Method for solving fracture and core shift of slender ceramic core of high-temperature alloy investment casting

Abstract

The invention relates to a method for solving fracture and core shift of a slender ceramic core of a high-temperature alloy investment casting. The method comprises the following steps: S1, structural design of the ceramic core; s2, manufacturing a ceramic core; s3, a corresponding wax mold is manufactured through wax mold manufacturing; s4, wax mold splicing and tree assembling are carried out, wherein the ceramic mold core and the casting wax mold are combined and spliced together; the spliced wax mold is bonded with an inner pouring gate and a pouring gate, and a complete pouring tree string is formed; and S5, shell making and dewaxing are conducted in a manual shell making mode, and the mold shell with the cavity is obtained. The ceramic core and the wax mold are precisely spliced, the design of a pouring system is optimized, specially designed bonding wax and a round hole structure are adopted to reduce the fracture risk of the ceramic core, and efficient manual shell making and post-treatment processes are combined, so that the precision, the surface quality and the production efficiency of a casting are remarkably improved, and the production cost is reduced. And the production flexibility and the environmental protection performance are enhanced, and the method is an important technical improvement in the field of investment casting.

Description

Technical Field

[0001] The invention relates to the technical field of casting, in particular to a method for solving the problem of fracture and core deviation of a slender ceramic core of a high-temperature alloy investment casting. Background Art

[0002] When discussing my country's high-temperature alloy industry, especially its key role in the aerospace field, we have to 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. These castings not only need to withstand extreme high temperature environments, but also have complex internal structures to optimize performance. Therefore, ceramic core technology plays a vital role in this field.

[0003] against 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 process, the ceramic core needs to withstand huge thermal and mechanical stress and is very easy to break.

[0004] After the alloy liquid solidifies, the slender core is tightly bonded to the inner wall of the casting and is difficult to completely remove by conventional methods (such as vibration and beating), which may cause internal defects in the casting.

[0005] Positioning and fixing of core:

[0006] The slender core will be impacted by high-temperature and high-pressure water vapor during the dewaxing step, and it is easy to break and deviate due to excessive bending moment, which will affect the dimensional accuracy and surface quality of the casting.

[0007] At the same time, during the pouring step, the alloy liquid will heat up rapidly during the pouring process, resulting in huge thermal stress between the ceramic core and the mold shell. The ceramic core will undergo complex phase changes, and the strength will be further reduced, increasing the risk of core breakage.

[0008] The difference in thermal expansion coefficients between the ceramic core and the shell material may cause the ceramic core to be unstable in positioning during heating and cooling, causing it to deflect in the shell, resulting in cracks or deformation, and causing the casting runner size to be out of tolerance or even scrapped.

[0009] Therefore, we propose a method to solve the fracture and deflection of slender ceramic cores in high-temperature alloy investment castings. Summary of the invention

[0010] In view of the shortcomings in the above-mentioned existing production technologies, the applicant provides a method for solving the breakage and eccentricity of slender ceramic cores in high-temperature alloy investment castings. The method not only significantly improves the precision, surface quality and production efficiency of the castings, but also enhances production flexibility and environmental protection performance. It is an important technical improvement in the field of investment casting.

[0011] The technical solution adopted by the present invention is as follows:

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

[0013] S1. Ceramic core structure design:

[0014] The shape of the ceramic core is drawn according to the flow channel cavity of the high-temperature alloy casting. The ceramic core structure includes:

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

[0016] A fixed end having a non-circular cross-sectional structure, and a maximum width of the cross-sectional area of ​​the fixed end is greater than a maximum width of the ceramic core body;

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

[0018] S2. Ceramic core production:

[0019] Design ceramic core molds and prepare ceramic core structures;

[0020] S3. Wax model manufacturing

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

[0022] S4. Wax model splicing and tree assembly

[0023] The ceramic core prepared by S2 and the casting wax mold prepared by S3 are assembled and spliced ​​together, and fixed with bonding wax;

[0024] A 4-5 mm thick bonding wax is brushed on the top of the free end 4 of the ceramic core; a 0.2-0.3 mm thick bonding wax is brushed on the outer side of a section of the free end of the ceramic core protruding from the wax mold surface, and after the bonding wax solidifies, at least one circular hole with a diameter of about 3-5 mm is ironed with a hot ironing knife to expose the ceramic core body;

[0025] The spliced ​​wax mold is glued with the inner gate and runner to form a complete casting tree string;

[0026] S5, shell making and dewaxing

[0027] The product tree string is made by hand, and slurry is sprayed and sanded. After the 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 will be wrapped by the mold shell. The top of the free end of the ceramic core and the exposed adhesive wax on the outside are melted and flowed out, forming a gap at the corresponding position on the mold shell. The ceramic core at the circular hole has no adhesive wax, so a mold shell contact point with a diameter of about 3-5mm is formed, so that the free end of the ceramic core will not form a long cantilever beam structure.

