Grain-oriented electrical steel sheet and method for producing same

Abstract

A grain-oriented electrical steel sheet is produced by subjecting a steel raw material having a prescribed component composition to hot rolling, cold rolling, and decarburization annealing concurrently with primary recrystallization annealing, applying an annealing separating agent to the surface of the steel sheet, performing final annealing, and then performing planarization annealing, forming a ceramic coating film on the surface of the steel sheet after the final annealing by electrodepositing a ceramic, preferably a ceramic comprising any one of carbides, nitrides, and oxides of one or more metal elements selected from Mg, Al, Si, Ti, Cr, Zr, and Y, or a ceramic comprising a composite of two or more of the carbides, nitrides, and oxides; as a result, a low-iron-loss grain-oriented electrical steel sheet having excellent uniformity and adhesion and capable of applying a coating film with high tension to the surface of the steel sheet is obtained. The coating film tension is preferably 5-40 MPa to the steel sheet.

Description

Technical Field

[0001] The present invention relates to an oriented electromagnetic steel sheet and a method for manufacturing the same, and more particularly, to an oriented electromagnetic steel sheet having extremely low iron loss and a method for manufacturing the same. Background Art

[0002] An oriented electromagnetic steel sheet is a soft magnetic material mainly used for cores of transformers and the like, and as its magnetic properties, low iron loss is particularly strongly required. As one of the methods for reducing iron loss, there is a method of imparting film tension to the steel sheet surface. Here, the above-mentioned film tension refers to the tensile stress imparted to the steel sheet from the film due to the difference in thermal properties between the steel sheet and the film formed on its surface. Specifically, this film tension utilizes the following situation: after forming a film having a lower thermal expansion rate than the steel sheet on the steel sheet surface at a high temperature and then cooling to room temperature, the steel sheet shrinks, but the film does not shrink so much, and thus a tensile stress is applied to the steel sheet. Therefore, the more a film having a lower thermal expansion rate and a higher Young's modulus than the steel sheet is formed, the more the film tension imparted to the steel sheet surface can be increased.

[0003] As a specific method for imparting film tension, there is usually the following method: after final annealing, a reagent composed of phosphate and silica is coated on the steel sheet surface, and then it is baked at a high temperature to form a film. For example, a method of forming a film composed of aluminum phosphate and silica is proposed in Patent Document 1, and a method of forming a film composed of magnesium phosphate and silica is proposed in Patent Document 2.

[0004] In addition, as another method, a technique has been proposed that focuses on the fact that since ceramics have a low thermal expansion rate and a high Young's modulus, it is easy to form a film that is favorable for imparting high tension. For example, a method of forming a ceramic film by vapor-depositing ceramics on the steel sheet surface using the PVD method or the CVD method is proposed in Patent Document 3, and a method of forming a ceramic film by coating a sol on the steel sheet surface using the sol-gel method and then baking it at a high temperature is proposed in Patent Document 4.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Publication No. 53-028375

[0008] Patent Document 2: Japanese Patent Publication No. 56-052117

[0009] Patent Document 3: Japanese Patent Publication No. 63-054767

[0010] Patent Document 4: Japanese Patent Laid-Open No. 02-243770 Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] However, for the methods of Patent Documents 1 and 2 above, although the film coating tension can be increased by increasing the thickness of the film coating, on the other hand, it will lead to a decrease in the duty factor. Therefore, there is actually a limit to increasing the film coating tension by this method. In addition, for the method of Patent Document 3 above, the film forming speed is slow, and decompression is required during film coating formation. Therefore, there are problems of poor manufacturability and increased manufacturing costs. In addition, for the method of Patent Document 4 above, in addition to the slow film forming speed, coating and baking need to be repeated. Therefore, there is still a problem of poor manufacturability.

[0013] The present invention has been completed in view of the above problems existing in the prior art, and its object is to provide a non-oriented electrical steel sheet with a film coating having excellent uniformity and adhesion and capable of imparting high tension to a steel sheet, and to provide a manufacturing method of a non-oriented electrical steel sheet capable of forming the above film coating in a short time.

