JP2021123753A - Grain-oriented electromagnetic steel sheet - Google Patents

Abstract

To provide a grain-oriented electromagnetic steel sheet that improves magnetostrictivity in a low magnetic field region, and enhances magnetic flux density and can avoid a deterioration of film adhesion.SOLUTION: Such a grain-oriented electromagnetic steel sheet is adopted that: it has a chemical composition comprising, in mass%, Si: 2.0-7.0% and Bi: 0.0005-0.0100%; it includes grain boundaries that satisfy boundary conditions BA and do not satisfy boundary conditions BB; and a magnetic flux density B8 in a rolling direction is 1.920 T or more.SELECTED DRAWING: Figure 3

Description

The present invention relates to grain-oriented electrical steel sheets.

The grain-oriented electrical steel sheet contains 7% by mass or less of Si and has a secondary recrystallization texture accumulated in the {110} <001> orientation (Gossi orientation). The {110} <001> orientation means that the {110} plane of the crystal is arranged parallel to the rolling surface, and the <001> axis of the crystal is arranged parallel to the rolling direction.

The magnetic properties of grain-oriented electrical steel sheets are greatly affected by the degree of integration in the {110} <001> orientation. In particular, it is considered that the relationship between the rolling direction of the steel sheet, which is the main magnetization direction when the steel sheet is used, and the <001> direction of the crystal, which is the easy magnetization direction, is important. Therefore, in recent practical grain-oriented electrical steel sheets, the angle formed by the <001> direction of the crystal and the rolling direction is controlled so as to be within a range of about 5 °.

The deviation between the actual crystal orientation of the directional electromagnetic steel plate and the ideal {110} <001> orientation is the deviation angle α around the rolling surface normal direction Z, the deviation angle β around the rolling perpendicular direction C, and the rolling direction. It can be represented by the three components of the deviation angle γ around L.

FIG. 1 is a schematic diagram illustrating a deviation angle α, a deviation angle β, and a deviation angle γ. As shown in FIG. 1, the deviation angle α is an angle formed by the <001> direction of the crystal projected on the rolled surface and the rolling direction L when viewed from the rolling surface normal direction Z. The deviation angle β is the angle formed by the <001> direction of the crystal projected on the L cross section (cross section with the rolling perpendicular direction as the normal) and the rolling direction L when viewed from the rolling perpendicular direction C (plate width direction). be. The deviation angle γ is an angle formed by the <110> direction of the crystal projected on the C cross section (cross section with the rolling direction as the normal) and the rolling surface normal direction Z when viewed from the rolling direction L.

Of the deviation angles α, β, and γ, the deviation angle β is known to affect magnetostriction. Magnetostriction is a phenomenon in which a magnetic material changes its shape when a magnetic field is applied. In grain-oriented electrical steel sheets used for transformers of transformers, magnetostriction causes vibration and noise, so that magnetostriction is required to be small.

For example, Patent Documents 1 to 3 disclose that the shift angle β is controlled. Further, it is disclosed in Patent Documents 4 and 5 that the deviation angle α is controlled in addition to the deviation angle β. Further, Patent Document 6 discloses a technique for improving the iron loss characteristics by classifying the degree of integration of crystal orientations in more detail by using the deviation angle α, the deviation angle β, and the deviation angle γ as indexes.

Further, for example, Patent Documents 7 to 9 disclose that not only the magnitude and the average value of the absolute values of the deviation angles α, β, and γ are controlled, but also the fluctuation (deviation) is included in the control. Further, Patent Documents 10 to 12 disclose that Nb, V and the like are added to the grain-oriented electrical steel sheet.

Further, the grain-oriented electrical steel sheet is required to have excellent magnetic flux density in addition to magnetostriction. So far, a method of controlling the growth of crystal grains in secondary recrystallization to obtain a steel sheet having a high magnetic flux density has been proposed. For example, in Patent Documents 13 and 14, a method of advancing secondary recrystallization while giving a temperature gradient to a steel sheet in the tip region of secondary recrystallized grains that are eroding the primary recrystallized grains in a finish annealing step. Is disclosed.

However, when the secondary recrystallized grains are grown using the temperature gradient, the grain growth is stable, but the crystal grains may become excessively large. If the crystal grains become excessively large, the effect of improving the magnetic flux density may be hindered by the influence of the curvature of the coil. For example, in Patent Document 15, when the secondary recrystallization is allowed to proceed while giving a temperature gradient, a process of suppressing the free growth of the secondary recrystallization generated at the initial stage of the secondary recrystallization (for example, in the width direction of the steel sheet). The process of applying mechanical strain to the end of the surface) is disclosed.

Further, Patent Document 16 discloses that the magnetic flux density of the grain-oriented electrical steel sheet is improved by adding Bi to the slab at the time of manufacturing the grain-oriented electrical steel sheet.

However, it is known that when Bi is added to the slab during the production of grain-oriented electrical steel sheets, the magnetic flux density is improved, but the film adhesion is lowered. When the film adhesion is lowered, it becomes difficult to apply tension to the steel sheet, and as a result, it becomes difficult to satisfy the iron loss characteristics required for the grain-oriented electrical steel sheet. For example, Patent Document 17 discloses a method of suppressing a decrease in film adhesion by precisely controlling the decarburization annealing conditions even when Bi is added to the slab. Patent Document 18 describes a method in which even if Bi is added to a slab, the amount of oxygen after decarburization and annealing is controlled, and a chlorine compound, an Sb compound, or the like is added to the annealing separator to suppress a decrease in film adhesion. Is disclosed.

Further, Patent Document 19 discloses a method for improving film adhesion by containing a rare earth metal element, a sulfide compound, or the like in a primary film containing forsterite as a main component.

Japanese Patent Application Laid-Open No. 2001-294996 Japanese Patent Application Laid-Open No. 2005-240102 Japanese Patent Application Laid-Open No. 2015-206114 Japanese Patent Application Laid-Open No. 2004-060026 International Publication No. 2016/056501 Japanese Patent Application Laid-Open No. 2007-314826 Japanese Patent Application Laid-Open No. 2001-192785 Japanese Patent Application Laid-Open No. 2005-240079 Japanese Patent Application Laid-Open No. 2012-052229 Japanese Patent Application Laid-Open No. 52-024116 Japanese Patent Application Laid-Open No. 02-200732 Japanese Patent No. 4962516 Japanese Patent Application Laid-Open No. 57-002839 Japanese Patent Application Laid-Open No. 61-190017 Japanese Patent Application Laid-Open No. 02-258923 Japanese Patent Application Laid-Open No. 6-88173 Japanese Patent Application Laid-Open No. 6-158169 Japanese Patent Application Laid-Open No. 8-2320119 Japanese Patent No. 5419459

As a result of the examination by the present inventors, it cannot be said that the conventional techniques disclosed in Patent Documents 1 to 9 are particularly sufficient in reducing magnetostriction even though the crystal orientation is controlled.

Further, since the conventional techniques disclosed in Patent Documents 10 to 12 merely contain Nb and V, it cannot be said that the reduction of magnetostriction is sufficient. Further, the conventional techniques disclosed in Patent Documents 13 to 15 not only have a problem in terms of productivity, but also cannot be said to sufficiently reduce magnetostriction.

Further, the conventional technique disclosed in Patent Document 16 merely adds Bi or the like, and it cannot be said that the film adhesion is sufficient. Further, the conventional techniques disclosed in Patent Documents 17 to 19 have a problem that a local decrease in film adhesion occurs due to fluctuations in the steel sheet condition during the manufacturing process, and a new film adhesion occurs. Sexual improvement technology is required. In addition to this, in these conventional techniques, from the viewpoint of ensuring film adhesion, there are restrictions on the upper limit of the amount of Bi added in the slab and the amount of Bi in the final product. Therefore, the effect of improving the magnetic flux density by Bi has not been fully enjoyed, and a technique capable of utilizing a larger amount of Bi is required.

The present invention has been made in view of the above problems. An object of the present invention is to provide a grain-oriented electrical steel sheet having improved magnetostriction in view of the current situation in which reduction of magnetostriction is required for grain-oriented electrical steel sheets. In particular, it is an object of the present invention to provide a grain-oriented electrical steel sheet having improved magnetostriction in a low magnetic field region (magnetic field of about 1.5 T).

Another object of the present invention is to provide a grain-oriented electrical steel sheet that can improve the magnetostriction in a low magnetic field region, improve the magnetic flux density, and at the same time avoid a decrease in film adhesion.

The gist of the present invention is as follows.

(1) The grain-oriented electrical steel sheet according to one aspect of the present invention is a grain-oriented electrical steel sheet having an texture oriented in the Goss direction.
The grain-oriented electrical steel sheet is by mass%
Si: 2.0-7.0%,
Bi: 0.0005-0.0100%,
Nb: 0 to 0.030%,
V: 0 to 0.030%,
Mo: 0-0.030%,
Ta: 0-0.030%,
W: 0 to 0.030%,
C: 0 to 0.0050%,
Mn: 0-1.0%,
S: 0 to 0.0150%,
Se: 0 to 0.0150%,
Al: 0-0.0650%,
N: 0-0.0050%,
Cu: 0-0.40%,
B: 0 to 0.080%,
P: 0 to 0.50%,
Ti: 0 to 0.0150%,
Sn: 0 to 0.10%,
Sb: 0 to 0.10%,
Cr: 0 to 0.30%,
Ni: 0-1.0%,
Has a chemical composition in which the balance is composed of Fe and impurities.
The deviation angle from the ideal Goss direction with the rolling surface normal direction Z as the rotation axis is defined as α.
The deviation angle from the ideal Goss direction with the rolling perpendicular direction C as the rotation axis is defined as β.
The deviation angle from the ideal Goss direction with the rolling direction L as the rotation axis is defined as γ.
The deviation angles of the crystal orientations measured at two measurement points adjacent to each other on the plate surface and having an interval of 1 mm are _{expressed as (α 1} β ₁ γ ₁ ) and (α ₂ β ₂ γ ₂ ).
Boundary condition BA _{is defined as | β 2-} β ₁ | ≧ 0.5 °,
When the boundary condition BB is defined as [(α _2- α ₁ ) ² + (β _2- β ₁ ) ² + (γ _2- γ ₁ ) ² ] ^1/2 ≥ 2.0 °
There is a grain boundary that satisfies the boundary condition BA and does not satisfy the boundary condition BB.
The magnetic flux density B _{8 in the} rolling direction is 1.920 T or more.
(2) The grain-oriented electrical steel sheet according to (1) above has an intermediate layer arranged in contact with the grain-oriented electrical steel sheet and an insulating coating arranged in contact with the intermediate layer, and has a diameter. The coating residual area ratio when wound around a 20 mm round bar and bent back may be 90 to 100%.
(3) In the grain-oriented electrical steel sheet according to (1) or (2) above, at least one selected from the group consisting of Nb, V, Mo, Ta, and W as the chemical composition is 0. It may be contained in an amount of 0030 to 0.030% by mass.
(4) above (1) In the oriented electrical steel sheet according to any one of - (3), wherein an average crystal grain size in the rolling direction L is defined as the particle size RA _L obtained based on the boundary conditions BA ,
When the average crystal grain size in the rolling direction L obtained based on the boundary condition BB is defined _{as the grain size RB L,}
The particle size RA _L and the particle size RB _L may satisfy 1.10 ≦ RB _L ÷ RA _L.
(5) above (1) In the oriented electrical steel sheet according to any one of - (4), defined as the particle size RA _C the average crystal grain size of the perpendicular to the rolling direction C obtained based on the boundary conditions BA death,
When the average crystal grain size of the perpendicular to the rolling direction C is defined as the particle diameter RB _C obtained based on the boundary conditions BB,
And the particle size RA _C and the particle diameter RB _C may fulfill the 1.10 ≦ RB _C ÷ RA _C.
(6) In the oriented electrical steel sheet according to any one of the above (1) to (5), wherein the average crystal grain size in the rolling direction L is defined as the particle size RA _L obtained based on the boundary conditions BA ,
When the average crystal grain size of the perpendicular to the rolling direction C is defined as the particle size RA _C obtained based on the boundary conditions BA,
And the particle size RA _L and the grain size RA _C may fulfill the 1.15 ≦ RA _C ÷ RA _L.
(7) In the directional electromagnetic steel sheet according to any one of (1) to (6) above, the average crystal grain size in the rolling direction L obtained based on the boundary condition BB is defined as the _{particle size RB L.} ,
When the average crystal grain size of the perpendicular to the rolling direction C is defined as the particle diameter RB _C obtained based on the boundary conditions BB,
The particle size RB _L and the particle size RB _C may satisfy 1.50 ≦ RB _C ÷ RB _L.
(8) above (1) oriented electrical steel sheet according to any one of (1) to (7), the average crystal grain size in the rolling direction L is defined as the particle size RA _L obtained based on the boundary conditions BA ,
The average crystal grain size in the rolling direction L obtained based on the boundary condition BB is defined as the _{grain size RB L.}
Wherein the average crystal grain size of the perpendicular to the rolling direction C is defined as the particle size RA _C obtained based on the boundary conditions BA,
When the average crystal grain size of the perpendicular to the rolling direction C is defined as the particle diameter RB _C obtained based on the boundary conditions BB,
And the particle size RA _L and the grain size RA _C and the particle diameter RB _L and the diameter RB _C is,
_{(RB C × RA L) ÷} (RB L × RA C) <1.0 may satisfy.

According to the above aspect of the present invention, there is provided a grain-oriented electrical steel sheet having improved magnetostriction in a low magnetic field region (particularly, a magnetic field of about 1.5 T).

In particular, according to the above aspect of the present invention, there is provided a grain-oriented electrical steel sheet that can improve the magnetostriction in a low magnetic field region, improve the magnetic flux density, and at the same time avoid a decrease in film adhesion.

It is a schematic diagram which illustrates the deviation angle α, the deviation angle β, and the deviation angle γ. It is a schematic diagram which illustrates the crystal grain boundary of the grain-oriented electrical steel sheet. It is sectional drawing of the grain-oriented electrical steel sheet which concerns on one Embodiment of this invention. It is a flow chart of the manufacturing method of the grain-oriented electrical steel sheet which concerns on one Embodiment of this invention.

A preferred embodiment of the present invention will be described in detail. However, the present invention is not limited to the configuration disclosed in the present embodiment, and various modifications can be made without departing from the spirit of the present invention. In addition, the lower limit value and the upper limit value are included in the numerical limitation range described below. Numerical values that indicate "greater than" or "less than" are not included in the numerical range. Further, "%" regarding the chemical composition means "mass%" unless otherwise specified.

Generally, in order to reduce the magnetostriction, the crystal orientation is set so that the deviation angle β becomes small (specifically, the maximum value and the average value of the absolute value | β | of the deviation angle β become small). Be controlled. In fact, until now, the strength of the magnetic field at the time of magnetization is generally the magnetic field strength near 1.7T, which is the strength of the magnetic field at the time of measuring the magnetic characteristics (hereinafter, simply referred to as "medium magnetic field region"). It has been confirmed that the correlation between the deviation angle β and the magnetostriction is relatively high.

On the other hand, secondary recrystallization in a practical grain-oriented electrical steel sheet proceeds in a state of being wound around a coil. That is, the secondary recrystallized grains grow in a state where the steel sheet has a curvature. Therefore, even if the crystal grains have a small deviation angle β in the initial stage of secondary recrystallization, the deviation angle β inevitably increases as the crystal grains grow.

Of course, if it is possible to generate a large number of crystals with a small deviation angle β at the stage of secondary recrystallization grains, it is almost ideal {110} even if those individual crystal grains do not grow so large. It is also possible to fill the entire region of the steel sheet with the secondary recrystallized grains in the <001> orientation. However, in reality, it is not possible to generate a large number of crystal grains having such alignment.

While investigating the relationship between the crystal orientation and noise of the material steel sheet used for the practical iron core, the present inventors have found that the correlation between the deviation angle β and noise may be weakened in some materials. I found out. That is, it was found that the noise in the actual use environment was not sufficiently reduced even if the grain-oriented electrical steel sheet having a small magnetostriction with the deviation angle β controlled as in the conventional case was used.

The present inventors presumed this cause as follows. First, in an actual use environment, the magnetic flux does not flow uniformly in the steel sheet, and there are places where the magnetic flux is locally concentrated. Along with this, there is a region where the magnetic flux density weakens, and the area is wider in the region where the magnetic flux weakens. Therefore, it is considered that the noise in the actual use environment is strongly influenced not only by the magnetostriction under the general excitation condition of about 1.7 T but also by the magnetostriction in the lower excitation region.

According to this estimation, we investigated the situation where the correlation between the deviation angle β and noise became low, and found that the behavior was the "difference between the minimum and maximum magnetostriction", which is the amount of magnetostriction at 1.5T (hereinafter referred to as "the difference between the minimum and maximum magnetostriction"). It was found that it can be evaluated by (denoted as "λpp@1.5T"). Then, if this behavior can be optimally controlled, it is possible to further reduce the noise of the transformer.

Therefore, the present inventors have investigated not to grow the secondary recrystallized grains while maintaining the crystal orientation at the stage of growth of the secondary recrystallized grains, but to grow the crystals with the orientation change. As a result, during the growth of the secondary recrystallized grains, a large number of local and small tilt angle changes that were not conventionally recognized as grain boundaries are generated, and one secondary recrystallized grain has a deviation angle β. It was found that the state of being divided into slightly different small regions is advantageous for reducing magnetostriction in the low magnetic field region.

Further, in order to control the above-mentioned orientation change, it is important to consider a factor that facilitates the orientation change itself and a factor that makes the orientation change continuously occur in one crystal grain. I found out. Then, in order to facilitate the occurrence of the orientation change itself, it is effective to start the secondary recrystallization from a lower temperature. For example, it was confirmed that the primary recrystallization particle size can be controlled and elements such as Nb can be utilized. .. Furthermore, by using a conventionally used inhibitor such as AlN in an appropriate temperature and atmosphere, it is possible to continuously generate an orientation change up to a high temperature region in one crystal grain in the secondary recrystallization. I confirmed that I could do it.

Further, the present inventors have studied to improve the magnetic flux density and at the same time avoid the decrease in film adhesion in addition to the reduction of the low magnetic field magnetostriction by the above-mentioned direction control.

According to the conventional knowledge, if Bi is added to the slab during the production of the grain-oriented electrical steel sheet, the Bi compound acts as an inhibitor, the degree of integration of the Goss orientation is increased, and as a result, the magnetic flux density of the grain-oriented electrical steel sheet is improved. Was known. On the other hand, if Bi is added to the slab, Bi in the silicon steel sheet is segregated at the interface between the silicon steel sheet and the primary coating (intermediate layer) formed by the finish annealing, and the fitting structure of this interface is relaxed. As a result, it has been known that the film adhesion is reduced.

Therefore, conventionally, when Bi is added to a slab, it is necessary to precisely control the decarburization annealing conditions at the time of production, or to newly add an additional compound, and Bi acting as an inhibitor It was necessary to quickly discharge Bi to the outside of the system by purification during finish annealing so that it would not finally remain on the grain-oriented electrical steel sheet. However, since the steel sheet is annealed in a coiled state during finish annealing, purification is suppressed and Bi remains in the grain-oriented electrical steel sheet in places such as the inside of the coil where the circulation of the purified atmosphere tends to be stagnant. At that location, there was a problem such as a local decrease in film adhesion. In addition, giving priority to quick and careful discharge of Bi and performing purification annealing at high temperature or for a long time reduces the residual amount of Bi in the grain-oriented electrical steel sheet, but the interface is fitted due to high temperature and long-term retention. The structure was relaxed, and the film adhesion was also reduced. It also leads to a decrease in productivity.

However, when the above-mentioned orientation change is controlled, the present inventors have a local and small tilt angle orientation change that has not been recognized as a grain boundary in one secondary recrystallized grain. Since a large number of occurrences occur (that is, the material structure is different from the conventional one), it is considered that the conventional knowledge does not apply to the above-mentioned characteristic change due to the Bi content. Therefore, the present inventors have controlled the above-mentioned orientation change, and then added Bi as a chemical composition to study in detail the changes in the characteristics of the magnetic flux density and the film adhesion.

As a result, when the above-mentioned orientation change is controlled, even if Bi is added to the slab, unlike the conventional knowledge, it is not necessary to precisely control the decarburization annealing conditions, and an additional compound is added. It was found that even if Bi acting as an inhibitor remains on the grain-oriented electrical steel sheet (silicon steel sheet) without the need for new addition, it is possible to improve the magnetic flux density and at the same time avoid a decrease in film adhesion.

That is, the present inventors can improve the magnetostriction in the low magnetic field region by controlling the orientation change, and further improve the magnetic flux density by effectively utilizing Bi, and at the same time, avoid the deterioration of the film adhesion. I found out.

