Non-oriented electrical steel sheet and method for manufacturing non-oriented electrical steel sheet

Abstract

A non-oriented electrical steel sheet according to an embodiment of the present invention comprises 2.0 wt% (inclusive) to 3.8 wt% (inclusive) of silicon (Si), 0.01 wt% (inclusive) to 1.5 wt% (inclusive) of manganese (Mn), 0 wt% (exclusive) to 0.02 wt% (exclusive) of sulfur (S), 0 wt% (exclusive) to 0.01 wt% (exclusive) of yttrium (Y), 0 wt% (exclusive) to 0.01 wt% (exclusive) of aluminum (Al), 0 wt% (exclusive) to 0.01 wt% (exclusive) of titanium (Ti), 0 wt% (exclusive) to 0.005 wt% (exclusive) of carbon (C), 0 wt% (exclusive) to 0.005 wt% (exclusive) of nitrogen (N), and the balance being iron (Fe) and other inevitable impurities, wherein the sum of the contents of silicon (Si) and manganese (Mn) satisfies 2.1 wt% (inclusive) to 4.8 wt% (inclusive), so that a non-oriented electrical steel sheet having excellent magnetic properties can be provided.

Description

Non-oriented electrical steel sheet and method for manufacturing non-oriented electrical steel sheet

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

[0002] Due to recent global environmental issues, interest in eco-friendly products is rising worldwide. In particular, in the automotive industry, conventional internal combustion engine vehicles are being rapidly replaced by eco-friendly vehicles such as hybrid, electric, and hydrogen cars.

[0003] As interest in and demand for such eco-friendly vehicles increase, the demand for electric motors, which generate the driving force for these vehicles, is also rising. An electric motor is a device that uses electricity to generate the driving force required for a vehicle. Electric motors must be able to guarantee high output to replace the output of internal combustion engines, and they must have high energy efficiency to operate for a longer period using the same amount of energy.

[0004] The output and energy efficiency of electric motors are related to the improvement of the magnetic properties of the non-oriented electrical steel sheets used as the core material. Representative magnetic properties of non-oriented electrical steel sheets include magnetic flux density and iron loss; to improve the output and energy efficiency of electric motors, iron loss must be lowered and magnetic flux density increased.

[0005] First, magnetic flux density represents the number of magnetic field lines induced in a material under a specific magnetic field. Generally, magnetic flux density is B induced under a magnetic field of 5,000 A / m. 50 The value is evaluated, and the unit used is 'T (Tesla)'. Factors that improve magnetic flux density include the chemical composition, grain size, and texture of the non-oriented electrical steel.

[0006] Next, core loss refers to the energy loss that occurs during the magnetization process of a material, and the unit used is 'W / kg'. Core loss is divided into hysteresis loss, which is caused by the magnetization phenomenon itself, and eddy current loss, which is caused by eddy currents induced during magnetization. Methods to reduce core loss include increasing resistivity by adding silicon (Si), manganese (Mn), and aluminum (Al), which are major alloying elements of non-oriented electrical steel, and reducing the thickness of the non-oriented electrical steel.

[0007] However, increasing the amount of alloying elements can reduce magnetic flux density and decrease rollability, which may lead to problems such as making thinning difficult. Furthermore, major alloying elements in non-oriented electrical steel, such as manganese (Mn) and aluminum (Al), can combine with carbon (C), nitrogen (N), and titanium (Ti) to form precipitates. These formed precipitates can impede magnetic properties by hindering the movement of magnetic domains.

[0008] Therefore, in order to improve the magnetic properties of non-oriented electrical steel sheets, it is necessary to optimize the alloy composition included in the non-oriented electrical steel sheets and to improve the microstructure and texture that affect magnetic flux density and iron loss.

[0009] [Prior Art Literature]

[0010] [Patent Literature]

[0011] Korean Registered Patent No. 10-2043289

[0012] The present invention has been devised to solve the above problems, and the objective of the present invention is to provide a non-oriented electrical steel sheet having excellent magnetic properties and a method for manufacturing a non-oriented electrical steel sheet.

[0013] The problems of the present invention are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0014] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises silicon (Si) 2.0 wt% or more and 3.8 wt% or less, manganese (Mn) 0.01 wt% or more and 1.5 wt% or less, sulfur (S) 0 wt% or more and less than 0.02 wt%, yttrium (Y) 0 wt% or more and less than 0.01 wt%, aluminum (Al) 0 wt% or more and less than 0.01 wt%, titanium (Ti) 0 wt% or more and less than 0.01 wt%, carbon (C) 0 wt% or more and less than 0.005 wt%, nitrogen (N) 0 wt% or more and less than 0.005 wt%, and the remainder being iron (Fe) and other unavoidable impurities, wherein the sum of the silicon (Si) and manganese (Mn) contents is 2.1 wt% or more and 4.8 wt% or less.

[0015] In addition, the following Equation 1 is 1.75 or less.

[0016] [Equation 1]

[0017]

[0018] In Equation 1, [S] is the sulfur (S) content in ppm units, and [Y] is the yttrium (Y) content in ppm units.

[0019] In addition, the following formula 2 may be in the range of 0.1 to 1.6.

[0020] [Equation 2]

[0021]

[0022] In Equation 2, [Al], [Ti], [C], and [N] are the contents of aluminum (Al), titanium (Ti), carbon (C), and nitrogen (N), respectively, in ppm units.

[0023] In addition, it includes a CSL grain boundary (Coincidence Site Lattice Boundary), and the CSL grain boundary may include a ∑5-type grain boundary, a ∑9-type grain boundary, a ∑11-type grain boundary, a ∑3-type grain boundary, and a ∑7-type grain boundary.

[0024] In addition, the following Equation 3 may be 1.9 or higher.

[0025] [Equation 3]

[0026]

[0027] In Equation 3, ∑5, ∑9, ∑11, ∑3, and ∑7 are the ∑5-type grain boundary length ratio, ∑9-type grain boundary length ratio, ∑11-type grain boundary length ratio, ∑3-type grain boundary length ratio, and ∑7-type grain boundary length ratio, respectively, of the total CSL grain boundary length.

[0028] And, iron loss (W 10 / 400 ) may be 12.5 W / kg or less.

[0029] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention includes the steps of reheating a slab containing the alloy composition described above and then hot rolling, hot rolling annealing, cold rolling, and cold rolling annealing in a temperature range of 900°C or higher and 1300°C or lower.

[0030] In addition, the above slab has a value of 1.75 or less in Formula 1 below.

[0031] [Equation 1]

[0032]

[0033] In Equation 1, [S] is the sulfur (S) content in ppm units, and [Y] is the yttrium (Y) content in ppm units.

[0034] In addition, the above cold rolling annealing step may be performed by heat treatment for 5 hours or more at a temperature range of 900°C or higher and 1300°C or lower.

[0035] In addition, the above slab may have a range of 0.1 or more and 1.6 or less for the following Equation 2.

[0036] [Equation 2]

[0037]

[0038] In Equation 2, [Al], [Ti], [C], and [N] are the contents of aluminum (Al), titanium (Ti), carbon (C), and nitrogen (N), respectively, in ppm units.

[0039] In addition, the non-oriented electrical steel sheet that has undergone the cold rolling and annealing step includes CSL grain boundaries (Coincidence Site Lattice Boundary), and the CSL grain boundaries may include ∑5 type grain boundaries, ∑9 type grain boundaries, ∑11 type grain boundaries, ∑3 type grain boundaries, and ∑7 type grain boundaries.

[0040] In addition, the following Equation 3 may be 1.9 or higher.

[0041] [Equation 3]

[0042]

[0043] In Equation 3, ∑5, ∑9, ∑11, ∑3, and ∑7 are the ∑5-type grain boundary length ratio, ∑9-type grain boundary length ratio, ∑11-type grain boundary length ratio, ∑3-type grain boundary length ratio, and ∑7-type grain boundary length ratio, respectively, of the total CSL grain boundary length.

[0044] And, the non-oriented electrical steel sheet that has undergone cold rolling annealing has iron loss (W 10 / 400 ) may be 12.5 W / kg or less.

[0045] According to one embodiment of the present invention, by controlling the content of alloying elements and manufacturing process conditions to form a microstructure and texture favorable to magnetic properties, a non-oriented electrical steel sheet having excellent magnetic properties and a method for manufacturing a non-oriented electrical steel sheet can be provided.

