CN113214687A - Inorganic insulating coating capable of modifying surface of oriented silicon steel and preparation and use methods thereof - Google Patents
Inorganic insulating coating capable of modifying surface of oriented silicon steel and preparation and use methods thereof Download PDFInfo
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Abstract
The invention provides an inorganic insulating coating capable of modifying the surface of oriented silicon steel and a preparation method and a use method thereof, wherein the coating comprises the following components in parts by weight: 5-35 parts of large-particle silica sol, 10-30 parts of aluminum dihydrogen phosphate, 5-35 parts of small-particle silica sol, 0.5-5 parts of chromic anhydride, 1-10 parts of thickening agent, 0.01-0.5 part of titanium pigment and 0-78.49 parts of deionized water; the solid content of the coating is 20-40%. The preparation method of the coating comprises the following steps: sequentially adding the thickening agent, deionized water, aluminum dihydrogen phosphate, large-particle silica sol, small-particle silica sol, chromic anhydride and titanium dioxide into a reactor, uniformly stirring, and standing at room temperature for 0.5-1 h. When the coating is used, the oriented silicon steel sheet is cleaned, dried and pretreated, and then the coating is coated on the oriented silicon steel sheet by a coating roller to be solidified and sintered, and the thickness of the coating is controlled. The coating prepared by the paint provided by the invention has the advantages of smooth and uniform surface, bright color, excellent adhesiveness, corrosion resistance, thermal stability and insulativity, and can modify the defect of crystal exposure bright spots caused by poor quality of a magnesium silicate bottom layer.
Description
Technical Field
The invention belongs to the technical field of coatings, and relates to an inorganic insulating coating and a preparation method and a use method thereof.
Background
The oriented silicon steel has excellent performance and the characteristics of high magnetic induction and low iron loss, is widely applied to the manufacture of iron cores of motors and transformers, and is an important functional material in the fields of military industry, energy sources and the like. In order to prevent the oriented silicon steel sheets from being bonded in the high-temperature annealing process, an MgO coating needs to be coated on the surface of the silicon steel, and when the temperature reaches 1000 ℃, MgO can react with a silicon dioxide film generated on the surface of a steel strip in the decarburization annealing process to generate a magnesium silicate bottom layer. In order to further improve the insulating property and the corrosion resistance of the silicon steel sheet, an insulating coating needs to be coated on the magnesium silicate bottom layer. The coating formed by the insulating coating coated on the surface of the oriented silicon steel can reduce the eddy current loss of an electrical steel plate due to good insulating property, adhesiveness, corrosion resistance and heat resistance, and is an important component of the oriented silicon steel.
The quality of the magnesium silicate bottom layer is closely related to the appearance quality of the silicon steel strip. The quality of the magnesium silicate bottom layer is obviously affected by the problems of chemical components of the raw material of the oriented silicon steel, the thin oxide film on the surface of the steel strip, the uneven coating of the magnesium oxide coating liquid and the like, so that the color of the steel strip is uneven, even the defects of crystal exposure, bright spots and the like occur, and the insulativity and the corrosion resistance of the magnesium silicate bottom layer are reduced.
Although in industrial production, the magnesium silicate base layer is often coated with an insulating coating to ensure the insulation, corrosion resistance and surface quality of the oriented silicon steel. However, these insulating coatings do not have the decorative properties, i.e., they do not effectively modify the crystal exposure and bright spot defects of the magnesium silicate underlayer. The surface insulating coatings of the oriented silicon steel, which are researched and used at home and abroad at present, mainly comprise three main types of organic coatings, semi-inorganic coatings and inorganic coatings. The organic coating is a traditional insulation coating in China, has good insulativity and impact resistance, and high shear punching property and interlayer resistance, but has low film hardness, large thermal shrinkage deformation, poor heat resistance and poor weldability, is easy to generate creep deformation after being heated, can volatilize harmful gases and pollute the environment; the semi-inorganic coating is an insulating coating formed by mixing phosphate and chromate inorganic solutions and a latex resin solution, and the performance of a coating after high-temperature treatment is greatly reduced due to the poor high-temperature resistance of organic resin parts in the coating; the pure inorganic insulating coating formed by a single inorganic substance, namely typical phosphate and aluminum phosphate-based coating, has the advantages of high temperature resistance, good electrical insulation, large tensile stress and the like after proper drying and curing treatment on the surface of the silicon steel, but the adhesiveness, the corrosion resistance and the like still need to be improved; and few research reports on the modified inorganic insulating coating suitable for the oriented silicon steel are available.