[0014] Method for solving the problem

[0015] In order to solve the above problems, the inventors focused on the method of forming a film coating on the surface of the steel sheet after final annealing and repeatedly conducted in-depth research. As a result, it was found that if the method of electrodepositing ceramics on the surface of the steel sheet is used, a film coating having excellent uniformity and adhesion and capable of imparting high tension can be formed in a short time, and a non-oriented electrical steel sheet with extremely low iron loss can be manufactured at low cost and with good productivity. Thus, the present invention was developed.

[0016] The present invention based on the above insights is a non-oriented electrical steel sheet, characterized in that it has an electrodeposited film coating on the surface of the steel sheet after final annealing, which is composed of any one of carbides, nitrides and oxides of one or more metal elements selected from Mg, Al, Si, Ti, Cr, Zr and Y, or a composite of two or more of the above carbides, nitrides and oxides.

[0017] The above non-oriented electrical steel sheet of the present invention is characterized in that the tensile stress imparted to the steel sheet by the electrodeposited film coating of the ceramics is in the range of 5 to 40 MPa.

[0018] In addition, the above non-oriented electrical steel sheet of the present invention is characterized in that it does not have a forsterite film coating.

[0019] In addition, the above non-oriented electrical steel sheet of the present invention is characterized in that it has a composition containing C: 0.0050% by mass or less, Si: 2.0 to 5.0% by mass, and Mn: 0.01 to 0.5% by mass, and the balance is composed of Fe and inevitable impurities.

[0020] In addition, the above-mentioned grain-oriented electrical steel sheet of the present invention is characterized in that, on the basis of the above composition, it further contains at least one of B: 0.0001 to 0.005% by mass, Ti: 0.001 to 0.01% by mass, P: 0.005 to 0.1% by mass, Cr: 0.01 to 0.5% by mass, Ni: 0.01 to 1.5% by mass, Cu: 0.01 to 0.5% by mass, Nb: 0.002 to 0.08% by mass, Mo: 0.005 to 0.1% by mass, Sn: 0.005 to 0.5% by mass, Sb: 0.005 to 0.5% by mass, and Bi: 0.001 to 0.05% by mass.

[0021] In addition, the present invention provides a method for manufacturing a grain-oriented electrical steel sheet. In this method, a steel raw material with a specified composition is hot-rolled, cold-rolled, and decarburized annealed which also serves as primary recrystallization annealing. An annealing separating agent is coated on the surface of the steel sheet, and then final annealing is carried out, followed by flattening annealing. The method for manufacturing the grain-oriented electrical steel sheet is characterized in that a ceramic composed of any one of carbides, nitrides, and oxides of one or more metal elements selected from Mg, Al, Si, Ti, Cr, Zr, and Y, or a ceramic composed of a composite of two or more of the above carbides, nitrides, and oxides is electrodeposited on the surface of the steel sheet after the above final annealing to form an electrodeposited film of the ceramic.

[0022] In addition, the method for manufacturing the above-mentioned grain-oriented electrical steel sheet of the present invention is characterized in that the tensile stress imparted to the steel sheet by the electrodeposited film of the ceramic is set within the range of 5 to 40 MPa.

[0023] In addition, the method for manufacturing the above-mentioned grain-oriented electrical steel sheet of the present invention is characterized in that the ceramic is electrodeposited on the surface of the steel sheet after the final annealing that does not have a forsterite film.

[0024] In addition, the above-mentioned steel raw material used in the method for manufacturing the grain-oriented electrical steel sheet of the present invention is characterized in that it has a composition containing C: 0.01 to 0.1% by mass, Si: 2.0 to 5.0% by mass, and Mn: 0.01 to 0.5% by mass, and further contains at least one inhibitor-forming component group of the following Group A and Group B, with the balance being composed of Fe and inevitable impurities.

[0025] · Group A: at least one of S: 0.005 to 0.03% by mass and Se: 0.005 to 0.03% by mass;

[0026] · Group B: Al: 0.010 to 0.04% by mass and N: 0.005 to 0.01% by mass.

