High-temperature-resistant precoated sand for casting and preparation process thereof

Abstract

The invention belongs to the technical field of precoated sand production, and particularly relates to high-temperature-resistant precoated sand for casting and a preparation technology of the high-temperature-resistant precoated sand. The high-temperature-resistant precoated sand for casting provided by the invention comprises the following raw materials in parts by weight: 1000 parts of base sand, 25-40 parts of composite resin, 10-18 parts of a high-temperature-resistant auxiliary agent, 5-15 parts of a curing agent, 5-15 parts of a silane coupling agent KH-570 and 2-3 parts of a lubricating agent. The high-temperature-resistant precoated sand for casting provided by the invention has excellent high-temperature resistance, mechanical property, thermal shock resistance, flowing property, environment-friendly economy and the like, the quality and efficiency of a casting process can be remarkably improved, and the requirements of aerospace, automobile engines and other high-end fields on high-performance precoated sand are met; the method has important application value and market prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of coated sand production, and in particular relates to high temperature resistant coated sand for casting and a preparation process thereof. Background Art

[0002] Coated sand is a casting material that forms a uniform film on the surface of sand particles through a resin coating process. Its core function is to improve the strength, fire resistance and dimensional accuracy of the sand mold. During the casting process, the coated sand is heated and solidified to form a high-strength sand mold or sand core that can withstand the impact and high temperature of molten metal. It is widely used in the production of precision castings such as automobile engine cylinders, turbine blades, and hydraulic valve bodies.

[0003] The main components of traditional coated sand include base sand (usually silica sand), binder (such as phenolic resin), curing agent (urotropine) and lubricant (calcium stearate). Although it can meet the needs of conventional castings, it often faces bottlenecks such as insufficient heat resistance, high gas generation and poor disintegration in high-temperature alloy casting or large and complex casting applications.

[0004] In the existing technology, the improvement of high-temperature resistant coated sand mostly relies on high-cost materials or complex processes. For example, some solutions use special resins (such as benzoxazine resins) to replace traditional phenolic resins to improve temperature resistance, but their high cost and significantly increased curing energy consumption make it difficult to meet the economic requirements of industrial production; other technologies attempt to introduce nanomaterials (such as alumina and zirconia) to improve refractory properties, but nanoparticles are easy to agglomerate and need to rely on additional dispersants. The increased process complexity may weaken the strength of the sand mold. In addition, the problem of insufficient material compatibility is common, such as the low interfacial bonding strength between the resin and the filler, which is prone to peeling at high temperatures, resulting in worse sand mold collapse.

[0005] Chinese patent CN107262662B discloses a super-high temperature resistant cast steel coated sand, and proposes to improve the high temperature resistance by adding chromite powder and ferroferric oxide sand. However, the high density of chromite causes a significant decrease in the air permeability of the sand mold, which is easy to cause pore defects during the pouring process, and the material cost is high, making it difficult to apply on a large scale. For example, Chinese patent CN107913974B discloses a coated sand for steel castings and a preparation method thereof, which uses a composite system of high-purity quartz silica sand and chromite sand. Although the high temperature strength of the sand mold is improved, the problem of low resin decomposition temperature is not effectively solved. There is still a risk of sand sticking at extremely high temperatures, and the casting yield rate fluctuates greatly.

[0006] What is more noteworthy is that existing technologies often sacrifice other characteristics in pursuit of a single performance indicator. For example, although excessive addition of refractory fillers improves temperature resistance, it causes a sharp drop in the permeability of the sand mold; although excessive use of resin enhances strength, excessive gas generation increases the risk of casting defects. This performance imbalance seriously restricts the application of coated sand in the field of high-end casting.

[0007] In summary, the existing high temperature resistant coated sand technology still has core problems such as high cost, complex process, and performance imbalance. An innovative solution is urgently needed to optimize the material ratio and process design, while ensuring high temperature stability, low gas emission and high strength, while taking into account economic and environmental protection. Summary of the invention

[0008] In order to solve the problems existing in the prior art, the object of the present invention is to provide a high temperature resistant coated sand for casting and a preparation process thereof.

