Non-oriented electrical steel sheet and its manufacturing method

Abstract

An object of the present invention is to provide a non-oriented electrical steel sheet in which a specific texture is developed and magnetic anisotropy is maximized through heating, first soaking, second soaking, and cooling steps in an annealing step after preliminary cold rolling, and a manufacturing method thereof. The non-oriented electrical steel sheet of the present invention is characterized in that it contains, by weight %, 1.5 to 5.0% Si, 0.1 to 2.0% Al, 0.1 to 2.0% Mn, residual Fe, and unavoidable impurities, and satisfies the following formula 1: [Formula 1] V{001} <001> / V{011} <001> ≦0.65 (In Equation 1, V{001} <001> is {001} <001> The percentage of grains with an orientation within 15° of V{011} <001> is {011} <001> This indicates the percentage of grains with orientations within 15° of the

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 a specific texture is developed and magnetic anisotropy is maximized through heating, first soaking, second soaking, and cooling processes in an annealing process after preliminary cold rolling, and a manufacturing method thereof. [Background technology]

[0002] Non-oriented electrical steel sheets are primarily used in motors that convert electrical energy into mechanical energy, and excellent magnetic properties are required for them to achieve high efficiency in this process.In particular, in recent years, environmentally friendly automobiles that are driven by motors instead of internal combustion engines have been gaining attention, and the demand for non-oriented electrical steel sheets used as drive motor core materials has increased, resulting in a need for non-oriented electrical steel sheets that have both excellent magnetic properties and strength.

[0003] The magnetic properties of non-oriented electrical steel are primarily evaluated by iron loss and magnetic flux density. Iron loss refers to the energy loss that occurs at a specific magnetic flux density and frequency, while magnetic flux density refers to the degree of magnetization achieved under a specific magnetic field. Lower iron loss means that more energy-efficient motors can be manufactured under the same conditions, while higher magnetic flux density means that motors can be made more compact and copper loss can be reduced. Therefore, non-oriented electrical steel with low iron loss and high magnetic flux density can be used to create drive motors with excellent efficiency and torque, thereby improving the mileage and power output of environmentally friendly vehicles.

[0004] The properties of non-oriented electrical steel sheets that should be considered vary depending on the operating conditions of the motor. The commonly used standard for evaluating the properties of non-oriented electrical steel sheets used in motors is W15 / 50, which is the iron loss when a magnetic field of 1.5 T is applied at a commercial frequency of 50 Hz. However, for non-oriented electrical steel sheets with a thickness of 0.35 mm or less used in the drive motors of environmentally friendly automobiles, magnetic properties are often important in low magnetic fields of 1.0 T or less and at high frequencies of 400 Hz or more, so W 10 / 400 The properties of non-oriented electrical steel sheets are often evaluated using iron loss.

[0005] Recently, non-oriented electrical steel sheets have been used in electric vehicle drive motors, and efforts are continuing to maximize magnetic anisotropy rather than uniform magnetic properties to increase motor output. Maximizing magnetic anisotropy increases motor output and improves overall efficiency. In this context, magnetic anisotropy refers to the large difference in magnetic flux density measured in the rolling direction and in a direction at a 45° angle to the rolling direction. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a non-oriented electrical steel sheet and a manufacturing method thereof, specifically, a non-oriented electrical steel sheet in which a specific texture is developed and magnetic anisotropy is maximized through heating, first soaking, second soaking, and cooling processes in an annealing process after preliminary cold rolling, and a manufacturing method thereof. [Means for solving the problem]

[0007] The non-oriented electrical steel sheet of the present invention is characterized by comprising, by weight %, 1.5 to 5.0% Si, 0.1 to 2.0% Al, 0.1 to 2.0% Mn, residual Fe and unavoidable impurities, and satisfying the following formula 1.

[0008] [Formula 1] V{001} <001> / V{011} <001> ≦0.65 (In Equation 1, V{001} <001> is {001} <001> The percentage of grains with an orientation within 15° of V{011} <001> is {011} <001> This indicates the percentage of grains with orientations within 15° of the

[0009] The non-oriented electrical steel sheet of the present invention satisfies the following formula 2.

[0010] [Formula 2] (V{100} <001> +V{100} <031> +V{100} <110> ) / (V{111} <112> +V{111} <011> ) ≧ 1.3 (In Equation 2, V{100} <001> is {100} <001> It indicates the percentage of grains with an orientation within 15° of V{100} <031> is {100} <031> It indicates the percentage of grains with an orientation within 15° of V{100} <110> is {100} <110> It indicates the percentage of grains with an orientation within 15° of V{111} <112> is {111} <112> It indicates the percentage of grains with an orientation within 15° of V{111} <011> is {111} <011> This indicates the percentage of grains with orientations within 15° of the

[0011] The non-oriented electrical steel sheet of the present invention may further contain one or more of P: 0.1% by weight or less (excluding 0%), C: 0.005% by weight or less (excluding 0%), S: 0.005% by weight or less (excluding 0%), Ti: 0.005% by weight or less (excluding 0%), and N: 0.005% by weight or less (excluding 0%).

[0012] The non-oriented electrical steel sheet of the present invention may further contain one or more of Sn, Sb, Bi, Pb, Ge and As in an amount of 0.005 to 0.200 wt % each or in total.

[0013] 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%, Ni: 0.05 wt% or less (excluding 0%), Zn: 0.01 wt% or less (excluding 0%), and Co: 0.05 wt% or less (excluding 0%).

