Insulating coating solution for grain-oriented silicon steel, preparation method and insulating coating

Abstract

The application relates to the technical field of silicon steel insulation coating preparation, in particular to an insulation coating solution for oriented silicon steel, a preparation method and an insulation coating. On the basis of the total mass of the insulation coating solution, the composition and the corresponding mass percentage of the insulation coating solution are as follows: 20-25% of an aluminum dihydrogen phosphate solution, 4-6% of aluminum oxalate, 30-35% of silicon sol, 3-5% of potassium fluozirconate, 1-2% of yttrium oxide, 2-3% of 1,4-butanediol and the balance of water. By adding aluminum oxalate, potassium fluozirconate, yttrium oxide and other components in the phosphate coating solution, the insulation, corrosion resistance and heat resistance of the oriented silicon steel are remarkably improved, the environmental pollution problem is solved, and the motor efficiency and service life are improved.

Description

Technical Field

[0001] This application relates to the field of silicon steel insulating coating preparation technology, and in particular to an insulating coating solution, preparation method and insulating coating for oriented silicon steel. Background Technology

[0002] The rapid development of new energy vehicles, especially pure electric vehicles, has placed higher demands on motor performance, particularly in terms of efficiency, lifespan, and energy efficiency. Motor performance directly impacts the competitiveness of the entire vehicle, and the stator and rotor cores, as core components of the motor, are primarily made of grain-oriented silicon steel. The insulation, corrosion resistance, and heat resistance of grain-oriented silicon steel significantly affect the efficiency and lifespan of the motor. However, traditional grain-oriented silicon steel surface coatings commonly use paints containing hexavalent chromium. While these coatings offer some insulation and corrosion resistance, the use of hexavalent chromium poses serious risks to the environment and human health.

[0003] To address the aforementioned issues, current research focuses on developing chromium-free, environmentally friendly insulating coatings. Several chromium-free coating technologies exist, but they suffer from drawbacks such as rough coating surfaces, poor adhesion, or unstable insulation performance. Furthermore, the uniformity and heat resistance of chromium-free coatings during high-temperature processing require further optimization. In summary, existing insulating coating technologies exhibit poor insulation, corrosion resistance, heat resistance, adhesion, and environmental performance, failing to meet application requirements. Summary of the Invention

[0004] The present invention provides an insulating coating solution, preparation method and insulating coating for oriented silicon steel, which at least solves the problems of poor insulation, corrosion resistance, heat resistance, adhesion and environmental performance of insulating coating technologies in related technologies.

[0005] According to a first aspect of the present invention, an insulating coating solution for oriented silicon steel is provided, wherein, based on the total mass of the insulating coating solution, the composition and corresponding mass percentages of the insulating coating solution are: 20%–25% aluminum dihydrogen phosphate solution, 4%–6% aluminum oxalate, 30%–35% silica sol, 3%–5% potassium fluorozirconate, 1%–2% yttrium oxide, 2%–3% 1,4-butanediol, and the balance being water.

[0006] According to an embodiment of the present invention, the aluminum dihydrogen phosphate solution is an aqueous solution of aluminum dihydrogen phosphate, wherein the mass percentage of aluminum dihydrogen phosphate in the aqueous solution of aluminum dihydrogen phosphate is 50%.

[0007] According to an embodiment of the present invention, the aluminum oxalate is aluminum oxalate dodecyl hydrate, and the solid content of the aluminum oxalate dodecyl hydrate is 99% or more.

[0008] According to an embodiment of the present invention, the average particle size of the silica sol is 5-8 nm, the mass percentage of SiO2 in the silica sol is 20-21%, the pH value is 10-11, and the viscosity is 2.0-2.5 MPa·s.

[0009] According to an embodiment of the present invention, the potassium fluorozirconate is a white crystal with a solid content of 99% or more.

[0010] According to an embodiment of the present invention, the yttrium oxide is in powder form with a solid content of 99.5% or higher.

[0011] According to an embodiment of the present invention, the 1,4-butanediol is a liquid with a mass percentage content of 99% or more.

[0012] According to a second aspect of the present invention, a method for preparing an insulating coating solution is provided, wherein the raw materials of the insulating coating solution, by mass percentage concentration, include: 20%–25% aluminum dihydrogen phosphate solution, 4%–6% aluminum oxalate, 30%–35% silica sol, 3%–5% potassium fluorozirconate, 1%–2% yttrium oxide, 2%–3% 1,4-butanediol, and the balance being water; the method includes:

[0013] Add the aluminum oxalate and the potassium fluorozirconate to water and stir.

