KR100721823B1 - A hot rolling method for grain-oriented electrical steel sheet - Google Patents

Abstract

The present invention relates to hot rolling of a grain-oriented electrical steel sheet, in particular, in order to omit hot-rolled sheet annealing in slab low temperature heating at the same time to control the rolling rate, rolling temperature, winding temperature at the same time to solve the magnetic defects It relates to a rolling method.

According to the present invention, it is possible to appropriately distribute the finish hot rolling start temperature, the end temperature, and the finish rolling ratio of the grain-oriented electrical steel sheet to reduce the magnetic deviation in the coil, thereby securing stable magnetic properties. This effect is caused by reducing the rolling rate in the high austenite fraction in the region where austenite and ferrite coexist during hot rolling and giving a lot of shear deformation during hot rolling to make the microstructure uniform.

Rolling rate, rolling temperature, coiling temperature, finishing hot rolling.

Description

A hot rolling method for grain-oriented electrical steel sheet

1 is a graph showing the magnetic flux density value when the late three-pass cumulative reduction ratio and winding temperature of the finish hot rolling are changed and the hot rolled sheet annealing is omitted.

The present invention relates to hot rolling of a grain-oriented electrical steel sheet, in particular, in order to omit hot-rolled sheet annealing in slab low temperature heating at the same time to control the rolling rate, rolling temperature, winding temperature at the same time to solve the magnetic defects It relates to a rolling method.

In general, oriented electrical steel sheet is an electrical steel sheet having an aggregate structure in which the grain orientation is oriented in the {110} <001> direction. Since it has extremely excellent magnetic properties in the rolling direction, such as transformers, motors, generators, and other electronic devices, Used as iron core material.

The grain-oriented electrical steel sheet is required to have excellent magnetic flux density and iron loss. The magnetic flux density is a value of B10 measured at 1000 Amp / m of magnetic field, and the iron loss is expressed as loss per kilogram (Watt) at 1.7 Tesla at a frequency of 50 Hz. The higher the magnetic flux density and the smaller the iron loss, the better the characteristics.

Since N.P.Goss invented a method for producing oriented electrical steel sheet by cold rolling, many improvements have been made. Until recently, the manufacture of oriented electrical steel sheet for almost 50 years has been made by slabs into slabs through the process of crushing or casting, then reheating the slabs to high temperature around 1400 ℃ for hot rolling and then hot rolling. Heat-treat the hot rolled plate and cold roll to the final thickness without two cold rolling or intermediate annealing to the final thickness, then decarbonization annealing as primary recrystallization, hot annealing causing secondary recrystallization, and then coating This is a common process.

Since the late 1960s, however, Japanese Kobe Steel Co., Ltd., such as Japanese Patent Publication No. 46-937, Small 46-4085, and Small 46-26621, has applied for a patent for slab low-temperature heating. Korean Patent Publication Nos. 1996-63078, 1996-71517, 1997-53791, 1997-37247, 1997-28305, 1997-32747, and Korean Patent Publications 1989-13200, 1992-702728, 1990-016461) .

That is, the conventional high temperature slab heating method has low recovery rate of materials and high manufacturing cost, while these methods characterized by low temperature slab heating have good recovery rate of material and very low loss of material in the post process. Since it does not require hot rolling, the heat source unit is low, and manufacturing cost can be drastically reduced.

The oriented electrical steel is divided into high quality high permeabilty grain oriented electrical steels (HGO) and conventional grain oriented electrical steels (CGO). Steel companies adopting the hot slab heating method usually omit hot rolled sheet annealing.

In the manufacturing method of low-temperature slab heating method, many hot-rolled sheet annealing methods such as Japanese Patent Application Laid-open No. Hei 3- 294427, Hei 2-274815, Hei 3-47920 have been proposed, but practically variations in quality in the width and length direction of the coil Is generated a lot and the magnetism is poor, and substantially hot-rolled sheet annealing is performed. In other words, in the low temperature slab heating method, the process without the hot-rolled sheet annealing proves technically very difficult to adopt commercially.

In the manufacturing method of the conventional grain-oriented electrical steel sheet characterized by low temperature slab heating, the production method of eliminating the hot-rolled sheet annealing for the improvement of the productivity is that the precipitates mainly based on AlN are fine and uneven by size and part, so the magnetic level is absolutely low and the degree of deviation is low. Big problems arise.

