Non-oriented magnetic steel sheet, iron core, manufacturing method of iron core, motor and manufacturing method of motor

Abstract

To provide a non-oriented magnetic steel sheet to be used as an iron core material for a motor, excellent in magnetic flux density, iron loss characteristics and punchability.SOLUTION: In a non-oriented magnetic steel sheet, when a base material steel sheet is observed in a cross section with a cutting direction parallel to a board thickness direction, an average Al concentration in a region from a surface of the base material steel sheet to a 1 / 10 board thickness is higher by 1.5 mass% or more in comparison to an Al concentration of a 1 / 4 board thickness part, and is higher by 3.0 mass% or more in comparison to an Al concentration of a 1 / 2 board thickness part, and an average Si concentration in a region from a surface of the base material steel sheet to a 1 / 10 board thickness is lower by 0.5 mass% or more in comparison to a Si concentration of a 1 / 4 board thickness part, and is lower by 1.0 mass% or more in comparison to a Si concentration of a 1 / 2 board thickness part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a non-oriented electrical steel sheet, an iron core, a manufacturing method of an iron core, a motor, and a manufacturing method of a motor. More specifically, the present invention relates to a non-oriented electrical steel sheet, an iron core, a manufacturing method of an iron core, a motor, and a manufacturing method of a motor, which have high magnetic flux density, excellent core loss characteristics, and excellent punchability. [Background technology]

[0002] Due to the need to reduce greenhouse gases, products that consume less energy are being developed in the industrial sector. For example, in the automotive sector, there are fuel-efficient vehicles such as hybrid vehicles that combine a gasoline engine and a motor, and electric vehicles that are driven by a motor. The common technology in these fuel-efficient vehicles is the motor, and miniaturizing and increasing the efficiency of motors are key technologies.

[0003] For example, there is a growing demand for miniaturization of drive motors for hybrid and electric vehicles due to space restrictions and the need to reduce fuel consumption through weight reduction. To miniaturize motors, it is necessary to increase the motor's torque. For this reason, there is a demand for further increasing the magnetic flux density of the non-oriented electrical steel sheets used as the iron core material for motors.

[0004] In addition, there is a limit to the battery capacity that can be installed in an automobile, so there is an increasing demand for high efficiency drive motors. To increase the efficiency of a motor, it is necessary to reduce energy loss. Therefore, there is a demand for further reduction in iron loss in non-oriented electrical steel sheets used as the iron core material of motors. In particular, in the motors of hybrid drive vehicles and electric vehicles, attempts are being made to increase the rotation speed of the motor to compensate for the decrease in torque that accompanies miniaturization. Therefore, there is a demand for non-oriented electrical steel sheets to further reduce iron loss from the commercial frequency range to the high frequency range.

[0005] In addition, the smaller the gap between the stator and rotor in the motor's internal structure, the better the motor's performance. Each component of the motor must have high shape precision. For this reason, the non-oriented electrical steel sheet used as the iron core material for the motor must also have excellent punching properties.

[0006] For example, Patent Document 1 discloses a silicon steel sheet in which the Si concentration in the surface layer of the steel sheet is higher than the Si concentration in the center portion of the sheet thickness, with the aim of improving high-frequency iron loss. Furthermore, Patent Document 2 discloses a non-oriented electrical steel sheet having an Al concentration gradient in the thickness direction for the purpose of improving high-frequency iron loss. Furthermore, Patent Document 3 discloses a non-oriented electrical steel sheet having an Al concentration gradient in the thickness direction for the purpose of improving magnetic properties. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 11-293422 [Patent Document 2] International Publication No. 2009 / 072394 [Patent Document 3] Japanese Patent Application Publication No. 8-60310 Summary of the Invention [Problem to be solved by the invention]

[0008] The techniques of Patent Documents 1 to 3 described above improve high-frequency iron loss to a certain extent. However, these techniques do not fully consider commercial-frequency iron loss. In addition, the techniques of Patent Documents 1 and 2 described above tend to reduce the punchability of the steel sheet due to the segregation of elements such as Si in the surface layer of the steel sheet, and do not fully consider the improvement of magnetic flux density.

[0009] The present invention has been made in view of the above problems. An object of the present invention is to provide a non-oriented electrical steel sheet that is excellent in magnetic flux density, iron loss characteristics (commercial frequency iron loss and high frequency iron loss), and punchability. Another object of the present invention is to provide an iron core including this non-oriented electrical steel sheet, a method for manufacturing the iron core, and a motor including this iron core, and a method for manufacturing the motor. [Means for solving the problem]

[0010] (1) A non-oriented electrical steel sheet according to one aspect of the present invention comprises a base steel sheet and an insulating coating, The base steel sheet has a chemical composition, in mass%, Si: 1.0% or more and 5.0% or less, Al: 1.0% or more and 10.0% or less, Sn: 0% or more and 10.000% or less, C: 0% or more and 0.005% or less, Mn: 0% or more and 3.0% or less, P: 0% or more and 0.30% or less, S: 0% or more and 0.010% or less, N: 0% or more and 0.010% or less, Zn: 0% or more and 0.100% or less, Sb: 0% or more and 0.100% or less, Ca: 0% or more and 0.010% or less, Cr: 0% or more and 10.0% or less, Ni: 0% or more and 5.0% or less, Cu: 0% or more and 5.0% or less, Ce: 0% or more and 0.100% or less, B: 0% or more and 0.100% or less, O: 0% or more and 0.100% or less, Mg: 0% or more and 0.100% or less, Ti: 0% or more and 0.100% or less, V: 0% or more and 0.100% or less, Zr: 0% or more and 0.100% or less, Nd: 0% or more and 0.100% or less, Bi: 0% or more and 0.100% or less, W: 0% or more and 0.100% or less, Mo: 0% or more and 0.10% or less, Nb: 0% or more and 0.100% or less, Y: 0% or more and 0.100% or less, with the remainder being Fe and impurities, The thickness of the base steel plate is 0.10 mm or more and 0.35 mm or less, When the base steel plate is viewed on a cut surface whose cutting direction is parallel to the plate thickness direction, The average Al concentration in the region from the surface of the base steel plate to 1 / 10 of the plate thickness is The Al concentration is 1.5 mass% or more higher than the Al concentration at 1 / 4 of the plate thickness, and The Al concentration is 3.0 mass% or more higher than the Al concentration at 1 / 2 the plate thickness. The Al concentration at the quarter thickness portion is The Al concentration is 1.5 mass% or more higher than the Al concentration at the half thickness portion, The average Si concentration in the region from the surface to 1 / 10 of the plate thickness of the base steel plate is The Si concentration is 0.5 mass% or more lower than the Si concentration at 1 / 4 of the plate thickness, and The Si concentration is 1.0 mass% or more lower than the Si concentration at 1 / 2 the plate thickness. The Si concentration at the quarter thickness portion is The Si concentration is 0.5 mass % or more lower than the Si concentration at the half thickness portion It is characterized by: (2) In the non-oriented electrical steel sheet described in (1) above, the chemical composition may contain, by mass%, Cr: 0.50% or more and 10.0% or less. (3) A non-oriented electrical steel sheet according to another aspect of the present invention is a non-oriented electrical steel sheet comprising a base steel sheet and an insulating coating, The base steel sheet has a chemical composition, in mass%, Si: 1.0% or more and 5.0% or less, Al: 0% or more and 10.0% or less, Sn: 1.0% or more and 10.000% or less, C: 0% or more and 0.005% or less, Mn: 0% or more and 3.0% or less, P: 0% or more and 0.30% or less, S: 0% or more and 0.010% or less, N: 0% or more and 0.010% or less, Zn: 0% or more and 0.100% or less, Sb: 0% or more and 0.100% or less, Ca: 0% or more and 0.010% or less, Cr: 0% or more and 10.0% or less, Ni: 0% or more and 5.0% or less, Cu: 0% or more and 5.0% or less, Ce: 0% or more and 0.100% or less, B: 0% or more and 0.100% or less, O: 0% or more and 0.100% or less, Mg: 0% or more and 0.100% or less, Ti: 0% or more and 0.100% or less, V: 0% or more and 0.100% or less, Zr: 0% or more and 0.100% or less, Nd: 0% or more and 0.100% or less, Bi: 0% or more and 0.100% or less, W: 0% or more and 0.100% or less, Mo: 0% or more and 0.10% or less, Nb: 0% or more and 0.100% or less, Y: 0% or more and 0.100% or less, with the remainder being Fe and impurities, The thickness of the base steel plate is 0.10 mm or more and 0.35 mm or less, When the base steel plate is viewed on a cut surface whose cutting direction is parallel to the plate thickness direction, The average Sn concentration in the region from the surface of the base steel plate to 1 / 10 of the plate thickness is The Sn concentration is 1.5 mass% or more higher than the Sn concentration at 1 / 4 of the plate thickness, and The Sn concentration is 3.0 mass% or more higher than the Sn concentration at 1 / 2 the plate thickness. The Sn concentration at the quarter thickness portion is The Sn concentration is 1.5 mass% or more higher than the Sn concentration at the half thickness portion, The average Si concentration in the region from the surface to 1 / 10 of the plate thickness of the base steel plate is The Si concentration is 0.5 mass% or more lower than the Si concentration at 1 / 4 of the plate thickness, and The Si concentration is 1.0 mass% or more lower than the Si concentration at 1 / 2 the plate thickness. The Si concentration at the quarter thickness portion is The Si concentration is 0.5 mass % or more lower than the Si concentration at the half thickness portion It is characterized by: (4) In the non-oriented electrical steel sheet described in (3) above, the chemical composition may contain, by mass%, Cr: 0.50% or more and 10.0% or less. (5) A non-oriented electrical steel sheet according to still another aspect of the present invention is a non-oriented electrical steel sheet comprising a base steel sheet and an insulating coating, The base steel sheet has a chemical composition, in mass%, Si: 1.0% or more and 5.0% or less, Al: 1.0% or more and 10.0% or less, Sn: 1.0% or more and 10.000% or less, C: 0% or more and 0.005% or less, Mn: 0% or more and 3.0% or less, P: 0% or more and 0.30% or less, S: 0% or more and 0.010% or less, N: 0% or more and 0.010% or less, Zn: 0% or more and 0.100% or less, Sb: 0% or more and 0.100% or less, Ca: 0% or more and 0.010% or less, Cr: 0% or more and 10.0% or less, Ni: 0% or more and 5.0% or less, Cu: 0% or more and 5.0% or less, Ce: 0% or more and 0.100% or less, B: 0% or more and 0.100% or less, O: 0% or more and 0.100% or less, Mg: 0% or more and 0.100% or less, Ti: 0% or more and 0.100% or less, V: 0% or more and 0.100% or less, Zr: 0% or more and 0.100% or less, Nd: 0% or more and 0.100% or less, Bi: 0% or more and 0.100% or less, W: 0% or more and 0.100% or less, Mo: 0% or more and 0.10% or less, Nb: 0% or more and 0.100% or less, Y: 0% or more and 0.100% or less, with the remainder being Fe and impurities, The thickness of the base steel plate is 0.10 mm or more and 0.35 mm or less, When the base steel plate is viewed on a cut surface whose cutting direction is parallel to the plate thickness direction, The sum of the average Al concentration and the average Sn concentration in the region from the surface of the base steel plate to 1 / 10 of the plate thickness, The Al concentration and Sn concentration at the 1 / 4 part of the plate thickness are 1.5 mass% or more higher than the total concentration, and The Al concentration and Sn concentration at the half thickness portion are 3.0 mass% or more higher than the total concentration, The sum of the Al concentration and the Sn concentration at the quarter thickness portion is The Al concentration and the Sn concentration in the plate thickness 1 / 2 portion are 1.5 mass% or more higher than the total of the Al concentration and the Sn concentration, The average Si concentration in the region from the surface to 1 / 10 of the plate thickness of the base steel plate is The Si concentration is 0.5 mass% or more lower than the Si concentration at 1 / 4 of the plate thickness, and The Si concentration is 1.0 mass% or more lower than the Si concentration at 1 / 2 the plate thickness. The Si concentration at the quarter thickness portion is The Si concentration is 0.5 mass % or more lower than the Si concentration at the half thickness portion It is characterized by: (6) In the non-oriented electrical steel sheet according to (5) above, the base steel sheet may contain, as the chemical composition, in mass%, Cr: 0.50% or more and 10.0% or less. (7) An iron core according to one aspect of the present invention includes the non-oriented electrical steel sheet according to any one of (1) to (6) above. (8) A method for producing an iron core according to one aspect of the present invention includes a step of laminating the non-oriented electrical steel sheets according to any one of (1) to (6) above. (9) A motor according to one aspect of the present invention includes the iron core described in (7) above. (10) A method for manufacturing a motor according to one aspect of the present invention includes a step of laminating the non-oriented electrical steel sheets described in any one of (1) to (6) above to obtain an iron core, and a step of assembling the iron core to obtain a motor. Effect of the Invention

[0011] According to the above aspects of the present invention, it is possible to provide a non-oriented electrical steel sheet that is excellent in magnetic flux density, iron loss characteristics (commercial frequency iron loss and high frequency iron loss), and punchability. In addition, according to the above aspects of the present invention, it is possible to provide an iron core including this non-oriented electrical steel sheet, a method for manufacturing an iron core, and a motor including this iron core, and a method for manufacturing a motor. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional schematic diagram of a non-oriented electrical steel sheet according to an embodiment of the present invention. [Diagram 2] 1 is a flow diagram of a method for producing a non-oriented electrical steel sheet according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A preferred embodiment of the present invention will be described in detail below. However, the present invention is not limited to the configuration disclosed in this embodiment, and various modifications are possible without departing from the spirit of the present invention. In addition, the numerical ranges described below include lower and upper limits. Numerical values ​​indicated as "greater than" or "less than" are not included in the numerical range. "%" regarding the content of each element means "mass %".

