A soluble ceramic shell / core and its preparation method and application

Abstract

The present invention proposes a soluble ceramic shell / core and a preparation method and application, which belong to the technical field related to rapid casting. The preparation method comprises the following steps: Step S1: ball-milling and drying the raw materials containing calcium oxide and a modified solution to obtain modified calcium oxide powder; Step S2: printing the modified calcium oxide powder into a ceramic shell / core blank, heating and curing, infiltration, and drying to obtain a ceramic shell / core blank; Step S3: sintering the ceramic shell / core blank to obtain the soluble ceramic shell / core. The present invention prepares the ceramic shell / core through a 3DP molding process, which has a simple process, a short production cycle, and does not require support. The solubility of calcium oxide makes the casting easier to shell after pouring. In addition, the raw materials cannot be decomposed during the sintering process, which reduces the shrinkage during the sintering process and can meet the needs of molding large and complex structure ceramic shells / cores.

Description

Technical Field

[0001] The present invention relates to the technical field related to rapid casting, and in particular to a soluble ceramic shell / core and a preparation method and application thereof. Background Art

[0002] 3DP molding technology is an additive manufacturing method based on a powder bed process. Using an inkjet nozzle, a binder is selectively sprayed layer by layer onto a powder bed, forming a green part. Subsequent curing, impregnation, degreasing, and sintering processes result in densification and yield parts with excellent mechanical properties. Compared to other additive manufacturing technologies, 3DP technology does not require laser or assisted heating for molding. It offers advantages such as a wide range of materials, high efficiency, low cost, support-free operation, and environmental friendliness. It has a wide range of applications and holds great potential for preparing ceramic shells and cores.

[0003] Traditionally, ceramic shell / core materials suitable for titanium alloy casting include ZrO2, Y2O3, and CaO. The main advantage of these materials is that they can avoid interfacial reactions with titanium alloys during pouring, which can affect the precision and performance of the casting. However, ZrO2 and Y2O3 are expensive, which greatly increases production costs, and it is difficult to remove the ceramic shell / core after pouring. Although the CaO shell / core can be hydrolyzed and deshelled, it is difficult to achieve powder bed 3DP printing due to the fact that the CaO material easily absorbs water and agglomerates in the air. Therefore, there is an urgent need to develop a method for preparing soluble ceramic shells / cores to solve the problems existing in the above preparation technologies and ceramic shell / core materials and meet the needs of industrial production. Summary of the Invention

[0004] In response to the above-mentioned deficiencies or improvement needs of the prior art, the present invention provides a soluble ceramic shell / core based on droplet jet bonding molding, as well as its preparation method and application. The ceramic shell / core material is CaO, which is directly dissolved in water. The ceramic shell / core will collapse and be easily separated from the casting, greatly simplifying the subsequent shelling process. The solubility of the dissolved product Ca(OH)2 is relatively low, and most of it will form a precipitate, which is convenient for later recycling and processing. Due to the modification of CaO in the present invention, the printing problem caused by powder agglomeration during the droplet jet bonding molding process is optimized. CaO does not decompose during the sintering process, and the shrinkage deformation of the ceramic shell / core after sintering is relatively small, which can meet the needs of industrial production.

[0005] The technical solution of the present invention is achieved as follows: The present invention provides a method for preparing a soluble ceramic shell / core, the preparation method comprising the following steps:

[0006] Step S1: ball-milling, drying, and sieving the raw materials containing calcium oxide and modified solution to obtain modified calcium oxide powder;

[0007] Step S2: Printing the modified calcium oxide powder into a ceramic shell / core blank, heating and curing, infiltration, and drying to obtain a ceramic shell / core blank;

[0008] Step S3: sintering the ceramic shell / core blank to obtain the soluble ceramic shell / core.

[0009] On the basis of the above technical solution, preferably, in the step S1, the modified solution includes a modifier and a modified solvent.

[0010] On the basis of the above technical solution, preferably, the modifier is selected from at least one of ethyl bromide, benzene bromide, a silane coupling agent, stearic acid, and n-octadecyltrichlorosilane.

[0011] On the basis of the above technical solution, preferably, the modified solvent is selected from at least one of methanol, ethanol, glycerol and acetone.

[0012] On the basis of the above technical solution, preferably, the amount of the modifier is 1 to 10 parts by mass, and the amount of the modification solvent is 90 to 99 parts by mass.

[0013] On the basis of the above technical solution, preferably, the amount of the modifier is independently selected from any value of 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 8 parts, 10 parts or a range between any two of the above parts by mass.

