Non-oriented electrical steel sheet and method for producing same

Abstract

The non-oriented electrical steel sheet according to one embodiment of the present invention comprises, in wt%, 2.8 to 4.0% of Si, 0.5 to 1.7% of Al, 0.3 to 2.0% of Mn, 0.0005 to 0.005% of Se, 0.005 to 0.06% of Sn, 0.001 to 0.007% of REM, and the balance of Fe and unavoidable impurities.

Description

Technical Field

[0001] One embodiment of the present invention relates to a non-oriented electrical steel sheet and a method for manufacturing the same. Specifically, one embodiment of the present invention relates to a non-oriented electrical steel sheet and a method for manufacturing the same, which improves the high-frequency iron loss by adjusting the contents of Se, Sn, and REM in the alloy components of the steel sheet. Background Art

[0002] Recently, due to the increasing disasters caused by climate change, countries have successively issued carbon neutral roadmaps for 2050. The total carbon emissions in 2020 reached 3.9 billion tons, of which the emissions from internal combustion engines accounted for 24%, that is, 940 million tons. Therefore, the demand for achieving carbon neutrality in this field through the electrification of internal combustion engines is very urgent. For this reason, in the field of mobility, electrification led by electric vehicles is rapidly advancing. In new mobility, the requirements for drive motors are to extend the driving range and increase the maximum speed. This is directly related to the low iron loss characteristics of electrical steel sheets. If the iron loss of the electrical steel sheet is low, the efficiency can be further improved, thereby extending the driving range. Therefore, the high-frequency low iron loss characteristics of electrical steel sheets are essential. For this purpose, electrical steel sheets usually contain a large amount of Si and a large amount of elements such as Al, Mn, and Cr are added to ensure high-frequency low iron loss.

[0003] However, in addition to reducing the iron loss by adding a large amount of resistivity elements such as Si, Al, Mn, and Cr, it is also necessary to reduce the anisotropy inside the material to improve the material properties. Summary of the Invention

[0004] (1) Technical Problems to be Solved

[0005] In one embodiment of the present invention, it aims to provide a non-oriented electrical steel sheet and a method for manufacturing the same. Specifically, one embodiment of the present invention aims to provide a non-oriented electrical steel sheet and a method for manufacturing the same, which improves the high-frequency iron loss by adjusting the contents of Se, Sn, and REM in the alloy components of the steel sheet.

[0006] (2) Technical Solutions

[0007] The non-oriented electrical steel sheet according to one embodiment of the present invention, in terms of weight %, comprises Si: 2.8 to 4.0%, Al: 0.5 to 1.7%, Mn: 0.3 to 2.0%, Se: 0.0005 to 0.005%, Sn: 0.005 to 0.06%, REM: 0.001 to 0.007%, and the balance comprises Fe and unavoidable impurities.

[0008] The non-oriented electrical steel sheet according to one embodiment of the present invention can satisfy the following formula 1.

[0009] [Formula 1]

[0010] 30 ≤ [Se] / ([Sn] × [REM]) ≤ 140

[0011] In Formula 1, [Se], [Sn], and [REM] each represent the contents (wt%) of Se, Sn, and REM, respectively.

[0012] The non-oriented electrical steel sheet according to an embodiment of the present invention may further contain one or more of C, N, S, Ti, Nb, and V, and their contents are each 0.005 wt% or less.

[0013] The non-oriented electrical steel sheet according to an embodiment 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.

[0014] The non-oriented electrical steel sheet according to an embodiment of the present invention may further contain one or two or more of Bi, Pb, Ge, and As, and their contents are each or in total 0.200 wt% or less.

[0015] The non-oriented electrical steel sheet according to an embodiment 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.

[0016] The resistivity of the non-oriented electrical steel sheet according to an embodiment of the present invention may be 50 μΩ·cm or more.

[0017] The average grain size of the non-oriented electrical steel sheet according to an embodiment of the present invention may be 30 to 140 μm.

[0018] In the non-oriented electrical steel sheet according to an embodiment of the present invention, the area fraction of grains having a particle size of 30% to 170% of the average grain size may be 70% or more.

