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%, 1.5-4.5% of Si, 0.1-2.0% of Al, 0.1-2.0% of Mn, and the balance of Fe and inevitable impurities, and the ratio of the number (PS) of precipitates per unit area in the surface portion from the surface of the steel sheet to the interior of 1 / 20 of the total thickness to the number (PI) of precipitates per unit area in the central portion from more than 1 / 20 to 1 / 2 of the total thickness is 1.2 or less.

Description

Non-oriented electrical steel sheet and manufacturing method thereof

[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 enhances magnetism by controlling the dew point and tension during an annealing process prior to cold rolling to form appropriate precipitates according to the steel sheet thickness.

[0002] Non-oriented electrical steel is primarily used in motors that convert electrical energy into mechanical energy. This process requires excellent magnetic properties to achieve high efficiency. In particular, with the recent rise in eco-friendly vehicles powered by motors instead of internal combustion engines, demand for non-oriented electrical steel, used as a drive motor core material, is increasing. This demand is driven by the need for non-oriented electrical steel with both superior magnetic properties and strength.

[0003] The magnetic properties of non-oriented electrical steel are primarily assessed by core loss and magnetic flux density. Core loss refers to the energy loss occurring at a specific magnetic flux density and frequency, while magnetic flux density represents the degree of magnetization achieved under a specific magnetic field. Lower core loss allows for more energy-efficient motors under similar conditions, while higher flux density allows for smaller motors and reduced copper loss. Therefore, non-oriented electrical steel with low core loss and high flux density can be used to create drive motors with superior efficiency and torque, thereby improving the driving range and power output of eco-friendly vehicles.

[0004] The characteristics of non-oriented electrical steel sheets that must be considered also vary depending on the operating conditions of the motor. The general standard for evaluating the characteristics of non-oriented electrical steel sheets used in motors is widely used as W15 / 50, which is the iron loss when a 1.5T magnetic field is applied at a commercial frequency of 50Hz. However, in the case of non-oriented electrical steel sheets with a thickness of 0.35mm or less used in eco-friendly vehicle drive motors, magnetic characteristics are often important at low fields of 1.0T or less and high frequencies of 400Hz or higher, so W 10 / 400 The properties of non-oriented electrical steel sheets are often evaluated by iron loss.

[0005] A common method for improving the magnetic properties of non-oriented electrical steel is to add alloying elements such as Si, Al, and Mn. These alloying elements increase the steel's resistivity, reducing eddy current losses and lowering overall core loss. Furthermore, these alloying elements act as substitutional elements in the steel, strengthening it and increasing its strength. However, increasing the amount of Si, Al, and Mn alloying elements results in lower magnetic flux density and increased brittleness. Beyond a certain level, cold rolling becomes impossible, making commercial production impossible. In particular, thinner electrical steel sheets exhibit superior high-frequency core loss, but the resulting brittleness can be a critical issue. The maximum combined Si, Al, and Mn content for commercial production is known to be approximately 4.5 wt%. Optimizing the content of trace elements beyond this level can produce premium non-oriented electrical steel with superior magnetism and strength.

[0006] Methods for improving magnetic properties by controlling the grain structure of non-oriented electrical steel sheets are also widely used. Texture control is a method for promoting the development of crystal orientations favorable for magnetism and suppressing crystal orientations unfavorable to magnetism during the process of deforming, recovering, and recrystallizing a material through various methods. It is known that crystal orientations with {001} planes are favorable for magnetism, while crystal orientations with {111} planes are unfavorable. Many methods are known for selectively developing several crystal orientations by varying the manufacturing conditions of non-oriented electrical steel sheets.

[0007] When non-oriented electrical steel sheets are produced through a double-rolling and double-annealing process, the {111} / ND crystal orientation, which is unfavorable to magnetism, can be suppressed, and crystal orientations such as {001} / ND, which are favorable to magnetism, can be strengthened. The above process is well known to be excellent in improving the texture, but compared to the existing single-rolling method, the manufacturing cost increases somewhat due to the addition of cold rolling and intermediate annealing processes, and the surface oxide layer formation behavior is unstable during the annealing and cold rolling processes, so there is a problem that the magnetic properties deteriorate due to additional formation of precipitates on the surface layer or uneven formation of the surface oxide layer, and therefore, there were limitations in applying it to actual mass production processes.

[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 enhances magnetism by controlling the dew point and tension during an annealing process prior to cold rolling to form appropriate precipitates according to the steel sheet thickness.

[0009] A non-oriented electrical steel sheet according to one embodiment of the present invention contains Si: 1.5 to 4.5% by weight, Al: 0.1 to 2.0%, Mn: 0.1 to 2.0%, and the remainder includes Fe and inevitable impurities.

[0010] The number of precipitates per unit area (P) in the center exceeding 1 / 20 to 1 / 2 of the total thickness I ) The number of precipitates per unit area (P) on the surface of the steel plate up to 1 / 20 of the total thickness S ) is less than 1.2.

[0011] It includes an oxide layer existing from the surface to the inside, and the thickness of the oxide layer may be 5 to 300 nm.

[0012] The maximum length of the oxide layer break portion in which the thickness of the oxide layer is 5 nm or less in the cross-section including the rolling direction of the steel plate may be 500 nm or less in the rolling direction.

[0013] The length of the oxide layer break portion having an oxide layer thickness of 5 nm or less in a cross-section including the rolling direction of the steel plate may be 0.01 to 1000 nm per 10 um in the rolling direction.

[0014] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include at least one of P: 0.1 wt% or less (excluding 0%), C: 0.005 wt% or less (excluding 0%), S: 0.005 wt% or less (excluding 0%), Ti: 0.005 wt% or less (excluding 0%), and N: 0.005 wt% or less (excluding 0%).

[0015] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include 0.005 to 0.200 wt% of each or a combined amount of one or more of Sn, Sb, Bi, Pb, Ge, and As.

[0016] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include at least one 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%).

[0017] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include at least one of Mo: 0.03 wt% or less (excluding 0%), B: 0.0050 wt% or less (excluding 0%), V: 0.0050 wt% or less (excluding 0%), Ca: 0.0050 wt% or less (excluding 0%), Nb: 0.0050 wt% or less (excluding 0%), Zr: 0.005 wt% or less (excluding 0%), Te: 0.01 wt% or less (excluding 0%), and Mg: 0.0050 wt% or less (excluding 0%).

