A method for producing a composite mold

Abstract

The application discloses a preparation method of a composite mold and relates to the technical field of casting. A first graphite mold is prepared, a mold dismounting sheet is arranged on the back of a flange of the first graphite mold, and a second graphite mold is obtained; the second graphite mold is subjected to vacuum degassing treatment, and a third graphite mold is obtained; a core mold is prepared; water glass binder type sand is prepared through the core mold; a water glass binder composite core is prepared through sand hanging of the water glass binder type sand, and the water glass binder composite core is subjected to ceramic treatment to obtain a mold shell core; the third graphite mold is combined and assembled with the mold shell core, and a composite mold is obtained. The water glass binder composite core is subjected to ceramic treatment, the strength and high-temperature resistance of the mold shell core are enhanced, and the mold shell core can still maintain shape stability under extreme casting conditions. The mold shell core is prepared by using water glass, the preparation period is relatively short, the cost is more economical, and powerful support is provided for large-scale production.

Description

Technical Field

[0001] This application relates to the field of casting technology, and in particular to a method for preparing a composite mold. Background Technology

[0002] In the field of metal casting, graphite molds are widely used in the production of titanium, zirconium, and their alloy castings due to their excellent thermal conductivity, high-temperature stability, and chemical inertness. However, with the continuous advancement of industrial technology and the increasing diversification of market demands, higher requirements are being placed on the quality, production efficiency, and cost control of castings.

[0003] Traditional graphite molds face numerous technical bottlenecks in dismantling and recycling, gas treatment, and mold core preparation, limiting the further development of casting technology. On the one hand, after casting, traditional graphite molds are often difficult to dismantle quickly and effectively due to their complex structure and tight bonding. This not only increases labor intensity but also prolongs the production cycle and raises production costs. Furthermore, dismantling can easily damage the mold, further exacerbating resource waste. On the other hand, as a key component in the casting process, the performance of the mold core directly affects the final quality of the casting. Traditional mold core materials are insufficient in terms of strength, high-temperature resistance, and preparation time, making it difficult to meet the production requirements of complex castings. Especially under extreme casting conditions, the mold core is prone to deformation or damage, leading to casting defects and increasing the scrap rate. Summary of the Invention

[0004] This application provides a composite casting mold preparation method, which solves the technical problems of complex graphite mold structure, cumbersome disassembly process and easy damage, and easy deformation and damage of mold shell and core in the prior art.

[0005] This application provides a method for preparing a composite mold, comprising: preparing a first graphite mold and setting a demolding sheet on the back of the flange of the first graphite mold to obtain a second graphite mold; vacuum degassing the second graphite mold to obtain a third graphite mold; preparing a core mold; preparing water glass binder molding sand through the core mold; preparing a water glass binder composite core by applying sand to the water glass binder molding sand, and ceramicizing the water glass binder composite core to obtain a mold shell core; and assembling the third graphite mold with the mold shell core to obtain a composite mold.

[0006] In one possible implementation, a first graphite mold is prepared, and a demolding sheet is provided on the back of the flange of the first graphite mold to obtain a second graphite mold, including: providing a sand-removing groove on the back of the demolding sheet, and the sand-removing groove having a depth of 1.5-10mm.

[0007] In one possible implementation, when the outer diameter of the demolding sheet is no more than 300 mm, the sand cleaning groove is a single-ring four-support structure; when the outer diameter of the demolding sheet is greater than 300 mm, the sand cleaning groove is a double-ring eight-support structure.

[0008] In one possible implementation, the second graphite mold is vacuum degassed to obtain the third graphite mold, including: loading the second graphite mold into a furnace, ensuring that the vacuum degree inside the furnace reaches ≤100Pa, and then starting the heating process; gradually increasing the furnace temperature to 300-400℃ and holding it at this temperature range for 4-6 hours; continuing to increase the furnace temperature to 900-1000℃ and holding it at this temperature range for 4-6 hours; after the holding period, allowing the furnace body to cool naturally to 400℃ or below, and then removing the second graphite mold to obtain the third graphite mold.

[0009] In one possible implementation, when the second graphite mold is loaded into the furnace, the larger and thicker components of the second graphite mold are placed near the heat source; gaps should be left between the components of the second graphite mold.

[0010] In one possible implementation, the core mold is prepared by means of: the core mold being a wooden mold, a metal mold, or a 3D printed plastic mold.

[0011] In one possible implementation, the material of the 3D printed plastic mold is PSB polystyrene powder, PLA polylactic acid, or photosensitive resin, and its plastic filler ratio is 15-60%.

