JPH10306319A - Manufacturing method of grain-oriented electrical steel sheet with extremely high magnetic flux density - Google Patents

Abstract

(57) [Problem] To provide a method for manufacturing a grain-oriented electrical steel sheet having an extremely high magnetic flux density. SOLUTION: In weight%, 0.010% ≦ C ≦ 0.14%, 0.010%
A slab containing ≦ acid-soluble Al ≦ 0.050%, 0.0030% ≦ N ≦ 0.0150%, with the balance being Fe and unavoidable impurities, after heating and hot rolling, including final cold rolling with a draft of 50 to 75% 1
Cold rolling more than once to final thickness, decarburization annealing, and then Ac
_{In a} method for producing a grain-oriented electrical steel sheet that is finally annealed in a temperature range of not more than _one transformation point, a sheet bar obtained by roughly rolling a slab is wound so as to satisfy the following formula (1), and then the wound sheet is wound. A method for producing a grain-oriented electrical steel sheet having an extremely high magnetic flux density, wherein the 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 thickness, R (mm): winding 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 an extremely high magnetic flux density.

[0002]

2. Description of the Related Art A grain-oriented electrical steel sheet is characterized in that the grain of the steel sheet is highly oriented in a specific direction by secondary recrystallization. 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, the prior art uses MnS, Al
N, MnSe and the like have been used as inhibitors.

[0006] 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. Littlem
There is a manufacturing method disclosed by Ann 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, 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. 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 Mn disclosed in JP-B-51-13469 by Imanaka and others.
This is a method in which S, MnSe, and Sb are used and are manufactured by a double cold rolling method.

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 temporarily 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.

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 a method for producing 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.

In order to meet such demands of customers for the development of grain-oriented electrical steel sheets having a higher magnetic flux density, the inventors have conducted intensive studies to develop a process for producing grain-oriented electrical steel sheets having a high magnetic flux density. .

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a grain-oriented electrical steel sheet having an extremely high magnetic flux density in response to such a recent market demand.

[0012]

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 After heating and hot rolling the slab composed of unavoidable impurities, the slab is subjected to at least one cold rolling including a final cold rolling with a reduction ratio of 50 to 75% to a final sheet thickness. After decarburizing annealing, Ac ₁ In a method for producing a grain-oriented electrical steel sheet that is finally annealed in a temperature range below the transformation point, a sheet bar obtained by roughly rolling a slab is wound so as to satisfy the following formula (1), and then the wound sheet bar is obtained. And producing a grain-oriented electrical steel sheet having an extremely high magnetic flux density. 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 portion of the sheet bar is joined to the rear end portion of the preceding sheet bar to integrate the plurality of sheet bars, and the integrated plurality of sheets are provided. 2. The method for producing a grain-oriented electrical steel sheet having an extremely high magnetic flux density according to claim 1, wherein the bar is continuously subjected to finish hot rolling.

In order to solve the above-mentioned problems, the present inventors have focused on the hot-rolling finishing technique as an integral part of the inhibitor control technique which has been the focus of the study in the prior art. 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, 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 has been found that it is possible to manufacture it.

Further, when the sheet bar once wound into 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. If the content of C is less than 0.010%, the secondary recrystallization becomes unstable and the magnetic flux density is remarkably reduced. On the other hand, 0.1
If it exceeds 4%, 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 influence of the winding conditions of the sheet bar after the rough rolling on the magnetic properties of the product. Steel having the components shown in Table 1 and the balance consisting of Fe and unavoidable impurities was melted and made into a slab having a thickness of 200 mm by a continuous caster. Next, this was processed into a sheet bar by rough rolling, and then wound into a coil shape. The temperature of the sheet bar at the time of winding was 1000 ° C.

[0021]

[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 termination temperature was 900 ° C., and after passing through the final hot-rolling final stand, it was cooled and wound at 550 ° C.

The obtained hot rolled sheet was subjected to hot rolling annealing at 825 ° C. for 2 minutes, followed by pickling and cold rolling of 56% to 1.1 mm. This was subjected to decarburizing annealing at 830 ° C. in a wet hydrogen atmosphere. Thereafter, the final cold rolling rate was reduced to 63.6% by rolling at 0.4%.
The sample was cold-rolled to a thickness of 0 mm, and then decarburization annealing was performed at 830 ° C. for 5 minutes 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 1000.
The value B100 of the magnetic flux density at 0 A / m was measured.

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
(Mm): 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. According to the experimental results, in the present invention, the condition for winding the sheet bar is 1.20 ≦ log (ωt / R) +2
And On the other hand, if 4.00 <log (ωt / R) +2, the winding speed or the thickness of the sheet bar becomes excessively large, and the edge of the sheet bar is easily cracked during winding, so that log (ωt / R) +2. ≦ 4.00.

