Anti-caking coated sand and method of making same

Abstract

The present application relates to a kind of anti-caking coated sand and its preparation method, the preparation method includes: S1.Silica sand is heated to 200~280 ℃;S2.Add phenolic resin, after mixing, add urotropin aqueous solution mixing, cooling to 110~150 ℃, obtain mixed sand;S3.Urotropin aqueous solution, calcium stearate and release agent are sequentially added to the mixed sand and mixed, to obtain anti-caking coated sand.In the technical scheme of the present application, through secondary coating process, the lubricating component and the release component can be more evenly and firmly attached to the surface of sand grain;This process forms an effective physical isolation layer between sand grains, greatly reduces the friction and bonding tendency between sand grains, even if the ambient temperature is higher, sand grains can also maintain independent loose state.

Description

Technical Field

[0001] This invention relates to the field of thin film technology, specifically to an anti-caking coated sand and its preparation method. Background Technology

[0002] With the rapid development of my country's industry, the market demand for casting quality is increasing, especially for high-end castings with thin walls and precision. Coated sand technology has become the mainstream production method for castings due to its superior performance. As an important casting molding material, coated sand can meet the stringent requirements of high-end castings for dimensional accuracy and surface quality, occupying a key position in the modern casting industry.

[0003] In industrial production, the coated sand process typically involves heating raw sand and adding binders such as resin to mix it, causing the sand grains to be coated with a solid resin film. The finished product is then produced through cooling, crushing, and sieving. This preparation process endows the sand core with good fluidity and solidification properties, and it is widely used in the molding process of complex structural castings.

[0004] However, the current coated sand process still faces serious challenges, mainly manifested in the problem of coated sand easily agglomerating under high-temperature environments. Especially in summer when the ambient temperature is high, coated sand is prone to adhesion and agglomeration during transportation or in equipment storage. This problem not only seriously affects production cycle and efficiency, but also leads to a decline in the surface quality of the sand core, ultimately resulting in a rough surface of the casting and restricting further improvement in product quality. Summary of the Invention

[0005] Based on the above description, the present invention provides an anti-caking coated sand and its preparation method, aiming to improve the anti-caking performance of coated sand.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: This invention provides a method for preparing anti-caking coated sand, comprising: S1. Heat the silica sand to 200℃~280℃; S2. Add phenolic resin, mix, then add lotropine aqueous solution and mix, cool to 110℃~150℃ to obtain mixed sand; S3. Phenolic resin, hexamethylenetetramine aqueous solution, calcium stearate and release agent are added sequentially to the mixed sand and mixed to obtain anti-caking coated sand.

[0007] Furthermore, the separating agent includes microsilica powder, aluminum powder, iron oxide powder, and graphite; The mass ratio of silica powder, aluminum powder, iron oxide powder and graphite is (10~30):(30~60):(5~10):(10~20).

[0008] Furthermore, in step S2: The mass concentration of the rotropine aqueous solution is 60 wt%~70 wt%; The mass ratio of silica sand, phenolic resin and rotropine aqueous solution is 100:(0.5~1.5):(0.1~0.5).

[0009] Furthermore, in step S2, after adding the phenolic resin, the mixing time is 10 s to 50 s; and / or, In step S2, after adding the lotropine aqueous solution, the mixing time is 10 s to 50 s.

[0010] Furthermore, in step S3: The mass concentration of the rotropine aqueous solution is 60 wt%~70 wt%; The mass ratio of mixed sand, phenolic resin, hexamethylenetetramine aqueous solution, calcium stearate and release agent is (100~102):(0.5~1.5):(0.1~0.5):(0.1~0.2):(0.1~0.2).

[0011] Furthermore, in step S3, after adding the phenolic resin, the mixing time is 10 s to 50 s.

[0012] Furthermore, in step S3, after adding the lotropine aqueous solution, the mixing time is 10 s to 50 s.

[0013] Furthermore, in step S3, after adding calcium stearate, the mixing time is 10 s to 20 s.

[0014] Furthermore, in step S3, after adding the separating agent, the mixing time is 10 s to 20 s.

[0015] The present invention also proposes an anti-caking coated sand, which is prepared according to the aforementioned method for preparing anti-caking coated sand.