[0014] It has been known for some time that the iron loss of non-oriented electrical steel sheets can be improved by grading the Si or Al concentration, but it has been difficult to achieve both magnetic flux density, iron loss characteristics (commercial frequency iron loss and high frequency iron loss), and punchability by simply grading the Si or Al concentration.

[0015] Therefore, the inventors focused on the combination of Al and Si and came up with the idea of ​​grading both the Al concentration and the Si concentration in the thickness direction of the base steel sheet. Specifically, they thought that by providing a gradient in which the Al concentration decreases while the Si concentration increases from the surface of the base steel sheet to the center of the sheet thickness, it would be possible to improve the magnetic flux density, iron loss characteristics (commercial frequency iron loss and high frequency iron loss), and punchability.

[0016] Like Si, Al is an element that increases the resistivity of a steel sheet when contained in the steel sheet. The eddy currents that flow when an electromagnetic steel sheet is excited by AC increase from the center of the steel sheet toward the surface, so increasing the resistivity near the surface of the steel sheet is effective in suppressing the generation of eddy currents and reducing eddy current loss. The eddy currents increase as the excitation frequency increases, and when the excitation frequency increases and the skin effect occurs, causing magnetic flux to concentrate near the surface of the steel sheet, the eddy currents near the surface of the steel sheet become larger. Therefore, the higher the excitation frequency, the greater the effect of improving the resistivity by increasing the Al concentration near the surface of the steel sheet. On the other hand, when the Al concentration increases, the saturation magnetic flux density decreases, making it difficult for magnetic flux to pass through, and magnetic flux concentrates near the center of the sheet thickness. Therefore, by providing a gradient such that the Si concentration increases from the surface of the base steel sheet toward the center of the sheet thickness, the concentration of magnetic flux near the center of the sheet thickness can be suppressed. Furthermore, when the Al and Si concentrations increase, the hardness of the steel sheet increases and the punchability deteriorates. Therefore, it is believed that punchability can be improved by reducing the Si content, which has a greater effect on increasing hardness, from the surface layer of the base steel sheet.

[0017] In addition to the combination of Al and Si, the inventors also focused on the combination of Sn and Si, and came up with the idea of ​​grading both the Sn concentration and the Si concentration in the thickness direction of the base steel sheet. Specifically, it was thought that by providing a gradient such that the Sn concentration decreases while the Si concentration increases from the surface of the base steel sheet toward the center of the sheet thickness, it would be possible to improve the magnetic flux density, iron loss characteristics (commercial frequency iron loss and high frequency iron loss), and punchability, as in the case of the combination of Al and Si.

[0018] Like Al and Si, Sn is an element that, when contained in a steel sheet, increases the resistivity of the steel sheet, decreases the saturation magnetic flux density, and increases the hardness. That is, in the case of a combination of Sn and Si, as in the case of the combination of Al and Si described above, it is considered that the effect of reducing eddy current loss is increased and punchability can be improved when the base steel sheet has a gradient in which both the Sn concentration and the Si concentration decrease from the surface to the center of the thickness of the base steel sheet, as compared with the case where the base steel sheet has a gradient in which the Sn concentration decreases and the Si concentration increases from the surface to the center of the thickness of the base steel sheet, as compared with the case where the base steel sheet has a gradient in which the Sn concentration decreases but the Si concentration does not increase from the surface to the center of the thickness of the base steel sheet.

[0019] Furthermore, the inventors considered that the magnetic flux density, iron loss characteristics (commercial frequency iron loss and high frequency iron loss), and punchability could be further improved by decreasing the concentrations of Al and Sn from the surface of the base steel sheet toward the center of the sheet thickness and providing a gradient such that the concentration of Si increases. In other words, they considered that the magnetic flux density, iron loss characteristics (commercial frequency iron loss and high frequency iron loss), and punchability could be further improved by increasing the concentrations of Al and Sn near the surface layer of the base steel sheet and decreasing the concentration of Si near the surface layer.

[0020] It is considered difficult to control the concentration gradient as described above by simply including Al and Sn in the raw materials of the base steel sheet from the steelmaking stage, but it is considered possible to control the concentration gradient as described above by diffusing Al and / or Sn into the base steel sheet (particularly near the surface layer of the base steel sheet) during the manufacturing process. The present inventors have investigated various process conditions for realizing the concentration gradient as described above. For example, they attempted to diffuse Al and / or Sn into the surface layer of the steel sheet and provide a gradient in the Si concentration by applying Al plating and / or Sn plating to the steel sheet during the manufacturing process and then heat treating it.

[0021] However, although various plating conditions were investigated, this method did not allow Al and / or Sn to be favorably diffused into the steel sheet surface layer, and the Si concentration gradient was insufficient. The inventors considered that it would be difficult to impart a concentration gradient to these elements in the steel sheet by controlling the plating conditions alone, and focused on the heat treatment conditions and investigated the effects of these conditions on the diffusion of Al and / or Sn and imparting a gradient to the Si concentration. As a result, the inventors found that it is possible to favorably diffuse Al and / or Sn into the steel sheet surface layer and impart a gradient to the Si concentration by controlling the temperature rise conditions, soaking conditions, etc., during the intermediate stages of the manufacturing process, particularly the finish annealing stage.

[0022] Furthermore, the inventors produced steel sheets having various concentration gradients by changing plating conditions and heat treatment conditions, and evaluated the magnetic flux density, iron loss characteristics, and punchability of these steel sheets. As a result, the inventors found a gradient of Al concentration and / or Sn concentration, and a gradient of Si concentration that can favorably improve the magnetic flux density, iron loss characteristics, and punchability.

[0023] The non-oriented electrical steel sheet according to this embodiment, which has been completed based on the above findings, will be described in detail below.

[0024] (First embodiment) [Non-oriented electrical steel sheet] The non-oriented electrical steel sheet according to this embodiment has the following features.

[0025] The non-oriented electrical steel sheet according to this embodiment includes a base steel sheet and an insulating coating, The thickness of the base steel plate is 0.10 mm or more and 0.35 mm or less, When the base steel plate is viewed on a cut surface whose cutting direction is parallel to the plate thickness direction, The average Al concentration in the region from the surface of the base steel plate to 1 / 10 of the plate thickness is The Al concentration is 1.5 mass% or more higher than the Al concentration at 1 / 4 of the plate thickness, and The Al concentration is 3.0 mass% or more higher than the Al concentration at 1 / 2 the plate thickness. The Al concentration at the quarter thickness portion is The Al concentration is 1.5 mass% or more higher than the Al concentration at the half thickness portion, The average Si concentration in the region from the surface to 1 / 10 of the plate thickness of the base steel plate is The Si concentration is 0.5 mass% or more lower than the Si concentration at 1 / 4 of the plate thickness, and The Si concentration is 1.0 mass% or more lower than the Si concentration at 1 / 2 the plate thickness. The Si concentration at the quarter thickness portion is The Si concentration is lower by 0.5 mass % or more than the Si concentration at the half plate thickness portion.

[0026] In addition, the non-oriented electrical steel sheet according to this embodiment has The base steel sheet has a chemical composition, in mass%, of: Si: 1.0% or more and 5.0% or less, Al: 1.0% or more and 10.0% or less, Sn: 0% or more and 10.000% or less, C: 0% or more and 0.005% or less, Mn: 0% or more and 3.0% or less, P: 0% or more and 0.30% or less, S: 0% or more and 0.010% or less, N: 0% or more and 0.010% or less, Zn: 0% or more and 0.100% or less, Sb: 0% or more and 0.100% or less, Ca: 0% or more and 0.010% or less, Cr: 0% or more and 10.0% or less, Ni: 0% or more and 5.0% or less, Cu: 0% or more and 5.0% or less, Ce: 0% or more and 0.100% or less, B: 0% or more and 0.100% or less, O: 0% or more and 0.100% or less, Mg: 0% or more and 0.100% or less, Ti: 0% or more and 0.100% or less, V: 0% or more and 0.100% or less, Zr: 0% or more and 0.100% or less, Nd: 0% or more and 0.100% or less, Bi: 0% or more and 0.100% or less, W: 0% or more and 0.100% or less, Mo: 0% or more and 0.10% or less, Nb: 0% or more and 0.100% or less, Y: 0% or more and 0.100% or less, and the remainder being Fe and impurities.

[0027] In addition, the non-oriented electrical steel sheet according to this embodiment has The base steel sheet has the chemical composition, in mass%, Cr: 0.5 or more and 10.0% or less, It is preferred that the compound contains

[0028] FIG. 1 shows a schematic cross-sectional view of a non-oriented electrical steel sheet according to this embodiment. As shown in Fig. 1, the non-oriented electrical steel sheet 1 according to this embodiment includes a base steel sheet 12 and an insulating coating 11. Below, each feature of the non-oriented electrical steel sheet according to this embodiment will be described in detail.

[0029] Plate Thickness In the non-oriented electrical steel sheet 1 according to this embodiment, the sheet thickness of the base steel sheet 12 is set to 0.35 mm or less, preferably 0.30 mm or less. On the other hand, since excessive thinning significantly reduces the productivity of the steel sheet and motors, the sheet thickness of the base steel sheet 12 is set to 0.10 mm or more, preferably 0.15 mm or more.

[0030] The thickness of the base steel sheet 12 may be measured with a micrometer. If the non-oriented electrical steel sheet to be measured has an insulating coating on its surface, the insulating coating is removed before the measurement. For example, the insulating coating may be removed by the following method.

[0031] A non-oriented electrical steel sheet having an insulating coating or the like is immersed in an aqueous solution of sodium hydroxide, an aqueous solution of sulfuric acid, and an aqueous solution of nitric acid in that order, and then washed. Finally, it is dried with hot air. In this way, a non-oriented electrical steel sheet (base steel sheet) from which the insulating coating has been removed can be obtained.

[0032] [Al concentration gradient] In the non-oriented electrical steel sheet 1 according to the present embodiment, as shown in FIG. 1, when the base steel sheet 12 is viewed on a cut surface in which the cutting direction is parallel to the sheet thickness direction, the average Al concentration in the region 12a (surface layer region) from the surface of the base steel sheet 12 to 1 / 10 of the sheet thickness is 1.50 mass% or more higher than the Al concentration in the 1 / 4 sheet thickness portion 12b, and is 3.0 mass% or more higher than the Al concentration in the 1 / 2 sheet thickness portion 12c. From the viewpoint of reducing eddy current loss, the average Al concentration in the surface layer region 12a is preferably 1.8 mass% or more higher than the Al concentration in the 1 / 4 sheet thickness portion 12b, and more preferably 2.0 mass% or more higher. Moreover, the average Al concentration in the surface layer region 12a is preferably 3.5 mass% or more higher than the Al concentration in the 1 / 2 sheet thickness portion 12c, and more preferably 4.0 mass% or more higher.

[0033] Furthermore, in the non-oriented electrical steel sheet 1 according to this embodiment, when viewed in the above-mentioned cross section, the Al concentration in the sheet thickness 1 / 4 portion 12b is higher by 1.50 mass % or more than the Al concentration in the sheet thickness 1 / 2 portion 12c. From the viewpoint of reducing eddy current loss, the Al concentration in the sheet thickness 1 / 4 portion 12b is preferably higher by 1.8 mass % or more, and more preferably higher by 2.0 mass % or more, than the Al concentration in the sheet thickness 1 / 2 portion 12c.

[0034] The average Al concentration of the surface region 12a, the Al concentration of the thickness 1 / 4 portion 12b, and the Al concentration of the thickness 1 / 2 portion 12c may satisfy the above relationship. Therefore, the Al concentration as a chemical composition in the surface region 12a, the thickness 1 / 4 portion 12b, and the thickness 1 / 2 portion 12c is not particularly limited. However, the average Al concentration of the surface region 12a where the Al concentration is maximum in the cut surface is preferably 15 mass% or less, more preferably 12 mass% or less, in terms of chemical composition. The average Al concentration of the surface region 12a is preferably 3.0 mass% or more, more preferably 5.0 mass% or more, and even more preferably 7.0 mass% or more, in terms of chemical composition. Similarly, the Al concentration of the thickness 1 / 2 portion 12c where the Al concentration is minimum in the cut surface is preferably 0.001 mass% or more, more preferably 0.01 mass% or more, in terms of chemical composition. The Al concentration in the plate thickness 1 / 2 portion 12c, as a chemical composition, is preferably 8.0 mass % or less, more preferably 4.0 mass % or less, and further preferably 2.0 mass % or less.

[0035] The above-mentioned Al concentration gradient can be confirmed by examining a cut surface parallel to the sheet thickness direction using an EPMA (Electron Probe Micro Analyzer).

[0036] Specifically, first, the insulating coating 11 and the like are removed from the non-oriented electrical steel sheet 1 by the method described above to obtain a base steel sheet 12. A test piece is cut out from this base steel sheet 12 so that the cutting direction is parallel to the sheet thickness direction. The cross-sectional structure of this cut surface is observed with an EPMA at a magnification that allows the sheet thickness of the base steel sheet 12 to fit in the observation field. When the sheet thickness of the base steel sheet 12 does not fit in the observation field, the cross-sectional structure is observed in multiple consecutive fields of view.

