Non-oriented electrical steel sheet and its manufacturing method

Abstract

To provide a non-oriented electrical steel sheet that has excellent magnetic flux density and iron loss but low strength, and a method for manufacturing the same. [Solution] The present invention provides a non-oriented electrical steel sheet containing, by weight, 2.10 to 3.80% Si, 0.001 to 0.600% Mn, 0.001 to 0.600% Al, 0.001 to 0.100% P, 0.0005 to 0.0100% C, 0.001 to 0.010%, S: 0.0001 to 0.010%, N: 0.0001 to 0.010%, Ti: 0.0005 to 0.0050%, Sn: 0.001 to 0.080%, Sb: 0.001 to 0.080%, Se: 0.0005 to 0.0030%, and Ge: 0.0003 to 0.0010%, with the remainder being Fe and unavoidable impurities. The present invention can provide a non-oriented electrical steel sheet that has excellent core loss and magnetic flux density characteristics and low strength.

Description

[Technical Field]

[0001] The present invention relates to a non-oriented electrical steel sheet and a manufacturing method thereof, and more specifically to a non-oriented electrical steel sheet and a manufacturing method thereof, which are excellent in magnetic flux density and core loss and low strength, and which are obtained by controlling alloy components to selectively form and control precipitates, thereby minimizing the effects of the precipitates and improving the texture. [Background technology]

[0002] Electrical steel sheets are used as materials for transformers, motors, and electrical equipment, and unlike ordinary carbon steel, which emphasizes workability such as mechanical properties, they are functional products that emphasize electrical properties, such as low iron loss, high magnetic flux density, high magnetic permeability, and high space factor.

[0003] Electrical steel sheets are further divided into grain-oriented and non-oriented types. Grain-oriented electrical steel sheets are produced by utilizing the abnormal grain growth phenomenon known as secondary recrystallization, which results in a Goss texture ({110} <001> Non-oriented electrical steel sheet has excellent magnetic properties in all directions on the rolled sheet, due to the formation of a texture throughout the steel sheet.

[0004] The production process for non-oriented electrical steel sheets involves manufacturing a slab, then hot rolling, cold rolling and final annealing to form an insulating coating layer. The manufacturing process for grain-oriented electrical steel sheets involves manufacturing a slab, then hot rolling, pre-annealing, cold rolling, decarburization annealing, and final annealing, followed by the formation of an insulating coating layer.

[0005] Among these, non-oriented electrical steel sheets have uniform magnetic properties in all directions and are generally used as materials for motor cores, generator cores, electric motors, and small transformers. The main magnetic properties of non-oriented electrical steel sheets are iron loss and magnetic flux density. The lower the iron loss of non-oriented electrical steel sheets, the less iron loss occurs during the magnetization process of the core, improving efficiency. The higher the magnetic flux density, the larger the magnetic steel can be induced with the same energy, and since less current can be applied to achieve the same magnetic flux density, copper loss can be reduced, improving energy efficiency.

[0006] The most common method for improving the magnetic properties of non-oriented electrical steel sheets is to add alloying elements such as silicon. Adding alloying elements increases the resistivity of the steel, and the higher the resistivity, the lower the overall core loss due to reduced eddy current loss. However, the greater the amount of silicon added, the lower the magnetic flux density and the greater the brittleness. Adding more silicon than this makes cold rolling impossible, making commercial production impossible. While thinner electrical steel sheets tend to have lower core loss, the reduced rollability due to brittleness can be a critical issue. The maximum silicon content that can be commercially produced is approximately 3.5-4.0%. Adding elements such as aluminum and manganese to further increase the resistivity of the steel allows for the production of high-quality non-oriented electrical steel sheets with excellent magnetic properties. In actual motor applications, both high core loss and high magnetic flux density are sometimes required, which requires non-oriented electrical steel sheets with high resistivity, low core loss, and high magnetic flux density.