[0016] Compared with the prior art, the technical solution of this application has the following beneficial technical effects: 1. In the technical solution of the present invention, a two-stage coating process is used. Phenolic resin and lotropine solution are added for the first time at 200℃~280℃, and phenolic resin, lotropine solution, calcium stearate and release agent are added and mixed for the second time at 110℃~150℃. This allows the lubricating and release components to adhere more evenly and firmly to the surface of the sand particles. This process forms an effective physical isolation layer between the sand particles, which greatly reduces the friction and adhesion tendency between the sand particles. Even at high ambient temperatures, the sand particles can maintain an independent and loose state.

[0017] 2. The coated sand prepared by this process has excellent thermal stability, overcoming the defects of traditional processes where coated sand is prone to agglomeration and clumping due to heat accumulation in high-temperature working environments, long-distance transportation, or equipment storage silos during summer. The material can still maintain good looseness under long-term static conditions or high-temperature conditions, eliminating the problem of poor material flow caused by agglomeration. Attached Figure Description

[0018] Figure 1 This is a schematic flowchart of an embodiment of the method for preparing anti-caking coated sand provided by the present invention. Detailed Implementation

[0019] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[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 application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0021] 1.2 Comparison of Existing Technologies ① The invention disclosed in publication number CN121156170A discloses a low-gas-emission, high-heat-resistant coated sand and its preparation method, including the following steps: drying the recycled cast steel sand to reduce its moisture content to below 0.1%; taking 1000 parts by weight of the treated recycled cast steel sand, adding 5-10 parts by weight of silane coupling agent, and mixing evenly; heating the mixed material to 75-80℃, transferring it to a sand mixer, adding 30-40 parts by weight of organopolysilazane resin, and mixing sand; adding 6-8 parts by weight of carbon nanotube powder and mixing for 30 seconds; sequentially adding 5-7 parts by weight of vinyl silicone oil and 1.8-2.4 parts by weight of calcium stearate, mixing evenly, and obtaining the coated sand product.

[0022] This patent uses a novel binder system for low-temperature sand mixing, completely disregarding the high-temperature conditions of coated sand. This binder system undergoes a bonding reaction at 75~80℃. If used in the production process, the coated sand will clump together, interrupting production and rendering it unusable.

[0023] ② Invention patent CN119500968A discloses a high-precision coated sand, its preparation method, and its application. The coated sand includes raw sand, zircon powder, iron oxide red, iron sand, brown corundum powder, nano-metal powder, modified phenolic resin, potassium tripolyphosphate, polyoxypropylene polyoxyethylene propylene glycol ether, sodium polycarboxylate, magnesium dihydrogen phosphate, attapulgite clay, potassium chloride, etc. Through the synergistic effect of these components, the coated sand exhibits excellent bending strength and shell removal performance during the casting process, with low high-temperature expansion and low gas generation, meeting the requirements of high-precision coated sand. It effectively solves problems such as porosity, sand adhesion, cracking, and uneven thickness that are common in existing coated sand castings. The surface quality of the prepared castings is significantly improved, making it suitable for the production requirements of high-precision castings. Furthermore, the raw materials are widely available and inexpensive, giving it high practical value.

[0024] While the patent improves some properties of coated sand, it does not take into account the problem of high-temperature agglomeration encountered in actual production.

[0025] ③ The invention disclosed in CN120662757A discloses a high-performance coated sand and its preparation method. The formula includes silica sand, recycled sand, resin, hexamethylenetetramine, calcium stearate, and 0.1-1% ultrafine silica powder by weight of the total formula. The ultrafine silica powder has a SiO2 content of over 99%, an average particle size of 1-5 μm, and a particle size distribution span (D90-D10) / D50 < 0.5. The preparation method includes the following steps: S1, heating the silica sand and recycled sand to 125±10℃; S2, transferring the heated sand to a sand mixer, stirring at low speed for 4±0.5 min, adding ultrafine silica powder, and continuing to stir for 50±10 s; S3, adding resin, hexamethylenetetramine, and calcium stearate in sequence, and stirring at low speed for 180±10 s; S4, sieving and cooling the mixed sand, and packaging it after it reaches room temperature. The addition of 0.1-1% ultrafine silica powder improves the high-temperature strength of the coated sand, reduces sand mold cracking, and improves casting quality. At the same time, the use of recycled sand reduces costs.

[0026] While the patent improves some properties of coated sand, it does not take into account the problem of high-temperature agglomeration encountered in actual production.

