High-temperature-resistant metal casting demolding coating and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant metal casting demolding coating and a preparation method thereof, and belongs to the technical field of coatings. The components of the coating are optimized, the composite binder formed by compounding the organic binder and the inorganic binder is adopted, and the high-temperature-resistant auxiliary agent composed of the zirconite powder, the corundum powder and the nano cerium oxide is combined, so that the temperature tolerance of the coating is remarkably improved, and the service life of the coating is remarkably prolonged; the added hexagonal boron nitride can form a compact and smooth coating surface, the adhesion between a metal melt and a mold can be effectively reduced by combining the high-temperature-resistant auxiliary agents of different grades and utilizing the filling-supporting-lubricating synergistic effect and synergistic effect of particles of different sizes, and efficient and stable demolding performance is achieved; and the nano aluminum oxide can form chemical bonding with hexagonal boron nitride and the composite binder, so that the interface bonding force is further enhanced, the coating is prevented from being layered and peeled off under high-temperature impact, the thermal impact of molten metal on the mold is effectively buffered, and the service life of the mold is prolonged.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and more specifically, to a high-temperature resistant metal casting release coating and its preparation method. Background Technology

[0002] In metal casting processes (such as casting, forging, and die casting), the high-temperature molten metal comes into direct contact with the mold surface, easily leading to physical adhesion or chemical reactions. This results in decreased surface quality of the castings, shortened mold life, and reduced production efficiency. To address these issues, a release coating is typically applied to the mold surface to achieve physical-chemical isolation between the molten metal and the mold. However, during the pouring or filling of high-temperature molten metal, the molten metal readily undergoes physical-chemical reactions with the metal mold surface (such as wetting, corrosion, and alloying), causing severe sticking. This not only makes demolding difficult and reduces production efficiency but also easily damages the mold surface, shortens mold life, and causes quality defects such as black spots, cold shuts, and porosity on the casting surface, affecting the product's appearance and internal quality.

[0003] Currently, the industry commonly uses release coatings on mold surfaces. Commonly used release materials include graphite, silicone oil, and metal oxide coatings. However, the following technical problems remain: 1. Insufficient high-temperature resistance: Traditional organic release agents are prone to decomposition and failure at high temperatures (>800℃); while inorganic release agents have better temperature resistance, they usually require high-temperature sintering and curing, which can easily cause thermal damage to the mold, and their adhesion at room temperature is poor. 2. Poor release effect: High coating density can lead to difficulty in demolding, while low density can cause molten metal to easily penetrate and stick to the mold. 3. Limited coating function: Existing coatings often only focus on isolation properties, neglecting the uniformity of thermal conductivity. For example, in the ingot casting process, if the coating has excessive or uneven thermal resistance, it can lead to inconsistent cooling rates of the molten metal, resulting in uneven crystal structure, shrinkage cavities, or internal stress in the ingot. 4. Poor environmental performance: Traditional solvent-based release coatings contain a large amount of volatile organic compounds (VOCs), which do not meet increasingly stringent environmental regulations.

[0004] While some existing waterborne boron nitride coatings attempt to address the aforementioned issues, they still suffer from poor synergy between the binder and boron nitride, uneven dispersion, insufficient high-temperature stability of the coating, and low number of consecutive demolding cycles. Therefore, developing a waterborne metal casting release coating with excellent high-temperature resistance, good demolding performance, high adhesion, and environmental friendliness has significant industrial application value and market prospects. Summary of the Invention

[0005] In view of this, in order to solve one of the above-mentioned technical problems, the present invention provides a high-temperature resistant metal casting release coating and its preparation method, the specific technical solution of which is as follows:

[0006] A high-temperature resistant metal casting release coating, the metal casting release coating comprising the following raw materials in parts by weight: The composition consists of 25-30 parts of composite binder, 15-25 parts of hexagonal boron nitride, 1-3 parts of nano-alumina, 4-10 parts of high-temperature resistant auxiliary agent, 5-8 parts of suspending agent, 0.5-2 parts of dispersant, 0.1-2 parts of leveling agent, 5-15 parts of pigment, and 20-40 parts of water. The composite adhesive is composed of an organic adhesive and an inorganic adhesive in a mass ratio of 1:(0.5~2). The high-temperature resistant additive is composed of zircon powder, corundum powder and nano-cerium oxide in a mass ratio of (1~3):(1~5):(1~2).

