Non-oriented electrical steel sheet and its manufacturing method

Abstract

The present invention provides a non-oriented electrical steel sheet and a manufacturing method thereof that improves high-frequency iron loss by adjusting the Se, Sn, and REM contents in the alloy composition of the steel sheet. The present invention includes the steps of: hot rolling a slab containing, by weight, 2.8-4.0% Si, 0.5-1.7% Al, 0.3-2.0% Mn, 0.0005-0.005% Se, 0.005-0.06% Sn, 0.001-0.007% REM, and the balance being Fe and unavoidable impurities, to produce a hot-rolled sheet; cold rolling the hot-rolled sheet to produce a cold-rolled sheet; and cold-rolling the cold-rolled sheet. The slab further contains one or more of C, N, S, Ti, Nb, and V in an amount of 0.005 wt% or less each, and the slab further contains one or more of Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, P: 0.08 wt% or less, Sb: 0.06 wt% or less, Ni: 0.05 wt% or less, and Zn: 0.01 wt% or less.

Description

[Technical Field]

[0001] The present invention relates to a non-oriented electrical steel sheet and a manufacturing method thereof, and more particularly to a non-oriented electrical steel sheet in which high-frequency iron loss is improved by adjusting the contents of Se, Sn, and REM in the alloy composition of the steel sheet, and a manufacturing method thereof. [Background technology]

[0002] As the threat of climate change grows, countries around the world have recently announced roadmaps for achieving carbon neutrality by 2050. Total carbon emissions are expected to reach 39 billion tons in 2020, with internal combustion engines accounting for 24% of that, at 9.4 billion tons. Therefore, there is a strong demand for achieving carbon neutrality in this sector through the electrification of internal combustion engines. As a result, electrification is rapidly progressing in the mobility sector, with electric vehicles at the forefront. The driving motors required for new mobility vehicles must be able to increase mileage and top speed. This is directly related to the low iron loss characteristics of electrical steel sheets. Low iron loss in electrical steel sheets leads to improved efficiency and increased mileage. Therefore, low iron loss at high frequencies is essential for electrical steel sheets. To achieve this, electrical steel sheets typically contain a large amount of silicon and other elements, such as aluminum, manganese, and chromium, to ensure low iron loss at high frequencies. However, in addition to the method of reducing iron loss by adding large amounts of resistivity elements such as Si, Al, Mn, and Cr, it is necessary to reduce the anisotropy within the material to improve the material properties. Summary of the Invention [Problem to be solved by the invention]

[0003] The present invention provides a non-oriented electrical steel sheet and a manufacturing method thereof, specifically a non-oriented electrical steel sheet in which the high-frequency iron loss is improved by adjusting the contents of Se, Sn, and REM in the alloy composition of the steel sheet, and a manufacturing method thereof. [Means for solving the problem]

[0004] The non-oriented electrical steel sheet of the present invention is characterized by the following composition by weight: Si: 2.8-4.0%, Al: 0.5-1.7%, Mn: 0.3-2.0%, Se: 0.0005-0.005%, Sn: 0.005-0.06%, REM: 0.001-0.007%, and the balance being Fe and unavoidable impurities.

[0005] The non-oriented electrical steel sheet of the present invention can satisfy the following formula 1. [Formula 1] 30≦[Se] / ([Sn]×[REM])≦140 (In formula 1, [Se], [Sn], and [REM] represent the contents (wt%) of Se, Sn, and REM, respectively.)

[0006] The non-oriented electrical steel sheet of the present invention may further contain one or more of C, N, S, Ti, Nb, and V in an amount of 0.005 wt % or less each.

[0007] The non-oriented electrical steel sheet of the present invention may further contain one or more of Cu: 0.005 to 0.2 wt %, Cr: 0.01 to 0.5 wt %, P: 0.08 wt % or less, Sb: 0.06 wt % or less, Ni: 0.05 wt % or less, and Zn: 0.01 wt % or less.

