JP5037796B2 - Method for producing grain-oriented electrical steel sheet - Google Patents

Description

The present invention relates to a method of manufacturing a square oriented electrical steel sheet, it is intended to inexpensively obtain particularly superior grain-oriented electrical steel sheet of the magnetic properties.

  A grain-oriented electrical steel sheet is a material suitable as a material for an iron core used in a transformer or the like. In recent years, in order to save energy, grain oriented electrical steel sheets are required to have a low iron loss at a commercial frequency and a high magnetic flux density in a low excitation field. Therefore, further improvement of magnetic properties is required to meet such demands.

  A grain-oriented electrical steel sheet has a crystal structure in which the <001> orientation, which is the easy axis of iron, is highly aligned with the rolling direction of the steel sheet. Such a texture is formed through secondary recrystallization, which preferentially grows crystal grains with a (110) [001] orientation, so-called Goss orientation, during finish annealing during the production process of grain-oriented electrical steel sheets. It is formed. Therefore, the crystal orientation of the secondary recrystallized grains has a great influence on the magnetic properties.

  Conventionally, such grain-oriented electrical steel sheets are hot-rolled after heating a slab containing about 4.5 mass% or less of Si and an inhibitor component such as MnS, MnSe, or AlN to 1300 ° C or higher. After carrying out hot-rolled sheet annealing, the final sheet thickness is obtained by cold rolling at least once with one or intermediate annealing, followed by primary recrystallization annealing in a wet hydrogen atmosphere, so that primary recrystallization and It has been manufactured by decarburizing and then applying an annealing separator mainly composed of magnesia, followed by final finishing annealing at 1200 ° C for about 5 hours for secondary recrystallization and purification of inhibitor components. . For example, the technology is disclosed in Patent Literature 1, Patent Literature 2, Patent Literature 3, and the like.

  However, in order to carry out such a technique accurately, special equipment suitable for the production process of grain-oriented electrical steel sheets is necessary and the process is complicated. As a result, the manufacturing cost of the grain-oriented electrical steel sheet has been extremely high.

On the other hand, as a method for improving magnetic properties, a method for controlling the form of C in steel by controlling the cooling process after annealing before the final cold rolling has been reported. For example, Patent Document 4 discloses a technique for increasing the solid solution C after cooling by cooling from 600 ° C. to 300 ° C. at a rate of 150 ° C./min or higher in cooling after annealing.
Patent Document 5 discloses that after annealing, it is rapidly cooled to 300 ° C. and gradually cooled between 300 to 150 ° C., or rapidly cooled to 100 ° C. and subjected to a short-term aging treatment in the temperature range of 300 to 150 ° C. , A technique for precipitating fine carbides of 100 to 500 kg is disclosed.

  The various methods described above are considered to apply the technical idea of fixing a solid solution C or the like to a defect portion such as dislocation introduced during cold rolling to form a so-called Cottrell atmosphere. Such an effect is well known as a technique for increasing the (110) strength in the texture after recrystallization in the annealing after cold rolling even in general steel. Since the (110) structure serves as a good nucleus for secondary recrystallization, the magnetic properties are improved as a result. Therefore, in grain-oriented electrical steel sheets, texture improvement during recrystallization annealing is an extremely important factor.

  However, in order to carry out the technology using solute C and fine carbides, after annealing, rapid cooling treatment, aging treatment between passes in the cold rolling process, or warm rolling that passes the plate at 200 ° C. or higher, intermediate annealing In addition, processes such as aging treatment and the like are necessary, which again complicates the process and introduces special equipment. Moreover, the steel plate hardened | cured and deform | transformed by carrying out rapid cooling after annealing, and the problem that it became difficult to pass was also seen.

US Patent No. 1965559 Japanese Patent Publication No. 40-15611 Japanese Patent Publication No.51-13469 Japanese Patent Publication No.56-3892 JP 58-1557917 A

As described above, in the grain-oriented electrical steel sheet, in order to improve the magnetic properties by using C in the steel, it is necessary to cause solid solution C to remain in the grains by rapid cooling or to finely precipitate as carbide. In addition, these techniques are effective in combination with appropriate rolling conditions and an aging treatment, so that the process is complicated and the manufacturing cost is high.
Therefore, in order to sufficiently meet the recent demand for high-performance materials with low cost and easy manufacturing, a method for improving the texture that does not depend on solute C or fine carbide is required.