[0007] Furthermore, the organic binder is at least one of silicone resin, acrylic resin, and epoxy resin; the inorganic binder is at least one of phosphate, silicate, and alumina sol.

[0008] Furthermore, the hexagonal boron nitride is composed of nanoscale h-BN, submicron-scale h-BN and micron-scale h-BN in a mass ratio of (1~2):(1~3):(1~2).

[0009] Furthermore, the particle size distribution of the high-temperature resistant auxiliary agent is as follows: 40% to 50% of the total mass of the high-temperature resistant auxiliary agent is 300 to 350 mesh; 30% to 40% of the total mass of the high-temperature resistant auxiliary agent is 500 to 800 mesh; and 10% to 20% of the total mass of the high-temperature resistant auxiliary agent is 1000 mesh or larger.

[0010] Furthermore, the suspending agent is a mixture of sodium bentonite and xanthan gum in a mass ratio of (1~5):1.

[0011] Furthermore, the dispersant is at least one of fatty alcohol polyoxyethylene ether and ammonium polyacrylate.

[0012] Furthermore, the leveling agent is at least one of polyether-modified polydimethylsiloxane and polyacrylate leveling agent.

[0013] In addition, the present invention also provides a method for preparing a metal casting release coating, the preparation method comprising the following steps: S1. Add hexagonal boron nitride, nano-alumina and high-temperature resistant additives to a ball mill and ball mill to obtain mixture A; S2. Add the composite binder, suspending agent, dispersant, leveling agent, pigment and water to the mixing tank, stir and process until uniform, to obtain mixture B; S3. Add the mixture A to the mixture B, stir until homogeneous, and obtain the mixture C; S4. Place the mixture C in an ultrasonic oscillator and treat it with ultrasonic oscillation to obtain a metal casting release coating.

[0014] Furthermore, in step S1, the ball milling speed is 100 r / min to 300 r / min, and the time is 30 min to 60 min.

[0015] Furthermore, in step S4, the frequency of the ultrasonic oscillation treatment is 20kHz~40kHz, and the time is 10min~30min.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention optimizes the composition of the coating by using a composite binder formed by combining organic and inorganic binders, and incorporates a high-temperature resistant auxiliary agent composed of zircon powder, corundum powder, and nano-cerium oxide. The coating can maintain structural stability during high-temperature metal casting processes, is not easily decomposed or fail, and has no obvious peeling or pores. This significantly improves the coating's temperature resistance and service life, meeting the temperature resistance requirements of various metal casting processes such as aluminum alloys, steel, and titanium alloys.

[0017] 2. The hexagonal boron nitride (h-BN) added in this invention has a layered structure, low coefficient of friction, and excellent lubricity. Through the particle size distribution of nanoscale, submicron, and micron, it can form a dense and smooth coating surface. Combined with high-temperature resistant additives of different gradations, the synergistic effect of filling, supporting, and lubricating particles of different sizes can effectively reduce the adhesion force between the molten metal and the mold, achieving efficient and stable demolding performance.

[0018] 3. The present invention adds nano-alumina, which can form chemical bonds (such as Al-OB bonds) with hexagonal boron nitride and composite binder at high temperatures, further enhancing the interfacial bonding force, preventing the coating from delaminating and peeling off under high temperature impact, effectively buffering the thermal shock of molten metal to the mold, and extending the service life of the mold. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0021] A high-temperature resistant metal casting release coating according to one embodiment of the present invention comprises the following raw materials in parts by weight: The composition consists of 25-30 parts of composite binder, 15-25 parts of hexagonal boron nitride, 1-3 parts of nano-alumina, 4-10 parts of high-temperature resistant auxiliary agent, 5-8 parts of suspending agent, 0.5-2 parts of dispersant, 0.1-2 parts of leveling agent, 5-15 parts of pigment, and 20-40 parts of water. The composite adhesive is composed of an organic adhesive and an inorganic adhesive in a mass ratio of 1:(0.5~2). The high-temperature resistant additive is composed of zircon powder, corundum powder and nano-cerium oxide in a mass ratio of (1~3):(1~5):(1~2).

[0022] In one embodiment, the organic binder is at least one of silicone resin, acrylic resin, and epoxy resin; the inorganic binder is at least one of phosphate, silicate, and alumina sol.

