JPH11189851A - Grain oriented silicon steel sheet with extremely high magnetic flux density, and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grain oriented silicon steel sheet having high magnetic flux density, which has saturation magnetic flux density, in high magnetic field, higher than that of products obtained by the conventional manufacturing method, and its manufacture. SOLUTION: The grain oriented silicon steel sheet has a composition consisting of, by weight, <=0.0030% C, <=0.050% acid soluble Al, <=0.0150% N, and the balance Fe with inevitable impurities and also has >=75% integration degree to <=10 deg. from [100] rolling direction of crystal. Further, in this steel sheet, B8 >=1.90T and B100 >=2.10T are satisfied, where B8 and B100 represent magnetic flux density at 800 A/m and magnetic flux density at 10,000 A/m, respectively.

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 it is a product in which crystal grains of the steel sheet are highly oriented in a specific direction by a secondary recrystallization method. It is composed of crystal grains having a so-called Goss orientation having a <100> axis.

[0003] The use of grain-oriented electrical steel sheets is mainly used as a soft magnetic material for core materials of transformers and other electrical equipment. In recent years, social demands for energy saving and resource saving have become increasingly severe. Therefore, demands for reduction of iron loss and improvement of magnetization characteristics of grain-oriented electrical steel sheets 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 iron loss characteristics, W _17/50 (iron loss per unit weight when magnetized to a magnetic flux density of 1.7 T at 50 Hz) is used.

Iron loss consists of eddy current loss and hysteresis loss. The eddy current loss is governed by factors such as the electrical resistivity of the steel sheet, the thickness of the steel sheet, the grain size, the form of magnetic domains, and the 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.

Conventionally, in order to reduce iron loss, it has been practiced to increase the Si content and increase the electrical resistance of a steel sheet. However, since the saturation magnetic flux density decreases with an increase in the Si content, 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.

[0007] 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 azimuth integration, and improving magnetic flux density. For this purpose, the prior art uses Mn
S, AlN, MnSe and the like have been used as inhibitors.

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.

The first is by MFLittmann,
No. 3651 discloses an inhibitor Mn.
This is a method of manufacturing by cold rolling twice using S. Second, a production method using AlN as an inhibitor in addition to MnS, disclosed by Taguchi and Sakakura et al. In Japanese Patent Publication No. 40-15644. By using AlN for this inhibitor, B ₈ of the grain-oriented electrical steel sheet was improved to 1.870 T or more, and the improvement of magnetic properties contributed greatly to energy saving. Third, MnS and Sb or MnS, M disclosed in Ichinaka et al. In JP-B-51-13469.
This is a method in which nSe and Sb are used and are manufactured by a double cold rolling method.

In these conventional 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.

In these conventional methods, the primary goal is to reduce iron loss, and the feature is to increase the magnetic flux density in order to achieve the goal. Because, between the effect of the film tension of the grain-oriented electrical steel sheet and the magnetic flux density, J.
Appl.Phys., As pointed out in vol.41.no.7.p2981-2984 (1970), it is known that the iron loss reducing effect as the value of the magnetic flux density B ₈ is high is large. The method of reducing iron loss by magnetic domain refining is described in JP-A-58-5968 and JP-A-58-26405. However, the effect increases as the magnetic flux density of the plain material before the magnetic domain refining process increases. Is known to be large.

On the other hand, in recent years, in order to improve the size and the weight and the performance of the transformer core, in particular, unlike conventional grain-oriented electrical steel sheets, there is an increasing demand from consumers who place importance on high magnetic flux density rather than iron loss. Therefore, 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 and increase the saturation magnetic flux density in addition to increasing the degree of azimuth integration as emphasized in the prior art. Iron has a high saturation magnetic flux density of 2.16T. However, when a nonmagnetic impurity such as Si is added to iron, the saturation magnetic flux density decreases. For example, when 3% of Si is added to iron, the saturation magnetic flux density decreases to 2.03T. Therefore, improvement of the saturation magnetic flux density by reducing impurities is very effective for obtaining a high magnetic flux density.

For this purpose, the inventors have disclosed a method of manufacturing a high magnetic flux density grain-oriented electrical steel sheet in Japanese Patent Publication No. 7-122093 and Japanese Patent Application Laid-Open No. Hei 4-301553. However, in recent years, iron core materials of small transformers and the like are required to have a higher saturation magnetic flux density in a high magnetic field than a high magnetic flux density grain-oriented electrical steel sheet manufactured by these methods.

[0014]

SUMMARY OF THE INVENTION As described above, the present invention relates to a high magnetic flux density grain-oriented electrical steel sheet, which is required in recent years for iron materials for small transformers and the like, and can be obtained by a conventional manufacturing method. It is an object of the present invention to provide a high magnetic flux density grain-oriented electrical steel sheet having a higher saturation magnetic flux density in a high magnetic field than a product which has been used, and a method for manufacturing the same.

