KR20240098846A - Non-oriented electrical steel sheet and method of manufacturing the same - Google Patents

Abstract

The present invention relates to a non-oriented electrical steel sheet and a method of manufacturing the same, wherein the non-oriented electrical steel sheet has an area fraction of grain size less than 1/3 times the average grain size of less than 5% and a dislocation density of more than 10 ¹² /m ² 10 ¹⁶ The fraction of the area where dislocations are concentrated below /m ² may be less than 5% of the total area.

Description

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

The present invention relates to electrical steel sheets, and more specifically to non-oriented electrical steel sheets and methods for manufacturing the same.

Electrical steel is a product used as a material for transformers, motors, and electronic devices. Unlike general carbon steel, which places importance on processability such as mechanical properties, it is a functional product that places importance on electrical properties. The electrical properties include characteristics such as iron loss, magnetic flux density, permeability, and space factor, and the electrical steel sheet is characterized by low iron loss and high magnetic flux density, magnetic permeability, and space factor.

The electrical steel sheet is largely divided into oriented electrical steel sheet and non-oriented electrical steel sheet. The grain-oriented electrical steel sheet is an electrical steel sheet with excellent magnetic properties in the rolling direction by forming {110}<001> texture, which is a Goos texture, throughout the steel sheet using an abnormal grain growth phenomenon called secondary recrystallization. The non-oriented electrical steel sheet is an electrical steel sheet whose magnetic properties are uniform in all directions on the rolled sheet.

In the case of the non-oriented electrical steel sheet, it is mainly used in motors that convert electrical energy into mechanical energy. In order to achieve high efficiency in this energy conversion process, the magnetic properties of the non-oriented electrical steel sheet must be excellent.

In addition, globally, the industrial structure is being reorganized into an eco-friendly, low-carbon focused industry to prepare for a carbon neutral era. According to this trend, in the case of automobiles, internal combustion engines are rapidly being replaced by electric vehicles, and the drive motors used in the electric vehicles account for the majority of electric energy usage, and non-directional electricity is used as the core material of the drive motors. Demand for steel plates continues to increase. Against this background, improving the iron loss of non-oriented electrical steel sheets is very important as a way to increase the efficiency of the drive motor.

In the case of general non-oriented electrical steel, magnetic properties are mainly evaluated by iron loss at 50 Hz and iron loss at 400 Hz. Since the iron loss refers to energy loss occurring at a specific magnetic flux density and frequency, the iron loss at 50 Hz is regarded as energy loss occurring at normal frequencies, and the iron loss at 400 Hz is regarded as energy loss occurring at high frequencies. do.

It is known that when a non-oriented electrical steel sheet with low iron loss is used in the core of the motor, heat loss occurring in the core of the motor is reduced, making it possible to manufacture a highly efficient motor. Since the motor driven through inverter control operates at various driving speeds, it is a method to manufacture a motor with higher efficiency by lowering iron loss at normal frequencies, iron loss at high frequencies, or even higher, iron loss at ultra-high frequencies. is one of

One of the methods used to improve the iron loss of the non-oriented electrical steel sheet is to add alloy elements such as silicon (Si), aluminum (Al), and manganese (Mn), minimize impurities, and reduce the thickness of the steel sheet. As the resistivity of steel increases through the addition of the alloy elements, eddy current loss is reduced, thereby lowering the total iron loss.

In addition, when the impurities are minimized, the structure of the magnetic domains in the steel sheet changes to a form that generates less loss during magnetization, and the number of closed magnetic domains fixed by inclusions or precipitates in the steel sheet is reduced, thereby improving iron loss. In addition, when the thickness of the steel sheet is reduced, the eddy current loss, which increases in proportion to the square of the thickness, is reduced, thereby effectively reducing iron loss.

Depending on the design intent of the motor, the overall iron loss as well as the iron loss in the rolling direction in particular can act as important factors. Generally, in cases where the direction of magnetization does not rotate, such as a large-sized rotary machine or linear motor, or when electrical steel sheets with improved iron loss in the rolling direction are used in motors that drive using reluctance during magnetization. There is.

However, among the technologies used to improve iron loss, increasing the amount of alloy increases production costs due to an increase in alloy raw material costs and a rapid decrease in cold rolling properties, and there is a problem that it is impossible to increase the amount of the alloy from the current level. Lowering the thickness has the problem of increasing production costs and sharply decreasing production per hour as heat treatment and rolling times increase. In addition, lowering impurities has problems such as a decrease in productivity due to limitations in steelmaking technology and an increase in refining time, and problems such as increased costs due to the use of strict alloy raw material components, making it difficult to reduce the iron loss. .

In addition, in improving the iron loss in the rolling direction, methods for improving the iron loss only in the rolling direction other than the methods described above are very limited, making it difficult to apply it to the actual manufacturing process. As such, conventional technologies increase manufacturing costs or reduce productivity and error rate, so research is needed on technologies that can solve the above-mentioned problems and effectively reduce iron loss.

The technical problem to be solved by the present invention is to provide a non-oriented electrical steel sheet that reduces manufacturing costs, increases productivity and error rate, and improves iron loss.

Another technical problem to be solved by the present invention is to provide a method of manufacturing a non-oriented electrical steel sheet having the above advantages.

The non-oriented electrical steel sheet according to an embodiment of the present invention has an area fraction of grains having a grain size less than 1/3 times the average grain diameter of less than 5%, and a dislocation density of grains exceeding 10 ¹² /m ² and less than 10 ¹⁶ /m ² The area fraction may be less than 5% of the total area. In one embodiment, the area fraction of grains having a grain diameter that is more than 3 times the average grain diameter may be less than 5%.

In one embodiment, in weight percent: Si: 0.1 to 6.5%, Al: 0.001 to 6.5%, Mn: 0.01 to 20%, C: 0.0010 to 0.015%, N: 0.0003 to 0.001%, S: 0.0003 to 0.001%. , Ti: 0.0003 to 0.001%, and may include the balance of Fe and inevitable impurities. In one embodiment, the average grain size may be 40 to 250 ㎛. In one embodiment, the thickness may be 0.03 to 0.5 mm.

In one embodiment, the iron loss (W10/400) and the thickness (t) of the non-oriented electrical steel sheet may satisfy Equation 1 below.

<Equation 1>

W10/400 iron loss (W/kg) < 6 + (t/0.04) ^1.1

(In Equation 1 above, t means the thickness (mm) of the non-oriented electrical steel sheet)

In one embodiment, the iron loss (W15/50) and the thickness (t) of the non-oriented electrical steel sheet may satisfy Equation 2 below.

