JPH06100996A - Grain-oriented silicon steel sheet with ultrahigh magnetic flux density - Google Patents

Abstract

PURPOSE:To provide an ultrahigh magnetic flux density grain-oriented silicon steel sheet having high magnetic flux density and excellent in iron loss after magnetic domain control by specifying the crystalline grain size of the matrix of a silicon steel sheet with specific composition. CONSTITUTION:Si is incorporated, as essential component, into a grain-oriented silicon steel sheet by 2.5-4.0% by weight, and magnetic flux density B8 is regulated to a value as high as >=1.95T. The crystalline grain size of the matrix of the steel sheet is regulated so that the grains of 5-50mm, in a direction perpendicular to cold rolling direction, and 10-300mm, in a cold rolling direction, comprise >=80% by area ratio. Further, the grains including fine crystals of >=5mm average grain size comprise >=50% of the matrix grains. By this method, this steel sheet can greatly contribute to energy saving for electrical equipment, such as transformer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high magnetic flux density unidirectional electrical steel sheet which is used for an iron core of a transformer or the like and has a highly developed {110} <001> orientation on the surface of the steel sheet.

[0002]

2. Description of the Related Art Unidirectional electrical steel sheets are mainly used as a soft magnetic material for iron core materials of transformers and other electric equipment. They have good magnetic characteristics, especially excitation characteristics and iron loss characteristics. Must-have.

As an index showing this excitation characteristic, a normal magnetic flux density B ₈ (magnetic flux density at a magnetic field strength of 800 A / m)
Is used. In addition, as an index showing the iron loss characteristic, W
_{17/5 0} (iron loss per unit weight when magnetized to 1.7 T at 50 Hz) and the like are used.

In recent years, social demands for energy saving and resource saving have become more and more strict, and demands for reducing iron loss and improving magnetization characteristics of unidirectional electrical steel sheets have also become strict. In particular, iron loss reduction is strongly desired.

As is well known, iron loss consists of hysteresis loss and eddy current loss. Hysteresis loss depends on the crystal orientation, purity, internal strain, etc. of the steel sheet. The thickness, grain size, magnetic domain size, steel sheet coating tension, etc. make a large contribution.

Among them, the purity and the internal strain have been considered from the viewpoint of manufacturing technology for a long time, and the limit has been almost reached. Although attempts have been made to increase the Si content to reduce the eddy current loss in order to increase the electric resistance, increasing the Si content has a limit because workability during manufacturing and products deteriorates.

Various attempts have been made to reduce the eddy current loss by reducing the plate thickness, but secondary recrystallization is basically difficult, and it takes time and labor to process a transformer or the like. If the loss value is large, it can be said that a thick plate is industrially superior. Therefore, there is a limit in thinning the plate thickness.

A method for imparting film tension to a steel sheet to improve iron loss characteristics is disclosed in Japanese Examined Patent Publication Nos. 51-12451 and 53.
No. 28375, the tension effect depends on the directionality, and the higher the magnetic flux density B ₈ is, the larger the effect is. Appl. Phys., Vol. 41, No. 7, 2
981-2984, June 1970. Therefore, if B ₈ is about 1.93T, which is commercially available as a so-called high magnetic flux density grain-oriented electrical steel sheet, improvement in iron loss is limited.

The size of the magnetic domain is also related to the size of the crystal grain, but recently, a technique for artificially subdividing the magnetic domain to reduce the iron loss is disclosed in Japanese Patent Publication Nos. 58-5968 and 58-26.
As disclosed in Japanese Patent No. 405, etc., the iron loss reducing effect of these methods also depends on the magnetic flux density B ₈ and is 1.
At about 93T, there is a limit to iron loss reduction.

[0010] The most shortcut method for reducing iron loss is to reduce the size of secondary recrystallized grains, which has been reported in Japanese Patent Publication No. 57-9419, but generally the secondary recrystallized grains are made smaller. Since there is a phenomenon that it is difficult to obtain a high magnetic flux density if a measure is taken, there is a limit to reducing the iron loss by making the crystal grains fine.

