An alloy shell, a method for producing an alloy shell, and use of an alloy shell

Abstract

The present application relates to the field of alloy investment casting, in particular, relates to an alloy shell, a preparation method of the alloy shell and the use of the alloy shell. The surface layer coating of the alloy shell comprises a first refractory material, a first binder and a pH regulator, the first refractory material comprises calcium zirconate-yttria composite and calcium tungstate; the weight ratio of the first refractory material to the first binder is 1.5-2:1; the pH value of the surface layer coating is 4-6. Thus, the problem of affecting the quality of alloy castings formed after the molten alloy is cast by the existing alloy shell is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of alloy investment casting, in particular, to an alloy shell, a preparation method of the alloy shell and an application of the alloy shell. BACKGROUND

[0002] Titanium alloy castings have excellent characteristics such as light weight, high strength, high temperature resistance and corrosion resistance, and are widely used in the fields of aviation, aerospace, navigation and the like. With the design of the structure and function of key components in the above fields tending to be more and more integrated and lightweight, in order to meet the design requirements, the precision investment casting of titanium alloy castings with no machining allowance and complex inner cavity structure becomes the preferred process method.

[0003] In the preparation process of the titanium alloy precision investment casting shell, the cost of the shell surface layer is relatively high, which accounts for more than 60% of the total cost. At present, yttria is usually used as the refractory aggregate of the surface layer coating in the titanium alloy investment casting. The use of yttria as the surface layer refractory material can obtain a good surface quality of the castings, but is limited by the price factor and the production process, resulting in high production cost of the titanium alloy castings.

[0004] Calcium zirconate, as a high-temperature refractory material with good inertness and low chemical activity, can be prepared into a precision investment casting shell surface layer coating with various binders, and can stably exist, and is cheaper than yttria and zirconia. However, the use of calcium zirconate as the shell surface layer refractory material will produce a thick pollution layer with molten titanium, and the process parameters such as the powder-liquid ratio, the additive proportion, the subsequent drying process and the sintering temperature are required to be high.

[0005] Therefore, in order to realize the low-cost shell preparation suitable for the titanium alloy investment casting, it is necessary to study the preparation process of the calcium zirconate shell, realize the high-quality and low-cost precision investment casting shell preparation of the titanium alloy, and thus reduce the production cost of the titanium alloy castings. SUMMARY

[0006] In order to solve the problem that the existing alloy shell affects the quality of the alloy castings formed after the molten alloy is poured, the present application provides an alloy shell, a preparation method of the alloy shell and an application of the alloy shell.

[0007] In a first aspect, the present application provides an alloy shell, comprising:

[0008] The surface layer coating of the alloy shell comprises a first refractory material, a first binder and a pH adjuster, the first refractory material comprises a calcium zirconate-yttria compound and calcium tungstate, the weight ratio of the first refractory material to the first binder is 1.5-2:1, and the pH value of the surface layer coating is 4-6.

[0009] Preferably, the first refractory material accounts for 62-66% by weight, and the first binder accounts for 34-38% by weight; in the first refractory material, the calcium zirconate-yttria compound accounts for 99% or more by weight, and the calcium tungstate accounts for 1% or less by weight.

[0010] Preferably, the first binder comprises zirconium acetate; and the pH regulator comprises ammonium metatungstate.

[0011] Preferably, in the calcium zirconate-yttria compound, the calcium zirconate accounts for 55-65% by weight, and the yttria accounts for 35-45% by weight.

[0012] The calcium zirconate-yttria compound has a particle size of 300-345 mesh, and the calcium tungstate has a particle size of 50-100 nm.

[0013] Preferably, the face coating further comprises a first wetting agent and a first defoaming agent, each accounting for 0.3% or less by weight, and a second refractory material having a particle size of 35-50 mesh, the second refractory material comprising calcium zirconate.

[0014] Preferably, the back coating of the alloy shell comprises a third refractory material and a second binder, the third refractory material accounting for 35-45% by weight, and the second binder accounting for 55-65% by weight, the third refractory material comprising bauxite having a particle size of 260-300 mesh, and the second binder comprising silica sol.

[0015] Preferably, the back coating further comprises a second wetting agent and a second defoaming agent, each accounting for 0.3% or less by weight, and a fourth refractory material having a particle size of 35-50 mesh, the fourth refractory material comprising bauxite.

[0016] Preferably, the wetting agent comprises JFC (polyoxyethylene alkyl phenol ether).

