JP5594302B2 - Method for producing grain-oriented electrical steel sheet - Google Patents

Description

  The present invention relates to a method for producing a grain-oriented electrical steel sheet used for a core material such as a transformer.

  A grain-oriented electrical steel sheet is a material mainly used as an iron core of a transformer. From the viewpoint of increasing the efficiency and reducing the noise of the transformer, the material characteristics of the directional electromagnetic steel sheet are required to have characteristics such as low iron loss and low magnetostriction.

For this purpose, it is important to highly align the secondary recrystallized grains in the steel sheet in the {110} <001> orientation (so-called Goth orientation). However, it is also known that if the orientation is too high, the iron loss increases.
Therefore, in order to eliminate this drawback, a technique for introducing a strain or a groove on the surface of the steel sheet to subdivide the magnetic domain width to reduce the iron loss, that is, a magnetic domain subdivision technique has been developed.

For example, Patent Document 1 proposes a technique for reducing the iron loss by narrowing the magnetic domain width by irradiating the final product plate with laser and introducing a linear high dislocation density region into the steel sheet surface layer. .
Patent Document 2 proposes a technique for controlling the magnetic domain width by irradiation with an electron beam (electron beam). If this method of reducing iron loss by electron beam irradiation is used, electron beam scanning can be performed at high speed by magnetic field control.
Furthermore, since the electron beam irradiation does not require a mechanical moving part as seen in an optical scanning mechanism of a laser, the magnetic domain fragmentation process is performed continuously and at a high speed, particularly for a wide continuous strip of 1 m or more. This is advantageous when applied.

Japanese Patent Publication No.57-2252 Japanese Patent Publication No. 6-072266

  As described above, when the magnetic domain subdivision process is performed using electron beam irradiation, it is important to evacuate the processing chamber in which the process is performed in order to continuously and stably irradiate the electron beam. However, when industrial production is performed, the processing chamber for continuous electron beam irradiation treatment through a steel strip is widened, so that the degree of vacuum in the processing chamber is as low as possible. It is desirable.

  Also, when irradiating the steel strip by scanning the electron beam in a direction perpendicular to the through plate and irradiating the full width of the steel strip with a single electron gun, the irradiation quality in the steel strip width direction is homogenized. For this purpose, it is advantageous to place an electron gun that irradiates an electron beam as far as possible from the steel plate and scan it. That is, it is desirable that the deflection angle for electrically deflecting and scanning the electron beam is made as small as possible to reduce the difference in irradiation quality between the portion immediately below the electron gun and the end of the steel plate. However, for that purpose, there has been a problem that an electron gun is installed at a distance, and a processing chamber that needs to be kept in a vacuum is enlarged.

  The present invention has been developed in view of the above situation, and can perform an effective magnetic domain subdivision process even when the degree of vacuum is low and the distance between the electron beam irradiation part (electron gun) and the steel sheet is short. It aims at proposing the manufacturing method of a grain-oriented electrical steel sheet.

The inventors have a low degree of vacuum, and even when the distance between the electron gun and the steel plate is short, the electron gun can obtain a uniform iron loss reduction effect in the width direction of the grain-oriented electrical steel plate We intensively investigated the irradiation conditions and clarified the relationship between the distance between the electron gun and the steel plate surface, the deflection angle of the electron gun, and the degree of vacuum in the processing chamber.
The present invention is based on the above findings.

That is, the gist configuration of the present invention is as follows.
1. When producing a grain-oriented electrical steel sheet by introducing thermal strain by electron beam irradiation on a grain-oriented electrical steel sheet having a forsterite film and a tension coating on the steel sheet surface,
In the electron beam irradiation, the distance from the electron beam irradiation part to the steel sheet surface is L [mm], the deflection angle when performing electron beam irradiation is θ [°], and the vacuum degree of the irradiation processing chamber is P [Pa]. The following formula (1-cos (θ / 2)) · L·log [1000P] ≦ 40
(However, P ≧ 0.02)
A method for producing a grain-oriented electrical steel sheet, which is performed under a condition that satisfies the following conditions.