  An object of the present invention is to solve the above-mentioned problems advantageously and to propose an advantageous method for producing a grain-oriented electrical steel sheet capable of obtaining excellent magnetic properties at low cost.

The elucidation process of the present invention will be described below.
Now, as a result of diligent research focusing on the form of carbide (carbide) that precipitates after annealing before cold rolling, the inventors found that when the final sheet thickness is obtained by one cold rolling, On the other hand, it was found that it is effective in improving the texture to precipitate a suitable amount of coarse carbides of 2 μm or more in crystal grains before cold rolling.

FIG. 1 shows the results of investigating the influence of the grain size of carbides precipitated after annealing before cold rolling and the frequency of their presence on the texture of a single cold rolled / recrystallized plate.
As can be seen from the figure, the texture is improved by the presence of coarse carbide having a particle size of 2 μm or more to some extent.

In addition, the quality of the texture in the above experiment is evaluated by the (211) inverse strength at the center of the plate thickness, and (211) the case where the inverse strength is 1.1 or less is good, than 1.1 When it was high, it was regarded as defective.
This is because a total of six crystal planes (211), (110), (200), (222), (321), and (411) at the center of the thickness of the primary recrystallized plate after one cold rolling. As a result of measuring the inverse strength of each and correlating each value with the magnetic properties (magnetic flux density) in the final product plate, it has been conventionally known that it functions as a good nucleus for secondary recrystallization (110 This is because (211) inverse strength was more strongly correlated with magnetic characteristics than inverse strength.

FIG. 2 shows the results of examining the relationship between (211) inverse strength and magnetic flux density B ₈ of the final product plate for two types of steel plates A and B having different compositions.
As is clear from the figure, both the steel plates A and B have a good magnetic flux density B ₈ when the (211) inverse strength is 1.1 or less.

Carbide is observed with a scanning electron microscope, and the observation field of view is a cross section in the direction perpendicular to the rolling from the central part in the coil width direction, and a range of 100 μm vertically from the center of the plate thickness and 5 mm in the width direction are observed. The existence frequency of coarse carbides of 1 μm or more was determined.
In general, when carbide is gradually cooled from 600 ° C. or lower, carbide precipitates at a grain boundary at a high temperature, and precipitates in the crystal grain at a lower temperature. At this time, it is known that acicular coarse grains precipitate by holding for a long time even at relatively high or low temperatures (WCLeslie, RLRickett, CP Stroble, and G. Konoval; Trans-ASM, 1961, Vol. .53, P.715, Fig.12).

As a result, as described above, the magnetic characteristics are improved by depositing 50 μm / mm ² or more of needle-shaped or plate-shaped carbide of 2 μm or more within the range of 100 μm above and below the center of the thickness in the cross section perpendicular to the rolling direction. It was confirmed that

Then, next, the means for depositing an appropriate amount of such coarse carbides was examined.
As a result, in order to obtain a coarse carbide of 2 μm or more necessary for texture improvement in the annealing cooling process, it is necessary to slowly cool the temperature range of 550 to 300 ° C., that is, to stay in the temperature range for at least 45 seconds or more. Turned out to be.

FIG. 3 is a photomicrograph showing the state of precipitation of carbides when retained for 10 seconds, 30 seconds and 45 seconds in a temperature range of 550 to 300 ° C.
As shown in the figure, it can be seen that when the residence time in the temperature range of 550 to 300 ° C. is 45 seconds, needle-like carbides are clearly formed.
FIG. 4 shows a micrograph showing the precipitation of carbides when another sample was retained in the temperature range of 550 to 300 ° C. for 10 seconds, 30 seconds and 45 seconds. When the residence time in the temperature range is 45 seconds, plate-like carbide is clearly precipitated.

By the way, it is conceivable that needle-like or plate-like carbides can be obtained by subjecting the steel sheet after hot-rolled sheet annealing cooled to room temperature to heat treatment.
Thus, when the steel sheet after hot-rolled sheet cooling cooled to room temperature was subjected to heat treatment at 100 ° C., 200 ° C., and 300 ° C. for 1 hour, respectively, as shown in FIG. It was confirmed that when the heat treatment was carried out for a long time, a needle-like or plate-like coarse carbide having a particle size of 2 μm or more was obtained.

