Non-oriented electrical steel sheet and method for manufacturing same

Abstract

The present invention provides a method for manufacturing a non-oriented electrical steel sheet, the method comprising: a hot rolling step of hot rolling a slab to prepare a hot-rolled sheet, the slab containing, in wt%, 1.0 wt% to 1.5 wt% of silicon (Si), 0.1 wt% to 0.4 wt% of manganese (Mn), 0.1 wt% to 0.4 wt% of aluminum (Al), 0 wt% (exclusive) to 0.003 wt% (inclusive) of sulfur (S), 0.0006 wt% (exclusive) to 0.0030 wt% (inclusive) of the sum of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y), and the balance being iron (Fe) and inevitable impurities; a cold rolling step of cold rolling the hot-rolled sheet to prepare a cold-rolled sheet; and a cold-rolling annealing step of subjecting the cold-rolled sheet to cold-rolling annealing.

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] As environmental regulations have become increasingly stringent worldwide, the automobile industry is shifting from conventional internal combustion engines to eco-friendly vehicles (e.g., hybrids and electric vehicles). Unlike conventional fossil fuel-powered internal combustion engines, eco-friendly vehicles are powered by motors powered by batteries.

[0003] Drive motors for electric vehicles require improved magnetic properties of non-oriented electrical steel sheets used as motor core material to improve motor efficiency, and the development of drive motors for electric vehicles is accelerating as demand for electric vehicles increases.

[0004] Generally, electrical steel is divided into grain-oriented and non-oriented types. Grain-oriented electrical steel is primarily used for fixed components such as transformers. Non-oriented electrical steel, on the other hand, possesses consistent magnetic properties in all directions, regardless of rolling direction, making it primarily used in rotating automotive drive motors.

[0005] Non-oriented electrical steel sheets are easy to magnetize. <100> The directional aggregate structure must be uniformly generated throughout the plate, and for energy efficiency, core loss must be reduced and magnetic flux density increased. Here, core loss refers to the energy loss generated during the magnetization process, and magnetic flux density refers to the power that generates power.

[0006] There are various directions in research to improve the magnetic properties of existing non-oriented electrical steel sheets, but in terms of component control, there is a tendency to remain limited to the level of adding elements such as tin (Sn) and antimony (Sb) to the basic components such as silicon (Si), aluminum (Al), and manganese (Mn).

[0007] However, in order to develop electrical steel sheets with higher-performance magnetic properties, research on various elements is necessary.

[0008] Embodiments of the present invention can provide a non-oriented electrical steel sheet with improved magnetic properties by controlling the alloy composition of the non-oriented electrical steel sheet and a method for manufacturing the same.

[0009] One embodiment of the present invention is a method for manufacturing a non-oriented electrical steel sheet, comprising: a hot rolling step of manufacturing a hot-rolled sheet by hot-rolling a slab including, in wt%, silicon (Si): 1.0 wt% to 1.5 wt%, manganese (Mn): 0.1 wt% to 0.4 wt%, aluminum (Al): 0.1 wt% to 0.4 wt%, sulfur (S): more than 0 wt% and 0.003 wt% or less, a total of at least one element selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y): more than 0.0006 wt% and 0.0030 wt% or less, the remainder iron (Fe) and unavoidable impurities; a cold rolling step of manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet; A method for manufacturing a non-oriented electrical steel sheet is provided, including a cold rolling annealing step of cold rolling and annealing the cold rolled sheet.

[0010] In this embodiment, the proportion of sulfide inclusions having a diameter of 10 nm to 100 nm among all sulfide inclusions can satisfy the following relationship 1.

[0011] <Relationship 1>

[0012] A / B * 100 ≤ 15%

[0013] In the above relational expression 1, A may be the number of sulfide inclusions having a diameter of 10 nm to 100 nm, and B may be the total number of sulfide inclusions.

[0014] In the present embodiment, the ratio of sulfide inclusions having a diameter of 10 nm to 50 nm among sulfide inclusions having a diameter of 10 nm to 100 nm and the ratio of sulfide inclusions having a diameter of 50 nm to 100 nm among sulfide inclusions having a diameter of 10 nm to 100 nm can satisfy the following relationship 2.

[0015] <Relationship 2>

[0016] (S 10~50 ) 2 / (S 50~100 ) ≤ 20

[0017] In the above relational expression 2, S 10~50 corresponds to the ratio of sulfide inclusions having a diameter of 10 nm to 50 nm among sulfide inclusions having a diameter of 10 nm to 100 nm, and S 50~100 The ratio of sulfide inclusions having a diameter of 50 nm to 100 nm among sulfide inclusions having a diameter of 10 nm to 100 nm may correspond to the ratio of sulfide inclusions having a diameter of 50 nm to 100 nm.

[0018] In this embodiment, the non-oriented electrical steel sheet can have a magnetic flux density (based on B50) of 1.695 T or more.

[0019] In this embodiment, the average grain size of the non-oriented electrical steel sheet may be 50 µm to 100 µm.

[0020] In the present embodiment, in the hot rolling step, the slab may be reheated to 1100°C to 1250°C, and the reheated slab may be hot rolled at a finishing rolling temperature of 800°C to 1000°C.

[0021] In the present embodiment, in the cold rolling annealing step, the cold rolled sheet may be heated to a temperature of 900°C to 1100°C at a heating rate of 10°C / s or more, maintained at a temperature of 900°C to 1100°C for a time of 30 s to 90 s, and then cooled at a cooling rate of 30°C / s or more.

[0022] In the present embodiment, the slab may contain at least one element selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y), in a total amount of 0.0007 wt% or more and 0.0030 wt% or less.

