JPH10280043A - Production of grain-oriented silicon steel sheet high in magnetic flux density - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a grain-oriented silicon steel sheet high in magnetic flux density and used as the material for the iron core of electrical equipment. SOLUTION: A slab contg., by weight, 0.025 to 0.075% C, 2.5 to 4.5% Si, <=0 015% S, 0.010 to 0.050% acid soluble Al, 0.0010 to 0.0120% N, 0.050 to 0.45% Mn, and the balance Fe with inevitable impurities is heated at <=1280 deg.C, is thereafter subjected to hot rolling, after hot rolled sheet annealing or without executing this, it is regulated to rolling for one time or two times including process annealing to regulate the final rolling ratio to >=80%, and next, till the start of secondary recrystallization annealing in finish annealing after the completion of decarburizing annealing, the steel sheet is subjected to nitriding treatment. 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<=long (ωt/R)+2<=4.00, and then, the coiled sheet bar is recoiled and is subjected to 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 a 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 for reducing iron loss, it is also effective to reduce the secondary recrystallized grain size.
No. 419 was proposed. 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.

However, in these methods, in order to obtain an essential or good magnetic flux density, high-temperature slab heating is required for controlling the precipitation of the inhibitor. That is,
At the time of slab heating, the precipitate constituting the inhibitor is once dissolved into a solution, which is then subjected to a hot rolling process or Japanese Patent Publication No. 46-2382.
As disclosed in Japanese Patent Publication No. 0, it is necessary to precipitate finely during annealing of a hot-rolled sheet. During this high-temperature slab heating, slag occurs and the treatment is a problem, and furthermore, component adjustment in the steel making stage and product properties are almost determined in the hot rolling stage, and adjustment of magnetic characteristics in the subsequent process And there remains a problem in the flexibility of the manufacturing process.

As a means for solving the problems of the conventional process for producing a grain-oriented electrical steel sheet by the high-temperature slab heating method, the applicants have disclosed a method disclosed in Japanese Patent Publication No. 6-86631 and others at 1280 ° C.
A method is proposed in which an inhibitor is formed by nitriding between the following low-temperature slab heating and the start of secondary recrystallization after decarburizing annealing. With this method, it becomes possible to acquire inhibitors whose properties were determined almost at the stage of the conventional steelmaking stage and hot rolling at the stage of hot rolling and were difficult to adjust in the subsequent process. In addition to being able to solve the problem, the improvement of the magnetic properties has led to a certain progress in the manufacturing method of grain-oriented electrical steel sheets.

[0013] However, the market demands for energy savings in recent years have been even more severe. For magnetic steel sheets used as iron cores to save energy consumption and contribute to environmental improvement, the magnetic flux density and iron loss have been improved. There is an increasing demand for reduction. Unlike electrical steel sheets used for rotating machines, etc., directional electrical steel sheets used for transformers and other applications are always used in an energized state.
The importance of loss reduction in terms of occupancy is very important.
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.

[0014]

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 the product in relation to the hot rolling conditions in the production of grain-oriented electrical steel sheets in the prior art. It is another object of the present invention to provide a method for producing a grain-oriented electrical steel sheet having a high magnetic flux density.

[0015]

