KR102468076B1 - Grain oriented electrical steel sheet and manufacturing method of the same - Google Patents

Abstract

Grain-oriented electrical steel sheet according to an embodiment of the present invention contains, by weight, Si: 2.5 to 6.5%, Mn: 0.03 to 0.2%, Al: 0.01 to 0.04%, C: 0.005% or less (excluding 0%), N: 0.0015% or less (excluding 0%) and S: 0.025% or less (excluding 0%), including the balance Fe and unavoidable impurities,
The fraction of crystal grains having an orientation within 3° of the (90,87,43) orientation expressed in Euler orientation is 30% by volume or more.

Description

Grain-oriented electrical steel sheet and its manufacturing method {GRAIN ORIENTED ELECTRICAL STEEL SHEET AND MANUFACTURING METHOD OF THE SAME}

One embodiment of the present invention relates to a grain-oriented electrical steel sheet and a manufacturing method thereof. Specifically, it relates to a grain-oriented electrical steel sheet having improved magnetism by strengthening the (90,87,43) orientation by introducing a unique process during hot rolling and a manufacturing method thereof.

Grain-oriented electrical steel sheet has obtained excellent magnetic properties in the rolling direction by using a technique of controlling the crystal orientation of the steel sheet to have a <100> direction, which is an easy magnetic axis, in the rolling direction. Generally, magnetic properties can be expressed in terms of magnetic flux density, magnetic permeability, and iron loss, and it is known that high magnetic flux density, high magnetic permeability, and low iron loss can be obtained by orienting crystal grains close to the <100> axis in the rolling direction.

This is a very effective method to increase the magnetic flux density and magnetic permeability. However, in iron loss, it is helpful to lower hysteresis loss, but the size of the magnetic domain is the main factor determining the eddy current loss caused by the movement of the magnetic domain. In this case, as the size of the magnetic domain increases, the vortex loss also tends to increase.

On the other hand, when the <100> axis, which is the magnetic easy axis, is aligned in a direction deviated by about 3 degrees from the direction of magnetization, the width of the magnetic domain narrows and the abnormal vortex loss decreases, while the hysteresis loss, which is expected to increase, increases very little. Therefore, it is known that the total core loss tends to be minimized in the sum.

Iron loss at this time is the power loss consumed as thermal energy when an arbitrary alternating magnetic field is applied to the steel plate, and consists of hysteretic loss, vortex loss, and abnormal vortex loss. Iron loss varies greatly depending on the magnetic flux density and thickness of the steel sheet, the amount of impurities in the steel sheet, the specific resistance, the size of the secondary recrystallized grains, and the size of the magnetic domain as described above.

More specifically, the higher the magnetic flux density and resistivity, the lower the sheet thickness and the amount of impurities in the steel sheet, and when the size of the magnetic domain is within a certain range, the lower the iron loss and the higher the efficiency of the electric device.

Accordingly, if the <100> axis, which is an easy axis of magnetism, can be aligned in a direction that is offset by about 3 degrees from the direction of magnetization, an electrical steel sheet having low core loss, high magnetic flux density and high permeability can be manufactured using this.

One embodiment of the present invention is to provide a grain-oriented electrical steel sheet and a manufacturing method thereof. Specifically, it is intended to provide a grain-oriented electrical steel sheet having improved magnetism by strengthening the (90,87,43) orientation by introducing a unique process during hot rolling and a manufacturing method thereof.

Grain-oriented electrical steel sheet according to an embodiment of the present invention contains, by weight, Si: 2.5 to 6.5%, Mn: 0.03 to 0.2%, Al: 0.01 to 0.04%, C: 0.005% or less (excluding 0%), N: 0.0015% or less (excluding 0%) and S: 0.025% or less (excluding 0%), including the balance Fe and unavoidable impurities,

The fraction of crystal grains having an orientation within 3° of the (90,87,43) orientation expressed in Euler orientation is 30% by volume or more.

(90,87,43) The fraction of crystal grains having an orientation within 3˚ of the orientation (V _(90,87,43) ) and the fraction of grains having an orientation of within 3˚ of the (90,90,45) orientation ( V _(90,90,45) ) may satisfy Equation 1 below.

[Equation 1]

V _(90,87,43) ≥ 3.0 × V _(90,90,45)

The fraction of grains whose <16,1,0> axis is within 3 degrees from the rolling direction (V _<16,1,0> ) and whose <1,0,0> axis is within 3 degrees from the rolling direction The grain fraction (V _<1,0,0> ) may satisfy Equation 2 below.

[Equation 2]

V _<16,1,0> ≥ 2× V _<1,0,0>

The fraction of crystal grains whose <16,1,0> axis is within 3 degrees from the rolling direction is 50% by volume or more, and the fraction of crystal grains whose <1,0,0> axis is within 3 degrees from the rolling direction ( V _<1,0,0> ) may be 25% by volume or more.

Based on the ND plane, the average grain size is 10 mm to 40 mm, the area ratio occupied by crystal grains having a grain size of 100 mm or more is 10 area% or less, and the average width of magnetic domains in a demagnetized state may be 0.0003 to 0.0030 of the average grain size.

The magnetic flux density (B ₈ ) is 1.89 T or more, the maximum relative magnetic permeability (μ _max ) measured at 50 Hz is 40000 or more, and Equations 3 to 4 below may be satisfied.

[Equation 3]

(W _10/50 /W _17/50 ) ≤ 0.32

[Equation 4]

(μ _1.7T / μ _1.0T ) ≥ 0.850

Here, B ₈ means the magnetic flux density value measured at 800 A/m under 50 Hz AC electricity, and the maximum relative permeability (μ _max ) is the largest of the calculated relative permeability (μ) values in the range from 0.01T to 1.95T. value, and the relative permeability (μ) means the value calculated by setting the magnetic flux density B measured at 0Hz and the strength of the magnetic field H as B/H, and W _10/50 and W _17/50 are the applied magnetic field, respectively are 10T and 15T, mean iron loss values measured at a frequency of 50Hz, and μ _1.0T and μ _1.7T represent relative magnetic permeability (μ) values calculated at 1.0T and 1.7T, respectively.

