JPH10280039A - Production of grain-oriented silicon steel sheet high in magnetic flux density and low in core loss - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a grain-oriented silicon steel sheet high in magnetic flux density, low in core loss and used as the material for the iron core of electrical equipment. SOLUTION: This is a method for producing a grain-oriented silicon steel sheet in which a slab contg., by weight, 0.035 to 0.10% C, 2.5 to 4.5% Si, 0.010 to 0.040% S, 0.010 to 0.050% sol-Al, 0.0030 to 0.0150% N, 0.020 to 0.40%. Mn, and the balance Fe with inevitable impurities is heated to >=1280 deg.C, is thereafter subjected to hot rolling, is subjected to hot rolled sheet annealing before cold rolling, is cooled, is subjected rolling for one time or >= two times including process annealing so as to regulate the final rolling ratio to >=80%, is then subjected to decarburizing annealing, is coated with a separation agent for annealing and is subjected to secondary recrystallization and purification by finish annealing. In this case, the sheet bar obtd. by subjecting the slab to rough rolling is coiled so as to satisfy the inequality of 1.20<=log (ωt/R)+2<=4.00, and the coiled sheet bar is recoiled and is subjected to the finish hot rolling, where ω (rpm) denotes the rotational speed in the coiling of the sheet bar, t (mm) denotes the sheet thickness of the sheet bar, and R (mm) denotes the coiling radius.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet having a high magnetic flux density, which is used as an iron core material of electric equipment.

[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.

As an attempt to reduce iron loss by controlling these factors, in order to increase the electric resistance of
Increasing the i content has been performed, but increasing the Si content is accompanied by the problem that the secondary recrystallization becomes unstable, and the workability of the manufacturing process and products is degraded. Is the current situation.

On the other hand, the purity and internal strain of a steel sheet have been studied in the manufacturing process, and the reduction of iron loss due to these reductions has reached the limit. Attempts have been made to reduce eddy current loss by reducing the thickness of the sheet, but from the standpoint of manufacturing, there is a problem in that secondary recrystallization is difficult to control as the thickness is reduced. On the other hand, on the consumer side, thicker materials are preferred and used as long as the iron loss values are equal, since the cost of transformer production increases.

As a means of reducing iron loss, it is also effective to reduce the secondary recrystallized grain size.
No. 7-9419. However, when the secondary recrystallized grain size is small, there is a problem that the degree of orientation integration is reduced and it is difficult to obtain a high magnetic flux density.

[0007] Between the effect of the film tension and the magnetic flux density of the grain-oriented electrical steel sheet, J. Appl. Phys., Vol. 41, no. 7, p2981-2984 (19)
As pointed out in 70), it is known that the iron loss reducing effect as the value of the magnetic flux density B ₈ is high is large. A method for reducing iron loss by magnetic domain refining is disclosed in Japanese Patent Application Laid-Open No. 58-5968.
As described in JP-A-58-26405, it is known that the effect is greater as the magnetic flux density of the plane material before the magnetic domain refining process is higher.

Attempts to reduce iron loss in this way include electrical resistivity, sheet thickness, grain size,
Since the improvement of purity, internal strain, etc. is approaching the limit in the conventional technology, by improving the degree of integration of the secondary recrystallization orientation and increasing the magnetic flux density, the effect of the film tension and the effect of domain segmentation can be improved. It has become important to reduce iron loss by further improving.

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.

[0010] Conventional methods for manufacturing 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, it is disclosed by MFLittmann in Japanese Patent Publication No. 30-3651. This production method is characterized in that MnS is used as an inhibitor and the production is performed by a double cold rolling method. Next, Tokiko 40-15
No. 644, MnS disclosed by Taguchi, Sakakura et al.
In addition to this, a production method using AlN as an inhibitor.
By using AlN for the inhibitor, the magnetic flux density of the grain-oriented electrical steel sheet was improved to 1.870 T or more, and the magnetic properties were improved to greatly contribute to energy saving. Third, MnS and Sb or MnS, MnSe disclosed in Ichinaka et al. In Japanese Patent Publication No. 51-13469.
This is a method of manufacturing by cold rolling twice using Sb and Sb.

