A method for solving the problem of fracture and core deviation of slender ceramic core of high-temperature alloy investment casting

Abstract

The present application relates to a kind of methods for solving high-temperature alloy investment casting slender ceramic core fracture and core deviation, comprising S1, ceramic core structure design;S2, ceramic core production;S3, wax mold manufacturing corresponding wax mold;S4, wax mold splicing and group tree are combined together with the ceramic core and casting wax mold;The wax mold after splicing is bonded inner gate and runner, forms complete pouring tree string;S5, shell making dewaxing adopts manual shell making mode, obtains the mold shell with cavity.The present application is accurate by splicing ceramic core and wax mold, optimizes pouring system design, adopts special design bonding wax and round hole structure to reduce the risk of ceramic core fracture, and is combined with efficient manual shell making and post-processing process, not only significantly improves the precision of casting, surface quality and production efficiency, also enhances production flexibility and environmental performance, is an important technical improvement in investment casting field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of casting, in particular to a method for solving the fracture and core deviation of slender ceramic cores of high-temperature alloy investment castings. BACKGROUND

[0002] When discussing the high-temperature alloy industry in China, especially its key role in the aerospace field, we must pay attention to the complexity of the configuration of precision investment castings and the importance of ceramic core technology. With the development of aviation technology, the requirements for high-temperature alloy castings are increasing, and these castings not only need to withstand extreme high-temperature environments, but also need to have complex internal structures to optimize performance. Therefore, ceramic core technology plays a crucial role in this field.

[0003] For Figure 1 The high-temperature alloy investment casting shown in the figure has a small and long flow channel diameter, and the ceramic core itself becomes slender, which greatly reduces its mechanical strength. During the dewaxing, pouring and cooling processes, the ceramic core needs to withstand huge thermal and mechanical stresses, and is prone to fracture.

[0004] After the alloy liquid solidifies, the slender core is difficult to be completely removed by conventional methods (such as vibration and knocking) due to its close combination with the inner wall of the casting, which may cause internal defects in the casting.

[0005] Positioning and fixing of the core:

[0006] The slender core is subjected to high-temperature and high-pressure steam impact during the dewaxing step, and is prone to fracture and core deviation due to excessive bending moment, which affects the dimensional accuracy and surface quality of the casting.

[0007] At the same time, during the pouring step, the alloy liquid will rapidly heat up during pouring, causing huge thermal stress between the ceramic core and the mold shell, complex phase transformation of the ceramic core, and further reduction of the strength, aggravating the risk of core fracture.

[0008] The difference in thermal expansion coefficient between the ceramic core and the mold shell material may cause the ceramic core to be unstable in positioning during heating and cooling, and to deviate in the mold shell, resulting in cracks or deformation, causing the flow channel size of the casting to be out of tolerance or scrapped.

[0009] Therefore, we propose a method for solving the fracture and core deviation of slender ceramic cores of high-temperature alloy investment castings. SUMMARY

[0010] The applicant provides a method for solving the fracture and core deviation of slender ceramic cores of high-temperature alloy investment castings, which not only significantly improves the precision, surface quality and production efficiency of the castings, but also enhances the production flexibility and environmental performance, which is an important technical improvement in the field of investment casting.

[0011] The technical scheme adopted by the present application is as follows:

[0012] A method for solving the fracture and core deviation of a slender ceramic core of a high-temperature alloy investment casting, comprising:

[0013] S1, ceramic core structure design:

[0014] According to the shape of the ceramic core drawn according to the runner cavity of the high-temperature alloy casting, the ceramic core structure comprises:

[0015] The ceramic core body has an elongated structure;

[0016] The fixed end has a non-circular cross-sectional structure, and the maximum width of the cross section of the fixed end is greater than the maximum width of the ceramic core body;

[0017] The free end is connected to the other end of the ceramic core body;

[0018] S2, ceramic core manufacturing:

[0019] Design a ceramic core mold and prepare a ceramic core structure;

[0020] S3, wax mold manufacturing

[0021] Manufacture a corresponding wax mold, the wax mold comprising two open and closed mold halves, and a cavity corresponding to the ceramic core is arranged in the two mold halves;

