A silicon steel sheet having excellent moisture resistance and a method for manufacturing the same

Abstract

The present application discloses a silicon steel plate with excellent moisture resistance, which comprises a silicon steel substrate and a coating layer coated on the surface of the silicon steel substrate; the content of P element in the coating layer gradually increases from the coating interface side in contact with air to the coating base side in contact with the silicon steel substrate, and the ratio of the P content at the coating interface side to the P content at the coating base side is 0< P content at the coating interface side / P content at the coating base side ≤0.4. The present application also discloses a manufacturing method of the silicon steel plate, which comprises the following steps: obtaining a silicon steel substrate; coating a coating material on the surface of the silicon steel substrate, and controlling the environmental dew point during coating of the coating material to be higher than 35℃; the effective components of the coating material comprise metal phosphate and organic resin; and high-temperature baking is performed to form the coating layer on the silicon steel substrate.

Description

Technical Field

[0001] This invention relates to a steel plate and its manufacturing method, and more particularly to a silicon steel plate and its preparation method. Background Technology

[0002] Silicon steel can be used to manufacture the cores of electric motors, generators, transformers, and ballasts, and is an indispensable magnetic material in the power, electronics, and military industries.

[0003] Applying an insulating and anti-corrosion coating to the surface of silicon steel can reduce eddy current losses in silicon steel plates, while ensuring that the surface of silicon steel has a high resistivity, thus minimizing interlayer power loss and protecting silicon steel from corrosion by various corrosive media.

[0004] Silicon steel coatings often use chromium-containing organic-inorganic composite coatings, but chromates can cause environmental pollution and are carcinogenic. Existing patents have explored introducing phosphates to replace chromates in these semi-organic coatings.

[0005] For example, US Patent No. 5945212A, published on August 31, 1999, entitled "Insulating Film Treatment Agent with Excellent Film Properties and Method for Manufacturing Non-Oriented Electrical Steel Sheet Using the Treatment Agent", discloses an environmentally friendly coating that uses dihydrogen phosphate instead of chromate and adds organic emulsion and silica sol. Although it solves the environmental problem, it still has a significant gap with chromate coating in terms of adhesion and wettability. Summary of the Invention

[0006] One of the objectives of this invention is to provide a silicon steel sheet with excellent moisture resistance. This silicon steel sheet has a moisture-resistant silicon steel coating, which can significantly improve the silicon steel sheet's ability to resist environmental humidity corrosion, thereby enabling the silicon steel sheet to be stored and used for a long time, effectively extending the service life of the silicon steel sheet. At the same time, it can also maintain excellent insulation properties, meeting the higher requirements of modern high-efficiency motors and power equipment for material reliability and durability.

[0007] To achieve the above objectives, the present invention provides a silicon steel sheet with excellent moisture resistance, comprising a silicon steel substrate and a coating applied to the surface of the silicon steel substrate.

[0008] The phosphorus (P) content in the coating gradually increases from the coating interface side in contact with air to the coating substrate side in contact with the silicon steel substrate, and 0 < the ratio of P content on the coating interface side to P content on the coating substrate side ≤ 0.4.

[0009] The inventors discovered through research that the current causes of whitening, powdering, and decreased adhesion in silicon steel sheet surface coatings are due to phosphates in the coating. Phosphates combine with moisture in the air to form microcrystals or amorphous substances containing free water, causing the coating structure to swell and become porous, resulting in powdering. If this process continues, moisture may penetrate to the bottom layer of the coating and contact the metal steel sheet, causing corrosion and rendering the steel sheet unusable. Based on this research, this invention controls the phosphorus (P) element in the coating.

[0010] This invention involves coating a silicon steel substrate with a coating material and curing it to form an insulating film. The phosphorus (P) content in the coating is controlled to gradually increase from the coating interface side to the coating substrate side, and the ratio of P content at the coating interface side to that at the coating substrate side is kept below 0.4. This control method ensures the coating's moisture resistance. This phenomenon can be explained by the coating curing process and the chemical reactions that occur within it.

