Preparation method of ultra-large size high temperature alloy precision casting thin wall casing

Abstract

This invention provides a method for preparing ultra-large-sized high-temperature alloy precision-cast thin-walled casings in the field of precision casting. The method includes: Step 1: Preparation of separate casing wax models and welding of the overall wax model assembly; designing the separate wax model structure and mold structure; pressing the separate wax models; and aligning, cooling, and welding the separate wax models. Step 2: Assembly of large-sized casing modules to form casing wax model modules. Step 3: Preparation of a large-sized casing ceramic shell; uniformly applying a surface slurry containing a refining agent to the surface of the wax model using a spraying tool, followed by sanding and drying; applying a transition layer and a back layer layer by layer, followed by sanding; after 20 layers of shell coating, sealing and drying; and then dewaxing in a steam dewaxing kettle followed by firing. Step 4: Melting and pouring the casing casting; slowly cooling the poured casting. Step 5: Post-processing of the casting. This invention achieves precision casting of ultra-large-sized casings, and the key dimensions of the high-temperature alloy precision-cast casing casting reach CT7 level, with metallurgical defects meeting the requirements for castings.

Description

Technical Field

[0001] This invention relates to the field of precision casting technology for high-temperature alloys, and in particular to a method for manufacturing casings that enables precision casting of ultra-large casings and improves dimensional accuracy. Background Technology

[0002] The engine casing is the most important load-bearing structural component of an aero-engine, bearing all the engine's thrust and vibration loads. Its mass directly affects the engine's performance, lifespan, and reliability, ranking alongside blades, turbine disks, and turbine shafts as one of the four key components of an aero-engine. Due to limitations in forming technology, early engine large components typically employed increased casting wall thickness and simplified casting design. Large, complex, thin-walled components were often welded from separate traditional castings, forgings, and sheet metal parts to form load-bearing members. This resulted in long development cycles, large raw material consumption, and poor overall performance for large, complex, thin-walled components. In the 1970s, advanced engine manufacturing powers, represented by the United States, adopted investment casting technology to mass-produce large castings such as engine casings with diameters exceeding 1 meter. This improved the integrity and reliability of large, thin-walled components while reducing manufacturing costs and engine weight. With the increasing demands for engine performance and reliability, high thrust-to-weight ratio engines require increasingly complex structures with integrated, lightweight, and hollow thin-walled designs, prompting the development of manufacturing technologies for these key structural components towards integral precision casting. Integral precision casting technology has become the mainstream technology for manufacturing large integral components of aero-engines worldwide, and is one of the important technological foundations for advanced aero-engines to move towards lightweight, precision, and long service life. Chinese aviation enterprises and research institutes began research on the manufacturing technology of large integral precision castings at the end of the 20th century, mastering the integral precision casting technology for large high-temperature alloy castings with diameters of approximately (1-1.2) m. Shanghai Jiao Tong University has developed a large-size casing with a diameter of 1.8 m. However, for the precision casting technology of large integral components exceeding 2 m, existing equipment and processes are insufficient, necessitating the construction of related infrastructure and the development of basic research and key technologies for the precision casting of large castings.

[0003] Therefore, how to achieve precision casting of ultra-large casings and improve dimensional accuracy is an urgent problem to be solved in the industry. Summary of the Invention

[0004] A primary objective of this invention is to overcome at least one of the deficiencies of the prior art and to provide a method for preparing ultra-large high-temperature alloy precision-cast thin-walled casings that enables precision casting of ultra-large casings and improves dimensional accuracy.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] According to one aspect of the present invention, a method for manufacturing an ultra-large high-temperature alloy precision-cast thin-walled casing is provided, comprising:

[0007] Step 1: Preparation of separate wax molds for the casing and welding of the overall wax mold. Based on the structure of the overall casing, design the structure of the separate wax molds and the mold structure, press the separate wax molds, and then align, cool, and weld the pressed separate wax molds.

[0008] Step 2: Assembly of large-size casing modules. Based on the overall casing structure, load-bearing fixtures are assembled, and the casing wax mold, gating system, and load-bearing fixtures are connected together to form the casing wax mold module.

[0009] Step 3 involves the preparation of the ceramic shell for the three-dimensional casing. A surface slurry containing a refining agent is evenly applied to the wax mold surface using a spraying fixture, followed by sanding and drying. Transition and back layers are then applied layer by layer, with sanding repeated after each layer, for a total of 20 layers. After the 6th and 11th layers, a two-dimensional flexible metal truss mesh is added for reinforcement and impregnated with a reinforcing agent. After the 11th layer, a collapsing treatment is added to the support plate, followed by grouting and sealing. After the shell is coated with 20 layers, it is sealed and dried, then placed in a steam dewaxing kettle for dewaxing and calcination. A surface slurry one, prepared with large-particle silica sol, is used to wet the entire module. A second surface slurry is sprayed onto the entire module while the central shaft is continuously rotated. After even coating, sand is sprinkled on top. The surface slurry is then fed into a spraying fixture after being stirred evenly to remove air bubbles under low vacuum. The bubble-removed surface slurry is then pumped into the spray nozzle for spraying. The silica sol used in surface slurry one has a SiO2 content of 40±1% and a particle size of 55-65nm. The weight ratio of silica sol to surface refractory powder is 1:0.7-1.2. The silica sol used in surface slurry two has a SiO2 content of 30-31% and a particle size of 10-20nm. The weight ratio of silica sol to surface refractory powder in surface slurry two is 1:4.2-4.6.

