Casting process of closed impeller
Through the precise splicing and bottom-filling casting system of the upper cover plate and lower cover plate molds, combined with multi-layer coating shell making and steam dewaxing, the wax mold forming reliability and casting defects in closed impeller casting are solved, and the casting yield rate of high-quality runners and deep processing accuracy is improved.
Patent Information
- Application Number
- CN202510661332.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-22
- Publication Date
- 2025-07-22
AI Technical Summary
In the prior art, the wax molding reliability is poor, the tree exhaust is difficult, the casting defects occur frequently, and the shell cleaning is not thorough, resulting in the inability to guarantee the inner surface quality of the runner and the deep processing accuracy is difficult to control.
The upper cover mold and the lower cover mold with blades are respectively wax-filled. The positioning grooves are accurately spliced and repaired for wax liquid filling. Combined with the bottom injection casting system and multi-internal gate design, and combined with the multi-layer coating shell making and steam dewaxing, a high-quality cavity shell mold is formed and high-temperature casting is carried out.
It improves the inner surface quality of the runner, controls casting defects, ensures the accuracy requirements for deep processing, and significantly improves the yield and machining stability of closed impeller castings.
Smart Images
Figure CN120347161A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of precision casting, and in particular to a casting process for a closed impeller. Background Art
[0002] The impeller is a key part of a water pump, usually divided into an open impeller, a semi-open impeller, a closed impeller, etc. Since the function of the impeller is to transport liquid, it is required that the flow path part must be flat, smooth, free of burrs and protrusions, which makes the casting process of the closed impeller have a certain casting difficulty. The impeller described in the present invention needs to be deeply processed at both the upper and lower covers, and it is necessary to ensure that there are no defects in the processing, so the casting difficulty is greater. Referring to Figure 1 As shown, the impeller is composed of an upper cover plate, five groups of blades, and a lower cover plate. The contour dimensions are a diameter of 254 mm, a height of 90 mm, an inlet diameter of 158 mm, a flow path width of 22 mm, and the surface roughness of the inner surface of the flow path is 6.3 μm. There are casting hot spots at both the upper and lower cover plates and deep processing is required at the hot spots, so the casting difficulty is great.
[0003] The casting process of the closed impeller generally includes the following steps: 1. Wax pattern forming: Generally, a water-soluble core or a urea core is used for integral forming. The advantage is high production efficiency, but the disadvantage is high mold cost, and the core is extremely easy to break during the wax injection process, resulting in an increase in the scrap rate of the wax parts. The urea core and the water-soluble core are also extremely easy to be affected by moisture and change, and are not easy to store, which will cause the surface quality of the flow path in the wax parts to be unable to be guaranteed; 2. Tree assembly: Conventional tree assembly generally only places a single gate flat group on the central axis. The advantage is high tree assembly efficiency, but the disadvantage is that after conventional flat assembly, the pouring channel is both the molten steel inlet and the exhaust outlet. Although some processes will build air channels to relieve the exhaust problem, it can never be fundamentally solved, and the molten steel directly impacts the product, which is extremely easy to cause turbulence and entrain air to cause gas slag holes on the surface of the casting; 3. Shell making: The conventional process is to repeatedly dip in slurry, sprinkle sand, and dry, repeat many times to form a shell with a certain strength. However, the drying in the flow path is not thorough, and the flow path bulges and runs iron after pouring, and the subsequent cleaning is cumbersome. The dead corners in the flow path cannot be cleaned, resulting in product scrapping. Summary of the Invention
[0004] Therefore, the technical problem to be solved by the present invention is to overcome the problems in the prior art such as poor reliability of wax pattern forming, difficult exhaust in tree assembly, frequent pouring defects, and incomplete shell cleaning during the casting process of the closed impeller, and provide a casting process for the closed impeller, which can effectively improve the inner surface quality of the flow path, control the generation of casting defects, and ensure the accuracy requirements of deep processing, thereby improving the qualification rate and stability of the overall casting.
[0005] To solve the above technical problems, the present invention provides a casting process for a closed impeller, including: Provide a wax mold die, including an upper cover plate die and a lower cover plate die with blades; wherein, a positioning groove conforming to the shape of the blades is provided on the upper cover plate wax mold; By injecting wax into the upper cover plate die and the lower cover plate die, an upper cover plate wax part and a lower cover plate wax part are respectively formed; Splice the upper cover plate wax part and the lower cover plate wax part through the positioning groove to obtain a spliced wax mold; Trim the splicing position of the spliced wax mold to obtain an integral impeller wax mold; Assemble the integral impeller wax mold into the gating system through its internal gating to form a wax mold assembly; Perform shell making on the surface of the wax mold assembly to obtain a shell mold; Remove the wax material of the shell mold through a steam dewaxing kettle to form a cavity shell mold; Roast the cavity shell mold and then perform casting to obtain a closed impeller casting.
