Non-oriented electrical steel sheet and manufacturing method therefor

Abstract

The present invention provides a non-oriented electrical steel sheet, comprising, in wt%: 2-3.8 wt% of silicon (Si); 0.2-0.4 wt% of manganese (Mn); 0.8-1.5 wt% of aluminum (Al); greater than 0 and less than or equal to 0.005 wt% of carbon (C); greater than 0 and less than or equal to 0.015 wt% of phosphorus (P); greater than 0 and less than or equal to 0.005 wt% of sulfur (S); greater than 0 and less than or equal to 0.003 wt% of nitrogen (N); greater than 0 and less than or equal to 0.005 wt% of titanium (Ti); 0.005-0.02 wt% of at least one of boron (B), cerium (Ce), and yttrium (Y); and the remainder of iron (Fe) and inevitable impurities.

Description

Non-oriented electrical steel sheet and manufacturing method thereof

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

[0002] Due to policies to reduce carbon dioxide (CO2) emissions to prevent global warming, existing internal combustion engine vehicles are being rapidly replaced by eco-friendly vehicles (hybrid vehicles (HEVs), electric vehicles (EVs), etc.), especially electric vehicles (EVs).

[0003] Electric vehicles (EVs) must produce high torque at low speeds or during acceleration, and rotate at high speeds (e.g., over 200 Hz) at constant and high speeds. Therefore, the core material of the motor, non-oriented electrical steel, must satisfy both high magnetic flux density and low iron loss.

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

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

[0006] Methods for reducing core loss in non-oriented electrical steel include: 1) reducing sheet thickness, 2) improving resistivity, and 3) improving grain structure. Among these, improving grain structure is a key factor in improving core loss and magnetic flux density. For example, the grain structure of non-oriented electrical steel significantly influences its magnetic properties.

[0007] Embodiments of the present invention can provide a non-oriented electrical steel sheet with improved magnetic properties and a manufacturing method thereof by controlling the alloy composition of the non-oriented electrical steel sheet.

[0008] One embodiment of the present invention provides a non-oriented electrical steel sheet, which comprises, 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): 0 to 0.005 wt%, phosphorus (P): 0 to 0.015 wt%, sulfur (S): 0 to 0.005 wt%, nitrogen (N): 0 to 0.003 wt%, titanium (Ti): 0 to 0.005 wt%, at least one of boron (B), cerium (Ce), and yttrium (Y): 0.005 wt% to 0.02 wt%, 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 of formula 1 ( ) can be satisfied.

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

[0012] In this embodiment, the non-oriented electrical steel sheet may have a core loss (based on W10 / 400) of 13.0 W / kg or less.

[0013] In this embodiment, the non-oriented electrical steel sheet can have a magnetic flux density (based on B50) of 1.65 T or more.

[0014] One embodiment of the present invention is a method for manufacturing a non-oriented electrical steel sheet, comprising the steps of: hot-rolling a slab including, 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): 0 to 0.005 wt% or less, phosphorus (P): 0 to 0.015 wt% or less, sulfur (S): 0 to 0.005 wt% or less, nitrogen (N): 0 to 0.003 wt% or less, titanium (Ti): 0 to 0.005 wt% or less, at least one of boron (B), cerium (Ce), and yttrium (Y) in an amount of 0.005 wt% to 0.02 wt%, the remainder being iron (Fe) and unavoidable impurities, to manufacture a hot-rolled sheet; A method for manufacturing a non-oriented electrical steel sheet is provided, comprising: a step of hot-rolling and annealing the hot-rolled sheet to produce a hot-rolled and annealed sheet; a step of cold-rolling the hot-rolled and annealed sheet to produce a cold-rolled sheet; and a step of cold-rolling and annealing the cold-rolled sheet to produce a cold-rolled and annealed 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 of formula 2 ( ) can be satisfied.