The present invention for solving the above problems is to improve the hot rolling method to provide a hot rolling method of oriented electrical steel sheet to solve the problems caused by omitting the hot-rolled sheet annealing to improve the productivity of the grain-oriented electrical steel sheet process It is done.

An object of the present invention is to provide a hot rolling method of oriented electrical steel sheet to solve the magnetic defects by simultaneously controlling the rolling rate, rolling temperature, winding temperature in hot rolling to omit the hot rolled sheet annealing in slab low temperature heating.

Hot rolling method of the grain-oriented electrical steel sheet of the present invention for achieving the above object is, in weight%, Si: 2.5 to 4%, C: 0.03 to 0.07%, Mn: 0.05 to 0.5, sol-Al: 0.025 to 0.04 %, N: 0.002% to 0.01%, P: 0.01% to 0.04%, S: 0.004% to 0.010%, and the remainder is the first step of reheating the slab composed of iron and unavoidable impurities to a temperature range of 1250 ° C or lower; Rough rolling with a reversible rolling mill, rolling rate of 94% or more with tandem rolling mill, cumulative rolling rate of 90% or more in the last three stands, hot rolling to finish temperature of 940 ℃ or less and winding after hot rolling Two steps of winding up to 700 ° C or higher ; Performing cold rerolling to form a final thickness, and then performing primary recrystallization annealing as well as decarbonization and nitriding in a wet atmosphere of hydrogen and nitrogen containing ammonia gas; 4 steps of applying the annealing separator in the form of slurry to the cota-roll, drying at a temperature of 700 ° C. or lower, and forming a large coil; During the final high temperature annealing, the entire zone is 25% or less of nitrogen-containing hydrogen atmosphere, and it is cooled after cracking for 20 hours or more at 1200 ± 10 ℃ while maintaining the temperature raising rate of 700 to 1200 ℃ over 15 ℃ / hr. Characterized in that it comprises a step.

The present invention is characterized in that, in the second stage, the finish rolling start temperature is set to 960 ℃ or less, and in the last three stands, the cumulative reduction ratio is set to 95% or more. Is set at 960 ° C., the finish rolling start thickness is changed to 40-50 mm, the final thickness of the hot rolled sheet is changed to 1.8-2.8 mm, and the total cumulative reduction ratio is set to 95% in the last three stands. It is done.

In the second step, the finish rolling start temperature is 960 ° C. or less, the finish rolling rate is 94% or more, the cumulative rolling rate is 95% or more in the last three stands, and the winding temperature is 720 ° C. or more. Characterized in that.

Hereinafter, the hot rolling method of the grain-oriented electrical steel sheet of the present invention will be described.

1 is a graph showing the magnetic flux density value when the late three-pass cumulative reduction ratio and winding temperature of the finish hot rolling are changed and the hot rolled sheet annealing is omitted.

The steel component and manufacturing conditions of the present invention will be described.

In the present invention, Si is an element that serves to lower the iron loss by increasing the resistivity value, the iron loss characteristics are worse when the content is less than 2.5%, the steel is vulnerable if excessively added more than 4%, cold rolling properties are extremely bad, It is preferable to add at 2.5-4%.

C is an element that plays a role of fine solid dispersion of AlN precipitate, rolling structure formation, imparting processing energy during cold rolling, and preferably 0.03 to 0.07%. If it is 0.03% or less, fine crystal grains are formed in the central part of the final product, and the magnetic properties are deteriorated. If it is 0.07% or more, it is difficult to control the precipitates and it is difficult to decarburize less than 30 ppm in a short time, and thus magnetic aging may occur.

Acid-soluble Al (sol-Al) is an element that forms a precipitate of AlN together with N to secure grain growth inhibition. If the acid-soluble Al is less than 0.025%, fine AlN is precipitated and if it is more than 0.04%, AlN becomes too coarse. No primary recrystallization inhibitory effect

Mn lowers the solid solution temperature of the precipitate during reheating and prevents cracks formed at both ends of the material during hot rolling. It should be added at least 0.05% in order to obtain such an effect. However, when excessively added, Mn oxide is formed to deteriorate iron loss, so the content range is preferably set to 0.05 to 0.5%.

The amount of N is preferably made 20 ppm or more and 100 ppm or less. If the amount of N is 100 ppm or more, the rolling property is impaired, AlN coarsens, and the magnetism deteriorates. The exact cause is unknown, but if the amount of N is less than 20 ppm empirically no secondary recrystallization occurs.

