Non-oriented electrical steel sheet and manufacturing method therefor

Abstract

A method for manufacturing a non-oriented electrical steel sheet, according to one embodiment of the present invention, includes the steps of: (a) preparing steel that is a half-finished product including 2.5-2.8 wt% of silicon (Si), 1.45 wt% or more of nickel (Ni), 0.05 wt% or less of aluminum (Al), and the balance of iron (Fe) and other inevitable impurities; (b) hot rolling the sheet, thereby forming a hot-rolled steel sheet; (c) cold rolling the hot-rolled steel sheet, thereby forming a cold-rolled steel sheet; and (d) cold roll annealing the cold-rolled steel sheet, in which step (d) includes the steps of: (d-1) increasing the temperature from room temperature to a first temperature at which austenite phase is stable, and then maintaining same for a first set time; (d-2) lowering the temperature to a second temperature at which a two-phase region where austenite phase and ferrite phase coexist is stable, and then maintaining same for a second set time; and (d-3) lowering the temperature to room temperature, and the phase transformation heat treatment in the cold roll annealing step can improve the texture such that an orientation favorable to magnetism is developed, and can enhance magnetic properties.

Description

[TECHNICAL FIELD]

[0001] The present invention relates to a non-oriented steel sheet and a manufacturing method therefor and more particularly, to a non-oriented steel sheet in which phase transformation heat treatment in a cold roll annealing step improves a texture such that an orientation favorable to magnetism is developed and a manufacturing method therefor.[BACKGROUND ART]

[0002] A non-oriented electrical steel sheet is used as a material for an iron core of motors, generators, and small transformers and is mainly used to convert electrical energy into kinetic energy, change a voltage, or convert other energy.

[0003] Such a non-oriented electrical steel sheet is used as a key material of components of electric vehicles. Recently, as global environmental issues have increased interest in eco-friendly products, the demand thereof is growing even further.

[0004] A characteristic required for the non-oriented electrical steel sheet is a low iron loss and a high magnetic flux density. In the related art, in order to lower the iron loss of the electrical steel sheet, a method of increasing a specific resistance of steel or reducing a thickness of the material was used. If an added amount of silicon (Si), aluminum (Al), or manganese (Mn) in the steel is increased, the specific resistance of steel is increased and an iron loss is lowered to a predetermined range, but the magnetic flux density is reduced and a rollability is degraded, which makes it difficult to reduce the thickness.

[0005] The magnetic flux density of the electrical steel sheet is determined by a fraction of iron (Fe) atoms in the steel and the arrangement of grains of steel. Iron monoatomic <100> texture is easily magnetized by magnetic isotropy of iron atoms, and it is hard to magnetize the <110> texture and the <111> texture.

[0006] Accordingly, if the atomic arrangement in the steel is oriented such that a magnetization direction is parallel to the <100> axis, the steel has a high magnetic flux density even under a low magnetic field. In contrast, even when an axis favorable to magnetization is oriented or an axis which is difficult to be magnetized is not oriented, a high magnetic flux density may be achieved even under a low magnetic field.

[0007] In addition, in the related art, in order to manufacture a non-oriented electrical steel sheet having an excellent magnetic property, a method for controlling a texture by adjusting an alloying composition system or a heat treatment temperature condition has been mainly studied.

[0008] In Prior Art Document 1, a heat treatment method based on phase transformation from an austenite phase to a ferrite phase has been disclosed, but there is a problem in that secondary rolling for surface deformation and secondary heat treatment for removing a residual stress need to be followed.

[0009] In Prior Art Document 2, a heat treatment method in a ferrite single-phase region without performing phase transformation has been disclosed, but there is a problem in that a high temperature condition of 1200°C and a long heat treatment time of at least 12 hours are necessary so that it is difficult to be applied for mass production.

[0010] As described above, the improvement of the property by improvement of refined structure and the texture is insignificant only with the related art process and mere change of the constituent composition. Specifically, it is more difficult to achieve an obvious improvement effect of the texture which significantly affects the magnetic property only with an additive element or improvement of partial process condition. Accordingly, it is necessary to improve another control method and process to enhance a magnetic property.[Related Art Document][Patent Document]

[0011] Prior Art Document 1: Korean Unexamined Patent Application Publication No. 10-2009-0079056 Prior Art Document 2: Korean Registered Patent No. 10-2376026 [DISCLOSURE] [TECHNICAL PROBLEM]

[0012] The present invention has been devised to solve the above-described problem and an object of the present invention is to provide a non-oriented electrical steel sheet which improves texture and improves a magnetic property so as to develop an orientation favorable to magnetism by means of phase transformation heat treatment in a cold roll annealing step and a manufacturing method therefor.

[0013] Objects of the present invention are not limited to the above-mentioned objects, and other objects, which are not mentioned above, can be clearly understood by those skilled in the art from the following descriptions.[TECHNICAL SOLUTION]

[0014] According to an aspect of the present invention, a manufacturing method for a non-oriented electrical steel sheet includes the steps of: (a) preparing a steel material which is a half-finished product including 2.5 to 3.8 wt% of silicon (Si), 1.45 wt% or more of nickel (Ni), 0.05 wt% or less of aluminum (Al), and the balance of iron (Fe) and other inevitable impurities, (b) hot rolling the steel material, thereby forming a hot-rolled steel sheet, (c) cold rolling the hot-rolled steel sheet, thereby forming a cold-rolled steel sheet, and (d) cold roll annealing the cold-rolled steel sheet. The step (d) includes the steps of: (d-1) increasing the temperature from room temperature to a first temperature at which austenite phase is stable and then maintaining the same for a first set time, (d-2) lowering the temperature to a second temperature at which a two-phase region where the austenite phase and the ferrite phase coexist is stable, and then maintaining the same for a second set time; and (d-3) lowering the temperature to the room temperature.

[0015] In the two-phase region, a ratio {200} / {112} which is a ratio of a peak of a {200} texture and a peak of a {112} texture may be 1.3 or larger.

[0016] The second temperature may be 930 to 970°C.

[0017] The second set time may be five seconds or longer.

[0018] Between the step (b) and the step (c), the manufacturing method may further include a step of hot roll annealing the hot-rolled steel sheet.

[0019] The steel material may further include 0.005 wt% or less of carbon (C), 0.005 wt% or less of sulfur (S), 0.005 wt% or less of nitrogen (N), 0.005 wt% or less of titanium (Ti), and 0.015 wt% or less of phosphorus (P).

