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

Abstract

A non-oriented electrical steel sheet according to one embodiment contains 1.8 to 2.8 wt% silicon (Si), 0.6 wt% or less manganese (Mn) (excluding 0), 1.0 wt% or less aluminum (Al) (excluding 0), 0.0045 wt% or less of total rare earth elements (REE) (excluding 0), and the remainder being iron (Fe) and other unavoidable elements, thereby having mechanical properties suitable for use as a motor core material and excellent magnetic properties.

Description

Technology Field

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

[0002] With environmental regulations tightening globally in recent years, conventional internal combustion engine vehicles are being rapidly replaced by eco-friendly vehicles such as hybrid, electric, and hydrogen cars. Eco-friendly vehicles utilize electric motors to generate the driving force required for the vehicle and can reduce environmental pollution by significantly decreasing the emission of harmful exhaust gases.

[0003] As interest in and demand for such eco-friendly vehicles increase, the demand for electric motors, which generate the driving force required for the vehicle, is also rising. An electric motor is a device that uses electricity to generate the driving force needed for a vehicle, and energy efficiency—the ability to operate for a longer period using the same amount of energy—is a crucial technical factor.

[0004] To increase the energy efficiency of such electric motors, it is essential to improve the magnetic performance of the non-oriented electrical steel sheets used as the core material. Non-oriented electrical steel is a material that possesses uniform magnetic properties in all directions regardless of the rolling direction; to enhance energy efficiency, it is necessary to lower iron losses and increase magnetic flux density. Prior art literature

[0005] Prior Art 1: Korean Registered Patent No. 10-0709056 The problem to be solved

[0006] The present invention has been devised to solve the above problems, and the objective of the present invention is to provide a non-oriented electrical steel sheet and a method for manufacturing a non-oriented electrical steel sheet that have magnetic properties suitable for use as a motor core and simultaneously have excellent mechanical properties by controlling the alloy composition.

[0007] The problems of the present invention are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0008] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises silicon (Si) 1.8 to 2.8 wt%, manganese (Mn) 0.6 wt% or less (excluding 0), aluminum (Al) 1.0 wt% or less (excluding 0), a total content of rare earth elements (REE) 0.0045 wt% or less (excluding 0), and the remainder being iron (Fe) and other unavoidable elements.

[0009] The above rare earth elements are scandium (Sc), hafnium (Hf), and tantalum (Ta), and the content of the above rare earth elements may be scandium (Sc) 0.0015 wt% or less, hafnium (Hf) 0.0015 wt% or less, and tantalum (Ta) 0.0015 wt% or less.

[0010] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include 0.005 weight% or less of sulfur (S) and 0.005 weight% or less of titanium (Ti).

[0011] The content of the above sulfur (S), titanium (Ti), scandium (Sc), hafnium (Hf), and tantalum (Ta) can satisfy the following Equation 1.

[0012] [Equation 1]

[0013] 2.2≤ln(3[S]+15[Ti]+18[Sc]+20[Hf]+23[Ta])≤4.5

[0014] (However, in the above Formula 1, [S], [Ti], [Sc], [Hf], and [Ta] may each represent the content of S, Ti, Sc, Hf, and Ta in weight%.)

[0015] A non-oriented electrical steel sheet according to one embodiment of the present invention has an effective packing ratio (α effective ) can be 89% or more.

[0016] A non-oriented electrical steel sheet according to one embodiment of the present invention has iron loss (W 15 / 50 ) 3.85 W / kg or less, and magnetic flux density (B 50 ) can be 1.66 T or more.

[0017] A non-oriented electrical steel sheet according to one embodiment of the present invention can satisfy the following Equation 2.

[0018] [Equation 2]

[0019] 1.85≤M t ≤3.00

[0020] (Mt=0.001*{(0.144*B 50 -.0115)*[83.2+[266.1 / (W 15 / 50 +15.8)]]}*α effective And, Kt is the motor torque coefficient, η is the motor efficiency coefficient, α effective is the effective fill rate, B 50 is the magnetic flux density (T) at 5000 A / m, and W 15 / 50 is the iron loss value (W / kg) at 50Hz and 1.5T.

[0021] A non-oriented electrical steel sheet according to one embodiment of the present invention may further contain 0.003 weight% or less of carbon (C), 0.015 weight% or less of phosphorus (P), and 0.004 weight% or less of nitrogen (N).

[0022] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises: a first step of preparing a steel material comprising silicon (Si) 1.8 to 2.8 wt%, manganese (Mn) 0.6 wt% or less (excluding 0), aluminum (Al) 1.0 wt% or less (excluding 0), a total content of rare earth elements (REE) 0.0045 wt% or less (excluding 0), and the remainder being iron (Fe) and other unavoidable elements; a second step of hot rolling the steel material to form a hot-rolled steel sheet; a third step of hot-rolling annealing the hot-rolled steel sheet; a fourth step of cold-rolling the hot-rolled steel sheet obtained from the third step to form a cold-rolled steel sheet; and a fifth step of cold-rolling annealing the cold-rolled steel sheet.

[0023] The above rare earth elements are scandium (Sc), hafnium (Hf), and tantalum (Ta), and the content of the above rare earth elements may be scandium (Sc) 0.0015 wt% or less, hafnium (Hf) 0.0015 wt% or less, and tantalum (Ta) 0.0015 wt% or less.

[0024] The above steel may further contain 0.005 weight% or less of sulfur (S) and 0.005 weight% or less of titanium (Ti).

[0025] The content of the above sulfur (S), titanium (Ti), scandium (Sc), hafnium (Hf), and tantalum (Ta) can satisfy the following Equation 1.

[0026] [Equation 1]

[0027] 2.2≤ln(3[S]+15[Ti]+18[Sc]+20[Hf]+23[Ta])≤4.5

[0028] (However, in the above Formula 1, [S], [Ti], [Sc], [Hf], and [Ta] may each represent the content of S, Ti, Sc, Hf, and Ta in weight%.)

[0029] In the above fourth step, the surface roughness (Ra) of the roll used for the cold rolling may be 0.07 to 3.0 μm.

[0030] Between the second step and the third step, it may further include a shot blasting step in which a shot of 2 to 1200 μm in size is rotated at a speed of 2000 rpm or more and sprayed under high-speed conditions of 50 to 120 m / s, and a pickling treatment step in which acid is supplied to a pickling tank in which a reaction with the steel plate takes place. Effects of the invention

[0031] According to one embodiment of the present invention, by controlling the amount of rare earth elements added and mechanical properties, a non-oriented electrical steel sheet having magnetic and mechanical properties suitable for use as a motor core material and a method for manufacturing a non-oriented electrical steel sheet can be realized.

