Anti-oxidation coating and preparation method thereof, coating and oriented silicon steel billet

Abstract

The invention discloses an anti-oxidation coating and a preparation method thereof, a coating and an oriented silicon steel billet, the anti-oxidation coating comprises alumina slurry and powder, and the mass ratio of the alumina slurry to the powder is 0.2: 1-0.6: 1; the powder material comprises the following raw material components in parts by weight: 60-85 parts of magnesium oxide, 10-30 parts of zirconium oxide and 5-10 parts of barium sulfate. A coating prepared from the anti-oxidation coating can effectively reduce the thickness of a decarburized layer of oriented silicon steel and the yield of oxidized scale, and the product quality of the oriented silicon steel is improved.

Description

Technical Field

[0001] The present application belongs to the technical field of high-temperature resistant coatings for oriented silicon steel, and in particular relates to an anti-oxidation coating and a preparation method thereof, a coating and an oriented silicon steel billet. Background Art

[0002] As an important soft magnetic material, oriented silicon steel is widely used in transformers, mutual inductors and other fields. The heating temperature of medium-temperature and high-temperature oriented silicon steel slabs is generally above 1300°C. However, the long-term high-temperature heating process will lead to serious high-temperature oxidation, burning and decarburization on the slab surface, which will not only cause a large amount of metal material loss, but also the iron oxide scale formed on the slab surface will significantly deteriorate the surface quality and plate shape control accuracy of the subsequent hot rolling process, and increase surface defects and plate shape problems during the rolling process. What is more serious is that the high-temperature oxidation process is usually accompanied by significant surface decarburization. High-temperature decarburization will lead to a significant reduction in the carbon content on the surface of the oriented silicon steel slab, forming a surface decarburization layer, which reduces the strength, hardness and plastic toughness of the surface metal of the slab. Summary of the Invention

[0003] The embodiments of the present application provide an anti-oxidation coating, a preparation method thereof, a coating and an oriented silicon steel billet. The coating prepared by the anti-oxidation coating can effectively reduce the thickness of the decarburization layer of oriented silicon steel and the output of iron oxide scale, thereby improving the product quality of oriented silicon steel.

[0004] In a first aspect, an anti-oxidation coating is provided, which includes alumina slurry and powder, the mass ratio of alumina slurry to powder being 0.2:1-0.6:1; the powder includes the following raw material components in parts by weight: magnesium oxide: 60-85 parts, zirconium oxide: 10-30 parts, and barium sulfate: 5-10 parts.

[0005] The inventors have discovered that the coating prepared from the anti-oxidation coating of the present application can effectively isolate the oxidizing atmosphere from oxidation of the steel billet surface during the high-temperature heating process of grain-oriented silicon steel, thereby reducing decarburization and oxidative burning on the steel surface. Furthermore, the magnesium oxide and aluminum oxide in the anti-oxidation coating have the characteristic of undergoing a spinel reaction and expanding at high temperatures. The expansion of the coating matches the expansion of the steel billet, which can effectively reduce problems such as cracking of the coating during high-temperature heating, improve hot rolling processability, and thus enhance magnetic properties. Furthermore, the coating has good non-wettability and corrosion resistance to slag, which can reduce the generation of iron oxide scale, reduce steel loss, and improve the yield rate.

[0006] In some specific embodiments, the solid phase in the alumina slurry is boehmite, and the mass percentage of boehmite in the alumina slurry is 4-6 wt %.

[0007] In the above embodiment, boehmite is dehydrated and converted into activated alumina (γ-Al2O3), which reacts with magnesium oxide to form spinel (MgAl2O4). This reaction is accompanied by a volume expansion of approximately 5-8%, which matches the thermal expansion coefficient of grain-oriented silicon steel and prevents cracking of the coating at high temperatures.

[0008] Furthermore, the γ-Al2O3 generated by boehmite at low temperatures preferentially absorbs O2 in the furnace atmosphere, reducing the oxidation of carbon on the silicon steel surface (C+O2→CO2). Furthermore, the densification of the spinel phase effectively blocks the inward diffusion of oxygen, reducing surface oxidation of the oriented silicon steel and thus reducing the thickness of the decarburized layer.

[0009] In some specific embodiments, the boehmite includes plate-shaped boehmite, and the plate-shaped boehmite has a particle size of 0.1-3 μm.