[0014] On the basis of the above technical solution, preferably, the amount of the modified solvent is independently selected from any value among 99 parts, 98 parts, 97 parts, 96 parts, 95 parts, 94 parts, 92 parts, 90 parts or a range value between any two of the above parts by mass.

[0015] On the basis of the above technical solution, preferably, in the step S1, the amount of calcium oxide used is 30 to 70 parts by mass, and the amount of the modified solution used is 70 to 30 parts by mass.

[0016] On the basis of the above technical solution, preferably, in step S1, the amount of calcium oxide is independently selected from any value among 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, or a range between any two of the above parts, calculated by mass.

[0017] On the basis of the above technical solution, preferably, in step S1, the amount of the modified solution is independently selected from any value among 70 parts, 60 parts, 50 parts, 40 parts, 30 parts, or a range between any two of the above parts, in parts by mass.

[0018] Based on the above technical solution, preferably, in step S1, the ball milling time is 6 to 12 hours.

[0019] On the basis of the above technical solution, preferably, during the ball milling, the diameter of the grinding balls is 0.8-2 mm.

[0020] On the basis of the above technical solution, preferably, during the ball milling, the mass fraction of the grinding balls is 5-15% of the raw material.

[0021] On the basis of the above technical solution, preferably, the drying temperature is 50-100° C., and the drying time is 6 h to 24 h.

[0022] On the basis of the above technical solution, preferably, when sieving after drying, the mesh size of the sieve is 100 to 500 meshes.

[0023] On the basis of the above technical solution, preferably, in the step S2, the temperature of the heating and curing is 150° C. to 180° C., and the time of the heating and curing is 2 h to 5 h.

[0024] On the basis of the above technical solution, preferably, the drying temperature is 50° C. to 90° C., and the drying time is 8 h to 24 h.

[0025] On the basis of the above technical solution, preferably, the impregnation time is 30s to 3min.

[0026] On the basis of the above technical solution, preferably, in the step S2, the impregnation liquid used in the impregnation is selected from at least one of nano-SiO2 ethanol dispersion, nano-ZrO2 ethanol dispersion, and nano-YiO2 ethanol dispersion.

[0027] On the basis of the above technical solution, preferably, in step S2, the printed layer height is 0.05 mm to 0.20 mm.

[0028] On the basis of the above technical solution, preferably, the printed adhesive is phenolic resin, and the saturation of the adhesive is 70% to 140%.

[0029] On the basis of the above technical solution, preferably, in the step S3, the sintering includes a first sintering and a second sintering.

[0030] On the basis of the above technical solution, preferably, the temperature of the first sintering is 600° C. to 800° C., and the time of the first sintering is 1 hour to 3 hours.

[0031] On the basis of the above technical solution, preferably, the temperature of the second sintering is 1300° C. to 1500° C., and the time of the second sintering is 2 h to 3 h.

[0032] On the basis of the above technical solution, preferably, the heating rate of the sintering is 1-5°C / min.

[0033] According to another aspect of the present application, a soluble ceramic shell / core prepared by the above-mentioned preparation method is provided.

[0034] According to another aspect of the present application, there is provided an application of the above-mentioned soluble ceramic shell / core in a cast structural part, wherein the material of the cast structural part is selected from at least one of cast iron, cast steel, aluminum alloy, titanium alloy, and magnesium alloy.

[0035] On the basis of the above technical solution, preferably, after the pouring is completed, the structural part with the ceramic shell / core is placed in water. The ceramic shell / core reacts with water to crack and disintegrate, and is separated from the structural part, completing the shelling process.

[0036] As an optional embodiment, the present invention is implemented by the following technical solutions:

[0037] The method for preparing the soluble ceramic shell / core of the present invention comprises the following steps:

[0038] (1) First, 1 to 10 parts of a modifier and 99 to 90 parts of a modifying solvent are mixed by weight, heated in a water bath at 40 to 80° C. for 1 to 4 hours, and mixed to obtain a modified solution; 30 to 70 parts of calcium oxide, 70 to 30 parts of the modifying solution, and ball milling beads are added to a ball milling jar, and ball milling is performed using a planetary ball mill. The ball milled slurry is then dried and sieved through a mesh to obtain a modified calcium oxide powder;

[0039] (2) using modified calcium oxide powder as raw material, a ceramic shell / core blank is prepared by a droplet jet bonding molding process, which is then heated and solidified, impregnated with an impregnation liquid, and completely dried to obtain a ceramic shell / core blank;

[0040] (3) Designing a sintering temperature curve, and sintering the ceramic shell / core blank obtained in step (2) to obtain the soluble ceramic shell / core.

