JP7010321B2 - Directional electrical steel sheet and its manufacturing method - Google Patents

Description

The present invention relates to a grain-oriented electrical steel sheet suitable for an iron core material such as a transformer and a method for manufacturing the same.

A grain-oriented electrical steel sheet having a crystal structure whose <001> orientation, which is an axis for easily magnetizing iron, is highly aligned in the rolling direction of the steel sheet, is particularly used as an iron core material for a power transformer. Such power transformers are roughly classified into stacked iron core transformers and wound iron core transformers according to their iron core structures.

A product core transformer is a transformer that forms an iron core by laminating steel plates cut into a predetermined shape. On the other hand, a wound iron core transformer is one in which steel plates are wound to form an iron core. There are various characteristics required for a transformer core, but the most important one is that the iron loss is small.

From this point of view, a characteristic required for grain-oriented electrical steel sheets, which is an iron core material, is that the iron loss value is small, and this characteristic is important. Here, there is a magnetic domain subdivision technique as one of the techniques for reducing iron loss. The magnetic domain subdivision technique is a technique for subdividing the width of a magnetic domain and reducing iron loss by introducing non-uniformity of magnetic flux into the surface of a steel sheet by a physical method.

For example, Patent Document 1 describes a technique for subdividing a magnetic domain by forming a linear groove in a direction intersecting the rolling direction of a grain-oriented electrical steel sheet. Further, in Patent Document 2, a groove having a depth of more than 5 μm is formed in the base metal portion with a load of 882 to 2156 MPa (90 to 220 kgf / mm ² ) on the finish-annealed steel sheet, and then heated at a temperature of 750 ° C. or higher. A technique for subdividing a magnetic domain by processing is described. These techniques are so-called heat-resistant magnetic domain subdivision techniques in which the effect does not disappear even if the strain is removed and annealed after the transformer is assembled.

Here, a typical index showing the iron loss characteristics of the steel sheet is the value of the iron loss W _17/50 at a frequency of 50 Hz and a maximum magnetic flux density of 1.7 T, and the steel sheets are graded according to their size. In addition, as a result of the recent tightening of environmental regulations, the efficiency of transformers is required to be improved, and as a result, steel plates are often used in the magnetization region with a magnetic flux density lower than 1.7T. Furthermore, in transformers used in small-scale systems connected to solar power generation, which has increased in recent years, it is also necessary to deal with exciting inrush current, which is the magnetic flux density in the high magnetization region, that is, the magnetization force of 800 A / m. It is also necessary to have excellent magnetic characteristics such as the magnetic flux density B ₈ in.

Japanese Unexamined Patent Publication No. 63-76819 Special Publication No. 63-44804

As mentioned above, recently, not only the iron loss W _17/50 in the magnetization region that determines the steel plate grade such as the maximum magnetic flux density of 1.7T is small, but also the magnetization force is low so that the magnetic flux density is as low as 1.0 to 1.5T. Excellent iron loss in the magnetized region (hereinafter simply referred to as low magnetization region), and magnetic characteristics such as magnetic flux density B ₈ in the region magnetized with a high magnetization force of 800 A / m (hereinafter simply referred to as high magnetization region). There is also a demand for an excellent directional electromagnetic steel plate.

In order to improve the magnetic properties in the low magnetization region, the iron loss at 1.0 to 1.5T may be reduced. Here, in order to reduce the iron loss in such a region, the volume of the non-uniform portion formed for the subdivision of the magnetic domain, that is, the groove portion or the like may be increased to strengthen the effect of subdividing the magnetic domain. However, there is a problem that the magnetic flux density in a high magnetization region such as B ₈ deteriorates when the volume of the formed non-uniform portion is increased.

An object of the present invention is to overcome the above-mentioned problems and to provide a grain-oriented electrical steel sheet having excellent magnetic properties from a low magnetization region to a high magnetization region. Another object of the present invention is to provide a method for manufacturing a grain-oriented electrical steel sheet having excellent magnetic properties.

It is known that it is the volume and distribution of the non-uniform portion formed during the magnetic domain subdivision process that affects the magnetic properties such as iron loss.

Here, increasing the volume of the non-uniform portion (meaning a portion where the magnetic flux becomes non-uniform such as a groove portion) introduced per unit area of the steel sheet, that is, narrowing the linear groove spacing introduced in the rolling direction or making a groove. The main magnetic domain is further subdivided by increasing the volume of one row of linear grooves by increasing the depth.

When the magnetic domain is subdivided by increasing the volume of the non-uniform part in this way, in the low magnetization region, the magnetization progresses due to the 180 ° domain wall movement of the main magnetic domain. Distance and speed become smaller. As a result, the eddy current loss is reduced and the iron loss is reduced. On the other hand, in the high magnetization region, when the volume of the non-uniform portion is increased, the cross-sectional area of iron is reduced by the amount of the groove portion, so that the magnetic flux is concentrated and the magnetic characteristics are deteriorated. Furthermore, in the high magnetization region, magnetization cannot proceed only by moving the domain wall by 180 ° in the main magnetic domain, so magnetization rotation occurs. However, when the volume of the groove introduced per unit area of the steel plate increases, the groove portion rotates. Therefore, the magnetic properties are deteriorated including that amount.

Therefore, it is not possible to produce a steel sheet having excellent magnetic properties from a low magnetization region to a high magnetization region by simply controlling the volume of the non-uniform portion.
Here, in the past publicly known knowledge, for example, Japanese Patent No. 3885239 (hereinafter referred to as Patent Gazette), especially in the case of a thick material having a plate thickness of about 0.30 to 0.35 mm, the magnetic flux density B ₈ and iron loss A method for manufacturing a heat-resistant magnetic domain subdivided grain-oriented electrical steel sheet having an excellent distribution W _17/50 is disclosed.

According to the above patent gazette, a directional silicon steel plate material containing Si: 2.0 to 4.5% by weight is used to form linear grooves in the width direction of rolling in the process after final cold rolling and before secondary recrystallization annealing. It has been shown that by alternately arranging the linear grooves having shallow grooves and the linear grooves having deep grooves, W _17/50 is improved without lowering the magnetic property B ₈ in the high magnetization region. ing. That is, in the conventional magnetic domain subdivided steel sheet, uniform linear groove forming portions are lined up at periodic intervals as shown in FIG. 1, but in the invention described in the above patent gazette, it is described in FIG. By controlling the linear groove formation depth to be different for each line, both the magnetic properties B ₈ and W _17/50 in the high magnetization region are achieved.