[First Embodiment]
In the grain-oriented electrical steel sheet according to the first embodiment of the present invention, the secondary recrystallized grains are divided into a plurality of regions having slightly different deviation angles β. That is, in the grain-oriented electrical steel sheet according to the present embodiment, in addition to the grain boundaries having a relatively large angle difference corresponding to the grain boundaries of the secondary recrystallized grains, the inside of the secondary recrystallized grains is locally divided. It has a small grain boundary.

In addition, the grain-oriented electrical steel sheet according to the first embodiment contains 0.00050 to 0.010% of Bi as a chemical composition in mass%.

Specifically, the grain-oriented electrical steel sheet according to the present embodiment is a grain-oriented electrical steel sheet having an texture oriented in the Goss direction.
By mass%, Si: 2.0 to 7.0%, Bi: 0.0005 to 0.0100%, Nb: 0 to 0.030%, V: 0 to 0.030%, Mo: 0 to 0. 030%, Ta: 0 to 0.030%, W: 0 to 0.030%, C: 0 to 0.0050%, Mn: 0 to 1.0%, S: 0 to 0.0150%, Se: 0 to 0.0150%, Al: 0 to 0.0650%, N: 0 to 0.0050%, Cu: 0 to 0.40%, B: 0 to 0.080%, P: 0 to 0.50 %, Ti: 0 to 0.0150%, Sn: 0 to 0.10%, Sb: 0 to 0.10%, Cr: 0 to 0.30%, Ni: 0 to 1.0%. , The balance has a chemical composition consisting of Fe and impurities.
Further, the deviation angle from the ideal Goss direction with the rolling surface normal direction Z as the rotation axis is defined as α, and the deviation angle from the ideal Goss direction with the rolling perpendicular direction (plate width direction) C as the rotation axis is defined as β. Defined, the deviation angle from the ideal Goss direction with the rolling direction L as the rotation axis is defined as γ, and
The deviation angles of the crystal orientations measured at two measurement points adjacent to each other on the plate surface and having an interval of 1 mm are _{expressed as (α 1} β ₁ γ ₁ ) and (α ₂ β ₂ γ ₂ ), respectively, and the boundary condition BA is defined as | Β _2- β ₁ | ≧ 0.5 °, and the boundary condition BB is [(α _2- α ₁ ) ² + (β _2- β ₁ ) ² + (γ _2- γ ₁ ) ² ] ^{1 / When defining 2} ≧ 2.0 °,
In the directional electromagnetic steel plate according to the present embodiment, in addition to the grain boundaries satisfying the boundary condition BB (grain boundaries corresponding to the secondary recrystallized grain boundaries), the boundary condition BA is satisfied and the boundary condition BB is satisfied. It has unsatisfactory grain boundaries (grain boundaries that divide secondary recrystallized grains).
Further, the grain-oriented electrical steel sheet according to the present embodiment has a magnetic flux density B _{8 in the} rolling direction of 1.920 T or more.

The grain boundaries satisfying the boundary condition BB substantially correspond to the secondary recrystallized grain boundaries observed when the conventional grain-oriented electrical steel sheet is macro-etched. The directional electromagnetic steel plate according to the present embodiment has, in addition to the grain boundaries satisfying the above boundary condition BB, relatively frequently having grain boundaries satisfying the boundary condition BA and not satisfying the above boundary condition BB. The grain boundaries that satisfy the boundary condition BA and do not satisfy the boundary condition BB correspond to the local and small tilt angle grain boundaries that divide the secondary recrystallized grains. That is, in the present embodiment, the secondary recrystallized grains are in a state of being finely divided by small regions having slightly different displacement angles β.

Conventional grain-oriented electrical steel sheets may have secondary recrystallized grain boundaries that satisfy the boundary condition BB. Further, the conventional grain-oriented electrical steel sheet may have a displacement of a shift angle β within the grains of the secondary recrystallized grains. However, in the conventional grain-oriented electrical steel sheet, the displacement angle β tends to be continuously displaced in the secondary recrystallized grain, so that the displacement of the grain angle β existing in the conventional grain-oriented electrical steel sheet is the above boundary. It is difficult to satisfy the condition BA.

For example, in a conventional grain-oriented electrical steel sheet, the displacement of the displacement angle β may be discriminated in the long range region in the secondary recrystallized grain, but the displacement of the displacement angle β in the short range region in the secondary recrystallized grain. Is difficult to identify because it is very small (it is difficult to satisfy the boundary condition BA). On the other hand, in the grain-oriented electrical steel sheet according to the present embodiment, the deviation angle β is locally displaced in a short range region and can be identified as a grain boundary. _{Specifically, the displacement at which the value of | β 2-} β ₁ | is 0.5 ° or more is relatively high between two measurement points adjacent to each other and having an interval of 1 mm in the secondary recrystallized grain. Exists with frequency.

In the grain-oriented electrical steel sheet according to the present embodiment, by precisely controlling the manufacturing conditions as described later, the grain boundaries (grains that divide the secondary recrystallized grains) that satisfy the boundary condition BA and do not satisfy the boundary condition BB are satisfied. The world) is intentionally created. In the grain-oriented electrical steel sheet according to the present embodiment, the secondary recrystallized grains are divided into small regions having slightly different displacement angles β, and magnetostriction in the low magnetic field region is reduced.

In addition, the grain-oriented electrical steel sheet according to the present embodiment contains 0.0005 to 0.0100% by mass of Bi as a chemical composition. Since the material structure of the grain-oriented electrical steel sheet according to the present embodiment is different from the conventional one as described above, the conventional knowledge regarding the decrease in the film adhesion due to the Bi content does not apply, and the magnetic flux density is improved and the film is formed at the same time by the Bi content. Deterioration of adhesion is avoided.

Hereinafter, the grain-oriented electrical steel sheet according to the present embodiment will be described in detail.

1. 1. Crystal Orientation First, the description of the crystal orientation in the present embodiment will be described.
In the present embodiment, two {110} <001> orientations of "actual crystal {110} <001>orientation" and "ideal {110} <001>orientation" are distinguished. The reason for this is that in the present embodiment, it is necessary to distinguish between the {110} <001> orientation when displaying the crystal orientation of the practical steel sheet and the {110} <001> orientation as the academic crystal orientation. Because.

Generally, in the measurement of the crystal orientation of a recrystallized practical steel sheet, the crystal orientation is defined without strictly distinguishing the angle difference of about ± 2.5 °. In the case of conventional grain-oriented electrical steel sheets, the angular range of about ± 2.5 ° centered on the geometrically exact {110} <001> orientation is defined as the "{110} <001> orientation". .. However, in this embodiment, it is necessary to clearly distinguish the angle difference of ± 2.5 ° or less.

Therefore, in the present embodiment, when the orientation of the grain-oriented electrical steel sheet is meant in a practical sense, it is simply described as "{110} <001> orientation (Goss orientation)" as in the conventional case. On the other hand, when the {110} <001> orientation as a geometrically exact crystal orientation is meant, in order to avoid confusion with the {110} <001> orientation used in conventional publicly known documents and the like, " "Ideal {110} <001> direction (ideal Goss direction)" is described.

Therefore, in the present embodiment, for example, there is a description that "the {110} <001> orientation of the grain-oriented electrical steel sheet according to the present embodiment deviates by 2 ° from the ideal {110} <001> orientation." Sometimes.

Further, in the present embodiment, the following four angles α, β, γ, and φ related to the crystal orientation observed in the directional electromagnetic steel plate are used.

Deviation angle α: The deviation angle of the crystal orientation observed on the grain-oriented electrical steel sheet from the ideal {110} <001> orientation around the rolling surface normal direction Z.
Deviation angle β: The deviation angle of the crystal orientation observed on the grain-oriented electrical steel sheet from the ideal {110} <001> orientation around the rolling perpendicular direction C.
Deviation angle γ: The deviation angle of the crystal orientation observed on the grain-oriented electrical steel sheet from the ideal {110} <001> orientation around the rolling direction L.
A schematic diagram of the deviation angle α, the deviation angle β, and the deviation angle γ is shown in FIG.

Angle φ: The deviation angles of the crystal orientations measured at two measurement points adjacent to each other on the rolled surface of the directional electromagnetic steel plate and having an interval of 1 mm are (α ₁ , β ₁ , γ ₁ ) and (α _{2), respectively.} , Β ₂ , γ ₂ ), the angle obtained by φ = [(α _2- α ₁ ) ² + (β _2- β ₁ ) ² + (γ _2- γ ₁ ) ² ] ^1/2.
This angle φ may be described as “spatial three-dimensional directional difference”.

2. Crystal grain boundaries of directional electromagnetic steel sheets The directional electromagnetic steel sheets according to the present embodiment are conventionally recognized as grain boundaries, which occur during the growth of secondary recrystallized grains in order to control the deviation angle β. Utilize local changes in crystal orientation that were not present. In the following description, the above-mentioned orientation change that occurs so as to divide the inside of one secondary recrystallized grain into small regions having slightly different displacement angles β may be described as “switching”.
Further, the crystal grain boundary (grain boundary satisfying the boundary condition BA) considering the angle difference of the deviation angle β is described as "β grain boundary", and the crystal grain distinguished by the β grain boundary as the boundary is described as "β crystal grain". Sometimes.

Further, regarding the magnetostriction (λp−p@1.5T) when excited at 1.5T, which is a characteristic related to the present embodiment, in the following description, it is simply described as “low magnetic field (at) magnetostriction”. There is.

It is considered that the above switching occurs in the process in which the change in crystal orientation is about 1 ° (less than 2 °) and the growth of the secondary recrystallized grains continues. Details will be described later in relation to the production method, but it is important to grow the secondary recrystallized grains in a situation where switching is likely to occur. For example, it is important to start the secondary recrystallization at a relatively low temperature by controlling the primary recrystallization particle size and to continue the secondary recrystallization to a high temperature by controlling the type and amount of the inhibitor.

The reason why the control of the shift angle β affects the low magnetic field magnetostriction is not always clear, but it is presumed as follows.

Generally, the magnetization behavior in a low magnetic field is caused by the movement of 180 ° magnetic domains. It is considered that this movement of the magnetic domain is affected by the continuity of the magnetic domain with the adjacent crystal grains especially in the vicinity of the grain boundary, and the orientation difference with the adjacent grain may be linked to the magnitude of the obstacle of the magnetization behavior. As described above, since secondary recrystallization in a practical grain-oriented electrical steel sheet proceeds in a state of being wound around a coil, it is conceivable that the difference in the deviation angle β between adjacent crystal grains at the grain boundaries becomes large. .. In the switching controlled in the present embodiment, switching (local orientation change) occurs frequently in one secondary recrystallized grain, so that the relative orientation difference with the adjacent grain is reduced and the directionality is directional. It is considered that it acts to enhance the continuity of the crystal orientation of the entire electromagnetic steel sheet.

In this embodiment, two types of boundary conditions are defined for changes in crystal orientation including switching. In this embodiment, the definition of "grain boundaries" based on these boundary conditions is important.

Currently, the crystal orientation of practically manufactured grain-oriented electrical steel sheets is controlled so that the deviation angle between the rolling direction and the <001> direction is approximately 5 ° or less. This control is the same for the grain-oriented electrical steel sheet according to the present embodiment. Therefore, when defining the "grain boundaries" of grain-oriented electrical steel sheets, the "boundary where the orientation difference between adjacent regions is 15 ° or more", which is the general definition of grain boundaries (large tilt angle grain boundaries), is applied. Can't. For example, in a conventional grain-oriented electrical steel sheet, grain boundaries are revealed by macro-etching of the steel sheet surface, and the crystal orientation difference between the two side regions of the grain boundaries is usually about 2 to 3 °.

In this embodiment, as will be described later, it is necessary to strictly define the boundary between crystals. Therefore, as a method for specifying grain boundaries, a visual-based method such as macro etching is not adopted.

In the present embodiment, in order to specify the grain boundaries, measurement lines including at least 500 measurement points are set on the rolled surface at 1 mm intervals, and the crystal orientation is measured. For example, the crystal orientation may be measured by an X-ray diffraction method (Laue method). The Laue method is a method of irradiating a steel sheet with an X-ray beam and analyzing the transmitted or reflected diffraction spots. By analyzing the diffraction spots, the crystal orientation of the place where the X-ray beam is irradiated can be identified. By analyzing the diffraction spots at a plurality of locations by changing the irradiation position, the crystal orientation distribution at each irradiation position can be measured. The Laue method is a method suitable for measuring the crystal orientation of a metal structure having coarse crystal grains.

The number of measurement points for the crystal orientation may be at least 500, but it is preferable to appropriately increase the number of measurement points according to the size of the secondary recrystallized grains. For example, when the number of secondary recrystallized grains contained in the measurement line is less than 10 when the measurement point for measuring the crystal orientation is 500 points, 10 or more secondary recrystallized grains are included in the measurement line. It is preferable to extend the above measurement line by increasing the number of measurement points at 1 mm intervals.

The crystal orientation is measured at 1 mm intervals on the rolled surface, and then the above-mentioned deviation angle α, deviation angle β, and deviation angle γ are specified for each measurement point. Based on the deviation angle at each specified measurement point, it is determined whether or not there is a grain boundary between two adjacent measurement points. Specifically, it is determined whether or not the two adjacent measurement points satisfy the above-mentioned boundary condition BA and / or boundary condition BB.

Specifically, when the deviation angles of the crystal orientations measured at two adjacent measurement points are expressed as (α ₁ , β ₁ , γ ₁ ) and (α ₂ , β ₂ , γ ₂ ), respectively, the boundary condition BA Is defined as | β _{2- β 1} | ≧ 0.5 °, and the boundary condition BB is [(α _2- α ₁ ) ² + (β _2- β ₁ ) ² + (γ _2- γ ₁ ) ² ] ^{1 It is defined as / 2} ≧ 2.0 °. It is determined whether or not there is a grain boundary satisfying the boundary condition BA and / or the boundary condition BB between two adjacent measurement points.

The grain boundary satisfying the boundary condition BB has a spatial three-dimensional orientation difference (angle φ) between two points sandwiching the grain boundary of 2.0 ° or more, and this grain boundary was recognized by macro etching. It can be said that it is almost the same as the grain boundary of the conventional secondary recrystallized grains.

Apart from the grain boundaries that satisfy the above boundary condition BB, the grain boundaries strongly related to "switching", specifically, the boundary condition BA is satisfied and the boundary condition is satisfied in the grain boundary according to the present embodiment. Grain boundaries that do not satisfy BB are present at a relatively high frequency. The grain boundaries defined in this way correspond to the grain boundaries that divide one secondary recrystallized grain into small regions with slightly different shift angles β.

The above two grain boundaries can also be determined using different measurement data. However, considering the time and effort of measurement and the deviation from the actual situation due to the difference in data, the deviation angle of the crystal orientation obtained from the same measurement line (at least 500 measurement points at 1 mm intervals on the rolled surface) is used. Therefore, it is preferable to obtain the above two grain boundaries.

Since the directional electromagnetic steel plate according to the present embodiment has a grain boundary satisfying the boundary condition BB and a grain boundary satisfying the boundary condition BA and not satisfying the boundary condition BB at a relatively high frequency, it is secondary. The inside of the recrystallized grains is divided into small regions having slightly different deviation angles β, and as a result, magnetostriction in the low magnetic field region is reduced.

In this embodiment, it is sufficient that the steel sheet has a "grain boundary that satisfies the boundary condition BA and does not satisfy the boundary condition BB". However, in order to substantially reduce the magnetostriction in the low magnetic field region, it is preferable that grain boundaries that satisfy the boundary condition BA and do not satisfy the boundary condition BB exist at a relatively high frequency.

For example, the present embodiment is characterized in that the inside of the secondary recrystallized grains is divided into small regions having slightly different deviation angles β, so that the β grain boundaries are relatively larger than those of the conventional secondary recrystallized grain boundaries. It is preferably present at a high frequency.

Specifically, when the crystal orientation is measured at at least 500 measurement points at 1 mm intervals on the rolled surface, the deviation angle is specified at each measurement point, and the boundary condition is determined at two adjacent measurement points. The "grain boundaries satisfying the boundary condition BA" may be present at a ratio of 1.1 times or more the "grain boundaries satisfying the boundary condition BB". That is, when the boundary condition is determined as described above, the value obtained by dividing the "number of boundaries satisfying the boundary condition BA" by the "number of boundaries satisfying the boundary condition BB" may be 1.1 or more. In the present embodiment, when the above value is 1.1 or more, it is determined that the grain grain boundary satisfying the boundary condition BA and not satisfying the boundary condition BB exists in the grain-oriented electrical steel sheet.

Further, the value obtained by dividing the above-mentioned "number of boundaries satisfying the boundary condition BA" by "the number of boundaries satisfying the boundary condition BB" is preferably 1.3 or more, and more preferably 1.5 or more. preferable.

The upper limit of the value obtained by dividing the "number of boundaries satisfying the boundary condition BA" by the "number of boundaries satisfying the boundary condition BB" is not particularly limited. For example, this value may be 80 or less, 40 or less, and 30 or less.

3. 3. Chemical composition The chemical composition of the grain-oriented electrical steel sheet according to this embodiment will be described in detail later. However, the grain-oriented electrical steel sheet (silicon steel sheet) according to the present embodiment contains 0.0005 to 0.0100% by mass of Bi.

As described above, as a conventional knowledge, it has been known that if Bi is added to a slab during the production of grain-oriented electrical steel sheets, the Bi compound acts as an inhibitor to increase the magnetic flux density. However, it has also been known that when Bi is added to the slab, Bi segregates at the interface between the silicon steel plate and the primary coating, and the coating adhesion is lowered. In particular, if purification annealing is performed with the steel sheet wound in a coil during finish annealing, the purified state of Bi changes in the steel sheet according to fluctuations in the purification atmosphere, and the film adhesion of the grain-oriented electrical steel sheet becomes local. May drop to.

However, the grain-oriented electrical steel sheet according to the present embodiment contains the above-mentioned content of Bi, but unlike the conventional knowledge, the magnetic flux density is improved and at the same time the deterioration of the film adhesion is avoided.

The details of the mechanism for obtaining the above effects, which are different from the conventional findings, are not clear at this time. However, the grain-oriented electrical steel sheet according to the present embodiment intentionally creates a grain boundary having a small inclination angle that divides the inside of the secondary recrystallized grain, so that the material structure is different from the conventional one, and therefore, the effect different from the conventional knowledge is obtained. It is thought that it will be obtained. For example, the present inventors finely disperse the precipitates in the steel as compared with the conventional production conditions under the production conditions in which the grain boundaries having a small tilt angle that divides the inside of the secondary recrystallized grains are intentionally created. By segregation of Bi in steel on the surface of this finely dispersed precipitate, or by segregation of Bi at the small grain boundaries in the secondary recrystallized grains introduced under the above production conditions. It is considered that the Bi segregated at the interface between the silicon steel plate and the primary coating is relatively reduced, and as a result, the deterioration of the coating adhesion is suppressed.

That is, in the grain-oriented electrical steel sheet according to the present embodiment, unlike the conventional findings, even if Bi remains in the steel after purification annealing, the Bi does not segregate at the interface between the silicon steel sheet and the primary coating, and this Bi is not segregated. Since Bi segregates mainly on the surface of the precipitate peculiar to the present embodiment and the grain boundary having a small tilt angle, Bi does not adversely affect the film adhesion, and the magnetic flux density is improved and at the same time the film adhesion is avoided. It is thought that it can be done.

Further, in the prior art, since it is premised that Bi is discharged to the outside of the system by purification annealing, the upper limit of the amount of Bi added is limited even when Bi is added to the slab. Therefore, in the prior art, the effect of improving the magnetic flux density obtained by Bi is also limited. On the other hand, in the grain-oriented electrical steel sheet according to the present embodiment, since Bi is allowed to remain after purification annealing, the amount of Bi added can be increased more than before even when Bi is added to the slab. Therefore, in the grain-oriented electrical steel sheet according to the present embodiment, the effect of improving the magnetic flux density obtained by Bi can be enjoyed more than before. In the grain-oriented electrical steel sheet according to the present embodiment, as described above, even if Bi remains after purification annealing, Bi is unlikely to adversely affect the film adhesion.

For example, when Bi is added to the slab, the film adhesion deteriorates even if the addition amount is several ppm. In order to avoid this deterioration, even if known measures such as controlling the temperature and atmospheric conditions of decarburization annealing or adding special elements to the annealing separator are taken, the upper limit of the allowable amount of Bi added to the slab is At most 20 ppm. On the other hand, in the steel sheet utilizing the precipitates in the steel and the grain boundaries having a small inclination angle peculiar to the present embodiment, the upper limit of the Bi allowable amount added to the slab is expanded to 100 ppm. Further, if the effect of the present application is used in combination with a known Bi-measured material, further improvement in film adhesion can be expected in a region where the amount of Bi added to the slab is up to 20 ppm.