[0009] The technical solution of the present invention is:

[0010] A high temperature resistant coated sand for casting, comprising the following raw materials in parts by weight:

[0011] 1000 parts of base sand, 25-40 parts of composite resin, 10-18 parts of high temperature resistant additive, 5-15 parts of curing agent, 5-15 parts of silane coupling agent KH 570, and 2-3 parts of lubricant.

[0012] Furthermore, the high temperature resistant coated sand for casting is prepared from the following raw materials in parts by weight:

[0013] 1000 parts of base sand, 35 parts of composite resin, 13 parts of high temperature resistant additive, 12 parts of curing agent, 10 parts of silane coupling agent KH-570, and 2.5 parts of lubricant; the composite resin is composed of modified epoxy resin and phenolic resin in a weight ratio of 3 to 5:1.

[0014] Furthermore, the base sand is a composite sand of silica sand and zircon sand, and the weight ratio of the silica sand to the zircon sand is 7:3.

[0015] Furthermore, the silica sand has a SiO2 content of ≥99%, the zircon sand has a ZrSiO4 content of ≥98%, and the particle size is 50-140 mesh;

[0016] Furthermore, the modified epoxy resin is prepared from the following raw materials in parts by weight:

[0017] 100 parts of bisphenol A epoxy resin, 30-50 parts of deionized water, 12-18 parts of inorganic high temperature resistant modifier, 3-8 parts of silane coupling agent KH-560, 2-5 parts of polyvinyl pyrrolidone K30, and 15-25 parts of water-based polyamide curing agent.

[0018] Furthermore, the modified epoxy resin is prepared from the following raw materials in parts by weight:

[0019] 100 parts of bisphenol A epoxy resin, 40 parts of deionized water, 15 parts of inorganic high temperature resistant modifier, 5 parts of silane coupling agent KH-560, 3 parts of polyvinyl pyrrolidone K30, and 20 parts of water-based polyamide curing agent.

[0020] Furthermore, the bisphenol A type epoxy resin is epoxy resin E51.

[0021] Furthermore, the inorganic high temperature resistant modifier is composed of nano yttrium oxide and silicon carbide whiskers in a weight ratio of 2:3.

[0022] Furthermore, the particle size of the nano yttrium oxide is 30-50 nm; the diameter of the silicon carbide whisker is 0.1-1 um, and the length is 5-30 um.

[0023] Furthermore, the water-based polyamide curing agent is Huntsman VERSAMID 140.

[0024] Furthermore, the preparation method of the modified epoxy resin comprises the following preparation steps:

[0025] S1. Mix bisphenol A epoxy resin and silane coupling agent KH-560, stir for 20 to 30 minutes at a speed of 500 to 600 r / min and a temperature of 60° C. to allow the silane coupling agent to be fully grafted onto the epoxy molecular chain to obtain an epoxy resin premix;

[0026] S2, dispersing nano yttrium oxide and silicon carbide whiskers in deionized water respectively, then adding polyvinyl pyrrolidone K30, and performing ultrasonic treatment to obtain a suspension;

[0027] S3, slowly adding the suspension obtained in step S2 to the epoxy resin premix obtained in step S1, using a high-speed shear emulsifier, and treating at 8000-10000 r / min for 20-30 min to form a uniform slurry;

[0028] S4, adding the water-based polyamide curing agent to the slurry obtained in step S3, stirring at 40° C. and 200 r / min for 40 to 60 min, and then degassing in a vacuum degassing tank for 2 h to obtain the slurry.

[0029] Furthermore, in step S2, the ultrasonic frequency is 30-40 kHz, the ultrasonic temperature is 50° C., and the ultrasonic treatment time is 30-40 min.

[0030] Furthermore, in the step S4, the vacuum degree in the vacuum degassing tank is -0.095 MPa and the temperature is 60°C.

[0031] Furthermore, the high temperature resistant additive is composed of aluminum titanate, magnesium oxide and a polymer block copolymer in a weight ratio of 5:3:2. Furthermore, the polymer block copolymer is Pluronic F127.

[0032] Furthermore, the curing agent is a 25-35% urotropine aqueous solution.

[0033] Furthermore, the lubricant is calcium stearate.