[0019] A method for manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention includes: a step of hot rolling a slab to manufacture a hot rolled sheet, wherein, by weight%, the slab contains Si: 2.8 to 4.0%, Al: 0.5 to 1.7%, Mn: 0.3 to 2.0%, Se: 0.0005 to 0.005%, Sn: 0.005 to 0.06%, REM: 0.001 to 0.007%, and the balance contains Fe and inevitable impurities; a step of cold rolling the hot rolled sheet to manufacture a cold rolled sheet; and a step of annealing the cold rolled sheet.

[0020] The slab may further contain one or more of C, N, S, Ti, Nb, and V, with their contents being 0.005 wt% or less respectively.

[0021] 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.

[0022] The slab may further contain one or two or more of Bi, Pb, Ge, and As, with their contents being 0.200 wt% or less each or in total, except 0%.

[0023] The slab may further contain one or more of Mo: 0.03 wt% or less, except 0%, B: 0.0050 wt% or less, except 0%, Ca: 0.0050 wt% or less, except 0%, and Mg: 0.0050 wt% or less, except 0%.

[0024] In the cold-rolled sheet annealing step, at the inlet side of the annealing furnace, the difference between the maximum tension and the minimum tension in the rolling direction of the cold-rolled sheet may be 0.017 kgf / mm with respect to a length of 2000 mm. 2 or less.

[0025] At the inlet side of the annealing furnace, the average tension may be 0.07 to 0.5 kgf / mm. 2 .

[0026] In the cold-rolled sheet annealing step, the maximum temperature of the annealing furnace may be 875 to 1000 °C.

[0027] In the cold-rolled sheet annealing step, the soaking time may be 25 to 60 seconds.

[0028] (III) Advantageous Effects

[0029] The non-oriented electrical steel sheet according to an embodiment of the present invention can have more excellent properties by optimizing the addition amounts of elements segregated or precipitated at grain boundaries to improve iron loss anisotropy.

[0030] The non-oriented electrical steel sheet according to an embodiment of the present invention can have more excellent properties by adjusting the deviation of the annealing tension in the cold-rolled sheet annealing process to uniformly control the grain size and by improving iron loss anisotropy.

[0031] Ultimately, the non-oriented electrical steel sheet according to an embodiment of the present invention contributes to the manufacture of motors for environmentally friendly vehicles, motors for high-efficiency household appliances, and ultra-high-end electric motors. Detailed Embodiments

[0032] The terms "first", "second", "third", etc. are used to describe various parts, components, regions, layers, and / or segments, but these parts, components, regions, layers, and / or segments should not be limited by these terms. These terms are only used to distinguish one part, component, region, layer, or segment from another part, component, region, layer, or segment. Thus, within the scope of not departing from the present invention, the first part, component, region, layer, or segment described below can also be described as the second part, component, region, layer, or segment.

[0033] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present invention. Unless otherwise clearly indicated to the contrary in the context, the singular forms used herein are also intended to include the plural forms. The use of "comprising" in the specification can specifically refer to a certain property, field, integer, step, action, element, and / or component, but does not exclude the existence or addition of other properties, fields, integers, steps, actions, elements, and / or components.

[0034] If a part is described as being above another part, there may be other parts directly above or between the other part. When a part is described as being directly above another part, there are no other parts therebetween.

[0035] Although not otherwise defined, the meanings of all terms (including technical and scientific terms) used herein are the same as those commonly understood by a person of ordinary skill in the art to which the present invention pertains. For terms defined in a dictionary, they should be interpreted as having a meaning consistent with the relevant technical literature and the content disclosed herein, and should not be interpreted in an idealized or overly formal sense.

[0036] In addition, unless otherwise specifically stated, % represents weight %, and 1 ppm is 0.0001 weight %.

[0037] In one embodiment of the present invention, further comprising additional elements means that the additional elements replace the remaining iron (Fe), and the replacement amount is equivalent to the added amount of the additional elements.

[0038] Hereinafter, embodiments of the present invention will be described in detail so that a person of ordinary skill in the art to which the present invention pertains can easily implement the present invention. However, the present invention can be implemented in various different ways and is not limited to the embodiments described herein.

[0039] In one embodiment of the present invention, the contents of Se, Sn, and REM in the alloy components of the steel plate are adjusted, and the added amounts of the elements segregated or precipitated at the grain boundaries are optimized, thereby improving the iron loss anisotropy.

[0040] An non-oriented electrical steel sheet according to an embodiment of the present invention, in weight %, the non-oriented electrical steel sheet contains Si: 2.8 to 4.0%, Al: 0.5 to 1.7%, Mn: 0.3 to 2.0%, Se: 0.0005 to 0.005%, Sn: 0.005 to 0.06%, REM: 0.001 to 0.007%, and the balance contains Fe and inevitable impurities.