[0010] In the above specific embodiment, the alumina slurry uses boehmite (γ-AlOOH) as raw material, and its morphology is a flaky structure. When the particle size is controlled at 0.1-3 μm, it is beneficial to improve the stability of the slurry and the density of the coating, and at the same time will not have a negative impact on the performance and surface quality of oriented silicon steel.

[0011] In some specific embodiments, the powder may further include 0-2 parts of yttrium oxide; and / or the anti-oxidation coating may further include 0-1 parts of sodium carboxymethyl cellulose.

[0012] In the above-mentioned specific embodiment, a small amount of yttrium oxide stabilizes the zirconia crystal form, improving the high-temperature performance of the zirconia and further enhancing the high-temperature stability and thermal shock resistance of the coating. Sodium carboxymethyl cellulose (CMC) improves the adhesion and suspension properties of the anti-oxidation coating, facilitating application. It also provides a certain strength during the drying process, preventing the coating from shedding. CMC decomposes and volatilizes at high temperatures and does not affect the high-temperature performance of the coating.

[0013] In a second aspect, a method for preparing the anti-oxidation coating of the first aspect comprises: dispersing alumina in a solvent to obtain alumina slurry; mixing and dispersing magnesium oxide, zirconium oxide and barium sulfate to obtain a powder; adding the powder to the alumina slurry at a mass ratio of alumina slurry to powder of 0.2:1-0.6:1, and stirring and mixing to obtain the anti-oxidation coating.

[0014] In some specific embodiments, the step of dispersing alumina in a solvent to obtain an alumina slurry includes: mixing alumina with deionized water and then adding a dispersant for pre-dispersion to obtain a pre-dispersion liquid; ball-milling the pre-dispersion liquid to obtain a first slurry, wherein the viscosity of the first slurry at 25°C is 50-200mPa·s, optionally, the ball-to-material ratio of the ball milling treatment is 2.5:1-3.5:1, and the ball milling treatment time is 4-6h; adjusting the pH of the first slurry to a first value to enhance the electrostatic stabilization of the alumina particles and reduce sedimentation, filtering to obtain the alumina slurry, optionally, the first value is 8-9.

[0015] In the above specific embodiment, when the viscosity of the first slurry at 25° C. is 50-200 mPa·s, the spraying uniformity and stability of the anti-oxidation coating can be effectively improved.

[0016] In some specific embodiments, the step of mixing and dispersing magnesium oxide, zirconium oxide and barium sulfate to obtain a powder includes: mixing and dispersing magnesium oxide, zirconium oxide, barium sulfate and yttrium oxide to obtain a powder; and / or, the step of adding the powder to alumina slurry at a mass ratio of alumina slurry to powder of 0.2:1-0.6:1, and stirring to obtain an anti-oxidation coating includes: adding the powder to alumina slurry at a mass ratio of alumina slurry to powder of 0.2:1-0.6:1, mixing, adding sodium carboxymethyl cellulose, and stirring until the sodium carboxymethyl cellulose is dissolved to obtain an anti-oxidation coating.

[0017] In a third aspect, a coating for oriented silicon steel is provided, wherein the coating is prepared by the anti-oxidation coating of the first aspect and / or the anti-oxidation coating prepared by the preparation method of the second aspect. Optionally, the coating has a thickness of 0.5-2 mm.

[0018] In a fourth aspect, a oriented silicon steel billet comprises a coating provided on the surface of a steel slab, wherein the coating is a coating formed by the anti-oxidation coating of the first aspect and / or a coating formed by the anti-oxidation coating prepared by the preparation method of the second aspect and / or a coating of the third aspect, and the oriented silicon steel billet is processed to obtain oriented silicon steel.

[0019] In some specific embodiments, the oriented silicon steel satisfies at least one of the following conditions: (1) the decarburized layer thickness of the oriented silicon steel is ≤30 μm; (2) the amount of iron oxide scale of the oriented silicon steel is ≤60 g / m 2 ; (3) The edge cracking rate of the oriented silicon steel is ≤0.5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 This is a metallographic structure diagram of one location of the grain-oriented silicon steel in Example 1 of the present application.

[0022] Figure 2 This is another metallographic structure diagram of the oriented silicon steel in Example 1 of the present application.

[0023] Figure 3 This is a metallographic structure diagram of a portion of the oriented silicon steel without coating in the present application.