[0034] In addition, the present invention also provides a method for preparing the high temperature resistant coated sand for casting, comprising the following preparation steps:

[0035] (1) soaking the base sand in a hydrochloric acid solution with a mass concentration of 5-8% for 1-1.5 hours, washing with water until neutral, and then drying at 150° C. for 1-2 hours to obtain pretreated base sand;

[0036] (2) The pretreated base sand obtained in step (1) is added to a sand mixer, heated to 130-160° C., then silane coupling agent KH-570, composite resin and high temperature resistant additive are added, and stirred at a speed of 1200-1500 r / min for 15-30 min; then a urotropine aqueous solution is sprayed, and cured at 180-200° C. for 30-60 min; then a lubricant is added, and stirred at a speed of 600-800 r / min for 5-10 min, and finally crushed through a 40-80 mesh sieve, and air-cooled to room temperature to obtain the product.

[0037] The present invention provides a high-performance high-temperature resistant coated sand for casting, which significantly improves the comprehensive performance of the product by optimizing the pretreatment of base sand, the formula of composite resin and the composition of high-temperature resistant additives. Among them, after the base sand is pretreated with a hydrochloric acid solution, the surface roughness and specific surface area of ​​the base sand increase, which can effectively enhance the binding force with the resin; the modified epoxy resin (containing nano yttrium oxide and silicon carbide whiskers) in the composite resin synergizes with the phenolic resin and has excellent mechanical properties and high-temperature resistance; and the modified epoxy resin significantly improves the thermal stability and mechanical strength of the resin by introducing nano yttrium oxide and silicon carbide whiskers as inorganic high-temperature resistant modifiers, while the phenolic resin has excellent high-temperature resistance and chemical stability, which can make up for the shortcomings of the modified epoxy resin under high temperature conditions. The two interact through intermolecular hydrogen bonds and physical entanglements to form a uniformly distributed composite network structure, achieving performance complementarity.

[0038] Furthermore, the high temperature resistant additive composed of aluminum titanate, magnesium oxide and Pluronic F127 added to the high temperature resistant coated sand for casting provided by the present invention, aluminum titanate provides low thermal expansion coefficient and thermal shock resistance, magnesium oxide provides high melting point and thermal conductivity, Pluronic F127 improves filler dispersibility and interface bonding strength, the three act synergistically, so that the coated sand exhibits excellent comprehensive performance under high temperature conditions, and significantly improves the high temperature resistance of the coated sand.

[0039] Compared with the prior art, the high temperature resistant coated sand for casting and the preparation method thereof provided by the present invention have the following advantages:

[0040] The high-temperature resistant coated sand for casting provided by the present invention significantly improves the bonding force between the base sand and the resin through the combined action of hydrochloric acid pretreatment of the base sand and the silane coupling agent; and the modified epoxy resin and the phenolic resin form a composite system with both mechanical properties and high-temperature resistance through molecular interaction, which synergizes with the high-temperature resistant additives, and significantly improves the high-temperature resistance, mechanical properties, thermal shock resistance, fluidity, environmental protection and economy of the coated sand. It can significantly improve the quality and efficiency of the casting process, meet the needs of high-end fields such as aerospace, automobile engines, etc. for high-performance coated sand, and has important application value and market prospects. DETAILED DESCRIPTION

[0041] The present invention is further illustrated below through the description of specific implementation methods, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements based on the basic idea of ​​the present invention, but as long as they do not deviate from the basic idea of ​​the present invention, they are all within the protection scope of the present invention.

[0042] In the following examples and comparative examples, reagents not otherwise specified are conventional reagents and can be purchased from conventional reagent production and sales companies. The methods used are all prior art unless otherwise specified.

[0043] Example 1

[0044] A high temperature resistant coated sand for casting is prepared from the following raw materials in parts by weight:

[0045] 1000 parts of base sand, 25 parts of composite resin, 10 parts of high temperature resistant additive, 5 parts of 25% urotropine aqueous solution, 5 parts of silane coupling agent KH-570, and 2 parts of calcium stearate; the composite resin is composed of modified epoxy resin and phenolic resin in a weight ratio of 3:1.

