Shell manufacturing method for overcoming defects of iron inclusion and steel shots in narrow groove of high-temperature alloy casting
By optimizing the shell manufacturing process, configuring surface silica sol with specific parameters and module pre-wetting treatment, combined with multiple slurry application and brush cleaning, the problems of iron inclusions and steel pellet defects in narrow slots of high-temperature alloy castings were solved, improving casting quality and production efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 重庆三耐科技有限责任公司
- Filing Date
- 2025-12-30
- Publication Date
- 2026-04-14
AI Technical Summary
In the investment casting process, narrow groove areas of high-temperature alloy castings are prone to defects such as iron inclusions and steel pellets, which affect the quality and aerodynamic performance of the castings, leading to increased production costs and extended delivery cycles.
By configuring specific parameters for the surface silica sol, pre-wetting the module, applying slurry multiple times, brushing and cleaning the narrow groove area, and drying in layers, the shell manufacturing process is optimized to ensure uniform coverage and removal of impurities in the narrow groove area.
It effectively reduces defects such as iron inclusions and steel pellets, improves casting quality and yield, and reduces production costs.
Smart Images
Figure CN121847728A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of investment casting technology, and particularly relates to a method for manufacturing mold shells to solve the defects of iron inclusions and steel pellets in narrow grooves of high-temperature alloy castings. Background Technology
[0002] Turbine guide vanes, as key components of aero-engines, play a crucial role in efficiently converting the thermal energy of high-temperature combustion gases into kinetic energy and precisely guiding airflow to impact the turbine, thus driving continuous engine operation. These blades are generally manufactured using high-temperature alloy materials through investment casting. Their internal structure includes complex hollow air cooling channels to maintain blade stability under extreme high-temperature environments. In the trailing edge region of the blade, a row of cast narrow slots is designed for effective exhaust of the cooling airflow. These slots are subsequently machined using electrical discharge machining to form tiny exhaust holes, such as... Figure 1 As shown.
[0003] However, due to the narrow width and deep geometry of the narrow groove, the slurry is difficult to evenly wet the inner surface of the groove during the shell manufacturing process of investment casting. This easily leads to air bubbles or impurities becoming trapped in the narrow groove area. When the shell strength is insufficient or local defects exist, iron inclusions (metal debris embedded in the shell) and steel bead defects (small metal spheres adhering to the groove wall) can easily occur inside the narrow groove. These defects not only damage the geometric integrity and venting function of the narrow groove but may also cause airflow channel blockage or uneven thermal stress distribution, severely affecting the aerodynamic performance and service life of the turbine guide vanes. In actual production, such problems frequently cause casting quality issues, resulting in a large number of products failing to meet aerospace standards, leading to a significant increase in production costs and extended delivery cycles.
[0004] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention
[0005] The purpose of this invention is to provide a method for manufacturing a mold shell to solve the defects of iron inclusion and steel pellets in narrow slots of high-temperature alloy castings, so as to effectively reduce the defects of iron inclusion and steel pellets in narrow slots of high-temperature alloy castings, improve casting quality and yield, and reduce production costs.
[0006] To achieve the above objectives, the technical solution of the present invention is as follows: a method for manufacturing a mold shell to solve the defects of iron inclusion and steel pellets in narrow grooves of high-temperature alloy castings, comprising the following steps:
[0007] S1. Prepare a surface layer silica sol, wherein the mass percentage of SiO2 in the surface layer silica sol is 29%-30%, the powder-to-liquid ratio is 1:3.0 to 1:3.3, and the viscosity value is 24-26s;
[0008] S2. Assemble the modules and immerse the assembled modules completely in distilled water for pre-wetting;
[0009] S3, Topcoat Forming: Immerse the pre-wetted module from step S2 into the topcoat silica sol for the first topcoat coating treatment. After the first topcoat coating treatment is completed, remove the module and use a cleaning brush to clean the narrow groove area of the module. Then perform the second topcoat coating treatment. After the second topcoat coating treatment is completed, remove the module for slurry control and perform topcoat sanding treatment on the surface of the module after slurry control. Then perform topcoat drying.
