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

Abstract

One embodiment of the present invention is a method for manufacturing a non-oriented electrical steel sheet, comprising the steps of: manufacturing a hot-rolled sheet by hot-rolling a slab comprising, in weight percent, silicon (Si): 2.5% or more and 3.6% or less, manganese (Mn): 0.1% or more and 0.3% or less, Al: 0.3% or more and 0.8% or less, carbon (C): greater than 0% and 0.003% or less, sulfur (S): greater than 0% and 0.003% or less, nitrogen (N): greater than 0% and 0.003% or less, titanium (Ti): greater than 0% and 0.003% or less, and the remainder being iron (Fe) and unavoidable impurities; manufacturing a hot-rolled sheet by hot-rolling the hot-rolled sheet at a temperature of 90°C to 300°C to manufacture a hot-rolled sheet; and manufacturing a final annealed sheet by finally annealing the hot-rolled sheet, wherein, in the step of manufacturing the hot-rolled sheet, the hot-rolling reduction ratio is 85% or more and 91% or less. A method for manufacturing a steel sheet and a non-oriented electrical steel sheet manufactured thereby are disclosed.

Description

Technology Field

[0001] Embodiments of the present invention relate to non-oriented electrical steel sheets and a method for manufacturing the same. Background Technology

[0002] Recently, there has been an increasing demand for environmental conservation and improved energy efficiency. In particular, the transition from internal combustion engine vehicles to electric or hybrid vehicles is accelerating.

[0003] Non-oriented electrical steel is primarily used as a material for transformers and rotating machinery such as motors. To improve the efficiency of motors used to drive electric vehicles, it is required to enhance the magnetic properties of non-oriented electrical steel.

[0004] Non-oriented electrical steel is a material that possesses relatively uniform magnetic properties in all directions regardless of the rolling direction; it must have low magnetic anisotropy, which is the deviation of magnetic properties between the rolling direction and other directions at a certain angle relative to the rolling direction. High magnetic anisotropy can hinder motor rotation and reduce energy efficiency.

[0005] The magnetic properties required for non-oriented electrical steel are high magnetic flux density and low iron loss. Iron loss refers to energy loss caused by the iron core material; to reduce iron loss in non-oriented electrical steel, the sheet thickness can be reduced or the resistivity can be increased. However, reducing the sheet thickness may lower productivity during the manufacturing process, and increasing the content of alloying elements with high resistivity, such as Si, to increase resistivity may lead to reduced magnetic flux density and decreased rollability, thereby lowering productivity. The magnetic properties of non-oriented electrical steel can also be determined by factors such as the ratio of the texture. For instance, if a texture conducive to magnetization is not developed, iron loss increases and magnetic flux density decreases, which may result in a degradation of magnetic properties.

[0006] Related technologies include Korean Registered Patent Publication No. 10-1992-005619 (Title of Invention: Method for Manufacturing Non-Oriented Electrical Steel Sheet with Excellent Magnetic Properties). Prior art literature

[0007] Republic of Korea Registered Patent Publication No. 10-1992-005619 The problem to be solved

[0008] Embodiments of the present invention include a warm rolling step following a hot rolling step, and by controlling the process conditions during the warm rolling step, can provide a non-oriented electrical steel sheet with excellent magnetic properties and reduced magnetic anisotropy. However, this problem is exemplary and does not limit the scope of the present invention. means of solving the problem

[0009] According to one aspect of the present invention, a method for manufacturing a non-oriented electrical steel sheet comprises the steps of: hot rolling a slab comprising, in weight percent, silicon (Si): 2.5% or more and 3.6% or less, manganese (Mn): 0.1% or more and 0.3% or less, Al: 0.3% or more and 0.8% or less, carbon (C): greater than 0% and 0.003% or less, sulfur (S): greater than 0% and 0.003% or less, nitrogen (N): greater than 0% and 0.003% or less, titanium (Ti): greater than 0% and 0.003% or less, and the remainder being iron (Fe) and unavoidable impurities to produce a hot-rolled sheet; and hot rolling the hot-rolled sheet at a temperature of 90°C to 300°C to produce a hot-rolled sheet. A method for manufacturing a non-oriented electrical steel sheet is disclosed, comprising the step of manufacturing a final annealed sheet by finally annealing the hot rolling sheet; wherein, in the step of manufacturing the hot rolling sheet, the hot rolling reduction rate is 85% or more and 91% or less.

[0010] In one embodiment, in the step of manufacturing the hot rolling plate, the hot rolling temperature and the hot rolling reduction rate may satisfy the following Equation 1.

[0011] <Equation 1>

[0012]

[0013] Here, T w represents the warm rolling temperature (°C), and R represents the warm rolling reduction rate (%).

[0014] In one embodiment, the step of manufacturing a hot-rolled plate by hot-rolling the hot-rolled plate can be performed in a mixed atmosphere of nitrogen (N2) and 25% to 40% hydrogen (H2).

[0015] In one embodiment, the method may further include a step of pre-annealing the hot-rolled plate to produce a hot-rolled annealed plate between the step of producing the hot-rolled plate and the step of producing the hot-rolled plate.

[0016] In one embodiment, the method may further include a coating step of forming a coating layer on the final annealed plate.