[0014] The non-oriented electrical steel sheet of the present invention 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%), V: 0.0050% by weight or less (excluding 0%), Ca: 0.0050% by weight or less (excluding 0%), Nb: 0.0050% by weight or less (excluding 0%), Zr: 0.005% by weight or less (excluding 0%), Te: 0.01% by weight or less (excluding 0%), and Mg: 0.0050% by weight or less (excluding 0%).

[0015] The non-oriented electrical steel sheet of the present invention satisfies the following formula 3.

[0016] [Formula 3] B 50L -B 50D ≧0.08T (In Equation 3, B 50L is the magnetic flux density B measured in the rolling direction 50 indicates B 50D is the magnetic flux density B measured in a direction at an angle of 45° to the rolling direction. 50 indicates.)

[0017] The non-oriented electrical steel sheet of the present invention satisfies the following formula 4. [Formula 4] B 50C -B 50D ≧0.03T (In Equation 4, B 50C is the magnetic flux density B measured in the direction perpendicular to the rolling direction 50 indicates B 50D is the magnetic flux density B measured in a direction at an angle of 45° to the rolling direction. 50 indicates.) The non-oriented electrical steel sheet of the present invention satisfies the following formula 5.

[0018] [Formula 5] (B 50L +B 50C ) / 2≧1.68T (In Equation 5, B 50L is the magnetic flux density B measured in the rolling direction 50 indicates B 50C is the magnetic flux density B measured in the direction perpendicular to the rolling direction 50indicates.)

[0019] 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, 1.5 to 5.0% Si, 0.1 to 2.0% Al, 0.1 to 2.0% Mn, residual Fe, and unavoidable impurities to produce a hot-rolled steel sheet; pre-cold rolling the hot-rolled steel sheet; a first annealing step of annealing the pre-cold-rolled steel sheet; cold rolling the annealed steel sheet to produce a cold-rolled sheet; and a second annealing step of annealing the cold-rolled sheet.

[0020] The first annealing step includes a step of heating the cold-rolled sheet from 40°C to a first soaking temperature (T1) at a rate of 10 to 50°C / s, a first soaking step of soaking the cold-rolled sheet at a first soaking temperature (T1) of 950 to 1100°C, a second soaking step of soaking the cold-rolled sheet at a second soaking temperature (T2) of 800 to 950°C, and a cooling step of cooling from the second soaking temperature (T2) to 670°C for 10 to 40 seconds.

[0021] The slab may further contain one or more of P: 0.1% by weight or less (excluding 0%), C: 0.005% by weight or less (excluding 0%), S: 0.005% by weight or less (excluding 0%), Ti: 0.005% by weight or less (excluding 0%), and N: 0.005% by weight or less (excluding 0%).

[0022] The slab may further contain one or more of Sn, Sb, Bi, Pb, Ge, and As in an amount of 0.005 to 0.200 wt % each or in total.

[0023] The slab may further contain one or more of Cu: 0.005 to 0.2 wt %, Cr: 0.01 to 0.5 wt %, Ni: 0.05 wt % or less (excluding 0%), and Zn: 0.01 wt % or less (excluding 0%).

[0024] 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%), V: 0.0050% by weight or less (excluding 0%), Ca: 0.0050% by weight or less (excluding 0%), Nb: 0.0050% by weight or less (excluding 0%), Zr: 0.005% by weight or less (excluding 0%), Te: 0.01% by weight or less (excluding 0%), Co: 0.050% by weight or less (excluding 0%), and Mg: 0.0050% by weight or less (excluding 0%).

[0025] After the hot-rolled steel sheet is produced, the subsequent steps can be carried out while the scale present on the hot-rolled steel sheet remains.

[0026] In the preliminary cold rolling step, the reduction ratio may be 40 to 79%.

[0027] The soaking time in the first soaking stage can be 20 to 60 seconds.

[0028] After the first soaking step, the method may further include a step of cooling to a second soaking temperature at a cooling rate of 1 to 20° C. / s.

[0029] The soaking time in the second soaking stage may be 40 to 100 seconds. [Effects of the Invention]

[0030] By appropriately adjusting the alloying composition of the steel sheet and annealing it through a suitable process in the annealing step after preliminary cold rolling, it is possible to develop a specific texture and maximize the magnetic anisotropy. DETAILED DESCRIPTION OF THE INVENTION

[0031] 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.

[0032] 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 this specification, the term "comprising" refers to the inclusion of specific 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.

[0033] When a part is referred to as being "on" or "on" 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 specified, % means % by weight, and 1 ppm is 0.0001% by weight.

[0034] 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. 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.

[0035] 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.

[0036] A non-oriented electrical steel sheet according to one embodiment of the present invention contains, by weight, 1.5 to 5.0% Si, 0.1 to 2.0% Al, 0.1 to 2.0% Mn, residual Fe, and unavoidable impurities. The reasons for limiting the components of the non-oriented electrical steel sheet will be explained below.

[0037] Si:1.5~5.0wt% Silicon (Si) increases the resistivity of the material, reducing iron loss, and increases strength through solid solution strengthening. Too little Si can result in insufficient iron loss and strength improvement, while excessive Si can increase the brittleness of the material, dramatically reducing rolling productivity and forming an oxide layer or oxides on the surface that are harmful to magnetic properties. Therefore, the Si content can be 1.5 to 5.0 wt.%, more specifically 2.0 to 4.5 wt.%, and even more specifically 2.5 to 4.0 wt.%.

