Non-oriented electrical steel sheet and manufacturing method therefor

Abstract

The present invention provides a non-oriented electrical steel sheet comprising 3-3.8 wt% of silicon (Si), 0.2-0.4 wt% of manganese (Mn), 0.8-1.5 wt% of aluminum (Al), carbon (C) in an amount greater than 0 and less than or equal to 0.005 wt%, phosphorus (P) in an amount greater than 0 and less than or equal to 0.02 wt%, sulfur (S) in an amount greater than 0 and less than or equal to 0.005 wt%, nitrogen (N) in an amount greater than 0 and less than or equal to 0.005 wt%, titanium (Ti) in an amount greater than 0 and less than or equal to 0.005 wt%, and the balance of iron (Fe) and inevitable impurities, wherein the non-oriented electrical steel sheet has, under an induced magnetic flux density of 1T, an average of slopes for respective frequency sections satisfying relation 1 ((A+B+C+D+E+F) / 6 < 0.0553).

Description

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

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

[0002] In the case of non-oriented electrical steel sheets used in motors, the automotive industry is shifting toward reducing the production of internal combustion engine vehicles and increasing the production of electric vehicles. Furthermore, along with the recent increase in demand for electric vehicles, there is a requirement for electrical steel sheets, which are key components, to possess high efficiency and high output.

[0003] The efficiency of a motor depends on the iron loss of electrical steel sheets. Iron loss is the energy loss that occurs during the magnetization process of the electrical steel material, and its unit is W / kg. Types of iron loss include hysteresis loss, eddy current loss, and anomalous loss. Hysteresis loss is the loss caused by hindering domain wall movement and refers to the area inside the hysteresis loss graph. Hysteresis loss is influenced by the distribution of secondary phases, grain size, and texture. Eddy current loss is a type of eddy current loss caused by currents generated when magnetic moments are induced in the opposite direction to the applied magnetic field; it is influenced by the thickness of the electrical steel sheet and resistivity (chemical composition). Anomalous loss is the loss caused by eddy currents formed within grains or domains, and it is influenced by the thickness of the steel sheet, grain size, and domain width.

[0004] To improve the iron loss of electrical steel sheets, there are methods to increase resistivity by adding major alloying elements such as silicon (Si), manganese (Mn), and aluminum (Al), or to thin the material. However, when resistivity is increased by adding alloying elements, increasing the amount of alloying elements can lead to a decrease in magnetic flux density and reduced rolling performance, making thinning difficult. Furthermore, major alloying elements readily combine with impurity elements such as carbon (C), sulfur (S), nitrogen (N), and titanium (Ti) to form precipitates, and these formed precipitates can hinder the movement of magnetic domains formed by an applied magnetic field, thereby acting as a cause for the deterioration of magnetic properties.

[0005] Embodiments of the present invention can provide non-oriented electrical steel sheets having low iron loss at various frequencies.

[0006] One embodiment of the present invention is a non-oriented electrical steel sheet comprising, in wt%, silicon (Si): 3 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.4 wt%, aluminum (Al): 0.8 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.005 wt%, phosphorus (P): greater than 0 and less than or equal to 0.02 wt%, sulfur (S): greater than 0 and less than or equal to 0.005 wt%, nitrogen (N): greater than 0 and less than or equal to 0.005 wt%, titanium (Ti): greater than 0 and less than or equal to 0.005 wt%, and the remainder being iron (Fe) and unavoidable impurities, wherein the non-oriented electrical steel sheet satisfies Equation 1 ((A+B+C+D+E+F) / 6 < 0.0553) for the average slope of the slope for each frequency range under an induced magnetic flux density of 1T. It is provided.

[0007] In this embodiment, the W 10 / 50 ε is the iron loss at a frequency of 50 Hz under an induced magnetic flux density of 1T, and W 10 / 100 ε is the iron loss at a frequency of 100 Hz under an induced magnetic flux density of 1T, and the above W 10 / 200ε is the iron loss at a frequency of 200 Hz under an induced magnetic flux density of 1T, and W 10 / 400 ε is the iron loss at a frequency of 400 Hz under an induced magnetic flux density of 1T, and the above W 10 / 600 is the iron loss at a frequency of 600 Hz under an induced magnetic flux density of 1T, and the above W 10 / 800 ε is the iron loss at a frequency of 800 Hz under an induced magnetic flux density of 1T, and the above W 10 / 1000 It can be an iron loss at a frequency of 1000 Hz under an inductive flux density of 1T.

[0008] In this embodiment, the non-oriented electrical steel sheet has an initial iron loss (W 10 / 50 ) and under an induced magnetic flux density of 1T, the average of the slopes for each frequency range is Equation 2(W 10 / 50 * (A+B+C+D+E+F) / 6 < 0.046) can be satisfied.

[0009] In this embodiment, the efficiency of the motor manufactured by punching and laminating the non-oriented electrical steel sheet can be 90% or more.

[0010] One embodiment of the present invention is a method for manufacturing a non-oriented electrical steel sheet, comprising the steps of: hot rolling a slab comprising, in wt%, silicon (Si): 3 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.4 wt%, aluminum (Al): 0.8 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.005 wt%, phosphorus (P): greater than 0 and less than or equal to 0.02 wt%, sulfur (S): greater than 0 and less than or equal to 0.005 wt%, nitrogen (N): greater than 0 and less than or equal to 0.005 wt%, titanium (Ti): greater than 0 and less than or equal to 0.005 wt%, and the remainder being iron (Fe) and unavoidable impurities to produce a hot-rolled sheet; hot rolling annealing the hot-rolled sheet to produce a hot-rolled annealed sheet; and cold rolling the hot-rolled annealed sheet to produce a cold-rolled sheet. and a step of manufacturing a cold-rolled annealed plate by cold-rolling and annealing the cold-rolled plate; wherein the tension applied to the cold-rolled plate in the step of manufacturing the cold-rolled annealed plate is 0.2 kgf / mm 24.0 kgf / mm or more 2 A method for manufacturing a non-oriented electrical steel sheet with less than [amount] is provided.

[0011] In this embodiment, the non-oriented electrical steel sheet can satisfy Equation 1 ((A+B+C+D+E+F) / 6 < 0.0553) for the average slope of each frequency range under an inductive magnetic flux density of 1T.

[0012] In this embodiment, the W 10 / 50 ε is the iron loss at a frequency of 50 Hz under an induced magnetic flux density of 1T, and W 10 / 100 ε is the iron loss at a frequency of 100 Hz under an induced magnetic flux density of 1T, and the above W 10 / 200 ε is the iron loss at a frequency of 200 Hz under an induced magnetic flux density of 1T, and W 10 / 400 ε is the iron loss at a frequency of 400 Hz under an induced magnetic flux density of 1T, and the above W 10 / 600 is the iron loss at a frequency of 600 Hz under an induced magnetic flux density of 1T, and the above W 10 / 800 ε is the iron loss at a frequency of 800 Hz under an induced magnetic flux density of 1T, and the above W 10 / 1000 It can be an iron loss at a frequency of 1000 Hz under an inductive flux density of 1T.

[0013] In this embodiment, the non-oriented electrical steel sheet has an initial iron loss (W 10 / 50 ) and under an induced magnetic flux density of 1T, the average of the slopes for each frequency range is given by the following Equation 2(W 10 / 50 * (A+B+C+D+E+F) / 6 < 0.046) can be satisfied.