In the method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention, by weight, Si: 2.5 to 6.5%, Mn: 0.03 to 0.2%, Al: 0.01 to 0.04%, C: 0.03 to 0.1%, N: 0.009 % or less (excluding 0%) and S: 0.025% or less (excluding 0%), and hot-rolling a slab containing Fe and unavoidable impurities to prepare a hot-rolled steel sheet; Manufacturing a cold-rolled steel sheet by cold-rolling the hot-rolled steel sheet; Primary recrystallization annealing of the cold-rolled steel sheet; and performing secondary recrystallization annealing on the primary recrystallization annealed cold-rolled steel sheet.

In the step of manufacturing a hot-rolled steel sheet, two or more passes are included in which the angle between the rolling direction and the steel sheet traveling direction is 0.25° or more.

In the step of manufacturing the hot-rolled steel sheet, the rolling reduction ratio may be 30% or more in a pass in which the angle between the rolling direction and the steel sheet traveling direction is 0.25° or more.

In the step of manufacturing the cold-rolled steel sheet, a retention step in which a temperature of 150° C. or higher is maintained for at least 10 minutes after the cold-rolling reduction ratio is 5% may be further included.

In the secondary recrystallization annealing step, the temperature increase rate in the 1100 to 1150 °C section may be 1 to 10 °C/h higher than the temperature increase rate in the 900 to 1100 °C section.

The heating rate in the 900 to 1100 °C section may be 3 to 15 °C/h, and the temperature raising rate in the 1100 to 1150 °C section may be 4 to 25 °C/h.

After the step of manufacturing the hot-rolled steel sheet, the hot-rolled steel sheet has a fraction (V _(90,87,43) ) and (90,90,45) of grains having an orientation within 3˚ of the (90,87,43) orientation and The fraction (V _(90,90,45) ) of crystal grains having an orientation within 3˚ may satisfy Equation 5 below.

[Equation 5]

V _(90,87,43) ≥ 2 × V _(90,90,45)

After the step of manufacturing the hot-rolled steel sheet, further comprising the step of annealing the hot-rolled steel sheet,

After annealing the hot-rolled steel sheet, the hot-rolled steel sheet has a fraction (V _(90,87,43) ) and (90,90,45) orientation of crystal grains having an orientation within 3˚ of (90,87,43) orientation and The fraction (V _(90,90,45) ) of crystal grains having an orientation within 3˚ may satisfy Equation 6 below.

[Equation 6]

V _(90,87,43) ≥ 2.5 × V _(90,90,45)

The step of manufacturing a cold-rolled steel sheet is rolled at a reduction ratio of 82% to 93%, and the thickness deviation may be less than 5%.

Here, the thickness deviation is calculated as 1 - (thickness inside 2 cm from the edge of the steel plate / thickness of the center).

After the primary recrystallization annealing, the average grain size at 1/8 thickness of the steel sheet is 13 to 25 μm, and the number of grains having a grain size three or more times the average grain size may be 0.001% to 0.5% of the total number of grains.

After the primary recrystallization annealing, the cold-rolled steel sheet has a fraction (V _(90,87,43) ) and (90,90,45) orientation and 3 The fraction (V _(90,90,45) ) of crystal grains having an orientation within ˚ may satisfy Equation 7 below.

[Equation 7]

V _(90,87,43) ≥ 3 × V _(90,90,45)

After primary recrystallization annealing, the cold-rolled steel sheet has a (90,87,43) orientation and a crystal grain size of 40㎛ having an orientation within 3˚. The number of grains may be 4/cm ³ or more.

After the primary recrystallization annealing, the fraction of crystal grains in which the angle difference with the <100> axis is smaller than the angle difference with the Goss orientation may be 30% or more in the cold-rolled steel sheet.

After the primary recrystallization, the amount of carbon in the steel may be reduced by 0.04 to 0.065% by weight.

After the primary recrystallization annealing, the amount of oxygen in the steel may be increased by 0.005 to 0.1% by weight.

After the primary recrystallization annealing, the amount of nitrogen in the steel may be increased by 0.01 to 0.03% by weight.

Grain-oriented electrical steel sheet according to an embodiment of the present invention forms a large number of crystal grains of {90,87,43} orientation, which have a small magnetic domain width and excellent magnetic flux density, thereby improving iron loss due to a high magnetic flux density and an appropriate magnetic domain width. can make it

1 is a schematic diagram showing the Goss orientation ({90, 90, 45}) and the {90, 87, 43} orientation.
2 is a schematic diagram showing the magnetic domain widths of the Goss orientation and the {90,87,43} orientation.
3 is a schematic diagram showing an example in which the angle between the rolling direction and the steel sheet traveling direction is twisted in one embodiment of the present invention.
4 is a schematic diagram showing crystal grains having a smaller angular difference from the <100> axis and the Goss orientation.

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 only used to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a first part, component, region, layer or section described below may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is only for referring to specific embodiments and is not intended to limit the present invention. As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite. The meaning of "comprising" as used herein specifies particular characteristics, regions, integers, steps, operations, elements and/or components, and the presence or absence of other characteristics, regions, integers, steps, operations, elements and/or components. Additions are not excluded.

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 followed by another part therebetween. In contrast, when a part is said to be “directly on” another part, there is no intervening part between them.

Although not defined differently, all terms including technical terms and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Terms defined in commonly used dictionaries are additionally 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.

In addition, unless otherwise specified, % means weight%, and 1ppm is 0.0001 weight%.

In one embodiment of the present invention, the meaning of further including an additional element means replacing and including iron (Fe) as much as the additional amount of the additional element.

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 embodied in many different forms and is not limited to the embodiments described herein.

If the <100> axis, which is the easy axis of magnetism, can be aligned in a direction offset by about 3 degrees from the direction of magnetization, it is possible to manufacture an electrical steel sheet having low core loss, high magnetic flux density and high permeability. The (90,87,43) orientation corresponds to this, and the <100> axis, which is the easy axis of magnetism, is deviated by about 3.23˚ from the direction of magnetization, and is deviated by about 3.6˚ from Goss.

The (90,87,43) orientation is expressed as an Euler orientation, and since this is widely known, a detailed description thereof will be omitted.

As such, in one embodiment of the present invention, by forming a large number of crystal grains with a {90,87,43} orientation having a small magnetic domain width and excellent magnetic flux density, iron loss can be improved because the magnetic domain width is appropriate while the magnetic flux density is high. .

Specifically, the fraction of crystal grains having an orientation of (90,87,43) and within 3˚ is 30% by volume or more. As the fraction of crystal grains having an orientation within 3˚ of the (90,87,43) orientation increases, the magnetism can be further improved due to the aforementioned effect. More specifically, it may be 50% by volume or more. More specifically, it may be 75 to 99% by volume or more.

