Non-oriented electromagnetic steel sheet and method for manufacturing the same

Abstract

A non-oriented electromagnetic steel sheet, the chemical composition of its base material, in mass percent, is as follows: C: less than 0.0050%, Si: 2.80-4.50%, Mn: 0.10-2.00%, Al: 0.10-2.00%, P: less than 0.030%, S: less than 0.0050%, N: less than 0.0050%, Sn: more than 0% and less than 0.06%, the remainder being Fe and impurities; the orientation intensities I of (110), (200) and (222) obtained by X-ray diffraction are respectively derived from the surface orientation intensities I of (110), (200) and (222). （110） I （200） and I （222） Satisfying [0.10≤I] （110） ≤0.40], [1.00≤I （200） ≤3.00] and [2.00≤I] （222） ≤7.00].

Description

Technical Field

[0001] This invention relates to a non-oriented electromagnetic steel sheet and its manufacturing method. Background Technology

[0002] In recent years, global environmental issues have garnered significant attention, leading to increased demands for energy conservation. This includes a strong expectation for higher efficiency in electrical equipment. Consequently, the demand for improved magnetic properties in non-oriented electromagnetic steel sheets, widely used as core materials for motors and generators, has intensified. This trend is particularly pronounced in drive motors for electric and hybrid vehicles, as well as compressor motors for air conditioners. Furthermore, there is a growing expectation for miniaturized and efficiently high-output drive and compressor motors.

[0003] To achieve high efficiency in motors, reducing iron losses and copper losses, which are the main sources of energy loss, becomes crucial. For reducing iron losses, improving the iron loss of the electromagnet used in the motor core is effective; for reducing copper losses, increasing the magnetic flux density of the electromagnet is effective. On the other hand, to achieve high output in motors, high torque becomes important. For high torque, increasing the magnetic flux density of the electromagnet is effective. Therefore, to advance both high efficiency and high output in motors, electromagnets with low iron losses and high magnetic flux density are needed.

[0004] For example, Patent Document 1 discloses a non-oriented electromagnetic steel sheet with excellent magnetic properties and its manufacturing method.

[0005] Prior technology documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2022-74677 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] However, through repeated research, the inventors have found that there is room for further improvement in magnetic properties.

[0010] This invention was made to solve such a problem, and its purpose is to provide a non-oriented electromagnetic steel sheet with excellent magnetic properties.

[0011] Technical means for solving technical problems

[0012] The subject of this invention is the following non-oriented electromagnetic steel sheet and its manufacturing method.

[0013] (1) A non-oriented electromagnetic steel sheet, wherein the chemical composition of its base material, in mass percent, is:

[0014] C: Below 0.0050%

[0015] Si: 2.80–4.50%

[0016] Mn: 0.10~2.00%

[0017] Al: 0.10–2.00%

[0018] P: below 0.030%

[0019] S: Below 0.0050%

[0020] N: below 0.0050%

[0021] Sn: More than 0% and less than 0.06%

[0022] Remaining components: Fe and impurities.

[0023] The surface orientation intensities I, derived from (110), (200), and (222) using X-ray diffraction, respectively, are respectively derived from the surface orientation intensities I. （110） I （200） and I （222） Satisfying the following equations (i) to (iii),

[0024] 0.10≤I （110） ≤0.40・・・(i)

[0025] 1.00≤I （200） ≤3.00・・・(ii)

[0026] 2.00≤I （222） ≤7.00・・・(iii).

[0027] (2) The non-oriented electromagnetic steel sheet as described in (1) above, wherein,

[0028] In the chemical composition of the parent material, a portion replacing Fe contains [material from...].

[0029] Ca: below 0.0050%

[0030] Zn: below 0.0050%

[0031] Mg: less than 0.0050%

[0032] Ti: below 0.015%

[0033] Cr: less than 0.20%

[0034] Sb: below 0.20%

[0035] Mo: 0.015% or less,

[0036] Nb: below 0.015%, and

[0037] Cu: less than 0.20%

[0038] Choose one or more.

[0039] (3) A method for manufacturing a non-oriented electromagnetic steel sheet, wherein the steel sheet is subjected to a hot rolling process, a pickling process, a cold rolling process, and a final annealing process in sequence.

[0040] In the final annealing process, the temperature is increased from room temperature to 350-450°C at a rate of 10-500°C / s from 100°C to 350°C, and then held at 350-450°C for 0.1-100 seconds. Next, the temperature is increased from 350-450°C to the reached temperature at a rate of 700°C / s or higher from 600°C to 840-950°C.

[0041] The chemical composition of the steel billet, expressed as a percentage by mass, is:

[0042] C: Below 0.0050%,

[0043] Si: 2.80–4.50%,

[0044] Mn: 0.10~2.00%,

[0045] Al: 0.10–2.00%,

[0046] P: below 0.030%,

[0047] S: below 0.0050%,

[0048] N: below 0.0050%

[0049] Sn: greater than 0% and less than 0.06%,

[0050] Remaining components: Fe and impurities.

[0051] (4) The manufacturing method of the non-oriented electromagnetic steel sheet as described in (3) above, wherein,

[0052] The chemical composition of the steel sheet contains, in place of a portion of Fe, elements derived from...

[0053] Ca: below 0.0050%

[0054] Zn: below 0.0050%

[0055] Mg: less than 0.0050%

[0056] Ti: below 0.015%

[0057] Cr: less than 0.20%

[0058] Sb: below 0.20%

[0059] Mo: 0.015% or less,

[0060] Nb: below 0.015%, and

[0061] Cu: less than 0.20%

[0062] Choose one or more.