[0027] In addition, the above-mentioned steel raw material used in the manufacturing method of the above-mentioned grain-oriented electrical steel sheet of the present invention is characterized in that it has a component composition containing C: 0.01-0.1 mass%, Si: 2.0-5.0 mass% and Mn: 0.01-0.5 mass%, and also contains S: less than 0.005 mass%, Se: less than 0.005 mass%, Al: less than 0.010 mass% and N: less than 0.005 mass%, and the balance is Fe and inevitable impurities.

[0028] In addition, the above-mentioned steel raw material used in the above-mentioned method for manufacturing the grain-oriented electrical steel sheet of the present invention is characterized in that, in addition to the above-mentioned component composition, it also contains at least one of B: 0.0001-0.005 mass%, Ti: 0.001-0.01 mass%, P: 0.005-0.1 mass%, Cr: 0.01-0.5 mass%, Ni: 0.01-1.5 mass%, Cu: 0.01-0.5 mass%, Nb: 0.002-0.08 mass%, Mo: 0.005-0.1 mass%, Sn: 0.005-0.5 mass%, Sb: 0.005-0.5 mass% and Bi: 0.001-0.05 mass%.

[0029] Effects of the Invention

[0030] According to the present invention, by electrodepositing ceramics on the surface of the steel sheet after final annealing, a coating having excellent uniformity and adhesion and capable of imparting high tension can be formed in a short time, thereby making it possible to manufacture a grain-oriented electrical steel sheet with extremely low iron loss at low cost and with good productivity. DETAILED DESCRIPTION

[0031] First, the experiment that led to the development of the present invention will be described.

[0032] A steel raw material having a composition containing C: 0.07 mass%, Si: 3.4 mass%, Mn: 0.07 mass%, S: 0.002 mass%, Al: 0.023 mass% and N: 0.008 mass%, with the balance being Fe and inevitable impurities, was hot-rolled to produce a hot-rolled sheet. Then, the hot-rolled sheet was subjected to hot-rolled sheet annealing, and then cold-rolled twice with intermediate annealing to produce a cold-rolled sheet with a final sheet thickness of 0.23 mm. Then, the cold-rolled sheet was subjected to decarburization annealing which also served as a primary recrystallization annealing, and an annealing separator mainly composed of MgO was applied to the surface of the steel sheet, and then final annealing was performed to produce a final annealed sheet having a forsterite coating.

[0033] Next, on the surface of the steel sheet after the above-mentioned final annealing, an electrodeposited film of silicon dioxide (SiO 2 ) was formed in a 10 mass % sodium orthosilicate solution under the various conditions shown in Table 1.

[0034] Next, after performing flattening annealing on the above steel sheet under the conditions of 850°C × 60 s and baking the coating film, test pieces were cut from the steel sheet, and the coating film properties (film thickness, uniformity, adhesion, and coating film tension) and magnetic properties (magnetic flux density B8, iron loss W 17 / 50 ) were evaluated. Here, the film thickness of the coating film was measured by observing the cross-section of the coating film with SEM. In addition, regarding the uniformity of the coating film, the surface of the steel sheet was visually observed. If it was uniform, it was evaluated as ○; if it was slightly non-uniform, it was evaluated as △; if it was non-uniform, it was evaluated as ×. In addition, regarding the adhesion of the coating film, the steel sheet was wound around round bars of various diameters, and the minimum diameter at which the coating film did not peel off (hereinafter referred to as the "bending peel-off diameter") was used for evaluation. In addition, regarding the coating film tension, the warpage amount of the steel sheet after removing the coating film on one side was measured, and it was calculated by the following formula (1).

[0035] Coating film tension (MPa) = Young's modulus of the steel sheet (GPa) × thickness of the steel sheet (mm) × warpage amount of the steel sheet (mm) ÷ (length of the steel sheet (mm)) 2 × 10 3 …(1)

[0036] (It should be noted that the Young's modulus of the above steel sheet was 132 GPa.)

[0037] Furthermore, the magnetic properties were measured in accordance with JIS C 2556 (1996).

[0038]

[0039] The above measurement results were recorded in Table 1 together. According to Table 1, by increasing the current density or extending the energization time, the thickness of the coating film increased, and the coating film tension also increased, while the iron loss decreased. However, if the coating film was thin and the coating film tension was too small, the effect of reducing the iron loss was insufficient. On the contrary, if the coating film was thick and the coating film tension was too large, the adhesion deteriorated instead, and the iron loss also deteriorated. From these results, it can be seen that the method of electro-depositing silica on the surface of the steel sheet to form a coating film is not only excellent in productivity, but also an extremely effective means for improving the coating film properties and magnetic properties.

