A combined sand core

Abstract

The utility model provides a kind of combined sand core, including pedestal sand core and at least one extension sand core, pedestal sand core includes base sand core and top end sand core, the base sand core and top end sand core are sequentially stacked from bottom to top, at least one positioning and fitting groove is set in the base sand core and the top end sand core;The extension sand core is provided with the positioning and fitting head of corresponding the positioning and fitting groove plug-in, so that the extension sand core is embedded between the base sand core and the top end sand core, and hollow part is formed between the outside of pedestal sand core.The utility model is split into base sand core and top end sand core by pedestal sand core, then cooperate extension sand core, to provide the positioning of extension sand core and top end sand core under the positioning mortise and tenon type plug-in of positioning and fitting groove and positioning and fitting head, and form hollow part, so that the volume of split sand core is smaller, complex structure is split into simple structure split sand core, more easily separated into shape production and assembly.

Description

Technical Field

[0001] This utility model relates to the field of casting manufacturing technology, specifically to a combined sand core. Background Technology

[0002] As a core component of the automotive transmission system, the rear axle final drive housing is typically made of cast aluminum alloy. To achieve lightweight, high rigidity, and integration, the internal structure of this type of housing is becoming increasingly complex, commonly incorporating numerous perforated ribs for reinforcement and heat dissipation, as well as intricate lubrication channels. These complex internal perforated structures place extremely high demands on casting processes, especially core-making technology.

[0003] In the prior art, castings with complex internal cavities are generally formed using integral sand cores. Specifically, an integral sand core is produced by a coated sand core shooter, the shape of which corresponds perfectly to the final internal cavity of the casting. For example, Chinese Patent 202511105900.7 discloses a coated sand core shooter for castings, including a frame, a moving mold assembly, a fixed mold assembly, a sand shooting assembly, and a sand supply assembly. The fixed mold assembly includes an upper mold.

[0004] For existing monolithic sand cores, when the monolithic sand core is removed from the core box, those slender, fragile or slightly buckled structural parts are very prone to breakage or damage during the molding process, resulting in the scrapping of the sand core and making it difficult to improve the production yield. Utility Model Content

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a combined sand core to solve the technical problem that the integral sand core in the prior art breaks or is damaged during the molding process, resulting in the scrapping of the sand core.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: This utility model provides a combined sand core, comprising: A base sand core, comprising a base sand core and a top sand core, wherein the base sand core and the top sand core are stacked sequentially from bottom to top, and each of the base sand core and the top sand core has at least one positioning and fitting groove; and At least one extended sand core is provided with a positioning fitting head that is inserted into the corresponding positioning fitting groove, so that the extended sand core is fitted between the base sand core and the top sand core, and forms a hollow part between the extended sand core and the outer side of the base sand core, which is used to limit the base sand core and the top sand core and form a hollow structure inside the casting.

[0007] In some embodiments, the base sand core further includes at least one support layer sand core, which is stacked from bottom to top between the base sand core and the top sand core.

[0008] In some embodiments, the positioning fitting heads are respectively arranged at the top and bottom ends of the extended sand core, and the positioning fitting groove has an inclination downward toward the central axis of the base sand core.

[0009] In some embodiments, the support layer sand core has a support portion extending to the base sand core, and the base sand core has a matching groove for fitting the support portion, for positioning the support layer sand core.

[0010] In some embodiments, at least one positioning groove is provided on the support layer sand core, and an extension is provided on the positioning fitting head at the top. The extension extends downward and is inserted into the positioning groove to form a multi-level positioning.

[0011] In some embodiments, the positioning groove on the top sand core extends upward and penetrates the top of the top sand core.

[0012] In some embodiments, the extended sand core is provided with embedded parts to provide support strength.

[0013] In some embodiments, the embedded part is water-soluble ceramic fiber or low-temperature molten metal wire.