[0046] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims.

[0047] Hereinafter, preferred embodiments of the present invention are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention is not limited or restricted by the following embodiments.

[0048] Additionally, when it is stated that a component (or area, layer, part, etc.) is "on," "connected," or "combined" with another component, it means that it may be directly placed / connected / combined with the other component, or that a third component may be placed between them.

[0049] Terms such as "include" or "have" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0050] In order to clearly explain the present invention, detailed descriptions of related prior art that are irrelevant to the explanation or that may unnecessarily obscure the essence of the invention have been omitted. Furthermore, when assigning reference numerals to the components of each drawing in this specification, identical or similar reference numerals are assigned to identical or similar components throughout the entire specification.

[0051] Furthermore, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0052] Unless otherwise specified, the notation 'A ~ B' or 'A to B' for numerical values ​​A and B shall mean 'A or greater and B or less'. In such notation, if a unit is attached only to numerical value B, that unit shall also apply to numerical value A.

[0053] Also, unless specifically noted otherwise, 1 ppm is 0.0001 wt%.

[0054]

[0055] Non-oriented electrical steel sheets

[0056] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises silicon (Si) 2.0 wt% or more and 3.8 wt% or less, manganese (Mn) 0.01 wt% or more and 1.5 wt% or less, sulfur (S) 0 wt% or more and less than 0.02 wt%, yttrium (Y) 0 wt% or more and less than 0.01 wt%, aluminum (Al) 0 wt% or more and less than 0.01 wt%, titanium (Ti) 0 wt% or more and less than 0.01 wt%, carbon (C) 0 wt% or more and less than 0.005 wt%, nitrogen (N) 0 wt% or more and less than 0.005 wt%, and the remainder being iron (Fe) and other unavoidable impurities.

[0057] Hereinafter, the role and content of alloying elements included in a non-oriented electrical steel sheet according to one embodiment of the present invention will be described in detail.

[0058]

[0059] Silicon (Si)

[0060] Silicon (Si) is an element that increases the resistivity of steel and reduces iron loss, and is a major element of non-oriented electrical steel sheets. If the silicon content is too low, the effect of improving iron loss may be insufficient. On the other hand, if silicon is added in excess, permeability and magnetic flux density may decrease. In addition, brittleness may increase as the silicon content increases.

[0061] If the silicon content is less than 2.0 wt%, the effect of reducing iron loss may be insufficient. On the other hand, if the silicon content exceeds 3.8 wt%, brittleness increases, and cracks or plate breakage may occur during cold rolling or stamping.

[0062] Accordingly, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain silicon in an amount of 2.0 weight% or more and 3.8 weight% or less.

[0063]

[0064] Manganese (Mn)

[0065] Manganese (Mn), along with silicon (Si), increases the resistivity of steel to reduce iron loss and is a major element of non-oriented electrical steel. In addition, manganese has a positive effect on the formation of a texture that is favorable for magnetic properties.

[0066] More specifically, manganese combines with sulfur (S) in the steel to form precipitates such as MnS, and these precipitates react with hydrogen (H2) in the atmosphere during cold rolling annealing in a reducing atmosphere, so that manganese (Mn) is redissolved in the steel and sulfur (S) vaporizes in the form of hydrogen sulfide (H2S) and is absorbed into the atmosphere.

[0067] As a result, the surface energy of grains with an orientation favorable to magnetic properties becomes lower than that of grains with an orientation unfavorable to magnetic properties, and as the grains with an orientation favorable to magnetic properties grow larger, a texture favorable to magnetic properties can be formed.

[0068] If the manganese content is less than 0.01 wt%, it may be difficult to secure the aforementioned effects, and fine MnS precipitates may be formed. The formed fine precipitates inhibit grain growth, which can cause deterioration of magnetic properties due to the fine grains. On the other hand, if the manganese content exceeds 1.5 wt%, coarse MnS precipitates may be formed. Coarse precipitates can reduce magnetic flux density and lower cold rolling performance.

[0069] Accordingly, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain manganese in an amount of 0.01 weight% or more and 1.5 weight% or less.

[0070]

[0071] In the present invention, the sum of the silicon (Si) and manganese (Mn) content, which are major elements of the non-oriented electrical steel sheet, is 2.1 wt% or more and 4.8 wt% or less. If the sum of the silicon (Si) and manganese (Mn) content falls short of the lower limit described above, the increase in resistivity is small, and thus the low iron loss characteristics targeted in the present invention cannot be achieved. On the other hand, if the sum of the silicon (Si) and manganese (Mn) content exceeds the upper limit described above, grain boundary segregation and ordered phases are formed, which may cause slab breakage and cracking during the manufacturing process.

[0072] In the present invention, by controlling the respective contents of silicon (Si) and manganese (Mn) to the above-described contents, as well as simultaneously controlling the total contents of silicon (Si) and manganese (Mn), it is possible to control non-directional resistance, grain boundary segregation, and order phase compared to the case where only the respective contents are controlled, thereby providing a non-oriented electrical steel sheet capable of securing excellent magnetic properties intended in the present invention.

[0073]

[0074] Yellow (S)

[0075] In the present invention, sulfur (S) is a key additive element added to control the surface energy of the product.

[0076] More specifically, sulfur combines with manganese (Mn) to form MnS precipitates, and these MnS precipitates react with hydrogen (H2) in the atmosphere during cold rolling annealing in a reducing atmosphere, so that manganese (Mn) is redissolved in the steel and sulfur (S) vaporizes in the form of hydrogen sulfide (H2S) and is absorbed into the atmosphere.

[0077] As a result, the surface energy of grains with an orientation favorable to magnetic properties becomes lower than that of grains with an orientation unfavorable to magnetic properties, and as the grains with an orientation favorable to magnetic properties grow larger, a texture favorable to magnetic properties can be formed.

[0078] When the sulfur content is 0 wt%, the above-described effect cannot be obtained. On the other hand, when the sulfur content is 0.02 wt% or more, sulfur may segregate at grain boundaries or MnS may precipitate in excess, hindering the growth of crystal grains, which may result in deterioration of magnetic properties due to fine crystal grain size.

[0079] Accordingly, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain sulfur in an amount greater than 0 weight% and less than 0.02 weight%.

[0080]

[0081] Yttrium (Y)

[0082] Yttrium (Y) is a key additive element and is utilized as a key element for surface energy control in this invention.

[0083] Yttrium is a segregated element, and the orientation of the texture that develops stably varies depending on the yttrium content. For example, when the yttrium content is greater than 0 wt% and less than 0.01 wt%, the magnetic properties can be improved as crystal grains with an orientation favorable to magnetic properties develop.

[0084] On the other hand, if the yttrium (Y) content is 0.01 wt% or more, it acts as a grain boundary embrittlement element, which can increase the brittleness of the steel, and as a result, the rolling performance may decrease, leading to a decrease in productivity. In addition, if the yttrium content is excessive, it can promote the growth of grains with orientations that are unfavorable to magnetic properties, so it is necessary to control the content.

[0085] Accordingly, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain yttrium in an amount greater than 0 weight% and less than 0.01 weight%.

[0086]

[0087] At this time, the relationship between the content of the added elements sulfur (S) and yttrium (Y) in Equation 1 below may be less than or equal to a certain value.

[0088] [Equation 1]

[0089]

[0090] In Equation 1, [S] is the sulfur (S) content in ppm units, and [Y] is the yttrium (Y) content in ppm units.

[0091] The upper limit of Formula 1 may be 1.75 or less, 1.65 or less, 1.55 or less, 1.45 or less, 1.35 or less, 1.25 or less, 1.15 or less, 1.05 or less, 0.95 or less, 0.85 or less, 0.75 or less, 0.65 or less, 0.55 or less, 0.45 or less, 0.35 or less, or 0.25 or less, and the lower limit is not specifically limited.

[0092] As described above, sulfur (S) and yttrium (Y) are segregated elements, and the surface energy of the crystal grains can be controlled by the content of sulfur (S) and yttrium (Y).

[0093] If Equation 1 exceeds the upper limit described above, the surface energy of grains with orientations favorable to magnetic properties becomes higher than the surface energy of grains with orientations unfavorable to magnetic properties due to large segregation, and grains with orientations unfavorable to magnetic properties may develop. As a result, grains with orientations unfavorable to magnetic properties grow, and the magnetic properties may become inferior.