[0032] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims. Brief explanation of the drawing

[0033] FIG. 1 is a flowchart illustrating the schematic sequence of a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention. Specific details for implementing the invention

[0034] Hereinafter, preferred embodiments of the present invention are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention is not limited or restricted by the following embodiments.

[0035] Additionally, when it is stated that a component (or area, layer, part, etc.) is "on," "connected," or "combined" with another component, it means that it may be directly placed / connected / combined with the other component, or that a third component may be placed between them.

[0036] Terms such as "include" or "have" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0037] In order to clearly explain the present invention, detailed descriptions of related prior art that are irrelevant to the explanation or that may unnecessarily obscure the essence of the invention have been omitted. Furthermore, when assigning reference numerals to the components of each drawing in this specification, identical or similar reference numerals are assigned to identical or similar components throughout the entire specification.

[0038] Furthermore, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0039] Unless otherwise specified, the notation 'A ~ B' for numerical values ​​A and B shall mean 'A or greater, B or less'. In such notation, if a unit is attached only to numerical value B, that unit shall also apply to numerical value A.

[0040] Also, unless specifically noted otherwise, 1 ppm is 0.0001 wt%.

[0041] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0043] Non-oriented electrical steel sheets

[0044] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises silicon (Si) 1.8 to 2.8 wt%, manganese (Mn) 0.6 wt% or less (excluding 0), aluminum (Al) 1.0 wt% or less (excluding 0), a total content of rare earth elements (REE) 0.0045 wt% or less (excluding 0), and the remainder being iron (Fe) and other unavoidable elements.

[0045] Hereinafter, the role and content of alloying elements included in a non-oriented electrical steel sheet according to one embodiment of the present invention will be described in detail.

[0047] Silicon (Si)

[0048] Silicon is a major additive element in electrical steel sheets, and it improves magnetic properties by increasing the resistivity of the steel and reducing eddy current losses. If the silicon content is too low, the increase in resistivity may not be sufficient, making it difficult to obtain low iron loss values. On the other hand, as the amount of silicon added increases, the permeability and magnetic flux density may decrease, and the brittleness of the material may increase, leading to inferior cold rolling performance and punchability. Therefore, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain silicon in an amount of 1.8 to 2.8 weight%.

[0050] Manganese (Mm)

[0051] Manganese (Mn) is an element that improves magnetic properties by increasing resistivity together with silicon (Si) and reducing iron loss, and can be added for the purpose of forming a texture favorable to magnetic properties. If manganese is not added, the increase in resistivity is insufficient, which may lead to an increase in high-frequency iron loss. On the other hand, if the manganese content is excessive, a coarse secondary phase is formed, and a {111} texture unfavorable to magnetization is formed, which may result in inferior magnetic properties. Accordingly, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain manganese in an amount of 0.6 wt% or less (excluding 0), and preferably 0.01 wt% or more and 0.6 wt% or less.

[0053] Aluminum (Al)

[0054] Aluminum is an element that, along with silicon (Si) and manganese (Mn), increases resistivity and reduces iron loss, and is a major additive element in electrical steel sheets. Generally, aluminum can improve the workability of cold rolling by improving the rollability of IF steel (Interstitial Free steel). In addition, aluminum can combine with nitrogen (N) present in the steel to form nitrides such as AlN. Therefore, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain 1.0 weight% or less of aluminum, and preferably 0.1 weight% or more and 1.0 weight% or less.

[0056] Rare Earth Elements (REE)

[0057] Rare-earth elements (REE) are added to promote grain boundary segregation and magnetic flux density formation in steel. A non-oriented electrical steel sheet according to one embodiment of the present invention may have a total content of rare-earth elements described below of 0.0045 weight% or less (excluding 0). By adding the rare-earth elements described below, the electrical steel sheet according to one embodiment of the present invention can facilitate the improvement of the elastic modulus within the metal material, thereby improving mechanical resistance characteristics.

[0058] The reason for the improvement in the aforementioned mechanical properties is as follows. When rare earth elements are added, physical interactions occur at the nuclear and electronic levels between atoms with atomic radii differing by 15 to 30 percent, resulting in lattice distortion. This lattice distortion affects the elastic modulus properties, and the degree of lattice distortion can improve the elastic modulus properties. Additionally, the Peierls-Nabarro stress increases, which can lead to improved mechanical properties. Therefore, the addition of appropriate rare earth elements can improve mechanical properties while maintaining the intrinsic properties of non-oriented electrical steel sheets.

[0059] The content and role of the above rare earth elements will be described in more detail below.

[0060] A rare earth element (REE) according to one embodiment of the present invention includes scandium (Sc), hafnium (Hf), and tantalum (Ta).

[0061] The content of the above-mentioned rare earth elements may be 0.0015 wt% or less for scandium (Sc), 0.0015 wt% or less for hafnium (Hf), and 0.0015 wt% or less for tantalum (Ta).

[0062] At this time, the roles of each rare earth element are as follows.

[0063] Scandium (Sc) can improve strength and inhibit grain growth by forming compounds such as Sc3C4, ScN, and Fe2Sc. Furthermore, if the amount exceeds 0.0015 weight%, deterioration of magnetic properties may occur due to the coarsening of compounds, and additionally, premature fracture of the material or inferior elastic properties may occur during the processing process, which has the disadvantage of making it difficult to utilize as a structural material. Therefore, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain scandium (Sc) in an amount of 0.0015 weight% or less. Additionally, when added to the steel within the above range, elastic modulus properties can be improved.

[0064] Hafnium (Hf) can improve strength and inhibit grain growth by forming compounds such as HfN and HfC. Furthermore, if the amount exceeds 0.0015 weight%, deterioration of magnetic properties may occur due to the coarsening of compounds, and additionally, premature fracture of the material or inferior elastic properties may occur during the processing process, which has the disadvantage of making it difficult to utilize as a structural material. Therefore, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain hafnium (Hf) in an amount of 0.0015 weight% or less. Additionally, when added to the steel within the above range, elastic modulus properties can be improved.

[0065] Tantalum (Ta) forms compounds such as TaN, TaC, and FeTa to improve strength and inhibit grain growth. Furthermore, if the amount exceeds 0.0015 weight%, deterioration of magnetic properties may occur due to the coarsening of compounds, which may lead to premature fracture of the material during processing or inferior elastic properties, and consequently, there is a disadvantage that it may be difficult to utilize it as a structural material. Therefore, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain tantalum (Ta) in an amount of 0.0015 weight% or less. Additionally, when added to the steel within the above range, elastic modulus properties can be improved.

