Lost foam water-based hollow shell vibration coating, preparation method and mold making method

Abstract

The present invention discloses a lost foam water-based hollow shell vibration coating, a preparation method and a mold making method, which relate to the technical field of lost foam casting. By weight, it includes 55-60 parts of bauxite, 6-10 parts of quartz powder, 8-8.5 parts of liquid industrial phosphoric acid, 3-3.5 parts of aluminum dihydrogen phosphate, 7-9 parts of tapioca starch, 4-6 parts of corn starch, 4-6 parts of latex powder, 2-4 parts of silicate, and 3-4 parts of wood fiber. The liquid industrial phosphoric acid is an aqueous phosphoric acid solution with a phosphoric acid mass content of 80-85%. After the liquid industrial phosphoric acid is stirred with the quartz powder, it is dried and then made into powder. The preparation method of the lost foam water-based hollow shell vibration coating is used to prepare the aforementioned lost foam water-based hollow shell vibration coating. Compared with the prior art, the dry powder coating made by the present invention can gasify the white mold before pouring and form a tempered mold shell, which has the properties of compression resistance, earthquake resistance and crack resistance, and helps to improve the performance and precision of the lost foam castings poured out.

Description

Technical Field

[0001] The present invention relates to the technical field of lost foam casting, and specifically relates to a water-based hollow shell vibration coating for lost foam casting, a preparation method and a mold making method. Background Art

[0002] When using lost foam casting, it is cast while vibrating, and high requirements are placed on the performance of the lost foam coating. Currently, the commonly used coatings for lost foam casting are divided into two types. One is dry powder coating. For example, a coating for lost foam casting disclosed in Chinese Patent Publication No. CN106216595A includes the following components in parts by weight: 55-65 parts of bauxite, 25-35 parts of quartz powder, 1.0-1.5 parts of plant gum powder, 0.3-0.6 parts of CMC, 0.4-0.8 parts of yellow dextrin, 1.2-1.6 parts of organic bentonite, 0.3-0.7 parts of wood fiber, 1.2-1.7 parts of polyurethane resin, 1.5-2.5 parts of modified phenolic resin, and 3.0-4.0 parts of wollastonite. This solution has the advantages of being able to be applied to the foam model by adding water and stirring, simple operation, convenient transportation, and long storage time. However, it also has certain disadvantages. Since this solution uses an organic binder, it can only be used at room temperature and will fail and cannot be formed during high-temperature roasting. Therefore, after the mold is formed, it cannot be roasted into a hollow shell, so the foam pattern cannot be removed first and can only be cast with the foam pattern. During casting, the free carbon generated by the gasification of the foam model will penetrate into the molten steel to form segregation of the low-carbon alloy steel components in the casting, and the uneven distribution of ferrite and pearlite in the matrix is an inherent defect that cannot be remedied by heat treatment, seriously affecting the mechanical properties and quality of the product. Therefore, the existing dry powder coatings are only suitable for the production of ordinary gray iron castings and castings with lower performance requirements, and cannot meet the needs of the production of high-end castings with strict requirements; the other is silica sol coating. For example, the lost foam mold shell and its preparation method disclosed in Chinese Patent Publication No. CN110479957A, the preparation method includes (1) making a pattern (2) preparing the coating: mixing moler powder, silica sol and distilled water in a weight ratio of (2-4):(1-3):(4-6); (3) making the mold shell: coating the coating on the EPS foam pattern to make the mold shell, and drying the mold shell; (4) low-temperature softening (5) high-temperature gasification roasting: completely gasifying the EPS foam pattern at a temperature of 1000-1200°C to form a carbon-free hollow shell, and then cooling for standby. This method gasifies the white film (commonly known as the foam pattern) before pouring, overcoming the free carbon increase phenomenon of lost foam. However, due to the use of silica sol, it needs to be prepared and used immediately, so the operation and preparation process are troublesome and the production cost is relatively high. Summary of the Invention

[0003] The technical problems to be solved by the present invention are: to provide a dry powder type lost foam water-based hollow shell vibration coating, a preparation method of the dry powder type lost foam water-based hollow shell vibration coating, and a mold making method of a lost foam using the dry powder type coating.

