Title of the invention: grain-oriented electrical steel sheet and its manufacturing method
Technical field
[0001]
The present invention relates to a grain-oriented electrical steel sheet and a method for producing the same.
The present application claims priority based on Japanese Patent Application No. 2018-022233 filed in Japan on February 9, 2018, the contents of which are incorporated herein by reference.
Background technology
[0002]
As a steel sheet for an iron core of a transformer, a grain-oriented electrical steel sheet that exhibits excellent magnetic characteristics in a specific direction is known. The grain-oriented electrical steel sheet is a steel sheet whose crystal orientation is controlled so that the easily magnetized axis of the crystal grains and the rolling direction coincide with each other by a combination of cold rolling treatment and annealing treatment.
[0003]
As a technique for reducing eddy current loss, which is a kind of iron loss of grain-oriented electrical steel sheet, a grain-oriented electrical steel sheet in which an insulating film is formed on the surface of a base steel sheet whose crystal orientation is controlled is known. The insulating film plays a role of imparting not only electrical insulation but also tension and rust resistance to the base steel sheet.
[0004]
Further, as another method for reducing the abnormal eddy current loss, the width of the 180 ° magnetic domain is formed by forming strain regions and grooves formed in the direction intersecting the rolling direction at predetermined intervals along the rolling direction. There is known a magnetic domain control method that narrows the magnetic domain (subdivides the 180 ° magnetic domain). Therefore, the magnetic domain control method is classified into a method of applying strain to the base steel sheet of the grain-oriented electrical steel sheet and a method of forming a groove on the surface of the base steel sheet in which a coating film for applying tension to the base steel sheet exists.
[0005]
When a wound core is manufactured using a grain-oriented electrical steel sheet that has been subjected to magnetic domain control by grooves, the grooves are not eliminated by performing strain removing and annealing treatment, so that the magnetic domain subdivision effect can be maintained. Therefore, for the wound core, this magnetic domain control method may be adopted as a method for reducing the abnormal eddy current loss.
[0006]
FIG. 1 is a diagram showing an outline of an electromagnetic steel sheet having a groove formed therein. FIG. 1 shows a state in which a plurality of grooves 11 are formed on the surface of the base steel plate 10 so as to be adjacent to each other in the rolling direction of the base steel plate 10. In FIG. 1, reference numeral θ indicates an angle formed by a direction orthogonal to the rolling direction and the plate thickness direction (plate width direction) of the base steel plate 10 and the longitudinal direction of the groove 11. Reference numeral W indicates the width of the groove 11, reference numeral D indicates the depth of the groove 11, and reference numeral d indicates the distance between adjacent grooves 11 in the rolling direction. Various methods for forming grooves in electrical steel sheets have been proposed.
[0007]
Patent Document 1 discloses an electrolytic etching method for forming a groove on the surface of a grain-oriented electrical steel sheet by electrolytic etching.
[0008]
Patent Document 2 discloses a gear pressing method in which a groove is formed on the surface of a steel sheet by mechanically pressing the gear on the surface of the grain-oriented electrical steel sheet.
[0009]
Patent Document 3 discloses a laser irradiation method for melting and evaporating a steel sheet (laser irradiation portion) by laser irradiation.
[0010]
Further, in Patent Document 4, as a groove structure for obtaining stable iron loss characteristics, a scattered alloy layer in which a melt melted by an electromagnetic steel sheet by laser irradiation is resolidified by a steel sheet is uniformly distributed in the groove portion. Electrical steel sheets are disclosed.
Prior art literature
Patent documents
[0011]
Patent Document 1: Japanese Patent Application Laid-Open No.
62-54873 Patent Document 2
: Japanese Patent Application Publication No. 62-53579 Patent Document 3: Japanese Patent Application Laid-Open
No. 2003-129135 Patent Document 4: Japan Special Table 2016-532767 Gazette
Outline of the invention
Problems to be solved by the invention
[0012]
The method of forming a groove on a cold-rolled steel sheet by a laser is excellent in productivity. However, there are cases where the magnetostriction is good and cases where the magnetostriction is inferior depending on the electromagnetic steel sheet, and there is a problem that a stable low magnetostrictive directional magnetostriction cannot be obtained.
