Non-oriented electrical steel sheet and method for manufacturing non-oriented electrical steel sheet

Abstract

A non-oriented electrical steel sheet according to an embodiment comprises 2.0 to 3.8 wt% of silicon (Si), 0.5 wt% or less (excluding 0) of manganese (Mn), 0.6 wt% or less (excluding 0) of aluminum (Al), 0.0015 wt% or less of scandium (Sc), 0.0015 wt% or less of hafnium (Hf), 0.0015 wt% or less of tantalum (Ta), and the balance being iron (Fe) and other inevitable elements, and thus may have mechanical properties suitable for use as a motor core material.

Description

Non-oriented electrical steel sheet and method for manufacturing non-oriented electrical steel sheet

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

[0002] As environmental regulations have become increasingly stringent worldwide, conventional internal combustion engine vehicles are rapidly being replaced by eco-friendly vehicles such as hybrid, electric, and hydrogen-powered vehicles. Eco-friendly vehicles utilize electric motors to generate the necessary power and significantly reduce harmful exhaust gas emissions, thereby reducing environmental pollution.

[0003] As interest in and demand for eco-friendly vehicles grows, so does the demand for electric motors, which generate the power required for these vehicles. Electric motors use electricity to generate the power needed for vehicles. Energy efficiency, which allows them to operate for longer periods of time using the same amount of energy, is a crucial technological element.

[0004] Since motors mounted in automobiles rotate at high speeds (over 200 Hz) during both constant and high-speed driving, the ideal core material for these motors, non-oriented electrical steel, should simultaneously meet high elasticity and high tensile strength to ensure mechanical stability. To achieve this, various methods, including controlled rolling and ambient heat treatment, are being explored.

[0005] [Prior Art Literature]

[0006] [Patent Document]

[0007] (Patent Document 1) Korean Patent No. 10-0709056

[0008] The present invention has been devised to solve the above problems, and the object of the present invention is to provide a non-oriented electrical steel sheet and a method for manufacturing a non-oriented electrical steel sheet having excellent mechanical properties for use as a motor core by controlling alloy components.

[0009] The tasks of the present invention are not limited to the tasks mentioned above, and other tasks not mentioned will be clearly understood by those skilled in the art from the description below.

[0010] A non-oriented electrical steel sheet according to one embodiment of the present invention contains 2.0 to 3.8 wt% of silicon (Si), 0.5 wt% or less of manganese (Mn) (excluding 0), 0.6 wt% or less of aluminum (Al) (excluding 0), 0.0015 wt% or less of scandium (Sc), 0.0015 wt% or less of hafnium (Hf), 0.0015 wt% or less of tantalum (Ta), and the remainder of iron (Fe) and other inevitable elements.

[0011] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include carbon (C) 0.003 wt% or less, phosphorus (P) 0.015 wt% or less, nitrogen (N) 0.003 wt% or less, sulfur (S) 0.003 wt% or less, and titanium (Ti) 0.003 wt% or less.

[0012] According to one embodiment of the present invention, a non-oriented electrical steel sheet can have a shear modulus (G) and a bulk modulus (B) that satisfy the following equation 1.

[0013] [Formula 1]

[0014] 0.5≤ G / B ≤0.85

[0015] A non-oriented electrical steel sheet according to one embodiment of the present invention may have a Young's modulus (E) of 150 GPa or more and a tensile strength (TS) of 665 MPa or more.

[0016] A non-oriented electrical steel sheet according to one embodiment of the present invention can satisfy the following equation 2.

[0017] [Formula 2]

[0018] 0.05≤(C 12 -C 44 ) / E

[0019] (C 12 is the elastic modulus, which represents the elastic resistance to expansion when subjected to compressive stress, and C 44is the elastic modulus, which indicates the resistance to shear deformation, and E is the Young's modulus.)

[0020] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may include a first step of preparing a steel material including 2.0 to 3.8 wt% of silicon (Si), 0.5 wt% or less (excluding 0) of manganese (Mn), 0.6 wt% or less (excluding 0) of aluminum (Al), 0.0015 wt% or less of scandium (Sc), 0.0015 wt% or less of hafnium (Hf), 0.0015 wt% or less of tantalum (Ta), and the remainder iron (Fe) and other inevitable elements, a second step of hot-rolling the steel material to form a hot-rolled steel sheet, a third step of hot-rolling and annealing the hot-rolled steel sheet, a fourth step of cold-rolling the hot-rolled steel sheet on which the third step has been performed to form a cold-rolled steel sheet, and a fifth step of cold-rolling and annealing the cold-rolled steel sheet.

[0021] The above steel may further contain carbon (C) 0.003 wt% or less, phosphorus (P) 0.015 wt% or less, nitrogen (N) 0.003 wt% or less, sulfur (S) 0.003 wt% or less, and titanium (Ti) 0.003 wt% or less.

