Double-wall cooling ceramic core and hot-press injection integral molding method

Abstract

The present invention relates to a double-wall cooling ceramic core and a hot-press injection integral molding method. The method comprises the following steps: carrying out hot-press injection molding on a resin mold preparation slurry to obtain a resin mold, wherein the raw materials for preparing the resin mold preparation slurry include: 50-60 parts by weight of a cross-linking agent, 20-30 parts by weight of a hydrotrope, 5-10 parts by weight of an additive, 5-10 parts by weight of a reinforcing agent, and 5-30 parts by weight of a viscosity modifier; assembling the resin mold in a profile mold, injecting a ceramic core slurry into the profile mold, and carrying out hot-press injection molding to obtain a green body wrapping the resin mold; removing the resin mold from the green body wrapping the resin mold to obtain a double-wall cooling ceramic core green body; and carrying out degreasing treatment and sintering treatment on the double-wall cooling ceramic core green body to obtain the double-wall cooling ceramic core. The present invention solves the common problems in existing hot-press injection molding processes of numerous molds, long periods, and poor assembly accuracy caused by segmented preparation followed by assembly during the preparation of ceramic cores having complex structures.

Description

Double-wall cold ceramic core and hot-pressing injection molding method

[0001] This disclosure claims priority to a Chinese patent application filed with the Patent Office of China on March 14, 2024, with application number 202410293252.1 and invention name “A double-wall cold ceramic core and hot injection molding method,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present invention relates to the technical field of precision casting of key aviation components, and in particular to a double-wall cold ceramic core and a hot-pressing and injection-molding integrated molding method. Background Art

[0003] With the increasing demand for high power and high efficiency in advanced propulsion systems for aerospace technology, especially in aircraft / space engines and gas turbines, efficient cooling of single-crystal superalloy blades is an inevitable development trend for future advanced aircraft engine turbine blades. The use of double-walled cooled single-crystal superalloy blades is currently an effective solution for significantly improving aircraft engine combustion efficiency.

[0004] Ceramic cores are key transitional components for forming the cooling channels of complex double-walled, cooled single-crystal superalloy blades. The fabrication process for these complex, finely structured ceramic cores is a critical technology that urgently needs to be mastered.

[0005] To overcome this key technology, existing techniques primarily utilize multiple sets of metal molds for separate preparation, which are then assembled into a double-walled cold ceramic core. However, this existing technique suffers from technical issues such as long preparation cycles, high mold design and production costs, assembly errors, and low core yield. Therefore, a process is urgently needed that reduces the number of molds and allows for the integrated production of double-walled cold ceramic cores.

[0006] Summary of the Invention

[0007] In view of this, the present invention provides a double-wall cold ceramic core and a hot injection molding method, the main purpose of which is to provide a double-wall cold ceramic core preparation process with a small number of molds and integrated molding.

[0008] To achieve the above objectives, the present invention mainly provides the following technical solutions:

[0009] In one aspect, an embodiment of the present invention provides a method for hot-pressing and injection-molding a double-walled cold ceramic core, comprising the following steps:

[0010] The step of preparing a resin mold comprises hot-pressing and injection-molding a slurry prepared for the resin mold to obtain a resin mold; wherein, in parts by weight, the raw materials for preparing the slurry for the resin mold include: 50-60 parts by weight of a cross-linking agent, 20-30 parts by weight of a hydrotrope, 5-10 parts by weight of an additive, 5-10 parts by weight of a strengthening agent, and 5-30 parts by weight of a viscosity modifier; wherein the resin mold is used to form a slit between the outer wall and the inner wall of a double-walled cold ceramic core;

[0011] Preparation of green blank: assembling the resin mold in the outer mold, then injecting ceramic core slurry into the outer mold, performing hot injection molding, and obtaining a green blank wrapped with the resin mold;

[0012] Resin mold removal step: removing the resin mold from the green blank wrapped with the resin mold to obtain a double-wall cold ceramic core green blank;

[0013] Degreasing and sintering treatment steps: performing degreasing treatment and sintering treatment on the double-wall cold ceramic core blank to obtain a double-wall cold ceramic core.

[0014] Preferably, in the step of preparing the resin mold: the cross-linking agent is selected from one or both of paraffin wax and beeswax; and / or the hydrotrope is selected from one or more of acrylic emulsion, polyurethane, and acrylic ester (acrylic ester is a resin soluble in acidic solution formed by cross-linking acrylic ester polymers and methacrylic ester polymers); and / or the additive is polydimethylsiloxane, 3-aminopropyltriethoxysilane, N-(β-aminoethyl-γ-aminopropyl)methyldimethoxysilane, 3-(isopropyl)methylsiloxane, 1,2-dimethoxy- ... One or more (preferably, the viscosity of the additive is 10-5000cp in (preferably, the viscosity of the additive is 10-5000cp, and here, the viscosity is for the matching of the formula and the temperature, to avoid the defect of insufficient filling in the resin mold forming process); and / or the strengthening agent is one or more of alumina whiskers, zirconia whiskers, mullite whiskers, and silica whiskers; and / or the viscosity modifier is one or both of water-based epoxy resin and water-soluble acrylic resin; and / or the strengthening agent and cross-linking agent are mixed, after mechanical stirring for 360-3600min at a temperature of 120-220°C, a hydrotrope, additive, and viscosity modifier are added thereto, and at a temperature of 80-120°C, after mechanical stirring for 120-360min, a resin mold is obtained and prepared in slurry.