[0067] Yellow (S)

[0068] Sulfur (S) is an impurity element in steel that is inevitably contained during the manufacturing process and can cause brittleness when added in large amounts. In addition, it can increase iron loss by combining with manganese (Mn) to form precipitates such as MnS and can degrade magnetic properties by inhibiting grain growth. Therefore, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain sulfur in an amount of 0.005 weight% or less.

[0070] Titanium (Ti)

[0071] Titanium (Ti) is an element with a very strong tendency to form precipitates in steel. It combines with carbon (C) or nitrogen (N) to form precipitates such as TiC and TiN, which inhibit grain growth. As titanium is added, magnetic properties become inferior, so it is desirable to add as little as possible. Accordingly, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain titanium (Ti) in an amount of 0.005 weight% or less.

[0073] A non-oriented electrical steel sheet according to one embodiment of the present invention may satisfy the following formula 1 for the content of sulfur (S), titanium (Ti), scandium (Sc), hafnium (Hf), and tantalum (Ta).

[0074] [Equation 1]

[0075] 2.2≤ln(3[S]+15[Ti]+18[Sc]+20[Hf]+23[Ta])≤4.5

[0076] (However, in the above Formula 1, [S], [Ti], [Sc], [Hf], and [Ta] may each represent the content of S, Ti, Sc, Hf, and Ta in weight%.)

[0077] Equation 1 above is a relationship between impurity elements S and Ti and rare earth elements Sc, Hf, and Ta among the alloy components of a non-oriented electrical steel sheet according to one embodiment of the present invention. Here, the additive elements may include solid solution strengthening elements added to enhance resistance to deformation of the crystal lattice due to precipitation formation and lattice deformation, and grain boundary embrittlement elements that are unintentionally included in the steel during the manufacture of the electrical steel sheet and reduce the magnetic properties or mechanical strength of the electrical steel sheet, requiring control of the amount added.

[0078] In Equation 1 above, the coefficients preceding each element represent the respective weights assigned to grain boundary embrittlement elements and solid solution strengthening elements. More specifically, the weights are assigned based on the bond energy derived from the difference in atomic radii of each element relative to iron (Fe) and the heat of sublimation. In this case, elements with higher weights may exhibit stronger lattice distortion effects due to physical interactions occurring at the nuclear and electron levels between atoms. For elements with lower weights, a large amount must be added to achieve the same effect as elements with higher weights.

[0079] Accordingly, the non-oriented electrical steel sheet according to one embodiment of the present invention can design an alloy composition that improves magnetic properties and mechanical strength by controlling the natural logarithm (ln) value obtained by multiplying the content of sulfur (S), titanium (Ti), and rare earth elements and the weighting factor for those elements through Equation 1, thereby controlling the appropriate content of solid solution strengthening elements and grain boundary embrittlement elements.

[0080] Meanwhile, if the above Equation 1 is less than 2.2, the effect of improving magnetic properties by the additive element may be insufficient. If the above Equation 1 is greater than 4.5, there may be too many impurities, which may result in inferior magnetic properties. Therefore, in one embodiment of the present invention, the above Equation 1 may be between 2.2 and 4.5, thereby allowing excellent elastic properties to be imparted to the steel sheet without degrading magnetic properties.

[0082] Carbon (C)

[0083] Carbon (C) can increase iron loss by combining with titanium (Ti) and niobium (Nb) to form carbides such as TiC and NbC, so it is desirable to have less of it. If the carbon content exceeds 0.003 weight%, it can cause magnetic aging and degrade magnetic properties. Therefore, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain carbon at 0.003 weight% or less.

[0085] Ph(P)

[0086] Phosphorus (P) is a grain boundary segregation element that improves texture, thereby increasing resistivity and contributing to lowering iron loss. However, if a large amount of phosphorus is added with a content exceeding 0.015 weight%, it can form excessive grain boundary segregation, which may lead to inhibition of grain growth, deterioration of magnetic properties, and reduced cold rolling performance. Therefore, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain phosphorus (P) in an amount of 0.015 weight% or less.

[0088] Nitrogen (N)

[0089] Nitrogen (N) combines with aluminum (Al) and titanium (Ti) to form precipitates such as AlN and TiN, which increase iron loss and inhibit grain growth. Therefore, it is desirable to add as little nitrogen as possible, and a non-oriented electrical steel sheet according to one embodiment of the present invention may contain 0.004 weight% or less of nitrogen (N).

[0091] In addition to the components of the steel described above, the remainder may contain Fe and unavoidable impurities. Unavoidable impurities are those introduced during the steelmaking stage and the manufacturing process of non-oriented electrical steel sheets; as this is widely known in the field, a detailed explanation is omitted.

[0092] In one embodiment of the present invention, the addition of elements other than the aforementioned alloy components is not excluded, and various elements may be included within a scope that does not impair the technical spirit of the present invention. If additional elements are included, they may be included to replace the remainder of Fe.

[0093] A non-oriented electrical steel sheet having the alloy composition described above and manufactured by a manufacturing method according to one embodiment of the present invention to be described below has an effective packing ratio (α effective ) can be 89% or more.

[0094] Generally, when manufacturing a motor, electrical steel sheets punched into a specific shape are laminated and bonded. At this time, the more aesthetically pleasing the surface shape, the more uniform the adhesion between opposing sheets is when laminated, and the less empty space is achieved. This is quantified as the 'fill factor,' which is, more specifically, the ratio of the area occupied by the substrate steel within a given space; the higher the value, the better the magnetic properties inherent to the material can be realized.

[0095] To increase motor efficiency, it is important to realize the material's inherent properties as closely as possible, and it is necessary to maximize the fill factor by minimizing voids.

[0096] The concept of "effective fill ratio" devised in this invention redefines the concept of the aforementioned "fill ratio" to reflect the "dent" characteristics that inevitably occur due to friction between the roll and the steel plate and the application of load during the steel plate production process. The effective fill ratio can be defined as follows.

[0097] Effective Drainage Rate = (Drainage Rate [1 - (0.0001 * Dent Volume) / 100)]

[0098] Generally, when operating an AC synchronous motor, torque ripple can become severe if the fill factor is low. Torque ripple is a phenomenon in which the output torque periodically increases or decreases during motor rotation, and the larger the torque ripple, the more likely it is to cause problems such as noise and vibration. The above problem becomes prominent at an effective fill factor of 80% or less; however, in order to satisfy a level where motor commercialization is possible and there are no motor driving problems caused by torque ripple, the present invention utilizes an effective fill factor (α effective ) can be 89% or more.

[0099] In the case of a grade of high-grade material (Si: 1.8 ~ 2.8 wt%) that is lower than the highest grade material, the magnetic properties of the material itself are inferior, and since the application of the manufactured motor is different, the fill factor standard can be set differently from the highest grade material and the fill factor range.

