Iron core comprising non-oriented electrical steel sheet and method for manufacturing same

Abstract

An iron core, according to one embodiment of the present invention, comprises a laminate in which a plurality of non-oriented electrical steel sheets are laminated, the non-oriented electrical steel sheets comprising, by weight %, 1.5% to 5.0% of Si, 0.1% to 2.5% of Al, and 0.1% to 2.5% of Mn, with the remainder being Fe and unavoidable impurities, wherein each of the non-oriented electrical steel sheets has a nitrogen diffusion layer that extends inward from the side surface of the laminate to a depth of up to 30 ㎛, wherein the nitrogen content in the nitrogen diffusion layer ranges from 0.005 wt% to 0.020 wt%.

Description

Steel core including non-oriented electrical steel sheet and method for manufacturing the same One embodiment of the present invention relates to a core including a non-oriented electrical steel sheet and a method for manufacturing the same. Specifically, one embodiment of the present invention relates to a core including a non-oriented electrical steel sheet, in which the strength is improved by controlling the atmospheric conditions during stress relief annealing (SRA) to partially infiltrate nitrogen into the side surface of a steel sheet laminate, and a method for manufacturing the same. Non-oriented electrical steel is mainly used in motors that convert electrical energy into mechanical energy, and in this process, excellent magnetic properties of non-oriented electrical steel are required to achieve high efficiency. In particular, as eco-friendly cars driven by motors instead of internal combustion engines have been gaining attention recently, demand for non-oriented electrical steel used as a drive motor core material is increasing, and for this purpose, non-oriented electrical steel with excellent magnetic properties and strength is required. The magnetic properties of non-oriented electrical steel sheets are mainly evaluated by iron loss and magnetic flux density. Iron loss refers to the energy loss that occurs at a specific magnetic flux density and frequency, and magnetic flux density refers to the degree of magnetization obtained under a specific magnetic field. The lower the iron loss, the more energy-efficient the motor can be manufactured under the same conditions, and the higher the magnetic flux density, the more miniaturized the motor or reduced the copper loss. Therefore, using non-oriented electrical steel sheets with low iron loss and high magnetic flux density, a drive motor with excellent efficiency and torque can be manufactured, which can improve the driving range and output of eco-friendly vehicles. The characteristics of non-oriented electrical steel sheets that should be considered also vary depending on the operating conditions of the motor. As a general standard for evaluating the characteristics of non-oriented electrical steel sheets used in motors, W15 / 50, which is the iron loss when a 1.5T magnetic field is applied at a commercial frequency of 50Hz, is widely used. However, in the case of non-oriented electrical steel sheets with a thickness of 0.35mm or less used in eco-friendly vehicle drive motors, magnetic characteristics are often important at low fields of 1.0T or less and high frequencies of 400Hz or higher, so W 10 / 400 The characteristics of non-oriented electrical steel sheets are often evaluated by iron loss. In addition, strength characteristics, which were not considered important in the past, are also evaluated as important characteristics due to the increase in rotation speed. Therefore, reflecting the recent energy efficiency improvement policy and the direction of utilization of non-oriented electrical steel sheets, it can be said that the development technology of non-oriented electrical steel sheets with low high-frequency iron loss, high magnetic flux density, and excellent strength is essential. The most basic and efficient way to reduce iron loss among the important magnetic properties of non-oriented electrical steel sheets is to increase the amount of Si, Al, and Mn, which are elements with high resistivity, or to make the steel sheet thinner. Increasing the amount of Si, Al, and Mn increases the resistivity of the steel, which reduces the eddy current loss among the iron loss of non-oriented electrical steel sheets, thereby reducing iron loss. In the case of high-frequency iron loss, the proportion of eddy current loss among the iron loss is greater, so it can be a very effective method for reducing high-frequency iron loss. However, the effect varies depending on the addition ratio, and the magnetic flux density deteriorates as the amount of alloying elements increases, so in order to secure excellent iron loss and magnetic flux density, the appropriate amount of addition and the addition ratio between the Si, Al, and Mn additions must be appropriately controlled. The method of making the thickness thinner is also a method that greatly reduces eddy current loss, and is very effective in reducing iron loss, but thin steel sheets have the disadvantage of poor productivity and workability. Various technologies have been reported to improve the magnetic flux density while lowering the core loss of non-oriented electrical steel sheets, such as improving the texture by utilizing special additive elements such as REM to improve the magnetic properties, or introducing additional manufacturing processes such as warm rolling, double rolling, and double annealing. However, all of these technologies cause an increase in manufacturing cost or are accompanied by difficulties in mass production, so it can be said that there is a need to develop a technology that is both excellent in magnetism and easy to produce commercially. In addition, technologies are being developed to suppress and control the formation of inclusions by minimizing the addition of impurities and adding elements such as Ca, but these also cause an increase in manufacturing cost and it is not easy to clearly secure their effects. The strength of steel plates tends to increase as the alloy content increases. However, since Si, Al, etc. are brittle elements and have different effects on strength, the content and ratio of the components must be optimized to secure high strength characteristics. On the other hand, the finer the grain size, the higher the strength, but there is an optimal grain size that minimizes iron loss, so in order to secure both low iron loss and high strength characteristics, a technology to appropriately control the grain size is also necessary. Meanwhile, when manufacturing a motor using non-oriented electrical steel sheets, the characteristics required for the rotor and stator of the motor are different from each other. That is, in the case of the stator, mechanical characteristics are not very important other than magnetic characteristics, but in the case of the rotor, the temperature increases during high-speed rotation and the mechanical characteristics deteriorate, so that mechanical characteristics are required along with magnetic characteristics. In this way, although the characteristics required for the stator and the rotor are different, it is also required to manufacture the stator and the rotor using the same non-oriented electrical steel sheets in order to improve the yield during motor manufacturing. One embodiment of the present invention provides a non-oriented electrical steel sheet and a method for manufacturing the same. Specifically, one embodiment of the present invention provides a core including a non-oriented electrical steel sheet in which strength is improved by controlling the atmospheric conditions during stress relief annealing (SRA) to partially infiltrate nitrogen into the side surface of a steel sheet laminate, and a method for manufacturing the same. According to one embodiment of the present invention, a core comprises a laminate in which a plurality of non-oriented electrical steel sheets are laminated, the non-oriented electrical steel sheets including, in weight %, Si: 1.5 to 5.0%, Al: 0.1 to 2.5%, and Mn: 0.1 to 2.5%, with the remainder being Fe and unavoidable impurities, wherein the non-oriented electrical steel sheets have a nitrogen diffusion layer extending inward from a side surface of the laminate to 30 ㎛, and the nitrogen content in the nitrogen diffusion layer is 0.005 to 0.020 wt %. Non-oriented electrical steel sheets may further include at least one of P: 0.1 wt% or less (excluding 0%), C: 0.005 wt% or less (excluding 0%), S: 0.005 wt% or less (excluding 0%), Ti: 0.005 wt% or less (excluding 0%), and N: 0.020 wt% or less (excluding 0%). The non-oriented electrical steel sheet may further contain 0.005 to 0.200 wt% of each or a combined amount of one or more of Sn, Sb, Bi, Pb, Ge, and As. The non-oriented electrical steel sheet may further include at least one of Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Ni: 0.05 wt% or less (excluding 0%), Zn: 0.01 wt% or less (excluding 0%), and Co: 0.05 wt% or less (excluding 0%). The non-oriented electrical steel sheet may further include at least one of Mo: 0.03 wt% or less (excluding 0%), B: 0.0050 wt% or less (excluding 0%), V: 0.0050 wt% or less (excluding 0%), Ca: 0.0050 wt% or less (excluding 0%), Nb: 0.0050 wt% or less (excluding 0%), Zr: 0.005 wt% or less (excluding 0%), Te: 0.01 wt% or less (excluding 0%), and Mg: 0.0050 wt% or less (excluding 0%). Non-oriented electrical steel sheets can satisfy the following equation 1. [Formula 1] 0.45 ≤ (VA+VB+VC) / (VD+VE+VF) ≤ 1.45 (In Equation 1, VA, VB, VC, VD, VE, and VF are (001)[0-10], (001)[-1-10], (100) respectively.

