Two-directional electromagnetic steel sheet and method for manufacturing the same

Abstract

By adjusting the reduction rate in the second cold rolling and the final annealing time, <001> The present invention aims to provide a bi-directional electrical steel sheet and a manufacturing method thereof, which has excellent magnetic properties in both the rolling direction and the direction perpendicular to the rolling direction and has very little magnetic deviation by increasing the fraction of oriented crystal grains. The present invention provides a two-dimensional electrical steel sheet with a {100} <001> The fraction of crystal grains with orientations within 15° of {100} is 50-75%. <380> The fraction of crystal grains with orientations within 15° of the grain boundary is 50 to 75%. Furthermore, the bi-directional electrical steel sheet according to the present invention has a {100} <001> The fraction of crystal grains with orientations within 10° of {100} is 20-50%. <380> The fraction of crystal grains with orientations within 10° of the grain boundary is 20 to 50%. The bi-directional electrical steel sheet according to the present invention may contain, by weight, 1.0% to 7.0% Si, 0.02% or less (excluding 0%) Al, 0.02 to 0.50% Mn, 0.004% or less (excluding 0%) C, and 0.0005 to 0.005% S, with the remainder being Fe and other unavoidable impurities.

Description

Technical Field

[0001] The present invention relates to a non-oriented electrical steel sheet and a method for manufacturing the same. More specifically, by adjusting the reduction ratio and the final annealing time in secondary cold rolling to increase the fraction of crystal grains having a {100}<001> orientation, the present invention relates to a non-oriented electrical steel sheet having excellent magnetic properties in the rolling direction and the direction perpendicular to the rolling direction and a very small magnetic deviation, and a method for manufacturing the same.

Background Art

[0002] Electrical steel sheets are classified into oriented electrical steel sheets having excellent magnetic properties in one direction and non-oriented electrical steel sheets showing uniform magnetic properties in all directions. Considering the magnetic anisotropy of iron having a BCC structure, the atomic arrangement is controlled according to the use of the steel sheet to control and change the magnetic properties. Oriented electrical steel sheets utilize the secondary recrystallization phenomenon and have only a {110}<001> Goss texture, but no other textures outside the Goss texture have been commercialized using the secondary recrystallization phenomenon. The {100}<001> orientation, that is, the Cube orientation, has an <001> axis that is easy to magnetize not only in the RD direction but also in the TD direction, unlike the Goss orientation. The Cube orientation has been recognized as useful in the past, but only a method of manufacturing through equipment that makes large-scale industrial production impossible, such as performing cross rolling or vacuum annealing, is known. In particular, the cross rolling method cannot be utilized because continuous production of the material is impossible. In the case of large generators, since a cylindrical core with a diameter of several meters must be manufactured, it cannot be applied to a process that divides the core into several to several tens on the plate surface and assembles them, and the productivity is extremely low.

Summary of the Invention

Problems to be Solved by the Invention

[0003] An object of the present invention is to provide a non-oriented electrical steel sheet and a method for manufacturing the same. Specifically, by adjusting the rolling reduction rate and the final annealing time in the secondary cold rolling to increase the fraction of crystal grains having the {100}<001> orientation, a non-oriented electrical steel sheet having extremely excellent magnetic properties in the rolling direction and the direction perpendicular to the rolling direction and a very small magnetic deviation, and a method for manufacturing the same are to be provided. Means for Solving the Problems

[0004] The non-oriented electrical steel sheet according to the present invention has a fraction of crystal grains having an orientation within 15° from {100}<001> of 50 to 75%, and a fraction of crystal grains having an orientation within 15° from {100}<380> of 50 to 75%. The non-oriented electrical steel sheet according to the present invention has a fraction of crystal grains having an orientation within 10° from {100}<001> of 20 to 50%, and a fraction of crystal grains having an orientation within 10° from {100}<380> of 20 to 50%. The non-oriented electrical steel sheet according to the present invention contains, in weight %, Si: 1.0% to 7.0%, Al: 0.02% or less (excluding 0%), Mn: 0.02 to 0.50%, C: 0.004% or less (excluding 0%) and S: 0.0005 to 0.005%, and the balance can consist of Fe and other unavoidable impurities. The average grain size of the crystal grains may be 2000 μm or more. The non-oriented electrical steel sheet of the present invention may have a deviation of the magnetic flux density (B50) in the rolling direction (L direction) defined by the following formula 1 and the magnetic flux density (B50) in the direction perpendicular to the rolling direction (C direction) of 3 or less. [Formula 1] TIFF0007698649000001.tif17128 (In formula 1, B L 50 and B C 50 are the magnetic flux densities (B50) in the rolling direction and the direction perpendicular to the rolling direction, respectively, and MAX(B L 50 , B C 50 ) represents the larger value of the magnetic flux densities (B50) in the rolling direction and the direction perpendicular to the rolling direction.)

