Non-oriented electrical steel sheet

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 due to improved crystallographic texture.

Description

Non-oriented electrical steel sheet

[0001] This application relates to a non-oriented electrical steel sheet.

[0002] Due to recent policies to reduce CO2 emissions to combat global warming, conventional internal combustion engine vehicles are rapidly being replaced by eco-friendly vehicles such as hybrid electric vehicles (HEVs) and, especially, electric vehicles (EVs). These EVs require high torque at low speeds and during acceleration, and high-speed rotation at speeds exceeding 200 Hz at constant and high speeds. Consequently, the non-oriented electrical steel used as the core material for the motor must simultaneously meet high magnetic flux density and low core loss.

[0003] In general, non-oriented electrical steel sheets are manufactured through the processes of steelmaking / casting, hot rolling, intermediate annealing, cold rolling, final annealing, and coating, and by optimizing each process condition, they can have excellent magnetic properties.

[0004] In order to reduce iron loss in these non-oriented electrical steel sheets, methods such as reducing plate thickness and improving resistivity and texture are used.

[0005] Among these, the grain structure is one of the important factors for improving the core loss and magnetic flux density. In other words, the grain structure of non-oriented electrical steel sheets has a great influence on the magnetic properties. In terms of grain structure, the {001} plane is easily magnetized, and the {111} plane is unfavorable for magnetization. The fewer {111} planes there are and the more {001} planes there are, the higher the magnetic flux density and lower the iron loss can be obtained. Due to this magnetocrystalline anisotropy, the magnetic flux density and iron loss in non-oriented electrical steel sheets are greatly dependent on the grain structure. However, when the volume fraction of the {111} grain structure, which is unfavorable for magnetization, develops, a problem arises that adversely affects the magnetic properties.

[0006] Therefore, in order to solve these problems, there is a need for a non-oriented electrical steel sheet and a manufacturing method thereof that improves magnetic properties by improving the aggregate structure of the non-oriented electrical steel sheet.

[0007] The object of the present application is to provide a non-oriented electrical steel sheet having excellent magnetic properties by improving the aggregate structure of the non-oriented electrical steel sheet and a method for manufacturing the same.

[0008] In order to solve the above problem, the non-oriented electrical steel sheet of the present application contains, in wt%, Si: 0.1% or more and 1.6% or less, Mn: 0.2% or more and 0.4% or less, Al: more than 0% and 0.5% or less, and at least one of B, Y, and Ce: 0.005% or more and 0.01% or less, and the remainder includes Fe and other inevitable impurities, and satisfies the following general formula 1.

[0009] [General Formula 1]

[0010]

[0011] In the above general formula 1, f{001} <130> Silver {001} <130> is the volume fraction of the aggregate tissue having an orientation of 15° or less from f{113} <251> Silver {113} <251> is the volume fraction of the aggregate tissue having an orientation of 15° or less from f{334} <483> Silver {334} <483> is the volume fraction of the aggregate tissue having an orientation of 15° or less from f{111} <110> Silver {111} <110> is the volume fraction of the aggregate tissue having an orientation of 15° or less from {11 11 9}<9 9 22>, and f{11 11 9}<9 9 22> is the volume fraction of the aggregate tissue having an orientation of 15° or less from {11 11 9}<9 9 22>.

[0012] The above f{111} <110> can be between 1.0% and 15.0%.

[0013] In addition, the non-oriented electrical steel sheet may further include, in wt%, at least one selected from C: more than 0% and 0.005% or less, S: more than 0% and 0.005% or less, P: more than 0% and 0.100 wt% or less, N: more than 0% and 0.003% or less, and Ti: more than 0% and 0.005% or less.

[0014] In addition, the above non-oriented electrical steel sheet has iron loss W measured at angles of 0° and 90° with respect to the rolling direction. 15 / 50 The average may be less than 8.0 W / kg.

[0015] In addition, the non-oriented electrical steel sheet has a magnetic flux density (B) measured at angles of 0° and 90° with respect to the rolling direction. 50 ) may have an average of 1.70 T or more.