P is an element that is partially useful for suppressing grain growth of primary recrystallization, and it is effective to add 0.01 to 0.04%. If it is 0.01% or less, it will have no effect, and if it is 0.04% or more, brittleness will increase and it will damage rolling property.

S is preferably 0.004% to 0.01%. To manage at 0.004% or less, the cost of steelmaking increases, and if it is 0.01% or more, MnS precipitates are formed and the primary recrystallized grains become fine, which is disadvantageous for the development of secondary recrystallization.

The steel slab formed as described above is preferably reheated to a temperature range of 1250 ° C. or less in consideration of hot rolling properties and aspects of securing magnetic properties, and then hot rolled to hot roll to a thickness of 2.3 mm. Hot rolling is divided into two stages, rough rolling and finishing rolling, and the hot rolling thickness can be changed in the range of 1.5 to 3.0 mm as necessary.

The slabs are extracted from the furnace, roughly rolled with a reversible rolling mill consisting of one or two stands and finished rolled with a tandem rolling mill. Finish rolling temperature shall be 970 degreeC or less. The limit of the finish rolling temperature to 970 ° C. or lower is to improve the magnetic properties by avoiding the fine distribution of precipitates mainly based on AlN.

The finish rolling rolling rate is made into 94% or more. The rolling rate of finish rolling is obtained by dividing the difference in the rolling rate from the exit side to the exit thickness by 94%, which is good for magnetism. Finish rolling is usually a tandem rolling mill with six or seven successive stands. It is better to increase the second half rolling rate even if the same finish rolling rate is largely rolled in the first half. It is desirable for the magnet to have a cumulative rolling rate of 90% or more plus the rolling rate of each stand in the last three stands of finish rolling. The finishing temperature of finish rolling shall be 940 degrees C or less. If the finish rolling temperature is 940 ℃ or more is not good for magnetism.

After hot rolling, the coiling temperature is maintained at 700 ℃ or higher. If it is less than 700 ° C, the magnetic properties deteriorate.

Cold rolling is carried out to the final thickness, and then primary recrystallization annealing is performed together with decarbonization and nitriding in a humid atmosphere of hydrogen and nitrogen containing ammonia gas.

Thereafter, the annealing separator is applied in a slurry state and coated with cotarol, dried at a temperature of 700 ° C. or lower, and then wound to make a large coil.

After application of the annealing separator, the final finishing high temperature annealing is carried out, and the entire section is a nitrogen atmosphere containing 25% or less, and the temperature rising rate of 700 to 1200 ° C is maintained at 1200 ± 10 ° C over 15 ° C / hr. It is preferable to carry out by cooling after cracking for 20 hours or more at the temperature of.

Thereafter, a coating agent consisting of phosphate, colloidal silica, chromic anhydride and the like is finally applied.

If the hot rolled sheet annealing of the grain oriented electrical steel is omitted, the magnetism is very poor. The present inventors have discovered that AlN precipitates are finely and nonuniformly distributed due to the omission of hot rolled sheet annealing. Figure 1 shows the AlN micro precipitates of the primary recrystallization plate. The function of the hot-rolled sheet annealing is to re-use the finely precipitated AlN in the hot rolling process while heating the hot-rolled sheet, to re-precipitate in the AlN precipitate that is not completely dissolved, ultimately to distribute the AlN precipitate within a certain size. A grain-oriented electrical steel sheet is formed by grains called {110} <001> aggregates, so-called Goss tissues, by secondary recrystallization. Hot annealing, which causes secondary recrystallization, is to heat the coil at a constant heating rate from room temperature to 1200 ° C. Usually, it heats up at 15 degreeC per hour.

The magnetic property of the grain-oriented electrical steel sheet is determined by the degree to which the <001> direction, which is the biaxial magnetization, is arranged in parallel in the rolling direction, that is, the orientation. The driving force of the secondary recrystallization is the grain boundary energy of the primary recrystallized grain. Therefore, in order for the secondary recrystallization to occur, the growth of the primary recrystallized grains up to the temperature at which the secondary recrystallization takes place is required. At this time, a precipitate such as AlN is required. High temperature annealing, which usually has a slow heating rate of about 15 ° C. per hour, is a long time annealing that takes 5 days or more. At high temperature annealing, {110} <001> grains in secondary recrystallization range from 950 ° C to 1200 ° C. At temperatures below 950 ° C, the AlN precipitates causing secondary recrystallization are finely and uniformly distributed. The growth of recrystallized grains should be suppressed. In the section where the second recrystallization occurs, as AlN gradually coarsens, it is necessary to slowly lose the inhibitory power to secure excellent magnetism.

