Non-oriented electromagnetic steel plate, motor iron core and motor

Abstract

The present invention relates to a steel sheet having a composition capable of an alpha-gamma transformation, containing 0.3-0.7% of sol.Al and 0.0005-0.0020% of Ti, such that the contents of Si, Mn and sol.Al are in a predetermined relationship, and when the area ratio of crystal grains having a {hkl} < uvw > orientation (margin within 10 DEG) with respect to the entire field of view when the surface of the steel sheet is measured by a scanning electron microscope (SEM-EBSD) with electron beam backscatter diffraction is expressed as Ahkl-uvw, A411-011 is 15% or more, and the area ratio of crystal grains having a {hkl} < uvw > orientation (margin within 10 DEG) with respect to the entire field of view is Ahkl-uvw. And the number density of the precipitates is 0.0001 / [mu] m < 2 > to 0.3000 / [mu] m < 2 >.

Description

Technical Field

[0001] The present invention relates to a non-oriented electromagnetic steel sheet, a motor core, and a motor. This application claims priority based on Japanese Patent Application No. 2023-023379 filed in Japan on February 17, 2023, and incorporates the content of the application into this application. Background Art

[0002] Electromagnetic steel sheets are used as raw materials for the iron cores of motor equipment. Examples of motor equipment include drive motors mounted on automobiles, motors for various compressors such as those used in air conditioners and refrigerators, and generators for household or industrial use. These motor equipment require high energy efficiency, miniaturization, and high output. Therefore, electromagnetic steel sheets used as the iron cores of motor equipment require low iron loss and high magnetic flux density. As a solution, there is texture control, and a technology has been proposed: Previously, having an easy magnetization axis within the surface of a steel sheet was beneficial for improving magnetic properties, and it was relatively easy to improve the development of aggregated tissue (α fibers) through rolling processing in hot rolling and cold rolling, which are necessary steps in the manufacture of steel sheets. Specifically, a tissue is formed in which the <110> direction is roughly parallel to the rolling direction (RD).

[0003] Patent Documents 1 to 3 all disclose a method for developing the {100}<011> orientation and describe reducing the phase transition temperature and rapidly cooling after hot rolling to refine the structure.

[0004] Specifically, Patent Document 1 describes cooling the steel sheet to 250°C or below within 3 seconds after hot rolling at a cooling rate of 200°C / sec or higher, without annealing between hot and cold rolling, and setting the cumulative reduction ratio during cold rolling to 88% or higher. This allows the production of electromagnetic steel sheet with a {100}<011> orientation concentrated on the steel sheet surface.

[0005] In addition, Patent Document 2 discloses a method for manufacturing an electromagnetic steel sheet containing 0.6 mass% to 3.0 mass% Al, and describes that an electromagnetic steel sheet having a {100}<011> orientation concentrated in the steel sheet surface can be manufactured by the same steps as the method described in Patent Document 1.

[0006] On the other hand, Patent Document 3 describes setting the finishing temperature during hot rolling to above the Ac3 transformation point and cooling the steel sheet to 2050°C within 3 seconds after hot rolling, or setting the finishing temperature to below the Ac3 transformation point -50°C and cooling at a cooling rate exceeding the cooling rate. Furthermore, the manufacturing method described in Patent Document 3 involves performing two cold rolling cycles with intermediate annealing, with no annealing performed between the hot rolling and the first cold rolling, and setting the cumulative reduction ratio in the second cold rolling cycle to 5-15%. This method enables the production of electromagnetic steel sheets with a {100}<011> orientation concentrated on the steel sheet surface.

[0007] All of the methods described in Patent Documents 1 to 3 require immediate rapid cooling during hot rolling, after setting the finishing rolling temperature to the Ac3 point or higher, when producing electromagnetic steel sheets with a {100}<011> orientation on the steel sheet surface. Rapid cooling increases the cooling load after hot rolling. Considering operational stability, a method that reduces the load on the rolling mill performing cold rolling is desired.

[0008] Meanwhile, a technique has been proposed to enhance magnetic properties by developing a {411} orientation, which is rotated 20° from the {100} orientation. Patent Documents 4 to 7 disclose techniques for developing the {411} orientation, and describe optimizing the grain size in hot-rolled sheets or strengthening the α fibers in the texture of the hot-rolled sheets.

[0009] Specifically, Patent Document 4 describes cold rolling a hot-rolled sheet with a higher concentration of {211} orientation than {411}, with the cumulative reduction ratio during cold rolling set to 80% or higher. This enables the production of an electromagnetic steel sheet with a {411} orientation concentrated on the sheet surface.

[0010] Patent Documents 5 and 6 describe setting the slab heating temperature to 700°C to 1150°C, the start temperature of finish rolling to 650°C to 850°C, the end temperature of finish rolling to 550°C to 800°C, and the cumulative reduction ratio during cold rolling to 85-95%. This allows the production of electromagnetic steel sheets with a concentration of {100} and {411} orientations on the steel sheet surface.

[0011] On the other hand, Patent Document 7 states that when α fibers are grown near the surface of a hot-rolled steel sheet by strip casting or the like, the {h11}<1 / h12> orientation, especially the {100}<012> to {411}<148> orientation, will recrystallize during the subsequent hot-rolled sheet annealing.

[0012] The present inventors have studied the above-mentioned technology and have determined that, according to Patent Documents 1 to 3, strengthening the {100}<011> orientation to improve magnetic properties requires rapid cooling immediately after hot rolling, resulting in a problem of high manufacturing load. Furthermore, they have recognized that, when steel sheets strengthened with the {100}<011> orientation are used as raw materials for riveted cores, the core properties expected from the raw materials may not be achieved. Research into the cause of this has revealed that the {100}<011> orientation significantly increases the deterioration (stress sensitivity) of magnetic properties in response to stress, specifically, the deterioration of magnetic properties under compressive stress.

[0013] Furthermore, the techniques of Patent Documents 4 to 7 reveal that, despite the development of the {411} orientation, the concentration of the in-plane <011> orientation is weak, resulting in insufficient improvement in magnetic properties in the direction 45° from the steel sheet rolling direction, a characteristic of α-fibers. It is also possible that the lack of uniformity in the in-plane orientation with the <011> orientation, i.e., the significant deviation from the α-fiber orientation, is the primary factor hindering the concentration of the in-plane {411} orientation, thus preventing sufficient improvement in magnetic properties.

[0014] Furthermore, in non-oriented electrical steel sheets for automotive applications, there is a strong demand not only for higher magnetic flux density but also for lower iron loss. This reduction in iron loss has been achieved by reducing sheet thickness. However, reducing sheet thickness can lead to a decrease in motor production efficiency, so a method is needed to maintain sheet thickness while reducing iron loss.

[0015] Prior art literature

[0016] Patent Literature

[0017] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-145462

[0018] Patent Document 2: Japanese Patent Application Laid-Open No. 2017-193731

[0019] Patent Document 3: Japanese Patent Application Publication No. 2019-178380

[0020] Patent Document 4: Japanese Patent No. 4218077

[0021] Patent Document 5: Japanese Patent No. 5256916

[0022] Patent Document 6: Japanese Patent Application Laid-Open No. 2011-111658

[0023] Patent Document 7: Japanese Patent Application Publication No. 2019-183185 Summary of the Invention

[0024] Technical problem to be solved by the invention

[0025] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a non-oriented electrical steel sheet that achieves both low iron loss and high magnetic flux density without increasing the manufacturing load and without requiring a thinner sheet.

