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

Abstract

The present invention provides a non-oriented electrical steel sheet comprising, in wt%, silicon (Si): 2.0 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.4 wt%, aluminum (Al): 0.8 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.005 wt%, phosphorus (P): greater than 0 and less than or equal to 0.015 wt%, sulfur (S): greater than 0 and less than or equal to 0.005 wt%, nitrogen (N): greater than 0 and less than or equal to 0.003 wt%, titanium (Ti): greater than 0 and less than or equal to 0.005 wt%, at least one of boron (B), cerium (Ce), and yttrium (Y) in an amount of 0.005 wt% to 0.02 wt%, and the remainder being iron (Fe) and unavoidable impurities.

Description

Technology Field

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

[0002] Due to policies aimed at reducing carbon dioxide (CO2) emissions to prevent global warming, existing internal combustion engine vehicles are being rapidly replaced by eco-friendly vehicles (hybrid vehicles (HEV), electric vehicles (EV), etc.), particularly electric vehicles (EV).

[0003] Since electric vehicles (EVs) must generate high torque at low speeds or during acceleration, and rotate at high speeds (e.g., 200 Hz or higher) during constant speed and high-speed driving, the non-oriented electrical steel sheets used as the core material for the motor must simultaneously satisfy high magnetic flux density and low iron loss.

[0004] Factors affecting the magnetic properties of these non-oriented electrical steel sheets include chemical composition, sheet thickness, microstructure, insulating coating layer, and texture. Furthermore, these various factors are influenced by the manufacturing process conditions of the non-oriented electrical steel sheets.

[0005] Non-oriented electrical steel sheets are manufactured through the processes of steelmaking / continuous casting, hot rolling, heat treatment after hot rolling, cold rolling, heat treatment after cold rolling, and coating, and non-oriented electrical steel sheets with excellent magnetic properties can be manufactured by optimizing the conditions of each process.

[0006] To reduce iron loss in non-oriented electrical steel sheets, methods such as 1) reducing sheet thickness, 2) increasing resistivity, and 3) improving texture can be used. Among these, improving texture is one of the important factors for improving iron loss and magnetic flux density. For example, the texture of non-oriented electrical steel sheets has a significant impact on magnetic properties. The problem to be solved

[0007] Embodiments of the present invention can provide a non-oriented electrical steel sheet with improved magnetic properties and a method for manufacturing the same by controlling the alloy components of the non-oriented electrical steel sheet. means of solving the problem

[0008] One embodiment of the present invention provides a non-oriented electrical steel sheet comprising, in wt%, silicon (Si): 2.0 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.4 wt%, aluminum (Al): 0.8 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.005 wt%, phosphorus (P): greater than 0 and less than or equal to 0.015 wt%, sulfur (S): greater than 0 and less than or equal to 0.005 wt%, nitrogen (N): greater than 0 and less than or equal to 0.003 wt%, titanium (Ti): greater than 0 and less than or equal to 0.005 wt%, at least one of boron (B), cerium (Ce), and yttrium (Y) in an amount of 0.005 wt% to 0.02 wt%, and the remainder being iron (Fe) and unavoidable impurities.

[0009] In this embodiment, the sum of the contents of the boron (B), the cerium (Ce), and the yttrium (Y) may be 0.005 wt% to 0.02 wt%.

[0010] In this embodiment, the non-oriented electrical steel sheet is Formula 1 ( Can satisfy ).

[0011] In this embodiment, the average grain size of the non-oriented electrical steel sheet may be 90㎛ to 160㎛.

[0012] In this embodiment, the non-oriented electrical steel sheet has an iron loss (W) of 13.0 W / kg or less. 10 / 400 Can have a standard.

[0013] In this embodiment, the non-oriented electrical steel sheet has a magnetic flux density (B) of 1.65 T or more. 50 Can have a standard.

[0014] One embodiment of the present invention is a method for manufacturing a non-oriented electrical steel sheet, comprising the step of manufacturing a hot-rolled sheet by hot-rolling a slab comprising, in wt%, silicon (Si): 2.0 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.4 wt%, aluminum (Al): 0.8 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.005 wt%, phosphorus (P): greater than 0 and less than or equal to 0.015 wt%, sulfur (S): greater than 0 and less than or equal to 0.005 wt%, nitrogen (N): greater than 0 and less than or equal to 0.003 wt%, titanium (Ti): greater than 0 and less than or equal to 0.005 wt%, at least one of boron (B), cerium (Ce), and yttrium (Y) in an amount of 0.005 wt% to 0.02 wt%, and the remainder being iron (Fe) and unavoidable impurities; A method for manufacturing a non-oriented electrical steel sheet is provided, comprising: a step of manufacturing a hot-rolled annealed sheet by hot-rolling and annealing the hot-rolled sheet; a step of manufacturing a cold-rolled sheet by cold-rolling the hot-rolled annealed sheet; and a step of manufacturing a cold-rolled annealed sheet by cold-rolling and annealing the cold-rolled sheet.

[0015] In this embodiment, the sum of the contents of the boron (B), the cerium (Ce), and the yttrium (Y) may be 0.005 wt% to 0.02 wt%.

[0016] In this embodiment, the non-oriented electrical steel sheet is Equation 2 ( Can satisfy ).

[0017] In this embodiment, the step of manufacturing a hot-rolled annealed plate by hot-rolling the hot-rolled plate can be performed under conditions of a heating rate of 10℃ / s or more, a hot-rolled annealing temperature of 900℃ to 1050℃, a hot-rolled annealing time of 30s to 120s, and a cooling rate of 30℃ / s or more.