[0010] Step 4: Melting and casting of the casing casting. After the mold shell is wrapped with cotton and filled with sand and preheated, it is sent into a vacuum furnace for casting. The casting is then slowly cooled.

[0011] Step 5: Post-treatment of castings. After casting is poured, the shell is cleaned, and after passing inspection, solution treatment and aging treatment are carried out.

[0012] According to a specific embodiment of the present invention, the process further includes step six, welding repair on the casting. The parts of the casting that are easy to grind and inspect are welded, and the welding material is HGH4169.

[0013] According to a specific embodiment of the present invention, in step one, a mixture of medium-temperature unfilled wax and binder wax is used, wherein the medium-temperature unfilled wax accounts for 20-30% and the binder wax accounts for 70-80%.

[0014] According to a specific embodiment of the present invention, in step two, the dimensions of two adjacent separate wax molds after splicing are corrected. The correction fixture is positioned according to the upper limit of the theoretical model of the wax mold. The spliced ​​wax mold is placed on the fixture, and the fixture is heated to 35-50°C. After the lower flange outer ring of the wax mold is fully contacted and fixed with the fixture by the flexible adjustment positioning block on the fixture, the heating is stopped and the mold is cooled for 20-60 minutes.

[0015] According to a specific embodiment of the present invention, in step two, the assembly and welding of the separate wax models is carried out on a positioning assembly and welding fixture. Two separate housings are spliced ​​together using mixed adhesive wax. During the splicing process, the housing wax model is fixed on the positioning assembly and welding fixture. After splicing, the dimensions of two adjacent separate wax models are corrected using a calibration fixture with heating and dimension adjustment functions. After all separate wax models are spliced, the dimensions of the overall wax model after splicing and welding are detected. Based on the detection results, calibration is performed on the calibration fixture to ensure that the dimensional accuracy of the overall housing wax model is within ±1mm.

[0016] According to a specific embodiment of the present invention, in step two, the load-bearing fixture includes a main load-bearing shaft, a double-layered support frame with coaxial inner and outer ring spokes, and a load-bearing connecting rod. The main load-bearing shaft is located at the center position and serves as the main gating channel for the central column in addition to bearing load. The support frame is arranged around the outside of the main load-bearing shaft. The load-bearing connecting rod connects the main load-bearing shaft and the support frame. The support frame is provided with an annular gating channel and a Y-shaped gating channel. The annular gating channel is arranged around the central column, and the Y-shaped gating channel extends inward to connect to the central column. The annular gating channel and the Y-shaped gating channel are connected to the wedge-shaped riser.

[0017] According to a specific embodiment of the present invention, in step three, the internal collapse treatment of the support plate is performed by inserting a φ15mm wax rod obliquely from one end of the inner cavity of the support plate to the other end, leaving a wax discharge end of ≥30mm. The surface slurry of the wax discharge end is scraped off during subsequent coating. After inserting the wax rod, the pores in the support plate are filled with a mixture of 100# and 36# quartz sand, and both ends are sealed with a sealing material made of silica sol, corundum powder and corundum sand.

[0018] According to a specific embodiment of the present invention, in step three, the shell is fired in a bogie-type sintering furnace, from room temperature to 400°C for 1 hour, with the air supply turned on, and held at 400°C for 2 hours, then from 400°C to 600°C for 3 hours, and held at 600°C for 1 hour. After holding, the air supply is turned off, and the temperature is raised from 600°C to the final firing temperature for 1 hour. The final firing temperature is 1100-1150°C, and the holding time is 2-4 hours.

[0019] According to a specific embodiment of the present invention, in step four, the casting after pouring is slowly cooled in the mold slow cooling chamber of the vacuum furnace. The slow cooling chamber is preheated to 650°C. After the sand box is placed in the slow cooling chamber, it is kept at 650°C for 2 hours. After being kept at 650°C, it is cooled down to 450°C for 8-15 hours. After being kept at 450°C for 1 hour, it is cooled down to 300°C for 4 hours. After reaching 300°C, the slow cooling chamber is de-energized.

[0020] As can be seen from the above technical solution, the advantages and positive effects of the method for preparing ultra-large-size high-temperature alloy precision-cast thin-walled casing of the present invention are as follows:

[0021] This invention not only enables the precision casting of ultra-large casings, but also achieves CT7 level in the key dimensions of high-temperature alloy precision casting casings, and meets the requirements for metallurgical defects. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the positioning and welding without an outer ring alignment block in the method for preparing ultra-large high-temperature alloy precision-cast thin-walled casing of the present invention.