[0007] The manufacturing process of motor cores, generator cores, electric motors, small transformers, etc. using non-oriented electrical steel sheets involves processing steps such as punching and die-cutting. Regular high-efficiency non-oriented electrical steel sheets have high contents of Si and Al, which are resistivity elements, and therefore high hardness. These characteristics can cause damage to the dies required for punching and die-cutting, leading to increased processing costs for electrical steel sheets. Summary of the Invention [Problem to be solved by the invention]

[0008] One embodiment of the present invention provides a non-oriented electrical steel sheet and a manufacturing method thereof. More specifically, one embodiment of the present invention provides a non-oriented electrical steel sheet and a manufacturing method thereof that has excellent magnetic flux density and core loss but low strength by adding Se and Ge to selectively form and control precipitates to improve the texture. [Means for solving the problem]

[0009] A non-oriented electrical steel sheet according to one embodiment of the present invention may contain, by weight percent, 2.10 to 3.80% Si, 0.001 to 0.600% Mn, 0.001 to 0.600% Al, 0.0005 to 0.0030% Se, and 0.0003 to 0.0010% Ge, with the remainder consisting of Fe and unavoidable impurities.

[0010] The non-oriented electrical steel sheet may further contain, by weight, P: 0.001 to 0.100%, C: 0.0005 to 0.0100%, S: 0.001 to 0.010%, N: 0.0001 to 0.010%, Ti: 0.0005 to 0.0050%, Sn: 0.001 to 0.080%, and Sb: 0.001 to 0.080%.

[0011] The non-oriented electrical steel sheet may further contain at least one of Cu, Ni, and Cr in an amount of 0.07 wt % or less.

[0012] The non-oriented electrical steel sheet may further contain one or more of Zr, Mo, and V in an amount of 0.01 wt % or less each.

[0013] When performing EBSD on the 1 / 2 to 1 / 3 thickness area of ​​the non-oriented electrical steel sheet, the rolling direction is used as the basis on the ODF. <112> The intensity of the {111} planes facing in the direction may have a random orientation ratio of 2.5 or less.

[0014] The non-oriented electrical steel sheet may have a ratio of {tensile strength (MPa) - yield strength (MPa)} to the average crystal grain size (μm) of 1.10 to 1.40.

[0015] The non-oriented electrical steel sheet may have an average crystal grain size of 80 to 130 μm. The non-oriented electrical steel sheet may have a yield strength of 350 to 400 MPa. The non-oriented electrical steel sheet may have a tensile strength of 490 to 550 MPa.

[0016] A method for producing a non-oriented electrical steel sheet according to one embodiment of the present invention includes the steps of heating a slab containing, by weight, 2.10 to 3.80% Si, 0.001 to 0.600% Mn, 0.001 to 0.600% Al, 0.0005 to 0.0030% Se, and 0.0003 to 0.0010% Ge, with the remainder being Fe and unavoidable impurities; hot-rolling the slab to produce a hot-rolled sheet; cold-rolling the hot-rolled sheet to produce a cold-rolled sheet; and final annealing the cold-rolled sheet.

[0017] The slab may further contain P: 0.001 to 0.100%, C: 0.0005 to 0.0100%, S: 0.001 to 0.010%, N: 0.0001 to 0.010%, Ti: 0.0005 to 0.0050%, Sn: 0.001 to 0.080%, and Sb: 0.001 to 0.080%.

[0018] After the step of preparing the hot-rolled sheet, the method may further include the step of annealing the hot-rolled sheet at a temperature of 900 to 1195° C. for 40 to 100 seconds.

[0019] The step of final annealing the cold-rolled sheet may involve annealing at a temperature of 850 to 1080° C. for 60 to 150 seconds. [Effects of the Invention]

[0020] According to one embodiment of the present invention, it is possible to provide a non-oriented electrical steel sheet that has an improved texture, excellent core loss and magnetic flux density, but low strength. DETAILED DESCRIPTION OF THE INVENTION

[0021] 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. Therefore, 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.

[0022] The terminology used herein is merely for the purpose of referring to particular embodiments and is not intended to limit the present invention. As used herein, the singular forms "a," "an," and "the" include the plural forms unless the context clearly dictates otherwise. As used in the specification, the term "comprising" 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.

[0023] When we say that a part is "on" another part, it means that it is directly on top of the other part, or that there are other parts between them. In contrast, when we say that a part is "directly on top" of another part, there are no other parts between them.

[0024] Unless otherwise specified, % means % by weight, and 1 ppm is 0.0001% by weight.

[0025] In one embodiment of the present invention, the term "additionally containing an additional element" means that the remaining iron (Fe) is replaced by the additional amount of the additional element.

[0026] 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.

