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

Abstract

An embodiment of the present invention provides a non-oriented electrical steel sheet containing 1.8-2.9 wt% of silicon (Si), 0.3-0.8 wt% of aluminum (Al), 0.1-0.4 wt% of manganese (Mn), more than 0 wt% and not more than 0.003 wt% of tin (Sn), and more than 0 wt% and not more than 0.003 wt% of yttrium (Y), with the remainder comprising iron (Fe) and other inevitable impurities, and satisfying Equation 1, and thus having 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] In line with recent global policies to reduce carbon dioxide emissions to combat global warming, conventional internal combustion engine vehicles are rapidly being replaced by eco-friendly vehicles such as hybrid, electric, and hydrogen-powered vehicles. Eco-friendly vehicles utilize electric motors to generate the necessary driving force and significantly reduce harmful exhaust gas emissions, thereby minimizing environmental pollution.

[0003] As interest in and demand for eco-friendly vehicles grows, so does the demand for electric motors, which power these vehicles. Electric motors use electricity to generate the power needed for vehicles. Energy efficiency, which allows them to operate for longer periods of time using the same amount of energy, is a crucial technological element.

[0004] The energy efficiency of an electric motor is influenced by the magnetic properties of the non-oriented electrical steel used as the motor's core material. A representative magnetic characteristic of non-oriented electrical steel is core loss. Core loss is the energy loss that occurs during the magnetization process of the material. Lower core loss can improve energy efficiency.

[0005] To achieve low core loss, steel sheet thickness must be reduced, resistivity increased, and impurity elements controlled. Typically, resistivity is increased by adding elements such as silicon (Si), manganese (Mn), and aluminum (Al), thereby lowering core loss. However, increasing the amount of silicon (Si) and aluminum (Al) added can decrease cold-rollability, increase processing costs, and potentially lead to lower production yields.

[0006] Additionally, as the amount of silicon (Si), manganese (Mn), aluminum (Al), and impurity elements added increases, the formation of precipitates increases, and the formed precipitates can cause grain refinement. In this case, the hardness of the material increases, which can lead to plate breakage during rolling.

[0007] [Prior Art Literature]

[0008] [Patent Document]

[0009] (Patent Document 1) Japanese Patent No. 4658840

[0010] The present invention has been devised to solve the above problems, and the object of the present invention is to provide a non-oriented electrical steel sheet having excellent magnetic properties and excellent mechanical properties and a method for manufacturing a non-oriented electrical steel sheet.

[0011] The tasks of the present invention are not limited to the tasks mentioned above, and other tasks not mentioned will be clearly understood by those skilled in the art from the description below.

[0012] According to one embodiment of the present invention, a non-oriented electrical steel sheet contains silicon (Si) of 1.8 wt% or more and 2.9 wt% or less, aluminum (Al) of 0.3 wt% or more and 0.8 wt% or less, manganese (Mn) of 0.1 wt% or more and 0.4 wt% or less, tin (Sn) of 0 wt% or more and 0.003 wt% or less, yttrium (Y) of 0 wt% or more and 0.003 wt% or less, the remainder iron (Fe) and other unavoidable impurities, and the sum of silicon (Si) and aluminum (Al) is 2.1 wt% or more and less than 3.5 wt%, and the sum of tin (Sn) and yttrium (Y) is 0 wt% or more and less than 0.005 wt%, and satisfies the following equation 1.

[0013] [Formula 1]

[0014] 80 ≤ Hv - [(100×ρ) / d] ≤ 150

[0015] In the above equation 1, Hv is the Vickers hardness, ρ is the resistivity, and d is the grain size.

[0016] The resistivity (ρ) is a value calculated by Equation 2 below,

[0017] [Formula 2]

[0018] ρ=10.1169 + 11.7499[Si] + 8.76[Al] + 6.1985[Mn] - 10.3715(10 -4 )[S] + 14.3269(10 -4 )[P] + 13.17(10 -2 )([Sn]+[Y])

[0019] In the above formula 2, [Si], [Al], [Mn], [S], [P], [Sn] and [Y] represent the contents of Si, Al, Mn, S, P, Sn and Y in wt%, respectively.

[0020] Additionally, the resistivity (ρ) may be greater than or equal to 47.29 μΩ·cm.

[0021] Also, iron loss (W 15 / 50 ) may be less than or equal to 4.64 W / kg.

[0022] Additionally, the crystal grain size (d) can be 92 to 173 μm.

[0023] Additionally, the Vickers hardness (Hv) can be 118 to 182 HV.

[0024] In addition, it may further include at least one of carbon (C) exceeding 0 wt% and 0.003 wt% or less, sulfur (S) exceeding 0 wt% and 0.003 wt% or less, nitrogen (N) exceeding 0 wt% and 0.003 wt% or less, titanium (Ti) exceeding 0 wt% and 0.003 wt% or less, and phosphorus (P) exceeding 0 wt% and 0.003 wt% or less.

[0025] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises a steel preparation step including the above-described alloy composition, a hot rolling step of hot-rolling the steel sheet to form a hot-rolled steel sheet, a hot-rolling annealing step of annealing the hot-rolled steel sheet, a cold rolling step of cold-rolling the hot-rolled steel sheet that has undergone the hot-rolling annealing step to form a cold-rolled steel sheet, and a cold-rolling annealing step of annealing the cold-rolled steel sheet.

[0026] Additionally, the cold-rolled annealing step may anneal the cold-rolled steel sheet at 800 to 1100°C for 5 to 600 seconds.