[0015] Preferably, the diameter of the enhancer is 10-500 nm and the length is 10-800 μm; and / or the viscosity of the viscosity modifier is 0.1-100 cp.

[0016] Preferably, the resin mold preparation slurry has a viscosity of 1000-5000 cp at a temperature of 80-120°C.

[0017] Preferably, in the step of preparing the resin mold, the parameters of hot compression molding are set as follows: hot compression injection temperature is 50-100°C, mold temperature is 30-80°C, injection pressure is 2-4MPa, injection time is 30-60s, and holding time is 60-360s.

[0018] Preferably, in the step of preparing the green body: the ceramic core slurry includes paraffin wax and ceramic powder; preferably, the step of preparing the ceramic core slurry includes: stirring the paraffin wax and silica ceramic powder at a temperature of 120-180°C to obtain the ceramic core slurry. Preferably, in the ceramic core slurry, the mass fraction of the paraffin wax is 20-30%, and the mass fraction of the silica ceramic powder is 70-80%; preferably, the component of the silica ceramic powder is SiO2, or the main component of the silica ceramic powder is SiO2, and preferably further includes additives (the additives mainly include Al2O3 and ZrSiO4).

[0019] Preferably, in the step of preparing the green blank, the parameters of the hot injection molding are set as follows: hot injection temperature is 80-150°C, mold temperature is 50-100°C, injection pressure is 3.5-5.5Mpa, injection time is 60-90s, and holding time is 60-120s.

[0020] Preferably, in the step of removing the resin mold: the green blank wrapped with the resin mold is placed in a core-removing liquid, taken out after soaking for a set time, and dried to obtain a double-wall cold ceramic core green blank; preferably, the preparation step of the core-removing liquid is as follows: adding acid to water; wherein the volume fraction of the acid in the core-removing liquid is 10-20%; wherein the acid is one or more of carbonic acid, acetic acid, silicic acid, nitrous acid, hydrosulfuric acid, hydrofluoric acid, hypochlorous acid, and hydrocyanic acid; preferably, the purity of the acid is 80-100%; preferably, the water is distilled water; preferably, the set time is 30-90 min; preferably, the temperature of the drying treatment is room temperature, and the time of the drying treatment is 360-720 min.

[0021] Preferably, the degreasing step comprises: heating the double-wall cold ceramic core blank to 400-500°C, keeping it warm for 180-270 minutes, and then cooling it to room temperature to obtain a degreasing double-wall cold ceramic core blank; preferably, the heating rate is 1-5°C / min, and the cooling rate is 1-5°C / min; preferably, the atmosphere for the degreasing treatment is air.

[0022] Preferably, the sintering step includes: heating the degreased double-wall cold ceramic core blank to 1000-1400°C, keeping it warm for 240-360 minutes, and then cooling it to room temperature to obtain a double-wall cold ceramic core; preferably, the heating rate is 5-8°C / min, and the cooling rate is 5-8°C / min; preferably, the atmosphere for the sintering treatment is air.

[0023] In another aspect, an embodiment of the present invention provides a double-walled cold ceramic core, wherein the double-walled cold ceramic core is produced by the hot-pressing integral molding method described in any of the above-mentioned double-walled cold ceramic cores. Preferably, a slit of 0.1-2 mm is formed between the outer and inner walls of the double-walled cold ceramic core.

[0024] Compared with the prior art, the double-walled cold ceramic core and hot-pressing and injection molding method of the present invention have at least the following beneficial effects:

[0025] An embodiment of the present invention provides a hot-pressing integrated molding method for a double-walled cold ceramic core, which comprises first preparing a resin mold that can be removed later, assembling the resin mold into an outer mold, and injecting a ceramic core slurry into the outer mold to obtain a blank coated with the resin mold; after removing the resin mold from the blank coated with the resin mold, further degreasing and sintering are performed to obtain a double-walled cold ceramic core. Here, the present invention utilizes a prefabricated resin mold in conjunction with an outer mold to achieve integrated molding of a double-walled cold ceramic core. Therefore, the concept of the present invention solves the common problems of the existing hot-pressing process for preparing ceramic cores with complex structures, such as the large number of molds, long cycles, and poor assembly accuracy caused by the assembly after the mold preparation.