[0018] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention comprises the steps of: hot-rolling a slab containing, by weight %, Si: 1.5 to 4.5%, Al: 0.1 to 2.0%, Mn: 0.1 to 2.0%, and the remainder including Fe and inevitable impurities, to manufacture a hot-rolled steel sheet; and hot-rolling the steel sheet in an atmosphere containing a dew point of -50°C to -10°C, 3 to 30 volume % of hydrogen, and 0.2 kgf / mm 2 3.0kgf / mm 2 It includes a preliminary annealing step before cold rolling in which tension is applied and annealed; a step of cold rolling the annealed steel sheet to manufacture a cold rolled sheet; and a cold rolled sheet annealing step in which the cold rolled sheet is annealed.

[0019] The slab may further include at least one of P: 0.1 wt% or less (excluding 0%), C: 0.005 wt% or less (excluding 0%), S: 0.005 wt% or less (excluding 0%), Ti: 0.005 wt% or less (excluding 0%), and N: 0.005 wt% or less (excluding 0%).

[0020] The slab may further contain 0.005 to 0.200 wt% of each or a combination of one or more of Sn, Sb, Bi, Pb, Ge and As.

[0021] The slab may further include at least one of Cu: 0.005 to 0.2 wt%, Cr: 0.01 to 0.5 wt%, Ni: 0.05 wt% or less (excluding 0%), and Zn: 0.01 wt% or less (excluding 0%).

[0022] The slab may further include at least one of Mo: 0.03 wt% or less (excluding 0%), B: 0.0050 wt% or less (excluding 0%), V: 0.0050 wt% or less (excluding 0%), Ca: 0.0050 wt% or less (excluding 0%), Nb: 0.0050 wt% or less (excluding 0%), Zr: 0.005 wt% or less (excluding 0%), Te: 0.01 wt% or less (excluding 0%), Co: 0.05 wt% or less (excluding 0%), and Mg: 0.0050 wt% or less (excluding 0%).

[0023] After manufacturing a hot-rolled steel sheet, subsequent steps can be performed while the scale remaining on the hot-rolled steel sheet remains.

[0024] A step of pickling and preliminary cold rolling of the hot-rolled sheet may be further included before the annealing step prior to cold rolling.

[0025] The reduction ratio in the preliminary cold rolling stage can be 30 to 80%.

[0026] The cracking temperature in the annealing step before cold rolling is 800 to 1100°C, and the annealing time can be 1 to 30 minutes.

[0027] In the process of manufacturing cold rolled sheets, the reduction ratio can be 40 to 85%.

[0028] The cold rolled sheet annealing step can be performed at a soaking temperature of 850 to 1100°C in an atmosphere with a dew point of 0°C or lower.

[0029]

[0030] A non-oriented electrical steel sheet according to one embodiment of the present invention has further improved magnetic properties without causing surface deterioration.

[0031] Ultimately, the non-oriented electrical steel sheet according to one embodiment of the present invention contributes to the manufacture of eco-friendly automobile motors, high-efficiency home appliance motors, and super-premium-class electric motors.

[0032] Figure 1 is a drawing schematically illustrating a cross-section of a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0033] FIG. 2 is a drawing schematically illustrating a cut portion in a cross-section of a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0034] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0035] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0036] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0037] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0038] In one embodiment of the present invention, the inclusion of additional elements means including the remaining iron (Fe) in an amount equivalent to the additional amount of the additional elements.

[0039] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0040] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0041]

[0042] A non-oriented electrical steel sheet according to one embodiment of the present invention contains, in wt%, Si: 1.5 to 4.5%, Al: 0.1 to 2.0%, Mn: 0.1 to 2.0%, and the remainder includes Fe and unavoidable impurities.

[0043] Below, the reasons for the limitation of the components of non-oriented electrical steel sheets are explained.

[0044]

[0045] Si: 1.5 to 4.5 wt%

[0046] Silicon (Si) increases the resistivity of the material, thereby reducing iron loss, and enhances strength through solid solution strengthening. If too little Si is added, the iron loss and strength improvement effects may be insufficient. If too much Si is added, the material becomes brittle, leading to a sharp decline in rolling productivity and the formation of a surface oxide layer and oxides that are detrimental to magnetism. Therefore, Si may be included in an amount of 1.5 to 4.5 wt%. More specifically, it may be included in an amount of 2.0 to 4.3 wt%. Even more specifically, it may be included in an amount of 2.5 to 4.2 wt%.

[0047]

[0048] Al: 0.1 to 2.0 wt%

[0049] Aluminum (Al) increases the resistivity of the material, thereby reducing iron loss, and enhances strength through solid solution strengthening. If too little Al is added, fine nitrides may form, making it difficult to achieve the effect of improving magnetism. If too much Al is added, excessive nitrides may form, deteriorating magnetism and causing problems in all processes, such as steelmaking and continuous casting, which can significantly reduce productivity. Therefore, Al may be included in an amount of 0.1 to 2.0 wt%. More specifically, it may be included in an amount of 0.2 to 1.6 wt%. Even more specifically, it may be included in an amount of 0.3 to 1.5 wt%.

[0050]

[0051] Mn: 0.1 to 2.0 wt%

[0052] Manganese (Mn) improves iron loss by increasing the resistivity of the material and plays a role in forming sulfides. If too little Mn is added, fine sulfides are formed, causing magnetic deterioration, and if too much Mn is added, fine MnS is excessively precipitated and promotes the formation of {111} texture, which is unfavorable for magnetism, resulting in a rapid decrease in magnetic flux density. Therefore, Mn may be included in an amount of 0.1 to 2.0 wt%. More specifically, it may be included in an amount of 0.2 to 1.6 wt%. More specifically, it may be included in an amount of 0.3 to 1.5 wt%.

[0053]

[0054] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include at least one of P: 0.1 wt% or less (excluding 0%), C: 0.005 wt% or less (excluding 0%), S: 0.005 wt% or less (excluding 0%), Ti: 0.005 wt% or less (excluding 0%), and N: 0.005 wt% or less (excluding 0%).

[0055] P: 0.1 wt% or less

[0056] Phosphorus (P) is a grain boundary segregation element that can improve magnetic flux density, but if added in too large a quantity, it increases the brittleness of the steel plate, resulting in poor weldability. More specifically, P may be included in an amount of 0.0001 to 0.0500 wt%.