[0018] In this embodiment, the average grain size of the hot-rolled annealed plate may be 100㎛ to 250㎛.

[0019] In this embodiment, the step of manufacturing a cold-rolled annealed plate by cold-rolling the cold-rolled plate can be performed under conditions of a heating rate of 10℃ / s or more, a cold-rolled annealing temperature of 900℃ to 1100℃, a cold-rolled annealing time of 5s to 70s, and a cooling rate of 20℃ / s or more.

[0020] In this embodiment, the average grain size of the non-oriented electrical steel sheet may be 90㎛ to 160㎛.

[0021] In this embodiment, the non-oriented electrical steel sheet has an iron loss (W) of 13.0 W / kg or less. 10 / 400 Can have a standard.

[0022] In this embodiment, the non-oriented electrical steel sheet has a magnetic flux density (B) of 1.65 T or more. 50 Can have a standard.

[0023] Other aspects, features, and advantages other than those described above will become clear from the specific details, claims, and drawings for implementing the invention below. Effects of the invention

[0024] According to one embodiment of the present invention as described above, the magnetic properties of a non-oriented electrical steel sheet can be improved by controlling the alloy components of the non-oriented electrical steel sheet. Of course, the scope of the present invention is not limited by this effect. Brief explanation of the drawing

[0025] FIG. 1 is a flowchart schematically illustrating a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention. Specific details for implementing the invention

[0026] The present invention is capable of various modifications and may have various embodiments; specific embodiments are illustrated in the drawings and described in detail in the detailed description. The effects and features of the present invention, and the methods for achieving them, will become clear by referring to the embodiments described below in detail together with the drawings. However, the present invention is not limited to the embodiments disclosed below but can be implemented in various forms.

[0027] In the following embodiments, terms such as first, second, etc. are used not in a limiting sense, but for the purpose of distinguishing one component from another component.

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

[0029] In the following embodiments, terms such as "include" or "have" mean that the features or components described in the specification are present, and do not preclude the possibility that one or more other features or components may be added.

[0030] In the drawings, the size of components may be exaggerated or reduced for convenience of explanation. For example, the size and thickness of each component shown in the drawings are depicted arbitrarily for convenience of explanation, and therefore the present invention is not necessarily limited to what is illustrated.

[0031] Where an embodiment can be implemented differently, a specific process sequence may be performed differently from the order described. For example, two processes described consecutively may be performed substantially simultaneously or proceed in the reverse order of the description.

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

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

[0034] FIG. 1 is a flowchart schematically illustrating a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0035] Referring to FIG. 1, a method for manufacturing a non-oriented electrical steel sheet may include a hot rolling step (S100), a hot rolling annealing step (S200), a cold rolling step (S300), and a cold rolling annealing step (S400).

[0036] In the hot rolling step (S100), the slab may be reheated, then hot-rolled at a predetermined finishing rolling temperature, and then cooled and coiled. At this time, in the method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention, the semi-finished product subject to hot rolling may be a slab. The slab in the semi-finished product state can be obtained through a continuous casting process after obtaining molten steel of a predetermined composition through a steelmaking process.

[0037] In one embodiment, the slab may comprise silicon (Si), manganese (Mn), aluminum (Al), carbon (C), phosphorus (P), sulfur (S), nitrogen (N), titanium (Ti), the remainder being iron (Fe) and unavoidable impurities. Additionally, the slab may comprise at least one of boron (B), cerium (Ce), and yttrium (Y).

[0038] Specifically, the slab may comprise, in wt%, silicon (Si): 2.0 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.4 wt%, aluminum (Al): 0.8 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.005 wt%, phosphorus (P): greater than 0 and less than or equal to 0.015 wt%, sulfur (S): greater than 0 and less than or equal to 0.005 wt%, nitrogen (N): greater than 0 and less than or equal to 0.003 wt%, titanium (Ti): greater than 0 and less than or equal to 0.005 wt%, at least one of boron (B), cerium (Ce), and yttrium (Y) in an amount of 0.005 wt% to 0.02 wt%, and the remainder being iron (Fe) and unavoidable impurities.

[0039] Silicon (Si) can be a major additive element as a component that lowers iron loss by increasing resistivity. Silicon (Si) may be included in an amount of 2.0 wt% to 3.8 wt%. If silicon (Si) is included in an amount less than 2.0 wt%, the reduction of iron loss may be insufficient. That is, if silicon (Si) is included in an amount less than 2.0 wt%, it may be difficult to obtain low iron loss. On the other hand, if silicon (Si) exceeds 3.8 wt%, the permeability and magnetic flux density may decrease. In the present invention, although the slab (or non-oriented electrical steel sheet) has a low silicon content, a low iron loss value similar to that obtained with a high silicon content can be obtained by improving the texture.

[0040] Manganese (Mn) can increase the resistivity of non-oriented electrical steel sheets manufactured together with silicon and improve the texture. Manganese (Mn) may be included in an amount of 0.2 wt% to 0.4 wt%. If manganese (Mn) is included in an amount less than 0.2 wt%, fine MnS precipitates are formed, which can inhibit grain growth. On the other hand, if manganese (Mn) is added in an amount greater than 0.4 wt%, coarse MnS precipitates are formed, which may degrade magnetic properties such as reduced magnetic flux density. Additionally, if manganese (Mn) is included in an amount greater than 0.4 wt%, the effect of reducing iron loss may decrease relative to the amount added, and a decrease in cold rolling performance may occur.