<Equation 2>

W15/50 iron loss (W/kg) < 0.7+(t/0.03) ^1/5

(In Equation 2 above, t means the thickness (mm) of the non-oriented electrical steel sheet)

According to another embodiment of the present invention, a method of manufacturing a non-oriented electrical steel sheet includes the steps of manufacturing a hot-rolled steel sheet by hot-rolling a slab, manufacturing a cold-rolled steel sheet by cold-rolling the hot-rolled steel sheet, and annealing the cold-rolled steel sheet. A cold-rolled steel sheet annealing step is included, and in the cold-rolled steel sheet annealing step, a tension of more than 0.01 to less than 1.0 kgf/mm ² is applied in the rolling direction (RD direction) of the coil at a temperature of 650 ° C. or higher, and applied to the cold-rolled steel sheet. The direction of tension may form an angle of less than 3° with the rolling direction (RD direction) of the coil, and may form an angle of more than 87° and less than 93° with the normal direction of the rolling surface of the cold rolled steel sheet (ND direction). In one embodiment, the slab has, in weight percent: Si: 0.1 to 6.5%, Al: 0.001 to 6.5%, Mn: 0.01 to 20%, C: 0.0010 to 0.015%, N: 0.0003 to 0.01%, S: 0.0003 to 0.01%, Ti: 0.0003 to 0.01%, and may include the balance of Fe and inevitable impurities.

In one embodiment, the method further includes a hot-rolled steel sheet annealing step of heating the hot-rolled steel sheet, and the hot-rolled steel sheet annealing step may be a step of heating the hot-rolled steel sheet to 850 to 1,150°C. In one embodiment, the annealing of the cold rolled steel sheet may include a temperature raising step of heating the cold rolled steel sheet to 820°C or higher and a cooling step of cooling the cold rolled steel sheet from 820 to 900°C to 750 to 820°C.

In one embodiment, in the annealing step of the cold rolled steel sheet, the temperature raising step may be performed for less than 60 seconds. In one embodiment, in the annealing step of the cold rolled steel sheet, the cooling step may be performed for 5 seconds or more.

In one embodiment, in the annealing step of the cold rolled steel sheet, the cooling step may cool the sheet surface perpendicular to the direction of gravity. In one embodiment, the annealing step of the cold rolled steel sheet may be annealed in a reducing atmosphere.

The non-oriented electrical steel sheet according to an embodiment of the present invention improves by lowering the iron loss in the rolling direction by controlling the area ratio of the grain size, specifically, the grain size area fraction and dislocation density that are 1/3 times the average grain size, and at the same time, the iron loss of the grains is improved. It is possible to provide a non-oriented electrical steel sheet with an even distribution and uniform dislocation density.

According to another embodiment of the present invention, the method of manufacturing a non-oriented electrical steel sheet distributes homogenized grains within the steel sheet by controlling the direction and size of the cooling rate and tension in the heat treatment process, thereby producing a non-oriented electrical steel sheet having the above-mentioned advantages. A method for manufacturing can be provided.

Figure 1a shows the arrangement of the steel sheet in the cold-rolled steel sheet annealing step according to an embodiment of the present invention, and Figures 1b and 1c show the moving direction of the steel sheet according to the moving direction and tension direction, respectively, in a plan view. .
Figures 2a and 2b are cross-sectional views showing the moving direction of the steel sheet according to the moving direction and tension direction of the steel sheet, respectively.
Figure 3 shows a region where dislocations are dense, according to an embodiment of the present invention.
Figures 4A to 4E are enlarged illustrations of a region where dislocations are concentrated according to an embodiment of the present invention and a comparative example.

Terms such as first, second, and third 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, the first part, component, region, layer or section described below may be referred to as the second part, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is only intended to refer to specific embodiments and is not intended to limit the invention. As used herein, singular forms include plural forms unless phrases clearly indicate the contrary. As used in the specification, “comprising” means specifying a particular characteristic, area, integer, step, operation, element and/or ingredient, and the presence or presence of another characteristic, area, integer, step, operation, element and/or ingredient. This does not exclude addition.

When a part is referred to as being “on” or “on” another part, it may be directly on or on the other part or may be accompanied by another part in between. In contrast, when a part is said to be "directly on top" of another part, there is no intervening part between them.

Although not defined differently, all terms including technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted as having meanings consistent with related technical literature and currently disclosed content, and are not interpreted in ideal or very formal meanings unless defined.

Additionally, unless specifically stated, % means weight%, and 1ppm is 0.0001% by weight. In one embodiment of the present invention, further including an additional element means replacing the remaining iron (Fe) by the amount of the additional element.

Additionally, in the present invention, the Goss orientation refers to an orientation corresponding to {110}<001> in the Miller index, and the cube orientation refers to the orientation corresponding to {100}<001> in the Miller index.

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

According to an embodiment of the present invention, the non-oriented electrical steel sheet has, in weight%, Si: 0.1 to 6.5% by weight, Al: 0.001 to 6.5% by weight, Mn: 0.01 to 20% by weight, C: 0.0010 to 0.0150% by weight. , and 0.0003 to 0.01% by weight of one or more of N, S, and Ti, respectively, and the balance includes Fe and inevitable impurities.

Hereinafter, the reason for limiting the components of non-oriented electrical steel sheet will be explained.

Si: 0.1 to 6.5% by weight

Silicon (Si) plays a role in lowering iron loss by increasing the resistivity of the material and is an ingredient used as a deoxidizer in the steelmaking process. In addition, silicon is an element that is inevitably added in the electrical steel sheet manufacturing process and is an element that forms oxides during the manufacturing process. The Si content may be 0.1 to 6.5 weight%. Specifically, the Si content may be 1.0 to 4.5 weight%.

If the silicon content is excessively high, the brittleness of the material increases, causing a sharp decrease in rolling productivity, a thick oxide layer harmful to magnetism is formed, and iron loss may be inhibited by the internal oxide. Additionally, if the silicon content is excessively high, a secondary phase may be formed and magnetism may be greatly deteriorated. If the silicon content is excessively small, low-temperature Si oxide is formed, resulting in deterioration of iron loss.

Al: 0.001 to 6.5% by weight

Aluminum (Al), like silicon, plays a role in lowering iron loss by increasing the resistivity of the material, and can be used as a strong deoxidizer in steelmaking. The content of aluminum may be 0.001 to 6.5% by weight. Specifically, the aluminum content may be 0.1 to 2.0 weight%.

Mn: 0.01 to 20% by weight

Manganese (Mn) is an element that can improve iron loss by increasing the resistivity of materials, and can play a role in forming sulfides in steel. The content of manganese may be 0.01 to 20% by weight. Specifically, the content of manganese may be 0.01 to 6.5% by weight. More specifically, the content of manganese may be 0.01 to 2.0% by weight.

