Non-oriented electrical steel sheet and method for manufacturing same

Abstract

The present application relates to a non-oriented electrical steel sheet and a method for manufacturing same. The non-oriented electrical steel sheet and the method for manufacturing same, according to the present application, can provide excellent magnetic properties, and, specifically, the non-oriented electrical steel sheet may have low iron loss and a low angle-specific average iron loss.

Description

Non-oriented electrical steel sheet and method of manufacturing the same

[0001] The present application relates to a non-oriented electrical steel sheet and a method for manufacturing the same.

[0002] Recently, due to policies aimed at reducing CO2 emissions to prevent global warming, conventional internal combustion engine vehicles are being rapidly replaced by eco-friendly vehicles such as hybrid electric vehicles (HEVs) and, in particular, electric vehicles (EVs). These electric vehicles (EVs) must generate high torque at low speeds or during acceleration, and rotate at high speeds of over 200 Hz during constant speed and high-speed driving. Consequently, non-oriented electrical steel sheets, which serve as the core material for motors, must simultaneously satisfy high magnetic flux density and low iron loss.

[0003] Factors affecting the magnetic properties of such non-oriented electrical steel include chemical composition, the size and distribution of inclusions, thickness, microstructure, insulating coating layer, and / or texture. These various factors are influenced by the manufacturing process conditions of the non-oriented electrical steel. Generally, non-oriented electrical steel is manufactured through the processes of steelmaking / continuous casting, hot rolling, pre-annealing, cold rolling, final annealing, and coating, and excellent magnetic properties can be achieved by optimizing the conditions of each process.

[0004] Furthermore, to reduce iron loss in non-oriented electrical steel sheets, the sheet thickness must be reduced and the resistivity increased. However, reducing the sheet thickness requires advanced manufacturing technology and lowers productivity during the process, leading to increased costs during machining and lamination in the motor core manufacturing process.

[0005] In addition, high-alloy elements such as Si, Al, and Mn are added to increase the resistivity of non-oriented electrical steel sheets. At this time, elements such as Ni and P may be added to improve the texture, including the {001} orientation which facilitates magnetization, and high-efficiency non-oriented electrical steel sheets can be manufactured through chemical composition control, such as managing impurities such as C, S, N, and Ti to extremely low levels to produce clean steel that does not interfere with magnetization.

[0006] Patent Document 1 (Korean Published Patent No. 10-2024-0081966) discloses a method for manufacturing a non-oriented electrical steel sheet with excellent magnetic properties by reheating a semi-finished product, performing hot rolling, and then performing cold rolling and final annealing without performing a hot-rolled steel sheet annealing process after hot rolling. However, when the hot-rolled steel sheet annealing process is not performed, the microstructure becomes non-homogeneous, causing an increase in the average value of the iron loss value by angle of the final product, which results in a problem that it is not suitable for use as a core material for motors. Therefore, a non-oriented electrical steel sheet and a method for manufacturing the same are required to solve these problems.

[0007] The objective of the present application is to provide a non-oriented electrical steel sheet with excellent magnetic properties and a method for manufacturing the same.

[0008] To solve the above problem, the non-oriented electrical steel sheet of the present application comprises, in weight percent, C: greater than 0% and less than or equal to 0.0030%, Si: greater than 2.8% and less than or equal to 4.0%, Mn: greater than 0.1% and less than or equal to 0.5%, Al: greater than 0.3% and less than or equal to 0.9%, S: greater than 0% and less than or equal to 0.0030%, N: greater than 0% and less than or equal to 0.0015%, Ti: greater than 0% and less than or equal to 0.0030%, P: greater than 0% and less than or equal to 0.01%, and the remainder being Fe and other unavoidable impurities, and {001} represented by the following formula 1. <130> The ratio of the fraction of directions to the fraction of directions is 1.45 or greater and 1.80 or less.

[0009] [Equation 1]

[0010] {001} <130> Fraction of directions / {334}<4-83> Fraction of directions

[0011] In addition, the above non-oriented electrical steel sheet has iron loss (W) measured at azimuth angles of 0° and 90° with respect to the rolling direction, respectively. 10 / 400 The average value of ) may be 11.5 W / Kg or less.

[0012] In addition, the iron loss (W) of the above-mentioned non-oriented electrical steel sheet measured at azimuth angles of 0°, 30°, 45°, 60°, and 90° with respect to the rolling direction, respectively 10 / 400 The average value of ) may be 11.5 W / Kg or less.

[0013] In addition, the method for manufacturing a non-oriented electrical steel sheet according to the present application comprises the steps of: reheating a slab composed of, in weight percent, C: greater than 0% and less than or equal to 0.0030%, Si: greater than 2.8% and less than or equal to 4.0%, Mn: greater than 0.1% and less than or equal to 0.5%, Al: greater than 0.3% and less than or equal to 0.9%, S: greater than 0% and less than or equal to 0.0030%, N: greater than 0% and less than or equal to 0.0015%, Ti: greater than 0% and less than or equal to 0.0030%, P: greater than 0% and less than or equal to 0.01%, and the remainder being Fe and other unavoidable impurities, and then hot-rolling the slab to produce a hot-rolled steel sheet; the step of annealing the hot-rolled steel sheet to produce a hot-rolled annealed material; and the step of cold-rolling the hot-rolled annealed material to produce a cold-rolled steel sheet. The above cold-rolled steel sheet includes a step of final annealing, and the non-oriented electrical steel sheet manufactured through the final annealing step is {001} represented by the following formula 1. <130> The ratio of the fraction of directions to the fraction of directions is 1.45 or greater and 1.80 or less.

[0014] [Equation 1]

[0015] {001} <130> Fraction of directions / {334}<4-83> Fraction of directions

[0016] In addition, the size of the crystal grains of the hot-rolled annealed material may be 350㎛ or more and 500㎛ or less.

