Grain-oriented electrical steel sheet and its manufacturing method

Abstract

When a steel material having a prescribed component composition is hot-rolled, cold-rolled, and subjected to decarburization and annealing which also serves as primary recrystallisation annealing, an annealing separator is applied to the surface of the steel sheet, finishing annealing is carried out, and then flattening annealing is carried out to manufacture a grain-oriented electromagnetic steel sheet: a ceramic, preferably a ceramic comprising a carbide, a nitride, or an oxide of one or more metal elements selected from Mg, Al, Si, Ti, Cr, Zr, or Y, or a ceramic comprising a complex of two or more substances from among the abovementioned carbides, nitrides, and oxides, is electrodeposited on the surface of the finishing-annealed steel sheet, and a ceramic coating is formed; and a coating tension of preferably 5-40 MPa is applied to the steel sheet, whereby a low-iron-loss grain-oriented electromagnetic steel sheet having a coating that has excellent uniformity and adhesion and that is capable of imparting high tension to the steel sheet surface is obtained.

Description

[Technical Field]

[0001] The present invention relates to a grain-oriented electrical steel sheet and a manufacturing method thereof, and more particularly to a grain-oriented electrical steel sheet with extremely low iron loss and a manufacturing method thereof. [Background technology]

[0002] Grain-oriented electrical steel sheets are soft magnetic materials primarily used in the cores of transformers and other devices. Low iron loss, in particular, is a highly desirable magnetic property. One method for reducing iron loss is to apply a coating tension to the surface of a steel sheet. Here, the coating tension refers to the tensile stress imparted to the steel sheet by the coating formed on its surface due to the difference in thermal properties between the steel sheet and the coating formed on its surface. Specifically, this coating tension utilizes the fact that, when a coating with a lower thermal expansion coefficient than the steel sheet is formed on the surface of a steel sheet at high temperatures and then cooled to room temperature, the steel sheet shrinks while the coating does not shrink as much, resulting in tensile stress being applied to the steel sheet. Therefore, the coating tension imparted to the surface of the steel sheet can be increased by forming a coating with a lower thermal expansion coefficient and a higher Young's modulus than the steel sheet.

[0003] A typical specific method for imparting coating tension is to apply a chemical solution containing phosphate and silica to the surface of the steel sheet after finish annealing, and then bake the solution at a high temperature to form a coating. For example, Patent Document 1 proposes a method for forming a coating containing aluminum phosphate and silica, and Patent Document 2 proposes a method for forming a coating containing magnesium phosphate and silica.

[0004] Another proposed method is to take advantage of the fact that ceramics have a low coefficient of thermal expansion and a high Young's modulus, making it easy to form a coating that is advantageous for applying high tension. For example, Patent Document 3 proposes a method of forming a ceramic coating by vapor-depositing ceramic onto the surface of a steel sheet using a PVD method or a CVD method, and Patent Document 4 proposes a method of forming a ceramic coating by applying a sol to the surface of a steel sheet and then baking it at a high temperature using a sol-gel method. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 53-028375 [Patent Document 2] Special Publication No. 56-052117 [Patent Document 3] Special Publication No. 63-054767 [Patent Document 4] Japanese Patent Application Publication No. 02-243770 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the methods of Patent Documents 1 and 2, while increasing the thickness of the coating can increase the coating tension, this results in a decrease in the space factor, and in practice, there is a limit to how much the coating tension can be increased. Furthermore, the method of Patent Document 3 has problems such as a slow coating rate and the need to reduce the pressure during coating formation, which makes it difficult to manufacture and increases manufacturing costs. Furthermore, the method of Patent Document 4 has problems such as a slow coating rate and the need to repeat coating and baking, which also makes it difficult to manufacture.

