Technical field
[0001]
　The present invention relates to a grain-oriented electrical steel sheet.
　Priority is claimed on Japanese Patent Application No. 2015-086300 filed in Japan on April 20, 2015, which is incorporated herein by reference.
Background technique
[0002]
　Conventionally, as a steel sheet for transformer iron core (core) is oriented electrical steel sheet exhibiting excellent magnetic properties in a particular direction are known. The oriented electrical steel sheet, by a combination of cold rolling process and annealing process, a steel sheet crystal orientation is controlled so that the crystal grains of the easy magnetization axis and the rolling direction coincides. It is desirable iron loss oriented electrical steel sheet is as low as possible.
[0003]
　Iron loss is classified into a eddy current loss and hysteresis loss. Further, the eddy current loss is classified into a classical eddy current loss and abnormal eddy current loss. To reduce the classical eddy current loss, grain-oriented electrical steel sheet insulating film formed on the surface of the crystal orientation as described above is controlled steel (the base steel) is generally known. The insulating coating is not only electrically insulating, also serves to provide tension and heat resistance and the like to the steel sheet. Incidentally, in recent years, are also known oriented electrical steel sheet glass coating film is formed between the steel sheet and the insulating film.
[0004]
　On the other hand, as a method for reducing abnormal eddy current loss, the stress-strain portion and groove portion extending in a direction crossing the rolling direction, by forming at a predetermined distance along the rolling direction, to narrow the width of the 180 ° domains (performing subdivision of 180 ° magnetic domain) magnetic domain control method is known. In the method of forming a stress strain utilizes 180 ° magnetic domain refining effect of closure domain generated by the distortion portion. Typical method is to utilize shock waves and rapid heating by laser irradiation. The surface shape of the irradiation portion hardly changes in this way. Meanwhile, a method of forming a groove is to utilize the demagnetizing field effect magnetic poles generated at the groove side walls. In this case, the cross-sectional shape of the groove has been known to have higher magnetic domain control effect close to rectangular (Patent Document 4). That domain control are classified into the strain-applying and the groove-forming.
[0005]
　When manufacturing a transformer winding core using the grain-oriented electrical steel sheet, in order to remove the deformation strain caused by the fact that grain oriented electrical steel sheet is coiled, it is necessary to implement a strain relief annealing treatment is there. When manufacturing the winding core using the grain-oriented electrical steel sheet was subjected to magnetic domain control by the distortion imparting method, the distortion is eliminated by the practice of strain relief annealing, domain refining effect (i.e. the effect of reducing the abnormal eddy current loss) also disappear.
[0006]
　On the other hand, when manufacturing wound cores using grain-oriented electrical steel sheet was subjected to magnetic domain control by the groove forming method, the groove is not lost by the practice of the strain relief annealing treatment, it is possible to maintain the domain refining effect. Therefore, the magnetic domain control material manufacturing method for a winding core, the groove-forming is employed.
　Incidentally, when manufacturing transformers of the product core, because it does not implement the strain relief annealing, distortion-imparting, it is possible to selectively employ one of the groove-forming.
　Incidentally, the laser method is a typical method of strain-applying, for example, as disclosed in Patent Document 5, when the laser of relatively high strength, the steel sheet surface is melted to a depth 10μm approximately slightly sometimes shallow gentle depressions are formed. However, in such a shallow gradual indentations not pole occurs with a magnetic domain control effect, as a result, after the strain relief annealing is known to disappear magnetic domain control effect.
[0007]
　As magnetic domain control method of the groove-forming, press electrolytic etching to form a groove on the steel sheet surface oriented electrical steel sheet (see Patent Document 1), the surface of the steel sheet mechanically oriented electrical steel gears by electrolytic etching by gear pressing method of forming a groove on the steel sheet surface (see Patent Document 2), a laser irradiation method of forming a groove on the steel sheet surface oriented electrical steel sheet by laser irradiation (see Patent Document 3) , it is generally known.
[0008]
　The electrolytic etching method, for example, after removing the insulating coating of the steel sheet surface (or the glass coating film) linearized by laser or mechanical means, by performing electrolytic etching in a portion steel is exposed, to form a groove on the steel sheet surface . When adopting such electrolytic etching method, the manufacturing process of the grain-oriented electrical steel sheet becomes complicated, resulting in a problem that manufacturing cost becomes high. Further, in the gear press method, since the steel sheet of the grain-oriented electrical steel sheet is very hard steel sheet containing Si of about 3 wt%, wear and damage of the gear is likely to occur. When adopting such gear pressing method, the gear becomes shallow groove when worn, and because the variation occurs in the depth of the grooves, there is a problem that the effect of reducing the abnormal eddy current loss can not be sufficiently obtained.
[0009]
　On the other hand, when the laser irradiation method, a complicated process such as etching for a direct machining unnecessary, the grooves in the teeth stably steel sheet surface without abrasion, such as press working for a non-contact machining it can be formed. For example, the following Patent Document 4, in the oriented electrical steel sheet in which grooves are formed on the surface of the steel sheet by laser irradiation method, the contour of the grooves appearing on the cross section perpendicular to the extending direction of the groove shape (groove cross-sectional shape) by closer to a rectangle, a technique for improving the magnetic domain subdivision effect (iron loss reducing effect) is disclosed.
CITATION
Patent Literature
[0010]
Patent Document 1: Japanese Patent Publication 62-54873 Patent Publication
Patent Document 2: Japanese Patent Publication 62-53579 Patent Publication
Patent Document 3: Japanese Patent Laid-Open 6-57335 discloses
Patent Document 4: Japanese Patent 2012-177164 JP
Patent Document 5: Japanese Patent 2007-2334 JP
Summary of the Invention
Problems that the Invention is to Solve
[0011]
　As an index representing the performance of a grain-oriented electromagnetic steel sheet, (magnetic flux density B8 that occurs in a magnetic field of for example 800A / m) in addition to the magnetic flux density of the iron loss is. In the grain-oriented electrical steel sheet, iron loss is desirably low, the magnetic flux density is high it is desirable. However, if the groove is formed on the surface of the steel sheet, the magnetic flux density decreases. In particular, as disclosed in Patent Document 4, grooves sectional shape is closer to a rectangle, the volume of the iron is removed from the steel sheet is increased, there is a problem that lowering of the magnetic flux density becomes remarkable. Further, an electromagnetic steel sheet with a high heat source such as a laser to form a groove, when bending when used in winding iron core, steel as a starting point groove is a problem that is easily broken.
[0012]
　The present invention has been made in view of the above problems, with respect to grain oriented electrical steel sheet having grooves formed on the surface of the steel sheet for domain refining, and minimization of maximizing the magnetic flux density decreases iron loss reducing effect It aims to achieve both good balance.
Means for Solving the Problems
[0013]
　The gist of the present invention is as follows.
(1) grain-oriented electrical steel sheet according to an embodiment of the present invention comprises a steel plate having grooves and the groove depth direction extends in a direction crossing the rolling direction is the thickness direction is formed steel sheet surface, the average depth D of the groove is at 10μm ultra 40μm or less, when viewed the groove in the groove width direction cross section perpendicular to Mizonobe lengthwise direction, when defining around the groove width center of the groove in the groove width direction , with the deepest portion of the groove is offset from the groove width center to one side of the groove width direction, the sectional shape of the groove, is asymmetrical shape relative to the said groove width center in the groove width direction, said groove when the width direction cross-section as viewed said groove, said groove having a first groove surface and a second groove surface is a pair of inclined surfaces inclined toward the deepest portion of the groove from the surface of the steel sheet cage, contact located on the side of the second groove surface the groove width center as viewed from the deepest portion Ri, the first groove end angle and forms linear with the thickness direction obtained by linear approximation of the first groove surface is defined as the first angle .theta.1, second obtained by linearly approximating the second groove surface groove end when the angle between the straight line and the plate thickness direction is defined as a second angle .theta.2, the first angle θ1 and the second angle .theta.2 is, to satisfy the following conditional expressions (1) to (3).
　　　　　　　　° ≦ .theta.1 0 ≦ 50 ° ... (1)
　　　　　　　　.theta.1 <.theta.2 ≦ 75 ° ... (2)
　　　　　　　　.theta.2-.theta.1 ≧ 10 ° ... (3)
[0014]
(2) In the oriented electrical steel sheet according to (1), the particle diameter of the crystal grains in contact with the groove in the steel plate may be 5μm or more.
[0015]
(3) in the oriented electrical steel sheet according to the above (2), when viewed with the groove in the groove width direction cross section, the crystal grains of the thickness direction diameter existing in a lower portion of said groove in said steel sheet, 5μm or more, it may be and less thickness of the steel plate.