[0008] The non-oriented electrical steel sheet of the present invention may further contain one or more of Bi, Pb, Ge, and As in an amount of 0.200 wt % or less, respectively or in total.

[0009] The non-oriented electrical steel sheet of the present invention may further contain one or more of Mo: 0.03 wt % or less, B: 0.0050 wt % or less, Ca: 0.0050 wt % or less, and Mg: 0.0050 wt % or less.

[0010] The non-oriented electrical steel sheet of the present invention may have a resistivity of 50 μΩ·cm or more.

[0011] The non-oriented electrical steel sheet of the present invention may have an average crystal grain size of 30 to 140 μm.

[0012] In the non-oriented electrical steel sheet of the present invention, the area fraction of crystal grains having a grain size that is 30% to 170% of the average crystal grain size may be 70% or more.

[0013] The method for producing a non-oriented electrical steel sheet of the present invention is characterized by comprising the steps of: hot rolling a slab containing, by weight, 2.8 to 4.0% Si, 0.5 to 1.7% Al, 0.3 to 2.0% Mn, 0.0005 to 0.005% Se, 0.005 to 0.06% Sn, 0.001 to 0.007% REM, and the balance being Fe and unavoidable impurities, to produce a hot-rolled sheet; cold-rolling the hot-rolled sheet to produce a cold-rolled sheet; and cold-rolling the cold-rolled sheet.

[0014] The slabs may further include one or more of C, N, S, Ti, Nb, and V in amounts of up to 0.005 wt. % each.

[0015] The slab may further contain one or more of Cu: 0.005 to 0.2 wt %, Cr: 0.01 to 0.5 wt %, P: 0.08 wt % or less, Sb: 0.06 wt % or less, Ni: 0.05 wt % or less, and Zn: 0.01 wt % or less.

[0016] The slab may further contain one or more of Bi, Pb, Ge, and As in an amount of 0.200% by weight or less (excluding 0%), either individually or in total.

[0017] The slab may further contain one or more of Mo: 0.03% by weight or less (excluding 0%), B: 0.0050% by weight or less (excluding 0%), Ca: 0.0050% by weight or less (excluding 0%), and Mg: 0.0050% by weight or less (excluding 0%).

[0018] During the annealing stage of the cold-rolled sheet, at the entrance of the annealing furnace, the difference between the maximum tension and the minimum tension for a length of 2000 mm in the rolling direction of the cold-rolled sheet is 0.017 kgf / mm 2 It may be the following:

[0019] At the entrance of the annealing furnace, the average tension is 0.07 to 0.5 kgf / mm2 may be. In the cold-rolled sheet annealing stage, the maximum temperature of the annealing furnace may be 875 to 1000°C. In the cold-rolled sheet annealing step, the soaking time may be 25 to 60 seconds. [Effects of the Invention]

[0020] The non-oriented electrical steel sheet of the present invention can have even more excellent properties by optimizing the amount of elements added that segregate or precipitate at grain boundaries to improve core loss anisotropy. The non-oriented electrical steel sheet of the present invention can have more excellent properties by controlling the deviation of the annealing tension in the cold-rolled sheet annealing process, thereby uniformly controlling the grain size and improving the iron loss anisotropy. Ultimately, the non-oriented electrical steel sheet of the present invention contributes to the production of environmentally friendly motors for automobiles, highly efficient motors for home appliances, and super premium class electric motors. DETAILED DESCRIPTION OF THE INVENTION