[0041] Based on the above technical solution, preferably, the modifier can be decomposed before sintering in the first stage of sintering.

[0042] On the basis of the above technical solution, preferably, 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%.

[0043] In the present invention, the solute molecules in the impregnation liquid used for the impregnation do not decompose above 1500°C; the solute components of the impregnation liquid will not react with the structural parts during the pouring process; the impregnation liquid is used to penetrate into the pores between the calcium oxide powders, keep the shape of the ceramic shell / core intact, avoid the collapse of the green body during the sintering process, and enhance the strength of the green body after sintering. In the present invention, the impregnation liquid is used to penetrate into the pores between the calcium oxide powders, keep the shape of the ceramic shell / core intact, avoid the collapse of the green body during the sintering process; the solute molecules in the impregnation liquid can react with calcium oxide to enhance the strength of the sample after sintering; the solute components of the impregnation liquid will not react with the structural parts during the pouring process. After the pouring is completed, the structural part with the ceramic shell / core is placed in water, and the calcium oxide in the ceramic shell / core reacts with water to cause the ceramic shell / core to crack and disintegrate, separate from the structural part, and complete the shelling.

[0044] In the present invention, calcium oxide is modified using a modification solution, the solution is evenly mixed by ball milling and dried, and after the solvent evaporates, the modifier is fully coated on the surface of the CaO powder, reducing the contact of CaO with air and reducing the impact of denaturation and agglomeration during the printing process on the final printing quality.

[0045] The soluble ceramic shell / core of the present invention has the following advantages over the prior art:

[0046] (1) The present invention utilizes a microdroplet jetting bonding process to prepare ceramic shells / cores, which can overcome the limitations of conventional processes in forming large, complex ceramic shells / cores, shorten production cycles, reduce production costs, and meet the production needs of the market. Furthermore, compared to other additive manufacturing technologies, the microdroplet jetting bonding process does not require laser or auxiliary heating molding, and offers advantages such as a wide range of materials, high efficiency, low cost, a support-free molding process, and environmental friendliness, thus paving the way for a wide range of applications.

[0047] (2) The present invention uses modified CaO to prepare the ceramic shell / core. The raw material price is low. Since CaO reacts with water, the casting with the ceramic shell / core can be fully immersed in hot water. The ceramic shell / core hydrolyzes and disintegrates in the water, realizing the automatic separation of the ceramic shell / core from the casting, greatly simplifying the subsequent shelling process. The process of dissolving the CaO ceramic shell / core is as follows:

[0048] CaO+H2O=Ca(OH)2

[0049] The solubility of the reaction product Ca(OH)2 is low, 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 is green and environmentally friendly, and has broad application prospects.

[0050] (3) The present invention adopts ball milling and modifier modification methods to modify CaO powder, and prepares CaO modified powder with good water resistance, which solves the problems of difficulty in 3DP molding and powder denaturation of traditional CaO powder during printing. The present invention provides a feasible production method for 3DP manufacturing of CaO soluble ceramic cores, opening up a new direction for the low-cost manufacturing of soluble ceramic cores. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0052] Figure 1 This is a process flow chart for preparing a soluble ceramic shell / core according to the present invention. DETAILED DESCRIPTION

[0053] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0054] Example 1

[0055] The method for preparing the soluble ceramic shell / core provided in Example 1 of the present invention mainly comprises the following steps:

[0056] (1) 5 g of stearic acid and 95 g of anhydrous ethanol were mixed and heated in a water bath at 60°C for 2 h. After mixing, a modified solution was obtained. 65 g of calcium oxide and 35 g of the modified solution were added to a ball mill. Zirconia balls with a diameter of 1 mm and a mass fraction of 8% of the raw material were then added. The mixture was ball milled for 12 h using a planetary ball mill. The ball milled slurry was then dried at 50°C for 24 h, crushed, and sieved through a 200-mesh sieve to obtain a coarse modified calcium oxide powder.

[0057] The designed three-dimensional STL structure of the ceramic shell / core is imported into a computer printing program, and the printing parameters are adjusted (print layer height 0.15mm, binder saturation 80%). The powder feed cylinder is then filled with sieved modified calcium oxide powder. A ceramic backing plate and a stainless steel base are placed on the surface of the working cylinder and the calcium oxide powder is evenly spread. After printing begins, the printhead begins spraying phenolic resin binder according to the path sliced ​​by the computer. After the printhead completes a single inkjet, the powder feed cylinder and working cylinder respectively rise and fall one layer height. The powder spreading process is completed by the rotation and movement of the powder spreading roller. This cycle repeats, completing the entire ceramic shell / core printing process.