[0016]
(4) In the oriented electrical steel sheet according to any one of the above (1) to (3), when viewed with the grooves in the groove longitudinal cross section including the Mizonobe extension direction and the thickness direction, the groove arithmetic average height Ra of the roughness curve forming the contour of the groove bottom region of, and at 1μm or more 3μm or less, the average length RSm of a roughness curve element forming the contour of the groove bottom region, 10 [mu] m or more 150μm or less it may be.
Effect of the invention
[0017]
　According to this aspect of the present invention, with respect to grain oriented electrical steel sheet having grooves formed on the surface of the steel sheet for domain refining, to achieve both the minimization of maximizing the magnetic flux density decreases iron loss reducing effect well-balanced it is possible.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018]
FIG. 1 is a plan view of a grain-oriented electrical steel sheet 1 according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line A-A in FIG. 1 (a view as viewed groove 5 in cross-section including the Mizonobe extension direction).
3 is a sectional view taken along line the line B-B in FIG. 1 (Mizonobe view of the groove 5 in the cross section perpendicular to the lengthwise direction).
4 is a first explanatory diagram concerning a method of specifying an average depth D of the groove 5.
It is a second explanatory diagram concerning a method of specifying an average depth D of FIG. 5A] groove 5.
Is a third explanatory view relating to a method of identifying the average depth D of FIG. 5B] groove 5.
6 is a fourth explanatory diagram concerning a method of specifying an average depth D of the groove 5.
It is a first explanatory diagram concerning a method of identifying a contour of the grooves 5 in FIG 7A] groove width direction cross-section.
Is a second explanatory diagram concerning a method of identifying a contour of the grooves 5 in FIG. 7B] groove width direction cross-section.
8 is a third explanatory view relating to a method of identifying a contour of the groove 5 in the groove width direction cross-section.
Is a plan view schematically showing a secondary recrystallized grains existing in [9] the steel plate 2.
FIG. 10 is a first explanatory diagram concerning a method of specifying the groove bottom region 5d of the groove 5 in the groove longitudinal section.
11 is a second explanatory diagram concerning a method of specifying the groove bottom region 5d of the groove 5 in the groove longitudinal section.
Is a flowchart showing a manufacturing process of FIG. 12 oriented electrical steel sheet 1.
13 is a first explanatory view relating to a laser irradiation step S08 in the oriented electrical steel sheet 1 of the manufacturing process.
It is a second explanatory view relating to a laser irradiation step S08 in FIG. 14A] oriented electrical steel sheet 1 of the manufacturing process.
It is a third explanatory view relating to a laser irradiation step S08 in FIG. 14B] oriented electrical steel sheet 1 of the manufacturing process.
Is a fourth explanatory view relating to a laser irradiation step S08 in FIG. 14C] oriented electrical steel sheet 1 of the manufacturing process.
It is a fifth explanatory view relating to a laser irradiation step S08 in the manufacturing process of FIG. 15 oriented electrical steel sheet 1.
DESCRIPTION OF THE INVENTION
[0019]
　It will be described in detail preferred embodiments of the present invention. However, the present invention is not limited only to the configuration disclosed in this embodiment, and various modifications are possible without departing from the scope of the present invention. In addition, the numerical limitation range below the lower limit value and the upper limit value is included in the range.
　However, the numerical limitation range indicated as "super" the lower limit is not included lower limit does not include the upper limit value in the numerical limitation range indicated as "less than" the upper limit value.
[0020]
　It will be described in detail with reference to the accompanying drawings, an embodiment of the present invention.
　Figure 1 is a plan view of a grain-oriented electrical steel sheet 1 according to this embodiment. Figure 2 is a cross-sectional view taken along the line A-A in FIG. Figure 3 is a cross-sectional view taken along line B-B of FIG. Note that, in FIGS. 1 to 3, the rolling direction of the grain-oriented electrical steel sheet 1 X, grain-oriented electrical steel sheet 1 in the sheet width direction (direction perpendicular to the rolling direction in the same plane) Y, of the grain-oriented electrical steel sheet 1 the thickness direction (direction perpendicular to the XY plane) is defined as Z.
[0021]
　As shown in FIGS. 1-3, the grain-oriented electrical steel sheet 1, in combination with the cold rolling process and annealing process, the crystal orientation as the crystal grains of the easy magnetization axis and the rolling direction X matches is controlled a steel plate (the base steel) 2, a glass coating film 3 formed on the surface of the steel plate 2 (the surface of the steel sheet 2a), and an insulating film 4 formed on the surface of the glass coating film 3.
[0022]
　As shown in FIG. 1, the surface of the steel sheet 2a, for domain refining, a plurality of grooves 5 and the groove depth direction extends in a direction coincides with the thickness direction Z crossing the rolling direction X, They are formed at predetermined intervals along the rolling direction X. That is, FIG. 2, the one groove 5, a diagram viewed in cross-section including the Mizonobe running direction and the thickness direction Z. 3, the one groove 5, a diagram viewed in cross section perpendicular to Mizonobe lengthwise direction. Incidentally, the groove 5 may be provided so as to cross the rolling direction X, need not necessarily Mizonobe the extending direction and the rolling direction X is perpendicular. However, in the present embodiment, for convenience of descriptions, illustrate the case where the Mizonobe extending direction and the rolling direction X is perpendicular. The groove 5, when viewed from a thickness direction Z (if the grooves 5 in a plan view), may have an arcuate shape. However, in the present embodiment, for convenience of descriptions, it illustrates the groove 5 having a linear shape.
[0023]
　Steel plate 2 as chemical components, in mass fraction, Si: 0.8% ~ 7%, C: 0% ultra-0.085%, acid-soluble Al: 0% ~ 0.065%, N: 0% ~ 0.012%, Mn: 0% ~ 1%, Cr: 0% ~ 0.3%, Cu: 0% ~ 0.4%, P: 0% ~ 0.5%, Sn: 0% ~ 0 .3%, Sb: 0% ~ 0.3%, Ni: 0% ~ 1%, S: 0% ~ 0.015%, Se: 0% ~ 0.015%, containing the balance Fe and consisting of impurities.
[0024]
　Chemical components of the steel plate 2 is a preferred chemical composition in order to control the crystal orientation {110} <001> to Goss texture was integrated in orientation. Among the elements, Si and C is a basic element, acid-soluble Al, N, Mn, Cr, Cu, P, Sn, Sb, Ni, S, and Se are a selective element. Additional optional elements are not necessary to limit the lower limit value so may be contained according to the purpose, the lower limit value may be 0%. These selection elements be contained as an impurity, the effect of the present embodiment is not impaired. Steel 2 above, the remainder of the basic elements and selective elements described above may consist of Fe and impurities. Note that the impurities, in producing the steel plate 2 industrially means inevitably mixed elemental ore as a raw material, scrap or from the manufacturing environment and the like.
　Furthermore, it is common to undergo purification annealing during the secondary recrystallization in the electromagnetic steel sheets. Emissions to the outside of the system of the inhibitor-forming element occurs in the purification annealing. In particular N, decrease in concentration pronounced for S, it becomes 50ppm or less. If ordinary purification annealing conditions, 9 ppm or less, more 6ppm or less, if sufficiently performed purification annealing, reaches a degree that can not be detected (1 ppm or less) in the general analysis.
[0025]
　Chemical composition of the steel plate 2 may be measured by general analytical methods of steel. For example, the chemical components of the steel plate 2 may be measured using an ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Specifically, a test piece of 35mm angle from the central position of the steel plate 2 after film removal, by Shimadzu ICPS-8100, etc. (measuring device), by measuring under the conditions based on a previously prepared calibration curve It can be identified. Incidentally, C and S are combustion - infrared absorption method using, N is the inert gas fusion - can be measured with a thermal conductivity method.
[0026]
　Glass film 3, for example, forsterite (Mg 2 SiO 4 ), spinel (MgAl 2 O 4 ) or cordierite (Mg, 2 Al 4 Si 5 O 16 is constituted by a composite oxide such as). Although details will be described later, the glass coating film 3, the finish annealing step which is one of the manufacturing processes of the grain-oriented electrical steel sheet 1, a film formed to prevent the seizure occurs in the steel plate 2. Thus, the glass coating film 3 is not an essential element as a component of a grain-oriented electrical steel sheet 1.
[0027]
　Insulating film 4, for example, containing colloidal silica and phosphate, as well as electrical insulation, tension, has a role to provide corrosion resistance and heat resistance such as a steel plate 2.