[0017] In another aspect of the present invention, a non-oriented electrical steel sheet is disclosed, comprising, in weight percent, silicon (Si): 2.5% or more and 3.6% or less, manganese (Mn): 0.1% or more and 0.3% or less, Al: 0.3% or more and 0.8% or less, carbon (C): greater than 0% and 0.003% or less, sulfur (S): greater than 0% and 0.003% or less, nitrogen (N): greater than 0% and 0.003% or less, titanium (Ti): greater than 0% and 0.003% or less, and the remainder being iron (Fe) and unavoidable impurities, wherein the non-oriented electrical steel sheet has an area fraction of a texture with {100} / / ND orientation of 18% or more.

[0018] In one embodiment, the {100} / / ND orientation texture, {111} / / ND orientation texture, and {110} / / ND orientation texture included in the non-oriented electrical steel sheet may satisfy the following Equation 2.

[0019] <Equation 2>

[0020]

[0021] Here, X {100} / / NDis the area fraction (%) of the texture of the {100} / / ND orientation, X {111} / / ND is the area fraction (%) of the texture of the {111} / / ND orientation, X {110} / / ND represents the area fraction (%) of the aggregate of the {110} / / ND orientation.

[0022] In one embodiment, the non-oriented electrical steel sheet may have an area fraction of {111} / / ND orientation texture of 25% or more.

[0023] In one embodiment, the non-oriented electrical steel sheet may have an area fraction of {110} / / ND orientation texture of 7% or less.

[0024] In one embodiment, the non-oriented electrical steel sheet has an average iron loss defined by the following Equation 3 ( ) may be 12.7 W / kg or less.

[0025] <Equation 3>

[0026]

[0027] Here, W 0° is iron loss in the rolling direction (W 10 / 400 Standard), W 45° is the iron loss in the 45° direction relative to the rolling direction, W 90° represents iron loss in the 90° direction relative to the rolling direction.

[0028] In one embodiment, the non-oriented electrical steel sheet has a magnetic flux density (B) according to the angle of the measurement direction in the range where the angle of the measurement direction with respect to the rolling direction is 0° to 45°. 50 The absolute value of the slope of the reference) may be 0.0015 or less.

[0029] Other aspects, features, and advantages other than those described above will become clear from the following specific details, claims, and drawings for implementing the invention. Effects of the invention

[0030] According to one embodiment of the present invention as described above, by including a warm rolling step after a hot rolling step and controlling the process conditions during the warm rolling step, it is possible to provide a non-oriented electrical steel sheet with excellent magnetic properties and reduced magnetic anisotropy. Of course, the scope of the present invention is not limited by these effects. Brief explanation of the drawing

[0031] FIG. 1 is a flowchart schematically illustrating a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention. FIG. 2 is an image showing the surface of a non-oriented electrical steel sheet according to one embodiment and a comparative example of the present invention. FIG. 3 is a graph showing magnetic flux density values ​​according to the magnetic flux density measurement direction (angle of the measurement direction relative to the rolling direction) of a non-oriented electrical steel sheet according to one embodiment and a comparative example of the present invention. Specific details for implementing the invention

[0032] The present invention is capable of various modifications and may have various embodiments; specific embodiments are illustrated in the drawings and described in detail in the detailed description. The effects and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the drawings. However, the present invention is not limited to the embodiments disclosed below but can be implemented in various forms.

[0033] In the following embodiments, terms such as first, second, etc. are used not in a limiting sense, but for the purpose of distinguishing one component from another component.

[0034] In the following examples, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0035] In the following embodiments, terms such as "include" or "have" mean that the features or components described in the specification are present, and do not preclude the possibility that one or more other features or components may be added.

[0036] In the following embodiments, when a part such as a film, region, or component is described as being on or above another part, it includes not only cases where it is directly on top of another part, but also cases where another film, region, or component is interposed in between.

[0037] In the drawings, the size of components may be exaggerated or reduced for convenience of explanation. For example, the size and thickness of each component shown in the drawings are depicted arbitrarily for convenience of explanation, and therefore the present invention is not necessarily limited to what is illustrated.

[0038] Where an embodiment can be implemented differently, a specific process sequence may be performed differently from the order described. For example, two processes described consecutively may be performed substantially simultaneously or proceed in the reverse order of the description.

[0039] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings, and when describing with reference to the drawings, identical or corresponding components will be given the same reference numerals.

[0040] FIG. 1 is a flowchart schematically illustrating a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0041] Referring to FIG. 1, a method for manufacturing a non-oriented electrical steel sheet according to one embodiment may include a hot rolling step (S100), a preliminary annealing step (S200), a warm rolling step (S300), a final annealing step (S400), and a coating step (S500).

[0042] In a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention, the semi-finished product subject to hot rolling may be a slab. The slab in the semi-finished product state can be obtained through a continuous casting process after obtaining molten steel of a predetermined composition through a steelmaking process.

[0043] In one embodiment, the slab may comprise, in weight percent, silicon (Si): 2.5% or more and 3.6% or less, manganese (Mn): 0.1% or more and 0.3% or less, Al: 0.3% or more and 0.8% or less, carbon (C): greater than 0% and 0.003% or less, sulfur (S): greater than 0% and 0.003% or less, nitrogen (N): greater than 0% and 0.003% or less, titanium (Ti): greater than 0% and 0.003% or less, and the remainder being iron (Fe) and unavoidable impurities.

