High-precision coated sand, and preparation method and application thereof

Abstract

The application belongs to the technical field of coated sand for casting, and particularly discloses high-precision coated sand, a preparation method and application thereof.The coated sand comprises raw sand, zirconium powder, red iron oxide, iron sand, brown corundum powder, nano metal powder, modified phenolic resin, potassium tripolyphosphate, polyoxypropylene polyoxyethylene propylene glycol ether, sodium polycarboxylate, magnesium dihydrogen phosphate, attapulgite, potassium chloride and the like.Through the synergistic effect of the components, the coated sand has excellent bending strength and shell removal performance in the casting process, small high-temperature expansion and low gas evolution, meets the requirements of high-precision coated sand, effectively solves the problems of pores, sand sticking, cracking and uneven thickness of castings, and the surface quality of the prepared castings is significantly improved, which is suitable for the production requirements of high-precision castings, and the raw materials are widely sourced and low in price, and have high practical value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coated sand for casting, in particular to a high-precision coated sand and a preparation method and application thereof. BACKGROUND

[0002] Coated sand refers to a sand or core sand with a layer of solid resin film on the surface of the sand particles before molding. Coated sand technology originated in the mid-1950s, and in the 1980s, due to the rapid development of the automobile, aviation and shipbuilding industries and the need for mechanical product exports, higher quality requirements were put forward for castings, thereby promoting the rapid development of coated sand production and application technology. With the continuous progress of casting technology, in recent years, some structures with high process difficulty have appeared, and higher requirements are put forward for coated sand.

[0003] However, the traditional silica sand coated sand has low rigidity of silica sand, which leads to poor dimensional accuracy of the castings, and the castings are prone to problems such as sand blow, sand inclusion, porosity, burr and uneven thickness, etc., which is difficult to meet the casting requirements of high dimensional accuracy. In order to solve the above problems, the casting industry currently adds a high content of pearl sand to the coated sand. Although this kind of coated sand can basically meet the casting requirements of high dimensional accuracy, the production cost of the sand mold will increase by 40-50%. Therefore, it is of great significance for the development of high-precision casting products to develop a high-precision coated sand with low cost and which can effectively improve the quality of castings. SUMMARY

[0004] Based on the low precision of the coated sand in the prior art, which easily leads to problems such as porosity, burr, cracking and high production cost of the castings, the present application provides a high-precision coated sand and a preparation method and application thereof.

[0005] To solve the above technical problems, the technical scheme provided by the present application is as follows:

[0006] A high-precision coated sand comprises the following components in mass fraction: 90-110 parts of raw sand, 2-3 parts of zirconium powder, 0.1-0.2 parts of iron oxide red, 6-8 parts of iron sand, 2-3 parts of brown corundum powder, 1.3-1.7 parts of nano metal powder, 1-3 parts of modified phenolic resin, 0.6-1 part of potassium tripolyphosphate, 0.2-0.3 parts of lubricant, 0.2-0.4 parts of curing agent, 0.01-0.02 parts of polyoxypropylene polyoxyethylene propylene glycol ether, 0.01-0.02 parts of sodium polycarboxylate, 0.02-0.03 parts of dispersant, 3-5 parts of magnesium dihydrogen phosphate, 0.1-0.2 parts of attapulgite, 0.1-0.2 parts of potassium chloride, 0.01-0.02 parts of penetrating agent, 0.02-0.04 parts of defoaming agent, 0.1-0.2 parts of toughening agent and 6-12 parts of water.