[0037] A line analysis is performed in the thickness direction of the base steel plate 12 in the above-mentioned observation field by EPMA, and the average Al concentration in the region 12a (surface region) from the surface of the base steel plate to 1 / 10 of the plate thickness, the Al concentration in the 1 / 4 plate thickness portion 12b, and the Al concentration in the 1 / 2 plate thickness portion 12c are obtained. The 1 / 2 plate thickness portion 12c corresponds to the center portion in the thickness direction of the base steel plate 12 on the above-mentioned cut surface, and the 1 / 4 plate thickness portion 12b corresponds to the intermediate portion in the thickness direction between the surface of the base steel plate 12 and the 1 / 2 plate thickness portion 12c on the above-mentioned cut surface. In the line analysis, the measurement line of the average Al concentration in the surface region 12a, the measurement line of the Al concentration in the 1 / 2 plate thickness portion 12c, and the measurement line of the Al concentration in the 1 / 4 plate thickness portion 12b are assumed to overlap along the plate thickness direction. In addition, the average Al concentration in the surface region 12a is determined by analyzing the Al concentration in the region 12a from the surface of the base steel plate 12 to 1 / 10 of the plate thickness at equal intervals in the depth direction (for example, at 0.5 μm pitch), and the average value is defined as the "average Al concentration in the region from the surface of the base steel plate to 1 / 10 of the plate thickness."

[0038] Furthermore, in the non-oriented electrical steel sheet 1 according to this embodiment, the above-mentioned cut surface is observed at any 10 observation locations spaced apart from each other on the sheet surface, and the Al concentration gradient satisfies the above condition at 5 or more of the observation locations. If the Al concentration gradient satisfies the above condition at 5 or more observation locations, the Al concentration in the base steel sheet 12 preferably has a gradient.

[0039] [Si concentration gradient] In the non-oriented electrical steel sheet 1 according to the present embodiment, when the base steel sheet 12 is viewed on a cut surface parallel to the sheet thickness direction, the average Si concentration in the region 12a (surface region) from the surface of the base steel sheet 12 to 1 / 10 of the sheet thickness is 0.50 mass% or more lower than the Si concentration in the 1 / 4 sheet thickness portion 12b, and is 1.0 mass% or more lower than the Si concentration in the 1 / 2 sheet thickness portion 12c. In order to favorably improve the magnetic flux density, the iron loss characteristics, and the punchability, the average Si concentration in the surface region 12a is preferably 0.55 mass% or more lower than the Si concentration in the 1 / 4 sheet thickness portion 12b, and more preferably 0.60 mass% or more lower. Moreover, the average Si concentration in the surface region 12a is preferably 1.1 mass% or more lower than the Si concentration in the 1 / 2 sheet thickness portion 12c, and more preferably 1.2 mass% or more lower.

[0040] In the non-oriented electrical steel sheet 1 according to this embodiment, when viewed in the above-mentioned cross section, the Si concentration in the sheet thickness ¼ portion 12b is lower by 0.50 mass % or more than the Si concentration in the sheet thickness ½ portion 12c. The Si concentration in the sheet thickness ¼ portion 12b is preferably lower by 0.55 mass % or more, and more preferably lower by 0.60 mass % or more, than the Si concentration in the sheet thickness ½ portion 12c.

[0041] The average Si concentration of the surface region 12a, the Si concentration of the 1 / 4 thickness portion 12b, and the Si concentration of the 1 / 2 thickness portion 12c may satisfy the above relationship. Therefore, the Si concentration as a chemical composition in the surface region 12a, the 1 / 4 thickness portion 12b, and the 1 / 2 thickness portion 12c is not particularly limited. However, the average Si concentration of the surface region 12a where the Si concentration is the minimum value in the cut surface is preferably 0.5 mass% or more, and more preferably 0.7 mass% or more, in terms of chemical composition. The average Si concentration of the surface region 12a is preferably 4.0 mass% or less, more preferably 3.0 mass% or less, and even more preferably 2.0 mass% or less, in terms of chemical composition. Similarly, the Si concentration of the 1 / 2 thickness portion 12c where the Si concentration is the maximum value in the cut surface is preferably 3.5 mass% or less, and even more preferably 3.3 mass% or less, in terms of chemical composition. The Si concentration in the sheet thickness 1 / 2 portion 12c, as a chemical composition, is preferably 1.0 mass % or more, more preferably 2.0 mass % or more, and even more preferably 3.0 mass % or more.

[0042] The above-mentioned Si concentration gradient can be confirmed, in the same manner as the Al concentration gradient, by examining a cut surface parallel to the sheet thickness direction using an EPMA (Electron Probe Micro Analyzer).

[0043] As with the Al concentration gradient, in the non-oriented electrical steel sheet 1 according to this embodiment, the cut surface is observed at any 10 observation points spaced apart from one another on the sheet surface, and the Si concentration gradient satisfies the above condition at 5 or more of the observation points. If the Si concentration gradient satisfies the above condition at 5 or more observation points, the magnetic flux density, iron loss characteristics, and punchability are preferably improved.

[0044] [Chemical composition] The non-oriented electrical steel sheet 1 according to this embodiment is effective as long as the Al concentration gradient and the Si concentration gradient are controlled as described above, so the chemical composition of the base steel sheet 12 is not particularly limited. The base steel sheet 12 may contain Si and Al as a chemical composition, and may contain optional elements as necessary, with the balance being Fe and impurities. Each element will be described below. Note that the chemical composition of the base steel sheet 12 described below is an average value for the base steel sheet 12 as a whole.

[0045] Si: 1.0% or more and 5.0% or less Silicon (Si) is an element that is effective in increasing the resistivity of steel sheet and reducing iron loss. Therefore, the Si content is set to 1.0% or more. The Si content is preferably 1.3%, and more preferably 1.5% or more. On the other hand, excessive inclusion of silicon significantly reduces the magnetic flux density. Therefore, the Si content is set to 5.0% or less. The Si content is preferably 4.5% or less, and more preferably 4.0% or less.

[0046] Al: 1.0% or more and 10.0% or less Al (aluminum) is an element effective in grading the Al concentration in the base steel sheet. Therefore, the Al content is set to 1.0% or more as an average of the entire base steel sheet. The Al content is preferably 1.5% or more, and more preferably 2.0% or more. On the other hand, even if an excessive amount is contained, the above effect is saturated. Therefore, the Al content is set to 10.0% or less as an average of the entire base steel sheet. The Al content is preferably 9.0% or less, and more preferably 8.0% or less. In this embodiment, Al means acid-soluble aluminum (sol.Al).

[0047] C: 0% or more and 0.005% or less C (carbon) is an optional element. However, if it is contained in excess, the magnetic properties deteriorate. Therefore, the C content is set to 0.005% or less. The C content is preferably set to 0.003% or less. On the other hand, since it is preferable that the C content is low, there is no need to set a lower limit, and the lower limit may be 0%. However, since it is not easy to set the content to 0% industrially, the lower limit may be set to 0.001%.

[0048] Mn: 0% or more and 3.0% or less Mn (manganese) is an optional element. Mn has the effect of increasing the resistivity of the steel sheet and reducing iron loss. However, since Mn has a higher alloying cost than Si and Al, a high Mn content is economically disadvantageous. For this reason, the Mn content is set to 3.0% or less, and preferably 2.50% or less. There is no need to limit the lower limit of Mn, and the lower limit may be 0%. However, in order to more reliably obtain the above effect, the Mn content is preferably 0.0010% or more, and more preferably 0.010% or more.

[0049] P: 0% or more and 0.30% or less P (phosphorus) is an optional element. P has the effect of improving the texture of non-oriented electrical steel sheet and enhancing the magnetic properties. However, since P is also a solid solution strengthening element, if the P content is excessive, the steel sheet becomes hard and cold rolling becomes difficult. For this reason, the P content is set to 0.30% or less. The P content is preferably 0.20% or less. There is no need to set a lower limit for P, and the lower limit may be 0%. However, in order to more reliably obtain the above effects, the P content is preferably 0.0010% or more, and more preferably 0.0150% or more.

[0050] S: 0% or more and 0.010% or less S (sulfur) is an optional element. However, S combines with Mn in the steel to form fine MnS, which inhibits the growth of crystal grains during annealing and may deteriorate the magnetic properties of the non-oriented electrical steel sheet. For this reason, the S content is set to 0.010% or less. The S content is preferably 0.0050% or less, and more preferably 0.0030% or less. Since a small S content is preferable, there is no need to limit the lower limit, and the lower limit may be 0%. However, since it is not easy to industrially set the content to 0%, the lower limit may be set to 0.00010%.

[0051] N: 0% or more and 0.010% or less N (nitrogen) is an optional element. However, N combines with Al to form fine AlN, which may inhibit the growth of crystal grains during annealing and deteriorate the magnetic properties. For this reason, 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. Since a low N content is preferable, there is no need to limit the lower limit, and the lower limit may be 0%. However, since it is not easy to industrially set the content to 0%, the lower limit may be 0.00010% or more, may be more than 0.00150%, or may be 0.00250% or more.

[0052] Zn: 0% or more and 0.100% or less Zn (zinc) is an optional element. However, Zn is an element that reacts with S in molten steel during casting of the molten steel to form precipitates of sulfides or oxysulfides, or both. The grain size of Zn-based precipitates is about 1 μm to 2 μm, which is much larger than the grain size (about 100 nm) of fine precipitates such as MnS, TiN, and AlN. Therefore, these fine precipitates adhere to the precipitates of elements that form coarse precipitates, and are less likely to inhibit recrystallization and grain growth during annealing such as intermediate annealing. However, if Zn is contained in excess, the above effect is saturated, and the total amount of sulfides or oxysulfides, or both, becomes excessive, inhibiting recrystallization and grain growth during annealing such as intermediate annealing. Therefore, the Zn content is set to 0.100% or less. The Zn content is preferably 0.005% or less, and more preferably 0.002% or less. There is no need to limit the lower limit of Zn, and the lower limit may be 0%. However, in order to more reliably obtain the above effects, the Zn content is preferably 0.0005% or more, more preferably 0.001% or more, and even more preferably 0.0015% or more.

[0053] Sn: 0% or more and 10.000% or less Sn (tin) is an optional element. Sn has the effect of improving the texture of non-oriented electrical steel sheets and improving magnetic properties (e.g., magnetic flux density). However, excessive inclusion of Sn can embrittle the steel, causing cold rolling fracture, and can also deteriorate the magnetic properties. For this reason, the Sn content is set to 10.000% or less. There is no need to limit the lower limit of Sn, and the lower limit may be 0%. However, in order to more reliably obtain the above effects, the Sn content is preferably 0.0010% or more, and more preferably 0.010% or more.

[0054] In the first embodiment, Sn is a selective element, but in the second embodiment described later, Sn is a basic element in order to provide a gradient in the Sn concentration instead of the Al concentration.

[0055] Sb: 0% or more and 0.100% or less Sb (antimony) is an optional element. Sb has the effect of improving the texture of non-oriented electrical steel sheet and improving magnetic properties (e.g., magnetic flux density). However, excessive inclusion of Sb may embrittle the steel, causing cold rolling fracture, and may also deteriorate the magnetic properties. For this reason, the Sb content is set to 0.100% or less. There is no need to limit the lower limit of Sb, and the lower limit may be 0%. However, in order to more reliably obtain the above effects, the Sb content is preferably 0.0010% or more, more preferably 0.0020% or more, more preferably 0.010% or more, and even more preferably more than 0.0250%.

[0056] Ca: 0% or more and 0.010% or less Ca (calcium) is an optional element. Ca suppresses the precipitation of fine sulfides (MnS, Cu2S, etc.) by generating coarse sulfides, so it is effective in inclusion control. When Ca is added in an appropriate amount, it has the effect of improving the crystal grain growth and improving magnetic properties (for example, iron loss). However, if it is contained in an excessive amount, the above effect saturates and leads to an increase in cost. Therefore, the Ca content is set to 0.010% or less. The Ca content is preferably 0.0080% or less, and more preferably 0.0050% or less. There is no need to limit the lower limit of Ca, and the lower limit may be 0%. However, in order to obtain the above effect more reliably, the Ca content is preferably 0.00030% or more. The Ca content is preferably 0.0010% or more, and more preferably 0.0030% or more.

[0057] Cr: 0% or more and 10.0% or less Cr (chromium) is an optional element. Cr has the effect of increasing resistivity and improving magnetic properties (for example, iron loss). However, excessive inclusion of Cr may reduce saturation magnetic flux density, and the above effect is saturated, resulting in increased costs. Therefore, the Cr content is set to 10.0% or less. The Cr content is preferably 8.0% or less, and more preferably 6.0% or less. There is no need to limit the lower limit of Cr, and the lower limit may be 0%. However, in order to obtain the above effect more reliably, the Cr content is preferably 0.0010% or more. In addition, Cr suppresses the formation of Kirkendall voids when Zn or Al is diffused into the base steel sheet. Therefore, the Cr content is preferably 0.50% or more.

[0058] Ni: 0% or more and 5.0% or less Ni (nickel) is an optional element. Ni has the effect of improving magnetic properties (e.g., saturation magnetic flux density). However, if excessively contained, the above effect saturates, resulting in increased costs. Therefore, the Ni content is set to 5.0% or less. The Ni content is preferably 0.50% or less, and more preferably 0.10% or less. There is no need to set a lower limit for Ni, and the lower limit may be 0%. However, to more reliably obtain the above effect, the Ni content is preferably 0.0010% or more.

[0059] Cu: 0% or more and 5.0% or less Cu (copper) is an optional element. Cu has the effect of improving the strength of the steel sheet. However, excessive Cu content may decrease the saturation magnetic flux density, and the above effect saturates, resulting in an increase in costs. Therefore, the Cu content is set to 5.0% or less. The Cu content is preferably 0.10% or less. There is no need to set a lower limit for Cu, and the lower limit may be 0%. However, to obtain the above effect more reliably, the Cu content is preferably 0.0010% or more.