[0027] According to one embodiment of the present invention, a non-oriented electrical steel sheet and a method for manufacturing a non-oriented electrical steel sheet having excellent magnetic properties and excellent mechanical properties can be realized by adding tin (Sn) and yttrium (Y) to increase resistivity and reduce iron loss.

[0028] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0029] FIG. 1 is a flowchart schematically illustrating a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0030] Hereinafter, preferred embodiments of the present invention will be 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.

[0031] Additionally, when a component (or region, layer, portion, etc.) is referred to as being "on," "connected to," or "coupled to" another component, it means that it can be directly placed / connected / coupled to the other component, or that a third component may be placed between them.

[0032] Terms such as "include" or "have" should be understood to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but not to exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0033] In order to clearly explain the present invention, a detailed description of a part that is irrelevant to the description or a related known technology that may unnecessarily obscure the gist of the present invention has been omitted, and when adding reference signs to components of each drawing in this specification, the same or similar reference signs are attached to the same or similar components throughout the specification.

[0034] In addition, terms and words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0035] Unless otherwise specified, the notation 'A ~ B' for numerical values ​​A and B means 'A or more and B or less'. In such notation, if a unit is attached only to numerical value B, the unit shall be applied to numerical value A as well.

[0036] Also, unless otherwise stated, 1 ppm is 0.0001 wt%.

[0037]

[0038] Non-oriented electrical steel sheet

[0039] It contains silicon (Si) 1.8 wt% or more and 2.9 wt% or less, aluminum (Al) 0.3 wt% or more and 0.8 wt% or less, manganese (Mn) 0.1 wt% or more and 0.4 wt% or less, tin (Sn) 0 wt% or more and 0.003 wt% or less, yttrium (Y) 0 wt% or more and 0.003 wt% or less, the remainder iron (Fe) and other unavoidable impurities.

[0040] Hereinafter, the role and content of alloy elements included in a non-oriented electrical steel sheet according to one embodiment of the present invention will be described in detail.

[0041]

[0042] Silicon (Si)

[0043] Silicon (Si) is an element that increases the resistivity of steel and reduces iron loss, making it a key additive in electrical steel. If the silicon content is too low, the iron loss improvement effect may be insufficient. Conversely, excessive silicon addition can reduce permeability and magnetic flux density. Furthermore, increasing silicon content can increase brittleness. Therefore, appropriate silicon content control is essential.

[0044] When the silicon content is less than 1.8 wt%, the iron loss reduction effect may be insufficient. On the other hand, when the silicon content exceeds 2.9 wt%, cracks or plate breakage may occur during cold rolling or stamping.

[0045] Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain silicon in an amount of 1.8 wt% or more and 2.9 wt% or less.

[0046]

[0047] Aluminum (Al)

[0048] Aluminum (Al), along with silicon (Si), increases resistivity and reduces iron loss, making it a key additive in electrical steel. However, excessive addition of Al can combine with nitrogen (N) in the steel to form AlN particles. These AlN particles can hinder the formation of a magnetically favorable texture and hinder domain wall movement, thereby degrading magnetic properties.

[0049] When the aluminum content is less than 0.3 wt%, the iron loss reduction effect may be insufficient. On the other hand, when the aluminum content exceeds 0.8 wt%, the problems described above may occur, and cold rolling properties may deteriorate and magnetic flux density may decrease.

[0050] Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain aluminum in an amount of 0.3 wt% or more and 0.8 wt% or less.

[0051]

[0052] According to one embodiment of the present invention, a non-oriented electrical steel sheet has a total amount of silicon (Si) and aluminum (Al) of 2.1 wt% or more and less than 3.5 wt%. When the total amount of silicon (Si) and aluminum (Al) is less than 2.1 wt%, the increase in resistivity is not sufficient, which may result in poor iron loss. When the total amount of silicon (Si) and aluminum (Al) is 3.5 wt% or more, the brittleness of the material increases, which may cause sheet fracture during cold rolling and punching.

[0053]

[0054] manganese (Mn)

[0055] Manganese (Mn), like silicon (Si) and aluminum (Al), is an element that improves magnetic properties by increasing resistivity and reducing iron loss. It can also enhance the fraction of aggregate structures beneficial to magnetic properties. If the manganese content is less than 0.1 wt%, the aforementioned effects cannot be achieved.

[0056] On the other hand, if the manganese content exceeds 0.4 wt%, it can combine with sulfur (S) in the steel to form MnS precipitates. These precipitates can inhibit grain growth and hinder domain wall movement, thereby degrading magnetic properties. Furthermore, if the formed precipitates grow coarsely, mechanical strength may be reduced.

[0057] Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain manganese in an amount of 0.1 wt% or more and 0.4 wt% or less.

[0058]

[0059] Sn

[0060] Tin (Sn) is an element that increases the resistivity of steel and reduces iron loss. However, if added in excessive amounts, the gamma fiber (γ-fiber) increases, which may increase the (111) / ND orientation fraction, which is detrimental to magnetic properties. In addition, when yttrium is added together with tin, if the tin content exceeds 0.003 wt%, it reacts with yttrium (Y) to form fine precipitates such as Sn2Y and Sb5Y2, which may increase iron loss.

[0061] Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain tin in an amount of more than 0 wt% and less than or equal to 0.003 wt%.

[0062]

[0063] Yttrium (Y)

[0064] Yttrium (Y) is an element that reduces iron loss by increasing the resistivity of steel when added. However, if yttrium is added in excess of 0.003 wt%, fine precipitates such as Y2O3, YS, Y2S3, Sn2Y, and Sn5Y2 may form. These fine precipitates can increase iron loss by impeding domain wall movement, and can also cause grain refinement, increasing the hardness of the steel and reducing the rollability.

