Non-oriented electrical steel sheet and manufacturing method therefor

Abstract

A non-oriented electrical steel sheet according to one embodiment of the present invention comprises, by wt%, 1.5-5.0% of Si, 0.1-3.0% of Al, 0.1-3.0% of Mn, 0.0001-0.002% of Zr and 0.0005-0.003% of Ti, and the balance of Fe and inevitable impurities, wherein the ratio of the number of ZrS and TiS to the number of MnS is 1-5.

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, which simultaneously improves strength and ultra-high frequency iron loss by controlling the generation of sulfides by controlling the tension applied to the steel sheet during hot-rolled sheet annealing along with the addition of Zr and Ti.

[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] Meanwhile, the strength of steel sheets tends to increase as the alloy content increases. However, since elements such as Si and Al are highly brittle and have varying effects on strength, the component content and ratio must be optimized to ensure high strength characteristics.

[0008] 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 simultaneously improves strength and ultra-high frequency iron loss by controlling the generation of sulfides by controlling the tension applied to the steel sheet during hot-rolled sheet annealing along with the addition of Zr and Ti.

[0009] 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%, Zr: 0.0001 to 0.002%, and Ti: 0.0005 to 0.003%, the remainder being Fe and unavoidable impurities, and the ratio of the number of ZrS and TiS to the number of MnS is 1 to 5.

[0010] A non-oriented electrical steel sheet according to one embodiment of the present invention can satisfy the following Equation 1.

[0011] [Equation 1]

[0012] 0.2 ≤ [Zr] / [Ti] ≤ 1.0

[0013] (In Equation 1, [Zr] and [Ti] represent the content (weight%) of Zr and Ti, respectively.)

[0014] The number density of ZrS and TiS is 5 particles / ㎛ 2 It could be more than that.

[0015] 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, and N: 0.005 wt% or less.

[0016] 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.

[0017] 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.

[0018] 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, Te: 0.01 wt% or less, and Mg: 0.0050 wt% or less.

[0019] 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 comprising, 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.

[0020] Tensile force during the annealing stage of hot-rolled plates is 1.3 kgf / mm 2 Up to 3 kgf / mm 2 It is granted as.

[0021] 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, and N: 0.005 wt% or less.

[0022] 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.

[0023] 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.

[0024] 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, Te: 0.01 wt% or less, and Mg: 0.0050 wt% or less.

[0025] The time spent at 800°C or higher during the hot-rolled sheet annealing and cold-rolled sheet annealing stages may be 100 to 300 seconds.

[0026] A non-oriented electrical steel sheet according to one embodiment of the present invention simultaneously improves strength 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.

[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 "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.

[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%, Zr: 0.0001 to 0.002% and Ti: 0.0005 to 0.003%, and the remainder is Fe and unavoidable impurities.

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

[0037] Si: 1.50 to 5.00 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 the formation of surface oxide layers 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 2.50 to 4.50 weight%. Even more specifically, it may be included in an amount of 3.30 to 4.10 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 2.50 weight% of Al. More specifically, it may contain 1.00 to 2.30 weight%. More specifically, it may contain 1.20 to 2.20 weight%.

[0041] Mn: 0.10 to 3.00 wt%

[0042] 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 0.20 to 2.50 weight%. Even more specifically, it may be included in an amount of 0.50 to 2.00 weight%.

[0043] Zr: 0.0001 to 0.0020 wt%

[0044] Zirconium (Zr) plays a role in forming sulfides by combining with Ti or Cu. If too little Zr is added, Ti and Cu precipitate independently as fine carbonitrides and sulfides, and thus cannot play a role in forming Zr complex sulfides. If too much Zr is added, the amount of Zr sulfides increases, which actually degrades the magnetic properties. Therefore, Zr may be included in an amount of 0.0001 to 0.0020 weight%. More specifically, it may be included in an amount of 0.0005 to 0.0018 weight%.

[0045] Ti: 0.0005 to 0.0030 wt%

[0046] Titanium (Ti) is an element that forms carbonitrides, but it also plays a role in precipitating sulfides by combining with Zr. If too little Ti is added, a problem may arise where complex sulfides with Zr are not formed properly. If too much Ti is added, a problem may arise where the amount of fine Ti(C,N) precipitating alone increases, thereby degrading magnetic properties. Therefore, it may contain 0.0005 to 0.0030 weight% of Ti. More specifically, it may contain 0.0007 to 0.0028 weight%. Even more specifically, it may contain 0.0010 to 0.0025 weight%.