[0012] In one possible implementation, water glass binder molding sand is prepared using a core mold, comprising: using mullite molding sand and / or corundum sand as base materials, adding graphite powder or wood chips, and stirring until uniformly mixed to obtain mixed sand; when using graphite powder, the weight of graphite powder accounts for 5-25% of the total weight of the mixed sand; when using wood chips, the weight of wood chips accounts for 1-5% of the total weight of the mixed sand; adding water glass to the mixed sand and stirring until uniformly mixed to form binder molding sand, wherein the weight ratio of water glass to mixed sand is 1-4:20; filling the binder molding sand into the core mold and compacting it, covering the mold cover and then introducing carbon dioxide for hardening treatment; placing the hardened binder molding sand in a calcining furnace and drying it at a temperature of 100-300℃ for at least 24 hours, and performing surface trimming treatment to obtain water glass binder molding sand.

[0013] In one possible implementation, the preparation of a water glass binder composite core via water glass binder molding sand includes: dipping water glass binder molding sand into a special transition layer slurry tank for titanium-zirconium castings, applying it evenly, removing excess slurry, and then placing it in a transition layer sand coating device for sand coating and drying for at least 24 hours to obtain a transition layer core; dipping the transition layer core into a special slurry tank for titanium-zirconium castings, applying it evenly, removing excess slurry, and then placing it in a first surface layer sand coating device for sand coating and drying for at least 24 hours to obtain a first surface layer core; and dipping the first surface layer core into a special surface layer slurry tank for titanium-zirconium castings, applying it evenly, removing excess slurry, and then placing it in a second surface layer sand coating device for sand coating and drying for at least 24 hours to obtain water glass binder molding sand.

[0014] In one possible implementation, the water glass binder composite core is ceramicized to obtain the mold shell core, including: loading water glass binder molding sand into the furnace, starting the air dust removal system, and then heating; gradually increasing the furnace temperature to 450℃ and holding it for 1-2 hours; continuing to increase the furnace temperature to 700℃ and holding it for 1-2 hours; then increasing the furnace temperature to 900-1150℃ and holding it for 1-2 hours; and then naturally cooling it with the furnace until the furnace exit temperature does not exceed 200℃ to obtain the mold shell core.

[0015] One or more technical solutions provided in the embodiments of this application have at least the following technical effects:

[0016] This application incorporates a dismantling sheet in the first graphite mold, facilitating mold dismantling and recycling, effectively reducing production costs and improving efficiency. The second graphite mold utilizes vacuum degassing technology, which thoroughly removes gases and inclusions, significantly improving the internal quality of the casting and drastically reducing common defects such as porosity and shrinkage cavities, ensuring high casting quality. Regarding the preparation of the mold core, this application uses water glass as a raw material, carefully formulated and prepared to obtain a water glass binder composite core. Furthermore, this application performs a ceramicization treatment on the water glass binder composite core, enhancing its strength and high-temperature resistance, enabling it to maintain shape stability even under extreme casting conditions, effectively preventing casting defects caused by mold core deformation or damage. In addition, using water glass to prepare the mold core not only has a relatively short preparation cycle but is also more cost-effective, providing strong support for large-scale production. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating the method for preparing a composite mold according to an embodiment of this application;

[0019] Figure 2 This is a schematic diagram of the structure of the valve body casting prepared by the composite mold provided in the embodiments of this application;

[0020] Figure 3 This is a schematic diagram of the structure of the core mold provided in the embodiments of this application;

[0021] Figure 4 A schematic diagram of a 300mm outer diameter sheet provided in an embodiment of this application;

[0022] Figure 5 A schematic diagram of a 300mm outer diameter sheet provided in an embodiment of this application;

[0023] Figure 6 This is a schematic diagram of the structure of the water glass binder molding sand provided in the embodiments of this application;

[0024] Figure 7 A schematic diagram of vacuum degassing of the second graphite mold provided in an embodiment of this application;

[0025] Figure 8 This is a schematic diagram of the structure of the pump body casting prepared by the composite mold provided in the embodiment of this application.

[0026] Icons: 1-Graphite upper mold; 2-Demolding sheet; 3-Graphite middle mold; 4-Graphite lower mold; 5-Mold shell core; 6-Core mold; 7-Mold cover; 8-Gate; 9-Core skeleton. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] In the description of the embodiments of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the embodiments of this application and for 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. Therefore, they should not be construed as limitations on this application. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, the terms "installed," "connected," and "linked" 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; 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 embodiments of this application according to the specific circumstances.

