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 comprises, by wt%, 1.5 to 5.0% of Si, 0.1 to 3.0% of Al, and 0.1 to 3.0% of Mn, with the balance being Fe and unavoidable impurities, and satisfies Expression 1. [Expression 1] (KAMc+KAMg) / 2KAMt ≤ 0.90 (In Expression 1, KAMc refers to the KAM value of grains having an orientation within 15° of {100}<001>, KAMg refers to the KAM value of grains having an orientation within 15° of {110}<001>, and KAMt refers to the average KAM value of all grains.)

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 and a method for manufacturing the same, wherein the KAM value by orientation is controlled by adjusting the tension when winding the annealed cold-rolled sheet after annealing, thereby improving ultra-high frequency iron loss.

[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 and a method for manufacturing the same, which improves ultra-high frequency iron loss by controlling the KAM value by orientation by adjusting the tension when winding the annealed cold-rolled sheet after annealing the cold-rolled sheet.

[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: 0.1 to 3.0%, Mn: 0.1 to 3.0%, the remainder being Fe and unavoidable impurities, and satisfies Formula 1 below.

[0009] [Equation 1]

[0010] (KAM c +KAM g ) / 2KAM t ≤ 0.90

[0011] (KAM in Equation 1 c is {100} <001> It refers to the KAM value of grains having an orientation within 15° from, and KAM g is {110} <001> It refers to the KAM value of grains having an orientation within 15° from, and KAM t represents the average KAM value of the entire grain.)

[0012] The area fraction of grains with a KAM value of 0.5 or less may be 77% or more.

[0013] Average KAM value of all grains (KAM t ) may be 0.63 or less.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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 containing, in weight%, Si: 1.5 to 5.0%, Al: 0.1 to 3.0%, Mn: 0.1 to 3.0%, and the remainder being Fe and unavoidable impurities; 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.

[0019] The cold-rolled sheet annealing step includes a step of cracking the cold-rolled sheet and a step of winding the cracked cold-rolled sheet, and the tension applied to the steel sheet in the winding step is 3 to 7 kgf / mm 2 am.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] During the winding stage, the maximum deviation of the tension from the average value of the tension applied to steel plates of length 3000m or more may be 50% or less.

[0025] The difference in tension values ​​between the cracking stage and the winding stage is 2.0 to 6.5 kgf / mm 2 It could be.

[0026] A non-oriented electrical steel sheet according to one embodiment of the present invention has improved 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0031] 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.

[0032] 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.

[0033] 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.

[0034]

[0035] A non-oriented electrical steel sheet according to one embodiment of the present invention comprises, in weight%, Si: 1.5 to 5.0%, Al: 0.1 to 3.0%, Mn: 0.1 to 3.0%, and the remainder being Fe and unavoidable impurities.

[0036] Below, we will explain the reason for limiting the composition of non-oriented electrical steel sheets.

[0037] Si: 1.5 to 5.0 wt%

[0038] 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 1.50 to 5.00 weight%. More specifically, it may be included in an amount of 2.00 to 4.50 weight%. Even more specifically, it may be included in an amount of 3.50 to 4.20 weight%.

[0039] Al: 0.10 to 3.00 wt%

[0040] 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 0.50 to 2.5 weight% of Al. More specifically, it may contain 0.75 to 2.20 weight%.

[0041]

[0042] Mn: 0.1 to 3.0 wt%

[0043] 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. Therefore, Mn may be included in an amount of 0.10 to 3.00 weight%. More specifically, it may be included in an amount of 0.30 to 2.50 weight%. More specifically, it may be included in an amount of 0.50 to 2.00 weight%.

[0044] 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.

[0045] P: 0.1 wt% or less

[0046] 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.

[0047] C: 0.005 wt% or less

[0048] 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.

[0049] S: 0.005 wt% or less

[0050] 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.

[0051] Ti: 0.005 wt% or less

[0052] 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.

[0053] N: 0.005 wt% or less

[0054] 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.

[0055]

[0056] 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.

[0057] Sn and Sb

[0058] 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.

[0059] Bi, Pb, Ge, and As

[0060] 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.

[0061]

[0062] 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%).