[0100] In addition, the non-oriented electrical steel sheet according to one embodiment of the present invention has iron loss (W 15 / 50 ) 3.85 W / kg or less, and magnetic flux density (B 50 ) can be 1.66 T or more.

[0101] In addition, a non-oriented electrical steel sheet according to one embodiment of the present invention can satisfy the following Equation 2.

[0102] [Equation 2]

[0103] 1.85≤M t ≤3.00

[0104] (Mt=0.001*{(0.144*B 50 -.0115)*[83.2+[266.1 / (W 15 / 50 +15.8)]]}*α effective And, Kt is the motor torque coefficient, η is the motor efficiency coefficient, α effective is the effective fill rate, B 50 is the magnetic flux density (T) at 5000 A / m, and W 15 / 50 is the iron loss value (W / kg) at 50Hz and 1.5T.

[0105] Mt may be a value indicating the soundness of the motor. The 'motor efficiency coefficient' and 'motor torque coefficient' values ​​were obtained by substituting material characteristics into a fitting equation derived from motor manufacturing and evaluation using electrical steel sheets. Each of the 'motor efficiency coefficient' and 'motor torque coefficient' can be derived from the following calculation formulas.

[0106] The 'motor efficiency coefficient' and 'motor torque coefficient' can each be derived from the following formulas.

[0107] Kt = (0.144*B 50 -0.0115)

[0108] η = [83.2 + [266.1 / (W 15 / 50 +15.8)]]

[0109] The equation regarding the motor efficiency coefficient is derived by establishing the relationship between iron loss and maximum efficiency based on a motor rotational speed of 1300-1500 rpm. The equation regarding the motor torque coefficient is B of the torque-current curve 50 This is the relationship equation expanded using the logistic function after plotting for .

[0110] Since a motor can be considered sound the higher its torque, the lower its losses, and the higher its 'effective fill factor,' as mentioned above, M t It was composed.

[0111] In a non-oriented electrical steel sheet according to one embodiment of the present invention, if Equation 2 is less than 1.85, the magnetic properties are inferior, making it unsuitable for moving a structure with a torque that can be achieved in a motor, and if it exceeds 3.00, there is a problem that the process economy is lowered due to the material yield.

[0112] Accordingly, in the case of a non-oriented electrical steel sheet according to one embodiment of the present invention, by satisfying Equation 2 above, the formation of dents in the sheet material can be minimized according to sound elastic characteristics, and the surface characteristics can be improved by reducing the volume of dents formed.

[0113] A non-oriented electrical steel sheet according to one embodiment of the present invention may have excellent elastic properties within the steel sheet without deteriorating magnetic properties when the composition of the alloy is composed of the rare earth elements described above and the composition range of the components satisfies Equation 1.

[0114] In addition, if Equation 2 is satisfied, it is possible to realize a non-oriented electrical steel sheet that forms a motor laminate having a high effective fill rate, high motor efficiency, and high torque due to excellent surface characteristics.

[0115] Hereinafter, a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention will be described in detail.

[0117] Method for manufacturing non-oriented electrical steel sheets

[0118] Hereinafter, a method for manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention will be described with reference to FIG. 1.

[0119] FIG. 1 is a flowchart illustrating the schematic sequence of a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0120] Referring to FIG. 1, a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises: a first step (S1) of preparing a steel material comprising silicon (Si) 1.8 to 2.8 wt%, manganese (Mn) 0.6 wt% or less (excluding 0), aluminum (Al) 1.0 wt% or less (excluding 0), a total content of rare earth elements (REE) 0.0045 wt% or less (excluding 0), and the remainder being iron (Fe) and other unavoidable elements; a second step (S2) of hot rolling the steel material to form a hot-rolled steel sheet; a third step (S3) of hot-rolling annealing the hot-rolled steel sheet; a fourth step (S4) of cold-rolling the hot-rolled steel sheet obtained in the third step (S3) to form a cold-rolled steel sheet; and a fifth step (S5) of cold-rolling annealing the cold-rolled steel sheet.

[0121] As the content of alloy components has been explained in the section on the alloy composition of non-oriented electrical steel sheets, a redundant explanation is omitted. Furthermore, since the content of alloy components does not substantially change during the manufacturing process described later, the composition of the steel material and the alloy composition of the non-oriented electrical steel sheets are substantially identical.

[0122] First, the first step (S1) is a step of preparing steel having the alloy composition range described above. More specifically, it may be a step of manufacturing a semi-finished product by designing the alloy components to the alloy composition range described above. The semi-finished product may be a slab, but is not necessarily limited thereto. In addition, the manufacturing of the slab may be carried out by a process known in the relevant technical field, such as a steelmaking process or a continuous casting process.

[0123] In a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention, the second step (S2) may form a hot-rolled steel sheet by hot-rolling the steel material that has undergone the first step (S1).

[0124] More specifically, the second step (S2) may include a reheating process and may include a hot rolling process and a coiling process.

[0125] First, the reheating process described above is a process performed prior to the hot rolling process, and may involve reheating the steel for a subsequent process. More specifically, it may be a step of charging the steel into a furnace and heating it uniformly to facilitate plastic deformation.

[0126] At this time, if the reheating temperature is less than 1000℃, the rolling load increases during hot rolling, which may reduce rolling performance. On the other hand, if the reheating temperature exceeds 1250℃, precipitates such as carbon (C), sulfur (S), and nitrogen (N) in the semi-finished product may be re-dissolved, and fine precipitates of grains and grain boundaries may be formed upon cooling. While these fine precipitates may be advantageous for improving strength, they can inhibit grain growth and reduce iron loss. Therefore, in the present invention, the reheating temperature can be controlled to 1000 to 1250℃.

[0127] In addition, the reheating time according to the present invention is 350 to 850 minutes. If the reheating time is less than 350 minutes, sufficient time for the precipitate to be dissolved is not secured, and the material may become non-homogeneous. In addition, if the reheating time exceeds 850 minutes, a problem of increased production costs due to prolonged heating may occur.

[0128] Next, a hot rolling process to form a hot-rolled steel sheet may be performed. The hot rolling process may include rough rolling and finish rolling. Rough rolling may involve making the steel into a rolled material having a suitable shape, thickness, and width, and finish rolling may involve adjusting the steel to a predetermined thickness and width and rolling it at a finishing temperature suitable for the application to achieve a good surface and shape.

[0129] At this time, the finishing temperature of the hot rolling process is preferably 850 to 1000℃. If the finishing rolling temperature is below 850℃, rolling is performed in a two-phase region, and a non-uniform structure may be formed. On the other hand, if the finishing rolling temperature exceeds 1000℃, a problem of rapidly reducing strength may occur.