  The present invention has been developed as a result of sincerity of application on an industrial scale based on the above knowledge.

That is, the gist configuration of the present invention is as follows.
(1) Hot rolled steel sheet slab containing mass%, C containing 0.01% or more and 0.10% or less, Si containing 2.0% or more and 4.5% or less, balance Fe and inevitable impurities, and hot-rolled sheet annealing After that, the rolling reduction ratio is set to a final sheet thickness by one cold rolling of 80% or more, followed by a primary recrystallization annealing, followed by an annealing separator and then a secondary recrystallization annealing. In the manufacturing method of grain-oriented electrical steel sheet,
Adjust the residence time to stay in the temperature range of 550 to 300 ° C during cooling after the hot-rolled sheet annealing, or cool to room temperature after the hot-rolled sheet annealing, and then the temperature range from 200 ° C to 550 ° C. in adjusting the heat treatment time of heat treatment, the steel sheet before the cold rolled, needle-like or plate-like carbides 2μm or more seen in the direction perpendicular to the rolling direction cross-section of the steel plate, the thickness of the perpendicular to the rolling direction cross-section A method for producing a grain-oriented electrical steel sheet, wherein at least 50 pieces / mm ² are present within a range of 100 μm above and below the center.

(2) pre-Symbol residence time in the temperature range of 550 to 300 ° C. is above, wherein at least 45 seconds der Rukoto (1) The method of producing oriented electrical steel sheet according.

(3) heat treatment time in the temperature range of the previous SL 200 ° C. or higher 550 ° C. or less, the production method of the grain-oriented electrical steel sheet of the above (1), wherein the at least 30 seconds.
(4) In the electromagnetic steel material slab, Al: 0.010 to 0.080%, N: 0.005 to 0.015%, Mn: 0.02 to 1.0%, Se: 0.001 to 0.05% and S: 0.001 to 0.05%. The method for producing a grain-oriented electrical steel sheet according to any one of the above (1) to (3), comprising one or more selected from among them.
(5) In addition to B, Bi, Sb, Mo, Te, Sn, P, Ge, As, Nb, Cr, Ti, Cu, Pb, Zn, and In, in addition to the electromagnetic steel material slab. 1 or 2 types or more are contained 0.0005-1.0%, respectively, The manufacturing method of the grain-oriented electrical steel sheet in any one of said (1)-(4) characterized by the above-mentioned.

  According to the present invention, the production of grain-oriented electrical steel sheets does not require a rapid cooling process in the annealing before cold rolling or a special apparatus in rolling, and the texture of the texture is formed by only one cold rolling and recrystallization annealing. As a result, a grain-oriented electrical steel sheet having excellent magnetic properties can be obtained inexpensively and easily.

Hereinafter, the present invention will be specifically described. Unless otherwise specified, “%” in relation to ingredients means mass%.
The slab of the present invention is produced by a known method such as a steelmaking-continuous casting method or an ingot-bundling rolling method. At that time, the slab composition is limited as follows.
C: 0.01% or more and 0.10% or less C is an element useful for improving the primary recrystallization texture, and is also necessary for developing coarse carbides. However, if the content is less than 0.01%, the amount of carbide is too small to achieve the effect of improving the texture. On the other hand, if it exceeds 0.10%, decarburization by the product plate becomes extremely difficult, and magnetic aging due to residual C occurs. Therefore, the C content is limited to a range of 0.01% to 0.10%.

Si: 2.0% to 4.5%
Si is a useful element that improves iron loss by increasing electrical resistance. However, if the content is less than 2.0%, the effect of addition is poor, while if it exceeds 4.5%, cold rolling becomes extremely difficult. , Si was limited to the range of 2.0% to 4.5%.

In addition to the above-mentioned elements, Al, N, Mn, Se, etc. are contained in the steel as Al: 0.010-0.080%, N: 0.005-0.015%, Mn: 0.02-1.0%. , Se and / or S: About 0.001 to 0.05% can be contained. In addition, inhibitor-forming elements such as B, Bi, Sb, Mo, Te, Sn, P, Ge, As, Nb, Cr, Ti, Cu, Pb, Zn, and In, each of about 5 ppm to 1.0%, each alone or in combination. Can be contained as appropriate.
Furthermore, the present invention can also be applied to grain-oriented electrical steel sheets that are produced without using an inhibitor, as disclosed in JP-A-2000-129356.