[0006] In an embodiment of the present invention, by injecting wax into the upper cover plate die and the lower cover plate die, an upper cover plate wax part and a lower cover plate wax part are respectively formed, including: Both the upper cover plate die and the lower cover plate die include an upper die and a lower die. A mold cavity is formed between the upper die and the corresponding lower die. By injecting wax into the corresponding mold cavity, an upper cover plate wax part and a lower cover plate wax part are fabricated.
[0007] In an embodiment of the present invention, splicing the upper cover plate wax part and the lower cover plate wax part through the positioning groove to obtain a spliced wax mold includes: Insert the blades on the lower cover plate wax part into the positioning groove of the upper cover plate wax part, and use glue to paste and fix the contact parts of the two.
[0008] In an embodiment of the present invention, trimming the splicing position of the spliced wax mold to obtain an integral impeller wax mold includes: Select any one blade, slowly drip repair wax liquid at the fitting interface between the blade and the positioning groove, and at the same time slowly rotate the spliced wax mold to make the repair wax liquid gradually fill the entire bonding gap along the fitting track to form a sealing edge structure; After the repair wax liquid naturally cools and solidifies, use a wax trimming knife to trim the bonding part at the root of the blade to trim out a smooth R corner; Repeat the above steps to trim the root positions of the remaining blades in turn.
[0009] In an embodiment of the present invention, assembling the integral impeller wax mold into the gating system through its internal gating to form a wax mold assembly includes: The gating system is a bottom gating type, including a top die head, an intermediate channel, and a bottom gating module; wherein, the top die head is provided with a pouring cup for receiving molten steel, the intermediate channel is used to guide the molten steel to flow to the bottom gating module, and the bottom gating module is used to introduce the molten steel into the impeller cavity from bottom to top; Paste the internal gates on the integral impeller wax mold corresponding to the top die head and the bottom gating module onto the bottom gating module and the top die head respectively.
[0010] In an embodiment of the present invention, a first internal gate and a second internal gate are respectively arranged on one side of the upper cover plate wax part away from the lower cover plate wax part, a third internal gate, a fourth internal gate, and a fifth internal gate are respectively arranged on one side of the lower cover plate wax part away from the upper cover plate wax part, and a channel gate is arranged on one side of the lower cover plate wax part close to the upper cover plate wax part; the channel gate and the fourth internal gate are integrally connected to form the intermediate channel; Simultaneously apply bonding wax to the third internal gate, the fourth internal gate, and the fifth internal gate and then paste them onto the top die head; Simultaneously apply bonding wax to the first internal gate, the second internal gate, and the channel gate and then paste them onto the bottom gating module, and the pouring cup is connected to the intermediate channel; In the wax mold module, the first internal gate and the second internal gate are arranged at the annular deep processing area position of the upper cover plate wax part and are symmetrically distributed on both sides of the intermediate channel; the third internal gate and the fifth internal gate are arranged at the annular deep processing area position of the lower cover plate wax part and are symmetrically distributed on both sides of the intermediate channel.
[0011] In an embodiment of the present invention, perform shell making operation on the surface of the wax mold module to obtain a shell mold, including: Make seven shell making layers, and the manufacturing steps of each layer are as follows: For the surface layer, use a mixed slurry prepared by zirconium silicate powder of 300 mesh and silica sol in a weight ratio of 3 - 3.5:1 for dipping and coating. When dipping and coating, immerse the wax mold module at an inclination angle of 25° - 45°, so that the slurry enters from the water outlet of the wax mold module and overflows from the water inlet of the wax mold module, making the slurry fill the entire gating system; then perform sand spraying operation, evenly spray 120 - mesh zirconium sand on the surface of the entire gating system, and dry it for 4 - 6 hours in a windless or blowing state before making the next layer; For the second and third layers, both use a mixed slurry prepared by mullite powder of 270 mesh and silica sol in a weight ratio of 1.2 - 1.3:1 for dipping and coating. When dipping and coating, immerse the wax mold module at an inclination angle of 25° - 45°, so that the slurry enters from the water outlet of the wax mold module and overflows from the water inlet of the wax mold module, making the slurry fill the entire gating system; then perform sand spraying operation, evenly spray 30 - 60 - mesh mullite sand on the surface of the entire gating system, and dry it for 12 - 24 hours in a blowing state; For the fourth to sixth layers, a mixed slurry prepared by mixing mullite powder of 270 mesh and silica sol in a weight ratio of 1.2 - 1.3:1 is used for dipping and coating. When dipping and coating, the wax mold module is immersed in the slurry at an inclination angle of 25° - 45°, so that the slurry enters from the water outlet of the wax mold module and overflows from the water inlet of the wax mold module, filling the entire gating system with the slurry. Subsequently, a sand spraying operation is carried out, and mullite sand of 16 - 30 mesh is evenly sprayed on the surface of the entire gating system and dried for 24 hours under a blowing state; For the sealant layer, a mixed slurry prepared by mixing mullite powder of 270 mesh and silica sol in a weight ratio of 1 - 1.3:1 is used for dipping and coating. When dipping and coating, the wax mold module is immersed in the slurry at an inclination angle of 25° - 45°, so that the slurry enters from the water outlet of the wax mold module and overflows from the water inlet of the wax mold module, filling the entire gating system with the slurry. The sand spraying operation is no longer carried out, and it is dried for 48 hours under a blowing state.
