Non-oriented electrical steel sheet and manufacturing method therefor

Abstract

The present application relates to a non-oriented electrical steel sheet and a manufacturing method therefor. According to the non-oriented electrical steel sheet and the manufacturing method therefor of the present application, the non-oriented electrical steel sheet can have excellent magnetic properties, and specifically, can have low iron loss.

Description

Non-oriented electrical steel sheet and manufacturing method thereof

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

[0002] Currently, greenhouse gas emissions from various industries and daily lives are steadily increasing worldwide, and global efforts are underway to reduce this carbon footprint. Electric vehicles are gaining attention as a viable alternative to fossil fuel-powered, internal combustion engine vehicles, which emit significant greenhouse gases. Consequently, research into electric vehicles is actively underway.

[0003] Drive motors are the driving force behind electric vehicles and serve as a key component. Therefore, research into improving drive motor efficiency is crucial for achieving carbon neutrality. Non-oriented electrical steel sheets are used as the material for these drive motors, typically manufactured by punching and laminating cold-rolled steel sheets 0.65 mm or thinner.

[0004] These non-oriented electrical steel sheets form a BCC crystal structure and spin most rapidly when the magnetic domains are aligned at 0˚ and 90˚ with respect to the BCC crystal axis. This rapid spinning facilitates domain wall movement, resulting in excellent magnetic properties. However, forming crystals close to these angles is extremely difficult, requiring a reduction in sheet thickness, an increase in Si content, and meticulous control of impurity elements to address these challenges. Therefore, a non-oriented electrical steel sheet and its manufacturing method are in demand to address these challenges.

[0005] The object of the present application is to provide a non-oriented electrical steel sheet having excellent magnetic properties and a method for manufacturing the same.

[0006] In order to solve the above problem, the non-oriented electrical steel sheet of the present application includes Si: 0.6 wt% or more and 1.6 wt% or less, Al: 0.1 wt% or more and 0.5 wt% or less, and Mn: 0.2 wt% or more and 0.4 wt% or less, and includes at least one of C: 0 ppm to 30 ppm or less, S: 0 ppm to 30 ppm or less, N: 0 ppm to 30 ppm or less, Ti: 0 ppm to 30 ppm or less, and P: 0 ppm to 1000 ppm or less, and includes at least one of Y: 0 ppm to 30 ppm or less and Ho: 0 ppm to 30 ppm or less, and includes the remainder of Fe and other inevitable impurities, and has an average (M) of the magnetic domain spin alignment value (M) calculated by the following general formula 1. AVG ) is less than or equal to 1.22.

[0007] [General Formula 1]

[0008] M = (sin 2 αsin 2 β)+(sin 2 βsin 2 γ)+(sin 2 γsin 2 α)

[0009] In the above general formula 1, α, β, and γ are obtained from crystal orientations measured under the condition of a step size of 10 ㎛ for a specimen of 20 mm in width and 20 mm in length manufactured from a non-oriented electrical steel sheet by EBSD, and when the x-axis, y-axis, and z-axis defined in the three-dimensional crystal coordinate system are used as the standard, α is the angle between the x-axis and the crystal grain orientation, β is the angle between the y-axis and the crystal grain orientation, and γ is the angle between the z-axis and the crystal grain orientation.

[0010] The above non-oriented electrical steel sheet may include Y: more than 0 ppm and less than 30 ppm and Ho: more than 0 ppm and less than 30 ppm.

[0011] In addition, the non-oriented electrical steel sheet may include C: more than 0 ppm and less than 30 ppm, S: more than 0 ppm and less than 30 ppm, N: more than 0 ppm and less than 30 ppm, Ti: more than 0 ppm and less than 30 ppm, and P: more than 0 ppm and less than 1000 ppm.

[0012] Additionally, the non-oriented electrical steel sheet may have a thickness of more than 0.3 mm and less than or equal to 0.6 mm.

[0013] In addition, the method for manufacturing a non-oriented electrical steel sheet of the present application comprises the steps of: reheating and then hot-rolling a slab containing Si: 0.6 wt% or more and 1.6 wt% or less, Al: 0.1 wt% or more and 0.5 wt% or less, and Mn: 0.2 wt% or more and 0.4 wt% or less, and at least one of C: 0 ppm to 30 ppm or less, S: 0 ppm to 30 ppm or less, N: 0 ppm to 30 ppm or less, Ti: 0 ppm to 30 ppm or less, and P: 0 ppm to 1000 ppm or less, and at least one of Y: 0 ppm to 30 ppm or less and Ho: 0 ppm to 30 ppm or less, and the remainder including Fe and other inevitable impurities; pre-annealing the hot-rolled hot-rolled steel sheet; cold-rolling the pre-annealed hot-rolled steel sheet to manufacture a cold-rolled steel sheet; And a method for manufacturing a non-oriented electrical steel sheet including a step of final annealing the cold rolled steel sheet, wherein the non-oriented electrical steel sheet has an average (M) of the magnetic domain spin alignment value (M) calculated by the following general formula 1 AVG ) is less than or equal to 1.22.

[0014] [General Formula 1]

[0015] M = (sin 2 αsin 2 β)+(sin 2 βsin 2 γ)+(sin 2 γsin 2 α)

[0016] In the above general formula 1, α, β, and γ are obtained from crystal orientations measured under the condition of a step size of 10 ㎛ for a specimen of 20 mm in width and 20 mm in length manufactured from a non-oriented electrical steel sheet by EBSD, and when the x-axis, y-axis, and z-axis defined in the three-dimensional crystal coordinate system are used as the standard, α is the angle between the x-axis and the crystal grain orientation, β is the angle between the y-axis and the crystal grain orientation, and γ is the angle between the z-axis and the crystal grain orientation.