[0130] After the above hot rolling process, a coiling process may be performed. The coiling temperature is preferably 550 to 750°C. If the coiling temperature is below 550°C, the grain size becomes too small, and the grains may not grow sufficiently even after annealing. If the coiling temperature exceeds 750°C, fine precipitates may be generated, which may degrade magnetic properties.

[0131] The thickness of the hot-rolled steel sheet formed through the second step (S2) above may be 1.8 to 3.5 mm. As the thickness of the hot-rolled steel sheet increases, the reduction rate during cold rolling increases, and the texture may deteriorate. Therefore, it is desirable to make the thickness of the hot-rolled steel sheet 3.5 mm or less. On the other hand, if the thickness of the hot-rolled steel sheet is excessively thin, less than 1.8 mm, the thickness of the steel sheet obtained after cold rolling is insufficient, which may cause shape defects when applied to products.

[0132] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may perform a third step (S3) of hot-rolling annealing the hot-rolled steel sheet after the second step (S2). The third step (S3) may be a hot-rolling annealing step in which annealing is performed to ensure microstructural uniformity and cold-rollability of the steel material that has undergone hot rolling.

[0133] At this time, the temperature preferred for the hot rolling annealing may be 900 to 1100°C. If the hot rolling annealing temperature is below 900°C, the elongated cast structure remaining after hot rolling may cause microstructural non-uniformity. In addition, the elongated cast structure inhibits grain growth, resulting in the formation of small grains, which may act as an interfering factor during cold rolling. On the other hand, if the hot rolling annealing temperature exceeds 1100°C, it may cause texture imbalance in the final product and reduce magnetic properties. The annealing temperature may be 900 to 1100°C to form a uniform microstructure with an average of 50 μm to 200 μm with the elongated cast structure removed.

[0134] The above hot rolling annealing may be performed for a certain period of time in the range of 10 to 180 seconds so as to form an appropriate grain size under each temperature condition. At this time, the heating rate and cooling rate may be 20℃ / s or higher.

[0135] In addition, a shot blast and pickling process may be additionally performed between the second step (S2) and the third step (S3) described later. First, the shot blast can be performed by rotating a shot of 2 to 1200 μm in size at a speed of 2000 rpm or more and spraying it under high-speed conditions of 50 to 120 m / s. The pickling process can be performed by supplying 18% hydrochloric acid to a pickling tank where it reacts with the iron plate, thereby reacting with fine residual scale that is not removed by mechanical means.

[0136] Subsequently, a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may perform a fourth step (S4) of cold-rolling a hot-rolled steel sheet to form a cold-rolled steel sheet. The fourth step (S4) may be a process of rolling the hot-rolled steel sheet at a temperature below the recrystallization temperature to further reduce the thickness of the steel sheet. More specifically, it may be a process of rolling the hot-rolled steel sheet to a thickness and width that meet the specifications of the final product.

[0137] The surface roughness (Ra) of the roll used for cold rolling in the above fourth step (S4) may be 0.07 to 3.0 μm.

[0138] In addition, the above cold rolling may be performed as warm rolling by raising the temperature of the sheet metal to 75 to 200°C to improve the ease of rolling.

[0139] The cold-rolled steel sheet formed through the above fourth step (S4) may be 0.5 mm or less. At this time, the final reduction rate may be 50% or more.

[0140] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may perform a fifth step (S5) of cold-rolling annealing the cold-rolled steel sheet after the fourth step (S4). The cold-rolling annealing may be performed to soften the cold-rolled steel sheet, which has been hardened by recrystallization during cold rolling. Additionally, the cold-rolling annealing may be performed at a temperature that derives an optimal grain size, taking into account iron loss reduction and mechanical properties.

[0141] Preferably, the cold rolling annealing temperature may be 800 to 1100°C. If the cold rolling annealing temperature is below 800°C, the size of the crystal grains formed after cold rolling annealing is fine, and hysteresis loss may increase. On the other hand, if the cold rolling annealing temperature exceeds 1100°C, the size of the crystal grains becomes coarse, and eddy current loss may increase.

[0142] Accordingly, in step 5 (S5) according to one embodiment of the present invention, heat treatment can be performed by raising the temperature of a cold-rolled steel sheet to 800 to 1100°C, maintaining it for 10 to 10000 seconds, and cooling it. At this time, the heating rate and cooling rate are preferably 20°C / s or higher.

[0143] In addition, the above 5th step (S5) can be performed in a mixed atmosphere of nitrogen and hydrogen to prevent oxidation and nitridation of the surface of the cold-rolled steel sheet, thereby improving the surface quality of the cold-rolled steel sheet.

[0144] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may further include a coating step after the fifth step (S5). The coating step may be performed to ensure the insulation properties and improve the punchability of the non-oriented electrical steel sheet, and may refer to forming an insulating film on the surface of the cold-rolled steel sheet that has undergone the fifth step (S5). At this time, forming the insulating film may be performed using a process known in the art.

[0145] A non-oriented electrical steel sheet and a manufacturing method according to one embodiment of the present invention satisfy the alloy composition and Equation 1 described above, and by controlling the cold-rolled roll roughness conditions, the dent volume of the sheet material after cold rolling is controlled. Through this, as a result, an electrical steel sheet satisfying excellent torque characteristics and magnetic characteristics satisfying Equation 2 can be manufactured.

[0147] Comparative Examples and Examples

[0148] The structure and operation of the present invention will be explained in more detail below through preferred comparative examples and embodiments. However, these are provided to aid in understanding the present invention and do not limit the invention.

[0149] Tables 1 and 2 below show the major elements and impurity elements of the alloy composition constituting the comparative example and the example. Tables 3 and 4 show the content of rare earth elements included in the comparative example and the example and whether Equation 1 is satisfied. Tables 5 and 6 show the roll roughness conditions, dent characteristics, effective fill rate, and fill rate of the comparative example and the example. Tables 7 and 8 show the mechanical properties, magnetic properties, and whether Equation 2 is satisfied.

[0150] The comparative example and the embodiment were manufactured in the following manner. Slabs having alloy compositions listed in Tables 1 to 6 below were heated to 1150°C and hot-rolled to produce a 2.3 mm thick hot-rolled steel sheet, and then pickled and cold-rolled to produce a 0.5 mm thick cold-rolled steel sheet. Subsequently, the cold-rolled steel sheet was subjected to continuous heat treatment in a nitrogen atmosphere for 3 minutes. During this process, the heating rate was 20°C / s. Afterward, the final product, a non-oriented electrical steel sheet, was manufactured through a coating process. Process conditions not listed were controlled variables and were controlled in the same manner according to the method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention described above.