[0023] Figure 2 This is a schematic diagram of the positioning and welding band outer ring alignment block in the preparation method of ultra-large high-temperature alloy precision casting thin-walled casing of the present invention.

[0024] Figure 3 This is a top view schematic diagram of the overall wax model structure in the preparation method of the ultra-large high-temperature alloy precision casting thin-walled casing of the present invention.

[0025] Figure 4 This is a schematic diagram of the main structure of the integral wax model in the preparation method of the ultra-large high-temperature alloy precision casting thin-walled casing of the present invention.

[0026] Figure 5 This is a schematic diagram of the three-dimensional structure of the integral wax model in the preparation method of the ultra-large high-temperature alloy precision casting thin-walled casing of the present invention.

[0027] Figure 6 This is a schematic diagram of the slurry coating structure in the preparation method of the ultra-large high-temperature alloy precision-cast thin-walled casing of the present invention.

[0028] Figure 7 This is a schematic diagram of the truss mesh structure in the method for preparing ultra-large high-temperature alloy precision-cast thin-walled casing of the present invention.

[0029] Drawing number explanation:

[0030] 1. Split wax mold; 2. Upper alignment block; 3. Positioning block; 4. Outer ring alignment block; 5. Base plate; 6. Main load-bearing shaft; 7. Support frame; 8. Annular runner; 9. Y-shaped runner; 10. Wedge riser; 11. Vacuum pump; 12. Slurry tank; 13. Slurry pump; 14. Slurry nozzle. Detailed Implementation

[0031] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that the invention will be thorough and complete, and the concept of the exemplary embodiments will be fully conveyed to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore their detailed description will be omitted.

[0032] According to one aspect of the present invention, a method for manufacturing an ultra-large high-temperature alloy precision-cast thin-walled casing is provided, comprising:

[0033] Step 1: Preparation of the separate wax model 1 of the casing and welding of the overall wax model. Based on the structure of the overall casing, the structure of the separate wax model 1 and the mold structure are designed. The separate wax model 1 is pressed, and after pressing, the separate wax model 1 is shaped, cooled, and welded together. The wax model structure is as follows: Figures 3 to 5 As shown.

[0034] Step Two: Assembling the Large-Scale Casing Module. Based on the overall casing structure, assemble the load-bearing fixtures, connecting the casing wax model, gating system, and load-bearing fixtures together to form the casing wax model module. (Reference) Figure 1 and Figure 2 As shown.

[0035] Step 3: Preparation of the large-size ceramic shell casing. A surface slurry containing a refining agent is evenly applied to the wax model surface using a spraying tool, followed by sanding and drying. Transition and back layers are then applied layer by layer, with sanding repeated after each layer. A total of 20 layers are applied. A two-dimensional flexible metal truss mesh is added for reinforcement after the 6th and 11th layers. The truss mesh structure is as follows: Figure 7 As shown. After impregnation with reinforcing agent, 11 layers are applied, followed by a collapsing treatment inside the support plate and grouting for sealing. After 20 layers of coating are applied to the shell, the grout is sealed and dried. The shell is then sent to a steam dewaxing kettle for dewaxing and calcination. A surface slurry, prepared using large-particle silica sol, is used to wet the entire module. A second surface slurry is then sprayed onto the entire module while the central shaft is continuously rotated. After the surface slurry is evenly coated, sand is sprinkled on top. The surface slurry, after being thoroughly mixed, is fed into a special spraying fixture to de-vacuum and break bubbles. The de-bubbled surface slurry is then pumped into spray nozzle 14 for spraying and coating. The silica sol used in surface slurry one has a SiO2 content of 40±1%, a silica sol particle size of 55-65nm, and a weight ratio of silica sol to surface refractory powder of 1:0.7-1.2. The silica sol used in surface slurry two has a SiO2 content of 30-31%, a silica sol particle size of 10-20nm, and a weight ratio of silica sol to surface refractory powder of 1:4.2-4.6.

[0036] Step 4: Melting and casting of the casing casting. After the mold shell is wrapped with cotton and filled with sand and preheated, it is sent into a vacuum furnace for casting. The casting is then slowly cooled.

[0037] Step 5: Post-treatment of castings. After casting, the shell is cleaned and the casting passes inspection. After that, solution treatment and aging treatment are carried out.

[0038] According to a specific embodiment of the present invention, the process further includes step six, welding repair on the casting. The parts of the casting that are easy to grind and inspect are welded, and the welding material is HGH4169.