[0060] Ce: 0% or more and 0.100% or less Ce (cerium) is an optional element. Ce has the effect of suppressing the precipitation of fine sulfides (MnS, Cu2S, etc.) by generating coarse sulfides and oxysulfides, improving grain growth, and reducing iron loss. However, if it is contained in excess, oxides are also generated in addition to sulfides and oxysulfides, which may deteriorate iron loss, and the above effect will saturate and lead to an increase in costs. Therefore, the Ce content is set to 0.100% or less. The Ce content is preferably 0.010% or less, more preferably 0.0090% or less, and even more preferably 0.0080% or less. There is no need to limit the lower limit of Ce, and the lower limit may be 0%. However, in order to obtain the above effect more reliably, the Ce content is preferably 0.0010% or more. The Ce content is more preferably 0.0020% or more, more preferably 0.0030% or more, and even more preferably 0.0050% or more.

[0061] The chemical composition of the non-oriented electrical steel sheet according to the present embodiment may contain, in addition to the above elements, optional elements such as B, O, Mg, Ti, V, Zr, Nd, Bi, W, Mo, Nb, and Y. 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. B: 0% or more and 0.100% or less, O: 0% or more and 0.100% or less, Mg: 0% or more and 0.100% or less, Ti: 0% or more and 0.100% or less, V: 0% or more and 0.100% or less, Zr: 0% or more and 0.100% or less, Nd: 0% or more and 0.100% or less, Bi: 0% or more and 0.100% or less, W: 0% or more and 0.100% or less, Mo: 0% or more and 0.10% or less, Nb: 0% or more and 0.100% or less, Y: 0% or more and 0.100% or less.

[0062] Further, the non-oriented electrical steel sheet according to this embodiment has a chemical composition, in mass%, C: 0.001% or more and 0.005% or less, Mn: 0.0010% or more and 3.0% or less, P: 0.0010% or more and 0.30% or less, S: 0.00010% or more and 0.010% or less, N: more than 0.00150% and less than 0.010%, Zn: 0.00010% or more and 0.010% or less, B: 0.00010% or more and 0.100% or less, O: 0.00010% or more and 0.100% or less, Mg: 0.00010% or more and 0.100% or less, Ca: 0.00030% or more and 0.010% or less, Ti: 0.00010% or more and 0.100% or less, V: 0.00010% or more and 0.100% or less, Cr: 0.0010% or more and 10.0% or less, Ni: 0.0010% or more and 5.0% or less, Cu: 0.0010% or more and 5.0% or less, Zr: 0.00020% or more and 0.10% or less, Sn: 0.0010% or more and 0.100% or less, Sb: 0.0010% or more and 0.100% or less, Ce: 0.0010% or more and 0.100% or less, Nd: 0.0020% or more and 0.100% or less, Bi: 0.0020% or more and 0.100% or less, W: 0.0020% or more and 0.100% or less, Mo: 0.0020% or more and 0.10% or less, Nb: 0.00010% or more and 0.100% or less, Y: 0.0020% or more and 0.100% or less, It is preferable that the compound contains at least one of the above.

[0063] Also, 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 Nb content is preferably 0.0020% or less, and the Y content is preferably 0.010% or less. Also, 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.

[0064] The above-mentioned chemical composition may be measured by a general analysis method for steel. For example, the chemical composition may be measured by ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Al may be measured as acid-soluble Al by ICP-AES using the filtrate obtained by thermally decomposing a sample with acid. C and S may be measured by the combustion-infrared absorption method, N by the inert gas fusion-thermal conductivity method, and O by the inert gas fusion-non-dispersive infrared absorption method.

[0065] In the non-oriented electrical steel sheet according to the present embodiment, the crystal grain size of the base steel sheet is not particularly limited, but for example, the crystal grain size is preferably 40 μm or more and 200 μm or less on average. The average crystal grain size of the base steel sheet is preferably 60 μm or more, and more preferably 80 μm or more. On the other hand, the average crystal grain size of the base steel sheet is preferably 150 μm or less, and more preferably 120 μm or less.

[0066] The average grain size may be measured by the intercept method specified in JIS G0551:2020. For example, the average grain size measured by the intercept method in the plate thickness direction and the rolling direction in a longitudinal section structure photograph may be used. As the longitudinal section structure photograph, an optical microscope photograph may be used, and for example, a photograph taken at a magnification of 50 times may be used.

[0067] [Manufacturing method of non-oriented electrical steel sheets] An example of a method for manufacturing the non-oriented electrical steel sheet according to the present embodiment will be described below. Note that the manufacturing method of the non-oriented electrical steel sheet according to the present embodiment is not particularly limited as long as it has the above-mentioned configuration. The manufacturing method described below is one example for manufacturing the non-oriented electrical steel sheet according to the present embodiment, and is a suitable example of the method for manufacturing the non-oriented electrical steel sheet according to the present embodiment.

[0068] For example, the manufacturing method of the non-oriented electrical steel sheet according to the present embodiment may include a casting step, a hot rolling step, a cold rolling step, a surface treatment step, and a finish annealing step. The surface treatment step is a step of plating an Al-containing metal layer on the surface of the steel sheet, and may be carried out, for example, after the hot rolling step or the cold rolling step. The finish annealing step is generally a step of controlling the recrystallization and grain size of steel, but in the present embodiment, it also serves as a heat treatment for diffusing the Al plated in the surface treatment step into the steel sheet.

[0069] Specifically, the method for producing the non-oriented electrical steel sheet according to this embodiment includes the steps of: The method includes a casting process, a hot rolling process, a cold rolling process, a surface treatment process, and a finish annealing process. In the casting process, the chemical composition is, in mass%, Si: 1.0% or more and 5.0% or less, Al: 0.001% or more and 0.03% or less, C: 0% or more and 0.005% or less, Mn: 0% or more and 3.0% or less, P: 0% or more and 0.30% or less, S: 0% or more and 0.010% or less, N: 0% or more and 0.010% or less, Zn: 0% or more and 0.100% or less, Sn: 0% or more and 0.100% or less, Sb: 0% or more and 0.100% or less, Ca: 0% or more and 0.010% or less, Cr: 0% or more and 10.0% or less, Ni: 0% or more and 5.0% or less, Cu: 0% or more and 5.0% or less, Ce: 0% or more and 0.100% or less, B: 0% or more and 0.100% or less, O: 0% or more and 0.100% or less, Mg: 0% or more and 0.100% or less, Ti: 0% or more and 0.100% or less, V: 0% or more and 0.100% or less, Zr: 0% or more and 0.100% or less, Nd: 0% or more and 0.100% or less, Bi: 0% or more and 0.100% or less, W: 0% or more and 0.100% or less, Mo: 0% or more and 0.10% or less, Nb: 0% or more and 0.100% or less, Y: 0% or more and 0.100% or less, and the balance being Fe and impurities, In the hot rolling step, the slab is hot rolled, In the cold rolling step, the steel sheet is subjected to cold rolling, In the surface treatment step, a metal layer (Al-containing metal layer) consisting of Al and impurities is plated on the surface of the steel sheet to a thickness of 3 μm to 35 μm, In the above-mentioned finish annealing process, In the heating process, the steel sheet plated with an Al-containing metal layer is heated to a temperature range of 1,000°C to 1,200°C in an atmosphere of 95% by volume to 100% by volume hydrogen with a dew point of -50°C to 0°C in a heating time of 1 second to 15 hours, and then maintained at the temperature range of 1,000°C to 1,200°C for 1 minute to 10 minutes. In the soaking process, the steel plate after the heating process is cooled to a temperature range of 800°C to 1,100°C, and then soaked at a temperature range of 800°C to 1,100°C (soaking temperature) for 1 minute to 20 hours. In the cooling process, the steel sheet after the soaking process may be cooled to a temperature range of room temperature or higher and 400° C. or lower at an average cooling rate of 0.1° C. / min to 10° C. / min. In addition, the term "room temperature" in this specification corresponds to the "normal temperature" defined in JIS Z 8703, and refers to a range of 20±15°C (5 to 35°C).

[0070] The method for producing a non-oriented electrical steel sheet according to the present embodiment may further include a hot-rolled sheet annealing step after the hot rolling step. The method for producing a non-oriented electrical steel sheet according to the present embodiment may further include a pickling step after the hot rolling step or the hot-rolled sheet annealing step. The method for producing a non-oriented electrical steel sheet according to the present embodiment may further include a coating formation step after the finish annealing step.

[0071] A flow chart of the method for producing a non-oriented electrical steel sheet according to this embodiment is shown in Figure 2. Each step will be described in detail below.

[0072] [Casting process] In the casting process, a slab (steel billet) having the above-mentioned chemical composition may be cast. The chemical composition of the slab is substantially the same as that of the base steel sheet of the non-oriented electrical steel sheet, except for Al. Al is formed as an Al-containing metal layer on the steel sheet by plating in the surface treatment process, and is diffused into the steel sheet in the finish annealing process. Therefore, in this embodiment, the Al content is different between the slab and the final product.

[0073] The casting method is not particularly limited, but for example, a slab may be produced by a continuous casting method, or an ingot may be produced by using molten steel and then blooming the ingot to produce a slab. Alternatively, a slab may be produced by other methods.

[0074] The thickness of the slab is not particularly limited, but may be, for example, 150 mm or more and 350 mm or less. The thickness of the slab is preferably 220 mm or more and 280 mm or less. As the slab, a so-called thin slab having a thickness of 10 mm or more and 70 mm or less may be used.

[0075] [Hot rolling process] 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, but for example, the thickness (finishing thickness) of the hot rolled steel sheet is preferably 1.0 mm or more and 2.5 mm or less. If the thickness is 1.0 mm or more, the load on the hot rolling machine is small, and the productivity in the hot rolling process is high.

[0076] The heating temperature of the slab before hot rolling is not particularly limited, but may be 1000° C. or more and 1300° C. or less from the viewpoint of costs, etc. In the finish hot rolling after the rough rolling, the final rolling temperature of the finish hot rolling is preferably 900° C. or more, and more preferably 950° C. or more.

[0077] [Cold rolling process] 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 (finishing thickness) of the cold-rolled steel sheet is set to 0.10 mm or more and 0.35 mm or less. If the thickness of the cold-rolled steel sheet exceeds 0.35 mm, the magnetic properties may be deteriorated. The steel sheet to be cold-rolled may be any 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, and a steel sheet after a surface treatment process.

[0078] Other cold rolling conditions are not particularly limited, but for example, the cumulative reduction in cold rolling is preferably 60% to 95%. When the reduction is 60% or more, the effect of P on the texture of the non-oriented electrical steel sheet can be more stably obtained. Also, when the reduction is 95% or less, the non-oriented electrical steel sheet can be stably produced on an industrial scale.

[0079] The temperature of the steel sheet during cold rolling may be room temperature. Alternatively, the cold rolling may be warm rolling in which the steel sheet temperature is 100° C. to 200° C. In order to heat the steel sheet to a temperature of 100° C. to 200° C., the steel sheet may be preheated or the rolls may be preheated.

[0080] [Surface treatment process] In the surface treatment step, a metal layer (Al-containing metal layer) consisting of Al and impurities may be plated on the surface of the steel sheet to a thickness of 3 μm to 35 μm. The steel sheet to be surface treated may be any of a steel sheet after a hot rolling step, a steel sheet after a hot-rolled sheet annealing step, a steel sheet after a pickling step, and a steel sheet after a cold rolling step.

[0081] The Al-containing metal layer plated on the surface of the steel sheet preferably contains 90% by mass or more of Al, and more preferably 95% by mass or more. The metal layer may contain impurities as long as they do not impair the function and effect of the present embodiment. For example, the Al-containing metal layer may contain about 5% Si and / or about 0.5% REM. The Al content in the Al-containing metal layer may be 100% by mass.

[0082] The thickness of the Al-containing metal layer plated on the surface of the steel sheet is preferably 4 μm or more, more preferably 5 μm or more. On the other hand, the coating weight is preferably 30 μm or less, more preferably 25 μm or less. When the Al-containing metal layer is plated before cold rolling, the thickness of the Al-containing metal layer is reduced to about 1 / 5 by cold rolling, so it is preferable to set the thickness taking into account the reduction in thickness by cold rolling. For example, it is preferable to set the thickness to 15 μm or more and 35 μm or less within the above-mentioned numerical range.

[0083] The method for plating the surface of the steel sheet with an Al-containing metal layer is not particularly limited, but may be, for example, hot-dip plating, electroplating, molten salt electrolysis, PVD (Physical Vapor Deposition), or CVD (Chemical Vapor Deposition). Among these, hot-dip plating is preferred in consideration of the fact that the material is for motors and the processing costs.

[0084] [Finishing annealing process] In the final annealing process, the steel sheet plated with the Al-containing metal layer is subjected to a heating process, a soaking process, and a cooling process. This final annealing recrystallizes the steel, grows the crystal grains to a desired grain size, and diffuses Al into the steel sheet.

[0085] [Temperature rise process] In the heating process of the final annealing step, the steel sheet is heated to a temperature range of 1,000°C to 1,200°C (heating temperature) in an atmosphere of 95% by volume to 100% by volume hydrogen and a dew point of -50°C to 0°C in a heating time of 1 second to 15 hours, and then held at the temperature range of 1,000°C to 1,200°C for 1 minute to 10 minutes.

