Non-oriented electrical steel sheet and its manufacturing method

Abstract

Provided is a non-oriented electrical steel sheet capable of reducing thickness deviation by performing pickling multiple times after hot rolling without annealing the hot-rolled sheet, and a method for manufacturing the same. [Solution] The non-oriented electrical steel sheet according to one embodiment of the present invention contains, by weight, 1.4-3.0% Si, 0.001-1.5% Mn, and 0.001-0.2% Al, with the remainder being Fe and unavoidable impurities, and has a thickness deviation of 1.5 μm or less in the direction perpendicular to the rolling direction per 5 mm of length, and a thickness deviation of 10 μm or less in the rolling direction per 1000 m of length.

Description

[Technical field]

[0001] An embodiment of the present invention relates to a non-oriented electrical steel sheet and a manufacturing method thereof. More specifically, an embodiment of the present invention relates to a non-oriented electrical steel sheet in which thickness deviation can be reduced without annealing hot-rolled sheet by performing pickling multiple times after hot rolling with an appropriately adjusted final pass reduction rate, and a manufacturing method thereof. [Background technology]

[0002] Motors and generators are energy conversion devices that convert electrical energy into mechanical energy or mechanical energy into electrical energy. Recently, as regulations for environmental conservation and energy saving have become stronger, there has been an increasing demand for improving the efficiency of motors and generators. As a result, there has been an increasing demand for the development of materials with better properties for non-oriented electrical steel sheets used as iron core materials for such motors, generators, small transformers, and the like.

[0003] In motors and generators, the energy efficiency is the ratio of input energy to output energy, and in order to improve efficiency, it is important to reduce energy losses such as iron loss, copper loss, and mechanical loss that occur during the energy conversion process. The iron loss and magnetic flux density of commonly known non-oriented electrical steel sheets affect the iron loss and copper loss of motors. In addition, the surface characteristics of electrical steel sheets can induce additional iron loss or mechanical loss due to processing errors that may occur when processing electrical steel sheets and shape differences that may occur when laminating individual electrical steel sheets. Therefore, in order to improve the energy efficiency of motors, it is essential to develop not only non-oriented electrical steel sheets with excellent magnetic properties but also non-oriented electrical steel sheets with excellent surface properties.

[0004] One efficient method to reduce the iron loss of non-oriented electrical steel sheets is to increase the amount of Si, Al, and Mn, which are elements with high resistivity. However, while increasing the amount of Si, Al, and Mn increases the resistivity of the steel and reduces the eddy current loss of the iron loss of non-oriented electrical steel sheets, it is not true that the iron loss decreases unconditionally in proportion to the amount of addition. Conversely, increasing the amount of alloying elements decreases the magnetic flux density, so it is not easy to ensure excellent magnetic flux density while reducing iron loss, even if the composition and manufacturing process are optimized. However, improving texture is a method that can simultaneously improve both iron loss and magnetic flux density without sacrificing either one. The more the {100} and {110} textures, which are favorable for magnetism, are increased, and the less the {111} and {112} textures, which are unfavorable for magnetism, are decreased, the more the iron loss and magnetic flux density can be improved.

[0005] For this reason, in order to improve the texture of non-oriented electrical steel sheets having excellent magnetic properties, a technology for improving the texture by performing a hot-rolled sheet annealing process after hot rolling a slab and before cold rolling the hot-rolled sheet is widely used. However, this method also has problems such as an increase in production costs due to the addition of a process called the hot-rolled sheet annealing process, and in the case where crystal grains are coarsened by performing the hot-rolled sheet annealing, the cold rollability becomes inferior. Therefore, if it is possible to manufacture a non-oriented electrical steel sheet having excellent magnetic properties without performing the hot-rolled sheet annealing process, that is, a non-oriented electrical steel sheet having little magnetic inferiority even without performing the hot-rolled sheet annealing process, it is possible to reduce the production cost and solve the productivity problem caused by the hot-rolled sheet annealing process.