[0029] This application provides a method for preparing a composite mold, such as... Figures 1 to 8 As shown, the method for preparing this composite mold includes:

[0030] S1: Prepare a first graphite mold and set a demolding sheet 2 on the back of the flange of the first graphite mold to obtain a second graphite mold.

[0031] S2: The second graphite mold is vacuum degassed to obtain the third graphite mold.

[0032] S3: Prepare the core mold 6.

[0033] S4: Prepare water glass binder molding sand using core mold 6.

[0034] S5: A water glass binder composite core is prepared by coating sand with water glass binder molding sand, and the water glass binder composite core is ceramicized to obtain the mold shell core 5.

[0035] S6: Assemble the third graphite mold with the mold shell core 5 to obtain a composite mold.

[0036] Furthermore, the composite mold is placed in a vacuum solidification furnace for vacuum casting to obtain the casting. The process in this embodiment reduces the quenching effect of the composite mold, thereby lowering the viscosity of the molten metal during casting and increasing its fluidity. This improvement effectively avoids defects caused by premature cooling and solidification of the casting, and enhances the flow and filling capacity of molten titanium, zirconium, and other metals. Simultaneously, this process significantly reduces the probability of defects such as under-casting and insufficient filler during casting, improves the surface finish of the core area, and further reduces the difficulty of cleaning the sand core.

[0037] Furthermore, the third graphite mold, after casting, is disassembled and recycled. Specifically, a disassembly sheet 2 is installed on the back of the flange of the first graphite mold.

[0038] like Figure 2 As shown, the third graphite mold structure consists of a lower graphite mold 4, a middle graphite mold 3, a stripping sheet 2, and an upper graphite mold 1, arranged from bottom to top, with all components tightly connected. A gating gate 8 is located on the side of the upper graphite mold 1 furthest from the stripping sheet 2, and this gate is used for pouring. After pouring, the upper graphite mold 1 and the lower graphite mold 4 are disassembled first, then the stripping sheet 2 is cleaned, and finally the middle graphite mold 3 is disassembled. This design not only shortens the manufacturing cycle of the third graphite mold but also allows for the recycling and reuse of all parts, effectively reducing the time cost of casting production and significantly shortening the overall manufacturing cycle. Furthermore, the third graphite mold of this application breaks through the size limitations of traditional molds, flexibly adapting to the casting needs of large, medium, and small titanium and zirconium castings, providing an efficient and economical solution for production projects of different scales.

[0039] It should be noted that the first graphite mold in this application is equipped with a demolding sheet 2. The design of the demolding sheet 2 facilitates the demolding and subsequent recycling process, effectively reducing production costs and improving production efficiency. The second graphite mold adopts vacuum degassing technology, which can thoroughly remove gases and inclusions from the second graphite mold, thereby improving the internal quality of the casting and significantly reducing the occurrence of common defects such as porosity and shrinkage cavities, ensuring the high quality of the casting. In terms of the preparation of the mold shell core 5, this application uses water glass as a raw material. Through careful formulation and preparation, a water glass binder composite core is obtained. Furthermore, this application performs ceramic treatment on the water glass binder composite core, enhancing the strength and high-temperature resistance of the mold shell core 5, enabling it to maintain shape stability even under extreme casting conditions, effectively avoiding casting defects caused by deformation or damage to the mold shell core 5. In addition, the use of water glass to prepare the mold shell core 5 not only has a relatively short preparation cycle but is also more economical, providing strong support for large-scale production.

[0040] In this embodiment of the application, a first graphite mold is prepared, and a demolding sheet 2 is provided on the back of the flange of the first graphite mold to obtain a second graphite mold, including:

[0041] S101: A sand-cleaning groove is provided on the back of the sheet 2, and the depth of the sand-cleaning groove is 1.5-10mm.

[0042] It should be noted that a sand-removing groove is provided on the side where the disassembly sheet 2 contacts the graphite intermediate mold 3 to provide sufficient space for the sand-removing tools to operate, thus facilitating disassembly. After the casting is poured, due to the shrinkage during the metal solidification process, the disassembly sheet 2 may be subjected to pre-tightening force due to the metal solidification shrinkage, which may cause the disassembly sheet 2 and the graphite intermediate mold 3 to be tightly bonded together, making direct disassembly difficult. However, the design of the disassembly sheet 2 and its matching sand-removing groove in this application effectively solves the disassembly problem. By using sand-removing tools for meticulous cleaning, this application can effectively remove the pre-tightening force generated by solidification shrinkage, thereby easily removing the remaining part of the intermediate mold. This process not only reduces the amount of deformation caused by equidistant shrinkage of the casting, but also improves labor efficiency, reduces the difficulty of disassembling the third graphite mold, and improves the working environment and conditions for graphite workers during mold disassembly operations.

