JPH1150152A - Manufacturing method of grain-oriented electrical steel sheet with stable and extremely high magnetic flux density in the longitudinal direction of the coil - Google Patents

Abstract

(57) [Problem] To provide a method for manufacturing a grain-oriented electrical steel sheet in which the magnetic flux density in the coil longitudinal direction is stable and extremely high. SOLUTION: In weight%, 0.010% ≦ C ≦ 0.14.
%, 0.010% ≦ acid-soluble Al ≦ 0.050%, 0.1%
A slab containing 0030% ≦ N ≦ 0.0150%, the balance being Fe and unavoidable impurities, is heated and hot-rolled, then cold-rolled one or more times to a final sheet thickness, and after decarburizing annealing, This is a method for producing a grain-oriented electrical steel sheet that is finally annealed in a temperature range not higher than the Ac ₁ transformation point.
Perform under the condition that satisfies the formula, and set the final cold rolling reduction
A method for producing a grain-oriented electrical steel sheet having a very high magnetic flux density in a longitudinal direction of a coil, which is characterized by being made super. (Equation 1)

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a grain-oriented electrical steel sheet having a stable and high magnetic flux density in the longitudinal direction of a coil.

[0002]

2. Description of the Related Art A grain-oriented electrical steel sheet is characterized in that it is a product in which the crystal grains of the steel sheet are highly oriented in a specific direction by secondary recrystallization, and the {110} plane is on the rolling surface and the rolling direction is And a crystal grain having a Goss orientation having a <100> axis. The applications of grain-oriented electrical steel sheets are mainly used as soft magnetic materials for core materials of transformers and other electrical equipment, and in recent years social demands for energy saving and resource saving have become increasingly severe. From
Demands for reduction of iron loss and improvement of magnetization characteristics of a grain-oriented electrical steel sheet have become strict. For this reason, magnetic characteristics, particularly good excitation characteristics and iron loss characteristics, have been required.

A magnetic flux density B ₈ (magnetic flux density at a magnetic field strength of 800 A / m) is usually used as an index indicating the excitation characteristics of a grain-oriented electrical steel sheet. As an index indicating the iron loss characteristics, W _17/50 (iron loss per unit weight when magnetized to 1.7 T at 50 Hz) and the like are used. Iron loss consists of eddy current loss and hysteresis loss, and eddy current loss is the electrical resistivity, thickness, crystal grain size, magnetic domain form,
It is governed by factors such as film tension on the steel sheet surface. On the other hand, the hysteresis loss is governed by the crystal orientation, purity, internal strain and the like of the steel sheet that governs the magnetic flux density.

[0004] In order to reduce iron loss by controlling these factors, the Si content has been increased in order to increase the electrical resistance of the steel sheet. However, since the saturation magnetic flux density decreases with this, the prior art has compensated for this by increasing the degree of integration of the secondary recrystallization orientation to produce a high magnetic flux density grain-oriented electrical steel sheet. For this reason, in the prior art, the role of the inhibitor is important as a factor for stably expressing secondary recrystallization, increasing the degree of azimuthal integration, and improving magnetic flux density. For this purpose, MnS, AlN, MnSe and the like have been used as inhibitors in the prior art.

[0005] Conventional methods for producing grain-oriented electrical steel sheets are roughly classified into three types depending on the type of inhibitor used for controlling the secondary recrystallization orientation. First of all, M. F. Lite
There is a production method disclosed by Tmann in Japanese Patent Publication No. 30-3651. This production method uses MnS as an inhibitor.
It is characterized in that it is manufactured by cold rolling twice. Next, there is disclosed a production method disclosed in Japanese Patent Publication No. 40-15644 by Taguchi, Sakakura et al. Using AlN as an inhibitor in addition to MnS. The magnetic flux density of the grain-oriented electrical steel sheet is 1.870 by the method using AlN for this inhibitor.
T, and greatly contributed to energy saving by improving magnetic properties. Third, Japanese Patent Publication No. 51-1346
No. 9 discloses a method in which MnS and Sb or MnS or MnSe and Sb disclosed in Ichinaka et al. Are produced by a double cold rolling method.

[0006] In these production methods, in order to obtain an essential or good magnetic flux density, for the purpose of controlling the precipitation of the inhibitor, the precipitate constituting the inhibitor is once dissolved by high-temperature slab heating, and this is subjected to a hot rolling step or As disclosed in JP-B-46-23820, it is necessary to precipitate finely during hot-rolled sheet annealing. As described above, in the conventional method, the properties of the product are almost determined at the stage of the component adjustment at the steel making stage and at the stage of hot rolling. Therefore, it is an important issue to establish the stability of the material building in the upper process.

