Non-oriented electrical steel sheet

Abstract

The present invention provides a non-oriented electrical steel sheet characterized by comprising silicon (Si): 1.8 to 2.3 wt%, manganese (Mn): 0.2 to 0.4 wt%, aluminum (Al): 0.1 to 0.5 wt%, carbon (C): greater than 0 and less than or equal to 0.01 wt%, sulfur (S): greater than 0 and less than or equal to 0.01 wt%, phosphorus (P): greater than 0 and less than or equal to 0.08 wt%, nitrogen (N): greater than 0 and less than or equal to 0.01 wt%, titanium (Ti): greater than 0 and less than or equal to 0.01 wt%, the sum of at least one of tin (Sn) and antimony (Sb): 0.01 to 0.1 wt%, and the remainder being iron (Fe) and other unavoidable impurities, wherein the content of silicon (Si), manganese (Mn), and aluminum (Al) satisfies the following formula 1 and has an iron loss (W15 / 50) of 2.6 W / kg or less. Equation 1: 1.99 ≤ ([Si]0.3+[Mn]0.7+[Al]0.8) ≤ 2.18 (However, [Si], [Mn], and [Al] represent the content of silicon, manganese, and aluminum (unit: weight%).)

Description

Technology Field

[0001] The present invention relates to a non-oriented electrical steel sheet, and more specifically, to a non-oriented electrical steel sheet having excellent high-frequency iron loss. Background Technology

[0002] Electrical steel sheets can be classified into oriented and non-oriented electrical steel sheets based on their magnetic properties. Oriented electrical steel sheets are manufactured to facilitate magnetization in the rolling direction, resulting in particularly excellent magnetic properties in that direction; therefore, they are primarily used as cores for large, medium, and small-sized transformers that require low iron loss and high permeability. In contrast, non-oriented electrical steel sheets possess uniform magnetic properties regardless of the sheet's orientation, making them widely used as core materials for small electric motors, small power transformers, and ballasts. Prior art literature

[0003] Republic of Korea Patent Publication No. 2015-0001467A The problem to be solved

[0004] The technical problem that the present invention aims to solve is to provide a non-oriented electrical steel sheet with excellent high-frequency iron loss.

[0005] However, these tasks are exemplary and do not limit the scope of the invention. means of solving the problem

[0006] A non-oriented electrical steel sheet according to one aspect of the present invention for solving the above problem comprises silicon (Si): 1.8 to 2.3 wt%, manganese (Mn): 0.2 to 0.4 wt%, aluminum (Al): 0.1 to 0.5 wt%, carbon (C): greater than 0 and less than or equal to 0.01 wt%, sulfur (S): greater than 0 and less than or equal to 0.01 wt%, phosphorus (P): greater than 0 and less than or equal to 0.08 wt%, nitrogen (N): greater than 0 and less than or equal to 0.01 wt%, titanium (Ti): greater than 0 and less than or equal to 0.01 wt%, the sum of at least one of tin (Sn) and antimony (Sb): 0.01 to 0.1 wt%, and the remainder being iron (Fe) and other unavoidable impurities, wherein the content of silicon (Si), manganese (Mn), and aluminum (Al) satisfies the following Formula 1, and has an iron loss (W) of 2.6 W / kg or less. 15 / 50 It is characterized by having ).

[0007] Equation 1: 1.99 ≤ ([Si] 0.3 +[Mn] 0.7 +[Al] 0.8 ) ≤ 2.18

[0008] (However, [Si], [Mn], and [Al] represent the content of silicon, manganese, and aluminum (unit: weight%).)

[0009] For the above non-oriented electrical steel sheet, the distribution density (r1) of secondary phase particles with an average size of 0.1 to 1 μm in the microstructure cross-section is 3,000 particles / mm² 2 Up to 18,000 pieces / mm 2 And, the distribution density (r2) of secondary phase particles with an average size of 1 to 10 µm is 4000 particles / mm 2 Up to 8000 pieces / mm 2 It can be characterized as being.

[0010] The above non-oriented electrical steel sheet may be characterized by having an average magnetic domain width value (d) of 0.09 to 0.2 μm in the microstructure cross-section.

[0011] The above non-oriented electrical steel sheet may be characterized in that the distribution density of secondary phase particles and the average value of magnetic domain width in the microstructure cross-section satisfy the following Equation 2.

[0012] Equation 2: 0.08 ≤ {1 / (d · r1 0.8 · r2 0.1 )} · 100 ≤ 2.7

[0013] (wherein d is the average domain width (unit: μm) in the microstructure cross-section of the electrical steel sheet, and r1 is the distribution density (unit: particles / mm²) of secondary phase particles with an average size of 0.1 to 1 μm in the microstructure cross-section of the electrical steel sheet 2 ) and r2 is the distribution density of secondary phase particles with an average size of 1 to 10 μm in the microstructure cross-section of the electrical steel sheet (unit: particles / mm² 2 )lim)

[0014] In the above-mentioned non-oriented electrical steel sheet, the secondary phase particles may be characterized as being nitride, sulfide, and oxide particles. Effects of the invention

[0015] According to an embodiment of the present invention, a non-oriented electrical steel sheet with excellent high-frequency iron loss and a method for manufacturing the same can be provided.

[0016] Of course, the scope of the present invention is not limited by these effects. Brief explanation of the drawing

[0017] Figure 1 is a photograph of the microstructure taken to measure the magnetic domain width of a non-oriented electrical steel sheet according to one embodiment of the present invention. FIG. 2 is a flowchart illustrating a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention. Specific details for implementing the invention

[0018] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention is described in detail. The terms described below are appropriately selected considering their functions in the present invention, and the definitions of these terms should be based on the content throughout this specification.

[0019] Generally, electrical steel is classified into oriented electrical steel and non-oriented electrical steel. Oriented electrical steel is primarily used in stationary equipment such as transformers, while non-oriented electrical steel is mainly used in rotating machinery such as motors and generators. In response to recent global environmental issues, there is a rapid technological shift from conventional internal combustion engines to replacements such as hybrid electric vehicles (HEVs), electric vehicles (EVs), and hydrogen vehicles.