[0017] In addition, the step of manufacturing the hot-rolled steel sheet may have a finishing rolling temperature of 860°C or higher and 900°C or lower during hot rolling.

[0018] In addition, prior to the step of manufacturing the hot-rolled annealed material, the method further includes a step of coiling the hot-rolled steel sheet, and the coiling step may have a coiling temperature of 660°C or higher and 710°C or lower.

[0019] In addition, the thickness of the hot-rolled steel sheet may be 1.8 mm or more and 2.6 mm or less.

[0020] In addition, the step of manufacturing the cold-rolled steel sheet may be performed such that the ratio of the roll speed of the upper cold-rolling roll located at the top of the steel sheet to the roll speed of the lower cold-rolling roll located at the bottom of the steel sheet (roll speed of the lower cold-rolling roll / roll speed of the upper cold-rolling roll) is 1.5 or more and 1.7 or less.

[0021] In addition, the step of annealing the hot-rolled plate may have a heat treatment temperature of 950°C or higher and 1100°C or lower.

[0022] In addition, the step of annealing the hot-rolled plate may have an average heating rate of 15℃ / s or more up to the heat treatment temperature.

[0023] In addition, the step of annealing the hot-rolled plate can be heat-treated for 200 seconds or more and 500 seconds or less.

[0024] In addition, the final annealing step can be performed in a mixed atmosphere of hydrogen and nitrogen.

[0025] In addition, the final annealing step may have a heat treatment temperature of 900°C or higher and 1100°C or lower.

[0026] In addition, the above final annealing step may have an average cooling rate of 30℃ / s or more after heat treatment.

[0027] According to the non-oriented electrical steel sheet and the method for manufacturing the same of the present application, excellent magnetic properties can be achieved, and specifically, low iron loss and a low average iron loss value per angle can be achieved.

[0028] Embodiments of the present invention will be described in detail below. Furthermore, the scope of the present invention is not limited to the embodiments described below, and may be implemented with arbitrary modifications within the scope that does not deviate from the gist of the present invention.

[0029] In the description of numerical ranges in this specification, the notation “X~Y” indicates X or greater and Y or less, unless otherwise specifically stated. Additionally, “greater than or equal to” may be replaced with “greater than,” and “less than or equal to” may be replaced with “less than.”

[0030] In the numerical ranges described stepwise in this specification, an upper or lower limit value described in any numerical range may be substituted with an upper or lower limit value of another numerical range described stepwise, or may also be substituted with a value shown in the examples.

[0031] The present application relates to a non-oriented electrical steel sheet, which is a core material used in motors that convert electrical energy into mechanical energy. The non-oriented electrical steel sheet is {001} represented by the following Formula 1. <130> The ratio of the fraction of directions to the fraction of directions is 1.45 or greater and 1.80 or less.

[0032] [Equation 1]

[0033] {001} <130> Fraction of directions / {334}<4-83> Fraction of directions

[0034] The above non-oriented electrical steel sheet is {001} represented by Equation 1 above. <130> The ratio of the fraction of orientation to the fraction of {334}<4-83> orientation may be 1.47 or higher, 1.48 or higher, or 1.49 or higher, and may be 1.79 or lower, 1.78 or lower, or 1.77 or lower. According to the non-oriented electrical steel sheet of the present application, the value calculated by the aforementioned Equation 1 satisfies the aforementioned numerical range, thereby having excellent magnetic properties, specifically, low iron loss and a low average iron loss value per angle. On the other hand, if the value calculated by the aforementioned Equation 1 exceeds the upper limit of the aforementioned numerical range, the texture of a specific orientation develops strongly, causing a deviation in the iron loss value per angle and deteriorating the magnetic properties; and if the value calculated by the aforementioned Equation 1 is below the lower limit of the aforementioned numerical range, the {111} / ND orientation, which is disadvantageous to magnetization, develops significantly compared to the {001} / ND orientation, which is favorable to magnetization, and the magnetic properties may deteriorate. In addition, the magnetic properties of non-oriented electrical steel sheets are influenced by their texture, and the higher the ratio of {001} / ND orientations which are favorable for magnetization, the better the magnetic properties. Also, the lower the ratio of ND / {111} orientations which are unfavorable for magnetization, the better the magnetic properties.

[0035] The above non-oriented electrical steel sheet may be composed of, in weight percent, C: greater than 0% and less than or equal to 0.0030%, Si: greater than or equal to 2.8% and less than or equal to 4.0%, Mn: greater than or equal to 0.1% and less than or equal to 0.5%, Al: greater than or equal to 0.3% and less than or equal to 0.9%, S: greater than 0% and less than or equal to 0.0030%, N: greater than 0% and less than or equal to 0.0015%, Ti: greater than 0% and less than or equal to 0.0030%, P: greater than 0% and less than or equal to 0.01%, and the remainder being Fe and other unavoidable impurities.

[0036] The composition of the above steel plate is explained below.

[0037] C: Exceeding 0 wt% and up to 0.0030 wt%

[0038] Carbon (C) is an element that can increase iron loss by combining with other unavoidable impurities to form carbides such as TiC and / or NbC. If the carbon is included in the non-oriented electrical steel sheet in an amount exceeding the upper limit of the aforementioned range, it may cause magnetic aging and adversely affect magnetic properties. Therefore, the carbon may be included in the non-oriented electrical steel sheet in an amount greater than 0 wt% and less than or equal to 0.0030 wt%, and specifically, in an amount greater than 0 wt% and less than or equal to 0.0020 wt%.

[0039] Si: 2.8 wt% or more, 4.0 wt% or less

[0040] Silicon (Si) is an element that increases the resistivity of a material and lowers iron loss. If the silicon is included in the non-oriented electrical steel sheet in an amount less than the lower limit of the aforementioned range, the effect of reducing iron loss may be insufficient. Additionally, if the silicon is included in the non-oriented electrical steel sheet in an amount exceeding the upper limit of the aforementioned range, the permeability and magnetic flux density may decrease. Therefore, the silicon may be included in the non-oriented electrical steel sheet in an amount of 2.8 weight% or more and 4.0 weight% or less.

