Technical field
[0001]The present invention relates to an excellent grain-oriented electrical steel sheet to film adhesion. In particular, the present invention relates to oriented electrical steel sheet excellent in film adhesion of the insulating film even without forsterite coating.
　This application, on July 13, 2017, claiming priority on Japanese Patent Application No. 2017-137443 filed in Japan, the contents of which are incorporated herein.
BACKGROUND
[0002]
　Oriented electrical steel sheet is a soft magnetic material, mainly because it is used as a core material of a transformer, the magnetic characteristics are required of high magnetic characteristics and low iron loss. The magnetic properties, a magnetic flux density induced when exciting the iron core. Higher magnetic flux density is high, it is possible to reduce the size of the core is advantageous in terms of transformer device configuration, and is advantageous in terms of cost of manufacturing the transformer.
[0003]
　To increase the magnetization characteristics, aligned in parallel to {110} plane in the steel sheet surface, and it is necessary to control the texture to <100> crystal orientation axes are aligned in the rolling direction (Goss orientation). To integrate the crystal orientation Goss orientation, AlN, MnS, and inhibitors of such MnSe by finely precipitated in the steel, it is possible to control the secondary recrystallization, usually performed.
[0004]
　The iron loss, when excited core with alternating magnetic field, a power loss consumed as heat energy. From the viewpoint of energy saving of power, iron loss, it is required as low as possible. The level of the iron loss, magnetic susceptibility, the plate thickness, film tension, the amount of impurities, electrical resistivity, grain size, domain size and the like is affected. Relates electromagnetic steel, even in currently various techniques have been developed to enhance the energy efficiency, research and development to reduce the iron loss is continued constantly.
[0005]
　Another characteristic required of the grain-oriented electrical steel sheet, there is a characteristic of the film formed on the base steel sheet surface. Usually, in the grain-oriented electrical steel sheet, as shown in FIG. 1, Mg on the base steel sheet 1 2 SiO 4 forsterite film 2 composed mainly of (forsterite) Forsterite film and the insulating coating, the base material steel plate surface electrically insulating and has a function of reducing the iron loss by imparting a tension to the base steel sheet. Note that the forsterite coating Mg 2 SiO 4 in addition, impurities or additives contained in the base steel sheet and annealing separator, and their reaction products are also included in the trace.
[0006]
　Insulating coating, in order to exert the insulation and the required tension insulating coating must not peeled from the electromagnetic steel sheet, therefore, a high film adhesion is required for the insulating film. However, increasing both the tension and the film adhesion to impart to the base steel sheet at the same time is not easy. Even in the current, research and development to enhance both of them at the same time is being continued incessantly.
[0007]
　Oriented electrical steel sheet is usually produced by the following procedure. 2.0 to 4.0 mass% content for silicon steel slab Si, and hot rolled, annealed if necessary after hot rolling, then between one or more times of cold sandwiching the intermediate annealing subjected to rolling, finish steel final thickness. Then, the final thickness of the steel sheet is subjected to a decarburization annealing in a humid hydrogen atmosphere, in addition to decarburization, as well as promote the primary recrystallization, SiO on the steel sheet surface layer 2 oxide layer by oxidizing precipitate (silica)
[0008]
　The steel sheet having an oxide layer, an annealing separator composed mainly of MgO (magnesia) and applied and dried, after drying, wound into a coil. Then, finish-annealed into a coil of steel sheet, to promote the secondary recrystallization, the crystal grains were integrated in the Goss orientation, further, SiO oxide layer and MgO in the annealing separator 2 is reacted with , the base steel sheet surface, Mg 2 SiO 4 to form a forsterite coating inorganic mainly of.
[0009]
　Then subjected to purification annealing in a steel sheet having a forsterite film, it is removed by diffusing impurities of the base material steel plate in outward. Further, after performing flattening annealing the steel sheet, the steel sheet surface with a forsterite film to form an insulating film and baked by applying a solution mainly composed of phosphate and colloidal silica. At this time, the base material steel plate is crystalline, between the insulating film is substantially amorphous, tension is applied from the difference in the thermal expansion coefficient.
[0010]
　Mg 2 SiO 4 interface between the forsterite film mainly composed of (in FIG. 1 "2") and steel (in FIG. 1 "1") is usually no uneven uneven (Fig. 1, reference ). The interface of uneven shape, is offset slightly the iron loss reducing effect by tension. Therefore the interface is it if iron loss is smoothed is reduced, to date, the development such as the following have been carried out.
[0011]
　Patent Document 1, to remove forsterite films by means of pickling or the like, a manufacturing method of smoothing the surface of the steel sheet by chemical polishing or electrolytic polishing is disclosed. However, in the manufacturing method of Patent Document 1, there is a case where the base steel sheet surface hard insulating coating adhered.
[0012]
　Therefore, in order to improve the film adhesion of the insulation coating on smooth finished steel sheet surface, as shown in FIG. 2, the intermediate layer 4 between the base steel sheet and the insulating film (or undercoat) to form a was suggested. Patent Document 2, before formation of the insulating film, and annealing the steel sheet in particular weakly oxidizing atmosphere, the surface of the steel sheet, SiO external oxidation type 2 method of forming a film as the intermediate layer is disclosed .
[0013]
　Further, Patent Document 3, before the formation of the insulating film, the base material steel plate surface, 100 mg / m 2 or less of the external oxidation type SiO 2 method of forming a film as the intermediate layer is disclosed. Further, Patent Document 4, when the insulating film is an insulating film of crystalline mainly composed of boric acid compound and alumina sol, SiO 2 method of forming an outer oxide layer of amorphous, such as an intermediate layer is disclosed ing.
[0014]
　These external oxidation type of SiO 2 film, over several tens of seconds to several minutes by a heat treatment which is appropriately controlling the temperature and the atmosphere are formed on the base steel sheet surface, and functions as a base of the smooth surface (middle layer), to improve the film adhesion of the insulating film, which exert a certain effect. However, SiO external oxidation type 2 in order to ensure the adhesion of the insulating film formed on the film more stably, further development has been promoted.
[0015]
　Patent Document 5, the base material steel plate was smooth surfaces, subjected to a heat treatment in an oxidizing atmosphere, the surface of the steel sheet, Fe 2 SiO 4 (fayalite) or (Fe, Mn) 2 SiO 4 of (Kuneberaito) to form an intermediate layer of crystalline, a method of forming an insulating film is disclosed thereon.
[0016]
　However, the base steel sheet surface, Fe 2 SiO 4 or (Fe, Mn) 2 SiO 4 in an oxidizing atmosphere to form a, by oxidation of Si in the base steel sheet in the surface layer, SiO 2 oxides such as will precipitate and will, there is a case in which the iron loss characteristics are degraded.
[0017]
　Further, Fe intermediate layer 2 SiO 4 and (Fe, Mn) 2 SiO 4 is crystalline, whereas, the insulating film formed by the coating solution mainly composed of phosphate and colloidal silica is largely amorphous is the quality. Crystalline and intermediate layer, in a substantially amorphous insulating film, there is a case adhesion is not stable.
[0018]
　Patent Document 6, a smooth base steel sheet surface, the sol - gel method, an intermediate layer, to form a 0.1 ~ 0.5 [mu] m thick gel film, on the intermediate layer, forming an insulating film how to have been disclosed. However, deposition conditions disclosed in Patent Document 6, a typical sol - in the range of gel method, may not be firmly secured to film adhesion.
[0019]
　Patent Document 7, a smooth base material steel plate surface by anodic electrolysis in the aqueous solution of silicate, to form a siliceous film as an intermediate layer, then, a method of forming an insulating film are disclosed.
[0020]
　Patent Document 8, a smooth base steel sheet surface, TiO 2 oxides such as (Al, Si, Ti, Cr , 1 or more oxides selected from Y) is present in a layer or an island shape, the above, the silica coating is present and further thereon, an electromagnetic steel sheet insulating coating is present is disclosed.
[0021]
　By forming an intermediate layer such as these, can improve the film adhesion, the newly requires large-scale facilities such as electrolytic treatment facilities and dry coating, it is difficult to secure the site, and there are cases where the production cost is increased.
[0022]
　Patent Document 9, the interface between the tensioning insulating coating and the base steel sheet, in addition to an external oxide film having a film thickness mainly composed of silica 2 ~ 500 nm, one having a particulate external oxide based on silica oriented silicon steel sheet is disclosed. Further, Patent Document 10, likewise, silica externally oxidized oxide film mainly made of, it is disclosed oriented silicon steel sheet having 30% or less of the cavity in the cross-sectional area ratio.
[0023]
　Patent Document 11, a smooth base steel sheet surface, the film thickness is at 2 ~ 500 nm, containing a cross-section area of ​​30% or less of the metallic iron to form an external oxide film of silica mainly as an intermediate layer, the intermediate a method of forming an insulating film on the layer have been disclosed.