[0024] Figure 4 This is another metallographic structure diagram of the non-coated oriented silicon steel of the present application. DETAILED DESCRIPTION

[0025] In order to make the invention purpose, technical solution and beneficial technical effect of this application clearer, this application is further described in detail with reference to the following embodiments. It should be understood that the embodiments described in this specification are only for explaining this application and are not intended to limit this application.

[0026] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and similarly, any upper limit can be combined with any other upper limit to form an unspecified range. In addition, although not explicitly stated, each point or individual value between the endpoints of a range is included in the range. Thus, each point or individual value can serve as its own lower limit or upper limit and be combined with any other point or individual value, or with other lower limits or upper limits, to form an unspecified range.

[0027] In the description herein, when a composition is described as containing, comprising or including specific components, or when a process is described as containing, comprising or including specific process steps, it is intended that the composition of the present application also consists essentially of or consists of the components, and the process of the present application also consists essentially of or consists of the process steps.

[0028] The use of the terms "including," "comprising," "containing," and "having" should generally be construed as open ended and non-limiting unless expressly stated otherwise.

[0029] In the description of this article, it should be noted that, unless otherwise specified, “above” and “below” are inclusive of the number themselves, and “a variety” in “one or more” means more than two.

[0030] The above summary of the invention of this application is not intended to describe every disclosed embodiment or every implementation in this application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided by a series of examples, which can be used in various combinations. In each example, the enumeration is intended only as a representative group and should not be construed as exhaustive.

[0031] As an important soft magnetic material, oriented silicon steel is widely used in transformers, mutual inductors and other fields. In the production process of oriented silicon steel, slab heating is a key process. According to the different heating temperatures before hot rolling, oriented silicon steel is divided into low-temperature, medium-temperature and high-temperature oriented silicon steel. The slab heating temperature of medium-temperature and high-temperature oriented silicon steel is generally above 1300℃ to ensure the full solid solution of inhibitors and the full growth of equiaxed crystals, laying the foundation for the magnetic properties of the final product. However, the long-term high-temperature heating process inevitably causes the surface of the oriented silicon steel slab to undergo complex physical and chemical reactions with the atmosphere in the furnace, resulting in serious high-temperature oxidation, burning and decarburization on the slab surface. This will not only cause a large amount of metal material loss, directly reduce the yield rate and production efficiency of oriented silicon steel, and seriously affect the economic benefits of the production enterprise, but also the iron oxide scale formed on the slab surface will significantly deteriorate the surface quality and plate shape control accuracy of the subsequent hot rolling process, and increase surface defects and plate shape problems during the rolling process. What is more serious is that the high-temperature oxidation process is usually accompanied by significant surface decarburization. High-temperature decarburization will lead to a significant decrease in the carbon content on the surface of the oriented silicon steel slab, forming a surface decarburization layer, which reduces the strength, hardness and plastic toughness of the surface metal of the slab, and thus causes the mechanical properties of the edge area of ​​the slab to deteriorate. It is very easy to produce a series of serious quality defects such as edge cracks, tears and even broken strips during the subsequent hot rolling deformation process, which ultimately seriously restricts the large-scale production efficiency of oriented silicon steel materials and the further improvement of the performance of the finished products.

[0032] Based on the above problems, the present application provides an anti-oxidation coating, a preparation method thereof, a coating and oriented silicon steel. The coating prepared by the anti-oxidation coating can effectively reduce the thickness of the decarburization layer of oriented silicon steel and the output of iron oxide scale, thereby improving the product quality of oriented silicon steel.

[0033] The anti-oxidation coating of the present application is first introduced below.

[0034] Anti-oxidation coating

[0035] An anti-oxidation coating comprises aluminum oxide slurry and powder, wherein the mass ratio of the aluminum oxide slurry to the powder is 0.2:1-0.6:1; the powder comprises the following raw material components in parts by weight: 60-85 parts of magnesium oxide, 10-30 parts of zirconium oxide, and 5-10 parts of barium sulfate.

[0036] As an example, the mass ratio of alumina slurry to powder can be 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1 or a range consisting of any two values ​​therein. For example, the anti-oxidation coating can include 20-60 parts by mass of alumina slurry and 100 parts by mass of powder.