For this purpose, in the hot rolling process of grain-oriented electrical steel sheets, from the viewpoint of more stably controlling precipitates,
A great deal of effort has been put into controlling the precipitates in the longitudinal direction of the coil by taking measures such as using a heat retaining cover for the sheet bar after the rough rolling and cooling control on the run-out table. However, the variation of hot rolling conditions of grain-oriented electrical steel sheets still has a large effect on the magnetic properties of products, and the stability of hot rolling conditions,
There was a problem in terms of yield.

However, in recent years, unlike conventional directional magnetic steel sheets for transformer core applications, such as yoke materials and magnetic shield materials, there has been a demand for directional magnetic steel sheets for applications where higher magnetic flux density is more important than iron loss. Is increasing,
The establishment of the manufacturing technology was urgent. In order to obtain a high magnetic flux density, it is effective to increase the content of iron itself in the material to increase the saturation magnetic flux density in addition to increasing the degree of azimuth integration as emphasized in the prior art.

The present inventors have, for this purpose,
JP-B-7-122093, JP-A-4-30105
No. 3 discloses such a method of manufacturing a grain-oriented electrical steel sheet having a high magnetic flux density. However, even with the high magnetic flux density grain-oriented electrical steel sheets produced by these manufacturing methods, demands for higher magnetic flux densities have emerged from consumers with respect to magnetic flux densities at high magnetic fields required for yoke materials and the like. At present, the development of products that exceed the characteristics of the conventional high magnetic flux density grain-oriented electrical steel sheets has been urgently required.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a grain-oriented electrical steel sheet which has a stable and high magnetic flux density in the longitudinal direction of the coil in response to the demands of the market in recent years. Things.

[0011]

The gist of the present invention is as follows. (1) In% by weight, 0.010% ≦ C ≦ 0.14%, 0.010% ≦ acid-soluble Al ≦ 0.050%, 0.0030% ≦ N ≦ 0.0150%, and the balance Fe A directional slab that heats and hot-rolls a slab composed of unavoidable impurities, performs one or more cold-rollings to a final sheet thickness, decarburizes it, and finally anneals in a temperature range below the Ac ₁ transformation point. A method for producing a steel sheet, wherein finishing hot rolling is performed under a condition satisfying the following expression (1).
A method for producing a grain-oriented electrical steel sheet having a stable and extremely high magnetic flux density in a longitudinal direction of a coil, wherein the final cold-rolling rate is more than 75%.

(Equation 2)

(2) The leading end of the sheet bar obtained by roughly rolling the slab is joined to the trailing end of the preceding sheet bar to integrate a plurality of sheet bars. (1) The method for producing a grain-oriented electrical steel sheet according to the above (1), wherein the oriented magnetic steel sheet has a stable and extremely high magnetic flux density in a longitudinal direction of the coil.

[0013] The inventors of the present invention have studied the manufacturing process other than the inhibitor control technique, which was the main focus of the study in the prior art, as the control of the hot rolling conditions and the magnetic flux in the longitudinal direction of the coil due to the formation of the hot rolled sheet. As a result of intensive studies on the manufacturing method of grain-oriented electrical steel sheets with stable and high density, we found that the strain rate during finish rolling had a close effect on the magnetic properties of finished products during finish hot rolling. The magnetic properties in the longitudinal direction of the coil are stabilized by suppressing
Further, it has been found that it is possible to manufacture a grain-oriented electrical steel sheet having a high magnetic flux density.

Further, in order to suppress such a variation in the strain rate during the finish rolling, the sheet bar after the rough rolling is joined to the preceding sheet bar, and two or more sheet bars are continuously connected to the finishing heat. It has also been found that it is preferable to provide it.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
First, the components will be described. C has a content of 0.0
If it is less than 10%, secondary recrystallization becomes unstable and the magnetic flux density is remarkably reduced. On the other hand, if it exceeds 0.14%, the time required for decarburization annealing becomes too long, which is uneconomical.

The acid-soluble Al combines with N to form AlN, an inhibitor. If the content is less than 0.010%, the amount of inhibitor deposited becomes insufficient and secondary recrystallization becomes unstable. Therefore, the content is set to 0.010% or more. On the other hand, if the content exceeds 0.050%, the precipitation state becomes coarse, the inhibitor effect is impaired, and the magnetic flux density is reduced.
0.050% or less.