[0011]

DISCLOSURE OF THE INVENTION The present invention provides a new, that is, an ultrahigh magnetic flux density unidirectional electrical steel sheet having an improved residual crystal orientation, which is an alternative to various means for reducing iron loss.

[0012]

The features of the present invention are as follows. 1) A grain-oriented electrical steel sheet containing Si: 2.5 to 4.0% by weight as an essential component and having an extremely high magnetic flux density B ₈ of 1.95 T or more, and a matrix crystal. An ultra-high magnetic flux density unidirectional electrical steel sheet characterized by having an area ratio of 80% or more in a grain size of 50 mm or less and 5 mm or more in the cold rolling direction at right angles to 300 mm or less in the cold rolling direction.

2) The ultrahigh magnetic flux density unidirectional electrical steel sheet according to 1), wherein 50% or more of the matrix grains contain fine crystals having an average grain size of 5 mm or less.

3) Matrix grain of (110) [00
1] The tilt angle of the orientation from the rolling surface is around the TD axis and ND
Crystals within 5 ° around the axis occupy 90% or more in area ratio,
In addition, (110) [00 of fine crystals in matrix grains
1] The tilt angle of the orientation from the rolling surface is around the TD axis and ND
The ultrahigh magnetic flux density unidirectional electrical steel sheet according to 2), characterized in that crystals within 10 ° around the axis occupy 90% or more of the fine grains.

The details of the present invention will be described below. The present inventor has conducted various studies on the conditions that a product for reducing iron loss should have, and has found that the matrix of secondary recrystallized grains of the grain-oriented electrical steel sheet containing 2.5 to 4.0% Si and the matrix. By controlling the fine secondary recrystallized grains existing in the matrix grains, we have succeeded in developing an ultra-high magnetic flux density unidirectional electrical steel sheet with extremely high magnetic flux density and remarkable iron loss reduction effect.

First, the reasons for limiting the component conditions will be described. The Si content largely affects the iron loss characteristics through the electrical resistance of the product, but if it is less than 2.5%, the electrical resistance is small and the eddy current loss increases, which is not preferable. On the other hand, if it exceeds 4.0%, the workability is deteriorated, which makes manufacturing and product processing difficult, which is not preferable.

Next, the reason for limiting the magnetic flux density will be described. FIG. 1 shows the relationship between the magnetic flux density and the iron loss of a product of a steel plate containing 3% Si having a plate thickness of 0.30 mm, which was subjected to laser irradiation after macro irradiation and magnetically measured at a tension of 1.5 kg / mm ² . Iron loss W
_17/50 is said to be particularly excellent even for 0.30 mm products 0.9
The magnetic flux density is limited to 1.95 T or more in the present invention, so the magnetic flux density is limited to 1.95 T or more in the present invention.

Next, the reason for limiting the grain size of the secondary recrystallized grains will be described. As described above, the magnetic flux density generally decreases as the secondary recrystallized grain size decreases. However, the present inventor has studied in detail the relationship between the crystal grain size and the magnetic flux density of products manufactured by various manufacturing methods, and FIG. , 3 were obtained.

The grain size of the secondary recrystallized grains is 5 in the cold rolling direction.
Averaged for matrices above mm. Fig. 2 shows the relationship between the crystal grain size in the cold rolling direction and the magnetic flux density. The variation in the magnetic flux density is large, but the magnetic flux density above 1.95T is 10 mm.
In the above cases, when the length was less than 10 mm, a product exceeding 1.95T could not be obtained.

It can be seen that a product having an extremely high magnetic flux density of 1.95 T or more can be obtained although some particles having a particle size of 10 mm or more are less than 1.95 T. Similarly, as shown in FIG. 3, when the grain size in the direction perpendicular to the cold rolling is 5 mm or more, it is 1.9 for the first time.
It turns out that it will be a product of 5T or more.