[0017] Additionally, the slab may contain Y: more than 0 ppm and less than or equal to 30 ppm and Ho: more than 0 ppm and less than or equal to 30 ppm.

[0018] Additionally, the slab may contain C: more than 0 ppm and less than or equal to 30 ppm, S: more than 0 ppm and less than or equal to 30 ppm, N: more than 0 ppm and less than or equal to 30 ppm, Ti: more than 0 ppm and less than or equal to 30 ppm, and P: more than 0 ppm and less than or equal to 1000 ppm.

[0019] In addition, the above preliminary annealing step can be performed by heat treating the hot-rolled hot-rolled steel sheet at 950°C or higher and 1100°C or lower for 30 seconds or higher and 150 seconds or lower.

[0020] According to the non-oriented electrical steel sheet of the present application and the method for manufacturing the same, it can have excellent magnetic properties, and specifically, it can have low iron loss.

[0021] The present application relates to a non-oriented electrical steel sheet, which is a core material used in a motor that converts electrical energy into mechanical energy. The non-oriented electrical steel sheet comprises Si: 0.6 wt% or more and 1.6 wt% or less, Al: 0.1 wt% or more and 0.5 wt% or less, and Mn: 0.2 wt% or more and 0.4 wt% or less, and includes at least one of C: 0 ppm to 30 ppm or less, S: 0 ppm to 30 ppm or less, N: 0 ppm to 30 ppm or less, Ti: 0 ppm to 30 ppm or less, and P: 0 ppm to 1000 ppm or less, and includes at least one of Y: 0 ppm to 30 ppm or less and Ho: 0 ppm to 30 ppm or less, and includes the remainder of Fe and other inevitable impurities, and has an average (M) of a magnetic domain spin alignment value (M) calculated by the following general formula 1 AVG ) is less than or equal to 1.22.

[0022] [General Formula 1]

[0023] M = (sin 2 αsin 2 β)+(sin 2 βsin 2 γ)+(sin 2 γsin 2 α)

[0024] In the above general formula 1, α, β, and γ are obtained from crystal orientations measured under the condition of a step size of 10 ㎛ for a specimen of 20 mm in width and 20 mm in length manufactured from a non-oriented electrical steel sheet by EBSD, and when the x-axis, y-axis, and z-axis defined in the three-dimensional crystal coordinate system are used as the standard, α is the angle between the x-axis and the crystal grain orientation, β is the angle between the y-axis and the crystal grain orientation, and γ is the angle between the z-axis and the crystal grain orientation.

[0025] Specifically, the non-oriented electrical steel sheet has an average (M) of the magnetic domain spin alignment value (M AVG) may be 1.22 or less or 1.219 or less. At this time, the non-oriented electrical steel sheet has an average (M) of the magnetic domain spin alignment value (M AVG ) may be 1.0 or more, 1.05 or more, 1.1 or more, or 1.15 or more. The non-oriented electrical steel sheet may have an average (M) of the magnetic domain spin alignment value (M AVG ) has the above-mentioned range, it can have excellent magnetic properties, and specifically, it can have low iron loss. At this time, M AVG means the average of the magnetic domain spin alignment values ​​(M) measured from the crystal orientations of all crystals under the conditions described above.

[0026] The components of the above non-oriented electrical steel sheet are described below.

[0027] Si: 0.6 wt% or more and 1.6 wt% or less

[0028] Silicon (Si) is an element that increases the resistivity of non-oriented electrical steel sheets and reduces core 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, it may be difficult to obtain the low core loss characteristics required for the non-oriented electrical steel sheet. In addition, if the silicon is included in the non-oriented electrical steel sheet in an amount greater than the upper limit of the aforementioned range, the permeability and magnetic flux density may decrease, and the strength and brittleness of the steel sheet may increase, which may cause problems such as an increase in the difficulty of the production process. Therefore, the silicon may be included in the non-oriented electrical steel sheet in an amount of 0.6 wt% or more and 1.6 wt% or less, and specifically, may be included in an amount of 0.63 wt% or more and 1.6 wt% or less.

[0029] Mn: 0.2 wt% or more and 0.4 wt% or less

[0030] Manganese (Mn) is an element that, together with Si, increases resistivity, lowers iron loss, and improves grain structure. When 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. In addition, when the manganese is included in the non-oriented electrical steel sheet in an amount greater than the upper limit of the aforementioned range, coarse MnS may precipitate, increasing iron loss and deteriorating magnetic properties such that magnetic flux density decreases. Therefore, the manganese may be included in the non-oriented electrical steel sheet in an amount of 0.2 wt% or more and 0.4 wt% or less, and specifically, may be included in an amount of 0.2 wt% or more and 0.39 wt% or less.

[0031] Al: 0.1 wt% or more and 0.5 wt% or less

[0032] Aluminum (Al) is an element that increases resistivity together with Si, thereby lowering iron loss, and induces precipitation of AlN when combined with nitrogen (N). If the aluminum is included in the non-oriented electrical steel sheet in an amount less than the lower limit of the aforementioned range, iron loss may increase due to insufficient resistivity. In addition, if the aluminum is included in the non-oriented electrical steel sheet in an amount exceeding the upper limit of the aforementioned range, cold rolling properties may be reduced, and magnetic flux density may decrease, thereby deteriorating magnetic properties. Therefore, the aluminum 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, and specifically, may be included in an amount of 0.1 wt% or more and 0.49 wt% or less.