The distribution state of AlN precipitates is very important for magnetism, and the finer and more uniform the precipitate, the stronger the suppression force. If the suppression force is weak, secondary recrystallization occurs at a low temperature, and if secondary recrystallization occurs at a low temperature, the orientation is poor and the magnetism is bad. The shape of the most preferred precipitate is fine and uniform. In particular, the size of the precipitate is very important. If the precipitate size is non-uniform, the so-called Oswald repening phenomenon causes small precipitates to be quickly extinguished and large precipitates to grow, resulting in lower overall grain growth inhibition. If the distribution of the precipitate is uneven, secondary recrystallization occurs at a low temperature during the elevated temperature of the high temperature annealing, the orientation of the <001> axis is not good, and the magnetic properties deteriorate.

Fine precipitation of AlN in hot-rolled sheet annealing cannot be avoided by omitting the hot-rolled sheet annealing, but can be largely compensated by properly controlling the component conditions and the hot-rolled conditions. In particular, the control of the hot rolling factor is very important. The hot rolling of the grain-oriented electrical steel sheet is performed in the region where the ferrite phase and the austenitic phase coexist, but the AlN solid solution limit of the austenite phase is larger than that of ferrite. desirable. In the conventional component system of a grain-oriented electrical steel sheet, the austenite region becomes maximum at 1200 ° C. Therefore, rolling in a high temperature range of austenite fraction is disadvantageous to magnetism. Hot rolling consists of rough rolling and finish rolling. In particular, it has been found that the magnetism is significantly improved when the rolling temperature of the finish rolling is important and the finish rolling start temperature is 970 ° C. or lower, and the finish rolling end temperature is 940 ° C. or lower.

It was found that the rolling rate of the finish rolling also significantly affected the magnetism. The rolling rate of finish rolling is effective to reduce the magnetic deviation of the coil. The slabs of oriented electrical steel sheets are usually 15 ton or more per sheet. When rolling a lot in rough rolling, the thickness of the slab becomes thin during finishing rolling, and thus the degree of cooling of the first rolled part and the last part of the slab during finishing rolling usually made over a few minutes. There is a lot of temperature deviation because it is wrong. In particular, when the finish rolling starts, a large amount of coolant is injected to remove the scale layer on the surface, and when the thickness of the slab is thin during rough rolling, the length of the slab becomes longer. The temperature deviation is large. Therefore, it is effective to reduce the magnetic deviation by reducing the cooling deviation by making the slab thickness thicker by reducing the rolling amount in rough rolling. When the finish rolling rate is more than 94%, it is effective to reduce the magnetic deviation.

 Even if it is the same finish rolling rate, it is better to make the latter half rolling rate larger than rolling much in the first half. That is, the back dropping is good for magnetism. In the conventional hot rolling method, the rolling rate is increased at the front side and the rolling rate is reduced at the last rolling for the shape improvement.

Typical carbon content of oriented electrical steel sheet is 0.02 ~ 0.08%, which becomes austenite and ferrite two-phase zone. At a temperature of 1100 ° C, the austenite fraction is the largest and has an austenite fraction of up to 20-30%, depending on the carbon content. When it becomes 800 degrees C or less, it will become a ferrite single phase. Compared to ferrite, the austenite phase is a much harder tissue. Since hot rolling starts at 1050 ° C, the larger the rolling rate of the front pass, the more the austenite fraction is rolled in the temperature range, so the energy accumulated in ferrite and austenite is different, which causes the microstructure to be uneven in the subsequent process. . It is desirable for the magnet to have a cumulative rolling rate of 90% or more plus the rolling rate of each stand in the last three stands of finish rolling.

The finishing temperature of finish rolling shall be 940 degrees C or less. If the finish rolling temperature is 940 ℃ or more is not good for magnetism. The reason for defining the second half rolling rate and the finishing end temperature in finish rolling is to avoid the temperature range in which the austenite phase has a lot during hot rolling.