[0044] Silicon (Si) can be a component that increases resistivity and lowers eddy current losses. In one embodiment, silicon (Si) may be included in a weight percentage of 2.5% or more and 3.6% or less relative to the total weight of the slab. If silicon (Si) is included in an amount less than 2.5% relative to the total weight of the slab, it may be difficult to obtain low iron loss values. On the other hand, as the content of silicon (Si) included in the slab increases, the permeability and magnetic flux density may decrease. In addition, if silicon (Si) is included in an amount exceeding 3.6% relative to the total weight of the slab, brittleness increases, which reduces cold rolling performance and may lower productivity.

[0045] Manganese (Mn) can be a component that increases resistivity and improves texture together with silicon (Si). In one embodiment, manganese (Mn) may be included in an amount of 0.1% or more and 0.3% or less by weight relative to the total weight of the slab. When manganese (Mn) is included in an amount of less than 0.1% relative to the total weight of the slab, fine MnS precipitates may be formed to inhibit grain growth. On the other hand, when manganese (Mn) is included in an amount of more than 0.3% relative to the total weight of the slab, coarse MnS precipitates may be formed, which may degrade magnetic properties such as reducing magnetic flux density.

[0046] Aluminum (Al) can be a component that increases resistivity along with silicon (Si) to lower eddy current losses. Additionally, aluminum (Al) can play a role in reducing magnetic deviation by reducing magnetic anisotropy. In one embodiment, aluminum (Al) may be included in a weight percentage of 0.3% or more and 0.8% or less relative to the total weight of the slab. If aluminum (Al) is included in less than 0.3% relative to the total weight of the slab, it may be difficult to obtain low iron loss values. Furthermore, fine AlN nitrides may be formed, which may increase deviations in magnetic properties. On the other hand, if aluminum (Al) is included in more than 0.8% relative to the total weight of the slab, cold rolling performance may be reduced, and excessive nitrides may be formed during final annealing, which may degrade magnetic properties.

[0047] Carbon (C) may be a component that increases iron loss by forming carbides such as TiC and NbC. In one embodiment, carbon (C) may be included in a weight percentage of greater than 0% and less than or equal to 0.003% with respect to the total weight of the slab. If carbon (C) is included in a weight percentage of greater than 0.003% with respect to the total weight of the slab, it may cause self-aging and degrade the magnetic properties of the slab. If carbon (C) is included in a weight percentage of greater than 0% and less than or equal to 0.003% with respect to the total weight of the steel plate, the self-aging phenomenon may be suppressed.

[0048] Sulfur (S) can form precipitates such as MnS and CuS, which can increase iron loss and inhibit grain growth. In one embodiment, sulfur (S) may be included in a weight percentage of greater than 0% and less than or equal to 0.003% relative to the total weight of the slab. When sulfur (S) is included in a weight percentage of greater than 0.003% relative to the total weight of the slab, precipitates such as MnS and CuS may be formed, which can increase iron loss and inhibit grain growth.

[0049] Nitrogen (N) can form precipitates such as AlN, TiN, and NbN, which can increase iron loss and inhibit grain growth. In one embodiment, nitrogen (N) may be included in a weight percentage of greater than 0% and less than or equal to 0.003% relative to the total weight of the slab. When nitrogen (N) is included in a weight percentage of greater than 0.003% relative to the total weight of the slab, precipitates such as AlN, TiN, and NbN may be formed, which can increase iron loss and inhibit grain growth.

[0050] Titanium (Ti) can inhibit grain growth by forming precipitates such as TiC and TiN. In one embodiment, titanium (Ti) may be included in a weight percentage of greater than 0% and less than or equal to 0.003% relative to the total weight of the slab. If titanium (Ti) is included in a weight percentage of greater than 0.003% relative to the total weight of the slab, precipitates such as TiC and TiN may be formed, and magnetic properties may deteriorate.

[0051] In the hot rolling step (S100), the slab can be heated to form a hot-rolled plate after hot rolling. In the hot rolling step (S100), the slab can be heated first. In one embodiment, the slab heating temperature in the hot rolling step (S100) may be approximately 1,100°C to approximately 1,200°C. If the slab heating temperature exceeds approximately 1,200°C, precipitates such as C, S, and N within the slab are re-dissolved, and fine precipitates are formed during subsequent rolling and annealing steps, which may inhibit grain growth and degrade magnetic properties. On the other hand, if the slab heating temperature is less than 1,100°C, the rolling load increases during hot rolling, which may reduce rollability.

[0052] In the hot rolling step (S100), the heated slab can be rolled at a predetermined finishing rolling temperature. In one embodiment, the finishing delivery temperature (FDT) of the hot rolling step (S100) may be about 700°C to about 1000°C.

[0053] In the hot rolling step (S100), the hot-rolled plate can be cooled to a predetermined coiling temperature (CT) and coiled. In one embodiment, the coiling temperature may be about 500°C to about 700°C.

[0054] In one embodiment, the thickness of the hot-rolled plate after hot rolling may be about 1.6 mm or more and about 2.8 mm or less. At this time, if the thickness of the hot-rolled plate exceeds about 2.8 mm, the cold rolling reduction rate increases, which may result in a decrease in texture.

[0055] A preliminary annealing step (S200) may be performed after the hot rolling step (S100). However, the present invention is not limited thereto. The preliminary annealing step (S200) may be omitted. In this case, a warm rolling step (S300) may be performed after the hot rolling step (S100).

