JP2020509153A - Grain-oriented electrical steel sheet and its manufacturing method - Google Patents

Abstract

The grain-oriented electrical steel sheet according to one embodiment of the present invention is, by weight%, Si: 1.0 to 7.0%, B: 0.001 to 0.1%, and Ba and Y each alone or in a combined amount. It is characterized by containing 0.005% by weight to 0.5% by weight, with the balance containing Fe and other unavoidable impurities. [Selection diagram] Fig. 1

Description

  The present invention relates to a grain-oriented electrical steel sheet and a method for producing the same, and more particularly, to a grain-oriented electrical steel sheet containing B, Ba, and Y in a certain amount and segregated at crystal grain boundaries, and a method for producing the same.

A grain-oriented electrical steel sheet is a soft magnetic material having excellent magnetic properties in the rolling direction, made of crystal grains having a crystal orientation of {110} <001>, also known as a Goss orientation.
In general, magnetic properties are expressed by magnetic flux density and iron loss, and high magnetic flux density can be obtained by accurately arranging crystal grains in the {110} <001> direction. An electromagnetic steel sheet having a high magnetic flux density not only can reduce the size of the iron core material of an electric device, but also can reduce the history loss and increase the efficiency as well as the size of the electric device. Iron loss is the power loss that is consumed as thermal energy when an arbitrary alternating magnetic field is applied to a steel sheet, and the magnetic flux density and thickness of the steel sheet, the amount of impurities in the steel sheet, the specific resistance, and the secondary recrystallization It changes greatly depending on the size of the grains and the like, and the higher the magnetic flux density and the specific resistance, and the lower the thickness and the amount of impurities in the steel plate, the lower the iron loss and the higher the efficiency of the electric equipment.

Currently, in order to deal with global warming by reducing the worldwide CO ₂ occurs, it tends to aim higher efficiency market with energy saving, high-efficiency electrical appliances to use less electrical energy As the demand for expansion and spread has increased, social demands for the development of grain-oriented electrical steel sheets having better low iron loss characteristics have increased.
In general, a grain-oriented electrical steel sheet having excellent magnetic properties must have a strong {110} <001> -oriented Goss texture in the rolling direction of the steel sheet. In this case, the crystal grains in the Goss orientation must form an abnormal crystal grain growth called secondary recrystallization. Such abnormal crystal growth is different from normal crystal growth, and the movement of normal crystal growth is normally caused by precipitates, inclusions, or solid solution or segregated elements at the crystal boundaries. Occurs when is suppressed. Such precipitates and inclusions that suppress the growth of crystal grains are particularly referred to as crystal growth inhibitors (inhibitors), and are studied on the manufacturing technology of grain-oriented electrical steel sheets by secondary recrystallization of {110} <001> orientation. Has focused on forming secondary recrystallization with a high degree of integration in the {110} <001> orientation using a strong grain growth inhibitor to ensure excellent magnetic properties.

In the existing grain-oriented electrical steel sheet technology, a precipitate such as AlN or MnS [Se] is mainly used as a grain growth inhibitor. As an example, an Al-based steel which exerts a strong crystal grain growth suppressing effect by supplying nitrogen to the inside of the steel sheet by a separate nitriding step using ammonia gas after performing one strong cold rolling and then decarburizing. There is a manufacturing method in which secondary recrystallization is caused by the nitride.
However, the instability of precipitates due to denitrification or denitrification in the furnace atmosphere during the high-temperature annealing process, and the necessity of long-time purification annealing for 30 hours or more at high temperatures is a complicated process. And costs.

For these reasons, recently, a method for producing a grain-oriented electrical steel sheet without using a precipitate such as AlN or MnS as a crystal grain growth inhibitor has been proposed. As an example, there is a manufacturing method using grain boundary segregation elements such as barium (Ba) and yttrium (Y).
Ba and Y have such an advantage that the formation of secondary recrystallized crystals is excellent in suppressing the growth of crystal grains so that they are not affected by the atmosphere in the furnace during the high-temperature annealing process. There are drawbacks. Therefore, there is a problem that a large number of grain boundary cracks are generated in a cold rolling process that requires a strong reduction, and a reduction in productivity cannot be avoided.

  An object of the present invention is to provide a grain-oriented electrical steel sheet and a method for manufacturing the same.

