RU2847308C2 - Shihted core - Google Patents

Abstract

FIELD: compound core.

SUBSTANCE: the invention relates to a laminated core and can be used as a magnetic circuit in an electric machine. The laminated core comprises a plurality of electrical steel sheets laminated on top of each other and an insulating coating which is provided between the electrical steel sheets adjacent to each other in the direction of lamination and bonds the electrical steel sheets to each other. The insulating coating has a hardness of 200-300 MPa.

EFFECT: ensuring both high adhesive strength and excellent magnetic characteristics by controlling the hardness of the insulating coating.

4 cl, 1 dwg, 4 tbl

Description

Field of technology to which the invention relates

[0001] The present invention relates to a laminated core.

Priority is claimed from Japanese Patent Application No. 2022-063474, filed on April 6, 2022, the contents of which are incorporated herein by reference.

Prior art

[0002] As a core (magnetic circuit) used in a rotating electric machine, a laminated core is known, in which a plurality of electrical steel sheets are laminated and connected. As a method for connecting electrical steel sheets, mutual interlocking and welding are known. However, in the case of mutual interlocking and welding, the magnetic properties of the electrical steel sheet may deteriorate due to mechanical and thermal stress during processing, as well as interlayer short circuit, and the performance of the laminated core may deteriorate. Therefore, in recent years, an adhesive connection method has attracted attention as a connection method different from mutual interlocking and welding. Since the steel sheet is not processed in the same way as in mutual interlocking, the deterioration of the magnetic properties is suppressed by the lamination and connection of the laminated core (the glued and laminated core).

[0003] As an adhesive for bonding electrical steel sheets together, for example, as shown in Patent Document 1, an epoxy resin having a small volume change and excellent heat resistance, oil resistance, and chemical resistance is known. On the other hand, since it is necessary to set the temperature relatively high to cure the epoxy resin, mechanical stress is applied to the steel sheet during bonding, and there is a risk that magnetic loss will deteriorate. Therefore, for example, Patent Documents 2 to 7 propose using a urethane resin as an adhesive, which can bond at a lower temperature than the epoxy resin.

Bibliographic list

Patent documents

[0004] Patent Document 1: Unexamined Japanese Patent Application, First Publication No. 2022-000888

Patent Document 2: Unexamined Japanese Patent Application, First Publication No. 2017-179233

Patent Document 3: Unexamined Japanese Patent Application, First Publication No. 2017-186542

Patent Document 4: Unexamined Japanese Patent Application, First Publication No. H06-182929

Patent Document 5: Unexamined Japanese Patent Application, First Publication No. H06-271834

Patent Document 6: Unexamined Japanese Patent Application, First Publication No. H07-268051

Patent Document 7: Unexamined Japanese Patent Application, First Publication No. 2002-293864

The essence of the invention

Problems solved by the invention

[0005] However, in the case of joining using an adhesive as described above, it is generally known that a resin having a higher adhesive strength is harder, and the steel sheet is subjected to deformation along with shrinkage during curing, resulting in deterioration of the magnetic properties. That is, it was considered that the adhesive strength and magnetic properties are in conflict with each other. Therefore, traditionally, it was difficult to achieve both high adhesive strength and excellent magnetic properties in a bonded and laminated core. Therefore, an object of the present invention is to provide a laminated core (bonded and laminated core) having high adhesive strength and excellent magnetic properties.

Solution to the problem

[0006] The present inventors studied a method for achieving both high adhesive strength and excellent magnetic properties in a laminated core formed by laminating a plurality of electrical steel sheets with an insulating coating having adhesive ability. As a result, the present inventors found that it is possible to achieve both high adhesive strength and excellent magnetic properties by controlling the hardness of the order of μm measured by a nanoindenter in the insulating coating. In addition, it was found that by setting the weight average molecular weight of the sol component of the insulating coating within a predetermined range, the balance between suppressing the deterioration of magnetic properties and improving the adhesion strength is further improved.

[0007] The present invention was created on the basis of the above-described discovered facts. The essence of the present invention is as follows.

[1] A laminated core according to an embodiment of the present invention includes a plurality of electrical steel sheets laminated to each other; and an insulating coating that is provided between the electrical steel sheets adjacent to each other in the laminating direction and adheres the electrical steel sheets to each other, wherein the insulating coating has a hardness of 200~300 MPa.

[2] In the laminated core according to point [1], the average molecular weight of the sol component of the insulating coating may be 10,000-100,000.

[3] In the laminated core according to [1] or [2], in a plurality of sheets of electrical steel, when the area ratio of grains in the {hkl}<uvw> orientation relative to the full field of view, when the surface parallel to the rolled surface, having a depth of 1/2 the thickness of the sheet from the surface, is measured by the SEM-EBSD method, is expressed as Ahkl-uvw, A411-011 may be 15.0% or more.

[4] In the laminated core according to item [3], the electrical steel sheet may contain: 0.0100% or less C, 1.50%-4.00% Si, 0.0001%-1.0000% sol. Al, 0.0100% or less S, 0.0100% or less N, 2.50%-5.00% in total of one or more selected from the group consisting of Mn, Ni and Cu, 0.000%-1.000% Co, 0.000%-0.400% Sn, 0.000%-0.400% Sb, 0.000%-0.400% P and 0.0000%-0.0100% in total of one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd, in units of % by weight of the chemical composition, wherein when the Mn content is designated as [Mn], the Ni content is designated as [Ni], the Cu content is designated as [Cu], the Si content is designated as [Si], the sol. Al content is designated as [sol. Al], and the P content is denoted as [P] in units of % by mass, the following formula (1) is satisfied, and the rest is Fe and impurities.

(2×[Mn] + 2.5×[Ni] + [Cu]) - ([Si] + 2×[sol. Al] + 4×[P]) ≥ 1.50% (1)

Effects of invention

[0008] According to the above aspect of the present invention, it is possible to provide a laminated core having high adhesive strength and excellent magnetic characteristics.

Brief description of the drawings

[0009] Fig. 1 is a diagram illustrating an example of a side view of a laminated core according to the present embodiment.

Embodiments of the invention

[0010] As illustrated in Fig. 1, a laminated core according to an embodiment of the present invention (the laminated core according to the present embodiment) includes: a plurality of electrical steel sheets 21 laminated on each other; and an insulating coating 22 that is provided between the electrical steel sheets 21 and 21 adjacent to each other in the laminating direction and bonds the electrical steel sheets 21 and 21 to each other, wherein the insulating coating has a hardness of 200-300 MPa.

Each of the above is described below.

<Insulation coating>

[Hardness]

[0011] The insulating coating 22 included in the laminated core 1 according to the present embodiment provides insulating properties and bonds the electrical steel sheets 21 and 21 adjacent to each other in the lamination direction by adhesion. The insulating coating is an insulating coating having the adhesive ability of a heat-curable adhesive during formation on the surface of the electrical steel sheet (since it does not have an insulating coating, it may be called a "base steel sheet"). The insulating coating having the adhesive ability is formed on the base steel sheet, and a plurality of electrical steel sheets with the insulating coating are laminated and bonded by heating and pressure, whereby the electrical steel sheets are bonded by adhesion. In general, a resin with higher adhesive strength is harder, and the steel sheet is subjected to deformation and shrinkage during curing, resulting in deterioration of the magnetic properties. Therefore, it is difficult to achieve both high adhesive strength and excellent magnetic properties at a high level. In the laminated core 1 according to the present embodiment, it is possible to increase the adhesion strength while suppressing the deterioration of the magnetic properties by controlling the hardness of the insulating coating of 22 μm, which is measured with a nanoindenter. Specifically, the hardness of the insulating coating is set to 200-300 MPa. When the hardness of the insulating coating is less than 200 MPa, sufficient adhesion strength (for example, 10.0 MPa or more) cannot be obtained. On the other hand, when the hardness of the insulating coating exceeds 300 MPa, deterioration of the magnetic properties becomes noticeable.