[0040] In addition, the inventor also formed an electro-deposited coating film in the same manner as above for ceramics other than the above-mentioned silica (SiO2), and conducted an experiment to confirm its effect. As a result, it was confirmed that if the electro-deposited coating film was composed of any one of carbides, nitrides, and oxides of one or more metal elements selected from Mg, Al, Si, Ti, Cr, Zr, and Y, or a composite of two or more of the above carbides, nitrides, and oxides, the same effect could be obtained. The present invention was developed based on the above new insights.

[0041] Next, the composition of the steel raw material (slab) used for manufacturing the grain-oriented electrical steel sheet of the present invention will be described.

[0042] C: 0.01 to 0.1% by mass

[0043] C is an element effective in improving the primary recrystallization texture. When it is less than 0.01% by mass, the above effects cannot be obtained sufficiently. On the other hand, when it exceeds 0.1% by mass, it is difficult to decarburize to a level where magnetic aging does not occur by decarburizing annealing. Therefore, C is preferably set in the range of 0.01 to 0.1% by mass. More preferably, it is in the range of 0.02 to 0.08% by mass.

[0044] Si: 2.0 to 5.0% by mass

[0045] Si is an element effective in increasing the resistivity of the steel and improving the magnetic properties. When it is less than 2.0% by mass, the above effects cannot be obtained sufficiently. On the other hand, when it exceeds 5.0% by mass, the steel is hardened / brittled and it becomes difficult to cold roll. Therefore, Si is preferably set in the range of 2.0 to 5.0% by mass. More preferably, it is in the range of 2.5 to 4.5% by mass.

[0046] Mn: 0.01 to 0.5% by mass

[0047] Similar to Si, Mn has the effect of increasing the resistivity of the steel and improving the magnetic properties. In addition, it is also an element effective in improving the hot rollability. However, when the Mn content is less than 0.01% by mass, the above effects cannot be obtained sufficiently. On the other hand, when it exceeds 0.5% by mass, γ-phase transformation is induced after secondary recrystallization, resulting in deterioration of the magnetic properties. Therefore, Mn is preferably set in the range of 0.01 to 0.5% by mass. More preferably, it is in the range of 0.01 to 0.2% by mass.

[0048] In addition, in the case of using inhibitors such as MnS, MnSe, and AlN for secondary recrystallization, it is different from the case of not using such inhibitors in the steel raw material (slab) for manufacturing the grain-oriented electrical steel sheet of the present invention.

[0049] For example, in the case of utilizing inhibitors to exhibit secondary recrystallization, when using MnS and / or MnSe as inhibitors, it is preferable to contain at least one of S: 0.005 to 0.03% by mass and Se: 0.005 to 0.03% by mass in addition to the above Mn. In addition, when using AlN as an inhibitor, it is preferable to contain Al: 0.010 to 0.04% by mass and N: 0.005 to 0.01% by mass. It should be noted that the above inhibitors can be used alone or in combination of two or more.

[0050] On the other hand, in the case where secondary recrystallization occurs without using an inhibitor, it is preferable to reduce the above-mentioned inhibitor-forming components as much as possible. Specifically, it is preferable that S: is less than 0.005% by mass, Se: is less than 0.005% by mass, Al: is less than 0.010% by mass, and N: is less than 0.005% by mass.

[0051] It should be noted that in the above-mentioned steel raw material used in the present invention, the balance other than the above-mentioned components is substantially Fe and inevitable impurities. However, for the purpose of improving magnetic properties, it may also contain at least one of B: 0.0001 to 0.005% by mass, Ti: 0.001 to 0.01% by mass, P: 0.005 to 0.1% by mass, Cr: 0.01 to 0.5% by mass, Ni: 0.01 to 1.5% by mass, Cu: 0.01 to 0.5% by mass, Nb: 0.002 to 0.08% by mass, Mo: 0.005 to 0.1% by mass, Sn: 0.005 to 0.5% by mass, Sb: 0.005 to 0.5% by mass, and Bi: 0.001 to 0.05% by mass on the basis of the above-mentioned components.