[0012] In an embodiment of the present invention, before preparing each layer of the shell layer, compressed air is used to blow away the floating sand on the surface of the previous layer and / or the floating sand accumulated inside the runner.
[0013] In an embodiment of the present invention, the mullite sand used starting from the second layer of the shell layer needs to be screened before use, and the caked or agglomerated large - particle sand materials are removed by filtering through a sieve.
[0014] In an embodiment of the present invention, after baking the cavity shell mold, pouring and molding are carried out, including: Before baking the cavity shell mold, rock wool is coated on the outer side of the top mold head; The cavity shell mold is placed in a baking furnace for baking, the baking temperature is 1050°C, and the baking time is not less than 45 minutes; After the shell baking is completed, pouring is carried out, and the pouring temperature is controlled at 1600°C - 1620°C; After pouring is completed, the shell mold is kept in a suspended state and horizontally placed on a placement rack for cooling.
[0015] The above - mentioned technical solution of the present invention has the following advantages compared with the prior art: The casting process of a closed impeller described in the present invention is to obtain an upper cover plate wax part and a lower cover plate wax part through an upper cover plate mold and a lower cover plate mold with blades; the upper cover plate wax part and the lower cover plate wax part are spliced into a spliced wax mold of the impeller; the spliced integral impeller wax mold is assembled into a pouring system; the wax mold module with the pouring system is surface coated to form an outer shell mold with a certain strength; the wax material in the shell mold is removed through a steam dewaxing kettle, and a cavity shell mold is formed and then melted and poured. This process can effectively improve the inner surface quality of the flow channel, control the generation of casting defects, and ensure the precision requirements of deep processing, thereby greatly improving the yield rate of closed impeller castings and greatly improving the stability of subsequent machining.
[0016] The present invention divides the complex closed impeller into two parts, an upper cover plate wax mold and a lower cover plate wax mold with blades. The two parts are respectively formed by wax injection and then precisely spliced through a positioning groove structure. The blades on the lower cover plate wax part can be accurately embedded in the positioning grooves of the upper cover plate wax part. The sealing filling and structural transition are performed by repairing wax liquid, thereby ensuring the continuity and smoothness of the flow channel at the splicing point, thereby providing guarantee for the subsequent flow channel smoothness and defect-free processing.
[0017] The present invention adopts a bottom pouring system to introduce molten steel into the mold cavity from the bottom, connects the top die head and the bottom pouring module through an intermediate channel to form a filling path from bottom to top, and uses multiple inner gates to supply liquid to the deep processing hot node areas of the upper and lower cover plates to effectively remove the air in the mold cavity and reduce turbulence. The multiple inner gates can accurately control the flow path and the shrinkage path of the liquid metal to prevent the formation of shrinkage holes, looseness and other defects in the hot node area due to insufficient liquid metal supply.
[0018] When making each layer of shell, the wax mold module is immersed in the slurry at an angle of 25° to 45°, and the slurry is controlled to enter from the water outlet of the wax mold module and overflow from the water inlet. The slurry is controlled by gravity and flow direction to penetrate into the complex flow channel of the impeller from top to bottom, ensuring that the slurry can cover all dead corners, effectively preventing slurry accumulation and incomplete coverage in the dead corners, and improving the overall density and consistency of the subsequent shell molds; before preparing each layer of shell, compressed air is used to blow away the floating sand on the surface of the previous layer, especially the sand in the flow channel. The accumulated floating sand can greatly reduce the accumulation in the flow channel, speed up the drying speed, reduce the process time, save production time and cost; the mullite sand used from the second shell layer onwards must be screened before use, and the sieve is used to filter the mullite sand to be used, in order to filter out the large particles of agglomeration and clustering, so as to avoid large particles of mullite sand entering the product flow channel to form bulges when pouring sand, causing blockage and bridging in the flow channel, resulting in incomplete drying of the shell mold, and leading to problems such as shell cracking or steel leakage during pouring. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] To make the content of the present invention easier to be clearly understood, the following further elaborates on the present invention in detail according to specific embodiments of the present invention in combination with the accompanying drawings.