In the grain-oriented electrical steel sheet according to the present embodiment, when the Bi content is 0.0005 to 0.0100% as described above, the magnetic flux density is preferably improved and at the same time the decrease in film adhesion is avoided. This effect is critically obtained when Bi has the above content. For example, if the amount of Bi added to the slab is 0%, the Bi content in the steel sheet is 0%, and the effect of improving the magnetic flux density cannot be obtained in the first place. On the other hand, when Bi is added to the slab for the purpose of improving the magnetic flux density, the Bi content in the steel sheet is subjected to appropriate purification after taking measures to avoid a decrease in film adhesion according to a known technique. If is controlled to less than 0.0005%, it is possible to obtain a steel sheet having a high magnetic flux density and ensuring film adhesion, and there is no problem in the region where the Bi content of the steel sheet is less than 0.0005%. Therefore, in the present embodiment, the target region of the present embodiment is a Bi content of 0.0005% or more in the steel sheet, for which both high magnetic flux density and good film adhesion cannot be realized by the prior art. Further, when the Bi content is more than 0.0100%, the Bi in the steel is excessive, and this Bi not only segregates on the surface of the finely dispersed precipitates and the grain boundaries having a small tilt angle, but also the Bi Since a large amount of segregation occurs at the interface between the silicon steel plate and the primary coating, the coating adhesion tends to decrease. Therefore, in the grain-oriented electrical steel sheet according to the present embodiment, the Bi content is controlled to 0.0005 to 0.0100%.

The Bi content described above is preferably 0.0005 to 0.0010%. When the Bi content is in this range, the magnetic flux density is improved and at the same time, the decrease in film adhesion can be preferably avoided.

Further, the Bi content described above may be 0.0010 to 0.0100%. As a conventional knowledge, it has been known that when the Bi content is in this range, the Bi in the steel is excessive and the film adhesion is remarkably lowered. However, in the grain-oriented electrical steel sheet according to the present embodiment, even if the Bi content is in the above range, the magnetic flux density can be preferably improved and at the same time, the decrease in film adhesion can be preferably avoided.

According to this embodiment, even if the Bi content is in the above range, sufficient film adhesion can be obtained. Specifically, in the above range of Bi content, the coating residual area ratio when the grain-oriented electrical steel sheet is wound around a round bar having a diameter of 20 mm and bent back is preferably 90 to 100%. This film residual area ratio is an index showing the quality of film adhesion. The lower limit of the coating residual area ratio is preferably 95%.

The coating residual area ratio is evaluated by performing a bending adhesion test. An 80 mm × 80 mm flat plate-shaped test piece collected from a grained grain-oriented electrical steel sheet is wound around a round bar having a diameter of 20 mm, stretched flat, and the film (insulating film and / or intermediate) that has not been peeled off from the electrical steel sheet. The area of the layer) is measured, and the value obtained by dividing the area not peeled by the area of the steel sheet is defined as the film residual area ratio (%). For example, a transparent film with a 1 mm grid scale may be placed on the test piece, and the area where the coating is not peeled off may be measured.

Further, if the Bi content is controlled within the above range, the magnetic flux density is preferably increased. Specifically, if the Bi content is controlled within the above range, the magnetic flux density B _{8 in the} rolling direction is preferably 1.920 T or more. The magnetic flux density B ₈ is more preferably 1.930 T or more. The upper limit of the magnetic flux density B ₈ is not particularly limited, but the saturation magnetic flux density depending on the component is allowed.

The magnetic flux density of the grain-oriented electrical steel sheet may be measured based on the single plate magnetic property test method (SST: Single Sheet Tester) specified in JIS C 2556: 2015. For the magnetic flux density B ₈ (T), the magnetic flux density in the rolling direction of the steel sheet when excited at 800 A / m may be measured. For example, the magnetic flux density B ₈ may be measured at least three times using test pieces collected from different locations, and the average value may be obtained based on these measurement results.

As described above, in the grain-oriented electrical steel sheet according to the present embodiment, the magnetostriction in the low magnetic field region is improved and the magnetic flux density is improved by controlling the orientation change and also the chemical composition. At the same time, it is possible to avoid a decrease in film adhesion.

[Second Embodiment]
Subsequently, the grain-oriented electrical steel sheet according to the second embodiment of the present invention will be described below. Further, in each of the embodiments described below, the differences from the first embodiment will be mainly described, and the other features will be the same as those of the first embodiment, and duplicate description will be omitted.

In the directional electromagnetic steel sheet according to the second embodiment of the present invention, the particle size of the β crystal grains in the rolling direction is smaller than the particle size of the secondary recrystallized grains in the rolling direction. That is, the grain-oriented electrical steel sheet according to the present embodiment has β crystal grains and secondary recrystallized grains whose particle size is controlled with respect to the rolling direction.

Specifically, the grain-oriented electrical steel sheet according to the present embodiment, the average crystal grain size in the rolling direction L obtained based on the boundary conditions BA defined as the particle size RA _L, the rolling direction L obtained based on the boundary conditions BB when the average crystal grain size of the defined as the particle diameter RB _L,
The particle size RA _L and the particle size RB _L satisfy 1.10 ≦ RB _L ÷ RA. Further, it is preferable that RB _L ÷ RA _L ≦ 80.

This provision describes the above-mentioned "switching" situation with respect to the rolling direction. _{That is, the boundary where | β 2-} β ₁ | is 0.5 ° or more and the angle φ is less than 2 ° in the secondary recrystallized grain whose grain boundary is the boundary where the angle φ is 2 ° or more. It means that the crystal grains containing at least one of the above are present at an appropriate frequency with respect to the rolling direction. In the present embodiment, the status of this switch, defined and evaluated by the rolling direction of the grain size RA _L and particle size RB _L.

FIG. 2 is a schematic view showing the grain boundaries of the secondary recrystallized grains of the grain-oriented electrical steel sheet and the switching situation occurring in the secondary recrystallized grains. In FIG. 2, the steel sheet immediately after finish annealing (immediately after secondary recrystallization) is wound around a coil and has a curvature, and the steel sheet after flattening (during use) is unwound from the coil. Is shown.

As shown in FIG. 2, when the steel sheet is wound around a coil, the rolling direction of the steel sheet (longitudinal direction of the steel sheet) is curved according to the curvature of the steel sheet in space. On the other hand, in general, a crystal that grows during secondary recrystallization does not change its orientation in space. Therefore, in one crystal grain, the angle formed by the rolling direction and the crystal direction changes depending on the position in the space. This change increases as the crystal grains grow. That is, in the vicinity of the grain boundaries of the secondary recrystallized grains, which are coarsened enough to reach other secondary recrystallized grains at the final stage of grain growth, the orientation change due to the curvature of the steel sheet becomes particularly large.

When such secondary recrystallized grains are adjacent to each other, the orientation difference between the adjacent crystal grains (direction difference at the crystal grain boundary) is larger than the orientation difference that each crystal grain had at the time of formation. growing. That is, even if each crystal grain itself (recrystallized nucleus) is generated as a crystal grain that is close to the Goss orientation and has a relatively small orientation difference, the orientation difference at the grain boundary at the time when the grain grows and is adjacent to each other. Will be bigger.

For example, consider the case where secondary recrystallization proceeds in a state where the steel sheet is wound as a coil having a diameter of about 1000 mm. When this steel sheet is finished and annealed and then rewound from the coil and flattened, an orientation change of about 0.1 ° per 1 mm in the rolling direction occurs due to the curvature of the steel sheet. The secondary recrystallized grains of the directional electromagnetic steel plate are coarse. For example, if the crystal grain size in the rolling direction is 50 mm, the orientation difference at the grain boundaries of the crystal grains adjacent to the rolling direction is as much as 5 °.

In general secondary recrystallization, that is, secondary recrystallization in a conventional grain-oriented electrical steel sheet, switching (local change in crystal orientation) does not occur during grain growth of secondary recrystallized grains. Therefore, if the particle size in the rolling direction is about 50 mm, the orientation difference at the grain boundaries of the crystal grains adjacent to the rolling direction caused by the curvature of the steel sheet during secondary recrystallization is about 5 °.

On the other hand, in the grain-oriented electrical steel sheet according to the present embodiment, a local orientation change (switching) occurs during the progress of secondary recrystallization. As will be described later, this orientation change acts to suppress an increase in the grain boundary energy and surface energy of the crystal, and occurs so as to approach the orientation in which the crystal has high symmetry. In the directional electromagnetic steel plate according to the present embodiment, the crystal orientation is controlled in the vicinity of the Goss orientation, and the above switching basically occurs so as to approach the orientation in which the crystal symmetry is high, that is, the Goss orientation. That is, the switching acts to eliminate the orientation change caused by the curvature of the steel plate and return it to the Goss orientation for each secondary recrystallized grain. As a result, the orientation difference of the crystal grains adjacent to the rolling direction at the grain boundaries is smaller than that in the case where the switching does not occur.

As will be described later, the above switching is considered to be caused by the rearrangement of the dislocations remaining in the secondary recrystallized grains during the secondary recrystallization. At the time of this rearrangement, the dislocations take a local arrangement, and the orientation change corresponding to the switching can be identified as a local boundary, that is, the above-mentioned grain boundary. _{In the grain-oriented electrical steel sheet according to the present embodiment, the orientation change such that | β 2-} β ₁ | ≧ 0.5 ° is established between two measurement points adjacent to each other and having an interval of 1 mm in the secondary recrystallized grain. Can be identified.

In the directional electromagnetic steel plate according to the present embodiment, the particle size of the β crystal grains in the rolling direction is made smaller than the particle size of the secondary recrystallized grains in the rolling direction by controlling the above-mentioned “switching”. Specifically, beta crystal grains and grain size RA _L of a particle size RB _L of the secondary recrystallized grains, satisfy 1.10 ≦ RB _L ÷ RA _L. A particle size RA _L and a particle size RB _L is, by satisfying the above condition, magnetostriction in a low magnetic field region is preferably reduced.

For particle size RB _L is small, or because the particle size RB _L is larger switches less particle size RA _L is _large, the RB L / RA _L value is less than 1.10, the switching frequency is not sufficient , Low magnetic field magnetostriction may not be sufficiently improved. RB _L / RA _L value is preferably 1.30 or more, more preferably 1.50 or more, more preferably 2.0 or more, more preferably 3.0 or more, more preferably 5.0 or more.

There is no particular limitation on the upper limit of RB _L / RA _L value. The greater the higher RB L _/ RA _L value occurrence frequency of the switching, since the continuity of the crystal orientation of the whole grain-oriented electromagnetic steel sheet is increased, preferred for improvement of the magnetostriction. On the other hand, since switching is also a residual lattice defect in the crystal grains, there is a concern that if the frequency of occurrence is too high, the effect of improving iron loss may be particularly reduced. _Therefore, 80 may be mentioned as a practical maximum of RB L / RA _L value. If particular care must be taken about the iron _loss, preferably 40, more preferably include 30 as the maximum value of RB L / RA _L value.

_{Incidentally,} RB L / RA _L value may be less than 1.0. RB _L is an average particle diameter in the rolling direction defined based on the grain boundaries at which the angle φ is 2 ° or more. On the other hand, RA _L is _| β ₂ -β ₁ | is the average particle size of the defined rolling direction on the basis of the grain boundary becomes 0.5 ° or more. Simply put, it seems that grain boundaries with a smaller lower limit of the angle difference are detected more frequently. That, RB _L is always greater than the RA _L, RB _L / RA _L value appears always to be 1.0 or more.

However, RB _L is the particle diameter determined by the grain boundary based on the angle phi, a particle diameter determined by the grain boundary based on RA _L off angle beta, the particle for obtaining the particle size at RB _L and RA _L The definition of the world is different. _Therefore, there is a case where RB L / RA _L value is less than 1.0.

For example, even if | β _2- β ₁ | is less than 0.5 ° (for example, 0 °), if the deviation angle α and / or the deviation angle γ is large, the angle φ becomes sufficiently large. That is, there is a grain boundary that does not satisfy the boundary condition BA but satisfies the boundary condition BB. If such grain boundaries increase, _{the value of the particle size RB L} becomes small, and as a result, the RB _L / RA _L value can be less than 1.0. In the present embodiment, each condition is controlled so that the frequency of switching due to the shift angle β increases. When the switching control is not sufficient and the deviation from the present embodiment is large, the shift angle β does not change and the RB _L / _{R A L} value becomes less than 1.0. Note that sufficiently increases the incidence of β grain boundaries in the present embodiment, it is preferable RB L _/ RA _L value is 1.10 or more, as already described.

Regarding the grain-oriented electrical steel sheet according to the present embodiment, the boundaries between two measurement points adjacent to each other on the rolled surface and having an interval of 1 mm are classified into Cases 1 to 4 in Table 1. The above particle diameter RB _L is determined based on the grain boundaries satisfying the casing 1 and / or case 2 of Table 1, the particle size RA _L is the grain boundary satisfying the casing 1 and / or the case 3 in Table 1 Find based on. For example, the deviation angle of the crystal orientation is measured on a measurement line including at least 500 measurement points along the rolling direction, and the average value of the line segment lengths sandwiched between the grain boundaries of Case 1 and / or Case 2 on this measurement line is calculated. The particle size is RB _L. Similarly, in the above measuring line, a line segment length of the average value held between the grain boundaries of the case 1 and / or the case 3 and the particle size RA _L.

Although the control of the RB L _/ RA _L value is not affected reason always clear downfield magnetostriction, as described schematically in Figure 2, the switching is one in the secondary recrystallized grains (local orientation By causing a change), the relative orientation difference with the adjacent grains is reduced (the crystal orientation change near the grain boundaries becomes gentle), and the continuity of the crystal orientation in the entire directional electromagnetic steel plate is enhanced. It is thought that it is acting on.

Even in the grain-oriented electrical steel sheet according to the present embodiment, since the orientation change is controlled and the chemical composition is also controlled as described above, the magnetostriction in the low magnetic field region is improved and the magnetic flux density is improved. At the same time, it is possible to avoid a decrease in film adhesion.

[Third Embodiment]
Subsequently, the grain-oriented electrical steel sheet according to the third embodiment of the present invention will be described below. In the following, the differences from the above-described embodiment will be mainly described, and duplicate description will be omitted.

In the directional electromagnetic steel sheet according to the third embodiment of the present invention, the particle size of β crystal grains in the direction perpendicular to rolling is smaller than the particle size of secondary recrystallized grains in the direction perpendicular to rolling. That is, the grain-oriented electrical steel sheet according to the present embodiment has β crystal grains and secondary recrystallized grains whose particle size is controlled in the direction perpendicular to rolling.

Specifically, the grain-oriented electrical steel sheet according to the present embodiment, perpendicular to the rolling of the average crystal grain size of the perpendicular to the rolling direction C determined based on the boundary conditions BA defined as the particle size RA _C, determined on the basis of the boundary conditions BB when defining the particle diameter RB _C the average crystal grain size of the direction C,
A particle size RA _C and a particle size RB _C satisfies the 1.10 ≦ RB _C ÷ RA _C. Further, it is preferable that an RB _C ÷ RA _C ≦ 80.

This provision describes the above-mentioned "switching" situation with respect to the direction perpendicular to rolling. _{That is, the boundary where | β 2-} β ₁ | is 0.5 ° or more and the angle φ is less than 2 ° in the secondary recrystallized grain whose grain boundary is the boundary where the angle φ is 2 ° or more. It means that the crystal grains containing at least one of the above are present at a reasonable frequency with respect to the direction perpendicular to the rolling direction. In the present embodiment, the status of this switch, defined and evaluated by the particle size RA _C and particle size RB _C in the direction perpendicular to the rolling direction.

For particle size RB _C is small, or because the particle size RB _C is larger switches less particle size RA _C is _large, the RB C / RA _C value is less than 1.10, the switching frequency is not sufficient , Low magnetic field magnetostriction may not be sufficiently improved. RB _C / RA _C value is preferably 1.30 or more, more preferably 1.50 or more, more preferably 2.0 or more, more preferably 3.0 or more, more preferably 5.0 or more.

There is no particular limitation on the upper limit of the RB _C / RA _C value. The greater the higher RB C _/ RA _C value occurrence frequency of the switching, since the continuity of the crystal orientation of the whole grain-oriented electromagnetic steel sheet is increased, preferred for improvement of the magnetostriction. On the other hand, since switching is also a residual lattice defect in the crystal grains, there is a concern that if the frequency of occurrence is too high, the effect of improving iron loss may be particularly reduced. _Therefore, 80 may be mentioned as a practical maximum of RB C / RA _C value. Particularly if necessary considerations for iron _loss, as the maximum value of RB C / RA _C values, preferably 40, more preferably include 30.

Incidentally, RB _C is the particle diameter determined by the grain boundary based on the angle phi, is the particle diameter determined by the grain boundary based on RA _C off angle beta. Since RB _C and RA _C of the grain boundary for obtaining the particle diameter Defining _different, there are cases where RB C / RA _C value is less than 1.0.

The above particle diameter RB _C is determined based on the grain boundaries satisfying the casing 1 and / or case 2 of Table 1, the particle size RA _C is the grain boundary satisfying the casing 1 and / or the case 3 in Table 1 Find based on. For example, the deviation angle of the crystal orientation is measured on a measurement line including at least 500 measurement points along the rolling perpendicular direction, and the average value of the line segment lengths sandwiched between the grain boundaries of Case 1 and / or Case 2 on this measurement line. It is referred to as particle size RB _C. Similarly, in the above measuring line, a line segment length of the average value held between the grain boundaries of the case 1 and / or the case 3 and the particle size RA _C.

RB control of C _/ RA _C value is not affected reason always clear downfield magnetostriction, but in one of the secondary recrystallized grains that switch (local orientation changes) occurs, the adjacent grains It is considered that the relative orientation difference is reduced and the continuity of the crystal orientation in the entire grain-oriented electrical steel sheet is enhanced.

Even in the grain-oriented electrical steel sheet according to the present embodiment, since the orientation change is controlled and the chemical composition is also controlled as described above, the magnetostriction in the low magnetic field region is improved and the magnetic flux density is improved. At the same time, it is possible to avoid a decrease in film adhesion.

[Fourth Embodiment]
Subsequently, the grain-oriented electrical steel sheet according to the fourth embodiment of the present invention will be described below. In the following, the differences from the above-described embodiment will be mainly described, and duplicate description will be omitted.

In the directional electromagnetic steel sheet according to the fourth embodiment of the present invention, the particle size of the β crystal grains in the rolling direction is smaller than the particle size of the β crystal grains in the direction perpendicular to the rolling direction. That is, the grain-oriented electrical steel sheet according to the present embodiment has β crystal grains whose particle size is controlled with respect to the rolling direction and the rolling perpendicular direction.

Specifically, the grain-oriented electrical steel sheet according to the present embodiment, perpendicular to the rolling direction of an average grain size in the rolling direction L obtained based on the boundary conditions BA defined as the particle size RA _L, obtained based on the boundary conditions BA When the average crystal grain size of _C is defined as the grain size RAC,
A particle size RA _L and a particle size RA _C satisfies the 1.15 ≦ RA _C ÷ RA _L. Further, it is preferable that an RA _C ÷ RA _L ≦ 10.

In the following description, the shape of the crystal grains may be described as "(in-plane) anisotropy" or "flat (shape)". The shape of these crystal grains describes the shape when observed from the surface (rolled surface) of the steel sheet. That is, the shape of the crystal grains does not consider the size in the plate thickness direction (observed shape in the plate thickness cross section). Incidentally, in the grain-oriented electrical steel sheet, almost all the crystal grains have the same size as the sheet thickness in the plate thickness direction. That is, in the grain-oriented electrical steel sheet, the thickness of the steel sheet is often occupied by one crystal grain except for a peculiar region such as the vicinity of the crystal grain boundary.

The provisions of RA C _/ RA _L value described above, for the rolling direction and the direction perpendicular to the rolling direction, indicating the status of the "switching" described above. That is, it means that the frequency with which the local crystal orientation changes to the extent that it is recognized as switching differs depending on the in-plane direction of the steel sheet. In this embodiment, the status of this switch was assessed by a particle size RA _C and particle size RA _L of two orthogonal directions in the steel sheet surface to define.

That RA C _/ RA _L value of greater than 1 is, beta grains are defined by switching Viewed on average, and stretched in the direction perpendicular to the rolling direction, and shown to have a flat form collapsed in the rolling direction There is. That is, it shows that the morphology of the crystal grains defined by the β grain boundaries has anisotropy.

