Non-oriented electrical steel sheet and its manufacturing method

Abstract

Provided are a non-oriented electrical steel sheet with improved magnetic properties and texture characteristics, and a method for manufacturing the same. [Solution] A non-oriented electrical steel sheet characterized by comprising, by weight, Si: 1.5-4.0%, Al: 0.1-1.5%, Mn: 0.1-1.5%, C: 0.005% or less (excluding 0%), N: 0.005% or less (excluding 0%), Ti: 0.005% or less (excluding 0%), S: 0.001-0.005%, P: 0.1% or less (excluding 0%), one or more of Sn and Sb: 0.02-0.2%, the balance being Fe and unavoidable impurities, and satisfying the following formulas 1 and 2, and having uniform crystal grain size at the surface and center. [Formula 1] 0.9≦[Al]+[Mn]≦2.1 [Formula 2] 0.2≦([Si]+[Al]+[Mn] / 2)*([P]+[Sn]+[Sb])≦0.4 (In the formula, [Al], [Mn], [Si], [P], [Sn], and [Sb] represent the content (wt%) of the element in [ ].)

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 having low core loss and excellent magnetic properties by controlling the crystal grain size in the sheet thickness direction, and a manufacturing method thereof. [Background technology]

[0002] Non-oriented electrical steel sheets are used as iron core materials in rotating equipment such as motors and generators, and electrical equipment such as small transformers, and play an important role in converting mechanical energy into electrical energy, or electrical energy into mechanical energy, or in the interconversion between electrical energies. As such, non-oriented electrical steel sheets are a very important material that determines the energy efficiency of electrical equipment in energy conversion systems, and therefore there is a continuous demand for the development of non-oriented electrical steel sheets with better properties, especially non-oriented electrical steel sheets with excellent core loss, in order to conserve and save energy, and it is an issue that should be continuously studied to improve the properties in the future.

[0003] The representative magnetic properties of non-oriented electrical steel sheets are iron loss and magnetic flux density. Iron loss is related to the energy lost during the use of electrical equipment, and magnetic flux density is related to the torque of electrical equipment. Recently, low iron loss is very important for the high efficiency characteristics required for electric motors and generators, so non-oriented electrical steel sheets with lower iron loss properties are required. An efficient method for lowering iron loss is to increase the amount of Si, which is an important essential alloy element added to non-oriented electrical steel sheets and has a high resistivity, or to reduce the thickness of the steel sheet. Iron loss in electrical steel sheets is divided into hysteretic loss and eddy current loss, and such a method can be said to be very effective in reducing eddy current loss. However, thin steel sheets have the disadvantage of poor workability and increased processing costs. Therefore, in the highest quality products, the amount of Si, Al, and Mn added is increased to further reduce iron loss through increased resistivity. However, even if the amount of Si, Al, and Mn added is increased, iron loss does not decrease unconditionally, but must be controlled in an optimal combination. Also, since it cannot be said that iron loss will be dramatically reduced by controlling Si, Al, and Mn alone, it is not easy to develop a technology that can dramatically improve iron loss.

[0004] Meanwhile, non-oriented electrical steel sheets used in motors and generators are used as iron core materials for rotating electrical equipment, so unlike oriented electrical steel sheets, in which only the characteristics in one direction, the rolling direction, are important, it is better for them to have uniform characteristics in all directions. Therefore, it is preferable for the iron loss deviation between the rolling direction and the direction perpendicular to the rolling direction to be small, but non-oriented electrical steel sheets produced by commercially available methods have a certain degree of iron loss deviation, and it is not yet easy to find a way to reduce this deviation. Therefore, in order to improve the iron loss, attempts have been made to improve the texture and magnetic properties by using special additive elements such as REM. However, while these technologies were developed to improve the iron loss, they all lead to increased manufacturing costs and are difficult to mass-produce, so there is a need to develop technology that not only has excellent iron loss properties but also allows for easy commercial production. Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to control the composition through the relational expression of the Si, Al, Mn, P, Sn, and Sb contents, and to control the average heating rate and Heating Temperature Heating The present invention provides a non-oriented electrical steel sheet having improved magnetic properties and texture characteristics by controlling process conditions through the time ratio, and a manufacturing method thereof. [Means for solving the problem]

[0006] The non-oriented electrical steel sheet according to one embodiment of the present invention contains, by weight, Si: 1.5 to 4.0%, Al: 0.1 to 1.5%, Mn: 0.1 to 1.5%, C: 0.005% or less (excluding 0%), N: 0.005% or less (excluding 0%), Ti: 0.005% or less (excluding 0%), S: 0.001 to 0.005%, P: 0.1% or less (excluding 0%), Sn, and Sb. Total amount : 0.02 to 0.2%, the balance being Fe and unavoidable impurities, Contains both Sn and Sb It is characterized in that the following formulas 1, 2, and 3 are satisfied. [Formula 1] 0.9≦[Al]+[Mn]≦2.1 [Formula 2] 0.2≦([Si]+[Al]+[Mn] / 2)*([P]+[Sn]+[Sb])≦0.4 [Formula 3] 0.29≦ (Gscenter-Gssurface) / (Gscenter*t)≦0.5 (In formulas 1 and 2, [Al], [Mn], [Si], [P], [Sn] and [Sb] respectively represent the contents (weight %) of Al, Mn, Si, P, Sn and Sb, and in formula 3, t represents the thickness (mm) of the non-oriented electrical steel sheet, Gssurface represents the average crystal grain size (μm) at 0~t / 4 or 3t / 4~t based on the thickness direction of the non-oriented electrical steel sheet, and Gscenter represents the average crystal grain size (μm) above t / 4 and below 3t / 4 based on the thickness direction of the non-oriented electrical steel sheet.)