[0039] According to a specific embodiment of the present invention, in step one, a mixture of medium-temperature non-filled wax and binder wax is used, with the medium-temperature non-filled wax accounting for 20-30% and the binder wax accounting for 70-80%. In step one, the assembly and welding of the separate wax models is carried out on a positioning assembly and welding fixture, and the two separate housings are spliced ​​together using the mixed binder wax. During the splicing process, the housing wax model is fixed on the positioning assembly and welding fixture, and the dimensions of adjacent two separate wax models after splicing are corrected using a calibration fixture with heating and dimension adjustment functions. After all the separate wax models are spliced, the dimensions of the overall wax model after splicing and welding are checked, and the dimensions are calibrated on the calibration fixture according to the check results to ensure that the overall housing wax model has a dimensional accuracy of ±1mm.

[0040] The resulting technical effects are: when using separate wax molds to make an integral wax mold, the use of low-shrinkage and low-viscosity adhesives reduces the deformation of the wax mold caused by the adhesives; the design of assembly and welding positioning fixtures and the calibration fixtures, and the calibration based on the wax mold size inspection results, reduce the dimensional deviations caused when the separate wax molds are welded into an integral whole.

[0041] According to a specific embodiment of the present invention, in step two, the dimensions of two adjacent separate wax molds after splicing are corrected. The correction fixture is positioned according to the upper limit of the theoretical model of the wax mold. The spliced ​​wax mold is placed on the fixture, and the fixture is heated to 35-50°C. After the lower flange outer ring of the wax mold is fully contacted and fixed with the fixture by the flexible adjustment positioning block 3 on the fixture, the heating is stopped and the mold is cooled for 20-60 minutes.

[0042] According to a specific embodiment of the present invention, in step two, the assembly and welding of the separate wax models is carried out on a positioning assembly and welding fixture. Two separate housings are spliced ​​together using mixed adhesive wax. During the splicing process, the housing wax model is fixed on the positioning assembly and welding fixture. After splicing, the dimensions of two adjacent separate wax models are corrected using a calibration fixture with heating and dimension adjustment functions. After all separate wax models are spliced, the dimensions of the overall wax model after splicing and welding are detected. Based on the detection results, calibration is performed on the calibration fixture to ensure that the dimensional accuracy of the overall housing wax model is within ±1mm.

[0043] According to a specific embodiment of the present invention, in step two, the load-bearing fixture includes a main load-bearing shaft 6, a double-layered support frame 7 with coaxial inner and outer ring spokes, and a load-bearing connecting rod. The main load-bearing shaft 6 is located at the center and, in addition to bearing load, also serves as the main sprue for the central column. The support frame 7 is arranged around the outside of the main load-bearing shaft 6. The load-bearing connecting rod connects the main load-bearing shaft 6 and the support frame 7. The support frame 7 is provided with an annular sprue 8 and a Y-shaped sprue 9. The annular sprue 8 is arranged around the central column, and the Y-shaped sprue 9 extends inward to connect to the central column. The annular sprue 8 and the Y-shaped sprue 9 connect to the wedge-shaped riser 10. The design of the support frame 7 and the load-bearing connecting rod is not only conducive to the flipping and transportation of the module, but also provides load-bearing support, reducing the deformation of the split wax mold 1 due to its own weight and the wet deformation of the shell during the shell-making process. During pouring, the molten metal can fill the mold according to the preset sprue, avoiding the generation of cold shuts and shrinkage cavities.

[0044] According to a specific embodiment of the present invention, in step three, a surface slurry is prepared using large-particle-size silica sol to wet the entire module. The surface slurry is then sprayed onto the entire module while the central shaft is continuously rotated. After the surface slurry is evenly coated, sand is sprinkled on top. After being thoroughly stirred, the surface slurry is fed into a special spraying fixture to de-vacuum and break bubbles. The de-bubbled surface slurry is then pumped into the spray nozzle 14 for spraying. This process avoids uneven or missed coating of the surface slurry in special structures such as grooves, corners, and narrow gaps.

[0045] The silica sol used in surface slurry one has a SiO2 content of (40±1)% and a particle size of (55-65) nm; the silica sol used in surface slurry two has a SiO2 content of (30-31)% and a particle size of (10-20) nm. The weight ratio of silica sol to surface refractory powder in surface slurry one is 1:(0.7-1.2). When preparing the surface slurry, first add 1 / 3 of the refractory powder to the silica sol and stir for (3-5) min, then add (12-14)% of distilled water by weight of silica sol, then add (30-40)% of the refining agent by weight of refractory powder, and finally gradually add the remaining refractory powder to the silica sol. After thorough stirring and wetting, add (4-6)% of the wetting agent and (2-4)% of the defoamer by weight of silica sol. After stirring for 10 min, surface slurry one can be put into use. The weight ratio of silica sol to refractory powder in the second layer slurry is 1:(4.2-4.6). When preparing the slurry, first add 1 / 3 of the refractory powder to the silica sol and stir for (10-15) min. Then add a finer agent of (7-15)% by weight of the refractory powder. Finally, gradually add the remaining refractory powder to the silica sol and stir and wet thoroughly. Then add a wetting agent of (0.3-1)% by weight of the silica sol and a defoamer of (0.3-1)% by weight of the silica sol. After stirring for 10 min, the second layer slurry can be put into use.