  The grain-oriented electrical steel sheet according to one embodiment of the present invention is, by weight%, Si: 1.0 to 7.0%, B: 0.001 to 0.1%, and Ba and Y each alone or in a combined amount. It is characterized by containing 0.005% by weight to 0.5% by weight, with the balance containing Fe and other unavoidable impurities.

The grain-oriented electrical steel sheet according to one embodiment of the present invention may satisfy Equation 1 below.
[Equation 1]
0.5 ≦ ([Ba] + [Y]) / ([B] * 10) ≦ 3
(However, in Formula 1, [Ba], [Y], and [B] indicate the contents (% by weight) of Ba, Y, and B, respectively.)
C: 0.005% or less (excluding 0%), Al: 0.005% or less (excluding 0%), N: 0.0055% or less (excluding 0%), and S: 0.0055% or less (Except 0%).

Mn: 0.01 to 0.5%.
The average grain size of the crystal grains having a grain size of 2 mm or more is preferably 10 mm or more.
B and Ba or Y segregated at the crystal grain boundary can be contained.

  The method for manufacturing a grain-oriented electrical steel sheet according to one embodiment of the present invention is as follows: Si is 1.0 to 7.0%, B is 0.001 to 0.1%, and Ba and Y are used alone or in weight%. A step of heating a slab containing Fe and other unavoidable impurities, a step of manufacturing a hot-rolled sheet by hot-rolling the slab, A cold-rolled sheet to produce a cold-rolled sheet, a step of subjecting the cold-rolled sheet to primary recrystallization annealing, and a step of subjecting the cold-rolled sheet after the primary recrystallization annealing to secondary recrystallization annealing. Characterized by

The slab can satisfy the following equation 1.
[Equation 1]
0.5 ≦ ([Ba] + [Y]) / ([B] * 10) ≦ 3
(However, in Formula 1, [Ba], [Y], and [B] indicate the contents (% by weight) of Ba, Y, and B, respectively.)
Slabs: C: 0.001 to 0.1%, Al: 0.01% or less (excluding 0%), N: 0.0055% or less (excluding 0%), and S: 0.0055% or less (Except 0%).

The slab may further include Mn: 0.01% to 0.5%.
In the step of heating the slab, the slab is preferably heated to 1000 to 1280 ° C.
It is preferable that the final rolling reduction is 80% or more at the stage of manufacturing the cold-rolled sheet by cold rolling the hot-rolled sheet.
The stage of secondary recrystallization annealing includes a heating stage and a soaking stage, and the temperature of the soaking stage may be 900 to 1250 ° C.

The grain-oriented electrical steel sheet according to one embodiment of the present invention has excellent magnetic properties by stably forming Goss crystal grains.
Further, since AlN and MnS are not used as a crystal grain growth inhibitor, it is not necessary to heat the slab to a high temperature of 1300 ° C. or higher.
Further, due to the effect of strengthening the grain boundaries, the occurrence of grain boundary cracks is reduced even under strong cold rolling, so that productivity is improved and manufacturing costs are reduced.

It is a photograph of the cold rolled steel sheet in the manufacturing process of the invention material of sample number 2. It is a photograph of the cold rolled steel plate in the manufacturing process of the comparative material of sample number 1.

Terms such as first, second and third are used to describe various parts, components, regions, layers and / or sections, but are not limited to these. 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 portion, component, region, layer or section described below is referred to as a second portion, component, region, layer or section without departing from the scope of the invention.
The terminology used herein is merely for referring to particular embodiments and is not intended to limit the invention. As used herein, the singular includes the plural unless the language clearly indicates the opposite. As used herein, the meaning of "comprising" embodies a particular property, region, integer, step, action, element and / or component; other properties, area, integer, step, action, element and / or It does not exclude the presence or addition of components.

When referring to one part being “on” another, this may be directly on the other part, or may be accompanied by other parts in between. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements in between.
Unless defined otherwise, 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 additionally to be interpreted as having a meaning consistent with the relevant technical literature and the presently disclosed content, and are not to be interpreted in an ideal or very formal sense unless defined.
Unless otherwise specified,% means% by weight, and 1 ppm means 0.0001% by weight.