[0014] In this embodiment, the step of manufacturing the cold-rolled annealed plate may be performed under conditions of a heating rate of 10℃ / s or more, a cold-rolled annealing temperature of 900℃ to 1100℃, a cold-rolled annealing time of 30s to 90s, and a cooling rate of 30℃ / s or more.

[0015] In this embodiment, the step of manufacturing the cold-rolled annealed plate may be performed in a mixed atmosphere consisting of 20% to 50% hydrogen and the remainder nitrogen.

[0016] In this embodiment, the residual oxygen in the furnace where the step of manufacturing the cold-rolled annealed plate is performed may be less than 900 ppm.

[0017] In this embodiment, after the step of manufacturing the cold-rolled annealed plate, a coating step for forming an insulating coating layer on the cold-rolled annealed plate may be further performed.

[0018] In this embodiment, after the coating step, a step of punching and laminating the cold-rolled annealed plate having the insulating coating layer formed thereon may be further performed.

[0019] In this embodiment, the efficiency of the motor manufactured from the stamped and laminated cold-rolled annealed plate may be 90% or more.

[0020] 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.

[0021] According to one embodiment of the present invention as described above, a non-oriented electrical steel sheet can have low iron loss at various frequencies. Of course, the scope of the present invention is not limited by this effect.

[0022] 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.

[0023] Figure 2 is a schematic diagram illustrating a case where no abnormal grain growth (AGG) occurs in a non-oriented electrical steel sheet.

[0024] Figure 3 is a schematic diagram illustrating the case where abnormal grain growth occurs in a non-oriented electrical steel sheet.

[0025] Figure 4 is a graph showing the change in iron loss according to frequency in the case where no abnormal grain growth occurs in the non-oriented electrical steel sheet and in the case where abnormal grain growth occurs in the non-oriented electrical steel sheet.

[0026] 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.

[0027] 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.

[0028] In the following examples, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] In this specification, "A and / or B" indicates the case where it is A, B, or both A and B. And, "at least one of A and B" indicates the case where it is A, B, or both A and B.

[0033] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. When describing with reference to the drawings, identical or corresponding components are given the same reference numerals, and redundant descriptions thereof will be omitted.

[0034] A non-oriented electrical steel sheet according to one embodiment of the present invention may comprise, in wt%, silicon (Si): 3 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.4 wt%, aluminum (Al): 0.8 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.005 wt%, phosphorus (P): greater than 0 and less than or equal to 0.02 wt%, sulfur (S): greater than 0 and less than or equal to 0.005 wt%, nitrogen (N): greater than 0 and less than or equal to 0.005 wt%, titanium (Ti): greater than 0 and less than or equal to 0.005 wt%, and the remainder being iron (Fe) and unavoidable impurities.

[0035] Silicon (Si) can be a major additive element as it increases resistivity and lowers eddy current losses. Silicon (Si) may be included in an amount of 3 wt% to 3.8 wt%. If silicon (Si) is included in an amount less than 3 wt%, iron loss reduction may be insufficient. That is, if silicon (Si) is included in an amount less than 3.0 wt%, it may be difficult to obtain low iron loss. On the other hand, if silicon (Si) exceeds 3.8 wt%, permeability and magnetic flux density may decrease. In addition, if silicon (Si) exceeds 3.8 wt%, brittleness increases, making cold rolling difficult and potentially lowering productivity.

[0036] Manganese (Mn) can increase resistivity and improve texture together with silicon. Manganese (Mn) may be included in an amount of 0.2 wt% to 0.4 wt%. If manganese (Mn) is included in an amount less than 0.2 wt%, fine MnS precipitates may form, which may inhibit grain growth. On the other hand, if manganese (Mn) is added in an amount greater than 0.4 wt%, coarse MnS precipitates may form, which may degrade magnetic properties such as reduced magnetic flux density. Additionally, if manganese (Mn) is included in an amount greater than 0.4 wt%, the reduction in iron loss is small relative to the amount added, and a decrease in cold rolling performance may occur.

[0037] Aluminum (Al) can be a major additive element as a component that increases resistivity along with silicon to lower eddy current losses. Aluminum (Al) can play a role in reducing magnetic deviation by decreasing magnetic anisotropy. Aluminum (Al) can induce AlN precipitation upon contact with nitrogen. Aluminum (Al) may be included in an amount of 0.8 wt% to 1.5 wt%. If the aluminum (Al) content is less than 0.8 wt%, it is difficult to expect the aforementioned effects, and it may increase deviations in magnetic properties by forming fine nitrides. If the aluminum (Al) content exceeds 1.5 wt%, a decrease in cold rolling performance occurs, and magnetic properties may deteriorate due to the excessive formation of nitrides which reduces magnetic flux density.

[0038] Carbon (C) is an element that increases iron loss by forming carbides such as TiC and NbC, so it may be desirable to have a lower carbon content in non-oriented electrical steel sheets. Carbon may be included in an amount greater than 0 and less than or equal to 0.005 wt%. When converted to ppm units, carbon may be included in an amount greater than 0 and less than or equal to 50 ppm. If carbon is included in an amount greater than 0.005 wt%, it may cause self-aging and degrade the magnetic properties of the non-oriented electrical steel sheets. If carbon is included in an amount less than or equal to 0.005 wt%, the self-aging phenomenon may be suppressed.

[0039] Phosphorus (P) is a grain boundary segregation element that can develop texture. Phosphorus (P) may be included in an amount greater than 0 and less than or equal to 0.02 wt%. When converted to ppm units, phosphorus may be included in an amount greater than 0 and less than or equal to 200 ppm. If phosphorus (P) is included in an amount greater than 0.02 wt%, grain growth may be inhibited due to segregation effects, magnetic properties may deteriorate, and cold rolling performance may decrease.

[0040] Sulfur (S) forms precipitates such as MnS and CuS, which increase iron loss and inhibit grain growth, so it may be desirable to add it in the lowest possible amount. Sulfur (S) may be included in an amount greater than 0 and less than or equal to 0.005 wt%. When converted to ppm units, sulfur may be included in an amount greater than 0 and less than or equal to 50 ppm. If sulfur (S) is included in an amount greater than 0.005 wt%, precipitates such as MnS and CuS may be formed, which may increase iron loss and inhibit grain growth.

[0041] Nitrogen (N) forms precipitates such as AlN, TiN, and NbN, which increase iron loss and inhibit grain growth; therefore, it may be desirable to add it in the lowest possible amount. Nitrogen (N) may be included in an amount greater than 0 and less than or equal to 0.005 wt%. When converted to ppm units, nitrogen may be included in an amount greater than 0 and less than or equal to 50 ppm. If nitrogen (N) is included in an amount greater than 0.005 wt%, precipitates such as AlN, TiN, and NbN may be formed, which may increase iron loss and inhibit grain growth.

[0042] Titanium (Ti) can inhibit grain growth by forming fine precipitates such as TiC and TiN. Since magnetic properties deteriorate as titanium (Ti) is added, it may be desirable to add as little titanium (Ti) as possible. Titanium (Ti) may be included in an amount greater than 0 and less than or equal to 0.005 wt%. When converted to ppm units, titanium may be included in an amount greater than 0 and less than or equal to 50 ppm. If titanium is included in an amount greater than 0.005 wt%, fine precipitates such as TiC and TiN may be formed, which may inhibit grain growth and deteriorate magnetic properties.