Although the holding time of the wound sheet bar is not particularly specified, it 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 parameter 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, precipitation of AlN in the hot-rolled steel sheet is not clear. It can be guessed that the cause is to affect the state.

Further, when the rolled sheet bar is unwound and subjected to the finishing hot rolling, the rolled sheet bar may meander at the entrance of the finishing hot rolling machine to stop rolling. As a method for solving this problem, it is particularly effective to join the sheet bar to the preceding sheet bar and continuously perform finish hot rolling.

Here, as a method of joining the preceding sheet bar and the succeeding sheet bar, a method of welding the butting portion with the rear end of the preceding sheet bar and the leading end of the succeeding 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.

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 is 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.

In the process after the hot rolling, the hot rolled sheet may be annealed 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. Here, in order to obtain a high magnetic flux density, control of the final cold rolling reduction is important. That is, it needs to be 50 to 75% or less. If the final cold rolling reduction is out of this range, the ultra-high magnetic flux density aimed at by the present invention cannot be obtained, so the final cold rolling reduction is set to 50% or more and 75% or less.

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.

[0034]

【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 2.5 mm by a finishing mill.

[0035]

[Table 2]

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 1000 ° 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 bite the unwound sheet bar into the finishing hot rolling machine, the sheet bar after the rough rolling was joined to the preceding sheet bar, and the finishing hot rolling was continuously performed. At this time, the hot-rolling finishing temperature was 900 ° 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 825 ° C. for 2 minutes, followed by pickling and cold-rolling at 56% to finish to a thickness of 1.1 mm. This was subjected to decarburizing annealing at 830 ° C. in a wet hydrogen atmosphere. Thereafter, the final cold rolling rate was reduced to 63.6% by rolling to 0.40.
After cold rolling to a thickness of mm, decarburizing annealing at 830 ° C. for 5 minutes was performed in a wet hydrogen atmosphere. Thereafter, finish annealing at 890 ° C. × 10 hours was performed.

After the strained Epstein sample was subjected to strain relief annealing, the value B100 of the magnetic flux density at a magnetic field intensity of 10,000 A / m was measured.

Table 3 shows the relationship between the value of log (ωt / R) +2 and the magnetic properties after finish annealing. From Table 3, log
It can be seen that the magnetic flux density is high when the value of (ωt / R) +2 is 1.20 or more.

[0039]

[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 2.8 mm by a finishing mill.

[0041]

[Table 4]

At this time, the sheet bar is changed to log (ωt /
R) +2 was wound in a range of 1.50 to 3.50. The temperature of the sheet bar at the time of winding was 1000 ° C., and after 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 bite the unwound sheet bar into the finishing hot rolling machine, the sheet bar after the rough rolling was joined to the preceding sheet bar, and the finishing hot rolling was continuously performed. At this time, the hot-rolling finishing temperature was 900 ° C., and the film was cooled with water and wound at 550 ° C.

The resulting hot-rolled sheet was subjected to decarburizing annealing in a wet hydrogen atmosphere at 830 ° C. Thereafter, the final cold-rolling rate was changed to a finished plate thickness, and then decarburization annealing was performed in a wet hydrogen atmosphere. Thereafter, finish annealing at 890 ° C. × 10 hours was performed.

An Epstein sample was taken at the center of the product coil in the longitudinal direction corresponding to one sheet bar in the middle of continuously rolled, and after the cut Epstein sample was subjected to strain relief annealing, the magnetic field strength was 10,000 A / m2. The value of the magnetic flux density B100 was measured.

Table 5 shows the relationship between the final cold rolling ratio and the magnetic properties after the finish annealing. From Table 5, the final cold rolling rate is 50% or more and 7
It can be seen that the value of the magnetic flux density B100 in a high magnetic field is as high as 2.10 T or more in the range of 5 or less.

[0046]

[Table 5]

[0047]

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

[Brief description of the drawings]

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

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. After heating and hot-rolling the slab comprising the balance of Fe and unavoidable impurities, the slab is subjected to one or more cold-rollings including a final cold-rolling with a draft of 50 to 75% to a final sheet thickness, and after decarburization annealing, In a method for producing a grain-oriented electrical steel sheet that is finally annealed in a temperature range below the Ac ₁ transformation point, a sheet bar obtained by roughly rolling a slab is wound up so as to satisfy the following formula (1), and then wound up. A method for producing a grain-oriented electrical steel sheet having an extremely high magnetic flux density, wherein the 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. The method for producing a grain-oriented electrical steel sheet having an extremely high magnetic flux density according to claim 1, wherein the steel sheet is continuously subjected to finish hot rolling.