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 weight%, 1.3 to 5.5 % of Si, 0.1 to 3.5 % of Al, and 0.1 to 3.5 % of Mn, with the balance being Fe and inevitable impurities, wherein a ratio of an average grain size of grains having an orientation within 15° of {110}<001> to an average grain size of grains in the steel sheet is 0.45 to 1.00.

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 controls the residence time at different temperatures during the cracking and cooling process of hot-rolled sheet annealing, {110} <001> The present invention relates to a non-oriented electrical steel sheet that simultaneously improves magnetic flux density and iron loss by controlling the particle size, and a method for manufacturing the same.

[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 controls the residence time at different temperatures during the cracking and cooling process of hot-rolled sheet annealing, {110} <001> The present invention provides a non-oriented electrical steel sheet and a method for manufacturing the same, which simultaneously improves magnetic flux density and iron loss by controlling the particle size.

[0008] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises, in weight percent, Si: 1.3 to 5.5%, Al: 0.1 to 3.5%, Mn: 0.1 to 3.5%, the remainder being Fe and unavoidable impurities, and the average grain size (GS) of the crystal grains within the steel sheet t {110} for ) <001> Average grain size of crystal grains having an orientation within 15° from (GS g The ratio of ) (GS g / GS t) is 0.45 to 1.00.

[0009] The average grain size of the crystal grains in the steel sheet is 50 to 100 μm, and {110} <001> The average grain size of crystal grains having an orientation within 15° from may be 25 to 100 μm.

[0010] 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, C: 0.005 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, and N: 0.005 wt% or less.

[0011] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include 0.005 to 0.200 weight% of one or more of Sn, Sb, Bi, Pb, Ge, and As, respectively or in their combined amount.

[0012] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Ni: 0.05 wt% or less, Zn: 0.01 wt% or less, and Co: 0.05 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 Mo: 0.03 wt% or less, B: 0.0050 wt% or less, V: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Nb: 0.0050 wt% or less, Zr: 0.005 wt% or less, Te: 0.01 wt% or less, and Mg: 0.0050 wt% or less.

[0014] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises the steps of: manufacturing a hot-rolled steel sheet by hot-rolling a slab containing, in weight%, Si: 1.3 to 5.5%, Al: 0.1 to 3.5%, Mn: 0.1 to 3.5%, and the remainder being Fe and unavoidable impurities; a hot-rolled sheet annealing step for annealing the hot-rolled steel sheet; a step for manufacturing a cold-rolled sheet by cold-rolling the annealed hot-rolled steel sheet; and a cold-rolled sheet annealing step for annealing the cold-rolled sheet.

[0015] The ratio of the residence time of steel plates at 600°C or higher and less than 900°C to the residence time of steel plates at 900°C or higher during the cracking and cooling stages is 0.06 to 0.25.

[0016] The slab may further include one or more of P: 0.1 wt% or less, C: 0.005 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, and N: 0.005 wt% or less.

[0017] The slab may further contain 0.005 to 0.200 weight% of one or more of Sn, Sb, Bi, Pb, Ge, and As, either individually or in their combined amount.

[0018] The slab may further include one or more of Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Ni: 0.05 wt% or less, Zn: 0.01 wt% or less, and Co: 0.05 wt% or less.

[0019] The slab may further include one or more of Mo: 0.03 wt% or less, B: 0.0050 wt% or less, V: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Nb: 0.0050 wt% or less, Zr: 0.005 wt% or less, Te: 0.01 wt% or less, and Mg: 0.0050 wt% or less.

[0020] Tension is 0.2 to 1.0 kgf / mm during the annealing stage of hot-rolled plates. 2It can be granted as.

[0021] After the hot-rolled plate annealing step, the average KAM value of the hot-rolled plate may be 0.6° or less.

[0022] A non-oriented electrical steel sheet according to one embodiment of the present invention simultaneously improves magnetic flux density and iron loss, and can be usefully utilized as an iron core for a motor. More specifically, it can be usefully utilized as an iron core for a new mobility drive motor.

[0023] 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.

[0024] 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.

[0025] When it is stated that one part is "on" or "on" another part, it may be directly on or on the other part, or another part may be involved in between. In contrast, when it is stated that one part is "directly on" another part, no other part is interposed in between.

[0026] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0027] 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.

[0028] 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.

[0029] 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.

