Non-oriented electrical steel sheet, core, method for manufacturing core, motor, and method for manufacturing motor

Abstract

The non-oriented electrical steel sheet is provided with a base material steel sheet having a prescribed chemical composition and a sheet thickness of 0.10-0.35 mm (inclusive), and an insulating coating film, and when the base material steel sheet is viewed from a cross section in which the cutting direction is parallel to the sheet thickness direction, the average crystal grain size is 10 [mu] m or less in a surface region from the surface of the base material steel sheet to 1 / 20 of the sheet thickness.

Description

Technical Field

[0001] The present invention relates to a non-oriented electromagnetic steel sheet, an iron core, a method for manufacturing the iron core, a motor, and a method for manufacturing the motor. More specifically, the present invention relates to a non-oriented electromagnetic steel sheet having good high-frequency iron loss, an iron core including the non-oriented electromagnetic steel sheet, a method for manufacturing the iron core, a motor including the iron core, and a method for manufacturing the motor.

[0002] This application claims priority based on Special Application No. 2022-156745 filed in Japan on September 29, 2022, and the contents are incorporated herein by reference. Background Art

[0003] In order to reduce global greenhouse gases, products that consume less energy are being developed in the industrial field. For example, in the automotive field, there are low-fuel-consumption vehicles such as hybrid vehicles that combine gasoline engines and motors, and electric vehicles driven by motors. The common technology of these low-fuel-consumption vehicles is the motor, and the miniaturization and efficiency of the motor have become important technologies.

[0004] For example, the drive motors of hybrid vehicles and electric vehicles are required to be miniaturized due to space limitations and reduced weight to reduce fuel consumption. In order to miniaturize the motor, it is necessary to increase the torque of the motor. Therefore, the non-oriented electromagnetic steel sheets used as the core material of the motor are required to have further improved magnetic properties.

[0005] In addition, since the battery capacity that can be installed in the car is limited, the need for high efficiency of the drive motor has increased. In order to make the motor more efficient, it is necessary to reduce energy loss. Therefore, for the non-oriented electromagnetic steel sheet used as the core material of the motor, further low iron loss is required. In particular, in the motors of hybrid drive vehicles and electric vehicles, in order to compensate for the torque reduction associated with miniaturization, attempts have been made to increase the speed of the motor. Therefore, it is required to further reduce the iron loss in the high frequency range for non-oriented electromagnetic steel sheets.

[0006] For example, Patent Document 1 discloses an electromagnetic steel sheet that has a three-layer cladding structure in which both sides of an inner layer of oriented electromagnetic steel sheet are sandwiched by non-oriented electromagnetic steel sheets as the surface layer, thereby achieving both high magnetic flux density and high frequency and low iron loss. In addition, Patent Document 2 discloses an Fe-based metal sheet that has a high magnetic flux density and high strength by changing the chemical composition in the plate thickness direction and changing the crystal grain size in the plate thickness direction.

[0007] Prior Art Literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2010-132938

[0010] Patent Document 2: Japanese Patent Application Publication No. 2016-183358 Summary of the invention

[0011] Technical problem to be solved by the invention

[0012] In the past, studies have been conducted on non-oriented electromagnetic steel sheets used as core materials for motors to improve magnetic flux density, iron loss characteristics, etc. However, there is a demand for further improvement in magnetic characteristics, especially high-frequency iron loss, of non-oriented electromagnetic steel sheets.

[0013] One embodiment of the present invention is completed in view of the above problems. One embodiment of the present invention aims to provide a non-oriented electromagnetic steel sheet with good high-frequency iron loss. In addition, one embodiment of the present invention aims to provide an iron core including the non-oriented electromagnetic steel sheet and a method for manufacturing the iron core, as well as a motor including the iron core and a method for manufacturing the motor.

[0014] Technical means for solving technical problems

[0015] (1) A non-oriented electrical steel sheet according to one embodiment of the present invention,

[0016] It has a base steel plate and an insulating film.

[0017] The base steel plate contains, as a chemical composition, in mass %,

[0018] Si: 1.0% to 5.0%

[0019] C: 0% or more and 0.0050% or less,

[0020] Mn: 0% to 3.0% or less,

[0021] P: 0% or more and 0.30% or less,

[0022] S: 0% or more and 0.010% or less,

[0023] Al: 0% to 3.0%

[0024] Zn: 0% or more and 0.10% or less,

[0025] N: 0% or more and 0.010% or less,

[0026] Sn: 0% or more and 0.10% or less,

[0027] Sb: 0% or more and 0.10% or less,

[0028] Ca: 0% or more and 0.010% or less,

[0029] Cr: 0% or more but less than 5.0%

[0030] Ni: 0% to 5.0%

[0031] Cu: 0% or more and 5.0% or less,

[0032] Ce: 0% or more and 0.10% or less,

[0033] B: 0% or more but less than 0.10%

[0034] O: 0% or more and 0.10% or less,

[0035] Mg: 0% or more and 0.10% or less,

[0036] Ti: 0% or more and 0.10% or less,

[0037] V: 0% or more and 0.10% or less,

[0038] Zr: 0% or more and 0.10% or less,

[0039] Nd: 0% or more and 0.10% or less,

[0040] Bi: 0% or more and 0.10% or less,

[0041] W: 0% or more and 0.10% or less,

[0042] Mo: 0% or more and 0.10% or less,

[0043] Nb: 0% or more and 0.10% or less,

[0044] Y: 0% or more and 0.10% or less,

[0045] The remainder is composed of Fe and impurities;

[0046] The thickness of the base steel plate is not less than 0.10 mm and not more than 0.35 mm.

[0047] When the base steel plate is observed from a cut surface in which the cutting direction is parallel to the plate thickness direction, the average crystal grain size is 10 μm or less in a surface region from the surface of the base steel plate to 1 / 20 of the plate thickness.

[0048] (2) In the non-oriented electrical steel sheet described in (1) above, it may be that:

[0049] When observing the base steel plate from the cut surface,

[0050] In the intermediate region from 1 / 20 to 1 / 4 of the plate thickness based on the surface, the average crystal grain size is 50 μm or more and 200 μm or less,

[0051] In a central region from 1 / 4 to 1 / 2 of the plate thickness based on the surface, the average crystal grain size is 50 μm or more and 200 μm or less.

[0052] (3) In the non-oriented electrical steel sheet described in (1) or (2),

[0053] The base steel plate has the following chemical composition, expressed in mass %,

[0054] The limit is Sn: 0% or more and less than 0.030%.

[0055] (4) In the non-oriented electrical steel sheet described in any one of (1) to (3) above,

[0056] The parent steel plate is observed from the cut surface, and

[0057] When the R value calculated using the Si content, Al content, and Mn content in mass % contained in the base steel plate as the chemical composition is defined as R=9.9+12.4[Si]+10.0[Al]+6.6[Mn],

[0058] In the area from the surface to 1 / 10 of the plate thickness, the R value is 60 or more and 250 or less.

[0059] In a region from 1 / 10 to 1 / 2 of the plate thickness based on the surface, the R value is 30 or more and less than 60.

[0060] (5) In the non-oriented electrical steel sheet described in any one of (1) to (4) above,

[0061] The {100} plane strength is 2.4 or more at a 1 / 2 thickness portion based on the surface, and the area ratio of {100} oriented grains is 18% or more relative to the observation field of view.

[0062] (6) An iron core according to one embodiment of the present invention,

[0063] The non-oriented electrical steel sheet as described in any one of (1) to (5) above may be included.

[0064] (7) A method for manufacturing an iron core according to one embodiment of the present invention,

[0065] The method may further include a step of laminating the non-oriented electrical steel sheets as described in any one of (1) to (5) above.

[0066] (8) A motor according to one embodiment of the present invention,

[0067] It may also include an iron core as described in (6) above.

[0068] (9) A method for manufacturing a motor according to one embodiment of the present invention may include the following steps:

[0069] A step of laminating the non-oriented electromagnetic steel sheets as described in any one of (1) to (5) above to obtain an iron core; and a step of assembling the iron core to obtain a motor.

[0070] Effects of the Invention

[0071] According to the above aspects of the present invention, a non-oriented electromagnetic steel sheet having excellent high-frequency iron loss can be provided, and an iron core including the non-oriented electromagnetic steel sheet, a method for manufacturing the iron core, and a motor including the iron core and a method for manufacturing the motor can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 It is a schematic cross-sectional view of a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0073] Figure 2 This is a flowchart of a method for producing a non-oriented electrical steel sheet according to one embodiment of the present invention. DETAILED DESCRIPTION

[0074] Hereinafter, a preferred embodiment of the present invention will be described in detail. However, the present invention is not limited to the configuration disclosed in the present embodiment, and various changes can be made within the scope of the gist of the present invention. In addition, the following numerical ranges include lower limits and upper limits within their ranges. The value indicated by "exceeds" or "is less than" is not included in the numerical range. The "%" about the content of each element refers to "mass %".

[0075] [Non-oriented electrical steel sheet]

[0076] The non-oriented electrical steel sheet according to the present embodiment has the following characteristics.

[0077] The non-oriented electrical steel sheet of this embodiment includes a base steel sheet and an insulating film.

[0078] The base steel plate contains, as a chemical composition, in mass %,

[0079] Si: 1.0% to 5.0%

[0080] C: 0% or more and 0.0050% or less,

[0081] Mn: 0% to 3.0% or less,

[0082] P: 0% or more and 0.30% or less,

[0083] S: 0% or more and 0.010% or less,

[0084] Al: 0% to 3.0%

[0085] Zn: 0% or more and 0.10% or less,

[0086] N: 0% or more and 0.010% or less,

[0087] Sn: 0% or more and 0.10% or less,

[0088] Sb: 0% or more and 0.10% or less,

[0089] Ca: 0% or more and 0.010% or less,

[0090] Cr: 0% or more but less than 5.0%

[0091] Ni: 0% to 5.0%

[0092] Cu: 0% or more and 5.0% or less,

[0093] Ce: 0% or more and 0.10% or less,

[0094] B: 0% or more but less than 0.10%

[0095] O: 0% or more and 0.10% or less,

[0096] Mg: 0% or more and 0.10% or less,

[0097] Ti: 0% or more and 0.10% or less,

[0098] V: 0% or more and 0.10% or less,

[0099] Zr: 0% or more and 0.10% or less,

[0100] Nd: 0% or more and 0.10% or less,

[0101] Bi: 0% or more and 0.10% or less,

[0102] W: 0% or more and 0.10% or less,

[0103] Mo: 0% or more and 0.10% or less,

[0104] Nb: 0% or more and 0.10% or less,

[0105] Y: 0% or more and 0.10% or less,

[0106] The remainder is composed of Fe and impurities;

[0107] The thickness of the base steel plate is 0.10 mm or more and 0.35 mm or less.

[0108] When the base steel plate is observed from a cut surface in which the cutting direction is parallel to the plate thickness direction, the average crystal grain size is 10 μm or less in a surface region from the surface of the base steel plate to 1 / 20 of the plate thickness.