[0021] Terms such as "first," "second," and "third" are used to describe various portions, components, regions, layers, and / or sections, but are not limited thereto. These terms are used only to distinguish one portion, component, region, layer, or section from another portion, component, region, layer, or section. Therefore, a first portion, component, region, layer, or section described below can be referred to as a second portion, component, region, layer, or section without departing from the scope of the present invention. The terminology used herein is merely for the purpose of referring to particular embodiments and is not intended to limit the present invention. As used herein, the singular forms "a," "an," and "the" include the plural forms unless the context clearly dictates otherwise. As used in the specification, the term "comprising" refers to the inclusion of certain features, regions, integers, steps, operations, elements, and / or components, and does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0022] When a part is referred to as being "on" or "above" another part, it means that it is directly on or above the other part, or there may be other parts between them. In contrast, when a part is referred to as being "directly on" another part, there are no other parts between them. Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains. Terms defined in commonly used dictionaries are additionally interpreted to have a meaning consistent with the relevant technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal sense unless otherwise defined. Unless otherwise specified, % means % by weight, and 1 ppm is 0.0001% by weight. In one embodiment of the present invention, the inclusion of an additional element means that the remaining iron (Fe) is replaced by the additional amount of the additional element.

[0023] Although the present invention may be embodied in many different forms and is not limited to the embodiments set forth herein, the present invention will be described in detail below so that those skilled in the art can easily practice the present invention. The contents of Se, Sn, and REM in the alloy composition of the steel sheet of the present invention are adjusted, and the amounts of elements that segregate or precipitate at the grain boundaries are optimized to improve the core loss anisotropy. The non-oriented electrical steel sheet of the present invention is composed of, by weight %, 2.8 to 4.0% Si, 0.5 to 1.7% Al, 0.3 to 2.0% Mn, 0.0005 to 0.005% Se, 0.005 to 0.06% Sn, 0.001 to 0.007% REM, and the balance being Fe and unavoidable impurities.

[0024] First, the reasons for limiting the components of non-oriented electrical steel sheets will be explained. Si::2.8~4.0wt% Silicon (Si) must be added in relatively large amounts because it increases the resistivity of the material and reduces iron loss. If too little Si is added, the effect of improving high-frequency iron loss may be minimal. If too much Si is added, the hardness of the material increases, which is undesirable as it reduces productivity and punchability. More specifically, the Si content may be 3.0 to 3.7 wt %.

[0025] Al: 0.5~1.7% by weight Aluminum (Al) must be added in large amounts because it increases the material's resistivity and reduces iron loss. If too little Al is added, it is ineffective in reducing high-frequency iron loss and can cause the formation of fine nitrides, which can degrade magnetic properties. If too much Al is added, it can change the physical properties of the mold flux during the continuous casting process, significantly reducing productivity. More specifically, the Al content can be 0.7 to 1.5 wt.%.

[0026] Mn:0.3~2.0wt% Manganese (Mn) increases the resistivity of the material, improves iron loss, and forms sulfides. If too little Mn is added, fine MnS precipitates, which can degrade magnetic properties. If too much Mn is added, it can promote the formation of a

[0111] texture, which is unfavorable to magnetic properties, and can cause a rapid decrease in magnetic flux density. More specifically, Mn can be included in an amount of 0.5 to 1.5 wt.%.

[0027] Specific resistance 50 μΩ cm or more Higher resistivity is better for reducing eddy current loss in high-frequency rotating machines, but excessively high resistivity can result in poor magnetic flux density. In this invention, resistivity can be calculated as 13.25 + 11.3 × ([Si] + [Al] + [Mn] / 2), where [Si], [Al], and [Mn] represent the Si, Al, and Mn contents (weight percent), respectively. Higher resistivity reduces iron loss. If resistivity is too low, iron loss will be poor, making it difficult to use as a high-efficiency motor. More specifically, the resistivity may be 50 to 90 μΩ·cm. Even more specifically, the resistivity may be 60 to 85 μΩ·cm.