[0024]
　Patent Document 12, a smooth base steel sheet surface, the film thickness is at 0.005 ~ 1 [mu] m, containing 1 to 70% of metallic iron or iron-containing oxides in a volume fraction, consisting mainly of silicon oxide to form an intermediate layer of the coating, a method of forming an insulating film on the intermediate layer is disclosed.
[0025]
　In Patent Document 13, a smooth base steel sheet surface, the film thickness is at 2 ~ 500 nm, the metallic oxide (Si-Mn-Cr oxide, Si-Mn-Cr-Al-Ti oxides, Fe oxide), containing 50% or less in sectional area ratio, the external oxide type oxide film of silica entity formed as an intermediate layer, a method of forming an insulating film on the intermediate layer is disclosed.
[0026]
　Thus, an intermediate layer of silica principal particulate outer oxide described above, the cavity, metallic iron, iron-containing oxides, or, when containing a metal-based oxide, is to some degree improved film adhesion of the insulating film. However, when a thin thickness of the intermediate layer of silica principal particulate external oxide underlying cavity, metallic iron, iron-containing oxides, it becomes difficult to control the existence form of the metal oxide. Therefore, when a thin thickness of the intermediate layer of silica entities also further improve the film adhesion is expected.
[0027]
　In Patent Document 14, if not oriented electrical steel sheet finish annealing film, SiO was produced by interfacial oxidation reaction 2 a through oxide film mainly, SiO was formed by coating baking 2 coating layer mainly composed of there exists, thereon oriented electrical steel sheet tension-imparting insulating film is present is disclosed.
[0028]
　The above techniques, extremely low-oriented electrical steel sheet excellent and the iron loss in the insulating film adhesion is obtained. However, in the above technique, SiO 2 for coating layer mainly composed of relatively thick, the diffusion of the oxygen source in the coating layer can not be sufficiently expected, to cause the interfacial oxidation reaction, pre-oxidizing source on the surface of the steel sheet It requires step or annealing step previously formed and there is a problem in productivity.
[0029]
　Further, SiO 2 to form a coating layer mainly composed of, it is necessary to add the step of applying a coating solution such as colloidal silica newly, it remains a problem in terms of facilities.
CITATION
Patent Document
[0030]
Patent Document 1: Japanese Sho 49-096920 Patent Publication
Patent Document 2: Japanese Patent Laid-Open 06-184762 discloses
Patent Document 3: Japanese Patent Laid-Open 09-078252 discloses
Patent Document 4: Japanese Patent 07- 278833 JP
Patent Document 5: Japanese Patent Laid-Open 08-191010 discloses
Patent Document 6: Japanese Patent Laid-Open 03-130376 discloses
Patent Document 7: Japanese Unexamined Japanese Patent Application Laid-Open No. 11-209891
Patent Document 8: Japanese Patent 2004-315880 JP
Patent Document 9: Japanese Patent 2002-322566 JP
Patent Document 10: Japanese Patent 2002-363763 JP
Patent Document 11: Japanese Patent 2003-313644 JP
Patent Document 12: Japanese JP 2003-171773 JP
Patent Document 13: Japanese Patent 2002-348643 JP
Patent Document 14: Japanese Patent No. 2004-342679 Publication
Summary of the Invention
Problems that the Invention is to Solve
[0031]
　Usually, coating structure of the grain-oriented electrical steel sheet having no forsterite coating, forms between the three-layer structure of "base material steel plate - - interlayer insulating film" as the basic form, the base steel sheet and the insulating coating, macro it is a uniform and smooth in (Fig. 2, reference). The difference in the thermal expansion coefficient of each layer, after heat treatment, work is the surface tension between the layers, while it is possible to impart tension to the base steel sheet, each layer is easily peeled off.
[0032]
　In the film structure of the three-layer structure, a silicon oxide (silica, SiO 2 ) in the case of relatively thin thickness of the intermediate layer mainly composed of (intermediate layer of silicon oxide entity) is the variation in the thickness of the intermediate layer thinner point than the allowable lower limit of the thickness due to, rare Re albeit but locally present, at this point is to decrease film adhesion, insulating film is estimated to easily peel. Such reduction in localized film adhesion is, because it affects the tension applied to the base steel sheet, also affect the core loss property.
[0033]
　To accommodate social demand for energy conservation policies, such as the recent home and abroad, not only to provide a high-performance oriented electrical steel sheet, it is expected to increase its productivity. Such in order to meet the expectations, it is necessary to briefly the specific intermediate layer forming step in the production of grain oriented electrical steel sheet having no forsterite coating.
[0034]
　Therefore, the thickness of the intermediate layer is inevitably minimized within a range capable of securing the film adhesion. Also, if so annealing for the intermediate layer formation is a cost factor should be set low to the extent possible the annealing temperature from an economic point of view, the thickness of the intermediate layer formed is minimized inevitably.
[0035]
　The present invention, on the entire surface of the intermediate layer of silicon oxide mainly, an insulating film so as not to cause unevenness in film adhesion, even if the thickness is thin and uneven even film adhesion and of the intermediate layer it is an object of the present invention to enhance the. That is, the present invention, even at the thin nonuniform thickness of the forsterite film without and intermediate layer, and to provide an excellent grain-oriented electrical steel sheet in film adhesion of the insulating film.
Means for Solving the Problems
[0036]
　In the prior art, to improve the film adhesion and iron loss characteristics of the insulating film, the smooth finished base steel sheet surface, an intermediate layer of silicon oxide mainly be more uniform and smooth surface. However, in practice, as described above, the film adhesion of the insulating film formed by baking by applying a coating solution mainly composed of phosphate and colloidal silica may plaques insulating film locally peel to. Instability of such film adhesion becomes remarkable when the thickness of the intermediate layer is thin.
[0037]
　The present inventors have intensively studied a technique for solving the above problems.
[0038]
　In the prior art, the annealing in an atmosphere having a controlled dew point against the base steel sheet (thermal oxidation annealing, the intermediate layer formed annealing) by performing, after forming the external oxidation of the intermediate layer of silicon oxide mainly intermediate the surface of the layer and baked by applying an insulating film coating solution to form an insulating film. The present inventors have found that when baking annealing of the coating solution, considered that it would be the structure of the intermediate layer is changed, by changing the baking annealing conditions when baking by applying an insulating film coating solution, intermediate layer structure the changes were investigated.
[0039]
　As a result, it led to obtain the following findings.
[0040]
　(One) insulating film coating solution is interfacial oxide between the base steel sheet by heat treatment during baking, in the plane of the intermediate layer of silicon oxide mainly selective oxidation region of the silicon oxide principal intermediate layer and forms are different ( described later) is generated by discrete.
[0041]
　When (Vol.2) selective oxidation region is excessively formed, film adhesion of the insulating film is lowered.
[0042]
　(Ref) by adjusting the formation conditions of the formation conditions and insulating coating of the external oxidation type intermediate layer of silicon oxide entities, by controlling the production conditions of the selective oxidation region accurately, to improve the film adhesion of the insulating film can.
[0043]
　The gist of the present invention is as follows.
[0044]
　(1) grain-oriented electrical steel sheet according to an embodiment of the present invention, the base steel sheet and a base steel sheet on contact with arranged intermediate layer, the contact with arranged that in the outermost surface on the intermediate layer insulating film a grain-oriented electrical steel sheet having bets, when the cutting direction is viewed in cutting plane becomes parallel to the thickness direction, a middle layer of the selective oxidation region, the thickness of the intermediate layer in a region in which the selective oxidation region exists and a saga 50nm or more, is less than 50nm thickness of the intermediate layer in the region where there is no selective oxidation region.
[0045]
　(2) In the oriented electrical steel sheet according to (1), when viewed in the cutting plane, the direction and Lz the entire length of the direction of the observation field perpendicular to the thickness direction in the unit [mu] m, perpendicular to the thickness direction of the Lx the total length in units μm selective oxidation region, when defining the line segment ratio X of the selective oxidation region by formula 1 below, the line segment ratio X is 0.1% or more and equal to or less than 12% it may be.
　　　X = (Lx ÷ Lz) × 100 ··· ( Equation 1)
[0046]
　(3) In the oriented electrical steel sheet according to (1) or (2), not more than a thickness of 50nm or more and 400nm of the intermediate layer in a region in which the selective oxidation region exists, the region where there is no selective oxidation region the thickness of the intermediate layer may be and less than 50nm or more 2 nm.
The invention's effect
[0047]
　According to this aspect of the present invention, grain-oriented electrical steel sheet having an insulation coating unevenness is not in film adhesion, i.e., even if the thin nonuniform thickness of the forsterite film without and intermediate layer, the insulating film it is possible to provide a superior oriented electrical steel sheet coating adhesion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0048]
It is a cross-sectional view schematically showing the FIG. 1 coating structure of a conventional grain-oriented electrical steel sheet.