[0017] Preferably, the defoaming agent comprises an alcohol-based defoaming agent, the alcohol-based defoaming agent comprising n-octanol, n-pentanol or isopropyl alcohol.

[0018] In a second aspect, the present application provides a method for preparing an alloy shell as described above, comprising the following steps:

[0019] Preparation of the shell face layer: blending the first refractory material with the first binder to obtain a first mixed coating, adjusting the pH value of the first mixed coating to 4-6 using a pH regulator, adding a first wetting agent and a first defoaming agent to the first mixed coating after adjusting the pH value to obtain a second mixed coating; after applying the second mixed coating on the wax mold face layer, sprinkling a second refractory material, drying, and repeating the above steps 2-4 times.

[0020] Preparation of the shell reinforcing layer: a third mixed coating is prepared by blending a third refractory material, a second binder, a second wetting agent and a second defoaming agent; after the third mixed coating is applied on the back layer of the wax mold, a fourth refractory material is sprinkled and dried, and the above steps are repeated 6-8 times;

[0021] Dewaxing of the shell: dewaxing is performed at a temperature of 180-220℃;

[0022] Firing of the shell: the heating rate is controlled at 100-140℃ / h, and the temperature is raised to 400-500℃ and 700-800℃ respectively for segmented holding, the holding time is 1-2h, the temperature is raised to 1000-1100℃, and the holding time is 2-3h, and the furnace is discharged when the temperature is less than or equal to 200℃.

[0023] Preferably, the drying time is 14-16h, the temperature is 20-40℃, and the humidity is 40%-50%.

[0024] In a third aspect, the application provides a use of the alloy shell as described above for preparing a titanium alloy casting.

[0025] To solve the problem that the existing alloy shell affects the quality of the alloy casting formed after the molten alloy is poured, the application has the following advantages:

[0026] The application of ammonium metatungstate can reduce the use of yttria to the greatest extent, and thus the application can select a zirconium calcium-yttria composite refractory material with a suitable content of zirconium calcium and yttria. It can be seen that the application of ammonium metatungstate can not only adjust the pH value of the shell coating, but also reduce the interface reaction between the shell and the titanium alloy casting and reduce the use of yttria. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The figure shows the metallographic structure of the interface pollution layer of Example 1;

[0028] Figure 2 The figure shows the metallographic structure of the interface pollution layer of Example 2;

[0029] Figure 3 The figure shows the metallographic structure of the interface pollution layer of Example 3;

[0030] Figure 4 The figure shows the metallographic structure of the interface pollution layer of Comparative Example 1. DETAILED DESCRIPTION

[0031] The present disclosure will now be discussed with reference to a number of exemplary embodiments. It is to be appreciated that these embodiments are discussed solely for the purpose of enabling those with ordinary skill in the art to better understand and therefore implement the present disclosure, and are not intended to suggest any limitation as to the scope of the present disclosure.

[0032] As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or any other variation thereof, are to be construed as "including but not limited to." The term "based on" is to be construed as "based at least in part on." The terms "one embodiment" and "an embodiment" are to be construed as "at least one embodiment." The term "another embodiment" is to be construed as "at least one other embodiment." The terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "vertical," "horizontal," "lateral," "longitudinal," and similar terms are used for clarity in describing the figures and are not to be construed as limiting the present disclosure to only the positions as shown. These terms primarily serve to more particularly describe the orientations and positional relationships between various elements as shown in the figures. The terms are not to be construed as limiting the devices, elements or components to the particular orientation or configuration shown, but rather are used herein for the purpose of clarity in the description of particular embodiments. Also, the terms "mount," "set," "provided with," "connected," "linked" should be given broadest interpretation. For example, it can be fixed connection, detachable connection, or integral structure; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through intermediate medium; or it can be internal connection between two devices, elements or components. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. In addition, the terms "first," "second," and the like are primarily used to distinguish different devices, elements or components (the specific types and configurations can be the same or different), and are not intended to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise stated, the meaning of "a plurality" is two or more.

[0033] Currently, calcium zirconate and yttrium oxide are compounded as refractory materials for application in the field of titanium alloy investment casting, but the inventors have found in the research process that improving the coating preparation and sintering process after compounding calcium zirconate and yttrium oxide can improve the coating hanging performance and shell quality, thereby further reducing the cost of titanium alloy investment casting while maintaining a low pollution layer thickness.

