Lifting tube for high temperature alloy countergravity casting, manufacturing method and casting device

Abstract

The application provides a riser for high-temperature alloy counter-gravity casting, a manufacturing method and a casting device. The riser is a multilayer composite tubular structure, and sequentially comprises an inner ceramic coating, a first quartz transition layer, a graphite intermediate layer, a second quartz transition layer and an outer ceramic coating from inside to outside. The riser is externally provided with a condenser, the condenser is in thermal conduction contact with the riser, and the condenser is used for cooling the metal liquid flowing through the inner cavity of the riser. The application realizes rapid cooling of the metal liquid while ensuring the stability of the structure of the riser, effectively controls the grain size and reduces the pore defects, and improves the surface quality and comprehensive performance of the casting.

Description

Technical Field

[0001] This application relates to the field of materials processing, and more specifically, to a riser pipe for anti-gravity casting of high-temperature alloys, a manufacturing method thereon, and a casting apparatus. Background Technology

[0002] Anti-gravity casting is a common method for producing high-quality, complex, thin-walled parts. Its main principle is to apply pressure to force molten metal into the mold from bottom to top, overcoming gravity, and then solidify under controlled pressure. A significant advantage of this casting method is its thorough and stable filling, which effectively addresses the issue of subsequent feeding. However, for anti-gravity casting of high-temperature alloys, there is still room for improvement in casting quality, such as the need for finer grain refinement.

[0003] The riser pipe is a key component of anti-gravity casting systems, responsible for transporting molten metal from the holding furnace to the mold cavity. However, when high-temperature alloys (such as nickel-based and cobalt-based high-temperature alloys) are cast through riser pipes, the riser pipe itself is in a high-temperature environment, and the cooling rate of the molten metal flowing inside the pipe is relatively slow. This can easily lead to poor surface quality, internal porosity, and coarse grain structure in the castings. Macroscopic defects can easily affect the overall performance of the casting, while coarse grains can significantly reduce the mechanical properties of the material, such as strength, toughness, fatigue life, and creep resistance, especially under high-temperature conditions. Therefore, how to effectively control the cooling rate of high-temperature alloys during the process of passing through the riser pipe, achieve grain refinement, and improve the surface quality and overall performance of the castings is a technical problem that urgently needs to be solved in this field.

[0004] A search revealed that patent application CN109940152A discloses a riser tube for anti-gravity casting of high-temperature alloys and its manufacturing method. The riser tube, from the inside out, consists of an inner coating, an inner ceramic liner, a high-temperature resistant metal tube, an outer ceramic liner, and an outer coating. This patent suffers from severe thermal mismatch problems; due to the significant difference in thermal expansion coefficients between the metal tube and the ceramic layers on both sides, cracking of the ceramic layer or delamination of the interface is highly likely. Patent application CN118184324A discloses a riser tube for anti-gravity casting of high-melting-point alloys and its preparation method. The riser tube's structural feature is an embedded quartz glass tube within a silicon oxide-based ceramic matrix, with protective coatings applied to both the inner and outer surfaces. This patent uses a non-metallic system, but this material has poor toughness and is prone to brittle fracture, leading to the entire tube being scrapped. Furthermore, SiO2 is easily reduced by strong reducing elements (such as Al and Ti) in the high-temperature alloy melt, thus easily contaminating the melt. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the purpose of this application is to provide a riser pipe for anti-gravity casting of high-temperature alloys, a manufacturing method thereunder, and a casting apparatus.

[0006] In a first aspect, this application provides a riser tube for anti-gravity casting of high-temperature alloys, wherein the riser tube is a multi-layer composite tubular structure, consisting of, from the inside out: an inner ceramic coating, a first quartz transition layer, a graphite intermediate layer, a second quartz transition layer, and an outer ceramic coating. A condenser is provided outside the riser tube, and the condenser is in thermal conduction contact with the riser tube. The condenser is used to cool the molten metal flowing through the inner cavity of the riser tube.

