JP2022069944A - Manufacturing method and manufacturing device for iron core - Google Patents

Abstract

To provide a manufacturing method for an iron core that can improve productivity, while preventing a deterioration in characteristics.SOLUTION: A manufacturing method for an iron core includes a molding step of superimposing a plurality of directional electromagnetic steel plates and executing bending processing on the directional electromagnetic steel plates in a superimposed state to mold a bent processed body, and a lamination step of laminating the bent processed bodies in a plate thickness direction. The plate thickness of the directional electromagnetic steel plate is 0.23 mm or less. The coefficient of friction between layers of the directional electromagnetic steel plates in the superimposed state at the time of the bending processing is controlled to be 0.60 or less.SELECTED DRAWING: Figure 7

Description

The present invention relates to a method for manufacturing an iron core and a manufacturing apparatus.

The wound core is widely used as a magnetic core for transformers, reactors, noise filters, and the like.

As a method for manufacturing a wound iron core, after winding a steel plate into a cylindrical shape, the tubular laminated body is pressed so that the corners have a constant curvature to form a substantially rectangular shape, and then annealed to remove strain. A method of performing (distortion removal) and shape retention is widely known (see, for example, Patent Document 1).

Further, as another manufacturing method of the wound core, the steel plate portion to be the corner portion of the wound core is bent in advance so as to form a relatively small bending region having a radius of curvature of 3 mm or less, and the bending is performed. A manufacturing method for laminating steel plates to obtain a wound iron core is known (see, for example, Patent Documents 2 to 4). According to the manufacturing method, a large-scale pressing process is not required, and the steel sheet is finely bent to maintain the iron core shape. Further, since the processing strain is concentrated only on the bent portion (corner portion), it is possible to omit the strain removal by annealing (annealing step). Since of such great industrial advantages, the application of the manufacturing method is progressing.

Further, as described above, it is known that control of machining strain is important for an iron core in which machining strain is concentrated only in a bent portion (corner portion) and an annealing step for strain removal can be omitted. (See, for example, Patent Document 5).

Japanese Unexamined Patent Publication No. 2005-286169 Japanese Patent No. 6224468 Japanese Unexamined Patent Publication No. 2018-148036 AU2012337260A1 WO2018 / 131613

An object of the present invention is to provide a method and an apparatus for manufacturing an iron core capable of improving the productivity of the wound core while suppressing deterioration of the characteristics of the wound core.

In a manufacturing method in which an electromagnetic steel sheet is bent in advance and the bent electromagnetic steel sheet (referred to as a bent body) is laminated to obtain a wound steel core, a plurality of electromagnetic steel sheets are bent rather than one by one. Productivity is improved when bending is performed with the electromagnetic steel sheets of the above piled up.
The inventors of the present application have compared to the case of using the method of bending one by one unless the bending conditions are appropriately controlled when the method of bending with a plurality of electromagnetic steel sheets stacked is used. However, it was found that the characteristics of the wound steel core deteriorated. Specifically, if the inter-story friction coefficient (slip condition) of the laminated electromagnetic steel sheets is not appropriate, problems such as the generation of a large number of twins in the bent portion and deterioration of bending accuracy occur, and the core iron loss of the wound iron core occurs. Will occur.

The inventors of the present application have used a bending process in which a plurality of electrical steel sheets are overlapped with each other, but by appropriately controlling the bending conditions, the bending machine obtained by the method is used. The result is that the characteristics of the wound core manufactured by laminating the steel sheets can be equal to or higher than the characteristics of the wound core manufactured by laminating the bent products obtained by bending the electromagnetic steel sheets one by one. Obtained. As a result, the productivity of the wound core can be improved while suppressing the deterioration of the characteristics of the wound core.

In order to achieve the above object, the present invention is a method for manufacturing an iron core.
A molding process in which a plurality of grain-oriented electrical steel sheets are laminated and the laminated electrical steel sheets are bent to form a bent body, and the bent body is placed in the plate thickness direction. Including the laminating process of laminating
The thickness of the grain-oriented electrical steel sheet is 0.23 mm or less.
It is characterized in that the interlaminar friction coefficient at the time of the bending process of the laminated electrical steel sheets is controlled to be 0.60 or less.

Further, the method for manufacturing an iron core of the present invention is:
The grain-oriented electrical steel sheet located on the outside of the bent body is used as the outer steel sheet.
The grain-oriented electrical steel sheet located inside in the bent body is used as an inner steel sheet.
The amount of the outer steel sheet delivered to the device to be bent is defined as the first amount of delivery.
The amount of the inner steel sheet delivered to the device to be bent is defined as the second amount of delivery.
The increment of the first delivery amount with respect to the second delivery amount is defined as the first increment.
In the bent body, the length of the bent portion of the outer steel plate determined based on the geometric shape is defined as the first length.
In the bent body, the length of the bent portion of the inner steel plate determined based on the geometric shape is defined as the second length.
Assuming that the increment of the first length with respect to the second length is the second increment,
It is characterized in that the value obtained by dividing the first increment by the second increment is controlled to be 1.70 or less.

Further, the present invention is an iron core manufacturing apparatus provided with a processing apparatus for forming a bent body by bending a grain-oriented electrical steel sheet.
The processing apparatus puts a plurality of the grain-oriented electrical steel sheets in a laminated state, and bends the grain-oriented electrical steel sheets in the stacked state.
The thickness of the grain-oriented electrical steel sheet is 0.23 mm or less.
Immediately before the bending process, the interlayer friction coefficient of the laminated electrical steel sheets is 0.60 or less.

Further, the iron core manufacturing apparatus of the present invention is
A supply control device for controlling the supply of a plurality of the grain-oriented electrical steel sheets to the processing device is provided.
The grain-oriented electrical steel sheet located on the outside of the bent body is used as the outer steel sheet.
The grain-oriented electrical steel sheet located inside in the bent body is used as an inner steel sheet.
The amount of the outer steel sheet delivered to the device to be bent is defined as the first amount of delivery.
The amount of the inner steel sheet delivered to the device to be bent is defined as the second amount of delivery.
The increment of the first delivery amount with respect to the second delivery amount is defined as the first increment.
In the bent body, the length of the bent portion of the outer steel plate determined based on the geometric shape is defined as the first length.
In the bent body, the length of the bent portion of the inner steel plate determined based on the geometric shape is defined as the second length.
Assuming that the increment of the first length with respect to the second length is the second increment,
The supply control device is characterized in that the value obtained by dividing the first increment by the second increment is controlled to be 1.70 or less.

According to the present invention, it is possible to improve the productivity of the wound core while suppressing the deterioration of the characteristics of the wound core.

It is a perspective view which shows an example of a winding iron core schematically. It is a side view of the winding iron core shown in FIG. It is a side view which shows another example of a winding iron core schematically. It is a side view schematically showing an example of a bent body. It is a side view schematically showing another example of a bent body. It is a side view which shows an example of the bent part of a bent body schematically. It is a schematic diagram which shows an example of the manufacturing apparatus used in the manufacturing method which concerns on this invention. It is a figure which shows typically an example of the bending | bending body manufactured by the manufacturing method which concerns on this invention. It is a schematic diagram which shows an example of the bending process by the manufacturing apparatus which concerns on this invention, (a) shows the state before bending process, (b) shows the state which has been bending process, (a). c) shows a state in which the grain-oriented electrical steel sheet is cut after being bent. It is a schematic diagram which shows the dimension of the winding iron core manufactured in an Example (comparative example).

Hereinafter, the method for manufacturing the iron core and the manufacturing apparatus according to the present invention will be described in detail in order. However, the present invention is not limited to the configuration disclosed in the present embodiment, and various modifications can be made without departing from the spirit of the present invention. The numerical limit range described below includes the lower limit value and the upper limit value. Numerical values that indicate "greater than" or "less than" do not fall within the numerical range. Further, "%" regarding the chemical composition means "mass%" unless otherwise specified. In addition, as used in the present specification, terms such as "parallel", "vertical", "identical", "right angle", and values of length and angle, etc., which specify the shape and geometric conditions and their degrees, are used. Is not bound by the strict meaning, but is interpreted to include the range in which similar functions can be expected. Further, in the present specification, the “oriented electrical steel sheet” may be simply referred to as “steel sheet” or “electrical steel sheet”, and the “rolled steel core” may be simply referred to as “iron core”.