[0014] After the aluminum oxalate and potassium fluorozirconate are completely dissolved, the aluminum dihydrogen phosphate solution is added and stirred.

[0015] After the aluminum dihydrogen phosphate solution is fully mixed, add the yttrium oxide while stirring.

[0016] After the yttrium oxide is completely dissolved, the silica sol and the 1,4-butanediol are added and stirred until they are mixed evenly to obtain a mixed solution;

[0017] The mixed solution is filtered through a 1250-mesh filter to obtain the insulating coating solution.

[0018] According to a third aspect of the present invention, an insulating coating for oriented silicon steel is provided, wherein the insulating coating is obtained by coating oriented silicon steel with the insulating coating solution described in the first aspect.

[0019] According to an embodiment of the present invention, an insulating coating solution according to the first aspect is used to coat oriented silicon steel, followed by heating, drying, and sintering, ultimately forming an insulating coating on the surface of the oriented steel.

[0020] Beneficial effects of the embodiments of the present invention:

[0021] This invention significantly improves the insulation, corrosion resistance, and heat resistance of grain-oriented silicon steel by incorporating aluminum oxalate, potassium fluorozirconate, and yttrium oxide into a phosphate coating solution. The addition of aluminum oxalate effectively reduces the conductivity of the silicon steel, significantly enhancing the resistivity of the insulating coating. Potassium fluorozirconate, as an environmentally friendly alternative, not only completely eliminates the environmental and health pollution problems caused by chromium compounds but also gives the coating excellent corrosion resistance. The addition of yttrium oxide improves the stability of the coating at high temperatures, reduces iron loss caused by thermal expansion during silicon steel processing, and thus improves magnetic properties. After coating, baking, and high-temperature sintering, the insulating coating solution of this invention forms an environmentally friendly coating with excellent insulation, adhesion, corrosion resistance, and heat resistance on the surface of grain-oriented silicon steel. The coating is uniform and dense. Using grain-oriented silicon steel sheets coated with this solution to manufacture the stator and rotor cores of tram motors not only improves the motor's working efficiency and service life but also achieves energy-saving effects, providing reliable technical support for the efficient operation of tram motors while meeting environmental protection requirements, thus possessing significant industrial value and application prospects. Detailed Implementation

[0022] The embodiments of this embodiment will now be described in more detail. While some embodiments of this embodiment have been described, it should be understood that this embodiment can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this embodiment. It should be understood that the content of this embodiment is for illustrative purposes only and is not intended to limit the scope of protection of this embodiment.

[0023] This invention provides an insulating coating solution for oriented silicon steel and a method for preparing the same. The composition and proportion of the insulating coating solution are designed to ensure excellent performance of the coating in terms of high temperature, corrosion resistance, adhesion, and insulation properties.

[0024] The insulating coating solution for oriented silicon steel in this embodiment of the invention, based on the total mass of the insulating coating solution, comprises the following main components and their corresponding mass percentage ranges: 20%–25% aluminum dihydrogen phosphate solution, 4%–6% aluminum oxalate, 30%–35% silica sol, 3%–5% potassium fluorozirconate, 1%–2% yttrium oxide, 2%–3% 1,4-butanediol, and the balance being water. The specific function of each component and the basis for its selection will be explained below.

[0025] In this embodiment, the aluminum dihydrogen phosphate solution is an aqueous solution of aluminum dihydrogen phosphate, and the mass percentage of aluminum dihydrogen phosphate in the aqueous solution of aluminum dihydrogen phosphate is 50%.

[0026] In this embodiment, aluminum dihydrogen phosphate (ADPH) serves to provide film-forming properties and improve coating adhesion. Its unique chemical properties enable it to form a strong bond with the substrate material. By selecting a 50% (w / w) concentration of ADPH solution, it is ensured that ADPH can fully exert its film-forming and adhesion effects, while sufficient ADPH participates in the formation of a solid structure during coating curing, thereby improving the mechanical strength and electrical insulation properties of the coating. A 50% concentration allows for effective reaction with other components during subsequent mixing, while avoiding excessive dilution or concentration, ensuring the stability and effectiveness of the coating solution.