[0005] The double-directional electromagnetic steel sheet of the present invention Manufacturing method includes a step of hot-rolling a slab to produce a hot-rolled sheet, a step of cold-rolling the hot-rolled sheet for the first time to produce a first cold-rolled sheet, a step of intermediate annealing the first cold-rolled sheet, a step of cold-rolling the intermediate annealed sheet for the second time to produce a second cold-rolled sheet, and a step of final annealing the second cold-rolled sheet. In the step of producing the second cold-rolled sheet, the rolling reduction rate may be 55 to 85%. The final annealing step can be carried out for 6 to 60 hours. The slab contains, by weight%, Si: 1.0% to 7.0%, Al: 0.02% or less (excluding 0%), Mn: 0.02 to 0.50%, C: 0.004% or less (excluding 0%), and S: 0.0005 to 0.005%, and the balance can consist of Fe and other inevitable impurities. After the step of producing the hot-rolled sheet, it can further include a step of annealing the hot-rolled sheet. The step of producing the first cold-rolled sheet can include one cold rolling or two or more cold rollings with an intermediate annealing in between. The first cold-rolled sheet and the second cold-rolled sheet can be rolled in the same direction in the steps of producing them. The intermediate annealing step can be carried out in a reducing atmosphere. After the step of producing the second cold-rolled sheet, it can further include a step of applying an annealing release agent. The final annealing step can be carried out in a reducing atmosphere. The final annealing step can be carried out at a temperature of 1000 to 1200 °C.

Advantages of the Invention

[0006] According to the present invention, the double-directional electromagnetic steel sheet has similar magnetic values in the rolling direction and the direction perpendicular to rolling regardless of the direction, and exhibits excellent magnetic properties such as a high magnetic flux density and a low iron loss.

Brief Description of the Drawings

[0007]

Figure 1

Mode for Carrying Out the Invention

[0008] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are only used to distinguish one part, component, region, layer, or section from another. Thus, the first part, component, region, layer, or section described below can be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention. The technical terms used herein are for the purpose of referring to specific embodiments only and are not intended to limit the present invention. The singular forms used herein include the plural forms as well, unless the context clearly dictates otherwise. The meaning of "comprising" used in the specification does not exclude the presence or addition of other characteristics, regions, integers, steps, operations, elements, and / or components while specifying a particular characteristic, region, integer, step, operation, element, and / or component.

[0009] When a part is referred to as being "on" or "above" another part, this means directly on or above the other part, or there may be other parts therebetween. In contrast, when a part is referred to as being "directly above" another part, no other part intervenes therebetween. Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the presently disclosed content, and are not interpreted in an idealized or overly formal sense unless otherwise defined. Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %. In one embodiment of the present invention, the meaning of further including an additional element means including it by substituting iron (Fe), which is the remainder, by the additional amount of the additional element. Hereinafter, embodiments of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement them. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0010] The double-oriented electromagnetic steel sheet according to the present invention has a fraction of crystal grains having an orientation within 15° from {100}<001> of 50 to 75%, and a fraction of crystal grains having an orientation within 15° from {100}<380> of 50 to 75%. The crystal grains having an orientation within 15° from the aforementioned {100}<001> are referred to as Cube orientation crystal grains. In one embodiment of the present invention, by including the Cube orientation crystal grains with an area fraction of 50 to 75% and simultaneously including the crystal grains having an orientation within 15° from {100}<380> with an area fraction of 50 to 75%, it is possible to provide a double-oriented electromagnetic steel sheet having extremely excellent magnetic properties in the rolling direction and the direction perpendicular to rolling and a very small magnetic deviation. There is an overlapping portion within 15° between the {100}<001> orientation and the {100}<380> orientation. In one embodiment of the present invention, the crystal grains that simultaneously correspond to the crystal grains having an orientation within 15° from {100}<001> and the crystal grains having an orientation within 15° from {100}<380> are calculated repeatedly. Therefore, the total fraction of the crystal grains having an orientation within 15° from {100}<001> and the crystal grains having an orientation within 15° from {100}<380> can exceed 100%. More specifically, the fraction of the crystal grains having an orientation within 15° from {100}<001> is 50 to 65%, and the fraction of the crystal grains having an orientation within 15° from {100}<380> is 55 to 75%. More specifically, the fraction of the crystal grains having an orientation within 15° from {100}<001> is 60 to 65%, and the fraction of the crystal grains having an orientation within 15° from {100}<380> is 55 to 60%. The grain fraction can be evaluated by the area fraction with respect to a specific plane. At this time, the area fraction may be the grain area fraction measured based on a plane parallel to the rolling plane (the plane perpendicular to the ND direction).