First, a wound iron core manufactured by using the iron core manufacturing method according to the present invention will be described.
<Rolling iron core>
FIG. 1 is a perspective view schematically showing an embodiment of a wound iron core. FIG. 2 is a side view of the wound iron core shown in FIG. FIG. 3 is a side view schematically showing another embodiment of the wound iron core. In the present invention, the side view means to see in the width direction (Y-axis direction in FIG. 1) of the elongated grain-oriented electrical steel sheet constituting the wound steel core, and the side view is visually recognized by the side view. It is a figure (the figure in the Y-axis direction of FIG. 1) which showed the shape | shape. Further, the plate thickness direction is the plate thickness direction of the grain-oriented electrical steel sheet, and means a direction perpendicular to the peripheral surface of the wound steel core in a state of being formed into a rectangular wound steel core.

The wound steel core 10 has a laminated structure in which bent bodies 1 formed of grain-oriented electrical steel sheets are stacked in the plate thickness direction and have a substantially rectangular shape in a side view. The wound core 10 may be used as it is as the wound core, or if necessary, a known fastener such as a binding band or the like may be used to integrally fix the plurality of stacked bending bodies 1. May be provided.

The core length of the wound core 10 is preferably 0.6 m or more, and more preferably 0.7 m or more. The core length of the wound core 10 means the peripheral length at the center point in the stacking direction of the wound core 10 from the side view. Even if the iron core length changes in the iron core, the volume fraction of the bent portion is constant, so the iron loss generated at the bent portion is constant. The effect on is reduced.

The laminated thickness of the steel plate of the wound steel core 10 is not particularly limited, and is, for example, 45 mm. The laminated thickness of the steel plate of the wound core 10 means the maximum thickness in the laminated direction in the flat portion of the wound core 10 from the side view.

As shown in FIGS. 1 and 2, in the wound iron core 10, the flat surface portions 4 and the corner portions 3 are alternately continuous in the longitudinal direction, and the angles formed by the two flat surface portions 4 adjacent to each other with the corner portions 3 interposed therebetween. The bent body 1 having a temperature of 90 ° includes a portion stacked in the plate thickness direction, and has a substantially rectangular laminated structure 2 in a side view. Each corner portion 3 of the bent body 1 has two or more bent portions (bending portions) 5 having a curved shape in a side view, and the bent portion 5 existing in one corner portion 3 The total of each bending angle is 90 °. Further, the corner portion 3 has a flat surface portion 4a between the adjacent bent portions 5 and 5. The corner portion 3 is configured to include two or more bent portions 5 and one or more flat portions 4a. FIG. 2 shows a case where one corner portion 3 has two bent portions 5, and FIG. 3 shows a case where one corner portion 3 has three bent portions 5. Although not shown, one corner portion 3 may have one bending portion 5.

When one corner portion 3 is configured to have two or more bent portions 5, the bending angle φ (φ1, φ1, from the viewpoint of suppressing the occurrence of strain due to deformation during machining and suppressing iron loss). φ2, φ3) is preferably 60 ° or less, and more preferably 45 ° or less. When one corner portion 3 shown in FIG. 2 has two bent portions 5, for example, φ1 = 60 ° and φ2 = 30 °, φ1 = 45 ° and φ2 = 45 °, and the like can be set. preferable. When one corner portion 3 shown in FIG. 3 has three bent portions 5, it is preferable that, for example, φ1 = 30 °, φ2 = 30 °, φ3 = 30 °, and the like. Further, from the viewpoint of improving production efficiency, it is preferable that the bending angles are the same. Therefore, when one corner portion 3 shown in FIG. 2 has two bending portions 5, φ1 = 45 ° and φ2 = 45. In the case where one corner portion 3 shown in FIG. 3 has three bent portions 5, for example, φ1 = 30 °, φ2 = 30 ° and φ3 = 30 ° are preferable.

The bent portion 5 will be described in detail with reference to FIG. FIG. 6 is a diagram schematically showing an example of a bent portion 5 (curved portion) of the bent body 1. The bending angle of the bent portion 5 means the angle difference generated between the straight portion on the rear side and the straight portion on the front side in the bending direction in the bent portion 5 of the bent portion 1, and is the outer surface of the bent portion 1. In, two virtual portions obtained by extending a straight portion which is the surface of the flat surface portions 4, 4a sandwiching the bent portion 5, the flat surface portions 4a, 4a sandwiching the bent portion 5, or the flat surface portions 4, 4 sandwiching the bent portion 5. It is expressed as the angle φ of the complementary angle of the angle formed by the lines Lb-elongation1 and Lb-elongation2. At this time, the point where the extending straight line separates from the surface of the steel sheet is the boundary between the flat surface portion 4 and the bent portion 5 on the surface on the outer surface side of the steel sheet, and is the point F and the point G in FIG.

Further, a straight line perpendicular to the outer surface of the steel sheet is extended from each of the points F and G, and the intersections with the surface on the inner surface side of the steel sheet are defined as points E and D, respectively. The points E and D are the boundaries between the flat surface portion 4 or the flat surface portion 4a and the bent portion 5 on the inner surface side surface of the steel sheet. The bent portion 5 is a portion of the grain-oriented electrical steel sheet surrounded by the points D, E, F, and G in the side view of the bent body 1. In FIG. 6, the surface of the steel plate between the points D and E, that is, the inner surface of the bent portion 5 is La, and the surface of the steel plate between the points F and G, that is, the outer surface of the bent portion 5 is Lb.

Further, in this figure, the radius of curvature r on the inner surface side in the side view of the bent portion 5 is shown. By approximating the above La with an arc passing through the points E and D, the radius of curvature r of the bent portion 5 is obtained. The smaller the radius of curvature r, the steeper the bending of the curved portion of the bent portion 5, and the larger the radius of curvature r, the gentler the bending of the curved portion of the bent portion 5.
In the wound iron core of the present invention, the radius of curvature r in each bent portion 5 of each bent body 1 laminated in the plate thickness direction may have some variation. This fluctuation may be due to the molding accuracy, and it is possible that an unintended fluctuation may occur due to handling during laminating. Such an unintended error can be suppressed to about 0.2 mm or less in the current ordinary industrial manufacturing. When such fluctuation is large, a typical value can be obtained by measuring the radius of curvature of a sufficiently large number of steel plates and averaging them. It is also possible to change it intentionally for some reason, but the present invention does not exclude such a form.
The method for measuring the radius of curvature r of the bent portion 5 is not particularly limited, but it can be measured, for example, by observing at 200 times using a commercially available microscope (Nikon ECLIPSE LV150). Specifically, the point A at the center of curvature is obtained from the observation results. For example, the intersection of the line segment EF and the line segment DG extended inward on the opposite side of the point B is defined as A. For example, the magnitude of the radius of curvature r corresponds to the length of the line segment AC.

The radius of curvature r in the side view of the bent portion 5 is, for example, in the range of more than 1 mm and 3 mm or less.

FIG. 4 is a diagram schematically showing an example of the bent body 1. In the bent body 1 shown in FIG. 4, one grain-oriented electrical steel sheet has a substantially rectangular annular shape in a side view, and has four corner portions 3 and four flat surface portions 4. FIG. 4 shows a case where one bending body 1 constitutes one layer of the wound iron core 10. In the bent body 1 shown in FIG. 4, one flat surface portion 4 has a joint portion (gap) 6 which is an end face in the longitudinal direction, and the other three flat surface portions 4 do not have a joint portion 6.

FIG. 5 is a diagram schematically showing another example of the bent body 1. In the bent body 1 shown in FIG. 5, one grain-oriented electrical steel sheet has a substantially U-shape in a side view, and has two corner portions 3 and three flat surface portions 4. FIG. 5 shows a case where one bending body 1 constitutes about half a circumference of the wound core 10 and two bending bodies 1 form one layer of the wound core 10 via two joints 6. ing. In other words, FIG. 5 shows a case where two grain-oriented electrical steel sheets form a substantially rectangular annular shape in a side view and constitute one layer of the wound steel core 10. When the two bending bodies 1 form one layer of the wound iron core 10, a joint portion (gap) 6 is formed at a position where the end faces of the bending bodies 1 face each other. It should be noted that one bending body 1 shown in FIG. 5 may constitute one layer of the iron core 10. In that case, when the bent bodies 1 are laminated, a substantially U-shaped iron core 10 can be obtained in a side view.