However, such an invention exerts its effect in the case of a thick material having a plate thickness of about 0.30 to 0.35 mm. In the case of thin materials with a steel plate thickness of 0.27 mm or less, the eddy current loss reduced by magnetic domain subdivision is originally smaller than in the case of thick materials, so the effect of magnetic domain subdivision is limited, especially in the low magnetization region. be. Further, in the case of a thin material, the influence of the properties of the surface of the steel sheet including the linear groove shape on the magnetization rotation in the high magnetization region becomes larger than that in the case of a thick plate. That is, when the plate thickness becomes thin, the magnetic characteristics of the high magnetization region deteriorate even if the groove depth decreases in a similar shape. Therefore, in the case of a thin material having a steel plate thickness of 0.27 mm or less as in the present invention, it is difficult to achieve both low magnetic properties and high magnetic properties in the invention described in the patent document.

Therefore, the inventors have determined the grade of the steel sheet from the magnetic properties in the low magnetization region such as W _{13/50, especially when the sheet thickness is 0.27 mm or less, which is higher than W 17/50 .} We investigated whether it would be possible to achieve both magnetic characteristics that were difficult to achieve in the past, such as B ₈ , which is the magnetic characteristics in the magnetization region.

As a result, the inventors have found that when the linear groove is introduced so as to satisfy the following conditions, the magnetic properties in the low magnetization region and the high magnetization region can be compatible with each other.
(1) There are two or more types of introduced linear grooves with different cross-sectional areas in the rolling direction.
(2) It is preferable that the cross-sectional area in the rolling direction of (1) differs between the maximum and the minimum in a range of 10% or more and 60% or less.
(3) Linear grooves having different cross-sectional areas in the rolling direction of (2) are alternately arranged in the rolling direction.

Next, the experimental results that led to the present invention will be described.
<Experiment 1>
Si: 3.4% by mass, Mn: 0.06% by mass, Cu: 0.1% by mass, Ni: 0.01% by mass, Al: 240% by mass, S: 20% by mass, C: 0.07% by mass, N: 90% by mass, Sb: Steel slabs containing 0.025% by mass and Se: 180% by mass are manufactured by continuous casting, heated to 1430 ° C, hot-rolled to make a hot-rolled plate with a plate thickness of 2.4 mm, and then hot-rolled and annealed. Was given. Then, the intermediate plate thickness was adjusted to 0.40 mm by cold rolling, and intermediate annealing was carried out. Then, after removing the subscale on the surface by pickling with hydrochloric acid, cold rolling was carried out again to obtain a cold-rolled plate having a plate thickness of 0.23 mm.
Further, by the following procedure, cold-rolled steel sheets in which regions I and II of linear grooves having different cross-sectional areas in the rolling direction are alternately arranged in the rolling direction as shown in FIG. 3 were produced.
First, the surface of the cold-rolled steel sheet is masked by printing resist ink on the surface of the steel sheet with a groove roll having a predetermined groove width and a pitch of 6 mm shown in Table 1, and electrolytic etching is performed so as to have a predetermined groove depth. To form a region I of a linear groove (also simply referred to as a region I or a groove I in the present invention). The region I of the linear groove was formed at an angle of 10 ° with respect to the direction orthogonal to the rolling.
Next, after removing the ink printed first, the ink is shifted by 3 mm to have a predetermined groove width, and masking is performed by printing resist ink on the surface of the steel sheet with a groove roll having a pitch of 6 mm so as to have a predetermined groove depth. Electrolytic etching was performed to form a region II of the linear groove (also simply referred to as region II or groove II in the present invention). As a result, the regions I and II of the linear grooves are alternately arranged on the surface of the cold-rolled steel sheet at intervals of 3 mm.
Furthermore, the ink printed a second time is removed, annealed by decarburization, and then an annealed separator containing MgO as a main component is applied, and the final purpose is to form and purify a secondary recrystallization / forsterite film. Finish annealing was carried out. Further, after applying the insulating coat, it was baked at 850 ° C. to apply the coating. This coating coating process also serves as flattening annealing.

Under the conditions shown in Table 1, the magnetic properties of the steel sheets forming the linear grooves in regions I and II were compared. The magnetic characterization was performed by the Epstein magnetic characterization test specified in JIS C 2550. W _13/50 was evaluated as the magnetic characteristic in the low magnetization region, B ₈ was evaluated as the magnetic characteristic in the high magnetization region, and W _17/50 was evaluated as the characteristic that determines the steel sheet grade. Figure 4 shows the evaluation results of W _13/50 , Figure 5 shows the evaluation results of B ₈ , and Figure 6 shows the evaluation results of W _17/50 .

Under conditions 1, 4, and 7 in which grooves are formed in both regions I and II under the condition of a large groove volume, the magnetic characteristics W _{13/50 in the low magnetization region and the characteristics W 17/50 that} determine the steel sheet grade are good. , The magnetic property B ₈ in the high magnetization region was inferior. On the contrary, under the conditions 3, 6 and 9 in which the grooves are formed in both the regions I and II under the condition that the groove volume is small, the magnetic characteristics B ₈ in the high magnetization region are good, but the magnetic characteristics W in the low magnetization region. _{13/50, the characteristic W 17/50 that} determines the steel plate grade was inferior. On the other hand, under conditions 2, 5 and 8 in which grooves are formed in regions I and II that are alternately arranged under the condition that the groove volume is large and the condition that the groove volume is small, the magnetic characteristics W _13/50 and the steel plate grade in the low magnetization region are obtained. Both the determined characteristic W _17/50 and the magnetic characteristic B ₈ in the high magnetization region gave good results.

From the above experimental results, it was suggested that by arranging linear grooves having different groove volumes, it is possible to achieve both magnetic properties in a low magnetization region and a high magnetization region. Therefore, the inventors have investigated how to arrange linear grooves having different groove volumes.

First, the groove volume of each linear groove was quantified. As an index, the cross-sectional area in the rolling direction of the linear groove defined below was used.
Rolling direction cross-sectional area of linear groove = Rolling direction width of groove x Depth in plate thickness direction of groove x Groove formation ratio (The ratio of grooves formed in a dotted line is shown as a real number. Therefore, 1 for continuous grooves. If the groove is formed half as often, it will be 0.5)
The rolling direction width of the groove (also simply referred to as the groove width in the present invention) may be observed from the surface with an optical microscope and the width may be measured. As shown in FIG. 7-a, since the groove width in the present invention is formed to be approximately constant (variation within about 10% is permissible because it does not affect the effect of the present invention), the groove width is formed. Measure 5 points in the direction and use the average as the rolling direction width of the groove. In addition, as shown in Fig. 7-b, when the groove width is changed in the middle, 3 points are measured for each groove width, and the average weighted by the length of each groove is taken as the groove rolling direction width. .. Further, as shown in FIG. 7-c, when the grooves are formed in a row of dots, at least three points may be measured at least for each of the rolling direction widths of the portions where the grooves are formed.