[0109] In addition, the non-oriented electrical steel sheet of this embodiment is preferably

[0110] When observing the base steel plate from the above cut surface,

[0111] In the intermediate region from 1 / 20 to 1 / 4 of the plate thickness based on the above surface, the average grain size is 50 μm or more and 200 μm or less,

[0112] In a central region from 1 / 4 to 1 / 2 of the plate thickness based on the above-mentioned surface, the average crystal grain size is 50 μm or more and 200 μm or less.

[0113] In addition, the non-oriented electrical steel sheet of this embodiment is preferably

[0114] The base steel plate has the above chemical composition, expressed in mass %,

[0115] The limit is Sn: 0% or more and less than 0.030%.

[0116] In addition, the non-oriented electrical steel sheet of this embodiment is preferably

[0117] When observing the base steel plate from the above-mentioned cut surface,

[0118] When the R value calculated using the Si content, Al content, and Mn content in mass % contained in the base steel plate as the chemical composition is defined as R=9.9+12.4[Si]+10.0[Al]+6.6[Mn],

[0119] In the area from the above surface to 1 / 10 of the plate thickness, the R value is 60 or more and 250 or less.

[0120] In the region from 1 / 10 to 1 / 2 of the plate thickness based on the above-mentioned surface, the R value is 30 or more and less than 60.

[0121] In addition, the non-oriented electrical steel sheet of this embodiment is preferably

[0122] In the 1 / 2 thickness portion based on the above surface, the {100} plane strength is 2.4 or more, and the area ratio of {100} oriented grains is 18% or more relative to the observation field of view.

[0123] As Figure 1, a schematic cross-sectional view of a non-oriented electromagnetic steel sheet of the present embodiment is shown. The non-oriented electromagnetic steel sheet 1 of the present embodiment comprises an insulating coating 11 and a base steel sheet 12. In addition, when the base steel sheet 12 is observed from a cut surface parallel to the plate thickness direction in the cutting direction, it can be divided into a surface region 12a from the surface of the base steel sheet 12 to 1 / 20 of the plate thickness, an intermediate region 12b from 1 / 20 of the plate thickness to 1 / 4 of the plate thickness of the base steel sheet 12, and a central region 12c from 1 / 4 of the plate thickness to 1 / 2 of the plate thickness of the base steel sheet 12. Hereinafter, the various features of the non-oriented electromagnetic steel sheet of the present embodiment will be described in detail.

[0124] [Plate thickness]

[0125] In the non-oriented electromagnetic steel sheet of the present embodiment, the plate thickness of the base steel plate is set to 0.35 mm or less. Preferably, it is 0.30 mm or less. On the other hand, since excessive thinning will significantly reduce the productivity of the steel plate and the motor, and sometimes also reduce the magnetic properties, the plate thickness of the base steel plate is set to 0.10 mm or more. Preferably, it is 0.15 mm or more.

[0126] The thickness of the base steel plate can be measured using a micrometer. In addition, when the non-oriented electrical steel plate used as the measurement sample has an insulating film on the surface, it is removed before measurement. For example, the insulating film can be removed by the following method.

[0127] The non-oriented electrical steel sheet having the insulating film and the like is immersed in a sodium hydroxide aqueous solution, a sulfuric acid aqueous solution, and a nitric acid aqueous solution in sequence, and then washed. Finally, it is dried with hot air. In this way, a non-oriented electrical steel sheet (base steel sheet) with the insulating film removed can be obtained.

[0128] [Average crystal particle size]

[0129] In the non-oriented electrical steel sheet of the present embodiment, when the base steel sheet is observed from a cut plane whose cutting direction is parallel to the plate thickness direction, the average crystal grain size is 10 μm or less in the surface region from the surface of the base steel sheet to 1 / 20 of the plate thickness. In addition, the above-mentioned surface region is described with respect to one plate surface of the base steel sheet, but the above-mentioned conditions may be satisfied on both plate surfaces of the base steel sheet.

[0130] In the surface region, the average crystal grain size is preferably 9 μm or less, more preferably 8 μm or less. On the other hand, in the surface region, the lower limit of the average crystal grain size is not particularly limited. For example, in the surface region, the average crystal grain size may be 1 μm or more.

[0131] In the above-mentioned surface region, when the average crystal grain size satisfies the above-mentioned conditions, the high-frequency iron loss is appropriately increased. For example, iron loss refers to the loss obtained by adding eddy current loss and hysteresis loss. In commercial frequencies (for example, about 50 Hz), the ratio of hysteresis loss to iron loss is higher than that of eddy current loss. In addition, in commercial frequencies, the skin effect is not more significant as the frequency increases. On the other hand, in high frequencies (for example, about 1 kHz), the ratio of eddy current loss to iron loss increases, and the skin effect also becomes significant. In the present embodiment, it is presumed that since the average crystal grain size in the above-mentioned surface region becomes fine, that is, the magnetic domain width in the above-mentioned surface region becomes smaller, the iron loss, mainly the eddy current loss, which becomes significant at high frequencies, is reduced when the skin effect exists.

[0132] The average crystal grain size in the surface region is controlled by the manufacturing conditions unique to the present embodiment. The details of the manufacturing conditions for controlling the average crystal grain size will be described later.

[0133] In addition, in the non-oriented electrical steel sheet of the present embodiment, when the parent steel sheet is observed from the above-mentioned cut surface, the average crystal grain size in the intermediate region from 1 / 20 of the plate thickness to 1 / 4 of the plate thickness based on the above-mentioned surface is preferably 50 μm or more and 200 μm or less, and the average crystal grain size in the central region from 1 / 4 of the plate thickness to 1 / 2 of the plate thickness based on the above-mentioned surface is preferably 50 μm or more and 200 μm or less. In addition, the above-mentioned intermediate region and central region are described for one plate surface of the parent steel sheet, but the above-mentioned conditions may be satisfied for both plate surfaces of the parent steel sheet. The plate thickness 1 / 2 corresponds to the center of the plate thickness direction of the parent steel sheet in the above-mentioned cut surface.

[0134] In the above-mentioned middle region, the average crystal grain size is preferably more than 60 μm, more preferably more than 70 μm. In addition, in the above-mentioned middle region, the average crystal grain size is preferably less than 150 μm, more preferably less than 120 μm. Similarly, in the above-mentioned central region, the average crystal grain size is preferably more than 60 μm, more preferably more than 70 μm. In addition, in the above-mentioned central region, the average crystal grain size is preferably less than 150 μm, more preferably less than 120 μm.

[0135] In addition, as described above, the middle region is a region from 1 / 20 of the plate thickness to 1 / 4 of the plate thickness based on the surface of the base steel plate. In this middle region, when the region from 1 / 20 of the plate thickness to 1 / 10 of the plate thickness is divided based on the above-mentioned surface, the region from 1 / 20 of the plate thickness to 1 / 10 of the plate thickness preferably also has an average crystal grain size equivalent to that of the middle region. For example, when the average crystal grain size in the middle region exceeds 60 μm, the average crystal grain size in the region from 1 / 20 of the plate thickness to 1 / 10 of the plate thickness is also preferably greater than 60 μm. Similarly, when the average crystal grain size in the middle region is 150 μm or less, the average crystal grain size in the region from 1 / 20 of the plate thickness to 1 / 10 of the plate thickness is also preferably 150 μm or less. In addition, the region from 1 / 10 of the plate thickness to 1 / 4 of the plate thickness preferably also has an average crystal grain size equivalent to that of the middle region.

[0136] In the above-mentioned intermediate region and central region, when the average crystal grain size satisfies the above-mentioned conditions, the hysteresis loss and the magnetic permeability are well improved. In particular, in low magnetic fields (e.g., excitation magnetizing force of about 100A / m) and medium magnetic fields (e.g., excitation magnetizing force of about 1000A / m), the magnetization process is mainly carried out by the movement of magnetic walls, so it is hoped that there are fewer grain boundaries that are obstacles to the movement of magnetic walls. In this embodiment, it is estimated that by controlling the average crystal grain size in the above-mentioned intermediate region and central region to an appropriate size, the hysteresis loss is reduced, and the magnetic permeability increases from low magnetic fields to medium magnetic fields.

[0137] The average crystal grain size in the intermediate region and the central region is controlled by the manufacturing conditions unique to this embodiment. The details of the manufacturing conditions for controlling the average crystal grain size will be described later.

[0138] In addition, in the prior art, when the crystal grain size is changed along the plate thickness direction, the crystal grain size often changes gradually from the surface area toward the middle area and the central area. In this case, for example, the average crystal grain size in the middle area often becomes a value between the surface area and the central area. In particular, the average crystal grain size in the area from 1 / 20 of the plate thickness to 1 / 10 of the plate thickness is often fine. On the other hand, in the present embodiment, the average crystal grain size is controlled to be fine only in the surface area, and the average crystal grain size in the middle area and the central area is controlled to an appropriate size. Specifically, in the present embodiment, the average crystal grain size in the surface area is fine, but the average crystal grain size in the middle area becomes the same value as that in the central area. As a result, the high-frequency iron loss can be well improved.

[0139] The average crystal grain size of the base steel plate can be measured by the cutting method specified in JIS G0551:2020. For example, in the longitudinal section structure photograph, for the direction orthogonal to the plate thickness direction, the average value of the crystal grain size measured by the cutting method can be used. As the longitudinal section structure photograph, an optical microscope photograph can be used, for example, a photograph taken at a magnification of 100 times or more can be used. Under the above conditions, the average crystal grain size can be calculated in the surface area, the middle area and the central area respectively.

[0140] [Texture]

[0141] In the nonoriented electrical steel sheet of this embodiment, the {100} plane strength is preferably 2.4 or more at the 1 / 2 thickness part based on the surface of the base steel sheet, and the area ratio of {100} oriented grains is preferably 18% or more relative to the observation field.

[0142] In the above-mentioned 1 / 2 thickness portion, the {100} plane strength is preferably 3.5 or more, more preferably 3.8 or more. On the other hand, in the above-mentioned 1 / 2 thickness portion, the upper limit of the {100} plane strength is not particularly limited. For example, in the above-mentioned 1 / 2 thickness portion, the {100} plane strength can be 10 or less.

[0143] When the {100} plane strength satisfies the above conditions in the 1 / 2 portion of the plate thickness, the high magnetic field magnetic properties are suitably improved. The crystal orientation near {100} is a texture that helps to improve the magnetic flux density. For example, as the steel composition of the base steel plate, if the Si content and the like increase, the saturation magnetic flux density decreases, but as the texture of the base steel plate, if the {100} plane strength increases, the magnetic flux density increases. In this embodiment, by appropriately controlling the {100} plane strength together with other technical features, the magnetic properties in high magnetic fields, mainly the magnetic flux density in high magnetic fields (for example, an excitation magnetizing force of about 5000A / m), are improved.