[0043] 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.

[0044] Referring to FIG. 1, a method for manufacturing a non-oriented electrical steel sheet may include a hot rolling step (S100), a hot rolling annealing step (S200), a cold rolling step (S300), and a cold rolling annealing step (S400).

[0045] In the hot rolling step (S100), the slab may be reheated, then hot-rolled at a predetermined finishing rolling temperature, and then cooled and coiled. At this time, in the 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.

[0046] The slab may contain silicon (Si), manganese (Mn), aluminum (Al), carbon (C), phosphorus (P), sulfur (S), nitrogen (N), titanium (Ti), the remainder being iron (Fe) and unavoidable impurities. Specifically, the slab may contain, in wt%, silicon (Si): 3 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.4 wt%, aluminum (Al): 0.8 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.005 wt%, phosphorus (P): greater than 0 and less than or equal to 0.02 wt%, sulfur (S): greater than 0 and less than or equal to 0.005 wt%, nitrogen (N): greater than 0 and less than or equal to 0.005 wt%, titanium (Ti): greater than 0 and less than or equal to 0.005 wt%, the remainder being iron (Fe) and unavoidable impurities.

[0047] In the hot rolling step (S100), the slab can be reheated, and then the reheated slab can be hot-rolled to produce a hot-rolled plate. For example, the slab on which the hot rolling step (S100) is performed can be called a hot-rolled plate.

[0048] In the hot rolling step (S100), the slab may be reheated. The slab reheating temperature in the hot rolling step (S100) may be 1000°C to 1250°C. If the slab reheating temperature is less than 1000°C, it may be difficult to perform hot rolling. On the other hand, if the slab reheating temperature exceeds 1250°C, precipitates such as C, S, and N within the slab may be re-dissolved, and fine precipitates may be generated during subsequent rolling and annealing processes, which may inhibit grain growth and degrade magnetic properties. Therefore, if the slab reheating temperature in the hot rolling step (S100) satisfies 1000°C to 1250°C, the deterioration of hot rolling performance and the deterioration of magnetic properties can be prevented.

[0049] The hot rolling step (S100) may finish rolling the slab at a predetermined finish rolling temperature. At this time, the finish rolling temperature may be 860°C to 900°C. If the finish rolling temperature is less than 860°C, TiC precipitates that adversely affect magnetism may be formed, hindering the movement of magnetic domains of the final product and reducing the magnetic properties of the final product.

[0050] In addition, the hot rolling step (S100) may cool the hot-rolled slab to a predetermined coiling temperature (CT) and coil it. At this time, the coiling temperature may be 550°C to 650°C. If the coiling temperature is below 550°C, brittleness increases, and plate breakage may occur during coiling. On the other hand, if the coiling temperature exceeds 650°C, fine TiC precipitates may form during cooling, which may increase iron loss.

[0051] The thickness of the hot-rolled plate produced through the hot rolling step (S100) may be 1.8 mm to 2.6 mm. At this time, if the thickness of the hot-rolled plate exceeds 2.6 mm, the cold rolling reduction rate increases, which may result in a deterioration of the texture.

[0052] A hot rolling annealing step (S200) may be performed after the hot rolling step (S100). A hot-rolled plate in which the hot rolling annealing step (S200) has been performed may be called a hot-rolled annealed plate. The hot rolling annealing step (S200) may be performed under conditions where the heating rate is 20℃ / s or higher, the holding temperature (e.g., hot rolling annealing temperature) is 900℃ to 1100℃, the holding time (e.g., hot rolling annealing time) is 30s to 150s, and the cooling rate is 30℃ / s or higher. Specifically, in the hot rolling annealing step (S200), the hot-rolled sheet is heated at a heating rate (or heating rate) of 20°C / s or more, and the heated hot-rolled sheet is held (e.g., annealed) at a holding temperature (e.g., hot rolling annealing temperature) of 900°C to 1100°C for a holding time (e.g., hot rolling annealing time) of 30 s to 150 s, and can be cooled at a cooling rate of 30°C / s or more. If the holding temperature (e.g., hot rolling annealing temperature) is less than 900°C, grain growth is insufficient, and fine grains are formed, which may result in inferior magnetic properties of the non-oriented electrical steel sheet produced. On the other hand, if the holding temperature (e.g., hot rolling annealing temperature) exceeds 1100℃, the grains may grow excessively, leading to severe grain size variations and significant oxidation, and precipitates may be re-dissolved and finely precipitated during subsequent processes, which may result in inferior magnetic properties of the non-oriented electrical steel sheet produced.

[0053] A pickling step may be performed after the hot rolling annealing step (S200). In the pickling step, an oxide layer formed on the surface of the hot-rolled plate can be removed using a pickling solution. The pickling step may be performed before the cold rolling step (S300).

[0054] A cold rolling step (S300) may be performed after a hot rolling annealing step (S200). A hot rolling annealed plate that has undergone the cold rolling step (S300) may be called a cold rolled plate. In the cold rolling step (S300), the hot rolled plate may be cold rolled with a reduction rate of 70% or more. Cold rolling may be performed at room temperature. Alternatively, to impart rollability during cold rolling, the plate temperature may be raised to 100°C to 200°C and warm rolling may be performed. The thickness of the cold rolled plate that has undergone the cold rolling step (S300) may be 0.3mm or less.

[0055] A cold rolling annealing step (S400) may be performed after the cold rolling step (S300). A cold rolled plate in which the cold rolling annealing step (S400) has been performed may be called a cold rolling annealing plate. The cold rolling annealing step (S400) may be performed under conditions where the heating rate is 10℃ / s or higher, the holding temperature (e.g., cold rolling annealing temperature) is 900℃ to 1100℃, the holding time (e.g., cold rolling annealing time) is 30s to 90s, and the cooling rate is 30℃ / s or higher. Specifically, in the cold rolling annealing step (S400), the cold rolled plate is heated at a heating rate (or heating rate) of 10°C / s or more, and the heated cold rolled plate is held (e.g., annealed) at a holding temperature (e.g., cold rolling annealing temperature) of 900°C to 1100°C for a holding time (e.g., cold rolling annealing time) of 30 s to 90 s, and can be cooled at a cooling rate of 30°C / s or more. If the holding temperature (e.g., cold rolling annealing temperature) is less than 900°C, the grain size is fine, and iron loss may increase. On the other hand, if the holding temperature (e.g., cold rolling annealing temperature) is greater than 1100°C, the grain size becomes coarse, and eddy current loss may increase.

[0056] In one embodiment, the cold rolling annealing step (S400) may be performed in a mixed atmosphere consisting of 20% to 50% hydrogen and the remainder nitrogen. Additionally, the residual oxygen in the furnace where the cold rolling annealing step (S400) is performed may be less than 900 ppm. If the residual oxygen in the furnace where the cold rolling annealing step (S400) is performed is 900 ppm or more, the oxygen concentration in the furnace where the cold rolling annealing (or heat treatment) is performed is high, and a large amount of oxidation may occur.

