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 contains 2.8-3.7 wt% of silicon (Si), 0.8-1.5 wt% of aluminum (Al), 0.2-0.4 wt% of manganese (Mn), 0.02-0.07 wt% of chromium (Cr), 0.02-0.07 wt% of copper (Cu), 0.02-0.07 wt% of nickel (Ni), and more than 0 wt% and 0.002 wt% or less of niobium (Nb), with the remainder comprising iron (Fe) and other inevitable impurities, and thus has excellent magnetic properties.

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] Recently, in accordance with global policies to reduce carbon dioxide emissions and prevent global warming, conventional internal combustion engine vehicles are being rapidly replaced by eco-friendly vehicles such as hybrid, electric, and hydrogen cars. Eco-friendly vehicles utilize electric motors to generate the driving force required for the vehicle and can reduce environmental pollution by significantly decreasing the emission of harmful exhaust gases.

[0003] As interest in and demand for such eco-friendly vehicles increase, the demand for electric motors, which generate the driving force for the vehicle, is also rising. An electric motor is a device that uses electricity to generate the driving force required for a vehicle, and energy efficiency—the ability to operate for a longer period using the same amount of energy—is a crucial technical factor.

[0004] To increase the energy efficiency of such electric motors, it is essential to improve the magnetic performance of the non-oriented electrical steel sheets used as the core material. Non-oriented electrical steel is a material that possesses uniform magnetic properties in all directions regardless of the rolling direction; to enhance energy efficiency, iron loss must be reduced and magnetic flux density increased.

[0005] Iron loss and magnetic flux density are greatly influenced by the alloy composition of non-oriented electrical steel sheets, and in particular, the reduction of impurity elements is essential to achieve low iron loss and high magnetic flux density.

[0006] Conventionally, non-oriented electrical steel sheets were manufactured using slabs produced in blast furnaces to reduce impurities. However, manufacturing slabs in blast furnaces results in very high carbon and greenhouse gas emissions, which can cause environmental pollution. Consequently, research and development are currently underway to manufacture non-oriented electrical steel sheets using electric furnaces in order to solve the environmental pollution problems associated with the use of blast furnaces.

[0007] However, when slabs are manufactured using an electric furnace, a large amount of impurity elements may be included. Representative impurity elements include chromium (Cr), copper (Cu), and nickel (Ni), which are called tramp elements, and sulfur (S) and nitrogen (N) are also representative impurity elements. If the aforementioned impurity elements are present in large quantities, the magnetic properties of the final product, non-oriented electrical steel sheets, may be degraded.

[0008] Therefore, to improve the magnetic properties of non-oriented electrical steel sheets manufactured in electric furnaces, it is necessary to optimize alloying and impurity elements, 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. 10-1308722

[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 by controlling the alloy composition and the manufacturing process.

[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) 2.8 wt% or more and 3.7 wt% or less, aluminum (Al) 0.8 wt% or more and 1.5 wt% or less, manganese (Mn) 0.2 wt% or more and 0.4 wt% or less, chromium (Cr) 0.02 wt% or more and 0.07 wt% or less, copper (Cu) 0.02 wt% or more and 0.07 wt% or less, nickel (Ni) 0.02 wt% or more and 0.07 wt% or less, niobium (Nb) 0 wt% or more and 0.002 wt% or less, and the remainder being iron (Fe) and other unavoidable impurities.

[0015] In addition, it may further include carbon (C) greater than 0 wt% and less than or equal to 0.003 wt%, titanium (Ti) greater than 0 wt% and less than or equal to 0.003 wt%, sulfur (S) greater than 0 wt% and less than or equal to 0.005 wt%, nitrogen (N) greater than 0 wt% and less than or equal to 0.005 wt%, and phosphorus (P) greater than 0 wt% and less than or equal to 0.015 wt%.

[0016] In addition, the following Equation 1 can be satisfied.

[0017] [Equation 1]

[0018] [i(70, 0, 0) / i(23, 45, 45)] ≥ 0.8

[0019] In Equation 1, i(70, 0, 0) is the strength of the orientation distribution function of a grain with (φ1, φ, φ2) = (70±3, 0, 0) Euler angle (Bunge) orientation, and i(23, 45, 45) is the strength of the orientation distribution function of a grain with (φ1, φ, φ2) = (23±3, 45±5, 45±2) Euler angle (Bunge) orientation.

[0020] Also, i(70, 0, 0) may be 4.8 or greater and 6.5 or less.

[0021] Also, i(23, 45, 45) may be 5.3 or greater and 6.6 or less.

[0022] In addition, the number of CrN precipitates with a diameter of 10 nm or more per area (50 µm × 50 µm) may be 85 or fewer.

[0023] In addition, the number of NbN precipitates with a diameter of 10 nm or more per area (50 µm × 50 µm) may be 1 or more and 6 or less.

[0024] In addition, the average diameter of NbN precipitates per area (50㎛×50㎛) may be 130 nm or more and 227 nm or less.

[0025] Also, iron loss (W 10 / 400 ) may be 14.6 W / kg or less.

[0026] 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 and then hot rolling, hot rolling annealing, cold rolling, and cold rolling annealing.

[0027] At this time, the slab contains silicon (Si) 2.8 wt% or more and 3.7 wt% or less, aluminum (Al) 0.8 wt% or more and 1.5 wt% or less, manganese (Mn) 0.2 wt% or more and 0.4 wt% or less, chromium (Cr) 0.02 wt% or more and 0.07 wt% or less, copper (Cu) 0.02 wt% or more and 0.07 wt% or less, nickel (Ni) 0.02 wt% or more and 0.07 wt% or less, niobium (Nb) more than 0 wt% and 0.002 wt% or less, and the remainder being iron (Fe) and other unavoidable impurities.

[0028] In addition, the above cold rolling annealing step can be performed as a heat treatment in a temperature range of 800°C or higher and 1100°C or lower.

[0029] In addition, the slab may further contain carbon (C) greater than 0 wt% and less than or equal to 0.003 wt%, titanium (Ti) greater than 0 wt% and less than or equal to 0.003 wt%, sulfur (S) greater than 0 wt% and less than or equal to 0.005 wt%, nitrogen (N) greater than 0 wt% and less than or equal to 0.005 wt%, and phosphorus (P) greater than 0 wt% and less than or equal to 0.015 wt%.