In one embodiment of the present invention, the fraction (V _(90,87,43) ) of crystal grains having an orientation within 3˚ of (90,87,43) orientation and (90,90,45) orientation and within 3˚ The fraction of crystal grains having an orientation (V _(90,90,45) ) may satisfy Equation 1 below.

[Equation 1]

V _(90,87,43) ≥ 3.0 × V _(90,90,45)

More specifically, V _(90,87,43) / V _(90,90,45) may be 3.0 to 4.0.

As such, since more (90,87,43) orientations are formed than GOSS orientations (90,90,45) orientations, magnetism can be improved. In one embodiment of the present invention, the fraction of crystal grains is a volume fraction unless otherwise specified, and in the case of an area fraction, it is based on a rolling surface (ND surface). As described above, since the (90,90,45) orientation is deviated by about 3.6˚ from Goss, corresponding grains overlapping in both orientations may exist.

In FIG. 1, a schematic diagram for comparing the (90,90,45) orientation and the (90,87,43) orientation is shown.

The aforementioned (90,90,45) orientation can be expressed as <16,1,0> when expressed as a Miller index. However, the crystal grain fraction does not exactly match due to the difference in the expression method.

The fraction of grains whose <16,1,0> axis is within 3 degrees from the rolling direction (V _<16,1,0> ) and whose <1,0,0> axis is within 3 degrees from the rolling direction The fraction of crystal grains (V _<1,0,0> ) may satisfy Equation 2 below.

[Equation 2]

V _<16,1,0> ≥ 2× V _<1,0,0>

More specifically, V _<16,1,0> / V _<1,0,0> may be 3.0 or more. More specifically, it may be 3.0 to 4.0.

The effect according to one embodiment of the present invention is due to the above-described unique grain orientation distribution, and the above-described effect can be expressed regardless of the alloy component of the steel sheet.

The fraction of crystal grains whose <16,1,0> axis is within 3 degrees from the rolling direction is 50% by volume or more, and the fraction of crystal grains whose <1,0,0> axis is within 3 degrees from the rolling direction ( V _<1,0,0> ) may be 25% by volume or more.

Grain-oriented electrical steel sheet according to an embodiment of the present invention contains, by weight, Si: 2.5 to 6.5%, Mn: 0.03 to 0.2%, Al: 0.01 to 0.04%, C: 0.005% or less (excluding 0%), N: 0.0015% or less (excluding 0%) and S: 0.025% or less (excluding 0%), the balance including Fe and unavoidable impurities.

Si: 2.5 to 6.5% by weight

Silicon (Si) is a basic composition of an electrical steel sheet and serves to improve iron loss by increasing the resistivity of the material. When Si is too small, the specific resistance decreases and eddy current loss increases, resulting in poor iron loss characteristics. On the contrary, when too much Si is included, ductility and toughness among mechanical properties are reduced, making cold rolling extremely difficult, frequent plate breakage during rolling, and poor weldability and bendability between plates during continuous annealing for commercial production. There is a disadvantage that productivity deteriorates due to inferiority. Accordingly, the Si content may be in the range of 2.5 to 6.5% by weight. On the other hand, as the amount of Si increases, the magnetic anisotropy of the Fe-Si alloy decreases. Accordingly, the superior effect of magnetism on the <100> magnetic easy axis is gradually reduced compared to magnetism on other azimuthal axes. Accordingly, since the probability that magnetic domain walls formed parallel to the <100> magnetic easy axis are formed in various directions increases, the shape of the magnetic domain becomes complicated and there is a problem in that additional energy is lost during movement and rotation of the magnetic domain. , more specifically Si may be less than or equal to 4.0% by weight. This effect does not appear significantly when the amount of Si is less than 3.6% by weight because iron loss, which decreases according to the increase in resistivity due to the increase in Si, is more effective, and may be less than 3.6% by weight of Si.

Mn: 0.03 to 0.2% by weight

Manganese (Mn) not only has the effect of reducing iron loss by reducing eddy current loss by increasing specific resistance in the same way as Si, but also reacts with S present in steel to form Mn-based compounds or Al, Si, and N ions It reacts to form a nitride in the form of (Al,Si,Mn)N, thereby serving to form a grain growth inhibitor. If the Mn content is too small, the above effect cannot be expected, and if the Mn content is too large, the austenite phase transformation rate increases during secondary recrystallization annealing, resulting in a serious fraction of the {90,87,43} texture and its adjacent texture. As a result, the properties may deteriorate rapidly. Therefore, the content of Mn may be in the range of 0.03 to 0.2% by weight. The lower limit of the Mn content may be 0.06% by weight in view of its role as an inhibitor. More specifically, the lower limit of Mn may be 0.08% by weight. Considering the austenite fraction, the upper limit of the Mn content may be 0.18% by weight, more specifically 0.15% by weight.

Al: 0.01 to 0.04% by weight

Aluminum (Al) not only forms AlN-type nitride by combining with N ions introduced by ammonia gas, which is an atmospheric gas during the decarburization annealing process, but also combines with Si, Mn, and N ions present in a solid solution in steel. It serves to form a grain growth inhibitor by forming a nitride in the form of (Al, Si, Mn) N. When too little Al is included, the above effect cannot be expected, and when too much Al is included, very coarse nitride is formed, so that grain growth suppressing ability may be rapidly reduced. Therefore, the content of Al may be 0.01 to 0.04% by weight. The lower limit of the Al content may be 0.023% by weight, given the process-manageable suppression. More specifically, the lower limit of Al may be 0.028% by weight. The upper limit of the Al content may be 0.035% by weight, more specifically 0.033% by weight.

