KR20240048585A - Non-oriented elecrical steel sheet and method of manufacturing the same - Google Patents

Abstract

In the present invention, in weight percent, silicon (Si): 2.8% or more and 3.8% or less, manganese (Mn): 0.2% or more and 0.5% or less, aluminum (Al): 0.9% or more and 2.5% or less, carbon (C): 0% Exceeding 0.002% or less, Sulfur (S): Exceeding 0% and not exceeding 0.002%, Phosphorus (P): Exceeding 0% and not exceeding 0.015%, Nitrogen (N): Exceeding 0% and not exceeding 0.002%, Titanium (Ti): Exceeding 0% and not exceeding 0.002% % or less, preparing a slab containing the remaining iron (Fe) and inevitable impurities, hot rolling the slab to form a hot-rolled sheet, and forming a hot-rolled oxidation layer on the surface of the hot-rolled sheet 8㎛ or more. Winding the hot-rolled sheet to have a thickness of ㎛ or less, pre-annealing the hot-rolled sheet, removing the hot-rolled oxidation layer from the hot-rolled sheet, and cold rolling the hot-rolled sheet to form a cold-rolled sheet. A method for manufacturing a non-oriented electrical steel sheet is provided, including the step of cold rolling and annealing the cold rolled sheet.

Description

Non-oriented electrical steel sheet and method of manufacturing the same {NON-ORIENTED ELECRICAL STEEL SHEET AND METHOD OF MANUFACTURING THE SAME}

Embodiments of the present invention relate to a non-oriented electrical steel sheet and a method of manufacturing the same, and more specifically, to a non-oriented electrical steel sheet that has low iron loss by increasing resistivity and controlling the production of AlN and a method of manufacturing the same.

Recently, demands for environmental preservation and improved energy efficiency are increasing. In particular, the transition from internal combustion engine vehicles to electric or hybrid vehicles is accelerating. In these vehicles, non-oriented electrical steel sheets are mainly used as materials for transformers and motors, which are rotating devices. In order to improve the efficiency of electric vehicle motors, non-oriented electrical steel sheets must have excellent magnetic properties. Specifically, since electric vehicle motors are often used at high rotation speeds, non-oriented electrical steel sheets must have excellent magnetic properties in the high frequency range.

For example, non-oriented electrical steel sheets must have low iron loss and high magnetic flux density. Iron loss refers to energy loss that occurs at a specific magnetic flux density and frequency, and magnetic flux density refers to the degree of magnetization obtained in a specific magnetic field. The lower the iron loss, the more energy efficient a motor can be manufactured under the same conditions, and the higher the magnetic flux density, the more compact the motor or the reduction of copper loss. Therefore, non-oriented electrical steel sheets must have low iron loss and high magnetic flux density. For this purpose, the thickness of the non-oriented electrical steel sheet is reduced or the resistivity of the steel is increased.

The resistivity of steel can be increased by adding Si or Al. When Si is added, the resistivity of the steel increases, but brittleness also increases. Therefore, if Si is added in excess of a certain amount, cold rolling becomes impossible and commercial production becomes impossible. When adding Al, the degree of increase in specific resistance is almost the same as when adding Si, but the degree of increase in brittleness is slight. Accordingly, attempts were made to reduce the Si content and increase the Al content. As a related technology, there is Korean Patent Publication No. 10-2011-0023890 (title of the invention: Non-oriented electromagnetic steel cast piece and method for manufacturing the same).

No. 10-2011-0023890

However, this conventional non-oriented electrical steel sheet and its manufacturing method had a problem in that AlN generated during the manufacturing process of the non-oriented electrical steel sheet increased iron loss.

The present invention is intended to solve various problems including the problems described above, and provides a non-oriented electrical steel sheet with low iron loss and a method of manufacturing the same by increasing the resistivity and controlling the generation of AlN. However, these tasks are illustrative and do not limit the scope of the present invention.

According to one aspect of the present invention, in weight percent, silicon (Si): 2.8% or more and 3.8% or less, manganese (Mn): 0.2% or more and 0.5% or less, aluminum (Al): 0.9% or more and 2.5% or less, carbon ( C): More than 0% and less than 0.002%, Sulfur (S): More than 0% and less than 0.002%, Phosphorus (P): More than 0% and less than 0.015%, Nitrogen (N): More than 0% and less than 0.002%, Titanium (Ti) : Preparing a slab containing more than 0% and 0.002% or less of iron (Fe) and inevitable impurities, hot rolling the slab to form a hot-rolled sheet, and a hot-rolled oxidation layer formed on the surface of the hot-rolled sheet. Winding the hot-rolled sheet to have a thickness of 8 ㎛ or more and 18 ㎛ or less, pre-annealing the hot-rolled sheet, removing the hot-rolled oxidation layer from the hot-rolled sheet, and cold rolling the hot-rolled sheet. A method of manufacturing a non-oriented electrical steel sheet is provided, including forming a cold-rolled sheet and cold-rolling and annealing the cold-rolled sheet.

The step of winding the hot-rolled sheet may be a step of winding the hot-rolled sheet at a coiling temperature of 630°C or more and 700°C or less.

The step of forming the hot-rolled sheet may be a step of forming the hot-rolled sheet by heating the slab to a temperature of 1,000°C or more and 1,150°C or less and then rolling it.

The step of preliminary annealing the hot-rolled sheet may be a step of annealing the hot-rolled sheet at a temperature of 900°C or more and 1,100°C or less for 30 seconds or more and 90 seconds or less.

The step of removing the hot-rolled oxidation layer may be a step of acid-cleaning the hot-rolled sheet after shot blasting the hot-rolled sheet.

In the step of removing the hot-rolled oxidation layer, spraying short balls with a diameter of 0.4 mm to 0.8 mm on the hot-rolled sheet at a spray speed of 25 m/sec to 40 m/sec and a spray amount of 600 kg/min to 1200 kg/min. This may be a step of shot blasting the hot rolled sheet.

According to one aspect of the present invention, as a non-oriented electrical steel sheet, in weight percent, silicon (Si): 2.8% or more and 3.8% or less, manganese (Mn): 0.2% or more and 0.5% or less, aluminum (Al): 0.9% or more. 2.5% or less, Carbon (C): more than 0% and less than 0.002%, Sulfur (S): more than 0% and less than 0.002%, Phosphorus (P): more than 0% and less than 0.015%, Nitrogen (N): more than 0% and less than 0.002% Hereinafter, titanium (Ti): more than 0% and less than 0.002%, including the balance of iron (Fe) and inevitable impurities, and the number of AlN precipitates with a diameter of 100 nm or less in the cross section from the surface to a depth of 20 μm is 0.4 pieces/mm ² A non-oriented electrical steel sheet having a thickness of 0.8 pieces/mm ² or less is provided.

The non-oriented electrical steel sheet may have an iron loss (based on W10/400) of 10.0 W/kg or more and 13.0 W/kg or less.

The non-oriented electrical steel sheet may have a magnetic flux density (based on B50) of 1.60T or more and 1.70T or less.