[0030] In addition, the non-oriented electrical steel sheet that has undergone the above cold rolling and annealing step can satisfy Equation 1.

[0031] In addition, the non-oriented electrical steel sheet that has undergone the above cold rolling and annealing step may have i(70, 0, 0) of 4.8 or higher and 6.5 or lower.

[0032] In addition, the non-oriented electrical steel sheet that has undergone the above cold rolling and annealing step may have i(23, 45, 45) of 5.3 or higher and 6.6 or lower.

[0033] In addition, the non-oriented electrical steel sheet that has undergone the above cold rolling and annealing step has iron loss (W 10 / 400 ) may be 14.6 W / kg or less.

[0034] According to one embodiment of the present invention, by controlling the alloy composition and the heat treatment process to form a texture advantageous 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 realized.

[0035] 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.

[0036] Figure 1 is a photograph showing the texture and orientation distribution function of a non-oriented electrical steel sheet according to Example 1-3 of the experimental examples of the present invention.

[0037] Figure 2 is a photograph showing the texture and orientation distribution function of non-oriented electrical steel sheets according to Comparative Examples 1-7 among the experimental examples of the present invention.

[0038] 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.

[0039] Additionally, where 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] Unless otherwise specified, the notation 'A ~ B' for numerical values ​​A and B shall mean 'A or greater, 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.

[0044] Also, unless specifically noted otherwise, 1 ppm is 0.0001 wt%.

[0045]

[0046] Non-oriented electrical steel sheets

[0047] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises silicon (Si) 2.8 wt% or more and 3.7 wt% or less, aluminum (Al) 0.8 wt% or more and 1.5 wt% or less, manganese (Mn) 0.2 wt% or more and 0.4 wt% or less, chromium (Cr) 0.02 wt% or more and 0.07 wt% or less, copper (Cu) 0.02 wt% or more and 0.07 wt% or less, nickel (Ni) 0.02 wt% or more and 0.07 wt% or less, niobium (Nb) 0 wt% or more and 0.002 wt% or less, and the remainder being iron (Fe) and other unavoidable impurities.

[0048] 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.

[0049]

[0050] Silicon (Si)

[0051] Silicon (Si) is an element that increases the resistivity of steel and reduces iron loss, and is a major additive element in 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, the permeability and magnetic flux density may decrease. In addition, brittleness may increase as the silicon content increases. Therefore, it is necessary to appropriately control the silicon content.

[0052] If the silicon content is less than 2.8 weight%, the effect of reducing iron loss may be insufficient. On the other hand, if the silicon content exceeds 3.7 weight%, brittleness increases, and cracks or plate breakage may occur during cold rolling or stamping.

[0053] Accordingly, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain silicon in an amount of 2.8 weight% or more and 3.7 weight% or less.

[0054]

[0055] Aluminum (Al)

[0056] Aluminum (Al), along with silicon (Si), is an element that increases resistivity and reduces iron loss, and is a major additive element in electrical steel sheets. However, if an excessive amount of aluminum is added, it can combine with nitrogen (N) in the steel to form AlN particles. The formed AlN particles can impede the formation of a texture favorable for magnetic properties and impede domain wall movement, thereby degrading magnetic properties.

[0057] If the aluminum content is less than 0.8 weight%, the effect of reducing iron loss may be insufficient. On the other hand, if the aluminum content exceeds 1.5 weight%, the aforementioned problems may occur, cold rolling performance may be reduced, and magnetic flux density may be reduced.

[0058] Accordingly, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain aluminum in an amount of 0.8 weight% or more and 1.5 weight% or less.

[0059]

[0060] Manganese (Mn)

[0061] Manganese (Mn) is an element that improves magnetic properties by increasing resistivity and reducing iron loss, just like silicon (Si) and aluminum (Al). In addition, it can improve the fraction of textures that are favorable for magnetic properties. If the manganese content is less than 0.2 weight%, the above-mentioned effects cannot be obtained.

[0062] On the other hand, if the manganese content exceeds 0.4 wt%, it may combine with sulfur (S) in the steel to form coarse MnS precipitates. These precipitates can inhibit grain growth and hinder domain wall movement, thereby degrading magnetic properties. Additionally, if the formed precipitates grow coarsely, mechanical strength may decrease.

[0063] Accordingly, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain manganese in an amount of 0.2 weight% or more and 0.4 weight% or less.

[0064]

[0065] Chrome (Cr)

[0066] Chromium (Cr) is an inevitably added tramp element when producing non-oriented electrical steel sheets through electric furnaces. While chromium can increase the resistivity of steel and reduce iron loss, it can degrade magnetic properties by combining with nitrogen (N) and carbon (C) in the steel to form precipitates such as CrN and Cr7C3, which inhibit grain growth and hinder domain wall movement.

[0067] Furthermore, precipitates formed at grain boundaries can lead to the formation of a chromium-deficient layer around the precipitates near the grain boundaries. If a chromium-deficient layer is formed, the corrosion resistance effect of chromium is reduced, which can result in intergranular corrosion. Such intergranular corrosion can accelerate material fracture. For this reason, it is necessary to control the chromium content.

[0068] Accordingly, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain chromium in an amount greater than 0.02 weight% and less than or equal to 0.07 weight%. Preferably, the lower limit of the chromium content may be 0.0227 weight% or more, and the upper limit of the chromium may be 0.0645 weight% or less.

[0069]

[0070] Copper (Cu)

[0071] Copper (Cu), along with chromium (Cr), is one of the tramp elements inevitably added to non-oriented electrical steel sheets produced through electric furnaces. Due to its low solid solubility in steel, copper precipitates alone in the form of copper (Cu) or combines with sulfur (S) within the steel to form precipitates such as CuS. These precipitates can inhibit grain growth and hinder domain wall movement. As a result, iron loss increases, which can lead to a deterioration in magnetic properties.

[0072] Accordingly, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain copper of more than 0.02 weight% and less than or equal to 0.07 weight%. Preferably, the lower limit of the copper content may be 0.0274 weight% or more, and the upper limit of the copper content may be 0.065 weight% or less.