C: 0.005% by weight or less

Carbon (C) is an austenite stabilizing element, which is added to the slab to refine the coarse columnar structure generated in the casting process and serves to suppress the central segregation of S in the slab. On the other hand, during hot rolling, when rolling by rolling rolls between upper and lower rolling axes that are not parallel to each other, dislocations formed by deformation and dynamic recrystallization during recovery at high temperatures, movement speed of dislocations in the dynamic recovery process, slip system, deformation Influencing the bond strength of the interface, it has a major influence on the formation of crystal grains or stretching grains or recrystallized nuclei with {90,87,43} orientation, which are mainly formed at the strain interface. In addition, during cold rolling, rolling between non-parallel upper and lower rolling axes plays a role of promoting work hardening of the steel sheet to promote the formation of secondary recrystallization nuclei in the {110}<001> orientation in the steel sheet, similar to that in hot rolling. When rolled by rolls, crystal grains or elongated grains or recrystallized nuclei with {90,87,43} orientation are mainly formed at the strain interface, affecting the dislocation movement speed, slip system, and bond strength at the strain interface. have a major impact on However, if the amount of carbon in the slab is too small, it is difficult to fully expect the above effect, and if the amount of carbon in the slab is too large, an austenite phase is formed at the grain interface during hot rolling to prevent formation of the (90,87,43) orientation. On the other hand, during cold lead rolling, the carbide inside the steel sheet increases, which can deteriorate the cold rolling characteristics. Accordingly, the C content in the slab may be in the range of 0.03 to 0.1% by weight. The lower limit of the C content in the slab may be 0.04% by weight, more specifically 0.05% by weight, which is advantageous for the (90,87,43) orientation to be formed at the interface. The upper limit of the C content may be 0.08% by weight, more specifically 0.065% by weight in order to reduce the fraction of the austenite phase at the crystal interface that prevents formation of the (90,87,43) orientation during hot rolling. . On the other hand, since C contained in the finally obtained grain-oriented electrical steel sheet causes magnetic aging to deteriorate the magnetic flux density and low magnetic field characteristics, it undergoes decarburization annealing in the manufacturing process of the electrical steel sheet, and the grain-oriented electrical steel sheet finally obtained through such decarburization annealing The C content in the steel sheet may be 0.005% by weight or less.

N: 0.0015% or less

Nitrogen (N) is an important element that reacts with Si, Al, and Mn to form compounds such as AlN and (Al, Si, Mn) N, and may be included in an amount of 0.009% by weight or less in the slab. However, if the N content in the slab is too high, not only does it cause surface defects such as blisters due to nitrogen diffusion in the process after hot rolling, but also it is not easy to roll because excessive nitrides are formed in the slab state. cause the unit price to rise. Accordingly, the content of N in the slab may have a range of 0.009% or less (excluding 0%). The lower limit of the N content in the slab may be 0.0020% by weight in order to use the AlN precipitate as a precipitate to maintain the fraction of crystal grains in the {90.87,43} orientation during annealing of the hot-rolled sheet. In order to stabilize and utilize it at a higher temperature, the lower limit of N may be 0.0030% by weight. The upper limit of the N content may be 0.0065% by weight in order to set the re-dissolving temperature of the precipitate to 1150 ° C or less. In order to be 1100 ° C. or less, the upper limit of N in the slab may be 0.0050% by weight. This is the range for setting the temperature of the hot-rolled sheet annealing process. When the re-employment temperature is greatly exceeded, the size and distribution of precipitates change. Accordingly, in the process of primarily recrystallizing the cold-rolled steel sheet after 43} There may be cases that make it difficult to grow a direction. On the other hand, nitride reinforcement for the formation of secondary recrystallization of {90,87,43} texture is reinforced by performing nitriding treatment to diffuse N ions into steel by introducing ammonia gas into atmospheric gas during the primary recrystallization annealing process. do. In addition, N is also an element that causes magnetic aging, and since it can deteriorate magnetic flux density and low field iron loss characteristics, it is subjected to purification annealing in the secondary recrystallization annealing process, and N in the grain-oriented electrical steel sheet finally obtained through such purification annealing. The content of may be 0.0015% by weight or less.

S: 0.025% by weight or less (excluding 0%)

Sulfur (S) is an element that is unavoidably contained in the manufacturing process. When added in large amounts, it segregates in the center of the slab during casting, causing brittleness, causing hot shortening defects on the surface, deteriorating castability, and remaining on the surface even after casting is finished. In addition to being an element that causes many defects such as scab defects, it reacts with Mn in steel to form Mn-based sulfides, making the microstructure non-uniform and deteriorating rollability. Therefore, the content of S may have a range of 0.025% by weight or less (excluding 0%). The content of S may be 0.015% by weight or less, more specifically 0.008% by weight or less. On the other hand, formed MnS can be used as an inhibitor that exerts suppressive power during secondary recrystallization, and can help the growth of {90,87,43} orientation. Therefore, if the addition amount is below the appropriate level, there is no problem in exerting the desired effect of the invention. On the other hand, after the secondary recrystallization, the final S content in the steel sheet may be 0.0015% by weight or less in order to improve low field core loss characteristics.

It contains iron (Fe) as the remainder. In addition, it may contain unavoidable impurities. The unavoidable impurities refer to impurities that are unavoidably mixed in the manufacturing process of steelmaking and grain-oriented electrical steel sheets. Since unavoidable impurities are widely known, detailed descriptions are omitted. In one embodiment of the present invention, the addition of elements other than the above-described alloy components is not excluded, and may be variously included within a range that does not impair the technical spirit of the present invention. When additional elements are included, they are included in place of Fe, which is the remainder.

Based on the ND plane, the average grain size is 10 mm to 40 mm, the area ratio occupied by crystal grains having a grain size of 100 mm or more is 10 area% or less, and the average width of magnetic domains in a demagnetized state may be 0.0003 to 0.0030 of the average grain size.

2 shows the magnetic domain widths in the (90, 90, 45) and (90, 87, 43) orientations. As shown in FIG. 2, the formation of the lancet domain reduces the domain width.

The grain-oriented electrical steel sheet according to an embodiment of the present invention has a magnetic flux density (B ₈ ) of 1.89 T or more, a maximum relative permeability (μ _max ) measured at 50 Hz of 40000 or more, and may satisfy Equations 3 to 4 below. .

[Equation 3]

(W _10/50 /W _17/50 ) ≤ 0.32

[Equation 4]

(μ _1.7T / μ _1.0T ) ≥ 0.850

Here, B ₈ means the magnetic flux density value measured at 800 A/m under 50 Hz AC electricity, and the maximum relative permeability (μ _max ) is the largest of the calculated relative permeability (μ) values in the range from 0.01T to 1.95T. value, and the relative permeability (μ) means the value calculated by setting the magnetic flux density B measured at 0Hz and the strength of the magnetic field H as B/H, and W _10/50 and W _17/50 are the applied magnetic field, respectively are 10T and 15T, mean iron loss values measured at a frequency of 50Hz, and μ _1.0T and μ _1.7T represent relative magnetic permeability (μ) values calculated at 1.0T and 1.7T, respectively.

