JP3098628B2 - Ultra high magnetic flux density unidirectional electrical steel sheet - Google Patents

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 magnetic steel sheet having a {110} <001> direction, a so-called Goss direction, highly developed on a steel sheet surface, which is used for an iron core of a transformer or the like.

[0002]

2. Description of the Related Art A grain-oriented electrical steel sheet is mainly used as a soft magnetic material for core materials of transformers and other electric equipment, and has good magnetic properties, particularly excellent excitation properties and iron loss properties. Must-have.

As an index representing the excitation characteristics, a magnetic flux density B ₈ (magnetic flux density at a magnetic field strength of 800 A / m) is usually used.
Is used. Also, W is an index representing iron loss characteristics.
_{17/5 0} (iron loss per unit weight when magnetized to 1.7 T at 50 Hz) and the like are used.

[0004] In recent years, social demands for energy saving and resource saving have become increasingly severe, and demands for reduction of iron loss and improvement of magnetic properties of a grain-oriented electrical steel sheet have also become fierce. In particular, reduction of iron loss is strongly desired.

As is well known, iron loss consists of hysteresis loss and eddy current loss. The hysteresis loss depends on the crystal orientation, purity, internal strain, etc. of the steel sheet. Thickness, crystal grain size, size of magnetic domain, steel plate film tension, etc. contribute greatly.

[0006] Among them, in terms of purity and internal strain, they have been considered from the viewpoint of manufacturing technology for a long time and have almost reached the limit. Attempts have been made to reduce the eddy current loss by increasing the Si content in order to increase the electrical resistance, but increasing the Si content has limitations since the workability during production and in products is degraded.

Various attempts have been made to reduce the eddy current loss by reducing the thickness of the sheet. However, secondary recrystallization is basically difficult, and processing time is required in processing a transformer or the like. If the loss value is large, it can be said that a thicker plate is industrially superior. Therefore, there is a limit in reducing the thickness of the sheet.

[0008] A method for improving iron loss characteristics by imparting a coating tension to a steel sheet is disclosed in Japanese Patent Publication Nos.
Are described in -28375 JP, these tension effects depending on the direction of, be large enough magnetic flux density B ₈ high J. Appl. Phys., Vol. 7,2
981-2984, June 1970. Thus there is a limit to improvement of the iron loss is about 1.93T to B ₈ is commercially available as a so-called high flux density grain-oriented electrical steel sheet.

Although the size of magnetic domains is also related to the size of crystal grains, a technique for artificially subdividing magnetic domains to reduce iron loss has recently been disclosed in Japanese Patent Publication Nos. 58-5968 and 58-26.
Has been reported by 405 JP etc., also iron loss reducing effect of these methods is dependent on the magnetic flux density B _8, the commercially available 1.
At about 93T, there is a limit in reducing iron loss.

[0010] The shortest way to reduce iron loss is to reduce the size of secondary recrystallized grains, which is reported in Japanese Patent Publication No. 57-9419 and the like. Since there is such a phenomenon that it is difficult to obtain a high magnetic flux density if measures are taken, there is a limit to miniaturization of crystal grains as a means for reducing iron loss.

[0011]

SUMMARY OF THE INVENTION The present invention is to provide a new magnetic steel sheet having an ultra-high magnetic flux density and an improved remaining crystal orientation, which is an alternative to the various means for reducing the iron loss.

[0012]

The features of the present invention are as follows. 1) by weight, Si: contains 2.5 to 4.0% as an essential component, and the magnetic flux density B ₈ is a grain-oriented electrical steel sheet having a very high value of more than 1.95 T, the grain size An ultra-high magnetic flux density unidirectional electrical steel sheet, characterized in that matrix grains occupying an area ratio of 80% or more of 50 mm or less and 5 mm or more in a direction perpendicular to the cold rolling direction and 300 mm or less and 10 mm or more in the cold rolling direction.

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

3) (110) [00]
1] The inclination angle of the azimuth from the rolling surface is around the TD axis and ND
Crystals within 5 ° around the axis account for 90% or more in area ratio,
And (110) [00] of fine crystals in the matrix grains.
1] The inclination angle of the azimuth from the rolling surface is around the TD axis and ND
2. The ultra-high magnetic flux density unidirectional electrical steel sheet according to 2), wherein crystals within 10 ° around the axis occupy 90% or more of the fine grains in area ratio .

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

First, the reasons for limiting the component conditions will be described. The Si content greatly affects the iron loss characteristics through the electric resistance of the product, but if it is less than 2.5%, the electric resistance is small and the eddy current loss increases, which is not preferable. On the other hand, if the content exceeds 4.0%, the workability is deteriorated, so that production and product processing become 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 iron loss of a 3% Si-containing steel sheet having a 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 _0.90 which is said to be particularly excellent even for 0.30mm products
In the present invention, the magnetic flux density is limited to 1.95 T or more, since it is only below 1.95 T that the current is reduced below 0 W / kg.

