Shell reinforcement agents, their preparation methods and applications, shell

Abstract

This invention provides a shell reinforcing agent, comprising, by weight percentage, 55%–65% flocculent fibers and 35%–45% dispersant; wherein the flocculent fibers are prepared from raw materials including kaolin, alumina, quartz, dolomite, magnesium oxide, and zirconium silicate. When applied to shells, this shell reinforcing agent significantly improves the strength of the shell, effectively mitigating shell cracking during drying and dewaxing. Furthermore, the reinforcing agent fractures as the temperature decreases, significantly increasing the porosity within the shell. Its residual strength is lower than that of shells without the reinforcing agent, making shell removal or delamination easier, ultimately achieving a delamination effect.

Description

Technical Field

[0001] This invention relates to the field of investment casting, and in particular to a shell reinforcement agent, its preparation method and application, and the shell itself. Background Technology

[0002] With the development of industrial technology, the manufacturing industry has placed higher demands on the use of precision castings, resulting in increasingly complex product structures. Investment casting is characterized by its ability to produce castings with complex shapes and internal cavities containing deep holes and narrow grooves. In investment casting, shell preparation is a crucial step because it determines the dimensional accuracy and surface roughness of the casting, directly impacting manufacturing costs and production efficiency. Most shells suffer from defects such as low wet strength, long drying times, and severe breakage. Low wet strength leads to shell cracking during drying and dewaxing, while low high-temperature strength increases the rate of shell leakage, thus reducing casting quality.

[0003] To address the aforementioned issues, traditional methods have been used to prepare ethyl silicate shells for casting high-melting-point alloys such as steel and heat-resistant alloys. However, when casting light alloys, the shells often become difficult to remove due to their excessive strength, poor yielding properties, and high residual strength. This usually requires repeated acid soaking and shot blasting to resolve the problem.

[0004] Another traditional method involves increasing the number of refractory powder layers, i.e., increasing the shell thickness, to improve shell strength. When preparing large castings, this requires a significant number of shell layers. While increasing shell strength, it also increases cleaning workload, extends production cycles, and raises overall costs related to cleaning time, materials, and equipment power. Furthermore, the increased shell thickness leads to a greater amount of shell waste, causing severe environmental pollution. Summary of the Invention

[0005] Based on this, the present invention provides a shell reinforcing agent that can significantly improve the strength of the shell, achieve the purpose of shell layer reduction, reduce the difficulty of shell removal, and improve air permeability.

[0006] The present invention is achieved through the following technical solution.

[0007] A shell reinforcing agent, by weight percentage, comprises 55% to 65% flocculent fibers and 35% to 45% dispersant;

[0008] The flocculent fibers are made from the following raw materials: kaolin, alumina, quartz, dolomite, magnesium oxide and zirconium silicate.

[0009] In one embodiment, the flocculent fibers are made from raw materials comprising, by weight percentage:

[0010] It contains 8%–12% kaolin, 40%–50% alumina, 25%–35% quartz, 4%–6% dolomite, 4%–6% magnesium oxide, and 4%–6% zirconium silicate.

[0011] In one embodiment, the method for preparing the flocculent fibers includes the following steps:

[0012] The raw materials for mixing the flocculent fibers.

[0013] In one embodiment, the shell reinforcing agent comprises 58% to 62% flocculent fibers and 38% to 42% dispersant.

[0014] In one embodiment, the dispersant is kaolin.

[0015] The present invention also provides a method for preparing the shell reinforcing agent as described above, comprising the following steps:

[0016] The components of the mixed shell reinforcing agent.

[0017] The present invention also provides the application of the shell reinforcing agent as described above in the shell.

[0018] The present invention also provides a shell, the components of which include silica sol, mullite powder and the shell reinforcing agent as described above.

[0019] In one embodiment, the components, by weight, comprise 140 to 160 parts of silica sol, 220 to 230 parts of mullite powder, and 10 to 15 parts of the shell reinforcing agent.