[0033] C: 0 ppm or more and 30 ppm or less

[0034] 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 can cause magnetic aging, which can adversely affect magnetic properties. Therefore, the carbon may be included in the non-oriented electrical steel sheet in an amount exceeding 0 ppm and not exceeding 30 ppm.

[0035] S: 0 ppm or more and 30 ppm or less

[0036] Sulfur (S) is an element that forms sulfides such as MnS and / or CuS by combining with other unavoidable impurities. If it is included in an amount exceeding the upper limit of the aforementioned range, it may increase iron loss and inhibit grain growth. Therefore, the sulfur may be included in the non-oriented electrical steel sheet in an amount exceeding 0 ppm and not exceeding 30 ppm.

[0037] N: 0 ppm or more and 30 ppm or less

[0038] Nitrogen (N) is an element that forms nitrides such as AlN, TiN, and / or NbN by combining with other unavoidable impurities. If it is included in an amount exceeding the upper limit of the aforementioned range, it may increase iron loss and inhibit grain growth. Therefore, the nitrogen may be included in the non-oriented electrical steel sheet in an amount of more than 0 ppm and less than 30 ppm.

[0039] Ti: 0 ppm or more and 30 ppm or less

[0040] Titanium (Ti) is an element that forms fine carbides and / or nitrides, such as TiC and / or TiN, by combining with other unavoidable impurities. If it is included in excess of the upper limit of the aforementioned range, it may inhibit grain growth and deteriorate magnetic properties. Therefore, the titanium may be included in the non-oriented electrical steel sheet in an amount of more than 0 ppm and less than 30 ppm.

[0041] P: 0 ppm or more and 1000 ppm or less

[0042] Phosphorus (P) is an element that develops grain structure as a grain boundary segregation element. If the phosphorus is included in the non-oriented electrical steel sheet in an amount exceeding the upper limit of the aforementioned range, grain growth may be inhibited due to the segregation effect, magnetic properties may deteriorate, and cold-rollability may be reduced. Therefore, the phosphorus may be included in the non-oriented electrical steel sheet in an amount exceeding 0 ppm and not exceeding 1000 ppm.

[0043] Y: 0 ppm or more and 30 ppm or less

[0044] Yttrium (Y) is an element that combines with Ho to improve magnetic properties and reduce iron loss. If the yttrium is included in the non-oriented electrical steel sheet in an amount exceeding the upper limit of the aforementioned range, it may form coarse precipitates such as Y2O3, YS, and / or Y2S3, thereby increasing iron loss and deteriorating magnetic properties. Therefore, the yttrium may be included in the non-oriented electrical steel sheet in an amount exceeding 0 ppm and not exceeding 30 ppm.

[0045] Ho: 0 ppm or more and 30 ppm or less

[0046] Holmium (Ho) is an element that combines with Y to provide high permeability and excellent magnetic properties, i.e., reduce iron loss. If the yttrium is included in the non-oriented electrical steel sheet in an amount exceeding the upper limit of the aforementioned range, excessive precipitates may be formed, increasing iron loss and deteriorating magnetic properties. Therefore, the holmium may be included in the non-oriented electrical steel sheet in an amount exceeding 0 ppm and not exceeding 30 ppm.

[0047] The remaining Fe and other unavoidable impurities

[0048] The above-mentioned inevitable impurities are impurities mixed in during the steelmaking and manufacturing processes of non-oriented electrical steel sheets, and since this is widely known in the art, a detailed description thereof will be omitted. In addition to the components of the non-oriented electrical steel sheet described above in one embodiment of the present application, the addition of elements is not excluded, and various elements may be included within a scope that does not impair the technical spirit of the present application. When additional elements are included, they may be included to replace the remaining iron (Fe).

[0049] For example, the above-mentioned inevitable impurities may be zirconium (Zr) and / or niobium (Nb), and the non-oriented electrical steel sheet may include Zr: 0.0020 wt% or less and / or Nb: 0.0020 wt% or less.

[0050] In one example, the non-oriented electrical steel sheet may include both the Y and the Ho, for example, Y: more than 0 ppm and less than 30 ppm and Ho: more than 0 ppm and less than 30 ppm. Specifically, the non-oriented electrical steel sheet may include Y: 3 ppm or more and 30 ppm or less or 6 ppm or more and 29 ppm or less, and Ho: 3 ppm or more and 29 ppm or less or 6 ppm or more and 29 ppm or less. Since a specific description of the Y and the Ho is the same as described above, it will be omitted.

[0051] In another example, the non-oriented electrical steel sheet may include all of the C, the S, the N, the Ti, and the P, for example, C: more than 0 ppm and less than or equal to 20 ppm, S: more than 0 ppm and less than or equal to 20 ppm, N: more than 0 ppm and less than or equal to 20 ppm, Ti: more than 0 ppm and less than or equal to 20 ppm, and P: more than 0 ppm and less than or equal to 150 ppm. Specifically, the non-oriented electrical steel sheet may include C: 3 ppm or more and 30 ppm or less or 6 ppm or more and 29 ppm or less, S: 3 ppm or more and 30 ppm or less or 6 ppm or more and 29 ppm or less, N: 3 ppm or more and 29 ppm or less or 5 ppm or more and 28 ppm or less, Ti: 3 ppm or more and 30 ppm or less or 6 ppm or more and 30 ppm or less, and P: 30 ppm or more and 970 ppm or less or 60 ppm or more and 940 ppm or less. Since the specific descriptions of the C, S, N, Ti, and P are the same as those described above, they will be omitted.

