A method for preparing a mold for precision casting of an aluminum alloy with an internal cavity structure

Abstract

The present application relates to the technical field of aluminum alloy investment casting, and discloses a preparation method of an aluminum alloy investment casting mold with an inner cavity structure, which comprises mold group manufacturing, mold shell manufacturing, mold group inner cavity and pipeline pouring, dewaxing, baking, pouring, cleaning and inspection; the present application ensures the accuracy and stability of the mold shell through the designed surface layer and transition layer; during the mold group inner cavity and pipeline pouring stage, mixed and uniform pouring materials are used, which have good fluidity, hardening property and water-dispersibility, and can fill the fine parts of the mold shell inner cavity and pipeline; through reasonable baking temperature and time control, the heat conductivity, easy dewaxing property and strength of the mold shell are comprehensively ensured; thereby the metallurgical quality and appearance quality of the casting are improved. The whole preparation method greatly improves the production efficiency and product quality through the optimization of the process flow and material ratio of each step.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy investment casting technology, specifically relating to a method for preparing a mold with an internal cavity structure for aluminum alloy investment casting. Background Technology

[0002] With intensifying market competition, the rapid development of metal 3D printing, the reduced machining costs of forgings, and the stable internal quality, traditional aluminum alloy structural parts are gradually being phased out of our precision casting production site. In order to better capture the aluminum alloy precision casting business, some components of aero-engines, such as oil pump housings and gear pump housings, which have complex cavities, have become the focus of development in the aluminum alloy casting field.

[0003] The traditional manufacturing processes for this type of aluminum alloy casting with internal cavities and pipe structures fall into three categories: 3D printing sand mold core casting, investment casting with plaster mold, and water-soluble salt core wax casting. The problems with using 3D printed sand mold core casting for this type of casting are: the surface of the inner cavity and pipes of the casting is rough, and there is a risk of local sand adhesion. During the operation of the whole machine, vibration can easily bring sand particles into the air passage and oil passage, reducing the service life of the whole machine. The problems with using investment casting with plaster mold precision casting are: plaster mold has poor thermal conductivity and is prone to moisture absorption. The inner cavity and pipes of the casting are prone to defects such as porosity and dense pores, resulting in a low pass rate of non-destructive testing. Air bubbles are prone to appear in the plaster mold during the manufacturing process, causing aluminum beads to form in the inner cavity and pipes of the casting, which are difficult to remove and reduce the yield of castings. The problems with using water-soluble salt core wax pressing precision casting for this type of casting are: water-soluble salt core is prone to moisture absorption, causing reactive porosity defects in the inner cavity and pipes of the casting, reducing the service life of the whole machine. On the other hand, the production cycle of water-soluble salt core is long, and there is a risk of core breakage during the wax pressing process. X-ray inspection is required for each piece, which extends the production cycle. When castings produced using the above manufacturing processes are subjected to fluorescent penetrant testing, the surface quality of the casting's internal cavity and pipes is difficult to meet the relevant standard requirements.

[0004] In recent years, with the deepening of the concepts of high quality, high efficiency, and low cost, traditional manufacturing processes have become increasingly inadequate to meet the diverse and comprehensive market demands for these products, whether in terms of high quality requirements, production cycles, or cost reduction and efficiency improvement. Furthermore, when using traditional silica sol ceramic shell precision casting processes to manufacture such products, unlike stainless steel or high-temperature alloy precision castings, it is difficult to clean the ceramic material from the internal cavities and channels of aluminum alloy precision castings with complex cavities and channels using alkaline explosion or chemical methods. On the other hand, due to the relatively low hardness of aluminum alloy, physical methods for cleaning the refractory materials in the internal cavities and channels can easily lead to product deformation and damage. Therefore, there is an urgent need to develop a method for preparing molds with internal cavity structures for aluminum alloy investment casting to meet the current comprehensive market requirements for these products. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned problems and provide a method for preparing a mold for aluminum alloy investment casting with an internal cavity structure, so as to improve the overall surface roughness, dimensional accuracy, overall surface quality and overall shell removal difficulty of aluminum alloy castings with internal cavities and pipes, and shorten the production cycle and reduce production costs.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a method for preparing a mold for aluminum alloy investment casting with an internal cavity structure, comprising the following steps:

[0008] S1, Model creation and model grouping;

[0009] S2, Module Shell Creation: After the model group tree is completed, the module shell is created. The module shell creation includes a surface layer, a transition layer, and a first reinforcement layer.

[0010] S3, Injection of module cavity and pipes: The uniformly mixed injection material is introduced into the cavity and pipes of the module shell. The injection material includes α-gypsum powder, gypsum powder and silica sol.