[0052] Next, a method for manufacturing the grain-oriented electrical steel sheet of the present invention will be described.

[0053] First, the steel adjusted to the above-mentioned composition suitable for the present invention is melted by a generally well-known refining process, and then a steel raw material (steel billet) is manufactured by a generally well-known ingot-blooming rolling method or continuous casting method. It should be noted that a thin cast sheet of 100 mm or less can also be manufactured by a direct casting method.

[0054] Next, after reheating the above-mentioned steel billet to a specified temperature, hot rolling is performed to obtain a hot-rolled sheet. It should be noted that in the case where the inhibitor-forming component is not contained, after continuous casting, the steel billet can be directly supplied to hot rolling without reheating.

[0055] Next, for the above-mentioned hot-rolled sheet, hot-rolled sheet annealing is performed as needed. In the case of performing hot-rolled sheet annealing, it is preferable to set the annealing temperature in the range of 800 to 1150°C. When it is lower than 800°C, the banded structure formed by hot rolling remains, and a grain-uniform primary recrystallized structure cannot be obtained, which hinders the growth of secondary recrystallized grains. Therefore, it may not be possible to fully obtain the effect of hot-rolled sheet annealing. On the other hand, when it exceeds 1150°C, the grain size after hot-rolled sheet annealing becomes too large, and it is still difficult to obtain a grain-uniform primary recrystallized structure.

[0056] After the above-mentioned hot-rolled sheet or the hot-rolled sheet after annealing of the hot-rolled sheet is descaled by pickling or the like, it is cold-rolled once or cold-rolled more than twice with intermediate annealing to produce a cold-rolled sheet with the final sheet thickness. It should be noted that in the case of performing intermediate annealing, it is preferable to set the annealing temperature in the range of 900 to 1200 °C. When the annealing temperature is lower than 900 °C, the grain size after intermediate annealing is too small and the Goss nuclei in the primary recrystallized structure decrease, and the magnetic properties may deteriorate. On the other hand, when it exceeds 1200 °C, the grain size after intermediate annealing becomes too large, and it is difficult to obtain a uniformly grained primary recrystallized structure.

[0057] Next, decarburizing annealing that also serves as primary recrystallization annealing is performed on the cold-rolled sheet with the final sheet thickness. Here, the heating rate during the heating process of the above-mentioned decarburizing annealing between 500 and 700 °C is preferably set to 50 °C / s or more. Thereby, the number of Goss nuclei in the primary recrystallized structure increases, and the magnetic properties can be improved. In addition, the temperature during decarburizing annealing is preferably set in the range of 750 to 950 °C. When it is lower than 750 °C, decarburization itself becomes difficult. On the other hand, when it exceeds 950 °C, the grain size of the primary recrystallized grains becomes too large, which may hinder secondary recrystallization. In addition, for the atmosphere during decarburizing annealing, it is preferable to set the oxygen potential P H2O / P H2 in the range of 0.3 to 0.6. When P H2O / P H2 is less than 0.3, decarburization becomes difficult. On the other hand, when it exceeds 0.6, an excessive amount of FeO is generated on the steel plate surface, and the film-forming properties may deteriorate. By the above-mentioned decarburizing annealing, the C contained in the steel is reduced to less than 0.0050 mass% at which magnetic aging does not occur.

[0058] Next, for the steel plate after the above-mentioned decarburizing annealing, an annealing release agent is coated on the steel plate surface, and then, final annealing is performed to perform purification treatment after secondary recrystallization. Here, when the above-mentioned secondary recrystallization occurs during the heating of the final annealing, it is preferable to heat at a heating rate of 2 to 50 °C / s in the temperature range of 700 to 1100 °C. On the other hand, when secondary recrystallization occurs while maintaining a constant temperature, it is preferable to maintain for 25 hours or more at any temperature between 700 and 1100 °C. In addition, the purification treatment is preferably carried out in an H2-containing atmosphere at a temperature of 1120 to 1250 °C for 2 to 50 hours. When the temperature of the purification treatment is lower than 1120 °C and the holding time is less than 2 hours, the purification is insufficient. On the other hand, when the temperature of the purification treatment exceeds 1250 °C and the holding time exceeds 50 hours, there is a possibility that the coil is buckled and the shape of the steel plate deteriorates. By performing the above-mentioned purification treatment, the inhibitor-forming components added to the steel raw material are reduced to the inevitable impurity level.