[0012] The hardness of the insulating coating can be determined as follows. For example, a sample is taken by cutting out several sheets peeled off from a laminated core using a precision cutter so that the cross-section of the insulating coating can be observed. The sample for measurement is prepared by performing CP processing (ion milling processing) on the central section in the thickness direction of the section of the insulating coating of the sample glued by heat and pressure. The hardness is measured at room temperature (25°C) under a load of 250 μN using a TRIBOINDENTER manufactured by HYSITRON or an equivalent nanoindenter. Five points are measured, and the average value is taken as the hardness of the insulating coating.

[Average molecular weight of the sol component]

[0013] In the insulating coating 22 constituting the laminated core 1 according to the present embodiment, the weight average molecular weight (Mw) of the sol component of the insulating coating is preferably 10,000 to 100,000. When the weight average molecular weight of the sol component is 10,000 or more, a resin structure having rigidity can be obtained, and sufficient adhesive strength can be obtained. When the weight average molecular weight of the sol component is 100,000 or less, the resin is not excessively hard, and deterioration of magnetic characteristics can be suppressed. That is, when the weight average molecular weight of the sol component is in a predetermined range, the balance between suppressing deterioration of magnetic characteristics and improving the adhesive strength is further improved. The average molecular weight of the sol component of the insulating coating is preferably 20,000-70,000, and even more preferably 30,000-50,000. The average molecular weight of the sol component, rather than the average molecular weight of the entire insulating coating, is specified because the magnetic characteristics are affected by the average molecular weight of the non-cross-linked portion of the adhesive.

[0014] The weight average molecular weight of the sol component of the insulating coating can be measured using, for example, GPC (gel permeation chromatography, GPC), for example, a high-speed GPC system HLC-8320GPC manufactured by Toyo Soda Co., Ltd., for a measurement sample prepared by dipping a cured insulating coating (functioning as an adhesive), cut from several sheets peeled off from a laminated core using a precision cutter, into N,N-dimethylformamide containing 10 mmol of lithium bromide for 24 hours. The conditions are as follows.

Column: PLgel 5 μm Guard, PLgel 5 μm MIXED-Cx2 (Polymer Laboratories)

Mobile phase: N,N-dimethylformamide containing 10 mmol lithium bromide

Flow rate: 1.0 ml/min

Column temperature: 40°C

Data processing: EcoSEC-WorkStation

[0015] The insulating coating preferably contains 90% by mass or more of an acrylic resin which has a certain degree of rigidity after curing, can provide adhesive strength and has a low compressive stress on the steel sheet due to curing. Other components may include resin, inorganic salt and inorganic fine particles. Examples of the resin as another component include epoxy resin, urethane resin and phenolic resin. Examples of the inorganic salt include phosphate, chromate and borate. Examples of the inorganic fine particles include silicon dioxide, titanium oxide, magnesium oxide and zirconium hydroxide. The type of acrylic resin mainly constituting the insulating coating is not particularly limited.

[0016] In the laminated core according to the present embodiment, another coating having insulating properties may be provided as a base layer between the electrical steel sheet 21 and the insulating coating 22. In this case, the insulating coating adheres the electrical steel sheets to each other through the base layer. The base layer is not limited, and a known coating can be used. However, in order to avoid a decrease in the adhesion strength while improving the insulating properties, for example, a coating formed by applying a conventional processing agent such as a chromic acid-containing processing agent or a phosphate-containing processing agent and baking it is preferable. The base layer contributes to improving the insulating properties between the laminated steel sheets in the core. When this effect is obtained, the thickness of the base layer is preferably set to 0.1 μm or more. On the other hand, when the thickness of the base layer is large, the adhesion decreases and the base layer is easily peeled off. Therefore, the thickness of the base layer is preferably 1.0 μm or less.

[0017] If the thickness of the insulating coating is too large, the deterioration of the magnetic characteristics due to the curing stress increases, and if the thickness is too small, the bonding area is significantly reduced due to the influence of the surface roughness of the electrical steel sheet to be bonded, and a problem arises that the adhesive strength is insufficient. Therefore, when the thickness of the adhesive portion is A in units of μm, A and the arithmetic mean roughness Ra of the surface of the electrical steel sheet to be bonded, which is defined in JISB0601 (2013), preferably satisfy the following formula (3):

3.0×Ra ≤ A ≤ 3.0 (3).

[0018] The thickness A of the insulating coating can be measured by the magnetic method specified in JISK5600-1-7 (2014) using, for example, an LE-370 electromagnetic coating thickness gauge manufactured by Kett Electric Laboratory Co. Ltd. or an equivalent electromagnetic coating thickness gauge. The arithmetic mean roughness Ra of the surface of the electrical steel sheet can be measured using, for example, an SE3500 surface roughness measuring machine manufactured by Kosaka Laboratory Ltd. or an equivalent stylus roughness gauge. Here, the measurement direction is the width direction of the sheet (C direction), the measurement length is 8 mm, the speed is 0.1 mm/s, and the cutoff value is 0.8 mm. When the average arithmetic roughness of an electrical steel sheet surface is measured while an insulating coating or base layer is present on the sheet surface, for example, after the sheet has become a laminated core, the average arithmetic roughness can be measured after the insulating coating or base layer has been removed from the sheet surface. The insulating coating can be removed, for example, by immersing the insulating coating in dimethylformamide (DMF) for 10-60 minutes. The base layer can be removed, for example, by immersing the base layer in a 20% aqueous NaOH solution for 1-10 minutes.

<Electrical steel sheet>

[0019] The electrical steel sheet included in the laminated core 1 according to the present embodiment may be a known electrical steel sheet (anisotropic electrical steel sheet or an isotropic electrical steel sheet), and when intended for use in an electric motor or the like, the electrical steel sheet is preferably an isotropic electrical steel sheet. In the case of the isotropic electrical steel sheet, it is preferable to have the following texture and chemical composition.

[Texture]

[0020] In electrical steel sheets, the texture is controlled to achieve low magnetic loss and high magnetic flux density (magnetic induction). For example, magnetic properties are improved by developing a microstructure (α-fiber) that has an easy magnetization axis in the plane of the steel sheet, is beneficial for improving magnetic properties, and can be relatively easily increased in development through the rolling process in hot rolling and cold rolling, which are essential steps in the production of steel sheets. In particular, it is effective to form a microstructure in which the <110> direction is almost parallel to the rolling direction (RD).

On the other hand, when the {100}<011> orientation develops, the change in magnetic characteristics with respect to mechanical stress, in particular, the deterioration of magnetic characteristics (sensitivity to stress) increases in the case where compressive stress is applied.

On the other hand, with the development of the special orientation {411}<011>, the magnetic characteristics (in particular, the magnetic characteristics in the 45° direction relative to the rolling direction) are further improved.

Therefore, it is preferable to control the texture when the surface parallel to the rolled surface, having a depth of 1/2 of the sheet thickness from the surface, is measured using a scanning electron microscope with the electron backscatter diffraction function (SEM-EBSD). In particular, when the area ratio of the grains with the {hkl}<uvw> orientation (tolerance of 10° or less) relative to the full field of view obtained by the above measurement is expressed as Ahkl-uvw, A411-011 (hereinafter sometimes referred to as the "{411}<011> ratio"), it is preferably set to 15.0% or more.