[0046] According to a specific embodiment of the present invention, in step three, the internal collapse treatment of the support plate involves inserting a φ15mm wax rod obliquely from one end of the support plate cavity to the other, leaving a ≥30mm wax discharge end. The surface slurry at the wax discharge end is scraped off during subsequent coating. After inserting the wax rod, the pores in the support plate are filled with a mixture of 100# and 36# silica sand, and both ends are sealed with a sealing material made from a mixture of silica sol, corundum powder, and corundum sand. This prevents air bubbles in the surface slurry from being introduced into the surface coating and forming casting defects. Simultaneously, the use of a special spraying tool allows for effective coating of large-sized wax mold modules. In step three, the metal two-dimensional flexible truss mesh has a wire diameter of φ1mm and a triangle side length of 70mm. The metal two-dimensional flexible truss mesh increases the structural strength of the shell, increases the wet blank strength of the ceramic shell, and reduces the deformation of the wet blank; it also improves the high-temperature strength of the shell and reduces the self-weight deformation of the shell.

[0047] According to a specific embodiment of the present invention, in step three, the internal collapse treatment of the support plate involves inserting a φ15mm wax rod obliquely from one end of the support plate cavity to the other, leaving a wax discharge end of ≥30mm. The surface layer of slurry at the wax discharge end is scraped off during subsequent coating. After inserting the wax rod, the pores inside the support plate are filled with a mixture of 100# and 36# silica sand, and both ends are sealed with a sealing material made from a mixture of silica sol, corundum powder, and corundum sand. If shell powder is used to fill the support plate, its collapsibility is poor. Using a wax rod for oblique filling and dewaxing creates voids, reducing the strength of the shell inside the support plate. Using silica sand, whose coefficient of thermal expansion differs from that of the shell matrix material, increases the shell's collapsibility. These measures work together to reduce the strength of the shell inside the support plate, increase collapsibility, and facilitate shell removal. In step three, the shell is fired in a bogie-type sintering furnace. The temperature is raised from room temperature to 400℃ for 1 hour, with air supply simultaneously. The temperature is held at 400℃ for 2 hours, then raised to 600℃ for 3 hours, and held at 600℃ for 1 hour. After holding at 600℃, the air supply is turned off. The temperature is then raised from 600℃ to the final firing temperature for 1 hour, with the final firing temperature being 1100-1150℃, and held for 2-4 hours. Due to the thickness of the shell, low-temperature heating combined with air supply ensures complete combustion of the remaining organic matter. To ensure thorough firing of the shell in a short time, the final firing temperature is set at (1100-1150)℃.

[0048] According to a specific embodiment of the present invention, in step four, the casting after pouring is slowly cooled in the mold slow cooling chamber of a vacuum furnace. The slow cooling chamber is preheated to 650°C. After the sand box is placed in the slow cooling chamber, it is held at 650°C for 2 hours. After holding at 650°C, it is cooled to 450°C for 8-15 hours. After holding at 450°C for 1 hour, it is cooled to 300°C for 4 hours. After reaching 300°C, the power supply to the slow cooling chamber is stopped. Slow cooling helps with feeding and avoids defects such as cold shuts and porosity. At the same time, slow cooling is beneficial for the release of solidification stress, avoiding hot cracking of the casting and reducing casting deformation. In step four, the mold shell is wrapped with cotton and filled with sand. Before preheating the mold shell, each support plate is wrapped with 1cm thick insulation cotton. An 8-10cm thick layer of (2-3.5)mm quartz sand is filled at the bottom of the sand box. After placing the mold shell into the sand box, ensure the mold shell is in the middle of the sand box. Fill the space between the mold shell and the sand box wall with quartz sand up to the top of the support plate, not exceeding the flange. The remaining part (including the pouring cup) is wrapped with 2.5cm thick insulation cotton. This achieves sequential solidification of the casting and avoids defects such as cold shuts and porosity. In step four, the preheating temperature in the preheating furnace after wrapping and filling the mold shell with cotton and sand is (1150-1180)℃, and the preheating time at this temperature is ≥24h. Due to the thickness of the mold shell and the cotton and sand filling, this technique can avoid uneven heating inside the mold shell or insufficient local preheating temperature.

[0049] In step six, the welding of the casting is carried out on a special tooling. The tooling can locally heat the casting, and welding begins when the local temperature of the casting is ≥350℃ to avoid cracking during the welding process. The mixed binder wax is a mixture of medium-temperature unfilled wax and binder wax, with the medium-temperature unfilled wax accounting for (20-30)% and the binder wax accounting for (70-80)%. A high-strength, low-melting-point binder wax is obtained. The low-temperature wax has less heat transfer to the body of the split wax model 1, reducing the deformation of the wax model caused by splicing.