In one embodiment, the non-oriented electrical steel sheet may contain 0.0003 to 0.001% by weight of one or more of N, S, and Ti, respectively. Specifically, it may include at least one of N, S, and Ti, and more specifically, it may include all of N, S, and Ti.

C: (0.0005) to (0.015) weight%

Carbon (C) is an element that is inevitably included in the non-oriented electrical steel manufacturing process, and may be an element that plays a role in homogenizing the rolling structure of the steel during rolling. Specifically, the carbon content is 0.0005 to 0.015% by weight, further. Specifically, it may contain 0.0015 to 0.004% by weight.

If the carbon content is excessively high, carbides are formed, which hinders the movement of magnetic domains and requires additional energy for magnetization when the material is magnetized. If the carbon content is excessively small, there is a problem in that the material during rolling becomes non-uniform and the grain size of the recrystallization structure becomes non-uniform.

N: 0.0003 to 0.010% by weight

Nitrogen (N) not only forms fine AlN precipitates inside the steel sheet, but also combines with other impurities to form fine precipitates to suppress grain growth, thereby reducing iron loss and improving strength. The nitrogen content may be 0.0003 to 0.010% by weight. Specifically, the nitrogen content may be 0.0003 to 0.004% by weight.

S: 0.0003 to 0.010% by weight

Sulfur (S) forms a fine precipitate, MnS, which deteriorates the magnetic properties. Because it deteriorates hot workability, it is desirable to maintain a low content. The sulfur content may be 0.0003 to 0.010% by weight. Specifically, the sulfur content may be 0.0003 to 0.004% by weight.

If the sulfur content is excessively high, there is a problem that cracks may occur during playing. If the sulfur content is excessively low, it may be desirable in terms of the characteristics of the steel sheet, but there is a manufacturing cost problem that arises because selected raw materials must be used to control the sulfur content to a value lower than the lower limit.

Ti: 0.0003 to 0.010% by weight

Titanium (Ti) has a very strong tendency to form precipitates inside the steel sheet, and can deteriorate iron loss by suppressing grain growth by forming fine carbides, nitrides, or sulfides inside the steel sheet. The content of titanium may be 0.0003 to 0.010% by weight. Specifically, the titanium content may be 0.0003 to 0.003% by weight.

If the titanium content is excessively high, deterioration of iron loss may be a problem. If the titanium content is excessively small, there is a manufacturing cost problem that arises because selected raw materials must be used to control the titanium content.

The non-oriented electrical steel sheet according to an embodiment of the present invention contains Fe and inevitable impurities as a remainder. As for unavoidable impurities, they are impurities mixed during the steelmaking stage and the manufacturing process of non-oriented electrical steel sheets, and since these are widely known in the field, detailed explanations will be omitted. In one embodiment of the present invention, the addition of elements other than the above-described alloy components is not excluded, and various elements may be included within a range that does not impair the technical spirit of the present invention. If additional elements are included, they are included by replacing the remaining Fe.

A non-oriented electrical steel sheet according to an embodiment of the present invention having the above-described composition has the following physical properties.

According to an embodiment of the present invention, the non-oriented electrical steel sheet may have an average grain size of 40 to 250 ㎛. The crystal grains of the non-oriented electrical steel sheet are characterized in that they are evenly distributed. This is because the grain boundaries are where dislocations in the steel sheet are concentrated, and the structural stability of the grain boundaries can be obtained from the uniform distribution of grain sizes. Specifically, the average grain size may be 50 to 120 ㎛.

In order to obtain the distribution of the grain size, individual grains closed by grain boundaries are designated in the microscopic tissue photo, the area of each grain is calculated, and the diameter of each grain is expressed by the corresponding ECD (Equivalent Circle Diameter). You can. At this time, the average grain diameter can be calculated by obtaining the distribution of grain diameters using the ECD and calculating the arithmetic average thereof.

If the average grain diameter is outside the upper limit of the range, the dispersion in the size of the grain diameter in steel may increase. In a grain size distribution with large dispersion, there may be a problem in which more dislocations are formed around large grains and a sub-grain boundary is created within the grains. If the average grain diameter is outside the lower limit of the above range, the proportion of grain boundaries in the entire material increases and magnetization becomes difficult.

In one embodiment, the non-oriented electrical steel sheet may have an area fraction of grains having a grain size that is less than 1/3 times the average grain diameter of less than 5%. A crystal grain having a grain size less than 1/3 times the average grain size means a grain size smaller than 1/3 times the average grain size calculated above.

The area fraction of the grain size that is less than 1/3 times the average grain size means the ratio of the area occupied by the grain size that is 1/3 times the average grain size in the entire structure of the non-oriented electrical steel sheet.

The texture fraction can be measured using X-ray diffraction Pol Figure, neutron diffraction, X-ray transmission analysis, or EBSD of an electron microscope. The area fraction of crystal grains with misorientation within 15 degrees from the center of Goss orientation and cube orientation can be calculated.

If the area fraction of the grain size that is less than 1/3 times the average grain size accounts for an excessively large proportion, there is a problem of low magnetic permeability due to difficulty in magnetization in a low magnetic field. In one embodiment, the area fraction of the grain size that is more than 3 times the average grain size may be less than 5%. A grain size that is more than 3 times the average grain size means a grain size that is more than 3 times the average grain size calculated above.

The area fraction of grains having a grain diameter exceeding 3 times the average grain diameter means the ratio of the area of grains having a grain diameter exceeding 3 times the average grain diameter in the entire structure of the non-oriented electrical steel sheet. If the area fraction of the grain size exceeding 3 times the average grain size accounts for an excessively large proportion, there is a problem in that there is a difference in dislocation distribution between grains and the displacement is concentrated in locally coarse grains, greatly increasing iron content.

In one embodiment, the sum of the fraction of grains having a Goss orientation and the fraction of crystal grains having a Cube orientation of the non-oriented electrical steel sheet may exceed 5%.

In one embodiment, the dislocation density of the non-oriented electrical steel sheet may be greater than 10 ¹² /m ² and less than 10 ¹⁶ /m ² , and the fraction of the area where dislocations are concentrated may be less than 5% of the total area. Dislocation density can be measured using a Transmission Electron Microscope (TEM), or more simply calculated using a Scanning Electron Microscope (SEM). The density of dislocations can be measured using the line section method.

Through tension control during annealing according to the present invention, it is possible to control the formation of dislocations formed around grain boundaries after annealing is completed. The formation of dislocations at high temperatures occurs in a region tens of nm away from the grain boundaries, while dislocations are suppressed from being emitted to the grain boundaries and are aligned internally into sub-grain boundaries. The greater the tension during annealing, the greater the amount of dislocations constituting the sub-grain boundary, and thus the azimuth error angle between the regions between the sub-grain boundaries increases. As the above error angle increases, additional energy is consumed during magnetization and the magnetism deteriorates. If the grain boundaries are sufficiently numerous and the size of each grain is uniform, the occurrence of dislocations due to tension during annealing is suppressed by the accommodation of dislocations in the grain boundaries.

