Coating liquid for oriented silicon steel, oriented silicon steel plate and manufacturing method of oriented silicon steel plate

Abstract

The invention discloses a coating liquid for oriented silicon steel, the coating liquid contains first dihydric phosphate, second dihydric phosphate and colloidal silicon dioxide, the first dihydric phosphate is selected from at least one of dihydric phosphate of Al, Mg, Ca, Sr, Ba, Zn, Ni and Mn; the second dihydrogen phosphate comprises copper dihydrogen phosphate; the coating liquid does not contain Cr. The invention also discloses an oriented silicon steel plate which comprises a substrate and a coating, and the coating is formed by coating the substrate with the coating liquid. Correspondingly, the invention also discloses a manufacturing method of the oriented silicon steel plate, which comprises the following steps of: coating the coating liquid on the surface of the substrate, and sintering at the temperature of 800-900 DEG C. The coating of the oriented silicon steel plate has excellent tension, moisture absorption resistance, heat resistance, corrosion resistance and sheet sticking resistance.

Description

Technical Field

[0001] The present invention relates to a coating liquid, a steel plate and a manufacturing method thereof, and in particular to a coating liquid for oriented silicon steel, an oriented silicon steel plate and a manufacturing method thereof. Background Art

[0002] As we all know, oriented silicon steel refers to steel containing silicon and with easy magnetization axis (100) of the grains. <001> Electromagnetic steel sheet with basically the same rolling direction. Oriented silicon steel sheet is mainly used to manufacture transformer core. Its magnetic properties in the rolling direction are very excellent and it is an important soft magnetic material. When oriented silicon steel sheet is used as the material for manufacturing transformer core, it can effectively reduce the energy loss and noise level of the transformer.

[0003] Imparting high tension to oriented silicon steel through surface coating is an important technical means to improve the performance of oriented silicon steel. In the prior art, the surface coating of oriented silicon steel sheet is generally composed of a ceramic film mainly composed of forsterite (Mg2SiO4) and an insulating coating thereon, and the insulating coating can play the role of insulation, rust prevention and improvement of processing performance.

[0004] Under normal circumstances, the surface coating of oriented silicon steel is formed at high temperature. Due to its lower thermal expansion rate than the steel plate, when it drops to room temperature, the difference in thermal expansion rate between the steel plate and the coating will give tension to the steel plate. The tension given to the steel plate can reduce the loss of oriented silicon steel (reducing abnormal eddy current loss by narrowing the 180℃ magnetic domain width) and magnetostriction, thereby effectively reducing the energy loss and noise level of the transformer.

[0005] In recent years, in order to further improve the performance of oriented silicon steel, a large number of scientific and technological workers have made many beneficial attempts and designed many new surface coatings.

[0006] The Japanese patent document with the publication number of JP 48-39338, published on June 9, 1973, and entitled "Method for producing insulating film of oriented silicon steel sheet" discloses a coating liquid containing aluminum dihydrogen phosphate, colloidal silicon dioxide and chromic anhydride. The coating liquid is applied to the surface of oriented silicon steel, and MgO-P2O5-SiO2 and Al2O3-P2O5-SiO2 phosphate glass coating is formed on the surface of the steel sheet after heat treatment.

[0007] The Chinese patent document with publication number CN107923046A and publication date April 17, 2018, entitled "Insulation coating treatment liquid and method for manufacturing metal with insulation coating" discloses an insulation coating liquid containing at least one phosphate selected from Mg, Ca, Ba, Sr, Zn, Al and Mn and two or more colloidal silica with different average particle sizes, which optimizes and improves the tension of the insulation coating by using colloidal silica with different particle sizes. The above technical solution can improve the density of the coating to a certain extent by using mixed silica sols with different particle sizes, but the tension improvement space is limited.