[0059] Here, in the present invention, it is most important to form a ceramic coating film by electrodepositing ceramics on the surface of the steel sheet after the above-mentioned final annealing. As the ceramics to be electrodeposited, ceramics composed of any one of carbides, nitrides, and oxides of one or more metal elements selected from Mg, Al, Si, Ti, Cr, Zr, and Y, or ceramics composed of a composite of two or more of the above carbides, nitrides, and oxides are required. Since these ceramics have a low coefficient of thermal expansion and a high Young's modulus, they are advantageous for forming a coating film with a large tensile stress imparted to the steel sheet.

[0060] In addition, the coating film tension imparted by the above ceramic coating film to the steel sheet is preferably set in the range of 5 to 40 MPa. When the coating film tension is less than 5 MPa, the effect of reducing iron loss due to the coating film tension cannot be obtained sufficiently. On the other hand, when the coating film tension exceeds 40 MPa, the stress generated at the interface between the steel sheet and the coating film is too strong, and the adhesion of the coating film deteriorates instead. More preferably, it is in the range of 10 to 35 MPa.

[0061] In addition, the thickness of the above ceramic coating film is not particularly limited as long as it is within the range where the above coating film tension can be obtained. However, when the film thickness exceeds 5 μm, the duty factor decreases and the magnetic properties of the transformer deteriorate, so the upper limit is preferably set to 5 μm. More preferably, it is 3 μm or less.

[0062] In addition, in order to further increase the effect of the ceramic coating film and further reduce iron loss, it is preferable to electrodeposit ceramics on the surface of the steel sheet after final annealing, preferably on the surface of the steel sheet that has been mirror-finished by removing a vitreous coating film such as forsterite from the above steel sheet surface. Regarding the method of mirror finishing, there is no particular limitation. For example, a method of chemically or physically removing the forsterite coating film, a method of adding a chloride to the annealing release agent to peel off the forsterite coating film, a method of not forming a forsterite coating film by coating an annealing release agent mainly composed of Al2O3, etc. can be used.

[0063] In addition, there is no particular limitation on the method of electrodepositing ceramics either. For example, in the case of electrodepositing silicon dioxide (SiO2), it can be electrodeposited in a solution containing silicate ions, or it can be electrophoretically deposited in a solution in which silicon dioxide particles are dispersed. In addition, in the case of electrophoretic deposition, the dispersion medium can be water, an organic solvent, or a mixture of them. In addition, electrodeposition can also be carried out while applying tension to the steel sheet. The same applies to other ceramics.

[0064] In addition, in electrodeposition, it is easy to thicken the film thickness by increasing the current density, voltage, and energization time, so it is a means advantageous for forming a coating film. Appropriate electrodeposition conditions vary depending on the type of ceramic, but from the viewpoint of improving manufacturability, it is preferable to increase the current density and voltage and shorten the energization time.

[0065] In addition, there is no particular limitation on the energization method. For example, a method of indirectly energizing by alternately arranging an anode and a cathode non - contactingly in the through - plate direction can be used, or a method of directly energizing using an energization roll can be used.

[0066] Next, for the steel plate electroplated with the above - mentioned ceramics, then flattening annealing for correcting the shape of the steel plate is carried out, and the electroplated ceramics are baked to form a ceramic coating film. It should be noted that the baking of the coating film can also be carried out outside the flattening annealing equipment. Here, the above annealing temperature is preferably set in the range of 800 to 1000 °C. When the annealing temperature is lower than 800 °C, in addition to the flattening being likely to be insufficient, the adhesion of the ceramic coating film may also be insufficient. On the other hand, when the annealing temperature exceeds 1000 °C, creep deformation of the steel plate may occur and the magnetic properties may deteriorate instead.