The invention patent with the granted publication number of CN106243791B provides a high-covering-property insulating coating for oriented silicon steel, which consists of 1.5 to 7 percent of inorganic salt colorant, 1.5 to 6 percent of chromic anhydride, 30 to 50 percent of dihydric phosphate aqueous solution, 30 to 50 percent of silica sol and 8 to 35 percent of deionized water in percentage by mass, wherein the sum of the mass percentages is 100 percent, and the coating is coated on the oriented silicon steel and then needs to be coated on N2Or baking, sintering and curing under the protective atmosphere of Ar and the like. The coating prepared by the insulating coating disclosed by the invention is deep and uniform in color, has good covering property, can effectively cover surface patterns, color differences and defects generated in the preparation process of the oriented silicon steel, improves the appearance quality, has good corrosion resistance, insulativity, adhesiveness and high temperature resistance, can reduce the iron loss value of the oriented silicon steel, and can be placed in a room-temperature environment for a long timeThe coating was not tacky. But the coating conditions of the coating are strict and the coating is not suitable for popularization and application.
Disclosure of Invention
In order to solve the problems in the background art, the invention provides an inorganic insulating coating capable of modifying the surface of oriented silicon steel and a preparation method and a use method thereof.
An inorganic insulating paint capable of modifying the surface of oriented silicon steel comprises the following components in parts by weight: 5-35 parts of large-particle silica sol, 10-30 parts of aluminum dihydrogen phosphate, 5-35 parts of small-particle silica sol, 0.5-5 parts of chromic anhydride, 1-10 parts of thickening agent, 0.01-0.5 part of titanium pigment and 0-78.49 parts of deionized water; the solid content of the coating is 20-40%.
The large-particle silica sol comprises alkaline silica sol with the pH of 9-10, the content of silica is 20-35 wt%, and the particle size is 15-30 nm.
The small-particle silica sol comprises alkaline silica sol with the pH of 9-10, the content of silicon dioxide of the small-particle silica sol is 20-35 wt%, and the particle size of the small-particle silica sol is 5-10 nm.
The thickening agent is montmorillonite and/or kaolin.
The particle size of the titanium dioxide is 10-50 nm.
A preparation method of an inorganic insulating coating of modified oriented silicon steel comprises the following steps:
1) pouring a thickening agent and deionized water into a reactor, and stirring for 5min to form a pre-sol;
2) adding aluminum dihydrogen phosphate into the mixed solution obtained in the step 1), and stirring for 15 min;
3) sequentially adding large-particle silica sol and small-particle silica sol into the mixed solution obtained in the step 2), and stirring for 30 min;
4) sequentially adding chromic anhydride and titanium dioxide into the mixed solution obtained in the step 3), and stirring for 30 min;
5) standing the mixture obtained in the step 4) at room temperature for 0.5-1h to obtain the inorganic insulating coating.
In the steps 1) to 4), the stirring speed is 100-150 r/min.
A use method of an inorganic insulating coating capable of modifying the surface of oriented silicon steel comprises the following steps:
1) carrying out cleaning and drying pretreatment on the oriented silicon steel sheet;
2) coating the paint on an oriented silicon steel sheet by a roller, curing at 470-500 ℃ for 8-10s, and sintering at 800-850 ℃ for 40-60s, and controlling the coating thickness of the dry film to be 3-5 μm to form the inorganic insulating coating.
In the step 1), the cleaning and drying pretreatment method comprises the following steps: the oriented silicon steel sheet is washed clean by distilled water, ethanol, 5 vol.% sulfuric acid and distilled water in sequence and then is quickly dried. By the pretreatment, oil stains, oxide scales, dust and the like existing on the surface of the oriented silicon steel sheet can be cleaned, and the stability of an insulating coating formed after the coating is rolled by a roller is improved.
In the technical scheme of the invention, the aluminum dihydrogen phosphate and the large-particle silica sol form a net structure after high temperature, so that the bonding strength between the insulating coating and the oriented silicon steel sheet can be improved, the adhesion of the coating is improved, the brightness and the surface quality of the coating can be improved by the large-particle silica sol, and the aluminum dihydrogen phosphate and the large-particle silica sol have the characteristics of high temperature resistance and good insulating property. The small-particle silica sol can improve the compactness of the coating, further improve the corrosion resistance of the coating and improve the punching performance and the stacking coefficient of the coating. The chromic anhydride can improve the wettability between the insulating coating and the magnesium silicate bottom layer on the surface of the oriented silicon steel sheet, so that free phosphoric acid in phosphate is more stable, the corrosion of the coating to a substrate can be inhibited, and the wettability of the coating is improved. The titanium dioxide can modify the crystal exposure defect caused by poor quality of the magnesium silicate bottom layer. The thickening agent can adjust the viscosity core of the coating, and can improve the strength and stability of the coating.