[0006] However, when hot-rolled sheet annealing is omitted, the temperature range where phase transformation can occur varies depending on the amount of added elements such as Si, Al, and Mn, and also the structure of the oxide layer and the degree of dynamic recrystallization during hot rolling. These changes lead to deterioration of the surface characteristics of the non-oriented electrical steel sheet, which in turn has a significant impact on the efficiency of motors. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a non-oriented electrical steel sheet and a manufacturing method thereof. A specific object of the present invention is to provide a non-oriented electrical steel sheet and a manufacturing method thereof, which can reduce sheet thickness deviation without hot-rolled sheet annealing by performing pickling multiple times after hot rolling with an appropriately adjusted final pass reduction. [Means for solving the problem]

[0008] A non-oriented electrical steel sheet according to one embodiment of the present invention contains, by weight, 1.4-3% Si, 0.001-1.5% Mn, and 0.001-0.2% Al, with the remainder being Fe and unavoidable impurities, and is characterized in that the thickness deviation occurring in the direction perpendicular to the rolling direction per 5 mm of length is 1.5 μm or less, and the thickness deviation occurring in the rolling direction per 1000 m of length is 10 μm or less.

[0009] The non-oriented electrical steel sheet according to an embodiment of the present invention can satisfy the following formula 1. [Formula 1] 1.1575×([Si]+[Al])-1.6722≦[Mn]≦1.1575×([Si]+[Al])-1.4722 (In formula 1, [Si], [Al], and [Mn] represent the contents (wt%) of Si, Al, and Mn, respectively.)

[0010] The non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of P: 0.1 wt % or less, C: 0.005 wt % or less, S: 0.01 wt % or less, N: 0.005 wt % or less, Ti: 0.005 wt % or less, and Sb: 0.001 to 0.08 wt %.

[0011] The non-oriented electrical steel sheet according to an embodiment of the present invention may further contain one or more of Cr: 0.010 to 0.150% by weight, Sn: 0.003 to 0.080% by weight, and Cu: 0.01 to 0.20% by weight.

[0012] The non-oriented electrical steel sheet according to an embodiment of the present invention may further include 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.

[0013] The thickness of the steel plate may be 0.3 to 0.7 mm.

[0014] A method for producing a non-oriented electrical steel sheet according to an embodiment of the present invention includes the steps of: hot rolling a slab containing 1.4-3.0% Si, 0.001-1.5% Mn, and 0.001-0.2% Al, with the balance being Fe and inevitable impurities, to produce a hot-rolled sheet; pickling the hot-rolled sheet two to four times; and cold rolling the pickled hot-rolled sheet to produce a cold-rolled sheet, the step of producing the hot-rolled sheet including a rough rolling step and a finish rolling step of the slab, The finish rolling step is characterized in that the rolling is performed through multiple passes, and the rolling reduction of the final pass among the multiple passes is 17.0% or less.

[0015] Before the step of producing the hot rolled sheet, a slab heating step of heating the slab at a temperature range of 1100 to 1250° C. for 0.1 to 3 hours may be further included.

[0016] The reduction ratio in the first pass of the multiple passes may be 30% or more.

[0017] In the finish rolling stage, the ratio of the reduction in the first pass to the reduction in the final pass may be 2.45 to 3.55.

[0018] The finish rolling step can be carried out at 850°C to 950°C.

[0019] The step of producing a hot-rolled sheet may further include a step of coiling at a temperature of 800° C. or less after the finish rolling step.

[0020] In the pickling step, the plate may be immersed in a 3 to 22 wt % hydrochloric acid solution for 15 to 200 seconds each time.

[0021] The pickling step may further include removing the pickling solution from the steel sheet surface during pickling.

[0022] After the step of producing the hot rolled sheet, the steps until the end of the step of producing the cold rolled sheet can be performed at a temperature of 300° C. or less.