[0065] Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain yttrium in an amount of more than 0 wt% and less than or equal to 0.003 wt%.

[0066]

[0067] According to one embodiment of the present invention, a non-oriented electrical steel sheet has a total amount of tin (Sn) and yttrium (Y) of more than 0 wt% and less than or equal to 0.005 wt%. When the total amount of tin (Sn) and yttrium (Y) exceeds 0.005 wt%, fine Sn-Y precipitates may precipitate, which may impede magnetic wall movement and deteriorate magnetic properties. In addition, the fine precipitates may cause grain refinement, thereby increasing the hardness of the steel, and the increased hardness may result in a decrease in rollability.

[0068]

[0069] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include at least one of carbon (C) exceeding 0 wt% and 0.003 wt% or less, sulfur (S) exceeding 0 wt% and 0.003 wt% or less, nitrogen (N) exceeding 0 wt% and 0.003 wt% or less, titanium (Ti) exceeding 0 wt% and 0.003 wt% or less, and phosphorus (P) exceeding 0 wt% and 0.014 wt% or less.

[0070]

[0071] Carbon (C)

[0072] When the carbon (C) content exceeds 0.003 wt%, it can combine with titanium (Ti) in the steel to form fine carbides such as TiC. These fine carbides reduce the permeability and increase iron loss. In addition, magnetic aging may occur, resulting in poor magnetic properties.

[0073] Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain carbon in an amount of more than 0 wt% and less than or equal to 0.003 wt%.

[0074]

[0075] Yellow (S)

[0076] When the sulfur (S) content exceeds 0.003 wt%, it combines with manganese (Mn) in the steel to form precipitates such as MnS. These precipitates can inhibit grain growth and deteriorate magnetic properties.

[0077] Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain sulfur in an amount of more than 0 wt% and less than or equal to 0.003 wt%.

[0078]

[0079] Nitrogen (N)

[0080] When the nitrogen (N) content exceeds 0.003 wt%, it can combine with aluminum (Al) and titanium (Ti) in the steel to form precipitates such as AlN and TiN. These precipitates can impede domain wall movement, suppress grain growth, and deteriorate magnetic properties.

[0081] Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain nitrogen in an amount of more than 0 wt% and less than or equal to 0.003 wt%.

[0082]

[0083] Titanium (Ti)

[0084] When the content of titanium (Ti) exceeds 0.003 wt%, it can combine with carbon (C), nitrogen (N), etc. in the steel to form precipitates such as TiC and TiN. The formed precipitates can inhibit grain growth and deteriorate magnetic properties.

[0085] Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain titanium in an amount of more than 0 wt% and less than or equal to 0.003 wt%.

[0086]

[0087] Person (P)

[0088] Phosphorus (P) is a grain boundary segregation element. If the phosphorus content exceeds 0.014 wt%, grain boundary segregation may occur, inhibiting grain growth and potentially degrading magnetic properties. Furthermore, excessive phosphorus addition can deteriorate cold rolling properties.

[0089] Therefore, the non-oriented electrical steel sheet according to one embodiment of the present invention may contain phosphorus in an amount of more than 0 wt% and less than or equal to 0.014 wt%.

[0090]

[0091] In addition to the aforementioned steel components, the remainder may contain iron and unavoidable impurities. Unavoidable impurities are impurities introduced during the steelmaking process and the manufacturing process of non-oriented electrical steel sheets. Since these impurities are widely known in the field, a detailed description will be omitted.

[0092] 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 range that does not impair the technical spirit of the present invention. When additional elements are included, they may be included to replace the remaining Fe.

[0093]

[0094] A non-oriented electrical steel sheet according to one embodiment of the present invention can satisfy the following equation 1.

[0095] [Formula 1]

[0096] 80 ≤ Hv - [(100×ρ) / d] ≤ 150

[0097] In the above equation 1, Hv is the Vickers hardness, ρ is the resistivity, and d is the grain size.

[0098] Vickers hardness (Hv) was measured at room temperature according to the ASTM-384 standard, with a test load of 500 g and a dwell time of the test load of 15 seconds. The unit of Vickers hardness (Hv) is 'HV'.

[0099] The resistivity (ρ) was calculated using Equation 2 below, and the unit is ‘μΩ·cm’.

[0100] [Formula 2]

[0101] ρ = 10.1169 + 11.7499[Si] + 8.76[Al] + 6.1985[Mn] - 10.3715(10 -4 )[S] + 14.3269(10 -4 )[P] + 13.17(10 -2 )([Sn]+[Y])

[0102] In the above formula 2, [Si], [Al], [Mn], [S], [P], [Sn] and [Y] represent the contents of silicon (Si), aluminum (Al), manganese (Mn), sulfur (S), phosphorus (P), tin (Sn) and yttrium (Y) in wt%, respectively.

[0103] The above equation 2 is based on the resistivity calculation formula disclosed in the paper (Ludwigson, DC, & Schwerer, FC (1971, Metallurgical and Materials Transactions B, 2, 3500-3501)), and was created by experimentally deriving the resistivity change according to each alloying element. More specifically, the resistivity value according to the content of each alloying element was measured, and the resistivity change according to the increase in the alloying element was derived, thereby creating the above equation 2.

[0104] The crystal grain size (d) was measured using EBSD (Electron backscatter diffraction) and the analysis software TSL OIM software, and the unit is '㎛'.