[0028]
　Incidentally, the glass coating film 3 and the insulating film 4 of a grain-oriented electrical steel sheet 1, for example, can be removed by the following method. Oriented electrical steel sheet 1 having a glass coating film 3 or insulating coating 4, NaOH: 10% by mass + H 2 O: 90 wt% aqueous sodium hydroxide for 15 minutes at 80 ° C., immersion. Then, H 2 SO 4 : 10 wt% + H 2 O: 90 wt% aqueous solution of sulfuric acid, 3 minutes at 80 ° C., immersion. Thereafter, HNO 3 : 10 wt% + H 2 O: by the 90 wt% nitric acid aqueous solution, 1 minute weak at room temperature, washed immersed in. Finally, one minute less than with a blower of hot air and dried. Note that when removing the glass coating film 3 or insulating coating 4 from oriented electrical steel sheet 1 by the method described above, the shape and roughness of the groove 5 of the steel plate 2 is equivalent to the before forming a glass coating film 3 or insulating coating 4 it has been confirmed that there is.
[0029]
　As shown in FIG. 3, in this embodiment, (in this embodiment a direction parallel to the sheet width direction Y) extension direction Mizonobe viewing the groove 5 in cross section (groove width direction cross-sectional or groove widthwise cross section) perpendicular to the If the depth from the steel sheet surface 2a to the deepest of the groove 5 and groove depth Da, and about the groove width center GC of the groove 5 in the groove width direction (direction parallel to the rolling direction X in the present embodiment) to. As shown in FIG. 3, the grain-oriented electrical steel sheet 1 of the present embodiment, the deepest portion of the groove 5 is displaced to one side of the groove width direction from the groove width center GC, the cross-sectional shape of the groove 5 in the groove width direction it is asymmetrical shape relative to the groove width center GC.
[0030]
　Also, when viewing the groove 5 in the groove widthwise cross-section, the groove 5 has a first groove surface 5a and the second groove surface 5b is a pair of inclined surfaces inclined towards the surface of the steel sheet 2a at the deepest portion of the groove 5 have. Viewed from the deepest portion of the groove 5, the groove width center GC is located on the side of the second groove surface 5b. Further, a groove when viewed groove 5 in the widthwise cross section, the first groove end angle which the straight line Lb1 and the thickness direction Z is formed to obtain a first groove surface 5a is linearly approximated by a first angle .theta.1, second the angle between the second groove end straight line Lb2 and the plate thickness direction Z which is obtained by linear approximation groove face 5b and the second angle .theta.2.
[0031]
　In the present embodiment, the average depth D of the grooves 5 is at 10μm ultra 40μm or less, the grooves when viewing the groove 5 in the widthwise cross section, the deepest part of the groove 5 from the groove width center GC on one side of the groove width direction together are shifted, the cross-sectional shape of the groove 5 is asymmetrical shape relative to the groove width center GC in the groove width direction. Below, and referred to as the above depth condition characteristics relating to the average depth D of the groove 5, referred to above features relating to the cross-sectional shape of the groove 5 shape condition.
[0032]
　In a state where the depth conditions and the groove width of the shape satisfying the groove 5 as described above is fixed to a constant value, regardless of the value of the average depth D, the first angle θ1 is always acute, the second angle θ2 is always greater than the first angle .theta.1. In a state where the groove width of the groove 5 is fixed to a constant value, the first angle θ1 is smaller with increasing average depth D, the first angle θ1 with decreasing average depth D is increased .
[0033]
　If the average depth D is increased, the volume of the iron is removed from the steel plate 2 is increased, also increases the amount of decrease in magnetic flux density. However, if the first angle θ1 with increasing average depth D is reduced, since the demagnetizing field effects of the magnetic poles appearing on the sides of the groove 5 is increased, the magnetic domain subdivision effect (iron loss reducing effect) also increases. On the other hand, if the average depth D is reduced, the volume of the iron is removed from the steel plate 2 is decreased, which also decreases the amount of decrease in magnetic flux density. However, if the first angle θ1 with decreasing average depth D increases, the demagnetizing field effects of the magnetic poles appearing on the sides of the groove 5 becomes smaller, the iron loss reducing effect is also reduced.
[0034]
　Thus, when the maximum of the iron loss reducing effect by preferentially increasing the average depth D of the groove 5, while the decrease in the magnetic flux density becomes significant, the average of the groove 5 in preference to minimize the magnetic flux density decreases Decreasing the depth D, not obtain sufficient iron loss reducing effect. Result of the verification by the inventors, in order to achieve both a minimization of maximizing the magnetic flux density decreases iron loss reducing effect well-balanced, the groove 5, while satisfying the above shape conditions, the average of the groove 5 the depth D was found that it is important that meets the depth condition that 10μm ultra 40μm or less.
[0035]
　If the average depth D is 10 [mu] m or less (when the average depth D is shallower than 10 [mu] m), the volume of the iron is removed from the steel plate 2 is decreased, but also decreases the amount of decrease in magnetic flux density, the first angle θ1 because increases, demagnetization effects of the magnetic poles appearing on the sides of the groove 5 becomes smaller. As a result, if the average depth D is 10μm or less, sufficient iron loss reducing effect is obtained. On the other hand, (when the average depth D is deeper than 40 [mu] m) when the average depth D is greater than 40 [mu] m, since the first angle θ1 is smaller, the greater the demagnetizing field effects of the magnetic poles appearing on the sides of the groove 5, as a result , it obtained a large iron loss reducing effect. However, if the average depth D is greater than 40 [mu] m, the volume of the iron is removed from the steel plate 2 is increased, also increases the amount of decrease in magnetic flux density.
[0036]
　Thus, the case where the average depth D is 10μm or less, in the case where the average depth D is greater than 40μm, it is impossible to achieve both minimization of maximizing the magnetic flux density decreases iron loss reducing effect well-balanced . Accordingly, in the present embodiment, the above shape conditions, by average depth D is provided with a groove 5 that satisfies both the depth condition that 10μm ultrasonic 40μm or less in the steel plate 2, the maximum of the iron loss reducing effect flux and the minimization of density decrease is both well-balanced.
[0037]
　Incidentally, the depth condition and shape satisfying area is defined as the groove asymmetric regions in the groove 5, the existence ratio of the groove asymmetric region in Mizonobe extending direction alpha (= Mizonobe total length of the groove asymmetric region in the extension direction / grooves when defining the total length of 5), the larger α abundance of grooves asymmetric region in the groove 5, the effect of suppressing the lowering of the magnetic flux density is greater. Thus, the α abundance of grooves asymmetric region is preferably as large as possible. However, if there is a groove asymmetric region in at least some sections of the groove 5, the effect of the above can be obtained, the α abundance of grooves asymmetric regions may be greater than zero.
[0038]
　By the groove cross-sectional shape as the asymmetry, it is possible to achieve both the minimization of maximizing the magnetic flux density decreases iron loss reducing effect well-balanced. In other words, the groove of the cross-sectional shape asymmetrical, the volume of iron is suppressed that the cross-sectional shape is removed from the steel sheet as compared with the rectangular grooves, it is possible to suppress the decrease in magnetic flux density. The cross-sectional shape is asymmetrical grooves may be iron loss reducing effect is large cross section to suppress the decline of the iron loss effect by leaving a part shape close to a side surface of the rectangular groove.
　Asymmetric shape of the groove 5, it is preferable that the first angle θ1 and the second angle θ2 satisfies the following conditional expressions (1) to (3). Result of the verification by the present inventors, in order groove 5 satisfies the depth condition and shape condition, by a first angle θ1 and the second angle θ2 satisfies the following conditional expressions (1) to (3), balance between maximizing and minimizing the flux density reduction of the iron loss reducing effect is further optimized.
　　　　　　　　　　　　　° ≦ .theta.1 0 ≦ 50 ° ... (1)
　　　　　　　　　　　　　.theta.1 <.theta.2 ≦ 75 ° ... (2)
　　　　　　　　　　　　　.theta.2-.theta.1 ≧ 10 ° ... (3)
[0039]
　From the viewpoint of optimizing the balance between maximizing and minimizing the flux density reduction of the iron loss reducing effect, the lower limit value of the first angle θ1 is more preferably 20 °, also, a second angle θ2 between the first angle θ1 more preferably the difference (θ2-θ1) is 15 ° or more.
[0040]
　Meanwhile, when observing a groove widthwise cross section of the groove 5 with an electron microscope or the like, there is a case the boundary between the groove 5 and the steel sheet surface 2a, and the contour or the like of the groove 5 is unclear. Accordingly, the average depth D of the groove 5, the deepest portion of the groove 5 (groove depth Da), groove width center GC, how to identify a first groove surface 5a and the second groove surface 5b is important. In the following, an example of these specific methods.