On the other hand, the depth in the plate thickness direction of the groove (also simply referred to as the groove depth in the present invention) is measured by using a roughness meter such as a contact type or a laser method. The maximum depth of the groove bottom with the surface of the steel plate as the reference height is defined as the depth in the plate thickness direction of the groove.
As shown in FIG. 7-c, when the grooves are formed in a dotted line, the rolling direction cross-sectional area is the value of the rolling direction width of the groove × the depth in the plate thickness direction of the groove, and the groove formation ratio (= ( It is the product of the groove forming portion length a) / (groove forming portion length a + groove non-forming portion length b).

<Experiment 2>
In the same procedure as in Experiment 1, a cold rolled plate with a thickness of 0.23 mm was prepared, and under the conditions shown in Table 2-1 a cold rolled plate in which linear grooves having different groove cross-sectional areas were formed in various combinations was prepared. did. Similar to Experiment 1, the groove was formed by masking with resist ink and electrolytic etching. After forming groove I, the ink was peeled off, and masking with resist ink and electrolytic etching were performed again to form groove II. Under both conditions, the linear groove was formed at an angle of 10 ° with respect to the direction orthogonal to the rolling. Under some conditions, grooves were formed in a dot sequence as shown in FIGS. 8-a and b. Under the condition of "discontinuity 1" shown in FIG. 8-a, the groove forming portion length a = 3 mm and the groove non-forming portion length b = 2 mm, and under the condition of "discontinuity 2" shown in FIG. 8-b. A groove roll with a forming pattern was used in which the groove forming portion length a = 1.5 mm and the groove non-forming portion length b = 3.5 mm. In FIGS. 8-a and b, 1 is the groove forming portion length a, and 2 is the groove non-forming portion length b.

After forming the groove II, the ink is removed, decarburized and annealed, and then an annealing separator containing MgO as a main component is applied to form a secondary recrystallization / forsterite film and final finish annealing for the purpose of purification. Was carried out. Further, an insulating coat was applied and baked at 850 ° C.
After that, as in Experiment 1, according to the Epstein magnetic property test, W _13/50 is the magnetic property in the low magnetization region, B ₈ is the magnetic property in the high magnetization region, and W ₁₇ is the characteristic that determines the steel plate grade. Evaluated _{/ 50} .
Table 2-2 shows the magnetic measurement results. In addition, as a judgment as to whether the magnetic characteristics in the low magnetization region and the high magnetization region are compatible, the following conditions are arranged.

"◎": W _13/50 ≤ 0.40 W / kg and B ₈ ≥ 1.900T and W _17/50 ≤ 0.73 W / kg
"○": Does not meet the judgment of ◎ and W _13/50 ≤ 0.43 W / kg and B ₈ ≥ 1.890 T and W _17/50 ≤ 0.75 W / kg
"× 1": W 13/50 ＞ _0.43W / kg
"× 2": B ₈ <1.890T

Of the above judgments, the condition in which the judgment of ⊚ or ◯ is obtained is an excellent condition because the magnetic characteristics in the low magnetization region and the high magnetization region are compatible. The condition for determining × 1 is that the groove introduction volume is small and a sufficient magnetic domain subdivision effect is not obtained. On the other hand, the condition of determining × 2 is that the groove introduction volume is large and the magnetic characteristics in the high magnetization region are inferior.

In the above experiment, under the conditions where the judgments of ◎ and ○ were obtained, the cross-sectional areas of the grooves in regions I and II in the rolling direction differed in the range of 10% or more and 60% or less, and the conditions where the judgment of ◎ was obtained. Was different in the range where the rolling direction cross-sectional areas of the grooves of regions I and II were 15% or more and 40% or less.

From the above experiments, there are at least two types of linear grooves introduced on one side of the steel sheet in the rolling direction, and the linear grooves having different rolling direction cross-sectional areas of 10% or more and 60% or less are lined up in the rolling direction. It has been clarified that the directional electromagnetic steel sheet is a directional electromagnetic steel sheet that can achieve both magnetic properties in a low magnetization region and a high magnetization region in a thin steel sheet of 0.27 mm or less, and the present invention has been completed. ..

The inventors have found that when applied to a thin steel sheet having a thickness of 0.27 mm or less, it is possible to achieve both a low magnetization region and a magnetic property in a high magnetization region. However, unlike the publicly known knowledge in the past (the above-mentioned patent publication), the characteristic improvement is recognized by the control only by the groove depth, such as arranging the linear grooves having shallow grooves and the linear grooves having deep grooves alternately. However, it was found that the effect was small. That is, as described above, when the thickness of the steel sheet is thin, there is a problem that the magnetic characteristics in a particularly high magnetization region deteriorate in the groove. Therefore, when the plate thickness is thin, the rolling direction cross-sectional area of the linear groove is used as a parameter to change not only the depth but also the rolling direction width of the groove or change the length direction, that is, it is formed in a dotted shape. It is considered that magnetic flux concentration in a high magnetization region and deterioration of magnetic characteristics due to magnetization rotation can be suppressed only by three-dimensionally adjusting the groove formation pattern.

The present invention has been obtained based on the above findings, and the gist structure of the present invention is as follows.
1. 1. A grain-oriented electrical steel sheet having a plurality of linear grooves on one side of a steel sheet, which extends linearly in a direction crossing the rolling direction and is arranged at intervals in the rolling direction.
The linear groove has at least two types having different rolling direction cross-sectional areas, and in the linear groove, the largest rolling direction cross-sectional area is A (mm ² ) and the smallest rolling direction cross-sectional area is B (mm ² ). , {(AB) / A} × 100 is 10% or more and 60% or less, and the plate thickness is 0.27 mm or less.

2. 2. The grain-oriented electrical steel sheet according to 1 above, wherein the linear grooves having the cross-sectional area A and the linear grooves having the cross-section B are alternately and repeatedly provided in the rolling direction.

