are applied to the cross-sectional curve. When the long wavelength component and the short wavelength component are removed from the cross-sectional curve by applying the above, a wavy curve LWC1 that forms the contour of the groove 5 in the groove extending direction is obtained along the virtual line L1, as shown in FIG.
The waviness curve is a kind of contour curve together with the roughness curve RC described later, whereas the roughness curve RC is a contour curve particularly suitable for accurately indicating the surface roughness of the contour, whereas the waviness curve is This contour curve is suitable for simplifying the contour shape itself with a smooth line.

As shown in FIG. 6, when the waviness curve LWC1 is used, the plate thickness between the steel plate surface 2a and the contour of the groove 5 (that is, the waviness curve LWC1) at each of a plurality of (m) positions along the virtual line L1. A distance in the direction Z (depth d1 to dm: unit is μm) is obtained. Furthermore, an average value (groove average depth D1) of these depths d1 to dm is obtained. The groove average depths D2 to Dn are obtained for each of the other virtual lines L2 to Ln by the same measurement method.
In order to measure the distance between the steel plate surface 2a and the contour of the groove 5 (waviness curve LWC1), it is necessary to measure in advance the position (height) of the steel plate surface 2a in the Z direction.
For example, the position (height) in the Z direction is measured for each of a plurality of locations on the steel plate surface 2a within the observation range 50 using a laser-type surface roughness measuring instrument, and the average value of the measurement results is determined as the steel plate surface 2a. You may use as the height of.

In the present embodiment, among the virtual lines L1 to Ln, a virtual line that satisfies the condition that the groove average depth is maximum along the groove extending direction is selected as the groove reference line BL.
The average groove depth of the groove reference line BL is defined as the groove depth D (unit: μm) of the groove 5.
For example, as illustrated in FIG. 7, when the average groove depth D3 is the maximum among the average groove depths D1 to Dn obtained for the virtual lines L1 to Ln, the virtual line L3 is the groove reference line BL. The groove average depth D3 of the imaginary line L3 is defined as the groove depth D of the groove 5.
In order to obtain the effect of magnetic domain subdivision preferably, the groove width W of the groove 5 in this embodiment is preferably 10 μm to 250 μm. The groove width W is such that the depth from the steel plate surface 2a toward the surface of the groove 5 in the plate thickness direction Z on the undulation curve of the groove 5 in the groove short cross section perpendicular to the groove extending direction is the groove depth of the groove 5 What is necessary is just to obtain | require as length (groove opening part) of the line segment which ties two points which are 0.05 * D with respect to thickness D (refer FIG. 10).

8 is a cross-sectional view taken along line CC in FIG. That is, FIG. 8 is a view of the groove 5 in the groove longitudinal section including the groove reference line BL and the plate thickness direction Z.
In the present embodiment, as shown in FIG. 8, when the groove 5 is viewed in the groove longitudinal section including the groove reference line BL and the plate thickness direction Z, the outline of the groove 5 appearing in the observation range 50 is defined as the groove bottom region 5a. Define.

The groove bottom region 5a of the groove 5 is specified by the above method. That is, in the present embodiment, as shown in FIG. 9, it is obtained by converting the measurement cross-sectional curve that forms the contour of the groove bottom region 5 a of the groove 5 that appears in the groove longitudinal section including the groove reference line BL and the plate thickness direction Z. The average of the roughness curve elements obtained by converting the measured cross-sectional curve forming the contour of the groove bottom region 5a, with the arithmetic average height Ra of the roughness curve RC being 1.1 μm or more and 2.7 μm or less. The length RSm may be 50 μm or more and 150 μm or less.
The roughness curve RC is obtained by applying a low-pass filter having a cutoff value λs to the measured cross-sectional curve obtained for the groove reference line BL, and then obtaining a high-pass filter (cut-off value λc) on the cross-sectional curve. Is applied to remove a long wavelength component from the cross-sectional curve.