[0007] Optionally, the condenser includes a shell and condensate pipes densely distributed inside the shell. The shell is made of high-temperature refractory material, and the condensate pipes are steel pipes.

[0008] Optionally, the housing is provided with an inlet and an outlet for condensate, and both the inlet and the outlet are provided with connectors for connecting to an external cooling water system.

[0009] Optionally, the condenser and the riser pipe are connected by clamps or clips.

[0010] Optionally, the graphite intermediate layer is a graphite tube; The inner ceramic coating and the outer ceramic coating comprise zirconium oxide, alumina, magnesium oxide, binder, and dispersant; The first quartz transition layer and the second quartz transition layer comprise quartz powder, micron-sized quartz sand, and an inorganic binder.

[0011] A second aspect of this application provides a method for manufacturing the riser pipe for high-temperature alloy anti-gravity casting, comprising: We provide isostatically pressed graphite rods, which are then machined into graphite tubes that conform to the design dimensions and shapes. A quartz-based slurry is provided, and the quartz-based slurry is uniformly coated on the inner and outer surfaces of the graphite tube by dip coating or spin coating, and then dried and cured to obtain an inner quartz transition layer and an outer quartz transition layer. A composite ceramic slurry is provided, and the composite ceramic slurry is uniformly coated inside the inner quartz transition layer and outside the outer quartz transition layer by means of plasma spraying or slurry coating. The coated riser tube is then sintered at high temperature. A condenser that is in thermal contact with the riser tube is installed outside the sintered riser tube to obtain a riser tube for anti-gravity casting of high-temperature alloys.

[0012] Optionally, providing the quartz-based slurry includes: mixing quartz powder, micron-sized quartz sand and an inorganic binder to form a uniform slurry; The provision of the composite ceramic slurry includes: mixing zirconium oxide, alumina and magnesium oxide powders with a binder and a dispersant, and preparing the ceramic slurry by ball milling.

[0013] Optionally, the step of sintering the coated riser tube at high temperature includes: sintering at high temperature in an inert atmosphere according to a preset heating curve.

[0014] Optionally, the step of setting a condenser that is in thermal contact with the riser tube outside the sintered riser tube includes: vertically bending a prefabricated steel tube to insert it into the outer shell, and determining the number of condensate tubes according to the required cooling rate of the molten metal in the riser tube.

[0015] A third aspect of this application provides a casting apparatus comprising the aforementioned riser pipe for anti-gravity casting of high-temperature alloys.

[0016] The riser tube for anti-gravity casting of high-temperature alloys provided in this application adopts a multi-layered tubular structure to enhance thermal shock resistance, reduce thermal expansion and stress, and simplify filling. A condenser rapidly cools the molten metal flowing through the riser tube, thereby refining the grain size and improving the overall quality and performance of the casting. Through the synergistic effect of the multi-layered composite tubular structure and the external condenser, rapid cooling of the molten metal is achieved while ensuring the structural stability of the riser tube, effectively controlling grain size and reducing porosity defects, thus improving the surface quality and overall performance of the casting.

[0017] Other technical effects resulting from the additional features will be further illustrated in the corresponding embodiments. Attached Figure Description

[0018] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a longitudinal cross-sectional view of a riser tube according to an exemplary embodiment; Figure 2 This is a partially enlarged cross-sectional view of a riser tube according to an exemplary embodiment; Figure 3 This is a longitudinal cross-sectional view of a condenser according to an exemplary embodiment; Figure 4 This is a top view of a condenser and riser assembly according to an exemplary embodiment; Figure 5 The high-temperature alloy sample cast using the existing technology with a riser tube has loose pores; Figure 6 The high-temperature alloy sample cast by the riser pipe in this application has loose pores; Figure 7 The grain size distribution of high-temperature alloy samples cast using existing technologies with riser tubes; Figure 8 The grain size distribution of high-temperature alloy samples cast by the riser tube in the implementation of this application.