[0007] The non-oriented electrical steel sheet may further contain one or more of Cu: 0.05% or less (excluding 0%), Ni: 0.05% or less (excluding 0%), Cr: 0.05% or less (excluding 0%), Zr: 0.01% or less (excluding 0%), Mo: 0.01% or less (excluding 0%), and V: 0.01% or less (excluding 0%). It is preferable that the non-oriented electrical steel sheet satisfies the following formula 4. [Formula 4] 0.2≦(V{012} <121> +V{111} <112> ) / (V{001} <310> +V{139} <310> )≦0.8 (In formula 4, V{012} <121> , V{111} <112> , V{001} <310> and V{139} <310> are {012} <121> , {111} <112> , {001} <310> , {139} <310> This indicates the volume fraction of textures with orientations within 15°.)

[0008] A method for producing a non-oriented electrical steel sheet according to an embodiment of the present invention comprises the following components by weight: Si: 1.5 to 4.0%, Al: 0.1 to 1.5%, Mn: 0.1 to 1.5%, C: 0.005% or less (except 0%), N: 0.005% or less (except 0%), Ti: 0.005% or less (except 0%), S: 0.001 to 0.005%, P: 0.1% or less (except 0%), Sn, Sb Total amount : 0.02 to 0.2%, the balance being Fe and unavoidable impurities, Contains both Sn and Sb The method includes the steps of heating a slab that satisfies the following formulas 1 and 2, hot rolling the slab to produce a hot-rolled sheet, cold rolling the hot-rolled sheet to produce a cold-rolled sheet, and annealing the cold-rolled sheet so as to satisfy the following formula 5. The non-oriented electrical steel sheets thus manufactured satisfy the following formula 3. It is characterized by: [Formula 1] 0.9≦[Al]+[Mn]≦2.1 [Formula 2] 0.2≦([Si]+[Al]+[Mn] / 2)*([P]+[Sn]+[Sb])≦0.4 [Formula 3] 0.29≦Gs center -Gs surface ) / (Gs center *t)≦0.5 [Formula 5] 0.2≦v / s≦0.6 (In formulas 1 and 2, [Al], [Mn], [Si], [P], [Sn] and [Sb] represent the contents (wt%) of Al, Mn, Si, P, Sn and Sb, respectively. In formula 3, t represents the thickness of the non-oriented electrical steel sheet (mm), and Gs surface indicates the average grain size (μm) at 0~t / 4 or 3t / 4~t based on the thickness direction of the non-oriented electrical steel sheet, and Gs center indicates the average grain size (μm) in the thickness direction of non-oriented electrical steel sheet when it is more than t / 4 and less than 3t / 4, In formula 5, v is the starting temperature of 650 to 750°C from the cold-rolled sheet HeatingThe average heating rate (℃ / sec) up to the temperature of the cold-rolled sheet is Heating Maintaining at temperature Heating It means time (sec).

[0009] The slab may further contain one or more of Cu: 0.05% or less (excluding 0%), Ni: 0.05% or less (excluding 0%), Cr: 0.05% or less (excluding 0%), Zr: 0.01% or less (excluding 0%), Mo: 0.01% or less (excluding 0%), and V: 0.01% or less (excluding 0%). In the step of annealing the cold-rolled sheet, the sheet is annealed at a temperature of 850 to 1050°C. Heating It is preferable to anneal the cold-rolled sheet at a temperature of 100.degree. The method may further include annealing the hot-rolled sheet at 950 to 1150° C. after the step of producing the hot-rolled sheet. Effect of the Invention

[0010] According to the present invention, the non-oriented electrical steel sheet and the manufacturing method thereof are characterized in that the components are controlled through the relational expressions of the contents of Si, Al, Mn, P, Sn, and Sb, and the average heating rate and Heating Temperature Heating By controlling the process conditions through the time ratio, it is expected that the magnetic property can be improved. In addition, it is possible to expect an effect of improving the texture which is advantageous for magnetic properties and an effect of reducing the deviation in the average crystal grain size between the surface portion and the center portion based on the thickness direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 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 may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention. The terminology used herein is merely for the purpose of referring to particular embodiments and is not intended to limit the present invention. As used herein, the singular form includes the plural form unless the text clearly indicates otherwise. As used in the specification, the meaning of "comprising" embodies certain features, regions, integers, steps, operations, elements and / or components and does not exclude the presence or addition of other features, regions, integers, steps, operations, elements and / or components. When a part is referred to as being "on" another part, this means that it is directly on top of the other part, or there may be other parts interposed between them. In contrast, when a part is referred to as being "directly on" another part, there are no other parts interposed between them.

[0012] 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 belongs. Terms defined in commonly used dictionaries are interpreted in addition to those having meanings consistent with the relevant technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal sense unless defined. Moreover, unless otherwise specified, % means % by weight, and 1 ppm is 0.0001% by weight. In one embodiment of the present invention, the inclusion of an additional element means that the additional element is substituted for the remaining iron (Fe) by an amount corresponding to the additional element. 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.