[0056] In the preliminary annealing step (S200), a hot-rolled annealed plate can be manufactured by pre-annealing a coiled and cooled hot-rolled plate. Through the preliminary annealing step (S200), the uniformity of the microstructure and cold rolling properties of the hot-rolled plate can be ensured.

[0057] In the preliminary annealing step (S200), the hot-rolled sheet can be heated at a heating rate of about 5°C / s to about 30°C / s. Afterward, it can be annealed at an annealing temperature of about 900°C to about 1,100°C for a period of about 30 seconds to about 120 seconds. At this time, if the annealing temperature of the preliminary annealing step (S200) is too low, fine inclusions such as carbides and nitrides are formed from the surface layer, and the inclusions do not grow sufficiently, so the magnetism of the final product may be inferior. On the other hand, if the annealing temperature of the preliminary annealing step (S200) is too high, not only is the distribution of inclusions poor, but the grains grow excessively, causing a large variation in grain size and significant oxidation, which may have an adverse effect on the final product.

[0058] In the preliminary annealing step (S200), the hot-rolled annealed plate can be cooled at a cooling rate of about 10°C / s to about 40°C / s. Additionally, after the preliminary annealing step (S200), the oxide layer formed on the surface of the hot-rolled annealed plate can be removed by shot blasting or by using a pickling solution.

[0059] A warm rolling step (S300) may be performed after a preliminary annealing step (S200). In the warm rolling step (S300), a pre-annealed hot-rolled annealed plate may be heated and then warm-rolled to produce a warm-rolled plate. In the warm rolling step (S300), the pickled hot-rolled annealed plate may be warm-rolled to a thickness of about 0.15 mm or more and about 0.5 mm or less.

[0060] In the warm rolling step (S300), the hot-rolled annealed plate may be heated. The warm rolling step (S300) may be performed at a rolling temperature of approximately 90°C or higher and approximately 300°C or lower. That is, the temperature of the hot-rolled annealed plate may be raised to approximately 90°C to approximately 300°C to perform warm rolling. When the warm rolling step (S300) is performed at a rolling temperature of approximately 90°C or higher and approximately 300°C or lower, the generation of shear bands, which are shear deformation regions within the grains, is reduced, and the area fraction of the texture with {110} / / ND orientation growing in the shear bands may decrease. Additionally, as the dislocation density decreases due to recovery phenomena, the area fraction of the texture with {111} / / ND orientation growing in dislocations or grain boundaries may decrease. Since the area fraction of the {110} / / ND orientation texture and the {111} / / ND orientation texture in the final product are reduced, magnetic properties can be improved. In addition, magnetic anisotropy is reduced, which can decrease the deviation in iron loss and magnetic flux density depending on the measurement direction.

[0061] The warm rolling temperature can be set according to the warm rolling reduction rate. The reduction rate in the warm rolling step (S300) may be approximately 85% to approximately 91%. If the warm rolling reduction rate exceeds 91%, the formation of shear bands, which are internal grain shear deformation regions, becomes severe, and the area fraction of the {110} / / ND orientation texture growing in the shear bands may increase. Additionally, the internal dislocation density may increase, and the area fraction of the {111} / / ND orientation texture growing at dislocations or grain boundaries may increase. Consequently, as the area fraction of the {110} / / ND orientation texture and the area fraction of the {111} / / ND orientation texture in the final product increase, the magnetic properties deteriorate, and magnetic anisotropy increases, which may increase the deviation of iron loss and magnetic flux density depending on the measurement direction. On the other hand, if the warm rolling reduction rate is less than about 85%, the thickness of the steel sheet after warm rolling is thick, and the iron loss of the final product may increase.

[0062] Equation 1 below presents a relationship between the warm rolling temperature and the warm rolling reduction rate for forming a steel plate having an optimal texture orientation fraction.

[0063] <Equation 1>

[0064]

[0065] In Equation 1, T w θ represents the warm rolling temperature (°C), and R represents the warm rolling reduction ratio (%). According to Equation 2 described below, the value of the texture factor F, which exhibits the excellent magnetic properties of the present invention, is 0.6 or higher. Equation 1 represents the warm rolling temperature according to the warm rolling reduction ratio required to control the texture factor F to 0.6 or higher by optimizing the texture orientation fraction. Equation 1 can be derived as follows.

[0066] A texture factor F for each warm rolling reduction rate is derived for each warm rolling reduction rate at a warm rolling reduction rate of 85% to 91%, which satisfies the range of the warm rolling reduction rate of the present invention. Next, when a trend equation is derived between the derived texture factor F and the warm rolling temperature, a critical temperature value is obtained such that the texture factor F becomes 0.6 or greater in the equation. Subsequently, by performing a linear regression analysis with the critical temperature value obtained in this way and each warm rolling reduction rate, the following equation can be derived.

[0067] … (1)

[0068] T in Equation (1) w θ represents the warm rolling temperature (°C), and R represents the warm rolling reduction rate (%). In Equation (1), when the left-hand term is greater than the right-hand term, the texture factor F satisfies 0.6 or more, so the condition of Equation 1 can be presented.