[0023] After the step of producing the cold-rolled sheet, the method may further include a step of annealing the cold-rolled sheet. Effect of the Invention

[0024] The non-oriented electrical steel sheet according to an embodiment of the present invention can reduce thickness deviation without hot-rolled sheet annealing, which contributes to improving the space factor and ultimately improves the efficiency of a motor in which the non-oriented electrical steel sheet is used. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Thus, a first part, component, region, layer, or section described below can be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0026] The terminology used herein merely refers to particular embodiments and is not intended to limit the invention. As used herein, the singular form includes the plural form unless clearly indicated to the contrary. As used in the specification, the term "comprising" refers to the specification of particular 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.

[0027] When an element is referred to as being "on" or "on" another element, this means that it is directly on or above the other element, or there may be other elements between them. In contrast, when an element is referred to as being "directly on" another element, there are no other elements between them. 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 belongs. Terms defined in the dictionary are interpreted to have a meaning consistent with the relevant technical literature and the presently disclosed content, and are not interpreted as ideal or extreme meanings unless otherwise defined.

[0028] Moreover, unless otherwise specified, % means % by weight, and 1 ppm is 0.0001% by weight. In an embodiment of the present invention, the term "additionally contain an additional element" refers to the addition of an additional amount of the additional element in place of the remaining iron (Fe).

[0029] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to exemplary embodiments thereof, so that those skilled in the art will be able to easily practice the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments set forth herein.

[0030] According to an embodiment of the present invention, after hot rolling with an appropriately adjusted final pass reduction, pickling is performed multiple times, thereby reducing the thickness deviation of the sheet without annealing the hot-rolled sheet. A non-oriented electrical steel sheet according to one embodiment of the present invention contains, by weight, 1.4 to 3.0% Si, 0.001 to 1.5% Mn, and 0.001 to 0.2% Al, with the balance including Fe and unavoidable impurities. First, the reasons for limiting the components of non-oriented electrical steel sheets will be explained.

[0031] Si:1.4~3.0wt% Silicon (Si) is a major element added to increase the resistivity of steel and reduce eddy current loss among core losses. Si is a representative ferrite stabilizing element and is an element related to phase transformation during hot rolling. If too little Si is added, a problem of deterioration of core loss occurs. Therefore, increasing the Si content is advantageous from the viewpoint of core loss, but if too much Si is added, the magnetic flux density decreases significantly and problems with workability may occur. Therefore, Si can be included within the above range. More specifically, Si can be included in an amount of 1.4 to 2.6 wt %.

[0032] Mn:0.001~1.500wt% Manganese (Mn), together with Si and Al, increases resistivity and reduces core loss, while forming sulfides and stabilizing austenite, inducing phase transformation during hot rolling, and improving texture. If too little Mn is added, fine sulfides may precipitate, reducing magnetic properties. Conversely, if too much Mn is added, it may promote the formation of {111} texture, which is unfavorable to magnetic properties, reducing magnetic flux density. Therefore, Mn may be included within the above range. More specifically, Mn may be included in an amount of 0.30 to 1.40 wt %.

[0033] Al:0.001~0.200wt% Aluminum (Al) plays an important role in increasing resistivity together with Si to reduce iron loss, and also improves rollability or workability during cold rolling. If too little Al is added, it is ineffective in reducing high frequency iron loss, and the precipitation temperature of AlN is lowered, which may cause fine nitride formation and reduce magnetic properties. On the other hand, if too much Al is added, excessive nitrides are formed, which may cause magnetic properties to deteriorate, causing problems in all processes such as steelmaking and continuous casting, and greatly reducing productivity. In addition, Al is a ferrite stabilizing element and affects phase transformation during hot rolling. Therefore, Al can be contained within the above range. More specifically, it can be contained in 0.001 to 0.05 wt %. More specifically, it can be contained in 0.001 to 0.02 wt %.