[0057] In one embodiment, the tension applied to the cold-rolled plate (or cold-rolled annealed plate) during the cold-rolled annealing step (S400) is 0.2 kgf / mm 2 Up to 4 kgf / mm 2 It may be. Specifically, the tension applied to the cold-rolled plate (or cold-rolled annealed plate) in the furnace where the cold-rolled annealing step (S400) is performed is 0.2 kgf / mm 2 4 kgf / mm or more 2 It may be less than. Tension applied to the cold-rolled sheet (or cold-rolled annealed sheet) is 0.2 kgf / mm 2 If it is less than that, shape problems (e.g., edge waves) may occur, making it difficult to manufacture motors by punching and laminating non-oriented electrical steel sheets. On the other hand, the tension applied to the cold-rolled sheet (or cold-rolled annealed sheet) is 4 kgf / mm 2 In such cases, abnormal grain growth may occur (or be generated), where certain particles grow significantly larger than others, which may increase the iron loss of the manufactured non-oriented electrical steel sheet. Specifically, the tension applied to the cold-rolled sheet (or cold-rolled annealed sheet) is 4 kgf / mm 2In such cases, large grains are generated by Strain-Induced Boundary Migration (SIBM), which can increase the iron loss of the manufactured non-oriented electrical steel sheets. For example, while iron loss in non-oriented electrical steel sheets increases with increasing frequency, if abnormal grain growth occurs, the iron loss can increase sharply with increasing frequency. Therefore, the tension applied to the cold-rolled sheet (or cold-rolled annealed sheet) is 0.2 kgf / mm 2 Up to 4 kgf / mm 2 If this is satisfied, shape problems (e.g., edge waves) can be prevented and abnormal grain growth can be prevented, so iron loss can increase gradually as frequency increases. This will be explained in more detail below.

[0058] In one embodiment, a non-oriented electrical steel sheet can be manufactured through a hot rolling step (S100) to a cold rolling annealing step (S400). Additionally, a coating step for forming an insulating coating layer on the non-oriented electrical steel sheet can be performed after the cold rolling annealing step (S400). By forming an insulating coating layer on the non-oriented electrical steel sheet through the coating step, punchability can be improved and insulation can be ensured.

[0059] In addition, in one embodiment, a punching step may be performed after a cold rolling annealing step (or, coating step), and after stacking the punched non-oriented electrical steel sheets, a stress relief annealing step may be performed to remove stress present in the punched non-oriented electrical steel sheets.

[0060] However, the present invention is not limited thereto. At least one step (or process) among the coating step, stamping step, and stress relief annealing step following the cold rolling annealing step (S400) may be omitted.

[0061] Anomalous loss is a loss caused by eddy currents formed inside grains or magnetic domains, and can be affected by the thickness of the steel sheet, grain size, and magnetic domain width.

[0062] Anomalous loss(P a ) can be calculated by Equation 1 below.

[0063] <Equation 1>

[0064] P a = C1* B m 3 / 2 * f 3 / 2 = 1.628 * D / t * P e

[0065] In Equation 1, C1 is a material constant, and B m E is the applied magnetic field, f is the frequency, D is the domain width, t is the thickness of the steel plate, and P e This corresponds to the Eddy current loss.

[0066] Anomalous loss (Pa) can increase proportionally to the 3 / 2 power of the frequency. As frequency increases, iron loss can increase rapidly, and iron loss at high frequencies may deteriorate. In addition, Anomalous loss (P a ) can be affected by the width of the domains. For example, as the width of the domains increases, Anomalous loss(P a ) may increase. Therefore, the greater the abnormal grain growth, the greater the anomalous loss(P a ) can increase, and Anomalous loss(P a It can have a greater impact on ).

[0067] FIG. 2 is a schematic diagram illustrating the case where no abnormal grain growth occurs in the non-oriented electrical steel sheet, FIG. 3 is a schematic diagram illustrating the case where abnormal grain growth occurs in the non-oriented electrical steel sheet, and FIG. 4 is a graph illustrating the change in iron loss according to frequency in the case where no abnormal grain growth occurs in the non-oriented electrical steel sheet and in the case where abnormal grain growth occurs in the non-oriented electrical steel sheet.

[0068] Referring to Figures 2 to 4, it can be seen that iron loss increases as the frequency increases. When abnormal grain growth does not occur (or is not generated) in the non-oriented electrical steel sheet, it can be seen that iron loss increases gradually as the frequency increases compared to when abnormal grain growth occurs in the non-oriented electrical steel sheet. At this time, if there is an abnormal grain with a size of more than three times the average diameter of the grain, it can be determined that abnormal grain growth has occurred.

[0069] As described above, the tension applied to the cold-rolled plate (or cold-rolled annealed plate) in the furnace where the cold-rolled annealing step (S400) is performed is 0.2 kgf / mm 2 Up to 4 kgf / mm 2 It may be. The microstructure may vary depending on the tension applied to the cold-rolled plate (or cold-rolled annealed plate) in the furnace where the cold-rolled annealing step (S400) is performed. The tension applied to the cold-rolled plate (or cold-rolled annealed plate) is 4 kgf / mm 2In the event of abnormalities, abnormal grain growth may occur due to Strain-Induced Boundary Migration (SIBM), which causes iron loss to increase rapidly with increasing frequency, potentially leading to inferior iron loss performance in the high-frequency range. The tension applied to the cold-rolled sheet (or cold-rolled annealed sheet) is 0.2 kgf / mm 2 Up to 4 kgf / mm 2 If this condition is satisfied, abnormal grain growth does not occur, so iron loss increases gradually with increasing frequency, and iron loss in the high-frequency region can be excellent.

[0070] In one embodiment, the non-oriented electrical steel sheet can satisfy the following Equation 2 for the average slope of each frequency range under an inductive magnetic flux density of 1T.

[0071] <Equation 2>

[0072] (A+B+C+D+E+F) / 6 < 0.0553

[0073] In Equation 2, A is (W 10 / 100 - W 10 / 50 It corresponds to ) / 50, and B is (W 10 / 200 - W 10 / 100 It corresponds to ) / 100, and C is (W 10 / 400 - W 10 / 200 It corresponds to ) / 200, and D is (W 10 / 600 - W 10 / 400 It corresponds to ) / 200, and E is (W 10 / 800 - W 10 / 600 It corresponds to ) / 200, and F is (W 10 / 1000 - W 10 / 800 It corresponds to ) / 200.

[0074] For example, W 10 / 50 ε corresponds to the iron loss at a frequency of 50 Hz under an induced magnetic flux density of 1T, and W 10 / 100 ε corresponds to the iron loss at a frequency of 100 Hz under an induced magnetic flux density of 1T, and W 10 / 200ε corresponds to the iron loss at a frequency of 200 Hz under an induced magnetic flux density of 1T, and W 10 / 400 represents the iron loss at a frequency of 400 Hz under an induced magnetic flux density of 1T, and W 10 / 600 ε corresponds to the iron loss at a frequency of 600 Hz under an induced magnetic flux density of 1T, and W 10 / 800 represents the iron loss at a frequency of 800 Hz under an induced magnetic flux density of 1T, and W 10 / 1000 is the iron loss at a frequency of 1000 Hz under an induced magnetic flux density of 1T. Therefore, A, B, C, D, E, and F correspond to the ratio of the change in iron loss to the change in frequency (e.g., slope).

[0075] The tension applied to the cold-rolled plate (or cold-rolled annealed plate) in the cold-rolled annealing step (S400) is 0.2 kgf / mm 2 Up to 4 kgf / mm 2 If the condition is satisfied, the occurrence (or generation) of abnormal grain growth can be prevented or minimized, and if the occurrence of abnormal grain growth is prevented or minimized, the average of the slopes for each frequency range under an inductive flux density of 1T satisfies Equation 2, so that iron loss can increase relatively gradually with increasing frequency, and as a result, the motor efficiency of non-oriented electrical steel sheets punched and laminated can be excellent. For example, the motor efficiency can be 90% or more.