[0019] In the diagram: 1 is the inner ceramic coating, 2 is the first quartz transition layer, 3 is the graphite intermediate layer, 4 is the second quartz transition layer, 5 is the outer ceramic coating, 6 is the condensate pipe, and 7 is the outer shell. Detailed Implementation

[0020] The present application will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present application, but do not limit the present application in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application, and these all fall within the protection scope of the present application. Parts not described in detail in the following embodiments can be implemented using existing technology.

[0021] In existing technologies, during the anti-gravity casting process of high-temperature alloys, the riser tube is in a high-temperature environment and the molten metal cools slowly as it flows through the riser tube, resulting in coarse grains. These coarse grains significantly reduce the material's strength, toughness, and creep resistance under high-temperature conditions. To address these issues, this application provides a riser tube for anti-gravity casting of high-temperature alloys.

[0022] Reference Figures 1 to 4 As shown in one embodiment of this application, the riser tube for high-temperature alloy anti-gravity casting is a multi-layer composite tubular structure, consisting of, from the inside out: an inner ceramic coating 1, a first quartz transition layer 2, a graphite intermediate layer 3, a second quartz transition layer 4, and an outer ceramic coating 5; a condenser is provided outside the riser tube, and the condenser is in thermal conduction contact with the riser tube, and the condenser is used to cool the molten metal flowing through the inner cavity of the riser tube.

[0023] Specifically, the inner ceramic coating 1, in contact with the melt, primarily serves to achieve chemical inertness, isolate the melt from the first quartz transition layer 2, protect the melt from contamination, and protect the inner wall of the riser tube from melt erosion. High-temperature alloy melts often contain reactive elements such as Al and Ti; the inner ceramic coating 1 prevents the melt from reacting with the quartz layer. The first quartz transition layer 2, as an internal protective layer, primarily protects the graphite core layer (graphite intermediate layer 3) from erosion by the melt side and acts as a transition between the coating and graphite, preventing the melt from reacting with the graphite should it penetrate the coating. The graphite intermediate layer 3, as the core layer, forms the structural framework of the entire riser tube. The strength of graphite at high temperatures increases with increasing temperature (reaching a peak around 2500°C), and its high-temperature strength and creep resistance far exceed those of any metal. It provides the riser tube with the mechanical support required to withstand melt pressure and its own weight at extreme temperatures (such as 1500°C-1700°C). The second quartz transition layer 4 serves as an outer protective layer, resisting oxidation, isolating it from external air, and preventing oxygen from contacting the graphite. The outer ceramic coating 5 is the outermost protective layer, further enhancing its oxidation resistance and resisting chemical corrosion, providing the final external protection for the entire structure.

[0024] This application employs a multi-layered tubular structure, combined with the material configuration of each layer of the riser tube, to enhance thermal shock resistance, reduce thermal expansion and stress, and lower the difficulty of filling the mold. On the other hand, condensers are symmetrically arranged on the outer wall of the riser tube. Adding condensers to the outer periphery of the main structure of the riser tube allows for the introduction of cooling media (such as water, cooling oil, inert gas, etc.) to forcibly cool the molten metal flowing through the inner cavity of the riser tube, thereby improving the cooling efficiency of the molten metal, refining the grain structure, and enhancing the overall quality and comprehensive performance of the casting.

[0025] The embodiments described above employ a multi-layered tubular structure to enhance thermal shock resistance, reduce thermal expansion and stress, and simplify the mold filling process. A condenser is used to rapidly cool the molten metal flowing through the riser pipe, thereby refining the grain size and improving the overall quality and performance of the casting. Through the synergistic effect of the multi-layered composite tubular structure and the external condenser, rapid cooling of the molten metal is achieved while ensuring the structural stability of the riser pipe, effectively controlling grain size and reducing porosity defects, thus improving the surface quality and overall performance of the casting.

[0026] In order to improve the cooling rate of high-temperature alloy liquid, in some specific embodiments of this application, the condenser includes a shell 7 and condensate pipes 6 densely distributed inside the shell 7. The shell 7 is made of high-temperature refractory material, and the condensate pipes 6 are steel pipes.