[0030]

[0031] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises, in weight%, Si: 1.3 to 5.5%, Al: 0.1 to 3.5%, Mn: 0.1 to 3.5%, and the remainder being Fe and unavoidable impurities.

[0032] Below, we will explain the reason for limiting the composition of non-oriented electrical steel sheets.

[0033] Si: 1.3 to 5.5 wt%

[0034] 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. More specifically, it may contain 1.5 to 5.0 weight% of Si. More specifically, it may contain 2.0 to 4.5 weight%. More specifically, it may contain 3.0 to 3.7 weight%.

[0035] Al: 0.1 to 3.5 wt%

[0036] 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 0.3 to 2.5 weight% of Al. More specifically, it may contain 0.5 to 2.0 weight%. More specifically, it may contain 0.7 to 1.5 weight%.

[0037] Mn: 0.1 to 3.5 wt%

[0038] 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 0.2 to 3.0 weight% of Mn. More specifically, it may contain 0.3 to 1.0 weight%.

[0039] 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, C: 0.005 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, and N: 0.005 wt% or less.

[0040] P: 0.1 wt% or less

[0041] Phosphorus (P) can improve magnetic flux density as a grain boundary segregation element, but if added in excessive amounts, it increases the brittleness of the steel sheet and impairs weldability. More specifically, it may contain 0.0001 to 0.0500 weight% of P.

[0042] C: 0.005 wt% or less

[0043] Carbon (C) can cause magnetic aging and combine with other impurity elements to form carbides, which can impede grain boundary or domain wall movement and degrade magnetic properties. More specifically, it may contain 0.0001 to 0.003 weight% of C.

[0044] S: 0.005 wt% or less

[0045] Sulfur (S) can form fine precipitates, such as MnS and CuS, which can worsen magnetic properties and hot workability. More specifically, it may contain 0.0001 to 0.0030 weight% of S.

[0046] Ti: 0.005 wt% or less

[0047] Titanium (Ti) has a very strong tendency to form precipitates in steel and can degrade iron loss by forming fine carbides, nitrides, or sulfides within the base material, thereby inhibiting grain growth and domain wall movement. More specifically, it may contain 0.0001 to 0.003 weight% of Ti.

[0048] N: 0.005 wt% or less

[0049] Nitrogen (N) not only forms fine AlN precipitates inside the base material but also combines with other impurities to form fine precipitates, thereby inhibiting grain growth and domain wall movement, which can worsen iron loss. More specifically, it may contain 0.0001 to 0.0030 weight% of N.

[0050] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include 0.005 to 0.200 weight% of one or more of Sn, Sb, Bi, Pb, Ge, and As, respectively or in their combined amount.

[0051] Sn and Sb

[0052] Tin (Sn) and antimony (Sb) play a role in suppressing the development of {111} orientations, which degrade magnetism by segregating at the grain boundaries during the initial stage of final recrystallization annealing. If too much Sn and Sb are added, it can hinder the recovery and growth of coarse elongated band structures and degrade surface quality. Therefore, one or more of Sn and Sb may be added within the aforementioned range. More specifically, it may contain 0.005 to 0.200 wt% of Sn or 0.005 to 0.200 wt% of Sb. More specifically, it may contain 0.010 to 0.150 wt% of Sn or 0.010 to 0.150 wt% of Sb.

[0053] Bi, Pb, Ge, and As

[0054] When bismuth (Bi), lead (Pb), germanium (Ge), and arsenic (As) are added, they segregate at grain boundaries, alleviating stress concentration at grain boundaries during cold rolling, which in the subsequent recrystallization annealing process <111> By suppressing the recrystallization of the / ND orientation crystal 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 crystal grain growth and may result in inferior magnetic flux density and iron loss. More specifically, one or more of Bi: 0.005 to 0.200 wt%, Pb: 0.005 to 0.200 wt%, Ge: 0.005 to 0.200 wt%, and As: 0.005 to 0.200 wt% may be further included. More specifically, one or more of Bi: 0.010 to 0.150 wt%, Pb: 0.010 to 0.150 wt%, Ge: 0.010 to 0.150 wt%, and As: 0.010 to 0.150 wt% may be further included.

[0055] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include one or more of Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Ni: 0.05 wt% or less (excluding 0%), Zn: 0.01 wt% or less (excluding 0%), and Co: 0.05 wt% or less (excluding 0%).