[0063] Invention Effects

[0064] According to the present invention, it is possible to obtain non-oriented electromagnetic steel sheets with excellent magnetic properties. Detailed Implementation

[0065] In order to solve the above problems, the inventors conducted in-depth research and obtained the following understanding.

[0066] When Sn contains a predetermined amount or more, Sn will segregate to the interface between the grains that have broken apart due to cold rolling. Furthermore, by rapidly heating the final annealing after cold rolling while ensuring sufficient grain boundary segregation of Sn, it is possible to suppress the development of textures that are detrimental to magnetic properties and promote the development of textures with higher symmetry that are beneficial to magnetic properties. As a result, it has been found that the magnetic flux density can be increased.

[0067] On the other hand, Sn is an element that reduces cold rollability, so it is desirable to reduce its content. However, even with a reduced Sn content, it is possible to perform the final annealing in two stages, allowing it to remain in a predetermined temperature range between the first and second stages, thereby promoting Sn grain boundary segregation.

[0068] Furthermore, the inventors conducted experiments involving rapid heating to various temperatures. The results showed that even with rapid heating, no improvement in magnetic properties was confirmed at lower temperatures. However, the magnetic properties were improved by rapidly heating to temperatures above 840°C.

[0069] This invention is based on the above understanding. The various elements of this invention will now be described in detail.

[0070] 1. Overall Composition

[0071] The non-oriented electromagnetic steel sheet of one embodiment of the present invention has excellent magnetic properties. Furthermore, it is preferred that the non-oriented electromagnetic steel sheet of this embodiment includes an insulating film on the surface of the base material described below.

[0072] 2. Chemical composition of the parent material

[0073] The reasons for the limitations of each element are as follows. Additionally, in the following explanation, "%" for content means "mass %".

[0074] C: Below 0.0050%

[0075] Carbon (C) is an element that causes the deterioration of iron losses in non-oriented electromagnetic steel sheets. When the C content exceeds 0.0050%, the iron losses of the non-oriented electromagnetic steel sheet deteriorate, and good magnetic properties cannot be obtained. Therefore, the C content is set to 0.0050% or less. Preferably, the C content is 0.0040% or less, more preferably 0.0030% or less. Furthermore, the lower the C content, the better; therefore, there is no need to set a lower limit, and it can be 0%. However, extremely low C content can sometimes lead to increased manufacturing costs. In addition, C contributes to the high strength of non-oriented electromagnetic steel sheets. Therefore, preferably, the C content is more than 0%, more preferably 0.0005% or more, and even more preferably 0.0010% or more.

[0076] Si: 2.80–4.50%

[0077] Silicon (Si) is an element that increases the electrical resistance of steel, thereby reducing eddy current losses and improving the iron loss of non-oriented electromagnetic steel sheets. Furthermore, Si has a high solid solution strengthening ability, making it effective for increasing the strength of non-oriented electromagnetic steel sheets. To achieve these effects, the Si content is set to 2.80% or more. Regarding the Si content, it is preferable to be 3.00% or more, and more preferably 3.20% or more. On the other hand, when the Si content is excessive, the workability deteriorates significantly, making cold rolling difficult. Therefore, the Si content is set to 4.50% or less. Regarding the Si content, it is preferable to be 4.00% or less, and more preferably 3.70% or less.

[0078] Mn: 0.10~2.00%

[0079] Manganese (Mn) is an element that increases the electrical resistance of steel without deteriorating its workability, thereby reducing eddy current losses and effectively improving the iron loss of non-oriented electromagnetic steel sheets. Furthermore, although Mn has a lower solid solution strengthening ability compared to Si, it does not deteriorate workability and contributes to high strength. To achieve these effects, the Mn content is set to 0.10% or more. Regarding the Mn content, 0.20% or more is preferred, and 0.40% or more is more preferred. On the other hand, when the Mn content is excessive, not only does the decrease in magnetic flux density increase, but workability also deteriorates significantly, making cold rolling difficult. Therefore, the Mn content is set to 2.00% or less. Regarding the Mn content, 1.50% or less is preferred, and 1.00% or less is more preferred.

[0080] Al: 0.10–2.00%

[0081] Al (aluminum) is an element that reduces eddy current losses by increasing the electrical resistance of steel and improves the iron loss of non-oriented electromagnetic steel sheets. Furthermore, while not as strong as Si, Al also contributes to the high strength of non-oriented electromagnetic steel sheets through solid solution strengthening. Moreover, the addition of an appropriate amount of Al suppresses the refinement of AlN that occurs due to its combination with N in the steel, improving grain growth during final annealing. To achieve these effects, the Al content is set to 0.10% or more. Regarding the Al content, 0.20% or more is preferred, and 0.40% or more is more preferred. On the other hand, when the Al content is excessive, the toughness deteriorates, making cold rolling difficult. Therefore, the Al content is set to 2.00% or less. Regarding the Al content, 1.50% or less is preferred, and 1.00% or less is more preferred.

[0082] P: below 0.030%

[0083] Phosphorus (P) is contained in steel as an impurity, and when its content is excessive, the toughness of the non-oriented electromagnetic steel sheet will be significantly reduced. Therefore, the P content is set to 0.030% or less. Preferably, the P content is 0.025% or less, more preferably 0.020% or less, and even more preferably 0.010% or less. Furthermore, the lower the P content, the better; therefore, there is no need to set a lower limit, and it can be 0%. However, extremely low P content can sometimes lead to increased manufacturing costs; therefore, preferably, the P content is greater than 0%, more preferably 0.001% or more.