[0043] In this embodiment, the design of the split sheet 2 takes into account the requirements for different outer diameters. For example... Figure 4 and Figure 5 As shown, when the outer diameter of the disassembly sheet 2 is no greater than 300mm, a single-ring, four-support structure for the sand-cleaning trough is used; when the outer diameter is greater than 300mm, a double-ring, eight-support structure is used. This design helps to reduce casting deformation and improve disassembly efficiency during the disassembly process.

[0044] In this embodiment of the application, the second graphite mold is vacuum degassed to obtain the third graphite mold, including:

[0045] S201: After loading the second graphite mold into the furnace and ensuring that the vacuum degree inside the furnace reaches ≤100Pa, start the heating process;

[0046] S202: Gradually increase the furnace temperature to 300-400℃ and hold it within this temperature range for 4-6 hours;

[0047] S203: Continue to raise the furnace temperature to 900-1000℃ and hold it within this temperature range for 4-6 hours;

[0048] S204: After the heat preservation is completed, allow the furnace body to cool naturally to 400℃ or below, and then remove the second graphite mold to obtain the third graphite mold.

[0049] It should be noted that the cooling water supply is continuous throughout the entire vacuum degassing process of this application, and can only be stopped when the furnace temperature drops below 65°C. Furthermore, argon gas is strictly prohibited from being introduced during the entire cooling process to avoid any factors that may affect the quality or safety of the mold.

[0050] Specifically, the treated third graphite mold should be kept away from direct contact with the ground, damp or oily environments, and should be assembled and poured promptly to ensure stable performance. If pouring is not scheduled immediately, it should be stored in a drying oven (or holding furnace) at a temperature controlled between 50-80℃. When handling the third graphite mold, the furnace door must be closed quickly to prevent temperature and humidity changes from affecting the mold. The third graphite mold should be poured within five days of being removed from the furnace; otherwise, vacuum degassing treatment must be repeated.

[0051] When removing the third graphite mold from the drying oven (holding furnace), be sure to close the furnace door quickly. Do not leave the furnace door open for extended periods to prevent adverse effects from changes in external temperature and humidity. Finally, the third graphite mold should be assembled and poured within five days of exiting the furnace; otherwise, vacuum degassing must be repeated to ensure the quality of the castings.

[0052] In this embodiment, placing larger and thicker components closer to the heat source ensures that these components reach the required heating temperature more quickly. Because these components are relatively large in size and mass, they require more heat to heat evenly. Proximity to the heat source shortens heating time, improves heating efficiency, thereby saving energy and shortening production cycles.

[0053] In this embodiment of the application, the preparation of the core mold 6 includes: the core mold 6 is a wooden mold, a metal mold, or a 3D printed plastic mold.

[0054] In this embodiment, the core mold 6 can be a wooden mold, a metal mold, or a 3D printed plastic mold. The material of the 3D printed plastic mold is PSB polystyrene powder, PLA polylactic acid, or photosensitive resin, and the plastic filling rate is 15-60% to enhance the structural strength.

[0055] In this embodiment of the application, the preparation of water glass binder molding sand using the core mold 6 includes:

[0056] S401: Using mullite molding sand and / or corundum sand as base materials, add graphite powder or wood chips and stir until uniformly mixed to obtain mixed sand.

[0057] It should be noted that the mullite molding sand or corundum sand is 60-100 mesh, and the graphite powder is 60-300 mesh. The mixed sand in this application can be processed manually or mechanically.

[0058] S402: When using graphite powder, the weight of the graphite powder shall account for 5-25% of the total weight of the mixed sand; when using wood chips, the weight of the wood chips shall account for 1-5% of the total weight of the mixed sand.

[0059] S403: After adding water glass to the mixed sand, stir until the mixture is uniform to form a binder molding sand, wherein the weight ratio of water glass to mixed sand is 1-4:20.

[0060] It should be noted that the stirring time is 5-10 minutes to ensure thorough mixing.

[0061] S404: Fill the core mold 6 with binder molding sand and compact it. After covering it with mold cover 7, introduce carbon dioxide for hardening treatment.

[0062] It should be noted that, as Figure 8 As shown, this application allows the binder molding sand to be placed inside the core mold 6, and the core rib 9 to be added inside the core mold 6. The addition method is as follows: fill the core mold 6 with binder molding sand to 30% to 60% of its sand volume, place the core rib 9, and then fill in the remaining binder molding sand before proceeding with subsequent operations. The core rib 9 in this application reduces the amount of sand required, increases the strength of the binder molding sand, and prevents deformation and breakage of the binder molding sand during the later preparation, firing, and use processes.