[0026] Furthermore, an embodiment of the present invention provides a method for hot-pressing integrated molding of a double-walled cold ceramic core. By designing the components of the resin mold, the components in the resin mold and the components and processes have synergistic effects, thereby greatly improving the forming integrity and forming accuracy of the fine structure of the double-walled cold ceramic core. For example, paraffin wax and beeswax are used as the main components, which have high strength at room temperature. The fine structure can withstand the impact of the slurry without deformation during the ceramic slurry injection molding process, thereby improving the molding accuracy of the fine structure; using a water-soluble additive as the main additive, the resin mold can be removed without damaging the ceramic core blank through the resin mold core removal liquid, retaining the high-precision blank fine structure; the addition of ceramic whiskers as a reinforcing agent can greatly improve the toughness and deformation recovery ability of the resin mold at the injection temperature, and has a significant synergistic effect on the fine structure of the molded ceramic core; the addition of a viscosity regulator ensures the forming accuracy and forming integrity of the resin mold. In addition, the forming temperature and forming pressure of the resin mold and the pressure and temperature of the ceramic slurry injection molding are coordinated with the cross-linking temperature, decomposition temperature and strength of the above components, thereby ensuring the forming and high-precision requirements of the fine structure of the double-wall cold ceramic core.

[0027] In summary, the present invention provides a double-walled cold ceramic core and a method for hot-pressing and integrally molding it. This significantly reduces the number of molds required in the currently commonly used hot-pressing and parting process for manufacturing double-walled cold ceramic cores, shortening the manufacturing cycle and reducing costs. This integral molding method significantly eliminates errors introduced by core assembly and significantly improves core precision.

[0028] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG1 is a flow chart of a hot-pressing and injection-molding method for a double-walled cold ceramic core provided by an embodiment of the present invention.

[0030] FIG2 is a physical picture of a double-walled cold ceramic core prepared according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] To further illustrate the technical means and effects employed by the present invention to achieve its intended objectives, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention is provided in conjunction with the accompanying drawings and preferred embodiments. In the following description, different references to "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0032] The present invention utilizes a prefabricated resin mold to form a semi-enclosed slit in a double-walled cold ceramic core (a 0.1-2 mm slit exists between the inner and outer walls of the double-walled cold ceramic core). Prior to degreasing and sintering, the resin mold is removed to produce a double-walled cold ceramic core blank. By controlling the degreasing and sintering parameters, the complex and fine structure of the double-walled cold ceramic core product can be fabricated. The specific embodiments of the present invention are as follows:

[0033] An embodiment of the present invention provides a method for hot-pressing and injection-molding a double-walled cold ceramic core, as shown in FIG1 , comprising the following steps:

[0034] The step of preparing a resin mold is as follows: hot-pressing and injection-molding the slurry for preparing the resin mold to obtain the resin mold; wherein, in parts by weight, the raw materials for preparing the slurry for preparing the resin mold include: 50-60 parts by weight of a cross-linking agent, 20-30 parts by weight of a hydrotrope, 5-10 parts by weight of an additive, 5-10 parts by weight of a strengthening agent, and 5-30 parts by weight of a viscosity modifier.

[0035] In this step, the resin mold preparation slurry includes, by weight, 50-60 parts by weight of a cross-linking agent, 20-30 parts by weight of a hydrotrope, 5-10 parts by weight of an additive, 5-10 parts by weight of a strengthening agent, and 5-30 parts by weight of a viscosity modifier.

[0036] The crosslinking agent is paraffin and / or beeswax; the hydrotrope is one or more of acrylic emulsion, polyurethane, and acrylic ester (the addition of the hydrotrope is mainly to facilitate its miscibility with water); the additive is one or more of polydimethylsiloxane, 3-aminopropyltriethoxysilane, N-(β-aminoethyl-γ-aminopropyl)methyldimethoxysilane, and 3-(isomethylacryloyloxy)propyltrimethoxysilane; the strengthening agent is one or more of aluminum oxide whiskers, zirconium oxide whiskers, mullite whiskers, and silicon dioxide whiskers; and the viscosity modifier is one or more of water-based epoxy resin and water-soluble acrylic resin.

[0037] The diameter of the reinforcing agent is 10-500 nm, the length is 10-800 μm, and the viscosity of the viscosity modifier is 0.1-100 cp.

[0038] The viscosity of the resin mold preparation slurry at 100° C. is 1000-5000 cp.

[0039] Preferably, the parameters of hot injection molding are set as follows: hot injection temperature of 50-100°C, mold temperature of 30-80°C, injection pressure of 2-4 MPa, injection time of 30-60s, and holding time of 60-360s.

[0040] The step of preparing a green blank is as follows: assembling the resin mold in the outer mold, then injecting ceramic core slurry into the outer mold, and performing hot injection molding to obtain a green blank wrapped with the resin mold.

[0041] In this step, paraffin wax and silicon dioxide ceramic powder are mechanically stirred at a temperature of 120-180° C. to obtain ceramic core slurry.

[0042] Among them, the parameters of hot injection molding are set as follows: hot injection temperature is 80-150℃, mold temperature is 50-100℃, injection pressure is 3.5-5.5Mpa, injection time is 60-90s, and holding time is 60-120s.

[0043] Resin mold removal step: removing the resin mold from the green blank wrapped with the resin mold to obtain a double-wall cold ceramic core green blank.