[0037] The inventors have discovered that the coating prepared using the anti-oxidation coating of the present application can effectively isolate the surface of the steel billet from oxidation by the oxidizing atmosphere during the high-temperature heating process of grain-oriented silicon steel, thereby reducing surface decarburization and oxidative burns. Furthermore, the magnesium oxide and aluminum oxide in the anti-oxidation coating have the characteristic of undergoing a spinel reaction and expanding at high temperatures. The expansion of the coating matches the expansion of the steel billet, which can effectively reduce problems such as cracking of the coating during high-temperature heating, improve hot rolling processability, and thus enhance magnetic properties. Furthermore, the coating has good non-wettability and corrosion resistance to slag, which can reduce the generation of iron oxide scale, reduce steel loss, and improve the yield rate.

[0038] In this application's anti-oxidation coating, the aluminum oxide slurry reacts with magnesium oxide during the steel billet heating process (>1000°C) to form spinel (MgAl2O4). This reaction is accompanied by approximately 5% volume expansion, matching the thermal expansion coefficient of grain-oriented silicon steel and preventing cracking of the coating at high temperatures. The densification of the spinel phase effectively blocks oxygen diffusion, reducing surface oxidation of the grain-oriented silicon steel and ultimately reducing the thickness of the decarburized layer (<30μm).

[0039] Magnesium oxide (MgO): A primary component of anti-oxidation coatings, it participates in a high-temperature spinel reaction with aluminum oxide. Magnesium oxide and aluminum oxide begin to react above 1000°C, forming spinel (MgAl2O4) with accompanying volume expansion. This expansion matches the expansion of the steel billet at high temperatures, effectively alleviating thermal stress between the coating and the billet and preventing cracking. Furthermore, magnesium oxide itself exhibits a certain degree of resistance to high temperatures and slag corrosion.

[0040] Zirconia (ZrO2): An optional ingredient, it further enhances the coating's high-temperature stability, thermal shock resistance, and slag erosion resistance. Zirconia has a high melting point and chemical stability, enhancing the coating's serviceability in extreme high-temperature environments. The preferred addition level is 10-30 parts per million. A lower level will have little effect, while a higher level may affect the spinel reaction and increase costs.

[0041] Barium sulfate (BaSO4): Added as a sintering aid and binder, it decomposes during heating, promoting the sintering of ceramic powders such as magnesium oxide and aluminum oxide, and improving the density and strength of the coating. The addition of barium sulfate should be controlled at 5-10 parts per million. A lower concentration will result in poor sintering, while a higher concentration may cause pores or cracks in the coating. BaSO4 also decomposes at 800-1000°C to form BaO, which forms a eutectic liquid phase with SiO2, promoting low-temperature sintering of the spinel phase. This allows the coating to densify before 1300°C, establishing an oxidation barrier in advance.

[0042] In some embodiments, the solid phase in the alumina slurry is boehmite, and the mass percentage of boehmite in the alumina slurry is 4-6wt%. For example, the mass percentage of boehmite in the alumina slurry can be 4wt%, 4.2wt%, 4.5wt%, 4.8wt%, 5wt%, 5.2wt%, 5.5wt%, 5.8wt%, 6wt% or a range consisting of any two of these values.

[0043] In the above-described embodiment, the γ-Al2O3 generated by boehmite dehydration is highly active and rapidly reacts with MgO at 1000-1200°C to form spinel (MgAl2O4), prematurely forming a dense protective layer and reducing oxidation burns during the initial heating period (<1300°C). Conventional alumina, however, requires higher temperatures (>1500°C), resulting in delayed coating protection during the critical heating period (1200-1400°C) of the oriented silicon steel slab, and increased scale formation. The volume expansion (5-8%) during boehmite dehydration and spinelization synchronizes with the thermal expansion of the silicon steel, preventing cracking of the coating at high temperatures. This allows the coating to remain intact and free of flaking throughout the entire heating cycle. Conventional alumina, however, exhibits poor compatibility with silicon steel in terms of expansion behavior, making it susceptible to cracking at high temperatures due to stress concentration, resulting in poor anti-oxidation effectiveness. Furthermore, the γ-Al2O3 generated by boehmite at low temperatures preferentially adsorbs O2 in the furnace atmosphere, reducing the oxidation of carbon on the silicon steel surface (C + O2 → CO2). The decarburized layer thickness is less than 30μm (up to 120μm for uncoated slabs), improving hot rolling workability. However, ordinary alumina has insufficient reactivity and the decarburized layer thickness is greater than 80μm, which can easily cause defects such as edge cracking and alloy element depletion.