[0015]

The gist of the present invention is as follows. (1) In% by weight, C ≦ 0.0030%, acid-soluble Al ≦ 0.050%, N ≦ 0.0150%, and the balance consists of Fe and unavoidable impurities. A grain-oriented electrical steel sheet having a degree of integration within 10 ° from the rolling direction of 75% or more, and is 800A /
Magnetic flux density at m: B ₈ ≧ 1.90T and 10,000A
Magnetic flux density at / m: B ₁₀₀ ≧ 2.10T, a grain-oriented electrical steel sheet having an extremely high magnetic flux density.

(2) 0.010% ≦ C ≦ 0.14%, 0.010% ≦ acid-soluble Al ≦ 0.050%, 0.0030% ≦ N ≦ 0.0150% by weight A slab consisting of Fe and unavoidable impurities is heated and hot-rolled, cold-rolled one or more times to a final thickness, decarburized, and finally annealed in a temperature range below the Ac ₁ transformation point. The method for producing a grain-oriented electrical steel sheet having an extremely high magnetic flux density according to claim 1, wherein the final cold rolling reduction is 75% or more and 90% or less.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The inventors of the present invention have studied a manufacturing process other than the inhibitor control technology, which has been the focus of the prior art, to reduce the eddy current loss component in iron loss. In order to reduce the thickness of the product and to achieve high magnetic flux density, the inventors studied the method of manufacturing grain-oriented electrical steel sheets with high magnetic flux density by controlling the cold rolling conditions. As a result, the final cold rolling reduction was 75% or more. %, The degree of integration of the crystal in the product within [10] from the rolling direction of [100] was improved to 75% or more, and the magnetic flux density was improved. Thus, the invention was completed.

Hereinafter, the present invention will be described in detail. First, the components contained in the slab used in the production method of the present invention 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, 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 0.0030% or more and 0.0150% or less. 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.

The steel of the present invention is obtained by using the slab as a starting material by the process described below. Hereinafter, the components of the steel of the present invention will be described. C is reduced by decarburizing annealing, but if the content of C in the steel of the present invention as a product exceeds 0.0030%, magnetic aging becomes a problem. Further, the acid-soluble Al contained as a component of the slab in an amount of 0.010% to 0.050% is slightly consumed in an oxide film or the like formed on the surface of the steel sheet. 050% or less, and no lower limit was provided. As for N, since a small amount of N comes out of the steel sheet during decarburization annealing or the like, the steel of the present invention has
No lower limit was set as 50% or less.

In the present invention, the degree of integration of the crystal within [100] from the rolling direction of [100] is set to 75% or more.
If the value is less than 75%, a desired high magnetic flux density cannot be obtained. Conventionally, in the field of non-oriented electrical steel sheets, improving the magnetic flux density by increasing the purity of iron has been performed. However, in the field of grain-oriented electrical steel sheets as in the present invention, it is usual to add Si to reduce iron loss, and it has not been conventionally performed to improve the magnetic flux density by increasing the purity of iron. . Thus, the degree of integration of the crystal within 10 ° from the rolling direction of [100] in the product is 75
%, The final cold-rolling rate may be controlled as described later.

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, it is important that the heating temperature of the slab is appropriately controlled so that the main inhibitor AlN is re-dissolved in the steel.

This slab is hot-rolled into a hot-rolled sheet having a predetermined thickness. In the steps after the hot rolling, if the final sheet thickness is obtained by one rolling for the purpose of controlling precipitates, the sheet may be annealed before the final cold rolling. When the final thickness is obtained by performing the cold rolling two or more times, the hot rolled sheet annealing may be performed before the first cold rolling. 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, 75% or more and 90%
Must be: If the final cold rolling ratio is out of this range, the crystal direction of the obtained product cannot be controlled, and the ultra-high magnetic flux density aimed at by the present invention cannot be obtained. Determine.

Next, decarburization annealing is performed in an atmosphere such as a wet hydrogen atmosphere. This annealing is an annealing for reducing C, which degrades the magnetic properties of the product sheet due to magnetic aging or the like, to an amount that does not cause a problem, and is performed by a generally known process.

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.

In order to secure insulation between plates and reduce iron loss as an iron core, the product obtained in this manner may be coated with an insulating film to form a final product, or may not be coated. It may be a final product.

The relationship between the cold rolling reduction and the product magnetic flux density in the production method according to the present invention will be described based on experimental results. C: 0.05%, acid-soluble Al: 0.018%,
N: A slab containing 0.0065%, the balance being Fe and unavoidable impurities is heated and then hot-rolled to a thickness of 2.1.
mm hot rolled sheet. The obtained hot-rolled sheet is subjected to hot-rolled sheet annealing at 825 ° C. for 2 minutes, and after pickling, cold-rolled at a rolling reduction of 73.8 to 91.9% to a final sheet thickness of 0.55 to 0.17 mm. Finished. This was subjected to decarburizing annealing for 5 minutes in a wet hydrogen atmosphere at 830 ° C., and then to finish annealing at 890 ° C. × 10 hours in dry hydrogen. Cold rolling reduction and magnetic field strength 800,100
Table 1 shows the relationship between the magnetic flux density at 00 A / m: B ₈ and B ₁₀₀ .