[0027] Specifically, aluminum dihydrogen phosphate, as the main film-forming component of the coating solution of this invention, possesses excellent high-temperature resistance, anti-peeling properties, and insulation performance. The aluminum ions in aluminum dihydrogen phosphate form a strong bond with the coating surface, and its small atomic radius promotes a tight bond between the coating and the substrate, ensuring that the coating is not easily peeled off during use and exhibits good insulation after curing. Its mass percentage accounts for 20% to 25% of the total mass of the coating solution, providing sufficient film formation and adhesion to ensure a stable and durable coating.

[0028] In an optional embodiment, when preparing the aluminum dihydrogen phosphate solution, firstly, prepare the solid raw material of aluminum dihydrogen phosphate and deionized water. Take an appropriate amount of aluminum dihydrogen phosphate powder and weigh it accurately to ensure that the mass percentage content of aluminum dihydrogen phosphate in the final solution is 50%. Then, add deionized water to a stirring container and slowly add the aluminum dihydrogen phosphate powder. To ensure complete dissolution, the mixture can be gently stirred with the help of a stirrer until the aluminum dihydrogen phosphate is completely dissolved, forming a clear and transparent solution.

[0029] During the dissolution process, the stirring speed can be adjusted to ensure a uniform and stable dissolution rate of aluminum dihydrogen phosphate in water. If the solution temperature is found to rise too quickly, the stirring speed should be appropriately reduced, and the temperature of the solution can be controlled by using a cooling water bath to prevent excessive reactions of certain components in the solution due to excessive temperature.

[0030] Furthermore, to ensure the aluminum dihydrogen phosphate solution concentration reaches 50%, the final solution concentration can be confirmed by comparing the actual mass of dissolved aluminum dihydrogen phosphate with the solution volume. If the concentration is insufficient, aluminum dihydrogen phosphate powder can be added as needed and stirring can continue until the solution concentration meets the requirements.

[0031] Ultimately, the prepared aluminum dihydrogen phosphate solution should have uniform concentration and stability, and be able to serve as an important component in the coating solution, playing a role in film formation and adhesion enhancement during the subsequent coating preparation process.

[0032] In this embodiment, aluminum oxalate is aluminum oxalate dodecyl hydrate, and the solid content of aluminum oxalate dodecyl hydrate is above 99%.

[0033] Aluminum oxalate dodecahydrate (solid content ≥99%) was chosen as the raw material to ensure its high purity and low impurity content, enabling it to react stably and function fully during the preparation process. High-purity aluminum oxalate can effectively reduce the impact of impurities on coating performance, ensuring that the final coating has good adhesion, high-temperature resistance, and corrosion resistance.

[0034] Specifically, aluminum oxalate plays two important roles in the coating solution: firstly, it removes dirt adhering to the silicon steel surface, improving the coating performance; secondly, it can complex metallic impurity ions on the silicon steel surface, reacting with the impurities during high-temperature baking to form an oxide film, further enhancing the coating's insulation properties. Aluminum oxalate accounts for 4%–6% of the total mass of the coating solution, effectively strengthening the adhesion between the coating and the substrate, improving the coating's adhesion and durability.

[0035] In this embodiment, the average particle size of the silica sol is 5-8 nm, the mass percentage of SiO2 in the silica sol is 20-21%, the pH value is 10-11, and the viscosity is 2.0-2.5 MPa·s.

[0036] Silica sol is an important component of the coating solution. As an auxiliary film-forming substance, it plays a crucial role in the coating's adhesion, surface smoothness, and heat resistance. Its small particle size (5–8 nm) can improve the coating's density and reduce micropore formation, thereby improving the coating's mechanical strength and electrical insulation properties. A SiO2 mass percentage content of 20–21% provides sufficient film-forming material, ensuring a uniform and stable coating.

[0037] Meanwhile, the pH value and viscosity of the silica sol are also crucial to the quality of the coating. A pH value of 10–11 is beneficial for enhancing the stability of the silica sol and promoting its compounding with other components. A viscosity of 2.0–2.5 MPa·s ensures that the coating solution has appropriate fluidity and wettability, facilitating application to the silicon steel surface and forming a uniform coating.