[0020] The steel material may satisfy the following Relation 1. Ni ≥ 2.52 Si − 5.3 ([Ni] and [Si] refer to wt% of Ni and Si, respectively.)

[0021] According to an aspect of the present invention, a non-oriented electrical steel sheet is manufactured by a method of hot rolling and cold rolling a steel material including 2.5 to 3.8 wt% of silicon (Si), 1.45 wt% or more of nickel (Ni), 0.05 wt% or less of aluminum (Al), and the balance of iron (Fe) and other inevitable impurities to form a cold-rolled steel sheet, cold roll annealing the cold-roll steel sheet to manufacture a finished product, and during the cold roll annealing, by increasing a temperature to a first temperature at which the austenite phase is stable at a room temperature and maintaining the same for a first set time, and then lowering the temperature to a second temperature at which a two-phase region where the austenite phase and the ferrite phase coexist is stable, and then maintaining the same for a second set time, and then lowering the temperature to room temperature.

[0022] In the two-phase region, a ratio {200} / {112} which is a ratio of a peak of a {200} texture and a peak of a {112} texture may be 1.3 or larger.

[0023] The second temperature may be 930 to 970°C.

[0024] The second set time may be five seconds or longer.

[0025] The steel material may satisfy the following Relation 1. Ni ≥ 2.52 Si − 5.3 ([Ni] and [Si] refer to wt% of Ni and Si, respectively.)

[0026] The steel material may further include 0.005 wt% or less of carbon (C), 0.005 wt% or less of sulfur (S), 0.005 wt% or less of nitrogen (N), 0.005 wt% or less of titanium (Ti), and 0.015 wt% or less of phosphorus (P).

[0027] A sum of {100} / ND fraction and {110} / ND fraction of the finished product may be 46.0% or higher.

[0028] {100} / ND fraction of the finished product may be 28.8% or higher and {112} / ND fraction may be 23.3% or lower.

[0029] A non-oriented electrical steel sheet according to one embodiment of the present invention includes 2.5 to 3.8 wt% of silicon (Si), 1.45 wt% or more of nickel (Ni), 0.05 wt% or less of aluminum (Al), and the balance of iron (Fe) and other inevitable impurities. The magnetic flux density B 50 may be 1.68 T or higher and the iron loss W 10 / 400 may be 11.88 W / kg or lower

[0030] Contents of silicon and nickel of the non-oriented electrical steel sheet according to the embodiment of the present invention may satisfy the following Relation 1. Ni ≥ 2.52 Si − 5.3 ([Ni] and [Si] refer to wt% of Ni and Si, respectively.)

[0031] In the non-oriented electrical steel sheet according to the embodiment of the present invention, a sum of {100} / ND fraction and {110} / ND fraction may be 46.0% or higher.

[0032] In the non-oriented electrical steel sheet according to the embodiment of the present invention, {100} / ND fraction may be 28.8% or higher and {112} / ND fraction may be 23.3% or lower.

[0033] The non-oriented electrical steel sheet according to the embodiment of the present invention may further include 0.005 wt% or less of carbon (C), 0.005 wt% or less of sulfur (S), 0.005 wt% or less of nitrogen (N), 0.005 wt% or less of titanium (Ti), and 0.015 wt% or less of phosphorus (P).[ADVANTAGEOUS EFFECTS]

[0034] A non-oriented electrical steel sheet according to one embodiment of the present invention and a manufacturing method thereof may improve the texture by means of phase transformation heat treatment in a cold roll annealing step to develop a {100} / ND orientation favorable to magnetism and enhance the magnetic property.[DESCRIPTION OF DRAWINGS]

[0035] FIG. 1 is a flowchart illustrating a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention. FIG. 2 is a flowchart specifically illustrating a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention. FIG. 3 is a view illustrating a cold roll annealing step in a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention. [BEST MODE]

[0036] Hereinafter, the present invention will be described more fully with reference to the accompanying drawings, in which embodiments of the invention are shown. However, the present invention can be realized in various different forms, and is not limited to the embodiments described herein.

[0037] It should be understood that a term "include" or "have" indicates that a feature, a number, a step, an operation, a component, a part or a combination thereof described in the specification is present, but does not exclude a possibility of presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof, in advance.

[0038] In order to clearly describe the present invention, detailed descriptions of parts which are unrelated to the description or well-known related technologies which may unnecessarily obscure the gist of the present invention will be omitted. Further, when reference numerals are denoted to components of each drawing in the present specification, throughout the specification, the same or like components are denoted by the same or like reference numerals.

[0039] Further, terms or words used in the specification and the claims should not be restrictively analyzed as a general or dictionary meaning and should be analyzed as a meaning and a concept which conform to the technical spirit of the present invention based on a principle that the inventor can appropriately define a concept of a term in order to describe his / her own invention by the most method.

[0040] Unless otherwise specified, the notation "A ~ B" with respect to numerical values A and B refers to A or more and B or less. In this notation, when a unit is attached only to the numerical value B, the corresponding unit is also applied to the numerical value A.

[0041] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.Non-oriented electrical steel sheet

[0042] A non-oriented electrical steel sheet according to one embodiment of the present invention includes 2.5 to 3.8 wt% of silicon (Si), 1.45 wt% or more of nickel (Ni), 0.05 wt% or less of aluminum (Al), and the balance of iron (Fe) and other inevitable impurities. To be more specific, a steel material having the above-mentioned contents of silicon (Si), nickel (Ni), and aluminum (Al) is hot-rolled, and then cold-rolled to form a cold-rolled steel sheet and the cold-rolled steel sheet is cold-rolling annealed to manufacture a non-oriented electrical steel sheet which is a finished product. Accordingly, hereinafter, it is understood that an alloying constituent included in a steel material which is a half-finished product is included in the cold-rolled steel sheet and the non-oriented electrical steel sheet which is a finished product in the same range.

[0043] According to the embodiment of the present invention, during the cold roll annealing, the non-oriented electric steel sheet is manufactured by increasing a temperature to a first temperature at which the austenite phase is stable at a room temperature and maintaining the same for a first set time, and then lowering the temperature to a second temperature at which a two-phase region where the austenite phase and the ferrite phase coexist is stable, and then maintaining the same for a second set time, and then lowering the temperature to room temperature.

[0044] As described above, the non-oriented electric steel sheet according to one embodiment of the present invention may improve the texture by means of the phase transformation heat treatment in the cold roll annealing such that an orientation favorable to magnetism is developed and enhance the mechanical property and the magnetic property.

