CN115673241B - Soluble ceramic shell or ceramic core material and preparation method and application thereof - Google Patents

Abstract

The present invention relates to a soluble ceramic shell or ceramic core and a preparation method and application thereof, and belongs to the technical field related to rapid casting. The method comprises the following steps: (1) preparing a ceramic shell/core blank by a 3DP molding process, and obtaining a ceramic shell or ceramic core blank after heating and curing, sol infiltration, and drying; (2) placing the ceramic blank into a high-temperature sintering furnace for sintering, and obtaining a soluble ceramic shell or ceramic core after cooling with the furnace; wherein the shell/core material used in the molding process is calcium carbonate. The present invention prepares a ceramic shell/core by a 3DP molding process, which has a simple process, a short production cycle, no support, and is suitable for molding large-scale complex structure ceramic shells/cores. The calcium carbonate material can prevent the material from absorbing moisture during the printing process and affecting the performance of the shell/core. After high-temperature sintering, the calcium carbonate decomposes into calcium oxide, which can avoid interfacial reaction with titanium alloy during subsequent pouring. At the same time, due to the solubility of calcium oxide, the casting is easier to shell after pouring.

Description

A soluble ceramic shell or ceramic core material and its preparation method and application

Technical Field

The present invention belongs to the technical field related to rapid casting, and more specifically, relates to a soluble ceramic shell or ceramic core and a preparation method and application thereof, and in particular to a soluble ceramic shell/core for titanium alloy casting based on 3DP molding and a preparation method thereof.

Background technique

Titanium alloys have been widely used in aerospace, energy and chemical, medical and health care fields due to their low density, high specific strength, long fatigue life, good corrosion resistance, high temperature resistance, and good strength and stiffness matching with composite materials. However, forging, welding and other methods are difficult to process due to the high chemical activity, low plasticity, and low thermal conductivity of titanium alloys. Investment casting technology has solved the above problems well and has become one of the mainstream methods for preparing titanium alloy structural parts. Traditional investment casting technology uses wax molds, resin molds and other materials to prepare part models, and then obtains precision parts through processes such as slurry hanging, drying, sanding, demoulding, roasting and pouring. However, in traditional investment casting technology, the preparation of ceramic shells/cores requires multiple processes, with a long production cycle, high production costs, and complex production processes. It has great limitations in molding large and complex ceramic shells/cores, and it is difficult to meet the current production needs of society. Therefore, how to simplify the production process, shorten the production cycle, and reduce the preparation cost is an urgent problem to be solved.

Additive manufacturing technology refers to the process of slicing the 3D model of a part and printing it layer by layer under the control of a computer to finally form a complete part. This technology can be used to directly form a ceramic shell/core, and a ceramic shell/core suitable for casting requirements can be obtained through processes such as drying, degreasing and sintering, which greatly shortens the production cycle and reduces production costs. Currently, the additive manufacturing technologies commonly used to produce ceramic shells/cores include photocuring molding technology, laser selective sintering technology, and layered extrusion molding technology, but these technologies are more or less faced with problems such as high equipment cost, low surface accuracy of ceramic shells/cores, and the need for support to form large and complex components. Compared with the above-mentioned additive manufacturing technologies, 3DP molding technology does not require laser or auxiliary heating molding, and has the advantages of a wide range of materials, high molding accuracy, no support, and green environmental protection. It has a wide range of applications and has great potential for preparing ceramic shells/cores.

In terms of the preparation materials of the ceramic shell/core, the traditional materials suitable for preparing the ceramic shell/core for titanium alloy casting mainly include ZrO ₂ , Y ₂ O ₃ , CaO, etc. These materials can avoid the violent interface reaction between the ceramic shell/core and the titanium alloy during pouring, so as to prevent affecting the casting accuracy and reducing the casting performance. However, these materials still have some problems, such as ZrO ₂ and Y ₂ O ₃ are expensive, which greatly increases the production cost, and it is difficult to remove the ceramic shell/core after pouring; although the CaO shell/core can be hydrolyzed and deshelled, CaO is very easy to absorb water during the preparation process, which causes the shell/core to crack and affects the use. Therefore, it is urgent to develop a soluble ceramic shell/core preparation method suitable for titanium alloy casting, solve the problems existing in the above preparation technology and ceramic shell/core materials, and meet the needs of industrial production.