[0022] S4, wax mold splicing and assembly

[0023] The ceramic core prepared in S2 and the casting wax mold prepared in S3 are combined and spliced together, and are fixedly bonded by bonding wax;

[0024] A layer of 4-5mm bonding wax is brushed on the top end of the free end 4 of the ceramic core; a layer of 0.2-0.3mm thick bonding wax is brushed on the outside of the protruding wax mold surface of the free end of the ceramic core, and at least one circular hole with a diameter of about 3-5mm is formed on the free end of the ceramic core after the bonding wax is solidified, and the ceramic core body is exposed;

[0025] The spliced wax mold is bonded with the ingate and the runner to form a complete pouring tree string;

[0026] S5, shell making and dewaxing

[0027] The product tree string is sprayed and sand is hung by adopting a manual shell making mode; after shell making is completed, high-temperature steam dewaxing is carried out to obtain a mold shell with a cavity; the fixed end of the ceramic core is wrapped by the mold shell; the top end of the free end of the ceramic core and the exposed bonding wax outside are melted and flow out, so that a gap is formed at the corresponding position on the mold shell, and the ceramic core at the round hole forms a mold shell contact point with a diameter of about 3-5mm, so that the free end of the ceramic core does not form a long cantilever beam structure.

[0028] Further, the fixed end is a square boss.

[0029] Further, a groove is formed on the outer surface of the fixed end.

[0030] Further, the number of the round holes is three.

[0031] Further, the depth of the groove is greater than 0.5mm.

[0032] Further, the preparation method of the ceramic core in S2 is that a silicon-based material is injected into a mold to be sintered and cooled to be formed.

[0033] Further, in S3, the MJF technology is adopted to print the casting wax mold 5 by using blue wax.

[0034] Further, the method further comprises the following steps:

[0035] S6: smelting and pouring:

[0036] The alloy bar material is melted by adopting a three-chamber vacuum furnace and is poured into the mold shell cavity.

[0037] The method for solving the fracture and core deviation of the slender ceramic core of the high-temperature alloy investment casting part as claimed in claim 8 further comprises the following steps:

[0038] S7: post-cleaning

[0039] The mold shell after cooling is subjected to shell vibration, cutting, polishing and cleaning;

[0040] S8: removing the ceramic core:

[0041] The ceramic core is removed by adopting a strong alkali corrosion method, i.e., soaking and reacting in a strong alkali solution, so that the target casting can be obtained after sand blasting.

[0042] The beneficial effects of the present application are as follows:

[0043] The present application reduces the risk of ceramic core fracture by precisely splicing the ceramic core and wax mold, optimizing the design of the pouring system, using specially designed bonding wax and round hole structure, and combining with efficient manual shell making and post-processing technology, which not only significantly improves the precision, surface quality and production efficiency of the castings, but also enhances the production flexibility and environmental performance, and is an important technical improvement in the field of investment casting.

[0044] Meanwhile, the present application also has the following advantages:

[0045] 1. Improve the precision and surface quality of the castings: By precisely splicing the ceramic core and wax mold, and strictly controlling the thickness and strength of the mold shell during shell making, the dimensional accuracy and surface quality of the final castings are ensured. The introduction of the ceramic core, especially the design of its free end, effectively reduces the risk of ceramic core deformation and fracture, ensuring the formation of the castings' slender runner and the dimensional accuracy, thereby improving the overall quality of the castings.

[0046] 2. Reduce the risk of ceramic core fracture: The design of brushing bonding wax on the top and outside of the free end of the ceramic core and opening a round hole is the key to preventing the ceramic core from breaking during pouring. These bonding waxes form gaps after shell making and dewaxing, and the mold shell at the round hole reduces the length of the cantilever beam structure formed by the free end of the ceramic core during pouring, thereby reducing the risk of fracture. This design not only improves the service life of the ceramic core, but also reduces the rejection rate of the castings due to ceramic core fracture.