[0058] (2) After printing is completed, the powder and the ceramic shell / core blank are placed in a drying oven together with a stainless steel base plate and heated and cured at 160°C. After curing for 4 hours, the drying oven is closed and the stainless steel plate is removed after cooling in the furnace. Next, the blank is removed from the powder bed and the residual powder on the ceramic shell / core blank is cleaned with a brush. Subsequently, the ceramic shell / core blank is placed in a basin and a 20% nano-ZrO2 ethanol dispersion is poured into it. The timer is started after all parts of the blank are completely impregnated. After 3 minutes, the impregnated ceramic shell / core blank is removed and placed on a tray. It is placed in a drying oven at 60°C and dried for 12 hours before being removed.

[0059] (3) The sintering of the ceramic shell / core blank adopts the buried firing method. 0.2mm plate-shaped corundum powder is evenly spread on a special ceramic plate for sintering. 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. Then it is placed in a high-temperature sintering furnace and sintered according to the process parameters of sintering at 600℃ for 2h, 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.

[0060] Example 2

[0061] The method for preparing the soluble ceramic shell / core provided in Example 2 of the present invention mainly comprises the following steps:

[0062] (1) 7 g of silane coupling agent and 93 g of acetone were mixed and heated in a water bath at 80°C for 2 h. After mixing, a modified solution was obtained. 60 g of calcium oxide and 40 g of the modified solution were added to a ball mill jar. Zirconia balls with a diameter of 1.5 mm and a mass fraction of 10% of the raw material were added. The mixture was ball milled using a planetary ball mill for 10 h. The ball-milled slurry was then dried at 55°C for 24 h, crushed, and sieved through a 250-mesh sieve to obtain a coarse modified calcium oxide powder.

[0063] The designed three-dimensional STL structure of the ceramic shell / core is imported into a computer printing program, and the printing parameters are adjusted (print layer height 0.10mm, binder saturation 120%). The powder feed cylinder is then filled with sieved modified calcium oxide powder. A ceramic backing plate and a stainless steel base are placed on the surface of the working cylinder and the calcium oxide powder is evenly spread. After printing begins, the printhead begins spraying phenolic resin binder according to the path sliced ​​by the computer. After the printhead completes a single inkjet, the powder feed cylinder and working cylinder rise and fall one layer height respectively. The powder spreading process is completed by the rotation and movement of the powder spreading roller. This cycle repeats, completing the entire ceramic shell / core printing process.

[0064] (2) After printing is completed, the powder and the ceramic shell / core blank are placed in a drying oven together with a stainless steel base plate and heated and cured at 180°C. After curing for 4 hours, the drying oven is closed and the stainless steel plate is removed after cooling in the furnace. Next, the blank is removed from the powder bed and the residual powder on the ceramic shell / core blank is cleaned with a brush. Subsequently, the ceramic shell / core blank is placed in a basin and a 20% by mass nano-YiO2 ethanol dispersion is poured into it. The timer is started after all parts of the blank are completely impregnated. After 2.5 minutes, the impregnated ceramic shell / core blank is taken out and placed on a tray. It is placed in a drying oven at 80°C and dried for 12 hours before being taken out.

[0065] (3) The sintering of the ceramic shell / core blank adopts the buried firing method. 0.2mm plate-shaped corundum powder is evenly spread on a special ceramic plate for sintering. 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. Then it is placed in a high-temperature sintering furnace and sintered according to the process parameters of sintering at 600℃ for 2h, sintering at 1500℃ for 2h, and a heating rate of 2℃ / min. Finally, it is cooled in the furnace to obtain a soluble ceramic shell / core.

[0066] Example 3

[0067] The method for preparing the soluble ceramic shell / core provided in Example 3 of the present invention mainly comprises the following steps:

[0068] (1) 3 g of ethyl bromide and 97 g of acetone were mixed and heated in a water bath at 60°C for 2 h. After mixing, a modified solution was obtained. 70 g of calcium oxide and 30 g of the modified solution were added to a ball mill. Zirconia balls with a diameter of 0.8 mm and a mass fraction of 8% of the raw material were added. The mixture was ball milled for 12 h using a planetary ball mill. The ball-milled slurry was then dried at 60°C for 24 h, crushed, and sieved through a 320-mesh sieve to obtain a coarse modified calcium oxide powder.