[0020] Figure 1 It is a schematic structural diagram of the upper cover plate mold and the lower cover plate mold with blades of the present invention.
[0021] Figure 2 It is a schematic structural diagram of the lower cover plate with blades of the present invention.
[0022] Figure 3 For Figure 1 The sectional structural schematic diagram.
[0023] Figure 4 It is a front view structural schematic diagram of the upper cover plate wax part of the present invention.
[0024] Figure 5 It is a first axonometric structural schematic diagram of the upper cover plate wax part of the present invention.
[0025] Figure 6 It is a second axonometric structural schematic diagram of the upper cover plate wax part of the present invention.
[0026] Figure 7 It is a front view structural schematic diagram of the lower cover plate wax part of the present invention.
[0027] Figure 8 It is an axonometric structural schematic diagram of the lower cover plate wax part of the present invention.
[0028] Figure 9 It is a combined splicing schematic diagram of the upper cover plate wax part and the lower cover plate wax part of the present invention.
[0029] Figure 10 It is a front view structural schematic diagram of the gating of the integral impeller wax mold of the present invention.
[0030] Figure 11 It is a first axonometric structural schematic diagram of the gating of the integral impeller wax mold of the present invention.
[0031] Figure 12 It is a second axonometric structural schematic diagram of the gating of the integral impeller wax mold of the present invention.
[0032] Figure 13 It is a schematic structural diagram of the gating system of the present invention.
[0033] Explanation of the reference numerals in the drawings of the specification: 1. Upper cover plate mold; 2. Lower cover plate mold; 3. Blade; 4. Positioning groove; 5. Upper cover plate wax part; 51. First internal gate; 52. Second internal gate; 6. Lower cover wax part; 61. Third internal gate; 62. Fourth internal gate; 63. Fifth internal gate; 64. Channel gate; 7. Pouring system; 71. Top die head; 72. Intermediate channel; 73. Bottom pouring module; 74. Sprue cup; 75. Rock wool; 8. Integral impeller wax pattern. Specific embodiments
[0034] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the embodiments cited are not intended to limit the present invention.
[0035] In the present invention, when directions (up, down, left, right, front and back) are described, it is only for the convenience of describing the technical solution of the present invention, rather than indicating or implying that the technical features referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.
[0036] In the present invention, the meaning of "several" is one or more, the meaning of "multiple" is two or more, and "greater than", "less than", "exceeding", etc. are understood not to include the present number; "above", "below", "within", etc. are understood to include the present number. In the description of the present invention, if "first" and "second" are described, they are only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.
[0037] In the present invention, unless otherwise clearly defined, words such as "set", "installed", "connected", etc. should be understood in a broad sense. For example, they can be directly connected, or indirectly connected through an intermediate medium; they can be fixedly connected, or detachably connected, or integrally formed; they can be mechanically connected, or electrically connected or capable of communicating with each other; they can be the communication inside two components or the interaction relationship between two components. Those skilled in the art can reasonably determine the specific meaning of the above words in the present invention in combination with the specific content of the technical solution.
[0038] Refer to Figures 1 to 3 As shown, a casting process for a closed impeller, the closed impeller includes three parts: an upper cover plate, a lower cover plate and an impeller, and the process includes the following steps: S1. Provide a wax pattern mold, including an upper cover plate mold 1 and a lower cover plate mold 2 with blades 3; wherein, the upper cover plate wax pattern is provided with a positioning groove 4 following the shape of the blades 3.
[0039] S2. By injecting wax into the upper cover plate mold 1 and the lower cover plate mold 2, an upper cover plate wax part 5 and a lower cover plate wax part 6 are respectively formed. Refer toFigures 4 to 8 as shown
[0040] Specifically, both the upper cover die 1 and the lower cover die 2 include an upper die and a lower die. A mold cavity is formed between the upper die and the corresponding lower die. By injecting wax into the corresponding mold cavity, an upper cover wax part 5 and a lower cover wax part 6 are produced.
[0041] Through the above steps, the difficulty of wax mold forming can be reduced, the forming accuracy of wax molds with complex structures can be improved, and the risk of wax core fracture caused by an integral mold can be avoided.
[0042] S3. Splice the upper cover wax part 5 and the lower cover wax part 6 through the positioning groove 4 to obtain a spliced wax mold. Refer to Figure 9 as shown
[0043] Specifically, embed the blade 3 on the lower cover wax part 6 into the positioning groove 4 of the upper cover wax part 5, and use glue to paste and fix the contact parts of the two.