[0056] Cu: 0.005 to 0.200 wt%

[0057] Copper (Cu) plays a role in forming sulfides together with Mn. If more Cu is added, or if too little is added, (Cu · Mn)S may precipitate finely, which can degrade magnetism. If too much Cu is added, high-temperature brittleness occurs, which can form cracks during continuous casting or hot rolling. More specifically, it may contain 0.01 to 0.10 weight% of Cu.

[0058] Cr: 0.01 to 0.50 wt%

[0059] Chromium (Cr) plays a role in improving iron loss by increasing resistivity. If too little Cr is added, the effect of increasing resistivity may not be sufficient. If too much Cr is included, magnetic flux density may decrease. More specifically, 0.050 to 0.20 weight% of Cr may be included.

[0060] Ni: 0.05 wt% or less

[0061] Nickel (Ni) can react with impurity elements to form fine sulfides, carbides, and nitrides, which can have a harmful effect on magnetism. More specifically, it may contain 0.001 to 0.03 weight percent of Ni.

[0062] Zn: 0.01 wt% or less

[0063] 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%.

[0064] Co: 0.05 wt% or less

[0065] Cobalt (Co) does not form fine precipitates that reduce the magnetism of steel sheets, but it increases high-temperature strength, which can cause the coil shape to be defective after hot rolling.

[0066] 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: 0.0050 wt% or less, V: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Nb: 0.0050 wt% or less, Zr: 0.0050 wt% or less, Te: 0.0100 wt% or less, and Mg: 0.0050 wt% or less.

[0067] Mo: 0.030 wt% or less

[0068] If molybdenum (Mo) is added in excess, it may suppress the segregation of segregated elements, thereby reducing the texture improvement effect. Therefore, Mo may be included in an amount of 0.03 weight% or less. The lower limit is not specifically limited, but since it plays a role in improving the texture by segregating at the surface and grain boundaries, it may be included in an amount of 0.001 weight% or more. More specifically, Mo may be included in an amount of 0.001 to 0.010 weight%. Even more specifically, Mo may be included in an amount of 0.005 to 0.010 weight%.

[0069] B: 0.0050 wt% or less

[0070] If an excessive amount of boron (B) is added, it may cause deterioration of magnetic properties through the formation of inclusions within the steel. Therefore, B may be included in an amount of 0.005 weight% or less. The lower limit is not specifically limited, but it may be 0.0001 weight% due to steelmaking costs. More specifically, B may be included in an amount of 0.0001 to 0.0030 weight%.

[0071] V: 0.0050 wt% or less

[0072] Vanadium (V) has a very strong tendency to form precipitates in steel and degrades iron loss by forming fine carbides or nitrides inside the base material, thereby inhibiting grain growth and domain wall movement. Therefore, the V content may be 0.0050 wt% or less. The lower limit is not specifically limited, but it may be 0.0003 wt% due to steelmaking costs. That is, V may be included in 0.0003 to 0.0050 wt%. More specifically, V may be included in 0.0003 to 0.0030 wt%.

[0073] Ca: 0.0050 wt% or less

[0074] Calcium (Ca) has a very strong tendency to form precipitates within the steel and degrades iron loss by forming fine sulfides inside the base material, thereby inhibiting grain growth and domain wall movement.

[0075] Nb: 0.0050 wt% or less

[0076] Niobium (Nb) has a very strong tendency to form precipitates in steel and degrades iron loss by forming fine carbides or nitrides within the base material, thereby inhibiting grain growth and domain wall movement. Therefore, the Nb content may be 0.0050 wt% or less. The lower limit is not specifically limited, but it may be 0.0003 wt% due to steelmaking costs. That is, it may contain 0.0003 to 0.0050 wt% of Nb. More specifically, it may contain 0.0003 to 0.0030 wt% of Nb.

[0077] Zr: 0.0050 wt% or less

[0078] If an excessive amount of zirconium (Zr) is added, it may cause deterioration of magnetic properties through the formation of inclusions within the steel. Therefore, Zr may be included in an amount of 0.005 weight% or less. The lower limit is not specifically limited, but it may be set to 0.0001 weight% due to steelmaking costs. That is, Zr may be included in an amount of 0.0001 to 0.0050 weight%. More specifically, it may be included in an amount of 0.0005 to 0.0030 weight%.