[0105] Below, the above equation 1 will be explained in more detail.

[0106] As mentioned above, higher resistivity is advantageous for magnetic properties. Therefore, in the present invention, to achieve high resistivity, the contents of silicon (Si), aluminum (Al), and manganese (Mn) were controlled, and tin (Sn) and yttrium (Y) were added.

[0107] However, when alloying elements are added to increase resistivity, precipitates may form. These precipitates can reduce grain size, and smaller grain sizes increase hardness. However, if hardness increases excessively, sheet fracture may occur during rolling.

[0108] The relationship between resistivity (ρ), Vickers hardness (Hv), and grain size (d) was defined through the above equation 1, and the resistivity (ρ), Vickers hardness (Hv), and grain size (d) were controlled simultaneously.

[0109] If the content of an alloying element that increases resistivity is excessive, the upper limit of Equation 1 may be exceeded. Specifically, if the addition of an alloying element that increases resistivity is excessive, resistivity increases, but a large amount of precipitates may be formed. These precipitates may reduce the grain size and increase the hardness of the material. As a result, plate fracture may occur during cold rolling or stamping.

[0110] If the content of the alloying element that increases the resistivity is insufficient, a value lower than the lower limit of the above equation 1 may be exhibited. Specifically, if the content of the alloying element that increases the resistivity is insufficient, the effect of reducing the iron loss may not be sufficient, resulting in inferior magnetic properties. In addition, since the formation of precipitates due to the added alloying element does not occur, the grain size may increase, resulting in a decrease in hardness.

[0111] On the other hand, if the above formula 1 is satisfied, no plate breakage or cracks occur during rolling or stamping, and at the same time, excellent magnetic properties and excellent mechanical properties can be achieved.

[0112] A non-oriented electrical steel sheet according to one embodiment of the present invention can have a high resistivity (ρ) by including an appropriate amount of tin (Sn) and yttrium (Y), which increase resistivity. Specifically, the resistivity (ρ) can be 47.29 μΩ·cm or more. When the resistivity (ρ) is less than 47.29 μΩ·cm, the iron loss may be high, resulting in poor magnetic properties.

[0113] In addition, as the resistivity increases, the iron loss decreases, so that excellent magnetic properties can be achieved. Specifically, the iron loss (W 15 / 50 ) may be less than or equal to 4.64 W / kg.

[0114] According to one embodiment of the present invention, a non-oriented electrical steel sheet may have a grain size of 92 to 173 μm. When the grain size is less than 92 μm, the sheet may fracture during rolling due to increased hardness resulting from grain refinement. Conversely, when the grain size exceeds 173 μm, problems such as increased iron loss and reduced strength may arise due to the grain size.

[0115] In addition, the Vickers hardness (Hv) may be 118 to 182 HV. If the Vickers hardness exceeds 182 HV, cold rolling properties may deteriorate. On the other hand, if the Vickers hardness is less than 118 HV, the shape may change due to external pressure, which may cause shape defects.

[0116] Hereinafter, a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention will be described in detail.

[0117]

[0118] Method for manufacturing non-oriented electrical steel sheet

[0119] Hereinafter, a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention will be described with reference to FIG. 1.

[0120] FIG. 1 is a flowchart schematically illustrating a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0121] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention includes a steel preparation step (S100), a hot rolling step (S200) of hot-rolling a steel sheet to form a hot-rolled steel sheet, a hot-rolling annealing step (S300) of annealing the hot-rolled steel sheet, a cold-rolling step (S400) of cold-rolling the hot-rolled steel sheet that has undergone the hot-rolling annealing step (S300) to form a cold-rolled steel sheet, and a cold-rolling annealing step (S500) of cold-rolling the cold-rolled steel sheet.

[0122] At this time, the steel contains silicon (Si) of 1.8 wt% or more and 2.9 wt% or less, aluminum (Al) of 0.3 wt% or more and 0.8 wt% or less, manganese (Mn) of 0.1 wt% or more and 0.4 wt% or less, tin (Sn) of 0 wt% or more and 0.003 wt% or less, yttrium (Y) of 0 wt% or more and 0.003 wt% or less, the remainder iron (Fe) and other unavoidable impurities.

[0123] In addition, the steel may further include at least one of carbon (C) exceeding 0 wt% and not more than 0.003 wt%, sulfur (S) exceeding 0 wt% and not more than 0.003 wt%, nitrogen (N) exceeding 0 wt% and not more than 0.003 wt%, titanium (Ti) exceeding 0 wt% and not more than 0.003 wt%, and phosphorus (P) exceeding 0 wt% and not more than 0.014 wt%.

[0124] The alloy composition has been previously described, so a detailed explanation will be omitted. Furthermore, since the alloy composition does not substantially change during the manufacturing process described below, the alloy composition of the steel material and the alloy composition of the final product, the non-oriented electrical steel sheet, are substantially identical.

[0125] Hereinafter, each step of a method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention will be described in detail.

[0126] The steel preparation step (S100) of preparing steel is a step for preparing a semi-finished product for manufacturing a non-oriented electrical steel sheet, which is the final product. More specifically, this step may be a step for manufacturing a semi-finished product by designing an alloy composition within the alloy composition range according to one embodiment of the present invention. The semi-finished product may be a slab, but is not necessarily limited thereto. Furthermore, the slab may be manufactured using a steelmaking process known in the art, such as a casting process.

[0127] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may perform a hot rolling step (S200) of hot-rolling steel to form a hot-rolled steel sheet after a steel preparation step (S100). The hot rolling step (S200) may include a reheating process, a hot rolling process, and a coiling process.