N must be not less than 0.0030% and not more than 0.0150%. If it exceeds 0.0150%, blisters called “blisters” occur on the steel sheet surface, and it becomes difficult to adjust the primary recrystallization structure. On the other hand, if the N content is less than 0.0030%, the formation of AlN, which is an inhibitor, becomes insufficient and secondary recrystallization becomes difficult, so the N content is made 0.0030% or more.

Next, the process of the present invention will be described. The electromagnetic steel slab of the present invention is obtained by melting steel in a melting furnace such as a converter or an electric furnace, subjecting the steel to vacuum degassing if necessary, and then performing continuous casting or ingot rolling after ingot casting. Can be Thereafter, slab heating is performed prior to hot rolling. In the process of the present invention, the heating temperature of the slab is appropriately controlled so that the main inhibitor, Al
It is important to re-dissolve N in steel. This slab is hot-rolled into a hot-rolled sheet having a predetermined thickness.

The following experiment was conducted to investigate the effect of the variation in strain rate during hot rolling on the finished product in the longitudinal direction of the coil. Steels having the components shown in Table 1 were melted and made into slabs having a thickness of 200 mm by a continuous casting machine. Next, this was rough-rolled into a sheet bar having a thickness of 70 mm, and then wound into a coil shape. The temperature of the sheet bar at the time of winding is 100
It was 0 ° C.

[0020]

[Table 1]

Thereafter, the sheet bar is unwound, and a pressing force is applied to the preceding sheet bar and welded, rough rolling is continuously performed, hot rolling is performed, and the magnetic properties of the product sheet obtained by changing the strain rate in the middle are obtained. The relationship between strain and strain rate was investigated.

The hot rolling end temperature is 900 ° C. and is 2.50 mm
After passing through the final hot rolling final stand, cool and
Wound at 0 ° C. The maximum strain rate of the final stand of this finish rolling was 370 s ^-1 .

The obtained hot-rolled sheet is subjected to hot-rolled sheet annealing at 825 ° C. for 2 minutes, then pickled, cold rolled to 0.40 mm by rolling at a cold rolling rate of 84.0%, and then at 830 ° C. for 5 minutes. The decarburization annealing was performed in a wet hydrogen atmosphere. Thereafter, finish annealing at 890 ° C. × 10 hours was performed. An Epstein sample was cut out from the obtained product, subjected to strain relief annealing, and then subjected to a magnetic field strength of 10%.
The value of the magnetic flux density at 000 A / m was measured. FIG. 1 shows the relationship between the variation of the strain rate of the final stand during the finishing hot rolling and the product magnetic flux density.

According to FIG. 1, the variation of the magnetic flux density is suppressed by keeping the variation of the strain rate within the range of the following equation (1), that is, the variation of the strain rate with respect to the maximum strain rate is within 25%. You can see that there is. Further, it can be seen that the variation of the magnetic flux density can be suppressed to a smaller range by setting the variation of the strain rate within the range of the following equation (2), that is, by setting the variation of the strain rate with respect to the maximum strain rate within 20%.

(Equation 3)

(Equation 4)

As described above, the variation of the magnetic flux density of the steel sheet can be suppressed by keeping the variation of the strain rate in the hot-rolling within a certain range. Therefore, in the finishing hot rolling of the sheet bar after the rough rolling, if the variation of the strain rate is within a certain range, it is possible to stabilize the magnetic properties of the product in the coil longitudinal direction.

As a method of controlling the strain rate in the finishing hot rolling, the distribution of the rolling reduction of the tandem stand is adjusted, and simultaneously the rolling rate is adjusted, the thickness of the sheet bar, the thickness of the hot rolled sheet in the finishing hot rolling are adjusted. The present invention can be implemented by a method such as appropriately setting the plate thickness. Also, the strain rate can be adjusted by changing the roll diameter of the stand.

From the viewpoint of further stabilizing the magnetic properties of the product in the longitudinal direction of the coil, the front end of the sheet bar obtained by roughly rolling the slab is joined to the rear end of the preceding sheet bar to form a plurality of sheets. It is preferable that the sheet bars are integrated and a plurality of integrated sheet bars are continuously subjected to hot rolling for finishing. It is difficult to control the strain rate of the final hot-rolling final stand within a certain range in order to secure rolling stability during biting of the hot-rolled steel and slippage of the tail, but the sheet bar is connected as described above. This is because if the hot rolling is continuously performed, the strain rate can be easily controlled.