The coating prepared by the coating provided by the invention has the advantages of smooth and uniform surface, bright color, excellent adhesiveness, corrosion resistance, thermal stability and insulativity, and can modify the defect of crystal exposure bright spots caused by poor quality of a magnesium silicate bottom layer; the application method of the oriented silicon steel insulating paint can be applied to the oriented silicon steel prepared by the existing rolling process, is low in debugging cost and easy to popularize.
Drawings
Fig. 1 is an electron microscope image of an oriented silicon steel sheet without a coating layer.
Fig. 2 is an electron microscope picture of an oriented silicon steel sheet containing an inorganic insulating coating.
Detailed Description
The present invention will be described in further detail with reference to specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention.
The oriented silicon steel inorganic insulating coating with the modification property comprises the following components in parts by weight: 5-35 parts of large-particle silica sol, 10-30 parts of aluminum dihydrogen phosphate, 5-35 parts of small-particle silica sol, 0.5-5 parts of chromic anhydride, 1-10 parts of thickening agent, 0.01-0.5 part of titanium pigment and 0-78.49 parts of deionized water; the solid content of the inorganic insulating coating is 20-40%.
The large-particle silica sol comprises alkaline silica sol with the pH of 9-10, the content of silica is 20-35 wt%, and the particle size is 15-30 nm.
The small-particle silica sol comprises alkaline silica sol with the pH of 9-10, the content of silicon dioxide of the small-particle silica sol is 20-35 wt%, and the particle size of the small-particle silica sol is 5-10 nm.
The thickening agent is montmorillonite and/or kaolin.
The particle size of the titanium dioxide is 10-50 nm.
In the coating, aluminum dihydrogen phosphate and large-particle silica sol form a net structure after high temperature, so that the bonding strength between an insulating coating and an oriented silicon steel sheet can be improved, the adhesiveness of the coating is improved, the brightness and the surface quality of the coating can be improved by the large-particle silica sol, and the coating has the characteristics of high temperature resistance and good insulating property. The small-particle silica sol can improve the compactness of the coating, further improve the corrosion resistance of the coating and improve the punching performance and the stacking coefficient of the coating. However, when the content of silica particles in the silica sol and the amount of silica sol added exceed the appropriate ranges, irregular agglomeration of silica particles occurs in the coating layer, which lowers the flatness of the coating layer and also deteriorates the corrosion resistance and tension of the coating layer. The chromic anhydride can improve the wettability between the insulating coating and the magnesium silicate bottom layer on the surface of the oriented silicon steel sheet, so that free phosphoric acid in phosphate is more stable, the corrosion of the coating to a substrate can be inhibited, and the wettability of the coating is improved. The titanium dioxide can modify the crystal exposure defect caused by poor quality of a magnesium silicate bottom layer or poor coating process, but the stability of the coating is reduced by adding too much titanium dioxide, and the components of the coating are unevenly distributed due to the agglomeration of the titanium dioxide, so that the corrosion resistance of the coating is reduced. The thickening agent has the functions of improving the strength of the coating, enhancing the stability and adjusting the viscosity, and the viscosity and the stability of the coating can not meet the use requirements when the viscosity exceeds or falls below a proper range, so that the comprehensive performance of the coating is finally damaged.
The preparation method of the inorganic insulating paint comprises the following steps:
1) pouring the thickening agent and the deionized water into a reactor, and stirring for 5min at the stirring speed of 100-150r/min to form pre-sol;
2) adding aluminum dihydrogen phosphate into the mixed solution obtained in the step 1), and stirring for 15min at the stirring speed of 100-150 r/min;
3) adding large-particle silica sol and small-particle silica sol into the mixed solution obtained in the step 2) in sequence, and stirring for 30min at a stirring speed of 100-150 r/min;
4) sequentially adding chromic anhydride and titanium dioxide into the mixed solution obtained in the step 3), and stirring for 30min at the stirring speed of 100-150 r/min;
5) standing the mixture obtained in the step 4) at room temperature for 0.5-1h to obtain the inorganic insulating coating.
When the stirring speed is lower than 100r/min, the mixing efficiency is low, the bentonite cannot effectively form a pre-sol, the titanium dioxide cannot effectively disperse to form a stable system, but when the stirring speed is higher than 150r/min, air can be introduced into the coating system in the stirring process, so that the stability of the product is reduced, and the coating of the coating is not facilitated.