[0020] All rotary machines that use electric energy as their driving force generate mechanical energy by rotating an internal iron core. The iron core inside the rotary machine is formed by stacking multiple sheets of non-oriented electrical steel that have been punched into the shapes of the stator and rotor; in this process, the magnetic properties of the electrical steel sheets exert a dominant influence on the performance of the motor core.

[0021] The magnetic properties of non-oriented electrical steel sheets are typically evaluated by magnetic flux density and iron loss. Magnetic flux density is B 50 , in the case of iron loss, generally W 15 / 50 While is primarily evaluated, in cases where high-frequency characteristics are required, such as with electric vehicles, W 10 / 400 It is evaluated as an iron loss. B 50 represents the magnetic flux density at 5000 A / m, and W 15 / 50 represents the iron loss at 50Hz and 1.5T, and W 10 / 400 represents the iron loss at 400 Hz and 1.0 T. Magnetic flux density is related to the motor's torque, and iron loss is the amount of energy lost as heat.

[0022] Therefore, to increase the energy efficiency of a motor, iron loss must be reduced; in particular, to effectively reduce iron loss at high frequencies, it is important to increase the resistivity of the material. In other words, non-oriented electrical steel sheets used as motor core materials play a role in converting electrical energy into mechanical energy in rotating machinery, and for energy saving, it is important for them to possess magnetic properties—namely, low iron loss and high magnetic flux density.

[0023] To satisfy these required characteristics, Si content, product thickness, grain size, texture, and precipitates can be appropriately controlled. Increasing Si content and decreasing product thickness are effective in reducing iron loss, but they have the disadvantage of lowering magnetic flux density. To compensate for this, controlling magnetic domain width, grain size, texture, and precipitates is crucial when realizing non-oriented electrical steel sheets. This is because magnetic properties (iron loss, magnetic flux density) change very sensitively depending on domain width, grain size, texture, and precipitates.

[0024] The motor core has a structure in which dozens to hundreds of sheets of non-oriented electrical steel are laminated. If non-oriented electrical steel sheets with large variations in magnetic properties are used in the manufacturing of such motor cores, problems may occur during motor operation.

[0025] The present invention aims to provide a non-oriented electrical steel sheet having an optimal magnetic domain width according to the size of the secondary phase.

[0026] First, the roles and content of the compositional components of the non-oriented electrical steel sheet according to the technical concept of the present invention will be explained.

[0027] Silicon (Si): 1.8 ~ 2.3 wt%

[0028] Silicon (Si) is a major additive element that increases resistivity and lowers iron loss (eddy current loss). If the silicon content is lower than 1.8 wt%, it is difficult to obtain the desired high-frequency low iron loss value, resulting in insufficient iron loss improvement effect. If the silicon content exceeds 2.3 wt%, the increase in alloying elements leads to a decrease in permeability and magnetic flux density, and increased brittleness makes cold rolling difficult, which can lower productivity and impair stamping ability.

[0029] Manganese (Mn): 0.2 ~ 0.4 wt%

[0030] Manganese (Mn) increases resistivity to lower iron loss and combines with sulfur (S) to form MnS sulfides. When the manganese content is less than 0.2 wt%, the effect of improving iron loss is insufficient, and when it exceeds 0.4 wt%, fine MnS precipitates are formed excessively, which can reduce the width of magnetic domains and increase iron loss, and a significant decrease in cold rolling performance may occur.

[0031] Aluminum (Al): 0.1 ~ 0.5 wt%

[0032] Aluminum (Al) is a major additive element that lowers iron loss (eddy current loss) by increasing resistivity. Aluminum plays a role in reducing magnetic deviation by decreasing magnetic anisotropy. Aluminum reacts with nitrogen to form AlN nitrides. If the aluminum content is less than 0.1 wt%, the insufficient resistivity leads to increased high-frequency iron loss; furthermore, the formation of fine nitrides reduces the magnetic domain width, thereby increasing iron loss and potentially increasing deviations in magnetic properties. If the aluminum content exceeds 0.5 wt%, it reacts with N2 during final annealing to form excessive nitrides, which reduces magnetic flux density and narrows the magnetic domain width, potentially degrading iron loss, causing a decrease in cold rolling performance, and leading to problems such as nozzle clogging during the continuous casting process.

[0033] Correlation between Silicon (Si), Manganese (Mn), and Aluminum (Al)

[0034] Silicon (Si), manganese (Mn), and aluminum (Al) each satisfy the composition range described above, and furthermore, have a correlation of silicon (Si), manganese (Mn), and aluminum (Al) that satisfies the following Equation 1.

[0035] Equation 1: 1.99 ≤ ([Si] 0.3 +[Mn] 0.7 +[Al] 0.8 ) ≤ 2.18

[0036] However, in the above Equation 1, [Si], [Mn], and [Al] correspond to the content of silicon, manganese, and aluminum constituting the non-oriented electrical steel sheet (unit: weight%).

[0037] When silicon (Si), manganese (Mn), and aluminum (Al) each satisfy the compositional ranges described above, and furthermore, simultaneously satisfy Equation 1 above, the non-oriented electrical steel sheet of the present invention has iron loss (W 15 / 50 The range satisfies 2.6 W / kg or less. Conversely, if the above Equation 1 is not satisfied, iron loss (W 15 / 50 ) cannot realize non-oriented electrical steel sheets with low iron loss characteristics exceeding 2.6W / kg.

[0038] Carbon (C): Greater than 0 and less than or equal to 0.01 wt%

[0039] Carbon (C) is an element that increases iron loss by forming carbides such as TiC and NbC, so it is limited to 0.01 wt% or less. If the carbon content exceeds 0.01 wt%, it can form carbides and have an adverse effect on magnetism and cause magnetic aging, thereby reducing magnetic properties, but at 0.01 wt% or less, the magnetic aging phenomenon is suppressed.