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

[0029] Furthermore, a groove is provided on the outer surface of the fixing end.

[0030] Furthermore, the number of the circular holes is three.

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

[0032] Furthermore, the ceramic core in S2 is prepared by injecting silicon-based material into a mold, sintering, cooling and molding.

[0033] Furthermore, in S3, the MJF technology is used to 3D print the casting wax model 5 using blue wax.

[0034] Furthermore, the following steps are included:

[0035] S6: Melting and pouring:

[0036] A three-chamber vacuum furnace is used to melt the alloy bars and pour them into the mold cavity.

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

[0038] S7: Post-cleaning

[0039] Vibrate, cut, and polish the cooled mold shell;

[0040] S8: Removal of ceramic core:

[0041] The strong alkaline corrosion method is adopted to remove the ceramic core by soaking reaction in a strong alkaline solution, and the target casting can be obtained after sandblasting.

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

[0043] The present invention achieves significant improvements in the precision, surface quality and production efficiency of castings, as well as enhanced production flexibility and environmental performance, by precisely joining ceramic cores and wax patterns, optimizing the design of the pouring system, using specially designed bonding wax and circular hole structures to reduce the risk of ceramic core breakage, and combining efficient manual shell making and post-processing processes. This is an important technical improvement in the field of investment casting.

[0044] At the same time, the present invention also has the following advantages:

[0045] 1. Improve casting accuracy and surface quality: By precisely splicing the ceramic core and wax mold, 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 the ceramic core, especially the design of its free end, effectively reduces the risk of deformation and breakage of the ceramic core, ensures the molding of the slender flow channel of the casting and the guarantee of dimensional accuracy, thereby improving the overall quality of the casting.

[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 circular hole is the key to preventing the ceramic core from breaking during the pouring process. These bonding waxes form gaps after shell dewaxing, and the mold shell at the circular hole reduces the length of the cantilever beam structure formed at the free end of the ceramic core during pouring, thereby reducing the risk of fracture. This design not only increases the service life of the ceramic core, but also reduces the scrap rate of castings caused by ceramic core fracture.

[0047] 3. Optimize the pouring system: Through the carefully designed pouring system and ingate layout, it is ensured that the alloy liquid can flow evenly and smoothly into each wax mold during the pouring process. This not only improves the pouring efficiency, but also helps to reduce the turbulence and eddy currents generated by the alloy liquid during the flow process, thereby reducing the occurrence of defects such as pores and inclusions. At the same time, a reasonable pouring system design can also help improve the solidification quality of the casting and reduce the occurrence of shrinkage and shrinkage holes. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic diagram of the casting structure containing a slender flow channel in the background technology.

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

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

[0051] Figure 4 It is a schematic diagram of the combined structure of the free end and the adhesive wax of the present invention.

[0052] in:

[0053] 1. Ceramic core body; 2. Fixed end; 3. Groove; 4. Free end; 5. Wax mold; 6. Adhesive wax; 7. Round hole. DETAILED DESCRIPTION

[0054] The specific implementation of the present invention 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. Adhesive wax; 7. Round hole. DETAILED DESCRIPTION

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

[0058] The slender ceramic cores in high-temperature alloy investment castings often face two challenges during the casting process: fracture and eccentricity. Fracture is mainly caused by the thermal and mechanical stresses on the slender structure of the ceramic core during the casting process; while eccentricity is closely related to the positioning stability of the ceramic core in the mold shell.

[0059] By rationally designing the combined application of the free end and the fixed end 2 of the ceramic core, and then designing a reasonable and feasible assembly scheme, the ceramic core can be perfectly positioned in the mold shell, reducing the axial and longitudinal position deviation fluctuations. The problems raised in the above background technology can be solved, and the one-time molding of the slender flow channel cavity of the high-temperature alloy investment casting can be achieved, including the following steps:

[0060] 1. Preliminary preparation and ceramic core structure design

[0061] S1: Ceramic core structure design

[0062] The first step of the present invention 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 flow channel cavity of the high-temperature alloy casting. The ceramic core body 1 can be a hollow tubular structure to reduce weight and optimize thermal conductivity; it can also be a solid structure, depending on the needs of the specific casting. Regardless of the structure, it is necessary to ensure sufficient strength and rigidity to resist various stresses during the casting process.