[0027] While the present invention may be embodied in various different forms, it is to be understood that the invention is not limited to the specific embodiments set forth herein, and that the invention may be embodied in various different forms, without departing from the spirit or scope of the present invention.

[0028] Resistivity elements added to non-oriented electrical steel sheets to reduce iron loss, such as Si, Al, and Mn, can lower the saturation magnetic flux density of the material. However, the addition of these elements increases the strength of the steel sheet, which can shorten the life of the die used in punching.

[0029] Therefore, it is necessary to improve the texture of non-oriented electrical steel sheets so that they can have low strength while increasing the magnetic flux density and reducing iron loss. However, this has been difficult to achieve in conventional steel production processes, and the present invention aims to improve this.

[0030] Each stage will be explained in detail below. A non-oriented electrical steel sheet according to an embodiment of the present invention contains, by weight, 2.10 to 3.80% Si, 0.001 to 0.600% Mn, 0.001 to 0.600% Al, 0.001 to 0.100% P, 0.0005 to 0.0100% C, 0.001 to 0.010% S, 0.0001 to 0.010% N, 0.0005 to 0.0050% Ti, 0.001 to 0.080% Sn, 0.001 to 0.080% Sb, 0.0005 to 0.0030% Se, and 0.0003 to 0.0010% Ge, with the remainder being Fe and unavoidable impurities.

[0031] The reasons for limiting the components of the non-oriented electrical steel sheet will be explained below. Si:2.10~3.80wt% Silicon (Si) is a major element added to increase the resistivity of steel and reduce eddy current loss in iron loss. If too little Si is added, iron loss deteriorates. Therefore, increasing the Si content is advantageous in terms of iron loss, but if too much Si is added, price competitiveness decreases, magnetic flux density decreases significantly, and workability problems may occur. Therefore, Si can be contained within the above-mentioned range. More specifically, Si can be contained in an amount of 2.10 to 3.80 wt%. Even more specifically, Si can be contained in an amount of 2.50 to 3.20 wt%.

[0032] Mn:0.001~0.600wt% Manganese (Mn), along with Si and Al, is an element that increases resistivity and reduces core loss, and also forms sulfides to improve texture. If too little Mn is added, fine sulfides may precipitate, reducing magnetic properties. Conversely, if too much Mn is added, it may promote the formation of a {111} texture, which is detrimental to magnetic properties, reducing magnetic flux density. Therefore, Mn can be contained within the aforementioned range. More specifically, Mn can be contained in an amount of 0.005 to 0.600 wt % or 0.050 to 0.350 wt %.

[0033] Al:0.001~0.600wt% Aluminum (Al), together with Si, plays an important role in increasing resistivity and reducing iron loss. It also improves rollability and workability during cold rolling. If too little Al is added, it is ineffective in reducing high-frequency iron loss, and the precipitation temperature of AlN is lowered, resulting in the formation of fine nitrides, which can reduce magnetic properties. Conversely, if too much Al is added, excessive nitrides are formed, which can deteriorate magnetic properties and cause problems in all processes, including steelmaking and continuous casting, significantly reducing productivity. Therefore, Al can be contained within the aforementioned range. More specifically, Al can be contained in an amount of 0.005 to 0.600 wt. %. Even more specifically, Al can be contained in an amount of 0.070 to 0.450 wt. %.

[0034] Se:0.0005~0.0030wt% Selenium (Se) is a segregating element that segregates at grain boundaries, thereby reducing the strength of the grain boundaries and suppressing the phenomenon of dislocations becoming pinned at the grain boundaries. This reduces the conditions under which precipitates can form, thereby contributing to the control of precipitates. If Se is contained in an excessively small amount, it is difficult to expect the above-mentioned functions. If Se is contained in an excessive amount, it may actually deteriorate the magnetic properties. Therefore, Se can be contained within the above-mentioned range. More specifically, Se can be contained in an amount of 0.0005 to 0.0020 wt %.

[0035] Ge: 0.0003 to 0.0010 wt% Like Se, germanium (Ge) also acts as a segregation element, and even the addition of trace amounts can affect the behavior of S, C, and N-based precipitates and contribute to precipitation control. If Ge is contained in an excessively small amount, it is difficult to expect the aforementioned role. If Ge is contained in an excessive amount, it may actually deteriorate the magnetic properties. Therefore, Ge can be contained within the aforementioned range. Specifically, Ge can be contained in an amount of 0.0003 to 0.0010 wt %.