[0023] In one embodiment, the hexagonal boron nitride is composed of nanoscale h-BN, submicron-scale h-BN and micron-scale h-BN in a mass ratio of (1~2):(1~3):(1~2).

[0024] In one embodiment, the particle size distribution of the high-temperature resistant auxiliary agent is as follows: 40% to 50% of the total mass of the high-temperature resistant auxiliary agent has a particle size of 300-350 mesh; 30% to 40% of the total mass of the high-temperature resistant auxiliary agent has a particle size of 500-800 mesh; and 10% to 20% of the total mass of the high-temperature resistant auxiliary agent has a particle size of 1000 mesh or larger. In this invention, zircon powder and corundum powder are used, which have excellent high-temperature erosion resistance. Nano-cerium oxide can promote coating densification and inhibit grain growth at high temperatures, helping the coating to maintain structural integrity without obvious peeling or pores under high-temperature conditions.

[0025] In one embodiment, the suspending agent is a mixture of sodium bentonite and xanthan gum in a mass ratio of (1~5):1.

[0026] In one embodiment, the dispersant is at least one of fatty alcohol polyoxyethylene ether and ammonium polyacrylate.

[0027] In one embodiment, the leveling agent is at least one of polyether-modified polydimethylsiloxane and polyacrylate leveling agent.

[0028] In addition, the present invention also provides a method for preparing a metal casting release coating, the preparation method comprising the following steps: S1. Add hexagonal boron nitride, nano-alumina and high-temperature resistant additives to a ball mill and ball mill to obtain mixture A; S2. Add the composite binder, suspending agent, dispersant, leveling agent, pigment and water to the mixing tank, stir and process until uniform, to obtain mixture B; S3. Add the mixture A to the mixture B, stir until homogeneous, and obtain the mixture C; S4. Place the mixture C in an ultrasonic oscillator and treat it with ultrasonic oscillation to obtain a metal casting release coating.

[0029] In one embodiment, in step S1, the ball milling speed is 100 r / min to 300 r / min, and the time is 30 min to 60 min.

[0030] In one embodiment, in step S1, the ball milling process uses zirconia balls as the grinding medium, and the ball-to-material ratio is (2~3):1.

[0031] In one embodiment, in step S2, the stirring speed is 300 r / min to 500 r / min, and the time is 40 min to 60 min.

[0032] In one embodiment, in step S3, the stirring speed is 300 r / min to 500 r / min, and the time is 1 h to 2 h.

[0033] In one embodiment, in step S4, the frequency of the ultrasonic oscillation treatment is 20kHz~40kHz, and the time is 10min~30min.

[0034] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0035] Example 1: A method for preparing a metal casting release coating includes the following steps: S1. By weight, 20 parts of hexagonal boron nitride, 2 parts of nano alumina and 7 parts of high temperature resistant additives are added to a ball mill, ball milled at a speed of 300 r / min for 40 min, and the mass ratio of zirconia balls to material is 2:1 to obtain mixture A. The hexagonal boron nitride is composed of nanoscale h-BN, submicron-scale h-BN and micron-scale h-BN in a mass ratio of 1:3:1; The high-temperature resistant additive is composed of zircon powder, corundum powder, and nano-cerium oxide in a mass ratio of 1:3:1; the particle size distribution of the high-temperature resistant additive is as follows: 45% of the total mass of the high-temperature resistant additive has a particle size of 300 mesh; 40% of the total mass of the high-temperature resistant additive has a particle size of 600 mesh; and 15% of the total mass of the high-temperature resistant additive has a particle size of 1000 mesh or larger. S2. By weight, add 28 parts of composite binder, 7 parts of suspending agent, 1 part of fatty alcohol polyoxyethylene ether, 1 part of polyether modified polydimethylsiloxane, 10 parts of pigment and 35 parts of water to a mixing tank, and stir at 500 r / min for 45 min to obtain mixture B. The composite adhesive is composed of an organic adhesive and an inorganic adhesive in a mass ratio of 1:1; the organic adhesive is silicone resin; and the inorganic adhesive is aluminum sol. The suspending agent is a mixture of sodium bentonite and xanthan gum in a mass ratio of 4:1; S3. Add the mixture A to the mixture B and stir at 500 r / min for 1 h to obtain the mixture C; S4. Place the mixture C in an ultrasonic oscillator and treat it with ultrasonic oscillation at a frequency of 25 kHz for 20 min to obtain a metal casting release coating.