[0011] During the curing process, the coating undergoes the following chemical reactions:

[0012] (1) Phosphate (using M) x (PO4) y (This indicates that M represents a metal ion) will dissociate:

[0013] M x (PO4) y →xM n+ +yPO4 m- , where n and m are the charges of the metal ion M and the phosphate ion PO4, respectively.

[0014] (2) Active groups are generated during the curing process of organic resins:

[0015] Taking organic resins containing active groups such as hydroxyl (-OH) and carboxyl (-COOH) as an example, the curing process further activates these groups, exposing more active sites. For instance, the carboxyl group may partially dissociate: R-COOH → ← R-COO - +H + The resulting carboxyl anions exhibit stronger reactivity. Here, R represents a portion of the organic resin molecular chain.

[0016] (3) The active groups generated during the curing of organic resins will undergo chemical bonding reactions with phosphate ions dissociated from phosphates. For example, hydroxyl groups react with phosphate ions as follows: R-OH + PO4 3- →RO-PO3 2- +OH - 3R-O-PO3 2- +2Mn + →(RO-PO3) m M nThe carboxyl anion can also react with phosphate ions: 3R-COO- + PO4- 3- →(R-COO)3PO+3O 2- .

[0017] Although different organic resins have different structures and functional groups, from a general perspective, the reaction sites of organic resins can be represented by R, which reacts with phosphate ions (PO4). m- The possible chemical bonding reaction can be represented by the following general formula: mR + PO4 m- →R m PO4.

[0018] The environment on the outer side of the coating (i.e., the coating interface side) is complex, containing factors such as air and moisture. Oxygen in the air may react with the active groups of the organic resin to form oxides on the surface of the organic resin. These oxides can cover some active sites R, thereby reducing the reactivity of the active groups with phosphate ions. For example, hydroxyl groups may be oxidized to carbonyl groups (C=O). Moisture may dilute the concentration of phosphate ions, making the reaction R-OH+PO4- less effective. 3- →RO-PO3 2- +OH - The equilibrium shifts to the left, which is unfavorable for the chemical bonding reaction between phosphate ions and organic resins. The presence of moisture also enhances the hydrolysis of phosphates, causing some phosphate ions to convert to other forms, such as hydrogen phosphate ions (HPO4). 2- Or dihydrogen phosphate ions H2PO4 - This reduces the number of phosphate ions that can chemically bond with organic resins. Simultaneously, moisture may hydrate the active sites R on the surface of the organic resin, hindering their contact and reaction with phosphate ions. In contrast, the reaction environment on the inner side of the coating (i.e., the coating substrate side) is relatively stable and more conducive to the chemical bonding of phosphate ions with the organic resin. Therefore, phosphate ions continuously diffuse from the outside to the inside to meet the chemical bonding reaction requirements on the inside, ultimately leading to the accumulation of phosphorus (P) elements from the outside to the inside.

[0019] Within the scope defined by this invention, the smaller the ratio of phosphorus (P) content on the coating interface side to that on the coating substrate side (hereinafter referred to as the P ratio), the better the improvement in moisture resistance. This is because the moisture absorption of a coating is closely related to its surface hydrophilicity. Phosphates, as hydrophilic substances, can attract water molecules and undergo hydrolysis reactions to generate soluble substances such as dihydrogen phosphate and phosphates. These substances may form micropores or loose structures on the coating surface, further increasing moisture absorption and the channels for water penetration. A lower P content on the coating interface side means a lower free energy of the coating surface in the presence of water molecules, reducing water adsorption. Therefore, a smaller P ratio results in less interaction between the coating and water molecules, enhancing the moisture resistance of the coating.

[0020] Furthermore, in the silicon steel plate of the present invention, the coating contains Si element with a mass percentage of ≥1%.

[0021] Furthermore, in the silicon steel sheet of the present invention, the mass percentage of Si element in the coating is 1-10%.

[0022] In this invention, by controlling the mass percentage of Si in the coating, the compatibility between the coating components can be further ensured. Furthermore, the presence of Si can further ensure the insulation performance of the coating. This is because:

[0023] Without silicon, the coating is primarily composed of organic resins and metal phosphates. The polar groups and macromolecular chains in the organic resins create electron or ion migration pathways, resulting in weak current channels within the coating. This can compromise the coating's insulation, especially under conditions of high humidity, high temperature, or chemical corrosion. Adding silicon, however, forms a stable three-dimensional network with oxygen, restricting free electron migration, reducing charge carriers and conductive pathways, and lowering the coating's porosity. This prevents the accumulation of moisture and ions, enhancing the coating's electrical insulation properties. Furthermore, silicon's high-temperature stability and chemical inertness improve the coating's durability and reliability.