[0063] Specifically, the core 9 can be a wire or steel rod with a diameter of 3mm-10mm.

[0064] The curing time of this application is 5-60 minutes. Once the binder-modified molding sand has fully cured, the mold can be removed. The introduction of carbon dioxide accelerates the curing process of the binder-modified molding sand, improving the curing rate and effect while reducing environmental pollution.

[0065] S405: The hardened binder molding sand is placed in a calcining furnace and dried at 100-300℃ for at least 24 hours, and then surface trimming is performed to obtain water glass binder molding sand.

[0066] It should be noted that after drying, surface finishing treatment is performed, including sanding to remove burrs and flash, and applying a titanium-zirconium-specific graphite repair paste (neutral or alkaline) to repair pits. This series of treatments improves the precision and appearance quality of the binder molding sand. Simultaneously, the drying process helps to further strengthen the structural strength of the binder molding sand and remove residual moisture.

[0067] In this embodiment of the application, the preparation of a water glass binder composite core by sand coating with water glass binder includes:

[0068] S501: Place the water glass binder molding sand into a special transition layer slurry bucket for titanium-zirconium castings for dipping. After spreading evenly, remove excess slurry and place it in a transition layer sand-coating device for sand application. Dry for at least 24 hours to obtain the transition layer core.

[0069] It should be noted that the transition layer slurry for titanium-zirconium castings should be kept neutral or alkaline.

[0070] First, the water glass binder molding sand is placed in a special transition layer slurry bucket for titanium-zirconium castings for dipping. After the slurry has dripped sufficiently and is evenly coated, the subsequent sand coating operation is carried out.

[0071] This application uses water glass slurry as an example for illustration.

[0072] The preparation method of the transition layer slurry for titanium-zirconium castings is as follows: High-grade alumina powder and / or mullite powder are mixed with water glass in a 4:1 ratio, and appropriate amounts of surface wetting agent and defoamer are added. Specifically, the amount of surface wetting agent added should be controlled between 0.1% and 0.5% of the total water glass, and the amount of defoamer added should be controlled between 0.01% and 0.25% of the total water glass. The viscosity of the prepared slurry should be maintained within the range of 10-40 seconds (s).

[0073] If the slurry viscosity is too high, it can be adjusted by adding an appropriate amount of water glass; conversely, if the slurry viscosity is too low, it can be adjusted by adding an appropriate amount of powder. After the slurry is adjusted, it needs to be stirred for 1-2 hours to ensure that all components are fully and evenly mixed. Once the performance parameters meet the standards, stop stirring and allow the slurry to recover its properties for at least 4 hours. Then, restart the stirring equipment, and it can be used for the slurry treatment of molding sand.

[0074] After the water glass binder molding sand has been bonded with mortar, excess mortar is first scraped off with a scraper to ensure even distribution and minimal excess mortar on the sand surface. Then, the water glass binder molding sand is placed in a specialized transition layer coating device. In this device, transition layer molding sand is evenly applied to the bonded water glass binder molding sand surface using a sand-spraying method. The transition layer molding sand can be made of zirconia, corundum, or mullite, and its mesh size should be controlled between 60-100 mesh to ensure the uniformity and density of the coating layer.

[0075] After the transition layer sand application is completed, the water glass binder molding sand needs to be placed in a specific dry environment for drying treatment for at least 24 hours. Drying conditions should be strictly controlled within the range of 20-22℃ and 55-65% humidity, while ensuring a visible breeze, but the wind speed must not exceed 2 m / s. Such drying conditions help the moisture in the molding sand evaporate evenly and slowly, avoiding problems such as cracks or deformation caused by excessively rapid drying, thus ensuring the quality of the transition layer.

[0076] S502: Place the transition layer core into a special slurry bucket for titanium-zirconium castings for slurry application. After even application, remove excess slurry and place it in the first surface layer sand coating equipment for sand coating. Dry for at least 24 hours to obtain the first surface layer core.

[0077] It should be noted that the titanium-zirconium casting slurry involved in this application is the first surface layer slurry. The first surface layer slurry is kept neutral or alkaline to ensure good compatibility with the casting material. In the first surface layer slurry, the refractory aggregate is carefully selected from high-purity yttrium oxide powder, high-purity zirconium oxide, and various artificially synthesized material powders (such as calcium yttrium oxide, calcium zirconate, etc.) specifically for the refractory requirements of titanium-zirconium. Its particle size is strictly controlled at 325 mesh to ensure the fineness and uniformity of the first surface layer slurry. As the bonding core, the first surface layer slurry uses a neutral or alkaline titanium-zirconium special binder, such as a modified silica sol specially customized for titanium-zirconium castings, to ensure a strong bond between the first surface layer slurry and the transition layer core.