[0041] Aluminum (Al) can be a major additive element as a component that increases resistivity along with silicon to lower eddy current losses. Aluminum (Al) can induce AlN precipitation upon contact with nitrogen. Aluminum (Al) may be included in an amount of 0.8 wt% to 1.5 wt% or less. If the aluminum (Al) content is less than 0.8 wt%, fine AlN precipitates may form, which can inhibit grain growth and hinder the movement of magnetic domains, thereby degrading magnetic properties. If the aluminum (Al) content exceeds 1.5 wt%, a decrease in cold rolling performance may occur, and magnetic properties may degrade due to a decrease in magnetic flux density.

[0042] Carbon (C) is an element that increases iron loss by forming carbides such as TiC and NbC, so it may be desirable to have a lower carbon content in the slab (or non-oriented electrical steel sheet). Carbon may be included in an amount greater than 0 and less than or equal to 0.005 wt%. If carbon is included in an amount greater than 0.005 wt%, self-aging may occur, which can degrade the magnetic properties of the manufactured non-oriented electrical steel sheet. If carbon is included in an amount less than or equal to 0.005 wt%, the self-aging phenomenon may be suppressed.

[0043] Phosphorus (P) is a grain boundary segregation element and can be a component that develops texture. Phosphorus (P) may be included in an amount greater than 0 and less than or equal to 0.015 wt%. If phosphorus (P) is included in an amount greater than 0.015 wt%, grain growth may be inhibited due to segregation effects, magnetic properties may be degraded, and cold rolling performance may be reduced.

[0044] Sulfur (S) forms precipitates such as MnS and CuS, which increase iron loss and inhibit grain growth, so it may be desirable to add it in the lowest possible amount. Sulfur (S) may be included in an amount greater than 0 and less than or equal to 0.005 wt%. If sulfur (S) is included in an amount greater than 0.005 wt%, precipitates such as MnS and CuS may be formed, which may increase iron loss and inhibit grain growth.

[0045] Nitrogen (N) forms precipitates such as AlN, TiN, and NbN, which increase iron loss and inhibit grain growth, so it may be desirable to add it as low as possible. Nitrogen (N) may be included in an amount greater than 0 and less than or equal to 0.003 wt%. If nitrogen (N) is included in an amount greater than 0.003 wt%, precipitates such as AlN, TiN, and NbN may be formed, which may increase iron loss and inhibit grain growth.

[0046] Titanium (Ti) can inhibit grain growth by forming fine precipitates such as TiC and TiN. Since magnetic properties deteriorate as titanium (Ti) is added, it may be desirable to add titanium (Ti) as low as possible. Titanium (Ti) may be included in an amount greater than 0 and less than or equal to 0.005 wt%. If titanium is included in an amount greater than 0.005 wt%, fine precipitates such as TiC and TiN may be formed, which may inhibit grain growth and deteriorate magnetic properties.

[0047] Boron (B), cerium (Ce), and yttrium (Y) may be elements that lower the grain boundary energy due to grain boundary segregation and reduce the recrystallization rate, thereby suppressing the nucleation growth of {111} and {112} orientations, reducing the volume fraction of orientations unfavorable to magnetic properties, and increasing {100} fibers and Goss orientations favorable to magnetic properties. In one embodiment, the slab may contain at least one of boron (B), cerium (Ce), and yttrium (Y) in an amount of 0.005 wt% to 0.02 wt%. Additionally, the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) contained in the slab may be 0.005 wt% or more and 0.02 wt% or less. When the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) contained in the slab satisfies 0.005 wt% to 0.02 wt%, a magnetically favorable texture {100} <130> and {113} <251> The fraction increases, and is unfavorable to magnetism {334} <483> and {111} <110> The final texture can be improved by reducing the fraction, which can improve magnetic properties. If the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) contained in the slab is less than 0.005 wt%, it may be difficult to achieve the aforementioned effect. On the other hand, if the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) contained in the slab exceeds 0.02 wt%, recrystallization grain growth is inhibited due to the pinning effect caused by grain boundary segregation, which may have an adverse effect on the texture.

[0048] In the hot rolling step (S100), the slab can be reheated, and then the reheated slab can be hot-rolled to produce a hot-rolled plate. For example, the slab on which the hot rolling step (S100) is performed can be called a hot-rolled plate.

[0049] In the hot rolling step (S100), the slab may be reheated. The slab reheating temperature in the hot rolling step (S100) may be 1000°C to 1200°C. Preferably, the slab reheating temperature in the hot rolling step (S100) may be 1110°C to 1150°C. If the slab reheating temperature is less than 1000°C, the rolling load increases, making it difficult to perform hot rolling. On the other hand, if the slab reheating temperature exceeds 1200°C, precipitates such as C, S, and N within the slab are re-dissolved, and fine precipitates may be generated during subsequent rolling and annealing processes, which may inhibit grain growth and impair magnetism. Accordingly, if the slab reheating temperature in the hot rolling step (S100) satisfies 1000℃ to 1200℃, the reduction in rolling performance can be prevented and the deterioration of magnetic properties can be prevented.

[0050] The hot rolling step (S100) can finish rolling the slab at a predetermined finish rolling temperature. At this time, the finish rolling temperature may be 800℃ to 1000℃.