The proportion of {411}<011> is more preferably 25.0% or more, still more preferably 30.0% or more, still more preferably 35.0% or more, and particularly preferably 40.0% or more. The upper limit is not particularly limited, but may be 80.0% or less from the viewpoint of the manufacturing load.

[0021] The area ratio of a specific oriented grain can be measured by the following method. Namely, to obtain the area ratio of a specific oriented grain, a specific orientation for the purpose (the tolerance is set to 10° and hereinafter expressed as a tolerance of 10° or less) is extracted from a measurement region by means of a scanning electron microscope (SEM) with an electron backscatter diffraction (EBSD) function observed under the following measurement conditions using OIM Analysis 7.3 (manufactured by TSL). The extracted area is divided by the area of the measurement region to obtain a percentage. This percentage is taken as the area ratio of a specific oriented grain.

In the present embodiment, "the area ratio of the grain with the crystallographic orientation {hkl}<uvw> (tolerance of 10° or less) from the measurement region" and "the area ratio of the grains with the orientation {hkl} (tolerance: 10° or less) from the measurement region" may also be simply referred to as "the {hkl}<uvw> ratio" and "the {hkl} ratio", respectively. In the description of the crystallographic orientation, it is assumed that the tolerance is 10° or less.

[0022] The details of the measurement conditions for obtaining the area fraction of each oriented grain are as follows.

- Measuring device: SEM with model number "JSM-6400" (manufactured by JEOL Ltd.), EBSD detector with model number "HIKARI" (manufactured by TSL) or equipment similar to those is used.

- Step interval: 5.0 µm

- Magnification: 100 times

- Object of measurement: surface parallel to the rolled surface, having a depth of 1/2 the sheet thickness from the surface

- Measurement area: rectangular area 1000 μm or more × 1000 μm or more

(Chemical composition)

[0023] Furthermore, the chemical composition of the electrical steel sheet constituting the laminated core according to the present embodiment is not limited and may be in a known range, but in the case where the above-described proportion of {411}<011> is obtained and excellent magnetic properties are achieved, the following chemical composition is preferable. In the description below, "%", which is a unit of content of each element, means "% by mass" unless otherwise specified. Furthermore, the range of numerical values represented by the symbol "-" means a range including the numerical values specified before and after the "-" as the lower and upper limits.

[0024] The electrical steel sheet constituting the laminated core according to the present embodiment has a chemical composition in which a ferrite-austenite transformation (hereinafter referred to as α-γ transformation) can occur to some extent (a chemical composition in which a certain amount of γ phase is generated upon heating even if all of γ is not transformed), and preferably has a chemical composition including 0.0100% or less C, 1.50%-4.00% Si, 0.0001%-1.0000% sol. Al, 0.0100% or less S, 0.0100% or less N, 2.50%-5.00% in total of one or more selected from the group consisting of Mn, Ni and Cu, 0.000%-1.000% of Co, 0.000%-0.400% Sn, 0.000%-0.400% Sb, 0.000%-0.400% P and 0.0000%-0.0100% in total of one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd, by weight of the chemical composition, and the rest is Fe and impurities. In addition, it is preferable that the contents of Mn, Ni, Cu, Si, soluble Al and P satisfy the specified conditions described below. Examples of impurities include impurities contained in raw materials such as ore and scrap, and impurities contained during the manufacturing stage.

(C: 0.0100% or less)

[0025] Carbon (C) is an element that increases magnetic loss or causes magnetic aging by precipitating fine carbides to inhibit grain growth. Therefore, the lower the C content, the better. This phenomenon is noticeable when the C content is more than 0.0100%. Therefore, the C content is preferably set to 0.0100% or less. The C content is more preferably 0.0050% or less, and even more preferably 0.0025% or less. The lower limit of the C content is not particularly limited, but the C content is preferably set to 0.0005% or more in consideration of the cost of decarburization treatment during refining.

(Si: 1.50%-4.00%)

[0026] Silicon (Si) is an element that increases electrical resistance, reduces eddy current loss, reduces magnetic loss, or increases the yield strength ratio, improving punching machinability during core manufacturing. When the Si content is less than 1.50%, these effects cannot be sufficiently obtained. Therefore, in the case of obtaining the above-mentioned effect, the Si content is preferably set to 1.50% or more. On the other hand, when the Si content is more than 4.00%, the magnetic flux density decreases, punching machinability decreases, or cold rolling becomes difficult due to an excessive increase in hardness. Therefore, the Si content is preferably set to 4.00% or less.

(sol. Al: 0.0001%-1.0000%)

[0027] Soluble aluminum (sol. Al) is an element that increases electrical resistance, reduces eddy current losses and reduces magnetic losses. Soluble Al is an element that also contributes to increasing the relative value of the B50 magnetic flux density relative to the saturation magnetic flux density. Here, the B50 magnetic flux density is the magnetic flux density in a magnetic field of 5000 A/m. When the content of sol. Al is less than 0.0001%, these effects cannot be obtained sufficiently. Al also has the effect of promoting desulfurization in steelmaking. Therefore, the content of sol. Al is preferably set to 0.0001% or more. The content of sol. Al is more preferably 0.0010% or more, even more preferably 0.1000% or more. On the other hand, when the content of sol. Al is more than 1.0000%, the magnetic flux density decreases. Therefore, the content of sol. Al is preferably set to 1.0000% or less.

(S: 0.0100% or less)

[0028] Sulfur (S) is not an essential element and is, for example, an element contained in steel as an impurity. S is precipitated as finely dispersed MnS and inhibits recrystallization and grain growth during annealing. Therefore, the lower the S content, the better. Such an increase in magnetic loss and a decrease in magnetic flux density due to the inhibition of recrystallization and grain growth are noticeable when the S content is more than 0.0100%. Therefore, the S content is preferably set to 0.0100% or less. The lower limit of the S content is not particularly limited, but the S content is preferably set to 0.0003% or more in consideration of the cost of desulfurization treatment during refining.

(N: 0.0100% or less)

[0029] Nitrogen (N) is an element that deteriorates magnetic properties due to the formation of fine precipitates such as TiN and AlN. Therefore, the lower the N content, the better. Such deterioration in magnetic properties is noticeable when the N content is more than 0.0100%, and therefore the N content is preferably set to 0.0100% or less. The lower limit of the N content is not particularly limited, but the N content is preferably set to 0.0010% or more in consideration of the cost of denitrification treatment during refining.

(One or more selected from the group consisting of Mn, Ni and Cu: 2.50%-5.00% in total)

[0030] These elements are necessary for causing the α-γ transformation. At least one of these elements is preferably contained in 2.50% or more in total. On the other hand, when the content of these elements exceeds 5.00% in total, not only the cost increases, but also the magnetic flux density may decrease. Therefore, at least one of these elements is preferably set at 5.00% or less in total. The amount of each of Mn, Ni, and Cu is not limited, but the content of Mn is preferably 1.50% or more from the viewpoint of specific resistance.

[0031] In addition, α-γ transformation occurs, and the following conditions are further satisfied as conditions for obtaining good magnetic characteristics. That is, when the Mn content (% by mass) is denoted as [Mn], the Ni content (% by mass) is denoted as [Ni], the Cu content (% by mass) is denoted as [Cu], the Si content (% by mass) is denoted as [Si], the sol. Al content (% by mass) is denoted as [sol. Al], and the P content (% by mass) is denoted as [P], the following formula (1) is preferably satisfied.