[0069] The designed three-dimensional STL structure of the ceramic shell / core is imported into a computer printing program, and the printing parameters are adjusted (print layer height 0.12mm, binder saturation 100%). The powder feed cylinder is then filled with sieved modified calcium oxide powder. A ceramic backing plate and a stainless steel base are placed on the surface of the working cylinder and the calcium oxide powder is evenly spread. After printing begins, the printhead begins spraying phenolic resin binder according to the path sliced ​​by the computer. After the printhead completes a single inkjet, the powder feed cylinder and working cylinder rise and fall one layer height respectively. The powder spreading process is completed by the rotation and movement of the powder spreading roller. This cycle repeats, completing the entire ceramic shell / core printing process.

[0070] (2) After printing is completed, the powder and the ceramic shell / core blank are placed in a drying oven together with a stainless steel base plate and heated and cured at 165°C. After curing for 3.5 hours, the drying oven is closed and the stainless steel plate is removed after cooling in the furnace. Next, the blank is removed from the powder bed and the residual powder on the ceramic shell / core blank is cleaned with a brush. Subsequently, the ceramic shell / core blank is placed in a basin and a 15% nano-ZrO2 ethanol dispersion is poured into it. The timer is started after all parts of the blank are completely impregnated. After 4 minutes, the impregnated ceramic shell / core blank is taken out and placed on a tray. It is placed in a drying oven at 50°C and dried for 18 hours before being taken out.

[0071] (3) The sintering of the ceramic shell / core blank adopts the buried firing method. 0.2mm plate-shaped corundum powder is evenly spread on a special ceramic plate for sintering. Then the dried ceramic shell / core blank is placed on the ceramic plate, and all parts of the blank are completely buried with plate-shaped corundum powder. Then it is placed in a high-temperature sintering furnace and sintered according to the process parameters of sintering at 700℃ for 2h, sintering at 1450℃ for 2h, and a heating rate of 2.5℃ / min. Finally, it is cooled in the furnace to obtain a soluble ceramic shell / core.

[0072] Example 4

[0073] The method for preparing the soluble ceramic shell / core provided in Example 4 of the present invention mainly comprises the following steps:

[0074] (1) 2 g of stearic acid and 98 g of anhydrous ethanol were mixed and heated in a water bath at 60°C for 2 h. After mixing, a modified solution was obtained. 30 g of calcium oxide and 70 g of the modified solution were added to a ball mill. Zirconia balls with a diameter of 0.8 mm and a mass fraction of 5% of the raw material were added. The mixture was ball milled using a planetary ball mill for 6 h. The ball-milled slurry was then dried at 70°C for 24 h, crushed, and sieved through a 100-mesh sieve to obtain a coarse modified calcium oxide powder.

[0075] The designed three-dimensional STL structure of the ceramic shell / core is imported into a computer printing program, and the printing parameters are adjusted (print layer height 0.05mm, binder saturation 140%). The powder feed cylinder is then filled with sieved modified calcium oxide powder. A ceramic backing plate and a stainless steel base are placed on the surface of the working cylinder and the calcium oxide powder is evenly spread. After printing begins, the printhead begins spraying phenolic resin binder according to the path sliced ​​by the computer. After the printhead completes a single inkjet, the powder feed cylinder and working cylinder respectively rise and fall one layer height. The powder spreading process is completed by the rotation and movement of the powder spreading roller. This cycle repeats, completing the entire ceramic shell / core printing process.

[0076] (2) After printing is completed, the powder and the ceramic shell / core blank are placed in a drying oven together with a stainless steel base plate and heated and cured at 150°C. After curing for 5 hours, the drying oven is closed and the stainless steel plate is removed after cooling in the furnace. Next, the blank is removed from the powder bed and the residual powder on the ceramic shell / core blank is cleaned with a brush. Subsequently, the ceramic shell / core blank is placed in a basin and a 20% nano-ZrO2 ethanol dispersion is poured into it. The timer is started after all parts of the blank are completely impregnated. After 3 minutes, the impregnated ceramic shell / core blank is taken out and placed on a tray. It is placed in a drying oven at 50°C and dried for 24 hours before being taken out.

[0077] (3) The sintering of the ceramic shell / core blank adopts the buried firing method. 0.2mm plate-shaped corundum powder is evenly spread on a special ceramic plate for sintering. 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. Then it is placed in a high-temperature sintering furnace and sintered according to the process parameters of sintering at 600℃ for 3h, sintering at 1300℃ for 3h, and a heating rate of 1℃ / min. Finally, it is cooled in the furnace to obtain a soluble ceramic shell / core.