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

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

[0019] In the present embodiment, the step of cold-rolling and annealing the cold-rolled sheet to manufacture the cold-rolled and annealed sheet may be performed under the following conditions: a heating rate of 10°C / s or more, a cold-rolling annealing temperature of 900°C to 1100°C, a cold-rolling annealing time of 5 s to 70 s, and a cooling rate of 20°C / s or more.

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

[0021] In this embodiment, the non-oriented electrical steel sheet may have a core loss (based on W10 / 400) of 13.0 W / kg or less.

[0022] In this embodiment, the non-oriented electrical steel sheet can have a magnetic flux density (based on B50) of 1.65 T or more.

[0023] Other aspects, features and advantages other than those described above will become apparent from the following detailed description, claims and drawings for carrying out the invention.

[0024] According to one embodiment of the present invention, which is achieved as described above, the magnetic properties of a non-oriented electrical steel sheet can be improved by controlling the alloy composition of the non-oriented electrical steel sheet. Of course, the scope of the present invention is not limited by these effects.

[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.

[0026] The present invention is capable of various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail in the detailed description. The effects and features of the present invention, as well as the methods for achieving them, will become clearer with reference to the embodiments described in detail below, along with the drawings. However, the present invention is not limited to the embodiments disclosed below and can be implemented in various forms.

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

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

[0029] In the following examples, terms such as “include” or “have” mean that a feature or component described in the specification is present, and do not preclude the possibility that one or more other features or components may be added.

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

[0031] In some embodiments, where implementations are otherwise feasible, specific process sequences may be performed in a different order than described. For example, two processes described in succession may be performed substantially simultaneously, or in a reverse order from the described order.

[0032] In this specification, “A and / or B” refers to the case where it is A, or B, or both A and B. And, “at least one of A and B” refers to the case where it is A, or 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 drawing 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 is 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 to be hot-rolled may be a slab. The slab in a semi-finished 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 include silicon (Si), manganese (Mn), aluminum (Al), carbon (C), phosphorus (P), sulfur (S), nitrogen (N), titanium (Ti), the remainder iron (Fe), and unavoidable impurities. Additionally, the slab may include at least one of boron (B), cerium (Ce), and yttrium (Y).

[0038] Specifically, the slab may contain, in wt%, silicon (Si): 2 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): 0 to 0.005 wt%, phosphorus (P): 0 to 0.015 wt%, sulfur (S): 0 to 0.005 wt% or less, nitrogen (N): 0 to 0.003 wt% or less, titanium (Ti): 0 to 0.005 wt% or less, at least one of boron (B), cerium (Ce), and yttrium (Y): 0.005 wt% to 0.02 wt%, the remainder iron (Fe) and unavoidable impurities.

[0039] Silicon (Si) can be a major additive element that increases resistivity and lowers iron loss. Silicon (Si) can be included in an amount of 2 wt% to 3.8 wt%. If silicon (Si) is included in an amount less than 2 wt%, iron loss reduction may be insufficient. That is, if silicon (Si) is included in an amount less than 2 wt%, it may be difficult to obtain low iron loss. On the other hand, if silicon (Si) is included in an amount greater than 3.8 wt%, 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, by improving the grain structure, a low iron loss value similar to that obtained with a high silicon content can be obtained.

[0040] Manganese (Mn) can increase the resistivity and improve the grain structure of non-oriented electrical steel sheets manufactured with silicon. Manganese (Mn) may be included in an amount of 0.2 wt% to 0.4 wt%. When manganese (Mn) is included in an amount less than 0.2 wt%, fine MnS precipitates may be formed, which may inhibit grain growth. On the other hand, when manganese (Mn) is added in an amount exceeding 0.4 wt%, coarse MnS precipitates may be formed, which may deteriorate magnetic properties such as a decrease in magnetic flux density. In addition, when manganese (Mn) is included in an amount exceeding 0.4 wt%, the effect of reducing iron loss may be reduced compared to the amount added, and cold-rollability may deteriorate.