[0007] The present invention has been made in view of the above-mentioned problems of the prior art, and has an object to provide a grain-oriented electrical steel sheet with low iron loss that has a coating that is excellent in uniformity and adhesion and that can impart high tension to the steel sheet, and to propose a method for manufacturing the grain-oriented electrical steel sheet that can form the coating in a short time. [Means for solving the problem]

[0008] In order to solve the above problems, the inventors have conducted extensive research, focusing on methods for forming a coating on the surface of a steel sheet after finish annealing. As a result, they have found that a method of electrodepositing ceramic on the surface of a steel sheet can form a coating that is highly uniform and adheres well and can impart high tension in a short period of time, and that can produce a grain-oriented electrical steel sheet with extremely low iron loss at low cost and with good productivity, which led to the development of the present invention.

[0009] Based on the above findings, the present invention provides a grain-oriented electrical steel sheet characterized in that the steel sheet surface after final annealing has an electrodeposited coating of ceramics consisting of any of carbides, nitrides and oxides of one or more metallic elements selected from Mg, Al, Si, Ti, Cr, Zr and Y, or ceramics consisting of a composite of two or more of the above carbides, nitrides and oxides.

[0010] The grain-oriented electrical steel sheet of the present invention is characterized in that the tensile stress imparted to the steel sheet by the ceramic electrodeposited coating is in the range of 5 to 40 MPa.

[0011] The grain-oriented electrical steel sheet of the present invention is characterized in that it does not have a forsterite coating.

[0012] The grain-oriented electrical steel sheet of the present invention is characterized by having a chemical composition containing 0.0050 mass% or less of C, 2.0 to 5.0 mass% of Si, 0.01 to 0.5 mass% of Mn, and the balance being Fe and unavoidable impurities.

[0013] Furthermore, the grain-oriented electrical steel sheet of the present invention is characterized in that, in addition to the above-mentioned chemical composition, it further contains at least one of B: 0.0001 to 0.005 mass%, Ti: 0.001 to 0.01 mass%, P: 0.005 to 0.1 mass%, Cr: 0.01 to 0.5 mass%, Ni: 0.01 to 1.5 mass%, Cu: 0.01 to 0.5 mass%, Nb: 0.002 to 0.08 mass%, Mo: 0.005 to 0.1 mass%, Sn: 0.005 to 0.5 mass%, Sb: 0.005 to 0.5 mass%, and Bi: 0.001 to 0.05 mass%.

[0014] The present invention also proposes a method for producing grain-oriented electrical steel sheet, which comprises hot-rolling a steel material having a predetermined chemical composition, cold-rolling it, subjecting it to decarburization annealing that also serves as primary recrystallization annealing, applying an annealing separator to the steel sheet surface, finish annealing, and then flattening annealing, characterized in that a ceramic consisting of any of carbides, nitrides, and oxides of one or more metallic elements selected from Mg, Al, Si, Ti, Cr, Zr, and Y, or a ceramic consisting of a composite of two or more of the above carbides, nitrides, and oxides, is electrodeposited on the steel sheet surface after the finish annealing to form an electrodeposited ceramic coating.

[0015] The method for producing the grain-oriented electrical steel sheet of the present invention is characterized in that the tensile stress imparted to the steel sheet by the ceramic electrodeposited coating is in the range of 5 to 40 MPa.

[0016] The method for producing the grain-oriented electrical steel sheet of the present invention is characterized in that ceramic is electrodeposited onto the surface of the steel sheet after finish annealing, which does not have a forsterite coating.

[0017] The steel material used in the method for producing the grain-oriented electrical steel sheet of the present invention is characterized by having a component composition that contains 0.01 to 0.1 mass% C, 2.0 to 5.0 mass% Si, and 0.01 to 0.5 mass% Mn, and further contains at least one inhibitor-forming component from the following groups A and B, with the balance being Fe and unavoidable impurities: Note Group A: At least one of S: 0.005 to 0.03 mass% and Se: 0.005 to 0.03 mass% Group B: Al: 0.010-0.04 mass% and N: 0.005-0.01 mass%

[0018] The steel material used in the method for producing the grain-oriented electrical steel sheet of the present invention is characterized by having a chemical composition containing 0.01 to 0.1 mass% C, 2.0 to 5.0 mass% Si, and 0.01 to 0.5 mass% Mn, and further containing less than 0.005 mass% S, less than 0.005 mass% Se, less than 0.010 mass% Al, and less than 0.005 mass% N, with the balance being Fe and unavoidable impurities.