[0079] Te: 0.0100 wt% or less

[0080] Tellurium (Te) can be added to prevent the oxide layer, which is fractured during rolling, from being pressed into the base material and to detach it, as it diffuses into the oxide layer on the surface of the hot-rolled coil, increases the coefficient of friction between the oxide layer and the rolling work roll, and increases hardness by concentrating beneath the oxide layer. If the amount of Te added is too small, the effect may be negligible. If too much Te is added, the oxide layer detaches easily, causing the base material to come into direct contact with the work roll, which reduces the above effect, and excessive deformation bands may be generated within the steel sheet during cold rolling, leading to the development of a {111} / ND texture that is unfavorable to magnetism. More specifically, it may contain 0.0001 to 0.007 weight% of tellurium.

[0081] Mg: 0.0050 wt% or less

[0082] Magnesium (Mg) is an element that primarily combines with S to form sulfides and can affect the surface oxide layer of the base iron. Therefore, Mg may be included in an amount of 0.0050 wt% or less. The lower limit is not specifically limited, but it may be 0.0001 wt% due to steelmaking costs. That is, Mg may be included in an amount of 0.0001 to 0.0050 wt%. More specifically, it may be included in an amount of 0.0005 to 0.0030 wt%.

[0083] The remainder comprises Fe and unavoidable impurities. The unavoidable impurities are those introduced during the steelmaking stage and the manufacturing process of non-oriented electrical steel sheets; as this is widely known in the field, a detailed description 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 replace the remainder, Fe.

[0084] {110} for the average grain size of crystal grains in steel sheets <001> The ratio of the average grain size of grains having an orientation within 15° from may be 0.45 to 1.00. The average grain size of the grains within the steel sheet can be measured by observing the cross-section of the steel sheet with an electron microscope. The grain size can be determined as the diameter of a virtual circle having an area equal to the area occupied by the grains. The average grain size may be the number average grain size. The cross-section of the steel sheet may be a cross-section including the thickness direction (ND direction) of the steel sheet, and more specifically, may be measured based on a plane perpendicular to the TD direction. {110} <001> Crystal grains having an orientation within 15° from (hereinafter, “{110} <001> (also referred to as "grain") is a grain in which the intragrain misorientation is 2° or less in OIM Analysis, and the mean orientation and {110} <001> It can be determined that the bearing difference is 15° or less, and {110} <001> The average grain size can be measured based on the grains determined to be crystal grains. Average grain size of crystal grains in the steel plate (GS T {110} for ) <001> Average grain size of crystal grains having an orientation within 15° from (GS {110}<001> The ratio of ) (GS {110}<001> / GS T If ) is too small: the average magnetism in the rolling direction and the rolling perpendicular direction may become unfavorable. That ratio (GS {110}<001> / GS T If ) is too large, the deviation in the circumferential characteristics of magnetism may increase. More specifically, the ratio (GS {110}<001> / GS T ) can be 0.47 to 0.85.

[0085] Average grain size (GS) within the steel plate T ) can be 50 to 100㎛. Average grain size of crystal grains in the steel sheet (GS T If ) is too small, hysteresis loss among iron losses can increase rapidly.

[0086] Average grain size (GS) within the steel plateT If ) is too large, eddy current loss among iron losses can increase rapidly. More specifically, the average grain size of crystal grains within the steel sheet (GS T ) can be 60 to 90 μm.

[0087] {110} <001> Average grain size of crystal grains having an orientation within 15° from (GS {110}<001> ) may be 25 to 100 μm. {110} <001> Average grain size of crystal grains having an orientation within 15° from (GS {110}<001> If ) is too small, the magnetic advantage {110} <001> As the orientation fraction decreases, the average magnetism in the rolling direction and the rolling perpendicular direction may become unfavorable. {110} <001> Average grain size of crystal grains having an orientation within 15° from (GS {110}<001> If ) is too large, magnetic anisotropy increases, which can lead to inferior circumferential characteristics of the motor. More specifically, {110} <001> Average grain size of crystal grains having an orientation within 15° from (GS {110}<001> ) can be 35 to 65 μm.

[0088] As previously mentioned, in one embodiment of the present invention, magnetic flux density and iron loss can be improved simultaneously. Specifically, the magnetic flux density (B50) may be 1.63T or higher. More specifically, B50 may be 1.64 to 1.73T. B50 refers to the magnetic flux density of a steel plate induced in a magnetic field of 5000 A / m.