[0044] In this step, the green blank wrapped with the resin mold is placed in a resin mold core-removing liquid, soaked for 30-90 minutes, taken out, and dried at room temperature for 360 minutes to 720 minutes to obtain a double-wall cold ceramic core green blank.

[0045] In this step, the core removal liquid is prepared as follows: 10-20% by volume of one or more of carbonic acid, acetic acid, silicic acid, nitrous acid, hydrosulfuric acid, hydrofluoric acid, hypochlorous acid, and hydrocyanic acid are added to distilled water.

[0046] Degreasing and sintering treatment steps: performing degreasing treatment and sintering treatment on the double-wall cold ceramic core blank to obtain a double-wall cold ceramic core.

[0047] In this step, the parameters of the degreasing treatment are set as follows: the heating rate and the cooling rate are 1-5°C / min; the degreasing treatment temperature is 400-500°C; the holding time is 180-270min; the degreasing atmosphere is air;

[0048] The parameters of the sintering treatment are set as follows: the heating rate and the cooling rate are 5-8°C / min; the sintering temperature is 1000-1400°C, the holding time is 240-360min; and the sintering atmosphere is air.

[0049] Here, the above-mentioned solution of the present invention is described as follows:

[0050] (1) The present invention proposes a double-wall cold ceramic core and a hot-pressing integrated molding method, which utilizes a resin mold in conjunction with an outer mold (outer metal mold) to achieve integrated molding; wherein, the various formula components and preparation processes in the resin mold work in synergy, greatly improving the forming integrity and forming accuracy of the fine structure of the double-wall cold ceramic core. With paraffin wax and beeswax as the main components, the strength is high at room temperature, and the fine structure can withstand the impact of the slurry during the ceramic slurry injection molding process without deformation, thereby improving the molding accuracy of the fine structure; with a water-soluble additive as the main additive, the resin mold can be removed without damaging the ceramic core blank through the resin mold core removal liquid, retaining the high-precision blank fine structure; the addition of ceramic whiskers as a reinforcing agent can greatly improve the toughness and deformation recovery ability of the resin mold at the injection temperature, and has a significant synergistic effect on the fine structure of the molded ceramic core; the addition of a viscosity modifier ensures the forming accuracy and forming integrity of the resin mold. In addition, the forming temperature and forming pressure of the resin mold and the pressure and temperature of the ceramic slurry injection molding are coordinated with the cross-linking temperature, decomposition temperature and strength of the above components, thereby ensuring the forming and high-precision requirements of the fine structure of the double-wall cold ceramic core.

[0051] (2) The present invention proposes a double-walled cold ceramic core and a hot-pressing integral molding method, which greatly reduces the number of molds in the currently commonly used hot-pressing parting process for preparing double-walled cold ceramic cores, shortens the preparation cycle, and reduces the preparation cost. The integral molding method significantly eliminates the errors caused by core assembly and significantly improves the accuracy of the core.

[0052] The present invention is further described below by means of specific examples:

[0053] Example 1

[0054] This embodiment prepares a double-walled cold ceramic core, which mainly includes the following steps:

[0055] 1) Preparing a resin mold: Hot-pressing the resin mold slurry to obtain a resin mold; wherein, in parts by weight, the resin mold slurry comprises: 60 parts by weight of a crosslinker, 20 parts by weight of a hydrotrope, 5 parts by weight of an additive, 5 parts by weight of a strengthening agent, and 10 parts by weight of a viscosity modifier. The crosslinker is a mixture of paraffin wax and beeswax in a mass ratio of 7:1; the hydrotrope is a mixed solution of an acrylic emulsion and polyurethane in a volume ratio of 3:2; the additive is a mixture of polydimethylsiloxane, 3-aminopropyltriethoxysilane, and 3-(isomethylacryloyloxy)propyltrimethoxysilane in a volume ratio of 3:2:1, and the viscosity of the additive is 2000 cp; the strengthening agent is alumina whiskers with a diameter of 100 nm and a length of 100 μm; and the viscosity modifier is a water-soluble acrylic resin with a viscosity of 10 cp.

[0056] The resin mold preparation slurry is prepared by mixing a strengthening agent and a crosslinking agent, then mechanically stirring the mixture at 120°C for 360 minutes to obtain a mixed liquid. A hydrotrope, additives, and a viscosity modifier are then added to the mixed liquid, and the mixture is stirred at 120°C for another 360 minutes to obtain a mixed resin mold preparation slurry. The viscosity of the resin mold preparation slurry at 100°C is 2000 cp.

[0057] In addition, the hot injection molding parameters are set as follows: hot injection temperature is 80°C, mold temperature is 60°C, injection pressure is 2 MPa, injection time is 30s, and holding time is 120s.

[0058] 2) Preparing a green blank: assembling the resin mold in the outer mold, then injecting ceramic core slurry into the outer mold, and performing hot injection molding to obtain a green blank wrapped with the resin mold.