[0011] The double-oriented electrical steel sheet of the present invention has a grain fraction of 20 to 50% for grains having an orientation within 10° from {100}<001>, and a grain fraction of 20 to 50% for grains having an orientation within 10° from {100}<380>. More specifically, the grain fraction of grains having an orientation within 10° from {100}<001> is 25 to 45%, and the grain fraction of grains having an orientation within 10° from {100}<380> is 20 to 45%. More specifically, the grain fraction of grains having an orientation within 10° from {100}<001> is 40 to 45%, and the grain fraction of grains having an orientation within 10° from {100}<380> is 30 to 35%. The total of the grain fraction of grains having an orientation within 10° from {100}<001> and the grain fraction of grains having an orientation within 10° from {100}<380> may be less than 100%, and the remainder is grains having an orientation outside the above-mentioned orientation range.

[0012] The double-oriented electrical steel sheet of the present invention contains, by weight, Si: 1.0% to 7.0%, Al: 0.02% or less (excluding 0%), Mn: 0.02 to 0.50%, C: 0.004% or less (excluding 0%) and S: 0.0005 to 0.005%, and the balance can consist of Fe and other inevitable impurities. The reasons for the component limitations of the double-oriented electrical steel sheet will be explained. Si: 1.0 to 7.0% by weight Silicon (Si) is an element that forms austenite in hot rolling. It is necessary to limit the addition amount so that the austenite fraction is around 10% by volume near the slab heating temperature and near the annealing temperature of the hot-rolled sheet. Also, in the final annealing, the formation of the recrystallized microstructure during annealing proceeds smoothly only when it is a single-phase ferrite, so it is necessary to limit the components to those that form a single-phase ferrite. In pure iron, when more than 1.0% by weight is added, a single-phase ferrite is formed, and the austenite fraction can be adjusted by adding C, so the lower limit of the Si content can be limited to 1.0% by weight. Also, when it exceeds 7.0% by weight, cold rolling becomes difficult and the saturation magnetic flux decreases, so this is restricted. More specifically, Si may be contained in an amount of 2.0 to 4.0% by weight. Even more specifically, in order to obtain a steel sheet with a high magnetic flux density, Si may be contained in an amount of 2.5 to 3.5% by weight.

[0013] Al: 0.02% by weight or less Aluminum (Al) can play a role in increasing the Al specific resistance. However, in a steel sheet with a large amount of Al added, Al2O3 is formed on the surface of the steel sheet during heat treatment. Al2O3 can penetrate from the surface into the grain boundaries, which inhibits the growth of grains and becomes a factor that hinders secondary recrystallization. Therefore, it is appropriate for Al to be 0.02% by weight or less. Even more specifically, Al may be contained in an amount of 0.01% by weight or less. Even more specifically, Al may be contained in an amount of 0.005% by weight or less. Mn: 0.02 to 0.50% by weight Manganese (Mn) is an element that increases the specific resistance. However, if the addition of Mn is excessive, during heat treatment, it will go too far into the Austenite region and there is a possibility of phase transformation. Also, an excessive amount of Mn has the effect of trapping sulfur more than necessary and preventing the diffusion of elemental S. An appropriate amount of Mn precipitates fine MnS and holds the grain boundaries with a weak force, and at an appropriate temperature, MnS melts away and secondary recrystallization occurs. The rate of volatilized S can also be controlled to some extent by Mn, so it can be considered that an appropriate amount of Mn plays a certain role in secondary recrystallization. Even more specifically, Mn can be contained in an amount of 0.05 to 0.30% by weight.

