KR20240077249A - Non-oriented elecrical steel sheet and method of manufacturing the same - Google Patents

Abstract

One embodiment of the present invention is by weight percentage, carbon (C): more than 0% and less than 0.003%, silicon (Si): more than 0.3% and less than 2.0%, manganese (Mn): more than 0.1% and less than 0.5%, aluminum (Al) ): More than 0.2% and less than 0.9%, Sulfur (S): More than 0% and less than 0.003%, Nitrogen (N): More than 0% and less than 0.003%, Titanium (Ti): More than 0% and less than 0.003%, Phosphorus (P): Preparing a slab containing more than 0% and 0.015% or less, the balance of iron (Fe) and inevitable impurities, hot rolling the slab to form a hot-rolled sheet, first cold rolling the hot-rolled sheet Forming a plate, intermediately annealing the first cold rolled annealed plate to form a first cold rolled annealed plate, performing secondary cold rolling on the first cold rolled annealed plate to form a second cold rolled plate, and forming the second cold rolled annealed plate. A step of final annealing a cold-rolled sheet to form a final annealed sheet, wherein the friction coefficient of the first upper roll used in the first cold rolling of the hot-rolled sheet is more than twice the friction coefficient of the first lower roll. Disclosed is a method of manufacturing a non-oriented electrical steel sheet, wherein the friction coefficient of the second upper roll used in the step of secondary cold rolling the first cold rolled annealed sheet is more than twice the friction coefficient of the second lower roll.

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 non-oriented electrical steel sheets and methods 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.

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 driving motors, improvement in the magnetic properties of non-oriented electrical steel sheets is required.

The characteristics required for non-oriented electrical steel sheets are high magnetic flux density and low iron loss. Core loss is energy loss caused by the iron core material, and in order to reduce iron loss in non-oriented electrical steel sheets, the sheet thickness must be reduced, the resistivity increased, or the texture must be improved. The magnetic properties of non-oriented electrical steel can also be determined by the ratio of texture, etc. If a texture that facilitates magnetization characteristics is not developed, iron loss increases and magnetic flux density decreases, which may deteriorate magnetic properties. On the surface of a steel sheet, the {100} texture is easiest to magnetize, and the {111} texture commonly found in recrystallized texture is not easy to magnetize. In addition, the {110} texture has a disadvantage in magnetization compared to the {100} texture, but has an advantage in magnetization compared to the {111} texture. As the {111} texture fraction decreases and the {100} and {110} texture fractions increase, the iron loss decreases, resulting in high magnetic flux density and low iron loss.

As a related technology, there is Republic of Korea Patent Publication No. 10-1992-005619 (title of the invention: Method for manufacturing non-oriented electrical steel sheet with excellent magnetic properties).

Republic of Korea Patent Publication No. 10-1992-005619

Embodiments of the present invention seek to provide a non-oriented electrical steel sheet with low silicon (Si) content and improved magnetic properties by controlling cold rolling conditions during the manufacturing process, and a method for manufacturing the same.

However, these tasks are illustrative and do not limit the scope of the present invention.

In one aspect of the present invention, in weight percent, carbon (C): more than 0% and less than 0.003%, silicon (Si): more than 0.3% and less than 2.0%, manganese (Mn): more than 0.1% and less than 0.5%, aluminum (Al) ): More than 0.2% and less than 0.9%, Sulfur (S): More than 0% and less than 0.003%, Nitrogen (N): More than 0% and less than 0.003%, Titanium (Ti): More than 0% and less than 0.003%, Phosphorus (P): Preparing a slab containing more than 0% and less than 0.015%, the balance of iron (Fe) and unavoidable impurities; Forming a hot-rolled plate by hot-rolling the slab; Forming a first cold rolled sheet by first cold rolling the hot rolled sheet; Forming a first cold rolled annealed sheet by intermediately annealing the first cold rolled sheet; Forming a second cold rolled sheet by performing secondary cold rolling on the first cold rolled annealed sheet; and final annealing the second cold rolled sheet to form a second cold rolled annealed sheet, wherein the friction coefficient of the first upper roll used in the step of first cold rolling the hot rolled sheet is that of the first lower roll. Manufacturing of a non-oriented electrical steel sheet wherein the friction coefficient is more than twice the friction coefficient of the second upper roll used in the step of secondary cold rolling the first cold rolled annealed sheet and the friction coefficient of the second lower roll is more than twice the friction coefficient of the second lower roll. Disclose the method.

In one embodiment, in the step of first cold rolling the hot-rolled sheet, the friction coefficient of the first upper roll may be greater than 0.2 and less than 0.4.

In one embodiment, in the step of first cold rolling the hot rolled sheet, the friction coefficient of the first lower roll may be greater than 0 and less than 0.2.

In one embodiment, in the step of secondary cold rolling the second cold rolled annealed plate, the friction coefficient of the second upper roll may be greater than 0.2 and less than 0.4.

In one embodiment, in the step of secondary cold rolling the second cold rolled annealed plate, the friction coefficient of the second lower roll may be greater than 0 and less than 0.2.

In one embodiment, the strain at point t/2 (t is the thickness of the first cold rolled sheet) in the thickness direction from the surface of the first cold rolled sheet may satisfy Equation 1 below.

<Equation 1>

ε ₁₃ /ε ₁₁ > 0.5

(Here, ε ₁₃ represents the shear strain component of the strain rate of the first cold rolled sheet and ε ₁₁ represents the plane strain component of the strain rate of the first cold rolled sheet.)

In one embodiment, the strain at point t'/2 (t' is the thickness of the first cold rolled sheet) in the thickness direction from the surface of the second cold rolled sheet may satisfy Equation 2 below.

<Equation 2>

ε' ₁₃ /ε' ₁₁ > 0.5

(Here, ε' ₁₃ represents the shear strain component of the strain rate of the second cold rolled sheet and ε' ₁₁ represents the plane strain component of the strain rate of the second cold rolled sheet.)