[0023] In the present embodiment, the slab may further include carbon (C): more than 0 wt% and less than or equal to 0.003 wt%, phosphorus (P): more than 0 wt% and less than or equal to 0.1 wt%, nitrogen (N): more than 0 wt% and less than or equal to 0.003 wt%, and titanium (Ti): more than 0 wt% and less than or equal to 0.003 wt%.

[0024] Another embodiment of the present invention provides a non-oriented electrical steel sheet, which comprises, in wt%, silicon (Si): 1.0 wt% to 1.5 wt%, manganese (Mn): 0.1 wt% to 0.4 wt%, aluminum (Al): 0.1 wt% to 0.4 wt%, sulfur (S): more than 0 wt% and 0.003 wt% or less, the sum of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y): more than 0.0006 wt% and 0.0030 wt% or less, the remainder being iron (Fe) and unavoidable impurities.

[0025] In this embodiment, the proportion of sulfide inclusions having a diameter of 10 nm to 100 nm among all sulfide inclusions can satisfy the following relationship 3.

[0026] <Relationship 3>

[0027] A / B * 100 ≤ 15%

[0028] In the above relational expression 3, A may be the number of sulfide inclusions having a diameter of 10 nm to 100 nm, and B may be the total number of sulfide inclusions.

[0029] In the present embodiment, the ratio of sulfide inclusions having a diameter of 10 nm to 50 nm among sulfide inclusions having a diameter of 10 nm to 100 nm and the ratio of sulfide inclusions having a diameter of 50 nm to 100 nm among sulfide inclusions having a diameter of 10 nm to 100 nm can satisfy the following relationship 4.

[0030] <Relationship 4>

[0031] (S 10~50 ) 2 / (S 50~100 ) ≤ 20

[0032] In the above relational expression 4, S 10~50 corresponds to the ratio of sulfide inclusions having a diameter of 10 nm to 50 nm among sulfide inclusions having a diameter of 10 nm to 100 nm, and S 50~100 corresponds to the ratio of sulfide inclusions having a diameter of 50 nm to 100 nm among sulfide inclusions having a diameter of 10 nm to 100 nm.

[0033] In this embodiment, the non-oriented electrical steel sheet can have a magnetic flux density (based on B50) of 1.695 T or more.

[0034] In this embodiment, the average grain size of the non-oriented electrical steel sheet may be 50 µm to 100 µm.

[0035] In the present embodiment, the slab may contain at least one element selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y), in a total amount of 0.0007 wt% or more and 0.0030 wt% or less.

[0036] In the present embodiment, the non-oriented electrical steel sheet may further include carbon (C): more than 0 wt% and 0.003 wt% or less, phosphorus (P): more than 0 wt% and 0.1 wt% or less, nitrogen (N): more than 0 wt% and 0.003 wt% or less, and titanium (Ti): more than 0 wt% and 0.003 wt% or less.

[0037] 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.

[0038] 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 composition of the non-oriented electrical steel sheet. Of course, the scope of the present invention is not limited by these effects.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] In the examples below, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] Referring to Fig. 1, a method for manufacturing a non-oriented electrical steel sheet may include a hot rolling step (S100), a cold rolling step (S200), and a cold rolling annealing step (S300).

[0050] In a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention, the semi-finished product subjected to hot rolling 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.

[0051] First, the slab can be manufactured through a continuous casting process. The slab can contain silicon (Si), manganese (Mn), aluminum (Al), sulfur (S), rare earth elements, the remainder iron (Fe), and unavoidable impurities. Here, the rare earth elements can include one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y). In addition, the slab can further contain carbon (C), phosphorus (P), nitrogen (N), and titanium (Ti).

[0052] Specifically, the slab may contain, in wt%, silicon (Si): 1.0 wt% to 1.5 wt%, manganese (Mn): 0.1 wt% to 0.4 wt%, aluminum (Al): 0.1 wt% to 0.4 wt%, sulfur (S): more than 0 wt% and 0.003 wt% or less, rare earth elements: more than 0.0006 wt% and 0.0030 wt% or less, the remainder iron (Fe) and unavoidable impurities. Here, the rare earth elements may include one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y). Accordingly, the slab may contain a total of more than 0.0006 wt% and less than or equal to 0.0030 wt% of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y). Preferably, the slab may contain a total of more than 0.0007 wt% and less than or equal to 0.0030 wt% of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y).

[0053] Additionally, the slab may further include carbon (C): more than 0 wt% and less than or equal to 0.003 wt%, phosphorus (P): more than 0 wt% and less than or equal to 0.1 wt%, nitrogen (N): more than 0 wt% and less than or equal to 0.003 wt%, and titanium (Ti): more than 0 wt% and less than or equal to 0.003 wt%.

[0054] Silicon (Si) can be a major additive element that increases the resistivity of the manufactured non-oriented electrical steel sheet and lowers the core loss. Silicon (Si) can be included in an amount of 1.0 wt% to 1.5 wt%. If silicon (Si) is included in an amount less than 1.0 wt%, it may be difficult for the manufactured non-oriented electrical steel sheet to achieve the target core loss value. That is, if silicon (Si) is included in an amount less than 1.0 wt%, it may be difficult to achieve low core loss. On the other hand, as the silicon (Si) content increases, the permeability and magnetic flux density may decrease. If silicon (Si) is included in an amount exceeding 1.5 wt%, the magnetic flux density may decrease, the difficulty of the production process may increase, and the manufacturing cost may increase. In addition, the present invention is characterized in that the magnetic characteristics of the manufactured non-oriented electrical steel sheet can be improved by reducing the number of sulfide inclusions having a diameter of 10 nm to 100 nm by adding one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y) to the slab in a total amount of more than 0.0006 wt% and less than 0.0030 wt% (preferably, more than 0.0007 wt% and less than 0.0030 wt%), and when the content of silicon (Si) is included in a total amount of more than 1.5 wt%, the total amount of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y) is more than 0.0006 wt% and less than 0.0030 wt% (preferably, more than 0.0007 wt%). Even if silicon (Si) is added in an amount of 0.0030 wt% or less, the number of sulfide inclusions having a diameter of 10 nm to 100 nm is not reduced, so that the effect of adding one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y) may be minimal. Preferably, silicon (Si) may be included in an amount of 1.1 wt% to 1.5 wt%. When silicon (Si) is included in an amount of 1.1 wt% to 1.5 wt%, the manufactured non-oriented electrical steel sheet may have a lower core loss.More preferably, silicon (Si) may be included in an amount of 1.2 wt% to 1.5 wt%.