[0144] In addition, in the above-mentioned 1 / 2 portion of the plate thickness, the area ratio of the {100} oriented grains is preferably 20% or more, and more preferably 22% or more relative to the observation field of view. On the other hand, in the above-mentioned 1 / 2 portion of the plate thickness, there is no particular upper limit on the area ratio of the {100} oriented grains. For example, in the above-mentioned 1 / 2 portion of the plate thickness, the area ratio of the {100} oriented grains can be 100% or less, and can also be 35% or less.

[0145] When the area ratio of {100} oriented grains in the above-mentioned 1 / 2 portion of the plate thickness satisfies the above-mentioned conditions, the high magnetic field magnetic properties are suitably improved. The crystal orientation near {100} is a texture that helps to improve the magnetic flux density. For example, as the steel composition of the base steel plate, if the Si content and the like increase, the saturation magnetic flux density decreases, but if the area ratio of {100} oriented grains in the 1 / 2 portion of the plate thickness of the base steel plate increases, the magnetic flux density increases. In this embodiment, by appropriately controlling the area ratio of {100} oriented grains together with other technical features, the magnetic properties in high magnetic fields, mainly the magnetic flux density in high magnetic fields (for example, an excitation magnetizing force of about 5000A / m), are improved.

[0146] The {100} plane strength and the area ratio of {100} oriented grains in the 1 / 2 thickness portion are controlled by manufacturing conditions unique to the present embodiment. The details of the manufacturing conditions for controlling the average grain size will be described later.

[0147] The {100} plane intensity of the base steel plate can be measured by comparing the integrated intensity of the diffraction of the {100} plane with the ideal intensity ratio in the randomly oriented material based on the X-ray diffraction spectrum. For example, the horizontal sample type high-power X-ray diffractometer RINT-TTR 3 and the powder X-ray diffractometer RINT-2000 manufactured by Rigaku Corporation can be used for measurement, but the measurement results are essentially independent of the measurement equipment. Under the above conditions, the {100} plane intensity of 1 / 2 of the plate thickness can be obtained. 1 / 2 of the plate thickness can be revealed by grinding the plate surface of the base steel plate in parallel and gradually reducing the thickness.

[0148] The area ratio of {100} oriented grains of the parent steel plate can be measured by a scanning electron microscope with an electron backscatter diffraction device (SEM-EBSD). For example, the scanning electron microscope JSM-6400 manufactured by JEOL, the EBSD detector HIKARI manufactured by TSL, and the OIM Analysis manufactured by TSL can be used for measurement, but the measurement results are essentially independent of the measurement equipment. In the measurement, for example, a sample ground for EB SD is used with care taken not to leave grinding strain on the surface, the step interval is set to 2μm, the measurement area is set to 8000μm×2400μm, the grain boundary judgment is set to an angle difference of crystal orientation of 15° or more, and the extraction of the area ratio of {100} oriented grains is set to a tolerance of 20°. Under the above conditions, the area ratio of {100} oriented grains in 1 / 2 of the plate thickness can be obtained. As described above, 1 / 2 of the plate thickness can be revealed by grinding the plate surface of the parent steel plate in parallel and gradually reducing the thickness. The plate thickness 1 / 2 corresponds to the center of the base steel plate in the plate thickness direction.

[0149] [Chemical composition]

[0150] In the non-oriented electrical steel sheet of the present embodiment, the base steel sheet may contain Si as a chemical composition, may contain a selected element as necessary, and the remainder may be composed of Fe and impurities.

[0151] Specifically, the base steel plate contains, as a chemical composition, in mass %,

[0152] Si: 1.0% to 5.0%

[0153] C: 0% or more and 0.0050% or less,

[0154] Mn: 0% to 3.0% or less,

[0155] P: 0% or more and 0.30% or less,

[0156] S: 0% or more and 0.010% or less,

[0157] Al: 0% to 3.0%

[0158] Zn: 0% or more and 0.10% or less,

[0159] N: 0% or more and 0.010% or less,

[0160] Sn: 0% or more and 0.10% or less,

[0161] Sb: 0% or more and 0.10% or less,

[0162] Ca: 0% or more and 0.010% or less,

[0163] Cr: 0% or more but less than 5.0%

[0164] Ni: 0% to 5.0%

[0165] Cu: 0% or more and 5.0% or less,

[0166] Ce: 0% or more and 0.10% or less,

[0167] B: 0% or more but less than 0.10%

[0168] O: 0% or more and 0.10% or less,

[0169] Mg: 0% or more and 0.10% or less,

[0170] Ti: 0% or more and 0.10% or less,

[0171] V: 0% or more and 0.10% or less,

[0172] Zr: 0% or more and 0.10% or less,

[0173] Nd: 0% or more and 0.10% or less,

[0174] Bi: 0% or more and 0.10% or less,

[0175] W: 0% or more and 0.10% or less,

[0176] Mo: 0% or more and 0.10% or less,

[0177] Nb: 0% or more and 0.10% or less,

[0178] Y: 0% or more and 0.10% or less,

[0179] The remainder is composed of Fe and impurities.

[0180] Hereinafter, each element will be described. In addition, the chemical composition of the base steel plate below is an average value of the entire base steel plate.

[0181] Si: 1.0% or more and 5.0% or less

[0182] Si (silicon) is an element that is effective in increasing the resistivity of the steel sheet and reducing the iron loss. Therefore, the Si content is 1.0% or more. The Si content is preferably 1.5% or more, and more preferably 2.0% or more. On the other hand, if it is excessively contained, the magnetic flux density is significantly reduced. Therefore, the Si content is 5.0% or less. The Si content is preferably 4.0% or less, and more preferably 3.50% or less.

[0183] C: 0% or more and 0.0050% or less

[0184] C (carbon) is a selective element. However, if it is contained excessively, the magnetic properties will deteriorate. Therefore, the C content is less than 0.0050%. The C content is preferably less than 0.0030%. On the other hand, the C content is preferably small, so there is no need to limit the lower limit, and the lower limit may also be 0%. However, since it is not easy to make the content 0% industrially, the lower limit may also be more than 0%, or 0.0010%.

[0185] Mn: 0% or more and 3.0% or less

[0186] Mn (manganese) is a selective element. Mn has the effect of increasing the resistivity of the steel plate and reducing the iron loss. However, compared with Si or Al, the alloy cost of Mn is high, so if the Mn content increases, it is economically disadvantageous. Therefore, the Mn content is 3.0% or less. Preferably, it is 2.50% or less. Mn does not need to be restricted to a lower limit value, and the lower limit value may also be 0%. However, in order to more reliably obtain the above-mentioned effect, the Mn content is preferably greater than 0%, preferably greater than 0.0010%, and more preferably greater than 0.010%.

[0187] P: 0% or more and 0.30% or less

[0188] P (phosphorus) is a selective element. P has the effect of improving the texture of non-oriented electromagnetic steel sheets and enhancing magnetic properties. However, since P is also a solid solution strengthening element, if the P content is excessive, the steel sheet will harden and cold rolling will become difficult. Therefore, the P content is less than 0.30%. The P content is preferably less than 0.20%. P does not need to be restricted to a lower limit value, and the lower limit value may also be 0%. However, in order to more reliably obtain the above-mentioned effect, the P content is preferably greater than 0%, preferably greater than 0.0010%, and more preferably greater than 0.0150%.

[0189] S: 0% or more and 0.010% or less

[0190] S (sulfur) is a selective element. However, S sometimes combines with Mn in steel to form fine MnS, which hinders the growth of grains during annealing and deteriorates the magnetic properties of the non-oriented electrical steel sheet. Therefore, the S content is 0.010% or less. The S content is preferably 0.0050% or less, and more preferably 0.0030% or less. The S content is preferably small, so there is no need to limit the lower limit, and the lower limit may be 0%. However, since it is not easy to make the content 0% industrially, the lower limit may be more than 0%, and may be 0.00010%.

[0191] Al: 0% or more and 3.0% or less

[0192] Al (aluminum) is a selective element. Al is a selective element that is effective in increasing the resistivity of the steel plate and reducing the iron loss, but if it is contained in excess, the magnetic flux density will be significantly reduced. Therefore, the Al content is less than 3.0%. Al does not need to be restricted to a lower limit value, and the lower limit value can also be 0%. However, in order to more reliably obtain the effect brought about by the above-mentioned action, it is preferred to set the Al content to more than 0.10%. In addition, in the present embodiment, Al refers to acid-soluble aluminum.

[0193] Zn: 0% or more and 0.10% or less

[0194] Zn (zinc) is a selective element. Zn is an element effective in improving magnetic flux density, iron loss characteristics and punchability, but even if it is contained in excess, the above effects are saturated. Therefore, the Zn content is less than 0.10%. Zn does not need to be limited to a lower limit value, and the lower limit value can also be 0%. However, in order to more reliably obtain the effects brought about by the above effects, it is preferred that the Zn content be set to more than 0.0010%.

[0195] N: 0% or more and 0.010% or less

[0196] N (nitrogen) is a selective element. However, N sometimes combines with Al to form fine AlN, which hinders the growth of grains during annealing and deteriorates the magnetic properties. Therefore, the N content is set to 0.010% or less. The N content is preferably 0.0050% or less, and more preferably 0.0030% or less. The N content is preferably small, so there is no need to limit the lower limit, and the lower limit may be 0%. However, since it is not easy to make the content 0% in industry, the lower limit may be more than 0%, or more than 0.00010%, or more than 0.00150%, or more than 0.00250%.

[0197] Sn: 0% or more and 0.10% or less

[0198] Sb: 0% or more and 0.10% or less

[0199] Sn (tin) and Sb (antimony) are selective elements. Sn and Sb have the effect of improving the texture of non-oriented electrical steel sheets and improving magnetic properties (for example, magnetic flux density). However, if contained in excess, the steel may become brittle and cause cold rolling fracture, and the magnetic properties may also deteriorate. Therefore, the contents of Sn and Sb are each less than 0.10%. In addition, in order to control the average crystal grain size in the surface area of ​​the base steel sheet to be fine, the Sn content is preferably less than 0.030%. On the other hand, Sn and Sb do not need to be restricted to the lower limit value, and the lower limit value may also be 0%. However, in order to more reliably obtain the above-mentioned effect, the Sn content is preferably greater than 0%, preferably greater than 0.0010%, and more preferably greater than 0.010%. In addition, the Sb content is preferably greater than 0%, preferably greater than 0.0010%, preferably greater than 0.0020%, more preferably greater than 0.010%, and further preferably greater than 0.0250%.

[0200] Ca: 0% or more and 0.010% or less

[0201] Ca (calcium) is a selective element. Ca suppresses the precipitation of fine sulfides (MnS, Cu2S, etc.) by generating coarse sulfides, so it is effective for inclusion control. If Ca is added moderately, it has the effect of improving grain growth and improving magnetic properties (for example, iron loss). However, if it is contained excessively, the above effects are saturated and the cost increases. Therefore, the Ca content is less than 0.010%. The Ca content is preferably less than 0.0080%, more preferably less than 0.0050%. Ca does not need to be restricted to a lower limit value, and the lower limit value may also be 0%. However, in order to more reliably obtain the above effect, it is preferred to set the Ca content to more than 0%, preferably to more than 0.00030%. The Ca content is preferably more than 0.0010%, more preferably more than 0.0030%.