[0089] Also, iron loss (W 10 / 400 ) may be 12.5 W / kg or less. More specifically, iron loss (W 10 / 400 ) can be 9.0 to 12.3 W / kg. In this case, W 10 / 400 is the iron loss when a magnetic flux density of 1.0T is induced at a frequency of 400Hz.

[0090] Iron loss and magnetic flux density can be measured by cutting five specimens of width 60 mm × length 60 mm × number of sheets for each specimen, measuring the rolling direction and the rolling perpendicular direction with a single sheet tester, and determining the average value.

[0091] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises: a step of manufacturing a hot-rolled steel sheet by hot-rolling a slab; a hot-rolled sheet annealing step of annealing the hot-rolled steel sheet; a step of manufacturing a cold-rolled sheet by cold-rolling the hot-rolled steel sheet; and a cold-rolled sheet annealing step of annealing the cold-rolled sheet.

[0092] Below, each step is explained in detail.

[0093] First, the slab is hot-rolled.

[0094] 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.

[0095] Specifically, the slab contains Si: 1.3 to 5.5%, Al: 0.1 to 3.5%, Mn: 0.1 to 3.5% by weight, and the remainder is Fe and unavoidable impurities.

[0096] As other additional elements have been explained in the alloy composition of non-oriented electrical steel sheets, redundant explanations are omitted.

[0097] 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.

[0098] Next, a hot-rolled plate is manufactured by hot-rolling a slab. The thickness of the hot-rolled plate may be 1.0 to 4.5 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 1.5 to 4.3 mm.

[0099] After manufacturing the hot-rolled steel sheet, the hot-rolled sheet is annealed. At this time, the cracking temperature may be 900 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 900 to 1100°C. The cracking time may be 30 to 300 seconds. The cracking stage refers to the stage during hot-rolled sheet annealing where the steel sheet is heated, reaches the maximum temperature, and then the temperature is maintained.

[0100] The hot-rolled sheet annealing step includes a cooling step for cooling the steel sheet after the cracking step. In one embodiment of the present invention, the ratio of the residence time of the steel sheet at 600°C or higher and less than 900°C to the residence time of the steel sheet at 900°C or higher in the cracking step and the cooling step is 0.06 to 0.25. If the ratio of the residence time of the steel sheet at 600°C or higher and less than 900°C to the residence time of the steel sheet at 900°C or higher is too small, residual stress may increase due to thermal shock caused by rapid cooling, which may result in inferior rolling performance. If the ratio of the residence time of the steel sheet at 600°C or higher and less than 900°C to the residence time of the steel sheet at 900°C or higher is too large, productivity may decrease due to increased processing time. More specifically, the ratio of the residence time of the steel sheet at 600°C or higher and less than 900°C to the residence time of the steel sheet at 900°C or higher in the cracking step and the cooling step may be 0.08 to 0.23.

[0101] The residence time of the steel sheet at 900°C or higher may be 80 to 190 seconds. If the residence time of the steel sheet at 900°C or higher is too short, the grains become fine, and the {111} orientation texture recrystallized at the grain boundaries increases, which may be detrimental to the magnetism of the final product. If the residence time of the steel sheet at 900°C or higher is too long, stress concentration at the grain boundaries increases, which may result in inferior rolling performance. More specifically, the residence time of the steel sheet at 900°C or higher may be 90 to 175 seconds.

[0102] The residence time of the steel sheet at 600°C or higher and less than 900°C may be 5 to 50 seconds. If the residence time of the steel sheet at 600°C or higher and less than 900°C is too short, thermal shock due to rapid cooling and uneven cooling rates within the steel sheet may increase residual stress. If the residence time of the steel sheet at 600°C or higher and less than 900°C is too long, productivity may decrease and the oxide layer may become thicker. More specifically, the residence time of the steel sheet at 600°C or higher and less than 900°C may be 9 to 30 seconds.

[0103] Tensile force during annealing of hot-rolled plates is 0.20 to 1.00 kgf / mm 2 It can be applied as follows. If the tension is too low, it may be difficult to control the sagging or meandering of the hot-rolled plate. If the tension is too high, residual stress increases, making it difficult to ensure adequate rollability. More specifically, during the annealing of the hot-rolled plate, the tension is 0.25 to 0.70 kgf / mm 2 It can be applied. Tension can be measured with a tension meter after cooling to 200°C or lower at the exit side of the annealing furnace.