[0016] Additionally, the non-oriented electrical steel sheet may further include a coating layer formed on the surface.

[0017] According to the non-oriented electrical steel sheet of the present application, excellent magnetic properties can be achieved by improving the aggregate structure.

[0018] 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 satisfies the following general formula 1.

[0019] [General Formula 1]

[0020]

[0021] In the above general formula 1, f{001} <130> Silver {001} <130> is the volume fraction of the aggregate tissue having an orientation of 15° or less from f{113} <251> Silver {113} <251> is the volume fraction of the aggregate tissue having an orientation of 15° or less from f{334} <483> Silver {334} <483> is the volume fraction of the aggregate tissue having an orientation of 15° or less from f{111} <110> Silver {111} <110> is the volume fraction of the aggregate tissue having an orientation of 15° or less from {11 11 9}<9 9 22>, and f{11 11 9}<9 9 22> is the volume fraction of the aggregate tissue having an orientation of 15° or less from {11 11 9}<9 9 22>.

[0022] Specifically, the value calculated by the above-mentioned general formula 1 may be 0.5 or more, and more specifically, may be 1.0 or more. At this time, the upper limit of the value calculated by the above-mentioned general formula 1 is not particularly limited, but may be, for example, 5.0 or less or 4.0 or less. According to the non-oriented electrical steel sheet of the present application, by satisfying the above-mentioned general formula 1, it can have excellent magnetic properties, and specifically, it can have low iron loss and high magnetic flux density. On the other hand, if the value calculated by the above-mentioned general formula 1 is less than the lower limit of the above-mentioned numerical range, the magnetic properties of the non-oriented electrical steel sheet may deteriorate.

[0023] In one example, {001} of the aggregate structure formed on the surface of the non-oriented electrical steel sheet <130> The direction is a direction favorable for magnetic properties. For example, the above f{001} <130> may be 2.2% or more. Specifically, the above f{001} <130> may be 2.4% or more. At this time, the above f{001} <130> The upper limit of {001} is not particularly limited, but may be, for example, 12% or less or 10% or less. <130> The aggregate structure having a direction can have excellent magnetic properties by having the aforementioned volume fraction, and specifically, can have low iron loss and high magnetic flux density.

[0024] In addition, the {113} texture formed on the surface of the non-oriented electrical steel sheet <251> The direction is a direction favorable for magnetic properties. For example, the above f{113} <251> may be 3.0% or more. Specifically, the above f{113} <251> may be 3.2% or more. At this time, the above f{113} <251> The upper limit of is not particularly limited, but may be, for example, 20% or less or 18% or less. The above {113} <251> The aggregate structure having a direction can have excellent magnetic properties by having the aforementioned volume fraction, and specifically, can have low iron loss and high magnetic flux density.

[0025] In addition, {334} of the aggregate structure formed on the surface of the non-oriented electrical steel sheet <483> The direction is unfavorable for magnetic properties. For example, the above f{334} <483> may be less than or equal to 20.5%. Specifically, the above f{334} <483> may be 20.4% or less, 20.3% or less, or 20.2% or less. In this case, the f{334} <483> The lower limit of is not particularly limited, but may be, for example, 1.0% or more, 2.0% or more, 3.0% or more, or 4.0% or more. The above {334} <483> The aggregate structure having a direction can have excellent magnetic properties by having the aforementioned volume fraction, and specifically, can have low iron loss and high magnetic flux density.

[0026] In addition, the {111} texture formed on the surface of the non-oriented electrical steel sheet <110> The direction is unfavorable for magnetic properties. For example, the above f{111} <110> can be 1.0% to 15.0%. Specifically, the f{111} <110> The upper limit may be 14.5% or less or 14.0% or less. In this case, the f{111} <110> The lower limit of may be 1.0% or more, 2.0% or more, or 3.0% or more. The above {111} <110> The aggregate structure having a direction can have excellent magnetic properties by having the aforementioned volume fraction, and specifically, can have low iron loss and high magnetic flux density.