[0202] Cr: 0% or more but less than 5.0%

[0203] Cr (chromium) is a selective element. Cr has the effect of increasing the intrinsic resistance and thus improving the magnetic properties (for example, iron loss). However, if it is contained in excess, the saturation magnetic flux density is sometimes reduced, and the above-mentioned effect is saturated, resulting in increased costs. Therefore, the Cr content is 5.0% or less. The Cr content is preferably 2.0% or less, and more preferably 1.0% or less. There is no need to limit the lower limit of Cr, and the lower limit may also be 0%. However, in order to more reliably obtain the above-mentioned effect, the Cr content is preferably greater than 0%, preferably greater than 0.0010%. In addition, Cr inhibits the formation of Kirkendall voids in the base steel plate. Therefore, the Cr content is preferably greater than 0.50%.

[0204] Ni: 0% or more and 5.0% or less

[0205] Ni (nickel) is a selective element. Ni has the effect of improving magnetic properties (for example, saturation magnetic flux density). However, if it is contained excessively, the above effect will be saturated and the cost will increase. Therefore, the Ni content is less than 5.0%. The Ni content is preferably less than 0.50%, more preferably less than 0.10%. Ni does not need to be restricted to a lower limit value, and the lower limit value may also be 0%. However, in order to more reliably obtain the above effect, the Ni content is preferably more than 0%, preferably more than 0.0010%.

[0206] Cu: 0% or more and 5.0% or less

[0207] Cu (copper) is a selective element. Cu has the effect of increasing the strength of the steel plate. However, if it is contained in excess, the saturation magnetic flux density may be reduced, and the above effect may be saturated, resulting in increased costs. Therefore, the Cu content is 5.0% or less. The Cu content is preferably 0.10% or less. Cu does not need to be restricted to a lower limit value, and the lower limit value may also be 0%. However, in order to more reliably obtain the above effect, the Cu content is preferably greater than 0%, preferably greater than 0.0010%.

[0208] Ce: 0% or more and 0.10% or less

[0209] Ce (cerium) is a selective element. Ce suppresses the precipitation of fine sulfides (MnS, Cu2S, etc.) by generating coarse sulfides and oxysulfides, and has the effect of improving grain growth and reducing iron loss. However, if it is contained excessively, oxides are sometimes generated in addition to sulfides and oxysulfides, which deteriorates iron loss. In addition, the above effect is saturated, resulting in increased costs. Therefore, the Ce content is less than 0.10%. The Ce content is preferably less than 0.010%, more preferably less than 0.0090%, and further preferably less than 0.0080%. Ce does not need to be restricted to a lower limit value, and the lower limit value may also be 0%. However, in order to more reliably obtain the above effect, the Ce content is preferably greater than 0%, preferably greater than 0.0010%. The Ce content is more preferably greater than 0.0020%, further preferably greater than 0.0030%, and further preferably greater than 0.0050%.

[0210] The chemical composition of the base steel sheet of the non-oriented electrical steel sheet of the present embodiment may contain, in addition to the above elements, B, O, Mg, Ti, V, Zr, Nd, Bi, W, Mo, Nb, and Y as optional elements. The contents of these optional elements may be controlled based on known knowledge. For example, the contents of these optional elements may be as follows. The lower limits of these optional elements may exceed 0%.

[0211] B: 0% or more but less than 0.10%

[0212] O: 0% or more and 0.10% or less,

[0213] Mg: 0% or more and 0.10% or less,

[0214] Ti: 0% or more and 0.10% or less,

[0215] V: 0% or more and 0.10% or less,

[0216] Zr: 0% or more and 0.10% or less,

[0217] Nd: 0% or more and 0.10% or less,

[0218] Bi: 0% or more and 0.10% or less,

[0219] W: 0% or more and 0.10% or less,

[0220] Mo: 0% or more and 0.10% or less,

[0221] Nb: 0% or more and 0.10% or less,

[0222] Y: 0% or more and 0.10% or less,

[0223] In addition, the non-oriented electrical steel sheet of the present embodiment preferably contains at least one of the following elements as a chemical composition, in terms of mass %.

[0224] C: 0.0010% or more and 0.0050% or less,

[0225] Mn: 0.0010% or more and 3.0% or less,

[0226] P: 0.0010% or more and 0.30% or less,

[0227] S: 0.00010% or more and 0.010% or less,

[0228] N: more than 0.00150% and less than 0.010%,

[0229] B: 0.00010% or more and 0.10% or less,

[0230] O: 0.00010% or more and 0.10% or less,

[0231] Mg: 0.00010% or more and 0.10% or less,

[0232] Ca: 0.00030% or more and 0.010% or less,

[0233] Ti: 0.00010% or more and 0.10% or less,

[0234] V: 0.00010% or more and 0.10% or less,

[0235] Cr: 0.0010% or more and 5.0% or less,

[0236] Ni: 0.0010% to 5.0%,

[0237] Cu: 0.0010% or more and 5.0% or less,

[0238] Zr: 0.00020% or more and 0.10% or less,

[0239] Sn: 0.0010% or more and 0.10% or less,

[0240] Sb: 0.0010% or more and 0.10% or less,

[0241] Ce: 0.0010% or more and 0.10% or less,

[0242] Nd: 0.0020% or more and 0.10% or less,

[0243] Bi: 0.0020% or more and 0.10% or less,

[0244] W: 0.0020% or more and 0.10% or less,

[0245] Mo: 0.0020% or more and 0.10% or less,

[0246] Nb: 0.00010% or more and 0.10% or less,

[0247] Y: 0.0020% or more and 0.10% or less.

[0248] In addition, the B content is preferably 0.010% or less, the O content is preferably 0.010% or less, the Mg content is preferably 0.0050% or less, the Ti content is preferably 0.0020% or less, the V content is preferably 0.0020% or less, the Zr content is preferably 0.0020% or less, the Nd content is preferably 0.010% or less, the Bi content is preferably 0.010% or less, the W content is preferably 0.010% or less, the Mo content is preferably 0.01% or less, the Nb content is preferably 0.0020% or less, and the Y content is preferably 0.010% or less. In addition, the Ti content is preferably 0.0010% or more, the V content is preferably 0.0020% or more, and the Nb content is preferably 0.0020% or more.

[0249] The above chemical composition can be measured by a general analytical method for steel. For example, the chemical composition can be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). In addition, Al, as acid-soluble Al, can be measured using ICP-AES using a filtrate after heating and decomposing the sample with acid. In addition, C and S can be measured using a combustion-infrared absorption method, N can be measured using an inert gas melting-thermal conductivity method, and O can be measured using an inert gas melting-non-dispersive infrared absorption method.

[0250] The chemical composition of the above-mentioned base steel plate is an average value of the whole base steel plate. In the non-oriented electrical steel plate of the present embodiment, when the base steel plate is observed from the above-mentioned cut surface, and the R value calculated using the Si content, Al content and Mn content contained in the base steel plate as the chemical composition is defined as R=9.9+12.4[Si]+10.0[Al]+6.6[Mn], the R value is preferably 60 or more and 250 or less in the region from the above-mentioned surface to 1 / 10 of the plate thickness, and the R value is preferably 30 or more and less than 60 in the region from 1 / 10 of the plate thickness to 1 / 2 of the plate thickness based on the above-mentioned surface. In addition, the above-mentioned regions are described for one plate surface of the base steel plate, but the above-mentioned conditions may be satisfied for both plate surfaces of the base steel plate.

[0251] In the region from the surface to 1 / 10 of the plate thickness, the R value is preferably 65 or more, more preferably 70 or more. In this region, the R value is preferably 240 or less, more preferably 230 or less. On the other hand, in the region from 1 / 10 of the plate thickness to 1 / 2 of the plate thickness based on the surface, the R value is preferably 35 or more, more preferably 40 or more. In this region, the R value is preferably 58 or less, more preferably 56 or less.

[0252] When the R value satisfies the above conditions in the region from the surface to 1 / 10 of the plate thickness and in the region from 1 / 10 of the plate thickness to 1 / 2 of the plate thickness, and particularly when the R value satisfies the above conditions in the region from the surface to 1 / 10 of the plate thickness, the high-frequency iron loss is appropriately improved. It is estimated that if the R value is controlled in this way, the inherent resistance near the surface of the steel plate is increased, and as a result, the iron loss, mainly the eddy current loss, is reduced when the skin effect that becomes significant at high frequencies exists.

[0253] The R value in the region from the surface to 1 / 10 of the plate thickness and in the region from 1 / 10 of the plate thickness to 1 / 2 of the plate thickness is controlled by manufacturing conditions unique to this embodiment. Details of the manufacturing conditions for controlling the R value will be described later.

[0254] The R value can be confirmed by EPMA (Electron Probe Micro Analyzer) on a cut surface parallel to the plate thickness direction. Specifically, a test piece is cut from the base steel plate in a manner that the cutting direction is parallel to the plate thickness direction. The cross-sectional structure of the cut surface is observed by EPMA at a magnification at which the plate thickness of the base steel plate enters the observation field of view. When the plate thickness of the base steel plate does not enter the observation field of view, the cross-sectional structure is observed in multiple consecutive fields of view.

[0255] For the base steel plate in the above observation field, EPMA can be used to perform line analysis along the plate thickness direction to obtain the Si content, Al content and Mn content in the region from the surface of the base steel plate to 1 / 10 of the plate thickness, and the Si content, Al content and Mn content in the region from 1 / 10 of the plate thickness to 1 / 2 of the plate thickness. Based on such line analysis results, the R value in the region from the surface to 1 / 10 of the plate thickness and the region from 1 / 10 of the plate thickness to 1 / 2 of the plate thickness can be obtained respectively. In addition, the plate thickness 1 / 2 corresponds to the center of the base steel plate in the plate thickness direction in the above-mentioned cut surface.

[0256] [Method for producing non-oriented electrical steel sheet]

[0257] An example of a method for manufacturing a non-oriented electromagnetic steel sheet according to the present embodiment is described below. In addition, as long as the non-oriented electromagnetic steel sheet according to the present embodiment has the above-mentioned structure, the manufacturing method is not particularly limited. The following manufacturing method is an example for manufacturing a non-oriented electromagnetic steel sheet according to the present embodiment, and is a preferred example of a method for manufacturing a non-oriented electromagnetic steel sheet according to the present embodiment.

[0258] For example, the method for producing the non-oriented electrical steel sheet of the present embodiment may include a casting step, a hot rolling step, a cold rolling step, a final annealing step, a nitriding annealing step, and a coating forming step.