[0036] P:0.001~0.100wt% Phosphorus (P) can be added because it not only increases the resistivity of the material but also segregates to grain boundaries to improve the texture, increasing resistivity and reducing iron loss. However, if too much P is added, it can lead to the formation of a texture unfavorable to magnetic properties, resulting in no texture improvement effect, and excessive segregation to grain boundaries can reduce rollability and workability, making production difficult. Therefore, P can be added within the aforementioned range. More specifically, P can be contained in an amount of 0.001 to 0.080 wt. More specifically, P can be contained in an amount of 0.010 to 0.080 wt.

[0037] Sn:0.001~0.080wt% Tin (Sn) segregates at grain boundaries and surfaces to improve the texture of the material and inhibit surface oxidation, so it can be added to improve magnetic properties. Adding too much Sn can lead to severe grain boundary segregation, degrading surface quality, and increasing hardness, which can cause breakage of the cold-rolled sheet and reduce rollability. Therefore, Sn can be added within the aforementioned range.

[0038] Sb:0.001~0.080wt% Antimony (Sb) segregates at grain boundaries and surfaces to improve the texture of the material and inhibit surface oxidation, so it can be added to improve magnetic properties. Adding too much Sb can severely segregate at grain boundaries, degrading surface quality and increasing hardness, potentially causing breakage of the cold-rolled sheet and reducing rollability. Therefore, Sb can be added within the aforementioned range. However, if the amount of Sb added is too small, the effects of improving texture and inhibiting surface oxidation cannot be expected.

[0039] C:0.0005~0.0100% by weight Carbon (C) bonds with Ti, Nb, etc. to form carbides, which reduces magnetic properties, and after processing into electrical appliances, the iron loss increases due to magnetic aging during use, which can reduce the efficiency of the electrical appliances. More specifically, C can be further included in an amount of 0.0010 to 0.0030 wt%.

[0040] S:0.001~0.010% by weight Sulfur (S) forms fine sulfides inside the base material, inhibiting grain growth and reducing iron loss, so it is preferable to add as little as possible. If S is included in large amounts, it may combine with Mn and other elements to form precipitates or induce high-temperature embrittlement during hot rolling. Therefore, S may be further included in an amount of 0.0100 wt% or less. Specifically, S may be further included in an amount of 0.001 to 0.005 wt% or less.

[0041] N:0.0001~0.010wt% Nitrogen (N) not only combines with Al, Ti, etc. to form fine, long precipitates inside the base material, but also combines with other impurities to form fine nitrides, which inhibit grain growth and worsen iron loss, so it is preferable to include a small amount of N. In one embodiment of the present invention, N may be further contained in an amount of 0.010 wt% or less. More specifically, N may be further contained in an amount of 0.0001 to 0.10 wt%. Even more specifically, N may be further contained in an amount of 0.0005 to 0.002 wt%.

[0042] Ti:0.0005~0.0050wt% Titanium (Ti) is an element with a strong tendency to form precipitates in steel, forming fine carbides or nitrides within the matrix and inhibiting grain growth. The more Ti added, the more carbides and nitrides are formed, degrading the iron and reducing magnetic properties. In one embodiment of the present invention, Ti may be further included in an amount of 0.0050 wt% or less. More specifically, Ti may be further included in an amount of 0.0005 to 0.0030 wt% or less.

[0043] The non-oriented electrical steel sheet according to an embodiment of the present invention may further contain at least one of Cu, Ni, and Cr in an amount of 0.07 wt% or less, and may further contain As, where the As content may be 0.0002 to 0.001%.

[0044] Copper (Cu), nickel (Ni), and chromium (Cr), which are elements inevitably added in the steelmaking process, react with impurity elements to form fine sulfides, carbides, and nitrides, which have a detrimental effect on magnetic properties, so their content is limited to 0.07% by weight or less.

[0045] The non-oriented electrical steel sheet according to an embodiment of the present invention may further contain at least one of Zr, Mo, and V in an amount of 0.01 wt % or less. Zirconium (Zr), molybdenum (Mo), vanadium (V), etc. are strong carbonitride-forming elements, so it is preferable to avoid adding them as much as possible, and each of them should be contained in an amount of 0.01 wt % or less.