[0047] 3. Optimize the pouring system: Through careful design of the pouring system and the layout of the ingates, it is ensured that the alloy liquid can flow uniformly and smoothly into each wax mold during pouring. This not only improves the pouring efficiency, but also helps to reduce the turbulence and vortex generated during the flow of the alloy liquid, thereby reducing the generation of defects such as pores and inclusions. At the same time, reasonable design of the pouring system also helps to improve the solidification quality of the castings and reduce the occurrence of problems such as shrinkage and porosity. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 It is a schematic diagram of the structure of the castings with slender runners in the background technology.

[0049] Figure 2 It is a schematic diagram of the structure of the ceramic core of the present application.

[0050] Figure 3 It is a schematic diagram of the combination structure of the ceramic core and wax mold of the present application.

[0051] Figure 4 It is a schematic diagram of the combination structure of the free end and bonding wax of the present application.

[0052] Among them:

[0053] 1, ceramic core body; 2, fixed end; 3, groove; 4, free end; 5, wax mold; 6, bonding wax; 7, round hole. DETAILED DESCRIPTION

[0054] The specific embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0055] 1, ceramic core; 2, boss; 3, groove; 4, free end; 5, wax mold; 6, bonding wax; 7, round hole. DETAILED DESCRIPTION

[0057] The specific embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0058] The slender ceramic core in the high-temperature alloy investment casting often faces the challenges of fracture and core deviation during the casting process. Fracture is mainly caused by the thermal stress and mechanical stress on the slender structure of the ceramic core during pouring; and core deviation is closely related to the positioning stability of the ceramic core in the mold shell.

[0059] By reasonably designing the combination of the free end and the fixed end 2 of the ceramic core, and redesigning a reasonable and feasible assembly scheme, the ceramic core is perfectly positioned in the mold shell, and the axial and longitudinal position deviation fluctuations are reduced. The problems raised in the above background art can be solved, and one-time forming of the slender runner cavity of the high-temperature alloy investment casting is realized, including the following steps:

[0060] I. Preliminary preparation and ceramic core structure design

[0061] S1: Ceramic core structure design

[0062] The first step of the present application is to carefully design the structure of the ceramic core to ensure its stability and durability during the casting process. The specific design is as follows:

[0063] Ceramic core body 1: As the main part of the ceramic core, its shape is accurately drawn according to the runner cavity of the high-temperature alloy casting. The ceramic core body 1 can be a hollow tubular structure to reduce weight and optimize heat conduction performance; or a solid structure according to the specific casting requirements. Regardless of which structure, it needs to ensure sufficient strength and stiffness to resist various stresses during pouring.

[0064] Fixed end 2: This part is designed as a non-circular cross-section structure, aiming to improve the fixing effect of the ceramic core in the mold shell. The cross-sectional shape of the fixed end 2 can be square, polygonal or other special-shaped, the key is that its maximum width needs to be greater than that of the ceramic core body 1 to ensure tight contact and stable fixation with the mold shell. In this embodiment, we particularly choose a square boss as the design of the fixed end 2 because of its simple structure, easy processing and accurate positioning.

[0065] Groove 3 (Optional Design): In some cases, to improve the axial positioning accuracy of the fixed end 2 with the mold shell, a groove 3 can be opened on the outer surface of the fixed end 2. The depth of the groove 3 needs to be greater than 0.5mm to ensure its effectiveness. However, it is worth noting that the presence or absence of the groove 3 depends on the shape of the outer surface of the fixed end 2 and the contact with the mold shell. If the outer surface of the fixed end 2 already has sufficient width variation to achieve axial positioning, there is no need to open an additional groove.

[0066] Free end 4: Connected to the other end of the ceramic core body 1, i.e. the unfixed end. The design of the free end 4 facilitates the subsequent positioning of the unfixed end of the ceramic core body 1 and effectively avoids the problem of ceramic core deflection during pouring. Through the setting of the free end 4, the position of the ceramic core in the mold shell can be easily controlled, ensuring accurate centering.

[0067] II. Ceramic Core Manufacturing

[0068] S2: Ceramic Core Manufacturing

[0069] After completing the structural design of the ceramic core, the next step is to manufacture the physical ceramic core. The specific steps are as follows:

[0070] Designing the ceramic core mold: According to the structural design of the ceramic core, accurately manufacture the ceramic core mold. The design of the mold needs to consider factors such as the flowability of the material, shrinkage rate, and ease of demolding.