[0084] S: Below 0.0050%

[0085] Sulfur (S) is an element that increases iron loss and degrades the magnetic properties of non-oriented electromagnetic steel sheets by forming fine precipitates of MnS. Therefore, the S content is set to 0.0050% or less. Preferably, the S content is 0.0040% or less, more preferably 0.0030% or less. Furthermore, the lower the S content, the better; therefore, a lower limit is not required, and it can be 0%. However, extremely low S content can sometimes increase manufacturing costs; therefore, preferably, the S content is greater than 0%, more preferably 0.0001% or more, further preferably 0.0003% or more, and even more preferably 0.0005% or more.

[0086] N: below 0.0050%

[0087] Nitrogen (N) is an element that inevitably mixes into steel and forms nitrides, increasing iron loss and degrading the magnetic properties of non-oriented electromagnetic steel sheets. Therefore, the N content is set to 0.0050% or less. Preferably, the N content is 0.0040% or less, more preferably 0.0030% or less. A lower limit for the N content is not required, and it can be 0%. However, drastic reductions in the N content can sometimes increase manufacturing costs. Therefore, preferably, the N content is greater than 0%, more preferably 0.0001% or more, further preferably 0.0003% or more, and even more preferably 0.0005% or more.

[0088] Sn: More than 0% and less than 0.06%

[0089] Tin (Sn) segregates to grain boundaries during final annealing, suppressing the development of textures detrimental to magnetic properties and promoting the development of textures with higher symmetry beneficial to magnetic properties, thus improving the magnetic flux density of non-oriented electromagnetic steel sheets. To achieve these effects, the Sn content is set to more than 0%. Preferably, the Sn content is 0.01% or more. On the other hand, by reducing the Sn content, the reduction in steel toughness can be suppressed and cold rollability can be improved. Therefore, the Sn content is set to 0.06% or less. Preferably, the Sn content is 0.03% or less.

[0090] Ca: below 0.0050%

[0091] Ca (calcium) is an element that forms sulfides to fix sulfur, thus contributing to reduced iron loss, and can therefore be included as needed. However, excessive Ca content risks economic deterioration, so the Ca content is set to 0.0050% or less. Preferably, the Ca content is 0.0040% or less, more preferably 0.0030% or less. Furthermore, the lower limit of the Ca content is not particularly limited, and it can also be 0%. However, to achieve the aforementioned effects, it is preferable that the Ca content exceeds 0%, more preferably 0.0003% or more.

[0092] Zn: below 0.0050%

[0093] Like calcium (Ca), zinc (Zn) forms sulfides to fix sulfur (S), which helps reduce iron loss, and therefore can be included as needed. However, excessive zinc content risks economic deterioration, so the Zn content is set to 0.0050% or less. Preferably, the Zn content is 0.0040% or less, more preferably 0.0030% or less. Furthermore, the lower limit of the Zn content is not particularly limited, and it can also be 0%. However, to achieve the aforementioned effects, it is preferable that the Zn content exceeds 0%, more preferably 0.0003% or more.

[0094] Mg: less than 0.0050%

[0095] Like Ca and Zn, Mg (magnesium) forms sulfides to fix sulfur, which helps reduce iron loss, and therefore can be included as needed. However, excessive Mg content risks economic deterioration, so the Mg content is set to 0.0050% or less. Preferably, the Mg content is 0.0040% or less, more preferably 0.0030% or less. Furthermore, the lower limit of the Mg content is not particularly limited, and it can also be 0%. However, to achieve the aforementioned effects, it is preferable that the Mg content is more than 0%, more preferably 0.0003% or more.

[0096] Ti: below 0.015%

[0097] Like Ca, Zn, and Mg, titanium (Ti) forms sulfides to fix sulfur (S), which helps reduce iron loss, and therefore can be included as needed. However, excessive Ti content risks economic deterioration, so the Ti content is set to 0.015% or less. Preferably, the Ti content is 0.010% or less, more preferably 0.005% or less. Furthermore, the lower limit of the Ti content is not particularly limited, and it can be 0%. However, to achieve the aforementioned effects, it is preferable that the Ti content exceeds 0%, more preferably 0.001% or more.

[0098] Cr: less than 0.20%

[0099] Chromium (Cr) is an element that can be introduced as an impurity. However, Cr is also an element that improves magnetic properties, so it can be intentionally included. However, when it is present in excess, there is a risk of economic deterioration, so the Cr content in cases of intentional inclusion is set to 0.20% or less. Regarding the Cr content, it is preferable to be 0.15% or less, and more preferably 0.10% or less. In addition, the lower limit of the Cr content is not particularly limited, and it can also be 0%. However, in order to obtain the above-mentioned effects, it is preferable that the Cr content is more than 0%, and more preferably 0.01% or more.

[0100] Sb: below 0.20%

[0101] Antimony (Sb) is an element that can be introduced as an impurity. However, Sb is also an element that improves magnetic properties, so it can be intentionally included. However, excessive inclusion can lead to economic degradation, so the Sb content in cases of intentional inclusion is set to 0.20% or less. Regarding the Sb content, it is preferable to be 0.15% or less, and more preferably 0.10% or less. Furthermore, the lower limit of the Sb content is not particularly limited, and it can also be 0%. However, to obtain the aforementioned effects, it is preferable that the Sb content exceeds 0%, and more preferably 0.01% or more.

[0102] Mo: 0.015% or less

[0103] Mo (Mo) is an element that combines with carbon or nitrogen to form precipitates (carbides, nitrides), thereby contributing to high strength, and therefore can be included as needed. However, excessive inclusion poses a risk of economic degradation, so the Mo content is set to 0.015% or less. Preferably, the Mo content is 0.010% or less, more preferably 0.005% or less. Furthermore, the lower limit of the Mo content is not particularly limited, and it can also be 0%. However, to obtain the aforementioned effects, it is preferable that the Mo content exceeds 0%, more preferably 0.001% or more.