[0038] Specifically, silica sol, as an auxiliary film-forming agent, plays a crucial role in enhancing adhesion and improving surface quality in the coating solution. The addition of silica sol not only improves coating adhesion but also, in combination with phosphate binders, prevents shrinkage and blistering of single-phosphate coatings during high-temperature baking, avoids the formation of micropores, and enhances the smoothness and uniformity of the coating. The silica sol has an average particle size of 5–8 nm, a SiO2 mass percentage content of 20–21%, a pH value of 10–11, and a viscosity of 2.0–2.5 MPa·s. Its dosage accounts for 30%–35% of the total mass of the coating solution, ensuring excellent adhesion and surface quality of the coating.

[0039] In an optional embodiment, the silica sol of the present invention can be prepared as follows: First, prepare an appropriate amount of silicon tetrachloride and deionized water. Pour the deionized water into a stirring container and slowly add silicon tetrachloride while stirring. Silicon tetrachloride rapidly undergoes a hydrolysis reaction in water, generating silica gel and releasing hydrogen chloride gas. To control the reaction rate, ammonia water can be slowly added during the reaction to adjust the pH value of the solution, keeping it between approximately 10 and 11. By adjusting the amount of ammonia water added, the particle size distribution of the silica sol can be precisely controlled. After the reaction continues for a period of time, the generated silica sol will be filtered to remove impurities and concentrated by methods such as ultrafiltration to obtain the desired silica sol solution. Finally, the particle size of the silica sol can be further controlled by adjusting the reaction conditions (such as temperature, pH value, and the rate of ammonia water addition) to ensure that the particle size is between 5 and 8 nm. After purification and adjustment, a silica sol that meets the requirements of the present invention is finally obtained, with a SiO2 mass percentage content of 20-21% and the required viscosity and stability.

[0040] The silica sol prepared by this method has a uniform particle size distribution, which can meet the requirements of the coating solution for silica sol particle size, concentration and stability, and can ensure that the final coating has excellent adhesion, smoothness and thermal stability.

[0041] In this embodiment, potassium fluorozirconate is a white crystal with a solid content of over 99%.

[0042] Potassium fluorozirconate, as an important component in coating solutions, is mainly used to improve the corrosion resistance and impact resistance of coatings. In this embodiment of the invention, potassium fluorozirconate replaces traditional chromium-containing compounds, avoiding the potential environmental hazards of chromium compounds, while meeting environmental protection requirements while ensuring coating performance.

[0043] Potassium fluorozirconate with a solid content of over 99% is selected as the raw material to ensure its stability and high efficiency in the coating solution. High-purity potassium fluorozirconate can reduce the interference of impurities on the coating performance, ensuring the coating's corrosion resistance and mechanical strength.

[0044] Specifically, potassium fluorozirconate, as an environmentally friendly material, replaces traditional chromium-containing compounds, effectively improving the corrosion resistance of the coating and enhancing its stamping performance, preventing coating damage during the stamping and lamination of silicon steel sheets. This characteristic makes the coating more stable during manufacturing while maintaining its excellent electrical insulation properties. The potassium fluorozirconate constitutes 3% to 5% of the total mass of the coating solution, ensuring the stability of the coating during stamping and lamination while meeting environmental protection requirements.

[0045] In this embodiment, yttrium oxide is in powder form with a solid content of 99.5% or higher.

[0046] Yttrium oxide, due to its high melting and boiling points, exhibits excellent heat resistance, significantly improving the high-temperature resistance of coatings. In high-temperature environments, yttrium oxide reduces the thermal expansion of the coating, mitigating damage caused by thermal stress and thus enhancing its stability and durability. Furthermore, the addition of yttrium oxide can improve the magnetic and electrical insulation properties of the coating, which is particularly important in applications involving grain-oriented silicon steel.

[0047] Choosing yttrium oxide powder with a solid content of over 99.5% as the raw material ensures high purity, reduces the influence of other impurities, and thus improves the overall performance and stability of the coating. High-purity yttrium oxide provides better thermal stability and enhances the high-temperature resistance of the coating.

[0048] Specifically, yttrium oxide, due to its high melting and boiling points, significantly improves the high-temperature resistance of coatings. After adding yttrium oxide, the coating maintains good stability after high-temperature baking, making it suitable for applications in high-temperature environments. Yttrium oxide has a low coefficient of thermal expansion at high temperatures, meaning the coating will not crack due to thermal expansion during thermal cycling, helping to reduce thermal stress between the coating and the substrate, reduce iron loss, and improve magnetic properties. The yttrium oxide content is 1%–2% of the total mass of the coating solution, ensuring stability and long service life in high-temperature applications.

