Non-oriented electrical steel sheet and method for manufacturing same

Abstract

A non-oriented electrical steel sheet according to an embodiment of the present invention contains, in wt%, 1.5-5.0% of Si, 0.001-3.0% of Al, and 0.003-3.0% of Mn, with the remainder comprising Fe and inevitable impurities, wherein the area percentage of grains having an intragranular misorientation of 5° or less is 95% or more.

Description

Non-oriented electrical steel sheet and method of manufacturing the same

[0001] One embodiment of the present invention relates to a non-oriented electrical steel sheet and a method for manufacturing the same. Specifically, one embodiment of the present invention relates to a non-oriented electrical steel sheet with improved magnetism and a method for manufacturing the same by setting a high reduction ratio during cold rolling to uniformly control the orientation distribution within the crystal grains.

[0002] Non-oriented electrical steel sheets are used as core materials in rotating equipment such as motors and generators, as well as in stationary equipment such as small transformers, and play an important role in determining the energy efficiency of electrical equipment.

[0003] The magnetic properties of non-oriented electrical steel sheets are primarily evaluated based on iron loss and magnetic flux density. Iron loss refers to the energy loss occurring in the iron core of devices such as motors, transformers, and generators at a specific magnetic flux density and frequency, while magnetic flux density refers to the degree of magnetization obtained under a specific magnetic field. It is desirable to have low iron loss and high magnetic flux density. This is because when electricity is applied to the iron core to induce a magnetic field, lower iron loss reduces energy loss as heat, allowing for the manufacture of motors with higher energy efficiency under the same conditions. Conversely, higher magnetic flux density enables the induction of a larger magnetic field with the same amount of energy, and allows for motor miniaturization or reduction of copper loss. Therefore, using non-oriented electrical steel sheets with low iron loss and high magnetic flux density enables the production of motors with excellent efficiency and torque. This extends the operating time using the same power and allows for increased motor output through higher torque.

[0004] Depending on the operating conditions of the motor, the characteristics of non-oriented electrical steel sheets that need to be considered also vary. As a general standard for evaluating the characteristics of non-oriented electrical steel sheets used in motors, W15 / 50, which is the iron loss when a 1.5T magnetic field is applied at a commercial frequency of 50Hz, is widely used.

[0005] For non-oriented electrical steel sheets with a thickness of 0.35 mm or less used in drive motors for eco-friendly vehicles, magnetic properties are often important at low fields of 1.0 T or less and high frequencies of 400 to 800 Hz or higher. Therefore, the characteristics of non-oriented electrical steel sheets are often evaluated using W10 / 400 and W10 / 800 iron losses. As the rotational speed of eco-friendly vehicle drive motors increases, the required frequency band also rises, making iron losses at several kHZ important.

[0006] Meanwhile, as disasters caused by climate change increase, countries around the world are announcing carbon neutrality roadmaps. Internal combustion engines account for a significant portion of total carbon emissions, and there is a strong demand to achieve carbon neutrality in this sector through the electrification of internal combustion engines. To this end, electrification is progressing rapidly in the mobility sector, led by electric vehicles. The characteristics required for drive motors in new mobility are to increase driving range and top speed. To achieve this, while the low iron loss and high magnetic flux density characteristics of electrical steel sheets are important, iron loss at ultra-high frequencies is critical.

[0007] One embodiment of the present invention provides a non-oriented electrical steel sheet and a method for manufacturing the same. Specifically, one embodiment of the present invention provides a non-oriented electrical steel sheet with improved magnetism and a method for manufacturing the same by setting a high reduction ratio during cold rolling to uniformly control the orientation distribution within the crystal grains.

[0008] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises, in weight%, Si: 1.5 to 5.0%, Al: 0.001 to 3.0%, Mn: 0.003 to 3.0%, the remainder being Fe and unavoidable impurities, and has an area ratio of grains having an orientation distribution within 5° of 95% or more.

[0009] A non-oriented electrical steel sheet according to one embodiment of the present invention may have an area fraction of crystal grains having an angle of 15° or less between the {100} plane and the rolled plane of the steel sheet of 15° or less, an area fraction of crystal grains having an angle of 15° or less between the {111} plane and the rolled plane of the steel sheet of 5° or less, and an area fraction of crystal grains having an angle of 15° or less between the {110} plane and the rolled plane of the steel sheet of 0.1° or 15°.