[0104] Nb: below 0.015%

[0105] Niobium (Nb) is an element that combines with carbon or nitrogen to form precipitates (carbides, nitrides), thereby contributing to high strength, and therefore may be included as needed. However, excessive Nb content risks economic degradation, so the Nb content is set to 0.015% or less. Preferably, the Nb content is 0.010% or less, more preferably 0.005% or less. Furthermore, the lower limit of the Nb content is not particularly limited, and it may be 0%. However, to achieve the aforementioned effects, it is preferable that the Nb content exceeds 0%, more preferably 0.001% or more.

[0106] Cu: less than 0.20%

[0107] Cu (copper) is an element that can be included as an impurity. However, Cu is also an element that improves magnetic properties, so it can be intentionally included. However, excessive Cu content poses a risk of economic degradation, therefore the Cu content for intentional inclusion is set to 0.20% or less. Preferably, the Cu content is 0.15% or less, more preferably 0.10% or less. Furthermore, the lower limit of the Cu content is not particularly limited, and it can be 0%. However, to achieve the aforementioned effects, it is preferable that the Cu content exceeds 0%, more preferably 0.01% or more.

[0108] In the chemical composition of the base material of the non-oriented electromagnetic steel sheet of the present invention, the remaining part is Fe and impurities. Here, "impurities" refers to components that are mixed in during the industrial manufacturing of steel due to various factors such as raw materials (ore, waste, etc.) and manufacturing processes, and are therefore permissible within the range that will not adversely affect the present invention.

[0109] The chemical composition of the base material of the non-oriented electromagnetic steel sheet of this embodiment can be determined using various known methods. In this invention, the content of elements is determined using ICP emission spectrometry (ICP-AES) and ICP mass spectrometry (ICP-MS). Furthermore, C and S can be determined using combustion-infrared absorption spectroscopy, N can be determined using inert gas combustion-thermal conductivity spectroscopy, and O can be determined using inert gas melting-non-dispersive infrared absorption spectroscopy.

[0110] 3. Crystal grain size

[0111] In this embodiment, there is no particular limitation on the average grain size of the base material. However, to achieve both excellent magnetic properties and high strength, it is preferable that the average grain size of the base material is 50 to 150 μm. By setting the average grain size of the base material to 50 μm or more, the deterioration of hysteresis loss can be suppressed, and iron loss can be improved. On the other hand, by setting the average grain size to 150 μm or less, the strength of the steel can be improved, and the deterioration of iron loss due to the increase of eddy current loss can be suppressed. Regarding the average grain size, it is preferable to be 55 μm or more, and more preferably 60 μm or more. Furthermore, regarding the average grain size, it is preferable to be 140 μm or less, and more preferably 130 μm or less.

[0112] In addition, in this invention, the average grain size of the base material is determined according to JIS G 0551:2013 "Steel - Microscopic test method for grain size".

[0113] 4. Texture

[0114] In this embodiment, the development of textures that are detrimental to magnetic properties is suppressed, while textures with higher symmetry that are beneficial to magnetic properties are developed. From that point of view, in the non-oriented electromagnetic steel sheet of this embodiment, the planar orientation intensities I derived from (110), (200), and (222) using X-ray diffraction are respectively... （110） I （200） and I （222） It satisfies the following equations (i) to (iii).

[0115] 0.10≤I （110） ≤0.40・・・(i)

[0116] 1.00≤I （200） ≤3.00・・・(ii)

[0117] 2.00≤I （222） ≤7.00・・・(iii)

[0118] I （110）It originates from the orientation intensity of (110). The orientation of (110) has good symmetry, so it needs to be developed to improve magnetic properties. Therefore, I （110） Set it to 0.10 or higher. Regarding I... （110） Preferably, it is 0.13 or higher, and more preferably, it is greater than 0.15. （110） The higher the better, but the upper limit for industrial manufacturing would be 0.40.

[0119] I （200） It originates from the orientation intensity of (200). The orientation of (200) has extremely good symmetry, so it needs to be developed to improve magnetic properties. Therefore, I （200） Set to 1.00 or higher. As described above, by rapidly heating during the final annealing after cold rolling, while ensuring sufficient grain boundary segregation of Sn, I can be improved. （200） Regarding I （200） Preferably, the value is 1.50 or higher, and more preferably, it is 2.00 or higher. （200） The higher the better, but the upper limit for industrial manufacturing will be 3.00.

[0120] I （222） It originates from the orientation intensity of (222). The orientation of (222) is a texture that is detrimental to magnetic properties, so its development needs to be suppressed in order to improve magnetic properties. Therefore, I （222） Set it below 7.00. Regarding I... （222） Preferably, it is 6.00 or less; more preferably, it is 5.00 or less; and even more preferably, it is 4.00 or less. （222） The lower the better, but the lower limit for industrial manufacturing would be 2.00.

[0121] Furthermore, the planar orientation intensity was determined using reverse X-ray analysis with an X-ray diffraction apparatus. Planar orientation intensity refers to the integral value of the peak X-ray intensity along each orientation. The specific measurement method is as follows: First, a test piece with a diameter of 26 mm is punched from the non-oriented electromagnetic steel sheet of the test material. Furthermore, considering both measurement accuracy and experimental efficiency, the number of test pieces used for measurement is set to 10. The measurement is performed on the surface of the base material. If an insulating film is coated on the surface of the base material, the insulating film is removed using existing methods. For example, the insulating film can be removed by immersion in a 20% NaOH aqueous solution heated to 80°C for 5 minutes.