[0014] In some embodiments, the contact surfaces of the positioning fitting head and the positioning fitting groove have a stepped platform surface, a side mating surface and an inner mating surface, wherein the stepped platform surface and the side mating surface are provided with an adhesive layer for bonding and fixing, and a gap is formed between the positioning fitting head and the inner mating surface of the positioning fitting seat to form an upward exhaust channel.

[0015] In some embodiments, the gap is 0.2-0.5 mm.

[0016] Compared with existing technologies, the combined sand core provided by this utility model separates the base sand core into a base sand core and a top sand core, and then uses an extension sand core. The extension sand core provides positioning for the extension sand core and the top sand core through the positioning mortise and tenon joint of the positioning groove and the positioning mortise and tenon joint, and forms a hollow part. The hollow structure corresponds to the casting casting. The sand core is more refined, and the volume of the separate sand core is smaller. The complex structure is broken down into a simplified separate sand core, which is easier to separate for molding and assembly. Under the positioning mortise and tenon joint combination, it is not only easy to assemble, but also can meet the complex internal structure requirements of casting. It not only avoids the demolding difficulties of integral sand core molding, but also reduces the loss rate of sand core manufacturing. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the combined sand core provided in this embodiment of the utility model; Figure 2This is a schematic diagram of a reducer housing made of a combined sand core according to an embodiment of the present invention; Figure 3 This is a schematic diagram from another perspective of the reducer housing made of the combined sand core provided in this embodiment of the utility model.

[0018] Explanation of reference numerals in the attached figures: 1. Base sand core; 11. Base sand core; 11a. Matching groove; 12. Top sand core; 13. Support layer sand core; 13a. Support part; 13b. Positioning groove; 101. Positioning and fitting groove; 2. Extended sand core; 201. Positioning and fitting head; 201a. Extension part; 201b. Stepped platform surface; 201c. Side mating surface; 201d. Inner mating surface; 201e. Gap; 202. Hollowed-out part; 3. Gearbox housing; 301. Open opening; 302. Hollowed-out structure. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0020] To address the technical problem of integral sand cores breaking or breaking during demolding, leading to their scrapping, this invention provides a modular sand core. This modular sand core is achieved by separating the base sand core into a base sand core and a top sand core, and then combining them with an extension sand core. The extension sand core, through a mortise and tenon joint with a positioning groove and a positioning head, provides positioning for both the extension and top sand cores, forming a hollow section that corresponds to the hollow structure in the casting. This refines the sand core's modularity, making the individual sand cores smaller and simplifying complex structures into more easily separable components. The mortise and tenon joint not only facilitates assembly but also meets the complex internal structural requirements of castings. This design avoids the demolding difficulties associated with integral sand cores and reduces the loss rate during sand core manufacturing.

[0021] It should be noted that the combined sand core described in this utility model is used for, but not limited to, the aluminum housing of the rear axle main reducer. For ease of explanation, this utility model only uses the application of the combined sand core to the aluminum housing of the rear axle main reducer as an example. The principle of the combined sand core applied to other types of equipment is essentially the same as that applied to the aluminum housing of the rear axle main reducer, and will not be elaborated here.

[0022] Please see Figure 1 , Figure 1This is a schematic diagram of the structure of a combined sand core in one embodiment of the present invention. The combined sand core includes a base sand core 1 and at least one extended sand core 2. The base sand core 1 is the basic framework of the entire structure and adopts a layered design. The base sand core 1 includes a base sand core 11 and a top sand core 12. The base sand core 11 and the top sand core 12 are stacked sequentially from bottom to top, serving as the bottom and top of the structure. They together define the main outline of the casting cavity. At least one positioning and fitting groove 101 is provided on both the base sand core 11 and the top sand core 12. The extended sand core 2 is provided with a positioning and fitting head 201 that is inserted into the corresponding positioning and fitting groove 101, so that the extended sand core 2 is fitted into the... A hollow portion 202 is formed between the base sand core 11 and the top sand core 12, and between the base sand core 1 and the outer side of the base sand core 1. This is used to limit the base sand core 11 and the top sand core 12 and form a hollow structure inside the casting. The extended sand core is a key component in forming the complex hollow structure inside the casting, such as a reinforcing rib network. It penetrates and locks each layer of the base sand core through the positioning and fitting heads at both ends. At the same time, it forms the required hollow portion between itself and the outer side of the base sand core. This makes the extended sand core 2 not only form a hollow structure, but also play the role of a structural connector, firmly combining the layered base sand cores into a high-rigidity whole, effectively preventing delamination or displacement caused by the buoyancy of the molten metal during the pouring process.