A method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention includes the steps of hot-rolling a slab to prepare a hot-rolled steel sheet; Manufacturing a cold-rolled steel sheet by cold-rolling the hot-rolled steel sheet; Primary recrystallization annealing of the cold-rolled steel sheet; and performing secondary recrystallization annealing on the primary recrystallization annealed cold-rolled steel sheet.

Hereinafter, each step is described in detail.

First, a hot-rolled steel sheet is manufactured by hot-rolling a slab. Since the alloy composition of the slab has been described in relation to the alloy composition of the grain-oriented electrical steel sheet, overlapping descriptions will be omitted. Specifically, the slab contains, by weight, Si: 2.5 to 6.5%, Mn: 0.03 to 0.2%, Al: 0.01 to 0.04%, C: 0.03 to 0.1%, N: 0.009% or less (excluding 0%) and S : 0.025% or less (excluding 0%), the balance including Fe and unavoidable impurities.

Returning to the description of the manufacturing method, the step of heating the slab to 1300 ° C. or less may be further included before the step of manufacturing the hot-rolled steel sheet. It is also possible to hot-roll as it is without heating the slab.

Next, a hot-rolled steel sheet is manufactured by hot-rolling the slab. The thickness of the hot-rolled steel sheet may be 1.5 to 3 mm.

In the step of manufacturing a hot-rolled steel sheet, two or more passes are included in which the angle between the rolling direction and the steel sheet traveling direction is 0.25° or more. By hot rolling in this way, a large amount of crystal grains having an orientation of (90,87,43) and an orientation within 3° can be formed. The (90,90,45) orientation is more easily formed by the shear structure formed on the surface.

In general, hot rolling or cold rolling is performed in a direction parallel to the steel sheet traveling direction, but in one embodiment of the present invention, two or more passes are included in which the angle between the rolling direction and the steel sheet traveling direction is 0.25° or more. The hot-rolling step may include a plurality of passes, and may include two or more passes with the aforementioned angle twisted. More specifically, it may include 2 to 4 times.

In one embodiment of the present invention, unless otherwise specified, the RD direction is used as the same meaning as the traveling direction of the steel sheet.

The aforementioned pass may specifically form an angle of 1 to 3 degrees. In order to change the rolling direction as described above, rolling may be performed in a state where the axis of the rolling mill is distorted by 0.25 degrees or more.

3 shows an example in which the angle between the rolling direction and the steel sheet traveling direction is different. 3 shows examples 1 and 2 in which both the upper and lower rolls are twisted, but it is also possible to twist only the upper or lower roll. In addition, it is also possible when the angle of one of the backup roll or the work roll is distorted.

The aforementioned pass may be performed in a temperature range of 930 to 1050 °C.

Through the above-mentioned pass, it is possible to reduce the pressure by more than 30%. If the reduction ratio is too small, it may be difficult to form a large amount of (90,87,43) crystal grains. More specifically, 30 to 93% reduction may be achieved through a pass in which the angle between the rolling direction and the steel sheet advancing direction is 0.25° or more.

By hot rolling through the above-mentioned pass, the hot-rolled steel sheet has the fraction (V _(90,87,43) ) and (90,90,45) orientation of crystal grains having an orientation within 3˚ of the (90,87,43) orientation. The fraction (V _(90,90,45) ) of crystal grains having an orientation within 3 degrees of and may satisfy Equation 5 below.

[Equation 5]

V _(90,87,43) ≥ 2 × V _(90,90,45)

Thereafter, a step of annealing the hot-rolled steel sheet may be further included. At this time, the temperature may be 1020 to 1130 ° C. By further including the step of annealing the hot-rolled steel sheet, adjacent crystal grains of (90,90,45) orientation grow and can become recrystallization nuclei even after rolling, so that (90,87,43) orientation crystal grains are further formed. It can be.

After annealing the hot-rolled steel sheet, the hot-rolled steel sheet has a fraction (V _(90,87,43) ) and (90,90,45) orientation and 3 The fraction (V _(90,90,45) ) of crystal grains having an orientation within ˚ may satisfy Equation 6 below.

[Equation 6]

V _(90,87,43) ≥ 2.5 × V _(90,90,45)

Next, a cold-rolled steel sheet is manufactured by cold-rolling the hot-rolled steel sheet.

In the step of manufacturing a cold-rolled steel sheet, cold rolling may be performed two or more times including one cold rolling or intermediate annealing. Specifically, it may be made of a step of cold rolling the hot-rolled steel sheet once.

The thickness of the cold-rolled steel sheet should be less than 0.65mm. On the other hand, when cold rolling is performed, the cold rolling reduction ratio may be 82% to 93%. The reduction ratio during cold rolling is a factor that governs the amount of dislocations of deformed grains in steel, and thus directly affects the energy accumulation of deformed grains. In addition, in the case of a non-rolling stable bearing, the process of changing the bearing to an adjacent rolling stable bearing according to the rolling reduction ratio is a cold rolling process, and the rolling reduction ratio may be 82% to 93%. If the reduction rate is too small, crystal grains of a desired size cannot be obtained by short annealing during primary recrystallization, and if the reduction rate is too large, an annealed sheet satisfying the desired texture condition cannot be obtained.

In the step of manufacturing the cold-rolled steel sheet, a retention step in which a temperature of 150° C. or higher is maintained for at least 10 minutes after the cold-rolling reduction ratio is 5% may be further included. By further including a retention step, thickness variation can be reduced. Specifically, the thickness deviation may be less than 5%. If it is within 5% of the total thickness based on the width of the entire coil, it can be seen that the steel sheet has been rolled through plane deformation, so it is limited to less than 5%.

Here, the thickness deviation is calculated as 1 - (thickness inside 2 cm from the edge of the steel plate / thickness of the center).

In the step of manufacturing the cold-rolled steel sheet, a retention step in which a temperature of 150° C. or higher is maintained for at least 10 minutes after the cold-rolling reduction ratio of 5% may be further included. The retention phase controls the activity of carbon in the steel.

Next, the cold-rolled sheet is subjected to primary recrystallization annealing. At this time, the step of primary recrystallization annealing may include a decarburization step and a nitriding step. The decarburization step and the nitriding step may be performed regardless of the order. That is, the nitriding step may be performed after the decarburization step, the decarburization step may be performed after the nitriding step, or the decarburization step and the nitriding step may be performed simultaneously.