3. 3. The method for manufacturing a directional electromagnetic steel sheet according to 1 or 2 above, wherein the slab for directional electromagnetic steel sheets is hot-rolled, then annealed by hot-rolled sheet as necessary, and then once or intermediately. After cold rolling two or more times with annealing in between to finish the final plate thickness, decarburization annealing is performed, then an annealing separator is applied to the surface of the steel sheet, then final finish annealing is performed, and then tension is applied. In a method for manufacturing a directional electromagnetic steel sheet having linear grooves to be coated and flattened and annealed.
(1) Make the final plate thickness 0.27 mm or less
(2) The linear grooves are a plurality of linear grooves that extend linearly across the rolling direction and are lined up at intervals in the rolling direction on one side of the steel sheet, and are formed before final finishing annealing. do
(3) When forming the linear groove, at least two types having different rolling direction cross-sectional areas are formed, and in the linear groove, the largest rolling direction cross-sectional area is A (mm ² ) and the smallest rolling direction break. A method for manufacturing a directional electromagnetic steel plate that continuously or discontinuously forms a groove in which {(AB) / A} × 100 is in the range of 10% or more and 60% or less when the area is B (mm ² ). ..

4. When the linear groove having the cross-sectional area A or the linear groove having the cross-sectional area B is formed in the rolling direction, and then the linear groove having the cross-sectional area A is formed, the linear groove having the cross-sectional area B is formed. The method for manufacturing a directional electromagnetic steel plate according to 3 above, wherein when a linear groove having a cross-sectional area B is formed, a linear groove having a cross-sectional area A is formed.

According to the present invention, it is possible to provide a grain-oriented electrical steel sheet having excellent magnetic properties in a wide range from a low magnetization region to a high magnetization region. In addition, it is possible to provide a manufacturing method for effectively obtaining the grain-oriented electrical steel sheet.

It is a figure which shows the region of the linear groove of the steel sheet which performed the conventional magnetic domain subdivision processing. It is a figure which shows the linear groove of the steel sheet which performed the magnetic domain subdivision processing described in the patent gazette. It is a figure which shows the linear groove of the steel sheet which performed the magnetic domain subdivision treatment in the experiment which carried out to guide this invention. It is the figure which showed the value of W _13/50 of the steel sheet for each groove volume formation condition. It is the figure which showed the value of B ₈ of the steel sheet for each formation condition of the groove volume. It is the figure which showed the value of W _17/50 of the steel sheet for each groove volume formation condition. FIGS. 7-a, 7-b, and 7-c are conceptual diagrams illustrating the definition of the groove region, respectively. FIG. 8-a is a conceptual diagram illustrating a discontinuous groove region, and FIG. 8-b is a conceptual diagram illustrating another discontinuous groove region.

Hereinafter, the details of the present invention will be described.
As described above, for grain-oriented electrical steel sheets with excellent magnetic properties from the low magnetization region to the high magnetization region, they extend linearly on one side of the steel sheet in the direction crossing the rolling direction and are spaced in the rolling direction under the following conditions. It is important to form multiple linear grooves that are lined up side by side.
(1) There are two or more types of introduced linear grooves with different cross-sectional areas in the rolling direction.
(2) It is preferable that the cross-sectional area in the rolling direction of (1) differs between the maximum one and the minimum one in the range of 10% or more and 60% or less.
(3) It is preferable that linear grooves having different cross-sectional areas in the rolling direction of (2) are alternately arranged in the rolling direction.
(4) The range of different cross-sectional areas in the rolling direction is 15% or more and 40% or less.
(5) The linear groove periodically extends linearly at an angle within 30 degrees in the direction perpendicular to the rolling direction.

In a directional electromagnetic steel plate having a linear groove according to the present invention, the rolling direction cross-sectional area of the linear groove is at least two types (for example, regions I and II), and the region I having a large rolling direction cross-sectional area is A (mm ² ). ), When the small region II is B (mm ² ), the ratio (%) of A and B is 10% or more and 60% or less (= {(AB) / A} × 100) (cross-sectional area in the present invention). Also called the difference). Further, it is preferable that the linear groove having the cross-sectional area A and the linear groove having the cross-sectional area B are alternately repeated in the rolling direction.
In the present invention, the ratio (%) of A and B is in the range of 10% or more and 60% or less as described above. This is because the magnetic properties in the low magnetization region and the high magnetization region can be effectively compatible with each other. Preferably, the ratio is in the range of 15% or more and 40% or less. Further, in order to obtain the cross-sectional area difference, it is preferable to change not only the depth of the groove but also the width direction of the groove. It is also desirable to change the length direction of the groove three-dimensionally.

In the present invention, the cross-sectional area of the linear groove in the rolling direction is defined and measured as follows, as described above.
[Cross-sectional area in the rolling direction of the linear groove] = [Width in the rolling direction of the groove] x [Depth in the plate thickness direction of the groove] x [Groove formation ratio]

The [rolling direction width of the groove] may be observed from the surface with an optical microscope and the width may be measured. As shown in FIG. 7-a, since the groove width in the present invention is formed to be approximately constant (variation within about 10% is permissible because it does not affect the effect of the present invention), the groove is formed. Five points are measured at appropriate intervals in the steel plate width direction, which is the direction, and the average thereof is taken as the rolling direction width of the groove. In addition, as shown in Fig. 7-b, when the groove width is changed in the middle, the width of each groove is measured at three points at appropriate intervals, and the average weighted by the length of each groove is rolled. The width of the direction. Further, as shown in FIG. 7-c, when the grooves are formed in a row of dots, the rolling direction width of the portions where the grooves are formed may be measured at three points at least at appropriate intervals.

[Depth in the plate thickness direction of the groove] is measured using a roughness meter such as a contact type or a laser method. The maximum depth of the groove bottom with the surface of the steel plate as the reference height is defined as [the depth in the thickness direction of the groove].
Further, as shown in FIG. 7-c, when the grooves are formed in a row of dots, the cross-sectional area in the rolling direction is the numerical value of the rolling direction width of the groove × the depth in the plate thickness direction of the groove, and [groove formation ratio]. ] (= (Groove forming portion length a) / (Groove forming portion length a + Groove non-forming portion length b) shall be multiplied.

Since the formation of the groove is extremely reproducible, one linearly extending region (hereinafter referred to as one line) per the region (for example, region I) is measured at five points at appropriate intervals as described above. Just do it. So, for example, if there are two types of regions with different volumes (region I and region II), one line for each type of linearly extending region with different volumes, that is, one line for each of region I and region II. If selected and measured, the width in the rolling direction of the groove, the depth in the plate thickness direction of the groove, and the groove formation ratio can be obtained.