[0025] , (223)[1-10], (111)[3-41], and (112)[1-10], which represents the area fraction (%) of the aggregates having orientations within 15°. Non-oriented electrical steel sheets can satisfy the following equation 2. [Formula 2] 0.35 ≤ VC / VE ≤ 1.35 (In Equation 2, VC and VE represent the area fraction (%) of the aggregate structure having orientations within 15° from (100)

[0025] and (111)[3-41], respectively.) A method for manufacturing a core according to one embodiment of the present invention comprises the steps of: preparing a non-oriented electrical steel sheet containing, in wt%, Si: 1.5 to 5.0%, Al: 0.1 to 2.5%, and Mn: 0.1 to 2.5%, with the remainder being Fe and unavoidable impurities; stamping and laminating the non-oriented electrical steel sheets to manufacture a laminate; and annealing the laminate in an atmosphere containing a nitriding gas. The atmosphere may contain from 0.7 to 95 volume percent of nitriding gas. The atmosphere may contain remaining nitrogen and hydrogen. The stress relief annealing step can be performed at a temperature of 530 to 920°C for 550 seconds to 60 minutes. Non-oriented electrical steel sheets can satisfy the following equation 1. [Formula 1] 0.45 ≤ (VA+VB+VC) / (VD+VE+VF) ≤ 1.45 (In Equation 1, VA, VB, VC, VD, VE, and VF represent the area fraction (%) of the aggregate structure having an orientation within 15° from (001)[0-10], (001)[-1-10], (100)

[0025] , (223)[1-10], (111)[3-41], and (112)[1-10], respectively.) Non-oriented electrical steel sheets can satisfy the following equation 2. [Formula 2] 0.35 ≤ VC / VE ≤ 1.35 (In Equation 2, VC and VE represent the area fraction (%) of the aggregate structure having orientations within 15° from (100)