Further, although not shown, the bending machine 1 has one grain-oriented electrical steel sheet having a substantially L-shape in a side view and has one corner portion 3 and two flat surface portions 4. May be. In that case, when the bent bodies 1 are laminated, a substantially L-shaped iron core 10 can be obtained in a side view.

<Manufacturing method of iron core>
Next, a method for manufacturing an iron core according to the present invention will be described. The method for manufacturing an iron core according to the present invention includes (1) a preparation step, (2) a pretreatment step, (3) a molding step, and (4) a laminating step.

(1) Preparation step The preparation step is a step of preparing (manufacturing) a general grain-oriented electrical steel sheet having a film formed on the surface of a grain steel whose composition / crystal orientation is controlled.
(2) Pretreatment step This is a step of performing pretreatment to control the friction coefficient of the grain-oriented electrical steel sheet (interlayer friction coefficient described later).
(3) Forming step This is a step of forming a bent body by putting a plurality of grain-oriented electrical steel sheets in a stacked state and bending the laminated grain-oriented electrical steel sheets. Hereinafter, the operation of stacking a plurality of grain-oriented electrical steel sheets before bending is performed may be referred to as a first stacking.
(4) Laminating step This is a step of laminating bent bodies to form a laminated body. Hereinafter, the operation of laminating the bent bodies may be referred to as a second laminating.

(1) Preparation process (mother steel plate)
The grain steel can be appropriately selected and used from those known as grain-oriented electrical steel sheets. The mother steel sheet is a steel sheet in which the orientation of the crystal grains in the mother steel plate is highly integrated in the {110} <001> orientation, and has excellent magnetic properties in the rolling direction. Hereinafter, an example of a preferable mother steel sheet will be described, but the present invention is not limited to the following.

The chemical composition of the base steel sheet is mass%, contains Si: 2.0% to 7.0%, and the balance consists of Fe and impurities. This chemical composition is for controlling the crystal orientation to a Goss texture integrated in the {110} <001> orientation (Goss orientation) and ensuring good magnetic properties. The other elements are not particularly limited, and it is permissible to replace them with Fe and contain known elements in a known range. The typical content range of typical elements is as follows.
C: 0 to 0.0050%,
Mn: 0-1.0%,
S: 0 to 0.0150%,
Se: 0 to 0.0150%,
Al: 0 to 0.0650%,
N: 0 to 0.0050%,
Cu: 0 to 0.40%,
Bi: 0 to 0.010%,
B: 0 to 0.080%,
P: 0 to 0.50%,
Ti: 0 to 0.0150%,
Sn: 0 to 0.10%,
Sb: 0 to 0.10%,
Cr: 0 to 0.30%,
Ni: 0-1.0%,
Nb: 0 to 0.030%,
V: 0 to 0.030%,
Mo: 0 to 0.030%,
Ta: 0 to 0.030%,
W: 0 to 0.030%,
Since these selective elements may be contained according to the purpose, it is not necessary to limit the lower limit value, and it is not necessary to substantially contain them. Further, these selective elements may be contained as impurities. The term "impurity" refers to an element that is unintentionally contained, and means an element that is mixed from ore, scrap, or the manufacturing environment as a raw material when the base steel sheet is industrially manufactured.

The chemical composition of the mother steel sheet may be measured by a general analysis method for steel. For example, the chemical composition of the mother steel sheet may be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectroscopy). Specifically, for example, by acquiring a 35 mm square test piece from the center position of the mother steel plate and measuring it with an ICPS-8100 manufactured by Shimadzu Corporation (measuring device) under conditions based on a calibration curve prepared in advance. Can be identified. In addition, C and S may be measured by using the combustion-infrared absorption method, and N may be measured by using the inert gas melting-thermal conductivity method.

The above chemical composition is a component of the mother steel sheet. If the grain-oriented electrical steel sheet used as the measurement sample has a primary coating (glass coating, intermediate layer) made of oxides, an insulating coating, etc. on the surface, these are removed by a known method before the chemical composition. To measure.

(Production method)
The method for manufacturing the grain-oriented electrical steel sheet is not particularly limited, and a conventionally known method for manufacturing grain-oriented electrical steel sheet can be appropriately selected. As a preferable specific example of the production method, for example, C is 0.04 to 0.1% by mass, and the other is necessary after heating a slab having the above chemical composition to 1000 ° C. or higher and hot rolling. The hot-rolled sheet is annealed according to the above, and then the cold-rolled steel sheet is obtained by cold-rolling once or two or more times with intermediate annealing sandwiched between them. A method of decarburizing and annealing by heating to ° C, further annealing and annealing as necessary, applying an annealing separator, finishing annealing at about 1000 to 1200 ° C, and forming an insulating film at about 900 ° C is mentioned. Be done. Further, after that, painting or the like for adjusting the friction coefficient may be carried out. Further, the steel sheet may be a steel sheet in which a process generally called "magnetic domain control" is performed by a method known in the steel sheet manufacturing process.

(Plate thickness)
As is known, it is advantageous to have a thin plate thickness in order to reduce the iron loss of the grain-oriented electrical steel sheet itself and the iron loss of the iron core produced thereby. Another object of the present invention is to eliminate the increase in the number of laminated sheets, that is, the increase in the number of bending processes, when the iron core is manufactured from a thin steel plate. This makes the present invention particularly useful in a manufacturing method using a thin steel sheet having a grain thickness of 0.23 mm or less. On the other hand, in the present invention, when the bending radius of the bending die is r and the number of laminated sheets in the first lamination is two, the thickness of the steel plates to be laminated and bent is t. The steel plate located on the outside of is also in a situation where it can be bent by a mold having a bending radius of r + t. This also eliminates the characteristics of the processing method targeted by the present invention, which has advantages by reducing the bending radius and localizing the bending strain region. From this point as well, the thickness of the grain-oriented electrical steel sheet used in the present invention is preferably 0.23 mm or less. The lower limit of the plate thickness is not particularly limited, but considering the manufacturing efficiency of the steel sheet itself, the lower limit of the plate thickness of the target grain-oriented electrical steel sheet is preferably 0.05 mm, more preferably 0. It is .09 mm, more preferably 0.12 mm. Further, when the number of laminated sheets in the first lamination is 3 or more, the directional electromagnetic steel to be laminated is considered in consideration of the production efficiency of bending and the substantial increase in the bending radius of the steel plate located outside the bending body. The plate thickness of the steel plate is preferably less than 0.23 mm. For example, when the number of laminated sheets in the first lamination is 3, the plate thickness is preferably 0.20 mm or less, and when the number of laminated sheets in the first lamination is 4, the plate thickness is 0.15 mm. The following is preferable.

In the present embodiment, a strip-shaped grain-oriented electrical steel sheet is wound around a coil to form a hoop material (coil material).

(2) Pretreatment process The friction coefficient (interlayer friction coefficient) of the directional electromagnetic steel plate manufactured in the preparation process is controlled. The pretreatment is performed by the pretreatment device. As a pretreatment, there is a treatment of applying a lubricant (lubricating substance) by spray injection, a roll coater, or the like. Further, as a pretreatment, there is a treatment of changing the surface roughness by light rolling with a rolling roll or the like.

(Measurement of inter-story friction coefficient)
After the pretreatment and before the bending process, the grain-oriented electrical steel sheet (sample) is taken out and the inter-story friction coefficient is measured. The inter-story friction coefficient is the friction coefficient between the steel plate surfaces of the grain-oriented electrical steel sheets laminated in the first lamination. When the pretreatment and the bending process are separate processes (separate lines), the predetermined grain-oriented electrical steel sheet (sample) that has been subjected to the pretreatment and before the bending process is extracted and friction between layers. Measure the coefficient. Although the details will be described later, a pretreatment device for pretreatment is provided immediately before the bending die for bending in the processing device, and the pretreatment and the bending process are continuously performed to manufacture a bent body. May be done. That is, the pretreatment process and the bending process may be performed on the same line. In that case, a sample of grain-oriented electrical steel sheet that has been subjected to only pretreatment is manufactured on a separate line, and the inter-story friction coefficient is measured using the sample.