[0086] The hydrogen in the atmosphere during the temperature rise process is preferably 96% by volume or more, more preferably 97% by volume or more. On the other hand, this hydrogen is preferably 99% by volume or less, more preferably 98% by volume or less. The dew point of the atmosphere during the temperature rise process is preferably -40°C or more, more preferably -30°C or more. On the other hand, this dew point is preferably -10°C or less, more preferably -20°C or less. The temperature range in the temperature rise process is preferably 1,030°C or more, more preferably 1,050°C or more. On the other hand, this temperature range is preferably 1,150°C or less, more preferably 1,130°C or less. The temperature rise time in the temperature rise process is preferably 2 seconds or more, more preferably 5 seconds or more. On the other hand, this temperature rise time is preferably 12 hours or less, more preferably 10 hours or less. The temperature rise time means the temperature rise time from the temperature at which the temperature rise starts to the temperature rise. The retention time is preferably 2 minutes or more, more preferably 3 minutes or more, while the retention time is preferably 8 minutes or less, more preferably 5 minutes or less.

[0087] It is believed that the above-mentioned temperature rise process causes Si to diffuse from the surface to the inside of the base steel sheet, increasing the Si concentration inside the base steel sheet.

[0088] [Soaking process] In the soaking process of the finish annealing step, the steel sheet after the heating process is cooled to a temperature range of 800°C to 1,100°C, and then soaked at a temperature range of 800°C to 1,100°C (soaking temperature) for 1 minute to 20 hours. In the soaking process, the temperature may fluctuate slightly during soaking as long as it is within the above soaking temperature range. The soaking temperature in the soaking process is lower than the holding temperature in the heating process.

[0089] The temperature range for soaking in the soaking process is preferably 850°C or higher, and more preferably 900°C or higher. On the other hand, this temperature range is preferably 1,080°C or lower, and more preferably 1,060°C or lower. Furthermore, the soaking time for the soaking process is preferably 10 minutes or longer, and more preferably 30 minutes or longer. On the other hand, this time is preferably 10 hours or shorter, and more preferably 5 hours or shorter.

[0090] The atmosphere in the soaking step is not particularly limited, but may be, for example, 95% by volume or more and 100% by volume or less of hydrogen with a dew point of -50°C or more and 0°C or less.

[0091] It is considered that the above-mentioned soaking process causes Al in the Al-containing metal layer to diffuse into the surface region of the base steel sheet, increasing the Al concentration in the surface region of the base steel sheet. This leads to a favorable balance between the Si concentration diffused into the inside of the base steel sheet during the heating process and the Al concentration in the surface region of the base steel sheet, thereby realizing the above-mentioned gradient of the Al concentration and the Si concentration in the base steel sheet.

[0092] [Cooling process] In the cooling process of the finish annealing step, the steel sheet after the soaking process may be cooled to a temperature range of room temperature or higher and 400°C or lower at an average cooling rate of 0.1°C / min to 10°C / min. The average cooling rate means the value obtained by dividing the temperature from the soaking temperature to 400°C by the cooling time from the soaking temperature to 400°C.

[0093] The average cooling rate during the cooling process is preferably 0.3°C / min or more, more preferably 0.5°C / min or more. Meanwhile, this average cooling rate is preferably 5°C / min or less, more preferably 3°C / min or less. Furthermore, the temperature range during the cooling process is preferably 100°C or more, more preferably 150°C or more. Meanwhile, this temperature range is preferably 370°C or less, more preferably 350°C or less.

[0094] Furthermore, if the average cooling rate during the cooling process is slower than the above range, or if the cooling temperature range during the cooling process is higher than the above range, not only may the concentration gradients of Al and Si in the base steel sheet, which are controlled during the soaking process and the heating process, be disturbed during the cooling process, but distortion may remain in the steel, resulting in deterioration of the magnetic properties.

[0095] [Hot-rolled sheet annealing process] The method for producing a non-oriented electrical steel sheet according to the present embodiment may include a hot-rolled sheet annealing step after the hot rolling step. By carrying out the hot-rolled sheet annealing, preferable magnetic properties can be obtained. This hot-rolled sheet annealing may be a heat retention treatment in which the hot-rolled steel sheet is kept at a temperature during cooling after hot rolling.

[0096] The conditions for the hot-rolled sheet annealing are not particularly limited and may be known conditions. For example, when box annealing is performed, it is preferable to hold the sheet in a temperature range of 700° C. to 900° C. for 60 minutes to 20 hours. When continuous annealing is performed, it is preferable to hold the sheet in a temperature range of 900° C. to 1100° C. for 1 second to 180 seconds.

[0097] [Pickling process] The method for producing a non-oriented electrical steel sheet according to the present embodiment may include a pickling step after the hot rolling step or the hot-rolled sheet annealing step. The pickling step may remove scale formed on the surface of the steel sheet. The pickling conditions are not particularly limited and may be known conditions.

[0098] [Film formation process] The method for producing a non-oriented electrical steel sheet according to this embodiment may include a coating formation step after the finish annealing step. In the coating formation step, the steel sheet after the finish annealing step may be subjected to a coating formation process and, if necessary, an annealing process.

[0099] The film formation conditions are not particularly limited and may be known conditions. For example, an insulating film consisting of only organic components, only inorganic components, or an organic-inorganic composite may be applied to the surface of the steel sheet to form the film. From the viewpoint of reducing the environmental load, an insulating film that does not contain chromium may be formed. The film formation process may also be a process of applying an insulating coating that exhibits adhesive properties by heating and pressing. Coating materials that exhibit adhesive properties include acrylic resins, phenolic resins, epoxy resins, and melamine resins.

[0100] [Annealing process] In the annealing process, the steel sheet may be held at a temperature in the range of 750° C. to 850° C. for 30 minutes to 150 minutes. The steel sheet subjected to the annealing process may be either a steel sheet after a coating process or a steel sheet that has been subjected to a punching process or other process to give a shape for forming an iron core after the coating process.

[0101] The temperature range maintained during the annealing process is preferably 760°C or higher, and more preferably 770°C or higher. On the other hand, this temperature range is preferably 840°C or lower, and more preferably 830°C or lower. Furthermore, the time maintained within the above temperature range during the annealing process is preferably 45 minutes or longer, and more preferably 60 minutes or longer. On the other hand, this time is preferably 135 minutes or shorter, and more preferably 120 minutes or shorter.

[0102] This annealing process removes residual strain in the steel, recrystallizes the steel, and may grow the crystal grains to a preferred grain size. Note that the steel sheet after the annealing process according to this embodiment maintains the concentration gradient of each element formed before the annealing process.

[0103] The atmosphere in the annealing process is not particularly limited. For example, the atmosphere in the annealing process may be a nitrogen atmosphere, a hydrogen atmosphere, or a mixed atmosphere of nitrogen and hydrogen. The dew point of the atmosphere in the annealing process is preferably -50°C or higher, more preferably -40°C or higher. On the other hand, the dew point is preferably 0°C or lower, more preferably -10°C or lower.

[0104] By the above-described manufacturing method, the non-oriented electrical steel sheet according to the first embodiment can be manufactured.

[0105] Second embodiment [Non-oriented electrical steel sheet] Next, a non-oriented electrical steel sheet according to a second embodiment will be described. The non-oriented electrical steel sheet according to this embodiment has the following features.

[0106] The non-oriented electrical steel sheet according to this embodiment includes a base steel sheet and an insulating coating, The thickness of the base steel plate is 0.10 mm or more and 0.35 mm or less, When the base steel plate is viewed on a cut surface whose cutting direction is parallel to the plate thickness direction, The average Sn concentration in the region from the surface of the base steel plate to 1 / 10 of the plate thickness is The Sn concentration is 1.5 mass% or more higher than the Sn concentration at 1 / 4 of the plate thickness, and The Sn concentration is 3.0 mass% or more higher than the Sn concentration at 1 / 2 the plate thickness. The Sn concentration at the quarter thickness portion is The Sn concentration is 1.5 mass% or more higher than the Sn concentration at the half thickness portion, The average Si concentration in the region from the surface to 1 / 10 of the plate thickness of the base steel plate is The Si concentration is 0.5 mass% or more lower than the Si concentration at 1 / 4 of the plate thickness, and The Si concentration is 1.0 mass% or more lower than the Si concentration at 1 / 2 the plate thickness. The Si concentration at the quarter thickness portion is The Si concentration is lower by 0.5 mass % or more than the Si concentration at the half plate thickness portion.

[0107] Moreover, the chemical composition of the base steel sheet of the non-oriented electrical steel sheet according to the second embodiment is substantially the same as that of the base steel sheet of the first embodiment, except for Al and Sn. Therefore, in the following, a description of the same configuration as in the first embodiment will be omitted, and only the characteristic parts of the second embodiment will be described in detail.

[0108] [Sn concentration gradient] In the non-oriented electrical steel sheet according to the second embodiment, when the base steel sheet is viewed on a cut surface parallel to the sheet thickness direction, the average Sn concentration in the region from the surface of the base steel sheet to 1 / 10 of the sheet thickness (surface layer region) is 1.50 mass% or more higher than the Sn concentration at 1 / 4 of the sheet thickness and 3.0 mass% or more higher than the Sn concentration at 1 / 2 of the sheet thickness. From the viewpoint of reducing eddy current loss, the average Sn concentration in the surface layer region is preferably 1.8 mass% or more higher, and more preferably 2.0 mass% or more higher than the Sn concentration at 1 / 4 of the sheet thickness. Moreover, the average Sn concentration in the surface layer region is preferably 3.5 mass% or more higher, and more preferably 4.0 mass% or more higher than the Sn concentration at 1 / 2 of the sheet thickness.

[0109] Furthermore, in the non-oriented electrical steel sheet according to this embodiment, when viewed from the above-mentioned cut surface, the Sn concentration at 1 / 4 of the sheet thickness is higher by 1.50 mass % or more than the Sn concentration at 1 / 2 of the sheet thickness. From the viewpoint of reducing eddy current loss, the Sn concentration at 1 / 4 of the sheet thickness is preferably higher by 1.8 mass % or more, and more preferably higher by 2.0 mass % or more, than the Sn concentration at 1 / 2 of the sheet thickness.

[0110] The average Sn concentration in the surface region, the Sn concentration in the 1 / 4 thickness portion, and the Sn concentration in the 1 / 2 thickness portion may satisfy the above relationship. Therefore, the Sn concentration in the surface region, the 1 / 4 thickness portion, and the 1 / 2 thickness portion as a chemical composition is not particularly limited. However, the average Sn concentration in the surface region where the Sn concentration is maximum in the cut surface is preferably 15 mass% or less, more preferably 12 mass% or less, as a chemical composition. The average Sn concentration in the surface region is preferably 3.0 mass% or more, more preferably 5.0 mass% or more, and even more preferably 7.0 mass% or more, as a chemical composition. Similarly, the Sn concentration in the 1 / 2 thickness portion where the Sn concentration is minimum in the cut surface is preferably 0.001 mass% or more, more preferably 0.01 mass% or more, as a chemical composition. The Sn concentration at the 1 / 2 plate thickness portion, in terms of the chemical composition, is preferably 9.0 mass % or less, more preferably 4.0 mass % or less, and even more preferably 2.0 mass % or less.

[0111] The Sn concentration gradient can be confirmed by checking a cut surface parallel to the sheet thickness direction with an EPMA (Electron Probe Micro Analyzer) in the same manner as in the first embodiment for checking the Al concentration gradient.

[0112] [Si concentration gradient] The Si concentration gradient in the non-oriented electrical steel sheet according to the second embodiment and the method for confirming the same are similar to the Si concentration gradient in the first embodiment.

[0113] [Chemical composition] The non-oriented electrical steel sheet according to the second embodiment can obtain the effect as long as the Sn concentration gradient and the Si concentration gradient are controlled as described above, so the chemical composition of the base steel sheet is not particularly limited. The base steel sheet may contain Si and Sn as a chemical composition, and may contain selected elements as necessary, with the balance being Fe and impurities. Each element will be described below, but the chemical composition of the base steel sheet of the non-oriented electrical steel sheet according to the second embodiment is substantially the same as the chemical composition of the base steel sheet of the first embodiment, except for Al and Sn. Therefore, in the following description of the chemical composition, the characteristic parts of the chemical composition of the second embodiment will be described in detail.

[0114] Sn: 0.300% or more and 10.000% or less Sn (tin) is an element effective in grading the Sn concentration in the base steel sheet. Therefore, the Sn content is set to 0.300% or more as an average of the entire base steel sheet. The Sn content is preferably 0.400% or more, and more preferably 0.500% or more. On the other hand, even if an excessive amount of Sn is contained, the above effect is saturated. Therefore, the Sn content is set to 10.000% or less as an average of the entire base steel sheet. The Sn content is preferably 5.000% or less, and more preferably 4.000% or less.

[0115] Al: 0% or more and 3.0% or less Al (aluminum) is an optional element. Al has the effect of improving the texture of the non-oriented electrical steel sheet and improving the magnetic properties (e.g., magnetic flux density). However, excessive Al content may embrittle the steel and cause cold rolling fracture, and may also deteriorate the magnetic properties. For this reason, the Al content is set to 3.0% or less. There is no need to limit the lower limit of Al, and the lower limit may be 0%. However, in order to more reliably obtain the above effect, the Al content is preferably 0.1% or more, and more preferably 0.2% or more. In this embodiment, Al means acid-soluble aluminum (sOL.Al).

[0116] Furthermore, the chemical composition of the non-oriented electrical steel sheet according to the second embodiment may further contain, as in the first embodiment, one or more of the following optional elements: B, O, Mg, Ti, V, Zr, Nd, Bi, W, Mo, Nb, and Y.