[0007] Compared with the prior art, the high-precision coated sand provided by the application reduces the possibility of molten iron entering the sand mold during the molding process by adding iron oxide red and iron sand, and promotes rapid solidification of the casting by the excellent heat storage capacity of the iron sand, and effectively reduces the occurrence of problems such as air holes and burrs on the surface of the casting by reducing the thermal permeability of the iron sand; the uniformity of mixing between the components can be improved by the synergistic effect of the polyoxypropylene polyoxyethylene propylene glycol ether and the sodium polycarboxylate, so that the prepared coated sand is not easy to cake, and the demolding property of the coated sand can also be improved; the carbonization speed of the modified phenolic resin is delayed by adding brown corundum powder and nano metal powder, so that the sand core has high strength during the solidification process of the molten iron, and the sand core is prevented from cracking; the nano metal powder, magnesium dihydrogen phosphate and zirconium powder are added to improve the refractoriness of the coated sand and avoid cracks on the surface of the casting; the compatibility and adhesion strength of the raw sand and the modified phenolic resin are enhanced by adding attapulgite, which also prevents other media from penetrating the interface and improves the surface quality of the casting; the flowability of the coated sand is improved by adding potassium chloride and potassium tripolyphosphate, so that the coated sand can fill complex castings, such as internal corners, deep recesses, flat holes and other difficult-to-fill parts, improve the compactness of the filling, and gradually improve the precision of the prepared casting.

[0008] Through the synergistic effect of the above components, the coated sand has excellent bending strength and shell removal performance during the molding process, and has small high-temperature expansion and low gas evolution, meeting the requirements of high-precision coated sand, and effectively solving the problems of air holes, sand sticking, cracking and uneven thickness of the casting which are prone to occur in the existing coated sand, and the surface quality of the prepared casting is significantly improved, which is suitable for the production requirements of high-precision castings, and the raw materials are widely available and low in price, having high practical value.

[0009] Preferably, the raw sand is composed of 25%-35% of pearl sand and the balance of Weichang sand, and the particle size is 70-140 mesh.

[0010] The preferred composition of the raw sand can improve the refractoriness and strength of the coated sand, and is beneficial to reducing the expansion defects of the casting.

[0011] Illustratively, the particle size of the zirconium powder is 300-400 mesh.

[0012] Illustratively, the particle size of the iron oxide red is 800-1000 mesh.

[0013] Illustratively, the particle size of the iron sand is 30-50 mesh.

[0014] Illustratively, the particle size of the brown corundum powder is 2000-3000 mesh.

[0015] The fineness of the preferred raw materials can improve the compactness of the coated sand, and is beneficial to improving the filling property of the coated sand for complex-shaped castings, thereby improving the precision of the castings.

[0016] Preferably, the nano metal powder is at least one of nano tungsten carbide or nano titanium carbide, and the mass content of the metal powder with a particle size of 60-70 μm in the nano metal powder is not less than 85%.

[0017] The preferred nano metal powder can improve the refractoriness of the coated sand and prevent the coated sand from being peeled off during the casting process.

[0018] Preferably, the preparation method of the modified phenolic resin comprises the following steps:

[0019] The polylactic acid, polyamide, 2-hydroxyethyl cellulose, clear type phenolic resin, 2-cyano acrylate and styrene-acrylic emulsion are uniformly mixed, heated to 270-280 DEG C, and stirred for 1-2 min to obtain the modified phenolic resin.

[0020] Further preferably, in combination with the above, the adding amount of the polylactic acid, polyamide, 2-hydroxyethyl cellulose, 2-cyano acrylate and styrene-acrylic emulsion is 5-10% of the mass of the clear type phenolic resin.

[0021] It should be noted that the above clear type phenolic resin is synthesized with reference to CN107151299A.

[0022] The preferred modified phenolic resin can effectively improve the compatibility of organic materials and inorganic materials, has excellent high temperature resistance, can maintain the stability of the overall structure and size of the coated sand at a higher casting temperature, improve the demouldability of the coated sand, has low gas evolution, can effectively reduce the casting defects caused by the binder, and further improve the yield of the castings.

[0023] Preferably, the lubricant is at least one of neopentyl glycol diheptanoate or zinc stearate.

[0024] The preferred lubricant can prevent the coated sand from caking, improve the fluidity and demouldability of the coated sand, and effectively prevent the coated sand from being peeled off during use.

[0025] Preferably, the curing agent is phthalic anhydride.

[0026] The present application can reduce the possibility of molten iron entering the sand mold during the casting process by adding iron oxide red and iron sand in the coated sand, accelerate the solidification of the castings by the excellent heat storage capacity of the iron sand in cooperation with the preferred curing agent, and reduce the thermal permeability by the iron sand, thereby effectively avoiding the pores on the surface of the castings.