[0049] In this embodiment, 1,4-butanediol is a liquid with a mass percentage content of 99% or more.

[0050] The role of 1,4-butanediol in the coating solution is to reduce the viscosity and improve the wettability of the solution, thereby enabling the solution to be uniformly coated on the silicon steel surface, forming a smooth and even coating. After high-temperature baking, the coating surface is smooth, the appearance quality is improved, and the coating thickness is uniform, making it less prone to bubbles or uneven coating.

[0051] Choosing liquid 1,4-butanediol with a mass percentage content of over 99% ensures its full dissolution and effectiveness in the coating solution. High-purity 1,4-butanediol contributes to better coating results, guaranteeing coating uniformity and appearance quality.

[0052] Specifically, 1,4-Butanediol, acting as a plasticizer, reduces the viscosity of the coating solution and increases its wettability, thereby ensuring uniform coating of the silicon steel surface and preventing uneven coating. After high-temperature baking, the coating solution forms a smooth and even insulating coating, improving its appearance quality. The mass percentage of 1,4-Butanediol in the coating solution is 2%–3% of the total mass, effectively improving the coatability and appearance of the coating.

[0053] Another embodiment of the present invention provides a method for preparing an insulating coating solution. The raw materials of the insulating coating solution in this embodiment, by mass percentage concentration, include: 20%–25% aluminum dihydrogen phosphate solution, 4%–6% aluminum oxalate, 30%–35% silica sol, 3%–5% potassium fluorozirconate, 1%–2% yttrium oxide, 2%–3% 1,4-butanediol, and the balance being water. The method includes:

[0054] Step S101: Add aluminum oxalate and potassium fluorozirconate to water and stir.

[0055] In this embodiment, aluminum oxalate and potassium fluorozirconate are first added to water and stirred. Aluminum oxalate is generally aluminum oxalate dodecahydrate, which releases aluminum ions upon dissolution, contributing to the adhesion and structural strength of the coating. Potassium fluorozirconate, as an additive, enhances the thermal stability and corrosion resistance of the coating. Stirring ensures that both aluminum oxalate and potassium fluorozirconate are completely dissolved in the water, providing a homogeneous solution base for subsequent steps.

[0056] Step S102: After aluminum oxalate and potassium fluorozirconate are completely dissolved, add aluminum dihydrogen phosphate solution and stir.

[0057] In this embodiment, after aluminum oxalate and potassium fluorozirconate are completely dissolved, an aluminum dihydrogen phosphate solution is added. The aluminum dihydrogen phosphate solution is an aqueous solution containing aluminum dihydrogen phosphate, which serves to provide an aluminum source, helping to improve the coating's high-temperature resistance and insulation properties. Stirring ensures that the aluminum dihydrogen phosphate is fully mixed in the solution, avoiding precipitation or uneven distribution.

[0058] Step S103: After the aluminum dihydrogen phosphate solution is fully mixed, add yttrium oxide while stirring.

[0059] In this embodiment, yttrium oxide is added after the aluminum dihydrogen phosphate solution is thoroughly mixed with other components. Yttrium oxide is a high-temperature stable material that can enhance the thermal stability and corrosion resistance of the coating. After addition, stirring needs to be continued to ensure that the yttrium oxide is completely dissolved or uniformly dispersed. By adding and stirring simultaneously, the yttrium oxide can be fully dissolved or dispersed in the solution, forming a stable mixed solution.

[0060] In step S104, after the yttrium oxide is completely dissolved, add silica sol and 1,4-butanediol and stir until the mixture is homogeneous to obtain a mixed solution.

[0061] In this embodiment, the solution obtained after the complete dissolution of yttrium oxide is mixed with silica sol and 1,4-butanediol to obtain a mixed solution. The SiO2 particles in the silica sol provide insulation properties and enhance the structural stability of the coating. 1,4-Butanediol, as a plasticizer, improves the flowability and uniformity of the coating, ensuring that a consistent thin film is formed on the metal surface.

[0062] In step S105, the mixed solution is filtered through a 1250-mesh filter to obtain an insulating coating solution.

[0063] In this embodiment, the solution is filtered through a 1250-mesh filter. This removes any possible solid impurities, ensuring the purity and uniformity of the coating solution, ultimately resulting in a clear, particulate-free coating solution, thus ensuring the quality and uniformity of the coating.