[0078] Regarding the physical properties of the slurry for titanium-zirconium castings, the viscosity needs to be maintained at 12±2S to ensure that the slurry is neither too thin nor too thick, making it easy to handle; the pH value of the slurry should be 10-11 to further enhance its chemical stability; at the same time, the solid content should be maintained at a high level of 80-85% to provide sufficient refractory and support properties; and the slurry density should be set within the range of 2.0-3.5 g / ml to meet the specific requirements of the casting process.

[0079] A flexible and precise method was used to adjust the viscosity of the slurry for titanium-zirconium castings: if the viscosity was too high, an appropriate amount of binder or deionized water could be added for dilution; conversely, if the viscosity was too low, an appropriate amount of powder needed to be added to increase the viscosity. For pH adjustment, if the pH was found to be below the set range, an appropriate amount of tetraethylammonium hydroxide was added to raise the pH, ensuring the stability and performance of the slurry.

[0080] After the titanium-zirconium casting slurry is prepared, it must be thoroughly stirred for at least 4 hours to ensure that all components are uniformly mixed and reach optimal performance. Only after all performance parameters have been tested and found to meet the standards can the titanium-zirconium casting slurry be put into practical use for subsequent slurry application.

[0081] The titanium-zirconium casting slurry of this application is neutral or alkaline. The refractory aggregate is high-purity yttrium oxide powder, high-purity zirconium oxide, or various synthetic powders suitable for titanium-zirconium refractory materials (such as calcium yttrium oxide, calcium zirconate, etc.), with a mesh size of 325. The binder is a neutral or alkaline titanium-zirconium-specific binder (such as modified silica sol for titanium-zirconium castings). The slurry viscosity is 12±2S, the slurry pH value is 10-11, the solid content is 80-85%, and the slurry density is 2.0-3.5 g / ml. The viscosity can be adjusted as follows: if the viscosity is too high, binder or deionized water can be added; if the viscosity is too low, powder can be added; if the pH value is too low, tetraethylammonium hydroxide needs to be added. The slurry must be stirred for at least 4 hours before use. Once the performance parameters meet the standards, it can be used for bonding.

[0082] First, apply sand to the surface layer: First, place the transition layer core in a special slurry container for titanium-zirconium castings, ensuring even slurry application. After the slurry has dripped sufficiently and evenly coated the surface of the transition layer core, apply sand. The molding sand used here includes high-purity yttrium oxide molding sand, high-purity zirconia molding sand, synthetic calcium zirconate molding sand, and synthetic calcium yttrium oxide molding sand, with a mesh size controlled between 45-100 mesh. Sand application methods can include immersion sand, fluidized bed sand, or manual sand application, with immersion sand being the preferred method due to its uniformity and efficiency.

[0083] First layer sand application and drying: After the first layer of sand application is completed, the transition layer core must be dried immediately for at least 24 hours. The drying conditions should be strictly controlled within the range of 24-26℃ and 60-65% humidity, and the environment should be kept dry to avoid unnecessary cracks or deformation on the core surface.

[0084] S503: Place the first surface layer core into a special surface layer slurry bucket for titanium-zirconium castings for dipping. After spreading evenly, remove excess slurry and place it in the second surface layer sand coating equipment for sand coating. Dry for at least 24 hours to obtain water glass binder molding sand.

[0085] It should be noted that the titanium-zirconium casting-specific surface layer slurry in this application is the second surface layer slurry, which must be neutral or alkaline. The refractory aggregate is high-purity yttrium oxide powder, high-purity zirconium oxide, or various artificially synthesized powders suitable for titanium-zirconium refractory materials (such as calcium yttriumate, calcium zirconate, etc.), with a mesh size of 325 mesh. The binder is a neutral or alkaline titanium-zirconium-specific binder (such as modified silica sol specifically for titanium-zirconium castings). Its preparation method is the same as the first surface layer, with only some parameters differing: slurry viscosity 15±2S, slurry pH value 10-11, solid content 82-85%, and slurry density 2.5-3.5 g / ml. The adjustment method for the second surface layer slurry is the same as that for the first surface layer slurry.