[0055] Manganese (Mn) can be an element that increases the resistivity of non-oriented electrical steel sheets manufactured with silicon, reduces iron loss, and forms sulfur (S) and sulfide inclusions (e.g., MnS). Manganese (Mn) can be included in an amount of 0.1 wt% to 0.4 wt%. If manganese (Mn) is included in an amount of less than 0.1 wt%, the iron loss improvement effect may be insufficient. On the other hand, if manganese (Mn) is included in an amount of more than 0.4 wt%, fine MnS precipitates may be formed, increasing iron loss.

[0056] Aluminum (Al) increases the resistivity of non-oriented electrical steel sheets manufactured with silicon, thereby reducing iron loss, and can form nitride-based inclusions (e.g., AlN) with nitrogen (N). Aluminum (Al) may be included in an amount of 0.1 wt% to 0.4 wt%. When the aluminum (Al) content is less than 0.1 wt%, fine nitride-based inclusions (e.g., AlN) may precipitate, which may have a negative effect on magnetism. On the other hand, when the aluminum (Al) content exceeds 0.4 wt%, problems may occur in the steelmaking / casting process.

[0057] Sulfur (S) may be a component that increases iron loss and inhibits grain growth by forming precipitates such as MnS and TiS. Therefore, it may be desirable to have a low sulfur content in the slab. Sulfur may be included in an amount greater than 0 wt% and less than or equal to 0.003 wt%. When sulfur is included in an amount greater than 0.003 wt%, precipitates such as MnS and TiS may be formed, increasing iron loss and inhibiting grain growth.

[0058] Carbon (C) is a component that increases iron loss by forming carbides such as TiC, so a lower carbon content within the slab may be desirable. Carbon may be included in an amount greater than 0 wt% and less than 0.003 wt%. If carbon is included in an amount greater than 0.003 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 0.003 wt%, the self-aging phenomenon may be suppressed.

[0059] Phosphorus (P) may be a grain boundary segregation element that develops the texture. Phosphorus may be included in an amount greater than 0 wt% and less than or equal to 0.1 wt%. If phosphorus is included in an amount greater than 0.1 wt%, grain growth may be suppressed due to the segregation effect, magnetic properties may be deteriorated, and cold rolling properties may be reduced.

[0060] Nitrogen (N) can form precipitates such as AlN and TiN, thereby increasing iron loss and inhibiting grain growth. Therefore, it may be desirable to have a low nitrogen content in the slab. Nitrogen may be included in an amount greater than 0 wt% and less than or equal to 0.003 wt%. If nitrogen is included in an amount greater than 0.003 wt%, precipitates such as AlN and TiN may be formed, thereby increasing iron loss and inhibiting grain growth.

[0061] Titanium (Ti) can inhibit grain growth by forming fine precipitates such as TiC, TiN, and TiS. As more titanium is added, the magnetic properties deteriorate, so it may be desirable to add as little titanium as possible. Titanium can be included in amounts greater than 0 wt% and less than or equal to 0.003 wt%. When titanium is included in amounts greater than 0.003 wt%, it can form fine precipitates such as TiC, TiN, and TiS, inhibiting grain growth and possibly resulting in deteriorated magnetic properties.

[0062] In one embodiment, the slab may comprise a total of greater than 0.0006 wt% and less than or equal to 0.0030 wt% of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y). Preferably, the slab may comprise a total of greater than or equal to 0.0007 wt% and less than or equal to 0.0030 wt% of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y). When the sum of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y) satisfies 0.0006 wt% to 0.0030 wt% (preferably 0.0007 wt% to 0.0030 wt%), the amount (or number) of sulfide inclusions having a diameter of 10 nm to 100 nm among the total sulfide inclusions is reduced, so that the iron loss of the manufactured non-oriented electrical steel sheet can be reduced and the magnetic flux density can be increased. For example, when the sum of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y) satisfies 0.0006 wt% to 0.0030 wt% (preferably 0.0007 wt% to 0.0030 wt%), the proportion of sulfide inclusions having a diameter of 10 nm to 100 nm among the total sulfide inclusions may be 15% or less, and the iron loss of the non-oriented electrical steel sheet manufactured through this may be reduced and the magnetic flux density may be increased.

[0063] When the sum of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y) is 0.0006 wt% or less, the content of rare earth elements is too small to exhibit the aforementioned effect. On the other hand, when the sum of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y) exceeds 0.0030 wt%, the aforementioned effect cannot be exhibited. Specifically, when the sum of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y) exceeds 0.0030 wt%, the amount (or number) of sulfide inclusions having a diameter of 10 nm to 100 nm among the total sulfide inclusions may increase, thereby increasing the iron loss of the manufactured non-oriented electrical steel sheet and decreasing the magnetic flux density. For example, when the sum of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y) exceeds 0.0030 wt%, the proportion of sulfide inclusions having a diameter of 10 nm to 100 nm among the total sulfide inclusions may exceed 15%, thereby increasing the iron loss of the manufactured non-oriented electrical steel sheet and decreasing the magnetic flux density. This will be described in more detail below.

[0064] In the hot rolling step (S100), the slab is reheated and then hot rolled to produce a hot-rolled sheet. For example, a steel sheet that has undergone the hot rolling step (S100) may be called a hot-rolled sheet.