[0024] Furthermore, in the silicon steel sheet of the present invention, the insulation resistance of the coating is >3 Ω·cm. 2 / piece.

[0025] Furthermore, in the silicon steel sheet of the present invention, the single-sided thickness of the coating is 1.0 g / m. 2 ~2.5g / m 2 .

[0026] Another object of the present invention is to provide a method for manufacturing a silicon steel plate, which can obtain a silicon steel plate with excellent moisture resistance and excellent insulation properties, and can meet the higher requirements of modern high-efficiency motors and power equipment for material reliability and durability.

[0027] To achieve the above objectives, the present invention provides a method for manufacturing silicon steel sheets, comprising the following steps:

[0028] Obtain silicon steel substrate;

[0029] A coating is applied to the surface of a silicon steel substrate, and the ambient dew point during coating is controlled to be ≥35℃; the effective components of the coating include: metal phosphates, organic resins, and silicon-containing additives.

[0030] High-temperature baking is used to form the coating on the silicon steel substrate.

[0031] Dew point reflects the condensation temperature of water vapor in the air and is usually closely related to ambient humidity. Phosphate compounds exhibit strong hydrolytic activity in the presence of water. A higher dew point means a higher partial pressure of water vapor in the air, increasing the ability of moisture to penetrate the coating. During the coating's curing process, moisture penetration may exacerbate the hydrolysis of phosphates, leading to the decomposition and dissolution of phosphates on the surface. The released phosphorus may further penetrate into the deeper layers of the coating or volatilize into the air, resulting in a significant reduction in the surface phosphorus content and a lower phosphorus ratio. Therefore, this invention controls the ambient dew point during coating application to be above 35°C.

[0032] Furthermore, in the manufacturing method described in this invention, the mass fraction of the effective component of the coating is:

[0033] Organic resin: 10-35 parts;

[0034] Metal phosphates: 50-80 parts;

[0035] Silicone additives: 3-15 parts.

[0036] Furthermore, in the manufacturing method described in this invention, the metal phosphate comprises one or more of zinc phosphate, cobalt phosphate, magnesium phosphate, aluminum phosphate, and calcium phosphate.

[0037] Furthermore, in the manufacturing method described in this invention, the organic resin includes one or more of acrylic resin, styrene resin, epoxy resin, polyester resin, phenolic resin, and polyurethane.

[0038] Furthermore, in the manufacturing method described in this invention, the silicon-containing additive includes one or more of nano-silicon, silicon oxide, silicates, and organosilanes.

[0039] Furthermore, in the manufacturing method described in this invention, the solid content of the coating is 35%-50%.

[0040] Compared with the prior art, the silicon steel sheet with excellent moisture resistance and its manufacturing method described in this invention have the following beneficial effects:

[0041] The silicon steel sheet with excellent moisture resistance described in this invention can effectively prevent the coating from absorbing moisture and swelling in a high-humidity environment by controlling the content and distribution of phosphate in the coating, avoiding problems such as coating whitening, powdering and decreased adhesion, significantly improving moisture resistance and ensuring long-term stable storage of silicon steel sheets.

[0042] The silicon steel sheet with excellent moisture resistance described in this invention greatly improves the adhesion and corrosion resistance of the coating through the synergistic effect of phosphate and organic resin. This makes the silicon steel less prone to coating peeling and corrosion during long-term use, thus enhancing corrosion resistance and extending the service life of core components of power equipment.

[0043] The silicon steel sheet with excellent moisture resistance described in this invention improves the coating structure by adding silicon-based additives, significantly enhancing the electrical insulation performance of the coating and ensuring the safety of equipment such as motors and transformers. Attached Figure Description

[0044] Figure 1 The result diagram of XPS depth sputtering of P element corresponding to Embodiment 9 of the present invention is shown.