[0008] The Chinese patent document with publication number CN104024474A and publication date September 3, 2014, entitled "Oriented electromagnetic steel sheet with coating and its manufacturing method" discloses an oriented silicon steel sheet, which is made into a coating containing elements of P, Si, Cr and O and at least one element selected from Mg, Al, Ni, Co, Mn, Zn, Fe, Ca and Ba, and more than 5% by mass is a crystalline phase of phosphate, thereby generating a higher tensile stress and reducing iron loss. The above technical solution increases the tension given to the steel sheet by the insulating coating by increasing the elastic modulus of the coating, but it needs to be achieved by increasing the amount of chromic anhydride added and increasing the sintering temperature of the coating. The range of the amount of chromic anhydride added in the phosphate coating is very narrow. When the chromic anhydride increases to a certain extent, the coating will crack and turbidity will occur; when the sintering temperature of the coating is higher than about 900°C, colloidal silica will produce crystallization. Although the formation of crystallinity in the coating can increase the tension, the corrosion resistance and transparency of the coating will decrease.

[0009] It can be seen that in the prior art, the performance of oriented silicon steel sheets given by phosphoric acid glass coating is still poor, and there are still problems of insufficient tension and low heat resistance. When the transformer core made of oriented silicon steel sheets is annealed to eliminate processing stress, the performance of the tension coating on the surface of oriented silicon steel will deteriorate, resulting in reduced tension, and it cannot effectively play the role of reducing transformer energy loss and noise level. Summary of the invention

[0010] One of the purposes of the present invention is to provide a coating liquid for oriented silicon steel, which is used for oriented silicon steel sheets to form a coating on their surface. The surface coating has good moisture absorption resistance, tension, corrosion resistance and anti-sticking properties, thereby further improving the magnetic properties of oriented silicon steel.

[0011] In order to achieve the above-mentioned object, the present invention proposes a coating liquid for oriented silicon steel, which contains a first dihydrogen phosphate, a second dihydrogen phosphate and colloidal silicon dioxide, wherein the first dihydrogen phosphate is selected from at least one of the dihydrogen phosphates of Al, Mg, Ca, Sr, Ba, Zn, Ni and Mn; the second dihydrogen phosphate includes the dihydrogen phosphate of Cu; and the coating liquid does not contain Cr.

[0012] Correspondingly, the present invention also provides a coating liquid for oriented silicon steel, whose effective ingredients consist of the following ingredients: a first dihydrogen phosphate, a second dihydrogen phosphate and colloidal silicon dioxide, wherein the first dihydrogen phosphate is selected from at least one of the dihydrogen phosphates of Al, Mg, Ca, Sr, Ba, Zn, Ni and Mn; and the second dihydrogen phosphate includes copper dihydrogen phosphate.

[0013] The solvent of the coating liquid described in the present invention is water. After being coated on the substrate of the oriented silicon steel plate, the above-mentioned coating liquid is subjected to heat treatment to form a coating, wherein the dihydrogen phosphate can form a phosphate coating with a mesh or chain structure on the surface of the steel plate after heat treatment. Colloidal silicon dioxide is used as a filler in the present invention to form a ceramic layer with a lower thermal expansion coefficient after heat treatment, thereby providing tension for the coating and facilitating the improvement of the coating's coating properties. During the heat treatment process, the dihydrogen copper phosphate is converted into the phosphate of Cu, which serves the purpose of fixing the phosphate radical and preventing the free phosphate radical from remaining in the coating, thereby improving the hygroscopicity resistance, tension, corrosion resistance and anti-sticking properties of the coating.

[0014] In the present invention, "colloidal silica" refers to a water dispersion system of nano-sized silica.

[0015] Furthermore, in the coating solution for oriented silicon steel of the present invention, the first dihydrogen phosphate is selected from at least one of dihydrogen phosphates of Al, Mg, Ca, Zn and Mn.

[0016] Furthermore, in the coating solution for oriented silicon steel of the present invention, the first dihydrogen phosphate includes at least one of magnesium dihydrogen phosphate, aluminum dihydrogen phosphate, calcium dihydrogen phosphate, zinc dihydrogen phosphate and manganese dihydrogen phosphate.

[0017] Furthermore, in the coating solution for oriented silicon steel of the present invention, the mass ratio of colloidal silicon dioxide to the total amount of the first dihydrogen phosphate and the second phosphate is 0.5-1.5.

[0018] Furthermore, in the coating solution for oriented silicon steel of the present invention, the mass ratio of colloidal silicon dioxide to the total amount of the first dihydrogen phosphate and the second phosphate is 0.8-1.2.