[0004] To solve the above technical problems, a lost foam water-based hollow shell vibration coating includes, by weight, 55 - 60 parts of bauxite, 6 - 10 parts of quartz powder, 8 - 8.5 parts of liquid industrial phosphoric acid, 3 - 3.5 parts of aluminum dihydrogen phosphate, 7 - 9 parts of cassava starch, 4 - 6 parts of corn starch, 4 - 6 parts of latex powder, 2 - 4 parts of silicate, 3 - 4 parts of wood fiber. The liquid industrial phosphoric acid is an aqueous phosphoric acid solution with a phosphoric acid mass content of 80 - 85%. After the liquid industrial phosphoric acid and the quartz powder are stirred, they are dried and then made into powder.

[0005] Preferably, it includes, by weight, 60 parts of bauxite, 6 parts of quartz powder, 8.5 parts of liquid industrial phosphoric acid, 3 parts of aluminum dihydrogen phosphate, 8 parts of cassava starch, 5 parts of corn starch, 5 parts of latex powder, 3 parts of silicate, 3 parts of wood fiber. The liquid industrial phosphoric acid is an aqueous phosphoric acid solution with a phosphoric acid mass content of 80%.

[0006] Preferably, the particle size of the quartz powder is 200 - 210 mesh.

[0007] Preferably, the silicate is sodium silicate.

[0008] A preparation method of a lost foam water-based hollow shell vibration coating includes the following steps:

[0009] S1: Stir the liquid industrial phosphoric acid and the quartz powder, and then dry to obtain a mixture;

[0010] S2: Re - pulverize the mixture into powder with a particle size of 150 - 250 mesh;

[0011] S3: Put the powder made in S2 and other formulations into a dry powder mixer and stir evenly to obtain the lost foam water-based hollow shell vibration coating.

[0012] Preferably, the stirring time in step S3 is 1 - 3 hours.

[0013] A mold making method of a lost foam, characterized by including the following steps:

[0014] U1: By weight, add 50 parts of water to a liquid mixer and start stirring. After adding 100 parts of the lost foam water-based hollow shell vibration coating to the liquid mixer, stir for another 150 minutes;

[0015] U2: Use the stirred mixture to coat and dry the foam model of the casting, and repeat the operation of coating and drying multiple times until the coating thickness of the coating reaches 3 - 6 mm;

[0016] U3: Heat the coated foam model to 80 °C within 1 h, then keep it at this temperature for 1 h. Next, heat it to 600 °C within 2 h and keep it at this temperature for 1 h. Finally, heat it to 700 °C within 0.5 h, keep it at this temperature for 1 h, then stop heating and cool it in the furnace to 200 °C. After taking it out of the furnace and cooling it to room temperature, the required empty shell for casting is formed.

[0017] The beneficial effects of the present invention are as follows: Compared with the prior art, the lost foam water-based empty shell vibration coating provided by the present invention can realize the casting of the empty shell. Under normal conditions, it is in powder form. When in use, it only needs to be mixed with water in a certain proportion to coat the foam model. Due to the use of a binder combining organic materials and inorganic materials, during the initial coating, the organic binder and the inorganic binder work together, making the coating easy to coat on the foam model and easy to maintain the shape. As the roasting progresses, the organic binder burns to form voids, improving the air permeability of the mold. The inorganic binder can be roasted at 700 °C and fuse the aggregate tightly to form a mold shell. It is not only convenient to use but also conducive to storage and transportation. The present invention can gasify the white mold before casting and form a tempered mold shell, which has the properties of compression resistance, earthquake resistance, and crack resistance, and helps to improve the performance and accuracy of the cast lost foam castings. Description of the Drawings

[0018] Figure 1 It is the mold shell after roasting the coating prepared in Example 1 of the present invention;

[0019] Figure 2 It is the mold shell of the coating prepared in Example 1 of the present invention buried in the sand box before casting;

[0020] Figure 3 It is the casting whose shell is being removed after the casting is completed and the box is opened for the coating prepared in Example 1 of the present invention;

[0021] Figure 4 It is the casting after shot blasting of the coating prepared in Example 1 of the present invention. Detailed Embodiments

[0022] For the instruments, reagents, materials, etc. involved in the following embodiments, unless otherwise specified, they are all conventional instruments, reagents, materials, etc. existing in the prior art and can be obtained through regular commercial channels. For the experimental methods, detection methods, etc. involved in the following embodiments, unless otherwise specified, they are all conventional experimental methods, detection methods, etc. existing in the prior art.