[0028] Se:0.0005~0.0050wt%, Sn0.005~0.060wt%, REM0.001~0.007wt% Selenium (Se), tin (Sn), and rare earth elements (REM) can segregate or precipitate at grain boundaries. They can also precipitate together to form SeSn intermetallic compounds or as sulfides. The segregation effect is maximized by the interaction of each element within the specified range. Outside of this range, elements precipitate as intermetallic compounds or sulfides, affecting magnetic properties. If one or more of Se, Sn, and REM are contained below the specified range, the desired effect cannot be achieved. If one or more of Se, Sn, and REM are contained in excess of the specified range, excessive segregation or precipitation may occur, resulting in poor core loss. More specifically, the alloy can contain 0.0010 to 0.0030 wt% Se, 0.010 to 0.050 wt% Sn, and 0.003 to 0.005 wt% REM.

[0029] In the present invention, rare earth elements (REM) refer to a total of 17 elements, including 15 elements with atomic numbers 57 to 71 and two elements, Sc and Y. When two or more elements are contained, the content of REM refers to the total of the two or more elements.

[0030] In the present invention, the following formula 1 can be satisfied. [Formula 1] 30≦[Se] / ([Sn]×[REM])≦140 (In formula 1, [Se], [Sn], and [REM] represent the contents (wt%) of Se, Sn, and REM, respectively.) Equation 1 shows the correlation between Se, Sn, and REM, where the interaction maximizes the segregation effect.

[0031] The non-oriented electrical steel sheet of the present invention may further contain one or more of Cu: 0.005 to 0.2 wt %, Cr: 0.01 to 0.5 wt %, P: 0.08 wt % or less, Sb: 0.06 wt % or less, Ni: 0.05 wt % or less, and Zn: 0.01 wt % or less.

[0032] Cu:0.005~0.200wt% Copper (Cu) acts to form sulfides with Mn. If Cu is added in an excessively small amount, fine CuMnS precipitates, which can deteriorate magnetic properties. If Cu is added in an excessively large amount, high-temperature brittleness occurs, which can lead to cracks during continuous casting or hot rolling. More specifically, Cu can be contained in an amount of 0.01 to 0.10 wt%.

[0033] Cr:0.010~0.50wt% Chromium (Cr) plays a role in increasing resistivity and improving iron loss. If too little Cr is added, the effect of increasing resistivity may be insufficient. If too much Cr is added, the magnetic flux density may decrease. More specifically, if Cr is further added, it may be contained in an amount of 0.050 to 0.20 wt %.

[0034] P: 0.08% by weight or less Phosphorus (P) is concentrated on the surface and plays a role in controlling the fraction of the internal oxide layer. If the amount of P added is too small, it may be difficult to form a uniform internal oxide layer. If the amount of P added is too large, the melting point of the Si-based oxide may fluctuate, causing the internal oxide layer to form suddenly. Therefore, the P content can be controlled within the above range. More specifically, P can be contained in an amount of 0.005 to 0.07 wt %.

[0035] Sb: 0.06% by weight or less Antimony (Sb) is an element that segregates at grain boundaries. It is added to suppress the diffusion of nitrogen through grain boundaries, suppress the {111} texture that is detrimental to magnetism, and increase the advantageous {100} texture, thereby improving magnetic properties. Addition of excessive Sb hinders grain growth, reducing magnetism and worsening rolling properties. Therefore, Sb can be added within the aforementioned range. More specifically, it can be contained in an amount of 0.005 to 0.060 wt. %. Even more specifically, it can be contained in an amount of 0.01 to 0.05 wt. %.

[0036] Ni: 0.05% by weight or less Nickel (Ni) reacts with impurity elements to form fine sulfides, carbides, and nitrides, which can have a detrimental effect on magnetic properties. More specifically, Ni can be contained in an amount of 0.001 to 0.03 wt %.

[0037] Zn: 0.01% by weight or less If the zinc (Zn) content is excessive, it may act as an impurity and cause deterioration of magnetic properties. Therefore, Zn may be further added within the above range. More specifically, it may be contained in an amount of 0.001 to 0.005 wt %.

[0038] The non-oriented electrical steel sheet of the present invention may further contain one or more of Bi, Pb, Ge, and As in an amount of 0.200 wt % or less, respectively or in total.