[0064] Fixed end 2: This part is designed as a non-circular cross-sectional structure 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 shapes. The key is that its maximum width must be greater than the maximum width of the ceramic core body 1 to ensure close contact and stable fixation with the mold shell. In this embodiment, we specifically 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, in order to improve the axial positioning accuracy between the fixed end 2 and 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 has a sufficient width change 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, that is, 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 the ceramic core swaying during the casting process. Through the setting of the free end 4, the position of the ceramic core in the mold shell can be easily controlled to ensure its precise centering.

[0067] 2. Ceramic core production

[0068] S2: Ceramic core production

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

[0070] Design ceramic core mold: According to the structural design of the ceramic core, the ceramic core mold is accurately made. The design of the mold needs to consider factors such as material fluidity, shrinkage rate, and ease of demoulding.

[0071] Preparation of ceramic core structure: Silicon-based materials are injected into the mold using appropriate molding processes, such as injection molding or compression molding. Silicon-based materials are widely used in the production of ceramic cores due to their good high-temperature performance and machinability. During the molding process, parameters such as temperature, pressure and time must 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 the sintering process, the appropriate sintering temperature and time need to be selected according to the material characteristics. After sintering, natural cooling or controlled cooling is required to avoid internal stress caused by excessive temperature gradient.

[0073] 3. Wax model manufacturing and splicing

[0074] S3: Wax model making

[0075] When the ceramic core is made, the wax model is made. The specific steps are as follows:

[0076] Adopting MJF technology: Using Multi Jet Fusion (MJF) technology, use blue wax to split 3D print casting wax models 5. MJF technology has the advantages of high precision, high efficiency and low cost, and is particularly suitable for the manufacture of wax models with complex shapes and high precision requirements.

[0077] Wax mold structure design: The wax mold consists of two open and closed mold halves, and a cavity corresponding to the ceramic core is set in the two mold halves. The shape and size of the cavity must be accurately matched with the ceramic core to ensure the molding of the casting flow channel and the guarantee of dimensional accuracy.

[0078] S4: wax model splicing and tree assembly

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

[0080] Precise splicing: Carefully insert the free end 4 of the ceramic core into the cavity of the wax model to ensure a tight and accurate fit between the two. The design of the free end 4 makes this operation more convenient and also helps to reduce the deflection of the ceramic core in the subsequent process.

[0081] Bonding and fixing: A layer of 4-5 mm thick bonding wax is applied to the top of the free end 4 of the ceramic core to increase the bonding strength with the wax mold. In addition, a layer of 0.2-0.3 mm thick bonding wax 6 is applied to the outer side of the free end 4 of the ceramic core protruding from the surface of the wax mold. This thin layer of bonding wax not only plays a fixing role, but also forms a specific void structure in the subsequent shell making process.

[0082] Opening round holes: After the bonding wax solidifies, use a hot stamping knife to stamp at least one round hole 7 with a diameter of about 3-5 mm on the bonding wax layer. The design of these round holes 7 is very critical. Since there is no bonding wax 6 on the ceramic core at the round hole 7, at least one mold shell contact point with a diameter of about 3-5 mm will be formed, so that the free end of the ceramic core will not form a long cantilever beam structure, effectively preventing the ceramic core from being subjected to high temperature and high pressure water vapor impact during the dewaxing process and the external force of shaking during the mold shell transportation. Excessive bending moment or axial rotation, resulting in deformation or breakage of the ceramic core.

[0083] Tree assembly operation: The spliced ​​wax models are assembled into a tree according to a certain layout, that is, the wax models are connected into a complete casting tree string through the gate and runner. This step requires careful planning to ensure that the alloy liquid can fill the mold evenly and smoothly during pouring.

[0084] Improve casting accuracy and surface quality: By precisely splicing the ceramic core and wax mold, 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 the ceramic core, especially the design of its free end, effectively reduces the risk of deformation and breakage of the ceramic core, ensures the molding of the slender flow channel of the casting and the guarantee of dimensional accuracy, thereby improving the overall quality of the casting.