[0026] Technical means for solving technical problems

[0027] The present inventors conducted intensive research to solve the above-mentioned problems. As a result, they clarified that it is important to optimize the chemical composition, grain size after hot rolling, and reduction ratio during cold rolling. Specifically, based on the chemical composition of the α-γ transformation system, cooling is performed under predetermined conditions after hot rolling to optimize the grain size, and then cold rolling is performed at a predetermined reduction ratio. The temperature of the intermediate annealing is controlled within a predetermined range, and annealing is performed after the second cold rolling at an appropriate reduction ratio. In this way, it is important to facilitate the development of grains with the {411}<011> orientation, which is usually difficult to develop. Based on this understanding, the present inventors further conducted intensive research and came up with the various schemes of the invention shown below. (1)

[0029] A non-oriented electromagnetic steel sheet, characterized in that:

[0030] The chemical composition is as follows: in mass %,

[0031] C: 0.010% or less,

[0032] Si: 1.50% to 4.00%,

[0033] sol.Al: 0.3%~0.7%,

[0034] S: 0.010% or less,

[0035] N: 0.010% or less,

[0036] Ti: 0.0005% to 0.0020%,

[0037] One or more selected from the group consisting of Mn, Ni, and Cu: 2.50% to 5.00% in total, Co: 0.000% to 1.000%,

[0038] Sn: 0.000% to 0.400%,

[0039] Sb: 0.000% to 0.400%, and

[0040] P: 0.000%~0.400%,

[0041] When the Mn content (mass %) is represented by [Mn], the Ni content (mass %) is represented by [Ni], the Cu content (mass %) is represented by [Cu], the Si content (mass %) is represented by [Si], the sol.Al content (mass %) is represented by [sol.Al], and the P content (mass %) is represented by [P], the following equations (1) and (2) are satisfied:

[0042] The remainder is composed of Fe and impurities;

[0043] When the surface of the steel sheet is measured using a scanning electron microscope with electron beam backscatter diffraction (SEM-EBSD), the area ratio of grains with an orientation of {hkl}<uvw> (within a tolerance of 10°) relative to the entire field of view is expressed as Ahkl-uvw. For A411-011, the area ratio is 15% or more.

[0044] The number density of precipitates is 0.0001 / μm 2 ~0.3000 / μm 2 .

[0045] (2×[Mn]+2.5×[Ni]+[Cu])-([Si]+2×[sol.Al]+4×[P])≥3.0%···(1)

[0046] 10.5≤([Si]+[Mn])÷[sol.Al]≤12.5···(2)

[0047] A motor core, characterized in that:

[0048] The non-oriented electrical steel sheets described in (1) above are stacked. (3)

[0050] A motor, characterized in that

[0051] A motor core as described in (2) above is provided.

[0052] Effects of the Invention

[0053] According to the present invention, it is possible to provide a non-oriented electromagnetic steel sheet, a motor core, and a motor that achieve both low iron loss and high magnetic flux density without increasing the manufacturing load and without requiring thinning of the sheet thickness. DETAILED DESCRIPTION

[0054] Hereinafter, embodiments of the present invention will be described in detail.

[0055] First, the chemical compositions of the non-oriented electrical steel sheets, the steel materials used in the manufacturing methods thereof, and the cold-rolled steel sheets used to manufacture the non-oriented electrical steel sheets according to the embodiments of the present invention will be described. In the following description, "%," which represents the content of each element in the non-oriented electrical steel sheets or steel materials, means "mass %" unless otherwise specified. Furthermore, numerical ranges expressed with "to" indicate a range that includes the numerical values ​​listed before and after "to" as the lower and upper limits.

[0056] The non-oriented electrical steel sheet, cold-rolled steel sheet and steel material of the present embodiment have a chemical composition capable of generating a ferrite-austenite transformation (hereinafter referred to as α-γ transformation), and contain C: 0.010% or less, Si: 1.50% to 4.00%, sol. Al: 0.3% to 0.7%, S: 0.010% or less, N: 0.010% or less, Ti: 0.0005% to 0.0020%, one or more elements selected from the group consisting of Mn, Ni and Cu: 2.50% to 5.00% in total, Co: 0.000% to 1.000%, Sn: 0.000% to 0.400%, Sb: 0.000% to 0.400%, and P: 0.000% to 0.400%, with the remainder consisting of Fe and impurities. Furthermore, the contents of Mn, Ni, Cu, Si, sol.Al, and P satisfy predetermined conditions described below. Examples of impurities include those contained in raw materials such as ores and scraps, and those contained in the manufacturing process.

[0057] (C: 0.010% or less)

[0058] C precipitates as fine carbides, hindering grain growth and increasing iron loss, or causing magnetic aging. Therefore, the lower the C content, the better. This phenomenon is more pronounced when the C content exceeds 0.010%. Therefore, the C content is set to 0.010% or less. While there is no specific lower limit for the C content, it is preferably set to 0.0005% or more, considering the cost of decarburization during refining.

[0059] (Si: 1.50% to 4.00%)

[0060] Si increases electrical resistance to reduce eddy current loss, lowers iron loss, or increases yield ratio to improve punching workability in the iron core. When the Si content is less than 1.50%, these effects are not fully achieved. Therefore, the Si content is set to 1.50% or more. On the other hand, when the Si content exceeds 4.00%, the magnetic flux density decreases, or the punching workability decreases due to excessive increase in hardness, or cold rolling becomes difficult. Therefore, the Si content is set to 4.00% or less.

[0061] (sol.Al: 0.3% to 0.7%)

[0062] Sol.Al increases electrical resistance, reduces eddy current loss, and reduces iron loss. Sol.Al also helps to increase the relative size of magnetic flux density B50 relative to saturation magnetic flux density. Here, the so-called magnetic flux density B50 refers to the magnetic flux density in a magnetic field of 5000A / m. In addition, in order to reduce TiN, which is a fine precipitate that hinders the growth of {411}<110> particles due to expansion, it is necessary to make AlN, which is relatively coarse compared to TiN, easier to precipitate and reduce the number density of precipitates. When the sol.Al content is less than 0.3%, these effects are not fully achieved. In addition, sol.Al also has a desulfurization promoting effect in steelmaking. Therefore, the sol.Al content is set to 0.3% or more. On the other hand, when the sol.Al content exceeds 1.0%, the magnetic flux density decreases or the yield ratio decreases, thereby reducing the punching workability. Therefore, the sol.Al content is set to 0.7% or less. Preferably, the sol.Al content is 0.5% to 0.6%.

[0063] (S: 0.010% or less)

[0064] S is not an essential element and is contained in steel as an impurity, for example. S hinders recrystallization and grain growth during annealing due to the precipitation of fine MnS. Therefore, the lower the S content, the better. The increase in iron loss and the decrease in magnetic flux density caused by such hindrance of recrystallization and grain growth are more significant when the S content exceeds 0.010%. Therefore, the S content is set to 0.010% or less. In addition, the lower limit of the S content is not particularly limited, but it is determined based on the cost of desulfurization treatment during refining.