[0057] C: 0.005 wt% or less

[0058] Carbon (C) can cause magnetic aging and combine with other impurity elements to form carbides, thereby hindering grain boundary or domain wall movement and deteriorating magnetic properties. More specifically, C can be included in an amount of 0.0001 to 0.003 wt%.

[0059] S: 0.005 wt% or less

[0060] Sulfur (S) can form fine precipitates, MnS and CuS, which can deteriorate magnetic properties and hot workability. More specifically, S can be included in an amount of 0.0001 to 0.0030 wt%.

[0061] Ti: 0.005 wt% or less

[0062] Titanium (Ti) has a strong tendency to form precipitates within the steel, and can deteriorate iron loss by forming fine carbides, nitrides, or sulfides within the parent material, thereby inhibiting grain growth and domain wall migration. More specifically, it can contain 0.0001 to 0.003 wt% of Ti.

[0063] N: 0.005 wt% or less

[0064] Nitrogen (N) not only forms fine AlN precipitates within the base material, but also combines with other impurities to form fine precipitates, thereby inhibiting grain growth and domain wall migration, thereby worsening iron loss. More specifically, N may be included in an amount of 0.0001 to 0.0030 wt%.

[0065]

[0066] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include 0.005 to 0.200 wt% of each or a combined amount of one or more of Sn, Sb, Bi, Pb, Ge, and As.

[0067] Sn and Sb

[0068] Tin (Sn) and antimony (Sb) play a role in suppressing the development of {111} orientation, which segregates at the grain boundaries during the initial stage of final recrystallization annealing and worsens magnetism. If too much Sn and Sb are added, the recovery and growth of coarse stretched band structures may be hindered and the surface quality may be deteriorated. Therefore, at least one of Sn and Sb may be further added within the above-mentioned range. More specifically, Sn may be included in an amount of 0.005 to 0.200 wt% or Sb may be included in an amount of 0.005 to 0.200 wt%.

[0069] Bi, Pb, Ge, and As

[0070] When added, bismuth (Bi), lead (Pb), germanium (Ge) and arsenic (As) segregate at grain boundaries, thereby relieving stress concentration at grain boundaries during cold rolling, and thus reducing stress concentration in the subsequent recrystallization annealing process. <111> / ND By suppressing the recrystallization of the grains, the magnetic flux density is improved. If these are added appropriately, the aforementioned effects can be additionally obtained. However, if they are included in excessive amounts, segregation may occur in large quantities, inhibiting grain growth and lowering the magnetic flux density and iron loss.

[0071]

[0072] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include at least one 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%).

[0073] Cu: 0.005 to 0.200 wt%

[0074] Copper (Cu) forms sulfides with manganese (Mn). If too little Cu is added, fine precipitation of (Cu · Mn)S may occur, degrading magnetism. If too much Cu is added, high-temperature embrittlement may occur, leading to cracks during rolling or hot rolling. More specifically, Cu may be included in an amount of 0.01 to 0.10 wt%.

[0075] Cr: 0.01 to 0.50 wt%

[0076] Chromium (Cr) increases resistivity and improves iron loss. If too little Cr is added, the resistivity-enhancing effect may not be sufficient. If too much Cr is added, the magnetic flux density may decrease. More specifically, Cr may be included in an amount of 0.050 to 0.20 wt%.

[0077] Ni: 0.05 wt% or less

[0078] Nickel (Ni) can react with impurity elements to form fine sulfides, carbides, and nitrides, which can have a detrimental effect on magnetism. More specifically, it can contain 0.001 to 0.03 wt% of Ni.

[0079] Zn: 0.01 wt% or less

[0080] Zinc (Zn) can act as an impurity and degrade magnetism if the content is excessive. Therefore, Zn may be added further within the aforementioned range. More specifically, Zn may be included in an amount of 0.001 to 0.005 wt%.

[0081] Co: 0.05 wt% or less

[0082] Cobalt (Co) does not form fine precipitates that reduce the magnetism of steel sheets, but it can increase high-temperature strength and cause poor coil shape after hot rolling.

[0083]

[0084] A non-oriented electrical steel sheet according to one embodiment of the present invention may further include at least one of Mo: 0.03 wt% or less (excluding 0%), B: 0.0050 wt% or less (excluding 0%), V: 0.0050 wt% or less (excluding 0%), Ca: 0.0050 wt% or less (excluding 0%), Nb: 0.0050 wt% or less (excluding 0%), Zr: 0.0050 wt% or less (excluding 0%), Te: 0.0100 wt% or less (excluding 0%), and Mg: 0.0050 wt% or less (excluding 0%).

[0085] Mo: 0.030 wt% or less

[0086] When molybdenum (Mo) is added in excessive amounts, it may suppress segregation of segregating elements, thereby reducing the effect of improving the texture. Therefore, Mo may be included in an amount of 0.03 wt% or less. The lower limit is not particularly limited, but since it plays a role in improving the texture by segregating on the surface and grain boundaries, it may be included in an amount of 0.001 wt% or more. More specifically, Mo may be included in an amount of 0.001 to 0.010 wt%. More specifically, Mo may be included in an amount of 0.005 to 0.010 wt%.

[0087] B: 0.0050 wt% or less

[0088] Excessive addition of boron (B) can cause deterioration of magnetism through the formation of inclusions in the steel. Therefore, B may be included in an amount of 0.005 wt% or less. The lower limit is not particularly limited, but may be 0.0001 wt% due to steelmaking costs. More specifically, B may be included in an amount of 0.0001 to 0.0030 wt%.

[0089] V: 0.0050 wt% or less

[0090] Vanadium (V) has a very strong tendency to form precipitates within the steel, and forms fine carbides or nitrides within the base metal, thereby inhibiting grain growth and domain wall migration, thereby deteriorating iron loss. Therefore, the V content may be 0.0050 wt% or less. The lower limit is not particularly limited, but may be 0.0003 wt% due to steelmaking costs. That is, V may be included in an amount of 0.0003 to 0.0050 wt%. More specifically, V may be included in an amount of 0.0003 to 0.0030 wt%.

[0091] Ca: 0.0050 wt% or less

[0092] Calcium (Ca) has a strong tendency to form precipitates within the steel, and forms fine sulfides within the parent material, which inhibits grain growth and domain wall movement, thereby deteriorating iron loss.