[0094] On the other hand, when the content of sulfur (S) and yttrium (Y) satisfies Equation 1, the surface energy of the crystal grains having an orientation favorable to magnetic properties becomes lower than the surface energy of the crystal grains having an orientation unfavorable to magnetic properties, so that crystal grains having an orientation favorable to magnetic properties can develop. As a result, crystal grains having an orientation favorable to magnetic properties grow, and the magnetic properties are improved, thereby securing the excellent magnetic properties intended in the present invention.

[0095] Here, a direction favorable to magnetic characteristics may refer to the {001} direction, and a direction unfavorable to magnetic characteristics may refer to the {111} direction and the {112} direction.

[0096]

[0097] Aluminum (Al)

[0098] Aluminum (Al) is an element that reduces iron loss by increasing resistivity along with manganese (Mn) and silicon (Si). In addition, aluminum can reduce magnetic deviation by reducing magnetic anisotropy.

[0099] However, if the aluminum content is excessive, it combines with nitrogen (N) in the steel to form nitrides such as AlN. The formed nitrides can degrade magnetic properties by inhibiting grain growth, hindering magnetic field wall movement, and significantly reducing magnetic flux density.

[0100] If aluminum is not added, the above-mentioned effects cannot be expected, and if the aluminum content is 0.01 weight% or more, the above-mentioned problems may occur due to the excessive formation of nitrides.

[0101] Accordingly, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain aluminum in an amount greater than 0 weight% and less than 0.01 weight%.

[0102]

[0103] Titanium (Ti)

[0104] Titanium (Ti) can combine with carbon (C), nitrogen (N), and others within the steel to form fine precipitates such as TiC and TiN. These formed fine precipitates can inhibit grain growth, thereby degrading magnetic properties.

[0105] Therefore, there is a need to control the titanium (Ti) content, and in the present invention, titanium is controlled to be greater than 0 weight% and less than 0.01 weight%.

[0106]

[0107] Carbon (C)

[0108] Carbon (C) can combine with titanium (Ti) in steel to form carbides such as TiC. In this case, if the carbon content is 0.005 wt% or more, a large amount of fine carbides is formed, which can degrade magnetic properties by increasing iron loss. Additionally, if the carbon content is 0.005 wt% or more, magnetic aging may occur, which can degrade magnetic properties.

[0109] Accordingly, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain carbon in an amount greater than 0 weight% and less than 0.005 weight%.

[0110]

[0111] Nitrogen (N)

[0112] When the nitrogen (N) content is 0.005 wt% or more, nitrogen can combine with aluminum (Al), titanium (Ti), etc., in the steel to form fine nitrides. These fine nitrides inhibit grain growth and increase iron loss, thereby degrading magnetic properties.

[0113] Accordingly, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain nitrogen in an amount greater than 0 weight% and less than 0.005 weight%.

[0114]

[0115] At this time, the relationship between the aluminum (Al), titanium (Ti), carbon (C), and nitrogen (N) content may be within a certain range according to the following Equation 2.

[0116] [Equation 2]

[0117]

[0118] In Equation 2, [Al], [Ti], [C], and [N] are the contents of aluminum (Al), titanium (Ti), carbon (C), and nitrogen (N), respectively, in ppm units.

[0119] The upper limit of Equation 2 may be approximately 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, or 0.3, and the lower limit may be approximately 0.1, 0.2, 0.3, 0.4, or 0.5. The range of Equation 2 may be within the range of being less than or equal to the upper limit mentioned above, or greater than or equal to the lower limit mentioned above.

[0120] As described above, aluminum, titanium, carbon, and nitrogen are elements with a strong tendency to precipitate and react with other alloying elements in steel to form precipitates. In particular, aluminum combines with nitrogen in steel to form AlN precipitates, and titanium combines with carbon in steel to form TiC precipitates. Since the formed precipitates can have a negative effect on magnetic properties, there is a need to control the formation of precipitates. Therefore, the present invention aims to control the formation of precipitates by utilizing Equation 2.

[0121] If the value of Equation 2 falls below the lower limit described above, the formation of carbides and nitrides may be facilitated. If the formation of carbides and nitrides is facilitated, a large amount of carbides and nitrides may be formed, and as a result, magnetic properties may be degraded. Additionally, if the value of Equation 2 exceeds the upper limit described above, the formation of aluminum-based precipitates and titanium-based precipitates may be promoted. If the formation of aluminum and titanium precipitates is promoted, a large amount of precipitates may be formed, and magnetic properties may be degraded.

[0122]

[0123] In addition to the steel components described above, the remainder may contain iron (Fe) and unavoidable impurities. These unavoidable impurities are those introduced during the steelmaking stage and the manufacturing process of non-oriented electrical steel sheets; as this is widely known in the field, a detailed explanation is omitted.

[0124] In one embodiment disclosed herein, the addition of elements other than the aforementioned alloy components is not excluded, and various elements may be included within a scope that does not impair the technical spirit of the invention disclosed herein. If additional elements are included, they may be included to replace the remainder of iron (Fe).

[0125]

[0126] A non-oriented electrical steel sheet according to one embodiment of the present invention may include CSL grain boundaries (Coincidence site lattice boundaries), and the CSL grain boundaries may include ∑3 type grain boundaries, ∑5 type grain boundaries, ∑7 type grain boundaries, ∑9 type grain boundaries, and ∑11 type grain boundaries.

[0127] A CSL (Coincidence site lattice, hereinafter referred to as "CSL") refers to a condition in which lattice sites coincide according to an angle at the boundary surface between two adjacent grain boundaries. Additionally, a CSL grain boundary (Coincidence site lattice boundary) refers to a special grain boundary in a low energy state that satisfies the CSL condition due to a special orientation relationship between grains.

[0128] CSL grain boundaries are named with a ∑ value according to the degree of lattice point matching, that is, the degree of lattice matching. For example, CSL grain boundaries can be named ∑3-type grain boundaries, ∑5-type grain boundaries, etc., according to the degree of lattice matching, where ∑3-type grain boundaries mean that the degree of lattice matching is 1 / 3, and ∑5-type grain boundaries mean that the degree of lattice matching is 1 / 5.

[0129] More specifically, a ∑3-type grain boundary is a grain boundary where the atomic arrangement is rotated by 60°, resulting in one lattice position overlapping for every three atoms, while a ∑5-type grain boundary is a grain boundary where one lattice position overlaps for every five atoms. The lower the value of the number represented by ∑, the higher the frequency of lattice position overlap and the lower the energy.

[0130] Representative orientations with low grain boundary energy include the {111} orientation, which is disadvantageous to magnetic properties, and the {100} orientation, which is advantageous to magnetic properties; CSL grain boundaries can develop around such {111} and {100} orientations.

[0131] In the present invention, taking into account that the tendency for CSL grain boundaries to develop differs in the {111} orientation, which is unfavorable to magnetic properties, and the {100} orientation, which is favorable to magnetic properties, the CSL grain boundary formation ratio capable of securing excellent magnetic properties is expressed as Equation 3. In the present invention, Equation 3 below may be greater than a certain value.

[0132] [Equation 3]

[0133]

[0134] In Equation 3, ∑5, ∑9, ∑11, ∑3, and ∑7 represent the ∑5-type grain boundary length ratio, ∑9-type grain boundary length ratio, ∑11-type grain boundary length ratio, ∑3-type grain boundary length ratio, and ∑7-type grain boundary length ratio, respectively, of the total CSL grain boundary length, and represent the proportion of the total grain boundary length occupied by ∑5, ∑9, ∑11, ∑3, and ∑7 grain boundaries within the area measured by EBSD.

[0135] The lower limit of Equation 3 may be 1.9 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, or 8 or more. The upper limit is not specifically restricted.

[0136] When satisfying the alloy composition according to one embodiment of the present invention, Equation 3 may be greater than the lower limit described above. When Equation 3 is greater than the lower limit described above, it means that the CSL grain boundary that does not hinder the movement of magnetic domains is more developed compared to the CSL grain boundary that hinders the movement of magnetic domains, so it may mean that the movement of magnetic domains is smooth and the magnetic properties are improved.