The reason why the low magnetic field magnetostriction is improved by the in-plane anisotropy of the β crystal grain shape is not clear, but it is considered as follows. As mentioned above, in a low magnetic field, "continuity" with adjacent crystal grains is important when the 180 ° magnetic domain moves. For example, when one secondary recrystallized grain is divided into small regions by switching, if the number of these small regions is the same (the area of the small regions is the same), the shape of the small regions is more than isotropic. , The more anisotropic, the larger the abundance ratio of the boundary (β grain boundary) due to switching. That results in that the presence frequency of switching is a local change of orientation increases the control of RA C _/ RA _L value, is considered to enhance the continuity of the crystal orientation of the whole grain-oriented electromagnetic steel sheet.

The anisotropy of the occurrence of such switching is some anisotropy existing in the steel plate before the secondary recrystallization: for example, the anisotropy of the shape of the primary recrystallized grain; the anisotropy of the shape of the hot-rolled plate crystal grain. Anisotropy (colony distribution) of the crystal orientation distribution of the primary recrystallized grains due to It is considered to be caused by the distribution of precipitates due to fluctuations in the thermal history in the longitudinal direction; the anisotropy of the crystal particle size distribution; and the like. However, the details of the generation mechanism are unknown. However, if the steel sheet in the secondary recrystallization has a temperature gradient, it gives direct anisotropy to the growth of crystal grains (dislocation disappearance and grain boundary formation). That is, the temperature gradient in the secondary recrystallization is a very effective control condition for controlling the anisotropy defined in the present embodiment. Details will be described in relation to the manufacturing method.

Further, although it is related to the above-mentioned process of giving anisotropy by the temperature gradient at the time of secondary recrystallization, the current general production is that the direction in which the β crystal grains are stretched in the present embodiment is the direction perpendicular to rolling. It is preferable to consider the method. In this case, the rolling direction of the grain size RA _L becomes a value smaller than the particle size RA _C in the direction perpendicular to the rolling direction. The relationship between the rolling direction and the direction perpendicular to the rolling will be described in relation to the manufacturing method. The direction in which the β crystal grains are stretched is determined not by the temperature gradient but by the frequency of occurrence of β grain boundaries.

For particle size RA _C is small, or because the particle size RA _C is larger in particle size RA _L is _large, the RA C / RA _L value is less than 1.15, the switching frequency is not sufficient, downfield Magnetostriction may not be sufficiently improved. RA _C / RA _L value is preferably 1.50 or more, more preferably 1.80 or more, more preferably 2.10 or more.

There is no particular limitation on the upper limit of RA _C / RA _L value. Frequency and the extending direction of the switching is limited to a particular direction, the larger the RA C _/ RA _L value, since the continuity of the crystal orientation of the whole grain-oriented electromagnetic steel sheet is increased, preferred for improvement of the magnetostriction. On the other hand, switching is also a residual lattice defect in the crystal grains, so if the frequency of occurrence is too high, there is a concern that the effect of improving iron loss may be reduced. _Therefore, it includes 10 as a practical maximum of RA C / RA _L value. Particularly if necessary considerations for iron loss, as the maximum of RA C _/ RA _L value, preferably 6, more preferably include 4.

Further, grain-oriented electrical steel sheet according to the present embodiment, in addition to the control of _RA C / RA _L value described above, as in the second embodiment, and the particle size RA _L and particle size RB _L, 1.10 preferably satisfies ≦ RB _L ÷ RA _L.

This provision clarifies that a "switch" is occurring. For example, particle size RA _C and RA _L is between two adjacent measuring points _| β ₂ -β ₁ | While it is the particle size based on the grain boundaries to be 0.5 ° or more, "switching" at all occurs not without and, even if all the angles of the grain boundary φ was at 2.0 ° or more, may be the above-mentioned RA C _/ RA _L value is satisfied. Be likened RA C _/ RA _L value is satisfied, if the angle of all the grain boundaries φ is 2.0 ° or more, only been generally recognized secondary recrystallized grains are simply becomes flat shape Therefore, the above-mentioned effect of the present embodiment cannot be preferably obtained. In the present embodiment, since it is assumed that the grain boundaries satisfy the boundary condition BA and do not satisfy the boundary condition BB (grain boundaries that divide the secondary recrystallized grains), the angles φ of all the grain boundaries are 2. situation hardly occurs that is .0 ° or more, but in addition to satisfying the _RA C / RA _L value described _above, it is preferable to satisfy the RB L / RA _L value.

Further, in the present embodiment, in addition to controlling the _RB L / RA _L values for the rolling direction, for the direction perpendicular to the rolling direction, as in the third embodiment, and a particle size RA _C and a particle diameter RB _C 1 be satisfied .10 ≦ RB _{C /} RA C does not become any problem, but rather preferable in view of enhancing the continuity of the crystal orientation of the whole grain-oriented electromagnetic steel sheet.

Further, in the grain-oriented electrical steel sheet according to the present embodiment, it is preferable that the grain sizes of the secondary recrystallized grains in the rolling direction and the direction perpendicular to the rolling are controlled.

Specifically, in the directional electromagnetic steel plate according to the present embodiment, the average crystal grain size of the rolling direction L obtained based on the boundary condition BB _{is defined as the particle size RB L,} and the rolling orthogonal direction obtained based on the boundary condition BB. When the average crystal grain size of _C is defined as the grain size RB C,
It is preferable that the particle size RB _L and the particle size RB _C satisfy 1.50 ≦ RB _C ÷ RB _L. Further, it is preferable that _{RB C} ÷ RB _{L ≦ 20.}

This provision has nothing to do with the "switching" described above and indicates that the secondary recrystallized grains are stretched in the direction perpendicular to rolling. Therefore, this feature itself is not special. However, in this _embodiment, after controlling the RA C / RA _{L value,} it is preferred that RB C / RB _L value satisfies the numerical range mentioned above.

In the present embodiment, in relation to the switching described above, when the RA C _/ RA _L value of β grains is controlled tends to be planar anisotropy becomes larger form of secondary recrystallized grains. From the opposite point of view, when switching the shift angle β is generated as in the present embodiment, the shape of the β crystal grain is also controlled by controlling the shape of the secondary recrystallized grain so as to have in-plane anisotropy. Tends to have in-plane anisotropy.

RB _C / RB _L value is preferably 1.80 or more, more preferably 2.00 or more, more preferably 2.50 or more. The upper limit of the RB _C / RB _L value is not particularly limited.

As _{a practical method for controlling the RB C} / RB _L value, for example, preferential heating is performed from the end of the coil width during finish annealing to give a temperature gradient in the coil width direction (coil axis direction). Examples include the process of growing secondary recrystallized grains. At this time, while maintaining the particle size of the secondary recrystallized grains in the coil circumferential direction (for example, the rolling direction) at about 50 mm, the particle size of the secondary recrystallized grains in the coil width direction (for example, the direction perpendicular to rolling) is defined as the coil width. It is also possible to control in the same way. For example, one crystal grain can occupy the entire width of a coil having a width of 1000 mm. In this case, 20 is mentioned as the upper limit value of _{the RB C} / RB _{L value.}

If the secondary recrystallization is carried out by a continuous annealing process so as to have a temperature gradient in the rolling direction instead of the rolling perpendicular direction, the maximum value of the particle size of the secondary recrystallized grains is not limited to the coil width. It is also possible to make it a larger value. Even in this case, according to the present embodiment, it is possible to obtain the above-mentioned effect of the present embodiment by appropriately dividing the crystal grains by the β grain boundary due to switching.

Further, in the grain-oriented electrical steel sheet according to the present embodiment, it is preferable that the frequency of switching with respect to the deviation angle β is controlled with respect to the rolling direction and the rolling perpendicular direction.

Specifically, the grain-oriented electrical steel sheet according to the present embodiment, the average crystal grain size in the rolling direction L obtained based on the boundary conditions BA defined as the particle size RA _L, the rolling direction L obtained based on the boundary conditions BB the average crystal grain size is defined as the particle diameter RB _L of the average crystal grain size of the perpendicular to the rolling direction C determined based on the boundary conditions BA defined as the particle size RA _C, perpendicular to the rolling direction C determined based on the boundary conditions BB when the average crystal grain size of the defined as the particle diameter RB _C,
A particle size RA _L and a particle size RA _C and particle size RB _L and a particle size RB _C preferably satisfy the _{(RB C × RA L) ÷} (RB L × RA C) <1.0. Although the lower limit is not particularly limited, if the state of the art assumes, may be a _{0.2 <(RB C × RA L} ) ÷ (RB L × RA C).

This regulation represents the in-plane anisotropy of the frequency of occurrence of the above-mentioned "switching". That is, the _{(RB C · RA L) /} (RB L · RA C) is "occurrence of about switching of dividing the secondary recrystallized grains in the direction perpendicular to the rolling _direction: RB _C / RA C" and "secondary generation degree of switching dividing the recrystallized grains in the rolling direction: has the ratio of the RB L _/ RA _L ". When this value is less than 1, it means that one secondary recrystallized grain is divided into many in the rolling direction by switching (β grain boundary).

In addition, a different viewpoint, the above-mentioned _{(RB C · RA L) /} (RB L · RA C) , the "degree of secondary recrystallized grains of _flat: RB C / RB _L" and, "β crystal grains of the extent of the _flat: which is the ratio of the RA C / RA _L ". When this value is less than 1, it means that the β crystal grains that divide one secondary recrystallized grain have a flatter shape than the secondary recrystallized grain.

That is, the β grain boundary tends to divide the secondary recrystallized grains in the rolling direction rather than in the direction perpendicular to the rolling direction. That is, the β grain boundary tends to be stretched in the direction in which the secondary recrystallized grains are stretched. It is considered that this tendency of the β grain boundary acts so that the switching increases the occupied area of the crystal in a specific direction when the secondary recrystallized grain is stretched.

The value of _{(RB C · RA L) /} (RB L · RA C) is preferably 0.9 or less, more preferably 0.8 or less, more preferably 0.5 or less. As described _above, the lower limit of _{(RB C · RA L) /} (RB L · RA C) is not particularly limited, but in consideration of industrial feasibility, may be a greater than 0.2.

The above particle size RB _L and particle size RB _C is determined based on the grain boundaries satisfying the casing 1 and / or case 2 of Table 1. The above particle size RA _L and particle size RA _C is determined based on the grain boundaries satisfying the casing 1 and / or the case 3 in Table 1. For example, the deviation angle of the crystal orientation is measured on a measurement line including at least 500 measurement points along the rolling perpendicular direction, and the average value of the line segment lengths sandwiched between the grain boundaries of Case 1 and / or Case 3 on this measurement line. It is referred to as particle size RA _C. Particle size RA _L, particle size RB _L, particle diameter RB _C also may be obtained as well.

Even in the grain-oriented electrical steel sheet according to the present embodiment, since the orientation change is controlled and the chemical composition is also controlled as described above, the magnetostriction in the low magnetic field region is improved and the magnetic flux density is improved. At the same time, it is possible to avoid a decrease in film adhesion.

[Technical features common to each embodiment]
Subsequently, common technical features of the grain-oriented electrical steel sheets according to each of the above-described embodiments will be described below.

The oriented electrical steel sheet according to the embodiments of the present invention, the average crystal grain size in the rolling direction L obtained based on the boundary conditions BB is defined as the particle diameter RB _L, the direction perpendicular to the rolling direction C determined based on the boundary conditions BB when defining the mean crystal grain size and grain size RB _C,
Particle size RB _L and particle size RB _C is preferably at 22mm or more.

Switching is thought to be caused by dislocations that accumulate during the growth of secondary recrystallized grains. That is, it is necessary that the secondary recrystallized grains grow to a considerable extent after the switching occurs once and then before the next switching occurs. Therefore, when the particle size RB _L and particle size RB _C is less than 15 mm, the switching is less likely to occur, a sufficient improvement in the low magnetic field magnetostriction may become difficult due to switching. Particle size RB _L and particle size RB _C is preferably 15mm or more. Particle size RB _L and particle size RB _C is preferably not 22mm or more, more preferably 30mm or more, still more preferably 40mm or more.

The upper limit of the particle size RB _L and particle size RB _C is not particularly limited. In the production of general directional electromagnetic steel sheets, a steel sheet for which primary recrystallization has been completed is wound around a coil, and crystal grains with {110} <001> orientation are generated by secondary recrystallization in a state where the steel sheet has a curvature in the rolling direction. Since it is grown, the deviation angle β continuously changes depending on the position in the rolling direction within one crystal grain. Therefore, if the increase in particle size RB _L is, deviation angle β is increased, and could also result in the magnetostrictive is increased. Therefore, increasing the particle size RB _L indefinitely is preferably avoided. Also considering industrial feasibility, the particle size RB _L, 400 mm as a preferable upper limit, 200 mm More preferable upper limit can be mentioned 100mm More preferable upper limit.

Further, in the production of a general directional electromagnetic steel sheet, a steel sheet for which primary recrystallization has been completed is heated in a coiled state, and crystal grains in the {110} <001> orientation are generated and grown by secondary recrystallization. Therefore, the secondary recrystallized grains grow from the coil end side where the temperature rise precedes to the coil center side where the temperature rise is delayed. In such a process, for example, if the coil width and 1000 mm, can be exemplified 500mm which is about half the coil width as an upper limit of particle size RB _C. Of course in the embodiments, it does not exclude that the total width of the coil is a particle diameter of RB _C.

The oriented electrical steel sheet according to the embodiments of the present invention, the average crystal grain size in the rolling direction L obtained based on the boundary conditions BA defined as the particle size RA _L, the direction perpendicular to the rolling direction C determined based on the boundary conditions BA when defining the mean crystal grain size and grain size RA _C,
Particle size RA _L is at 30mm or less, it is preferred particle size RA _C is 400mm or less.

As the value of the particle size RA _L is small, the higher the frequency of occurrence of switching the rolling direction. Particle size RA _L is may be at 40mm or less, more preferably 30mm or less, and more preferably 20mm or less.

Further, if sufficient switching availability increased particle size RA _C is not happening, the shift angle β is increased, could also result in the magnetostriction is increased. Therefore, increasing the particle size RA _C indefinitely is preferably avoided. Also considering industrial feasibility, the particle size RA _C, 400 mm as a preferable upper limit, more preferably 200mm upper limit, more preferably 100mm upper limit, more preferably 40mm upper limit, can be cited more preferably 30mm upper limit.

The lower limit of the particle size RA _L and particle size RA _C is not particularly limited. In each embodiment, the measurement interval of the crystal orientation since it is a 1 mm, minimum value of the particle size RA _L and particle size RA _C becomes 1 mm. However, in each embodiment, for example, by the measurement interval and less than 1 mm, does not exclude the steel plate such as particle size RA _L and particle size RA _C is less than 1 mm. However, since the switching is accompanied by the presence of lattice defects in the crystal, although it is slight, if the switching frequency is too high, there is a concern that the magnetic characteristics may be adversely affected. Furthermore, considering even industrial feasibility, the particle size RA _L and particle size RA _C, mention may be made of 5mm as preferred lower limit.

In the measurement of the crystal grain size of the grain-oriented electrical steel sheet according to each embodiment, the grain size of one crystal grain includes an ambiguity of up to 2 mm. Therefore, the particle size measurement (measurement of at least 500 points on the rolled surface at 1 mm intervals) is performed at positions sufficiently separated from the direction defining the particle size in the direction orthogonal to the steel plate surface, that is, the measurement of different crystal grains. It is preferable to carry out the measurement at a total of 5 or more locations. Then, the above ambiguity can be eliminated by averaging all the particle sizes obtained by a total of 5 or more measurements. For example, for the particle size RA _C and particle size RB _C above 5 points sufficiently spaced to the rolling direction, for the particle size RA _L and particle size RB _L measurements were performed at least 5 locations sufficiently spaced perpendicular to the rolling direction The average particle size may be obtained by performing orientation measurement at a total of 2500 or more measurement points.

In the directional electromagnetic steel plate according to each embodiment of the present invention, the standard deviation σ (| β |) of the absolute value of the deviation angle β is preferably 0 ° or more and 1.70 ° or less.

Low magnetic field magnetostriction is not sufficiently reduced if switching does not occur very often. This is considered to indicate that the reduction of the low magnetic field magnetostriction makes the deviation angles uniform in a specific direction. That is, it is considered that the reduction of the low magnetic field magnetostriction is not due to the orientation selection by silkworm erosion at the early stage of development or the growth stage including the nucleation of secondary recrystallization. That is, in order to obtain the effect of the above embodiment, it is not a particularly necessary condition to bring the crystal orientation closer to a specific direction as in the conventional orientation control, for example, to reduce the absolute value and standard deviation of the deviation angle. .. However, in a steel sheet in which the above-mentioned switching is sufficiently performed, the "deviation angle" is easily controlled within a characteristic range. For example, when the crystal orientation changes little by little due to the switching with respect to the deviation angle β, the fact that the absolute value of the deviation angle approaches zero does not hinder the above embodiment. Further, for example, when the crystal orientation changes little by little due to switching with respect to the deviation angle β, the crystal orientation itself converges to a specific orientation, and as a result, the standard deviation of the deviation angle approaches zero. It does not interfere with.

Therefore, in each embodiment, the standard deviation σ (| β |) of the absolute value of the deviation angle β may be 0 ° or more and 1.70 ° or less.

The standard deviation σ (| β |) of the absolute value of the deviation angle β is calculated as follows.
In the grain-oriented electrical steel sheet, the degree of integration in the {110} <001> orientation is increased by secondary recrystallization in which crystal grains grown to a size of about several cm are formed. In each embodiment, it is necessary to recognize the change in crystal orientation with such grain-oriented electrical steel sheets. Therefore, 500 or more crystal orientations are measured in a region containing at least 20 secondary recrystallized grains.

In each embodiment, it should not be considered that "one secondary recrystallized grain is regarded as a single crystal and the inside of the secondary recrystallized grain has exactly the same crystal orientation". That is, in each embodiment, there is a local orientation change that is not conventionally recognized as a grain boundary in one coarse secondary recrystallized grain, and it is necessary to detect this orientation change.

Therefore, for example, it is preferable to distribute the measurement points of the crystal orientation at equal intervals within a fixed area set regardless of the boundary of the crystal grains (grain boundaries). Specifically, the measurement points are distributed at equal intervals of 5 mm in the vertical and horizontal directions within the area of L mm × M mm (where L, M> 100) so as to contain at least 20 crystal grains on the steel plate surface. , It is preferable to measure the crystal orientation at each measurement point and obtain data of 500 points or more in total. If the measurement point is a grain boundary or some singularity, that data is not used. Further, it is necessary to expand the above measurement range according to the region required for determining the magnetic characteristics of the target steel sheet (for example, in the case of an actual coil, the range for measuring the magnetic characteristics described on the mill sheet). be.

Then, the deviation angle β is determined for each measurement point, and the standard deviation σ (| β |) of the absolute value of the deviation angle β is calculated. In the grain-oriented electrical steel sheet according to each embodiment, it is preferable that σ (| β |) is within the above-mentioned numerical range.

In addition, σ (| β |) is a factor generally considered to be small in order to improve the magnetic characteristics or magnetostriction in a medium magnetic field of about 1.7 T. However, there was a limit to the characteristics that could be achieved by controlling only σ (| β |). In each of the above-described embodiments, in addition to the above-mentioned technical features, σ (| β |) is also controlled to preferably affect the continuity of the crystal orientation in the entire grain-oriented electrical steel sheet.

The standard deviation σ (| β |) of the absolute value of the deviation angle β is more preferably 1.50 or less, further preferably 1.30 or less, and further preferably 1.10 or less. Of course, σ (| β |) may be 0.

The directional electromagnetic steel sheet according to the present embodiment may have an intermediate layer, an insulating film, or the like on the steel sheet, but the above-mentioned crystal orientation, grain boundary, average crystal grain size, etc. have a film or the like. It may be specified based on no steel plate. That is, when the grain-oriented electrical steel sheet to be the measurement sample has an insulating coating or the like on the surface, the crystal orientation or the like may be measured after removing the coating or the like.

For example, as a method for removing the insulating coating, a grain-oriented electrical steel sheet having a coating may be immersed in a high-temperature alkaline solution. Specifically, NaOH: 30 to 50 _wt% + H 2 O: the 50 to 70% by weight aqueous sodium hydroxide, for 5-10 min at 80-90 ° C., after immersion, and dried by washing with water, The insulating coating can be removed from the grain-oriented electrical steel sheet. The time of immersion in the above sodium hydroxide aqueous solution may be changed according to the thickness of the insulating film.