[0051] Additionally, the hot rolling step (S100) may cool the hot-rolled slab to a predetermined coiling temperature (CT) and coil it. At this time, the coiling temperature may be 550°C to 650°C. If the coiling temperature is below 550°C, the brittleness increases, and plate breakage may occur during coiling. On the other hand, if the coiling temperature exceeds 650°C, the coil may be cooled in the air during coiling, and fine TiC precipitates may be formed, which may result in a decrease in magnetic properties.

[0052] The thickness of the hot-rolled plate produced through the hot rolling step (S100) may be 1.8 mm to 2.6 mm. At this time, if the thickness of the hot-rolled plate exceeds 2.6 mm, the cold rolling reduction rate increases, and the texture may deteriorate.

[0053] A hot rolling annealing step (S200) may be performed after the hot rolling step (S100). A hot-rolled plate on which the hot rolling annealing step (S200) has been performed may be called a hot-rolled annealed plate. The hot rolling annealing step (S200) may be performed under conditions where the heating rate is 10℃ / s or higher, the holding temperature (e.g., hot rolling annealing temperature) is 900℃ to 1050℃, the holding time (e.g., hot rolling annealing time) is 30s to 120s, and the cooling rate is 30℃ / s or higher. Specifically, in the hot rolling annealing step (S200), the hot-rolled sheet is heated at a heating rate of 10°C / s or more, and the heated hot-rolled sheet is held at a holding temperature of 900°C to 1050°C (e.g., hot rolling annealing temperature) for a holding time of 30 s to 120 s (e.g., hot rolling annealing time) (e.g., annealing), and can be cooled at a cooling rate of 30°C / s or more. If the holding temperature (e.g., hot rolling annealing temperature) is less than 900°C, grain growth is insufficient, and fine grains are formed, which may result in inferior magnetic properties of the non-oriented electrical steel sheet produced. On the other hand, if the holding temperature (e.g., hot rolling annealing temperature) is greater than 1050°C, the grains grow excessively, which may result in severe grain size variation and significant oxidation, and precipitates may be re-dissolved and finely precipitated during subsequent processes, which may result in inferior magnetic properties of the non-oriented electrical steel sheet produced.

[0054] Although not illustrated, a pickling step may be performed after the hot rolling annealing step (S200). In the pickling step, an oxide layer formed on the surface of the hot rolling annealed plate can be removed using a pickling solution. The pickling step may be performed before the cold rolling step (S300).

[0055] In one embodiment, the average grain size of the hot-rolled annealed sheet after the hot-rolled annealing step (S200) may be 100 μm to 250 μm. As the hot-rolled annealing temperature in the hot-rolled annealing step (S200) increases, the average grain size of the hot-rolled annealed sheet increases, and as the average grain size of the hot-rolled annealed sheet increases, the texture of the non-oriented electrical steel sheet after the cold-rolled annealing step (S400) may have a texture favorable to magnetism. When the hot-rolled annealed sheet is maintained (e.g., annealed) for a holding time (e.g., hot-rolled annealing time) of 30 s to 120 s at a holding temperature (e.g., hot-rolled annealing temperature) of 900°C to 1050°C in the hot-rolled annealing step (S200), the precipitates may become coarser than 500 nm, and the number of precipitates having a size of less than 500 nm that adversely affect magnetism may be reduced. If the hot rolling annealing temperature in the hot rolling annealing step (S200) is less than 900°C or the hot rolling annealing time is less than 30 s, the hot rolling annealed plate may have an average grain size of less than 100 µm, and if the hot rolling annealed plate having grains of that size is cold rolled and cold rolled annealed, the texture of the non-oriented electrical steel sheet may have a texture that is unfavorable to magnetism, with a higher fraction of (111) compared to the fraction of (100). On the other hand, if the hot rolling annealing temperature in the hot rolling annealing step (S200) is greater than 1050°C or the hot rolling annealing time is greater than 120 s, the hot rolling annealed plate may have an average grain size of greater than 250 µm, and if the hot rolling annealed plate having grains of that size is cold rolled and cold rolled annealed, the texture of the non-oriented electrical steel sheet improves, but orientation colonies may form in the microstructure, which may actually worsen the magnetic properties.Accordingly, when the hot-rolled annealing step (S200) is maintained at a holding temperature of 900°C to 1050°C (e.g., hot-rolled annealing temperature) for a holding time of 30 s to 120 s (e.g., hot-rolled annealing time), the hot-rolled annealed sheet may have an average grain size of 100 µm to 250 µm, and the texture of the non-oriented electrical steel sheet after cold rolling and cold-rolled annealing may have a texture favorable to magnetism and the formation of orientation colonies in the microstructure may be prevented.

[0056] A cold rolling step (S300) may be performed after a hot rolling annealing step (S200). A hot-rolled annealed plate that has undergone the cold rolling step (S300) may be called a cold-rolled plate. In the cold rolling step (S300), the hot-rolled annealed plate may be cold-rolled with a reduction rate of 80% to 90%. The thickness of the cold-rolled plate that has undergone the cold rolling step (S300) may be less than 0.35 mm.