[0036] Example 2: A method for preparing a metal casting release coating includes the following steps: S1. By weight, 22 parts of hexagonal boron nitride, 1 part of nano alumina and 5 parts of high temperature resistant additives are added to a ball mill, ball milling is performed at a speed of 300 r / min for 45 min, and the mass ratio of zirconia balls to material is 2:1 to obtain mixture A. The hexagonal boron nitride is composed of nanoscale h-BN, submicron-scale h-BN and micron-scale h-BN in a mass ratio of 1:2:2; The high-temperature resistant additive is composed of zircon powder, corundum powder, and nano-cerium oxide in a mass ratio of 2:2:1; the particle size distribution of the high-temperature resistant additive is as follows: 45% of the total mass of the high-temperature resistant additive has a particle size of 300 mesh; 40% of the total mass of the high-temperature resistant additive has a particle size of 600 mesh; and 15% of the total mass of the high-temperature resistant additive has a particle size of 1000 mesh or larger. S2. By weight, add 30 parts of composite binder, 8 parts of suspending agent, 1 part of fatty alcohol polyoxyethylene ether, 1 part of polyether modified polydimethylsiloxane, 10 parts of pigment and 35 parts of water to a mixing tank, and stir at 500 r / min for 40 min to obtain mixture B. The composite adhesive is composed of an organic adhesive and an inorganic adhesive in a mass ratio of 1:1; the organic adhesive is silicone resin; and the inorganic adhesive is aluminum sol. The suspending agent is a mixture of sodium bentonite and xanthan gum in a mass ratio of 4:1; S3. Add the mixture A to the mixture B and stir at 500 r / min for 1 h to obtain the mixture C; S4. Place the mixture C in an ultrasonic oscillator and treat it with ultrasonic oscillation at a frequency of 25 kHz for 20 min to obtain a metal casting release coating.

[0037] Example 3: A method for preparing a metal casting release coating includes the following steps: S1. By weight, 20 parts of hexagonal boron nitride, 3 parts of nano alumina and 8 parts of high temperature resistant additives are added to a ball mill, ball milled at a speed of 300 r / min for 45 min, and the mass ratio of zirconia balls to material is 2:1 to obtain mixture A. The hexagonal boron nitride is composed of nanoscale h-BN, submicron-scale h-BN and micron-scale h-BN in a mass ratio of 1:3:1; The high-temperature resistant additive is composed of zircon powder, corundum powder, and nano-cerium oxide in a mass ratio of 1:2:2; the particle size distribution of the high-temperature resistant additive is as follows: 45% of the total mass of the high-temperature resistant additive has a particle size of 300 mesh; 40% of the total mass of the high-temperature resistant additive has a particle size of 600 mesh; and 15% of the total mass of the high-temperature resistant additive has a particle size of 1000 mesh or larger. S2. By weight, add 29 parts of composite binder, 6 parts of suspending agent, 1 part of fatty alcohol polyoxyethylene ether, 1 part of polyether modified polydimethylsiloxane, 10 parts of pigment and 35 parts of water to a mixing tank, and stir at 500 r / min for 40 min to obtain mixture B. The composite adhesive is composed of an organic adhesive and an inorganic adhesive in a mass ratio of 1:1; the organic adhesive is silicone resin; and the inorganic adhesive is aluminum sol. The suspending agent is a mixture of sodium bentonite and xanthan gum in a mass ratio of 4:1; S3. Add the mixture A to the mixture B and stir at 500 r / min for 1 h to obtain the mixture C; S4. Place the mixture C in an ultrasonic oscillator and treat it with ultrasonic oscillation at a frequency of 25 kHz for 20 min to obtain a metal casting release coating.

[0038] Comparative Example 1: The difference between Comparative Example 1 and Example 3 is that Comparative Example 1 uses a single silicone resin as the binder, while the rest is the same as Example 1.

[0039] Comparative Example 2: The difference between Comparative Example 2 and Example 3 is that the hexagonal boron nitride in Comparative Example 2 is only a single-size nano-sized h-BN, while the rest is the same as in Example 3.