Further, for example, as a method for removing the intermediate layer, an electromagnetic steel sheet from which the insulating film has been removed may be immersed in high-temperature hydrochloric acid. Specifically, the concentration of hydrochloric acid preferable for removing the intermediate layer to be dissolved is investigated in advance, and the mixture is immersed in hydrochloric acid having this concentration, for example, 30 to 40% by mass of hydrochloric acid at 80 to 90 ° C. for 1 to 5 minutes. The intermediate layer can be removed by washing with water and drying. Normally, an alkaline solution is used to remove the insulating coating, and hydrochloric acid is used to remove the intermediate layer, so that each coating is removed by using different treatment liquids.

Next, the chemical composition of the grain-oriented electrical steel sheet according to each embodiment will be described. The grain-oriented electrical steel sheet of each embodiment contains a basic element as a chemical composition, and if necessary, a selective element, and the balance is composed of Fe and impurities.

The directional electromagnetic steel plate according to each embodiment has Si (silicon): 2.0 to 7.0% and Bi (bismas): 0.0005 to 50% by mass as basic elements (main alloy elements). Contains 0.0100%.

The content of Si is preferably 2.0 to 7.0% in order to accumulate the crystal orientation in the {110} <001> orientation.

Bi is an element that preferably improves the magnetic flux density if it is contained in a silicon steel sheet as a chemical composition. In addition, although the film adhesion is generally lowered, if Bi is contained after the inside of the secondary recrystallized grains is divided at the grain boundaries having a small inclination angle as described above, the deterioration of the film adhesion is a problem. It doesn't become. Therefore, by containing Bi in a range of 0.0005 to 0.0100%, which is higher than the conventional one, it is possible to obtain a remarkable magnetic flux density improving effect while ensuring the film adhesion, unlike the conventional knowledge. It becomes. The Bi content is preferably 0.0005 to 0.0010%. The Bi content may be 0.0010 to 0.0100%.

In each embodiment, impurities may be contained as a chemical composition. The term "impurity" refers to an element mixed from ore or scrap as a raw material, or from the manufacturing environment, etc., when steel is industrially manufactured. The upper limit of the total content of impurities may be, for example, 5%.

Further, in each embodiment, a selective element may be contained in addition to the above-mentioned basic elements and impurities. For example, instead of a part of Fe which is the balance described above, Nb, V, Mo, Ta, W, C, Mn, S, Se, Al, N, Cu, B, P, Ti, Sn are selected elements. , Sb, Cr, Ni and the like may be contained. These selective elements may be contained according to the purpose. Therefore, it is not necessary to limit the lower limit values of these selected elements, and the lower limit value may be 0%. Further, even if these selective elements are contained as impurities, the above effect is not impaired.

Nb (niobium): 0 to 0.030%
V (vanadium): 0 to 0.030%
Mo (molybdenum): 0 to 0.030%
Ta (tantalum): 0 to 0.030%
W (tungsten): 0 to 0.030%
Nb, V, Mo, Ta, and W can be utilized as elements having characteristic effects in each embodiment. In the following description, one or more elements of Nb, V, Mo, Ta, and W may be collectively referred to as "Nb group element".

The Nb group elements preferably act on the formation of switching, which is a characteristic of grain-oriented electrical steel sheets according to each embodiment. However, since the Nb group element acts on the switching generation during the manufacturing process, it is not necessary that the Nb group element is finally contained in the grain-oriented electrical steel sheet according to each embodiment. For example, the Nb group elements tend to be discharged to the outside of the system due to purification in the finish annealing described later. Therefore, even if the slab contains Nb group elements and the frequency of switching is increased by utilizing the Nb group elements in the manufacturing process, the Nb group elements may be discharged to the outside of the system by the subsequent purification annealing. Therefore, Nb group elements may not be detected as the chemical composition of the final product.

Therefore, in each embodiment, only the upper limit of the content of the Nb group element is specified as the chemical composition of the grain-oriented electrical steel sheet which is the final product. The upper limit of the Nb group elements may be 0.030%, respectively. On the other hand, as described above, even if the Nb group elements are utilized in the manufacturing process, the content of the Nb group elements may become zero in the final product. Therefore, the lower limit of the content of the Nb group element is not particularly limited, and the lower limit may be 0% for each.

In the grain-oriented electrical steel sheet according to each embodiment of the present invention, at least one selected from the group consisting of Nb, V, Mo, Ta, and W as a chemical composition is 0.0030 to 0.030% by mass in total. It is preferable to contain it.

Since it is unlikely that the content of Nb group elements will increase during manufacturing, if Nb group elements are detected as the chemical composition of the final product, it is suggested that switching control by Nb group elements was performed during the manufacturing process. NS. In order to preferably control switching in the manufacturing process, the total content of Nb group elements in the final product is preferably 0.0030% or more, and more preferably 0.0050% or more. On the other hand, if the total content of Nb group elements in the final product exceeds 0.030%, the frequency of switching can be maintained, but the magnetic characteristics may deteriorate. Therefore, the total content of Nb group elements in the final product is preferably 0.030% or less. The action of the Nb group elements will be described later in relation to the production method.

C (carbon): 0 to 0.0050%
Mn (manganese): 0 to 1.0%
S (sulfur): 0 to 0.0150%
Se (selenium): 0 to 0.0150%
Al (acid-soluble aluminum): 0 to 0.0650%
N (nitrogen): 0 to 0.0050%
Cu (copper): 0 to 0.40%
B (boron): 0 to 0.080%
P (phosphorus): 0 to 0.50%
Ti (titanium): 0 to 0.0150%
Sn (tin): 0 to 0.10%
Sb (antimony): 0 to 0.10%
Cr (chromium): 0 to 0.30%
Ni (nickel): 0 to 1.0%
These selective elements may be contained according to a known purpose. It is not necessary to set the lower limit of the content of these selective elements, and the lower limit may be 0%. The total content of S and Se is preferably 0 to 0.0150%. The total of S and Se means that at least one of S and Se is included and is the total content thereof.

In the grain-oriented electrical steel sheet, a relatively large change in chemical composition (decrease in content) occurs due to undergoing decarburization annealing and purification annealing during secondary recrystallization. Depending on the element, purification annealing may reduce the content to a level (1 ppm or less) that cannot be detected by a general analytical method. The chemical composition of the grain-oriented electrical steel sheet according to each embodiment is the chemical composition of the final product. Generally, the chemical composition of the final product is different from the chemical composition of the starting material, the slab.

The chemical composition of the grain-oriented electrical steel sheet according to each embodiment may be measured by a general method for analyzing steel. For example, the chemical composition of grain-oriented electrical steel sheets may be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrum). Specifically, a 35 mm square test piece collected from a grain-oriented electrical steel sheet is measured with an ICPS-8100 or the like (measuring device) manufactured by Shimadzu Corporation under conditions based on a calibration curve prepared in advance to obtain a chemical composition. Be identified. C and S may be measured by using the combustion-infrared absorption method, and N may be measured by using the inert gas melting-thermal conductivity method.

Further, the content of the element contained in a trace amount in the above chemical composition may be measured by using ICP-MS (Inductively Coupled Plasma-Mass Spectrometry). For example, it is preferable to measure the content of Bi using ICP-MS instead of ICP-AES in the range of less than 0.001%.

The above chemical composition is a component of grain-oriented electrical steel sheets. When the grain-oriented electrical steel sheet to be the measurement sample has an insulating coating or the like on the surface, the coating or the like is removed by the above method, and then the chemical composition is measured.

The grain-oriented electrical steel sheet according to each embodiment of the present invention is characterized in that the secondary recrystallized grains are divided into small regions having slightly different displacement angles β, and this feature reduces magnetostriction in a low magnetic field region. Will be done. Further, in the grain-oriented electrical steel sheet according to each embodiment, by also controlling the chemical composition, the magnetic flux density is improved and at the same time, the deterioration of the film adhesion is avoided. The grain-oriented electrical steel sheet according to each embodiment has the above-mentioned effect depending on the characteristics of the silicon steel sheet (oriented electrical steel sheet) regardless of the coating structure on the steel sheet and the presence or absence of the magnetic domain subdivision treatment. Therefore, in the grain-oriented electrical steel sheet according to each embodiment, the coating structure on the steel sheet and the presence or absence of magnetic domain subdivision treatment are not particularly limited. In each embodiment, an arbitrary film may be formed on the steel sheet according to the purpose, and magnetic domain subdivision treatment may be performed as necessary.

The grain-oriented electrical steel sheet according to each embodiment of the present invention may have an intermediate layer arranged in contact with the grain-oriented electrical steel sheet (silicon steel sheet) and an insulating film arranged in contact with the intermediate layer. good.

FIG. 3 is a schematic cross-sectional view of a grain-oriented electrical steel sheet according to a preferred embodiment of the present invention. As shown in FIG. 3, the grain-oriented electrical steel sheet 10 (silicon steel sheet) according to the present embodiment is placed on the grain-oriented electrical steel sheet 10 (silicon steel sheet) when viewed from a cut surface whose cutting direction is parallel to the plate thickness direction. It may have an intermediate layer 20 arranged in contact with the intermediate layer 20 and an insulating coating 30 arranged in contact with the intermediate layer 20.

For example, the above-mentioned intermediate layer includes a layer mainly composed of oxide, a layer mainly composed of carbide, a layer mainly composed of nitride, a layer mainly composed of boride, a layer mainly composed of silice, and a phosphoric compound. It may be a layer mainly composed of a sulfide, a layer mainly composed of an intermetallic compound, or the like. These intermediate layers can be formed by heat treatment, chemical vapor deposition (CVD), physical vapor deposition (PVD), or the like in an atmosphere in which redox properties are controlled.

In the grain-oriented electrical steel sheet according to each embodiment of the present invention, the intermediate layer may be a forsterite coating having an average thickness of 1 to 3 μm. The forsterite film is a film mainly composed of _{Mg 2} SiO _4. The interface between the forsterite coating and the grain-oriented electrical steel sheet is the interface in which the forsterite coating is fitted into the steel sheet when viewed in the above cross section.

In the grain-oriented electrical steel sheet according to each embodiment of the present invention, the intermediate layer may be an oxide film having an average thickness of 2 to 500 nm. The oxide film is a film mainly composed of _{SiO 2.} The interface between the oxide film and the grain-oriented electrical steel sheet is a smooth interface when viewed in the above cross section.

The above-mentioned insulating coating is mainly composed of phosphate and colloidal silica and has an average thickness of 0.1 to 10 μm, or is mainly composed of alumina sol and boric acid and has an average thickness of 0.5 to 8 μm. It may be an insulating film.

In the grain-oriented electrical steel sheet according to each embodiment of the present invention, the magnetic domains may be subdivided by at least one of local microstraining or local groove formation. The local minute strain and the local groove may be applied or formed by a laser, plasma, mechanical method, etching, or other method. For example, local micro-strains or local grooves are linear or dotted so as to extend in a direction intersecting the rolling direction on the rolling surface of the steel sheet, and the intervals in the rolling direction are 2 mm to 10 mm. It may be given or formed in.

[Manufacturing method of grain-oriented electrical steel sheet]
Next, a method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention will be described.
The method for manufacturing the grain-oriented electrical steel sheet according to the present embodiment is not limited to the following method. The following manufacturing method is an example for manufacturing the grain-oriented electrical steel sheet according to the present embodiment.

FIG. 4 is a flow chart illustrating a method for manufacturing a grain-oriented electrical steel sheet according to an embodiment of the present invention. As shown in FIG. 4, the method for manufacturing the directional electromagnetic steel plate (silicon steel plate) according to the present embodiment includes a casting step, a hot rolling step, a hot rolled sheet annealing step, a cold rolling step, and decarburization. It includes an annealing step, an annealing separator coating step, and a finish annealing step. Further, if necessary, the nitriding treatment may be performed at an arbitrary timing from the decarburization annealing step to the finish annealing step, and an insulating film forming step and a magnetic domain control step may be further provided after the finish annealing step.

Specifically, the method for manufacturing a grain-oriented electrical steel sheet (silicon steel sheet) according to the present embodiment is described.
In the casting process, the chemical composition is Si: 2.0 to 7.0%, Bi: 0.0010 to 0.0200%, Nb: 0 to 0.030%, V: 0 to 0.030 in mass%. %, Mo: 0 to 0.030%, Ta: 0 to 0.030%, W: 0 to 0.030%, C: 0 to 0.0850%, Mn: 0 to 1.0%, S: 0 ~ 0.0350%, Se: 0 to 0.0350%, Al: 0 to 0.0650%, N: 0 to 0.0120%, Cu: 0 to 0.40%, B: 0 to 0.080% , P: 0 to 0.50%, Ti: 0 to 0.0150%, Sn: 0 to 0.10%, Sb: 0 to 0.10%, Cr: 0 to 0.30%, Ni: 0 to 0 A slab containing 1.0% and the balance consisting of Fe and impurities was cast.
In the decarburization annealing step, the primary recrystallization particle size is controlled to 24 μm or less.
In the finish annealing process,
When the total content of Nb, V, Mo, Ta, and W in the chemical composition of the slab is 0.0030 to 0.030%, PH ₂ O / PH _{2 at 700 to 800 ° C. in the heating process.} At least one of 0.10 to 1.0 or PH ₂ O / PH ₂ at 950 to 1000 ° C. is set to 0.010 to 0.070, and 850 to 950. The holding time at ° C is 120 to 600 minutes.
When the total content of Nb, V, Mo, Ta, and W in the chemical composition of the slab is not 0.0030 to 0.030%, PH ₂ O / PH _{2 at 700 to 800 ° C. is applied in the heating process.} The pH is set to 0.10 to 1.0, the pH ₂ O / PH ₂ at 950 to 1000 ° C. is set to 0.010 to 0.070, and the holding time at 850 to 950 ° C. is set to 120 to 600 minutes.

_{PH 2} O / _PH 2 of the is called the oxygen potential is the ratio of the steam partial pressure PH ₂ O and hydrogen partial pressure PH ₂ of the atmosphere gas.

The "switching" of the present embodiment is mainly a factor that facilitates the orientation change (switching) itself and a factor that causes the orientation change (switching) to continuously occur in one secondary recrystallized grain. It is controlled by two things.

In order to facilitate the occurrence of switching itself, it is effective to start the secondary recrystallization from a lower temperature. For example, by controlling the primary recrystallization particle size and utilizing Nb group elements, the start of secondary recrystallization can be controlled to a lower temperature.

In order to continuously generate switching within one secondary recrystallized grain, it is effective to continuously grow the secondary recrystallized grain from a low temperature to a high temperature. For example, by using a conventionally used inhibitor such as AlN in an appropriate temperature and atmosphere, secondary recrystallized grains are generated at a low temperature, the inhibitor effect is continuously applied to a high temperature, and switching is one. It can be continuously generated up to a high temperature in the secondary recrystallized grains.

That is, in order to preferably generate switching, it is effective to preferentially grow the secondary recrystallized grains generated at a low temperature up to a high temperature while suppressing the generation of the secondary recrystallized grains at a high temperature.

Further, in the present embodiment, in addition to the above two factors, in-plane anisotropy is imparted to the shape of β crystal grains, so that the growth of secondary recrystallized grains differs in the final secondary recrystallization process. A method of giving anisotropy may be adopted.

The above factors are important for controlling switching, which is a feature of the present embodiment. For other manufacturing conditions, a conventionally known method for manufacturing grain-oriented electrical steel sheets can be applied. For example, there are a production method using MnS and AlN formed by high temperature slab heating as an inhibitor, and a production method using AlN formed by low temperature slab heating and subsequent nitriding treatment as an inhibitor. The switching, which is a feature of the present embodiment, can be applied to any manufacturing method, and is not limited to a specific manufacturing method. In the following, a method of controlling switching by a manufacturing method to which nitriding treatment is applied will be described as an example.

(Casting process)
In the casting process, slabs are prepared. An example of a slab manufacturing method is as follows. Manufacture (melt) molten steel. Manufacture slabs using molten steel. The slab may be manufactured by a continuous casting method. An ingot may be produced using molten steel, and the ingot may be lump-rolled to produce a slab. The thickness of the slab is not particularly limited. The thickness of the slab is, for example, 150-350 mm. The thickness of the slab is preferably 220 to 280 mm. As the slab, a so-called thin slab having a thickness of 10 to 70 mm may be used. When a thin slab is used, rough rolling before finish rolling can be omitted in the hot rolling step.

The slab may contain the basic elements Si and Bi as a chemical composition, and if necessary, contain a selection element, and the balance may consist of Fe and impurities. As the chemical composition other than the above-mentioned basic elements, the chemical composition of the slab used in the production of general grain-oriented electrical steel sheets can be used. The chemical composition of the slab contains, for example, the following elements:

C: 0 to 0.0850%
Carbon (C) is an element effective in controlling the primary recrystallization structure in the manufacturing process, but if the C content of the final product is excessive, it adversely affects the magnetic properties. Therefore, the C content of the slab may be 0 to 0.0850%. The preferred upper limit of the C content is 0.0750%. C is purified in the decarburization annealing step and the finish annealing step described later, and becomes 0.0050% or less after the finish annealing step. When C is contained, the lower limit of the C content may be more than 0% or 0.0010% in consideration of productivity in industrial production.

Si: 2.0-7.0%
Silicon (Si) increases the electrical resistance of grain-oriented electrical steel sheets and reduces iron loss. If the Si content is less than 2.0%, austenite transformation occurs during finish annealing, and the crystal orientation of the grain-oriented electrical steel sheet is impaired. On the other hand, if the Si content exceeds 7.0%, the cold workability is lowered and cracks are likely to occur during cold rolling. The lower limit of the Si content is preferably 2.50%, more preferably 3.0%. The preferred upper limit of the Si content is 4.50%, more preferably 4.0%.

Bi: 0.0010 to 0.0200%
Bismuth (Bi) can increase the magnetic flux density of the final product if added to the slab as a chemical composition when adopting manufacturing conditions that intentionally create small tilt angle grain boundaries that divide the secondary recrystallized grains. It is an element that preferably improves. At this time, it is not necessary to consider the decrease in film adhesion of the final product as in the prior art. The amount of Bi added may be 0.0010 to 0.0200%. When the amount of Bi added is 0%, the effect of improving the magnetic flux density of the final product cannot be obtained in the first place. On the other hand, even if Bi is added to the slab with the aim of improving the magnetic flux density, if it is less than 0.0010%, it will inevitably be discharged to the outside of the system in the purification process of finish annealing, and the remaining amount of the final product will be reduced. It becomes difficult to control it to 0.0005% or more. However, as will be described later, by adding the Bi-containing compound to the annealing separator, it is possible to enjoy the effect of improving the magnetic flux density by Bi even if the amount of Bi added in the slab is zero. Therefore, the lower limit of the amount of Bi added in the slab is only a value as a target. Further, when the amount of Bi added to the slab becomes excessive, the generation and progress of appropriate secondary recrystallization are hindered, and the magnetic flux density in the final product is remarkably hindered. In addition, the formation of the primary coating is also adversely affected, and it becomes difficult to ensure the adhesion of the coating. Further, in order to reduce Bi added to the slab at a high concentration to 0.0100% or less required by the above embodiment by purification, careful purification at a high temperature for a long time is required, as described above. It also relaxes the fitting structure of the interface and becomes a factor of lowering the film adhesion. From these facts, excessive addition of Bi in the slab should be avoided, and the upper limit of the addition amount is 0.0200%.

Mn: 0-1.0%
Manganese (Mn) binds to S or Se to produce MnS or MnSe and functions as an inhibitor. The Mn content may be 0 to 1.0%. When Mn is contained, it is preferable that the secondary recrystallization is stable when the Mn content is in the range of 0.05 to 1.0%. In the present embodiment, a part of the function of the inhibitor can be carried by the nitride of the Nb group element. In this case, the MnS or MnSe intensity as a general inhibitor is controlled to be weak. Therefore, the preferable upper limit of the Mn content is 0.50%, and more preferably 0.20%.

S: 0 to 0.0350%
Se: 0-0.0350%
Sulfur (S) and selenium (Se) combine with Mn to produce MnS or MnSe, which functions as an inhibitor. The S content may be 0 to 0.0350%, and the Se content may be 0 to 0.0350%. When at least one of S and Se is contained, it is preferable that the total content of S and Se is 0.0030 to 0.0350% because secondary recrystallization is stable. In the present embodiment, a part of the function of the inhibitor can be carried by the nitride of the Nb group element. In this case, the MnS or MnSe intensity as a general inhibitor is controlled to be weak. Therefore, the preferable upper limit of the total S and Se contents is 0.0250%, and more preferably 0.010%. When S and Se remain after finish annealing, they form compounds and deteriorate iron loss. Therefore, it is preferable to reduce S and Se as much as possible by purifying during finish annealing.

Here, "the total content of S and Se is 0.0030 to 0.0350%" means that the chemical composition of the slab contains only either S or Se, and either S or Se. One content may be 0.0030 to 0.0350%, the slab contains both S and Se, and the total content of S and Se is 0.0030 to 0.0350%. You may.