In one embodiment, the thickness of the non-oriented electrical steel sheet may be 0.03 to 0.5 mm. Specifically, the thickness of the non-oriented electrical steel sheet may be 0.15 to 0.3 mm.

If the thickness is excessively thick, the tension during annealing varies depending on the plate thickness, and there is a problem in which dislocations are complexly formed due to tension in the thickness direction due to the difference in tension between the surface and the center. If the thickness is excessively thin, there is a problem that tension control in the annealing furnace becomes industrially impossible.

In one embodiment, the iron loss (W10/400) and the thickness (t) at a high frequency of 400 Hz and 1.0T of the non-oriented electrical steel sheet may satisfy Equation 1 below.

<Equation 1>

W10/400 iron loss (W/kg) < 6+(t/0.04) ^1.1

(In Equation 1 above, t refers to the thickness of the non-oriented electrical steel sheet)

By satisfying Equation 1 above, it is possible to provide a non-oriented electrical steel sheet with excellent magnetic properties such as core loss. If the above equation 1 is not satisfied, there is a problem in that a steel sheet with excellent high-frequency iron loss compared to the sheet thickness cannot be obtained.

In one embodiment, in the non-oriented electrical steel sheet, the iron loss and the thickness (t) at a normal frequency of 50 Hz and 1.5T of the non-oriented electrical steel sheet may satisfy Equation 2 below.

<Equation 2>

W15/50 iron loss (W/kg) < 0.7+(t/0.03) ^1/5

(In Equation 2 above, t refers to the thickness of the non-oriented electrical steel sheet)

By satisfying Equation 2 above, it is possible to provide a non-oriented electrical steel sheet with excellent magnetic properties such as core loss. If the above equation 2 is not satisfied, there is a problem that the iron loss under high magnetic flux density conditions is low and the motor loss at high torque greatly increases.

In one embodiment, in the non-oriented electrical steel sheet, the iron loss and the thickness (t) at a normal frequency of 50 Hz and 1.5T of the non-oriented electrical steel sheet may satisfy Equation 3 below.

<Equation 3>

W15/50 Iron loss in rolling direction (W/kg) < 0.6+(t/0.03) ^1/6

(In Equation 3 above, t refers to the thickness of the non-oriented electrical steel sheet)

By satisfying Equation 3 above, it is possible to provide a non-oriented electrical steel sheet with excellent magnetic properties such as core loss. If the above equation 3 is not satisfied, there is a problem that motor loss at high torque increases when using a split core made by cutting a part of the motor part in the rolling direction and assembling it.

In one embodiment, the iron loss (W10/400) and the thickness (t) at a high frequency of 400 Hz and 1.0T of the non-oriented electrical steel sheet may satisfy Equation 4 below.

W10/400 Rolling direction iron loss (W/kg) < 5+(t/0.04) ^1.1

<In Equation 4 above, t refers to the thickness of the non-oriented electrical steel sheet>

By satisfying Equation 4 above, it is possible to provide a non-oriented electrical steel sheet with excellent magnetic properties such as iron loss. If the above equation 4 is not satisfied, there is a problem that motor loss greatly increases when the rotation speed increases when using a split core made by cutting a part of the motor part in the rolling direction and assembling it.

According to another embodiment of the present invention, a method of manufacturing a non-oriented electrical steel sheet includes the steps of manufacturing a hot-rolled steel sheet by hot rolling a slab, manufacturing a cold-rolled steel sheet by cold-rolling the hot-rolled steel sheet, and annealing the cold-rolled steel sheet. It includes a cold rolled steel sheet annealing step.

The step of hot rolling the slab may include hot rolling the slab that satisfies the alloy composition of the present invention. Since the alloy components of the slab were described in the steel composition components of the non-oriented electrical steel sheet described above, redundant explanations will be omitted. During the manufacturing process of the non-oriented electrical steel sheet, the alloy composition is substantially the same as the final product.

The step of hot rolling the slab may include the step of heating the slab. In the step of heating the slab, the heating temperature is not limited, but can be specifically heated to 1,200°C or lower. When the slab heating temperature is excessively high, precipitates present in the slab, for example, AlN and MnS, are re-dissolved and then finely precipitated during hot rolling and annealing, which may inhibit grain growth and reduce magnetism. .

Thereafter, the heated slab can be hot rolled to produce a hot rolled steel sheet. The hot rolled steel sheet may be manufactured to have a thickness of 1 to 3 mm.

In one embodiment, in the step of hot rolling the slab, the finish rolling temperature may be 700° C. or higher. Specifically, the finish rolling temperature may be 800 to 1,000°C.

After manufacturing the hot rolled steel sheet, a hot rolled sheet annealing step of heating the hot rolled steel sheet may be included. In one embodiment, the hot-rolled sheet annealing step may be performed by heating the hot-rolled steel sheet to 850 to 1,150 °C.

In one embodiment, after manufacturing the hot rolled steel sheet, a step of pickling the annealed hot rolled steel sheet may be included.

After manufacturing the hot-rolled steel sheet, the method may include manufacturing a cold-rolled steel sheet by cold-rolling the hot-rolled steel sheet. The cold rolling may be final rolling to a thickness of 0.03 to 0.5 mm. In one embodiment, the cold rolling step may further include an intermediate annealing step between a plurality of cold rolling steps.

After manufacturing the cold rolled steel sheet by cold rolling the hot rolled steel sheet, annealing the cold rolled steel sheet may be included. The step of annealing the cold rolled steel sheet may include a temperature raising step and a cooling step of cooling.

In one embodiment, annealing the cold-rolled steel sheet may include annealing the cold-rolled steel sheet at a cracking temperature of 820 to 1150 degrees Celsius. If it exceeds the upper limit of the cracking temperature, coarse crystal grains are formed and the grain size distribution is outside the scope of the invention, causing a problem in that the area with high dislocation density increases significantly. If it exceeds the lower limit of the cracking temperature, recrystallization occurs. There is a problem of magnetism deteriorating due to incomplete crystal grains remaining.

In one embodiment, the annealing of the cold rolled steel sheet may include a temperature raising step of heating the cold rolled steel sheet to 820°C or higher and a cooling step of cooling the cold rolled steel sheet from 820 to 900°C to 750 to 820°C. Specifically, the step of annealing the cold rolled steel sheet may include a temperature raising step of heating the cold rolled steel sheet to 850°C or higher and a cooling step of cooling from 850 to 900°C to 750 to 850°C.