[0045] That is, in the cold roll annealing step, the phase transformation heat treatment may be performed in the order of a ferrite phase (α), an austenite phase (γ), and a ferrite phase (α). Specifically, when the phase transformation is performed from the austenite phase to the ferrite phase, core generation may be induced in a temperature region where {100} / ND orientation favorable to magnetism is most developed and be grown to improve the texture.

[0046] According to the embodiment of the present invention, the steel material may satisfy an alloying constituent range of the following relation 1. Ni ≥ 2.52 Si − 5.3 ([Ni] and [Si] refer to wt% of Ni and Si, respectively.)

[0047] At this time, as described above, the cold roll annealing step is performed based on the phase transformation heat treatment to the ferrite phase (α), the austenite phase (γ), and the ferrite phase (α) and when the phase transformation is performed from the austenite phase (y) to the a ferrite phase (α), preferentially formed orientations are different formed according to the temperature condition. Using this characteristic, the effect of improving the texture is maximized. At this time, since the phase transformation region disappears as the added amount of silicon which is a ferrite phase (α)-stabilizing element is increased, in order to enable the phase transformation heat treatment, nickel (Ni) which is an austenite phase (y)-stabilizing element is added. As the silicon (Si) content is increased, it is necessary to gradually increase an added amount of nickel (Ni).

[0048] Accordingly, according to the present invention, in the above-described [Relation 1], a minimum added amount is derived by the relationship with the content of silicon (Si) and to be more specific, in the range of silicon (Si) from 2.5 to 3.8wt%, a minimum added amount of nickel (Ni) is derived by [Relation 1]. According to the present invention, nickel (Ni) needs to be included so as to satisfy [Relation 1] to ensure the austenite phase (y) region under the temperature condition of 1100°.

[0049] In the meantime, the steel material may further include 0.005 wt% or less of carbon (C), 0.005 wt% or less of sulfur (S), 0.005 wt% or less of nitrogen (N), 0.005 wt% or less of titanium (Ti), and 0.015 wt% or less of phosphorus (P).

[0050] In the two-phase region, a ratio {200} / {112} which is a ratio of a peak of a {200} texture and a peak of a {112} texture may be 1.3 or larger. Here, a two-phase region may refer to a region where an austenite phase and a ferrite phase coexist. As {200} / {112} is larger, more improved magnetic property may be achieved.

[0051] According to the exemplary embodiment of the present invention, a second temperature at which a two-phase region is stable to allow a ratio {200} / {112} which is a ratio of a peak of a {200} texture and a peak of a {112} texture to be 1.3 or larger may be 930 to 970°C and a second set time may be 5 seconds or longer. A detailed manufacturing method of a non-oriented electrical steel sheet according to the present invention, other than the second temperature and the second set time, will be described below.

[0052] Further, a sum of {100} / ND fraction and {110} / ND fraction of the finished product may be 46% or larger and {100} / ND fraction of the finished product may be 28.8% or higher and {112} / ND fraction of the finished product may be 23.3% or lower.

[0053] By doing this, according to the embodiment of the present invention, the texture is improved to provide a non-oriented electrical steel sheet having excellent magnetic property having a high magnetic flux density B 50 and a low iron loss W 10 / 400 . To be more specific, the magnetic flux density B 50 may be 1.68 T or higher and the iron loss W 10 / 400 may be 11.88 W / kg or lower.

[0054] Further, the non-oriented electrical steel sheet manufactured with the above-described alloying composition and the manufacturing method may have a yield strength YS of 250 MPa or higher and a tensile strength TS of 400 MPa or higher.

[0055] Hereinafter, a component and a component range of steel will be described.[Silicon (Si)]

[0056] Silicon (Si) is a component which increases specific resistance to lower an eddy current loss. Further, silicon is an element which improves the yield strength of steel and stabilizes ferrite and residual austenite at a room temperature. If the silicon content is small, the iron loss improvement effect may be insufficient. Further, if the content is excessive, an alloying element constituent is increased to reduce the magnetic flux density. To be more specific, if silicon is excessively added, brittleness is increased, which makes it difficult to perform cold rolling, which degrades the productivity. Accordingly, an appropriate amount of silicon needs to be added and the steel material according to the embodiment of the present invention may include 2.5 wt% or more and 3.8 wt% or less of silicon.[Nickel (Ni)]

[0057] Nickel (Ni) is an element which stabilizes the austenite phase and partially increases a specific resistance. In order to improve the iron loss, if 1.5 wt% or more of silicon (Si) is added to the steel material, only ferrite single-phase region may exist. Accordingly, nickel may be added to ensure the austenite phase region at a high temperature. The steel material according to one embodiment of the present invention may include 1.45 wt% or more of nickel.

[0058] Further, in the present invention, an added amount of nickel (Ni) may be adjusted according to the silicon (Si) content so as to satisfy the above-described [Relation 1].[Aluminum (Al)]

[0059] Aluminum (Al) is an element which increases a specific resistance to lower an eddy current loss, together with Si. Aluminum reacts with nitrogen to derive AlN precipitation. Accordingly, if a content of aluminum is excessive, the cold rollability is degraded and the magnetic flux density is reduced to deteriorate the magnetic property.

[0060] Further, aluminum is an element which expands a ferrite phase region so that aluminum reduces a phase transformation region and forms a secondary phase, such as AlN to hinder the magnetic property. The steel material according to one embodiment of the present invention may include 0.05 wt% or less of aluminum.[Carbon (C)]

[0061] Carbon (C) is coupled to Ti or Nb to form carbide, such as TiC and NbC and increases an iron loss, to deteriorate the magnetism. Accordingly, a lower content of carbon is desirable. If the carbon content is excessive, it may serve as an element which increases the iron loss due to magnetic aging. To be more specific, if a content of carbon exceeds 0.005 wt% of a total weight, it may cause magnetic aging, to deteriorate the magnetic property. Accordingly, the steel material according to the embodiment of the present invention may include 0.005 wt% or less of carbon.[Sulfur (S)]

[0062] Sulfur (S) is an impurity element of the steel and may hinder ductility and weldability of steel. Sulfur forms precipitate, such as MnS or CuS which is harmful to the magnetic property, to increase the iron loss and suppress grain growth, so that it is desirable to add a small amount. The steel material according to one embodiment of the present invention may include 0.005 wt% or less of sulfur.[Nitrogen (N)]

[0063] Nitrogen (N) is an element which contributes to strength and corrosion resistance of steel. Specifically, nitrogen is an element which stabilizes austenite to improve toughness together with carbon and specifically, is an element advantageous to improve the strength by enhancing solid solution, together with carbon.