[0019] In this embodiment, controlling the mass ratio of colloidal silica to the total amount of the first dihydrogen phosphate and the second phosphate to be within the above range is beneficial to obtaining better coating performance.

[0020] Furthermore, in the coating solution for oriented silicon steel of the present invention, the mass ratio of copper dihydrogen phosphate to the total amount of the first dihydrogen phosphate and the second dihydrogen phosphate is 0.05-0.25.

[0021] Furthermore, in the coating solution for oriented silicon steel of the present invention, the mass ratio of copper dihydrogen phosphate to the total amount of the first dihydrogen phosphate and the second dihydrogen phosphate is 0.1-0.15.

[0022] In this embodiment, when the mass ratio of cupric phosphate to the total amount of the first dihydrogen phosphate and the second dihydrogen phosphate in the coating solution is above 0.05, the hygroscopic resistance of the coating can be significantly improved. However, when the mass ratio of cupric phosphate to the total amount of the first dihydrogen phosphate and the second dihydrogen phosphate is greater than 0.25, the tension of the coating will be reduced. Therefore, it is preferred to control the mass ratio within this range.

[0023] Furthermore, in the coating solution for oriented silicon steel coating of the present invention, the particle size of the colloidal silicon dioxide is 5-50 nm.

[0024] By adjusting the particle size of colloidal silica, it is beneficial to form a dense ceramic layer after heat treatment, and obtain better tension effect and coating surface morphology.

[0025] Another object of the present invention is to provide a oriented silicon steel sheet, which includes a substrate and a coating, wherein the coating is formed by coating the coating liquid as described above on the surface of the substrate, and the coating has a network or chain structure; the coating contains a first phosphate, a second phosphate and silicon dioxide, wherein the first phosphate is selected from at least one of the phosphates of Al, Mg, Ca, Sr, Ba, Zn, Ni and Mn; the second phosphate includes a phosphate of Cu; and the coating layer does not contain the Cr element.

[0026] The present invention has no particular limitation on the substrate of oriented silicon steel, and any oriented silicon steel substrate commonly used in the art may be used, for example, an oriented silicon steel substrate with a Si content of 2-4 wt %.

[0027] The present invention does not particularly limit the thickness of the substrate of oriented silicon steel. For example, a substrate with a thickness of 0.20-0.30 mm may be used.

[0028] Furthermore, in the oriented silicon steel sheet described in the present invention, the phosphate in the coating is converted from dihydrogen phosphate in the coating solution, so the first phosphate can be selected from at least one of the phosphates of Al, Mg, Ca, Zn and Mn.

[0029] Furthermore, in the oriented silicon steel sheet of the present invention, the first phosphate in the coating layer includes at least one of magnesium phosphate, aluminum phosphate, calcium phosphate, zinc phosphate and manganese phosphate.

[0030] Furthermore, in the oriented silicon steel sheet of the present invention, the mass percentage of the first phosphate and the second phosphate in the total mass of the coating is 34-73%.

[0031] Furthermore, in the oriented silicon steel sheet of the present invention, the mass percentage of Cu element in the total mass of the coating is 2-11%.

[0032] Further, in some embodiments, the substrate has a magnesium silicate base layer, and the coating is formed on the magnesium silicate base layer.

[0033] Furthermore, in the oriented silicon steel sheet of the present invention, the coating meets the following performance requirements: coating tension>6MPa; phosphorus dissolution content characterizing moisture absorption resistance<75μg / 150cm 2 .

[0034] Furthermore, in the oriented silicon steel sheet of the present invention, the single-sided dry film weight of the coating is 2-7 g / m 2 .

[0035] In this embodiment, if the single-sided dry film weight of the coating is less than 2 g / m 2 , the coating may not provide sufficient tension; if the single-sided dry film weight of the coating is higher than 7g / m 2 , the amount of coating is too much, making the coating thickness uneven after heat treatment, which can easily lead to a decrease in the lamination factor of the steel plate.

[0036] Accordingly, another object of the present invention is to provide a method for manufacturing the above-mentioned oriented silicon steel sheet, by which the above-mentioned oriented silicon steel sheet can be effectively manufactured.