[0041] Aluminum (Al) can be a major additive element that, together with silicon, increases resistivity and reduces eddy current loss. Aluminum (Al) can induce AlN precipitation when combined with nitrogen. Aluminum (Al) can be included at 0.8 wt% to 1.5 wt%. When the aluminum (Al) content is less than 0.8 wt%, fine AlN precipitates can be formed, which can inhibit grain growth and hinder the movement of magnetic domains, which can result in poor magnetic properties. When the aluminum (Al) content exceeds 1.5 wt%, cold rolling properties can deteriorate, and the magnetic flux density can decrease, which can result in poor magnetic properties.

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

[0043] Phosphorus (P) may be a component that develops the grain structure as a grain boundary segregation element. 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 suppressed due to the segregation effect, magnetic properties may be deteriorated, and cold rolling properties may be reduced.

[0044] Sulfur (S) increases iron loss by forming precipitates such as MnS and CuS and inhibits grain growth, so it may be desirable to add it in as low a amount as possible. Sulfur (S) may be included in an amount greater than 0 and less than 0.005 wt%. When 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) increases iron loss and inhibits grain growth by forming precipitates such as AlN, TiN, and NbN, so it may be desirable to add it in as low a amount as possible. Nitrogen (N) may be included in an amount greater than 0 and less than 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. As more titanium (Ti) is added, the magnetic properties deteriorate, so it may be desirable to add as little titanium (Ti) as possible. Titanium (Ti) can be included in an amount greater than 0 and less than 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, inhibiting grain growth and resulting in deteriorated magnetic properties.

[0047] Boron (B), cerium (Ce), and yttrium (Y) may be elements that lower grain boundary energy due to grain boundary segregation, reduce the recrystallization rate, suppress nucleation of {111} and {112} orientations, reduce the volume fraction of orientations that are unfavorable for magnetic properties, and increase {100} fiber and Goss orientations that are favorable for magnetic properties. In one embodiment, the slab may include at least one of boron (B), cerium (Ce), and yttrium (Y) in an amount of 0.005 wt% to 0.02 wt%. In addition, the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) included 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 {100} aggregate structure favorable for magnetism <130> and {113} <251> The fraction increases, and the {334} is unfavorable for magnetism. <483> and {111} <110> The final grain structure can be improved by reducing the fraction, which can improve the 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%, the pinning effect due to grain boundary segregation may hinder recrystallization grain growth, which may suppress grain growth and have a negative effect on the grain structure.

[0048] In the hot rolling step (S100), the slab is reheated and then hot rolled to produce a hot-rolled sheet. For example, a slab that has undergone the hot rolling step (S100) may be referred to as a hot-rolled sheet.

[0049] In the hot rolling step (S100), the slab can 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 in the slab are re-dissolved, and fine precipitates are generated in the subsequent rolling and annealing processes, which may inhibit grain growth and deteriorate magnetism. Therefore, when the slab reheating temperature in the hot rolling step (S100) satisfies 1000°C to 1200°C, the rollability can be prevented from deteriorating and the magnetic properties can be prevented from deteriorating.

[0050] The hot rolling step (S100) can finish-roll the slab at a predetermined finishing rolling temperature. At this time, the finishing rolling temperature can be 800°C to 1000°C.

[0051] In addition, the hot rolling step (S100) can cool the hot-rolled slab to a predetermined coiling temperature (CT) and coil it. At this time, the coiling temperature can be 550°C to 650°C. If the coiling temperature is lower than 550°C, brittleness increases, which may cause plate breakage during coiling. On the other hand, if the coiling temperature exceeds 650°C, the coil may be cooled in air during coiling, which may form fine TiC precipitates, which may deteriorate the magnetism.

[0052] The thickness of the hot-rolled sheet manufactured through the hot rolling step (S100) may be 1.8 mm to 2.6 mm. In this case, if the thickness of the hot-rolled sheet exceeds 2.6 mm, the cold rolling reduction ratio increases, which may result in a deteriorated texture.

