Chromium-free environment-friendly insulating coating paint and thin electrical steel strip

Abstract

The invention relates to a chromium-free environment-friendly insulating coating paint and a thin electrical steel strip. The chromium-free environment-friendly insulating coating comprises the following components in percentage by mass: 15%-23% of phosphate; 8%-13% of epoxy resin emulsion; 0.3%-1.2% of boric acid; 0.4%-4.7% of a metal inorganic salt additive; 0.3%-1.1% of a metal hydroxide; 0.1%-0.44% of a coupling agent; 7%-26% of hollow ceramic microsphere particles; and 30.56% to 68.9% of deionized water. The metal inorganic salt additive is at least one of barium oxalate, strontium sulfate and aluminum silicate. The phenomena that solid components in the coating sink to the bottom and water is separated from the surface can be avoided, the compactness of the coating is improved, the wear resistance and corrosion resistance of the coating are improved, the resistivity of the insulating coating can be remarkably improved through the nanoscale hollow ceramic microsphere particles, the loss of electrical steel is reduced, the adhesiveness of the coating is enhanced, and cracks of the coating are reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of surface insulation coating of thin-gauge electrical steel, and particularly relates to a chromium-free environment-friendly insulation coating paint and thin-gauge electrical steel strip. BACKGROUND

[0002] The electrical steel generally contains about 3% to 4.5% of silicon, which makes it have unique magnetic properties and electrical conductivity, and is widely used in core components of power equipment such as electric motors, transformers and generators. The surface layer of the electrical steel is usually treated by electroplating, spraying and other methods to form an insulation protective layer on the surface of the electrical steel, which can effectively reduce the eddy current loss and improve the service life of the equipment. The protective layer of the electrical steel is composed of three categories of organic coating, inorganic coating and semi-inorganic coating. The organic coating has the advantages of good adhesion, good punching and shearing properties and good insulation performance, but has poor heat resistance and is easily carbonized at high temperatures, which cannot meet the protection requirements of the electrical steel. The inorganic coating has high hardness, and has high requirements for the mold in the production process, thereby limiting the development of downstream manufacturers.

[0003] Most of the traditional electrical steel coatings contain chromate, which can effectively improve the water resistance and corrosion resistance of the coating. However, chromium can cause serious damage to the human body and the environment, so the European Union has introduced relevant regulations to restrict the production of chromium-containing coatings. At present, the main environmental protection electrical steel coating is phosphate coating, which does not add chromate, thereby effectively reducing the environmental pollution of the electrical steel coating liquid. Compared with the traditional electrical steel coating, the environmental protection electrical steel coating is easy to absorb moisture in the air, resulting in sticky coating and poor corrosion resistance, thereby limiting the application range of the environmental protection electrical steel coating. How to improve the water resistance and corrosion resistance of the environmental protection electrical steel coating has become two major problems to be solved.

[0004] Therefore, it is urgent to provide a new chromium-free environment-friendly insulation coating paint for thin-gauge electrical steel and an electrical steel strip to solve the problems of poor corrosion resistance, high water absorption and low insulation resistivity of the chromium-free environment-friendly insulation coating. SUMMARY

[0005] The purpose of the present application is to solve the problems of poor corrosion resistance, high water absorption and low insulation resistivity of the chromium-free environment-friendly insulation coating. The purpose of the present application is achieved by adopting the following technical solutions: The present application provides a chromium-free environment-friendly insulation coating paint, which comprises the following components in percentage by mass: Phosphate 15% to 23%; Epoxy resin emulsion 8% to 13%; Boric acid 0.3% to 1.2%; Metal inorganic salt additive 0.4% to 4.7%; Metal hydroxide 0.3% to 1.1%; coupling agent 0.1%~0.44%; hollow ceramic microsphere particles 7%~26%; deionized water 30.56%~68.9%; The metal inorganic salt additive is at least one of barium oxalate, strontium sulfate, and aluminum silicate.

[0006] Preferably, the metal inorganic salt additive is a mixture of barium oxalate and aluminum silicate or a mixture of strontium sulfate and aluminum silicate or a mixture of barium oxalate, strontium sulfate, and aluminum silicate.