Summary of the invention

In view of the above defects or improvement needs of the prior art, the present invention provides a soluble ceramic shell or ceramic core based on droplet jet bonding molding and a preparation method and application thereof. The ceramic shell or ceramic core material adopts CaCO ₃ , which can be completely decomposed into CaO after sufficient sintering. It can be directly dissolved with water, and the ceramic shell or ceramic core will collapse and be easily separated from the casting, which greatly simplifies the subsequent shelling process. The solubility of the dissolved product Ca(OH) ₂ is relatively small, and most of it will form a precipitate, which is convenient for subsequent recycling and treatment. At the same time, compared with direct printing with CaO, CaCO ₃ can avoid the volume change of the powder due to moisture absorption during the printing process, thereby preventing the cracking of the ceramic shell or ceramic core.

According to a first aspect of the present invention, there is provided a method for preparing a soluble ceramic shell or ceramic core, comprising the following steps:

(1) Using calcium carbonate powder as a raw material, a ceramic shell or ceramic core blank is prepared by a droplet jet bonding molding process, and then heated, solidified, impregnated and dried to obtain a ceramic shell or ceramic core blank;

(2) Sintering the ceramic shell or ceramic core blank obtained in step (1) to react calcium carbonate to generate calcium oxide, thereby obtaining the soluble ceramic shell or ceramic core.

Preferably, in step (2), the sintering is divided into two stages, namely, sintering at 900°C to 1000°C for 1h to 3h, and then sintering at 1300°C to 1500°C for 2h to 3h, and the heating rate during the sintering process is 2 to 5°C/min.

Preferably, in step (1), the temperature of the heating curing is 190° C. to 205° C., and the time is 2 h to 4 h.

Preferably, in step (1), the solute molecules in the impregnation solution used for the impregnation do not decompose above 1500° C.; the solute components of the impregnation solution do not react with the structural parts during the casting process; the impregnation solution is used to penetrate into the pores between the calcium carbonate powders, keep the shape of the ceramic shell or the ceramic core intact, avoid the collapse of the green body during the sintering process, and enhance the strength of the green body after sintering.

Preferably, in step (1), the impregnation liquid is at least one of a nano _ZrO2 dispersion or a yttrium sol, and the impregnation time is 30 seconds to 3 minutes.

Preferably, the particle size of the calcium carbonate powder is 325 mesh to 800 mesh; the binder used in the droplet jet bonding molding process is phenolic resin; the printing parameters are: printing layer height 0.05mm to 0.20mm, adhesive saturation 70% to 140%.

According to another aspect of the present invention, a soluble ceramic shell or ceramic core prepared by any of the methods described above is provided.

According to another aspect of the present invention, there is provided a use of the soluble ceramic shell or ceramic core in a cast structure.

Preferably, the structural member is made of titanium alloy, cast steel, cast iron, aluminum alloy or magnesium alloy.

Preferably, after the pouring is completed, the structural component with the ceramic shell or the ceramic core is placed in water. The ceramic shell or the ceramic core will react with water to crack and disintegrate, and separate from the structural component, thus completing the shelling process.

In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

(1) The present invention adopts a micro-droplet jet bonding molding process to prepare a ceramic shell/core, which can solve the limitations of traditional processes in molding large and complex structure ceramic shells/cores, shorten the production cycle, reduce production costs, and meet the production needs of the social market. At the same time, compared with other additive manufacturing technologies, the micro-droplet jet bonding molding process does not require laser or auxiliary heating molding, has the advantages of a wide range of materials, high molding precision, no support, green and environmental protection, and has a wide range of applications.

(2) The ceramic shell/core prepared by the present invention using CaCO ₃ can be completely decomposed into CaO after sufficient sintering. Since _CaO can react with water, in the shelling process after pouring, the casting with the ceramic shell/core can be fully immersed in hot water, and the ceramic shell/core will be hydrolyzed and disintegrated, and can be easily separated from the casting; while the ceramic shell/core prepared by using materials such as ZrO ₂ and Y ₂ O ₃ is often shelled by applying external force to knock after pouring, which is time-consuming and labor-intensive. Therefore, using CaCO ₃ to prepare the ceramic shell/core can greatly simplify the later shelling process. The process of CaO ceramic shell/core dissolution is:

CaO+ _H2O ＝Ca(OH) ₂

A large amount of heat is released during this reaction, and the solubility of the reaction product Ca(OH) ₂ is relatively low, only 1.65g/L at 20°C, and its solubility decreases with increasing temperature. Therefore, most of the Ca(OH) ₂ will form a precipitate, which is convenient for later recovery and treatment. It has low pollution, is environmentally friendly, and has broad application prospects.