[0053] A hot rolling annealing step (S200) may be performed after the hot rolling step (S100). A hot-rolled sheet on which the hot rolling annealing step (S200) has been performed may be referred to as a hot-rolled annealed sheet. The hot rolling annealing step (S200) may be performed under the following conditions: a heating rate of 10°C / s or more, a holding temperature (e.g., hot rolling annealing temperature): 900°C to 1050°C, a holding time (e.g., hot rolling annealing time): 30 s to 120 s, and a cooling rate of 30°C / s or more. Specifically, in the hot-rolled annealing step (S200), the hot-rolled sheet is heated at a heating rate of 10°C / s or more, the heated hot-rolled sheet is maintained (e.g., annealed) at a holding temperature (e.g., hot-rolled annealing temperature) of 900°C to 1050°C for a holding time (e.g., hot-rolled annealing time) of 30 s to 120 s, and can be cooled at a cooling rate of 30°C / s or more. If the holding temperature (e.g., hot-rolled annealing temperature) is less than 900°C, grain growth may not be sufficient, so that fine grains are formed, which may result in poor magnetic properties of the manufactured non-oriented electrical steel sheet. On the other hand, if the holding temperature (e.g., hot-rolled annealing temperature) exceeds 1050°C, grains may grow excessively, which may result in a severe grain size deviation, a large amount of oxidation, and re-dissolved precipitates that are finely precipitated during the subsequent process, which may result in poor magnetic properties of the manufactured non-oriented electrical steel sheet.

[0054] Although not shown, a pickling step may be performed after the hot-rolled annealing step (S200). In the pickling step, an oxide layer formed on the surface of the hot-rolled annealed sheet may 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 that is favorable for magnetism. When the hot-rolled annealing step (S200) is maintained (e.g., annealed) at a holding temperature (e.g., hot-rolled annealing temperature) of 900°C to 1050°C for a holding time (e.g., hot-rolled annealing time) of 30 s to 120 s, the precipitates may become coarse to be 500 nm or larger, and the number of precipitates having a size less than 500 nm, which adversely affects magnetism, may be reduced. If the hot-rolled annealing temperature in the hot-rolled annealing step (S200) is less than 900℃ or the hot-rolled annealing time is less than 30s, the hot-rolled annealed sheet may have an average grain size of less than 100㎛, and if the hot-rolled annealed sheet with grains of that size is cold rolled and cold rolled, the texture of the non-oriented electrical steel sheet may have a texture that is unfavorable for magnetism because the (111) fraction is high compared to the (100) fraction. On the other hand, if the hot-rolled annealing temperature in the hot-rolled annealing step (S200) is more than 1050℃ or the hot-rolled annealing time is more than 120s, the hot-rolled annealed sheet may have an average grain size of more than 250㎛, and if the hot-rolled annealed sheet with grains of that size is cold rolled and cold rolled, the texture of the non-oriented electrical steel sheet may improve, but orientation colonies may be formed in the microstructure, which may actually deteriorate the magnetic properties.Accordingly, when the hot-rolled annealing step (S200) is maintained (e.g., annealed) at a holding temperature (e.g., hot-rolled annealing temperature) of 900°C to 1050°C for a holding time (e.g., hot-rolled annealing time) of 30 s to 120 s, the hot-rolled annealed sheet can 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 can have a texture favorable to magnetism, and the formation of orientation colonies in the microstructure can be prevented.

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

[0057] After the cold rolling step (S300), a cold rolling annealing step (S400) may be performed. A cold rolled sheet on which the cold rolling annealing step (S400) has been performed may be called a cold rolled annealed sheet (or, non-oriented electrical steel sheet). The cold rolling annealing step (S400) may be performed under the following conditions: a heating rate of 10°C / s or more, a holding temperature (e.g., cold rolling annealing temperature): 900°C to 1100°C, a holding time (e.g., cold rolling annealing time): 5 s to 70 s, and a cooling rate of 20°C / s or more. Specifically, in the cold rolling annealing step (S400), the cold rolled sheet is heated at a heating rate of 10°C / s or more, the heated cold rolled sheet is maintained (e.g., annealed) at a holding temperature (e.g., cold rolling annealing temperature) of 900°C to 1100°C for a holding time (e.g., cold rolling annealing time) of 5 s to 70 s, and can be cooled at a cooling rate of 20°C / s or more. When the holding temperature (e.g., cold rolling annealing temperature) is less than 900°C, the grain size may be fine, which may increase the hysteresis loss. On the other hand, when the holding temperature (e.g., cold rolling annealing temperature) exceeds 1100°C, the grain size may become coarse, which may increase the eddy current loss.