[0065] Preferably, it is set to 0.0003% or more.

[0066] (N: 0.010% or less)

[0067] Nitrogen degrades magnetic properties through the formation of fine precipitates such as TiN, so the lower the N content, the better. Therefore, the N content is set to 0.010% or less. While there is no particular lower limit for the N content, it is preferably set to 0.001% or more based on the cost of denitrification treatment during refining.

[0068] (Ti: 0.0005% to 0.0020%)

[0069] Ti is an element commonly contained in molten steel during the steelmaking process. From the perspective of refining costs, the Ti content is set to 0.0005% or higher. Furthermore, if the Ti content exceeds 0.0020%, a large amount of TiN forms as fine precipitates, degrading magnetic properties. Therefore, the Ti content is set to 0.0020% or lower. Preferably, the Ti content is between 0.0010% and 0.0015%.

[0070] (One or more selected from the group consisting of Mn, Ni, and Cu: 2.50% to 5.00% in total)

[0071] These elements are essential for the α-γ transformation and, as described later, contribute to the formation of AlN. Therefore, the total content of at least one of these elements must be 2.50% or more. On the other hand, if the total content exceeds 5.00%, costs may increase and magnetic flux density may decrease. Therefore, the total content of at least one of these elements should be set to 5.00% or less.

[0072] Furthermore, as a condition for the occurrence of the α-γ transformation, the following condition is also satisfied. That is, when the Mn content (mass %) is expressed as [Mn], the Ni content (mass %) is expressed as [Ni], the Cu content (mass %) is expressed as [Cu], the Si content (mass %) is expressed as [Si], the sol.Al content (mass %) is expressed as [sol.Al], and the P content (mass %) is expressed as [P], the following formula (1) is satisfied in terms of mass %.

[0073] (2×[Mn]+2.5×[Ni]+[Cu])-([Si]+2×[sol.Al]+4×[P])≥3.0%···(1)

[0074] If the above-mentioned formula (1) is not satisfied, the α-γ phase transformation will not occur, or even if the α-γ phase transformation occurs, it will become impossible to roll at the temperature of the γ region or the γ-α mixed region (above the Ar1 point) in the subsequent rolling process, so the magnetic flux density will become low.

[0075] Furthermore, it is understood that, in order to reduce the number density of fine precipitates such as TiN, when the component balance is adjusted in specific components, AlN, which is coarser than TiN, is easily generated, and the number density of fine precipitates can be reduced.

[0076] Since when Si is highly concentrated, the α phase is stabilized during the heating process of the slab, it is possible to reduce MnS derived from S that is easily dissolved in the α phase and increase AlN derived from N that is easily dissolved in the γ phase. On the other hand, when Si is highly concentrated, the amount of C dissolved in the steel is reduced during cold rolling, making it easy to generate TiC. In addition, when Mn is highly concentrated, MnS is easily generated, and when Al is highly concentrated, AlN is easily generated. The inventors have conducted various studies focusing on the generation balance of these precipitates, and in order to reduce the number density of fine precipitates, they have discovered a correlation between Si content, Mn content and Al content. Specifically, in the relationship between Si content, sol.Al content and Mn content, the following formula (2) is satisfied.

[0077] 10.5≤([Si]+[Mn])÷[sol.Al]≤12.5···(2)

[0078] Furthermore, when the upper and lower limits in formula (2) are set at 10.5 and 12.5, respectively, it becomes difficult to control the formation of AlN when these ranges are exceeded. In formula (2), when ([Si] + [Mn]) ÷ [sol.Al] is less than 10.5, AlN formation becomes excessive, and grain growth is hindered by AlN. On the other hand, when ([Si] + [Mn]) ÷ [sol.Al] exceeds 12.5, AlN formation becomes insufficient, and precipitates such as TiC and MnS increase, making it impossible to reduce the number density of fine precipitates.

[0079] (Co: 0.000% to 1.000%)

[0080] Co is an element effective in causing the α-γ transformation, so it can be contained as needed. However, if it is contained in excess, the cost may increase and the magnetic flux density may decrease. Therefore, the Co content is set to 1.000% or less.

[0081] (Sn: 0.000%~0.400%, Sb: 0.000%~0.400%)

[0082] Sn and Sb improve the texture after cold rolling and recrystallization, thereby increasing the magnetic flux density. Therefore, these elements may be included as needed, but excessive inclusion can embrittle the steel. Therefore, both the Sn and Sb contents are set to 0.400% or less. To achieve further effects on magnetic properties, as described above, it is preferred to include one or more selected from the group consisting of 0.020% to 0.400% Sn and 0.020% to 0.400% Sb.

[0083] (P: 0.000% to 0.400%)

[0084] P can be included to ensure the hardness of the steel sheet after recrystallization, but excessive inclusion can cause embrittlement of the steel. Therefore, the P content is set to 0.400% or less. To achieve further effects on magnetic properties, etc., a P content of 0.020% to 0.400% is preferred.

[0085] Next, the method for measuring the area ratio of specifically oriented grains in the non-oriented electrical steel sheet of this embodiment will be described. Regarding the area ratio of specifically oriented grains, OMI Analysis 7.3 (manufactured by TSL) was used to extract the target specific orientation (with a tolerance of 10°, hereinafter referred to as "within 10°") from the measurement area of ​​a scanning electron microscope (SEM) using electron beam backscatter diffraction (EBSD) under the following measurement conditions. The extracted area was divided by the area of ​​the measurement area to calculate the percentage. This percentage was used as the area ratio of specifically oriented grains. Hereinafter, the "area ratio of grains with a {hkl}<uvw> orientation (within 10° tolerance) relative to the measurement area" and the "area ratio of grains with a {hkl} orientation (within 10° tolerance) relative to the measurement area" may be referred to as the "{hkl}<uvw> ratio" and the "{hkl} ratio," respectively. In the following description of crystal orientation, it is assumed that the margin is within 10°.

[0086] In the non-oriented electrical steel sheet of this embodiment, when the steel sheet surface is measured using SEM-EBSD, the {411}<011> ratio is set to 15% or greater. If the {411}<011> ratio is less than 15%, excellent magnetic properties cannot be achieved. Therefore, the {411}<011> ratio is set to 15% or greater, preferably 25% or greater.

[0087] In addition, the details of the measurement conditions for obtaining the area ratio of each oriented grain are as follows.

[0088] Measurement equipment: SEM model "JSM-6400 (manufactured by JEOL), EBSD detector model "HIKARI (manufactured by TSL)"

[0089] Step interval: 0.3μm (after intermediate annealing and skin-pass rolling), or 5.0μm (after final annealing)

[0090] · Magnification: 1000 times (after intermediate annealing and skin-pass rolling), or 100 times (after final annealing)

[0091] ·Measurement object: The center layer (1 / 2 of the plate thickness) of the Z plane (the cross section obtained by cutting the steel plate along the plate thickness direction) in the center of the C direction of the steel plate

[0092] Measurement area: 1000 μm or more in the L direction and 1000 μm or more in the C direction

[0093] In addition, it is preferable that when the steel plate surface is measured by SEM-EBSD, When Φ=20°, Has maximum strength and Among Φ=0~90°, Φ=5~35° has the maximum strength. When Φ=20°, Having the maximum intensity is synonymous with having the maximum intensity near the {411}<011> orientation in the {411}<uvw> orientation. Compared with {411}<148> and the like, the {411}<011> orientation has excellent magnetic properties in the 45° direction. When Φ=20°, It is more preferred when it has the maximum strength.