[0063] Cu: 0.005 to 0.200 wt%

[0064] 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.

[0065] Cr: 0.01 to 0.50 wt%

[0066] 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.

[0067] Ni: 0.05 wt% or less

[0068] 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.

[0069] Zn: 0.01 wt% or less

[0070] 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%.

[0071] Co: 0.05 wt% or less

[0072] 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.

[0073]

[0074] 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.

[0075] Mo: 0.030 wt% or less

[0076] 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%.

[0077] B: 0.0050 wt% or less

[0078] 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%.

[0079] V: 0.0050 wt% or less

[0080] 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%.

[0081] Ca: 0.0050 wt% or less

[0082] 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.

[0083] Nb: 0.0050 wt% or less

[0084] 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.

[0085] Zr: 0.0050 wt% or less

[0086] 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%.

[0087] Te: 0.0100 wt% or less

[0088] 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.

[0089] Mg: 0.0050 wt% or less

[0090] 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%.

[0091]

[0092] 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.

[0093]

[0094] A non-oriented electrical steel sheet according to one embodiment of the present invention can satisfy the following Equation 1.

[0095] [Equation 1]

[0096] (KAM c +KAM g ) / 2KAM t ≤ 0.90

[0097] (KAM in Equation 1 c is {100} <001> It refers to the KAM value of grains having an orientation within 15° from, and KAM g is {110} <001> It refers to the KAM value of grains having an orientation within 15° from, and KAM trepresents the average KAM value of the entire grain.)

[0098] Equation 1 implies that the stress in the cube and goss textures, which are favorable for magnetism, must be reduced. If Equation 1 is too large, the magnetism may be degraded due to stress during the magnetization process. The lower limit of the left side of Equation 1 is not specifically limited, but it may be limited for reasons of operational stability of mass production facilities. More specifically, the value of the left side of Equation 1 may be between 0.70 and 0.90.

[0099] KAM (Kernel Average Misorientation) refers to the difference in orientation between a pixel and the kernel surrounding it, regardless of grains or grain boundaries.

[0100] The KAM for grains in each orientation and for all grains can be measured using the EBSD program, a texture analysis tool. In this case, the average refers to the numerical average of the number of grains. The reference plane for grain measurement is not specifically limited, but may be a cross-section parallel to the rolling plane (ND plane). More specifically, it may be an ND plane between 1 / 8 and 7 / 8 of the steel plate thickness. More specifically, it may be an ND plane between 1 / 4 and 3 / 4 of the steel plate thickness. More specifically, it may be an ND plane at 1 / 2 of the steel plate thickness.

[0101] The area fraction of grains with a KAM value of 0.5 or less may be 77% or more. If there are many grains with a KAM value exceeding 0.5, magnetic deterioration due to residual stress may occur. More specifically, the area fraction of grains with a KAM value of 0.5 or less may be 77% to 90%.

[0102] Average KAM value of all grains (KAM t ) may be 0.63 or less. The average KAM value of all grains (KAM tIf ) is too large, stress-induced magnetism may be degraded. More specifically, the average KAM value of the entire grain (KAM t ) may be 0.40 to 0.60. More specifically, it may be 0.41 to 0.59.

[0103] {100} <001> KAM value of grains having an orientation within 15° from (KAM c ) may be 0.58 or less. {100} <001> KAM value of grains having an orientation within 15° from (KAM c If ) is too large, internal stress can hinder the magnetization process. More specifically, {100} <001> KAM value of grains having an orientation within 15° from (KAM c ) can be 0.38 to 0.55.

[0104] {110} <001> KAM value of grains having an orientation within 15° from (KAM g ) may be 0.55 or less. {110} <001> KAM value of grains having an orientation within 15° from (KAM g If ) is too large, internal stress can interfere with the magnetization process. More specifically, {110} <001> KAM value of grains having an orientation within 15° from (KAM g ) can be 0.35 to 0.53.

[0105] A non-oriented electrical steel sheet according to one embodiment of the present invention may have an average grain size of 50 to 150 μm. If the average grain size is too small, high-frequency iron loss is poor, and if the average grain size is too large, magnetic flux density is poor. More specifically, the average grain size may be 60 to 130 μm.