  ADVANTAGE OF THE INVENTION According to this invention, the magnetic property of a steel strip width direction can be equalize | homogenized effectively in the grain-oriented electrical steel sheet which reduced the iron loss by distortion introduction by electron beam irradiation.

It is the figure which showed the relationship between the distance of electron gun and steel plate in this invention: L, and the deflection angle of an electron beam: (theta). It is the figure which evaluated the difference of the ultimate iron loss value in the center and edge part of a steel plate by the relationship of log [1000P] and (1-cos ((theta) / 2)) * L.

Hereinafter, the present invention will be specifically described.
First, a 0.23 mm-thick directional electrical steel sheet, which has been subjected to final annealing accompanied by secondary recrystallization and then subjected to continuous annealing that serves as the formation of an insulating coating and the flattening of the steel sheet, has a length of 300 mm and a width of 300 mm. A number of samples necessary for the electron beam irradiation experiment were prepared.
Next, using an electron beam irradiation apparatus having an electron gun with an acceleration voltage of 40 kV, the electron beam was scanned in a direction perpendicular to the rolling, and the entire width of 300 mm was irradiated at once. The irradiation treatment was repeated by shifting in the rolling direction at intervals of 5 mm to process the entire sample surface. At that time, the distance between the electron gun and the sample: L, and the degree of vacuum in the irradiation processing chamber: P were changed in various combinations. Then, it sheared to 10 evaluation samples of 30 mm width, and evaluated the magnetic characteristic of the sample.
In addition, the vacuum exhaust system of the irradiation processing chamber combines an oil rotary pump and an oil diffusion pump, and can maintain a degree of vacuum: P in a range from 0.01 Pa to 7 Pa. FIG. 1 shows the relationship between the distance between the electron gun and the steel plate in the present invention: L, and the deflection angle of the electron beam: θ.

As a result of considering the above test, when the iron loss W _17/50 value of 10 samples after the irradiation treatment was measured, a tendency to deteriorate to an ultimate iron loss value was observed toward the end portion with respect to the central portion. In the present invention, with respect to the iron loss value of the central part, up to a sample position where the difference does not exceed 0.01 Wkg is evaluated as uniform irradiation, and the length from the sample position to the central part is uniformly irradiated. The width.

In FIG. 2, the horizontal axis is log [1000P], the vertical axis is (1-cos (θ / 2)) · L, and the difference between the iron loss values at the center and the end is 0.01 W / kg or less. That is, the case where the sample was regarded as uniform irradiation was plotted as a mark ◯, and the sample larger than 0.01 W / kg was plotted as a mark X.
From the figure, uniform irradiation is possible in the range where the value of (1-cos (θ / 2)) · L·log [1000P], which is the product of the horizontal and vertical axes, is 40 or less (below the solid line in the figure). It can be seen that it is.

Here, the horizontal axis is a so-called index of the degree of vacuum, and the degree of vacuum is higher on the left side. On the other hand, the vertical axis is a parameter corresponding to the distance difference between the electron beams at the center and the steel plate end. That is, as the distance between the electron gun and the steel plate: L or the deflection angle: θ is larger, the flight distance of the electron beam in the end portion in the vacuum is longer. In addition, although the processing chamber is evacuated, it is presumed that the electron beam is scattered by a small amount of residual gas molecules and the like that are present depending on the degree of vacuum, and the intensity is reduced.
Therefore, the electron beam is more susceptible to scattering due to the influence of residual gas molecules as the degree of vacuum is lower or the flight distance is longer, so that it is considered that a difference occurs in the effect of the electron beam irradiation treatment in the width direction.
Therefore, the inventors consider that the desired electron beam irradiation effect can be obtained by setting the value of (1-cos (θ / 2)) · L·log [1000P] to 40 or less. Yes.