[0052] In one example, the non-oriented electrical steel sheet may have a thickness of greater than 0.3 mm and less than or equal to 0.6 mm, specifically, greater than or equal to 0.35 mm and less than or equal to 0.58 mm, greater than or equal to 0.40 mm and less than or equal to 0.56 mm, or greater than or equal to 0.45 mm and less than or equal to 0.54 mm. Since the non-oriented electrical steel sheet has a thickness within the aforementioned range, eddy current loss is reduced, thereby allowing it to have excellent core loss.

[0053] For example, the above non-oriented electrical steel sheet has a core loss W 15 / 50 This may be 6.1 W / kg or less, and specifically, may be 6.09 W / kg or less. The non-oriented electrical steel sheet has a core loss W 15 / 50The lower limit is not particularly limited in terms of the magnetic properties being better the lower the value, but it can be, for example, 1 W / kg or more. The iron loss W 15 / 50 It refers to the iron loss when a magnetic flux density of 1.5 T is induced at a low frequency of 50 Hz. At this time, the iron loss was measured according to the IEC 60404 2 standard.

[0054] In addition, the non-oriented electrical steel sheet may have an average grain size of 50 ㎛ or more and 150 ㎛ or less, and the processed structure formed during cold rolling may be entirely, that is, 99% or more, recrystallized during the final annealing process. The non-oriented electrical steel sheet may have excellent magnetic properties, specifically, low core loss, because the average grain size satisfies the above-mentioned range. In contrast, if the average grain size of the non-oriented electrical steel sheet is less than the lower limit of the above-mentioned range, hysteresis loss may increase due to the fine grain size, and further, if it exceeds the upper limit of the above-mentioned range, eddy current loss may increase, which may increase core loss.

[0055] In one example, the non-oriented electrical steel sheet may further include a coating layer on the surface. 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 thereof will be omitted. For example, the coating layer may be formed by applying a chromium-free coating solution, i.e., an organic-inorganic composite coating solution that does not contain chromium, to the surface of a final annealed steel sheet and then baking it. At this time, the coating layer may be formed to a thickness of 0.2 ㎛ to 5 ㎛. The non-oriented electrical steel sheet further includes a coating layer formed on the surface, thereby maintaining insulation between upper and lower non-oriented electrical steel sheets when a plurality of non-oriented electrical steel sheets are stacked, thereby reducing eddy current loss.

[0056] The present application also relates to a method for manufacturing a non-oriented electrical steel sheet. The method for manufacturing the non-oriented electrical steel sheet relates to the method for manufacturing the non-oriented electrical steel sheet described above. Since the specific details of the non-oriented electrical steel sheet described below are equally applicable to the non-oriented electrical steel sheet described above, they will be omitted.

[0057] The method for manufacturing a non-oriented electrical steel sheet of the present application includes a hot rolling step, a preliminary annealing step, a cold rolled steel sheet manufacturing step, and a final annealing step, and the manufactured non-oriented electrical steel sheet has an average (M) of the magnetic domain spin alignment value (M) calculated by the general formula 1 described above. AVG ) is 1.22 or less. According to the manufacturing method of the non-oriented electrical steel sheet of the present application, the average (M) of the magnetic domain spin alignment value (M) calculated by the general formula 1 described above AVG ) By satisfying the aforementioned range, the manufactured non-oriented electrical steel sheet can have excellent magnetic properties, specifically, low iron loss.

[0058] The above hot rolling step 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 composition of the slab is the same as that of the non-oriented electrical steel sheet, so all the contents described in the non-oriented electrical steel sheet are equally applied, and therefore, it is omitted. The reheating temperature of the slab is not particularly limited, but may be, for example, 1000°C or more and 1250°C or less, and specifically, 1100°C or more and 1150°C or less. If the reheating temperature of the slab is less than the lower limit of the above-mentioned range, the rolling load increases during hot rolling, and if it exceeds the upper limit of the above-mentioned range, precipitates such as C, S, N, Y and / or Ho in the slab are re-dissolved, and fine precipitates are generated in the subsequent process, which may inhibit grain growth and adversely affect magnetic properties.

[0059] In addition, the finishing rolling temperature during the hot rolling may be 860°C or more and 900°C or less, and specifically, 880°C or more and 900°C or less. In addition, the hot-rolled steel sheet obtained through the hot rolling may be coiled at 550°C or more and 650°C or less. The thickness of the hot-rolled steel sheet may be 1.8 mm or more and 2.6 mm or less. If the thickness of the hot-rolled steel sheet exceeds the upper limit of the above-mentioned range, the reduction ratio may increase during cold rolling, which may result in a deteriorated texture. Therefore, the thickness of the hot-rolled steel sheet may be controlled within the above-mentioned range.