[0047] A non-oriented electrical steel sheet according to one embodiment of the present invention can satisfy the following Equation 1.

[0048] [Equation 1]

[0049] 0.2 ≤ [Zr] / [Ti] ≤ 1.0

[0050] (In Equation 1, [Zr] and [Ti] represent the content (weight%) of Zr and Ti, respectively.)

[0051] The value of Equation 1 implies that the ratio of Zr to Ti must be within an appropriate range to form complex sulfides. Ti may precipitate alone as fine carbonitrides. If the value of Equation 1 is too large, the amount of Zr sulfide increases, which may actually degrade the magnetic properties. Therefore, the value of Equation 1 can be 0.20 to 1.00. More specifically, it can be 0.38 to 0.95.

[0052] 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, and N: 0.005 wt% or less.

[0053] P: 0.1 wt% or less

[0054] 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.

[0055] C: 0.005 wt% or less

[0056] 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.

[0057] S: 0.005 wt% or less

[0058] 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.

[0059] N: 0.005 wt% or less

[0060] 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.

[0061]

[0062] 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.

[0063] Sn and Sb

[0064] 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.

[0065] Bi, Pb, Ge, and As

[0066] 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.

[0067]

[0068] According to one embodiment of the present invention, one or more of non-oriented 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 may be further included.

[0069] Cu: 0.005 to 0.200 wt%

[0070] 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.

[0071] Cr: 0.01 to 0.50 wt%

[0072] 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.

[0073] Ni: 0.05 wt% or less

[0074] 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.

[0075] Zn: 0.01 wt% or less

[0076] 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%.

[0077] Co: 0.05 wt% or less

[0078] 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.

[0079]

[0080] 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, Te: 0.0100 wt% or less, and Mg: 0.0050 wt% or less.

[0081] Mo: 0.030 wt% or less

[0082] 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%.

[0083] B: 0.0050 wt% or less

[0084] 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%.

[0085] V: 0.0050 wt% or less

[0086] 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%.

[0087] Ca: 0.0050 wt% or less

[0088] 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.

[0089] Nb: 0.0050 wt% or less

[0090] 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.

[0091] Te: 0.0100 wt% or less

[0092] 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.

[0093] Mg: 0.0050 wt% or less

[0094] 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%.

[0095]

[0096] 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.

[0097] A non-oriented electrical steel sheet according to one embodiment of the present invention has a ratio of the number of ZrS and TiS to the number of MnS of 1.00 to 5.00. As such, a higher ratio of ZrS and TiS to MnS is advantageous in that it can suppress the formation of carbonitrides containing fine Ti and sulfides containing Mn. Conversely, if the ratio of ZrS and TiS is too high, problems may arise regarding grain growth and inhibition of magnetic domain movement. More specifically, the ratio of ZrS and TiS to the number of MnS may be 1.10 to 3.50. The number of MnS, ZrS, and TiS can be measured using conventional precipitate analysis methods, such as TEM using replica specimens or electrolytic extraction. The measurement standard may be a cross-section including the thickness direction. More specifically, it may be a plane perpendicular to the TD direction. To reduce errors due to resolution, sulfides with a grain size of 5 nm or more are recognized as the number. The particle size is determined by the diameter of a virtual circle having an area equal to the occupied area of ​​the sulfide. For complex sulfides containing two or more of Mn, Zr, and Ti, the count is calculated by duplication with each individual.

[0098] The number density of ZrS and TiS is 5 particles / ㎛ 2This may be the case. As previously mentioned, ZrS and TiS are advantageous for magnetism by suppressing the formation of fine Ti carbonitride and Mn sulfide. More specifically, the number density of ZrS and TiS is 5 to 30 atoms / µm 2 It may be. More specifically, the density is 5 to 25 particles / ㎛ 2 It could be.

[0099] As described above, in one embodiment of the present invention, strength and magnetism can be simultaneously improved by appropriately forming sulfides. Specifically, the non-oriented electrical steel sheet according to one embodiment of the present invention may have a yield strength of 400 MPa or more. More specifically, it may be 400 to 600 MPa. Even more specifically, it may be 480 to 550 MPa. The yield strength can be measured using a conventional tensile test specified in ASTM.

[0100] A non-oriented electrical steel sheet according to one embodiment of the present invention may have a tensile strength of 500 MPa or more. More specifically, it may be 550 to 700 MPa. More specifically, it may be 570 to 650 MPa. Tensile strength can be measured using a conventional tensile test specified in ASTM.