[0010] A non-oriented electrical steel sheet according to one embodiment of the present invention may have a thickness of 0.01 to 0.10 mm.

[0011] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of C: 0.005 wt% or less, N: 0.030 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, Nb: 0.005 wt% or less, and V: 0.005 wt% or less.

[0012] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of P: 0.1 wt% or less, Cu: 0.2 wt% or less, Cr: 0.5 wt% or less, Sn: 0.1 wt% or less, Sb: 0.1 wt% or less, Ni: 0.05 wt% or less, and Zn: 0.01 wt% or less.

[0013] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Bi: 0.200 wt% or less, Pb: 0.200 wt% or less, Ge: 0.200 wt% or less, and As: 0.200 wt% or less.

[0014] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Mo: 0.03 wt% or less, B: 0.01 wt% or less, Ca: 0.01 wt% or less, Zr: 0.01 wt% or less, Te: 0.01 wt% or less, and Mg: 0.01 wt% or less.

[0015] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises the steps of: hot rolling a slab comprising, in weight%, Si: 1.5 to 5.0%, Al: 0.001 to 3.0%, Mn: 0.003 to 3.0%, and the remainder being Fe and unavoidable impurities to produce a hot-rolled sheet; cold rolling the hot-rolled sheet to produce a cold-rolled sheet; and annealing the cold-rolled sheet.

[0016] In the cold rolling stage of the cold-rolled sheet, the reduction rate can be 97% or more.

[0017] The slab may further include one or more of C: 0.005 wt% or less, N: 0.030 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, Nb: 0.005 wt% or less, and V: 0.005 wt% or less.

[0018] The slab may further include one or more of P: 0.1 wt% or less, Cu: 0.2 wt% or less, Cr: 0.5 wt% or less, Sn: 0.1 wt% or less, Sb: 0.1 wt% or less, Ni: 0.05 wt% or less, and Zn: 0.01 wt% or less.

[0019] The slab may further include one or more of Bi: 0.200 wt% or less, Pb: 0.200 wt% or less, Ge: 0.200 wt% or less, and As: 0.200 wt% or less.

[0020] The slab may further include one or more of Mo: 0.03 wt% or less, B: 0.01 wt% or less, Ca: 0.01 wt% or less, Zr: 0.01 wt% or less, Te: 0.01 wt% or less, and Mg: 0.01 wt% or less.

[0021] In the step of manufacturing a hot-rolled plate, the thickness of the hot-rolled plate may be 2 to 10 mm.

[0022] In the step of manufacturing a cold-rolled sheet, the thickness of the cold-rolled sheet may be 0.01 to 0.10 mm.

[0023] A non-oriented electrical steel sheet according to one embodiment of the present invention has improved magnetic flux density and ultra-high frequency iron loss, and can be usefully utilized as an iron core for high-speed motors. More specifically, it can be usefully utilized as an iron core for new mobility drive motors.

[0024] 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 solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0025] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0026] When it is stated that one part is "above" or "on" another part, it may be directly above or on the other part, or other parts may be involved in between. In contrast, when it is stated that one part is "directly above" another part, no other parts are interposed in between.

[0027] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0028] In one embodiment of the present invention, the meaning of including additional elements is that the remainder of iron (Fe) is replaced by an amount of the additional element.

[0029] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0030] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0031]

[0032] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises, in weight%, Si: 1.5 to 5.0%, Al: 0.001 to 3.0%, Mn: 0.003 to 3.0%, and the remainder being Fe and unavoidable impurities.

[0033] Below, we will explain the reason for limiting the composition of non-oriented electrical steel sheets.

[0034] Si: 1.5 to 5.0 wt%

[0035] Silicon (Si) plays a role in increasing the resistivity of the material to lower iron loss and increasing strength through solid solution strengthening. If too little Si is added, the effect of improving iron loss and strength may be insufficient. If too much Si is added, the brittleness of the material increases, causing a sharp decrease in rolling productivity and potentially forming a surface oxide layer and oxides that are harmful to magnetism. Therefore, Si may be included in an amount of 1.5 to 5.0 weight%. More specifically, it may be included in an amount of 2.0 to 4.5 weight%. Even more specifically, it may be included in an amount of 3.0 to 3.6 weight%.