Here, the term "periodic" of the present invention means that the material extends linearly at a predetermined interval in the rolling direction at an angle within 30 degrees with respect to the direction perpendicular to the rolling direction, and that the area is 90% or more of the steel sheet. It shall include the case where the conditions of the invention are satisfied. This is because the effect of the present invention can be obtained in either case.

[[Groove formation method]]
Examples of the formation of the linear groove include a method of locally etching, a method of scratching with a blade, a method of rolling with a roll with protrusions, etc., but the most preferable method is printing on a steel sheet after final cold rolling. This is a method of forming a linear groove by electrolytic etching treatment in a non-adhesive region after attaching an etching resist. Further, since it is preferable to form a forsterite film on the bottom of the groove for magnetic domain subdivision, it is preferable to perform the groove formation before the final finish annealing in which the forsterite film is formed.
The deviation of the linear groove with respect to the direction perpendicular to the rolling direction is preferably within ± 30 °. Further, in the present invention, the term "linear" includes not only a solid line but also a dotted line such as a dotted line or a broken line.

[[Method of forming linear grooves with different rolling direction cross-sectional areas]]
Any method can be used as long as the conditions for forming the linear groove are satisfied. For example, in the method using an etching resist and electrolytic etching, linear grooves having different rolling direction cross-sectional areas can be formed in a desired range by repeating printing and etching a plurality of times. Further, in the case of etching resist printing using a groove roll, if the groove pattern on the groove roll side (groove width, dotted groove, etc.) is changed within a desired range, a linear groove having a different rolling direction cross-sectional area is also obtained. Can be formed in a desired range. Further, in the method of rolling with a roll with protrusions, if the protrusion pattern of the roll with protrusions is periodically changed, linear grooves having different rolling direction cross-sectional areas can be formed in a desired range.

Further, in order to form a linear groove having at least two types of cross-sectional areas in the rolling direction according to the present invention, it is preferable to use the following method using a laser.
In this method, resist ink is applied to the entire surface of the steel sheet, a laser is scanned on the coated surface in a direction intersecting the rolling direction to remove the resist linearly, and then electrolytic etching is performed to remove the resist (region (). A linear groove is formed in the non-adhesive area). At that time, by changing the laser irradiation conditions such as irradiation energy and beam diameter for each scanning position, it is possible to easily change the shape such as the rolling direction width and discontinuity of the resist non-adherent region, and as a result, It is possible to obtain a linear groove formation pattern having a different rolling direction cross-sectional area, which is desired in the present invention.
To change the laser irradiation conditions, for example, prepare multiple laser irradiation devices, change the laser irradiation conditions in each device, and irradiate the same steel strip with the laser, or use a single laser irradiation device. Methods such as changing the scanning speed and forming a non-adhesive region discontinuously by turning on / off the laser irradiation can be mentioned.

The following items are important in the method for manufacturing grain-oriented electrical steel sheets according to the present invention.
(1) The final thickness of the steel plate shall be 0.27 mm or less.
(2) The linear grooves on the surface of the steel sheet are multiple linear grooves that extend linearly across the rolling direction and are lined up at intervals in the rolling direction on one side of the steel sheet, and are before final finishing annealing. Form to.
(3) When forming the linear groove, at least two types having different rolling direction cross-sectional areas are formed, and in the linear groove, the largest rolling direction cross-sectional area is A (mm ² ) and the smallest rolling direction break. When the area is B (mm ² ), the grooves in which {(AB) / A} × 100 is in the range of 10% or more and 60% or less are continuously or discontinuously formed.

Further, when the groove is formed, the linear groove having the cross-sectional area A or the linear groove having the cross-sectional area B is formed in the rolling direction, and then the linear groove having the cross-sectional area A is formed. When a linear groove having a cross-sectional area B is formed and a linear groove having a cross-sectional area B is formed, it is preferable to take a procedure of forming a linear groove having a cross-sectional area A.

In the method for producing grain-oriented electrical steel sheets of the present invention, matters not directly related to the magnetic domain subdivision treatment are not particularly limited, but the recommended suitable component composition and the production method other than the points of the present invention will be described below.

[Ingredient composition]
In the present invention, the component composition of the slab for grain-oriented electrical steel sheets may be any component composition that causes secondary recrystallization. Further, when an inhibitor is used, for example, when an AlN-based inhibitor is used, Al and N are contained, and when an MnS / MnSe-based inhibitor is used, Mn and Se and / or S are contained in appropriate amounts. good. Of course, both inhibitors may be used in combination. In this case, the preferable contents of Al, N, S and Se are Al: 0.01 to 0.065% by mass, N: 0.005 to 0.012% by mass, S: 0.005 to 0.03% by mass and Se: 0.005 to 0.03% by mass, respectively. be. In the final finish annealing, Al, N, S and Se are purified and each of them is reduced to the content of unavoidable impurities.

Furthermore, the present invention can also be applied to grain-oriented electrical steel sheets that do not use inhibitors and have limited contents of Al, N, S and Se. In this case, the amounts of Al, N, S and Se are preferably suppressed to Al: 100 mass ppm or less, N: 50 mass ppm or less, S: 50 mass ppm or less and Se: 50 mass ppm or less, respectively.

The other basic components and optional additive components are as follows.
C: 0.08% by mass or less If the amount of C exceeds 0.08% by mass, it becomes difficult to reduce C to 50% by mass or less where magnetic aging does not occur during the manufacturing process. Therefore, it is preferably 0.08% by mass or less. As for the lower limit, since secondary recrystallization is possible even with a material containing no C, it is not necessary to provide it in particular, and 0% by mass may be used. In decarburization annealing, C is removed from the steel and the content is reduced to the extent of unavoidable impurities.

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

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

In addition to the above basic components, the following elements can be appropriately contained as magnetic property improving components.
Ni: 0.03 to 1.50% by mass, Sn: 0.01 to 1.50% by mass, Sb: 0.005 to 1.50% by mass, Cu: 0.03 to 3.0% by mass, P: 0.03 to 0.50% by mass, Mo: 0.005 to 0.10% by mass and Cr: At least one selected from 0.03 to 1.50% by mass

Ni is a useful element for improving the thermal rolled plate structure and improving the magnetic properties. However, if the content is less than 0.03% by mass, the effect of improving the magnetic characteristics is small, while if it exceeds 1.50% by mass, the secondary recrystallization becomes unstable and the magnetic characteristics deteriorate. Therefore, the amount of Ni is preferably in the range of 0.03 to 1.50% by mass.