[0027] Specifically, for the high-temperature refractory shell, which refers to a material capable of withstanding temperatures above 800℃, high-strength, high-temperature resistant, and thermally shock resistant refractory castables or refractory bricks can be selected. These materials must simultaneously meet the mechanical strength requirements under high-temperature conditions and the pressure resistance required for cooling medium circulation, while leveraging the high thermal conductivity of the metal to improve heat exchange efficiency. For the steel condensate pipes, carbon steel or low-alloy steel pipes with good thermal conductivity and certain corrosion resistance can be selected. Multiple steel condensate pipes are arranged parallel to the axis of the riser pipe (i.e., vertically), forming a single (or multiple) ring array, densely arranged on the outside of the riser pipe. As the cooling medium flows within the steel pipes, it continuously absorbs the heat transferred from the riser pipe through the pipe walls, creating a directional temperature gradient in the molten metal during its flow. This temperature gradient promotes heterogeneous nucleation of the molten metal during the flow stage, thereby shortening the solidification time and refining the grain size.

[0028] In the embodiments described above, the outer casing 7 isolates the cooling system from the influence of the external high-temperature environment while maintaining a stable heat conduction path between the outer casing 7 and the riser pipe. The internal condensate pipe 6 increases the contact area between the cooling medium and the outer wall of the riser pipe, forming a uniformly distributed forced convection heat transfer area. This achieves uniform cooling of the riser pipe in both the axial and circumferential directions, while avoiding vaporization caused by direct contact between the cooling medium and the high-temperature pipe wall, significantly improving the stability and controllability of the cooling system.

[0029] In order to connect with the cooling water system, in some specific embodiments of this application, the outer casing is provided with an inlet and an outlet for condensate water, and both the inlet and the outlet are provided with connectors for connecting with the external cooling water system.

[0030] Specifically, the inlet refers to the channel interface through which cooling water enters the condenser, and the outlet refers to the channel interface through which cooling water exits the condenser.

[0031] For example, the connectors are flanges or joints to facilitate connection to an external cooling water system and ensure the sealing reliability of the cooling water circulation system under high pressure conditions.

[0032] The embodiments described above achieve a reliable sealed connection between the cooling water system and the riser condenser, effectively avoiding the problem of reduced cooling efficiency due to interface leakage. Furthermore, modular connectors enable rapid assembly and maintenance of the cooling water system.

[0033] In order to achieve heat conduction contact connection between the condenser and the outer wall of the riser pipe at high temperatures, in some specific embodiments of this application, the condenser and the riser pipe are connected by clamps or clips.

[0034] Specifically, a clamp refers to a ring-shaped metal fastener, while a clip refers to a strip-shaped connector with a locking or fastening mechanism. The clamping force of the clamp or clip is applied to the contact interface between the condenser shell and the ceramic coating 5 on the riser pipe, forcing them to form a rigid, gapless contact. Under high-temperature conditions, the metal clamp or clip generates additional clamping force due to thermal expansion, further enhancing the heat transfer efficiency of the contact surface. Using clamps or clips ensures good heat transfer contact between the condenser and the riser pipe. When disassembly and maintenance are required, the condenser and riser pipe can be separated by loosening the bolts or unlocking the latches, avoiding disassembly damage caused by welding or bonding.

[0035] It should be noted that other mechanical connection methods can also be used, as long as they can achieve the same function as described above.

[0036] The embodiments described above in this application utilize the elastic clamping characteristics of clamps or clips to adaptively compensate for differences in thermal expansion at high temperatures. This solves the problem of reduced heat transfer efficiency caused by thermal stress deformation at the contact interface between the condenser and the riser pipe, ensuring that the cooling system maintains a stable heat exchange capacity under high-temperature conditions. At the same time, uniform pressing of the contact surface can be achieved without a complex installation structure, providing a convenient operation method for equipment maintenance that allows for repeated disassembly.