[0011] S4, Subsequent shell making, dewaxing and firing: After the filling is completed, the shell is dried by air, and then the subsequent module shell making work is carried out. After the shell is made, dewaxing and firing are carried out.

[0012] A further improvement of the present invention is that it also includes casting, cleaning and inspection of the mold shell. The specific method is as follows: the modified high-pressure water gun and sandblasting machine are used to clean the mold shell and refractory material residues attached to the casting and the inner cavity pipes. Then, an endoscope is used to inspect the inner cavity and pipes of the casting and to perform fluorescence penetration inspection and low magnification inspection.

[0013] A further improvement of the present invention is that, in step S1, the model is made by wax modeling or 3D printing.

[0014] A further improvement of the present invention is that, in step S2, the surface layer of the module shell uses silica sol / zircon powder 320# as slurry and zircon sand 100# as sprinkling sand; the transition layer of the module shell includes a first transition layer and a second transition layer, the first transition layer uses silica sol / zircon powder 320# as slurry and chromite sand 80# as sprinkling sand, the second transition layer uses silica sol / shangdian powder 200# as slurry and shangdian sand 30~60# as sprinkling sand; the first reinforcing layer uses silica sol / shangdian powder 200# as slurry and shangdian sand 16~30# as sprinkling sand.

[0015] A further improvement of the present invention is that, when the minimum size of the pipe or inner cavity is 3.5mm < X ≤ 6mm, the modular shell fabrication includes a surface layer, a first transition layer, and a second transition layer; when the minimum size of the pipe or inner cavity is X > 6mm, the modular shell fabrication includes a surface layer, a first transition layer, a second transition layer, and a first reinforcing layer.

[0016] A further improvement of the present invention is that the components of the filling material for the module cavity and pipe in step S3 include: α-gypsum powder and gypsum powder as powder, and silica sol as solvent, wherein gypsum powder accounts for 25-35% of the total weight of the powder and silica sol accounts for 25-35% of the total weight of the powder.

[0017] A further improvement of the present invention is that, in step S3, ribs are pre-embedded before filling the inner cavity and pipes of the module, and the ribs are φ2~φ4 stainless steel wires.

[0018] A further improvement of the present invention is that the particle size of the powder is 200 mesh.

[0019] A further improvement of the present invention is that, in step S4, a steam kettle is used for dewaxing, and then the module is placed in a resistance furnace and heated at a rate of 200~250℃ / h, heated to 850±10℃ and held for 2~3h to remove the crystal water of the module shell and ceramicize the module shell, and then cooled down with the furnace.

[0020] A further improvement of this invention is that the method is applicable to the preparation of aluminum castings with a minimum internal cavity and pipe dimension X > 3.5 mm.

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

[0022] This invention provides a method for preparing an aluminum alloy investment casting mold with an internal cavity structure. Through carefully designed surface and transition layers, the accuracy and stability of the mold shell are ensured. During the cavity and pipe filling stage, a uniformly mixed filling material with good fluidity, hardening properties, and water-disintegrating properties is used to fill the fine parts of the mold shell's internal cavity and pipes. By rationally controlling the firing temperature and time, the thermal conductivity, ease of release, and strength of the mold shell are comprehensively guaranteed, thereby improving the metallurgical and appearance quality of the casting. The entire preparation method significantly improves production efficiency and product quality by optimizing the process flow and material ratios of each step. Attached Figure Description

[0023] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and do not specifically limit the shapes and proportions of the components of the invention.

[0024] Figure 1 This is a schematic flowchart of the preparation method of the present invention;

[0025] Figure 2 This is a cross-sectional view of the aluminum alloy impeller casting of Embodiment 1 of the present invention;

[0026] Figure 3 This is an isometric view of the aluminum alloy impeller casting of Embodiment 1 of the present invention;

[0027] Figure 4 This is a partial sectional view of the aluminum alloy shell casting of Embodiment 2 of the present invention;

[0028] Figure 5 This is another partial cross-sectional view of the aluminum alloy shell casting of Embodiment 2 of the present invention.

[0029] The components are: 1. Impeller; 2. Flow channel; 3. Shell; 4. Pipeline. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0031] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0032] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0033] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0034] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0035] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0036] The present invention will now be described in further detail with reference to the accompanying drawings:

[0037] like Figure 1 As shown, the present invention provides a method for preparing a mold for aluminum alloy investment casting with an internal cavity structure, comprising the following steps:

[0038] Step S1: Model making, using wax modeling or 3D printing rapid prototyping model, and assembling the model into a tree structure;

[0039] Step S2, Module Shell Fabrication: After the model tree is completed, the module shell is fabricated. The module shell fabrication includes a surface layer, a transition layer, and a first reinforcing layer. The selection and proportion of materials for each layer are carefully designed to ensure the strength and precision of the shell.