(2×[Mn] + 2.5×[Ni] + [Cu]) - ([Si] + 2×[sol. Al] + 4×[P]) ≥ 1.50% (1)

When the above formula (1) is not satisfied, the α-γ transformation does not occur, or even if the α-γ transformation occurs, the transformation point is high, so that a sufficient magnetic flux density cannot be obtained even if the manufacturing method described below is adopted.

[0032] The chemical composition of the electrical steel sheet is based on the fact that the electrical steel sheet contains the above elements, and the rest is Fe and impurities (impurities other than the above), but instead of part of the rest of Fe, one or more of Co, Sn, Sb, P, Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd may be contained in the following ranges. Since these elements are not necessarily contained, the lower limit is 0%. In addition, these elements are not intentionally added and are acceptable even if they are contained as impurities.

(Co: 0.000%-1.000%)

[0033] Cobalt (Co) is an element that increases magnetic flux density. Therefore, it can be contained if necessary. On the other hand, when Co is contained excessively, the cost increases. Therefore, the Co content is preferably set to 1.000% or less.

(Sn: 0.000%-0.400%, Sb: 0.000%-0.400%)

[0034] Tin (Sn) and antimony (Sb) are elements that improve the texture after cold rolling and recrystallization, improving the magnetic flux density. Therefore, these elements can be contained as needed. In the case of imparting an additional effect such as magnetic characteristics, it is preferable to contain one or more selected from the group consisting of 0.020% to 0.400% Sn and 0.020% to 0.400% Sb. On the other hand, when these elements are contained excessively, the steel becomes brittle. Therefore, the Sn content and the Sb content are both set to 0.400% or less.

(P: 0.000%-0.400%)

[0035] Phosphorus (P) is an element effective in ensuring the hardness of the steel sheet after recrystallization. P is also an element having a favorable effect on magnetic characteristics. Therefore, it can be contained. In the case of obtaining these effects, the P content is preferably set to 0.020% or more. On the other hand, when P is contained excessively, the steel becomes brittle. Therefore, the P content is preferably set to 0.400% or less.

(One or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd: 0.0000%-0.0100% in total)

[0036] Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd are elements that react with S in molten steel during casting of molten steel and form sulfide or oxysulfide, or precipitates of both. Hereinafter, Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd may be collectively referred to as "coarse precipitate-forming element." The grain size of the precipitate of the coarse precipitate-forming element is approximately 1 μm to 2 μm, and is significantly larger than the grain size (approximately 100 nm) of fine precipitates such as MnS, TiN, and AlN. Therefore, these fine precipitates "stick" to the precipitate of the coarse precipitate-forming element, and it becomes difficult to inhibit recrystallization and grain growth during annealing such as intermediate annealing. To sufficiently achieve these effects, these elements preferably constitute 0.0005% or more in total. Their content is more preferably 0.0010% or more. On the other hand, when the total amount of these elements exceeds 0.0100%, the total amount of sulfide or oxysulfide, or both, is excessive, and recrystallization and grain growth during annealing, such as intermediate annealing, are inhibited. Therefore, the content of the coarse precipitate-forming element is preferably set to 0.0100% or less in total.

[0037] The chemical composition can be measured by a general steel analysis method. For example, the chemical composition can be measured using ICP-AES (inductively coupled plasma atomic emission spectrometry). Specifically, the chemical composition is determined by measuring a test sample taken from the steel sheet using a predetermined measuring device under a condition based on a calibration curve prepared in advance. C and S can be measured using a combustion infrared absorption method, and N can be measured using a thermal conductivity inert gas fusion method. When the electrical steel sheet has an insulating coating on its surface, the insulating coating can be mechanically removed by polishing, grinding, or the like, and then subjected to analysis.

[0038] The laminated core according to the present embodiment can obtain the effect provided that it has the above-mentioned characteristics regardless of the manufacturing method. However, manufacturing according to the following method is preferable since it can be stably manufactured.

(I) A step of forming an insulating coating with the formation of an insulating coating with adhesive ability on the surface of the electrical steel sheet, and

(II) A lamination stage involving punching of a sheet of electrical steel on which an insulating coating has been formed to a given shape, if necessary, then lamination of a plurality of sheets of electrical steel, and heating and gluing the sheets of electrical steel under pressure to form a laminated core.

Preferred terms will be described below. Known terms may apply to terms not described.

<Stage of formation of the insulating coating>

[0039] In the step of forming an insulating coating, an insulating coating having adhesive ability is formed on an electrical steel sheet consisting of a base steel sheet. The insulating coating may be formed on only one surface or on both surfaces. The insulating coating is formed by applying a processing liquid to the base steel sheet and then performing baking. During baking, the material is heated so that the achieved temperature Tmax (°C) of the material is less than 200°C and the following formula (4) is satisfied, where Tr (°C) is the curing temperature of the insulating coating in units of °C. In addition, it is preferable that the temperature increase rate is set to 6.0°C/s or less, and the time tr at which the material temperature is Tr or more is set to 30-60 seconds.

Tr+30 ≤ Tmax ≤ Tr+50 (4)

[0040] When the temperature Tmax (°C) of the material reached during firing is 200°C or higher, a problem arises that the resin becomes oxidized. In addition, when Tmax exceeds Tr+50°C, stress increases due to excessive curing and magnetic properties deteriorate, and when Tmax is less than Tr+30°C, the adhesion strength decreases due to insufficient curing. When the temperature increase rate is more than 6.0°C/s, curing does not proceed properly, resulting in insufficient adhesion strength. In general, when the temperature increase rate is decreased, it is considered that it is necessary to increase the length of the furnace or decrease the linear speed, which is not preferable from the viewpoint of limiting the operation of the equipment and productivity. However, in the method for producing a laminated core according to the present embodiment, the temperature increase rate is intentionally decreased based on the newly discovered fact that the above-mentioned effect can be obtained by decreasing the temperature increase rate.

[0041] The curing temperature Tr is the temperature at which the logarithmic decrement measured by a rigid pendulum tester decreases with curing. When the crosslinked structure develops as the curing reaction proceeds, the movement of the pendulum is limited, and the swing cycle of the pendulum decreases rapidly. Therefore, the curing temperature Tr can be determined based on the change in the swing period of the pendulum. The logarithmic decrement is measured at a temperature increase rate of 10°C/s by a rigid pendulum test using a rigid pendulum with a cylindrical edge in accordance with ISO12013-2. By measuring the logarithmic decrement, the dynamic viscoelasticity of the coating can be estimated. The logarithmic decrement can be measured using, for example, the RPT-3000W instrument manufactured by A & D Company, Limited, or an equivalent rigid pendulum tester. The temperature range of the logarithmic decrement measurement can be set appropriately and can be, for example, from room temperature (25°C) to 300°C.

[0042] Regarding the processing liquid used for forming the insulating coating having adhesive ability, it is preferable that the acrylic resin having a certain degree of hardness after curing, capable of providing adhesive strength, and a small compressive stress on the steel sheet due to curing, accounts for 90% or more by mass of the total processing liquid in terms of solid content. Other components may include a resin, an inorganic salt, and inorganic fine particles. Examples of the resin include epoxy resin, urethane resin, and phenolic resin. Examples of the inorganic salt include phosphate, chromate, and borate. Examples of the inorganic fine particles include silicon dioxide, titanium oxide, magnesium oxide, and zirconium hydroxide. However, when the inorganic fine particles are foamable, air bubbles form in the insulating coating, deteriorating the coating adhesion. Therefore, foamable inorganic fine particles are not used. From the standpoint of adhesion strength, the inorganic fine particles are preferably set at a content of 0.05% by weight or less.