[0014] C: 0.004 wt% or less Carbon (C) is an element that, unlike the other elements mentioned above, is not substituted for Fe atoms but enters the interstitial sites. Due to its characteristics, when a large amount of C enters, it inhibits the movement of the potential and hinders the growth of crystal grains. More specifically, C can be contained at 0.003 wt% or less. S: 0.0005 - 0.0050 wt% Sulfur (S) changes the surface energy depending on the content of S segregated on the surface, and the changed surface energy may cause the recrystallization phenomenon of crystal grains in a specific orientation. On the surface without any S, the {110} plane is stable; on the surface with weak S segregation, the {100} plane is stable; and on the surface with a large amount of S segregation, the {111} plane is stable. The S content is adjusted to a very small amount to weakly segregate S on the surface. Mn also plays a role in additionally segregating S further to help S weakly segregate on the surface. More specifically, S can be contained at 0.0010 - 0.0040 wt%. Also, for the non - oriented electrical steel sheet according to an embodiment of the present invention, the balance other than the aforementioned components is Fe and unavoidable impurities. However, the inclusion of other elements is not excluded as long as the effects of the present invention are not inhibited.

[0015] The non - oriented electrical steel sheet according to an embodiment of the present invention may have an average crystal grain size of 2000 μm or more. If the average crystal grain size is excessively small, the fraction of the {100}<001> and {100}<380> texture may be low, and the magnetic properties may be inferior. The crystal grain size can be measured based on a plane parallel to the rolling surface (ND plane) of the steel sheet. The grain size means the diameter of a virtual circle having the same area as the crystal grain. More specifically, the average crystal grain size may also be 2500 μm or more. The non-oriented electrical steel sheet according to an embodiment of the present invention has excellent magnetic properties in both the rolling direction and the direction perpendicular to rolling. Specifically, B8 in both the rolling direction and the direction perpendicular to rolling may be 1.65 T or more. More specifically, B8 in both the rolling direction and the direction perpendicular to rolling may be 1.70 T or more. Even more specifically, B8 in both the rolling direction and the direction perpendicular to rolling may be 1.73 T or more. The non-oriented electrical steel sheet according to an embodiment of the present invention has excellent magnetic properties in both the rolling direction and the direction perpendicular to rolling. Specifically, B 50 in both the rolling direction and the direction perpendicular to rolling may be 1.80 T or more. More specifically, B 50 in both the rolling direction and the direction perpendicular to rolling may be 1.85 T or more. Even more specifically, B 50 in both the rolling direction and the direction perpendicular to rolling may be 1.88 T or more. The non-oriented electrical steel sheet according to an embodiment of the present invention may have a deviation of 3 or less between the magnetic flux density (B50) in the rolling direction (L direction) defined by the following formula 1 and the magnetic flux density (B50) in the direction perpendicular to rolling (C direction). [Formula 1] TIFF0007698649000002.tif17128 (In formula 1, B L 50 and B C 50 are the magnetic flux densities (B50) in the rolling direction and the direction perpendicular to rolling, respectively, and MAX(B L 50 , B C 50 ) indicates the larger value of the magnetic flux densities (B50) in the rolling direction and the direction perpendicular to rolling.) More specifically, the deviation may be 2 or less.

[0016] The method for manufacturing the non-oriented electrical steel sheet of the present invention includes the steps of hot rolling a slab to produce a hot-rolled sheet, cold rolling the hot-rolled sheet once to produce a first cold-rolled sheet, intermediate annealing the first cold-rolled sheet, cold rolling the intermediate annealed sheet twice to produce a second cold-rolled sheet, and final annealing the second cold-rolled sheet. Hereinafter, each step will be specifically described. First, a slab is manufactured. The reason for limiting the addition ratio of each composition in the slab is the same as the reason for limiting the composition of the above-described grain-oriented electrical steel sheet, so repeated explanations are omitted. Since the element content does not substantially vary during the manufacturing processes such as hot rolling, hot-rolled sheet annealing, first cold rolling, intermediate annealing, second cold rolling, and final annealing described below, the composition of the slab is substantially the same as the composition of the grain-oriented electrical steel sheet. The slab can be manufactured using the thin slab method or the strip casting method. The thickness of the slab may be 200 to 300 mm. The slab can be heated if necessary. The heating temperature may be 1100 to 1250 °C, and the heating time may be 30 minutes or more.