[0036] Al: 0.001 to 3.000 wt%

[0037] Aluminum (Al) plays a role in increasing the resistivity of the material to lower iron loss and increasing strength through solid solution strengthening. If too little Al is added, fine nitrides may form, making it difficult to obtain the effect of improving magnetism. If too much Al is added, excessive nitrides are formed, degrading magnetism and causing problems in all processes, such as steelmaking and continuous casting, which can significantly reduce productivity. More specifically, it may contain 0.10 to 2.50 weight% of Al. More specifically, it may contain 0.30 to 1.50 weight%.

[0038] Mn: 0.003 to 3.000 wt%

[0039] Manganese (Mn) plays a role in improving iron loss by increasing the resistivity of the material and forming sulfides. If too little Mn is added, fine sulfides are formed, causing magnetic degradation; if too much Mn is added, fine MnS is excessively precipitated, promoting the formation of a {111} texture that is unfavorable to magnetism, which causes a rapid decrease in magnetic flux density. More specifically, it may contain 0.10 to 2.50 weight% of Mn. More specifically, it may contain 0.30 to 2.00 weight%. More specifically, it may contain 0.50 to 1.50 weight%.

[0040] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of P: 0.1 wt% or less, Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Sn: 0.1 wt% or less, Sb: 0.1 wt% or less, Ni: 0.05 wt% or less, and Zn: 0.01 wt% or less.

[0041] P: 0.1 wt% or less

[0042] Phosphorus (P) is a grain boundary segregation element, and if added in excessive amounts, it can delay recrystallization and degrade strength uniformity in the rolling direction and the rolling perpendicular direction. More specifically, P may be 0.005 to 0.03 weight%.

[0043] Cu: 0 0.200 wt% or less

[0044] Copper (Cu) plays a role in forming sulfides together with Mn. If more Cu is added, if too much is added, high-temperature brittleness occurs, which can lead to the formation of cracks during continuous casting or hot rolling. More specifically, Cu may be included in an amount of 0.01 to 0.100 weight%.

[0045] Cr: 0.50 wt% or less

[0046] Chromium (Cr) plays a role in improving iron loss by increasing resistivity. If too much Cr is included, magnetic flux density may decrease. More specifically, Cr may be included in an amount of 0.050 wt% to 0.300 wt%.

[0047] Sn: 0.10 wt% or less

[0048] Tin (Sn) is added to improve magnetic properties by acting as a segregating element at grain boundaries to inhibit the diffusion of nitrogen through the grain boundaries, suppressing the {111} texture harmful to magnetism, and increasing the {100} texture beneficial to magnetism. If too much Sn is added, it hinders grain growth, reduces magnetism, and results in poor rolling properties. Therefore, Sn can be added within the aforementioned range. More specifically, Sn may be included in an amount of 0.005 to 0.08 weight%.

[0049] Sb: 0.10 wt% or less

[0050] Antimony (Sb) is added to improve magnetic properties by acting as a segregating element at grain boundaries to inhibit the diffusion of nitrogen through the grain boundaries, suppressing the {111} texture harmful to magnetism, and increasing the {100} texture beneficial to magnetism. If too much Sb is added, it hinders grain growth, thereby reducing magnetism and resulting in poor rolling properties. Therefore, Sb can be added within the aforementioned range. More specifically, Sb may be included in an amount of 0.005 to 0.08 weight%.

[0051] Ni: 0.05 wt% or less

[0052] Nickel (Ni) can react with impurity elements to form fine sulfides, carbides, and nitrides, which can have a harmful effect on magnetism. More specifically, Ni may be included in an amount of 0.005 to 0.03 weight%.

[0053] Zn: 0.01 wt% or less

[0054] If the content of zinc (Zn) is excessive, it can act as an impurity and impair magnetism. Therefore, Zn may be added within the aforementioned range. More specifically, Zn may be included in an amount of 0.001 to 0.005 weight%.

[0055] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more types of Bi: 0.200 wt% or less, Pb: 0.200 wt% or less, Ge: 0.200 wt% or less, and As: 0.200 wt% or less.