[0064] However, nitrogen is strongly coupled to Al, Ti, or Nb to form precipitate, such as AlN, TiN, or NbN to increase the iron loss and suppress the grain growth, so that it is desirable to add a small amount. The steel material according to one embodiment of the present invention may include 0.005 wt% or less of nitrogen.[Titanium (Ti)]

[0065] Titanium (Ti) is coupled to C and N to form minute precipitate, such as TiC or TiN and suppress grain growth. Titanium may reduce nitrogen in the steel. However, if the content of titanium is excessive, the texture is deteriorated due to the increased carbide and nitride, to deteriorate the magnetic property. As titanium is added, the magnetic property deteriorates so that it is desirable to add a small amount.

[0066] Accordingly, the steel material according to the embodiment of the present invention may include 0.005 wt% or less of titanium.[Phosphorus (P)]

[0067] Phosphorus (P) is an impurity element in the steel and may generate cracks during the casting and deteriorate the weldability. If the content of phosphorus is excessive, the castability is deteriorated and the brittleness of steel is highly likely to be caused, and a possibility of dent defect may also be increased. Accordingly, it is desirable to add a small amount of phosphorus. The steel material according to one embodiment of the present invention may include 0.015 wt% or less of phosphorus.

[0068] In the meantime, in addition to the above-described elements, if necessary, austenite phase-stabilizing elements, such as Mn, Co, or Cr may be added to stabilize the austenite phase.

[0069] A balance other than the above-described components of steel may include Fe and inevitable impurities. The inevitable impurities are impurities mixed during a steelmaking step and a manufacturing process of an electrical steel sheet and are widely known in the art so that a detailed description thereof will be omitted. In the embodiment of the present invention, the addition of an element other than the above-described alloying constituents is not excluded, but various elements may be included without departing from the technical spirit of the present invention. If an additional element is further included, the balance Fe is replaced.Manufacturing method for non-oriented electrical steel sheet

[0070] Hereinafter, the manufacturing method for a non-oriented electrical steel sheet according to one embodiment of the present invention will be described with reference to FIG. 1.

[0071] Referring to FIGS. 1 and 2, the manufacturing method for a non-oriented electrical steel sheet according to one embodiment of the present invention includes the steps of: (a) preparing a steel material which is a half-finished product including 2.5 to 3.8 wt% of silicon (Si), 1.45 wt% or more of nickel (Ni), 0.05 wt% or less of aluminum (Al), and the balance of iron (Fe) and other inevitable impurities, (b) hot rolling the steel material, thereby forming a hot-rolled steel sheet, (c) cold rolling the hot-rolled steel sheet, thereby forming a cold-rolled steel sheet, and (d) cold roll annealing the cold-rolled steel sheet.

[0072] Further, referring to FIGS. 2 and 3, in the manufacturing method for a non-oriented electrical steel sheet according to one embodiment of the present invention, the step (d) of cold roll annealing the cold-rolled steel sheet includes the steps of: (d-1) increasing the temperature from the room temperature to a first temperature T1 at which an austenite phase is stable and then maintaining the same for a first set time t1, (d-2) lowering the temperature to a second temperature T2 at which a two-phase region where the austenite phase and the ferrite phase coexist is stable, and then maintaining the same for a second set time t2, and (d-3) lowering the temperature to the room temperature.

[0073] However, the embodiment is not necessarily limited thereto and the manufacturing method for a non-oriented electrical steel sheet may further include a hot rolling annealing step and a coating step, which will be described below. Hereinafter, individual steps of the manufacturing method for a non-oriented electrical steel sheet will be described in detail.

[0074] First, in the step (a) of preparing a steel material which is a half-finished product, a steel material including 2.5 to 3.8 wt% of silicon (Si), 1.45 wt% or more of nickel (Ni), 0.05 wt% or less of aluminum (Al), and the balance of iron (Fe) and other inevitable impurities is manufactured. The half-finished product may be a slab, but is not necessarily limited thereto. Further, the slab may be manufactured by a known process in the art, such as an iron making process, a steelmaking process or a continuous casting process.

[0075] The steel material may further include 0.005 wt% or less of carbon (C), 0.005 wt% or less of sulfur (S), 0.005 wt% or less of nitrogen (N), 0.005 wt% or less of titanium (Ti), and 0.015 wt% or less of phosphorus (P).

[0076] Further, nickel (Ni) may be added to the steel material according to the content of silicon (Si). In order to reduce the iron loss, in the non-oriented electrical steel sheet, silicon is added to the steel material. If an added amount of silicon is 1.7 wt% or more, the austenite region disappears and only the ferrite single-phase region may exist. Accordingly, in order to ensure the austenite phase at the high temperature, a predetermined amount of nickel may be added. A content of nickel according to a content of silicon may satisfy the following Relation 1. Ni ≥ 2.52 Si − 5.3 ([Ni] and [Si] refer to wt% of Ni and Si, respectively.)

[0077] Here, [Si] applied to Relations 1 may be 2.5 wt% or more and 3.8 wt% or less. For example, a silicon (Si) content of the steel material is 2.5 wt%, a content of nickel (Ni) may be included in the range of 1.45 wt% or more. If a silicon (Si) content is 2.68 wt%, a content of nickel (Ni) may be included so as to satisfy [Relation 1] in the range of 1.45 wt% or more.

[0078] According to the embodiment of the present invention, as the austenite phase-stabilizing element, a nickel (Ni) content may be adjusted. However, the embodiment is not limited thereto and another austenite phase-stabilizing element, such as Mn, Co, or Cr is further used or replaces nickel (Ni) to achieve the corresponding effect.

[0079] Next, the step (b) of hot rolling the steel material, thereby forming a hot-rolled steel sheet is a step of hot rolling the half-finished product prepared in the step (a) to form a hot-rolled steel sheet. The hot rolling may include reheating, rough rolling, finishing rolling, cooling, and coiling processes.

[0080] First, in the reheating process, the half-finished product may be reheated for the subsequent process. The half-finished product may be reheated under the condition of 1110°C or higher and 1150°C or lower of a slab reheating temperature (SRT). If SRT is lower than 1110°C, during the hot rolling, a deformation resistance is increased and the rolling load is increased to deteriorate the rollability. If SRT exceeds 1150°C, precipitates in the slab, such as C, S, or N, are re-dissolved to generate minute precipitates in the subsequent rolling and annealing process, which may suppress the grain growth and deteriorate the magnetism. Accordingly, in the present invention, the half-finished product may be reheated at the temperature of 1110°C or higher and 1150°C or lower.