[0060] The above preliminary annealing step is a step for increasing the orientation favorable to the magnetic properties, and can be performed by heat treating the hot-rolled hot-rolled steel sheet. Specifically, the preliminary annealing step can be performed by heating to 950°C or more and 1100°C or less at a heating rate of 20°C / s or more in a nitrogen atmosphere, maintaining the temperature range for 30 seconds or more and 150 seconds or less, and then cooling at a cooling rate of 30°C or more. At this time, the preliminary annealing can be performed by uncoiling the coiled hot-rolled steel sheet. If the annealing temperature of the hot-rolled steel sheet exceeds the upper limit of the above-mentioned range during the preliminary annealing, the grains may grow excessively, resulting in a severe grain size deviation and a large amount of oxidation, which may adversely affect the magnetic properties of the final product. In addition, if the annealing temperature of the hot-rolled steel sheet during preliminary annealing is below the lower limit of the aforementioned range, grain growth may not be sufficient, resulting in the formation of fine grains, which may adversely affect the magnetic properties of the final product. In addition, if the holding time of the hot-rolled steel sheet during annealing is below the lower limit of the aforementioned range, uneven grain growth may occur, which may adversely affect the magnetic properties of the final product. Thereafter, the annealed hot-rolled steel sheet may be cooled at a cooling rate of 30°C / s or more. Thereafter, the annealed hot-rolled steel sheet may be further pickled using a pickling solution to remove an oxide layer formed on the surface.

[0061] The step of manufacturing the above cold-rolled steel sheet is a step for manufacturing the hot-rolled steel sheet into a cold-rolled steel sheet, and is performed through cold rolling. The reduction ratio during the cold rolling may be 60% or more and 90% or less. The thickness of the cold-rolled steel sheet may be greater than 0.3 mm and less than 0.60 mm.

[0062] The final annealing step is a step for securing magnetic properties by growing crystal grains to a specific size, and is performed by heat treating the cold-rolled cold-rolled steel sheet. For example, the final annealing may be performed by heat treating the cold-rolled cold-rolled steel sheet at 800°C to 1150°C for 20 to 150 seconds. Specifically, the final annealing may be performed by heating the cold-rolled cold-rolled steel sheet to 800°C to 1150°C or 850°C to 1050°C at a heating rate of 10°C / s or more and heat treating it at this temperature range for 20 to 150 seconds or 30 to 120 seconds. Thereafter, the final annealed steel sheet may be cooled at a cooling rate of 30°C / s or more. The final annealing step is performed at the heating rate, temperature, time, and cooling rate within the aforementioned ranges, thereby reducing iron loss and deriving an optimal grain size considering mechanical properties. In contrast, if the heating rate, temperature, and time of the final annealing step are below the lower limit of the aforementioned range, the grain size may become fine, which may increase hysteresis loss. In addition, if the heating rate, temperature, and time of the final annealing step exceed the upper limit of the aforementioned range, the grain size may become coarse, which may increase eddy current loss.

[0063] At this time, the final annealing step may be performed under mixed atmosphere conditions to prevent surface oxidation and nitriding. Specifically, the final annealing step may be performed in an atmosphere of 1% to 30% hydrogen and 70% to 99% nitrogen, specifically, 1% to 40% hydrogen and 60% to 99% nitrogen. The method for manufacturing the non-oriented electrical steel sheet can further smoothen the surface condition of the manufactured non-oriented electrical steel sheet by performing the final annealing step under an atmosphere within the aforementioned range.

[0064] The above non-oriented electrical steel sheet may have an average grain size formed on the surface during the final annealing process of 40 ㎛ or more and 100 ㎛ or less, and all of the processed structure formed during the previous cold rolling process, that is, 99% or more, may be recrystallized. If the average grain size of the above non-oriented electrical steel sheet during the final annealing process is less than the lower limit of the above-mentioned range, hysteresis loss may increase due to the fine grain size, and if it exceeds the upper limit of the above-mentioned range, eddy current loss may increase, which may increase iron loss.

[0065] In another example, the method for manufacturing the non-oriented electrical steel sheet may further include a step of forming a coating layer. The step of forming the coating layer may be performed on the surface of the final annealed steel sheet, and specifically, may be performed on the surface of the steel sheet that has undergone heat treatment during the final annealing. A detailed description of the coating layer is the same as that described for the non-oriented electrical steel sheet, and therefore will be omitted.

[0066]

[0067] Hereinafter, the present application will be described in more detail through examples 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 examples presented below.

[0068]

[0069] Example 1

[0070] Manufacturing of non-oriented electrical steel sheets

[0071] A slab was manufactured by steelmaking and continuous casting using the components shown in Table 1 below, the remaining Fe, and other unavoidable impurities, and after reheating at a temperature of 1150°C, hot rolling was performed at a finishing temperature of 890°C to manufacture a hot-rolled steel plate having a thickness of 2.0 mm.

[0072] Afterwards, the hot-rolled steel sheet was coiled at a coiling temperature of 600°C.

[0073] Afterwards, the hot-rolled steel sheet was annealed by heating it to 1000°C at a heating rate of 20°C / s in an atmosphere of 100% nitrogen, maintaining it at this temperature for 100 seconds, and then cooling it at a cooling rate of 30°C / s.

[0074] Afterwards, the annealed hot-rolled steel plate was cold-rolled at a reduction ratio of 75% to manufacture a cold-rolled steel plate with a thickness of 0.5 mm.

[0075] Thereafter, the cold-rolled steel sheet was heated to 850°C at a heating rate of 20°C / s in an atmosphere of 10% hydrogen and 90% nitrogen, maintained at this temperature for 60 seconds, and then cooled at a cooling rate of 30°C / s to perform final annealing, thereby manufacturing a non-oriented electrical steel sheet.