[0050] As can be seen from the above technical solution, the advantages and positive effects of the method for preparing ultra-large-size high-temperature alloy precision-cast thin-walled casing of the present invention are as follows:

[0051] This invention not only enables the precision casting of ultra-large casings, but also achieves CT7 level in the key dimensions of high-temperature alloy precision casting casings, and meets the requirements for metallurgical defects.

[0052] Figure 1 and Figure 2 In the middle, the structure of the split wax model 1 is as follows: Figures 3 to 5 As shown, two separate wax molds 1 are placed on the base plate 5 of the welding fixture. The placement position of the separate wax molds 1 is determined by the positioning block 3. During the welding process, the upper alignment block 2 and the outer ring alignment block 4 ensure that the separate wax molds 1 do not deform during the welding process.

[0053] Figure 5In the middle, the split wax mold 1 is connected to the main metal bearing shaft 6 through the support sprue. The main bearing shaft 6 is the main bearing unit of the entire module. The support frame 7 is used to connect the various parts of the split wax mold 1 to make its gravity distribution uniform. The annular sprue 8 is used to fill the outer ring of the mold. The Y-shaped sprue 9 is used to divert the fluid to the annular sprue 8. The wedge riser 10 is used for shrinkage compensation.

[0054] Figure 6 In the process, vacuum pump 11 is used to extract air from the tank to reduce air bubbles in the surface slurry, slurry tank 12 is used to hold the material, slurry pump 13 is used to pump the slurry, and spray nozzle 14 sprays the surface slurry evenly. Example 1

[0055] First, based on the overall casing structure, the separate wax model structure and mold structure of the casing are designed. The separate wax models are then pressed, shaped, cooled, and welded, and their dimensions are checked. The welding of the separate wax models is carried out on a positioning welding fixture, using a mixed bonding wax to join the two separate casings. The mixed bonding wax is a mixture of medium-temperature non-filled wax and bonding wax, with the medium-temperature non-filled wax accounting for 20% and the bonding wax accounting for 80%. During the joining process, the casing wax model is fixed on the positioning welding fixture. After joining, the dimensions of adjacent separate wax models are corrected using a calibration fixture with heating and dimensional adjustment functions. The method for correcting the dimensions of adjacent separate wax models after joining is as follows: the calibration fixture is positioned according to the upper limit of the theoretical model of the wax model. The joined wax model is placed on the fixture, and the fixture is heated to 40℃. The lower flange outer ring of the wax model is then fully contacted and fixed with the fixture using the flexible adjustment positioning block 3 on the fixture. Heating is then stopped, and the model is allowed to cool for 30 minutes. After all the individual wax models are assembled, the dimensions of the overall wax model after welding are checked. Based on the test results, the model is calibrated on the calibration fixture to ensure that the overall dimensional accuracy of the casing wax model is ±1mm. According to the structural design of the overall casing, a load-bearing fixture is assembled, connecting the casing wax model, gating system, and load-bearing fixture together to form the casing wax model module. The load-bearing fixture includes a main load-bearing shaft, a double-layer reinforced support frame with coaxial inner and outer ring spokes, and load-bearing connecting rods. High-strength adhesive wax is used to connect the gating system and the load-bearing fixture. In addition to bearing load, the load-bearing shaft also serves as the main runner for the central column. The upper and lower flanges of the casing wax model are connected to an annular runner. The annular runner is connected to the central column via a radial horizontal runner and a Y-shaped support runner. The outer ring horizontal ribs are compensated for shrinkage by wedge-shaped risers.

[0056] The topcoat slurry containing a refining agent is evenly applied to the wax model surface using a spraying fixture, and then sanded and dried. A transition layer and a back layer are then applied layer by layer, with sanding applied after each layer, for a total of 20 layers. For the topcoat slurry application, a first topcoat slurry is prepared using large-particle silica sol and used to wet the entire model, especially grooves, corners, and narrow gaps. Then, a second topcoat slurry is sprayed onto the entire model while continuously rotating the central shaft. Once the second topcoat slurry is evenly coated, sand is applied. After thorough mixing, the topcoat slurry is fed into a dedicated spraying fixture. A low-vacuum process is first applied to break bubbles. The bubble-broken topcoat slurry is then pumped into spray nozzle 14 via a pump to achieve spray coating. The weight ratio of silica sol to surface refractory powder in the first layer slurry is 1:1. When preparing the surface slurry, first add 1 / 3 of the refractory powder to the silica sol and stir for 5 minutes. Then add 12% of the weight of the silica sol in distilled water, followed by 40% of the weight of the refractory powder in a refining agent. Finally, gradually add the remaining refractory powder to the silica sol and stir thoroughly to wet it. Then add 5% of the weight of the silica sol in a wetting agent and 3% in a defoamer. After stirring for 10 minutes, the first layer slurry is ready for use. The weight ratio of silica sol to refractory powder in the second layer slurry is 1:4.2. When preparing the slurry, first add 1 / 3 of the refractory powder to the silica sol and stir for 15 minutes. Then add 8% of the weight of the refractory powder as a refining agent. Finally, gradually add the remaining refractory powder to the silica sol and stir thoroughly to wet it. Then add 0.3% of the weight of the silica sol as a wetting agent and 0.3% as a defoamer. After stirring for 10 minutes, the second layer slurry is ready for use. After the 6th and 11th layers, a two-dimensional flexible metal truss mesh is added for reinforcement and then impregnated with a reinforcing agent. After the 11th layer, a φ15mm wax rod is inserted obliquely from one end of the inner cavity of the support plate to the other end, leaving a wax discharge end of ≥30mm. The surface layer of slurry at the wax discharge end is scraped off during subsequent coating. After inserting the wax rod, the pores in the support plate are filled with a mixture of 100# and 36# silica sand, and both ends are sealed with a sealing material made of silica sol, corundum powder, and corundum sand. After 20 layers of coating are applied to the shell, the sealant is dried and then sent to a steam dewaxing kettle for dewaxing and firing. The shell firing is carried out in a bogie-type sintering furnace. The heating process is as follows: from room temperature to 400℃, heating for 1 hour while the air supply is turned on, and holding at 400℃ for 2 hours; from 400℃ to 600℃, heating for 3 hours, holding at 600℃ for 1 hour, and then turning off the air supply; from 600℃ to the final firing temperature, heating for 1 hour, the final firing temperature is 1150℃, and the holding time is 2 hours.