[0046] Cu, Ni, and Cr are elements that are inevitably added in the steelmaking process, but they react with impurity elements to form fine sulfides, carbides, and nitrides, which have a detrimental effect on magnetic properties, so their content is limited to 0.07 wt% or less.Zr, Mo, and V are also strong carbonitride-forming elements, so their addition is preferably avoided as much as possible, and each should be limited to 0.01 wt% or less.

[0047] The balance is composed of Fe and inevitable impurities. The inevitable impurities are impurities that are mixed in during the steelmaking stage and the manufacturing process of grain-oriented electrical steel sheets, and since this is widely known in the art, a detailed description will be omitted. In one embodiment of the present invention, additional elements other than the above-mentioned alloy components are not excluded, and various elements may be included within a range that does not impair the technical concept of the present invention. When an additional element is further included, it is included as a substitute for the balance of Fe.

[0048] As mentioned above, by appropriately controlling the amounts of Si, Mn, Al, Se, and Ge added, it is possible to selectively form and control precipitates and improve the texture.

[0049] Specifically, when EBSD testing was performed on the 1 / 2 to 1 / 3 thickness of the steel plate, the {111} <112> The random orientation ratio of the non-oriented electrical steel sheet may be 2.5 or less. The magnetization of the non-oriented electrical steel sheet is such that the direction of the crystal plane is <100> It is most advantageous when <110> , <111> Therefore, the {111} orientation, which is unfavorable for magnetization, <112> If the ratio of {111} on the ODF is reduced, the orientation of the crystal grains constituting the steel sheet will be configured in a direction favorable for magnetization, improving the magnetic properties. <112> The intensity of the random orientation contrast may be 1.0 to 2.5. <112> The intensity may be a random orientation contrast of 1.5 to 2.2.

[0050] The non-oriented electrical steel sheet may have an average crystal grain size of 80 to 130 μm, specifically, 90 to 125 μm or 100 to 125 μm.

[0051] The non-oriented electrical steel sheet may have a yield strength of 350 to 400 MPa. Specifically, the yield strength may be 350 to 380 MPa. The non-oriented electrical steel sheet may have a tensile strength of 490 to 550 MPa, specifically, a yield strength of 500 to 510 MPa.

[0052] Furthermore, the ratio of {tensile strength (MPa) - yield strength (MPa)} to the average crystal grain size (μm) may be 1.10 or more and 1.40 or less. If the average crystal grain size is small, strength increases, but magnetic properties may deteriorate. In the present invention, we aim to improve workability by reducing strength while minimizing deterioration in core loss. Therefore, it is necessary to control the average crystal grain size in relation to strength. More specifically, the ratio may be 1.10 to 1.39 or 1.10 to 1.30.

[0053] As mentioned above, by appropriately controlling the amounts of Si, Mn, Al, Se, and Ge added, it is possible to selectively form and control precipitates to improve the texture and thereby improve the magnetic properties.

[0054] Specifically, the iron loss (W15 / 50) of the non-oriented electrical steel sheet may be 2.20 W / kg or less. Specifically, it may be 2.10 W / kg or less. The iron loss (W15 / 50) is the iron loss when a magnetic flux density of 1.5 T is induced at a frequency of 50 Hz. Even more specifically, the iron loss (W15 / 50) of the electrical steel sheet may be 2.00 W / kg or less. Even more specifically, the iron loss (W15 / 50) of the electrical steel sheet may be 1.80 to 1.95 W / kg. In this case, the standard for measuring magnetism is a steel sheet with a thickness of 0.27 to 0.35 mm.

[0055] A method for manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention includes the steps of hot-rolling a slab to manufacture a hot-rolled sheet, cold-rolling the hot-rolled sheet to manufacture a cold-rolled sheet, and final annealing the cold-rolled sheet.

[0056] 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.

[0057] Specifically, the slab may contain, by weight, 2.10 to 3.80% Si, 0.001 to 0.600% Mn, 0.001 to 0.600% Al, 0.001 to 0.100% P, 0.0005 to 0.0100% C, 0.001 to 0.010% S, 0.0001 to 0.010% N, 0.0005 to 0.0050% Ti, 0.001 to 0.080% Sn, 0.001 to 0.080% Sb, 0.0005 to 0.0030% Se, and 0.0003 to 0.0010% Ge, 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 duplicate explanations will be omitted.