The inter-story friction coefficient of the grain-oriented electrical steel sheets is one set in which three grain-oriented electrical steel sheets are laminated (first laminated), and for example, a total of 10 sets are measured. The inter-story friction coefficient of the grain-oriented electrical steel sheet is obtained from the relationship between the load and the tensile force by pulling the central steel sheet while uniformly applying a load in the stacking direction in a state where three sheets are stacked for each set. Specifically, the maximum value of the tensile force is divided by the load to obtain the inter-story friction coefficient of the grain-oriented electrical steel sheet. Then, the average value of the 10 sets of measurement results is used as the interlaminar friction coefficient of the grain-oriented electrical steel sheet. The interlayer friction coefficient obtained by the above operation is generally a static friction coefficient, but it does not have to be a static friction coefficient and may be a dynamic friction coefficient. In the present invention, the invention is defined by setting the maximum interlaminar friction coefficient in the above measurement to 0.60 or less. The interlaminar friction coefficient of the grain-oriented electrical steel sheet is preferably 0.03 or more and 0.50 or less, and more preferably 0.05 or more and 0.40 or less.

In addition, instead of providing the pretreatment step as an independent step, the pretreatment, that is, the control of the inter-story friction coefficient may be performed in the above-mentioned preparation step. The control of the inter-story friction coefficient is adjusted according to the type of coating and the surface condition such as surface roughness. The method is not particularly limited, and a known method may be used as appropriate. For example, the roughness of the mother steel sheet is controlled by appropriately controlling the roll roughness of the hot-rolled steel sheet and / or the cold-rolled steel sheet, grinding the surface of the mother steel sheet, and chemically etching such as pickling. There is a way to do it. Further, for example, a method of increasing the baking temperature of the coating film or extending the time to promote surface smoothing of the vitreous coating film, reduce the roughness, increase the contact area between the steel sheets, and increase the static friction coefficient. There is. In reality, it may be necessary to control the coefficient of friction to the final target while observing the surface condition of the steel sheet actually manufactured as a trial, but the product is rolled and surface-treated on a daily basis. It is not difficult for those skilled in the art who adjust the surface condition of. When the pretreatment is performed in the pretreatment step, the pretreated hoop material is prepared.

As described above, the pretreatment step may not be provided as an independent step, but the pretreatment may be performed immediately before the bending process is performed in the molding step shown below. That is, a device for performing pretreatment (pretreatment device) may be further provided in front of the processing device for bending, and the bending may be performed in the processing device after the pretreatment is performed in the pretreatment device. .. Hereinafter, in the present embodiment, a case where the pretreatment is performed immediately before the bending process is performed, that is, a case where the pretreatment and the bending process are continuously performed will be described. The pretreatment device may be provided integrally with the processing device. In the present embodiment, the pretreatment device controls the interlaminar friction coefficient to be 0.60 or less at the time of bending of the laminated grain-oriented electrical steel sheets. In other words, the pretreatment device controls so that the inter-story friction coefficient of the laminated grain-oriented electrical steel sheets is 0.60 or less immediately before the bending process.

(3) Forming process A bent product is formed from grain-oriented electrical steel sheets that have been pretreated. In this embodiment, an example is shown in which two grain-oriented electrical steel sheets as a plurality of grain-oriented electrical steel sheets are laminated (first laminated) and bent. In addition, you may perform bending processing by superimposing three or more grain-oriented electrical steel sheets. Further, it is not necessary to set an upper limit for the number of laminated sheets in the first lamination, but the larger the number of laminated sheets, the larger the bending radius of the steel sheet located on the outside, so that the processing is performed with a small bending radius. The merit of the iron core manufactured by the present invention may be lost. Further, considering the complexity in controlling the amount of steel sheets to be fed out depending on the stacking position in the iron core, which will be described later, it is practically preferable that the number of stacked steel sheets is 4 or less, although it depends on the thickness of the steel sheets to be laminated. .. In the following description, in particular, the control of the delivery amount will be described assuming that the number of stacked sheets is two.

FIG. 7 is a schematic view showing an example of a manufacturing apparatus 100 used for manufacturing a wound iron core. The manufacturing apparatus 100 includes a supply control device (feeder) 20, a pretreatment device 40, a processing device 30, and the like. The hoop materials 10a and 10b shown in FIG. 7 are manufactured in the preparatory step, and are arranged (set) at positions separated from the processing apparatus 30 by a predetermined distance. In the manufacturing apparatus 100, the line to be pretreated and the line to be bent are the same line.

Of the two hoop materials 10a and 10b, the grain-oriented electrical steel sheet 8A is supplied from the hoop member 10a arranged above, and the grain-oriented electrical steel sheet 8B is supplied from the hoop material 10b arranged below.

The supply control device 20 is provided between the hoop materials 10a and 10b and the processing device 30, and is a strip-shaped grain-oriented electrical steel sheet (in this example, grain-oriented electrical steel sheet 8A and grain-oriented electrical steel sheet 8B). It is intermittently conveyed toward the processing apparatus 30 side along the longitudinal direction of. It can be said that the supply control device 20 controls the supply of the grain-oriented electrical steel sheet to the processing device 30 side. As shown in FIG. 7, the direction from the hoop materials 10a and 10b to the processing apparatus 30 side is defined as the transport direction X. The supply control device 20 sends out a grain-oriented electrical steel sheet having a predetermined length in a predetermined time in the direction of the transport direction X. Here, the predetermined length of the grain-oriented electrical steel sheet delivered by the supply control device 20 per predetermined time is defined as the delivery amount (supply amount).
In the supply control device 20, the feeding amount of the grain-oriented electrical steel sheet 8A, which is located on the outside in the stacking direction of the bent body (the stacking direction of the second laminate), is that of the grain-oriented electrical steel sheet 8B located on the inside. It is preferable to control the feed amount to be larger than the feed amount. The laminating direction of the bent body is a direction from the central portion (inside) of the bent body 1 to the outside when the substantially rectangular annular bent body 1 is laminated toward the outside, and has a substantially U-shape. When the bent body 1 is laminated toward the outside, the direction is from the concave side (inside) of the bent body 1 to the outside. Further, when the substantially L-shaped bending bodies 1 are laminated toward the outside, the direction is from the inside of the L-shape to the outside of the L-shape in the bending work body 1.

Temporarily, the feeding amount of the grain-oriented electrical steel sheet 8A (hereinafter, also simply referred to as the outer steel sheet 8A) is not made larger than the feeding amount of the grain-oriented electrical steel sheet 8B (hereinafter, also simply referred to as the inner steel sheet 8B) located inside. When both are set to the same feed amount, there arises a problem that the ends of the outer steel plate 8A and the inner steel plate 8B are not aligned in the feed direction when the bent body 1 is used. That is, the length of the outer steel plate 8A is shorter than that of the inner steel plate 8B. In other words, the end portion of the inner steel plate 8B is in a state of protruding from the end portion of the outer steel plate 8A. This is because the bending radius of the outer steel plate 8A is larger than the bending radius of the inner steel plate 8B in the bending process (the extension distance is longer on the outer peripheral side, and the extension distance of the outer steel plate 8A is larger than the extension distance of the inner steel plate 8B). It is caused by the shortage of the outer steel plate 8A. The "extension distance" is the length in the longitudinal direction of the steel sheet for the laminated steel sheets having different steel sheet laminating positions in the iron core. The steel plate located on the outer surface side of the iron core has a geometrically longer circumference (extension distance) (larger diameter). The geometrical peripheral length increases as the steel plate is located on the outer side, but by increasing the amount of feeding of the outer steel plate by the amount corresponding to the increase in the peripheral length (increasing the length of the bent portion). , It is possible to suppress the occurrence of unevenness at the edges as described above.