[0027] In view of this, see Figure 1 This invention provides a method for preparing anti-caking coated sand, comprising: S1. Heat the silica sand to 200℃~280℃; S2. Add phenolic resin, mix, then add lotropine aqueous solution and mix, cool to 110℃~150℃ to obtain mixed sand; S3. Phenolic resin, hexamethylenetetramine aqueous solution, calcium stearate and release agent are added sequentially to the mixed sand and mixed to obtain anti-caking coated sand.

[0028] In the technical solution of this invention, a two-stage coating process is used. Phenolic resin and tropine solution are added for the first time at 200℃~280℃, and phenolic resin, tropine solution, calcium stearate and release agent are added and mixed for the second time at 110℃~150℃. This allows the lubricating and release components to adhere more evenly and firmly to the surface of the sand particles. This process forms an effective physical isolation layer between the sand particles, which greatly reduces the friction and adhesion tendency between the sand particles. Even at high ambient temperatures, the sand particles can maintain an independent and loose state.

[0029] The coated sand prepared by this process has excellent thermal stability, overcoming the defects of traditional processes where coated sand is prone to agglomeration and clumping due to heat accumulation in high-temperature working environments in summer, long-distance transportation, or equipment storage silos. The material can still maintain good looseness under long-term static conditions or high-temperature conditions, eliminating the problem of poor material flow caused by agglomeration.

[0030] Furthermore, the separating agent includes microsilica powder, aluminum powder, iron oxide powder, and graphite; The mass ratio of silica powder, aluminum powder, iron oxide powder and graphite is (10~30):(30~60):(5~10):(10~20).

[0031] In the technical solution of this invention, by using the above-mentioned proportion of isolating agent, the highly thermally conductive aluminum powder and graphite can accelerate the dissipation of heat from the surface of the sand particles, avoiding local heat accumulation that would cause the resin to soften and become sticky prematurely; at the same time, an appropriate amount of microsilica powder and iron oxide powder ensures the overall fluidity of the mixture, preventing uneven dispersion caused by powders that are too fine or too coarse; this balance of thermal and mechanical properties allows the coated sand to maintain an excellent loose state even in high summer temperatures or in the residual heat environment of equipment, ensuring that it does not clump.

[0032] Furthermore, in step S2: The mass concentration of the rotropine aqueous solution is 60 wt%~70 wt%; The mass ratio of silica sand, phenolic resin and rotropine aqueous solution is 100:(0.5~1.5):(0.1~0.5).

[0033] In the technical solution of this invention, by adopting the above-mentioned concentration, the curing agent is ensured to be uniformly dispersed in the resin phase and the effects of excessive moisture causing the sand particles to become damp and sticky, or insufficient moisture causing severe local reactions, are avoided. The combination of low resin dosage and precise curing agent ratio results in only a very thin and uniform pre-cured resin film forming on the surface of the silica sand. This effectively avoids the phenomenon of bridging between sand particles and softening and sticking of local hot spots caused by excessive resin accumulation. Thus, a low-viscosity and highly dispersible sand particle state is constructed in the early stage of preparation, eliminating the early agglomeration risk caused by uneven resin distribution or excessive dosage during high-temperature sand mixing. This lays a solid material foundation for obtaining excellent high-temperature anti-agglomeration performance in subsequent processes.

[0034] Furthermore, in step S2, after adding the phenolic resin, the mixing time is 10 s to 50 s; and / or, In step S2, after adding the lotropine aqueous solution, the mixing time is 10 s to 50 s.

[0035] In the technical solution of this invention, by adjusting the mixing time to 10 s to 50 s, it is ensured that the resin and curing agent can be rapidly and uniformly dispersed and adhered to the surface of the silica sand to form a liquid coating layer of uniform thickness. This avoids uneven dispersion and local resin enrichment caused by too short a mixing time, which leads to high-temperature "hot spot" agglomeration. It also prevents the resin film from prematurely pre-curing or abnormally increasing in viscosity under shear heat due to too long a mixing time. This eliminates the agglomeration of sand particles caused by excessive frictional heat generation or resin stickiness during the sand mixing stage, ensuring that the sand particles are always in an ideal loose and low-viscosity state before entering the high-temperature heating process. This further eliminates the cause of high-temperature agglomeration from the process control level.

[0036] Furthermore, in step S3: The mass concentration of the rotropine aqueous solution is 60 wt%~70 wt%; The mass ratio of mixed sand, phenolic resin, hexamethylenetetramine aqueous solution, calcium stearate and release agent is (100~102):(0.5~1.5):(0.1~0.5):(0.1~0.2):(0.1~0.2).