[0019] Furthermore, the steel material used in the method for producing the grain-oriented electrical steel sheet of the present invention is characterized in that, in addition to the above-mentioned chemical composition, it further contains at least one of B: 0.0001 to 0.005 mass%, Ti: 0.001 to 0.01 mass%, P: 0.005 to 0.1 mass%, Cr: 0.01 to 0.5 mass%, Ni: 0.01 to 1.5 mass%, Cu: 0.01 to 0.5 mass%, Nb: 0.002 to 0.08 mass%, Mo: 0.005 to 0.1 mass%, Sn: 0.005 to 0.5 mass%, Sb: 0.005 to 0.5 mass%, and Bi: 0.001 to 0.05 mass%. [Effects of the Invention]

[0020] According to the present invention, by electrodepositing ceramic onto the surface of a steel sheet after finish annealing, it is possible to form a coating that is uniform and highly adhesive and can impart high tension in a short time, making it possible to inexpensively and productively produce grain-oriented electrical steel sheets with extremely low iron loss. DETAILED DESCRIPTION OF THE INVENTION

[0021] First, the experiment that led to the development of the present invention will be described. A steel material having a chemical composition containing 0.07 mass% C, 3.4 mass% Si, 0.07 mass% Mn, 0.002 mass% S, 0.023 mass% Al, and 0.008 mass% N, with the balance being Fe and unavoidable impurities, was hot-rolled to form a hot-rolled sheet. The hot-rolled sheet was then subjected to hot-rolled sheet annealing, followed by two cold-rolling steps with intermediate annealing in between to form a cold-rolled sheet with a final thickness of 0.23 mm. The cold-rolled sheet was then subjected to decarburization annealing, which also served as primary recrystallization annealing, and the surface of the steel sheet was coated with an annealing separator mainly composed of MgO. The steel sheet was then subjected to finish annealing to form a finish-annealed sheet with a forsterite coating.

[0022] Next, an electrodeposition coating of silica (SiO2) was formed on the surface of the steel sheet after the above-mentioned finish annealing in a 10 mass % sodium orthosilicate solution under various conditions shown in Table 1.

[0023] Next, the steel sheet was subjected to flattening annealing at 850°C for 60 seconds to bake the coating, and then test pieces were taken from the steel sheet to measure the coating characteristics (film thickness, uniformity, adhesion, and coating tension) and magnetic properties (magnetic flux density B8, iron loss W 17 / 50 ) was evaluated. Here, the film thickness of the coating was measured by observing the cross section of the coating using an SEM. The uniformity of the coating was evaluated by visually observing the surface of the steel sheet, with a rating of ○ if uniform, △ if slightly uneven, and × if uneven. The adhesion of the coating was evaluated by wrapping the steel sheet around round bars of various diameters and measuring the smallest diameter at which the coating did not peel off (hereinafter referred to as the "bending peeling diameter"). The coating tension was calculated using the following formula (1) by measuring the amount of warping of the steel sheet after removing the coating from one side. Coating tension (MPa) = Young's modulus of steel plate (GPa) × thickness of steel plate (mm) × warpage of steel plate (mm) ÷ (length of steel plate (mm)) 2 x10 3 ···(1) (The Young's modulus of the steel plate used was 132 GPa.) Furthermore, the magnetic properties were measured in accordance with JIS C 2556 (1996).

[0024] [Table 1]

[0025] The results of the above measurements are also shown in Table 1. As can be seen from Table 1, by increasing the current density or extending the current application time, the thickness of the coating increases, as does the coating tension, reducing iron loss. However, if the coating is too thin and the coating tension is too low, the effect of reducing iron loss is insufficient. Conversely, if the coating is too thick and the coating tension is too high, adhesion deteriorates and iron loss also deteriorates. These results demonstrate that the method of forming a coating by electrodepositing silica on the surface of steel sheet is not only highly productive, but also an extremely effective means of improving coating properties and magnetic properties.

