Casting system and casting method based on casting for post-processing trepanning

Abstract

The invention discloses a casting system and a casting method based on castings for post-processing trepanning, and belongs to the technical field of casting. Comprising a sand box, a cavity is formed in the sand box to form a pouring unit and at least one mold cavity, the pouring unit forms an opening in the upper surface of the sand box, the mold cavity is communicated with the pouring unit, in the casting process, molten iron enters the mold cavity from the pouring unit, and a casting is formed after the mold cavity is filled with the molten iron. The pouring device is characterized in that the pouring unit sequentially comprises a pouring gate box, a pouring gate box base, a transverse track and at least one riser according to the molten iron injection sequence, and a boss which is gradually shrunk towards the interior of the riser is arranged on the side surface of the riser. The position, needing to be drilled, of the casting has no defect on the hole wall.

Description

Technical Field

[0001] This invention belongs to the field of casting technology, and more specifically, relates to a casting system and casting method for castings with post-processed openings. Background Technology

[0002] Castings often require additional drilling due to the need for post-processing and the small size of the holes, making them difficult to form through casting alone. However, drilling tests the strength and internal porosity of the casting; for example, planetary carriers require drilling during installation. The planetary carrier is a core component of the planetary gear transmission system, and its casting quality directly affects the reliability and lifespan of the entire transmission system. Integrated planetary carriers offer several significant advantages by molding key components such as the planetary carrier side plates and connecting plates—which traditionally required separate manufacturing and assembly—into a single unit. The high precision and high rigidity of the integrated planetary carrier complement each other. The high-precision bore positions ensure good load sharing during the initial meshing of the planetary gears; while the high rigidity ensures that this precise geometric relationship will not be destroyed by structural deformation under load, thus maintaining excellent load sharing performance and resulting in smoother transmission, lower noise and vibration.

[0003] The integrated design not only eliminates potential points of failure such as loose bolts and micro-slippage at connection surfaces, but its overall integrity also means superior force transmission. This is crucial for applications subjected to frequent forward and reverse rotations or impact loads (such as heavy machinery and automated robots), significantly improving equipment lifespan and operational reliability.

[0004] Despite the significant advantages of integrated planetary carriers, several challenges remain. For instance, manufacturing their blanks (such as large, complex castings or forgings) is relatively difficult and costly, requiring stringent casting or forging processes to mitigate defects. Furthermore, the complex internal structure can present challenges for machining.

[0005] A search revealed a Chinese patent application (application number 202311282899.6, publication date January 16, 2024) disclosing a vertical planetary carrier sand casting process. This patented casting process employs vertical pouring and includes the following steps: S1, mold making and sand preparation; S2, placing the mold in a sand box and filling it with molding sand to form a mold; S3, setting the gating gate, riser, and sprue, and closing the mold; S4, heating the sand box; S5, pouring molten iron into the sand mold, and after solidification to form the casting, performing sand removal and shot blasting; S6, inspection and warehousing. However, this vertical process is unsuitable for complex, irregularly shaped castings with uneven wall thickness, and the feeding effect is poor.

[0006] For irregularly shaped planetary carriers with uneven wall thickness, especially those planetary carriers that require drilling, in order to ensure the strength of the frame and the surface quality of the finished drilled holes, the existing technology usually makes them into separate parts. However, the separate splicing structure is prone to bolt loosening and poor overall structural stability. Therefore, it is necessary to design a casting system and casting method based on post-processing hole-opening castings. Summary of the Invention

[0007] 1. The problem to be solved One objective of this invention is to provide a casting system for post-processed hole-drilling castings, aiming to achieve defect-free hole walls at the locations where drilling is required. This further results in hollow frame-shaped castings with uneven wall thickness.

[0008] Another objective of this invention is to provide a casting method for the above-mentioned castings, so as to obtain castings with high strength and no defects on the hole surface after drilling.

[0009] 2. Technical Solution To solve the above problems, the technical solution adopted by the present invention is as follows: According to the purpose of this invention, a first aspect of the invention provides a casting system based on post-processed opening castings, including a sand box, a cavity formed in the sand box to form a gating unit and at least one mold cavity, the gating unit having an opening on the upper surface of the sand box, the mold cavity communicating with the gating unit, during the casting process, molten iron enters the mold cavity from the gating unit, and after filling the mold cavity, a casting is formed, the gating unit including a gating box, a gating box base, a transverse runner and at least one riser in sequence according to the molten iron injection order, the side surface of the riser being provided with a boss that gradually tapers inwards into the riser, the position of the riser flowing into the mold cavity corresponding to a protruding hot spot portion formed at the casting.