[0085] S5: Shell making and dewaxing

[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: The product tree strings are manually coated with slurry and sand. In this process, special refractory slurry and sand are used to form a hard shell on the outer surface of the wax mold through multiple layers of coating and drying. The thickness and strength of the shell need to be adjusted according to the size, shape and material requirements of the casting.

[0088] High temperature steam dewaxing: After the shell is made, the tree string with the shell is placed in a high temperature steam chamber for dewaxing. The high temperature steam can quickly melt the wax pattern and the bonding wax, allowing it to flow out of the shell. This process requires strict control of temperature and time to avoid damage to the shell or leaving residue.

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

[0090] S6: Melting and pouring

[0091] Alloy Melting: A three-chamber vacuum furnace is used to melt alloy bars. The three-chamber vacuum furnace can provide a high-purity melting environment and effectively reduce the impurities and gas content in the alloy. The temperature and time must be strictly controlled during the melting process to ensure that the chemical composition and physical properties of the alloy meet the requirements.

[0092] Pouring operation: The molten alloy liquid is quickly and smoothly injected into the mold cavity of the mold shell through the pouring system. During the pouring process, 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, wait for the alloy liquid to solidify and cool to room temperature before carrying out post-cleaning work.

[0095] Vibration shell treatment: Use vibration equipment to vibrate the mold shell to separate and break the mold shell from the casting. This step helps to remove sand and residues attached to the surface of the casting.

[0096] Cutting and grinding: Cut and grind the casting after shell vibration to remove excess parts such as pouring risers, flash and burrs, and make the casting surface meet the required roughness and precision requirements.

[0097] S8: Removal of ceramic core

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

[0099] Strong alkali corrosion method: Use strong alkaline solution to immerse the casting. The strong alkaline solution can react chemically with the ceramic core and gradually dissolve or peel it off. In this process, the immersion time and solution concentration must be strictly controlled to avoid corrosion or damage to the casting.

[0100] In summary, the present invention not only significantly improves the precision, surface quality and production efficiency of castings, but also enhances production flexibility and environmental protection performance by precisely splicing ceramic cores and wax patterns, optimizing the design of the pouring system, using specially designed bonding wax and circular hole structures to reduce the risk of ceramic core breakage, and combining efficient manual shell making and post-processing processes. It is an important technical improvement in the field of investment casting.

[0101] Reduce the risk of ceramic core breakage: The design of brushing bonding wax on the top and outside of the free end of the ceramic core and opening a circular hole is the key to preventing the ceramic core from breaking during the pouring process. These bonding waxes form gaps after shell dewaxing, and the mold shell at the circular hole reduces the length of the cantilever beam structure formed at the free end of the ceramic core during pouring, thereby reducing the risk of breakage. This design not only increases the service life of the ceramic core, but also reduces the scrap rate of castings caused by ceramic core breakage.

[0102] Optimize the pouring system: Through the well-designed pouring system and ingate layout, it is ensured that the alloy liquid can flow evenly and smoothly into each wax mold during the pouring process. This not only improves the pouring efficiency, but also helps to reduce the turbulence and eddy currents generated by the alloy liquid during the flow process, thereby reducing the occurrence of defects such as pores and inclusions. At the same time, a reasonable pouring system design can also help improve the solidification quality of castings and reduce the occurrence of shrinkage and shrinkage holes.

[0103] Embodiment 1

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

[0105] S1: Ceramic core design:

[0106] like Figure 2As shown; the shape of the ceramic core is drawn according to the flow channel cavity of the high-temperature alloy casting; the ceramic core has a diameter of 5.6 mm and a total length of 202.58 mm, and has a complex S-shaped channel structure.

[0107] Design fixed end 2: A rectangular boss 10mm long, 10mm wide and 25mm high is designed on the core head fixed end 2, which is higher than the surface of the main body, and a groove 3 with a length of 6mm, a width of 3mm and a depth of 0.5mm is opened on the rectangular boss for positioning; the mold shell is in direct contact 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 of 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 production:

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

[0111] S3: Wax model making

[0112] Using MJF technology to 3D print casting wax model 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; the technology uses fine powder materials (such as plastic, metal or ceramic powder) as building materials, and sprays molten binder materials through multiple nozzles 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 a wider range of material selection;

[0114] Blue wax is a material designed for 3D printing, especially suitable for high-precision, high-definition models and prototypes; it is printed using MJM (Multi-Nozzle 3D Printing) technology or the similar SCP (Curve Smooth Printing) technology; Blue wax material has the following characteristics:

[0115] High precision: The printing precision of blue wax can reach 0.01~0.025mm, which is much higher than the 0.1mm precision of general resin materials. It is very suitable for making wax molds for castings that require fine details.