[0057] A cold rolling annealing step (S400) may be performed after the cold rolling step (S300). A cold-rolled sheet that has undergone the cold rolling annealing step (S400) may be called a cold-rolled annealed sheet (or, non-oriented electrical steel sheet). The cold rolling annealing step (S400) may be performed under conditions where the heating rate is 10℃ / s or higher, the holding temperature (e.g., cold rolling annealing temperature) is 900℃ to 1100℃, the holding time (e.g., cold rolling annealing time) is 5s to 70s, and the cooling rate is 20℃ / s or higher. Specifically, in the cold rolling annealing step (S400), the cold rolled plate is heated at a heating rate of 10°C / s or more, and the heated cold rolled plate is held at a holding temperature of 900°C to 1100°C (e.g., cold rolling annealing temperature) for a holding time of 5 s to 70 s (e.g., cold rolling annealing time) (e.g., annealing), and can be cooled at a cooling rate of 20°C / s or more. If the holding temperature (e.g., cold rolling annealing temperature) is less than 900°C, the grain size is fine, and hysteresis loss may increase. On the other hand, if the holding temperature (e.g., cold rolling annealing temperature) is greater than 1100°C, the grain size becomes coarse, and eddy current loss may increase.

[0058] Iron loss is expressed as the sum of hysteresis loss and eddy current loss. As the grain size increases, hysteresis loss decreases, but eddy current loss increases. The reason hysteresis loss decreases as the grain size increases is that during initial recrystallization, the (111) orientation is recrystallized first, and as the grain grows, recrystallization and growth of various orientations begin. As the grain grows, the fraction of (111) grains decreases relatively, and as the fraction of orientations that are texture-friendly to magnetism increases, hysteresis loss decreases. On the other hand, the reason eddy current loss increases as the grain size increases is that loss occurs due to eddy currents formed inside the grains or magnetic domains. As the grain size increases, the eddy currents generated inside the grains increase, and this leads to increased loss. Therefore, the average grain size of the cold-rolled annealed sheet (or non-oriented electrical steel sheet) after the cold-rolled annealing step (S400) can be 90㎛ to 160㎛. When the average grain size of the cold-rolled annealed sheet (or, non-oriented electrical steel sheet) after the cold-rolled annealing step (S400) satisfies 90㎛ to 160㎛, the cold-rolled annealed sheet (or, non-oriented electrical steel sheet) can have low iron loss.

[0059] The cold rolling annealing step (S400) can be performed in a mixed atmosphere equipped with about 30% hydrogen and about 70% nitrogen. By performing the cold rolling annealing step (S400) in a mixed atmosphere of nitrogen and hydrogen, the surface condition can be made smoother.

[0060] In one embodiment, a non-oriented electrical steel sheet can be manufactured through a hot rolling step (S100) to a cold rolling annealing step (S400). Additionally, although not illustrated, a coating step for forming an insulating coating layer on the non-oriented electrical steel sheet can be performed after the cold rolling annealing step (S400). By forming an insulating coating layer on the non-oriented electrical steel sheet through the coating step, punchability can be improved and insulation can be ensured.

[0061] The non-oriented electrical steel sheet produced by the above-described manufacturing method may contain silicon (Si), manganese (Mn), aluminum (Al), carbon (C), phosphorus (P), sulfur (S), nitrogen (N), titanium (Ti), the remainder being iron (Fe) and unavoidable impurities. Additionally, the non-oriented electrical steel sheet may contain at least one of boron (B), cerium (Ce), and yttrium (Y).

[0062] Specifically, the non-oriented electrical steel sheet may comprise, in wt%, silicon (Si): 2.0 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.4 wt%, aluminum (Al): 0.8 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.005 wt%, phosphorus (P): greater than 0 and less than or equal to 0.015 wt%, sulfur (S): greater than 0 and less than or equal to 0.005 wt%, nitrogen (N): greater than 0 and less than or equal to 0.003 wt%, titanium (Ti): greater than 0 and less than or equal to 0.005 wt%, at least one of boron (B), cerium (Ce), and yttrium (Y) in an amount of 0.005 wt% to 0.02 wt%, and the remainder being iron (Fe) and unavoidable impurities.

[0063] In one embodiment, the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) contained in the non-oriented electrical steel sheet may be 0.005 wt% or more and 0.02 wt% or less.

[0064] In one embodiment, the non-oriented electrical steel sheet has an iron loss (W) of 13.0 W / kg or less. 10 / 400( 기준) can have. In one embodiment, the non-oriented electrical steel sheet has a magnetic flux density of 1.65 T or more (B 50 It can have a standard. In this case, the iron loss is the iron loss at a frequency of 400 Hz and a magnetic flux density of 1.0 Tesla, and the magnetic flux density is the magnetic flux density at 5000 A / m.

[0065] The inventors [have] {100} which is advantageous to magnetism depending on the content of boron (B), cerium (Ce), and yttrium (Y) contained in a non-oriented electrical steel sheet (or slab). <130> Volume fraction of grains with orientation and {113} <251> The volume fraction of oriented grains increases, and is unfavorable to magnetism {334} <483> Volume fraction of grains with orientation and {111} <110> It was confirmed that the magnetic properties of non-oriented electrical steel sheets are improved by reducing the volume fraction of oriented grains, thereby improving the final texture. In addition, {100} <130> Volume fraction of grains with orientation, {113} <251> Volume fraction of grains with orientation, {334} <483> Volume fraction of grains having orientation, and {111} <110> It was confirmed that when the volume fraction of the oriented grains satisfies Equation 1 below, the non-oriented electrical steel sheet has low iron loss and high magnetic flux density.

[0066] <Equation 1>

[0067]

[0068] f in Equation 1 {100}<130> 100 <130> It is the volume fraction (%) of grains with orientation, and f {113}<251> 113} <251> It is the volume fraction (%) of grains with orientation, f {334}<483> 334 <483> It is the volume fraction (%) of grains with orientation, and f {111}<110> 111} <110> It is the volume fraction (%) of oriented grains.