[0026] Furthermore, the inventors conducted experiments to form electrodeposited coatings on ceramics other than the above-mentioned silica (SiO2) in the same manner as above and to confirm their effects. As a result, they confirmed that similar effects can be obtained with electrodeposited coatings of ceramics consisting of carbides, nitrides, and oxides of one or more metal elements selected from Mg, Al, Si, Ti, Cr, Zr, and Y, or ceramics consisting of a composite of two or more of the above carbides, nitrides, and oxides. The present invention was developed based on the above-mentioned novel findings.

[0027] Next, the chemical composition of the steel material (slab) used in manufacturing the grain-oriented electrical steel sheet of the present invention will be described. C: 0.01 to 0.1 mass% C is an effective component for improving the primary recrystallization texture, and if its content is less than 0.01 mass%, this effect cannot be fully achieved. On the other hand, if its content exceeds 0.1 mass%, it becomes difficult to decarburize to a level that does not cause magnetic aging during decarburization annealing. Therefore, the C content is preferably in the range of 0.01 to 0.1 mass%, and more preferably in the range of 0.02 to 0.08 mass%.

[0028] Si: 2.0 to 5.0 mass% Silicon is an effective component for increasing the resistivity of steel and improving its magnetic properties, but if its content is less than 2.0 mass%, these effects are not fully achieved. On the other hand, if its content exceeds 5.0 mass%, the steel becomes hard and embrittled, making cold rolling difficult. Therefore, the silicon content is preferably in the range of 2.0 to 5.0 mass%, and more preferably in the range of 2.5 to 4.5 mass%.

[0029] Mn: 0.01 to 0.5 mass% Like Si, Mn has the effect of increasing the resistivity of steel and improving magnetic properties. It is also an effective component for improving hot rollability. However, if the Mn content is less than 0.01 mass%, the above effect cannot be fully obtained. On the other hand, if the Mn content exceeds 0.5 mass%, it induces γ transformation after secondary recrystallization, resulting in deterioration of magnetic properties. Therefore, the Mn content is preferably in the range of 0.01 to 0.5 mass%, and more preferably in the range of 0.01 to 0.2 mass%.

[0030] Furthermore, apart from the above-mentioned essential components, the steel material (slab) used in the production of the grain-oriented electrical steel sheet of the present invention differs depending on whether or not an inhibitor such as MnS, MnSe, or AlN is used to induce secondary recrystallization.

[0031] For example, when an inhibitor is used to induce secondary recrystallization, if MnS and / or MnSe are used as the inhibitor, it is preferable to further contain at least one of S: 0.005-0.03 mass% and Se: 0.005-0.03 mass% in addition to the above-mentioned Mn. Furthermore, if AlN is used as the inhibitor, it is preferable to contain Al: 0.010-0.04 mass% and N: 0.005-0.01 mass%. The above inhibitors may be used alone or in combination.

[0032] On the other hand, when no inhibitor is used to induce secondary recrystallization, it is preferable to reduce the above-mentioned inhibitor-forming components as much as possible, specifically, 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%.

[0033] The steel material used in the present invention essentially consists of Fe and unavoidable impurities, except for the above-mentioned components. However, for the purpose of improving magnetic properties, the steel material may further contain at least one of the following elements: 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%.

[0034] Next, a method for producing the grain-oriented electrical steel sheet of the present invention will be described. First, steel having the above-described chemical composition suitable for the present invention is melted by a commonly known refining process, and then a steel material (slab) is produced by a commonly known ingot-making and blooming method or a continuous casting method. Alternatively, thin cast pieces of 100 mm or less may be produced by a direct casting method.

[0035] Next, the slab is reheated to a predetermined temperature and then hot-rolled to form a hot-rolled sheet. If the slab does not contain an inhibitor-forming component, the slab may be directly subjected to hot rolling after continuous casting without being reheated.