[0041] Mn: 0.1 wt% or more and 0.5 wt% or less

[0042] Manganese (Mn) is an element that, together with Si, increases resistivity to lower iron loss and improve texture. If the manganese is included in the non-oriented electrical steel sheet in an amount less than the lower limit of the aforementioned range, fine MnS may precipitate, inhibiting grain growth and increasing iron loss. Additionally, if the manganese is included in the non-oriented electrical steel sheet in an amount exceeding the upper limit of the aforementioned range, the reduction in iron loss is small relative to the amount added, and cold rolling performance may be reduced. Therefore, the manganese may be included in the non-oriented electrical steel sheet in an amount of 0.1 wt% or more and 0.5 wt% or less.

[0043] Al: 0.3 wt% or more, 0.9 wt% or less

[0044] Aluminum (Al) is an element that, together with the above Si, increases resistivity to lower iron loss and forms AlN nitride with nitrogen (N). If the above aluminum is included in the above non-oriented electrical steel sheet in an amount exceeding the upper limit of the aforementioned range, cold rolling performance is reduced and magnetic flux density is reduced, which may lead to deterioration of magnetic properties. Therefore, the above aluminum may be included in the above non-oriented electrical steel sheet in an amount of 0.3 weight% or more and 0.9 weight% or less.

[0045] S: Greater than 0 wt% and less than or equal to 0.0030 wt%

[0046] Sulfur (S) is an element that combines with other unavoidable impurities to form sulfides such as MnS and / or CuS. When included in the non-oriented electrical steel sheet in an amount exceeding the upper limit of the aforementioned range, it can increase iron loss and inhibit grain growth. Accordingly, the sulfur may be included in the non-oriented electrical steel sheet in an amount greater than 0 weight% and less than or equal to 0.0030 weight%.

[0047] N: Greater than 0 wt% and less than or equal to 0.0015 wt%

[0048] Nitrogen (N) is an element that combines with other unavoidable impurities to form nitrides such as AlN, TiN, and / or NbN. When included in the non-oriented electrical steel sheet in an amount exceeding the upper limit of the aforementioned range, it can increase iron loss and inhibit grain growth. Accordingly, the nitrogen may be included in the non-oriented electrical steel sheet in an amount greater than 0 weight% and less than or equal to 0.0015 weight%.

[0049] Ti: Greater than 0 wt% and less than or equal to 0.0030 wt%

[0050] Titanium (Ti) is an element that combines with other unavoidable impurities to form fine carbides and / or nitrides such as TiC and / or TiN. If included in the non-oriented electrical steel sheet in an amount exceeding the upper limit of the aforementioned range, it can increase iron loss and inhibit grain growth, thereby degrading magnetic properties. Therefore, the titanium may be included in the non-oriented electrical steel sheet in an amount greater than 0 weight% and less than or equal to 0.0030 weight%.

[0051] P: Greater than 0 wt% and less than or equal to 0.01 wt%

[0052] Phosphorus (P) is a grain boundary segregation element that develops texture. If it is included in the above-mentioned non-oriented electrical steel sheet in an amount exceeding the upper limit of the aforementioned range, grain growth is inhibited due to the segregation effect, magnetic properties are deteriorated, and cold rolling performance may be reduced. Therefore, the above-mentioned phosphorus may be included in the above-mentioned non-oriented electrical steel sheet in an amount greater than 0 weight% and less than or equal to 0.01 weight%.

[0053] Remaining Fe and other unavoidable impurities

[0054] The aforementioned unavoidable impurities are impurities introduced during the steelmaking and manufacturing processes of non-oriented electrical steel sheets. Since this is widely known in the industry, a detailed description is omitted. In one embodiment of this application, the addition of elements other than the components of the steel sheet described above is not excluded, and various elements may be included within a scope that does not impair the technical concept of this application. If additional elements are included, they may be included to replace the remainder of iron (Fe).

[0055] In addition, the above non-oriented electrical steel sheet may have a thickness of less than 0.35 mm, and specifically, may be 0.25 mm or less.

[0056] In addition, the above non-oriented electrical steel sheet may have an average grain size of 80㎛ or more and 200㎛ or less, and specifically, 80㎛ or more and 160㎛ or less.

[0057] In addition, the above non-oriented electrical steel sheet has iron loss (W) measured at azimuth angles of 0° and 90° with respect to the rolling direction, respectively. 10 / 400 The average value of ) may be 11.5 W / Kg or less, specifically 11.1 W / Kg or less. Here, the iron loss (W) measured at azimuth angles of 0° and 90° with respect to the rolling direction, respectively 10 / 400 The average value of ) refers to the average of the iron loss value measured at 0° and the iron loss value measured at 90°. If the average value of the iron loss measured at 0° and 90°, respectively, falls within the aforementioned range, the efficiency of the motor can be improved when using non-oriented electrical steel sheets as the iron core material of the motor. The iron loss W 10 / 400 represents the iron loss when a magnetic flux density of 1.0 T is induced at 400 Hz. In addition, the iron loss can be obtained by measuring the iron loss value 2 to 4 times each in the L direction parallel to the rolling direction and the C direction perpendicular to the rolling direction using a Single Sheet Tester on a specimen manufactured by cutting the non-oriented electrical steel sheet to a width of 60 mm x a length of 60 mm, and then calculating the average of all measured values.