[0013]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a grain-oriented electrical steel sheet having low iron loss and low magnetostriction, and a method for producing the grain-oriented electrical steel sheet for stably producing the grain-oriented electrical steel sheet. ..
Means to solve problems
[0014]
The present inventors have caused variations in the magnetostrictive value when manufacturing a grain-oriented electrical steel sheet having a base steel sheet having a plurality of grooves on the surface and a glass coating formed on the surface of the base steel sheet. investigated. As a result, it was found that the value of magnetostriction varies due to the difference in the root structure of the glass coating inside the groove (hereinafter referred to as "groove"). As a result of further research based on the results of this investigation, the present inventors stably control the magnetostrictive value to a low level value by controlling the root structure of the glass coating so as to satisfy a specific condition. I found that I could control it. The present invention has been made based on the above findings, and the gist thereof is as follows.
[0015]
(1) The grain-oriented electrical steel sheet according to one aspect of the present invention includes a base steel sheet having a plurality of grooves on the surface and a glass coating formed on the surface of the base steel sheet. The angle formed by the direction orthogonal to the rolling direction and the plate thickness direction of the base steel plate and the longitudinal direction of the groove is 0 to 40 °, the width of the groove is 20 to 300 μm, and the depth of the groove is Is 10 to 40 μm, and the distance between the grooves in the rolling direction is 2 to 30 mm. When the region including the groove is viewed in a cross section orthogonal to the longitudinal direction of the groove, a point existing on the contour line of the glass coating and existing at the highest position in the plate thickness direction is defined as a peak point. A straight line passing through the peak point and parallel to the groove width direction orthogonal to the plate thickness direction in the cross section is defined as a reference line, and exists on the boundary line between the glass coating and the base steel plate and is in the plate thickness direction. The point existing at the lowest position is defined as the deepest point, and is located on the boundary line in the region having a length of 2 μm in the groove width direction with the deepest point as the center and at the highest position in the plate thickness direction. When the existing point is defined as the shallowest point, the relationship between the shortest distance A between the reference line and the deepest point and the shortest distance B between the reference line and the shallowest point is as follows (1). ) Satisfy the equation.
0.1 μm ≤ AB ≤ 5.0 μm ... (1)
[0016]
(2) The method for manufacturing a grain-oriented electrical steel sheet according to one aspect of the present invention is the method for manufacturing a grain-oriented electrical steel sheet according to (1) above, in which a groove is formed on the surface of the cold-rolled steel sheet by a laser. Includes steps. In the step, the atmosphere including the laser irradiation site is air or an inert gas, the dew point of the air is −30 ° C. to 0 ° C., and the dew point of the inert gas is −20 ° C. to 20 ° C.
Effect of the invention
[0017]
According to the present invention, a grain-oriented electrical steel sheet having low iron loss and low magnetostriction can be obtained.
A brief description of the drawing
[0018]
[Fig. 1] Fig. 1 is a diagram showing an outline of an electromagnetic steel sheet in which a groove is formed.
[Fig. 2] It is a schematic view around a groove.
[Fig. 3] Fig. 3 is a schematic diagram illustrating a mixed interface region.
Mode for carrying out the invention
[0019]
First, the contents of the study by the present inventors will be described in detail.
[0020]
The present inventors investigated the cause of the variation in the magnetostrictive value when manufacturing a grain-oriented electrical steel sheet having a base steel sheet having a plurality of grooves on the surface and a glass coating formed on the surface of the base steel sheet. did. Regarding low magnetostriction, the details of the influencing factors in groove formation are unknown, and the investigation was conducted considering that it depends on the orientation integration after secondary recrystallization, groove depth and film tension, but as a result, after secondary recrystallization, There was no difference in orientation integration, groove depth and coat tension. Therefore, the present inventors considered that the variation in magnetostriction was caused by the difference in the shape of the groove, and investigated the groove cross section in detail. As a result, it was found that the grain-oriented electrical steel sheets having different magnetostrictions had different root conditions of the glass coating in the groove.