[0093] Nb: 0.0050 wt% or less

[0094] Niobium (Nb) has a very strong tendency to form precipitates in steel, and forms fine carbides or nitrides inside the base metal, which inhibits grain growth and domain wall migration, thereby deteriorating iron loss. Therefore, the Nb content may be 0.0050 wt% or less. The lower limit is not particularly limited, but may be 0.0003 wt% due to steelmaking costs. That is, Nb may be included in an amount of 0.0003 to 0.0050 wt%. More specifically, Nb may be included in an amount of 0.0003 to 0.0030 wt%.

[0095] Zr: 0.0050 wt% or less

[0096] Excessive addition of zirconium (Zr) can cause deterioration of magnetism through the formation of inclusions in the steel. Therefore, Zr can be included in an amount of 0.005 wt% or less. The lower limit is not particularly limited, but may be 0.0001 wt% due to steelmaking costs. That is, Zr can be included in an amount of 0.0001 to 0.0050 wt%. More specifically, it can be included in an amount of 0.0005 to 0.0030 wt%.

[0097] Te: 0.0100 wt% or less

[0098] Tellurium (Te) diffuses into the oxide layer on the surface of a hot-rolled coil, increases the coefficient of friction between the oxide layer and the rolling work rolls, and concentrates under the oxide layer to improve hardness. Therefore, it can be added to prevent the fractured oxide layer during rolling from being pressed into the base metal and to be removed. If the amount of Te added is too small, the effect may be minimal. If too much Te is added, the oxide layer is easily removed, and the base metal comes into direct contact with the work rolls, reducing the effect. In addition, deformation bands may be excessively generated in the steel sheet during cold rolling, which may lead to the development of a {111} / ND texture that is unfavorable for magnetism. More specifically, tellurium may be included in an amount of 0.0001 to 0.007 wt%.

[0099] Mg: 0.0050 wt% or less

[0100] Magnesium (Mg) is an element that mainly combines with sulfur to form sulfides, and can affect the surface oxide layer of the steel base. Therefore, Mg may be included in an amount of 0.0050 wt% or less. The lower limit is not particularly limited, but may be set to 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%.

[0101]

[0102] The remainder comprises iron (Fe) and unavoidable impurities. Unavoidable impurities are impurities mixed in during the steelmaking process and the manufacturing process of non-oriented electrical steel sheets. Since these impurities are widely known in the art, a detailed description thereof will be 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. When additional elements are included, they are included in place of the remainder, iron (Fe).

[0103]

[0104] As described above, in one embodiment of the present invention, by appropriately controlling the alloy composition of the steel plate and appropriately forming precipitates according to thickness, magnetism can be improved.

[0105] Figure 1 shows a schematic diagram of a cross-section of a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0106] As shown in Fig. 1, a non-oriented electrical steel plate (100) includes a surface portion (20) extending from the surface of the steel plate to 1 / 20 of the total thickness inward based on a cross-section including the thickness direction (ND direction) and a central portion (10) extending from more than 1 / 20 to 1 / 2 of the total thickness. In Fig. 1, for convenience, the surface portion (20) is shown to exist only on one side, but the surface portion (20) exists on both sides.

[0107] In one embodiment of the present invention, by appropriately controlling the ratio of precipitates present in the central portion (10) and the surface portion (20), the magnetic properties can be improved without causing deterioration of the surface portion of the non-oriented electrical steel sheet.

[0108] Specifically, the number of precipitates per unit area (P) in the center (10) I ) for the surface (20) per unit area of ​​the precipitate (P) S ) ratio (P S / P I ) may be 1.20 or less. If this ratio is too high, it means that there are a lot of precipitates on the surface (20) or too few precipitates on the center (10). If there are a lot of precipitates on the surface (20), the magnetism of the surface (20) is deteriorated due to the many precipitates, and ultimately the magnetism of the entire non-oriented electrical steel sheet (100) is deteriorated. If there are too few precipitates on the center (10), the grains may grow significantly, which may also increase the iron loss. More specifically, the number of precipitates per unit area of ​​the center (10) (P I ) for the surface (20) per unit area of ​​the precipitate (P) S ) ratio (P S / P I ) can be between 0.90 and 1.19.

[0109] In one embodiment of the present invention, the precipitate means a particle formed by the agglomeration of elemental components existing in the electrical steel sheet. More specifically, it means a particle formed by combining at least one element among Si, Al, Mn, Ti, Nb, Cu, and Zr with at least one element among C, N, S, and O. The precipitate has a thickness of at least 200 μm with respect to a cross-section including the thickness direction (ND direction), and more specifically, a plane perpendicular to the steel sheet rolling direction (TD plane). 2The area can be measured by observing it through TEM. Since precipitates with a particle size of less than 0.03 μm do not have a significant effect on magnetism, they are excluded from the ratio calculation. In this case, the particle size refers to the diameter of an imaginary circle having the same area as the area occupied by the precipitate. As described later, an oxide layer (30) may exist on the surface layer of the surface portion (20), but the oxide layer (30) is excluded from the calculation of the precipitate density (both the measured area and the number of precipitates are excluded).

[0110] More specifically, the precipitate density of the surface (20) is 0.5 / ㎛. 2 2.5 pieces / ㎛ 2 And the density of precipitates in the center (10) is 0.3 / ㎛. 2 2.0 pieces / ㎛ 2 It could be.

[0111] Figure 2 shows a schematic diagram of a cross-section of a non-oriented electrical steel sheet according to one embodiment of the present invention.

[0112] As shown in Fig. 2, it includes an oxide layer (30) existing from the surface of the non-oriented electrical steel sheet (100) toward the inside.

[0113] An oxide layer (30) can be formed when oxygen penetrates into the steel sheet during the manufacturing process of the electrical steel sheet.

[0114] The oxide layer (30) is defined as a portion containing 0.01 wt% or more of oxygen from the surface of the steel plate toward the inside. The detection and thickness of the oxide layer (30) can be determined by processing the TD surface of the specimen with FIB and observing it with TEM and EDS, and determining the portion containing 0.01 wt% or more of oxygen as the oxide layer. At this time, the steel plate sample may be a sample in which no insulating film is formed, or a sample in which the insulating film is removed if formed. In order to reduce measurement errors depending on the location, the specimen may be measured 20 times or more at intervals of 1 μm or more in the TD direction with a length of at least 200 μm in the RD direction, and the average value may be measured.