As a method of joining the preceding sheet bar and the succeeding sheet bar, a method of welding the leading end of the preceding sheet bar to the leading end of the succeeding sheet bar and welding the butted portion, or a method of applying a pressing force to the butted portion is used. In addition, there is a method of performing pressure contact, a method of performing pressure contact after welding a butt portion, and the like. Also, welding may be performed while applying a pressing force to the butted portion. In addition, as a method of welding the butt portion, for example, a laser welding method, a method by induction heating, and the like can be mentioned.

The strain rate is calculated by the following equation. Here, r is the rolling reduction% / 100, n is the number of revolutions of the roll (rpm), R is the radius of the rolling roll (mm), and H ₀ is the thickness (mm) before rolling. Strain rate = (2πn / (60r ^0.5 )) (R / H ₀ ) ^0.5 ln
(1 / (1-r))

The sheet bar before joining may be wound up on a coil and stand by in order to continuously perform rolling. At this time, the wound sheet bar may be inserted into a heat retaining cover to keep the temperature or the temperature in order to suppress a decrease in the temperature of the outer surface portion. Further, the sheet bar may be wound directly into the coil box to keep the heat. Although the holding time of the wound sheet bar is not particularly specified, in the case of a grain-oriented electrical steel sheet of the present component system, if the holding time of the wound sheet bar becomes excessively long, the inhibitor coarsely precipitates and the finish annealing time is reduced. Since the secondary recrystallization becomes unstable, the time is preferably within 180 seconds. A more preferable sheet bar winding time is 30 seconds or more and 120 seconds in consideration of productivity and magnetic properties of the product.
Within seconds. And, in order to avoid the stop of hot rolling during the delay of the wound sheet bar and to ensure the productivity of the hot rolling, a plurality of sheet bar coil boxes are installed,
It is preferable to store the sequentially wound sheet bar and perform a delay, and after the delay is completed, unwind the sheet bar and apply it to finish hot rolling.

Although it is not clear why the provisions of the formulas (1) and (2) stabilize the magnetic properties in the longitudinal direction of the product, the change in the strain rate during the finish rolling is caused by the change in the AlN content in the hot-rolled steel sheet. It is presumed that the cause is that the precipitation state is affected, and the orientation selectivity serving as a nucleus of secondary recrystallized grains is improved over the entire longitudinal direction of the steel sheet.

In the process after the hot rolling, the hot rolled sheet may be annealed for the purpose of controlling precipitates. After pickling, the final thickness is obtained by cold rolling once or twice or more including intermediate annealing.

In the present invention, in order to obtain a high magnetic flux density, the rolling reduction of the final cold rolling is set to more than 75%. If it is less than 75%, the ultra-high magnetic flux density aimed at by the present invention cannot be obtained, so the final cold rolling reduction is determined to be more than 75%.

Next, decarburization annealing is performed in an atmosphere such as a wet hydrogen atmosphere. Next, an annealing separator is applied and finish annealing is performed, and secondary recrystallization and subsequent purification are performed. Since the steel of the present invention has an αγ transformation, the finish annealing temperature is set to be lower than the αγ transformation point in order to maintain a good secondary recrystallization orientation.
The purification annealing after the completion of the secondary recrystallization is performed in a hydrogen atmosphere.

[0035]

【Example】

Example 1 After heating a slab containing the components shown in Table 2 and the balance of Fe and unavoidable impurities, the slab was heated by a roughing mill to obtain a slab.
The sheet bar had a thickness of 0 mm. Thereafter, the sheet bar was formed into a hot-rolled sheet having a thickness of 2.50 mm by a finishing mill.

[0036]

[Table 2]

At that time, in order to suppress the fluctuation of the strain rate during the finishing hot rolling, the sheet bar after the rough rolling was joined to the preceding sheet bar, and the finishing hot rolling was continuously performed. Finish rolling was performed so that the maximum strain rate of the final hot rolling final stand of the intermediate sheet bar was 360 s ^-1 and the distortion rate of the final stand during rolling did not fall below 80% of the maximum strain rate. The pass schedule was constant during rolling, and the rolling reduction of the final hot rolling stand was 20%. Finish hot rolling was performed while controlling the rolling speed so that the strain rate was within the range of the present invention.

As a comparative material, the sheet bar after the rough rolling was subjected to finishing hot rolling alone. At this time, the pass schedule was constant during the rolling, but the strain rate of the final stand was 234 at the start of the finish rolling to stabilize the bite of the sheet bar.
and s ^-1, then accelerated to perform finish hot rolled at 360s ^-1 in the steady state, the strain rate of the sheet bar rearmost end portion 28
It was set to 1 s ^-1 .