[0117] Further, the non-oriented electrical steel sheet according to the second embodiment has a chemical composition, in mass%, C: 0.001% or more and 0.005% or less, Mn: 0.0010% or more and 3.0% or less, P: 0.0010% or more and 0.30% or less, S: 0.00010% or more and 0.010% or less, N: more than 0.00150% and less than 0.010%, Zn: 0.00010% or more and 0.010% or less, B: 0.00010% or more and 0.100% or less, O: 0.00010% or more and 0.100% or less, Mg: 0.00010% or more and 0.100% or less, Ca: 0.00030% or more and 0.010% or less, Ti: 0.00010% or more and 0.100% or less, V: 0.00010% or more and 0.100% or less, Cr: 0.0010% or more and 10.0% or less, Ni: 0.0010% or more and 5.0% or less, Cu: 0.0010% or more and 5.0% or less, Zr: 0.00020% or more and 0.10% or less, Al: 0.1% or more and 3.0% or less, Sb: 0.0010% or more and 0.100% or less, Ce: 0.0010% or more and 0.100% or less, Nd: 0.0020% or more and 0.100% or less, Bi: 0.0020% or more and 0.100% or less, W: 0.0020% or more and 0.100% or less, Mo: 0.0020% or more and 0.10% or less, Nb: 0.00010% or more and 0.100% or less, Y: 0.0020% or more and 0.100% or less, It is preferable that the compound contains at least one of the above.

[0118] [Manufacturing method of non-oriented electrical steel sheets] The method for producing a non-oriented electrical steel sheet according to the second embodiment is substantially the same as that of the first embodiment, except for the chemical composition of the slab during casting and the surface treatment step.

[0119] In the casting process of the second embodiment, the chemical composition is, in mass%, Si: 1.0% or more and 5.0% or less, Sn: 0% or more and 0.100% or less, C: 0% or more and 0.005% or less, Mn: 0% or more and 3.0% or less, P: 0% or more and 0.30% or less, S: 0% or more and 0.010% or less, N: 0% or more and 0.010% or less, Zn: 0% or more and 0.100% or less, Al: 0% or more and 0.10% or less, Sb: 0% or more and 0.100% or less, Ca: 0% or more and 0.010% or less, Cr: 0% or more and 10.0% or less, Ni: 0% or more and 5.0% or less, Cu: 0% or more and 5.0% or less, Ce: 0% or more and 0.100% or less, B: 0% or more and 0.100% or less, O: 0% or more and 0.100% or less, Mg: 0% or more and 0.100% or less, Ti: 0% or more and 0.100% or less, V: 0% or more and 0.100% or less, Zr: 0% or more and 0.100% or less, Nd: 0% or more and 0.100% or less, Bi: 0% or more and 0.100% or less, W: 0% or more and 0.100% or less, Mo: 0% or more and 0.10% or less, Nb: 0% or more and 0.100% or less, Y: 0% or more and 0.100% or less, The cast slab contains 0.01% by weight of Cr, with the balance being Fe and impurities.

[0120] [Surface treatment process] In the surface treatment step of the second embodiment, a metal layer made of Sn and impurities (Sn-containing metal layer) is plated onto the surface of the steel sheet to a thickness of 3 μm or more and 35 μm or less.

[0121] In the surface treatment step, a metal layer containing Sn and impurities may be plated on the surface of the steel sheet to a thickness of 3 μm to 35 μm. The steel sheet to be surface treated may be any of a steel sheet after a hot rolling step, a steel sheet after a hot-rolled sheet annealing step, a steel sheet after a pickling step, and a steel sheet after a cold rolling step.

[0122] The Sn-containing metal layer plated on the surface of the steel sheet preferably contains 90% by mass or more, more preferably 95% by mass or more of Sn. The metal layer may contain impurities as long as they do not impair the function and effect of the present embodiment. For example, the Sn-containing metal layer may contain about 5% Si and / or about 0.5% REM. The Sn content in the Sn-containing metal layer may be 100% by mass.

[0123] In addition, the thickness of the Sn-containing metal layer plated on the surface of the steel sheet is preferably 4 μm or more, more preferably 5 μm or more. On the other hand, the coating weight is preferably 30 μm or less, more preferably 25 μm or less. When the Sn-containing metal layer is plated before cold rolling, the thickness of the Sn-containing metal layer is reduced to about 1 / 5 by cold rolling, so it is preferable to set the thickness taking into account the reduction in thickness by cold rolling. For example, it is preferable to set the thickness to 15 μm or more and 35 μm or less within the above-mentioned numerical range.

[0124] The method for plating the surface of the steel sheet with the Sn-containing metal layer is not particularly limited, but may be, for example, hot-dip plating, electroplating, molten salt electrolysis, PVD (Physical Vapor Deposition), or CVD (Chemical Vapor Deposition) as in the first embodiment. Among these, hot-dip plating is preferred in consideration of the fact that the material is for motors and the processing costs.

[0125] Other manufacturing steps and conditions thereof are similar to those of the first embodiment. By the above-described manufacturing method, the non-oriented electrical steel sheet according to the second embodiment can be manufactured.

[0126] Third embodiment [Non-oriented electrical steel sheet] Next, a non-oriented electrical steel sheet according to a third embodiment will be described. The non-oriented electrical steel sheet according to this embodiment has the following features.

[0127] The non-oriented electrical steel sheet according to this embodiment includes a base steel sheet and an insulating coating, The thickness of the base steel plate is 0.10 mm or more and 0.35 mm or less, When the base steel plate is viewed on a cut surface whose cutting direction is parallel to the plate thickness direction, The sum of the average Al concentration and the average Sn concentration in the region from the surface of the base steel plate to 1 / 10 of the plate thickness, The Al concentration and Sn concentration at the 1 / 4 part of the plate thickness are 1.5 mass% or more higher than the total concentration, and The Al concentration and Sn concentration at the half thickness portion are 3.0 mass% or more higher than the total concentration, The sum of the Al concentration and the Sn concentration at the quarter thickness portion is The Al concentration and the Sn concentration in the plate thickness 1 / 2 portion are 1.5 mass% or more higher than the total of the Al concentration and the Sn concentration, The average Si concentration in the region from the surface to 1 / 10 of the plate thickness of the base steel plate is The Si concentration is 0.5 mass% or more lower than the Si concentration at 1 / 4 of the plate thickness, and The Si concentration is 1.0 mass% or more lower than the Si concentration at 1 / 2 the plate thickness. The Si concentration at the quarter thickness portion is The Si concentration is lower by 0.5 mass % or more than the Si concentration at the half plate thickness portion.

[0128] Moreover, the chemical composition of the base steel sheet of the non-oriented electrical steel sheet according to this embodiment is substantially the same as that of the base steel sheet of the first embodiment, except that Al and Sn are both basic elements. Therefore, in the following, a description of the same configuration as in the first embodiment will be omitted, and only the characteristic parts of the third embodiment will be described in detail.

[0129] [Al concentration gradient and Sn concentration gradient] In the non-oriented electrical steel sheet according to the third embodiment, when the base steel sheet is viewed on a cut surface parallel to the sheet thickness direction, the sum of the average Al concentration and the average Sn concentration in the region (surface layer region) from the surface of the base steel sheet to 1 / 10 of the sheet thickness is 1.50 mass% or more higher than the sum of the Al concentration and the Sn concentration at 1 / 4 of the sheet thickness, and is 3.0 mass% or more higher than the sum of the Al concentration and the Sn concentration at 1 / 2 of the sheet thickness. From the viewpoint of reducing eddy current loss, the sum of the average Al concentration and the average Sn concentration in the surface layer region is preferably 1.8 mass% or more higher, more preferably 2.0 mass% or more higher, than the sum of the Al concentration and the Sn concentration at 1 / 4 of the sheet thickness. In addition, the sum of the average Al concentration and the average Sn concentration in the surface layer region is preferably 3.5 mass% or more higher, more preferably 4.0 mass% or more higher than the sum of the Al concentration and the Sn concentration at 1 / 2 of the sheet thickness.

[0130] In the first and second embodiments, either the Al concentration or the Sn concentration is controlled to have a gradient along the sheet thickness direction, but in the third embodiment, both the Al concentration and the Sn concentration may be controlled to have a gradient. By providing a concentration gradient in both the Al concentration and the Sn concentration in the sheet thickness direction, the high-frequency iron loss (W 10 / 400 In addition to the effect of reducing low-frequency iron loss (W 15 / 50 )) can also be reduced.

[0131] Furthermore, in the non-oriented electrical steel sheet according to this embodiment, when viewed from the above-mentioned cut surface, the sum of the Al concentration and the Sn concentration at 1 / 4 of the sheet thickness is higher by 1.50 mass % or more than the sum of the Al concentration and the Sn concentration at 1 / 2 of the sheet thickness. From the viewpoint of reducing eddy current loss, the sum of the Al concentration and the Sn concentration at 1 / 4 of the sheet thickness is preferably higher by 1.8 mass % or more, and more preferably by 2.0 mass % or more, than the sum of the Al concentration and the Sn concentration at 1 / 2 of the sheet thickness.

[0132] The average Al concentration and the average Sn concentration of the surface layer region, the sum of the average Al concentration and the average Sn concentration, the Al concentration and the Sn concentration of the 1 / 4 plate thickness portion, the sum of the average Al concentration and the average Sn concentration, and the Al concentration and the Sn concentration of the 1 / 2 plate thickness portion, the sum of the average Al concentration and the average Sn concentration, may satisfy the above relationship. Therefore, the Al concentration, the Sn concentration, the sum of the average Al concentration and the average Sn concentration as the chemical composition in the surface layer region, the 1 / 4 plate thickness portion, and the 1 / 2 plate thickness portion are not particularly limited. However, the average Al concentration and the average Sn concentration of the surface layer region where the Al concentration and the Sn concentration are maximum in the above-mentioned cut surface are both preferably 15 mass% or less, more preferably 12 mass% or less, as the chemical composition. The average Al concentration and the average Sn concentration of the surface layer region are both preferably 1.0 mass% or more, more preferably 3.0 mass% or more, and even more preferably 4.0 mass% or more, as the chemical composition. The sum of the average Al concentration and the average Sn concentration in the surface region is preferably 30% by mass or less, more preferably 24% by mass or less. The sum of the average Al concentration and the average Sn concentration in the surface region is preferably 2.0% by mass or more, more preferably 5.0% by mass or more, and even more preferably 7.0% by mass or more. Similarly, the Al concentration and the Sn concentration in the 1 / 2 plate thickness portion where the Al concentration and the Sn concentration in the cut surface are the minimum values ​​are preferably 0.001% by mass or more, and even more preferably 0.01% by mass or more, in terms of chemical composition. The Al concentration and the Sn concentration in the 1 / 2 plate thickness portion are preferably 10.0% by mass or less, more preferably 4.0% by mass or less, and even more preferably 2.0% by mass or less, in terms of chemical composition. The sum of the average Al concentration and the average Sn concentration in the 1 / 2 plate thickness portion is preferably 0.002% by mass or more, and even more preferably 0.02% by mass or more. The sum of the average Al concentration and the average Sn concentration at the 1 / 2 sheet thickness portion is preferably 20.0 mass % or less, more preferably 10.0 mass % or less, and further preferably 4.0 mass % or less.

[0133] The above-mentioned Al concentration gradient and Sn concentration gradient can be confirmed by using an EPMA (Electron Probe Micro Analyzer) on a cut surface cut in a direction parallel to the sheet thickness direction, in the same manner as in the method for confirming the Al concentration gradient in the first embodiment.

[0134] [Si concentration gradient] The Si concentration gradient and the method for confirming it in the non-oriented electrical steel sheet according to the third embodiment are similar to the Si concentration gradient in the first embodiment.

[0135] [Chemical composition] The non-oriented electrical steel sheet according to the third embodiment can obtain the effect as long as the Al concentration gradient, Sn concentration gradient, and Si concentration gradient are controlled as described above, so the chemical composition of the base steel sheet is not particularly limited. The base steel sheet may contain Si, Al, and Sn as a chemical composition, and may contain selected elements as necessary, with the balance being Fe and impurities. Each element will be described below, but the chemical composition of the base steel sheet of the non-oriented electrical steel sheet according to the third embodiment is substantially the same as the chemical composition of the base steel sheet of the first embodiment, except for Sn. Therefore, in the following description of the chemical composition, the characteristic parts of the chemical composition of the third embodiment will be described in detail.

[0136] Al: 1.0% or more and 10.0% or less Al (aluminum) is an element effective in grading the Al concentration in the base steel sheet. Therefore, the Al content is set to 1.0% or more as an average of the entire base steel sheet. The Al content is preferably 1.5% or more, and more preferably 2.0% or more. On the other hand, even if an excessive amount is contained, the above effect is saturated. Therefore, the Al content is set to 10.0% or less as an average of the entire base steel sheet. The Al content is preferably 9.0% or less, and more preferably 8.0% or less. In this embodiment, Al means acid-soluble aluminum (sol.Al).

[0137] Sn: 0.3% or more and 10.0% or less Sn (tin) is an element effective in grading the Sn concentration in the base steel sheet. Therefore, the Sn content is set to 0.3% or more as an average of the entire base steel sheet. The Sn content is preferably 0.4% or more, and more preferably 0.5% or more. On the other hand, even if the Sn content is excessively high, the above effect saturates. Therefore, the Sn content is set to 10.0% or less as an average of the entire base steel sheet. The Sn content is preferably 8.0% or less, and more preferably 6.0% or less.