[0137] That is, in the non-oriented electrical steel sheet according to one embodiment disclosed in the present invention, by controlling the alloy composition described above, CSL grain boundaries that do not hinder the movement of magnetic domains can be developed, and thereby, the non-oriented electrical steel sheet according to one embodiment disclosed in the present invention can secure excellent magnetic properties.

[0138] On the other hand, if the value of Equation 3 does not reach the lower limit described above, it may mean that CSL grain boundaries that hinder the movement of magnetic domains are more developed compared to CSL grain boundaries that do not hinder the movement of magnetic domains. In this case, magnetic properties may be inferior because the movement of magnetic domains is not smooth.

[0139] Through this, it can be confirmed that the non-oriented electrical steel sheet according to one embodiment disclosed in the present invention can secure magnetic properties by controlling Equation 3 by controlling the CSL grain boundaries that develop around the orientation and / or orientation that hinder magnetic domain movement and / or affect magnetic properties.

[0140] As a result, the non-oriented electrical steel sheet according to one embodiment of the present invention has iron loss (W 10 / 400 ) may be 12.5W / kg or less.

[0141]

[0142] Method for manufacturing non-oriented electrical steel sheets

[0143] Hereinafter, a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention will be described in detail.

[0144] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention includes the steps of reheating a slab containing the alloy composition described above and then hot rolling, hot rolling annealing, cold rolling, and cold rolling annealing.

[0145] At this time, the slab contains silicon (Si) 2.0 wt% or more and 3.8 wt% or less, manganese (Mn) 0.01 wt% or more and 1.5 wt% or less, sulfur (S) 0 wt% or more and less than 0.02 wt%, yttrium (Y) 0 wt% or more and less than 0.01 wt%, aluminum (Al) 0 wt% or more and less than 0.01 wt%, titanium (Ti) 0 wt% or more and less than 0.01 wt%, carbon (C) 0 wt% or more and less than 0.005 wt%, nitrogen (N) 0 wt% or more and less than 0.005 wt%, and the remainder being iron (Fe) and other unavoidable impurities, and the sum of the silicon (Si) and manganese (Mn) content is 2.1 wt% or more and 4.8 wt% or less.

[0146] At this time, the slab may satisfy Equation 1, which is the relationship between the sulfur (S) and yttrium (Y) content. Alternatively, the slab may satisfy Equation 2, which is the relationship between the carbon (C), nitrogen (N), aluminum (Al), and titanium (Ti) content.

[0147] As the content of the alloy components has been explained previously, a redundant explanation will be omitted. In addition, since the content of the alloy components does not substantially change in the manufacturing process described later, the alloy composition of the slab and the alloy composition of the final product, the non-oriented electrical steel sheet, are substantially the same.

[0148] Hereinafter, each step of the method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention will be described in detail.

[0149] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may perform the step of reheating a slab and then hot rolling. More specifically, the step of reheating a slab and then hot rolling may include a reheating process, a hot rolling process, and a coiling process.

[0150] First, the reheating process is a process performed prior to the hot rolling process and may involve reheating the steel for a subsequent process. More specifically, it may be a step of loading the steel into a furnace and heating it uniformly to facilitate plastic deformation.

[0151] At this time, if the reheating temperature is below 1050℃, the rolling load increases, which may cause difficulties in performing hot rolling. On the other hand, if the reheating temperature exceeds 1250℃, precipitates formed by carbon (C), sulfur (S), nitrogen (N), etc., within the steel are redissolved, and fine precipitates may be formed during the subsequent rolling and annealing processes. These fine precipitates can inhibit grain growth and increase iron loss.

[0152] Accordingly, the reheating process according to one embodiment of the present invention can be performed at a temperature of 1050°C or higher and 1250°C or lower.

[0153] Next, a hot rolling process may be performed to form a hot-rolled steel sheet by hot rolling the reheated steel. The hot rolling process may include rough rolling and finish rolling. Here, rough rolling may refer to making the steel into a rolled material having a suitable shape, thickness, and width, and finish rolling may refer to adjusting the steel to a predetermined thickness and width and rolling it at a finishing temperature suitable for the application to achieve a good surface finish.

[0154] At this time, the finishing temperature of the hot rolling process may be carried out at a temperature for the formation of a uniform structure and appropriate strength improvement, and the finishing temperature may be between 800°C and 900°C. If the finishing temperature is below 800°C, dynamic recrystallization may not occur sufficiently, making it difficult to homogenize the microstructure; consequently, the uniformity of the final texture may be low, which may lead to a deterioration in magnetic properties. If the finishing temperature exceeds 900°C, a problem may arise in which the strength of the steel decreases rapidly.

[0155] Subsequently, a coiling process may be performed to coil the hot-rolled steel sheet formed through the hot rolling process. At this time, the coiling temperature may be 500°C or higher and 700°C or lower. If the coiling temperature is below 500°C, brittleness may increase, causing the sheet to break, and the grain size may decrease, preventing the grains from growing sufficiently even after annealing. On the other hand, if the coiling temperature exceeds 700°C, fine precipitates may be generated, which may increase iron loss.

[0156] The thickness of the hot-rolled steel sheet formed through the step of reheating the slab and then hot-rolling it may be 1.6 mm or more and 2.6 mm or less. If the thickness of the hot-rolled steel sheet is excessively thin, less than 1.6 mm, the thickness obtained after cold rolling is insufficient, which may cause shape defects when applied to products. On the other hand, if the thickness of the hot-rolled steel sheet exceeds 2.6 mm, the cold-rolling reduction rate increases, and the fraction of textures unfavorable to magnetic properties increases, which may result in inferior magnetic properties.

[0157] A non-oriented electrical steel sheet according to one embodiment of the present invention may perform a hot-rolled annealing step after the step of reheating the slab and then hot-rolling it. The hot-rolled annealing step may be performed to ensure uniformity of the microstructure of the steel material that has undergone hot rolling.

[0158] The hot rolling annealing step according to the present invention can be performed in a continuous heat treatment facility or a batch-type heat treatment facility as needed.

[0159] First, when a hot rolling annealing step is performed in a continuous heat treatment facility, the appropriate temperature for hot rolling annealing is 940°C or higher and 1110°C or lower, and the heat treatment can be performed for 30 seconds or higher and 180 seconds or lower within the above-mentioned temperature range. At this time, the heating rate to the above-mentioned heat treatment temperature range and the cooling rate after heat treatment may be 20°C / s or higher.

[0160] Next, when a hot rolling annealing step is performed in a batch-type heat treatment facility, the appropriate temperature for hot rolling annealing is 700°C or higher and 1300°C or lower, and heat treatment can be performed for 0.5 hours or more within the aforementioned temperature range. At this time, the heating rate to the aforementioned heat treatment temperature range may be 0.5°C / min or higher, and the cooling rate after heat treatment may be 0.5°C / min or lower.

[0161] If the hot rolling annealing temperature falls below the lower limit of the temperature range for each facility, the elongated cast structure remaining after hot rolling may cause microstructural non-uniformity. Conversely, if the hot rolling annealing temperature exceeds the upper limit of the temperature range for each facility, it may cause texture imbalance in the final product and degrade magnetic properties.

[0162] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may further include a pickling step after a hot rolling annealing step.

[0163] Specifically, when annealing is performed in a continuous heat treatment facility, a pickling step can be performed continuously following the hot rolling annealing. When annealing is performed in a batch heat treatment facility, a separate pickling step can be performed.

[0164] The pickling step according to the present invention can be performed by supplying an acidic solution to a pickling tank in which a reaction takes place with an iron plate to react with residual scales, but is not limited thereto and can be performed by a pickling method conventionally performed in the field.

[0165] Subsequently, the method for manufacturing a non-oriented electrical steel sheet according to the present invention may perform a cold rolling step. The cold rolling step may be a process of rolling a hot-rolled steel sheet, which has undergone hot-rolled annealing, at a temperature below the recrystallization temperature to further reduce the thickness of the steel sheet.

[0166] More specifically, the process may be to roll a hot-rolled steel sheet to a thickness and width that meet the specifications of the final product. The cold rolling step according to the present invention may cold-roll the hot-rolled steel sheet into a cold-rolled steel sheet having a thickness of 0.3 mm or less.