[0038] Al:0.1~2.0wt% Aluminum (Al) increases the material's resistivity, reducing iron loss and improving rollability, improving workability during cold rolling. If the Al content is too low, the high-frequency iron loss reduction effect is difficult to achieve, and the precipitation temperature of AlN decreases, resulting in the formation of fine nitrides, which can reduce magnetic properties. Adding too much Al not only reduces magnetic properties due to the excessive formation of nitrides, but also causes problems in all processes, including steelmaking and continuous casting, significantly reducing productivity. Therefore, the Al content can be 0.1 to 2.0 wt%, more specifically 0.3 to 1.9 wt%, and even more specifically 0.6 to 1.5 wt%. Mn:0.1~2.0wt% Manganese (Mn) increases the resistivity of the material, improving iron loss, and plays a role in forming sulfides. If the Mn content is too low, fine sulfides are formed, causing magnetic deterioration. If the Mn content is too high, fine MnS precipitates excessively, promoting the formation of a {111} texture that is unfavorable to magnetic properties and resulting in a rapid decrease in magnetic flux density. Therefore, Mn can be contained in an amount of 0.1 to 2.0 wt%, more specifically 0.2 to 1.6 wt%, and even more specifically 0.3 to 1.4 wt%.

[0039] A non-oriented electrical steel sheet according to one embodiment of the present invention may further contain one or more of P: 0.1% by weight or less (excluding 0%), C: 0.005% by weight or less (excluding 0%), S: 0.005% by weight or less (excluding 0%), Ti: 0.005% by weight or less (excluding 0%), and N: 0.005% by weight or less (excluding 0%).

[0040] P: 0.1% by weight or less Phosphorus (P) not only increases the resistivity of the material but also increases the magnetic flux density as a grain boundary segregation element. However, excessive P addition increases the brittleness of the steel sheet and deteriorates the weldability. More specifically, P can be contained in an amount of 0.0001 to 0.0500 wt%, and even more specifically, 0.0010 to 0.0200 wt%.

[0041] C: 0.005% by weight or less Carbon (C) can cause magnetic aging, combine with other impurity elements to form carbides, and inhibit the movement of grain boundaries or domain walls, potentially deteriorating magnetic properties. More specifically, the alloy may contain 0.0001 to 0.003 wt % C. S: 0.005% by weight or less Sulfur (S) forms fine precipitates such as MnS and CuS, which can deteriorate magnetic properties and hot workability. More specifically, S can be contained in an amount of 0.0001 to 0.0030 wt %.

[0042] Ti: 0.005% by weight or less Titanium (Ti) has a strong tendency to form precipitates in steel, forming fine carbides, nitrides, or sulfides inside the base material, which inhibit grain growth and domain wall motion, thereby deteriorating iron loss. More specifically, the Ti content can be 0.0001 to 0.0030 wt %. N: 0.005% by weight or less Nitrogen (N) not only forms fine AlN precipitates inside the base material, but also combines with other impurities to form fine precipitates, which may inhibit grain growth and domain wall motion, thereby worsening iron loss. More specifically, N may be contained in an amount of 0.0001 to 0.0030 wt %. The non-oriented electrical steel sheet according to one embodiment of the present invention may further contain one or more of Sn, Sb, Bi, Pb, Ge, and As in an amount of 0.005 to 0.200 wt % each or in total.

[0043] Sn Tin (Sn) segregates at grain boundaries and surfaces, improving the texture of the material and suppressing surface oxidation, and can therefore be added to improve magnetic properties. Too much Sn can cause significant grain boundary segregation, degrading surface quality, increasing hardness, potentially causing breakage of the cold-rolled sheet and reducing rollability. Specifically, the Sn content can be 0.005 to 0.200 wt %, more specifically 0.010 to 0.080 wt %.

[0044] Sb Antimony (Sb) segregates at grain boundaries and surfaces, improving the texture of the material and suppressing surface oxidation, and can therefore be added to improve magnetic properties. Too much Sb can cause significant grain boundary segregation, degrading surface quality, increasing hardness, potentially causing breakage of the cold-rolled sheet and reducing rollability. Specifically, Sb can be added in an amount of 0.005 to 0.200 wt %, more specifically 0.010 to 0.080 wt %.

[0045] Bi, Pb, Ge and As

[0046] When bismuth (Bi), lead (Pb), germanium (Ge) and arsenic (As) are added, they segregate at the grain boundaries to relieve stress concentration at the grain boundaries during cold rolling, and then reduce the stress concentration during the recrystallization annealing process. <111> / / Improves magnetic flux density by suppressing the recrystallization of ND-oriented crystal grains. If these are added appropriately, the above effect can be obtained additionally, but if they are added in excess, large amounts of segregation occur, suppressing crystal grain growth and possibly deteriorating magnetic flux density and core loss. A non-oriented electrical steel sheet according to one 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%, Ni: 0.05 wt% or less (excluding 0%), Zn: 0.01 wt% or less (excluding 0%), and Co: 0.05 wt% or less (excluding 0%).

[0047] Cu:0.005~0.200wt% Copper (Cu) plays a role in forming sulfides with Mn. If Cu is added, too little (Cu Mn)S may precipitate in fine particles, which may deteriorate the magnetic properties. If there is too much Cu, 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%.

[0048] Cr:0.01~0.50wt% Chromium (Cr) plays a role in increasing resistivity and improving iron loss. If the Cr content is too low, the resistivity increase effect may be insufficient, and if the Cr content is too high, the magnetic flux density may decrease. More specifically, the Cr content may be 0.050 to 0.20 wt %.

[0049] Ni: 0.05% by weight or less Nickel (Ni) reacts with impurity elements to form fine sulfides, carbides, and nitrides, which may have a detrimental effect on magnetic properties. More specifically, Ni may be contained in an amount of 0.001 to 0.03 wt %.

[0050] Zn: 0.01% by weight or less If the zinc (Zn) content is excessive, it may act as an impurity and deteriorate the magnetic properties. Therefore, Zn can be further added within the above-mentioned range. More specifically, Zn can be contained in an amount of 0.001 to 0.005 wt %.