  In the present invention, the lower limit of the degree of vacuum in the processing chamber: P is not limited, but it is not necessary to make a high vacuum of 0.005 Pa or less from the viewpoint of productivity. The upper limit is preferably about 7 Pa or less at which the electron beam can be stably irradiated.

  The distance between the electron gun and the steel plate: L is not particularly limited, but is preferably about 10 cm to 1 m. If it is smaller than 10 cm, a large number of electron guns are required to irradiate the entire steel sheet having a width of 1000 mm or more. Conversely, if it is separated from 1 m, the space volume required for evacuation becomes large. This is because it is also uneconomical.

  The smaller the deflection angle: θ, the better. When the angle is larger than 60 °, the electron beam is incident on the steel plate in an oblique direction, so that the beam spot becomes elliptical, apart from scattering based on the distance difference, and a uniform electron beam irradiation effect is obtained. There is a risk of not.

  Other electron beam irradiation conditions are not particularly limited, but the acceleration voltage is generally from about 20 kV to 200 kV. The direction of electron beam scanning is preferably in the range of 90 ° to 45 ° with respect to the rolling direction of the steel sheet. In addition, if the electron beam irradiation in this invention is performed on the above-mentioned conditions, it will not be continuous, but even if it is dot-shaped irradiation, the reduction effect of iron loss will be expressed.

Next, the manufacturing conditions of the grain-oriented electrical steel sheet according to the present invention will be specifically described.
In the present invention, the component composition of the slab for grain-oriented electrical steel sheet is not particularly limited as long as it is a component composition that causes secondary recrystallization.
Also, when using an inhibitor, for example, when using an AlN-based inhibitor, Al and N should be included. When using an MnS / MnSe-based inhibitor, an appropriate amount of Mn and Se and / or S should be included. Good. Of course, both inhibitors may be used in combination. In this case, preferable contents of Al, N, S and Se are respectively Al: 0.01 to 0.065 mass%, N: 0.005 to 0.012 mass%, and S: 0.005 to 0.03. Mass%, Se: 0.005 to 0.03 mass%.

Further, the present invention can also be applied to a directional electrical steel provisional in which the content of Al, N, S and Se is limited and an inhibitor is not used.
In this case, the amounts of Al, N, S, and Se are preferably suppressed to Al: 100 mass ppm or less, N: 50 mass ppm or less, S: 50 mass ppm or less, and Se: 50 mass ppm or less.

In addition, the basic components and optional added components of the slab for grain-oriented electrical steel sheets according to the present invention are specifically described as follows.
C: 0.08 mass% or less C is added to improve the hot-rolled sheet structure, but if it exceeds 0.08 mass%, C is reduced to 50 massppm or less where magnetic aging does not occur during the manufacturing process. Since it becomes difficult to do, it is preferable to set it as 0.08 mass% or less. In addition, regarding the lower limit, since a secondary recrystallization is possible even for a material not containing C, it is not particularly necessary to provide it.

Si: 2.0-8.0 mass%
Si is an element effective for increasing the electrical resistance of steel and improving iron loss. However, if the content is less than 2.0% by mass, a sufficient iron loss reduction effect cannot be achieved. If it exceeds 0% by mass, the workability is remarkably reduced and the magnetic flux density is also reduced. Therefore, the Si content is preferably in the range of 2.0 to 8.0% by mass.

Mn: 0.005 to 1.0% by mass
Mn is an element necessary for improving the hot workability, but if the content is less than 0.005% by mass, the effect of addition is poor, whereas if it exceeds 1.0% by mass, the magnetic flux density of the product plate Therefore, the amount of Mn is preferably in the range of 0.005 to 1.0 mass%.

