Coating for grain-oriented silicon steel coating layer, grain-oriented silicon steel sheet and manufacturing method thereof

Abstract

A coating is provided, comprising a phosphate, colloidal silicon dioxide and a chromate compound, wherein the phosphate comprises magnesium dihydrogen phosphate and aluminum dihydrogen phosphate, and the molar ratio of Al to Mg in the phosphate is 0.02-0.15. A grain-oriented silicon steel sheet is provided, comprising a substrate and a coating layer on a surface of the substrate, wherein the coating layer is formed by the coating. A manufacturing method for grain-oriented silicon steel sheet is provided, the method comprising the steps of: covering a surface of a substrate with a coating, and then subjecting it to a sintering process, wherein the plate temperature during the sintering process is 800-880°C. The coating layer formed by the coating can provide grain-oriented silicon steel with higher tensile strength and better heat resistance, and has good promotion prospects and application effect.

Description

[Technical field]

[0001] Technical Field The present disclosure relates to coatings and steel sheets and methods for producing the same, in particular to coatings for grain-oriented silicon steel coating layers, and grain-oriented silicon steel sheets and methods for producing the same. [Background technology]

[0002] Background technology As is well known in the art, grain oriented silicon steel is a steel that contains silicon and has grains with the easy axis of magnetization oriented in the (100) direction. <001> Grain-oriented silicon steel sheet refers to an electrical steel sheet in which the rolling direction is substantially consistent with the rolling direction. Grain-oriented silicon steel sheet is mainly used to manufacture transformer cores, which have excellent electromagnetic properties in the rolling direction and are important soft magnetic materials. When grain-oriented silicon steel sheet is used as a material to manufacture transformer cores, the energy loss and noise level of the transformer can be effectively reduced.

[0003] At present, imparting high tensile strength to grain-oriented silicon steel by surface coating layer is an important technical method for improving the performance of grain-oriented silicon steel. In the prior art, the surface coating layer of grain-oriented silicon steel sheet is generally composed of a forsterite (Mg2SiO4)-based ceramic film and an insulating coating layer thereon. The insulating coating layer can play the role of insulation, rust prevention and improving processability.

[0004] Under normal circumstances, the surface coating layer of grain-oriented silicon steel is formed at high temperature. When the temperature of the grain-oriented silicon steel sheet with the surface coating layer on it is lowered to room temperature, the surface coating layer has a lower thermal expansion coefficient than the steel sheet, so the difference in thermal expansion coefficient between the steel sheet and the coating layer gives tension to the steel sheet. The tension given to the steel sheet can reduce the loss (the abnormal eddy current loss is reduced by narrowing the width of the 180° magnetic domain) and magnetostriction of the grain-oriented silicon steel. Therefore, the energy loss and noise level of the transformer can be effectively reduced.

[0005] In recent years, in order to further improve the performance of grain-oriented silicon steel, many scientists and engineers have made many fruitful attempts and designed many new surface coating layers.

[0006] Japanese patent publication number JPS4839338A, entitled "Method for forming an insulating coating on grain-oriented silicon steel sheet" and publication date June 9, 1973, discloses a coating containing aluminum dihydrogen phosphate, colloidal silica and chromic anhydride. After applying the coating onto the surface of grain-oriented silicon steel and subjecting it to heat treatment, a MgO-P2O5-SiO2 and Al2O3-P2O5-SiO2 phosphate-based glass coating layer is formed on the surface of the steel sheet.

[0007] A Chinese patent document entitled "Insulating Coating Treatment Solution and Method for Producing Metal with Insulating Coating" with publication number CN107923046A and publication date April 17, 2018, discloses an insulating coating treatment solution containing at least one phosphate selected from the group consisting of Mg, Ca, Ba, Sr, Zn, Al and Mn; and two or more colloidal silicas with different average particle sizes. In this application, the tension of the insulating coating layer is optimized and improved by colloidal silicas with different particle sizes. In the above technical solution, the tightness of the coating layer can be improved to a certain extent by using a mixture of silica sols with different particle sizes, but the room for improving the tension is very limited.