It is a cross-sectional view schematically showing the FIG. 2 another film structure of the conventional oriented electrical steel sheet.
3 is a schematic sectional view showing a film structure of the grain-oriented electrical steel sheet according to an embodiment of the present invention.
DESCRIPTION OF THE INVENTION
[0049]
　The following describes 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. A number indicating the "super" or "less than", the value is not included in the numerical range.
[0050]
　Excellent oriented electrical steel sheet coating adhesion according to the present embodiment (hereinafter sometimes referred to as "the present invention electrical steel sheet".) Has no forsterite coating on the surface of the base steel sheet, on the surface of the base material steel plate in an intermediate layer of silicon oxide mainly a oriented electrical steel sheet having an insulating film coating solution is burned to form mainly of phosphate and colloidal silica onto the intermediate layer,
　the intermediate layer and the interface between the base steel sheet, there is selectively oxidized region of the silicon oxide mainly the base steel sheet surface is formed by selective oxidation during baking annealing of the coating solution is discrete.
[0051]
　Specifically, oriented electrical steel sheet according to the present embodiment, the direction of having a base steel sheet, and an insulating film disposed on the outermost surface, and an intermediate layer disposed between the base steel sheet and the insulating coating an electromagnetic steel sheet,
　cut surface cutting direction is parallel to the thickness direction (specifically, the plate thickness direction and parallel to and rolling direction and a cutting plane perpendicular) when viewed in, it has a said intermediate layer is selectively oxidized region and,
　it is not less 50nm or more thickness of the intermediate layer in a region in which the selective oxidation region is present, is less than 50nm thickness of the intermediate layer in the region where there is no selective oxidation region.
[0052]
　Here, the not-oriented electrical steel sheets forsterite film, the grain-oriented electrical steel sheet produced by removing the forsterite coating after manufacture, or is the oriented electrical steel sheet produced by suppressing the formation of forsterite coating .
[0053]
　The following describes the present invention electrical steel sheet.
[0054]
　In the prior art, forsterite film annealing in an atmosphere having a controlled dew point against the base steel sheet having no (thermal oxidation treatment, an intermediate layer formed annealing) silicon oxide and external oxide on the surface of the base steel sheet by performing a like an intermediate layer of the main body (hereinafter, simply. referred to as "intermediate layer") is formed to form an insulating film by performing annealing baking by applying an insulating film coating solution onto the intermediate layer. The cross-sectional structure of a conventional electromagnetic steel sheet, as shown in FIG. 2 a three-layer structure of "insulating film - - intermediate layer base steel sheet".
[0055]
　The present inventors have intensively studied a result the technique for improving the film adhesion of the insulating coating, and obtained the following findings.
[0056]
　When baking annealing of the insulating film coating solution, and the interface between the base steel sheet is selectively oxidized, the interface between the intermediate layer and the base steel sheet of silicon oxide mainly selective oxidation region of the silicon oxide principal intermediate layer and form different discrete to be generated (knowledge (one)).
[0057]
　When the selective oxidation region is excessively formed, film adhesion of the insulating film is lowered (findings (Vol.2)). On the other hand, if optimally control the selective oxidized region, film adhesion of the insulating film is remarkably improved. Phenomena base steel sheet surface during baking annealing of the insulating film coating solution is selective oxidation, the conditions of thermal oxidation annealing for forming the intermediate layer (annealing in an atmosphere having a controlled dew point), and for forming an insulating film adjust the baking annealing conditions, it can be controlled to some extent. Thus, by controlling the production conditions of the selective oxidation region accurately, it is possible to improve the film adhesion of the insulating film (findings (Ref)).
[0058]
　The present invention electrical steel sheet has been made based on the above findings, improvement technique of film adhesion of conventional insulating film, i.e., prior to more uniform and smooth surface of the intermediate layer of silicon oxide mainly in the base steel sheet surface the fundamentally different approach from the approach to improve the film adhesion of the insulating film.
[0059]
　3, a film structure of the present invention electrical steel sheet schematically showing. Sectional structure of the present invention electrical steel sheet, conventional unlike coating structure of three-layer structure of "base material steel plate - - interlayer insulating film" (see FIG. 2), as shown in FIG. 3, "the base steel sheet 1- "intermediate layer 4+ selective oxidized region 5a, 5b, 5c" - is irregular three-layer structure of the insulating film 3 '.
[0060]
　That is, in the present invention electrical steel sheet, instead of the thickness of the intermediate layer is uniform, and the interface of the intermediate layer is assumed that it is not smooth. The interface between the intermediate layer and the base steel sheet, the intermediate layer in the presence of a selective oxidation region forms differ by the intermediate layer is "intermediate layer 4+ selective oxidized region 5a, 5b, 5c ', the insulating coating film improved adhesion.
[0061]
　Hereinafter, each layer will be described of the present invention electrical steel sheet.
[0062]
　The present invention electrical steel sheet has a base steel sheet, and an insulating film disposed on the outermost surface, and an intermediate layer disposed between the base steel sheet and the insulating coating. That is, the present invention electrical steel sheet has a base steel sheet, and the base steel sheet on an intermediate layer disposed in contact, and an insulating film serving as a contact with arranged that in the outermost surface on the intermediate layer.
[0063]
　The base steel sheet
　in the above-mentioned irregular three-layer structure, the base material steel plate as the base material has a texture having a crystal orientation is controlled to the Goss orientation. Surface roughness of the base steel sheet is not particularly limited, in that by applying a large tension to the base steel sheet reduced iron loss, preferably 0.5μm or less in arithmetic average roughness (Ra), 0. more preferably equal to or less than 3μm. The lower limit of the arithmetic mean roughness of the base material steel plate (Ra) is not particularly limited, the lower limit may be 0.1μm since the iron loss improvement effect comes saturated with 0.1μm or less.
[0064]
　Also the thickness of the base material steel plate is not particularly limited, in order to further reduce the iron loss, the thickness is preferably 0.35mm or less in average, more preferably not more than 0.30 mm. The lower limit of the thickness of the base material steel plate is not particularly limited, from the viewpoint of production equipment capacity and the cost may be 0.10 mm.
[0065]
　The base steel sheet, a high concentration of Si (e.g., 0.80 to 4.00 wt%) because it contains a chemical affinity is expressed between the intermediate layer of silicon oxide mainly.
[0066]
　Insulating film
　in the above-mentioned irregular three-layer structure, the insulating film is an insulating film of vitreous formed by baking by applying a coating solution mainly composed of phosphate and colloidal silica. The insulating coating can impart a high surface tension in the base steel sheet.
[0067]
　During baking annealing of the coating solution, the interface between the intermediate layer and the base steel sheet of silicon oxide mainly forms the intermediate layer is different, although selective oxidation region of the silicon oxide mainly generated, which will be described later.
[0068]
　If the thickness of the insulation coating is less than 0.1 [mu] m, since it is difficult to impart the required surface tension in the base material steel plate, the thickness of the insulating coating or 0.1 [mu] m on average is preferred. More preferably 0.5μm or more.
[0069]
　On the other hand, if the thickness of the insulating film exceeds 10 [mu] m, the formation step of the insulating film, there is a possibility that cracks occur in the insulating film, the thickness of the insulating film is preferably 10 [mu] m or less in average. More preferably 5μm or less.
[0070]
　Incidentally, if necessary, laser, plasma, mechanical methods, etching, and other methods, or make local micro strain may be subjected to magnetic domain refining treatment or to form a local groove.
[0071]
　An intermediate layer of silicon oxide main
　contact in the above-mentioned irregular three-layer structure, an intermediate layer of silicon oxide mainly (including selective oxidation region) is provided between the base steel sheet and the insulating coating, and the base steel sheet insulating coating It has a function to.
[0072]
　The intermediate layer is cut surface cutting direction is parallel to the thickness direction (specifically, the plate thickness direction and parallel to and rolling direction and a cutting plane perpendicular) when viewed in has a selective oxidation region, selectively oxidized in the region where the region is present and the thickness of the intermediate layer is 50nm or more, the thickness of the intermediate layer is less than 50nm in the region where there is no selective oxidation region.
[0073]
　Silicon oxide forming a main body of the intermediate layer, SiO alpha (alpha = 1.0 ~ 2.0) is preferable. SiO alpha If (α = 1.5 ~ 2.0), since the silicon oxide is more stable, more preferred. If sufficiently performed oxidation annealing in forming a silicon oxide on the surface of the base material steel plate, SiO alpha can be formed (α ≒ 2.0).