[0058] In addition, the iron loss (W) of the above-mentioned non-oriented electrical steel sheet measured at azimuth angles of 0°, 30°, 45°, 60°, and 90° with respect to the rolling direction, respectively 10 / 400 The average value of ) may be 11.5 W / Kg or less, specifically, 11.4 W / kg or less. Here, the iron loss (W) measured at azimuth angles of 0°, 30°, 45°, 60°, and 90°, respectively, with respect to the rolling direction 10 / 400The average value of ) refers to the average of the iron loss values ​​measured at 0°, 30°, 45°, 60°, and 90°. When the average value of the iron loss measured at 0°, 30°, 45°, 60°, and 90° falls within the aforementioned range, the non-oriented electrical steel sheet can have excellent magnetic properties in all directions regardless of the rolling direction, specifically, it can have low iron loss, and is also suitable as a core material for a motor, so when the non-oriented electrical steel sheet is used as a core material for a motor, the efficiency of the motor can be improved. In addition, the iron loss can be obtained by measuring the iron loss value 2 to 4 times each at 0°, 30°, 45°, 60°, and 90° in the rolling direction using a Single Sheet Tester on a specimen manufactured by cutting the non-oriented electrical steel sheet to a width of 60 mm x a length of 60 mm, and then calculating the average of all measured values.

[0059] Accordingly, the iron loss (W) of the above-mentioned non-oriented electrical steel sheet measured at azimuth angles of 0° and 90° with respect to the rolling direction, respectively 10 / 400 The average value of ) is 11.5 W / Kg or less, and furthermore, the iron loss (W) measured at azimuth angles of 0°, 30°, 45°, 60°, and 90° respectively with respect to the rolling direction 10 / 400 Since the average value of ) is 11.5 W / Kg or less, it can have excellent magnetic properties in all directions regardless of the rolling direction and can have low iron loss. In addition, the above non-oriented electrical steel sheet is suitable as a core material for a motor because the average value of iron loss measured at an azimuth angle of 0° and 90° with respect to the rolling direction, respectively, and the average value of iron loss measured at an azimuth angle of 0°, 30°, 45°, 60°, and 90° with respect to the rolling direction, respectively, satisfies the aforementioned range, so when the non-oriented electrical steel sheet is used as a core material for a motor, the efficiency of the motor can be improved.

[0060] In addition, the above non-oriented electrical steel sheet may have a yield strength (YS) of 400 MPa or more.

[0061] In addition, the above non-oriented electrical steel sheet may have a tensile strength (TS) of 500 MPa or more.

[0062] In addition, the non-oriented electrical steel sheet may further include a coating layer. The coating layer is an insulating coating layer formed on the surface of the non-oriented electrical steel sheet and may be referred to as an insulating film. Since the insulating film is widely known, a detailed description is omitted. For example, the coating layer may be formed by applying a chromium-free (Cr-free) coating solution, that is, an organic-inorganic composite coating solution that does not contain chromium, to the surface of the final annealed steel sheet and then baking it. At this time, the coating layer may be formed with a thickness of 0.1 μm or more and 5 μm or less. By further including a coating layer formed on the surface of the non-oriented electrical steel sheet, insulation between the upper and lower non-oriented electrical steel sheets is maintained when multiple non-oriented electrical steel sheets are stacked, thereby reducing eddy current losses.

[0063] This application also relates to a method for manufacturing non-oriented electrical steel sheets. The method for manufacturing non-oriented electrical steel sheets relates to a method for manufacturing the aforementioned non-oriented electrical steel sheets. Since specific details regarding the non-oriented electrical steel sheets described below can be applied in the same way as those described above, they will be omitted.

[0064] The method for manufacturing a non-oriented electrical steel sheet according to the present application comprises the steps of: reheating a slab composed of, in weight percent, C: greater than 0% and less than or equal to 0.0030%, Si: greater than 2.8% and less than or equal to 4.0%, Mn: greater than 0.1% and less than or equal to 0.5%, Al: greater than 0.3% and less than or equal to 0.9%, S: greater than 0% and less than or equal to 0.0030%, N: greater than 0% and less than or equal to 0.0015%, Ti: greater than 0% and less than or equal to 0.0030%, P: greater than 0% and less than or equal to 0.01%, and the remainder being Fe and other unavoidable impurities, and then hot-rolling the slab to produce a hot-rolled steel sheet; the step of annealing the hot-rolled steel sheet to produce a hot-rolled annealed material; the step of cold-rolling the hot-rolled annealed material to produce a cold-rolled steel sheet; and the step of finally annealing the cold-rolled steel sheet, wherein the non-oriented electrical steel sheet produced through the final annealing step comprises the following formula {001} represented by 1 <130> The ratio of the orientation fraction to the {334}<4-83> orientation fraction is 1.45 or higher and 1.80 or lower. According to the method for manufacturing a non-oriented electrical steel sheet of the present application, magnetic properties can be excellent, and specifically, a non-oriented electrical steel sheet having low iron loss and a low average iron loss value per angle can be manufactured.

[0065] A detailed description of the composition of the above slab is omitted because it is identical to the composition described in the above non-oriented electrical steel sheet.

[0066] The step of manufacturing the hot-rolled steel sheet is a step for manufacturing a slab into a hot-rolled steel sheet, and is performed by reheating the slab and then hot-rolling it. The reheating temperature of the slab is not particularly limited, but, for example, it may be 1110°C or higher and less than 1250°C, and specifically, it may be 1110°C or higher and less than 1160°C. If the reheating temperature of the slab is below the lower limit of the aforementioned range, the rolling load increases, making it difficult to perform hot-rolling; and if it is above the upper limit of the aforementioned range, precipitates such as C, S, and N within the slab are re-dissolved, and fine precipitates are generated during subsequent rolling and annealing processes, which can inhibit grain growth and impair magnetism.

[0067] In addition, the finishing rolling temperature during the above hot rolling may be 860℃ or higher and 900℃ or lower.