[0008] A Chinese patent document entitled "Grain-oriented electrical steel sheet with coating layer and method for its manufacture" with publication number CN104024474A and publication date September 3, 2014, discloses a grain-oriented silicon steel sheet. In this application, a coating layer is prepared which contains elements P, Si, Cr and O and at least one element selected from the group consisting of Mg, Al, Ni, Co, Mn, Zn, Fe, Ca and Ba, and contains at least 5 wt% phosphoric acid crystal phase, and thus a higher tensile stress is achieved and iron loss is reduced. In the above technical solution, the tension provided to the steel sheet by the insulating coating layer is improved by increasing the elastic modulus of the coating layer, but needs to be realized by increasing the amount of chromic anhydride added and increasing the temperature at which the coating layer is sintered. However, the range of the amount of chromic anhydride added to the phosphoric acid coating layer is very narrow. When the amount of chromic anhydride is increased to a certain extent, cracks and turbidity / cloudiness will occur in the coating layer. When the temperature at which the coating layer is sintered is higher than about 900°C, it causes the crystallization of colloidal silica. The crystalline phase formed in the coating layer can increase the tension, which results in a decrease in the corrosion resistance and transparency of the coating layer.

[0009] From the above, it can be seen that in the prior art, the performance given to grain-oriented silicon steel by the phosphoric acid-based glass coating layer is still not good, and still has the defects of insufficient tensile strength and low heat resistance. When the transformer core made of grain-oriented silicon steel is subjected to stress relief annealing treatment, the performance of the coating layer on the surface of the grain-oriented silicon steel will deteriorate, resulting in a decrease in tensile strength, so that the energy loss and noise level of the transformer cannot be effectively reduced. Summary of the Invention [Means for solving the problem]

[0010] Summary of the Invention In view of the above technical problems in this field, the present inventor has creatively designed a new coating through much research. The coating can be applied to the surface of grain-oriented silicon steel to form a coating layer with improved tensile and heat resistance. The formed coating layer can effectively reduce the energy loss and noise level of the transformer. The coating according to the present disclosure has good promotion prospects and application effect.

[0011] One of the objectives of the present disclosure is to provide a coating that can be used to form a surface coating layer of grain-oriented silicon steel sheet. The surface coating layer can provide the grain-oriented silicon steel sheet with higher tensile strength and better heat resistance.

[0012] To achieve the above object, the present disclosure provides a coating comprising: a phosphate, colloidal silica, and a chromate compound; wherein the phosphate comprises magnesium dihydrogen phosphate and aluminum dihydrogen phosphate, and the molar ratio of element Al to element Mg (Al / Mg) in the phosphate is 0.02-0.15.

[0013] Preferably, the coating according to the present disclosure has an active component consisting of: a phosphate, colloidal silica and a chromate compound; and wherein the phosphate comprises magnesium dihydrogen phosphate and aluminum dihydrogen phosphate, and the molar ratio of element Al to element Mg in the phosphate is 0.02-0.15.

[0014] In one embodiment, water can be used as the solvent for coating.In one embodiment, the coating comprises soluble phosphate, colloidal silica and chromate compound.In one embodiment, the phosphate can form a net-like structure on the surface of the steel plate after being subjected to sintering heat treatment.In one embodiment, the colloidal silica and the phosphate can form a coating layer with low thermal expansion coefficient after being subjected to sintering heat treatment.

[0015] It should be noted that in the coating according to the present disclosure, the phosphates include magnesium dihydrogen phosphate and aluminum dihydrogen phosphate, which contain a certain amount of free phosphate ions. The phosphates easily absorb water and dissolve, thereby destroying the integrity of the coating layer formed. Therefore, in the coating according to the present disclosure, a chromate compound needs to be further added, so that a stable CrPO4 can be formed. The chromate compound plays a role in fixing the phosphate ions and improving the water resistance of the coating layer.