[0122] <Determination Method>

[0123] A 26 mm diameter test piece was placed in the sample holder. At the same time, a standard sample provided by the manufacturer that does not have aggregation to a specific orientation was also placed. As the measurement conditions for reverse X-ray analysis, the measurement axis was set to 2θ / θ, the measurement method was set to FT, and the counting unit was set to CPS. In addition, the step size was set to 0.010°, the counting time to 0.6 s, the voltage to 50 kV, the voltage to 200 mA, the divergence and scattering slits to 1°, the divergence longitudinal slit to 10 mm, and the light-receiving slit to 0.15 mm. As the measurement range, it was set to (110): 2θ = 18.000~21.500°, (200): 2θ = 27.750~29.500°, and (222): 2θ = 49.750~52.000°.

[0124] <Analytical Methods>

[0125] The analysis software "Invpole.cnd" was used. A standard result needed to be selected, so the data was set to refer to the standard sample measured along with the test piece. Smoothing, peak correction, and background removal were not performed. The intensity calculation was performed using "integral intensity," and for crystallization, cubic crystals (α-axis: 2.866 Å) were selected.

[0126] 5.Magnetic properties

[0127] In the non-oriented electromagnetic steel sheet of this embodiment, the term "excellent magnetic properties" means that the iron loss W 10 / 400 Lower, magnetic flux density B 50 Relatively high.

[0128] Here, the magnetic properties (iron loss W) are made possible. 10 / 400 and magnetic flux density B 50 The following method is used for measurement. First, a small test piece of 55mm × 55mm is made from a non-oriented electromagnetic steel sheet. Then, iron loss and magnetic flux density are measured using a small single-sheet tester corresponding to the small test piece. At this time, the measurement principle is made in accordance with the Single Sheet Tester (SST) method for determining magnetic properties as specified in JIS C 2556:2015.

[0129] When measuring iron loss and magnetic flux density, the excitation direction is set to two directions: parallel to the rolling direction (hereinafter referred to as the L direction) and perpendicular to the rolling direction (hereinafter referred to as the C direction). The average value of the measured values ​​in each direction is used to calculate the magnetic property value of the material. Considering both measurement accuracy and experimental efficiency, the number of small test pieces (55mm × 55mm) is set to 10. Additionally, the iron loss W... 10 / 400 This means that under conditions of a maximum magnetic flux density of 1.0T and a frequency of 400Hz, the iron loss generated is related to the magnetic flux density B.50 This means the magnetic flux density in a magnetic field of 5000 A / m.

[0130] The magnetic property values ​​obtained using the SST method were corrected using a correction factor. Specifically, Epstein test pieces and the aforementioned small test pieces were collected beforehand from several types of non-oriented electromagnetic steel sheets. Magnetic property values ​​were measured using the Epstein method as specified in JIS C 2550-1:2011 and the aforementioned SST method, and a conversion formula was derived beforehand based on the relationship between the two measured values. Then, the magnetic property values ​​measured using the single-plate tester were corrected using the aforementioned conversion formula to make them equivalent to the magnetic property values ​​measured using the Epstein method.

[0131] The density of the steel plate used in the Epstein test was set as a value calculated using [7.865 - 0.065 × (Si + 1.7 × Al)]. Here, Si and Al represent their respective contents (mass%) in the steel plate. Furthermore, when determining the magnetic properties according to the Epstein test, the excitation directions were set as two directions: L and C. Test pieces excited along the L and C directions were measured using half the amount of each direction.

[0132] In the non-oriented electromagnetic steel sheet of this embodiment, the so-called iron loss W 10 / 400 The values ​​are relatively low: below 14.5 W / kg for plate thicknesses above 0.26 mm, below 12.5 W / kg for plate thicknesses between 0.21 and 0.25 mm, and below 11.2 W / kg for plate thicknesses below 0.20 mm. Furthermore, the so-called magnetic flux density B... 50 The value is relatively high. When the plate thickness is above 0.26mm, it means above 1.63T; when the plate thickness is between 0.21 and 0.25mm, it means above 1.62T; and when the plate thickness is below 0.20mm, it means above 1.61T.

[0133] 6. Mechanical properties

[0134] In this embodiment, there are no particular limitations on strength. However, regarding tensile strength, it is preferable to have 340 MPa or more, more preferably 400 MPa or more, and even more preferably 430 MPa or more. Here, tensile strength is determined by performing a tensile test (by offset method) in accordance with JIS Z 2241:2022.

[0135] For the test piece, the plate thickness is kept constant, the rolling direction is taken as the long side, and it is machined into the shape of a JIS 5 test piece. Alternatively, if the extraction of a JIS 5 test piece is difficult due to the size of the steel plate, a tensile test can be performed using a proportional shape.

[0136] 7.Plate thickness

[0137] There are no particular limitations on the thickness of the non-oriented electromagnetic steel sheet in this embodiment. However, from the viewpoint of reducing manufacturing costs associated with cold rolling and final annealing, it is preferable that the thickness of the base material is 0.10 mm or more. On the other hand, from the viewpoint of reducing iron loss, it is preferable that the thickness of the base material is 0.30 mm or less. Regarding the thickness, it is more preferably 0.15 mm or more, further preferably 0.20 mm or more, and even more preferably 0.25 mm or less.

[0138] 8. Insulating film

[0139] In the non-oriented electromagnetic steel sheet of this embodiment, it is preferable that an insulating film is provided on the surface of the base material. Since the non-oriented electromagnetic steel sheet is used after being stacked following the cutting of the core blank, eddy currents between the sheets can be reduced by providing an insulating film on the surface of the base material, and eddy current losses can be reduced as a core.