[0044] In some embodiments, the boehmite includes plate-shaped boehmite, and the plate-shaped boehmite has a particle size of 0.1-3 μm.

[0045] For example, the particle size of the boehmite can be its equivalent diameter. For example, the particle size of the boehmite can be measured using a laser particle size analyzer and, based on physical properties such as scattered light energy distribution, can be expressed as the diameter of one or a group of homogeneous spheres with the most similar physical properties. The particle size of the boehmite can be 0.1 μm, 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, or a range consisting of any two of these values.

[0046] In the above embodiment, the alumina slurry uses boehmite (γ-AlOOH) as raw material, and its morphology is a flaky structure. When the particle size is controlled at 1-3 μm, it is beneficial to improve the stability of the slurry and the density of the coating, and at the same time will not have a negative impact on the performance and surface quality of oriented silicon steel.

[0047] In some embodiments, the powder may further include 0-2 parts of yttrium oxide. For example, the powder may include 0.01 parts of yttrium oxide, 0.1 parts of yttrium oxide, 0.3 parts of yttrium oxide, 0.5 parts of yttrium oxide, 0.7 parts of yttrium oxide, 1 part of yttrium oxide, 1.2 parts of yttrium oxide, 1.5 parts of yttrium oxide, 1.7 parts of yttrium oxide, 2 parts of yttrium oxide, or a range consisting of any two of these values.

[0048] In the above embodiment, a small amount of yttrium oxide (Y2O3) can stabilize the crystal form of zirconium oxide, improve the high-temperature performance of zirconium oxide, and further enhance the high-temperature stability and thermal shock resistance of the coating. Excessive addition may adversely affect other properties of the coating and increase costs.

[0049] In some embodiments, the anti-oxidation coating may further include 0-1 parts of sodium carboxymethyl cellulose (CMC). For example, the anti-oxidation coating may include 0.01 parts of CMC, 0.1 parts of CMC, 0.3 parts of CMC, 0.5 parts of CMC, 0.7 parts of CMC, 0.9 parts of CMC, 1 part of CMC, or a range consisting of any two of these values.

[0050] In the above examples, sodium carboxymethyl cellulose (CMC) improves the adhesion and suspension properties of the anti-oxidation coating, facilitating application. It also provides strength during the drying process, preventing the coating from shedding. CMC decomposes and volatilizes at high temperatures and does not affect the high-temperature performance of the coating. The amount of CMC added should be limited to 1 part.

[0051] Preparation method of anti-oxidation coating

[0052] A method for preparing the above-mentioned anti-oxidation coating includes: dispersing aluminum oxide in a solvent to obtain aluminum oxide slurry; mixing and dispersing magnesium oxide, zirconium oxide and barium sulfate to obtain powder; adding the powder to the aluminum oxide slurry at a mass ratio of aluminum oxide slurry to powder of 0.2:1-0.6:1, and stirring and mixing to obtain the anti-oxidation coating.

[0053] As an example, after the powder is added to the alumina slurry, during the stirring process, an appropriate amount of dispersant may be added as needed to improve the stability and fluidity of the slurry.

[0054] In another example, a powder raw material with higher purity and finer particle size can be selected to improve the performance and coating effect of the coating.

[0055] In some embodiments, the steps of dispersing alumina in a solvent to obtain an alumina slurry include: mixing alumina with deionized water and then adding a dispersant for pre-dispersion to obtain a pre-dispersion liquid; ball milling the pre-dispersion liquid to obtain a first slurry, wherein the viscosity of the first slurry at 25°C is 50-200mPa·s; adjusting the pH of the first slurry to a first value to enhance the electrostatic stabilization of the alumina particles and reduce sedimentation, and filtering to obtain the alumina slurry.

[0056] In the above embodiment, when the viscosity of the first slurry at 25° C. is 50-200 mPa·s, the spraying uniformity and stability of the anti-oxidation coating can be effectively improved.