[0021]
FIG. 2 shows an outline of the glass coating around the groove. FIG. 2 is a cross-sectional view of a grain-oriented electrical steel sheet provided with a base steel sheet and a glass coating, and more specifically, is a view of a region including a groove in a cross section orthogonal to the longitudinal direction of the groove. The glass coating 21 is an oxide layer usually formed during secondary recrystallization annealing as described later, and is composed of an oxide mainly composed of forsterite, and the content of forsterite may be 70% by volume or more. Generally, the balance consists of oxides containing aluminum, calcium and the like. A groove 11 is formed in the base steel sheet 10, and a glass coating 21 made of the above oxide is formed on the surface of the base steel sheet 10 including the surface of the groove 11. A tension coating 22 may be further provided on the surface of the glass coating 21. The root 23 of the glass coating 21 is a portion where the glass coating 21 extends toward the inside of the base steel plate 10, and usually exists at intervals of about 0.1 to 2 μm.
[0022]
As a result of the investigation, when the magnetostriction is large, the root 23 of the glass coating 21 in the groove is excessively developed, and when the magnetostriction is good, the degree of development of the root 23 of the glass coating 21 is the part other than the groove. It was about the same. It is not clear why the magnetostriction increases when the root 23 of the glass coating 21 is excessively developed, but it is presumed that a 90 ° magnetic domain is likely to be generated starting from the root 23 of the glass coating 21.
[0023]
If the root 23 of the glass coating 21 is too short, it is considered that the magnetostriction is not adversely affected, but the adhesion between the glass coating 21 and the base steel (base steel plate 10) is lowered, so that the coating in the groove is cracked. It is more likely to occur. When moisture enters from these cracks, rust is generated, and the insulation, space factor, and appearance are impaired.
[0024]
As a result of investigating a method in which the root 23 of the glass coating 21 in the groove does not develop excessively, the present inventors have controlled the dew point of the assist gas at the time of groove formation to an appropriate range, so that the root 23 of the glass coating 21 can be formed. It was found that the depth generated can be controlled.
[0025]
Hereinafter, the configuration of the grain-oriented electrical steel sheet (hereinafter, abbreviated as the electrical steel sheet) according to the present embodiment will be described.
[0026]
The electromagnetic steel sheet includes a base steel sheet 10 having a plurality of grooves 11 on its surface and a glass coating 21 formed on the surface of the base steel sheet 10 (see FIGS. 1 and 3). In this electrical steel sheet, a tension coating (insulating coating) 22 may be formed on the surface of the glass coating 21. As shown in FIG. 1, on the surface of the base steel plate 10, the plurality of grooves 11 are formed so as to be adjacent to each other in the rolling direction of the base steel plate 10. The direction (angle θ) of the groove 11, the width W, the depth D, and the interval d of the groove 11 do not affect the magnetostriction and the crack of the groove portion, which are the subjects of the present invention, and are the same as those of a normal grain-oriented electrical steel sheet. , Determined in consideration of iron loss.
[0027]
If the angle θ formed by the rolling direction of the base steel sheet 10 and the direction orthogonal to the plate thickness direction (plate width direction) and the longitudinal direction of the groove 11 is too large, the iron loss improving effect cannot be obtained, so 0 to 40 ° And. The width W of the groove 11 is set to 20 to 300 μm because good iron loss cannot be obtained if it is too wide or too narrow. The depth D of the groove 11 is set to 10 to 40 μm because good iron loss cannot be obtained if it is too shallow or too deep. The grooves 11 are formed at intervals d of 2 to 30 mm in the rolling direction. The intervals d of the grooves 11 do not have to be evenly spaced.
[0028]
The configuration of the roots of the glass coating 21 in the interfacial mixed region and the groove portion in this electrical steel sheet will be described with reference to FIG. FIG. 3 is a cross-sectional view of the electrical steel sheet, and more specifically, is a view of a region including the groove 11 in a cross section orthogonal to the longitudinal direction of the groove 11.
[0029]
In this electrical steel sheet, the roots of the glass coating 21 inside the groove 11 formed on the base steel sheet 10 are not excessively developed and are controlled within an appropriate range. Specifically, as shown in FIG. 3, when the region including the groove 11 is viewed in a cross section orthogonal to the longitudinal direction of the groove 11, it exists on the contour line 21a of the glass coating 21 and is the highest in the plate thickness direction. The point existing at the position is defined as the peak point 35. A straight line passing through the peak point 35 and parallel to the groove width direction orthogonal to the plate thickness direction in the cross section shown in FIG. 3 is defined as the reference line 31. In the cross section shown in FIG. 3, the point existing on the boundary line 12 between the glass coating 21 and the base steel plate 10 and at the lowest (deep) position in the plate thickness direction is defined as the deepest point 32. Further, in the cross section shown in FIG. 3, in the region having a length of 2 μm (that is, ± 1 μm) in the groove width direction about the deepest point 32, it exists on the boundary line 12 and is the highest (shallowest) in the plate thickness direction. ) The point existing at the position is defined as the shallowest point 33.