[0027] Preferably, the dispersing agent is a fatty alcohol sodium succinate.

[0028] The preferred dispersing agent cooperates with polyoxypropylene polyoxyethylene propylene glycol ether and sodium polycarboxylate to improve the mixing uniformity among the components, so that the prepared coated sand is not easy to be caked, and the demoulding property of the coated sand is improved, and the gas generation amount of the coated sand during use is reduced.

[0029] Preferably, the penetrating agent is at least one of alkyl phenol polyoxyethylene ether or sodium diisooctyl sulfosuccinate.

[0030] Preferably, the defoaming agent is at least one of ethanol, polyoxypropylene ethylene glycol ether or polyoxyethylene polyoxypropyl amine ether.

[0031] The preferred penetrating agent and defoaming agent are used in combination to enhance the flowability of the sand particles, prevent sand sticking, make the surface of the sand core smooth and fine, and effectively reduce the generation of bubbles during use of the coated sand, thereby improving the surface quality of the castings and reducing defects.

[0032] Preferably, the toughening agent is a mixture of manganese carbide and potassium silicate with a mass ratio of 1:1-1.2, wherein the particle size of the manganese carbide is 250-350 mesh, and the particle size of the potassium silicate is 200-250 mesh.

[0033] The preferred toughening agent can improve the heat resistance and toughness of the coated sand.

[0034] The application also provides a preparation method of high-precision coated sand.

[0035] Step a: according to the design ratio, the components are weighed, the weighed potassium tripolyphosphate is added to 10%-15% water, and is ground to obtain a potassium tripolyphosphate stock solution;

[0036] The weighed raw sand is preheated to 100-120 DEG C, the preheated raw sand is uniformly mixed with potassium chloride, the potassium tripolyphosphate stock solution, nano metal powder, red iron oxide and iron sand, heated to 180-185 DEG C, and stirred for 3-4 min to obtain a first mixture;

[0037] Step b: the weighed magnesium dihydrogen phosphate, attapulgite, zirconium powder and 15%-20% water are uniformly mixed to obtain a second mixture;

[0038] Step c: the second mixture is added to the first mixture and uniformly mixed to obtain a third mixture;

[0039] Step d: when the third mixture is cooled to 130-140 DEG C, the weighed modified phenolic resin, penetrating agent, defoaming agent, polyoxypropylene polyoxyethylene propylene glycol ether, sodium polycarboxylate, dispersing agent and remaining water are uniformly mixed, and then the brown corundum powder and 1 / 3-1 / 2 of the lubricant are uniformly mixed to obtain a fourth mixture;

[0040] Step e, when the fourth mixture is cooled to 105-115 DEG C, the weighed curing agent and toughening agent are added, mixed uniformly, then the remaining lubricant is added, cooled, crushed and sieved to obtain high-precision coated sand.

[0041] The preparation method of high-precision coated sand provided by the application has wide raw material sources, simple operation and facilitates industrialized production and application.

[0042] The application also provides application of the high-precision coated sand in any of the above aspects in the field of casting.

[0043] The coated sand provided by the application has the advantages of high strength, good toughness, high temperature resistance, low gas evolution, fast crust formation and non-sticking of the product to sand, can effectively solve the problems of pores, sticking and uneven thickness of the castings in the existing coated sand, significantly improves the surface quality of the castings, meets the casting requirements of the castings with high dimensional accuracy, has simple preparation process, convenient operation, low cost and is suitable for industrialized production and application, and has wide application prospect in the field of high-precision castings. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the application more clear, the application is further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the application and not to limit the application.

[0045] In order to better illustrate the application, the following examples are further illustrated.

[0046] Example 1

[0047] The application provides a preparation method of modified phenolic resin, specifically comprising the following steps:

[0048] The polylactic acid, polyamide, 2-hydroxyethyl cellulose, clear type phenolic resin, 2-cyano acrylate and styrene-acrylic emulsion are uniformly mixed, heated to 280 DEG C and stirred for 2 min to obtain the modified phenolic resin.