[0076]

[0077] Examples 2 to 20 and Comparative Examples 1 to 54

[0078] Manufacturing of non-oriented electrical steel sheets

[0079] Each non-oriented electrical steel sheet was manufactured in the same manner as Example 1, except that the composition of the slab was changed to the components shown in Table 1 below, the remaining Fe, and other unavoidable impurities, the pre-annealing conditions were changed to the conditions shown in Table 2 below, and the steel sheet was finally annealed by reducing at each reduction ratio during cold rolling to have the thickness shown in Table 1 below.

[0080] Thickness (mm) Slab Composition Weight % ppm SiAl Mn C S NT i P Y Ho Example 10.48 0.93 0.100.37 229 14 16 7 9 32 222 Example 20.49 0.65 0.24 0.39 6 12 17 1 1 6 6 4 298 Example 30.48 0.78 0.20 0.31 1 3 6 11 1 8 7 9 17 1 2 Example 40.5 0 1.07 0.12 0.29 28 20 7 8 8 07 1 5 1 9 Example 50.48 0.63 0.34 0.35 14 1 1 5 16 1 4 2 7 26 Example 60.5 10.91 0.13 0.36 28 9 23 7 5 9 4 20 20 Example 70.491.090.410.3411277164502721 Example 80.510.710.290.2314229233901314 Example 90.500.840.350.29720277782020 Example 100.470.690.400.23762120805136 Example 110.530.790.340.32828867742024 Example 120.520.640.390.30159111416496 Example 130.500.810.290.23202211221711625 Example 140.500.750.220.2591076329296Example 150.490.980.390.281813727815925Example 160.520.630.160.39272815116062124Example 170.530.690.490.2720192865151515Example 180.541.070.290.2924157142401724Example 190.490.970.180.2725271973701211Example 200.500.940.190.3720292079361617Comparative Example 10.520.520.400.23261227117601412Comparative Example 20.490.540.530.328930285632910Comparative Example 30.490.580.510.37321212144841012Comparative Example 40.530.560.540.33151328142673519Comparative Example 50.510.550.090.23173139262971722Comparative Example 60.480.560.280.1820251627999824Comparative example 70.500.570.080.2352528158663224Comparative example 80.500.570.210.35132418118403431Comparative Example 90.540.580.090.392072623653190Comparative Example 100.480.570.080.211314629558019Comparative Example 110.490.590.220.3735246226953014Comparative Example 120.540.560.110.25332532391432829Comparative Example 130.470.590.210.36152938292751435Comparative Example 140.490.570.320.291092826648329Comparative Example 150.520.580.320.30213433132201717Comparative Example 160.530.540.200.13102518512201127Comparative Example 170.510.580.210.3626916322002139Comparative Example 180.510.530.150.4536292811712828Comparative Example 190.500.510.250.47242637151283159Comparative Example 200.500.590.470.25185122020008Comparative Example 210.490.790.070.3891679887237Comparative Example 220.471.410.080.2817263222396012Comparative Example 230.491.020.040.347342922833036Comparative Example 240.511.350.080.291587835100Comparative Example 250.471.490.070.331922722205180Comparative Example 260.510.870.060.26561216441027Comparative Example 270.470.890.200.1414815104442828Comparative Example 280.541.170.190.17252336267722625Comparative example 290.460.770.120.1333391921295517Comparative example 300.471.090.290.18131027232713417Comparative example 310.490.780.120.28373222163651428Comparative example 320.481.040.400.3738911123553216Comparative example 330.481.510.370.35369281491307Comparative example 340.481.490.190.22361192094200Comparative example 350.491.210.190.23113922139981624Comparative example 360.481.530.350.20133110929200Comparative Example 370.480.760.130.2529353964822711Comparative Example 380.521.240.240.20283473311751027Comparative Example 390.471.110.310.3863138171201828Comparative Example 400.481.240.200.30104010182833238Comparative Example 410.461.320.160.2613233415872018Comparative Example 420.510.920.120.2024103132228138Comparative Example 430.491.520.260.35221635136903836Comparative Example 440.460.910.330.29810331342700Comparative Example 450.460.800.260.22131011363461116Comparative Example 460.531.370.230.361512133211251627Comparative Example 470.530.700.150.3211209346161731Comparative Example 480.541.520.250.3872610314203539Comparative Example 490.481.110.180.246152596283213Comparative example 500.501.300.170.30171021222593131Comparative example 510.460.680.160.2829109302282236Comparative example 520.471.390.420.312723118233025Comparative example 530.480.810.230.292462430835230Comparative example 540.481.230.460.232314242593500.

[0081]

[0082] Preliminary Annealing ConditionsMaintenance Temperature (℃)Maintenance Time (sec)Example 1100090Example 2100090Example 3100090Example 4100090Example 5100090Example 6100090Example 7100090Example 8100090Example 9100090Example 10100090Example 11100090Example 12100090Example 13100090Example 14100090Example 15100090Example 16100090Example 17100090Example 18100090Example 19100090Example 20100090Comparison Example 1100090Comparison Example 2100090Comparison Example 3100090Comparison Example 4100090Comparison Example 5100090Comparison Example 6100090Comparison Example 7100090Comparison Example 8100090Comparison Example 9100090Comparison Example 10100090Comparison Example 11100090Comparison Example 12100090Comparison Example 13100090Comparison Example 14100090Comparison Example 15100090Comparison Example 16100090Comparison Example 17100090Comparison Example 18100090Comparison Example 19100090Comparison Example 20100090Comparison Example 21100090Comparison Example 22100090Comparison Example 23100090Comparison Example 24100090Comparison Example 25100090Comparison Example 26100090Comparison Example 27100090Comparison Example 28100090Comparison Example 29100090Comparison Example 30100090Comparison Example 31100090Comparison Example 32100090Comparison Example 33100090Comparison Example 34100090Comparison Example 35100090Comparison Example 36100090Comparison Example 37100090Comparison Example 38100090Comparison Example 39100090Comparison Example 40100090Comparison Example 41100090Comparison Example 42100090Comparison Example 43100090Comparison Example 44100090Comparison Example 45100090Comparison Example 46100090Comparison Example 47100090Comparison Example 48100090Comparison Example 49100090Comparison Example 50100090Comparison Example 51100090Comparison Example 52100090Comparison Example 5390090Comparison Example 54120090