The non-oriented electrical steel sheet may have an area ratio of 95% or more and 98% or less.

Other aspects, features and advantages other than those described above will become apparent from the detailed description, claims and drawings for carrying out the invention below.

According to an embodiment of the present invention made as described above, an electrical steel sheet with low iron loss and a method of manufacturing the same can be implemented by increasing the specific resistance and controlling the generation of AlN. Of course, the scope of the present invention is not limited by this effect.

Figure 1 is a flow chart schematically showing a method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention.

Since the present invention can be modified in various ways and can have various embodiments, specific embodiments will be illustrated in the drawings and described in detail in the detailed description. The effects and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various forms.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. When describing with reference to the drawings, identical or corresponding components will be assigned the same reference numerals and redundant description thereof will be omitted. .

In this specification, terms such as first and second are used not in a limiting sense but for the purpose of distinguishing one component from another component.

In this specification, singular expressions include plural expressions, unless the context clearly dictates otherwise.

In this specification, terms such as include or have mean that the features or components described in the specification exist, and do not exclude in advance the possibility of adding one or more other features or components.

In this specification, when a part of a film, region, component, etc. is said to be on or on another part, it does not only mean that it is directly on top of the other part, but also when another film, region, component, etc. is interposed between them. Includes.

In this specification, “A and/or B” refers to A, B, or A and B. And, “at least one of A and B” indicates the case of A, B, or A and B.

In this specification, the x-axis, y-axis, and z-axis are not limited to the three axes in the Cartesian coordinate system, but can be interpreted in a broad sense including these. For example, the x-axis, y-axis, and z-axis may be orthogonal to each other, but may also refer to different directions that are not orthogonal to each other.

In cases where an embodiment can be implemented differently in this specification, a specific process sequence may be performed differently from the described sequence. For example, two processes described in succession may be performed substantially at the same time, or may be performed in an order opposite to the order in which they are described.

In the drawings, the sizes of components may be exaggerated or reduced for convenience of explanation. For example, the size and thickness of each component shown in the drawings are shown arbitrarily for convenience of explanation, so the present invention is not necessarily limited to what is shown.

Figure 1 is a flow chart schematically showing a method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention.

Referring to Figure 1, the method of manufacturing a non-oriented electrical steel sheet according to an embodiment includes a hot rolling step (S100), a coiling step (S200), a preliminary annealing step (S300), a hot-rolled oxidation layer removal step (S400), and a cold rolling step. (S500) and a cold rolling annealing step (S600).

In the method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention, the semi-finished product subject to hot rolling may be a slab. Slabs in a semi-finished state can be obtained through a continuous casting process after obtaining molten steel of a predetermined composition through a steelmaking process.

In one embodiment, the slab has, by weight percent, silicon (Si): 2.8% to 3.8%, manganese (Mn): 0.2% to 0.5%, aluminum (Al): 0.9% to 2.5%, carbon (C ): More than 0% and less than 0.002%, Sulfur (S): More than 0% and less than 0.002%, Phosphorus (P): More than 0% and less than 0.015%, Nitrogen (N): More than 0% and less than 0.002%, Titanium (Ti): It may contain more than 0% and less than 0.002%, the balance iron (Fe) and unavoidable impurities.

Silicon (Si) may be a component that increases resistivity and lowers iron loss. In one embodiment, silicon (Si) may be included in an amount of 2.8% to 3.8% by weight based on the total weight of the slab. If silicon (Si) is included in less than 2.8% by weight based on the total weight of the slab, the resistivity of the non-oriented electrical steel sheet is low, making it difficult to obtain low core loss values. On the other hand, as the content of silicon (Si) contained in the slab increases, permeability and magnetic flux density may decrease. Additionally, if silicon (Si) is included in an amount of more than 3.8% by weight based on the total weight of the slab, brittleness may increase and cold rolling properties may decrease, thereby reducing productivity.

Manganese (Mn), along with silicon (Si), may be an ingredient that increases resistivity and lowers iron loss. Manganese (Mn) can produce MnS precipitates by combining with sulfur (S). In one embodiment, manganese (Mn) may be included in an amount of 0.2% to 0.5% by weight based on the total weight of the slab. If manganese (Mn) is included in less than 0.2% by weight based on the total weight of the slab, the resistivity of the non-oriented electrical steel sheet is low, making it difficult to obtain low core loss values. On the other hand, if manganese (Mn) is included in excess of 0.5% by weight based on the total weight of the slab, MnS precipitates are excessively generated, increasing iron loss and promoting the formation of a texture unfavorable to magnetic properties, thereby deteriorating the magnetic properties. may deteriorate. When manganese (Mn) is included in an amount of 0.2% to 0.5% by weight based on the total weight of the slab, the microstructure and texture in the slab (or non-oriented electrical steel sheet) can be appropriately controlled.

Aluminum (Al), along with silicon (Si), may be a component that increases resistivity and lowers iron loss. Aluminum (Al) can produce AlN precipitates by combining with nitrogen (N). Additionally, aluminum (Al) can play a role in reducing magnetic property deviation by reducing magnetic anisotropy. In one embodiment, aluminum (Al) may be included in an amount of 0.9% to 2.5% by weight based on the total weight of the slab. If aluminum (Al) is included in less than 0.9% by weight based on the total weight of the slab, the resistivity of the non-oriented electrical steel sheet is low, making it difficult to obtain low core loss values. Additionally, magnetic property deviation may increase. On the other hand, if aluminum (Al) is included in more than 2.5% by weight based on the total weight of the slab, excessive AlN precipitates may be generated, which may increase iron loss and thereby deteriorate magnetic properties. Additionally, a decrease in cold rollability may occur. When aluminum (Al) is contained in an amount of 0.9% to 2.5% by weight based on the total weight of the slab, the microstructure and texture in the slab (or non-oriented electrical steel sheet) can be appropriately controlled.

Carbon (C) may be a component that reduces magnetic properties by combining with other impurity elements to create carbide. In one embodiment, carbon (C) may be included in an amount of more than 0% and less than or equal to 0.002% by weight based on the total weight of the slab. If carbon (C) is included in more than 0.002% by weight based on the total weight of the slab, self-aging may occur and the magnetic properties of the manufactured non-oriented electrical steel sheet may be deteriorated. If carbon (C) is included in an amount of more than 0% and less than 0.002% by weight based on the total weight of the slab, the self-aging phenomenon can be suppressed.

Phosphorus (P) is a grain boundary segregation element and may be a component that develops texture. In one embodiment, phosphorus (P) may be included in an amount of more than 0% and less than or equal to 0.015% by weight based on the total weight of the slab. If phosphorus (P) is included in an amount of more than 0.015% by weight based on the total weight of the slab, grain growth may be suppressed due to a segregation effect, magnetic properties may be reduced, and cold rolling properties may be reduced.