[0059] In this step, the ceramic core slurry is prepared as follows: paraffin wax and silica ceramic powder are mechanically stirred at a temperature of 180°C to obtain the ceramic core slurry. The mass fraction of the paraffin wax in the ceramic core slurry is 30%, and the mass fraction of the silica ceramic powder is 70%; the silica ceramic powder is composed of silicon dioxide.

[0060] The parameters of the hot injection molding are set as follows: the hot injection molding temperature is 150°C, the mold temperature is 90°C, the injection pressure is 4 MPa, the injection time is 60s, and the holding time is 120s.

[0061] 3) Resin mold removal step: removing the resin mold from the green blank wrapped with the resin mold to obtain a double-walled cold ceramic core green blank.

[0062] The resin-molded green blank is placed in a core stripping solution, soaked for 60 minutes, removed, and dried at room temperature for 360 minutes to obtain a double-walled cold ceramic core green blank. The core stripping solution is prepared from distilled water and acid. The volume fraction of the acid is 20%, and the volume ratio of carbonic acid, acetic acid, and silicic acid is 3:2:1.

[0063] 4) Degreasing and Sintering Step: The double-walled cold ceramic core blank is degreased and sintered to obtain a double-walled cold ceramic core. A photo of the double-walled cold ceramic core prepared in this example is shown in Figure 2. As shown in Figure 2, the double-walled cold ceramic core has a 0.1-2 mm slit 3 between the outer wall 1 and the inner wall 2.

[0064] The parameters of the degreasing treatment were set as follows: the heating rate and cooling rate were 3°C / min; the degreasing treatment temperature was 460°C; the holding time was 180 min; the degreasing atmosphere was air;

[0065] The parameters of the sintering treatment are set as follows: the heating rate and the cooling rate are 5°C / min; the sintering temperature is 1200°C, the holding time is 360min; and the sintering atmosphere is air.

[0066] Example 2

[0067] This embodiment prepares a double-walled cold ceramic core, which mainly includes the following steps:

[0068] 1) Preparing a resin mold: Hot-pressing a slurry for preparing a resin mold to obtain a resin mold; wherein, in parts by weight, the raw materials for preparing the resin mold slurry include: 50 parts by weight of a crosslinker, 30 parts by weight of a hydrotrope, 5 parts by weight of an additive, 10 parts by weight of a strengthening agent, and 5 parts by weight of a viscosity modifier. The crosslinker is a mixture of paraffin wax and beeswax in a mass ratio of 3:1; the hydrotrope is a mixed solution of acrylic acid ester and polyurethane in a volume ratio of 5:2; the additive is a mixture of N-(β-aminoethyl-γ-aminopropyl)methyldimethoxysilane and 3-(isomethylacryloyloxy)propyltrimethoxysilane in a volume ratio of 3:1, and the viscosity of the additive is 5000 cp; the strengthening agent is alumina whiskers with a diameter of 500 nm and a length of 800 μm; and the viscosity modifier is a water-based epoxy resin with a viscosity of 30 cp.

[0069] The resin mold preparation slurry is prepared by mixing a strengthening agent and a cross-linking agent, mechanically stirring the mixture at 220°C for 360 minutes, adding a hydrotrope, additives, and a viscosity modifier, and mechanically stirring the mixture at 100°C for 270 minutes to obtain the resin mold preparation slurry. The viscosity of the resin mold preparation slurry at 100°C is 5000 cp.

[0070] In addition, the hot injection molding parameters are set as follows: hot injection temperature is 100°C, mold temperature is 80°C, injection pressure is 3 MPa, injection time is 60s, and holding time is 180s.

[0071] 2) Preparing a green blank: assembling the resin mold in the outer mold, then injecting ceramic core slurry into the outer mold, and performing hot injection molding to obtain a green blank wrapped with the resin mold.

[0072] In this step, the ceramic core slurry is prepared as follows: paraffin wax and silica ceramic powder are mechanically stirred at a temperature of 120° C. to obtain the ceramic core slurry. The mass fraction of the paraffin wax in the ceramic core slurry is 25%, and the mass fraction of the silica ceramic powder is 75%; the silica ceramic powder is composed of silicon dioxide.

[0073] The parameters of the hot injection molding are set as follows: the hot injection molding temperature is 120°C, the mold temperature is 100°C, the injection pressure is 5.5 MPa, the injection time is 90s, and the holding time is 100s.

[0074] 3) Resin mold removal step: removing the resin mold from the green blank wrapped with the resin mold to obtain a double-walled cold ceramic core green blank.

[0075] The resin-molded green blank is placed in a core stripping solution, soaked for 90 minutes, removed, and dried at room temperature for 720 minutes to obtain a double-walled cold ceramic core green blank. The core stripping solution is prepared from distilled water and acid. The volume fraction of the acid is 10%, and the volume ratio of hydrosulfuric acid, hydrofluoric acid, and hydrocyanic acid is 2:2:1.

[0076] 4) Degreasing and sintering steps: performing degreasing and sintering on the double-wall cold ceramic core blank to obtain a double-wall cold ceramic core.