[0068] In addition, the thickness of the hot-rolled steel sheet may be 1.8 mm or more and 2.6 mm or less, specifically, 1.8 mm or more and 2.5 mm or less. If the thickness of the hot-rolled steel sheet exceeds the upper limit of the aforementioned range, the reduction rate during cold rolling increases, which may result in a deterioration of the texture. Therefore, the thickness of the hot-rolled steel sheet can be controlled within the aforementioned range.

[0069] In one example, the method for manufacturing the above-described non-oriented electrical steel sheet may further include the step of winding the above-described hot-rolled steel sheet. The winding step may be performed by winding the above-described hot-rolled steel sheet obtained by hot rolling at a temperature of 660°C or higher and 710°C or lower.

[0070] In one example, the step of manufacturing a hot-rolled annealed material by annealing the hot-rolled sheet may be performed by increasing the temperature to 950°C or higher and 1100°C or higher and 1000°C or lower at an average heating rate of 15°C / s or more, and then heat treating the material for 100 seconds or more and 500 seconds or less, specifically, 200 seconds or more and 500 seconds or 300 seconds or more and 500 seconds or less, within this temperature range. Afterward, the annealed hot-rolled steel sheet may be cooled at an average cooling rate of 30°C / s or more. Additionally, if the heating temperature during the annealing of the hot-rolled sheet is below the lower limit of the aforementioned condition range, the variation in the grain size of the hot-rolled annealed material at different locations increases, which may deteriorate the magnetic properties of the non-oriented electrical steel sheet.

[0071] In one example, the grain size of the hot-rolled annealed material may be 350 μm or more and 500 μm or less. Specifically, it may be 360 ​​μm or more, 370 μm or more, 380 μm or more, or 420 μm or more, and 490 μm or less or 480 μm or less. As the grain size of the hot-rolled annealed material satisfies the aforementioned range, the magnetic properties of the non-oriented electrical steel sheet are excellent, and specifically, a non-oriented electrical steel sheet having low iron loss and a low average iron loss value per angle can be manufactured. In addition, the grain size of the hot-rolled annealed material is influenced by the manufacturing process conditions of the non-oriented electrical steel sheet. Specifically, by adjusting the annealing temperature and heat treatment time, etc., in the step of annealing the hot-rolled sheet to the aforementioned range, it may be 350 μm or more and 500 μm or less. In addition, the grain size of the hot-rolled annealed material is also affected by the reduction rate during hot rolling, stress changes such as the skin pass, changes in composition where phase change occurs, and the heating rate. For example, the grain size of the hot-rolled annealed material can be 350 μm or more and 500 μm or less by controlling the reduction rate during hot rolling to 98% or more, the reduction rate during the skin pass performed before annealing the hot-rolled sheet to within 3% of the sheet thickness, and the composition and heating rate of the sheet to the aforementioned ranges.

[0072] In addition, the annealed hot-rolled steel sheet may undergo further pickling. As a result, the oxide layer formed on the surface of the hot-rolled steel sheet can be removed through the pickling solution.

[0073] The step of manufacturing the above cold-rolled steel sheet is a step for manufacturing the above hot-rolled steel sheet into a cold-rolled steel sheet, and is performed through cold rolling.

[0074] In one example, the step of manufacturing the cold-rolled steel sheet may be performed under conditions where the roll speed of the upper cold-rolling roll located above the steel sheet and the roll speed of the lower cold-rolling roll located below the steel sheet are different from each other. Specifically, the ratio of the roll speed of the upper cold-rolling roll located above the steel sheet and the roll speed of the lower cold-rolling roll located below the steel sheet (roll speed of the lower cold-rolling roll / roll speed of the upper cold-rolling roll) may be performed at 1.5 or more and 1.7 or less, and specifically, at 1.5 or more and 1.6 or less. By satisfying the aforementioned range, the magnetic properties of the final product may be excellent. Specifically, a non-oriented electrical steel sheet with low iron loss and a low average iron loss value per angle can be manufactured.

[0075] The roll speeds of the upper and lower cold rolling rolls mentioned above can be controlled by a separate control system during cold rolling, and the specific control method is not particularly limited.

[0076] The thickness of the above cold-rolled steel sheet may be less than 0.35 mm, and specifically, may be 0.25 mm or less.

[0077] In addition, the reduction rate during the above cold rolling may be 85.0% or more and 87.5% or less.

[0078] The final annealing step described above is performed by heat treating the cold-rolled steel sheet. For example, the final annealing step may be performed by heating from 900°C to 1100°C at an average heating rate of 20°C / s or more, heat treating at this temperature range for 30 seconds or more and 120 seconds or less, and then cooling at an average cooling rate of 30°C / s or more. By performing the final annealing step within the aforementioned ranges of heating rate, temperature, time, and cooling rate, iron loss can be reduced and an optimal grain size considering mechanical properties can be derived. Conversely, if the temperature of the final annealing step exceeds the upper limit of the aforementioned range, the grain size becomes coarse, and eddy current loss may increase. Furthermore, if the temperature of the final annealing step is below the lower limit of the aforementioned range, the grain size becomes fine, and hysteresis loss may increase.

[0079] At this time, the final annealing step can be performed in a mixed atmosphere of hydrogen and nitrogen, specifically, in an atmosphere of 30% hydrogen and 70% nitrogen. The method for manufacturing the non-oriented electrical steel sheet can produce a non-oriented electrical steel sheet with a smooth surface condition by performing the final annealing step under the atmosphere of the aforementioned range.

[0080] In addition, the non-oriented electrical steel sheet manufactured through the above final annealing step may have an average grain size of 50㎛ or more and 180㎛ or less.

[0081] In addition, the non-oriented electrical steel sheet manufactured through the above final annealing step may have a thickness of less than 0.35 mm, and specifically, may be 0.25 mm or less.

[0082] In addition, the method for manufacturing the above-mentioned non-oriented electrical steel sheet may further include a step of forming a coating layer to improve punchability and secure insulation. Specifically, the step of forming the coating layer is a step of forming a coating layer to impart insulation to the surface of the final annealed steel sheet, and is performed after the final annealing step.