[0065] First, the hot rolling step (S100) can reheat the slab. The slab reheating temperature can be 1100°C to 1250°C. If the slab reheating temperature is lower than 1100°C, the rolling load may increase during hot rolling (e.g., rough rolling and / or finish rolling), which may reduce the rollability. On the other hand, if the slab reheating temperature exceeds 1250°C, precipitates such as C, S, and N within the slab may be re-dissolved, forming fine precipitates during subsequent rolling and annealing steps, which may inhibit grain growth and deteriorate magnetic properties.

[0066] The hot rolling step (S100) can hot-roll the slab at a predetermined finishing rolling temperature (or rolling temperature). At this time, the finishing rolling temperature can be 800°C to 1000°C.

[0067] Additionally, the hot rolling step (S100) can cool and coil the hot-rolled steel plate to a predetermined coiling temperature (CT). At this time, the coiling temperature can be 600°C to 700°C.

[0068] The thickness of the hot-rolled sheet manufactured through the hot rolling step (S100) may be 1.6 mm to 2.7 mm. In this case, if the thickness of the hot-rolled sheet exceeds 2.7 mm, the cold rolling reduction ratio increases, which may result in a deteriorated texture.

[0069] A cold rolling step (S200) may be performed after the hot rolling step (S100). In the cold rolling step (S200), a hot-rolled hot-rolled sheet may be cold-rolled to produce a cold-rolled sheet. For example, a steel sheet that has undergone the cold rolling step (S200) may be referred to as a cold-rolled sheet.

[0070] The oxide layer formed on the surface of the hot-rolled sheet can be removed using a pickling solution before the cold rolling step (S200).

[0071] In the cold rolling step (S200), the hot-rolled sheet can be cold rolled to a thickness of 0.7 mm or less. For example, the thickness of the cold-rolled sheet manufactured through the cold rolling step (S200) may be 0.2 mm to 0.7 mm. At this time, in order to impart rollability, the sheet temperature may be increased to 150°C to 200°C to perform warm rolling. However, the present invention is not limited thereto. Cold rolling may also be performed at room temperature.

[0072] The reduction ratio in the cold rolling step (S200) may be 70% to 95%. Preferably, the reduction ratio in the cold rolling step (S200) may be 75% to 95%. More preferably, the reduction ratio in the cold rolling step (S200) may be 75% to 90%.

[0073] A cold rolling annealing step (S300) may be performed after the cold rolling step (S200). At this time, the cold rolling annealing step (S300) may be referred to as the final annealing step. In the cold rolling annealing step (S300), a cold-rolled cold-rolled sheet may be annealed.

[0074] In the cold rolling annealing step (S300), the cold-rolled cold-rolled sheet is heated to a cold rolling annealing temperature (e.g., holding temperature) at a heating rate (or heating rate) of 10°C / s or more, then annealed (e.g., held) at the cold rolling annealing temperature for 30 to 90 seconds, and then cooled at a cooling rate of 30°C / s or more. At this time, the cold rolling annealing temperature (e.g., held temperature) may be 900°C to 1100°C. When the 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 cold rolling annealing temperature is more than 1100°C, the grain size may become coarse, which may increase the eddy current loss.

[0075] In one embodiment, the average grain size after annealing may be from 50 μm to 100 μm.

[0076] The cold rolling annealing step (S300) can be performed under a mixed gas atmosphere to prevent surface oxidation and nitriding. For example, a mixed gas atmosphere of nitrogen and hydrogen can be used to further smooth the surface.

[0077] After the cold-rolled annealing step (S300), a coating layer can be formed on the cold-rolled annealed cold-rolled sheet. By forming the coating layer, the punchability can be improved and the insulation can be secured.

[0078] In one embodiment, a non-oriented electrical steel sheet can be manufactured through a hot rolling step (S100) to a cold rolling annealing step (S300).

[0079] A non-oriented electrical steel sheet according to one embodiment of the present invention may include silicon (Si), manganese (Mn), aluminum (Al), sulfur (S), rare earth elements, the remainder iron (Fe), and unavoidable impurities. In this case, the rare earth elements may include one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y).

[0080] Specifically, the non-oriented electrical steel sheet may contain, in wt%, silicon (Si): 1.0 wt% to 1.5 wt%, manganese (Mn): 0.1 wt% to 0.4 wt%, aluminum (Al): 0.1 wt% to 0.4 wt%, sulfur (S): more than 0 wt% and 0.003 wt% or less, rare earth elements total: more than 0.0006 wt% and 0.0030 wt% or less, the remainder iron (Fe) and unavoidable impurities. At this time, the rare earth elements may include one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y). Accordingly, the non-oriented electrical steel sheet may contain a total of more than 0.0006 wt% and less than 0.0030 wt% of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y). Preferably, the non-oriented electrical steel sheet may contain a total of more than 0.0007 wt% and less than 0.0030 wt% of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y).

[0081] In addition, the non-oriented electrical steel sheet may further include carbon (C): more than 0 wt% and less than 0.003 wt%, phosphorus (P): more than 0 wt% and less than 0.1 wt%, nitrogen (N): more than 0 wt% and less than 0.003 wt%, and titanium (Ti): more than 0 wt% and less than 0.003 wt%.

[0082] In one embodiment, the average grain size of the non-oriented electrical steel sheet may be 50 μm to 100 μm.

[0083] In one embodiment, the core loss of the non-oriented electrical steel sheet (e.g., W 15 / 50 The standard) may be 4.21 W / kg or less. Specifically, the iron loss of non-oriented electrical steel sheet (e.g., W 15 / 50 The standard) may be 3.7 W / kg or more and 4.21 W / kg or less. Preferably, the iron loss of the non-oriented electrical steel sheet (e.g., W 15 / 50The standard) may be 3.7 W / kg or more and less than 4.09 W / kg. More preferably, the iron loss of the non-oriented electrical steel sheet (e.g., W 15 / 50 The standard) may be 3.7 W / kg or more and 4.05 W / kg or less.