[0034] The non-oriented electrical steel sheet according to an embodiment of the present invention can satisfy the following formula 1. [Formula 1] 1.1575×([Si]+[Al])-1.6722≦[Mn]≦1.1575×([Si]+[Al])-1.4722 (In formula 1, [Si], [Al], and [Mn] respectively represent the contents (weight %) of Si, Al, and Mn.) When formula 1 is satisfied, the elements Si, Al, and Mn that affect the phase fraction are adjusted, and magnetic properties can be further improved.

[0035] The non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of P: 0.1 wt % or less, C: 0.005 wt % or less, S: 0.01 wt % or less, N: 0.005 wt % or less, Ti: 0.005 wt % or less, and Sb: 0.001 to 0.08 wt %.

[0036] P: 0.100% by weight or less Phosphorus (P) not only increases the resistivity of the material, but also segregates to the grain boundaries to improve the texture, increase the resistivity, and reduce iron loss, so it can be added additionally. However, if the amount of P added is too large, it may lead to the formation of a texture unfavorable to magnetism, resulting in no effect of improving the texture, and may segregate excessively to the grain boundaries, reducing rollability and workability, making production difficult. Therefore, P may be added within the above-mentioned range. More specifically, P may be further contained in an amount of 0.001 to 0.050 wt %.

[0037] C: 0.005% by weight or less Carbon (C) combines with Ti, Nb, etc. to form carbides, which impairs magnetism, and when processed into an electrical product as a final product, iron loss increases due to magnetic aging, which can reduce the efficiency of the electrical device. More specifically, C can be further included in an amount of 0.0005 to 0.0020 wt%.

[0038] S: 0.0100% by weight or less Sulfur (S) forms fine sulfides inside the base material, inhibits grain growth, and weakens iron loss, so it is preferable to add it in as small an amount as possible. If a large amount of S is included, it may combine with Mn, etc. to form precipitates or induce high-temperature brittleness during hot rolling. Therefore, S may be further included in an amount of 0.0100 wt% or less. Specifically, S may be further included in an amount of 0.0010 to 0.0050 wt% or less.

[0039] N: 0.0050% by weight or less Nitrogen (N) not only combines with Al, Ti, etc. to form fine, long precipitates inside the base material, but also combines with other impurities to form fine nitrides that inhibit grain growth and worsen iron loss, so it is preferable to contain a small amount of N. In one embodiment of the present invention, N may be further contained in an amount of 0.0050 wt% or less. More specifically, N may be further contained in an amount of 0.0010 to 0.0050 wt%. More specifically, N may be further contained in an amount of 0.0010 to 0.0030 wt%.

[0040] Ti: 0.0050% by weight or less Titanium (Ti) is an element that has a strong tendency to form precipitates in steel, and forms fine carbides or nitrides inside the matrix to inhibit grain growth. The more Ti is added, the more carbides and nitrides are formed, which deteriorates the iron and reduces the magnetic properties. In one embodiment of the present invention, Ti may be further included in an amount of 0.0050 wt% or less. More specifically, Ti may be further included in an amount of 0.0005 to 0.0030 wt% or less.

[0041] Sb:0.001~0.080wt% Antimony (Sb) segregates at the grain boundaries and surface to improve the texture of the material and inhibit surface oxidation, and can be added to improve magnetic properties. If too much Sb is added, grain boundary segregation becomes severe, deteriorating surface quality, and hardness increases, causing breakage of the cold-rolled sheet and reducing rollability, and peeling of the coating layer may occur after final annealing. Therefore, Sb can be added within the above range. However, if the amount of Sb added is too small, the texture improvement and surface oxidation inhibition effects cannot be expected. More specifically, Sb can be included in an amount of 0.01 to 0.07 wt %.