[0023] The lost foam water-based empty shell vibration coating is prepared by the following steps:

[0024] S1: Stir liquid industrial phosphoric acid and quartz powder, and then dry to obtain a mixture;

[0025] S2: Redisperse the mixture into powder with a particle size of 150 - 250 mesh;

[0026] S3: Put the powder made in S2 and other formulations into a dry powder mixer and stir for 1 - 3 hours until homogeneous, then the lost foam water - based hollow shell vibration coating is obtained.

[0027] The lost foam water - based hollow shell vibration coating provided by the present invention is applied by the following steps:

[0028] U1: By weight, add 50 parts of water to a liquid mixer and start stirring. After adding 100 parts of the lost foam water - based hollow shell vibration coating to the liquid mixer, stir for another 150 minutes. After stirring is completed, take part of the sample to measure the suspension property;

[0029] U2: Use the stirred mixture to coat and dry the foam model of the casting. Repeat the operations of coating and drying multiple times until the thickness of the coating reaches the required thickness. The required thickness of the coating is determined according to the size of the casting, generally 3 - 6 mm. The coating thickness in the following examples and control examples is 4 mm;

[0030] U3: Heat the coated foam model to 80 °C within 1 h and keep it warm for 1 h, then heat it to 600 °C within 2 h and keep it warm for 1 h, and finally heat it to 700 °C within 0.5 h and keep it warm for 1 h, then stop heating. After cooling, the required hollow shell for casting is formed.

[0031] Example 1

[0032] Example 1 prepares the lost foam water - based hollow shell vibration coating using the following formulation:

[0033] By weight: 60 parts of bauxite, 6 parts of quartz powder, 8.5 parts of liquid industrial phosphoric acid, 3 parts of aluminum dihydrogen phosphate, 8 parts of tapioca starch, 5 parts of corn starch, 5 parts of latex powder, 3 parts of sodium silicate, 3 parts of wood fiber.

[0034] Among them, the liquid industrial phosphoric acid is an aqueous phosphoric acid solution with a phosphoric acid mass content of 80%, and the particle size of the quartz powder is 200 - 210 mesh.

[0035] The process of casting the casting using the coating of this example is shown in Figures 1-4 .

[0036] Example 2

[0037] The difference between Example 2 and Example 1 is that the weight parts of each component in the formulation are different, and others are the same. The lost foam water - based hollow shell vibration coating is prepared using the following formulation:

[0038] By weight parts: 55 parts of bauxite, 10 parts of quartz powder, 8 parts of liquid industrial phosphoric acid, 3.5 parts of aluminum dihydrogen phosphate, 7 parts of cassava starch, 4 parts of corn starch, 4 parts of latex powder, 2 parts of potassium silicate, 3 parts of wood fiber.

[0039] Example 3

[0040] The difference between Example 3 and Example 1 lies in the different weight parts of each component in the formula, and the others are the same. The lost foam water-based hollow shell vibration coating is prepared with the following formula:

[0041] By weight parts: 60 parts of bauxite, 6 parts of quartz powder, 8.5 parts of liquid industrial phosphoric acid, 3.5 parts of aluminum dihydrogen phosphate, 9 parts of cassava starch, 6 parts of corn starch, 6 parts of latex powder, 4 parts of potassium silicate, 4 parts of wood fiber.

[0042] Example 4

[0043] The difference between Example 4 and Example 1 lies in the different weight parts of each component in the formula, and the others are the same. The lost foam water-based hollow shell vibration coating is prepared with the following formula:

[0044] By weight parts: 60 parts of bauxite, 6 parts of quartz powder, 8.5 parts of liquid industrial phosphoric acid, 3 parts of aluminum dihydrogen phosphate, 8 parts of cassava starch, 5 parts of corn starch, 5 parts of latex powder, 4 parts of sodium silicate, 3 parts of wood fiber.

[0045] Control Example 1

[0046] The difference between Control Example 1 and Example 1 is that solid phosphoric acid is used instead of liquid industrial phosphoric acid in the formula, and the preparation steps are different, and the others are the same. The lost foam water-based hollow shell vibration coating is prepared with the following formula:

[0047] By weight parts: 60 parts of bauxite, 6 parts of quartz powder, 7 parts of solid phosphoric acid, 3 parts of aluminum dihydrogen phosphate, 8 parts of cassava starch, 5 parts of corn starch, 5 parts of latex powder, 3 parts of sodium silicate, 3 parts of wood fiber.