[0025] and (111)[3-41], respectively.) The step of preparing a non-oriented electrical steel sheet includes a step of hot-rolling a slab containing, in wt%, Si: 1.5 to 5.0%, Al: 0.1 to 2.5%, and Mn: 0.1 to 2.5%, with the remainder being Fe and unavoidable impurities, to produce a hot-rolled steel sheet; a step of cold-rolling the hot-rolled steel sheet to produce a cold-rolled sheet; and a cold-rolled sheet annealing step of annealing the cold-rolled sheet. The step of manufacturing a hot rolled steel sheet includes a rough rolling step and a finish rolling step, and the finish rolling step is performed through n passes, where n is 2 or more, and satisfies the following equation 3. [Formula 3] R1 / (R1+R2+……+Rn) ≥ 0.2 (In Equation 3, R1 to Rn represent the pressure reduction ratios (%) of the 1st to nth passes, respectively.) The thought rolling step satisfies the following equation 4. [Formula 4] R1 / Rn ≤ 8 (In Equation 4, R1 and Rn represent the pressure reduction ratios (%) of the 1st and nth passes, respectively.) A method for manufacturing a non-oriented electrical steel sheet includes a step of hot-rolling a slab containing, in wt%, Si: 1.5 to 5.0%, Al: 0.1 to 2.5%, and Mn: 0.1 to 2.5%, with the remainder being Fe and unavoidable impurities, to manufacture a hot-rolled steel sheet; a step of cold-rolling the hot-rolled steel sheet to manufacture a cold-rolled sheet; and a cold-rolled sheet annealing step of annealing the cold-rolled sheet. The step of manufacturing a hot rolled steel sheet includes a rough rolling step and a finish rolling step, and the finish rolling step is performed through n passes, where n is 2 or more, and satisfies Equation 3. [Formula 3] R1 / (R1+R2+……+Rn) ≥ 0.2 (In Equation 3, R1 to Rn represent the pressure reduction ratios (%) of the 1st to nth passes, respectively.) The slab may further contain at least one of P: 0.1 wt% or less (excluding 0%), C: 0.005 wt% or less (excluding 0%), S: 0.005 wt% or less (excluding 0%), Ti: 0.005 wt% or less (excluding 0%), and N: 0.005 wt% or less (excluding 0%). The slab may further contain 0.005 to 0.200 wt% of each or a combination of one or more of Sn, Sb, Bi, Pb, Ge and As. The slab may further contain at least one of Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Ni: 0.05 wt% or less (excluding 0%), and Zn: 0.01 wt% or less (excluding 0%). The slab may further include at least one of Mo: 0.03 wt% or less (excluding 0%), B: 0.0050 wt% or less (excluding 0%), V: 0.0050 wt% or less (excluding 0%), Ca: 0.0050 wt% or less (excluding 0%), Nb: 0.0050 wt% or less (excluding 0%), Zr: 0.005 wt% or less (excluding 0%), Te: 0.01 wt% or less (excluding 0%), Co: 0.05 wt% or less (excluding 0%), and Mg: 0.0050 wt% or less (excluding 0%). According to one embodiment of the present invention, the strength of the core is improved by the penetration of nitrogen during the stress relief annealing process, and the magnetism is also improved during the stress relief annealing process. Accordingly, the core can be usefully used as a rotor of a motor. According to one embodiment of the present invention, the core has an improved aggregate structure of non-oriented electrical steel sheets, so that the magnetic flux density, iron loss, and yield strength are simultaneously excellent, and the efficiency of the motor can be improved. Ultimately, the iron core according to one embodiment of the present invention contributes to the manufacture of eco-friendly automobile motors, high-efficiency home appliance motors, and super premium-grade electric motors. The terms first, second, and third, etc. are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are only used to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Thus, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms include the plural forms as well, unless the context clearly dictates otherwise. The word "comprising," as used herein, specifies particular features, regions, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components. When a part is referred to as being "on" or "on" another part, it may be directly on or above the other part, or there may be other parts intervening. In contrast, when a part is referred to as being "directly on" another part, there are no other parts intervening. Also, unless otherwise specified, % means weight%, and 1 ppm is 0.0001 weight%. In one embodiment of the present invention, the inclusion of an additional element means including the remainder of iron (Fe) in an amount equivalent to the additional amount of the additional element. Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Terms defined in commonly used dictionaries are additionally interpreted as having a meaning consistent with the relevant technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal sense unless defined. Hereinafter, embodiments of the present invention will be described in detail so that those with ordinary skill in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. According to one embodiment of the present invention, a core comprises a laminate in which a plurality of non-oriented electrical steel sheets are laminated, the non-oriented electrical steel sheets including, in weight %, Si: 1.5 to 5.0%, Al: 0.1 to 2.5%, and Mn: 0.1 to 2.5%, the remainder being Fe and unavoidable impurities, and the non-oriented electrical steel sheets include a nitrogen diffusion layer extending inward from a side surface of the laminate. In one embodiment of the present invention, the iron core refers to an iron core used in a motor and can be used for a stator or a rotor. More specifically, it can be an iron core for a stator. In one embodiment of the present invention, the core may be an integral punched core or a split core, and more specifically, may be an integral punched core. The core may be formed by laminating two or more non-oriented electrical steel sheets, and an insulating film may exist between the non-oriented electrical steel sheets. The non-oriented electrical steel sheet contains, in weight %, Si: 1.5 to 5.0%, Al: 0.1 to 2.5%, and Mn: 0.1 to 2.5%, with the remainder being Fe and inevitable impurities. Below, the reasons for the limitation of the components of non-oriented electrical steel sheets are explained. Si: 1.50 to 5.00 wt% Silicon (Si) increases the resistivity of the material, thereby reducing iron loss, and increases strength through solid solution strengthening. If too little Si is added, the iron loss and strength improvement effects may be insufficient. If too much Si is added, the magnetic flux density may decrease significantly and the rollability may become inferior due to increased brittleness. Therefore, Si may be included in an amount of 1.5 to 5.0 wt%. More specifically, it may be included in an amount of 2.50 to 4.50 wt%. More specifically, it may be included in an amount of 2.70 to 3.85 wt%. Al: 0.10 to 2.50 wt% Aluminum (Al) increases the resistivity of the material, thereby lowering iron loss and improving rollability, and reduces magnetic anisotropy, thereby reducing magnetic deviation in the rolling direction and the direction perpendicular to the rolling direction. If too little Al is added, it may be difficult to obtain the effect of reducing high-frequency iron loss. If too much Al is added, nitrides may be excessively formed, which may deteriorate magnetism. Therefore, Al may be included in an amount of 0.10 to 2.50 wt%. More specifically, it may be included in an amount of 0.50 to 2.50 wt%. More specifically, it may be included in an amount of 0.60 to 2.30 wt%. Mn: 0.10 to 2.50 wt% Manganese (Mn) improves iron loss by increasing the resistivity of the material and plays a role in improving the aggregate structure. If too little Mn is added, fine sulfides are formed, causing magnetic deterioration, and if too much Mn is added, it can have a negative effect on the magnetic flux density. Therefore, Mn may be included in an amount of 0.10 to 2.50 wt%. More specifically, it may be included in an amount of 0.2 to 1.8 wt%. More specifically, it may be included in an amount of 0.50 to 2.50 wt%. In one embodiment of the present invention, the non-oriented electrical steel sheet may have a resistivity of 63.0 μΩ cm or more at 25°C. The iron loss of the non-oriented electrical steel sheet is divided into hysteresis loss and eddy current loss. By adding elements such as Si, Al, and Mn, the resistivity of the steel increases, and the eddy current loss can be significantly reduced. In particular, as the frequency increases, the proportion of the total iron loss occupied by the eddy current loss increases. Therefore, in order to obtain excellent high-frequency iron loss, it is necessary to control the resistivity of the steel to a certain level or more. Through the present invention, when the resistivity (ρ) of the steel is 63 μΩ cm or more, excellent characteristics can be secured. More specifically, the resistivity (ρ) can be 64.0 to 90.0 μΩ cm. In one embodiment of the present invention, resistivity can be measured by a four-terminal method, a Van Der Pawu method, a Four-Point Probe method, and an Eddy Current method. A non-oriented electrical steel sheet according to one embodiment of the present invention may further include at least one of P: 0.1 wt% or less (excluding 0%), C: 0.005 wt% or less (excluding 0%), S: 0.005 wt% or less (excluding 0%), Ti: 0.005 wt% or less (excluding 0%), and N: 0.020 wt% or less (excluding 0%). P: 0.1 wt% or less Phosphorus (P) is an element that improves the grain structure of steel by segregating grain boundaries and surfaces. However, if too much P is added, it may lower the iron loss by suppressing grain growth and lower the rolling property due to grain boundary segregation, which may also lower the productivity. More specifically, P may be included in an amount of 0.0001 to 0.0500 wt%. More specifically, P may be included in an amount of 0.0020 to 0.0200 wt%. C: 0.0050 wt% or less Carbon (C) can cause magnetic aging and combine with other impurity elements to form carbides, thereby hindering grain boundary or domain wall movement and deteriorating magnetic properties. More specifically, C can be included in an amount of 0.0005 to 0.0035 wt%. S: 0.0050 wt% or less Sulfur (S) can form fine precipitates, MnS and CuS, thereby deteriorating magnetic properties and hot workability. More specifically, S can be included in an amount of 0.0005 to 0.0040 wt%. Ti: 0.0050 wt% or less Titanium (Ti) has a very