[0016] Through thorough research, the inventors have found that by adjusting the ratio of magnesium dihydrogen phosphate and aluminum dihydrogen phosphate in a certain range, the tensile strength of the coating layer formed after the coating is applied on the surface of grain-oriented silicon steel can be significantly improved, and the tensile deterioration degree of the coating layer after the coating layer is subjected to stress relief annealing can be reduced. Therefore, in order to ensure the quality of the coating layer, the molar ratio of element Al to element Mg in the phosphate is controlled to be 0.02-0.15, preferably 0.02-0.085.

[0017] It should be noted that when the molar ratio of element Al to element Mg is lower than 0.02, the effect of improving the tensile strength of the coating layer is not obvious; when the molar ratio of Al to Mg is higher than 0.15, the effect of improving the tensile strength of the coating layer is not obvious, and the tensile strength of the coating layer deteriorates after stress relief annealing. Therefore, in the coating according to the present disclosure, the molar ratio of element Al to element Mg is controlled between 0.02 and 0.15.

[0018] Preferably, in the coating according to the present disclosure, the mass ratio of colloidal silica to phosphate (colloidal silica / phosphate) is 0.8-1.2. By controlling the mass ratio of colloidal silica to phosphate between 0.8 and 1.2, the tension effect of the coating layer of grain-oriented silicon steel can be better exerted.

[0019] In the technical solution of the present disclosure, the addition of chromate compound can play the role of fixing phosphate ions and improving the water resistance of the coating layer.When the mass ratio of chromate compound to phosphate is 0.1 or more, the moisture resistance of the coating layer can be improved.When the mass ratio of chromate compound to phosphate is 0.5 or less, the turbidity / cloudiness and cracks of the coating layer can be reduced, and the tension and corrosion resistance of the coating layer can be improved.

[0020] Therefore, in the coating according to the present disclosure, it is also preferred to further control the mass ratio of the chromate compound to the phosphate in order to achieve better moisture resistance, tension, and corrosion resistance of the coating layer, and to reduce the turbidity / cloudiness and cracking of the coating layer. In a preferred embodiment, the mass ratio of the chromate compound to the phosphate (chromate compound / phosphate) is 0.1-0.5, more preferably 0.2-0.4.

[0021] Another object of the present disclosure is to provide a grain-oriented silicon steel sheet coated with a coating according to the present disclosure, so that the grain-oriented silicon steel sheet has excellent properties. The tension applied to the grain-oriented silicon steel sheet by the coating layer formed from the coating according to the present disclosure can effectively reduce the loss and magnetostriction of the grain-oriented silicon steel. The grain-oriented silicon steel sheet according to the present disclosure can be used as a material for manufacturing a transformer core, which can effectively reduce the energy loss and noise level of the transformer.

[0022] To achieve the above objectives, the present disclosure provides a grain-oriented silicon steel sheet, comprising a substrate and a coating layer on a surface of the substrate, wherein the coating layer is formed from the coating described in the present disclosure.

[0023] Preferably, the grain oriented silicon steel sheet according to the present disclosure has a surface tension of >8 MPa and a tensile degradation before and after stress relief annealing treatment of ≦5%.

[0024] Preferably, the grain-oriented silicon steel sheet according to the present disclosure has an iron loss P of 0.6 to 1.37 W / kg after stress relief annealing treatment. 17 / 50 has.

[0025] In the grain-oriented silicon steel sheet according to the present disclosure, in order to achieve better tensile and insulating effects of the coating layer while increasing the lamination factor of the steel sheet, the coating layer can be controlled to have a single-sided dry film amount within a certain range. 2 When the coating layer has a single-sided dry film amount of 8 g / m or more, the tensile strength and insulating effect of the coating layer can be improved. 2 The lamination factor of the steel sheet can be improved when it has the following single-sided dry film amount: Therefore, in the grain-oriented silicon steel sheet according to the present disclosure, the coating layer is 2-8 g / m 2 In a further preferred embodiment, the coating layer has a dry film weight per side of 3 to 6 g / m 2 The amount of dry film on one side is 100%.