[0046] The base sand is composed of silica sand and zircon sand in a weight ratio of 7:3; the silica sand has a SiO2 content of ≥99%, the zircon sand has a ZrSiO4 content of ≥98%, and the particle size is 60 mesh.

[0047] The high temperature resistant additive is composed of aluminum titanate, magnesium oxide and Pluronic F127 in a weight ratio of 5:3:2.

[0048] The modified epoxy resin is prepared from the following raw materials in parts by weight:

[0049] 100 parts of bisphenol A epoxy resin E51, 30 parts of deionized water, 12 parts of inorganic high temperature resistant modifier, 3 parts of silane coupling agent KH-560, 2 parts of polyvinyl pyrrolidone K30, and 15 parts of Huntsman VERSAMID 140.

[0050] The inorganic high temperature resistant modifier is composed of nano yttrium oxide and silicon carbide whiskers in a weight ratio of 2:3; the particle size of the nano yttrium oxide is 30-50nm; the diameter of the silicon carbide whiskers is 0.1-1um and the length is 5-30um.

[0051] The preparation method of the modified epoxy resin comprises the following preparation steps:

[0052] S1, mixing bisphenol A epoxy resin E51 and silane coupling agent KH-560, stirring for 20 minutes at a speed of 500 r / min and a temperature of 60° C., so that the silane coupling agent is fully grafted onto the epoxy molecular chain to obtain an epoxy resin premix;

[0053] S2, respectively dispersing nano yttrium oxide and silicon carbide whiskers in deionized water, then adding polyvinyl pyrrolidone K30, treating at an ultrasonic frequency of 30 kHz and a temperature of 50° C. for 30 min to obtain a suspension;

[0054] S3, slowly adding the suspension obtained in step S2 to the epoxy resin premix obtained in step S1, using a high-speed shear emulsifier, and treating at 8000 r / min for 20 minutes to form a uniform slurry;

[0055] S4. Add Huntsman VERSAMID 140 to the slurry obtained in step S3, stir at 40° C. and 200 r / min for 40 min, and then degas in a vacuum degassing tank (vacuum degree of -0.095 MPa, temperature of 60° C.) for 2 h to obtain the slurry.

[0056] The method for preparing the high temperature resistant coated sand for casting comprises the following preparation steps:

[0057] (1) Soaking the base sand in a 5% hydrochloric acid solution for 1.5 hours, washing with water until neutral, and then drying at 150° C. for 1 hour to obtain pretreated base sand;

[0058] (2) adding the pretreated base sand obtained in step (1) into a sand mixer, heating to 130° C., then adding silane coupling agent KH-570, composite resin and high temperature resistant additive, stirring at a speed of 1200 r / min for 30 min; then spraying an aqueous solution of urotropine, curing at 180° C. for 15 min; then adding a lubricant, stirring at a speed of 600 r / min for 10 min, finally crushing through a 40-mesh sieve, and air-cooling to room temperature to obtain the product.

[0059] Example 2

[0060] A high temperature resistant coated sand for casting is prepared from the following raw materials in parts by weight:

[0061] 1000 parts of base sand, 35 parts of composite resin, 13 parts of high temperature resistant additive, 12 parts of 30% urotropine aqueous solution, 10 parts of silane coupling agent KH-570, and 2.5 parts of calcium stearate; the composite resin is composed of modified epoxy resin and phenolic resin in a weight ratio of 4:1.

[0062] The base sand is composed of silica sand and zircon sand in a weight ratio of 7:3; the silica sand has a SiO2 content of ≥99%, the zircon sand has a ZrSiO4 content of ≥98%, and the particle size of both is 100 meshes.

[0063] The high temperature resistant additive is composed of aluminum titanate, magnesium oxide and Pluronic F127 in a weight ratio of 5:3:2.

[0064] The modified epoxy resin is prepared from the following raw materials in parts by weight:

[0065] 100 parts of bisphenol A epoxy resin E51, 40 parts of deionized water, 15 parts of inorganic high temperature resistant modifier, 5 parts of silane coupling agent KH-560, 3 parts of polyvinyl pyrrolidone K30, and 20 parts of Huntsman VERSAMID 140.