[0056] When the aforementioned elements are added, they segregate at the grain boundaries, alleviating stress concentration at the grain boundaries during cold rolling, and thus during the subsequent recrystallization annealing process <111> By suppressing the recrystallization of the / ND orientation grains, the magnetic flux density is improved. If these are added appropriately, the aforementioned effects can be additionally obtained, but if they are included in too much, a large amount of segregation occurs, which suppresses grain growth and may result in inferior magnetic flux density and iron loss. More specifically, one or more of Bi: 0.001 to 0.100 wt%, Pb: 0.001 to 0.100 wt%, Ge: 0.001 to 0.100 wt%, and As: 0.001 to 0.100 wt% may be further included.

[0057] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Mo: 0.03 wt% or less, B: 0.0100 wt% or less, Ca: 0.0100 wt% or less, Zr: 0.0100 wt% or less, Te: 0.0100 wt% or less, and Mg: 0.0100 wt% or less.

[0058] Since these can react with inevitably included C, S, N, etc. to form fine carbides, nitrides, or sulfides that may adversely affect magnetism, an upper limit may be set as described above. More specifically, one or more of Mo: 0.001 to 0.01 wt%, B: 0.0010 to 0.0030 wt%, Ca: 0.0010 to 0.0030 wt%, Zr: 0.0010 to 0.0030 wt%, Te: 0.0010 to 0.0050 wt%, and Mg: 0.0010 to 0.0050 wt% may be further included.

[0059] Other impurities

[0060] In addition to the aforementioned elements, inevitably incorporated impurities such as carbon (C), sulfur (S), nitrogen (N), titanium (Ti), niobium (Nb), and vanadium (V) may be included.

[0061] N combines with Ti, Nb, and V to form nitrides and plays a role in reducing grain growth.

[0062] C reacts with N, Ti, Nb, V, etc., to form fine carbides, which hinder grain growth and domain movement.

[0063] S forms sulfides, which impair grain growth.

[0064] In cases where impurity elements are further included as described above, one or more of C: 0.005 wt% or less, N: 0.005 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, Nb: 0.005 wt% or less, and V: 0.005 wt% or less may be further included. More specifically, one or more of C: 0.001 to 0.003 wt%, N: 0.001 to 0.005 wt%, S: 0.001 to 0.005 wt%, Ti: 0.001 to 0.005 wt%, Nb: 0.001 to 0.005 wt%, and V: 0.001 to 0.005 wt% may be further included.

[0065] In addition, unavoidable impurities may be included. These unavoidable impurities are those introduced during the steelmaking stage and the manufacturing process of non-oriented electrical steel sheets; since this is widely known in the field, a detailed explanation is omitted. In one embodiment of the present invention, the addition of elements other than the aforementioned alloy components is not excluded, and various elements may be included within a scope that does not impair the technical spirit of the present invention. If additional elements are included, they are included to replace the remainder, Fe.

[0066] In one embodiment of the present invention, the area ratio of grains with an internal orientation distribution of 5° or less is 95.0% or more. Grains with an internal orientation distribution of 5° or less form a uniform lattice where the atoms inside the grain are not twisted in various directions. This is advantageous for magnetic domain movement and thus beneficial for improving magnetism. More specifically, the area ratio of grains with an internal orientation distribution of 5° or less may be 97.0% to 99.0%. Grains with an internal orientation distribution of 5° or less can be analyzed using EBSD. Specifically, it refers to the area ratio of grains that satisfy a tolerance angle of deviation of 5° or less relative to the average internal orientation, by measuring the orientation distribution according to the position within the grain. The area fraction can be measured in a cross-section including the thickness direction (ND direction) of the steel plate, more specifically, in a plane perpendicular to the TD direction. When measuring, the Grain Orientation Spread (GOS) method is applied to calculate the difference between the orientation of all measurement points within each grain and the average orientation of the corresponding grain, and grains with an average value of 5° or less are defined as “grains with an orientation distribution of 5° or less.” The EBSD analysis conditions can be set such that the step size is 0.5 to 5 µm, the analysis area is 3000 µm or more in the rolling direction (RD direction), and the thickness direction (ND direction) is the entire thickness of the steel plate.