[0057] In some embodiments, in the step of ball-milling the pre-dispersed liquid to obtain the first slurry, the ball-to-material ratio during ball milling is 2.5:1-3.5:1, and the ball milling time is 4-6 hours. Too short a ball milling time may result in uneven particle dispersion, while too long a ball milling time may affect the structure of the alumina (e.g., the flaky structure of boehmite).

[0058] In some embodiments, after adjusting the pH of the first slurry to a first value to enhance the electrostatic stabilization of the alumina particles and reduce sedimentation, in the step of filtering to obtain the alumina slurry, the first value is 8-9.

[0059] In some embodiments, the step of mixing and dispersing magnesium oxide, zirconium oxide, and barium sulfate to obtain a powder includes: mixing and dispersing magnesium oxide, zirconium oxide, barium sulfate, and yttrium oxide to obtain a powder.

[0060] In some embodiments, the powder is added to the alumina slurry at a mass ratio of 0.2:1-0.6:1 of the alumina slurry to the powder, and the step of stirring and mixing to obtain the anti-oxidation coating includes: adding the powder to the alumina slurry at a mass ratio of 0.2:1-0.6:1 of the alumina slurry to the powder, mixing, adding sodium carboxymethyl cellulose, and stirring until the sodium carboxymethyl cellulose is dissolved to obtain the anti-oxidation coating.

[0061] Coatings for grain-oriented silicon steel

[0062] A coating for oriented silicon steel is prepared by the above-mentioned anti-oxidation coating and / or by the anti-oxidation coating prepared by the above-mentioned preparation method.

[0063] In some embodiments, the coating has a thickness of 0.5-2 mm. For example, the coating may have a thickness of 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, or a range consisting of any two of these values.

[0064] Oriented silicon steel billet

[0065] An oriented silicon steel billet comprises a steel slab and a coating arranged on the surface of the steel slab, wherein the coating is a coating formed by the above-mentioned anti-oxidation coating and / or a coating formed by the anti-oxidation coating prepared by the above-mentioned preparation method and / or the above-mentioned coating. The oriented silicon steel billet is processed to obtain oriented silicon steel.

[0066] As an example, the oriented silicon steel billet may be processed to obtain the oriented silicon steel, which may include: feeding the oriented silicon steel billet into a heating furnace and keeping the temperature at 1300-1400° C. for 2-4 hours.

[0067] In some specific embodiments, the oriented silicon steel meets at least one of the following conditions: (1) the decarburized layer thickness of the oriented silicon steel is ≤30 μm; (2) the amount of iron oxide scale of the oriented silicon steel is ≤60 g / m 2 ; (3) The edge cracking rate of the oriented silicon steel is ≤0.5%.

[0068] Preparation method of oriented silicon steel billet

[0069] A method for preparing an oriented silicon steel billet comprises: providing a steel slab, wherein the temperature of the steel slab is ≥300°C; spraying an anti-oxidation coating onto the surface of the steel slab, drying the anti-oxidation coating to form a coating, and obtaining the oriented silicon steel billet.

[0070] Example

[0071] The following examples describe the present disclosure in more detail and are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further processing, and all instruments used in the examples are commercially available.

[0072] The steel slab used in this embodiment is a grain-oriented silicon steel slab.

[0073] Example 1

[0074] An anti-oxidation coating includes 40 parts of alumina slurry and 100 parts of powder, wherein the powder includes 75 parts of magnesium oxide (MgO), 20 parts of zirconium oxide (ZrO2), 5 parts of barium sulfate (BaSO4) and 0.5 parts of CMC; the alumina slurry includes 5wt% of boehmite, and the average particle size of the boehmite is 1μm.

[0075] The anti-oxidation coating is prepared by the following method:

[0076] Magnesium oxide, zirconium oxide, yttrium oxide and barium sulfate are mixed and ball-milled for 2 hours to obtain anti-oxidation coating powder.

[0077] Preparation of alumina slurry: 1) boehmite powder and deionized water are mixed in a mass ratio of 5:95, 0.2 parts (based on the mass of boehmite) of sodium polyacrylate dispersant is added, and the mixture is pre-dispersed in a high-speed stirrer (speed ≥ 1000 rpm) for 30 minutes to fully wet and preliminarily disperse the boehmite particles; 2) the pre-dispersed slurry is transferred to a ball mill, and zirconium oxide balls are used as grinding media (ball-to-material ratio 3:1), and ball milled for 4 hours to further refine and uniformly disperse the boehmite particles. The final viscosity of the slurry is controlled at 200 mPa·s (25°C); 3) the pH value of the slurry is adjusted to 8-9 using dilute nitric acid or ammonia water to enhance the electrostatic stabilization of the boehmite particles and prevent sedimentation; 4) the slurry is filtered through a 200-mesh sieve to remove undispersed agglomerated particles to obtain a uniform and stable alumina slurry.