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

[0117] Good casting effect: Blue wax material performs well in the lost wax casting process, ensuring high precision and high quality of the castings;

[0118] S4: wax model splicing and tree assembly

[0119] like Figure 3 As shown, the ceramic core prepared by S2 and the wax mold 5 prepared by S3 are assembled and spliced ​​together, and fixed with bonding wax;

[0120] In this embodiment, the wax mold 5 includes two open and close mold halves, and the ceramic core is engaged in the preset cavity on the two mold halves. The ceramic core is placed in the cavity and the two mold halves are merged to combine and splice the wax mold 5 prepared by the ceramic core and S3 together.

[0121] like Figure 4 As shown, at the same time, a layer of 4-5mm thick bonding wax is brushed on the top of the free end of the ceramic core; a layer of 0.2-0.3mm thick bonding wax 6 is brushed on the outer side of a section of the free end of the ceramic core protruding from the surface of the wax mold with a brush, and after the bonding wax solidifies, three round holes 7 with a diameter of about 3-5mm are ironed with a hot ironing knife to expose the ceramic core body;

[0122] The spliced ​​wax mold is glued with the inner gate and runner to form a complete casting tree string.

[0123] S5: Shell making and dewaxing

[0124] The shell is made manually, and the product tree string is sprayed with slurry and sanded; after the shell is made, high-temperature steam dewaxing is carried out to obtain a mold shell with a cavity; the fixed end 2 of the ceramic core, that is, the rectangular boss, will be wrapped by the mold shell, and the mold shell in the groove 3 can effectively prevent the movement of the ceramic core. The top of the free end 4 of the ceramic core and the exposed adhesive wax 6 on the outside are melted and flowed out, forming a gap at the corresponding position on the mold shell, and the ceramic core at the circular hole 7 has no adhesive wax 6, so 3 mold shell contact points with a diameter of about 3-5mm will be formed, so that the free end of the ceramic core will not form a long cantilever beam structure, which effectively prevents the ceramic core from being subjected to high-temperature and high-pressure water vapor impact during the dewaxing process and the external force of shaking during the mold shell transportation. Excessive bending moment or axial rotation caused by the external force, resulting in deformation or breakage of the ceramic core.

[0125] In the casting process, the product tree strings are sprinkled with slurry and sanded by manual shell making, and then dewaxed by high-temperature steam.

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

[0127] Manual shell making is the process of wrapping the product tree string (i.e. a structure where multiple wax molds are connected together through a gate system) in refractory materials to form a solid mold shell. Slurry pouring and sand hanging are the core links in this process.

[0128] Prepare materials: Select suitable refractory materials (such as quartz sand, ceramic slurry, etc.) and binders, and prepare them into slurry in a certain proportion.

[0129] Slurry pouring: pour the prepared slurry evenly on the product tree string to ensure that each wax model is fully covered by the slurry. The slurry will form a thin refractory layer on the surface of the wax model.

[0130] Sanding: Before the slurry is completely dry, sand (usually screened refractory sand) is evenly sprinkled on the surface of the slurry. The sand will adhere to the slurry to form a rough sand layer, which will enhance the strength of the mold shell.

[0131] Repeated operation: If necessary, the steps of pouring slurry and hanging sand can be repeated to form a multi-layered shell. The slurry viscosity and sand mesh size of each layer may be different to achieve the best shell performance.

[0132] Drying: Place the product tree string after slurry spraying and sand hanging in a suitable environment for drying to ensure 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 discharging the wax mold in the mold shell by the action of high temperature steam. This is to obtain a mold shell with a cavity for subsequent pouring of molten metal.

[0135] Prepare dewaxing equipment: Use a high-pressure steam dewaxing kettle as the dewaxing equipment and make sure it is in good working condition.

[0136] Loading the mold shell: Load the dried mold shell into a special transport vehicle and transport it to the processing area next to the high-pressure steam dewaxing kettle. Pay attention to placing the pouring cup of the mold shell downwards so that the wax liquid can be discharged smoothly.

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

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

[0139] Take out the mold shell: After dewaxing is completed, open the dewaxing chamber door and take out the mold shell. At this time, a cavity with the opposite shape of the wax model has been formed in the mold shell.