[0066] The inorganic high temperature resistant modifier is composed of nano yttrium oxide and silicon carbide whiskers in a weight ratio of 2:3; the particle size of the nano yttrium oxide is 30-50nm; the diameter of the silicon carbide whiskers is 0.1-1um and the length is 5-30um.

[0067] The preparation method of the modified epoxy resin comprises the following preparation steps:

[0068] S1. Mix bisphenol A epoxy resin E51 and silane coupling agent KH-560, and stir for 25 minutes at a speed of 550 r / min and a temperature of 60° C. to allow the silane coupling agent to be fully grafted onto the epoxy molecular chain to obtain an epoxy resin premix;

[0069] S2, respectively dispersing nano yttrium oxide and silicon carbide whiskers in deionized water, then adding polyvinyl pyrrolidone K30, treating at an ultrasonic frequency of 35 kHz and a temperature of 50° C. for 35 min to obtain a suspension;

[0070] S3, slowly adding the suspension obtained in step S2 to the epoxy resin premix obtained in step S1, using a high-speed shear emulsifier, and treating at 9000 r / min for 25 minutes to form a uniform slurry;

[0071] S4. Add Huntsman VERSAMID 140 to the slurry obtained in step S3, stir at 40° C. and 200 r / min for 50 min, and then degas in a vacuum degassing tank (vacuum degree of -0.095 MPa, temperature of 60° C.) for 2 h to obtain the slurry.

[0072] The method for preparing the high temperature resistant coated sand for casting comprises the following preparation steps:

[0073] (1) Soaking the base sand in a 6% hydrochloric acid solution for 1.2 hours, washing with water until neutral, and then drying at 150° C. for 1.5 hours to obtain pretreated base sand;

[0074] (2) Add the pretreated base sand obtained in step (1) into a sand mixer, heat it to 150° C., then add silane coupling agent KH-570, composite resin and high temperature resistant additive, stir at a speed of 1400 r / min for 25 min; then spray the urotropine aqueous solution, and cure at 190° C. for 12 min; then add the lubricant, stir at a speed of 700 r / min for 8 min, finally crush it through a 60-mesh sieve, and air-cool it to room temperature to obtain the product.

[0075] Example 3

[0076] A high temperature resistant coated sand for casting is prepared from the following raw materials in parts by weight:

[0077] 1000 parts of base sand, 40 parts of composite resin, 18 parts of high temperature resistant additive, 15 parts of 35% urotropine aqueous solution, 15 parts of silane coupling agent KH-570, and 3 parts of calcium stearate; the composite resin is composed of modified epoxy resin and phenolic resin in a weight ratio of 5:1.

[0078] The base sand is composed of silica sand and zircon sand in a weight ratio of 7:3; the silica sand has a SiO2 content of ≥99%, the zircon sand has a ZrSiO4 content of ≥98%, and the particle size is 120 mesh.

[0079] The high temperature resistant additive is composed of aluminum titanate, magnesium oxide and Pluronic F127 in a weight ratio of 5:3:2.

[0080] The modified epoxy resin is prepared from the following raw materials in parts by weight:

[0081] 100 parts of bisphenol A epoxy resin E51, 50 parts of deionized water, 8 parts of inorganic high temperature resistant modifier, 8 parts of silane coupling agent KH-560, 5 parts of polyvinyl pyrrolidone K30, and 25 parts of Huntsman VERSAMID 140.

[0082] The inorganic high temperature resistant modifier is composed of nano yttrium oxide and silicon carbide whiskers in a weight ratio of 2:3;

[0083] The particle size of the nano yttrium oxide is 30-50 nm; the diameter of the silicon carbide whisker is 0.1-1 um, and the length is 5-30 um.