[0048] The steps for preparing the coating in Control Example 1 are: putting each component in the formula into a dry powder mixer and stirring for 1 - 3 hours until uniform.

[0049] Control Example 2

[0050] The difference between Control Example 2 and Example 1 is that the particle size of the quartz powder used is 100 mesh, and the others are the same.

[0051] Control Example 3

[0052] The difference between Control Example 3 and Example 1 is that the particle size of the quartz powder used is 300 mesh, and the others are the same.

[0053] Control Example 4

[0054] The difference between Comparative Example 4 and Example 1 is that sodium silicate is not added to the formulation, and the others are the same. The lost foam water-based hollow shell vibration coating is prepared using the following formulation:

[0055] By weight: 60 parts of bauxite, 6 parts of quartz powder, 8.5 parts of liquid industrial phosphoric acid, 3 parts of aluminum dihydrogen phosphate, 8 parts of tapioca starch, 5 parts of corn starch, 5 parts of latex powder, and 3 parts of wood fiber.

[0056] Comparative Example 5

[0057] The difference between Comparative Example 5 and Example 1 is that tapioca starch and corn starch are not added to the formulation, and the others are the same. The lost foam water-based hollow shell vibration coating is prepared using the following formulation:

[0058] By weight: 60 parts of bauxite, 6 parts of quartz powder, 8.5 parts of liquid industrial phosphoric acid, 3 parts of aluminum dihydrogen phosphate, 5 parts of latex powder, 3 parts of sodium silicate, and 3 parts of wood fiber.

[0059] The properties of the coatings prepared in each example and comparative example are shown in Table 1.

[0060] Table 1 Properties of the coatings prepared in each example and comparative example

[0061]

[0062]

[0063] Bauxite and quartz powder are used as refractory aggregates to support the entire cavity during shell burning, block the molten metal liquid during box embedding and pouring, prevent it from leaking out and contacting with the molding sand, and ensure the smoothness of the casting surface.

[0064] The present invention uses quartz powder with a mesh size of 200 - 210. Before preparing the coating, the liquid industrial phosphoric acid and quartz powder are mixed and dried first, and then crushed into powder with a mesh size of 150 - 250. This processing method not only facilitates the addition of liquid industrial phosphoric acid to the coating, but also enables the quartz powder to be uniformly coated with phosphoric acid, making the phosphoric acid have better fluidity, facilitating the dispersion of phosphoric acid, enabling the phosphoric acid to better contact with the aggregate, and making the phosphoric acid play a better binding role during the sintering process. The selection of quartz powder with a mesh size of 200 - 210 is because quartz powder with too large a particle size is likely to damage the phosphoric acid coated on the outside of the quartz powder during re-crushing, reducing the binding effect of phosphoric acid; quartz powder with too small a particle size is difficult to completely coat with phosphoric acid due to its larger specific surface area, and multiple quartz powder particles are likely to agglomerate during the crushing process.

[0065] Phosphoric acid and aluminum dihydrogen phosphate jointly play a role in strengthening the impact resistance of the coating during high-temperature pouring, improving the mechanical properties of the shell mold, helping to stabilize the shell mold during the pouring process, and improving the quality of the poured finished product.

[0066] Cassava starch, corn starch and latex powder act as thickeners and suspending and dispersing agents for aggregates when the coating is in a liquid state at room temperature, making it easier to apply the coating to the foam model; after drying, they ensure the room-temperature strength of the coating, and burn to create voids during the sintering process, improving the air permeability of the mold shell.

[0067] The function of wood fiber is to increase strength during the process of drying moisture at 80°C to prevent cracking.

[0068] Sodium silicate, as an inorganic binder, is evenly distributed in the aggregates after the temperature rise and melting phase change of sodium silicate between 200°C and 600°C during the roasting process. Part of the phosphoric acid reacts with sodium silicate to form a silicate cementitious material. The acidic environment provided by aluminum dihydrogen phosphate can promote the reaction between phosphoric acid and sodium silicate. After high-temperature sintering, part of the aluminum dihydrogen phosphate forms a meta-aluminum phosphate glass body. The silicate cementitious material and the meta-aluminum phosphate glass body are mutually melted and joined in the aggregates, and penetrate into the voids left after the high-temperature burnout of the room-temperature binder, tightly bonding all the refractory materials together to prevent the collapse of the coating after the carbonization and failure of the organic binder material.