[0073]

[0074] Nickel (Ni)

[0075] Nickel (Ni) is one of the tramp elements that is inevitably added to non-oriented electrical steel sheets produced through an electric furnace, just like chromium (Cr) and copper (Cu). When nickel is added in small amounts, it can develop (100) and (110) orientations that are advantageous for magnetic properties. However, if it exceeds 0.07 weight%, it can refine the grain size and degrade magnetic properties.

[0076] Accordingly, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain nickel in an amount greater than 0.02 weight% and less than or equal to 0.07 weight%. Preferably, the lower limit of the nickel content may be 0.0264 weight% or more, and the upper limit of the nickel content may be 0.0682 weight% or less.

[0077]

[0078] The aforementioned chromium (Cr), copper (Cu), and nickel (Ni) are tramp elements that are inevitably added when manufacturing non-oriented electrical steel sheets in an electric furnace. These tramp elements generate a large amount of precipitates, which can degrade the magnetic properties of the final product. For example, if the content of chromium (Cr) and nitrogen (N) increases, fine CrNs with a diameter of 100 nm or less may precipitate within the steel, hindering grain growth due to the pinning effect. As a result, the magnetic properties may be degraded due to grain refinement. Additionally, fine CrNs may hinder domain wall movement, which can also degrade the magnetic properties.

[0079] In order to solve this problem, the present invention can prevent the formation of fine CrN by adding niobium (Nb) to form NbN instead of CrN at around 1000°C during hot rolling, hot rolling annealing, and cold rolling annealing. More specifically, it can prevent the deterioration of magnetic properties by forming coarse NbN with a diameter of 130 nm or more during the heat treatment process and suppressing the formation of a large amount of fine CrN with a diameter of 100 nm or less.

[0080] The content and role of niobium (Nb) according to one embodiment of the present invention will be explained in more detail below.

[0081]

[0082] Niobium (Nb)

[0083] As described above, when niobium (Nb) is added, magnetic properties can be improved by suppressing the precipitation of fine CrN by combining with nitrogen (N) in the steel. However, if the niobium (Nb) content exceeds 0.002 wt%, fine NbC and / or NbN may be precipitated by combining with carbon (C) and / or nitrogen (N) in the steel. These fine precipitates can impair magnetic properties by hindering domain wall movement during the magnetization process.

[0084] Accordingly, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain niobium in an amount greater than 0 wt% and less than or equal to 0.002 wt%. Preferably, the lower limit of the niobium content may be 0.0003 wt% or more, 0.0004 wt% or more, 0.0005 wt% or more, 0.0006 wt% or more, 0.0007 wt% or more, or 0.0008 wt% or more. Additionally, the upper limit of the preferred niobium content may be 0.0018 wt% or less.

[0085]

[0086] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include carbon (C) greater than 0 wt% and less than or equal to 0.003 wt%, titanium (Ti) greater than 0 wt% and less than or equal to 0.003 wt%, sulfur (S) greater than 0 wt% and less than or equal to 0.005 wt%, nitrogen (N) greater than 0 wt% and less than or equal to 0.005 wt%, and phosphorus (P) greater than 0 wt% and less than or equal to 0.015 wt%.

[0087] The roles and contents of each alloying element will be explained in detail below.

[0088]

[0089] Carbon (C)

[0090] When carbon (C) is added in excess, it can combine with titanium (Ti) and niobium (Nb) to form fine carbides. Fine carbides can reduce permeability and increase iron loss. Additionally, if the carbon (C) content exceeds 0.003 weight%, magnetic aging may occur, which can degrade magnetic properties.

[0091] 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 or equal to 0.003 weight%.

[0092]

[0093] Titanium (Ti)

[0094] Titanium (Ti) can combine with carbon (C) and nitrogen (N) in steel to form precipitates such as TiC and TiN. Since these formed precipitates can inhibit grain growth and impair magnetic properties, it is necessary to include them in as small a quantity as possible.

[0095] Accordingly, a non-oriented electrical steel sheet according to one embodiment of the present invention may contain titanium in an amount greater than 0 weight% and less than or equal to 0.003 weight%.

[0096]

[0097] Yellow (S)

[0098] Sulfur (S) is a grain boundary segregating element, so it is necessary to appropriately control its content. Furthermore, sulfur can increase iron loss by combining with elements such as manganese (Mn) and copper (Cu) to form precipitates. Additionally, these formed precipitates hinder grain growth, which can lead to a deterioration of magnetic properties due to grain refinement.

[0099] 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 or equal to 0.005 weight%.

[0100]

[0101] Nitrogen (N)

[0102] When the nitrogen (N) content exceeds 0.005 wt%, it can combine with aluminum (Al), titanium (Ti), and chromium (Cr) in the steel to form precipitates such as AlN, TiN, and CrN. These precipitates can impede domain wall movement and inhibit grain growth, thereby degrading magnetic properties.

[0103] 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 or equal to 0.005 weight%.

[0104]

[0105] Ph(P)

[0106] Phosphorus is a grain boundary segregation element, and if added in excess, problems such as inhibition of grain growth, deterioration of magnetic properties, and reduction of cold rolling performance may occur due to the segregation effect. Therefore, it is desirable to add as little as possible, and a non-oriented electrical steel sheet according to one embodiment of the present invention may contain phosphorus in an amount greater than 0 weight% and less than or equal to 0.015 weight%.

[0107]

[0108] In addition to the components of the steel described above, the remainder may contain Fe and unavoidable impurities. 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.

[0109] In one embodiment of the present invention, 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 present invention. If additional elements are included, they may be included to replace the remainder of Fe.

[0110]

[0111] A non-oriented electrical steel sheet according to one embodiment of the present invention satisfies the following Equation 1.

[0112] [Equation 1]

[0113] [i(70, 0, 0) / i(23, 45, 45)] ≥ 0.8

[0114] In Equation 1, i(70, 0, 0) is the strength of the orientation distribution function of a grain with (φ1, φ, φ2) = (70±3, 0, 0) Euler angle (Bunge) orientation, and i(23, 45, 45) is the strength of the orientation distribution function of a grain with (φ1, φ, φ2) = (23±3, 45±5, 45±2) Euler angle (Bunge) orientation.