[0007] Barium oxalate and strontium sulfate are both metal salts with high lattice energy and extremely low solubility, which are difficult to form a saturated solution in the coating and can significantly reduce the deliquescence power of the coating, fundamentally solving the problem of easy moisture absorption and stickiness of the chromium-free coating (one of the core functions of traditional chromate), and the low solubility characteristics reduce the free ions in the coating and reduce the possibility of electrochemical corrosion; at the same time, both can fill the pores of the coating and form a dense structure with phosphate to hinder the penetration of moisture and corrosive media, replacing the corrosion protection of chromate.

[0008] Aluminum silicate, as a superfine inorganic particle, can be adsorbed on the surface of other solid components to reduce particle agglomeration and avoid the phenomenon of sedimentation and water separation of the coating during storage; the particle morphology and density of barium oxalate and strontium sulfate are moderate, which can cooperate with aluminum silicate to maintain the uniformity of the coating system and ensure the uniformity of the coating thickness during construction. The three work together to improve the dispersibility and storage stability of the coating: Preferably, the hollow ceramic microsphere particles are at least one of aluminum oxide, zirconium dioxide, and silicon dioxide, and the diameter of the hollow ceramic microsphere particles is 50~200nm, and the cavity volume is not less than 4 / 5 of the particle volume.

[0009] Preferably, the phosphate includes at least one of magnesium dihydrogen phosphate, aluminum dihydrogen phosphate, titanium dihydrogen phosphate, and sodium dihydrogen phosphate.

[0010] Preferably, the metal hydroxide is at least one of cobalt hydroxide and strontium hydroxide.

[0011] Preferably, the coupling agent is a chelating type water-based titanate coupling agent.

[0012] The application also provides a thin-gauge electrical steel strip, which comprises a substrate, and the surface of the substrate has a coating formed by coating the substrate with the chromium-free environmentally friendly insulating coating material according to any one of claims 1~6.

[0013] Preferably, the substrate is a magnesium-free forsterite ceramic film substrate or a magnesium-containing forsterite ceramic film substrate, and the thickness of the substrate is 0.03~0.27mm.

[0014] Preferably, the substrate surface is coated with the chromium-free environment-friendly insulating coating paint and then subjected to a sintering treatment, the sintering temperature being 480-600 DEG C, and the holding time being 20-120 s.

[0015] Preferably, the thickness of the surface coating after sintering and solidification is 0.4-3 mu m, and the mass is 0.1%-1.1% of the mass of the electrical steel strip.

[0016] Compared with the prior art, the present application has the following beneficial effects: The chromium-free environment-friendly insulating coating paint of the present application comprises the following components in percentage by mass: phosphate 15%-23%; epoxy resin emulsion 8%-13%; boric acid 0.3%-1.2%; metal inorganic salt additive 0.4%-4.7%; metal hydroxide 0.3%-1.1%; coupling agent 0.1%-0.44%; hollow ceramic microsphere particles 7%-26%; deionized water 30.56%-68.9%. The metal inorganic salt additive is at least one of barium oxalate, strontium sulfate and aluminum silicate. The present application uses barium oxalate, strontium sulfate and aluminum silicate to replace the existing chromate, which can avoid the solid component sinking to the bottom and the surface water separation phenomenon in the paint, increase the compactness of the coating, and improve the wear resistance and corrosion resistance of the coating. The lattice energy of barium oxalate and strontium sulfate is high, the solubility is low, it is difficult to form a saturated solution, and the deliquescence power is weak, which can effectively solve the problem of poor water resistance of the existing chromium-free chromate insulating coating. Aluminum silicate has good reinforcing effect, can refine the coating grain, and improve the compactness and hardness of the coating, and enhance the wear resistance. The addition of nanoscale hollow ceramic microsphere particles can significantly improve the resistivity of the insulating coating, reduce the loss of electrical steel, enhance the adhesion of the coating, reduce the generation of coating cracks, and improve the working stability of the electrical steel coating. 16 BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The figure is the surface coating morphology of the electrical steel strip of Example 1 of the present application. DETAILED DESCRIPTION

[0018] The technical solutions of the present application will be further described in detail below with reference to specific examples. It should be understood that the following examples are only illustrative and explanatory of the present application, and should not be interpreted as limiting the scope of protection of the present application. Any technology realized based on the above description of the present application is covered within the scope of protection intended by the present application.