(3) The present invention requires the ceramic shell/core to be infiltrated before high-temperature sintering. The purpose of the infiltration treatment is that the infiltration liquid can enter the gaps in the calcium carbonate powder to improve the strength of the ceramic shell/core; after the binder is completely decomposed, the shape of the ceramic shell/core can be maintained to avoid collapse; the solute components in the infiltration liquid can also avoid interfacial reaction with the titanium alloy during the casting process, thereby ensuring the quality of the casting.

(4) Compared with directly using CaO to prepare the ceramic shell/core, the present invention uses CaCO ₃ to prepare the ceramic shell/core. This can avoid the volume change caused by the powder being exposed to the air and absorbing moisture during the printing process, and prevent the ceramic shell/core from cracking. In addition, compared with other ceramic powders such as ZrO ₂ and Y ₂ O ₃ , CaCO ₃ is low in price and widely available, and has great development potential.

Based on the preparation characteristics of soluble ceramic shell/core, the present invention studies and designs a method for preparing soluble ceramic shell/core with simple preparation process, no support required in the molding process, low cost, and convenient shelling in the later stage. The method adopts the soluble ceramic shell/core prepared by the droplet jet bonding molding process, which can solve the limitations of the traditional process in molding large-scale complex structure ceramic shell/core, shorten the production cycle, and reduce the production cost. The droplet jet bonding molding process has the advantages of wide range of materials, high molding precision, no support, green and environmental protection, and has a wide range of application fields; and it is low in price and widely available, and has huge development potential.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic flow diagram of a method for preparing a soluble ceramic shell/core according to the present invention.

FIG. 2 is a physical picture of the ceramic test samples constructed according to the present invention, wherein sample a is infiltrated with silica sol and sample b is infiltrated with nano ZrO ₂ dispersion.

FIG. 3 is a physical picture of a ceramic sample undergoing a disintegration test.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

As shown in FIG1 , a method for preparing a soluble ceramic shell/core based on droplet jetting bonding molding mainly comprises the following steps:

(1) Calcium carbonate powder is placed in a powder cylinder, a ceramic shell/core three-dimensional structure model is introduced, and printing parameters are adjusted, and then a ceramic shell/core blank is printed;

(2) placing the printed blank together with the powder bed into a drying oven for heating and curing;

(3) The solidified green body is taken out from the powder bed, the powder is cleaned and the green body is infiltrated with sol, and then placed in a drying oven for low-temperature drying;

(4) Sintering the ceramic shell/core blank obtained in step (3) to decompose calcium carbonate to generate calcium oxide, thereby obtaining the soluble ceramic shell/core.

Furthermore, in step (1), the particle size of the calcium carbonate powder is 325 mesh to 800 mesh.

Furthermore, in step (4), the sintering is divided into two stages, namely, sintering at 700°C to 1000°C for 1h to 3h, and then sintering at 1300°C to 1500°C for 2h to 3h, and the heating rate during the sintering process is 2 to 5°C/min.

Furthermore, in step (2), the temperature of the heating curing is 160° C. to 220° C., and the time is 2 h to 5 h.

Furthermore, in step (3), the impregnation liquid used for the impregnation can exist stably at high temperatures; the solute components of the impregnation liquid will not react with the titanium alloy during the casting process; after the impregnation liquid penetrates into the pores between the calcium carbonate powders, it can maintain the integrity of the shape of the ceramic shell/core, avoid the collapse of the green body during the sintering process, and build the strength of the ceramic shell/core.

Furthermore, the impregnation liquid is one of nano _ZrO2 dispersion or yttrium sol or a mixed solution of the two, and the impregnation time is 30s to 3min.

Furthermore, in step (1), the binder used in the droplet jet bonding molding process is phenolic resin; the printing parameters are: printing layer height 0.05mm~0.20mm, adhesive saturation 70%~140%.