Next, regarding the abundance ratio of large crystal grains larger than the limit size in the matrix grains, it is 10 mm as described above.
Since the magnetic grains of less than (5 mm in the direction perpendicular to cold rolling) have a low magnetic flux density, if the abundance ratio exceeds 20%, it will also affect the magnetic flux density of the entire product, making it difficult to exceed 1.95 T, so 80%. Limited to the above.

The reason for limiting the fine secondary recrystallized grains in the matrix grains will be described. FIG. 4 shows the relationship between the magnetic flux density and the iron loss of a product (with a tension coating) having a plate thickness of 0.30 mm containing 3% Si. Black circles are cases where the ratio of fine secondary recrystallized particles having a grain size of 5 mm or less in the coarse secondary recrystallized matrix is 50% or more, and white circles are cases where the ratio is less than 50%.

Unlike the laser-irradiated material shown in FIG. 1, it seems that there is no clear correlation between the magnetic flux density and the iron loss, but there are some excellent products that are comparable to the iron-irradiated material of the laser-irradiated material. Can be seen.

As a result of a detailed investigation by the present inventors on these products having excellent iron loss, as shown in the figure, the coarse secondary recrystallized grain matrix contains fine secondary recrystallized grains of 5 mm or less. Iron loss is 0.9 only when the content is 50% or more
It was found that an excellent product of 5 W / kg or less was obtained.

Therefore, in the present invention, the probability of including fine secondary recrystallization is limited to 50% or more. Although the mechanism for reducing the iron loss is not always clear, the present inventors have found that in the ultrahigh magnetic flux density unidirectional electrical steel sheet of the present invention, which has an extremely high magnetic flux density, when fine secondary recrystallized grains are not included. It is presumed that, while the domain walls continue to penetrate through the crystal grains and the magnetic domains become coarser, when fine crystal grains are included, new magnetic domains are generated from the fine crystals, producing the domain refinement effect. ing.

It is well known that there is a relation between the magnetic flux density of the product and the orientation of the secondary recrystallized grains, but as in the present invention, the matrix coarse secondary recrystallized grains and finer secondary recrystallized grains within the crystals are present. There was no clarification of the orientation distribution in the case of containing grains. Especially as in the present invention, 1.9
There was no known example of orientation distribution for an ultra-high magnetic flux density grain-oriented electrical steel sheet of 5T or more.

Therefore, the present inventor succeeded in obtaining the following new knowledge by performing detailed azimuth measurement on the material of the present invention. That is, (110) [001] of matrix grains
Crystals having an orientation angle of 5 ° or less about the TD axis and about the ND axis occupy 90% or more in area ratio, and the fine secondary recrystallized grains (110) [0
01] azimuth angle from the rolling surface is about TD axis and N
Crystals within 10 ° around the D axis are 90% of fine secondary recrystallized grains.
It was found that it is necessary to occupy at least%.

When the crystal having the orientation dispersion of the matrix grains exceeding 5 ° from the ideal Goth orientation exists over 10 °, the magnetic flux density of the obtained product becomes less than 1.95T, and similarly, the orientation of the fine secondary recrystallized grains is the same. Dispersion is 10 ° from the ideal Goth direction
Similarly, the magnetic flux density becomes less than 1.95T. From the above points, the scope of the present invention is limited.

Next, a method for manufacturing the super high magnetic flux density grain-oriented electrical steel sheet of the present invention will be described. First, the first condition is the material composition, but C: 0.03 to 0.15%, Si: 2.5 to
4.0%, Mn: 0.02-0.80%, S: 0.04
0% or less, acid-soluble Al: 0.010 to 0.065%,
It is essential to contain N: 0.0030 to 0.0150% as a basic component and further contain Bi in an amount of 0.0005 to 0.05%. In addition, Sn: 0.
It is allowed to contain 05 to 0.50% and Cu: 0.01 to 0.10%. It does not hinder the supplementary use of other inhibitor elements that are usually used in the production of grain-oriented electrical steel sheets.

The feature of this manufacturing method lies in the addition of Bi. When Bi is less than 0.0005%, the effect of improving the magnetic flux density of the product is small, the secondary recrystallized grain size is small, and the directionality is not good. On the other hand, if it exceeds 0.05%, the effect of improving the magnetic flux density is saturated, and end cracking occurs during hot rolling, which is not preferable.