[0019] Examples 1-6 and Comparative Examples 1-4 ​1) The environmental-friendly chromium-free insulating coating paint formula (by mass percentage) comprises phosphate, epoxy resin emulsion, boric acid, metal inorganic salt additive, metal hydroxide, coupling agent, hollow ceramic microsphere particles and deionized water. The chemical composition of the insulating coating liquid for electrical steel strip in Examples 1-6 meets the preferred design control requirements of the present application. The chemical composition of the comparative coating liquid in Comparative Examples 1-4 meets the design requirements of the present application, but the proportion of some chemical components in the coating liquid does not meet the parameters of the preferred design scheme of the present application. See Table 1 for details.

[0020] 2) Preparation and application: Mix the phosphate according to the formula proportion, add an appropriate amount of deionized water, and stir until completely dissolved. Take the hollow ceramic microsphere particles, add the chelating waterborne titanate coupling agent, and use a high-speed dispersing machine to disperse, so that the coupling agent uniformly coats the surface of the microspheres. Add the epoxy resin emulsion in the stirring kettle, start stirring, slowly add the pretreated phosphate solution, and stir until a uniform emulsion system is formed. Then add the metal inorganic salt additive and metal hydroxide, continue stirring, and add boric acid dropwise to adjust the pH of the system to 4.5-5.5 during the process. Finally, add the surface-treated hollow ceramic microspheres, stir until the microspheres are uniformly dispersed, add deionized water to adjust the viscosity, and the environmental-friendly chromium-free insulating coating is obtained. Use a roller coater to apply the coating to the substrate of an electrical steel strip with a thickness of 0.03-0.27 mm. After coating the surface of the substrate with the insulating coating, perform sintering treatment at a sintering temperature of 480-600°C for 20-120s. The thickness of the surface coating after sintering and curing is about 0.4-3μm. See Table 2 for specific process parameters.

[0021] It should be noted that the mass percentage of each chemical element in the steel slab substrate of the oriented silicon steel plate of each example and comparative example is the same, and in particular, the mass percentage of Si in the steel should be controlled between 1.2-6.5%.

[0022] Table 1 Coating formula

[0023] Note: the balance is deionized water.

[0024] Table 2 Process parameters

[0025] For the obtained electrical steel strip with coating, the interlayer resistivity, corrosion resistance, adhesion performance and coating hardness of the insulating coating need to be tested. Table 3 lists the test results of the related properties of the electrical steel strips in Examples 1-6 and Comparative Examples 1-4.

[0026] Table 3 Test results

[0027] As can be seen from Table 3, in Examples 1-6, using the insulating coating liquid meeting the design control requirements of the present application, an electric steel sheet with very excellent performance can be obtained, and the sintered and cured coating layer simultaneously exhibits high resistivity, excellent adhesion, strong corrosion resistance and high hardness. The high interlayer resistivity can greatly reduce the eddy current loss of the electric steel strip, the excellent adhesion, strong corrosion resistance and high hardness can significantly improve the service performance of the electric steel strip, and the high environmental friendliness and high performance of the electric steel strip can be matched at a high level, which has good popularization prospect and application effect.

[0028] The chemical composition of the comparative coating liquid in Comparative Examples 1-4 meets the design requirements of the present application, but the chemical composition ratio or component size in the coating liquid does not meet the parameters of the preferred design scheme of the present application. In Comparative Example 1, the coating adhesion is greatly reduced due to the too low content of dihydrogen phosphate and the too large thickness of the coating layer; in Comparative Example 2, the corrosion resistance and hydrolysis performance of the coating layer are deteriorated due to the too low content of metal salt such as barium oxalate and the too low sintering and curing temperature of the coating layer, and the coating adhesion is also greatly reduced; in Comparative Example 3, the resistivity, adhesion and hardness of the coating layer are greatly reduced due to the too large particle size, too low content and too large thickness of the hollow ceramic microspheres; in Comparative Example 4, the coating adhesion is significantly deteriorated due to the too small particle size of the hollow ceramic microspheres and the high sintering temperature.