[0106] The average grain size can be measured by observing the ND plane at 1 / 8 of the total thickness when using EBSD. It is the area-based average grain size used in TSL, and the measurement area can be the average value measured over an area of ​​3mm × 3mm or larger.

[0107] A non-oriented electrical steel sheet according to one embodiment of the present invention may have a resistivity of 58 μΩ·cm or higher. While a higher resistivity is preferable for reducing eddy current losses in high-frequency rotating machines, if it becomes too large, the magnetic flux density may be inferior. In one embodiment of the present invention, the resistivity can be calculated from 13.25 + 11.3 × ([Si] + [Al] + [Mn] / 2). The elements in brackets represent the weight percent of each element, and if the corresponding element is not included, it is calculated as 0.

[0108] As previously stated, in one embodiment of the present invention, ultra-high frequency iron loss can be improved. Specifically, W 10 / 400 and W 10 / 800 The sum of may be 40.0 W / kg or less. More specifically, W 10 / 400 and W 10 / 800 The sum of the values ​​may be 20.0 to 39.0 W / kg.

[0109] 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 10 / 400 ε is the iron loss when a magnetic flux density of 1.0T is induced at a frequency of 400Hz. W 10 / 800 is the iron loss when a magnetic flux density of 1.0T is induced at a frequency of 800Hz.

[0110] In one embodiment of the present invention, the sum of the tensile strength and yield strength may be 1070 MPa or more. In one embodiment of the present invention, it is used as an iron core for a motor with a high rotational speed, and for this purpose, it is necessary to secure appropriate tensile strength and yield strength. More specifically, the sum of the tensile strength and yield strength may be 1080 to 1300 MPa.

[0111]

[0112] 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 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.

[0113] Below, each step is explained in detail.

[0114] First, the slab is hot-rolled.

[0115] 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.

[0116] Specifically, the slab contains Si: 1.5 to 5.0%, Al: 0.1 to 3.0%, Mn: 0.1 to 3.0% by weight, and the remainder is Fe and unavoidable impurities.

[0117] As other additional elements have been explained in the alloy composition of non-oriented electrical steel sheets, redundant explanations are omitted.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] Next, a cold-rolled sheet is manufactured by cold-rolling a hot-rolled steel sheet. 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.

[0122] In one embodiment of the present invention, cold rolling can be performed in a single step without intermediate annealing.

[0123] Next, the cold-rolled sheet is annealed. During the cold-rolled sheet annealing stage, the cracking temperature can be 750°C 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 cold-rolled sheet annealing stage can be 800°C to 1000°C.

[0124] The tensile strength during the cracking stage of the cold-rolled sheet annealing process is 0.1 to 1.0 kgf / mm 2 It may be. In this case, if the tension is too low, workability may be compromised. Conversely, if the tension is too high, magnetic properties may be compromised. More specifically, the tension at the cracking stage is 0.2 to 0.7 kgf / mm 2 It may be. The tension at the cracking stage is the tension at the exit side of the cracking zone, and for a steel plate having a length of at least 3000 m, the tension applied to the steel plate may be averaged as tension per unit area and fall within the aforementioned range. The tension can be controlled in various ways, such as by controlling the tension of the rolls in the equipment.

[0125] Next, the cracked cold-rolled sheet is wound. At this time, the tension applied to the steel sheet is 3.0 to 7.0 kgf / mm 2 By adjusting the tension during the winding stage, the internal stress applied to the final product plate can be controlled, thereby adjusting the KAM values ​​for each grain orientation within the steel plate and ultimately improving both iron loss and strength simultaneously. However, if the tension is too low, control may be difficult from an operational perspective. Conversely, if the tension is too high, the magnetic properties may deteriorate due to internal stress within the plate. More specifically, the tension during the winding stage is 3.3 to 7.0 kgf / mm² 2 The tension at the winding stage is the tension applied to the material when winding the product plate into a coil, and for a steel plate having a length of at least 3000 m, the tension applied to the steel plate can be averaged as tension per unit area and fall within the aforementioned range. The tension can be controlled in various ways, such as by controlling the tension of the roll in the equipment.