[0115] At this time, the orientation distribution function (ODF) and the strength on the orientation distribution function were obtained through Electron Backscatter Diffraction (EBSD). Here, strength on the orientation distribution function refers to relative strength with the strength of a structure without any texture set to 1. The strength of a structure without texture can be obtained from steel in powder form. The method for measuring strength on the orientation distribution function is the method disclosed in "3. Orientation Distribution Function and Strength on Orientation Distribution Function" of the examples described below.

[0116] The above Equation 1 will be explained in more detail below.

[0117] As mentioned above, when tramp elements such as chromium (Cr), copper (Cu), and nickel (Ni) are added, fine precipitates may be formed. As a result, these fine precipitates can increase iron loss by hindering domain wall movement during the magnetization process. Furthermore, the development of orientations favorable for magnetic properties is suppressed by these fine precipitates, and crystal grains unfavorable to magnetic properties may develop.

[0118] For example, if chromium (Cr) reacts with nitrogen in the steel to form a large amount of fine CrN, an orientation unfavorable to magnetic properties may develop. On the other hand, if an appropriate amount of niobium (Nb) is added within the aforementioned range to suppress the formation of CrN, the development of an orientation unfavorable to magnetic properties is suppressed, thereby making it easier for an orientation favorable to magnetic properties to develop.

[0119] Here, an orientation unfavorable to magnetic properties may be the (φ1, φ, φ2) = (23±3, 45±5, 45±2) Euler angle (Bunge) orientation on the orientation distribution function, and an orientation favorable to magnetic properties may be the (φ1, φ, φ2) = (70±3, 0, 0) Euler angle (Bunge) orientation on the orientation distribution function. The above two orientations are representative special orientations that mainly appear during the manufacture of non-oriented electrical steel sheets and can affect the magnetic properties of the non-oriented electrical steel sheets.

[0120] With reference to FIGS. 1 and FIGS. 2, a more detailed explanation will be provided. FIGS. 1 is a photograph showing the texture and orientation distribution function of a non-oriented electrical steel sheet according to Example 1-3 of the experimental examples of the present invention, and FIGS. 2 is a photograph showing the texture and orientation distribution function of a non-oriented electrical steel sheet according to Comparative Example 1-7 of the experimental examples of the present invention.

[0121] In a non-oriented electrical steel sheet according to one embodiment of the present invention, as shown in FIG. 1, it can be confirmed that an orientation favorable to magnetic properties is developed compared to an orientation unfavorable to magnetic properties, and a texture favorable to magnetic properties is developed. This texture is an effect that occurs because niobium (Nb) suppresses the formation of fine CrN precipitates.

[0122] On the other hand, in a non-oriented electrical steel sheet that does not satisfy the alloy composition of the present invention, as shown in FIG. 2, it can be seen that an orientation unfavorable to magnetic properties has developed compared to an orientation favorable to magnetic properties, and a texture unfavorable to magnetic properties has developed. Here, the development of a texture unfavorable to magnetic properties is due to the fact that the niobium (Nb) content did not reach the lower limit mentioned above, and thus fine CrN precipitates were formed.

[0123] As seen above, if the alloy composition is controlled within the range disclosed in this specification, a texture advantageous for magnetic properties can be secured; however, if the alloy composition is not controlled within the range disclosed in this specification, it may be difficult to secure a texture advantageous for magnetic properties.

[0124] Thus, a non-oriented electrical steel sheet having an alloy composition according to one embodiment of the present invention can have excellent magnetic properties by developing an orientation favorable to magnetic properties. More specifically, it can satisfy Equation 1 above.

[0125] The left side of Equation 1 above is the ratio of the intensity of the orientation distribution function between an orientation favorable to magnetic properties and an orientation unfavorable to magnetic properties, and the higher the proportion of the corresponding orientation, the higher the intensity of the orientation distribution function.

[0126] In cases where the value of the left side of Equation 1 above does not reach the lower limit, fine precipitates are formed and orientations unfavorable to magnetic properties develop, which may lead to magnetic degradation. On the other hand, in cases where Equation 1 above is satisfied, niobium (Nb) is added to hinder the formation of fine precipitates, thereby suppressing the development of orientations unfavorable to magnetic properties. In such cases, orientations favorable to magnetic properties develop compared to orientations unfavorable to magnetic properties, and thus the magnetic properties can be improved.

[0127] At this time, in the non-oriented electrical steel sheet according to one embodiment of the present invention, i(70, 0, 0) may be 4.8 or higher and 6.5 or lower.

[0128] In addition, the non-oriented electrical steel sheet according to one embodiment of the present invention may have i (23, 45, 45) of 5.3 or more and 6.6 or less.

[0129] Thus, by securing an orientation favorable to magnetic properties, it is possible to possess excellent magnetic properties.

[0130]

[0131] As described above, in the present invention, the deterioration of magnetic properties can be prevented by controlling the alloy composition to suppress the formation of a large amount of fine precipitates. More specifically, by adding niobium (Nb) to suppress the formation of fine CrN and forming coarse NbN relative to CrN, the deterioration of magnetic properties can be prevented.

[0132] More specifically, when having an alloy composition according to one embodiment of the present invention, the number of CrN precipitates with a diameter of 10 nm or more within a unit area (50 μm × 50 μm) may be 85 or fewer.

[0133] In addition, the number of NbN precipitates with a diameter of 10 nm or more within a unit area (50 µm × 50 µm) may be 1 or more and 6 or less. At this time, the average diameter of the NbN precipitates per unit area (50 µm × 50 µm) may be 130 nm or more and 227 nm or less.

[0134] As a result, orientations favorable to magnetic properties develop compared to orientations unfavorable to magnetic properties, and superior magnetic properties can be obtained.

[0135]

[0136] A non-oriented electrical steel sheet according to one embodiment of the present invention can secure excellent magnetic properties by controlling the alloy composition as described above to suppress the formation of fine precipitates and suppressing the development of orientations unfavorable to magnetic properties.

[0137] More specifically, by adding niobium (Nb) to form NbN, the formation of fine CrN is suppressed, and the development of orientations unfavorable to magnetic properties is suppressed, thereby satisfying Equation 1 above and securing excellent magnetic properties.