[0067] The area fraction of crystal grains having an angle of 15° or less between the {100} plane and the rolled plane of the steel plate may be 15.0 to 40.0%. If the area fraction of crystal grains having an angle of 15° or less between the {100} plane and the rolled plane of the steel plate is too small, the fraction of the easy-to-magnetize axis decreases, which may be disadvantageous for magnetism. If the area fraction of crystal grains having an angle of 15° or less between the {100} plane and the rolled plane of the steel plate is too high, magnetic anisotropy increases, which is disadvantageous for magnetism. More specifically, the area fraction of crystal grains having an angle of 15° or less between the {100} plane and the rolled plane of the steel plate may be 20.0 to 35.0%. More specifically, it may be 25.0 to 35.0%. The area fraction of crystal grains having an angle of 15° or less between the {100} plane and the rolled plane of the steel plate can be analyzed through EBSD. Specifically, the fraction of orientations with a tolerance angle of 15° or less from the orientation can be measured. The term "area fraction" refers to the ratio of the area occupied by grains of a specific orientation to the total area of ​​the steel sheet as measured by electron backscatter diffraction (EBSD). The range of 15° or less means that the angle between the vertical axis of the steel sheet surface and any plane containing the corresponding orientation is within 15°.

[0068] The area fraction of crystal grains having an angle of 15° or less between the {111} plane and the rolled plane of the steel plate may be 5.0 to 20.0%. If the area fraction of crystal grains having an angle of 15° or less between the {111} plane and the rolled plane of the steel plate is too small, plastic anisotropy may decrease, and formability may decrease. If the area fraction of crystal grains having an angle of 15° or less between the {111} plane and the rolled plane of the steel plate is too high, magnetic flux density may decrease rapidly. More specifically, the area fraction of crystal grains having an angle of 15° or less between the {111} plane and the rolled plane of the steel plate may be 10.5 to 14.5%.

[0069] The area fraction of crystal grains having an angle of 15° or less between the {110} plane and the rolled plane of the steel plate may be 0.1 to 15.0%. If the area fraction of crystal grains having an angle of 15° or less between the {110} plane and the rolled plane of the steel plate is too small, the fraction of the easy-to-magnetize axis decreases, which may be disadvantageous to magnetism. If the area fraction of crystal grains having an angle of 15° or less between the {110} plane and the rolled plane of the steel plate is too high, magnetic anisotropy increases, and the magnetic deviation between the RD and TD directions may increase. More specifically, the area fraction of crystal grains having an angle of 15° or less between the {110} plane and the rolled plane of the steel plate may be 1.5 to 10.0%.

[0070] When measuring, the difference between the determined orientation of each measurement point and the target orientation ({100}, {111}, {110}) is calculated, and the area where the tolerance angle is 15° or less is defined as the corresponding orientation. The EBSD analysis conditions can be set such that the step size is 0.5 to 5 µm, the analysis area is 3000 µm or more in the rolling direction (RD direction), and the thickness direction (ND direction) is the entire thickness of the steel plate.

[0071] The area fraction is calculated as the ratio of the area occupied by the grains defined by the corresponding orientation to the total measurement area.

[0072] As previously stated, in one embodiment of the present invention, ultra-high frequency iron loss can be improved. Specifically, W 5 / 2000 ... may be 25.0 W / kg or less. More specifically, W 5 / 2000 It can be 20.0 to 23.5 W / kg.

[0073] Iron loss can be measured by cutting five specimens of 60mm width × 60mm length × number of sheets for each specimen, measuring the rolling direction and the rolling perpendicular direction using a single sheet tester, and calculating the average value. At this time, W 5 / 2000 is the iron loss when a magnetic flux density of 0.5T is induced at a frequency of 2000Hz.

[0074] Also, magnetic flux density (B 25 ) can be 1.500T or more. More specifically, magnetic flux density (B 25 ) can be 1.510T to 1.800T. B 25 represents the magnetic flux density of the steel plate induced in a magnetic field of 2500 A / m.

[0075]

[0076] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises the step of manufacturing a hot-rolled sheet by hot-rolling a slab; the step of manufacturing a cold-rolled sheet by cold-rolling the hot-rolled sheet; and the step of annealing the cold-rolled sheet.

[0077] Below, each step is explained in detail.