The obtained hot-rolled sheet was subjected to hot-rolled sheet annealing at 825 ° C. for 2 minutes, then pickled, cold rolled to 0.40 mm by rolling at a cold rolling rate of 84.0%, and then at 830 ° C. for 5 minutes. The decarburization annealing was performed in a wet hydrogen atmosphere. Thereafter, finish annealing at 890 ° C. × 10 hours was performed.

The Epstein sample was a T sample taken at a location 100 m from the end of the product coil corresponding to the tip of one sheet bar, an M sample measured at the center of the product coil in the longitudinal direction, and a hot rolled end side. A sample taken at a distance of 100 m from the sample was taken as a B sample, which was sampled from an intermediate sheet bar in the example of the present invention and from each part of one sheet bar in the comparative example. After performing the strain relief annealing on the cut out Epstein sample, the value of the magnetic flux density at a magnetic field intensity of 10,000 A / m B100
Was measured.

Table 3 shows the results of measuring the magnetic flux density of each sample and the ratio of the strain rate of the final stand at the sample collection position to the maximum value of the strain rate. From Table 3, it can be seen that by suppressing the variation in the strain rate during hot rolling, it is possible to obtain a grain-oriented electrical steel sheet with little variation in the magnetic properties in the coil longitudinal direction.

[0042]

[Table 3]

Example 2 The components shown in Table 4 were contained and the balance F
After heating the slab consisting of e and inevitable impurities, a 70 mm thick sheet bar was formed by a rough rolling mill. Thereafter, the sheet bar was formed into a hot-rolled sheet having a thickness of 2.50 mm by a finishing mill. In this example, finish rolling was performed using a single sheet bar in both the present invention example and the comparative example, and continuous finishing hot rolling by joining the sheet bars was not performed.

[0044]

[Table 4]

At this time, as an example of the present invention, the sheet bar was subjected to the finish hot rolling while suppressing the fluctuation of the strain rate during the finish hot rolling according to the formula (1). The maximum strain rate at the final stand of the finish hot rolling was 375 s ^-1 . The pass schedule was constant during rolling.

In the comparative material, the pass schedule was the same as that of the example of the present invention, and was constant during the hot rolling. However, in order to stabilize the bite of the sheet bar, the strain rate of the final stand was set to 255 s ^-1 at the start of the finish rolling. performs finishing hot rolling at 375S ^-1 in a steady state and then accelerated, the strain rate of the sheet bar rearmost portion was 296s ^-1. The hot-rolling finishing temperature was 900 ° C., water-cooled and wound at 550 ° C.

The obtained hot-rolled sheet was subjected to hot-rolled sheet annealing at 825 ° C. for 2 minutes, then pickled, cold-rolled to 0.40 mm by rolling at a cold rolling rate of 84.0%, and then at 830 ° C. for 5 minutes. The decarburization annealing was performed in a wet hydrogen atmosphere. Thereafter, finish annealing at 890 ° C. × 10 hours was performed.

From this, an Epstein sample was cut out and its magnetic properties were measured. The Epstein sample was a T sample taken at a position 100 m from the end of the coil corresponding to the tip of one sheet bar, an M sample measured at the center of the coil in the longitudinal direction, and a M sample at a position 100 m from the end of hot rolling. The sample was taken as a B sample, which was sampled from an intermediate sheet bar in the present invention, and from each part of one sheet bar in the comparative example.

Table 5 shows the results of measuring the magnetic flux density of each sample and the ratio of the strain rate to the maximum value of the strain at the final stand at the sample collection position. As described above, by suppressing the variation in the strain rate during the hot rolling in the finish, it is possible to obtain a grain-oriented electrical steel sheet with little variation in the magnetic properties in the coil longitudinal direction.

[0050]

[Table 5]

Example 3 The components shown in Table 6 were contained and the balance F
After heating the slab consisting of e and inevitable impurities, a 70 mm thick sheet bar was formed by a rough rolling mill. Thereafter, the sheet bar was formed into a hot-rolled sheet having a thickness of 3.00 mm by a finishing mill.