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 belongs can be easily implemented. However, the invention can be implemented in various different forms and is not limited to the embodiments described here.
In the existing grain-oriented electrical steel sheet technology, precipitates such as AlN and MnS are used as a grain growth inhibitor, and in all processes, the distribution of the precipitates is strictly controlled and secondary recrystallization is performed. The process conditions were extremely limited by the conditions for removing precipitates remaining in the steel sheet.
On the other hand, in one embodiment of the present invention, a precipitate such as AlN or MnS is not used as a grain growth inhibitor. In one embodiment of the present invention, by using B, Ba or Y as a crystal grain growth inhibitor, the fraction of Goss crystal grains can be increased, and an electrical steel sheet excellent in magnetism can be obtained.

The grain-oriented electrical steel sheet according to an embodiment of the present invention is, as a percentage by weight, Si: 1.0 to 7.0%, Mn: 0.01% to 0.5%, B: 0.001 to 0.1%. Ba and Y are contained individually or in a total amount of 0.005% by weight to 0.5% by weight, and the balance contains Fe and other unavoidable impurities.
Hereinafter, each component will be described specifically.

  In one embodiment of the present invention, barium (Ba) and yttrium (Y) act as a crystal grain growth inhibitor, and during secondary recrystallization annealing, crystal grains having a direction other than Goss crystal grains grow. And improve the magnetism of the magnetic steel sheet. Ba and Y may be added alone or in combination. Ba and Y may be contained individually or in a total amount of 0.005% by weight to 0.5% by weight. That is, when Ba or Y is added alone, respectively, the content of Ba or Y may be 0.005% by weight to 0.5% by weight, and when Ba and Y are added simultaneously, And the total content of Y (i.e., the total amount) may be 0.005% by weight to 0.5% by weight. If Ba or Y or its combined amount is too small, it is difficult to exert sufficient suppressing power, and if Ba or Y or its combined amount is too large, the brittleness of the steel sheet increases and cracks may occur during rolling. .

Boron (B, boron) segregates at the grain boundaries and strengthens the grain boundary bonding force, and thus plays a role in reducing the occurrence of cracks during rolling and the number of times of rolling. In addition, BN reacts with nitrogen in steel to partially form BN precipitates. BN is excellent in high-temperature stability and can act as an auxiliary inhibitor that suppresses crystal grain growth together with Ba and Y described above. is there. The content of B may be 0.001 to 0.1% by weight. If B is contained in an excessively small amount, it may be insufficient to reduce grain boundary brittleness due to Ba and Y. When B is excessively contained, segregation of grain boundaries of Ba and Y is suppressed, and a large number of inclusions are formed during the high-temperature annealing process, so that magnetic properties may be deteriorated.
B can satisfy the following expression 1 in relation to Ba and Y.
[Equation 1]
0.5 ≦ ([Ba] + [Y]) / ([B] * 10) ≦ 3
(However, in Formula 1, [Ba], [Y], and [B] indicate the contents (% by weight) of Ba, Y, and B, respectively.)
When the value of Equation 1 is less than 0.5, segregation of grain boundaries of Ba and Y is suppressed, and a large number of inclusions are formed during the high-temperature annealing process, so that magnetic properties may be deteriorated. If the value of Equation 1 exceeds 3, it may be insufficient to alleviate grain boundary brittleness due to Ba and Y.

Silicon (Si) plays a role in increasing the specific resistance of the material and reducing iron loss. When the Si content in the slab and the magnetic steel sheet is less than 1.0% by weight, the specific resistance decreases and the iron loss characteristics may decrease. Conversely, if the Si content in the grain-oriented electrical steel sheet exceeds 7% by weight, it is difficult to process the transformer during the manufacture of the transformer. Therefore, the Si content in the grain-oriented electrical steel sheet is preferably 7% by weight or less.
Carbon (C) is an austenite stabilizing element, and is added to a slab in an amount of 0.001% by weight or more to reduce a coarse columnar structure generated in a continuous casting process and suppress slab center segregation of S. Can be. Further, it is possible to promote the work hardening of the steel sheet during the cold rolling, thereby promoting the nucleation of secondary recrystallization of {110} <001> orientation in the steel sheet. However, if it exceeds 0.1%, edge-cracks may occur during hot rolling. However, the carbon steel sheet is subjected to decarburization annealing during the production of the magnetic steel sheet, and the C content in the final magnetic steel sheet after the decarburization annealing is preferably 0.005% by weight or less. More specifically, the content is 0.003% by weight or less.