[0027] In addition, the {11 11 9}<9 9 22> orientation of the texture formed on the surface of the non-oriented electrical steel sheet is an orientation that is unfavorable for magnetic properties. For example, the f{11 11 9}<9 9 22> may be 10.0% or less. Specifically, the f{11 11 9}<9 9 22> may be 8.5% or less or 7.0% or less. At this time, the lower limit of the f{11 11 9}<9 9 22> is not particularly limited, but may be, for example, 1.0% or more, 2.0% or more, or 3.0% or more. The texture having the {11 11 9}<9 9 22> orientation may have excellent magnetic properties by having the aforementioned volume fraction, and specifically, may have low iron loss and high magnetic flux density.

[0028] The above non-oriented electrical steel sheet has iron loss W measured at angles of 0° and 90° with respect to the rolling direction, specifically, the rolling direction during cold rolling. 15 / 50 The average of may be 8.0 W / kg or less. Specifically, the non-oriented electrical steel sheet has a core loss W measured by the method described above. 15 / 50 The average of the above non-oriented electrical steel sheet may be 7.0 W / kg or less. The iron loss W of the above non-oriented electrical steel sheet 15 / 50 The lower limit is not particularly limited in terms of the lower the average, the better the magnetic properties are, but it can be, for example, 1 W / kg or more or 3 W / kg or more. The iron loss W 15 / 50 It means the iron loss when a magnetic flux density of 1.5 T is induced at a low frequency of 50 Hz. In this case, the iron loss W 15 / 50 was measured using a single sheet tester.

[0029] In addition, the non-oriented electrical steel sheet has a magnetic flux density (B) measured at angles of 0° and 90° with respect to the rolling direction. 50 ) may be 1.70 T or more. Specifically, the non-oriented electrical steel sheet has a magnetic flux density (B) measured by the method described above. 50) may be 1.71 T or more. In addition, the magnetic flux density (B) of the non-oriented electrical steel sheet 50 ) is not particularly limited in terms of the fact that the higher the average, the better the magnetic properties, but it can be, for example, 2.0 T or less. The magnetic flux density (B 50 ) refers to the magnetic flux density induced in a magnetic field of 5000 A / m. At this time, the magnetic flux density was measured using a single sheet tester.

[0030] In one example, the non-oriented electrical steel sheet may have a thickness of less than 0.7 mm. In addition, the lower limit of the thickness of the non-oriented electrical steel sheet may be 0.01 mm or more. By having the aforementioned thickness, the non-oriented electrical steel sheet may have excellent magnetic properties, and specifically, may have low core loss and high magnetic flux density.

[0031] The above non-oriented electrical steel sheet contains, in wt%, Si: 0.1% or more and 1.6% or less, Mn: 0.2% or more and 0.4% or less, Al: more than 0% and 0.5% or less, and at least one of B, Y, and Ce: 0.005% or more and 0.01% or less, and may contain the remainder of Fe and other unavoidable impurities.

[0032] The components of the above non-oriented electrical steel sheet are described below.

[0033] Si: 0.1 wt% or more and 1.6 wt% or less

[0034] Silicon (Si) is an element that increases the resistivity of a material and reduces eddy current 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 iron loss reduction effect may be insufficient. 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 magnetic permeability and magnetic flux density may decrease. In addition, if the silicon is included in the non-oriented electrical steel sheet in the aforementioned range, the texture may be improved to obtain a low iron loss value similar to that obtained through a high silicon content. Therefore, the silicon may be included in the non-oriented electrical steel sheet in an amount of 0.1 wt% or more and 1.6 wt% or less, and specifically, may be included in an amount of 0.2 wt% or more and 1.4 wt% or less.

[0035] Mn: 0.2 wt% or more and 0.4 wt% or less

[0036] 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 exceeding the upper limit of the aforementioned range, coarse MnS may be precipitated, which may reduce the magnetic flux density and cause a decrease in cold rolling properties. In addition, 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 be precipitated, which may suppress grain growth and increase iron loss. Therefore, the manganese may be included in the non-oriented electrical steel sheet in an amount of 0.1 wt% or more and 0.4 wt% or less, and specifically, may be included in an amount of 0.1 wt% or more and 0.3 wt% or less.