[0067] For the steel plate after the above - mentioned flattening annealing, then a magnetic domain refinement treatment is carried out as needed to produce a product plate. In addition, a generally well - known insulating coating film can be further formed on the above - mentioned ceramic coating film as needed. However, when the film thickness increases, the duty factor decreases, so it is preferably set in the above - mentioned film thickness range (5 μm or less) together with the ceramic coating film.

[0068] Example 1

[0069] A steel raw material (slab) having a composition containing C: 0.03 mass%, Si: 3.4 mass%, Mn: 0.07 mass%, S: 0.003 mass%, and the balance being composed of Fe and inevitable impurities is hot - rolled to produce a hot - rolled sheet, and the hot - rolled sheet is subjected to hot - rolled sheet annealing. Next, the steel plate after the above - mentioned hot - rolled sheet annealing is cold - rolled to produce a cold - rolled sheet with a final thickness of 0.23 mm. After decarburization annealing that also serves as primary recrystallization annealing, an annealing release agent mainly composed of MgO is coated on the surface of the steel plate, and final annealing is carried out. Then, hydrochloric acid pickling is carried out to remove the forsterite coating film, and mirror finishing is carried out by chemical polishing using hydrofluoric acid. Next, electrophoretic deposition is carried out in a mixed solution of water and ethanol in which various ceramics shown in Table 2 are dispersed, and baking is carried out under the conditions of 850 °C × 60 s in flattening annealing to produce a product plate.

[0070] A test piece is cut out from the product plate thus obtained, and the coating film properties (film thickness, uniformity, adhesion, and coating film tension) and magnetic properties (magnetic flux density B8, iron loss W 17 / 50 ) are evaluated. It should be noted that the properties of the ceramic coating film are evaluated by the method described in the foregoing experiment. In addition, the magnetic properties are measured in accordance with JIS C 2556 (1996).

[0071]

[0072] The results of the above evaluations are all recorded in Table 2. As can be seen from Table 2, by electro-depositing ceramics on the surface of the steel sheet after final annealing under the conditions of the present invention, a ceramic coating film with excellent uniformity, adhesion, and capable of imparting high tension can be formed in a short time. Therefore, an oriented electromagnetic steel sheet with extremely low iron loss can be manufactured inexpensively and with good productivity.

[0073] Example 2

[0074] A hot-rolled sheet is made by hot-rolling a steel raw material (slab) having a composition containing various components shown in Table 3 and the balance being composed of Fe and inevitable impurities. The hot-rolled sheet is subjected to hot-rolled sheet annealing, and then cold-rolled to make a cold-rolled sheet with a final thickness of 0.23 mm. Next, after subjecting the above cold-rolled sheet to decarburizing annealing which also serves as primary recrystallization annealing, an annealing separating agent mainly composed of MgO and containing antimony chloride is coated on the surface of the steel sheet, and final annealing is carried out to make a final annealed sheet without a forsterite coating film. Then, on the above final annealed sheet, a ceramic coating film is electrophoretically deposited in a mixed solution of water and ethanol in which alumina (Al2O3) is dispersed under the conditions of 5V×40 seconds, and then baked under the conditions of 850°C×60s in a flattening annealing to make a product sheet.

[0075] Test pieces are cut from the product sheet thus obtained, and the coating film characteristics (film thickness, uniformity, adhesion, and coating film tension) and magnetic characteristics (magnetic flux density B8, iron loss W 17 / 50 ) are evaluated. It should be noted that the characteristics of the ceramic coating film are evaluated by the method described in the aforementioned experiment. In addition, the magnetic characteristics are measured in accordance with JIS C 2556 (1996).

[0076]

[0077] The results of the above evaluations are all recorded in Table 3. According to Table 3, even when using steel raw materials with greatly different raw material compositions, steel sheets that meet the composition conditions of the present invention can obtain good coating film characteristics and magnetic characteristics.

Claims

1. An oriented electromagnetic steel sheet, characterized in that, The electroplated film on the surface of the steel sheet after final annealing is a ceramic composed of any one of carbides, nitrides, and oxides of one or more metal elements selected from Mg, Al, Si, Ti, Cr, Zr, and Y, or a ceramic composed of a composite of two or more of the carbides, nitrides, and oxides.