[0037] To enhance the thermal shock resistance of the riser tube and reduce thermal expansion and stress, in some specific embodiments of this application, the graphite intermediate layer 3 is made of graphite tube; the inner ceramic coating 1 and the outer ceramic coating 5 include zirconium oxide, alumina, magnesium oxide, binder and dispersant; the first quartz transition layer 2 and the second quartz transition layer 4 include quartz powder, micron-sized quartz sand and inorganic binder.

[0038] Specifically, the components of the inner ceramic coating 1 and the outer ceramic coating 5 are as follows: by weight percentage, 20-30% zirconium oxide and 15-30% magnesium oxide; the proportions of binder and dispersant added are as follows: by weight percentage, 1-5 parts binder per 100 parts ceramic powder, 0.5-3 parts dispersant per 100 parts ceramic powder, 20-50 parts solvent per 100 parts ceramic powder, and the balance being alumina; the sum of the weight percentages of each component is 100%.

[0039] The components of the first quartz transition layer 2 and the second quartz transition layer 4 are as follows: by weight percentage, micron-sized quartz sand (coarse material) 65-80%; quartz powder (fine material) 20-35%; 5-20 parts of inorganic binder per 100 parts of quartz powder; the sum of the weight percentages of each component is 100.

[0040] For example, the inorganic adhesive uses silica sol.

[0041] The ceramic coating, comprising zirconium oxide, alumina, and magnesium oxide, meets the requirements of chemical inertness, resistance to melt erosion, and inherent toughness to withstand thermal and mechanical shock. By using a ceramic coating containing these components, melt erosion can be resisted without contaminating the melt. Utilizing the phase transformation toughening mechanism of ZrO2 and the microcrack deflection mechanism of spinel, this coating exhibits extremely high fracture toughness, far surpassing that of brittle quartz.

[0042] The quartz transition layer comprises quartz powder, quartz sand, and silica sol to meet requirements for thermal expansion coefficient and resistance to shrinkage and cracking. Graphite tubes have an extremely low thermal expansion coefficient (approximately 1-3 × 10⁻⁶). -6 / K). Quartz (fused silica) also has an extremely low coefficient of thermal expansion (approximately 0.5 × 10⁻⁶ K). -6 / K). This combination is one of the most compatible among all materials. Quartz has good oxidation resistance; graphite oxidizes at high temperatures, and quartz, being a dense oxide, can isolate oxygen. The quartz transition layer containing these components solves the thermal mismatch problem between graphite and the protective layer, preventing interlayer stress in the riser tube under drastic temperature changes and exhibiting extremely strong thermal shock resistance. It protects the internal graphite tube from ablation at high temperatures, ensuring mechanical strength. The average particle size of the quartz powder is 1-20 micrometers, and the average particle size of the micron-sized quartz sand is 30-300 micrometers. A design combining coarse and fine quartz powder and micron-sized quartz sand is used, with fine quartz powder filling the gaps and coarse quartz sand acting as a framework. This reduces the volume shrinkage rate during drying and sintering, effectively preventing coating cracking and allowing for the preparation of thicker, denser coatings.

[0043] In the embodiments described above, the coating system's thermal shock resistance reduces microcracks caused by temperature fluctuations, preventing pipe corrosion due to molten metal penetration. The thermal stress buffering effect of the transition layer extends the service life of the riser pipe under high-temperature cyclic conditions. The use of a condenser accelerates heat dissipation from the molten metal within the riser pipe, promoting rapid nucleation undercooling and thus refining the grain size of the solidification structure.

[0044] In the above embodiments of this application, the riser tube is designed with an inner ceramic coating 1, which separates the quartz tube from the melt. This ensures the purity of the alloy melt (no Si contamination) and protects the riser tube structure from corrosion, greatly extending its service life. Compared with the prior art CN109940152A, the above embodiments of this application employ a multi-layer ceramic structure with matched thermal expansion coefficients. The thermal expansion coefficients of the two are highly matched; therefore, the thermal shock resistance, structural stability, and cycle life of the above embodiments of this application are far superior to CN109940152A, and cracking and delamination caused by thermal stress will not occur.