　As described above, when the reference line 31, the deepest point 32 and the shallowest point 33 are defined in the cross section shown in FIG. 3, in this electrical steel sheet, the shortest distance A between the reference line 31 and the deepest point 32 is defined. The root structure of the glass coating 21 is controlled so that the relationship between the shortest distance B between the reference line 31 and the shallowest point 33 satisfies the following equation (1).
　Here, the shortest distance A between the reference line 31 and the deepest point 32 is the length of the straight line when the deepest point 32 and the reference line 31 are connected by a straight line perpendicular to the reference line 31. is there. Further, the shortest distance B between the reference line 31 and the shallowest point 33 is the length of the straight line when the shallowest point 33 and the reference line 31 are connected by a straight line perpendicular to the reference line 31. Is.
　In the following, the region between the deepest point 32 and the shallowest point 33 in the plate thickness direction is defined as the interface mixed region 34, and the value (= AB) obtained by subtracting the shortest distance B from the shortest distance A is obtained. It is defined as the thickness of the interface mixed region 34. In the interface mixed region 34, steel and a glass coating are mixed.
0.1 μm ≤ AB ≤ 5.0 μm ... (1)
[0030]
The cross section of the groove portion is observed with a scanning electron microscope at five arbitrary locations (however, different grooves 11 are used) of the base steel plate 10 in which the groove 11 is present, and the thickness of the interface mixed region 34 is observed from the photograph of the cross section. Is obtained, and the average value of the thicknesses at the five locations is taken as the thickness of the interface mixed region 34.
When the thickness (= AB) of the interface mixed region 34 is less than 0.1 μm, the adhesion between the glass coating 21 and the base steel (base steel plate 10) is lowered, so that cracks occur in the groove coating. It will be easier. Therefore, the lower limit of the thickness of the interface mixed region 34 is 0.1 μm. On the other hand, when the thickness of the interface mixed region 34 exceeds 5.0 μm, the value of magnetostriction increases due to the excessive development of the roots of the glass coating 21. Therefore, the upper limit of the thickness of the interface mixed region 34 is 5.0 μm. In order to obtain a good balance between the effect of improving the adhesion of the coating film and the effect of reducing magnetostriction, the thickness of the interface mixed region 34 is preferably 1 μm or more and 3 μm or less.
[0031]
Next, a method for manufacturing the electrical steel sheet to have the above configuration will be described.
[0032]
First, a cold-rolled steel sheet for this electrical steel sheet is manufactured by a conventional method. The method for producing the cold-rolled steel sheet is not particularly limited, and a generally known method may be used.
[0033]
Next, by irradiating the cold-rolled steel sheet with a laser, a plurality of grooves are formed at predetermined intervals in the directions intersecting the rolling directions.
[0034]
As the laser light source, a high-power laser generally used for industrial purposes such as a fiber laser, a YAG laser, a semiconductor laser, or a CO 2 laser can be used. A pulsed laser or a continuous wave laser may be used as long as the groove can be stably formed. As the irradiation conditions of the laser beam, for example, the laser output is set to 200 to 3000 W, and the focused spot diameter in the rolling direction of the laser beam (diameter including 86% of the laser output, hereinafter referred to as "86% diameter") is set to 10 to 1000 μm. The focused spot diameter (86% diameter) of the laser beam in the plate width direction can be set to 10 to 1000 μm, and the laser scanning speed can be set to 5 m / s to 100 m / s.
[0035]
Simultaneously with the irradiation of the laser beam, the assist gas is sprayed on the portion of the steel sheet to be irradiated with the laser beam. The assist gas plays a role of removing molten or evaporated components from the steel sheet by laser irradiation. By spraying the assist gas, the laser beam stably reaches the steel sheet, so that the groove is stably formed. The flow rate of the assist gas can be, for example, 10 to 1000 liters per minute.