[0010] With the above technical solution, a tapering boss is installed at the top of the riser, which increases the density and opening quality of the hot spot area. Since the boss itself is a new and larger hot spot, through the "hot spot induction" effect, the feeding channels of the casting's hot spot area are "attracted" and connected to this new hot spot. According to the solidification principle, the molten metal will feed towards the last solidified area (i.e., the highest temperature), thus allowing the casting body to solidify before the boss and riser neck, and the boss to solidify before the riser body. This achieves sequential solidification from the casting to the riser, transferring shrinkage defects to the riser, significantly increasing the density of the hot spot area of ​​the casting body, essentially eliminating shrinkage cavities and porosity defects, and resulting in uniform, dense, and high-quality openings. In summary, the tapering boss design at the top of the riser, by actively guiding and controlling the position and solidification sequence of the hot spot, successfully transfers defects to the riser, a "process waste," thereby achieving high density and excellent internal quality in the key parts of the casting body (i.e., the hot spot area). This not only ensures the performance of the casting itself, but also provides a reliable base for its subsequent machining (drilling), ensuring the integrity and strength of the final hole wall.

[0011] As one possible implementation, the boss includes a first sanded surface and a second sanded surface, and the included angle between the first sanded surface and the second sanded surface is less than 30~50°.

[0012] When the above technical solution is adopted, the boss that gradually shrinks into the riser forms a triangular cross section, which is conducive to molding in the sand box. The molding sand is not easily damaged by the molten metal. However, the more complex the shape of the boss, the more likely the molding sand forming the boss will be short of material. The molding sand with short material has poor strength and is easily damaged by the molten metal injection, causing the molding sand to enter the molten metal and mix into the casting.

[0013] As one possible implementation, the angle between the first sand surface and the second sand surface is 35°.

[0014] As one possible implementation, the riser is a cylindrical cavity with a diameter of D and a height of H. The depth of the boss within the riser is d, and the height of the boss within the riser is h, satisfying the following relationship: d = (0.6~0.7) × D; h = (0.3~0.5) × H.

[0015] As one possible implementation, when D=50 mm and H=105 mm, d=32 mm and h=40 mm.

[0016] With the above technical solution, the tapered boss with a triangular cross-section has high stability. Designed according to the above dimensions, the boss has more stable strength and better feeding effect on the casting.

[0017] As one possible implementation, a core is placed inside the cavity to form the internal casting surface of the hollow frame-shaped casting.

[0018] As one possible implementation, three risers are provided for each cavity.

[0019] As one possible implementation, two cavities are formed inside the sand box.

[0020] A second aspect of the present invention provides a casting method for the above-described casting system, comprising the following steps: S1. Preparation of sand box: A model that matches the outer surface of the casting to be formed is embedded in an empty sand box with molding sand to form a cavity, and a pouring unit connected to the cavity is set up. After heating the sand box in step S1 to form the molding sand, the model is removed to complete the preparation of the sand box; wherein, the sand box is divided into upper and lower parts. S2. Pouring: Molten metal is poured into the pouring unit of the sand box until the cavity and pouring unit are filled. After the molten metal solidifies and forms, the sand box is opened and the corresponding part of the pouring unit is removed to obtain the casting.

[0021] As one possible implementation, in step S2, the clay core used to form the internal casting surface of the casting is first placed in the mold cavity, the sand box is closed, and then the casting is performed.

[0022] 3. Beneficial effects Compared with the prior art, the beneficial effects of the present invention are as follows: the casting system of the present invention can process castings with complex structures, multiple windows, and uneven wall thickness, such as castings of integrated planetary carriers; the castings can be well fed, have strong gas density, and are less prone to shrinkage defects during drilling. Attached Figure Description

[0023] Figure 1 This is a front view of the casting system of the present invention (molding sand is not shown). Figure 2 This is a reverse schematic diagram of the casting system of the present invention (molding sand is not shown). Figure 3 This is a three-dimensional rendering of the casting system of the present invention (molding sand is not shown). Figure 4 This is a cross-sectional schematic diagram of the casting system of the present invention; Figure 5 This is a cross-sectional rendering of the casting system of the present invention; Figure 6 This is a perspective view of the first core of the casting system in the embodiment; Figure 7 This is a perspective view of the second core of the casting system in the embodiment; Figure 8 This is an assembly diagram of the first and second cores in the embodiment; Figure 9 This is an assembly diagram of the first core, the second core, and the casting in the embodiment; Figure 10 A front view of the integrated planetary carrier casting as an example; Figure 11 A reverse view of the integrated planetary carrier casting used in this embodiment; Figure 12 Metallographic image of the casting at the hot spot region in the example; In the picture: 1. Sand box; 2. Gating unit; 21. Sprue box; 22. Sprue box base; 23. Horizontal runway; 24. Riser; 241. Boss; 2411. First sand surface; 2412. Second sand surface; 3. Cavity; 4. Clay core; 5. Casting; 51. Hot spot. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments.