Sulfur (S) may be a component that reduces magnetic properties by forming precipitates such as MnS. Additionally, sulfur (S) can worsen hot workability. In one embodiment, sulfur (S) may be included in an amount of more than 0% and less than or equal to 0.002% by weight based on the total weight of the slab. If sulfur (S) is included in excess of 0.002% by weight based on the total weight of the slab, precipitates such as MnS may be generated and magnetic properties may be reduced.

Nitrogen (N) may be a component that reduces magnetic properties by forming precipitates such as AlN. Specifically, nitrogen (N) generates precipitates such as AlN, and AlN precipitates can increase iron loss by interfering with the movement of domain walls of the final product (eg, non-oriented electrical steel sheet). In one embodiment, nitrogen (N) may be included in an amount of more than 0% and less than or equal to 0.002% by weight based on the total weight of the slab. If nitrogen (N) is included in excess of 0.002% by weight based on the total weight of the slab, precipitates such as AlN may be generated, which may interfere with the movement of the domain wall in the final product and increase iron loss of the final product.

Titanium (Ti) may be a component that reduces magnetic properties by forming precipitates such as TiC or TiN. In one embodiment, titanium (Ti) may be included in an amount of more than 0% and less than or equal to 0.002% by weight based on the total weight of the slab. If titanium (Ti) is included in more than 0.002% by weight based on the total weight of the slab, precipitates such as TiC or TiN may be generated and magnetic properties may be reduced.

In the hot rolling step (S100), a hot rolled sheet can be obtained by heating the slab and then hot rolling it. First, the slab can be heated in the hot rolling step (S100). AlN precipitates may exist within the slab, but AlN precipitates larger than a certain size do not increase iron loss. If the slab heating temperature is too high, precipitates such as AlN present in the slab may be re-dissolved to generate AlN precipitates of a certain size or less. AlN precipitates below a certain size may deteriorate the magnetic properties of the final product (eg, non-oriented electrical steel sheet) by interfering with the movement of the magnetic domain wall in the final product. On the other hand, if the slab heating temperature is too low, the rolling load increases during hot rolling, which may reduce rollability.

In one embodiment, the slab heating temperature in the hot rolling step (S100) may be about 1,000°C or more and about 1,150°C or less. At this time, if the slab heating temperature is less than about 1,000°C, the rolling load increases during hot rolling and the rolling performance may decrease. If the slab heating temperature exceeds about 1,150°C, precipitates such as AlN present in the slab may be re-dissolved to generate AlN precipitates of a certain size or less. Accordingly, the movement of the domain wall of the final product is hindered and the magnetic properties of the final product may be deteriorated.

In the hot rolling step (S100), the heated slab may be hot rolled at a predetermined finish rolling temperature. In one embodiment, the finishing delivery temperature (FDT) of the hot rolling step (S100) may be about 800°C or more and about 900°C or less.

In one embodiment, the thickness of the hot rolled sheet may be about 1.6 mm or more and about 2.2 mm or less. At this time, if the thickness of the hot rolled sheet exceeds about 2.2 mm, the cold rolling reduction rate increases and the texture may be inferior.

In the coiling step (S200), the hot-rolled sheet can be cooled to a predetermined coiling temperature (CT) and then coiled. In one embodiment, the coiling temperature may be greater than or equal to about 630°C and less than or equal to about 700°C. Preferably, the coiling temperature may be about 650°C or more and about 700°C or less.

Meanwhile, a hot-rolled oxidation layer may be formed on the surface of the hot-rolled sheet. The thermal oxide layer may contain silicon (Si), iron (Fe), and oxygen (O). The thermal oxidation layer may be a layer containing oxide. These oxides are formed when silicon (Si) and/or iron (Fe) contained in the part of the slab adjacent to the surface of the slab combine with oxygen (O) in the atmosphere, or are contained in the part of the hot-rolled sheet adjacent to the surface of the hot-rolled sheet. It can be formed by combining silicon (Si) and/or iron (Fe) with oxygen (O) in the atmosphere. That is, this hot-rolled oxidation layer may be formed in the hot rolling step (S100) and/or the coiling step (S200).

Specifically, the hot rolling step (S100) of heating and then hot rolling the slab is performed at a high temperature, so some of the silicon (Si) and/or iron (Fe) contained in the slab is exposed to oxygen (O) in the atmosphere. It can combine with to form an oxide. Moreover, although the coiling temperature (CT) is lower than the finish rolling temperature (FDT), the winding step (S200) of winding the hot-rolled sheet is also performed at a sufficiently high temperature, so the thickness of the hot-rolled oxidation layer formed on the surface of the hot-rolled sheet is further increased. It can increase.

Generally, the preliminary annealing step (S300) after the winding step (S200) is performed in an atmosphere containing nitrogen (N). In this preliminary annealing step (S300), nitrogen (N) in the atmosphere penetrates into the interior of the hot-rolled sheet and combines with aluminum (Al) of the hot-rolled sheet to generate AlN precipitates. The hot-rolled oxidation layer serves to prevent nitrogen (N) in the atmosphere from penetrating into the interior of the hot-rolled sheet in this preliminary annealing step (S300). Therefore, the hot-rolled oxidation layer can suppress AlN from being generated inside the hot-rolled sheet in the preliminary annealing step (S300). However, this hot-rolled oxidation layer may fracture during cold rolling and reduce the magnetic properties of the final product. Therefore, the hot-rolled oxidation layer is removed after the preliminary annealing step (S300).

In one embodiment, the thickness of the thermal oxidation layer after the winding step (S200) may be about 8 μm or more and about 18 μm or less. At this time, if the thickness of the thermal oxidation layer is less than about 8㎛, the aforementioned effect of suppressing AlN production may not sufficiently occur in the preliminary annealing step (S300). If the thickness of the hot-rolled oxidation layer exceeds about 18㎛, it may not be easy to remove the hot-rolled oxidation layer after the preliminary annealing step (S300). Accordingly, fracture may occur during cold rolling and the magnetic properties of the final product may deteriorate.

Regarding the coiling temperature, if the coiling temperature is less than about 630°C, the thickness of the hot-rolled oxidation layer may not be sufficiently thick so that the aforementioned effect of suppressing AlN production can occur in the preliminary annealing step (S300). If the coiling temperature exceeds about 700°C, the thickness of the hot-rolled oxidation layer becomes too thick, so it may not be easy to remove the hot-rolled oxidation layer after the preliminary annealing step (S300). Accordingly, fracture may occur during cold rolling and the magnetic properties of the final product may deteriorate.

A preliminary annealing step (S300) may be performed after the winding step (S200). In the preliminary annealing step (S300), the coiled and cooled hot-rolled sheet can be annealed. Through the preliminary annealing step (S300), the uniformity of the microstructure and cold rolling properties of the hot-rolled sheet can be secured.

The preliminary annealing step (S300) may be performed at an annealing temperature of about 900°C or more and about 1,100°C or less, a holding time of about 30 seconds or more and about 90 seconds or less, and a temperature increase rate of about 10°C/s or more. At this time, if the annealing temperature in the preliminary annealing step (S300) is too low, fine inclusions such as carbides and nitrides are formed from the surface layer, and the inclusions do not grow sufficiently, so the magnetic properties of the final product may be inferior. On the other hand, if the annealing temperature in the preliminary annealing step (S300) is too high, not only inclusions are distributed but also grains grow excessively, resulting in increased grain size deviation and excessive oxidation, which may adversely affect the final product.