[0077] The parameters of the degreasing treatment were set as follows: the heating rate and cooling rate were 1°C / min; the degreasing treatment temperature was 400°C; the holding time was 270 min; the degreasing atmosphere was air;

[0078] The parameters of the sintering treatment are set as follows: the heating rate and the cooling rate are 8°C / min; the sintering temperature is 1150°C, the holding time is 240min; and the sintering atmosphere is air.

[0079] Example 3

[0080] 1) Preparing a resin mold: Hot-pressing the resin mold slurry to obtain a resin mold; wherein, in parts by weight, the resin mold slurry comprises: 50 parts by weight of a crosslinker, 25 parts by weight of a hydrotrope, 10 parts by weight of an additive, 8 parts by weight of a strengthening agent, and 7 parts by weight of a viscosity modifier. The crosslinker is a mixture of paraffin wax and beeswax in a mass ratio of 3:2; the hydrotrope is a mixed solution of acrylic acid ester and polyurethane in a volume ratio of 4:1; the additive is 3-aminopropyltriethoxysilane with a viscosity of 100 cp; the strengthening agent is zirconium oxide whiskers with a diameter of 50 nm and a length of 10 μm; and the viscosity modifier is a water-soluble epoxy resin with a viscosity of 80 cp.

[0081] The resin mold preparation slurry is prepared by mixing a strengthening agent and a crosslinking agent, then mechanically stirring the mixture at 200°C for 2700 minutes to obtain a mixed liquid. A hydrotrope, additives, and a viscosity modifier are then added to the mixed liquid, and the mixture is stirred at 100°C for another 270 minutes to obtain a mixed resin mold preparation slurry. The viscosity of the resin mold preparation slurry at 100°C is 3000 cp.

[0082] In addition, the hot injection molding parameters are set as follows: hot injection temperature is 100°C, mold temperature is 80°C, injection pressure is 4 MPa, injection time is 60s, and holding time is 360s.

[0083] 2) Preparing a green blank: assembling the resin mold in the outer mold, then injecting ceramic core slurry into the outer mold, and performing hot injection molding to obtain a green blank wrapped with the resin mold.

[0084] In this step, the ceramic core slurry is prepared as follows: 30% by mass of paraffin wax and 70% by mass of silica ceramic powder (component is silica) are mechanically stirred at a temperature of 160° C. to obtain the ceramic core slurry.

[0085] The parameters of the hot injection molding are set as follows: the hot injection molding temperature is 120°C, the mold temperature is 80°C, the injection pressure is 5.5 MPa, the injection time is 80s, and the holding time is 100s.

[0086] 3) Resin mold removal step: removing the resin mold from the green blank wrapped with the resin mold to obtain a double-walled cold ceramic core green blank.

[0087] The resin-molded green blank was placed in a core stripping solution, soaked for 90 minutes, removed, and dried at room temperature for 600 minutes to obtain a double-walled cold ceramic core blank. The core stripping solution was prepared from distilled water and acid. The volume fraction of the acid was 15%, and the volume ratio of nitrous acid, hydrofluoric acid, and carbonic acid was 5:1:4.

[0088] 4) Degreasing and sintering: Degreasing and sintering the double-wall cold ceramic core blank to obtain a double-wall cold ceramic core. The degreasing parameters are set as follows: heating and cooling rates of 4°C / min; degreasing temperature of 500°C; holding time of 250 minutes; degreasing atmosphere of air;

[0089] The parameters of the sintering treatment are set as follows: the heating rate and the cooling rate are 8°C / min; the sintering temperature is 1310°C, the holding time is 270min; and the sintering atmosphere is air.

[0090] Example 4

[0091] 1) Preparing a resin mold: Hot-pressing the resin mold slurry to obtain a resin mold; wherein, in parts by weight, the resin mold slurry comprises: 55 parts by weight of a crosslinker, 20 parts by weight of a hydrotrope, 10 parts by weight of an additive, 10 parts by weight of a strengthening agent, and 5 parts by weight of a viscosity modifier. The crosslinker is a mixture of paraffin wax and beeswax in a mass ratio of 9:1; the hydrotrope is a mixed solution of an acrylic emulsion and an acrylic acid ester in a volume ratio of 1:2; the additive is a mixture of polydimethylsiloxane and 3-(methacryloyloxy)propyltrimethoxysilane in a volume ratio of 2:1, and the viscosity of the additive is 50 cp; the strengthening agent is mullite whiskers with a diameter of 50 nm and a length of 800 μm; and the viscosity modifier is a water-soluble acrylic resin with a viscosity of 80 cp.

[0092] The resin mold preparation slurry is prepared by mixing a strengthening agent and a crosslinking agent, then mechanically stirring the mixture at 180°C for 720 minutes to obtain a mixed liquid. A hydrotrope, additives, and a viscosity modifier are then added to the mixed liquid, and the mixture is stirred at 100°C for 270 minutes to obtain a mixed resin mold preparation slurry. The viscosity of the resin mold preparation slurry at 120°C is 5000 cp.