[0045] Another embodiment of this application provides a method for manufacturing the above-mentioned riser tube for high-temperature alloy anti-gravity casting, the method comprising the following steps: S1. Provide isostatically pressed graphite rods, which are then machined into graphite tubes that conform to the design dimensions and shapes. S2. Provide a quartz-based slurry, and use an impregnation or spin coating method to uniformly coat the quartz-based slurry on the inner and outer surfaces of the graphite tube, and then dry and cure it to obtain an inner quartz transition layer (first quartz transition layer 2) and an outer quartz transition layer (second quartz transition layer 4). S3. Provide composite ceramic slurry, and use plasma spraying or slurry coating to uniformly coat the composite ceramic slurry inside the inner quartz transition layer and outside the outer quartz transition layer. S4. The coated riser tube is sintered at high temperature; S5. A condenser that is in thermal contact with the riser tube is installed outside the sintered riser tube to obtain a riser tube for high-temperature alloy anti-gravity casting.

[0046] Specifically, in S1, to prepare the graphite intermediate layer, high-purity, high-density isostatically pressed graphite rods are first selected, and then graphite tubes conforming to the design dimensions and shapes are manufactured through machining methods such as turning and drilling. Before use, the graphite tubes undergo surface cleaning and pretreatment to remove oil and impurities.

[0047] To prepare the quartz transition layer, in some specific embodiments of this application, a quartz-based slurry is provided, comprising: mixing quartz powder, micron-sized quartz sand and an inorganic binder to form a uniform slurry; Specifically, after uniformly coating the outer surface of the graphite tube with quartz-based slurry, it is initially dried and cured at a specific temperature.

[0048] For example, the mixture is left to stand at room temperature (25°C) for 2 hours to allow most of the solvent to evaporate naturally; then it is transferred to an oven and kept at 75°C for 4 hours to further remove the solvent. After drying, the temperature is raised to about 150°C and kept there for 4 hours. This temperature is higher than the boiling point of water, which is sufficient to remove physically adsorbed water and bound water, and to cause irreversible gelation and hardening of binders such as silica sol, forming a coating with initial strength.

[0049] In order to coat a ceramic coating on a surface, in some specific embodiments of this application, a composite ceramic slurry is provided, including: mixing zirconium oxide, alumina and magnesium oxide powders in a predetermined weight ratio (e.g. 1:2:1) with a binder and a dispersant, and preparing the ceramic slurry by ball milling.

[0050] Specifically, the aforementioned composite ceramic slurry considers the formation of high-temperature phases and the stabilization of zirconium oxide to achieve a balance of properties such as strength, toughness, and chemical inertness. Al2O3 provides high hardness and high strength; ZrO2 (after stabilization) provides a "phase transformation toughening" effect; and spinel (MgAl2O4) provides excellent thermal shock resistance. Al2O3 and MgO react at high temperatures to form spinel (MgAl2O4), which has excellent thermal shock resistance and resistance to melt erosion. Pure ZrO2 undergoes a destructive phase transformation at around 1100°C. Introducing MgO (or Al2O3) can act as a stabilizer, allowing ZrO2 to maintain a stable phase state from room temperature to high temperatures (such as partially stabilized tetragonal t-ZrO2 or cubic c-ZrO2).

[0051] Through the above formulation and subsequent high-temperature sintering, the final coating is not a simple mixture of the three oxides, but a multiphase ceramic coating with an alumina-spinel matrix and dispersed stable zirconium oxide particles. The transformation toughening mechanism of the sintered MgAl2O4 spinel phase and the partially stabilized ZrO2 particles works synergistically to give the coating extremely high fracture toughness and excellent thermal shock resistance, making it less prone to cracking under drastic temperature changes. The Al2O3 matrix ensures the coating's high-temperature strength and hardness. Both ZrO2 and the spinel phase possess excellent chemical inertness, effectively resisting the erosion of high-temperature alloy melts (especially active melts containing Al and Ti). Therefore, it possesses the advantages of high toughness and thermal shock resistance, high strength and corrosion resistance.