In the preliminary annealing step (S300), the hot-rolled sheet can be cooled at a cooling rate of about 20°C/s or more. At this time, the hot rolled sheet may be cooled to about 200°C or more and about 250°C or less. The preliminary annealing step (S300) may be performed in an atmosphere containing nitrogen (N) of about 80 volume% or more and about 100 volume% or less. In the preliminary annealing step (S300), nitrogen (N) in the atmosphere may penetrate into the interior of the hot-rolled sheet and combine with aluminum (Al) of the hot-rolled sheet to generate AlN precipitates.

After the preliminary annealing step (S300), a thermal oxidation layer removal step (S400) may be performed. Since the hot-rolled oxidation layer formed on the surface of the hot-rolled sheet deteriorates magnetic properties and may break during cold rolling, it is desirable to completely remove it before the cold rolling step (S500). All of the hot-rolled oxidation layer formed on the surface of the hot-rolled sheet can be removed through the hot-rolled oxidation layer removal step (S400). In the hot-rolled oxidation layer removal step (S400), the hot-rolled oxidation layer present on the surface of the hot-rolled sheet can be removed.

First, the hot rolled sheet can be shot blasted. A hot-rolled oxidation layer exists on the surface of the hot-rolled sheet, and shot balls can be sprayed uniformly in the thickness direction on this hot-rolled sheet. Specifically, short balls having a diameter of 0.4 mm or more and 0.8 mm or less can be sprayed on the hot rolled sheet at a spray speed of 25 m/sec or more and 40 m/sec or less and a spray amount of 600 kg/min or more and 1,200 kg/min or less. If the injection rate of the shot ball is less than 600 kg/min, the removal of the thermal oxidation layer is not sufficient, which may cause surface defects in the final product. Accordingly, the packing ratio of the final product may be reduced. If the injection amount of the shot ball exceeds 1200 kg/min, the hot rolled sheet in addition to the hot rolled oxidation layer may be removed. Accordingly, the recovery rate of the final product may be reduced. In addition, the surface roughness of the hot rolled sheet from which the hot rolled oxidation layer has been removed increases, and the surface roughness of the final product may also increase. Accordingly, the packing ratio of the final product may be reduced.

On the other hand, if the diameter of the shot ball is less than 0.4 mm, the removal efficiency of the thermal oxidation layer may be reduced. On the other hand, if the particle diameter exceeds 0.8 mm, the roughness of the hot-rolled sheet from which the hot-rolled oxidation layer has been removed may increase. If the injection speed of the short ball is less than 25 m/sec, the removal efficiency of the thermal oxidation layer may be reduced. On the other hand, when the injection speed of the shot ball exceeds 40 m/sec, the amount of impact applied to the hot-rolled sheet increases, and the roughness of the hot-rolled sheet from which the hot-rolled oxidation layer has been removed may increase. The injection speed can be controlled by adjusting the speed of the shot blast wheel, but the present invention is not limited to this.

Afterwards, the hot rolled sheet from which the hot rolled oxidation layer has been removed can be pickled. Accordingly, the hot-rolled oxidation layer or foreign substances remaining on the surface of the hot-rolled sheet can be removed. Specifically, the hot-rolled sheet from which the hot-rolled oxidation layer has been removed can be acid cleaned by immersing the hot-rolled sheet in a hydrochloric acid solution (concentration of approximately 15% by weight) at a temperature of approximately 82°C for approximately 78 seconds. However, the present invention is not limited to this. For example, if it is an acidic solution commonly used to remove oxides or foreign substances remaining on the surface of a hot-rolled sheet, this acidic solution may be used to acid-clean the hot-rolled sheet in the hot-rolled oxide layer removal step (S400).

A cold rolling step (S500) may be performed after the hot rolling oxidation layer removal step (S400). In the cold rolling step (S500), the hot rolled sheet from which the hot rolled oxidation layer has been removed can be cold rolled. At this time, the cold rolled hot rolled sheet may be called a cold rolled sheet. In the cold rolling step (S500), the hot rolled sheet from which the hot rolled oxidation layer has been removed can be cold rolled to a thickness of about 0.15 mm or more and about 0.30 mm or less. At this time, in order to provide rolling properties, warm rolling can be performed by raising the sheet temperature (e.g., the temperature of the hot-rolled sheet from which the hot-rolled oxidation layer has been removed) to about 150°C or more and about 200°C or less. The final reduction ratio in the cold rolling step (S500) may be about 81% or more and about 93% or less. Accordingly, the cold rolled sheet may have a thickness of 0.15 mm or more and 0.3 mm or less.

A cold rolling annealing step (S600) may be performed after the cold rolling step (S500). In the cold-rolled annealing step (S600), the cold-rolled cold-rolled sheet can be annealed. At this time, the annealed cold-rolled sheet may be called an annealed cold-rolled sheet.

The cold rolling annealing step (S600) may be performed at a temperature that results in the optimal grain size considering the final magnetic and mechanical properties. For example, the cold rolling annealing step (S600) may be performed at an annealing temperature of about 950°C or more and 1,100°C or less, a holding time of about 30 seconds or more and about 90 seconds or less, and a temperature increase rate of about 10°C/s or more. If the annealing temperature in the cold rolling annealing step (S600) is too low, the hysteresis loss may increase due to the fine grain size. On the other hand, if the annealing temperature in the cold rolling annealing step (S600) is too high, the grain size may increase too much, resulting in increased iron loss.

Additionally, the cold rolling annealing step (S600) may be performed in an atmosphere containing about 20 volume% or more and 50 volume% or less of hydrogen (H) to prevent surface oxidation and nitriding. Through this hydrogen-containing atmosphere, the surface condition of the cold rolled annealed plate can be made smoother.

In the cold-rolled annealing step (S600), the cold-rolled annealed plate can be cooled at a cooling rate of about 20°C/s or more. At this time, the cold rolled annealed plate may be cooled to about 200°C or more and about 250°C or less.

After the cold rolling annealing step (S600), a coating step may be performed. In the coating step, a coating layer can be formed on the annealed cold rolled annealed plate. By forming a coating layer through the coating step, punching properties can be improved and insulation properties can be secured.

A non-oriented electrical steel sheet manufactured through the method for manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention may have an iron loss (based on W10/400) of about 13.0 W/kg or less, and a magnetic flux density (based on W10/400) of about 1.60 T or more. B50 standard). Additionally, the manufactured non-oriented electrical steel sheet may have an area ratio of 95% or more.