[0031]

[Table 1]

According to Table 1, the rolling reduction of the cold rolling was 75% or more and 90% or more.
With the following range, the crystal direction of the steel sheet can be controlled as desired, and as a result, the magnetic flux density B ₈ ≧ 1.
It can be seen that a grain-oriented electrical steel sheet having an extremely excellent magnetic flux density of 90, B ₁₀₀ ≧ 2.10T can be obtained.

[0033]

EXAMPLES Example 1 The components shown in Table 2 were contained, and the balance Fe
The slab comprising unavoidable impurities was heated and hot-rolled to obtain a hot-rolled sheet having a thickness of 2.1 mm. 8 on the obtained hot rolled sheet
The hot-rolled sheet is annealed at 30 ° C. for 2 minutes, and then is pickled and washed 73.8
It was cold rolled to 〜91.9% and finished to 0.55 to 0.17 mm. This was subjected to decarburization annealing at 830 ° C. in a wet hydrogen atmosphere. Thereafter, finish annealing at 890 ° C. × 10 hours was performed.

[0034]

[Table 2]

Table 3 shows the relationship between the cold rolling reduction and the magnetic properties after finish annealing. From Table 3, the cold rolling reduction is 75 to 90.
%, The crystal direction of the steel sheet can be controlled as desired, and as a result, the magnetic flux densities B ₈ ≧ 1.90 and B ₁₀₀ ≧ 2.
It can be seen that a grain-oriented electrical steel sheet having a good magnetic flux density of 10T can be obtained.

[0036]

[Table 3]

Example 2 The components shown in Table 4 were contained and the balance F
After heating the slab comprising e and the inevitable impurities, the slab was hot-rolled into a hot-rolled sheet having a thickness of 3.0 mm. The obtained hot-rolled sheet was subjected to hot-rolled sheet annealing at 830 ° C. for 2 minutes, followed by acid washing.
A single cold rolling of 3 to 91.7% is performed, and 0.80 to 0.2
Finished to 5mm. This was subjected to decarburization annealing at 830 ° C. in a wet hydrogen atmosphere. Thereafter, finish annealing at 890 ° C. × 10 hours was performed.

[0038]

[Table 4]

Table 5 shows the relationship between the cold rolling reduction and the magnetic properties after finish annealing. From Table 5, the cold rolling reduction is 75 to 90.
%, The crystal direction of the steel sheet can be controlled as desired, and as a result, the magnetic flux density B ₈ ≧ 1.90, B ₁₀₀ ≧
It can be seen that a grain-oriented electrical steel sheet having a good magnetic flux density of 2.10 T is obtained.

[0040]

[Table 5]

Example 3 The components shown in Table 6 were contained and the balance F
After heating the slab comprising e and the inevitable impurities, the slab was hot-rolled into a hot-rolled sheet having a thickness of 3.5 mm. The obtained hot-rolled sheet was annealed at 800 ° C. for 90 seconds and pickled. Then, it finished to 2.1 mm by the first cold rolling. Further, this was subjected to an intermediate annealing at 830 ° C. for 90 seconds, and then to a final cold rolling at a reduction of 73.8 to 91.9%,
Finished to 0.55 to 0.17 mm. This was subjected to decarburization annealing at 830 ° C. in a wet hydrogen atmosphere. Then, 890 ° C x
Finish annealing was performed for 10 hours.

[0042]

[Table 6]

Table 7 shows the relationship between the cold rolling reduction and the magnetic properties after finish annealing. From Table 7, the cold rolling reduction is 75 to 90.
%, The crystal direction of the steel sheet can be controlled as desired, and as a result, the magnetic flux density B ₈ ≧ 1.90, B ₁₀₀ ≧
It can be seen that a grain-oriented electrical steel sheet having a good magnetic flux density of 2.10 T is obtained.

[0044]

[Table 7]

[0045]

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.

Claims (2)

[Claims] 1. The composition contains, by weight%, C ≦ 0.0030%, acid-soluble Al ≦ 0.050%, and N ≦ 0.0150%, with the balance being Fe and unavoidable impurities, ] A grain-oriented electrical steel sheet having a degree of integration of 75% or more within 10 ° from the rolling direction of 800 A /
Magnetic flux density at m: B ₈ ≧ 1.90T and 10,000A
Magnetic flux density at / m: B ₁₀₀ ≧ 2.10T, a grain-oriented electrical steel sheet having an extremely high magnetic flux density. 2. The composition according to claim 1, further comprising: 0.010% ≦ C ≦ 0.14%, 0.010% ≦ acid-soluble Al ≦ 0.050%, 0.0030% ≦ N ≦ 0.0150% by weight. A slab consisting of Fe and unavoidable impurities is heated and hot-rolled, and then cold-rolled one or more times to a final sheet thickness. After decarburizing annealing, final annealing is performed in a temperature range below the Ac ₁ transformation point. 2. The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein the final cold rolling reduction is 75% or more and 90% or less.