[0074]
　By performing the oxidation annealing at normal temperature (1150 ° C. or less), silicon oxide, since the remains amorphous, has a high strength to withstand thermal stresses and elasticity increases, the thermal stress easily can be alleviated, it is possible to form the intermediate layer of dense material.
[0075]
　Select the middle layer in the region where the oxidation region is not present
　annealing process for forming the intermediate layer, from the economic point of view, it is preferable that a shorter time at lower temperatures. Therefore, the thickness of the intermediate layer formed is inevitably to a minimum. In the present invention electrical steel sheet, the thickness of the intermediate layer in the region where there is no selective oxidation region is less than 50nm.
[0076]
　On the other hand, if the thickness of the intermediate layer in this region is thin, the thermal stress relaxation effect is not exhibited sufficiently, the thickness of the intermediate layer in this region is more than 2nm in average are preferable. More preferably 5nm or more. That is, the thickness of the intermediate layer in the region where there is no selective oxidation region may less than 2nm and not more than 50nm.
[0077]
　The present invention electrical steel sheets, since the high productivity in mind, it is preferable to produce the time required for the intermediate layer forming step is minimized. Therefore, the thickness of the intermediate layer in the region where there is no selective oxidation region may be a minimum within the range capable of securing the film adhesion, it is sufficient 20nm or less for example on average.
[0078]
　An intermediate layer in the region in which the selective oxidation region is present
　on the intermediate layer of silicon oxide mainly during the formation of the insulating coating of vitreous baked by applying a coating solution mainly composed of phosphate and colloidal silica, when baking by the heat treatment is the base steel sheet surface is oxidized, the selective oxidation region of the interface silicon oxide mainly between the intermediate layer and the base steel sheet is produced by discrete (Figure 3, reference).
[0079]
　If selective oxidation region at the interface between the intermediate layer and the base steel sheet is excessively formed, film adhesion of the insulating film is lowered. On the other hand, if accurately to control the generation of the selective oxidation region, it is possible to improve the film adhesion of the insulating film (findings (Ref)).
[0080]
　If selective oxidation region is present in excess, why film adhesion of the insulating film is lowered is not clear, is considered as follows. Selective oxidation region, Si of the base material steel plate in the SiO is oxidized 2 is an area generated is volume than the base steel sheet is increased. If selective oxidation region is present in excess, by volume expansion, excessive stress on the insulating coating is applied, easily insulating coating is peeled off.
[0081]
　Forming the selective oxidation region is the baking step of the insulating film, the water vapor component or the insulating film in the atmosphere is, to reach the intermediate layer by diffusing in the insulating film, further, the base steel sheet to diffuse the intermediate layer reaches the surface, the result is believed to oxidize the Si of the base material steel plate in.
[0082]
　Diffusion of water vapor components to be rate-limiting in the middle layer of a dense silicon oxide mainly reach the amount of the base material steel plate as portions thickness of the intermediate layer is thin in many cases. Therefore, the selective oxidation region is thinner the thickness of the intermediate layer, tends film adhesion is produced at the site of inferior. Selective oxidation region, the film adhesion in the intermediate layer is generated on the site of the subordinate, film adhesion of the insulating film at this site is presumed to be improved.
[0083]
　Therefore, in the present invention electrical steel sheet, possible to appropriately control the generation of the selective oxidation region is important to ensure and excellent film adhesion without unevenness. By appropriately controlling the generation of the selective oxidation region, the thickness of the intermediate layer in a region in which the selective oxidation region exists becomes more 50nm.
[0084]
　The upper limit of the thickness of the intermediate layer in this region is not particularly limited, for example, it may be an 812nm in average. Further, the thickness of the intermediate layer in this region uniform and, in order to suppress the defects of voids and cracks in the layer occurs, the thickness of this region is preferably 400nm or less on average. More preferably 300nm or less. That is, the thickness of the intermediate layer in a region in which the selective oxidation region is present may be any 50nm or more and 812nm or less, may be at 50nm or more and 400nm or less.
[0085]
　In addition, the present inventors investigated the preferable generation state of the selective oxidation region. Consequently, as an index that defines the preferred form of the selective oxidized region, we were introduced following the line segment ratio is defined by (Equation 1) X (%).
　　　X = (Lx ÷ Lz) × 100 ··· ( Equation
　　　1) Lx ([mu] m): total length in the direction perpendicular to the thickness direction of the selective oxidation region
　　　Lz (μm): a plate thickness direction of the selective oxidation region the total length of the direction of the observation area that is orthogonal
[0086]
　Line rate X of the selective oxidation region (hereinafter, simply referred to as "a line segment ratio X".) It will be described on the basis of the film structure shown in FIG.
[0087]
　In Figure 3, the intermediate layer 4 has a selective oxidation region 5a, 5b, and 5c. Selective oxidized region 5a is a length in the direction perpendicular to the thickness direction La, selectively oxidized region 5b is a length in the direction perpendicular to the thickness direction Lb, selectively oxidized region 5b is thickness length in the direction perpendicular to the direction is Lc. Selective oxidized region 5a, 5b, and 5c are present discretely from each other. Note that (horizontal length in FIG. 3) direction of the length of the observation field of view perpendicular to the thickness direction is L.
[0088]
　For Figure 3, the line rate X of the selective oxidation region is {(La + Lb + Lc) ÷ L} × 100.
[0089]
　The present inventors have controlled the generation state of the selective oxidation region forming conditions for forming conditions and the insulating film of the intermediate layer different varied. Then, the line segment ratio X of the selective oxidation region, film residual rate of the insulating film after bending test (hereinafter, simply referred to as "film-remaining ratio".) Investigated the relationship between, the line segment ratio X preferably range was confirmed.
[0090]
　If selected line index X of the oxidized region than 21%, can be achieved a coating residual rate of over 83%.
[0091]
　Furthermore, increasing the film adhesion coating adhesion reinforces the site of inferior, in order to obtain preferably the effect of reducing the film adhesion of plaque, the line segment ratio X is preferably at least 0.1%. According to the test results of the present inventors, a line segment ratio X0.1% or more, can be achieved a coating residual rate of 85% or more. More preferred segment ratio X is 0.3% or more.
[0092]
　On the other hand, when the line segment ratio X is too large, the selective oxidation region is stress increases on the insulating film, easily insulating coating is peeled off, the film residual rate of the insulating film may be lowered. Therefore, the line segment ratio X is preferably 12% or less. According to the inventors' test results, the line segment ratio X is 12% or less, it is possible to achieve a film residual rate of 85% or more. More preferred segment ratio X is less than 7%.
[0093]
　That is, in the present invention electrical steel sheet, when the cutting direction is viewed in cutting plane becomes parallel to the thickness direction, and Lz the entire length of the direction of the observation field perpendicular to the thickness direction in the unit [mu] m, perpendicular to the thickness direction and Lx total length in the direction of the selective oxidation region in units [mu] m, when defining the line segment ratio X of the selective oxidation region in equation 1 above, the line segment ratio X is 0.1% or more and 12% or less it is preferable.
[0094]
　Incidentally, the layer thickness of the selective oxidation region, selectively oxidized region, film adhesion thickness of the intermediate layer is thin is produced at the site of the inferior and homogenized to reinforce the film adhesion of the insulating film at this site considering that an action, to obtain a uniform effect of film adhesion due to the reinforcing reliably, the thickness of the selective oxidation region (in FIG. 3, t, reference), it exceeds the thickness of the intermediate layer It is preferred.
[0095]
　For example, for selective oxidation region 5b thickness in FIG. 3 is t, when the thickness of the intermediate layer in the region (thickness of the intermediate layer excluding the selective oxidation region 5b) is 2 ~ 20 nm on average, it is preferable that the thickness of the selective oxidation region 5b is 80 ~ 400 nm in average. If the thickness of the selective oxidation region is 80nm or more, uniform effect of film adhesion due to the reinforcing is obtained preferably. On the other hand, preferably equal to the 400nm or less the thickness of the selective oxidation region, the insulating film is hardly peeled off.
[0096]
　As described above, features of the present invention electrical steel sheet, the interface between the intermediate layer and the base steel sheet, the base steel sheet surface is produced by oxidation in the heat treatment at the time of baking of the insulating film coating solution, there is a selective oxidation region It is to be.
[0097]
　Composition of the base material steel plate (chemical composition) is not particularly limited, oriented electrical steel sheet, because it is produced through various steps, the preferred material steel strip in manufacturing the present invention electrical steel sheet (slabs) and the chemical composition of the base material steel plate will be described below. Hereinafter,% of the component composition of the material steel strip and the base steel sheet refers to mass%.
[0098]
　Composition of the base material steel plate
　base material steel plate of the present invention electrical steel sheet, for example, Si: contains 0.8 ~ 7.0%, C: 0.005 % or less, N: 0.005% or less, S and the total amount of Se: 0.005% or less, and acid-soluble Al: limited to 0.005% or less, the balance being Fe and impurities.