The use method of the inorganic insulating paint comprises the following steps: the method comprises the steps of pretreating the oriented silicon steel sheet in the sequence of distilled water cleaning → ethanol cleaning → 5 vol.% sulfuric acid cleaning → distilled water cleaning, removing dirt such as oil stain, oxide skin and dust existing on the surface of the oriented silicon steel sheet, quickly drying the cleaned oriented silicon steel for later use, finally coating a coating roller on the oriented silicon steel sheet, curing at 470 and 500 ℃ for 8-10s, sintering at 800 and 850 ℃ for 40-60s, and controlling the coating thickness of a dry film to be 3-5 mu m, namely forming an inorganic insulating coating on the surface of the oriented silicon steel sheet.
Coating the coating on the oriented silicon steel sheet with the crystal exposure bright spots on the surface, observing the surface morphology by naked eyes, checking whether the crystal exposure bright spots and other morphology defects exist, and testing the insulation property and the adhesion property of the prepared oriented silicon steel sheet containing the inorganic insulating coating according to GB/T2522 and 2007 test method for the surface insulation resistance and the coating adhesion of the electrical steel sheet (strip); according to the regulation of GB/T10125-2012 salt spray test for artificial atmosphere corrosion test, the corrosion resistance of the coated oriented silicon steel sheet is detected, and the neutral NaCl solution is used for accelerating corrosion by adopting continuous spraying and testing; the magnetic properties of the oriented silicon steel sheet are measured according to GB/T13789-2008 'method for measuring the magnetic properties of electrical steel sheet (strip) by using single-sheet tester'.
Example 1
The inorganic insulating paint I comprises the following components: 50g of large-particle silica sol, 100g of aluminum dihydrogen phosphate, 50g of small-particle silica sol, 5g of chromic anhydride, 10g of thickening agent, 0.1g of titanium dioxide and 784.9g of deionized water.
The large-particle silica sol is alkaline silica sol with the pH value of 10, the content of silicon dioxide is 20 wt%, and the particle size is 15 nm. The small-particle silica sol is alkaline silica sol with pH of 10, the content of silica is 35 wt%, and the particle size is 5 nm. The thickening agent is montmorillonite. The particle size of the titanium dioxide is 20 nm.
The preparation method of the inorganic insulating coating I comprises the following steps: 1) pouring the thickening agent and deionized water into a reactor, and stirring for 5min at a stirring speed of 100r/min to form pre-sol; 2) adding aluminum dihydrogen phosphate into the mixed solution obtained in the step 1), and stirring for 15min at a stirring speed of 100 r/min; 3) adding large-particle silica sol and small-particle silica sol into the mixed solution obtained in the step 2) in sequence, and stirring for 30min at a stirring speed of 100 r/min; 4) sequentially adding chromic anhydride and titanium dioxide into the mixed solution obtained in the step 3), and stirring for 30min at a stirring speed of 100 r/min; 5) standing the mixture obtained in the step 4) at room temperature for 0.5h to obtain the inorganic insulating paint I.
The use method of the inorganic insulating paint I comprises the following steps: the method comprises the steps of pretreating the oriented silicon steel sheet in the sequence of distilled water washing → ethanol washing → 5 vol.% sulfuric acid washing → distilled water washing, removing dirt such as oil stain, oxide skin and dust existing on the surface of the oriented silicon steel sheet, quickly drying the washed oriented silicon steel for standby, finally coating a coating roller on the oriented silicon steel sheet, curing at 470 ℃ for 8s, sintering at 800 ℃ for 60s, and controlling the coating thickness of a dry film to be 3 mu m, namely forming an inorganic insulating coating I on the surface of the oriented silicon steel sheet.
Example 2
The inorganic insulating coating II comprises the following components: 50g of large-particle silica sol, 100g of aluminum dihydrogen phosphate, 50g of small-particle silica sol, 5g of chromic anhydride, 10g of thickening agent, 0.1g of titanium dioxide and 784.9g of deionized water.
The large-particle silica sol is alkaline silica sol with the pH value of 10, the content of silicon dioxide is 20 wt%, and the particle size is 15 nm. The small-particle silica sol is alkaline silica sol with pH of 10, the content of silica is 35 wt%, and the particle size is 5 nm. The thickening agent is montmorillonite. The particle size of the titanium dioxide is 20 nm.