[0086] Second layer sand application: First, the first-layer core, after the first layer treatment, is placed in a special surface layer slurry container for titanium-zirconium castings for a second slurry application. After the second layer slurry has dripped sufficiently and evenly coated the core surface, sand application is performed. The types of molding sand used are the same as those used for the first layer, including high-purity yttrium oxide molding sand, high-purity zirconia molding sand, synthetic calcium zirconate molding sand, and synthetic calcium yttrium oxide molding sand, with the sand mesh size controlled between 45-100 mesh. Sand application methods can also include immersion sand, fluidized bed sand, or manual sand application, with immersion sand being the preferred method due to its high efficiency and uniformity.

[0087] Second layer drying: The first layer core after the second layer sanding operation needs to be dried for at least 24 hours. The drying conditions should be set within the range of 24-26℃ temperature and 60-65% humidity, and the environment should be windless to prevent cracks or deformation on the core surface.

[0088] During or after the drying process, the water glass binder molding sand must be carefully inspected for defects such as cracks and holes. Any defects found must be repaired promptly. For repair, use the same slurry as the second layer, carefully applying it to the defect with a brush to ensure a tight bond between the repair material and the surrounding molding sand. After repair, a second drying process is required, lasting at least 6-12 hours, to ensure the repaired area is fully cured.

[0089] In this embodiment of the application, the water glass adhesive composite core is ceramicized to obtain the mold shell core 5, including:

[0090] S504: After loading the water glass binder molding sand into the furnace and starting the air dust removal system, heating is then carried out.

[0091] S505: Gradually increase the furnace temperature to 450℃ and hold for 1-2 hours; continue to increase the furnace temperature to 700℃ and hold for 1-2 hours.

[0092] S506: Raise the furnace temperature to 900-1150℃ and hold for 1-2 hours; allow it to cool naturally in the furnace until the exit temperature is no higher than 200℃ to obtain the mold core 5.

[0093] It should be noted that the water glass binder core to be fired should be carefully inspected, and its surface should be intact and free of defects. After the water glass binder molding sand is loaded into the furnace, first turn on the air dust removal system, then connect the power supply and fire according to the process specifications.

[0094] During the natural cooling process in the furnace, it is essential to ensure that the temperature upon exiting the furnace does not exceed 200℃. When the furnace temperature drops below 700℃, the furnace door can be opened moderately to accelerate the cooling process; however, this operation must be carried out with caution to avoid adverse effects on the mold core 5 due to drastic temperature changes. Simultaneously, the control of firing temperature and time is crucial. If the firing time is too long, the mold core 5 may burn due to overheating, which will not only reduce its strength but may also lead to serious deformation problems. Conversely, if the temperature is too low or the time is too short, the mold may not be able to sinter sufficiently, thus affecting its permeability and leading to adverse conditions during casting, such as gas retention and poor metal penetration. Therefore, in actual operation, the firing temperature and time must be precisely set according to the specific material characteristics and process requirements, and the entire firing process must be strictly monitored to ensure that the quality and performance of the mold core 5 meet the needs of subsequent processing and use.

[0095] The manufacturing process of the mold core 5 in this application is significantly optimized, requiring only three layers of sand. Compared to the prior art, which requires several layers of sand in the core mold 6 and a complex demolding process, this application not only simplifies the operation steps but also greatly shortens the manufacturing cycle and effectively reduces production costs. Furthermore, by reducing processing steps, this application also reduces the product defect rate caused by improper operation, further improving product quality and production efficiency.

[0096] Existing technologies generally employ methods such as integral high-temperature calcination of yttrium oxide or zirconium oxide cores, or layer-by-layer sand coating techniques to prepare the mold shell core 5 in composite castings. However, both methods suffer from long preparation cycles and high costs, especially for titanium or zirconium castings, which already have high material costs, further increasing manufacturing costs.

[0097] Furthermore, the graphite powder or wood chips introduced during the preparation of the mold core 5 will vaporize into carbon dioxide and be discharged during the subsequent calcination stage, thus forming a unique irregular hollow structure inside the mold core 5. This structure not only endows the mold core 5 with excellent sintering strength but also gives it excellent collapsibility. Therefore, in subsequent processing, the mold core 5 can be cleaned using various efficient methods such as water jet sand removal or vibration sand removal to meet different production needs.

[0098] The method described in this application optimizes the manufacturing process of the mold core 5, shortens the manufacturing cycle, and reduces production costs. Simultaneously, through a unique sand-cleaning groove design and ceramic treatment technology, the surface finish of the casting's internal cavity and overall quality are improved.