[0036] Next, the hot-rolled sheet is subjected to hot-rolled sheet annealing as necessary. When hot-rolled sheet annealing is performed, the annealing temperature is preferably in the range of 800 to 1150°C. If the annealing temperature is less than 800°C, the band structure formed by hot rolling remains, a granular primary recrystallized structure is not obtained, and the growth of secondary recrystallized grains is inhibited, so there is a risk that the effect of hot-rolled sheet annealing will not be fully obtained. On the other hand, if the annealing temperature exceeds 1150°C, the grain size after hot-rolled sheet annealing becomes too large, again making it difficult to obtain a granular primary recrystallized structure.

[0037] The hot-rolled sheet after the hot rolling or hot-rolled sheet annealing is descaled by pickling or the like, and then cold-rolled once or two or more times with intermediate annealing in between to produce a cold-rolled sheet of the final thickness. If intermediate annealing is performed, the annealing temperature is preferably in the range of 900 to 1200°C. If the annealing temperature is less than 900°C, the grain size after intermediate annealing will be too small, reducing the number of Goss nuclei in the primary recrystallized structure and potentially degrading the magnetic properties. On the other hand, if the annealing temperature exceeds 1200°C, the grain size after intermediate annealing will be too large, making it difficult to obtain a uniformly sized primary recrystallized structure.

[0038] Next, the cold-rolled sheet having the final thickness is subjected to decarburization annealing, which also serves as primary recrystallization annealing. Here, the heating rate between 500 and 700°C during the heating process of the decarburization annealing is preferably 50°C / s or more. This increases the number of Goss nuclei in the primary recrystallization structure, improving the magnetic properties. The temperature during decarburization annealing is preferably in the range of 750 to 950°C. If the temperature is less than 750°C, decarburization itself becomes difficult. On the other hand, if the temperature exceeds 950°C, the grain size of the primary recrystallization grains becomes too large, which may inhibit secondary recrystallization. Furthermore, the atmosphere during decarburization annealing should be such that the oxygen potential P H2O / P H2 It is preferable that P is in the range of 0.3 to 0.6. H2O / P H2 If the ratio is less than 0.3, decarburization becomes difficult. On the other hand, if it exceeds 0.6, excessive FeO is generated on the steel sheet surface, which may deteriorate the coating properties. By the above-mentioned decarburization annealing, the C content in the steel is reduced to 0.0050 mass% or less, at which point magnetic aging does not occur.

[0039] Next, the steel sheet after the decarburization annealing is coated with an annealing separator on its surface, and then subjected to secondary recrystallization and finish annealing for purification. If the secondary recrystallization is to occur during the temperature rise in the finish annealing, it is preferable to heat the steel sheet at a temperature range of 700 to 1100°C at a temperature rise rate of 2 to 50°C / s. On the other hand, if the secondary recrystallization is to occur by maintaining the steel sheet at a constant temperature, it is preferable to maintain the steel sheet at any temperature between 700 and 1100°C for 25 hours or more. Furthermore, it is preferable to perform the purification treatment at a temperature of 1120 to 1250°C for 2 to 50 hours in an H2-containing atmosphere. If the purification treatment temperature is less than 1120°C and the holding time is less than 2 hours, the purification will be insufficient. On the other hand, if the purification treatment temperature is higher than 1250°C and the holding time is longer than 50 hours, the coil may buckle and deform, resulting in deterioration of the steel sheet shape. By carrying out the above purification treatment, the inhibitor-forming components added to the steel material are reduced to the level of unavoidable impurities.

[0040] The most important aspect of the present invention is to form a ceramic coating by electrodepositing a ceramic on the surface of the steel sheet after the above-mentioned finish annealing. The ceramic to be electrodeposited must be 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. These ceramics have a low thermal expansion coefficient and a high Young's modulus, making them advantageous for forming a coating that imparts a large tensile stress to the steel sheet.

[0041] The coating tension applied to the steel sheet by the ceramic coating is preferably in the range of 5 to 40 MPa. If the coating tension is less than 5 MPa, the iron loss reduction effect due to the coating tension cannot be sufficiently obtained. On the other hand, if the coating tension exceeds 40 MPa, the stress generated at the interface between the steel sheet and the coating is too strong, and the adhesion of the coating may actually deteriorate. A more preferred range is 10 to 35 MPa.