[0049] The adding amount of the polylactic acid, polyamide, 2-hydroxyethyl cellulose, 2-cyano acrylate and styrene-acrylic emulsion is 8% of the mass of the clear type phenolic resin.

[0050] The modified phenolic resin prepared by using other conditions defined in the application can also achieve the technical effect of the modified phenolic resin prepared under the above conditions.

[0051] The clear type phenolic resin is synthesized according to CN107151299A.

[0052] Example 2

[0053] The embodiment of the present application provides high-precision coated sand, which comprises the following components in mass fraction: 100 parts of raw sand, 2.5 parts of zirconium powder, 0.2 parts of iron oxide red, 7 parts of iron sand, 3 parts of brown corundum powder, 1.5 parts of nano tungsten carbide powder, 2 parts of modified phenolic resin, 0.8 parts of potassium tripolyphosphate, 0.2 parts of zinc stearate, 0.3 parts of phthalic anhydride, 0.02 parts of polyoxypropylene polyoxyethylene propylene glycol ether, 0.02 parts of sodium polycarboxylate, 0.03 parts of fatty alcohol sodium succinate, 4 parts of magnesium dihydrogen phosphate, 0.15 parts of attapulgite, 0.15 parts of potassium chloride, 0.01 parts of alkylphenol polyoxyethylene ether OP-10, 0.03 parts of anhydrous ethanol, 0.2 parts of toughening agent and 10 parts of water.

[0054] The raw sand is composed of 30% of pearl sand and 70% of weichang sand, and the particle size is 120 meshes; the particle size of the zirconium powder is 300 meshes; the particle size of the iron oxide red is 1000 meshes; the particle size of the iron sand is 40 meshes; the particle size of the brown corundum powder is 2000 meshes; the mass content of the metal powder with a particle size of 60-70 mu m in the nano tungsten carbide powder is not less than 85%; the toughening agent is a mixture of manganese carbide and potassium silicate with a mass ratio of 1:1.1, wherein the particle size of the manganese carbide is 300 meshes, and the particle size of the potassium silicate is 200 meshes.

[0055] The preparation method of the high-precision coated sand comprises the following steps:

[0056] In step a, the components are weighed according to the design ratio, the weighed potassium tripolyphosphate is added to 12wt% water, and grinding is performed to obtain a potassium tripolyphosphate solution;

[0057] In step b, the weighed magnesium dihydrogen phosphate, attapulgite, zirconium powder and 18wt% water are uniformly mixed to obtain a second mixture;

[0058] In step b, the weighed magnesium dihydrogen phosphate, attapulgite, zirconium powder and 18wt% water are uniformly mixed to obtain a second mixture;

[0059] In step c, the second mixture is added to the first mixture, and uniform mixing is performed to obtain a third mixture;

[0060] In step d, when the third mixture is cooled to 135 DEG C, the weighed modified phenolic resin, penetrant, defoaming agent, polyoxypropylene polyoxyethylene propylene glycol ether, sodium polycarboxylate, dispersant and remaining water are uniformly mixed, and then the brown corundum powder and 1 / 3 of the lubricant are uniformly mixed to obtain a fourth mixture;

[0061] Step e, when the fourth mixture is cooled to 110℃, the weighed curing agent and toughening agent are added, after mixing uniformly, the remaining lubricant is added, cooled, crushed and sieved to obtain high-precision coated sand.

[0062] Example 3

[0063] The embodiment of the present application provides a kind of high-precision coated sand, including the components of the following mass fraction: 90 parts of raw sand, 3 parts of zirconium powder, 0.1 parts of red iron oxide, 8 parts of iron sand, 2.5 parts of brown corundum powder, 1.7 parts of nano titanium carbide powder, 3 parts of modified phenolic resin, 0.6 parts of potassium tripolyphosphate, 0.25 parts of zinc stearate, 0.2 parts of phthalic anhydride, 0.01 parts of polyoxypropylene polyoxyethylene propylene glycol ether, 0.02 parts of sodium polycarboxylate, 0.02 parts of fatty alcohol sodium succinate, 5 parts of magnesium dihydrogen phosphate, 0.2 parts of attapulgite, 0.1 parts of potassium chloride, 0.02 parts of sodium succinate diisooctyl sulfonate T-80, 0.02 parts of polyoxyethylene polyoxypropylamine ether, 0.15 parts of toughening agent and 6 parts of water.