[0126] In the winding stage, the maximum deviation of the tension relative to the average value of the tension applied to a steel plate having a length of 3000m or more can be 50% or less. At this time, by reducing the deviation, the deviation of internal stress remaining in the plate can be reduced, thereby reducing the deviation of magnetism.

[0127] The deviation can be calculated as (|average tension value - tension value at a specific location| / average tension value) × 100 (%). Values ​​between || represent absolute values. More specifically, the maximum deviation of the tension may be 50% or less. More specifically, the maximum deviation of the tension may be 1.0 to 45.0%.

[0128] The difference in tension values ​​between the cracking stage and the winding stage is 2.0 to 6.5 kgf / mm 2 It may be. Since the tension value in the winding stage is large, it can be calculated as tension stage winding - cracking stage winding. If the difference in tension values ​​is too small, operation may not be properly performed. If the difference in tension values ​​is too large, magnetism may deteriorate. More specifically, the difference in tension values ​​between the cracking stage and the winding stage is 2.6 to 6.4 kgf / mm 2 It could be.

[0129] After annealing and coiling the cold-rolled sheet, an insulating film can be formed on the steel sheet. 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.

[0130]

[0131] 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.

[0132]

[0133] Examples

[0134] Slabs containing the components and other impurities summarized in Table 1 below were 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 slabs were heated to 1150°C and hot-rolled at a finishing temperature of 850°C to produce hot-rolled sheets. The hot-rolled sheets were annealed at 1100°C for 4 minutes and then pickled. Subsequently, they were cold-rolled to produce sheets with a thickness of 0.25 mm. Cold-rolled sheet annealing was performed at 965°C for 90 seconds. The tension at the exit side of the cold-rolled sheet annealing furnace (tension at the cracking stage exit side) was controlled as shown in Table 1 below, and the tension at the coiling stage was controlled as shown in Table 1 below. The tension at each stage refers to the average tension measured during operation for a steel sheet with a length of 3000 m. The maximum deviation also summarizes the degree of deviation from the average tension over a length of 3000 m.

[0135] Regarding manufactured steel plates, KAM c , KAM g , KAM t The KAM values ​​were measured and summarized in Table 2 below. In addition, the area fraction of grains with a KAM of 0.5 or less was measured and summarized in Table 2. The KAM values ​​were measured using EBSD, a conventional texture measurement tool, on samples of the final product plate, and the reference plane was the ND plane at half the thickness of the steel plate.

[0136] Iron loss was measured using an Epstein Tester at a magnetization force of 1.0 T, 400 Hz, and 800 Hz, respectively. Yield strength and tensile strength were measured by conventional methods using specimens of JIS No. 13 as defined by ASTM standards.

[0137] Classification SiAlMn Crack Stage Exit Tension (kgf / mm²) 2 ) Average tension at winding stage (kgf / mm²) 2 )Tension difference (kgf / mm 2)Tension Maximum Deviation(%) 13.7 0 1.2 10.5 8 0.3 3.5 3.2 17.1 2 3.3 6 1.5 2 1.2 3 0.3 6.4 6.1 4.7 3 3.5 1 1.3 6 0.8 5 0.5 5.1 4.6 2.0 4 3.6 0 2.0 1 1.1 3 0.4 6.8 6.4 16.2 5 3.5 7 1.3 3 1.2 5 0.5 4.1 3.6 7.3 6 3.4 3 2.1 10.79 0.54.23.731.073.001.721.250.76.45.76.383.081.671.330.67.06.411.492.891.891.690.26.26.019.4103.661.660.870.55.24.77.7113.711.451.690.63.32.730.312 3.111.711.530.65.14.527.5133.501.631.350.25.35.17.5143.401.900.670.54.54.04.4154.101.251.510.23.43.241.2163.771.621.130.76.35.620.6172.802.110.74 0.75.24.521.2183.441.351.030.45.85.412.1193.401.951.040.58.78.29.2202.941.760.730.67.36.712.3213.810.991.450.66.66.016.7223.351.490.830.36.05.75.0