[0042] The thickness of the ceramic coating is not particularly limited as long as it is within the range in which the above-mentioned coating tension can be obtained. However, if the thickness exceeds 5 μm, the space factor decreases and the magnetic properties of the transformer deteriorate, so the upper limit is preferably 5 μm. More preferably, it is 3 μm or less.

[0043] In order to further enhance the effect of the ceramic coating and further reduce iron loss, it is preferable to electrodeposit ceramic on the steel sheet surface after finish annealing, preferably on a steel sheet surface that has been mirror-finished by removing a glassy coating such as forsterite from the steel sheet surface. The method for mirror-finishing is not particularly limited. For example, a method of chemically or physically removing the forsterite coating, a method of adding a chloride to an annealing separator to strip the forsterite coating, or a method of applying an annealing separator mainly containing Al2O3 or the like to prevent the formation of a forsterite coating may be used.

[0044] The method for electrodepositing ceramics is not particularly limited. For example, when electrodepositing silica (SiO2), electrodeposition may be performed in a solution containing silicate ions, or electrophoretic deposition may be performed in a solution in which silica particles are dispersed. When electrophoretic deposition is performed, water or an organic solvent may be used as the dispersion medium, or a mixture of these may be used. Electrodeposition may also be performed while applying tension to the steel sheet. The same applies to other ceramics.

[0045] Furthermore, electrodeposition is an advantageous method for forming a coating because the film thickness can be easily increased by increasing the current density, voltage, and current application time. Suitable electrodeposition conditions vary depending on the type of ceramic, but from the perspective of improving manufacturability, it is preferable to increase the current density and voltage and shorten the current application time.

[0046] The method of applying current is not particularly limited. For example, a method of indirectly applying current by alternately arranging anodes and cathodes in a non-contact manner in the sheet passing direction may be used, or a method of directly applying current by using a current-carrying roll may be used.

[0047] Next, the steel sheet with the ceramic electrodeposited thereon is subjected to flattening annealing to correct the shape of the steel sheet, and the electrodeposited ceramic is baked to form a ceramic coating. The coating may be baked using a facility other than the flattening annealing facility. The annealing temperature is preferably in the range of 800 to 1000°C. Annealing temperatures below 800°C tend to result in insufficient flattening, and the adhesion of the ceramic coating may also be insufficient. On the other hand, annealing temperatures above 1000°C may cause creep deformation of the steel sheet, which may actually deteriorate the magnetic properties.

[0048] The steel sheet after the planarization annealing is then subjected to magnetic domain refinement treatment as needed to produce a finished product. Furthermore, if needed, a commonly known insulating coating may be formed on the ceramic coating. However, since an increase in the coating thickness reduces the space factor, it is preferable to keep the thickness of the ceramic coating and the insulating coating within the above-mentioned range (5 μm or less). [Example]

[0049] A steel material (slab) containing 0.03 mass% C, 3.4 mass% Si, 0.07 mass% Mn, and 0.003 mass% S, with the remainder consisting of Fe and unavoidable impurities, was hot-rolled to form a hot-rolled sheet, which was then subjected to hot-rolled sheet annealing. The hot-rolled sheet was then cold-rolled to a final thickness of 0.23 mm. This steel sheet was then subjected to decarburization annealing, which also served as primary recrystallization annealing. The steel sheet surface was then coated with an annealing separator primarily composed of MgO and subjected to finish annealing. The forsterite coating was then removed by pickling with hydrochloric acid, and the surface was then polished to a mirror finish by chemical polishing with hydrofluoric acid. Next, various ceramics shown in Table 2 were dispersed in a water-ethanol mixture, and the resulting product was electrophoretically deposited. The resulting product was then baked at 850°C for 60 seconds during planarization annealing to form a finished sheet.