Binder saturation (Bs) is one of the important influencing parameters in the droplet jet printing process. It is defined as the proportional relationship between the volume of a single layer of binder (V _binder ) and the void volume (V _air ) in the corresponding powder layer. Its expression is:

Where _ρstacking is the packing density of the powder; _ρtrue is the true density of the powder; S is the printing area of a single layer; and H is the layer thickness.

The present invention also provides a soluble ceramic shell/core, which is prepared by the preparation method of the soluble ceramic shell/core as described above. The soluble ceramic shell/core is mainly used for the casting of structural parts, and can also be used for the casting of structural parts made of cast steel, cast iron, aluminum alloy, and magnesium alloy. After the casting is completed, the structural part with the ceramic shell/core is placed in hot water, and the ceramic shell/core reacts with water to crack and disintegrate, and is easily separated from the structural part, completing the shelling process.

The present invention is further described in detail below in conjunction with several specific embodiments.

Example 1

The method for preparing the soluble ceramic shell/core provided in Example 1 of the present invention mainly comprises the following steps:

S1, dry the 325 mesh calcium carbonate powder for printing at 80℃ for 12h, take it out and sieve the powder. Then spread the sieved calcium carbonate powder all over the powder supply cylinder, place a stainless steel plate on the surface of the working cylinder and spread a layer of ceramic powder, import the designed three-dimensional structure model of the ceramic shell/core into the computer and adjust the printing parameters, the nozzle starts to spray the phenolic resin binder according to the path of the computer slice, after the nozzle completes one inkjet, the working cylinder will drop a layer thickness, the powder supply cylinder will rise a layer thickness, and the powder spreading process will be completed by the rotation and movement of the powder spreading roller, and reciprocate in sequence to complete the entire ceramic shell/core printing process. Among them, the printing parameters of the 3D printing equipment are: printing layer height 0.15mm, binder saturation 80%.

S2, after the printing is completed, first, remove the excess powder on the edge of the stainless steel plate, place it in a drying oven and heat it at 205°C for curing, close the drying oven after curing for 4 hours, and take out the stainless steel plate after cooling with the furnace. Next, use a shovel to remove the powder around the ceramic shell/core blank, take the blank out of the powder bed, and use a brush to clean the residual powder on the ceramic shell/core blank. Subsequently, place the ceramic shell/core blank in a basin, pour 40% nano _ZrO2 dispersion into it, start timing after all parts of the blank are completely infiltrated, take out the infiltrated ceramic shell/core blank after 3 minutes, place it on a tray, put it in a drying oven at 70°C, and take it out after drying for 6 hours.

S3, the sintering of the ceramic shell/core blank adopts the buried firing method. 0.2mm plate-shaped corundum powder is evenly spread on the ceramic plate dedicated to sintering, and then the dried ceramic shell/core blank is placed on the ceramic plate. The various parts of the blank are completely buried with plate-shaped corundum powder, and then it is placed in a high-temperature sintering furnace and sintered according to the process parameters of sintering at 1000℃ for 3h, sintering at 1400℃ for 2h, and a heating rate of 2℃/min. Finally, it is cooled in the furnace to obtain a soluble ceramic shell/core for titanium alloy casting.

Example 2

The preparation method of the soluble ceramic shell/core provided in Example 2 of the present invention mainly comprises the following steps:

S1, dry the 500 mesh calcium carbonate powder for printing at 90℃ for 10h, take it out and sieve the powder. Then spread the sieved calcium carbonate powder all over the powder supply cylinder, place a stainless steel plate on the surface of the working cylinder and spread a layer of ceramic powder, import the designed three-dimensional structure model of the ceramic shell/core into the computer and adjust the printing parameters, the nozzle starts to spray the binder according to the path of the computer slice, after the nozzle completes one inkjet, the working cylinder will drop a layer thickness, the powder supply cylinder will rise a layer thickness, and the powder spreading process will be completed by the rotation and movement of the powder spreading roller, and reciprocate in sequence to complete the entire ceramic shell/core printing process. Among them, the printing parameters of the 3D printing equipment are: printing layer height 0.12mm, binder saturation 100%.