[0045] Figure 2 The surface morphology of the scanning electron microscope corresponding to Example 4 is shown. Detailed Implementation

[0046] The following will further explain and illustrate the silicon steel plate with excellent moisture resistance and its manufacturing method according to the present invention with reference to specific embodiments. However, such explanation and illustration do not constitute an improper limitation on the technical solution of the present invention.

[0047] Examples 1-9 and Comparative Examples 1-13

[0048] To implement this invention, the coating to be used in this invention is first prepared. The effective components of the coating include: metal phosphates, organic resins, and silicon-containing additives.

[0049] In some specific embodiments, the effective components of the coating are in the following proportions by mass: organic resin: 10-35 parts; metal phosphate: 50-80 parts; silicone additives: 3-15 parts.

[0050] In some more specific embodiments, the metal phosphate may comprise one or more of zinc phosphate, cobalt phosphate, magnesium phosphate, aluminum phosphate, and calcium phosphate.

[0051] In some more specific embodiments, the organic resin may include one or more of acrylic resin, styrene resin, epoxy resin, polyester resin, phenolic resin, and polyurethane.

[0052] In some more specific embodiments, the silicon-containing additive may include one or more of nano-silicon, silicon oxide, silicates, and organosilanes.

[0053] In some specific implementations, water is used to adjust the solid content of the coating to 35%-50%.

[0054] Based on the above coating, silicon steel plates of Examples 1-9 and comparative steel plates of Examples 1-13 of the present invention were prepared:

[0055] (1) Obtaining a silicon steel substrate;

[0056] (2) Coating the surface of the silicon steel substrate with a coating, and controlling the ambient dew point during coating to be above 35°C.

[0057] (3) High-temperature baking to form a coating on the silicon steel substrate.

[0058] In some specific implementations, the temperature range for high-temperature baking can be controlled to be 180-350℃, and the baking time can be 1-6 minutes.

[0059] In some specific embodiments, the coating thickness on one side is 1.0 g / m. 2 ~2.5g / m 2 .

[0060] Table 1 lists the effective components of the coatings in Examples 1-9 of the present invention and the effective components of the comparative coatings in Comparative Examples 1-13.

[0061] Table 1.

[0062]

[0063]

[0064] Table 2 lists the environmental dew point and coating thickness after curing of the silicon steel plates of Examples 1-9 and Comparative Examples 1-13 when coated with the coating.

[0065] Table 2.

[0066]

[0067]

[0068] The silicon steel plates of Examples 1-9 and the comparative plates of Comparative Examples 1-13 were sampled and subjected to various tests. The test results are listed in Table 4. Wherein:

[0069] P content ratio detection: X-ray photoelectron spectroscopy (XPS) was used to perform depth testing according to GB / T 24167-2009 "X-ray Photoelectron Spectroscopy (XPS) Analysis Method" (steel plate size 10×20mm). The sample surface was bombarded with an ion beam, and depth analysis was performed simultaneously with ion sputtering. The signal intensity of each element was converted into the corresponding area, and the ratio of the area of ​​surface P element to the area of ​​the bottom layer P element in the coating was used as the P ratio in this invention.

[0070] Si element content test: The Si element content in the coating was measured by scanning electron microscopy. The coated steel plate was cut into 20×20mm pieces and scanned using an accelerating voltage of 10kV to 30kV. The test was conducted in accordance with GB / T15062-2006 "Electron Probe X-ray Analysis Method".

[0071] Insulation resistance test: The insulation resistance of the coating is tested according to the method in GB / T 2522—2017 "Test method for insulation resistance and adhesion of coating on electrical steel sheets (strips)".

[0072] Moisture absorption resistance test: The moisture absorption resistance of the coating is evaluated using the boiling water vapor exposure test method through the following steps. Wherein:

[0073] (1) Cut the sample to a size of 100×100mm. The sample surface must be free of dirt or scratches.

[0074] (2) Boiling water preparation: Put 300mL of pure water into a 300mL beaker, place it in a heater, and add boiling stones.

[0075] (3) Expose the sample to water vapor. After the water boils, place the sample in the center of the beaker and keep it for 30 minutes. Do not move the sample during this period.