In one embodiment, in the step of intermediately annealing the first cold rolled sheet to form the first cold rolled annealed sheet, the intermediate annealing temperature may be 900°C to 1000°C.

In one embodiment, in the step of intermediately annealing the first cold rolled sheet to form the first cold rolled annealed sheet, the intermediate annealing time may be 2 hours to 40 hours.

In one embodiment, the average grain size of the first cold rolled annealed plate may be 150 ㎛ to 250 ㎛.

In one embodiment, the method may further include a coating step of forming a coating layer on the second cold rolled annealed plate.

In another aspect of the present invention, as a non-oriented electrical steel sheet, in weight percentage, carbon (C): more than 0% and less than 0.003%, silicon (Si): 0.3% and more than 2.0%, manganese (Mn): 0.1% or more. 0.5% or less, Aluminum (Al): 0.2% or more and 0.9% or less, Sulfur (S): 0% or more and 0.003% or less, Nitrogen (N): 0% or more and 0.003% or less, Titanium (Ti): 0% and 0.003% or less Hereinafter, a non-oriented electrical steel sheet containing phosphorus (P): more than 0% and less than 0.015%, the balance iron (Fe) and inevitable impurities, and the non-oriented electrical steel sheet has a V _{110} of 35% or more. (Here, V _{110} represents the fraction of {110} texture relative to the sum of all orientations.)

In one embodiment, the non-oriented electrical steel sheet may have V _{111} of 10% or less. (Here, V _{111} represents the fraction of {111} texture relative to the sum of all orientations.)

In one embodiment, the non-oriented electrical steel sheet may have an iron loss of 14.0 W/kg or less (based on W _10/400 ) and a magnetic flux density of 1.65 T or more (based on B ₅₀ ).

In one embodiment, the non-oriented electrical steel sheet may have a yield strength of 400 MPa or more and a tensile strength of 500 MPa or more.

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 the embodiments of the present invention made as described above, the texture of the steel sheet can be improved and the magnetic properties can be improved by controlling the cold rolling conditions in the manufacturing process of the non-oriented electrical steel sheet. Additionally, since the steel sheet contains a relatively low silicon (Si) content, manufacturing costs can be reduced. Of course, the scope of the present invention is not limited by this effect.

1 is a flowchart 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.

In the following embodiments, 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 the following examples, singular terms include plural terms unless the context clearly dictates otherwise.

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

In the following embodiments, when a part of a film, region, component, etc. is said to be on or on another part, it is not only the case where it is directly on top of the other part, but also when another film, region, component, etc. is interposed between them. Also includes cases where there are.

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.

In cases where an embodiment can be implemented differently, 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 that in which they are described.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, and when described with reference to the drawings, identical or corresponding components will be assigned the same reference numerals.

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

Referring to FIG. 1, the method of manufacturing a non-oriented electrical steel sheet according to an embodiment includes a hot rolling step (S100), a first cold rolling step (S200), an intermediate annealing step (S300), and a second cold rolling step (S400). , may include a final annealing step (S500) and a coating 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 is, in weight percent, carbon (C): greater than 0% and less than or equal to 0.003%, silicon (Si): greater than or equal to 0.3% and less than or equal to 2.0%, manganese (Mn): greater than or equal to 0.1% and less than or equal to 0.5%, and aluminum (Al). ): More than 0.2% and less than 0.9%, Sulfur (S): More than 0% and less than 0.003%, Nitrogen (N): More than 0% and less than 0.003%, Titanium (Ti): More than 0% and less than 0.003%, Phosphorus (P): It may contain more than 0% and less than 0.015%, the balance iron (Fe) and unavoidable impurities.

Carbon (C) may be a component that increases iron loss by forming carbides such as TiC and NbC. In one embodiment, carbon (C) may be included in an amount of more than 0% and less than or equal to 0.003% by weight based on the total weight of the slab. If carbon (C) is included in more than 0.003% of the total weight of the slab, self-aging may occur and the magnetic properties of the slab may be reduced. When carbon (C) is contained in an amount of more than 0% and less than 0.003% by weight based on the total weight of the steel sheet, the self-aging phenomenon can be suppressed.

Silicon (Si) may be a component that increases resistivity and reduces eddy current loss. In one embodiment, silicon (Si) may be included in an amount of 0.3% to 2.0% by weight based on the total weight of the slab. If silicon (Si) is included in less than 0.3% of the total weight of the slab, it may be 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 more than 2.0% of the total weight of the slab, brittleness may increase, cold rolling properties may decrease, and productivity may decrease. In one embodiment, silicon (Si) may preferably be included in an amount of 0.7% to 1.7% by weight based on the total weight of the slab. In one embodiment, silicon (Si) may preferably be included in an amount of 0.9% to 1.5% by weight based on the total weight of the slab. If silicon (Si) is contained in an amount of 0.3% to 2.0% by weight based on the total weight of the slab, the manufacturing cost of the non-directional electric blanket can be reduced.

Aluminum (Al), along with silicon (Si), may be a component that increases specific resistance and reduces eddy current loss. Additionally, aluminum (Al) can play a role in reducing magnetic deviation by reducing magnetic anisotropy. In one embodiment, aluminum (Al) may be included in an amount of 0.2% to 0.9% by weight based on the total weight of the slab. If aluminum (Al) is included in less than 0.2% of the total weight of the slab, it may be difficult to obtain low core loss values. In addition, the formation of fine AlN nitride can increase the variation in magnetic properties. On the other hand, if aluminum (Al) is included in an amount of more than 0.9% based on the total weight of the slab, cold rolling performance may be reduced, and nitride may be formed excessively, thereby reducing magnetic flux density and thus magnetic properties.