S2, after the printing is completed, first, remove the excess powder on the edge of the stainless steel plate, place it in a drying oven and heat it at 200°C for curing, close the drying oven after curing for 3 hours, and take out the stainless steel plate after cooling with the furnace. Next, use a shovel to remove the powder around the ceramic shell/core blank, take the blank out of the powder bed, and use a brush to clean the residual powder on the ceramic shell/core blank. Subsequently, place the ceramic shell/core blank in a basin, pour 30% nano _ZrO2 dispersion into it, start timing after all parts of the blank are completely infiltrated, take out the infiltrated ceramic shell/core blank after 2 minutes, place it on a tray, put it in a drying oven at 60°C, and take it out after drying for 5 hours.

S3, the sintering of the ceramic shell/core blank adopts the buried firing method. 0.2mm plate-shaped corundum powder is evenly spread on the ceramic plate dedicated to sintering, and then the dried ceramic shell/core blank is placed on the ceramic plate, and each part of the blank is completely buried with the plate-shaped corundum powder. Subsequently, it is placed in a high-temperature sintering furnace and sintered at 950°C for 2h, 1350°C for 2h, and a heating rate of 3°C/min. Finally, it is cooled in the furnace to obtain a soluble ceramic shell/core for titanium alloy casting.

Example 3

The preparation method of the soluble ceramic shell/core provided in Example 3 of the present invention mainly comprises the following steps:

S1, dry the 600 mesh calcium carbonate powder for printing at 100℃ for 8h, take it out and sieve the powder. Then spread the sieved calcium carbonate powder all over the powder supply cylinder, place a stainless steel plate on the surface of the working cylinder and spread a layer of ceramic powder, import the designed three-dimensional structure model of the ceramic shell/core into the computer and adjust the printing parameters, the nozzle starts to spray the binder according to the path of the computer slice, after the nozzle completes one inkjet, the working cylinder will drop a layer thickness, the powder supply cylinder will rise a layer thickness, and the powder spreading process will be completed by the rotation and movement of the powder spreading roller, and reciprocate in sequence to complete the entire ceramic shell/core printing process. Among them, the printing parameters of the 3D printing equipment are: printing layer height 0.10mm, binder saturation 120%.

S2, after the printing is completed, first, remove the excess powder on the edge of the stainless steel plate, place it in a drying oven and heat it at 195°C for curing, close the drying oven after curing for 2 hours, and take out the stainless steel plate after cooling with the furnace. Next, use a shovel to remove the powder around the ceramic shell/core blank, take the blank out of the powder bed, and use a brush to clean the residual powder on the ceramic shell/core blank. Subsequently, place the ceramic shell/core blank in a basin, pour 15% nano _ZrO2 dispersion into it, start timing after all parts of the blank are completely infiltrated, take out the infiltrated ceramic shell/core blank after 1.5 minutes, place it on a tray, put it in a drying oven at 50°C, and take it out after drying for 4 hours.

S3, the sintering of the ceramic shell/core blank adopts the buried firing method. 0.2mm plate-shaped corundum powder is evenly spread on the ceramic plate dedicated to sintering, and then the dried ceramic shell/core blank is placed on the ceramic plate, and each part of the blank is completely buried with plate-shaped corundum powder. It is then placed in a high-temperature sintering furnace and sintered according to the process parameters of sintering at 900°C for 1h, sintering at 1300°C for 1.5h, and a heating rate of 3°C/min. Finally, it is cooled in the furnace to obtain a soluble ceramic shell/core for titanium alloy casting.

Application Examples

As an important component of the engine, the impeller has been widely used in the fields of automobiles, aerospace, etc. Taking the preparation of the impeller as an example, a soluble impeller shell is prepared according to the method in the above specific embodiment, the impeller shell is placed in a pressure casting device, and the molten titanium alloy liquid is poured into the gate above the shell with a crucible, and then pressurized to fill the shell with titanium alloy. After cooling, the cast impeller shell is taken out and soaked in hot water. After the ceramic shell material on the surface is completely collapsed, the impeller is taken out of the water, and the residual ceramic on it is cleaned, and the water is wiped off and placed in a drying box to obtain an impeller casting.