[0041]
　As shown in FIG. 4, when viewing the groove 5 from a thickness direction Z (if the grooves 5 in a plan view), the observation range 50 and sets a part of the groove 5, along the Mizonobe extension direction more set virtually virtual lines L1 ~ Ln the observation range 50 of the (n lines). Observation range 50 is a region (i.e., a region where the shape of the groove bottom is stable) excluding the end portions in the extending direction of the groove 5 is preferably set to. For example, the observation range 50 may be an observation region, such as the length of Mizonobe extension direction is about 30 [mu] m ~ 300 [mu] m. Next, using a laser type surface roughness measuring instrument or the like, as measured along the surface roughness of the groove 5 to the virtual line L1, as shown in FIG. 5A, the measurement cross-section forming a Mizonobe extending direction of the contour of the groove 5 curve MCL1 is obtained in line with imaginary line L1.
[0042]
　After obtaining the profile curve by applying a low pass filter (cut-off value [lambda] s) to the measured profile curve MCL1 obtained for the imaginary line L1 as described above, the band filter in its cross-section curve (cut-off value .lambda.f, [lambda] c) by applying and removal of long wavelength components and short wavelength components from the profile curve, as shown in FIG. 5B, waviness curve LWC1 forming a Mizonobe extending direction of the contour of the groove 5 can be obtained in line with imaginary line L1. Waviness curve is a kind of contour curve together with the roughness curve described later, a roughness curve is particularly surface roughness of the contour whereas a profile curve that is suitable to indicate accurately, waviness curve contour a profile curve that is suitable for simplifying the shape itself in smooth lines.
[0043]
　As shown in Figure 5B, the use of waviness curve LWC1, at each location of the plurality along the imaginary line L1 (k pieces), the thickness between the outline of the steel sheet surface 2a and the groove 5 (i.e. waviness curve LWC1) distance direction Z (depth e1 ~ ek: unit [mu] m) is obtained. Furthermore, these depth e1 ~ mean value of ek (average depth D1) is obtained.
　The same measurement technique, for each well of the other virtual lines L2 ~ Ln, average depth D2 ~ Dn is obtained.
　In order to measure the distance between the contour of the steel sheet surface 2a and the groove 5 (waviness curve LWC1), it is necessary to measure the position of the steel sheet surface 2a in the Z direction (height) previously. For example, for each of a plurality of locations on the steel sheet surface 2a in the observation range 50, using a laser type surface roughness measuring instrument measures the position in the Z direction (height), the measurement results of the average surface of the steel sheet 2a it may be used as the height.
[0044]
　In the present embodiment, among the virtual lines L1 ~ Ln, the imaginary line in along and average depth Mizonobe extension direction satisfies the condition that is maximized is selected as the groove base line BL, for the groove base line BL average depth D of the groove 5 and the resulting average depth (in [mu] m) to define. For example, among the average depth D1 ~ Dn obtained for each of the virtual lines L1 ~ Ln, when the average depth D3 is maximum, as shown in FIG. 6, the virtual line L3 is defined as the groove base line BL , average depth D3 obtained for the imaginary line L3 is defined as the average depth D of the groove 5.
[0045]
　Further, as shown in FIG. 6, when viewing the groove 5 from a thickness direction Z (if the grooves 5 in a plan view), a direction orthogonal to Mizonobe extension direction (groove width direction: the rolling direction X in this embodiment virtually setting the observation range 50 in parallel imaginary line LS direction) parallel to the. As a virtual line LS is to be set to an arbitrary height in the thickness direction Z, using a laser type surface roughness measuring instrument, etc., measured along the surface roughness of the steel plate 2 which includes a groove 5 to the virtual line LS Then, as shown in FIG. 7A, the measurement cross-section curves MLS forming a groove width direction of the contour of the groove 5 obtained in line with imaginary line LS.
[0046]
　After obtaining the profile curve by applying a low pass filter (cut-off value [lambda] s) to the measured profile curve MLS obtained for the phantom line LS as described above, the band filter in its cross-section curve (cut-off value .lambda.f, [lambda] c) by applying and removal of long wavelength components and short wavelength components from the profile curve, as shown in FIG. 7B, waviness curve that forms the groove width direction of the contour of the groove 5 (hereinafter, referred to as the groove widthwise waviness curve) SWC is obtained in line with imaginary line LS. Waviness curve is a kind of contour curve together with the roughness curve described later, a roughness curve is particularly surface roughness of the contour whereas a profile curve that is suitable to indicate accurately, waviness curve contour a profile curve that is suitable for simplifying the shape itself in smooth lines.
[0047]
　As shown in FIG. 7B, the use of groove widthwise waviness curve SWC, at each location of the plurality (m pieces) along the imaginary line LS, the groove width direction of the contour surface of the steel sheet 2a and the groove 5 (i.e. groove widthwise thickness direction Z distance (depth d1 ~ dm between the waviness curve SWC): unit [mu] m) is obtained. In the present embodiment, as shown in FIG. 7B, the maximum value has waviness curve SWC is only one minimum value do not. In the present embodiment, of the depth d1 ~ dm obtained as described above, the largest value and the groove depth Da (the depth of the deepest portion of the groove 5). Further, as shown in FIG. 7B, the groove in the short waviness curve SWC, a region that satisfies the following conditional expression (4) defines a groove area 5c, the groove center GC of the center of the groove width direction of the groove area 5c to.
　　　　　　　　　　　≧ 0.05 × di Da ... (4)
　　　　　　　　　　(where, i is an integer of 1 ~ m)
[0048]
　Further, as shown in FIG. 8, on the groove widthwise waviness curve SWC showing the outline of the groove 5, a first groove surface 5a of the line segment which is inclined towards the surface of the steel sheet 2a at the deepest portion of the groove 5 and the second groove and surface 5b. As shown in FIG. 8, in the first groove surface 5a on the groove widthwise waviness curve SWC, the point at which the depth of the thickness direction Z from the steel sheet surface 2a becomes 0.05 × Da and P1, the steel sheet surface 2a the depth of the thickness direction Z from is to the point where the 0.50 × Da P2. In a second groove surface 5b on the groove widthwise waviness curve SWC, the point at which the depth of the thickness direction Z from the steel sheet surface 2a becomes 0.05 × Da and P3, the thickness direction Z from the steel sheet surface 2a depth and the point where the 0.50 × Da P4.
[0049]
　Furthermore, as shown in FIG. 8, a straight line connecting the point P1 and the point P2 in the first groove surface 5a and the first groove end straight line Lb1, the straight line connecting the points P3 and P4 in the second groove surface 5b second and Mizobata straight line Lb2. Thus, the angle formed between the first groove end straight line Lb1 and the thickness direction Z obtained from the groove widthwise waviness curve SWC is a first angle .theta.1, second groove end straight line obtained from the groove widthwise waviness curve SWC angle between Lb2 and the plate thickness direction Z is second angle .theta.2.
　Thus, in the present embodiment, the straight line connecting two points on the first groove surface 5a, although the first groove surface 5a has exemplified a case in which the linear approximation, linear approximation of the first groove surface 5a it may be used another method as a method for. For example, a first groove surface 5a may be linearly approximated using the least square method. The same applies to the linear approximation of the second groove surface 5b.
　Incidentally, the groove width W of the groove 5 is defined as the distance the surface of the steel sheet 2a and the intersection of the first groove surface 5a, and the surface of the steel sheet 2a and the intersection of the second groove surface 5b. Specifically, as shown in FIG. 8, when viewed in the groove widthwise cross section of the groove 5 may be calculated length of a line connecting the above point P1 and the point P3 (the groove opening) . The groove width W, in order to obtain preferred effects of magnetic domain refining is preferably 10 [mu] m ~ 250 [mu] m.
[0050]
　Incidentally, in the manufacturing process of the winding core, the processing is performed bending oriented electrical steel sheet 1. During bending, electromagnetic steel sheets processed grooves in the laser was found to be high probability that the steel sheet is broken starting from the groove. The present inventors have result of analyzing in detail the crystal structure of the groove or the like, if there is a small part of the particle size in the groove, that is broken when there is molten resolidified layers found that prone.
　As the molten resolidified layer in the groove 5 in the steel plate 2 is present, when a grain-oriented electrical steel sheet 1 is bent, breakage tends to occur starting from the molten resolidified layer. That is, when there are molten resolidified layer in the groove 5 in the steel plate 2, flexural properties of oriented electrical steel sheet 1 has concluded that lower.