[0064] Another embodiment of the present invention provides an insulating coating for oriented silicon steel, which is prepared by coating oriented silicon steel with the insulating coating solution in the above embodiment.

[0065] In this embodiment, the insulating coating solution described in the above embodiment is used to coat the oriented silicon steel. After coating, the surface is heated, dried, and sintered, and finally an insulating coating is formed on the surface of the oriented steel.

[0066] In practical applications, the thickness of the insulating coating for oriented silicon steel provided in this embodiment of the invention can be 0.5 to 1 μm.

[0067] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0068] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0069] Example 1

[0070] The environmentally friendly insulating coating solution prepared according to the formula shown in Table 1 was used to coat the grain-oriented silicon steel. After coating, the temperature was increased by 50℃ / s, and the steel was dried at 300℃ for 30s. Then, it was sintered at 800℃ for 30 seconds, and finally an insulating coating of 0.5 to 1 μm was formed on the surface of the grain-oriented silicon steel.

[0071] The specific preparation steps are as follows: Potassium fluorozirconate solid, aluminum oxalate solid, and deionized water are added to a stirring container and stirred thoroughly until the solids are completely dissolved. Aluminum dihydrogen phosphate solution is added to the above solution and stirred until homogeneous. Then, yttrium oxide powder is added while stirring until completely dissolved. The solution obtained from the above two steps is mixed with silica sol and 1,4-butanediol and stirred until homogeneous. The mixture is then filtered through a 1250-mesh screen to obtain an environmentally friendly insulating coating solution for use on the surface of grain-oriented silicon steel used in the manufacture of electric vehicle motors.

[0072] The formulations of each component are shown in Table 1 (the remainder is deionized water):

[0073] Table 1 Composition of the coating solution

[0074]

[0075]

[0076] Note: The balance is deionized water (by mass percentage).

[0077] The aluminum dihydrogen phosphate solution used in Examples 1-10 had a mass percentage of 50%.

[0078] The aluminum oxalate used in Examples 1-10 is dodecahydrate with a solid content of 99.5%.

[0079] The silica sol used in Examples 1-10 had an average particle size of 6 nm, a SiO2 mass percentage content of 20.5%, a pH value of 10.5, and a viscosity of 2.2 MPa·s.

[0080] The potassium fluorozirconate used in Examples 1-10 was a white crystal with a solid content of 99.2%.

[0081] The yttrium oxide used in Examples 1-10 was in powder form with a solid content of 99.9%.

[0082] The 1,4-butanediol used in Examples 1-10 was a liquid with a mass percentage of 99.5%.

[0083] The aluminum dihydrogen phosphate solution, aluminum oxalate, silica sol, potassium fluorozirconate, yttrium oxide, and 1,4-butanediol used in Comparative Examples 1-10 and Examples 1-10 were all from the same batch of raw materials.

[0084] Table 2 shows the various properties of the environmentally friendly insulating coating prepared according to the formula and method in Table 1; the oriented silicon steel sheets coated with the insulating coating are stamped and stacked to make motor stator cores and rotor cores, and the performance of the tram motor assembled using the stator core, rotor core and windings is shown.

[0085] Coating: Appearance is determined by SEM (scanning electron microscope), gloss meter, and roughness meter.

[0086] Insulation performance was measured using an insulation resistance tester (assessed by interlayer resistance). Insulation was considered excellent when the interlayer resistance was >30 Ω·(cm²·piece)⁻¹. Insulation was considered good when the interlayer resistance was between 15 and 30 Ω·(cm²·piece)⁻¹. Insulation was considered fair when the interlayer resistance was between 5 and 15 Ω·(cm²·piece)⁻¹. Insulation was considered poor when the interlayer resistance was <5 Ω·(cm²·piece)⁻¹.

[0087] Adhesion was tested according to the method specified in GB2522-2007 "Test Method for Adhesion of Insulation Resistance Coating on Surface of Electrical Steel Sheet (Strip)". The sample was bent 180° with a diameter of 30mm, and the surface coating cracking and peeling were checked.

[0088] The corrosion resistance test was conducted in a cyclic corrosion chamber. Corrosion conditions: continuous spraying with a 5% salt solution at 35℃ for 5 hours, followed by observation of the sample surface. The corrosion resistance evaluation criteria were: rust area <5% was excellent, rust area 5%–29% was good, rust area 30%–59% was fair, and rust area >60% was poor.