[0081] Next, during the rough rolling process, the half-finished product may be created as a rolled material with appropriate shape, thickness, and width and during the finishing rolling process, the half-finished product may be adjusted to have predetermined thickness and width and be rolled to have a satisfactory surface and shape at a correct finishing temperature.

[0082] At this time, finishing delivery temperature (FDT) may be 800°C or higher and 900°C or lower. If FDT is lower than 800°C, rolling is generated at the two-phase region, which results in a non-uniform structure and significant deterioration of impact toughness. Further, if FDT exceeds 900°C, the ductility and the toughness may be excellent, but the strength may be sharply lowered. Accordingly, FDT is desirably 800°C or higher and 900°C or lower.

[0083] Further, a coiling temperature (CT) may be 500°C or higher and 700°C or lower. If the CT is lower than 500°C, a size of the grain is too small so that the grain may not sufficiently grow even after annealing and if the CT exceeds 700°C, minute precipitates are increased to degrade the magnetic property. Accordingly, CT is desirably 500°C or higher and 700°C or lower.

[0084] After the step (b), a thickness of the hot-rolled steel sheet is desirably 2.6 mm or smaller. The larger the thickness of the hot-rolled steel sheet, the higher the cold rolling thickness reduction rate so that the texture may be deteriorated. Accordingly, the thickness of the hot-rolled steel sheet is desirably 2.6 mm or smaller.

[0085] However, if the thickness of the hot-rolled steel sheet is excessively thin, a thickness obtained after the cold rolling is not sufficient, which may cause a shape defect when it is applied to the product. Accordingly, the thickness of the hot-rolled steel sheet may be more desirably 1.6 mm or larger and 2.6 mm or smaller.

[0086] A hot rolling annealing step may be further performed between the steps (b) and (c). In the hot rolling annealing step, the hot-rolled steel sheet may be thermally treated for 30 to 180 seconds at the temperature of 940°C or higher and 1110°C or lower. In the heat treatment temperature range, the minute structure of the hot-rolled steel sheet may be uniformly formed to be 50 to 200 mm. If the annealing temperature is too low, the elongated cast structure remaining after the hot rolling remains to cause minute structure irregularity and form small grains, thereby deteriorating the cold rollability. In contrast, if the annealing temperature is too high, unbalanced texture of the finished product may be caused.

[0087] Accordingly, the hot roll annealing step may be performed at a temperature of 940°C or higher and 1110°C or lower for 30 to 180 seconds. However, the hot roll annealing step may be optionally performed if necessary so that after the hot rolling step, the cold rolling step may be immediately performed without performing the hot roll annealing step.

[0088] After the hot roll annealing step, cooling may be performed and at this time, the cooling rate may be 20°C / second or more.

[0089] Further, after the step (b), an acid pickling step may be performed. The acid pickling step may be a step of removing an oxide scale layer formed on a surface of the hot-rolled steel sheet using an acid-pickling agent and more particularly, may be performed before the step (c).

[0090] Next, the step (c) of cold rolling the hot-rolled steel sheet, thereby forming a cold-rolled steel sheet may be performed. The step (c) of cold rolling the hot-rolled steel sheet, thereby forming a cold-rolled steel sheet may be a process of rolling the cooled and coiled hot-rolled steel sheet below a recrystallization temperature to further reduce the thickness of the steel sheet. The cold rolling may be a process of warm rolling the steel sheet at a thickness reduction rate of 50 to 90%, after increasing a temperature of the steel sheet to 75°C or higher and 200°C or lower to assign the rollability to the pickled hot-rolled steel sheet. A thickness of the cold-rolled steel sheet formed as described above may be 0.1 mm or larger and 0.5 mm or smaller.

[0091] After the step (c), the step (d) of cold roll annealing the cold-rolled steel sheet may be performed. The cold roll annealing may be a process of exposing and maintaining the steel material at a recrystallization temperature or higher and then cooling same to soften a material of the steel material which is hardened during the cold rolling.

[0092] In the manufacturing method for an electrical steel sheet according to the embodiment of the present invention, the step (d) of cold roll annealing the cold-rolled steel sheet includes the steps of (d-1) increasing the temperature from room temperature to a first temperature T1 at which austenite phase is stable and then maintaining the same for a first set time t1, (d-2) lowering the temperature to a second temperature T2 at which a two-phase region where austenite phase and ferrite phase coexist is stable, and then maintaining the same for a second set time t2, and (d-3) lowering the temperature to room temperature.

[0093] Hereinafter, the steps (d-1), (d-2), and (d-3) will be described in detail.

[0094] First, in the step (d-1), the temperature is increased from the room temperature to a first temperature T1 at which an austenite phase is stable and then is maintained for a first set time t1. Here, the first temperature T1 may refer to a temperature at which austenite single-phase region is stable. The first temperature T1 may be desirably 1000 to 1200°C, but is not necessarily limited thereto and may include all the temperatures at which the austenite single-phase region is stable. Further, the first set time t1 maybe 20 to 50 seconds.

[0095] Next, the step (d-2) may be a step of lowering the temperature to a second temperature T2 at which a two-phase region where the austenite phase and the ferrite phase coexist is stable, and then maintaining the same for a second set time t2. That is, the second temperature T2 may refer to a temperature at which a two-phase region of the austenite phase and the ferrite phase are stably maintained, and in this case, a ratio {200} / {112} which is a ratio of a peak of {200} texture and a peak of {112} texture may be 1.3 or larger.

[0096] In the step (d-2), the second temperature T2 may be 930°C or higher and 970°C or lower to smoothly generate a core of the ferrite phase. If the second temperature T2 is lower than 930°C, a grain size is minute so that a hysteresis loss may be increased and if the second temperature T2 exceeds 970°C, the grain size is coarse so that the eddy current loss may be increased. The second temperature T2 may be desirably 935°C or higher and 970°C or lower.

[0097] Further, the second set time t2 may be 5 seconds or longer and desirably, 5 to 45 seconds.

[0098] Next, the step (d-3) of lowering the temperature to the room temperature may be performed.

[0099] Further, additionally, the coating of the cold-rolled steel sheet may be performed to ensure the punching property and the insulating property and may form an insulating film on a surface of the cold-rolled steel sheet which is finally annealed.

[0100] The manufacturing method of a non-oriented electrical steel sheet according to the embodiment of the present invention designs to an alloying composition to sequentially transform the phases to a ferrite phase, an austenite phase, and a ferrite phase during the cold roll annealing, lowering the temperature to a temperature at which two-phase region where the austenite phase and the ferrite phase coexist is stable and then maintaining same, thereby improving the texture to develop an orientation favorable to magnetism and improving the magnetic property and the mechanical property.