<Experimental example>

Below, the present invention will be described in more detail through experimental examples. However, the following experimental examples are intended to illustrate the present invention in more detail, and the scope of the present invention is not limited by the following experimental examples. The following experimental examples can be appropriately modified and changed by those skilled in the art within the scope of the present invention.

division Si
(weight%) Mn
(weight%) Al
(weight%) C
(weight%) S
(weight%) P
(weight%) N
(weight%) Ti
(weight%) Example 1 3.3 0.3 0.9 0.0015 0.0017 0.0083 0.0018 0.0015 Example 2 3.3 0.3 1.2 0.0015 0.0018 0.0083 0.0015 0.0017 Example 3 3.3 0.3 1.2 0.0015 0.0018 0.0083 0.0015 0.0017 Example 4 3.3 0.3 1.2 0.0015 0.0018 0.0083 0.0015 0.0017 Example 5 3.3 0.3 1.2 0.0015 0.0018 0.0083 0.0015 0.0017 Example 6 3.3 0.3 1.2 0.0015 0.0018 0.0083 0.0015 0.0017 Example 7 3.3 0.3 2.2 0.0016 0.0016 0.0083 0.0015 0.0016 Example 8 3.3 0.3 2.4 0.0015 0.0016 0.0081 0.0015 0.0015 Comparative Example 1 3.3 0.3 0.5 0.0016 0.0017 0.0082 0.0017 0.0015 Comparative example 2 3.3 0.3 1.2 0.0015 0.0018 0.0083 0.0015 0.0017 Comparative example 3 3.3 0.3 1.2 0.0015 0.0018 0.0083 0.0015 0.0017 Comparative example 4 3.3 0.3 1.2 0.0015 0.0018 0.0083 0.0015 0.0017 Comparative Example 5 3.3 0.3 1.2 0.0015 0.0018 0.0083 0.0015 0.0017 Comparative Example 6 3.3 0.3 2.2 0.0016 0.0016 0.0083 0.0015 0.0016 Comparative Example 7 3.3 0.3 2.2 0.0016 0.0016 0.0083 0.0015 0.0016 Comparative example 8 3.3 0.3 2.7 0.0014 0.0018 0.0082 0.0014 0.0017

Table 1 shows the component composition of Examples 1 to 8 and Comparative Examples 1 to 8.

Slabs containing the component compositions listed in Table 1 were prepared so that Examples 1 to 8 and Comparative Examples 1 to 8 had the component compositions in Table 1. The amount of slabs lost during the manufacturing process of non-oriented electrical steel sheets due to oxidation, etc. is insignificant. Therefore, each of the slabs for manufacturing Examples 1 to 8 and Comparative Examples 1 to 8 has substantially the same composition as Examples 1 to 8 and Comparative Examples 1 to 8. These slabs were heated to approximately 1,130°C and hot-rolled under FDT conditions of approximately 880°C to produce hot-rolled plates with a thickness of approximately 2.0 mm. The manufactured hot-rolled sheets were wound at the coiling temperature (CT) shown in Table 2 below. The hot-rolled oxidation layers formed on the surfaces of the wound hot-rolled sheets had the thicknesses shown in Table 2 below. Preliminary annealing was performed on the rolled hot-rolled sheets at about 975°C for about 60 seconds. Thereafter, shot balls with a diameter of 0.6 mm were sprayed onto the pre-annealed hot-rolled sheets at a spray speed of 35 m/sec and the spray amount shown in Table 2 below, and then the hot-rolled sheets were pickled. Afterwards, the hot-rolled sheets from which the hot-rolled oxidation layers were removed were cold-rolled to produce cold-rolled sheets with a thickness of 0.25 mm, and the manufactured cold-rolled sheets were cold-rolled and annealed at about 950°C for about 45 seconds. At this time, cold rolling annealing was carried out in a mixed atmosphere of approximately 30 volume% hydrogen and approximately 70 volume% nitrogen, and the temperature increase rate was approximately 30°C/s and the cooling rate was approximately 30°C/s.

division Winding temperature (℃) Thermal oxide layer thickness (㎛) Spray amount (kg/min) Example 1 650 10 1000 Example 2 630 9 1000 Example 3 650 10 1000 Example 4 690 15 1000 Example 5 650 11 700 Example 6 650 10 1100 Example 7 650 10 1000 Example 8 650 10 1000 Comparative Example 1 650 10 1000 Comparative example 2 550 6 1000 Comparative example 3 650 10 500 Comparative Example 4 650 10 1300 Comparative Example 5 750 28 1300 Comparative Example 6 550 5 1000 Comparative Example 7 750 28 1300 Comparative example 8 650 10 1000

Table 2 shows the coiling temperature, the thickness of the hot oxide layer, and the spray amount of Examples 1 to 8 and Comparative Examples 1 to 8. Specifically, the coiling temperature in Table 2 means the coiling temperature (CT) in the coiling step (S200). The thickness of the hot-rolled oxidation layer in Table 2 refers to the thickness of the hot-rolled oxidation layer present on the surface of the hot-rolled sheet after the winding step (S200). In other words, the thickness of the hot-rolled oxidation layer in Table 2 is the thickness of the hot-rolled oxidation layer present on the surface of the hot-rolled sheet in the preliminary annealing step (S300). The injection amount in Table 2 refers to the injection amount of shot balls sprayed on the hot rolled sheet in the hot rolled oxidation layer removal step (S400).

Referring to Table 2, in the case of Examples 1 to 8, Comparative Example 1, Comparative Example 3, Comparative Example 4, and Comparative Example 8, in the winding step (S200), the hot rolled sheets were heated at a temperature of 630°C or more and less than 700°C. It was wound. Accordingly, in the case of Examples 1 to 8, Comparative Example 1, Comparative Example 3, Comparative Example 4, and Comparative Example 8, the hot-rolled oxidation layers present on the surface of the hot-rolled sheets had a thickness of 8 ㎛ or more and 18 ㎛ or less. Specifically, in Examples 1, 3, 5 to 8, Comparative Example 1, Comparative Example 3, Comparative Example 4, and Comparative Example 8, hot-rolled sheets were wound at a temperature of 650°C during the manufacturing process. . After winding, hot-rolled oxidation layers with a thickness of 10㎛ or 11㎛ existed on the surfaces of the hot-rolled sheets. In Example 2, hot-rolled sheets were wound at a temperature of 630°C during the manufacturing process. After winding, 9㎛ thick hot-rolled oxidation layers existed on the surfaces of the hot-rolled sheets. In Example 4, hot-rolled sheets were wound at a temperature of 690°C. After winding, 15㎛ thick hot-rolled oxidation layers existed on the surfaces of the hot-rolled sheets.

On the other hand, in Comparative Example 2 and Comparative Example 6, hot-rolled sheets were wound at a temperature of less than 630°C in the winding step (S200). Accordingly, in Comparative Example 2 and Comparative Example 6, the hot-rolled oxidation layers present on the surface of the hot-rolled sheets had a thickness of less than 8 μm. Specifically, in Comparative Example 2 and Comparative Example 6, hot-rolled sheets were wound at a temperature of 550°C during the manufacturing process. After winding, hot-rolled oxidation layers with a thickness of 5㎛ or 6㎛ existed on the surfaces of the hot-rolled sheets. Meanwhile, in Comparative Examples 5 and 7, hot-rolled sheets were wound at a temperature exceeding 700°C in the winding step (S200). Accordingly, in Comparative Examples 5 and 7, the hot-rolled oxidation layers present on the surfaces of the hot-rolled sheets had a thickness of more than 18㎛. Specifically, in Comparative Examples 5 and 7, hot-rolled sheets were wound at a temperature of 750°C during the manufacturing process. After winding, hot-rolled oxidation layers with a thickness of 28 μm existed on the surfaces of the hot-rolled sheets.