[0034] Compared with the existing calcium zirconate-yttria composite refractory material, the shell surface layer coating of the present application has better performance through different refractory material compositions, powder-liquid ratios, drying processes and sintering processes. Since the calcium zirconate-yttria composite refractory material can only exist stably in a weak acidic environment, the suspension stability and coating performance of the coating are difficult to control, and sedimentation is prone to occur, which makes it difficult to ensure the quality of the shell surface layer. At the same time, the physical and chemical reactions in the drying and sintering processes also make it difficult to ensure the strength and yield of the shell as a whole. Since the calcium zirconate-yttria composite refractory material has high requirements for the coating environment, the addition of a pH regulator can maintain the stability of the coating in an acidic or alkaline environment, and can also relax the requirements for the powder-liquid ratio, simplifying the coating preparation process. At the same time, it can also facilitate the subsequent drying and sintering processes.

[0035] The refractory material used in the shell surface layer coating of the present application has very weak reaction with molten titanium, and will not cause contamination of titanium alloy during the investment casting of titanium alloy.

[0036] At the same time, the refractory material used in the shell surface layer coating of the present application is a calcium zirconate-yttria composite refractory material, which can effectively reduce production costs while maintaining a low pollution layer thickness, and can also effectively simplify the production process.

[0037] Example 1

[0038] A method for preparing a titanium alloy casting, comprising the following steps:

[0039] A binder, which is 10wt.% zirconium acetate, is added to a container, and 300-345 mesh calcium zirconate-yttria and 50nm calcium tungstate refractory material are added to the container in batches during stirring, wherein the weight percentage of the refractory material is 65%, the weight percentage of the binder is 35%, the weight percentage of calcium zirconate in the refractory material is 65%, the weight percentage of yttria is 34%, and the weight percentage of calcium tungstate is 1%. After adding an appropriate amount of ammonium metatungstate to adjust the pH value to 6, a wetting agent with a weight percentage of 0.3% and a defoaming agent with a weight percentage of 0.3% are added, and the mixture is stirred for 12 hours before coating the wax mold surface layer and sprinkling 35-50 mesh calcium zirconate sand. The above steps are repeated twice before coating the back layer.

[0040] The refractory material selected for the shell back layer is bauxite with a specification of 260-300 mesh and a weight percentage of 45%, and the binder selected is silica sol with a weight percentage of 55%. The bauxite is added to the binder while stirring begins, and a wetting agent and a defoaming agent are mixed in during stirring, each with a weight percentage of 0.3%. After continuous stirring for 12 hours, the mixture is coated and sprinkled with 35-50 mesh bauxite sand, and then dried for 14 hours in an environment with a temperature of 25°C and an air humidity of 40%. The above steps are repeated six times.

[0041] After coating, the wax is removed by infrared radiation at a temperature of 180°C, and the shell is sintered at a temperature of 1050°C, and then cooled to less than 200°C to obtain an alloy shell for use.

[0042] Preferably, the calcium zirconate-yttria compound is prepared by mechanically mixing the composite powders.

[0043] Preferably, the temperature is raised at a rate of 100-140°C / h, and the temperature is maintained at 400-500°C and 700-800°C for 1-2h, respectively, and then the temperature is raised to 1050°C and maintained for 2-3h.

[0044] Example 2

[0045] A method for preparing a titanium alloy casting comprises the following steps:

[0046] The binder is added to the container, and the binder is 10w.t% zirconium acetate. During stirring, 300-345 mesh calcium zirconate-yttria and 100nm calcium tungstate refractory material are added to the container in batches, wherein the weight percentage of the refractory material is 60%, the weight percentage of the binder is 40%, the weight percentage of calcium zirconate in the refractory material is 55%, the weight percentage of yttria is 44%, and the weight percentage of calcium tungstate is 1%. After adding an appropriate amount of ammonium metatungstate to adjust the pH value to 5, a wetting agent with a weight percentage of 0.3% and a defoaming agent with a weight percentage of 0.3% are added. After stirring for 12h, the wax mold surface layer is coated, and 35-50 mesh calcium zirconate sand is sprinkled. The environment is dried at a temperature of 25°C and an air humidity of 40% for 14h. The above steps are repeated twice, and then the back layer is coated.