In addition to the above basic components, the following elements can be appropriately contained as magnetic property improving components.
Ni: 0.03-1.50 mass%, Sn: 0.01-1.50 mass%, Sb: 0.005-1.50 mass%, Cu: 0.03-3.0 mass%, P: At least one selected from 0.03 to 0.50 mass% and Mo: 0.005 to 0.10 mass% Ni is an element useful for improving the hot rolled sheet structure and improving the magnetic properties It is. However, if the content is less than 0.03% by mass, the effect of improving the magnetic properties is small. On the other hand, if it exceeds 1.50% by mass, the secondary recrystallization becomes unstable and the magnetic properties deteriorate. Therefore, the amount of Ni is preferably in the range of 0.03 to 1.50 mass%.

Sn, Sb, Cu, P, and Mo are elements that are useful for improving the magnetic properties. However, if any of them is less than the lower limit of each component described above, the effect of improving the magnetic properties is small. When the upper limit amount of each component is exceeded, the development of secondary recrystallized grains is hindered.
The balance other than the above components is inevitable impurities and Fe mixed in the manufacturing process.

Next, the slab having the above-described component composition is heated and subjected to hot rolling according to a conventional method, but may be immediately hot rolled after casting without being heated. In the case of a thin slab, hot rolling may be performed, or the hot rolling may be omitted and the process may proceed as it is.
Furthermore, hot-rolled sheet annealing is performed as necessary. At this time, in order to develop a goth structure at a high level in the product plate, a range of 800 to 1100 ° C. is preferable as the hot-rolled sheet annealing temperature. If the hot-rolled sheet annealing temperature is less than 800 ° C., the band structure in hot rolling remains, making it difficult to achieve a sized primary recrystallized structure and inhibiting the development of secondary recrystallization. . On the other hand, when the hot-rolled sheet annealing temperature exceeds 1100 ° C., the grain size after the hot-rolled sheet annealing is excessively coarsened, so that it is extremely difficult to realize a sized primary recrystallized structure.

  After hot-rolled sheet annealing, after performing cold rolling of 1 time or 2 times or more sandwiching intermediate annealing, recrystallization annealing is performed and an annealing separator is applied. After applying the annealing separator, a final finish annealing is performed for the purpose of secondary recrystallization and forsterite film formation.

  It is effective to correct the shape of the steel sheet by performing flattening annealing after the final finish annealing. In addition, when using it, laminating | stacking a steel plate, it is effective to give a tension coating to the steel plate surface before or after planarization annealing in order to improve an iron loss. The tension coating is generally a phosphate-colloidal silica-based glass coating, but may also be an oxide having a low thermal expansion coefficient such as alumina borate. In addition, carbides, nitrides, and the like having a large Young's modulus are also effective as coatings that generate higher tension.

  In applying tension coating in the present invention, it is important to adjust the coating amount and baking conditions so that the generated tension is fully exhibited. In the present invention, the magnetic domain is subdivided by irradiating the surface of the steel sheet with an electron beam at the time after applying the tension coating.

  In addition, in this invention, conventionally well-known electron gun irradiation methods and the manufacturing method of grain-oriented electrical steel sheet can be used suitably except the process and manufacturing conditions mentioned above.

[Example 1]
Si: 3% by mass of final plate thickness: Cold-rolled sheet rolled to 0.23 mm is decarburized and subjected to primary recrystallization annealing, followed by applying an annealing separator mainly composed of MgO, A final annealing process including a crystallization process and a purification process was performed to obtain a grain-oriented electrical steel sheet having a forsterite film. A tension coat consisting of 50% colloidal silica and magnesium phosphate was applied and baked at 850 ° C. Thereafter, a sample having a length of 280 mm and a width of 30 mm was cut out.
In addition, the magnetic domain refinement process was performed by irradiating an electron beam at right angles to the rolling direction. Further, the acceleration voltage was 60 kV, the scanning of the electron beam on the steel plate was performed by a deflection coil, and irradiation was continuously performed, and the interval between irradiation rows in the rolling direction was constant at 5 mm.