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 in a solution 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 the grain-oriented electrical steel sheet, 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 the hot rolling conditions of the grain-oriented electrical steel sheet still has a large effect on the magnetic properties of the product, leaving a problem in the stability of the hot rolling conditions.

[0013] Furthermore, there are more severe market demands for energy savings in recent years. For an electromagnetic steel sheet used as an iron core to save energy consumption and contribute to environmental improvement, an improvement in magnetic flux density and iron loss are required. There is an increasing demand for reduction.

Unlike electromagnetic steel sheets used for rotating machines,
Since the grain-oriented electrical steel sheets used for transformers and the like are always used in an energized state, it is very important to reduce the loss in view of the operation rate. For this reason, the energy saving effect by the improvement of the magnetic properties is very large, and the customer has been required to supply a product having a higher magnetic flux density to increase the efficiency of the iron core while suppressing the cost as much as possible.

The present inventors have developed a technique for reducing the influence of the hot rolling conditions of the grain-oriented electrical steel sheet by the high-temperature slab heating on the magnetic properties of the product and stably producing the grain-oriented electrical steel sheet. For the purpose, the hot rolling process was studied.

Further, the present inventors have developed a high magnetic flux density grain-oriented electrical steel sheet in order to meet the severe demands of consumers for energy saving in recent years, and to overcome the limitations of the low iron loss attainment technology which is in a dead end with the improvement by the prior art. We worked diligently to develop the manufacturing process.

[0017]

SUMMARY OF THE INVENTION The present invention meets the demands of the market in recent years and solves the problem of the stability of the magnetic properties of a product to the hot rolling conditions in the production of grain-oriented electrical steel sheets by high-temperature slab heating in the prior art. It is an object of the present invention to provide a method of manufacturing a grain-oriented electrical steel sheet having a higher magnetic flux density while solving the problems.

[0018]

The gist of the present invention is as follows. (1) 0.035% ≦ C ≦ 0.1% by weight
0%, 2.5% ≦ Si ≦ 4.5%,
0.010% ≦ S ≦ 0.040%, 0.010
% ≦ sol-Al ≦ 0.05%, 0.0030% ≦ N
≦ 0.0150%, 0.020% ≦ Mn ≦
A slab containing 0.40%, with the balance being Fe and unavoidable impurities, is heated to a temperature of 1280 ° C. or higher, hot-rolled, subjected to hot-rolled sheet annealing and cooled before cold rolling, and once or intermediately. A final rolling reduction of 80 by rolling two or more times with annealing
% Or more, then decarburizing annealing, applying an annealing separator, and performing a secondary recrystallization and purification by finish annealing in a method for producing a grain-oriented electrical steel sheet. 1) A method for producing a grain-oriented electrical steel sheet having a high magnetic flux density and a low iron loss, wherein the grain is wound so as to satisfy formula (1) and then subjected to finish hot rolling. 1.20 ≦ log (ωt / R) + 2 ≦ 4.00 (1) where ω (rpm): rotation speed of sheet bar winding t (mm): sheet bar thickness R (mm) : Winding radius

(2) After unwinding the wound sheet bar, the front end of the sheet bar is joined to the rear end of the preceding sheet bar to integrate a plurality of sheet bars, and the integrated plurality of sheets are provided. The method for producing a grain-oriented electrical steel sheet having a high magnetic flux density and a low iron loss according to the above (1), wherein the bars are continuously subjected to finish hot rolling.

In order to solve the above-mentioned problems, the present inventors have focused on the finishing hot-rolling technology as a research problem in the manufacturing process other than the inhibitor control technology, which has been the focus of the conventional technology. went. As a result, in a manufacturing process in which the sheet bar obtained by roughly rolling the slab is wound, and then the wound sheet bar is unwound and subjected to finish hot rolling, when the sheet bar is wound in a coil shape, We found that there was a close relationship between the parameters newly defined by the sheet thickness, winding speed and winding radius and the magnetic properties of the product, and simply controlled the sheet bar by controlling the temperature and winding radius. It has been found that by appropriately controlling these parameters during the winding of the sheet bar, it is possible to manufacture a grain-oriented electrical steel sheet having excellent magnetic properties in a very stable manner.