[0259] Specifically, the method for producing a non-oriented electrical steel sheet according to the present embodiment includes a casting step, a hot rolling step, a cold rolling step, a final annealing step, a nitriding annealing step, and a coating forming step.

[0260] In the above casting process, the following slab is cast: as a chemical composition, in terms of mass %,

[0261] Si: 1.0% to 5.0%

[0262] C: 0% or more and 0.0050% or less,

[0263] Mn: 0% to 3.0% or less,

[0264] P: 0% or more and 0.30% or less,

[0265] S: 0% or more and 0.010% or less,

[0266] Al: 0% to 3.0%

[0267] Zn: 0% or more and 0.10% or less,

[0268] N: 0% or more and 0.010% or less,

[0269] Sn: 0% or more and 0.10% or less,

[0270] Sb: 0% or more and 0.10% or less,

[0271] Ca: 0% or more and 0.010% or less,

[0272] Cr: 0% or more but less than 5.0%

[0273] Ni: 0% to 5.0%

[0274] Cu: 0% or more and 5.0% or less,

[0275] Ce: 0% or more and 0.10% or less,

[0276] B: 0% or more but less than 0.10%

[0277] O: 0% or more and 0.10% or less,

[0278] Mg: 0% or more and 0.10% or less,

[0279] Ti: 0% or more and 0.10% or less,

[0280] V: 0% or more and 0.10% or less,

[0281] Zr: 0% or more and 0.10% or less,

[0282] Nd: 0% or more and 0.10% or less,

[0283] Bi: 0% or more and 0.10% or less,

[0284] W: 0% or more and 0.10% or less,

[0285] Mo: 0% or more and 0.10% or less,

[0286] Nb: 0% or more and 0.10% or less,

[0287] Y: 0% or more and 0.10% or less,

[0288] The rest is made up of Fe and impurities.

[0289] In the hot rolling process, the slab is hot rolled.

[0290] In the cold rolling process, the steel sheet is cold rolled.

[0291] In the above-mentioned final annealing process,

[0292] As an oxidation process, the steel sheet heated from room temperature is kept in an atmosphere containing 5 volume % to 15 volume % hydrogen and a dew point of 40° C. to 60° C. within a temperature range of 170° C. to 190° C. for 90 seconds to 110 seconds.

[0293] As a heating process, the steel sheet after the oxidation process is heated to a temperature range of 680° C. to 720° C. at an average heating rate of 40° C. / second to 60° C. / second in an atmosphere containing 5% by volume to 15% by volume of hydrogen and a dew point of 40° C. to 60° C.,

[0294] Then, in an atmosphere of 5 volume % to 25 volume % hydrogen and a dew point of -20°C to 20°C, the temperature is increased at an average temperature increase rate of 40°C / second to 60°C / second to a temperature range of 780°C to 1050°C.

[0295] As a soaking process, the steel sheet after the heating process is kept in an atmosphere containing 5 volume % to 25 volume % of hydrogen and a dew point of -20°C to 20°C for 10 seconds to 20 seconds within a temperature range of 780°C to 1050°C.

[0296] As a cooling process, the steel plate after the soaking process is cooled to a temperature range of above room temperature and below 720°C.

[0297] In the above nitriding annealing process,

[0298] The steel sheet after the final annealing step is held in an atmosphere having a nitrogen content of 95% by volume to 100% by volume and a dew point of -50°C to 0°C for 70 seconds to 90 seconds within a temperature range of 680°C to 720°C.

[0299] In the above-mentioned film forming step,

[0300] As a coating forming process, a coating is formed on the steel sheet after the nitriding annealing step.

[0301] As the annealing process, the steel sheet may be held in a temperature range of 750° C. to 850° C. inclusive for 30 minutes to 150 minutes inclusive, as necessary.

[0302] In addition, the method for manufacturing a non-oriented electrical steel sheet of the present embodiment may also include a hot-rolled sheet annealing step after the hot rolling step. In addition, the method for manufacturing a non-oriented electrical steel sheet of the present embodiment may also include a pickling step after the hot rolling step or after the hot-rolled sheet annealing step. In addition, the method for manufacturing a non-oriented electrical steel sheet of the present embodiment may also include a surface treatment step after the hot rolling step, after the hot-rolled sheet annealing step, after the pickling step, or after the cold rolling step.

[0303] As Figure 2 , a flow chart of the method for producing a non-oriented electrical steel sheet according to the present embodiment is shown. Hereinafter, each step will be described in detail.

[0304] [Casting process]

[0305] In the casting step, a slab (steel sheet) having the above chemical composition may be cast. The chemical composition of the slab is substantially the same as the chemical composition of the base steel sheet of the non-oriented electrical steel sheet.

[0306] In addition, in order to control the average crystal grain size in the surface region from the surface to 1 / 20 of the plate thickness of the base steel plate of the final non-oriented electrical steel plate to be fine, the Sn content is preferably less than 0.030%. In order to properly nitride the steel plate surface in the nitriding annealing step as a post-process, it is preferred that Sn is not segregated in the surface layer of the steel plate, or the Sn content itself is small.

[0307] The casting method is not particularly limited, and for example, the slab may be produced by continuous casting, or an ingot may be produced using molten steel and then the ingot may be subjected to bloom rolling to produce the slab. Alternatively, the slab may be produced by other methods.

[0308] The thickness of the slab is not particularly limited, and may be, for example, 150 mm to 350 mm. The thickness of the slab is preferably 220 mm to 280 mm. As the slab, a so-called thin slab having a thickness of 10 mm to 70 mm may be used.

[0309] In order to appropriately control the {100} plane strength and the area ratio of {100} oriented grains in the 1 / 2 thickness portion of the base steel plate of the final non-oriented electrical steel plate, it is preferred to adopt a thin slab continuous casting method, set the slab thickness to 30 mm or more and 60 mm or less, fully develop columnar crystals in which the {100} plane is parallel to the steel plate surface in the thin slab, and make the {100} obtained by hot rolling the columnar crystals into a uniform structure. <011> Therefore, it is preferred not to implement electromagnetic stirring during continuous casting, and it is also preferred to minimize fine inclusions in the molten steel that promote the formation of solidification nuclei.

[0310] The fine inclusions in molten steel can be reduced by, for example, reducing the content of elements forming fine inclusions, such as Ti. In addition, the fine inclusions in molten steel can be measured by, for example, electrolytically extracting a steel ingot obtained by rapidly cooling a sample extracted from molten steel and analyzing the residue.

[0311] [Hot rolling process]

[0312] In the hot rolling process, the slab is hot rolled to obtain a hot rolled steel sheet. The hot rolling conditions are not particularly limited. For example, the thickness (final thickness) of the hot rolled steel sheet is preferably set to be 1.0 mm or more and 2.5 mm or less. If the thickness is 1.0 mm or more, the load applied to the hot rolling mill is small, and the productivity in the hot rolling process is high.

[0313] The heating temperature of the slab before hot rolling is not particularly limited, but may be 1000° C. to 1300° C. from the viewpoint of cost, etc. In the final hot rolling after the rough rolling, the final rolling temperature is preferably 900° C. or higher, more preferably 950° C. or higher.

[0314] [Cold rolling process]

[0315] In the cold rolling process, the steel sheet is cold rolled to obtain a cold rolled steel sheet. In the cold rolling process, the thickness (final thickness) of the cold rolled steel sheet is set to be 0.10 mm or more and 0.35 mm or less. In addition, the steel sheet subjected to cold rolling may be any one of a steel sheet after a hot rolling process, a steel sheet after a hot rolled sheet annealing process, a steel sheet after a pickling process, or a steel sheet after a surface treatment process.

[0316] Other cold rolling conditions are not particularly limited. For example, the cumulative reduction ratio in cold rolling is preferably 60% to 95%. If the reduction ratio is 60% or more, the effect of P on the texture of the non-oriented electrical steel sheet can be more stably obtained. In addition, if the reduction ratio is 95% or less, the non-oriented electrical steel sheet can be stably manufactured industrially.

[0317] The steel sheet temperature during cold rolling may be room temperature. Alternatively, cold rolling may be warm rolling at a steel sheet temperature of 100° C. to 200° C. In order to heat the steel sheet temperature to 100° C. to 200° C., the steel sheet may be preheated or the roll may be preheated.

[0318] [Final annealing process]

[0319] In the final annealing process, the steel sheet may be subjected to an oxidation process, a heating process, a soaking process, and a cooling process. In the final annealing process, it is preferred that a pretreatment for appropriately nitriding the surface of the steel sheet be performed in a nitriding annealing process as a post-process. In addition, the steel sheet subjected to the final annealing may be either a steel sheet after a cold rolling process or a steel sheet after a surface treatment process.

[0320] [Oxidation process]

[0321] In the oxidation process of the final annealing step, the steel sheet after the cold rolling step or the surface treatment step can be maintained in an atmosphere with hydrogen of 5 volume % to 15 volume % and a dew point of 40° C. to 60° C., within a temperature range of 170° C. to 190° C. for 90 seconds to 110 seconds.

[0322] The hydrogen content of the atmosphere during the oxidation process is preferably 7% by volume or more, more preferably 9% by volume or more. On the other hand, the hydrogen content is preferably 13% by volume or less, more preferably 11% by volume or less. In addition, the dew point of the atmosphere during the oxidation process is preferably 42°C or more, more preferably 44°C or more. On the other hand, the dew point is preferably 58°C or less, more preferably 56°C or less. In addition, the temperature range maintained during the oxidation process is preferably 173°C or more, more preferably 175°C or more. On the other hand, the temperature range is preferably 188°C or less, more preferably 185°C or less. In addition, the time during the oxidation process maintained within the above-mentioned temperature range is preferably 93 seconds or more, more preferably 95 seconds or more. On the other hand, the time is preferably 108 seconds or less, more preferably 105 seconds or less.

[0323] In the above-mentioned oxidation process, the atmosphere is preferably set to a WET atmosphere, so that fayalite (Fe2SiO4) is formed on the surface of the steel plate. In the past, nitriding annealing was almost never performed as a post-process of final annealing, and there was no view that oxides were actively formed on the surface of the steel plate by final annealing for the purpose of nitriding annealing as a post-process of final annealing. In addition, it is generally believed that if oxides are formed on the surface of the steel plate, nitridation is hindered in the post-process. The inventors of the present invention have found that, in the oxidation process of the final annealing process, fayalite is formed on the surface of the steel plate, so that it is suitably nitrided in the post-process. It is believed that the fayalite has a catalytic effect and promotes nitridation in the post-process.

[0324] [Heating process]

[0325] In the temperature raising process of the final annealing step, the steel sheet after the oxidation process may be heated to a temperature range of 680°C to 720°C at an average heating rate of 40°C / sec to 60°C / sec in an atmosphere of 5% to 15% by volume of hydrogen and a dew point of 40°C to 60°C. Thereafter, the steel sheet may be heated to a temperature range of 780°C to 1050°C at an average heating rate of 40°C / sec to 60°C / sec in an atmosphere of 5% to 25% by volume of hydrogen and a dew point of -20°C to 20°C.