strong tendency to form precipitates inside the steel, and can deteriorate iron loss by forming fine carbides, nitrides, or sulfides inside the parent material, thereby inhibiting grain growth and domain wall movement. More specifically, it can contain 0.0005 to 0.0035 wt% of Ti. N: 0.0200 wt% or less Nitrogen (N) not only forms fine AlN precipitates inside the base material, but also combines with other impurities to form fine precipitates, which inhibits grain growth and domain wall movement and can worsen iron loss. More specifically, after slab and cold rolled sheet annealing, N may be included in an amount of 0.0005 to 0.0040 wt%. In one embodiment of the present invention, some N may penetrate through nitriding gas in the atmosphere during the stress relief annealing process. However, a small amount of N may penetrate into the side of the steel sheet, and there may be no substantial change in the N content when considering the entire composition of the steel sheet. Specifically, after stress relief annealing, N may be included in an amount of 0.0200 wt% or less. More specifically, it may be included in an amount of 0.0010 to 0.0100 wt%. A non-oriented electrical steel sheet according to one embodiment of the present invention may further contain 0.005 to 0.200 wt% of each or a combined amount of one or more of Sn, Sb, Bi, Pb, Ge, and As. Sn Tin (Sn) can be added to improve magnetism because it improves the aggregate structure of the material by segregating at grain boundaries and surfaces and plays a role in suppressing surface oxidation. If too much Sn is added, grain boundary segregation becomes severe, deteriorating the surface quality, increasing the hardness and causing fracture of the cold-rolled sheet, which can reduce the rollability. Specifically, Sn can be further included in an amount of 0.005 to 0.200 wt%. More specifically, it can be further included in an amount of 0.010 to 0.080 wt%. Sb Antimony (Sb) improves the material's aggregate structure by segregating at grain boundaries and surfaces and suppresses surface oxidation, so it can be additionally added to improve magnetism. If too much Sb is added, grain boundary segregation becomes severe, deteriorating the surface quality, increasing the hardness and causing breakage of the cold-rolled sheet, which can reduce the rollability. Specifically, 0.005 to 0.200 wt% of Sb can be further included. More specifically, 0.010 to 0.080 wt% can be further included. Bi, Pb, Ge and As When added, bismuth (Bi), lead (Pb), germanium (Ge) and arsenic (As) segregate at grain boundaries, thereby relieving stress concentration at grain boundaries during cold rolling, and thus reducing stress concentration in the subsequent process of recrystallization annealing. <111> / ND By suppressing the recrystallization of the orientation grains, the magnetic flux density is improved. If these are added appropriately, the aforementioned effects can be additionally obtained, but if they are included in too much, a large amount of segregation may occur, suppressing grain growth and thus lowering the magnetic flux density and iron loss. A non-oriented electrical steel sheet according to one embodiment of the present invention may further include at least one of Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Ni: 0.05 wt% or less (excluding 0%), Zn: 0.01 wt% or less (excluding 0%), and Co: 0.05 wt% or less (excluding 0%). Cu: 0.005 to 0.200 wt% Copper (Cu) plays a role in forming sulfides with Mn. If Cu is added more, if too little is added, (Cu Mn)S may be finely precipitated, which may deteriorate magnetism. If too much Cu is added, high-temperature embrittlement may occur, which may form cracks during rolling or hot rolling. More specifically, Cu may be included in an amount of 0.01 to 0.10 wt%. Cr: 0.01 to 0.50 wt% Chromium (Cr) plays a role in improving iron loss by increasing resistivity. If too little Cr is added, the resistivity-increasing effect may not be sufficient. If too much Cr is included, the magnetic flux density may decrease. More specifically, Cr may be included in an amount of 0.050 to 0.20 wt%. Ni: 0.05 wt% or less Nickel (Ni) may react with impurity elements to form fine sulfides, carbides, and nitrides, which may have a detrimental effect on magnetism. More specifically, it may contain 0.001 to 0.03 wt% of Ni. Zn: 0.01 wt% or less Zinc (Zn) may act as an impurity and deteriorate magnetism when the content is excessive. Therefore, Zn may be added more within the above-mentioned range. More specifically, Zr may be included in an amount of 0.001 to 0.005 wt%. Co: 0.05 wt% or less Cobalt (Co) does not form fine-sized precipitates that reduce the magnetism of steel plates, but it can increase high-temperature strength and cause poor coil shape after hot rolling. A non-oriented electrical steel sheet according to one embodiment of the present invention may further include at least one of Mo: 0.03 wt% or less (excluding 0%), B: 0.0050 wt% or less (excluding 0%), V: 0.0050 wt% or less (excluding 0%), Ca: 0.0050 wt% or less (excluding 0%), Nb: 0.0050 wt% or less (excluding 0%), Zr: 0.0050 wt% or less (excluding 0%), Te: 0.0100 wt% or less (excluding 0%), and Mg: 0.0050 wt% or less (excluding 0%). Mo: 0.030 wt% or less Molybdenum (Mo) may suppress segregation of segregating elements when added in excess, thereby reducing the effect of improving the grain structure. Therefore, Mo may be included at 0.03 wt% or less. The lower limit is not particularly limited, but since it plays a role in improving the grain structure by segregating on the surface and grain boundaries, it may be included at 0.001 wt% or more. More specifically, Mo may be included at 0.001 to 0.010 wt%. More specifically, Mo may be included at 0.005 to 0.010 wt%. B: 0.0050 wt% or less If boron (B) is added in excessive amounts, it may cause deterioration of magnetism through the formation of inclusions in the steel. Therefore, B may be included in an amount of 0.005 wt% or less. The lower limit is not particularly limited, but may be 0.0001 wt% due to steelmaking costs. More specifically, B may be included in an amount of 0.0001 to 0.0030 wt%. V: 0.0050 wt% or less Vanadium (V) has a very strong tendency to form precipitates inside the steel, and forms fine carbides or nitrides inside the parent material, thereby inhibiting grain growth and domain wall movement, thereby deteriorating iron loss. Therefore, the V content may be 0.0050 wt% or less, respectively. The lower limit is not particularly limited, but may be 0.0003 wt% due to steelmaking costs. That is, V may be included in an amount of 0.0003 to 0.0050 wt%. More specifically, V may be included in an amount of 0.0003 to 0.0030 wt%. Ca: 0.0050 wt% or less Calcium (Ca) has a very strong tendency to form precipitates within the steel, and forms fine sulfides within the parent metal, which inhibits grain growth and domain wall movement, thereby deteriorating iron loss. Nb: 0.0050 wt% or less Niobium (Nb) has a very strong tendency to form precipitates inside steel, and forms fine carbides or nitrides inside the base metal, thereby inhibiting grain growth and domain wall movement, thereby deteriorating iron loss. Therefore, the Nb content may be 0.0050 wt% or less. The lower limit is not particularly limited, but may be 0.0003 wt% due to steelmaking costs. That is, Nb may be included in an amount of 0.0003 to 0.0050 wt%. More specifically, Nb may be included in an amount of 0.0003 to 0.0030 wt%. Zr: 0.0050 wt% or less If zirconium (Zr) is added in excessive amounts, it may cause deterioration of magnetism through the formation of inclusions in the steel, etc. Therefore, Zr may be included in an amount of 0.005 wt% or less. The lower limit is not particularly limited, but may be set to 0.0001 wt% due to steelmaking costs. That is, Zr may be included in an amount of 0.0001 to 0.0050 wt%. More specifically, it may be included in an amount of 0.0005 to 0.0030 wt%. Te: 0.0100 wt% or less Tellurium (Te) can be added to prevent the oxide layer fractured during rolling from being pressed into the base metal and being removed by diffusing into the oxide layer on the surface of a hot-rolled coil and increasing the coefficient of friction between the oxide layer and the rolling work rolls, while being concentrated under the oxide layer to improve hardness. If the amount of Te added is too small, the effect may be minimal. If too much Te is added, the oxide layer is easily removed and the base metal comes into direct contact with the work rolls, reducing the effect, and during cold rolling, deformation bands may be excessively generated in the steel sheet, which may lead to the development of a {111} / ND texture, which is unfavorable to magnetism. More specifically, tellurium may be included in an amount of 0.0001 to 0.007 wt%. Mg: 0.0050 wt% or less Magnesium (Mg) is an element that mainly forms sulfide by combining with S, and can affect the surface oxide layer of the steel. Therefore, Mg may be included in an amount of 0.0050 wt% or less. The lower limit is not particularly limited, but may be set to 0.0001 wt% due to the cost of steelmaking. That is, Mg may be included in an amount of 0.0001 to 0.0050 wt%. More specifically, it may be included in an amount of 0.0005 to 0.0030 wt%. The remainder includes Fe and unavoidable impurities. The unavoidable impurities are impurities mixed in during the steelmaking step and the manufacturing process of the non-oriented electrical steel sheet, and since this is widely known in the relevant field, a detailed description is omitted. In one embodiment of the present invention, the addition of elements other than the alloy components described above is not excluded, and various elements may be included within a range that does not impair the technical idea of ​​the present invention. When additional elements are further included, they are included in place of the remainder Fe. As described above, in one embodiment of the present invention, by developing a specific aggregate structure of a non-oriented electrical steel sheet, strength and magnetism can be improved simultaneously. Specifically, the non-oriented electrical steel sheet satisfies the following equation 1. [Formula 1] 0.45 ≤ (VA+VB+VC) / (VD+VE+VF) ≤ 1.45 (In Equation 1, VA, VB, VC, VD, VE, and VF represent the area fraction (%) of the aggregate structure having an orientation within 15° from (001)[0-10], (001)[-1-10], (100)