The preparation method of the inorganic insulating coating II comprises the following steps: 1) pouring the thickening agent and deionized water into a reactor, and stirring for 5min at a stirring speed of 100r/min to form pre-sol; 2) adding aluminum dihydrogen phosphate into the mixed solution obtained in the step 1), and stirring for 15min at a stirring speed of 100 r/min; 3) adding large-particle silica sol and small-particle silica sol into the mixed solution obtained in the step 2) in sequence, and stirring for 30min at a stirring speed of 100 r/min; 4) sequentially adding chromic anhydride and titanium dioxide into the mixed solution obtained in the step 3), and stirring for 30min at a stirring speed of 100 r/min; 5) standing the mixture obtained in the step 4) at room temperature for 0.5h to obtain the inorganic insulating paint II.
The use method of the inorganic insulating paint II comprises the following steps: the method comprises the steps of pretreating the oriented silicon steel sheet in the sequence of distilled water washing → ethanol washing → 5 vol.% sulfuric acid washing → distilled water washing, removing dirt such as oil stain, oxide skin and dust existing on the surface of the oriented silicon steel sheet, quickly drying the washed oriented silicon steel for standby, finally coating a coating roller on the oriented silicon steel sheet, curing at 470 ℃ for 8s, sintering at 800 ℃ for 60s, and controlling the coating thickness of a dry film to be 5 mu m, namely forming an inorganic insulating coating II on the surface of the oriented silicon steel sheet.
Example 3
The inorganic insulating coating III comprises the following components: 150g of large-particle silica sol, 130g of aluminum dihydrogen phosphate, 200g of small-particle silica sol, 15g of chromic anhydride, 60g of thickening agent, 2g of titanium dioxide and 443g of deionized water.
The large-particle silica sol is alkaline silica sol with pH of 9, the content of silicon dioxide is 35 wt%, and the particle size is 25 nm. The small-particle silica sol is alkaline silica sol with pH of 9, the content of silica is 20 wt%, and the particle size is 8 nm. The thickening agent is kaolin. The particle size of the titanium dioxide is 10 nm.
The preparation method of the inorganic insulating paint III comprises the following steps: 1) pouring the thickening agent and deionized water into a reactor, and stirring for 5min at a stirring speed of 120r/min to form pre-sol; 2) adding aluminum dihydrogen phosphate into the mixed solution obtained in the step 1), and stirring for 15min at a stirring speed of 120 r/min; 3) adding large-particle silica sol and small-particle silica sol into the mixed solution obtained in the step 2) in sequence, and stirring for 30min at a stirring speed of 120 r/min; 4) sequentially adding chromic anhydride and titanium dioxide into the mixed solution obtained in the step 3), and stirring for 30min at a stirring speed of 120 r/min; 5) standing the mixture obtained in the step 4) at room temperature for 1.0h to obtain the inorganic insulating paint III.
The use method of the inorganic insulating paint III comprises the following steps: the method comprises the steps of pretreating the oriented silicon steel sheet in the sequence of distilled water washing → ethanol washing → 5 vol.% sulfuric acid washing → distilled water washing, removing dirt such as oil stain, oxide skin and dust existing on the surface of the oriented silicon steel sheet, quickly drying the washed oriented silicon steel for standby, finally coating a coating roller on the oriented silicon steel sheet, curing at 500 ℃ for 10s, sintering at 820 ℃ for 45s, and controlling the coating thickness of a dry film to be 5 mu m, namely forming an inorganic insulating coating III on the surface of the oriented silicon steel sheet.
Example 4
The inorganic insulating coating IV comprises the following components: 200g of large-particle silica sol, 300g of aluminum dihydrogen phosphate, 150g of small-particle silica sol, 20g of chromic anhydride, 80g of thickening agent, 4g of titanium dioxide and 246g of deionized water.
The large-particle silica sol is alkaline silica sol with pH of 9, the content of silicon dioxide is 30 wt%, and the particle size is 30 nm. The small-particle silica sol is alkaline silica sol with pH of 9, the content of silica is 25 wt%, and the particle size is 10 nm. The thickening agent is a mixture of montmorillonite and kaolin with the mass ratio of 2: 1. The particle size of the titanium dioxide is 50 nm.
The preparation method of the inorganic insulating paint IV comprises the following steps: 1) pouring the thickening agent and deionized water into a reactor, and stirring at a stirring speed of 150r/min for 5min to form pre-sol; 2) adding aluminum dihydrogen phosphate into the mixed solution obtained in the step 1), and stirring at the stirring speed of 150r/min for 15 min; 3) adding large-particle silica sol and small-particle silica sol into the mixed solution obtained in the step 2) in sequence, and stirring for 30min at a stirring speed of 150 r/min; 4) sequentially adding chromic anhydride and titanium dioxide into the mixed solution obtained in the step 3), and stirring for 30min at a stirring speed of 150 r/min; 5) standing the mixture obtained in the step 4) at room temperature for 0.8h to obtain the inorganic insulating paint IV.