[0138] Furthermore, the chemical composition of the non-oriented electrical steel sheet according to the third embodiment may further contain, as in the first embodiment, one or more selected elements, for example, B, O, Mg, Ti, V, Zr, Nd, Bi, W, Mo, Nb, and Y.

[0139] In addition, the non-oriented electrical steel sheet according to the third embodiment further comprises, as a chemical composition, in mass%, C: 0.001% or more and 0.005% or less, Mn: 0.0010% or more and 3.0% or less, P: 0.0010% or more and 0.30% or less, S: 0.00010% or more and 0.010% or less, N: more than 0.00150% and less than 0.010%, Zn: 0.00010% or more and 0.010% or less, B: 0.00010% or more and 0.100% or less, O: 0.00010% or more and 0.100% or less, Mg: 0.00010% or more and 0.100% or less, Ca: 0.00030% or more and 0.010% or less, Ti: 0.00010% or more and 0.100% or less, V: 0.00010% or more and 0.100% or less, Cr: 0.0010% or more and 10.0% or less, Ni: 0.0010% or more and 5.0% or less, Cu: 0.0010% or more and 5.0% or less, Zr: 0.00020% or more and 0.100% or less, Sb: 0.0010% or more and 0.100% or less, Ce: 0.0010% or more and 0.100% or less, Nd: 0.0020% or more and 0.100% or less, Bi: 0.0020% or more and 0.100% or less, W: 0.0020% or more and 0.100% or less, Mo: 0.0020% or more and 0.10% or less, Nb: 0.00010% or more and 0.100% or less, Y: 0.0020% or more and 0.100% or less, It is preferable that the compound contains at least one of the above.

[0140] [Manufacturing method of non-oriented electrical steel sheets] The method for producing a non-oriented electrical steel sheet according to the third embodiment is substantially the same as that of the first embodiment, except for the chemical composition of the slab during casting and the surface treatment step.

[0141] In the casting process of the third embodiment, the chemical composition is, in mass%, Si: 1.0% or more and 5.0% or less, Sn: 0% or more and 0.100% or less, C: 0% or more and 0.005% or less, Mn: 0% or more and 3.0% or less, P: 0% or more and 0.30% or less, S: 0% or more and 0.010% or less, N: 0% or more and 0.010% or less, Zn: 0% or more and 0.100% or less, Al: 0% or more and 0.10% or less, Sb: 0% or more and 0.100% or less, Ca: 0% or more and 0.010% or less, Cr: 0% or more and 10.0% or less, Ni: 0% or more and 5.0% or less, Cu: 0% or more and 5.0% or less, Ce: 0% or more and 0.100% or less, B: 0% or more and 0.100% or less, O: 0% or more and 0.100% or less, Mg: 0% or more and 0.100% or less, Ti: 0% or more and 0.100% or less, V: 0% or more and 0.100% or less, Zr: 0% or more and 0.100% or less, Nd: 0% or more and 0.100% or less, Bi: 0% or more and 0.100% or less, W: 0% or more and 0.100% or less, Mo: 0% or more and 0.10% or less, Nb: 0% or more and 0.100% or less, Y: 0% or more and 0.100% or less, The cast slab contains 0.01% by weight of Cr, with the balance being Fe and impurities.

[0142] [Surface treatment process] In the surface treatment step of the third embodiment, a metal layer made of Al, Sn and impurities (Al+Sn-containing metal layer) is plated on the surface of the steel sheet to a thickness of 3 μm to 35 μm.

[0143] In the surface treatment step, a metal layer consisting of Al, Sn and impurities may be plated on the surface of the steel sheet to a thickness of 3 μm to 35 μm. The steel sheet to be surface treated may be any of a steel sheet after a hot rolling step, a steel sheet after a hot-rolled sheet annealing step, a steel sheet after a pickling step, and a steel sheet after a cold rolling step.

[0144] The total amount of Al and Sn contained in the Al+Sn-containing metal layer plated on the surface of the steel sheet is preferably 90% by mass or more, more preferably 95% by mass or more. The Sn content is preferably 10% by mass or more and 90% by mass or less, more preferably 20% by mass or more and 80% by mass or less. The Al content is preferably 10% by mass or more and 90% by mass or less, more preferably 20% by mass or more and 80% by mass or less. The metal layer may contain impurities as long as they do not impair the action and effect of the present embodiment. For example, the Al+Sn-containing metal layer may contain about 5% Si and / or about 0.5% REM. The Al+Sn content in the Al+Sn-containing metal layer may be 100% by mass.

[0145] The thickness of the Al+Sn-containing metal layer plated on the surface of the steel sheet is preferably 4 μm or more, more preferably 5 μm or more. On the other hand, the coating weight is preferably 30 μm or less, more preferably 25 μm or less. When the Al+Sn-containing metal layer is plated before cold rolling, the thickness of the Al+Sn-containing metal layer is reduced to about 1 / 5 by cold rolling, so it is preferable to set the thickness taking into account the reduction in thickness by cold rolling. For example, it is preferable to set the thickness to 15 μm or more and 35 μm or less within the above-mentioned numerical range.

[0146] The method for plating the Al+Sn-containing metal layer on the surface of the steel sheet is not particularly limited, but may be, for example, hot-dip plating, electroplating, molten salt electrolysis, PVD (Physical Vapor Deposition), or CVD (Chemical Vapor Deposition) as in the first embodiment. Among these, hot-dip plating is preferred in consideration of the fact that the material is for motors and the processing costs.

[0147] Other manufacturing steps and conditions thereof are similar to those of the first and second embodiments. By the above-described manufacturing method, the non-oriented electrical steel sheet according to the third embodiment can be manufactured.

[0148] [Iron core] The iron core according to this embodiment may include any one of the non-oriented electromagnetic steel sheets according to the first to third embodiments described above. In particular, the iron core according to this embodiment may be a laminated body obtained by stacking and integrating non-oriented electromagnetic steel sheets having the above-mentioned characteristics and a shape for forming the iron core. The iron core according to this embodiment may be an integral punched core or a split core.

[0149] [Manufacturing method of iron core] The manufacturing method of the iron core according to this embodiment may include a step of stacking the non-oriented electromagnetic steel sheets according to any one of the first to third embodiments described above. More specifically, the manufacturing method of the iron core according to this embodiment may include a stacking step of stacking and integrating non-oriented electromagnetic steel sheets having the above-mentioned characteristics and a shape for forming the iron core. The number of stacked non-oriented electromagnetic steel sheets and the stacking conditions may be adjusted according to the purpose.

[0150] In addition, when the steel plate to be used in the method for manufacturing an iron core according to this embodiment does not have a shape for forming an iron core, a punching process may be performed before the lamination process to obtain a punched member by punching the steel plate. The punched shape and punching conditions of the steel plate may be adjusted according to the purpose.

[0151] Furthermore, the method for manufacturing an iron core according to this embodiment may include a stress relief annealing step after the above punching step or after the above lamination step.

[0152] When the stress relief annealing step is performed in the manufacturing method of the iron core according to the present embodiment, the annealing step of the coating step may be omitted in the manufacturing method of the non-oriented electrical steel sheet described above. For example, the steel sheet after the above-mentioned finish annealing step may be subjected to the coating step of the coating step, and the steel sheet after the coating step may be subjected to the punching step without being subjected to the annealing step of the coating step, and the punched member may be subjected to the lamination step. Then, the stress relief annealing step may be performed after the punching step or the lamination step.

[0153] This stress relief annealing process removes residual strain in the steel, recrystallizes the steel, and may grow the crystal grains to a preferred grain size. Note that the steel sheet after stress relief annealing according to this embodiment maintains the concentration gradient of each element formed before stress relief annealing.

[0154] In the stress relief annealing step, the punched member or the laminate may be held at a temperature in the range of 750°C to 850°C for 30 minutes to 150 minutes. The atmosphere in the stress relief annealing step is not particularly limited. For example, the atmosphere in the stress relief annealing step may be a nitrogen atmosphere, a hydrogen atmosphere, or a mixed atmosphere of nitrogen and hydrogen. The dew point of the atmosphere in the stress relief annealing step may be -50 to 0°C.

[0155] [Motor] The motor according to this embodiment may include the above-mentioned iron core. More specifically, the motor mainly includes a stator, a rotor, bearings, a bracket, and lead wires, and the motor according to this embodiment may include the above-mentioned iron core as the iron core of the stator or rotor. The motor according to this embodiment is preferably a drive motor for a hybrid drive vehicle or an electric vehicle, and is preferably a PM motor such as an IPM motor or an SPM motor.

[0156] [Motor manufacturing method] The manufacturing method of the motor according to this embodiment may include a step of laminating any one of the non-oriented electromagnetic steel sheets according to the first to third embodiments described above to obtain an iron core, and a step of assembling this iron core to obtain a motor. More specifically, the manufacturing method of this motor may include a lamination step of laminating non-oriented electromagnetic steel sheets having the above-mentioned characteristics and a shape for forming an iron core to obtain an iron core, and an assembly step of assembling this iron core as a stator core or a rotor core to obtain a motor. The number of layers of the non-oriented electromagnetic steel sheets, the lamination conditions, and the assembly conditions of the iron core may be adjusted according to the purpose.

[0157] As in the above-described method for manufacturing an iron core, if the steel plate used in the method for manufacturing a motor according to this embodiment does not have a shape for forming an iron core, a punching step may be included before the lamination step, in which the steel plate is punched to obtain a punched member. The punched shape and punching conditions of the steel plate may be adjusted according to the purpose.

[0158] Furthermore, similarly to the above-described method for manufacturing the iron core, the method for manufacturing the motor according to this embodiment may include a stress relief annealing step after the punching step or after the lamination step. When this stress relief annealing step is performed, the annealing step of the coating formation step may be omitted in the above-described method for manufacturing the non-oriented electrical steel sheet. The stress relief annealing conditions in the method for manufacturing the motor according to this embodiment may be the same as the stress relief annealing conditions in the above-described method for manufacturing the iron core. EXAMPLES

[0159] The effects of one aspect of the present invention will be explained in more detail by way of examples, but the conditions in the examples are merely examples of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to these examples. Various conditions may be adopted in the present invention as long as they do not deviate from the gist of the present invention and the object of the present invention is achieved. The present invention will be explained in detail below by way of examples of the present invention and comparative examples.

[0160] Non-oriented electrical steel sheets were manufactured by carrying out each step under the conditions shown in Tables 3A to 3C using slabs having the chemical compositions shown in Tables 1A to 1F. The chemical compositions of the base steel sheets of the manufactured non-oriented electrical steel sheets are as shown in Tables 2A to 2F. In each manufacturing process, pickling was performed after hot rolling or after hot-rolled sheet annealing, and an Al-containing metal layer was plated on the steel sheet after cold rolling. After finish annealing, the steel sheet was subjected to a coating formation process to form an insulating coating.

[0161] Moreover, non-oriented electrical steel sheets were manufactured by carrying out each step under the conditions shown in Tables 6A to 6C using slabs having the chemical compositions shown in Tables 1A to 1F. The chemical compositions of the base steel sheets of the manufactured non-oriented electrical steel sheets are as shown in Tables 5A to 5F. Moreover, in each manufacturing process, pickling was performed after hot rolling or after hot-rolled sheet annealing, and after cold rolling, a Sn-containing metal layer was plated on the steel sheet, and after finish annealing, the steel sheet was subjected to a coating formation process to form an insulating coating.

[0162] Furthermore, non-oriented electrical steel sheets were manufactured by carrying out each process under the conditions shown in Tables 9A to 9C using slabs having the chemical compositions shown in Tables 1A to 1F. The chemical compositions of the base steel sheets of the manufactured non-oriented electrical steel sheets are as shown in Tables 8A to 8F. In each manufacturing process, pickling was performed after hot rolling or after hot-rolled sheet annealing, and an Al+Sn-containing metal layer was plated on the steel sheet after cold rolling, and after finish annealing, the steel sheet was subjected to a coating formation process to form an insulating coating.

[0163] The base steel sheet of the manufactured non-oriented electrical steel sheet was measured for sheet thickness, Si concentration gradient, Al concentration gradient, chemical composition, average crystal grain size, etc. The measurement methods are as described above. The measurement results are shown in Tables 4A to 4C, 7A to 7C, and 10A to 10C.

[0164] "-" in each table means that the content of the corresponding element is 0% in the significant figures (numbers up to the least significant digit) specified in the embodiment. In addition, the manufacturing conditions represented by "-" in each table indicate that the control was not performed. In addition, the "surface layer region" shown in each table corresponds to the region from the surface of the base steel sheet to 1 / 10 of the sheet thickness. In addition, the remainder other than Al and / or Sn in the "Al-containing metal layer", "Sn-containing metal layer" or "Al+Sn-containing metal layer" shown in each table is impurities such as Fe. In addition, the sheet thickness of the base steel sheet of the manufactured non-oriented electrical steel sheet was the same as the sheet thickness of the steel sheet after the cold rolling process.

[0165] The magnetic flux density, core loss characteristics, and punchability of the produced non-oriented electrical steel sheets were evaluated.

[0166] The magnetic flux density and core loss characteristics were evaluated based on the Single Sheet Tester (SST) defined in JIS C 2556:2015 using steel sheets subjected to the annealing process (800°C for 60 minutes) after the above-mentioned coating process. Note that instead of taking test pieces of the size defined in JIS, smaller test pieces, for example, test pieces of width 55 mm x length 55 mm, may be taken and measurements based on the Single Sheet Magnetic Property Tester. In addition, if a test piece of width 55 mm x length 55 mm cannot be taken, two test pieces of width 8 mm x length 16 mm may be used to make a test piece of width 16 mm x length 16 mm, and measurements based on the Single Sheet Magnetic Property Tester may be performed. In this case, the Epstein equivalent value converted to the measurement value using the Epstein tester defined in JIS C 2550:2011 may be used.