[0099] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0100] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A method for preparing a composite casting mold, characterized in that, include: A first graphite mold is prepared, and a demolding sheet is set on the back of the flange of the first graphite mold to obtain a second graphite mold; the second graphite mold is vacuum degassed to obtain a third graphite mold; the structure of the third graphite mold is as follows from bottom to top: a lower graphite mold, a middle graphite mold, a demolding sheet, and an upper graphite mold, with each component tightly abutting against each other, and a sand-removing groove is set on the side of the demolding sheet that contacts the middle graphite mold; Preparation of core molds; Water glass binder molding sand is prepared using a core mold; A water glass binder composite core is prepared by coating sand with water glass binder molding sand, and the water glass binder composite core is then ceramicized to obtain a mold shell core. The third graphite mold is combined and assembled with the mold shell core to obtain a composite mold.

2. The method for preparing the composite mold according to claim 1, characterized in that, A first graphite mold is prepared, and a demolding sheet is placed on the back of the flange of the first graphite mold to obtain a second graphite mold, comprising: A sand-removing groove is provided on the back of the sheet to be disassembled, and the depth of the sand-removing groove is 1.5-10mm.

3. The method for preparing the composite mold according to claim 2, characterized in that, When the outer diameter of the sheet being disassembled is no more than 300mm, the sand cleaning groove is a single-ring, four-support structure. When the outer diameter of the sheet being disassembled is greater than 300mm, the sand cleaning trough has a double-ring, eight-support structure.

4. The method for preparing the composite mold according to claim 1, characterized in that, The second graphite mold is vacuum degassed to obtain the third graphite mold, which includes: The second graphite mold is placed into the furnace, and the heating process begins after ensuring that the vacuum degree inside the furnace reaches ≤100Pa. Gradually increase the furnace temperature to 300-400℃ and maintain it within this temperature range for 4-6 hours; Continue to raise the furnace temperature to 900-1000℃ and maintain it within this temperature range for 4-6 hours; After the heat preservation is completed, allow the furnace body to cool naturally to 400℃ or below, and then remove the second graphite mold to obtain the third graphite mold.

5. The method for preparing the composite mold according to claim 1, characterized in that, The preparation of core molds includes: The core mold can be made of wood, metal or 3D printed plastic.

6. The method for preparing the composite mold according to claim 5, characterized in that, The materials used for 3D printed plastic molds are PSB polystyrene powder, PLA polylactic acid, or photosensitive resin, with a plastic filling rate of 15-60%.

7. The method for preparing the composite mold according to claim 1, characterized in that, The preparation of water glass binder molding sand using a core mold includes: Mullite molding sand and / or corundum sand are used as base materials. Graphite powder or wood chips are added and stirred until they are evenly mixed to obtain mixed sand. When using graphite powder, the weight of the graphite powder accounts for 5-25% of the total weight of the mixed sand; when using sawdust, the weight of the sawdust accounts for 1-5% of the total weight of the mixed sand. After adding water glass to the mixed sand, stir until the mixture is uniform to form a binder molding sand, wherein the weight ratio of water glass to mixed sand is 1-4:

20. The binder molding sand is filled into the core mold and compacted. After the mold cover is closed, carbon dioxide is introduced for hardening. The hardened binder molding sand is placed in a calcining furnace and dried at 100-300℃ for at least 24 hours, and then surface trimming is performed to obtain water glass binder molding sand.

8. The method for preparing the composite mold according to claim 7, characterized in that, The preparation of water glass binder composite cores by sand coating with water glass binder includes: Water glass binder molding sand is placed into a special transition layer slurry bucket for titanium-zirconium castings for dipping. After spreading evenly, excess slurry is removed, and the sand is placed in a transition layer sand coating equipment for sand coating and drying for at least 24 hours to obtain the transition layer core. The transition layer core is dipped into a special slurry bucket for titanium-zirconium castings. After even coating, excess slurry is removed, and the core is placed in the first surface layer sand coating equipment for sand coating and dried for at least 24 hours to obtain the first surface layer core. The first surface layer core is placed in a special surface layer slurry bucket for titanium-zirconium castings for dipping. After spreading evenly, excess slurry is removed, and then the core is placed in a second surface layer sand-coating device for sand coating. It is dried for at least 24 hours to obtain water glass binder molding sand.

9. The method for preparing the composite mold according to claim 8, characterized in that, The core of the mold shell is obtained by ceramicizing the composite core with water glass binder, including: The water glass binder molding sand is loaded into the furnace, the air dust removal system is started, and then heating is carried out; Gradually increase the furnace temperature to 450℃ and hold for 1-2 hours; Continue to raise the furnace temperature to 700℃ and hold for 1-2 hours; Then raise the furnace temperature to 900-1150℃ and hold it for 1-2 hours; The core is obtained by naturally cooling it in the furnace until the furnace exit temperature does not exceed 200℃.

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