[0057] Before casting, the mold shell needs to be preheated by wrapping it with cotton and filling it with sand. Each support plate is wrapped with 1cm thick insulation cotton. A 10cm thick layer of (2-3.5)mm quartz sand is filled at the bottom of the sand box. After placing the mold shell into the sand box, ensure that the mold shell is located in the middle of the sand box. Fill the space between the mold shell and the sand box wall with quartz sand up to the top of the support plate, not exceeding the flange. The remaining part (including the pouring cup) is wrapped with 2.5cm thick insulation cotton. After wrapping the mold shell with cotton and filling it with sand, the preheating temperature in the preheating furnace is 1150℃. After preheating at this temperature for 30 hours, it is sent to a five-chamber vacuum furnace for casting. The casting is then slowly cooled after casting. The casting is slowly cooled in the mold cooling chamber of a five-chamber vacuum furnace. The cooling chamber is preheated to 650℃. After the sand box is placed in the cooling chamber, it is held at 650℃ for 2 hours. After holding at 650℃, it is cooled to 450℃ for (8-15) hours. After holding at 450℃ for 1 hour, it is cooled to 300℃ for 4 hours. After reaching 300℃, the cooling chamber is de-energized. After casting, the shell is mechanically cleaned, the risers are cut and trimmed, and homogenization is performed. After passing fluorescence and X-ray inspection, solution treatment and aging treatment are carried out. Parts of the casting that are easy to grind and inspect are allowed to be repaired by welding. HGH4169 is selected as the welding material. The welding of the casting is carried out on a special tooling. The tooling can locally heat the casting. Welding begins when the local temperature of the casting is ≥350℃.

[0058] Those skilled in the art should understand that the specific structures and processes shown in the above detailed embodiments are merely exemplary and not restrictive. Furthermore, those skilled in the art can combine the various technical features described above in various possible ways to form new technical solutions or make other modifications, all of which fall within the scope of this invention.

Claims

1. A method for manufacturing an ultra-large high-temperature alloy precision-cast thin-walled casing, characterized in that, include: Step 1: Preparation of separate wax molds for the casing and welding of the overall wax mold. Based on the structure of the overall casing, design the structure of the separate wax molds and the mold structure, press the separate wax molds, and then align, cool, and weld the pressed separate wax molds. Step 2: Assembly of large-size casing modules. Based on the overall casing structure, load-bearing fixtures are assembled, and the casing wax mold, gating system, and load-bearing fixtures are connected together to form the casing wax mold module. Step 3 involves the preparation of the ceramic shell for the three-dimensional casing. A surface slurry containing a refining agent is evenly applied to the wax mold surface using a spraying fixture, followed by sanding and drying. Transition and back layers are then applied layer by layer, with sanding repeated after each layer, for a total of 20 layers. After the 6th and 11th layers, a two-dimensional flexible metal truss mesh is added for reinforcement and impregnated with a reinforcing agent. After the 11th layer, a collapsing treatment is added to the support plate, followed by grouting and sealing. After the shell is coated with 20 layers, it is sealed and dried, then placed in a steam dewaxing kettle for dewaxing and calcination. A surface slurry one, prepared with large-particle silica sol, is used to wet the entire module. A second surface slurry is sprayed onto the entire module while the central shaft is continuously rotated. After even coating, sand is sprinkled on top. The surface slurry is then fed into a spraying fixture after being stirred evenly to remove air bubbles under low vacuum. The bubble-removed surface slurry is then pumped into the spray nozzle for spraying. The silica sol used in surface slurry one has a SiO2 content of 40±1% and a particle size of 55-65nm. The weight ratio of silica sol to surface refractory powder is 1:0.7-1.