[0037] In order to achieve the above object, the present invention proposes a method for manufacturing an oriented silicon steel sheet, which comprises the steps of: coating a coating liquid on the surface of a substrate, and then performing a sintering treatment, wherein the sheet temperature during the sintering treatment is 800-900°C.

[0038] In the manufacturing method of the oriented silicon steel sheet described in the present invention, the plate temperature during the sintering process is controlled between 800-900°C because: if the plate temperature during the sintering process is lower than 800°C, the steel plate is not flat enough and the tension effect of the coating on the steel plate is not significant; and if the plate temperature during the sintering process is higher than 900°C, the silicon dioxide in the coating is easy to crystallize, which will lead to a decrease in the density and tension effect of the coating.

[0039] Compared with the prior art, the coating liquid for oriented silicon steel, oriented silicon steel sheet and the manufacturing method thereof described in the present invention have the following advantages and beneficial effects:

[0040] The coating liquid of the present invention does not contain harmful metal element chromium, has little pollution to the surrounding environment, and has good environmental benefits;

[0041] The coating liquid of the present invention has good stability and coating properties and can be industrially produced and used.

[0042] The coating of the oriented silicon steel sheet of the present invention has good moisture absorption resistance, tension, corrosion resistance, heat resistance and anti-sticking properties, and can further improve the magnetic properties of the oriented silicon steel.

[0043] In some embodiments, the coating meets the following properties: surface tension>6MPa; phosphorus dissolution content characterizing moisture absorption resistance<75μg / 150cm 2 . DETAILED DESCRIPTION

[0044] The coating liquid for oriented silicon steel, the oriented silicon steel sheet and the manufacturing method thereof described in the present invention will be further explained and illustrated below in conjunction with specific embodiments. However, such explanation and illustration do not constitute an improper limitation on the technical solution of the present invention.

[0045] Examples 1-16 and Comparative Examples 1-3

[0046] The oriented silicon steel sheets of Examples 1-16 and Comparative Examples 1-3 were prepared by the following steps:

[0047] (1) Preparation of coating solutions. Table 1 lists the mass fractions and mass ratios of the components in the coating solutions used in Examples 1-16 and the comparative coating solutions used in Comparative Examples 1-3.

[0048] Table 1.

[0049]

[0050] Although not listed in the above embodiments 1-16, in other embodiments, the first dihydrogen phosphate may also be at least one of dihydrogen phosphates of Sr, Ba, Ni and Mn.

[0051] (2) Apply the coating liquid on the substrate of the oriented silicon steel sheet. The single-sided dry film weight of the coating can be 2-7g / m 2 In each embodiment and comparative example of the invention, the mass percentage of each chemical element in the substrate is the same, namely: C: 0.045%, Si: 3.32%, S: 0.006%, soluble Al: 0.028%, N: 0.006%, Mn: 0.015%, and the remainder is Fe and other inevitable impurities.

[0052] It should be noted that in the present invention, the substrate may or may not have a magnesium silicate primer layer.

[0053] (3) performing a sintering process, wherein the plate temperature during the sintering process is 800-900° C., and the sintering time can be more than 20 seconds.

[0054] Table 2 lists the contents of phosphate and Cu element in the coatings formed in Examples 1-16 and Comparative Examples 1-3.

[0055] Table 2.

[0056]

[0057] Table 3 lists the relevant process parameters of the oriented silicon steel sheets of Examples 1-16 and Comparative Examples 1-3 in the above manufacturing process.

[0058] Table 3.

[0059] Substrate thickness (mm) Sintering temperature(℃) Sintering time(s) <![CDATA[Single-sided dry film coating (g / m 2 )]]> Example 1 0.23 800 50 4.8 Example 2 0.23 850 30 4.5 Example 3 0.23 880 20 4.6 Example 4 0.23 850 30 4.5 Example 5 0.23 850 30 4.1 Example 6 0.23 800 30 7.0 Example 7 0.23 830 30 4.5 Example 8 0.23 850 30 4.8 Example 9 0.23 870 30 4.7 Example 10 0.23 880 30 4.3 Embodiment 11 0.23 900 30 4.0 Example 12 0.23 850 30 4.8 Example 13 0.23 850 30 4.5 Embodiment 14 0.20 850 30 5.8 Embodiment 15 0.27 850 30 5.2 Example 16 0.30 850 30 2.0 Comparative Example 1 0.23 850 30 4.9 Comparative Example 2 0.23 850 30 4.5 Comparative Example 3 0.23 850 30 4.6