[0078] First, the slab is hot-rolled.

[0079] As the alloy composition of the slab has been explained in the aforementioned section on the alloy composition of non-oriented electrical steel sheets, a redundant explanation is omitted. Since the alloy composition does not substantially change during the manufacturing process of non-oriented electrical steel sheets, the alloy composition of the non-oriented electrical steel sheets and the slab is substantially the same.

[0080] Specifically, the slab contains Si: 1.5 to 5.0%, Al: 0.001 to 3.0%, Mn: 0.003 to 3.0% by weight, and the remainder is Fe and unavoidable impurities.

[0081] As other additional elements have been explained in the alloy composition of non-oriented electrical steel sheets, redundant explanations are omitted.

[0082] The slab may be heated before hot rolling. The heating temperature of the slab is not limited, but the slab may be heated to 1200°C or lower. If the heating temperature of the slab is too high, precipitates within the slab may be re-dissolved and then finely precipitated, which may adversely affect magnetism. If the re-heating temperature is too low, hot rolling may be difficult. More specifically, it may be heated to a temperature of 1050 to 1200°C.

[0083] Next, a hot-rolled plate is manufactured by hot-rolling a slab. The thickness of the hot-rolled plate may be 2.0 to 10.0 mm. In the step of manufacturing the hot-rolled plate, the finish rolling temperature may be 800°C or higher. Specifically, it may be 800 to 1000°C. The hot-rolled plate may be coiled at a temperature of 600°C or higher. More specifically, the thickness of the hot-rolled plate may be 2.5 to 5.0 mm.

[0084] After manufacturing the hot-rolled steel sheet, an additional step of annealing the hot-rolled sheet may be included. At this time, the cracking temperature may be 800 to 1150°C. If the annealing temperature is too low, a recrystallization structure is not formed or grows finely, resulting in a small increase in magnetic flux density; if the annealing temperature is too high, magnetic properties may actually deteriorate, and rolling workability may worsen due to deformation of the sheet shape. More specifically, the temperature range may be 830 to 1100°C. The cracking time may be 30 to 300 seconds. The hot-rolled sheet annealing step may also be omitted.

[0085] Next, a hot-rolled steel sheet is cold-rolled to produce a cold-rolled sheet. In the step of producing the cold-rolled sheet, the reduction ratio may be 97% or higher. If the reduction ratio is too low, appropriate grains may not be formed. More specifically, in the step of producing the cold-rolled sheet, the total reduction ratio may be 97 to 99%. In one embodiment of the present invention, cold rolling may be performed in a single step without intermediate annealing.

[0086] After cold rolling, the thickness may be 0.01 to 0.10 mm. If the thickness is too thin, problems may arise in terms of the strength of the steel sheet, and if the thickness is too thick, the reduction ratio is low, making it difficult to form an appropriate texture. More specifically, the thickness may be 0.03 to 0.08 mm.

[0087] In the annealing stage of the cold-rolled sheet, the cracking temperature may be 700 to 950°C. If the annealing temperature is too low, it is difficult to obtain appropriate magnetic properties. Conversely, if the annealing temperature is too high, surface defects may occur and high-frequency iron loss may deteriorate. More specifically, the annealing stage of the cold-rolled sheet may be 750°C to 930°C. The cracking time may be 30 seconds to 300 seconds.

[0088] After annealing the cold-rolled sheet, an insulating film can be formed. The insulating film can be treated with organic, inorganic, or organic-inorganic composite films, and it is also possible to treat it with other insulating coating materials.

[0089]

[0090] The present invention will be explained in more detail below through examples. However, these examples are merely for illustrating the invention and the invention is not limited thereto.

[0091]

[0092] Examples

[0093] A slab containing the components and other impurities listed in Table 1 below was manufactured. In addition to the components listed in Table 1, C, S, N, and Ti were all controlled to be 0.003 wt% or less. The slab was heated to 1150°C and hot-rolled at a finishing temperature of 850°C to produce a hot-rolled plate with the thickness listed in Table 1 below. The hot-rolled hot-rolled plate was annealed at 1100°C for 4 minutes, and then cold-rolled to produce a cold-rolled plate with the reduction ratio and thickness listed in Table 1 below. The cold-rolled plate was annealed at 750°C for 60 seconds.