[0071] Preparing the ceramic core structure: Use appropriate forming processes such as injection molding or compression molding to inject silicon-based materials into the mold. Silicon-based materials are widely used in the manufacture of ceramic cores due to their good high-temperature performance and processability. During the forming process, parameters such as temperature, pressure, and time need to be strictly controlled to ensure the dimensional accuracy and surface quality of the ceramic core.

[0072] Sintering and cooling: The formed ceramic core needs to be sintered to achieve the required physical and chemical properties. During sintering, the appropriate sintering temperature and time need to be selected according to the material properties. After sintering, natural cooling or controlled cooling is required to avoid internal stress caused by excessive temperature gradient.

[0073] III. Wax Pattern Manufacturing and Assembly

[0074] S3: Wax Pattern Manufacturing

[0075] While the ceramic core is being manufactured, the wax pattern is being manufactured. The specific steps are as follows:

[0076] MJF technology: Using the Multi Jet Fusion (MJF) technology, the wax pattern 5 is 3D printed with blue wax. MJF technology has the advantages of high precision, high efficiency and low cost, and is particularly suitable for the manufacturing of wax patterns with complex shapes and high precision requirements.

[0077] Wax pattern structure design: The wax pattern includes two open and close mold halves, and there are cavities corresponding to the ceramic core in the two mold halves. The shape and size of the cavity need to be accurately matched with the ceramic core to ensure the formation and size accuracy of the casting runner.

[0078] S4: Wax pattern splicing and tree assembly

[0079] After the preliminary preparation of the ceramic core and wax pattern is completed, the key splicing and tree assembly stage is entered. This step is crucial to ensure the stability of the ceramic core during pouring and the quality of the final casting.

[0080] Precise splicing: The free end 4 of the ceramic core is carefully inserted into the cavity of the wax pattern, ensuring that the fit between the two is tight and accurate. Due to the design of the free end 4, this operation is more convenient, and it also helps to reduce the deflection of the ceramic core in the subsequent process.

[0081] Bonding and fixing: A layer of 4-5mm thick bonding wax is brushed on the top end of the free end 4 of the ceramic core to increase the bonding strength with the wax pattern. In addition, a layer of 0.2-0.3mm thick bonding wax 6 is brushed on the outside of the part of the ceramic core that protrudes from the surface of the wax pattern. This thin layer of bonding wax not only serves as a fixing function, but also forms a specific gap structure during the subsequent shell forming process.

[0082] Drilling round holes: After the bonding wax solidifies, at least one round hole 7 with a diameter of about 3-5mm is drilled on the bonding wax layer using a hot iron. The design of these round holes 7 is very critical, as the ceramic core at the round hole 7 is not bonded with the wax 6, forming at least one shell contact point with a diameter of about 3-5mm, so that the free end of the ceramic core does not form a long cantilever beam structure, effectively preventing the ceramic core from being subjected to high temperature and high pressure steam impact during the dewaxing process and excessive bending moment or axial rotation caused by external forces during the shell transfer process, resulting in deformation or fracture of the ceramic core.

[0083] Tree assembly operation: The spliced wax pattern is arranged according to a certain layout, i.e. connected into a complete pouring tree string through the ingate and runner. This step needs to be carefully planned to ensure that the alloy liquid can uniformly and smoothly fill the mold during pouring.

[0084] Improving casting precision and surface quality: By precisely assembling ceramic cores and wax patterns, and strictly controlling the thickness and strength of the mold shell during the shell-making process, the dimensional accuracy and surface quality of the final casting are ensured. The introduction of ceramic cores, especially the design of their free ends, effectively reduces the risk of ceramic core deformation and breakage, ensuring the formation and dimensional accuracy of the casting's slender runners, thereby improving the overall quality of the casting.

[0085] S5: Shell-making and wax removal

[0086] Shell-making is one of the key steps in investment casting, which determines the surface quality and dimensional accuracy of the final casting.