[0083]

[0084] Evaluation Example 1. Average of the magnetic domain spin alignment values ​​(M AVG ) evaluation

[0085] After manufacturing a specimen with an area of ​​20 ㎛ × 20 ㎛ from the non-oriented electrical steel sheet manufactured in each of the examples and comparative examples, a ctf file capable of extracting the crystal orientation of all crystals under the condition of a step size of 2 ㎛ through electron backscatter diffraction (EBSD) for each specimen can be obtained, and by converting the obtained crystal orientation into an ang file through OIM software, each α, β, and γ can be obtained, and each α, β, and γ is substituted into the following general formula 1 to calculate the magnetic domain spin matching value (M), and then their average (M AVG ) was obtained, and the results are shown in Table 3 below.

[0086] [General Formula 1]

[0087] M = (sin 2 αsin 2 β)+(sin 2 βsin 2 γ)+(sin 2 γsin 2 α)

[0088] In the above general formula 1, α, β, and γ are obtained from crystal orientations measured under the condition of a step size of 10 ㎛ for a specimen of 20 mm in width and 20 mm in length manufactured from a non-oriented electrical steel sheet by EBSD, and when the x-axis, y-axis, and z-axis defined in the three-dimensional crystal coordinate system are used as the standard, α is the angle between the x-axis and the crystal grain orientation, β is the angle between the y-axis and the crystal grain orientation, and γ is the angle between the z-axis and the crystal grain orientation.

[0089]

[0090] Evaluation Example 2. Iron Loss Evaluation

[0091] In each of the examples and comparative examples, a chromium-free coating solution was applied to the surface of the non-oriented electrical steel sheet manufactured, heated to 300°C, and then slowly cooled and dried to form a coating layer. Then, the iron loss W was measured according to the method described in IEC 60404 2 for the non-oriented electrical steel sheet on which the coating layer was formed on the surface. 15 / 50 was measured, and the results are shown in Table 3 below. At this time, W 15 / 50 It refers to the iron loss when a magnetic flux density of 1.5 T is induced at a low frequency of 50 Hz.

[0092] M AVG W 15 / 50Example 11.2066.02 Example 21.2065.98 Example 31.1885.84 Example 41.1835.69 Example 51.2146.09 Example 61.1945.87 Example 71.2195.55 Example 81.1965.96 Example 91.2155.99 Example 101.1925.81 Example 111.1995.84 Example 121.1885.93 Example 131.2035.99 Example 141.2015.93 Example 151.1965.83 Example 161.1815.90 Example 171.2045.97 Example 181.1815.53 Example 191.1995.97 Example 201.2085.89 Comparative Example 11.2546.37 Comparative Example 21.2436.32 Comparative Example 31.2376.29 Comparative Example 41.2446.32 Comparative Example 51.2486.34 Comparative Example 61.2316.25 Comparative Example 71.2486.34 Comparative Example 81.2476.33 Comparative Example 91.2496.34 Comparative Example 101.2356.27 Comparative Example 111.2526.36 Comparative Example 121.2336.26 Comparative Example 131.2326.26 Comparative Example 141.2476.33Comparative example 151.2566.38Comparative example 161.2536.36Comparative example 171.2546.37Comparative example 181.2326.26Comparative example 191.2556.38Comparative example 201.2446.32Comparative example 211.2316.26Comparative example 221.2386.29Comparative example 231.2316.25Comparative example 241.2316.26Comparative example 251.2356.27Comparative example 261.2326.26Comparative example 271.2336.27Comparative example 281.2596.40Comparative example 291.2586.39Comparative example 301.2416.31 Comparative example 311.2596.39 Comparative example 321.2436.32 Comparative example 331.2416.31 Comparative example 341.2566.38 Comparative example 351.2536.37 Comparative example 361.2486.34 Comparative example 371.2406.30 Comparative example 381.2336.26 Comparative example 391.2396.29 Comparative example 401.2366.28 Comparative example 411.2486.34 Comparative example 421.2586.39 Comparative example 431.2466.33 Comparative example 441.2496.34 Comparative example 451.2366.28 Comparative example 461.2466.33Comparative example 471.2356.28Comparative example 481.2546.37Comparative example 491.2466.33Comparative example 501.2346.27Comparative example 511.2466.33Comparative example 521.2386.29Comparative example 531.2456.32Comparative example 541.2306.25.

[0093] As shown in Table 2 and Table 3 above, the non-oriented electrical steel sheets manufactured in each of Examples 1 to 20 are manufactured under specific pre-annealing conditions, and the component ratio of the non-oriented electrical steel sheets (slabs) satisfies a specific range, so that M AVG It was confirmed that the non-oriented electrical steel sheets manufactured in each of Comparative Examples 1 to 52 satisfy specific pre-annealing conditions, but the composition ratio of the non-oriented electrical steel sheets (slabs) does not satisfy a specific range, so M AVG It was confirmed that it does not satisfy a specific range and thus has a high iron loss.