[0084] In one embodiment, the magnetic flux density of the non-oriented electrical steel sheet (e.g., B 50 The standard) can be 1.695 T or more. Specifically, the magnetic flux density of the non-oriented electrical steel sheet (e.g., B 50 The standard) can be 1.695T or more and 1.72T or less.

[0085] Inclusions formed by impurities can interfere with the magnetization process of non-oriented electrical steel sheets, which can increase iron loss and decrease magnetic flux density. Specifically, the movement of domain walls is essential during the magnetization process, and sulfide inclusions (e.g., MnS, TiS, etc.) formed by sulfur (S) contained in the slab (or non-oriented electrical steel sheet) can interfere with the movement of the domain walls, which can increase iron loss and decrease magnetic flux density. In this case, among the sulfide inclusions, sulfide inclusions having a diameter of 10 nm to 100 nm, which is similar to the thickness of the domain walls, can interfere with the movement of the domain walls the most. Additionally, among the sulfide inclusions having a diameter of 10 nm to 100 nm, the sulfide inclusions having a diameter of 10 nm to 50 nm can hinder the movement of the domain wall more than the sulfide inclusions having a diameter of 50 nm to 100 nm.

[0086] Therefore, when the amount (or number, ratio) of sulfide inclusions having a diameter of 10 nm to 100 nm among the sulfide inclusions is reduced, the iron loss of the non-oriented electrical steel sheet can be reduced and the magnetic flux density can be increased. In addition, when the amount (or number) of sulfide inclusions having a diameter of 10 nm to 50 nm among the sulfide inclusions having a diameter of 10 nm to 100 nm is reduced, the iron loss of the non-oriented electrical steel sheet can be reduced and the magnetic flux density can be increased.

[0087] In one embodiment, when a rare earth element is added to a slab (or a non-oriented electrical steel sheet), the rare earth element reacts with sulfur to form sulfide inclusions. When the rare earth element is added, the diameter of the formed sulfide inclusions may increase. For example, the amount (or number, ratio) of sulfide inclusions having a diameter greater than 100 nm may increase, and the amount (or number, ratio) of sulfide inclusions having a diameter of 10 nm to 100 nm may decrease. At this time, the rare earth element may include neodymium (Nd), praseodymium (Pr), and / or yttrium (Y).

[0088] In a non-oriented electrical steel sheet and a manufacturing method thereof according to one embodiment of the present invention, a rare earth element is added to a slab (or a non-oriented electrical steel sheet) to reduce the amount (or number, ratio) of sulfide inclusions having a diameter of 10 nm to 100 nm among sulfide inclusions, thereby improving the magnetic properties of the manufactured non-oriented electrical steel sheet.

[0089] Specifically, by adding one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y) to a slab (or non-oriented electrical steel sheet) in a total amount of more than 0.0006 wt% and less than 0.0030 wt% (preferably, more than 0.0007 wt% and less than 0.0030 wt%) so that neodymium (Nd), praseodymium (Pr), and / or yttrium (Y) react with sulfur (S) to form sulfide inclusions, the iron loss of the manufactured non-oriented electrical steel sheet can be reduced and the magnetic flux density can be increased by reducing the amount (or number, ratio) of sulfide inclusions having a diameter of 10 nm to 100 nm among the sulfide inclusions.

[0090] As described above, the slab (or non-oriented electrical steel sheet) may contain one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y) in a total amount of more than 0.0006 wt% and less than or equal to 0.0030 wt% (preferably, more than or equal to 0.0007 wt% and less than or equal to 0.0030 wt%). When the sum of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y) satisfies 0.0006 wt% to 0.0030 wt% (preferably 0.0007 wt% to 0.0030 wt%), the amount (or number) of sulfide inclusions having a diameter of 10 nm to 100 nm among the total sulfide inclusions is reduced, so that the iron loss of the manufactured non-oriented electrical steel sheet can be reduced and the magnetic flux density can be increased.

[0091] In one embodiment, the proportion of sulfide inclusions having a diameter of 10 nm to 100 nm among the total sulfide inclusions may be 15% or less. For example, when the number of the total sulfide inclusions is B and the number of sulfide inclusions having a diameter of 10 nm to 100 nm is A, the proportion of sulfide inclusions having a diameter of 10 nm to 100 nm among the total sulfide inclusions may satisfy the following relationship 1.

[0092] <Relationship 1>

[0093] A / B * 100 ≤ 15%

[0094] At this time, if the proportion of sulfide inclusions having a diameter of 10 nm to 100 nm among the total sulfide inclusions exceeds 15%, the amount (or number) of sulfide inclusions having a diameter of 10 nm to 100 nm that impede the movement of the domain wall may be too large, which may impede the movement of the domain wall, thereby increasing iron loss and decreasing magnetic flux density. For example, if the proportion of sulfide inclusions having a diameter of 10 nm to 100 nm among the total sulfide inclusions exceeds 15%, the non-oriented electrical steel sheet may have high iron loss and low magnetic flux density.

[0095] In one embodiment, the ratio of sulfide inclusions having a diameter of 10 nm to 50 nm among sulfide inclusions having a diameter of 10 nm to 100 nm is S 10~50 And, the ratio of sulfide inclusions having a diameter of 50 nm to 100 nm among sulfide inclusions having a diameter of 10 nm to 100 nm is S 50~100 If so, S 10~50 and S 50~100 can satisfy the following relationship 2.