[0128] First, the reheating process, performed prior to the hot rolling process, may reheat the steel for subsequent processing. Specifically, it may be a step where the steel is placed in a heating furnace and uniformly heated, facilitating plastic deformation.

[0129] At this time, if the reheating temperature is below 1000℃, the rolling load increases, which may make hot rolling difficult. On the other hand, if the reheating temperature exceeds 1250℃, precipitates formed by tin (Sn), carbon (C), sulfur (S), nitrogen (N), etc. in the steel are re-dissolved, which may form fine precipitates during the subsequent rolling and annealing processes. These fine precipitates can inhibit grain growth and increase iron loss.

[0130] Therefore, the reheating process according to one embodiment of the present invention can be performed at a temperature of 1000 to 1250°C.

[0131] Next, a hot rolling process can be performed, in which the reheated steel is hot-rolled to form a hot-rolled steel sheet. The hot rolling process can include rough rolling and finish rolling. Here, rough rolling can refer to forming the steel into a rolled sheet with an appropriate shape, thickness, and width, while finish rolling can refer to adjusting the steel to a specified thickness and width and rolling it at a finishing temperature appropriate for the intended use to achieve a good surface finish and shape.

[0132] At this time, the finishing temperature of the hot rolling process can be carried out at a temperature that allows for uniform tissue formation and appropriate strength enhancement, and the finishing temperature can be 850 to 900℃. If the finishing temperature is below 850℃, dynamic recrystallization may not occur sufficiently, making it difficult to homogenize the microstructure, which may lower the uniformity of the final texture and result in inferior magnetic properties. If the finishing temperature exceeds 900℃, the problem of a rapid decrease in the strength of the steel may occur.

[0133] Afterwards, a coiling process can be performed to coil the hot-rolled steel sheet formed through the hot rolling process. The coiling temperature can range from 550 to 750°C. If the coiling temperature is below 550°C, brittleness increases, potentially leading to sheet fracture. Furthermore, the grain size decreases, preventing sufficient grain growth even after annealing. Conversely, if the coiling temperature exceeds 750°C, fine precipitates can form, increasing iron loss.

[0134] The thickness of the hot-rolled steel sheet formed through the hot rolling step (S200) is preferably 1.8 to 3.5 mm. If the hot-rolled steel sheet is excessively thin, less than 1.8 mm, the thickness obtained after cold rolling may be insufficient, which may cause shape defects during product application. On the other hand, if the hot-rolled steel sheet is thicker than 3.5 mm, the cold rolling reduction ratio increases, and the fraction of grain structures unfavorable to magnetic properties increases, which may result in poor magnetic properties.

[0135] According to one embodiment of the present invention, a non-oriented electrical steel sheet may be subjected to a hot rolling annealing step (S300) of hot rolling annealing a hot-rolled steel sheet after a hot rolling step (S200). The hot rolling annealing step (S300) may be a hot rolling annealing step (S300) performed to ensure uniformity of the microstructure of the steel material subjected to hot rolling.

[0136] The reasons for performing hot-rolled annealing are as follows. When the silicon content is 1.8 wt% or more, the α-ferrite single phase is maintained without phase transformation into a solid state during heating from room temperature to the melting point. However, dynamic recrystallization (DRX) does not occur during this process, resulting in the formation of elongated unrecrystallized parts. These unrecrystallized parts have high internal residual stresses and are unstable, which can lead to increased anisotropy and plate failure.

[0137] Therefore, the hot-rolled annealing step (S300) may be a step of performing heat treatment at an appropriate temperature to promote recrystallization of unrecrystallized grains and to have a uniform equiaxed grain.

[0138] The hot-rolling annealing temperature according to the present invention may be 900 to 1150°C. If the hot-rolling annealing temperature is lower than 900°C, the elongated cast structure may remain after hot rolling, causing microstructural inhomogeneity. On the other hand, if the hot-rolling annealing temperature exceeds 1150°C, the grains may grow excessively, leading to severe grain size deviations, and oxidation may occur, which may deteriorate the magnetic properties of the final product.

[0139] Additionally, hot rolling annealing may include a heat treatment step for 30 to 120 seconds 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°C / s or more, and the cooling rate after the heat treatment may be 30°C / s or more.

[0140] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention may further include a pickling treatment step after the hot-rolled annealing step (S300). The pickling treatment can be performed by supplying 18% hydrochloric acid to a pickling tank where it reacts with the steel sheet, thereby reacting fine residual scale that cannot be removed mechanically.

[0141] Thereafter, the method for manufacturing a non-oriented electrical steel sheet according to the present invention may perform a cold rolling step (S400) of cold rolling the hot-rolled steel sheet that has undergone the hot-rolled annealing step (S300) to form a cold-rolled steel sheet. The cold rolling step (S400) may be a cold rolling process that further thins the thickness of the steel sheet by rolling the hot-rolled annealed hot-rolled steel sheet at a temperature below the recrystallization temperature.

[0142] More specifically, it may be a process for rolling a hot-rolled steel sheet to a thickness and width that meet the specifications of the final product. The cold rolling step (S400) according to the present invention may include a step of cold rolling a hot-rolled steel sheet to produce a cold-rolled steel sheet having a thickness of 0.3 to 0.55 mm. At this time, the reduction ratio may be 70 to 95%.

[0143] 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 (S500) of cold rolling the cold rolled steel sheet after the cold rolling step (S400). The cold rolling annealing may be performed at an appropriate temperature to improve magnetic and mechanical properties.