[0094] The area ratio of grains in which the distribution of orientation within the grain is within 5° with respect to the plane perpendicular to the TD direction of the manufactured steel plate was measured using EBSD, and the area fraction of grains in which the angle between the {100} plane and the rolled plane of the steel plate is within 15°, the area fraction of grains in which the angle between the {111} plane and the rolled plane of the steel plate is within 15°, and the area fraction of grains in which the angle between the {110} plane and the rolled plane of the steel plate is within 15° were measured using EBSD. During measurement, the Grain Orientation Spread (GOS) method was applied to calculate the difference between the orientation of all measurement points within each grain and the average orientation of the corresponding grain, and grains in which the average value is 5° or less are defined as “grains with an orientation distribution within 5°”.

[0095] In addition, the difference between the determination orientation of each measurement point and the target orientation ({100}, {111}, {110}) is calculated, and the area where the tolerance angle is 15° or less is defined as the corresponding orientation, and the area fraction is calculated as the ratio of the area occupied by the grains defined as the corresponding orientation to the total measurement area.

[0096] The EBSD analysis conditions were set such that the step size was 0.5 to 5 µm, the analysis area was 3000 µm or more in the rolling direction (RD direction), and the thickness direction (ND direction) was the entire thickness of the steel plate.

[0097] Iron loss (W 5 / 2000 ) and magnetic flux density (B 25 ) was measured as the average of the rolling direction and the rolling vertical direction using a single sheet tester.

[0098] Classification SiAlMn Hot Rolled Sheet Thickness (mm) Cold Rolling Reduction Rate (%) Cold Rolled Sheet Thickness (mm) 1 3.40 0.70 1.00 2.49 7.50.06 2 3.40 0.70 1.00 3.09 8.00.06 3 3.40 0.70 1.00 6.09 9.00.06 4 3.40 1.00 0.80 4.09 7.50.10 5 3.40 1.00 0.80 5.09 8.00. 1063.600.701.002.497.50.0673.600.701.003.098.00.0683.600.701.006.099.00.0693.601.000.804.097.50.10103.601.000.805.098.00.101 11.500.701.004.097.50.10125.000.701.004.097.50.10133.400.051.004.097.50.10143.403.001.004.097.50.10153.400.700.054.097.50.10 163.400.703.004.097.50.10173.400.700.302.097.00.06183.400.700.503.397.00.10193.400.700.702.095.00.10203.401.000.901.090.00.10

[0099] Grain fraction (%) where the distribution of intra-grain orientations is within 5° {100} plane fraction (%) {111} plane fraction (%) {110} plane fraction (%) B25(T)W5 / 2k(W / kg) 197.0 25.9 14.1 9.1 1.5 192 1.1 Example 2 97.1 26.2 14.0 8.9 1.5 202 0.8 Example 3 97.6 26.6 13.9 3.8 1.5 182 0.8 Example 4 98.2 29.8 12.4 2.9 1.5 262 3.5 Example 5 98.4 30.2 12.16 .01.52723.1 Example 698.127.613.19.11.51721.0 Example 798.028.812.91.51.51720.9 Example 898.329.812.57.01.51320.4 Example 998.932.311.57.81.52722.7 Example 1098.934.110.74.71.525 22.5 Example 1197.324.614.21.11.77524.7 Example 1297.024.914.01.21.50220.3 Example 1397.320.214.91.21.52524.5 Example 1497.220.814.01.01.51123.8 Example 1597.321.714.31.01.52424. 4 Example 1697.120.7 14.8 1.01.5 1223.7 Example 1797.220.2 14.8 1.11.5 1121.6 Example 1897.121.4 14.9 1.11.5 2224.3 Example 1993.8 14.3 34.6 0.11.4 2125.6 Comparative Example 2094.3 13.1 39.3 0.7 1.3 7126.5 Comparative Example

[0100] As shown in Tables 1 and 2, when the reduction ratio is appropriately controlled during cold rolling, a large amount of grain fraction with an orientation distribution of within 5° is formed, and it can be confirmed that the magnetism is excellent.

[0101] On the other hand, if the reduction ratio during cold rolling is insufficient, it can be confirmed that a grain fraction with an orientation distribution of 5° or less is not sufficiently formed and the magnetism is inferior.