[0326] The hydrogen of the atmosphere in the first half of the heating process is preferably 7% by volume or more, more preferably 9% by volume or more. On the other hand, the hydrogen is preferably 13% by volume or less, more preferably 11% by volume or less. In addition, the dew point of the atmosphere in the first half of the heating process is preferably 42°C or more, more preferably 44°C or more. On the other hand, the dew point is preferably 58°C or less, more preferably 56°C or less. In addition, the average heating rate in the first half of the heating process is preferably 43°C / second or more, more preferably 45°C / second or more. On the other hand, the average heating rate is preferably 58°C / second or less, more preferably 55°C / second or less. The average heating rate refers to the value obtained by dividing the heating temperature from the heating start temperature to the heating arrival temperature by the heating time from the heating start temperature to the heating arrival temperature. In addition, the temperature range of the heating in the first half of the heating process is preferably 685°C or more, more preferably 690°C or more. On the other hand, the temperature range is preferably 715°C or less, more preferably 710°C or less.

[0327] The hydrogen of the atmosphere in the second half of the heating process is preferably 7% by volume or more, more preferably 9% by volume or more. On the other hand, the hydrogen is preferably 23% by volume or less, more preferably 21% by volume or less. In addition, the dew point of the atmosphere in the second half of the heating process is preferably -18°C or more, more preferably -16°C or more. On the other hand, the dew point is preferably 18°C ​​or less, more preferably 16°C or less. In addition, the average heating rate in the second half of the heating process is preferably 43°C / second or more, more preferably 45°C / second or more. On the other hand, the average heating rate is preferably 58°C / second or less, more preferably 55°C / second or less. The average heating rate refers to the value obtained by dividing the heating temperature from the heating start temperature to the heating arrival temperature by the heating time from the heating start temperature to the heating arrival temperature. In addition, the temperature range of the heating in the second half of the heating process is preferably 785°C or more, more preferably 790°C or more. On the other hand, the temperature range is preferably 1040°C or less, more preferably 1030°C or less.

[0328] [Heat soaking process]

[0329] In the soaking process of the final annealing step, the steel sheet after the temperature increase process may be soaked in an atmosphere having a hydrogen content of 5 volume % to 25 volume % and a dew point of -20°C to 20°C, within a temperature range of 780°C to 1050°C for 10 seconds to 20 seconds.

[0330] The hydrogen content of the atmosphere during the soaking process is preferably 7% by volume or more, more preferably 9% by volume or more. On the other hand, the hydrogen content is preferably 23% by volume or less, more preferably 21% by volume or less. In addition, the dew point of the atmosphere during the soaking process is preferably -18°C or more, more preferably -16°C or more. On the other hand, the dew point is preferably 18°C ​​or less, more preferably 16°C or less. In addition, the temperature range maintained during the soaking process is preferably 785°C or more, more preferably 790°C or more. On the other hand, the temperature range is preferably 1040°C or less, more preferably 1030°C or less. In addition, the time during the soaking process maintained within the above-mentioned temperature range is preferably 12 seconds or more, more preferably 14 seconds or more. On the other hand, the time is preferably 18 seconds or less, more preferably 16 seconds or less.

[0331] [Cooling process]

[0332] In the cooling process of the final annealing step, the steel sheet after the soaking process may be cooled to a temperature in the range of room temperature or higher and 720° C. or lower.

[0333] The temperature range of cooling during the cooling process is preferably 100°C or more, more preferably 150°C or more. On the other hand, the temperature range is preferably 700°C or less, more preferably 650°C or less. In addition, the average cooling rate during the cooling process is not particularly limited. However, the average cooling rate is preferably 5°C / second or more, more preferably 7°C / second or more. On the other hand, the average cooling rate is preferably 20°C / second or less, more preferably 15°C / second or less. The average cooling rate refers to the value obtained by dividing the temperature from the soaking temperature to the cooling completion temperature by the cooling time from the soaking temperature to the cooling completion temperature.

[0334] [Nitriding annealing process]

[0335] In the nitriding annealing step, the steel sheet after the final annealing step may be held in an atmosphere having a nitrogen content of 95 volume % to 100 volume % and a dew point of -50°C to 0°C within a temperature range of 680°C to 720°C for 70 seconds to 90 seconds.

[0336] The nitrogen in the atmosphere of the nitriding annealing process is preferably 96% by volume or more, more preferably 97% by volume or more. On the other hand, the nitrogen is preferably 99% by volume or less, more preferably 98% by volume or less. In addition, the dew point of the atmosphere of the nitriding annealing process is preferably above -45°C, more preferably above -40°C. On the other hand, the dew point is preferably below -5°C, more preferably below -10°C. In addition, the temperature range maintained in the nitriding annealing process is preferably above 685°C, more preferably above 690°C. On the other hand, the temperature range is preferably below 715°C, more preferably below 710°C. In addition, the time for maintaining the above-mentioned temperature range in the nitriding annealing process is preferably 73 seconds or more, more preferably 75 seconds or more. On the other hand, the time is preferably 88 seconds or less, more preferably 85 seconds or less.

[0337] By the above-mentioned nitriding annealing, nitrides (such as AlN, etc.) are formed on the surface layer of the steel sheet, and by the nitrides, the average crystal grain size in the surface region from the surface of the base steel sheet to 1 / 20 of the plate thickness of the final non-oriented electromagnetic steel sheet is controlled to be fine. Conventionally, when manufacturing non-oriented electromagnetic steel sheets, unlike the present embodiment, nitrides are not actively formed on the surface layer of the steel sheet. In addition, it is generally believed that if nitrides are formed on the surface layer of the steel sheet, it will have an adverse effect on the magnetic properties of the non-oriented electromagnetic steel sheet. The present inventors have found that by performing nitriding annealing after the final annealing, the average crystal grain size in the surface region of the base steel sheet of the final non-oriented electromagnetic steel sheet is controlled to be fine, and as a result, the iron loss and mainly the eddy current loss when the skin effect that becomes significant at high frequencies exists are reduced.

[0338] [Film forming process]

[0339] In the coating forming step, the steel sheet after the nitriding annealing step may be subjected to the coating forming process and, if necessary, to the annealing process.

[0340] [Film formation process]

[0341] The film forming conditions in the film forming process are not particularly limited and may be set to known conditions. For example, an insulating film consisting only of organic components, only of inorganic components, or of an organic-inorganic composite may be applied to the surface of a steel plate to form a film. From the viewpoint of reducing the environmental load, an insulating film that does not contain chromium may also be formed. In addition, the film forming step may also be a step of implementing an insulating coating that exerts adhesive ability by heating and pressurizing. Coating materials that exert adhesive ability include acrylic resins, phenolic resins, epoxy resins, melamine resins, and the like.

[0342] [Annealing process]

[0343] In the annealing process, the steel sheet may be kept in a temperature range of 750° C. to 850° C. for 30 minutes to 150 minutes. In addition, the steel sheet used in the annealing process may be a steel sheet after the coating process or a steel sheet that has been punched and processed after the coating process to give a shape for forming an iron core.

[0344] The temperature range maintained during the annealing process is preferably 760°C or more, more preferably 770°C or more. On the other hand, the temperature range is preferably 840°C or less, more preferably 830°C or less. In addition, the time maintained in the above temperature range during the annealing process is preferably 45 minutes or more, more preferably 60 minutes or more. On the other hand, the time is preferably 135 minutes or less, more preferably 120 minutes or less.

[0345] Through this annealing process, the residual strain in the steel is removed, and the steel is recrystallized, and the grains grow to a preferred grain size. At this time, in the surface region of the base steel plate, the average crystal grain size is controlled to be fine by the above-mentioned nitrides. The non-oriented electrical steel sheet manufactured by the annealing process in the film forming step has the above-mentioned characteristics of the non-oriented electrical steel sheet.

[0346] The atmosphere during the annealing process is not particularly limited. For example, the atmosphere during the annealing process may be a nitrogen atmosphere, a hydrogen atmosphere, or a mixed atmosphere of nitrogen and hydrogen. In addition, the dew point of the atmosphere during the annealing process is preferably above -50°C, more preferably above -40°C. On the other hand, the dew point is preferably below 0°C, more preferably below -10°C.

[0347] [Hot rolled sheet annealing process]

[0348] The method for manufacturing the non-oriented electrical steel sheet of the present embodiment may also include a hot-rolled sheet annealing step after the hot rolling step. By performing the hot-rolled sheet annealing, preferred magnetic properties can be obtained. The hot-rolled sheet annealing may also be a heat preservation treatment in which the hot-rolled steel sheet is kept hot during the cooling process after hot rolling.

[0349] The conditions for annealing the hot-rolled sheet are not particularly limited and may be any known conditions. For example, in the case of box annealing, it is preferably kept in a temperature range of 700°C to 900°C for 60 minutes to 20 hours. In the case of continuous annealing, it is preferably kept in a temperature range of 900°C to 1100°C for 1 second to 180 seconds.

[0350] [Pickling process]

[0351] The method for manufacturing the non-oriented electrical steel sheet of the present embodiment may also include a pickling step after the hot rolling step or after the hot rolled sheet annealing step. The scale formed on the surface of the steel sheet may be removed by pickling. The pickling conditions are not particularly limited and may be any known conditions.

[0352] [Surface treatment process]

[0353] The method for producing a non-oriented electrical steel sheet of the present embodiment may include a surface treatment step after the hot rolling step, after the hot rolled sheet annealing step, after the pickling step, after the cold rolling step, after the final annealing step, or after the nitriding annealing step.

[0354] In the surface treatment process, AlSi plating, AlMn plating, AlSiMn plating, etc. can be applied to the surface of the steel sheet. These plating alloys diffuse in the steel sheet through final annealing, nitriding annealing, and film forming annealing, and the R value is appropriately controlled in the region from the surface of the base steel sheet to 1 / 10 of the sheet thickness and in the region from 1 / 10 to 1 / 2 of the sheet thickness of the final non-oriented electromagnetic steel sheet.

[0355] The Al contained in the coating disposed on the surface of the steel sheet is preferably 90% by mass or more, more preferably 95% by mass or more. On the other hand, the Al is preferably 100% by mass or less, more preferably 99% by mass or less. In addition, the Si contained in the coating disposed on the surface of the steel sheet is preferably 0.1% by mass or more, more preferably 0.3% by mass or more. On the other hand, the Si is preferably 10% by mass or less, more preferably 7% by mass or less. In addition, the Mn contained in the coating disposed on the surface of the steel sheet is preferably 0.01% by mass or more, more preferably 0.1% by mass or more. On the other hand, the Mn is preferably 5% by mass or less, more preferably 3% by mass or less.