As described above, as the coiling temperature (CT) increases in the coiling step (S200), the thickness of the hot-rolled oxidation layer present on the surface of the hot-rolled sheet after coiling also increases. Accordingly, in order to remove the hot-rolled oxidation layer, the amount of shot balls sprayed on the hot-rolled sheet in the hot-rolled oxidation layer removal step (S400) must also be increased.

Specifically, in the case of Examples 1 to 4, Examples 7 to 8, Comparative Example 1 and Comparative Example 8, hot rolled oxidation layers with a thickness of 9㎛, 10㎛ or 15㎛ were formed on the surface of the hot rolled sheets after winding. As it exists, shot balls of 1000 kg/min were sprayed onto the hot rolled sheets in the hot rolled oxidation layer removal step (S400). On the other hand, in the case of Comparative Example 5 and Comparative Example 7, 28㎛ thick hot rolled oxidation layers were present on the surface of the hot rolled sheets after winding, and in the hot rolled oxidized layer removal step (S400), a short ball of 1300 kg/min was applied to the hot rolled sheets. This was sprayed.

Meanwhile, in the case of Comparative Example 3, Example 5, Example 6, and Comparative Example 4, hot rolled oxidation layers with a thickness of 10 μm or 11 μm exist on the surfaces of the hot rolled sheets after winding. However, in order to check the effect of the injection amount of the short balls sprayed on the hot-rolled sheet, in the hot-rolled oxidation layer removal step (S400), short balls were sprayed on the hot-rolled sheet at a spray rate of 500 kg/min, 700 kg/min, 1100 kg/min, or 1300 kg/min. was sprayed. In the case of Comparative Example 2 and Comparative Example 6, hot rolled oxidation layers with a thickness of 5 μm or 6 μm exist on the surfaces of the hot rolled sheets after winding. However, in order to confirm the effect of the amount of shot balls sprayed on the hot-rolled sheets, 1000 kg/min of short balls were sprayed on the hot-rolled sheets in the hot-rolled oxide layer removal step (S400).

division resistivity
(μΩ·cm) Number of AlN precipitates (piece/mm ² ) W10/400
(W/kg) B50
(T) Spot rate
(%) Example 1 59 0.52 12.0 1.68 96 Example 2 61 0.70 12.1 1.66 96 Example 3 61 0.55 11.8 1.66 96 Example 4 61 0.45 12.0 1.66 96 Example 5 61 0.54 12.0 1.67 96 Example 6 61 0.55 11.9 1.66 96 Example 7 70 0.55 10.2 1.63 96 Example 8 72 0.53 10.0 1.61 96 Comparative Example 1 55 0.42 14.3 1.68 96 Comparative example 2 61 1.77 13.8 1.63 96 Comparative example 3 61 0.52 11.8 1.66 94 Comparative example 4 61 0.49 11.7 1.67 93 Comparative Example 5 61 0.49 11.9 1.66 93 Comparative Example 6 70 1.53 13.3 1.59 96 Comparative example 7 70 0.53 10.2 1.60 93 Comparative example 8 75 0.84 10.1 1.55 96

Table 3 shows the specific resistance, number of AlN precipitates, W10/400, B50, and space ratio of Examples 1 to 8 and Comparative Examples 1 to 8.

In Table 3, the number of AlN precipitates with a diameter of 100 nm or less was measured in the cross section from the surface to a depth of 20 μm. Specifically, the diameter and number of AlN precipitates were measured based on cross-sections cut parallel to the thickness direction of each of the non-oriented electrical steel sheets of Examples 1 to 8 and Comparative Examples 1 to 8.

In Table 3, W10/400 is the iron loss when a magnetic flux density of 1.0 Tesla(T) is induced at a frequency of 400 Hz, and B50 is the magnetic flux density at 5000 A/m. In non-oriented electrical steel sheets with a thickness of 0.35 mm or less used in electric vehicle motors, magnetic properties at high frequencies above 400 Hz and low magnetic fields below 1.0 T are important, so the iron loss of W10/400 was measured. Magnetic properties such as magnetic flux density and iron loss were measured using a single sheet tester (SST). Specifically, the iron loss value and magnetic flux density value of each of Examples 1 to 8 and Comparative Examples 1 to 8 were measured in the rolling direction and the direction perpendicular to rolling, and the average values were shown.

The space factor was measured by stacking a plurality of specimens for each of Examples 1 to 8 and Comparative Examples 1 to 8. Specifically, the theoretical weight was calculated by applying a uniform pressure of 1 MPa to the stacked specimens and then measuring the height, width, and length of the stacked specimens. Afterwards, the actual weight was divided by the theoretical weight to measure the drop rate. However, the present invention is not limited to this.

As the content of aluminum (Al) in the slab increases, the resistivity of the non-oriented electrical steel sheet increases. However, the number of AlN precipitates generated during the manufacturing process of non-oriented electrical steel also increases. Accordingly, in the past, in order to prevent iron loss from increasing due to excessive formation of AlN precipitates, aluminum (Al) was included in an amount of 0.9% by weight or less based on the total weight of the slab. However, in the embodiments of the present invention, the generation of AlN precipitates can be controlled by adjusting the thickness of the hot-rolled oxidation layer, so that aluminum (Al) is included at 0.9% by weight or more based on the total weight of the slab. That is, Examples 1 to 8 contain aluminum (Al) in an amount of 0.9% by weight or more based on the total weight of the non-oriented electrical steel sheet.

Referring to Table 3, it can be seen that the specific resistance increases in the order of Example 1, Example 3, Example 7, and Example 8. This is because the content of aluminum (Al) component increases in the order of Example 1, Example 3, Example 7, and Example 8. That is, as described above, aluminum (Al) increases the resistivity together with silicon (Si), so the resistivity of Example 1 containing 0.9 wt% of aluminum (Al) is higher than that of Example 1 containing 0.9 wt% of aluminum (Al). The resistivity of Example 3 may be high. Similarly, the resistivity of Example 7 containing 2.2% by weight of aluminum (Al) is greater than that of Example 3 containing 1.2% by weight of aluminum (Al), and the resistivity of Example 7 containing 2.2% by weight of aluminum (Al) is greater than that of Example 3 containing 1.2% by weight of aluminum (Al). The resistivity of Example 8 containing 2.4% by weight of aluminum (Al) may be greater than that of Example 7. Example 2 and Examples 4 to 6 contain 1.2% by weight of aluminum (Al), and may have the same resistivity as that of Example 3.