[0051]
　Therefore, in this embodiment, the steel plate 2, it is preferred particle size of the crystal grains in contact with the groove 5 is 5μm or more in average. Surrounding groove 5, when there is a melt resolidification layer resulting from the formation of the groove 5, may not be obtained preferably flexural properties becomes high. Therefore, the periphery of the groove 5, it is preferred that no melting resolidification layer. If there is no near the molten resolidified layer of the groove 5, the particle diameter of the crystal grains in contact with the groove 5 (the secondary recrystallized grains) is 5μm or more in average. For example, the crystal shape of the molten resolidified layer may be a long columnar shape from the surface extending in the vertical direction. Therefore, the particle size of the crystal grains in contact with the groove 5 (the secondary recrystallized grains) is not a major axis length of columnar crystal is preferably short axis is 5μm or more. That is, the crystal grains in contact with the groove 5, when viewed in the direction electrical steel sheet 1 of the plate surface and the parallel viewing surface, it is preferable that the particle diameter of 5μm or more in average. The particle size of the crystal grains, for example, may be determined by a general grain diameter measuring standard method such as ASTM E112 reference, or EBSD may be obtained by (Electron Back Scattering Diffraction Pattern) method. Groove no melt solidification region of the 5, for example, it can be obtained by the manufacturing method described below.
[0052]
　In particular, the grooves even when viewing the groove 5 in the widthwise cross section, crystal grains existing in the lower portion of the groove 5 in the steel plate 2 thickness direction particle diameter 5μm or more and the thickness of the steel plate 2 (the secondary recrystallized grains) by more preferably less. This feature, the bottom of the groove 5 in the steel plate 2, the plate thickness direction grain size of crystal grains is meant that there is no fine particle layer of about 1 [mu] m (melting resolidification layer).
[0053]
　As shown in FIG. 9, when viewed the steel plate 2 from a thickness direction Z, of the secondary recrystallized grains present in the steel plate 2 particle size becomes 100mm about a maximum. On the other hand, when viewing the groove 5 in the groove widthwise cross-section thickness direction particle diameter of crystal grains present in the bottom of the groove 5 in the steel plate 2 (secondary recrystallized grains) is minimum becomes 5μm about, steel sheets up 2 having a thickness (e.g., 0.1 ~ 0.4 mm) the degree. Therefore, the lower limit of the secondary recrystallized grains in the thickness direction diameter that exists at the bottom of the groove 5 in the steel plate 2 is set to 5 [mu] m, it is preferable to set the upper limit to the thickness of the steel plate 2. Thus, by adopting the structure that no molten resolidified layer at the bottom of the groove 5, it is possible to improve the flexural characteristics of the grain-oriented electrical steel sheet 1.
[0054]
　The thickness of the insulating film 4 in the region where the groove 5 is formed is greater than the thickness of the insulating film 4 in the other region, the steel plate 2 and the insulating film 4 in the region where the groove 5 is formed adhesion is deteriorated as compared to other regions. As a result, cracks or peeling is likely to occur in the insulating film 4 around the groove 5. A crack or peeling occurs in the insulating film 4, rust is generated in the steel plate 2.
[0055]
　Therefore, in this embodiment, as shown in FIG. 2, when viewing the groove 5 in cross section (groove longitudinal cross section) including the Mizonobe running direction and the thickness direction Z, forms the contour of the groove bottom region 5d of the groove 5 arithmetic average height Ra of the roughness curve, and at 1μm or more 3μm or less, preferably 1.2μm or 2.5μm or less, or less even more preferably 1.3μm or more 2.3 .mu.m, the groove bottom region 5a the average length RSm of a roughness curve element forming the contour is at 10μm or 150μm or less, preferably 40μm or 145μm or less, it is preferable and more preferably is 60μm or more 140μm or less.
[0056]
　Surface roughness parameters (Ra, RSm) by satisfies the above range, since the groove bottom region 5d of the groove 5 is roughened certain degree, the steel plate 2 and the glass coating film 3 or the insulating film 4 by the anchor effect adhesion is improved. Therefore, cracks or peeling hardly occurs in the glass coating film 3 or the insulating film 4 in the peripheral groove 5. As a result, it is possible to improve the rust resistance of the grain-oriented electrical steel sheet 1.
[0057]
　However, as shown in FIG. 3, in the width direction of the groove 5, the depth of the groove 5 is not necessarily constant. Therefore, how to identify the groove bottom region 5d when viewing the groove 5 in the groove longitudinal section is important. Hereinafter, an example of a specific method of the groove bottom region 5d when viewing the groove 5 in the groove longitudinal section.
[0058]
　Figure 10 is a cross-sectional view taken along line C-C of FIG. That is, FIG. 10 is a view of the groove 5 in the groove longitudinal cross section including a groove base line BL and the plate thickness direction Z of the above. As shown in FIG. 10, those obtained by converting the measured profile curve forming the outline of the groove 5 appearing in the groove longitudinal sectional undulation curve defining the groove longitudinal waviness curve LWC. The groove longitudinal waviness curve LWC after obtaining the profile curve by applying a low pass filter (cut-off value [lambda] s) to the measured profile curve obtained for the groove reference line BL, and the band filter (cut-off value on the profile curve .lambda.f, by applying the [lambda] c), obtained by excluding the longer wavelength component and a shorter wavelength component from the cross section curve. It is a cross-sectional view taken along line C-C of FIG. That is, FIG. 10 is a view of the groove 5 in the groove longitudinal cross section including a groove base line BL and the plate thickness direction Z of the above. In this embodiment, as shown in FIG. 10, when viewing the groove 5 in the groove longitudinal cross section including a groove base line BL and the plate thickness direction Z, the contour of the groove 5 appearing in the observation range 50 and the groove bottom region 5d to.
[0059]
　The groove bottom region 5d of the groove 5 are identified by the methods described above. That is, in this embodiment, as shown in FIG. 11, a measurement section curve forming the contour of the groove bottom region 5d of the grooves 5 to appear in the observation range 50 of the groove longitudinal cross section including a groove base line BL and the plate thickness direction Z transform arithmetic average height Ra of the obtained roughness curve RC and the are at 1μm or more 3μm or less, preferably 1.2μm or 2.5μm or less, more preferably be 1.3μm or 2.3μm or less the groove bottom region 5d measuring section average length of curve converted roughness curve element obtained RSm forming the contour of, and at 10μm or 150μm or less, preferably 40μm or 145μm or less, more preferably the it is 60μm above 140μm or less. Roughness curve RC, after obtaining section curves by applying a low-pass filter cut-off values ​​λs on the measurement cross section curves obtained for the groove reference line BL, and a high-pass filter in its cross-section curve (cut-off value [lambda] c) by applying, obtained by excluding the long wavelength component from the profile curve. As described above, the roughness curve RC is a contour curve suitable for particular indicate accurately the surface roughness of the contour. The definition of the mean length RSm of the roughness curve RC of the arithmetic mean height Ra and roughness profile elements are according to Japanese Industrial Standard JIS B 0601 (2013).
[0060]
　As described above, according to the grain-oriented electrical steel sheet 1 according to this embodiment, since the depth condition and shape satisfying the groove 5 is provided on the steel plate 2, maximizing the magnetic flux density of the iron loss reducing effect it is possible to achieve both minimization of decrease in good balance.
　Further, according to this embodiment, because it uses a structure in which there is no lower in melting resolidification layer of the groove 5 in the steel plate 2, thereby improving the flexural properties of the grain-oriented electrical steel sheet 1.
　Further, according to this embodiment, the groove bottom region 5d arithmetic average height Ra of the roughness curve RC which forms the outline of is at 1μm or more 3μm or less, the average length of roughness curve element RSm is at 10μm or 150μm or less because it uses a configuration that there, it is possible to improve the rust resistance of the grain-oriented electrical steel sheet 1.
[0061]
　Further, as shown in FIG. 3, in the above embodiment, although the absence of the glass coating film 3 in the groove 5 (the average thickness of that is the glass coating film 3 is a state of 0 .mu.m) illustrates, the groove 5, the average thickness of 0μm super 5μm below the glass coating film 3, average thickness and a 5μm or less of the insulating film 4 over 1μm may be disposed. In addition, the steel sheet surface 2a, a glass coating film 3 of 0.5μm or more 5μm or less the average thickness, the average thickness of the and 5μm or less of the insulating film 4 over 1μm may be disposed. Furthermore, the average thickness of the glass coating film 3 in the groove 5 may be thinner than the average thickness of the glass coating film 3 in the steel sheet surface 2a.
[0062]
　As described above, by setting the thickness of the glass coating film 3 and the insulating film 4, since the cracking or peeling is less likely to occur in the insulating film 4 around the groove 5, rust resistance of the grain-oriented electrical steel sheet 1 There is further improved. Further, by adopting a configuration in which no glass film 3 in the groove 5 (that is configured average thickness of the glass coating film 3 is 0μm in groove 5), the walls of the grooves facing each other the distance (groove width) since it is possible to more narrowly, it is possible to further improve the iron loss reducing effect by the groove 5.