Al: 0-0.0650%
Aluminum (Al) binds to N and precipitates as (Al, Si) N, and functions as an inhibitor. The Al content may be 0 to 0.0650%. When Al is contained, when the Al content is in the range of 0.010 to 0.065%, AlN as an inhibitor formed by nitriding described later expands the secondary recrystallization temperature range, particularly. It is preferable because the secondary recrystallization in the high temperature range is stable. The lower limit of the Al content is preferably 0.020%, more preferably 0.0250%. From the viewpoint of stability of secondary recrystallization, the preferable upper limit of the Al content is 0.040%, more preferably 0.030%.

N: 0 to 0.0120%
Nitrogen (N) binds to Al and functions as an inhibitor. The N content may be 0 to 0.0120%. Since N can be contained by nitriding in the middle of the manufacturing process, the lower limit may be 0%. On the other hand, when N is contained, if the N content exceeds 0.0120%, blister, which is a kind of defect, is likely to occur in the steel sheet. The preferred upper limit of the N content is 0.010%, more preferably 0.0090%. N is purified in the finish annealing step and becomes 0.0050% or less after the finish annealing step.

Nb: 0 to 0.030%
V: 0 to 0.030%
Mo: 0-0.030%
Ta: 0-0.030%
W: 0 to 0.030%
Nb, V, Mo, Ta, and W are Nb group elements. The Nb content may be 0 to 0.030%, the V content may be 0 to 0.030%, the Mo content may be 0 to 0.030%, and the Ta content may be 0. It may be ~ 0.030%, and the W content may be 0 to 0.030%.

Further, as the Nb group element, it is preferable to contain at least one selected from the group consisting of Nb, V, Mo, Ta, and W in a total amount of 0.0030 to 0.030% by mass.

When the Nb group elements are used for switching control, the total content of the Nb group elements in the slab is 0.030% or less (preferably 0.0030% or more and 0.030% or less) at an appropriate timing. Initiate secondary recrystallization. In addition, the orientation of the generated secondary recrystallized grains becomes very preferable, and in the subsequent growth process, the switching characteristic of the present embodiment is likely to occur, and finally the structure can be controlled to be preferable for the magnetic characteristics.

By containing the Nb group element, the primary recrystallization particle size after decarburization annealing is preferably smaller than that in the case where the Nb group element is not contained. It is considered that the miniaturization of the primary recrystallized grains can be obtained by a pinning effect due to precipitates such as carbides, carbonitrides, and nitrides, and a drug effect as a solid solution element. In particular, Nb and Ta are preferably effective.

By reducing the particle size of the primary recrystallization by the Nb group elements, the driving force of the secondary recrystallization is increased, and the secondary recrystallization starts at a lower temperature than before. Further, since the precipitate of the Nb group element decomposes at a relatively lower temperature than the conventional inhibitor such as AlN, secondary recrystallization starts at a lower temperature than the conventional one in the temperature raising process of finish annealing. Although these mechanisms will be described later, the initiation of secondary recrystallization at a low temperature facilitates switching, which is a feature of the present embodiment.

When the precipitate of the Nb group element is used as an inhibitor of the secondary recrystallization, the carbide and the carbonitride of the Nb group element become unstable in a temperature range lower than the temperature range in which the secondary recrystallization is possible. Therefore, it is considered that the effect of shifting the secondary recrystallization start temperature to a low temperature is small. Therefore, in order to shift the secondary recrystallization start temperature to a preferably low temperature, it is preferable to utilize a nitride of Nb group elements that is stable up to a temperature range in which secondary recrystallization is possible.

Precipitates of Nb group elements (preferably nitrides) that preferably shift the start temperature of secondary recrystallization to a low temperature, and conventional inhibitors such as AlN and (Al, Si) N that are stable up to high temperatures even after the start of secondary recrystallization. When used in combination, the preferential growth temperature range of the {110} <001> oriented grains, which are secondary recrystallized grains, can be expanded as compared with the conventional case. Therefore, switching occurs in a wide temperature range from low temperature to high temperature, and the orientation selection continues in a wide temperature range. As a result, the frequency of existence of the final β grain boundaries is increased, and the degree of {110} <001> orientation integration of the secondary recrystallized grains constituting the grain-oriented electrical steel sheet can be effectively increased.

When aiming for miniaturization of primary recrystallized grains by the pinning effect of carbides and carbonitrides of Nb group elements, it is preferable to set the C content of the slab to 50 ppm or more at the time of casting. However, since nitride is preferable to carbide or carbonitride as an inhibitor in secondary recrystallization, the C content is reduced to 30 ppm or less, preferably 20 ppm or less by decarburization annealing after the completion of primary recrystallization. It is preferable that the amount is 10 ppm or less so that the carbides and carbonitrides of the Nb group elements in the steel are sufficiently decomposed. By decarburizing and annealing, most of the Nb group elements are left in a solid solution state, and in the subsequent nitriding treatment, the nitride (inhibitor) of the Nb group elements is a preferred form (secondary recrystallization) for the present embodiment. It can be adjusted to a form in which crystals can easily progress).

The total content of the Nb group elements is preferably 0.0040% or more, and more preferably 0.0050% or more. The total content of the Nb group elements is preferably 0.020% or less, more preferably 0.010%.

The rest of the chemical composition of the slab consists of Fe and impurities. It should be noted that the "impurity" referred to here is unavoidably mixed from the components contained in the raw material or the components mixed in the manufacturing process when the slab is industrially manufactured, and substantially affects the effect of the present embodiment. It means an element that does not affect.

Further, the slab may contain a known selective element instead of a part of Fe in consideration of the enhancement of the inhibitor function by compound formation and the influence on the magnetic properties in addition to solving the problems in production. .. Examples of the selection element include the following elements.

Cu: 0-0.40%
B: 0 to 0.080%
P: 0 to 0.50%
Ti: 0 to 0.0150%
Sn: 0 to 0.10%
Sb: 0 to 0.10%
Cr: 0 to 0.30%
Ni: 0-1.0%
These selective elements may be contained according to a known purpose. It is not necessary to set the lower limit of the content of these selective elements, and the lower limit may be 0%.

(Hot rolling process)
The hot rolling step is a step of hot rolling a slab heated to a predetermined temperature (for example, 1100 to 1400 ° C.) to obtain a hot rolled steel sheet. In the hot rolling step, for example, after rough rolling of a silicon steel material (slab) heated after the casting step, finish rolling is performed to perform hot rolling having a predetermined thickness, for example, 1.8 to 3.5 mm. Use a steel plate. After the finish rolling is completed, the hot-rolled steel sheet is wound at a predetermined temperature.

Since the MnS strength as an inhibitor is not so required, the slab heating temperature is preferably 1100 ° C. to 1280 ° C. in consideration of productivity.

In the hot rolling process, by providing a temperature gradient within the above range in the width or longitudinal direction of the steel strip, non-uniformity is caused in the in-plane position of the steel sheet with respect to the crystal structure, crystal orientation, and precipitate. You may. As a result, the growth of the secondary recrystallized grains in the final secondary recrystallization process is imparted with anisotropy, and the shape of the β crystal grains required for the present embodiment is preferably imparted with in-plane anisotropy. Is possible. For example, by slab heating, a temperature gradient is provided in the plate width direction to refine the precipitates in the high temperature part and enhance the inhibitor function in the high temperature part, so that priority is given to the high temperature part from the low temperature part at the time of secondary recrystallization. It is possible to induce grain growth.

(Hot rolled plate annealing process)
The hot-rolled sheet annealing step is a step of annealing the hot-rolled steel sheet obtained in the hot-rolled step under predetermined temperature conditions (for example, 750 to 1200 ° C. for 30 seconds to 10 minutes) to obtain a hot-rolled annealed sheet. ..

In the hot-rolled sheet annealing step, by providing a temperature gradient within the above range in the width or longitudinal direction of the steel strip, the crystal structure, crystal orientation, and precipitates are non-uniform at the in-plane position of the steel sheet. It may occur. As a result, the growth of the secondary recrystallized grains in the final secondary recrystallization process is imparted with anisotropy, and the shape of the β crystal grains required for the present embodiment is preferably imparted with in-plane anisotropy. Is possible. For example, in hot-rolled sheet annealing, a temperature gradient is provided in the plate width direction to refine the precipitates in the high-temperature portion and enhance the inhibitor function of the high-temperature portion, so that the temperature is directed from the low-temperature portion to the high-temperature portion during secondary recrystallization. It is possible to induce preferential grain growth.

(Cold rolling process)
In the cold rolling step, the hot-rolled annealed sheet obtained in the hot-rolled sheet annealing step is cold-rolled once or multiple times (two or more times) through annealing (intermediate annealing) (for example, total). It is a step of obtaining a cold-rolled steel sheet having a thickness of, for example, 0.10 to 0.50 mm by a cold rolling ratio (80 to 95%).

(Decarburization annealing process)
The decarburization annealing step is a step of performing decarburization annealing (for example, at 700 to 900 ° C. for 1 to 3 minutes) on a cold rolled steel sheet obtained in the cold rolling step to obtain a decarburized annealed steel sheet in which primary recrystallization has occurred. be. By decarburizing and annealing the cold-rolled steel sheet, C contained in the cold-rolled steel sheet is removed. The decarburization annealing is preferably performed in a moist atmosphere in order to remove "C" contained in the cold-rolled steel sheet.

In the method for producing grain-oriented electrical steel sheet according to the present embodiment, it is preferable to control the primary recrystallization grain size of the decarburized annealed steel sheet to 24 μm or less. By refining the primary recrystallization particle size, the secondary recrystallization start temperature can be preferably shifted to a low temperature.

For example, the primary recrystallization grain size can be reduced by controlling the above-mentioned conditions of hot rolling and hot-rolled sheet annealing, or by lowering the decarburization annealing temperature as necessary. Alternatively, the slab may contain Nb group elements, and the primary recrystallized grains can be reduced by the pinning effect of the carbides and carbonitrides of the Nb group elements.

Since the amount of decarboxylation and the state of the surface oxide layer due to decarburization annealing affect the formation of the intermediate layer (glass film), a conventional method is used to exert the effect of the present embodiment. It may be adjusted as appropriate.

At this point, the Nb group element, which may be contained as an element that facilitates switching, exists as a carbide, a carbonitride, a solid solution element, or the like, and has an effect on reducing the primary recrystallization particle size. The primary recrystallization particle size is preferably 23 μm or less, more preferably 20 μm or less, and even more preferably 18 μm or less. The primary recrystallization particle size may be 8 μm or more, and may be 12 μm or more.

In the decarburization annealing step, by providing a temperature gradient and a decarburization behavior difference within the above range in the width or longitudinal direction of the steel strip, the crystal structure, crystal orientation, and precipitates are measured at the in-plane position of the steel sheet. May cause non-uniformity. As a result, the growth of the secondary recrystallized grains in the final secondary recrystallization process is imparted with anisotropy, and the shape of the β crystal grains required for the present embodiment is preferably imparted with in-plane anisotropy. Is possible. For example, by slab heating, a temperature gradient is provided in the plate width direction to refine the primary recrystallization particle size in the low temperature portion to increase the driving force for starting the secondary recrystallization, and to accelerate the secondary recrystallization in the low temperature portion. By starting, it is possible to induce preferential grain growth from the low temperature portion to the high temperature portion during the growth of the secondary recrystallized grains.

Further, in the decarburization annealing step, known annealing conditions may be applied in order to avoid a decrease in film adhesion in the final product due to the addition of Bi to the slab. For example, if necessary, as disclosed in Patent Document 17, the temperature of the front region of decarburization annealing is set to 800 to 880 ° C, and the temperature of the subsequent rear region is set to 850 to 930 ° C for 10 to 30 seconds. PH ₂ O / PH ₂ may be controlled to 0.15 or less. Further, if necessary, as disclosed in Patent Document 18, the amount of oxygen in the oxide film after decarburization annealing may be controlled to 600 to 900 ppm.

(Nitriding treatment)
Nitriding is performed to adjust the strength of the inhibitor in secondary recrystallization. In the nitriding treatment, the nitrogen content of the steel sheet may be increased to about 40 to 300 ppm at an arbitrary timing from the start of the decarburization annealing described above to the start of secondary recrystallization in the finish annealing described later. As the nitriding treatment, for example, a treatment of annealing a steel sheet in an atmosphere containing a nitriding gas such as ammonia, or a decarburized annealed steel sheet coated with an annealing separator containing a powder having nitriding ability such as MnN is finished. An example is a process of annealing.

When the slab contains the Nb group element in the above numerical range, the nitride of the Nb group element formed by the nitriding treatment functions as an inhibitor in which the grain growth suppressing function disappears at a relatively low temperature, so that secondary recrystallization occurs. Starts from a lower temperature than before. It is also possible that this nitride has an advantageous effect on the selectivity of nucleation of secondary recrystallized grains and realizes a high magnetic flux density. In addition, AlN is also formed in the nitriding treatment, and this AlN functions as an inhibitor in which the grain growth suppressing function continues until a relatively high temperature. In order to obtain these effects, the amount of nitriding after the nitriding treatment is preferably 130 to 250 ppm, more preferably 150 to 200 ppm.

In the nitriding treatment, the inhibitor strength may be non-uniform at the in-plane position of the steel sheet by providing a difference in the amount of nitriding within the above range in the width or longitudinal direction of the steel strip. As a result, the growth of the secondary recrystallized grains in the final secondary recrystallization process is imparted with anisotropy, and the shape of the β crystal grains required for the present embodiment is preferably imparted with in-plane anisotropy. Is possible. For example, by providing a difference in the amount of nitriding in the plate width direction to enhance the inhibitor function of the high nitriding portion, it is possible to induce preferential grain growth from the low nitriding portion to the high nitriding portion during secondary recrystallization. Is.

(Annealing separator application process)
The annealing separator application step is a step of applying an annealing separator to a decarburized annealed steel sheet. As the annealing separator, for example, an annealing separator containing MgO as a main component or an annealing separator containing alumina as a main component can be used.

When an annealing separator containing MgO as a main component is used, a forsterite film ( _{a film mainly composed of Mg 2} SiO ₄ ) is likely to be formed as an intermediate layer by finish annealing, and annealing containing alumina as a main component is likely to occur. When a separating agent is used, an oxide film ( _{a film mainly composed of SiO 2} ) is likely to be formed as an intermediate layer by finish annealing. These intermediate layers may be removed if necessary.

The decarburized annealed steel sheet after applying the annealing separating agent is subjected to finish annealing in the next finish annealing step in a coiled state.

Further, in the annealing separating agent application step, a known annealing separating agent may be used in order to avoid a decrease in film adhesion in the final product due to the addition of Bi to the slab. For example, as required, as disclosed in Patent Document 18, 0.01 to 0.10 parts by weight of the chlorine compound as chlorine content with respect to 100 parts by weight of MgO, and / or Sb, B, Sr, Ba, Ce, A quenching separator may be used in which one or more of the Ca compounds are added in an amount of 0.05 to 2.0 parts by weight. Alternatively, as disclosed in Patent Document 19, one or two of rare earth metal oxides, sulfides, sulfates, silicides, phosphates, hydroxides, carbonates, boronides, chlorides and fluorides. 0.1 to 10% by mass of species or more in terms of rare earth metals, oxides, sulfides, sulfates, silicides, phosphates, of one or more alkaline earth metals selected from Ca, Sr or Ba. One or more of hydroxides, carbonates, boroides, chlorides and fluorides in terms of alkaline earth metals 0.1-10% by mass, and sulfur compounds in terms of S 0.01-5% by mass % Addition of the annealed separator may be used. Furthermore, a compound containing Bi is added to the annealing separator, Bi is diffused in the steel sheet in the first half of the finish annealing step, and the inhibitor is strengthened by this Bi to the {110} <001> orientation in the secondary recrystallization. It is also possible to contribute to the improvement of the degree of integration. In this case, the Bi content in the product may exceed the Bi addition amount in the slab.

(Finish annealing process)
The finish annealing step is a step of subjecting a decarburized annealed steel sheet coated with an annealing separator to finish annealing to generate secondary recrystallization. In this step, the {100} <001> oriented grains are preferentially grown and the magnetic flux density is dramatically improved by advancing the secondary recrystallization in a state where the growth of the primary recrystallized grains is suppressed by the inhibitor.

Finish annealing is an important step for controlling switching, which is a feature of this embodiment. In the present embodiment, the shift angle β is controlled by finish annealing based on the following three conditions (A), (B), and (D).

The "total content of Nb group elements" in the description of the finish annealing step means the total content of Nb group elements in the steel sheet (decarburized annealed steel sheet) immediately before finish annealing. In other words, it is the chemical composition of the steel sheet immediately before finish annealing that affects the finish annealing conditions, and what is the chemical composition after finish annealing and purification (for example, the chemical composition of the directional electromagnetic steel sheet (finish annealing steel sheet))? It is irrelevant.

_{(A) When PH 2} O / PH ₂ for the atmosphere in the temperature range of 700 to 800 ° C. is set to PA in the heating process of finish annealing.
PA: 0.10 to 1.0
_{(B) When PH 2} O / PH ₂ for the atmosphere in the temperature range of 950 to 1000 ° C. is PB in the heating process of finish annealing.
PB: 0.010 to 0.070
(D) When the holding time in the temperature range of 850 to 950 ° C. is TD in the heating process of finish annealing.
TD: 120-600 minutes

When the total content of the Nb group elements is 0.0030 to 0.030%, at least one of the conditions (A) and (B) and the condition (D) may be satisfied.

When the total content of the Nb group elements is not 0.0030 to 0.030%, the three conditions (A), (B), and (D) may be satisfied.

Regarding the conditions (A) and (B), when the Nb group element is contained in the above range, "start of secondary recrystallization in the low temperature range" and "high temperature range" due to the recovery recrystallization suppressing effect of the Nb group element. The two factors of "continuation of secondary recrystallization until" act strongly. As a result, the control conditions for obtaining the effect of the present embodiment are relaxed.

The PA is preferably 0.30 or more, and preferably 0.60 or less.
The PB is preferably 0.020 or more, and preferably 0.050 or less.
The TD is preferably 180 minutes or more, more preferably 240 minutes or more, preferably 480 minutes or less, and more preferably 360 minutes or less.

The details of the mechanism by which the switch occurs are not clear at this time. However, in consideration of the observation results of the secondary recrystallization process and the manufacturing conditions under which switching can be preferably controlled, "start of secondary recrystallization in the low temperature range" and "continuation of secondary recrystallization up to the high temperature range" are two. I speculate that two factors are important.

With these two factors in mind, the reasons for limitation (A), (B), and (D) will be described. In the following explanation, the description of the mechanism includes guessing.

Condition (A) is a condition in a temperature range sufficiently lower than the temperature at which secondary recrystallization occurs, and this condition does not directly affect the phenomenon recognized as secondary recrystallization. However, this temperature range is a temperature range in which the surface layer of the steel sheet is oxidized by moisture or the like brought in by the annealing separator applied to the surface of the steel sheet, that is, a temperature range that affects the formation of the primary coating (intermediate layer). The condition (A) is important to enable the subsequent "continuation of secondary recrystallization up to a high temperature region" through controlling the formation of this primary coating. By setting this temperature range as the above atmosphere, the primary coating has a dense structure and prevents the constituent elements of the inhibitor (for example, Al, N, etc.) from being discharged to the outside of the system at the stage where secondary recrystallization occurs. Acts as a barrier. As a result, the secondary recrystallization continues to a high temperature, and switching can be sufficiently caused.

Condition (B) is a condition in a temperature range corresponding to the middle stage of grain growth of secondary recrystallization, and this condition affects the adjustment of inhibitor strength in the process of secondary recrystallization grain growth. By setting this temperature range to the above atmosphere, the growth of secondary recrystallized grains proceeds at the rate of inhibitor decomposition in the middle stage of grain growth. Although the details will be described later, depending on the condition (B), dislocations are efficiently accumulated at the grain boundaries in front of the growth direction of the secondary recrystallized grains, so that the frequency of switching occurs and the switching occurs continuously.

Condition (D) is a condition in a temperature range corresponding to the initial stage of grain growth from nucleation of secondary recrystallization. Retention in this temperature range is important for good secondary recrystallization, but the longer the retention time, the easier it is for primary recrystallized grains to grow. For example, when the particle size of the primary recrystallized grains becomes large, the accumulation of dislocations (dislocation accumulation at the grain boundaries in front of the growth direction of the secondary recrystallized grains), which is the driving force for the generation of switching, is less likely to occur. If the holding time in this temperature range is 600 minutes or less, the growth of the secondary recrystallized grains in the initial stage can proceed in a state where the coarsening of the primary recrystallized grains is suppressed. It will increase the selectivity. In the present embodiment, the shift angle β is frequently switched and continued against the background of shifting the secondary recrystallization start temperature to a low temperature by refining the primary recrystallized grains and utilizing Nb group elements.