[0017] Next, the slab is hot-rolled to produce a hot-rolled sheet. At the stage of manufacturing the hot-rolled sheet, the thickness of the hot-rolled sheet may be 2.0 to 3.0 mm. After the stage of manufacturing the hot-rolled sheet, the stage of annealing the hot-rolled sheet can be further included. The stage of annealing the hot-rolled sheet can be performed at a temperature of 1000 to 1150 °C. Also, it can be annealed for 60 to 150 seconds. After annealing the hot-rolled sheet, an acid pickling stage can be further included. Next, the hot-rolled sheet is first cold-rolled to produce a first cold-rolled sheet. The stage of manufacturing the first cold-rolled sheet can include one cold rolling or two or more cold rollings with an intermediate annealing in between. At the stage of manufacturing the first cold-rolled sheet and the stage of manufacturing the second cold-rolled sheet, rolling can be performed in the same direction. Next, the first cold-rolled sheet is intermediate annealed. Since the degree of recrystallization is sufficient at the stage of intermediate annealing, it can be annealed at 900 to 1100 °C for 60 to 150 seconds. The stage of intermediate annealing can be performed in a reducing atmosphere. Since second cold rolling must be performed after intermediate annealing, it can be annealed in an atmosphere rich in hydrogen so as not to be oxidized during annealing. The remaining atmosphere may be air.

[0018] Next, the intermediate annealed sheet is second cold-rolled to produce a second cold-rolled sheet. The second cold rolling can adjust the reduction ratio to 55-85%. When the reduction ratio is excessively small, the crystal grains in the {100}<001> and {100}<380> orientations may be formed less. When the reduction ratio is excessively high, after recrystallization, the <001> direction of the crystal grains rotates, and secondary recrystallization occurs in directions such as <250> and <120> that rotate further than <380>. More specifically, the reduction ratio may be 55-80%. More specifically, the reduction ratio may be 55-65%. The reduction ratio can be calculated by ([thickness of the steel sheet before rolling] - [thickness of the steel sheet after rolling]) / [thickness of the steel sheet before rolling]. After the stage of the second cold rolling, an annealing release agent can be applied for long-time annealing. The annealing release agent can contain alumina (Al2O3). Next, the second cold-rolled sheet is subjected to final annealing. The stage of final annealing can anneal for 6-60 hours. When the annealing time is excessively short, the crystal grains in the {100}<001> and {100}<380> orientations may not be properly formed. When the annealing time is excessively long, energy waste may occur. More specifically, the stage of final annealing can anneal for 12-48 hours. The stage of final annealing can be annealed in a reducing atmosphere. The stage of final annealing can be annealed at a temperature of 1000-1200 °C. If the annealing temperature is excessively low, recrystallization may not occur properly. Even if the annealing temperature is higher, it is difficult to improve the magnetism.

Example

[0019] Hereinafter, preferred examples and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples. Experimental Example 1 A slab composed of the components shown in Table 1 and the balance Fe and inevitable impurities was produced, heated at 1130 °C for 2 hours, and then hot-rolled to 2.5 mm. The hot-rolled sheet was heat-treated at 1070 °C for 2 minutes, pickled, and then subjected to first cold rolling. The final thickness was fixed at 0.2 mm, and experiments were conducted while varying the reduction rate of the second cold rolling from 40% to 80%. Therefore, during the first cold rolling, the final thicknesses were 2 mm (90%), 1 mm (80%), 0.67 mm (70%), 0.50 mm (60%), and 0.33 mm (40%), respectively. The specimens after the first rolling were heat-treated at 1050 °C for about 2 minutes. At this time, it was carried out in a 100% hydrogen atmosphere. The specimens were finally adjusted to a thickness of 0.2 mm through the second cold rolling. Each specimen was cut into a size of 60×60 mm for measuring magnetism with a single sheet tester (SST). The specimens with the adjusted size were heat-treated in a hydrogen atmosphere in a heating furnace adjusted to 1100 °C for 48 hours. The area fraction and grain size of the crystal grains having the {100}<001> and {100}<380> orientations in Table 1 were measured and arranged. The ODF results are shown in Fig. 1. It can be confirmed that when the reduction rate of the second cold rolling is 60 - 80%, a large number of crystal grains having the {100}<001> and {100}<380> orientations are formed. It can be confirmed that other directions having the {001} plane are widely spread in addition to 50% of the {100}<001> and {100}<380> orientations. Also, B8 and B50 were measured and arranged in Table 2.