[0063]
　The direction in the above embodiment has exemplified the oriented electrical steel sheet 1 with a glass coating film 3, since the glass film 3 is not an essential component, as, to be composed of only the steel plate 2 and the insulating film 4 for even sex electromagnetic steel sheets, by applying the present invention, the above effect can be obtained. The grain-oriented electrical steel sheet comprised of only the steel plate 2 and the insulating film 4, the groove 5, the average thickness is arranged 5μm or less of the insulating film 4 over 1 [mu] m, the steel sheet surface 2a, an average thickness of 1 [mu] m or more 5μm or less insulating film 4 may be disposed.
[0064]
　Next, a method for manufacturing a grain-oriented electrical steel sheet 1 according to this embodiment.
　Figure 12 is a flowchart showing a manufacturing process of the grain-oriented electrical steel sheet 1. As shown in FIG. 12, the first casting step S01, a mass fraction, Si: 0.8% ~ 7% , C: 0% ultra-0.085%, acid-soluble Al: 0% ~ 0.065 %, N: 0% ~ 0.012 %, Mn: 0% ~ 1%, Cr: 0% ~ 0.3%, Cu: 0% ~ 0.4%, P: 0% ~ 0.5%, Sn: 0% ~ 0.3%, Sb: 0% ~ 0.3%, Ni: 0% ~ 1%, S: 0% ~ 0.015%, Se: 0% ~ 0.015%, containing and the balance is supplied to the molten steel continuous casting machine having a chemical composition consisting of Fe and impurities, the slab is issued manufactured continuously.
[0065]
　Subsequently, the hot-rolling step S02, after the slab obtained from the casting step S01 is heated to a predetermined temperature (e.g. 1150 ~ 1400 ° C.), the hot rolling is performed on the slabs. Thus, for example, hot-rolled steel sheet is obtained having a thickness of 1.8 ~ 3.5 mm.
[0066]
　Subsequently, the annealing step S03, with respect to hot-rolled steel sheet obtained from hot rolling step S02, the annealing treatment under a predetermined temperature condition (e.g., conditions of heating at 750 - 1200 ° C. 30 seconds to 10 minutes) It is carried out. Subsequently, the cold-rolling step S04, after the pickling process is carried out on the surface of the hot-rolled steel sheet annealing process is performed at the annealing step S03, the cold rolling is performed on the hot-rolled steel sheet. Thus, for example, cold rolled steel sheet is obtained having a thickness of 0.15 ~ 0.35 mm.
[0067]
　Subsequently, the decarburization annealing step S05, with respect to cold-rolled steel sheet obtained from the cold-rolling step S04, under a predetermined temperature condition (e.g., conditions of heating 1-3 minutes at 700 ~ 900 ° C.) heat treatment ( that is, the decarburization annealing process) is performed. When such decarburization annealing process is performed, in cold-rolled steel sheet, the carbon is reduced below a predetermined amount, the primary recrystallization structure is formed. Further, in the decarburization annealing step S05, the surface of the cold rolled steel sheet, silica (SiO 2 oxide layer containing)
[0068]
　Then, the annealing separator application step S06, the annealing separator containing magnesia (MgO) as the main component, is applied to the surface (the surface of the oxide layer) of the cold-rolled steel sheet. Subsequently, the final annealing step S07, with respect to cold-rolled steel sheet annealing separator is coated, heat treated under predetermined temperature conditions (e.g. conditions of heating at 1100 ~ 1300 ℃ 20 ~ 24 hours) (i.e., finish annealing treatment) is performed. If such final annealing process is performed, the secondary recrystallization with resulting cold-rolled steel sheets, cold-rolled steel sheet is purified. As a result, has a chemical composition of the steel plate 2 described above, the groove 5 of the cold-rolled steel sheet (i.e. oriented electrical steel sheet 1 which crystal orientation is controlled so that the crystal grains of the easy magnetization axis and the rolling direction X coincide steel 2) in a state before forming is obtained.
[0069]
　Further, when such final annealing process as described above is performed, an oxide layer containing silica as a main component reacts with annealing separator containing magnesia as a main component, forsterite on the surface of the steel plate 2 ( mg 2 SiO 4 glass coating film 3 containing) composite oxide or the like is formed. In the finish annealing step S07, finish annealing process is performed in a state in which the steel plate 2 is coiled. By glass coating film 3 is formed on the surface of the steel plate 2 during the finish annealing process, it is possible to prevent the burn-in steel plate 2 which is coiled occurs.
[0070]
　Plurality Then, the laser irradiation step S08, by irradiating the laser with respect to the glass coating film 3 is formed steel sheet second surface (one side only), the surface of the steel plate 2, extending in a direction crossing the rolling direction X grooves 5 of are formed at predetermined intervals along the rolling direction X. Hereinafter, with reference to FIGS. 13 to 15, it will be described in detail laser irradiation step S08.
[0071]
　As shown in FIG. 13, in the laser irradiation step S08, the laser light YL emitted from the laser light source (not shown) is transmitted through the optical fiber 9 to the laser irradiation apparatus 10. The laser irradiation apparatus 10 incorporates a polygon mirror and its rotary drive (both not shown).
　The laser irradiation apparatus 10, by the rotation of the polygon mirror, and irradiates toward a laser beam YL on the surface of the steel plate 2, the laser beam is scanned YL substantially parallel to the plate width direction Y of the steel plate 2.
[0072]
　Simultaneously with the irradiation of the laser beam YL, assist gas 25 such as air or an inert gas, is blown to the portion of the steel plate 2 that laser light YL is irradiated. The inert gas, for example, nitrogen or argon. Assist gas 25 is responsible for removing the melted or vaporized components from the steel plate 2 by the laser irradiation. By blowing the assist gas 25, since the laser beam YL reaches the steel plate 2 without being inhibited by melting or evaporated components described above, the groove 5 is formed stably. Further, by blowing the assist gas 25, the components can be prevented from adhering to the steel plate 2. As a result, the groove 5 along a scanning line of the laser beam YL are formed. Further, as described above, by blowing the assist gas 25, the result of component has been removed, it is possible to obtain a structure that no molten resolidified layer at the bottom of the groove 5.
[0073]
　In the laser irradiation step S08, while being conveyed along the sheet passing direction steel plate 2 coincides with the rolling direction X, the laser light YL is irradiated to the surface of the steel plate 2. Here, as the grooves 5 are formed along the rolling direction X at a predetermined interval PL, the rotational speed of the polygon mirror is controlled synchronously with respect to the conveying speed of the steel plate 2. As a result, as shown in FIG. 13, the surface of the steel plate 2, a plurality of grooves 5 crossing the rolling direction X, it is formed at predetermined intervals PL along the rolling direction X.
[0074]
　As the laser light source can be used, for example a fiber laser. YAG laser, semiconductor laser, or CO, 2 generally high power laser used in industrial laser or the like may be used as a laser light source. Further, as long as it is possible to form the groove 5 in a stable manner may be used pulsed laser or a continuous wave laser, a laser light source. As the laser beam YL, light harvesting high, it is preferable to use a single mode laser suitable for forming the grooves.
[0075]
　As the irradiation conditions of the laser beam YL, e.g., a laser output to 200 W ~ 3000W, (diameter containing 86% of i.e. laser output, less 86% diameter abbreviated described) condensing spot diameter in the rolling direction X of the laser beam YL a to 10 [mu] m ~ 1000 .mu.m, focusing spot diameter in the sheet width direction Y of the laser beam YL (86% diameter) in 10 [mu] m ~ 1000 .mu.m, the laser scanning speed 5m / s ~ 100m / s, the laser scanning pitch (interval PL) it is preferable to set to 4mm ~ 10mm. As desired groove depth D is obtained, it may be suitably adjusted to these laser irradiation conditions. For example, in the case of obtaining a deeper groove depth D is set slow laser scanning speed may be set higher laser output.
[0076]
　As shown in FIG. 14A, when viewing the groove 5 from the laser scanning direction (Mizonobe lengthwise direction), the angle (laser irradiation angle) between the irradiation direction in the thickness direction Z and the laser light YL is defined as φ1 when, as the first angle θ1 in the groove widthwise cross section of the groove 5 desired to obtain, it is preferable to set the laser irradiation angle φ1 in the range of 10 ~ 45 °. Thus, it is possible to make the cross-sectional shape of the groove 5 in the asymmetric shape as shown in FIG. Although the assist gas 25 is injected so as to follow the laser beam YL, when the laser irradiation angle φ1 is set within the range described above, the injection direction (injection angle) of the assist gas 25 is not particularly limited.