[0023] For further details, please refer to Figure 1 To further refine the sand core components, the base sand core 1 also includes at least one support layer sand core 13. The support layer sand core 13 is stacked sequentially from bottom to top between the base sand core 11 and the top sand core 12, including the base sand core 11, the top sand core 12, and optionally one or more support layer sand cores 13, which are stacked sequentially from bottom to top. The support layer sand core 13, located between the base and the top, refines the internal cavity structure, forming complex features at different heights within the casting, and provides intermediate support, offering additional and reliable intermediate positioning points for the extended sand core 2, thus constituting a multi-level positioning system.

[0024] Understandably, when the height of the base sand core 1 is too high and the middle structure is complex, it can be divided into layers within the middle height range to make multiple support layer sand cores 13. By disassembling the complex structure and stacking them together, the volume of a single sand core can be made smaller. Therefore, the number of support layer sand cores 13 is not limited here, and layers can be made according to the actual situation.

[0025] In one embodiment, for ease of assembly, please refer to [link / reference]. Figure 1The positioning and fitting heads 201 are respectively arranged at the top and bottom of the extended sand core 2. The positioning and fitting groove 101 has an inclination downward toward the central axis of the base sand core 1. The positioning and fitting groove has an inclination downward toward the central axis of the base sand core, which prevents errors and facilitates assembly. This inclination generates a downward component force when the extended sand core 2 is inserted, guiding it into place smoothly and ensuring that all mating surfaces are in close contact. At the same time, it provides space for the subsequent exhaust channel.

[0026] Understandably, its inclination is matched and set according to the shape and weight of the extended sand core 2 that needs to be manufactured, and there is no single limitation here.

[0027] In one embodiment, please refer to Figure 1 To improve the stacking stability and positioning accuracy of the support layer sand core 13, the support layer sand core 13 is provided with a support portion 13a extending to the base sand core 11. The base sand core 11 has a matching groove 11a for the support portion 13a to fit into, which is used for positioning the support layer sand core 13. The support portion 13a is provided at the lower part of the support layer sand core 11, which can be accurately embedded into the matching groove 11a of the base sand core. This ensures that the sand cores do not move radially when stacked, thus guaranteeing the stacking accuracy of the overall structure.

[0028] In one embodiment, please refer to Figure 1 In order to perform multi-level positioning of each layer of sand core, at least one positioning groove 13b is provided on the support layer sand core 13, and an extension 201a is provided on the positioning fitting head 201 at the top. The extension 201a extends downward and is inserted into the positioning groove 13b to form multi-level positioning. The positioning fitting head 201 at the top of the extension sand core 2 may be provided with an extension 201a. The extension 201a can continue to be inserted downward into the positioning groove 13b of the support layer sand core 13, so that one extension sand core can be positioned with the top, more than one layer of support layer and base sand core at the same time, forming a stable multi-level positioning in three-dimensional space.

[0029] In one embodiment, please refer to Figure 1 In order for the positioning and fitting groove 101 on the top sand core 12 to extend upward and penetrate through the top of the top sand core 12, the positioning and fitting groove 101 on the top sand core 12 penetrates upward, and the gas generated inside the sand core during casting can be smoothly discharged along this path, which greatly reduces the risk of porosity in the casting.