[0013] Non-oriented electrical steel sheet In one embodiment of the present invention, the composition of the non-oriented electrical steel sheet and the ranges of the added elements Si, Al, and Mn are optimized, and at the same time, the grain boundary segregation elements such as P, Sn, and Sb are adjusted, thereby significantly improving the magnetic properties. The non-oriented electrical steel sheet according to one embodiment of the present invention contains, by weight, Si: 1.5 to 4.0%, Al: 0.1 to 1.5%, Mn: 0.1 to 1.5%, C: 0.005% or less (except 0%), N: 0.005% or less (except 0%), Ti: 0.005% or less (except 0%), S: 0.001 to 0.005%, P: 0.1% or less (except 0%), Sn, Sb Total amount : 0.02 to 0.2%, with the balance being Fe and unavoidable impurities. First, the reasons for limiting the components of non-oriented electrical steel sheets will be explained below.

[0014] Si:1.5~4.0wt% Silicon (Si) increases the resistivity of the material and reduces eddy current loss in iron loss, and if too little is added, the iron loss improvement effect may be insufficient. On the other hand, if too much is added, it may reduce the magnetic flux density and reduce rollability. Therefore, it is preferable to add silicon (Si) within the above-mentioned range.

[0015] Al: 0.1~1.5% by weight Aluminum (Al) is an element that, together with Si, increases the resistivity of the material, lowers iron loss, and reduces magnetic anisotropy, thereby reducing the magnetic deviation in the rolling direction and the direction perpendicular to the rolling direction. If too little is added, fine nitrides may be formed, increasing the iron loss deviation in the rolling direction and the direction perpendicular to the rolling direction. On the other hand, if too much is added, excessive nitrides may be formed, significantly reducing the magnetic flux density. Therefore, it is preferable to add aluminum (Al) within the above-mentioned range.

[0016] Mn:0.1~1.5wt% Manganese (Mn) is an element that increases the resistivity of the material, reduces iron loss, and improves the texture. If a small amount is added, the iron loss improvement effect may be insufficient. On the other hand, if too much Mn is added, MnS is excessively precipitated, which may cause a large decrease in magnetic flux density. Therefore, it is preferable to add manganese (Mn) within the above-mentioned range.

[0017] C: 0.005% by weight or less Carbon (C) combines with elements such as Ti to form carbides, so if too much is added, it can reduce magnetism and increase iron loss due to magnetic aging during use after processing into electrical products. Therefore, it is preferable to add carbon (C) within the above-mentioned range.

[0018] N: 0.005% by weight or less Nitrogen (N) strongly bonds with elements such as Al and Ti to form nitrides, so if added in excess, it may inhibit grain growth and deteriorate magnetic properties. Therefore, it is preferable to add nitrogen (N) within the above-mentioned range.

[0019] Ti: 0.005% by weight or less Titanium (Ti) combines with C and N to form carbides and nitrides, so if added in excess, it can inhibit grain growth and cause the texture to deteriorate due to the carbides and nitrides, resulting in poor magnetic properties. Therefore, it is preferable to add titanium (Ti) within the above-mentioned range.

[0020] S:0.001~0.005% by weight Sulfur (S) is an element that forms sulfides such as MnS, CuS, and (Cu, Mn)S that are harmful to magnetic properties. If too little is added, it may be detrimental to the formation of texture and may reduce magnetic properties. On the other hand, if too much is added, the magnetic properties may decrease due to an increase in fine sulfides. Therefore, it is preferable to add sulfur (S) within the above-mentioned range.

[0021] P: 0.1% by weight or less Phosphorus (P) is an element that increases resistivity and reduces iron loss, and improves texture by segregating at grain boundaries. If added in excessive amounts, it may inhibit grain growth and reduce cold rolling properties. Therefore, it is preferable to add phosphorus (P) within the above-mentioned range.

[0022] Sn, Sb Total amount :0.02~0.2wt% Tin (Sn) and antimony (Sb) are grain boundary segregation elements that suppress the diffusion of nitrogen through grain boundaries and the formation of gamma fiber aggregates, thereby improving magnetic properties. If too little is added, the effect of improving magnetic properties is negligible, and if too much is added, it may suppress grain growth, reduce magnetism, and deteriorate rollability and surface quality. Therefore, it is recommended to use tin (Sn) and antimony (Sb) within the above range. )of When tin (Sn) or antimony (Sb) is contained alone, 0.02 to 0.2 wt% of Sn and 0.02 to 0.2 wt% of Sb can be contained. When tin (Sn) or antimony (Sb) is contained simultaneously, it is preferable that the total amount of Sn and Sb is 0.02 to 0.2 wt%.

[0023] Impurity elements In addition to the above elements, impurity elements such as Cu, Ni, Cr, Zr, Mo, and V may be included that are inevitably mixed in. Cu, Ni, and Cr may react with impurity elements to form fine sulfides, carbides, and nitrides that may have a detrimental effect on magnetic properties, and Zr, Mo, and V are elements that form strong carbonitrides, so they must be controlled to Cu: 0.05 wt% or less, Ni: 0.05 wt% or less, Cr: 0.05 wt% or less, Zr: 0.01 wt% or less, Mo: 0.01 wt% or less, and V: 0.01 wt% or less. The remainder of the composition other than the above is composed of Fe and other unavoidable impurities.