[0039] When the above elements are added, they segregate at the grain boundaries, alleviating stress concentration at the grain boundaries during cold rolling, and in the subsequent recrystallization annealing process, <111> / / They improve magnetic flux density by suppressing recrystallization of ND-oriented crystal grains. While the aforementioned effects can be achieved by adding these elements appropriately, excessive amounts can cause significant segregation, suppressing grain growth and potentially resulting in poor magnetic flux density and core loss. More specifically, the alloy may further contain 0.0001 to 0.200 wt.% of one or more of Bi, Pb, Ge, and As, individually or in total. More specifically, the alloy may further contain 0.001 to 0.100 wt.%. The alloy may further contain 0.005 to 0.050 wt.%.

[0040] The non-oriented electrical steel sheet of the present invention may further contain one or more of Mo: 0.03 wt % or less, B: 0.0050 wt % or less, Ca: 0.0050 wt % or less, and Mg: 0.0050 wt % or less. These react with the unavoidably contained C, S, N, etc. to form fine carbides, nitrides, or sulfides, which can adversely affect the magnetic properties, so the upper limit can be set as described above.

[0041] Other impurities In addition to the elements mentioned above, unavoidable impurities such as carbon (C), sulfur (S), nitrogen (N), titanium (Ti), niobium (Nb), and vanadium (V) may be included. C, N, and Ti can be limited because they form carbonitrides and play a role in hindering magnetic domain movement, and S can form sulfides and impair grain growth, so its upper limit can be limited. Each of these elements can be contained in an amount of 0.0040 wt% or less. N combines with Ti, Nb, and V to form nitrides, which reduces grain growth. C reacts with N, Ti, Nb, V, etc. to form fine carbides, which serve to hinder grain growth and magnetic domain movement. S forms sulfides and impairs grain growth.

[0042] When impurity elements are further contained in this way, one or more of C, S, N, Ti, Nb, and V may be contained in an amount of 0.005 wt % or less each. The non-oriented electrical steel sheet according to the present invention may have an average grain size of 30 to 140 μm. By appropriately adjusting the average grain size, magnetic properties can be further improved. The grain size of the present invention can be measured in a plane parallel to the sheet surface of the steel sheet. More specifically, it can be measured in a thickness range of 1 / 4t to 3 / 4t, where t is the total thickness of the steel sheet. The grain size can be measured by imagining an imaginary circle having the same area as the grain, and the diameter of the circle is taken as the grain size. The average grain size can be measured by dividing the number of grains present within the area to be measured by the area to be measured. More specifically, the non-oriented electrical steel sheet according to an embodiment of the present invention may have an average grain size of 50 to 100 μm. The grain size can be measured using an optical microscope, and the grain size distribution can be measured using SEM-EBSD.

[0043] In the non-oriented electrical steel sheet of the present invention, the area fraction of crystal grains having a grain size that is 30% to 170% of the average crystal grain size may be 70% or more. The grain size within a non-oriented electrical steel sheet has a distribution, and forming the grain size uniformly improves core loss and reduces anisotropy. In particular, it is best to adjust the grain size so that it is similar to the average grain size. To achieve this, it is helpful to reduce the tension deviation during annealing, and it is also helpful to reduce the magnitude of the tension during annealing. This will be explained in detail in the manufacturing method of a non-oriented electrical steel sheet described below. More specifically, the area fraction of grains in a non-oriented electrical steel sheet may be 85% to 95% and have a grain size that is 30% to 170% of the average grain size.