[0022] According to one embodiment of the present invention, by controlling the amount of rare earth elements added and the mechanical properties, a non-oriented electrical steel sheet and a method for manufacturing a non-oriented electrical steel sheet having mechanical properties suitable for use as a motor core material can be implemented.

[0023] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0024] FIG. 1 is a drawing showing a range satisfying Equations 1 and 2 in a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0025] FIG. 2 is a flowchart schematically illustrating a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0026] Hereinafter, preferred embodiments of the present invention will be 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.

[0027] Additionally, when a component (or region, layer, portion, etc.) is referred to as being "on," "connected to," or "coupled to" another component, it means that it can be directly placed / connected / coupled to the other component, or that a third component may be placed between them.

[0028] Terms such as "include" or "have" should be understood to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but not to exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0029] In order to clearly explain the present invention, a detailed description of a part that is irrelevant to the description or a related known technology that may unnecessarily obscure the gist of the present invention has been omitted, and when adding reference signs to components of each drawing in this specification, the same or similar reference signs are attached to the same or similar components throughout the specification.

[0030] In addition, terms and words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0031] Unless otherwise specified, the notation 'A to B' for numerical values ​​A and B means 'A or more and B or less'. In such notation, if a unit is attached only to numerical value B, the unit shall be applied to numerical value A as well.

[0032] Also, unless otherwise stated, 1 ppm is 0.0001 wt%.

[0033] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0034]

[0035] Non-oriented electrical steel sheet

[0036] A non-oriented electrical steel sheet according to one embodiment of the present invention contains 2.0 to 3.8 wt% of silicon (Si), 0.5 wt% or less of manganese (Mn) (excluding 0), 0.6 wt% or less of aluminum (Al) (excluding 0), 0.0015 wt% or less of scandium (Sc), 0.0015 wt% or less of hafnium (Hf), 0.0015 wt% or less of tantalum (Ta), and the remainder of iron (Fe) and other inevitable elements.

[0037] Hereinafter, the role and content of alloy elements included in a non-oriented electrical steel sheet according to one embodiment of the present invention will be described in detail.

[0038]

[0039] Silicon (Si)

[0040] Silicon is a major additive element in electrical steel sheets, which improves magnetic properties by increasing the resistivity of the steel and reducing eddy current loss. If the silicon content is too low, the increase in resistivity is insufficient, making it difficult to obtain a low core loss value. On the other hand, as the added silicon content increases, the permeability and magnetic flux density may decrease, and the brittleness of the material may increase, resulting in poor cold-rollability and punchability. Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain silicon in an amount of 2.0 to 3.8 wt%.

[0041]

[0042] Manganese (Mm)

[0043] 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 that is advantageous to magnetic properties. If manganese is not added, the increase in resistivity is insufficient, which may increase high-frequency iron loss. On the other hand, if the manganese content is excessive, a coarse secondary phase is formed, and a {111} texture that is unfavorable for magnetization is formed, which may deteriorate magnetic properties. Therefore, a non-oriented electrical steel sheet according to an embodiment of the present invention may contain manganese in an amount of 0.5 wt% or less (excluding 0).

[0044]

[0045] Aluminum (Al)

[0046] Aluminum, along with silicon (Si) and manganese (Mn), is an element that increases resistivity and reduces iron loss, and is a major additive element in electrical steel sheets. In general, aluminum can improve the workability of cold rolling by improving the rollability of IF (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 aluminum in an amount of 0.6 wt% (excluding 0) or less.

[0047]

[0048] rare earth elements (REE)

[0049] Rare-earth elements (REE) are added to promote grain boundary segregation and magnetic flux density formation in steel. The 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 wt% or less (excluding 0). The 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.

[0050] An electrical steel sheet according to one embodiment of the present invention can easily improve the elastic modulus of a metal material by adding rare earth elements to be described later, thereby improving mechanical resistance characteristics.

[0051] The reasons for the improvement in mechanical properties described above are as follows. When rare earth elements are added, physical interactions occur at the nuclear and electronic levels between atoms whose atomic radii differ by 15 to 30%, resulting in lattice distortion. This lattice distortion affects the elastic modulus properties, and the degree of lattice distortion can improve the elastic modulus properties. In addition, Peierls-Nabarro stress increases, which can improve mechanical properties. Therefore, the addition of appropriate rare earth elements can maintain the essential properties of non-oriented electrical steel while simultaneously improving its mechanical properties.

[0052] Below, the content and role of the rare earth elements will be described in more detail.

[0053]

[0054] *Rare earth elements (REE) according to one embodiment of the present invention include scandium (Sc), hafnium (Hf), and tantalum (Ta).

[0055] The content of the above-mentioned 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, respectively.

[0056] At this time, the role of each rare earth element is as follows.

[0057] Scandium (Sc) can form compounds such as Sc3C4, ScN, and Fe2Sc to improve strength and suppress grain growth. In addition, when it exceeds 0.0015 wt%, the magnetic properties may deteriorate due to coarsening of the compound, and in addition, the material may be prematurely destroyed or its elastic properties may be inferior during the processing, which may make it difficult to utilize it as a structure. Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain scandium (Sc) in an amount of 0.0015 wt% or less. Additionally, when added to the steel in the above range, the elastic modulus properties can be improved.