[0138] As a result, iron loss (W 10 / 400 ) may be 14.6 W / kg or less.

[0139]

[0140] Method for manufacturing non-oriented electrical steel sheets

[0141] Hereinafter, a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention will be described in detail.

[0142] 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 and then hot rolling, hot rolling annealing, cold rolling, and cold rolling annealing.

[0143] At this time, the slab contains silicon (Si) 2.8 wt% or more and 3.7 wt% or less, aluminum (Al) 0.8 wt% or more and 1.5 wt% or less, manganese (Mn) 0.2 wt% or more and 0.4 wt% or less, chromium (Cr) 0.02 wt% or more and 0.07 wt% or less, copper (Cu) 0.02 wt% or more and 0.07 wt% or less, nickel (Ni) 0.02 wt% or more and 0.07 wt% or less, niobium (Nb) more than 0 wt% and 0.002 wt% or less, and the remainder being iron (Fe) and other unavoidable impurities.

[0144] In addition, it may further include carbon (C) greater than 0 wt% and less than or equal to 0.003 wt%, titanium (Ti) greater than 0 wt% and less than or equal to 0.003 wt%, sulfur (S) greater than 0 wt% and less than or equal to 0.005 wt%, nitrogen (N) greater than 0 wt% and less than or equal to 0.005 wt%, and phosphorus (P) greater than 0 wt% and less than or equal to 0.015 wt%.

[0145] As the content of the alloy components has been explained previously, a redundant explanation is omitted. Furthermore, since the content of the alloy components does not substantially change during the manufacturing process described below, the alloy composition of the steel and the alloy composition of the final product, the non-oriented electrical steel sheet, are substantially identical.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] At this time, if the reheating temperature is below 1000℃, 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.

[0150] Accordingly, the reheating process according to one embodiment of the present invention can be performed at a temperature of 1000°C or higher and 1250°C or lower.

[0151] 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.

[0152] 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 850°C and 900°C. If the finishing temperature is below 850°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.

[0153] 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 550°C or higher and 750°C or lower. If the coiling temperature is below 550°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 750°C, fine precipitates may be generated, which may increase iron loss.

[0154] The thickness of the hot-rolled steel sheet formed through the step of reheating the slab and then hot-rolling it is preferably 1.8 mm or more and 3.5 mm or less. If the thickness of the hot-rolled steel sheet is excessively thin, less than 1.8 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 3.5 mm, the cold-rolling reduction rate increases, and the fraction of textures unfavorable to magnetic properties increases, which may result in inferior magnetic properties.

[0155] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may perform a step of hot rolling and annealing after the step of reheating the slab and then hot rolling.

[0156] The hot-rolled annealing step may be performed to ensure microstructural uniformity of the hot-rolled steel. Accordingly, the hot-rolled annealing step may be a step of performing heat treatment at an appropriate temperature to promote the recrystallization of unrecrystallized grains so that uniform equiaxed grains can be obtained.

[0157] The hot rolling annealing temperature according to the present invention may be 900°C or higher and 1150°C or lower. If the hot rolling annealing temperature is less than 900°C, the elongated cast structure after hot rolling may remain, causing microstructural non-uniformity. On the other hand, if the hot rolling annealing temperature exceeds 1150°C, the grains may grow excessively, leading to severe grain size variation, and oxidation may occur, which may degrade the magnetic properties of the final product.

[0158] In addition, hot rolling annealing may include a step of heat treatment for a period of 30 seconds or more and 120 seconds or less to form an appropriate grain size under the above-described temperature conditions. At this time, the heating rate to the heat treatment temperature may be 20℃ / s or more, and the cooling rate after heat treatment may be 30℃ / s or more.

[0159] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may further include a pickling step between the hot-rolling annealing step and the cold-rolling step described later. Specifically, the pickling step refers to a step of supplying hydrochloric acid to a pickling tank in which a reaction with the steel sheet takes place, thereby removing the oxide layer formed on the surface of the steel sheet through a pickling solution. At this time, the pickling treatment may be performed using a process known in the relevant art.

[0160] Subsequently, a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may perform a cold rolling step. The cold rolling step may be a process of rolling a hot-rolled annealed steel sheet at a temperature below the recrystallization temperature to further reduce the thickness of the steel sheet.

[0161] More specifically, the process may involve rolling the 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 0.35 mm or less. At this time, the total reduction rate of cold rolling may be 70 to 95%.

[0162] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may perform a cold rolling annealing step after a cold rolling step. The cold rolling annealing may be performed at an appropriate temperature to improve magnetic and mechanical properties.

[0163] Here, the temperature suitable for performing cold rolling annealing may be a temperature of 800°C or higher and 1100°C or lower. If the cold rolling annealing temperature is below 800°C, the growth of the crystal grains is insufficient, and as a result of grain refinement, the magnetic properties may be degraded. On the other hand, if the cold rolling annealing temperature exceeds 1100°C, the magnetic and mechanical properties may be degraded due to excessive crystal grain growth.

[0164] In addition, during cold rolling annealing, heat treatment can be performed at the aforementioned temperature for a period of 30 seconds or more and 400 seconds or less. If the cold rolling annealing heat treatment time is less than 30 seconds, the heat treatment time is insufficient, and time for grain growth may not be secured; as a result, the grain size may be refined, and magnetic properties may be degraded. On the other hand, if the cold rolling annealing heat treatment time exceeds 400 seconds, iron loss may increase due to excessive grain growth.

[0165] At this time, the heating rate up to the above-mentioned temperature range may be 10℃ / s or more, and the cooling rate after heat treatment may be 20℃ / s or more.

[0166] In addition, to prevent oxidation and nitriding of the steel sheet surface during cold rolling annealing, heat treatment can be performed under mixed atmosphere conditions containing nitrogen (N2) and hydrogen (H2). Through this, the surface of the steel sheet can be made smoother, thereby improving the surface quality of the steel sheet.

[0167] 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.

[0168] A non-oriented electrical steel sheet according to one embodiment of the present invention has a texture advantageous for magnetic properties and can have excellent magnetic properties.