[0044] S4. Trim the splicing position of the spliced wax mold to obtain an integral impeller wax mold 8. Refer to Figures 10 to 12 as shown
[0045] Specifically, select any one blade 3, slowly drop repair wax liquid at the fitting interface between the blade 3 and the positioning groove 4, and at the same time slowly rotate the spliced wax mold to make the repair wax liquid gradually fill the entire bonding gap along the fitting track to form a sealing edge structure; After the repair wax liquid naturally cools and solidifies, use a wax trimming knife to trim the bonding part at the root of the blade 3 to trim out a smooth transition R angle; Repeat the above steps to trim the root positions of the remaining blades 3 in turn. In this embodiment, the operation is repeated five times to complete the treatment of the five roots of the blades 3. Eliminate the splicing gap, enhance the continuity of the overall structure of the mold, reduce the risk of air holes and slag inclusion in the subsequent castings, and improve the casting quality of the runner transition zone.
[0046] S5. Assemble the integral impeller wax mold 8 into the gating system 7 through its ingate to form a wax mold assembly (with the gating system 7).
[0047] Specifically, refer to Figure 13 as shown, the gating system 7 is a bottom gating type, including a top mold head 71, an intermediate channel 72, and a bottom gating module 73; among them, the top mold head 71 is provided with a sprue cup 74 for receiving molten steel, the intermediate channel 72 is used to guide the molten steel to flow to the bottom gating module 73, and the bottom gating module 73 is used to introduce the molten steel into the impeller mold cavity from bottom to top.
[0048] The molten steel is filled from the bottom upwards, which can completely avoid the molten steel splashing and turbulence directly entering the product and affecting the quality of the casting. It can also play a good role in exhausting air and avoid the formation of air holes due to air entrapment in the casting.
[0049] Paste the internal gates on the integral impeller wax pattern 8 corresponding to the top die head 71 and the bottom gating module 73 onto the bottom gating module 73 and the top die head 71 correspondingly.
[0050] In this embodiment, referring to Figure 4 、 Figure 7 、 Figure 10 、 Figure 13 As shown, on one side of the end of the upper cover plate wax part 5 away from the lower cover plate wax part 6, a first internal gate 51 and a second internal gate 52 are respectively arranged. On one side of the lower cover plate wax part 6 away from the upper cover plate wax part 5, a third internal gate 61, a fourth internal gate 62 and a fifth internal gate 63 are respectively arranged. On the side of the lower cover plate wax part 6 close to the upper cover plate wax part 5, a channel gate 64 is arranged; the channel gate 64 and the fourth internal gate 62 are integrally connected to form the middle channel 72; Dip the third internal gate 61, the fourth internal gate 62 and the fifth internal gate 63 with bonding wax at the same time and then paste them onto the top die head 71; Dip the first internal gate 51, the second internal gate 52 and the channel gate 64 with bonding wax at the same time and then paste them onto the bottom gating module 73, and the sprue cup 74 is connected to the middle channel 72; In the wax pattern module, the first internal gate 51 and the second internal gate 52 are arranged at the annular deep processing area position of the upper cover plate wax part 5 and are symmetrically distributed on both sides of the middle channel 72; the third internal gate 61 and the fifth internal gate 63 are arranged at the annular deep processing area position of the lower cover plate wax part 6 and are symmetrically distributed on both sides of the middle channel 72.
[0051] Through the above settings, the integral impeller wax pattern 8 is incorporated into the gating system 7 through its internal gates, and the two deep processing positions of the upper cover plate and the lower cover plate are compensated by the corresponding internal gates to prevent processing defects.
[0052] It should be noted that during pouring, the molten steel is first poured into the sprue cup 74 arranged on the top die head 71; the molten steel flows along the middle channel 72 from the sprue cup 74 and flows into the bottom gating module 73; the molten steel enters the mold cavity from multiple positions at the bottom through the first internal gate 51 and the second internal gate 52; The molten steel gradually rises and fills the upper cover plate area, the blade area and the lower cover plate area of the closed impeller; as the molten steel rises and fills the mold cavity, the molten steel flows out through the third internal gate 61 and the fifth internal gate 63.
[0053] S6. Perform shell making operation on the surface of the wax pattern module to obtain a shell mold.
[0054] Specifically, the surface of the wax pattern module is formed into a shell with strength through multiple repetitions of slurry dipping, sand spraying, and drying. The wax pattern module of the gating system 7 needs to be coated on the surface, and the thickness and strength of the coating directly affect the quality of the runner inner cavity.