In the decarburization step, the amount of carbon in the steel may be reduced by 0.04 to 0.065% by weight. If the change in carbon content is small, it may mean that the carbon content before annealing is small. In this case, it is a case of annealing without forming a desired orientation during cold rolling. On the other hand, a large reduction in carbon content may mean a large amount of carbon before annealing. In this case, an orientation other than the desired orientation is formed during cold rolling, and the rollability may be significantly inferior. On the other hand, as the amount of carbon decreases to an appropriate level during annealing, empty spaces are formed in the steel, and nitrogen newly injected during nitriding settles in these empty spaces to easily form precipitates, thereby reducing the amount of carbon by decarburization. limit

Also, the amount of oxygen may be increased by 0.005 to 0.1% by weight at the same time. The formation of MgO ₂ SiO ₄ , which is a complex oxide of MgO-SiO ₂ formed on the surface during annealing, can be evaluated through the amount of oxygen in steel. When at least 0.005% by weight or more of oxygen is introduced into steel, a beautiful oxide layer without defects is formed on the surface. On the other hand, when the amount of oxygen is increased too much, oxygen does not stay only on the surface of steel, but also forms an oxide layer inside the plate, so that the formation of magnetic domains changes irregularly, resulting in extremely poor iron loss.

In the nitriding step, the amount of nitrogen in the steel may be increased by 0.01 to 0.03% by weight. Nitride formed during annealing forms AlN, an inhibitor that can control the timing of secondary recrystallization. The size and distribution of AlN thus formed can be evaluated by the amount of nitrogen in steel that changes during annealing. If the amount of nitrogen increase is too small, the nitrogen injected into the steel may settle only on the surface and not have adequate restraint inside the plate. If the amount of nitrogen increase is too large, a strong restraining force is given to both the surface portion and the interior portion, resulting in the formation of very coarse crystal grains after secondary recrystallization. Accordingly, a problem in which the size of the magnetic domain may greatly increase may occur regardless of the crystal orientation.

The soaking temperature of the primary recrystallization annealing step may be 840 °C to 900 °C. Even if the primary recrystallization annealing is performed at a temperature lower than 840 ° C. or higher than 900 ° C., there is no problem in exhibiting the functions suggested by the present invention.

After the primary recrystallization annealing step, the average grain size in the 1/8 thickness of the steel sheet is 13 to 25 μm, and the number of grains having a grain size of 3 times or more of the average grain size may be 0.001% to 0.5% of the total number of grains. .

In addition, in the step of primary recrystallization annealing, the grains in the (90,87,43) orientation further increase, and the fraction of grains having an orientation within 3˚ of the (90,87,43) orientation (V _{(90,87,43) )} ) and (90,90,45) and the fraction (V _(90,90,45) ) of crystal grains having an orientation within 3˚ may satisfy Equation 7 below.

[Equation 7]

V _(90,87,43) ≥ 3 × V _(90,90,45)

Specifically, the number of crystal grains having a grain size of 40 μm having a direction of (90,87,43) and an orientation within 3˚ may be 4/cm ³ or more.

In addition, the fraction of crystal grains having a smaller angular difference from the <100> axis and the Goss orientation may be 30% or more.

In FIG. 4, the angular difference with the <100> axis represents a crystal grain having a smaller angular difference with the Goss orientation.

After the primary recrystallization annealing step, an annealing separator may be applied to the steel sheet. Since the annealing separator is widely known, a detailed description thereof will be omitted. For example, an annealing separator containing MgO as a main component may be used.

Next, the cold-rolled sheet subjected to primary recrystallization annealing is subjected to secondary recrystallization annealing.

The purpose of the secondary recrystallization annealing is to form a {110}<001> texture by secondary recrystallization, to impart insulation by forming a glassy film by the reaction between the oxide layer formed during primary recrystallization annealing and MgO, and to remove impurities that harm magnetic properties. is the removal As a method of secondary recrystallization annealing, in the temperature rising section before secondary recrystallization occurs, a mixed gas of nitrogen and hydrogen is maintained to protect nitride, which is a grain growth inhibitor, so that secondary recrystallization can develop well, and secondary recrystallization is completed. In the post-soaking step, impurities are removed by maintaining for a long time in a 100% hydrogen atmosphere.

In the secondary recrystallization annealing step, secondary recrystallization may be completed at a soaking temperature of 1150 to 1210 °C.

In one embodiment of the present invention, a larger amount of (90,87,43) oriented crystal grains may be formed by adjusting the heating rate before reaching the above-described soaking temperature.

Specifically, the temperature increase rate in the range of 1100 to 1150°C is 1 to 10°C/h higher than the rate of temperature increase in the range of 900 to 1100°C.

In general, a technique for increasing the Exact Goss orientation by lowering the heating rate as the crack temperature approaches is well known. This method is a useful technique for making GO steel have high magnetic flux density characteristics, but it has a problem that the iron loss increases due to the increase in the width of the magnetic domain as the fraction of the Exact Goss orientation within 3 degrees from the rolling direction, which is the direction of magnetization, increases greatly. have. Therefore, in one embodiment of the present invention, by increasing the heating rate as the soaking temperature approaches, a larger amount of (90,87,43) oriented crystal grains can be formed.

More specifically, the heating rate in the 900 to 1100 °C section is 3 to 15 °C/h, and the heating rate in the 1100 to 1150 °C section may be 4 to 25 °C/h.

The atmospheric gas in the furnace at this time is also important. In the range of 900 to 1100 ° C and 1100 to 1150 ° C, the atmospheric gas in the furnace is a mixed gas containing more than 50% by volume of nitrogen and other H ₂ O and trace amounts of nitrogen, and the dew point is in the range of 0 to 50 ° C. can be limited to The range of nitrogen in the atmosphere must be 50% by volume or more, so that the nitride inside the steel does not decompose to the target temperature and is stable. While obtaining an electrical steel sheet, it can be limited because it also affects the decomposition of nitrides and sulfides.

Hereinafter, specific embodiments of the present invention will be described. However, the following examples are only specific examples of the present invention, but the present invention is not limited to the following examples.