The coiling temperature is mainly focused on preventing the coarse precipitation of carbides below 600 ° C. in the conventional manufacturing method. However, when the coiling temperature is controlled at a low winding temperature by quenching, the precipitation state and the microstructure of AlN are uneven. It is rather disadvantageous to magnetism because it does not perform hot-rolled sheet annealing to adjust this. Therefore, it is advantageous to the magnet to keep the coiling temperature at 700 ℃ or more. Moreover, when the coiling temperature is 700 ° C or higher, there is an advantage that the hot rolled coil shape is improved without quenching.

Hereinafter, the present invention will be described in more detail with reference to Examples.

First it will be described a first embodiment, in weight%, Si: 3.15%, C : 0.052%, Mn: 0.13, sol-Al: 0.033%, N: 0.005%, P: 0.025%, S: with 0.005% glass The department reheated the slab made of iron and unavoidable impurities at a temperature of 1250 ° C. or lower, and changed the hot rolling finish starting temperatures to 1000, 980, and 960 ° C. At this time, the finish rolling ratio was 95% to make a hot rolled sheet having a thickness of 2.3 mm.

The total reduction rate of each of the last three stands of the finish rolling consisting of a total of six rollings was performed at 95%. After hot rolling, the hot rolled sheet was annealed and cold rolled to make a 0.3mm thick plate.The cold rolled sheet was denitrated, primary recrystallized, and nitrided in a wet atmosphere containing nitrogen, hydrogen, and ammonia for 3 minutes at 850 ℃. Combined heat treatment was performed.

The high temperature annealing was performed under a heat treatment condition in which the temperature was raised to 15 ° C. per hour up to 1200 ° C. in a mixed atmosphere of hydrogen and nitrogen. After recrystallization at high temperature annealing, insulation coating and iron loss were measured.

Table 1 shows the magnetic flux density values B10 and iron loss W17 / 50 depending on the finish rolling start temperature. B10 is the value of magnetic field measured at 1000 Amp * turn / m. The unit is Tesla, iron loss is 1.7 Tesla, and the loss per kg measured in 50 Hz is measured in Watt.

Finish rolling start temperature Magnetic flux density B10 Iron loss W17 / 50 Remarks 1020 ℃ 1.76 Tesla 1.89 W / kg Comparative material 1000 ℃ 1.80 Tesla 1.64 W / kg Comparative material 980 ℃ 1.85Tesla 1.45 W / kg Comparative material 960 ℃ 1.89 Tesla 1.21 W / kg Invention 950 ℃ 1.91 Tesla 1.14 W / kg Invention

Further, when describing the second embodiment, in weight%, Si: 3.2%, C : glass and 0.007%: 0.045%, Mn: 0.11, sol-Al: 0.032%, N: 0.006%, P: 0.025%, S The part reheated the slab consisting of iron and unavoidable impurities at a temperature of 1250 ° C. or lower, and changed the hot rolling finish starting temperature to 960 ° C.

At this time, the starting thickness of the finish rolling was changed to 35 mm (rolling rate 93.4%), 40 mm (rolling rate 99.4%), and 45 mm (rolling rate 99.4%) to change the final thickness to 2.3 mm. The total reduction rate of each of the last three stands of the finish rolling consisting of a total of six rollings was performed at 95%. Cold rolled sheet was rolled out to make 0.3mm thick plate without cold annealing.The cold rolled plate was heated at 850 ℃ for 3 minutes in a humid atmosphere mixed with nitrogen, hydrogen, and ammonia. Was carried out.

The high temperature annealing was performed under a heat treatment condition in which the temperature was raised to 15 ° C. per hour up to 1200 ° C. in a mixed atmosphere of hydrogen and nitrogen. After secondary recrystallization at high temperature annealing, it is shown in Table 2 by insulation coating and magnetic measurement.

Rolling start thickness Magnetic flux density B10 Iron loss W17 / 50 Remarks 35 mm (93.4% rolling ratio) 1.84 Tesla 1.46 W / kg Comparative material 40 mm (94.3% rolling ratio) 1.88 Tesla 1.28 W / kg Invention 45 mm (94.9% rolling ratio) 1.90Tesla 1.19 W / kg Invention 50 mm (95.4% rolling rate) 1.91 Tesla 1.14 W / kg Invention

Furthermore, when explaining the embodiment 3, in weight%, Si: 3.1%, C : glass and 0.007%: 0.055%, Mn: 0.11, sol-Al: 0.032%, N: 0.005%, P: 0.03%, S The part reheated the slab consisting of iron and unavoidable impurities at a temperature of 1250 ° C. or lower, and changed the hot rolling finish starting temperature to 960 ° C.