[0101] The iron loss (W10 / 400) may be 11.00 W / Kg or less, and the iron loss (W10 / 800) may be 30.00 W / Kg or less. The thickness standard may be 0.30 mm or less. More specifically, the iron loss (W10 / 400) may be 9.00 to 10.85 W / kg. Also, the iron loss (W10 / 800) may be 25.00 to 29.00 W / kg. The iron loss (W10 / 400) is the iron loss when a magnetic flux density of 1.0 T is induced at a frequency of 400 Hz. The iron loss (W10 / 800) is the iron loss when a magnetic flux density of 1.0 T is induced at a frequency of 800 Hz. Iron loss (W10 / 400) and iron loss (W10 / 800) can be measured using a single sheet tester for the rolling direction and the rolling vertical direction, and the average value can be determined.

[0102]

[0103] 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.

[0104] Below, each step is explained in detail.

[0105] First, the slab is hot-rolled.

[0106] 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.

[0107] Specifically, the slab comprises, in weight percent, Si: 1.5 to 5.0%, Al: 0.1 to 3.0%, Mn: 0.1 to 3.0%, Zr: 0.0001 to 0.002% and Ti: 0.0005 to 0.003%, and the remainder is Fe and unavoidable impurities.

[0108] As other additional elements have been explained in the alloy composition of non-oriented electrical steel sheets, redundant explanations are omitted.

[0109] 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.

[0110] 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.

[0111] 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, the recrystallization structure is not formed or grows finely, resulting in a small increase in magnetic flux density; if the annealing temperature is too high, the 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.

[0112] During the annealing stage of the hot-rolled plate, the tensile strength is 1.30 kgf / mm 2 Up to 3.00 kgf / mm 2 It can be applied as follows. If the tensile strength is too low, not only is there a problem with operational stability, but the formation of Zr-containing sulfides is also inhibited. If the tensile strength is too high, there may be a problem where the number of Zr-containing sulfides increases excessively. More specifically, the tensile strength during annealing is 1.40 kgf / mm 2 Up to 2.90 kgf / mm 2 It can be granted as.

[0113] 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 total reduction rate may be 75 to 90%. The total reduction rate can be calculated from the thickness of the steel sheet before cold rolling and the thickness after cold rolling. If the reduction rate is too low, additional rolling is required to obtain an appropriate final thickness, and productivity may be inferior. If the reduction rate is too high, a texture unfavorable to magnetism is formed, and iron loss may be inferior. More specifically, in the step of producing the cold-rolled sheet, the total reduction rate may be 77 to 88%.

[0114] After cold rolling, the thickness may be 0.10 to 0.30 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 0.25 mm.

[0115] In one embodiment of the present invention, cold rolling can be performed in a single step without intermediate annealing.

[0116] In the annealing stage of the cold-rolled sheet, the cracking temperature may 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 annealing stage of the cold-rolled sheet may be 800°C to 1000°C.

[0117] In the hot-rolled sheet annealing and cold-rolled sheet annealing stages, the time spent at 800°C or higher may be 100 to 300 seconds. If the time spent at 800°C or higher is too short, there may be a problem in that sulfides containing Zr are not sufficiently formed. If the time spent at 800°C or higher is too long, the number of sulfides containing Zr increases too much, which may result in a problem of inferior magnetic properties. More specifically, in the hot-rolled sheet annealing and cold-rolled sheet annealing stages, the time spent at 800°C or higher may be 105 to 290 seconds.

[0118] 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.

[0119]

[0120] 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.

[0121]

[0122] Examples

[0123] 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, and N 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. The hot-rolled hot-rolled plate was annealed at 1100°C and then pickled. Subsequently, it was cold-rolled to produce a thickness of 0.25 mm. During cold rolling, the annealing of the cold-rolled plate was carried out at 965°C.

[0124] The number of MnS, ZrS, and TiS was measured using TEM on carbon replica specimens.

[0125] Iron loss was measured using a Single Sheet Tester at a magnetization force of 1.0T at 400Hz and at a magnetization force of 1.0T at 800Hz.

[0126] In addition, yield strength and tensile strength were measured using standard tensile tests according to ASTM standards.