In one embodiment of the present invention, since a precipitate such as AlN or MnS is not used as a grain growth inhibitor, aluminum (Al), nitrogen (N), sulfur (S) and the like are indispensable for general grain-oriented electrical steel sheets. The element used as is controlled in the impurity range. That is, when unavoidably further containing Al, N, S, etc., it may further contain 0.005% by weight or less of Al, 0.0055% by weight or less of S, and 0.0055% by weight or less of N.
In one embodiment of the present invention, since AlN does not need to be used as a crystal grain growth inhibitor, the aluminum (Al) content can be positively suppressed. Therefore, in one embodiment of the present invention, Al may not be added to the grain-oriented electrical steel sheet, or may be controlled to 0.005% by weight or less. In the slab, since Al is removed during the manufacturing process, Al can be contained at 0.01% by weight or less.

Since nitrogen (N) forms precipitates such as AlN, (Al, Mn) N, (Al, Si, Mn) N, Si3N4, and BN, N is not added in one embodiment of the present invention. , 0.0055% by weight or less. More specifically, it may be 0.0030% by weight or less. In one embodiment of the present invention, since the nitriding step can be omitted, the N content in the slab and the N content in the final magnetic steel sheet can be substantially the same.
Sulfur (S) is an element having a high solid solution temperature and severe segregation during hot rolling. Therefore, in one embodiment of the present invention, sulfur (S) is not added or can be controlled to 0.0055% by weight or less. . More specifically, it may be 0.0035% by weight or less.

In one embodiment of the present invention, manganese (Mn) does not have to be added because MnS is not used as a grain growth inhibitor. However, since Mn is a specific resistance element and has an effect of improving magnetism, it may be additionally contained as an optional component in the slab and the magnetic steel sheet. When Mn is additionally contained, the content of Mn may be 0.01% by weight or more. However, when the content exceeds 0.5% by weight, phase transformation may occur after the secondary recrystallization and magnetism may be deteriorated. In one embodiment of the present invention, when an additional element is further included, it is understood that iron (Fe) is added instead of the remaining iron.
In addition, as other unavoidable impurities, components such as Ti, Mg, and Ca react with oxygen in steel to form oxides, which interfere with the magnetic domain movement of the final product as inclusions, thereby causing magnetic deterioration. It may be a cause, so it is necessary to suppress it strongly. Therefore, when these are inevitably contained, they can be controlled at 0.005% by weight or less for each component.

In the grain-oriented electrical steel sheet according to one embodiment of the present invention, the average grain size of crystal grains having a grain size of 2 mm or more is 10 mm or more. When the average grain size of the crystal grains having a grain diameter of 2 mm or more is less than 10 mm, the crystal grains may not grow sufficiently and the magnetism may be reduced. In one embodiment of the present invention, the grain size of a crystal grain means the length of the diameter of the crystal grain corresponding to a circle.
The grain-oriented electrical steel sheet according to one embodiment of the present invention has excellent magnetic properties by stably forming Goss crystal grains. Specifically, the grain-oriented electrical steel sheet according to one embodiment of the present invention may have a magnetic flux density B8 measured at a magnetic field of 800 A / m of 1.88 T or more.

  The method for manufacturing a grain-oriented electrical steel sheet according to one embodiment of the present invention is as follows: Si is 1.0 to 7.0%, B is 0.001 to 0.1%, and Ba and Y are used alone or in weight%. A step of heating a slab containing Fe and other unavoidable impurities, a step of manufacturing a hot-rolled sheet by hot-rolling the slab, A cold-rolled sheet to produce a cold-rolled sheet, a step of subjecting the cold-rolled sheet to primary recrystallization annealing, and a step of subjecting the cold-rolled sheet after the primary recrystallization annealing to secondary recrystallization annealing. .

Hereinafter, a method for manufacturing a grain-oriented electrical steel sheet will be specifically described for each step.
First, the slab is heated.
The composition of the slab has been specifically described in relation to the composition of the magnetic steel sheet, and therefore, redundant description will be omitted.
The heating temperature of the slab is not limited, but when the slab is heated to a temperature of 1280 ° C. or less, the columnar crystal structure of the slab is prevented from growing coarsely, and the plate is prevented from cracking in the hot rolling process. can do. Therefore, the heating temperature of the slab may be between 1000C and 1280C. In particular, in one embodiment of the present invention, since AlN and MnS are not used as a grain growth inhibitor, it is not necessary to heat the slab to a high temperature of 1300 ° C. or higher.