[0077]
　On the other hand, by setting as follows the injection direction of the assist gas 25, it is possible to make the cross-sectional shape of the groove 5 in the asymmetric shape as shown in FIG. As shown in FIG. 14B, a steel plate 2 which is conveyed along a parallel sheet passing direction TD in the rolling direction X in a plan view, in the laser scanning direction SD of the laser beam YL (direction parallel to the sheet width direction Y) from a direction having an inclination angle φ2 for the assist gas 25 is injected so as to follow the laser beam YL. Further, as shown in FIG. 14C, when viewed the steel sheet 2 is conveyed along the sheet passing direction TD from the plate width direction Y (the laser scanning direction SD), a direction having an inclination angle φ3 relative to the surface of the steel sheet 2a from the assist gas 25 is injected so as to follow the laser beam YL. Angle φ2 is preferably set in a range of less than 180 ° 90 ° or more, the angle φ3 is preferably set in the range of 1 ° or more 85 ° or less.
　Additionally, present in the sheet passing the atmosphere of the steel plate 2, the number of particles having a size of at least 0.5μm is, 1CF is preferably performed in an atmosphere controlled so that the (cubic feet) 10 or more than 10,000 per.
[0078]
　In particular, by the assist gas injection angle φ3 for the assist gas injection angle φ2 and the steel sheet surface 2a relative to the laser scanning direction is set in the above range, it is possible controlled asymmetrically showing a sectional shape of the groove 5 in FIG. 3, the groove bottom surface roughness of the region 5d and (Ra, RSm) can be accurately controlled. In addition, by the quantity of particles having a size of at least 0.5μm present in the sheet passing atmosphere set in the above range, the surface roughness of the groove bottom region 5d (particularly RSm) can be more accurately controlled . Further, the flow rate of the assist gas 25, it is preferable to set within the following range per minute 10-1000 liters. However, when the flow rate of the assist gas 25 is below min 50 liters, the lower the melt resolidified layer of the groove 5 tends to occur. Accordingly, the flow rate lower limit value of the assist gas 25, and more preferably min 50 l greater.
[0079]
　Conventionally, when forming the groove by the laser irradiation, for cross-section to form efficiently a rectangular groove (i.e. groove having a symmetrical shape), the direction (thickness direction) perpendicular to the surface of the steel sheet, It was injected toward the assist gas to the steel sheet surface so as to follow the laser. In contrast, the present inventors have result of intensive studies, by defining a jetting direction of the irradiation direction and the assist gas 25 of the laser beam YL 3-dimensionally as shown in FIG. 14A ~ FIG 14C, the groove 5 the cross-sectional shape can not only accurately controlled asymmetrical shape satisfying the above (1) to (3), by the amount of particles in the strip passing atmosphere during laser irradiation also defines a surface roughness of the groove bottom region 5d (Ra, RSm) was found to be able to accurately control the.
[0080]
　The present inventors have, by a novel manufacturing method as described above, to form a groove having an asymmetrical shape that satisfies the above (1) to (3) in the oriented electrical steel sheet, the greatest iron loss reducing effect of the the minimization of the magnetic flux density decreases be compatible with good balance, found to be able to further improve the rust resistance, it was accomplished the present invention. Therefore, the manufacturing method of the grain-oriented electrical steel sheet according to the present embodiment (in particular laser irradiation step) is a novel manufacturing method by those skilled in the art can not expect, the grain oriented electrical steel sheet 1 also those skilled obtained thereby and it has a novel structure which can not be expected (the surface roughness of the cross-sectional shape and a groove bottom region 5d of the groove 5).
[0081]
　By one laser irradiation apparatus 10, when it is difficult to form the groove 5 in the entire plate width direction Y of the steel plate 2, as shown in FIG. 15, by using the laser irradiation apparatus 10 in a plurality, a groove may be formed 5 across the plate width direction Y of the steel plate 2. In this case, as shown in FIG. 15, a plurality laser irradiation unit 10 are arranged at predetermined intervals along the rolling direction X. Further, when viewed from the rolling direction X, so that the laser scanning line of the laser irradiation apparatus 10 do not overlap each other, the position in the sheet width direction Y of the laser irradiation device 10 is set. By adopting the laser irradiation method shown in this FIG. 15, it is possible to form a plurality of grooves 5 as shown in FIG. 1 on the surface of the steel sheet 2a.
[0082]
　Referring back to FIG. 12, the end of the insulating film forming step S09, the laser irradiation process steel sheet surface 2a of the groove 5 is formed by S08 described above, containing, for example, colloidal silica and phosphate insulation coating liquid is applied from above the glass coating film 3. Then, by heat treatment under predetermined temperature conditions (e.g. 840 ~ 920 ° C.) is carried out, finally, as shown in FIGS. 1 to 3, the steel plate 2 groove 5 is formed, the glass coating film 3 and It is oriented electrical steel sheet 1 and a dielectric film 4 is obtained.
[0083]
　Steel plate 2 oriented electrical steel sheet 1 manufactured as described above, as chemical components, in mass fraction, Si: 0.8% ~ 7%, C: 0% ultra-0.085%, acid-soluble Al : 0% ~ 0.065%, N: 0% ~ 0.012%, Mn: 0% ~ 1%, Cr: 0% ~ 0.3%, Cu: 0% ~ 0.4%, P: 0 % ~ 0.5%, Sn: 0% ~ 0.3%, Sb: 0% ~ 0.3%, Ni: 0% ~ 1%, S: 0% ~ 0.015%, Se: 0% ~ 0.015%, it contains, with the balance being Fe and impurities.
[0084]
　In the above embodiment, before the insulating film 4 is formed on the surface of the steel sheet 2a, a groove 5 on the surface of the steel sheet 2a by the laser irradiation, a manufacturing process of subsequently forming an insulating film 4 on the surface of the steel sheet 2a the case of employing illustrated. In the present embodiment, not limited to this, after the insulating film 4 is formed on the surface of the steel sheet 2a, by irradiating a laser beam YL toward the surface of the steel sheet 2a from above the insulating film 4, the groove 5 on the surface of the steel sheet 2a it may be adopted a manufacturing process of forming a. In this case, since the groove 5 immediately after the laser irradiation is exposed to the outside, after the formation of the groove 5, again, it is necessary to form the insulating film 4 on the steel plate 2. Or, in this embodiment, after the groove 5 is formed on the steel plate 2, the glass coating film 3 or insulating coating 4 may be formed.
[0085]
　Therefore, the grain-oriented electrical steel sheet according to the present embodiment include, but are oriented electrical steel sheet 1 which high-temperature annealing has the completed and coating of the glass coating film 3 and the insulating film 4 has been completed for the secondary recrystallization, similarly to also include oriented electrical steel sheet after the it was and groove 5 is formed before the coating of the glass coating film 3 or insulating coating 4 is completed. That is, using the grain-oriented electrical steel sheet according to the present embodiment, as a post-process, may be obtained a final product by performing the formation of the glass coating film 3 or insulating coating 4. Incidentally, as described above, when removing the glass coating film 3 or the insulating film 4 by the above-described film removal process from the glass coating film 3 or insulating coating 4 oriented electrical steel sheet 1 which is formed, the shape and roughness of the groove 5 it has been confirmed that the equivalent before forming the glass coating film 3 or insulating coating 4.
[0086]
　In the above embodiment, a case has been exemplified for implementing the laser irradiation step S08 after the finish annealing step S07, the laser irradiation step may be carried out between the cold rolling steps S04 and decarburization annealing step S05 . That is, by performing laser irradiation and the assist gas injection against cold-rolled steel sheet obtained from the cold-rolling step S04, after forming the trench 5 on the steel sheet surface 2a of the cold-rolled steel sheet, leaving for the cold-rolled steel sheet charcoal annealing may be performed.
Example
[0087]
　Hereinafter, a more detailed explanation of the effect of one embodiment of the present invention through examples, conditions in examples are an example of conditions adopted for confirming the workability and effects of the present invention, the invention is not limited to this single example of conditions. The present invention does not depart from the gist of the present invention, as far as it achieves the object of the present invention may employ various conditions.
[0088]
[Verification of balance between maximizing and minimizing the flux density reduction of the iron loss reducing effect 1]
　First, the grain-oriented electrical steel sheet used in this validation 1 was prepared as follows.
In mass fraction, Si: 3.0%, C: 0.08%, acid-soluble Al: 0.05%, N: 0.01 %, Mn: 0.12%, Cr: 0.05%, Cu : 0.04%, P: 0.01% , Sn: 0.02%, Sb: 0.01%, Ni: 0.005%, S: 0.007%, Se: 0.001%, containing and the balance hot rolling is performed on a slab having a chemical composition consisting of Fe and impurities, hot-rolled steel plate having a thickness of 2.3mm was obtained.