Manganese (Mn), along with silicon (Si), may be an ingredient that increases resistivity and improves texture. In one embodiment, manganese (Mn) may be included in an amount of 0.1% to 0.5% by weight based on the total weight of the slab. If manganese (Mn) is included in less than 0.1% of the total weight of the slab, fine MnS precipitates may be formed to suppress grain growth. On the other hand, if manganese (Mn) is included in an amount of more than 0.5% based on the total weight of the slab, coarse MnS precipitates may be formed and magnetic properties may deteriorate, such as reducing magnetic flux density.

Sulfur (S) can form precipitates such as MnS and CuS, increasing iron loss and suppressing grain growth. In one embodiment, sulfur (S) may be included in an amount of more than 0% and less than or equal to 0.003% by weight based on the total weight of the slab. If sulfur (S) is included in excess of 0.003% based on the total weight of the slab, precipitates such as MnS and CuS may be formed, which may increase iron loss and suppress grain growth.

Nitrogen (N) can increase iron loss and inhibit grain growth by forming precipitates such as AlN, TiN, and NbN. In one embodiment, nitrogen (N) may be included in an amount of more than 0% and less than or equal to 0.003% by weight based on the total weight of the slab. If nitrogen (N) is contained in excess of 0.003% based on the total weight of the slab, precipitates such as AlN, TiN, NbN, etc. may be formed, which may increase iron loss and suppress grain growth.

Titanium (Ti) can suppress grain growth by forming precipitates such as TiC and TiN. In one embodiment, titanium (Ti) may be included in an amount of more than 0% and less than or equal to 0.003% by weight based on the total weight of the slab. If titanium (Ti) is included in excess of 0.003% based on the total weight of the slab, precipitates such as TiC and TiN may be formed and magnetic properties may be deteriorated.

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 contained in excess of 0.015% based on the total weight of the slab, grain growth may be suppressed due to a segregation effect, magnetic properties may be deteriorated, and cold rolling properties may be reduced.

In the hot rolling step (S100), the slab may be heated to form a hot rolled sheet after hot rolling. In the hot rolling step (S100), the slab may first be heated. In one embodiment, the slab heating temperature in the hot rolling step (S100) may be about 1,000°C to about 1,200°C. When the slab heating temperature exceeds about 1,200°C, precipitates such as C, S, and N in the slab are re-dissolved and fine precipitates are formed in the subsequent rolling and annealing stages, which can inhibit grain growth and deteriorate magnetic properties. You can do it. On the other hand, if the slab heating temperature is less than 1,000°C, the rolling load increases during hot rolling, which may result in poor rolling performance.

In the hot rolling step (S100), the heated slab can be rolled at a predetermined finish rolling temperature. In one embodiment, the finishing delivery temperature (FDT) of the hot rolling step (S100) may be about 860°C to about 900°C.

In the hot rolling step (S100), the hot rolled sheet can be cooled to a predetermined coiling temperature (CT) and then rolled. In one embodiment, the coiling temperature may be about 550°C to about 650°C.

In one embodiment, the thickness of the hot rolled sheet after hot rolling may be about 1.8 mm to about 2.6 mm. At this time, if the thickness of the hot-rolled sheet exceeds about 2.6 mm, the cold rolling reduction rate may increase, resulting in poor texture.

A first cold rolling step (S200) may be performed after the hot rolling step (S100). In the first cold rolling step (S200), the hot rolled sheet can be cold rolled. At this time, the cold rolled hot rolled sheet may be called the first cold rolled sheet. In the first cold rolling step (S200), the hot rolled sheet may be cold rolled to a thickness of less than about 1.0 mm. The final reduction ratio in the first cold rolling step (S200) may be about 50%. Preferably, the final reduction ratio in the first cold rolling step (S200) may be about 50% to about 85%.

In one embodiment, the friction coefficient of the first upper roll used for rolling in the first cold rolling step (S200) may be more than twice the friction coefficient of the first lower roll.

In one embodiment, the friction coefficient of the first upper roll used in the first cold rolling step (S200) may be greater than about 0.2 and less than about 0.4. Preferably, the friction coefficient of the first upper roll used in the first cold rolling step (S200) may be greater than about 0.25 and less than about 0.35.

In one embodiment, the friction coefficient of the first lower roll used in the first cold rolling step (S200) may be greater than 0 and less than about 0.2. Preferably, the friction coefficient of the first lower roll used in the first cold rolling step (S200) may be greater than about 0.05 and less than about 0.25.

In the first cold rolling step (S200), the friction coefficient of the first upper roll used for rolling is more than twice the friction coefficient of the first lower roll, and the friction coefficient of the first upper roll and the first lower roll is as above. By satisfying each range, the strain rate of the first cold rolled sheet can be controlled.

The strain rate at a point t/2 in the thickness direction from the surface of the first cold rolled sheet (t is the thickness of the first cold rolled sheet) may satisfy Equation 1 below.

<Equation 1>

ε ₁₃ /ε ₁₁ > 0.5

In Equation 1, ε ₁₃ represents the shear strain component of the strain rate of the first cold rolled sheet, and ε ₁₁ represents the plane strain component of the strain rate of the first cold rolled sheet.

In other words, since shear deformation begins to occur from the surface of the first cold rolled sheet during the first cold rolling process, when the strain is measured at points at preset intervals arranged in the thickness direction from the surface of the first cold rolled sheet, each point The strain rates in the fields can all satisfy Equation 1 above. For example, the strain rate at the surface of the first cold rolled sheet, at point t/4 from the surface in the thickness direction, and at point t/2 from the surface may all satisfy Equation 1 above.

By controlling the strain rate of the first cold rolled sheet to satisfy Equation 1, the texture of the first cold rolled sheet can be optimized. Specifically, the {111} texture fraction can be reduced and the {110} texture fraction can be increased.