Next, the reason for limiting the particle 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 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 crystal grain size of the secondary recrystallized grains is 5 in the cold rolling direction.
Averaged for matrices ≥ 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 becomes 1.95 T or more at 10 mm.
In the above case, if it is less than 10 mm, a product exceeding 1.95 T could not be obtained.

Some of the particles having a particle diameter of 10 mm or more have a particle diameter of less than 1.95 T, but it is understood that a product having an extremely high magnetic flux density of 1.95 T or more can be obtained. Similarly, FIG. 3 shows that the crystal grain size in the direction perpendicular to the cold rolling direction is 1.9 for the first time when the grain size is 5 mm or more.
It turns out that it becomes a product of 5T or more.

Next, the ratio of the presence of large crystal grains larger than the critical size in the matrix grains is 10 mm as described above.
Crystal grains less than (5 mm in the direction perpendicular to cold rolling) have a low magnetic flux density, so if their abundance exceeds 20%, it also affects the magnetic flux density of the whole product, and it becomes difficult to exceed 1.95T, so that 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 3% Si-containing steel sheet having a thickness of 0.30 mm (with a tension coating). The solid circles indicate the case where the ratio of fine secondary recrystallized grains having a particle size of 5 mm or less in the coarse secondary recrystallized grain matrix is 50% or more, and the white circles indicate the case where it is less than 50%.

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

As a result of a detailed investigation conducted 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 in the matrix. Iron loss is 0.9 only when the content is 50% or more
It turned out that an excellent product of 5 W / kg or less was obtained.

Therefore, in the present invention, the secondary particles having a large crystal grain size are used.
The probability that the recrystallized matrix grains contain fine secondary recrystallization is 5
Limited to 0% or more. Although the mechanism of this iron loss reduction is not necessarily clear, the present inventor has found that in the case of the ultra-high magnetic flux density unidirectional magnetic steel sheet of the present invention having an extremely high magnetic flux density, in the case where fine secondary recrystallized grains are not included, While the domain wall penetrates through the crystal grains and continues, and the magnetic domain becomes coarse,
It is presumed that when a fine crystal grain is included, a new magnetic domain is generated from the fine crystal, thereby producing a magnetic domain refining effect.

It is well known that there is a relationship between the magnetic flux density of the product and the orientation of the secondary recrystallized grains. Nothing was clarified about the orientation distribution for the case including grains. In particular, as in the present invention, 1.9.
There was no known example of the orientation distribution of the ultra-high magnetic flux density unidirectional magnetic steel sheet of 5T or more.

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

When crystals having an orientation dispersion of matrix grains exceeding 5 ° from the ideal Goss orientation are present in an area ratio of more than 10% , the magnetic flux density of the obtained product is less than 1.95 T, and the fine secondary recrystallization is similarly performed. When the orientation dispersion of the grains exceeds 10 ° from the ideal Goss orientation, the magnetic flux density becomes less than 1.95T similarly. From the above points, the scope of the present invention is limited.

Next, a method for producing the ultra-high magnetic flux density unidirectional magnetic steel sheet of the present invention will be described. First, the first condition is a material component, but C: 0.03 to 0.15%, Si: 2.5 to
4.0%, Mn: 0.02 to 0.80%, S: 0.04
0% or less, acid-soluble Al: 0.010 to 0.065%,
N: 0.0030 to 0.0150% is contained as a basic component, and Bi must be contained to 0.0005 to 0.05% as an essential requirement. In addition, Sn: 0.
It is permissible to contain 0.05 to 0.50% and Cu: 0.01 to 0.10%. In addition, it does not prevent the use of an inhibitor element used in the production of a normal grain-oriented electrical steel sheet.

The feature of this production method lies in the addition of Bi. If Bi is less than 0.0005%, the effect of improving the magnetic flux density of the product is small, and 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 cracks occur during hot rolling, which is not preferable.

It is not clear why Bi influences the secondary recrystallization, increases the magnetic flux density and further changes the shape of the secondary recrystallized grains, but the present inventor is the main inhibitor by adding Bi. It is presumed that the precipitation state of nitrides and sulfides is changed, or that the effect is an inhibitory effect due to segregation of grain boundaries of Bi itself. Melting, casting and hot rolling may be the usual methods used in the production of unidirectional magnetic steel sheets.

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

The cold rolling is performed in one stage or two or more stages. However, since it is a high magnetic flux density unidirectional magnetic steel sheet, the final cold rolling is preferably performed under high-pressure cold rolling at a rolling reduction of 65 to 95%. The rolling rates of stages other than the final cold rolling need not be particularly defined. This cold rolling method is to be used if necessary.
It is advantageous to apply the aging cold rolling described in JP-A-13846.

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

The surface of the steel sheet after the decarburizing annealing is coated with an ordinary annealing separator containing MgO as a main component by an ordinary method to prevent seizure in the secondary recrystallization annealing and to form a glass film. Subsequent secondary recrystallization annealing may be performed at a temperature of 1000 ° C. or more for 5 hours or more in an atmosphere of hydrogen, nitrogen, or a mixture thereof.