[0025] Example This embodiment uses a hollow frame-shaped casting with uneven wall thickness, such as an integrated planetary carrier, as an example. Figure 1 and Figure 2 These are schematic diagrams of the front and back of a casting system after removing molding sand and mold box. Figure 3 To remove the molding sand and mold box from the 3D rendering of the casting system, Figure 4 This is a cross-sectional schematic diagram of the casting system of the present invention. Figure 5 for Figure 4 The rendering shows a casting system for post-processed open-hole castings, comprising a sand box 1. A cavity is formed within the sand box 1 to create a pouring unit 2 and at least one mold cavity 3. The pouring unit 2 has an opening on its upper surface. The mold cavity 3 communicates with the pouring unit 2. During the casting process, molten iron enters the mold cavity 3 from the pouring unit 2, filling the mold cavity 3 to form a casting 5. Specifically: The casting unit 2 includes a sprue box 21, a sprue box base 22, a cross runner 23 and at least one riser 24 in the order of molten iron injection. In this embodiment, three risers 24 are provided in each cavity 3. The risers 24 are connected to each other through the gating system, that is, each riser 24 injects molten iron into the cavity 3.

[0026] In this embodiment, the riser 24 is a cylindrical cavity with a boss 241 that tapers inward from the side surface. The position of the flow cavity 3 of the riser 24 corresponds to the protruding hot spot portion 51 formed at the casting 5. The boss 241 includes a first sand surface 2411 and a second sand surface 2412. The included angle between the first sand surface 2411 and the second sand surface 2412 is less than 30~50°, and in this embodiment it is 35°. The riser 24 has a diameter of 50 mm, a height of 105 mm, a depth of 32 mm for the boss 241 within the riser 24, and a height of 40 mm for the boss 241 within the riser 24.

[0027] In this embodiment, to cast an integrated planetary carrier with uneven wall thickness, a core 4 is placed inside the mold cavity 3 to form the internal casting surface of the hollow frame-like casting. Due to the complex structure of the integrated planetary carrier, the inner surface of the integrated planetary carrier is formed by combining the first core and the second core. Figure 6 This is a schematic diagram of the structure of the first core sample. Figure 7 This is a schematic diagram of the structure of the second core. Figure 8 This is a schematic diagram of the combination of the first and second core samples.

[0028] The casting method in this embodiment is as follows: S1. Preparation of sand box 1: The model with the same size as the integrated planetary carrier structure to be formed is embedded in the empty sand box 1 with molding sand to form a cavity 3, and a casting unit 2 connected to the cavity 3 is set up. After the sand box 1 in step S1 is heated to form the molding sand, the model is taken out to complete the preparation of sand box 1; wherein, the sand box 1 is divided into upper and lower parts. S2. Casting: First, assemble the first and second clay cores and place them in the mold cavity 3. Close the sand box 1, and then proceed with casting. Pour molten iron into the casting unit 2 of the sand box 1 until the mold cavity 3 and casting unit 2 are filled. The casting process is as follows: casting temperature: 1380-1470℃, single mold casting time: 10-17s, single ladle casting time: within 8 minutes, continuous casting, single ladle molten iron weight: 500kg. After the molten iron has solidified, open the sand box 1 and remove the corresponding part of the casting unit 2, such as... Figure 9 The diagram shows the assembly of the first core, the second core, and the integrated planetary support after the sand removal box is installed. Figure 9 After the two cores are vibrated and sanded, an integrated planetary frame is obtained, as shown in the picture. Figure 10 and 11 As shown.

[0029] The product grade of molten iron is: ductile iron 500-7, with a tensile strength of 500 MPa and an elongation of ≥7%.

[0030] The specific composition of the molten iron is: C: 3.7-3.8%, Si: 2.7-2.8%, Mn: 0.2-0.3%, Mg: 0.04-0.05%, Cu: 0.1-0.2%, Sn: 0.03-0.04%. It adopts a high carbon, high silicon, and high carbon equivalent composition. The molten iron with this composition has high fluidity and a low tendency to turn white.