An intermediate annealing step (S300) may be performed after the first cold rolling step (S200). In the intermediate annealing step (S300), the first cold rolled sheet may be annealed. At this time, the first intermediately annealed cold rolled sheet may be called a first cold rolled annealed sheet.

The intermediate annealing step (S300) may be performed at an annealing temperature of about 900°C or higher, a holding time of about 2 hours or more and about 40 hours or less, a temperature increase rate of about 10°C/s or more, and a cooling rate of about 100°C/hr or more. If the annealing temperature in the intermediate annealing step (S300) is less than about 900°C, or the holding time is less than about 2 hours at a temperature of about 900°C or higher, the crystal grain size of the first cold rolled annealed plate after intermediate annealing appears fine and the desired magnetic properties are obtained. Enemy characteristics cannot be obtained. On the other hand, special equipment is required to raise the annealing temperature in the intermediate annealing step (S300) to about 900℃ or higher. If the holding time at a temperature of about 900℃ or higher exceeds about 40 hours, the effect of improving magnetic properties is saturated and the cost increases. may also increase.

In one embodiment, the average grain size of the first cold rolled annealed plate may be 150 ㎛ to 250 ㎛. If the average grain size of the first cold rolled annealed plate is less than 150㎛, the {111} texture fraction of the final product may increase and the magnetic properties may deteriorate. If the average grain size of the first cold rolled annealed plate exceeds 250 ㎛, the grain size of the final product may become non-homogeneous and magnetic properties may deteriorate.

After the intermediate annealing step (S300), a secondary cold rolling step (S400) may be performed.

In the second cold rolling step (S400), the first cold rolled annealed plate may be second cold rolled. At this time, the cold rolled first cold rolled annealed plate may be called a second cold rolled plate. In the second cold rolling step (S400), the second cold rolled sheet may be cold rolled to a thickness of less than about 0.35 mm. The final reduction ratio in the second cold rolling step (S400) may be about 25 to about 75%. Preferably, the final reduction ratio in the second cold rolling step (S400) may be about 40% to about 60%.

In one embodiment, the friction coefficient of the second upper roll used for rolling in the second cold rolling step (S400) may be more than twice the friction coefficient of the second lower roll.

In one embodiment, the friction coefficient of the second upper roll used in the second cold rolling step (S400) may be greater than about 0.2 and less than about 0.4. Preferably, the friction coefficient of the second upper roll used in the second cold rolling step (S400) may be greater than about 0.25 and less than about 0.35.

In one embodiment, the friction coefficient of the second lower roll used in the second cold rolling step (S400) may be greater than 0 and less than about 0.2. Preferably, the friction coefficient of the second lower roll used in the second cold rolling step (S400) may be greater than about 0.05 and less than about 0.25.

In the second cold rolling step (S400), the friction coefficient of the second upper roll used for rolling is more than twice the friction coefficient of the second lower roll, and the friction coefficient of the second upper roll and the second lower roll is as above. By satisfying each range, the strain rate of the second cold rolled sheet can be controlled.

In one embodiment, the strain at point t'/2 (t' is the thickness of the second cold rolled sheet) in the thickness direction from the surface of the second cold rolled sheet may satisfy Equation 2 below.

<Equation 2>

ε' ₁₃ /ε' ₁₁ > 0.5

In Equation 2, ε' ₁₃ represents the shear strain component of the strain rate of the second cold rolled sheet, and ε' ₁₁ represents the plane strain component of the strain rate of the second cold rolled sheet.

In other words, since shear deformation begins to occur from the surface of the second cold rolled sheet during the secondary cold rolling process, when the strain is measured at points at preset intervals arranged in the thickness direction from the surface of the second cold rolled sheet, each point The strain rates in the fields can all satisfy Equation 2 above. For example, the strain at the surface of the second cold rolled sheet, at a point t'/4 from the surface in the thickness direction, and at a point t'/2 from the surface may all satisfy Equation 2 above.

By controlling the strain rate of the second cold rolled sheet to satisfy Equation 2 above, the texture of the second cold rolled sheet can be optimized. Specifically, shear deformation during rolling can cause the {111} texture fraction, which has unfavorable magnetic properties, to decrease and the {110} texture fraction, which has favorable magnetic properties, to increase. Therefore, the iron loss of the final product can be reduced, the magnetic flux density can be increased, and the magnetic properties can be improved.

A final annealing step (S500) may be performed after the second cold rolling step (S400). In the final annealing step (S500), the second cold rolled sheet can be annealed. At this time, the final annealed second cold rolled sheet may be called the final annealed sheet.

The final annealing step (S500) may be performed at a temperature that results in the optimal grain size considering the final magnetic and mechanical properties. For example, the final annealing step (S500) may be performed at an annealing temperature of about 850°C to about 1,000°C, a holding time of about 5 seconds to about 70 seconds, and a temperature increase rate of about 10°C/s or more. If the annealing temperature in the final annealing step (S500) is less than about 850°C, the hysteresis loss may increase due to the fine grain size. On the other hand, if the annealing temperature in the final annealing step (S500) exceeds about 1,000° C., the grain size may increase too much and eddy current loss may increase.

Additionally, the final annealing step (S500) may be performed under mixed atmosphere conditions to prevent surface oxidation and nitriding. For example, the surface state of the final annealed plate can be made smoother through a mixed atmosphere of nitrogen and hydrogen. In the intermediate annealing step (S300), the final annealed plate can be cooled at a cooling rate of about 20°C/s or more.

After the final annealing step (S500), a coating step (S600) may be performed. In the coating step (S600), a coating layer can be formed on the final annealed plate. By forming a coating layer through the coating step (S600), punching properties can be improved and insulation properties can be secured.

The 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 average grain size of about 80 ㎛ to about 150 ㎛.