[0169] More specifically, when the method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention is satisfied, Equation 1 above can be satisfied. As a result, it can be confirmed that excellent magnetic properties are achieved by developing an orientation favorable to magnetic properties compared to an orientation unfavorable to magnetic properties.

[0170] At this time, i(70, 0, 0) may be 4.8 or greater and 6.5 or less, and i(23, 45, 45) may be 5.3 or greater and 6.6 or less.

[0171] In addition, when satisfying the method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention, excellent magnetic properties can be obtained. More specifically, iron loss (W 10 / 400 ) may be 14.6 W / kg or less.

[0172]

[0173] The structure and operation of the present invention will be explained below through experimental examples. However, these are presented as examples to aid in understanding the present invention and do not limit the invention.

[0174]

[0175] (Method for measuring the physical properties of non-oriented electrical steel specimens)

[0176] 1. Grain size

[0177] The size of the grains can be determined as follows. First, a 2cm × 2cm specimen for EBSD (Electron backscatter diffraction) measurement was prepared and measured so that the ND (Normal direction plane) of the non-oriented electrical steel specimen could be observed, and the area of ​​each grain was calculated using TSL OIM software, an analysis software for EBSD measurements.

[0178] Afterwards, the area of ​​the crystal grain obtained by the method described above was assumed to be a virtual circle with the same area, and the diameter of the virtual circle was determined as the crystal grain size.

[0179] At this time, at least 5,000 grain sizes were obtained using the method described above, and the average of the grain sizes was calculated and listed in Table 2 below.

[0180]

[0181] 2. Number and diameter of precipitates

[0182] 20×20mm on the surface of the non-oriented electrical steel sheet specimen 2 In a specimen of a certain size, any 50×50㎛ 2 Ten regions were observed using a Scanning Electron Microscope (SEM), and the number of precipitates with a diameter of 10 nm or more within the regions was measured.

[0183] In addition, the diameter of the precipitate may refer to the diameter of a virtual circle formed when the virtual circle has the same area as the observed precipitate.

[0184] In addition, the number and diameter of CrN and NbN were measured as follows. After qualitative analysis using SEM-EDS, CrN and NbN were quantitatively analyzed by analyzing the TEM diffraction pattern.

[0185] At this time, the SEM conditions for analyzing the number and diameter of precipitates are a voltage of 15 kV and a working distance (WD) of 10 mm.

[0186]

[0187] 3. Orientation distribution function and intensity on the orientation distribution function

[0188] The orientation distribution function (ODF) and the intensity of the orientation distribution function were obtained through Electron Backscatter Diffraction (EBSD).

[0189] More specifically, a 20×20 mm EBSD test specimen was prepared to observe the ND plane (Normal direction plane) of the steel plate, and EBSD analysis was performed with a step size of 3 µm. Subsequently, the orientation distribution function and the intensity of the orientation distribution function were derived using an OIM analysis program. At this time, the intensity of the orientation distribution function was derived at φ2 = 45°.

[0190] Other OIM analysis program setting conditions are as follows.

[0191] Grain tolerance angle = 5°

[0192] Minimum confidence index = 1°

[0193]

[0194] 4. Iron loss

[0195] Iron loss (W) of the non-oriented electrical steel sheet specimen of the present invention 10 / 400 ) was measured based on the test method specified in the IEC 60404-2 international standard and using the Epstein frame test method. At this time, the dimensions of the specimen were length (300±0.5)mm and width (30±0.2)mm.

[0196]

[0197] (Preparation and Evaluation of Non-Oriented Electrical Steel Specimens)

[0198] Through the embodiments and comparisons of the present invention, the alloy composition, the number and diameter of precipitates, and Equation 1 of the non-oriented electrical steel sheet disclosed in this specification were confirmed.

[0199] In Experimental Example 1, 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).

[0200] In Table 1 below, the units for silicon (Si), manganese (Mn), and aluminum (Al) content are weight%. Additionally, the units for chromium (Cr), copper (Cu), nickel (Nb), niobium (Nb), carbon (C), titanium (Ti), sulfur (S), nitrogen (N), and phosphorus (P) content are ppm.

[0201] Classification Alloy Composition SiAlMnCrCuNiNbCTiSNP Example 1-1 2.9 10.8 30.2 26 305 19392 15 1428 46 3685 Example 1-2 3.38 0.98 0.355 274 123728 207 1140 104 Example 1-3 3.66 1.15 0.30 4765 15435 18299 144975 Example 1-4 3.58 0.87 0.2922731526482811371680 Example 1-53.081.330.29645629661141320384267 Example 1-63.421.170.3364027437582126484257 Example 1-73.201.200.285614346821127164239111 Example 1-83.53 0.980.34338650466161612242491Comparative Example 1-13.070.920.43216444541161435356796Comparative Example 1-22.870.710.304222356562433131321113Comparative Example 1-33.621.480.23914640275102523314990Comparative Example 1 -42.941.000.39108630369381519405799 Comparative Example 1-53.641.430.231018289838828163641145 Comparative Example 1-63.221.500.35555546280462526154471 Comparative Example 1-73.241.130.2466963533802722291696

[0202] A slab having the alloy composition listed in Table 1 above was reheated to the temperature listed in Table 2 below, and then hot rolling was performed under conditions of a finishing temperature of 870°C and a coiling temperature of 600°C to produce a hot-rolled steel sheet. Afterwards, the hot-rolled steel sheet was annealed at 1000°C for 90 seconds and pickled.

[0203] Afterwards, cold rolling was performed to produce a cold-rolled steel sheet with a thickness of (0.25 ± 0.02) mm. At this time, the cold rolling reduction rate was controlled to 82%. Subsequently, the cold-rolled steel sheet was annealed for 220 seconds at the temperature listed in Table 2 below, and cold rolling annealing was performed in a mixed atmosphere of nitrogen (N2) and hydrogen (H2).

[0204] Other process conditions not listed in the paragraph above and Table 2 below 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.

[0205] For the examples and comparative examples prepared by the above-described method, the grain size, the number and size of precipitates, the intensity of the orientation distribution function, and the value of Equation 1 were measured, and the iron loss (W 10 / 400 ) was measured and shown in Table 2 below.