[0043] The acrylic resin contained in the processing liquid is not particularly limited. Examples of the monomer used for the acrylic resin include unsaturated carboxylic acids such as acrylic acid and methacrylic acid, and (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and hydroxypropyl (meth)acrylate. Here, (meth)acrylate means acrylate or methacrylate. As the acrylic resin, one kind may be used alone, or two or more kinds may be used in combination.

<Batching stage>

[0044] In the lamination step, the electrical steel sheet on which the insulating coating is formed is punched (stamped) to the required predetermined shape (the shape required when used in the stator core, rotor core, etc.), if necessary, and then bonded by heating and pressure to form a laminated core. Meanwhile, in order to set the hardness of the insulating coating after the formation of the laminated core to be 200-300 MPa, it is preferable to set the conditions under which the pressure bonding force is 10-60 kgf/ ^cm2 , and the pressure bonding temperature Tp (°C) satisfies the following formula (2):

Tr+60 ≤ Tp ≤ Tr+100 (2).

[0045] In addition, in the case where A411-011 is 15.0% or more in the laminated electrical steel sheets, a manufacturing method including the following steps can be used. Hereinafter, in the present embodiment, temperatures obtained by the following methods are used as the Ar3 temperature, the Ar1 temperature, and the Ac1 temperature (all in units of °C). The Ar3 temperature and the Ar1 temperature are determined by the change in thermal expansion of steel (steel sheet) during cooling at an average cooling rate of 1°C/s, and the Ac1 temperature is determined by the change in thermal expansion of steel (steel sheet) during heating at an average heating rate of 1°C/s.

<Hot rolling stage>

[0046] In the hot rolling stage, steel satisfying a specified chemical composition (preferably the chemical composition described above) is hot rolled to produce hot-rolled steel sheet. The hot rolling stage includes a heating process and a rolling process.

[0047] For example, steel is a slab produced by normal continuous casting, and steel having the above-described chemical composition is produced by a known method. For example, molten steel is produced in a converter, an electric furnace, or the like. The produced molten steel is refining using degassing equipment or the like, obtaining molten steel having the above-described chemical composition (the chemical composition remains virtually unchanged in the subsequent steps). The slab is cast by a continuous casting method or a method of producing ingots using molten steel. Blooming of the cast slab can be performed.

[0048] During the heating process, it is preferable to heat the steel having the above-described chemical composition to 1000-1200°C. Specifically, the steel is loaded into a heating furnace or a soaking furnace and heated in the furnace. The holding time at the heating temperature in the heating furnace or soaking furnace is not specifically limited and ranges, for example, from 1 to 200 hours.

[0049] In the rolling process, steel heated in the heating process is rolled in multiple passes to produce a hot-rolled steel sheet. "Pass" means that the steel sheet passes through one rolling stand with a pair of work rolls and is rolled. Hot rolling can be performed, for example, by performing tandem rolling using a tandem rolling mill including a plurality of rolling stands (each rolling stand has a pair of work rolls) arranged in a line to perform multi-pass rolling, or by performing reverse rolling with a pair of work rolls to perform multi-pass rolling. From the standpoint of productivity, it is preferable to perform multiple rolling passes using a tandem rolling mill.

[0050] Rolling in the rolling process (rough rolling and finish rolling) is preferably performed at a temperature in the γ region (Ar3 temperature or higher). That is, it is preferable to perform hot rolling such that the temperature during passing through the final pass of finish rolling (finish rolling temperature FT (°C)) is equal to or higher than the Ar3 temperature.

[0051] The finish rolling temperature FT means the temperature (°C) of the surface of the steel sheet on the exit side of the rolling stand when the final rolling pass is performed in the rolling process during the hot rolling step. The finish rolling temperature FT can be measured, for example, by a thermometer installed on the exit side of the rolling stand on which the final rolling pass is performed. The finish rolling temperature FT means, for example, the average value of the measured temperatures of the sections excluding one section at the front end and one section at the rear end, in the case where the total length of the steel sheet is divided into 10 equal sections in the rolling direction, to obtain 10 sections.

<Cooling stage>

[0052] In the cooling step, the steel sheet (hot-rolled steel sheet) is cooled after the hot rolling step (after finishing the finish rolling). Moderately fine grains with high deformation are obtained by transforming from austenite to ferrite during this cooling. As a cooling condition, it is preferable that the cooling is started 0.10 seconds or more after passing through the final pass of finish rolling (after 0.10 seconds or more have passed), and that the cooling is performed such that the surface temperature of the hot-rolled steel sheet becomes 300°C or more and the Ar1 temperature or less after 3 seconds (rapid cooling is not performed immediately after). Therefore, by excluding rapid cooling immediately after hot rolling, a special rapid cooling device becomes unnecessary, which is also advantageous from the viewpoint of manufacturing (cost). In addition, the texture of the hot-rolled steel sheet becomes a microstructure in which unrecrystallized austenite is transformed immediately after quenching, and it tends to become a texture accumulated in the {100}<011> orientation in the microstructure after the final annealing performed thereafter. On the other hand, when rapid cooling is not performed immediately after, a microstructure transformed from partially recrystallized austenite is formed, and it is expected that the {411}<011> orientation will likely accumulate in the microstructure after the subsequent final annealing. That is, in order to increase the proportion of {411}<011>, it is important to transform the partially recrystallized austenite, and it is preferable not to immediately perform rapid cooling.

Cooling conditions are preferably set so that the average grain size of the hot-rolled steel sheet before cold rolling is 3-10 μm. With a suitable grain size that is not excessively refined, subsequent cold rolling enables the development of α-fibers after intermediate annealing; the {411}<011> orientation can develop, which is normally less likely to develop after skin pass and final annealing. On the other hand, when the grains are excessively coarse, the α-fiber is almost not developed after cold rolling and intermediate annealing, and the desired proportion of {411}<011> cannot be obtained.

To achieve an average grain size of 3-10 μm in hot-rolled steel sheets before cold rolling, the temperature can be set to Ar1 or lower for 3 seconds after the final finishing pass. However, when the cooling stop temperature is below 300°C, the average grain size in the hot-rolled steel sheets becomes excessively small. Therefore, the cooling stop temperature is preferably set to 300°C or higher.

[0053] The temperature of the hot-rolled steel sheet (in particular, the finish rolling temperature) and the surface temperature of the hot-rolled steel sheet 3 seconds after passing through the final pass of the finish rolling are measured by the following method.

In a hot rolling equipment line used for producing electrical steel sheet, if a cooling device and a conveying line (for example, a conveying roll) are located downstream of the hot rolling mill, a thermometer for measuring the surface temperature of the hot rolled steel sheet is located on the exit side of the rolling stand for performing the final pass of the hot rolling mill, and a plurality of thermometers are also located along the conveying line on the conveying roll located downstream of the rolling stand, the hot rolling temperature and the surface temperature of the hot rolled steel sheet 3 seconds after passing through the final pass of finish rolling can be measured by the thermometer located in the hot rolling equipment line.

Cooling is accomplished using a cooling device located downstream of the rolling stand where the final pass is performed. Typically, multiple water cooling devices are arranged, with a thermometer located at the inlet of each water cooling device. The cooling device may be, for example, a well-known water cooling device or a well-known forced-air cooling device. Preferably, the cooling device is a water cooling device. The cooling medium of the water cooling device may be water or a mixed fluid of water and air.