Further, Sn, Sb, Cu, P, Mo and Cr are each elements useful for improving the magnetic properties, but if all of them do not meet the lower limit of each component described above, the effect of improving the magnetic properties is small. On the other hand, if the upper limit of each component described above is exceeded, the development of secondary recrystallized grains is inhibited. Therefore, it is preferable to contain each in the above range. The rest other than the above components are unavoidable impurities and Fe mixed in the manufacturing process.

Next, the method for manufacturing the grain-oriented electrical steel sheet of the present invention will be described.
[heating]
The slab having the above-mentioned composition is heated according to a conventional method. The heating temperature is preferably in the range of 1150 to 1450 ° C.

[Hot rolling]
After the above heating, hot rolling is performed. After casting, hot rolling may be performed immediately without heating. In the case of thin slabs, hot rolling may be performed immediately, or hot rolling may be omitted.
When hot rolling is carried out, it is preferable to carry out the rolling temperature of the rough rolling final pass at 900 ° C. or higher and the rolling temperature of the finish rolling final pass at 700 ° C. or higher.

[Annealed hot-rolled plate]
After hot rolling, hot-rolled sheet is annealed as necessary. At this time, in order to develop the Goth structure in the product plate to a high degree, the hot-rolled plate annealing temperature in the range of 800 to 1100 ° C. is suitable. When the hot-rolled plate annealing temperature is less than 800 ° C., the band structure in hot rolling remains, it becomes difficult to realize a sized primary recrystallization structure, and the development of secondary recrystallization is hindered. .. On the other hand, when the hot-rolled plate annealing temperature exceeds 1100 ° C., the particle size after hot-rolled plate annealing becomes too coarse, and it becomes extremely difficult to realize a sized primary recrystallized structure.

[Cold rolling]
After hot rolling or hot rolling plate annealing, cold rolling is performed once or two or more times with intermediate annealing sandwiched between them. The intermediate annealing temperature is preferably 800 ° C or higher and 1150 ° C or lower. The intermediate annealing time is preferably about 10 to 100 sec.

[Decarburization annealing]
After cold rolling, decarburization annealing is performed. For decarburization annealing, it is preferable that the annealing temperature is 750 to 900 ° C., the atmosphere is oxidizing (degree of oxidation) PH ₂ O / PH ₂ : 0.25 to 0.60, and the annealing time is about 50 to 300 sec.

[Applying annealing separator]
After decarburization and annealing, an annealing separator is applied. It is preferable that the main component of the annealing separator is MgO and the coating amount is about 8 to 15 g / m ² on both sides.

[Final finish annealing]
After the application of the annealing separator, final finish annealing is performed for the purpose of secondary recrystallization and formation of a forsterite film. The final finish annealing may be carried out by a conventional method, but it is preferable that the annealing temperature is 1100 ° C. or higher and the annealing time is 30 minutes or longer.

[Flatration and insulation coating]
After the final finish annealing, it is effective to perform flattening annealing to correct the shape. The flattening annealing is preferably carried out at an annealing temperature of 750 to 950 ° C. and an annealing time of about 10 to 200 sec.
In the present invention, an insulating coating is applied to the surface of the steel sheet before or after flattening and annealing. The insulating coating here means a coating (tension coating) that applies tension to a steel sheet in order to reduce iron loss. Examples of the tension coating include an inorganic coating containing silica and a ceramic coating by a physical vapor deposition method, a chemical vapor deposition method, or the like.

[Magnetic domain subdivision processing]
The magnetic domain subdivision treatment, which is one of the features of the present invention, forms a linear groove between any of the above steps, but as described above, it is important to comply with the conditions specified in the present invention. be.
In particular, it is preferable to carry out after the final cold rolling and before the final finish annealing in which the forsterite film is formed.

(Example 1)
Contains Si: 3.4% by mass, Mn: 0.1% by mass, Ni: 0.2% by mass, Al: 240% by mass, S: 20% by mass, C: 0.07% by mass, N: 90% by mass and Se: 180% by mass. A steel slab consisting of Fe and unavoidable impurities is manufactured by continuous casting, heated to 1430 ° C, hot-rolled to make a hot-rolled plate with a thickness of 2.4 mm, and then 20 at 1100 ° C. A second hot-rolled plate was annealed. The steel sheet after such hot-rolled sheet annealing was subjected to intermediate annealing under the conditions of an intermediate sheet thickness of 0.40 mm by cold rolling, an oxidation degree of PH ₂ O / PH ₂ = 0.40, a temperature of 1000 ° C., and a time of 70 seconds. .. Then, the surface subscale of the steel sheet after the intermediate annealing was removed by pickling with hydrochloric acid, and then cold rolling was performed again to obtain a cold-rolled sheet having a plate thickness of 0.27, 0.23, 0.20 mm.
Under the conditions shown in Table 3-1 cold-rolled plates were prepared by alternately arranging linear grooves having various combinations of different groove cross-sectional areas. As in Experiment 1, first, the groove I was formed by masking with resist ink and electrolytic etching. Then, the resist ink used for forming the groove I was peeled off, and masking with the resist ink and electrolytic etching were performed again to form the groove II. Under both conditions, the linear groove was formed at an angle of 10 ° with respect to the direction orthogonal to the rolling. Note that "discontinuity 1" and "discontinuity 2" have the same shapes shown in FIGS. 8-a and b as in Experiment 2, and are shown in FIGS. 8-a under the condition of "discontinuity 1". The groove forming portion length a = 3 mm and the groove non-forming portion length b = 2 mm, and under the condition of "discontinuity 2", the groove forming portion length a = 1.5 mm and the groove non-forming portion length b = 3.5 shown in Fig. 8-b. The formation pattern was mm.
Then, the cold rolled plate was subjected to decarburization annealing by holding it at an oxidation degree of PH ₂ O / PH ₂ = 0.44 and a soaking temperature of 820 ° C for 300 seconds, and then an annealing separator containing MgO as a main component was applied. The final finish annealing for the purpose of secondary recrystallization, forsterite film formation and purification was carried out at 1160 ° C. under the condition of holding for 10 hours. Then, an insulating coat made of 60% colloidal silica and aluminum phosphate was applied to the steel sheet after the final finish annealing, and baked at 850 ° C. This coating coating process also serves as flattening annealing.
The steel sheet thus obtained is magnetically measured by the Epstein test to evaluate the magnetic property W _{13/50 in the low magnetization region, the characteristic W 17/50 that} determines the steel sheet grade, and the magnetic property B ₈ in the high magnetization region. did.