[0024] The non-oriented electrical steel sheet according to one embodiment of the present invention satisfies the following formula 1. [Formula 1] 0.9≦[Al]+[Mn]≦2.1 (In formula 1, [Al] and [Mn] represent the contents (wt%) of Al and Mn, respectively.) Al and Mn are elements that both increase resistivity and reduce iron loss. Therefore, the content of Al and Mn can be controlled by their total amount. In general, to manufacture non-oriented electrical steel sheets with low iron loss and high magnetic flux density, it is necessary to add more than the appropriate amount of Si, Al, and Mn. However, if [Al]+[Mn] is less than 0.9, the Si content becomes relatively high, which can be a fatal problem in terms of reducing rollability and productivity. On the other hand, if it exceeds 2.1, the magnetic flux density may decrease rapidly due to a decrease in saturation magnetic flux density. The non-oriented electrical steel sheet according to an embodiment of the present invention satisfies the following formula 2. [Formula 2] 0.2≦([Si]+[Al]+[Mn] / 2)*([P]+[Sn]+[Sb])≦0.4 (In formula 2, [Al], [Mn], [Si], [P], [Sn] and [Sb] represent the contents (wt%) of Al, Mn, Si, P, Sn and Sb, respectively.)

[0025] Si, Al, and Mn are alloy elements added to reduce the iron loss of non-oriented electrical steel sheets, and a certain amount must be added to achieve low iron loss characteristics. However, while low iron loss characteristics are important for the magnetic properties of non-oriented electrical steel sheets, high magnetic flux density characteristics are also important. Although low iron loss characteristics can be achieved by adding Si, Al, and Mn, a decrease in magnetic flux density cannot be avoided, making it difficult to achieve high magnetic flux density characteristics, and therefore it is necessary to simultaneously improve both iron loss and magnetic flux density through texture improvement. Therefore, P, Sn and Sb are added as grain boundary segregation elements that can improve the texture according to formula 2, but the content of P, Sn and Sb must be considered along with the content of Si, Al and Mn, which are elements related to magnetic flux density. This makes it possible to simultaneously secure low core loss properties and high magnetic flux density properties. When ([Si]+[Al]+[Mn] / 2)*([P]+[Sn]+[Sb]) is less than 0.2, the contents of P, Sn and Sb are relatively small and the effect of improving the texture is not significant, so it may be difficult to ensure high magnetic flux density characteristics.

[0026] On the other hand, when ([Si]+[Al]+[Mn] / 2)*([P]+[Sn]+[Sb]) exceeds 0.4, the content of P, Sn and Sb is relatively high, which excessively suppresses grain growth, resulting in fine grains. As a result, it may be difficult to ensure low core loss characteristics.

[0027] The non-oriented electrical steel sheet according to one embodiment of the present invention satisfies the following formula 3. [Formula 3] 0.29≦ (Gscenter-Gssurface) / (Gscenter*t)≦0.5(mm-1) (In formula 3, t represents the thickness (mm) of the non-oriented electrical steel sheet, Gssurface represents the average crystal grain size (μm) at 0 to t / 4 or 3t / 4 to t based on the thickness direction of the non-oriented electrical steel sheet, and Gscenter represents the average crystal grain size (μm) at more than t / 4 and less than 3t / 4 based on the thickness direction of the non-oriented electrical steel sheet.) For example, when t is the thickness of a non-oriented electrical steel sheet, Gssurface can mean the grain size of the crystal grains present between the bottom surface and t / 4 of the non-oriented electrical steel sheet, or the grain size of the crystal grains present between 3t / 4 and the top surface of the non-oriented electrical steel sheet. In other words, it can mean the average grain size of the surface part of the non-oriented electrical steel sheet. Gscenter can mean the grain size of the crystal grains present in the range exceeding t / 4 and less than 3t / 4. In other words, it can mean the average grain size of the center part of the non-oriented electrical steel sheet.

[0028] The lower the value of (Gscenter-Gssurface) / (Gscenter*t), the smaller the deviation between Gscenter and Gssurface, which may mean that the grain size at the surface and center in the thickness direction of the steel sheet is uniform.

[0029] With regard to iron loss, the sum of hysteresis loss and eddy current loss is minimized at the optimal crystal grain size. However, even if the average crystal grain size is the same, if the crystal grain size deviation in the thickness direction is large, iron loss increases compared to when the crystal grain size deviation is small and uniform. Therefore, it is better for the crystal grain size at the surface and center in the thickness direction to have a smaller deviation. In order to satisfy (Gscenter-Gssurface) / (Gscenter*t)≦0.5(mm-1), the heating rate and Heating Through time control, texture can be further improved, as will be discussed later.

[0030] The non-oriented electrical steel sheet according to an embodiment of the present invention satisfies the following formula 4. [Formula 4] 0.2≦(V{012} <121> +V{111} <112> ) / (V{001} <310> +V{139} <310> )≦0.8 (In formula 4, V{012} <121> , V{111} <112> , V{001} <310> and V{139} <310> are {012} <121> , {111} <112> , {001} <310> , {139} <310> This indicates the volume fraction of textures with orientations within 15°.)

[0031] Collective organization {012} <121> and {111} <112> Since magnetization is difficult in this orientation, the {001} texture is unfavorable for magnetism. <310> and {139} <310> are, respectively, <100> / / It is a part of ND-fiber or has a similar orientation that favors magnetic properties. Therefore, (V{012} <121> +V{111} <112> ) / (V{001} <310> +V{139} <310> ) indicates that the texture is improved. By controlling the content of the components, a texture that is favorable for magnetic properties is created. <310> and {139} <310> The ratio of V{012} <121> +V{111} <112> ) / (V{001} <310> +V{139} <310> ) is less than 0.2, the texture is not significantly improved, and when it exceeds 0.8, the texture becomes inferior and there is no improvement.