[0356] In addition, the thickness of the coating disposed on the surface of the steel sheet is preferably 5 μm or more, more preferably 7 μm or more. On the other hand, the thickness is preferably 30 μm or less, more preferably 25 μm or less. In addition, when the coating is applied before cold rolling, since the thickness of the coating is reduced to about 1 / 5 by cold rolling, it is preferably set to a thickness that is expected to be reduced in thickness during cold rolling. For example, within the above numerical range, it is preferably set to 25 μm or more and 35 μm or less.

[0357] The method of arranging the coating on the surface of the steel sheet is not particularly limited, and may be, for example, hot dip coating, electroplating, molten salt electrolysis, PVD (Physical Vapor Deposition), or CVD (Chemical Vapor Deposition). Among them, hot dip coating is preferred in consideration of the material for motors and processing costs.

[0358] [Iron core]

[0359] The iron core of this embodiment only needs to include the above-mentioned non-oriented electromagnetic steel sheet. Specifically, the iron core only needs to be a laminated body formed by overlapping and integrating the non-oriented electromagnetic steel sheets having the above-mentioned characteristics and having a shape for forming the iron core. The iron core of this embodiment can be an integral punching type iron core or a split type iron core.

[0360] [Method for manufacturing iron core]

[0361] The manufacturing method of the iron core of the present embodiment only needs to include a step of stacking the above-mentioned non-oriented electromagnetic steel sheets. Specifically, the manufacturing method of the iron core only needs to include a stacking step of stacking and integrating the non-oriented electromagnetic steel sheets having the above-mentioned characteristics and having a shape for forming the iron core. The stacking number and stacking conditions of the non-oriented electromagnetic steel sheets can be adjusted according to the purpose.

[0362] In addition, when the steel sheet used in the method for manufacturing the iron core of the present embodiment does not have a shape for forming the iron core, a punching step of punching the steel sheet to obtain a punched component may be included before the lamination step. The punching shape and punching conditions of the steel sheet may be adjusted according to the purpose.

[0363] Furthermore, the method for manufacturing the core of the present embodiment may include a stress relief annealing step after the punching step or after the laminating step.

[0364] In addition, when the stress relief annealing process is performed by the manufacturing method of the iron core of the present embodiment, the annealing process of the coating forming process can also be omitted in the manufacturing method of the non-oriented electromagnetic steel sheet. For example, the steel sheet after the nitriding annealing process is subjected to the coating forming process of the coating forming process, but not subjected to the annealing process of the coating forming process, and the steel sheet after the coating forming process is subjected to the punching process, and the punched component is subjected to the lamination process. On this basis, the stress relief annealing process can be performed after the punching process or after the lamination process.

[0365] Through this stress relief annealing process, the strain remaining in the steel is removed, and at the same time, the steel is recrystallized and the grains grow to a preferred grain size. At this time, in the surface area of ​​the base steel plate of the blanking component, the average crystal grain size is controlled to be fine by the above-mentioned nitride. That is, the blanking component after the stress relief annealing process (or the blanking component constituting the laminated body after the stress relief annealing process) has the characteristics of the above-mentioned non-oriented electromagnetic steel sheet. Therefore, it can be determined whether the non-oriented electromagnetic steel sheet taken out by disassembling the iron core has the characteristics of the above-mentioned non-oriented electromagnetic steel sheet.

[0366] In the stress relief annealing process, the blanked component or the laminated body is kept in a temperature range of 750°C to 850°C for 30 minutes to 150 minutes. The atmosphere of the stress relief annealing process is not particularly limited. For example, the atmosphere of the stress relief annealing process can be a nitrogen atmosphere, a hydrogen atmosphere, or a mixed atmosphere of nitrogen and hydrogen. In addition, the dew point of the atmosphere of the stress relief annealing process can be

[0367] [Motor]

[0368] The motor of this embodiment only needs to include the above-mentioned iron core. In detail, the motor mainly includes a stator (stator), a rotor (rotor), a bearing, a bracket, and a wire, but the motor of this embodiment only needs to include the above-mentioned iron core as the iron core of the stator and the rotor. The motor of this embodiment is preferably a drive motor of a hybrid drive vehicle or an electric vehicle, for example, a PM motor such as an IPM motor or an SPM motor.

[0369] [Manufacturing method of electric motor]

[0370] The manufacturing method of the motor of the present embodiment only needs to include a step of stacking the above-mentioned non-oriented electromagnetic steel sheets to obtain an iron core and a step of assembling the iron core to obtain a motor. Specifically, the manufacturing method of the motor only needs to include a stacking step and an assembling step. The stacking step stacks the non-oriented electromagnetic steel sheets having the above-mentioned characteristics and having a shape for forming an iron core to obtain an iron core, and the assembling step assembles the iron core as a stator iron core or a rotor iron core to obtain a motor. The stacking number of non-oriented electromagnetic steel sheets, the stacking conditions, and the assembly conditions of the iron core can be adjusted according to the purpose.

[0371] In addition, similarly to the above-mentioned method for manufacturing an iron core, when the steel sheet provided for the method for manufacturing the motor of this embodiment does not have a shape for forming an iron core, a punching step of punching the steel sheet to obtain a punched component may be provided before the above-mentioned lamination step. The punching shape and punching conditions of the steel sheet may be adjusted according to the purpose.

[0372] In addition, similar to the above-mentioned method for manufacturing the iron core, the method for manufacturing the motor of the present embodiment may also include a stress relief annealing step after the above-mentioned punching step or after the above-mentioned lamination step. When the stress relief annealing step is implemented, the annealing process of the coating forming step may be omitted in the method for manufacturing the non-oriented electromagnetic steel sheet. As described above, the component after the stress relief annealing step has the characteristics of the above-mentioned non-oriented electromagnetic steel sheet. Therefore, it is possible to determine whether the non-oriented electromagnetic steel sheet taken out by disassembling the motor has the characteristics of the above-mentioned non-oriented electromagnetic steel sheet. In addition, the stress relief annealing conditions in the method for manufacturing the motor of the present embodiment may be the same as the stress relief annealing conditions in the above-mentioned method for manufacturing the iron core.

[0373] Example

[0374] The effect of one mode of the present invention is more specifically described by embodiments, but the conditions in the embodiments are a conditional example adopted to confirm the implementation possibility and effect of the present invention, and the present invention is not limited to this conditional example. As long as the present invention does not depart from the gist of the present invention and achieves the purpose of the present invention, various conditions can be adopted. Below, examples of the present invention and comparative examples are illustrated to specifically describe the present invention.

[0375] The non-oriented electrical steel sheets were manufactured by performing the steps under the conditions shown in Tables 7 to 42 using the slabs with adjusted chemical compositions. In any of the manufacturing methods, the slabs were manufactured by continuous casting, and pickling was performed after hot-rolled sheet annealing. In addition, hot-dip galvanizing was performed on the cold-rolled steel sheets as a surface treatment as needed.

[0376] In addition, except for the test No. 136 shown in the table, the nitriding annealing process was performed after the final annealing process. On the other hand, in the test No. 136, the final annealing process was performed after the nitriding annealing process. Regarding the nitriding annealing of the test No. 136, the nitrogen content of the atmosphere was 100%, the dew point of the atmosphere was -25°C, the annealing temperature was 770°C, and the annealing time was 80 seconds.

[0377] In addition, except for the test No. 137 shown in the table, in the film forming process, the annealing process was performed after the film forming process was performed. On the other hand, in the test No. 137, in the film forming process, after the film forming process was performed, punching was performed to give a shape for forming the iron core, and then stress relief annealing was performed at 800° C. for 60 minutes as an annealing process.

[0378] In the table, "Presence of electromagnetic stirring" indicates whether electromagnetic stirring was performed during continuous casting. "Presence of fine inclusions" indicates whether there are fine inclusions in the molten steel that promote the formation of solidification nuclei. "Cooling temperature" indicates the cooling completion temperature controlled when cooling the steel plate after the soaking process. "Coating type" indicates the type of insulating coating formed on the steel plate after the nitriding annealing process.

[0379] For the manufactured non-oriented electromagnetic steel sheets, the chemical composition, plate thickness, average crystal grain size, R value, plane strength and area ratio of {100} oriented grains were measured. Their measurement methods are as described above. Their measurement results are shown in Tables 1 to 51. In addition, the average crystal grain size and R value are the same values ​​in the two plate surfaces of the base steel plate. In addition, the plate thickness of the base steel plate is the same as the final plate thickness of the steel plate after the cold rolling process. In addition, the chemical composition of the base steel plate of the manufactured non-oriented electromagnetic steel plate is equivalent to the chemical composition of the slab except Al, Si, and Mn. The elements represented by "-" in the table indicate that no intentional control and manufacturing are performed.

[0380] The produced non-oriented electrical steel sheets were evaluated for magnetic flux density, magnetic permeability, and iron loss characteristics.

[0381] The magnetic flux density, magnetic permeability and iron loss characteristics are evaluated based on the single sheet magnetic property test method (Single Sheet Tester: SST) specified in JIS C2556:2015. In addition, a smaller test piece, such as a test piece with a width of 55 mm and a length of 55 mm, can be collected instead of collecting a test piece of the size specified in JIS, and the measurement according to the single sheet magnetic property test method can be carried out. In addition, when it is impossible to collect a test piece with a width of 55 mm and a length of 55 mm, two test pieces with a width of 8 mm and a length of 16 mm can be used as test pieces with a width of 16 mm and a length of 16 mm, and the measurement according to the single sheet magnetic property test method can be carried out. At this time, it can also be set as an Epstein equivalent value converted to the measured value in the Epstein tester specified in JIS C2550:2011.

[0382] As the high magnetic field flux density, the magnetic flux density B in the rolling direction when the steel sheet is magnetized with a magnetizing force of 5000 A / m is measured in units of T (Tesla). 50 The magnetic flux density B 50 The case with a value of 1.60 T or more is considered acceptable. 50 When it exceeds 1.63 T, it is judged that the high-field magnetic flux density is suitably excellent.

[0383] As the high-frequency iron loss characteristic, the iron loss W in the rolling direction when the steel sheet is magnetized at 1 kHz to a magnetic flux density of 1.0 T is measured in units of W / kg. 10 / 1k The iron loss W 10 / 1k The case with a value of 36 W / kg or less is considered acceptable. 10 / 1k When the power is less than 35 W / kg, it is judged that the high-frequency iron loss characteristics are suitably excellent.

[0384] The magnetic permeability is determined by measuring the magnetic permeability in the rolling direction of the steel plate when the steel plate is magnetized to 1.0 T in a DC magnetic field in units of H / m. The case where the magnetic permeability is 0.007 H / m or more is judged to be acceptable. In addition, the case where the magnetic permeability is 0.010 H / m or more is judged to be suitably excellent in magnetic permeability, and the case where the magnetic permeability is 0.013 H / m or more is judged to be more excellent in magnetic permeability.

[0385] In addition, as the commercial frequency iron loss, the iron loss W in the rolling direction when the steel sheet is magnetized at 50 Hz to a magnetic flux density of 1.5 T is measured in units of W / kg. 15 / 50 The iron loss W 15 / 50 The case with a value of 2.22 W / kg or less is considered acceptable. 15 / 50 The case of 2.20 W / kg or less was judged to be suitably excellent in commercial frequency iron loss, and the case of less than 2.10 W / kg was judged to be more suitably excellent in commercial frequency iron loss.