[0041] First, the reasons for the composition limitations of the non-oriented electrical steel sheet will be described.

[0042] Si: 2.8 to 4.0 wt%

[0043] Silicon (Si) plays a role in increasing the resistivity of the material to reduce iron loss, so a relatively large amount needs to be added. 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, and productivity and punching properties deteriorate, so it is not preferred. More specifically, Si may contain 3.0 to 3.7 wt%.

[0044] Al: 0.5 to 1.7 wt%

[0045] Aluminum (Al) plays a role in increasing the resistivity of the material to reduce iron loss, so a large amount needs to be added. If too little Al is added, there is no effect on reducing high-frequency iron loss, fine nitrides are formed, and magnetic properties may deteriorate. If too much Al is added, problems such as changing the physical properties of the mold powder during the continuous casting process may occur, and productivity may be greatly reduced. More specifically, Al may contain 0.7 to 1.5 wt%.

[0046] Mn: 0.3 to 2.0 wt%

[0047] Manganese (Mn) plays a role in increasing the resistivity of the material to improve iron loss and forming sulfides. If too little Mn is added, fine precipitation of MnS may occur, and magnetic properties may deteriorate. If too much Mn is added, it promotes the formation of a

[111] texture that is unfavorable for magnetism, and the magnetic flux density may decrease sharply. More specifically, Mn may contain 0.5 to 1.5 wt%.

[0048] The resistivity is 50 μΩ·cm or more

[0049] To reduce eddy current losses in high-frequency rotating motors, a larger resistivity is better. However, when the resistivity is too large, the magnetic flux density may deteriorate. In an embodiment of the present invention, the resistivity can be calculated by 13.25 + 11.3×([Si] + [Al] + [Mn] / 2). At this time, [Si], [Al], and [Mn] respectively represent the contents (weight %) of Si, Al, and Mn. The higher the resistivity, the more helpful it is to reduce iron loss. The lower the resistivity, the worse the iron loss, and it is difficult to be used in an efficient motor. More specifically, the resistivity can be 50 to 90 μΩ·cm. More specifically, the resistivity can be 60 to 85 μΩ·cm.

[0050] Se: 0.0005 to 0.0050 wt%, Sn 0.005 to 0.060 wt%, REM 0.001 to 0.007 wt%

[0051] Selenium (Se), tin (Sn), and rare earth elements (REM) can segregate or precipitate at grain boundaries. They can form intermetallic compounds of SeSn by eutectoid or form sulfides by eutectoid. The interaction of each element within this range maximizes the segregation effect, while outside this range, they precipitate in the form of intermetallic compounds or sulfides, etc., thus affecting magnetism. If the content of one or more elements among Se, Sn, and REM is less than this range, the expected effect cannot be obtained. If the content of one or more elements among Se, Sn, and REM is more than this range, a large amount of segregation or precipitation occurs, and instead, the iron loss deteriorates. More specifically, it can contain Se: 0.0010 to 0.0030 wt%, Sn: 0.010 to 0.050 wt%, REM: 0.003 to 0.005 wt%.

[0052] In an embodiment of the present invention, the rare earth elements (REM) refer to 15 elements with atomic numbers from 57 to 71 and 2 elements of Sc and Y, a total of 17 elements. When two or more elements are included, the content of REM refers to the sum of two or more elements.

[0053] In an embodiment of the present invention, the following formula 1 can be satisfied.

[0054] [Formula 1]

[0055] 30 ≤ [Se] / ([Sn]×[REM]) ≤ 140

[0056] In formula 1, [Se], [Sn], and [REM] respectively represent the contents (weight %) of Se, Sn, and REM.

[0057] Formula 1 represents the correlation between Se, Sn, and REM that maximizes the segregation effect through interaction.

[0058] The non-oriented electrical steel sheet according to an embodiment of the present invention may further contain one or more of Cu: 0.005 to 0.2% by weight, Cr: 0.01 to 0.5% by weight, P: 0.08% by weight or less, Sb: 0.06% by weight or less, Ni: 0.05% by weight or less, and Zn: 0.01% by weight or less.