[0069] Orientation refers to the arrangement of crystal planes and crystal directions within a single grain. Orientation can be expressed by Miller indices, Euler angles, and pole figures. Among the three methods of expressing orientation, Miller indices are the most commonly used; Miller indices can represent orientation using ND (hkl) perpendicular to the rolling plane and RD [uvw] in the rolling direction. For example, {100} <130> The orientation is such that the rolling plane is the {100} plane and the rolling direction is <130> It can mean the direction in which it is positioned.

[0070] In the case where at least one of boron (B), cerium (Ce), and yttrium (Y) is included in a non-oriented electrical steel sheet (or slab) in an amount of 0.005 wt% to 0.02 wt%, and the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) satisfies 0.005 wt% to 0.02 wt%, the texture of the manufactured non-oriented electrical steel sheet can be improved. For example, among the textures of the manufactured non-oriented electrical steel sheet, {100} which is favorable to magnetism <130> Volume fraction of grains with orientation and {113} <251> The volume fraction of oriented grains may increase, which is unfavorable to magnetism {334} <483> Volume fraction of grains having orientation, and {111} <110> The volume fraction of oriented grains may decrease.

[0071] Also, {100} <130> Volume fraction of grains with orientation, {113} <251> Volume fraction of grains with orientation, {334} <483> Volume fraction of grains with orientation and {111} <110> When the volume fraction of oriented grains satisfies Equation 1, the manufactured non-oriented electrical steel sheet has an iron loss (W) of 13.0 W / kg or less 10 / 400 Standard) and magnetic flux density of 1.65 T or higher (B 50 It may have a standard. If the value of Equation 1 is less than 3.0, the volume fraction of the texture favorable to magnetism is small and the volume fraction of the texture unfavorable to magnetism is large, so the magnetic properties of the manufactured non-oriented electrical steel sheet may be inferior.

[0072] Experimental Example

[0073] The present invention will be explained in more detail below through experimental examples. However, the following experimental examples are intended to explain the present invention more specifically, and the scope of the present invention is not limited by the following experimental examples. The following experimental examples may be appropriately modified or changed by those skilled in the art within the scope of the present invention.

[0074] Tables 1 and 2 below show the composition of the slabs used in the experimental examples of the present invention. In Tables 1 and 2, the slabs contain the remainder of iron (Fe) and unavoidable impurities. Examples 1 to 14 and Comparative Examples 1 to 9 have the same content of silicon (Si), manganese (Mn), aluminum (Al), carbon (C), phosphorus (P), sulfur (S), nitrogen (N), and titanium (Ti).

[0075] The non-oriented electrical steel sheets of Examples 1 to 14 and Comparative Examples 1 to 9 were manufactured by the following method.

[0076] Slabs were prepared having the components shown in Tables 1 and 2, with the remainder being iron (Fe) and unavoidable impurities. The slabs were then hot-rolled to produce hot-rolled plates with a thickness of 2.0 mm. At this time, the hot rolling was performed under conditions of a reheat temperature of 1130°C, a finish rolling temperature of 880°C, and a coiling temperature of 600°C.

[0077] The obtained hot-rolled plate was hot-rolled and annealed to produce a hot-rolled annealed plate. At this time, the hot-rolled annealing was performed under conditions of a heating rate: 10℃ / s, a hot-rolled annealing temperature (e.g., holding temperature): 1000℃, a hot-rolled annealing time (e.g., holding time): 100s, and a cooling rate: 30℃ / s. In addition, pickling was performed after the hot-rolled annealing.

[0078] The obtained hot-rolled annealed plate was cold-rolled to produce a cold-rolled plate with a thickness of 0.25 mm. At this time, the cold rolling was performed under conditions of a reduction rate of 88%.

[0079] Subsequently, the obtained cold-rolled sheet was subjected to cold-roll annealing and coating to produce a final product (e.g., non-oriented electrical steel sheet). At this time, the cold-roll annealing was performed under conditions of a heating rate of 20℃ / s, a cold-roll annealing temperature (e.g., holding temperature) of 1000℃, a cold-roll annealing time (e.g., holding time) of 60s, and a cooling rate of 30℃ / s. The cold-roll annealing was carried out in a mixed atmosphere of 30% hydrogen and 70% nitrogen.

[0080] Collective organization

[0081] The orientation fraction of the texture of the final product (e.g., non-oriented electrical steel sheet) was measured using EBSD. Specifically, after mechanical polishing and / or chemical polishing were performed on each specimen, an area of ​​1 cm x 1 cm was measured on the ND plane at the 1 / 4 thickness position using EBSD with an electron beam step size of 10 µm. At this time, the fraction was calculated after measuring at least 5,000 grains during the texture measurement.

[0082] Self-characteristics

[0083] Magnetic properties were determined by measuring iron loss and magnetic flux density values ​​in the L direction (parallel to the rolling direction) and C direction (perpendicular to the rolling direction) using a single sheet tester (SST) and calculating the average value.

[0084] Specifically, for a specimen with a size of 60mm x 60mm, measurements were taken twice in the L direction and twice in the C direction for a total of four measurements, and the average value was calculated. At this time, the specimen was manufactured by stamping using a 60mm x 60mm stamping die.