[0058] Hafnium (Hf) can form compounds such as HfN and HfC to improve strength and suppress grain growth. In addition, when it exceeds 0.0015 wt%, the magnetic properties may deteriorate due to coarsening of the compound, and in addition, the material may be prematurely destroyed or its elastic properties may be inferior during the processing, which may make it difficult to use as a structure. Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain hafnium (Hf) in an amount of 0.0015 wt% or less. Additionally, when added to the steel in the above range, the elastic modulus properties can be improved.

[0059] Tantalum (Ta) forms compounds such as TaN, TaC, and FeTa to enhance strength and suppress grain growth. In addition, when it exceeds 0.0015 wt%, the magnetic properties may deteriorate due to coarsening of the compounds, which may lead to premature destruction of the material or poor elastic properties during the processing, making it difficult to utilize it as a structure. Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain tantalum (Ta) in an amount of 0.0015 wt% or less. Additionally, when added to the steel in the above range, the elastic modulus properties can be improved.

[0060]

[0061] Yellow (S)

[0062] Sulfur (S) is an impurity element that is inevitably contained in steel during the manufacturing process, and when added in large quantities, it can cause brittleness. Furthermore, it combines with manganese (Mn) to form precipitates such as MnS, thereby increasing iron loss and inhibiting grain growth, which can deteriorate magnetic properties. Therefore, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain sulfur in an amount of 0.003 wt% or less.

[0063]

[0064] Titanium (Ti)

[0065] Titanium (Ti) is an element with a strong tendency to form precipitates within steel. It combines with carbon (C) or nitrogen (N) to form precipitates such as TiC and TiN, thereby inhibiting grain growth. As more titanium is added, magnetic properties deteriorate, so it is desirable to add as little as possible. Therefore, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain titanium (Ti) in an amount of 0.003 wt% or less.

[0066]

[0067] carbon (C)

[0068] Carbon (C) can increase iron loss by combining with titanium (Ti) and niobium (Nb) to form carbides such as TiC and NbC, so the lower the carbon content, the better. If carbon exceeds 0.003 wt%, it can cause self-aging, which can deteriorate magnetic properties. Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain carbon at 0.003 wt% or less.

[0069]

[0070] Person (P)

[0071] Phosphorus (P) is a grain boundary segregation element that improves the grain structure, thereby increasing resistivity and contributing to reducing iron loss. However, when phosphorus is added in large amounts exceeding 0.015 wt%, excessive grain boundary segregation may form, which may inhibit grain growth, deteriorate magnetic properties, and reduce cold rolling properties. Therefore, a non-oriented electrical steel sheet according to an embodiment of the present invention may contain phosphorus (P) in an amount of 0.015 wt% or less.

[0072]

[0073] Nitrogen (N)

[0074] Nitrogen (N) combines with aluminum (Al) and titanium (Ti) to form precipitates such as AlN and TiN, thereby increasing iron loss and inhibiting grain growth. Therefore, it is preferable to add as little nitrogen as possible, and the non-oriented electrical steel sheet according to one embodiment of the present invention may contain nitrogen (N) in an amount of 0.003 wt% or less.

[0075] In addition to the aforementioned steel components, the remainder may contain iron and unavoidable impurities. Unavoidable impurities are impurities introduced during the steelmaking process and the manufacturing process of non-oriented electrical steel sheets. Since these impurities are widely known in the field, a detailed description will be omitted.

[0076] 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 range that does not impair the technical spirit of the present invention. When additional elements are included, they may be included to replace the remaining Fe.

[0077]

[0078] A non-oriented electrical steel sheet according to one embodiment of the present invention can improve elastic behavior through the above-described alloy composition and addition of rare earth elements, and can have high mechanical stability against centrifugal force and multi-axial repeated loads generated when manufacturing or operating a motor laminate.

[0079] In addition, since the electrical steel sheet according to the embodiment has high elastic properties and high tensile strength, it can be used as a core material for EV / HEV.

[0080] A non-oriented electrical steel sheet having the above-described alloy composition and manufactured using a manufacturing method according to an embodiment of the present invention to be described later can satisfy the following Equation 1 in terms of shear modulus (G) and bulk modulus (B).

[0081] [Formula 1]

[0082] 0.5≤ G / B ≤0.85

[0083] When the shear modulus (G) / bulk modulus (B) of the electrical steel sheet according to the present embodiment is less than 0.5, it can exhibit ductile properties, escaping from the boundary condition of the ductile-brittle transition. However, the process economy may be significantly reduced, and furthermore, due to excessive ductility, when punching, non-uniform deformation may strongly appear around the punching part of the sheet material, which may cause edge wrinkles. In such a case, it is difficult to assemble and utilize it as a normal motor structure. When the G / B value exceeds 0.85, it exhibits significant brittleness. Excessive brittleness makes the processing of the material difficult, and in particular, it may cause the material to break during punching, and therefore it is desirable to avoid it if possible. Therefore, the non-oriented electrical steel sheet according to the present embodiment can secure the ductility-brittleness balance of the material by satisfying the above-described Equation 1, thereby exhibiting excellent processing characteristics and process economy.