[0099]
　Si: 0.80% or more and 7.0% or less
　Si (silicon) reduces the iron loss by increasing the electrical resistance of the grain-oriented electrical steel sheet. A preferable lower limit of Si content is 0.8%, more preferably 2.0%. On the other hand, when the Si content exceeds 7.0%, the saturation magnetic flux density of the base material steel plate is lowered, size of the core is hard. The preferable upper limit of the Si content is 7.0%.
[0100]
　C: 0.005% or less
　C (carbon) forms a compound in the base steel sheet in order to degrade the iron loss, the less preferred. C content is preferably limited to 0.005% or less. The preferable upper limit of the C content is 0.004%, more preferably 0.003%. Since C is as small as preferred, including 0% lower limit, the reduce C to less than 0.0001%, the manufacturing cost is greatly increased, manufacturing, 0.0001% is substantially the lower.
[0101]
　N: 0.005% or less
　N (nitrogen) forms a compound in the base steel sheet in order to degrade the iron loss, the less preferred. N content is preferably limited to 0.005% or less. The preferable upper limit of the N content is 0.004%, more preferably 0.003%. Since N as less preferable, the lower limit need only be 0%.
[0102]
　The total amount of S and Se: 0.005% or less
　S (sulfur) and Se (selenium) forms a compound in the base steel sheet in order to degrade the iron loss, the less preferred. One of S or Se, or it is preferred to limit the sum of both the 0.005% or less. The total amount of S and Se is preferably 0.004% or less, more preferably 0.003% or less. Because the content of S or Se is the less preferred, the lower limit need only be 0%, respectively.
[0103]
　Acid-soluble Al: 0.005% or less
　acid-soluble Al (acid soluble Aluminum) is to form a compound base steel sheet in order to degrade the iron loss, the less preferred. Acid-soluble Al is preferably 0.005% or less. Acid-soluble Al is preferably 0.004% or less, more preferably 0.003% or less. Since the acid-soluble Al is as small as possible preferably, the lower limit need only be 0%.
[0104]
　Balance of composition of the base material steel plate described above is Fe and impurities. Note that the "impurities", in manufacturing the steel industrially, refers to those mixed ores as raw material, scrap or from the manufacturing environment and the like.
[0105]
　Also, the base material steel plate of the present invention electrical steel sheet, in a range that does not disturb a property as a selective element in place of part of Fe is the balance, for example, Mn (manganese), Bi (bismuth), B (boron) , Ti (titanium), Nb (niobium), V (vanadium), Sn (tin), Sb (antimony), Cr (chromium), Cu (copper), P (phosphorus), Ni (nickel), Mo (molybdenum) it may contain at least one member selected from.
[0106]
　The content of the selected element as described above may be, for example, less. The lower limit of the selection element is not particularly limited, the lower limit may be 0%. These selection elements be contained as an impurity, the effect of the present invention electrical steel sheet is not impaired.
　Mn: 0% or more and 0.15% or
　less, Bi: 0% or more and 0.010% or
　less, B: 0% or more and 0.080% or
　less, Ti: 0% or more and 0.015% or
　less, Nb: 0% or more and 0.20% or
　less, V: 0% or more and 0.15% or
　less, Sn: 0% or more and 0.30% or
　less, Sb: 0% or more and 0.30% or
　less, Cr: 0% not more than 0.30% or less,
　Cu: 0% or more and 0.40% or
　less, P: 0% or more and 0.50% or
　less, Ni: 0% or more and 1.00% or less, and
　Mo: 0% or more and 0.10% or less.
[0107]
　Chemical composition of the material billet (slab)
　C (carbon) is an element effective in controlling the primary recrystallized texture. C is preferably 0.005% or more. Further, C is 0.02% or more, 0.04% or more, more preferably 0.05% or more. When C exceeds 0.085% decarburization in decarburization process does not proceed sufficiently, since the required magnetic properties are not obtained, C is preferably less 0.085%. More preferably 0.065% or less.
[0108]
　When Si (silicon) is less than 0.80%, austenite transformation occurs during finish annealing, since accumulation in grain Goss orientation is inhibited, Si is preferably at least 0.80%. On the other hand, when the Si is more than 4.00% the base steel sheet is hardened workability is deteriorated, since the cold rolling becomes difficult, it is necessary to make the equipment measures such as warm rolling. From the viewpoint of processability, Si is preferably not more than 4.00%. More preferably not more than 3.80%.
[0109]
　When Mn (manganese) is less than 0.03%, the toughness is lowered, so cracks hot rolling is likely to occur, Mn is preferably at least 0.03%. More preferably 0.06% or more. On the other hand, when the Mn exceeds 0.15%, MnS and / or MnSe is large amount and unevenly generated, since the secondary recrystallization does not proceed stably, Mn is preferably 0.15% or less. More preferably not more than 0.13%.
[0110]
　When the acid-soluble Al (acid soluble Aluminum) is less than 0.010%, insufficient precipitation amount of AlN that functions as inhibitor, since the secondary recrystallization does not proceed stably and sufficiently, acid-soluble Al is 0. more than 010 percent is preferred. More preferably 0.015% or more. On the other hand, if the acid soluble Al is more than 0.065%, AlN is coarsened, since the function as an inhibitor decreases, acid-soluble Al is preferably 0.065% or less. More preferably 0.060% or less.
[0111]
　When N (nitrogen) is less than 0.004% or, insufficient precipitation amount of AlN that functions as inhibitor, since the secondary recrystallization does not proceed stably and sufficiently, N represents preferably 0.004% or more. More preferably 0.006% or more. On the other hand, when N exceeds 0.015%, nitride during hot rolling it is a large amount and unevenly deposited, since hinders the progress of recrystallization, N is preferably 0.015% or less. More preferably not more than 0.013%.
[0112]
　When one or both sum of S (sulfur) and Se (selenium) is less than 0.005%, insufficient precipitation amount of MnS and / or MnSe functioning as inhibitors, secondary recrystallization is sufficiently stable does not proceed Te, total of one or both of S and Se is preferably 0.005% or more. More preferably 0.007% or more. On the other hand, if the total amount of S and Se exceeds 0.050% during final annealing, purification is insufficient, since iron loss is reduced, the total of one or both of S and Se is 0.050% or less It is preferred. More preferably not more than 0.045%.
[0113]
　The remainder of the chemical composition of the material steel strip described above is Fe and impurities. Note that the "impurities", in manufacturing the steel industrially, refers to those mixed ores as raw material, scrap or from the manufacturing environment and the like.
[0114]
　Also, material steel strip of the present invention electrical steel sheet, in a range that does not disturb a property as a selective element in place of part of Fe is the balance, for example, P, Cu, Ni, Sn, and one Sb or it may contain two or more. The lower limit of the selection element is not particularly limited, the lower limit may be 0%.
[0115]
　P (phosphorus) is to increase the electrical resistivity of the base material steel plate, but an element which contributes to the reduction of iron loss, when it exceeds 0.50%, since the rolling resistance decreases excessively increases the hardness , preferably 0.50% or less. More preferably not more than 0.35%.
[0116]
　Cu (copper) is to form fine CuS and CuSe functioning as an inhibitor, but an element contributing to the improvement of the magnetic properties, when it exceeds 0.40%, the effect of improving the magnetic properties is saturated, heat rolling, it may cause surface defects, preferably 0.40% or less. More preferably not more than 0.35%.
[0117]
　Ni (nickel) is to increase the electrical resistivity of the base material steel plate, but an element which contributes to the reduction of iron loss, when it exceeds 1.00%, since the secondary recrystallization becomes unstable, Ni is 1.00% or less. More preferably not more than 0.75%.
[0118]
　Sn (tin) and Sb (antimony) is segregated at the grain boundaries, during decarburization annealing, is an element of an action of adjusting the degree of oxidation, it exceeds 0.30%, during the decarburization annealing, de because coal is less likely to proceed, Sn and Sb are both preferably 0.30% or less. More preferably, each element also below 0.25%.
[0119]
　Also, material steel strip of the present invention electrical steel sheet further as a selection element in place of part of Fe is the balance, for example, as an element for forming the inhibitor, Cr, Mo, V, Bi, Nb, the Ti one or more may contain a supplementary. The lower limit of these elements is not particularly limited, the lower limit may be 0%. The upper limit of these elements, respectively Cr: 0.30%, Mo: 0.10%, V: 0.15%, Bi: 0.010%, Nb: 0.20%, Ti: 0.015% it is sufficient.
[0120]
　Next, a method for manufacturing of the present invention electrical steel sheet.