[0101] That is, the improvement effect of the texture may be maximized to develop {100} / ND orientation using a characteristic that an orientation preferentially formed at each temperature region varies when the phase transformation from the austenite phase to the ferrite phase is performed.

[0102] In the non-oriented electrical steel sheet according to the embodiment of the present invention manufactured by the above-described manufacturing method, a sum of {100} / ND fraction and {110} / ND fraction may be 46.0% or larger, {100} / ND fraction may be 28.8% or higher, and {112} / ND fraction may be 23.3% or lower. Here, ND is an abbreviation of normal direction and may refer to a direction perpendicular to a plane including a rolling direction, that is, a direction perpendicular to a surface of the plate.

[0103] Further, the mechanical property of the non-oriented electrical steel sheet which is a final product thereby may have a yield strength (YS) of 250 MPa or higher and a tensile strength (TS) of 400 MPa or higher.

[0104] Further, a product with an improved magnetic property as compared with a product manufactured without going through a process of maintaining the temperature for the preset time in the two-phase region during the cold roll annealing may be obtained. At this time, the magnetic property refers to an iron loss (W 10 / 400 ) and a magnetic flux density B 50 and more particularly, W 10 / 400 refers to an iron loss at 400 Hz and 1.0 T and B 50 refers to a magnitude of the magnetic flux density induced when a magnetic field of 5000 A / m is applied.Comparative Example and Experimental Example

[0105] Hereinafter, a configuration and an operation of the present invention will be described in more detail with reference to preferred Comparative Examples and Experimental Examples of the present invention. However, these are just illustrative for better understanding of the present invention so that the present invention is not limited thereby.

[0106] Table 1 represents a primary alloying element composition of Comparative Examples and Experimental Examples and Table 2 represents a result obtained by performing In-situ XRD analysis on F / H samples having a composition proposed in Table 1 under the processing conditions of Table 2. The processing conditions which are not presented in Table 2 are controlled to satisfy the above-described manufacturing method of a non-oriented electrical steel sheet according to the embodiment of the present invention and to be the same in all Comparative Examples and Experimental Examples. [Table 1]ClassificationAdditive element (wt.%)Whether to satisfy Relation 1Impurity element (ppm)SiAlNiCSNTiPA02.52-1.88O3028261875A12.89-1.51X2231152388A22.89-2.45O1825211665A33.01-2.69O3228162775A43.07-1.6X2119111778A53.110.532.98O1218161968A63.15-2.9O2524182186A73.210.9-X1921141577A83.25--X1420122081A93.32-3.15O2516211991A103.55-3.7O2019161585 [Table 2] Classificati onCompositi onStep (d-1)Step (d-2)Peak ratioTextureMagnetic propertyFirst temperatur e(°C)First set time (second)Second temperatur e(°C)Second set time (second){200} / { 112}{100} / / N D fraction (%){110} / / N D fraction (%){112} / / N D fraction (%)B 50 (T)W 10 / 400 (W / kg)Comp. Ex. 1A996545---0.30.083.61.5813.58Experi. Ex. 1A0110045935451.5932.317.220.51.7111.79Experi. Ex. 2A011002093571.5931.016.822.31.7011.88Comp. Ex. 2A0110045550450.778.16.441.91.6813.21Comp. Ex. 3A1100045--0.727.65.538.61.6713.14Experi. Ex. 3A2112540950451.4730.218.119.61.7011.71Comp. Ex. 4A2112540550450.779.17.837.21.6712.95Experi. Ex. 4A3110045950451.4530.815.421.51.6911.67Comp. Ex. 5A3110045550450.758.87.836.71.6712.87Comp. Ex. 6A4100045--0.656.15.542.21.6713.02Comp. Ex. 7A5100045--0.666.66.340.31.6712.58Experi. Ex. 5A6110045960451.4129.416.623.31.6911.45Comp. Ex. 8A6110045550450.747.59.136.61.6712.32Comp. Ex. 9A7100045--0.735.57.040.11.6712.51Comp. Ex. 10A8115045--0.756.27.542.21.6813.51Experi. Ex. 6A9115040965451.3728.818.817.71.6811.34Comp. Ex. 11A9115040550450.738.25.639.01.6612.32Experi. Ex. 7A10115045970451.3529.117.418.01.6811.15Comp. Ex. 12A10115045550450.726.77.239.71.6512.25Comp. Ex. 13A10115045920450.757.27.338.41.6712.58Comp. Ex. 14A10115045980450.739.07.638.61.6612.47Comp. Ex. 15A1011504593530.768.77.136.91.6712.11

[0107] First, referring to Table 1, Comparative Examples 3, 6, 9, and 10 having allying compositions A1, A4, A7, and A8 did not satisfy Relation 1 which represents a minimum added amount of nickel content according to a content of silicon according to the embodiment of the present invention. Further, Comparative Example 7 having an alloying composition A5 satisfied Relation 1, but an added amount of aluminum (Al) exceeded 0.05 wt%. As a result, it is confirmed that in Comparative Examples 3, 6, 7, 9, and 10, phase transformation did not occur and as compared with Experimental Examples, {100} / ND favorable to magnetism was formed less and {112} / ND unfavorable to magnetism was formed more.

[0108] Next, referring to Table 2, in Comparative Example 1, the step (d-2) of lowering the temperature to a second temperature at which a two-phase region where the austenite phase and the ferrite phase coexist is stable, and then maintaining the same for a second set time was not performed. Specifically, in Comparative Example 1, a texture and a magnetic property were confirmed under a condition in which an F / H sample of a constituent composition A9 was heated from a room temperature to 965°C and was maintained for 45 seconds, and then the temperature was lowered. As a result, as the texture property, 0.3% of {100} / ND favorable to magnetism and 83.6% of {112} / ND unfavorable to magnetism were formed. Further, it is understood that the magnetic properties B 50 = 1.58 T and W 10 / 400 = 13.58 W / kg, which were inferior to those of Experimental Example, were obtained.