[0052] Specifically, ultrafine zirconium oxide, alumina, and magnesium oxide powders are mixed with binders, dispersants, etc. in a predetermined weight ratio of 1:2:1. The average particle size of the powder is less than 500 nm, and the overall particle size is between 100 nm and 1000 nm. The mixture is then ball-milled to prepare a highly stable ceramic slurry.

[0053] In some specific embodiments of this application, the coated riser tube is subjected to high-temperature sintering, including: high-temperature sintering under an inert atmosphere according to a preset heating curve.

[0054] Specifically, high-temperature sintering is carried out under an argon atmosphere, following a pre-set heating curve. The heating curve consists of four stages: Stage 1 is a slow, low-temperature heating stage to remove organic matter, increasing the temperature from room temperature to 600°C at a rate of 5°C / min. Stage 2 is a normal heating stage, increasing the temperature to the target sintering temperature of 1700°C at a rate of 10°C / min. Stage 3 is a isothermal sintering stage, holding the target sintering temperature of 1700°C for 4 hours. Stage 4 is a fixed-rate cooling stage, cooling to room temperature at a rate of 8°C / min. During this process, the ceramic powder crystallizes or melts, forming a dense, robust, and non-porous ceramic protective layer on the graphite / quartz matrix surface. Precise temperature control is crucial. For example, a riser furnace is used. Before use, high-precision thermocouples are used to ensure accurate temperature measurement. During use, external thermocouples are connected to maintain temperature accuracy. Any fluctuations can be adjusted via the furnace's control buttons to ensure complete densification of the ceramic and a good metallurgical bond with the matrix.

[0055] In some specific embodiments of this application, a condenser that is in thermal contact with the riser tube is installed outside the sintered riser tube, including: vertically bending a prefabricated steel pipe to insert it into the outer shell, and determining the number of condensate pipes according to the required cooling rate of the molten metal in the riser tube.

[0056] For example, a straight steel pipe is bent into a U-shape and placed vertically into the casing, with its two straight arms parallel to the riser pipe, thus creating a complete flow loop where cooling water enters from one end and exits from the other. Depending on the required cooling rate of the molten metal in the riser pipe, 5-8 condensate pipes are added.

[0057] Another embodiment of this application provides a casting apparatus, which includes the aforementioned riser pipe for anti-gravity casting of high-temperature alloys. Due to the technical effects of the aforementioned riser pipe, the casting apparatus in this embodiment also has the same technical effects, and will not be described again here.

[0058] To further illustrate the aforementioned technical effects, a comparison is made with existing ceramic riser pipes that lack a layered design. Figure 5 and Figure 6 This illustrates the porous structure of a high-temperature alloy sample cast using existing technology and the riser tubes described in the above embodiments of this application. Figure 7 and Figure 8 The illustration shows the grain size distribution of high-temperature alloy samples cast using the riser tube in the above embodiments of this application, applying existing technology and demonstrating that the riser tube in the above embodiments of this application can effectively control grain size and reduce porosity defects, thereby improving the overall quality and performance of the casting.

[0059] The embodiments described above in this application, by installing a condenser around the riser tube, forcefully and rapidly cool the molten metal flowing through the riser tube, significantly improving the cooling rate and effectively refining the as-cast grains of the high-temperature alloy. For parts cast directly using this riser tube, their overall quality and performance can be improved. The refined grains can improve casting quality and significantly enhance the comprehensive mechanical properties of the high-temperature alloy, such as tensile strength, yield strength, plasticity, toughness, fatigue strength, and creep rupture life at both room temperature and high temperature.

[0060] The embodiments described above in this application reduce the difficulty of mold filling by optimizing the riser pipe material and adding a graphite layer with good airtightness. By adjusting the type, flow rate, and temperature of the cooling medium, the cooling process of the molten metal can be more precisely controlled, enhancing process controllability and making it possible to customize the solidification structure of castings with specific performance requirements.