[0064] The raw sand is composed of 35% of pearl sand and 65% of weichang sand, and the particle size is 140 meshes; the particle size of the zirconium powder is 400 meshes; the particle size of the red iron oxide is 900 meshes; the particle size of the iron sand is 30 meshes; the particle size of the brown corundum powder is 3000 meshes; the mass content of metal powder with a particle size of 60-70 μm in the nano titanium carbide powder is not less than 85%; the toughening agent is a mixture of manganese carbide and potassium silicate with a mass ratio of 1:1, wherein the particle size of the manganese carbide is 250 meshes, and the particle size of the potassium silicate is 200 meshes.

[0065] The preparation method of the high-precision coated sand comprises the following steps:

[0066] Step a, weigh each component according to the designed ratio, grind the weighed potassium tripolyphosphate in 10 wt% water to obtain a potassium tripolyphosphate solution;

[0067] Preheat the weighed raw sand to 100℃, mix the preheated raw sand with potassium chloride, potassium tripolyphosphate solution, nano metal powder, red iron oxide and iron sand uniformly, heat to 180℃, and stir for 3 min to obtain a first mixture;

[0068] Step b, mix the weighed magnesium dihydrogen phosphate, attapulgite, zirconium powder and 15 wt% water uniformly to obtain a second mixture;

[0069] Step c, add the second mixture to the first mixture and mix uniformly to obtain a third mixture;

[0070] Step d, when the third mixture is cooled to 130℃, weighed modified phenolic resin, penetrant, defoaming agent, polyoxypropylene polyoxyethylene propylene glycol ether, sodium polycarboxylate, dispersant and the rest of the water are added, mixed uniformly, then brown corundum powder and 1 / 2 lubricant are added, mixed uniformly, the fourth mixture is obtained;

[0071] Step e, when the fourth mixture is cooled to 105℃, weighed curing agent and toughening agent are added, mixed uniformly, then the rest of the lubricant is added, cooled, broken, sieved, high-precision coated sand is obtained.

[0072] Example 4

[0073] The embodiment of the present application provides a kind of high-precision coated sand, including the following mass fraction of components: raw sand 110 parts, zirconium powder 2 parts, iron oxide red 0.15 parts, iron sand 6 parts, brown corundum powder 2 parts, nano tungsten carbide powder 1.3 parts, modified phenolic resin 1 part, potassium tripolyphosphate 1 part, neopentyl glycol diheptanoate 0.3 parts, phthalic anhydride 0.4 parts, polyoxypropylene polyoxyethylene propylene glycol ether 0.02 parts, sodium polycarboxylate 0.01 parts, fatty alcohol sodium succinate 0.03 parts, magnesium dihydrogen phosphate 3 parts, attapulgite 0.1 parts, potassium chloride 0.2 parts, alkylphenol polyoxyethylene ether OP-10 0.01 parts, polyoxypropylene glycol ether 0.04 parts, toughening agent 0.1 parts and water 12 parts.

[0074] Wherein, the raw sand is composed of 25% of pearl sand and 75% of weichang sand, and the particle size is 70 meshes; the particle size of the zirconium powder is 350 meshes; the particle size of the iron oxide red is 800 meshes; the particle size of the iron sand is 50 meshes; the particle size of the brown corundum powder is 3000 meshes; the mass content of the metal powder with a particle size of 60-70 μm in the nano tungsten carbide powder is not less than 85%; the toughening agent is a mixture of manganese carbide and potassium silicate with a mass ratio of 1:1.2, wherein the particle size of the manganese carbide is 350 meshes, and the particle size of the potassium silicate is 250 meshes.