[0059] Cu: 0.005 to 0.200% by weight

[0060] Copper (Cu) functions to form sulfides together with Mn. When further adding Cu, if too little is added, fine precipitation of CuMnS may occur, which may lead to magnetic deterioration. If too much Cu is added, high-temperature brittleness will occur, and cracks may form during continuous casting or hot rolling. More specifically, Cu may contain 0.01 to 0.10% by weight.

[0061] Cr: 0.010 to 0.50% by weight

[0062] Chromium (Cr) functions to improve the resistivity to improve the iron loss. If too little Cr is added, the effect of increasing the resistivity may be insufficient. If too much Cr is added, the magnetic flux density may decrease. More specifically, when further containing Cr, it may contain 0.050 to 0.20% by weight.

[0063] P: 0.08% by weight or less

[0064] Phosphorus (P) is enriched on the surface, thus functioning to control the fraction of the internal oxide layer. If too little P is added, it may be difficult to form the internal oxide layer. If too much P is added, the melting point of the Si-based oxide changes, which may lead to the rapid formation of the internal oxide layer. Therefore, the content of P can be controlled within the aforementioned range. More specifically, P may contain 0.005 to 0.07% by weight.

[0065] Sb: 0.06% by weight or less

[0066] Antimony (Sb) is a grain boundary segregation element, which inhibits the diffusion of nitrogen through the grain boundary, inhibits the {111} texture (texture) harmful to magnetism, and increases the favorable {100} texture to improve the magnetic properties. If too much Sb is added, it hinders grain growth, thereby reducing the magnetism and deteriorating the rollability. Therefore, Sb can be added within the aforementioned range. More specifically, it may contain 0.005 to 0.060% by weight. More specifically, it may contain 0.01 to 0.05% by weight.

[0067] Ni: 0.05% by weight or less

[0068] Nickel (Ni) reacts with impurity elements to form fine sulfides, carbides, and nitrides, which may have an adverse effect on magnetism. More specifically, Ni may contain 0.001 to 0.03% by weight.

[0069] Zn: 0.01% by weight or less

[0070] When the content of zinc (Zn) is excessive, as an impurity, it may cause magnetism. Therefore, Zn can be further added within the aforementioned range. More specifically, it may contain 0.001 to 0.005% by weight.

[0071] The non-oriented electrical steel sheet according to an embodiment of the present invention may further contain one or more of Bi, Pb, Ge, and As, and the content thereof is 0.200% by weight or less individually or in total.

[0072] When the aforementioned elements are further added, they segregate at the grain boundaries, relieve the stress concentration at the grain boundaries during cold rolling, and suppress the recrystallization of <111> / / ND-oriented grains during subsequent process recrystallization annealing, thereby increasing the magnetic flux density. When these elements are further added, the aforementioned effects can be further obtained, but if too much is contained, a large amount of segregation will occur, thereby suppressing grain growth, and the magnetic flux density and iron loss will deteriorate instead. More specifically, it may further contain one or more of Bi, Pb, Ge, and As, and the content thereof is 0.0001 to 0.200% by weight individually or in total. More specifically, it may further contain 0.001 to 0.100% by weight. It may further contain 0.005 to 0.050% by weight.

[0073] The non-oriented electrical steel sheet according to an embodiment of the present invention may further contain one or more of Mo: 0.03% by weight or less, B: 0.0050% by weight or less, Ca: 0.0050% by weight or less, and Mg: 0.0050% by weight or less.

[0074] These elements react with inevitably contained C, S, N, etc. to form carbides, nitrides, or sulfides, which may have an adverse effect on magnetism. Therefore, the upper limit can be restricted as described above.

[0075] Other impurities

[0076] In addition to the aforementioned elements, it may further contain inevitably mixed impurities such as carbon (C), sulfur (S), nitrogen (N), titanium (Ti), niobium (Nb), vanadium (V), etc.

[0077] C, N, and Ti can be restricted because the formation of carbonitrides hinders the movement of magnetic domains, and the upper limit of S can be restricted because the formation of sulfides results in poor grain growth property. These elements can be contained at 0.0040% by weight or less respectively.

[0078] N combines with Ti, Nb, and V to form nitrides and plays a role in reducing grain growth.

[0079] C reacts with N, Ti, Nb, V, etc. to form fine carbides, thereby playing a role in hindering grain growth and magnetic domain movement.

[0080] S forms sulfides, resulting in poor grain growth.