[0076] On the other hand, the tension applied to the cold-rolled plate (or cold-rolled annealed plate) in the cold-rolled annealing step (S400) is 4 kgf / mm 2In the above case, abnormal grain growth occurs, and the average slope of the frequency interval under an induced magnetic flux density of 1T does not satisfy Equation 2, so iron loss may increase rapidly relative to the increase in frequency, and as a result, the efficiency of non-oriented electrical steel sheets punched and laminated into motors may be inferior. For example, the efficiency of the motor may be less than 90%.

[0077] In addition, while iron loss in the high-frequency region is important in non-oriented electrical steel sheets, initial iron loss can be just as important as iron loss in the high-frequency region. In this case, initial iron loss can be affected by the content of major elements (e.g., silicon (Si), aluminum (Al), and manganese (Mn)). For example, if the silicon (Si) content is less than 3 wt%, the resistivity is low and the initial iron loss may be high; if the aluminum (Al) content is less than 0.8 wt%, the resistivity is low and the initial iron loss may be high; and if the manganese (Mn) content is less than 0.2 wt%, the resistivity is low and the initial iron loss may be high.

[0078] In one embodiment, the non-oriented electrical steel sheet can satisfy the following Equation 3 for the average slope of each frequency range under initial iron loss (W10 / 50) and induced magnetic flux density 1T.

[0079] <Equation 3>

[0080] W 10 / 50 * (A+B+C+D+E+F) / 6 < 0.046

[0081] W in Equation 3 10 / 50 corresponds to the iron loss at an induced magnetic flux density of 1T and a frequency of 50Hz, and A is (W 10 / 100 - W 10 / 50 It corresponds to ) / 50, and B is (W 10 / 200 - W 10 / 100 It corresponds to ) / 100, and C is (W 10 / 400 - W 10 / 200 It corresponds to ) / 200, and D is (W 10 / 600 - W 10 / 400It corresponds to ) / 200, and E is (W 10 / 800 - W 10 / 600 It corresponds to ) / 200, and F is (W 10 / 1000 - W 10 / 800 It corresponds to ) / 200.

[0082] Initial iron loss (W when alloy composition and manufacturing conditions are met 10 / 50 ) and under an induced magnetic flux density of 1T, the average of the slopes for each frequency range can satisfy Equation 3, and the initial iron loss (W 10 / 50 ) and under an induced magnetic flux density of 1T, if the average of the slopes for each frequency range satisfies Equation 3, the final motor efficiency can be 90% or higher. Specifically, if the resistivity increases due to the content of major elements (e.g., silicon (Si), aluminum (Al), and manganese (Mn)), the initial iron loss can be lowered, and the tension applied to the cold-rolled plate (or cold-rolled annealed plate) during the cold-rolling annealing step (S400) is 0.2 kgf / mm 2 Up to 4 kgf / mm 2 If this condition is satisfied, the occurrence of abnormal grain growth can be prevented or minimized, thereby reducing initial iron loss (W 10 / 50 Under ) and an induced magnetic flux density of 1T, the average of the slopes for each frequency range can satisfy Equation 3, and the final motor efficiency can be 90% or higher. On the other hand, the resistivity is low due to the low content of major elements (e.g., silicon (Si), aluminum (Al), and manganese (Mn)), or the tension applied to the cold-rolled plate (or cold-rolled annealed plate) during the cold-rolling annealing step (S400) is 4 kgf / mm 2 If abnormal grain growth occurs due to abnormality, Equation 3 is not satisfied, and the final motor efficiency may be less than 90%.

[0083] Experimental Example

[0084] 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.

[0085] Tables 1 and 2 below show the composition of the slabs used in the experimental examples of the present invention. The slabs in Tables 1 and 2 contain the remainder of iron (Fe) and unavoidable impurities.

[0086] The specimens of Examples 1 to 19 and Comparative Examples 1 to 14 (e.g., non-oriented electrical steel sheets) were manufactured by the following method.

[0087] A slab having the composition shown in Table 1 was prepared. The slab was then hot-rolled to produce a hot-rolled plate with a thickness of 2.3 mm. At this time, the hot rolling was performed under conditions of a reheat temperature of 1050°C, a finish rolling temperature of 870°C, and a coiling temperature of 550°C.

[0088] The obtained hot-rolled plate was hot-rolled and annealed. At this time, the hot-rolled annealing was performed under conditions of heating rate: 20℃ / s, hot-rolled annealing temperature (holding temperature): 950℃, hot-rolled annealing time (holding time): 50s, and cooling rate: 30℃ / s.

[0089] The obtained hot-rolled annealed plate was cold-rolled to produce a cold-rolled plate with a thickness of 0.3 mm.

[0090] Subsequently, the obtained cold-rolled sheet was subjected to cold-roll annealing and coating to produce a final product (e.g., non-oriented electrical steel sheet). At this time, the cold-roll annealing was performed under conditions of a heating rate of 10℃ / s, a cold-roll annealing temperature (holding temperature) of 950℃, a cold-roll annealing time (holding time) of 45s, and a cooling rate of 30℃ / s. In addition, the cold-roll annealing was carried out in a mixed atmosphere of 30% hydrogen and 70% nitrogen. At this time, the tension applied to the steel sheet (e.g., cold-rolled sheet (or cold-rolled annealed sheet)) in the furnace was carried out under the conditions listed in Tables 3 and 4.

[0091] EBSD measurement

[0092] To measure the average grain size of specimens (e.g., non-oriented electrical steel sheets), specimens for EBSD measurement were extracted with the ND direction as the observation plane. Electron beam backscatter diffraction (EBSD) measurements were performed on the extracted specimens using a low-accelerating voltage field emission scanning electron microscope (JEOL’s JSM-7900F). Subsequently, data analysis of the measurement results was performed using the analysis software OIM Analysis 8. Grain size was measured on the ND plane, and among the methods calculated using the grain area, the grain size was measured based on the diameter.

[0093] Check for the occurrence of abnormal grain growth

[0094] It was determined that abnormal grain growth occurred when there were grains with a size more than 3 times the average diameter of the grains.

[0095] Iron loss measurement

[0096] Iron loss (W / kg) was measured according to the international standard IEC 60404-2 using an Epstein steel strip with a length of 300 mm and a width of 30 mm.

[0097] Measurement of electric motor core efficiency

[0098] An IPM motor (8-pole) was fabricated after performing a stress relief heat treatment by stamping and laminating non-oriented electrical steel sheets, heating at 12.6 ℃ / min under an N2 atmosphere, maintaining at 760 ℃ for 2 hours, and furnace cooling. The efficiency of the motor corresponds to the average efficiency when driven at 2 Nm (torque) at 750 rpm, 1500 rpm, 3000 rpm, 6000 rpm, 9000 rpm, 12000 rpm, and 15000 rpm, respectively.