[0094] On the other hand, when the steel plate surface is measured by SEM-EBSD, The maximum strength at Φ = 5 to 35° in the range of Φ = 0 to 90° is equivalent to the maximum strength near the {411} <011> orientation in the {hkl} <011> orientation. The {411} <011> orientation has excellent magnetic properties and is less stress-sensitive than the {100} <011> orientation, so magnetic degradation in riveted cores, etc. is less. Among Φ=0 to 90°, Φ=20 to 30° is more preferred as it has the highest strength.

[0095] Here, the method for determining the maximum strength within a specific orientation range in a steel plate is described. In the measurement area based on SEM-EBSD, OMI Analysis 7.3 was used to create an orientation distribution function (ODF) under the following conditions. Then, the data of the created ODF was output and the maximum strength within a specific orientation range (in The point where the ODF value is the largest within the range specified by the angle Φ is taken as the maximum intensity.

[0096] In addition, the determination method of the ODF strength of a specific orientation in a steel plate is described. In the measurement area based on SEM-EBSD, OMI Analysis 7.3 is used to prepare an ODF under the following conditions. Then, the data of the prepared ODF is output and the specific orientation (in The ODF value (the orientation is specified by the angle Φ) is taken as the ODF intensity.

[0097] In addition, the details of the production conditions of ODF are as follows.

[0098] Series Rank [L]: 16

[0099] Gaussian Half-Width (degrees): 5

[0100] Sample Symmetry: Triclinic (None)

[0101] Bunge Euler Angles: Φ=0~90°

[0102] Furthermore, the area ratio of grains having a specific orientation (within a tolerance of 10°) relative to the entire field of view when measured by SEM-EBSD is expressed as follows: When the area ratio of grains having a crystal orientation of {hkl}<uvw> (within a tolerance of 10°) relative to the entire field of view is expressed as Ahkl-uvw, and the area ratio of grains having a crystal orientation of {hkl} (within a tolerance of 10°) relative to the entire field of view is expressed as Ahkl, both the following equations (3) and (4) are satisfied.

[0103] A411-011 / A411-148≥1.1··· (3)

[0104] A411-011 / A100-011≥2··· (4)

[0105] Furthermore, magnetic properties are superior when there are more grains with a {411} orientation, but inferior when there are more grains with a {111} orientation. Therefore, it is preferable that the {411} ratio exceeds the {111} ratio, and more preferably, the {411} ratio is at least twice the {111} ratio.

[0106] Next, the number density of precipitates in the non-oriented electrical steel sheet of this embodiment will be described. Here, the precipitates are mainly fine precipitates such as TiN, but also include fine precipitates such as AlN and MnS. Since the chemical composition contains Ti and Al, the number density of these precipitates is substantially less than 0.0001 precipitates / μm. 2 On the other hand, when the number of precipitates increases, the number density of precipitates is less than 0.3000 / μm. 2 If the value is larger, the amount of TiN (or AlN) as precipitates will be excessive, and the magnetic properties will deteriorate. Therefore, the number density of precipitates in the non-oriented electrical steel sheet is set to 0.0001 pieces / μm. 2 ~0.3000 / μm 2 .

[0107] The number density of precipitates is determined, for example, by observing the sample using a transmission electron microscope (TEM) by the extraction replication method and calculating the number density. Specifically, a transmission electron microscope is used to observe the surface at a depth of 1 / 2 relative to the plate thickness t from the surface of the steel plate by the extraction replication method, and in the same sample, the number of fine precipitates with an equivalent circle diameter of 20 to 500 nm in a field of view of 5 μm × 5 μm is measured. However, during the observation, coarse precipitates (equivalent circle diameter of 1 μm or more) that are not included in the calculation of the number density are not included in the field of view. Then, in the same sample, the number of precipitates is measured in more than 10 fields of view, and the average value is calculated as the number density of precipitates. In addition, image analysis software can also be used when measuring the number of precipitates.

[0108] Next, the thickness of the non-oriented electromagnetic steel sheet of the present embodiment will be described. The thickness of the non-oriented electromagnetic steel sheet of the present embodiment is not particularly limited. The preferred thickness of the non-oriented electromagnetic steel sheet of the present embodiment is 0.25 to 0.50 mm. Generally, although the iron loss decreases as the plate thickness decreases, the magnetic flux density also decreases. Based on this, when the plate thickness is 0.25 mm or more, the iron loss is lower and the magnetic flux density becomes higher. In addition, when the plate thickness is 0.50 mm or less, low iron loss can be maintained. A more preferred lower limit of the plate thickness is 0.30 mm.

[0109] Furthermore, the non-oriented electrical steel sheet of this embodiment preferably has excellent magnetic properties such as a magnetic flux density B50 at a 45° angle relative to the rolling direction of 1.70 T or greater, and an iron loss W10 / 400 at a 45° angle relative to the rolling direction of 14 W / kg or less. Furthermore, regarding strength, a tensile strength of 600 MPa or greater is preferred.

[0110] The tensile strength was determined by taking a JIS No. 5 test piece with the rolling direction of the non-oriented electrical steel sheet as the longitudinal direction and performing a tensile test in accordance with JIS Z2241:2011.

[0111] The above-mentioned non-oriented electrical steel sheet is characterized by the non-oriented electrical steel sheet manufactured by final annealing. Hereinafter, the characteristics of the non-oriented electrical steel sheet before final annealing (after skin pass rolling) will be described.

[0112] The non-oriented electrical steel sheet after skin-pass rolling (before final annealing) of the present embodiment has the following GOS (Grain Orientation Spread) value (Gs). Here, the GOS value is obtained by averaging the orientation differences between all measurement points (pixels) within the same grain. When the grain has a large strain, the GOS value becomes higher. After skin-pass rolling, the GOS value Gs is small, that is, when it is in a low strain state, grain growth due to expansion is likely to occur in the next step, namely, final annealing. Therefore, the upper limit of the GOS value Gs after skin-pass rolling is set to 3.0. On the other hand, when the GOS value Gs is less than 0.8, the strain amount becomes too small, and the final annealing time spent on grain growth due to expansion becomes longer. Therefore, the GOS value Gs after skin-pass rolling is set to be greater than 0.8 and less than 3.0.

[0113] Here, the calculation method of Gs in the steel plate is described: SEM-EBSD data when the crystal orientation is specified as described above is analyzed using OIM Analysis 7.3, and the number average of the GOS values ​​is calculated and used as Gs.