[0081] Thus, when further containing impurity elements, one or more of C, S, N, Ti, Nb, and V may be contained at 0.005 wt% or less, respectively.

[0082] For the non-oriented electrical steel sheet according to an embodiment of the present invention, its average grain diameter may be 30 to 140 μm. When the average grain diameter is appropriately adjusted, the magnetic properties can be further improved. In an embodiment of the present invention, the grain diameter can be measured with respect to the plane parallel to the plate surface of the steel sheet. More specifically, with respect to the entire thickness t of the steel sheet, it can be measured at a thickness in the range of 1 / 4t to 3 / 4t. For the grain diameter, assuming a virtual circle with the same area as the grain area, the diameter of this circle is the grain diameter. The average grain diameter can be measured by dividing the number of grains present in the area to be measured by the area to be measured. More specifically, for the non-oriented electrical steel sheet according to an embodiment of the present invention, its average grain diameter may be 50 to 100 μm. The grain diameter is observed with an optical microscope, and the grain diameter distribution can be measured using SEM-EBSD.

[0083] For the non-oriented electrical steel sheet according to an embodiment of the present invention, the area fraction of grains with a diameter of 30% to 170% of the average grain diameter may be 70% or more.

[0084] In the non-oriented electrical steel sheet, the grain diameters are distributed. When the diameters of these grains are formed to be a certain size, the iron loss is improved, and the anisotropy can be reduced. In particular, it is best to adjust the grain diameter to be similar to the average grain diameter. For this purpose, reducing the tension deviation during annealing and reducing the magnitude of the tension during annealing will both be helpful. This will be specifically described in the manufacturing method of the non-oriented electrical steel sheet described below. More specifically, in the non-oriented electrical steel sheet, the area fraction of grains with a diameter of 30% to 170% of the average grain diameter may be 85% to 95%.

[0085] For the non-oriented electrical steel sheet according to an embodiment of the present invention, its high-frequency iron loss is excellent, especially the high-frequency iron loss in the rolling direction and at a 60-degree angle is excellent. Specifically, the iron loss (W 10 / 400 ) in the rolling direction of the non-oriented electrical steel sheet may be 11.0 W / kg or less. The iron loss (W 10 / 400) is the iron loss when excited at a frequency of 400HZ with a magnetic flux density of 1.0T. More specifically, the iron loss (W 10 / 400 ) in the rolling direction of the non-oriented electrical steel sheet can be 9.0 to 10.5W / kg. In addition, the iron loss (W 10 / 400 ) in the direction forming a 60-degree angle with the rolling direction of the non-oriented electrical steel sheet can be 14.0W / kg or more. More specifically, the iron loss (W 10 / 400 ) in the direction forming a 60-degree angle with the rolling direction can be 11.0 to 13.0W / kg.

[0086] For the non-oriented electrical steel sheet according to an embodiment of the present invention, the ratio of the iron loss (W60 10 / 400 ) in the direction forming a 60-degree angle with the rolling direction to the iron loss (WRD 10 / 400 ) in the rolling direction (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 adopted, when manufacturing a drive motor, the driving distance can be increased and the maximum speed can be improved.

[0087] A method for manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention includes: a step of hot-rolling a slab to manufacture a hot-rolled sheet, wherein, by weight%, the slab contains Si: 2.8 to 4.0%, Al: 0.5 to 1.7%, Mn: 0.3 to 2.0%, Se: 0.0005 to 0.005%, Sn: 0.005 to 0.06%, REM: 0.001 to 0.007%, and the balance contains Fe and unavoidable impurities; a step of cold-rolling the hot-rolled sheet to manufacture a cold-rolled sheet; and a step of annealing the cold-rolled sheet.

[0088] The following describes each step in detail.

[0089] First, a slab is manufactured. The reasons for restricting the addition ratios of the components in the slab are the same as those for restricting the components of the aforementioned non-oriented electrical steel sheet, so the repeated description is omitted. During the following manufacturing processes such as hot rolling, hot-rolled sheet annealing, cold rolling, and cold-rolled sheet annealing, the components of the slab do not substantially change, so the components of the slab are substantially the same as those of the non-oriented electrical steel sheet.

[0090] Before the step of manufacturing the hot-rolled sheet, the slab can be heated. Specifically, the slab is loaded into a heating furnace and heated to 1100 to 1250°C. When heated at a temperature higher than 1250°C, the precipitates will redissolve and may precipitate finely after hot rolling.