[0020] In one embodiment, the size of the mollusks is 180 mesh to 220 mesh.

[0021] Compared with the prior art, the shell reinforcement agent of the present invention has the following beneficial effects:

[0022] This invention produces flocculent fibers from kaolin, alumina, quartz, dolomite, magnesium oxide, and zirconium silicate. These flocculent fibers are then compounded with a dispersant at specific weight percentages to obtain a shell reinforcing agent. This agent significantly improves the shell's strength, effectively mitigating shell cracking during drying and dewaxing. Furthermore, throughout the entire process from shell firing to high-temperature steel casting, the reinforcing agent maintains a network structure distributed across different parts of the shell, providing strong support. As the shell cools, the reinforcing agent fractures with decreasing temperature, significantly increasing the porosity of the shell. Its residual strength is lower than that of a shell without the reinforcing agent, making shell removal or demolding easier.

[0023] In summary, the shell reinforcement agent of the present invention enables the shell to stably support the strength during dewaxing and melting / casting, thereby achieving the purpose of reducing layers and improving permeability and reducing surface defects of castings. Furthermore, the shell reinforcement agent of the present invention can achieve the effects of saving overall costs and being environmentally friendly. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 The microstructure of the shell reinforcement agent provided by the present invention;

[0026] Figure 2 Shell strength test provided for this invention;

[0027] Figure 3 The shell permeability test provided for this invention;

[0028] Figure 4 The image shows a physical model of the shell provided for this invention. Detailed Implementation

[0029] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of the invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. In the description of the present invention, "a number" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0031] The terms "preferred," "more preferably," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0032] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0033] Unless otherwise specified, all percentages, fractions, and ratios are calculated based on the total mass of the compositions of the present invention. Unless otherwise specified, all masses of the listed ingredients are given as the content of the active substance, and therefore do not include solvents or byproducts that may be present in commercially available materials. The term "percentage by mass" herein may be expressed by the symbol "%". Unless otherwise specified, all molecular weights herein are weight-average molecular weights expressed in Daltons. Unless otherwise specified, all formulations and tests herein are conducted at 25°C. The terms "comprising," "including," "containing," "containing," "having," or other variations herein are intended to cover non-closed inclusions, and no distinction is made between these terms. The term "comprising" means additional steps and ingredients that may be added without affecting the final result. The compositions and methods / processes of the present invention comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. No distinction is made between the terms "efficacy," "performance," "effect," and "potency" herein.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0035] The present invention provides a shell reinforcing agent, wherein the shell reinforcing agent comprises 55% to 65% flocculent fibers and 35% to 45% dispersant by weight percentage;

[0036] The flocculent fibers are made from the following raw materials: kaolin, alumina, quartz, dolomite, magnesium oxide and zirconium silicate.

[0037] This invention uses kaolin, alumina, quartz, dolomite, magnesium oxide, and zirconium silicate as raw materials to prepare flocculent fibers. These flocculent fibers are then compounded with a dispersant in a specific ratio to obtain a shell reinforcing agent. This agent can be applied to shells to significantly improve their strength, specifically by enhancing both wet and high-temperature strength.

[0038] (1) Wet strength: When the shell is naturally dried under relatively constant conditions (humidity and temperature), the shell reinforcing agent added to the original shell process slurry is more evenly coated on the shell and can form a network structure, thereby significantly improving the wet strength of the shell. The shell with improved strength can effectively improve the shell cracking phenomenon that is prone to occur during drying and dewaxing.

[0039] (2) High temperature strength: The shell reinforcement provided by the present invention is a high temperature resistant material. During the entire process from the firing of the shell to the high temperature casting of molten steel, the shell reinforcement of the present invention can always be distributed in different parts of the shell in a mesh structure, forming a strong support effect. After the shell cools down, the shell reinforcement will break as the temperature drops, and the porosity inside the shell will increase significantly. Its residual strength is lower than that of the shell without the addition of the shell reinforcement, so it is easier to remove or peel off the shell.