[0060] The oriented silicon steel sheets of Examples 1-16 and Comparative Examples 1-3 were subjected to performance tests, including testing of coating tension, moisture absorption resistance, heat resistance, corrosion resistance, anti-sticking property, magnetic induction and iron loss, and the test results are listed in Table 4. The test methods are as follows:

[0061] (1) Coating tension σ: With the rolling direction as the length direction, the oriented silicon steel sheet was cut into a sample with a length of 300 mm and a width of 30 mm. The coating was then removed and the sample was bent to test its warpage. The coating tension σ was calculated using the following formula:

[0062]

[0063] In the above formula, σ represents the coating tension, and its unit can be MPa; E represents the Young's modulus of the steel plate, and its unit can be GPa; t represents the thickness of the steel plate, and its unit can be mm; H represents the warpage, and its unit can be mm; L represents the length of the steel plate, and its unit can be mm.

[0064] (2) Moisture absorption resistance: The oriented silicon steel sheet was boiled in pure water at 100°C, and then the phosphorus content dissolved in the coating per unit area was quantitatively analyzed in μg / 150cm 2 .

[0065] (3) Heat resistance: The tension deterioration and insulation deterioration of the surface coating of the oriented silicon steel sheet after stress relief annealing treatment were tested, wherein the process conditions of the stress relief annealing treatment were 850°C and 100% N2 atmosphere for 4 hours. The four levels of heat resistance evaluation are: "excellent" (tension and insulation reduction <20%), "good" (20%≤tension and insulation reduction <30%), "medium" (30%≤tension and insulation reduction <40%) and "poor" (tension and insulation reduction ≥40%).

[0066] (4) Corrosion resistance: The corrosion resistance of the coating was evaluated by a salt spray test. The salt spray test solution was a 5% NaCl solution, the test temperature was 35°C, and the test time was 10 hours. The four levels of corrosion resistance were: "excellent" (corrosion area <5%), "good" (5% ≤ corrosion area <10%), "medium" (10% ≤ corrosion area <30%), and "poor" (corrosion area ≥30%).

[0067] (5) Anti-sticking property: Stack the oriented silicon steel sheets of the same size together and apply 80kg / cm2 of pressure vertically to the stacked oriented silicon steel sheets. 2 The coating was then heat treated at 850℃ for 4h in N2 gas with a dew point of 10℃. The anti-sticking property of the coating was evaluated by testing the average value of the peeling force F between each oriented silicon steel sheet. The smaller the peeling force, the better the anti-sticking property. The four levels for evaluating the anti-sticking property are: "excellent" (F<100g / m 2 ), "good" (100≤F<250g / m 2 ), "Medium" (250≤F<500g / m 2 ) and "poor" (F ≥ 500g / m 2 ).

[0068] Table 4 lists the relevant performance test results of the oriented silicon steel sheets of Examples 1-16 and Comparative Examples 1-3.

[0069] Table 4.

[0070]

[0071]

[0072] It can be seen from Table 4 that the coatings of the oriented silicon steel sheets of Examples 1-16 of the present invention have good tension effects, the tension range is 6.2-8.3 MPa, and the phosphorus dissolution content characterizing the moisture absorption resistance is <75 μg / 150 cm 2 , and it also has excellent heat resistance, corrosion resistance and anti-sticking properties. Therefore, compared with comparative examples 1-3, the embodiments of the present invention have more excellent magnetic properties.

[0073] Since Comparative Example 1 does not use a coating solution containing copper dihydrogen phosphate, its tension, moisture absorption resistance, heat resistance, corrosion resistance and anti-sticking properties are all poor.

[0074] Comparative Example 2 and Comparative Example 3 both use a coating solution containing copper dihydrogen phosphate, so their tension and moisture absorption resistance are much better than that of Comparative Example 1.

[0075] However, the content of copper dihydrogen phosphate in Comparative Example 2 is lower than that in the preferred embodiment of the present invention, and the content of copper dihydrogen phosphate in Comparative Example 3 is higher than that in the preferred embodiment of the present invention, resulting in its tension, moisture absorption resistance, heat resistance, corrosion resistance and anti-sticking properties being inferior to those of Examples 1-16 of the present invention.