[0031] Melting temperature: 1500-1550℃, the weight of molten iron in the whole furnace is 1000Kg, and the molten iron in one furnace is delivered in 2 ladles.

[0032] Pregnancy: Three pregnancies are performed.

[0033] The first inoculation is added at the initial stage of transferring molten iron from the furnace to the transfer ladle, using 0.2-0.4% barium-silicon long-lasting inoculant containing 75% Si; When the molten iron from the transfer ladle is transferred to the casting ladle at a rate of 50-150 kg, a second inoculant is added to ensure that the inoculant is fully dissolved. Use 0.3-0.6% barium-silicon long-acting inoculant containing 75% Si.

[0034] Instant inoculation is performed during the casting process, using 0.1-0.3% barium-silicon long-acting inoculant containing 75% Si, and employing multiple inoculation methods to reduce the tendency for white cast iron.

[0035] The following performance tests were performed on the integrated planetary carrier casting of this embodiment: (1) Metallographic testing: such as Figure 12 The image shown is a metallographic test diagram of the hot spot area of ​​the integrated planetary carrier casting. The spheroidization rate is 85-90%, the pearlite is 50-60%, and there is no white iron, which meets the customer's requirements.

[0036] (2) Strength test: tensile strength 700-800 MPa, yield strength 450-550 MPa, elongation 8-10%, meeting customer requirements. (3) Product density: The product has virtually no shrinkage porosity, and there are no defects in the machining and drilling positions, meeting customer requirements. The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct (indirect) applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A casting system for post-processed open-hole castings, comprising a sand box (1), wherein a cavity is formed in the sand box (1) to form a pouring unit (2) and at least one mold cavity (3), the pouring unit (2) having an opening on the upper surface of the sand box (1), the mold cavity (3) being connected to the pouring unit (2), wherein during the casting process, molten iron enters the mold cavity (3) from the pouring unit (2), and after filling the mold cavity (3), a casting (5) is formed, characterized in that: The casting unit (2) includes, in the order of molten iron injection, a casting box (21), a casting box base (22), a cross runner (23) and at least one riser (24), and the side surface of the riser (24) is provided with a boss (241) that gradually shrinks into the riser (24).

2. The casting system based on post-processed opening castings according to claim 1, characterized in that: The boss (241) includes a first sanded surface (2411) and a second sanded surface (2412), and the included angle formed by the first sanded surface (2411) and the second sanded surface (2412) is 30~50°.

3. A casting system based on post-processed opening castings according to claim 2, characterized in that: The angle between the first sand surface (2411) and the second sand surface (2412) is 35°.

4. A casting system based on post-processed opening castings according to claim 3, characterized in that: The riser (24) is a cylindrical cavity with a diameter of D and a height of H. The boss (241) forms a depth of d and a height of h within the riser (24), satisfying the following relationship: d = (0.6~0.7) × D; h = (0.3~0.5) × H.

5. A casting system for post-processed opening castings according to claim 4, characterized in that: When D=50mm and H=105 mm, d=32mm and h=40 mm.

6. A casting system based on post-processed opening castings according to any one of claims 1 to 5, characterized in that: A core (4) is placed inside the cavity (3) to form the internal casting surface of the hollow frame casting.

7. A casting system based on post-processed opening castings according to any one of claims 1 to 5, characterized in that: Each cavity (3) is provided with 3 risers (24).

8. A casting system based on post-processed opening castings according to claim 7, characterized in that: Two cavities (3) are opened inside the sand box (1).

9. A casting method for the casting system according to claims 1-8, characterized in that: The steps are as follows: S1. Preparation of sand box (1): The model that matches the outer surface of the casting to be formed is embedded in the empty sand box (1) with molding sand to form a cavity (3), and a pouring unit (2) connected to the cavity (3) is set up. The sand box (1) of step S1 is heated to form the molding sand, and the model is taken out to complete the preparation of the sand box (1); wherein, the sand box (1) is divided into upper and lower parts; S2, Casting: Inject molten metal into the casting unit (2) of the sand box (1) until the cavity (3) and casting unit (2) are filled. After the molten iron solidifies and forms, open the sand box (1), remove the corresponding part of the casting unit (2), and obtain the casting (5).

10. The casting method according to claim 9, characterized in that: In step S2, the clay core (4) used to form the internal casting surface of the casting (5) is first placed in the cavity (3), the sand box (1) is closed, and then the casting is performed.

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