As shown in FIG. 3, when the groove 5 is viewed in a short cross section perpendicular to the groove extending direction, the boundary G between the groove 5 and the steel plate surface 2 a may be unclear. Therefore, it is necessary to clarify the boundary G between the groove 5 and the steel plate surface 2a.
Below, an example of the specific method of the boundary G of the groove | channel 5 and the steel plate surface 2a at the time of seeing the groove | channel 5 in a groove | channel short cross section is demonstrated.

FIG. 10 is a cross-sectional view taken along line EE in FIG. That is, FIG. 10 is a view of the groove 5 as viewed in a short cross section perpendicular to the groove extending direction.
As shown in FIG. 10, when the groove 5 is viewed in the short cross section of the groove, the measured cross section curve that forms the outline of the groove 5 appearing in the short cross section of the groove is converted into a wavy curve. Define.
As shown in FIG. 10, a virtual line Ls perpendicular to the groove reference line BL is virtually set in the XY plane, and the surface roughness of the steel sheet 2 including the groove 5 is measured using a laser-type surface roughness measuring instrument or the like. Is measured along the imaginary line Ls, a measurement cross-sectional curve that forms the contour of the groove 5 in the short cross section of the groove is obtained along the imaginary line Ls.
The groove short wave undulation curve SWC appearing in the groove short cross section is obtained by applying a low-pass filter (cutoff value λs) to the measurement cross sectional curve obtained for the virtual line Ls as described above, This is obtained by applying band-pass filters (cut-off values λf and λc) to the cross-sectional curve and removing the long wavelength component and the short wavelength component from the cross-sectional curve.

As shown in FIG. 10, when the groove short swell curve SWC that forms the contour of the groove 5 appearing in the groove short cross section is used, the steel plate surface 2 a and the groove at each of a plurality of (p) positions along the virtual line Ls. A distance (depth f1 to fp: unit is μm) in the thickness direction Z between the five contours (that is, the groove short swell curve SWC) is obtained.
In the present embodiment, as shown in FIG. 10, in the groove short-wave undulation curve SWC, a region that satisfies the following conditional expression (1) is defined as a groove region 5b, and a region other than the groove region 5b is defined as a steel plate region 2b. To do.
A boundary between the groove region 5b and the steel plate region 2b is specified as a boundary G between the groove 5 and the steel plate surface 2a.
The width of the groove region 5b corresponds to the groove width W.
fi ≧ 0.05 × D (1)
(Where i is an integer from 1 to p)

(3) Wrapped iron core A wound iron core can be manufactured by a conventionally known method.
For example, a wound iron core is manufactured by shearing a hoop and winding it into a donut shape, pressing a corner portion, forming it into a rectangular shape, annealing it, and removing the strain and holding the shape.
And the junction part used as the butt | matching part of a steel plate is formed. In order to suppress iron loss deterioration due to an increase in magnetic resistance at the butt portion, this butt is usually arranged in a step shape.
The wound iron core may be fixed using a known fastener such as a binding band as required.
In the present disclosure, the shape of the corner portion of the wound core is not particularly limited.
In the present disclosure, the number of joints of the wound iron core is not particularly limited.

In addition, this indication is not limited to the said embodiment. The above-described embodiments are exemplifications, and the present disclosure has any configuration that has substantially the same configuration as the technical idea described in the claims of the present disclosure and that exhibits the same operational effects. Are included in the technical scope.
Hereinafter, the present disclosure will be specifically described with reference to examples. These descriptions do not limit the present disclosure.