[0010] S4. Transition layer coating molding: Remove the surface sand of the module after drying in step S3 and pre-wet it. Then immerse the module in the transition layer slurry for transition layer coating treatment. After the transition layer coating treatment is completed, take out the module and use a cleaning brush to clean the narrow groove part of the module. After cleaning, perform transition layer coating treatment again and take out the module to control the slurry. After the slurry control is completed, perform transition layer sanding treatment on the surface of the module and then dry the transition layer.
[0011] S5. Forming of the reinforcement layer coating: Remove the loose sand from the surface of the module after drying in step S4, then immerse the module in the reinforcement layer slurry for reinforcement layer coating treatment. After the reinforcement layer coating treatment is completed, take out the module to control the slurry. After the slurry control is completed, sprinkle sand on the surface of the module for reinforcement layer treatment, and then dry the reinforcement layer.
[0012] S6. Repeat step S5 to form a module with multiple reinforcement layers;
[0013] S7. Sealing layer coating molding: Immerse the module from step S6 into the sealing layer slurry for sealing layer coating treatment. After the sealing layer coating treatment is completed, remove the module to control the slurry. After the slurry control is completed, dry the sealing layer.
[0014] S8. Coating treatment: Add distilled water to the remaining surface layer silica sol to make the viscosity of the surface layer silica sol vary within ±2s.
[0015] Furthermore, the pre-wetting operation steps are as follows: immerse the entire module in distilled water for 3-5 seconds, then remove it and drain it for 40-60 seconds.
[0016] Furthermore, the viscosity of the transition layer slurry is 13-17s; the viscosity of the reinforcing layer slurry is 9-13s; and the viscosity of the sealing layer slurry is 9-13s.
[0017] Furthermore, in step S3, the drying time for the surface layer is 15-18 hours, the ambient humidity for surface layer drying is 65%-75%, and the drying temperature is 22±2℃.
[0018] Furthermore, in step S4, the drying time of the transition layer is not less than 6 hours, and the ambient humidity of the transition layer is 30-55℃.
[0019] Furthermore, in step S5, the drying time of the reinforcement layer is not less than 6 hours, and the ambient humidity for drying the reinforcement layer is 30-45℃.
[0020] Furthermore, in step S8, the drying time of the sealing layer is not less than 24 hours, and the ambient humidity for drying the sealing layer is 30-45℃.
[0021] The beneficial effects of this technical solution are as follows:
[0022] This invention provides a shell manufacturing method to solve the defects of iron inclusions and steel pellets in narrow slots of high-temperature alloy castings. The method includes steps such as configuring a surface silica sol with specific parameters, pre-wetting the module, multiple slurry application treatments and brushing cleaning of the narrow slot area, and layered drying. By optimizing the shell manufacturing process and adjusting parameters such as slurry ratio, the method ensures uniform coverage and impurity removal in the narrow slot area, effectively reducing iron inclusions and steel pellets in the narrow slots of high-temperature alloy castings, improving casting quality and yield, and reducing production costs. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the narrow slot structure of the blade in the prior art of this invention;
[0024] Figure 2 This is a schematic diagram of the module structure in an embodiment of the present invention;
[0025] Figure 3 This is a schematic flowchart of the manufacturing method of the present invention. Detailed Implementation
[0026] The following detailed description illustrates the specific implementation method:
[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] The basic implementation examples are as follows: Figure 1 The following is a method for manufacturing a mold shell to solve the defects of iron inclusions and steel pellets in narrow slots of high-temperature alloy castings, comprising the following steps:
[0029] S1. Prepare the surface silica sol, wherein the surface silica sol contains 29%-30% SiO2 by mass, has a powder-to-liquid ratio of 1:3.0 to 1:3.3, and a viscosity of 24-26 s. For example, the SiO2 by mass percentage is 29.5%, the powder-to-liquid ratio is 1:3.2, and the viscosity is 23.5 s. Specifically, the surface silica sol is the first coating layer in the mold shell manufacturing process, directly contacting the mold surface and directly affecting the surface quality and precision of the casting. The composition and physical properties of the silica sol, especially the SiO2 by mass percentage, powder-to-liquid ratio, and viscosity, are precisely controlled to ensure that it forms a uniform and dense coating on the mold surface and has good adhesion. A viscosity value of 24-26s refers to the total time taken from the start of flow to the first breakage of the flow filament when a specified volume (100mL) of the liquid to be tested is allowed to flow naturally through a small hole at the bottom of the cup using a Chinese standard flow cup (Ford-4 viscometer) at a set temperature (usually 23℃ or 25℃). In this embodiment, the viscosity value can be selected as 25s.