2. The silica sol used in surface slurry two has a SiO2 content of 30-31% and a particle size of 10-20nm. The weight ratio of silica sol to surface refractory powder in surface slurry two is 1:4.2-4.

6. Step 4: Melting and casting of the casing casting. After the mold shell is wrapped with cotton and filled with sand and preheated, it is sent into a vacuum furnace for casting. The casting is then slowly cooled. Step 5: Post-treatment of castings. After casting is poured, the shell is cleaned, and after passing inspection, solution treatment and aging treatment are carried out.

2. The method for manufacturing ultra-large high-temperature alloy precision-cast thin-walled casing according to claim 1, characterized in that: It also includes step six, welding repair of the casting. Welding is performed on parts of the casting that are easy to grind and inspect, and HGH4169 is selected as the welding material.

3. The method for manufacturing ultra-large high-temperature alloy precision-cast thin-walled casing according to claim 1, characterized in that: In step one, a mixture of medium-temperature unfilled wax and binder wax is used, with the medium-temperature unfilled wax accounting for 20-30% and the binder wax accounting for 70-80%.

4. The method for preparing ultra-large size high-temperature alloy precision-cast thin-walled casing according to claim 2, characterized in that: In step two, the dimensions of the two adjacent separate wax models after splicing are corrected. The correction fixture is positioned according to the upper limit of the theoretical model of the wax model. The spliced ​​wax model is placed on the fixture, and the fixture is heated to 35-50℃. After the lower flange outer ring of the wax model is fully contacted and fixed with the fixture by the flexible adjustment positioning block on the fixture, the heating is stopped and the model is cooled for 20-60 minutes.

5. The method for manufacturing ultra-large size high-temperature alloy precision-cast thin-walled casing according to claim 1, characterized in that: In step two, the assembly and welding of the separate wax models is carried out on a positioning and welding fixture. Two separate housings are spliced ​​together using a mixed adhesive wax. During the splicing process, the housing wax model is fixed on the positioning and welding fixture. After splicing, the dimensions of the two adjacent separate wax models are corrected using a calibration fixture with heating and dimension adjustment functions. After all the separate wax models are spliced, the dimensions of the overall wax model after splicing and welding are checked. Based on the test results, calibration is performed on the calibration fixture to ensure that the overall dimensions of the housing wax model are within ±1mm.

6. The method for preparing ultra-large size high-temperature alloy precision-cast thin-walled casing according to claim 5, characterized in that: In step two, the load-bearing fixture includes a main load-bearing shaft, a double-layered support frame with coaxial inner and outer ring spokes, and a load-bearing connecting rod. The main load-bearing shaft is located at the center and serves as the main gating system for the central column in addition to bearing load. The support frame is arranged around the outside of the main load-bearing shaft. The load-bearing connecting rod connects the main load-bearing shaft and the support frame. The support frame is equipped with an annular gating system and a Y-shaped gating system. The annular gating system is arranged around the central column, and the Y-shaped gating system extends inward to connect to the central column. The annular gating system and the Y-shaped gating system are connected to the wedge-shaped riser.

7. The method for manufacturing ultra-large size high-temperature alloy precision-cast thin-walled casing according to claim 1, characterized in that: In step three, the internal collapse treatment of the support plate is carried out by inserting a φ15mm wax rod obliquely from one end of the support plate cavity to the other end, leaving a wax discharge end of ≥30mm. The surface slurry of the wax discharge end is scraped off during subsequent coating. After inserting the wax rod, the pores in the support plate are filled with a mixture of 100# and 36# quartz sand, and both ends are sealed with a sealing material made of silica sol, corundum powder and corundum sand.

8. The method for preparing ultra-large size high-temperature alloy precision-cast thin-walled casing according to claim 7, characterized in that: In step three, the shell is fired in a bogie-type sintering furnace. The temperature is raised from room temperature to 400℃ for 1 hour while the air supply is turned on. The temperature is held at 400℃ for 2 hours, then raised from 400℃ to 600℃ for 3 hours, and held at 600℃ for 1 hour. After holding, the air supply is turned off, and the temperature is raised from 600℃ to the final firing temperature for 1 hour. The final firing temperature is 1100-1150℃, and the holding time is 2-4 hours.

9. The method for manufacturing ultra-large size high-temperature alloy precision-cast thin-walled casing according to claim 1, characterized in that: In step four, the castings are slowly cooled in the mold cooling chamber of the vacuum furnace. The cooling chamber is preheated to 650°C. After the sand box is placed in the cooling chamber, it is kept at 650°C for 2 hours. After being kept at 650°C, it is cooled down to 450°C for 8-15 hours. After being kept at 450°C for 1 hour, it is cooled down to 300°C for 4 hours. After reaching 300°C, the power supply to the cooling chamber is stopped.

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