[0104] After the annealing stage of the hot-rolled plate, the average KAM value of the hot-rolled plate may be 0.6° or less. KAM (kernel Average Misorientation) represents the difference in orientation between a pixel and the kernel surrounding that pixel, regardless of grains or grain boundaries. More specifically, the average KAM value may be 0.10 to 0.55°. The KAM value can be obtained by observing the cross-section of the steel plate using Electron Backscatter Diffraction (EBSD), measuring the value using OIM Analysis with the nearest neighbor 1st, maximum misorientation of 5°, and using three or more samples with a thickness of 3mm in the TD direction or 3mm in the ND direction, and averaging the values.

[0105] Next, a cold-rolled sheet is manufactured by cold-rolling a hot-rolled steel sheet. In the step of manufacturing the cold-rolled sheet, the reduction ratio may be 75 to 90%. If the reduction ratio is too low, additional rolling is required to obtain an appropriate final thickness, and productivity may be inferior. If the reduction ratio is too high, a texture unfavorable to magnetism is formed, and iron loss may be inferior. More specifically, in the step of manufacturing the cold-rolled sheet, the total reduction ratio may be 77 to 88%.

[0106] After cold rolling, the thickness may be 0.10 to 0.35 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, it may have an adverse effect on ultra-high frequency iron loss. More specifically, the thickness may be 0.15 to 0.30 mm.

[0107] In one embodiment of the present invention, cold rolling can be performed in a single step without intermediate annealing.

[0108] In the annealing stage of the cold-rolled sheet, the cracking temperature may be 700 to 1050°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 to 980°C. The cracking time may be 30 seconds to 300 seconds.

[0109] 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.

[0110]

[0111] 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.

[0112]

[0113] Examples

[0114] A slab containing the components and other impurities summarized in Table 1 below was manufactured. In addition to the components summarized in Table 1, C, S, N, and Ti were all controlled to 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. The hot-rolled plate was annealed under the conditions summarized in Table 1 below, cooled for the residence time at each temperature summarized in Table 1 below, and then pickled. Subsequently, it was cold-rolled to a thickness of 0.25 mm. Afterward, the cold-rolled plate was annealed at 970°C for 1 minute.

[0115] Eight manufactured steel plates were stacked and subjected to 2mm x 3mm TD direction SEM-EBSD measurement, and the average grain size and {110} were determined through the averaging of three or more plates. <001> The average grain size was calculated.

[0116] Iron loss and magnetic flux density were measured using a single sheet tester as the average of the rolling direction and the rolling perpendicular direction.

[0117] Classification Si(wt%) Al(wt%) Mn(wt%) Hot Rolled Plate Annealing Tension (kgf / mm²) 2 Residence time above 900℃(s) 600℃-900℃ Residence time(s) Time above 600℃ / Time above 900℃ 13.40.70.30.25125100.08 23.41.00.50.25125150.123 3.41.30.70.35125200.16 43.41.50.90.35125250.20 53.60.70.30.45150100.07 63.61.00.50.45150150.107 3.61.30.70.25150200.1383.61.50.90.25150250.1793.20.70.30.35100100.10103.21.00.50.35100150.15111.31.30.70.45100200.20125.61.50.90.45100250.251 33.40.090.30.25125100.08143.43.50.30.25125150.12153.40.70.090.35125200.16163.40.73.60.35125250.20173.40.70.30.15125100.08183.41.00.51.2012515 0.12193.41.30.70.2570150.21203.41.50.90.25200400.20213.60.70.30.358040.05223.61.00.50.3512540.03233.61.30.70.4512550.04243.61.50.90.4512560.05

[0118] Classification KAM Value (°) Average Grain Size (㎛) {110} <001> Particle size (㎛){110} <001> Grain size / Average grain size, Magnetic flux density (B50, Tesla), Iron loss (W 10 / 400, W / kg)10.4264510.801.6711.920.3172460.641.6510.730.4575480.641.651 0.140.3678390.501.649.850.2576580.761.6611.560.5184520.621.6410.47 0.3381610.751.6510.280.4186420.491.649.690.4388620.701.6512.2100.4575460.611.6411.1110.4335210.601.7112.6121.2233160.441.5814.2130. 7580370.431.6013.4140.8465320.491.6312.5150.54110350.321.6114.5160.7846210.431.5713.2170.8775260.351.6012.7180.8380220.281.5912.919 0.4545160.361.6112.9200.43105430.411.6312.8211.0580210.261.6212.6220.9675240.321.6112.7230.8280320.401.6113.5240.7690270.301.6113.3