[0087] Manual shell-making: A manual method is used to spray slurry and hang sand on the product tree string. During this process, special refractory material slurry and sand particles are used, and through multiple layers of coating and drying, a hard mold shell is formed on the outer surface of the wax pattern. The thickness and strength of the mold shell need to be adjusted according to the size, shape and material requirements of the casting.

[0088] High-temperature steam wax removal: After shell-making is completed, the tree string with the mold shell is placed in a high-temperature steam chamber for wax removal treatment. High-temperature steam can quickly melt the wax and bonding wax, causing them to flow out of the mold shell. This process requires strict control of temperature and time to avoid damage to the mold shell or leaving residues.

[0089] After the wax removal treatment, a cavity that is identical in shape to the wax pattern is formed inside the mold shell, which is the mold cavity to be poured. At this time, the fixed end 2 of the ceramic core is tightly wrapped by the mold shell, while the bonding wax at the top and outside of the free end 4 has completely melted and flowed out, forming a predetermined gap, and a mold shell contact point with a diameter of about 3-5 mm is formed at the circular hole structure.

[0090] S6: Melting and pouring

[0091] Melting of the alloy: The three-chamber vacuum furnace is used to melt the alloy bar. The three-chamber vacuum furnace can provide a high-purity melting environment, effectively reducing the impurity and gas content in the alloy. The temperature and time during melting need to be strictly controlled to ensure that the chemical composition and physical properties of the alloy meet the requirements.

[0092] Pouring operation: The molten alloy is quickly and smoothly poured into the mold cavity of the mold shell through the pouring system. During pouring, attention should be paid to the flow rate and pouring temperature of the alloy liquid to avoid defects such as pores and slag inclusions. At the same time, it is also necessary to ensure that the alloy liquid can completely fill the mold cavity and form a good solidification structure.

[0093] S7: Post-cleaning

[0094] After pouring is completed, after the alloy liquid solidifies and cools to room temperature, post-cleaning work is carried out.

[0095] Shell processing: Use vibration equipment to vibrate the shell, making it separate from the casting and break. This step helps remove sand particles and residues attached to the surface of the casting.

[0096] Cutting and polishing: After shell vibration, the casting is cut and polished to remove excess parts such as sprues, runners, and burrs, and to achieve the required roughness and precision of the casting surface.

[0097] S8: Remove the ceramic core

[0098] The final step is to remove the ceramic core to obtain the final casting.

[0099] Strong alkali corrosion method: Use a strong alkaline solution to soak the casting. The strong alkaline solution can chemically react with the ceramic core and gradually dissolve or peel off. The soaking time and solution concentration must be strictly controlled to avoid corrosion or damage to the casting.

[0100] In summary, the present application precisely splices the ceramic core with the wax mold, optimizes the design of the pouring system, uses specially designed bonding wax and round hole structures to reduce the risk of ceramic core fracture, and combines efficient manual shell making and post-processing technology. Not only significantly improves the precision, surface quality and production efficiency of the casting, but also enhances the production flexibility and environmental performance, which is an important technical improvement in the field of investment casting.

[0101] Reducing the risk of ceramic core fracture: The design of brushing bonding wax on the top and outside of the free end of the ceramic core and opening a round hole is the key to preventing the ceramic core from breaking during pouring. These bonding waxes form gaps after shell making and dewaxing, and the shell at the round hole reduces the length of the cantilever beam structure formed by the free end of the ceramic core during pouring, thereby reducing the risk of fracture. This design not only improves the service life of the ceramic core, but also reduces the rejection rate of the casting due to the fracture of the ceramic core.

[0102] Optimizing the pouring system: Through careful design of the pouring system and the layout of the ingate, it is ensured that the alloy liquid can flow uniformly and smoothly into each wax mold during pouring. This not only improves the pouring efficiency, but also helps to reduce the turbulence and vortex generated during the flow of the alloy liquid, thereby reducing the generation of defects such as pores and inclusions. At the same time, reasonable design of the pouring system also helps to improve the solidification quality of the casting and reduce the occurrence of problems such as shrinkage and porosity.