[0040] Comparative Example 3: The difference between Comparative Example 3 and Example 3 is that hexagonal boron nitride was not added in Comparative Example 3, but otherwise the same as in Example 3.

[0041] Comparative Example 4: The difference between Comparative Example 4 and Example 3 is that no nano-alumina was added in Comparative Example 4, but otherwise it is the same as Example 3.

[0042] Comparative Example 5: The difference between Comparative Example 5 and Example 3 is that the high-temperature resistant additive in Comparative Example 5 is a single zircon powder, while the rest is the same as in Example 3.

[0043] Comparative Example 6: The difference between Comparative Example 6 and Example 3 is that the high-temperature resistant additive in Comparative Example 6 is a single corundum powder, while the rest is the same as in Example 3.

[0044] Comparative Example 7: The difference between Comparative Example 7 and Example 3 is that the high-temperature resistant auxiliary agent in Comparative Example 7 is a single nano-cerium oxide, while the rest is the same as in Example 3.

[0045] Comparative Example 8: The difference between Comparative Example 8 and Example 3 is that no high-temperature resistant additive was added in Comparative Example 8, but otherwise it is the same as Example 3.

[0046] The coating samples prepared in Examples 1-3 and the coating samples prepared in Comparative Examples 1-8 were uniformly brushed onto the surface of a metal mold preheated to 65°C, with the coating thickness controlled at 0.3 mm. The molds were then baked at 180°C for 20 min to form a dense, sintered, and cured coating. The test results are shown in Table 1 below.

[0047] 1. High-temperature demolding force: After the coated mold is poured with molten metal (ADC12 aluminum alloy, 680℃), the maximum tensile force when the casting separates from the mold is measured using a universal testing machine. Unit: N. Each group of samples is tested 5 times and the average value is taken.

[0048] 2. Number of consecutive demolding cycles: The number of valid demolding cycles is recorded when the same coating is in the continuous cycle of pouring molten metal → cooling → demolding → re-pouring until the coating shows obvious peeling or sticking to the mold (demolding force > 200 N or obvious adhesion on the surface of the casting).

[0049] 3. Thermal shock stability: Place the coated sample (e.g., a 50mm × 50mm steel plate) in an 800℃ high-temperature furnace for 15 minutes, then remove it and quickly immerse it in 25℃ water to cool. This constitutes one cycle. Record the number of cycles at which cracks, peeling, or flaking begin to appear on the coating surface.

[0050] 4. High-temperature adhesion: The coating sample is kept at 800℃ for 30 minutes and then naturally cooled to room temperature. The bonding strength between the coating and the substrate is tested using an adhesion tester (pull-off method) and rated on a scale of 0-5 (0 being the best and 5 being the worst). The cross-cut adhesion test (GB / T 9286-2021) can also be used for auxiliary rating.

[0051] 5. High temperature resistance: Place the coated sample in a muffle furnace at 800℃ (or higher, such as 1000℃) for 2 hours. After cooling, observe whether the coating shows powdering, discoloration, cracking or peeling.

[0052] Table 1: Test Results

[0053] Analysis of the data in Table 1 shows that by combining organic and inorganic binders and incorporating a high-temperature resistant auxiliary agent composed of zircon powder, corundum powder, and nano-cerium oxide, the coating can maintain structural stability during high-temperature metal casting, is not easily decomposed or failed, and has no obvious peeling or pores. Furthermore, nano-alumina can increase interfacial chemical bonding and enhance the bonding strength between the lubricating phase and the binder. The synergistic effect of zircon, corundum, and nano-cerium oxide provides erosion resistance, high strength, and self-healing functions, significantly improving thermal shock stability and high-temperature adhesion. Compared with Example 3, Comparative Example 1 used a single organic binder (silicone resin), which weakened the anchoring effect on the inorganic filler, resulting in a loose coating structure, which led to a sharp increase in demolding resistance and a decrease in coating durability. Comparative Example 2 used a single nano-scale hexagonal boron nitride. Although the single nano-scale h-BN can form a dense layer, it lacks the skeletal support of submicron and micron-scale particles. The coating is prone to microcracks under thermal shock, and the continuity of the lubrication layer is destroyed. Comparative Example 3 did not add hexagonal boron nitride. The coating relied solely on the physical isolation effect of the high-temperature resistant auxiliary agent, which could not effectively reduce the adhesion between the molten metal and the mold, resulting in mold sticking. Comparative Example 4 did not add nano-alumina. At high temperatures, the nano-alumina reacted with the hydroxyl groups at the edge of the hexagonal boron nitride and the aluminum sol in the binder to form Al-OB chemical bonds, which enhanced the interfacial bonding strength between the lubricating phase and the binder. Without nano-alumina, the lubricating phase is easily eroded and peeled off by the molten metal during repeated demolding cycles, resulting in coating performance inferior to Example 3. Comparative Examples 5-7 used single-component high-temperature resistant additives, but their performance was still inferior to Example 3. This indicates that the components of the high-temperature resistant additives in this invention work synergistically to achieve a gradient matching of thermal expansion coefficients and induce microcrack closure through the phase transformation of cerium oxide during thermal shock, significantly improving thermal shock resistance. Comparative Example 8, without the addition of high-temperature resistant additives, experienced significant volume shrinkage at high temperatures, leading to interface stress concentration and peeling, resulting in performance inferior to Example 3. Overall, this demonstrates that the synergistic effect of the components in this application can balance high-temperature adhesion and good demolding performance.