[0051] Co: 0.05% by weight or less Cobalt (Co) does not form fine precipitates that reduce the magnetic properties of steel sheets, but it increases the high-temperature strength and may cause defects in the coil shape after hot rolling.

[0052] The non-oriented electrical steel sheet according to one embodiment of the present invention 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%), V: 0.0050% by weight or less (excluding 0%), Ca: 0.0050% by weight or less (excluding 0%), Nb: 0.0050% by weight or less (excluding 0%), Zr: 0.0050% by weight or less (excluding 0%), Te: 0.0100% by weight or less (excluding 0%), and Mg: 0.0050% by weight or less (excluding 0%).

[0053] Mo: 0.030% by weight or less If molybdenum (Mo) is added in excess, it may inhibit the segregation of segregating elements, reducing the texture improvement effect. Therefore, the Mo content can be set to 0.03 wt% or less. There is no particular lower limit, but Mo can be contained in an amount of 0.001 wt% or more because it segregates to the surface and grain boundaries to improve the texture. More specifically, it can be contained in an amount of 0.001 to 0.010 wt%, and even more specifically, 0.005 to 0.010 wt%.

[0054] B: 0.0050% by weight or less If excessive boron (B) is added, there is a possibility that magnetic properties may be deteriorated due to the formation of inclusions in the steel. Therefore, B can be contained at 0.005% by weight or less. There is no particular lower limit, but it can be set to 0.0001% by weight from the viewpoint of steelmaking costs. More specifically, B can be contained at 0.0001 to 0.0030% by weight.

[0055] V: 0.0050% by weight or less Vanadium (V) has a strong tendency to form precipitates in steel, forming fine carbides or nitrides inside the base material, which inhibit grain growth and domain wall motion and deteriorate core loss. Therefore, the V content can be set to 0.0050 wt% or less. While there is no particular lower limit, it can be set to 0.0003 wt% from the perspective of steelmaking costs. In other words, V can be contained in an amount of 0.0003 to 0.0050 wt%, and more specifically, 0.0003 to 0.0030 wt%.

[0056] Ca: 0.0050% by weight or less Calcium (Ca) has a strong tendency to form precipitates in steel, forming fine sulfides inside the base material, which inhibits grain growth and domain wall movement, and deteriorates iron loss.

[0057] Nb: 0.0050% by weight or less Niobium (Nb) has a strong tendency to form precipitates in steel, forming fine carbides or nitrides inside the base material, which inhibit grain growth and domain wall motion and deteriorate core loss. Therefore, the Nb content can be set to 0.0050 wt% or less. There is no particular lower limit, but it can be set to 0.0003 wt% from the perspective of steelmaking costs. In other words, Nb can be contained in an amount of 0.0003 to 0.0050 wt%, and more specifically, 0.0003 to 0.0030 wt%.

[0058] Zr: 0.0050% by weight or less Adding excessive zirconium (Zr) can result in the formation of inclusions in the steel, which can degrade magnetic properties. Therefore, Zr can be contained at 0.005% by weight or less. There is no particular lower limit, but it can be set to 0.0001% by weight from the perspective of steelmaking costs. In other words, Zr can be contained at 0.0001 to 0.0050% by weight, and more specifically, at 0.0005 to 0.0030% by weight.

[0059] Te: 0.0100% by weight or less Tellurium (Te) diffuses into the oxide layer on the surface of hot-rolled coils, increasing the coefficient of friction between the oxide layer and the rolling work roll. It also concentrates at the bottom of the oxide layer, improving hardness. It can be added to prevent the oxide layer from being crushed during rolling and falling off without being pressed into the base material. Adding too little Tellurium can result in minimal effect. Adding too much Tellurium can also cause the oxide layer to easily fall off, resulting in direct contact of the base material with the work roll. This can also reduce the effect. In addition, excessive Tellurium can cause excessive deformation bands to form in the steel sheet during cold rolling, potentially leading to the development of a {111} / / ND texture, which is detrimental to magnetic properties. More specifically, Tellurium can be added in a range of 0.0001 to 0.007 wt%.

[0060] Mg: 0.0050% by weight or less Magnesium (Mg) is an element that mainly combines with S to form sulfides, which may affect the surface oxide layer of the base steel. Therefore, Mg may be contained in an amount of 0.0050 wt% or less. There is no particular lower limit, but it can be set to 0.0001 wt% from the perspective of steelmaking costs. In other words, Mg may be contained in an amount of 0.0001 to 0.0050 wt%, and more specifically, 0.0005 to 0.0030 wt%.

[0061] The balance is Fe and unavoidable impurities. Affected impurities are impurities that are mixed in during the steelmaking process and the manufacturing process of non-oriented electrical steel sheets, and are widely known in the art, so detailed description will be omitted. In one embodiment of the present invention, the addition of elements other than the alloy components is not excluded, and various elements may be included within a range that does not impair the technical concept of the present invention. When additional elements are further included, they are included to replace the balance Fe.

[0062] As described above, in one embodiment of the present invention, by appropriately adjusting the alloying components of the steel sheet and annealing it through an appropriate process in the annealing step after preliminary cold rolling, it is possible to develop a specific texture and maximize the magnetic anisotropy.

[0063] Specifically, the non-oriented electrical steel sheet according to one embodiment of the present invention satisfies the following formula 1.