Meanwhile, Comparative Example 1 may contain less than 0.9% by weight of aluminum (Al). Specifically, Comparative Example 1 may contain 0.5% by weight of aluminum (Al). Accordingly, Comparative Example 1 may have low resistivity and high iron loss value. Comparative Example 8 may include more than 2.5% by weight aluminum (Al). Specifically, Comparative Example 8 may contain 2.7% by weight of aluminum (Al). Accordingly, Comparative Example 8 may have high resistivity. However, as it contains more than 2.5% by weight of aluminum (Al), Comparative Example 8 may have a low magnetic flux density. In order for a non-oriented electrical steel sheet to have excellent magnetic properties, the non-oriented electrical steel sheet must have low iron loss and high magnetic flux density. Therefore, Comparative Examples 1 and 8 may have inferior magnetic properties.

Meanwhile, Comparative Examples 2 to 5 may have the same ingredient composition as Example 3. However, Comparative Examples 2 and 5 may be different from Example 3 in coiling temperature (CT) and thickness of the thermal oxide layer. Specifically, in the coiling step (S200) during the manufacturing process, the hot rolled sheet of Example 3 was wound at a temperature of 650°C. Accordingly, a 10㎛ thick hot-rolled oxidation layer was formed on the surface of the hot-rolled sheet of Example 3. On the other hand, the hot-rolled sheet of Comparative Example 2 was wound at a temperature of 550°C, and the hot-rolled sheet of Comparative Example 5 was wound at a temperature of 750°C. Accordingly, a 6㎛-thick hot-rolled oxidation layer was formed on the surface of the hot-rolled sheet of Comparative Example 2, and a 28㎛-thick hot-rolled oxidation layer was formed on the surface of the hot-rolled sheet of Comparative Example 5.

As described above, the hot rolled oxidation layer may prevent nitrogen (N) in the atmosphere from penetrating into the hot rolled sheet during the preliminary annealing step (S300). Therefore, the hot-rolled oxidation layer can suppress AlN precipitates from being generated inside the hot-rolled sheet in the preliminary annealing step (S300). In other words, as the thickness of the hot-rolled oxidation layer becomes thicker, the number of AlN precipitates generated inside the hot-rolled sheet may decrease. Since the preliminary annealing step (S300) is performed in an atmosphere containing nitrogen (N), a significant portion of the AlN precipitates of the non-oriented electrical steel sheet may be generated in the preliminary annealing step (S300). Therefore, the number of AlN precipitates in the non-oriented electrical steel sheet may be the same or similar to the number of AlN precipitates in the hot-rolled sheet after the preliminary annealing step (S300).

AlN precipitates contained in non-oriented electrical steel prevent the movement of the magnetic domain wall and magnetization. Accordingly, the iron loss of the non-oriented electrical steel sheet increases. Therefore, a small number of AlN precipitates must be generated inside the hot-rolled sheet. Example 3 has 0.55/mm ² AlN precipitates. On the other hand, the hot rolled sheet of Comparative Example 2 had 1.77 pieces/mm ² of AlN precipitates, and Comparative Example 5 had 0.49 pieces/mm ² of AlN precipitates. That is, the hot rolled sheet of Comparative Example 2 had 1.77 pieces/mm ² of AlN precipitates, so Comparative Example 2 had a higher iron loss value than Example 3. Specifically, Comparative Example 2 had an iron loss value of 13.8 W/kg, and Example 3 had an iron loss value of 11.8 W/kg.

On the other hand, Comparative Example 5 has 0.49 pieces/mm ² of AlN precipitates. Accordingly, Comparative Example 5 has an iron loss value corresponding to that of Example 3. Specifically, Comparative Example 5 has an iron loss value of 11.9 W/kg, and Example 3 has an iron loss value of 11.8 W/kg. As described above, the hot-rolled oxide layer may fracture during cold rolling and reduce the magnetic properties of the final product, so the hot-rolled oxide layer is removed through shot blasting in the hot-rolled oxide layer removal step (S400). However, if the thickness of the hot oxidation layer exceeds about 18㎛, removal of the hot oxidation layer may not be easy. Since the thickness of the thermally oxidized layer of Comparative Example 5 is 28㎛, it can be removed at a spray rate of 1300 kg/min in the thermally oxidized layer removal step (S400). Accordingly, the surface roughness of the hot-rolled sheet from which the hot-rolled oxidation layer has been removed increases, and the space factor of the final product may decrease. Therefore, Comparative Example 5 has a drop rate of 93%.

Meanwhile, the hot-rolled sheet of Comparative Example 3 and the hot-rolled sheet of Comparative Example 4 were wound at the same temperature as the hot-rolled sheet of Example 3, and the thickness of the hot-rolled oxidation layer of Comparative Example 3 and the thickness of the hot-rolled oxidation layer of Comparative Example 4 were those of Example 3. It is the same as the thickness of the thermal oxidation layer. However, unlike the heat oxidation layer of Example 2, the heat oxidation layer of Comparative Example 3 was removed at a spray rate of 500 kg/min in the heat ash layer removal step (S400), and the heat ash oxidation layer of Comparative Example 4 was removed in the heat ash layer removal step (S400). It was removed at a spray rate of 1300 kg/min. Accordingly, the thermal oxidation layer of Comparative Example 3 is not sufficiently removed, and the space factor may decrease. Therefore, Comparative Example 3 has a drop rate of 94%. Since the hot-rolled oxidation layer of Comparative Example 4 is removed with an excessive spray amount in the hot-rolled oxidation layer removal step (S400), the surface roughness of the hot-rolled sheet from which the hot-rolled oxidation layer of Comparative Example 4 has been removed increases, and the area ratio of the final product may decrease. Therefore, Comparative Example 4 has a drop rate of 93%.

On the other hand, in the case of Examples 5 and 6 in which 10㎛ thick hot-rolled oxidation layers exist on the surface of the hot-rolled sheets after winding, in the hot-rolled oxidation layer removal step (S400), a weight of 600 kg/min or more and 1,200 kg/min or less is applied to the hot-rolled sheets. Short balls were sprayed at the spray amount. Accordingly, in the case of Examples 5 and 6, the surface roughness of the hot-rolled sheet from which the hot-rolled oxidation layer was removed does not increase excessively, and the area ratio of the final product may not decrease. Therefore, Example 5 has a footprint of 96%, and Example 6 has a footprint of 96%.

Meanwhile, Comparative Examples 6 and 7 may have the same ingredient composition as Example 7. However, Comparative Examples 6 and 7 may be different from Example 7 in terms of coiling temperature (CT) and thickness of the thermal oxide layer. Accordingly, the contents described above for Comparative Example 2, Comparative Example 5, and Example 3 can be equally applied to Comparative Example 6, Comparative Example 7, and Example 7.