[0099] Classification Component (wt%) (ppm) SiAlMnCSNTiP Example 1 3.00.80.216181824103 Example 2 3.00.80.22020112389 Example 3 3.00.80.221231623118 Example 4 3.00.80.221141515188 Example 5 3.00.80.211231720143 Example 6 3.31.20.324171412124 Example 7 3.31.20.312161018170 Example 8 3.31.20.316161617177 Example 9 3.31.20.32015171884 Example 1 03.31.20.315102413132 Example 113.31.20.325191914125 Example 123.31.20.319212214187 Example 133.81.50.412212121183 Example 143.81.50.412221613135 Example 153.81.50.41914241351 Example 163.81.50.410152517171 Example 173.81.50.415251419185 Example 183.81.50.416162325187 Example 193.81.50.417191116188

[0100] Comparative Example 1 2.8 0.8 0.2 16 21 19 10 18 8 Comparative Example 2 3.0 0.7 0.2 23 15 20 12 10 8 Comparative Example 3 3.0 0.8 0.1 15 18 21 11 9 7 Comparative Example 4 2.8 0.7 0.1 10 21 21 23 16 1 Comparative Example 5 2.8 0.7 0.1 11 22 24 18 18 8 Comparative Example 6 2.8 0.7 0.1 15 16 23 23 8 5 Comparative Example 7 3.0 0.8 0.2 12172520160Comparative Example 83.00.80.21316211393Comparative Example 93.31.20.323231514172Comparative Example 103.81.50.42022161064Comparative Example 113.91.50.423131420194Comparative Example 123.81.70.415162521170Comparative Example 133.81.50.611252418188Comparative Example 143.51.30.21022302397

[0101] Classification tension (kgf / mm²) 2 ) AGG Occurrence Iron Loss (W / kg) W 10 / 50 W 10 / 100 W 10 / 200 W 10 / 400 W 10 / 600 W 10 / 800 W 10 / 1000Example 1 0.20 x 0.83 10 2.01 28 4.90 65 12.01 062 2.21 35 3 4.07 08 47.98 48 Example 2 0.49 x 0.83 60 2.08 00 5.1 260 12.60 40 23.23 20 3 5.45 60 49.65 40 Example 3 1.52 x 0.8 41 02.14725.345513.197424.356837.192052.0999 Example 4 2.47x0.84402.21245.563013.788825.479638.926054.5438 Example 5 3.01x0.85202.28265.78551 4.385226.607440.665056.9927 Example 60.20x0.75501.76584.614911.458721.266532.826145.2673 Example 70.51x0.75701.82104.820012.024022.34803 4.516047.6120 Example 8 1.53x0.76201.87925.028212.592423.432636.209049.9598 Example 9 2.51x0.76501.93545.234313.158724.515137.899952.3055 Example Example 10 3.02x0.76701.99065.439513.724125.596739.589954.6503 Example 11 3.52x0.77002.04685.645614.290426.679241.280856.9960 Example 12 3.99x0.77 102.10105.849814.854827.759842.969859.3398 Example 130.20x0.71801.67754.481010.886820.038231.271943.3151 Example 140.52x0.71901.72904.680 011.423021.056032.881045.5580Example 151.51x0.72201.78254.881111.961222.075934.492147.8030Example 162.53x0.72501.83605.082112.499423.0 95736.103250.0479 Example 172.99x0.72901.89055.284213.038624.116637.715352.2939 Example 183.51x0.73101.94305.484213.575825.135439.325454.5378 Example 19 3.99x0.73301.99555.684314.113026.154340.935556.7818.

[0102] Classification tension (kgf / mm²) 2 ) AGG occurrence status Iron loss W 10 / 50 W 10 / 100 W 10 / 200 W 10 / 400 W 10 / 600 W 10 / 800 W 10 / 1000 Comparative Example 1 0.20X1.04902.19745.372313.724025.083238.172052.1657 Comparative Example 20.48X1.05102.21105.418013.854025.328038.549052.6840 Comparative Example 3 1.50X1.05302.27105.638414.496226.54394 0.425955.2677 Comparative Example 42.45X1.05502.33105.858715.138327.759742.302857.8513 Comparative Example 54.01O1.06402.66487.090518.732134.566352.811272.3175 Comparative Example 65.00O1.06802.86607.836920 .912738.697459.189981.0992Comparative Example 74.01O0.85702.72307.292018.509034.451052.787074.0840Comparative Example 85.01O0.85902.78727.508519.099435.572854.520076.5269Comparative Example 95.01O0.77302 .42227.070718.236934.239153.099573.3983Comparative Example 105.00O0.73402.37027.150818.074533.679952.836473.3732Comparative Example 11---------Comparative Example 12---------Comparative Example 13---------Comparative Example 140.1--------

[0103] Classification ABCDEF Example 1 0.0236360.0289370.0355210.0510150.0592870.069570 Example 2 0.0248800.0304600.0373900.0531400.0611200.070990 Example 3 0.0261240 .0319830.0392600.0557970.0641760.074540 Example 40.0273680.0335060.0411290.0584540.0672320.078089 Example 50.0286120.0350290.0429990.0611 110.0702880.081639 Example 60.0202160.0284910.0342190.0490390.0577980.062206 Example 70.0212800.0299900.0360200.0516200.0608400.065480 Example 80.0223440.0314900.0378210.0542010.0638820.068754 Example 90.0234080.0329890.0396220.0567820.0669240.072028 Example 100.0244720.0344890.0 414230.0593630.0699660.075302 Example 110.0255360.0359880.0432240.0619440.0730080.078576 Example 120.0266000.0374880.0450250.0645250.0760 500.081850 Example 130.0191900.0280350.0320290.0457570.0561690.060216 Example 140.0202000.0295100.0337150.0481650.0591250.063385 Example 150.02 12100.0309860.0354010.0505740.0620810.066555 Example 160.0222200.0324610.0370870.0529820.0650380.069724 Example 170.0232300.0339370.03877 20.0553900.0679940.072893 Example 180.0242400.0354120.0404580.0577980.0709500.076062 Example 190.0252500.0368880.0421440.0602070.0739060.079232.

[0104] Classification ABCDEF Comparative Example 1 0.022968 0.031749 0.041759 0.056796 0.065444 0.069969 Comparative Example 2 0.0232000.0320700.0421800.0573700.066105 0.070675 Comparative Example 3 0.0243600.0336740.044289 0.0602390.0694100.074209Comparative Example 40.0255200.0352770.0463980.0631070.0727160.077743Comparative Example 50.0320160.0442570.0582080.0791710.0912250.097532Comparative Example 60.035960 0.0497090.0653790.0889240.1024630.109547Comparative Example 70.03730.04570.05610.07970.09170.1065Comparative Example 80.0385640.0472130.0579550.0823670.0947360.110035Comparative Example 90.03 29840.0464850.0558310.0800110.0943020.101494Comparative Example 100.0327240.0478060.0546190.0780270.0957830.102684Comparative Example 11------Comparative Example 12------Comparative Example 13------Comparative Example 14------

[0105] Value of Classification Formula 2 Value of Formula 3 Motor Efficiency (%) Example 1 0.044661 0.03711391.42 Example 2 0.0463300.03873291.33 Example 3 0.0486470.04091291.08 Example 4 0.0509630.04301390.83 Example 5 0.0532800.04539490.81 Example 6 0.0419950.03170691.91 Example 7 0.0442050.03346391.77 Example 8 0.0464150.03536891.70 Example 9 0.0486260.03719991.35 Example 100.0508360.0 3899191.33 Example 1 10.053046 0.04084591.02 Example 1 20.055256 0.04260390.88 Example 1 30.0402333 0.02888792.20 Example 1 40.042350 0.03045092.05 Example 1 50.044468 0.03210691.89 Example 1 60.046585 0.03377491.72 Example 1 70.048703 0.03550491.56 Example 1 80.0508200.03714991.40 Example 1 90.052938 0.03880391.24