[0040] The surface layer uses silica sol / zircon powder 320# as slurry and zircon sand 100# as sand, which improves the smoothness and precision of the shell.

[0041] The transition layer includes a first transition layer and a second transition layer. The first transition layer uses silica sol / zircon powder 320# as slurry and chromite sand 80# as sprinkling sand. The second transition layer uses silica sol / Shangdian powder 200# as slurry and Shangdian sand 30~60# as sprinkling sand.

[0042] The first reinforcement layer uses silica sol / Shangdian powder 200# as slurry and Shangdian sand 16~30# as sand.

[0043] The transition layer and the first reinforcing layer use different materials and particle sizes depending on the size of the pipe or inner cavity. This ensures the strength of the mold shell while avoiding the impact of an excessively thick ceramic mold shell layer on the subsequent cleaning of the casting's inner cavity and pipe. Specifically, when the minimum size of the pipe or inner cavity is 3.5mm < X ≤ 6mm, the mold shell fabrication includes a surface layer, a first transition layer, and a second transition layer; when the minimum size of the pipe or inner cavity is X > 6mm, the mold shell fabrication includes a surface layer, a first transition layer, a second transition layer, and a first reinforcing layer.

[0044] Step S3: First, weigh out powder α gypsum powder and gypsum powder, where the gypsum powder accounts for 25-35% of the total weight of the powder. Thoroughly mix the weighed powder. Then, weigh out the solvent silica sol, where the silica sol accounts for 25-35% of the total weight of the powder. Pour the thoroughly mixed powder into the solvent and stir thoroughly for 1-3 minutes. Use a diversion rod or thin iron wire to divert the casting material into the inner cavity and pipes of the module shell.

[0045] As a preferred option, the particle size of Shangdian powder is 200 mesh.

[0046] It should be noted that ribs need to be pre-embedded before filling the inner cavity and pipes of the module. The ribs are φ2~φ4 stainless steel wires.

[0047] Step S4, subsequent shell making, dewaxing and firing: After the filling is completed, the shell is allowed to dry for more than 3 hours. Then the subsequent module shell making work is carried out. After the shell is made, dewaxing and firing are carried out.

[0048] The process involves dewaxing using a steam autoclave, followed by placing the module in a resistance furnace and heating it at a rate of 200~250℃ / h. The temperature is then raised to 850±10℃ and held for 2~3 hours. Finally, the temperature is lowered with the furnace to the specified casting temperature for later use.

[0049] Step S5: Pour, clean, and inspect the shell.

[0050] Specifically, modified high-pressure water guns and sandblasting machines were used to clean the refractory material residue adhering to the casting mold shell and inner cavity pipes, improving cleaning efficiency and cleanliness. Then, an endoscope was used to inspect the inner cavity and pipes of the casting to ensure their integrity and quality. Fluorescent penetrant testing and low-magnification inspection were also performed.

[0051] It should be noted that the high-pressure water gun and sandblasting machine used in this invention are both improved versions, specifically as follows:

[0052] By matching the screw-on thread specifications of the high-pressure water gun nozzle interface of the existing hydraulic shell cleaning machine and the nozzle interface of the sandblasting machine, the nozzles of the two post-cleaning equipment are modified. A stainless steel external thread adapter matching the screw-on thread of the high-pressure water gun nozzle interface and stainless steel pipes of different diameters with a wall thickness greater than 1mm are selected. Based on the internal cavity and pipe structure of the corresponding product, suitable stainless steel pipes are selected and adaptively bent and modified. These are then welded to the stainless steel external thread adapter and screwed into the high-pressure water gun nozzle interface of the hydraulic shell cleaning machine to clean the refractory materials of the casting's internal cavity and pipes. Considering that the bent sandblasting nozzle is prone to wear due to high-speed friction with sand particles during operation, an adaptively bent nozzle data model is designed based on the internal cavity and pipe structure of the corresponding product. An external thread adapter portion is reserved at the tail for machining. The K4169 high-temperature alloy scrap is used for casting using a 3D printing rapid prototyping mold + investment casting method. Subsequently, the external thread of the adapter is realized through machining and screwed into the sandblasting machine nozzle interface to achieve deep cleaning of the casting's internal cavity and pipes.