In one embodiment, in the annealing step of the cold rolled steel sheet, the temperature raising step may be performed for less than 60 seconds. If the process is carried out longer than the above time, there is a problem in that the distribution of grains falls outside the scope of the invention and a grain size distribution with a wide dispersion occurs.

In one embodiment, in the annealing step of the cold rolled steel sheet, the cooling step may be performed for 5 seconds or more. If the process is performed for less than the above time, there is a problem in that stress in the thickness direction is generated due to heat shrinkage and thermal stress is generated due to differences in cooling of the plate surface in the width direction of the plate. In one embodiment, in the annealing step of the cold rolled steel sheet, the cooling step may include cooling the sheet surface perpendicular to the direction of gravity.

In one embodiment, in the annealing step of the cold rolled steel sheet, a tension of more than 0.01 to less than 1.0 kgf/mm ² may be applied in the rolling direction (RD direction) of the coil at a temperature of 650° C. or higher. Specifically, the tension may be in the range of 0.05 to 0.8 kgf/mm ² . If the range of the tension exceeds the upper limit, there is a problem in that the area ratio of the region with high dislocation density increases significantly due to the tension. If the range of tension exceeds the lower limit, there is a problem that the direction of movement of the plate is not in the horizontal plane or the stress of the plate cannot be analyzed due to complex deformation stress.

Figure 1a shows the arrangement of the steel sheet in the cold-rolled steel sheet annealing step according to an embodiment of the present invention, and Figures 1b and 1c show the moving direction of the steel sheet according to the moving direction and tension direction, respectively, in a plan view. .

Referring to FIG. 1A, when annealing a cold-rolled steel sheet, the cold-rolled steel sheet 10 is placed on the roll 30 disposed in the annealing furnace 20, and then, as the roll 30 rotates, the cold-rolled steel sheet 10 It moves and becomes annealed. Tension may be applied in the step of annealing the cold rolled steel sheet, and the tension may be calculated by a forward progress force applied to the thickness and width of the steel sheet. Specifically, the tension applied to the plate is measured when cooling of the furnace is performed. However, in the actual manufacturing process, when measurement is difficult due to problems with the structure of the annealing furnace, the measured value of the tension of the plate at the output side of the annealing furnace and the annealing furnace are measured. It can be calculated by the method of dividing the difference between the tension measurements measured at the entrance side by the cross-sectional area of the plate in the annealing furnace. At this time, the cross-sectional area of the plate within the annealing furnace can be regarded as the cross-sectional area value at the exit side of the annealing furnace.

Figure 1b shows a case where the moving direction and tension direction of the cold rolled steel sheet 10 are applied in the same direction.

Looking at FIG. 1B, the direction in which the tension is applied (TSD _{1_1} , Tensile Stress Direction 1_1) may be generally consistent with the direction D1 of the cold rolled steel sheet.

In Figure 1c, the moving direction (D2) and the tension direction (TSD _{1_2} , Tensile Stress Direction 1 _- 2) of the cold rolled steel sheet 10 may form an angle within a predetermined range. In one embodiment, in the annealing step of the cold rolled steel sheet, the direction of tension (TSD _{1_2} ) applied to the cold rolled steel sheet may form an angle of less than 3° with the rolling direction (RD direction) of the coil. If the angle is excessively large, there is a problem in that the stress applied to the plate surface during cooling is not constant across the plate width, and the area with high dislocation density within the plate varies greatly depending on the position on the plate. In addition, in contrast to the case where the direction in which tension is applied (TSD) and the rolling direction of the coil match, when the direction in which tension is applied (TSD) and the rolling direction of the coil form an angle of less than 3°, the plate surface during cooling The stress applied is constant across the plate width, which has the advantage of preventing high stress from being concentrated in a specific area.

Figures 2a and 2b are cross-sectional views showing the moving direction of the steel sheet according to the moving direction and tension direction of the steel sheet, respectively.

Figure 2a shows that the direction of tension applied to the cold-rolled steel sheet during the cold-rolled steel sheet annealing step is the direction perpendicular to the tension direction (TSD) and the steel sheet surface when forming an angle of more than 87 and less than 93 ° with the rolling surface normal direction (ND direction). (SVD) is shown. When the above angle range is achieved, it can be confirmed that the tension direction (TSD) and the vertical direction (SVD) of the steel plate surface are perpendicular.

Figure 2b shows a case where the lower and upper limits of the angle deviate from the normal by more than 3 °, and a complex stress is applied in the thickness direction of the plate, causing the tension direction (TSD) and the vertical direction of the steel plate surface ( It can be seen that there is a problem in which stress is not constant because SVD) is not constant.

As such, in the present invention, in the annealing step of the cold rolled steel sheet, the direction of the tension is adjusted to the rolling direction (RD direction) of the coil and the rolling surface normal direction (ND direction) of the cold rolled steel sheet within the above range. By minimizing the pulling force and minimizing the friction in the cooling zone that takes into account the friction that occurs as the plate progresses in the annealing furnace and the change in length due to thermal expansion, it has a uniform average grain size, good iron loss, and excellent magnetic properties. Grain-oriented electrical steel sheets can be manufactured.

In one embodiment, the annealing step of the cold rolled steel sheet may be performed in a reducing atmosphere. The reducing atmosphere may include at least one of hydrogen (H ₂ ), nitrogen (N ₂ ), and an inert gas. As annealing is performed in the reducing atmosphere, it may be possible to manufacture a non-oriented electrical steel sheet with excellent iron loss.

Hereinafter, specific examples of the present invention will be described. However, the following example is only a specific example of the present invention and the present invention is not limited to the following example.

Slavic composition

Table 1 below shows the composition of the slab, and the slab was manufactured using the components listed in Table 1 below, including the balance of Fe and inevitable impurities. Thereafter, the slab was heated to 1,180°C and hot-rolled at a finishing temperature of 880°C to produce a hot-rolled steel sheet with a thickness of 2.0 mm. The hot rolled steel sheet was annealed under the preliminary annealing conditions shown in Table 1 below. Specifically, the preliminary annealing is a step of heating the hot rolled steel sheet at the temperature shown in Table 1 below.