[0040] In a specific example, the flocculent fibers, by weight percentage, are made from raw materials including:

[0041] It contains 8%–12% kaolin, 40%–50% alumina, 25%–35% quartz, 4%–6% dolomite, 4%–6% magnesium oxide, and 4%–6% zirconium silicate.

[0042] More preferably, the flocculent fibers are made from raw materials comprising, by weight:

[0043] 10% kaolin, 45% alumina, 30% quartz, 5% dolomite, 5% magnesium oxide and 5% zirconium silicate.

[0044] More specifically, the kaolin is V60 kaolin.

[0045] More specifically, the alumina is RC100 alumina.

[0046] In a specific example, the method for preparing flocculent fibers includes the following steps:

[0047] Raw materials for mixed flocculent fibers.

[0048] More specifically, the raw materials for the mixed flocculent fibers are dry-mixed.

[0049] In one specific example, the shell reinforcement component comprises 58% to 62% flocculent fibers and 38% to 42% dispersant by weight percentage.

[0050] More specifically, by weight percentage, the shell reinforcement comprises 60% flocculent fibers and 40% dispersant.

[0051] In a specific example, the dispersant is kaolin.

[0052] The present invention also provides a method for preparing the above-mentioned shell reinforcing agent, comprising the following steps:

[0053] Components of a hybrid shell reinforcing agent.

[0054] More specifically, the components of the mixed shell reinforcement are dry-mixed. The dry-mixed material is in the form of sand powder.

[0055] The present invention also provides the application of the above-mentioned shell reinforcing agent in the shell.

[0056] The shell reinforcing agent of this invention enables the shell to stably support its strength during dewaxing and melting / casting, thereby achieving the goal of reducing shell layers. The direct benefits of shell layer reduction include, but are not limited to, saving shell-making materials, easier shell removal, more thorough firing, better permeability, and reducing surface defects in castings. It also reduces cleaning workload, shortens the production cycle, and lowers the overall costs of casting cleaning, including labor, materials, and equipment power. Furthermore, the amount of shell waste emitted is significantly reduced, minimizing environmental pollution and promoting a greener, more environmentally friendly approach.

[0057] The present invention also provides a shell, the components of which include silica sol, mullite powder and the above-mentioned shell reinforcing agent.

[0058] Investment casting typically designs the weight, dimensions, yield, and assembly scheme of the casting based on the casting drawings. To ensure that the shell does not crack or leak molten steel during dewaxing and pouring, shells of varying thicknesses are required depending on the weight and structure of the casting. The strength of the shell is affected by the quality of silica sol, mullite, and mullite powder, and mullite and powder from different regions have different physicochemical properties, calcination processes, and dust content, resulting in significant strength fluctuations in the produced shell. This invention adds a certain amount of shell additive to the slurry, improving the strength of the shell, which can stably support the strength during dewaxing and molten steel pouring, thereby achieving a layer reduction effect.

[0059] In one specific example, the components, by weight, include 140 to 160 parts of silica sol, 220 to 230 parts of mullite powder, and 10 to 15 parts of the shell reinforcing agent.

[0060] In a specific example, the murex powder has a mesh size of 180 to 220 mesh. It is understood that in this invention, the murex powder size includes, but is not limited to, 180, 185, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 215, and 220 mesh. Preferably, the murex powder has a mesh size of 200.

[0061] The present invention also provides a method for preparing a shell, comprising the following steps:

[0062] The shell reinforcement agent is mixed with silica sol, mullite powder, mullite sand, zircon powder and zircon sand to form a slurry. Then the mold is degreased and degreased, then coated, sanded, dried, hardened, air-dried, and waxed before demolding.