Here, it is assumed that two steel plates having a thickness of t [mm] are stacked and bent at a bending angle of φ [°] by a mold having a radius of curvature r [mm]. At this time, the extension distance on the inner surface side of the bent portion of the inner steel plate 8B is 2πr × φ / 360. On the other hand, the extension distance of the bent portion of the outer steel plate 8A on the inner surface side is 2π (r + t) × φ / 360. Therefore, when bending the inner steel plate 8B and the outer steel plate 8A in an overlapping state to form one bent portion, in order to align the ends of the inner steel plate 8B and the outer steel plate 8A, the outer steel plate 8A is placed inside. It is necessary to make it longer than the steel plate 8B by a predetermined length (2πt × φ / 360). This predetermined length is calculated based on the increment of the length (perimeter) of the bent portion of the laminated steel sheet forming the iron core. It should be noted that it is not calculated based on the increment of the total circumference of the laminated steel sheet forming the iron core, but is an amount irrelevant to the length of the flat surface portion (flat surface portion 4 in FIG. 2). .. This predetermined length is determined as an absolute value by the steel plate plate thickness t and the bending angle φ. Alternatively, it is also possible to use the extension distance (2πr × φ / 360) on the inner surface side of the bent portion of the inner steel plate 8B as a “reference” and express it as a ratio (relative value) to it. That is, (2πt × φ / 360) / (2πr × φ / 360) = t / r, and can be expressed as a ratio of the steel plate plate thickness t and the radius of curvature r.
In the present invention, the extension distance of the inner steel plate 8B (inner steel plate) of the extension distance of the outer steel plate 8A (the first length of the bent portion of the outer steel plate 8A) determined based on this increment, that is, the geometric shape. The increment with respect to the second length of the bent portion of 8B) is called "increment determined based on geometric shape" (second increment) and is defined by using the ratio. In the above, the "increment determined based on the geometric shape" has been described for the case where two steel plates are stacked and bent, but the generalized "geometry" including the case where three or more steel plates are stacked and bent. The formula for obtaining the "increment determined based on the geometrical shape" is shown below. That is, the "increment determined based on the geometric shape" of the nth steel sheet (n is 2 or more) counted from the inside is obtained by the following equation.
t × (n-1) / r

Here, regarding the feed amount of the steel plate controlled by the supply control device 20, the increment of the feed amount of the outer steel plate 8A (first feed amount) with respect to the feed amount (second feed amount) of the inner steel plate 8B is "increment of the feed amount". (First increment). This first increment is an increment per bent portion. If the feed amount at the time of processing is not appropriate, the ends of the bent body will not be aligned as described above, and when assembled as an iron core, a gap will be created in the joint portion and the iron loss characteristics will deteriorate. Furthermore, not only such a geometrical adverse effect, but also the influence of the coefficient of friction between the stacked steel plates, an inadvertent force acts during bending, and the magnetic characteristics of the bent body itself, and by extension, it is assembled. Deteriorates the magnetic properties of the iron core.
In this embodiment, in order to improve the joining of the ends and avoid the action of inadvertent force during machining, "increase in the amount of feed" and "increase determined based on the geometric shape" ( The ratio to the second increment), that is, the "increase in feed amount" / "increment determined based on the geometric shape" (value obtained by dividing the first increment by the second increment) is 1. It is preferably 70 or less. That is, it is preferable that the supply control device 20 controls the feed amount of the steel sheet so that the value obtained by dividing the first increment by the second increment is 1.70 or less. If the value obtained by dividing the first increment by the second increment exceeds 1.70, the amount of feed of the outer steel sheet 8A becomes excessive, which promotes unevenness of the edges and careless force generation during bending. It ends up. Although the lower limit is not particularly limited, if this value is less than 0.30, the effect of correcting the difference in the geometrical extension distance between the outer steel plate 8A and the inner steel plate 8B becomes small. Therefore, the value obtained by dividing the first increment by the second increment is preferably 0.60 to 1.40, and the closer it is to 1.00, the more preferable. The case where the value obtained by dividing the first increment by the second increment is 0 is the case where the first increment is 0, in other words, the feed amount of the inner steel plate 8B and the feed amount of the outer steel plate 8A. Is the same.
Further, when a plurality of bending portions are provided in one bending body, the value obtained by dividing the first increment by the second increment is the sum of the first increments (the first increment is multiplied by the number of bending portions). It may be a value obtained by dividing the value) by the sum of the second increments (the value obtained by multiplying the second increment by the number of bending portions).
When three or more steel plates are stacked and bent, the above conditions (first increment / second increment ≤ 1.70) are satisfied for at least one of each steel plate (excluding the innermost steel plate). If so, it is possible to obtain the effect of the invention.

Although FIG. 7 shows a supply control device 20 and a processing device 30 separately provided, the supply control device 20 may be integrally configured with the processing device 30.

The pretreatment device 40 is provided between the supply control device 20 and the processing device 30, and pretreats the grain-oriented electrical steel sheet 8A and the grain-oriented electrical steel sheet 8B. As a result, the inter-story friction coefficient between the grain-oriented electrical steel sheet 8A and the grain-oriented electrical steel sheet 8B is controlled. The pretreatment device 40 may be provided separately from the processing device 30, or may be provided integrally with the processing device 30.

The processing device 30 includes a roll member. The processing apparatus 30 sandwiches the grain-oriented electrical steel sheet 8A and the grain-oriented electrical steel sheet 8B from above and below with roll members, and puts them in a stacked state (first laminated state). Then, the directional electromagnetic steel sheets 8A and 8B in the overlapped state are bent to form a bent body.

FIG. 8 is a diagram schematically showing an example of a bending body 1 manufactured by the processing apparatus 30. In the bent body 1, the flat surface portion 4 and the corner portion 3 are alternately continuous, and each corner portion 3 is provided with at least one bent portion 5. The bent body 1 shown in FIG. 8A has a substantially rectangular annular shape in side view, has four corner portions 3, and each corner portion 3 is provided with two bent portions 5. The bent body 1 shown in FIG. 8B has a substantially U-shaped side view, has two corner portions 3, and each corner portion 3 is provided with two bent portions 5. ..

Here, an example of the bending method will be described. FIG. 9 is a schematic view showing an example of a bending method. As shown in FIG. 9A, the processing apparatus 30 includes a bending die 31 for performing bending. The bending die 31 includes a die (lower die) 31b and a punch (upper die) 31a for press working. Further, as shown in FIG. 9B, the processing apparatus 30 according to the present embodiment presses (sandwiches) the directional electromagnetic steel sheets 8A and 8B in an overlapped state when bending. I have. In FIG. 9B, the pressing die 32 is provided on the front side (steel plate supply side) of the bending die 31, but the pressing die 32 is located on the rear side (steel sheet feeding side) of the bending die 31. It may be provided.

Hereinafter, in the transport direction X, the front side in the traveling direction of the grain-oriented electrical steel sheet is referred to as the front side (tip side) of the grain-oriented electrical steel sheet, and the side opposite to the traveling direction is the rear side (rear end side) of the grain-oriented electrical steel sheet. That is.

The grain-oriented electrical steel sheets 8A and 8B are transported along the transport direction X and stop at a predetermined position. Since the outer steel plate 8A is sent out more than the inner steel plate 8B by the supply control device 20, the tip of the outer steel plate 8A is in a state of protruding from the tip of the inner steel plate 8B as shown in FIG. 9B. Further, the rear side of the outer steel plate 8A and the inner steel plate 8B is sandwiched and fixed by the pressing die 32. Then, bending is performed as shown in FIG. 9 (c).

Since the outer steel plate 8A shifts relatively to the rear side (the side facing away from the die 31b side in the vertical direction) with respect to the inner steel plate 8B due to the bending process, the protrusion amount of the outer steel plate 8A on the tip side becomes zero and bending occurs. When the processing is completed, the tips of the outer steel plate 8A and the inner steel plate 8B are aligned.

When the rear side (rear end side) of the outer steel plate 8A and the inner steel plate 8B is fixed in this way, the presser die 32 is moved along with the bending process (bending process) as in the case of fixing the front side described later. Since it is not necessary, the device can be easily configured and controlled.

Further, the processing apparatus 30 includes a cutting portion (not shown). After bending the outer steel plate 8A and the inner steel plate 8B, the processing apparatus 30 cuts the outer steel plate 8A and the inner steel plate 8B to a predetermined length on the rear side of the bent portion. As a result, the rear end sides of the outer steel plate 8A and the inner steel plate 8B are also aligned. As a result, the substantially L-shaped bending body 1 in which one bending portion 5 is formed is sent out from the processing device 30.

In the present embodiment, the rear side of the outer steel plate 8A and the inner steel plate 8B is fixed by the pressing die 32 so that they do not shift, but the rear side is a coil (hoop material) without being fixed by the pressing die 32. It may be fixed by 10a and the hoop material 10b) and controlled so that the outer steel plate 8A and the inner steel plate 8B do not shift.