<Cold rolling stage>

[0054] In the cold rolling step, the hot rolled steel sheet is subjected to cold rolling to obtain a cold rolled steel sheet. The hot rolled steel sheet is preferably not subjected to hot strip annealing before the cold rolling step in order to develop α fiber after cold rolling. The hot strip annealing mentioned herein means, for example, a heat treatment in which the heating temperature is an Ac1 temperature or lower and 300°C or higher. Cold rolling can be performed, for example, by performing tandem rolling using a tandem rolling mill including a plurality of rolling stands (each rolling stand has a pair of work rolls) arranged in a line to perform multi-pass rolling. Alternatively, reversible rolling can be performed by a Sendzimir rolling mill or the like having a pair of work rolls, and the rolling can be performed by single-pass rolling or multi-pass rolling. From the productivity point of view, it is preferable to perform multi-pass rolling using a tandem rolling mill.

[0055] In cold rolling, cold rolling is performed without annealing treatment in the middle of cold rolling. For example, when reversing rolling is performed and multi-pass cold rolling is performed, the multi-pass cold rolling is performed without intermediate annealing treatment between cold rolling passes. When annealing is performed between passes, the desired orientation cannot be developed in the step described below. Cold rolling can be performed in only one pass using a reversing rolling mill. When cold rolling is performed using a tandem rolling mill, cold rolling is continuously performed in a plurality of passes (passes in each rolling stand).

[0056] In the present embodiment, in order to develop the α-fiber, it is preferable to set the rolling reduction RR1 (%) in cold rolling to 75-95%. The rolling reduction RR1 is more preferably 78-92%. The rolling reduction RR1 is determined as follows:

Rolling reduction RR1 (%) = (1 - sheet thickness after the final rolling pass in cold rolling/sheet thickness before the first rolling pass in cold rolling) × 100.

<Intermediate annealing stage>

[0057] In the intermediate annealing step, the steel sheet after the cold rolling step (cold rolled steel sheet) is subjected to intermediate annealing.

In the present embodiment, it is preferable to perform annealing by raising the temperature (heating) to an annealing temperature (intermediate annealing temperature T1) (°C) from 600°C to an Ac1 temperature or less at a temperature increase rate of 300°C/s or more.

When the temperature increase rate to the annealing temperature is less than 300°C/s, a problem arises: insufficient recovery occurs and the desired texture cannot be achieved. The temperature increase rate is preferably 400°C/s or more. The faster the temperature increase rate, the more favorable it is for texture formation. However, achieving a temperature increase rate greater than 2000°C/s significantly increases costs because a special device or control is required. Therefore, the temperature increase rate can be set to 2000°C/s or less. More preferably, it is 1000°C/s or less.

The rate of temperature rise is calculated by dividing the temperature change from room temperature (e.g. 25°C) to the annealing temperature by the time required for the temperature to rise.

In addition, when the intermediate annealing temperature exceeds the Ac1 temperature, part of the microstructure of the steel sheet is transformed into austenite, and the grains with the {411}<011> orientation may not grow sufficiently during the subsequent temper rolling and final annealing due to the accompanying change in crystallographic orientation, and the magnetic flux density may not increase.

On the other hand, if the intermediate annealing temperature is too low, recrystallization does not occur, and the grains with the {411}<011> orientation do not grow sufficiently during the subsequent skin-pass rolling and final annealing, and the magnetic flux density may not increase. Therefore, the intermediate annealing temperature T1 (°C) is preferably set to 600°C or higher.

The intermediate annealing temperature T1 (°C) is the sheet temperature (surface temperature) in the vicinity of the annealing furnace opening intended for excavation.

The holding time at the intermediate annealing temperature T1 (°C) during the intermediate annealing step may be a time well known to those skilled in the art. The holding time at the intermediate annealing temperature T1 (°C) ranges, for example, from 5 to 60 seconds, but is not limited thereto.

Furthermore, the atmosphere during intermediate annealing is not specifically limited; for example, a dry gaseous atmosphere containing 20% _H2 by volume and the remainder being _N2 is used. The cooling rate of the steel sheet after intermediate annealing is not specifically limited and ranges, for example, from 5.0 to 60.0°C/s.

<Temperature rolling stage>

[0058] In the temper rolling stage, the cold-rolled steel sheet is rolled (cold rolled) at room temperature in air after the intermediate annealing stage. For temper rolling, for example, a reversible rolling mill is used, represented as a typical example by the Sendzimir rolling mill or tandem rolling mill described above.

During the skin-pass rolling stage, rolling is performed without an intermediate annealing treatment. For example, when reversing rolling and skin-pass rolling is performed in multiple passes, rolling is performed without intermediate annealing treatment between passes. Skin-pass rolling can be performed in just one pass using a reversing rolling mill. When skin-pass rolling is performed using a tandem rolling mill, rolling is performed continuously in multiple passes (passes in each rolling stand).

In the present embodiment, after the deformation is introduced into the steel sheet by hot rolling and cold rolling, the deformation introduced into the steel sheet is temporarily reduced by intermediate annealing. Then, skin-pass rolling is performed. As a result, by performing intermediate annealing to reduce the deformation excessively introduced by cold rolling, the preferential recrystallization of {111} grains on the surface of the steel sheet is suppressed during the intermediate annealing, and grains with a crystallographic orientation of {411}<011> remain. Then, an appropriate amount of deformation is introduced into each grain in the steel sheet by skin-pass rolling, and grain growth through swelling is easily caused during the final annealing of the next stage.

The rolling reduction of RR2 in skin-pass rolling is preferably set to 10-15%. When the rolling reduction of RR2 is less than 10%, the deformation amount becomes too small, and the final annealing time required for grain growth by blistering becomes long. On the other hand, when the rolling reduction of RR2 exceeds 15%, the deformation amount becomes too large, normal grain growth occurs instead of blistering, and the {411}<148> or {111}<112> orientation increases due to final annealing.

[0059] Here, the rolling reduction RR2 is defined as follows:

Rolling reduction RR2 (%) = (1 - sheet thickness after the final rolling pass in temper rolling/sheet thickness before the first rolling pass in temper rolling) × 100.

[0060] The number of passes in the temper rolling may be only one pass (i.e., only one rolling is performed), or it may be multi-pass. The temper rolling performed in the present embodiment is significantly different in effect from the temper rolling performed after the final annealing. By performing hot rolling, cooling, cold rolling, intermediate annealing, temper rolling, and final annealing in this order under predetermined conditions, a predetermined microstructure can be obtained.

<Final annealing stage>

[0061] In the final annealing step, the steel sheet after the skin-pass rolling step is annealed by holding the steel sheet at an annealing temperature T2 (°C) of 750°C or more and an Ac1 temperature or less for 2 hours or more. When the final annealing temperature T2 (°C) is lower than 750°C, a problem arises that grain growth due to swelling does not occur sufficiently. In this case, the development degree of the {411}<011> orientation decreases.

On the other hand, when the final annealing temperature T2 (°C) exceeds the Ac1 temperature, part of the microstructure of the steel sheet is transformed into austenite, grain growth due to swelling does not occur, and the desired proportion of {411}<011> cannot be obtained.

In addition, in the case where the annealing time is less than 2 hours, even if the final annealing temperature T2 (°C) is 750°C or higher and the Ac1 temperature or lower, the grain growth due to swelling does not occur sufficiently, and a problem arises that the development degree of the {411}<011> orientation may decrease.

On the other hand, the final annealing time is not specifically limited and can be 10 hours or less, since the effect is saturated even if the annealing time exceeds 10 hours.

[0062] The rate of increasing the temperature TR2 to the final annealing temperature T2 in the final annealing step may be any rate of increasing the temperature known to those skilled in the art. Examples include 40°C/hour or more and less than 200°C/hour, but the present invention is not limited to this range.