At this time, the finish rolling rate was 95%, and the final thickness was changed to 2.3 mm. The total rolling reduction of each of the last three stands of the finish rolling consisting of six rollings was changed to 77%, 86%, and 95%. The coiling temperature was changed to 580 and 720 ° C for each. The cold rolled sheet is annealed and cold rolled to make a 0.3mm thick plate.The cold rolled plate is then heated at 850 ℃ for 3 minutes in a wet atmosphere mixed with nitrogen, hydrogen, and ammonia. Was carried out.

The high temperature annealing was performed under a heat treatment condition of raising the temperature to 15 ° C. per hour up to 1200 ° C. in a mixed atmosphere of hydrogen and nitrogen. After recrystallization at high temperature annealing, insulation coating and iron loss were measured.

The graph shown in FIG. 1 shows that the magnetic flux density value is higher in the late three-pass cumulative reduction ratio of the finish rolling, and the magnetic properties are excellent under the condition that the winding temperature is 720 ° C rather than 580 ° C.

The present invention eliminates annealing of the hot rolled sheet in slab low-temperature heating to improve productivity during the process of grain-oriented electrical steel sheet, and solves the magnetic defect by controlling the rolling rate, rolling temperature, winding temperature at the same time in hot rolling.

While the present invention described so far has been described with reference to specific embodiments, it has been described for illustrative purposes only and is not intended to limit the invention to the embodiments described above. Those skilled in the art will appreciate that various modifications and changes of the present invention can be made without departing from the spirit and scope of the invention as set forth in the claims below. The present invention intends to make clear that all such modifications and variations are included within the scope of the present invention.

According to the present invention as described above, there is an effect that can secure the stable magnetic properties by reducing the magnetic deviation in the coil by appropriately distributing the finish hot rolling start temperature, the end temperature, the finish rolling rate of the grain-oriented electrical steel sheet.

This effect is caused by reducing the rolling rate in the high austenite fraction of the zone where austenite and ferrite coexist during hot rolling and giving a lot of shear deformation during hot rolling to make the microstructure uniform.

Claims (4)

By weight%, Si: 2.5-4%, C: 0.03-0.07%, Mn: 0.05-0.5, sol-Al: 0.025-0.04%, N: 0.002-0.01%, P: 0.01-0.04%, S: 0.004 1 step of reheating the slab composed of iron and unavoidable impurities to a temperature range of 1250 ° C. or less; Rough rolling with a reversible rolling mill, rolling rate of 94% or more with tandem rolling mill, cumulative rolling rate of 90% or more in the last three stands, hot rolling to finish temperature of 940 ℃ or less and winding after hot rolling Two steps of winding up to 700 ° C or higher ; Performing cold rerolling to form a final thickness, and then performing primary recrystallization annealing as well as decarbonization and nitriding in a wet atmosphere of hydrogen and nitrogen containing ammonia gas; 4 steps of applying the annealing separator in the form of slurry to the cota-roll, drying at a temperature of 700 ° C. or lower, and forming a large coil; During the final high temperature annealing, the entire zone is 25% or less of nitrogen-containing hydrogen atmosphere, and it is cooled after cracking for 20 hours or more at 1200 ± 10 ℃ while maintaining the temperature raising rate of 700 to 1200 ℃ over 15 ℃ / hr. Method for producing a grain-oriented electrical steel sheet comprising the step. The method of claim 1, In the second step, Finish rolling start temperature is 960 ℃ or less, the method of producing a grain-oriented electrical steel sheet comprising the step of setting the total cumulative reduction ratio to 95% or more in the last three stands. The method of claim 1, In the second step, The finish rolling start temperature is set to 960 ° C, the finish rolling start thickness is changed to 40-50 mm, the final thickness of the hot rolled sheet is changed to 1.8 to 2.8 mm, and the cumulative reduction ratio of the final three stands is set to 95%. Method for producing a grain-oriented electrical steel sheet comprising a. The method of claim 1, In the second step, The finish rolling start temperature is 960 ℃ or less, the finish rolling rate is 94% or more, the cumulative rolling rate is 95% or more in the last three stands, the winding temperature is characterized in that it comprises 720 ℃ or more Method of manufacturing electrical steel sheet.

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