[0050] Test pieces were taken from the product sheets thus obtained, and the coating characteristics (film thickness, uniformity, adhesion, and coating tension) and magnetic properties (magnetic flux density B8, iron loss W 17 / 50The properties of the ceramic coating were evaluated using the method explained in the previous experiment. The magnetic properties were measured in accordance with JIS C 2556 (1996).

[0051] [Table 2]

[0052] The results of the above evaluations are also shown in Table 2. Table 2 shows that by electrodepositing ceramic onto the surface of steel sheet after finish annealing under conditions that satisfy the present invention, a ceramic coating that is excellent in uniformity and adhesion and can impart high tensile strength can be formed in a short time, and therefore grain-oriented electrical steel sheet with extremely low iron loss can be produced inexpensively and with good productivity. [Example]

[0053] A steel material (slab) containing the various components shown in Table 3, with the remainder consisting of Fe and unavoidable impurities, was hot-rolled to form a hot-rolled sheet, which was then annealed and cold-rolled to a final thickness of 0.23 mm. The cold-rolled sheet was then subjected to decarburization annealing, which also served as primary recrystallization annealing. An annealing separator primarily composed of MgO and containing antimony chloride was applied to the surface of the cold-rolled sheet, followed by finish annealing to produce a finish-annealed sheet without a forsterite coating. A ceramic coating was then electrophoretically deposited on the finish-annealed sheet in a mixed solution of water and ethanol containing dispersed alumina (Al2O3) at 5 V for 40 seconds, followed by baking at 850°C for 60 seconds in a planarization annealing process to produce a finished sheet.

[0054] Test pieces were taken from the product sheets thus obtained, and the coating characteristics (film thickness, uniformity, adhesion, and coating tension) and magnetic properties (magnetic flux density B8, iron loss W 17 / 50 The properties of the ceramic coating were evaluated using the method explained in the previous experiment. The magnetic properties were measured in accordance with JIS C 2556 (1996).

[0055] [Table 3]

[0056] The results of the above evaluations are also shown in Table 3. Table 3 shows that even when steel materials with significantly different material compositions are used, steel sheets that satisfy the composition conditions of the present invention have good coating properties and magnetic properties.

Claims

1. a steel sheet surface after finish annealing has an electrodeposited coating of ceramics made of carbides or nitrides of one or more metal elements selected from Mg, Al, Si, Ti, Cr, Zr and Y, or ceramics made of a composite containing the carbides or nitrides; A grain-oriented electrical steel sheet characterized in that the tensile stress imparted to the steel sheet by the ceramic electrodeposited coating is in the range of 5 to 40 MPa.

2. A steel sheet having an electrodeposited ceramic coating made of an oxide of one or more metal elements selected from Mg, Al, Si, Ti, Cr, Zr, and Y on the surface thereof after finish annealing, A grain-oriented electrical steel sheet characterized in that the tensile stress imparted to the steel sheet by the ceramic electrodeposited coating is in the range of 17.57 to 40 MPa.

3. The grain-oriented electrical steel sheet according to claim 1, characterized in that it does not have a forsterite film.

4. The grain-oriented electrical steel sheet according to claim 2, characterized in that it does not have a forsterite film.

5. The grain-oriented electrical steel sheet according to any one of claims 1 to 4, characterized in that it has a component composition containing C: 0.0050 mass% or less, Si: 2.0 to 5.0 mass%, and Mn: 0.01 to 0.5 mass%, with the balance being Fe and unavoidable impurities.

6. 6. The grain-oriented electrical steel sheet according to claim 5, further comprising, in addition to the above-mentioned component composition, at least one of B: 0.0001 to 0.005 mass%, P: 0.005 to 0.1 mass%, Ti: 0.001 to 0.01 mass%, Cr: 0.01 to 0.5 mass%, Ni: 0.01 to 1.5 mass%, Cu: 0.01 to 0.5 mass%, Nb: 0.002 to 0.08 mass%, Mo: 0.005 to 0.1 mass%, Sn: 0.005 to 0.5 mass%, Sb: 0.005 to 0.5 mass%, and Bi: 0.001 to 0.05 mass%.