Example 1

After vacuum melting the steel composition of Table 1 and the remainder of the Fe alloy components, an ingot was made, then heated to a temperature of 1250 ° C., then hot-rolled 5 passes under the conditions of Table 2 below, pickled, and wound. After that, it is heat treated, cold rolled once to a thickness of 0.30 mmt, and the cold rolled sheet is subjected to simultaneous decarburization and annealing at a temperature of 860 ° C so that the carbon content is 30 ppm and the nitrogen content is 190 ppm in a humid mixed gas atmosphere of hydrogen, nitrogen and ammonia. Heat treatment was performed. Subsequently, MgO, an annealing separator, was applied to the steel sheet, and then secondary recrystallization annealing was performed. Next, after reaching 1200 ° C., it was maintained in a 100% hydrogen atmosphere for 10 hours or more and then furnace cooled.

steel grade Si Mn Al C N S One 2.54 0.061 0.031 0.059 0.0052 0.0039 2 4.13 0.109 0.023 0.051 0.0048 0.0082 3 3.00 0.073 0.027 0.061 0.0047 0.0117 4 2.71 0.069 0.032 0.060 0.0067 0.0196 5 3.85 0.049 0.021 0.046 0.0059 0.0184 6 3.18 0.108 0.031 0.058 0.0047 0.0615 7 3.16 0.120 0.022 0.045 0.0038 0.0006 8 4.49 0.066 0.024 0.051 0.0027 0.0018 9 3.15 0.083 0.027 0.032 0.0048 0.0163 10 2.54 0.061 0.031 0.059 0.0052 0.0039

steel grade Hot rolling pass twisted over 0.25˚ Retention time above 150℃ during cold rolling (minutes) Temperature increase rate (℃/h) in the range of 900 to 1100℃ Temperature increase rate (℃/h) in the range of 1100 to 1150℃ pass order Reduction rate (%) One doesn't exist 15 10 15 2 1st, 2nd 15 15 10 15 3 2nd, 3rd 30 5 10 15 4 3rd, 4th 50 15 15 15 5 4th, 5th 60 15 20 25 6 3rd, 4th, 5th 70 15 5 10 7 4th, 5th 80 15 10 15 8 2nd, 3rd, 4th, 5th, 50 15 10 15 9 2nd, 3rd 30 15 10 15 10 3rd, 4th 50 15 10 15

steel grade hot rolled steel After primary recrystallization annealing After secondary recrystallization annealing Average grain size (mm) Grain area ratio (%) of 100 mm or more Mean domain width (μm) (90,87,43)
azimuth fraction (90,90,45) azimuth fraction (90,87,43)
azimuth fraction (90,90,45) azimuth fraction (90,87,43)
azimuth fraction (90,90,45) azimuth fraction One 0.05% 0.04% 0.003% 0.001% 22.6% 7.6% 35.9 4.6 186 2 0.03% 0.04% 0.006% 0.006% 16.4% 6.1% 37.0 3.6 175 3 0.02% 0.03% 0.004% 0.001% 26.2% 5.2% 37.6 8.9 130 4 0.06% 0.03% 0.017% 0.002% 23.6% 9.9% 44.0 12.4 257 5 0.08% 0.02% 0.015% 0.001% 16.3% 8.6% 42.9 14.4 274 6 0.37% 0.09% 0.040% 0.000% 45.6% 13.7% 32.1 1.5 57 7 0.27% 0.06% 0.020% 0.000% 44.2% 12.6% 30.4 0.7 63 8 0.22% 0.04% 0.027% 0.001% 55.1% 10.8% 28.0 4.1 10 9 0.12% 0.04% 0.134% 0.000% 39.9% 11.1% 29.0 1.2 12 10 0.13% 0.00% 0.031% 0.001% 48.6% 13.2% 18.8 4.1 11

steel grade magnetic flux density maximum relative permeability W10/50, W/kg W17/50, W/kg μ _1.0T μ _1.7T One 1.899 39562 0.37 1.10 36910 24109 2 1.886 32181 0.36 1.12 30415 24138 3 1.882 32381 0.4 1.21 39299 26969 4 1.876 39266 0.39 1.11 37939 33543 5 1.881 31504 0.41 1.19 27231 25298 6 1.895 34300 0.32 1.00 33637 30603 7 1.909 46679 0.36 1.07 43087 40278 8 1.935 57726 0.35 1.07 53893 46301 9 1.901 39437 0.33 1.03 37307 32440 10 1.938 61385 0.36 1.07 59260 55192

As shown in Tables 1 to 4, steel grades 6 to 10 appropriately satisfying the hot rolling conditions, cold rolling conditions, and secondary recrystallization annealing conditions have a large number of (90,87,43) oriented crystal grains, the magnetic domain width is narrow, It can be confirmed that the magnetic properties are excellent.

On the other hand, steel grades 1 to 5 that did not satisfy the hot rolling conditions, cold rolling conditions, and secondary recrystallization annealing conditions did not properly form crystal grains with (90,87,43) orientation, had a relatively wide magnetic domain width, and had relatively poor magnetism. can confirm.

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 to which the present invention belongs may change the technical spirit or essential features of the present invention. It will be appreciated that it may be embodied in other specific forms without Therefore, it should be understood that implementations and/or examples described above are illustrative in all respects and not restrictive.

Claims (18)