[0078] Example 5

[0079] The method for preparing the soluble ceramic shell / core provided in Example 5 of the present invention mainly comprises the following steps:

[0080] (1) 8 g of stearic acid and 92 g of anhydrous ethanol were mixed and heated in a water bath at 60°C for 2 h. After mixing, a modified solution was obtained. 40 g of calcium oxide and 60 g of the modified solution were added to a ball mill, and 15% of the raw material mass fraction of 2 mm diameter zirconium oxide ball milling beads were added. The mixture was ball milled using a planetary ball mill for 12 h. The ball milled slurry was then dried at 100°C for 6 h, crushed, and sieved through a 500-mesh sieve to obtain a coarse modified calcium oxide powder.

[0081] The designed three-dimensional STL structure of the ceramic shell / core is imported into a computer printing program, and the printing parameters are adjusted (print layer height 0.20mm, binder saturation 70%). The powder feed cylinder is then filled with sieved modified calcium oxide powder. A ceramic backing plate and a stainless steel base are placed on the surface of the working cylinder and the calcium oxide powder is evenly spread. After printing begins, the printhead begins spraying phenolic resin binder according to the path sliced ​​by the computer. After the printhead completes a single inkjet, the powder feed cylinder and working cylinder respectively rise and fall one layer height. The powder spreading process is completed by the rotation and movement of the powder spreading roller. This cycle repeats, completing the entire ceramic shell / core printing process.

[0082] (2) After printing is completed, the powder and the ceramic shell / core blank are placed in a drying oven together with a stainless steel base plate and heated and cured at 180°C. After curing for 2 hours, the drying oven is closed and the stainless steel plate is removed after cooling in the furnace. Next, the blank is removed from the powder bed and the residual powder on the ceramic shell / core blank is cleaned with a brush. Subsequently, the ceramic shell / core blank is placed in a basin and a 20% nano-ZrO2 ethanol dispersion is poured into it. The timer is started after all parts of the blank are completely impregnated. After 30 seconds, the impregnated ceramic shell / core blank is taken out and placed on a tray. It is placed in a drying oven at 90°C and dried for 8 hours before being taken out.

[0083] (3) The sintering of the ceramic shell / core blank adopts the buried firing method. 0.2mm plate-shaped corundum powder is evenly spread on a special ceramic plate for sintering. 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. Then it is placed in a high-temperature sintering furnace and sintered according to the process parameters of 800℃ for 1h, 1500℃ for 2h, and a heating rate of 5℃ / min. Finally, it is cooled in the furnace to obtain a soluble ceramic shell / core.

[0084] Example 6

[0085] The method for preparing the soluble ceramic shell / core provided in Example 6 of the present invention mainly comprises the following steps:

[0086] (1) 1 g of stearic acid and 99 g of anhydrous ethanol were mixed and heated in a water bath at 60°C for 2 h. After mixing, a modified solution was obtained. 65 g of calcium oxide and 35 g of the modified solution were added to a ball mill. Zirconia balls with a diameter of 1 mm and a mass fraction of 8% of the raw material were then added. The mixture was ball milled for 12 h using a planetary ball mill. The ball milled slurry was then dried at 50°C for 24 h, crushed, and sieved through a 200-mesh sieve to obtain a coarse modified calcium oxide powder.

[0087] The designed three-dimensional STL structure of the ceramic shell / core is imported into a computer printing program, and the printing parameters are adjusted (print layer height 0.15mm, binder saturation 80%). The powder feed cylinder is then filled with sieved modified calcium oxide powder. A ceramic backing plate and a stainless steel base are placed on the surface of the working cylinder and the calcium oxide powder is evenly spread. After printing begins, the printhead begins spraying phenolic resin binder according to the path sliced ​​by the computer. After the printhead completes a single inkjet, the powder feed cylinder and working cylinder respectively rise and fall one layer height. The powder spreading process is completed by the rotation and movement of the powder spreading roller. This cycle repeats, completing the entire ceramic shell / core printing process.

[0088] (2) After printing is completed, the powder and the ceramic shell / core blank are placed in a drying oven together with a stainless steel base plate and heated and cured at 160°C. After curing for 4 hours, the drying oven is closed and the stainless steel plate is removed after cooling in the furnace. Next, the blank is removed from the powder bed and the residual powder on the ceramic shell / core blank is cleaned with a brush. Subsequently, the ceramic shell / core blank is placed in a basin and a 20% nano-ZrO2 ethanol dispersion is poured into it. The timer is started after all parts of the blank are completely impregnated. After 3 minutes, the impregnated ceramic shell / core blank is removed and placed on a tray. It is placed in a drying oven at 60°C and dried for 12 hours before being removed.