[0069] According to Equation 1, it can be seen that the higher the warm rolling temperature, the more favorable it is for the texture. However, if the rolling temperature of the warm rolling step (S300) exceeds 300℃, oxides are formed on the surface during the rolling process, which deteriorates the appearance quality and reduces the packing density, which may have an adverse effect on the magnetic quality of the final product.

[0070] The warm rolling step (S300) may be carried out under mixed atmosphere conditions to prevent the formation of surface oxides. In one embodiment, the warm rolling step (S300) may be carried out in an atmosphere of 25% to 40% hydrogen (H2) and the remainder nitrogen (N2).

[0071] A final annealing step (S400) may be performed after the warm rolling step (S300). In the final annealing step (S400), the warm rolling plate may be annealed to produce a final annealed plate.

[0072] The final annealing step (S400) can be performed at a temperature that derives the optimal grain size by considering the final magnetic and mechanical properties. For example, the final annealing step (S400) can be performed at an annealing temperature of about 900°C to about 1,100°C, a holding time of about 30 seconds to about 120 seconds, and a heating rate of about 10°C / s or more. If the annealing temperature in the final annealing step (S400) is less than about 900°C, the grain size is fine, and hysteresis loss may increase. On the other hand, if the annealing temperature in the final annealing step (S400) exceeds about 1,100°C, the grain size increases too much, and eddy current loss may increase.

[0073] In addition, the final annealing step (S400) may be carried out under mixed atmosphere conditions to prevent surface oxidation and nitriding. For example, a mixed atmosphere of nitrogen and hydrogen can be used to make the surface condition of the final annealed plate smoother.

[0074] After the final annealing step (S400), a coating step (S500) may be performed. In the coating step (S500), a coating layer may be formed on the final annealed plate. By forming a coating layer through the coating step (S500), punchability may be improved and insulation may be ensured.

[0075] In one embodiment, the non-oriented electrical steel sheet produced by the method for producing a non-oriented electrical steel sheet according to one embodiment may comprise, in weight percent, silicon (Si): 2.5% or more and 3.6% or less, manganese (Mn): 0.1% or more and 0.3% or less, Al: 0.3% or more and 0.8% or less, carbon (C): greater than 0% and 0.003% or less, sulfur (S): greater than 0% and 0.003% or less, nitrogen (N): greater than 0% and 0.003% or less, titanium (Ti): greater than 0% and 0.003% or less, and the remainder being iron (Fe) and unavoidable impurities. The {100} / / ND orientation texture, {111} / / ND orientation texture, and {110} / / ND orientation texture contained in the produced non-oriented electrical steel sheet may satisfy the following Equation 2.

[0076] <Equation 2>

[0077]

[0078] In Equation 2, X {100} / / ND is the area fraction (%) of the texture of the {100} / / ND orientation, X {111} / / ND is the area fraction (%) of the texture of the {111} / / ND orientation, X {110} / / ND represents the area fraction (%) of the texture of the {110} / / ND orientation. F represents the texture factor. F can be 0.6 or greater. If F is less than 0.6, the texture is inferior, resulting in low magnetic flux density and high iron loss when magnetized by an external magnetic field, and the variation in magnetic properties may increase with respect to the rolling direction.

[0079] A texture with {100} / / ND orientation refers to a structure where the {100} plane is parallel to the rolled plane (ND plane) of the steel sheet within 15°. A texture with {111} / / ND orientation refers to a structure where the {111} plane is parallel to the rolled plane (ND plane) of the steel sheet within 15°. Additionally, a texture with {110} / / ND orientation refers to a structure where the {110} plane is parallel to the rolled plane (ND plane) of the steel sheet within 15°. The area fraction of each texture can be measured based on the plane parallel to the rolled plane (ND plane). Since the texture with {100} / / ND orientation is easily magnetized, increasing the fraction of the corresponding texture can reduce iron loss and increase magnetic flux density in the final product. Since the texture with {111} / / ND orientation is unfavorable for magnetization, increasing the fraction of the corresponding texture can increase iron loss and decrease magnetic flux density in the final product. In addition, as the fraction of the {110} / / ND orientation texture decreases, magnetic anisotropy decreases, which can reduce the deviations in iron loss and magnetic flux density measured in the rolling direction and in other directions having a certain angle relative to the rolling direction.

[0080] By controlling the texture of a non-oriented electrical steel sheet produced through a method for manufacturing a non-oriented electrical steel sheet according to one embodiment to satisfy Equation 2, the magnetic properties of the non-oriented electrical steel sheet can be improved, and the deviation of the magnetic properties can be reduced. By forming many orientations that facilitate magnetization, the average iron loss of the non-oriented electrical steel sheet can be reduced. When a non-oriented electrical steel sheet with reduced magnetic deviation is applied to an electric motor core, a high-efficiency motor can be manufactured. On the other hand, if the non-oriented electrical steel sheet does not satisfy Equation 2, the magnetic properties and the deviation of the magnetic properties, that is, magnetic anisotropy, may not be improved.

[0081] In one embodiment, the manufactured non-oriented electrical steel sheet may have a fraction of {100} / / ND orientation texture of 18% or more, a fraction of {111} / / ND orientation texture of 25% or less, and an area fraction of {110} / / ND orientation texture of 7% or less.

[0082] In one embodiment, the manufactured non-oriented electrical steel sheet has an average iron loss defined by the following Equation 3 ( ) may be 12.7 W / kg or less. Preferably, the manufactured non-oriented electrical steel sheet has an average iron loss ( ) may be 12.68 W / kg or less.