[0138] Classification KAM t KAM c KAM gKAM 0.5 or less Percentage (%) 10.58 0.55 0.4478 0.852 0.52 0.50 0.4179 0.883 0.52 0.51 0.4083 0.884 0.55 0.50 0.3682 0.785 0.50 0.48 0.4080 0.886 0.59 0.52 0.5085 0.867 0.58 0.49 0.4582 0.818 0.54 0.44 0.4085 0.789 0.49 0.47 0.3584 0.841 0.47 0.42 0.4285 0.8911 0.47 0.41 0.4080 0.861 20.540.470.36800.77130.490.460.37780.85140.450.430.38850.90150.410.400.31780.87160.510.500.38850.86170.410.360.35820.87180.570.510.50770.89190.660.650.62730.96200.650.600.60740.92210.470.410.35820.81220.490.430.41850.86

[0139] Classification YP(MPa)TS(MPa)W 10 / 400 W 10 / 800 (W / kg)(W / kg)14865869.626.6 Invention Example 247762910.526.8 Invention Example 35085919.826.5 Invention Example 453559910.627.9 Invention Example 553458610.326.5 Invention Example 652058110.125.8 Invention Example 752260910.427.8 Invention Example 84976169.525.6 Invention Example 94835909.725.7 Invention Example 1048459410.626.6 Invention Example 1148563211.027.2 Invention Example 1 254063710.625.8 Invention Example 1353059310.127.7 Invention Example 1450359310.126.2 Invention Example 155345749.825.7 Invention Example 1647763610.426.2 Invention Example 1753362611.027.0 Invention Example 1852558410.226.8 Invention Example 1949862612.428.2 Comparative Example 2048259812.129.1 Comparative Example 214855899.827.8 Invention Example 2249061010.027.8 Invention Example

[0140] As shown in Tables 1 to 3, when the steel composition is appropriately controlled and the tension is appropriately controlled during winding after annealing of the cold-rolled sheet, the KAM value for each orientation is appropriately controlled and satisfies Equation 1, confirming that both iron loss and strength are excellent.

[0141] On the other hand, if the tension is not properly controlled during winding, the KAM values ​​for each orientation are not properly obtained, and it can be confirmed that the iron loss is inferior.

[0142]

[0143] 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: 0.1 to 3.0%, Mn: 0.1 to 3.0%, and the remainder being Fe and unavoidable impurities, and Non-oriented electrical steel sheet satisfying the following Equation 1. [Equation 1] (WHY c +WHAT g ) / 2KAM t ≤ 0.90 (KAM in Equation 1 c is {100} <001> It refers to the KAM value of grains having an orientation within 15° from, and KAM g is {110} <001> It refers to the KAM value of grains having an orientation within 15° from, and KAM t represents the average KAM value of the entire grain.) 2. In Paragraph 1, Non-oriented electrical steel sheet having an area fraction of grains with a KAM value of 0.5 or less of 77% or more.

3. In Paragraph 1, Average KAM value of all grains (KAM t Non-oriented electrical steel sheet with ) 0.63 or less.

4. 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.

5. 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.

6. 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.

7. 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.

8. A step of manufacturing a hot-rolled steel sheet by hot-rolling a slab containing, by weight%, Si: 1.5 to 5.0%, Al: 0.1 to 3.0%, Mn: 0.1 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 steel plate and A cold-rolled sheet annealing step for annealing the above cold-rolled sheet; comprising, The above cold-rolled sheet annealing step includes a step of cracking the cold-rolled sheet and a step of winding the cracked cold-rolled sheet, and The tension applied to the steel plate in the above winding step is 3 to 7 kgf / mm 2 Method for manufacturing non-oriented electrical steel sheets.

9. 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, 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.

10. In Paragraph 8, 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.

11. In Paragraph 8, 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.

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: 0.0050 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.

13. In Paragraph 8, A method for manufacturing a non-oriented electrical steel sheet in which the maximum deviation of the tension relative to the average value of the tension applied to a steel sheet of 3000m or more in the above-mentioned winding step is 50% or less.

14. In Paragraph 8, The difference in tension values ​​during the cracking and winding steps is 2.0 to 6.5 kgf / mm 2 Method for manufacturing non-oriented electrical steel sheets.