In the bending process, the outer steel plate 8A and the inner steel plate 8B are pressed by a predetermined force (pressure) preset by the punch 31a. As a result, the bent portion 5 having a bending angle φ is formed on the outer steel plate 8A and the inner steel plate 8B. There is no particular limitation on the method of setting the radius of curvature r of the bent portion 5 to a range of more than 1 mm and 3 mm or less, but usually, by changing the distance between the die 31b and the punch 31a or the shape of the die 31b and the punch 31a, The radius of curvature r of the bent portion 5 can be adjusted to the above-mentioned specific range. The radius of curvature r at the bent portion 5 of the bending body 1 laminated in the plate thickness direction is set to match, but the radius of curvature of the processed steel sheet has an error depending on the roughness and shape of the surface layer of the steel sheet. May occur. When an error occurs, the error is preferably 0.1 mm or less. The error here refers to an error when the outer steel plates 8A are compared with each other and an error when the inner steel plates 8B are compared with each other in the bending body 1. Since the inner steel plate 8B is bent with a curvature r and the outer steel plate 8A is bent with a curvature (r + t), there is a difference in plate thickness between the two.

Here, another example of bending will be described. First, the tip ends of the outer steel plate 8A and the inner steel plate 8B are aligned by abutting or the like. Next, the tip ends of the outer steel plate 8A and the inner steel plate 8B are sandwiched and fixed by the pressing die 32 that suppresses the displacement. Then, bending is performed. In this case, in the bending process, it is necessary to appropriately move the pressing die 32 in synchronization with the bending die 31 (punch 31a). When the presser die 32 is moved, the outer steel plate 8A is automatically dragged along with the bending process, and the feeding amount of the outer steel plate 8A increases.

After the outer steel plate 8A and the inner steel plate 8B are bent, they are cut to a predetermined length on the rear side of the bent portion. As a result, the rear end sides of the outer steel plate 8A and the inner steel plate 8B are also aligned.

In this example, after the tip ends of the outer steel plate 8A and the inner steel plate 8B are aligned, the tip ends of the outer steel plate 8A and the inner steel plate 8B may not be sandwiched by the pressing die 32. In that case, at the same time as the bending process, that is, as the bending process progresses, the extension distance of the outer steel plate 8A becomes longer, and at the same time, the supply control device 20 sends out only the outer steel plate 8A. That is, the supply control device 20 increases the feed amount of the outer steel plate 8A in accordance with the increase in the length of the bent portion so that the tip side does not shift due to the longer extension distance of the outer steel plate 8A.

(Bending multiple times)
Next, an example in which the outer steel plate 8A and the inner steel plate 8B are bent a plurality of times and then cut will be described. First, in the first bending process (first step), the tip of the outer steel plate 8A is projected from the tip of the inner steel plate 8B, and the rear side is fixed by the pressing die 32, and the bending process is performed. Then, the bent portion 5 is formed at one place, and the tips of the outer steel plate 8A and the inner steel plate 8B are aligned. When the bent portion 5 is formed at one position in this way, the front side (tip side) is in a state of being restrained so that the steel plate does not shift. That is, the state is substantially equivalent to that the front side of the grain-oriented electrical steel sheets 8A and 8B is fixed. It can be said that the front side is naturally restrained by the bent portion 5 (bent portion).

In the second and subsequent bending processes, the rear side of the outer steel plate 8A and the inner steel plate 8B is bent without being pressed by the pressing die 32, and the supply amount of the steel plate from the rear side is adjusted. That is, while bending is performed, the outer steel plate 8A is supplied in a larger amount than the inner steel plate 8B in accordance with the increase in the length of the bent portion.

The outer steel plate 8A and the inner steel plate 8B are bent a predetermined number of times and then have a predetermined length (for example, about half the length of the wound iron core) on the rear side of the bent portion. Will be disconnected. As a result, the rear end sides of the outer steel plate 8A and the inner steel plate 8B are also aligned. Then, the bending body 1 is sent out from the processing device 30.

(Bending after cutting)
In the present embodiment, the outer steel plate 8A and the inner steel plate 8B are cut after being bent, but the outer steel plate 8A and the inner steel plate 8B may be cut first and then bent. First, the outer steel plate 8A and the inner steel plate 8B are cut to a predetermined length on the front side of the bending die 31. At this time, the cut-out length of the outer steel plate 8A is set to be longer than that of the inner steel plate 8B by the length of the extension distance in the bending process. The processing apparatus 30 includes, for example, a first cutting portion for cutting the outer steel plate 8A and a second cutting portion for cutting the inner steel plate 8B.

Next, the processing apparatus 30 superimposes the outer steel plate 8A and the inner steel plate 8B. The processing apparatus 30 superimposes the outer steel plate 8A on the upper side and the inner steel plate 8B on the lower side, for example. At this time, the rear end of the outer steel plate 8A and the rear end of the inner steel plate 8B are aligned and the rear side is fixed, and the tip of the outer steel plate 8A is projected forward from the inner steel plate 8B. There is the first way of stacking. As the first stacking method, for example, when one bending process is performed by the bending die 31, the outer steel plate 8A moves relative to the inner steel plate 8B with the bending process, and the tips are aligned after the bending process. Will be.

Further, it may be a second stacking method in which the tip of the outer steel plate 8A and the tip of the inner steel plate 8B are aligned and the front side is fixed, and the rear end of the outer steel plate 8A is projected rearward. In the second stacking method, as described above, it is necessary to appropriately move the pressing die 32 in synchronization with the bending die 31 (punch 31a). As the second stacking method, for example, when one bending process is performed by the bending die 31, the outer steel plate 8A moves relative to the inner steel plate 8B with the bending process, and the rear ends are aligned after the bending process. Will be.

Further, for example, the outer steel plate 8A is on the bottom and the inner steel plate 8B is on the top, and the protrusion length (protrusion amount) of the outer steel plate 8A with respect to the inner steel plate 8B is substantially uniform (1/2 each) on the front end side and the rear end side. It may be a third method of stacking in such a stacked state. The third stacking method does not require pressing (fixing) on the front side or the rear side. For example, when a die having a V-groove and a punch having a V-shaped tip are used to pressurize the central portion of the stacked steel plates from above to downward with a punch, the bent portion becomes the center. , The outer steel plate 8A is displaced equally in the front-rear direction (inside) with respect to the inner steel plate 8B. As a result, after bending, the tip of the outer steel plate 8A and the tip of the inner steel plate 8B are aligned, and the rear end of the outer steel plate 8A and the rear end of the inner steel plate 8B are aligned.

Further, the grain-oriented electrical steel sheets in a state of being cut to a predetermined length and stacked in advance may be bent a plurality of times. For example, the outer steel plate 8A is on the top and the inner steel plate 8B is on the bottom, and the outer steel plate 8A is made to protrude more than the inner steel plate 8B on the front end side and the rear end side. Here, the amount of protrusion of the tip of the outer steel plate 8A with respect to the tip of the inner steel plate 8B is S, and the amount of protrusion of the rear end of the outer steel plate 8A with respect to the rear end of the inner steel plate 8B is T. In the first bending process, the bending process is performed with the rear side pressed by the pressing die 32. After the first bending process, the protrusion amount S becomes zero and the tips are aligned, and the steel sheet is restrained so as not to shift on the tip side. Then, in the second and subsequent bending processes, the bending process is performed without pressing the rear side. Then, when the bending process is performed a predetermined number of times, the protrusion amount T becomes zero and the rear ends are aligned.

(Plate presser pressure during bending)
As described above, at the time of bending, the pressing die 32 may press the front side or the rear side of the overlapped steel plates with a predetermined force (predetermined pressure). This predetermined force is called the plate pressing pressure. The presser die 32 applies a predetermined plate presser pressure from the plate thickness direction of the steel plate. In the present embodiment, the predetermined plate pressing pressure is 0.10 MPa or more and 1.0 MPa or less. By pressing the outer steel plate 8A and the inner steel plate 8B, that is, by applying the plate pressing pressure to the outer steel plate 8A and the inner steel plate 8B, the difference in the extension length (extension distance) between the inside and the outside during bending is generated. It is possible to avoid unintended misalignment of the accompanying steel sheet and align the front end or the rear end.