[0037] Al: More than 0 wt% and less than or equal to 0.5 wt%

[0038] Aluminum (Al) is an element that increases resistivity together with Si, thereby reducing eddy current 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 exceeding the upper limit of the aforementioned range, cold rolling properties may deteriorate and magnetic flux density may decrease. Therefore, the aluminum may be included in the non-oriented electrical steel sheet in an amount of more than 0 wt% and less than or equal to 0.5 wt%, and specifically, may be included in an amount of more than 0.001 wt% and less than or equal to 0.4 wt%.

[0039] At least one of B, Y and Ce: 0.005 wt% or more and 0.01 wt% or less

[0040] Boron (B), yttrium (Y), and cerium (Ce) are elements that lower grain boundary energy due to grain boundary segregation, suppress nucleation of {111} and {112} orientations while decreasing the recrystallization rate, thereby reducing the volume fraction of orientations that are unfavorable to magnetic properties, and increase {100} orientation and Goss orientation that are favorable to magnetic properties. When at least one of the boron, yttrium, and cerium is included in the non-oriented electrical steel sheet in an amount exceeding the upper limit of the above-mentioned range, the pinning effect due to grain boundary segregation hinders recrystallization grain growth, preventing grain growth and rather having a negative effect on the texture. In addition, when at least one of the boron, yttrium, and cerium is included in the non-oriented electrical steel sheet in an amount less than the lower limit of the aforementioned range, it may be disadvantageous in terms of the aggregate structure, and the magnetic flux density may be low, resulting in inferior magnetic properties. Therefore, at least one of the boron, yttrium, and cerium may be included in the non-oriented electrical steel sheet in an amount of 0.005 wt% or more and 0.01 wt% or less, and specifically, may be included in an amount of 0.006 wt% or more and 0.009 wt% or less.

[0041] The remaining Fe and other unavoidable impurities

[0042] 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).

[0043] For example, the above-mentioned inevitable impurities may be zirconium (Zr), niobium (Nb), and / or copper (Cu), and the non-oriented electrical steel sheet may include Zr: 0.005 wt% or less, Nb: 0.005 wt% or less, and / or Cu: 0.005 wt% or less.

[0044] In one example, the non-oriented electrical steel sheet may further include, in wt%, at least one selected from C: more than 0% and 0.005% or less, S: more than 0% and 0.005% or less, P: more than 0% and 0.100 wt% or less, N: more than 0% and 0.003% or less, and Ti: more than 0% and 0.005% or less.

[0045] C: More than 0 wt% and less than or equal to 0.005 wt%

[0046] 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 of more than 0% and less than or equal to 0.005% by weight, and specifically, may be included in an amount of more than 0.001% by weight and less than or equal to 0.003% by weight.

[0047] S: More than 0 wt% and less than or equal to 0.005 wt%

[0048] 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 excess of 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 of more than 0 wt% and less than 0.005 wt%.

[0049] P: More than 0 wt% and less than or equal to 0.100 wt%

[0050] 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 suppressed due to the segregation effect, magnetic properties may deteriorate, and cold-rollability may decrease. However, in terms of improving strength, the phosphorus may be included in the non-oriented electrical steel sheet in an amount exceeding 0 wt% and not exceeding 0.100 wt%.

[0051] N: More than 0 wt% and less than or equal to 0.003 wt%

[0052] 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 exceeding 0 wt% and not exceeding 0.003 wt%.

[0053] Ti: More than 0 wt% and less than or equal to 0.005 wt%

[0054] 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 wt% and less than 0.005 wt%.

[0055] In one example, the non-oriented electrical steel sheet may further include a coating layer. The coating layer is a coating formed on the surface of the non-oriented electrical steel sheet and may be called 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 0.1 ㎛ 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 above non-oriented electrical steel sheet may have an average grain size of 80 ㎛ or more and 150 ㎛ or less, and the processed structure formed during cold rolling may be entirely, i.e., 99% or more, recrystallized through final annealing. If the average grain size of the above 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 if it exceeds the upper limit of the above-mentioned range, eddy current loss may increase, which may increase iron loss.