[0083] In addition, according to the method for manufacturing a non-oriented electrical steel sheet of the present application, {001} represented by the following formula 1 <130> It is possible to manufacture non-oriented electrical steel sheets in which the ratio of the orientation fraction to the {334}<4-83> orientation fraction is 1.45 or more and 1.80 or less.

[0084] [Equation 1]

[0085] {001} <130> Fraction of directions / {334}<4-83> Fraction of directions

[0086] Specifically, {001} represented by the above Equation 1 <130> The ratio of the fraction of directions to the fraction of directions may be 1.47 or greater and 1.77 or less.

[0087] According to the non-oriented electrical steel sheet of the present application, the value calculated by the above-described Equation 1 satisfies the above-described numerical range, thereby having excellent magnetic properties, and specifically, a non-oriented electrical steel sheet having low iron loss and a low average iron loss value per angle can be manufactured.

[0088] In addition, according to the non-oriented electrical steel sheet of the present application, iron loss (W) measured at azimuth angles of 0° and 90° with respect to the rolling direction, respectively 10 / 400 It is possible to manufacture non-oriented electrical steel sheets with an average value of 11.5 W / Kg or less.

[0089] In addition, according to the non-oriented electrical steel sheet of the present application, iron loss (W) measured at azimuth angles of 0°, 30°, 45°, 60°, and 90° with respect to the rolling direction, respectively 10 / 400 It is possible to manufacture non-oriented electrical steel sheets with an average value of 11.5 W / Kg or less.

[0090] Iron loss (W) measured at azimuth angles of 0° and 90° with respect to the rolling direction, respectively 10 / 400 The average value of ) is 11.5 W / Kg or less, and furthermore, the iron loss (W) measured at azimuth angles of 0°, 30°, 45°, 60°, and 90° respectively with respect to the rolling direction 10 / 400 As the average value of ) is 11.5 W / Kg or less, it is possible to manufacture non-oriented electrical steel sheets with low iron loss and low average iron loss values ​​per angle.

[0091]

[0092] The present application will be described in more detail below through embodiments according to the present application and comparative examples not according to the present application, but the scope of the present application is not limited by the embodiments presented below.

[0093]

[0094] Manufacturing of non-oriented electrical steel sheets

[0095] Example 1

[0096] A slab was manufactured by steelmaking and continuous casting with the components shown in Table 1 below, the remainder being Fe and other unavoidable impurities, and then reheated at a temperature of 1130°C and hot-rolled at a finishing temperature of 880°C to produce a hot-rolled steel sheet with a thickness of 2.0 mm.

[0097] Afterwards, the above hot-rolled steel sheet was coiled at a coiling temperature of 690℃.

[0098] Subsequently, the hot-rolled steel sheet was annealed by heating it to 1050°C at an average heating rate of 15°C / s under a nitrogen atmosphere, maintaining it at this temperature for 200 seconds, and then cooling it at an average cooling rate of 20°C / s. Afterward, pickling was performed.

[0099] Subsequently, an annealed and pickled hot-rolled steel sheet was cold-rolled under conditions of a reduction rate of 87.5% and a ratio of the roll speed of the upper cold-rolling roll to the roll speed of the lower cold-rolling roll (roll speed of the lower cold-rolling roll / roll speed of the upper cold-rolling roll) of 1.5 to produce a cold-rolled steel sheet with a thickness of 0.25 mm.

[0100] Subsequently, a non-oriented electrical steel sheet was manufactured by final annealing the cold-rolled steel sheet by heating it to 985°C at an average heating rate of 20°C / s under an atmosphere of 30% hydrogen and 70% nitrogen, maintaining it for 45 seconds, and then cooling it at an average cooling rate of 30°C / s.

[0101]

[0102] Slab Composition (wt%) CsiMnAlSNTiP 0.0018 3.48 0.42 0.85 0.0017 0.0015 0.0013 0.0059

[0103]

[0104] Examples 2 to 7 and Comparative Examples 1 to 24

[0105] Each non-oriented electrical steel sheet was manufactured in the same manner as in Example 1, except that the temperature and holding time during annealing of the hot-rolled sheet, and the roll speeds of the upper cold-rolling roll and the lower cold-rolling roll were changed as shown in Table 2 below.

[0106]

[0107] Hot-rolled plate annealing temperature (°C) Hot-rolled plate annealing holding time (s) Size of recrystallized grains after hot-rolled annealing (㎛) Roll speed of lower cold-rolling roll / Roll speed of upper cold-rolling roll Example 1 10 50 200 38 21.5 Example 2 10 50 200 38 21.7 Example 3 10 50 300 42 5 1.5 Example 4 10 50 300 42 5 1.6 Example 5 10 50 300 42 5 1.7 Example 6 10 75 500 48 0 1.5 Example 7 10 75 500 48 0 1.7 Comparative Example 1 9 75 45 18 0 1.0 Comparative Example 2 9 75 45 18 0 1.5 Comparative Example 3 9 75 45 18 0 2.0 Comparative Example 4 10 00 45 22 5 1.0 Comparative Example 51000452251.4 Comparative Example 61000452252.0 Comparative Example 71025603001.0 Comparative Example 81025603001.5 Comparative Example 91025603002.0 Comparative Example 101050603311.0 Comparative Example 111050603311.6 Comparative Example 121050603312.0 Comparative Example 1310502003821.0 Comparative Example 1410502003821.3 Comparative Example 1510502003821.8 Comparative Example 1610502003822.0 Comparative Example 1710503004251.0 Comparative Example 18 10503004251.4 Comparative Example 19 10503004251.8 Comparative Example 20 10755004801.0 Comparative Example 21 10755004801.3 Comparative Example 22 10755004801.9 Comparative Example 23 11001005301.0 Comparative Example 24 11001005301.6

[0108]

[0109] Evaluation Example 1. Evaluation of whether Equation 1 is satisfied

[0110] For the non-oriented electrical steel sheets prepared in each of the examples and comparative examples, the {001} of the texture in an area of ​​10 mm × 10 mm or larger was determined using electron backscatter diffraction (EBSD). <130> and {334}<4-83> measure the orientation, and through the Orientation Distribution Function (ODF), {001} <130> and {334}<4-83> The strength of the bearing was calculated, and the results are shown in Table 3 below.