[0091] The heated slab is hot-rolled to 2 to 2.3mm to manufacture a hot-rolled sheet. In the step of manufacturing the hot-rolled sheet, the finish rolling temperature can be 800 to 1000°C.

[0092] After the step of manufacturing the hot-rolled sheet, a step of annealing the hot-rolled sheet may be included. At this time, the hot-rolled sheet annealing temperature may be 850 to 1150 °C. If the hot-rolled sheet annealing temperature is lower than 850 °C, the structure will not grow or grow microscopically, so the effect of increasing the magnetic flux density is small. If the annealing temperature is higher than 1150 °C, the magnetic properties will instead decrease, and due to the deformation of the sheet shape, the rolling workability may deteriorate. 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. For the annealing of the hot-rolled sheet, it is carried out as needed to increase the orientation favorable for magnetism, and the annealing of the hot-rolled sheet may also be omitted.

[0093] Next, the hot-rolled sheet is pickled and cold-rolled to a predetermined sheet thickness. Depending on the thickness of the hot-rolled sheet, different reduction ratios may be used, but a reduction ratio of 70 to 95% may be used to cold-roll to a final thickness of 0.2 to 0.65 mm. In order to adjust the reduction ratio, one cold-rolling or two or more cold-rollings including intermediate annealing may be carried out.

[0094] The cold-rolled sheet after cold-rolling is annealed.

[0095] On the inlet side of the annealing furnace in the cold-rolled sheet annealing step, the difference between the maximum tension and the minimum tension in the rolling direction of the cold-rolled sheet with respect to a length of 2000 mm may be 0.017 kgf / mm 2 or less.

[0096] On the inlet side and the outlet side of the annealing furnace of the cold-rolled sheet, tension is applied to the steel sheet using bridle rolls. At this time, ideally, uniform tension is applied in the length direction of the steel sheet, but due to various reasons such as slip between the bridle roll and the steel sheet, speed changes of the bottom rolls inside the annealing furnace, and thermal expansion of the steel sheet due to heating, it is actually very difficult to continuously maintain it uniformly. In one embodiment of the present invention, it was found that a difference in grain size is generated due to the difference in the tension applied to the steel sheet, and thus the high-frequency iron loss is improved by optimizing the difference between the maximum tension and the minimum tension. In order to reduce the tension deviation, methods such as minimizing the slip between the bridle roll and the steel sheet and speed linkage of the speed of the bottom rolls in the annealing furnace and the thermal expansion of the steel sheet may be adopted. More specifically, on the inlet side of the annealing furnace, the difference between the maximum tension and the minimum tension in the rolling direction of the cold-rolled sheet with respect to a length of 2000 mm is 0.001 to 0.015 kgf / mm 2 。

[0097] On the inlet side of the annealing furnace, the average tension applied to the steel sheet may be 0.07 to 0.5 kgf / mm 2 。If the average tension is applied excessively, the anisotropy of the iron loss may become large, so the upper limit can be adjusted as described above. More specifically, it may be 0.1 to 0.5 kgf / mm2 .

[0098] In the annealing step of the cold-rolled sheet, the maximum temperature of the annealing furnace can be 875 to 1000 °C. If the maximum temperature of the annealing furnace is too high, defects such as surface micro dents increase, the grain growth property becomes larger, and the grain size uniformity may deteriorate. More specifically, the maximum temperature of the annealing furnace can be 900 to 997 °C.

[0099] The soaking time is the time when the temperature remains uniform and unchanged after reaching the soaking temperature. The soaking time can be 25 to 60 seconds. More specifically, it can be 30 seconds to 50 seconds.

[0100] Then, a step of forming an insulating layer may also be included. As for the method of forming the insulating layer, it is well known in the technical field of non-oriented electrical steel sheets, and thus the detailed description is omitted.

[0101] The preferred embodiments and comparative examples of the present invention are described below. However, the following embodiments are only a preferred embodiment of the present invention, and the present invention is not limited to the following embodiments.

[0102] Example 1

[0103] A slab having the components shown in Table 1 below is manufactured. Except for the components shown in Table 1, C, S, N, Ti, Nb, and V are all controlled to be 0.003 wt% or less each, and the balance is Fe. REM includes Ce, Y, and Sc.