Further, when the sheet bar once wound in a coil shape is rewound and bitten into the finishing hot rolling machine, the sheet bar is likely to meander. In order to prevent the meandering of the sheet bar and stably perform the hot rolling having the sheet bar winding step as in the present invention, after unwinding the sheet bar, the sheet bar is joined to the preceding sheet bar. It is effective to continuously provide a plurality of sheet bars for finish hot rolling.

Hereinafter, the present invention will be described in detail. First, the components will be described. The Si content greatly affects the iron loss characteristics via the specific resistance of the magnetic steel sheet. However, if it is less than 2.5%, the specific resistance is small and the eddy current loss is undesirably increased. On the other hand, if it exceeds 4.5%, the workability deteriorates,
Product processing becomes difficult, which is not preferable.

When the content of C is less than 0.035%, secondary recrystallization becomes unstable and the magnetic flux density is remarkably reduced. On the other hand, if it exceeds 0.10%, the time required for decarburization annealing becomes too long and is uneconomical, so it is set to 0.10% or less.

If the content of S is less than 0.010%, the amount of inhibitor deposited becomes insufficient and secondary recrystallization becomes unstable, so the content of S is set to 0.010% or more. On the other hand, if the content exceeds 0.040%, the precipitates are excessively coarsened, the inhibitor effect is impaired, and the magnetic flux density decreases.
0.040% or less.

Sol.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 decreases.
50% or less.

N needs to be not less than 0.0030% and not more than 0.0150%. If it exceeds this, blisters called blisters are generated 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%, it becomes difficult to develop secondary recrystallization, so the N content is 0.0030%.
Above.

If the Mn content exceeds 0.40%, the magnetic flux density of the product is reduced, while if it is less than 0.020%, the secondary recrystallization becomes unstable, so the Mn content is 0.020% or more. 0.40% or less.

It should be noted that the inclusion of trace amounts of Sn, Cu, P, and Ti in steel for stabilization of secondary recrystallization and other purposes does not impair the effects of the present invention.

Next, the process of the present invention will be described. The electromagnetic steel slab is obtained by smelting 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 slab rolling after ingot making.

Thereafter, slab heating is performed prior to hot rolling. In the process of the present invention, the heating temperature of the slab is set to 1280 ° C. or more, and the main inhibitor Mn is used.
It is important to re-dissolve S and AlN in steel. This slab is hot-rolled into a hot-rolled sheet having a predetermined thickness.

The following experiment was conducted in order to investigate the influence of the winding conditions of the sheet bar after the rough rolling on the magnetic properties of the product. A steel having the composition shown in Table 1 was melted, and 20
The slab was 0 mm thick. Next, this was processed into a sheet bar by rough rolling, and the sheet bar was wound into a coil shape. At that time, sheet bar thickness, sheet bar winding speed,
The test was performed with variously changed sheet bar winding radii. The temperature of the sheet bar at the time of winding was kept constant at 1180 ° C.

[0032]

[Table 1]

The wound sheet bar is rewound again, and the leading end of the sheet bar is joined to the trailing end of the preceding sheet bar to integrate the plurality of sheet bars. The sample was continuously subjected to hot rolling. The hot-rolling end temperature was 1070 ° C., the sheet was cooled immediately after passing through the final hot-rolling final stand, and was wound at 570 ° C.

The obtained hot-rolled sheet was subjected to hot-rolled sheet annealing at 1100 ° C. × 2 minutes 30 seconds, cooled in hot water at 100 ° C., then pickled, cold rolled to 0.30 mm, and then heated at 830 ° C. A second decarburization annealing was performed. Thereafter, an annealing separator containing MgO as a main component was applied, and finish annealing was performed at 1200 ° C. for 20 hours.