[0111]

[0112] Evaluation Example 2. Iron Loss Evaluation

[0113] Table 3 below shows the iron loss (W) measured at azimuth angles of 0° and 90° with respect to the rolling direction, respectively. 10 / 400 The average value of ) and the iron loss (W) measured at azimuth angles of 0°, 30°, 45°, 60°, and 90° with respect to the rolling direction, respectively 10 / 400 The average value of ). For the iron loss, specimens were prepared by cutting the non-oriented electrical steel sheets manufactured in each of the Examples and Comparative Examples into widths of 60 mm × lengths of 60 mm. Then, using a Single Sheet Tester, the iron loss values ​​were measured twice each in the L direction parallel to the rolling direction, the C direction perpendicular to the rolling direction, and at 30°, 45°, and 60°. Subsequently, the average of all iron loss values ​​measured at 0° and 90°, and the average of all iron loss values ​​measured at 0°, 30°, 45°, 60°, and 90° were calculated. At this time, the iron loss W 10 / 400 represents the iron loss when a magnetic flux density of 1.0 T is induced at 400 Hz.

[0114]

[0115] Aspect ratio formula 1W 10 / 400{001} <130> {334}<4-83>{001} <130> / {334}<4-83>0°, 90° Average 0°, 30°, 45°, 60°, 90° Average Example 17.34.9 1.49 11.10 11.35 Example 27.55.11.47 10.90 11.40 Example 37.54.5 1.67 10.71 11.30 Example 47.84.4 1.77 10.65 11.05 Example 57.64.8 1.58 10.80 11.01 Example 67.64.7 1.62 10.90 11.23 Example 77.54.6 1.63 11.01 11.35 Comparative Example 15.16.80.75 13.21 13.90 Comparative Example 25.5 6.20.8 9 12.8 7 13.81 Comparative Example 35.7 6.30.9 13.32 13.88 Comparative Example 45.9 6.50.9 112.8 3 13.23 Comparative Example 56.4 6.11.05 12.6 13.15 Comparative Example 66.6 5.9 1.12 12.7 13.31 Comparative Example 75.8 6.10.9 12.5 13.05 Comparative Example 86.15.7 1.0 7 12.30 13.20 Comparative Example 96.2 5.5 1.1 3 12.5 9 13.10 Comparative Example 10 6.15.9 1.0 3 11.6 12.20 Comparative Example 116.35.51.15 11.48 12.11 Comparative Example 126.45.31.21 11.61 12.32 Comparative Example 136.96.21.11 11.80 12.41 Comparative Example 147.05.31.32 11.70 12.23 Comparative Example 157.15.41.31 11.45 12.10 Comparative Example 167.05.51.27 11.58 12.24 Comparative Example 176.45.41.19 11.16 12.11 Comparative Example 186.64.71.40 11.31 12.24 Comparative Example 197.15.21.37 11.20 11.94 Comparative Example 206.65.61.18 11.20 11.80 Comparative Example 216.95.31.30 11.35 11.74 Comparative Example 227.25.11.41 11.40 12.11 Comparative Example 237.94.31.84 11.31 12.10 Comparative Example 247.84.21.86 11.20 11.80

[0116]

[0117] As shown in Table 3 above, the non-oriented electrical steel sheets produced in each of Examples 1 to 7 satisfy the condition that the grain size of the hot-rolled annealed material is 350 μm or more and 500 μm or less, and as the ratio of the roll speed of the upper cold-rolling roll to the roll speed of the lower cold-rolling roll (roll speed of the lower cold-rolling roll / roll speed of the upper cold-rolling roll) during cold rolling is performed at 1.5 or more and 1.7 or less, the value calculated by Equation 1 satisfies 1.45 or more and 1.80 or less, and the iron loss (W) measured at azimuth angles of 0° and 90° with respect to the rolling direction, respectively 10 / 400 The average value of ) is 11.5 W / Kg or less, and the iron loss (W) measured at azimuth angles of 0°, 30°, 45°, 60°, and 90° with respect to the rolling direction, respectively 10 / 400 It was confirmed that the average value of ) was 11.5 W / Kg or less.

[0118] In contrast, for Comparative Examples 1 to 12, 23, and 24, since the grain size of the hot-rolled annealed material falls outside a specific range, the value calculated by Equation 1 did not correspond to the specific range, regardless of whether the ratio of the roll speed of the upper cold-rolling roll to the roll speed of the lower cold-rolling roll satisfied the specific range. Accordingly, for Comparative Examples 1 to 12, the iron loss (W) measured at azimuth angles of 0° and 90° with respect to the rolling direction, respectively 10 / 400 The average value of ) and the iron loss (W) measured at azimuth angles of 0°, 30°, 45°, 60°, and 90° with respect to the rolling direction, respectively 10 / 400 It was confirmed that the average value of ) also exceeded a specific range. In addition, Comparative Examples 23 and 24 showed iron loss (W) measured at azimuth angles of 0° and 90°, respectively, with respect to the rolling direction. 10 / 400 The average value of ) satisfies a specific range, but the iron loss (W) measured at azimuth angles of 0°, 30°, 45°, 60°, and 90° respectively with respect to the rolling direction 10 / 400 It was confirmed that the average value of ) also exceeded a specific range.