[0104] The slab is 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 after hot rolling is annealed at 1100 °C for 4 minutes and then pickled. Then, a cold-rolled sheet of 0.25 mm is manufactured by cold rolling, and cold-rolled sheet annealing is performed under the conditions shown in Table 2 below.

[0105] For iron loss, specimens with a width of 60 mm × a length of 60 mm × 5 sheets are cut out, and for each specimen, the direction forming a 60-degree angle with the rolling direction is measured using a single-sheet tester.

[0106] The grain size is observed with an optical microscope, and the grain size distribution is measured using SEM-EBSD.

[0107] For the tension, the force applied to the tension roll is measured using a load cell.

[0108] [Table 1]

[0109]

[0110]

[0111] [Table 2]

[0112]

[0113]

[0114] [Table 3]

[0115]

[0116]

[0117] As shown in Tables 1 to 3, the precipitation characteristics of the alloy components are appropriately adjusted, and it can be confirmed that the iron loss and the anisotropy of the iron loss are improved.

[0118] If the tension deviation is adjusted during the annealing of the cold-rolled sheet, a certain grain distribution will be formed, and it can be confirmed that the iron loss and the anisotropy of the iron loss are further improved.

[0119] The present invention can be implemented in various different ways and is not limited to the above embodiments. Those of ordinary skill in the technical field to which the present invention pertains can understand that without changing the technical idea and essential features of the present invention, the present invention can be implemented by other specific ways. Therefore, it should be understood that the above embodiments are exemplary in all aspects and not restrictive.

Claims

1. An non-oriented electrical steel sheet, wherein, by weight%, the non-oriented electrical steel sheet contains Si: 2.8 to 4.0%, Al: 0.5 to 1.7%, Mn: 0.3 to 2.0%, Se: 0.0005 to 0.005%, Sn: 0.005 to 0.06% and REM: 0.001 to 0.007%, and the balance contains Fe and inevitable impurities.

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

3. The non-oriented electrical steel sheet according to claim 1, wherein, the non-oriented electrical steel sheet further contains one or more of C, N, S, Ti, Nb and V, and their contents are each 0.005% by weight or less.

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

5. The non-oriented electrical steel sheet according to claim 1, wherein, the non-oriented electrical steel sheet further contains one or two or more of Bi, Pb, Ge and As, and their contents are each or in total 0.200% by weight or less.

6. The non-oriented electrical steel sheet according to claim 1, wherein, the non-oriented electrical steel sheet further contains one or more of Mo: 0.03% by weight or less, B: 0.0050% by weight or less, Ca: 0.0050% by weight or less and Mg: 0.0050% by weight or less.

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

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

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

10. A method for manufacturing a non-oriented electrical steel sheet, which includes: a step of hot rolling a slab to manufacture a hot rolled sheet, by weight%, the slab contains Si: 2.8 to 4.0%, Al: 0.5 to 1.7%, Mn: 0.3 to 2.0%, Se: 0.0005 to 0.005%, Sn: 0.005 to 0.06%, REM: 0.001 to 0.007%, and the balance contains Fe and inevitable impurities; a step of cold rolling the hot rolled sheet to manufacture a cold rolled sheet; and a step of 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 one or more of C, N, S, Ti, Nb, and V, and their contents are each 0.005 wt% or less.

12. The method for manufacturing an 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. The method for manufacturing an non-oriented electrical steel sheet according to claim 10, wherein the slab further contains one or two or more of Bi, Pb, Ge, and As, and their contents are each or in total 0.200 wt% or less and excluding 0%.

14. The method for manufacturing an non-oriented electrical steel sheet according to claim 10, wherein the slab further contains one or more of Mo: 0.03 wt% or less and excluding 0%, B: 0.0050 wt% or less and excluding 0%, Ca: 0.0050 wt% or less and excluding 0%, and Mg: 0.0050 wt% or less and excluding 0%.

15. The method for manufacturing an non-oriented electrical steel sheet according to claim 10, wherein In the cold-rolled sheet annealing step, on the inlet side of the annealing furnace, the difference between the maximum tension and the minimum tension in the rolling direction of the cold-rolled sheet is 0.017 kgf / mm with respect to a length of 2000 mm 2 or less.

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

17. The method for manufacturing an non-oriented electrical steel sheet according to claim 10, wherein in the annealing step of the cold-rolled sheet, the maximum temperature of the annealing furnace is 875 to 1000 °C.

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

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