Parameters calculated from the magnetic flux density of the product obtained as described above and the sheet bar winding conditions:
FIG. 1 shows the relationship with log (ωt / R) +2. here,
ω (rpm): rotation speed of sheet bar winding, t (m
m): Sheet bar thickness, R (mm): Winding radius.

The winding radius R (mm) refers to the distance between the center of the sheet bar winder and the center of the sheet bar thickness. That is, the inner diameter of the wound sheet bar is r
(Mm) and the thickness of the sheet bar is t (mm), R = r
+ T / 2. In the case where the winding speed of the sheet bar changes during winding, the above parameters are calculated using the winding speed at the time when the sheet bar starts to be wound into a coil with a radius R.

FIG. 1 shows that the magnetic properties of the product are improved by winding the sheet bar after the completion of the rough rolling under specific conditions. That is, from the experimental results, in the present invention, the condition for winding the sheet bar is 1.20 ≦ log (ωt /
R) +2. On the other hand, 4.00 <log (ωt / R) +
If it is set to 2, the winding speed or the sheet bar thickness becomes excessive, and the sheet bar is easily cracked at the time of winding, so that log (ωt / R) + 2 ≦ 4.00.

Although the winding temperature of the sheet bar is not specified, it is preferably from 950 ° C. to 1250 ° C. The reason is that if the winding temperature is lower than 950 ° C., M
This is because an appropriate precipitation state of the inhibitors of nS and AlN cannot be obtained, the formation of secondary recrystallized grains of the product is inhibited, fine grains are formed, or the secondary recrystallization orientation is liable to be significantly deteriorated. If the temperature exceeds ℃, the rigidity of the sheet bar itself will be insufficient when it is wound up, and creep deformation will occur due to its own weight, and the shape of the sheet bar will be poor. For this reason, the winding temperature of the sheet bar is 950 ° C. or more and 1250
C. or less is preferred.

Although the holding time of the wound sheet bar is not particularly limited, it is preferably 5 seconds or more in order to promote the effect of improving the magnetic properties by winding.
Conversely, if the holding time exceeds 2 hours, an oxide is formed on the surface of the wound sheet bar, and the temperature distribution becomes uneven, so that the magnetic properties in the longitudinal direction of the coil become unstable. The following is preferred. A more preferable sheet bar winding time is 30 seconds or more and 10 minutes or less from the viewpoint of productivity.

Although the detailed reason why controlling the parameters defined by the equation (1) when winding the sheet bar brings about the effect of improving the magnetic flux density of the present invention is not clear, MnS and AlN in the hot-rolled steel sheet are not clear. Changes the precipitation state of
As a result, it can be inferred that the cause is that the orientation selectivity as a nucleus of the secondary recrystallized grains is improved.

In the process after hot rolling, hot strip annealing may be performed for the purpose of controlling precipitates. After the pickling, the final thickness is obtained by cold rolling once or twice or more including intermediate annealing. Since the final cold rolling rate can not be obtained is the high magnetic flux density B ₈ in less than 80%, the final cold rolling rate of 80%
Above. Although the properties are slightly inferior, the hot rolled sheet annealing may be omitted for cost reduction. In order to reduce the crystal grain size of the final product and reduce iron loss, the final thickness may be obtained by performing rolling twice or more including intermediate annealing.

Next, decarburizing annealing is performed in wet hydrogen or a mixed gas of wet hydrogen and nitrogen. The temperature at this time is not particularly defined in the present invention, but is preferably from 800 ° C to 900 ° C.

Next, an annealing separator is applied and finish annealing is performed, and secondary recrystallization and subsequent purification are performed. For this reason, the annealing temperature is usually set to a high temperature of 1100 ° C to 1200 ° C. The purification annealing after the completion of the secondary recrystallization is performed in a hydrogen atmosphere.

According to the present invention, in order to stably perform the finishing hot rolling of the unwound sheet bar, after the unwound sheet bar is unwound, the leading end of the sheet bar is moved to the rear end of the preceding sheet bar. And a plurality of sheet bars may be integrated, and the integrated plurality of sheet bars may be continuously subjected to finish hot rolling.