[0106] Value of Formula 2 Value of Formula 3 Motor Efficiency (%) Comparison Example 1 0.048 114 0.050 4728 6.31 Comparison Example 2 0.048 6000 0.051 0798 6.25 Comparison Example 3 0.051 0300 0.053 7358 6.00 Comparison Example 4 0.053 4600 0.0564008 5.75 Comparison Example 5 0.067068 0.071 3608 2.27 Comparison Example 6 0.0753300 .08045381.52 Comparative Example 70.06950.059686.77 Comparative Example 80.0718120.06168686.01 Comparative Example 90.0685180.05296486.13 Comparative Example 100.0686070.05035887.85 Comparative Example 11---Comparative Example 12---Comparative Example 13---Comparative Example 14---

[0107] Tables 5 and 6A are (W 10 / 100 - W 10 / 50 It corresponds to ) / 50, and B is (W 10 / 200 - W 10 / 100 It corresponds to ) / 100, and C is (W 10 / 400 - W10 / 200 It corresponds to ) / 200, and D is (W 10 / 600 - W 10 / 400 It corresponds to ) / 200, and E is (W 10 / 800 - W 10 / 600 It corresponds to ) / 200, and F is (W 10 / 1000 - W 10 / 800 It corresponds to ) / 200.

[0108] In Tables 7 and 8, the value of Equation 2 corresponds to the value of (A+B+C+D+E+F) / 6, and the value of Equation 3 is W 10 / 50 * Corresponds to the value of (A+B+C+D+E+F) / 6.

[0109] Referring to Tables 1 through 8, when the component composition (e.g., content of major elements (Si, Mn, Al)) and manufacturing conditions (e.g., tension) were satisfied, abnormal grain growth did not occur (or was not generated), the average of the slopes for each frequency range under an induced magnetic flux density of 1T satisfied Equation 2, and the initial iron loss (W 10 / 50 It can be confirmed that the average of the slopes for each frequency range under ) and an induced magnetic flux density of 1T satisfies Equation 3, and that the motor efficiency is 90% or higher.

[0110] On the other hand, if the manufacturing conditions are not satisfied, abnormal grain growth occurs (or is generated), so the average of the slopes for each frequency range under an induced magnetic flux density of 1T does not satisfy Equation 2, and the initial iron loss (W 10 / 50 It can be confirmed that the average slope of the frequency range under ) and induced magnetic flux density 1T does not satisfy Equation 3, and the motor efficiency is less than 90%. In addition, even when manufacturing conditions are satisfied, if the component composition (e.g., content of major elements (Si, Mn, Al)) is not satisfied, the initial iron loss (W10 / 50) and the average slope of the frequency range under induced magnetic flux density 1T do not satisfy Equation 3, and it can be confirmed that the initial iron loss is high and the motor efficiency is less than 90%.

[0111] Comparative Example 1 is a case where the silicon content is less than 3 wt%, wherein the initial iron loss (W 10 / 50 It can be confirmed that the initial iron loss and the average slope of each frequency range under an inductive flux density of 1T are high, and that the motor efficiency is less than 90%, as Equation 3 is not satisfied.

[0112] Comparative Example 2 is a case where the aluminum content is less than 0.8 wt%, wherein the initial iron loss (W 10 / 50 It can be confirmed that the initial iron loss and the average slope of each frequency range under an inductive flux density of 1T are high, and that the motor efficiency is less than 90%, as Equation 3 is not satisfied.

[0113] Comparative Example 3 is a case where the manganese content is less than 0.2 wt%, wherein the initial iron loss (W 10 / 50 It can be confirmed that the initial iron loss and the average slope of each frequency range under an inductive flux density of 1T are high, and that the motor efficiency is less than 90%, as Equation 3 is not satisfied.

[0114] Comparative Example 4 is a case where the silicon content is less than 3 wt%, the aluminum content is less than 0.8 wt%, and the manganese content is less than 0.2 wt%, wherein the initial iron loss (W 10 / 50 It can be confirmed that the initial iron loss and the average slope of each frequency range under an inductive flux density of 1T are high, and that the motor efficiency is less than 90%, as Equation 3 is not satisfied.

[0115] Comparative Examples 5 to 10 have a tension of 4 kgf / mm² applied to the steel sheet in the cold rolling annealing furnace. 2 In the case where the tension is 4 kgf / mm 2In the above case, Abnormal Grain Growth (AGG) occurs (or is generated), and it can be confirmed that under an induced magnetic flux density of 1T, the average slope across frequency ranges does not satisfy Equation 2, and the motor efficiency is less than 90%. For example, with a tension of 4 kgf / mm 2 In such cases, Abnormal Grain Growth (AGG) occurs, which can lead to a decrease in motor efficiency due to a rapid increase in iron loss with increasing frequency.

[0116] Comparative Example 11 is a case where the silicon content exceeds 3.8 wt%, and when the silicon content exceeds 3.8 wt%, the brittleness increases and fracture occurs during cold rolling.

[0117] Comparative Example 12 is a case where the aluminum content exceeds 1.5 wt%, and when the aluminum content exceeds 1.5 wt%, brittleness increases and fracture occurs during cold rolling.

[0118] Comparative Example 13 is a case where the manganese content exceeds 0.4 wt%, and when the manganese content exceeds 0.4 wt%, brittleness increases and fracture occurs during cold rolling.

[0119] Comparative Example 14 is a steel sheet with a tension of 0.2 kgf / mm² in a cold rolling annealing furnace. 2 In the case where it is less than, the tension is 0.2 kgf / mm 2 In cases where it is less than that, shape problems (e.g., Edge Wave) occur, making it impossible to measure iron loss and manufacture the motor.

[0120] The present invention has been described with reference to the embodiments illustrated in the drawings, but this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative 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

1. As a non-oriented electrical steel sheet, In wt%, silicon (Si): 3 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.4 wt%, aluminum (Al): 0.8 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.005 wt%, phosphorus (P): greater than 0 and less than or equal to 0.02 wt%, sulfur (S): greater than 0 and less than or equal to 0.005 wt%, nitrogen (N): greater than 0 and less than or equal to 0.005 wt%, titanium (Ti): greater than 0 and less than or equal to 0.005 wt%, and the remainder being iron (Fe) and unavoidable impurities, The above non-oriented electrical steel sheet is a non-oriented electrical steel sheet in which the average of the slopes for each frequency range satisfies the following Equation 1 under an induced magnetic flux density of 1T. <Equation 1> (A+B+C+D+E+F) / 6 < 0.0553 In the above Equation 1, A is (W 10 / 100 - W 10 / 50 It corresponds to ) / 50, and B is (W 10 / 200 - W 10 / 100 It corresponds to ) / 100, and C is (W 10 / 400 - W 10 / 200 It corresponds to ) / 200, and D is (W 10 / 600 - W 10 / 400 It corresponds to ) / 200, and E is (W 10 / 800 - W 10 / 600 It corresponds to ) / 200, and F is (W 10 / 1000 - W 10 / 800 It corresponds to ) / 200.