[0167] If the thickness of the cold-rolled steel sheet exceeds 0.3 mm, iron loss increases, which may lead to a deterioration in magnetic properties. Additionally, prolonged annealing may be required to decompose MnS precipitated within the steel, which can cause problems such as increased production costs and reduced productivity.

[0168] The cold rolling step according to one embodiment of the present invention may be performed as a single-stage cold rolling or a two-stage cold rolling including intermediate annealing.

[0169] First, when performed as a single-stage cold rolling, it can be rolled to a final thickness with a reduction rate of 98%. At this time, the desirable final thickness is 0.3 mm or less. If the final thickness exceeds 0.3 mm, the magnetic properties may be degraded.

[0170] Next, we will explain in detail the case where it is performed by two-stage cold rolling including intermediate annealing.

[0171] In the case of two-stage cold rolling including intermediate annealing, the cold rolling stage may include first cold rolling, intermediate annealing, and second cold rolling.

[0172] The first cold rolling step may be a step of rolling a hot-rolled steel sheet, which has undergone a hot-rolling annealing step, to a thickness of 1.0 mm or less. At this time, the reduction rate may be 50% or more and 98% or less.

[0173] Subsequently, intermediate annealing may be performed. Intermediate annealing may be performed when rolling to the final target thickness is not performed in the first cold rolling, or when it is necessary to adjust the reduction ratio between the first and second cold rolling. Additionally, it may be performed after the first cold rolling and before the second cold rolling to remove residual stress within the rolled structure and to secure a uniform microstructure.

[0174] Depending on the requirements, intermediate annealing can be performed in a continuous heat treatment facility or a batch heat treatment facility.

[0175] In the case of a continuous heat treatment facility, heat treatment can be performed for a period of 30 seconds to 120 seconds in a temperature range of 900°C to 1100°C. At this time, the heating rate to the aforementioned temperature range may be 10°C / s or more, and the cooling rate after heat treatment may be 20°C / s or more. In the case of a batch heat treatment facility, heat treatment can be performed for 0.5 hours or more in a temperature range of 700°C to 1300°C. At this time, the heating rate to the aforementioned temperature range may be 0.5°C / min or more, and the cooling rate may be 0.5°C / min or less.

[0176] A second cold rolling may be performed after intermediate annealing. The second cold rolling may roll the steel sheet that has undergone intermediate annealing to a final target thickness. At this time, the final thickness is 0.3 mm or less, and the reduction rate may be 20% or more and 96% or less.

[0177] A cold rolling step according to one embodiment of the present invention may be performed as a warm rolling step in which the temperature of the sheet is raised to 100°C or higher and 200°C or lower to facilitate rolling.

[0178] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may further include a step of applying an anti-adhesion coating and a spacing agent after a step of cold rolling.

[0179] When using batch-type heat treatment equipment, the high heat treatment temperature during cold rolling annealing can cause adhesion between materials. To solve this, ceramic coatings such as MgO coatings capable of withstanding high temperatures are applied to the plates, or a spacer or ceramic powder is applied between the plates, and then coiling is performed to prevent adhesion between materials during the final heat treatment.

[0180] In this case, for ceramic coating, the final coating process can be performed immediately after cold rolling annealing; however, if a spacing agent or powder is applied, an additional process to remove or recover the spacing agent or powder must be performed before the final coating process is carried out after cold rolling annealing.

[0181] Subsequently, the method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may perform a cold rolling annealing step. The cold rolling annealing step may be performed using a batch-type heat treatment facility and may be performed at an appropriate temperature to improve magnetic and mechanical properties.

[0182] Here, the appropriate temperature may be a temperature such that the average grain size of the final non-oriented electrical steel sheet is 0.2 mm or more, and the cold rolling annealing heat treatment temperature according to the present invention may be 900°C or higher and less than 1300°C.

[0183] If the cold rolling annealing temperature is below 900°C, grains with the {001} orientation, which is advantageous for magnetic properties, cannot grow sufficiently, and thus the magnetic properties may be inferior. On the other hand, if the cold rolling annealing temperature exceeds 1300°C, grains other than those with the {001} orientation may grow together, or process problems may occur due to the high temperature. In addition, excessive heat treatment increases heat treatment costs and may lead to problems such as increased production costs.

[0184] At this time, cold rolling annealing can be performed for 5 hours or more within the temperature range described above. There is no specific upper limit on the heat treatment time during the cold rolling annealing stage. If the cold rolling annealing heat treatment time is less than 5 hours, crystal grains with {001} orientations favorable for magnetic properties may not grow sufficiently, and as a result, it may be difficult to improve magnetic properties.

[0185] When performing a cold rolling annealing step at a temperature of 900°C or higher and 1300°C or lower and a heat treatment of 5 hours or more as described above, a slab having the alloy composition described above can promote the development of CSL grain boundaries that do not hinder magnetic domain movement. The development of CSL grain boundaries that do not hinder magnetic domain movement means the development of orientations favorable to magnetic properties, and may mean that the magnetic properties of the non-oriented electrical steel sheet according to one embodiment disclosed in the present invention are excellent.

[0186] More specifically, the non-oriented electrical steel sheet of the present invention, which has undergone the cold rolling annealing step described above, may have a value greater than or equal to a certain value of the following Equation 3.

[0187] [Equation 3]

[0188]

[0189] In Equation 3, ∑5, ∑9, ∑11, ∑3, and ∑7 are the ∑5-type grain boundary length ratio, ∑9-type grain boundary length ratio, ∑11-type grain boundary length ratio, ∑3-type grain boundary length ratio, and ∑7-type grain boundary length ratio, respectively, of the total CSL grain boundary length.

[0190] The lower limit of Equation 3 may be 1.9 or higher, 2 or higher, 3 or higher, 4 or higher, 5 or higher, 6 or higher, 7 or higher, or 8 or higher. The upper limit is not specifically limited. An explanation regarding this, more specifically a detailed explanation of ∑3, ∑5, ∑7, ∑9, and ∑11, is as described in the non-oriented electrical steel sheet disclosed in the present invention described above.

[0191] In addition, the heating rate up to the above-mentioned temperature range may be 0.1℃ / min or higher, and the cooling rate after heat treatment may be 0.1℃ / min or lower.

[0192] The cold rolling annealing step of the present invention can be performed in a reducing atmosphere. More specifically, it can be performed under mixed atmosphere conditions including hydrogen (H2). Here, under mixed atmosphere conditions, the remainder excluding hydrogen (H2) may be argon (Ar) and / or nitrogen (N2).

[0193] When cold rolling annealing is performed in a reducing atmosphere, the formed MnS reacts with hydrogen (H2) in the atmosphere, so that manganese (Mn) is dissolved in the steel and sulfur (S) vaporizes in the form of H2S and is absorbed into the atmosphere. At this time, the surface energy of grains with orientations favorable for magnetic properties decreases, causing grains with orientations favorable for magnetic properties to grow. As a result, the fraction of grains with orientations favorable for magnetic properties increases, thereby improving magnetic properties.

[0194] In addition, when cold rolling annealing is performed under mixed atmosphere conditions, oxidation and nitriding of the steel sheet surface can be prevented, and the surface condition of the non-oriented electrical steel sheet becomes smoother, thereby improving surface quality.

[0195] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may further include a coating step after the cold rolling and annealing step. The coating step may be performed to ensure the insulation properties and improve the punchability of the non-oriented electrical steel sheet, and may refer to forming an insulating film on the surface of the cold-rolled steel sheet that has undergone the cold rolling and annealing step. The coating step may be performed using a process known in the art.

[0196] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may further include a laser scribing step after a coating step. Laser scribing may be performed to refine the magnetic domains of a non-oriented electrical steel sheet that has undergone cold rolling, annealing, or coating. At this time, the laser scribing pattern spacing is 0.1 mm or more, and while the applied energy is not particularly limited, it is preferable to set it considering the process conditions.

[0197]

[0198] A non-oriented electrical steel sheet manufactured by the method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention has an alloy composition and texture characteristics favorable to magnetic properties, thereby enabling the securing of excellent magnetic properties intended by the present invention.

[0199] More specifically, by satisfying the alloy composition and manufacturing process according to the present invention and securing a CSL grain boundary formation ratio favorable for magnetic properties, excellent magnetic properties intended by the present invention can be secured.