[0026] Preferably, the substrate has a thickness of 0.15 to 0.50 mm.

[0027] In the grain-oriented silicon steel plate according to the present disclosure, the composition of the substrate in the grain-oriented silicon steel plate is not particularly limited. Any prior art composition system that can achieve the technical effect of the present disclosure may be used. Preferably, the substrate is a ferrosilicon alloy with Goss texture, and the substrate has an elemental Si content of 2% to 4% by mass percent.

[0028] Preferably, the substrate has a forsterite-free or forsterite-containing ceramic film on a surface thereof.

[0029] A further object of the present disclosure is to provide a method for manufacturing the grain-oriented silicon steel sheet, which can be efficiently produced by the method.

[0030] In order to achieve the above object, the present disclosure provides a method for producing grain-oriented silicon steel sheet, comprising the steps of: providing a coating on a surface of a substrate, and then performing a sintering treatment, in which the substrate has a temperature of 800-880°C (i.e., substrate temperature), and the sintering treatment is performed at this temperature.

[0031] In the method for producing grain-oriented silicon steel sheet according to the present disclosure, the substrate temperature, at which the sintering process is carried out, is controlled to be between 800°C and 880°C. This is because: if the substrate temperature during the sintering process is lower than 800°C, the purpose of the flatness of the steel sheet cannot be achieved, and the effect of tensioning the steel sheet by the coating layer is not significant. If the substrate temperature during the sintering process is higher than 880°C, the silica in the coating layer will tend to form crystalline silica, resulting in the tightness and tension of the coating layer being reduced.

[0032] Compared with the prior art, the coating and grain-oriented silicon steel sheet and manufacturing method therefor according to the present disclosure have the following advantages and beneficial effects:

[0033] In the coating according to the present disclosure, the inventors have designed and controlled the molar ratio of element Al and element Mg in the mixed phosphate of magnesium dihydrogen phosphate and aluminum dihydrogen phosphate. By controlling the molar ratio of the two between 0.02 and 0.15, it is ensured that the coating layer formed by applying the coating on the surface of grain-oriented silicon steel can provide the steel plate with higher tensile strength and better heat resistance.

[0034] The grain-oriented silicon steel plate coated with the above coating according to the present disclosure has extremely excellent performance. The tension applied to the steel plate by the coating layer formed from the coating according to the present disclosure can effectively reduce the loss and magnetostriction of the grain-oriented silicon steel. The grain-oriented silicon steel plate according to the present disclosure can be used as a material for manufacturing the iron core of a transformer, and can effectively reduce the energy loss and noise level of the transformer. [Brief description of the drawings]

[0035] [Figure 1] FIG. 1 shows diagrammatically the relationship between the molar ratio of element Al to element Mg in the phosphate in the coating and the tensile stress imparted to the steel sheet by the coating layer (coating layer tension). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Detailed Description All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs, unless expressly indicated otherwise. It should be understood that the terms used in the description of this disclosure are for the purpose of describing particular embodiments only and are not intended to be limiting.

[0037] In this specification, the tension can be determined by a method commonly used in the art, such as the method described in the Examples.

[0038] In this specification, the expression "degree of tensile deterioration before and after stress relief annealing" refers to the rate of change (%) of tension before and after stress relief annealing, i.e., rate of change (%) = (tensile value before stress relief annealing - tensile value after stress relief annealing) / tensile value before stress relief annealing * 100%.

[0039] In this specification, the amount of dry film on one side refers to the mass per unit area of ​​the coating layer on the surface of one side of the steel plate, which is determined by removing the coating layer on the surface to be measured and calculating based on the change in weight of the steel plate before and after removing the coating layer and the area of ​​the steel plate.