[0037] In the technical solution of this invention, by using a 60 wt%~70 wt% lotropine aqueous solution concentration and adjusting the mixing ratio, a synergistic system of micro-resin film formation and dual lubrication and isolation is constructed. The small amount of phenolic resin ensures that only an ultra-thin cured layer is formed on the surface of the sand particles, avoiding the sticky bridging between sand particles caused by excessive resin. At an addition amount of 0.1~0.2 parts, calcium stearate and composite isolation agent, utilizing their compatibility with the resin and specific dispersion behavior, precisely fill the microscopic defects of the resin film and form an efficient physical and chemical isolation barrier at the sand particle contact point. This reduces the free energy and friction coefficient of the sand particle surface at high temperatures, thereby blocking the thermoplastic adhesion path and avoiding the problem of damage to the final strength of the coated sand or uneven dispersion caused by excessive additives. Thus, in the secondary sand mixing stage, the long-term anti-caking performance of the coated sand under harsh high-temperature environments is further consolidated and improved.

[0038] Furthermore, in step S3, after adding the phenolic resin, the mixing time is 10 s to 50 s.

[0039] In the technical solution of this invention, by strictly controlling the mixing time after adding phenolic resin to 10 s~50 s, a synergistic process of rapid and uniform dispersion and low-temperature shear control is constructed. This specific short mixing window ensures that the trace amount of phenolic resin added secondarily rapidly penetrates to the surface of the sand particles and between the lubricating isolation layer under shear action, forming a continuous and extremely thin supplementary adhesive film. This avoids high-temperature adhesion caused by uneven resin dispersion and local enrichment due to excessively short mixing time. At the same time, this upper limit of time effectively limits the accumulation of mechanical shear heat, preventing the resin from prematurely pre-curing or viscosity surge due to overheating during the sand mixing stage. This eliminates the agglomeration phenomenon caused by frictional heat generation and stickiness of sand particles, ensuring the optimal distribution of each component in the resin matrix. This eliminates the causes of high-temperature agglomeration from the process control level, providing a key guarantee for finally obtaining coated sand with excellent looseness and uniform strength at high temperatures.

[0040] Furthermore, in step S3, after adding the lotropine aqueous solution, the mixing time is 10 s to 50 s.

[0041] In the technical solution of this invention, by strictly controlling the mixing time after adding the rotropine aqueous solution in step S3 to 10 s~50 s, a synergistic process of rapid penetration and low-temperature dispersion of the curing agent is constructed. This specific short mixing window ensures that the rotropine aqueous solution is rapidly and uniformly distributed on the surface of the sand particles and in the resin film under shear action, realizing effective contact and initial activation of the curing agent and resin. This avoids early curing and agglomeration caused by uneven dispersion of the curing agent and excessively high local concentration due to excessively short mixing time. At the same time, this upper limit of time effectively limits the accumulation of mechanical shear heat, preventing excessively rapid evaporation of water or rise in system temperature that leads to abnormal increase in resin viscosity and premature occurrence of pre-curing reaction. This eliminates the agglomeration of sand particles caused by local overheating or stickiness, ensuring that the coated sand maintains an ideal loose state before entering the subsequent heating process. In turn, the uniformity of the curing reaction is optimized from a kinetic perspective, significantly improving the anti-agglomeration performance of the coated sand in high-temperature environment and the surface quality of the final casting.

[0042] Furthermore, in step S3, after adding calcium stearate, the mixing time is 10 s to 20 s.

[0043] In the technical solution of this invention, by strictly controlling the mixing time after adding calcium stearate to 10 s~20 s in step S3, a synergistic process of precise lubricant coating and low shear heat accumulation is constructed. This specific extremely short mixing window ensures that calcium stearate rapidly and uniformly adheres to the outer layer of the resin film and micropores on the surface of the sand grains under mechanical shearing, forming a continuous and dense hydrophobic lubricating isolation layer, which effectively reduces the friction coefficient between sand grains. At the same time, this strict time limit minimizes the frictional heat generated by excessive shearing, preventing calcium stearate from melting and agglomerating due to local heating or excessive penetration into the resin, thereby avoiding the problem of uneven lubricant distribution, ensuring the integrity of the isolation barrier at the sand grain contact point, and thus blocking the thermoplastic adhesion path at high temperature from the microstructure, significantly improving the looseness and anti-caking performance of the coated sand during storage and high-temperature casting.

[0044] Furthermore, in step S3, after adding the separating agent, the mixing time is 10 s to 20 s.