[0047] The refractory material selected for the back layer of the shell is bauxite with a size of 260-300 mesh and a weight percentage of 45%. The binder selected is silica sol with a weight percentage of 55%. The bauxite is added to the binder while stirring begins. During stirring, a wetting agent and a defoaming agent are mixed in, each with a weight percentage of 0.3%. After continuous stirring for 12h, the coating is applied, and then 35-50 mesh bauxite sand is sprinkled. The environment is dried at a temperature of 25°C and an air humidity of 40% for 14h. The above steps are repeated 6 times.

[0048] After coating, the wax is removed by infrared radiation at a temperature of 180°C, and the shell is sintered at a temperature of 1050°C, and then cooled to less than 200°C to obtain an alloy shell for use. The titanium alloy is poured into the alloy shell to obtain a titanium alloy casting.

[0049] Preferably, the calcium zirconate-yttria compound is prepared by mechanically mixing the composite powders.

[0050] Preferably, the heating rate during sintering is controlled at 100-140℃ / h, and the temperature is kept at 400-500℃ and 700-800℃ for 1-2h respectively, and then the temperature is increased to 1050℃ and kept for 2-3h.

[0051] Example 3

[0052] A method for preparing a titanium alloy casting comprises the following steps:

[0053] A binder is added into a container, the binder is 10wt.% zirconium acetate, 300-345 mesh calcium zirconate-yttria, and refractory material are added into the container in batches during stirring, wherein the weight percentage of the refractory material is 65%, the weight percentage of the binder is 35%, the weight percentage of calcium zirconate in the refractory material is 55%, and the weight percentage of yttria in the refractory material is 45%, then an appropriate amount of ammonium metatungstate is added to adjust the pH value to 5.5, and then a wetting agent with a weight percentage of 0.3% and a defoaming agent with a weight percentage of 0.3% are added, and after stirring for 12h, coating is performed, and 35-50 mesh calcium zirconate sand is scattered, and drying is performed at a temperature of 25℃ and an air humidity of 40% for 14h. The above steps are repeated twice, and then back coating is performed.

[0054] The refractory material selected for the back layer of the mold shell is bauxite with a size of 260-300 mesh and a weight percentage of 45%, and the binder selected is silica sol with a weight percentage of 55%. The bauxite is added into the binder while stirring is started, and a wetting agent and a defoaming agent are mixed in during stirring, both with a weight percentage of 0.3%. After continuous stirring for 12h, coating is performed, and then 35-50 mesh bauxite sand is scattered, and drying is performed at a temperature of 25℃ and an air humidity of 40% for 14h, and the above steps are repeated 6 times. After coating is completed, dewaxing is performed at 180℃, and sintering is performed at 1100℃. After the furnace is cooled to less than 200℃, an alloy mold shell is obtained for standby use. A titanium alloy casting is obtained by casting a titanium alloy into the alloy mold shell.

[0055] Preferably, the calcium zirconate-yttria composite is prepared by mechanical mixing.

[0056] Preferably, the heating rate during sintering is controlled at 100-140℃ / h, and the temperature is kept at 400-500℃ and 700-800℃ for 1-2h respectively, and then the temperature is increased to 1050℃ and kept for 2-3h.

[0057] Comparative Example 1

[0058] A method for preparing a titanium alloy casting comprises the following steps:

[0059] The binder is added into the container, which is 10wt.% zirconium acetate, and 300-350 mesh calcium zirconate is added into the container during stirring, wherein the weight ratio of refractory material is 60%, and the weight ratio of binder is 40%. 0.3% wetting agent and 0.3% defoaming agent are added, and after stirring for 12 hours, coating is carried out, and 35-50 mesh calcium zirconate sand is scattered, and drying is carried out at a temperature of 25℃ and an air humidity of 40% for 14 hours. The above steps are repeated twice, and then back coating is carried out.

[0060] The selected refractory material for the back layer of the mold shell is bauxite, with a size of 260-300 mesh and a weight ratio of 45%, and the selected binder is silica sol, with a weight ratio of 55%. Bauxite is added to the binder, and stirring is started at the same time. During stirring, wetting agent and defoaming agent are mixed, each with a weight ratio of 0.3%. After continuous stirring for 12 hours, coating is carried out, and 35-50 mesh bauxite sand is scattered, and drying is carried out at a temperature of 25℃ and an air humidity of 40% for 14 hours. The above steps are repeated 6 times. After coating is completed, dewaxing is carried out at 180℃, and sintering is carried out at 1050℃. After furnace cooling to less than 200℃, the alloy mold shell is obtained for standby. Titanium alloy is cast into the alloy mold shell to obtain a titanium alloy casting.