[0140] The type of insulating film is not particularly limited, and known insulating films used as insulating films for non-oriented electromagnetic steel sheets can be used. Examples of such insulating films include composite insulating films that are primarily inorganic and also contain organic materials. Here, a composite insulating film refers, for example, an insulating film primarily composed of at least one of inorganic materials such as metal chromate salts, metal phosphate salts, colloidal silica, Zr compounds, or Ti compounds, and in which fine organic resin particles are dispersed. In particular, from the viewpoint of reducing the environmental impact of manufacturing processes, which has been increasingly demanded in recent years, insulating films using metal phosphate salts, Zr or Ti coupling agents, or Zr or Ti carbonates or ammonium salts as starting materials are preferred.

[0141] There is no particular limitation on the amount of insulating film applied, but it is preferred, for example, to be 200-1500 mg / m² per single side. 2 More preferably, it is set at 300–1200 mg / m² per single surface. 2 By forming the insulating film with an adhesion amount within the aforementioned range, excellent uniformity can be maintained. Furthermore, when subsequently measuring the adhesion amount of the insulating film, various known measurement methods can be used, such as methods that appropriately measure the mass difference before and after immersion in a sodium hydroxide aqueous solution, or fluorescence X-ray methods using calibration curves, etc.

[0142] 9. Manufacturing method

[0143] The non-oriented electromagnetic steel sheet of this embodiment is not particularly limited in its manufacturing method, but for steel sheets having the above-mentioned chemical composition, it can be manufactured, for example, by sequentially performing a hot rolling process, a pickling process, a cold rolling process, and a final annealing process under the conditions shown below. Alternatively, the hot-rolled sheet annealing process can be performed between the hot rolling process and the pickling process, or between the pickling process and the cold rolling process. Furthermore, when an insulating film is formed on the surface of the base material, the insulating film forming process is performed after the aforementioned final annealing process. Hereinafter, each process will be described in detail.

[0144] <Hot Rolling Process>

[0145] The steel sheet having the above-mentioned chemical composition is heated, and then hot-rolled to obtain a hot-rolled plate. The heating temperature of the steel sheet used for hot rolling is not particularly specified, but it is preferably set to, for example, 1050–1250°C. Furthermore, the thickness of the hot-rolled plate is not particularly specified, but considering the final thickness of the base material, it is preferably set to approximately 1.0–3.0 mm. Preferably, the hot rolling process is completed when the temperature of the steel plate is in the range of 700–1000°C.

[0146] <Hot-rolled sheet annealing process>

[0147] Then, to reduce iron loss in the steel sheet, hot-rolled sheet annealing is performed as needed. In the case of continuous annealing, for example, hot-rolled sheet can be subjected to homogenous annealing at 750–1200°C for 10 seconds to 10 minutes. Alternatively, in the case of box annealing, hot-rolled steel sheet can be subjected to homogenous annealing at 650–950°C for 30 minutes to 24 hours. In addition, compared with the case of performing the hot-rolled sheet annealing process, the magnetic properties will be worse, but in order to reduce costs, the hot-rolled sheet can be annealed itself, or the hot-rolled sheet annealing process can be omitted.

[0148] <Pickling Process>

[0149] For the steel sheets after hot rolling or annealing, pickling is performed to remove the oxide scale layer formed on the surface of the base material. Furthermore, when the hot-rolled sheet undergoes box annealing, from the viewpoint of descaling, it is preferable to perform the pickling process before the hot-rolled sheet annealing. Here, the pickling conditions, such as the concentration of the acid used for pickling, the concentration of the pickling accelerator used for pickling, and the temperature of the pickling solution, are not particularly limited and can be set to known pickling conditions.

[0150] <Cold rolling process>

[0151] The steel sheet after descaling is then subjected to cold rolling. In cold rolling, for example, rolling is performed at a reduction rate such that the final sheet thickness of the base material is 0.10 to 0.30 mm.

[0152] <Final Annealing Process>

[0153] After the aforementioned cold rolling, a final annealing is performed. In the manufacturing method of the non-oriented electromagnetic steel sheet of this embodiment, it is preferable to use a continuous annealing furnace for the final annealing. The final annealing consists of at least three steps: a first heating step, a second heating step, and a soaking step. In the first heating step, Sn segregation is promoted, and in the second heating step, the {111} orientation, which is detrimental to magnetic properties, is reduced. Both steps are for controlling the production of recrystallization orientation nuclei that optimize magnetic properties. In the subsequent soaking step, the coarsening of the recrystallization orientation nuclei that optimize magnetic properties is controlled, i.e., grain growth control.

[0154] <First heating process>

[0155] First, in the first heating step of the final annealing, the temperature is increased from room temperature to 350–450°C at a heating rate of 10–500°C / s, from 100°C to 350°C. When the heating rate in the first stage is less than 10°C / s, it increases manufacturing costs. On the other hand, when the heating rate exceeds 500°C / s, it is insufficient to promote grain boundary segregation of Sn.

[0156] Next, a residence time of 0.1 to 100 s is ensured within a temperature range of 400 ± 50 °C. This is because it is believed that grain boundary segregation of Sn is easily promoted within this temperature range. By maintaining the residence time within this temperature range for a predetermined period, sufficient grain boundary segregation of Sn can be achieved.

[0157] <Second heating process>

[0158] In the second heating step of the final annealing, the temperature is raised to a target temperature within the range of 840–950°C. At this point, rapid heating is performed, so that the heating rate from 600°C to the target temperature is 700°C / s or higher.