[0089] The heat resistance test was conducted in a high-temperature box-type resistance furnace. Heat resistance conditions: N2 was introduced at 850℃, and the sample was continuously heated for 2 hours. The sample surface was then observed after removal. The heat resistance evaluation criteria were: dark gray with a glossy finish was excellent; gray with a glossy finish was good; gray without a glossy finish was average; and a whitish, powdery surface was poor.

[0090] Motor: Insulation resistance is measured using a 500V megohmmeter. Connect the two leads of the megohmmeter to any two phases to obtain the insulation resistance value for that phase. The insulation resistance value of the motor should be greater than 1 megohm. If the measured insulation resistance value is less than 1 megohm, it indicates poor insulation performance of the motor, which may lead to problems such as leakage, short circuit, and overheating. Motors with good insulation performance have a relatively longer service life and higher operating efficiency.

[0091] Efficiency is measured indirectly. First, the motor's input power is measured: by measuring the motor's current and voltage, the input power is calculated using the power formula P = UI. Then, the motor's output power is measured: by measuring the motor's load torque (T) and speed (ω), the output power is calculated using the power formula P = Tω. Finally, the motor's output power is divided by the input power and multiplied by 100% to obtain the motor's operating efficiency.

[0092] The temperature rise test uses the thermal balance method. After running the motor for 2 hours at an ambient temperature of 25℃, an infrared thermometer is used to measure the temperature of various parts of the motor. The temperature rise of the motor is calculated by subtracting the ambient temperature from the measured temperature. The standard temperature rise for the motor is between 60 and 80℃, which is a relatively safe range to ensure that the motor will not be damaged due to excessive temperature during normal operation. If the motor temperature rise is too high, it will accelerate the aging of the motor insulation, affect the service life of the motor, and may even cause accidents such as motor burnout.

[0093] Table 2 Performance Comparison

[0094]

[0095]

[0096] As can be seen from Table 2, under the conditions of Examples 1 to 10, the coating performance, such as appearance, insulation, adhesion, corrosion resistance, and heat resistance, is excellent. The oriented silicon steel sheets coated with this environmentally friendly insulating coating are stamped and stacked to make motor stator cores and rotor cores. The tram motors assembled using the stator cores, rotor cores, and windings have good insulation performance, high working efficiency, low temperature rise level, and long service life.

[0097] Compared with Comparative Example 1 and Example 1, the addition of aluminum oxalate can significantly improve the insulation of the coating. The tram motor assembled using oriented silicon steel sheets coated with an insulating coating containing aluminum oxalate has good insulation performance, high working efficiency, and temperature rise within a safe range.

[0098] Compared to Comparative Example 2 and Example 2, when the aluminum oxalate content increased to over 6%, there was no significant improvement in the performance of the coating and the motor. As can be seen from the examples, when the aluminum oxalate content is between 4% and 6%, the performance of the coating and the motor is excellent.

[0099] Compared with Comparative Example 3 and Example 3, due to insufficient addition of silica sol, there were a few pinhole-like holes on the coating surface, and the insulation, adhesion and corrosion resistance of the coating decreased. The insulation and working efficiency of the tram motor assembled using the oriented silicon steel sheet coated with this coating decreased.

[0100] Compared to Comparative Example 4 and Example 4, the excessive amount of silica sol resulted in a slightly rough coating surface, the precipitation of a small number of small particles, and a decrease in the coating's insulation and heat resistance. Consequently, the assembled motor exhibited insufficient insulation performance, significantly reduced operating efficiency, and a temperature rise exceeding the safe range. As can be seen from the examples, a silica sol content between 30% and 35% resulted in excellent performance of both the coating and the motor.

[0101] Compared with Comparative Example 5 and Example 5, the addition of potassium fluorozirconate can give the coating excellent corrosion resistance, improve the insulation and heat resistance of the coating, and improve the insulation performance and working efficiency of the trolley motor.

[0102] Compared to Comparative Example 6 and Example 6, the performance of the coating and motor did not significantly improve with increasing potassium fluorozirconate content. As can be seen from the examples, the coating and motor exhibit excellent performance when the potassium fluorozirconate content is between 3% and 5%.

[0103] Compared with Comparative Example 7 and Example 7, the addition of yttrium oxide significantly improved the heat resistance and insulation of the coating. The electric vehicle motor assembled using oriented silicon steel sheets coated with an insulating coating without yttrium oxide had insufficient insulation performance, significantly reduced working efficiency, and excessive temperature rise.