[0064] [Formula 1] V{001} <001> / V{011} <001> ≦0.65 (In Equation 1, V{001} <001> is {001} <001> The percentage of grains with an orientation within 15° of V{011} <001> is {011} <001> This indicates the percentage of grains with orientations within 15° of the

[0065] {001} <001> The texture is called the Exact Cube structure, which is desirable for non-oriented electrical steel sheets. <001> The texture is called an Exact Goss texture, which is known as a desirable texture for grain-oriented electrical steel sheets. In one embodiment of the present invention, unlike conventional non-oriented electrical steel sheets, the ratio of Exact Cube is lower than that of Exact Goss to maximize magnetic anisotropy. Problems may arise if the smaller the value of the left side of Equation 1, the better the anisotropy. More specifically, the value of the left side of Equation 1 may be 0.30 to 0.64.

[0066] In one embodiment of the present invention, the texture fraction can be measured by EBSD. More specifically, the TD plane of a non-oriented electrical steel sheet is measured at a depth of 0.5 to 2 mm. 2 The specimens are prepared in sizes of 100 mm and measurements can be taken from at least eight specimens.

[0067] Furthermore, the non-oriented electrical steel sheet according to one embodiment of the present invention can satisfy the following formula 2.

[0068] [Formula 2] ((V{100} <001> +V{100} <031> +V{100} <110> ) / (V{111} <112> +V{111} <011> ) ≧ 1.3

[0069] {100} <001> , {100} <031> , {100} <110> The texture is a Rotated Cube texture, which is advantageous for ensuring magnetic flux density and iron loss characteristics. <112> , {111} <011> Texture is known to be unfavorable for magnetic flux density and core loss. In one embodiment of the present invention, we attempted to maximize magnetic anisotropy by suppressing the fraction of {111} planes, as in conventional non-oriented electrical steel sheets. If the value of the left side of Equation 2 is too small, deterioration in magnetic flux density and core loss may occur. More specifically, the value of the left side of Equation 2 may be 1.3 to 2.3.

[0070] As described above, in one embodiment of the present invention, a specific texture can be developed to maximize magnetic anisotropy. Specifically, the non-oriented electrical steel sheet according to one embodiment of the present invention can satisfy the following formula 3:

[0071] [Formula 3] B 50L -B 50D ≧0.08T (In Equation 3, B 50L is the magnetic flux density B measured in the rolling direction 50 indicates B 50D is the magnetic flux density B measured in a direction at an angle of 45° to the rolling direction. 50 indicates.)

[0072] Equation 3 shows the difference in magnetic flux density between the rolling direction (RD direction) and the direction forming a 45° angle with the rolling direction, and the larger the difference, the higher the magnetic anisotropy. Specifically, the value of the left side of Equation 3 can be set to 0.08 to 0.13 T.

[0073] The non-oriented electrical steel sheet according to one embodiment of the present invention can satisfy the following formula 4.

[0074] [Formula 4] B 50C -B 50D ≧0.03T (In Equation 4, B 50C is the magnetic flux density B measured in the direction perpendicular to the rolling direction 50 indicates B 50Dis the magnetic flux density B measured in a direction at an angle of 45° to the rolling direction. 50 indicates.)

[0075] Equation 4 shows the difference in magnetic flux density between the direction perpendicular to the rolling direction (TD direction) and the direction at a 45° angle to the rolling direction, and the larger the difference, the higher the magnetic anisotropy. Specifically, the value of the left side of Equation 4 can be 0.03 to 0.06 T.

[0076] The non-oriented electrical steel sheet according to one embodiment of the present invention can satisfy the following formula 5.

[0077] [Formula 5] (B 50L +B 50C ) / 2≧1.680T (In Equation 5, B 50L is the magnetic flux density B measured in the rolling direction 50 indicates B 50C is the magnetic flux density B measured in the direction perpendicular to the rolling direction 50 indicates.)

[0078] Equation 5 shows the average magnetic flux density in the rolling direction and the direction perpendicular to the rolling direction, and the higher this value, the more advantageous it is. More specifically, the value of the left side of Equation 5 can be 1.680 to 1.770 T.

[0079] As described above, in one embodiment of the present invention, the iron loss (W 10 / 400 ) can be 12.5W / Kg or less. Iron loss (W 10 / 400 ) indicates the iron loss when a magnetic flux density of 1.0 T is excited at a frequency of 400 Hz. More specifically, the iron loss (W 10 / 400 ) can be 10.0 to 12.0 W / kg.

[0080] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention includes the steps of hot-rolling a slab to manufacture a hot-rolled steel sheet, pre-cold-rolling the hot-rolled steel sheet, a first annealing step of annealing the pre-cold-rolled steel sheet, cold-rolling the annealed steel sheet to manufacture a cold-rolled sheet, and a second annealing step of annealing the cold-rolled sheet.

[0081] Each stage will be explained in detail below.

[0082] First, the slab is hot rolled.

[0083] The alloy composition of the slab has been explained in the alloy composition of the non-oriented electrical steel sheet, so a duplicate explanation will be omitted. Since the alloy composition does not substantially change during the manufacturing process of the non-oriented electrical steel sheet, the alloy composition of the non-oriented electrical steel sheet and the slab is substantially the same.

[0084] Specifically, the slab contains, by weight, 1.5 to 5.0% Si, 0.1 to 2.0% Al, and 0.1 to 2.0% Mn, with the remainder being Fe and unavoidable impurities. Other additional elements have been explained in the alloy components of the non-oriented electrical steel sheet, so a duplicate explanation will be omitted.

[0085] The slab may be heated before hot rolling. The heating temperature of the slab is not particularly limited, but the slab can be heated to 1200°C or less. If the slab heating temperature is too high, precipitates such as AlN and MnS present in the slab will redissolve and then precipitate finely during hot rolling and annealing, suppressing the growth of crystal grains and possibly reducing magnetic properties.