[0127] Classification (Wt%) SiAlMnZrTiZr / Ti 13.97 1.54 1.72 0.000 20.000 70.29 23.77 1.54 1.27 0.001 70.002 10.81 33.35 2.10 0.82 0.001 60.002 50.64 43.65 1.75 1.33 0.001 60.002 80.57 53.4 11.40 1.01 0.000 80.002 50.32 63.90 1.65 0.74 0.001 70.001 80.94 73 .981.651.430.00100.00270.3783.321.601.790.00150.00280.5493.752.091.200.00150.00160.94103.311.471.740.00020.00090.22113.531.591.690.00100.00140.71124.041.681.550.00060.00170.35133.262.121.100.00110.0 0280.39143.521.260.550.00130.00200.65153.841.450.530.00120.00130.92163.441.670.580.00070.00300.23173.961.410.830.00150.00111.36184.021.571.470.00030.00280.11193.381.701.470.00080.00061.33203.971.411 .180.00200.00102.00213.811.811.620.00170.00180.94223.351.430.770.00090.00160.56233.412.030.630.00200.00230.87243.771.890.550.00120.00230.52253.291.980.840.00090.00130.69263.821.811.130.00050.00160.31

[0128] Classification Hot-rolled Plate Annealing Tension (kgf / mm 2 Holding time above 800℃ (s) MnS density (pieces / ㎛) 2 )ZrS, TiS Density (pieces / ㎛) 2)(ZrS + TiS) / MnS12.1412910191.9022.282839202.2231.662716152.5042.8823310111.1051.7819015211.4061.7927110131.3072.831376142.3381.742229242.6792.5310815191.27102.881915142.80112.5419310111.10121.85163351.67131.4018682 43.00142.68287351.67151.591707202.86161.701465122.40171.801611630.19182.962582020.10192.62201540.80202.18200830.38212.791827162.29222.29143372.33230.861801010.10244.40289430.75251.801418202.50262.35240691.50

[0129] Classification YP(MPa) TS(MPa) W10 / 400(W / kg) W10 / 800(W / kg) 15 20 6 229.8 3 26.04 Invention Example 2 50 56 06 9.5 9 25.55 Invention Example 3 50 26 129.8 9 26.58 Invention Example 4 51 36 26 9.7 5 26.48 Invention Example 5 50 96 239.9 25.95 Invention Example 6 52 66 16 10.2 8 26.45 Invention Example 7 52 16 09 9.6 5 25.87 Invention Example 850258810.2028.52 Invention Example 948959510.2926.93 Invention Example 1051262210.0428.11 Invention Example 114875899.6226.57 Invention Example 125066039.7725.86 Invention Example 1350359910.4227.74 Invention Example 1451359 510.1726.34 Invention Example 154995849.8726.02 Invention Example 1648658810.1527.89 Invention Example 1750759611.3831.00 Comparative Example 1852160811.8631.69 Comparative Example 1949060712.7233.85 Comparative Example 2050159312.753 2.72 Comparative Example 21 4986149.8927.99 Invention Example 22 48459410.0627.30 Invention Example 23 49758011.7331.20 Comparative Example 24 50960612.3732.64 Comparative Example 25 48758810.8326.35 Invention Example 26 50461910.4827.07 Invention Example

[0130] As shown in Tables 1 to 3, when the steel composition is appropriately controlled and the tension is appropriately controlled during the annealing of the hot-rolled plate, it can be confirmed that ZrS and TiS are produced in large amounts compared to MnS, and that magnetism and strength are excellent at the same time.

[0131] On the other hand, if Ti and Zr are not properly included or if the tension is not properly controlled during the annealing of the hot-rolled plate, it can be confirmed that ZrS and TiS are formed in smaller amounts compared to MnS, and the high-frequency iron loss is inferior.

[0132]

[0133] 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%, comprising Si: 1.5 to 5.0%, Al: 0.1 to 3.0%, Mn: 0.1 to 3.0%, Zr: 0.0001 to 0.002% and Ti: 0.0005 to 0.003%, and the remainder comprising Fe and unavoidable impurities, Non-oriented electrical steel sheet having a ratio of the number of ZrS and TiS to the number of MnS of 1 to 5.

2. In Paragraph 1, Non-oriented electrical steel sheet satisfying the following Equation 1. [Equation 1] 0.2 ≤ [Zr] / [Ti] ≤ 1.0 (In Equation 1, [Zr] and [Ti] represent the content (weight%) of Zr and Ti, respectively.) 3. In Paragraph 1, The number density of ZrS and TiS is 5 particles / ㎛ 2 Non-oriented electrical steel sheet of the above type.

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, 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, Te: 0.01 wt% or less, and Mg: 0.0050 wt% or less.