Specifically, in the coiling step (S200) during the manufacturing process, the hot rolled sheet of Example 7 was wound at a temperature of 650°C. Accordingly, a 10 μm thick hot rolled oxidation layer was formed on the surface of the hot rolled sheet of Example 7. On the other hand, the hot-rolled sheet of Comparative Example 6 was wound at a temperature of 550°C, and the hot-rolled sheet of Comparative Example 7 was wound at a temperature of 750°C. Accordingly, a 5㎛-thick hot-rolled oxidation layer was formed on the surface of the hot-rolled sheet of Comparative Example 6, and a 28㎛-thick hot-rolled oxidation layer was formed on the surface of the hot-rolled sheet of Comparative Example 7.

Accordingly, Example 7 has 0.55 pieces/mm ² of AlN precipitates and an iron loss value of 10.2 W/kg. On the other hand, Comparative Example 6 has 1.53 pieces/mm ² of AlN precipitates and has a high iron loss value of 13.3 W/kg. Meanwhile, Comparative Example 7 has 0.53 pieces/mm ² of AlN precipitates and has the same iron loss value as Example 7 of 10.2 W/kg. Since the thickness of the thermally oxidized layer of Comparative Example 7 is 28㎛, it can be removed at a spray rate of 1300 kg/min in the thermally oxidized layer removal step (S400). Accordingly, the surface roughness of the hot-rolled sheet from which the hot-rolled oxidation layer has been removed increases, and the space factor of the final product may decrease. Therefore, Comparative Example 7 has a drop rate of 93%.

As a result, it can be confirmed that Examples 1 to 8 have low iron loss and high magnetic flux density. Specifically, for Examples 1 to 8, the measured iron loss (based on W10/400) values all satisfied 10.0 W/kg or more and 13.0 W/kg or less, and for Examples 1 to 8, the measured magnetic flux The densities (B50 standard) all satisfied the range of 1.60T or more and 1.70T or less. Moreover, it can be confirmed that Examples 1 to 8 have a high drop ratio. Specifically, in the case of Examples 1 to 8, the measured static ratios all satisfied 95% or more and 98% or less. To this end, in Examples 1 to 8, the number of AlN precipitates with a diameter of 100 nm or less in the cross section from the surface to a depth of 20 μm may be 0.4 or more/mm ² and 0.8 or less/mm ² .

On the other hand, it can be seen that Comparative Examples 1, 2, and 6 have high iron loss (based on W10/400). Specifically, in the case of Comparative Example 1, Comparative Example 2, and Comparative Example 6, the measured iron loss (based on W10/400) exceeded 13.0 W/kg. However, in the case of Comparative Examples 3 to 5, Comparative Example 7, and Comparative Example 8, the measured iron loss (based on W10/400) satisfied 10.0 W/kg or more and 13.0 W/kg or less. As mentioned above, magnetic properties are evaluated by comprehensively considering iron loss and magnetic flux density. However, in the case of Comparative Example 8, since the measured magnetic flux density (based on B50) is less than 1.60T, Comparative Examples 1, 2, 6, and 8 have inferior magnetic properties. That is, compared to these comparative examples, the examples have excellent magnetic properties. In other words, by controlling the generation of AlN while increasing the resistivity, the embodiments have excellent magnetic properties.

Meanwhile, in Comparative Examples 3 to 5 and Comparative Example 7, the measured space ratio was less than 95%. That is, comparative examples may have inferior magnetic properties or inferior space factors. Compared to these comparative examples, the examples have excellent magnetic properties and at the same time have excellent space factors.

The present invention has been described with reference to the embodiments shown in the drawings, but these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true scope of technical protection of the present invention should be determined by the technical spirit of the attached patent claims.

Claims (10)

By weight percentage, Silicon (Si): 2.8% to 3.8%, Manganese (Mn): 0.2% to 0.5%, Aluminum (Al): 0.9% to 2.5%, Carbon (C): 0% to 0.002% Hereinafter, sulfur (S): more than 0% and less than 0.002%, phosphorus (P): more than 0% and less than 0.015%, nitrogen (N): more than 0% and less than 0.002%, titanium (Ti): more than 0% and less than 0.002%, Preparing a slab containing the remainder of iron (Fe) and inevitable impurities;
Forming a hot-rolled plate by hot-rolling the slab;
Winding the hot-rolled sheet so that the hot-rolled oxidation layer formed on the surface of the hot-rolled sheet has a thickness of 8 ㎛ or more and 18 ㎛ or less;
Preliminarily annealing the hot rolled sheet;
removing the hot-rolled oxidation layer from the hot-rolled sheet;
forming a cold-rolled sheet by cold-rolling the hot-rolled sheet; and
Cold-rolling and annealing the cold-rolled sheet;
Method for manufacturing a non-oriented electrical steel sheet, including. According to paragraph 1,
The step of winding the hot rolled sheet is,
A method of manufacturing a non-oriented electrical steel sheet, which is a step of winding the hot-rolled sheet at a coiling temperature of 630 ℃ or more and 700 ℃ or less. According to paragraph 1,
The step of forming the hot rolled sheet is,
A method of manufacturing a non-oriented electrical steel sheet, which is a step of forming the hot-rolled sheet by heating the slab to a temperature of 1,000 ℃ or more and 1,150 ℃ or less and then rolling. According to paragraph 1,
The step of preliminary annealing the hot rolled sheet,
A method of manufacturing a non-oriented electrical steel sheet, which is a step of annealing the hot-rolled sheet at a temperature of 900 ℃ or more and 1,100 ℃ or less for 30 seconds or more and 90 seconds or less. According to paragraph 1,
The step of removing the thermal oxidation layer is,
A method of manufacturing a non-oriented electrical steel sheet, comprising the step of subjecting the hot-rolled sheet to shot blasting and then pickling the hot-rolled sheet. According to clause 5,
The step of removing the thermal oxidation layer is,
Shot blasting the hot-rolled sheet by spraying shot balls having a diameter of 0.4 mm to 0.8 mm at a spray speed of 25 m/sec to 40 m/sec and a spray amount of 600 kg/min to 1200 kg/min. A method of manufacturing a non-oriented electrical steel sheet. As a non-oriented electrical steel sheet,
By weight percentage, Silicon (Si): 2.8% to 3.8%, Manganese (Mn): 0.2% to 0.5%, Aluminum (Al): 0.9% to 2.5%, Carbon (C): 0% to 0.002% Hereinafter, sulfur (S): more than 0% and less than 0.002%, phosphorus (P): more than 0% and less than 0.015%, nitrogen (N): more than 0% and less than 0.002%, titanium (Ti): more than 0% and less than 0.002%, Contains the remainder of iron (Fe) and inevitable impurities,
Non-oriented electrical steel sheet in which the number of AlN precipitates with a diameter of 100 nm or less in the cross section from the surface to a depth of 20㎛ is 0.4 or more/mm ² and 0.8 or less/mm ² In clause 7,
The non-oriented electrical steel sheet has an iron loss (based on W10/400) of 10.0 W/kg or more and 13.0 W/kg or less. In clause 7,
The non-oriented electrical steel sheet has a magnetic flux density (based on B50) of 1.60T or more and 1.70T or less. In clause 7,
The non-oriented electrical steel sheet is a non-oriented electrical steel sheet having an area ratio of 95% or more and 98% or less.

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