[0040] Sulfur (S): Greater than 0 and less than or equal to 0.01 wt%

[0041] Sulfur (S) forms precipitates in the form of sulfides such as MnS and CuS, which increase iron loss and inhibit grain growth, so it is limited to 0.002 wt% or less. If the sulfur content exceeds 0.02 wt%, a problem arises in which iron loss increases.

[0042] Phosphorus (P): Greater than 0 and less than or equal to 0.08 wt%

[0043] Phosphorus (P) is a grain boundary segregation element that develops texture. When the phosphorus content exceeds 0.08 weight%, the segregation effect inhibits grain growth, degrades magnetic properties, and reduces cold rolling performance.

[0044] Nitrogen (N): Greater than 0 and less than or equal to 0.01 wt%

[0045] Nitrogen (N) forms precipitates in the form of nitrides such as AlN, TiN, and NbN, which increase iron loss and inhibit grain growth, so it is limited to 0.01 wt% or less. If the nitrogen content exceeds 0.01 wt%, the problem of increased iron loss appears.

[0046] Titanium (Ti): Greater than 0 and less than or equal to 0.01 wt%

[0047] Titanium (Ti) inhibits grain growth by forming fine precipitates in the form of carbides or nitrides, such as TiC and TiN. Since magnetic properties deteriorate as titanium is added, the amount is limited to 0.01 wt% or less. If the titanium content exceeds 0.01 wt%, a problem arises in which magnetic properties deteriorate.

[0048] Sum of at least one of tin (Sn) and antimony (Sb): 0.01 to 0.1 wt%

[0049] Tin (Sn) and antimony (Sb) are surface precipitation elements that are concentrated in the surface layer of the steel sheet to suppress nitrogen adsorption and nitride formation, thereby lowering iron loss. They are elements that increase magnetic flux density and reduce iron loss deviation by reducing the strength of specific directional planes that are detrimental to magnetic properties. If the sum of at least one of tin (Sn) and antimony (Sb) is less than 0.01 weight%, the effect of suppressing the formation of the nitride layer is insufficient and it is difficult to expect the aforementioned effect. If the sum of at least one of tin (Sn) and antimony (Sb) exceeds 0.1 weight%, the grain boundaries become embrittled, which lowers fatigue resistance, worsens cold rolling performance, and increases manufacturing costs. Therefore, the sum of at least one of tin (Sn) and antimony (Sb) can be limited to a range of 0.01 to 0.1 weight%.

[0050] The remaining component of the above-mentioned non-oriented electrical steel sheet is iron (Fe). However, since unintended impurities from raw materials or the surrounding environment may inevitably be incorporated during the normal manufacturing process, they cannot be excluded. As these impurities are known to any person skilled in the normal manufacturing process, all details thereof are not specifically mentioned in this specification.

[0051] In the microstructure cross-section of a non-oriented electrical steel sheet according to one embodiment of the present invention, the distribution density (r1) of secondary phase particles with an average size of 0.1 to 1 μm is 3000 particles / mm² 2 Up to 18,000 pieces / mm 2 And, the distribution density (r2) of secondary phase particles with an average size of 1 to 10 µm is 4000 particles / mm 2 Up to 8000 pieces / mm 2 It can have characteristics.

[0052] In the microstructure of a non-oriented electrical steel sheet according to one embodiment of the present invention, the secondary phase particles may be precipitates or inclusion particles, and may be nitride, sulfide, and oxide particles. For example, the nitride may be AlN or TiN, the sulfide may be MnS or CuS, and the oxide may be Al2O3 or SiO2. The size and number of the secondary phase particles were measured by preparing a sample by performing mirror polishing of 1 μm or less and utilizing SEM-EDS equipment, wherein the analysis area was measured over an area of ​​2000 fields or more based on an ECD of 0.4 μm in detecting pixel units. The average size of a single secondary phase particle may be calculated as the average of the smallest width and the largest width among the sizes of the single secondary phase particles.

[0053] In a cross-sectional microstructure of a non-oriented electrical steel sheet according to one embodiment of the present invention, the distribution density (r1) of secondary phase particles with an average size of 0.1 to 1 μm ranges from 3,000 particles / mm 2 Up to 18,000 pieces / mm 2 If it does not satisfy, or the distribution density (r2) range of secondary phase particles with an average size of 1 to 10 µm is 4000 particles / mm 2 Up to 8000 pieces / mm 2 If is not satisfied, the iron loss (W of the non-oriented electrical steel sheet) 15 / 50 ) may not be able to realize non-oriented electrical steel sheets with low iron loss characteristics if this exceeds 12.5W / kg.

[0054] In the microstructure cross-section of a non-oriented electrical steel sheet according to one embodiment of the present invention, the average value of the magnetic domain width (d) may be 0.09 to 0.2 μm.

[0055] The magnetic properties of electrical steel are influenced by the structure of magnetic domains. A magnetic domain refers to a group of atoms where the magnetic moments of atoms are aligned in one direction. In the absence of an external magnetic field, multiple magnetic domains exist within the electrical steel. When an external magnetic field is applied, the domain walls—the boundaries of the domains—move, causing the entire steel sheet to merge into a single domain. During this magnetization process, the faster the movement of the domain walls, the lower the iron loss and the higher the magnetic flux density. The movement of the domain walls is influenced by the structure of the magnetic domains in the absence of an external magnetic field.

[0056] When no external magnetic field is applied to the non-oriented electrical steel sheet of the present invention, multiple magnetic domains exist within the grain (corresponding to the inner region bounded by the solid line in FIG. 1). That is, the widths of the multiple magnetic domains existing within the grains constituting the electrical steel sheet are each measured. The width of a single magnetic domain is measured as the distance between the magnetic walls constituting the boundary of the magnetic domain, and the largest distance among the measured distances is selected as the width of the magnetic domain (W in FIG. 1). The average value of the magnetic domain width (d) may be calculated as the average of the smallest magnetic domain width and the largest magnetic domain width among the magnetic domain widths of the grains.