[0025] , (223)[1-10], (111)[3-41], and (112)[1-10], respectively.) In one embodiment of the present invention, the fractions of (001) planes and (111) planes parallel to the rolling plane, which have been mainly examined as textures that greatly affect magnetism in the past, are important, but (223) and (112) planes, which are similar textures, are also important. In one embodiment of the present invention, the fractions and integration degrees of (001)[0-10], (001)[-1-10], (100)

[0025] textures that are advantageous to magnetization are strengthened, and the fractions and integration degrees of (223)[1-10], (111)[3-41], (112)[1-10] textures that are disadvantageous to magnetization are reduced, thereby improving magnetism. If the value of Equation 1 is too small, magnetization may be inferior and iron loss may increase. Even if the value of Equation 1 is larger, no additional magnetic improvement occurs, and the process for achieving this may become complicated. More specifically, Equation 1 can be between 0.50 and 1.40. In Equation 1, (hkl) <uvw>The texture orientation indicated by means of the texture orientation indication in the Miller index notation. The Miller index is a notation used in crystallography to indicate the direction and plane of the crystal lattice, and (hkl) is the plane parallel to the steel sheet rolling plane in the measured texture. Also, the vector <uvw>refers to the direction parallel to the rolling direction in the measurement set structure. In one embodiment of the present invention, the value of Equation 1 can be calculated by observing and analyzing the fraction of the aggregate structure through electron backscatter diffraction (EBSD) measurement and using the results. In order to ensure the reliability of the data, the measurement can be performed so that at least 5,000 crystal grains can be included. The tolerance angle can be set to 15° or less. In addition, the non-oriented electrical steel sheet can satisfy the following equation 2. [Formula 2] 0.35 ≤ VC / VE ≤ 1.35 (In Equation 2, VC and VE represent the area fraction (%) of the aggregate structure having orientations within 15° from (100)

[0025] and (111)[3-41], respectively.) Equation 2 is a formula that, among the aggregate structures, (100)

[0025] has a more favorable effect on magnetism, and (111)[3-41] has a more adverse effect on magnetism. If the value of Equation 2 is too small, magnetization may not occur well during magnetization, which may greatly reduce iron loss. Even if the value of Equation 2 is larger, no additional magnetic enhancement occurs, and the process for achieving this may become complicated. More specifically, Equation 2 may be 0.35 to 1.30. In one embodiment of the present invention, the aggregate structure of the non-oriented electrical steel sheet described above is specified through cold-rolled sheet annealing, and the aggregate structure characteristics may not be substantially changed through subsequent punching and stress relief annealing. As described above, in one embodiment of the present invention, a specific aggregate structure can be developed to simultaneously improve strength and magnetism. Specifically, a non-oriented electrical steel sheet according to one embodiment of the present invention may have a core loss (W10 / 400) of 12.0 W / kg or less and a magnetic flux density (B50) of 1.60 T or more. The thickness standard may be 0.20 mm. More specifically, the core loss (W10 / 400) may be 9.0 to 11.0 W / kg. The magnetic flux density (B50) may be 1.61 to 1.70 T. The iron loss (W10 / 400) is the iron loss when a magnetic flux density of 1.0 T is induced at a frequency of 400 Hz. The magnetic flux density (B50) means a magnetic flux density induced in a magnetic field of 5000 A / m. Iron loss (10 / 400) and magnetic flux density (B50) can be measured with a single sheet tester in the rolling direction and the direction perpendicular to the rolling, and the average values ​​can be measured. In addition, one embodiment of the present invention also has excellent mechanical strength. More specifically, the yield strength may be 480 MPa or more and 570 MPa or less. The yield strength can be measured using the 0.2% off-set method during a tensile test. The properties of the non-oriented electrical steel sheet described above can be measured by separating the non-oriented electrical steel sheet from the iron core. In one embodiment of the present invention, the core is formed by laminating the aforementioned non-oriented electrical steel sheets, thereby achieving high efficiency and excellent strength. A nitriding diffusion layer exists from the side of the laminate toward the inside, thereby further improving the strength. The nitrogen content in the nitrogen diffusion layer from the side of the laminate to 30 μm inward may be 0.005 to 0.020 wt%. If the nitrogen content in the nitrogen diffusion layer is too small, appropriate strength enhancement may not be achieved. In addition, if the amount of nitrogen in the nitrogen diffusion layer from the side of the laminate to the inside is too large, domain movement may be hindered, which may have a negative effect on magnetism. In one embodiment of the present invention, only the rotor core among the cores may have the above-described characteristics. The stator core has a relatively small importance in strength characteristics and may not have the above characteristics. More specifically, the nitrogen content in the nitrogen diffusion layer from the side of the laminate to 30 μm inward may be 0.010 to 0.015 wt%. The side surface of the laminate refers to a surface parallel to the thickness direction of the non-oriented electrical steel sheet (i.e., the lamination direction of the laminate). When the non-oriented electrical steel sheet is punched into a cylindrical shape, the circumference becomes the side surface. The nitrogen content up to 30㎛ from the side surface can be measured by methods such as combustion analysis, energy dispersive spectrometry, and GDS (glow discharge spectrometer). The nitrogen content refers to the average nitrogen content within 30㎛ of the side surface. A method for manufacturing a core according to one embodiment of the present invention comprises the steps of: preparing a non-oriented electrical steel sheet containing, in wt%, Si: 1.5 to 5.0%, Al: 0.1 to 2.5%, and Mn: 0.1 to 2.5%, with the remainder being Fe and unavoidable impurities; stamping and laminating the non-oriented electrical steel sheets to manufacture a laminate; and annealing the laminate in an atmosphere containing a nitriding gas. First, prepare a non-oriented electrical steel sheet. The steel composition and texture characteristics of the non-oriented electrical steel sheet have been described in relation to the non-oriented electrical steel sheet in the core, so redundant descriptions are omitted. As described above, the steel composition and texture characteristics of the non-oriented electrical steel sheet in the core and the non-oriented electrical steel sheet before core manufacturing may not substantially change. Non-oriented electrical steel sheets can be manufactured as follows. Specifically, the manufacturing process can include a step of hot-rolling a slab to manufacture a hot-rolled steel sheet; a step of cold-rolling the hot-rolled steel sheet to manufacture a cold-rolled sheet; and a cold-rolled sheet annealing step of annealing the cold-rolled sheet. Below, each step is explained in detail. First, the slabs are hot rolled. Since the alloy composition of the slab has been described in the alloy composition of the non-oriented electrical steel sheet mentioned above, a duplicate description will be omitted. Since the alloy composition does not substantially change during the manufacturing process of the non-oriented electrical steel sheet, the alloy composition of the non-oriented electrical steel sheet and the slab are substantially the same. Specifically, the slab contains Si: 1.5 to 5.0% by weight, Al: 0.1 to 2.5%, Mn: 0.1 to 2.5%, and the remainder includes Fe and inevitable impurities. As for other additional elements, they have been described in the alloy composition of non-oriented electrical steel sheets, so any duplicate description will be omitted. The slab can be heated before hot rolling. The heating temperature of the slab is not limited, but the slab can be heated to 1200℃ or lower. If the slab heating temperature is too high, precipitates such as AlN and MnS present in the slab may be re-dissolved and then finely precipitated during hot rolling and annealing, which may inhibit grain growth and reduce magnetism. Next, the slab is hot rolled to produce a hot-rolled plate. In one embodiment of the present invention, it was found that in order to improve the aggregate structure, it is necessary to precisely control the conditions from the hot rolling stage. Specifically, it was found that it is necessary to control the reduction ratio of each pass in the rolling. In one embodiment of the present invention, the step of manufacturing a hot rolled steel sheet includes a rough rolling step and a finish rolling step. The rough rolling stage is the process of manufacturing bars by first rolling the slabs moved from the casting machine into the form of steel plates, and is composed of 3 to 4 rolling mills. The finishing rolling is the process of rolling the rough rolled steel plates (bars) to the final hot rolling target thickness to make hot rolled coils, and is composed of a continuous multi-stage rolling mill. The thought rolling step is performed through n passes, where n is 2 or more, and satisfies Equation 3. [Formula 3] R1 / (R1+R2+……+Rn) ≥ 0.20 (In Equation 3, R1 to Rn represent the pressure reduction ratios (%) of the 1st to nth passes, respectively.) In one embodiment of the present invention, since the reduction ratio and the first reduction ratio at each stage of the finishing rolling have a significantly large effect on the formation of the grain structure, if the reduction ratio of each pass is appropriately adjusted as in Equation 3, the α-fiber and γ-fiber grain structures can be weakened, thereby improving the magnetism. R1 means the first pass, and the number of passes can be based on passing through the work roll. In addition, the nth pass is the last pass, and R1+R2+… …+Rn means the sum of the reduction ratios of all passes. The reduction ratio can be obtained by (steel plate thickness before pass - steel plate thickness after pass) / (steel plate thickness before pass) × 100(%). In Equation 3, R1+R2+… …+Rn means the total sum obtained from the reduction ratio (%) of the first pass of the finishing rolling to the reduction ratio (%) of the last pass. In one embodiment of the present invention, the rolling process may be 3 to 7 passes (i.e., n is 3 to 7). If the number of passes is too small, the rolling load may be too large, making the work difficult. If the number of passes is too large, productivity may be reduced. If the reduction ratio R1 of the first pass of the rolling process is too large to satisfy Equation 3, the γ-fiber may be greatly strengthened, resulting in poor magnetism. More specifically, the value of Equation 3 may be between 0.21 and 0.45. The thought rolling step can satisfy the following equation 4. [Formula 4] R1 / Rn ≤ 8.0 (In Equation 4, R1 and Rn represent the pressure reduction ratios (%) of the 1st and nth passes, respectively.) If the reduction ratio Rn of the last pass of the rolling process is too small to satisfy Equation 4, the improvement effect of the magnetization-friendly directions (001)[0-10], (001)[-1-10], (100)