In the production method of the present embodiment, when the Nb group elements are utilized, if one of the conditions (A) and (B) is not satisfied but one of them is selectively satisfied, the switching condition of the present embodiment is satisfied. It is possible to obtain electrical steel sheets. That is, if the switching frequency at a specific deviation angle (deviation angle β in the case of the present embodiment) is controlled at the initial stage of the secondary recrystallization, the secondary recrystallization grains grow while maintaining the orientation difference due to the switching. , The effect will continue until the latter period, and the final switching frequency will also increase. Further, even if a new switching occurs continuously until the latter period, the switching with a large change in the deviation angle β occurs, and the final switching frequency of the deviation angle β also increases. Of course, even if the Nb group elements are utilized, it is optimal to satisfy both the conditions (A) and (B).

Based on the method for manufacturing grain-oriented electrical steel sheets according to the present embodiment described above, the secondary recrystallized grains may be controlled to be divided into small regions having slightly different displacement angles β. Specifically, based on the above method, as described as the first embodiment, in addition to the grain boundaries satisfying the boundary condition BB in the grain-oriented electrical steel sheet, the boundary condition BA is satisfied and the boundary condition BA is satisfied. It suffices to create a grain boundary that does not satisfy BB.

Next, preferable manufacturing conditions regarding the manufacturing method according to the present embodiment will be described.

In the production method according to the present embodiment, when the total content of Nb, V, Mo, Ta, and W in the chemical composition of the slab is not 0.0030 to 0.030% in the finish annealing step, in the heating process, The holding time at 1000 to 150 ° C. is preferably 300 to 1500 minutes.

Similarly, in the production method according to the present embodiment, when the total content of Nb, V, Mo, Ta, and W in the chemical composition of the slab is 0.0030 to 0.030% in the finish annealing step, heating is performed. In the process, the holding time at 1000 to 1050 ° C. is preferably 150 to 900 minutes.

In the following, the above manufacturing conditions will be referred to as condition (E-1).
(E-1) When the holding time (total residence time) in the temperature range of 1000 to 150 ° C. is set to TE1 in the heating process of finish annealing.
When the total content of Nb group elements is 0.0030 to 0.030%,
TE1: 150 minutes or more When the total content of Nb group elements is out of the above range,
TE1: 300 minutes or more

When the total content of the Nb group elements is 0.0030 to 0.030%, TE1 is preferably 200 minutes or more, more preferably 300 minutes or more, and preferably 900 minutes or less. It is more preferably 600 minutes or less.
When the total content of the Nb group elements is out of the above range, TE1 is preferably 360 minutes or more, more preferably 600 minutes or more, preferably 1500 minutes or less, and 900 minutes or less. Is more preferable.

The condition (E-1) is a factor that controls the stretching direction in the steel sheet surface of the β grain boundary where the switching occurs. Sufficient holding at 1000 to 1050 ° C. makes it possible to increase the frequency of switching in the rolling direction. It is considered that the frequency of switching in the rolling direction increases due to the change in the morphology (for example, arrangement and shape) of the precipitate in the steel containing the inhibitor during the holding in the above temperature range.

Since the steel sheet subjected to finish annealing has undergone hot rolling and cold rolling, the arrangement and shape of the precipitates (particularly MnS) in the steel have anisotropy in the surface of the steel sheet and are oriented in the rolling direction. It is considered to have a tendency to be biased. Although the details are unknown, the retention in the above temperature range changes the degree of deflection of the morphology of such precipitates in the rolling direction, and the β grain boundaries are within the surface of the steel sheet during the growth of the secondary recrystallized grains. It is considered that it affects which direction it is easy to stretch. Specifically, when the steel sheet is held at a relatively high temperature of 1000 to 1050 ° C., the deflection of the precipitate morphology in the rolling direction disappears in the steel, and thus the ratio of β grain boundaries extending in the rolling direction decreases. As a result, the tendency to stretch in the direction perpendicular to rolling becomes stronger. As a result, it is considered that the frequency of β grain boundaries measured in the rolling direction increases.

When the total content of the Nb group elements is 0.0030 to 0.030%, the frequency of existence of β grain boundaries itself is high, so even if the holding time of the condition (E-1) is short, the present embodiment It is possible to obtain an effect.

By the production method including the above condition (E-1), the particle size of the β crystal grains in the rolling direction can be controlled to be smaller than the particle size of the secondary recrystallized grains in the rolling direction. Specifically, by controlling the combined above-mentioned condition (E-1), as described as the second embodiment, by the directional electromagnetic steel plates, and a particle size RA _L and particle size RB _L, 1.10 can be controlled to satisfy ≦ RB _L ÷ RA _L.

Further, in the production method according to the present embodiment, when the total content of Nb, V, Mo, Ta, and W in the chemical composition of the slab is not 0.0030 to 0.030% in the finish annealing step, the heating process is performed. Therefore, the holding time at 950 to 1000 ° C. is preferably 300 to 1500 minutes.

Similarly, in the production method according to the present embodiment, when the total content of Nb, V, Mo, Ta, and W in the chemical composition of the slab is 0.0030 to 0.030% in the finish annealing step, heating is performed. In the process, the holding time at 950 to 1000 ° C. is preferably 150 to 900 minutes.

In the following, the above manufacturing conditions will be referred to as condition (E-2).
(E-2) When the holding time (total residence time) in the temperature range of 950 to 1000 ° C. is set to TE2 in the heating process of finish annealing.
When the total content of Nb group elements is 0.0030 to 0.030%,
TE2: 150 minutes or more When the total content of Nb group elements is out of the above range
TE2: 300 minutes or more

When the total content of Nb group elements is 0.0030 to 0.030%, TE2 is preferably 200 minutes or more, more preferably 300 minutes or more, and preferably 900 minutes or less. More preferably, it is 600 minutes or less.
When the total content of the Nb group elements is out of the above range, TE2 is preferably 360 minutes or more, more preferably 600 minutes or more, preferably 1500 minutes or less, and 900 minutes or less. Is more preferable.

The condition (E-2) is a factor that controls the stretching direction in the steel sheet surface of the β grain boundary where the switching occurs. Sufficient holding at 950 to 1000 ° C. makes it possible to increase the frequency of switching in the direction perpendicular to rolling. It is considered that the frequency of switching in the direction perpendicular to rolling increases due to the change in the morphology (for example, arrangement and shape) of the precipitate in the steel containing the inhibitor during the holding in the above temperature range.

Since the steel sheet subjected to finish annealing has undergone hot rolling and cold rolling, the arrangement and shape of the precipitates (particularly MnS) in the steel have anisotropy in the surface of the steel sheet and are oriented in the rolling direction. It is considered to have a tendency to be biased. Although the details are unknown, the retention in the above temperature range changes the degree of deflection of the morphology of such precipitates in the rolling direction, and the β grain boundaries are within the surface of the steel sheet during the growth of the secondary recrystallized grains. It is considered that it affects which direction it is easy to stretch. Specifically, when the steel sheet is held at a relatively low temperature of 950 to 1000 ° C., the deflection of the precipitate morphology in the rolling direction increases in the steel, so that the β grain boundary stretches in the direction perpendicular to the rolling direction. The tendency to decrease and stretch in the rolling direction becomes stronger. As a result, it is considered that the frequency of β grain boundaries measured in the direction perpendicular to rolling increases.

When the total content of the Nb group elements is 0.0030 to 0.030%, the frequency of existence of β grain boundaries itself is high, so even if the holding time of the condition (E-2) is short, the present embodiment It is possible to obtain an effect.

By the production method including the above condition (E-2), the particle size in the direction perpendicular to the rolling of the β crystal grains can be controlled to be smaller than the particle size in the direction perpendicular to the rolling of the secondary recrystallized grains. Specifically, by controlling the combined above-mentioned condition (E-2), as described as the third embodiment, by the directional electromagnetic steel plates, and a particle size RA _C and particle size RB _C, 1.10 can be controlled so as to satisfy the ≦ RB _C ÷ RA _C.

Further, in the manufacturing method according to the present embodiment, in the heating process of finish annealing, a temperature gradient of more than 0.5 ° C./cm is applied to the boundary portion between the primary recrystallization region and the secondary recrystallization region in the steel sheet. It is preferable to cause secondary recrystallization. For example, it is preferable to give the above temperature gradient to the steel sheet during the growth of the secondary recrystallized grains within the temperature range of 800 ° C. to 1150 ° C. in the heating process of finish annealing.

Further, it is preferable that the direction in which the temperature gradient is given is the rolling perpendicular direction C.

The finish annealing step can be effectively utilized as a step of imparting in-plane anisotropy to the shape of β crystal grains. For example, in a box-type annealing furnace, when a coiled steel plate is installed in the furnace and heated, the position, arrangement, and annealing of the heating device so that a sufficient temperature difference occurs between the outside and the inside of the coil. The temperature distribution in the furnace may be controlled. Alternatively, a temperature distribution may be formed in the coil to be annealed by arranging an induction heating, a high frequency heating, an energization heating device, or the like to positively heat only a part of the coil.

The method of applying the temperature gradient is not particularly limited, and a known method may be applied. When a temperature gradient is applied to the steel sheet, secondary recrystallized grains with sharp orientations are generated from the part in the coil that reached the secondary recrystallization start state early, and these secondary recrystallized grains are caused by the temperature gradient. It grows with anisotropy. For example, secondary recrystallized grains can be grown over the entire coil. Therefore, it is possible to preferably control the in-plane anisotropy of the shape of β crystal grains.

When heating a coiled steel sheet, the coil edge is easily heated, so a temperature gradient is applied from one end side to the other end side in the width direction (plate width direction of the steel sheet) to form secondary recrystallized grains. It is preferable to grow it.

Considering that the desired magnetic characteristics can be obtained by controlling the Goss direction, and further considering industrial productivity, the temperature exceeds 0.5 ° C./cm (preferably 0.7 ° C./cm or more). The secondary recrystallized grains may be grown by performing finish annealing while giving a temperature gradient of. The direction for giving the temperature gradient is preferably the rolling perpendicular direction C. The upper limit of the temperature gradient is not particularly limited, but it is preferable to continuously grow the secondary recrystallized grains while maintaining the temperature gradient. Considering the heat conduction of the steel sheet and the growth rate of the secondary recrystallized grains, in a general manufacturing process, for example, the upper limit of the temperature gradient may be 10 ° C./cm.

By the production method including the temperature gradient under the above conditions, the particle size of the β crystal grains in the rolling direction can be controlled to be smaller than the particle size of the β crystal grains in the direction perpendicular to the rolling direction. Specifically, by controlling the combined temperature gradient conditions described above, as described as the fourth embodiment, by the directional electromagnetic steel plates, and a particle size RA _L and particle size RA _C, 1. It can be controlled so as to satisfy 15 ≦ RA _C ÷ RA _L.

Further, in the production method according to the present embodiment, the holding time at 1050 to 1100 ° C. may be set to 300 to 1200 minutes in the heating process of finish annealing.

In the following, the above manufacturing conditions will be referred to as condition (F).
(F) When the holding time in the temperature range of 1050 to 1100 ° C. is TF in the heating process of finish annealing.
TF: 300-1200 minutes

If the secondary recrystallization is not completed by 1050 ° C in the heating process of finish annealing, the heating rate of 1050 to 1100 ° C is lowered (slow heating) to specifically increase the TF to 300 to 1200. By setting the amount to minutes, the secondary recrystallization continues up to a high temperature and the magnetic flux density is preferably increased. For example, the TF is preferably 400 minutes or more, and preferably 700 minutes or less. If the secondary recrystallization is completed by 1050 ° C. in the heating process of finish annealing, the condition (F) does not have to be controlled. For example, when the secondary recrystallization is completed by 1050 ° C., the cost can be reduced by increasing the temperature rise rate and shortening the finish annealing time in the temperature range of 1050 ° C. or higher. ..

In the manufacturing method according to the present embodiment, in the finish annealing step, the conditions (A), the condition (B), and the condition (D) are basically controlled as described above, and if necessary, the condition ( The conditions of E-1), the condition (E-2), and the temperature gradient may be combined. For example, a plurality of conditions of the condition (E-1), the condition (E-2), and / or the temperature gradient condition may be combined. Further, the condition (F) may be combined as necessary.

The method for manufacturing grain-oriented electrical steel sheets according to the present embodiment includes the above-mentioned steps. In the method for manufacturing grain-oriented electrical steel sheets according to the present embodiment, since the orientation change is controlled and the chemical composition is also controlled, the magnetostriction in the low magnetic field region is improved and the magnetic flux density is improved, and at the same time, the coating film is formed. Deterioration of adhesion is avoided.

The production method according to the present embodiment may further include an insulating film forming step after the finish annealing step, if necessary.

(Insulation film forming process)
The insulating film forming step is a step of forming an insulating film on the grain-oriented electrical steel sheet (finish-annealed steel sheet) after the finish-annealing step. An insulating film mainly composed of phosphate and colloidal silica or an insulating film mainly composed of alumina sol and boric acid may be formed on the steel sheet after finish annealing.

For example, a coating solution containing phosphoric acid or phosphate, chromic anhydride or chromate and colloidal silica is applied to a steel sheet after finish annealing and baked (for example, at 350 ° C to 1150 ° C for 5 to 300 seconds). ), An insulating film may be formed. At the time of forming the film, the degree of oxidation and the dew point of the atmosphere may be controlled as necessary.

Alternatively, a coating solution containing alumina sol and boric acid may be applied to the steel sheet after finish annealing and baked (for example, at 750 ° C. to 1350 ° C. for 10 to 100 seconds) to form an insulating film. At the time of forming the film, the degree of oxidation and the dew point of the atmosphere may be controlled as necessary.

Further, the manufacturing method according to the present embodiment may further include a magnetic domain control step, if necessary.

(Magnetic domain control process)
The magnetic domain control step is a step of subdividing the magnetic domain of the grain-oriented electrical steel sheet. For example, a local fine strain or a local groove may be formed on the grain-oriented electrical steel sheet by a known method such as laser, plasma, mechanical method, or etching. Such magnetic domain subdivision processing does not impair the effect of the present embodiment.

The above-mentioned local microstrain and local groove become abnormal points when measuring the crystal orientation and the particle size specified in the present embodiment. Therefore, in the measurement of the crystal orientation, the measurement points should not overlap with the local microstrain and the local groove. In addition, in the measurement of particle size, local minute strains and local grooves are not recognized as grain boundaries.

(About the mechanism of switching occurrence)
The switching defined in this embodiment occurs in the process of growing the secondary recrystallized grains. This phenomenon is influenced by various control conditions such as the chemical composition of the material (slab), the incorporation of inhibitors leading up to the growth of the secondary recrystallized grains, and the control of the grain size of the primary recrystallized grains. For this reason, switching does not have to simply control one condition, but it is necessary to control a plurality of control conditions in a complex and indivisible manner.

Switching is believed to occur due to grain boundary energy and surface energy between adjacent crystal grains.

Regarding the above-mentioned grain boundary energy, if two crystal grains having an angle difference are adjacent to each other, the grain boundary energy becomes large, so that the grain boundary energy should be reduced in the process of growing the secondary recrystallized grains. That is, it is conceivable that switching occurs so as to approach a specific same direction.

Regarding the above surface energy, if the orientation is slightly deviated from the {110} plane, which has a high degree of symmetry, the surface energy will increase. Therefore, the surface energy is generated in the process of growing the secondary recrystallized grains. It is conceivable that switching occurs so as to reduce the amount of energy, that is, to approach the {110} plane direction and reduce the deviation angle.

However, in a general situation, these energy differences are not energy differences that cause a change in orientation until switching occurs in the process of growth of secondary recrystallized grains. Therefore, in a general situation, the secondary recrystallized grains grow while having an angle difference or a deviation angle. For example, the shift angle β corresponds to the angle caused by the orientation variation at the time of generation of the secondary recrystallized grains in the initial stage of secondary recrystallization. When the secondary recrystallized grains having the deviation angle β grow, especially when the secondary recrystallized grains grow in a state of having a curvature in the rolling direction, the angle of the deviation angle β with respect to the steel sheet surface changes. That is, the secondary recrystallized grains are controlled so that the shift angle β becomes small at the time of generation, but the shift angle β inevitably becomes large at the tip of the secondary recrystallized grains grown to a certain size. To go.

On the other hand, when the secondary recrystallization is started from a lower temperature and the growth of the secondary recrystallized grains is continued for a long time up to a high temperature as in the grain-oriented electrical steel sheet according to the present embodiment, the switching is remarkable. Get up. The reason for this is not clear, but in the process of growth of secondary recrystallized grains, relatively high density and geometrical deviation is eliminated in the front part of the growth direction, that is, the region adjacent to the primary recrystallized grains. It is conceivable that dislocations will remain. It is considered that the remaining dislocations correspond to the switching and β grain boundaries of the present embodiment.

In the present embodiment, since the secondary recrystallization starts at a lower temperature than before, the disappearance of dislocations is delayed, and the dislocations are accumulated in such a way that the dislocations are swept up at the grain boundaries in front of the growing secondary recrystallized grains in the growth direction. The dislocation density increases. For this reason, atomic rearrangement is likely to occur in front of the growing secondary recrystallized grains, and as a result, the angle difference from the adjacent secondary recrystallized grains is reduced, that is, the grain boundary energy is reduced. , Or it is thought that switching is caused to reduce the surface energy.

This switching leaves grain boundaries (β grain boundaries) having a special orientation relationship in the secondary recrystallized grains. If another secondary recrystallized grain is generated before the switching occurs and the growing secondary recrystallized grain reaches the generated secondary recrystallized grain, the grain growth is stopped, so that the switching itself Will not occur. Therefore, in the present embodiment, the frequency of occurrence of new secondary recrystallized grains is reduced at the growth stage of the secondary recrystallized grains, and only the existing secondary recrystallized grains continue to grow by inhibitor rate control. It is advantageous to do. Therefore, in the present embodiment, it is preferable to use an inhibitor that preferably shifts the secondary recrystallization start temperature to a low temperature and an inhibitor that is stable up to a relatively high temperature.

In this embodiment, the reason why the switching with the deviation angle β as the main directional change occurs is not clear, but it is considered as follows. The type of dislocation that can be said to be the basic unit of dislocation (that is, the Burgers vector in the dislocation that is swept in front of the secondary recrystallized grains during the growth process) is considered to affect the type of dislocation that causes the switching. In the present embodiment, the inhibitor control (condition (B) above) in the early to middle stages of the secondary recrystallization process has a large effect on the control of the shift angle β. For example, when the inhibitor intensity changes depending on the atmosphere in the temperature range of 950 ° C. or lower or 1000 ° C. or higher, the contribution of the shift angle β in switching becomes small. That is, the weakening timing of the inhibitor affects the change in the primary recrystallized structure (change in orientation and particle size), the disappearance of dislocations swept up, and the growth rate of the secondary recrystallized grains, and as a result, the secondary recrystallization that grows. It is considered to change the direction of switching formed in the crystal grains (that is, the type and amount of dislocations incorporated in the secondary recrystallized grains).

Since the grain-oriented electrical steel sheet according to the present embodiment controls the orientation change and also controls the chemical composition, the magnetostriction in the low magnetic field region is improved, the magnetic flux density is improved, and at the same time, the film adheres. Gender deterioration is avoided.

Next, the effect of one aspect of the present invention will be described in more detail by way of examples. However, the present invention is not limited to this one-condition example. In the present invention, various conditions can be adopted as long as the gist of the present invention is not deviated and the object of the present invention is achieved.

(Example 1)
Using the slabs having the chemical compositions shown in Tables 2 and 3 as materials, grain-oriented electrical steel sheets (silicon steel sheets) having the chemical compositions shown in Tables 4 and 5 were produced. These chemical compositions were measured based on the above method. In Tables 2 to 5, "-" indicates that the content is not controlled and manufactured in consideration of the content, and the content is not measured. Further, in Tables 2 to 5, the numerical values marked with "<" are the measured values having sufficient reliability as the content, although the content was measured by carrying out control and manufacturing in consideration of the content. Was not obtained (the measurement result is below the detection limit).

The grain-oriented electrical steel sheet was manufactured based on the manufacturing conditions shown in Tables 6 to 17. Specifically, slabs are cast, hot-rolled, hot-rolled, cold-rolled, and decarburized and annealed. If necessary, the steel sheet after decarburization and annealing is mixed with hydrogen-nitrogen-ammonia. Nitriding treatment (nitriding annealing) was performed in.