Steel grade Si
[wt%] Al
[wt%] Mn
[wt%] N
[wt%] S
[wt%] Ti
[wt%] Hot rolled steel sheet heating temperature
[℃] Steel grade 1 3.3 One 0.5 0.0026 0.0027 0.0022 950 Steel grade 2 3.95 1.01 0.56 0.0110 0.0033 0.0022 1020 Steel grade 3 3.36 1.61 0.60 0.0024 0.0110 0.0020 1020 Steel grade 4 3.70 1.05 0.76 0.0037 0.0025 0.0110 1020 Steel grade 5 3.32 1.32 0.62 0.0025 0.0034 0.0013 1009 Steel grade 6 3.62 1.21 0.58 0.0029 0.0032 0.0017 1058 Steel grade 7 2.78 0.61 0.31 0.0040 0.0037 0.0007 1056 Steel grade 8 3.4 0.9 0.5 0.0019 0.0022 0.0025 967 Steel grade 9 3.07 1.0 0.37 0.0036 0.0035 0.0040 1084

Table 2 below shows that the hot-rolled annealed steel sheet manufactured from Table 1 was cold-rolled to the thickness of the steel sheet shown in Table 2, and then the cold-rolled sheet was annealed under the conditions shown in Table 2 below. The following reducing atmosphere was used by mixing 80% nitrogen and 20% hydrogen when annealing cold rolled sheets. If annealing was performed in the reducing atmosphere created in this way, it was indicated as “O”, and if annealing was not carried out in the reducing atmosphere, it was indicated as “X”.

Heating time refers to the annealing time performed above 850 ℃, and cooling time refers to the time when cooling from 850 ℃ to 800 ℃.

Steel grade reducing atmosphere
[existence and nonexistence] heating time
[candle] Cooling time [sec] Tension rolling direction angle
[°] tension vertical angle
[°] Tension size
[kgf/mm ² ] Steel plate thickness
[mm] Steel grade 1 O 15 15 0.006 89.2 0.6 0.270 Steel grade 2 X 10 10 0.008 89.6 0.62 0.270 Steel grade 3 O 10 10 0.007 90.6 0.62 0.270 Steel grade 4 X 10 10 0.000 89.7 0.64 0.270 Steel grade 5 O 14 14 0.002 89.8 0.71 0.298 Steel grade 6 O 14 11 0.008 90.4 0.69 0.297 Steel grade 7 O 16 18 0.003 90.2 0.68 0.238 Steel grade 8 O 15 17 0.000 89.9 0.66 0.245 Steel grade 9 O 17 17 0.007 89.5 0.72 0.234

In Table 3 below, the average grain size and area fraction by grain size were derived for the cold-rolled sheet annealed sheet using an optical microscope, and the fraction of areas with high dislocation density in the steel sheet was measured using ECCI of an electron microscope. In addition, the iron loss of the manufactured steel sheet was measured, and the iron loss in the rolling direction was measured and listed in Table 3 below.

As described above, the average grain size designates individual grains closed by grain boundaries in a microscope tissue photograph, calculates the area of each grain, and indicates the diameter of each grain with the corresponding ECD (Equivalent Circle Diameter), At this time, the distribution of grain diameters was obtained using the ECD, and the average grain size was calculated by taking the arithmetic mean.

The 1/3 grain size fraction in Table 3 below means the area fraction of grains having a grain diameter less than 1/3 of the average grain diameter of the steel sheet, and the 3 times grain size fraction means the grain diameter is the average grain diameter of the steel sheet. It means the area fraction of crystal grains with a grain diameter exceeding 3 times.

Additionally, the aggregate tissue fraction was analyzed through EBSD in the cross sections of the plates. In order to measure the fraction in a sufficient area, the cross sections of the plates were stacked and the fraction of aggregate tissue was measured in an area of 10 mm x 5 mm. The area fraction of grains with misorientation within 15 degrees from the center of Goss and Cube orientations was calculated. In order to measure the area fraction of the crystal grains, the area of more than 2,000 grains with an average grain size was measured and the area fraction was statistically performed.

Additionally, for magnetic measurement, measurements are made using Epstein specimens using IEC 60404 regulations. The shape of the Epstein test piece is a rectangular shape with a length of 305 mm in the long direction and 30 mm in the short direction. The Epstein test specifications for non-oriented electrical steel include half of the test piece cut lengthwise in the rolling direction and half of the test piece cut lengthwise in the direction perpendicular to rolling. The iron loss was derived by charging half of it together into a measuring instrument. The iron loss in the rolling direction was measured by loading the specimens into an Epstein frame with all specimens cut so that the rolling direction was 305 mm and the vertical rolling direction was 30 mm.

In addition, the dislocation density was calculated using electron channeling contrast image in FE-SEM (Scanning Electron Microsope). The density of dislocations was calculated through Equation 5 below using the line intercept method.

<Equation 5>

Dislocation density = 2 N/lt

In Equation 5 above, N is the number of dislocations contacting a randomly drawn line, l is the length of the randomly drawn line, and t is the depth shown in the image. In ECCI, the value is proportional to the intensity of the electron beam, the composition of the specimen, and the intensity of the current. When steel is measured using an electron beam of 15 kV, it has a depth of about 70 nm, so the density was calculated taking this into account.

Figure 3 shows a region where dislocations are dense, according to an embodiment of the present invention.

Referring to Figure 3, when measuring the sheet surface of the non-oriented electrical steel sheet of steel grade 2 of Example 2 of the present invention using ECCI, an area where dislocations are concentrated due to strain, for example, the red circle area in Figure 2, can be confirmed.

Figures 4a to 4e are enlarged illustrations of areas where dislocations are concentrated in steel grade 2 of a comparative example and steel grade 10 of an example of the present invention.

Referring to FIGS. 4A and 4B, it can be seen that contrast occurs locally in the image due to strain, based on a 2 ㎛ accumulation standard. Referring to FIG. 3C, it can be seen that when FIGS. 3A and 3B are enlarged based on 1 ㎛ accumulation, the dislocation density can be observed in the ECCI image to the extent that it can be specifically calculated.

Figures 3d and 3e show the results for steel grade 10 of an embodiment of the present invention, showing enlarged areas of unshaded areas on the ECCI image, and unlike Figures 3a to 3c, dense areas of dislocations cannot be confirmed.

Based on the above-mentioned information, looking at Table 3 below, it is as follows.

Steel grade average grain size
[㎛] 1/3 grain fraction
[%] 3x grain fraction
[%] Dislocation density (m ^-2 ) 10 ¹² exceed 10 ¹⁶ less than fraction
[%] W15/50
[W/kg] W15/50 rolling direction
[W/kg] W10/400
[W/kg] W10/400 rolling direction
[W/kg] Steel grade 1 81.5 3 3 0.93 1.95 1.69 12.1 11.07 invention Steel grade 2 59.0 5.3 0.0 0.50 2.40 2.31 16.5 16.1 comparative goods Steel grade 3 55.0 5.1 0.0 0.41 2.45 2.38 17.8 17.1 comparative goods Steel grade 4 53.0 6.3 0.0 0.38 2.55 2.48 17.6 17.0 comparative goods Steel grade 5 62.8 3.1 3.3 0.64 2.27 1.80 14.3 12.6 invention Steel grade 6 121.3 3.5 3.3 1.97 2.19 1.95 14.8 13.6 invention Steel grade 7 40.4 2.7 2.6 0.11 1.43 1.32 12.8 11.7 invention Steel grade 8 69.2 3.0 2.9 0.77 1.80 1.51 12.9 11.7 invention Steel grade 9 72.2 2.8 2.5 0.87 1.74 1.56 12.7 11.8 invention

When the slab composition, pre-annealing conditions, and cold-rolled sheet annealing conditions that satisfy the conditions of the invention shown in Table 1, Table 2, and Table 3 are satisfied, the size of the crystal grains in the steel sheet is uniform and dislocations are concentrated in the steel sheet. Since there is no gap, it is possible to manufacture an electrical steel sheet that has very excellent iron loss in the rolling direction and also has excellent average iron loss in the rolling direction and the rolling direction perpendicular to the rolling direction.