  The slab is subjected to hot rolling after slab heating. Slab heating requires different temperatures depending on the slab components. Usually, in steel types using inhibitors such as AlN, MnS and MnSe, it is necessary to completely dissolve the inhibitor component during slab heating. Therefore, it is desirable to heat these steel types at a high temperature of 1350 ° C. or higher. On the other hand, when using a technique (inhibitorless method) in which secondary recrystallization is performed without containing an inhibitor component, it is preferable to set the temperature to about 1050 ° C. to 1250 ° C. High-temperature slab heating above 1250 ° C is not necessary for steel types that do not contain an inhibitor component in the slab, while slabs cannot be smoothly rolled below 1050 ° C.

Next, hot-rolled sheet annealing is performed on the hot-rolled steel sheet. During this cooling, the temperature range of 550 to 300 ° C. is slowly cooled, that is, stays in this temperature range for 45 seconds or more to precipitate needle-like or plate-like carbides of 2 μm or more.
Here, as shown in FIG. 3, the acicular carbide refers to a carbide that is one-dimensionally coarsened, and the plate-like carbide is two-dimensionally coarsened as shown in FIG. It shall refer to carbide.

With regard to carbide precipitation in the cooling process after hot-rolled sheet annealing, it is possible to obtain needle-like carbides at temperatures below 600 ° C, but at temperatures exceeding 550 ° C, precipitation at grain boundaries also proceeds, and crystal grains As a result, the amount of coarse carbide decreases, and the effect of improving the texture cannot be obtained. On the other hand, even if the temperature is lower than 300 ° C., needle-like carbides are produced, but the time required for coarsening becomes too long, so that the process becomes difficult.
Therefore, a temperature range of 550 to 300 ° C. was determined as a temperature range where gentle cooling should be performed. The residence time needs at least 45 seconds, but if the residence time is too long, productivity is hindered, so the upper limit of the residence time is preferably about 100 seconds.

In addition, when the slow cooling cannot be performed in the cooling process, the carbide can be coarsened to 2 μm or more by performing a heat treatment in a temperature range of 200 ° C. or more and 550 ° C. or less. If the heat treatment temperature is less than 200 ° C. and more than 600 ° C., acicular carbide cannot be obtained, and in the temperature range of more than 550 ° C. and less than 600 ° C., as described above, precipitation at grain boundaries also proceeds, so The C concentration in the grains decreases, the amount of coarse carbides decreases, and the effect of improving the texture cannot be obtained.
Therefore, for such heat treatment, the treatment temperature is limited to the range of 200 ° C. or more and 550 ° C. or less. It was also found that the processing time required at least 30 seconds. It should be noted that an excessively long processing time leads to a decrease in productivity, so the upper limit is preferably about 10 hours.

  The obtained hot-rolled steel sheet is not subjected to intermediate annealing, and the final sheet thickness is obtained by one cold rolling with a reduction ratio of 80% or more. If the rolling reduction is less than 80%, the texture improvement during recrystallization will be insufficient. This is considered to be because rolling at a high pressure is indispensable once in order to accumulate dislocations around coarse carbides. In this regard, in the two-roll rolling with intermediate annealing, dislocations are primarily released during intermediate annealing, and the dislocations are not accumulated sufficiently, so that a satisfactory texture improvement effect cannot be obtained.

  Next, after subjecting the final cold-rolled sheet to primary recrystallization annealing, an annealing separator is applied to the surface of the steel sheet. Any conventionally known annealing separator is suitable. In particular, it is preferable to apply magnesia as a main agent, and to which additives such as titania, strontium compounds, sulfides, chlorides and borides are applied as a water slurry. Silica, alumina, etc. can also be used as other annealing separation agents.

Next, secondary recrystallization annealing is performed. The secondary recrystallization annealing is not particularly limited, and any method using an inhibitor or an inhibitorless method may be performed according to a conventionally known method.
After the above finish annealing, an insulating film can be applied and baked on the surface of the steel sheet. The type of insulating coating is not particularly limited, but any conventionally known insulating coating is suitable. For example, a coating solution containing phosphate-chromic acid-colloidal silica described in JP-A-50-79442 and JP-A-48-39338 is applied to a steel plate at about 800 ° C. A baking method is preferred.
Further, the shape of the steel sheet can be adjusted by the planarization annealing, and further, the planarization annealing that doubles the baking of the insulating film can be performed.