[0094] Meanwhile, the non-oriented electrical steel sheets manufactured in Comparative Examples 53 and 54 did not satisfy specific pre-annealing conditions, and the component ratio of the non-oriented electrical steel sheets (slabs) did not satisfy a specific range, so M AVG It was confirmed that it does not satisfy a specific range, resulting in high iron loss.

Claims

1. Si: Contains 0.6 wt% or more and 1.6 wt% or less, Al: 0.1 wt% or more and 0.5 wt% or less, and Mn: 0.2 wt% or more and 0.4 wt% or less, and includes at least one of C: more than 0 ppm and 30 ppm or less, S: more than 0 ppm and 30 ppm or less, N: more than 0 ppm and 30 ppm or less, Ti: more than 0 ppm and 30 ppm or less, and P: more than 0 ppm and 1000 ppm or less, and includes at least one of Y: more than 0 ppm and 30 ppm or less and Ho: more than 0 ppm and 30 ppm or less, and includes the remainder of Fe and other inevitable impurities. The average (M) of the magnetic domain spin alignment values ​​(M) calculated by the following general formula 1 AVG ) Non-oriented electrical steel sheet with a value of 1.22 or less: [General formula 1] M = (sin 2 asin 2 b)+(sin 2 βsin 2 c)+(sin 2 gsin 2 a) In the above general formula 1, α, β, and γ are obtained from crystal orientations measured under the condition of a step size of 10 ㎛ for a specimen of 20 mm in width and 20 mm in length manufactured from a non-oriented electrical steel sheet by EBSD, and when the x-axis, y-axis, and z-axis defined in the three-dimensional crystal coordinate system are used as the basis, α is the angle between the x-axis and the crystal grain orientation, β is the angle between the y-axis and the crystal grain orientation, and γ is the angle between the z-axis and the crystal grain orientation.

2. In paragraph 1, Non-oriented electrical steel sheet containing Y: more than 0 ppm and less than or equal to 30 ppm and Ho: more than 0 ppm and less than or equal to 30 ppm.

3. In paragraph 1, Non-oriented electrical steel sheet containing C: more than 0 ppm and less than or equal to 30 ppm, S: more than 0 ppm and less than or equal to 30 ppm, N: more than 0 ppm and less than or equal to 30 ppm, Ti: more than 0 ppm and less than or equal to 30 ppm, and P: more than 0 ppm and less than or equal to 1000 ppm.

4. In paragraph 1, Non-oriented electrical steel sheet with a thickness of more than 0.3 mm and less than or equal to 0.6 mm.

5. A step of hot-rolling a slab, which comprises Si: 0.6 wt% or more and 1.6 wt% or less, Al: 0.1 wt% or more and 0.5 wt% or less, and Mn: 0.2 wt% or more and 0.4 wt% or less, and at least one of C: more than 0 ppm and 30 ppm or less, S: more than 0 ppm and 30 ppm or less, N: more than 0 ppm and 30 ppm or less, Ti: more than 0 ppm and 30 ppm or less, and P: more than 0 ppm and 1000 ppm or less, and at least one of Y: more than 0 ppm and 30 ppm or less and Ho: more than 0 ppm and 30 ppm or less, and the remainder including Fe and other unavoidable impurities; A step of pre-annealing a hot-rolled hot-rolled steel sheet; A step of manufacturing a cold rolled steel sheet by cold rolling a pre-annealed hot rolled steel sheet; and A method for manufacturing a non-oriented electrical steel sheet, comprising a step of final annealing the cold rolled steel sheet, The above non-oriented electrical steel sheet has an average (M) of the magnetic domain spin alignment value (M) calculated by the following general formula 1 AVG ) Manufacturing method of non-oriented electrical steel sheet having a melting point of 1.22 or less: [General formula 1] M = (sin 2 asin 2 b)+(sin 2 βsin 2 c)+(sin 2 gsin 2 a) In the above general formula 1, α, β, and γ are obtained from crystal orientations measured under the condition of a step size of 10 ㎛ for a specimen of 20 mm in width and 20 mm in length manufactured from a non-oriented electrical steel sheet by EBSD, and when the x-axis, y-axis, and z-axis defined in the three-dimensional crystal coordinate system are used as the basis, α is the angle between the x-axis and the crystal grain orientation, β is the angle between the y-axis and the crystal grain orientation, and γ is the angle between the z-axis and the crystal grain orientation.

6. In paragraph 5, The above slab is a method for manufacturing a non-oriented electrical steel sheet including Y: more than 0 ppm and less than 30 ppm and Ho: more than 0 ppm and less than 30 ppm.

7. In paragraph 5, The above slab is a method for manufacturing a non-oriented electrical steel sheet including C: more than 0 ppm and less than 30 ppm, S: more than 0 ppm and less than 30 ppm, N: more than 0 ppm and less than 30 ppm, Ti: more than 0 ppm and less than 30 ppm, and P: more than 0 ppm and less than 1000 ppm.

8. In paragraph 5, A method for manufacturing a non-oriented electrical steel sheet, wherein the above preliminary annealing step is performed by heat treating the hot-rolled hot-rolled steel sheet at 950°C or higher and 1100°C or lower for 30 seconds or longer and 150 seconds or shorter.