[0200] Here, excellent magnetic properties refer to iron loss (W 10 / 400 ) It may be 12.5W / kg or less.

[0201]

[0202] The structure and operation of the present invention will be explained below through Experimental Example 1 and Experimental Example 2. However, this is presented as an example to aid in understanding the present invention, and the present invention is not limited by this.

[0203]

[0204] (Method for measuring the physical properties of non-oriented electrical steel specimens)

[0205] 1. CSL grain boundary

[0206] A 10 mm × 10 mm specimen was taken from a non-oriented electrical steel sheet. Subsequently, the specimen was mirror-polished by reducing its thickness via chemical polishing on the rolling plane (ND plane, Normal direction plane) so that the observation surface was positioned at a thickness equivalent to 1 / 4 of the original thickness. Electron backscatter diffraction (EBSD) measurements were performed on the mirror-polished observation surface to obtain CSL grain boundary data. At this time, the step size was 1 µm and the measurement area was 100 mm. 2 The above was done. The measured data was analyzed using the analysis software TSL OIM to quantify the CSL grain boundary data.

[0207]

[0208] 2. Thickness of the specimen

[0209] The thickness of the specimen was measured using a micrometer. When measuring the thickness of the specimen using a micrometer, the thickness of the steel plate was measured at 20mm intervals, starting from the edge point 20mm away. Subsequently, the average value of the steel plate thickness measured at the measurement points was calculated, and the calculated average value was used as the thickness of the steel plate.

[0210]

[0211] 3. Iron loss

[0212] A measurement specimen was taken from a non-oriented electrical steel sheet specimen, and iron loss (W) was calculated using the Epstein frame test according to the international standard IEC 60404-2. 10 / 400 ) was measured. If necessary, the measurement can be performed using a Single sheet test measuring instrument according to the international standard IEC 60404-2, and the specimen for the Single sheet test measuring instrument may be any one of the sizes of 30mm×30mm, 30mm×50mm, 60mm×60mm, and 500mm×500mm.

[0213]

[0214] (Preparation and Evaluation of Non-Oriented Electrical Steel Specimens)

[0215] Experimental Example 1

[0216] In the following, through Experimental Example 1 of the present invention, the alloy composition of the non-oriented electrical steel sheet disclosed in this specification and Equations 1 to 3 were confirmed.

[0217] The non-oriented electrical steel sheet specimen contains the alloy components listed in Table 1 below, and the remainder other than the alloy components listed in Table 1 below contains iron (Fe).

[0218] In Table 1 below, the units for silicon (Si) and manganese (Mn) content are 'weight%', and the units for sulfur (S), yttrium (Y), carbon (C), nitrogen (N), aluminum (Al), and titanium (Ti) content are 'ppm'.

[0219] Steel typeSiMnSYCNAlTiA12.240.121248648439061A22.410.94876925468565A32.540.691098749394929A42.640.06397442486555A52.731. 38184748223280A62.960.561752124408089A73.20.53566627155549A83.260.83175624332923A93.290.771752426448327A103.30.76 131817232521A113.350.28502118212120A123.410.67324627152827A133.480.03892619182051A143.510.71442726453298A153.621 .09518518394958A161.920.02782233167849A172.010.05514227372453A183.771.211985744305292A193.920.721027349201678A202 .570.342134735292128A213.360.782068831249918A223.31113611243248037A233.290.743411733417765A243.440.4923711745152 469A253.170.431878634415677A263.210.24862554331411A272.540.731598261306859A283.190.86834248571714A293.240.9139594 6627091A302.450.811036851562459A313.30.651974058511311A322.520.418324273412178A332.740.397650151211286A342.60.02 14417432235101A352.90.6210576111493109A362.690.631274128101104A373.170.65114861614116104A383.260.4729384732107131

[0220] Experimental Example 1 was prepared by the following method.

[0221] A slab having the alloy composition according to Table 1 above was manufactured, reheated at 1130°C, and then hot rolling was performed under conditions of a finish rolling temperature of 880°C and a coiling temperature of 580°C. Subsequently, hot rolling annealing was performed at 1000°C for 100 seconds, and after the hot rolling annealing was completed, a pickling step was performed to remove the oxide layer. Afterward, cold rolling was performed to manufacture a cold-rolled steel sheet with a thickness of 0.2 mm. Cold rolling annealing was performed using a batch-type heat treatment facility, and heat treatment was carried out at 1150°C for 12 hours. Subsequently, a final coating was performed to manufacture a specimen of a non-oriented electrical steel sheet.

[0222] Other process conditions not described in the above paragraph were controlled as control variables and were similarly controlled within the range described in the method for manufacturing non-oriented electrical steel sheets according to one embodiment of the present invention.

[0223] For Experimental Example 1 prepared by the above-described method, the CSL grain boundary fraction and iron loss (W 10 / 400 The values ​​were measured and shown in Table 2 below.

[0224] In Table 2 below, the unit of 'Si+Mn' is 'weight%', and iron loss (W 10 / 400 The unit of ) is 'W / kg'.

[0225] Steel grade Si+Mn type 1 type 2 type 3W 10 / 400A12.361.480.396.7912.41A23.351.130.57.7711.87A33.231.420.217.7711.54A42.70.940.32.411.17A54.110.560.265.5810.97A63.521.090.587.3710.84A73.730.940.537.5810.74A84.090.650.218.0410.25A94.061.120.438.169.95A104.060.250.26 8.349.91A113.630.460.238.669.76A124.080.620.277.2510.34A133.510.710.338.459.84A144.220.490.328.39.79A154.711.110.414.810.14A161.940.610.596.8113.17A172.060.680.227.1712.74A184.981.560.36--A194.641.240.19--A202.911.540. 151.4813.29A214.141.910.591.0812.66A224.311.80.420.9712.62A234.031.340.441.1812.91A243.932.360.240.912.58A253.61.80.361.3413.12A263.450.680.060.413.05A273.271.620.30.3213.32A284.050.840.070.5813.01A294.150.790.310.741 2.99A303.261.20.147.5413.19A313.951.390.050.0712.75A322.930.660.790.5313.74A333.130.881.650.4613.35A342.620.890.340.1713.76A353.521.291.710.5813.14A363.290.430.620.2313.24A373.821.431.610.0312.98A383.730.530.60.2312.88

[0226] Referring to Tables 1 and 2, steel grades A1 to A15 satisfy the alloy composition range according to one embodiment of the present invention, the sum of the silicon (Si) and manganese (Mn) content is 2.1 wt% or more and 4.8 wt% or less, and the values ​​of Equation 1 and Equation 2 satisfy the above-described range. In addition, for steel grades A1 to A15, it can be confirmed that Equation 3 satisfies the above-described range by forming a CSL grain boundary ratio favorable for magnetic properties. As a result, it can be confirmed that steel grades A1 to A15 can secure excellent magnetic properties intended in the present invention.

[0227]

[0228] Referring further to Tables 1 and 2, it can be seen that steel grades A16 to A19 do not satisfy the silicon (Si) content according to one embodiment of the present invention and / or the sum of the silicon (Si) and manganese (Mn) content according to the present invention. At this time, it can be seen that steel grades A16 to A19 cannot secure the excellent magnetic properties intended in the present invention.

[0229] More specifically, steel grade A16 is a steel grade in which the sum of silicon (Si) content and manganese (Mn) content falls short of the lower limit described above, and as the increase in resistivity is insufficient and iron loss is inferior, it can be confirmed that the excellent magnetic properties intended in the present invention cannot be secured.

[0230] Steel grade A17 satisfies the silicon (Si) and manganese (Mn) content according to the present invention, but the sum of the silicon (Si) and manganese (Mn) content falls short of the lower limit described above, so it can be confirmed that the excellent magnetic properties intended by the present invention cannot be secured due to the small increase in resistivity.

[0231] Steel grade A18 satisfied the silicon (Si) and manganese (Mn) content according to the present invention, but the sum of the silicon (Si) and manganese (Mn) content exceeded the upper limit described above, and grain boundary segregation and regular phases were formed, causing slab breakage and cracks during the manufacturing process.

[0232] Steel grade A19 is a steel grade that exceeds the upper limit of silicon (Si) content according to the present invention, and as the silicon (Si) content is excessive and the brittleness of the steel increases, plate fracture occurs during cold rolling.