Table 4 below shows the components including Si: 3.4 wt%, Al: 0.8 wt%, Mn: 0.5 wt%, N: 0.002 wt%, S: 0.002 wt%, Ti: 0.002 wt%, the balance of Fe, and inevitable impurities. A slab was manufactured, heated to 1,150°C, and then hot-rolled at a finishing temperature of 900°C to produce a hot-rolled steel sheet with a plate thickness of 1.8 mm. The hot rolled steel sheet was preannealed at a temperature of 1,050°C. This was cold rolled to 0.3 mm, and cold rolled sheet annealing was performed by raising the temperature to a temperature of 850°C or higher in a reducing atmosphere in 11 seconds and cooling from 850°C to 800°C in 10 seconds.

In addition to the conditions described above, other conditions were carried out under the conditions shown in Table 4 below, and the average grain diameter, the fraction of grains less than 1/3 the size of the average grain diameter, and the fraction of grains exceeding 3 times the average grain size were measured, , the area in the area where dislocations are concentrated was derived. Additionally, magnetism was measured and listed in Table 4.

Tension rolling direction angle
[°] tension vertical angle
[°] Tension size
[kgf/mm ² ] Steel plate thickness
[mm] average grain size
[㎛] 1/3 grain fraction
[%] 3 times grain hardness ratio
[%] Dislocation density (m ^-2 ) 10 ¹² exceed 10 ¹⁶ less than fraction
[%] W15/50
[W/kg] W15/50 rolling direction
[W/kg] W10/400
[W/kg] W10/400 rolling direction
[W/kg] Steel grade 10_1 0.01 90 0.60 0.30 75.0 2.5 3.0 0.3 1.95 1.85 14.5 13.5 invention Steel grade 10_2 2.5 90 0.60 0.30 75.0 2.5 3.0 2.3 2.00 1.90 14.7 13.7 invention Steel grade 10_3 5 90 1.00 0.30 75.0 2.5 3.0 5.7 2.03 1.95 14.9 14.2 comparative goods Steel grade 10_4 0.01 85 1.00 0.30 75.0 2.5 3.0 6.1 2.05 1.98 15.0 14.6 comparative goods Steel grade 10_5 0.01 94 1.00 0.30 75.0 2.5 3.0 5.3 2.10 2.03 15.0 14.7 comparative goods

Looking at Table 4 above, it can be seen that in cold-rolled sheet annealing, the area where dislocations are concentrated is significantly different depending on the angular relationship between tension and the sheet surface, and the iron loss and average iron loss in the rolling direction change significantly accordingly.

Table 5 below shows the manufacturing of a slab containing the following components, the balance of Fe and inevitable impurities, This was heated to 1,150°C and hot-rolled at a finishing temperature of 900°C to produce a hot-rolled steel sheet with a thickness of 1.8 mm. The hot rolled steel sheet was preannealed at a temperature of 1,050°C. This was cold rolled to 0.3 mm, the temperature was raised to 850°C or higher in a reducing atmosphere in 12 seconds, and cold rolled sheet annealing was performed by cooling from 850°C to 800°C in 10 seconds.

In addition to the conditions described above, other conditions were performed as shown in Table 5 below, the average grain diameter, the fraction of grains less than 1/3 the size of the average grain diameter, and the fraction of grains exceeding 3 times the average grain size were measured, and the dislocation The area of the concentrated area was derived. Additionally, magnetism was measured and listed in Table 5 below.

Steel grade reducing atmosphere
heating time
[candle] cooling time
[candle] Tension rolling direction angle
[°] tension vertical angle
[°] Tension size
[kgf/mm ² ] Steel plate thickness
[mm] average grain size
[㎛] 1/3 grain fraction
[%] 3 times grain hardness ratio
[%] Dislocation density (m ^-2 ) 10 ¹² exceed 10 ¹⁶ less than fraction
[%] W15/50
[W/kg] W15/50 rolling direction
[W/kg] W10/400
[W/kg] W10/400 rolling direction
[W/kg] Steel grade 11_1 O 12 10 0.01 90 0.10 0.30 75.0 2.5 3.0 0.0 2.00 1.96 14.4 14.1 invention Steel grade 11_2 O 12 10 0.02 90 0.80 0.30 75.0 2.5 3.0 1.0 1.95 1.85 14.5 13.5 invention Steel grade 11_3 O 12 10 0.01 90 2.00 0.30 75.0 2.5 3.0 5.7 2.20 2.10 15.6 15.0 comparative goods

As shown in Table 5 above, it can be seen that there is a significant difference in the size of the tension between the tension and the plate surface in the final annealing, and the dislocation concentration area in the angle between the tension and the plate surface. Accordingly, the iron loss in the rolling direction and the average iron loss are significantly different. You can see the change. Therefore, when the conditions of the present invention are satisfied, a steel sheet excellent in both average iron loss and iron loss in the rolling direction can be manufactured.

The average iron loss refers to the iron loss measurement of a typical non-oriented electrical steel sheet, and is the result of measuring iron loss by charging half of the samples of the Epstein measurement method in the rolling direction and the other half in the vertical direction of rolling into the iron loss measuring machine, and measuring the iron loss in the rolling direction. Iron loss refers to the iron loss value measured by preparing a sample only in the rolling direction, such as grain-oriented electrical steel, and loading it into an iron loss measuring device.

Table 6 below describes whether steel grades 1 to 11_3 satisfy Equations 1 to 4 of the present invention.