Impregnation comparison

According to the specific embodiment 1, the strip sample was obtained after sintering using 325 mesh calcium carbonate, wherein the strip sample a was infiltrated with silica sol for 3min, and the strip sample b was infiltrated with nano _ZrO2 dispersion for 3min. As can be seen from Figure 2, the shape of the strip sample a infiltrated with silica sol changed greatly after sintering, while the shape of the strip sample b infiltrated with nano _ZrO2 dispersion remained intact without any concave deformation. In addition, the strip sample a broke when it was taken out of the sintering furnace, which shows that the strength is far less than that of the strip sample b infiltrated with nano _ZrO2 dispersion, which shows that silica sol is not suitable for the infiltration of calcium carbonate ceramic shell/core blank, and nano _ZrO2 dispersion can well maintain the shape of the blank, prevent fracture, and is suitable for the infiltration of calcium carbonate ceramic shell/core blank.

Test Example

(1) Collapse test

Fill two beakers with hot water and put the ceramic samples for testing in them. Both samples are prepared by droplet jet bonding molding process. Except for the raw materials, the other molding process parameters are the same. The raw material of the ceramic sample in beaker a is 800 mesh alumina, and the raw material of the ceramic sample in beaker b is 800 mesh calcium carbonate. After sintering, the calcium carbonate has been completely decomposed into calcium oxide. After being placed in hot water for 40 minutes, the status of the two test samples is shown in Figure 3. As can be seen from Figure 3, after 40 minutes, the sample in beaker a did not collapse, and there was no obvious difference in shape and strength compared with before being placed in hot water; the sample in beaker b has completely collapsed and dissolved, meeting the expected requirements.

(2) Strength test

The samples in specific embodiments 1, 2 and 3 were tested for bending strength, and the obtained data are shown in the following table:

It will be easily understood by those skilled in the art that 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 and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A method for preparing a soluble ceramic shell or ceramic core, characterized in that it comprises the following steps: (1) Using calcium carbonate powder as raw material, a ceramic shell or ceramic core blank is prepared by a droplet jet bonding molding process, wherein the binder used in the droplet jet bonding molding process is a phenolic resin; then heating, curing, impregnation and drying are performed to obtain a ceramic shell or ceramic core blank; the impregnation liquid is a nano _ZrO2 dispersion; (2) Sintering the ceramic shell or ceramic core blank obtained in step (1) to react calcium carbonate to generate calcium oxide, thereby obtaining the soluble ceramic shell or ceramic core. 2. The method for preparing a soluble ceramic shell or ceramic core as described in claim 1 is characterized in that in step (2), the sintering is divided into two stages, namely sintering at 900°C to 1000°C for 1h to 3h, and then sintering at 1300°C to 1500°C for 2h to 3h, and the heating rate during the sintering process is 2 to 5°C/min. 3. The method for preparing a soluble ceramic shell or ceramic core according to claim 1, characterized in that in step (1), the heating and curing temperature is 190°C to 205°C and the time is 2h to 4h. 4. The method for preparing a soluble ceramic shell or ceramic core as described in claim 1 is characterized in that, in step (1), the solute molecules in the impregnation solution used for the impregnation can not decompose at 1500°C and below; the solute components of the impregnation solution will not react with the structural parts during the casting process; the impregnation solution is used to penetrate into the pores between the calcium carbonate powder to keep the shape of the ceramic shell or ceramic core intact, avoid the collapse of the green body during the sintering process, and enhance the strength of the green body after sintering. 5. The method for preparing a soluble ceramic shell or ceramic core according to claim 4, characterized in that in step (1), the impregnation time is 30 seconds to 3 minutes. 6. The method for preparing a soluble ceramic shell or ceramic core as claimed in claim 1, characterized in that the particle size of the calcium carbonate powder is 325 mesh to 800 mesh; the printing parameters are: printing layer height 0.05 mm to 0.20 mm, and adhesive saturation 70% to 140%. 7. A soluble ceramic shell or ceramic core prepared by the method according to any one of claims 1 to 6. 8. Use of the soluble ceramic shell or ceramic core as claimed in claim 7 in a cast structure. 9. The use according to claim 8, characterized in that the structural member is made of titanium alloy, cast steel, cast iron, aluminum alloy or magnesium alloy. 10. The use as claimed in claim 8 or 9, characterized in that after the pouring is completed, the structural part with the ceramic shell or the ceramic core is placed in water, and the ceramic shell or the ceramic core reacts with water to crack and disintegrate, and is separated from the structural part, completing the shelling process.