[0083] <Equation 3>

[0084]

[0085] In Equation 3, W 0° is iron loss in the rolling direction (W 10 / 400 Standard), W 45° is the iron loss in the 45° direction relative to the rolling direction, W 90° represents the iron loss in the 90° direction with respect to the rolling direction. Here, iron loss (W 10 / 400 The standard corresponds to the energy loss (W / kg) generated in the iron core when subjected to an alternating magnetic field of 1.0 T at 400 Hz.

[0087] The present invention will be explained in more detail below through experimental examples. However, the following experimental examples are intended to explain the present invention more specifically, and the scope of the present invention is not limited by the following experimental examples. The following experimental examples may be appropriately modified or changed by those skilled in the art within the scope of the present invention.

[0089] division Si (wt%) Al (weight%) Mn (weight%) C (weight%) S (Weight%) N (weight%) Ti (weight%) Examples 1 to 12 3.43 0.706 0.239 0.0014 0.0009 0.0011 0.0010 Comparative Examples 1–13 3.43 0.706 0.239 0.0014 0.0009 0.0011 0.0010

[0090] Table 1 shows the component compositions of Examples 1 to 12 and Comparative Examples 1 to 13.

[0091] Examples 1 to 12 and Comparative Examples 1 to 13 produced hot-rolled plates having the thickness after hot rolling shown in Table 2 below by heating a slab containing the component composition listed in Table 1 at a temperature of about 1130°C for 200 minutes, and then performing hot rolling under conditions of a finishing rolling temperature of about 880°C and a coiling temperature of about 580°C.

[0092] Subsequently, the manufactured hot-rolled plate was pre-annealed at 1000°C for 100 seconds, and shot blasting and pickling were performed on the pre-annealed hot-rolled plate. At this time, the pre-annealing was carried out in an atmosphere of 100% N2, and the heating rate was approximately 30°C / s and the cooling rate was approximately -10°C / s.

[0093] Subsequently, the manufactured hot-rolled annealed plate was hot-rolled at the hot-rolling temperature and reduction rate shown in Table 2 below to produce a hot-rolled plate with a thickness of approximately 0.25 mm. At this time, the hot-rolling was carried out in a mixed atmosphere of 40% hydrogen (H2) and 60% nitrogen (N2).

[0094] The manufactured hot plate was subjected to final annealing at a temperature of approximately 1000°C for approximately 45 seconds to produce a final annealed plate. At this time, the final annealing was carried out in a mixed atmosphere of 40% hydrogen (H2) and 60% nitrogen (N2), and the heating rate was approximately 100°C / s. Subsequently, a final product (e.g., non-oriented electrical steel) was produced through a coating step.

[0096] division Thickness after hot rolling (mm) Warm rolling temperature (°C) Warm rolling reduction ratio (%) Equation 1( ) Collective Organization Fraction (%) F {100} / / ND {111} / / ND {110} / / ND Comparative Example 1 1.67 25 85 X 17.5 25 6.2 0.56 Comparative Example 2 1.92 25 87 X 17.1 26.2 6.5 0.52 Comparative Example 3 2.27 25 89 X 16.8 27.5 6.9 0.49 Comparative Example 4 2.78 25 91 X 16.5 28.1 7.4 0.46 Example 1 1.67 100 85 O 18.1 24.2 5.9 0.60 Comparative Example 5 1.92 100 87 X 17.5 25.7 6.3 0.55 Comparative Example 6 2.27 100 89 X 17.1 26.6 6.8 0.51 Comparative Example 7 2.78 100 91 X 16.7 27.3 7.4 0.48 Example 2 1.67 150 85 O 18.7 23.4 5.4 0.65 Example 3 1.92 150 87 O 18.5 24.2 5.6 0.62 Example 4 2.27 150 89 O 18.3 24.6 5.7 0.60 Comparative Example 8 2.50 150 90 X 18.2 24.9 5.9 0.59 Comparative Example 9 2.78 150 91 X 18.1 25.9 6.3 0.56 Example 5 1.67 200 85 O 19.9 20.7 4.7 0.78 Example 6 1.92 200 87 O 19.6 21.5 4.9 0.74 Example 7 2.27 200 89 O 19.2 22.6 5.3 0.69 Example 8 2.78 200 91 O 18.9 23.1 5.8 0.65 Example 9 1.67 300 85 O 22.2 19.4 4.1 0.94 Example 10 1.92 300 87 O 21.8 20.4 4.3 0.88 Example 11 2.27 300 89 O 21.4 21.2 4.7 0.83 Example 12 2.78 300 91 O 20.9 21.8 5.2 0.77 Comparative Example 10 1.67 400 85 O 22.8 18.7 3.7 1.02 Comparative Example 11 1.92 400 87 O 22.3 19.6 3.9 0.95 Comparative Example 12 2.27 400 89 O 21.9 20.5 4.4 0.88 Comparative Example 13 2.78 400 91 O 21.1 21.3 4.9 0.81

[0098] Table 2 shows the hot rolling conditions, area fraction of texture, and values ​​of texture factor F for Examples 1 to 12 and Comparative Examples 1 to 13.