[0114] Furthermore, in non-oriented electrical steel sheets after skin-pass rolling (before final annealing), the greater the α-fiber ratio, the more superior the magnetic properties after final annealing. Here, the method for measuring the α-fiber ratio is described. In this embodiment, α-fibers are assumed to have an orientation of {hkl}<011>. Within the measurement area using SEM-EBSD, OMIAnalysis 7.3 is used to extract (within a tolerance of 10°) the {hkl}<011> orientation. The extracted area is divided by the area of ​​the measurement area to calculate the percentage. This percentage is referred to as the α-fiber ratio.

[0115] In the non-oriented electrical steel sheet after skin pass rolling (before final annealing), the α fiber ratio is set to 20% or more, preferably 25% or more.

[0116] In addition, in the non-oriented electrical steel sheet after skin temper rolling (before final annealing), the ODF strength of the {100}<011> orientation is set to 15 or less. Here, the ODF strength of the {100}<011> orientation is the ODF strength prepared by the SEM-EBSD data when the above-mentioned crystal orientation is specified. ODF Value at Φ = 0°. The {411}<011> orientation has excellent magnetic properties and is less stress-sensitive than the {100}<011> orientation, resulting in less magnetic degradation in rivet cores, etc. By setting the ODF strength of the {100}<011> orientation to 15 or less after skin pass rolling (before final annealing), the {411}<011> orientation after the subsequent final annealing can be strengthened.

[0117] The non-oriented electromagnetic steel sheets of this embodiment can be used to form an iron core and are widely applicable to applications requiring magnetic properties (high magnetic flux density and low iron loss). They can also be used in applications requiring particularly high strength, such as rotors. Specifically, the non-oriented electromagnetic steel sheets of this embodiment are laminated to form a motor iron core and are widely applicable to applications such as motors having such a motor iron core. They can also be used to form rotors of motors.

[0118] Next, an example of a method for producing a non-oriented electrical steel sheet according to the present embodiment is described. In the present embodiment, hot rolling, cold rolling, intermediate annealing, second soft reduction cold rolling (hereinafter referred to as skin pass rolling), and final annealing are performed.

[0119] In hot rolling, a steel material satisfying the above chemical composition is hot-rolled to produce a hot-rolled sheet. The hot rolling process includes a heating process and a rolling process.

[0120] The steel material is, for example, a slab produced by conventional continuous casting. The steel material with the above-mentioned composition is produced using well-known methods. For example, molten steel is produced in a converter or electric furnace. The produced molten steel is then subjected to secondary refining using degassing equipment or the like to produce molten steel with the above-mentioned chemical composition. The molten steel is then cast into slabs using a continuous casting method or an ingot casting method. Alternatively, the cast slabs may be subjected to bloom rolling.

[0121] During the heating process, to prevent Ti from dissolving and precipitating as TiN, the steel material having the above chemical composition is preferably heated to 1000-1080°C. Specifically, the steel material is placed in a heating furnace or soaking furnace and heated within the furnace. The holding time at the above heating temperature in the heating furnace or soaking furnace is not particularly limited, but is, for example, 30-200 hours. Furthermore, during slab heating, to prevent Ti from dissolving, the heating rate from 600°C to the heating temperature is set to 0.02°C / second or less.

[0122] In the rolling process, the steel material heated in the heating process is subjected to multiple rolling passes to produce hot-rolled plates. Here, the so-called "pass" means that the steel plate is pressed down by a rolling mill having a pair of work rolls. For example, hot rolling can be performed by tandem rolling using a tandem rolling mill comprising a plurality of rolling mills arranged in a row (each rolling mill having a pair of work rolls) and performing multiple rolling passes, or by reversible rolling using a pair of work rolls and performing multiple rolling passes. From the perspective of productivity, it is preferable to perform multiple rolling passes using a tandem rolling mill.

[0123] The rolling process (rough rolling and finishing rolling) is performed at a temperature in the γ region or the γ-α mixed region (Ar1 point or higher). In other words, hot rolling is performed so that the temperature at the final pass of finishing rolling (finishing rolling temperature FT (°C)) is at or above the Ar1 point.

[0124] Here, the finishing temperature FT refers to the surface temperature (°C) of the steel plate at the exit of the rolling stand where the final reduction pass is performed during the hot rolling process. The finishing temperature FT can be measured, for example, using a thermometer installed at the exit of the rolling stand where the final reduction pass is performed. Furthermore, when the entire length of the steel plate is divided into 10 equal sections along the rolling direction, the finishing temperature FT refers to the average of the temperature measurements taken for the sections excluding the front and rear sections.

[0125] Then, by cooling after the rolling process, austenite transforms into ferrite, thereby obtaining high-strain and moderately fine grains. As cooling conditions, immediate rapid cooling is not performed in the following manner: cooling begins after 0.1 seconds in the final pass of finish rolling, and after 3 seconds, the surface temperature of the hot-rolled sheet reaches above 300°C and below the Ar1 point. By avoiding immediate rapid cooling in this way, no special rapid cooling equipment is required, which also has a manufacturing (cost) advantage. At a preferred grain size that will not be excessively refined, when cold rolling is subsequently performed, α fibers will develop after intermediate annealing, and after the subsequent flattening and final annealing, the {411}<011> orientation, which is usually difficult to develop, can be developed.

[0126] Furthermore, it can be inferred that the texture of the hot-rolled sheet, when immediately quenched, results in a structure in which unrecrystallized austenite undergoes phase transformation, while when immediate quenching is omitted, it results in a structure in which partially recrystallized austenite undergoes phase transformation. When immediate quenching is performed after finish rolling, the structure after the subsequent final annealing is concentrated in the {100}<011> orientation. When immediate quenching is omitted after finish rolling, the structure after the subsequent final annealing is concentrated in the {411}<011> orientation. Therefore, it is believed that in order to strengthen the {411}<011> orientation, it is important to transform the partially recrystallized austenite.

[0127] Here, as cooling conditions, it is preferable to set the conditions such that the average grain size in the hot-rolled sheet before cold rolling is 3 to 10 μm. When the grains are too coarse, it will be difficult for α fibers to develop after cold rolling and intermediate annealing, and the desired {411}<011> ratio may not be obtained. In addition, when excessive miniaturization is performed, the desired {411}<011> ratio will not be obtained. Therefore, in order to set the average grain size in the hot-rolled sheet before cold rolling to 3 to 10 μm, the temperature is set to be below the Ar1 point within 3 seconds from the final pass of the finish rolling. The particle size can be measured, for example, by the cutting method.

[0128] In addition, the surface temperature of the hot-rolled plate 3 seconds after passing the final pass of the finish rolling is measured by the following method. In the hot rolling equipment line of the electromagnetic steel plate, a cooling device and a conveyor line (for example, a conveyor roller) are arranged downstream of the hot rolling mill. A thermometer for measuring the surface temperature of the hot-rolled plate is arranged on the outlet side of the rolling stand that implements the final pass of the hot rolling mill. In addition, a plurality of thermometers are also arranged along the conveyor line on the conveyor rollers arranged downstream of the rolling stand. The cooling device is arranged downstream of the rolling stand that implements the final pass. A thermometer is arranged on the inlet side of the water cooling device. The cooling device can be, for example, a well-known water cooling device or a well-known forced air cooling device. Preferably, the cooling device is a water cooling device. The coolant of the water cooling device can be either water or a mixed fluid of water and air.