[0025] may not be sufficient. More specifically, the value of Equation 4 may be 1.5 to 7.5. The first pass reduction ratio (R1) in the rolling process can be 40 to 80%, more specifically 42 to 80%. The reduction ratio (Rn) of the last pass in the rolling process can be 7 to 35%, more specifically 10 to 30%. The hot rolled sheet may have a thickness of 1.0 to 4.5 mm. The finishing rolling temperature in the step of manufacturing the hot rolled sheet may be 800°C or higher. Specifically, it may be 800 to 1000°C. The hot rolled sheet may be coiled at a temperature of 700°C or lower. More specifically, the thickness of the hot rolled sheet may be 1.5 to 4.3 mm. After manufacturing the hot-rolled steel plate, a step of annealing the hot-rolled plate may be further included. At this time, the soaking temperature may be 850 to 1100°C. If the annealing temperature is too low, the recrystallized structure may not be formed or may grow finely, so that the effect of increasing the magnetic flux density is small. If the annealing temperature is too high, the magnetic properties may rather deteriorate, and the rolling workability may deteriorate due to deformation of the plate shape. More specifically, the temperature range may be 830 to 1080°C. The soaking time may be 10 to 300 seconds. The hot-rolled plate annealing step may be omitted. Next, the hot rolled steel sheet is cold rolled to manufacture a cold rolled sheet. At this time, cold rolling can be performed at a reduction ratio of 40 to 85%. If the reduction ratio is too low, the accumulated strain energy in the rolled steel sheet is small, making it difficult to recrystallize in the subsequent annealing process, so that the rolled structure remains, which can cause problems in improving the magnetic flux density and iron loss. On the other hand, if the reduction ratio is too high, it can cause problems in the subsequent annealing process. <111> / ND The problem may occur that recrystallization of the orientation grains is promoted and the grains become finer, resulting in inferior magnetic flux density and increased iron loss. More specifically, the reduction ratio may be 60 to 75%. The cold rolling step may use a Tandem cold rolling mill that continuously cold-rolls the steel sheet using a plurality of rolling stands, or a Reverse rolling mill that discontinuously cold-rolls the steel sheet using 12 or more rolling rolls. The final rolled thickness may be 0.1 mm to 0.35 mm. The process of manufacturing cold rolled sheets can be performed once or twice or more with intermediate annealing in between. Next, the cold rolled sheet is annealed in the cold rolled sheet annealing step. In the process of annealing the cold rolled sheet, the annealing temperature is not particularly limited as long as it is a temperature that is usually applied to non-oriented electrical steel sheets. The iron loss of non-oriented electrical steel sheets is closely related to the grain size. The iron loss of non-oriented electrical steel sheets can be divided into hysteresis loss and eddy current loss. The hysteresis loss decreases as the grain size increases, and conversely, the eddy current loss increases as the grain size increases. Therefore, there is an optimal grain size at which the sum of the hysteresis loss and the eddy current loss is minimized. Therefore, it is important to derive and apply an annealing temperature that can secure the optimal grain size, and the annealing temperature is appropriate if it is 850 to 1100℃. If the annealing temperature is too low, the grains are too fine, which increases the hysteresis loss, and if it is too high, the grains are too coarse, which increases the eddy current loss, resulting in poor iron loss. Also, the annealing time is appropriate if it is 10 to 300 seconds, and annealing can be performed in a mixed atmosphere of hydrogen or argon and nitrogen to prevent magnetic deterioration due to the formation of an oxide layer. During the cold rolled sheet annealing process, all (i.e., more than 99%) of the processed structures formed during the cold rolling stage can be recrystallized. After cold-rolled sheet annealing, an insulating film can be formed. The insulating film can be treated with an organic, inorganic, or organic-inorganic composite film, and it can also be treated with other insulating film agents. The non-oriented electrical steel sheet manufactured in this manner has the steel composition and texture characteristics described above. Returning to the description of the method of manufacturing the core, the laminate is manufactured by stamping and laminating non-oriented electrical steel sheets. Stamping means cutting the non-oriented electrical steel sheets into the shape of the core of the motor, and can be stamped into a ring shape. Laminating means stacking the electrical steel sheets in the thickness direction. Next, in the stress relief annealing step, the laminate is annealed in an atmosphere containing a nitriding gas. In one embodiment of the present invention, a nitrogen diffusion layer can be formed from the side of the laminate toward the inside through nitriding by adding a nitriding gas to the atmosphere during stress relief annealing. Nitriding gas can be used without limitation as long as it can nitridize the side of the laminate during the stress relief annealing process. However, nitrogen (N2) is excluded from the nitriding gas because it contains N but has low reactivity and practically does not nitridize. Specifically, the nitriding gas can be any gas that can dissociate nitrogen at a temperature higher than room temperature, such as ammonia or cyanite, and diffuse into the steel to nitride. More specifically, it can contain ammonia. The nitriding gas may be included in the atmosphere at 0.7 to 95 volume %. If the nitriding gas is included too little, the strength enhancement may not be sufficiently achieved. If the nitriding gas is included too much, a large amount of nitride may be formed on the side, which may adversely affect the magnetism. More specifically, the nitriding gas may be included in the atmosphere at 1.0 to 15.0 volume %. The remainder of the atmosphere may comprise nitrogen (N2) and hydrogen (H2). Specifically, it may comprise 5 to 15 volume % hydrogen and the remainder nitrogen. More specifically, it may comprise 90 volume % or less nitrogen. The soaking temperature of the stress relief annealing step can be 530 to 920°C. If the soaking temperature is too low, residual stress may remain at the time of punching, which may adversely affect the magnetism. If the soaking temperature is too high, the strength may be adversely affected. More specifically, it can be 550 to 900°C. The soaking time can be 550 seconds to 60 minutes. More specifically, it can be 10 to 30 minutes. Hereinafter, the present invention will be described in more detail through examples. However, these examples are only for illustrating the present invention, and the present invention is not limited thereto. Example 1 Table 1 and the remainder Fe and unavoidable impurities were