[0044] The non-oriented electrical steel sheet of the present invention is excellent in high frequency iron loss, particularly in high frequency iron loss at an angle of 60 degrees to the rolling direction. Specifically, the iron loss (W 10 / 400 ) can be 11.0 W / kg or less. Core loss (W 10 / 400 ) is the iron loss when a magnetic flux density of 1.0 T is induced at a frequency of 400 Hz. More specifically, the iron loss in the rolling direction of non-oriented electrical steel sheets (W 10 / 400 ) can be 9.0 to 10.5 W / kg. In addition, the iron loss (W 10 / 400 ) can be 14.0 W / kg or less. More specifically, the iron loss (W 10 / 400 ) can be 11.0 to 13.0 W / kg. The non-oriented electrical steel sheet according to one embodiment of the present invention has a low iron loss in the rolling direction (WRD) 10 / 400 ) in the direction at an angle of 60 degrees to the rolling direction (W60 10 / 400 ) ratio (W60 10 / 400 / WRD 10 / 400 ) can be 1.27 or less. More specifically, it can be 1.10 to 1.25. When this ratio is low, it can increase the mileage and the maximum speed when manufactured into a drive motor.

[0045] The method for producing a non-oriented electrical steel sheet of the present invention includes the steps of hot rolling a slab containing, by weight, 2.8 to 4.0% Si, 0.5 to 1.7% Al, 0.3 to 2.0% Mn, 0.0005 to 0.005% Se, 0.005 to 0.06% Sn, 0.001 to 0.007% REM, and the balance being Fe and unavoidable impurities to produce a hot-rolled sheet, cold rolling the hot-rolled sheet to produce a cold-rolled sheet, and cold-rolling the cold-rolled sheet.

[0046] Each stage will be explained in detail below. First, a slab is manufactured. The reasons for limiting the addition ratio of each component in the slab are the same as those for limiting the composition of the non-oriented electrical steel sheet described above, so a repeated explanation will be omitted. The composition of the slab does not substantially change during manufacturing processes such as hot rolling, hot-rolled sheet annealing, cold rolling, and cold-rolled sheet annealing, which will be described later, so the composition of the slab and the composition of the non-oriented electrical steel sheet are substantially the same. The slab can be heated before producing the hot-rolled sheet. Specifically, the slab is placed in a heating furnace and heated to 1100-1250°C. When heated at temperatures exceeding 1250°C, precipitates may remelt and precipitate finely after hot rolling. The heated slab is hot-rolled to 2 to 2.3 mm to produce a hot-rolled sheet. In the step of producing the hot-rolled sheet, the finish rolling temperature may be 800 to 1000°C.

[0047] After the step of producing the hot-rolled sheet, the method may further include a step of annealing the hot-rolled sheet. Here, the annealing temperature may be 850 to 1150°C. If the annealing temperature is less than 850°C, the structure does not grow or grows finely, resulting in little effect in increasing magnetic flux density. If the annealing temperature exceeds 1150°C, the magnetic properties may deteriorate and the rolling workability may be impaired due to deformation of the sheet shape. More specifically, the temperature range may be 950 to 1125°C. More specifically, the annealing temperature of the hot-rolled sheet is 900 to 1100°C. Hot-rolled sheet annealing is performed to increase orientation favorable for magnetic properties as needed, and may be omitted.

[0048] Next, the hot-rolled sheet is pickled and cold-rolled to the desired thickness. Depending on the thickness of the hot-rolled sheet, a reduction of 70-95% can be applied, and cold-rolling can be performed to a final thickness of 0.2-0.65 mm. To achieve the desired reduction, cold rolling can be performed once, or two or more times with intermediate annealing.

[0049] The cold-rolled sheet is subjected to cold-rolled sheet annealing. During the annealing stage of the cold-rolled sheet, the difference between the maximum and minimum tensions for a length of 2000 mm in the rolling direction of the cold-rolled sheet at the entrance of the annealing furnace is 0.017 kgf / mm 2 It can be the following: Bridle rolls are used to apply tension to steel sheets at the entry and exit of an annealing furnace. Ideally, uniform tension should be applied along the length of the steel sheet. However, maintaining this tension consistently is difficult due to various factors, including slippage between the bridle roll and the steel sheet, fluctuations in the speed of the hearth rolls inside the annealing furnace, and thermal expansion of the steel sheet due to heating. In one embodiment of the present invention, it has been discovered that differences in the tension applied to the steel sheet cause differences in grain size. High-frequency iron loss is improved by minimizing the difference between the maximum and minimum tensions. To reduce tension deviation, methods such as minimizing slippage between the bridle roll and the steel sheet and linking the speed of the hearth rolls inside the annealing furnace with the thermal expansion of the steel sheet can be used. More specifically, the difference between the maximum and minimum tensions is 0.001 to 0.015 kgf / mm for a 2000 mm length of the cold-rolled sheet in the rolling direction at the entry side of the annealing furnace. 2 may be.