[0129] The hot-rolled sheet temperature was measured using a thermometer installed in the hot rolling line, and the temperature was determined 3 seconds after the final pass of the finish rolling.

[0130] Then, the hot-rolled sheet is coiled without annealing, and the hot-rolled sheet is cold-rolled. Note that the hot-rolled sheet annealing referred to here means, for example, a heat treatment at a heating temperature of Ac1 point or lower and 300° C. or higher.

[0131] Hot-rolled sheets are not annealed, but instead cold rolled. Cold rolling can be performed, for example, using a tandem rolling mill comprised of multiple rolling stands arranged in a row (each with a pair of work rolls), with tandem rolling performed in multiple passes. Alternatively, reversible rolling using a Sendzimir mill with a pair of work rolls, or similar, can be performed in a single or multiple passes. From a productivity perspective, multiple-pass rolling using a tandem rolling mill is preferred.

[0132] During cold rolling, cold rolling is performed without annealing during the cold rolling process. For example, when reversible rolling is performed in multiple passes, cold rolling is performed in multiple passes without annealing between the passes. Alternatively, cold rolling may be performed in only one pass using a reversible rolling mill. Furthermore, when cold rolling is performed using a tandem rolling mill, cold rolling is performed continuously in multiple passes (passes at each rolling stand).

[0133] In this embodiment, it is preferable that the reduction ratio RR1 (%) in cold rolling be set to 75 to 95%. Here, the reduction ratio RR1 is defined as follows.

[0134] Reduction ratio RR1 (%) = (1-plate thickness after final cold rolling pass / plate thickness before first cold rolling pass) × 100

[0135] When the cold rolling is completed, intermediate annealing is continued. In this embodiment, it is preferred to control the intermediate annealing temperature T1 (°C) to below the Ac1 point. When the intermediate annealing temperature exceeds the Ac1 point, part of the structure of the steel sheet will transform into austenite, and the strain in the steel sheet will be excessively reduced. In addition, when the intermediate annealing temperature is too low, recrystallization will not occur, and during the subsequent skin-pass rolling and final annealing, the {411}<011> oriented grains will not grow sufficiently, and sometimes the magnetic flux density will not increase. Therefore, it is preferred to set the intermediate annealing temperature T1 (°C) to above 600°C.

[0136] Here, the intermediate annealing temperature T1 (° C.) is defined as the sheet temperature (the temperature of the steel sheet surface) near the extraction port of the annealing furnace. The sheet temperature of the annealing furnace can be measured by a thermometer disposed at the extraction port of the annealing furnace.

[0137] The holding time at the intermediate annealing temperature T1 in the intermediate annealing step may be any time known to those skilled in the art. The holding time at the intermediate annealing temperature T1 is, for example, 5 to 60 seconds, but the holding time at the intermediate annealing temperature T1 is not limited to this. Furthermore, the heating rate to the intermediate annealing temperature T1 may also be any known condition. The heating rate to the intermediate annealing temperature T1 is, for example, 10.0 to 20.0°C / second, but the heating rate to the intermediate annealing temperature T1 is not limited to this.

[0138] The atmosphere during the intermediate annealing is not particularly limited, but an atmosphere containing 20% ​​H2 and the remainder N2 (dry) is used. The cooling rate of the steel sheet after the intermediate annealing is not particularly limited, but is, for example, 5.0 to 60.0°C / second.

[0139] When the intermediate annealing is completed under the above conditions, the resulting cold-rolled steel sheet exhibits an α fiber ratio (within a tolerance of 10°) of 15% or more as measured by SEM-EBSD. To achieve this α fiber ratio (within a tolerance of 10°) of 15% or more before skin-pass rolling, it is necessary to adopt an α-γ transformation system composition (high concentrations of γ-constituent elements such as Mn, Ni, and Cu, hereinafter referred to as "high Mn") and maintain the aforementioned conditions from hot rolling to intermediate annealing. The cooling conditions after finish rolling are particularly important. Regarding the formation of α fibers, which favor the {411}<011> orientation, the hot-rolled sheet, which has an average grain size of 3 to 10 μm after hot rolling, is cold-rolled and then intermediate annealed, resulting in a structure characterized by transformation of unrecrystallized austenite, rather than a structure characterized by transformation of partially recrystallized austenite. As previously mentioned, immediate rapid cooling results in a structure characterized by transformation of unrecrystallized austenite, rather than a structure characterized by transformation of partially recrystallized austenite. The cold-rolled steel sheet manufactured in this manner is subjected to skin pass rolling under the conditions described below and further subjected to final annealing to obtain the non-oriented electrical steel sheet of the present invention.

[0140] After the intermediate annealing is completed, skin pass rolling is performed. Specifically, the cold-rolled steel sheet after the intermediate annealing step is subjected to rolling (cold rolling) at room temperature in the atmosphere. The skin pass rolling here is performed using, for example, a reversing rolling mill or a tandem rolling mill, such as the Sendzimir mill described above.

[0141] In skin-pass rolling, rolling is performed without annealing. For example, when reversing rolling is performed in multiple passes, skin-pass rolling is performed multiple times without annealing between passes. Alternatively, skin-pass rolling may be performed in only one pass using a reversing rolling mill. Furthermore, when skin-pass rolling is performed using a tandem rolling mill, rolling is performed continuously in multiple passes (passes in each rolling stand).

[0142] As described above, in this embodiment, after strain is introduced into the steel sheet through hot and cold rolling, the introduced strain is temporarily reduced through intermediate annealing. Skin pass rolling is then performed. This reduces the strain excessively introduced by cold rolling during intermediate annealing, while the intermediate annealing simultaneously suppresses the preferential recrystallization of {111} grains within the steel sheet surface, allowing {411}<011> oriented grains to remain. Skin pass rolling then introduces an appropriate amount of strain into each grain within the steel sheet, facilitating grain growth due to expansion during the next step, final annealing.

[0143] In this embodiment, the reduction ratio RR2 in skin pass rolling is set to 5 to 20%. Here, the reduction ratio RR2 is defined as follows.

[0144] Reduction ratio RR2 (%) = (1-plate thickness after final pass in skin-pass rolling / plate thickness before first pass in skin-pass rolling) × 100

[0145] Here, if the reduction ratio RR2 is less than 5%, the strain becomes too small, and the final annealing time required for grain growth due to expansion becomes longer. Furthermore, if the reduction ratio RR2 exceeds 20%, the strain becomes too large, causing normal grain growth rather than expansion, and {411}<148> or {111}<011> to grow during the final annealing. Therefore, the reduction ratio RR2 is set to 5-20%.

[0146] The number of passes in skin-pass rolling may be only one pass (ie, only one rolling pass) or may be rolling performed in multiple passes.

[0147] As described above, the aforementioned GOS value and α fiber ratio are obtained by recrystallizing a steel sheet having an α-γ transformation composition (high Mn, etc.) during intermediate annealing and then performing skin pass rolling under the above conditions.