Steel grade Equation 1 Is Equation 1 satisfied? Equation 2 Is equation 2 satisfied? Equation 3 Equation 3 Satisfied Equation 4 Is equation 4 satisfied? W10/400 iron loss (W/kg) < 6+(t/0.04) ^1.1 W15/50 iron loss (W/kg) < 0.7+(t/0.03) ^1/5 W15/50 iron loss in rolling direction (W/kg) < 0.6+(t/0.03) ^1/6 W10/400 rolling direction iron loss (W/kg) < 5+(t/0.04) ^1.1 Steel grade 1 14.17 TRUE 2.50 TRUE 2.10 TRUE 13.17 TRUE Steel grade 2 14.17 FALSE 2.50 TRUE 2.10 FALSE 13.17 FALSE Steel grade 3 14.17 FALSE 2.50 TRUE 2.10 FALSE 13.17 FALSE Steel grade 4 14.17 FALSE 2.50 FALSE 2.10 FALSE 13.17 FALSE Steel grade 5 15.11 TRUE 2.69 TRUE 2.26 TRUE 14.11 TRUE Steel grade 6 15.07 TRUE 2.68 TRUE 2.25 TRUE 14.07 TRUE Steel grade 7 13.11 TRUE 2.29 TRUE 1.92 TRUE 12.11 TRUE Steel grade 8 13.34 TRUE 2.33 TRUE 1.96 TRUE 12.34 TRUE Steel grade 9 12.98 TRUE 2.26 TRUE 1.90 TRUE 11.98 TRUE Steel grade 10_1 15.17 TRUE 2.70 TRUE 2.27 TRUE 14.17 TRUE Steel grade 10_2 15.17 TRUE 2.70 TRUE 2.27 TRUE 14.17 TRUE Steel grade 10_3 15.17 TRUE 2.70 TRUE 2.27 TRUE 14.17 FALSE Steel grade 10_4 15.17 TRUE 2.70 TRUE 2.27 TRUE 14.17 FALSE Steel grade 10_5 15.17 TRUE 2.70 TRUE 2.27 TRUE 14.17 FALSE Steel grade 11_1 15.17 TRUE 2.70 TRUE 2.27 TRUE 14.17 TRUE Steel grade 11_2 15.17 TRUE 2.70 TRUE 2.27 TRUE 14.17 TRUE Steel grade 11_3 15.17 FALSE 2.70 TRUE 2.27 TRUE 14.17 FALSE

Referring to Table 6, it can be confirmed that the embodiments of the present invention satisfy Equations 1 to 4 above, thereby effectively reducing iron loss. On the other hand, it was confirmed that the comparative examples did not satisfy at least one of Equations 1 to 4 above. In this way, through Tables 1 to 6, the present invention confirmed that a steel sheet with excellent rolling direction and average iron loss can be manufactured by satisfying the conditions of the present invention.

The present invention is not limited to the above embodiments and/or examples, but can be manufactured in various different forms, and those skilled in the art may change the technical idea or essential features of the present invention. You will be able to understand that it can be implemented in other specific forms without doing so. Therefore, the implementation examples and/or embodiments described above should be understood in all respects as illustrative and not restrictive.

Claims (15)

The area fraction of grains having a grain size less than 1/3 times the average grain diameter is less than 5%,
Non-oriented electrical steel sheet in which the area fraction of grains with a dislocation density of more than 10 ¹² /m ² but less than 10 ¹⁶ /m ² is less than 5% of the total area.
According to claim 1,
A non-oriented electrical steel sheet in which the area fraction of grains having a grain diameter exceeding 3 times the average grain diameter is less than 5%.
According to claim 1,
In weight percent, Si: 0.1 to 6.5%, Al: 0.001 to 6.5%, Mn: 0.01 to 20%, C: 0.0010 to 0.015%, N: 0.0003 to 0.001%, S: 0.0003 to 0.001%, Ti: 0.0003 to 0.0003%. Non-oriented electrical steel sheet containing 0.001%, the balance of Fe and inevitable impurities.
According to claim 1,
The non-oriented electrical steel sheet has an average grain size of 40 to 250 ㎛.
According to claim 1,
Non-oriented electrical steel sheet with a thickness of 0.03 to 0.5 mm.
According to clause 5,
A non-oriented electrical steel sheet in which the iron loss (W10/400) and the thickness (t) of the non-oriented electrical steel sheet satisfy the following equation 1.
<Equation 1>
W10/400 iron loss (W/kg) < 6 + (t/0.04) ^1.1
(In Equation 1 above, t means the thickness (mm) of the non-oriented electrical steel sheet)
According to clause 5,
A non-oriented electrical steel sheet in which the iron loss (W15/50) and the thickness (t) of the non-oriented electrical steel sheet satisfy Equation 2 below.
<Equation 2>
W15/50 iron loss (W/kg) < 0.7+(t/0.03) ^1/5
(In Equation 2 above, t means the thickness (mm) of the non-oriented electrical steel sheet)
Manufacturing a hot-rolled steel sheet by hot-rolling a slab;
Manufacturing a cold-rolled steel sheet by cold-rolling the hot-rolled steel sheet; and
Including a cold rolled steel sheet annealing step of annealing the cold rolled steel sheet,
In the cold rolled steel sheet annealing step,
Applying a tension of more than 0.01 to less than 1.0 kgf/mm ² in the rolling direction (RD direction) of the coil at a temperature of 650 ℃ or higher,
The direction of tension applied to the cold rolled steel sheet forms an angle of less than 3 ° with the rolling direction (RD direction) of the coil,
A method of manufacturing a non-oriented electrical steel sheet forming an angle of more than 87 and 93 ° or less with the normal direction (ND direction) of the rolling surface of the cold rolled steel sheet.
According to clause 8,
The slab has, in weight percent, Si: 0.1 to 6.5%, Al: 0.001 to 6.5%, Mn: 0.01 to 20%, C: 0.0010 to 0.015%, N: 0.0003 to 0.01%, S: 0.0003 to 0.01%, Ti : A method of manufacturing a non-oriented electrical steel sheet containing 0.0003 to 0.01%, with the balance containing Fe and inevitable impurities.
According to clause 8,
A method of manufacturing a non-oriented electrical steel sheet further comprising a hot-rolled steel sheet annealing step of heating the hot-rolled steel sheet, wherein the hot-rolled steel sheet annealing step is a step of heating the hot-rolled steel sheet to 850 to 1,150 ° C.
According to clause 8,
The step of annealing the cold-rolled steel sheet includes a temperature raising step of heating the cold-rolled steel sheet to 820 ℃ or more and a cooling step of cooling from 820 to 900 ℃ to 750 to 820 ℃. A method of manufacturing a non-oriented electrical steel sheet.
According to clause 8,
In the cold rolled steel sheet annealing step, the temperature raising step is performed for less than 60 seconds.
According to clause 8,
In the cold-rolled steel sheet annealing step, the cooling step is performed for a time of 5 seconds or more.
According to clause 8,
In the cold-rolled steel sheet annealing step, the cooling step is a method of manufacturing a non-oriented electrical steel sheet in which the sheet surface is cooled perpendicular to the direction of gravity.
According to clause 8,
The cold-rolled steel sheet annealing step is a method of manufacturing a non-oriented electrical steel sheet in which annealing is performed in a reducing atmosphere.