[0036]
In the present invention, the assist gas is air or an inert gas, and in the case of air, the dew point is −30 to 0 ° C., and in the case of an inert gas, the dew point is −20 to 20 ° C. Thereby, the root of the glass coating satisfying the above-mentioned equation (1) can be formed.
[0037]
After forming the grooves in the steel sheet, the cold-rolled steel sheet is decarburized and nitrided by a known method, then an annealing separator mainly composed of MgO is applied, and the steel sheet is heated, retained and then cooled to form a glass film. Tension can be applied to the steel sheet only with the glass coating, but in order to enhance the magnetic domain control effect, a normal tension coating (insulating coating) is usually formed on the glass coating.
[0038]
The decarburization conditions can be general known conditions. For example, the temperature is raised to 850 ° C., the temperature is retained for 60 seconds, and then cooling is performed. The decarburization atmosphere is a hydrogen-inert gas atmosphere and PH 2 O / PH 2. The range is preferably 0.15 to 0.65, and particularly good characteristics can be obtained in the vicinity of 0.33. Nitriding can also be a known general method, and the amount of nitriding can be, for example, in the range of 50 to 400 ppm, and particularly good characteristics can be obtained in the vicinity of 200 ppm. The composition of the annealing separator can be a known general one, for example, MgO: 100 parts by mass, TiO 2 : 5 parts by mass, and as an additive, for example, FeCl 2 is added so as to be 200 ppm with chlorine. Can be done. As will be described later, the glass film is formed by winding a steel sheet into a coil, holding it at a maximum temperature of 1200 ° C. for about 20 hours, and then cooling it. The tension coating can be, for example, made of aluminum phosphate as a main component and can have a thickness of 1 μm.
[0039]
The mechanism by which the composition and dew point of the assist gas affect the root development of the glass coating in the groove is considered as follows.
[0040]
The roots of the glass coating are mainly composed of forsterite, which is formed during secondary recrystallization annealing after groove formation. The raw material for forming forsterite consists of SiO 2 existing on the surface of the steel sheet before secondary recrystallization and MgO, which is an annealing separator. SiO 2 present on the surface of the steel sheet is usually derived from the decarboxylation layer. In addition to this, the moisture in the annealing separator may be released during the secondary recrystallization annealing temperature rise to oxidize the steel sheet and further increase SiO 2 . Oxidation of the steel sheet by the water in the annealing separator is called additional oxidation, and it is considered that when the additional oxidation occurs, the glass film is excessively formed and the roots of the glass film develop.
[0041]
Measures to prevent additional oxidation are to optimize the amount of annealing separator applied and to control the amount of water in the annealing separator. If the amount of the annealing separator applied is too small, the amount of Mg, which is the raw material of forsterite, is small, so that a good glass film cannot be formed. Further, if the water content is too small, SiO 2 is decomposed during the temperature rise of the secondary recrystallization annealing, the amount of the raw material for forsterite is reduced, and a good glass coating cannot be formed. There is no particular harm if there is too much annealing separator, but it is not economical because the amount of unreacted annealing separator increases and it is applied wastefully. If the amount of water is too large, excessive internal oxidation occurs as described above, causing a problem that the roots of the glass coating are excessively formed.
[0042]
If there are no grooves, only the amount of coating and the amount of water are sufficient to control when applying the annealing separator, but since the annealing separator accumulates in the grooves, additional oxidation is more likely to occur than in other parts of the steel sheet.
[0043]
If the amount of annealing separator applied or the amount of water is reduced in order to obtain an appropriate amount of glass film in the groove portion, a sound glass film will not be formed in the portion other than the groove, so the amount of annealed separator applied And the amount of water cannot solve the problem.
[0044]
Therefore, the dew point control of the assist gas at the time of groove formation suppresses the additional oxidation of the groove portion, thereby suppressing the excessive development of the root of the glass coating in the groove portion. This mechanism is considered as follows.
[0045]
When an atmosphere having an appropriate oxygen potential is created by heating with a laser to form a groove, an oxide film having a good atmosphere sealing property is formed. In order to control the oxygen potential, the assist gas has a dew point of −30 to 0 ° C. in the air composition. If there is an oxide film formed under such conditions, it functions as a barrier layer that prevents oxygen from entering the steel even if a large amount of water is released from the annealing separator at the groove when the temperature of the secondary recrystallization rises. It is thought that.