The degree of vacuum at the time of electron beam irradiation: P, the distance between the electron gun and the sample: L, and the deflection angle of the electron beam: θ were changed as shown in Table 1. At that time, the scanning width in the width direction is uniquely determined by L and θ.
The iron was obtained at N = 10 from the reached iron loss value W _{17/50 of} both samples, with the samples placed at the scanning positions at both ends, just below the electron gun with a scanning angle of 0 ° and when deflected to the maximum. The loss difference _{ΔW 17/50} is also shown in Table 1.

  From the same table, in the irradiation conditions No. 1, 3, 5, and 7 that do not satisfy the relationship of (1-cos (θ / 2)) · L·log [1000P] ≦ 40, which is the electron beam irradiation condition of the present invention. It can be seen that the difference in the ultimate iron loss value is large between the central portion and the end portion, and it is not possible to perform a uniform magnetic domain refinement process in the width direction of the steel plate. On the other hand, in Nos. 2, 4, 6 and 8 satisfying the electron beam irradiation condition of the present invention, it is understood that the iron loss difference is sufficiently small and uniform irradiation can be performed in the width direction.

[Example 2]
Si: Final sheet thickness containing 3% by mass: Cold-rolled sheet rolled to 0.23 mm, decarburized and subjected to primary recrystallization annealing, and then applied with an annealing separator mainly composed of MgO, Final annealing including a secondary recrystallization process and a purification process was performed to obtain a grain-oriented electrical steel sheet having a forsterite film. Next, a tension coat composed of 60% colloidal silica and aluminum phosphate was applied and baked at 800 ° C. Thereafter, a sample having a length of 280 mm and a width of 30 mm was cut out.
In addition, the magnetic domain fragmentation process was implemented by irradiating an electron beam at right angles to the rolling direction. The acceleration voltage was 40 kV, and scanning of the electron beam on the steel plate was performed by a deflection coil. Further, the electron beam was not irradiated continuously, but was irradiated in the form of dots, the interval between the dot rows in the scanning direction was constant at 0.2 mm, and the interval between the irradiation rows in the rolling direction was 4 mm.

The degree of vacuum during electron beam irradiation: P, the distance between the electron gun and the sample: L, and the deflection angle of the electron beam: θ were changed as shown in Table 2. At that time, the scanning width in the width direction is uniquely determined by L and θ.
A sample is placed immediately below the electron gun with a scan angle of 0 ° and at a position where the scan angle is deflected to the maximum, and the reached _iron loss values W _17/50 are compared at N = 10, and the iron loss difference ΔW _17/50 was _calculated and shown in Table 2.

  As shown in the table, in the irradiation conditions No. 2, 3, 6, and 8 that do not satisfy (1-cos (θ / 2)) · L·log [1000P] ≦ 40 of the present invention, the center portion and the end portion It can be seen that the difference in the reached iron loss value is large with respect to the part, and the magnetic domain refinement treatment cannot be performed uniformly in the width direction of the steel sheet. On the other hand, in the irradiation conditions No. 1, 4, 5 and 7 according to the present invention, it can be seen that the iron loss difference is sufficiently small and uniform irradiation can be performed in the width direction.

Claims (1)

When producing a grain-oriented electrical steel sheet by introducing thermal strain by electron beam irradiation on a grain-oriented electrical steel sheet having a forsterite film and a tension coating on the steel sheet surface,
In the electron beam irradiation, the distance from the electron beam irradiation part to the steel sheet surface is L [mm], the deflection angle when performing electron beam irradiation is θ [°], and the vacuum degree of the irradiation processing chamber is P [Pa]. The following formula (1-cos (θ / 2)) · L·log [1000P] ≦ 40
(However, P ≧ 0.02)
A method for producing a grain-oriented electrical steel sheet, which is performed under a condition that satisfies the following conditions.

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