Example 1
C: 0.04%, Si: 3.35%, Mn: 0.1%, S: 0.01% and Se: 0.02%, and the remainder after heating to 1350 ° C, an electromagnetic steel material slab with a composition of Fe and inevitable impurities A hot-rolled sheet having a thickness of 2.3 mm was obtained by hot rolling. Next, after annealing at 1030 ° C. for 60 seconds, the temperature range of 550 to 300 ° C. during cooling was cooled at a cooling rate of 30 ° C./s, 10 ° C./s, 5 ° C./s, 3 ° C./s. The materials cooled at 30 ° C./s and 10 ° C./s were held at 350 ° C. for 0 second, 20 seconds, 30 seconds, and 45 seconds, and then cooled to 300 ° C. at the same cooling rate.
Cut the cross section in the direction perpendicular to the rolling direction from the center of the coil width direction of the hot-rolled annealed sheet thus obtained, observe the range of 100 μm vertically from the center of the plate thickness, and 5 mm in the width direction, and the presence frequency of coarse carbides of 2 μm or more. Asked.

Next, a cold rolled sheet having a thickness of 0.23 mm was formed by one cold rolling with a rolling reduction of 90%, and then primary recrystallization annealing was performed at a soaking temperature of 800 ° C. and a soaking time of 30 s. _{Then, MgO: 95mass%, TiO 2} : a 5 mass% of the annealing separator was applied on the surface of the steel sheet as a water slurry, and subjected to secondary recrystallization annealing. A coating solution containing phosphate-chromate-colloidal silica at a weight ratio of 3: 1: 3 was applied to the surface of the finish annealed plate thus obtained and baked at 800 ° C.

The magnetic properties at the center of the width of the product plate coil thus obtained were investigated. The magnetic characteristics were evaluated based on the magnetic flux density B ₈ when excited at 800 A / m after strain relief annealing at 800 ° C. for 3 hours.
The obtained results are shown in Table 1 in relation to the cooling rate after hot-rolled sheet annealing and the presence frequency of coarse carbides of 2 μm or more.
Regarding the existence frequency of coarse carbides of 2 μm or more, the case where there are 50 carbide / mm ² or more of coarse carbides of 2 μm or more within the range of 100 μm above and below the sheet thickness center of the cross section in the direction perpendicular to the rolling is less than that. Cases are indicated by x.

As is clear from the table, according to the present invention, in the cooling process after hot-rolled sheet annealing, it stays in the temperature range of 550 to 300 ° C. for 45 seconds or more, and the range of 100 μm above and below the sheet thickness center in the cross section perpendicular to the rolling direction. In the case where 50 carbide / mm ² or more of coarse carbides of 2 μm or more were deposited, a high magnetic flux density could be obtained.

Example 2
Inhibitor component containing C: 0.03%, Si: 3.5% and Mn: 0.05%, suppressing S, Se and O to less than 50 ppm and N to less than 60 ppm respectively, with the balance being a composition of Fe and inevitable impurities Slabs that do not contain steel are heated to 1220 ° C, hot-rolled to a thickness of 1.60 mm, annealed at 1050 ° C for 40 seconds, and room temperature at a rate of 50 ° C / s After cooling to 100 ° C., aging treatment was performed at 100 to 400 ° C. for 60 minutes.
Cut the cross section in the direction perpendicular to the rolling direction from the center of the coil width direction of the hot-rolled annealed sheet thus obtained, observe the range of 100 μm vertically from the center of the plate thickness, and 5 mm in the width direction, and the presence frequency of coarse carbides of 2 μm or more. Asked.

Next, after a single cold rolling, the sheet thickness was set to 0.30 mm (rolling rate: 81%), 0.35 mm (rolling rate: 78%), and the soaking temperature was 880 ° C. and the soaking time was 30 s. Recrystallization annealing was performed. _{Then, MgO: 95mass%, SrSO 4} : a 5 mass% of the annealing separator was applied to the steel sheet as a water slurry, and subjected to secondary recrystallization annealing. A coating solution containing phosphate-chromate-colloidal silica at a weight ratio of 3: 1: 2 was applied to the surface of the finish annealed plate thus obtained and baked at 800 ° C.