[0046]
If the dew point is too high, a large amount of SiO 2 is generated, and a phenomenon similar to excessive additional oxidation occurs. On the other hand, the dew point is too the sealing of the oxide film becomes excessively good to produce low, SiO formed during decarburization 2 oxide layer is not sufficiently developed, the roots of healthy glass film is not formed.
For the above reasons, in the method for producing an electromagnetic steel sheet, when the atmosphere including the laser irradiation site is air in the step of forming a groove on the surface of the cold-rolled steel sheet with a laser, that is, when air is used as an assist gas, the air is used. The dew point of is controlled to -30 ° C to 0 ° C.
[0047]
When an inert gas is used as the assist gas, the dew point of the inert gas is controlled to −20 to 20 ° C. Examples of the inert gas include nitrogen, helium, argon and the like.
[0048]
By the above manufacturing method, the roots of the glass coating are appropriately developed, and a grain-oriented electrical steel sheet having good magnetostriction can be obtained.
Conventionally, a dehumidified assist gas is used in order to prevent the generation of water during laser irradiation, but a gas having a specially controlled dew point is not used as such an assist gas. It is common general knowledge that the dew point of so-called dry gas, which is generally used industrially, is about −35 ° C. On the other hand, in the method for manufacturing this electrical steel sheet, the dew point of the assist gas is positively controlled in a specific range to control the root of the glass coating in the groove to a specific state (a state satisfying the equation (1)). As a result, it was possible to achieve both improvement in magnetic properties (magnetostriction) and adhesion of the glass coating. The problem that moisture is generated during laser irradiation by controlling the dew point of the assist gas within the above-mentioned specific range can be solved by maintaining the atmospheric temperature at the time of laser irradiation at about 90 ° C.
Example
[0049]
Hereinafter, the present invention will be specifically described with reference to Examples. The present invention is not limited to the embodiments described below.
[0050]
[Example 1]
Si: 3.4% by mass, Mn: 0.15% by mass, S: 0.006% by mass, C: 0.045% by mass, acid-soluble Al: 0.022% by mass, N: A slab containing 0.007% by mass was hot-rolled by a known method, and then hot-rolled and annealed to obtain a steel plate having a final plate thickness of 0.22 mm by cold rolling.
[0051]
Subsequently, the surface of the steel sheet was irradiated with a laser to form a plurality of grooves extending in a direction intersecting the rolling direction at intervals of 5 mm along the rolling direction. The groove forming direction was a direction inclined by 20 ° in the L direction with respect to the C direction of the steel sheet, the groove width was 50 μm, and the groove depth was 25 μm.
[0052]
The irradiation conditions of the laser light are as follows: the laser output is 200 to 3000 W, the focused spot diameter (86% diameter) in the rolling direction of the laser light is 10 to 1000 μm, and the focused spot diameter (86% diameter) in the plate width direction of the laser light. Was adjusted in the range of 10 to 1000 μm and the laser scanning speed was adjusted in the range of 5 to 100 m / s.
[0053]
Assist gas was sprayed at 100 liters / minute in order to efficiently remove the metal of the steel sheet melted and evaporated by the laser during laser irradiation. The composition and dew point of the assist gas are as shown in Table 1.
[0054]
The grooved cold-rolled steel sheet was decarburized and further subjected to nitriding treatment. The decarburization condition was that the temperature was raised to 850 ° C. and then retained for 60 seconds for cooling. The decarburized atmosphere was a hydrogen-nitrogen atmosphere, and PH 2 O / PH 2 was set to 0.33. The amount of nitriding was 200 ppm.
[0055]
Then, an annealing separator mainly containing MgO was applied so that the coating amount was 4 g / m 2 on one side . The composition of the annealing separator is, MgO: 100 parts by weight, TiO 2 : to 5 parts by weight, FeCl 2 was added so as to be 200ppm with chlorine.
[0056]
Subsequently, the steel sheet was wound into a coil, held at a maximum temperature of 1200 ° C. for 20 hours, and then cooled to form a glass film on the surface. Further, a tension film containing aluminum phosphate as a main component was formed so as to have a thickness of 1 μm to obtain a grain-oriented electrical steel sheet. The tension at this time was 12 MPa with respect to the rolling direction including the glass coating.