The use method of the inorganic insulating paint IV comprises the following steps: the method comprises the steps of pretreating the oriented silicon steel sheet in the sequence of distilled water washing → ethanol washing → 5 vol.% sulfuric acid washing → distilled water washing, removing dirt such as oil stain, oxide skin and dust existing on the surface of the oriented silicon steel sheet, quickly drying the washed oriented silicon steel for standby, finally coating a coating roller on the oriented silicon steel sheet, curing at 500 ℃ for 10s, sintering at 850 ℃ for 40s, and controlling the coating thickness of a dry film to be 5 mu m, namely forming an inorganic insulating coating IV on the surface of the oriented silicon steel sheet.
Example 5
The inorganic insulating coating V comprises the following components: 250g of large-particle silica sol, 250g of aluminum dihydrogen phosphate, 250g of small-particle silica sol, 25g of chromic anhydride, 50g of thickening agent, 0.5g of titanium dioxide and 174.5g of deionized water.
The large-particle silica sol is alkaline silica sol with the pH value of 10, the content of silicon dioxide is 20 wt%, and the particle size is 20 nm. The small-particle silica sol is alkaline silica sol with pH of 9, the content of silica is 25 wt%, and the particle size is 5 nm. The thickening agent is kaolin. The particle size of the titanium dioxide is 35 nm.
The preparation method of the inorganic insulating paint V comprises the following steps: 1) pouring the thickening agent and deionized water into a reactor, and stirring at a stirring speed of 140r/min for 5min to form pre-sol; 2) adding aluminum dihydrogen phosphate into the mixed solution obtained in the step 1), and stirring at the stirring speed of 140r/min for 15 min; 3) adding large-particle silica sol and small-particle silica sol into the mixed solution obtained in the step 2) in sequence, and stirring for 30min at a stirring speed of 140 r/min; 4) sequentially adding chromic anhydride and titanium dioxide into the mixed solution obtained in the step 3), and stirring for 30min at a stirring speed of 140 r/min; 5) standing the mixture obtained in the step 4) at room temperature for 0.6h to obtain the inorganic insulating paint V.
The use method of the inorganic insulating paint V comprises the following steps: the method comprises the steps of pretreating the oriented silicon steel sheet in the sequence of distilled water washing → ethanol washing → 5 vol.% sulfuric acid washing → distilled water washing, removing dirt such as oil stain, oxide skin and dust existing on the surface of the oriented silicon steel sheet, quickly drying the washed oriented silicon steel for standby, finally coating a coating roller on the oriented silicon steel sheet, curing at 500 ℃ for 9s, sintering at 850 ℃ for 40s, and controlling the coating thickness of a dry film to be 5 mu m, namely forming an inorganic insulating coating V on the surface of the oriented silicon steel sheet.
Example 6
The inorganic insulating coating VI comprises the following components: 300g of large-particle silica sol, 170g of aluminum dihydrogen phosphate, 130g of small-particle silica sol, 30g of chromic anhydride, 30g of thickening agent, 0.8g of titanium dioxide and 339.2g of deionized water.
The large-particle silica sol is alkaline silica sol with pH of 9, the content of silicon dioxide is 25 wt%, and the particle size is 20 nm. The small-particle silica sol is alkaline silica sol with pH of 10, the content of silica is 35 wt%, and the particle size is 5 nm. The thickening agent is montmorillonite. The particle size of the titanium dioxide is 45 nm.
The preparation method of the inorganic insulating coating VI is the same as that of example 5.
The inorganic insulating coating VI was used in the same manner as in example 5 to obtain an inorganic insulating coating VI.
Example 7
The inorganic insulating coating VII comprises the following components: 350g of large-particle silica sol, 200g of aluminum dihydrogen phosphate, 50g of small-particle silica sol, 45g of chromic anhydride, 10g of thickening agent, 1g of titanium dioxide and 344g of deionized water.
The large-particle silica sol is alkaline silica sol with the pH value of 10, the content of silicon dioxide is 20 wt%, and the particle size is 25 nm. The small-particle silica sol is alkaline silica sol with pH of 10, the content of silica is 30 wt%, and the particle size is 5 nm. The thickening agent is kaolin. The particle size of the titanium dioxide is 35 nm.
The preparation method of the inorganic insulating paint VII was the same as in example 4.
The inorganic insulating coating VII was used in the same manner as in example 4 to obtain an inorganic insulating coating VII.