included to manufacture a slab. It was heated to 1170℃, hot-rolled to a thickness of 2.2 mm, and then coiled at 680℃. At this time, 7 passes were performed in the sand rolling, and the reduction ratio of each pass was performed as shown in Table 2 below. The hot-rolled steel sheet was hot-rolled at 1000℃ for 50 seconds. After the hot-rolled sheet annealing, the pickled specimen was cold-rolled to a thickness of 0.2 mm, and finally cold-rolled sheet annealing was performed. At this time, the cold-rolled sheet annealing was performed at 1000℃ for 50 seconds. The aggregate structure was analyzed by cutting the steel plate in the rolling direction to obtain a specimen and using EBSD. At this time, the tolerance angle was set to 15°. Thereafter, the stator core manufacturing process was simulated, and stress relief annealing was performed at 750°C for 1800 seconds in an atmosphere of 90% by volume of nitrogen and 10% by volume of hydrogen. In addition, stress relief annealing was performed in an ammonia-containing atmosphere at the temperature, time, and as summarized in Table 3 below, simulating the rotor core manufacturing process. The atmosphere was composed of ammonia, 10 vol% hydrogen, and the remainder nitrogen as summarized in Table 3 below. Yield strength was measured by the 0.2% off-set method during tensile testing. Iron loss (W10 / 400) and magnetic flux density (B50) were measured using a single sheet tester. The nitrogen content in the nitrogen diffusion layer up to 30 μm from the rotor side was measured using an energy dispersive X-ray spectrometer. Steel type SiMnAlCPSTiN Resistivity (μΩ cm) 13.281.452.080.00150.0040.00400.00070.002782.023.642.291.470.00200.0090.00090.00180.002383.933.281.530 .630.00130.0080.00380.00320.003766.143.110.751.070.00110.0130.00140.00290.001864.753.281.812.240.00220.0100.00110.00130.00168 5.963.482.070.630.00140.0090.00140.00150.001571.472.950.821.480.00100.0100.00230.00140.002867.983.810.672.050.00290.0130.0019 0.00200.001483.393.340.560.960.00140.0100.00090.00270.002865.0103.441.291.340.00290.0070.00330.00360.001574.6112.861.501.560. 00240.0070.00360.00240.002271.7123.261.100.990.00110.0090.00270.00180.003767.5133.010.541.640.00260.0120.00130.00130.002868.8 142.742.502.120.00320.0120.00160.00090.002782.3153.551.341.510.00130.0060.00260.00280.002778.0162.410.981.300.00070.0070.0008 0.00270.001260.7172.990.850.450.00370.0030.00190.00150.003456.9183.061.110.700.00080.0070.00270.00210.002162.0193.150.621.320 .00360.0040.00300.00290.002367.3203.720.381.540.00120.0050.00370.00260.001474.8213.830.671.640.00180.0070.00380.00250.004078.8223.061.991.610.00090.0060.00150.00170.001277.3232.620.752.030.00120.0100.00100.00320.002670.0243.901.791.600.00210.0110.00210.00300.003185.5253.301.610.540.00320.0100.00370.00230.001565.7263.711.440.890.00350.0 030.00270.00340.001673.4272.890.671.480.00240.0130.00280.00180.001066.4283.512.050.500.00190.0080.00120.00220.003870.1292.981.030.830.00390.0130.00150.00360.003462.1303.200.500.570.00200.0080.00280.00120.002958.7. SteelR1 (%)R1+R2+…+Rn (%)Rn (%)Formula 3 4173286130.265.6253235290.231.8344209220.212.0436168110.213.3558228250.252.3638100120.383.2771180250.392.8852180140.293.7980324130.256.21042201230.211.81155262160.213.41266221160.304.11366151170.443.91471285100.257.11564286150.224.31 653254130.214.1173813150.297.61836132180.272.01932181240.181.3207120670.3410.1215028860.178.32243238180.182.42328178280.161.0246018650.3212.0256520360.3210.8268025490.318.92732350260.091.2286333670.199.0293820140.199.5304022140.1810.0 Kang Jong-sik 1 type 2Maintenance temperature (℃)Maintenance time (sec)Ammonia (vol%)Nitrogen content in nitrogen diffusion layer (wt%)11.090.375005000.50.001821.370.925005001.00.002031.150.8450050010.00.002340.550.8850050090.00.003851.300.705506000.50.003760.770.425506001.00.005470.500.4055060010.00.007580.651.285506009 0.00.013890.720.6890018000.50.0043100.670.3590018001.00.0068111.180.82900180010.00.0117121.091.05900180090.00.0183131.021.0595020000.50.0045140.960.9295020001.00.0352151.290.38950200010.00.04731 61.200.375005000.50.0012171.060.575005001.00.0019180.890.6050050010.00.0024190.850.3350050090.00.0035200.380.655506000.50.0037210.200.235506001.00.0054220.430.2955060010.00.0078230.380.555506009 0.00.0143240.560.3390018000.50.0041250.350.3390018001.00.0071260.360.47900180010.00.0129270.480.28900180090.00.0173280.410.2995020000.50.0041290.370.3395020001.00.0243300.400.26950200010.00.0457 Yield strength (MPa) W10 / 400 (W / Kg) B50 (T) Steel grade Stator Rotor Stator Rotor Stator Rotor Classification 15305329.129.521.621.61 Comparative example 25215229.209.231.621.61 Comparative example 34854869.8810.091.631.62 Comparative example 448749110.0210.151.631.63 Comparative example 55305339.359.511.621.62 Comparative example 65175279.809.941.631.62 Invention example 74814929.779.971 .621.62Invention example 85235539.199.351.621.61Invention example 95125139.809.911.631.62Comparative example 105445519.659.711.621.61Invention example 114985139.829.971.631.61Invention example 1250452510.1810.521.641.63Invention example 135115149.869.891.631.63Comparative example 145305579.5012.081.621.59Comparative example 1554257410.1313.581.6 41.59Comparative Example 1641441613.1515.211.591.57Comparative Example 1742943213.2115.101.591.58Comparative Example 1845846112.5314.891.581.57Comparative Example 1950851212.5515.131.571.57Comparative Example 2049049213.1013.241.591.58Comparative Example 2150651612.9814.551.591.57Comparative Example 2252053612.8014.861.591.58Comparative Example 2349051212 .7313.981.581.57Comparative Example 2458759013.1215.421.591.57Comparative Example 2548348813.8615.481.571.56Comparative Example 2653955412.4014.841.581.58Comparative Example 2748651212.9414.941.581.57Comparative Example 2850250312.8214.751.581.56Comparative Example 2946747213.2015.421.591.58Comparative Example 3046147313.6815.761.581.56Comparative Example As shown in Tables 1 to 4, when the steel composition and rolling reduction ratio are appropriately controlled and the conditions during SRA are appropriately controlled, the characteristics of both the stator and the rotor are excellent, and in particular, the strength of the rotor is improved. On the other hand, if the steel composition or electrical steel sheet manufacturing process conditions are not properly controlled, such as steel grades 16 to 30, and a specific aggregate structure is not developed, it can be confirmed that the characteristics of both the stator and rotor are inferior. In addition, it can be confirmed that steel grades 1 to 5, 9, 13 to 15 did not have appropriate conditions during the SRA process of the rotor, so that nitrogen in the nitrogen diffusion layer on the rotor side did not properly penetrate, and the strength of the rotor was not sufficiently improved. The present invention is not limited to the embodiments, but can be manufactured in various different forms, and a person having ordinary skill in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical idea or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.< / uvw> < / uvw>