[0063] Understandably, in order to improve the ability of the coating to wet the module surface, the oil on the module surface needs to be removed in advance. Therefore, before applying the coating, the module needs to be soaked in a neutral soap flake or an aqueous solution of surfactant to remove oil and grease.

[0064] Understandingly, applying the coating specifically refers to applying the coating. Before applying the coating, the coating should be stirred evenly and its viscosity or specific gravity adjusted. When applying the coating, immerse the mold in the coating and shake it left and right, up and down, to ensure the coating thoroughly wets the mold and evenly covers the mold surface. There should be no localized paint accumulation or insufficient material on the mold, and it should not contain air bubbles. To improve the coating quality, a brush can be used to apply the coating to the mold surface. After the coating is applied, sand can be sprinkled on.

[0065] As can be understood, sand application refers to attaching a layer of granular refractory material to the outside of the coating layer. The purpose is to rapidly thicken the shell, disperse stress that may occur in subsequent processes, and ensure good adhesion between the next coating layer and the previous one. Specific sand application processes include, but are not limited to, rain-type sand application and fluidized bed sand application.

[0066] Understandably, the purpose of drying is to transform the binder in the coating from a sol to a gel or jelly, thus binding the refractory particles together.

[0067] Understandably, drying alone is not enough to fully harden the mold shell; the coated and sanded mold shell must be immersed in a hardener for further hardening. Specifically, hardeners include, but are not limited to, ammonium chloride, polyaluminum chloride, and crystalline aluminum chloride.

[0068] Understandably, air drying is a drying step performed after hardening, aimed at removing residual hardener and further promoting penetration and hardening. The drying time and temperature depend on the type of hardener chosen and the hardening time; generally, the longer the hardening time, the longer the drying time.

[0069] Understandably, after the shell has completely hardened, the mold needs to be melted out of the shell. This process is called dewaxing, or wax melting and demolding. Dewaxing methods include, but are not limited to, hot water method and high-pressure steam method.

[0070] The following detailed description, in conjunction with specific embodiments, illustrates the shell reinforcement agent, shell, and preparation method of the present invention. Unless otherwise specified, all raw materials used in the following embodiments are commercially available products.

[0071] Example 1

[0072] This embodiment provides a shell reinforcing agent, a shell, and a method for preparing the same, as detailed below:

[0073] Step 1: Preparation of flocculent fibers

[0074] (1) Prepare the raw materials according to the following formula, by weight percentage:

[0075] 10% V60 kaolin, 45% RC100 alumina, 30% quartz, 5% dolomite, 5% magnesium oxide and 5% zirconium silicate.

[0076] (2) The above raw materials are placed in a mixing hopper for dry mixing to prepare flocculent fibers.

[0077] Step 2: Preparation of shell reinforcing agent

[0078] (1) Prepare the flocculent fiber obtained in step one and the dispersant (kaolin) at a mass ratio of 3:2, that is, the weight percentage of flocculent fiber is 60% and the weight percentage of dispersant is 40%.

[0079] (2) The prepared materials are dry-mixed to obtain a shell-forming agent in the form of a sand-like powder. The microstructure of the shell-forming agent is as follows: Figure 1 As shown, it exhibits good dispersibility and high suspension properties.

[0080] Step 3: Preparation of the shell

[0081] (1) Prepare the raw materials according to the following:

[0082] 9.35 kg (12 parts) of the shell reinforcing agent obtained in step two, 110 kg (141 parts) of silica sol and 175 kg (225 parts) of molybdenum powder.

[0083] (2) Mix into a slurry, then degrease the mold, apply coating, sprinkle sand, dry, harden, air dry, melt wax and demold.

[0084] Comparative Example 1

[0085] This comparative example provides a shell without adding a shell reinforcing agent. Except for not adding a shell reinforcing agent, the specific steps for preparing the shell in this comparative example are the same as the component formulation in Example 1.