[0042] Cr:0.010~0.150wt%, Sn:0.003~0.080wt%, Cu:0.01~0.20wt% Chromium (Cr) and tin (Sn) segregate on the surface when the annealing conditions are properly adjusted. Segregation occurs properly only when Cr, Sn, and Sb are contained within the above-mentioned ranges. If the amount is less than the range, there is no surface segregation effect, and if it is too much, the brittleness of the material is strengthened, which may cause problems. More specifically, one or more of 0.010-0.100 wt% Cr, 0.005-0.050 wt% Sn, and 0.01-0.20 wt% Cu may be further contained.

[0043] Copper (Cu) plays a role in forming sulfides together with Mn. If too little Cu is added, fine CuMnS may precipitate, deteriorating the magnetic properties. If too much Cu is added, high temperature brittleness may occur, which may cause cracks during continuous casting or hot rolling. More specifically, Cu may be contained in an amount of 0.01 to 0.10 wt%.

[0044] The non-oriented electrical steel sheet according to an embodiment of the present invention may further include 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 inevitably contained C, S, N, etc. to form fine carbides, nitrides, or sulfides, which can adversely affect magnetic properties, so the upper limit can be limited as described above.

[0045] The balance includes Fe and inevitable impurities. The inevitable impurities are impurities that are mixed in during the steelmaking stage and the manufacturing process of the non-oriented electrical steel sheet, and are widely known in the art, so a detailed description will be omitted. In one embodiment of the present invention, the addition of elements other than the above-mentioned alloy components is not excluded, and various elements may be included within a range that does not harm the technical idea of ​​the present invention. When an additional element is further included, it is included in place of the balance Fe.

[0046] In the non-oriented electrical steel sheet according to an embodiment of the present invention, the thickness deviation occurring in the direction perpendicular to the rolling direction per 5 mm length is 1.5 μm or less, and the thickness deviation occurring in the rolling direction per 1000 m length is 10 μm or less. In this case, the thickness deviation occurring in the direction perpendicular to the rolling direction can be measured by measuring the difference between the minimum and maximum values ​​observed on one side in an area of ​​5.0 mm x 5.0 mm or more through a confocal microscope. The thickness deviation occurring in the rolling direction can be measured by measuring the difference between the minimum and maximum values ​​measured at the center of the sheet through an X-ray thickness gauge. More specifically, the thickness deviation occurring in the direction perpendicular to the rolling direction per 5 mm length is 0.5 to 1.1 μm, and the thickness deviation occurring in the rolling direction per 1000 m length is 2 to 8.0 μm. The thickness of the steel plate may be 0.3 to 0.7 mm, or more specifically, 0.35 to 0.65 mm.

[0047] A method for producing a non-oriented electrical steel sheet according to one embodiment of the present invention includes the steps of: hot rolling a slab containing 1.4-3.0% Si, 0.001-1.5% Mn, and 0.001-0.2% Al, with the balance being Fe and unavoidable impurities, to produce a hot-rolled sheet; pickling the hot-rolled sheet two to four times; and cold rolling the pickled hot-rolled sheet to produce a cold-rolled sheet.

[0048] First, the slab is hot-rolled to produce a hot-rolled sheet. 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 repeated explanations will be omitted. The composition of the slab does not substantially change during the manufacturing processes such as hot rolling, cold rolling, and cold-rolled sheet annealing described below, so the composition of the slab and the composition of the non-oriented electrical steel sheet are substantially the same. Before the step of producing the hot-rolled sheet, a slab heating step of heating the slab at a temperature range of 1100 to 1250°C for 0.1 to 3 hours may be further included. If the slab heating temperature is too high, precipitates such as AlN and MnS present in the slab may be re-dissolved and then finely precipitated during hot rolling and annealing, suppressing grain growth and reducing magnetic properties. Specifically, a heating step at a temperature range of 1130 to 1200°C for 0.1 to 2 hours may be further included. In the step of producing the hot-rolled sheet, the thickness of the hot-rolled sheet may be 1.6 to 2.7 mm. Specifically, the thickness of the hot-rolled sheet may be 2.0 to 2.5 mm.