[0050] The average tension applied to the steel sheet at the entry side of the annealing furnace is 0.07 to 0.5 kgf / mm 2 If an excessive average tension is applied, the anisotropy of iron loss may increase, so the upper limit can be adjusted as described above. More specifically, it is 0.1 to 0.5 kgf / mm 2 may be. The maximum temperature of the annealing furnace in the cold-rolled sheet annealing step may be 875 to 1000°C. If the maximum temperature of the annealing furnace is too high, defects such as surface microdents may increase, and the grain growth rate may increase, resulting in poor grain size uniformity. More specifically, the maximum temperature of the annealing furnace may be 900 to 997°C. The cracking time is the time during which the temperature remains constant without any fluctuations after the cracking temperature is reached. The cracking time may be 25 to 60 seconds. More specifically, it may be 30 to 50 seconds. Thereafter, a step of forming an insulating layer may be further included. A method of forming an insulating layer is widely known in the technical field of non-oriented electrical steel sheets, and therefore, detailed description thereof will be omitted. Preferred examples and comparative examples of the present invention will be described below. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples. [Example]

[0051] The slabs were manufactured as shown in Table 1 below. The elements C, S, N, Ti, Nb, and V other than those listed in Table 1 were all controlled to 0.003 wt% or less, with the remainder being Fe. REM included Ce, Y, and Sc. The slab was heated to 1150°C and hot-finish rolled at 850°C to produce a hot-rolled sheet with a thickness of 2.0 mm. The hot-rolled sheet was annealed at 1100°C for 4 minutes and then pickled. It was then cold-rolled to produce a cold-rolled sheet with a thickness of 0.25 mm, and cold-rolled sheet annealing was performed under the conditions summarized in Table 2 below. The iron loss was measured by cutting five specimens of 60 mm width x 60 mm length for each specimen, and measuring the direction at an angle of 60 degrees to the rolling direction using a single sheet tester. The grain size was investigated using an optical microscope, and the grain size distribution was measured using SEM-EBSD. The tension was measured by using a load cell to measure the force applied to the bridle roll.

[0052] [Table 1]

[0053] [Table 2]

[0054] [Table 3]

[0055] As shown in Tables 1 to 3, it can be seen that the alloy element deposition characteristics are appropriately adjusted, and the iron loss and the anisotropy of the iron loss are improved. When the tension deviation during annealing of the cold-rolled sheet is adjusted, it can be confirmed that the distribution of crystal grains is uniformly formed, and the iron loss and iron loss anisotropy are further improved. The present invention is not limited to the above-described embodiments, and can be manufactured in various different forms, and those skilled in the art will understand that the present invention can be embodied in other specific forms without changing the technical concept or essential features of the present invention. Therefore, it should be understood that the above-described embodiments are illustrative in all respects and not limiting.

Claims

1. A non-oriented electrical steel sheet comprising, by weight%, 2.8 to 4.0% Si, 0.5 to 1.7% Al, 0.3 to 2.0% Mn, 0.0005 to 0.005% Se, 0.005 to 0.06% Sn, and 0.001 to 0.007% REM, with the balance being Fe and unavoidable impurities.

2. 2. The non-oriented electrical steel sheet according to claim 1, wherein the following formula 1 is satisfied: [Formula 1] 30≦[Se] / ([Sn]×[REM])≦140 (In formula 1, [Se], [Sn], and [REM] represent the contents (wt%) of Se, Sn, and REM, respectively.)