[0032] Manufacturing method of non-oriented electrical steel sheet By weight, Si: 1.5-4.0%, Al: 0.1-1.5%, Mn: 0.1-1.5%, C: 0.005% or less (excluding 0%), N: 0.005% or less (excluding 0%), Ti: 0.005% or less (excluding 0%), S: 0.001-0.005%, P: 0.1% or less (excluding 0%), Sn, Sb Total amount : 0.02-0.2%, balance Fe and unavoidable impurities and containing Sn and Sb at the same time, Formula 1 , Equation 2 and Equation 3 the steps of: heating a slab satisfying Equation 5; hot rolling the slab to produce a hot-rolled sheet; cold rolling the hot-rolled sheet to produce a cold-rolled sheet; and annealing the cold-rolled sheet so as to satisfy Equation 5.

[0033] Each step will be explained in detail below. First, the slab is heated. The reason for limiting the addition ratio of each component in the slab is the same as the reason for limiting the composition of the non-oriented electrical steel sheet described above, so repeated explanation will be omitted. The composition of the slab does not substantially change during manufacturing processes such as hot rolling, hot-rolled sheet annealing, cold rolling, and cold-rolled sheet annealing, which will be described later, so the composition of the slab and the composition of the non-oriented electrical steel sheet are substantially the same. In addition, since the composition of the slab and the composition of the non-oriented electrical steel sheet are substantially the same, the slab satisfies the above formulas 1 and 2. The effects of satisfying formulas 1 and 2 are explained above.

[0034] The slab is placed in a heating furnace and heated to 1200°C or less. If the heating temperature exceeds 1200°C, precipitates such as AlN and MnS present in the slab will be re-dissolved and then finely precipitated during hot rolling, suppressing grain growth and reducing magnetism, so the heating temperature is limited to 1200°C or less. The heated slab is hot-rolled to produce hot-rolled sheet. During hot rolling, the finishing rolling is performed at a final reduction rate of 20% or less to correct the sheet shape. The hot-rolled sheet is then coiled at 700°C and cooled in air.

[0035] Next, the hot-rolled sheet may be annealed. At this time, the annealing temperature of the hot-rolled sheet may be 950 to 1150° C. If the annealing temperature of the hot-rolled sheet is less than 950° C., the structure does not grow or grows finely, making it difficult to obtain a texture advantageous for magnetic properties. If the annealing temperature exceeds 1150° C., the crystal grains grow excessively, which may result in excessive defects on the sheet surface. Next, the hot-rolled sheet is pickled and cold-rolled to a desired sheet thickness. Cold-rolling can be performed to produce a cold-rolled sheet with a final thickness of 0.10 to 0.70 mm. If necessary, a second cold rolling can be performed after the first cold rolling and intermediate annealing to improve magnetic properties, and the final reduction can be in the range of 50 to 95%.

[0036] In the step of annealing the cold-rolled sheet, the cold-rolled sheet is annealed so as to satisfy the following formula 5. [Formula 5] 0.2≦v / s≦0.6 (In formula 5, v is the starting temperature of 650 to 750°C from the cold-rolled sheet Heating The average heating rate (℃ / sec) up to the temperature of the cold-rolled sheet is Heating Maintaining at temperature Heating It means time (sec). During annealing of cold-rolled steel sheets, the important metallurgical changes that determine the microstructural and texture changes that occur are recrystallization and grain growth. During annealing of structures deformed by cold rolling, the factors that have an important effect on recrystallization and grain growth are the average heating rate, Heating temperature, Heating Temperature Heating Examples include time.

[0037] In non-oriented electrical steel sheets, there is an appropriate grain size that minimizes iron loss. This is because as the grain size increases, the hysteresis loss in iron loss decreases but the eddy current loss increases. Therefore, while the average grain size of the entire non-oriented electrical steel sheet is important, the uniformity of the grain size in the thickness direction of the steel sheet is also a very important factor that must be controlled because it is used as a core material for rotating electrical equipment and must have uniform properties in all directions in terms of iron loss. Heating Temperature Heating If the time is controlled under appropriate conditions, the uniformity of the grain size in the thickness direction can be ensured, and the texture can also be controlled by the average heating rate and Heating Temperature Heating Since they are greatly affected by time, if these two conditions are appropriately controlled, the magnetic properties can be dramatically improved.

[0038] If v / s is less than 0.2, the average heating rate is too slow or during annealing, Heating If the time is too long, the fraction of texture unfavorable to magnetic properties may become high. If v / s is greater than 0.6, the heating rate is too fast or Heating If the time is too short, the crystal grains do not grow smoothly, and the magnetic properties may decrease due to the refinement of the crystal grains. Therefore, when 0.2≦v / s≦0.6 is satisfied, (Gscenter-Gssurface) / (Gscenter*t) of the non-oriented electrical steel sheet is 0.5(mm -1 ) can be made to look like this:

[0039] The cold-rolled sheet that has been subjected to the final cold rolling is subjected to cold-rolled sheet annealing. Heating The temperature can be 850-1050℃. Heating If the temperature is too low, recrystallization will not occur sufficiently. Heating If the temperature is too high, rapid growth of crystal grains may occur, resulting in a decrease in magnetic flux density and high frequency core loss. Hereinafter, specific examples of the present invention will be described. However, the following examples are merely specific examples of the present invention, and the present invention is not limited to the following examples. EXAMPLES

[0040] [Example 1] The slabs with the composition shown in Table 1 below are manufactured through vacuum melting, and the amounts of Si, Mn, Al, P, Sn, and Sb are changed to determine the composition elements, the composition addition amounts, and the cold-rolled sheet annealing temperature from 700℃ to Heating The average heating rate v (℃ / sec) Heating Temperature Heating The effect of time s (sec) on magnetic properties was confirmed. Each slab was heated to 1200°C, hot rolled to a thickness of 2.5 mm, and then coiled. The hot-rolled steel sheets were coiled and cooled in air, then hot-rolled sheet annealed at 1060°C and pickled, then cold-rolled to a thickness of 0.35 mm, and finally cold-rolled sheet annealed. At this time, the target annealing temperature for cold-rolled sheets is 1000°C, and the temperature is increased from 700°C to Heating The average heating rate v (℃ / sec) Heating At a temperature of 1000°C Heating The effect of the change in v / s on magnetic properties was confirmed by controlling the time s (sec).