[0040] In this specification, iron loss P 17 / 50 refers to the iron loss value measured under the conditions of a magnetic flux density of 1.7 T and a frequency of 50 Hz.

[0041] Hereinafter, the coating according to the present disclosure, as well as the grain-oriented silicon steel sheet and the manufacturing method therefor, will be further explained and described based on the drawings and examples, but the explanations and descriptions do not constitute undue limitations on the technical solutions of the present disclosure. All reagents used in the examples can be obtained through commercial channels. Experimental methods for which no specific conditions were specified in the examples were carried out according to conventional conditions known in the art or conditions recommended by the manufacturers.

[0042] Examples 1 to 15 and Comparative Examples 1 to 7 The coatings of Examples 1-15 and Comparative Examples 1-7 were prepared by mixing phosphate, colloidal silica, and chromate compounds. Table 1 lists the parts by weight and weight ratios of each component in the coatings of Examples 1-15 and Comparative Examples 1-7.

[0043] [Table 1]

[0044] It should be noted that all phosphates contained Mg-containing dihydrogen phosphate and Al-containing dihydrogen phosphate in Examples 1-15 and Comparative Examples 1-7. The molar ratios of element Al to element Mg in the phosphates of the Examples and Comparative Examples are listed in Table 2 below.

[0045] [Table 2]

[0046] It should be noted that in Examples 1-15 and Comparative Examples 1-7, all chromate compounds used in the examples and comparative examples were chromic anhydride. Of course, in some other embodiments, chromate salts (such as magnesium dichromate, calcium chromate, and zinc chromate) can also be used as the chromate compound.

[0047] Next, grain-oriented silicon steel sheets were prepared by coating the coatings in Examples 1 to 15 and Comparative Examples 1 to 7 on the substrate of grain-oriented silicon steel sheet, respectively. Here, the substrate was a ferrosilicon alloy having a Goss structure.

[0048] The same substrate steel slab was used for the grain-oriented silicon steel sheet in the examples and comparative examples, where the mass percentage of each chemical element was as follows: C: 0.047%, Si: 3.23%, S: 0.008%, Als: 0.029%, N: 0.006%, Mn: 0.012%, and the balance is Fe and other unavoidable impurities. Indeed, in some other embodiments, substrate steel slabs with other chemical compositions can also be used, and the substrate can be controlled to have a content of element Si between 2% and 4% by mass percentage.

[0049] The grain-oriented silicon steel sheets in Examples 1 to 15 and Comparative Examples 1 to 7 were prepared by the following steps: (1) Smelting and casting according to the mass percentages of the above chemical elements to obtain a base steel slab; (2) heating the steel slab at a temperature of 1150°C, and then hot rolling the slab to obtain a hot-rolled plate having a thickness of 2.8 mm; (3) The hot-rolled plate is pickled and then cold-rolled to obtain a cold-rolled plate having a thickness of 0.15-0.50 mm, in which the cold rolling can be performed once, or two or more passes of cold rolling can be performed, with intermediate annealing being optionally performed in between; (4) subjecting the cold-rolled plate to decarburization annealing treatment, and then carrying out continuous nitriding treatment under a moist protective atmosphere of nitrogen and hydrogen with ammonia gas; (5) Applying a separator containing magnesium oxide as a main component to the steel sheet after nitriding treatment; (6) After coiling, secondary recrystallization annealing is performed in a dry protective atmosphere of nitrogen and hydrogen, where the annealing is performed at a temperature of 1200°C and controlled to hold at that temperature for 25 hours to obtain a substrate coated with a forsterite ceramic film thereon and having a Goss structure, where the substrate has a thickness of 0.15-0.50 mm; (7) applying a coating onto the surface of the substrate; (8) Sintering at a temperature of 800-880 °C for 10s or more to obtain grain-oriented silicon steel sheet, and the coating layer is 2-8 g / m 2 The amount of dry film on one side is controlled to be 100%.