[0103] Example 1

[0104] In this embodiment, combined with the actual processing method, the following steps are included:

[0105] S1: Ceramic core design:

[0106] For example Figure 2As shown; according to the high-temperature alloy casting runner cavity to draw ceramic core shape; the ceramic core diameter is 5.6mm, the total length is 202.58mm, and it is a complex S-shaped channel structure.

[0107] Design the fixed end 2: the core head fixed end 2 is designed with a 10mm long, 10mm wide and 25mm high rectangular boss above the body surface, and a 6mm long, 3mm wide and 0.5mm deep groove 3 is opened on the rectangular boss as positioning; the mold shell directly contacts with the ceramic core, and the mold shell in the groove 3 can better limit the possible axial movement of the ceramic core.

[0108] Design the free end 4: the free end 4 is designed to be 15mm higher than the body surface as a positioning core head to meet the needs of ceramic core positioning;

[0109] S2: ceramic core manufacturing:

[0110] Design the ceramic core mold, and inject silicon-based material into the mold to sinter and cool to form the ceramic core;

[0111] S3: wax mold manufacturing

[0112] MJF technology is used to print the casting wax mold 5 with blue wax;

[0113] In this embodiment, MJF (Multi Jet Fusion) technology is an advanced 3D printing technology that combines the principles of powder bed fusion and material jetting; this technology uses fine powder materials (such as plastic, metal or ceramic powder) as building materials, and through multiple nozzles to spray molten adhesive material to solidify the powder layer by layer, thereby building a three-dimensional entity; compared with traditional 3D printing technology, MJF technology has higher printing speed, better surface quality and wider material selection;

[0114] Blue wax is a material specially designed for 3D printing, especially suitable for high-precision, high-definition model and prototype manufacturing; it uses MJM (Multi Jet Modeling) technology or similar SCP (Smooth Curvature Printing) technology for printing; blue wax material has the following characteristics:

[0115] High precision: the precision of blue wax printing can reach 0.01-0.025mm, which is much higher than the general resin material of 0.1mm precision, and is very suitable for making casting wax mold with fine details;

[0116] High definition: the model printed by blue wax has very high definition, which can accurately restore the design details and reduce the difficulty of subsequent processing;

[0117] Good reverse mold effect: blue wax material performs well in the process of lost wax casting, which can ensure that the castings have high precision and high quality;

[0118] S4: Wax model splicing and assembly tree

[0119] As shown in the figure, the ceramic core prepared in S2 and the wax model 5 prepared in S3 are combined and spliced together, and are fixed by bonding wax; Figure 3

[0120] In this embodiment, the wax model 5 includes two open and close mold halves, and the ceramic core is engaged in the pre-set cavity of the two mold halves. The ceramic core is placed into the cavity, and then the two mold halves are combined to realize the combination and splicing of the ceramic core and the wax model 5 prepared in S3.

[0121] As shown in the figure, Figure 4 At the same time, the free end of the ceramic core is brushed with a layer of 4-5mm bonding wax; the outside of the part of the ceramic core protruding from the surface of the wax model is brushed with a layer of 0.2-0.3mm thick bonding wax 6, and after the bonding wax solidifies, three circular holes 7 with a diameter of about 3-5mm are burned out by a hot iron to expose the ceramic core body;

[0122] The spliced wax model is bonded with the ingate and the runner to form a complete pouring tree string.

[0123] S5: Shell making and dewaxing

[0124] In this embodiment, the product tree string is sprayed with slurry and hung with sand by manual shell making. After the shell making is completed, high-temperature steam dewaxing is performed to obtain a mold shell with a cavity. The fixed end 2 of the ceramic core, i.e. the rectangular boss, is wrapped by the mold shell, and the mold shell in the groove 3 can effectively prevent the movement of the ceramic core. The top end of the free end 4 of the ceramic core and the exposed bonding wax 6 on the outside are both melted and flowed out, so that gaps are formed at the corresponding positions on the mold shell. The ceramic core at the circular hole 7 has no bonding wax 6, and three mold shell contact points with a diameter of about 3-5mm are formed, so that the free end of the ceramic core does not form a long cantilever beam structure, effectively preventing the ceramic core from being subjected to excessive bending moment or axial rotation caused by high-temperature and high-pressure steam impact in the dewaxing process and external force shaking in the mold shell transfer process, resulting in deformation or fracture of the ceramic core.