[0099] Table 2 shows the warm rolling temperature, warm rolling reduction ratio, and whether Equation 1 is satisfied under the warm rolling conditions of Examples 1 to 12 and Comparative Examples 1 to 13. Equation 1 is It corresponds to, where T w represents the warm rolling temperature (°C), and R represents the warm rolling reduction rate (%).

[0100] In addition, for Examples 1 to 12 and Comparative Examples 1 to 13, the area fractions of {100} / / ND, {111} / / ND, and {110} / / ND textures were measured via EBSD analysis, and the texture factor F value was derived. The results are shown in Table 2 above. The texture factor F is Defined as, and X {100} / / ND is the area fraction (%) of the texture of the {100} / / ND orientation, X {111} / / ND is the area fraction (%) of the texture of the {111} / / ND orientation, X {110} / / ND represents the area fraction (%) of the aggregate of the {110} / / ND orientation.

[0101] Referring to Table 2, it can be seen that Comparative Examples 1 to 4 satisfy the warm rolling reduction ratio range of 85% to 91%, but do not satisfy the warm rolling temperature range of 90°C to 300°C and Equation 1. It can be seen that Comparative Examples 5 to 9 satisfy the warm rolling reduction ratio range and the warm rolling temperature range, but do not satisfy Equation 1. It can be seen that Comparative Examples 10 to 13 satisfy the warm rolling reduction ratio range and Equation 1, but do not satisfy the warm rolling temperature range. On the other hand, it can be seen that Examples 1 to 12 satisfy the warm rolling reduction ratio range, the warm rolling temperature range, and Equation 1.

[0102] It can be seen that Comparative Examples 1 to 9 have a texture factor F value of less than 0.6, and thus do not satisfy Equation 2 (F≥0.6). It can be seen that Examples 1 to 12 and Comparative Examples 10 to 13 have a texture factor F value of 0.6 or greater, and thus satisfy Equation 2 (F≥0.6).

[0103] FIG. 2 is an image showing the surface of a non-oriented electrical steel sheet according to an embodiment and a comparative example of the present invention, showing the surface of the steel sheets of Example 5, Example 9, and Comparative Example 10. Referring to FIG. 2, Examples 5 and 9, with warm rolling temperatures of 200°C and 300°C respectively, showed good appearance quality. However, in the case of Comparative Example 10, with a warm rolling temperature of 400°C, oxides were formed on the surface, and it was found that the appearance quality deteriorated. Therefore, it can be seen that Comparative Examples 10 to 13 in Table 2 have a deteriorated appearance quality because the warm rolling temperature exceeds 300°C.

[0105] division Magnetic measurement Comparative Example 1 12.78 0.0016 Comparative Example 2 12.97 0.0017 Comparative Example 3 13.13 0.0020 Comparative Example 4 13.28 0.0022 Example 1 12.68 0.0015 Comparative Example 5 12.84 0.0016 Comparative Example 6 13.02 0.0020 Comparative Example 7 13.11 0.0022 Example 2 12.43 0.0013 Example 3 12.55 0.0014 Example 4 12.64 0.0015 Comparative Example 8 12.71 0.0016 Comparative Example 9 12.78 0.0016 Example 5 12.02 0.0011 Example 6 12.27 0.0012 Example 7 12.51 0.0013 Example 8 12.66 0.0015 Example 9 11.95 0.0008 Example 10 12.18 0.0009 Example 11 12.36 0.0011 Example 12 12.59 0.0013 Comparative Example 10 12.71 0.0007 Comparative Example 11 12.88 0.0008 Comparative Example 12 13.09 0.0010 Comparative Example 13 13.24 0.0012

[0107] Table 3 shows the magnetic measurement results of Examples 1 to 12 and Comparative Examples 1 to 13. Magnetic measurements were performed using the Epstein Frame measurement method by taking 12 specimens of size 300 mm × 30 mm in the rolling direction and 12 specimens perpendicular to the rolling direction.

[0108] Average iron loss in Table 3 silver It can be derived as. W 0° is iron loss in the rolling direction (W 10 / 400 Standard), W 45° is the iron loss in the 45° direction relative to the rolling direction, W 90° represents the iron loss in the 90° direction with respect to the rolling direction. W 10 / 400 is the iron loss at 400 Hz and a magnetic flux density of 1.0 Tesla.

[0109] FIG. 3 shows the magnetic flux density (B) according to the magnetic flux density measurement direction (angle with respect to the rolling direction of the measurement direction) of non-oriented electrical steel sheets according to Comparative Examples 4, 7, 2, and 9 of the present invention. 50This is a graph showing the values. As shown in FIG. 3, in the case of a general non-oriented electrical steel sheet, the magnetic flux density is highest in the rolling direction (0°), and the magnetic flux density is lowest in the direction from 45° to 60° relative to the rolling direction. The magnetic flux density values ​​according to the magnetic flux density measurement direction (angle of the measurement direction relative to the rolling direction) tend to be mirror-symmetric with respect to the direction perpendicular to the rolling direction (90°).

[0110] For non-oriented electrical steel sheets, magnetic flux density (B) according to the angle of the measurement direction in the range where the angle of the measurement direction with respect to the rolling direction is 0° to 45° 50 By performing regression analysis on the values ​​(based on the standard), the magnetic flux density (B) according to the angle of the above measurement direction 50 Criteria) The absolute value of the slope ...was derived. The results are shown in Table 3. Of a non-oriented electrical steel sheet according to one embodiment of the present invention The value may be 0.0015 or less. When the value is 0.0015 or less, magnetic anisotropy may be low. In other words, the deviation of magnetic flux density (or iron loss) in the rolling direction and in other directions having a certain angle relative to the rolling direction may be reduced.