[0078] 100 parts of the powder were added to 40 parts of the above alumina slurry and stirred rapidly to mix thoroughly. Finally, sodium carboxymethyl cellulose (CMC) was slowly added and stirred for 1 hour to form a uniform aqueous slurry to prepare an anti-oxidation coating ready for spraying.

[0079] On the basis of the above, a screw sprayer is used to spray the coating on the surface of the oriented silicon steel slab, and the coating thickness is controlled to be about 1.0 mm (slab temperature > 300°C). At the slab's own temperature, the anti-oxidation coating quickly forms an anti-oxidation coating to obtain a coated oriented silicon steel slab.

[0080] The coated oriented silicon steel billet and the uncoated slab were placed in a heating furnace at 1350℃ for 4 hours and then hot rolled. The oriented silicon steel samples after hot rolling were sampled for comparative experiments. Figures 1-4 As shown in the figure, the anti-oxidation coating forms a complete protective coating on the surface of the slab under the high temperature of the heating furnace, and after being removed from the furnace, the anti-oxidation coating is well separated from the slab surface and falls off through the descaling system, leaving no residue on the slab surface. At the same time, the amount of iron oxide scale generated on the surface of the slab coated with the anti-oxidation coating is significantly less than that of the uncoated slab, and the coating has a significant protective effect. Further metallographic examination of the decarburization layer on the surface of the oriented silicon steel shows that the protective effect of the anti-oxidation coating is good, and the thickness of the decarburization layer is very small ( Figure 1 and Figure 2 ), while the uncoated slab has a clear decarburized layer after rolling (such as Figure 3 and Figure 4 As shown, the decarburized layer appears obviously white at the interface area).

[0081] Example 2

[0082] The only difference between Example 2 and Example 1 is that the anti-oxidation coating contains 65 parts of magnesium oxide, 30 parts of zirconium oxide, 5 parts of barium sulfate, and 0.8 parts of CMC.

[0083] Example 3

[0084] The only difference between Example 3 and Example 1 is that the anti-oxidation coating contains 80 parts of magnesium oxide, 15 parts of zirconium oxide, 1 part of yttrium oxide, 4 parts of barium sulfate, and 0.6 parts of CMC.

[0085] Example 4

[0086] The only difference between Example 4 and Example 1 is that the anti-oxidation coating contains 70 parts of magnesium oxide, 25 parts of zirconium oxide, 2 parts of yttrium oxide, 3 parts of barium sulfate, and 0.9 parts of CMC.

[0087] Example 5

[0088] The only difference between Example 5 and Example 1 is that the anti-oxidation coating contains 85 parts of magnesium oxide, 10 parts of zirconium oxide, 5 parts of barium sulfate, and 0.7 parts of CMC.

[0089] Comparative Example 1

[0090] The only difference between Comparative Example 1 and Example 1 is that the alumina slurry is replaced by alumina powder.

[0091] Comparative Example 2

[0092] The only difference between Comparative Example 2 and Example 1 is that the morphology of the boehmite is adjusted to nanorods with a diameter of 20-50 nm and a length of 0.5-2 μm. During heating, the axial and radial directions expand unevenly, resulting in microcracks.

[0093] Comparative Example 3

[0094] The only difference between Comparative Example 3 and Example 1 is that the concentration of boehmite is adjusted to 2%. Due to the large spacing between boehmite particles, discontinuous necks are formed during high-temperature sintering, resulting in a porous structure and a large increase in iron oxide scale.

[0095] Comparative Example 4

[0096] The only difference between Comparative Example 4 and Example 1 is that the concentration of boehmite is adjusted to 10%. Since the boehmite particles are densely packed, the solvent evaporates and the stress is concentrated, causing microcracks.

[0097] The coated oriented silicon steel billets obtained in Examples 1-5 and Comparative Example 1 were processed into oriented silicon steels, and the effects of coating protection, scale, decarburization layer, coating peeling and shedding, as well as the iron loss P were evaluated. 17 / 50 And magnetic induction intensity B8 test, the results are shown in Table 1.