[0085] Ingredients (wt%) Si Mn Al C P S N Ti 3.3 0.206 0.903 0.002 0.011 0.0018 0.0012 0.0013

[0086] division B (wt%) Y (wt%) Ce (wt%) B+Y+Ce (wt%) Example 1 0.0050 0.0025 0.0011 0.0086 Example 2 0.0015 0.0052 0.0025 0.0092 Example 3 0.002 0.0028 0.0051 0.0099 Example 4 0.0011 0.0015 0.0078 0.0104 Example 5 0.0055 0.0025 0.0033 0.0113 Example 6 0.0065 0.004 0.003 0.0135 Example 7 0.004 0.0053 0.0065 0.0158 Example 8 0.0053 0.0062 0.0068 0.0183 Example 9 0.019 - - 0.019 Example 10 - 0.019 - 0.019 Example 11 - - 0.019 0.019 Example 12 0.007 - - 0.007 Example 13 - 0.007 - 0.007 Example 14 - - 0.007 0.007 Comparative Example 1 0.0055 0.008 0.007 0.0205 Comparative Example 2 0.0055 0.0087 0.0064 0.0206 Comparative Example 3 0.0083 0.0058 0.0068 0.0209 Comparative Example 4 0.0063 0.0065 0.0088 0.0216 Comparative Example 5 0.0065 0.0075 0.0082 0.0222 Comparative Example 6 - - - - Comparative Example 7 0.003 - - 0.003 Comparative Example 8 - 0.003 - 0.003 Comparative Example 9 - - 0.003 0.003

[0087] division Volume fraction (%) Value of Equation 1 Self-characteristics {100}<130> {113}<251> {334}<483> {111}<110> Iron loss (W / kg) Magnetic flux density (T) Example 1 23.2 21.8 18.2 15.1 3.30 12.67 1.66 Example 2 24.1 23.8 15.7 14.2 3.93 12.34 1.66 Example 3 25.8 25.3 12.4 11.8 5.22 12.02 1.68 Example 4 33.8 25.9 13.1 11.5 6.13 11.99 1.68 Example 5 30.1 28.8 11.5 5.1 8.05 11.75 1.68 Example 6 33.4 30.1 10.8 9.2 7.83 12.08 1.67 Example 7 28.3 21.2 15.2 14.3 4.29 12.43 1.67 Example 8 26.1 22.9 17.7 15.8 3.64 12.55 1.66 Example 9 25.8 20.8 12.5 20.1 3.88 12.67 1.67 Example 10 24.8 22.4 13.4 22.5 3.54 12.78 1.67 Example 11 25.7 21.8 11.8 25.8 3.55 12.58 1.67 Example 12 23.5 20.8 13.5 26.5 3.05 12.89 1.66 Example 13 22.8 19.9 14.1 24.2 3.02 12.98 1.66 Example 14 24.6 21.5 14.5 22.5 3.33 12.70 1.66 Comparative Example 1 25.8 20.7 20.1 22.5 2.83 13.12 1.65 Comparative Example 2 20.5 20.8 22.8 21.2 2.30 13.21 1.64 Comparative Example 3 18.3 15.7 20.2 25.3 1.95 13.82 1.64 Comparative Example 4 18.9 17.8 28.0 27.1 1.66 14.49 1.62 Comparative Example 5 15.8 13.5 30.8 28.5 1.24 14.48 1.59 Comparative Example 6 21.5 20.8 19.8 20.5 2.63 13.35 1.66 Comparative Example 7 22.8 21.0 18.4 19.2 2.94 13.08 1.65 Comparative Example 8 23.4 22.1 20.1 18.5 2.92 13.11 1.65 Comparative Example 9 22.7 23.7 19.4 18.9 2.98 13.15 1.65

[0088] Referring to Tables 1 to 3, if a non-oriented electrical steel sheet (or slab) contains at least one of boron (B), cerium (Ce), and yttrium (Y) in an amount of 0.005 wt% to 0.02 wt%, and the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) satisfies 0.005 wt% to 0.02 wt%, then Equation 1 has a value of 3.0 or higher, and if Equation 1 has a value of 3.0 or higher, the manufactured non-oriented electrical steel sheet has an iron loss (W) of 13.0 W / kg or less. 10 / 400 Having the standard) and a magnetic flux density of 1.65 T or more (B 50 It can be confirmed that it has a standard.

[0089] Comparative Examples 1 to 5 are cases where the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) exceeds 0.02 wt%. When the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) exceeds 0.02 wt%, recrystallization grain growth is inhibited due to the pinning effect caused by grain boundary segregation, resulting in no grain growth and instead adversely affecting the texture. For example, when the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) exceeds 0.02 wt%, {100} which is favorable for magnetism <130> Volume fraction of grains with orientation and {113} <251> The volume fraction of oriented grains decreases, and is unfavorable to magnetism {334} <483> Volume fraction of grains with orientation and {111} <110> As the volume fraction of oriented grains increases, Equation 1 has a value less than 3.0, and the manufactured non-oriented electrical steel sheet has an iron loss (W) exceeding 13.0 W / kg. 10 / 400 having the standard) or a magnetic flux density of less than 1.65 T (B 50 Can have a standard.

[0090] Comparative Examples 6 to 9 are cases where at least one of boron (B), cerium (Ce), and yttrium (Y) is not contained in an amount of 0.005 wt% or more, and the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) is less than 0.005 wt%. In cases where at least one of boron (B), cerium (Ce), and yttrium (Y) is not contained in an amount of 0.005 wt% or more, and the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) is less than 0.005 wt%, the grain boundary segregation effect is not significant, and since there are relatively few orientations favorable to the texture, the magnetic properties may be inferior. For example, when the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) is less than 0.005 wt%, {100} favorable to magnetism <130> Volume fraction of grains with orientation and {113} <251> The volume fraction of oriented grains decreases, and is unfavorable to magnetism {334} <483> Volume fraction of grains with orientation and {111} <110> As the volume fraction of oriented grains increases, Equation 1 has a value less than 3.0, and the manufactured non-oriented electrical steel sheet has an iron loss (W) exceeding 13.0 W / kg. 10 / 400 Can have a standard.