[0102] Even among the examples, when the steel composition and the thickness of the hot-rolled and cold-rolled plates are appropriately controlled, even better magnetism can be obtained.

[0103]

[0104] The present invention is not limited to the embodiments described above but can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without altering the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. In weight%, it comprises Si: 1.5 to 5.0%, Al: 0.001 to 3.0%, Mn: 0.003 to 3.0%, and the remainder comprises Fe and unavoidable impurities, Non-oriented electrical steel sheet having an area ratio of grains with an intra-grain orientation distribution of 5° or less of 95% or more.

2. In Paragraph 1, A non-oriented electrical steel sheet having an area fraction of grains having an angle of 15° or less between the {100} plane and the rolled plane of the steel sheet of 15° or less, an area fraction of grains having an angle of 15° or less between the {111} plane and the rolled plane of the steel sheet of 5° or less, and an area fraction of grains having an angle of 15° or less between the {110} plane and the rolled plane of the steel sheet of 0.1° or 15°.

3. In Paragraph 1, Non-oriented electrical steel sheet with a thickness of 0.01 to 0.10 mm.

4. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of C: 0.005 wt% or less, N: 0.030 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, Nb: 0.005 wt% or less, and V: 0.005 wt% or less.

5. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of P: 0.1 wt% or less, Cu: 0.2 wt% or less, Cr: 0.5 wt% or less, Sn: 0.1 wt% or less, Sb: 0.1 wt% or less, Ni: 0.05 wt% or less, and Zn: 0.01 wt% or less.

6. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of Bi: 0.200 wt% or less, Pb: 0.200 wt% or less, Ge: 0.200 wt% or less, and As: 0.200 wt% or less.

7. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of Mo: 0.03 wt% or less, B: 0.01 wt% or less, Ca: 0.01 wt% or less, Zr: 0.01 wt% or less, Te: 0.01 wt% or less, and Mg: 0.01 wt% or less.

8. A step of manufacturing a hot-rolled plate by hot-rolling a slab comprising, by weight, Si: 1.5 to 5.0%, Al: 0.001 to 3.0%, Mn: 0.003 to 3.0%, and the remainder being Fe and unavoidable impurities; A step of manufacturing a cold-rolled plate by cold-rolling the above hot-rolled plate; and The above cold-rolled plate includes the step of annealing the cold-rolled plate, and A method for manufacturing a non-oriented electrical steel sheet in which the reduction rate is 97% or more during the cold rolling step of the above cold-rolled sheet.

9. In Paragraph 8, A method for manufacturing a non-oriented electrical steel sheet, wherein the above slab further comprises one or more of C: 0.005 wt% or less, N: 0.030 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, Nb: 0.005 wt% or less, and V: 0.005 wt% or less.

10. In Paragraph 8, A method for manufacturing a non-oriented electrical steel sheet, wherein the above slab further comprises one or more of P: 0.1 wt% or less, Cu: 0.2 wt% or less, Cr: 0.5 wt% or less, Sn: 0.1 wt% or less, Sb: 0.1 wt% or less, Ni: 0.05 wt% or less, and Zn: 0.01 wt% or less.

11. In Paragraph 8, A method for manufacturing a non-oriented electrical steel sheet, wherein the above slab further comprises one or more of Bi: 0.200 wt% or less, Pb: 0.200 wt% or less, Ge: 0.200 wt% or less, and As: 0.200 wt% or less.

12. In Paragraph 8, A method for manufacturing a non-oriented electrical steel sheet, wherein the above slab further comprises one or more of Mo: 0.03 wt% or less, B: 0.01 wt% or less, Ca: 0.01 wt% or less, Zr: 0.01 wt% or less, Te: 0.01 wt% or less, and Mg: 0.01 wt% or less.

13. In Paragraph 8, A method for manufacturing a non-oriented electrical steel sheet in which the thickness of the hot-rolled sheet is 2 to 10 mm in the step of manufacturing the hot-rolled sheet.

14. In Paragraph 8, A method for manufacturing a non-oriented electrical steel sheet in which, in the step of manufacturing the above cold-rolled sheet, the thickness of the cold-rolled sheet is 0.01 to 0.10 mm.