[0086] Comparative Example 2

[0087] This comparative example provides a shell reinforcing agent, a shell, and a method for preparing the same, as detailed below:

[0088] Step 1: Preparation of flocculent fibers

[0089] (1) Prepare the raw materials according to the following formula, by weight percentage:

[0090] 7% V60 kaolin, 49% RC100 alumina, 35% quartz, 2% dolomite, 2% magnesium oxide and 5% zirconium silicate.

[0091] (2) The above raw materials are placed in a mixing hopper for dry mixing to prepare flocculent fibers.

[0092] Step 2: Preparation of shell reinforcing agent

[0093] (1) Prepare the flocculent fiber obtained in step one and the dispersant (kaolin) at a mass ratio of 3:2, that is, the weight percentage of flocculent fiber is 60% and the weight percentage of dispersant is 40%.

[0094] (2) The specific steps for preparing the shell reinforcement are the same as in Example 1.

[0095] Step 3: Preparation of the shell

[0096] The specific steps for preparing the shell are the same as those for the component formulation in Example 1.

[0097] Comparative Example 3

[0098] This comparative example provides a shell reinforcing agent, a shell, and a method for preparing the same, as detailed below:

[0099] Step 1: Preparation of flocculent fibers

[0100] (1) Prepare the raw materials according to the following formula, by weight percentage:

[0101] 13% V60 kaolin, 41% RC100 alumina, 25% quartz, 8% dolomite, 8% magnesium oxide and 5% zirconium silicate.

[0102] (2) The above raw materials are placed in a mixing hopper for dry mixing to prepare flocculent fibers.

[0103] Step 2: Preparation of shell reinforcing agent

[0104] (1) Prepare the flocculent fiber obtained in step one and the dispersant (kaolin) at a mass ratio of 3:2, that is, the weight percentage of flocculent fiber is 60% and the weight percentage of dispersant is 40%.

[0105] (2) The specific steps for preparing the shell reinforcement are the same as in Example 1.

[0106] Step 3: Preparation of the shell

[0107] The specific steps for preparing the shell are the same as those for the component formulation in Example 1.

[0108] Comparative Example 4

[0109] This comparative example provides a shell reinforcing agent, a shell, and a method for preparing the same, as detailed below:

[0110] Step 1: Preparation of flocculent fibers

[0111] (1) Prepare the raw materials according to the following formula, by weight percentage:

[0112] 10% V60 kaolin, 45% RC100 alumina, 30% quartz, 5% dolomite, 5% magnesium oxide and 5% zirconium silicate.

[0113] (2) The above raw materials are placed in a mixing hopper for dry mixing to prepare flocculent fibers.

[0114] Step 2: Preparation of shell reinforcing agent

[0115] (1) Prepare the flocculent fiber obtained in step one and the dispersant (kaolin) at a mass ratio of 27:23, that is, the weight percentage of flocculent fiber is 54% and the weight percentage of dispersant is 46%.

[0116] (2) The specific steps for preparing the shell reinforcement are the same as in Example 1.

[0117] Step 3: Preparation of the shell

[0118] The specific steps for preparing the shell are the same as those for the component formulation in Example 1.

[0119] Comparative Example 5

[0120] This comparative example provides a shell reinforcing agent, a shell, and a method for preparing the same, as detailed below:

[0121] Step 1: Preparation of flocculent fibers

[0122] (1) Prepare the raw materials according to the following formula, by weight percentage:

[0123] 10% V60 kaolin, 45% RC100 alumina, 30% quartz, 5% dolomite, 5% magnesium oxide and 5% zirconium silicate.

[0124] (2) The above raw materials are placed in a mixing hopper for dry mixing to prepare flocculent fibers.

[0125] Step 2: Preparation of shell reinforcing agent

[0126] (1) Prepare the flocculent fiber obtained in step one and the dispersant (kaolin) at a mass ratio of 33:17, that is, the weight percentage of flocculent fiber is 66% and the weight percentage of dispersant is 34%.

[0127] (2) The specific steps for preparing the shell reinforcement are the same as in Example 1.