[0115] The thickness of the oxide layer (30) may be 5 to 300 nm. If the thickness of the oxide layer (30) is too thin, Al enrichment in the oxide layer (30) may not be properly achieved, and the aforementioned AlN suppression effect may not be sufficiently achieved. If the thickness of the oxide layer (30) is too thick, a large amount of oxygen may penetrate into the steel sheet, resulting in poor magnetism. More specifically, the thickness of the oxide layer (30) may be 10 to 290 nm. The thickness of the oxide layer (30) may be the average thickness of the oxide layer (30) in the measured specimen.

[0116] As shown in Fig. 2, there is an oxide layer break with a thickness of 5 nm or less in the cross-section including the rolling direction of the steel sheet, and the maximum length of the oxide layer break with a thickness of 5 nm or less in the cross-section including the rolling direction of the steel sheet may be 500 nm or less in the rolling direction. When a break exceeding 500 nm exists, oxides or nitrides may be additionally formed by the atmospheric gas during the cold-rolled sheet annealing step, which may have a significant negative effect on magnetism. The measurement standard can be measured at 200 ㎛ or more in the rolling direction. More specifically, the maximum length of the oxide layer break with a thickness of 5 nm or less may be 50 to 490 nm in the rolling direction.

[0117] As shown in Fig. 2, there is an oxide layer break with a thickness of 5 nm or less in the cross-section including the rolling direction of the steel plate, and the length of this break (DC L ) can be 0.01 to 1000 nm per 10 ㎛ of rolling direction. As shown in Fig. 2, there may be multiple oxide layer breaks within the specimen, in which case the sum of the lengths of all oxide layer breaks can be included in the aforementioned range. It is most ideal in terms of magnetism to have almost no oxide layer breaks, but 0.2 kgf / mm 2 3.0kgf / mm 2During annealing and final cold rolling under tension, the formation of a break due to destruction of the oxide layer is inevitable. Therefore, except for the ideal case where there is no break in the oxide layer, the shorter the break, the more advantageous it may be in terms of magnetism. On the other hand, if the length of the break in the oxide layer is too long, additional oxidation and nitriding may occur at the break, which may cause problems in that it also increases the iron loss. More specifically, the length of the break (DC L ) can be 1 to 900 nm per 10 ㎛ in the rolling direction. More specifically, the length of the disconnection (DC L ) can be 100 to 800 nm per 10 ㎛ in the rolling direction. More specifically, the length of the disconnection (DC L ) can be 300 to 750 nm per 10 ㎛ in the rolling direction. The measurement and determination of the disconnection can be performed in the same manner as the measurement and determination method of the oxide layer described above. When multiple disconnections exist, the length can be expressed as the sum of the lengths of the multiple disconnections.

[0118] The oxide layer (30) and the oxide layer break can be appropriately formed by appropriately controlling conditions during the annealing process prior to cold rolling. A more specific method will be described later in relation to the method for manufacturing a non-oriented electrical steel sheet.

[0119] The oxide layer (30) may contain more than 50 wt% of Al due to the surface concentration of Al. More specifically, it may contain 50 to 70 wt% of Al. The remaining alloy components other than Al and O are the same as the alloy components of the non-oriented electrical steel sheet described above. Since the thickness of the oxide layer (30) is very thin compared to the thickness of the entire non-oriented electrical steel sheet (100), it has practically no effect on the alloy components of the non-oriented electrical steel sheet (100).

[0120]

[0121] As described above, in one embodiment of the present invention, by appropriately controlling the steel component and controlling the thickness and cut-off ratio of the surface oxide layer to a certain level or less, thereby appropriately forming precipitates at each site, magnetism can be improved. In general, as the steel plate thickness decreases, the iron loss tends to improve, and the iron loss according to the steel plate thickness according to the present invention was implemented using the following formula.

[0122] Iron Loss (W 10 / 400 ) ≤ 9.8×EXP(1.5×t), t: steel plate thickness (unit: mm)

[0123] Iron Loss (W 10 / 400 ) is the iron loss when a magnetic flux density of 1.0 T is induced at a frequency of 400 Hz. EXP represents the natural constant (e).

[0124] Specifically, the core loss (W) of the non-oriented electrical steel sheet of the present invention based on a thickness of 0.25 mm 10 / 400 ) may be less than 14.0 W / Kg. In addition, the magnetic flux density (B 50 ) can be greater than 1.63 T. The magnetic flux density (B 50 ) means the magnetic flux density induced in a magnetic field of 5000 A / m. More specifically, the iron loss (W) of non-oriented electrical steel sheet 10 / 400 ) can be 10.0 to 14.0 W / kg. The magnetic flux density (B50) can be 1.63 T to 1.75 T.

[0125]

[0126] A method for manufacturing a non-oriented electrical steel sheet according to one embodiment of the present invention includes a step of hot-rolling a slab to manufacture a hot-rolled steel sheet; a step of annealing the steel sheet before cold rolling; a step of cold-rolling the annealed steel sheet to manufacture a cold-rolled sheet; and a cold-rolled sheet annealing step of annealing the cold-rolled sheet.

[0127] Below, each step is explained in detail.

[0128] First, the slab is hot rolled.

[0129] The alloy composition of the slab has been described in the alloy composition of the previously mentioned non-oriented electrical steel sheet, so a duplicate description will be omitted. Since the alloy composition does not substantially change during the manufacturing process of the non-oriented electrical steel sheet, the alloy composition of the non-oriented electrical steel sheet and the slab are substantially identical.

[0130] Specifically, the slab contains Si: 1.5 to 4.5%, Al: 0.1 to 2.0%, Mn: 0.1 to 2.0% by weight, with the remainder being Fe and unavoidable impurities.

[0131] As other additional elements have been described in the alloy composition of non-oriented electrical steel sheets, redundant descriptions are omitted.

[0132] Slabs can be heated before hot rolling. The heating temperature of the slab is not limited, but the slab can be heated to 1200℃ or lower. If the slab heating temperature is too high, precipitates such as AlN and MnS present within the slab may be re-dissolved and then finely precipitated during hot rolling and annealing, inhibiting grain growth and reducing magnetism.