[0206] In Table 2 below, the unit of temperature is '°C', and the unit of grain size is '㎛'. Additionally, in Table 2 below, the number of precipitates refers to the number of precipitates with a minimum diameter of 10 nm or more, and the unit is 'pieces'. Furthermore, the unit of the average diameter of precipitates is 'nm'. Iron loss (W 10 / 400 The unit of ) is 'W / kg'.

[0207] Classification Reheating Temperature Cold Rolling Annealing Temperature Grain Size Number of Precipitates Precipitate Size i(70,0,0)i(23,45,45) Formula 1W 10 / 400CrNNbNCrNNbN Example 1-110501100137366371634.96.00.8214.0 Example 1-210501000122633281725.66.30.8913.8 Example 1-311001200171654651856.45.81.1012.4 Example 1-41200110014925 2311846.45.41.1911.9 Example 1-510501100138414432274.96.10.8014.3 Example 1-610501200164841721596.36.01.0513.1 Example 1-711001000113592241525.56.00.9213.5 Example 1-8120011 00140495481745.25.70.9112.7Comparative Example 1-1105012001281057721973.87.00.5416.2Comparative Example 1-210501200110789612244.76.10.7715.4Comparative Example 1-31050110099982521444.86.50.7415.1Comparative Example 1- 411001100103944281434.07.20.5616.6Comparative Example 1-510501100115923401664.66.40.7215.8Comparative Example 1-610501000936121211034.56.70.6714.8Comparative Example 1-71050100076148017-4.47.00.6315.3

[0208] Referring to Tables 1 and 2, it can be confirmed that in the case of Examples 1-1 to 1-8, which satisfy the alloy composition, slab reheating temperature, and cold rolling annealing temperature according to one embodiment of the present invention, excellent magnetic properties can be secured by satisfying the value of Equation 1.

[0209] On the other hand, in the case of Comparative Examples 1-1 to 1-10, it can be confirmed that the alloy composition according to one embodiment of the present invention is not satisfied. At this time, it can be confirmed that the iron loss value is higher compared to Examples 1-1 to 1-10.

[0210] Below, we will examine each comparative example in more detail.

[0211] Comparative Example 1-1 is a comparative example in which the content of manganese (Mn) and titanium (Ti) each exceeds the upper limits of the content of manganese, titanium, and nitrogen according to one embodiment of the present invention. In this case, precipitates may be formed due to the excessive content of manganese, titanium, and nitrogen, which may result in inferior magnetic properties. Additionally, it can be confirmed that a large amount of precipitates, such as CrN and / or NbN, are generated because the content of nitrogen (N) exceeds the upper limit of the content of nitrogen according to one embodiment of the present invention. As a result, an orientation unfavorable to magnetic properties develops, failing to satisfy Equation 1, and iron loss (W 10 / 400 It can be confirmed that the value exceeds 14.6 W / kg.

[0212] Comparative Example 1-2 is a comparative example in which the aluminum (Al) content falls short of the lower limit of the aluminum content according to one embodiment of the present invention; in this case, the iron loss reduction effect due to aluminum is small, which may result in inferior magnetic properties. Additionally, Comparative Example 1-4 has niobium (Nb) and carbon (C) contents that each exceed the upper limits of the niobium and carbon contents according to one embodiment of the present invention. As mentioned above, when the niobium and carbon contents are excessive, fine precipitates may form, which can degrade magnetic properties and lead to the development of orientations unfavorable to magnetic properties. In this case, it can be confirmed that a large amount of NbN is formed in Comparative Example 1-2. As a result, Comparative Example 1-2 does not satisfy Equation 1, and the iron loss (W 10 / 400 It can be confirmed that the value does not satisfy 14.6 W / kg or less.

[0213] Comparative Examples 1-3 are comparative examples in which the chromium (Cr) content exceeds the upper limit of the chromium content according to one embodiment of the present invention. At this time, it can be confirmed that a large amount of fine precipitates, such as CrN, are formed. As a result, an orientation unfavorable to magnetic properties develops, failing to satisfy Equation 1, and compared to the embodiment of the present invention, the iron loss (W 10 / 400 You can see that the value is high.

[0214] Comparative Examples 1-4 are comparative examples in which the chromium (Cr) and nitrogen (N) content exceeds the upper limit of the chromium and nitrogen content according to one embodiment of the present invention. When the chromium and nitrogen content is excessive, fine CrN precipitates are formed, making it difficult to develop orientations favorable for magnetic properties. As a result, in the case of Comparative Examples 1-4, it can be confirmed that a large amount of CrN precipitates are formed, and it can be confirmed that Equation 1 is not satisfied. At this time, the iron loss (W of Comparative Examples 1-4) 10 / 400 It can be confirmed that the value exceeds 14.6 W / kg.

[0215] Comparative Examples 1-5 are comparative examples in which the chromium (Cr) and nickel (Ni) content each exceeds the upper limits of the chromium and nickel content according to one embodiment of the present invention. When the chromium and nickel content is excessive, fine precipitates are formed, which can hinder the development of orientations favorable to magnetic properties. At this time, it can be confirmed that a large amount of fine CrN is generated. As a result, it can be confirmed that Equation 1 is not satisfied. At this time, the iron loss (W of Comparative Examples 1-5) 10 / 400 It can be confirmed that the value is higher than the iron loss value of the embodiment according to the present invention.

[0216] Comparative Examples 1-6 are comparative examples in which the niobium (Nb) content exceeds the upper limit of the niobium content according to one embodiment of the present invention. As previously mentioned, if the niobium content is excessive, fine NbN precipitates are formed, which can impede magnetic properties by hindering the movement of domain walls during the magnetization process, and the precipitates can hinder the development of orientations favorable to magnetic properties. In this case, in the case of Comparative Examples 1-6, it can be confirmed that a large amount of fine NbN precipitates are formed; as a result, Equation 1 is not satisfied, and iron loss (W 10 / 400 It can be confirmed that the value exceeds 14.6 W / kg.