[0058] Core loss is expressed as the sum of hysteresis loss and eddy current loss. As the grain size increases, hysteresis loss gradually decreases, but eddy current loss gradually increases. The reason why hysteresis loss decreases as the grain size increases is because the (111) orientation is first recrystallized during the initial recrystallization, and as the grains grow, various orientations begin to recrystallize and grow. As the grains grow, the fraction of (111) grains decreases relatively, so the fraction of orientations that are favorable for magnetism in terms of aggregate structure increases, which reduces hysteresis loss. On the other hand, the reason why eddy current loss increases as the grain size increases is because the loss occurs due to eddy currents formed within the grains or magnetic domains. As the grain size increases, the eddy current generated within the grains increases, which in turn increases the 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) may be 90 μm to 160 μm. If 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 containing approximately 30% hydrogen and approximately 70% nitrogen. By performing the cold rolling annealing step (S400) in a mixed atmosphere of nitrogen and hydrogen, the surface condition can be further improved.

[0060] In one embodiment, a non-oriented electrical steel sheet can be manufactured through a hot rolling step (S100) and a cold rolling annealing step (S400). Furthermore, 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, the punchability can be improved and the insulation can be secured.

[0061] The non-oriented electrical steel sheet manufactured 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 iron (Fe), and unavoidable impurities. In addition, 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 include, in wt%, silicon (Si): 2 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): 0 to 0.005 wt%, phosphorus (P): 0 to 0.015 wt%, sulfur (S): 0 to 0.005 wt% or less, nitrogen (N): 0 to 0.003 wt% or less, titanium (Ti): 0 to 0.005 wt% or less, at least one of boron (B), cerium (Ce), and yttrium (Y): 0.005 wt% to 0.02 wt%, the remainder iron (Fe) and unavoidable impurities.

[0063] In one embodiment, the sum of the contents of boron (B), cerium (Ce), and yttrium (Y) included 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 can have a core loss (based on W10 / 400) of 13.0 W / kg or less. In one embodiment, the non-oriented electrical steel sheet can have a magnetic flux density (based on B50) of 1.65 T or more. Here, the core loss is the core 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 present inventors have found that {100}, which is advantageous for magnetism, is formed by 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 {113} <251> The volume fraction of grains with orientation {334} increases, which is unfavorable for magnetism. <483> Volume fraction of grains with orientation {111} <110> It was confirmed that the final texture was improved by reducing the volume fraction of grains with orientation, thereby improving the magnetic properties of non-oriented electrical steel sheets. 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 {111}, and <110> It was confirmed that non-oriented electrical steel sheets have low iron loss and high magnetic flux density when the volume fraction of grains having an orientation satisfies Equation 1 below.

[0066] <Formula 1>

[0067]

[0068] In Equation 1, f{100} <130> Silver {100} <130> is the volume fraction (%) of grains having orientation f{113} <251> Silver {113} <251> is the volume fraction (%) of grains having orientation f{334} <483> Silver {334} <483> is the volume fraction (%) of grains having orientation f{111} <110> Silver {111} <110> It is the volume fraction (%) of crystal grains having a direction.

[0069] Orientation can refer to the arrangement of crystal planes and crystal directions in a crystal grain. Orientation can be expressed by the Miller index, Euler angle, and pole figure. Among the three orientation expressions, the Miller index is the most commonly used, and the Miller index can express the orientation by the direction perpendicular to the rolling plane, ND (hkl), and the rolling direction, RD [uvw]. For example, {100} <130> The rolling surface is {100} plane and the rolling direction is <130> It can mean a direction in which the direction is set.