[0055] In this embodiment, seven shell-making layers are fabricated, and the manufacturing steps for each layer are as follows: For the surface layer, an immersion slurry coating is performed using a mixed slurry prepared by mixing zircon powder with 300 mesh and silica sol in a weight ratio of 3 - 3.5:1. When performing the immersion slurry coating, the wax pattern module is immersed in the slurry at an inclination angle of 25° - 45°, allowing the slurry to enter from the water outlet of the wax pattern module (between the upper and lower covers, i.e., the water outlet in the direction of the outer circle of the impeller), and overflow from the water inlet of the wax pattern module, so that the entire gating system 7 is filled with the slurry. Subsequently, a sand spraying operation is carried out, and zircon sand with 120 mesh is evenly sprayed on the surface of the entire gating system 7, and it is dried for 4 - 6 hours under a windless or blowing state before proceeding to the next layer. For the second layer, an immersion slurry coating is performed using a mixed slurry prepared by mixing mullite powder with 270 mesh and silica sol in a weight ratio of 1.2 - 1.3:1. When performing the immersion slurry coating, the wax pattern module is immersed in the slurry at an inclination angle of 25° - 45°, allowing the slurry to enter from the water outlet of the wax pattern module and overflow from the water inlet of the wax pattern module, so that the entire gating system 7 is filled with the slurry. Subsequently, a sand spraying operation is carried out, and mullite sand with 30 - 60 mesh is evenly sprayed on the surface of the entire gating system 7, and it is dried for 12 - 24 hours under a blowing state. For the third layer, an immersion slurry coating is performed using a mixed slurry prepared by mixing mullite powder with 270 mesh and silica sol in a weight ratio of 1.2 - 1.3:1. When performing the immersion slurry coating, the wax pattern module is immersed in the slurry at an inclination angle of 25° - 45°, allowing the slurry to enter from the water outlet of the wax pattern module and overflow from the water inlet of the wax pattern module, so that the entire gating system 7 is filled with the slurry. Subsequently, a sand spraying operation is carried out, and mullite sand with 30 - 60 mesh is evenly sprayed on the surface of the entire gating system 7, and it is dried for 12 - 24 hours under a blowing state. For the fourth layer, an immersion slurry coating is performed using a mixed slurry prepared by mixing mullite powder with 270 mesh and silica sol in a weight ratio of 1.2 - 1.3:1. When performing the immersion slurry coating, the wax pattern module is immersed in the slurry at an inclination angle of 25° - 45°, allowing the slurry to enter from the water outlet of the wax pattern module and overflow from the water inlet of the wax pattern module, so that the entire gating system 7 is filled with the slurry. Subsequently, a sand spraying operation is carried out, and mullite sand with 16 - 30 mesh is evenly sprayed on the surface of the entire gating system 7, and it is dried for 24 hours under a blowing state. The fifth layer is dip-coated with a mixed slurry prepared from 270-mesh mullite powder and silica sol at a weight ratio of 1.2 - 1.3:1. When dip-coating, the wax mold assembly is immersed in the slurry at an inclination angle of 25° - 45°, so that the slurry enters from the water outlet of the wax mold assembly and overflows from the water inlet of the wax mold assembly, filling the entire gating system 7 with the slurry. Subsequently, a sand spraying operation is carried out, and 16 - 30-mesh mullite sand is evenly sprayed on the surface of the entire gating system 7 and dried for 24 hours under a blowing state; The sixth layer is dip-coated with a mixed slurry prepared from 270-mesh mullite powder and silica sol at a weight ratio of 1.2 - 1.3:1. When dip-coating, the wax mold assembly is immersed in the slurry at an inclination angle of 25° - 45°, so that the slurry enters from the water outlet of the wax mold assembly and overflows from the water inlet of the wax mold assembly, filling the entire gating system 7 with the slurry. Subsequently, a sand spraying operation is carried out, and 16 - 30-mesh mullite sand is evenly sprayed on the surface of the entire gating system 7 and dried for 24 hours under a blowing state; The sealant layer is dip-coated with a mixed slurry prepared from 270-mesh mullite powder and silica sol at a weight ratio of 1 - 1.3:1. When dip-coating, the wax mold assembly is immersed in the slurry at an inclination angle of 25° - 45°, so that the slurry enters from the water outlet of the wax mold assembly and overflows from the water inlet of the wax mold assembly, filling the entire gating system 7 with the slurry. The sand spraying operation is not carried out anymore, and it is dried for 48 hours under a blowing state.
[0056] By repeatedly performing coating, sand spraying, and drying in a slurry prepared in a specific ratio, a shell with strength can be formed.
[0057] In addition, before preparing each layer of the shell layer (the slurry layer and the sand layer are combined into one layer), the surface floating sand of the previous layer is blown away using compressed air, especially the accumulated floating sand in the runner. This can greatly reduce the accumulation in the runner, accelerate the drying speed, reduce the process time, and save production time and cost.