[0057]
The thickness (= AB) of the region where the base iron and the glass coating are mixed (interfacial mixed region) in the groove of the obtained grain-oriented electrical steel sheet, the magnetic characteristics (magnetostriction, magnetic flux density, iron loss) and the crack in the groove. The presence or absence of is shown below.
[0058]
[table 1]

[0059]
Magnetostriction, when the maximum magnetic flux density of the steel sheet at sinusoidal 50Hz is excited so as to be 1.7 T, the absolute value of the difference between the most contracted length as the length of the steel sheet is most stretched, 0.6 × 10 - 6 or less was considered good.
[0060]
The iron loss is the iron loss (W17 / 50) when the steel sheet is excited to have a maximum magnetic flux density of 1.7 T with a sine wave having a frequency of 50 Hz, and 0.8 W / kg or less is good.
[0061]
The cracks in the groove were observed with a scanning electron microscope in a range of 10 mm in the groove longitudinal direction of the coating of the groove of the obtained sample, and it was judged that there was no crack when there was no crack exceeding 0.5 μm in length.
[0062]
From the results of this example, when the composition and dew point of the assist gas are within the range of the present invention, the thickness of the interface mixed region is controlled within the range of 0.1 μm or more and 5.0 μm or less, and there is no crack in the groove. It was found that the magnetostriction and iron loss were good.
[0063]
[Example 2]
Si: 3.4% by mass, Mn: 0.15% by mass, S: 0.006% by mass, C: 0.045% by mass, acid-soluble Al: 0.022% by mass, N: A slab containing 0.007% by mass was used as a material for hot rolling by a known method, and then hot-rolled sheet was annealed to obtain a steel sheet having a final sheet thickness of 0.22 mm by cold rolling.
[0064]
Subsequently, the surface of the steel sheet was irradiated with a laser to form a plurality of grooves extending in a direction intersecting the rolling direction at intervals of 5 mm along the rolling direction. The groove forming direction was a direction inclined by 20 ° in the L direction with respect to the C direction of the steel sheet, and the groove width and the groove depth were the sizes shown in Table 2.
[0065]
The irradiation conditions of the laser beam were the same as in Example 1, and air having a dew point of −15 ° C. was blown at 100 liters / minute as an assist gas.
[0066]
The grooved cold-rolled steel sheet was decarburized and further subjected to nitriding treatment. The decarburization condition was that the temperature was raised to 850 ° C. and then retained for 60 seconds for cooling. The decarburized atmosphere was a hydrogen-nitrogen atmosphere, and PH 2 O / PH 2 was set to 0.33. The amount of nitriding was 200 ppm.
[0067]
Then, an annealing separator mainly containing MgO was applied so that the coating amount was 4 g / m 2 on one side . The composition of the annealing separator is, MgO: 100 parts by weight, TiO 2 : to 5 parts by weight, FeCl 2 was added so as to be 200ppm with chlorine.
[0068]
Subsequently, the steel sheet was wound into a coil, held at a maximum temperature of 1200 ° C. for 20 hours, and then cooled to form a glass film on the surface. Further, a tension film containing aluminum phosphate as a main component was formed so as to have a thickness of 1 μm to obtain a grain-oriented electrical steel sheet. The tension at this time was 12 MPa with respect to the rolling direction including the glass coating.
[0069]
The thickness of the interfacial grained region of the obtained grain-oriented electrical steel sheet, the magnetic characteristics (magnetostriction, magnetic flux density, iron loss) and the presence or absence of cracks in the groove are shown below.
[0070]
[Table 2]

[0071]
The method for evaluating magnetostriction, iron loss, and cracks in the groove is the same as in Example 1. From the results of this example, it was found that when the groove depth and the groove width were within the range of the present invention, there were no cracks in the groove portion, and magnetostriction and iron loss were good.
[0072]
[Example 3]
Si: 3.4% by mass, Mn: 0.15% by mass, S: 0.006% by mass, C: 0.045% by mass, acid-soluble Al: 0.022% by mass, N: A slab containing 0.007% by mass was used as a material for hot rolling by a known method, and then hot-rolled sheet was annealed to obtain a steel sheet having a final sheet thickness of 0.22 mm by cold rolling.