[0159] At temperatures below 840°C, the crystal grain size becomes smaller, and iron losses deteriorate, which is not preferable. At temperatures above 950°C, the strength becomes insufficient, and the magnetism deteriorates, which is also not preferable. To further reduce iron losses, a temperature of 870–930°C is preferred.

[0160] Furthermore, by rapidly heating under the conditions described above, I can be reduced. （222） And improve I （110） Furthermore, by rapidly heating Sn while it is in a state of sufficient grain boundary segregation, I can be particularly improved. （200）Therefore, the heating rate is set to 700°C / s or higher. Preferably, the heating rate is 1000°C / s or higher. The faster the heating rate in the second heating step, the better, so there is no need to set an upper limit. However, considering the limitations of the equipment, the heating rate is preferably 2000°C / s or lower, and more preferably 1600°C / s or lower.

[0161] Furthermore, rapid heating under the conditions of the second heating step is difficult in conventional gas combustion direct heating, radiant tubes, electric heaters, etc. Therefore, in this embodiment, it is preferable to use electric heating, induction heating, etc., for the second heating step.

[0162] <Heating Process>

[0163] In the final annealing soaking process, the temperature is maintained for 1 to 150 seconds within the range of 840–1200°C. Alternatively, the reached temperature and the soaking temperature may not necessarily be the same. In this case, the thermal cycle from the reached temperature to the soaking temperature can be arbitrary; for example, it could be a cycle of cooling to room temperature and then reheating at a rate of 10–50°C / s to the soaking temperature. However, this method has a high manufacturing load, therefore it is preferable that the heating rate from the reached temperature to the soaking temperature is controlled within the range of -100°C to +100°C.

[0164] Furthermore, in the final annealing, it is preferable to set the dew point of the atmosphere from 600°C to the aforementioned arrival temperature to -50 to 10°C. By controlling the dew point of the atmosphere during heating to a low level, internal oxidation of Si can be suppressed, and the reduction in magnetic properties can be suppressed. In addition, from the viewpoint of suppressing internal oxidation, it is preferable to set the atmosphere during the final annealing to a mixed atmosphere of H2 and N2 with a H2 ratio of 1 to 100 vol% (i.e., H2 + N2 = 100 vol%).

[0165] <Insulating film formation process>

[0166] After the final annealing described above, an insulating film forming process is performed as needed. The method for forming the insulating film is not particularly limited; a known processing solution for forming an insulating film, as described below, can be used, and the solution can be coated and dried using known methods. For example, a composite insulating film that is primarily inorganic and also contains organic matter can be cited as a known insulating film.

[0167] Composite insulating films, for example, refer to insulating films primarily composed of at least one of metal salts such as chromate and phosphate, or inorganic substances such as colloidal silica, Zr compounds, and Ti compounds, and containing dispersed fine organic resin particles. In particular, from the viewpoint of reducing the environmental burden during manufacturing, which has become increasingly important in recent years, insulating films using coupling agents of phosphate, Zr, or Ti as starting materials, or insulating films using carbonates or ammonium salts of Zr or Ti coupling agents as starting materials, are preferred.

[0168] For the surface of the base material to which an insulating film is formed, any pretreatment such as degreasing based on alkali or pickling based on hydrochloric acid, sulfuric acid, phosphoric acid, etc., can be performed before applying the coating solution. Alternatively, the coating solution can be applied to the surface of the base material after final annealing without performing these pretreatments.

[0169] The non-oriented electromagnetic steel sheet obtained in this embodiment as described above has excellent characteristics such as low iron loss and high magnetic flux density, and is therefore preferred as a raw material for rotor cores and stators.

[0170] The present invention will be described in more detail below through embodiments, but the present invention is not limited to these embodiments.

[0171] Example 1

[0172] A steel billet with the chemical composition shown in Table 1 was heated to 1150°C, then hot-rolled at a final temperature of 850°C and a final thickness of 2.0 mm, and coiled at 600°C to produce a hot-rolled steel sheet. After descaling the obtained hot-rolled steel sheet by pickling, it was annealed in a box annealing furnace at 750°C for 20 hours. The resulting steel sheet was then cold-rolled to produce a cold-rolled steel sheet with a thickness of 0.25 mm.

[0173] Following the first and second heating processes under the conditions described later, a final annealing was performed. This final annealing was carried out in a mixed atmosphere of H2: 20%, N2: 80%, and dew point: -30°C, with a homogenization process held at 1100°C for 30 seconds. Furthermore, all heating processes were conducted in a nitrogen atmosphere. As the first heating process, the temperature range from 100°C to 350°C was heated at a rate of 100°C / s, then held at 350–450°C for 1 second. Then, as the second heating process, rapid heating was performed at a rate of 1400°C / s, from 600°C to the final temperature of 880°C. The final annealed steel sheet was coated with an insulating film and sintered in atmosphere at 350°C.

[0174] Table 1

[0175]

[0176] For each of the obtained test materials, the surface orientation intensity was measured using reverse X-ray diffraction analysis with a Rigaku RINT-2500 X-ray diffractometer. The specific measurement and analysis methods are as described above. Next, small test pieces (55 mm × 55 mm) were fabricated from each test material, and the iron loss W was measured using the methods described above. 10 / 400 and magnetic flux density B 50 The average crystal grain size and tensile strength were then measured in the order described above.

[0177] The results are shown in Table 2.

[0178] Table 2

[0179]

[0180] As shown in Table 2, in tests No. 1 to 24 that meet the requirements of this invention, the results show excellent magnetic properties. In contrast, in tests No. 25 to 34 where the chemical composition exceeds the requirements of this invention, the results show that cold rolling is more difficult, making manufacturing impossible, or the magnetic flux density or iron loss is poor.