In one embodiment, the manufactured non-oriented electrical steel sheet may have V _{110} of about 35% or more. Preferably, the manufactured non-oriented electrical steel sheet may have V _{110} of about 40% or more. Additionally, the manufactured non-oriented electrical steel sheet may have V _{111} of about 15% or less. Preferably, the manufactured non-oriented electrical steel sheet may have V _{111} of about 10% or less. Here, V _{110} represents the fraction of {110} texture to the sum of all orientations, and V _{111} represents the fraction of {111} texture to the sum of all orientations. The manufactured non-oriented electrical steel sheet has a low {111} texture fraction and a high {110} texture fraction, and thus may have excellent magnetic properties.

In one embodiment, the manufactured non-oriented electrical steel sheet may have an iron loss (based on W _10/400 ) of about 14.0 W/kg or less and a magnetic flux density (based on B ₅₀ ) of about 1.65T or more. Preferably, the non-oriented electrical steel sheet may have an iron loss (based on W _10/400 ) of about 13.0 W/Kg or less. Additionally, preferably, the non-oriented electrical steel sheet may have a magnetic flux density (based on B ₅₀ ) of about 1.70T or more. Here, iron loss (based on W _10/400 ) is the energy loss (W/kg) that occurs in iron when an alternating magnetic field of 1.0 T is applied at 400 Hz. Here, iron loss (based on W _10/400 ) means the average value after measuring the iron loss values at 0° and 90°. Additionally, the manufactured non-oriented electrical steel sheet may have a yield strength (YP) of about 400 MPa or more and a tensile strength (TS) of about 500 MPa 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 1.32 0.27 0.23 0.0020 0.0025 0.0065 0.0020 0.0020 Comparative Example 1 3.18 0.25 0.88 0.0018 0.0021 0.0055 0.0019 0.0020 Comparative example 2 1.32 0.27 0.23 0.0020 0.0025 0.0065 0.0020 0.0020 Comparative Example 3 1.32 0.27 0.23 0.0020 0.0025 0.0065 0.0020 0.0020 Comparative example 4 1.32 0.27 0.23 0.0020 0.0025 0.0065 0.0020 0.0020 Comparative Example 5 1.32 0.27 0.23 0.0020 0.0025 0.0065 0.0020 0.0020 Comparative Example 6 1.32 0.27 0.23 0.0020 0.0025 0.0065 0.0020 0.0020

division Hot rolled annealed or not Primary cold rolling medium annealed Secondary cold rolling 1st upper roll
friction coefficient 1st lower roll
friction coefficient Reduction rate
(%) temperature
(℃) hour
(Hr) Second upper roll friction coefficient Second lower roll friction coefficient Reduction rate
(%) Example 1 X 0.3 0.1 77 900 7.5 0.3 0.1 46 Comparative Example 1 O 0.1 0.1 88 - - - - - Comparative example 2 X 0.1 0.1 88 - - - - - Comparative Example 3 X 0.1 0.1 77 900 7.5 0.1 0.1 46 Comparative Example 4 X 0.3 0.1 77 700 7.5 0.3 0.1 46 Comparative Example 5 X 0.3 0.1 77 900 One 0.3 0.1 46 Comparative Example 6 O 0.1 0.1 77 900 7.5 0.1 0.1 46

Table 1 shows the component composition of Example 1 and Comparative Examples 1 to 6, and Table 2 shows the process conditions of Example 1 and Comparative Examples 1 to 6.

Referring to Tables 1 and 2, Example 1 and Comparative Examples 3 to 6 were prepared by heating slabs containing the component compositions shown in Table 1 at a temperature of about 1130° C. for 2 hours and finishing rolling at a finish rolling temperature (FDT) of about. After hot rolling was performed at 850°C and a coiling temperature (CT) of about 610°C, a hot rolled sheet with a thickness of about 2.0 mm was manufactured (hot rolling step).

Afterwards, the manufactured hot-rolled sheet was first cold-rolled to produce a first cold-rolled sheet with a thickness of 0.46t (0.46mm). The first cold rolling was conducted under the reduction ratio conditions in Table 2, and the first upper roll and first lower roll that satisfied the friction coefficient conditions in Table 2 were used (first cold rolling step). The manufactured first cold rolled sheet was subjected to intermediate annealing under the intermediate annealing temperature and holding time conditions listed in Table 2. At this time, intermediate annealing was performed in an atmosphere of nitrogen (N ₂ , 100%), and the temperature increase rate was approximately 10°C/s and the cooling rate was approximately 100°C/hr (intermediate annealing step).

Afterwards, the produced first cold rolled annealed plate was subjected to secondary cold rolling to manufacture a second cold rolled plate having a thickness of 0.25t (0.25mm). The second cold rolling was conducted under the reduction ratio conditions in Table 2, and the second upper roll and second lower roll that satisfied the friction coefficient conditions in Table 2 were used (second cold rolling step). The manufactured second cold rolled sheet was subjected to final annealing at a temperature of approximately 950°C for approximately 60 seconds to produce a final annealed sheet. At this time, the final annealing was carried out in a mixed atmosphere of hydrogen (H ₂ ) (30%) and nitrogen (N ₂ ) (70%), and the temperature increase rate was approximately 20°C/s and the cooling rate was approximately 30°C/s. (Final annealing step). Afterwards, the final product (eg, non-oriented electrical steel sheet) was manufactured through a coating step (coating step).

Meanwhile, in Comparative Examples 1 and 6, a hot annealing step was additionally performed between the hot rolling step and the first cold rolling step. That is, the manufactured hot-rolled sheet was hot-annealed at about 1000°C for 60 seconds to manufacture a hot-rolled annealed sheet, and a first cold-rolling step was performed on the hot-rolled annealed sheet to manufacture a first cold-rolled sheet.