[0057] In the case where the average magnetic domain width value (d) in the microstructure cross-section of a non-oriented electrical steel sheet according to one embodiment of the present invention does not satisfy 0.09 to 0.2 μm, the iron loss (W) of the non-oriented electrical steel sheet 15 / 50 ) may not be able to realize non-oriented electrical steel sheets with low iron loss characteristics if this exceeds 12.5W / kg.

[0058] In the microstructure cross-section of a non-oriented electrical steel sheet according to one embodiment of the present invention, the distribution density of secondary phase particles and the average value of magnetic domain width may have the characteristic of satisfying Equation 2 below.

[0059] Equation 2: 0.08 ≤ {1 / (d · r1 0.8 · r2 0.1)} · 100 ≤ 2.7

[0060] Provided, however, that d is the average domain width value (unit: μm) in the microstructure cross-section of the electrical steel sheet, and r1 is the distribution density (unit: particles / mm²) of secondary phase particles with an average size of 0.1 to 1 μm in the microstructure cross-section of the electrical steel sheet. 2 ) and r2 is the distribution density of secondary phase particles with an average size of 1 to 10 μm in the microstructure cross-section of the electrical steel sheet (unit: particles / mm² 2 )am.

[0061] In the case where the distribution density of secondary phase particles and the average value of magnetic domain width in the microstructure cross-section of a non-oriented electrical steel sheet according to one embodiment of the present invention do not satisfy Equation 2 below, the iron loss (W) of the non-oriented electrical steel sheet 15 / 50 ) may not be able to realize non-oriented electrical steel sheets with low iron loss characteristics if this exceeds 12.5W / kg.

[0062] Hereinafter, an exemplary manufacturing method capable of realizing a non-oriented electrical steel sheet according to one embodiment of the present invention is described.

[0063] FIG. 2 is a flowchart illustrating a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0064] Referring to FIG. 2, a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises the steps of: providing a steel material containing silicon (Si), manganese (Mn) and aluminum (Al) (S10); hot rolling the steel material (S20); pre-annealing heat treating the hot-rolled steel material (S30); cold rolling the pre-annealed steel material (S40); and cold rolling annealing heat treating the cold-rolled steel material (S50).

[0065] Steel supply step (S10)

[0066] The steel material fed into the hot rolling process is a steel material for manufacturing non-oriented electrical steel sheets, and for example, comprises silicon (Si): 1.8 to 2.3 wt%, manganese (Mn): 0.2 to 0.4 wt%, aluminum (Al): 0.1 to 0.5 wt%, carbon (C): greater than 0 and less than or equal to 0.01 wt%, sulfur (S): greater than 0 and less than or equal to 0.01 wt%, phosphorus (P): greater than 0 and less than or equal to 0.08 wt%, nitrogen (N): greater than 0 and less than or equal to 0.01 wt%, titanium (Ti): greater than 0 and less than or equal to 0.01 wt%, the sum of at least one of tin (Sn) and antimony (Sb): 0.01 to 0.1 wt%, and the remainder being iron (Fe) and other unavoidable impurities.

[0067] Silicon (Si), manganese (Mn), and aluminum (Al) each satisfy the composition range described above, and furthermore, have a correlation of silicon (Si), manganese (Mn), and aluminum (Al) that satisfies the following Equation 1.

[0068] Equation 1: 1.99 ≤ ([Si] 0.3 +[Mn] 0.7 +[Al] 0.8 ) ≤ 2.18

[0069] However, in the above Equation 1, [Si], [Mn], and [Al] correspond to the content of silicon, manganese, and aluminum constituting the non-oriented electrical steel sheet (unit: weight%).

[0070] Hot rolling step (S20)

[0071] The steel having the composition described above undergoes a hot rolling process. The step (S20) of hot rolling the steel can be performed, for example, as a step of hot rolling a slab in a broad sense, under conditions of reheat temperature (SRT): 1000 ~ 1150℃, finish rolling temperature (FDT): 800 ~ 900℃, and coiling temperature (CT): 500 ~ 600℃.

[0072] The above slab may have dimensions of, for example, a width of 900 mm or more and a thickness of 200 to 300 mm. Before hot rolling, the slab may be reheated at the reheating temperature (SRT). If the slab reheating temperature exceeds 1150°C, precipitates such as C, S, and N within the slab are re-dissolved, and fine precipitates may form during subsequent rolling and annealing processes, which may inhibit grain growth and increase iron loss, thereby degrading magnetic properties. Meanwhile, if the above steel contains tin, if the slab reheating temperature of the tin additive is set higher than 1150°C, the amount of tin segregated at grain boundaries decreases, making it difficult to effectively inhibit grain growth during subsequent annealing processes. Furthermore, as the grains within the slab grow significantly, the number of grain boundaries where tin can segregate decreases greatly. In such cases, the tin that does not segregate at the grain boundaries eventually diffuses up to the surface of the slab to form an oxide layer. This oxide layer eventually becomes one of the major causes of reduced yield. In addition, heating the slab to a temperature higher than 1150°C has a negative aspect in that it reduces the overall yield by making precipitates finer, inhibiting the movement of domain walls, and promoting the formation of an oxide layer. If the slab reheating temperature is below 1000°C, the rolling load increases, and a problem of high iron loss in the final product may occur.

[0073] After performing the step (S20) of hot rolling the above steel material, the thickness of the hot-rolled plate may be, for example, 1.6 to 2.3 mm. As the thickness of the hot-rolled plate increases, the cold rolling reduction rate increases, and the texture deteriorates, so it is desirable to control the thickness to 2.3 mm or less.