[0030] S2. Assemble the modules and immerse the assembled modules completely in distilled water for pre-wetting. Specifically, the module is an integral structure composed of multiple wax models assembled through a gating and riser system. It is the original model used to form the shape of the casting in investment casting. During the shell manufacturing process, the shell will be formed around this module. In this embodiment, the mold is an application of existing technology in this context, such as... Figure 2 As shown, those skilled in the art can select modules with different structures according to actual production conditions, which will not be elaborated here. Pre-wetting is the operation of immersing the module in distilled water before the slurry coating process. This step aims to achieve uniform wetting of the module surface, thereby improving the wettability and adhesion of the subsequent slurry and reducing the generation of air bubbles. In this embodiment, the specific operation steps of the pre-wetting method described below are as follows: immerse the entire module (here, the module refers to the module after completing the corresponding processing steps) in distilled water for 3-5 seconds, then remove it and drain it for 40-60 seconds.
[0031] S3. Surface Coating Forming: Immerse the pre-wetted module from step S2 into the surface silica sol for the first surface coating treatment. After the first surface coating treatment, remove the module and use a cleaning brush to clean the narrow groove areas of the module. Then, perform the second surface coating treatment. After the second surface coating treatment, remove the module and control the coating. Then, apply surface sand to the surface of the module after the coating control is completed, followed by surface drying. The drying time for the surface layer is 15-18 hours, the ambient humidity is 65%-75%, the drying temperature is 22±2℃, and the moisture content measured by the moisture meter is 8-10. For example, if the drying time is 16 hours, the ambient humidity is controlled at 70%, and the drying temperature is 20℃, 21℃, 22℃, 23℃, or 24℃, the moisture content measured by the moisture meter is 9. Specifically, the slurry coating process involves immersing the module in the corresponding slurry, ensuring its surface is evenly covered. This process is fundamental to the formation of the shell layer. Through the adhesion and curing of the slurry, the thickness and strength of the shell are gradually built up. In this embodiment, a bristle brush is used to mechanically coat the narrow and deep grooved areas on the module, removing any trapped air bubbles, excess slurry, or impurities, ensuring the quality and integrity of the shell in the narrow grooves. Slurry control involves controlling the flow of excess slurry on the module surface after the slurry coating process using specific methods (e.g., tilting, vibration, or static placement) to achieve a uniform slurry thickness and prevent slurry accumulation or dripping. It is important to note that after slurry control, it is crucial to ensure that slurry does not accumulate in the narrow grooves. The sanding process involves evenly spreading sand particles of a specific material on the module surface before the slurry is completely dry. This increases the surface roughness of the shell layer, providing mechanical anchoring points for the subsequent adhesion of the slurry layer and enhancing the shell's strength and breathability. In this embodiment, the drying operations, including surface drying, can be achieved by means such as natural air drying at room temperature or short-term high-temperature baking in an oven. This is something that those skilled in the art can understand and will not be elaborated here.