[0045] In the technical solution of this invention, by strictly controlling the mixing time after adding the release agent to 10s~20s in step S3, a synergistic process of efficient film formation and microstructure protection of the release agent is constructed. This specific extremely short mixing window ensures that the release agent rapidly and uniformly covers the resin and lubricating layer on the surface of the sand particles under low shear heat conditions, forming a complete and uniform physical barrier that effectively blocks direct contact between sand particles. At the same time, this strict time limit avoids the accumulation of shear heat due to excessive mixing, preventing the release agent from melting, migrating, agglomerating, or excessively penetrating into the resin matrix due to local heating. This eliminates the problem of local adhesion caused by uneven distribution of the release agent, which weakens the resin bonding strength. It ensures that the release agent only acts on the sand particle contact interface and does not destroy the overall skeleton, thereby eliminating the risk of high-temperature agglomeration from the source of the process.

[0046] The present invention also proposes an anti-caking coated sand, which is prepared according to the aforementioned method for preparing anti-caking coated sand.

[0047] Since this anti-caking coated sand adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0048] The technical solution of this patent will be further described in detail below with reference to specific embodiments.

[0049] Example 1 This embodiment proposes a method for preparing anti-caking coated sand, the specific steps of which are as follows: 1. Take 100 parts of 50 / 100 silica sand, which can be either new or recycled sand.

[0050] 2. Heat the silica sand to 220°C and then put it into the sand mixer.

[0051] 3. Add 0.8 parts of phenolic resin and stir for 25 seconds.

[0052] 4. Add 0.3 parts of hexamethylenetetramine aqueous solution and stir for 30 seconds.

[0053] (Urotropin aqueous solution ratio = urotropin : water = 2 : 1) 5. After the sand mixing process is completed, the mixture is cooled to 130°C by air cooling.

[0054] 6. Add 0.6 parts of phenolic resin and stir for 30 seconds.

[0055] 7. Add 0.3 parts of urotropine aqueous solution and stir for 30 seconds.

[0056] 8. Add 0.1 part calcium stearate and stir for 10 seconds.

[0057] 9. Add 0.2 parts of the release agent and stir for 20 seconds. The release agent consists of 10% silica powder, 60% aluminum powder, 10% iron oxide powder, and 20% graphite.

[0058] 10. Obtain anti-caking coated sand.

[0059] Comparative Example 1 This comparative example proposes a method for preparing anti-caking coated sand, eliminating the sand mixing process 1 and employing a single-coating technique. All other implementation methods and conditions are the same as in Example 1. The specific steps are as follows: 1. Take 100 parts of 50 / 100 silica sand, which can be either new or recycled sand.

[0060] 2. Heat the silica sand to 130°C and then put it into the sand mixer.

[0061] 3. Add 1.4 parts of phenolic resin and stir for 55 seconds.

[0062] 4. Add 0.6 parts of urotropine aqueous solution and stir for 60 seconds.

[0063] (Urotropin aqueous solution ratio = urotropin : water = 2 : 1) 5. Add 0.1 part calcium stearate and stir for 10 seconds.

[0064] 6. Add 0.2 parts of the release agent and stir for 20 seconds. The release agent consists of 10% silica fume, 60% aluminum powder, 10% iron oxide powder, and 20% graphite.

[0065] 7. Obtain anti-caking coated sand.

[0066] Comparative Example 2 This comparative example presents a method for preparing anti-caking coated sand, which is similar to Example 1, except that step 9 is removed and no release agent is added. All other implementation methods and conditions are the same as in the example.

[0067] Comparative Example 3 This comparative example presents a method for preparing anti-caking coated sand, which is similar to Example 1, except that in step 1, the heating temperature of the raw sand is reduced to 150°C, and other implementation methods and conditions are the same as in the example.

[0068] The anti-caking coated sand provided in Example 1 and Comparative Examples 1 to 3 was subjected to performance tests. The test methods were in accordance with standard GB / T2684-2009. The test results are shown in Table 1.

[0069] Table 1 Physical and chemical properties of coated sand

[0070] Among them, shelf life refers to the number of days required for the coated sand to clump together when stored at 40℃.

[0071] Clogged nozzle frequency: refers to the number of times the nozzle is manually cleaned during a 24-hour continuous working period in the core-making process.

[0072] Core surface porosity rate: refers to the percentage of cores with porosity that occur when 100 cores are prepared.