[0233]

[0234] Referring to Tables 1 and 2, steel grades A20 to A25 are steel grades that do not satisfy the sulfur (S) content, yttrium (Y) content, and / or Formula 1 according to the present invention. At this time, it can be confirmed that steel grades A20 to A25 cannot secure the excellent magnetic properties intended in the present invention.

[0235] More specifically, steel grade A20 is a steel grade that exceeds the upper limit of sulfur (S) content according to the present invention. At this time, it can be confirmed that Equation 3 is not satisfied because segregation occurs due to the excessive sulfur (S) content, preventing the growth of orientations favorable for magnetic properties and preventing the development of CSL grain boundaries favorable for magnetic properties. As a result, it can be confirmed that steel grade A20 cannot secure the excellent magnetic properties intended in the present invention.

[0236] Steel grade A21 is a steel grade in which the sulfur (S) content and Equation 1 according to the present invention each exceed the upper limits described above. As a result, a large amount of segregation occurs, and the surface energy of grains having an orientation favorable to magnetic properties becomes higher than the surface energy of grains having an orientation unfavorable to magnetic properties, thereby causing grains having an orientation unfavorable to magnetic properties to develop. Furthermore, it can be confirmed that Equation 3 is not satisfied. Consequently, it can be confirmed that steel grade A21 cannot secure the excellent magnetic properties intended in the present invention.

[0237] Steel grade A22 is a steel grade in which the yttrium (Y) content and Equation 1 according to the present invention exceed the upper limit described above. In this case, a large amount of segregation occurs, and the surface energy of grains having an orientation favorable to magnetic properties becomes higher than the surface energy of grains having an orientation unfavorable to magnetic properties, thereby allowing grains having an orientation unfavorable to magnetic properties to develop. At this time, CSL grain boundaries unfavorable to magnetic properties develop, and Equation 3 may not be satisfied. As a result, it can be confirmed that steel grade A22 cannot secure the excellent magnetic properties intended in the present invention.

[0238] Steel grade A23 is a steel grade that exceeds the upper limit of the yttrium (Y) content of the present invention. The excessive yttrium (Y) content promotes the growth of crystal grains having orientations unfavorable to magnetic properties, thereby developing CSL grain boundaries unfavorable to magnetic properties and failing to satisfy Equation 3. As a result, it can be confirmed that steel grade A23 cannot secure the excellent magnetic properties intended in the present invention.

[0239] Steel grade A24 exceeds the upper limit of sulfur (S) and yttrium (Y) content according to the present invention, and is a steel grade in which Equation 1 exceeds the upper limit described above. In this case, a large amount of segregation occurs, and crystal grains having orientations unfavorable to magnetic properties may develop. At this time, CSL grain boundaries unfavorable to magnetic properties develop, and Equation 3 may not be satisfied. As a result, it can be confirmed that steel grade A24 cannot secure the excellent magnetic properties intended in the present invention.

[0240] Steel grade A25 satisfies the alloy composition according to one embodiment of the present invention, but is a steel grade that does not satisfy Equation 1 because it exceeds the upper limit of Equation 1. In this case, segregation by sulfur (S) and yttrium (Y) occurs, resulting in the development of crystal grains with orientations unfavorable to magnetic properties and the development of CSL grain boundaries that hinder the movement of magnetic domains, which may result in failure to satisfy Equation 3. Consequently, it can be confirmed that steel grade A25 cannot secure the excellent magnetic properties intended in the present invention.

[0241]

[0242] Referring to Tables 1 and 2, steel grades A26 to A38 are steel grades that do not satisfy any of the carbon (C) content, nitrogen (N) content, aluminum (Al) content, titanium (Ti) content, and Equation 2 according to the present invention. In this case, it can be confirmed that the excellent magnetic properties intended by the present invention cannot be secured.

[0243] More specifically, steel grades A26, A28, and A31 are steel grades in which the upper limit of carbon (C) and / or nitrogen (N) content according to the present invention is exceeded, and the value of Equation 2 falls short of the lower limit described above. In this case, magnetic properties may be degraded as a large amount of carbides and nitrides are formed. As a result, it can be confirmed that steel grades A26, A28, and A31 develop CSL grain boundaries that are unfavorable to magnetic properties, fail to satisfy Equation 3, and cannot secure the excellent magnetic properties intended by the present invention.

[0244] Steel grades A27, A29, and A30 are steel grades that exceed the upper limit of carbon (C) and / or nitrogen (N) content according to the present invention. In this case, a large amount of fine carbides and / or nitrides are formed, and the formed carbides and / or nitrides can increase iron loss by hindering the movement of magnetic domains. As a result, it can be confirmed that A27, A29, and A30 cannot secure the excellent magnetic properties intended by the present invention.

[0245] Steel grades A32, A34, A36, and A38 are steel grades that exceed the upper limit of aluminum (Al) and / or titanium (Ti) content according to the present invention. In this case, a large amount of fine precipitates are formed, and the formed fine precipitates inhibit grain growth and hinder the movement of magnetic domains, thereby degrading magnetic properties. In this case, it can be confirmed that A32, A34, A36, and A38 do not satisfy Equation 3 for the CSL grain boundary formation ratio, and thus cannot secure the excellent magnetic properties intended in the present invention.

[0246] Steel grades A33, A35, and A37 are steel grades in which the upper limit of the aluminum (Al) and / or titanium (Ti) content according to the present invention is exceeded, and the value of Equation 2 exceeds the upper limit described above. In this case, the formation of aluminum and titanium precipitates is promoted, and as a large amount of precipitates are formed, the magnetic properties may be degraded. As a result, it can be confirmed that steel grades A33, A35, and A37 cannot secure the excellent magnetic properties intended in the present invention.

[0247] Through Experimental Example 1, it was possible to confirm the alloy composition of the present invention in relation to Equations 1 to 3. More specifically, through Experimental Example 1, it was confirmed that in the case of a steel grade satisfying the content of alloy elements according to one embodiment of the present invention, Equation 1 and Equation 2, Equation 3 can be secured, and in this case, excellent magnetic properties can be secured.

[0248]

[0249] Experimental Example 2

[0250] In the following, through Experimental Example 2 of the present invention, the cold rolling annealing temperature of the non-oriented electrical steel sheet disclosed in this specification and Equation 3 were confirmed.

[0251] The non-oriented electrical steel sheet specimen contains the alloy components listed in Table 3 below, and the remainder other than the alloy components listed in Table 3 below contains iron (Fe).

[0252] In Table 3 below, the units for silicon (Si) and manganese (Mn) content are 'weight%', and the units for sulfur (S), yttrium (Y), carbon (C), nitrogen (N), aluminum (Al), and titanium (Ti) content are 'ppm'.

[0253] Composition SiMnSYCNAlTiB13.300.76131817232521B23.350.28502118212120

[0254] Experimental Example 2 was prepared by the following method.

[0255] A slab having the alloy composition according to Table 3 above was manufactured, reheated at 1130°C, and then hot rolling was performed under conditions of a finish rolling temperature of 880°C and a coiling temperature of 580°C. Subsequently, hot rolling annealing was performed at 1000°C for 100 seconds, and after the hot rolling annealing was completed, a pickling step was performed to remove the oxide layer. Afterward, cold rolling was performed to manufacture a cold-rolled steel sheet with a thickness of 0.2 mm. Cold rolling annealing was performed using a batch heat treatment facility, and heat treatment was carried out for 12 hours at the temperatures listed in Table 4 below. Subsequently, a final coating was performed to manufacture a specimen of a non-oriented electrical steel sheet.

[0256] Other process conditions not described in the above paragraph were controlled as control variables and were similarly controlled within the range described in the method for manufacturing non-oriented electrical steel sheets according to one embodiment of the present invention.

[0257] For Experimental Example 2 prepared by the above-described method, the CSL grain boundary fraction and iron loss (W 10 / 400 The values ​​were measured and shown in Table 2 below.

[0258] In Table 2 below, the unit of the cold rolling annealing temperature is '°C', and the iron loss (W 10 / 400 The unit of ) is 'W / kg'.