[0086] Next, the slab is hot-rolled to produce a hot-rolled sheet. The thickness of the hot-rolled sheet can be 1.0 to 4.5 mm. The finish rolling temperature in the hot-rolled sheet production stage can be 800°C or higher, specifically 870 to 950°C. The hot-rolled sheet may be coiled at a temperature of 600°C or higher. More specifically, the thickness of the hot-rolled sheet can be 1.5 to 4.3 mm.

[0087] After the hot-rolled steel sheet is manufactured, the next step can be carried out while the scale remains on the hot-rolled steel sheet, i.e., the next step can be carried out without removing the scale after hot rolling, such as pickling, shot blasting, or surface grinding.

[0088] By performing cold rolling without the pickling process, friction between the rolling work roll and the steel sheet increases, and shear deformation is simultaneously imparted to the steel sheet in addition to planar deformation during rolling, which causes a specific orientation to develop during recrystallization annealing.In one embodiment of the present invention, scale refers to the portion on the surface of the steel sheet where elements such as Fe, Al, and Si combine with oxygen to form a phase different from that of the base material.

[0089] Residual scale refers to the presence of at least 1 μm of scale remaining on the hot-rolled sheet. In this case, the scale thickness is the sum of the thicknesses of the scale formed on both surfaces of the steel sheet. If the remaining scale thickness is too thin, the effect of the remaining scale may not be fully realized. Even if the scale thickness is increased further, the effect will not improve and there is a problem of a decrease in the yield of the steel sheet. More specifically, scale of 0.1 to 1 μm in thickness may remain. Furthermore, the steel sheet may be subjected to preliminary cold rolling without external heating after hot rolling.

[0090] Next, the hot-rolled steel sheet is pre-cold rolled. Pre-cold rolling is distinguished from cold rolling, which will be described later, in that it is the first rolling step in the process of rolling to an intermediate thickness that is not the final product thickness, followed by intermediate annealing, and then cold rolling to the final product thickness.

[0091] Preliminary cold rolling can be performed at a reduction ratio of 40 to 79% to improve the productivity of final cold rolling and the grain size of the final product sheet. Furthermore, if rolling productivity is not a consideration, preliminary cold rolling can also be performed using a reverse mill in the present invention. The thickness of the preliminary cold-rolled sheet can be 0.3 to 1.5 mm. More specifically, the reduction ratio can be 50 to 75% and the thickness can be 0.6 to 1.3 mm.

[0092] The preliminary cold rolling reduction can be calculated by (steel plate thickness before rolling - steel plate thickness after rolling) / steel plate thickness before rolling x 100 (%). If the reduction rate in the preliminary cold rolling stage is too low, the rolling load increases during the final cold rolling, reducing productivity, and the final reduction rate increases, resulting in fine grains. <111> / / This may cause problems with promoting recrystallization in the ND orientation. Conversely, if the reduction is too high, the cold rolling load increases, increasing the possibility of sheet fracture.

[0093] The preliminary cold rolling stage can be carried out at a temperature of 60 to 300°C. This temperature can be raised naturally by friction between the steel sheet and the rolling rolls, or by applying heat from an external source. If the temperature is too low, the rolling load increases significantly, causing the steel sheet to slip between the rolling rolls instead of being rolled, leading to problems such as twisting. If the temperature is too high, a thick oxide layer can form on the surface of the steel sheet, degrading its magnetic properties and potentially causing problems such as the rolling oil catching fire. More specifically, it is desirable to carry out the process at a temperature of 70 to 250°C. The above temperatures refer to the temperature of the steel sheet.

[0094] As noted above, the preliminary cold rolling step may be omitted if desired.

[0095] Next, the pre-cold rolled steel sheet is annealed in a first annealing stage. In one embodiment of the present invention, a specific grain structure is formed through the heating, first soaking, second soaking, and cooling processes in the first annealing stage, thereby maximizing magnetic anisotropy.

[0096] First, the cold-rolled sheet is heated from 40°C to the first soaking temperature (T1) at a rate of 10 to 50°C / s. If the heating rate is too slow, a problem of a convergent structure having {111} planes may develop. On the other hand, if the heating rate is too fast, it becomes difficult to control the temperature, making it difficult to control the sheet temperature to the target. More specifically, the sheet can be heated at a heating rate of 15 to 30°C / s. In one embodiment of the present invention, the temperature reference is the surface temperature of the steel sheet.

[0097] Next, the cold-rolled sheet is soaked at a first soaking temperature (T1) of 950 to 1100°C. The first soaking temperature (T1) is any temperature selected within the range of 950 to 1100°C, and soaking refers to maintaining the temperature within ±10°C or less. If the first soaking temperature is too low, iron loss may deteriorate, and if it is too high, magnetic flux density and iron loss may deteriorate. More specifically, the first soaking temperature (T1) can be 950 to 1050°C. The soaking time in the first soaking stage can be 20 to 60 seconds.

[0098] After the first soaking stage, the steel sheet can be cooled to the second soaking temperature at a cooling rate of 1 to 30°C / s. By appropriately adjusting the cooling rate, residual stress in the steel sheet can be removed. More specifically, the cooling rate can be adjusted to 5 to 20°C / s.

[0099] Next, the cold-rolled sheet is soaked at a second soaking temperature (T2) of 800 to 950°C. The second soaking temperature (T2) can be set arbitrarily within the range of 800 to 950°C and may be lower than the first soaking temperature (T1). Performing soaking in two stages in this manner is advantageous in that it allows for the formation of an appropriate convergent structure while effectively reducing the cooling rate during continuous annealing. If the second soaking temperature is too low, the cooling rate increases between the first and second soaking stages, which may result in residual stress and deterioration of magnetic properties. If the second soaking temperature is too high, there is a problem in that the cooling rate cannot be sufficiently reduced during cooling. More specifically, the second soaking temperature (T2) can be set to 800 to 950°C. The soaking time in the second soaking stage can be 1 to 30 seconds, more specifically 5 to 20 seconds.