[0133] Next, the slab is hot-rolled to produce a hot-rolled sheet. The thickness of the hot-rolled sheet can be 1.0 to 4.5 mm. In the step of producing the hot-rolled sheet, the finishing rolling temperature can be 800°C or higher. Specifically, it can be 800 to 1000°C. The hot-rolled sheet can be coiled at a temperature of 600°C or higher. More specifically, the thickness of the hot-rolled sheet can be 1.5 to 4.3 mm.

[0134] After manufacturing a hot-rolled steel sheet, subsequent steps can be performed while the scale remaining on the hot-rolled steel sheet remains. That is, after hot rolling, scale removal processes such as pickling, shot blasting, or surface grinding can be omitted, and subsequent steps can be performed. By performing cold rolling without the pickling process, friction between the rolling work rolls and the steel sheet increases, so that shear deformation is simultaneously applied in addition to plane deformation during rolling, and a specific orientation develops during recrystallization annealing. In one embodiment of the present invention, scale refers to a portion on the surface of the steel sheet where elements such as Fe, Al, and Si combine with oxygen to form a phase different from that of the base metal. Remaining scale means that at least 1 μm of scale remains on the hot-rolled sheet. In this case, the scale thickness refers to the sum of the scale thicknesses formed on both surfaces of the steel sheet. If the remaining scale thickness is too thin, the effect due to the scale residue may not be fully exerted. Even if the scale thickness is thicker, the effect is not improved, and there is a problem of a reduced yield of the steel sheet. More specifically, scales with a thickness of 0.1 to 1 μm may remain.

[0135] In one embodiment of the present invention, after manufacturing a hot-rolled steel sheet, a pre-cold rolling annealing step for annealing the hot-rolled steel sheet may be performed immediately. Alternatively, a pre-cold rolling annealing step for annealing the pre-cold rolled steel sheet may be performed after performing preliminary cold rolling on the hot-rolled steel sheet.

[0136] Preliminary cold rolling is distinguished from cold rolling, which will be described later, in that it is the first rolling stage of the process of rolling to an intermediate thickness rather than the final product thickness, then performing intermediate annealing, and then cold rolling to the final product thickness.

[0137] Preliminary cold rolling can be performed at a reduction ratio of 30 to 80% to improve final cold rolling productivity and grain size in the final product sheet. Furthermore, if rolling productivity is not a consideration, the present invention also allows preliminary cold rolling to be performed in a reverse mill. The preliminarily cold rolled sheet can have a thickness of 0.3 to 1.5 mm. More specifically, the reduction ratio can be 60 to 75% and the thickness can be 0.6 to 1.3 mm.

[0138] The preliminary cold rolling reduction can be calculated as (steel plate thickness before rolling - steel plate thickness after rolling) / steel plate thickness before rolling. If the reduction ratio is too low in the preliminary cold rolling stage, the rolling load increases during the final cold rolling, which reduces productivity and increases the final reduction ratio, which causes fine grains. <111> / ND This can lead to problems that promote directional recrystallization. Conversely, if the reduction ratio is too high, the cold rolling load increases and the possibility of plate fracture increases.

[0139] The pre-cold rolling step can be performed at a temperature of 60 to 300°C. This temperature can be raised naturally by friction between the steel sheet and the rolling rolls, or by external heating. If the temperature is too low, the rolling load increases significantly, and the steel sheet may slip between the rolling rolls instead of being rolled, resulting in problems such as twisting. If the temperature is too high, a thick oxide layer may form on the steel sheet surface, which can deteriorate magnetism and cause problems such as ignition of the rolling oil. More specifically, it is preferably performed at a temperature of 70 to 250°C. The aforementioned temperature refers to the temperature of the steel sheet.

[0140] As mentioned above, the preliminary cold rolling step can be omitted if necessary.

[0141] Next, in the annealing step prior to cold rolling, hot-rolled steel sheets or pre-cold-rolled sheets are annealed. In one embodiment of the present invention, by controlling the dew point and tension in the annealing step prior to cold rolling, an oxide layer (30) can be appropriately formed.

[0142] In addition, the annealing step before cold rolling is performed in a hydrogen and nitrogen mixed gas atmosphere containing at least 3 to 30% by volume of hydrogen. If the hydrogen content is low, an additional oxide layer may be formed during heat treatment, which may remain in the final product and cause increased iron loss. The higher the hydrogen content, the better, but using more than necessary increases the process load, which is a factor in increasing processing costs. Therefore, annealing can be performed in an atmosphere containing 3 to 30% by volume of hydrogen gas. More specifically, it can contain 5 to 25% by volume of hydrogen. The remaining atmosphere is nitrogen.

[0143] The dew point can range from -50°C to -10°C. If the dew point is too low, nitriding by nitrogen gas in the atmosphere can occur, promoting nitride formation within the steel sheet and increasing iron loss. If the dew point is too high, additional surface oxidation can occur, leaving a residual surface oxide layer that can cause pickling problems and increase iron loss. More specifically, the dew point can range from -50°C to -20°C. More specifically, the dew point can be the dew point of the atmosphere during the cracking process.

[0144] Also, 0.2kgf / mm 2 3.0kgf / mm 2 The tension can be applied. If the tension is too low, the steel plate may come into contact with the inside of the furnace, causing scratches on the surface and problems in terms of surface quality. If the tension is too high, the steel plate may be deformed at high temperatures during annealing, causing problems in terms of deterioration of the magnetic flux density and iron loss. More specifically, the tension should be 0.3 to 2.5 kgf / mm. 2It can be. More specifically, the tension can be the tension measured at the exit of the annealing furnace, and can be measured using a tension meter device.

[0145] The soaking temperature during the annealing stage prior to cold rolling can range from 800 to 1100°C. If the annealing temperature is too low, the recrystallized structure may not form or may grow finely, thereby minimizing the effect of increasing the magnetic flux density. If the annealing temperature is too high, the magnetic properties may deteriorate, and the deformation of the plate shape may deteriorate the rolling workability. More specifically, the temperature range may be 830 to 1080°C. The soaking time may be 1 to 30 minutes.

[0146] The annealing before cold rolling mentioned above can be performed in vertical continuous annealing equipment or horizontal continuous annealing equipment. If the removal of the surface oxide layer after hot rolling is omitted, the removal of the surface oxide layer can be performed after annealing before cold rolling. It is known that if the surface oxide layer remains excessively on the final non-oriented electrical steel sheet manufactured, it will impair the magnetism. As a result of studying the effect of the remaining surface oxide layer on the magnetic properties of the present inventors, it was confirmed that there was almost no deterioration in the magnetic properties if it existed less than 300 nm in the final product sheet. In addition, it was confirmed that even if the surface oxide layer was completely removed before cold rolling, a surface oxide layer of about 3 nm was formed during the final annealing due to the influence of the atmospheric gas.