[0069] Heating from 600°C to 700°C and then holding the temperature can further promote the melting and flow of the high-temperature binder, further enabling the completely burned-out organic binder material after carbonization to create tiny pores, improving the air permeability of the mold. After the holding ends, the furnace is slowly cooled to 200°C to prevent the mold shell from cracking due to sudden cooling.

[0070] Compared with the prior art, the lost foam water-based hollow shell vibration coating provided by the present invention can achieve hollow shell casting. It is in a dry powder state at normal temperature and only needs to be mixed with water in a certain proportion during use to apply it to the foam model. Since inorganic materials are used as binders, it can be roasted at 700°C to closely fuse the aggregates to form a mold shell. It is not only convenient to use but also conducive to storage and transportation. The present invention can gasify the white mold before casting and form a tempered mold shell, which has the properties of compression resistance, earthquake resistance and crack resistance, and helps to improve the performance and accuracy of the cast lost foam casting.

[0071] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A lost foam water-based hollow shell vibration coating, characterized in that: It includes, by weight parts, 55 - 60 parts of bauxite, 6 - 10 parts of quartz powder, 8 - 8.5 parts of liquid industrial phosphoric acid, 3 - 3.5 parts of aluminum dihydrogen phosphate, 7 - 9 parts of tapioca starch, 4 - 6 parts of corn starch, 4 - 6 parts of latex powder, 2 - 4 parts of silicate, 3 - 4 parts of wood fiber. The liquid industrial phosphoric acid is an aqueous phosphoric acid solution with a phosphoric acid mass content of 80 - 85%. After the liquid industrial phosphoric acid is stirred with the quartz powder, it is dried and then made into powder. The particle size of the quartz powder is 200 - 210 mesh.

2. The lost foam water-based hollow shell vibration coating according to claim 1, characterized in that: It includes, by weight parts, 60 parts of bauxite, 6 parts of quartz powder, 8.5 parts of liquid industrial phosphoric acid, 3 parts of aluminum dihydrogen phosphate, 8 parts of tapioca starch, 5 parts of corn starch, 5 parts of latex powder, 3 parts of silicate, 3 parts of wood fiber. The liquid industrial phosphoric acid is an aqueous phosphoric acid solution with a phosphoric acid mass content of 80%.

3. The lost foam water-based hollow shell vibration coating according to any one of claims 1-2, characterized in that: The silicate described is sodium silicate.

4. A preparation method of a lost foam water-based hollow shell vibration coating as claimed in any one of claims 1-2, characterized in that: It includes the following steps: S1: After the liquid industrial phosphoric acid is stirred with the quartz powder, it is dried to obtain a mixture. S2: The mixture is reground into powder with a particle size of 150 - 250 mesh. S3: The powder made in S2 and other formulations are put into a dry powder mixer and stirred evenly to obtain the lost foam water - based hollow shell vibration coating.

5. The preparation method of the lost foam water-based hollow shell vibration coating according to claim 4, characterized in that: The stirring time in step S3 is 1 - 3 hours.

6. A method for manufacturing a lost foam pattern, characterized in that: Using the lost foam water - based hollow shell vibration coating described in any one of claims 1 - 2, it includes the following steps: U1: By weight parts, add 50 parts of water to a liquid mixer and start stirring. After adding 100 parts of the lost foam water - based hollow shell vibration coating to the liquid mixer, stir for another 150 minutes. U2: Use the stirred mixture to coat and dry the foam model of the casting, and repeat the operations of coating and drying multiple times until the coating thickness of the coating reaches 3 - 6 mm. U3: Heat the coated foam model to 80°C within 1 h and keep it warm for 1 h, then heat it to 600°C within 2 h and keep it warm for 1 h, and finally heat it to 700°C within 0.5 h and keep it warm for 1 h, then stop heating and cool it in the furnace to 200°C. After taking it out of the furnace and cooling it to room temperature, the required hollow shell for casting is formed.

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