[0144] At this time, the appropriate temperature for cold rolling annealing may be 800 to 1100°C. If the cold rolling annealing temperature is lower than 800°C, the cold rolling annealing temperature may be insufficient to relieve residual stress, resulting in poor iron loss. Furthermore, the grain size after annealing may be small, resulting in poor magnetic flux density and iron loss.

[0145] On the other hand, if the cold rolling annealing temperature exceeds 1100℃, excessive grain growth may lead to increased eddy current loss, which may increase iron loss. Furthermore, precipitates may re-dissolve, forming fine precipitates, which may deteriorate magnetic properties.

[0146] In addition, the cold rolling annealing according to the present invention can be maintained for 5 to 600 seconds within the aforementioned temperature range. The heating rate to the aforementioned temperature can be 10°C / s or more, and the cooling rate after the heat treatment can be 20°C / s or more.

[0147]

[0148] *The cold-rolled annealing step (S500) can be performed in a mixed atmosphere containing hydrogen (H2) and nitrogen (N2) to prevent oxidation or nitriding of the cold-rolled steel sheet surface. This can improve the surface quality of the cold-rolled steel sheet.

[0149] 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 annealing step (S500). The coating step may be performed to secure the insulation properties and improve the punchability of the non-oriented electrical steel sheet, and may mean forming an insulating film on the surface of the cold rolled steel sheet that has undergone the cold rolling annealing step (S500). The coating step may be performed using a process known in the art.

[0150] This allows for excellent magnetic properties. More specifically, the iron loss (W 15 / 50 ) may be less than or equal to 4.64 W / kg.

[0151]

[0152] Examples and Comparative Examples

[0153]

[0154] *Below, the composition and operation of the present invention will be explained through experimental examples. However, these examples are provided to aid understanding of the present invention and are not intended to limit the present invention.

[0155]

[0156] (Method for manufacturing non-oriented electrical steel sheet specimens)

[0157] The specimen of the non-oriented electrical steel sheet of the present invention includes the alloy components described in Tables 1 and 2 below, and the remainder other than the alloy components described in Tables 1 and 2 below includes iron (Fe).

[0158] Classification Alloy Element (Wt%) Alloy Element (ppm) Si + Al (Wt%) Sn + Y (Wt%) SiAlMnSnYCSNTiP Example 1 1.88 0.32 0.34 25 21 1 1 2 9 22 1 1 6 8 2.20 0.00 46 Example 2 2.20 0.5 10.36 7 25 10 20 23 17 1 1 2 2.71 0.00 32 Example 3 2.87 0.5 5 0.16 27 19 15 21 7 12 1 2 6 3.4 2 0.00 46 Example 4 2.63 0.75 0.16 8 7 30 17 1 9 28 7 5 3.38 0.00 15 Example 5 2.530 .400.10221210202891312.930.0034Example 62.470.670.28182719102722793.140.0045Example 72.370.550.4017723281922792.920.0024Example 82.220.430.11176202111221232.650.0023Example 92.610.480.206611172261033.090.0012

[0159] Classification Alloy Element (Wt%) Alloy Element (ppm) Si + Al (Wt%) Sn + Y (Wt%) SiAlMnSnYCSNTiP Comparative Example 11.650.350.201821201812101382.000.0038 Comparative Example 23.100.600.301026152222121183.700.0036 Comparative Example 32.220.240.1510152320258712.460.0025 Comparative Example 42.360.930.281511251168823.290.0026 Comparative Example 52 .810.760.32182619141922653.570.0044Comparative Example 62.680.480.2461937177191343.160.0025Comparative Example 72.680.540.33136194225211213.220.0019Comparative Example 82.650.490.38201213113881303.140.0032Comparative Example 92.290.530.32011182713131362 .820.0011Comparison Example 102.430.680.341602414218733.110.0016Comparison Example 112.410.600.35002011298713.010.0000Comparison Example 122.170.370.3035129151527692.540.0047Comparison Example 132.260.490.12937781112862.750.0046Comparison Example 142.630.770.302141 21149281113.400.0062Comparative Example 152.780.360.18282619261814983.140.0054Comparative Example 162.200.520.21142772620131032.720.0041Comparative Example 172.310.420.11111824262814912.730.0029Comparative Example 182.760.670.332424251529241043.430.0048

[0160] A specimen of the non-oriented electrical steel sheet of the present invention can be manufactured as follows. A slab having an alloy composition as described in Tables 1 and 2 is manufactured, the slab is reheated to 1100°C, and then hot rolling is performed under the conditions of the finishing temperature (FDT) and coiling temperature (CT) as described in Tables 3 and 4, thereby manufacturing a hot-rolled steel sheet having a thickness as described in Tables 3 and 4 below.

[0161] Afterwards, the hot-rolled steel sheet was hot-rolled and annealed at 850°C for 80 seconds. Next, the hot-rolled steel sheet that had been hot-rolled and annealed was pickled and cold-rolled to manufacture cold-rolled steel sheets having the thicknesses listed in Tables 3 and 4 below.

[0162] Next, the cold-rolled steel sheet was annealed at the temperature and time indicated in Tables 3 and 4 below, in a mixed atmosphere of nitrogen (N2) and hydrogen (H2). Subsequently, a final non-oriented electrical steel sheet specimen was manufactured through a coating process.

[0163] Other process conditions not described in the above-described manufacturing method were controlled as control variables and were identically controlled within the range described in the method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0164]

[0165] (Method for measuring the properties of non-oriented electrical steel sheets)

[0166] 1. Vickers hardness (Hv)

[0167] Vickers hardness (Hv) was measured at room temperature according to the ASTM-384 standard, with a test load of 500 g and a dwell time of the test load of 15 seconds.