7. A method for producing a grain-oriented electrical steel sheet, comprising hot rolling a steel material having a predetermined chemical composition, cold rolling the steel material, subjecting the steel material to decarburization annealing which also serves as primary recrystallization annealing, applying an annealing separator to the surface of the steel sheet, finish annealing the steel sheet, and then flattening annealing the steel sheet, a ceramic comprising a carbide or nitride of one or more metal elements selected from Mg, Al, Si, Ti, Cr, Zr, and Y, or a ceramic comprising a composite containing the carbide or the nitride, is electrodeposited on the surface of the steel sheet after the finish annealing to form an electrodeposited ceramic coating; A method for producing a grain-oriented electrical steel sheet, characterized in that the tensile stress imparted to the steel sheet by the ceramic electrodeposited coating is within a range of 5 to 40 MPa.

8. A method for manufacturing grain-oriented electrical steel sheet, comprising hot rolling a steel material having a predetermined chemical composition, cold rolling it, subjecting it to decarburization annealing which also serves as primary recrystallization annealing, applying an annealing separator to the surface of the steel sheet, finish annealing it, and then flattening annealing it, a ceramic comprising an oxide of one or more metal elements selected from Mg, Al, Si, Ti, Cr, Zr, and Y is electrodeposited on the surface of the steel sheet after the finish annealing to form an electrodeposited ceramic coating; A method for producing a grain-oriented electrical steel sheet, characterized in that the tensile stress imparted to the steel sheet by the ceramic electrodeposited coating is within a range of 17.57 to 40 MPa.

9. The method for producing a grain-oriented electrical steel sheet according to claim 7, wherein ceramic is electrodeposited on the surface of the steel sheet after finish annealing that does not have a forsterite coating.

10. The method for producing a grain-oriented electrical steel sheet according to claim 8, wherein ceramic is electrodeposited on the surface of the steel sheet after finish annealing that does not have a forsterite film.

11. The method for producing a grain-oriented electrical steel sheet according to any one of claims 7 to 10, characterized in that the steel material contains C: 0.01 to 0.1 mass%, Si: 2.0 to 5.0 mass%, and Mn: 0.01 to 0.5 mass%, and further contains at least one inhibitor-forming component selected from the following Groups A and B, with the balance consisting of Fe and unavoidable impurities: Note Group A: At least one of S: 0.005 to 0.03 mass% and Se: 0.005 to 0.03 mass% Group B: Al: 0.010 to 0.04 mass% and N: 0.005 to 0.01 mass%

12. 11. The method for producing a grain-oriented electrical steel sheet according to claim 7, wherein the steel material contains C: 0.01 to 0.1 mass%, Si: 2.0 to 5.0 mass%, Mn: 0.01 to 0.5 mass%, and further 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%, with the balance being Fe and unavoidable impurities.

13. The steel material further contains, in addition to the above-described component composition, B: 0.0001 to 0.005 mass%, P: 0.005 to 0.1 mass%, Ti: 0.001 to 0.01 mass%, Cr: 0.01 to 0.5 mass%, Ni: 0.01 to 1.5 mass%, Cu: 0.01 to 0.5 mass%, Nb: 0.002 to 0.08 mass%, Mo: 0.005 to 0.1 mass%, Sn: 0.005 to 0.5 mass%, Sb: 0.005 to 0.5 mass%, and Bi: 0.001 to 0.05 mass%. The method for producing a grain-oriented electrical steel sheet according to claim 11,

14. The steel material further contains, in addition to the above-described component composition, B: 0.0001 to 0.005 mass%, P: 0.005 to 0.1 mass%, Ti: 0.001 to 0.01 mass%, Cr: 0.01 to 0.5 mass%, Ni: 0.01 to 1.5 mass%, Cu: 0.01 to 0.5 mass%, Nb: 0.002 to 0.08 mass%, Mo: 0.005 to 0.1 mass%, Sn: 0.005 to 0.5 mass%, Sb: 0.005 to 0.5 mass%, and Bi: 0.001 to 0.05 mass%. The method for producing a grain-oriented electrical steel sheet according to claim 12,

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