Although it is not clear why Bi affects secondary recrystallization and makes the magnetic flux density extremely high and further changes the shape of secondary recrystallized grains, the present inventor is the main inhibitor by addition of Bi. It is speculated that the precipitation state of nitrides and sulfides may be changed, or that the inhibitor effect may be due to the segregation of grain boundaries of Bi itself. Melting, casting, and hot rolling may be the usual methods used for producing unidirectional electrical steel sheets.

The hot rolled sheet is annealed as necessary. This annealing is performed with a hot-rolled sheet in the case of the one-stage cold rolling method, and refers to annealing before the final cold rolling in the case of the two-stage or more cold rolling method. Annealing is 950
It may be annealed at ˜1200 ° C. for 30 seconds to 30 minutes, and may be subjected to a quenching treatment if necessary.

Cold rolling is carried out in one stage or in two or more stages, but since it is a high magnetic flux density unidirectional electrical steel sheet, it is preferable to carry out high pressure cold rolling with a rolling ratio of final cold rolling of 65 to 95%. The rolling ratio of stages other than final cold rolling may not be specified. This cold rolling method is used, but if necessary,
It is useful to perform the aging cold rolling described in Japanese Patent No. 13846.

The cold-rolled sheet rolled to the final product sheet thickness is subsequently decarburized and annealed by a usual method. The conditions of decarburization annealing are not particularly specified, but preferably 3 in the temperature range of 700 to 900 ° C.
It is preferable to perform the treatment in wet hydrogen or a mixed atmosphere of hydrogen and nitrogen for 0 seconds to 30 minutes.

On the surface of the steel sheet after decarburization annealing, an ordinary annealing separating agent containing MgO as a main component is applied by a usual method for preventing seizure in secondary recrystallization annealing and for forming a glass film. The subsequent secondary recrystallization annealing may be performed at a temperature of 1000 ° C. or higher for 5 hours or more in an atmosphere of hydrogen or nitrogen or a mixed atmosphere thereof.

After the secondary recrystallization annealing, the excess annealing separator is removed from the steel sheet, followed by continuous annealing for straightening the coil winding. Further, magnetic domain subdivision processing such as laser irradiation is performed if necessary. The method of subdividing the magnetic domains is not particularly limited.

The manufacturing method of the ultra-high magnetic flux density grain-oriented electrical steel sheet of the present invention has been described above. However, the manufacturing method is not limited to this method, and any method of using any inhibitor element except for the regulation of Si content can be used. Also, the process conditions are not limited to the above method.

[0038]

【Example】

(Example 1) C: 0.06 to 0.09%, Si: 3.0
~ 3.35%, Mn: 0.08%, S: 0.025%,
Acid soluble Al: 0.020 to 0.035%, N: 0.0
Immediately after hot rolling the slab for electrical steel sheets containing 08%, Sn: 0 to 0.15%, Cu: 0.05% and Bi: 0.0005 to 0.05% and other unavoidable impurities at 1320 ° C. A hot rolled sheet of 2.3 mm was prepared.

Cold rolling was performed up to 0.30 mm and 0.23 mm, 0.30 mm was subjected to 1-stage cold rolling, and 0.23 mm was subjected to 2-stage cold rolling with a final cold rolling rate of 87.5%. Some of the products were aged at 200 ° C. five times during the cold rolling pass.

Before the final cold rolling, high temperature annealing of 1120 ° C. × 2 minutes was performed. The cold-rolled sheet was subsequently subjected to decarburization annealing at 850 ° C., and after applying an annealing separating agent containing MgO as a main component, 120
Secondary recrystallization annealing was performed at 0 ° C.

After removing the residue of the annealing separator 60 × 300 mm
The magnetic measurement sample of No. 1 was sheared, strain relief annealing was performed at 850 ° C., and subsequently an insulating coating was applied and baked. Some of the samples were further irradiated with laser at 5 mm intervals and subjected to magnetic measurement. The magnetic measurement sample was measured with a strong acid after macro to measure the crystal grain size and the like.