[0057] 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.

[0058] The method for manufacturing a non-oriented electrical steel sheet of the present application includes a step of manufacturing a hot-rolled steel sheet, a step of manufacturing a cold-rolled steel sheet, and a step of final annealing, and the final annealed steel sheet satisfies the general formula 1 described above. According to the method for manufacturing a non-oriented electrical steel sheet of the present application, the final annealed steel sheet can satisfy the general formula 1 described above, and thus, can have excellent magnetic properties, and specifically, can have low iron loss and high magnetic flux density.

[0059] The step of manufacturing the above 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 may be, for example, 1000°C to 1250°C. If the reheating temperature of the slab is below the lower limit of the above-mentioned range, the rolling load increases, making it difficult to perform hot rolling, and if it exceeds the upper limit of the above-mentioned range, precipitates such as C, S, and N in the slab are re-dissolved, and fine precipitates are generated in the subsequent rolling and annealing processes, which may inhibit grain growth and deteriorate magnetism.

[0060] In addition, the finishing rolling temperature during the hot rolling may be 850°C to 1000°C, and specifically 900°C to 950°C. By performing the hot rolling under the conditions described above, the magnetic properties may be excellent. In contrast, if the finishing rolling temperature during the hot rolling is below the lower limit of the above-mentioned range, fine TiC precipitates may be formed, which may hinder the movement of the magnetic domains of the final material, thereby ultimately reducing the magnetic properties.

[0061] In addition, the thickness of the hot-rolled steel sheet may be 1.8 mm to 2.6 mm, and specifically, 2.0 mm to 2.5 mm or 2.2 mm to 2.4 mm. 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 poor bonding structure. Therefore, the thickness of the hot-rolled steel sheet may be controlled within the above-mentioned range.

[0062] In one example, the slab may contain, in wt%, Si: 0.1% or more and 1.6% or less, Mn: 0.2% or more and 0.4% or less, Al: 0% or more and 0.5% or less, and at least one of B, Y, and Ce: 0.005% or more and 0.01% or less, and may contain the remainder of Fe and other unavoidable impurities. A specific description of the components of the slab is omitted because the same description as that of the non-oriented electrical steel sheet applies.

[0063] In another example, the slab may further include, in wt%, one or more selected from C: more than 0% and less than or equal to 0.005%, S: more than 0% and less than or equal to 0.005%, P: more than 0% and less than or equal to 0.100 wt%, N: more than 0% and less than or equal to 0.003%, and Ti: more than 0% and less than or equal to 0.005%. A specific description of the additional components added to the slab is omitted because the same description as that of the non-oriented electrical steel sheet applies.

[0064] In addition, the method for manufacturing the non-oriented electrical steel sheet may further include a winding step. The winding step is performed to increase the orientation advantageous to magnetism, and is performed by winding the sheet onto a cylindrical winding member.

[0065] In one example, the coiling step may be performed by coiling the hot-rolled steel sheet at a coiling temperature of 550°C to 750°C. The coiling step is performed by coiling the hot-rolled steel sheet at the coiling temperature described above, so that, during coiling, the grain size of the hot-rolled steel sheet is made to be 40 μm to 100 μm, specifically, 40 μm to 60 μm, thereby reducing the cold-rolling load and, during the final annealing after cold rolling, improving the texture to be advantageous to magnetism, so that the non-oriented electrical steel sheet that has undergone the final annealing may satisfy the general formula 1 described above. In contrast, when the coiling temperature of the hot-rolled steel sheet in the coiling step is less than the lower limit of the above-mentioned range, the grains of the hot-rolled steel sheet do not grow, and fine grains or elongated grains exist, which may deteriorate the magnetism of the final product. In addition, if the coiling temperature of the hot-rolled steel sheet exceeds the upper limit of the above-mentioned range in the above-mentioned coiling step, internal oxidation may occur in the hot-rolled steel sheet, which may adversely affect the surface quality during cold rolling, and precipitates such as TiC and / or TiN may be generated with a size of 0.1 ㎛ or less, which may deteriorate the magnetism of the final product. Therefore, the above-mentioned coiling step may be performed by coiling the hot-rolled steel sheet at the above-mentioned coiling temperature.