[0104] Compared to Comparative Example 8 and Example 8, the performance of the coating and motor did not improve with increasing yttrium oxide content. As can be seen from the examples, when the yttrium oxide content is between 1% and 2%, the performance of the coating and motor is excellent.

[0105] Compared with Comparative Example 9 and Example 9, if the coating solution does not contain 1,4-butanediol, its wettability is insufficient. The insulating coating formed after high-temperature baking on the silicon steel surface is slightly rough and has white patterns. The insulation, adhesion, corrosion resistance and heat resistance of the coating are reduced. The insulation performance and working efficiency of the tram motor assembled using the oriented silicon steel sheet coated with the insulating coating without 1,4-butanediol are significantly reduced, and the temperature rise exceeds the safe range.

[0106] Compared to Comparative Example 10 and Example 10, there was no significant improvement in the performance of the coating and motor with increasing 1,4-butanediol content. As can be seen from the examples, the coating and motor exhibit excellent performance when the 1,4-butanediol content is between 2% and 3%.

[0107] In this invention, a roller coater is used to coat a cold-rolled oriented silicon steel substrate with a coating liquid. After coating, the temperature is increased at 50°C / s, and the substrate is dried at 300°C for 30s. Then, it is sintered at 800°C for 30s, and finally an insulating coating of 0.5 to 1 μm is formed on the surface of the oriented silicon steel.

[0108] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. An insulating coating solution for grain-oriented silicon steel, characterized in that, Based on the total mass of the insulating coating solution, the composition and corresponding mass percentage of the insulating coating solution are as follows: 20%~25% aluminum dihydrogen phosphate solution, 4%~6% aluminum oxalate, 30%~35% silica sol, 3%~5% potassium fluorozirconate, 1%~2% yttrium oxide, 2%~3% 1,4-butanediol, and the balance being water.

2. The insulating coating solution according to claim 1, characterized by, The aluminum dihydrogen phosphate solution is an aqueous solution of aluminum dihydrogen phosphate, and the mass percentage of aluminum dihydrogen phosphate in the aqueous solution of aluminum dihydrogen phosphate is 50%.

3. The insulating coating solution according to claim 1, wherein The aluminum oxalate is aluminum oxalate dodecahydrate, and the solid content of the aluminum oxalate dodecahydrate is above 99%.

4. The insulating coating solution according to claim 1, characterized by, The silica sol has an average particle size of 5-8 nm, a SiO2 mass percentage content of 20-21%, a pH value of 10-11, and a viscosity of 2.0-2.5 mPa·s.

5. The insulating coating solution according to claim 1, wherein The potassium fluorozirconate is a white crystal with a solid content of over 99%.

6. The insulating coating solution according to claim 1, characterized in that, The yttrium oxide is in powder form with a solid content of 99.5% or higher.

7. The insulating coating solution according to claim 1, characterized in that, The 1,4-butanediol is a liquid with a mass percentage content of 99% or more.

8. A method for preparing an insulating coating solution, characterized in that, The raw materials of the insulating coating solution, by mass percentage concentration, include: 20%~25% aluminum dihydrogen phosphate solution, 4%~6% aluminum oxalate, 30%~35% silica sol, 3%~5% potassium fluorozirconate, 1%~2% yttrium oxide, 2%~3% 1,4-butanediol, and the balance being water. The method includes: Add the aluminum oxalate and the potassium fluorozirconate to water and stir. After the aluminum oxalate and potassium fluorozirconate are completely dissolved, the aluminum dihydrogen phosphate solution is added and stirred. After the aluminum dihydrogen phosphate solution is fully mixed, add the yttrium oxide while stirring. After the yttrium oxide is completely dissolved, the silica sol and the 1,4-butanediol are added and stirred until they are mixed evenly to obtain a mixed solution; The mixed solution is filtered through a 1250-mesh filter to obtain the insulating coating solution.

9. An insulating coating for oriented silicon steel, wherein, The insulating coating is obtained by coating oriented silicon steel with the insulating coating solution according to any one of claims 1 to 7.

10. The insulating coating according to claim 9, characterized in that The insulating coating solution according to any one of claims 1 to 7 is used to coat oriented silicon steel. After coating, the surface is heated, dried, and sintered to finally form an insulating coating on the oriented steel surface.

Images