[0030] Furthermore, to bond the sand core without affecting the venting channel, the contact surfaces of the positioning fitting head 201 and the positioning fitting groove 101 have a stepped platform surface 201b, a side mating surface 201c, and an inner mating surface 201d. The stepped platform surface 201b and the side mating surface 201c are coated with an adhesive layer for bonding and fixing. A gap 201e is formed between the positioning fitting head 201 and the inner mating surface 201d of the positioning fitting seat, creating an upward venting channel. This bonds the supporting surface and the contact surfaces on both sides, leaving a clear gap on the inner side to form a venting gap connecting to the positioning fitting groove 101 on the top sand core 12. The stepped platform surface 201b and the side mating surface 201c are used for load-bearing and bonding, ensuring overall strength; while the inner mating surface 201d, which forms the venting channel, is not coated with adhesive, thus ensuring the reliability of the venting function.

[0031] The gap 201e is 0.2-0.5 mm.

[0032] In one embodiment, please refer to Figure 1 In order to improve the structural strength of the extended sand core 2 and reduce the risk of crushing that may occur during its assembly, the extended sand core 2 is provided with embedded parts to provide support strength.

[0033] Furthermore, the embedded part is a water-soluble ceramic fiber or a low-temperature molten metal wire. For particularly long or fragile extended sand cores 2, water-soluble ceramic fibers or low-temperature molten metal wires can be embedded during core making. It provides temporary reinforcement during core making and handling to prevent breakage; after casting, the former can be washed away by water, while the latter melts and does not remain in the casting.

[0034] Understandably, when fabricating the extended sand core 2 that forms the slender hollow section, micro-reinforcing ribs made of water-soluble ceramic fibers or low-temperature molten metal wires are pre-embedded inside. These reinforcing ribs provide additional support strength during the sand core manufacturing and handling stages. This significantly improves the impact and bending resistance of the slender sand core, preventing collapse and breakage.

[0035] This utility model also provides a casting method, including the following steps: Coated sand is used to prepare the sand core that forms the inner cavity of the casting through the hot core box method. Coated sand is a molding material in which a layer of solid phenolic resin film is pre-coated on the surface of sand grains. The coated sand is injected into the electrically heated core box and heated. At a temperature of 180-250℃, the resin film on the surface of the sand grains melts, cross-links, and solidifies, quickly forming a sand core with high strength and precise dimensions. Multiple sand cores are combined and bonded together to form a complete composite sand core. Special core sand adhesive is used to firmly bond the sand core components into a complete sand core assembly. The assembled sand core is impregnated with an alcohol-based refractory coating and dried. The assembled sand core assembly is then coated with the alcohol-based refractory coating, which uses organic solvents such as alcohol as a carrier and is combined with high-refractory aggregates such as zircon powder and graphite. The sand core assembly is immersed in the coating tank, ensuring that all surfaces are evenly covered before being removed. Subsequently, the alcohol vapors volatilized from its surface are directly ignited, causing the coating layer to dry and solidify rapidly within tens of seconds. The alcohol-based coating effectively prevents high-temperature aluminum liquid from seeping into the gaps between the sand cores through two key mechanisms, avoiding the formation of difficult-to-clean sand adhesion defects on the casting surface. The coating forms a hard and dense refractory layer on the surface of the sand core, which greatly improves the chemical inertness and refractoriness of the surface and prevents direct contact between the molten metal and the sand core. When the alcohol burns, a local reducing atmosphere is formed around the sand core, which inhibits the possible oxidation-reduction reaction between the molten metal and the silica sand, fundamentally avoiding the formation of chemical sand adhesion. Furthermore, there is no need for kiln drying, which greatly shortens the production cycle and avoids the problems of moisture absorption and strength reduction of the sand core that may be caused by drying water-based coatings. After drying, the combined sand core is placed into a low-pressure casting mold. Compressed air is introduced to fill the mold with molten metal under pressure, maintain pressure, and solidify to form a casting blank. Under a relatively low pressure, usually 0.01-0.08 MPa, the molten metal smoothly fills the mold cavity from bottom to top along the riser pipe. After filling is completed, a certain pressure is maintained until the casting is completely solidified. After cooling, the casting blank is subjected to sand removal and cleaning treatment to remove the sand core. Most of the sand blocks are shaken out by a vibrating sand removal machine, and then combined with high-pressure water jet, pneumatic tools and other methods to thoroughly clean all the residual sand core material in the complex internal cavity of the casting. After sand removal, the castings undergo post-processing. The gating system of low-pressure casting is usually small and concentrated. A band saw, band saw or special punch is used to remove the sprues and risers on the castings. Manual or robotic tools such as angle grinders and pneumatic chisels are used to remove burrs, flash, and residual metal protrusions at the parting line and core head of the castings. The castings are then subjected to T6 heat treatment to maximize their mechanical properties. The castings are then fed into a shot blasting machine, where a large amount of steel shot is blasted onto the surface of the castings using a high-speed rotating impeller. The processed casting blanks undergo quality inspection. Qualified products are stored in the warehouse for machining. The processed casting blanks undergo comprehensive quality inspection, including but not limited to visual inspection and coordinate measuring machine (CMM) to check for appearance defects and key dimensions, fluorescent penetrant testing or X-ray testing to detect shrinkage porosity, air holes, cracks and other defects on the surface and inside of the casting, spectral analysis to check chemical composition, and mechanical property testing of test bars.