[0049] The step of manufacturing a hot-rolled sheet includes a step of rough rolling a slab and a step of finish rolling. The step of rough rolling a slab is a step of manufacturing a bar by rough rolling the slab. The step of finish rolling is a step of rolling the bar to manufacture a hot-rolled sheet. The step of finish rolling is a step of rolling through a plurality of passes. A pass means a process of passing through a rolling roll once. In one embodiment of the present invention, the final pass reduction in the finish rolling step is adjusted to control recrystallization and oxide layer formation during coiling, thereby reducing thickness deviation of the steel sheet. Specifically, the final pass reduction is 17% or less. If the final pass reduction is too high, a problem of shape inferiority of the cold-rolled sheet due to shape inferiority of the hot-rolled sheet itself may occur. More specifically, the final pass reduction may be 13.0 to 16.5%. In one embodiment of the present invention, the reduction is calculated as ([steel sheet thickness before reduction]-[steel sheet thickness after reduction]) / [steel sheet thickness before reduction].

[0050] Meanwhile, the reduction in the first pass may be 30.0% or more. Only by ensuring the reduction in the first pass can the thickness of the hot-rolled sheet after the final pass be properly ensured. More specifically, the reduction in the first pass may be 35.0 to 50.0%. In the finish rolling step, the ratio of the reduction in the first pass to the reduction in the final pass may be 2.45 to 3.55. More specifically, it may be 2.75 to 3.45. The finish rolling step can be performed at 850°C to 950°C. In one embodiment of the present invention, the hot-rolled sheet annealing can be omitted, and if the temperature is not properly controlled in the finish rolling step, some of the fine structure existing in the hot-rolled sheet remains and affects the texture. If excessive phase transformation occurs in the finish rolling, the crystal grains of the hot-rolled recrystallized structure are refined, and the effect of improving the texture due to the deformation energy is reduced, ultimately resulting in a significant deterioration in magnetic properties. More specifically, the finish rolling step can be performed at 880°C to 920°C. The step of manufacturing the hot-rolled sheet may further include a step of coiling at a temperature of 800°C or less after the finish rolling step. By appropriately controlling the temperature in the coiling step, it is possible to appropriately form a microstructure after annealing of the cold-rolled sheet, which may contribute to improving magnetic properties. More specifically, the coiling temperature may be 650 to 750°C.

[0051] In one embodiment of the present invention, after the step of producing a hot-rolled sheet, the step of annealing the hot-rolled sheet can be omitted before cold rolling. That is, since cold rolling is also performed at a low temperature of 300°C or less, after the step of producing a hot-rolled sheet, the temperature can be kept at 300°C or less until the end of the step of producing a cold-rolled sheet. In one embodiment of the present invention, the thickness deviation of the steel sheet can be reduced even if annealing of the hot-rolled sheet is omitted by adjusting the reduction rate in the final pass during hot rolling and performing pickling 2 to 4 times. Next, the hot-rolled sheet is pickled two to four times. In the present invention, the number of times of pickling can be determined by immersing the steel sheet in a pickling solution, removing the steel sheet from the immersion solution, and removing the pickling solution remaining on the steel sheet surface. The pickling solution can be removed using a rinsing solution or the like.

[0052] In the pickling step, the steel sheet may be immersed in a 3.0-22.0 wt % hydrochloric acid solution for 15-200 seconds per cycle. If the hydrochloric acid concentration is too low or the immersion time is too short, the scale present on the surface of the hot-rolled steel sheet may not be sufficiently removed, whereas if the concentration is too high or the immersion time is too long, damage to the steel sheet surface may occur beyond the scale removal. More specifically, the steel sheet may be immersed in a 10.0-18.0 wt % hydrochloric acid solution for 20-100 seconds per cycle. When multiple pickling cycles are performed and the concentration of the pickling solution is different for each cycle, the concentration of the pickling solution refers to the average concentration for each cycle.