[0084] The preparation method of the modified epoxy resin comprises the following preparation steps:

[0085] S1, mixing bisphenol A epoxy resin E51 and silane coupling agent KH-560, stirring for 30 minutes at a speed of 600 r / min and a temperature of 60° C., so that the silane coupling agent is fully grafted onto the epoxy molecular chain to obtain an epoxy resin premix;

[0086] S2, respectively dispersing nano yttrium oxide and silicon carbide whiskers in deionized water, then adding polyvinyl pyrrolidone K30, treating at an ultrasonic frequency of 40 kHz and a temperature of 50° C. for 40 min to obtain a suspension;

[0087] S3, slowly adding the suspension obtained in step S2 to the epoxy resin premix obtained in step S1, using a high-speed shear emulsifier, and treating at 10000 r / min for 30 minutes to form a uniform slurry;

[0088] S4. Add Huntsman VERSAMID 140 to the slurry obtained in step S3, stir at 40° C. and 200 r / min for 60 min, and then degas in a vacuum degassing tank (vacuum degree of -0.095 MPa, temperature of 60° C.) for 2 h to obtain the slurry.

[0089] The method for preparing the high temperature resistant coated sand for casting comprises the following preparation steps:

[0090] (1) Soaking the base sand in 8% hydrochloric acid solution for 1 hour, washing with water until neutral, and then drying at 150° C. for 2 hours to obtain pretreated base sand;

[0091] (2) Add the pretreated base sand obtained in step (1) into a sand mixer, heat it to 160° C., then add silane coupling agent KH-570, composite resin and high temperature resistant additive, stir at a speed of 1500 r / min for 15 min; then spray the urotropine aqueous solution, and cure at 200° C. for 8 min; then add lubricant, stir at a speed of 800 r / min for 5 min, finally crush through an 80-mesh sieve, and air-cool to room temperature to obtain the product.

[0092] Comparative Example 1

[0093] Compared with Example 2, the difference is that the aluminum titanate in the high temperature resistant additive is replaced by zirconium oxide, and the other components and preparation method are the same as those in Example 2.

[0094] Comparative Example 2

[0095] Compared with Example 2, the difference is that Pluronic F127 in the high temperature resistant additive is replaced by polyvinyl pyrrolidone K30, and the other components and preparation method are the same as those in Example 2.

[0096] Comparative Example 3

[0097] Compared with Example 2, the difference is that the silicon carbide whiskers in the inorganic high temperature resistant modifier in the modified epoxy resin are replaced by nano boron nitride (particle size is 100 nm), and the other components and preparation method are the same as those in Example 2.

[0098] Comparative Example 4

[0099] Compared with Example 2, the difference is that the silicon carbide whiskers in the inorganic high temperature resistant modifier in the modified epoxy resin are replaced with nano silicon carbide (particle size is 50-100nm), and the other components and preparation method are the same as those in Example 2. Test Example 1: Performance test of coated sand prepared by the present invention

[0100] The coated sands obtained in Examples 1 to 3 of the present invention and Comparative Examples 1 to 4 were tested for room temperature flexural strength (MPa), hot flexural strength (MPa), room temperature tensile strength (MPa), hot tensile strength (MPa), loss on ignition (%), gas evolution (mL / g), high temperature heat resistance time (s), linear expansion rate (%) and other items according to the methods in the machinery industry standard JB / T8583-2008 "Coated Sand for Casting" and the machinery industry standard JB / T 13037-2017 "Test Method for High Temperature Performance of Coated Sand". The test results are shown in Table 1.

[0101] Table 1

[0102]

[0103] As shown in Table 1, the high temperature resistant coated sand for casting prepared in Examples 1 to 3 has excellent high temperature resistance and mechanical properties, high hot bending strength and hot tensile strength, low burning loss, low linear expansion rate, long high temperature heat resistance time, and can maintain structural integrity during high temperature casting, reduce deformation or cracking caused by high temperature, and the coated sand is not easy to break or peel off under the conditions of rapid cooling or repeated heating, which improves the service life and is particularly suitable for complex castings, such as thin-walled parts or parts with complex shapes; high room temperature bending strength and room temperature tensile strength effectively improve the bearing capacity and impact resistance of the coated sand, ensure excellent surface quality of the casting, reduce the risk of damage during the casting process, improve production efficiency, low gas emission, reduce the generation of pore defects during the casting process, and improve the compactness and mechanical properties of the casting. In Comparative Examples 1 to 4, when the types and proportions of raw materials in the preparation process of the coated sand were changed, the various indicators of the obtained coated sand decreased to varying degrees.