[0053] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0054] Example 1

[0055] This embodiment describes the preparation of a certain type of aluminum alloy impeller casting with the following outline dimensions: φ35×17.4mm. The impeller's flow channel cross-section is 3.6mm. The structure is shown in [reference needed]. Figure 2 and Figure 3 As shown, it is difficult to achieve the required technical indicators such as surface roughness, dimensional accuracy, and metallurgical quality using traditional casting processes. The preparation steps are as follows:

[0056] Step 1: Model creation, using 3D printing for rapid prototyping and model assembly;

[0057] Step 2: After the model tree is completed, the module shell is made according to the casting size. Since the flow channel cross-section of the impeller is 4.7mm, the module shell making only includes the first three layers, namely the surface layer, the first transition layer and the second transition layer.

[0058] Step 3: First, weigh 16.5g of α-gypsum powder and 5g of gypsum powder and mix them thoroughly. Then, weigh 6.5g of silica sol (5~10℃) and pour the thoroughly mixed powder into the solvent and stir for 1 minute. Use a thin iron wire to guide the flow into the impeller channel.

[0059] Step 4: After the filling process is completed and the machine has been air-dried for 4 hours, proceed with the subsequent module shell making work according to the process requirements;

[0060] Step 5: Dewaxing and roasting. Dewaxing is carried out using a steam kettle. Then, the module is placed in a resistance furnace at room temperature and heated at a rate of 240±10℃ / h. The temperature is raised to 850±10℃ and held for 2 hours before being cooled down in the furnace for later use.

[0061] Step 6: Cast the shell according to the process requirements;

[0062] Step 7: Use a high-pressure water gun with a modified nozzle to clean the residual gypsum refractory material adhering to the mold shell and inner cavity pipes of the casting. After cutting, use a sandblasting machine with a modified nozzle to perform surface treatment on the casting.

[0063] Step 8: Use an endoscope to inspect the inner cavity and pipes of the casting, and check the surface of the casting for defects such as porosity and slag inclusions;

[0064] Step 9: Inspect the surface of the casting for defects such as porosity, looseness, and slag inclusions using fluorescent penetrant testing;

[0065] Step 10: After heat treatment, dissect the casting and inspect the cross-section with low magnification to check for defects such as porosity and slag porosity.

[0066] The batch of castings underwent surface inspection, fluorescence inspection, and low-magnification inspection. The surface quality and fluorescence inspection of the castings met the HB963 Class II casting standard. After heat treatment, the pinholes were inspected under low magnification and were found to be better than Grade 1, which met the HB963 Class II casting standard.

[0067] Example 2

[0068] This embodiment describes the preparation of a certain type of aluminum alloy shell casting with outline dimensions of 276×201×197mm. The shell contains two large-diameter pipes with a maximum diameter of φ13mm and a length of 130mm. The structure is shown below. Figure 4 and Figure 5As shown, it is difficult to achieve the required technical indicators such as surface roughness, dimensional accuracy, and metallurgical quality using traditional casting processes. The preparation steps are as follows:

[0069] Step 1, Model making: Use wax modeling for rapid prototyping and create a model tree;

[0070] Step 2: After the model tree is completed, the modular shell is made according to the casting size. Since the maximum diameter of the shell's pipes is 13mm, the modular shell making includes the first four layers: the surface layer, the first transition layer, the second transition layer, and the first reinforcement layer.

[0071] Step 3: First, weigh 71g of α-gypsum powder and 21.3g of gypsum powder and mix them thoroughly. Then, weigh 27.7g of silica sol (5~10℃). Pour the thoroughly mixed powder into the solvent and stir for 1 minute. Use a diversion rod to pour it into the inner cavity and pipes of the module shell.

[0072] Step 4: After the filling is completed and the machine dries for 5 hours, proceed with the subsequent module shell making work according to the process requirements.

[0073] Step 5, dewaxing and roasting: Dewaxing is carried out using a steam kettle, and then the module is placed in a resistance furnace at room temperature and heated at a rate of 240±10℃ / h. The temperature is raised to 850±10℃ and held for 2 hours before being cooled down in the furnace for later use.

[0074] Step 6: Cast the shell according to the process requirements;

[0075] Step 7: Use a high-pressure water gun with a modified nozzle to clean the residual gypsum refractory material on the mold shell and inner cavity pipes of the casting. After cutting, use a sandblasting machine with a modified nozzle to perform surface treatment on the casting.

[0076] Step 8: Use an endoscope to inspect the inner cavity and pipes of the casting to check for defects such as porosity and slag inclusions on the surface of the casting.

[0077] Step 9: Inspect the surface of the casting for defects such as porosity, looseness, and slag inclusions using fluorescent penetrant testing.