3. 2. The non-oriented electrical steel sheet according to claim 1, further comprising at least one of C, N, S, Ti, Nb, and V in an amount of 0.005 wt. % or less.

4. 2. The non-oriented electrical steel sheet according to claim 1, further comprising one or more of Cu: 0.005 to 0.2 wt %, Cr: 0.01 to 0.5 wt %, P: 0.08 wt % or less, Sb: 0.06 wt % or less, Ni: 0.05 wt % or less, and Zn: 0.01 wt % or less.

5. 2. The non-oriented electrical steel sheet according to claim 1, further comprising one or more of Bi, Pb, Ge, and As in an amount of 0.200 wt % or less, respectively or in a total amount thereof.

6. 2. The non-oriented electrical steel sheet according to claim 1, further comprising one or more of Mo: 0.03 wt % or less, B: 0.0050 wt % or less, Ca: 0.0050 wt % or less, and Mg: 0.0050 wt % or less.

7. 2. The non-oriented electrical steel sheet according to claim 1, wherein the resistivity is 50 μΩ·cm or more.

8. 2. The non-oriented electrical steel sheet according to claim 1, wherein the average crystal grain size is 30 to 140 μm.

9. 2. The non-oriented electrical steel sheet according to claim 1, wherein the area fraction of crystal grains having a grain size that is 30% to 170% of the average crystal grain size is 70% or more.

10. a step of producing a hot-rolled sheet by hot-rolling a slab containing, in weight percent, 2.8 to 4.0% Si, 0.5 to 1.7% Al, 0.3 to 2.0% Mn, 0.0005 to 0.005% Se, 0.005 to 0.06% Sn, 0.001 to 0.007% REM, and the balance being Fe and unavoidable impurities; cold-rolling the hot-rolled sheet to produce a cold-rolled sheet; and annealing the cold-rolled sheet.

11. The method for manufacturing a non-oriented electrical steel sheet according to claim 10, wherein the slab further contains at least one of C, N, S, Ti, Nb, and V in an amount of 0.005 wt% or less.

12. 11. The method for producing a non-oriented electrical steel sheet according to claim 10, wherein the slab further contains one or more of Cu: 0.005 to 0.2 wt %, Cr: 0.01 to 0.5 wt %, P: 0.08 wt % or less, Sb: 0.06 wt % or less, Ni: 0.05 wt % or less, and Zn: 0.01 wt % or less.

13. 11. The method for producing a non-oriented electrical steel sheet according to claim 10, wherein the slab further contains one or more of Bi, Pb, Ge, and As in an amount of 0.200% by weight or less (excluding 0%), either individually or in total.

14. 11. The method for producing a non-oriented electrical steel sheet according to claim 10, wherein the slab further contains one or more of Mo: 0.03% by weight or less (excluding 0%), B: 0.0050% by weight or less (excluding 0%), Ca: 0.0050% by weight or less (excluding 0%), and Mg: 0.0050% by weight or less (excluding 0%).

15. During the annealing step of the cold-rolled sheet, the difference between the maximum tension and the minimum tension for a length of 2000 mm in the rolling direction of the cold-rolled sheet at the annealing furnace entry side is 0.017 kgf / mm ２ 11. The method for producing a non-oriented electrical steel sheet according to claim 10, wherein the following is true:

16. On the entry side of the annealing furnace, the average tension is 0.07 to 0.5 kgf / mm ２ The method for producing a non-oriented electrical steel sheet according to claim 10,

17. 11. The method of claim 10, wherein the maximum temperature of the annealing furnace in the cold-rolled sheet annealing step is 875 to 1000°C.

18. The method for manufacturing a non-oriented electrical steel sheet according to claim 10, wherein the cracking time in the cold-rolled sheet annealing step is 25 to 60 seconds.

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