[0074] The above hot-rolled steel can be coiled under conditions where the coiling temperature (CT) is 500 to 600°C. If the coiling temperature is below 500°C, brittleness increases, raising concerns about plate breakage during coiling, and there is no annealing effect on the steel, resulting in no grain growth. If the coiling temperature exceeds 600°C, fine AlN is formed during cooling after coiling, increasing iron loss, and oxidation may increase during cooling, which may lead to poor pickling performance.

[0075] Pre-annealing heat treatment step (S30)

[0076] A step (S30) of pre-annealing heat treatment of hot-rolled steel can be performed. The pre-annealing heat treatment can be understood as an Annealing and Pickling Line (APL) step for annealing and pickling hot-rolled plates, or as a pre-annealing treatment or a hot-rolled annealing treatment.

[0077] The above pre-annealing heat treatment step (S30) includes an annealing process in which, after heating at a rate of 10°C / s or more (e.g., 10°C / s or more and less than 50°C / s), annealing is started at a temperature of 900 to 1100°C and maintained for 30 to 120 seconds. After annealing, the steel may be cooled at a rate of 20°C / s or more (e.g., 20°C / s or more and less than 50°C / s). The atmosphere in the annealing furnace performing the heat treatment in the above pre-annealing heat treatment step (S30) may be nitrogen (N2) in a volume fraction of 80 to 100 volume%. A step of pickling after cooling may be further included.

[0078] A pre-annealing process is performed after hot rolling to ensure microstructural uniformity and cold rolling performance. The pre-annealing temperature is controlled between 900 and 1100°C to form a uniform microstructure with the elongated cast structure removed. If the pre-annealing temperature is too low, below 900°C, the elongated cast structure remaining after hot rolling persists, causing microstructural non-uniformity and resulting in small grain sizes, which can act as an impediment to cold rolling. On the other hand, if the pre-annealing temperature exceeds 1100°C, it causes texture imbalance in the final product, leading to anisotropy in properties.

[0079] If the steel is cooled at a cooling rate of less than 20℃ / s after pre-annealing heat treatment, the average grain size of the final microstructure may exceed 200㎛ and the total number of sulfides may increase, resulting in a problem where the mechanical properties of the non-oriented electrical steel sheet deteriorate. On the other hand, if the steel is cooled at a cooling rate of 50℃ / s or more after pre-annealing heat treatment, it may be difficult to secure time for manganese (Mn) to preferentially bond with sulfur (S) and form coarse MnS precipitates, which may lead to a problem where the formation of CuS and Cu2S precipitates becomes relatively easy and the magnetic properties deteriorate.

[0080] Cold rolling step (S40)

[0081] The step (S40) of cold rolling the above-mentioned pre-annealed steel is performed. Considering the thickness of the hot-rolled sheet and the target thickness of the cold roll, the reduction rate of the cold roll may be 90 to 95%. Conditions may be applied such that the reduction rate of the first pass of the cold roll is 40 to 50%, and the reduction rate per remaining pass is 30 to 45%. The thickness of the steel after cold rolling may be 0.35 to 0.5 mm. To impart rollability, the plate temperature may be raised to 150 to 300°C and hot rolling may be performed.

[0082] Cold rolling annealing heat treatment step (S50)

[0083] The above cold-rolled steel can be subjected to cold-roll annealing heat treatment. The above cold-roll annealing heat treatment can be understood as the ACL (Annealing and Coating Line) step for the final annealing of the cold-rolled plate.

[0084] The step (S50) of the above cold rolling annealing heat treatment may include an annealing process in which, after increasing the temperature by 10°C / s or more (e.g., 10°C / s or more and less than 50°C / s), annealing is started at a temperature of 950 to 1100°C and maintained for 30 to 90 seconds. The cold rolling annealing heat treatment is performed on a cold-rolled sheet obtained after cold rolling. A temperature is applied to derive the optimal grain size, taking into account the improvement of iron loss and mechanical properties. To prevent surface oxidation and nitriding during cold rolling annealing, heating is performed under mixed atmosphere conditions. The surface condition is made smoother through a mixed atmosphere of nitrogen and hydrogen. The atmosphere inside the annealing furnace in which the above cold rolling annealing heat treatment is performed may be hydrogen (H2): 20 volume% or more by volume fraction, and specifically, hydrogen (H2): 20 to 40 volume% and nitrogen (N2): 60 to 80 volume%. In the atmosphere inside the annealing furnace where the above cold rolling annealing heat treatment is performed, if hydrogen (H2) is less than 20 volume%, nitrogen may penetrate the surface of the steel plate and form nitrides, which can increase iron loss.

[0085] If the cold rolling annealing temperature is less than 950°C or the annealing holding time is less than 30 seconds, the size of the magnetic domains decreases rapidly, resulting in high iron loss; that is, the grain size becomes fine, which can increase hysteresis loss. On the other hand, if the cold rolling annealing temperature exceeds 1100°C or the annealing holding time exceeds 90 seconds, heat treatment cannot proceed due to problems such as deformation of the steel sheet during the process, and the grain size becomes coarse and eddy current loss increases.

[0086] Meanwhile, a coating process may be performed to form an insulating coating layer after the final cold rolling annealing. By forming an insulating coating layer, improved punchability and insulation properties can be secured. The insulating coating layer may be formed on at least one surface of the cold-rolled material. In this case, the thickness of the insulating coating layer may be about 1 to 2 μm. For example, the thickness of the insulating coating layer formed on one surface and the other surface of the cold-rolled material, respectively, may be about 1 to 2 μm.

[0087] Experimental Example

[0088] Preferred experimental examples are presented below to aid in understanding the present invention. However, the following experimental examples are intended only to aid in understanding the present invention, and the present invention is not limited by the following experimental examples.

[0089] In the present experimental example, specimens are provided that have the alloy element composition (unit: weight%) of Table 1. In addition to the alloy element composition disclosed in Table 1, the specimens have in common a composition of carbon (C): 0.0019 weight%, sulfur (S): 0.0017 weight%, phosphorus (P): 0.0008 weight%, nitrogen (N): 0.0017 weight%, titanium (Ti): 0.0016 weight%, tin (Sn): 0.05 weight%, and the remainder being iron (Fe).