[0125] In the casting process, the product tree string is sprayed with slurry and hung with sand by manual shell making, and then high-temperature steam dewaxing is performed.

[0126] Manual shell making-spraying slurry and hanging sand in this embodiment

[0127] Manual shell making is a process of wrapping the product tree string (i.e. a structure in which multiple wax models are connected together by a runner system) in refractory material to form a solid mold shell. Spraying slurry and hanging sand is a key link in this process.

[0128] ​Preparation of materials: Select appropriate refractory materials (such as quartz sand, ceramic slurry, etc.) and binders, and prepare the slurry according to the specified proportion.

[0129] Slurry application: Apply the prepared slurry evenly to the product tree string, ensuring that each wax mold is fully covered with slurry. The slurry will form a thin layer of refractory on the surface of the wax mold.

[0130] Sand application: Before the slurry has completely dried, evenly sprinkle sand particles (usually screened refractory sand) onto the surface of the slurry. The sand particles will adhere to the slurry, forming a rough sand layer that enhances the strength of the mold shell.

[0131] Repetition of operations: As needed, repeat the steps of slurry application and sand application to form a multi-layered mold shell. The viscosity of the slurry and the mesh size of the sand particles may vary for each layer to achieve optimal mold shell performance.

[0132] Drying: Place the product tree string after slurry application and sand application in a suitable environment for drying, ensuring that the mold shell is completely cured.

[0133] High-temperature steam dewaxing in this embodiment

[0134] High-temperature steam dewaxing is the process of melting and removing the wax mold from the mold shell through the action of high-temperature steam. This is done to obtain a mold shell with a cavity for subsequent pouring of metal liquid.

[0135] Preparation of dewaxing equipment: Use a high-pressure steam dewaxing kettle as the dewaxing equipment, and ensure that it is in good working condition.

[0136] Loading of mold shell: Place the dried mold shell into a special transport vehicle and transport it to the waiting area next to the high-pressure steam dewaxing kettle. Make sure that the sprue cup of the mold shell is placed downward to facilitate the smooth discharge of wax liquid.

[0137] Setting of dewaxing parameters: According to the material and size of the mold shell, set appropriate dewaxing temperature (usually between 160-170°C) and pressure (generally 6 atmospheres or 0.8 MPa).

[0138] Dewaxing: When the temperature in the dewaxing kettle reaches the set value, quickly push the dewaxing vehicle loaded with the mold shell into the dewaxing kettle, and close the dewaxing chamber door. Then open the inlet valve to introduce high-pressure steam for dewaxing. The dewaxing time is generally 10-15 minutes.

[0139] Removal of mold shell: After dewaxing is completed, open the dewaxing chamber door and remove the mold shell. At this time, the mold shell has formed a cavity in the shape opposite to the wax mold.

[0140] The slurry dipping and sanding and high-temperature steam dewaxing in the manual shell-making mode are key steps in the casting process. Through fine operation and strict parameter control, the quality of the shell and the accuracy of the cavity can be ensured, thereby laying a solid foundation for the subsequent metal pouring.

[0141] S6: smelting and pouring:

[0142] The alloy bar is melted in a three-chamber vacuum furnace and poured into the shell cavity.

[0143] S7: post-cleaning

[0144] The cooled shell is subjected to shell vibration, cutting and polishing and cleaning.

[0145] S8: removing the ceramic core:

[0146] The ceramic core is removed by soaking in a strong alkaline solution through a strong alkali corrosion method, and the target casting can be obtained after sand blasting.

[0147] The method of the present application has a wide application range, especially for high-temperature alloy investment castings with complex long tubular cavities. The method can not only solve the problems of fracture and core deviation of the long ceramic core during dewaxing, pouring and cooling, but also ensure the size of the product flow channel and ensure the smooth delivery of the product.

[0148] The above description is an explanation of the present application, not a limitation of the invention. The scope of the present application is defined in the claims, and any form of modification within the scope of the present application can be made.