[0032] S4. Transition Layer Coating Forming: Remove the surface sand from the dried module in step S3 and pre-wet it. Then, immerse the module in the transition layer slurry for transition layer coating treatment. After the transition layer coating treatment is completed, remove the module and use a cleaning brush to clean the narrow groove area of the module. After cleaning, perform transition layer coating treatment again and remove the module to control the slurry. After controlling the slurry, sprinkle sand on the transition layer surface of the module, and then dry the transition layer. In this embodiment, the viscosity value of the transition layer slurry is 13-17s. The drying time of the transition layer is not less than 6 hours, and the ambient humidity of the transition layer is 30-55℃. For example, if the viscosity value is selected as 15s, the drying time is 7 hours, and the ambient humidity of the transition layer is 45℃. Specifically, in this embodiment, the transition layer is set to 2 layers. This number of layers does not affect the air permeability of the shell. Before each layer of transition layer coating is formed, the surface sand must be removed and pre-wetted, and the narrow groove area must be brushed with a cleaning brush to enhance the interlayer bonding force and prevent delamination, which would lead to a decrease in surface layer strength.
[0033] S5. Forming of the reinforcing layer coating: Remove the surface sand of the module after drying in step S4, then immerse the module in the reinforcing layer slurry for reinforcing layer coating treatment. After the reinforcing layer coating treatment is completed, remove the module and control the slurry. After the slurry control is completed, perform reinforcing layer sand sprinkling treatment on the surface of the module, and then perform reinforcing layer drying. In this embodiment, the viscosity value of the reinforcing layer slurry is 9-13s; the drying time of the reinforcing layer is not less than 6 hours, and the ambient humidity of the reinforcing layer drying is 30-45℃. For example, the viscosity value is selected as 11s, the drying time is 7 hours, and the ambient humidity of the reinforcing layer drying is 38℃.
[0034] S6. Repeat step S5 to form a module with multiple reinforcing layers; specifically, the overall strength of the shell can be increased by increasing the number of layers to meet the requirements. In this embodiment, four layers are provided.
[0035] S7. Sealing Layer Coating Forming: Immerse the module from step S6 into the sealing layer slurry for sealing layer coating treatment. After the sealing layer coating treatment is completed, remove the module and control the slurry. After the slurry control is completed, dry the sealing layer. The viscosity of the sealing layer slurry is 9-13s. The drying time of the sealing layer is not less than 24 hours, and the ambient humidity for drying the sealing layer is 30-45℃. For example, the viscosity is selected as 11s, the drying time is 24 hours, and the ambient humidity for drying the sealing layer is 38℃.
[0036] The slurry composition of each layer, the material of the sand used for sprinkling, and the related shell-making process in this embodiment are shown in Table 1 below:
[0037]
[0038]
[0039] Table 1
[0040] S8. Coating treatment: After the work is completed each day, add distilled water to the remaining surface layer silica sol so that the viscosity value of the surface layer silica sol changes within ±2s. If the viscosity value suddenly rises sharply for more than 3s, the slurry should be discarded.
[0041] Castings manufactured using the above method effectively solve the problem of defects such as iron inclusions and steel pellets that easily occur in the narrow slots of turbine guide blades in traditional investment casting. This method significantly improves the strength, density, and surface quality of the mold shell in the narrow slot area through precise control of the surface silica sol, pre-wetting treatment of the mold assembly, targeted brushing and cleaning of the narrow slot area after applying slurry to the surface and transition layers, and multi-layer reinforcement and sealing treatment. This reduces the scrap rate of castings and increases the production qualification rate of high-temperature alloy castings. Verification shows that iron inclusions and steel pellet defects can be controlled within 5%, blade slag inclusion defects can be controlled within 10%, and the overall casting qualification rate can be consistently maintained above 70%.
[0042] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0043] The above descriptions are merely embodiments of the present invention. Commonly known structures and characteristics of the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.