[0020]

Table 1

Table 2

[0021] The present invention is not limited to the above-described embodiments, and can be manufactured in various different forms. Those having ordinary knowledge in the technical field to which the present invention pertains should be able to understand that other specific forms can be implemented without changing the technical idea and essential features of the present invention. Therefore, it should be understood that the embodiments described above are illustrative in all aspects and not restrictive.

Claims

1. By weight, Si: 1.0% to 7.0%, Al: 0.02% or less (excluding 0%), Mn: 0.02 to 0.50%, C: 0.004% or less (excluding 0%) and S: 0.0005 to 0.005%, and the balance consists of Fe and other inevitable impurities, a non-oriented electrical steel sheet characterized in that the fraction of crystal grains having an orientation within 15° from {100}<001> is 50 to 75%, and the fraction of crystal grains having an orientation within 15° from {100}<380> is 50 to 75%.

2. The non-oriented electrical steel sheet according to claim 1, characterized in that the fraction of crystal grains having an orientation within 10° from {100}<001> is 20 to 50%, and the fraction of crystal grains having an orientation within 10° from {100}<380> is 20 to 50%.

3. The non-oriented electrical steel sheet according to claim 1 or claim 2, characterized in that the average grain size of the crystal grains is 2000 μm or more.

4. The non-oriented electrical steel sheet according to any one of claims 1 to 3, characterized in that the deviation between the magnetic flux density (B50) in the rolling direction (L direction) and the magnetic flux density (B50) in the direction perpendicular to rolling (C direction) defined by the following formula 1 is 3 or less. [Formula 1] (In Formula 1, B Ｌ ５０ and B Ｃ ５０ are the magnetic flux densities (B50) in the rolling direction and the direction perpendicular to rolling, respectively, and MAX(B Ｌ ５０ , B Ｃ ５０ ) indicates the larger value of the magnetic flux densities (B50) in the rolling direction and the direction perpendicular to rolling.)

5. A method for manufacturing the non-oriented electrical steel sheet according to claim 1, comprising: hot rolling a slab to produce a hot-rolled sheet; performing primary cold rolling on the hot-rolled sheet to produce a primary cold-rolled sheet; intermediate annealing the primary cold-rolled sheet; performing secondary cold rolling on the intermediate annealed sheet to produce a secondary cold-rolled sheet; and finally annealing the secondary cold-rolled sheet, wherein the reduction ratio in the step of producing the secondary cold-rolled sheet is 55 to 85%, the final annealing step is performed for 6 to 60 hours, the slab contains, by weight, Si: 1.0% to 7.0%, Al: 0.02% or less (excluding 0%), Mn: 0.02 to 0.50%, C: 0.004% or less (excluding 0%) and S: 0.0005 to 0.005%, and the balance consists of Fe and other inevitable impurities, a method for manufacturing a non-oriented electrical steel sheet, characterized by not including decarburization annealing during the manufacturing process.

6. The method for manufacturing a non-oriented electrical steel sheet according to claim 5, further comprising a step of annealing the hot-rolled sheet after the step of producing the hot-rolled sheet.

7. The method for manufacturing a grain-oriented electrical steel sheet according to claim 5 or claim 6, wherein the step of manufacturing the primary cold-rolled sheet includes one cold rolling or two or more cold rollings with an intermediate annealing therebetween.

8. The method for manufacturing a grain-oriented electrical steel sheet according to any one of claims 5 to 7, characterized in that rolling is performed in the same direction in the step of manufacturing the primary cold-rolled sheet and the step of manufacturing the secondary cold-rolled sheet.

9. The method for manufacturing a grain-oriented electrical steel sheet according to any one of claims 5 to 8, characterized in that the step of intermediate annealing the primary cold-rolled sheet is annealing in a reducing atmosphere.

10. The method for manufacturing a grain-oriented electrical steel sheet according to any one of claims 5 to 9, further comprising a step of applying an annealing separator after the step of manufacturing the secondary cold-rolled sheet.

11. The method for manufacturing a grain-oriented electrical steel sheet according to any one of claims 5 to 10, characterized in that the final annealing step is annealing in a reducing atmosphere.

12. The method for manufacturing a grain-oriented electrical steel sheet according to any one of claims 5 to 11, characterized in that the final annealing step is annealing at a temperature of 1000 to 1200 °C.

Images