[0070] When 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%, 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 advantageous for magnetism <130> Volume fraction of grains with orientation {113} <251> The volume fraction of grains with orientation {334} may increase, which is unfavorable for magnetism. <483> Volume fraction of grains having orientation {111}, and <110> The volume fraction of grains having a direction may be reduced.

[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 {111} <110> When the volume fraction of grains having an orientation satisfies Equation 1, the manufactured non-oriented electrical steel sheet can have a core loss of 13.0 W / kg or less (based on W10 / 400) and a magnetic flux density of 1.65 T or more (based on B50). When the value of Equation 1 is less than 3.0, the magnetic properties of the manufactured non-oriented electrical steel sheet may be inferior because the volume fraction of the texture favorable to magnetism is small and the volume fraction of the texture unfavorable to magnetism is large.

[0072] Experimental example

[0073] Below, the present invention will be described in more detail through experimental examples. However, the following experimental examples are intended to further illustrate the present invention, and the scope of the present invention is not limited by these examples. Those skilled in the art may appropriately modify or alter the following experimental examples within the scope of the present invention.

[0074] Tables 1 and 2 below are tables showing the components 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 component contents 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 methods.

[0076] Slabs containing iron (Fe) and unavoidable impurities were prepared with the components and remainders shown in Tables 1 and 2. The slabs were then hot-rolled to produce hot-rolled sheets with a thickness of 2.0 mm. Hot-rolling was performed under the following conditions: reheating temperature: 1130°C, finishing rolling temperature: 880°C, and coiling temperature: 600°C.

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

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

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

[0080] collective organization

[0081] The orientation fraction of the grain structure 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 grain structure was measured at least 5,000 grains, and then the fraction was calculated.

[0082] magnetic properties

[0083] The magnetic properties were obtained by measuring the 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 then calculating the average value.

[0084] Specifically, for a specimen measuring 60 mm x 60 mm, 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 obtained. At this time, the specimen was manufactured by punching using a 60 mm x 60 mm punching die.

[0085] Composition (wt%)SiMnAlCPSNTi3.30.2060.9030.0020.0110.00180.00120.0013

[0086] Classification B (wt%)Y (wt%)Ce (wt%)B+Y+Ce (wt%)Example 10.00500.00250.00110.0086Example 20.00150.00520.00250.0092Example 30.0020.00280.00510.0099Example 40.00110.00150.00780.0104Example 50.00550.00250.00330.0113Example 60.00650.0040.0030.0135Example 70.0040.00530.00650.0158Example 80.00530.00620.00680.0183Example 90.019--0.019Example 10-0.019-0.019Example 11--0.0190.019Example 120.007--0.007Example 13-0.007-0.007Example 14--0.0070.007Comparative Example 10.00550.0080.0070.0205Comparative Example 20.00550.00870.00640.0206Comparative Example 30.00830.00580.00680.0209Comparative Example 40.00630.00650.00880.0216Comparative Example 50.00650.00750.00820.0222Comparative Example 6----Comparative Example 70.003--0.003Comparative Example 8-0.003-0.003Comparative Example 9--0.0030.003