[0076] It should be noted that the combination of the various technical features in this case is not limited to the combination described in the claims of this case or the combination described in the specific embodiments. All technical features recorded in this case can be freely combined or combined in any way unless there is a contradiction between them.

[0077] It should also be noted that the above-listed embodiments are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made therewith can be directly derived or easily associated with the contents disclosed by those skilled in the art from the present invention, and all should belong to the protection scope of the present invention.

Claims

1. A coating solution for oriented silicon steel, characterized in that: It contains a first dihydrogen phosphate, a second dihydrogen phosphate and colloidal silicon dioxide, wherein the first dihydrogen phosphate is selected from at least one of dihydrogen phosphates of Al, Mg, Ca, Sr, Ba, Zn, Ni and Mn; the second dihydrogen phosphate includes copper dihydrogen phosphate; and the coating liquid does not contain Cr.

2. The coating solution for oriented silicon steel according to claim 1, characterized in that: Its effective components consist of the following components: a first dihydrogen phosphate, a second dihydrogen phosphate and colloidal silicon dioxide, wherein the first dihydrogen phosphate is selected from at least one of dihydrogen phosphates of Al, Mg, Ca, Sr, Ba, Zn, Ni and Mn; and the second dihydrogen phosphate includes copper dihydrogen phosphate.

3. The coating liquid for oriented silicon steel according to claim 1 or 2, characterized in that: The first dihydrogen phosphate is selected from at least one of dihydrogen phosphates of Al, Mg, Ca, Zn and Mn.

4. The coating liquid for oriented silicon steel according to claim 1 or 2, characterized in that: The first dihydrogen phosphate includes at least one of magnesium dihydrogen phosphate, aluminum dihydrogen phosphate, calcium dihydrogen phosphate, zinc dihydrogen phosphate and manganese dihydrogen phosphate.

5. The coating liquid for oriented silicon steel according to claim 1 or 2, characterized in that: The mass ratio of colloidal silicon dioxide to the total amount of the first dihydrogen phosphate and the second phosphate is 0.5-1.

5.

6. The coating liquid for oriented silicon steel according to claim 1 or 2, characterized in that: The mass ratio of copper dihydrogen phosphate to the total amount of the first dihydrogen phosphate and the second dihydrogen phosphate is 0.05-0.

25.

7. The coating liquid for oriented silicon steel coating according to claim 1 or 2, characterized in that: The particle size of the colloidal silicon dioxide is 5-50 nm.

8. A oriented silicon steel sheet, comprising a substrate and a coating, characterized in that: The coating is formed by coating the coating liquid as described in any one of claims 1 to 7 on the surface of the substrate, and the coating has a network or chain structure; the coating contains a first phosphate, a second phosphate and silicon dioxide, wherein the first phosphate is selected from at least one of the phosphates of Al, Mg, Ca, Sr, Ba, Zn, Ni and Mn; the second phosphate includes a phosphate of Cu; and the coating layer does not contain the Cr element.

9. The oriented silicon steel sheet according to claim 8, characterized in that: The mass percentage of the first phosphate and the second phosphate in the total mass of the coating is 34-73%.

10. The oriented silicon steel sheet according to claim 8, characterized in that: The mass percentage of Cu element in the total mass of the coating is 2-11%.

11. The oriented silicon steel sheet according to claim 8, characterized in that: The substrate has a magnesium silicate base layer, and the coating is formed on the magnesium silicate base layer.

12. The oriented silicon steel sheet according to claim 8, characterized in that: The coating meets the following performance requirements: coating tension>6MPa; phosphorus dissolution content indicating moisture absorption resistance<75μg / 150cm 2 .

13. The oriented silicon steel sheet according to claim 8, characterized in that: The single-sided dry film weight of the coating is 2-7 g / m 2 .

14. The method for manufacturing a grain-oriented silicon steel sheet according to any one of claims 8 to 13, characterized in that: The method comprises the following steps: coating the coating liquid on the surface of the substrate, and then performing sintering treatment, wherein the plate temperature during the sintering treatment is 800-900°C.

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