[0111] Referring to Table 3, Comparative Examples 1 to 13 have average iron loss ( It can be seen that the value exceeds 12.7 W / kg. In addition, Comparative Examples 1 to 9 are It can be seen that the value exceeds 0.0015. Comparative Examples 10 to 13 are The value is 0.0015 or less, but the average iron loss ( It can be seen that the value exceeds 12.7 W / kg. Examples 1 to 12 show average iron loss ( The value of ) is 12.7 W / kg or less, and It can be confirmed that the value is 0.0015 or less.

[0112] Although the present invention has been described with reference to an embodiment illustrated in the drawings, this is merely illustrative, and those skilled in the art will understand that various modifications and variations of the embodiments are possible therefrom. Accordingly, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims.

Claims

Claim 1 A method for manufacturing a non-oriented electrical steel sheet comprises the steps of: manufacturing a hot-rolled sheet by hot-rolling a slab comprising, in weight percent, silicon (Si): 2.5% or more and 3.6% or less, manganese (Mn): 0.1% or more and 0.3% or less, Al: 0.3% or more and 0.8% or less, carbon (C): greater than 0% and 0.003% or less, sulfur (S): greater than 0% and 0.003% or less, nitrogen (N): greater than 0% and 0.003% or less, titanium (Ti): greater than 0% and 0.003% or less, and the remainder being iron (Fe) and unavoidable impurities; and manufacturing a hot-rolled sheet by hot-rolling the hot-rolled sheet at a hot-rolling temperature of 90°C to 300°C. A method for manufacturing a non-oriented electrical steel sheet, comprising the step of finally annealing the hot rolling sheet to produce a final annealed sheet; wherein, in the step of manufacturing the hot rolling sheet, the hot rolling reduction rate is greater than 85% and less than or equal to 91%, and the hot rolling temperature and the hot rolling reduction rate satisfy the following Equation 1. (Here, Tw represents the warm rolling temperature (°C), and R represents the warm rolling reduction rate (%).) Claim 2 delete Claim 3 A method for manufacturing a non-oriented electrical steel sheet according to claim 1, wherein the step of manufacturing a hot-rolled sheet by hot-rolling the hot-rolled sheet is performed in a mixed atmosphere of nitrogen (N2) and 25% to 40% hydrogen (H2). Claim 4 A method for manufacturing a non-oriented electrical steel sheet according to claim 1, further comprising, between the step of manufacturing the hot-rolled sheet and the step of manufacturing the hot-rolled sheet, a step of pre-annealing the hot-rolled sheet to manufacture a hot-rolled annealed sheet. Claim 5 A method for manufacturing a non-oriented electrical steel sheet according to claim 1, further comprising a coating step of forming a coating layer on the final annealed sheet. Claim 6 A non-oriented electrical steel sheet comprising, in weight percent, silicon (Si): 2.5% or more and 3.6% or less, manganese (Mn): 0.1% or more and 0.3% or less, Al: 0.3% or more and 0.8% or less, carbon (C): greater than 0% and 0.003% or less, sulfur (S): greater than 0% and 0.003% or less, nitrogen (N): greater than 0% and 0.003% or less, titanium (Ti): greater than 0% and 0.003% or less, and the remainder being iron (Fe) and unavoidable impurities, wherein the non-oriented electrical steel sheet has an area fraction of a texture with {100} / / ND orientation of 18% or more. Claim 7 In claim 6, the {100} / / ND orientation texture, {111} / / ND orientation texture, and {110} / / ND orientation texture included in the above non-oriented electrical steel sheet satisfy the following Equation 2, the non-oriented electrical steel sheet. (Here, X {100} / / ND is the area fraction (%) of the texture of the {100} / / ND orientation, X {111} / / ND is the area fraction (%) of the texture of the {111} / / ND orientation, X {110} / / ND ... represents the area fraction (%) of the aggregate of the {110} / / ND orientation. Claim 8 In paragraph 6, the above non-oriented electrical steel is a non-oriented electrical steel having an area fraction of {111} / / ND orientation texture of 25% or less. Claim 9 In paragraph 6, the above non-oriented electrical steel sheet is a non-oriented electrical steel sheet having an area fraction of {110} / / ND orientation texture of 7% or less. Claim 10 In paragraph 6, the above-mentioned non-oriented electrical steel sheet has an average iron loss defined by the following Equation 3 ( Non-oriented electrical steel sheet having ) 12.7 W / kg or less. <Equation 3> (Here, W 0° is iron loss in the rolling direction (W 10 / 400 Standard), W 45° is the iron loss in the 45° direction relative to the rolling direction, W 90° represents the iron loss in the 90° direction relative to the rolling direction.) Claim 11 In claim 6, the above-mentioned non-oriented electrical steel sheet has a magnetic flux density (B) according to the angle of the measurement direction in the range where the angle of the measurement direction with respect to the rolling direction is 0° to 45°. 50 Non-oriented electrical steel sheet having an absolute value of the slope of the standard of 0.0015 or less.

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