[0096] <Relationship 2>

[0097] (S 10~50 ) 2 / (S 50~100 ) ≤ 20

[0098] At this time, S 10~50 and S 50~100 If the relation 2 is not satisfied, the amount (or number) of sulfide inclusions having a diameter of 10 nm to 50 nm among the sulfide inclusions having a diameter of 10 nm to 100 nm may be large, which may hinder the movement of the magnetic domain wall, thereby increasing the iron loss and decreasing the magnetic flux density. For example, S 10~50 and S 50~100 If the relationship 2 is not satisfied, the non-oriented electrical steel sheet may have high iron loss and low magnetic flux density.

[0099] Experimental example

[0100] 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.

[0101] Distinctive component (wt%) SiMnAl Rare earth element NdYPr Total Example 11.310.190.190.00060.00020.00020.0010 Example 21.310.200.220.00160.00010.00010.0018 Example 31.290.210.210.00020.00050.00010.0008 Example 41.290.210.190.00030. 00120.00010.0016Example 51.290.190.190.00020.00020.00100.0014Example 61.290.210.220.00020.00020.00200.0024Example 71.280.210.210.00070.00070.00020.0016Example 81.280.210.210. 00110.00090.00030.0023Example 91.320.200.200.00010.00100.00080.0019Example 101.290.190.220.00020.00120.00120.0026Example 111.300.190.220.00090.00010.00100.0020Example 121.310 .200.210.00130.00020.00140.0029Example 131.280.200.190.00080.00060.00090.0023Example 141.030.220.200.00070.00050.00060.0018Example 151.450.190.220.00070.00060.00060.0019

[0102] Distinctive component (wt%) CSPNTi Example 10.00170.00200.00640.00220.0019 Example 20.00160.00190.00950.00210.0023 Example 30.00210.00210.00980.00230.0024 Example 40.00220.002 20.00880.00180.0017Example 50.00190.00180.00770.00240.0017Example 60.00150.00190.00940.00170.0015Example 70.00210.00190.00700.00230.0021Example 80.00240. 00220.00840.00240.0020Example90.00150.00210.00770.00230.0018Example100.00190.00190.00630.00240.0021Example110.00250.00190.00950.00210.0018Example120. 00160.00190.00560.00180.0024Example 130.00220.00220.00970.00160.0024Example 140.00230.00190.00930.00190.0018Example 150.00240.00180.00880.00190.0021

[0103] Distinctive composition (wt%) SiMnAl Rare earth element NdYPr Total Comparative example 11.300.220.210.00020.00030.00010.0006 Comparative example 21.300.190.200.00300.00020.00020.0034 Comparative example 31.320.200.190.00020.00280.00020 .0032Comparative Example 41.280.200.210.00030.00020.00270.0032Comparative Example 50.950.180.200.00070.00070.00050.0019Comparative Example 61.550.190.200.00080.00050.00070.0020

[0104] Distinctive component (wt%) CSPNTiComparative example 10.00210.00210.00640.00180.0025Comparative example 20.00210.00220.00650.00190.0022Comparative example 30.00200.00200.00730.00200.0018Comparative example 40.00210.00180.00880.00160.0024Comparative example 50.00240.00220.00840.00180.0021Comparative example 60.00200.00190.00670.00150.0019

[0105] Hot rolling stage Slab reheating temperature (℃) 1220 Finish rolling temperature (℃) 940 Coiling temperature (℃) 680 Hot rolling thickness (mm) 2.3 Cold rolling stage Reduction ratio (%) 78.3 Cold rolling thickness (mm) 0.5 Cold rolling annealing stage Heating rate (℃ / s) 40 Annealing temperature (℃) 930 Holding time (s) 60 Cooling rate (℃ / s) 40

[0106] The ratio of sulfide inclusions of a specific diameter among all sulfide inclusions is shown in the value of equation 2. Magnetic properties are 10~50 nm (%), 50~100 nm (%), and 10~100 nm (%). Iron loss (W) 15 / 50 , W / kg) magnetic flux density (B 50 , T) Example 13.88.512.313.814.011.707 Example 23.36.39.618.0141.708 Example 33.48.912.310.563.991.71 Example 42.16.68.77.683.951.711 Example 53.9912.913.1041.711 Example 62.37.810.16.713.961.713 Example 73.88.612.413.543.971.706 Example 83.58.111.613.043.941.712 Example 93.57.911.413.603.961.71 Example 103.47.811.213.233.931.713 Example 113.66.910.517.893.971.709 Example 123.99.313.212.394.011.706 Example 133.36.19.418.993.941.712 Example 143.58.812.311.234.211.719 Example 153.68.812.411.853.81.695

[0107] The ratio of sulfide inclusions of a specific diameter among all sulfide inclusions is shown in the value of equation 2. Magnetic properties are 10~50 nm (%), 50~100 nm (%), and 10~100 nm (%). Iron loss (W) 15 / 50 , W / kg) magnetic flux density (B 50 , T) Comparative Example 110.11121.143.954.151.693 Comparative Example 28.711.219.933.964.11.694 Comparative Example 37.111.718.822.924.091.694 Comparative Example 46.610.817.423.184.091.693 Comparative Example 56.611.017.622.504.411.72 Comparative Example 66.711.718.420.853.811.692

[0108] Examples 1 to 15 and Comparative Examples 1 to 6 are samples manufactured using slabs composed of the components shown in Tables 1, 2, 3, and 4, the remainder iron (Fe), and unavoidable impurities, under the process conditions shown in Table 5. At this time, all samples were manufactured to the same size of 80 mm in width and 150 mm in length.

[0109] Examples 1 to 15 and Comparative Examples 1 to 6 were manufactured under the same process conditions, but with different component contents.