[0089] (3) The sintering of the ceramic shell / core blank adopts the buried firing method. 0.2mm plate-shaped corundum powder is evenly spread on a special ceramic plate for sintering. 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. Then it is placed in a high-temperature sintering furnace and sintered according to the process parameters of sintering at 600℃ for 2h, 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.

[0090] Example 7

[0091] The method for preparing the soluble ceramic shell / core provided in Example 1 of the present invention mainly comprises the following steps:

[0092] (1) 10 g of stearic acid and 90 g of anhydrous ethanol were mixed and heated in a water bath at 60°C for 2 h. After mixing, a modified solution was obtained. 65 g of calcium oxide and 35 g of the modified solution were added to a ball mill. Zirconia balls with a diameter of 1 mm and a mass fraction of 8% of the raw material were then added. The mixture was ball milled using a planetary ball mill for 12 h. The ball milled slurry was then dried at 50°C for 24 h, crushed, and sieved through a 200-mesh sieve to obtain a coarse modified calcium oxide powder.

[0093] The designed three-dimensional STL structure of the ceramic shell / core is imported into a computer printing program, and the printing parameters are adjusted (print layer height 0.15mm, binder saturation 80%). The powder feed cylinder is then filled with sieved modified calcium oxide powder. A ceramic backing plate and a stainless steel base are placed on the surface of the working cylinder and the calcium oxide powder is evenly spread. After printing begins, the printhead begins spraying phenolic resin binder according to the path sliced ​​by the computer. After the printhead completes a single inkjet, the powder feed cylinder and working cylinder respectively rise and fall one layer height. The powder spreading process is completed by the rotation and movement of the powder spreading roller. This cycle repeats, completing the entire ceramic shell / core printing process.

[0094] (2) After printing is completed, the powder and the ceramic shell / core blank are placed in a drying oven together with a stainless steel base plate and heated and cured at 160°C. After curing for 4 hours, the drying oven is closed and the stainless steel plate is removed after cooling in the furnace. Next, the blank is removed from the powder bed and the residual powder on the ceramic shell / core blank is cleaned with a brush. Subsequently, the ceramic shell / core blank is placed in a basin and a 20% nano-ZrO2 ethanol dispersion is poured into it. The timer is started after all parts of the blank are completely impregnated. After 3 minutes, the impregnated ceramic shell / core blank is removed and placed on a tray. It is placed in a drying oven at 60°C and dried for 12 hours before being removed.

[0095] (3) The sintering of the ceramic shell / core blank adopts the buried firing method. 0.2mm plate-shaped corundum powder is evenly spread on a special ceramic plate for sintering. 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. Then it is placed in a high-temperature sintering furnace and sintered according to the process parameters of sintering at 600℃ for 2h, 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.

[0096] Comparative Example 1

[0097] Step (1) in Example 1 was replaced by directly ball-milling 65 g of calcium oxide and anhydrous ethanol using a planetary ball mill for 12 h, followed by sieving through a 200-mesh sieve to obtain calcium oxide powder, which was then printed using the printing method in Example 1. The remaining preparation steps remained the same as those in Example 1. Because the calcium oxide was not modified with a modifying solution, direct printing with calcium oxide resulted in agglomeration, making it impossible to effectively print a ceramic shell / core preform.

[0098] Comparative Example 2

[0099] In step (1) of Example 1, "mixing 5 g of stearic acid and 95 g of anhydrous ethanol" was replaced with "mixing 0.8 g of stearic acid and 99.2 g of anhydrous ethanol", and the remaining preparation steps remained the same as those in Example 1. Compared with Example 1, due to the insufficient amount of stearic acid added, when the modified calcium oxide prepared using this method was printed, due to the small amount of stearic acid covering the surface of the calcium oxide powder, there was still a relatively obvious agglomeration phenomenon, resulting in the inability to effectively print a ceramic shell / core blank.

[0100] Comparative Example 3

[0101] The step (1) in Example 1, "mixing 5 g of stearic acid and 95 g of anhydrous ethanol", was replaced with "mixing 11 g of stearic acid and 89 g of anhydrous ethanol", and the remaining preparation steps remained the same as those in Example 1. Compared with Example 1, since the content of stearic acid was sufficiently high and the specific surface area of ​​the calcium oxide powder was constant, the increase in the content of stearic acid had little effect on the contact angle of the modified calcium oxide powder. The final printing effect was slightly different from the sample in Example 1, and the porosity of the ceramic core finally printed was slightly lower.