In the case of Comparative Example 1, a first cold rolled sheet having a thickness of 0.25t (0.25mm) was manufactured through the first cold rolling step, and unlike Example 1 and Comparative Examples 3 to 6, the intermediate annealing step and 2 Without performing the secondary cold rolling step, a final annealing step and a coating step were performed on the first cold rolled sheet to manufacture a final product (eg, non-oriented electrical steel sheet). The hot rolling step, primary cold rolling step, final annealing step, and coating step in Comparative Example 1 were conducted under the same conditions as described in relation to Example 1 and Comparative Examples 3 to 6.

In addition, in the case of Comparative Example 2, a first cold rolled sheet with a thickness of 0.25t (0.25mm) was manufactured through the first cold rolling step, and unlike Example 1 and Comparative Examples 3 to 6, an intermediate annealing step was performed. And, without performing the second cold rolling step, a final annealing step and a coating step were performed on the first cold rolled sheet to manufacture a final product (eg, non-oriented electrical steel sheet). The hot rolling step, primary cold rolling step, final annealing step, and coating step in Comparative Example 2 were conducted under the same conditions as previously described in relation to Example 1 and Comparative Examples 3 to 6.

division 1st cold rolling - value of <Equation 1>
(ε ₁₃ /ε ₁₁ > 0.5) medium annealed Secondary cold rolling - value of <Equation 2>
(ε' ₁₃ /ε' ₁₁ > 0.5) surface t/4 point t/2 point
(midpoint) Crystal grain size (㎛) surface point t'/4 point t'/2
(midpoint) Example 1 0.73 1.11 0.69 180 0.77 1.30 0.82 Comparative Example 1 0.93 0.87 0.13 - - - - Comparative example 2 0.93 0.87 0.13 - - - - Comparative example 3 0.84 0.83 0.06 175 0.89 0.82 0.23 Comparative example 4 0.73 1.11 0.69 25 0.77 1.30 0.82 Comparative Example 5 0.73 1.11 0.69 85 0.77 1.30 0.82 Comparative Example 6 0.84 0.83 0.06 175 0.89 0.82 0.23

Table 3 shows whether Example 1 and Comparative Examples 1 to 6 satisfy Equations 1 and 2.

In Table 3, ε ₁₃ represents the shear strain component of the strain rate of the first cold rolled sheet, and ε ₁₁ represents the plane strain component of the strain rate of the first cold rolled sheet. That is, ε ₁₃ /ε ₁₁ means the ratio of the shear strain component of the strain rate of the first cold rolled sheet and the plane strain component of the strain rate of the first cold rolled sheet. ε' ₁₃ represents the shear strain component of the strain rate of the second cold rolled sheet, and ε' ₁₁ represents the plane strain component of the strain rate of the second cold rolled sheet. That is, ε' ₁₃ /ε' ₁₁ means the ratio of the shear strain component of the strain rate of the second cold-rolled sheet and the plane strain component of the strain rate of the second cold-rolled sheet.

Whether the surface of the first cold-rolled sheet, the strain rate at point t/4 from the surface in the thickness direction (t is the thickness of the first cold-rolled sheet), and the strain rate at point t/2 from the surface all satisfy Equation 1, and whether the strain of the second cold-rolled sheet satisfies Equation 1. We measured and evaluated whether the strain at the surface, at point t'/4 in the thickness direction from the surface (t' is the thickness of the second cold rolled sheet), and at point t'/2 from the surface all satisfied Equation 2.

Referring to Figure 2 and Table 3, in the case of Comparative Example 1 and Comparative Example 2 in which cold rolling was performed first, the surface of the first cold rolled sheet manufactured by primary cold rolling and the point t/4 in the thickness direction from the surface It can be seen that the strain at (t is the thickness of the first cold rolled sheet) satisfies Equation 1, but the strain at point t/2 from the surface does not satisfy Equation 1.

Looking at Example 1 and Comparative Examples 3 to 6 in which cold rolling was performed twice, Example 1, Comparative Example 4, and Comparative Example 5 are the surface and thickness from the surface of the first cold rolled sheet manufactured by primary cold rolling. It can be seen that the strain at point t/4 in the direction (t is the thickness of the first cold rolled sheet) and at point t/2 from the surface all satisfy Equation 1. In addition, Example 1, Comparative Example 4, and Comparative Example 5 are the surface of the second cold rolled sheet manufactured by secondary cold rolling, point t'/4 in the thickness direction from the surface (t' is the thickness of the second cold rolled sheet), It can be seen that the strain rates from the surface to the point t'/2 all satisfy Equation 2.

On the other hand, in Comparative Example 3 and Comparative Example 6, the strain rate at point t/4 (t is the thickness of the first cold rolled sheet) in the thickness direction from the surface and the surface of the first cold rolled sheet manufactured by primary cold rolling is Equation 1. However, it can be confirmed that the strain at point t/2 from the surface does not satisfy Equation 1. In addition, in Comparative Example 3 and Comparative Example 6, the strain rate at point t'/4 (t' is the thickness of the second cold rolled sheet) in the thickness direction from the surface and the surface of the second cold rolled sheet manufactured by secondary cold rolling is expressed in the equation 2 is satisfied, but it can be confirmed that the strain at point t'/2 from the surface does not satisfy Equation 2.

Meanwhile, Table 3 shows whether Example 1 and Comparative Examples 1 to 6 satisfy the average grain size range after intermediate annealing. The average grain size was measured by measuring Electron Backscatter Diffraction (EBSD), and the measured data was measured using TSL OIM Analysis software.

Referring to Tables 2 and 3, it can be seen that in Example 1, Comparative Example 3, and Comparative Example 6, the average grain size of the first cold rolled annealed sheet after intermediate annealing falls within the range of 150 ㎛ to 250 ㎛.