Claims

A laminate comprising a plurality of non-oriented electrical steel sheets, each of which contains 1.5 to 5.0 wt% of Si, 0.1 to 2.5 wt% of Al, and 0.1 to 2.5 wt% of Mn, with the remainder being Fe and unavoidable impurities. The above non-oriented electrical steel sheet is an iron core having a nitrogen diffusion layer extending from the side of the laminate to an inner direction of 30 ㎛, and a nitrogen content in the nitrogen diffusion layer of 0.005 to 0.020 wt%. In the first paragraph, The above non-oriented electrical steel sheet is an iron core further comprising at least one of P: 0.1 wt% or less (excluding 0%), C: 0.005 wt% or less (excluding 0%), S: 0.005 wt% or less (excluding 0%), Ti: 0.005 wt% or less (excluding 0%), and N: 0.0@0 wt% or less (excluding 0%). In the first paragraph, The above non-oriented electrical steel sheet is an iron core further containing 0.005 to 0.200 wt% of each or a combined amount of one or more of Sn, Sb, Bi, Pb, Ge and As. In the first paragraph, The above non-oriented electrical steel sheet is an iron core further comprising at least one of Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Ni: 0.05 wt% or less (excluding 0%), Zn: 0.01 wt% or less (excluding 0%), and Co: 0.05 wt% or less (excluding 0%). In the first paragraph, The above non-oriented electrical steel sheet is an iron core further comprising at least one of Mo: 0.03 wt% or less (excluding 0%), B: 0.0050 wt% or less (excluding 0%), V: 0.0050 wt% or less (excluding 0%), Ca: 0.0050 wt% or less (excluding 0%), Nb: 0.0050 wt% or less (excluding 0%), Zr: 0.005 wt% or less (excluding 0%), Te: 0.01 wt% or less (excluding 0%), and Mg: 0.0050 wt% or less (excluding 0%). In the first paragraph, The above non-oriented electrical steel sheet is a core satisfying the following equation 1. [Formula 1] 0.45 ≤ (VA+VB+VC) / (VD+VE+VF) ≤ 1.45 (In Equation 1, VA, VB, VC, VD, VE, and VF represent the area fraction (%) of the aggregate structure having orientations within 15° from (001)[0-10], (001)[-1-10], (100)[025], (223)[1-10], (111)[3-41], and (112)[1-10], respectively.) In the first paragraph, The above non-oriented electrical steel sheet has a core satisfying the following formula 1: [Formula 2] 0.35 ≤ VC / VE ≤ 1.35 (In Equation 2, VC and VE represent the area fraction (%) of the aggregate structure having orientations within 15° from (100)[025] and (111)[3-41], respectively.) A step for preparing a non-oriented electrical steel sheet comprising Si: 1.5 to 5.0% by weight, Al: 0.1 to 2.5%, and Mn: 0.1 to 2.5% by weight, with the remainder being Fe and unavoidable impurities; A step of manufacturing a laminate by punching and laminating the above non-oriented electrical steel sheets; and A method for manufacturing a core, comprising a stress relief annealing step of annealing the laminate in an atmosphere containing a nitriding gas. In Article 8, A method for manufacturing an iron core, wherein the atmosphere contains 0.7 to 95 volume% of a nitriding gas. In Article 8, The above atmosphere is a method for manufacturing an iron core including the remainder nitrogen and hydrogen. In Article 8, A method for manufacturing a steel core, wherein the stress relief annealing step is performed at a temperature of 530 to 920°C for 550 seconds to 60 minutes. In Article 8, The above non-oriented electrical steel sheet is a method for manufacturing a core satisfying the following formula 1. [Formula 1] 0.45 ≤ (VA+VB+VC) / (VD+VE+VF) ≤ 1.45 (In Equation 1, VA, VB, VC, VD, VE, and VF represent the area fraction (%) of the aggregate structure having orientations within 15° from (001)[0-10], (001)[-1-10], (100)[025], (223)[1-10], (111)[3-41], and (112)[1-10], respectively.) In Article 8, The above non-oriented electrical steel sheet is a method for manufacturing a core satisfying the following formula 2. [Formula 2] 0.35 ≤ VC / VE ≤ 1.35 (In Equation 2, VC and VE represent the area fraction (%) of the aggregate structure having orientations within 15° from (100)[025] and (111)[3-41], respectively.) In Article 8, The steps for preparing the above non-oriented electrical steel sheet are: A step of manufacturing a hot-rolled steel sheet by hot-rolling a slab containing Si: 1.5 to 5.0% by weight, Al: 0.1 to 2.5%, and Mn: 0.1 to 2.5% by weight, with the remainder being Fe and unavoidable impurities; A step of manufacturing a cold rolled sheet by cold rolling the hot rolled steel sheet above, and A method for manufacturing an iron core, comprising: a cold rolled sheet annealing step of annealing the cold rolled sheet; In Article 14, The step of manufacturing the above hot rolled steel plate includes a rough rolling step and a finish rolling step, The thought rolling step is performed through n passes, where n is 2 or more, A method for manufacturing an iron core, comprising: [Formula 3] R1 / (R1+R2+……+Rn) ≥ 0.2 (In Equation 3, R1 to Rn represent the pressure reduction ratios (%) of the 1st to nth passes, respectively.) In Article 15, The above-mentioned rolling step is a method for manufacturing a core satisfying the following equation 4. [Formula 4] R1 / Rn ≤ 8 (In Equation 4, R1 and Rn represent the pressure reduction ratios (%) of the 1st and nth passes, respectively.)