The magnetic properties at the center of the width of the product plate coil thus obtained were investigated. The magnetic characteristics were evaluated based on the magnetic flux density B ₈ when excited at 800 A / m after strain relief annealing at 800 ° C. for 3 hours.
The obtained results are shown in Table 2 in relation to the cooling rate after the hot-rolled sheet annealing and the existence frequency of coarse carbides of 2 μm or more.
Regarding the existence frequency of coarse carbides of 2 μm or more, the case where there are 50 carbide / mm ² or more of coarse carbides of 2 μm or more within the range of 100 μm above and below the sheet thickness center of the cross section in the direction perpendicular to the rolling is less than that. Cases are indicated by x.

As is apparent from the table, even after cooling to room temperature after hot-rolled sheet annealing, it was then subjected to an aging treatment in the temperature range of 200 to 550, and 100 μm above and below the sheet thickness center of the cross section in the direction perpendicular to the rolling direction. When 50 carbide / mm ² or more of coarse carbides of 2 μm or more were deposited in the range, a high magnetic flux density could be obtained.

  According to the present invention, a grain-oriented electrical steel sheet having excellent magnetic properties can be stably obtained on an industrial scale, and its industrial value is extremely large.

It is the figure which showed the effect which the grain size of the carbide | carbonized_material precipitated after annealing before cold rolling, and its presence frequency have on the texture improvement of a strong cold rolling and a recrystallized board once. (211) is a diagram showing the relationship between the magnetic flux density B ₈ of inverse strength and the final product sheet. It is a microscope picture which shows the precipitation condition of the carbide | carbonized_material when it was made to stay in the temperature range of 550-300 degreeC for 10sec, 30sec, and 45sec. It is a microscope picture which shows the precipitation condition of the carbide | carbonized_material when another sample was made to stay for 10 seconds, 30 seconds, and 45 seconds in the temperature range of 550-300 degreeC. It is a microscope picture which shows the precipitation condition of the carbide | carbonized_material when the steel plate after hot-rolled sheet annealing cooled to room temperature was heat-processed at 100 degreeC, 200 degreeC, and 300 degreeC for 1 hour, respectively.

Claims (5)

In mass%, electrical steel slab containing 0.01% or more and 0.10% or less of C, 2.0% or more and 4.5% or less of Si, and the balance Fe and inevitable impurities, hot-rolled, hot-rolled sheet annealed, and then rolled Rate: Directional electromagnetic consisting of the steps of making the final sheet thickness by one cold rolling of 80% or more, then applying the primary recrystallization annealing, then applying the annealing separator and then applying the secondary recrystallization annealing In the manufacturing method of the steel sheet,
Adjust the residence time to stay in the temperature range of 550 to 300 ° C during cooling after the hot-rolled sheet annealing, or cool to room temperature after the hot-rolled sheet annealing, and then the temperature range from 200 ° C to 550 ° C. in adjusting the heat treatment time of heat treatment, the steel sheet before the cold rolled, needle-like or plate-like carbides 2μm or more seen in the direction perpendicular to the rolling direction cross-section of the steel plate, the thickness of the perpendicular to the rolling direction cross-section A method for producing a grain-oriented electrical steel sheet, wherein at least 50 pieces / mm ² are present within a range of 100 μm above and below the center.   The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein a residence time in the temperature range of 550 to 300 ° C is at least 45 seconds.   The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein the heat treatment time in the temperature range of 200 ° C to 550 ° C is 30 seconds or more.   The electromagnetic steel material slab is further selected by mass from Al: 0.010 to 0.080%, N: 0.005 to 0.015%, Mn: 0.02 to 1.0%, Se: 0.001 to 0.05% and S: 0.001 to 0.05%. The method for producing a grain-oriented electrical steel sheet according to any one of claims 1 to 3, further comprising at least one kind.   One type selected from B, Bi, Sb, Mo, Te, Sn, P, Ge, As, Nb, Cr, Ti, Cu, Pb, Zn, and In, in addition to the electromagnetic steel material slab. Or 2 or more types are contained 0.0005-1.0%, respectively, The manufacturing method of the grain-oriented electrical steel sheet in any one of Claims 1-4 characterized by the above-mentioned.