(4) Laminating Step In the laminating step, a plurality of bent bodies 1 are laminated in the plate thickness direction (second laminating). That is, the bent body 1 is laminated by aligning the corner portions 3 with each other in the plate thickness direction to form a laminated body. When the bent bodies 1 having a substantially rectangular annular shape in the side view are laminated in the plate thickness direction, a wound iron core 10 having a substantially rectangular annular shape in the side view can be obtained. Further, when the bent bodies 1 having a substantially U-shaped side view are laminated in the plate thickness direction, an iron core 10 having a substantially U-shaped side view can be obtained. By using two iron cores 10 having a substantially U-shaped side view, it is possible to obtain a wound iron core 10 having a substantially rectangular annular shape in the side view. Further, when the bending bodies 1 having a substantially L-shaped side view are laminated in the plate thickness direction, an iron core 10 having a substantially L-shaped side view can be obtained. By using four iron cores 10 having a substantially L-shaped side view, it is possible to obtain a wound iron core 10 having a substantially rectangular annular shape in the side view.

(Bending conditions)
When the inter-story friction coefficient of a plurality of laminated grain-oriented electrical steel sheets exceeds 0.60, the deformation of the grain-oriented electrical steel sheets (outer steel sheet 8A in this example) located on the outside at the bent portion 5 is restrained and the laminated surface side is restrained. A strong shear stress acts on the surface layer of the steel sheet of the steel sheet, and twins are remarkably generated in the bent portion 5. Twins are formed in streaks from the surface of the steel sheet toward the inside. When such remarkable twinning occurs, the characteristics of the iron core deteriorate. Specifically, the core iron loss of the iron core increases.

Further, if the interlaminar friction coefficient of the directional electromagnetic steel sheet in which a plurality of sheets are stacked is less than 0.05, the steel sheet is displaced during bending, and the bending accuracy is lowered. As the core shape deteriorates due to this decrease in bending accuracy, the characteristics of the iron core deteriorate. Specifically, the core iron loss of the iron core increases.

Further, it is preferable that the interlaminar friction coefficient μ and the tensile strength TS (MPa) of the steel sheet satisfy the following equations.
Interlayer friction coefficient μ × tensile strength TS ≦ 300

Roughly speaking, the inter-story friction coefficient μ is the friction between the flat surfaces that greatly contributes to the relative and macroscopic deviation between the outer steel plate and the inner steel sheet in the bending process, and the outer and inner steel plates in the bent portion 5 in the bending process. It acts as friction at the bent portion, which acts on the surface layer of the contact surface and contributes to the shear stress that causes the generation of deformed twin crystals.

The above formula is particularly related to the latter, and the load that the outer steel plate is pressed against the inner steel plate at the bending part during bending deformation is proportional to the deformation resistance force of the steel plate, that is, the tensile strength TS, and the shear stress is the deformation resistance force. It is thought that it is related to acting with a magnitude proportional to the product of the friction coefficients.

When the value of μ × TS exceeds 300, the occurrence of deformed twins may become remarkable in the contact surface surface layer of the laminated steel sheets. The value of μ × TS (value obtained by multiplying the interlaminar friction coefficient and the tensile strength of the grain-oriented electrical steel sheet) is preferably 300 or less, more preferably 250 or less, still more preferably 200 or less. The smaller the value of μ × TS, the more the generation of deformed twins is suppressed. However, if μ is excessively small, as described above, the bending accuracy is significantly reduced.

In the method for manufacturing an iron core according to the present embodiment, the thickness of the grain-oriented electrical steel sheets is 0.23 mm or less, and the inter-story friction coefficient of the grain-oriented electrical steel sheets 8A and 8B in a superposed state is 0.60 or less. It is controlled to be. Therefore, (1) the outer grain-oriented electrical steel sheet 8A at the bent portion 5 does not undergo tensile deformation, and the generation of twins at the bent portion 5 can be suppressed. As a result, it is possible to suppress an increase in core iron loss of the iron core. (2) Further, good bending accuracy can be realized without the steel sheet being displaced during bending. As a result, it is possible to suppress an increase in core iron loss of the iron core. (3) Further, in order to form a bent body by stacking a plurality of grain-oriented electrical steel sheets and bending the laminated grain-oriented electrical steel sheets, the grain-oriented electrical steel sheets are bent one by one. Productivity can be improved as compared with the case of molding a bent body.

(Modification example)
In the present embodiment, in the forming step, the processing apparatus 30 performs the first laminating of the grain-oriented electrical steel sheets, but in the preparatory step, the pretreatment (control of the inter-story friction coefficient) and the first laminating are performed. It may be wound around a coil. That is, in the preparation step, for example, a two-ply coil (a two-ply coil material) may be manufactured. When a double-layer coil is manufactured and bending is performed while unwinding the double-layer coil in the molding process, the steel plate laminated on the outer peripheral side at the time of the coil is set to the outer peripheral side even in the bent body. If the bending process is applied to the bent body, it is possible to reduce the unevenness at the end portion of the bent body. When the double-layered coil is used as described above, there is an advantage that the number of coils to be set can be reduced and that the supply control device 20 is not required, so that the device can be simplified. However, from the viewpoint of aligning the ends of the bent body, two coils (hoop materials 10a and 10b) are provided as in the present embodiment, and the supply control device 20 controls the feeding amount of each grain-oriented electrical steel sheet. Is preferable.

The present invention is not limited to the above embodiment. The above-described embodiment is an example, and any one having substantially the same structure as the technical idea described in the claims of the present invention and having the same effect and effect is the present invention. Is included in the technical scope of.

Hereinafter, the technical contents of the present invention will be further described with reference to examples of the present invention. The conditions in the examples shown below are examples of conditions adopted for confirming the feasibility and effect of the present invention, and the present invention is not limited to these conditions. Further, the present invention can adopt various conditions as long as the gist of the present invention is not deviated and the object of the present invention is achieved.

FIG. 10 is a diagram showing the size of the wound iron core manufactured in the example (comparative example).
A wound iron core is used in which two bent portions 5 are formed in one corner portion 3 and the side view is an octagonal substantially rectangular annular shape. Each steel plate of the wound steel core is a steel plate a, a steel plate b, a steel plate c, and a steel plate d from the inside to the outside. Although not shown, the wound core shown in FIG. 10 is divided into two at substantially the center of the flat surface portion constituting the inner surface side flat portion distance L1, and two bends having a substantially U-shape. It has a structure in which workpieces are combined.
The distance L1 between the flat portions on the inner surface side is 173 mm.
The distance L2 between the flat portions on the inner surface side is 93 mm.
The laminated thickness L3 is 45 mm.
The laminated plate thickness width L4 is 160 mm.
The innermost flat portion distance L5 is 16 mm.
The bending angle φ is 45 °.

以下の表３は、実施例および比較例（参考例）の評価結果を示すものである。

Tables 1 and 2 below summarize the configurations and manufacturing conditions of Examples (Comparative Examples).
The grain-oriented electrical steel sheet conforms to JIS C 2553, and the chemical composition is Si: 2.8% to 3.5%, C: 0.001%, Mn: 0.007 to 0.010%, S <0. 002%, Al <0.004%, N <0.002%, P: 0 to 0.2%. The strength was adjusted mainly by the contents of Si and P. Further, the coefficient of friction was adjusted by controlling the surface roughness of the mother steel sheet by transfer on a rolling roll having an adjusted surface roughness and controlling the baking temperature and time of the insulating coating.
Sample No. For A0 to A19, the thickness of the grain-oriented electrical steel sheet was 0.23 mm. Sample No. For B0 to B6, the thickness of the grain-oriented electrical steel sheet was 0.18 mm. Sample No. For A0 and B0, one piece of grain-oriented electrical steel sheet was bent to produce a bent body, and the bent body was laminated so that the number of laminated pieces was 192 to obtain a wound iron core. Sample No. For A1 to A19, bending is performed in a state where two grain-oriented electrical steel sheets are stacked to produce a bent body, and the bent body is laminated so that the number of laminated sheets is 192 to obtain a wound iron core. rice field. Sample No. B1 to B6 are bent by stacking three grain-oriented electrical steel sheets to produce a bent body, and the bent bodies are laminated so that the number of laminated sheets is 192 to obtain a wound iron core. rice field.
The control of the delivery amount is a value obtained by dividing the "increase in the delivery amount (first increment)" by the "increment determined based on the geometric shape (second increment)". The case where the value obtained by dividing the first increment by the second increment is 0 is the case where the first increment is 0, in other words, the feed amount of the inner steel plate 8B and the feed amount of the outer steel plate 8A. If they match. Further, in the control of the feed amount in Table 2, two values are described in the upper row and the lower row, and the upper row is the value obtained by dividing the first increment for the third steel plate from the inside by the second increment. The lower row is a value obtained by dividing the first increment for the second steel plate from the inside by the second increment.