Example 8
The inorganic insulating coating VIII comprises the following components: 200g of large-particle silica sol, 150g of aluminum dihydrogen phosphate, 80g of small-particle silica sol, 40g of chromic anhydride, 20g of thickening agent, 1g of titanium dioxide and 509g of deionized water.
The large-particle silica sol is alkaline silica sol with the pH value of 10, the content of silicon dioxide is 25 wt%, and the particle size is 25 nm. The small-particle silica sol is alkaline silica sol with pH of 10, the content of silica is 30 wt%, and the particle size is 5 nm. The thickening agent is a mixture of montmorillonite and kaolin with the mass ratio of 1: 1. The particle size of the titanium dioxide is 25 nm.
The preparation method of the inorganic insulating paint VIII was the same as in example 3.
The inorganic insulating coating VIII was used in the same manner as in example 3 to obtain an inorganic insulating coating VIII.
Example 9
The inorganic insulating coating IX comprises the following components: 200g of large-particle silica sol, 230g of aluminum dihydrogen phosphate, 200g of small-particle silica sol, 50g of chromic anhydride, 30g of thickening agent, 3g of titanium dioxide and 287g of deionized water.
The large-particle silica sol is alkaline silica sol with the pH value of 10, the content of silicon dioxide is 25 wt%, and the particle size is 25 nm. The small-particle silica sol is alkaline silica sol with pH of 10, the content of silica is 30 wt%, and the particle size is 5 nm. The thickening agent is kaolin. The particle size of the titanium dioxide is 25 nm.
The preparation method of the inorganic insulating coating IX was the same as in example 4.
The inorganic insulating coating IX was used in the same manner as in example 4 to obtain an inorganic insulating coating IX.
Example 10
The inorganic insulating coating X comprises the following components: 350g of large-particle silica sol, 200g of aluminum dihydrogen phosphate, 350g of small-particle silica sol, 5g of chromic anhydride, 90g of thickening agent and 5g of titanium dioxide.
The large-particle silica sol is alkaline silica sol with the pH value of 10, the content of silicon dioxide is 25 wt%, and the particle size is 25 nm. The small-particle silica sol is alkaline silica sol with pH of 10, the content of silica is 30 wt%, and the particle size is 5 nm. The thickening agent is montmorillonite. The particle size of the titanium dioxide is 25 nm.
The preparation method of the inorganic insulating coating material X was the same as in example 4.
The inorganic insulating coating material X was used in the same manner as in example 4 to obtain an inorganic insulating coating layer X.
The oriented silicon steel sheets containing the inorganic insulating coating prepared in each example were subjected to a performance test, and the results of the performance test are shown in table 1.
Fig. 1 is an electron microscope image of an oriented silicon steel sheet without a coating, the magnification is 10000 times, the surface of the oriented silicon steel sheet has a morphology defect of an exposed crystal bright point, it can be known from fig. 1 that a magnesium silicate bottom layer of the oriented silicon steel sheet is loose, gaps among particles are many, the oriented silicon steel sheet is in a loose particle bulk structure, a plurality of pits are also present on the surface of the oriented silicon steel sheet, the morphology characteristics of particle accumulation inside and outside the pits are different, and the bottom surface of the pit is flat. The element content of the surface of the oriented silicon steel sheet is analyzed, the analysis result is shown in table 2, the iron element content at the bottom of the pit with the crystal bright point exposed is the highest, the mass percent of the iron element reaches more than 90 percent and is the main component of the iron element, and the mass percent of the magnesium element, the silicon element and the oxygen element is very small; the normal surface of the oriented silicon steel sheet is in a state that the contents of iron element, magnesium element, silicon element and oxygen element are relatively balanced, which shows that the exposed crystal bright spot defect can directly expose the substrate of the oriented silicon steel sheet and seriously damage the performance of the oriented silicon steel sheet. The inorganic insulating coating is used for coating the surface of the oriented silicon steel sheet with the crystal exposure bright spots, so that a coating is formed on the surface of the oriented silicon steel sheet, fig. 2 is an electron microscopic picture of the oriented silicon steel sheet containing the inorganic insulating coating, the magnification is 50000 times, and under the magnification of 50000 times, the surface of the coating of the oriented silicon steel sheet is flat and compact, presents a complete and continuous molten state instead of a loose granular bulk structure, has no cracks and pores, has no pits or substrate exposure, and shows that the crystal exposure bright spots are successfully covered by the coating.