[0084] Meanwhile, G / B may be preferably 0.6 or more and 0.84 or less, and more preferably 0.66 or more and 0.84 or less.

[0085] In addition, the non-oriented electrical steel sheet according to the present embodiment may have a Young's modulus (E) of 150 GPa or more and a tensile strength (TS) of 665 MPa or more.

[0086] Meanwhile, a non-oriented electrical steel sheet according to one embodiment of the present invention can satisfy the following equation 2.

[0087] [Formula 2]

[0088] 0.05≤(C 12 -C 44 ) / E

[0089] (C 12 is the elastic modulus, which represents the elastic resistance to expansion when subjected to compressive stress, and C 44 is the elastic modulus, which indicates the resistance to shear deformation, and E is the Young's modulus.)

[0090] Through the above [Formula 2], it is possible to determine the ductile-brittle characteristics based on the bonding characteristics, and parameters such as [Formula 2] are introduced to distinguish materials having more specific desirable ductile characteristics from materials satisfying [Formula 1].

[0091] In order to describe the bonding properties, indices indicating elastic resistance to compressive stress and shear stress are required, and the indices are as follows: C12 is the elastic modulus indicating elastic resistance to expansion when subjected to compressive stress, and C44 is the elastic modulus indicating resistance to shear deformation. Normalized (C 12 -C 44 ) / E can be used to explain the bonding characteristics. Below 0 and with a negative value, it exhibits covalent bonding characteristics similar to intermetallic compounds, which makes it brittle. On the other hand, above 0 and with a positive value, it exhibits bonding characteristics of metals such as copper and nickel, which ensures ductility.

[0092] (C 12 -C 44 ) / E is less than 0.05, the bonding characteristics of the atoms forming the continuum may be close to covalent bonding due to the inclusion of undesirable impurities and rare earth element combinations in the steel. In this case, the material may have low resistance to transverse torsion under tensile and compressive loads, resulting in brittleness and low mechanical stability.

[0093] On the other hand (C 12 -C 44 ) / E is 0.05 or more, there is an advantage in that high mechanical stability can be secured by greatly increasing the material's resistance to transverse torsion under tensile and compressive loads.

[0094] Meanwhile, (C 12 -C 44 ) / E may preferably be 0.05 or more and 0.12 or less. (C 12 -C 44) / E exceeds 0.12, the bonding properties of atoms exhibit characteristics consistent with metallic bonding. In this case, there is an advantage in that high mechanical stability can be secured along with ductility because the material has high resistance to transverse torsion under tensile and compressive loads. However, since special heat treatment and processing equipment may be required to secure the corresponding values, there is a problem in that the process economy is significantly reduced when designing the mass production process. In addition, (C 12 -C 44 ) / E may be more preferably 0.065 or more and 0.11 or less.

[0095] The non-oriented electrical steel sheet according to this embodiment can produce a motor laminate product having high durability by combining the alloy composition described above and the manufacturing method described below.

[0096] In addition, referring to FIG. 1, the non-oriented electrical steel sheet according to the present embodiment has the advantage of having excellent processing characteristics as the ductility of the material is secured when the above-described Equation 1 is satisfied, and also having high mechanical stability as the resistance to the material's transverse torsion under tensile and compressive loads is increased when the Equation 2 is satisfied. In the area satisfying these conditions, a punched laminate having excellent mechanical characteristics can be economically manufactured without adding excessive additive elements.

[0097] Hereinafter, a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention will be described in detail.

[0098]

[0099] Method for manufacturing non-oriented electrical steel sheet

[0100] Hereinafter, a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention will be described with reference to FIG. 2.

[0101] FIG. 2 is a flowchart schematically illustrating a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0102] Referring to FIG. 2, a method for manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention includes a first step (S1) of preparing a steel material including silicon (Si) 2.0 to 3.8 wt%, manganese (Mn) 0.5 wt% or less (excluding 0), aluminum (Al) 0.6 wt% or less (excluding 0), scandium (Sc) 0.0015 wt% or less, hafnium (Hf) 0.0015 wt% or less, tantalum (Ta) 0.0015 wt% or less, the remainder iron (Fe) and other inevitable 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 and annealing the hot-rolled steel sheet, a fourth step (S4) of cold-rolling the hot-rolled steel sheet on which the third step (S3) has been performed to form a cold-rolled steel sheet, and a fifth step (S5) of cold-rolling and annealing the cold-rolled steel sheet.