[0181] Specifically, in Experiment No. 25, the carbon content was excessive; in Experiment No. 26, the silicon content was insufficient, resulting in high iron loss. In Experiment No. 27, the silicon content was excessive, making cold rolling difficult and preventing manufacturing. In Experiment No. 28, the manganese (Mn) content was insufficient, resulting in high iron loss. In Experiment No. 29, the manganese (Mn) content was excessive, making cold rolling difficult and preventing manufacturing.

[0182] In Experiment No. 30, the sulfur (S) content was excessive; in Experiment No. 31, the al (Al) content was insufficient, resulting in high iron loss. In Experiment No. 32, the al (Al) content was excessive, making cold rolling difficult and preventing manufacturing. In Experiment No. 33, the nitrogen (N) content was excessive, resulting in high iron loss. In Experiment No. 34, the phosphorus (P) content was excessive, making cold rolling difficult and preventing manufacturing.

[0183] Example 2

[0184] A portion of a steel billet with the chemical composition shown in Table 1 was heated to 1150°C, then hot-rolled to a final temperature of 850°C and a final thickness of 2.0 mm, and coiled at 600°C to produce a hot-rolled steel sheet. The resulting hot-rolled steel sheet was then annealed under the conditions shown in Table 3. Furthermore, during the annealing of the hot-rolled sheet, a continuous annealing furnace was used in tests No. 35–41 and 49, and a box annealing furnace was used in tests No. 42–48. For tests No. 35–41 and 49, a descaling treatment based on pickling and shot peening was performed after annealing; for tests No. 42–48, a descaling treatment based on pickling was performed before annealing. The resulting steel sheet was then cold-rolled to produce a cold-rolled steel sheet with a thickness of 0.25 mm.

[0185] Furthermore, final annealing was carried out in a mixed atmosphere of H2: 3%, N2: 97%, and dew point: -30°C, under the conditions described in Table 3. The heating rate in the first heating step was the rate of increase from 100°C to 350°C, and the residence time was the residence time within the temperature range of 350–450°C. The heating rate in the second heating step was the rate of increase from 600°C to the reached temperature. An insulating film was applied to the final annealed steel sheet, and it was sintered at 350°C in the atmosphere. Additionally, in Test No. 49, the "reached temperature" and "residence time" columns in the first heating step were marked with "-", indicating that heating continued continuously from room temperature until the reached temperature in the second heating step.

[0186] For each of the obtained test materials, the average crystal grain size, planar orientation intensity, tensile strength, and iron loss W were measured using the same method as in Example 1. 10 / 400 and magnetic flux density B 50 The determination.

[0187] The results above are shown in Table 3.

[0188] Table 3

[0189]

[0190] As shown in Table 3, the results in tests No. 35-38 and 42-45, which meet the requirements of this invention, show excellent magnetic properties. In contrast, in tests No. 39-41 and 46-49, where the heating rate or the temperature reached in the second heating step during final annealing deviates from the requirements of this invention, a texture with high symmetry cannot be developed, resulting in a decrease in magnetic flux density and an increase in iron loss.

[0191] Industrial availability

[0192] As described above, according to the present invention, a non-oriented electromagnetic steel sheet with excellent magnetic properties can be obtained.

Claims

1. A non-oriented electromagnetic steel sheet, wherein the chemical composition of its base material, in mass percent, is: C: Below 0.0050% Si: 2.80–4.50% Mn: 0.10~2.00% Al：0.10～2.00%、 P: below 0.030% S: Below 0.0050% N: below 0.0050% Sn: More than 0% and less than 0.06% Remaining components: Fe and impurities. The surface orientation intensities I, derived from (110), (200), and (222) using X-ray diffraction, respectively, are respectively derived from the surface orientation intensities I. （110） I （200） and I （222） Satisfying the following equations (i) to (iii), 0.10≤I （110） ≤0.40・・・(i) 1.00≤I （200） ≤3.00・・・(ii) 2.00≤I （222） ≤7.00・・・(iii)。 2. The non-oriented electromagnetic steel sheet as described in claim 1, wherein, In the chemical composition of the parent material, a portion replacing Fe contains [material from...]. Ca: below 0.0050% Zn: below 0.0050% Mg: less than 0.0050% Ti: below 0.015% Cr: less than 0.20% Sb: below 0.20% Mo: 0.015% or less, Nb: below 0.015%, and Cu: less than 0.20% Choose one or more.

3. A method for manufacturing a non-oriented electromagnetic steel sheet, comprising, for the steel sheet, sequentially performing a hot rolling process, a pickling process, a cold rolling process, and a final annealing process. In the final annealing process, the temperature is increased from room temperature to 350-450°C at a rate of 10-500°C / s from 100°C to 350°C, and then held at 350-450°C for 0.1-100 seconds. Next, the temperature is increased from 350-450°C to the reached temperature at a rate of 700°C / s or higher from 600°C to 840-950°C. in, The chemical composition of the steel sheet, in mass percent, is: C: Below 0.0050%, Si: 2.80–4.50%, Mn: 0.10~2.00%, Al：0.10～2.00%， P: below 0.030%, S: below 0.0050%, N: below 0.0050% Sn: greater than 0% and less than 0.06%, Remaining components: Fe and impurities.

4. The method for manufacturing non-oriented electromagnetic steel sheet as described in claim 3, wherein, The chemical composition of the steel sheet contains, in place of a portion of Fe, elements derived from... Ca: below 0.0050% Zn: below 0.0050% Mg: less than 0.0050% Ti: below 0.015% Cr: less than 0.20% Sb: below 0.20% Mo: 0.015% or less, Nb: below 0.015%, and Cu: less than 0.20% Choose one or more.

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