[0168]

[0169] 2. Resistivity (ρ)

[0170] The resistivity value of the non-oriented electrical steel sheet specimen was calculated using Equation 2 below. Here, the unit of resistivity is 'μΩ·cm'.

[0171] [Formula 2]

[0172] ρ=10.1169 + 11.7499[Si] + 8.76[Al] + 6.1985[Mn] - 10.3715(10 -4 )[S] + 14.3269(10 -4 )[P] + 13.17(10 -2 )([Sn]+[Y])

[0173] In the above formula 2, [Si], [Al], [Mn], [S], [P], [Sn] and [Y] represent the contents of Si, Al, Mn, S, P, Sn and Y in wt%, respectively.

[0174]

[0175] 3. Grain size (d)

[0176] In order to measure the grain size, a test piece for EBSD (Electron backscatter diffraction) measurement was manufactured so that the ND plane (Normal direction plane) of the steel plate was observed, and the grain size was calculated using the EBSD measurement values ​​analysis software, TSL OIM software.

[0177] At this time, the size of the test piece for measurement is 2 cm × 2 cm. In addition, the step size for EBSD measurement was 5 μm, the grain tolerance angle was 5 μm, and the CI value was 1.

[0178]

[0179] 4. Iron loss (W 15 / 50 )

[0180] Iron loss (W) of the non-oriented electrical steel sheet specimen of the present invention 15 / 50 ) was measured based on the test method specified in the IEC 60404-2 international standard, and was measured using the Epstein frame test method. At this time, the size of the specimen is (300±0.5) mm in length and (30±0.2) mm in width.

[0181]

[0182] (Evaluation results of non-oriented electrical steel sheets)

[0183] The hot rolling finishing temperature (FDT), coiling temperature (CT), and post-hot rolling thickness, cold rolling annealing temperature and time of the examples and comparative examples are shown in Tables 3 and 4 below.

[0184] In addition, the Vickers hardness (Hv), resistivity (ρ), grain size (d) and iron loss (W) of the examples and comparative examples 15 / 50 ) values ​​are shown in Tables 3 and 4 below.

[0185] Classification Hot rolled cold rolled steel sheet Thickness (mm) Cold rolled annealing Hv (HV) ρ (μΩ cm) d (μm) [Formula 1] Value W 15 / 50 (W / kg)FDT(℃)CT(℃)Thickness after rolling(mm)Temperature(℃)Time(s)Example 18606002.80.52100015014443.299296.94.31Example 28606002.70.51100015015347.02119113.53.84Example 38806102.70.48100015016855.77121121.92.97Example 48806002.80.51100015018250.65138145.33.25Example 5870600 2.80.5085015013448.699783.84.60Example 686056030.48105015012752.8214089.33.66Example 78505802.80.51100050011848.4617390.04.52Example 88806003.10.47100015014943.84107108.04.27Example 986060020.51100015015247.92136116.83.53

[0186] Classification Hot rolled cold rolled steel sheet Thickness (mm) Cold rolled annealing Hv (HV) ρ (μΩ cm) d (μm) [Formula 1] Value W 15 / 50(W / kg)FDT(℃)CT(℃)Thickness after rolling(mm)Temperature(℃)Time(s)Comparative Example 18606102.80.48100015010839.049165.15.21Comparative Example 28606102.80.48100015020158.51153162.8(Fracture)Comparative Example 38506002.70.53100015010642.6913875.14.65Comparative Example 48606002.60.47100015017351.29117129.2(Fracture)Comparative Example 586059 02.70.52100015021057.66162174.4(Fracture)Comparative Example 68606002.80.50100015014250.76140105.74.66Comparative Example 78606002.80.46100015014551.03138108.04.77Comparative Example 886060030.51100015015752.29152122.64.92Comparative Example 99006303.10.53100015010345.21112 62.65.30Comparative Example 108606002.80.47100015011048.8710061.14.83Comparative Example 118606102.80.5310001509245.9412254.35.08Comparative Example 128606002.80.50100015014346.988789.05.11Comparative Example 138505702.60.50100015016147.8793109.54.86Comparative Example 148606002.80.4 6100015017857.9977102.7(Fracture)Comparative Example 158606002.40.49100015016954.2585105.2(Fracture)Comparative Example 168605902.80.4870015012747.246655.45.63Comparative Example 178806002.80.4910003010445.609857.55.27Comparative Example 188606002.80.50100015019156.88150153.1(Fracture)

[0187] Referring to Table 1 and Table 3, it can be confirmed that in the case of an embodiment that satisfies the alloy composition and manufacturing method according to one embodiment of the present invention, the above formula 1 is satisfied. At this time, the iron loss (W) of the embodiment 15 / 50) value is 4.64 W / kg or less. On the other hand, referring to Table 2 and Table 4, in the case of comparative examples that do not satisfy the alloy composition and manufacturing method according to one embodiment of the present invention, it can be confirmed that the brittleness of the material increases, causing plate breakage during rolling, or that the magnetic properties are inferior to those of the examples.

[0188] In particular, in the case of comparative examples in which the content of silicon (Si) and aluminum (Al) exceeds each other or their combined amount exceeds 3.5 wt%, plate fracture occurs during cold rolling, resulting in iron loss (W 15 / 50 ) values ​​could not be measured. In addition, in the case of a comparative example in which the total amount of tin (Sn) and yttrium (Y) exceeded 0.005 wt%, plate fracture occurred during cold rolling, resulting in iron loss (W 15 / 50 ) could not measure the value.