[0103] Since the alloy composition content has been described in the alloy composition of non-oriented electrical steel sheets, a duplicate description will be omitted. In addition, since the alloy composition does not substantially change during the manufacturing process described below, the composition of the above steel and the alloy composition of the non-oriented electrical steel sheets are substantially identical.

[0104] First, Step 1 (S1) involves preparing steel having the above-described alloy composition range. More specifically, this step may involve designing alloy components within the above-described alloy composition range to manufacture a semi-finished product. The semi-finished product may be a slab, but is not necessarily limited thereto. Furthermore, the slab may be manufactured using any process known in the relevant technical field, such as a steelmaking process or a casting process.

[0105] 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).

[0106] More specifically, the second step (S2) may include a reheating process and may include a hot rolling process and a coiling process.

[0107] First, the reheating process may be performed prior to the hot rolling process, reheating the steel for subsequent processing. Specifically, it may be a step of uniformly heating the steel by loading it into a heating furnace to facilitate plastic deformation.

[0108] At this time, if the reheating temperature is less than 1000℃, the rolling load may increase during hot rolling, which may reduce the rollability. 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, which may form fine precipitates at the grain and grain boundaries during cooling. These fine precipitates may be beneficial for improving strength, but may inhibit grain growth and deteriorate iron loss. Therefore, in the present invention, the reheating temperature can be controlled to 1000 to 1250℃.

[0109] Additionally, 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 precipitates to be dissolved may not be secured, resulting in material inhomogeneity. Furthermore, if the reheating time exceeds 850 minutes, the problem of increased production costs due to prolonged heating may arise.

[0110] Next, a hot rolling process can be performed to form a hot-rolled steel plate. The hot rolling process can include rough rolling and finishing rolling. Rough rolling can be used to form steel into a rolled material with an appropriate shape, thickness, and width, while finishing rolling can be used to adjust the steel to a specified thickness and width and roll it at a finishing temperature appropriate for the intended use to achieve a good surface and shape.

[0111] At this time, the finishing temperature of the hot rolling process is preferably 850 to 1000°C. If the finishing rolling temperature is below 850°C, rolling may occur in the two-phase region, resulting in the formation of an uneven texture. Conversely, if the finishing rolling temperature exceeds 1000°C, a problem of rapid strength reduction may occur.

[0112] 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 lower than 550°C, the grain size may become too small, preventing sufficient grain growth even after annealing. If the coiling temperature exceeds 750°C, fine precipitates may be generated, which may deteriorate magnetic properties.

[0113] The thickness of the hot-rolled steel sheet formed through the above second step (S2) may be 1.8 to 3.5 mm. As the thickness of the hot-rolled steel sheet increases, the reduction ratio during cold rolling increases, and the texture may become inferior. Therefore, it is preferable to set the thickness of the hot-rolled steel sheet to 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 the product.

[0114] 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 and annealing the hot-rolled steel sheet after the second step (S2). The third step (S3) may be a hot-rolling and annealing step in which annealing is performed to secure microstructural uniformity and cold-rollability of the hot-rolled steel material.

[0115] At this time, the preferable temperature for the hot rolling annealing may be 900 to 1100°C. If the hot rolling annealing temperature is lower than 900°C, the elongated cast structure may remain after hot rolling, which may cause microstructural inhomogeneity. In addition, the elongated cast structure may inhibit the growth of crystal grains, resulting in the formation of small crystal grains, which may act as an obstacle during cold rolling. On the other hand, if the hot rolling annealing temperature exceeds 1100°C, it may cause an imbalance in the texture of the final product, and the magnetic properties may be reduced. The annealing temperature may be 900 to 1100°C so as to form a uniform microstructure with an average of 50 μm to 200 μm by removing the elongated cast structure.

[0116] The above hot rolling annealing may be performed for a certain period of time in the range of 10 to 180 seconds to form an appropriate grain size under each temperature condition. At this time, the heating rate and cooling rate may be 20°C / s or higher.

[0117] In addition, a shot blast and pickling treatment process can be additionally performed between the second step (S2) and the third step (S3) described below. First, the shot blast can be performed by rotating shot particles having a size of 2 to 1200 μm at a speed of 2000 rpm or more and spraying them at a high speed of 50 to 120 m / s. The pickling treatment can be performed by supplying 18% hydrochloric acid to a pickling tank where it reacts with the iron plate, thereby reacting and pickling fine residual scales that are not removed by mechanical methods.

[0118] Thereafter, the 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 thin 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.

[0119] In addition, the cold rolling can be performed as warm rolling in which the temperature of the plate is raised to 75 to 200°C to improve the ease of rolling.

[0120] The cold rolled steel sheet formed through the above fourth step (S4) may be 0.25 mm or less. At this time, the final reduction ratio may be 85% or more.

[0121] According to an embodiment of the present invention, a method for manufacturing a non-oriented electrical steel sheet may include, after the fourth step (S4), performing a fifth step (S5) of cold-rolling annealing the cold-rolled steel sheet. The cold-rolling annealing may be performed to soften the cold-rolled steel sheet that has been hardened through recrystallization during cold rolling. In addition, 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.