[0110] The number of sulfide inclusions was measured through SEM-EDS analysis. Specifically, observation specimens (15x15mm in size) were collected from the manufactured samples, and mirror-polished to less than 1㎛ were performed on the specimen surface (ND plane) and the center of the specimen (center of thickness), and then the analysis area was 160mm at the center of the thickness direction of the specimen. 2 Above, analysis was performed under the conditions of magnification: x100, dwell time: 0.1 second. In addition, after measuring more than 2000 fields based on a spherical diameter of 0.4㎛ per detecting pixel unit, 100 mm 2 The average number of inclusions per area was calculated.

[0111] The value of relation 2 is (S 10~50 ) 2 / (S 50~100 ) corresponds to the value of S 10~50 corresponds to the ratio of sulfide inclusions having a diameter of 10 nm to 50 nm among sulfide inclusions having a diameter of 10 nm to 100 nm, and S 50~100 corresponds to the ratio of sulfide inclusions having a diameter of 50 nm to 100 nm among sulfide inclusions having a diameter of 10 nm to 100 nm.

[0112] The magnetic properties were measured twice in the rolling direction and the direction perpendicular to the rolling direction using a Single Sheet Tester (SST) and the average value was obtained. At this time, W 15 / 50 refers to the iron loss when a magnetic flux density of 1.5 Tesla is induced at a frequency of 50 Hz, and B 50 It refers to the magnetic flux density induced when a magnetic field of 5000 A / m is applied.

[0113] Referring to Tables 6 and 7, it can be confirmed that in the case of Examples 1 to 15, the proportion of sulfide inclusions having a diameter of 10 nm to 100 nm among all sulfide inclusions is 15% or less. In addition, it can be confirmed that in the case of Examples 1 to 15, the value of Relationship 2 is 20 or less. Therefore, it can be confirmed that Examples 1 to 15 have low iron loss and high magnetic flux density.

[0114] On the other hand, Comparative Example 1 is a case where rare earth elements are added to a slab (or, non-oriented electrical steel sheet) at 0.0006 wt% or less, and it can be confirmed that Comparative Example 1 has a ratio of sulfide inclusions having a diameter of 10 nm to 100 nm among all sulfide inclusions exceeding 15%, and the value of Relationship 2 exceeds 20. In addition, it can be confirmed that Comparative Example 1 has a higher iron loss and / or lower magnetic flux density than the examples.

[0115] Comparative Example 2 is a case where a slab (or, non-oriented electrical steel sheet) contains rare earth elements in excess of 0.0030 wt%. It can be confirmed that Comparative Example 2 has a proportion of sulfide inclusions having a diameter of 10 nm to 100 nm among all sulfide inclusions exceeding 15%, and the value of Relationship 2 exceeds 20. In addition, it can be confirmed that Comparative Example 2 has a higher iron loss and / or lower magnetic flux density than the examples.

[0116] Comparative Example 3 is a case where a slab (or, non-oriented electrical steel sheet) contains rare earth elements in excess of 0.0030 wt%. It can be confirmed that Comparative Example 3 has a ratio of sulfide inclusions having a diameter of 10 nm to 100 nm among all sulfide inclusions exceeding 15%, and the value of Relationship 2 exceeds 20. In addition, it can be confirmed that Comparative Example 3 has a higher iron loss and / or lower magnetic flux density than the examples.

[0117] Comparative Example 4 is a case where a slab (or, non-oriented electrical steel sheet) contains rare earth elements in excess of 0.0030 wt%. It can be confirmed that Comparative Example 4 has a ratio of sulfide inclusions having a diameter of 10 nm to 100 nm among all sulfide inclusions exceeding 15%, and the value of Relationship 2 exceeds 20. In addition, it can be confirmed that Comparative Example 4 has a higher iron loss and / or lower magnetic flux density than the examples.

[0118] Comparative Examples 2 to 4 show that when rare earth elements are added to a slab (or non-oriented electrical steel sheet) in excess of 0.0030 wt%, the reduction effect of sulfide inclusions having a diameter of 10 nm to 100 nm is minimal. In addition, when the amount of rare earth elements added exceeds 0.0030 wt%, the manufacturing cost may increase, thereby reducing the economic feasibility of the manufacturing process.

[0119] Comparative Example 5 is a case where the slab (or non-oriented electrical steel sheet) contains less than 1.0 wt% of silicon (Si). It can be confirmed that Comparative Example 5 has a ratio of sulfide inclusions having a diameter of 10 nm to 100 nm among all sulfide inclusions exceeding 15%, and the value of Relationship 2 exceeds 20. In addition, it can be confirmed that Comparative Example 5 has a higher iron loss than the examples. Therefore, when the content of silicon (Si) contained in the slab (or non-oriented electrical steel sheet) is less than 1.0 wt%, even if rare earth elements are added in a total amount exceeding 0.0006 wt% and 0.0030 wt% or less, the effect of adding rare earth elements is minimal, and the manufactured non-oriented electrical steel sheet can have a high iron loss.

[0120] Comparative Example 6 is a case where the slab (or non-oriented electrical steel sheet) contains more than 1.5 wt% of silicon (Si). It can be confirmed that Comparative Example 6 has a ratio of sulfide inclusions having a diameter of 10 nm to 100 nm among all sulfide inclusions exceeding 15%, and the value of Relationship 2 exceeds 20. In addition, it can be confirmed that Comparative Example 6 has a lower magnetic flux density than the examples. Therefore, when the content of silicon (Si) contained in the slab (or non-oriented electrical steel sheet) exceeds 1.5 wt%, even if the rare earth elements are added in a total amount exceeding 0.0006 wt% and 0.0030 wt% or less, the effect of adding rare earth elements may be minimal, and the manufactured non-oriented electrical steel sheet may have a low magnetic flux density.