[0050] It should be noted that the coating according to the present disclosure can be effectively applied regardless of whether the substrate has a forsterite ceramic film on its surface. Thus, in the above manufacturing method, it is also possible to prevent the formation of a forsterite ceramic film on the surface of the steel sheet by controlling the decarburization annealing and the separator. The substrate may have a forsterite-free ceramic film or a forsterite-containing ceramic film on its surface.

[0051] Table 3 lists the relevant process parameters in the manufacturing methods for the grain-oriented silicon steel sheets in Examples 1-15 and Comparative Examples 1-7.

[0052] [Table 3]

[0053] Next, the tension given to the steel sheet by the coating layer was determined for the resulting grain-oriented silicon steel sheet having the coating layer. The performance of the coating layer was evaluated by measuring the rate of change in the coating layer tension before and after stress relief annealing. The coating layer tension was measured in the following manner. The test results are shown in Table 4.

[0054] (1) Tension σ of one-sided coating layer: The rolling direction is taken as the length direction, and the grain-oriented silicon steel plate is cut into a sample sheet having a length of 300 mm and a width of 30 mm, and then the one-sided coating layer is removed. The deflection amount of the sample sheet is measured, and the tension σ of the one-sided coating layer is calculated by the following formula:

[0055]

number

[0056] In the above formula, σ represents the tension of the coating layer, and its unit may be MPa; E represents the Young's modulus of the steel plate, and its unit may be GPa; t represents the thickness of the steel plate, and its unit may be mm; H represents the amount of warping, and its unit may be mm; and L represents the length of the steel plate, and its unit may be mm.

[0057] Thereby, the tension σ of the one-side coating layer of the grain-oriented silicon steel sheets in Examples 1 to 15 and Comparative Examples 1 to 7 was obtained, where the tension σ is the tension σ of the coating layer before stress relief annealing (SPA) treatment.

[0058] (2) The grain-oriented silicon steel plate was subjected to stress relief annealing, and then the coating layer tension on the grain-oriented silicon steel plate after stress relief annealing treatment was tested. The process conditions of the stress relief annealing treatment were as follows: the stress relief annealing heat treatment was carried out at 800°C for 2 hours, and the atmosphere was 100% N2. The test method for the coating layer tension on the grain-oriented silicon steel plate after SRA treatment was the same as the test method for the tension σ of the single-sided coating layer above.

[0059] The heat resistance of the grain-oriented silicon steel sheets in the examples and comparative examples was obtained by comparing the tensile values ​​of the coating layer of the grain-oriented silicon steel sheets before and after SRA treatment.The larger change in the tensile value of the coating layer before and after SRA heat treatment indicates the worse heat resistance of the steel sheet; in contrast, the smaller change in the tensile value of the coating layer before and after SRA heat treatment indicates the better heat resistance of the steel sheet.

[0060] (3) Iron loss: Iron loss P of the grain-oriented silicon steel sheets in the examples and comparative examples after stress relief annealing (SRA) treatment at a magnetic flux density of 1.7 T and a frequency of 50 Hz 17 / 50 was measured.

[0061] Table 4 shows the relevant performance test results of the grain-oriented silicon steel sheets in Examples 1 to 15 and Comparative Examples 1 to 7.

[0062] [Table 4]

[0063] From Table 3, it can be seen that in Examples 1 to 15 using coatings that satisfy the design control requirements of this disclosure, the performance of the resulting grain-oriented silicon steel sheets is very good: the core loss is low; and the surface coating layer tension σ before SRA is 8.56 to 14.56 MPa; and after stress relief annealing at high temperature, the coating layer tension σ does not deteriorate, i.e., the deterioration degree is small (≦5%). From the above, it can be seen that the grain-oriented silicon steel sheets in Examples 1 to 15 exhibited very good heat resistance.