[0122] Preferably, the cold rolling annealing temperature may be 800 to 1100°C. If the cold rolling annealing temperature is lower than 800°C, the grain size formed after cold rolling annealing may be fine, which may increase hysteresis loss, and the measurement of elastic modulus may be inaccurate due to grain boundary slip. On the other hand, if the cold rolling annealing temperature exceeds 1100°C, the grain size may become coarse, eddy current loss may increase, and tensile strength may be inferior.

[0123] Therefore, in the fifth step (S5) according to one embodiment of the present invention, heat treatment can be performed by heating the cold-rolled steel sheet to 800 to 1100°C, maintaining the temperature for 10 to 10,000 seconds, and then cooling the cold-rolled steel sheet. At this time, the heating rate and cooling rate are preferably 20°C / s or higher.

[0124] In addition, the fifth step (S5) can be performed in a mixed atmosphere of nitrogen and hydrogen to prevent oxidation and nitriding of the surface of the cold-rolled steel sheet, thereby improving the surface quality of the cold-rolled steel sheet.

[0125] 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 secure the insulation properties of the non-oriented electrical steel sheet and improve the punchability, and may mean forming an insulating film on the surface of the cold-rolled steel sheet on which the fifth step (S5) has been performed. At this time, forming the insulating film may be performed using a process known in the art.

[0126] According to one embodiment of the present invention, a non-oriented electrical steel sheet and a manufacturing method thereof satisfy the above-described alloy composition and Equations 1 and 2, and when the above-described manufacturing method is followed, a product having both high elastic properties and high tensile strength can be manufactured. In addition, a non-oriented electrical steel sheet product having high mechanical stability against centrifugal force and multi-axial cyclic load generated during the manufacturing and operation of a motor laminate can be manufactured.

[0127]

[0128] Comparative examples and examples

[0129] Below, the composition and operation of the present invention will be described in more detail through preferred comparative examples and examples. However, these examples are provided to aid understanding of the present invention and are not intended to limit the present invention.

[0130] Tables 1 and 2 below show the contents of major elements, impurity elements, and rare earth elements in the alloy compositions constituting comparative examples and examples. Tables 3 and 4 show the mechanical property values ​​of comparative examples and examples and whether or not Equations 1 and 2 are satisfied.

[0131] The present comparative examples and examples were manufactured by the following method. Slabs having the alloy compositions listed in Tables 1 and 2 below were heated to 1150°C, hot-rolled to produce a hot-rolled steel sheet having a thickness of 2.3 mm, and then pickled and cold-rolled to produce a cold-rolled steel sheet having a thickness of 0.25 mm. Next, the cold-rolled steel sheet was subjected to continuous heat treatment in a nitrogen atmosphere for 3 minutes. The heating rate was 20°C / s. Thereafter, a non-oriented electrical steel sheet as the final product was manufactured through a coating process. Process conditions that are not listed are control variables and were controlled identically according to the method for manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention described above.

[0132] The Young's modulus (E) and tensile strength (TS) of the comparative examples and examples were tested in accordance with the tensile test standard JIS Z 2241, and are values ​​representing the results measured using JIS No. 5 test pieces.

[0133] Additionally, shear modulus (G) and bulk modulus (B) were measured at room temperature using an Ultrasonic Bonda fide Acoustic Tang (U-BAT) following ASTM E 1876-01. At this time, they were calculated from the longitudinal and torsional frequencies.

[0134] In Tables 3 and 4 below, whether Equation 1 is satisfied indicates whether the G / B value, which is the relationship between the shear modulus (G) and the bulk modulus (B), satisfies the range of 0.5 or more and 0.85 or less.

[0135] In Tables 3 and 4 below, whether Equation 2 is satisfied or not (C 12 -C 44) / E value satisfies the range of 0.05 or more.

[0136] ClassificationMajor Element (Wt%)Impurity Element (ppm)Rare Earth Element (ppm)SiAlMnCSNTiPScHfTaREE Total Example 13.30.310.4721152615130106521 Example 22.830.530.43625172913397622 Example 32.710.450.22161616111309131436 Example 43.230.370.495111827129912930 Example 52.650.450.251416162166791329 Example 62.940.410.38259212173610925 Example 73.440.30.22681318759141336 Example 82.490.380.2581520895871025 Example 93.760.490.3115291029125671326 Example 103.690.250.29619201179611926 Example 112.320.460.1427102620661213833 Example 123.750.310.22272713299211111133 Example 132.550.360.22187171711114121036 Example 142.780.430.3919132592891027 Example 152.520.470.14148192914913141340 Comparative Example 11.920.380.3131811181226151435 Comparative Example 23.830.140.2915242027675131432 Comparative Example 32.8400.2991727221036121230 Comparative Example 42.680.780.4615142623691081028 Comparative Example 53.750.310272713299211111133 Comparative Example 62.550.360.61187171711114121036Comparative Example 74.081.10.8919132592891027Comparative Example 81.830023231527135681327Comparative Example 91.761.260.9272629251407111432