[0104] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A high temperature resistant coated sand for casting, characterized in that: The invention comprises the following raw materials in parts by weight: 1000 parts of base sand, 25-40 parts of composite resin, 10-18 parts of high temperature resistant additive, 5-15 parts of curing agent, 5-15 parts of silane coupling agent KH-570, and 2-3 parts of lubricant.

2. The high temperature resistant coated sand for casting according to claim 1, characterized in that: The high temperature resistant coated sand for casting is prepared from the following raw materials in parts by weight: 1000 parts of base sand, 35 parts of composite resin, 13 parts of high temperature resistant additive, 12 parts of curing agent, 10 parts of silane coupling agent KH-570, and 2.5 parts of lubricant; the composite resin is composed of modified epoxy resin and phenolic resin in a weight ratio of 3 to 5:

1.

3. The high temperature resistant coated sand for casting according to claim 1, characterized in that: The base sand is a composite sand of silica sand and zircon sand, and the weight ratio of the silica sand to the zircon sand is 7:

3.

4. The high temperature resistant coated sand for casting according to claim 1, characterized in that: The modified epoxy resin is prepared from the following raw materials in parts by weight: 100 parts of bisphenol A epoxy resin, 30-50 parts of deionized water, 12-18 parts of inorganic high temperature resistant modifier, 3-8 parts of silane coupling agent KH-560, 2-5 parts of polyvinyl pyrrolidone K30, and 15-25 parts of water-based polyamide curing agent.

5. The high temperature resistant coated sand for casting according to claim 4, characterized in that: The inorganic high temperature resistant modifier is composed of nano yttrium oxide and silicon carbide whiskers in a weight ratio of 2:3; the particle size of the nano yttrium oxide is 30-50nm; the diameter of the silicon carbide whiskers is 0.1-1um and the length is 5-30um.

6. The high temperature resistant coated sand for casting according to claim 4, characterized in that: The bisphenol A type epoxy resin is epoxy resin E51; the water-based polyamide curing agent is Huntsman VERSAMID 140.

7. The high temperature resistant coated sand for casting according to claim 4, characterized in that: The preparation method of the modified epoxy resin comprises the following preparation steps: S1, mixing bisphenol A epoxy resin and silane coupling agent, stirring at a speed of 500-600 r / min and a temperature of 60° C. for 20-30 min to obtain an epoxy resin premix; S2, dispersing nano yttrium oxide and silicon carbide whiskers in deionized water respectively, then adding polyvinyl pyrrolidone K30, and performing ultrasonic treatment to obtain a suspension; S3, adding the suspension obtained in step S2 to the epoxy resin premix obtained in step S1, using a high-speed shear emulsifier, and treating at 8000-10000 r / min for 20-30 min to form a uniform slurry; S4, adding the water-based polyamide curing agent to the slurry obtained in step S3, stirring at 40° C. and 200 r / min for 40 to 60 min, and then degassing in a vacuum degassing tank for 2 h to obtain the slurry.

8. The high temperature resistant coated sand for casting according to claim 1, characterized in that: The high temperature resistant additive is composed of aluminum titanate, magnesium oxide and a high molecular block copolymer in a weight ratio of 5:3:2; the high molecular block copolymer is Pluronic F127.

9. The high temperature resistant coated sand for casting according to claim 1, characterized in that: The curing agent is a urotropine aqueous solution with a concentration of 1.5-2.0; and the lubricant is calcium stearate.

10. The high temperature resistant coated sand for casting according to claim 1, characterized in that: The method for preparing the high temperature resistant coated sand for casting comprises the following preparation steps: (1) soaking the base sand in a hydrochloric acid solution with a mass concentration of 5-8% for 1-1.5 hours, washing with water until neutral, and then drying at 150° C. for 1-2 hours to obtain pretreated base sand; (2) adding the pretreated base sand obtained in step (1) into a sand mixer, heating to 130-160° C., then adding silane coupling agent KH-570, composite resin and high temperature resistant additive, stirring at a speed of 1200-1500 r / min for 15-30 min; then spraying a urotropine aqueous solution, curing at 180-200° C. for 30-60 min; then adding a lubricant, stirring at a speed of 600-800 r / min for 5-10 min, finally crushing through a 40-80 mesh sieve, and air cooling to room temperature to obtain the product.

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