The gist of the present invention is as follows. (1) 0.025% ≦ C ≦ 0.075% by weight,
2.5% ≦ Si ≦ 4.5% S ≦ 0.015%, 0.010% ≦ acid soluble A
l ≦ 0.050% 0.0010% ≦ N ≦ 0.0120%, 0.050%
A slab containing ≦ Mn ≦ 0.45%, the balance consisting of Fe and unavoidable impurities is heated to a temperature of 1280 ° C. or less and then hot-rolled, with or without hot-rolled sheet annealing, once or in the middle. A method for producing a grain-oriented electrical steel sheet in which a steel sheet is subjected to nitriding treatment after the completion of decarburization annealing and before the start of secondary recrystallization after finish of decarburization annealing by rolling two or more times including annealing, and then after completion of decarburizing annealing. Wherein the sheet bar obtained by roughly rolling the slab is wound so as to satisfy the following expression (1), and then the wound sheet bar is unwound and subjected to finish hot rolling. A method for manufacturing grain-oriented electrical steel sheets with high and low iron loss. 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. 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 sheet bar is continuously subjected to finish hot rolling.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In order to solve the above-mentioned problems, the present inventors have focused on the finishing hot rolling technology as a subject to be studied in the manufacturing process other than the inhibitor control technology, which was the main focus of the study in the prior art. And examined. As a result, when the sheet bar after rough rolling is wound into a coil, there is a close relationship between the parameters newly defined by the sheet bar thickness, winding speed, and winding radius and the magnetic properties of the product. In addition to simply controlling the temperature and winding radius of the sheet bar and winding the sheet bar, this parameter is appropriately controlled at the time of winding the sheet bar, making the grain-oriented electrical steel sheet with excellent magnetic properties extremely stable. It was also found that low-cost low-grade products can be manufactured by omitting hot-rolled sheet annealing.

Further, when the sheet bar once wound in a coil shape is rewound and bitten by 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 0.025%, secondary recrystallization becomes unstable and the magnetic flux density is remarkably reduced. On the other hand, if it exceeds 0.075%, the time required for decarburization annealing becomes too long, which is uneconomical.

The S content regulation is one of the differences between the conventional technology for manufacturing grain-oriented electrical steel sheets and the present invention. Because, in the present invention, (Al, Si) is mainly used as an inhibitor.
Since N is used, MnS is not particularly required and is rather detrimental to magnetic properties. Therefore, the S content is 0.015%
Or less, preferably 0.007% or less.

In the present invention, since nitriding is performed to form (Al, Si) N after the decarburizing annealing and before the start of the secondary recrystallization, free acid-soluble Al must be present in a certain amount or more. For this reason, 0.010% or more is added. On the other hand, if the acid-soluble Al content exceeds 0.050%, the secondary recrystallization becomes unstable.

N must be 0.0120% or less. If it exceeds this, blisters called blisters are generated on the surface of the steel sheet, and it becomes difficult to adjust the primary recrystallization structure. On the other hand, if the N content is less than 0.0010%, it becomes difficult to develop secondary recrystallization, so the N content is set to 0.0010% or more.

If the Mn content exceeds 0.45%, the magnetic flux density of the product is reduced, while if it is less than 0.050%, the secondary recrystallization becomes unstable, so the Mn content is 0.050% or more. It shall be less than 0.45%.

It should be noted that the inclusion of trace amounts of Sn, Cu, Cr, 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 a low temperature of 1280 ° C. or less to save heat source units, and to make the AlN in the steel into an incomplete solid solution state without completely dissolving the AlN in the steel.

The slab is hot-rolled into a hot-rolled sheet having a predetermined thickness. The following experiment was conducted in order to investigate the effect 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 200
The slab had a thickness of mm. Next, this was processed into a sheet bar by rough rolling, and then wound up in a coil shape. At that time, the test was performed by changing variously the sheet bar thickness, the sheet bar winding speed, and the sheet bar winding radius. The temperature of the sheet bar at the time of winding was kept constant at 1020 ° C.

[0027]

[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 970 ° C., cooled immediately after passing the final hot-rolling final stand, and wound at 540 ° C.

The obtained hot rolled sheet was heated at 1120 ° C. × 2 minutes + 90
A hot rolled sheet is annealed at 0 ° C. × 2 minutes, cooled in hot water at 100 ° C., then pickled, cold rolled to 0.30 mm, and then
Decarburization annealing was performed at 0 ° C. for 120 seconds. Next, nitriding treatment is performed at 750 ° C. × 3 in a hydrogen or nitrogen gas containing 1% of ammonia.
Performed for 0 seconds. 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.