[0075] The preparation method of the above high-precision coated sand specifically includes the following steps:

[0076] Step a, weigh each component according to the designed ratio, grind the weighed potassium tripolyphosphate in 15wt% water to obtain a potassium tripolyphosphate solution;

[0077] Preheat the weighed raw sand to 120℃, mix the preheated raw sand with potassium chloride, potassium tripolyphosphate solution, nano metal powder, iron oxide red and iron sand uniformly, heat to 185℃, stir for 3 min to obtain a first mixture;

[0078] Step b, mix the weighed magnesium dihydrogen phosphate, attapulgite, zirconium powder and 20wt% water uniformly to obtain a second mixture;

[0079] Step c, adding the second mixture into the first mixture, mixing uniformly to obtain a third mixture;

[0080] Step d, when the third mixture is cooled to 140℃, adding weighed modified phenolic resin, penetrating agent, defoaming agent, polyoxypropylene polyoxyethylene propylene glycol ether, sodium polycarboxylate, dispersant and the rest of water, mixing uniformly, then adding brown corundum powder and 1 / 2 of the lubricant, mixing uniformly to obtain a fourth mixture;

[0081] Step e, when the fourth mixture is cooled to 115℃, adding weighed curing agent and toughening agent, mixing uniformly, then adding the rest of the lubricant, cooling, crushing and sieving to obtain high-precision coated sand.

[0082] Comparative Example 1

[0083] This comparative example provides a coated sand, which has the same raw material composition as Example 2, except that the modified phenolic resin is replaced by an equal amount of ordinary phenolic resin. The preparation method of the ordinary phenolic resin is as follows:

[0084] S1, 12 parts of solid phenol are sent into a melter for heating and melting, and after melting, they are transferred into a reactor, 25 parts of formaldehyde are added, a stirrer is started with a speed of 45 r / min, 2 parts of ammonia water with a mass content of 10% are added, the temperature is slowly adjusted to 70℃, and reaction is carried out for 30 min, then the temperature of the reactor is adjusted to 95℃, 2 parts of sodium hydroxide aqueous solution with a mass content of 15% are added, and reaction is carried out for 30 min under insulation;

[0085] S2, the temperature of the reactor is gradually reduced to 50℃, 38 parts of furfuryl alcohol solution with a mass content of 95% are added and mixed uniformly, then the temperature of the reactor is increased to 98℃ at a temperature increasing speed of 3-4℃ / min, and 10 parts of benzenesulfonyl chloride are gradually added during the temperature increasing process, and after the dropping is completed, reaction is carried out for 1 h;

[0086] S3, the temperature of the reactor is increased to 110℃, 10 parts of hexamethylenetetramine are slowly added, and reaction is continued for 0.5 h, then the temperature is cooled to 90℃, 1 part of sodium hydroxide aqueous solution with a mass content of 15% is added, stirring is carried out for 12 min, the temperature is reduced to 50℃, and water is added for quenching, and the temperature is reduced to room temperature to obtain ordinary phenolic resin.

[0087] Comparative Example 2

[0088] This comparative example provides a coated sand, which has the same raw material composition as Example 2, except that the red iron oxide and iron sand are replaced by an equal amount of zircon powder.

[0089] Comparative Example 3

[0090] The comparative example 2 provides a coated sand, the raw material composition of which is completely same as that of the example 2, and the only difference is that the attapulgite is replaced by an equal amount of bauxite.

[0091] According to the coated sand standard for casting in JB / T 8583-2008, the coated sand prepared in the examples 2-4 and the comparative examples 1-3 is subjected to performance test, and the results are shown in Table 1.

[0092] Table 1

[0093]

[0094]