[0098] As can be seen from Table 1, the anti-oxidation coating of the present application exhibits good high-temperature oxidation resistance, thermal expansion matching and slag erosion resistance in the spraying and high-temperature performance tests.

[0099] Table 1 Performance results

[0100]

[0101] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present application, and such modifications or substitutions should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. An anti-oxidation coating, characterized in that: The anti-oxidation coating comprises aluminum oxide slurry and powder, and the mass ratio of the aluminum oxide slurry to the powder is 0.2:1-0.6:1; The powder comprises the following raw material components in parts by weight: Magnesium oxide: 60-85 parts, zirconium oxide: 10-30 parts, barium sulfate: 5-10 parts.

2. The anti-oxidation coating according to claim 1, characterized in that The solid phase in the alumina slurry is boehmite, and the mass percentage of the boehmite in the alumina slurry is 4-6 wt %.

3. The anti-oxidation coating according to claim 2, characterized in that: The boehmite includes flaky boehmite, and the particle size of the flaky boehmite is 0.1-3 μm.

4. The anti-oxidation coating according to claim 1, characterized in that: The powder further comprises 0-2 parts of yttrium oxide; And / or, the anti-oxidation coating further comprises 0-1 part of sodium carboxymethyl cellulose.

5. A method for preparing an anti-oxidation coating according to any one of claims 1 to 4, characterized in that: include: dispersing alumina in a solvent to obtain alumina slurry; Mixing and dispersing magnesium oxide, zirconium oxide and barium sulfate to obtain a powder; The powder is added to the alumina slurry at a mass ratio of the alumina slurry to the powder of 0.2:1-0.6:1, and the mixture is stirred and mixed to obtain the anti-oxidation coating.

6. The preparation method according to claim 5, characterized in that The step of dispersing aluminum oxide in a solvent to obtain an aluminum oxide slurry comprises: Aluminum oxide is mixed with deionized water and then a dispersant is added for pre-dispersion to obtain a pre-dispersion liquid; Ball milling the pre-dispersion liquid to obtain a first slurry, wherein the viscosity of the first slurry at 25° C. is 50-200 mPa·s, and optionally, the ball-to-material ratio of the ball milling treatment is 2.5:1-3.5:1, and the ball milling treatment time is 4-6 hours; After adjusting the pH of the first slurry to a first value, filtering to obtain the alumina slurry, the first value being 8-9.

7. The preparation method according to claim 5, characterized in that The step of mixing and dispersing magnesium oxide, zirconium oxide and barium sulfate to obtain a powder comprises: mixing and dispersing magnesium oxide, zirconium oxide, barium sulfate and yttrium oxide to obtain a powder; And / or, the powder is added to the alumina slurry in a mass ratio of the alumina slurry to the powder of 0.2:1-0.6:1, and the step of stirring and mixing to obtain the anti-oxidation coating includes: adding the powder to the alumina slurry in a mass ratio of the alumina slurry to the powder of 0.2:1-0.6:1, mixing, adding sodium carboxymethyl cellulose, and stirring until the sodium carboxymethyl cellulose is dissolved to obtain the anti-oxidation coating.

8. A coating for oriented silicon steel, characterized in that: The anti-oxidation coating is prepared by the anti-oxidation coating according to any one of claims 1 to 4 and / or prepared by the preparation method according to any one of claims 5 to 7. Optionally, the coating has a thickness of 0.5-2 mm.

9. An oriented silicon steel billet, characterized in that: The invention comprises a steel slab and a coating provided on the surface of the steel slab, wherein the coating is a coating formed by the anti-oxidation coating according to any one of claims 1 to 4 and / or a coating formed by the anti-oxidation coating prepared by the preparation method according to any one of claims 5 to 7 and / or the coating according to claim 8, and the steel slab is processed to obtain oriented silicon steel.

10. The oriented silicon steel billet according to claim 9, characterized in that: The oriented silicon steel satisfies at least one of the following: (1) The decarburized layer thickness of the oriented silicon steel is ≤30 μm; (2) The amount of iron oxide scale of the oriented silicon steel is ≤60g / m 2 ; (3) The edge crack generation rate of the oriented silicon steel is ≤0.5%.

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