[0148] After skin-pass rolling, final annealing is performed at a temperature of 750°C or higher and below the Ac1 point for at least 2 hours. If the final annealing temperature T2 (°C) is set below 750°C, grain growth due to expansion will not occur sufficiently. In this case, the concentration of the {411}<011> orientation will decrease. Furthermore, if the final annealing temperature T2 exceeds the Ac1 point, part of the steel sheet structure will transform into austenite, preventing grain growth due to expansion and failing to achieve the desired {411}<011> ratio. Furthermore, if the annealing time is less than 2 hours, even if the final annealing temperature T2 is 750°C or higher and below the Ac1 point, grain growth due to expansion will not occur sufficiently, and the concentration of the {411}<011> orientation will decrease. The upper limit of the final annealing time is not particularly limited, but the effect will saturate even if the annealing time exceeds 10 hours, so the preferred upper limit is 10 hours.

[0149] Here, the final annealing temperature T2 is set to the sheet temperature (the temperature of the steel sheet surface) near the extraction port of the annealing furnace. The temperature of the annealing furnace can be measured by a thermometer arranged at the extraction port of the annealing furnace.

[0150] In addition, the heating rate TR2 to the final annealing temperature T2 in the final annealing step may be a heating rate well known to those skilled in the art, and the holding time Δt2 (seconds) at the final annealing temperature T2 may also be a time well known to those skilled in the art. Here, the holding time Δt2 means the holding time from the time the surface temperature of the steel sheet reaches the final annealing temperature T2.

[0151] The preferred heating rate TR2 to the final annealing temperature T2 in the final annealing step is 0.1°C / second or higher and less than 10.0°C / second. When the heating rate TR2 is 0.1°C / second or higher and less than 10.0°C / second, grain growth due to expansion occurs sufficiently. In this case, the concentration of the {411}<011> crystal orientation is further increased, and the grains in the ND plane at the center of the plate thickness are further less likely to become disorganized.

[0152] The heating rate TR2 is determined by the following method. A thermocouple is attached to a steel plate having the above chemical composition and subjected to the above-described hot rolling and flattening process to prepare a sample steel plate. The sample steel plate with the thermocouple attached is heated, and the time from the start of heating to reaching the final annealing temperature T2 is measured. The heating rate TR2 is determined based on the measured time.

[0153] The holding time Δt2 at the final annealing temperature T2 in the final annealing step is 2 hours or longer. When the holding time Δt2 is 2 hours or longer, the {411}<110> grains grow due to expansion, and the strength is increased due to grain refinement strengthening. In this case, the concentration of the {411}<011> crystal orientation is further increased, and the grains in the ND plane at the center of the plate thickness are further difficult to scatter. The lower limit of the holding time Δt2 is 2 hours, preferably 3 hours. As mentioned above, the preferred upper limit of the holding time Δt2 is 10 hours, and more preferably 5 hours.

[0154] The atmosphere during the final annealing step is not particularly limited. For example, a dry atmosphere containing 20% ​​H₂ and the remainder N₂ is used. The cooling rate of the steel sheet after the final annealing step is not particularly limited. For example, the cooling rate is 5 to 20°C / second.

[0155] Alternatively, a method may be employed in which the non-oriented electrical steel sheets are shipped after skin-pass rolling without final annealing. For example, the processes up to skin-pass rolling may be performed at the steel sheet manufacturer, and the non-oriented electrical steel sheets may be blanked or laminated at the iron core manufacturer serving as the shipping destination. Subsequently, strain relief annealing may be performed as an alternative to final annealing at an annealing temperature of 750°C or higher and below the Ac1 point for an annealing time of 2 hours or longer.

[0156] As described above, the non-oriented electrical steel sheet of the present embodiment can be manufactured.

[0157] The method for producing a non-oriented electrical steel sheet according to the present embodiment is not limited to the above-mentioned production steps.

[0158] For example, shot peening and / or pickling may be performed after hot rolling and before cold rolling in the above-mentioned manufacturing process. In shot peening, the hot-rolled steel sheet is subjected to shot peening to destroy and remove the oxide scale formed on the surface of the hot-rolled steel sheet. In pickling, the hot-rolled steel sheet is subjected to a pickling treatment. For example, a hydrochloric acid aqueous solution is used as a pickling bath. Pickling removes the oxide scale formed on the surface of the steel sheet. Shot peening may be performed after hot rolling and before cold rolling, followed by pickling. Alternatively, pickling may be performed after hot rolling and before cold rolling without shot peening. Alternatively, shot peening may be performed after hot rolling and before cold rolling without pickling. Furthermore, shot peening and pickling are optional processes. Therefore, neither shot peening nor pickling may be performed after hot rolling and before cold rolling.

[0159] The method for producing an electromagnetic steel sheet according to this embodiment may further include coating after the final annealing. In the coating, an insulating film is formed on the surface of the steel sheet after the final annealing.

[0160] The type of insulating film is not particularly limited. The insulating film can be either an organic component or an inorganic component, and the insulating coating can also contain organic and inorganic components. Examples of inorganic components include dichromic acid-boric acid, phosphoric acid, silicon oxide, etc. Examples of organic components include general acrylic acid, acrylic styrene, acrylic silicone, silicon, polyester, epoxy, and fluorine resins. Considering the coating properties, the preferred resin is a latex-type resin. Alternatively, an insulating coating that exerts adhesive properties by heating and / or pressurizing may be applied. Examples of insulating coatings with adhesive properties include acrylic acid, phenolic, epoxy, and melamine resins.

[0161] In addition, coating is an optional step, and therefore, coating may not be performed after the final annealing.

[0162] The non-oriented electrical steel sheet according to the present embodiment is not limited to the above-mentioned manufacturing method. As long as the composition range is within the above-mentioned range, the area ratio of grains having a {411}<011> orientation (within a tolerance of 10°) relative to the entire field of view when the steel sheet surface is measured by electron beam backscatter diffraction (EBSD) is 15% or more, and the number density of precipitates is 0.0001 grains / μm. 2 ~0.3000 / μm 2 , it is not limited to the above-mentioned manufacturing method.

[0163] Example

[0164] Next, the non-oriented electrical steel sheet according to the embodiment of the present invention will be described in detail with reference to examples. However, the examples shown below are merely examples of the non-oriented electrical steel sheet according to the embodiment of the present invention, and the non-oriented electrical steel sheet according to the present invention is not limited to the examples described below.

[0165] (First embodiment)

[0166] By casting molten steel, ingots of the composition shown in the following Table 1 are produced. Here, the so-called "Formula (1)" in Table 1 represents the value on the left side of the aforementioned Formula (1), and the so-called "Formula (2)" in Table 1 represents the value of ([Si]+[Mn])÷[sol.Al] in the aforementioned Formula (2). Then, the produced ingot is heated to the slab heating temperature ST shown in Table 2, hot rolled, and finish rolled at the finishing temperature FT shown in Table 2. The heating rate from 600°C to the slab heating temperature ST is also shown in Table 2. Then, from the time of passing the final pass, cooling is carried out under the cooling conditions shown in Table 2 (the time from passing the final pass to the start of cooling, and the temperature of the steel plate 3 seconds after passing the final pass).

[0167] Next, the hot-rolled steel sheets were pickled to remove scale without hot-rolled sheet annealing, and then cold-rolled at a reduction ratio RR1 shown in Table 2. Then, intermediate annealing was performed in an atmosphere of 20% hydrogen and 80% nitrogen, with the intermediate annealing temperature T1 controlled at the temperature shown in Table 2, for 30 seconds.