[0109] Comparative Example 2 was out of the range of the second temperature according to the present invention. Specifically, Comparative Example 2 showed the texture and the magnetic property under the condition in which an F / H sample of a composition A0 was heated to 1100°C at which the austenite phase is stable from the room temperature and then was maintained for 45 seconds, lowered the temperature to 550°C at which the ferrite phase is stable, and then was maintained for 45 seconds again, and then was cooled down to the room temperature. Under the corresponding condition, {200} / {112} was 0.77 which was lower than 1.3 and 8.1% of {100} / ND favorable to magnetism was formed and 41.9% of {112} / ND unfavorable to magnetism was formed. Consequently, the magnetic properties, that is, B 50 = 1.68 T and W 10 / 400 = 13.21 W / kg, which were inferior to Experimental Example, were obtained.

[0110] Comparative Example 4 was out of the range of the second temperature according to the present invention. Specifically, Comparative Example 4 showed the texture and the magnetic property under the condition in which an F / H sample of a composition A2 was heated to 1125°C at which the austenite phase is stable from the room temperature and then was maintained for 40 seconds, lowered the temperature to 550°C at which the ferrite phase is stable, and then was maintained for 45 seconds again, and then was cooled down to the room temperature. Under the corresponding condition, {200} / {112} was 0.77 which was lower than 1.3 and 9.1% of {100} / ND favorable to magnetism was formed and 37.2% of {112} / ND unfavorable to magnetism was formed. Consequently, the magnetic properties, that is, B 50 = 1.67 T and W 10 / 400 = 12.95 W / kg, which were inferior to Experimental Example, were obtained.

[0111] Comparative Example 5 was out of the range of the second temperature according to the present invention. Specifically, Comparative Example 5 showed the texture and the magnetic property under the condition in which an F / H sample of a composition A3 was heated to 1100°C at which the austenite phase is stable from the room temperature and then was maintained for 45 seconds, lowered the temperature to 550°C at which the ferrite phase is stable, and then was maintained for 45 seconds again, and then was cooled down to the room temperature. Under the corresponding condition, {200} / {112} was 0.75, which was lower than 1.3 and 8.8% of {100} / ND favorable to magnetism was formed and 36.7% of {112} / ND unfavorable to magnetism was formed. Consequently, the magnetic properties, that is, B 50 = 1.67 T and W 10 / 400 = 12.87 W / kg, which were inferior to Experimental Example, were obtained.

[0112] Comparative Example 8 was out of the range of the second temperature according to the present invention. Specifically, Comparative Example 8 showed the texture and the magnetic property under the condition in which an F / H sample of a composition A6 was heated to 1100°C at which the austenite phase is stable from the room temperature and then was maintained for 45 seconds, lowered the temperature to 550°C at which the ferrite phase is stable, and then was maintained for 45 seconds again, and then was cooled down to the room temperature. Under the corresponding condition, {200} / {112} was 0.74 which was lower than 1.3 and 7.5% of {100} / ND favorable to magnetism was formed and 36.6% of {112} / ND unfavorable to magnetism was formed. Consequently, the magnetic properties, that is, B 50 = 1.67 T and W 10 / 400 = 12.32 W / kg which were inferior to Experimental Example, were obtained.

[0113] Comparative Example 11 was out of the range of the second temperature according to the present invention. Specifically, Comparative Example 11 showed the texture and the magnetic property under the condition in which an F / H sample of a composition A9 was heated to 1150°C at which the austenite phase is stable from the room temperature and then was maintained for 40 seconds, lowered the temperature to 550°C at which the ferrite phase is stable, and then was maintained for 45 seconds again, and then was cooled down to the room temperature. Under the corresponding condition, {200} / {112} was 0.73 which was lower than 1.3 and 8.2% of {100} / ND favorable to magnetism was formed and 39.0% of {112} / ND unfavorable to magnetism was formed. Consequently, the magnetic properties, that is, B 50 = 1.66 T and W 10 / 400 = 12.32 W / kg, which were inferior to Experimental Example, were obtained.

[0114] Comparative Example 12 was out of the range of the second temperature according to the present invention. Specifically, Comparative Example 12 showed the texture and the magnetic property under the condition in which an F / H sample of a composition A10 was heated to 1150°C at which the austenite phase is stable from the room temperature and then was maintained for 45 seconds, lowered the temperature to 550°C at which the ferrite phase is stable, and then was maintained for 45 seconds again, and then was cooled down to the room temperature. Under the corresponding condition, {200} / {112} was 0.72 which was lower than 1.3 and 6.7% of {100} / ND favorable to magnetism was formed and 39.7% of {112} / ND unfavorable to magnetism was formed. Consequently, the magnetic properties, that is, B 50 = 1.65 T and W 10 / 400 = 12.25 W / kg, which were inferior to Experimental Example, were obtained.

[0115] Comparative Example 13 was out of the range of the second temperature according to the present invention. Specifically, Comparative Example 13 showed the texture and the magnetic property under the condition in which an F / H sample of a composition A10 was heated to 1150°C at which the austenite phase is stable from the room temperature and then was maintained for 45 seconds, lowered the temperature to 920°C, and then was maintained for 45 seconds again, and then was cooled down to the room temperature. Under the corresponding condition, {200} / {112} was 0.75 which was lower than 1.3 and 7.2% of {100} / ND favorable to magnetism was formed and 38.4% of {112} / ND unfavorable to magnetism was formed. Consequently, the magnetic properties, that is, B 50 = 1.67 T and W 10 / 400 = 12.58 W / kg which were inferior to Experimental Example, were obtained.

[0116] Comparative Example 14 was out of the range of the second temperature according to the present invention. Specifically, Comparative Example 14 showed the texture and the magnetic property under the condition in which an F / H sample of a composition A10 was heated to 1150°C at which the austenite phase is stable from the room temperature and then was maintained for 45 seconds, lowered the temperature to 980°C, and then was maintained for 45 seconds again, and then was cooled down to the room temperature. Under the corresponding condition, {200} / {112} was 0.73 which was lower than 1.3 and 9.0% of {100} / ND favorable to magnetism was formed and 38.6% of {112} / ND unfavorable to magnetism was formed. Consequently, the magnetic properties, that is, B 50 = 1.66 T and W 10 / 400 = 12.47 W / kg, which were inferior to Experimental Example, were obtained.

[0117] Comparative Example 15 was out of the range of the second set time according to the present invention. Specifically, Comparative Example 15 showed the texture and the magnetic property under the condition in which an F / H sample of a composition A10 was heated to 1150°C at which the austenite phase is stable from the room temperature and then was maintained for 45 seconds, lowered the temperature to 980°C, and then was maintained for 3 seconds again, and then was cooled down to the room temperature. Under the corresponding condition, {200} / {112} was 0.76 which was lower than 1.3 and 8.7% of {100} / ND favorable to magnetism was formed and 36.9% of {112} / ND unfavorable to magnetism was formed. Consequently, the magnetic properties, that is, B 50 = 1.67 T and W 10 / 400 = 12.11 W / kg, which were inferior to Experimental Example, were obtained.