[0167] The magnetic flux density in the rolling direction when the steel sheet is magnetized with a magnetizing force of 5000 A / m is B. 50 The magnetic flux density B is measured in Tesla (T). 50 In addition, the iron loss characteristic was determined as being acceptable when the steel sheet was magnetized at a magnetic flux density of 1.500 T at 50 Hz, and the iron loss W 15 / 50 (commercial frequency iron loss), and iron loss W in the rolling direction when the steel sheet is magnetized at 1 kHz with a magnetic flux density of 1.0 T 10 / 1k (High frequency iron loss) was measured and calculated in units of W / kg. Iron loss W 15 / 50 is 2.200W / kg or less, and the iron loss W 10 / 1k However, it was judged to pass if it was 33W / kg or less.

[0168] The punchability was evaluated by punching a 5 mm circular mold with a steel die using a steel sheet that had been subjected to the above-mentioned coating formation process but not the annealing process, and measuring the burr height. The clearance was 6% of the sheet thickness, and punching was performed using quick-drying oil. A specimen was deemed to have passed the test when the number of punches required to reach a burr height of 50 μm or more was 500,000 or more. The evaluation results of each property are shown in Tables 4D to 4F, 7D to 7F, and 10D to 10F.

[0169] As shown in Tables 4D to 4F, 7D to 7F, and 10D to 10F, among Test Nos. 1 to 291, the inventive examples were all excellent in magnetic flux density, core loss characteristics, and punchability as non-oriented electrical steel sheets. On the other hand, among Test Nos. 1 to 291, the comparative examples were not excellent in at least one of magnetic flux density, core loss characteristics, or punchability.

[0170] Next, the manufactured non-oriented electromagnetic steel sheet that had been subjected to the coating formation process but not the annealing process was punched, and the punched parts were laminated to manufacture an iron core. The manufactured iron core contained the above-mentioned non-oriented electromagnetic steel sheet. In addition, the manufactured iron core was subjected to stress relief annealing, and the iron core was used as a stator core or a rotor core and assembled to manufacture a motor. The manufactured motor contained the above-mentioned iron core. In the above-mentioned stress relief annealing, the iron core was held at a temperature range of 750°C to 850°C for 30 minutes to 150 minutes.

[0171] The manufactured motor was connected to a load motor via a torque sensor (MAGTROL TM308). The manufactured motor was driven by supplying three-phase AC current from an inverter. The current and voltage supplied from the inverter were measured with a power meter (Yokogawa Electric Model WT1804E) and used as the input. From the torque T (unit: N m) measured by the torque sensor and the rotation speed N (rpm), 2πTN / 60 = output (W) was calculated. Efficiency (%) was calculated as output / input x 100. The manufactured cores and motors had excellent torque characteristics and energy efficiency when using the non-oriented electrical steel sheets that were examples of the present invention from among the above-mentioned Test Nos. 1 to 291. On the other hand, the manufactured cores and motors had poor torque characteristics and energy efficiency when using the non-oriented electrical steel sheets that were comparative examples from among the above-mentioned Test Nos. 1 to 291.

[0172] [Table 1A]

[0173] [Table 1B]

[0174]

Table 1C

[0175]

Table 1D

[0176]

Table 1E

[0177]

Table 1F

[0178]

Table 2A

[0179]

Table 2B

[0180]

Table 2C

[0181]

Table 2D

[0182]

Table 2E

[0183]

Table 2F

[0184]

Table 3A

[0185]

Table 3B

[0186]

Table 3C

[0187]

Table 4A

[0188]

Table 4B

[0189]

Table 4C

[0190]

Table 4D

[0191]

Table 4E

[0192] [Table 4F]

[0193]

Table 5A

[0194]

Table 5B

[0195]

Table 5C

[0196]

Table 5D

[0197]

Table 5E

[0198]

Table 5F

[0199]

Table 6A

[0200]

Table 6B

[0201]

Table 6C

[0202]

Table 7A

[0203]

Table 7B

[0204]

Table 7C

[0205]

Table 7D

[0206]

Table 7E

[0207]

Table 7F

[0208]

Table 8A

[0209]

Table 8B

[0210]

Table 8C

[0211]

Table 8D

[0212]

Table 8E

[0213]

Table 8F

[0214]

Table 9A

[0215]

Table 9B

[0216] [Table 9C]

[0217] [Table 10A]

[0218] [Table 10B]

[0219] [Table 10C]

[0220] [Table 10D]

[0221] [Table 10E]

[0222] [Table 10F] [Industrial Applicability]

[0223] According to the above aspects of the present invention, it is possible to provide a non-oriented electrical steel sheet that is excellent in magnetic flux density, iron loss characteristics (commercial frequency iron loss and high frequency iron loss) and punchability. In addition, it is possible to provide an iron core including this non-oriented electrical steel sheet, a method for manufacturing an iron core, and a motor including this iron core, and a method for manufacturing a motor, so that the present invention has high industrial applicability. [Explanation of symbols]

[0224] 1 Non-oriented electrical steel sheet 11 Insulation coating 12 Base steel plate 12a: The area from the surface of the base steel plate to 1 / 10 of the plate thickness (surface area) 12b 1 / 4 of the thickness of the base steel plate 12c 1 / 2 the thickness of the base steel plate

Claims

1. A non-oriented electrical steel sheet having a base steel sheet and an insulating coating, The base steel sheet has a chemical composition, in mass%, Si: 1.0% or more and 5.0% or less, Al: 1.0% or more and 10.0% or less, Sn: 0% or more and 10.000% or less, C: 0% or more and 0.005% or less, Mn: 0% or more and 3.0% or less, P: 0% or more and 0.30% or less, S: 0% or more and 0.010% or less, N: 0% or more and 0.010% or less, Zn: 0% or more and 0.100% or less, Sb: 0% or more and 0.100% or less, Ca: 0% or more and 0.010% or less, Cr: 0% or more and 10.0% or less, Ni: 0% or more and 5.0% or less, Cu: 0% or more and 5.0% or less, Ce: 0% or more and 0.100% or less, B: 0% or more and 0.100% or less, O: 0% or more and 0.100% or less, Mg: 0% or more and 0.100% or less, Ti: 0% or more and 0.100% or less, V: 0% or more and 0.100% or less, Zr: 0% or more and 0.100% or less, Nd: 0% or more and 0.100% or less, Bi: 0% or more and 0.100% or less, W: 0% or more and 0.100% or less, Mo: 0% or more and 0.10% or less, Nb: 0% or more and 0.100% or less, Y: 0% or more and 0.100% or less, with the remainder being Fe and impurities, The thickness of the base steel plate is 0.10 mm or more and 0.35 mm or less, When the base steel plate is viewed on a cut surface whose cutting direction is parallel to the plate thickness direction, The average Al concentration in the region from the surface of the base steel plate to 1 / 10 of the plate thickness is The Al concentration is 1.5 mass% or more higher than the Al concentration at 1 / 4 of the plate thickness, and The Al concentration is 3.0 mass% or more higher than the Al concentration at the half thickness portion of the plate, The Al concentration at the quarter thickness portion is The Al concentration is 1.5 mass% or more higher than the Al concentration at the half thickness portion, The average Si concentration in the region from the surface to 1 / 10 of the plate thickness of the base steel plate is The Si concentration is 0.5 mass% or more lower than the Si concentration at 1 / 4 of the plate thickness, and The Si concentration is 1.0 mass% or more lower than the Si concentration at 1 / 2 of the plate thickness, The Si concentration at the quarter thickness portion is The Si concentration is 0.5 mass % or more lower than the Si concentration at the half thickness portion A non-oriented electrical steel sheet.

2. The chemical composition is, in mass%, Cr: 0.50% or more and 10.0% or less, Contains The non-oriented electrical steel sheet according to claim 1 .

3. A non-oriented electrical steel sheet having a base steel sheet and an insulating coating, The base steel sheet has a chemical composition, in mass%, Si: 1.0% or more and 5.0% or less, Al: 0% or more and 10.0% or less, Sn: 1.0% or more and 10.000% or less, C: 0% or more and 0.005% or less, Mn: 0% or more and 3.0% or less, P: 0% or more and 0.30% or less, S: 0% or more and 0.010% or less, N: 0% or more and 0.010% or less, Zn: 0% or more and 0.100% or less, Sb: 0% or more and 0.100% or less, Ca: 0% or more and 0.010% or less, Cr: 0% or more and 10.0% or less, Ni: 0% or more and 5.0% or less, Cu: 0% or more and 5.0% or less, Ce: 0% or more and 0.100% or less, B: 0% or more and 0.100% or less, O: 0% or more and 0.100% or less, Mg: 0% or more and 0.100% or less, Ti: 0% or more and 0.100% or less, V: 0% or more and 0.100% or less, Zr: 0% or more and 0.100% or less, Nd: 0% or more and 0.100% or less, Bi: 0% or more and 0.100% or less, W: 0% or more and 0.100% or less, Mo: 0% or more and 0.10% or less, Nb: 0% or more and 0.100% or less, Y: 0% or more and 0.100% or less, with the remainder being Fe and impurities, The thickness of the base steel plate is 0.10 mm or more and 0.35 mm or less, When the base steel plate is viewed on a cut surface whose cutting direction is parallel to the plate thickness direction, The average Sn concentration in the region from the surface of the base steel plate to 1 / 10 of the plate thickness is The Sn concentration is 1.5 mass% or more higher than the Sn concentration at 1 / 4 of the plate thickness, and The Sn concentration is 3.0 mass% or more higher than the Sn concentration at the half thickness portion of the plate, The Sn concentration at the quarter thickness portion is The Sn concentration is 1.5 mass% or more higher than the Sn concentration at the half thickness portion, The average Si concentration in the region from the surface to 1 / 10 of the plate thickness of the base steel plate is The Si concentration is 0.5 mass% or more lower than the Si concentration at 1 / 4 of the plate thickness, and The Si concentration is 1.0 mass% or more lower than the Si concentration at 1 / 2 of the plate thickness, The Si concentration at the quarter thickness portion is The Si concentration is 0.5 mass % or more lower than the Si concentration at the half thickness portion A non-oriented electrical steel sheet.

4. The chemical composition is, in mass%, Cr: 0.50% or more and 10.0% or less, Contains The non-oriented electrical steel sheet according to claim 3 .

5. A non-oriented electrical steel sheet having a base steel sheet and an insulating coating, The base steel sheet has a chemical composition, in mass%, Si: 1.0% or more and 5.0% or less, Al: 1.0% or more and 10.0% or less, Sn: 1.0% or more and 10.000% or less, C: 0% or more and 0.005% or less, Mn: 0% or more and 3.0% or less, P: 0% or more and 0.30% or less, S: 0% or more and 0.010% or less, N: 0% or more and 0.010% or less, Zn: 0% or more and 0.100% or less, Sb: 0% or more and 0.100% or less, Ca: 0% or more and 0.010% or less, Cr: 0% or more and 10.0% or less, Ni: 0% or more and 5.0% or less, Cu: 0% or more and 5.0% or less, Ce: 0% or more and 0.100% or less, B: 0% or more and 0.100% or less, O: 0% or more and 0.100% or less, Mg: 0% or more and 0.100% or less, Ti: 0% or more and 0.100% or less, V: 0% or more and 0.100% or less, Zr: 0% or more and 0.100% or less, Nd: 0% or more and 0.100% or less, Bi: 0% or more and 0.100% or less, W: 0% or more and 0.100% or less, Mo: 0% or more and 0.10% or less, Nb: 0% or more and 0.100% or less, Y: 0% or more and 0.100% or less, with the remainder being Fe and impurities, The thickness of the base steel plate is 0.10 mm or more and 0.35 mm or less, When the base steel plate is viewed on a cut surface whose cutting direction is parallel to the plate thickness direction, The sum of the average Al concentration and the average Sn concentration in the region from the surface of the base steel plate to 1 / 10 of the plate thickness, The Al concentration is 1.5 mass% or more higher than the sum of the Al concentration and the Sn concentration at the quarter thickness portion of the plate, and The Al concentration is 3.0 mass% or more higher than the sum of the Al concentration and the Sn concentration at the plate thickness 1 / 2 part, The sum of the Al concentration and the Sn concentration at the quarter thickness portion is The Al concentration in the plate thickness 1 / 2 portion is 1.5 mass% or more higher than the total of the Al concentration and the Sn concentration, The average Si concentration in the region from the surface to 1 / 10 of the plate thickness of the base steel plate is The Si concentration is 0.5 mass% or more lower than the Si concentration at 1 / 4 of the plate thickness, and The Si concentration is 1.0 mass% or more lower than the Si concentration at 1 / 2 of the plate thickness, The Si concentration at the quarter thickness portion is The Si concentration is 0.5 mass % or more lower than the Si concentration at the half thickness portion A non-oriented electrical steel sheet.

6. The base steel sheet has a chemical composition, in mass%, Cr: 0.50% or more and 10.0% or less, Contains The non-oriented electrical steel sheet according to claim 5 .

7. An iron core comprising the non-oriented electrical steel sheet according to any one of claims 1 to 6.

8. A method for manufacturing an iron core, comprising a step of stacking the non-oriented electrical steel sheets according to any one of claims 1 to 6.

9. A motor including the iron core according to claim 7.

10. A method for manufacturing a motor, comprising the steps of: laminating the non-oriented electrical steel sheets according to any one of claims 1 to 6 to obtain an iron core; and assembling the iron core according to claim 7 to obtain a motor.

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