[0063] The temperature rise rate TR2 is obtained by the following method. A thermocouple is attached to a steel sheet having the above-mentioned chemical composition and obtained by hot rolling in a temper pass in order to obtain a test steel sheet. The temperature of the test steel sheet to which the thermocouple is attached is increased, and the time from the start of the temperature rise until the temperature reaches the final annealing temperature T2 is measured. The temperature rise rate TR2 is obtained based on the measured time.

[0064] The atmosphere during the final annealing step is not particularly limited. The atmosphere during the final annealing step may be, for example, a gaseous atmosphere (dry) containing 20% _H2 by volume percentage and _N2 as the balance, an atmosphere of 100% hydrogen ( _H2 ), or the like. The cooling rate of the steel sheet after the final annealing is not particularly limited. The cooling rate is, for example, 5-20°C/s.

[0065] In a method for producing an electrical steel sheet, for example, shot blasting and/or pickling may be performed after a cooling step and before a cold rolling step in the manufacturing step. In shot blasting, a steel sheet after hot rolling is subjected to shot blasting in order to break up and remove scale formed on the surface of the steel sheet after hot rolling. In pickling, the steel sheet after hot rolling is subjected to pickling treatment. In the pickling treatment, an aqueous solution of hydrochloric acid is used as a pickling bath, for example. The scale formed on the surface of the steel sheet is removed by pickling. Shot blasting may be performed after the cooling step and before the cold rolling step, and then pickling may be performed. Additionally, pickling may be performed after the cooling step and before the cold rolling step, and shot blasting may not be performed. Shot peening may be performed after the cooling stage and before cold rolling, but pickling treatment may be omitted. Shot peening and pickling are optional steps. Therefore, both shot peening and pickling may be omitted.

<Stage of formation of the base layer>

[0066] In the method for producing an electrical steel sheet according to the present embodiment, a coating (base layer) can be formed on the surface of a steel sheet (electrical steel sheet) after final annealing by applying a coating after the final annealing step. For example, the coating can be formed by applying and baking a conventional processing agent such as a chromic acid-containing processing agent or a phosphate-containing processing agent.

Examples

[0067] An ingot with the chemical composition shown in Table 1 was produced by casting molten steel. In Table 1, the left-hand side of formula (1) represents the value of the left-hand side of the formula (1) described above. In addition, a coarse precipitate-forming element such as Mg represents the sum of one or more elements selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd. Steel sheet No. e represented a component system in which α was stable and α-γ transformation did not occur.

This prepared ingot was heated to 1150°C, held for 1 hour, and then hot rolled to perform finish rolling so that the finish rolling temperature FT was the temperature shown in Table 2.

After the completion of hot rolling (after passing through the final pass), the time until the start of cooling was set as shown in Table 2, cooling was performed so that the temperature of the steel sheet 3 seconds after the start of cooling was the temperature shown in Table 2, and cooling was stopped at this temperature.

The hot rolled steel sheet thus obtained was not subjected to hot strip annealing, scale was removed by pickling, and cold rolling was performed with rolling reduction RR1 shown in Table 2, to obtain a steel sheet having a sheet thickness of 0.30 mm.

Then, an intermediate annealing was performed, in which heating was performed to the intermediate annealing temperature T1 shown in Table 2, at the temperature increase rate shown in Table 2, in an atmosphere consisting of 20% hydrogen and 80% nitrogen by volume percentage, and held at T1 for 30 seconds.

The steel sheet after intermediate annealing was subjected to temper rolling with rolling reduction RR2 shown in Table 2.

The steel sheet, after temper rolling, was then subjected to final annealing at a temperature increase rate of 100°C/hour and at the final annealing temperature T2 shown in Table 2, in a 100% hydrogen atmosphere. The holding time at the final annealing temperature T2 was set to 2 hours.

After the final annealing, annealing was performed under the conditions shown in Table 3 to form an insulating coating on the surface of the steel sheet.

[0068] Two steel sheets measuring 30 mm x 60 mm were cut from an electrical steel sheet having an insulating coating obtained in the manner described above, and the steel sheets were laminated (layered) in the direction of the sheet thickness so that areas of 10 mm x 30 mm overlapped each other. Heating and gluing under pressure were then performed under the conditions shown in Table 3.

[0069] For the bonded electrical steel sheet, the thickness, hardness and average molecular weight of the insulating coating were measured by the above-described method.

[0070] Separately from the above, two steel sheets of 30 mm × 60 mm in size were cut from an electrical steel sheet having an insulating coating on the surface, and the steel sheets were laminated (layered) in the direction of the sheet thickness so that areas of 10 mm × 30 mm overlapped each other. After this, heating and gluing under pressure were carried out under the conditions shown in Table 3.

[Adhesive strength]

[0071] The adhesive strength was measured by the following method.

<Analysis device>

Autograph AGS-10kNX

<Measurement conditions>

Tensile form: shear tensile test

Stretching temperature: 25°C

Stretching speed: 10 mm/min

For the measurement, a tensile test was performed at n=5 until failure, and the average value of the maximum strengths until failure was taken as the adhesive strength.

The results are shown in Table 4.

When the adhesive strength was 10.0 MPa or more, it was determined that sufficient adhesive strength had been obtained.

[0072] In addition, separately from the above, three steel sheets of 55 mm x 55 mm in size were cut from each electrical steel sheet having an insulating coating on the surface, and adhesive was applied to two of them, and then the steel sheets were layered in the direction of the sheet thickness so that all surfaces overlapped each other. After this, heating and pressure bonding were performed under the conditions shown in Table 3.

[Magnetic characteristics]

[0073] The deterioration factor of the magnetic characteristics of the obtained electrical steel sheet was measured by the following method.

First, the magnetic loss W10/400 (W/kg) in the 0° direction and the 90° direction relative to the rolling direction was measured according to JISC2556 (2015) for one steel sheet other than two steel sheets overlapped after cutting, and their average value was taken as the magnetic loss W1 without adhesion.

After that, the magnetic loss W10/400 (W/kg) of the bonded electrical steel sheets was measured in the 0° direction and the 90° direction relative to the rolling direction according to JISC2556 (2015), and their average value was taken as the magnetic loss W2 after bonding.

Based on W1 and W2, the magnetic loss deterioration coefficient Wa (%) was calculated based on the following equation:

Wa = (W2-W1)/W1×100.

The results are shown in Table 4.

When Wa is 10.0% or less, it is determined that the deterioration of magnetic characteristics is suppressed.

[0074] Table 1

Steel sheet No. Chemical composition (the rest is Fe and impurities) Mn+Ni+Cu The left side of formula (1) C Si sol.Al S N Mn Ni Cu Co Sn Sb P A large precipitating element such as Mg (wt.%) (wt.%) (wt.%) (wt.%) (wt.%) (wt.%) (wt.%) (wt.%) (wt.%) (wt.%) (wt.%) (wt.%) (wt.%) (wt.%) - a 0.0018 2.50 0.0050 0.0018 0.0011 3.00 0.00 0.00 0,000 0,000 0,000 0.020 0.0000 3.00 3.41 b 0.0012 2.40 0.1200 0.0015 0.0014 2.80 0.20 0.00 0,000 0.030 0.010 0.010 0.0040 3.00 3.42 c 0.0009 2.50 0.8000 0.0008 0.0008 4.00 0.00 0.00 0,000 0,000 0.110 0.100 0.0000 4.00 3.50 d 0.0012 2.60 0.5000 0.0015 0.0014 2.60 0.00 0.15 0,000 0.150 0,000 0,000 0.0000 2.75 1.75 e 0.0018 2.50 0.3000 0.0018 0.0011 2.00 0.00 0.00 0,000 0,000 0,000 0.020 0.0000 2.00 0.82 f 0.0018 2.50 0.0050 0.0018 0.0011 3.00 0.00 0.00 0,000 0,000 0,000 0.020 0.0000 3.00 3.41 g 0.0034 2.50 0.0050 0.0018 0.0019 3.00 0.00 0.00 0,000 0,000 0,000 0.020 0.0000 3.00 3.41 h 0.0022 3.43 0.0200 0.0042 0.0023 3.70 0.00 0.00 0,000 0,000 0,000 0.006 0.0050 3.70 3.91