[0041] The volume fraction of the texture was measured for each specimen through EBSD and X-ray pole figure test, and the grain size in the center and surface areas in the thickness direction was measured using the intercept method. 15 / 50 ) and magnetic flux density (B 50 ) were also measured and the results are shown in Table 2 below.

[0042] [Table 1]

[0043] [Table 2]

[0044] In Table 1, each value means weight percent. In Table 2, formula 1 means the value of [Al] + [Mn], formula 2 means the value of ([Si] + [Al] + [Mn] / 2) * ([P] + [Sn] + [Sb]), and [Al], [Mn], [Si], [P], [Sn] and [Sb] respectively indicate the contents (wt%) of Al, Mn, Si, P, Sn and Sb. In Table 2, formula 3 means the value of (Gscenter-Gssurface) / (Gscenter*t). t indicates the thickness (mm) of the non-oriented electrical steel sheet, Gssurface indicates the average grain size (μm) from 0 to t / 4 or from 3t / 4 to t based on the thickness direction of the non-oriented electrical steel sheet, and Gscenter indicates the average grain size (μm) from over t / 4 to less than 3t / 4 based on the thickness direction of the non-oriented electrical steel sheet. In formula 3 in Table 2, the values ​​in parentheses indicate Gscenter and Gsurface from the left.

[0045] In Example 1, t is 0.35 mm, so Gssurface indicates the average grain size in the region from the bottom surface upward to a thickness of 0.0875 mm or the region from a thickness of 0.2625 mm upward to the top surface, when the bottom surface of the non-oriented electrical steel sheet is regarded as the point where the thickness is 0. Gscenter indicates the average grain size in the region of the non-oriented electrical steel sheet that is greater than 0.0875 mm and less than 0.2625 mm. In Table 2, formula 4 is (V{012} <121> +V{111} <112> ) / (V{001} <310> +V{139} <310> ) and V{012} <121> , V{111} <112> , V{001} <310> and V{139} <310> are the textures {012} <121> , {111} <112> , {001} <310> , {139} <310> The volume fraction of

[0046] X-ray pole figure test and EBSD test were carried out to analyze the texture. After cold rolling and annealing, the surface of the specimen parallel to the rolling direction was polished to 3 / 4t of the thickness, and then EBSD measurement and X-ray diffraction analysis were used to measure the (110), (200), and (211) pole figures. <121> , {111} <112> , {001} <310> , {139} <310> Texture volume fraction V{012} <121> , V{111} <112> , V{001} <310> , V{139} <310> The grain size was measured by commonly used methods such as the line segment method and the area method.

[0047] In Table 2, formula 5 means the value of v / s. v is the temperature from the start temperature of 650 to 750°C to the cold-rolled sheet. Heating The average heating rate (℃ / sec) up to the temperature of the cold-rolled sheet is Heating Maintaining at temperature Heating The values ​​in parentheses in formula 5 of Table 2 indicate v and s from the left. In Table 2, iron loss (W15 / 50) is the average loss (W / kg) in the rolling direction and the direction perpendicular to the rolling direction when a magnetic flux density of 1.5 Tesla is induced at a frequency of 50 Hz, and magnetic flux density (B50) is the magnitude (Tesla) of the induced magnetic flux density when a magnetic field of 5000 A / m is applied.

[0048] The steel composition range and invention examples A1 and A2 that satisfy formulas 1, 2, and 5 、A No. 11 showed excellent core loss and magnetic flux density. The crystal grain deviation in the thickness direction was small at 0.5 or less, and the texture improvement effect was also excellent. A3 did not meet the steel composition range, and the iron loss and magnetic flux density were not better than the inventive example, A4 did not meet formula 2, and the iron loss and magnetic flux density were not better than the inventive example, A6 did not meet the steel composition range and formula 5, and the iron loss and magnetic flux density were not better than the inventive example, and A7 met formulas 1 and 2 but did not meet formula 5 during the manufacturing process, and the crystal grain deviation in the thickness direction exceeded 0.5. A9 did not satisfy formula 2 and formula 5, and the iron loss and magnetic flux density were not better than the examples of the invention. A12 did not satisfy formula 1, and the iron loss and magnetic flux density were not better than the examples of the invention.

[0049] [Example 2] The slabs with the composition shown in Table 3 below are manufactured through vacuum melting, and the amounts of Si, Mn, Al, P, Sn, and Sb are changed to determine the composition elements, the composition addition amounts, and the cold-rolled sheet annealing temperature from 700℃ to Heating The average heating rate v (℃ / sec) Heating Temperature Heating We attempted to confirm the effect of time s (sec) on magnetism. Each slab was heated to 1200°C, hot rolled to a thickness of 2.7 mm, and then coiled. The hot-rolled steel sheets were coiled and cooled in air, hot-rolled sheet annealed at 1000°C, pickled, cold-rolled to a thickness of 0.50 mm, and finally cold-rolled sheet annealed. At this time, the target annealing temperature for cold-rolled sheets is 1020°C, and the temperature is reduced from 700°C to Heating The average heating rate v (℃ / sec) Heating At temperature 1020℃ Heating The effect of the change in v / s on magnetic properties was confirmed by controlling the time s (sec).