[0058] The mullite sand (30 - 60 mesh, 16 - 30 mesh) used starting from the second shell layer needs to be screened before use. A sieve is used to filter the mullite sand to be used. The purpose is to filter out large agglomerated particles to avoid large particles of mullite sand entering the product runner during sand spraying, forming protrusions, causing blockage and bridging in the runner, resulting in incomplete drying of the shell mold, and leading to problems such as cracking or leakage of molten steel during casting.
[0059] S7. The wax material of the shell mold is removed through a steam dewaxing kettle to form a cavity shell mold.
[0060] S8. The cavity shell mold is roasted and then cast to obtain a closed impeller casting.
[0061] Specifically, before the cavity shell mold is baked, rock wool 75 is coated on the outer side of the top mold head 71. Since the top mold head 71 directly receives the pouring cup 74, heat is concentrated during the baking process. Without heat insulation, the local structure of the shell mold is prone to embrittlement and cracking due to excessive temperature rise. After being coated with rock wool 75, it can effectively block heat radiation and heat conduction, keep the temperature rise in the area of the top mold head 71 gentle, and avoid thermal shock. The cavity shell mold is placed in a baking furnace for baking. The baking temperature is 1050 °C, and the baking time is not less than 45 minutes. After the shell baking is completed, rapid pouring is carried out, and the pouring temperature is controlled at 1600 °C to 1620 °C. After pouring is completed, the shell mold is kept suspended and horizontally placed on a placement rack for cooling.
[0062] Finally, it should be noted that the above specific implementation manners are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.
Claims
1. A casting process for a closed impeller, characterized in that, Including: Providing a wax mold die, including an upper cover plate die (1) and a lower cover plate die (2) with blades (3); wherein, a positioning groove (4) conforming to the shape of the blades (3) is provided on the upper cover plate wax mold. By injecting wax into the upper cover plate die (1) and the lower cover plate die (2), an upper cover plate wax part (5) and a lower cover plate wax part (6) are respectively formed. The upper cover plate wax part (5) and the lower cover plate wax part (6) are spliced through the positioning groove (4) to obtain a spliced wax mold. The splicing position of the spliced wax mold is trimmed to obtain an integral impeller wax mold (8). The integral impeller wax mold (8) is assembled into a gating system (7) through its internal gate to form a wax mold assembly. The surface of the wax mold assembly is shelled to obtain a shell mold. The wax material of the shell mold is removed through a steam dewaxing kettle to form a cavity shell mold. The cavity shell mold is calcined and then cast to obtain a closed impeller casting.
2. The casting process of a closed impeller according to claim 1, characterized in that By injecting wax into the upper cover plate die (1) and the lower cover plate die (2), an upper cover plate wax part (5) and a lower cover plate wax part (6) are respectively formed, including: Both the upper cover plate die (1) and the lower cover plate die (2) include an upper die and a lower die. A mold cavity is formed between the upper die and the corresponding lower die. By injecting wax into the corresponding mold cavity, the upper cover plate wax part (5) and the lower cover plate wax part (6) are manufactured.
3. The casting process of a closed impeller according to claim 1, characterized in that, The upper cover plate wax part (5) and the lower cover plate wax part (6) are spliced through the positioning groove (4) to obtain a spliced wax mold, including: The blades (3) on the lower cover plate wax part (6) are inserted into the positioning groove (4) of the upper cover plate wax part (5), and the contact parts of the two are pasted and fixed with glue.
4. A casting process for a closed impeller according to claim 1 or 3, characterized in that, The splicing position of the spliced wax mold is trimmed to obtain an integral impeller wax mold (8), including: Select any one blade (3), slowly drip repair wax liquid at the fitting interface between the blade (3) and the positioning groove (4), and at the same time slowly rotate the spliced wax mold to make the repair wax liquid gradually fill the entire bonding gap along the fitting track to form a sealing edge structure. After the repair wax liquid naturally cools and solidifies, use a wax trimming knife to trim at the bonding position of the blade root to trim out a smooth R corner. Repeat the above steps to trim the root positions of the remaining blades (3) in turn.
5. The casting process of a closed impeller according to claim 1, characterized in that, The integral impeller wax mold (8) is assembled into a gating system (7) through its internal gate to form a wax mold assembly, including: The gating system (7) is a bottom gating type, including a top mold head (71), an intermediate channel (72), and a bottom gating module (73); wherein, the top mold head (71) is provided with a sprue cup (74) for receiving molten steel, the intermediate channel (72) is used to guide the molten steel to flow to the bottom gating module (73), and the bottom gating module (73) is used to introduce the molten steel into the impeller mold cavity from bottom to top. The internal gates on the integral impeller wax mold (8) corresponding to the top mold head (71) and the bottom gating module (73) are correspondingly pasted onto the bottom gating module (73) and the top mold head (71).