[0054] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0055] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A high-temperature resistant metal casting release coating, characterized in that, The metal casting release coating comprises the following raw materials in parts by weight: The composition consists of 25-30 parts of composite binder, 15-25 parts of hexagonal boron nitride, 1-3 parts of nano-alumina, 4-10 parts of high-temperature resistant auxiliary agent, 5-8 parts of suspending agent, 0.5-2 parts of dispersant, 0.1-2 parts of leveling agent, 5-15 parts of pigment, and 20-40 parts of water. The composite adhesive is composed of an organic adhesive and an inorganic adhesive in a mass ratio of 1:(0.5~2). The high-temperature resistant additive is composed of zircon powder, corundum powder and nano-cerium oxide in a mass ratio of (1~3):(1~5):(1~2).

2. The metal casting release coating according to claim 1, characterized in that, The organic binder is at least one of silicone resin, acrylic resin, and epoxy resin; the inorganic binder is at least one of phosphate, silicate, and alumina sol.

3. The metal casting release coating according to claim 1, characterized in that, The hexagonal boron nitride is composed of nanoscale h-BN, submicron-scale h-BN and micron-scale h-BN in a mass ratio of (1~2):(1~3):(1~2).

4. The metal casting release coating according to claim 1, characterized in that, The particle size distribution of the high-temperature resistant additive is as follows: 40% to 50% of the total mass of the high-temperature resistant additive is 300 to 350 mesh; 30% to 40% of the total mass of the high-temperature resistant additive is 500 to 800 mesh; and 10% to 20% of the total mass of the high-temperature resistant additive is 1000 mesh or larger.

5. The metal casting release coating according to claim 1, characterized in that, The suspending agent is a mixture of sodium bentonite and xanthan gum in a mass ratio of (1~5):

1.

6. The metal casting release coating according to claim 1, characterized in that, The dispersant is at least one of fatty alcohol polyoxyethylene ether and ammonium polyacrylate.

7. The metal casting release coating according to claim 1, characterized in that, The leveling agent is at least one of polyether-modified polydimethylsiloxane and polyacrylate leveling agent.

8. A method for preparing a metal casting release coating, characterized in that, The preparation method is used to prepare the metal casting release coating as described in any one of claims 1 to 7, and the preparation method includes the following steps: S1. Add hexagonal boron nitride, nano-alumina and high-temperature resistant additives to a ball mill and ball mill to obtain mixture A; S2. Add the composite binder, suspending agent, dispersant, leveling agent, pigment and water to the mixing tank, stir and process until uniform, to obtain mixture B; S3. Add the mixture A to the mixture B, stir until homogeneous, and obtain the mixture C; S4. Place the mixture C in an ultrasonic oscillator and treat it with ultrasonic oscillation to obtain a metal casting release coating.

9. The preparation method according to claim 8, characterized in that, In step S1, the ball milling speed is 100 r / min to 300 r / min, and the time is 30 min to 60 min.

10. The preparation method according to claim 8, characterized in that, In step S4, the frequency of the ultrasonic oscillation treatment is 20kHz~40kHz, and the time is 10min~30min.

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