[0147] Meanwhile, when cold rolling is performed with remaining scale, the scale is pressed into the surface and exists in a state where the scale is segmented by rolling. It is preferable that the length of the segmented, scale-free surface is 500 nm or less at most. If the disconnected length is 500 nm or more, a problem may occur in which nitride is formed due to penetration of nitrogen (N2) components in the atmospheric gas into the disconnected portion during the final annealing step, thereby increasing iron loss. Therefore, when the surface oxide layer exists in the final product sheet to be 300 nm or less and the length of the disconnected surface oxide layer is 500 nm or less at most, excellent magnetic properties as in the present invention can be secured.

[0148] Additionally, the pickling process prior to final cold rolling can completely remove the surface oxide layer, or leave it at a thickness of 300 nm or less. Pickling refers not only to acid immersion, but also to all physical and chemical descaling methods. Pickling methods can include acid immersion, shot blasting, or surface grinding.

[0149] Next, the annealed steel sheet is cold rolled to produce a cold rolled sheet. At this time, cold rolling can be performed at a reduction ratio of 40 to 85%. If the reduction ratio is too low, the accumulated strain energy in the rolled steel sheet is small, making it difficult to recrystallize in the subsequent annealing process, and the rolled structure remains, which can cause problems in improving the magnetic flux density and iron loss. On the other hand, if the reduction ratio is too high, it can cause problems in the subsequent annealing process. <111> / ND The recrystallization of the grains in the direction of orientation is promoted, and the grains become finer, which can cause problems such as poor magnetic flux density and increased iron loss. More specifically, the reduction ratio can be 60 to 75%. The cold rolling step can be performed using a tandem cold rolling mill that continuously cold rolls the steel sheet using multiple rolling stands, or a reverse rolling mill that discontinuously cold rolls the steel sheet using 12 or more rolling rolls. The final rolled thickness can be 0.1 mm to 0.35 mm.

[0150] Next, the cold-rolled sheet is annealed. The cold-rolled sheet annealing step can be performed in an atmosphere with a dew point temperature below 0°C. More specifically, the annealing can be performed in an atmosphere with a dew point temperature of -50°C to -10°C.

[0151] The cold-rolled sheet annealing step can be performed at a soaking temperature of 850 to 1100°C. If the soaking temperature is too low, grain growth may not be sufficient, resulting in increased hysteresis loss and deteriorated iron loss. If the soaking temperature is too high, eddy current loss may increase and magnetic flux density may decrease rapidly. More specifically, annealing can be performed at a temperature of 900 to 1050°C. The soaking time may be 10 to 300 seconds.

[0152] During the cold-rolled sheet annealing process, all (i.e., more than 99%) of the processed structure formed during the cold rolling stage can be recrystallized.

[0153] After cold-rolled sheet annealing, an insulating film can be formed. The insulating film can be treated with organic, inorganic, or organic-inorganic composite films, and can also be treated with other insulating film agents.

[0154]

[0155] The present invention will be described in more detail below through examples. However, these examples are intended only to illustrate the present invention and are not intended to limit the present invention.

[0156]

[0157] Example

[0158] A slab containing 3.4% Si, 0.8% Al, 1.2% Mn, and other impurities by weight was manufactured. This was heated to 1150℃ and hot-rolled at a finishing temperature of 900℃ to manufacture a hot-rolled sheet having a thickness of 2.3 mm. The hot-rolled hot-rolled sheet was pickled, then preliminarily cold-rolled to a thickness of 0.8 mm, and annealed before cold rolling under the temperature, dew point, hydrogen fraction, and tension conditions shown in Table 1. After cold-rolling to a thickness of 0.25 mm, a final recrystallization annealing was performed for 100 seconds under the conditions of a dew point of -50℃ and a soaking temperature of 1000℃.

[0159] The main characteristics of each specimen that went through the manufacturing process are summarized in Table 2.

[0160] The thickness of the oxide layer was measured at least 20 times at intervals of at least 1 μm in the area containing 5 wt% or more of Al and 3 wt% or more of O on the surface of the parent material when the TD surface of the specimen was processed with FIB and observed with TEM, and the average value was indicated.

[0161] The maximum length of the oxide layer disconnection is the maximum value measured in the rolling direction at the part where the oxide layer is not continuous but disconnected and the base material is exposed when the Al-containing oxide layer is observed in the rolling direction for more than 200 μm using TEM.

[0162] Additionally, the total length of the oxide layer break per 10㎛ in the rolling direction was indicated.

[0163] Analysis of precipitates by thickness within the steel plate was performed through TEM measurement at 200 um for the surface and center. 2 The ratio of the number of precipitates with a diameter of 0.03 um or more in the area was obtained.

[0164] Magnetic properties such as magnetic flux density and iron loss were measured by cutting 60 mm wide × 60 mm long × 5 sheets of each specimen and measuring the rolling direction and the direction perpendicular to the rolling with a single sheet tester, and the average value is shown. Here, W10 / 400 is the iron loss when a magnetic flux density of 1.0 T is induced at a frequency of 400 Hz, and B50 means the magnetic flux density of the steel sheet induced in a magnetic field of 5000 A / m.

[0165] No. Annealing temperature (℃)Dew point (℃)Hydrogen fraction (vol%)Annealing tension (kgf / mm) 2 )A1950-25151.5A2950-25152.5A3950-50151.5A4950-25153.5A5950-25251.5A6950- 5252.5A7950-25251.5A8950-60251.5A9950-25252.5A10950-1021.0A11950-10351.0

[0166] No.Al including oxide layer thickness (nm)Maximum length of oxide layer break (nm)Total length of oxide layer break (nm)Precipitate ratio (P S / P I )W10 / 400(W / kg)B50(Tesla)RemarksA1124506851.0512.91.65Inventive materialA2284006151.1012.91.65Inventive materialA3753306531.1913.11.66Inventive materialA412071010351.2514.51.63Comparative materialA52802004511.0 511.21.68Inventive material A63502505551.1214.71.62Comparative material A71103005691.1811.31.68Inventive material A831203231.2214.11.64Comparative material A9534807041.1511.11.68Inventive material A103302206411.0814.31.64Comparative material A11 1548011531.2114.81.64Comparative material

[0167] As shown in Tables 1 and 2, the remaining invention examples, in which the steel components are appropriately controlled and the process conditions are appropriately controlled, and the precipitate and oxide layer characteristics are appropriately formed by thickness, can be confirmed to have excellent iron loss and magnetic flux density.