[0053] Next, the pickled hot-rolled sheet is cold-rolled to produce a cold-rolled sheet. Depending on the thickness of the hot-rolled sheet, a rolling reduction of 70-95% can be applied, and cold rolling can be performed to a final thickness of 0.3-0.7 mm. To match the rolling reduction, one cold rolling pass or two or more cold rolling passes with intermediate annealing can be performed. Cold rolling can be performed through 3-7 passes. After the step of producing the cold-rolled sheet, the method may further include a step of annealing the cold-rolled sheet. The step of annealing the cold-rolled sheet may be soaked at 800 to 1070°C, and the soaking time may be 10 seconds to 5 minutes. More specifically, the step of soaking at 900 to 1050°C may be performed. The step of annealing the cold-rolled sheet may be omitted if necessary, and when the step of annealing the cold-rolled sheet is added, the magnetic properties may be further improved. In one embodiment of the present invention, the thickness deviation does not change before and after the step of annealing the cold-rolled sheet.

[0054] After the step of annealing the cold-rolled sheet, the core loss (W15 / 50) may be 3.50 W / kg or less, and the magnetic flux density (B50) may be 1.67 T or more. More specifically, the core loss (W15 / 50) may be 2.50 to 3.50 W / kg, and the magnetic flux density (B50) may be 1.67 to 1.80 T. 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 a 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. EXAMPLES

[0055] Experimental Example 1 The slabs with the composition shown in Table 1 below were heated at the temperatures shown in Table 2 below. Then, hot rolling was performed to the thickness shown in Table 2. At this time, the hot rolling finishing rolling temperature is shown in Table 2, and the first pass reduction and the last pass reduction in the hot rolling finishing rolling are also shown in Table 2. After hot rolling, the steel sheets were coiled at the temperatures shown in Table 2. The hot rolled steel sheets were cooled in air and pickled under the pickling conditions shown in Table 3, and then the hot rolled steel sheets were cold rolled at 0.5 mm without annealing. The surface condition of the final cold steel sheets is shown in Table 3 below. The thickness deviation in the direction perpendicular to the rolling direction was measured as the difference between the minimum and maximum values ​​on one side observed through a confocal microscope in an area of ​​1.8 mm x 1.8 mm or more. The thickness deviation in the rolling direction was measured as the difference between the minimum and maximum values ​​measured through an X-ray thickness gauge at the center of the sheet.

[0056] [Table 1]

[0057] [Table 2]

[0058] [Table 3]

[0059] As shown in Tables 1 to 3, it can be confirmed that the examples that satisfy the alloy components and manufacturing process conditions have small thickness deviations both in the direction perpendicular to the rolling of the steel sheet and in the rolling direction. Comparative Examples 1 to 6 are steel types containing a large amount of Al, and it can be seen that the thickness deviation is large in the direction perpendicular to the rolling of the steel plate or in the rolling direction. In Comparative Examples 7 and 9, the number of pickling cycles was small or large, and it can be seen that the thickness deviation was large in the direction perpendicular to the rolling direction or in the rolling direction of the steel sheet. In Comparative Example 8, it can be seen that the reduction rate of the final pass during finish rolling is excessively high, resulting in a large thickness deviation in the direction perpendicular to the rolling of the steel sheet or in the rolling direction.

[0060] Experimental Example 2 In order to confirm the magnetic properties after annealing of the cold-rolled sheet, the cold-rolled sheet produced in Example 1 was annealed at the temperatures summarized in Table 1 below.

[0061] [Table 4]

[0062] As shown in Table 4, it can be confirmed that the magnetic properties of the non-oriented electrical steel sheet according to an embodiment of the present invention are improved through cold-rolled sheet annealing. The present invention is not limited to the above-mentioned embodiments, and may be manufactured in various different forms, and a person skilled in the art to which the present invention pertains may embody other specific forms without changing the technical concept or essential features of the present invention. Therefore, the above-mentioned embodiments are illustrative in all respects and are not limiting.