[0119] In addition, for Comparative Examples 13 to 22, although the grain size of the hot-rolled annealed material satisfies a specific range, the ratio of the roll speed of the upper cold-rolling roll to the roll speed of the lower cold-rolling roll does not satisfy a specific range; therefore, the value calculated by Equation 1 does not correspond to the specific range, and accordingly, the iron loss (W) measured at azimuth angles of 0° and 90° with respect to the rolling direction, respectively 10 / 400 The average value of ) and / or the iron loss (W) measured at azimuth angles of 0°, 30°, 45°, 60°, and 90° with respect to the rolling direction, respectively 10 / 400 It was confirmed that the average value of ) also exceeded a specific range.

Claims

1. Composed of, in wt%, C: greater than 0% and less than or equal to 0.0030%, Si: greater than 2.8% and less than or equal to 4.0%, Mn: greater than 0.1% and less than or equal to 0.5%, Al: greater than 0.3% and less than or equal to 0.9%, S: greater than 0% and less than or equal to 0.0030%, N: greater than 0% and less than or equal to 0.0015%, Ti: greater than 0% and less than or equal to 0.0030%, P: greater than 0% and less than or equal to 0.01%, and the remainder being Fe and other unavoidable impurities, and {001} represented by the following Equation 1 <130> Non-oriented electrical steel sheet having a ratio of the fraction of orientation to the fraction of {334}<4-83> orientation of 1.45 or more and 1.80 or less. [Equation 1] {001} <130> Fraction of directions / {334}<4-83> Fraction of directions 2. In Paragraph 1, Iron loss (W) measured at azimuth angles of 0° and 90° with respect to the rolling direction, respectively 10 / 400 Non-oriented electrical steel sheet having an average value of ) 11.5 W / Kg or less.

3. In Paragraph 1 or 2, Iron loss (W) measured at azimuth angles of 0°, 30°, 45°, 60°, and 90° with respect to the rolling direction, respectively 10 / 400 Non-oriented electrical steel sheet having an average value of ) 11.5 W / Kg or less.

4. A step of manufacturing a hot-rolled steel sheet by reheating and hot-rolling a slab comprising, in weight%, C: greater than 0% and less than or equal to 0.0030%, Si: greater than 2.8% and less than or equal to 4.0%, Mn: greater than 0.1% and less than or equal to 0.5%, Al: greater than 0.3% and less than or equal to 0.9%, S: greater than 0% and less than or equal to 0.0030%, N: greater than 0% and less than or equal to 0.0015%, Ti: greater than 0% and less than or equal to 0.0030%, P: greater than 0% and less than or equal to 0.01%, and the remainder being Fe and other unavoidable impurities; A step of manufacturing a hot-rolled annealed material by annealing the above hot-rolled steel plate; A step of manufacturing a cold-rolled steel sheet by cold-rolling the above hot-rolled annealed material; A method for manufacturing a non-oriented electrical steel sheet comprising the step of finally annealing the above cold-rolled steel sheet, The non-oriented electrical steel sheet manufactured through the above final annealing step is {001} represented by the following Formula 1 <130> A method for manufacturing non-oriented electrical steel sheets in which the ratio of the orientation fraction to the {334}<4-83> orientation fraction is 1.45 or more and 1.80 or less. [Equation 1] {001} <130> Fraction of directions / {334}<4-83> Fraction of directions 5. In Paragraph 4, A method for manufacturing a non-oriented electrical steel sheet, wherein the crystal grain size of the hot-rolled annealed material is 350 μm or more and 500 μm or less.

6. In Paragraph 4 or 5, The step of manufacturing the above hot-rolled steel sheet is a method for manufacturing a non-oriented electrical steel sheet in which the finishing rolling temperature during hot rolling is 860°C or higher and 900°C or lower.

7. In Paragraph 4 or 5, Prior to the step of manufacturing the above hot-rolled annealed material, the method further includes the step of winding the hot-rolled steel sheet, The above-mentioned winding step is a method for manufacturing a non-oriented electrical steel sheet, wherein the winding temperature is 660°C or higher and 710°C or lower.

8. In Paragraph 4 or 5, A method for manufacturing a non-oriented electrical steel sheet, wherein the thickness of the hot-rolled steel sheet is 1.8 mm or more and 2.6 mm or less.

9. In Paragraph 4 or 5, A method for manufacturing a non-oriented electrical steel sheet, wherein the step of manufacturing the above cold-rolled steel sheet is performed such that the ratio of the roll speed of the upper cold-rolling roll located above the steel sheet to the roll speed of the lower cold-rolling roll located below the steel sheet (roll speed of the lower cold-rolling roll / roll speed of the upper cold-rolling roll) is 1.5 or more and 1.7 or less.

10. In Paragraph 4 or 5, The step of manufacturing the above hot-rolled annealed material is a method for manufacturing a non-oriented electrical steel sheet, wherein the heat treatment temperature is 950°C or higher and 1100°C or lower.

11. In Paragraph 10, The step of manufacturing the above hot-rolled annealed material is a method for manufacturing a non-oriented electrical steel sheet in which the average heating rate to the heat treatment temperature is 15℃ / s or higher.

12. In Paragraph 4 or 5, A method for manufacturing a non-oriented electrical steel sheet, comprising the step of manufacturing the above-mentioned hot-rolled annealed material and heat treating for 200 seconds or more and 500 seconds or less.

13. In Paragraph 4 or 5, A method for manufacturing non-oriented electrical steel sheets, wherein the final annealing step is performed in a mixed atmosphere of hydrogen and nitrogen.

14. In Paragraph 4 or 5, The above final annealing step is a method for manufacturing a non-oriented electrical steel sheet, wherein the heat treatment temperature is 900°C or higher and 1100°C or lower.

15. In Paragraph 4 or 5, The above final annealing step is a method for manufacturing a non-oriented electrical steel sheet in which the average cooling rate after heat treatment is 30℃ / s or higher.