[0093] In addition, the hot injection molding parameters are set as follows: hot injection temperature is 100°C, mold temperature is 45°C, injection pressure is 4 MPa, injection time is 60s, and holding time is 360s.

[0094] 2) Preparing a green blank: assembling the resin mold in the outer mold, then injecting ceramic core slurry into the outer mold, and performing hot injection molding to obtain a green blank wrapped with the resin mold.

[0095] In this step, the ceramic core slurry is prepared as follows: paraffin wax and silica ceramic powder are mechanically stirred at a temperature of 150° C. to obtain the ceramic core slurry. The mass fraction of the paraffin wax in the ceramic core slurry is 20%, and the mass fraction of the silica ceramic powder is 80%. The silica ceramic powder is composed of silicon dioxide.

[0096] The parameters of the hot injection molding are set as follows: the hot injection molding temperature is 130°C, the mold temperature is 75°C, the injection pressure is 3.8 MPa, the injection time is 80s, and the holding time is 110s.

[0097] 3) Resin mold removal step: removing the resin mold from the green blank wrapped with the resin mold to obtain a double-walled cold ceramic core green blank.

[0098] The resin-molded green blank was placed in a core stripping solution, soaked for 80 minutes, removed, and dried at room temperature for 560 minutes to obtain a double-walled cold ceramic core blank. The core stripping solution was prepared from distilled water and acid. The volume fraction of the acid was 12%, and the volume ratio of carbonic acid, hypochlorous acid, and hydrocyanic acid was 5:1:1.

[0099] 4) Degreasing and sintering: Degreasing and sintering the double-wall cold ceramic core blank to obtain a double-wall cold ceramic core. The degreasing parameters are set as follows: heating and cooling rates of 5°C / min; degreasing temperature of 400°C; holding time of 270 minutes; degreasing atmosphere of air;

[0100] The parameters of the sintering treatment are set as follows: the heating rate and the cooling rate are 7°C / min; the sintering temperature is 1400°C, the holding time is 240min; and the sintering atmosphere is air.

[0101] Comparative Example 1

[0102] Comparative Example 1: A double-walled cold ceramic core is prepared. The difference between this comparative example and Example 1 is that the quality of the strengthening agent is replaced with paraffin; the rest of the formula, preparation process, degreasing and sintering process are exactly the same as Example 1.

[0103] Comparative Example 2

[0104] Comparative Example 2: A double-walled cold ceramic core is prepared. The difference between this comparative example and Example 2 is that the hydrotrope and other qualities are replaced with paraffin wax; the rest of the formula, preparation process, degreasing and sintering process are exactly the same as Example 2.

[0105] Comparative Example 3

[0106] Comparative Example 3 prepares a double-wall cold ceramic core. The difference between this comparative example and Example 2 is that when preparing the resin mold, the hot pressing temperature is changed to 180°C and the injection pressure is 6 MPa; the rest of the formula, preparation process, degreasing and sintering process are exactly the same as Example 2.

[0107] Table 1

[0108] It can be seen from the above examples, comparative examples and Table 1 that:

[0109] (1) The resin mold of the embodiment of the present invention has high strength (can meet the use requirements), good dissolution performance of the resin mold, and high precision of the prepared ceramic core.

[0110] (2) The resin mold in Comparative Example 1 lacks a reinforcing agent, resulting in low strength of the resin mold and deformation during the subsequent ceramic core pressing process, which results in poor core precision;

[0111] (3) The resin mold in Comparative Example 2 was unable to be removed due to the lack of water-soluble additives, resulting in failure of the ceramic core injection molding.

[0112] (4) During the injection molding of the resin mold in Comparative Example 3, the viscosity of the slurry used to prepare the resin mold was too low due to the high injection temperature, which caused large shrinkage and deformation of the resin mold during the compression molding process, ultimately resulting in low precision of the ceramic core finally prepared.

[0113] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiment based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A hot-pressing and injection-molding method for a double-walled cold ceramic core, characterized in that: It includes the following steps: The step of preparing a resin mold comprises hot-pressing and injection-molding a slurry prepared for the resin mold to obtain a resin mold; wherein, in parts by weight, the raw materials for preparing the slurry for the resin mold include: 50-60 parts by weight of a cross-linking agent, 20-30 parts by weight of a hydrotrope, 5-10 parts by weight of an additive, 5-10 parts by weight of a strengthening agent, and 5-30 parts by weight of a viscosity modifier; wherein the resin mold is used to form a slit between the outer wall and the inner wall of a double-walled cold ceramic core; Preparation of green blank: assembling the resin mold in the outer mold, then injecting ceramic core slurry into the outer mold, performing hot injection molding, and obtaining a green blank wrapped with the resin mold; Resin mold removal step: removing the resin mold from the green blank wrapped with the resin mold to obtain a double-wall cold ceramic core green blank; Degreasing and sintering treatment steps: performing degreasing treatment and sintering treatment on the double-wall cold ceramic core blank to obtain a double-wall cold ceramic core.