[0121] 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. A method for manufacturing non-oriented electrical steel sheet, A hot rolling step of manufacturing a hot-rolled sheet by hot-rolling a slab including, in wt%, silicon (Si): 1.0 wt% to 1.5 wt%, manganese (Mn): 0.1 wt% to 0.4 wt%, aluminum (Al): 0.1 wt% to 0.4 wt%, sulfur (S): more than 0 wt% and 0.003 wt% or less, a total of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y): more than 0.0006 wt% and 0.0030 wt% or less, the remainder iron (Fe) and unavoidable impurities; A cold rolling step for manufacturing a cold rolled sheet by cold rolling the hot rolled sheet; and A cold rolling annealing step of cold rolling the above cold rolled sheet; A method for manufacturing a non-oriented electrical steel sheet, comprising:

2. In paragraph 1, A method for manufacturing a non-oriented electrical steel sheet, wherein the ratio of sulfide inclusions having a diameter of 10 nm to 100 nm among all sulfide inclusions satisfies the following relationship 1. <Relationship 1> A / B * 100 ≤ 15% In the above relational expression 1, A is the number of sulfide inclusions having a diameter of 10 nm to 100 nm, and B is the total number of sulfide inclusions.

3. In paragraph 1, A method for manufacturing a non-oriented electrical steel sheet, wherein a ratio of sulfide inclusions having a diameter of 10 nm to 50 nm among sulfide inclusions having a diameter of 10 nm to 100 nm and a ratio of sulfide inclusions having a diameter of 50 nm to 100 nm among sulfide inclusions having a diameter of 10 nm to 100 nm satisfy the following relationship 2. <Relationship 2> (S 10~50 ) 2 / (S 50~100 ) ≤ 20 In the above relation 2, S 10~50 S corresponds to the ratio of sulfide inclusions having a diameter of 10 nm to 50 nm among sulfide inclusions having a diameter of 10 nm to 100 nm, and 50~100 corresponds to the ratio of sulfide inclusions having a diameter of 50 nm to 100 nm among sulfide inclusions having a diameter of 10 nm to 100 nm.

4. In paragraph 1, The above non-oriented electrical steel sheet has a magnetic flux density (B) of 1.695 T or more. 50 A method for manufacturing a non-oriented electrical steel sheet having a standard.

5. In paragraph 1, A method for manufacturing a non-oriented electrical steel sheet, wherein the average grain size of the non-oriented electrical steel sheet is 50 ㎛ to 100 ㎛.

6. In paragraph 1, A method for manufacturing a non-oriented electrical steel sheet, wherein in the hot rolling step, the slab is reheated to 1100°C to 1250°C, and the reheated slab is hot rolled at a finishing rolling temperature of 800°C to 1000°C.

7. In paragraph 1, A method for manufacturing a non-oriented electrical steel sheet, wherein in the cold-rolled annealing step, the cold-rolled sheet is heated to a temperature of 900°C to 1100°C at a heating rate of 10°C / s or more, maintained at a temperature of 900°C to 1100°C for a time of 30 s to 90 s, and then cooled at a cooling rate of 30°C / s or more.

8. In paragraph 1, A method for manufacturing a non-oriented electrical steel sheet, wherein the above slab contains at least one element selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y), in a total amount of 0.0007 wt% or more and 0.0030 wt% or less.

9. In paragraph 1, A method for manufacturing a non-oriented electrical steel sheet, wherein the above slab further contains carbon (C) in wt% greater than 0 wt% and 0.003 wt% or less, phosphorus (P) in wt% greater than 0 wt% and 0.1 wt% or less, nitrogen (N) in wt% greater than 0 wt% and 0.003 wt% or less, and titanium (Ti) in wt% greater than 0 wt% and 0.003 wt% or less.

10. As a non-oriented electrical steel sheet, A non-oriented electrical steel sheet comprising, in wt%, silicon (Si): 1.0 wt% to 1.5 wt%, manganese (Mn): 0.1 wt% to 0.4 wt%, aluminum (Al): 0.1 wt% to 0.4 wt%, sulfur (S): more than 0 wt% and 0.003 wt% or less, a total of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y): more than 0.0006 wt% and 0.0030 wt% or less, the remainder iron (Fe) and unavoidable impurities.

11. In paragraph 10, A non-oriented electrical steel sheet, wherein the proportion of sulfide inclusions having a diameter of 10 nm to 100 nm among all sulfide inclusions satisfies the following relationship 3. <Relationship 3> A / B * 100 ≤ 15% In the above relational expression 3, A is the number of sulfide inclusions having a diameter of 10 nm to 100 nm, and B is the total number of sulfide inclusions.

12. In paragraph 10, A non-oriented electrical steel sheet, wherein a ratio of sulfide inclusions having a diameter of 10 nm to 50 nm among sulfide inclusions having a diameter of 10 nm to 100 nm and a ratio of sulfide inclusions having a diameter of 50 nm to 100 nm among sulfide inclusions having a diameter of 10 nm to 100 nm satisfy the following relationship 4. <Relationship 4> (S 10~50 ) 2 / (S 50~100 ) ≤ 20 In the above relation 4, S 10~50 S corresponds to the ratio of sulfide inclusions having a diameter of 10 nm to 50 nm among sulfide inclusions having a diameter of 10 nm to 100 nm, and 50~100 corresponds to the ratio of sulfide inclusions having a diameter of 50 nm to 100 nm among sulfide inclusions having a diameter of 10 nm to 100 nm.

13. In paragraph 10, The above non-oriented electrical steel sheet has a magnetic flux density (B) of 1.695 T or more. 50 Non-oriented electrical steel sheet having a standard.

14. In paragraph 10, A non-oriented electrical steel sheet having an average grain size of 50 ㎛ to 100 ㎛.

15. In paragraph 10, The above slab is a non-oriented electrical steel sheet containing a total of 0.0007 wt% or more and 0.0030 wt% or less of one or more elements selected from the group consisting of neodymium (Nd), praseodymium (Pr), and yttrium (Y).

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