[0078] Step 10: After heat treatment, dissect the casting and inspect the cross-section with low magnification to check for defects such as porosity and slag porosity.

[0079] The batch of castings underwent surface inspection, fluorescence inspection, and low-magnification inspection. The surface quality and fluorescence inspection of the castings met the HB963 Class II casting standard. After heat treatment, the pinholes were inspected under low magnification and were found to be better than Grade 1, which met the HB963 Class II casting standard.

[0080] Many embodiments and applications beyond the examples provided will be apparent to those skilled in the art upon reading the foregoing description. Therefore, the scope of this teaching should not be determined by reference to the foregoing description, but rather by reference to the foregoing claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the applicant has not considered that subject matter as part of the disclosed inventive subject matter.

[0081] The above content provides a further detailed description of the present invention. It should not be construed that the specific embodiments of the present invention are limited to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection of the present invention as defined by the submitted claims.

Claims

1. A method for preparing a mold for investment casting of aluminum alloy with an internal cavity structure, characterized in that, Includes the following steps: S1, Model creation and model grouping; S2, Module Shell Creation: After the model group tree is completed, the module shell is created. The module shell creation includes a surface layer, a transition layer, and a first reinforcement layer. S3, Injection of module cavity and pipes: The uniformly mixed injection material is introduced into the cavity and pipes of the module shell. The injection material includes α-gypsum powder, gypsum powder and silica sol. S4, after the filling is completed, it is allowed to dry on its own, and then the subsequent module shell making work is carried out. After the shell making is completed, it is dewaxed and fired. In step S2, the surface layer of the module shell uses silica sol / zircon powder 320# as slurry and zircon sand 100# as sprinkling sand; the transition layer of the module shell includes a first transition layer and a second transition layer. The first transition layer uses silica sol / zircon powder 320# as slurry and chromite sand 80# as sprinkling sand. The second transition layer uses silica sol / shangdian powder 200# as slurry and shangdian sand 30~60# as sprinkling sand; the first reinforcing layer uses silica sol / shangdian powder 200# as slurry and shangdian sand 16~30# as sprinkling sand.

2. The method for preparing a mold with an internal cavity structure for investment casting of aluminum alloy according to claim 1, characterized in that, It also includes pouring, cleaning and inspecting the mold shell. The specific methods are as follows: use a modified high-pressure water gun and sandblasting machine to clean the mold shell and refractory material residues attached to the casting and the inner cavity pipes. Then use an endoscope to inspect the inner cavity and pipes of the casting and perform fluorescent penetrant inspection and low magnification inspection.

3. The method for preparing a mold with an internal cavity structure for investment casting of aluminum alloy according to claim 1, characterized in that, In step S1, the model is made using wax modeling or 3D printing.

4. The method for preparing a mold with an internal cavity structure for investment casting of aluminum alloy according to claim 1, characterized in that, When the minimum dimension of the pipe or inner cavity is 3.5mm < X ≤ 6mm, the module shell fabrication includes a surface layer, a first transition layer, and a second transition layer; when the minimum dimension of the pipe or inner cavity is X > 6mm, the module shell fabrication includes a surface layer, a first transition layer, a second transition layer, and a first reinforcing layer.

5. The method for preparing a mold with an internal cavity structure for investment casting of aluminum alloy according to claim 1, characterized in that, The components of the filling material for the module cavity and pipes in step S3 include: α-gypsum powder and gypsum powder as powder, and silica sol as solvent, wherein gypsum powder accounts for 25-35% of the total weight of the powder and silica sol accounts for 25-35% of the total weight of the powder.

6. The method for preparing a mold with an internal cavity structure for investment casting of aluminum alloy according to claim 1, characterized in that, In step S3, ribs are pre-embedded before filling the inner cavity and pipes of the module. The ribs are φ2~φ4 stainless steel wires.

7. The method for preparing a mold with an internal cavity structure for investment casting of aluminum alloy according to claim 1, characterized in that, In step S3, the particle size of the powder used in the store is 200 mesh.

8. The method for preparing a mold with an internal cavity structure for investment casting of aluminum alloy according to claim 1, characterized in that, In step S4, the module is dewaxed using a steam autoclave, and then placed in a resistance furnace and heated at a rate of 200~250℃ / h. The temperature is raised to 850±10℃ and held for 2~3 hours to remove the crystal water from the module shell and ceramicize the module shell. Then, the temperature is lowered with the furnace.

9. The method for preparing a mold with an internal cavity structure for investment casting of aluminum alloys according to any one of claims 1 to 8, characterized in that, This method is applicable to the preparation of aluminum alloy castings with a minimum internal cavity and pipe dimension X > 3.5 mm.

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