[0050] For each specimen, the volume fraction of the texture was measured using EBSD and X-ray pole figure test, and the grain size in the center and surface areas in the sheet thickness direction was measured using the intercept method. The core loss (W15 / 50) and magnetic flux density (B50) were also measured and the results are shown in Table 4 below.

[0051] [Table 3]

[0052] [Table 4]

[0053] In Table 4, Equation 1 means the value of [Al] + [Mn], Equation 2 means the value of ([Si] + [Al] + [Mn] / 2) * ([P] + [Sn] + [Sb]), and [Al], [Mn], [Si], [P], [Sn] and [Sb] respectively indicate the contents (wt%) of Al, Mn, Si, P, Sn and Sb. In Table 4, formula 3 means the value of (Gscenter-Gssurface) / (Gscenter*t). t indicates the thickness (mm) of the non-oriented electrical steel sheet, Gssurface indicates the average grain size (μm) from 0 to t / 4 or from 3t / 4 to t based on the thickness direction of the non-oriented electrical steel sheet, and Gscenter indicates the average grain size (μm) from more than t / 4 to less than 3t / 4 based on the thickness direction of the non-oriented electrical steel sheet. In formula 3 of Table 4, the values ​​in parentheses indicate Gscenter and Gsurface from the left.

[0054] In Example 2, t is 0.50 mm, so Gssurface indicates the average grain size in the region from the bottom surface to a thickness of 0.125 mm or the region from a thickness of 0.375 mm to the top surface, assuming that the bottom surface of the non-oriented electrical steel sheet is the point where the thickness is 0. Gscenter indicates the average grain size in the region of the non-oriented electrical steel sheet that is greater than 0.125 mm and less than 0.375 mm. In Table 4, formula 4 is (V{012} <121> +V{111} <112> ) / (V{001} <310> +V{139} <310> ) and V{012} <121> , V{111} <112> , V{001} <310> and V{139} <310> are the textures {012} <121> , {111} <112> , {001} <310> , {139} <310> The volume fraction of

[0055] X-ray pole figure test and EBSD test were carried out to analyze the texture. After cold rolling and annealing, the surface of the specimen parallel to the rolling direction was polished to 3 / 4t of the thickness, and then EBSD measurement and X-ray diffraction analysis were used to measure the (110), (200), and (211) pole figures. <121> , {111} <112> , {001} <310> , {139} <310> Texture volume fraction V{012} <121> , V{111} <112> , V{001} <310> , V{139} <310> The grain size was measured by commonly used methods such as the line segment method and the area method.

[0056] In Table 4, formula 5 means the value of v / s. v is the temperature from the start temperature of 650 to 750°C to the cold-rolled sheet. Heating The average heating rate (℃ / sec) up to the temperature of the cold-rolled sheet is Heating Maintaining at temperature Heating The values ​​in parentheses in formula 5 of Table 4 indicate v and s from the left. In Table 4, the iron loss (W15 / 50) is the average loss (W / kg) in the rolling direction and the direction perpendicular to the rolling direction when a magnetic flux density of 1.5 Tesla is induced at a frequency of 50 Hz, and the magnetic flux density (B50) is the magnitude (Tesla) of the induced magnetic flux density when a magnetic field of 5000 A / m is applied.

[0057] B1 and B3 are examples of the invention that satisfy the range of steel components and formulas 1, 2, and 5. , B7 is The iron loss and magnetic flux density were excellent. The crystal grain deviation in the thickness direction was small at less than 0.5, and the texture was also improved. B2 did not satisfy the steel composition range and formula 1, and the iron loss and magnetic flux density were not better than those of the invention examples. Although B5 satisfied formulas 1 and 2, it did not satisfy formula 5 during the manufacturing process, and the crystal grain deviation in the thickness direction exceeded 0.5. B8 did not satisfy the steel composition range, formula 1 and formula 2, and the iron loss and magnetic flux density were not better than the inventive examples. B9 did not satisfy formula 2 and formula 5, the crystal grain deviation in the thickness direction exceeded 0.5, and the iron loss and magnetic flux density were not better than the inventive examples. B11 did not satisfy formula 1 and formula 2, and the iron loss and magnetic flux density were not better than the inventive examples. Although B12 satisfied formulas 1 and 2, it did not satisfy formula 5 during the manufacturing process, and the crystal grain deviation in the thickness direction exceeded 0.5.

[0058] The present invention is not limited to the above-described embodiment and / or examples, but can be manufactured in various different forms, and a person having ordinary skill in the art to which the present invention pertains should understand that the invention can be embodied in other specific forms without changing the technical concept or essential features of the invention. Therefore, it should be understood that the above-described embodiment and / or examples are illustrative in all respects and not limiting.