[0259] No. Composition Si+Mn Formula 1 Formula 2 Cold Rolling Annealing Temperature Formula 3 W 10 / 4001B14.050.250.268000.0512.742B14.050.250.268500.2712.653B14.050.250.269002.011 1.174B14.050.250.269502.4810.855B14.050.250.2610004.2410.546B14.050.250.26105 06.1410.377B14.050.250.2611007.5910.248B14.050.250.2611508.349.919B14.050.250 .2612008.449.8810B14.050.250.2612508.2810.1411B14.050.250.2613007.9710.1812B2 3.260.460.238000.0212.7113B23.260.460.238500.2312.6014B23.260.460.239002.0411 .1215B23.260.460.239502.6310.7316B23.260.460.2310004.5010.5517B23.260.460.231 0506.5110.2118B23.260.460.2311007.6110.1319B23.260.460.2311508.669.7620B23.26 0.460.2312008.719.6821B23.260.460.2312508.1710.0122B23.260.460.2313007.8110.34

[0260] Referring to Tables 3 and 4, steels No. 3 to 11 and steels No. 14 to 22 satisfy the alloy composition range according to one embodiment of the present invention, the sum of the silicon (Si) and manganese (Mn) content is 2.1 wt% or more and 4.8 wt% or less, the values ​​of each of Equation 1 and Equation 2 satisfy the ranges described above, and the cold rolling annealing temperature is 900°C or more and 1300°C or less.

[0261] At this time, crystal grains having an orientation favorable to magnetic properties grow, and accordingly, the development of CSL grain boundaries favorable to magnetic properties is promoted, thereby forming a ratio of CSL grain boundaries favorable to magnetic properties. As a result, it can be confirmed that the values ​​of Equation 3 for steels No. 3 to No. 11 and steels No. 14 to No. 22 satisfy the above-described range, and that excellent magnetic properties intended in the present invention can be secured.

[0262] On the other hand, steels No. 1, No. 2, No. 12, and No. 13 satisfy the alloy composition range and the sum of silicon (Si) and manganese (Mn) content according to one embodiment of the present invention, and the values ​​of Equation 1 and Equation 2 satisfy the range described above, but do not satisfy the cold rolling annealing temperature range according to the present invention.

[0263] At this time, the cold rolling annealing temperature is insufficient, so the development of texture and CSL grain boundaries favorable for magnetic properties may not occur. As a result, it can be confirmed that the values ​​of Equation 3 for steels No. 1, No. 2, No. 12, and No. 13 do not meet the lower limit described above, and it can be confirmed that the excellent magnetic properties intended in the present invention cannot be secured.

[0264] It was confirmed through Experimental Example 2 in relation to the cold rolling annealing temperature and Equation 3 of the present invention. More specifically, through Experimental Example 2, it was confirmed that when the cold rolling annealing temperature range according to one embodiment of the present invention is satisfied, a CSL grain boundary formation ratio favorable for magnetic properties can be secured, and in this case, excellent magnetic properties can be secured.

[0265]

[0266] As described above, preferred embodiments according to the present invention have been examined. It is obvious to those skilled in the art that, in addition to the embodiments described above, the present invention may be embodied in other specific forms without departing from its spirit or scope. Therefore, the embodiments described above should be regarded as illustrative rather than restrictive, and accordingly, the present invention is not limited to the description above but may be modified within the scope of the appended claims and their equivalents.

Claims

1. Containing silicon (Si) 2.0 wt% or more and 3.8 wt% or less, manganese (Mn) 0.01 wt% or more and 1.5 wt% or less, sulfur (S) greater than 0 wt% and less than 0.02 wt%, yttrium (Y) greater than 0 wt% and less than 0.01 wt%, aluminum (Al) greater than 0 wt% and less than 0.01 wt%, titanium (Ti) greater than 0 wt% and less than 0.01 wt%, carbon (C) greater than 0 wt% and less than 0.005 wt%, and nitrogen (N) greater than 0 wt% and less than 0.005 wt%, and the remainder being iron (Fe) and other unavoidable impurities, The sum of the silicon (Si) and manganese (Mn) content is 2.1 wt% or more and 4.8 wt% or less, and Non-oriented electrical steel sheet having the following Formula 1 of 1.75 or less: [Equation 1] In Equation 1, [S] is the sulfur (S) content in ppm units, and [Y] is the yttrium (Y) content in ppm units.

2. In Paragraph 1, Non-oriented electrical steel sheet in which the following formula 2 is within the range of 0.1 to 1.6: [Equation 2] In Equation 2, [Al], [Ti], [C], and [N] are the contents of aluminum (Al), titanium (Ti), carbon (C), and nitrogen (N), respectively, in ppm units.

3. In Paragraph 1, Includes CSL grain boundaries (Coincidence Site Lattice Boundary), and The above CSL grain boundary is, Non-oriented electrical steel sheet including ∑3 type grain boundaries, ∑5 type grain boundaries, ∑7 type grain boundaries, ∑9 type grain boundaries, and ∑11 type grain boundaries.

4. In Paragraph 3, Non-oriented electrical steel sheet having the following Equation 3 of 1.9 or higher: [Equation 3] In Equation 3, ∑5, ∑9, ∑11, ∑3, and ∑7 are the ∑5-type grain boundary length ratio, ∑9-type grain boundary length ratio, ∑11-type grain boundary length ratio, ∑3-type grain boundary length ratio, and ∑7-type grain boundary length ratio, respectively, of the total CSL grain boundary length.

5. In Paragraph 1, Iron loss (W 10 / 400 Non-oriented electrical steel sheet with a ) of 12.5 W / kg or less.

6. Step of hot rolling the slab after reheating; Hot rolling and annealing step; cold rolling step; and It includes a step of cold rolling annealing in a temperature range of 900℃ or higher and 1300℃ or lower, and The above slab is, Containing silicon (Si) 2.0 wt% or more and 3.8 wt% or less, manganese (Mn) 0.01 wt% or more and 1.5 wt% or less, sulfur (S) greater than 0 wt% and less than 0.02 wt%, yttrium (Y) greater than 0 wt% and less than 0.01 wt%, aluminum (Al) greater than 0 wt% and less than 0.01 wt%, titanium (Ti) greater than 0 wt% and less than 0.01 wt%, carbon (C) greater than 0 wt% and less than 0.005 wt%, and nitrogen (N) greater than 0 wt% and less than 0.005 wt%, and the remainder being iron (Fe) and other unavoidable impurities, The sum of the silicon (Si) and manganese (Mn) content is 2.1 wt% or more and 4.8 wt% or less, and Method for manufacturing non-oriented electrical steel sheets in which the following Formula 1 is 1.75 or less: [Equation 1] In Equation 1, [S] is the sulfur (S) content in ppm units, and [Y] is the yttrium (Y) content in ppm units.

7. In Paragraph 6, The above cold rolling annealing step is, A method for manufacturing non-oriented electrical steel sheets by performing heat treatment for 5 hours or more in a temperature range of 900℃ or higher and 1300℃ or lower.

8. In Paragraph 6, The above slab is, A method for manufacturing non-oriented electrical steel sheets, wherein the following formula 2 is within the range of 0.1 to 1.6: [Equation 2] In Equation 2, [Al], [Ti], [C], and [N] are the contents of aluminum (Al), titanium (Ti), carbon (C), and nitrogen (N), respectively, in ppm units.

9. In Paragraph 6, Non-oriented electrical steel sheets that have undergone the cold rolling and annealing step are, Includes CSL grain boundaries (Coincidence Site Lattice Boundary), and The above CSL grain boundary is, A method for manufacturing a non-oriented electrical steel sheet comprising ∑3 type grain boundaries, ∑5 type grain boundaries, ∑7 type grain boundaries, ∑9 type grain boundaries, and ∑11 type grain boundaries.

10. In Paragraph 9, The above CSL grain boundary is, A method for manufacturing non-oriented electrical steel sheets in which the formation ratio of Formula 3 below is 1.9 or higher: [Equation 3] In Equation 3, ∑5, ∑9, ∑11, ∑3, and ∑7 are the ∑5-type grain boundary length ratio, ∑9-type grain boundary length ratio, ∑11-type grain boundary length ratio, ∑3-type grain boundary length ratio, and ∑7-type grain boundary length ratio, respectively, of the total CSL grain boundary length.

11. In Paragraph 6, Non-oriented electrical steel sheets that have undergone cold-rolled annealing are, Iron loss (W 10 / 400 A method for manufacturing non-oriented electrical steel sheets in which ) is 12.5 W / kg or less.

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