[0066] In one example, the method for manufacturing the non-oriented electrical steel sheet may further include an intermediate annealing step. The intermediate annealing step is a step for increasing the orientation favorable to magnetism, and may be performed by heat treating the hot-rolled steel sheet.

[0067] In one example, the intermediate annealing step may be performed by heat treating the hot-rolled hot-rolled steel sheet at 950°C to 1100°C for 30 to 120 seconds. Specifically, the intermediate annealing step may be performed by heating the hot-rolled hot-rolled steel sheet from 950°C to 1100°C at a heating rate of 20°C / s or more and heat treating it at this temperature range for 30 to 120 seconds. In the intermediate annealing step, if the heat treatment temperature is lower than the lower limit of the aforementioned range, the grains may not have enough time to grow, resulting in the formation of fine grains, which may deteriorate the magnetism of the final product. On the other hand, in the intermediate annealing step, if the heat treatment temperature exceeds the upper limit of the aforementioned range, the grains may grow excessively, resulting in a severe grain size deviation and a large amount of oxidation, which may adversely affect the final product. Therefore, the intermediate annealing step may be performed at the aforementioned heat treatment temperature. Thereafter, the intermediately annealed hot-rolled steel sheet can be cooled at a cooling rate of 30°C / s or higher. Furthermore, the cooled hot-rolled steel sheet can then be further pickled. This allows the oxide layer formed on the surface of the hot-rolled steel sheet to be removed using a pickling solution.

[0068] The step of manufacturing the above cold-rolled steel sheet is a step for manufacturing the intermediately annealed hot-rolled steel sheet into a cold-rolled steel sheet, and is performed through cold rolling. At this time, the thickness of the cold-rolled steel sheet may be 0.70 mm or less, and specifically, may be 0.60 mm or less. In addition, the lower limit of the thickness of the cold-rolled steel sheet may be 0.10 mm or more or 0.30 mm or more. At this time, the reduction ratio during the cold rolling may be 70% to 90%.

[0069] The final annealing step is a step for securing magnetic properties by growing 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 heating to 800°C to 1000°C at a heating rate of 10°C / s or more, heat-treating at this temperature range for 5 to 70 seconds, and then cooling at a cooling rate of 20°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, when the heating rate, temperature, and time of the final annealing step exceed the upper limit of the aforementioned range, the grain size may become coarser, which may increase eddy current loss. In addition, when the heating rate, temperature, and time of the final annealing step are less than the lower limit of the aforementioned range, the grain size may become fine, which may increase hysteresis loss.

[0070] At this time, the final annealing step can be performed in an atmosphere of 0% to 100% hydrogen and 0% to 100% nitrogen, specifically, 20% to 40% hydrogen and 60% to 80% nitrogen. The method for manufacturing the non-oriented electrical steel sheet can further smoothen the surface condition of the steel sheet by performing the final annealing step in an atmosphere within the aforementioned range.

[0071] The above non-oriented electrical steel sheet may have an average grain size of 80 ㎛ to 150 ㎛ formed on the surface during the final annealing process, and all of the processed structure formed during the previous cold rolling process, that is, more than 99%, 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.

[0072] 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 by forming the coating layer on the surface of the heat-treated steel sheet 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.

[0073]

[0074] 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.

[0075]

[0076] Example 1

[0077] Manufacturing of non-oriented electrical steel sheets

[0078] 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 then reheated at a temperature of 1120°C and hot-rolled at a finishing temperature of 920°C to manufacture a hot-rolled steel sheet having a thickness of 2.3 mm.

[0079] Afterwards, the hot-rolled steel sheet was coiled at a coiling temperature of 680°C.