Claims

1. A non-oriented electrical steel sheet comprising, by weight, 1.5 to 4.0% Si, 0.1 to 1.5% Al, 0.1 to 1.5% Mn, 0.005% or less (excluding 0%), N: 0.005% or less (excluding 0%), Ti: 0.005% or less (excluding 0%), S: 0.001 to 0.005%, P: 0.1% or less (excluding 0%), a total amount of Sn and Sb: 0.02 to 0.2%, with the balance being Fe and unavoidable impurities, containing Sn and Sb simultaneously, containing 0.01 weight% or more Sn, and containing 0.01 weight% or more Sb, and satisfying the following formulas 1, 2, and 3. [Formula 1] 0.9≦[Al]+[Mn]≦2.1 [Formula 2] 0.2≦([Si]+[Al]+[Mn] / 2)*([P]+[Sn]+[Sb])≦0.4 [Formula 3] 0.29≦Gs ｃｅｎｔｅｒ -Gs ｓｕｒｆａｃｅ ) / (Gs ｃｅｎｔｅｒ *t)≦0.5 (In Formula 1 and Formula 2, [Al], [Mn], [Si], [P], [Sn] and [Sb] represent the contents (wt%) of Al, Mn, Si, P, Sn and Sb, respectively. In formula 3, t represents the thickness (mm) of the non-oriented electrical steel sheet, and Gs ｓｕｒｆａｃｅ indicates the average grain size (μm) at 0 to t / 4 or 3t / 4 to t based on the thickness direction of the non-oriented electrical steel sheet, and Gs ｃｅｎｔｅｒ indicates the average grain size (μm) in the thickness direction of the non-oriented electrical steel sheet at more than t / 4 and less than 3t / 4.)

2. 2. The non-oriented electrical steel sheet according to claim 1, further comprising one or more of Cu: 0.05% or less (except 0%), Ni: 0.05% or less (except 0%), Cr: 0.05% or less (except 0%), Zr: 0.01% or less (except 0%), Mo: 0.01% or less (except 0%) and V: 0.01% or less (except 0%).

3. The non-oriented electrical steel sheet according to claim 1 or 2, characterized in that the following formula 4 is satisfied: [Formula 4] 0.2≦(V{ ０１２｝＜１２１＞ +V ｛１１１｝＜１１２＞ ) / (V ｛００１｝＜３１０＞ +V ｛１３９｝＜３１０＞ )≦0.8 (In formula 4, V ｛０１２｝＜１２１＞ , V ｛１１１｝＜１１２＞ , V ｛００１｝＜３１０＞ and V ｛１３９｝＜３１０＞ indicate the volume fraction of textures having orientations within 15° of {012}<121>, {111}<112>, {001}<310>, and {139}<310>, respectively.)

4. a step of heating a slab which is composed of, by weight percent, 1.5 to 4.0% Si, 0.1 to 1.5% Al, 0.1 to 1.5% Mn, 0.005% or less (excluding 0%) C, 0.005% or less (excluding 0%) N, 0.005% or less (excluding 0%) Ti, 0.005% or less (excluding 0%) S, 0.001 to 0.005%, 0.1% or less (excluding 0%) P, a total amount of Sn and Sb: 0.02 to 0.2%, the balance being Fe and unavoidable impurities, which simultaneously contains Sn and Sb, contains 0.01% by weight or more Sn, contains 0.01% by weight or more Sb, and satisfies the following formulas 1 and 2; hot rolling the slab to produce a hot rolled sheet; cold rolling the hot rolled sheet to produce a cold rolled sheet; and Annealing the cold-rolled sheet so as to satisfy the following formula 5: A method for producing a non-oriented electrical steel sheet, characterized in that the produced non-oriented electrical steel sheet satisfies the following formula 3. [Formula 1] 0.9≦[Al]+[Mn]≦2.1 [Formula 2] 0.2≦([Si]+[Al]+[Mn] / 2)*([P]+[Sn]+[Sb])≦0.4 [Formula 3] 0.29≦(Gs ｃｅｎｔｅｒ -Gs ｓｕｒｆａｃｅ ) / (Gs ｃｅｎｔｅｒ *t)≦0.5 [Formula 5] 0.2≦v / s≦0.6 (In Formula 1 and Formula 2, [Al], [Mn], [Si], [P], [Sn] and [Sb] respectively represent the contents (wt%) of Al, Mn, Si, P, Sn and Sb, In formula 3, t represents the thickness (mm) of the non-oriented electrical steel sheet, and Gs ｓｕｒｆａｃｅ indicates the average grain size (μm) at 0 to t / 4 or 3t / 4 to t based on the thickness direction of the non-oriented electrical steel sheet, and Gs ｃｅｎｔｅｒ indicates the average crystal grain size (μm) in the thickness direction of the non-oriented electrical steel sheet at more than t / 4 and less than 3t / 4, In formula 5, v means the average heating rate (°C / sec) from the starting temperature of 650 to 750°C to the cold-rolled sheet soaking temperature, and s means the soaking time (sec) maintained at the cold-rolled sheet soaking temperature.

5. The slab is 5. The method for producing a non-oriented electrical steel sheet according to claim 4, further comprising one or more of Cu: 0.05% or less (except 0%), Ni: 0.05% or less (except 0%), Cr: 0.05% or less (except 0%), Zr: 0.01% or less (except 0%), Mo: 0.01% or less (except 0%) and V: 0.01% or less (except 0%).

6. In the step of annealing the cold-rolled sheet, The method for producing a non-oriented electrical steel sheet according to claim 4 or 5, characterized in that the cold-rolled sheet is annealed at a soaking temperature of 850 to 1050°C.

7. After the step of producing the hot rolled sheet, The method for producing a non-oriented electrical steel sheet according to any one of claims 4 to 6, further comprising the step of: annealing the hot-rolled sheet at 950 to 1150°C.

Images