[0087] The value of the fraction of the volume of the separation (%) formula 1 is the magnetic properties {100} <130> {113} <251> {334} <483> {111} <110> Iron loss (W / kg) Magnetic flux density (T) Example 1 23.2 21.8 18.2 15.13.30 12.67 1.66 Example 2 24.1 23.8 15.7 14.23.9 312.34 1.66 Example 3 25.8 25.3 12.4 11.85 22 12.0 21.68 Example 4 33.8 25.9 13.11 1.56 13 11.99 1.68 Example 5 30.128 8 11.5 5.18 05 11.75 1.68 Example 6 33.4 30.110 89.27.83 12.08 1.67 Example 7 28.3 21.215 214.34.29 12.431 .67 Example 8 26.1 22.9 17.7 15.83.64 12.55 1.66 Example 9 25.8 20.8 12.5 20.13.8 12.67 1.67 Example 10 24.8 22.4 13.4 22.53.5 4 12.78 1.67 Example 11 25.7 21.8 11.8 25.83.5 12.58 1.67 Example 12 23.5 20.8 13.5 26.53.0 12.89 1.66 Example 13 22.8 19.9 14.124.23.0 12.98 1.66 Example 14 24.6 21.5 14.5 22.53.3 3 12.70 1.66 Comparative Example 125.820.720.122.52.8313.121.65Comparative Example 220.520.822.821.22.3013.211.64Comparative Example 318.315.720.225.31.9513.821.64Comparative Example 418.917.828.027.11.6614.491.62Comparative Example 515.813.530.828.51.2414.481.59Comparative Example 621.520.819.820.52.6313.351.66Comparative Example 722.821.018.419.22.9413.081.65Comparative Example 823.422.120.118.52.9213.111.65Comparative example 922.723.719.418.92.9813.151.65

[0088] Referring to Tables 1 to 3, when the 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%, it can be confirmed that when Equation 1 has a value of 3.0 or more, the manufactured non-oriented electrical steel sheet has a core loss of 13.0 W / kg or less (based on W10 / 400) and a magnetic flux density of 1.65 T or more (based on B50).

[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%, the pinning effect due to grain boundary segregation suppresses the growth of recrystallized crystal grains, preventing crystal grain growth and rather having a negative effect on 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 advantageous for magnetism <130> Volume fraction of grains with orientation {113} <251> The volume fraction of grains with orientation {334} is reduced, which is unfavorable for magnetism. <483> Volume fraction of grains with orientation {111} <110> The volume fraction of grains having a direction increases so that Equation 1 has a value less than 3.0, and the manufactured non-oriented electrical steel sheet can have a core loss exceeding 13.0 W / kg (based on W10 / 400) or a magnetic flux density less than 1.65 T (based on B50).

[0090] Comparative Examples 6 to 9 are cases where at least one of boron (B), cerium (Ce), and yttrium (Y) is not included 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 included 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 large, so that the orientations favorable to the aggregate structure are relatively few, and thus 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}, which is favorable to magnetism, <130> Volume fraction of grains with orientation {113} <251> The volume fraction of grains with orientation {334} is reduced, which is unfavorable for magnetism. <483> Volume fraction of grains with orientation {111} <110> The volume fraction of grains having a direction increases so that Equation 1 has a value less than 3.0, and the manufactured non-oriented electrical steel sheet can have a core loss exceeding 13.0 W / kg (based on W10 / 400).

[0091] While the present invention has been described with reference to the embodiments illustrated in the drawings, these are merely exemplary, and those skilled in the art will appreciate that various modifications and equivalent alternative embodiments are possible. Therefore, the true scope of technical protection of the present invention should be determined by the technical spirit of the appended claims.

Claims

1. As a non-oriented electrical steel sheet, A non-oriented electrical steel sheet comprising, in wt%, silicon (Si): 2 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): 0 to 0.005 wt%, phosphorus (P): 0 to 0.015 wt%, sulfur (S): 0 to 0.005 wt% or less, nitrogen (N): 0 to 0.003 wt%, titanium (Ti): 0 to 0.005 wt% or less, at least one of boron (B), cerium (Ce), and yttrium (Y) in an amount of 0.005 wt% to 0.02 wt%, the remainder being iron (Fe) and unavoidable impurities.

2. In paragraph 1, A non-oriented electrical steel sheet, wherein the sum of the contents of the boron (B), the cerium (Ce), and the yttrium (Y) is 0.005 wt% to 0.02 wt%.

3. In paragraph 1, The above non-oriented electrical steel sheet is a non-oriented electrical steel sheet that satisfies Equation 1 below. <Formula 1> In the above equation 1, f{100} <130> Silver {100} <130> is the volume fraction of grains having orientation f{113} <251> Silver {113} <251> is the volume fraction of grains having orientation f{334} <483> Silver {334} <483> is the volume fraction of grains having orientation f{111} <110> Silver {111} <110> It is the volume fraction of crystal grains having a direction.