[0189] Continuing with reference to Table 2 and Table 4, in the case of a comparative example that satisfies the alloy composition according to one embodiment of the present invention but does not satisfy the above formula 1, it can be confirmed that the plate breaks during rolling or the magnetic properties are inferior to those of the embodiment.

[0190] More specifically, in the case of the comparative example that is below the lower limit of Equation 1, the magnetic properties are inferior, and the iron loss (W) targeted in the present invention is 15 / 50 ) does not satisfy the value of 4.64 W / kg or less. In addition, in the case of the comparative example exceeding the upper limit of Equation 1, plate fracture occurred during cold rolling, resulting in iron loss (W 15 / 50 ) can be confirmed that the value was not measured.

[0191] As described above, preferred embodiments of the present invention have been described. It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms, in addition to the embodiments described above, without departing from the spirit or scope thereof. Therefore, the above-described embodiments should be considered illustrative rather than restrictive, and accordingly, the present invention is not limited to the above description, but may be modified within the scope of the appended claims and their equivalents.

Claims

1. Contains 1.8 wt% or more of silicon (Si) and 2.9 wt% or less, 0.3 wt% or more of aluminum (Al) and 0.8 wt% or less, 0.1 wt% or more of manganese (Mn) and 0.4 wt% or less, 0 wt% or more of tin (Sn) and 0.003 wt% or less, 0 wt% or more of yttrium (Y) and 0.003 wt% or less, the remainder being iron (Fe) and other unavoidable impurities. The total amount of silicon (Si) and aluminum (Al) is 2.1 wt% or more and less than 3.5 wt%, The total amount of tin (Sn) and yttrium (Y) is greater than 0 wt% and less than 0.005 wt%, Non-oriented electrical steel sheet satisfying the following equation 1: [Formula 1] 80 ≤ Hv - [(100×ρ) / d] ≤ 150 In the above equation 1, Hv is the Vickers hardness, ρ is the resistivity, and d is the grain size. The resistivity (ρ) is a value calculated by Equation 2 below, [Formula 2] ρ=10.1169 + 11.7499[Si] + 8.76[Al] + 6.1985[Mn] - 10.3715(10 -4 )[S] + 14.3269(10 -4 )[P] + 13.17(10 -2 )([Sn]+[Y]) In the above formula 2, [Si], [Al], [Mn], [S], [P], [Sn] and [Y] represent the contents of Si, Al, Mn, S, P, Sn and Y in wt%, respectively.

2. In paragraph 1, Non-oriented electrical steel sheet with resistivity (ρ) of 47.29 μΩ·cm or more.

3. In paragraph 1, Non-oriented electrical steel sheet with iron loss (W15 / 50) of 4.64 W / kg or less.

4. In paragraph 1, Non-oriented electrical steel sheet with a grain size (d) of 92 to 173 ㎛.

5. In paragraph 1, Non-oriented electrical steel sheet with Vickers hardness (Hv) of 118 to 182 HV.

6. In paragraph 1, A non-oriented electrical steel sheet further comprising at least one of carbon (C) exceeding 0 wt% and not more than 0.003 wt%, sulfur (S) exceeding 0 wt% and not more than 0.003 wt%, nitrogen (N) exceeding 0 wt% and not more than 0.003 wt%, titanium (Ti) exceeding 0 wt% and not more than 0.003 wt%, and phosphorus (P) exceeding 0 wt% and not more than 0.014 wt%.

7. Steel preparation stage; A hot rolling step of hot rolling the above steel to form a hot rolled steel plate; A hot rolling annealing step for annealing the above hot rolled steel sheet; A cold rolling step of forming a cold rolled steel sheet by cold rolling the hot rolled steel sheet that has undergone the above hot rolling annealing step; and Including a cold rolling annealing step for annealing the above cold rolled steel sheet, The above steel is, Contains 1.8 wt% or more of silicon (Si) and 2.9 wt% or less, 0.3 wt% or more of aluminum (Al) and 0.8 wt% or less, 0.1 wt% or more of manganese (Mn) and 0.4 wt% or less, 0 wt% or more of tin (Sn) and 0.003 wt% or less, 0 wt% or more of yttrium (Y) and 0.003 wt% or less, the remainder being iron (Fe) and other unavoidable impurities. The total amount of silicon (Si) and aluminum (Al) is 2.1 wt% or more and less than 3.5 wt%, The total amount of tin (Sn) and yttrium (Y) is greater than 0 wt% and less than 0.005 wt%, A method for manufacturing a non-oriented electrical steel sheet satisfying the following equation 1: [Formula 1] 80 ≤ Hv - [(100×ρ) / d] ≤ 150 In the above equation 1, Hv is the Vickers hardness, ρ is the resistivity, and d is the grain size. The resistivity (ρ) is a value calculated by Equation 2 below, [Formula 2] ρ=10.1169 + 11.7499[Si] + 8.76[Al] + 6.1985[Mn] - 10.3715(10 -4 )[S] + 14.3269(10 -4 )[P] + 13.17(10 -2 )([Sn]+[Y]) In the above formula 2, [Si], [Al], [Mn], [S], [P], [Sn] and [Y] represent the contents of Si, Al, Mn, S, P, Sn and Y in wt%, respectively.

8. In paragraph 7, The above cold rolling annealing step is: A method for manufacturing a non-oriented electrical steel sheet by annealing the above cold-rolled steel sheet at 800 to 1100°C for 5 to 600 seconds.

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