[0100] Next, the material is cooled from the second soaking temperature (T2) to 670°C over a period of 10 to 40 seconds. If the cooling time is too short, residual stress due to rapid cooling may increase, resulting in a deterioration of magnetic properties. On the other hand, if the cooling time is too long, fine TiNb(C,N)-based precipitates may precipitate, resulting in a deterioration of magnetic properties. More specifically, the material can be cooled over a period of 15 to 30 seconds.

[0101] Returning to the explanation of the manufacturing method for non-oriented electrical steel sheet, after the first annealing stage, the annealed steel sheet is cold-rolled to produce a cold-rolled sheet. At this time, cold rolling can be performed at a reduction of 55 to 70%. If the reduction is too low, the deformation energy accumulated in the rolled steel sheet is small, making it difficult for recrystallization to proceed in the subsequent annealing process, and the rolled structure may remain, causing problems in improving magnetic flux density and iron loss. On the other hand, if the reduction is too high, it may be difficult to recrystallize in the subsequent annealing process. <111> / / The recrystallization of ND-oriented crystal grains is promoted, resulting in a finer grain size, a decrease in magnetic flux density, and an increase in iron loss. More specifically, the rolling reduction can be set to 58-67%.

[0102] In the cold rolling stage, a tandem cold rolling mill that uses multiple rolling stands to perform continuous cold rolling, or a reversing rolling mill that uses 12 or more roll stages to perform intermittent cold rolling, can be used. The final rolled thickness can be 0.1 to 0.35 mm.

[0103] Next, the cold-rolled sheet is annealed in the second annealing stage. The second annealing stage can be performed at 900°C or higher. If the soaking temperature is too low, the crystal grains may not grow sufficiently, which may increase hysteresis loss and worsen iron loss. More specifically, the sheet can be annealed at a temperature of 900 to 1050°C. The second annealing stage can be soaked for 50 to 120 seconds.

[0104] In the annealing process of cold-rolled sheets, all (99% or more) of the processed structure formed during the cold rolling stage can be recrystallized.

[0105] After annealing the cold-rolled sheet, an insulating film may be formed. The insulating film may be an organic film, an inorganic film, or an organic-inorganic composite film, or may be formed with other insulating coating agents.

[0106] 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]

[0107] Slabs were produced with the compositions shown in Tables 1 and 2, with the balance being Fe and unavoidable impurities, and were heated to 1150°C and hot rolled at a finishing temperature of 950°C to produce hot-rolled sheets with a thickness of 2.3 mm.

[0108] Thereafter, the annealing of the hot-rolled sheet was omitted, and preliminary cold rolling was performed at a rolling reduction of 65%, and the steel sheet was subjected to first annealing under the conditions in Table 3, followed by cold rolling to a final thickness of 0.25 mm. Furthermore, the cold-rolled steel sheet was subjected to second annealing under the conditions in Table 3.

[0109] The TD plane of the manufactured non-oriented electrical steel sheets was analyzed by EBSD, and the results are shown in Table 4. The magnetic flux density (B50) and iron loss (W10 / 400) were measured by the Epstein measurement method using specimens processed to a size of 305 mm x 30 mm in the rolling direction, the direction perpendicular to the rolling direction, and the direction at an angle of 45° to the rolling direction, with the weights of the Epstein specimens adjusted to 400 to 450 g for each of the rolling direction, the direction perpendicular to the rolling direction, and the direction at an angle of 45° to the rolling direction. 10 / 400 The average of the values ​​measured in the rolling direction and the direction perpendicular to the rolling direction was used. At this time, W 10 / 400 is the iron loss when a magnetic flux density of 1.0 T is induced at a frequency of 400 Hz, and B 50 means the magnetic flux density induced in a magnetic field of 5000 A / m.

[0110] [Table 1]

[0111] [Table 2]

[0112] [Table 3]

[0113] [Table 4]

[0114] [Table 5]

[0115] As shown in Tables 1 to 5, the examples of the present invention, in which the iron composition, process conditions, and texture were appropriately adjusted, exhibited excellent core loss and magnetic flux density, while simultaneously maximizing the magnetic anisotropy.

[0116] On the other hand, if the iron composition is not properly adjusted or if the process conditions are not properly adjusted and the texture is not properly formed, it has been confirmed that the iron loss and magnetic flux density are poor and sufficient magnetic anisotropy cannot be obtained.

[0117] 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, in weight percent, 1.5 to 5.0% Si, 0.1 to 2.0% Al, 0.1 to 2.0% Mn, residual Fe, and unavoidable impurities, and satisfying the following formula 1: [Formula 1] V{001}<001> / V{011}<001>≦0.65 (In formula 1, V{001}<001> represents the proportion of crystal grains having an orientation within 15° of {001}<001>, and V{011}<001> represents the proportion of crystal grains having an orientation within 15° of {011}<001>.)

2. 2. The non-oriented electrical steel sheet according to claim 1, wherein the following formula 2 is satisfied: [Formula 2] (V{100}<001>+V{100}<031>+V{100}<110>) / (V{111}<112>+V{111}<011>)≧1.3 (In formula 2, V{100}<001> represents the proportion of crystal grains having an orientation within 15° of {100}<001>, V{100}<031> represents the proportion of crystal grains having an orientation within 15° of {100}<031>, V{100}<110> represents the proportion of crystal grains having an orientation within 15° of {100}<110>, V{111}<112> represents the proportion of crystal grains having an orientation within 15° of {111}<112>, and V{111}<011> represents the proportion of crystal grains having an orientation within 15° of {111}<011>.)