[0080] Afterwards, the hot-rolled steel sheet was cold-rolled at a reduction ratio of approximately 78% to manufacture a cold-rolled steel sheet with a thickness of 0.5 mm.

[0081] Thereafter, the cold-rolled steel sheet was heated to 1000°C at a heating rate of 20°C / s in a mixed atmosphere of 30% hydrogen and 70% 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.

[0082] Slab composition (wt%)SiMnAlCSPNTiBYCe0.270.1410.0010.00150.00440.07800.00150.00070.00200.00100.0030

[0083]

[0084] Examples 2 to 9 and Comparative Examples 1 to 5

[0085] Manufacturing of non-oriented electrical steel sheets

[0086] Each non-oriented electrical steel sheet was manufactured in the same manner as Example 1, except that the composition of the slab was changed as shown in Table 2 below.

[0087] Slab composition (wt%) SiMnAlCSPNTiBYCeExample 20.350.2530.0010.00250.00410.06200.00140.00080.00150.00220.0025Example 30.720.2500.2930.00130.00450.00900.00110.00200.00100.00250.0040Example 40.920.3500.2110.00290.00340.03500.00140.00130.00150.00400.0030Example 50.840.3020.2370.00270.00330.02100.00210.00090.00400.00200.0025Example 61.250.2500.3470.00140.00330.00900.00140.00050.00050.00200.0050Example 71.270.2180.0010.00160.00220.08000.00120.00250.00530.00120.0025Example 81.320.2120.030.00120.00180.07500.00150.00200.00550.00100.0030Example 91.280.2000.030.00180.00220.08000.00120.00250.00530.00120.0025Comparative Example 10.330.2000.0010.00200.00400.07000.00150.00070.00500.00250.0035Comparative Example 20.720.3000.0010.00150.00500.06800.00130.00080.00220.00300.0055Comparative example 30.930.2100.2230.00130.00380.02300.00110.00100.00360.00650.0020Comparative example 41.290.2220.3050.00150.00300.01000.00130.00090.00650.00150.0024Comparative example 51.250.2300.2530.00100.00350.01200.00150.00100.00120.00250.0011

[0088]

[0089] Evaluation Example 1. Evaluation of Satisfaction with General Formula 1

[0090] For the non-oriented electrical steel sheets manufactured in each of the examples and comparative examples, the crystal orientation of the texture was measured in an area of ​​1000 ㎛ Х 1000 ㎛ or more using electron backscatter diffraction (EBSD), and {100} <130> , {113} <251> , {334} <483> , {111} <110> And the volume fraction of the {11 11 9}<9 9 22> direction was calculated using the following general formula 1, and whether the following general formula 1 was satisfied was evaluated, and the results are shown in Table 3 below.

[0091] [General Formula 1]

[0092]

[0093] In the above general formula 1, f{001} <130> Silver {001} <130> is the volume fraction of the aggregate tissue having an orientation of 15° or less from f{113} <251> Silver {113} <251> is the volume fraction of the aggregate tissue having an orientation of 15° or less from f{334} <483> Silver {334} <483> is the volume fraction of the aggregate tissue having an orientation of 15° or less from f{111} <110> Silver {111} <110> is the volume fraction of the aggregate tissue having an orientation of 15° or less from {11 11 9}<9 9 22>, and f{11 11 9}<9 9 22> is the volume fraction of the aggregate tissue having an orientation of 15° or less from {11 11 9}<9 9 22>.

[0094]

[0095] Evaluation Example 2. Iron loss and magnetic flux density evaluation

[0096] Iron Hand W 15 / 50 and magnetic flux density (B 50 ) was cut into 60 mm wide and 60 mm long non-oriented electrical steel sheets manufactured in each of the examples and comparative examples to manufacture specimens, and then measured twice at an angle of 0° (upper and lower surfaces of the specimen) and twice at an angle of 90° (upper and lower surfaces of the specimen) with respect to the rolling direction during cold rolling using a single sheet tester, and the average values ​​are shown in Table 3 below. At this time, W15 / 50 is the iron loss when a magnetic flux density of 1.5 T is induced at a low frequency of 50 Hz, and B 50 refers to the magnetic flux density induced in a magnetic field of 5000 A / m.