[0118] In contrast, Experimental Examples 1 to 7 satisfied the allowing composition according to the embodiment of the present invention and Relation 1 and performed a cold roll annealing process to perform two-phase region phase change heat treatment. By doing this, it is confirmed that the texture was improved to develop orientation favorable to magnetism and specifically, it is confirmed that a sum of {100} / ND fraction and {110} / ND fraction was 46.0% or higher and {100} / ND fraction was 28.8% or higher and {112} / ND fraction was 23.3% or lower. Further, it is confirmed that magnetic properties, for example, the magnetic flux density B 50 = 1.68 T or higher and the iron loss W 10 / 400 = 11.88 W / kg or lower were obtained.

[0119] As described above, even though the present disclosure has been described by the limited embodiment and drawings, the present disclosure is not limited thereto. Accordingly, various modifications and variations can be made by those skilled in the art within the spirit of the present disclosure and the equivalent scope of the claims to be described below.

Claims

1. A manufacturing method for a non-oriented electrical steel sheet, comprising steps of: (a) preparing a steel material which is a half-finished product including 2.5 to 3.8 wt% of silicon (Si), 1.45 wt% or more of nickel (Ni), 0.05 wt% or less of aluminum (Al), and a balance of iron (Fe) and other inevitable impurities, (b) hot rolling the steel material, thereby forming a hot-rolled steel sheet, (c) cold rolling the hot-rolled steel sheet, thereby forming a cold-rolled steel sheet, and (d) cold roll annealing the cold-rolled steel sheet, wherein the step (d) includes steps of: (d-1) increasing a temperature from a room temperature to a first temperature at which an austenite phase is stable and then maintaining the same for a first set time, (d-2) lowering the temperature to a second temperature at which a two-phase region where the austenite phase and a ferrite phase coexist is stable, and then maintaining the same for a second set time, and (d-3) lowering the temperature to the room temperature.

2. The manufacturing method for a non-oriented electrical steel sheet of claim 1, wherein in the two-phase region, a ratio {200} / {112} which is a ratio of a peak of a {200} texture and a peak of a {112} texture is 1.3 or larger.

3. The manufacturing method for a non-oriented electrical steel sheet of claim 1, wherein the second temperature is 930 to 970°C.

4. The manufacturing method for a non-oriented electrical steel sheet of claim 1, wherein the second set time is 5 seconds or longer.

5. The manufacturing method for a non-oriented electrical steel sheet of claim 1, further comprising: between the step (b) and the step (c), a step of hot roll annealing the hot-rolled steel sheet.

6. The manufacturing method for a non-oriented electrical steel sheet of claim 1, wherein the steel material further includes 0.005 wt% or less of carbon (C), 0.005 wt% or less of sulfur (S), 0.005 wt% or less of nitrogen (N), 0.005 wt% or less of titanium (Ti), and 0.015 wt% or less of phosphorus (P).

7. The manufacturing method for a non-oriented electrical steel sheet of claim 1, wherein the steel material satisfies the following Relation 1: Ni ≥ 2.52 Si − 5.3 ([Ni] and [Si] refer to wt% of Ni and Si, respectively.).

8. A non-oriented electrical steel sheet manufactured by a method of hot rolling and cold rolling a steel material including 2.5 to 3.8 wt% of silicon (Si), 1.45 wt% or more of nickel (Ni), 0.05 wt% or less of aluminum (Al), and a balance of iron (Fe) and other inevitable impurities to form a cold-rolled steel sheet, preparing a finished product by cold roll annealing the cold-roll steel sheet, and during the cold roll annealing, increasing a temperature from a room temperature to a first temperature at which an austenite phase is stable and maintaining the same for a first set time, and then lowering the temperature to a second temperature at which a two-phase region where the austenite phase and a ferrite phase coexist is stable, and then maintaining the same for a second set time, and then lowering the temperature to the room temperature.

9. The non-oriented electrical steel sheet of claim 8, wherein in the two-phase region, a ratio {200} / {112} which is a ratio of a peak of a {200} texture and a peak of a {112} texture is 1.3 or larger.

10. The non-oriented electrical steel sheet of claim 8, wherein the second temperature is 930 to 970°C.

11. The non-oriented electrical steel sheet of claim 8, wherein the second set time is 5 seconds or longer.

12. The non-oriented electrical steel sheet of claim 8, wherein the steel material satisfies the following Relation 1: Ni ≥ 2.52 Si − 5.3 ([Ni] and [Si] refer to wt% of Ni and Si, respectively.).

13. The non-oriented electrical steel sheet of claim 8, wherein the steel material further includes 0.005 wt% or less of carbon (C), 0.005 wt% or less of sulfur (S), 0.005 wt% or less of nitrogen (N), 0.005 wt% or less of titanium (Ti), and 0.015 wt% or less of phosphorus (P).

14. The non-oriented electrical steel sheet of claim 8, wherein a sum of {100} / ND fraction and {110} / ND fraction of the finished product is 46.0% or higher.

15. The non-oriented electrical steel sheet of claim 8, wherein {100} / ND fraction of the finished product is 28.8% or higher and {112} / ND fraction is 23.3% or lower.

16. A non-oriented electrical steel sheet including 2.5 to 3.8 wt% of silicon (Si), 1.45 wt% or more of nickel (Ni), 0.05 wt% or less of aluminum (Al), and a balance of iron (Fe) and other inevitable impurities, wherein a magnetic flux density B50 is 1.68 T or higher and an iron loss W10 / 400 is 11.88 W / kg or lower.

17. The non-oriented electrical steel sheet of claim 16, wherein a content of silicon and nickel satisfies the following Relation 1: Ni ≥ 2.52 Si − 5.3 ([Ni] and [Si] refer to wt% of Ni and Si, respectively.).

18. The non-oriented electrical steel sheet of claim 16, wherein a sum of {100} / ND fraction and {110} / ND fraction is 46.0% or higher.

19. The non-oriented electrical steel sheet of claim 16, wherein {100} / ND fraction is 28.8% or higher and {112} / ND fraction is 23.3% or lower.

20. The non-oriented electrical steel sheet of claim 16, further including 0.005 wt% or less of carbon (C), 0.005 wt% or less of sulfur (S), 0.005 wt% or less of nitrogen (N), 0.005 wt% or less of titanium (Ti), and 0.015 wt% or less of phosphorus (P).

Images