[0102] Test Examples

[0103] Porosity test

[0104] For the molded samples prepared in Examples 1, 6, 7 and Comparative Examples 1 to 3, preforms were prepared with different modifier contents and corresponding adjustment of the modified solvent (four groups of parallel test blank samples were prepared for samples with the same stearic acid content), and the porosity of the prepared soluble ceramic shell / core products was tested. The data obtained are shown in Table 1 below.

[0105] Table 1: Porosity of samples with different stearic acid contents.

[0106]

[0107] As shown in Table 1, four parallel experiments were conducted on molded samples with different contents. The modifier in Examples 1, 6, and 7 was stearic acid. The porosity of the samples in Examples 1, 6, and 7 was compared with that in Comparative Examples 1, 2, and 3. When the amount of the modifier was 1 to 10 parts by mass, the porosity of the prepared samples could meet the requirements.

[0108] The porosity of the samples in Comparative Example 2 was compared with that in Example 1. Since the amount of stearic acid used in Comparative Example 2 was relatively small, when the prepared modified calcium oxide was printed, there was still a relatively obvious agglomeration phenomenon due to the small amount of stearic acid covering the surface of the calcium oxide powder. As a result, the ceramic shell / core blank could not be effectively printed, and the porosity could not be measured.

[0109] Comparing the porosity of the samples in Comparative Example 3 with that in Example 1, since the content of stearic acid is high enough and the specific surface area of ​​the calcium oxide powder is constant, the increase in the content of stearic acid has little effect on the contact angle of the modified calcium oxide powder. The final printing effect is slightly different from that of the sample in Example 1, and the porosity of the ceramic core finally printed is slightly lower.

[0110] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a soluble ceramic shell / core, characterized in that: The preparation method comprises the following steps: Step S1: ball-milling, drying, and sieving the raw materials containing calcium oxide and modified solution to obtain modified calcium oxide powder; Step S2: Printing the modified calcium oxide powder into a ceramic shell / core blank, heating and curing, infiltration, and drying to obtain a ceramic shell / core blank; Step S3: sintering the ceramic shell / core blank to obtain the soluble ceramic shell / core; In the step S1, the modified solution includes a modifier and a modified solvent; The modifier is selected from at least one of ethyl bromide, benzene bromide, silane coupling agent, stearic acid, and n-octadecyltrichlorosilane; The modified solvent is selected from at least one of methanol, ethanol, glycerol, and acetone; By mass, the amount of the modifier is 1 to 10 parts, and the amount of the modified solvent is 99 to 90 parts; In step S1, the amount of calcium oxide used is 30 to 70 parts by mass, and the amount of the modified solution used is 70 to 30 parts by mass; In step S1, the ball milling time is 6 to 12 hours; During the ball milling, the diameter of the grinding balls is 0.8-2 mm; During the ball milling, the mass fraction of the grinding balls is 5-15% of the raw materials; The drying temperature is 50-100°C, and the drying time is 6-24 hours; When sieving after drying, the mesh number of the sieve is 100-500 meshes.

2. The preparation method according to claim 1, wherein In step S2, the heating and curing temperature is 150° C. to 180° C., and the heating and curing time is 2 h to 5 h; The drying temperature is 50°C to 90°C, and the drying time is 8h to 24h; The impregnation time is 30s~3min; In the step S2, the impregnation liquid used in the impregnation is at least one selected from nano-SiO2 ethanol dispersion, nano-ZrO2 ethanol dispersion, and nano-YiO2 ethanol dispersion.

3. The preparation method according to claim 1, wherein In step S2, the printed layer height is 0.05 mm to 0.20 mm; The printed binder is phenolic resin, and the saturation of the binder is 70% to 140%.

4. The preparation method according to claim 1, wherein In the step S3, the sintering includes a first sintering and a second sintering; The temperature of the first sintering is 600° C. to 800° C., and the time of the first sintering is 1 h to 3 h; The second sintering temperature is 1300° C. to 1500° C., and the second sintering time is 2 h to 3 h; The heating rate of the sintering is 1-5°C / min.

5. The soluble ceramic shell / core prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the soluble ceramic shell / core in casting structural parts according to claim 5, characterized in that: The material of the cast structure is selected from at least one of cast iron, cast steel, aluminum alloy, titanium alloy and magnesium alloy.

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