[0151] The magnetic properties of the comparative example and the example were measured in accordance with the international standard IEC 60404-2, and a test specimen with a length of 300 mm and a width of 30 mm was prepared and measured.

[0152] The magnetic flux density (B50) value was derived using the Epstein frame test in accordance with IEC60404-2, just like the iron loss.

[0153] In addition, the volume of the dent was calculated as follows after measuring the diameter and depth of the dent using an optical microscope.

[0154] Vd(Dent Volume) = 2 / 3 ** ((Dent Diameter * 1 / 2)) * (Dent Diameter * (1 / 2)) * (Dent Depth)) * Number of Dents

[0155] In addition, the packing density was measured in accordance with the method described in IEC 60404-13, and the specimen size used was a 300x30 Epstein frame specimen.

[0156] In Tables 3 and 4 below, the satisfaction of [Equation 1] indicates whether the value of ln(3[S]+15[Ti]+18[Sc]+20[Hf]+23[Ta]), which is the relationship between the content of the impurity elements and rare earth elements, satisfies the range of 2.2 to 4.5.

[0157] In Tables 7 and 8 below, whether [Equation 2] is satisfied is M t It indicates whether the value satisfies the range of 1.85 to 3.00.

[0158] In addition, 'W in Table 3 below 15 / 50 ' represents the iron loss value at 50Hz and 1.5T, and the unit used is W / kg. 'B 50' is the magnetic flux density at 5000 A / m, and the unit used is T.

[0159] division Major Elements (Weight%) Impurity elements (ppm) Si Al Mn C S N Ti P Example 1 1.8166 0.72 0.14 14 20 13 26 67 Example 2 1.8157 0.43 0.2 29 38 8 6 96 Example 3 2.6244 0.18 0.48 21 35 10 37 141 Example 4 2.7266 0.87 0.26 20 15 23 32 132 Example 5 2.5566 0.17 0.24 20 31 7 45 119 Example 6 2.7887 0.19 0.43 14 12 13 19 119 Example 7 2.2444 0.09 0.53 27 50 36 35 68 Example 8 2.2019 0.92 0.26 22 20 15 11 104 Example 9 2.3624 0.75 0.43 16 38 26 37 109 Example 10 1.9866 0.46 0.47 27 23 36 21 138 Example 11 1.9066 0.78 0.5 10 5 18 35 143 Comparative Example 1 0.8766 0.51 0.31 28 36 21 48 136 Comparative Example 2 3.1566 0.77 0.25 13 37 25 31 98 Comparative Example 3 2.0466 0.01 0.43 27 10 39 47 147 Comparative Example 4 2.2755 1.15 0.47 7 20 20 49 95 Comparative Example 5 2.0666 0.64 0.001 12 23 30 42 76 Comparative Example 6 3.0266 1.07 1.09 12 20 15 11 133 Comparative Example 7 1.6266 0.01 0.001 23 23 15 27 135 Comparative Example 8 1.629 1.42 0.92 7 26 29 25 140 Comparative Example 9 3.0266 0.01 1.21 12 26 7 8 74 Comparative Example 10 3.0666 1.28 0.001 27 23 25 29 137 Comparative Example 11 2.3036 0.77 0.38 29 0 12 38 83 Comparative Example 12 1.8166 0.69 0.5 22 110 18 23 137 Comparative Example 13 1.8266 0.31 0.23 24 15 0 9 105

[0160] division Major Elements (Weight%) Impurity elements (ppm) Si Al Mn C S N Ti P Comparative Example 14 2.2741 0.84 0.37 28 12 87 26 100 Comparative Example 15 2.0066 0.28 0.33 17 6 10 0 141 Comparative Example 16 1.8466 0.45 0.36 30 19 16 98 78 Comparative Example 17 1.8566 0.91 0.26 11 8 13 23 0 Comparative Example 18 1.9966 0.5 0.32 9 13 18 5 653 Comparative Example 19 1.9566 0.35 0.5 18 9 10 12 10 Comparative Example 20 1.8368 0.19 0.2 15 11 8 15 8 Comparative Example 21 2.0166 0.11 0.32 16 9 9 14 11 Comparative Example 22 2.088 0.89 0.54 20 10 39 30 6 Comparative Example 23 1.1212 0.22 0.4 30 20 20 15 14 Comparative Example 24 2.5412 0.46 0.4 27 23 30 42 8 Comparative Example 25 2.5724 0.57 0.46 24 11 30 19 10 Comparative Example 26 2.0666 0.36 0.4 21 23 36 39 10 Comparative Example 27 2.7628 0.41 0.45 17 38 28 16 7 Comparative Example 28 2.2308 0.83 0.22 8 18 18 42 10 Comparative Example 29 2.3266 0.64 0.24 27 37 25 13 6

[0161] division Rare earth elements (ppm) REE sum (ppm) [Equation 1] [Equation 1] Satisfaction Sc Hf Ta Example 1 14 7 11 32 2.218 O Example 2 7 13 15 35 2.39 O Example 3 11 1 6 18 2.259 O Example 4 8 10 5 23 2.316 O Example 5 1 10 3 14 2.269 O Example 6 10 9 6 25 2.516 O Example 7 8 5 3 16 2.315 O Example 8 12 11 9 32 2.424 O Example 9 3 12 7 22 2.211 O Example 10 8 5 11 24 2.427 O Example 11 4 12 10 26 2.239 O Comparative Example 1 11 6 15 32 1.902 X Comparative Example 2 13 15 6 34 2.102 X Comparative Example 3 10 12 9 31 1.999 X Comparative Example 4 14 12 12 38 1.857 X Comparative Example 5 12 12 9 33 2.002 X Comparative Example 6 6 9 8 23 2.65 O Comparative Example 7 9 7 6 22 2.388 O Comparative Example 8 9 13 14 36 2.129 X Comparative Example 9 9 12 9 30 2.524 O Comparative Example 10 7 9 13 29 2.203 O Comparative Example 11 8 15 10 33 2.096 X Comparative Example 12 6 7 13 26 2.104 X Comparative Example 13 6 13 15 34 2.432 O

[0162] division Rare earth elements (ppm) REE sum (ppm) [Equation 1] [Equation 1] Satisfaction Sc Hf Ta Comparative Example 14 12 9 8 29 2.291 O Comparative Example 15 13 9 9 31 2.738 O Comparative Example 16 8 7 14 29 1.544 X Comparative Example 17 13 11 15 39 2.144 X Comparative Example 18 13 12 10 35 2.501 O Comparative Example 19 0 10 9 19 2.84 O Comparative Example 20 36 14 6 56 1.987 X Comparative Example 21 9 0 10 19 2.722 O Comparative Example 22 6 71 8 85 1.587 X Comparative Example 23 11 6 0 17 2.777 O Comparative Example 24 14 9 82 105 1.192 X Comparative Example 25 0 0 0 0 3.461 O Comparative Example 26 47 74 93 214 0.681 X Comparative Example 27 98 0 0 98 1.464 X Comparative Example 28 0 67 0 67 1.665 X Comparative Example 29 0 0 54 54 1.869 X