3. 2. The non-oriented electrical steel sheet according to claim 1, further comprising one or more of P: 0.1% by weight or less (excluding 0%), C: 0.005% by weight or less (excluding 0%), S: 0.005% by weight or less (excluding 0%), Ti: 0.005% by weight or less (excluding 0%), and N: 0.005% by weight or less (excluding 0%).

4. 2. The non-oriented electrical steel sheet according to claim 1, further comprising one or more of Sn, Sb, Bi, Pb, Ge and As in an amount of 0.005 to 0.200 wt % each or in total.

5. 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 %, Ni: 0.05 wt % or less (excluding 0%), Zn: 0.01 wt % or less (excluding 0%), and Co: 0.05 wt % or less (excluding 0%).

6. 2. The non-oriented electrical steel sheet according to claim 1, further comprising one or more of Mo: 0.03% by weight or less (except 0%), B: 0.0050% by weight or less (except 0%), V: 0.0050% by weight or less (except 0%), Ca: 0.0050% by weight or less (except 0%), Nb: 0.0050% by weight or less (except 0%), Zr: 0.005% by weight or less (except 0%), Te: 0.01% by weight or less (except 0%), and Mg: 0.0050% by weight or less (except 0%).

7. 2. The non-oriented electrical steel sheet according to claim 1, wherein the following formula 3 is satisfied: [Formula 3] B ５０Ｌ - B ５０Ｄ ≧0.08T (In Equation 3, B ５０Ｌ is the magnetic flux density B measured in the rolling direction ５０ indicates B ５０Ｄ is the magnetic flux density B measured in a direction at an angle of 45° to the rolling direction ５０ Indicates.)

8. 2. The non-oriented electrical steel sheet according to claim 1, wherein the following formula 4 is satisfied: [Formula 4] B ５０Ｃ -B ５０Ｄ ≧0.03T (In Equation 4, B ５０Ｃ is the magnetic flux density B measured in the direction perpendicular to the rolling direction ５０ indicates B ５０Ｄ is the magnetic flux density B measured in a direction at an angle of 45° to the rolling direction ５０ Indicates.)

9. 2. The non-oriented electrical steel sheet according to claim 1, wherein the following formula 5 is satisfied: [Formula 5] (B ５０Ｌ +B ５０Ｃ ) / 2≧1.68T (In Equation 5, B ５０Ｌ is the magnetic flux density B measured in the rolling direction ５０ indicates B ５０Ｃ is the magnetic flux density B measured in the direction perpendicular to the rolling direction ５０ Indicates.)

10. hot rolling a slab containing, by weight %, 1.5 to 5.0% Si, 0.1 to 2.0% Al, 0.1 to 2.0% Mn, residual Fe, and unavoidable impurities to produce a hot-rolled steel sheet; pre-cold rolling the hot-rolled steel sheet; a first annealing step of annealing the pre-cold rolled steel sheet; cold rolling the annealed steel sheet to produce a cold-rolled sheet; a second annealing step of annealing the cold-rolled sheet; The first annealing step is performed by heating the cold-rolled sheet from 40° C. to a first soaking temperature (T １ ) at 10-50°C / s, The cold-rolled sheet is subjected to a first soaking temperature (T １ ) the first soaking stage, The cold-rolled sheet is subjected to a second soaking temperature (T ２ ) a second soaking stage in which the mixture is soaked in water; The second soaking temperature (T ２ ) to 670°C for 10 to 40 seconds.

11. 11. The method for producing a non-oriented electrical steel sheet according to claim 10, wherein the slab further contains one or more of P: 0.1% by weight or less (excluding 0%), C: 0.005% by weight or less (excluding 0%), S: 0.005% by weight or less (excluding 0%), Ti: 0.005% by weight or less (excluding 0%), and N: 0.005% by weight or less (excluding 0%).

12. The method for producing a non-oriented electrical steel sheet according to claim 10, wherein the slab further contains one or more of Sn, Sb, Bi, Pb, Ge, and As in an amount of 0.005 to 0.200 wt %, each or a total amount thereof.

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 Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Ni: 0.05 wt% or less (excluding 0%), Zn: 0.01 wt% or less (excluding 0%), and Co: 0.05 wt% or less (excluding 0%).

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 (except 0%), B: 0.0050% by weight or less (except 0%), V: 0.0050% by weight or less (except 0%), Ca: 0.0050% by weight or less (except 0%), Nb: 0.0050% by weight or less (except 0%), Zr: 0.005% by weight or less (except 0%), Te: 0.01% by weight or less (except 0%), and Mg: 0.0050% by weight or less (except 0%).

15. The method for manufacturing a non-oriented electrical steel sheet according to claim 10, wherein the subsequent steps are carried out in a state where scales present on the hot-rolled steel sheet remain after the hot-rolled steel sheet is manufactured.

16. The method for producing a non-oriented electrical steel sheet according to claim 10, wherein the reduction ratio in the preliminary cold rolling step is 40 to 79%.

17. The method for manufacturing a non-oriented electrical steel sheet according to claim 10, wherein the soaking time in the first soaking step is 20 to 60 seconds.

18. The method for manufacturing a non-oriented electrical steel sheet according to claim 10, further comprising the step of cooling to a second soaking temperature at a cooling rate of 1 to 20° C. / s after the first soaking step.

19. The method for manufacturing a non-oriented electrical steel sheet according to claim 10, wherein the soaking time in the second soaking step is 40 to 100 seconds.

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