[0061] Furthermore, compared to complex modifications to the entire casting system, the local improvements to the riser pipes in the above embodiments of this application are relatively simple in structure, easy to implement, and have the advantages of low cost, easy integration, and easy maintenance.

[0062] In the description of the embodiments of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0063] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0064] In the description of the embodiments in this application, "multiple" means two or more, unless otherwise explicitly specified. In this application, unless otherwise explicitly specified and limited, the terms "installed," "connected," "linked," "fixed," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0065] The terms "comprising" and "having," and any variations thereof, in the embodiments of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such processes, methods, products, or devices.

[0066] The foregoing has described some specific embodiments of this application. It should be understood that this application is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the substantive content of this application. The above-described preferred features can be used in any combination without conflict.

Claims

1. A method for manufacturing a riser pipe for anti-gravity casting of high-temperature alloys, characterized in that, The riser tube is a multi-layered composite tubular structure, consisting of, from the inside out: an inner ceramic coating, a first quartz transition layer, a graphite intermediate layer, a second quartz transition layer, and an outer ceramic coating; a condenser is provided outside the riser tube, and the condenser is in thermal conductive contact with the riser tube, and the condenser is used to cool the molten metal flowing through the inner cavity of the riser tube; The condenser includes an outer shell and condensate pipes densely distributed inside the outer shell. The outer shell is made of high-temperature refractory material, and the condensate pipes are steel pipes. The outer casing is provided with an inlet and an outlet for condensate water, and both the inlet and the outlet are provided with connectors for connecting to an external cooling water system; The condenser and the riser pipe are connected by clamps or clips; The graphite intermediate layer is made of graphite tube; The inner ceramic coating and the outer ceramic coating comprise zirconium oxide, alumina, magnesium oxide, binder, and dispersant; The first quartz transition layer and the second quartz transition layer comprise quartz powder, micron-sized quartz sand, and an inorganic binder; The method includes: We provide isostatically pressed graphite rods, which are then machined into graphite tubes that conform to the design dimensions and shapes. A quartz-based slurry is provided, and the quartz-based slurry is uniformly coated on the inner and outer surfaces of the graphite tube by dip coating or spin coating, and then dried and cured to obtain a first quartz transition layer and a second quartz transition layer. A composite ceramic slurry is provided, and the composite ceramic slurry is uniformly coated inside the first quartz transition layer and outside the second quartz transition layer by means of plasma spraying or slurry coating. The coated riser tube is then sintered at high temperature. A condenser that is in thermal contact with the riser tube is installed outside the sintered riser tube to obtain a riser tube for anti-gravity casting of high-temperature alloys.

2. The method for manufacturing a riser pipe for high-temperature alloy anti-gravity casting according to claim 1, characterized in that, The provision of the quartz-based slurry includes: mixing quartz powder, micron-sized quartz sand and inorganic binder to form a uniform slurry; The provision of the composite ceramic slurry includes: mixing zirconium oxide, alumina and magnesium oxide powders with a binder and a dispersant, and preparing the ceramic slurry by ball milling.

3. The method for manufacturing a riser pipe for high-temperature alloy anti-gravity casting according to claim 1, characterized in that, The process of sintering the coated riser tube at high temperature includes: sintering at high temperature in an inert atmosphere according to a preset heating curve.

4. The method for manufacturing a riser pipe for high-temperature alloy anti-gravity casting according to claim 1, characterized in that, The method of setting a condenser in heat conduction contact with the riser tube outside the sintered riser tube includes: vertically bending a prefabricated steel pipe to insert it into the outer shell, and determining the number of condensate pipes according to the required cooling rate of the molten metal in the riser tube.

5. A casting apparatus, characterized in that, This includes riser pipes for anti-gravity casting of high-temperature alloys manufactured using the method described in any one of claims 1-4.

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