[0090] In Table 1, silicon (Si), manganese (Mn), and aluminum (Al) represent the content (unit: wt%) constituting the non-oriented electrical steel sheet, and r1 is the distribution density (unit: # / mm²) of secondary phase particles with an average size of 0.1 to 1 μm in the microstructural cross-section of the non-oriented electrical steel sheet. 2 ) and r2 is the distribution density of secondary phase particles with an average size of 1 to 10 µm in the microstructure cross-section of non-oriented electrical steel (unit: # / mm² 2 ) and d is the average domain width (unit: μm) in the microstructure cross-section of the non-oriented electrical steel sheet, and F D is the relationship between the distribution density of secondary phase particles and the average domain width in the microstructural cross-section of non-oriented electrical steel, denoted as {1 / (d · r1 0.8 · r20.1 It corresponds to )} · 100.

[0091] In this experimental example, the magnetic domain width was measured using a Vibrating Sample Magnetometry (VSM) instrument and a microscope utilizing the Magneto-optic Kerr Effect (MOKE). The VSM instrument was developed in 1955 at the Lincoln Laboratory of MIT, and the MOKE microscope is used to determine the magnetic structure of a material by utilizing the phenomenon in which the polarization and reflectance of reflected light generated when light is incident on the surface of a magnetized material change due to magnetization. In this experimental example, the magnetic domain width at a specific magnetic field (0 Oe after demagnetization) was measured using a hysteresis loop and an analysis graph obtained from the MOKE microscope. To prepare the microscope sample, mirror polishing of 0.05 μm or less was performed, and measurements were taken five times using an optical microscope at 20x magnification on an analysis area with a diameter of 6 mm.

[0092] In this experimental example, other process conditions for manufacturing the specimen were applied as common values ​​within the range satisfying the process conditions described in the manufacturing method according to the technical concept of the present invention described above. For example, in the hot rolling step, conditions were applied as common: reheat temperature (SRT): 1160℃, hot rolling finish temperature: 880℃, coiling temperature (CT): 580℃, pre-annealing heat treatment annealing temperature: 1000℃, pre-annealing heat treatment annealing holding time: 100 seconds, total cold rolling reduction rate: 95%, cold rolling annealing heat treatment temperature: 1000℃, and cold rolling annealing heat treatment annealing holding time: 45 seconds.