[0089]
　Subsequently, to the above hot-rolled steel sheet, annealing under temperature conditions of heating for 1 minute was performed at 1000 ° C.. After the pickling treatment is carried out on the surface of the hot-rolled steel sheet annealing process is performed, cold rolling is performed on the hot-rolled steel sheet, cold-rolled steel plate having a thickness of 0.23mm were obtained. Subsequently, to the above cold-rolled steel sheet, after the decarburization annealing under the temperature condition is performed of heating 2 minutes at 800 ° C., annealing separator containing magnesia (MgO) as the main component, It applied to the surface of the cold rolled steel sheet.
[0090]
　Subsequently, with respect to cold-rolled steel sheet annealing separator is applied, final annealing process was performed under the temperature condition of heating at 1200 ° C. 20 hours. As a result, has the chemical composition described above, cold-rolled steel sheet crystal orientation is controlled so that the crystal grains of the easy magnetization axis and the rolling direction coincides (steel sheet glass coating film is formed on the surface) was obtained .
[0091]
　Subsequently, as described above, by the laser is irradiated to the surface of the steel sheet glass coating film is formed on the surface of the steel sheet, a plurality of grooves extending in a direction crossing the rolling direction, along the rolling direction It formed at a predetermined interval Te.
　The irradiation conditions of the laser beam YL, so that a desired groove depth D is obtained in the range laser output of 200 W ~ 3000W, focusing spot diameter in the rolling direction X of the laser beam YL (86% diameter) is 10μm in the range of ~ 1000 .mu.m, with the range of the focusing spot diameter (86% diameter) of 10 [mu] m ~ 1000 .mu.m in the sheet width direction Y of the laser beam YL, range laser scanning speed is 5m / s ~ 100m / s, the laser scanning pitch (interval PL) is adjusted in the range of 4 mm ~ 10 mm.
　Further, as desired first angle θ1 and the second angle θ2 is obtained in the groove widthwise cross section of the groove 5, the assist gas injection angle φ2 with respect to the laser scanning direction is adjusted in a range of 90 ° or more than 180 °, assist gas injection angle φ3 to the steel sheet surface was adjusted within the following range 85 ° to 1 °.
[0092]
　As described above, with respect to grooved steel sheet under the temperature condition that the insulating coating solution containing colloidal silica and phosphate is then coated over the glass coating film is heated for 1 minute at 850 ° C. in the heat treatment is performed, and finally, the steel sheet which the grooves are formed, oriented electrical steel sheet with a glass coating film and an insulating film was obtained.
[0093]
　Finally obtained steel sheet of the oriented electrical steel sheet (steel sheet in which grooves are formed) mainly, Si: contained 3.0%.
[0094]
　By the above-described processes, as shown in Table 1, as oriented electrical steel sheet that corresponds to the test numbers 1-8, (the unit [mu] m) average depth D of the grooves and groove width W (unit [mu] m) are different to prepare a grain-oriented electrical steel sheet. In all of the directional electromagnetic steel plates corresponding to the test Nos. 1 to 8, the first angle θ1 when viewing the groove 5 in the groove widthwise cross section is set to 45 °, the second angle θ2 is set to 60 ° .
[0095]
　Oriented electrical steel sheet that corresponds to the test numbers 3-7, provided that the average depth D of the groove is 10μm ultrasonic 40μm or less and (condition 1), the condition that the first angle θ1 is 0 ° to 50 ° (condition 2) If a condition that the second angle .theta.2 is larger and 75 ° or less than the first angle .theta.1 (condition 3), the difference value (.theta.2-.theta.1) is a proviso that more than 10 ° with the second angle .theta.2 first angle .theta.1 ( condition 4) a grain-oriented electrical steel sheet of the inventive example satisfying. Oriented electrical steel sheet that corresponds to the test numbers 1, 2 and 8 are oriented electrical steel sheets of the comparative examples satisfying only the condition 2-4. Further, in all of the grain-oriented electrical steel sheet that corresponds to the test numbers 1-8, the existence ratio of the groove asymmetric region in Mizonobe extension direction α was 70% or more. It is to be the embodiment that adjusts the laser irradiation conditions within the ranges described in the above embodiments, those deviating from the scope thereof are comparative examples.
[0096]
　For each corresponding oriented electrical steel sheet in the test numbers 1-8, the iron loss W17 / 50, were measured and decrease ΔB8 magnetic flux density B8. The results of the measurements are shown in Table 1. Note that the iron loss W17 / 50, the test pieces of a grain-oriented electrical steel sheet (for example, 100 mm × 500 mm test pieces), the magnetic flux density 1.7 T, per unit weight measured at excitation conditions at a frequency 50Hz energy loss (in W / kg) is. Further, the decrease amount ΔB8 magnetic flux density B8, a value obtained by subtracting the magnetic flux density B8 were measured after the groove formed from the magnetic flux density B8 were measured before groove formation (in G). The magnetic flux density B8 of the front groove forming is 1.910T (= 19100G), iron loss W17 / 50 before the groove formation was 0.97W / kg.
[0097]
　As shown in Table 1, the grain-oriented electrical steel sheet of the comparative example (hereinafter average depth D of the groove is 10 [mu] m) corresponding to the test Nos. 1 and 2, most of iron loss W17 / 50 as compared to prior grooved change not (that is, small iron loss improvement effect). Further, the grain-oriented electrical steel sheet of the comparative example (the average of the groove depth D is 40μm greater) corresponding to the test number 8, a small reduction effect of suppressing the decrease ΔB8 is very large (i.e. the magnetic flux density B8 of the magnetic flux density B8 ).
[0098]
　On the other hand, as shown in Table 1, the grain-oriented electrical steel sheet of the present invention examples corresponding to Test Nos 3-7, is large compared to iron loss W17 / 50 is significantly reduced by (i.e. iron loss improvement effect as before groove formation ) with, a large reduction effect of suppressing the decrease ΔB8 is suppressed to a relatively small value (i.e. the magnetic flux density B8 of the magnetic flux density B8). By this verification 1 as described above, in order to achieve both a minimization of maximizing the magnetic flux density decreases iron loss reducing effect good balance, it has been confirmed that it is necessary to satisfy all the above conditions 1-4.

The scope of the claims
[Claim 1]
　In grain-oriented electrical steel sheet comprising and groove depth direction extends in a direction crossing the rolling direction of the steel sheet having a become grooves formed steel surface thickness direction,
　average depth D of the groove 10μm ultrasonic 40μm or less,
　when viewed the groove in the groove width direction cross section perpendicular to Mizonobe lengthwise direction,
　when defining the groove width around the center of the groove in the groove width direction,
　the deepest portion of the groove is the groove width center wherein together are offset to one side of the groove width direction, wherein a asymmetrical shape relative to the said groove width center in the cross-sectional shape wherein the groove width direction of the groove, from
　when viewed the groove in the groove width direction cross section,
　said groove, said has a steel plate surface with a first groove surface and a second groove surface is a pair of inclined surfaces inclined toward the deepest portion of the groove,
　the groove width center are viewed from the deepest portion located on the side of the second groove surface,
　a straight line the first groove surface The angle between the first groove end straight line obtained by approximating said plate thickness direction is defined as a first angle .theta.1,
　the second groove end straight line obtained by linearly approximating the second groove surface and the thickness direction when the angle defined between the second angle .theta.2,
　the first angle θ1 and the second angle .theta.2 is, to satisfy the following conditional expressions (1) to (3)
oriented electrical steel sheet, characterized in that.
　　　　　　　　　° ≦ .theta.1 0 ≦ 50 ° ... (1)
　　　　　　　　　.theta.1 <.theta.2 ≦ 75 ° ... (2)
　　　　　　　　　.theta.2-.theta.1 ≧ 10 ° ... (3)
[Claim 2]
　Oriented electrical steel sheet according to claim 1 in the steel plate, wherein the grain size of the crystal grains in contact with the groove is 5μm or more.
[Claim 3]
　When viewed the groove in the groove width direction cross section,
　the thickness direction particle diameter of crystal grains present at the bottom of the groove in the steel plate, 5 [mu] m or more, and less thickness of the steel sheet
and wherein the oriented electrical steel sheet according to claim 2.
[Claim 4]
　When viewed the groove in groove longitudinal cross section including the Mizonobe extension direction and the thickness direction,
　the arithmetic mean height Ra of the roughness curve forming the contour of the groove bottom region of the groove, it is 1μm or more 3μm or less ,
　the average length RSm of a roughness curve element forming the contour of the groove bottom region is 10μm or more 150μm or less
oriented electrical steel sheet according to any one of claims 1 to 3, characterized in that.