Next, the slab is hot-rolled to produce a hot-rolled sheet. The hot rolling temperature is not limited, and the hot rolling can be completed at 950 ° C. or less as an example. Thereafter, the film can be cooled with water and wound at 600 ° C. or less.
Next, if necessary, the hot rolled sheet can be subjected to hot rolled sheet annealing. When performing hot-rolled sheet annealing, in order to make the hot-rolled structure uniform, the sheet can be heated to a temperature of 900 ° C. or higher, soaked and then cooled.
Next, the hot-rolled sheet is cold-rolled to produce a cold-rolled sheet. The cold rolling is performed by using a reverse rolling mill or a tandem rolling mill, and using a single cold rolling, a plurality of cold rollings, or a plurality of cold rolling processes including intermediate annealing. A cold rolled sheet having a thickness of 0.1 mm to 0.5 mm can be manufactured.
Further, it is possible to perform warm rolling in which the temperature of the steel sheet is maintained at 100 ° C. or higher during cold rolling.

Furthermore, the final draft by cold rolling may be 80% or more. In one embodiment of the present invention, as described above, by including B in the slab component in a specific content, segregation at the grain boundaries and strengthening of the grain boundary bonding force, the occurrence of cracks during rolling and the number of rolling times Can be reduced, and the final draft can be increased.
Next, the cold rolled cold rolled sheet is subjected to primary recrystallization annealing. In the primary recrystallization annealing step, primary recrystallization occurs in which nuclei of Goss crystal grains are generated. Decarburization of the cold rolled sheet is performed in the primary recrystallization annealing stage. For decarburization, annealing can be performed at a temperature of 800C to 900C. The atmosphere may be a mixed gas atmosphere of hydrogen and nitrogen. Further, when the decarburization is completed, the carbon content in the cold rolled sheet may be 0.005% by weight or less. In one embodiment of the present invention, since the AlN grain growth inhibitor is not used, the nitriding step can be omitted.

Next, the cold rolled sheet on which primary recrystallization annealing has been completed is subjected to secondary recrystallization annealing. At this time, after applying the annealing separating agent to the cold-rolled sheet on which the primary recrystallization annealing has been completed, secondary recrystallization annealing can be performed. At this time, the annealing separator is not particularly limited, and an annealing separator containing MgO as a main component can be used.
The stage of the secondary recrystallization annealing includes a heating stage and a soaking stage. The temperature raising step is a step of raising the temperature of the cold-rolled sheet after the first recrystallization annealing to the temperature in the soaking stage. The temperature in the soaking stage may be between 900C and 1250C. If the temperature is lower than 900 ° C., the Goss crystal grains do not grow sufficiently and the magnetism decreases. If the temperature exceeds 1250 ° C., the crystal grains grow coarsely and the properties of the magnetic steel sheet may deteriorate. The heating step is performed in a mixed gas atmosphere of hydrogen and nitrogen, and the soaking step is performed in a hydrogen atmosphere.

In the method for manufacturing a grain-oriented electrical steel sheet according to one embodiment of the present invention, since the grain growth inhibitor of AlN and MnS is not used, the purification annealing step can be omitted after the secondary recrystallization annealing is completed. In the conventional method for producing a grain-oriented electrical steel sheet using MnS and AlN as a grain growth inhibitor, high-temperature purification annealing for removing precipitates such as AlN and MnS was required. The method for manufacturing a grain-oriented electrical steel sheet according to one embodiment does not require a purification annealing step.
Thereafter, if necessary, an insulating film can be formed on the surface of the grain-oriented electrical steel sheet, or a magnetic domain refining process can be performed. In one embodiment of the present invention, the alloy component of the grain-oriented electrical steel sheet means a base steel sheet excluding a coating layer such as an insulating coating.
Hereinafter, the present invention will be described in more detail through examples. However, such an example is only for illustrating the present invention, and the present invention is not limited thereto.