[0164] division Roll roughness conditions (Ra, μm) Vd Dent Volume (㎛ 3 ) D# Number of dents (# / 1m 2 ) D d Dent depth (㎛) D di Dent diameter (㎛) α effective Effective fill rate[%] α-spotting rate[%] Example 1 0.08BTR Bright Roll 105.62 1 12 4.1 97.59 97.6 Example 2 747.22 3 5.5 9.3 94.13 94.2 Example 3 2808.5 5 5.8 13.6 93.537 93.8 Example 4 1148.645 2 19.5 7.5 91.794 91.9 Example 5 2.7 SBR Shot Blast Less Roll 3578.224 3 30.8 8.6 89.279 89.6 Example 6 7715.156 9 14.3 10.7 91.092 91.8 Example 7 3388.698 2 28.8 10.6 91.589 91.9 Example 8 10950.169 13 18.6 9.3 90.3 91.3 Example 9 7484.243 3 23.3 14.3 92.899 93.6 Example 10 10636.176 23 13.8 8 93.594 94.6 Example 11 10053.096 3 16 20 90.184 91.1 Comparative Example 1 0.08BTR Bright Roll 44684.098 9 34 16.7 83.972 87.9 Comparative Example 2 Panpadan Comparative Example 3 111170.126 15 38 19.3 74.573 83.9 Comparative Example 4 53616.515 8 50 16 84.323 89.1 Comparative Example 5 27597.635 10 36 12.1 81.585 83.9 Comparative Example 6 Panpadan Comparative Example 7 17375.191 17 41 6.9 86.471 88 Comparative Example 8 Onion, medium green onion Comparative Example 9 onion Comparative Example 10 onion Comparative Example 11 37782.168 17 38.5 10.5 78.902 82 Comparative Example 12 2.7 SBR Shot Blast Less Roll 87642.424 20 31.5 16.3 77.55 85 Comparative Example 13 37118.068 21 18.8 13.4 77.031 80

[0165] division Roll roughness conditions (Ra, μm) Vd Dent Volume (㎛ 3 ) D# Number of dents (# / 1m 2 ) D d Dent depth (㎛) D di Dent diameter (㎛) α effective Effective fill rate[%] α-spotting rate[%] Comparative Example 14 2.7 SBR Shot Blast Less Roll 100639.664 25 35.1 14.8 77.345 86 Comparative Example 15 40637.787 13 30.9 13.9 77.229 80.5 Comparative Example 16 45319.799 18 42 10.7 82.293 86.2 Comparative Example 17 44964.673 31 34.2 9 82.133 86 Comparative Example 18 Hot rolling cracks occur Comparative Example 19 25996.679 15 33.1 10 82.79 85 Comparative Example 20 27143.361 10 36 12 85.709 88.1 Comparative Example 21 16586.431 9 39 9.5 84.574 86 Comparative Example 22 37322.489 32 41.8 7.3 79.71 82.8 Comparative Example 23 13883.044 15 23.9 8.6 81.65 82.8 Comparative Example 24 80916.925 46 29.9 10.6 76.927 83.7 Comparative Example 25 70109.604 20 28.6 15.3 78.669 84.6 Comparative Example 26 159835.714 38 50.6 12.6 72.338 86.1 Comparative Example 27 27873.938 12 21.1 14.5 84.186 86.6 Comparative Example 28 52765.51 67 35.6 6.5 78.336 82.7 Comparative Example 29 78819.204 22 32.1 14.6 81.617 88.6

[0166] division Kt (Motor Torque Coefficient) [Nm / Amp.] η(Motor Efficiency Coefficient)[%] Mt [Equation 2] O / X W 15 / 50 [W / kg] B 50 [T] Example 1 0.239 97.438 2.273 O 2.89 1.74 Example 2 0.238 97.362 2.178 O 2.99 1.73 Example 3 0.238 97.499 2.167 O 2.81 1.73 Example 4 0.235 97.514 2.101 O 2.79 1.71 Example 5 0.226 97.468 1.967 O 2.85 1.65 Example 6 0.238 97.453 2.109 O 2.87 1.73 Example 7 0.238 97.654 2.125 O 2.61 1.73 Example 8 0.238 97.506 2.092 O 2.8 1.73 Example 9 0.238 97.537 2.153 O 2.76 1.73 Example 10 0.235 97.576 2.144 O 2.71 1.71 Example 11 0.238 97.46 2.089 O 2.86 1.73 Comparative Example 1 0.236 96.111 1.906 X 4.81 1.72 Comparative Example 2 Panpadan Comparative Example 3 0.233 96.639 1.681 X 4 1.7 Comparative Example 4 0.229 96.558 1.864 X 4.12 1.67 Comparative Example 5 0.228 96.646 1.794 X 3.99 1.66 Comparative Example 6 Panpadan Comparative Example 7 0.228 95.89 1.887 X 5.17 1.66 Comparative Example 8 Onion, medium green onion Comparative Example 9 onion Comparative Example 10 onion Comparative Example 11 0.229 96.599 1.745 X 4.06 1.67 Comparative Example 12 0.225 95.752 1.668 X 5.4 1.64 Comparative Example 13 0.228 96.735 1.696 X 3.86 1.66

[0167] division Kt (Motor Torque Coefficient) [Nm / Amp.] η(Motor Efficiency Coefficient)[%] Mt [Equation 2] O / X W 15 / 50 [W / kg] B 50 [T] Comparative Example 14 0.226 96.180 1.682 X 4.7 1.65 Comparative Example 15 0.229 96.439 1.705 X 4.3 1.67 Comparative Example 16 0.229 96.459 1.818 X 4.27 1.67 Comparative Example 17 0.23 96.505 1.826 X 4.2 1.68 Comparative Example 18 Hot rolling cracks occur Comparative Example 19 0.229 96.498 1.829 X 4.21 1.67 Comparative Example 20 0.228 96.518 1.882 O 4.18 1.66 Comparative Example 21 0.229 96.532 1.869 X 4.16 1.67 Comparative Example 22 0.229 96.572 1.763 X 4.1 1.67 Comparative Example 23 0.228 96.538 1.794 X 4.15 1.66 Comparative Example 24 0.228 96.525 1.69 X 4.17 1.66 Comparative Example 25 0.226 96.518 1.717 X 4.18 1.65 Comparative Example 26 0.229 96.465 1.598 X 4.26 1.67 Comparative Example 27 0.228 96.386 1.846 X 4.38 1.66 Comparative Example 28 0.228 96.68 1.723 X 3.94 1.66 Comparative Example 29 0.228 91.568 1.701 X 16 1.66

[0168] Referring to Tables 1 to 4 above, Examples 1 to 14 satisfy the alloy composition range according to one embodiment of the present invention, and the value of Formula 1 satisfies 2.2 to 4.5.