[0119] As shown in Tables 1 and 2, when the steel composition is appropriately controlled and the residence time at each temperature during hot-rolled plate annealing is appropriately controlled, {110} <001> It can be confirmed that the ratio of the average grain size of the crystals is properly controlled, and that magnetic flux density and iron loss are simultaneously excellent. On the other hand, if the steel composition is not properly controlled, or if the residence time at each temperature during the annealing of the hot-rolled plate is not properly controlled, {110} <001> It can be confirmed that the ratio of the average grain size of the crystals is not properly controlled, and the magnetic flux density or iron loss is inferior.

[0120]

[0121] 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. Contains Si: 1.3 to 5.5%, Al: 0.1 to 3.5%, Mn: 0.1 to 3.5% by weight, and the remainder being Fe and unavoidable impurities, Average grain size (GS) within the steel plate t {110} for ) <001> Average grain size of crystal grains having an orientation within 15° from (GS g The ratio of ) (GS g / GS t Non-oriented electrical steel sheet having a ) of 0.45 to 1.

00.

2. In Paragraph 1, The average grain size of the crystal grains in the steel sheet is 50 to 100 μm, and {110} <001> Non-oriented electrical steel sheet having an average grain size of 25 to 100 μm of crystal grains having an orientation within 15° from .

3. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of P: 0.1 wt% or less, C: 0.005 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, and N: 0.005 wt% or less.

4. In Paragraph 1, A non-oriented electrical steel sheet further comprising 0.005 to 0.200 weight% of one or more of Sn, Sb, Bi, Pb, Ge, and As, either individually or in their combined amount.

5. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Ni: 0.05 wt% or less, Zn: 0.01 wt% or less, and Co: 0.05 wt% or less.

6. In Paragraph 1, A non-oriented electrical steel sheet further comprising one or more of Mo: 0.03 wt% or less, B: 0.0050 wt% or less, V: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Nb: 0.0050 wt% or less, Zr: 0.005 wt% or less, Te: 0.01 wt% or less, and Mg: 0.0050 wt% or less.

7. A step of manufacturing a hot-rolled steel sheet by hot-rolling a slab containing, in weight percent, Si: 1.3 to 5.5%, Al: 0.1 to 3.5%, Mn: 0.1 to 3.5%, and the remainder being Fe and unavoidable impurities; A hot-rolled steel plate annealing step for annealing the above hot-rolled steel plate; A step of manufacturing a cold-rolled sheet by cold-rolling an annealed hot-rolled steel sheet and It includes a cold-rolled plate annealing step for annealing the above cold-rolled plate, and The above hot-rolled plate annealing step includes a cracking step and a cooling step, and A method for manufacturing a non-oriented electrical steel sheet in which the ratio of the residence time of the steel sheet at 600°C or higher and less than 900°C to the residence time of the steel sheet at 900°C or higher in the cracking and cooling steps is 0.06 to 0.

25.

8. In Paragraph 7, 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, C: 0.005 wt% or less, S: 0.005 wt% or less, Ti: 0.005 wt% or less, and N: 0.005 wt% or less.

9. In Paragraph 7, A method for manufacturing a non-oriented electrical steel sheet, wherein the above slab further comprises 0.005 to 0.200 weight% of one or more of Sn, Sb, Bi, Pb, Ge, and As, respectively or in their combined amount.

10. In Paragraph 7, A method for manufacturing a non-oriented electrical steel sheet, wherein the above slab further comprises one or more of Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Ni: 0.05 wt% or less, Zn: 0.01 wt% or less, and Co: 0.05 wt% or less.

11. In Paragraph 7, 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: 0.0050 wt% or less, V: 0.0050 wt% or less, Ca: 0.0050 wt% or less, Nb: 0.0050 wt% or less, Zr: 0.005 wt% or less, Te: 0.01 wt% or less, and Mg: 0.0050 wt% or less.

12. In Paragraph 7, In the above hot-rolled plate annealing step, the tensile strength is 0.2 to 1.0 kgf / mm 2 A method for manufacturing non-oriented electrical steel sheets imparted by 13. In Paragraph 7, A method for manufacturing a non-oriented electrical steel sheet in which the average KAM value of the hot-rolled sheet is 0.6° or less after the above-mentioned hot-rolled sheet annealing step.