Example 1
Containing, by weight%, 3.2% Si, 0.05% C, 0.06% Mn, 0.0048% S, 0.0032% N, and 0.005% Al; A slab containing barium (Ba), yttrium (Y), and boron (B) as shown in Table 1 below, and the balance being Fe and other impurities unavoidably mixed therein was prepared.
The slab was heated to a temperature of 1150 ° C. for 90 minutes and then hot-rolled to produce a hot-rolled sheet having a thickness of 2.6 mm. After heating this hot rolled sheet to a temperature of 1050 ° C. or higher, it was maintained at 910 ° C. for 90 seconds, cooled with water, and then pickled. Next, using a reverse (Reverse) rolling mill, cold rolling was performed to a thickness of 0.30 mm through a total of seven passes. The rolling reduction for each pass was the same for each test condition. After the temperature of the cold-rolled steel sheet is raised in a furnace, the carbon concentration is 0.002 weight by maintaining the mixed gas atmosphere of 50% by volume of hydrogen and 50% by volume of nitrogen and the annealing temperature of 850 ° C. for 120 seconds. % And primary recrystallization annealing together with decarburization. Then, after applying MgO, it was wound into a coil and subjected to secondary recrystallization annealing. In the secondary recrystallization annealing, the temperature is raised to 1200 ° C. in a mixed gas atmosphere of nitrogen: 25% by volume and hydrogen: 75% by volume, and after reaching 1200 ° C., maintained in a gas atmosphere of hydrogen: 100% by volume for 20 hours. Cooled down.

After the surface of the finally obtained steel sheet was cleaned, the magnetic flux density was measured under the condition of a magnetic field intensity of 800 A / m using a single sheet measurement method.

As can be seen from Table 1, when the content of B is controlled within the range of the present invention in accordance with the content of Ba and Y, there is no occurrence of rolling cracks and excellent magnetism as compared with the comparative material. I got it.
1 and 2 show photographs of the cold-rolled steel sheet during the manufacturing process of the inventive material of sample No. 2 and photographs of the cold-rolled steel plate during the manufacturing process of the comparative material of sample No. 1. In the case of the comparative material, it can be confirmed that rolling cracks clearly appear.

Example 2
% By weight, containing 3.2% of Si, 0.048% of C, 0.11% of Mn, 0.0051% of S, 0.0028% of N, and 0.008% of Al; A slab was prepared containing barium (Ba), yttrium (Y), and boron (B) as shown in Table 2 below, and the balance was Fe and other impurities unavoidably mixed.
The slab was heated to a temperature of 1150 ° C. for 90 minutes and then hot-rolled to produce a hot-rolled sheet having a thickness of 2.6 mm. After heating this hot rolled sheet to a temperature of 1050 ° C. or higher, it was maintained at 910 ° C. for 90 seconds, cooled with water, and then pickled. Next, using a reverse (Reverse) rolling mill, cold rolling was performed to a thickness of 0.30 mm through a total of seven passes. The rolling reduction for each pass was the same for each test condition. After the temperature of the cold-rolled steel sheet is raised in a furnace, the carbon concentration is 0.003 weight by maintaining the mixed gas atmosphere of 50% by volume of hydrogen and 50% by volume of nitrogen and the annealing temperature of 850 ° C. for 120 seconds. % And primary recrystallization annealing together with decarburization. Then, after applying MgO, it was wound into a coil and subjected to secondary recrystallization annealing. In the secondary recrystallization annealing, the temperature is raised to 1200 ° C. in a mixed gas atmosphere of nitrogen: 25% by volume and hydrogen: 75% by volume, and after reaching 1200 ° C., maintained in a gas atmosphere of hydrogen: 100% by volume for 20 hours. Cooled down.

After the surface of the finally obtained steel sheet was cleaned, the magnetic flux density was measured under the condition of a magnetic field intensity of 800 A / m using a single sheet measurement method. The grain size of the crystal grains was calculated by averaging according to the area after immersion in hydrochloric acid heated to 60 ° C. for 5 minutes to remove the surface coating layer.
Referring to Table 2, in the magnetic steel sheet according to one embodiment of the present invention, the average grain size of the crystal grains having a grain size of 2 mm or more was 10 mm or more, and it was clear that the magnetism was excellent.