[Table 1]

Sample Nos. 1, 6, 7 and 8 do not contain Bi as a material component and have a magnetic flux density of 1.95.
When it is less than T, the iron loss characteristic does not exceed the range of 0.30 mm and 0.23 mm of the conventional product regardless of the presence or absence of laser irradiation. Sample Nos. 2 and 3 contain Bi as a material component,
The magnetic flux density is over 1.95T, and the coarse grain area ratio of the matrix is over 80%, so the iron loss after laser irradiation is much better than 0.90W / kg, which is a wonderful property for a 0.30mm thick product. Can be said.

Sample Nos. 4 and 5 contain Bi, the magnetic flux density is 1.95 T or more, the coarse grain area ratio of the matrix exceeds 80%, and the fine secondary recrystallized grains contained in the coarse matrix grains are present. Since the ratio also exceeds 50%, excellent characteristics are obtained as a product of 0.30 mm thickness with an iron loss of 0.95 W / kg or less without magnetic domain control.

Sample Nos. 9, 10 and 11 also have a plate thickness of 0.23 mm
Although it is a product, it has an excellent Bi content and a matrix coarse grain area ratio satisfying the range of the present invention as in the case of the 0.30 mm product, and thus is a very excellent product as a laser irradiation domain control material for a 0.23 mm thick product.

Example 2 A 0.30 mm thick product manufactured by the same manufacturing method as in Example 1 was obtained. After measuring the magnetic properties, the orientation of each crystal grain was measured by the Laue method after macro with strong acid. The results are shown in Table 2.

[0046]

[Table 2]

As is clear from Table 2, in the sample having the magnetic flux density B ₈ of 1.95 T or more, the ideal Goss orientation, ie, {11
The area ratio where the rotation angle from 0} <001> is 5 ° or less in the matrix and 10 ° or less in the fine crystals is 90% or more.

[0048]

The ultra-high magnetic flux density grain-oriented electrical steel sheet of the present invention has an extremely high magnetic flux density as compared with the conventional product, and the iron loss after controlling the magnetic domain is 0.90 W / kg or less in the 0.30 mm product. Not only extremely excellent, but also 0.95W / kg without magnetic domain control when it contains fine secondary recrystallized grains with good orientation.
It can be said that the following excellent products are extremely large in that they contribute to energy saving of electric devices such as transformers.

[Brief description of drawings]

FIG. 1 is a chart showing a relationship between iron loss and magnetic flux density according to the present invention.

FIG. 2 is a chart showing the relationship between magnetic flux density and crystal grain size in the cold rolling direction.

FIG. 3 is a diagram showing a relationship between magnetic flux density and crystal grain size in the cold rolling right-angle direction.

FIG. 4 is a chart showing the relationship between iron loss and magnetic flux density.

Claims (3)

[Claims] 1. A unidirectional electrical steel sheet which contains Si: 2.5 to 4.0% by weight as an essential component and has an extremely high magnetic flux density B ₈ of 1.95 T or more, An ultra-high magnetic flux density unidirectional electrical steel sheet characterized in that the crystal grain size of the matrix is 50 mm or less in the direction perpendicular to cold rolling and 5 mm or more and the area ratio is 80 mm or more in the direction of 300 mm or less in the cold rolling direction. 2. The super high magnetic flux density unidirectional electrical steel sheet according to claim 1, wherein 50% or more of the matrix grains contain fine crystals having an average grain size of 5 mm or less. 3. A matrix grain of (110) [001].
The crystal having an orientation angle of 5 ° or less about the TD axis and the ND axis within 5 ° occupies 90% or more in area ratio, and the rolled surface of the (110) [001] orientation of fine crystals in matrix grains 3. The ultrahigh magnetic flux density unidirectional electrical steel sheet according to claim 2, wherein crystals having an inclination angle of 10 ° or less about the TD axis and about the ND axis occupy 90% or more of the fine grains.