The performance test result shows that the inorganic insulating coating formed on the oriented silicon steel sheet coated with the inorganic insulating coating has a uniform and flat surface, no crystal exposure bright spots and no cracks; the inorganic insulating coating has good adhesiveness through testing, and can reach the state that B level slightly falls off, even A level does not fall off; because the crystal exposure bright spots on the surface of the oriented silicon steel sheet are successfully covered by the inorganic insulating coating, the salt spray resistance of the oriented silicon steel sheet is excellent, the corrosion area is less than 3% even no corrosion occurs in 24h of a salt spray test, and the corrosion resistance of the oriented silicon steel sheet coated with the inorganic insulating coating is excellent; tests show that the inorganic insulating coating has excellent insulating property, and the oriented silicon steel sheet containing the inorganic insulating coating has good magnetic property.
It can be known that the inorganic insulating coating is suitable for the surface of the existing oriented silicon steel sheet, in particular for the oriented silicon steel sheet with surface defects such as crystal exposure and bright spot defects caused by poor quality of a magnesium silicate bottom layer.
Table 1 coating performance test results
Note: the area of corrosion is the area measured 24 hours after continuous salt spray.
TABLE 2 analysis results of elemental contents on the surface of grain-oriented silicon steel sheet
| Element(s) | Normal surface | Pit bottom with crystal bright spots |
| O | 16.28 | 2.11 |
| Mg | 22.18 | 1.39 |
| Si | 15.15 | 3.30 |
| Fe | 46.39 | 93.20 |
Claims (9)
1. The inorganic insulating coating capable of modifying the surface of the oriented silicon steel is characterized by comprising the following components in parts by weight: 5-35 parts of large-particle silica sol, 10-30 parts of aluminum dihydrogen phosphate, 5-35 parts of small-particle silica sol, 0.5-5 parts of chromic anhydride, 1-10 parts of thickening agent, 0.01-0.5 part of titanium pigment and 0-78.49 parts of deionized water; the solid content of the coating is 20-40%.
2. The inorganic insulating coating capable of modifying the surface of oriented silicon steel according to claim 1, wherein: the large-particle silica sol comprises alkaline silica sol with the pH of 9-10, the content of silica is 20-35 wt%, and the particle size is 15-30 nm.
3. The inorganic insulating coating capable of modifying the surface of oriented silicon steel according to claim 1, wherein: the small-particle silica sol comprises alkaline silica sol with the pH of 9-10, the content of silicon dioxide of the small-particle silica sol is 20-35 wt%, and the particle size of the small-particle silica sol is 5-10 nm.
4. The inorganic insulating coating capable of modifying the surface of oriented silicon steel according to claim 1, wherein: the thickening agent is montmorillonite and/or kaolin.
5. The inorganic insulating coating capable of modifying the surface of oriented silicon steel according to claim 1, wherein: the particle size of the titanium dioxide is 10-50 nm.
6. The method for preparing the inorganic insulating coating capable of modifying the surface of the oriented silicon steel according to any one of claims 1 to 5, which comprises the following steps:
1) pouring a thickening agent and deionized water into a reactor, and stirring for 5min to form a pre-sol;
2) adding aluminum dihydrogen phosphate into the mixed solution obtained in the step 1), and stirring for 15 min;
3) sequentially adding large-particle silica sol and small-particle silica sol into the mixed solution obtained in the step 2), and stirring for 30 min;
4) sequentially adding chromic anhydride and titanium dioxide into the mixed solution obtained in the step 3), and stirring for 30 min;
5) standing the mixture obtained in the step 4) at room temperature for 0.5-1h to obtain the inorganic insulating coating.
7. The method for preparing the inorganic insulating paint capable of modifying the surface of the oriented silicon steel according to the claim 6, wherein the method comprises the following steps: in the steps 1) to 4), the stirring speed is 100-150 r/min.
8. Use of the inorganic insulating coating for modifying the surface of oriented silicon steel according to any one of claims 1 to 5, comprising the following steps:
1) carrying out cleaning and drying pretreatment on the oriented silicon steel sheet;
2) coating the paint on an oriented silicon steel sheet by a roller, curing at 470-500 ℃ for 8-10s, and sintering at 800-850 ℃ for 40-60s, and controlling the coating thickness of the dry film to be 3-5 μm to form the inorganic insulating coating.
9. The use method of the modified inorganic insulating coating for oriented silicon steel according to claim 8, wherein the use method comprises the following steps: in the step 1), the cleaning and drying pretreatment method comprises the following steps: the oriented silicon steel sheet is washed clean by distilled water, ethanol, 5 vol.% sulfuric acid and distilled water in sequence and then is quickly dried.
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