[0386] As shown in Tables 1 to 51, in Test No. 1 to 214, the examples of the present invention all appropriately controlled the chemical composition, plate thickness and average crystal grain size as non-oriented electrical steel sheets, and were excellent in high-frequency iron loss. In addition, although not shown in the table, the average crystal grain size in the middle region of the examples of the present invention was equivalent to the average crystal grain size in the region from 1 / 20 of the plate thickness to 1 / 10 of the plate thickness.

[0387] Another invention is that in Test Nos. 1 to 214, at least one of the chemical composition, sheet thickness or average grain size of the comparative example was not properly controlled. In addition, the non-oriented electrical steel sheet of Test No. 124 did not have an insulating coating, and it was obvious that the magnetic properties were deteriorated when the non-oriented electrical steel sheets were stacked, so the magnetic flux density and iron loss characteristics were not evaluated.

[0388] Next, the manufactured non-oriented electromagnetic steel sheet is punched as required, and the punched components are stacked to manufacture an iron core. The manufactured iron core includes the above-mentioned non-oriented electromagnetic steel sheet. In addition, the manufactured iron core is subjected to stress relief annealing as required, and the iron core is used as a stator iron core or a rotor iron core for assembly to manufacture a motor. The manufactured motor includes the above-mentioned iron core. In addition, in the above-mentioned stress relief annealing, the iron core is kept in a temperature range of 750°C to 850°C for 30 minutes to 150 minutes.

[0389] The manufactured motor is connected to the load motor via a torque sensor (TM308 manufactured by MAGTROL). The manufactured motor is driven by supplying three-phase AC current from an inverter. The current and voltage supplied from the inverter are measured as input using a power meter (model WT1804E manufactured by Yokogawa Electric). Based on the torque T (unit: N·m) and the rotation speed N (rpm) measured by the torque sensor, 2πTN / 60=output (W) is set. The efficiency (%) is calculated by output / input×100.

[0390] When the iron cores and motors manufactured used the non-oriented electromagnetic steel sheets as examples of the present invention in the above-mentioned Tests No. 1 to 214, the torque characteristics and energy efficiency were excellent. On the other hand, when the iron cores and motors manufactured used the non-oriented electromagnetic steel sheets as comparative examples in the above-mentioned Tests No. 1 to 214, the torque characteristics and energy efficiency were not excellent compared with the case of using the non-oriented electromagnetic steel sheets as examples of the present invention.

[0391] In addition, since the annealing temperature in the annealing process of the coating formation step of the non-oriented electromagnetic steel sheet of Test No. 125 is 700°C, the average grain size of the intermediate region and the central region of the base steel sheet is not properly controlled. However, in the motor manufactured using the non-oriented electromagnetic steel sheet of Test No. 125, the average grain size of the intermediate region and the central region is properly controlled by stress relief annealing, so the torque characteristics and energy efficiency of the motor are equivalent to those of the motor manufactured using the non-oriented electromagnetic steel sheet of Test No. 9.

[0392] Furthermore, the non-oriented electrical steel sheets taken out by disassembling the iron cores and motors produced using the non-oriented electrical steel sheets of the present invention in the above Test Nos. 1 to 214 showed that the chemical composition, sheet thickness and average grain size were appropriately controlled, similar to the above results.

[0393] [Table 1]

[0394]

[0395] [Table 2]

[0396]

[0397] [Table 3]

[0398]

[0399] [Table 4]

[0400]

[0401] [Table 5]

[0402]

[0403] [Table 6]

[0404]

[0405] [Table 7]

[0406]

[0407] [Table 8]

[0408]

[0409] [Table 9]

[0410]

[0411] [Table 10]

[0412]

[0413] [Table 11]

[0414]

[0415] [Table 12]

[0416]

[0417] [Table 13]

[0418]

[0419] [Table 14]

[0420]

[0421] [Table 15]

[0422]

[0423] [Table 16]

[0424]

[0425] [Table 17]

[0426]

[0427] [Table 18]

[0428]

[0429] [Table 19]

[0430]

[0431] [Table 20]

[0432]

[0433] [Table 21]

[0434]

[0435] [Table 22]

[0436]

[0437] [Table 23]

[0438]

[0439] [Table 24]

[0440]

[0441] [Table 25]

[0442]

[0443] [Table 26]

[0444]

[0445] [Table 27]

[0446]

[0447] [Table 28]

[0448]

[0449] [Table 29]

[0450]

[0451] [Table 30]

[0452]

[0453] [Table 31]

[0454]

[0455] [Table 32]

[0456]

[0457] [Table 33]

[0458]

[0459] [Table 34]

[0460]

[0461] [Table 35]

[0462]

[0463] [Table 36]

[0464]

[0465] [Table 37]

[0466]

[0467] [Table 38]

[0468]

[0469] [Table 39]

[0470]

[0471] [Table 40]

[0472]

[0473] [Table 41]

[0474]

[0475] [Table 42]

[0476]

[0477] [Table 43]

[0478]

[0479] [Table 44]

[0480]

[0481] [Table 45]

[0482]

[0483] [Table 46]

[0484]

[0485] [Table 47]

[0486]

[0487] [Table 48]

[0488]

[0489] [Table 49]

[0490]

[0491] [Table 50]

[0492]

[0493] [Table 51]

[0494]

[0495] Industrial Availability

[0496] According to the above aspect of the present invention, a non-oriented electromagnetic steel sheet having excellent high-frequency iron loss can be provided. In addition, an iron core including the non-oriented electromagnetic steel sheet and a method for manufacturing the iron core, and a motor including the iron core and a method for manufacturing the motor can be provided, so that the industrial applicability is high.

[0497] Description of Reference Numerals

[0498] 1Non-oriented electromagnetic steel sheet

[0499] 11Insulation coating

[0500] 12 Base steel plate

[0501] 12a From the surface of the base steel plate to the surface area of ​​1 / 20 of the plate thickness

[0502] 12b The middle area from 1 / 20 to 1 / 4 of the thickness of the parent steel plate

[0503] 12c The central area from 1 / 4 to 1 / 2 of the base steel plate thickness

Claims

1. A non-oriented electrical steel sheet comprising a base steel sheet and an insulating film, characterized in that: The base steel plate contains, as a chemical composition, Si in mass %: 1.0% to 5.0%; C: 0% or more and 0.0050% or less, Mn: 0% to 3.0% or less, P: 0% or more and 0.30% or less, S: 0% or more and 0.010% or less, Al: 0% to 3.0% Zn: 0% or more and 0.10% or less, N: 0% or more and 0.010% or less, Sn: 0% or more and 0.10% or less, Sb: 0% or more and 0.10% or less, Ca: 0% or more and 0.010% or less, Cr: 0% or more but less than 5.0% Ni: 0% to 5.0% Cu: 0% or more and 5.0% or less, Ce: 0% or more and 0.10% or less, B: 0% or more but less than 0.10% O: 0% or more and 0.10% or less, Mg: 0% or more and 0.10% or less, Ti: 0% or more and 0.10% or less, V: 0% or more and 0.10% or less, Zr: 0% or more and 0.10% or less, Nd: 0% or more and 0.10% or less, Bi: 0% or more and 0.10% or less, W: 0% or more and 0.10% or less, Mo: 0% or more and 0.10% or less, Nb: 0% or more and 0.10% or less, Y: 0% or more and 0.10% or less, The remainder is composed of Fe and impurities; The thickness of the base steel plate is not less than 0.10 mm and not more than 0.35 mm. When the base steel plate is observed from a cut surface in which the cutting direction is parallel to the plate thickness direction, the average crystal grain size is 10 μm or less in a surface region from the surface of the base steel plate to 1 / 20 of the plate thickness.

2. The non-oriented electrical steel sheet according to claim 1, wherein: When observing the base steel plate from the cut surface, In the intermediate region from 1 / 20 to 1 / 4 of the plate thickness based on the surface, the average crystal grain size is 50 μm or more and 200 μm or less, In a central region from 1 / 4 to 1 / 2 of the plate thickness based on the surface, the average crystal grain size is 50 μm or more and 200 μm or less.

3. The non-oriented electrical steel sheet according to claim 1, wherein: The base steel plate has the following chemical composition, expressed in mass %, The content of Sn is limited to 0% or more and less than 0.030%.

4. The non-oriented electrical steel sheet according to claim 1, wherein: When observing the base steel plate from the cut surface, When the R value calculated using the Si content, Al content, and Mn content in mass % contained in the base steel plate as the chemical composition is defined as R=9.9+12.4[Si]+10.0[Al]+6.6[Mn], In the area from the surface to 1 / 10 of the plate thickness, the R value is 60 or more and 250 or less. In a region from 1 / 10 to 1 / 2 of the plate thickness based on the surface, the R value is 30 or more and less than 60.

5. The non-oriented electrical steel sheet according to claim 2, wherein: When observing the base steel plate from the cut surface, When the R value calculated using the Si content, Al content, and Mn content in mass % contained in the base steel plate as the chemical composition is defined as R=9.9+12.4[Si]+10.0[Al]+6.6[Mn], In the area from the surface to 1 / 10 of the plate thickness, the R value is 60 or more and 250 or less. In a region from 1 / 10 to 1 / 2 of the plate thickness based on the surface, the R value is 30 or more and less than 60.

6. The non-oriented electrical steel sheet according to claim 1, wherein: The {100} plane strength is 2.4 or more at a 1 / 2 thickness portion based on the surface, and the area ratio of {100} oriented grains is 18% or more relative to the observation field of view.

7. The non-oriented electrical steel sheet according to claim 2, wherein: The {100} plane strength is 2.4 or more at a 1 / 2 thickness portion based on the surface, and the area ratio of {100} oriented grains is 18% or more relative to the observation field of view.

8. The non-oriented electrical steel sheet according to claim 4, wherein: The {100} plane strength is 2.4 or more at a 1 / 2 thickness portion based on the surface, and the area ratio of {100} oriented grains is 18% or more relative to the observation field of view.

9. The non-oriented electrical steel sheet according to claim 5, wherein: The {100} plane strength is 2.4 or more at a 1 / 2 thickness portion based on the surface, and the area ratio of {100} oriented grains is 18% or more relative to the observation field of view.

10. An iron core, It comprises the non-oriented electrical steel sheet according to any one of claims 1 to 9.

11. A method for manufacturing an iron core, The method comprises the step of laminating the non-oriented electrical steel sheets according to any one of claims 1 to 9.

12. A motor, It comprises the core as claimed in claim 10.

13. A method for manufacturing a motor, comprising the following steps: A step of laminating the non-oriented electrical steel sheets according to any one of claims 1 to 9 to obtain an iron core; and A process of assembling the iron core to obtain a motor.

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