2. The hot-pressing and injection-molding method for a double-walled cold ceramic core according to claim 1, characterized in that: In the step of preparing the resin mold: The cross-linking agent is selected from one or both of paraffin and beeswax; and / or The hydrotrope is selected from one or more of acrylic emulsion, polyurethane, and acrylic ester; and / or The additive is one or more of polydimethylsiloxane, 3-aminopropyltriethoxysilane, N-(β-aminoethyl-γ-aminopropyl)methyldimethoxysilane, and 3-(isomethacryloyloxy)propyltrimethoxysilane; preferably, the viscosity of the additive is 10-5000cp; and / or The reinforcing agent is one or more of alumina whiskers, zirconia whiskers, mullite whiskers, and silica whiskers; and / or The viscosity modifier is one or both of water-based epoxy resin and water-soluble acrylic resin; and / or The reinforcing agent and the cross-linking agent are mixed, mechanically stirred at a temperature of 120-220° C. for 360-3600 minutes, and then a hydrotrope, an additive, and a viscosity modifier are added thereto. After mechanically stirring at a temperature of 80-120° C. for 120-360 minutes, a resin mold preparation slurry is obtained.

3. The hot-pressing and injection-molding method for a double-walled cold ceramic core according to claim 1 or 2, characterized in that: The reinforcing agent has a diameter of 10-500 nm and a length of 10-800 μm; and / or The viscosity of the viscosity modifier is 0.1-100 cp.

4. The hot-pressing and injection-molding method for a double-walled cold ceramic core according to any one of claims 1 to 3, characterized in that: The resin mold preparation slurry has a viscosity of 1000-5000 cp at a temperature of 80-120°C.

5. The hot-pressing and injection-molding method for a double-walled cold ceramic core according to any one of claims 1 to 4, characterized in that: In the step of preparing the resin mold, the parameters of the hot injection molding are set as follows: The hot pressing temperature is 50-100℃, the mold temperature is 30-80℃, the injection pressure is 2-4MPa, the injection time is 30-60s, and the holding time is 60-360s.

6. The hot-pressing and injection-molding method for a double-walled cold ceramic core according to any one of claims 1 to 5, characterized in that: In the process of preparing green billet: The ceramic core slurry includes paraffin wax and silicon dioxide ceramic powder; Preferably, in the ceramic core slurry, the mass fraction of paraffin wax is 20-30%, and the mass fraction of silicon dioxide ceramic powder is 70-80%; Preferably, the composition of the silicon dioxide ceramic powder is SiO2; Preferably, the step of preparing the ceramic core slurry comprises: stirring paraffin wax and ceramic powder at a temperature of 120-180° C. to obtain the ceramic core slurry.

7. The hot-pressing and injection-molding method for a double-walled cold ceramic core according to any one of claims 1 to 6, characterized in that: In the step of preparing the green blank, the parameters of the hot injection molding are set as follows: The hot pressing temperature is 80-150℃, the mold temperature is 50-100℃, the injection pressure is 3.5-5.5Mpa, the injection time is 60-90s, and the holding time is 60-120s.

8. The hot-pressing and injection-molding method for a double-walled cold ceramic core according to any one of claims 1 to 7, characterized in that: In the step of removing the resin mold: The green blank wrapped with the resin mold is placed in a core-removing liquid, soaked for a set time, taken out, and dried to obtain a double-wall cold ceramic core green blank; Preferably, the core removal liquid is prepared by the following steps: adding acid to water; wherein the volume fraction of the acid in the core removal liquid is 10-20%; wherein the acid is one or more of carbonic acid, acetic acid, silicic acid, nitrous acid, hydrosulfuric acid, hydrofluoric acid, hypochlorous acid, and hydrocyanic acid; preferably, the water is distilled water; Preferably, the purity of the acid is 80-100%; Preferably, the setting time is 30-90 minutes; Preferably, the drying temperature is room temperature, and the drying time is 360-720 minutes.

9. The hot-pressing and injection-molding method for a double-walled cold ceramic core according to any one of claims 1 to 8, characterized in that: In the degreasing and sintering steps: The degreasing step comprises: heating the double-wall cold ceramic core blank to 400-500°C, keeping the temperature for 180-270 minutes, and then cooling it to room temperature to obtain a degreasing double-wall cold ceramic core blank; preferably, the heating rate is 1-5°C / min, and the cooling rate is 1-5°C / min; preferably, the degreasing atmosphere is air; and / or The sintering step comprises: heating the degreased double-wall cold ceramic core blank to 1000-1400°C, keeping the temperature for 240-360 minutes, and then cooling it to room temperature to obtain a double-wall cold ceramic core; preferably, the heating rate is 5-8°C / min, and the cooling rate is 5-8°C / min; preferably, The atmosphere for the sintering process is air.

10. A double-walled cold ceramic core, characterized in that: The double-walled cold ceramic core is prepared by the hot injection molding method of the double-walled cold ceramic core according to any one of claims 1 to 9; preferably, a slit of 0.1-2 mm is provided between the outer wall and the inner wall of the double-walled cold ceramic core.

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