2. The oriented electromagnetic steel sheet according to claim 1, characterized in that, The tensile stress imparted to the steel sheet by the electroplated film of the ceramic is in the range of 5 to 40 MPa.

3. The oriented electromagnetic steel sheet according to claim 1 or 2, characterized in that, It does not have a forsterite film.

4. The grain-oriented electrical steel sheet according to any one of claims 1 to 3, characterized in that, It has a composition containing C: 0.0050% by mass or less, Si: 2.0 to 5.0% by mass, and Mn: 0.01 to 0.5% by mass, and the balance is composed of Fe and inevitable impurities.

5. The oriented electromagnetic steel sheet according to claim 4, wherein, On the basis of the above composition, it further contains at least one of B: 0.0001 to 0.005% by mass, P: 0.005 to 0.1% by mass, Ti: 0.001 to 0.01% by mass, Cr: 0.01 to 0.5% by mass, Ni: 0.01 to 1.5% by mass, Cu: 0.01 to 0.5% by mass, Nb: 0.002 to 0.08% by mass, Mo: 0.005 to 0.1% by mass, Sn: 0.005 to 0.5% by mass, Sb: 0.005 to 0.5% by mass, and Bi: 0.001 to 0.05% by mass.

6. A method for manufacturing an oriented electromagnetic steel sheet, wherein, The method for manufacturing the grain-oriented electrical steel sheet is characterized in that a steel raw material with a specified composition is hot-rolled, cold-rolled, decarburized annealed which also serves as primary recrystallization annealing, an annealing separator is coated on the surface of the steel sheet, final annealing is carried out, and then flattening annealing is carried out. On the surface of the steel sheet after the final annealing, a ceramic composed of any one of carbides, nitrides, and oxides of one or more metal elements selected from Mg, Al, Si, Ti, Cr, Zr, and Y, or a ceramic composed of a composite of two or more of the carbides, nitrides, and oxides is electroplated to form an electroplated film of the ceramic.

7. The manufacturing method of the oriented electromagnetic steel sheet according to claim 6, characterized in that, The tensile stress imparted to the steel sheet by the electroplated film of the ceramic is set in the range of 5 to 40 MPa.

8. The manufacturing method of the oriented electromagnetic steel sheet according to claim 6 or 7, characterized in that, Ceramic is electroplated on the surface of the steel sheet after final annealing that does not have a forsterite film.

9. The method for manufacturing an oriented electromagnetic steel sheet according to any one of claims 6 to 8, characterized in that, The steel raw material has a composition containing C: 0.01 to 0.1% by mass, Si: 2.0 to 5.0% by mass, and Mn: 0.01 to 0.5% by mass, and also contains at least one inhibitor-forming component in the following Group A and Group B, and the balance is composed of Fe and inevitable impurities. · Group A: at least one of S: 0.005 to 0.03% by mass and Se: 0.005 to 0.03% by mass; · Group B: Al: 0.010 to 0.04% by mass and N: 0.005 to 0.01% by mass.

10. The manufacturing method of the oriented electromagnetic steel sheet according to any one of claims 6 to 8, characterized in that, The steel raw material has a composition containing C: 0.01 to 0.1% by mass, Si: 2.0 to 5.0% by mass, and Mn: 0.01 to 0.5% by mass, and also contains S: less than 0.005% by mass, Se: less than 0.005% by mass, Al: less than 0.010% by mass, and N: less than 0.005% by mass, and the balance is composed of Fe and inevitable impurities.

11. The method for manufacturing an oriented electromagnetic steel sheet according to claim 9 or 10, characterized in that, On the basis of the above composition, the steel raw material further contains at least one of the following elements: B: 0.0001 - 0.005% by mass, P: 0.005 - 0.1% by mass, Ti: 0.001 - 0.01% by mass, Cr: 0.01 - 0.5% by mass, Ni: 0.01 - 1.5% by mass, Cu: 0.01 - 0.5% by mass, Nb: 0.002 - 0.08% by mass, Mo: 0.005 - 0.1% by mass, Sn: 0.005 - 0.5% by mass, Sb: 0.005 - 0.5% by mass, and Bi: 0.001 - 0.05% by mass.

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