[0075] Table 2

Steel sheet No. Transformation point Hot rolling stage Cooling stage Cold rolling stage Intermediate annealing stage Temper rolling stage Final annealing stage Texture Ar3 temperature Temperature Ar1 Temperature Ac1 Finish rolling temperature FT Time before cooling begins Temperature after 3 seconds Rolling compression RR1 Rate of temperature increase Annealing temperature T1 Rolling compression RR2 Annealing temperature T2 A411-011 (°C) (°C) (°C) (°C) (seconds) (°C) (%) (°C/second) (°C) (%) (°C) (%) a 812 779 932 950 0.10 700 88 500 700 15 800 47.9 b 809 777 929 950 0.50 400 88 1200 700 15 800 51.9 c 787 759 908 850 0.12 600 88 300 700 15 800 49.2 d 918 953 1059 950 0.50 400 88 800 700 15 800 49.3 e - - - 950 0.10 700 88 600 700 15 800 8.7 f 812 779 932 650 0.10 550 88 300 700 15 800 12.4 g 812 779 932 950 0.00 200 88 400 700 15 800 14.3 h 805 699 897 950 0.10 500 88 500 700 0 800 12.8

[0076] Table 3

Factory No. Manufacturing conditions Steel sheet No. Composition of the treatment solution for forming the insulating coating (solid content) Surface roughness of electrical steel sheet Ra (µm) Curing temperature of the insulating coating Tr (°C) The temperature of the material reached during firing Tmax
(°C) Rate of temperature increase (°C/s) Time tr at which the temperature of the material is Tr or more (seconds) Bonding force with pressure (kgf/ ^cm2 ) Pressure bonding temperature Tp (°C) 1 a Acrylic resin 0.32 122 167 3.2 55 30 202 2 b Acrylic resin + 5 wt.% epoxy resin 0.51 138 173 3.2 48 30 218 3 c Acrylic resin + 1 wt.% AlPO ₄ 0.47 131 171 3.2 45 30 211 4 d Acrylic resin + 0.05 wt.% MgO 0.61 127 159 3.2 36 30 207 5 e Acrylic resin 0.32 122 157 3.2 55 30 212 6 a Acrylic resin 0.32 122 212 4.2 55 30 217 7 b Acrylic resin 0.32 122 172 1.7 120 30 202 8 c Acrylic resin 0.32 122 167 8.5 20 30 202 9 e Acrylic resin 0.32 122 132 3.2 55 20 187 10 f Acrylic resin 0.32 122 162 3.2 55 5 187 11 g Acrylic resin 0.32 122 162 3.2 55 20 152 12 h Acrylic resin 0.32 122 162 3.2 55 30 272 13 a Epoxy resin + 5 wt.% acrylic resin 0.32 122 162 3.2 55 30 202 14 b Urethane resin 0.32 147 187 3.2 55 30 227 15 c Melamine resin 0.32 166 206 3.2 55 30 246 16 d Phenolic resin 0.32 193 233 3.2 55 30 273

[0077] Table 4

Factory No. Glued core Electrical steel sheet Steel sheet No. Hardness of insulating coating (MPa) Average molecular weight of the insulating coating Thickness of insulating coating (µm) Adhesive strength (MPa) Magnetic performance deterioration factor (W10/400) Wa (%) Magnetic losses (W10/400)
W1 (W/kg) 1 a 236 42070 2.7 14.7 5.4 12.9 2 b 265 31644 1.9 13.5 6.3 13.2 3 c 281 58764 2.1 11.5 8.1 13.4 4 d 225 26108 2.5 12.2 5.2 13.3 5 e 242 48647 2.8 13.8 8.3 14.3 6 a 321 143290 2.7 3.2 12.2 12.9 7 b 311 86731 2.7 8.9 11.1 13.2 8 c 173 5899 2.7 4.7 6.2 13.4 9 e 159 5438 2.7 3.8 5.9 14.3 10 f 188 7536 2.7 4.4 6.8 14.5 11 g 167 6431 2.7 3.1 7.7 13.0 12 h 181 123057 2.7 2.5 7.5 14.3 13 a 328 1191 2.7 13.6 13.3 12.9 14 b 338 5167 2.7 14.3 13.7 13.2 15 c 356 1876 2.7 15.1 14.5 13.4 16 d 372 167841 2.7 14.5 15.7 13.3

[0078] As can be seen from Tables 1-4, in the serial numbers 1-5, which are examples of the present invention, the composition and manufacturing conditions of the electrical steel sheet and the composition and manufacturing conditions of the insulating coating were within the scope of the present invention, the hardness of the insulating coating was within the scope of the present invention, the adhesion strength was high, and the deterioration in magnetic characteristics was small. On the other hand, in the serial numbers 6-16 of the comparative examples, the specified insulating coating was not ensured, and the deterioration rate of the adhesion strength or magnetic characteristics fell below the target.

Industrial application area

[0079] According to the present invention, it is possible to provide a laminated core having high adhesive strength and excellent magnetic properties. This core can be used for a rotating electric machine or the like and has wide industrial applicability.

Brief description of reference symbols

[0080] 1 - laminated core

21 - electrical steel sheet (base steel sheet)

22 - insulating coating

Claims (21)

1. Laminated core containing: a plurality of sheets of electrical steel laminated on top of each other; and an insulating coating that is provided between sheets of electrical steel adjacent to each other in the direction of lamination and that glues the sheets of electrical steel to each other, The insulating coating has a hardness of 200-300 MPa. 2. A laminated core according to claim 1, in which the average molecular weight of the sol component of the insulating coating is 10,000-100,000. 3. The laminated core according to claim 1 or 2, wherein in a plurality of sheets of electrical steel, when the area fraction of grains of orientation {hkl}<uvw> relative to the full field of view, when the surface parallel to the rolled surface, having a depth of 1/2 the thickness of the sheet from the surface, is measured by the SEM-EBSD method, is expressed as Ahkl-uvw, A411-011 is 15.0% or more. 4. The laminated core according to claim 3, wherein the electrical steel sheet contains: 0.0100% or less C, 1.50-4.00% Si, 0.0001-1.0000% soluble Al, 0.0100% or less S, 0.0100% or less N, 2.50-5.00% in sum of one or more selected from the group consisting of Mn, Ni and Cu, 0.000-1.000% Co, 0.000-0.400% Sn, 0.000-0.400% Sb, 0.000-0.400% P, and 0.0000-0.0100% in total of one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn and Cd, in units of % by weight of the chemical composition, at the same time when the Mn content is denoted as [Mn], the Ni content is denoted as [Ni], the Cu content is denoted as [Cu], the Si content is denoted as [Si], the soluble Al content is denoted as [sol. Al], and the P content is denoted as [P] in units of % by mass, the following formula (1) is satisfied, and the remainder is Fe and impurities, (2×[Mn] + 2.5×[Ni] + [Cu]) - ([Si] + 2×[sol. Al] + 4×[P]) ≥ 1.50%.