[0073] Based on the contents of Table 1, we can conclude that: Compared with the anti-caking coated sand prepared in Comparative Example 1, the anti-caking coated sand prepared in Example 1 has the same tensile strength, a melting point increased by 25°C, the same curing thickness, a shelf life longer by 160 days, requires 78 fewer nozzle cleanings, and the sand core porosity rate decreased from 30% to 0.

[0074] Compared with the anti-caking coated sand prepared in Comparative Example 2, the anti-caking coated sand prepared in Example 1 has the same tensile strength, a melting point that is 10°C higher, the same curing thickness, a shelf life that is 122 days longer, requires 56 fewer nozzle cleanings, and the sand core porosity rate is reduced from 13% to 0.

[0075] Compared with the anti-caking coated sand prepared in Comparative Example 3, the anti-caking coated sand prepared in Example 1 has a tensile strength 1.1 MPa higher, a melting point 22°C higher, a curing thickness 0.4 mm higher, a shelf life 150 days longer, requires 68 fewer nozzle cleanings, and the sand core porosity rate is reduced from 27% to 0%.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0077] In summary, the technical solution of this application has the following beneficial technical effects: 1. In the technical solution of the present invention, a two-stage coating process is used. Phenolic resin and lotropine solution are added for the first time at 200℃~280℃, and phenolic resin, lotropine solution, calcium stearate and release agent are added and mixed for the second time at 110℃~150℃. This allows the lubricating and release components to adhere more evenly and firmly to the surface of the sand particles. This process forms an effective physical isolation layer between the sand particles, which greatly reduces the friction and adhesion tendency between the sand particles. Even at high ambient temperatures, the sand particles can maintain an independent and loose state.

[0078] 2. The coated sand prepared by this process has excellent thermal stability, overcoming the defects of traditional processes where coated sand is prone to agglomeration and clumping due to heat accumulation in high-temperature working environments, long-distance transportation, or equipment storage silos during summer. The material can still maintain good looseness under long-term static conditions or high-temperature conditions, eliminating the problem of poor material flow caused by agglomeration.

Claims

1. A method for preparing anti-caking coated sand, characterized in that, include: S1. Heat the silica sand to 200℃~280℃; S2. Add phenolic resin, mix, then add lotropine aqueous solution and mix, cool to 110℃~150℃ to obtain mixed sand; S3. Phenolic resin, hexamethylenetetramine aqueous solution, calcium stearate and release agent are added sequentially to the mixed sand and mixed to obtain anti-caking coated sand.

2. The method for preparing anti-caking coated sand according to claim 1, characterized in that, The separating agent includes microsilica powder, aluminum powder, iron oxide powder, and graphite; The mass ratio of silica powder, aluminum powder, iron oxide powder and graphite is (10~30):(30~60):(5~10):(10~20).

3. The method for preparing anti-caking coated sand according to claim 1, characterized in that, In step S2: The mass concentration of the rotropine aqueous solution is 60 wt%~70 wt%; The mass ratio of silica sand, phenolic resin and rotropine aqueous solution is 100:(0.5~1.5):(0.1~0.5).

4. The method for preparing anti-caking coated sand according to claim 1, characterized in that, In step S2, after adding the phenolic resin, the mixing time is 10 s to 50 s; and / or, In step S2, after adding the lotropine aqueous solution, the mixing time is 10 s to 50 s.

5. The method for preparing anti-caking coated sand according to claim 1, characterized in that, In step S3: The mass concentration of the rotropine aqueous solution is 60 wt%~70 wt%; The mass ratio of mixed sand, phenolic resin, hexamethylenetetramine aqueous solution, calcium stearate and release agent is (100~102):(0.5~1.5):(0.1~0.5):(0.1~0.2):(0.1~0.2).

6. The method for preparing anti-caking coated sand according to claim 1, characterized in that, In step S3, after adding phenolic resin, the mixing time is 10 s to 50 s.

7. The method for preparing anti-caking coated sand according to claim 1, characterized in that, In step S3, after adding the lotropine aqueous solution, the mixing time is 10 s to 50 s.

8. The method for preparing anti-caking coated sand according to claim 1, characterized in that, In step S3, after adding calcium stearate, the mixing time is 10 s to 20 s.

9. The method for preparing anti-caking coated sand according to claim 1, characterized in that, In step S3, after adding the separating agent, the mixing time is 10 s to 20 s.

10. A type of anti-caking coated sand, characterized in that, It was prepared according to the method for preparing anti-caking coated sand as described in any one of claims 1 to 9.

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