[0121]
　Method for producing a grain-oriented electrical steel sheet according to the present embodiment (hereinafter sometimes referred to as "production method of the present invention".) Has
　a coating of inorganic mineral forsterite or the like produced in (a) finish annealing, pickling, annealing the base material steel plate was removed by means of grinding or the like, or,
　(b) finish annealing at annealing the base material steel plate that suppresses the generation of the film of the inorganic mineral,
　(c) the annealing (thermal oxidation annealing, by annealing) in an atmosphere having a controlled dew point, the intermediate layer of silicon oxide mainly formed on the surface of the base material steel plate,
　(d) an insulating film to the intermediate layer, composed mainly of phosphate and colloidal silica the coating solution baking was applied,
　by heat treatment at (e) above baking, the oxidation of the base material steel plate surface, the interface between the intermediate layer and the steel plate, the selective oxidation region of the silicon oxide principal intermediate layer and forms are different to form discretely.
　The present invention production process, it is possible to film adhesion thickness of the intermediate layer is thin to properly form the selective oxidation region on the site of inferior.
[0122]
　Folder pickling a coating of inorganic minerals stellite or the like, the base material steel plate was removed by means of grinding or the like, and, the base material steel plate that suppresses the generation of the film of the inorganic mineral, for example, in the following Preparation to.
[0123]
　The silicon steel strips containing 0.80 to 4.00 wt% of Si, preferably a silicon steel strips containing 2.0-4.0 mass% of Si, and hot rolled, optionally after hot rolling annealed Te, then once or is subjected to two or more cold rolling sandwiching the intermediate annealing, finish the steel sheet of the final sheet thickness. Then, the steel sheet of the final sheet thickness, subjected to decarburization annealing, in addition to decarburization, with the progress of the primary recrystallization, to form an oxide layer on the surface of the steel sheet.
[0124]
　Next, the surface of the steel sheet having an oxide layer, magnesia dried by applying an annealing separator mainly comprised of, after drying, wound in a coil shape, subjected to finish annealing (secondary recrystallization). The finish annealing, the steel sheet surface, forsterite (Mg 2 SiO 4 forsterite film composed mainly of) The forsterite coating, pickling, is removed by means of grinding or the like. After removal, preferably smoothly finished surface of the steel sheet by chemical polishing or electrolytic polishing.
[0125]
　On the other hand, as the above-described annealing separator, it is possible to use an annealing separator consisting mainly of alumina instead of magnesia. The surface of the steel sheet having an oxide layer, the alumina is dried by applying an annealing separator mainly comprised of, after drying, wound in a coil shape, subjected to finish annealing (secondary recrystallization). When using an annealing separator consisting mainly of alumina, even when the finish annealing, it is prevented to generate the coating of inorganic mineral forsterite or the like on the surface of the steel sheet. After finish annealing, preferably, smoothly finished surface of the steel sheet by chemical polishing or electrolytic polishing.
[0126]
　The base steel sheet to remove a film of inorganic mineral such as forsterite, or by annealing the base material steel plate that suppresses the generation of the film of the inorganic minerals such as forsterite, the surface silicon oxide mainly of the base material steel plate forming an intermediate layer.
[0127]
　The thickness of the intermediate layer, the annealing temperature, holding time, and controls one or more appropriate adjustment to the annealing atmosphere. In order to increase the productivity of the oriented electrical steel sheet, the intermediate layer forming step and a short annealing time is preferably low annealing temperature to the extent possible. Therefore, the thickness of the intermediate layer is inevitably minimized within a range capable of securing the film adhesion. Therefore, the thickness of the intermediate layer after the intermediate layer forming step, less than 50nm.
[0128]
　Annealing to form an intermediate layer, with a view to generating an external oxidation type oxide silicon on the surface of the steel sheet, it is preferable annealing temperature is 600 ~ 1150 ° C.. Atmosphere during heating at a temperature holding annealing, as internal steel sheet is not oxidized, preferably a reducing atmosphere, in particular, nitrogen mixed with hydrogen. For example, the hydrogen: nitrogen 75%: 25%, dew point preferably an atmosphere of -20 ~ 2 ° C..
[0129]
　In annealing for forming the intermediate layer (thermal oxidation annealing), the dew point and the degree of oxidation of atmosphere during the temperature holding (= water vapor partial pressure / hydrogen partial pressure) than, maintaining a low dew point and the degree of oxidation of the atmosphere during cooling. By changing the dew point and the degree of oxidation at the time of the temperature holding and cooling, the thickness of the intermediate layer further thinner locally thinner portion.
[0130]
　Thickness locally thinner portion of the intermediate layer is film adhesion is inferior site, by further reducing the thickness of this site, it is selectively oxidized region at this site during baking annealing of the insulating film priority It is easily generated by. As a result, it is possible to improve the film adhesion of the insulating film at this site.
[0131]
　In the present invention production process, when the annealing for forming the intermediate layer, change the dew point and the degree of oxidation at the time of cooling at a temperature holding, maintaining lower than during the temperature holding the dew point and the degree of oxidation of atmosphere in cooling . For example, after the temperature holding, the hydrogen: nitrogen 75%: 25%, dew point cools in an atmosphere of -50 ~ -20 ° C.. Hydrogen: Nitrogen 75%: 25%, less dew point is -20 ° C. corresponds to the degree of oxidation ≦ 0.0014. Low oxidation degree atmosphere during such after the intermediate layer forming cooling is one of the features of the present invention production process.
[0132]
　On the intermediate layer of silicon oxide mainly forming an insulating film and baked by applying an insulating film coating solution composed mainly of phosphate and colloidal silica. Baking of the coating solution, for example, hydrogen: nitrogen 75%: 25%, nitrogen dew point of 5 ~ 50 ° C. - a hydrogen mixed atmosphere, carried out by heat treatment 650 ~ 950 ° C..
[0133]
　By heat treatment at the time of baking, the thickness of the intermediate layer is the surface of the steel sheet of the locally thinner regions are selectively oxidized, the selective oxidation region at the interface between the intermediate layer and the steel sheet is produced by discrete.
[0134]
　The baking annealing of the coating solution, the dew point and the degree of oxidation of the atmosphere during baking, maintaining a low dew point and the degree of oxidation of the atmosphere during cooling. By changing the baking time and the cooling time of the dew point and degree of oxidation, inhibiting to change the form of the selective oxidation region. For example, the hydrogen: nitrogen 75%: 25%, in an atmosphere of a dew point of 5 ~ 10 ° C., while maintaining a low degree of oxidation of the atmosphere at the time of cooling for cooling than during baking.
[0135]
　In the present invention production process, it is preferable that the atmosphere of dew point or oxidation degree during cooling to 500 ° C., maintained lower than during baking. For example, to change the dew point and degree of oxidation after baking, during cooling until reaching 500 ° C., the hydrogen: nitrogen 75%: 25%, dew point atmosphere 5 ~ 10 ℃ (0.0116 ≦ oxidation degree ≦ 0 it preferably controlled to .0163). Low oxidation degree atmosphere during cooling after such an insulating film formation, which is one of the features of the present invention production process.
[0136]
　Selective oxidation region, by controlling the annealing conditions such as temperature and atmosphere, changes generation state. For example, becomes the internal oxidation if Tsuyomere oxidation resistance, an external oxide if Yowamere oxidizing. In the present invention production process, as long as selective oxidation region is preferably formed on the fine and small amounts, it may be an external oxide be internal oxidation.
[0137]
　Selective oxidation region formed efficiently is suitable internal oxidation, in order to improve the film adhesion is, external oxide is suitable. In order to achieve both improvement of the efficient formation and film adhesion of the selective oxidation region is preferably the mode of transition region between the internal oxidation and the outer oxide, mode of external oxidation near the internal oxidation is more preferable.
[0138]
　Incidentally, when the selective oxidation region is formed, cut away part of the base material steel plate in accordance with the progress of the oxidation reaction, there are cases where the steel is taken up selectively oxidized region. Further, the selective oxidation region, which may contain inclusions or precipitates. In this embodiment, the selective oxidation region may include such as steel and inclusions and precipitates.
[0139]
　Each layer of the present invention electrical steel sheet is observed as follows, measured.
[0140]
　Test pieces were cut out from the oriented electrical steel sheet having an insulating film, a film structure of the specimen, scanning electron microscope (SEM: Scanning Electron Microscope) and transmission electron microscope observation with (TEM Transmission Electron Microscope).
[0141]
　Specifically, first, the cutting direction is cut out a test specimen so as to be parallel to the thickness direction (specifically, a test piece so that the cut surface becomes the thickness direction and parallel to and rolling direction perpendicular cut), the cross-sectional structure of the cut surface is observed with SEM at a magnification of each layer enters into the observation field. For example, by looking at the reflection electron composition image (COMP image), or cross-sectional structure is composed of many layers it can be inferred. For example, the COMP image, steel sheet pale, (including selective oxidation region) intermediate layer is dark, the insulating coating can be determined as a neutral color.