[0128] Step 3: Preparation of the shell

[0129] The specific steps for preparing the shell are the same as those for the component formulation in Example 1.

[0130] The actual images of the shells prepared in Example 1 and Comparative Examples 1-5 are shown below. Figure 4 As shown, the results of the comparative test of the casting products show that the weight of the shell in Example 1 is reduced by about 20% compared with that in Comparative Example 1, which makes the shell strength guaranteed while the shell removal after the layer reduction is relatively easier.

[0131] The shells prepared in Example 1 and Comparative Examples 1-5 were subjected to wet strength and firing strength tests. The specific methods for testing wet strength and firing strength are as follows:

[0132] The high-temperature bending strength tester for investment casting shells was used, and the testing method followed JB / T 2980.2-1999, "Test Method for High-Temperature Bending Strength of Investment Casting Shells." Figure 2 As shown.

[0133] The test results of wet strength and sintering strength are shown in Table 2. The comparison between the results of Example 1 and Comparative Example 1 shows that the flexural strength of the shell after adding shell reinforcing agent is significantly improved, and the sintering strength of the shell after delamination is not much different from that of the shell in Comparative Example 1 without delamination.

[0134] Table 2

[0135]

[0136]

[0137] The air permeability of the shells prepared in Example 1 and Comparative Examples 1-5 was tested. The specific methods for testing air permeability are as follows:

[0138] The high-temperature air permeability tester for shells was used, and the test method was in accordance with JB / T 4153-1999, "Test Method for High-Temperature Air Permeability of Shells". Figure 3 As shown.

[0139] The results of the air permeability test are shown in Table 3. The test data in Table 3 show that the air permeability of the shells of Comparative Example 1 and Example 1 is almost the same when they have 5.5 layers. However, the air permeability of the 4.5-layer shell prepared in Example 1 is significantly better than that of the 5.5-layer shell of Comparative Example 1.

[0140] Table 3

[0141]

[0142] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0143] The embodiments described above are merely illustrative of several implementations of the present invention, designed to facilitate a detailed understanding of the technical solutions of the present invention, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided by the present invention through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this invention patent should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A shell enhancer characterized in that, The component of the shell reinforcing agent comprises 55% to 65% of flocculent fiber and 35% to 45% of dispersant by weight percentage; The flocculent fiber is made of raw materials comprising kaolin, alumina, quartz, dolomite, magnesia and zirconium silicate; The alumina is RC100 alumina.

2. The shell reinforcement of claim 1, wherein The flocculent fiber is made of raw materials comprising: 8% to 12% of kaolin, 40% to 50% of alumina, 25% to 35% of quartz, 4% to 6% of dolomite, 4% to 6% of magnesia and 4% to 6% of zirconium silicate by weight percentage.

3. The shell reinforcement of claim 1, wherein The preparation method of the flocculent fiber comprises the following steps: Mixing the raw materials of the flocculent fiber.

4. The shell reinforcement of claim 1, wherein The component of the shell reinforcing agent comprises 58% to 62% of flocculent fiber and 38% to 42% of dispersant.

5. The shell reinforcing agent according to any one of claims 1 to 4, characterized in that, The dispersant is kaolin.

6. A process for the preparation of a shell reinforcer according to any one of claims 1 to 5, characterized in that Comprising the following steps: Mixing the components of the shell reinforcing agent.

7. The use of the shell reinforcing agent of any one of claims 1 to 5 in a shell.

8. A shell characterized by, The components comprise silica sol, mullite powder and the shell reinforcing agent of any one of claims 1 to 5.

9. The mold shell of claim 8, wherein, The components comprise 140 to 160 parts of silica sol, 220 to 230 parts of mullite powder and 10 to 15 parts of the shell reinforcing agent by weight.

10. A shell according to any one of claims 8 to 9, characterised in that The size of the mullite powder is 180 to 220 mesh.

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