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

[0141] S6: Melting and pouring:

[0142] A three-chamber vacuum furnace is used to melt the alloy bars and pour them into the mold shell cavity;

[0143] S7: Post-cleaning

[0144] Vibrate, cut, and polish the cooled mold shell;

[0145] S8: Removal of ceramic core:

[0146] The strong alkaline corrosion method is adopted to remove the ceramic core by soaking reaction in a strong alkaline solution, and the target casting can be obtained after sandblasting.

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

[0148] The above description is an explanation of the present invention, not a limitation of the present invention. The scope of the present invention is defined in the claims. Any form of modification may be made within the scope of protection of the present invention.

Claims

1. A method for solving the problem of fracture and eccentricity of slender ceramic cores of high-temperature alloy investment castings, characterized in that: include: S1. Ceramic core structure design: The shape of the ceramic core is drawn according to the flow channel cavity of the high-temperature alloy casting. The ceramic core structure includes: The ceramic core body (1) is of an elongated structure; The fixed end (2) has a non-circular cross-sectional structure, and the maximum width of the cross-sectional area of ​​the fixed end (2) is greater than the maximum width of the ceramic core body (1); A free end (4) connected to the other end of the ceramic core body (1); S2. Ceramic core production: Design ceramic core molds and prepare ceramic core structures; S3. Wax model manufacturing Manufacturing a corresponding wax mold, wherein the wax mold comprises two open and closed mold halves, and a cavity corresponding to the ceramic core is arranged in the two mold halves; S4. Wax model splicing and tree assembly The ceramic core prepared by S2 and the wax mold (5) prepared by S3 are combined and spliced ​​together, and fixed with bonding wax; A 4-5 mm thick adhesive wax is applied to the top of the free end 4 of the ceramic core; a 0.2-0.3 mm thick adhesive wax (6) is applied to the outer side of a section of the free end (4) of the ceramic core protruding from the surface of the wax mold (5); after the adhesive wax solidifies, at least one circular hole (7) with a diameter of about 3-5 mm is ironed out with a hot ironing knife to expose the ceramic core body; The spliced ​​wax mold is glued with the inner gate and runner to form a complete casting tree string; S5, shell making and dewaxing The shell is made manually, and the product tree string is sprayed with slurry and sanded; after the shell is made, high-temperature steam dewaxing is carried out to obtain a shell with a cavity; the fixed end (2) of the ceramic core will be wrapped by the shell; the top of the free end (4) of the ceramic core and the exposed adhesive wax (6) on the outside are melted and flowed out, so that a gap is formed at the corresponding position on the shell, and the ceramic core at the circular hole (7) has no adhesive wax (6), so a shell contact point with a diameter of about 3-5 mm is formed, so that the free end of the ceramic core will not form a long cantilever beam structure.

2. A method for solving the problem of fracture and eccentricity of slender ceramic cores of high temperature alloy investment castings as claimed in claim 1, characterized in that: The fixed end (2) is a square boss.

3. A method for solving the problem of fracture and eccentricity of slender ceramic cores of high temperature alloy investment castings as claimed in claim 1, characterized in that: A groove (3) is provided on the outer surface of the fixed end (2).

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

5. A method for solving the problem of fracture and eccentricity of the slender ceramic core of high temperature alloy investment castings as claimed in claim 3, characterized in that: The depth of the groove (3) is greater than 0.5 mm.

6. A method for solving the problem of fracture and deflection of slender ceramic cores of high temperature alloy investment castings as claimed in claim 1, characterized in that: The ceramic core in S2 is prepared by injecting silicon-based material into a mold, sintering, cooling and molding.

7. A method for solving the problem of fracture and deflection of slender ceramic cores of high temperature alloy investment castings as claimed in claim 1, characterized in that: In S3, the MJF technology is used to 3D print the casting wax model 5 with blue wax.

8. A method for solving the problem of fracture and eccentricity of the slender ceramic core of high temperature alloy investment castings as claimed in claim 1, characterized in that: The following steps are also included: S6: Melting and pouring: A three-chamber vacuum furnace is used to melt the alloy bars and pour them into the mold cavity.

9. A method for solving the problem of fracture and eccentricity of the slender ceramic core of high temperature alloy investment castings as claimed in claim 8, characterized in that: The following steps are also included: S7: Post-cleaning Vibrate, cut, and polish the cooled mold shell; S8: Removal of ceramic core: The strong alkaline corrosion method is adopted to remove the ceramic core by soaking reaction in a strong alkaline solution, and the target casting can be obtained after sandblasting.

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