[0169] In addition, the effective drop rate of Examples 1 to 11 is 89% or higher, and the dent volume of Examples 1 to 11 is 11,000 μm 3 It can be confirmed that the surface characteristics are improved compared to the comparative examples described below.

[0170] In addition, Examples 1 to 11 have iron loss (W 15 / 50 The value of ) is 3.85 W / kg or less, and the magnetic flux density (B 50 It can be confirmed that ) has superior magnetic properties compared to the comparative examples described later, with a value of 1.66T or higher.

[0171] In addition, Examples 1 to 11 can be confirmed to satisfy Equation 2 for Mt according to iron loss and magnetic flux density values.

[0172] On the other hand, Comparative Examples 1 to 29 do not satisfy the alloy composition range according to one embodiment of the present invention or do not satisfy Formula 1. Therefore, it can be confirmed that Comparative Examples 1 to 29 do not satisfy the torque characteristics and magnetic characteristics targeted by the present invention.

[0173] That is, Comparative Examples 1 to 29 do not achieve the effective fill rate of 89% or more targeted in the present invention, and Mt is less than 1.85, so they do not satisfy Equation 2 and it can be confirmed that the torque characteristics are inferior.

[0174] Also, iron loss (W 15 / 50 The value of ) is greater than 3.85 W / kg, and the magnetic flux density (B 50 It can be confirmed that the magnetic properties are also inferior, with ) being less than 1.62T.

[0175] As described above, preferred embodiments according to the present invention have been examined. It is obvious to those skilled in the art that, in addition to the embodiments described above, the present invention may be embodied in other specific forms without departing from its spirit or scope. Therefore, the embodiments described above should be regarded as illustrative rather than restrictive, and accordingly, the present invention is not limited to the description above but may be modified within the scope of the appended claims and their equivalents.

Claims

Claim 1 A non-oriented electrical steel sheet comprising 1.8 to 2.8 wt% silicon (Si), 0.6 wt% or less manganese (Mn) (excluding 0), 1.0 wt% or less aluminum (Al) (excluding 0), 0.0015 wt% or less scandium (Sc) (excluding 0), 0.0015 wt% or less hafnium (Hf) (excluding 0), 0.0015 wt% or less tantalum (Ta) (excluding 0), 0.005 wt% or less sulfur (S), 0.005 wt% or less titanium (Ti), 0.003 wt% or less carbon (C), 0.015 wt% or less phosphorus (P), 0.004 wt% or less nitrogen (N), and the remainder being iron (Fe) and other unavoidable elements, wherein the content of sulfur (S), titanium (Ti), scandium (Sc), hafnium (Hf), and tantalum (Ta) satisfies the following Formula 1: [Formula 1]2.2≤ln(3[S]+15[Ti]+18[Sc]+20[Hf]+23[Ta])≤4.5(wherein in Equation 1 above, [S], [Ti], [Sc], [Hf], and [Ta] may each represent the content of S, Ti, Sc, Hf, and Ta in weight%.) Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 In paragraph 1, the effective fill rate (α effective ) is a non-oriented electrical steel sheet with a purity of 89% or higher. Claim 6 In paragraph 1, iron loss (W 15 / 50 ) 3.85 W / kg or less, and magnetic flux density (B 50 ) is a non-oriented electrical steel sheet with a thickness of 1.66 T or more. Claim 7 In claim 1, a non-oriented electrical steel sheet satisfying the following Equation 2. [Equation 2] 1.85 ≤ M t ≤3.00(Mt=0.001*{(0.144*B 50 -.0115)*[83.2+[266.1 / (W 15 / 50 +15.8)]]}*α effective And, Kt is the motor torque coefficient, η is the motor efficiency coefficient, α effective is the effective fill rate, B 50 is the magnetic flux density (T) at 5000 A / m, and W 15 / 50 is the iron loss value (W / kg) at 50Hz and 1.5T. Claim 8 delete Claim 9 A first step of preparing a steel material comprising 1.8 to 2.8 wt% silicon (Si), 0.6 wt% or less manganese (Mn) (excluding 0), 1.0 wt% or less aluminum (Al) (excluding 0), 0.0015 wt% or less scandium (Sc) (excluding 0), 0.0015 wt% or less hafnium (Hf) (excluding 0), 0.0015 wt% or less tantalum (Ta) (excluding 0), 0.005 wt% or less sulfur (S), 0.005 wt% or less titanium (Ti), 0.003 wt% or less carbon (C), 0.015 wt% or less phosphorus (P), 0.004 wt% or less nitrogen (N), and the remainder being iron (Fe) and other unavoidable elements; a second step of hot rolling the steel material to form a hot-rolled steel sheet; a third step of hot-rolling annealing the hot-rolled steel sheet; and cold rolling the hot-rolled steel sheet that has undergone the third step. A method for manufacturing a non-oriented electrical steel sheet comprising: a fourth step of forming a cold-rolled steel sheet by rolling; and a fifth step of cold-rolling annealing the cold-rolled steel sheet, wherein the content of sulfur (S), titanium (Ti), scandium (Sc), hafnium (Hf), and tantalum (Ta) satisfies the following Equation 1: [Equation 1] 2.2 ≤ ln(3[S] + 15[Ti] + 18[Sc] + 20[Hf] + 23[Ta]) ≤ 4.5 (wherein in Equation 1, [S], [Ti], [Sc], [Hf], and [Ta] may each represent the content of S, Ti, Sc, Hf, and Ta in weight%.) Claim 10 delete Claim 11 delete Claim 12 delete Claim 13 In claim 9, the fourth step is a method for manufacturing a non-oriented electrical steel sheet in which the surface roughness (Ra) of the roll used for cold rolling is 0.07 to 3.0 μm. Claim 14 A method for manufacturing a non-oriented electrical steel sheet according to claim 9, further comprising, between the second step and the third step, a shot blasting step in which a shot of 2 to 1200 μm in size is rotated at a speed of 2000 rpm or more and sprayed under high-speed conditions of 50 to 120 m / s, and a pickling treatment step in which acid is supplied to a pickling tank in which a reaction with the steel sheet takes place.

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