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, the lower limit temperature is preferably 800 ° C. or higher. The reason is that when the winding temperature is lower than 800 ° C., the rolling reaction force when the sheet bar is unwound and the finish rolling is performed becomes too large, so that the rolling becomes impossible.
On the other hand, the upper limit of the sheet bar winding temperature is preferably 1100 ° C. or less. The reason is that if the winding temperature is 1100 or more, if it seems to exceed 1100 ° C, the rigidity of the sheet bar itself is insufficient when winding, and creep deformation occurs due to its own weight, and the shape of the sheet bar is poor. Becomes Therefore, the winding temperature of the sheet bar is preferably 800 ° C. or more and 1100 ° C. or less.

The holding time of the wound sheet bar is not particularly limited, but is preferably 5 seconds or more in order to promote the effect of improving the magnetic properties by the 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) at the time of 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. It can be guessed that this may be caused by affecting the state of precipitation of.

According to the present invention, in order to stably perform hot rolling of the unwound sheet bar, the unwound sheet bar is unwound, and 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 succeeding sheet bar, a method of joining the rear end of the preceding sheet bar and the tip of the succeeding sheet bar and welding a butt portion, or a method of joining the butt 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.

In the process after hot rolling, hot strip annealing may be performed for the purpose of controlling precipitates. After pickling, although a final sheet thickness by performing once or twice or more cold rolling sandwiching the intermediate annealing, so the final rolling rate value of the magnetic flux density B ₈ is less than 80% is reduced, cold The elongation is 80% or more. 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.

In the present invention, after the completion of the decarburizing annealing, the steel sheet is subjected to a nitriding treatment until the start of the secondary recrystallization of the finish annealing to form fine (Al, Si) N in the steel sheet. As an embodiment thereof, nitriding is performed in a gas atmosphere having a nitriding ability after soaking during decarburizing annealing, or N 2 provided separately after decarburizing annealing.
It is passed through a heat treatment furnace having an atmosphere of H ₃ or the like to be nitrided, or MnN,
An appropriate amount of CrN or the like may be blended, or a gas such as NH _{3 having a} nitriding ability may be contained in the atmosphere during the temperature rise process of the finish annealing. Further, nitriding may be performed by a combination of the above methods.

[0042]

【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 1150 ° C and then made into a sheet bar having a thickness of 60 mm by a rough rolling mill. afterwards,
This sheet bar was formed into a hot-rolled sheet having a thickness of 2.1 mm by a finishing mill. 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 1020 ° 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 960 ° C., water-cooled and wound at 550 ° C.

[0043]

[Table 2]

The obtained hot rolled sheet was heated at 1120 ° C. × 2 minutes + 90
Anneal hot rolled sheet for 2 minutes at 0 ° C, and then pickle 0.23
Then, the steel sheet was cold-rolled to 830 mm, and then subjected to decarburization annealing at 830 ° C. for 90 seconds in a wet hydrogen and nitrogen atmosphere having a dew point of 58 ° C. Next, nitriding treatment was performed in an ammonia-containing atmosphere. Thereafter, an annealing separator containing MgO as a main component was applied, and finish annealing was performed at 1200 ° C. for 20 hours. After removing the annealing separator, the obtained coil was subjected to flattening annealing, and a tension film was baked to obtain a product.

Table 3 shows the relationship between the sheet bar take-up parameters during 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.

[0046]

[Table 3]

Example 2 The components shown in Table 4 were contained and the balance F
slab consisting of e and unavoidable impurities
After heating to 0 ° C., a sheet bar having a thickness of 65 mm was formed by a rough rolling mill. Thereafter, the sheet bar was subjected to 2.3 by a finishing mill.
A hot-rolled sheet having a thickness of mm was used. At this time, this sheet bar
Winding was performed with various values of g (ωt / R) +2, and the relationship with the magnetic properties was examined. The temperature of the sheet bar at the time of winding was 1030 ° C., and after the lapse of 60 seconds, the sheet bar after winding was wound back into 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 970
° C, cooled with water and wound at 550 ° C.

[0048]

[Table 4]

The obtained hot rolled sheet was subjected to hot rolled sheet annealing at 1120 ° C. × 2 minutes 30 seconds + 900 ° C. × 2 minutes, then pickled, cold rolled to 0.30 mm, and then decarbonized at 830 ° C. for 120 seconds. Annealing was performed. Next, nitriding treatment was performed in an ammonia-containing atmosphere. Thereafter, an annealing separator containing MgO as a main component was applied, and finish annealing was performed at 1200 ° C. for 20 hours. After removing the annealing separator, the obtained coil was subjected to flattening annealing, and a tension film was baked to obtain a product.