[0061] In the invention, the face layer needs a material with excellent high-temperature inertness to prevent the titanium alloy from reacting with the face layer, and the back layer only needs to provide strength, so bauxite with a lower price is selected. The surface of the mold shell that needs to be in direct contact with molten titanium is the face layer of the mold shell.

[0062] The properties of Examples 1-3 and Comparative Example 1 are compared, as shown in Table 1:

[0063] Table 1 Comparison of performance test results of Examples 1-3 and Comparative Example 1 of the invention:

[0064]

[0065] As shown in Table 1, the coating suspension rate of Examples 1, 2 and 3 is higher than that of Comparative Example 1. The casting pollution layer thickness of Examples 1, 2 and 3 is significantly lower than that of Comparative Example 1, and the casting pollution layer thickness of Example 2 is the smallest, and the mold shell of Example 2 has a casting pollution layer thickness of less than 50μm.

[0066] The titanium alloy castings of Examples 1-3 and Comparative Example 1 are scanned by SEM, and the interface pollution layer of the titanium alloy castings of Examples 1-3 and Comparative Example 1 is compared, as shown in Figures 1-4The reaction layer organization of examples 1-3 is relatively thick, and there is an obvious boundary between the interface reaction layer and the base organization, and the interface reaction layer of the alloy casting is relatively thin, and the average is about 50 mu m. It can be seen that the alloy shell of the application can control the reaction layer of the alloy casting to be less than 50 mu m. And in example 2, the alloy shell can control the reaction layer of the alloy casting to be as low as 30 mu m, even less than 30 mu m.

[0067] In comparative example 1, because the shell surface layer material reacts with the titanium alloy, the interface between the reaction layer and the casting substrate is blurred, and the thickness of the reaction layer of the alloy casting is much higher than 50 mu m.

[0068] The high-temperature inertness of yttrium oxide is the best, but the price is relatively high, the cost of calcium zirconate is lower than that of yttrium oxide, and the high-temperature performance is excellent, but the interface reaction between the titanium alloy and the shell still occurs during pouring, the application adopts a composite refractory material containing yttrium oxide and calcium zirconate to prepare the shell surface layer coating, which can reduce the production cost, reduce the interface reaction between the shell and the titanium alloy casting, and reduce the thickness of the pollution layer of the titanium alloy casting. The application can increase the density of the shell surface layer by using nano calcium tungstate, and calcium tungstate can effectively reduce the interface reaction between the shell and the titanium alloy casting, thereby further improving the surface quality of the titanium alloy casting.

[0069] Because zirconium acetate needs to be stable in an acidic environment, the pH value of the surface layer coating needs to be maintained at a low level, and the addition of calcium zirconate refractory aggregate will increase the pH value of the coating, and if the pH value of the coating is too low, yttrium oxide and calcium zirconate will agglomerate, affecting the stability of the coating, therefore, the application adjusts the pH value of the coating by adding ammonium metatungstate, so that the overall environment pH value of the coating is maintained at 4-6, which can ensure the stability of zirconium acetate and prevent the agglomeration of calcium zirconate and yttrium oxide.

[0070] The application adjusts the pH value of the shell surface layer coating by using ammonium metatungstate, and adds a small amount of nano calcium tungstate to increase the density of the surface layer, and when the pH value is high, calcium tungstate can be directly provided to improve the inertness of the surface layer.

[0071] Further, the addition of ammonium metatungstate can produce calcium tungstate during the calcination of the calcium zirconate shell, and calcium tungstate can effectively reduce the interface reaction between the shell and the titanium alloy casting, so the application can reduce the use of yttrium oxide to the greatest extent, and then the application can select a suitable calcium zirconate-yttrium oxide composite refractory material containing calcium zirconate and yttrium oxide. It can be seen that the application not only can adjust the pH value of the shell coating, but also has the characteristics of reducing the interface reaction between the shell and the titanium alloy casting and reducing the use of yttrium oxide.

[0072] The alloy shell has high strength, low pollution layer thickness and weak interface reaction, and greatly reduces the production cost.

[0073] It is to be understood that the above-described embodiments are merely illustrative of the principles of the present disclosure and that numerous and various modifications can be made by those skilled in the art without departing from the scope of the present disclosure.