[0073]
Subsequently, the surface of the steel sheet is irradiated with a laser, and a plurality of grooves extending in the direction intersecting the rolling direction are formed in Table 3 in the L direction with respect to the C direction of the steel sheet at intervals shown in Table 3 along the rolling direction. A groove was formed in the direction inclined at the indicated angle. The groove width was 50 μm and the groove depth was 25 μm.
[0074]
The irradiation conditions of the laser beam were the same as in Example 1, and air having a dew point of −15 ° C. was blown at 100 liters / minute as an assist gas.
[0075]
The grooved cold-rolled steel sheet was decarburized and further subjected to nitriding treatment. The decarburization condition was that the temperature was raised to 850 ° C. and then retained for 60 seconds for cooling. The decarburized atmosphere was a hydrogen-nitrogen atmosphere, and PH 2 O / PH 2 was set to 0.33. The amount of nitriding was 200 ppm.
[0076]
Then, an annealing separator mainly containing MgO was applied so that the coating amount was 4 g / m 2 on one side . The composition of the annealing separator is, MgO: 100 parts by weight, TiO 2 : to 5 parts by weight, FeCl 2 was added so as to be 200ppm with chlorine.
[0077]
Subsequently, the steel sheet was wound into a coil, held at a maximum temperature of 1200 ° C. for 20 hours, and then cooled to form a glass film on the surface. Further, a tension film containing aluminum phosphate as a main component was formed so as to have a thickness of 1 μm to obtain a grain-oriented electrical steel sheet. The tension at this time was 12 MPa with respect to the rolling direction including the glass coating.
[0078]
The thickness of the interfacial grained region of the obtained grain-oriented electrical steel sheet, the magnetic characteristics (magnetostriction, magnetic flux density, iron loss) and the presence or absence of cracks in the groove are shown below.
[0079]
[Table 3]

[0080]
　The method for evaluating magnetostriction, iron loss, and cracks in the groove is the same as in Example 1. From the results of this embodiment, when the groove pitch and the angle of inclination of the steel sheet in the L direction with respect to the groove forming direction are within the range of the present invention, there is no crack in the groove and magnetostriction and iron loss are good. It turned out to be.
Code description
[0081]
　10 Steel plate
　11 Groove
　21 Glass coating
　22 Tension coating
　23 Glass coating root
　31 Reference line
　32 Deepest point
　33 Shallow point
　34 Interface mixed region
　35 Peak point
　θ Angle formed by the
　groove perpendicular to the rolling direction W Groove width
　D Groove depth
　d Groove spacing
The scope of the claims
[Claim 1]
　A directional electromagnetic steel plate including a base steel plate having a plurality of grooves on the surface and a glass coating formed on the surface of the base material steel plate, which
　is orthogonal to the rolling direction and the plate thickness direction of the base material steel plate. The angle formed by the direction and the longitudinal direction of the groove is 0 to 40 °,
　the width of the groove is 20 to 300 μm,
　the depth of the groove is 10 to 40 μm, and the
　groove in the rolling direction. 　A point that exists on the contour line of the glass coating and exists at the highest position in the plate thickness direction
　when the region including the groove is viewed in a cross section orthogonal to the longitudinal direction of the groove with an interval of 2 to 30 mm.
Is defined as a
peak point, a straight line passing through the peak point and parallel to the groove width direction orthogonal to the plate thickness direction in the cross section is defined as a reference line, and
　on the boundary line between the glass coating and the base steel plate. The point existing in and at the lowest position in the plate thickness direction is defined as the
　deepest point, and exists on the boundary line in the region having a length of 2 μm in the groove width direction about the deepest point and said. When the point existing at the highest position in the plate thickness direction is defined as the shallowest point,
　the shortest distance A between the reference line and the deepest point and the shortest distance between the reference line and the shallowest point
A directional electromagnetic steel plate characterized in that the relationship with B satisfies the following equation (1) .
　　　　0.1 μm ≤ AB ≤ 5.0 μm ... (1)
[Claim 2]
The method for producing a directional electromagnetic steel sheet according to claim 1,
which comprises a step of forming a groove on the surface of the cold-rolled steel sheet with a laser, and in the step, the
atmosphere including the laser irradiation site is air or an inert gas. A
method for producing a directional electromagnetic steel sheet , wherein the dew point of the air is −30 ° C. to 0 ° C., and the dew point of the inert gas is −20 ° C. to 20 ° C.