Claims

1. A method of resolving the fracture and misrun of an elongated ceramic core of a superalloy investment casting, characterized in that, The application relates to a ceramic core structure and a manufacturing method thereof. S1, ceramic core structure design: According to the runner cavity of a high-temperature alloy casting, the shape of a ceramic core is drawn, and the ceramic core structure comprises: A ceramic core body (1) in an elongated structure; A fixed end (2) with a non-circular cross-section structure, and the maximum width of the cross-section of the fixed end (2) is greater than that of the ceramic core body (1); A free end (4) connected to the other end of the ceramic core body (1); S2, ceramic core manufacturing: A ceramic core mold is designed, and a ceramic core structure is prepared; S3, wax mold manufacturing A corresponding wax mold is manufactured, the wax mold comprises two open and closed mold halves, and cavities corresponding to the ceramic core are arranged in the two mold halves; S4, wax mold splicing and assembly The ceramic core prepared in S2 and the wax mold (5) prepared in S3 are combined and spliced together, and are fixed by bonding wax; A top end of the free end 4 of the ceramic core is brushed with a layer of 4-5mm bonding wax; a section of the free end (4) of the ceramic core protruding from the surface of the wax mold (5) is brushed with a layer of 0.2-0.3mm thick bonding wax (6), and at least one circular hole (7) with a diameter of 3-5mm is punched out by a hot iron after the bonding wax is solidified to expose the ceramic core body; The spliced wax mold is bonded with an ingate and a runner to form a complete pouring tree string; S5, shell making and dewaxing A manual shell making mode is adopted to spray slurry and hang sand on the product tree string; after shell making is completed, high-temperature steam dewaxing is carried out to obtain a mold shell with a cavity; the fixed end (2) of the ceramic core is wrapped by the mold shell; the top end of the free end (4) of the ceramic core and the exposed bonding wax (6) on the outside are both melted and flowed out, so that a gap is formed at the corresponding position on the mold shell, and the ceramic core at the circular hole (7) forms a mold shell contact point with a diameter of 3-5mm, so that the free end of the ceramic core does not form a long cantilever beam structure.

2. A method of resolving the problem of the fracture and deviation of the slender ceramic core of the high-temperature alloy investment casting mold according to claim 1, characterized in that: The fixed end (2) is a square boss.

3. A method of resolving the problem of the fracture and deviation of the elongated ceramic core of the high-temperature alloy investment casting mold according to claim 1, characterized in that: Grooves (3) are formed on the outer surface of the fixed end (2).

4. The method for solving the fracture and eccentricity of slender ceramic cores in high-temperature alloy investment castings as described in claim 1, characterized in that: The number of the circular holes (7) is three.

5. A method of resolving the problem of the fracture and misrun of the elongated ceramic core of the superalloy investment casting according to claim 3, characterized in that: The depth of the grooves (3) is greater than 0.5mm.

6. A method of resolving the problem of the fracture and misrun of the elongated ceramic core of the superalloy investment casting according to claim 1, characterized in that: In the S2, the ceramic core is prepared by injecting a silicon-based material into a mold, sintering and cooling to form.

7. A method of resolving the problem of the fracture and core deviation of the elongated ceramic core of the high-temperature alloy investment casting according to claim 1, characterized in that: In the S3, the MJF technology is adopted to print the casting wax mold 5 by using blue wax.

8. A method of resolving the problem of the fracture and core deviation of the elongated ceramic core of the superalloy investment casting according to claim 1, characterized in that: The application further comprises the following steps: S6, melting and pouring: An alloy bar is melted in a three-chamber vacuum furnace and poured into the mold cavity.

9. A method of resolving the problem of the fracture and core deviation of the elongated ceramic core of the superalloy investment casting according to claim 8, characterized in that: The application further comprises the following steps: S7, post-cleaning The cooled mold shell is subjected to shell vibration, cutting and polishing and cleaning; S8, removing the ceramic core: The ceramic core is removed by soaking in a strong alkali solution through a strong alkali corrosion method, and the target casting is obtained after sand blasting.

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