6. The casting process of a closed impeller according to claim 5, characterized in that, On one side of one end of the upper cover wax part (5) away from the lower cover wax part (6), a first ingate (51) and a second ingate (52) are respectively arranged. On one side of the lower cover wax part (6) away from the upper cover wax part (5), a third ingate (61), a fourth ingate (62) and a fifth ingate (63) are respectively arranged. On one side of the lower cover wax part (6) close to the upper cover wax part (5), a channel gate (64) is arranged; the channel gate (64) and the fourth ingate (62) are integrally connected to form the intermediate channel (72); Simultaneously dip the third ingate (61), the fourth ingate (62) and the fifth ingate (63) with bonding wax and then paste them onto the top die head (71); Simultaneously dip the first ingate (51), the second ingate (52) and the channel gate (64) with bonding wax and then paste them onto the bottom gating module (73), and the sprue cup (74) is connected to the intermediate channel (72); In the wax mold module, the first ingate (51) and the second ingate (52) are arranged at the annular deep processing area position of the upper cover wax part (5) and are symmetrically distributed on both sides of the intermediate channel (72); the third ingate (61) and the fifth ingate (63) are arranged at the annular deep processing area position of the lower cover wax part (6) and are symmetrically distributed on both sides of the intermediate channel (72).
7. The casting process of a closed impeller according to claim 1, characterized in that, Perform shell making operation on the surface of the wax mold module to obtain a shell mold, including: Make seven layers of shell making layers, and the manufacturing steps of each layer are as follows: The surface layer is dip-coated with a mixed slurry prepared from 300-mesh zircon powder and silica sol at a weight ratio of 3-3.5:
1. When dip-coating, immerse the wax mold module at an inclination angle of 25°-45° into the slurry, so that the slurry enters from the water outlet of the wax mold module and overflows from the water inlet of the wax mold module, making the slurry fill the entire gating system (7); then perform sand spraying operation, evenly spray 120-mesh zircon sand on the surface of the entire gating system (7), and dry for 4-6 hours under windless or blowing conditions before making the next layer; For the second and third layers, both are dip-coated with a mixed slurry prepared from 270-mesh mullite powder and silica sol at a weight ratio of 1.2-1.3:
1. When dip-coating, immerse the wax mold module at an inclination angle of 25°-45° into the slurry, so that the slurry enters from the water outlet of the wax mold module and overflows from the water inlet of the wax mold module, making the slurry fill the entire gating system (7); then perform sand spraying operation, evenly spray 30-60-mesh mullite sand on the surface of the entire gating system (7), and dry for 12-24 hours under blowing conditions; For the fourth to sixth layers, all are dip-coated with a mixed slurry prepared from 270-mesh mullite powder and silica sol at a weight ratio of 1.2-1.3:
1. When dip-coating, immerse the wax mold module at an inclination angle of 25°-45° into the slurry, so that the slurry enters from the water outlet of the wax mold module and overflows from the water inlet of the wax mold module, making the slurry fill the entire gating system (7), and then perform sand spraying operation, evenly spray 16-30-mesh mullite sand on the surface of the entire gating system (7), and dry for 24 hours under blowing conditions; The sealant layer is coated by dipping with a mixed slurry prepared from mullite powder of 270 mesh and silica sol at a weight ratio of 1 to 1.3:
1. When dipping and coating, the wax pattern module is immersed in the slurry at an inclination angle of 25° to 45°, so that the slurry enters from the water outlet of the wax pattern module and overflows from the water inlet of the wax pattern module, filling the entire gating system (7) with the slurry. The sand spraying operation is no longer carried out, and it is dried for 48 hours under a blowing state.
8. The casting process of a closed impeller according to claim 7, characterized in that, Before preparing each layer of the shell layer, compressed air is used to blow off the floating sand on the surface of the previous layer and / or the floating sand accumulated inside the runner.
9. The casting process of a closed impeller according to claim 7, characterized in that, The mullite sand used starting from the second layer of the shell layer needs to be screened before use, and the caked or agglomerated large particle sand materials are removed by filtering through a sieve.
10. The casting process of a closed impeller according to claim 1, characterized in that, The cavity shell mold is baked and then cast, including: Before the cavity shell mold is baked, rock wool (75) is wrapped outside the top die head (71); The cavity shell mold is placed in a baking furnace for baking, the baking temperature is 1050 °C, and the baking time is not less than 45 minutes; After the shell baking is completed, casting is carried out, and the casting temperature is controlled at 1600 °C to 1620 °C; After casting is completed, the shell mold is kept suspended and placed horizontally on the placement rack for cooling.