[0142]
　To identify each of the cross-sectional structure, using SEM-EDS (Energy Dispersive X-ray Spectroscopy), perform line analysis along a thickness direction, a quantitative analysis of chemical components of each layer. Element for quantitatively analyzing is Fe, P, Si, O, and 5 elements Mg.
[0143]
　Quantitative analysis of the observation results and the SEM-EDS in COMP image described above, a region where the Fe content is measurement noise except 80 atomic% or more, and a line of scanning lines of line analysis for this region if min (thickness) is 300nm or more, the area is determined to be the base steel sheet, determined that the region excluding the base steel sheet, (including selective oxidation region) intermediate layer and an insulating film to.
[0144]
　With respect to those regions except the base steel sheet specified above, from the quantitative analysis results of observation and SEM-EDS in COMP image, except for measurement noise, Fe content is less than 80 atomic%, P content is 5 atomic% above, Si content is less than 20 atomic%, O content of 50 atomic% or more, an area where the Mg content is 10 atomic% or less, and the line segment (thickness of the scanning line of the line analysis for this region if is) is 300nm or more, determines the area to be insulated coating.
[0145]
　Incidentally, when determining the area which is above the insulating coating, without a like precipitates and inclusions contained in the insulating film on the judgment of a subject, the region satisfying the above-mentioned quantitative analysis resulting matrix insulator it is determined that the coating. For example, if it is confirmed from the COMP image or line analysis results and precipitates and inclusions on a scanning line of the line analysis exists, not put this space to a subject with an insulating film by quantitative analysis of the matrix phase it is determined whether or not there. Incidentally, precipitates and inclusions, indistinguishable from the parent phase by the contrast in the COMP image, the quantitative analysis can be distinguished from the parent phase by the presence of the constituent elements.
[0146]
　A region excluding the identified base material steel plate and the insulating film above, and if the line segment on the scan line of the line analysis corresponding to this region (thickness) is 300nm or more, the area intermediate layer (selective oxidation determines that the region including the including the area).
[0147]
　The measurement of the above COMP image observation and SEM-EDS quantitative analysis each specific and thickness by, by changing the observation field is carried out in five locations or more. The thickness of the insulating film was determined by five or more locations, the maximum and minimum values ​​from the values ​​excluding the by the average value to the average value and the average thickness of the insulating film.
[0148]
　Incidentally, at least one 5 or more locations of the observation field as described above, if the line segment of the scanning line of the line analysis (thickness) is present insulating film is less than 300 nm, observing in detail the insulating film by TEM and, the measurement of specific and thickness of the insulating film by TEM.
[0149]
　Further, the region including an intermediate layer (including the selective oxidation region), since the spatial resolution in the SEM is low, observed in detail by TEM, the intermediate layer by TEM identification and thickness (including the selective oxidation region) the measurement is carried out.
[0150]
　Specimen including an intermediate layer (including the selective oxidation region), and a test piece including an insulating coating as necessary, by FIB (Focused Ion Beam) processing, cut into cutting direction is parallel to the thickness direction ( in particular, test piece was cut out so that the cut surface becomes the thickness direction and parallel to and rolling direction and perpendicular), STEM (Scanning at a magnification of a cross sectional structure of the cut surface, a layer corresponding to in the observation field of view enters observed in -TEM) to (bright-field image). If during the observation field of view from entering each layer, observing a cross section structure in successive multiple field-of-view.
[0151]
　An intermediate layer in the cross-sectional structure (including the selective oxidation region), and optionally to identify the individual layers of the insulating coating layer by using a TEM-EDS, perform line analysis along the thickness direction, each layer performing quantitative analysis of chemical components. Element for quantitatively analyzing is Fe, P, Si, O, and 5 elements Mg.
[0152]
　Quantitative analysis of bright field image observation and TEM-EDS in TEM described above, to identify the respective layers, the measurement of the thickness of each layer.
[0153]
　Regions Fe content in 50nm or more areas in succession becomes 80 atomic% or more except for measurement noise in the scanning line of the line analysis determines that the base steel sheet, a region excluding the base steel sheet, intermediate it is determined that the layer and the insulating film.
[0154]
　With respect to those regions except the specified base material steel plate by the above, the quantitative analysis results of observations and the TEM-EDS in the bright-field image, in the region of or more consecutive 50nm at a scan line of the line analysis, with the exception of the measurement noise, Fe content is less than 80 atomic%, P content is 5 atomic% or more, Si content of less than 20 atomic%, O content of 50 atomic% or more, the insulating regions Mg content is 10 atomic% or less coating it is determined that it is. Incidentally, when determining the area which is above the insulating coating, without a like precipitates and inclusions contained in the insulating film on the judgment of a subject, the region satisfying the above-mentioned quantitative analysis resulting matrix insulator it is determined that the coating.
[0155]
　Determining an area excluding the specified base material steel plate and the insulating film in the above that the intermediate layer (including the selective oxidation region). The intermediate layer (including the selective oxidation region), as the average of the entire intermediate layer is less than 80 atomic% Fe content on average, less than 5 atomic% P content of on average, 20 atomic% Si content is average above, O content is average 50 atomic% or more, Mg content may be satisfied 10 atomic% or less on average. Incidentally, the quantitative analysis of the intermediate layer described above does not include an analysis such as steel in the intermediate layer and the precipitates and inclusions, a quantitative analysis of the matrix phase.
[0156]
　Each layer specified above, to measure the line segment (thickness) by a scanning line of the line analysis. Incidentally, when the thickness of each layer is 5nm or less, it is preferable to use a TEM having a spherical aberration correction function in terms of spatial resolution. Further, when the thickness of each layer is 5nm or less, performs point analysis, for example, 2nm intervals along the thickness direction, to measure the respective layers of the segments (thickness), the line segment as the thickness of each layer it may be adopted. For example, with the use of the TEM with a spherical aberration correcting function, it is possible to EDS analysis in the spatial resolution of about 0.2 nm.
[0157]
　The observed and measured in the above TEM, by changing the observation field were performed at five or more locations, the measurement results obtained in a total of five points or more, with an average value from the values ​​excluding the maximum value and the minimum value, the adopting the mean value as the average thickness of the corresponding layers. If necessary, in the case of confirming the variation of the thickness of each layer is to calculate the standard deviation from the measurement result, it may be set to "(average) ± (standard deviation)."
[0158]
　Further, whether Kaya intermediate layer of the present invention electrical steel sheet having a selective oxidation region, and the thickness of the intermediate layer in a region in which the selective oxidation region exists, such as the thickness of the intermediate layer in the region where there is no selective oxidation region, identified in the following manner.
[0159]
　The observation of the TEM bright field image of identified layers by TEM-EDS analysis described above, the length in the direction perpendicular to the thickness direction is carried out in a region equal to or larger than 300μm in total. In this region, if the plate thickness direction thickness is determined that there is no selective oxidized region if present intermediate layer just below 50nm, the thickness direction thickness is present intermediate layer is 50nm or more determining a place selectively oxidized region is present. That is, the thickness of the intermediate layer in a region in which the selective oxidation region exists becomes more 50 nm, the thickness of the intermediate layer in the region where there is no selective oxidation region is less than 50nm.
[0160]
　Further, by image analysis, in the thickness direction thickness identify 50nm or more regions (the middle layer in the region where the selective oxidation region is present), and obtains the length in the direction perpendicular to the thickness direction of this region. Incidentally, regarded as the distance between the selective oxidized region adjacent (distance in the direction perpendicular to the thickness direction) is one continuous selective oxidation region is less than 0.5 [mu] m.
[0161]
　Based on the above image analysis results, the total length of the observation field of view, from the length of the total of the selective oxidation region, obtains a line segment ratio X as defined above (Equation 1). Incidentally, the binarized image for image analysis, based on the specification result of the selective oxidation region, the image by performing a coloring interlayer (including selective oxidation region) manually to tissue Photos it may be binarized.
[0162]
　In the present invention electrical steel sheet, the intermediate layer is present in contact with the base steel sheet, since the insulating film is present in contact with the intermediate layer, when identifying the respective layers in the above criteria, the base steel sheet, the intermediate layer ( including selective oxidation region), and a layer other than the insulating film is not present.
[0163]
　The above-mentioned base steel sheet, the intermediate layer (including the selective oxidation region), and Fe contained in the insulating film, P, Si, O, content such as Mg is the base steel sheet, intermediate layer, and an insulating film it is a criterion for determining the thickness of a particular manner.
[0164]
　Also, Ra (arithmetic average roughness) of the base material steel plate surface may be measured by using a stylus type surface roughness measuring instrument.