[0076] (4) Drying: Remove the sample from the beaker and dry it with a desiccator. Tweezers can be used to prevent burns.

[0077] (5) Visually assess the changes in appearance of the exposed surface of the sample.

[0078] The criteria for judging the moisture absorption resistance test are as follows:

[0079] A: The exposed portion of the water vapor remained unchanged.

[0080] B: Changes occur within 1 / 4 of the beaker's circumference.

[0081] C: Changes occur when the circle exceeds 1 / 4 of its circumference but is less than 1 / 2.

[0082] D: Changes occur when the circle exceeds 1 / 2 to 3 / 4 of its circumference.

[0083] E: More than 3 / 4 changed.

[0084] Table 4 lists the test results of the silicon steel plates of Examples 1-9 and the comparative plates of Comparative Examples 1-13 of the present invention.

[0085] Table 4.

[0086]

[0087]

[0088] As shown in Table 4, the ratio of P content on the coating interface side to P content on the coating substrate side of the silicon steel plates in Examples 1-9 of the present invention is less than 0.4, the mass percentage of Si element is between 1-10%, and the insulation resistance of the coating is greater than 3 Ω·cm. 2 / piece, therefore it has both good insulation and moisture resistance.

[0089] also, Figure 1 The results of XPS depth sputtering of P element corresponding to Embodiment 9 of the present invention are also shown.

[0090] like Figure 1 As shown, the characteristic peak of P element is around 132 eV. The figure shows the distribution of P element from the coating interface side to the coating substrate side. It can be seen from the figure that the P element content is the lowest at the interface side and gradually increases towards the bottom layer. The P ratio can be calculated to be 0.11 using XPS analysis software.

[0091] Figure 2 The surface morphology of the scanning electron microscope corresponding to Example 4 is shown.

[0092] from Figure 2 As can be seen, the coating surface of Example 4 shows uniform coating and no surface defects.

[0093] It should be noted that the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0094] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A silicon steel sheet with excellent moisture resistance, comprising a silicon steel substrate and a coating applied to the surface of the silicon steel substrate; characterized in that: The phosphorus (P) content in the coating gradually increases from the coating interface side in contact with air to the coating substrate side in contact with the silicon steel substrate, and 0 < the ratio of P content on the coating interface side to P content on the coating substrate side ≤ 0.

4.

2. The silicon steel sheet as described in claim 1, characterized in that, The coating contains Si element with a mass percentage of ≥1%.

3. The silicon steel plate as described in claim 2, characterized in that, The coating contains 1-10% Si by mass.

4. The silicon steel sheet as described in claim 1, characterized in that, The insulation resistance of the coating is >3Ω·cm 2 / piece.

5. The silicon steel sheet as described in claim 1, characterized in that, The coating has a single-sided thickness of 1.0 g / m. 2 ~2.5g / m 2 .

6. The method for manufacturing silicon steel sheet according to any one of claims 1-5, characterized in that, Including the following steps: Obtain silicon steel substrate; A coating is applied to the surface of a silicon steel substrate, and the ambient dew point during coating is controlled to be ≥35℃; the effective components of the coating include: metal phosphates, organic resins, and silicon-containing additives. High-temperature baking is used to form the coating on the silicon steel substrate.

7. The method for manufacturing silicon steel sheet as described in claim 6, characterized in that, The mass fraction of the effective component in the coating is: Organic resin: 10-35 parts; Metal phosphates: 50-80 parts; Silicone additives: 3-15 parts.

8. The method for manufacturing silicon steel sheet as described in claim 6, characterized in that, The metal phosphate includes one or more of zinc phosphate, cobalt phosphate, magnesium phosphate, aluminum phosphate, and calcium phosphate.

9. The method for manufacturing silicon steel sheet as described in claim 6, characterized in that, The organic resin includes one or more of acrylic resin, styrene resin, epoxy resin, polyester resin, phenolic resin, and polyurethane.

10. The method for manufacturing silicon steel sheet as described in claim 6, characterized in that, The silicon-containing additives include one or more of nano-silicon, silicon oxide, silicates, and organosilanes.

11. The method for manufacturing silicon steel sheet as described in claim 6, characterized in that, The solid content of the coating is 35%-50%.

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