[0137] ClassificationMajor Element (Wt%)Impurity Element (ppm)Rare Earth Element (ppm)SiAlMnCSNTiPScHfTaREETotal Comparison Example 103.9101.2112267874610925Comparison Example 113.931.160272325291376131534Comparison Example 122.130.580.22010131192129829Comparison Example 132.920.480.4112830192793139931Comparison Example 143.080.360.38290121183871429Comparison Example 152.040.370.522110182313788925Comparison Example 162.240.240.2324150910513121035Comparative Example 173.140.280.372812872610010111132Comparative Example 182.830.420.3317610014177923Comparative Example 192.430.580.363019169878661325Comparative Example 202.520.260.2611813230871328Comparative Example 212.370.30.32913185650661325Comparative Example 223.460.240.222862224136010515Comparative Example 233.380.390.23171029790219737Comparative Example 243.710.130.38151729241011001222Comparative Example 252.610.360.12151621101409471571Comparative Example 263.420.20.441871826831014024Comparative Example 272.620.230.17221510113995169Comparative Example 282.550.540.2829302761050000Comparative Example 2930.480.1724921128316182054Comparative Example 303.590.450.37624292377200020Comparative Example 313.130.310.3617112414122028028Comparative Example 322.960.360.31143079135002626Comparative Example 332.230.10.315162874273212Comparative Example 342.860.010.431277385101126

[0138] Classification TS(MPa)E(GPa)G(GPa)B(GPA)G / B Formula 1 Satisfaction C 12 (GPa)C 44 (GPa)(C 12-C 44) / E Formula 2 Satisfaction Example 1755185.5118.9141.70.839O119.5101.10.099O Example 2785186.2119.8145.70.823O120.199.60.110O Example 3718190.3123.9160.40.772O123.7105.60.095O Example 4723188.2123.8169.90.728O121.8103.50.097O Example 5791195.5130.3194.40.670O125.9109.30.085O Example 6770200.6133.8201.10.665O127.7110.20.087OExample 7797198.4132.0195.00.677O126.2107.50.094OExample 8830198.2132.1197.60.669O126.31080.092OExample 9850207.7136.7189.00.724O128.9111.70.083OExample 10816208.0135.8178.40.761O128.5110.90.085OExample 11735209.3135.4169.00.801O129.5110.50.091OExample 12748150.095.7118.80.805O96.186.20.067OExample 13743151.497.5119.40.817O98.688.70.065OExample 14690152.498.3121.20.811O96.985.40.075OExample 15685150.897.1118.50.820O96.785.80.072OComparative Example 1550141.387.891.30.962X90.178.80.080OComparison Example 2630143.188.892.40.961X93.581.80.082OComparison Example 3660144.291.399.70.916X92.380.90.079OComparison Example 4610144.591.8104.90.875X93.382.10.077OComparison Example 5625138.397.9114.50.855X97.3850.080OComparison Example 6630145.598.4110.60.890X101.290.20.071OComparative example 7655141.895.8103.30.927X97.486.10.074OComparative example 8535144.392.6135.70.682O112.3105.70.045X Comparison Example 9600143.894.2137.90.683O113.8106.60.049X.

[0139] Classification TS(MPa)E(GPa)G(GPa)B(GPA)G / B Formula 1 Satisfaction C 12 (GPa)C 44 (GPa)(C 12 -C 44) / E Formula 2 Satisfaction Comparison Example 10615144.3100.6142.20.707O115.4108.80.042X Comparison Example 11628149.799.8138.30.722O114.8107.30.049X Comparison Example 12610141.888.396.80.912X114.8110.90.028X Comparison Example 13 Edge cracks during hot rolling Comparison Example 14598147.894.8147.90.641O113.5106.80.045X Comparison Example 15 Plate breakage during casting due to hot brittleness Comparison Example 16582149.1101.5119.20.852X100.686.90.092OComparative example 17 Stretcher strain defect during hot-rolled plate coiling Comparative example 18630147.699.7109.20.913X99.687.00.084OComparative example 19 Stretcher strain defect during hot-rolled plate coiling Comparative example 20622149.7100.7110.90.908X100.890.10.071OComparative example 21 Plate breakage during hot-rolling due to hot embrittlement Comparative example 22585148.599.9116.50.857X115.9105.10.070OComparative example 23592146.398.6162.70.606O121.3115.70.037XComparative Example 24608149.699.2115.30.860X115.2104.80.069OComparative Example 25601148.1102.8154.80.664O130.5123.70.043XComparative Example 26631149.3103.1120.80.853X116.3105.30.070OComparative Example 27652148.3105.6160.30.659O122.7115.20.049XComparative Example 28645138.385.691.10.940X88.173.90.103OComparative Example 29 Edge crack occurrence in slab materialComparative Example 30 Edge crack and positive / medium wave occurrence in cold rollingComparative Example 31 Edge crack and positive / medium wave occurrence in cold rollingComparative Example 32 Edge crack and positive / medium wave occurrence in cold rollingComparative Example 33650205.1100.7208.80.48X135.0128.00.034XComparative Example 34610150.8101.2204.60.49X99.793.10.044X

[0140] Referring to Tables 1 and 2 above, Examples 1 to 15 include main elements, impurity elements, and rare earth elements, and all satisfy the alloy composition range according to one embodiment of the present invention.