Here, as a method of joining the preceding sheet bar and the following sheet bar, a method of welding the butting portion with the rear end portion of the preceding sheet bar and the tip of the following sheet bar, or a method of welding the butting portion is used. Pressing by applying pressing force,
There is a method of welding the butt portion and then pressing the butt portion. Also,
The 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.

[0046]

【Example】

Example 1 An electromagnetic steel slab containing the components shown in Table 2 and consisting of the balance Fe and unavoidable impurities was heated to 1320 ° C., and then formed into a 70 mm-thick sheet bar by a rough rolling mill. afterwards,
The sheet bar was formed into a hot-rolled sheet having a thickness of 2.2 mm by a finishing hot-rolling machine. At this time, the sheet bar is changed to log (ωt /
R) +2 was wound with various values, and the relationship with the magnetic properties was examined. The temperature of the sheet bar during winding is 1210 ° C
After elapse of 60 seconds, the sheet bar after winding was returned to a plate shape and subjected to finish hot rolling. At this time, in order to stably finish hot roll the sheet bar, the unwound sheet bar was welded to the preceding sheet bar, and finish hot rolling was continuously performed. At this time, the hot-rolling finishing temperature was 1060 ° C., and the film was cooled with water and wound at 570 ° C.

[0047]

[Table 2]

The obtained hot rolled sheet was annealed at 1100 ° C. for 2 minutes, cooled in hot water at 100 ° C., then pickled, cold rolled to 0.23 mm, and then heated at 830 ° C. for 90 seconds. The decarburization annealing was performed in a wet hydrogen and nitrogen atmosphere at a dew point of 50 ° C. After that, an annealing separator mixed with TiO ₂ is applied to MgO,
Finish annealing was performed at 1200 ° C. for 20 hours.

Table 3 shows the relationship between the sheet bar winding parameters at the time of finish hot rolling and the magnetic properties after finish annealing. Table 3
Thus, the value of the parameter defined by equation (1) is 1.2
It can be seen that the magnetic flux density increases when the value is 0 or more.

[0050]

[Table 3]

Example 2 The components shown in Table 4 were contained and the balance F
133 and the electromagnetic steel slab consisting of unavoidable impurities
After heating to 0 ° C., a sheet bar having a thickness of 75 mm was formed by a rough rolling mill. Thereafter, the sheet bar was subjected to 2.3 by a finishing hot rolling machine.
A hot rolled sheet having a thickness of mm was used.

[0052]

[Table 4]

At this time, the sheet bar is changed to log (ωt /
R) +2 was wound with various values, and the relationship with the magnetic properties was examined. The temperature of the sheet bar during winding is 1230 ° C
After elapse of 60 seconds, the sheet bar after winding was returned to a plate shape and subjected to finish hot rolling. At this time, in order to stably finish hot roll the sheet bar, the unwound sheet bar was welded to the preceding sheet bar, and finish hot rolling was continuously performed. At this time, the hot-rolling finishing temperature was set to 1070 ° C, and the film was cooled with water and wound at 550 ° C.

The obtained hot rolled sheet was subjected to hot rolled sheet annealing at 1100 ° C. × 2 and a half minutes, cooled in hot water at 100 ° C., then pickled, cold rolled to 0.30 mm, and then at 830 ° C. for 120 seconds. Was carried out in a wet hydrogen and nitrogen atmosphere at a dew point of 50 ° C. Thereafter, an annealing separator in which TiO ₂ was mixed into MgO was applied, and finish annealing was performed at 1200 ° C. for 20 hours.

Table 5 shows the relationship between the sheet bar winding parameters at the time of finish hot rolling and the magnetic properties after finish annealing. Table 5
Thus, the value of the parameter defined by equation (1) is 1.2
It can be seen that the magnetic flux density is higher when the value is 0 or more.