  The present invention is not limited to the embodiments described above, but can be manufactured in various forms different from each other, and those having ordinary knowledge in the technical field to which the present invention pertains need to understand the technical ideas and the present invention. It will be appreciated that the invention may be embodied in other specific forms without altering the essential characteristics. Therefore, it should be understood that the above-described embodiments are illustrative in every aspect and not restrictive.

Next, the slab is hot-rolled to produce a hot-rolled sheet. The hot rolling temperature is not limited, and the hot rolling can be completed at 950 ° C. or less as an example. Thereafter, the film can be cooled with water and wound at 600 ° C. or less.
Next, if necessary, the hot rolled sheet can be subjected to hot rolled sheet annealing. When performing hot-rolled sheet annealing, in order to make the hot-rolled structure uniform, the sheet can be heated to a temperature of 900 ° C. or higher, soaked and then cooled.
Next, the hot-rolled sheet is cold-rolled to produce a cold-rolled sheet. Cold rolling, using a reverse (Reverse) mill or a tandem (Tandem) rolling mill, one of the cold rolling, a plurality of times of cold rolling, or multiple cold rolling method including intermediate annealing 0 A cold rolled sheet having a thickness of 0.1 mm to 0.5 mm can be manufactured.
Further, it is possible to perform warm rolling in which the temperature of the steel sheet is maintained at 100 ° C. or higher during cold rolling.

Claims (13)

  % By weight, Si: 1.0 to 7.0%, B: 0.001 to 0.1%, and Ba and Y each alone or in an amount of 0.005 to 0.5% by weight, The balance is a grain-oriented electrical steel sheet containing Fe and other unavoidable impurities. The grain-oriented electrical steel sheet according to claim 1, which satisfies the following expression 1.
[Equation 1]
0.5 ≦ ([Ba] + [Y]) / ([B] * 10) ≦ 3
(However, in Formula 1, [Ba], [Y], and [B] indicate the contents (% by weight) of Ba, Y, and B, respectively.)   C: 0.005% or less (excluding 0%), Al: 0.005% or less (excluding 0%), N: 0.0055% or less (excluding 0%), and S: 0.0055% or less The grain-oriented electrical steel sheet according to claim 1, further comprising (excluding 0%).   The grain-oriented electrical steel sheet according to claim 1, further comprising Mn: 0.01% to 0.5%.   The grain-oriented electrical steel sheet according to claim 1, wherein the average grain size of the crystal grains having a grain size of 2 mm or more is 10 mm or more.   2. The grain-oriented electrical steel sheet according to claim 1, comprising B segregated at crystal grain boundaries and Ba or Y. 3. % By weight, Si: 1.0 to 7.0%, B: 0.001 to 0.1%, and Ba and Y each alone or in an amount of 0.005 to 0.5% by weight, Heating the slab containing Fe and other unavoidable impurities,
Hot rolling the slab to produce a hot rolled sheet,
Cold rolling the hot rolled sheet to produce a cold rolled sheet,
First recrystallization annealing the cold rolled sheet; and
Performing a secondary recrystallization annealing of the cold rolled sheet after the first recrystallization annealing is completed. The method for manufacturing a grain-oriented electrical steel sheet according to claim 7, wherein the slab satisfies Equation 1 below.
[Equation 1]
0.5 ≦ ([Ba] + [Y]) / ([B] * 10) ≦ 3
(However, in Formula 1, [Ba], [Y], and [B] indicate the contents (% by weight) of Ba, Y, and B, respectively.)   The slab contains C: 0.001 to 0.1%, Al: 0.01% or less (excluding 0%), N: 0.0055% or less (excluding 0%), and S: 0.0055% The method for producing a grain-oriented electrical steel sheet according to claim 7, further comprising the following (excluding 0%):   The method of claim 7, wherein the slab further includes Mn: 0.01% to 0.5%.   The method for producing a grain-oriented electrical steel sheet according to claim 7, wherein the slab is heated to 1000 to 1280 ° C. in the heating step.   The method of manufacturing a grain-oriented electrical steel sheet according to claim 7, wherein a final draft is 80% or more at a stage of manufacturing the cold-rolled sheet by cold-rolling the hot-rolled sheet.   8. The method of claim 7, wherein the step of performing the secondary recrystallization annealing includes a temperature raising step and a soaking step, and the temperature of the soaking step is 900 to 1250 ° C. 9.