[0141] In addition, it can be confirmed that Examples 1 to 15 satisfy Equation 1 regarding shear modulus (G) and bulk modulus (B) and Equation 2 regarding (C12-C44) / E in addition to the alloy composition described above.

[0142] In addition, it can be confirmed that the tensile strength (TS) of Examples 1 to 15 is 665 MPa or more, and the Young's modulus (E) is 150 GPa or more. Therefore, it can be confirmed that Examples 1 to 15 have higher elastic properties and higher tensile strength than the comparative examples described below, and thus have excellent processing properties and mechanical properties.

[0143] On the other hand, it can be confirmed that Comparative Examples 1 to 32 do not satisfy the alloy composition range according to one embodiment of the present invention. In addition, it can be confirmed that Comparative Examples 1 to 32 do not satisfy Equation 1 or Equation 2, or that defects such as cracks or fractures in the steel plate occur.

[0144] As a result, it can be confirmed that Comparative Examples 1 to 32 do not achieve the Young's modulus (E) and tensile strength (TS) targeted in the present invention, and thus have inferior processing and mechanical properties.

[0145] It can be confirmed that Comparative Examples 33 and 34 satisfy the alloy composition range according to one embodiment of the present invention, but do not satisfy Equation 1 or Equation 2. As a result, it can be confirmed that Comparative Examples 33 and 34 do not achieve the tensile strength (TS) targeted in the present invention and have inferior mechanical properties.

[0146] As described above, preferred embodiments of the present invention have been described. It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms, in addition to the embodiments described above, without departing from the spirit or scope thereof. Therefore, the above-described embodiments should be considered illustrative rather than restrictive, and accordingly, the present invention is not limited to the above description, but may be modified within the scope of the appended claims and their equivalents.

Claims

1. Non-oriented electrical steel sheet containing 2.0 to 3.8 wt% of silicon (Si), 0.5 wt% or less of manganese (Mn) (excluding 0), 0.6 wt% or less of aluminum (Al) (excluding 0), 0.0015 wt% or less of scandium (Sc), 0.0015 wt% or less of hafnium (Hf), 0.0015 wt% or less of tantalum (Ta), and the remainder iron (Fe) and other unavoidable elements.

2. In paragraph 1, Non-oriented electrical steel sheet further containing carbon (C) 0.003 wt% or less, phosphorus (P) 0.015 wt% or less, nitrogen (N) 0.003 wt% or less, sulfur (S) 0.003 wt% or less, and titanium (Ti) 0.003 wt% or less.

3. In paragraph 1, A non-oriented electrical steel sheet having a shear modulus (G) and a bulk modulus (B) that satisfy the following equation 1. [Formula 1] 0.5≤ G / B ≤0.85 4. In paragraph 1, Non-oriented electrical steel sheet with a Young's modulus (E) of 150 GPa or more and a tensile strength (TS) of 665 MPa or more.

5. In paragraph 1, Non-oriented electrical steel sheet satisfying the following equation 2. [Formula 2] 0.05≤(C 12 -C 44 ) / E (C 12 is the elastic modulus, which represents the elastic resistance to expansion when subjected to compressive stress, and C 44 is the elastic modulus that represents the resistance to shear deformation, and E is the Young's modulus.) 6. A first step of preparing a steel material containing 2.0 to 3.8 wt% of silicon (Si), 0.5 wt% or less of manganese (Mn) (excluding 0), 0.6 wt% or less of aluminum (Al) (excluding 0), 0.0015 wt% or less of scandium (Sc), 0.0015 wt% or less of hafnium (Hf), 0.0015 wt% or less of tantalum (Ta), and the remainder iron (Fe) and other unavoidable elements; A second step of hot rolling the above steel to form a hot-rolled steel plate; The third step of hot-rolling and annealing the above hot-rolled steel sheet; A fourth step of forming a cold-rolled steel sheet by cold rolling the hot-rolled steel sheet that has undergone the third step; and A method for manufacturing a non-oriented electrical steel sheet, comprising a fifth step of cold-rolling and annealing the cold-rolled steel sheet.

7. In paragraph 6, The above steel is, A method for manufacturing a non-oriented electrical steel sheet further comprising carbon (C) 0.003 wt% or less, phosphorus (P) 0.015 wt% or less, nitrogen (N) 0.003 wt% or less, sulfur (S) 0.003 wt% or less, and titanium (Ti) 0.003 wt% or less.

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