[0036] Specifically, please refer to Figure 2 and Figure 3 In the application of combined sand cores, a reducer housing 3 with a complex internal structure and open top and bottom 301 can be made, and the reducer housing 3 has a complex hollow structure 302 inside.

[0037] The specific embodiments of this utility model described above do not constitute a limitation on the scope of protection of this utility model. Any other corresponding changes and modifications made based on the technical concept of this utility model should be included within the scope of protection of the claims of this utility model.

Claims

1. A composite sand core, characterized in that, include: The base sand core includes a base sand core and a top sand core, which are stacked sequentially from bottom to top. At least one positioning and fitting groove is provided on both the base sand core and the top sand core. as well as At least one extended sand core is provided with a positioning fitting head that is inserted into the corresponding positioning fitting groove, so that the extended sand core is fitted between the base sand core and the top sand core, and forms a hollow part between the extended sand core and the outer side of the base sand core, which is used to limit the base sand core and the top sand core and form a hollow structure inside the casting.

2. The combined sand core according to claim 1, characterized in that, The base sand core also includes at least one support layer sand core, which is stacked between the base sand core and the top sand core from bottom to top.

3. The combined sand core according to claim 1, characterized in that, The positioning and fitting heads are respectively arranged at the top and bottom of the extended sand core, and the positioning and fitting groove has an inclination downward toward the central axis of the base sand core.

4. The combined sand core according to claim 2, characterized in that, The supporting sand core has a supporting portion extending to the base sand core, and the base sand core has a matching groove for fitting the supporting portion, which is used for positioning the supporting sand core.

5. The combined sand core according to claim 2, characterized in that, At least one positioning groove is provided on the support layer sand core, and an extension is provided on the top positioning fitting head. The extension extends downward and is inserted into the positioning groove to form a multi-level positioning.

6. The combined sand core according to claim 1, characterized in that, The positioning groove on the top sand core extends upward and penetrates the top of the top sand core.

7. The combined sand core according to claim 1, characterized in that, The extended sand core is equipped with embedded parts to provide support strength.

8. The combined sand core according to claim 7, characterized in that, The embedded part is water-soluble ceramic fiber or low-temperature molten metal wire.

9. The combined sand core according to claim 1, characterized in that, The contact surfaces of the positioning fitting head and the positioning fitting groove have a stepped platform surface, a side mating surface and an inner mating surface. The stepped platform surface and the side mating surface are provided with an adhesive layer for bonding and fixing. A gap is formed between the positioning fitting head and the inner mating surface of the positioning fitting seat to form an upward exhaust channel.

10. The combined sand core according to claim 9, characterized in that, The gap is 0.2-0.5 mm.

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