[0097] Volume fraction (%) of at least one type of aggregate tissue among B, Y and Ce (by weight) W calculated by general formula 1 15 / 50 (W / kg)B 50 (T){001} <130> {113} <251> {334} <483> {11 11 9}<9 9 22>{111} <110> Example 10.00608.515.817.34.49.12.926.161.75 Example 20.00622.44.24.76.28.31.285.821.75 Example 30.00755.613.319.15.313.91.775.171.74 Example 40.00852.75.04.24.97.41.735.091.74 Example 50.00854.45.25.04.13.62.964.701.75 Example 60.00755.116.920.26.212.81.944.031.73 Example 70.00753.33.24.04.07.41.694.031.71Example 80.00959.1213.512.83.55.33.993.81.72Example 90.00908.51313.84.24.83.573.991.72Comparative Example 10.01101.20.934.015.818.20.1315.001.72Comparative Example 20.01070.83.328.513.513.80.2512.251.70Comparative Example 30.01211.54.522.515.215.60.3910.851.70Comparative Example 40.01042.03.220.811.210.20.468.281.68Comparative example 50.00380.70.521.210.58.20.139.521.67

[0098] As shown in Table 3 above, it was confirmed that the non-oriented electrical steel sheets manufactured in each of Examples 1 to 9 satisfy General Formula 1 and have both low iron loss and high magnetic flux density since the content of at least one of B, Y, and Ce satisfies a specific range. In contrast, the non-oriented electrical steel sheets manufactured in each of Comparative Examples 1 to 4 do not satisfy General Formula 1, and have both low iron loss and high magnetic flux density since the content of at least one of B, Y, and Ce exceeds a specific range. In addition, it was confirmed that the non-oriented electrical steel sheets manufactured in Comparative Example 5 do not satisfy General Formula 1, and have both low iron loss and high magnetic flux density since the content of at least one of B, Y, and Ce is below a specific range.

Claims

1. A non-oriented electrical steel sheet containing, by weight%, Si: 0.1% or more and 1.6% or less, Mn: 0.2% or more and 0.4% or less, Al: more than 0% and 0.5% or less, and at least one of B, Y, and Ce: 0.005% or more and 0.01% or less, and the remainder including Fe and other inevitable impurities, and satisfying the following general formula 1: [General formula 1] In the above general formula 1, f{001} <130> Silver {001} <130> is the volume fraction of the aggregate tissue having an orientation of 15° or less from f{113} <251> Silver {113} <251> is the volume fraction of the aggregate tissue having an orientation of 15° or less from f{334} <483> Silver {334} <483> is the volume fraction of the aggregate tissue having an orientation of 15° or less from f{111} <110> Silver {111} <110> is the volume fraction of the aggregate tissue having an orientation of 15° or less from {11 11 9}<9 9 22>, and f{11 11 9}<9 9 22> is the volume fraction of the aggregate tissue having an orientation of 15° or less from {11 11 9}<9 9 22>.

2. In paragraph 1, The above f{111} <110> Non-oriented electrical steel sheet having a content of 1.0% to 15.0%.

3. In paragraph 1, Non-oriented electrical steel sheet further comprising at least one selected from among C: more than 0% but not more than 0.005%, S: more than 0% but not more than 0.005%, P: more than 0% but not more than 0.100 wt%, N: more than 0% but not more than 0.003%, and Ti: more than 0% but not more than 0.005%.

4. In paragraph 1, Iron loss W measured at angles of 0° and 90° to the rolling direction 15 / 50 Non-oriented electrical steel sheet with an average of 8.0 W / kg or less.

5. In paragraph 1, Magnetic flux density (B) measured at angles of 0° and 90° to the rolling direction 50 ) Non-oriented electrical steel sheet having an average of 1.70 T or more.

6. In paragraph 1, A non-oriented electrical steel sheet further comprising a coating layer formed on the surface.

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