Table 3 below shows the evaluation results of Examples and Comparative Examples (Reference Examples).

<Evaluation>
(1) Bending accuracy (evaluation method)
With respect to the target bending angle of 45 °, the actual bending angle at any n points (n is, for example, 24) in the bending body constituting the wound core was measured, and the standard deviation was obtained and used as an evaluation index of machining accuracy. ..
(criterion)
Those having a standard deviation (variation) of 0.5 ° or less in the measurement results at n points (n is, for example, 24) were regarded as acceptable.
(2) Number of twins (evaluation method)
A sample was taken from the corner 3 of the bent body constituting the wound core, and the number of twins was measured by a known method.
(criterion)
Those with less than 5 twins were considered acceptable.
(3) Core iron loss (evaluation method)
The primary coil (30 turns) and the secondary coil (30 turns) are wound around the straight part excluding the four corners of the core, a sine wave voltage of 50 Hz is applied to the primary coil, and the effective value voltage U2 of the secondary voltage of the secondary coil is applied. Was obtained from the required value of the magnetic flux density by the following equation.
U2 = 4.44 x f x N2 x A x J
In the above equation, f: the excitation frequency is 50 Hz, N2: the number of secondary coil turns is 30 turns, A: the core cross-sectional area is 45 mm × 160 mm = 0.0072 m ² , and J: the peak value of the magnetic flux density is 1. Assuming 5T, U2 = 71.9V. The iron loss value was measured by connecting the current of the primary circuit and the voltage of the secondary circuit to a wattmeter.
(criterion)
Sample No. For A1 to A19, the iron loss value of A0 was standardized as 100, and those with 105 or less were regarded as acceptable. Sample No. For B1 to B6, the iron loss value of B0 was standardized as 100, and those having an iron loss value of 105 or less were set as an allowable range. When the iron loss value exceeds 100, the core iron loss is inferior to that of the core of the normal construction method in which bending is performed one by one, but in the present invention, the pass / fail judgment of the invention is made in consideration of productivity. To 105 is the allowable range. In other words, considering the merit of improving productivity by nearly + 100% by bending two or more sheets at the same time, deterioration of about 5% of the core iron loss is allowed, and the invention is judged to be acceptable.
(4) Productivity The method of manufacturing a bent product by bending one grain-oriented electrical steel sheet is low in productivity (NG), and a state in which multiple (two or more) grain-oriented electrical steel sheets are stacked. The method of manufacturing a bent product by bending it is highly productive (Good, Very Good).

[Sample No. A0 and sample No. B0]
In order to obtain one iron core, the number of times of bending is performed in the molding process, and the number of times of laminating (second laminating) the bent body is increased in the laminating step. Therefore, productivity is low.
[Sample No. A1 to A4]
By using a steel plate with an appropriately controlled inter-story friction coefficient in bending with two layers, the bending accuracy within the acceptable range, the number of twins, and the core iron loss are ensured, and high productivity is achieved. can. If the inter-story friction coefficient is optimal, the generation of twins is suppressed, and improvement in core iron loss can be expected as compared with the case of processing one sheet at a time.
[Sample No. A5]
It can be confirmed that the inter-story friction coefficient is not properly controlled and exceeds 0.60, and the result within the passing range cannot be obtained.
[Sample No. A6 to A8]
Sample No. Compared with A1 to A4, by controlling the delivery amount more optimally, in addition to improving the combination of the ends, the processing accuracy is improved and the generation of twins is suppressed, and the sample No. It is possible to secure even better core iron loss than A1 to A4.
[Sample No. A9]
It can be confirmed that the inter-story friction coefficient is not properly controlled and exceeds 0.60, and the result within the passing range cannot be obtained.
[Sample No. A10]
Sample No. Compared with A8, it can be confirmed that by controlling μ × TS more optimally, the processing accuracy is improved, the generation of twins is suppressed, and the core iron loss can be improved.
[Sample No. A11]
Sample No. Compared with A10, it can be confirmed that μ × TS is not optimal, that is, μ × TS exceeds 300, but the result within the passing range can be obtained.
[Sample No. A12-A19]
Sample No. While it can be confirmed that the results of A12 to A18 are within the acceptable range, the sample No. It can be confirmed that the result within the passing range cannot be obtained in A19. Sample No. From the evaluation results of A12 to A19, the optimum range for controlling the feed amount can be confirmed, and if the feed amount on the outside is insufficient, the effect (adverse effect) is small, and if the feed amount on the outside is excessive. It can be confirmed that the effect (adverse effect) is large.
[Sample No. B1 to B5]
Even in the bending process with three layers, by using a steel plate with an appropriately controlled coefficient of friction between layers, the bending processing accuracy within the acceptable range, the number of twins, and the core iron loss are ensured, and high productivity is achieved. realizable. If the inter-story friction coefficient is optimal, the generation of twins is suppressed, and improvement in core iron loss can be expected as compared with the case of processing one sheet at a time.
[Sample No. B6]
It can be confirmed that the inter-story friction coefficient is not properly controlled and exceeds 0.60, and the result within the passing range cannot be obtained.

1 Bending body 10-roll iron core (iron core)
30 Processing equipment (device that performs bending)

Claims (4)

It is a manufacturing method of the iron core.
A molding process in which a plurality of grain-oriented electrical steel sheets are laminated and the laminated electrical steel sheets are bent to form a bent body, and the bent body is placed in the plate thickness direction. Including the laminating process of laminating
The thickness of the grain-oriented electrical steel sheet is 0.23 mm or less.
A method for manufacturing an iron core, characterized in that the interlaminar friction coefficient at the time of the bending of the grain-oriented electrical steel sheets in a superposed state is controlled to be 0.60 or less. The grain-oriented electrical steel sheet located on the outside of the bent body is used as the outer steel sheet.
The grain-oriented electrical steel sheet located inside in the bent body is used as an inner steel sheet.
The amount of the outer steel sheet delivered to the device to be bent is defined as the first amount of delivery.
The amount of the inner steel sheet delivered to the device to be bent is defined as the second amount of delivery.
The increment of the first delivery amount with respect to the second delivery amount is defined as the first increment.
In the bent body, the length of the bent portion of the outer steel plate determined based on the geometric shape is defined as the first length.
In the bent body, the length of the bent portion of the inner steel plate determined based on the geometric shape is defined as the second length.
Assuming that the increment of the first length with respect to the second length is the second increment,
The method for manufacturing an iron core according to claim 1, wherein the value obtained by dividing the first increment by the second increment is controlled to be 1.70 or less. It is an iron core manufacturing device equipped with a processing device for forming a bent body by bending a grain-oriented electrical steel sheet.
The processing apparatus puts a plurality of the grain-oriented electrical steel sheets in a laminated state, and bends the grain-oriented electrical steel sheets in the stacked state.
The thickness of the grain-oriented electrical steel sheet is 0.23 mm or less.
Immediately before the bending process, an iron core manufacturing apparatus characterized in that the interlayer friction coefficient of the laminated electrical steel sheets is 0.60 or less. A supply control device for controlling the supply of a plurality of the grain-oriented electrical steel sheets to the processing device is provided.
The grain-oriented electrical steel sheet located on the outside of the bent body is used as the outer steel sheet.
The grain-oriented electrical steel sheet located inside in the bent body is used as an inner steel sheet.
The amount of the outer steel sheet delivered to the device to be bent is defined as the first amount of delivery.
The amount of the inner steel sheet delivered to the device to be bent is defined as the second amount of delivery.
The increment of the first delivery amount with respect to the second delivery amount is defined as the first increment.
In the bent body, the length of the bent portion of the outer steel plate determined based on the geometric shape is defined as the first length.
In the bent body, the length of the bent portion of the inner steel plate determined based on the geometric shape is defined as the second length.
Assuming that the increment of the first length with respect to the second length is the second increment,
The iron core manufacturing apparatus according to claim 3, wherein the supply control device is controlled so that the value obtained by dividing the first increment by the second increment is 1.70 or less.

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