Table 3-2 shows the magnetic measurement results. In addition, as a judgment as to whether the magnetic characteristics in the low magnetization region and the high magnetization region are compatible, the following conditions are arranged.
Plate thickness: 0.27 mm
"◎": W _13/50 ≤ 0.48 W / kg and B ₈ ≥ 1.900 T and W _17/50 ≤ 0.85 W / kg
"○": Does not meet the judgment of ◎ and W _13/50 ≤ 0.50 W / kg and B ₈ ≥ 1.890 T and W _17/50 ≤ 0.88 W / kg
"× 1": W _13/50 ＞ 0.50W / kg
"× 2": B ₈ <1.890T
Plate thickness: 0.23 mm
"◎": W _13/50 ≤ 0.40 W / kg and B ₈ ≥ 1.900 T and W _17/50 ≤ 0.73 W / kg
"○": Does not meet the judgment of ◎ and W _13/50 ≤ 0.43 W / kg and B ₈ ≥ 1.890 T and W _17/50 ≤ 0.75 W / kg
"× 1": W 13/50 ＞ _0.43W / kg
"× 2": B ₈ <1.890T
Plate thickness: 0.20 mm
"◎": W _13/50 ≤ 0.37 W / kg and B ₈ ≥ 1.895 T and W _17/50 ≤ 0.67 W / kg
"○": Does not meet the judgment of ◎ and W _13/50 ≤ 0.38 W / kg and B ₈ ≥ 1.85 T and W _17/50 ≤ 0.69 W / kg
"× 1": W 13/50 ＞ _0.38W / kg
"× 2": B ₈ <1.885T

Under the conditions 4 to 12, 17 to 25, and 30 to 38 suitable for the present invention, the magnetic characteristics of the low magnetization region and the high magnetization region are excellent, and the magnetic characteristics of the low magnetization region and the high magnetization region can be compatible with each other. Was there.

(Example 2)
Contains Si: 3.4% by mass, Mn: 0.1% by mass, Ni: 0.2% by mass, Al: 240% by mass, S: 20% by mass, C: 0.07% by mass, N: 90% by mass and Se: 180% by mass. A steel slab consisting of Fe and unavoidable impurities is manufactured by continuous casting, heated to 1430 ° C, hot-rolled to make a hot-rolled plate with a thickness of 2.4 mm, and then 20 at 1100 ° C. A second hot-rolled plate was annealed. The steel sheet after such hot-rolled sheet annealing was subjected to intermediate annealing under the conditions of an intermediate sheet thickness of 0.40 mm by cold rolling, an oxidation degree of PH ₂ O / PH ₂ = 0.40, a temperature of 1000 ° C., and a time of 70 seconds. .. Then, the surface subscale of the steel sheet after the intermediate annealing was removed by pickling with hydrochloric acid, and then cold rolling was performed again to obtain a cold-rolled sheet having a plate thickness of 0.27, 0.23, 0.20 mm.
Under the conditions shown in Table 4-1, a cold-rolled plate in which three or more types of linear grooves having different groove cross-sectional areas in various combinations were arranged was produced. As in Experiment 1, first, groove I was formed by masking with resist ink and electrolytic etching. Then, the resist ink used for forming the groove I was peeled off, and masking with the resist ink and electrolytic etching were performed again to form the groove II. The same process was repeated to form the groove III, then the groove IV was formed in a part thereof, and the groove V was further formed in a part thereof. Under both conditions, the linear groove was formed at an angle of 10 ° with respect to the direction orthogonal to the rolling. Note that "discontinuity 1" and "discontinuity 2" have the same shapes as shown in FIGS. 8-a and b, and are shown in FIGS. 8-a under the condition of "discontinuity 1". The groove forming portion length a = 3 mm and the groove non-forming portion length b = 2 mm, and under the condition of "discontinuity 2", the groove forming portion length a = 1.5 mm and the groove non-forming portion length b = shown in Fig. 8-b. The formation pattern was 3.5 mm.
Then, the cold rolled plate was subjected to decarburization annealing by holding it at an oxidation degree of PH ₂ O / PH ₂ = 0.44 and a soaking temperature of 820 ° C for 300 seconds, and then an annealing separator containing MgO as a main component was applied. The final finish annealing for the purpose of secondary recrystallization, forsterite film formation and purification was carried out at 1160 ° C. under the condition of holding for 10 hours. Then, an insulating coat made of 60% colloidal silica and aluminum phosphate was applied to the steel sheet after the final finish annealing, and baked at 850 ° C. This coating coating process also serves as flattening annealing.
The steel sheet thus obtained is magnetically measured by the Epstein test to evaluate the magnetic property W _{13/50 in the low magnetization region, the characteristic W 17/50 that} determines the steel sheet grade, and the magnetic property B ₈ in the high magnetization region. did.

Table 4-2 shows the magnetic measurement results. In addition, as a judgment as to whether the magnetic characteristics in the low magnetization region and the high magnetization region are compatible, the following conditions are arranged.
Plate thickness: 0.27 mm
"◎": W _13/50 ≤ 0.48 W / kg and B ₈ ≥ 1.900 T and W _17/50 ≤ 0.85 W / kg
"○": Does not meet the judgment of ◎ and W _13/50 ≤ 0.50 W / kg and B ₈ ≥ 1.890 T and W _17/50 ≤ 0.88 W / kg
"× 1": W _13/50 ＞ 0.50W / kg
"× 2": B ₈ <1.890T
Plate thickness: 0.23 mm
"◎": W _13/50 ≤ 0.40 W / kg and B ₈ ≥ 1.900 T and W _17/50 ≤ 0.73 W / kg
"○": Does not meet the judgment of ◎ and W _13/50 ≤ 0.43 W / kg and B ₈ ≥ 1.890 T and W _17/50 ≤ 0.75 W / kg
"× 1": W 13/50 ＞ _0.43W / kg
"× 2": B ₈ <1.890T
Plate thickness: 0.20 mm
"◎": W _13/50 ≤ 0.37 W / kg and B ₈ ≥ 1.895 T and W _17/50 ≤ 0.67 W / kg
"○": Does not meet the judgment of ◎ and W _13/50 ≤ 0.38 W / kg and B ₈ ≥ 1.85 T and W _17/50 ≤ 0.69 W / kg
"× 1": W 13/50 ＞ _0.38W / kg
"× 2": B ₈ <1.885T

Under the conditions 3 to 9, 13 to 19, and 23 to 29 suitable for the present invention, the magnetic characteristics of the low magnetization region and the high magnetization region are excellent, and the magnetic characteristics of the low magnetization region and the high magnetization region can be compatible with each other. Was there.