[0029] Figure 1 The surface coating morphology of the electric steel strip of Example 1 is shown in the figure. As can be seen from the figure, the insulating coating liquid is tightly combined with the silicon steel substrate on both sides, and no obvious cracks or gaps are observed at the interface, and there is an obvious boundary line between the insulating coatings, as shown by the yellow dotted line in the figure. As can be seen from Figure b, the total thickness of the coating between the two silicon steel sheets is about 1.32 μm, the thickness of the coating on the upper coating surface is about 0.62 μm, and the thickness of the coating on the lower coating surface is about 0.7 μm, and the thickness of the surface coating is uniform as a whole without significant difference.

[0030] It should be noted that the combination of the technical features in the present case is not limited to the combination of the claims in the present case or the combination of the embodiments described in the present case. All the technical features described in the present case can be freely combined or combined in any way, unless they contradict each other.

[0031] The above is only an embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application is included in the scope of the claims of the present application.

Claims

1. A chromium-free, environmentally friendly insulating coating paint, characterized by, By mass percentage, comprising the following components: Phosphate 15%~23%; Epoxy resin emulsion 8%~13%; Boric acid 0.3%~1.2%; Metal inorganic salt additive 0.4%~4.7%; Metal hydroxide 0.3%~1.1%; Coupling agent 0.1%~0.44%; Hollow ceramic microsphere particles 7%~26%; Deionized water 30.56%~68.9%; The metal inorganic salt additive is at least one of barium oxalate, strontium sulfate, aluminum silicate.

2. The chrome-free, environmentally friendly insulating coating paint according to claim 1, characterized by, The metal inorganic salt additive is a mixture of barium oxalate and aluminum silicate or strontium sulfate, aluminum silicate or a mixture of barium oxalate, strontium sulfate and aluminum silicate.

3. The chrome-free, environmentally friendly insulating coating paint according to claim 1, characterized by, The hollow ceramic microsphere particles are at least one of aluminum oxide, zirconium dioxide and silicon dioxide, the diameter of the hollow ceramic microsphere particles is 50~200nm, and the cavity volume is not less than 4 / 5 of the particle volume.

4. The chrome-free, environmentally friendly insulating coating paint according to claim 1, characterized by, The phosphate includes at least one of magnesium dihydrogen phosphate, aluminum dihydrogen phosphate, titanium dihydrogen phosphate and sodium dihydrogen phosphate.

5. The chrome-free, environmentally friendly insulating coating paint according to claim 1, characterized in that, The metal hydroxide is at least one of cobalt hydroxide and strontium hydroxide.

6. The chrome-free, environmentally friendly insulating coating paint according to claim 1, characterized by, The coupling agent is a chelated water-based titanate coupling agent.

7. A thin gauge electrical steel strip comprising a substrate, characterized by, The substrate surface has a coating formed by coating the substrate with the chromium-free environmentally friendly insulating coating paint according to any one of claims 1~6.

8. The thin-gauge electrical steel strip of claim 7, wherein, The substrate is a magnesium-free forsterite ceramic membrane substrate or a magnesium-containing forsterite ceramic membrane substrate, and the substrate thickness is 0.03~0.27mm.

9. The thin-gauge electrical steel strip of claim 7, wherein, After the substrate surface is coated with the chromium-free environmentally friendly insulating coating paint, sintering treatment is performed, the sintering temperature is 480~600℃, and the holding time is 20~120s.

10. The thin-gauge electrical steel strip of claim 7, wherein, The thickness of the surface coating after sintering and curing is 0.4~3μm, and the mass is 0.1%~1.1% of the mass of the electrical steel strip.

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