[0093] No. Si Mn Al [Si] 0.3 +[Mn] 0.7 +[Al] 0.8 r1(# / mm 2 ) r2(# / mm 2 ) d(㎛) F D W 15 / 50 (W / kg) note 1 2.21 0.33 0.19 1.99 14297 6604 0.15 0.13 2.33 Invention lecture 2 2.16 0.28 0.33 2.08 4184 4813 0.09 0.94 2.45 Invention lecture 3 1.98 0.38 0.1 1.9 8723 5540 0.19 0.15 2.65 Comparative lecture 4 1.9 0.32 0.31 2.06 7217 5042 0.14 0.26 2.13 Invention lecture 5 2.03 0.35 0.2 1.99 17585 5226 0.19 0.09 2.58 Invention lecture 6 2.19 0.26 0.42 2.16 14112 6091 0.09 0.48 2.48 Invention lecture 7 2.29 0.38 0.12 1.97 237 4830 0.2 2.71 2.79 Comparative lecture 8 1.78 0.25 0.41 2.06 33624 4362 0.14 0.07 3.2 Comparative lecture 9 1.83 0.29 0.24 1.93 4884 5634 0.2 0.24 2.64 Comparative lecture 10 2.14 0.29 0.23 1.98 16321 68324 0.19 0.07 3.5 Comparative lecture 11 2.01 0.29 0.15 1.87 17534 23612 0.2 0.07 3.04 Comparative lecture 12 1.92 0.23 0.45 2.1 8817 7738 0.09 0.54 2.41 Invention lecture 13 2.02 0.36 0.12 1.9 14067 7448 0.19 0.11 2.62 Comparative lecture 14 2.27 0.27 0.19 1.95 17047 4312 0.05 0.34 2.69 Comparative lecture 15 2.24 0.18 0.2 1.85 8188 5824 0.53 0.06 3.36 Comparative lecture 16 1.8 0.29 0.29 1.98 7031 4182 0.61 0.06 3.47 Comparative lecture 17 2.11 0.22 0.27 1.95 3601 4454 0.07 0.86 2.65 Comparative lecture 18 1.77 0.27 0.25 1.92 211 3314 0.12 5.3 3.33 Comparative lecture 19 1.86 0.39 0.65 2.43 354 18621 0.12 2.87 3.32 Comparative lecture 20 2.2 0.25 0.35 2.08 9528 6965 0.09 0.55 2.43 Invention lecture 21 1.75 0.35 0.38 2.12 29311 3421 0.17 0.07 2.79 Comparative lecture 22 2.18 0.35 0.12 1.93 43211 1322 0.13 0.07 2.95 Comparative lecture 23 1.81 0.37 0.46 2.23 5784 4584 0.15 0.28 2.66 Comparative lecture 24 2.04 0.27 0.4 2.11 14991 5987 0.09 0.21 2.31 Invention lecture 25 2.01 0.28 0.17 1.88 15010 6621 0.06 0.31 2.63 Comparative lecture 26 2.03 0.39 0.41 2.25 236 4237 0.09 6.09 2.95 Comparative lecture 27 2.07 0.29 0.21 1.95 17549 5512 0.12 0.14 2.73 Comparative lecture 28 2.14 0.2 0.23 1.89 23511 4861 0.62 0.02 2.93 Comparative lecture 29 1.79 0.33 0.21 1.94 29311 6654 0.23 0.05 3.34 Comparative lecture 30 1.99 0.23 0.15 1.8 36116 4312 0.21 0.05 2.66 Comparative lecture 31 1.82 0.39 0.14 1.91 8439 3151 0.47 0.07 3.25 Comparative lecture 32 2.12 0.2 0.22 1.88 12901 6779 0.01 1.48 2.75 Comparative lecture 33 1.94 0.37 0.11 1.9 13632 4487 0.1 0.2 2.69 Comparative lecture 34 1.93 0.37 0.41 2.2 3345 19317 0.79 0.07 3.47 Comparative lecture 35 1.92 0.33 0.52 2.27 17050 26944 0.63 0.02 2.8 Comparative lecture 36 1.9 0.32 0.37 2.12 4978 7292 0.17 0.27 2.59 Invention lecture 37 1.93 0.45 0.26 2.13 12117 3122 0.73 0.03 2.89 Comparative lecture 38 2.25 0.22 0.28 1.98 26134 16781 0.26 0.04 2.81 Comparative lecture 39 2.13 0.3 0.55 2.3 45691 27523 0.09 0.07 2.96 Comparative lecture 40 1.88 0.28 0.48 2.17 15725 6553 0.15 0.12 2.56 Invention lecture 41 2.25 0.37 0.29 2.15 15239 7178 0.09 0.35 2.54 Invention lecture 42 2.27 0.27 0.19 1.95 17047 4312 0.05 0.34 2.93 Comparative lecture 43 2.25 0.22 0.44 2.14 16474 5619 0.13 0.14 2.14 Invention lecture 44 2.08 0.21 0.19 1.85 5517 7206 0.06 0.7 2.67 Comparative lecture 45 2.11 0.33 0.16 1.94 11420 4596 0.08 0.31 2.88 Comparative lecture 46 2.28 0.21 0.25 1.94 11665 4356 0.11 0.22 2.98 Comparative lecture 47 2.19 0.21 0.28 1.96 16428 6055 0.13 0.14 2.69 Comparative lecture 48 1.75 0.37 0.2 1.96 8858 7375 0.15 0.18 3.13 Comparative lecture 49 1.69 0.31 0.29 1.98 14504 6597 0.13 0.14 3.02 Comparative lecture 50 2 0.23 0.29 1.96 13905 5946 0.02 0.87 2.66 Comparative lecture 51 2.09 0.24 0.43 2.13 6115 6355 0.09 0.99 2.6 Invention lecture 52 1.82 0.39 0.22 2.02 13103 4110 0.19 0.12 2.2 Invention lecture 53 1.82 0.38 0.18 1.96 8822 5005 0.14 0.21 2.86 Comparative lecture 54 1.92 0.32 0.19 1.94 1623 18223 0.03 3.38 3.2 Comparative lecture 55 2.02 0.26 0.18 1.89 2813 46213 0.81 0.07 3.05 Comparative lecture 56 1.77 0.22 0.38 1.99 1315 41632 0.03 3.68 3.08 Comparative lecture 57 2.05 0.27 0.16 1.86 8071 6963 0.13 0.23 2.68 Comparative lecture 58 2.16 0.45 0.21 2.12 13719 5007 0.02 1.25 2.7 Comparative lecture 59 2.25 0.51 0.35 2.33 16439 6244 0.19 0.09 2.74 Comparative lecture 60 1.98 0.39 0.23 2.05 16657 5299 0.12 0.15 2.28 Invention lecture 61 1.87 0.35 0.53 2.28 65311 3184 0.09 0.07 2.71 Comparative lecture 62 2.08 0.24 0.28 1.98 2854 45632 0.79 0.07 3.4 Comparative lecture 63 2.08 0.27 0.45 2.18 5248 4851 0.09 0.88 2.22 Invention lecture 64 1.85 0.21 0.42 2.03 7354 7388 0.12 0.28 2.32 Invention lecture

[0094] Referring to Table 1, Experimental Examples 1, 2, 4, 5, 6, 12, 20, 24, 36, 40, 41, 43, 51, 52, 60, 63, and 64 are embodiments of the present invention, comprising silicon (Si): 1.8 to 2.3 wt%, manganese (Mn): 0.2 to 0.4 wt%, aluminum (Al): 0.1 to 0.5 wt%, carbon (C): greater than 0 and less than or equal to 0.01 wt%, sulfur (S): greater than 0 and less than or equal to 0.01 wt%, phosphorus (P): greater than 0 and less than or equal to 0.08 wt%, nitrogen (N): greater than 0 and less than or equal to 0.01 wt%, titanium (Ti): greater than 0 and less than or equal to 0.01 wt%, the sum of at least one of tin (Sn) and antimony (Sb): 0.01 to 0.1 wt%, and the remainder being iron (Fe). The composition range is satisfied, and the relationship between the content of silicon (Si), manganese (Mn), and aluminum (Al) satisfies Equation 1 below, and the distribution density (r1) of secondary phase particles with an average size of 0.1 to 1 μm in the microstructure cross-section of the electrical steel sheet is 3,000 particles / mm² 2 Up to 18,000 pieces / mm 2 And, the distribution density (r2) of secondary phase particles with an average size of 1 to 10 µm is 4000 particles / mm 2 Up to 8000 pieces / mm 2 And, the average value of the magnetic domain width (d) in the microstructure cross-section of the electrical steel sheet is 0.09 ~ 0.2 μm, and the distribution density of secondary phase particles and the average value of the magnetic domain width in the microstructure cross-section of the electrical steel sheet satisfy Equation 2 below, and the iron loss (W) of 2.6 W / kg or less 15 / 50 It can be confirmed that ) is satisfied.

[0095] Equation 1: 1.99 ≤ ([Si] 0.3 +[Mn] 0.7 +[Al] 0.8 ) ≤ 2.18

[0096] (However, [Si], [Mn], and [Al] represent the content of silicon, manganese, and aluminum (unit: weight%).)