[0058] The slab can be heated before hot rolling. There are no restrictions on the slab heating temperature, but it can be heated at a temperature range of 1150 to 1250°C for 0.1 to 1 hour. 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 grain growth and reducing magnetic properties. Specifically, this step involves heating at a temperature range of 1100 to 1200°C for 0.5 to 1 hour.

[0059] Next, the slab is hot-rolled to produce a hot-rolled sheet. The thickness of the hot-rolled sheet may be 1.6 to 2.5 mm. Specifically, the thickness of the hot-rolled sheet may be 1.6 to 2.3 mm. In the stage of producing the hot-rolled sheet, the finish rolling temperature may be 790 to 890°C. The hot-rolled sheet is coiled at a temperature of 580 to 680°C.

[0060] After the step of producing the hot-rolled sheet, the method may further include a step of annealing the hot-rolled sheet. The annealing temperature may be 900 to 1195°C, and the annealing time may be 40 to 100 seconds. If the annealing temperature of the hot-rolled sheet is too low, the texture may not grow or may grow too fine, making it difficult to obtain a texture favorable for magnetic properties during annealing after cold rolling. If the annealing temperature of the hot-rolled sheet is too high, recrystallized grains may grow excessively, resulting in excessive surface defects in the sheet. Hot-rolled sheet annealing is performed to increase the orientation favorable for magnetic properties, if necessary, and may be omitted. The annealed hot-rolled sheet may be pickled.

[0061] Next, the hot-rolled sheet is cold-rolled to produce a cold-rolled sheet. The thickness of the cold-rolled sheet may be 0.27 to 0.35 mm. Specifically, the thickness of the cold-rolled sheet may be 0.27 to 0.30 mm. If the thickness of the cold-rolled sheet is large, the iron loss may be poor. The cold-rolling step is a step of performing cold rolling once. The final reduction may be in the range of 72 to 88%.

[0062] Next, the cold-rolled sheet is subjected to final annealing. The annealing temperature in the final annealing process of the cold-rolled sheet is not particularly limited as long as it is a temperature typically used for non-oriented electrical steel sheets. Since the core loss of non-oriented electrical steel sheets is closely related to the grain size, final annealing can be performed at 850 to 1080°C for 60 to 150 seconds. If the temperature is too low, the grains will be too fine, increasing hysteresis loss, while if the temperature is too high, the grains will be too coarse, increasing eddy current loss and resulting in poor core loss. Specifically, the step of final annealing the cold-rolled sheet is performed at 1040 to 1060°C for 60 to 120 seconds.

[0063] The method for manufacturing the non-oriented electrical steel sheet may further include a step of coating the final-annealed cold-rolled sheet with an insulating coating. The insulating coating may be an organic, inorganic, or organic-inorganic composite coating, or may be any other insulating coating agent.

[0064] While the present invention may be embodied in various different forms, it is to be understood that the invention is not limited to the specific embodiments set forth herein, and that the invention may be embodied in various different forms, without departing from the spirit or scope of the present invention.

[0065] Example 1 Slabs with the compositions shown in Table 1 below were heated to 1150°C. Thereafter, they were hot rolled to a thickness of 1.8 mm, 2.3 mm, or 2.5 mm and coiled at 650°C. The hot-rolled steel sheets cooled in air were then annealed at 900 to 1100°C for 40 to 80 seconds.

[0066] [Table 1]

[0067] The annealed hot-rolled sheets were pickled and then cold-rolled to thicknesses of 0.27 mm, 0.30 mm, and 0.35 mm. Thereafter, the cold-rolled sheets were subjected to final annealing at an annealing temperature of 980 to 1060°C for 50 to 120 seconds to produce final annealed sheets.

[0068] The iron loss W15 / 50, magnetic flux density B50 and texture characteristics of the final annealed sheets produced are shown in Table 2 below. The respective measurement methods are as follows. The final annealed sheets thus produced were formed into Epstein test pieces with a length of 305 mm and a width of 30 mm in the L direction (rolling direction) and the C direction (direction perpendicular to the rolling direction) for magnetic measurements.