2. In Paragraph 1, The above W 10 / 50 ε is the iron loss at a frequency of 50 Hz under an induced magnetic flux density of 1T, and W 10 / 100 ε is the iron loss at a frequency of 100 Hz under an induced magnetic flux density of 1T, and the above W 10 / 200 ε is the iron loss at a frequency of 200 Hz under an induced magnetic flux density of 1T, and W 10 / 400 ε is the iron loss at a frequency of 400 Hz under an induced magnetic flux density of 1T, and the above W 10 / 600 is the iron loss at a frequency of 600 Hz under an induced magnetic flux density of 1T, and the above W 10 / 800 ε is the iron loss at a frequency of 800 Hz under an induced magnetic flux density of 1T, and the above W 10 / 1000 Non-oriented electrical steel sheet, iron loss at a frequency of 1000 Hz under an induced magnetic flux density of 1T.

3. In Paragraph 1, The above non-oriented electrical steel sheet has an initial iron loss (W 10 / 50 A non-oriented electrical steel sheet in which the average of the slopes for each frequency range satisfies the following Equation 2 under ) and an induced magnetic flux density of 1T. <Equation 2> W10 / 50 * (A+B+C+D+E+F) / 6 < 0.046 W in Equation 2 above 10 / 50 corresponds to the iron loss at an induced magnetic flux density of 1T and a frequency of 50Hz, and A is (W 10 / 100 - W 10 / 50 It corresponds to ) / 50, and B is (W 10 / 200 - W 10 / 100 It corresponds to ) / 100, and C is (W 10 / 400 - W 10 / 200 It corresponds to ) / 200, and D is (W 10 / 600 - W 10 / 400 It corresponds to ) / 200, and E is (W 10 / 800 - W 10 / 600 It corresponds to ) / 200, and F is (W 10 / 1000 - W 10 / 800 It corresponds to ) / 200.

4. In Paragraph 1, A non-oriented electrical steel sheet having an efficiency of 90% or more for a motor manufactured by punching and laminating the above non-oriented electrical steel sheet.

5. A method for manufacturing non-oriented electrical steel sheets, A step of manufacturing a hot-rolled plate by hot-rolling a slab comprising, in wt%, silicon (Si): 3 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.4 wt%, aluminum (Al): 0.8 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.005 wt%, phosphorus (P): greater than 0 and less than or equal to 0.02 wt%, sulfur (S): greater than 0 and less than or equal to 0.005 wt%, nitrogen (N): greater than 0 and less than or equal to 0.005 wt%, titanium (Ti): greater than 0 and less than or equal to 0.005 wt%, and the remainder being iron (Fe) and unavoidable impurities; A step of manufacturing a hot-rolled annealed plate by hot-rolling and annealing the above hot-rolled plate; A step of manufacturing a cold-rolled plate by cold-rolling the above hot-rolled annealed plate; and A step of manufacturing a cold-rolled annealed plate by cold-rolling and annealing the above cold-rolled plate; Includes, In the step of manufacturing the above cold-rolled annealed plate, the tension applied to the cold-rolled plate is 0.2 kgf / mm 2 4 kgf / mm or more 2 Method for manufacturing non-oriented electrical steel sheets of less than 6. In Paragraph 5, A method for manufacturing a non-oriented electrical steel sheet, wherein the average of the slopes for each frequency range satisfies the following Equation 1 under an induced magnetic flux density of 1T. <Equation 1> (A+B+C+D+E+F) / 6 < 0.0553 In the above Equation 1, A is (W 10 / 100 - W 10 / 50 It corresponds to ) / 50, and B is (W 10 / 200 - W 10 / 100 It corresponds to ) / 100, and C is (W 10 / 400 - W 10 / 200 It corresponds to ) / 200, and D is (W 10 / 600 - W 10 / 400 It corresponds to ) / 200, and E is (W 10 / 800 - W 10 / 600 It corresponds to ) / 200, and F is (W 10 / 1000 - W 10 / 800 It corresponds to ) / 200.

7. In Paragraph 6, The above W 10 / 50 ε is the iron loss at a frequency of 50 Hz under an induced magnetic flux density of 1T, and W 10 / 100 ε is the iron loss at a frequency of 100 Hz under an induced magnetic flux density of 1T, and the above W 10 / 200 ε is the iron loss at a frequency of 200 Hz under an induced magnetic flux density of 1T, and W 10 / 400 ε is the iron loss at a frequency of 400 Hz under an induced magnetic flux density of 1T, and the above W 10 / 600 is the iron loss at a frequency of 600 Hz under an induced magnetic flux density of 1T, and the above W 10 / 800 ε is the iron loss at a frequency of 800 Hz under an induced magnetic flux density of 1T, and the above W 10 / 1000 A method for manufacturing a non-oriented electrical steel sheet, wherein the iron loss is at a frequency of 1000 Hz under an inductive magnetic flux density of 1 T.

8. In Paragraph 5, The above non-oriented electrical steel sheet has an initial iron loss (W 10 / 50 A method for manufacturing a non-oriented electrical steel sheet, wherein the average of the slopes for each frequency range satisfies the following Equation 2 under ) and an induced magnetic flux density of 1T. <Equation 2> W10 / 50 * (A+B+C+D+E+F) / 6 < 0.046 In Equation 2 above, W10 / 50 corresponds to the iron loss at an inductive flux density of 1T and a frequency of 50Hz, and A is (W 10 / 100 - W 10 / 50 It corresponds to ) / 50, and B is (W 10 / 200 - W 10 / 100 It corresponds to ) / 100, and C is (W 10 / 400 - W 10 / 200 It corresponds to ) / 200, and D is (W 10 / 600 - W 10 / 400 It corresponds to ) / 200, and E is (W 10 / 800 - W 10 / 600 It corresponds to ) / 200, and F is (W 10 / 1000 - W 10 / 800 It corresponds to ) / 200.

9. In Paragraph 5, A method for manufacturing a non-oriented electrical steel sheet, wherein the step of manufacturing the above cold-rolled annealed sheet is performed under conditions of a heating rate of 10℃ / s or more, a cold-rolled annealing temperature of 900℃ to 1100℃, a cold-rolled annealing time of 30s to 90s, and a cooling rate of 30℃ / s or more.

10. In Paragraph 9, A method for manufacturing a non-oriented electrical steel sheet, wherein the step of manufacturing the above cold-rolled annealed sheet is performed in a mixed atmosphere comprising 20% ​​to 50% hydrogen and the remainder nitrogen.

11. In Paragraph 10, A method for manufacturing a non-oriented electrical steel sheet, wherein the residual oxygen in the heating furnace in which the step of manufacturing the above cold-rolled annealed sheet is performed is less than 900 ppm.

12. In Paragraph 5, After the step of manufacturing the above cold-rolled annealed plate, A method for manufacturing a non-oriented electrical steel sheet, wherein a coating step for forming an insulating coating layer on the above cold-rolled annealed sheet is further performed.

13. In Paragraph 12, After the above coating step, A method for manufacturing a non-oriented electrical steel sheet, wherein the step of punching and laminating a cold-rolled annealed sheet having the above-mentioned insulating coating layer formed thereon is further performed.

14. In Paragraph 13, A method for manufacturing a non-oriented electrical steel sheet, wherein the efficiency of the motor manufactured from the above-described stamped and laminated cold-rolled annealed sheet is 90% or higher.

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