[Example 1]
In order to change the groove bottom shape of the material 23ZH (iron loss W17 / 50 = 0.80 W / kg), the distance between the center lines of the grooves in the rolling direction is 3 mm, and the groove extending direction is in the rolling direction of the material steel plate. On the other hand, grooves intersecting at an angle of 10 ° were formed, and a magnetic domain controlled material was prepared.
Using the material under the conditions shown in Table 1, the wound core is such that the groove faces the outer winding side (core mass: 18.76 kg, capacity: 5 KVA, dimensions shown in FIG. 11 (unit is mm in FIG. 11)) Manufactured.
The BF of the wound core was calculated by evaluating the material core loss and the wound core loss by the method described in JIS C 2550-1 and dividing by the respective iron losses. The results are shown in Table 1.

[Examples 2 to 60, Comparative Examples 1 to 104]
The raw materials described in Tables 1 to 3 were prepared, wound cores were manufactured in the same manner as in Example 1, and BF was calculated. The results are shown in Tables 1 to 3. Tables 1 and 2 summarize data measured by changing Ra and RSm by unifying the radius of curvature of the innermost peripheral portion to 3 mm. Table 3 summarizes data measured by changing RSm to 120 μm and changing the radius of curvature and Ra of the innermost periphery.

[Summary of results]
As shown in the results of Tables 1 and 2, it has been clarified that the building core of the wound core of the example is reduced as compared with the wound core of the comparative example.
Specifically, when the radius of curvature of the bent portion of the innermost peripheral portion is 3 mm, Ra is 1.1 μm or more and 2.7 μm or less, and RSm is 50 μm or more and 150 μm or less, the groove is outside the wound core. It has been found that the iron loss of the wound core can be reduced by arranging it so as to face the winding side than when facing the inner winding side.
Further, as shown in Table 3, if the radius of curvature of the bent portion of the innermost peripheral portion is 3 mm or more and 50 mm or less, by arranging the groove so as to face the outer winding side of the wound core, It has been found that the iron loss of the wound core can be reduced to the same or less than the case of facing.
Further, as shown in Table 3, if the radius of curvature of the bent portion of the innermost peripheral portion is 3 mm or more and 30 mm or less, the groove is arranged so as to face the outer winding side of the wound core, so that the inner winding side It was found that the iron loss of the wound core can be reduced as compared with the case of facing, and that the effect of reducing the iron loss of the wound core can be obtained more than 3 mm and not more than 20 mm.

1 Directional electrical steel sheet 2 Steel sheet (base steel sheet)
2a Steel plate surface 2b Steel plate region 3 Glass coating 4 Insulating coating 5 Groove 5a Groove bottom region 5b Groove region 6 Iron-containing particle 50 Observation range G Boundary BL Groove reference line MCL1 Measurement cross section curve LWC1 Groove long waviness curve SWC Groove short waviness curve Ls Virtual line f Depth RC Roughness curve W Groove width X Rolling direction Y Sheet width direction Z Sheet thickness direction

Claims (4)

A wound iron core comprising a grain-oriented electrical steel sheet having a steel sheet surface extending in a direction intersecting with the rolling direction and having a groove for SRA magnetic domain control in which the groove depth direction is a sheet thickness direction,
The groove faces the outer winding side,
The interval between the center lines of the grooves in the rolling direction is 2 mm or more and less than 5 mm,
The radius of curvature of the bent portion of the innermost peripheral portion is 50 mm or less,
When the groove is viewed in the groove longitudinal section including the groove extending direction and the plate thickness direction, the arithmetic average height Ra of the roughness curve defining the groove bottom region of the groove is 1.1 μm or more and 2.7 μm. And
An average length RSm of a roughness curve element forming the contour of the groove bottom region is 50 μm or more and 150 μm or less.   The wound core according to claim 1, wherein the Ra is 1.3 µm or more and 2.5 µm or less, and the RSm is 60 µm or more and 130 µm or less.   The wound core according to claim 1 or 2, wherein an angle in a direction intersecting with a rolling direction of the groove is 0 <θ <30 ° with respect to the rolling direction.   The wound iron core according to any one of claims 1 to 3, wherein a radius of curvature of a bent portion of the innermost peripheral portion is 3 mm or more and less than 10 mm.