[0069] Additionally, a 5mm x 5mm area was observed using EBSD to measure the texture. The tensile test is performed according to the JIS 13-A standard, and the test is carried out while applying a force of 30 MPa / s to the tensile test piece up to an elongation rate of 0.2%, and a deformation rate of 0.007 / s at elongation rates of 0.2% or more.

[0070] In Table 2 below, I{111} <112> The area of ​​1 / 2 to 1 / 3 of the thickness of the steel sheet was measured using the {111} <112> This shows the intensity of the

[0071] [Table 2]

[0072] The present invention is not limited to the examples, and can be manufactured in various different forms, and a person skilled in the art to which the present invention pertains will understand that the present invention can be embodied in other specific forms without changing the technical idea or essential characteristics of the present invention. Therefore, it should be understood that the above-described examples are illustrative in all respects and not limiting.

Claims

1. A non-oriented electrical steel sheet comprising, by weight%, 2.10 to 3.80% Si, 0.001 to 0.600% Mn, 0.001 to 0.600% Al, 0.0005 to 0.0030% Se, and 0.0003 to 0.0010% Ge, with the balance being Fe and unavoidable impurities.

2. The non-oriented electrical steel sheet according to claim 1, further comprising, by weight%, P: 0.001 to 0.100%, C: 0.0005 to 0.0100%, S: 0.001 to 0.010%, N: 0.0001 to 0.010%, Ti: 0.0005 to 0.0050%, Sn: 0.001 to 0.080%, and Sb: 0.001 to 0.080%.

3. The non-oriented electrical steel sheet according to claim 1 , further comprising at least one of Cu, Ni, and Cr in an amount of 0.07 wt % or less each.

4. The non-oriented electrical steel sheet according to claim 1, further comprising at least one of Zr, Mo, and V in an amount of 0.01 wt% or less each.

5. 2. The non-oriented electrical steel sheet according to claim 1, wherein, when an EBSD experiment is performed on a region of ½ to ⅓ of the thickness of the non-oriented electrical steel sheet, the intensity of the {111} plane facing the <112> direction relative to the rolling direction on the ODF has a random orientation ratio of 2.5 or less.

6. 2. The non-oriented electrical steel sheet according to claim 1, wherein the ratio of {tensile strength (MPa) - yield strength (MPa)} to the average crystal grain size (μm) of the non-oriented electrical steel sheet is 1.10 to 1.

40.

7. 2. The non-oriented electrical steel sheet according to claim 1, wherein the average grain size of the non-oriented electrical steel sheet is 80 to 130 μm.

8. 2. The non-oriented electrical steel sheet according to claim 1, wherein the yield strength of the non-oriented electrical steel sheet is 350 to 400 MPa.

9. 2. The non-oriented electrical steel sheet according to claim 1, wherein the tensile strength of the non-oriented electrical steel sheet is 490 to 550 MPa.

10. 2. The non-oriented electrical steel sheet according to claim 1, wherein the core loss (W15 / 50) of the non-oriented electrical steel sheet is 2.20 W / kg or less.

11. heating a slab containing, in weight percent, 2.10 to 3.80% Si, 0.001 to 0.600% Mn, 0.001 to 0.600% Al, 0.0005 to 0.0030% Se, and 0.0003 to 0.0010% Ge, with the balance being Fe and unavoidable impurities; hot rolling the slab to produce a hot-rolled sheet; cold-rolling the hot-rolled sheet to produce a cold-rolled sheet; and a final annealing step of the cold-rolled sheet.

12. The method for producing a non-oriented electrical steel sheet according to claim 11, wherein the slab further contains P: 0.001 to 0.100%, C: 0.0005 to 0.0100%, S: 0.001 to 0.010%, N: 0.0001 to 0.010%, Ti: 0.0005 to 0.0050%, Sn: 0.001 to 0.080%, and Sb: 0.001 to 0.080%.

13. The method for manufacturing a non-oriented electrical steel sheet according to claim 11, further comprising the step of annealing the hot-rolled sheet at a temperature of 900 to 1195°C for 40 to 100 seconds after the step of manufacturing the hot-rolled sheet.

14. The method for manufacturing a non-oriented electrical steel sheet according to claim 11, wherein the final annealing of the cold-rolled sheet is performed at a temperature of 850 to 1080° C. for 60 to 150 seconds.

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