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.

[0051]

[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 sheet bar having a thickness of 65 mm was formed by a rough rolling mill. Thereafter, the sheet bar was subjected to 2.3 by a finishing mill.
A hot rolled sheet having a thickness of mm was used. At this time, this sheet bar
Winding was performed with various values of g (ωt / R) +2, and the relationship with the magnetic properties was examined. The temperature of the sheet bar at the time of winding was 1030 ° C., and after the lapse of 60 seconds, the sheet bar after winding was wound back into 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 970
° C, cooled with water and wound at 550 ° C.

[0053]

[Table 6]

The obtained hot rolled sheet was subjected to hot rolled sheet annealing at 1120 ° C. × 2 minutes 30 seconds + 900 ° C. × 2 minutes, then pickled, cold rolled to 0.30 mm, and then decarbonized at 830 ° C. for 120 seconds. Annealing was performed. Next, a nitriding treatment was performed in an atmosphere containing ammonia. Thereafter, an annealing separator containing MgO as a main component was applied, and finish annealing was performed at 1200 ° C. for 20 hours.
After removing the annealing separator, the obtained coil was subjected to flattening annealing, and a tension film was baked to obtain a product.

Table 7 shows the relationship between sheet bar winding parameters during hot rolling and 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.

[0056]

[Table 7]

Example 4 The components shown in Table 8 were contained and the balance F
slab consisting of e and unavoidable impurities
After heating to 0 ° C., a sheet bar having a thickness of 65 mm was formed by a rough rolling mill. Thereafter, the sheet bar is subjected to 2.
A hot-rolled sheet having a thickness of 3 mm was obtained. At this time, this sheet bar
Winding was performed while changing the value of log (ωt / R) +2 variously, and the relationship with the magnetic properties was examined. The temperature of the sheet bar at the time of winding was 1040 ° C., and after 80 seconds, the sheet bar after winding was rolled back into 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 970
° C, cooled with water and wound at 550 ° C.

[0058]

[Table 8]

The obtained hot rolled sheet was pickled, cold rolled to 0.30 mm by a tandem rolling mill, and then decarburized at 830 ° C. for 120 seconds. Next, a nitriding treatment was performed in an atmosphere containing ammonia. Thereafter, an annealing separator containing MgO as a main component was applied, and finish annealing was performed at 1200 ° C. for 20 hours.
After removing the annealing separator, the obtained coil was subjected to flattening annealing, and a tension film was baked to obtain a product.

Table 9 shows the relationship between the sheet bar winding parameters at the time of finish hot rolling and the magnetic properties after finish annealing. Table 9
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.

[0061]

[Table 9]

[0062]

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 (72) Inventor Yoshiyuki Ushigami 20-1 Shintomi, Futtsu City, Chiba Prefecture Nippon Steel Corporation Technology Development Division

Claims (2)

[Claims] 1. In% by weight, 0.025% ≦ C ≦ 0.075%, 2.5% ≦ Si ≦ 4.5%, S ≦ 0.015%, 0.010% ≦ acid-soluble Al ≦ 0 0.050%, 0.0010% ≦ N ≦ 0.0120%, 0.050% ≦ Mn ≦ 0.45%, with the balance Fe
The slab composed of unavoidable impurities is heated to a temperature of 1280 ° C. or lower and then hot-rolled, and is subjected to hot-rolled sheet annealing or not. % And then after the completion of decarburizing annealing, a sheet bar obtained by roughly rolling a slab in a method for producing a grain-oriented electrical steel sheet in which a steel sheet is subjected to nitriding treatment until the start of secondary recrystallization of finish annealing. And then subjecting the rolled sheet bar to rewinding and subjecting it to hot rolling for finishing, thereby producing a grain-oriented electrical steel sheet having a high magnetic flux density and a low iron loss. . 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.