(Example 3)
Contains Si: 3.4% by mass, Mn: 0.1% by mass, Ni: 0.2% by mass, Al: 240% by mass, S: 20% by mass, C: 0.07% by mass, N: 90% by mass and Se: 180% by mass. A steel slab consisting of Fe and unavoidable impurities is manufactured by continuous casting, heated to 1430 ° C, hot-rolled to make a hot-rolled plate with a thickness of 2.4 mm, and then 20 at 1100 ° C. A second hot-rolled plate was annealed. The steel sheet after such hot-rolled sheet annealing was subjected to intermediate annealing under the conditions of an intermediate sheet thickness of 0.40 mm by cold rolling, an oxidation degree of PH ₂ O / PH ₂ = 0.40, a temperature of 1000 ° C., and a time of 70 seconds. .. Then, the surface subscale of the steel sheet after the intermediate annealing was removed by pickling with hydrochloric acid, and then cold rolling was performed again to obtain a cold-rolled sheet having a plate thickness of 0.27, 0.23, 0.20 mm.
After applying the resist ink to the entire surface of the steel sheet, the laser was scanned in a direction orthogonal to the rolling direction to peel off the resist ink at predetermined row intervals in the rolling direction. For laser irradiation, a single-mode fiber laser was continuously peeled off from one end of the steel sheet to the other by a galvano scanner method using a plurality of laser devices, and then electrolytic etching was performed to form a linear groove. .. At that time, by changing the laser irradiation energy and beam diameter of each device, a cold-rolled plate in which two or three types of linear grooves having different groove cross-sectional areas in various combinations under the conditions shown in Table 5-1 are arranged. Was produced.
Then, the cold rolled plate was subjected to decarburization annealing by holding it at an oxidation degree of PH ₂ O / PH ₂ = 0.44 and a soaking temperature of 820 ° C for 300 seconds, and then an annealing separator containing MgO as a main component was applied. The final finish annealing for the purpose of secondary recrystallization, forsterite film formation and purification was carried out at 1160 ° C. under the condition of holding for 10 hours. Then, an insulating coat made of 60% colloidal silica and aluminum phosphate was applied to the steel sheet after the final finish annealing, and baked at 850 ° C. This coating coating process also serves as flattening annealing.
The steel sheet thus obtained is magnetically measured by the Epstein test to evaluate the magnetic property W _{13/50 in the low magnetization region, the characteristic W 17/50 that} determines the steel sheet grade, and the magnetic property B ₈ in the high magnetization region. did.

Table 5-2 shows the magnetic measurement results. In addition, as a judgment as to whether the magnetic characteristics in the low magnetization region and the high magnetization region are compatible, the following conditions are arranged.
Plate thickness: 0.27 mm
"◎": W _13/50 ≤ 0.48 W / kg and B ₈ ≥ 1.900 T and W _17/50 ≤ 0.85 W / kg
"○": Does not meet the judgment of ◎ and W _13/50 ≤ 0.50 W / kg and B ₈ ≥ 1.890 T and W _17/50 ≤ 0.88 W / kg
"× 1": W _13/50 ＞ 0.50W / kg
"× 2": B ₈ <1.890T
Plate thickness: 0.23 mm
"◎": W _13/50 ≤ 0.40 W / kg and B ₈ ≥ 1.900 T and W _17/50 ≤ 0.73 W / kg
"○": Does not meet the judgment of ◎ and W _13/50 ≤ 0.43 W / kg and B ₈ ≥ 1.890 T and W _17/50 ≤ 0.75 W / kg
"× 1": W 13/50 ＞ _0.43W / kg
"× 2": B ₈ <1.890T
Plate thickness: 0.20 mm
"◎": W _13/50 ≤ 0.37 W / kg and B ₈ ≥ 1.895 T and W _17/50 ≤ 0.67 W / kg
"○": Does not meet the judgment of ◎ and W _13/50 ≤ 0.38 W / kg and B ₈ ≥ 1.85 T and W _17/50 ≤ 0.69 W / kg
"× 1": W 13/50 ＞ _0.38W / kg
"× 2": B ₈ <1.885T

Under the conditions 3 to 6, 10 to 13, and 17 to 20 suitable for the present invention, the magnetic characteristics of the low magnetization region and the high magnetization region are excellent, and the magnetic characteristics of the low magnetization region and the high magnetization region can be compatible with each other. Was there.

1 Groove forming part length a
2 Groove non-forming part length b

Claims (2)

A grain-oriented electrical steel sheet having a plurality of linear grooves on one side of a steel sheet, which extends linearly in a direction crossing the rolling direction and is arranged at intervals in the rolling direction.
The linear groove has at least two types having different rolling direction cross-sectional areas, and in the linear groove, the largest rolling direction cross-sectional area is A (mm ² ) and the smallest rolling direction cross-sectional area is B (mm ² ). When {(AB) / A} × 100 is 10% or more and 60% or less, the linear groove having the cross-sectional area A and the linear groove having the cross-sectional area B are alternately alternated in the rolling direction. A directional electromagnetic steel plate with a thickness of 0.27 mm or less. The method for manufacturing a directional electromagnetic steel sheet according to claim 1, wherein the slab for the directional electromagnetic steel sheet is hot-rolled, then hot-rolled and annealed as necessary, and then once or intermediately annealed. After cold rolling two or more times to finish the final plate thickness, decarburization annealing is performed, then an annealing separator is applied to the surface of the steel sheet, then final finish annealing is performed, and then tension coating is performed. And in the method of manufacturing a directional electromagnetic steel sheet having a linear groove to be flattened and annealed.
(1) Make the final plate thickness 0.27 mm or less
(2) The linear grooves are a plurality of linear grooves that extend linearly across the rolling direction and are lined up at intervals in the rolling direction on one side of the steel sheet, and are formed before final finishing annealing. do
(3) When forming the linear groove, at least two types having different rolling direction cross-sectional areas are formed, and in the linear groove, the largest rolling direction cross-sectional area is A (mm ² ) and the smallest rolling direction break. When the area is B (mm ² ), the grooves in which {(AB) / A} × 100 is in the range of 10% or more and 60% or less are continuously or discontinuously formed.
(4) When the linear groove having the cross-sectional area A or the linear groove having the cross-sectional area B is formed in the rolling direction, and then the linear groove having the cross-sectional area A is formed, the line having the cross-sectional area B is formed. When a linear groove having a cross-sectional area B is formed, a linear groove having a cross-sectional area A is formed.
Manufacturing method of grain-oriented electrical steel sheet.

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