[0091] The present invention has been described with reference to the embodiments illustrated in the drawings, but this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims.

Claims

Claim 1 As a non-oriented electrical steel sheet, in wt%, silicon (Si): 2.0 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.4 wt%, aluminum (Al): 0.8 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.005 wt%, phosphorus (P): greater than 0 and less than or equal to 0.015 wt%, sulfur (S): greater than 0 and less than or equal to 0.005 wt%, nitrogen (N): greater than 0 and less than or equal to 0.003 wt%, titanium (Ti): greater than 0 and less than or equal to 0.005 wt%, at least one of boron (B), cerium (Ce), and yttrium (Y) in an amount of 0.005 wt% to 0.02 wt%, and the remainder being iron (Fe) and unavoidable impurities, wherein the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) is 0.005 wt% to 0.02 wt%, and the non-oriented electrical steel sheet satisfies the following Equation 1. f in Equation 1 above {100}<130> 100 <130> It is the volume fraction of grains with orientation, and f {113}<251> 113} <251> It is the volume fraction of grains with orientation, and f {334}<483> 334 <483> It is the volume fraction of grains with orientation, and f {111}<110> 111} <110> It is the volume fraction of crystal grains with orientation. Claim 2 delete Claim 3 delete Claim 4 A non-oriented electrical steel sheet according to claim 1, wherein the average grain size of the non-oriented electrical steel sheet is 90㎛ to 160㎛. Claim 5 In claim 1, the non-oriented electrical steel sheet has an iron loss (W) of 13.0 W / kg or less. 10 / 400 Non-oriented electrical steel sheet having a standard. Claim 6 In claim 1, the non-oriented electrical steel sheet has a magnetic flux density (B) of 1.65 T or more. 50 Non-oriented electrical steel sheet having a standard. Claim 7 A method for manufacturing a non-oriented electrical steel sheet, comprising the step of hot-rolling a slab comprising, in wt%, silicon (Si): 2.0 wt% to 3.8 wt%, manganese (Mn): 0.2 wt% to 0.4 wt%, aluminum (Al): 0.8 wt% to 1.5 wt%, carbon (C): greater than 0 and less than or equal to 0.005 wt%, phosphorus (P): greater than 0 and less than or equal to 0.015 wt%, sulfur (S): greater than 0 and less than or equal to 0.005 wt%, nitrogen (N): greater than 0 and less than or equal to 0.003 wt%, titanium (Ti): greater than 0 and less than or equal to 0.005 wt%, at least one of boron (B), cerium (Ce), and yttrium (Y) in an amount of 0.005 wt% to 0.02 wt%, and the remainder being iron (Fe) and unavoidable impurities to produce a hot-rolled sheet; and hot-rolling annealing the hot-rolled sheet. A method for manufacturing a non-oriented electrical steel sheet, comprising: a step of manufacturing a hot-rolled annealed sheet; a step of cold-rolling the hot-rolled annealed sheet to manufacture a cold-rolled sheet; and a step of cold-rolling and annealing the cold-rolled sheet to manufacture a cold-rolled annealed sheet; wherein the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) is 0.005 wt% to 0.02 wt%, and the non-oriented electrical steel sheet satisfies the following Equation 1. f in Equation 1 above {100}<130> 100 <130> It is the volume fraction of grains with orientation, and f {113}<251> 113} <251> It is the volume fraction of grains with orientation, and f {334}<483> 334 <483> It is the volume fraction of grains with orientation, and f {111}<110> 111} <110> It is the volume fraction of crystal grains with orientation. Claim 8 delete Claim 9 delete Claim 10 A method for manufacturing a non-oriented electrical steel sheet according to claim 7, wherein the step of manufacturing a hot-rolled annealed sheet by hot-rolling the hot-rolled sheet is performed under conditions of a heating rate of 10℃ / s or more, a hot-rolled annealing temperature of 900℃ to 1050℃, a hot-rolled annealing time of 30s to 120s, and a cooling rate of 30℃ / s or more. Claim 11 A method for manufacturing a non-oriented electrical steel sheet according to claim 7, wherein the average grain size of the hot-rolled annealed sheet is 100㎛ to 250㎛. Claim 12 A method for manufacturing a non-oriented electrical steel sheet according to claim 7, wherein the step of manufacturing a cold-rolled annealed sheet by cold-rolling the cold-rolled sheet is performed under conditions of a heating rate of 10℃ / s or more, a cold-rolled annealing temperature of 900℃ to 1100℃, a cold-rolled annealing time of 5s to 70s, and a cooling rate of 20℃ / s or more. Claim 13 A method for manufacturing a non-oriented electrical steel sheet according to claim 7, wherein the average grain size of the non-oriented electrical steel sheet is 90㎛ to 160㎛. Claim 14 In claim 7, the above non-oriented electrical steel sheet has an iron loss (W) of 13.0 W / kg or less. 10 / 400 A method for manufacturing non-oriented electrical steel sheets having a standard. Claim 15 In claim 7, the above non-oriented electrical steel sheet has a magnetic flux density of 1.65 T or more (B 50 A method for manufacturing non-oriented electrical steel sheets having a standard.

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