[0168] Next, except for No. 9 and No. 10, skin pass rolling was performed at the reduction ratio RR2 shown in Table 2. Then, except for No. 9, final annealing was performed in a 100% hydrogen atmosphere at the final annealing temperature T2 shown in Table 2. At this time, the holding time Δt2 at the final annealing temperature T2 was set to the time shown in Table 2. Furthermore, before the final annealing, the GOS value Gs was calculated under the aforementioned measurement conditions.

[0169] In addition, to investigate the texture after final annealing, a portion of the steel plate was removed, and the removed test piece was reduced to 1 / 2 its thickness. The {411}<011> ratio was determined by observing the measurement area using SEM-EBSD under the aforementioned measurement conditions. Furthermore, the number density of precipitates was determined by observing precipitates with an equivalent circle diameter of 20 to 500 nm using a transmission electron microscope with an accelerating voltage of 200 kV and the extraction replication method under the aforementioned measurement conditions. The respective results are shown in Table 3.

[0170] In addition, in order to investigate the magnetic properties and tensile strength after final annealing, the magnetic flux density B50 and iron loss W10 / 400 were measured, and the iron loss degradation rate of the iron loss W10 / 50 under compressive stress was calculated as an indicator of stress sensitivity. Regarding the magnetic flux density B50, as measurement samples, 55 mm square samples were collected along two directions of 0° and 45° to the rolling direction. Then, these two types of samples were measured, and the value in the direction of 45° relative to the rolling direction was taken as the magnetic flux density B50 in the 45° direction, and the average value of 0°, 45°, 90°, and 135° relative to the rolling direction was taken as the full-circle average of the magnetic flux density B50. Regarding the iron loss W10 / 400, among the above-mentioned measurement samples, a sample collected in the direction of 45° to the rolling direction was used, and the average value in the 45° direction was calculated. Furthermore, regarding the iron loss degradation rate W of the iron loss W10 / 50 under compressive stress, x [%], assuming that the iron loss W10 / 50 without stress is W10 / 50(0) and the iron loss W10 / 50 under a compressive stress of 10 MPa is W10 / 50(10), the iron loss degradation rate Wx was calculated using the following formula. The measurement results are shown in Table 3.

[0171] W x ={W10 / 50(10)-W10 / 50(0)} / W10 / 50(0)

[0172] [Table 1]

[0173]

[0174] [Table 2]

[0175]

[0176] [Table 3]

[0177] Table 3

[0178]

[0179] The underlined conditions in Tables 1 and 3 indicate conditions outside the scope of the present invention. Inventive Examples No. 1, No. 4, No. 7, and No. 13 all had good values ​​in terms of magnetic flux density B50, iron loss W10 / 400, iron loss degradation rate, and tensile strength.

[0180] On the other hand, in Comparative Example No. 2, the sol. Al content is insufficient, exceeding the upper limit of equation (2). Consequently, AlN is insufficient as fine precipitates. Furthermore, the slab heating temperature rise rate is high, causing Ti to dissolve, resulting in a correspondingly large amount of fine TiN precipitation. Furthermore, rapid cooling is performed after finish rolling, resulting in a low {411}<110> ratio, poor iron loss W10 / 400, and poor iron loss degradation rate. Comparative Example No. 3 has a composition in which the total of one or more selected from the group consisting of Mn, Ni, and Cu is insufficient, and α-γ transformation does not occur. Consequently, the {411}<011> ratio is low, poor magnetic flux density B50 (45° direction), poor iron loss W10 / 400, and poor iron loss degradation rate. Comparative Example No. 5 exceeds the upper limit of equation (2), resulting in insufficient AlN formation, resulting in a correspondingly large amount of fine TiN precipitation. As a result, the number density of precipitates increased, and the iron loss W10 / 400 and the iron loss degradation rate were poor. Comparative Example No. 6 fell below the lower limit of formula (2), resulting in excessive AlN formation and a high number density of precipitates. Consequently, the iron loss W10 / 400 and the iron loss degradation rate were poor.

[0181] Comparative Example No. 8 exceeded the upper limit of formula (2), and Ti was excessively contained. Consequently, the heating rate during slab heating was high, resulting in a high TiN production rate and a high number density. Consequently, Si was insufficient, resulting in a poor iron loss W10 / 400. Comparative Example No. 9, in which the total of one or more selected from the group consisting of Mn, Ni, and Cu was excessive, caused segregation and resulted in two sheets breaking during cold rolling, leading to the discontinuation of production. Comparative Example No. 10, in which skin pass rolling was not performed, had a low {411}<011> ratio, poor magnetic flux density B50 (45° direction), poor iron loss W10 / 400, and poor iron loss degradation rate. Comparative Example No. 11, in which the reduction ratio RR2 during skin pass rolling was excessively high, had a low {411}<011> ratio, poor magnetic flux density B50 (45° direction), and poor iron loss W10 / 400. In Comparative Example No. 12, the slab heating temperature ST was too high, so fine TiN was precipitated in large quantities, resulting in a high number density. As a result, the iron loss W10 / 400 was poor.

[0182] Industrial Availability

[0183] According to the present invention, a non-oriented electromagnetic steel sheet, a motor core, and a motor that achieve both low iron loss and high magnetic flux density without increasing the manufacturing load and without reducing the plate thickness can be provided, which has great industrial value.

Claims

1. A non-oriented electromagnetic steel sheet, characterized in that: Has the following chemical composition: C: 0.010% or less, Si: 1.50% to 4.00%, sol.Al: 0.3%~0.7%, S: 0.010% or less, N: 0.010% or less, Ti: 0.0005% to 0.0020%, One or more selected from the group consisting of Mn, Ni, and Cu: 2.50% to 5.00% in total, Co: 0.000% to 1.000%, Sn: 0.000% to 0.400%, Sb: 0.000% to 0.400%, and P：0.000％～0.400％， When the Mn content is expressed as [Mn] in mass%, the Ni content is expressed as [Ni] in mass%, the Cu content is expressed as [Cu] in mass%, the Si content is expressed as [Si] in mass%, the sol.Al content is expressed as [sol.Al] in mass%, and the P content is expressed as [P] in mass%, the following formulas (1) and (2) are satisfied: (2×[Mn]+2.5×[Ni]+[Cu])-([Si]+2×[sol.Al]+4×[P])≥3.0%···(1) 10.5≤([Si]+[Mn])÷[sol.Al]≤12.5···(2) The remainder is composed of Fe and impurities; When the surface of the steel sheet is measured using a scanning electron microscope with electron beam backscatter diffraction (SEM-EBSD), the area ratio of grains with an orientation of {hkl}<uvw> within a margin of 10° relative to the entire field of view is expressed as Ahkl-uvw. For A411-011, the area ratio is 15% or more. The number density of precipitates is 0.0001 / μm 2 ~0.3000 / μm 2 .

2. A motor core, characterized in that: The non-oriented electrical steel sheets according to claim 1 are laminated.

3. A motor, characterized in that: The invention has a motor core as claimed in claim 2.

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