The steel sheet after the secondary recrystallization annealing is continuously subjected to continuous annealing for correcting coil winding after removing an excessive annealing separating agent, and at the same time, an insulating film (also serving as a tension applying film) is applied and baked. Further, if necessary, a magnetic domain refining treatment such as laser irradiation is performed. There is no particular limitation on the method of magnetic domain subdivision.

Although the method for producing the ultra-high magnetic flux density unidirectional electrical steel sheet of the present invention has been described above, the production method is not limited to this method, and any method using an inhibitor element except for the regulation of Si content can be used. 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
A slab for an electromagnetic steel sheet containing 08%, Sn: 0 to 0.15%, Cu: 0.05% and Bi: 0.0005 to 0.05%, and other unavoidable impurities, is hot-rolled immediately after heating to 1320 ° C. Then, a 2.3 mm hot rolled sheet was obtained.

The cold rolling was performed to 0.30 mm and 0.23 mm, and 0.30 mm was subjected to one-stage cold rolling, and 0.23 mm was subjected to two-stage cold rolling at a final cold rolling rate of 87.5%. Some of them were aged 5 times at 200 ° C. between the cold rolling passes.

Before final cold rolling, high temperature annealing was performed at 1120 ° C. × 2 minutes. The cold rolled sheet was continuously decarburized at 850 ° C., and after applying an annealing separator containing MgO as a main component,
A second recrystallization annealing at 0 ° C. was performed.

After removing the residue of the annealing separator, 60 × 300 mm
Was sheared and subjected to strain relief annealing at 850 ° C., followed by application and baking of an insulating film. Some of the samples were further subjected to laser irradiation at 5 mm intervals for magnetic measurement. The macroscopic measurement of the magnetic measurement sample with a strong acid was followed by measurement of the crystal grain size and the like.

[Table 1]

Sample Nos. 1, 6, 7, and 8 were all made of a material component containing no Bi and having a magnetic flux density of 1.95.
Below T, the iron loss characteristics do not exceed the range of conventional products of 0.30 mm and 0.23 mm regardless of laser irradiation. Sample Nos. 2 and 3 contain Bi as a material component,
The magnetic flux density also exceeds 1.95T and the matrix coarse area ratio exceeds 80%, so the iron loss after laser irradiation is much less than 0.90W / kg. I can say

[0043] Sample No. 4 and 5 contain Bi, coarse grains area ratio of the matrix and the magnetic flux density is 1.95T or more even more than 80%, more matrix coarse grains, the probability of including a secondary recrystallization grains fine (Table 1 shows the percentage of fine crystals.
) Exceeds 50%, so that excellent characteristics are obtained as a 0.30 mm thick product having an iron loss of 0.95 W / kg or less without magnetic domain control.

Sample numbers 9, 10, and 11 were also 0.23 mm thick.
Although it is a product, the Bi content and the matrix coarse grain area ratio satisfy the range of the present invention similarly to the 0.30 mm product, so that it is a very excellent product as a laser irradiation magnetic 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 a strong acid. Table 2 shows the results.

[0046]

[Table 2]

As is apparent from Table 2, in the sample having a magnetic flux density B ₈ of 1.95 T or more, the ideal Goss orientation, ie, Δ11
The rotation angle from 0 <001> is 5 ° or less in the matrix, and the area ratio of 10 ° or less in the fine crystal 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 for the 0.30 mm product. Not only is it excellent, but also contains moderate secondary recrystallized grains with good orientation, 0.95 W / kg without magnetic domain control
These are the following excellent products, which can be said to be extremely large in contributing to the energy saving of electrical equipment such as transformers.

[Brief description of the drawings]

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

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

FIG. 3 is a table showing a relationship between a magnetic flux density and a crystal grain diameter in a direction perpendicular to cold rolling.

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

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 38/00 303 H01F 1/16 C21D 8/12

Claims (3)

(57) [Claims] 1. A grain-oriented electrical steel sheet containing 2.5 to 4.0% of Si as an essential component by weight and having a very high magnetic flux density B ₈ of 1.95 T or more, The crystal grain size is 50mm or less in the direction perpendicular to the cold rolling 5mm or more, cold rolling direction 3
80 mm or less and 10 mm or more matrix particles are 80
% Of ultra-high magnetic flux density unidirectional electrical steel sheet. 2. The ultra-high magnetic flux density grain- oriented electrical steel sheet according to claim 1, wherein matrix grains containing fine crystals having an average grain size of 5 mm or less in the matrix grains account for 50% or more. 3. The matrix grains of (110) [001]
A crystal whose inclination angle from the rolling surface within 5 ° around the TD axis and the ND axis occupies 90% or more in area ratio, and the (110) [001] direction rolling surface of the fine crystal in the matrix grains. 3. The ultra-high magnetic flux density unidirectional electrical steel sheet according to claim 2, wherein crystals having an inclination angle of about 10 ° or less around the TD axis and the ND axis occupy 90% or more of the fine grains in terms of area ratio .