[0168] On the other hand, if the steel component is not properly controlled, the process conditions are not properly controlled, and the precipitates and oxide layers by thickness are not properly formed, it can be confirmed that the iron loss and magnetic flux density are inferior.

[0169]

[0170] The present invention is not limited to the embodiments described herein, but can be manufactured in a variety of different forms. Those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

[0171]

[0172] [Explanation of symbols]

[0173] 100: Non-oriented electrical steel sheet, 10; Surface area,

[0174] 20: center, 30: oxide layer

Claims

Contains Si: 1.5 to 4.5% by weight, Al: 0.1 to 2.0%, Mn: 0.1 to 2.0%, and the remainder includes Fe and inevitable impurities. The number of precipitates per unit area (P) in the center exceeding 1 / 20 to 1 / 2 of the total thickness I ) The number of precipitates per unit area (P) on the surface of the steel plate from the surface to the inside up to 1 / 20 of the total thickness S ) Non-oriented electrical steel sheet having a ratio of 1.2 or less. In the first paragraph, Contains an oxide layer that exists from the surface to the inside, A non-oriented electrical steel sheet having a thickness of the oxide layer of 5 to 300 nm. In the first paragraph, A non-oriented electrical steel sheet having an oxide layer thickness of 5 nm or less in a cross-section including the rolling direction of the steel sheet and having a maximum length of an oxide layer break of 500 nm or less in the rolling direction. In the first paragraph, A non-oriented electrical steel sheet having a total length of a cut portion of an oxide layer of 0.01 to 1000 nm per 10 ㎛ in the rolling direction, the thickness of the oxide layer being 5 nm or less in a cross-section including the rolling direction of the steel sheet. In the first paragraph, Non-oriented electrical steel sheet further comprising at least one of P: 0.1 wt% or less (excluding 0%), C: 0.005 wt% or less (excluding 0%), S: 0.005 wt% or less (excluding 0%), Ti: 0.005 wt% or less (excluding 0%), and N: 0.005 wt% or less (excluding 0%). In the first paragraph, A non-oriented electrical steel sheet further comprising 0.005 to 0.200 wt% of each or a combined amount of one or more of Sn, Sb, Bi, Pb, Ge and As. In the first paragraph, A non-oriented electrical steel sheet further comprising at least one 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%). In the first paragraph, Non-oriented electrical steel sheet further comprising at least one of Mo: 0.03 wt% or less (excluding 0%), B: 0.0050 wt% or less (excluding 0%), V: 0.0050 wt% or less (excluding 0%), Ca: 0.0050 wt% or less (excluding 0%), Nb: 0.0050 wt% or less (excluding 0%), Zr: 0.005 wt% or less (excluding 0%), Te: 0.01 wt% or less (excluding 0%), and Mg: 0.0050 wt% or less (excluding 0%). A step of manufacturing a hot-rolled steel sheet by hot-rolling a slab containing Si: 1.5 to 4.5% by weight, Al: 0.1 to 2.0%, Mn: 0.1 to 2.0% by weight, and the remainder being Fe and unavoidable impurities; The above steel plate is treated at a dew point of -50°C to -10°C, an atmosphere containing 3 to 30 volume% of hydrogen, and a pressure of 0.2 kgf / mm 2 Within 3.0kgf / mm 2 An annealing step prior to cold rolling in which tension is applied and annealed; A step for manufacturing cold rolled steel sheets by cold rolling an annealed steel sheet, and A method for manufacturing a non-oriented electrical steel sheet, comprising: a cold rolled sheet annealing step of annealing the cold rolled sheet. In Article 9, A method for manufacturing a non-oriented electrical steel sheet, wherein the above slab further includes at least one of P: 0.1 wt% or less (excluding 0%), C: 0.005 wt% or less (excluding 0%), S: 0.005 wt% or less (excluding 0%), Ti: 0.005 wt% or less (excluding 0%), and N: 0.005 wt% or less (excluding 0%). In Article 9, A method for manufacturing a non-oriented electrical steel sheet, wherein the above slab further contains 0.005 to 0.200 wt% of each or a combined amount of one or more of Sn, Sb, Bi, Pb, Ge and As. In Article 9, A method for manufacturing a non-oriented electrical steel sheet, wherein the above slab further includes at least one 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%). In Article 9, A method for manufacturing a non-oriented electrical steel sheet, wherein the above slab further includes at least one of Mo: 0.03 wt% or less (excluding 0%), B: 0.0050 wt% or less (excluding 0%), V: 0.0050 wt% or less (excluding 0%), Ca: 0.0050 wt% or less (excluding 0%), Nb: 0.0050 wt% or less (excluding 0%), Zr: 0.005 wt% or less (excluding 0%), Te: 0.01 wt% or less (excluding 0%), and Mg: 0.0050 wt% or less (excluding 0%). In Article 9, A method for manufacturing a non-oriented electrical steel sheet, wherein the subsequent steps are performed while the scale remaining on the hot-rolled steel sheet remains after manufacturing the hot-rolled steel sheet. In Article 9, A method for manufacturing a non-oriented electrical steel sheet further comprising a step of preliminarily cold rolling a hot-rolled sheet prior to the above-mentioned pre-cold rolling annealing step. In Article 15, A method for manufacturing a non-oriented electrical steel sheet having a reduction ratio of 30 to 80% in the preliminary cold rolling step. In Article 9, A method for manufacturing a non-oriented electrical steel sheet, wherein the cracking temperature in the annealing step prior to the above cold rolling is 800 to 1100°C. In Article 9, A method for manufacturing a non-oriented electrical steel sheet having a reduction ratio of 40 to 85% in the step of manufacturing the cold rolled sheet. In Article 9, The above cold rolled sheet annealing step is a method for manufacturing a non-oriented electrical steel sheet, in which the annealing is performed at a soaking temperature of 850 to 1100°C in an atmosphere having a dew point of 0°C or lower.

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