4. In paragraph 1, A non-oriented electrical steel sheet having an average grain size of 90 ㎛ to 160 ㎛.

5. In paragraph 1, The above non-oriented electrical steel sheet is a non-oriented electrical steel sheet having a core loss of 13.0 W / kg or less (based on W10 / 400).

6. In paragraph 1, The above non-oriented electrical steel sheet is a non-oriented electrical steel sheet having a magnetic flux density of 1.65 T or more (based on B50).

7. A method for manufacturing a non-oriented electrical steel sheet, A step of manufacturing a hot-rolled sheet by hot-rolling a slab containing, in wt%, silicon (Si): 2 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): 0 to 0.005 wt% or less, phosphorus (P): 0 to 0.015 wt% or less, sulfur (S): 0 to 0.005 wt% or less, nitrogen (N): 0 to 0.003 wt% or less, titanium (Ti): 0 to 0.005 wt% or less, at least one of boron (B), cerium (Ce), and yttrium (Y) in an amount of 0.005 wt% to 0.02 wt%, the remainder being iron (Fe) and unavoidable impurities; A step of manufacturing a hot-rolled and annealed plate by hot-rolling and annealing the hot-rolled plate; A step of manufacturing a cold-rolled sheet by cold rolling the hot-rolled and annealed sheet; and A step of manufacturing a cold-rolled annealed plate by cold-rolling and annealing the above cold-rolled plate; A method for manufacturing a non-oriented electrical steel sheet, comprising:

8. In paragraph 7, A method for manufacturing a non-oriented electrical steel sheet, wherein the sum of the contents of the boron (B), the cerium (Ce), and the yttrium (Y) is 0.005 wt% to 0.02 wt%.

9. In paragraph 7, The above non-oriented electrical steel sheet is a method for manufacturing a non-oriented electrical steel sheet that satisfies Equation 2 below. <Formula 2> In the above equation 2, f{100} <130> Silver {100} <130> is the volume fraction of grains having orientation f{113} <251> Silver {113} <251> is the volume fraction of grains having orientation f{334} <483> Silver {334} <483> is the volume fraction of grains having orientation f{111} <110> Silver {111} <110> It is the volume fraction of crystal grains having a direction.

10. In paragraph 7, A method for manufacturing a non-oriented electrical steel sheet, wherein the step of manufacturing a hot-rolled and annealed sheet by hot-rolling the hot-rolled sheet is performed under the following conditions: a heating rate of 10°C / s or more, a hot-rolling annealing temperature of 900°C to 1050°C, a hot-rolling annealing time of 30s to 120s, and a cooling rate of 30°C / s or more.

11. In paragraph 7, A method for manufacturing a non-oriented electrical steel sheet, wherein the average grain size of the hot-rolled and annealed sheet is 100 ㎛ to 250 ㎛.

12. In paragraph 7, A method for manufacturing a non-oriented electrical steel sheet, wherein the step of manufacturing a cold-rolled annealed sheet by cold-rolling the cold-rolled sheet is performed under the following conditions: a heating rate of 10°C / s or more, a cold-rolled annealing temperature of 900°C to 1100°C, a cold-rolled annealing time of 5 s to 70 s, and a cooling rate of 20°C / s or more.

13. In paragraph 7, A method for manufacturing a non-oriented electrical steel sheet, wherein the average grain size of the non-oriented electrical steel sheet is 90 ㎛ to 160 ㎛.

14. In paragraph 7, A method for manufacturing a non-oriented electrical steel sheet, wherein the non-oriented electrical steel sheet has a core loss (based on W10 / 400) of 13.0 W / kg or less.

15. In paragraph 7, A method for manufacturing a non-oriented electrical steel sheet, wherein the non-oriented electrical steel sheet has a magnetic flux density of 1.65 T or more (based on B50).

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