[0097] Equation 2: 0.08 ≤ {1 / (d · r1 0.8 · r20.1 )} · 100 ≤ 2.7

[0098] (wherein d is the average domain width (unit: μm) in the microstructure cross-section of the electrical steel sheet, and r1 is the distribution density (unit: particles / mm²) of secondary phase particles with an average size of 0.1 to 1 μm in the microstructure cross-section of the electrical steel sheet 2 ) and r2 is the distribution density of secondary phase particles with an average size of 1 to 10 μm in the microstructure cross-section of the electrical steel sheet (unit: particles / mm² 2 )lim)

[0099] In contrast, Experimental Examples 3, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 37, 38, 39, 42, 44, 45, 46, 47, 48, 49, 50, 53, 54, 55, 56, 57, 58, 59, 61, and 62 are comparative examples of the present invention, wherein the iron loss (W) is 2.6 W / kg or less. 15 / 50 It can be confirmed that it does not satisfy ) and exceeds.

[0100] For example, Experimental Examples 3, 7, 9, 10, 11, 13, 14, 16, 17, 22, 23, 25, 26, 27, 28, 30, 31, 32, 33, 34, 38, 42, 44, 45, 46, 47, 50, 53, 54, 55, 57, and 62 satisfy the compositional range of silicon (Si): 1.8 ~ 2.3 wt%, manganese (Mn): 0.2 ~ 0.4 wt%, and aluminum (Al): 0.1 ~ 0.5 wt%, but do not satisfy the above Equation 1, and ultimately have an iron loss (W) of 2.6 W / kg or less. 15 / 50 It can be confirmed that it does not satisfy ) and exceeds.

[0101] In addition, Experimental Examples 8, 21, 37, 56, and 58 satisfy Equation 1 above, but do not simultaneously satisfy the compositional ranges of silicon (Si): 1.8 ~ 2.3 wt%, manganese (Mn): 0.2 ~ 0.4 wt%, and aluminum (Al): 0.1 ~ 0.5 wt%, and ultimately, iron loss (W) of 2.6 W / kg or less 15 / 50 It can be confirmed that it does not satisfy ) and exceeds.

[0102] Meanwhile, looking at the experimental examples in Table 1, i) the distribution density (r1) of secondary phase particles with an average size of 0.1 to 1 μm in the microstructural cross-section of the electrical steel sheet is 3,000 particles / mm² 2 Up to 18,000 pieces / mm 2 and ii) the distribution density (r2) of secondary phase particles with an average size of 1 to 10 µm is 4000 particles / mm 2 Up to 8000 pieces / mm 2 It can be confirmed that iii) the average value of the magnetic domain width (d) in the microstructure cross-section of the electrical steel sheet is 0.09 to 0.2 μm, and iv) the condition that the distribution density of secondary phase particles and the average value of the magnetic domain width in the microstructure cross-section of the electrical steel sheet satisfy Equation 2 simultaneously is not a sufficient condition but a necessary condition for the invention to be an example of the present invention.

[0103] Although the present invention has been described above with reference to embodiments, various changes and modifications may be made by those skilled in the art. Such changes and modifications are considered to be within the scope of the present invention as long as they do not depart from the scope of the present invention. Accordingly, the scope of rights of the present invention should be determined by the claims set forth below.

Claims

Claim 1 A non-oriented electrical steel sheet comprising silicon (Si): 1.8 ~ 2.3 wt%, manganese (Mn): 0.2 ~ 0.4 wt%, aluminum (Al): 0.1 ~ 0.5 wt%, carbon (C): greater than 0 and less than or equal to 0.01 wt%, sulfur (S): greater than 0 and less than or equal to 0.01 wt%, phosphorus (P): greater than 0 and less than or equal to 0.08 wt%, nitrogen (N): greater than 0 and less than or equal to 0.01 wt%, titanium (Ti): greater than 0 and less than or equal to 0.01 wt%, the sum of at least one of tin (Sn) and antimony (Sb): 0.01 ~ 0.1 wt%, and the remainder being iron (Fe) and other unavoidable impurities, wherein the content of silicon (Si), manganese (Mn), and aluminum (Al) satisfies the following Formula 1, and has an iron loss (W) of 2.6 W / kg or less. 15 / 50 Non-oriented electrical steel sheet characterized by having ). Formula 1: 1.99 ≤ ([Si] 0.3 +[Mn] 0.7 +[Al] 0.8 ) ≤ 2.18 (wherein [Si], [Mn], and [Al] represent the content of silicon, manganese, and aluminum (unit: weight%)) Claim 2 In claim 1, the distribution density (r1) of secondary phase particles with an average size of 0.1 to 1 μm in the microstructure cross-section of the electrical steel sheet is 3000 particles / mm² 2 Up to 18,000 pieces / mm 2 And, the distribution density (r2) of secondary phase particles with an average size of 1 to 10 µm is 4000 particles / mm 2 Up to 8000 pieces / mm 2 Phosphorus, non-oriented electrical steel sheet. Claim 3 A non-oriented electrical steel sheet according to claim 1, characterized in that the average value (d) of the magnetic domain width in the microstructure cross-section of the electrical steel sheet is 0.09 to 0.2 μm. Claim 4 A non-oriented electrical steel sheet according to claim 1, characterized in that the distribution density of secondary phase particles and the average value of magnetic domain width in the microstructure cross-section of the electrical steel sheet satisfy the following Equation 2. Equation 2: 0.08 ≤ {1 / (d · r1 0.8 · r2 0.1 )} · 100 ≤ 2.7(wherein d is the average domain width value (unit: μm) in the microstructure cross-section of the electrical steel sheet, and r1 is the distribution density (unit: particles / mm²) of secondary phase particles with an average size of 0.1 to 1 μm in the microstructure cross-section of the electrical steel sheet 2 ) and r2 is the distribution density of secondary phase particles with an average size of 1 to 10 μm in the microstructure cross-section of the electrical steel sheet (unit: particles / mm² 2 )lim) Claim 5 A non-oriented electrical steel sheet according to claim 4, characterized in that the secondary phase particles are nitride, sulfide, and oxide particles.

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