In % by weight, Si: 2.5 to 6.5%, Mn: 0.03 to 0.2%, Al: 0.01 to 0.04%, C: 0.005% or less (excluding 0%), N: 0.0015% or less (excluding 0%) and S: 0.025% or less (excluding 0%), the balance being Fe and unavoidable impurities,
A grain-oriented electrical steel sheet in which the fraction of crystal grains having an orientation within 3° from the (90,87,43) orientation expressed in Euler orientation is 30% by volume or more. According to claim 1,
(90,87,43) The fraction of crystal grains having an orientation within 3˚ of the orientation (V _(90,87,43) ) and the fraction of grains having an orientation within 3˚ of the (90,90,45) orientation ( A grain-oriented electrical steel sheet in which V _(90,90,45) ) satisfies Equation 1 below.
[Equation 1]
V _(90,87,43) ≥ 3.0 × V _(90,90,45) According to claim 1,
The fraction of grains whose <16,1,0> axis is within 3 degrees from the rolling direction (V _<16,1,0> ) and whose <1,0,0> axis is within 3 degrees from the rolling direction A grain-oriented electrical steel sheet in which the fraction of grains (V _<1,0,0> ) satisfies Equation 2 below.
[Equation 2]
V _<16,1,0> ≥ 2× V _<1,0,0> According to claim 1,
The fraction of crystal grains whose <16,1,0> axis is within 3 degrees from the rolling direction is 50% by volume or more, and the fraction of crystal grains whose <1,0,0> axis is within 3 degrees from the rolling direction ( Grain-oriented electrical steel sheet having V _<1,0,0> ) of 25% by volume or more. According to claim 1,
Grain-oriented electrical steel sheet having an average grain size of 10 mm to 40 mm based on the ND surface, an area ratio occupied by crystal grains with a grain size of 100 mm or more, less than 10 area%, and an average magnetic domain width in a demagnetized state of 0.0003 to 0.0030 of the average grain size. . According to claim 1,
The magnetic flux density (B ₈ ) is 1.89 T or more,
The maximum relative permeability (μ _max ) measured at 50 Hz is 40000 or more,
A grain-oriented electrical steel sheet that satisfies Formulas 3 to 4 below.
[Equation 3]
(W _10/50 /W _17/50 ) ≤ 0.32
[Equation 4]
(μ _1.7T / μ _1.0T ) ≥ 0.850
(Here, B ₈ means the magnetic flux density value measured at 800 A / m under 50 Hz AC electricity, and the maximum relative permeability (μ _max ) is the highest among the calculated relative permeability (μ) values in the range from 0.01T to 1.95T. It means a large value, and the relative permeability (μ) means the value calculated by setting the magnetic flux density B measured at 0Hz and the strength of the magnetic field H as B / H, and W _10/50 and W _17/50 are respectively It refers to the core loss value measured under the condition that the magnetic field is 10T and 15T and the frequency is 50Hz, and μ _1.0T and μ _1.7T represent the relative magnetic permeability (μ) values calculated at 1.0T and 1.7T, respectively.) In weight percent, Si: 2.5 to 6.5%, Mn: 0.03 to 0.2%, Al: 0.01 to 0.04%, C: 0.03 to 0.1%, N: 0.009% or less (excluding 0%) and S: 0.025% or less (Excluding 0%), preparing a hot-rolled steel sheet by hot-rolling a slab containing Fe and unavoidable impurities;
manufacturing a cold-rolled steel sheet by cold-rolling the hot-rolled steel sheet;
performing primary recrystallization annealing on the cold-rolled steel sheet; and
Including the step of secondary recrystallization annealing of the primary recrystallization annealed cold-rolled steel sheet,
In the step of manufacturing the hot-rolled steel sheet, at least two passes in which the angle between the rolling direction and the steel sheet traveling direction are 0.25 degrees or more are included,
In the step of manufacturing the hot-rolled steel sheet, the reduction ratio in the pass in which the angle between the rolling direction and the steel sheet traveling direction is 0.25 ° or more is 30% or more,
In the step of producing the cold-rolled steel sheet, after a cold rolling reduction of 5%, a stay step in which a temperature of 150 ° C. or higher is maintained for at least 10 minutes,
In the secondary recrystallization annealing step, the temperature increase rate in the 1100 to 1150 ° C section is 1 to 10 ° C / h higher than the temperature rise rate in the 900 to 1100 ° C section,
The temperature increase rate in the 900 to 1100 ° C section is 3 to 15 ° C / h, and the temperature increase rate in the 1100 to 1150 ° C section is 4 to 25 ° C / h. Method for producing a grain-oriented electrical steel sheet. delete According to claim 7,
After the step of manufacturing the hot-rolled steel sheet, the hot-rolled steel sheet has a fraction (V _(90,87,43) ) and (90,90,45) of crystal grains having an orientation within 3˚ of the (90,87,43) orientation. A method for producing a grain-oriented electrical steel sheet in which the fraction (V _(90,90,45) ) of crystal grains having an orientation within 3 ° of the orientation satisfies Equation 5 below.
[Equation 5]
V _(90,87,43) ≥ 2 × V _(90,90,45) According to claim 7,
Further comprising the step of annealing the hot-rolled steel sheet after the step of manufacturing the hot-rolled steel sheet,
After annealing the hot-rolled steel sheet, the hot-rolled steel sheet has a fraction (V _(90,87,43) ) and (90,90,45) orientation of crystal grains having an orientation within 3˚ of (90,87,43) orientation and A method for producing a grain-oriented electrical steel sheet in which the fraction (V _(90,90,45) ) of crystal grains having an orientation of 3˚ or less satisfies Equation 6 below.
[Equation 6]
V _(90,87,43) ≥ 2.5 × V _(90,90,45) According to claim 7,
The step of manufacturing the cold-rolled steel sheet is rolled at a reduction ratio of 82% to 93%, and a method for producing a grain-oriented electrical steel sheet having a thickness deviation of less than 5%.
(Here, the thickness deviation is calculated as 1- (thickness inside 2 cm from the edge of the steel plate / thickness of the center)) According to claim 7,
After the primary recrystallization annealing,
The average grain size at 1/8 thickness of the steel sheet is 13 to 25 μm, and the number of grains having a grain size of 3 times or more of the average grain size is 0.001% to 0.5% of the total number of grains. Method for producing a grain-oriented electrical steel sheet. According to claim 7,
After the primary recrystallization annealing, the cold-rolled steel sheet has a fraction (V _(90,87,43) ) and (90,90,45) orientation of crystal grains having an orientation within 3˚ of (90,87,43) orientation and A method for producing a grain-oriented electrical steel sheet in which the fraction (V _(90,90,45) ) of crystal grains having an orientation of 3˚ or less satisfies Equation 7 below.
[Equation 7]
V _(90,87,43) ≥ 3 × V _(90,90,45) According to claim 7,
After the primary recrystallization annealing, the cold-rolled steel sheet has a (90,87,43) orientation and a grain size of 40㎛ having an orientation within 3˚, and the number of grains is 4/cm ³ or more. Method of producing a grain-oriented electrical steel sheet. According to claim 7,
After the primary recrystallization annealing, the cold-rolled steel sheet has a <100> axis angle difference with the Goss direction and the fraction of crystal grains smaller than the angle difference is a method of manufacturing a grain-oriented electrical steel sheet of 30% or more. According to claim 7,
After the primary recrystallization annealing, a method for producing a grain-oriented electrical steel sheet in which the carbon content of the steel is reduced by 0.04 to 0.065% by weight. According to claim 7,
After primary recrystallization annealing, a method for producing a grain-oriented electrical steel sheet in which the amount of oxygen in the steel is increased by 0.005 to 0.1% by weight. According to claim 7,
After primary recrystallization annealing, a method for producing a grain-oriented electrical steel sheet in which the amount of nitrogen in the steel is increased by 0.01 to 0.03% by weight.

Images