Claims

1. In weight percent, the alloy contains 1.4 to 3% Si, 0.001 to 1.5% Mn, and 0.001 to 0.2% Al, with the balance being Fe and inevitable impurities; A non-oriented electrical steel sheet, characterized in that the thickness deviation occurring in a direction perpendicular to the rolling direction per 5 mm of length is 1.5 μm or less, and the thickness deviation occurring in the rolling direction per 1000 m of length is 10 μm or less.

2. 2. The non-oriented electrical steel sheet according to claim 1, which satisfies the following formula 1: [Formula 1] 1.1575×([Si]+[Al])-1.6722≦[Mn]≦1.1575×([Si]+[Al])-1.4722 (In formula 1, [Si], [Al], and [Mn] represent the contents (wt%) of Si, Al, and Mn, respectively.)

3. 2. The non-oriented electrical steel sheet according to claim 1, further comprising one or more of P: 0.1 wt % or less, C: 0.005 wt % or less, S: 0.01 wt % or less, N: 0.005 wt % or less, Ti: 0.005 wt % or less, and Sb: 0.001 to 0.08 wt %.

4. 2. The non-oriented electrical steel sheet according to claim 1, further comprising one or more of Cr: 0.010 to 0.150 wt %, Sn: 0.003 to 0.080 wt %, and Cu: 0.01 to 0.20 wt %.

5. 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.

6. 2. The non-oriented electrical steel sheet according to claim 1, wherein the thickness of the steel sheet is 0.3 to 0.7 mm.

7. A step of producing a hot-rolled sheet by hot rolling a slab containing, in weight percent, 1.4 to 3.0% Si, 0.001 to 1.5% Mn, and 0.001 to 0.2% Al, with the balance being Fe and unavoidable impurities; A pickling step of pickling the hot-rolled sheet two to four times; and cold rolling the pickled hot-rolled sheet to produce a cold-rolled sheet. Including, The step of producing the hot-rolled sheet includes a step of rough rolling the slab and a step of finish rolling the slab, The method for producing a non-oriented electrical steel sheet, wherein the finish rolling step includes rolling through multiple passes, and a rolling reduction of a final pass among the multiple passes is 17% or less.

8. The method for producing a non-oriented electrical steel sheet according to claim 7, further comprising, before the step of producing the hot-rolled sheet, a step of heating the slab at a temperature range of 1100 to 1250° C. for 0.1 to 3 hours.

9. The method for producing a non-oriented electrical steel sheet according to claim 7, characterized in that the reduction ratio of a first pass among the multiple passes is 30% or more.

10. The method for producing a non-oriented electrical steel sheet according to claim 9, wherein in the finish rolling step, a ratio of a reduction rate of a first pass to a reduction rate of a final pass is 2.45 to 3.

55.

11. The method of claim 7, wherein the finish rolling is performed at a temperature of 850°C to 950°C.

12. The method of claim 7, wherein the step of producing the hot-rolled sheet further comprises the step of coiling at a temperature of 800° C. or less after the finish rolling.

13. 8. The method of claim 7, wherein the pickling step is performed by immersing the steel sheet in a 3 to 22 wt % hydrochloric acid solution for 15 to 200 seconds each time.

14. The method of claim 7, further comprising removing the pickling solution from the surface of the steel sheet during the pickling.

15. The method for producing a non-oriented electrical steel sheet according to claim 7, wherein the steps from producing the hot rolled sheet to producing the cold rolled sheet are performed at a temperature of 300° C. or less.

16. The method of claim 7, further comprising the step of annealing the cold-rolled sheet at 800 to 1070° C. after the step of producing the cold-rolled sheet.

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