[0165]
　Film residual rate of the insulating film is evaluated by the bending adhesion test. A flat test piece 80 mm × 80 mm, after winding a round bar having a diameter of 20 mm, flat stretch, the area of ​​the insulating film is not peeled off from the test piece was measured, the area of ​​the area which is not peeled off the steel plate define a value obtained by dividing the film residual rate (area%), to evaluate the film adhesion of the insulating film. For example, a transparent film with a 1mm grid tick marks placed on the specimen may be calculated by measuring the area of ​​the release and non insulation coating.
Example
[0166]
　Will be further specifically described in detail the effects of an embodiment of the present invention through examples, the conditions in the examples, in one example of conditions adopted for confirming the workability and effects of the present invention There, the present invention is not limited to this single example of conditions. The present invention does not depart from the gist of the present invention, as long as they achieve the object of the present invention, it is capable of adopting various conditions.
[0167]
　(Example 1)
　Table subjected 1 to the steel material pieces compositions shown after heated 60 minutes soaking at 1150 ° C. to hot rolling to obtain a hot-rolled steel sheet 2.6mm thick. Then, this hot-rolled steel sheet, after holding for 200 seconds at 1120 ° C., and immediately cooled, and held for 120 seconds at 900 ° C., was subjected to hot rolled sheet annealing to subsequent quenching. After pickling the hot-rolled annealed sheets were subjected to cold rolling to obtain a cold rolled steel sheet of the final sheet thickness 0.27 mm.
[0168]
[Table 1]

[0169]
　This cold-rolled steel sheet (hereinafter "steel"), hydrogen: nitrogen 75%: 25% of the atmosphere, 850 ° C., was subjected to a decarburization annealing for holding 180 seconds. The steel sheet after decarburization annealing, hydrogen - nitrogen - in a mixed atmosphere of ammonia, 750 ° C., subjected to nitriding annealing for holding 30 seconds, was adjusted nitrogen content of the steel sheet to 230 ppm.
[0170]
　The steel sheet after nitriding annealing, the annealing separator consisting mainly of alumina was applied, then hydrogen - in a mixed atmosphere of nitrogen, and finish-annealed by heating to 1200 ° C. at a heating rate of 15 ° C. / time, then, in a hydrogen atmosphere, subjected to purification annealing holding at 1200 ° C. 20 h, allowed to cool, to produce a base material steel plate having a smooth surface.
[0171]
　The finish annealing was base material steel plate, 25% N 2 + 75% H 2 in the atmosphere, and heated to the holding temperature at a heating rate of 10 ° C. / sec and held for 30 seconds, as appropriate, immediately changing the dew point of the atmosphere , by air cooling, to form an intermediate layer of silicon oxide mainly.
[0172]
　The steel sheet forming the intermediate layer, and applying an insulating film coating solution composed mainly of phosphate and colloidal silica, hydrogen: nitrogen 75%: 25% of the atmosphere, and heated to the holding temperature was held for 30 seconds, optionally, as forms of the selective oxidized region does not change, immediately changing the dew point of the atmosphere, furnace cooled 500 ° C., and then naturally cooled, to form an insulating film.
[0173]
　Upper respiratory thermal oxidation annealing for forming an intermediate layer (intermediate layer formation annealing, annealing in an atmosphere having a controlled dew point), and by baking annealing for forming the insulating film, the selective oxidation is the surface of the base material steel plate is, the selective oxidation region at the interface between the intermediate layer and the steel sheet is produced.
[0174]
　According to the method of observation and measurement described above, cut out test pieces from the oriented electrical steel sheet having an insulating film, the cross-sectional structure of the specimen, was observed with a scanning electron microscope (SEM) and transmission electron microscope (TEM), the thickness of the intermediate layer in a region in which the selective oxidation region exists, determined the thickness of the intermediate layer in the region where there is no selective oxidation region, and the line segment ratio X. The results are shown in Table 2.
[0175]
[Table 2]

[0176]
　In the invention example having a selective oxidation region, has excellent film adhesion of the insulating film, has achieved a film residual rate of 90% or more in the particular invention example A3 ~ A5, it can be seen that markedly excellent. In Invention Examples A3 ~ A5 is variation in the thickness is relatively large cooling dew point of the intermediate layer formation annealing is as low as less than -20 ° C. The intermediate layer, the insulating film baking annealing the intermediate layer is in a local thin portions sometimes selective oxidation region is estimated that was easy formed.
[0177]
　Furthermore, the cooling dew point at the insulating film baking annealing is as low as 5 ~ 10 ° C., the formed selective oxide region is inferred that did not grow unnecessarily. Forming selectively oxidized region is, become a preferred thickness of 80 ~ 400 nm, in order to line rate X is present preferably 0.3 or more and 7% or less, the thickness is locally thin interlayer sites ( for film adhesion was generated selectively oxidized region sites) of inferior is considered that improved film adhesion of the insulating film.
[0178]
　In the invention examples A7 ~ A9, small variations in the thickness of the intermediate layer cooling dew point of the intermediate layer formation annealing is as high as -20 ° C. or higher, and that the selective oxidation region at the insulating film baking annealing were extensively formed Presumed. In the invention examples A6 ~ A9, cooled dew point at the insulating film baking annealing, although lower than the holding dew point, since relatively high 20 ° C. or more, is assumed that grew more extensively the selective oxidation region . Therefore, were seen to improve the film adhesion of the insulating film, it is considered the degree of improvement is small. In the invention examples A8 and A9, the line segment ratio X of the selective oxidation region is in the moderate range of 0.1 to 12% improvement in film adhesion of the insulating film was comparatively good.
[0179]
　In particular, the invention example A6 and A7 was seen to improve the film adhesion of the insulating film, exceeds the 400nm thickness of the selective oxidation region, and the line segment ratio X of the selective oxidation region is 12% the exceeded, believed insulating film stress applied to the insulating film is increased becomes liable slightly peeled.
[0180]
　In Invention Example A6, the thickness of the intermediate layer is present are places than locally 2 nm, because it is not sufficient to alleviate the thermal stress acting between the base steel sheet and the insulating film, the insulating film is It is considered to have become easier to peel.
[0181]
　On the other hand, Comparative Example A1 is inferred that selective oxidized region when the insulating film baking annealing were not generated.
[0182]
　Comparative Example A2 is, since the atmosphere at the time of the intermediate layer forming annealing and cooling the same as the atmosphere during the holding, the layer thickness of the formed intermediate layer have a uniform, because the locally thinner portion there is little , the selective oxidation region at the insulating film baking annealing is presumed that did not generate.
[0183]
　Comparative Example A10 & A11 are in either the intermediate layer forming annealing or the insulating film baking annealing, in order to not lower than the dew point at the time of baking the dew point during cooling, it is inferred that selective oxidation region is not preferred product.
Industrial Applicability
[0184]
　According to this aspect of the present invention, grain-oriented electrical steel sheet having an insulation coating unevenness is not in film adhesion, i.e., even without forsterite coating provides excellent oriented electrical steel sheet film adhesion of the insulating film be able to. Thus, there is a high availability of the industry.
DESCRIPTION OF SYMBOLS
[0185]
　1 the base steel sheet
　2 forsterite film
　3 insulating film
　4 intermediate layers
　5a, 5b, 5c selectively oxidized region
　La, Lb, the length of Lc selective oxidation region
　of t selective oxidation region thickness

The scope of the claims

[Requested item 1]A base steel sheet, and an intermediate layer disposed in contact on the base steel sheet, in the oriented electrical steel sheet having an insulating film serving as the intermediate layer in contact with arranged that in the uppermost surface,
　the cutting direction thickness when viewed in cutting plane is parallel to the direction, the an intermediate layer is selectively oxidized region,
　the is the thickness of the intermediate layer in the region where the selective oxidation region exists 50nm or more, not the selective oxidation region is present the thickness of the intermediate layer in the region is less than 50nm
oriented electrical steel sheet, characterized in that.
[Requested item 2]
　When viewed in the cutting plane, and Lz the entire length of the direction of the observation field perpendicular to the thickness direction in the unit [mu] m, and Lx the total length of the selectively oxidized region in a direction orthogonal to the thickness direction in the unit [mu] m, when defining a line segment ratio X of the selective oxidized region by formula 1 below, the line segment ratio X is less than 0.1% and not more than 12%
oriented electrical of claim 1, wherein the steel sheet.
　　　X = (Lx ÷ Lz) × 100 ··· ( Equation 1)
[Requested item 3]
　The thickness of the intermediate layer in a region where the selective oxidation region is present is at 50nm or more and 400nm or less, the thickness of the intermediate layer in a region where the selective oxidation region is not present is more and less than 50nm 2 nm
that oriented electrical steel sheet according to claim 1 or 2, characterized in.