Claims
1. A method for manufacturing a mold shell to solve the defects of iron inclusions and steel pellets in narrow slots of high-temperature alloy castings, characterized in that, Includes the following steps: S1. Prepare a surface layer silica sol, wherein the mass percentage of SiO2 in the surface layer silica sol is 29%-30%, the powder-to-liquid ratio is 1:3.0 to 1:3.3, and the viscosity value is 24-26s; S2. Assemble the modules and immerse the assembled modules completely in distilled water for pre-wetting; S3, Topcoat Forming: Immerse the pre-wetted module from step S2 into the topcoat silica sol for the first topcoat coating treatment. After the first topcoat coating treatment is completed, remove the module and use a cleaning brush to clean the narrow groove area of the module. Then perform the second topcoat coating treatment. After the second topcoat coating treatment is completed, remove the module for slurry control and perform topcoat sanding treatment on the surface of the module after slurry control. Then perform topcoat drying. S4. Transition layer coating molding: Remove the surface sand of the module after drying in step S3 and pre-wet it. Then immerse the module in the transition layer slurry for transition layer coating treatment. After the transition layer coating treatment is completed, take out the module and use a cleaning brush to clean the narrow groove part of the module. After cleaning, perform transition layer coating treatment again and take out the module to control the slurry. After the slurry control is completed, perform transition layer sanding treatment on the surface of the module and then dry the transition layer. S5. Forming of the reinforcement layer coating: Remove the loose sand from the surface of the module after drying in step S4, then immerse the module in the reinforcement layer slurry for reinforcement layer coating treatment. After the reinforcement layer coating treatment is completed, take out the module to control the slurry. After the slurry control is completed, sprinkle sand on the surface of the module for reinforcement layer treatment, and then dry the reinforcement layer. S6. Repeat step S5 to form a module with multiple reinforcement layers; S7. Sealing layer coating molding: Immerse the module from step S6 into the sealing layer slurry for sealing layer coating treatment. After the sealing layer coating treatment is completed, remove the module to control the slurry. After the slurry control is completed, dry the sealing layer. S8. Coating treatment: Add distilled water to the remaining surface layer silica sol to make the viscosity of the surface layer silica sol vary within ±2s.
2. The method for manufacturing a mold shell according to claim 1 to solve the defects of iron inclusions and steel pellets in narrow slots of high-temperature alloy castings, characterized in that, The pre-humidification is as follows: Immerse the entire module in distilled water for 3-5 seconds, then remove it and drain for 40-60 seconds.
3. The method for manufacturing a mold shell according to claim 1 to solve the defects of iron inclusions and steel pellets in narrow slots of high-temperature alloy castings, characterized in that: The viscosity of the transition layer slurry is 13-17s; the viscosity of the reinforcing layer slurry is 9-13s; and the viscosity of the sealing layer slurry is 9-13s.
4. The method for manufacturing a mold shell according to claim 1 to solve the defects of iron inclusion and steel pellets in narrow slots of high-temperature alloy castings, characterized in that: In step S3, the drying time for the surface layer is 15-18 hours, the ambient humidity for surface layer drying is 65%-75%, and the drying temperature is 22±2℃.
5. The method for manufacturing a mold shell according to claim 1 to solve the defects of iron inclusions and steel pellets in narrow slots of high-temperature alloy castings, characterized in that: In step S4, the drying time of the transition layer is not less than 6 hours, and the ambient humidity of the transition layer is 30-55℃.
6. The method for manufacturing a mold shell according to claim 1 to solve the defects of iron inclusions and steel pellets in narrow slots of high-temperature alloy castings, characterized in that: In step S5, the drying time of the reinforcement layer is not less than 6 hours, and the ambient humidity for drying the reinforcement layer is 30-45℃.
7. The method for manufacturing a mold shell according to claim 1 to solve the defects of iron inclusions and steel pellets in narrow slots of high-temperature alloy castings, characterized in that: In step S8, the drying time of the sealing layer is not less than 24 hours, and the ambient humidity for drying the sealing layer is 30-45℃.