[0217] Comparative Examples 1-7 are comparative examples in which niobium (Nb) is not added, with a niobium (Nb) content of 0 wt%. When niobium is not added, the formation of fine CrN cannot be suppressed, and it can be confirmed that fine CrN is formed. When such fine CrN is formed, the development of orientations favorable for magnetic properties may be suppressed by the fine precipitates. As a result, Comparative Examples 1-7 do not satisfy Equation 1, and the iron loss (W 10 / 400 It can be confirmed that the value does not satisfy 14.6 W / kg or less.

[0218] Through this, it was confirmed that when the alloy composition according to one embodiment of the present invention is satisfied, an orientation favorable to magnetic properties develops compared to an orientation unfavorable to magnetic properties, satisfying Equation 1, and as a result, excellent magnetic properties can be obtained.

[0219]

[0220] 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. Non-oriented electrical steel sheet comprising silicon (Si) 2.8 wt% or more and 3.7 wt% or less, aluminum (Al) 0.8 wt% or more and 1.5 wt% or less, manganese (Mn) 0.2 wt% or more and 0.4 wt% or less, chromium (Cr) 0.02 wt% or more and 0.07 wt% or less, copper (Cu) 0.02 wt% or more and 0.07 wt% or less, nickel (Ni) 0.02 wt% or more and 0.07 wt% or less, niobium (Nb) greater than 0 wt% and 0.002 wt% or less, and the remainder being iron (Fe) and other unavoidable impurities.

2. In Paragraph 1, A non-oriented electrical steel sheet further comprising carbon (C) greater than 0 wt% and less than or equal to 0.003 wt%, titanium (Ti) greater than 0 wt% and less than or equal to 0.003 wt%, sulfur (S) greater than 0 wt% and less than or equal to 0.005 wt%, nitrogen (N) greater than 0 wt% and less than or equal to 0.005 wt%, and phosphorus (P) greater than 0 wt% and less than or equal to 0.015 wt%.

3. In Paragraph 1, Non-oriented electrical steel sheet satisfying the following Equation 1: [Equation 1] [i(70, 0, 0) / i(23, 45, 45)] ≥ 0.8 In Equation 1, i(70, 0, 0) is the strength of the orientation distribution function of a grain with (φ1, φ, φ2) = (70±3, 0, 0) Euler angle (Bunge) orientation, and i(23, 45, 45) is the strength of the orientation distribution function of a grain with (φ1, φ, φ2) = (23±3, 45±5, 45±2) Euler angle (Bunge) orientation.

4. In Paragraph 3, Non-oriented electrical steel sheet in which i(70, 0, 0) is 4.8 or greater and 6.5 or less.

5. In Paragraph 3, Non-oriented electrical steel sheet in which i(23, 45, 45) is 5.3 or greater and 6.6 or less.

6. In Paragraph 1, A non-oriented electrical steel sheet having 85 or fewer CrN precipitates with a diameter of 10 nm or more per area (50 µm × 50 µm).

7. In Paragraph 1, A non-oriented electrical steel sheet having 1 to 6 NbN precipitates with a diameter of 10 nm or more per area (50㎛×50㎛).

8. In Paragraph 1, Non-oriented electrical steel sheet having an average diameter of NbN precipitates per area (50㎛×50㎛) of 130 nm or more and 227 nm or less.

9. In Paragraph 1, Iron loss (W 10 / 400 Non-oriented electrical steel sheet having a ) of 14.6 W / kg or less.

10. Step of hot rolling the slab after reheating; Hot rolling and annealing step; cold rolling step; and It includes a cold rolling and annealing step, The above slab is, A method for manufacturing a non-oriented electrical steel sheet comprising silicon (Si) 2.8 wt% or more and 3.7 wt% or less, aluminum (Al) 0.8 wt% or more and 1.5 wt% or less, manganese (Mn) 0.2 wt% or more and 0.4 wt% or less, chromium (Cr) 0.02 wt% or more and 0.07 wt% or less, copper (Cu) 0.02 wt% or more and 0.07 wt% or less, nickel (Ni) 0.02 wt% or more and 0.07 wt% or less, niobium (Nb) greater than 0 wt% and 0.002 wt% or less, and the remainder being iron (Fe) and other unavoidable impurities.

11. In Paragraph 10, The above cold rolling annealing step is, A method for manufacturing non-oriented electrical steel sheets by performing heat treatment in a temperature range of 800℃ or higher and 1100℃ or lower.

12. In Paragraph 10, The above slab is, A method for manufacturing a non-oriented electrical steel sheet, further comprising carbon (C) greater than 0 wt% and less than or equal to 0.003 wt%, titanium (Ti) greater than 0 wt% and less than or equal to 0.003 wt%, sulfur (S) greater than 0 wt% and less than or equal to 0.005 wt%, nitrogen (N) greater than 0 wt% and less than or equal to 0.005 wt%, and phosphorus (P) greater than 0 wt% and less than or equal to 0.015 wt%.

13. In Paragraph 10, The non-oriented electrical steel sheet that has undergone the above-mentioned cold rolling and annealing step is, A method for manufacturing a non-oriented electrical steel sheet satisfying the following Equation 1: [Equation 1] [i(70, 0, 0) / i(23, 45, 45)] ≥ 0.8 In Equation 1, i(70, 0, 0) is the strength of the orientation distribution function of a grain with (φ1, φ, φ2) = (70±3, 0, 0) Euler angle (Bunge) orientation, and i(23, 45, 45) is the strength of the orientation distribution function of a grain with (φ1, φ, φ2) = (23±3, 45±5, 45±2) Euler angle (Bunge) orientation.

14. In Paragraph 13, The non-oriented electrical steel sheet that has undergone the above-mentioned cold rolling and annealing step is, A method for manufacturing non-oriented electrical steel sheets in which i(70, 0, 0) is 4.8 or greater and 6.5 or less.

15. In Paragraph 13, The non-oriented electrical steel sheet that has undergone the above-mentioned cold rolling and annealing step is, A method for manufacturing non-oriented electrical steel sheets in which i(23, 45, 45) is 5.3 or more and 6.6 or less.

16. In Paragraph 10, The non-oriented electrical steel sheet that has undergone the above-mentioned cold rolling and annealing step is, Iron loss (W 10 / 400 A method for manufacturing non-oriented electrical steel sheets having a ) of 14.6 W / kg or less.

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