On the other hand, in Comparative Examples 4 and 5, it can be confirmed that the average grain size of the first cold rolled annealed sheet did not satisfy the range of 150 ㎛ to 250 ㎛ after intermediate annealing.

division Aggregate tissue fraction (%) V _{100} V _{110} V _{111} Example 1 8.2 45.8 8.6 Comparative Example 1 25.4 5.7 13.3 Comparative example 2 4.0 7.0 65.4 Comparative example 3 9.0 30.9 11.0 Comparative Example 4 8.4 21.5 30.4 Comparative Example 5 7.8 35.4 20.9 Comparative Example 6 15.3 20.1 15.0

Table 4 shows the texture fraction of Example 1 and Comparative Examples 1 to 6. For Example 1 and Comparative Examples 1 to 6, the texture was measured using EBSD (Electron Backscatter Diffraction) to measure the volume fraction of {100} cotton, {110} cotton, and {111} cotton. The results are shown in Table 4. In Table 4, V _{100} represents the fraction of {100} texture to the sum of all orientations, V _{110} represents the fraction of {110} texture to the sum of all orientations, and V _{111} represents the fraction of {111} texture to the sum of all orientations.

Referring to Table 4, it can be seen that in Comparative Example 2, compared to Comparative Example 1, V _{100} slightly increased, but V _{110} decreased and V _{111} increased significantly.

In addition, in Comparative Examples 3 to 6, compared to Comparative Example 1, V _{110} slightly increased, but V _{100} decreased and V _{111} increased. On the other hand, when Comparative Examples 3 to 6 are compared with Comparative Example 2, it can be seen that V _{100} and V _{110} increased and V _{111} decreased.

In Example 1, compared to Comparative Example 1, V _{100} is However, it can be seen that V _{110} increases significantly and V _{111} decreases. Specifically, in Example 1, it can be confirmed that V _{110} is 35% or more and V _{111} is 10% or less.

division Magnetic measurement results W _10/400 (W/kg) B ₅₀ (T) Example 1 12.35 1.75 Comparative Example 1 12.15 1.66 Comparative example 2 21.23 1.72 Comparative example 3 16.65 1.74 Comparative example 4 17.35 1.74 Comparative Example 5 16.32 1.74 Comparative Example 6 16.01 1.73

Table 5 shows the magnetic measurement results of Example 1 and Comparative Examples 1 to 6. For magnetic measurements, the iron loss and magnetic flux density values were measured in the L and C directions using a SST (Single Sheet Tester) and then calculated as the average values. In Table 5, B ₅₀ is the magnetic flux density at 5000 A/m, and W _10/400 is the iron loss at 400 Hz and 1.0 Tesla magnetic flux density.

Referring to Table 5, it can be seen that the magnetic flux densities (based on B ₅₀ ) of Example 1 and Comparative Examples 1 to 6 are all 1.65T or more. Specifically, it can be confirmed that the magnetic flux densities (based on B ₅₀ ) of Example 1 and Comparative Examples 2 to 6 are all greater than the magnetic flux densities (based on B ₅₀ ) of Comparative Example 1. In addition, it can be confirmed that the magnetic flux density (based on B ₅₀ ) of Example 1 is greater than the magnetic flux density (based on B ₅₀ ) of Comparative Examples 1 to 5.

In addition, in the case of Example 1 and Comparative Example 1, it can be confirmed that the iron loss (based on W _10/400 ) is 14.0 W/kg or less. Specifically, it can be confirmed that Example 1 and Comparative Example 1 have smaller iron loss (based on W _10/400 ) than Comparative Examples 2 to 6. It can be confirmed that Example 1 has a similar iron loss value to Comparative Example 1.

That is, Example 1 with a low silicon content (1.32 wt%) has a similar iron loss value and a higher magnetic flux density compared to Comparative Example 1 with a high silicon content (3.18 wt%), and therefore has a high silicon content (3.18 wt%). It can be seen that the magnetic properties are equal to or better than those of Comparative Example 1 having wt%).

In one embodiment, the strain rate of the first cold rolled sheet can be controlled by ensuring that the friction coefficient of the first upper roll used for rolling in the first cold rolling step is more than twice the friction coefficient of the first lower roll. The strain rate at point t/2 (t is the thickness of the first cold rolled sheet) in the thickness direction from the surface of the first cold rolled sheet may satisfy Equation 1 (ε13 /ε11 > 0.5). Specifically, when the strain was measured at points at preset intervals arranged in the thickness direction from the surface of the first cold-rolled sheet, the strain at each point was, for example, t/4 on the surface of the first cold-rolled sheet, from the surface to the thickness direction. If the strain rates from the point and surface to point t/2 all satisfy Equation 1 (ε13 /ε11 > 0.5), the texture of the steel plate can be optimized. Specifically, the {111} texture fraction can be decreased and the {110} texture fraction can be increased.

The step of intermediate annealing the first cold rolled sheet may be performed at a temperature of 900°C to 1000°C for 2 to 40 hours. In this case, the average grain size of the steel sheet after intermediate annealing is appropriately controlled, and the magnetic properties of the steel sheet can be improved.

In addition, the friction coefficient of the second upper roll used for rolling in the secondary cold rolling step is set to be more than twice the friction coefficient of the second lower roll, so that the strain rate of the second cold rolled plate can be controlled. The strain rate at point t'/2 (t' is the thickness of the second cold rolled sheet) in the thickness direction from the surface of the second cold rolled sheet may satisfy Equation 2 (ε'13 /ε'11 > 0.5). Specifically, when the strain is measured at points at preset intervals arranged in the thickness direction from the surface of the second cold-rolled sheet, the strain at each point is, for example, t'/ If the strain at all four points, from the surface to the point t'/2, satisfies Equation 2 (ε'13 /ε'11 > 0.5), the texture of the steel plate can be optimized. Specifically, the {111} texture fraction can be decreased and the {110} texture fraction can be increased.