[0052]

[Table 6]

At that time, in order to suppress the variation of the strain rate during the finishing hot rolling, the sheet bar after the rough rolling was joined to the preceding sheet bar, and the finishing hot rolling was continuously performed. The maximum strain rate of the intermediate sheet bar is 3 at the final hot-rolled final stand.
Finish rolling was performed so that the strain rate of the final stand at the time of rolling did not fall below 80% of the maximum strain rate so as to be 80 s ^-1 and satisfy the formula (2). The pass schedule was constant during rolling, and rolling was performed at a final rolling stand at a rolling reduction of 20%.

The obtained hot-rolled sheet is subjected to hot-rolled sheet annealing at 825 ° C. for 2 minutes, followed by pickling and cold-rolling once to obtain a final sheet thickness, and then decarburizing annealing in a wet hydrogen atmosphere. did. Thereafter, finish annealing at 890 ° C. × 10 hours was performed.

The Epstein sample was sampled at the center of the product coil in the longitudinal direction of a single sheet bar in the middle of continuous rolling, subjected to strain relief annealing on the cut Epstein sample, and then subjected to a magnetic flux at a magnetic field strength of 10,000 A / m. Density value B100
Was measured.

Table 7 shows the relationship between the final cold rolling ratio and the magnetic properties after the finish annealing. According to Table 7, the value of the magnetic flux density B100 in a high magnetic field is 2.10 T in the range where the final cold rolling reduction exceeds 75%.
It turns out that it is high above.

[0057]

[Table 7]

Example 4 The components shown in Table 8 were contained and the balance F
After heating the slab consisting of e and the unavoidable impurities, a sheet bar having a thickness of 60 mm was formed by a rough rolling mill. Thereafter, the sheet bar was formed into a hot rolled sheet having a thickness of 1.80 mm by a finish rolling mill.

[0059]

[Table 8]

At that time, in order to suppress the fluctuation of the strain rate during the finishing hot rolling, the sheet bar after the rough rolling was joined to the preceding sheet bar, and the finishing hot rolling was continuously performed. The maximum strain rate of the intermediate sheet bar is 3 at the final hot-rolled final stand.
Finish rolling was performed so that the strain rate of the final stand at the time of rolling did not fall below 80% of the maximum strain rate so as to be 80 s ^-1 and satisfy the formula (2). The pass schedule was constant during rolling, and rolling was performed at a final rolling stand at a rolling reduction of 20%.

The obtained hot-rolled sheet is subjected to hot-rolled sheet annealing at 825 ° C. for 2 minutes, then pickled, cold-rolled once to obtain a final sheet thickness, and then decarburized annealing is performed in a wet hydrogen atmosphere. did. Thereafter, finish annealing at 890 ° C. × 10 hours was performed.

The Epstein sample was sampled at the center of the product coil in the longitudinal direction of the product coil of a single sheet bar that was continuously rolled. After the cut Epstein sample was subjected to strain relief annealing, the magnetic flux at a magnetic field strength of 10,000 A / m was obtained. Density value B100
Was measured.

Table 9 shows the relationship between the final cold rolling ratio and the magnetic properties after the finish annealing. According to Table 9, the value of the magnetic flux density B100 at a high magnetic field was 2.10 T when the final cold rolling reduction was over 75%.
It turns out that it is high above.

[0064]

[Table 9]

[0065]

As described above, according to the present invention, it is possible to manufacture a grain-oriented electrical steel sheet in which the magnetic flux density in the longitudinal direction of the coil is stable and extremely high.

[Brief description of the drawings]

FIG. 1 shows the relationship between the ratio of the strain rate at each rolling position to the maximum strain rate at the final stand at the time of finishing hot rolling and the magnetic flux density of a product.

Claims (2)

[Claims] 1. The composition according to claim 1, comprising 0.010% ≦ C ≦ 0.14%, 0.010% ≦ acid-soluble Al ≦ 0.050%, 0.0030% ≦ N ≦ 0.0150% by weight. the slab and the balance Fe and unavoidable impurities, heating, after hot rolled, by performing the above cold-rolled once to a final thickness, after the decarburization annealing, the direction of final annealing at Ac ₁ transformation point of the temperature range A hot-rolling finish under conditions satisfying the following formula (1):
A method for producing a grain-oriented electrical steel sheet having a stable and extremely high magnetic flux density in a longitudinal direction of a coil, wherein the final cold-rolling rate is more than 75%. (Equation 1) 2. A front end of a sheet bar obtained by roughly rolling a slab is joined to a rear end of a preceding sheet bar to integrate a plurality of sheet bars, and the integrated plurality of sheet bars are continuously connected. 2. The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein the magnetic flux density is stabilized and extremely high in the longitudinal direction of the coil.