[0095] The above merely provides the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A high-precision coated sand, characterized in that: The invention is composed of the following components in parts by mass: 90-110 parts of raw sand, 2-3 parts of zircon powder, 0.1-0.2 parts of red iron oxide, 6-8 parts of iron sand, 2-3 parts of brown corundum powder, 1.3-1.7 parts of nano metal powder, 1-3 parts of modified phenolic resin, 0.6-1 parts of potassium tripolyphosphate, 0.2-0.3 parts of lubricant, 0.2-0.4 parts of curing agent, 0.01-0.02 parts of polyoxypropylene polyoxyethylene propylene glycol ether, 0.01-0.02 parts of sodium hydroxide, 0.02-0.03 parts of dispersant, 3-5 parts of magnesium dihydrogen phosphate, 0.1-0.2 parts of attapulgite, 0.1-0.2 parts of potassium chloride, 0.01-0.02 parts of penetrant, 0.02-0.04 parts of defoamer, 0.1-0.2 parts of toughening agent and 6-12 parts of water; the raw sand is composed of 25%-35% of Baozhu sand and the balance of paddock sand, and its particle size is 70 mesh to 140 mesh; The preparation method of the modified phenolic resin comprises the following steps: Polylactic acid, polyamide, 2-hydroxyethyl cellulose, fragrant phenolic resin, 2-cyanoacrylate and styrene acrylic emulsion are mixed evenly, heated to 270-280°C, and stirred for 1-2 minutes to obtain modified phenolic resin.

2. The high-precision coated sand according to claim 1, characterized in that: The particle size of the zircon powder is 300-400 mesh; and / or The particle size of the red iron oxide is 800 mesh to 1000 mesh; and / or The particle size of the iron sand is 30-50 mesh; and / or The particle size of the brown corundum powder is 2000 mesh to 3000 mesh.

3. The high-precision coated sand according to claim 1, characterized in that: The nano metal powder is at least one of nano tungsten carbide or nano titanium carbide, and the mass content of metal powder with a particle size of 60 μm-70 μm in the nano metal powder is not less than 85%.

4. The high-precision coated sand according to claim 1, characterized in that: The added amounts of the polylactic acid, polyamide, 2-hydroxyethyl cellulose, 2-cyanoacrylate and styrene acrylic emulsion are all 5%-10% of the mass of the light-fragrant phenolic resin.

5. The high-precision coated sand according to claim 1, characterized in that: The lubricant is at least one of neopentyl glycol diheptanoate or zinc stearate; and / or The curing agent is phthalic anhydride; and / or The dispersant is fatty alcohol sodium succinate.

6. The high-precision coated sand according to claim 1, characterized in that: The penetrant is at least one of alkylphenol polyoxyethylene ether or sodium dioctyl sulfosuccinate; and / or The defoaming agent is at least one of ethanol, polyoxypropylene oxyethylene glycerol ether or polyoxyethylene polyoxypropanolamine ether.

7. The high-precision coated sand according to claim 1, characterized in that: The toughening agent is a mixture of manganese carbide and potassium silicate in a mass ratio of 1:1-1.2, wherein the particle size of the manganese carbide is 250 meshes to 350 meshes, and the particle size of the potassium silicate is 200 meshes to 250 meshes.

8. The method for preparing high-precision coated sand according to any one of claims 1 to 7, characterized in that: The steps include: Step a, weighing each component according to the designed ratio, adding the weighed potassium tripolyphosphate to 10%-15% water, grinding, and obtaining a potassium tripolyphosphate liquid; Preheat the weighed raw sand to 100-120°C, mix the preheated raw sand with potassium chloride, potassium tripolyphosphate solution, nano metal powder, red iron oxide and iron sand, heat to 180-185°C, and stir for 3-4 minutes to obtain a first mixture; Step b, mixing the weighed magnesium dihydrogen phosphate, attapulgite, zircon powder and 15%-20% water to obtain a second mixture; Step c, adding the second mixed material to the first mixed material, and mixing them evenly to obtain a third mixed material; Step d, when the third mixture is cooled to 130° C.-140° C., the modified phenolic resin, penetrant, defoamer, polyoxypropylene polyoxyethylene glycol ether, sodium polycarboxylate, dispersant and remaining water are added and mixed evenly, and then brown corundum powder and 1 / 3-1 / 2 of lubricant are added and mixed evenly to obtain a fourth mixture; Step e: when the fourth mixture is cooled to 105° C.-115° C., the weighed curing agent and toughening agent are added, mixed evenly, and then the remaining lubricant is added. The mixture is cooled, crushed, and sieved to obtain high-precision coated sand.

9. Use of the high-precision coated sand according to any one of claims 1 to 7 in the field of casting.

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