Accordingly, the final product (eg, non-oriented electrical steel sheet) may have an iron loss of about 14.0 W/kg or less (based on W _10/400 ) and a magnetic flux density of about 1.65 T or more (based on B ₅₀ ). Specifically, the final product (eg, non-oriented electrical steel sheet) may have an iron loss of about 13.0 W/Kg or less (based on W _10/400 ) and a magnetic flux density of about 1.70 T or more (based on B ₅₀ ).

The present invention has been described with reference to an embodiment shown in the drawings, but this is merely an example, and those skilled in the art will understand that various modifications and variations of the embodiment are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the attached patent claims.

Claims (15)

In weight percent, carbon (C): more than 0% and less than 0.003%, silicon (Si): more than 0.3% and less than 2.0%, manganese (Mn): more than 0.1% and less than 0.5%, aluminum (Al): more than 0.2% and less than 0.9%. Hereinafter, sulfur (S): more than 0% and less than 0.003%, nitrogen (N): more than 0% and less than 0.003%, titanium (Ti): more than 0% and less than 0.003%, phosphorus (P): more than 0% and less than 0.015%, Preparing a slab containing the remainder of iron (Fe) and inevitable impurities;
Forming a hot-rolled plate by hot-rolling the slab;
Forming a first cold rolled sheet by first cold rolling the hot rolled sheet;
Forming a first cold rolled annealed sheet by intermediately annealing the first cold rolled sheet;
Forming a second cold rolled sheet by performing secondary cold rolling on the first cold rolled annealed sheet; and
Final annealing the second cold rolled sheet to form a final annealed sheet;
Including,
The friction coefficient of the first upper roll used in the step of primary cold rolling the hot rolled sheet is more than twice the friction coefficient of the first lower roll, and the friction coefficient used in the step of secondary cold rolling the first cold rolled annealed sheet A method of manufacturing a non-oriented electrical steel sheet, wherein the friction coefficient of the second upper roll is more than twice the friction coefficient of the second lower roll. According to paragraph 1,
In the step of first cold rolling the hot rolled sheet,
A method of manufacturing a non-oriented electrical steel sheet, wherein the friction coefficient of the first upper roll is greater than 0.2 and less than 0.4. According to paragraph 1,
In the step of first cold rolling the hot rolled sheet,
A method of manufacturing a non-oriented electrical steel sheet, wherein the friction coefficient of the first lower roll is greater than 0 and less than 0.2. According to paragraph 1,
In the step of secondary cold rolling the final annealed plate,
A method of manufacturing a non-oriented electrical steel sheet, wherein the friction coefficient of the second upper roll is greater than 0.2 and less than 0.4. According to paragraph 1,
In the step of secondary cold rolling the final annealed plate,
A method of manufacturing a non-oriented electrical steel sheet, wherein the friction coefficient of the second lower roll is greater than 0 and less than 0.2. According to paragraph 1,
The strain rate at point t/2 in the thickness direction from the surface of the first cold rolled sheet (t is the thickness of the first cold rolled sheet) satisfies the following equation 1.
<Equation 1>
ε ₁₃ /ε ₁₁ > 0.5
(Here, ε ₁₃ represents the shear strain component of the strain rate of the first cold rolled sheet and ε ₁₁ represents the plane strain component of the strain rate of the first cold rolled sheet.) According to paragraph 1,
The strain rate at point t'/2 (t' is the thickness of the first cold rolled sheet) in the thickness direction from the surface of the second cold rolled sheet satisfies Equation 2 below.
<Equation 2>
ε' ₁₃ /ε' ₁₁ > 0.5
(Here, ε' ₁₃ represents the shear strain component of the strain rate of the second cold rolled sheet and ε' ₁₁ represents the plane strain component of the strain rate of the second cold rolled sheet.) According to paragraph 1,
In the step of intermediately annealing the first cold rolled sheet to form a first cold rolled annealed sheet,
A method of manufacturing a non-oriented electrical steel sheet, wherein the intermediate annealing temperature is 900°C to 1000°C. According to paragraph 1,
In the step of intermediately annealing the first cold rolled sheet to form a first cold rolled annealed sheet,
A method for producing a non-oriented electrical steel sheet, wherein the intermediate annealing time is 2 hours to 40 hours. According to paragraph 1,
A method of manufacturing a non-oriented electrical steel sheet, wherein the average grain size of the first cold rolled annealed sheet is 150 ㎛ to 250 ㎛. According to paragraph 1,
A method of manufacturing a non-oriented electrical steel sheet, further comprising a coating step of forming a coating layer on the final annealed sheet. As a non-oriented electrical steel sheet,
In weight percent, carbon (C): more than 0% and less than 0.003%, silicon (Si): more than 0.3% and less than 2.0%, manganese (Mn): more than 0.1% and less than 0.5%, aluminum (Al): more than 0.2% and less than 0.9%. Hereinafter, sulfur (S): more than 0% and less than 0.003%, nitrogen (N): more than 0% and less than 0.003%, titanium (Ti): more than 0% and less than 0.003%, phosphorus (P): more than 0% and less than 0.015%, Contains the remainder of iron (Fe) and inevitable impurities,
The non-oriented electrical steel sheet is a non-oriented electrical steel sheet having V _{110} of 35% or more.
(Here, V _{110} represents the fraction of {110} texture relative to the sum of all orientations.) According to clause 12,
The non-oriented electrical steel sheet is a non-oriented electrical steel sheet having V _{111} of 10% or less.
(Here, V _{111} represents the fraction of {111} texture relative to the sum of all orientations.) According to clause 12,
The non-oriented electrical steel sheet has an iron loss of 14.0 W/kg or less (based on W _10/400 ) and a magnetic flux density of 1.65 T or more (based on B ₅₀ ). According to clause 12,
The non-oriented electrical steel sheet has a yield strength of 400 MPa or more and a tensile strength of 500 MPa or more.

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