[0064] However, in Comparative Examples 1-7, because the coating had parameters that did not meet the design control requirements of the present disclosure, and the molar ratio of element Al to element Mg did not meet the design requirements of the present disclosure, the properties of the surface coating layer of the obtained grain-oriented silicon steel sheet were poor: the coating layer tension was small, and the heat resistance was poor. After the grain-oriented silicon steel sheets in Comparative Examples 1-7 were subjected to stress relief annealing (SRA) at high temperature, the coating layer tension was significantly deteriorated, and the deterioration degree was much higher than that of the grain-oriented silicon steel sheets in Examples 1-15.

[0065] FIG. 1 shows diagrammatically the relationship between the molar ratio of element Al to element Mg in the phosphate in the coating and the tensile stress imparted to the steel sheet by the coating layer (coating layer tension).

[0066] As shown in FIG. 1, the coating layer in which the molar ratio of element Al to element Mg in the phosphate is controlled between 0.02 and 0.15 has higher tensile strength and excellent heat resistance.

[0067] It should be noted that the combination manner of the technical features in this disclosure is not limited to the combination manner described in the claims or the combination manner described in the specific embodiments. All technical features described in this disclosure can be combined or integrated in any manner as long as there is no contradiction between them.

[0068] It should also be noted that the above-mentioned embodiments are merely specific embodiments of the present disclosure. The present invention is not limited to the above-mentioned embodiments, and it is clear that all similar variations and modifications that can be directly obtained or easily conceived by a person skilled in the art from the contents disclosed in the present disclosure are included in the scope of the present disclosure.

Claims

1. Contains phosphates, colloidal silica and chromate compounds; and The coating, wherein the phosphate comprises magnesium dihydrogen phosphate and aluminum dihydrogen phosphate, and the molar ratio of element Al to element Mg in the phosphate is between 0.02 and 0.15, preferably between 0.02 and 0.

085.

2. having active ingredients consisting of phosphates, colloidal silica and chromate compounds; and 2. The coating according to claim 1, wherein the phosphate comprises magnesium dihydrogen phosphate and aluminium dihydrogen phosphate, and the molar ratio of element Al to element Mg in the phosphate is between 0.02 and 0.15, preferably between 0.02 and 0.

085.

3. 3. Coating according to claim 1 or 2, wherein the weight ratio of colloidal silica to phosphate is between 0.8 and 1.

2.

4. Coating according to any of claims 1 to 3, wherein the weight ratio of chromate compound to phosphate is between 0.1 and 0.5, and preferably the weight ratio of chromate compound to phosphate is between 0.2 and 0.

4.

5. A substrate; and a coating layer on the surface of the substrate A grain-oriented silicon steel sheet comprising the coating layer according to any one of claims 1 to 4.

6. The grain oriented silicon steel sheet according to claim 5, having a surface tension of >8 MPa and a tensile degradation before and after stress relief annealing of ≦5%.

7. After stress relief annealing, grain-oriented silicon steel sheet has an iron loss P of 0.6 to 1.37 W / kg. 17 / 50 The grain-oriented silicon steel sheet according to claim 5 or 6, having the following properties.

8. Coating layer: 2 to 8 g / m 2 , preferably 3 to 6 g / m 2 The grain-oriented silicon steel sheet according to any one of claims 5 to 7, having a one-sided dry film amount of

9. The grain-oriented silicon steel sheet according to any one of claims 5 to 8, wherein the substrate has a thickness of 0.15 to 0.50 mm.

10. The grain oriented silicon steel sheet according to any one of claims 5 to 9, wherein the substrate is a ferrosilicon alloy having a Goss texture, and preferably the substrate has a content of elemental Si of 2% to 4% by mass percent.

11. The grain oriented silicon steel sheet according to any one of claims 5 to 10, wherein the substrate has a forsterite-free or forsterite-containing ceramic film on a surface thereof.

12. A method for producing the grain-oriented silicon steel sheet according to any one of claims 6 to 11, comprising: providing a coating on a surface of a substrate, and then carrying out a sintering treatment, the substrate having a temperature of 800 to 880°C, and the sintering treatment is carried out at this temperature.

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