Claims

1. An alloy shell, characterized in that, The surface coating of the alloy shell includes a first refractory material, a first binder, and a pH adjuster. The first refractory material includes a calcium zirconate-yttrium oxide composite and calcium tungstate. The weight ratio of the first refractory material to the first binder is 1.5-2:

1. The pH value of the surface coating is 4-6. In the first refractory material, the calcium zirconate-yttrium oxide composite accounts for 99% or more by weight, and the calcium tungstate accounts for less than or equal to 1% by weight. The first binder comprises zirconium acetate; the pH adjuster comprises ammonium metatungstate.

2. The alloy shell according to claim 1, characterized in that, The first refractory material accounts for 62-66% by weight, and the first binder accounts for 34-38% by weight.

3. The alloy shell according to claim 1, characterized in that, In the calcium zirconate-yttrium oxide composite, the calcium zirconate accounts for 55-65% by weight, and the yttrium oxide accounts for 35-45% by weight. The calcium zirconate-yttrium oxide composite has a particle size of 300-345 mesh, and the calcium tungstate has a particle size of 50-100 nm.

4. The alloy shell according to claim 1, characterized in that, The topcoat also includes a first wetting agent and a first defoamer, each accounting for less than or equal to 0.3% by weight, and a second refractory material with a particle size of 35-50 mesh, the second refractory material including calcium zirconate.

5. The alloy shell according to claim 1, characterized in that, The back coating of the alloy shell includes a third refractory material and a second binder. The third refractory material accounts for 35-45% by weight, and the second binder accounts for 55-65% by weight. The third refractory material includes bauxite with a particle size of 260-300 mesh, and the second binder includes silica sol.

6. The alloy shell according to claim 5, characterized in that, The back coating also includes a second wetting agent and a second defoamer, accounting for less than or equal to 0.3% by weight, and a fourth refractory material with a particle size of 35-50 mesh, wherein the fourth refractory material includes bauxite.

7. A method for preparing an alloy shell, characterized in that, The surface coating of the alloy shell includes a first refractory material, a first binder, and a pH adjuster. The first refractory material includes a calcium zirconate-yttrium oxide composite and calcium tungstate. The weight ratio of the first refractory material to the first binder is 1.5-2:

1. The pH value of the surface coating is 4-6. In the first refractory material, the calcium zirconate-yttrium oxide composite accounts for 99% or more by weight, and the calcium tungstate accounts for less than or equal to 1% by weight. The first binder comprises zirconium acetate; the pH adjuster comprises ammonium metatungstate; The topcoat also includes a first wetting agent and a first defoamer, each accounting for less than or equal to 0.3% by weight, and a second refractory material with a particle size of 35-50 mesh, the second refractory material including calcium zirconate; The back coating of the alloy shell includes a third refractory material and a second binder. The third refractory material accounts for 35-45% by weight, and the second binder accounts for 55-65% by weight. The third refractory material includes bauxite with a particle size of 260-300 mesh, and the second binder includes silica sol. The back coating also includes a second wetting agent and a second defoamer accounting for less than or equal to 0.3% by weight, and a fourth refractory material with a particle size of 35-50 mesh, wherein the fourth refractory material includes bauxite; The method for preparing the alloy shell includes the following steps: Shell surface layer preparation: The first refractory material and the first binder are blended to obtain the first mixed coating. The pH value of the first mixed coating is adjusted to 4-6 using a pH adjuster. The first wetting agent and the first defoamer are added to the first mixed coating after pH adjustment to obtain the second mixed coating. After applying the second mixed coating onto the surface of the wax model, sprinkle the second refractory material, dry, and repeat the above steps 2-4 times; Preparation of shell reinforcement layer: The third mixed coating is prepared by blending the third refractory material, the second binder, the second wetting agent and the second defoamer; After the third mixed coating is applied to the back layer of the wax model, the fourth refractory material is sprinkled on it, and the process is dried. The above steps are repeated 6-8 times. Dewaxing of the shell: Dewaxing is carried out at a temperature of 180-220℃; Shell firing: The heating rate is controlled at 100-140℃ / h, and the temperature is held in sections at 400-500℃ and 700-800℃ for 1-2 hours. The temperature is then raised to 1000-1100℃ and held for 2-3 hours. The shell is removed from the furnace when the furnace temperature is less than or equal to 200℃.

8. The method for preparing an alloy shell according to claim 7, characterized in that, The drying time is 14-16 hours, the temperature is 20-40℃, and the humidity is 40%-50%.

9. The use of an alloy shell as described in any one of claims 1-6 in the manufacture of titanium alloy castings.

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