Further, an annealing separator containing MgO as a main component was applied to the steel sheet. Under the test conditions indicated as "Yes" in the "Presence / absence of improvement of annealing separator" column in the table, the amount of chlorine in MgO powder was adjusted to 0.03 to 0.04 parts by weight by adding _{MnCl 2.} An annealing separator was used in which 0.3 parts by weight of Sb ₂ (SO _{4 ) 3 and 5 parts by weight of TiO 2 were added.} Under the test conditions indicated as "None" in the "Presence / absence of improvement of annealing separator" column in the table, an annealing separator containing MgO as a main component without the above additives was used.

The steel sheet coated with the annealing separator was subjected to finish annealing. In the final process of finish annealing, the steel sheet was held (purified annealing) at 1200 ° C. in a hydrogen atmosphere for the purification time shown in Tables 6 to 17 and cooled.

A coating solution for forming an insulating film containing mainly phosphate and colloidal silica and containing chromium is applied on the primary coating (intermediate layer) formed on the surface of the manufactured directional electromagnetic steel sheet (finish-annealed steel sheet). Then, hydrogen: nitrogen was heated and held in an atmosphere of 75% by volume: 25% by volume and cooled to form an insulating film.

The manufactured grain-oriented electrical steel sheet is in contact with an intermediate layer arranged in contact with the grain-oriented electrical steel sheet (silicon steel sheet) and on the intermediate layer when viewed on a cut surface whose cutting direction is parallel to the plate thickness direction. It had an arranged insulating coating. The intermediate layer was a forsterite film having an average thickness of 2 μm, and the insulating film was an insulating film mainly composed of phosphate and colloidal silica having an average thickness of 1 μm.

Various characteristics of the obtained grain-oriented electrical steel sheets were evaluated. The evaluation results are shown in Tables 18 to 29.

(1) Crystal orientation of grain-oriented electrical steel sheet The crystal orientation of grain-oriented electrical steel sheet was measured by the above method. The deviation angle was specified from the crystal orientation of each of the measured measurement points, and the grain boundaries existing between the two adjacent measurement points were specified based on this deviation angle. The “BA / BB” shown in the table means a value obtained by dividing the “number of boundaries satisfying the boundary condition BA” by the “number of boundaries satisfying the boundary condition BB”. The "number of boundaries satisfying the boundary condition BA" corresponds to the grain boundaries of case 1 and / or case 3 in Table 1 described above, and the "number of boundaries satisfying the boundary condition BB" means cases 1 and / or Corresponds to the grain boundaries of Case 2. When the BA / BB value is 1.1 or more, it is determined that the grain grain boundary satisfying the boundary condition BA and not satisfying the boundary condition BB exists in the grain-oriented electrical steel sheet. In addition, if necessary, the average crystal grain size was calculated based on the specified grain boundaries. In addition, the standard deviation σ (| β |) of the absolute value of the deviation angle β was measured by the above method.

(2) Magnetic properties of grain-oriented electrical steel sheets The magnetic properties of grain-oriented electrical steel sheets were measured based on the single plate magnetic property test method (SST: Single Sheet Tester) specified in JIS C 2556: 2015.

_{As the magnetic characteristics, the iron loss W 17/50} (W / kg) defined as the power loss per unit weight (1 kg) of the steel sheet was measured under the conditions of AC frequency: 50 Hz and exciting magnetic flux density: 1.7 T. _{Further, the magnetic flux density B 8} (T) in the rolling direction of the steel sheet when excited at 800 A / m was measured. When B ₈ was 1.920 T or more, it was judged to be acceptable.

Further, as magnetic characteristics, the magnetostriction λpp@1.5T generated in the steel sheet under the conditions of AC frequency: 50 Hz and exciting magnetic flux density: 1.5 T was measured. _{Specifically, using the maximum length L max} and the minimum length L _min of the test piece (steel plate) under the above excitation conditions and _{the length L 0} of the test piece at the magnetic flux density 0 T, λpp It was calculated by @ 1.5T = (L _max −L _min ) ÷ L _0.
(3) Film adhesion of grain-oriented electrical steel sheet The film adhesion (coating residual area ratio) of grain-oriented electrical steel sheet was measured by the above method. When the film remaining area ratio was 90% or more, it was judged to be acceptable.

No. In 1 to 240, when λpp@1.5T was 0.3 or less, it was judged to be acceptable.

No. Of 1 to 240, all of the examples of the present invention satisfied the chemical composition and were excellent in low magnetic field magnetostriction, magnetic flux density, and film adhesion. On the other hand, the comparative example did not satisfy the chemical composition, or did not have sufficient low magnetic field magnetostriction, magnetic flux density, or film adhesion.

for example,
No. In Comparative Examples 1 to 12, the Bi content of the grain-oriented electrical steel sheet (silicon steel sheet) was less than 0.0005%, and there was no problem that the film adhesion was likely to decrease.
No. Comparative examples of 13, 17, 21, and 25 satisfied the Bi content of the grain-oriented electrical steel sheet (silicon steel sheet), but did not satisfy the film adhesion due to the small BA / BB.
No. Comparative Examples of 29 to 32, Bi content of the grain-oriented electrical steel sheet (silicon steel plate) is 0.0100%, and did not meet the _{B 8.}
Although not all comparative examples are considered, the same consideration as above can be made.

(Example A)
Using the slab having the chemical composition shown in Table 1A as a material, a grain-oriented electrical steel sheet (silicon steel sheet) having the chemical composition shown in Table 2A was produced. The method for measuring the chemical composition and the method for describing the chemical composition in the table are the same as those in Example 1 above.

The grain-oriented electrical steel sheet was manufactured based on the manufacturing conditions shown in Tables 3A to 7A. As the annealing separator, an annealing separator containing MgO as a main component to which no additive was added was used. In the final process of finish annealing, the steel sheet was held at 1200 ° C. for 20 hours (purification annealing) in a hydrogen atmosphere and cooled. Other manufacturing conditions are the same as in Example 1 above.

The same insulating coating as in Example 1 above was formed on the surface of the manufactured grain-oriented electrical steel sheet (finish-annealed steel sheet).

The manufactured grain-oriented electrical steel sheet is in contact with an intermediate layer arranged in contact with the grain-oriented electrical steel sheet (silicon steel sheet) and on the intermediate layer when viewed on a cut surface whose cutting direction is parallel to the plate thickness direction. It had an arranged insulating coating. The intermediate layer was a forsterite film having an average thickness of 2 μm, and the insulating film was an insulating film mainly composed of phosphate and colloidal silica having an average thickness of 1 μm.

Various characteristics of the obtained grain-oriented electrical steel sheets were evaluated. The evaluation method is the same as that of the first embodiment. The evaluation results are shown in Tables 8A to 12A.

The characteristics of grain-oriented electrical steel sheets vary greatly depending on the chemical composition and manufacturing method. Therefore, λpp@1.5T is evaluated for each grain-oriented electrical steel sheet according to some characteristic chemical composition and manufacturing method.
No. In 1001 to 1023, when λpp@1.5T was 0.303 or less, it was judged to be acceptable.
No. In 1024 to 1034, when λpp@1.5T was 0.373 or less, it was judged to be acceptable.
No. In 1035 to 1046, when λpp@1.5T was 0.293 or less, it was judged to be acceptable.
No. In 1047 to 1054, when λpp@1.5T was 0.278 or less, it was judged to be acceptable.
No. In 1055 to 1064, when λpp@1.5T was 0.323 or less, it was judged to be acceptable.
No. In 1065-1101, when λpp@1.5T was 0.243 or less, it was judged to be acceptable.

No. Of 1001 to 1101, all of the examples of the present invention were excellent in low magnetic field magnetostriction, magnetic flux density, and film adhesion. On the other hand, in the comparative example, the low magnetic flux magnetostriction, the magnetic flux density, or the film adhesion was not sufficient.

(Example B)
Using the slab having the chemical composition shown in Table 1B as a material, a grain-oriented electrical steel sheet having the chemical composition shown in Table 2B was produced. The method for measuring the chemical composition and the method for describing the chemical composition in the table are the same as those in Example 1 above.

The grain-oriented electrical steel sheet was manufactured based on the manufacturing conditions shown in Tables 3B to 7B. As the annealing separator, an annealing separator containing MgO as a main component to which no additive was added was used. In the final process of finish annealing, the steel sheet was held at 1200 ° C. for 20 hours (purification annealing) in a hydrogen atmosphere and cooled. Other manufacturing conditions are the same as in Example 1 above.

The same insulating coating as in Example 1 above was formed on the surface of the manufactured grain-oriented electrical steel sheet (finish-annealed steel sheet).

The manufactured grain-oriented electrical steel sheet is in contact with an intermediate layer arranged in contact with the grain-oriented electrical steel sheet (silicon steel sheet) and on the intermediate layer when viewed on a cut surface whose cutting direction is parallel to the plate thickness direction. It had an arranged insulating coating. The intermediate layer was a forsterite film having an average thickness of 1.5 μm, and the insulating film was an insulating film mainly composed of phosphate and colloidal silica having an average thickness of 2 μm.

Various characteristics of the obtained grain-oriented electrical steel sheets were evaluated. The evaluation method is the same as that of the first embodiment. The evaluation results are shown in Tables 8B to 12B.

The characteristics of grain-oriented electrical steel sheets vary greatly depending on the chemical composition and manufacturing method. Therefore, λpp@1.5T is evaluated for each grain-oriented electrical steel sheet according to some characteristic chemical composition and manufacturing method.
No. In 2001 to 2023, when λpp@1.5T was 0.283 or less, it was judged to be acceptable.
No. In 2024 to 2034, when λpp@1.5T was 0.353 or less, it was judged to be acceptable.
No. In 2035 to 2045, when λpp@1.5T was 0.293 or less, it was judged to be acceptable.
No. In 2046 to 2053, when λpp@1.5T was 0.278 or less, it was judged to be acceptable.
No. In 2054 to 2063, when λpp@1.5T was 0.323 or less, it was judged to be acceptable.
No. In 2064 to 2101, when λpp@1.5T was 0.243 or less, it was judged to be acceptable.

No. Of 2001 to 2101, all of the examples of the present invention were excellent in low magnetic field magnetostriction, magnetic flux density, and film adhesion. On the other hand, in the comparative example, the low magnetic flux magnetostriction, the magnetic flux density, or the film adhesion was not sufficient.

(Example C)
Using the slab having the chemical composition shown in Table 1C as a material, a grain-oriented electrical steel sheet having the chemical composition shown in Table 2C was produced. The method for measuring the chemical composition and the method for describing the chemical composition in the table are the same as those in Example 1 above.

The grain-oriented electrical steel sheet was manufactured based on the manufacturing conditions shown in Tables 3C to 6C. As the annealing separator, an annealing separator containing MgO as a main component to which no additive was added was used. In the finish annealing, in order to control the anisotropy of the switching generation direction, the heat treatment was performed with a temperature gradient in the direction perpendicular to the rolling of the steel sheet. In the final process of finish annealing, the steel sheet was held at 1200 ° C. for 20 hours (purification annealing) in a hydrogen atmosphere and cooled. Other manufacturing conditions are the same as in Example 1 above.

The same insulating coating as in Example 1 above was formed on the surface of the manufactured grain-oriented electrical steel sheet (finish-annealed steel sheet).

The manufactured grain-oriented electrical steel sheet is in contact with an intermediate layer arranged in contact with the grain-oriented electrical steel sheet (silicon steel sheet) and on the intermediate layer when viewed on a cut surface whose cutting direction is parallel to the plate thickness direction. It had an arranged insulating coating. The intermediate layer was a forsterite film having an average thickness of 3 μm, and the insulating film was an insulating film mainly composed of phosphate and colloidal silica having an average thickness of 3 μm.

Various characteristics of the obtained grain-oriented electrical steel sheets were evaluated. The evaluation method is the same as that of the first embodiment. The evaluation results are shown in Tables 7C to 10C.

In most directional electromagnetic steel sheets, the crystal grains were stretched in the direction of the temperature gradient, and the crystal grain size of the β crystal grains also increased in this direction. That is, the crystal grains were stretched in the direction perpendicular to the rolling. However, in some directional electromagnetic steel sheets having a small temperature gradient, the particle size in the direction perpendicular to rolling was smaller than the particle size in the rolling direction for β crystal grains. When the particle size in the direction perpendicular to rolling is smaller than the particle size in the rolling direction, it is indicated by "*" in the column of "Temperature gradient directions do not match" in the table.

No. In 3001 to 3071, when λpp@1.5T was 0.283 or less, it was judged to be acceptable.

No. Of 3001 to 3071, all of the examples of the present invention were excellent in low magnetic field magnetostriction, magnetic flux density, and film adhesion. On the other hand, in the comparative example, the low magnetic flux magnetostriction, the magnetic flux density, or the film adhesion was not sufficient.

(Example D)
Using the slab having the chemical composition shown in Table 1D as a material, a grain-oriented electrical steel sheet having the chemical composition shown in Table 2D was produced. The method for measuring the chemical composition and the method for describing the chemical composition in the table are the same as those in Example 1 above.

The grain-oriented electrical steel sheet was manufactured based on the manufacturing conditions shown in Table 3D.

In addition, No. Other than 4011, as an annealing separator, an annealing separator containing MgO as a main component to which no additive was added was applied to the steel sheet, and finish annealing was performed. On the other hand, No. In 4011, as an annealing separator, an annealing separator containing alumina as a main component was applied to the steel sheet, and finish annealing was performed. In the final process of finish annealing, the steel sheet was held at 1200 ° C. for 20 hours (purification annealing) in a hydrogen atmosphere and cooled. Other manufacturing conditions are the same as in Example 1 above.

The same insulating coating as in Example 1 above was formed on the surface of the manufactured grain-oriented electrical steel sheet (finish-annealed steel sheet).

The manufactured grain-oriented electrical steel sheet is in contact with an intermediate layer arranged in contact with the grain-oriented electrical steel sheet (silicon steel sheet) and on the intermediate layer when viewed on a cut surface whose cutting direction is parallel to the plate thickness direction. It had an arranged insulating coating.

In addition, No. In the directional electromagnetic steel sheets other than 4011, the intermediate layer was a forsterite film having an average thickness of 1.5 μm, and the insulating film was an insulating film mainly composed of phosphate and colloidal silica having an average thickness of 2 μm. .. On the other hand, No. In the directional electromagnetic steel plate of 4011, the intermediate layer is an oxide film ( _{a film mainly composed of SiO 2} ) having an average thickness of 20 nm, and the insulating film is mainly composed of phosphate and colloidal silica having an average thickness of 2 μm. It was an insulating film.

In addition, No. 4014 and No. In the directional electromagnetic steel sheet of 4015, after forming the insulating film, by laser irradiation, linear minute strains are applied so as to be stretched on the rolling surface of the steel sheet in a direction intersecting the rolling direction, and the interval in the rolling direction becomes 4 mm. Granted as. It can be seen that the effect of reducing the iron loss is obtained by applying the laser.

Various characteristics of the obtained grain-oriented electrical steel sheets were evaluated. The evaluation method is the same as that of the first embodiment. The evaluation results are shown in Table 4D.

No. In 4001 to 4015, when λpp@1.5T was 0.400 or less, it was judged that the magnetostrictive characteristics were good.

No. Of 4001 to 4015, all of the examples of the present invention were excellent in low magnetic field magnetostriction, magnetic flux density, and film adhesion. On the other hand, in the comparative example, the low magnetic flux magnetostriction, the magnetic flux density, or the film adhesion was not sufficient.

According to the above aspect of the present invention, there is provided a directional electromagnetic steel plate that can improve the magnetostriction in a low magnetic field region (particularly a magnetic field of about 1.5 T), improve the magnetic flux density, and at the same time avoid a decrease in film adhesion. Is possible, so it has high industrial applicability.

10 Directional electromagnetic steel sheet (silicon steel sheet)
20 Intermediate layer 30 Insulation film

Claims (8)

In grain-oriented electrical steel sheets having a texture oriented in the Goss orientation,
The grain-oriented electrical steel sheet is by mass%
Si: 2.0-7.0%,
Bi: 0.0005-0.0100%,
Nb: 0 to 0.030%,
V: 0 to 0.030%,
Mo: 0-0.030%,
Ta: 0-0.030%,
W: 0 to 0.030%,
C: 0 to 0.0050%,
Mn: 0-1.0%,
S: 0 to 0.0150%,
Se: 0 to 0.0150%,
Al: 0-0.0650%,
N: 0-0.0050%,
Cu: 0-0.40%,
B: 0 to 0.080%,
P: 0 to 0.50%,
Ti: 0 to 0.0150%,
Sn: 0 to 0.10%,
Sb: 0 to 0.10%,
Cr: 0 to 0.30%,
Ni: 0-1.0%,
Has a chemical composition in which the balance is composed of Fe and impurities.
The deviation angle from the ideal Goss direction with the rolling surface normal direction Z as the rotation axis is defined as α.
The deviation angle from the ideal Goss direction with the rolling perpendicular direction C as the rotation axis is defined as β.
The deviation angle from the ideal Goss direction with the rolling direction L as the rotation axis is defined as γ.
The deviation angles of the crystal orientations measured at two measurement points adjacent to each other on the plate surface and having an interval of 1 mm are _{expressed as (α 1} β ₁ γ ₁ ) and (α ₂ β ₂ γ ₂ ).
Boundary condition BA _{is defined as | β 2-} β ₁ | ≧ 0.5 °,
When the boundary condition BB is defined as [(α _2- α ₁ ) ² + (β _2- β ₁ ) ² + (γ _2- γ ₁ ) ² ] ^1/2 ≥ 2.0 °
There is a grain boundary that satisfies the boundary condition BA and does not satisfy the boundary condition BB.
The magnetic flux density B _{8 in the} rolling direction is 1.920 T or more.
A grain-oriented electrical steel sheet characterized by this. It has an intermediate layer arranged in contact with the grain-oriented electrical steel sheet and an insulating film arranged in contact with the intermediate layer, and the residual area ratio of the film when wound around a round bar having a diameter of 20 mm and bent back. Is 90-100%,
The grain-oriented electrical steel sheet according to claim 1. As the chemical composition, at least one selected from the group consisting of Nb, V, Mo, Ta, and W is contained in a total amount of 0.0030 to 0.030% by mass.
The grain-oriented electrical steel sheet according to claim 1 or 2. The average crystal grain size in the rolling direction L obtained based on the boundary conditions BA defined as the particle size RA _L,
When the average crystal grain size in the rolling direction L obtained based on the boundary condition BB is defined _{as the grain size RB L,}
The particle size RA _L and the particle size RB _L satisfy 1.10 ≦ RB _L ÷ RA _L.
The grain-oriented electrical steel sheet according to any one of claims 1 to 3. Wherein the average crystal grain size of the perpendicular to the rolling direction C is defined as the particle size RA _C obtained based on the boundary conditions BA,
When the average crystal grain size of the perpendicular to the rolling direction C is defined as the particle diameter RB _C obtained based on the boundary conditions BB,
And the particle size RA _C and the particle diameter RB _C satisfies the 1.10 ≦ RB _C ÷ RA _C,
The grain-oriented electrical steel sheet according to any one of claims 1 to 4, wherein the grain-oriented electrical steel sheet is characterized. The average crystal grain size in the rolling direction L obtained based on the boundary conditions BA defined as the particle size RA _L,
When the average crystal grain size of the perpendicular to the rolling direction C is defined as the particle size RA _C obtained based on the boundary conditions BA,
And the particle size RA _L and the grain size RA _C satisfies the 1.15 ≦ RA _C ÷ RA _L,
The grain-oriented electrical steel sheet according to any one of claims 1 to 5, characterized in that. The average crystal grain size in the rolling direction L obtained based on the boundary condition BB is defined as the _{grain size RB L.}
When the average crystal grain size of the perpendicular to the rolling direction C is defined as the particle diameter RB _C obtained based on the boundary conditions BB,
The particle size RB _L and the particle size RB _C satisfy 1.50 ≦ RB _C ÷ RB _L.
The grain-oriented electrical steel sheet according to any one of claims 1 to 6, characterized in that. The average crystal grain size in the rolling direction L obtained based on the boundary conditions BA defined as the particle size RA _L,
The average crystal grain size in the rolling direction L obtained based on the boundary condition BB is defined as the _{grain size RB L.}
Wherein the average crystal grain size of the perpendicular to the rolling direction C is defined as the particle size RA _C obtained based on the boundary conditions BA,
When the average crystal grain size of the perpendicular to the rolling direction C is defined as the particle diameter RB _C obtained based on the boundary conditions BB,
And the particle size RA _L and the grain size RA _C and the particle diameter RB _L and the diameter RB _C is,
Satisfy _{(RB C × RA L) ÷} (RB L × RA C) <1.0,
The grain-oriented electrical steel sheet according to any one of claims 1 to 7.

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