[0056]

[Table 5]

Example 3 The components shown in Table 6 were contained and the balance F
slab consisting of e and unavoidable impurities
After heating to 0 ° C., a 70 mm-thick sheet bar was formed by a rough rolling mill. Then, the sheet bar was subjected to 2.1 by a finishing hot rolling mill.
A hot-rolled sheet having a thickness of mm was used.

[0058]

[Table 6]

At this time, the sheet bar is changed to log (ωt /
R) +2 was wound with various values, and the relationship with the magnetic properties was examined. The temperature of the sheet bar during winding is 1240 ° C
After elapse of 60 seconds, the sheet bar after winding was returned to a plate shape and subjected to finish hot rolling. At this time, in order to stably finish hot roll the sheet bar, the unwound sheet bar was welded to the preceding sheet bar, and finish hot rolling was continuously performed. At this time, the hot-rolling finishing temperature was 1080 ° C., the film was cooled with water, and wound at 560 ° C.

The obtained hot-rolled sheet was subjected to hot-rolled sheet annealing at 1100 ° C. × 2 minutes, cooled in hot water at 100 ° C., then pickled, cold rolled to 0.23 mm, and then heated at 830 ° C. for 90 seconds. The decarburization annealing was performed in a wet hydrogen and nitrogen atmosphere at a dew point of 50 ° C. After that, an annealing separator mixed with TiO ₂ is applied to MgO,
Finish annealing was performed at 1200 ° C. for 20 hours.

Table 7 shows the relationship between the sheet bar winding parameters at the time of finish hot rolling and the magnetic properties after finish annealing. Table 7
Thus, the value of the parameter defined by equation (1) is 1.2
It can be seen that the magnetic flux density increases when the value is 0 or more.

[0062]

[Table 7]

[0063]

As described above, according to the present invention, it is possible to manufacture a grain-oriented electrical steel sheet having a high magnetic flux density and excellent magnetic properties.

[Brief description of the drawings]

FIG. 1 shows a relationship between a parameter value defined by Expression (1) and a magnetic flux density of a product at the time of winding a sheet bar before finish hot rolling.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shiro Tadokoro 1-1, Tobata-cho, Tobata-ku, Kitakyushu City Inside Nippon Steel Corporation Yawata Works (72) Inventor Kenichi Murakami 20-1 Shintomi, Futtsu-shi, Chiba New Nippon Steel Corporation Technology Development Division

Claims (2)

[Claims] 1.% by weight: 0.035% ≦ C ≦ 0.10%, 2.5% ≦ Si ≦ 4.5%, 0.010% ≦ S ≦ 0.040%, 0.010% ≦ A slab containing sol-Al ≦ 0.05%, 0.0030% ≦ N ≦ 0.0150%, 0.020% ≦ Mn ≦ 0.40%, and the balance of Fe and unavoidable impurities was 128
After being heated to a temperature of 0 ° C. or higher, hot rolling is performed, hot-rolled sheet annealing is performed before cold rolling, and cooling is performed, and a final rolling reduction of 80% or more is performed by one or two or more rollings including an intermediate anneal. In a method for producing a grain-oriented electrical steel sheet in which a carbon annealing treatment is applied by applying a carbon annealing annealing separator and subjecting to secondary recrystallization and purification by finish annealing, a sheet bar obtained by roughly rolling a slab satisfies the following expression (1). A method for producing a grain-oriented electrical steel sheet having a high magnetic flux density and a low iron loss, wherein the rolled sheet bar is unwound and subjected to finish hot rolling. 1.20 ≦ log (ωt / R) + 2 ≦ 4.00 (1) where, ω (rpm): rotation speed of sheet bar winding t (mm): sheet bar plate thickness R (mm) : Winding radius 2. After rewinding the wound sheet bar, the front end of the sheet bar is joined to the rear end of the preceding sheet bar to integrate the plurality of sheet bars, and the integrated plurality of sheet bars are provided. 2. The method for producing a grain-oriented electrical steel sheet having a high magnetic flux density and a low iron loss according to claim 1, wherein the steel sheet is continuously subjected to finish hot rolling.