A casting mold for exhausting a closed cavity sand core

Abstract

The utility model provides a kind of closed inner cavity sand core exhaust's casting mould, including upper box, middle box, lower box. Upper box, middle box, lower box are sequentially connected to form mould cavity, and sand core is connected in mould cavity. Lower box includes lower box plate and pouring plate. Lower box plate top is equipped with core part, and core part is arranged into mould cavity. Pouring plate is equipped with sprue, and pouring plate is equipped with downrunner near lower box plate side, and downrunner and mould cavity are communicated. The utility model is used for casting casting with closed inner cavity structure. The utility model divides casting mould into upper middle lower structure, simplifies complex core, adapts complex casting, and pouring plate is independently designed, convenient to replace and maintain downrunner, reduce maintenance cost, improve maintenance convenience.

Description

Technical Field

[0001] This utility model belongs to the field of sand casting technology, specifically relating to a casting mold with a closed internal cavity for venting sand core. Background Technology

[0002] Sand casting is a forming process in which molten metal is poured into the cavity of a mold made of molding sand, and after cooling and solidification, a casting of the desired shape is obtained. However, when casting parts with closed internal cavities, a key technical challenge is how to effectively remove the gas within these cavities. If the gas generated in the closed cavity cannot be smoothly and quickly expelled from the mold before the molten metal fills the cavity and solidifies, the gas is trapped inside the closed cavity, forming high-pressure bubbles. As the molten metal solidifies, these bubbles cannot escape, eventually forming pores or shrinkage cavities inside the casting, significantly reducing the casting's density, mechanical properties, and airtightness. Conventional venting methods typically include setting up open venting channels / venting holes, using venting pins / venting ropes, and increasing the permeability of the sand mold. However, these conventional venting methods often fail or have extremely limited effectiveness for completely closed internal cavity structures. The problem is particularly prominent for aluminum alloy castings, as aluminum alloy melts are prone to oxidation and gas absorption, are more likely to entrap gas during pouring, and have a high tendency to precipitate during solidification. Aluminum alloy molten metal requires high pouring temperatures to achieve good filling properties, which exacerbates gas generation in the molding sand (core). Aluminum alloy castings typically have strict requirements for internal quality (such as porosity), mechanical properties, and sealing. Defects caused by poor venting of the closed internal cavity often directly lead to the scrapping of the casting.

[0003] Therefore, the above problems urgently need to be solved. Utility Model Content

[0004] Purpose of the utility model: In order to overcome the above shortcomings, this utility model provides a casting mold with closed internal cavity sand core venting. The casting mold is divided into upper, middle and lower structures, which simplifies complex cores and is suitable for casting complex castings. The pouring plate is designed independently, which facilitates the replacement and maintenance of the gating system. A three-dimensional venting grid is set to form multi-stage venting, which reduces the residual gas rate. The perforated copper tube in the sand core forms a venting channel in the closed internal cavity, which avoids the formation of air holes or shrinkage cavities in the closed internal cavity and improves the quality of the casting.

[0005] Technical Solution: To achieve the above objectives, this utility model provides a casting mold with a closed internal cavity and sand core for venting, comprising an upper mold, a middle mold, and a lower mold. The upper mold, middle mold, and lower mold are connected sequentially to form a mold cavity, within which a sand core is connected. The lower mold includes a lower mold plate and a pouring plate. A core portion is provided at the top of the lower mold plate, extending into the mold cavity. The pouring plate has a gating gate, and a runner is provided on the side of the pouring plate near the lower mold plate, communicating with the mold cavity. This utility model is used for casting castings with a closed internal cavity structure. In this utility model, the connecting surfaces of the upper and middle molds, the connecting surfaces of the middle and lower molds, and the connecting surfaces of the lower mold plate and the pouring plate are respectively provided with positioning bosses and positioning holes. The positioning bosses and positioning holes are used for mold closing guidance to ensure mold closing accuracy; this is a conventional setting and will not be elaborated further. The casting steps of this utility model include: assembling the lower mold plate and the gating plate to form the lower mold; assembling the middle mold and the lower mold; placing a sand core inside; connecting the upper mold to the top of the middle mold and sealing it to form the mold cavity; pouring molten metal from the gating gate into the lower runner and flowing into the mold cavity; and separating the molds after the molten metal has cooled. This utility model divides the casting mold into upper, middle, and lower structures, simplifies complex cores, adapts to casting complex castings, and independently designs the gating plate, facilitating the replacement and maintenance of the gating system, reducing maintenance costs, and improving maintenance convenience.

[0006] Furthermore, in the aforementioned closed-cavity sand core venting casting mold, the sidewall of the sand core is inclined inward from top to bottom in an inverted conical shape. The sand core includes an inner core and an outer core, with the outer core connected to the outside of the inner core and integrally formed with the inner core via connecting posts. The outer core includes a top ring and a support post integrally connected to the lower side of the top ring, with a first vent hole provided from top to bottom on the support post. The inner core is a spirally extending tube extending from top to bottom, with connecting posts located at each pitch position of the inner core. The connecting posts are hollow cylinders, aligned with the first vent hole, and connected to the first vent hole. The spirally extending inner core forms a spiral cavity inside the casting, creating a cooling channel for the casting.

[0007] Furthermore, in the aforementioned closed-cavity sand core venting casting mold, the inner core includes an outer sand section and an inner copper tube. The outer sand section wraps around the outside of the inner copper tube, which has vent holes densely distributed along its outer circumference. The inner copper tube extends into the first vent hole via a connecting post, forming a venting channel. Using the copper tube as the inner core skeleton improves the core's joint strength. During casting, the molten metal envelops the inner core, forming a closed cavity. The vented inner copper tube allows gas within the closed cavity to escape through the first vent hole. The spirally arranged inner core and the first vent hole arranged along the pitch increase the venting surface area, preventing venting failure.

[0008] Furthermore, in the aforementioned closed-cavity sand core venting casting mold, the core is cylindrical, with a first upper gating groove at the top and a middle gating along the axis. After the mold is closed, the upper openings of the first upper gating groove and the middle gating are connected, and the lower opening of the middle gating is connected to the lower gating. The first upper gating groove is radially arranged on the top surface of the core.

[0009] Furthermore, in the aforementioned closed-cavity sand core venting casting mold, the upper mold near the middle mold is provided with a second upper gating channel and a riser channel. The second upper gating channel is radially arranged around the outer periphery of the riser channel. The second upper gating channel corresponds to the first upper gating channel. After the mold is closed, the second upper gating channel and the first upper gating channel form the upper gating system, and the riser channel is connected to the upper end of the middle gating system. The upper and lower gating systems are poured simultaneously, achieving uniform filling of the top of the mold cavity and reducing cold shut defects.

[0010] Furthermore, in the aforementioned closed-cavity sand core venting casting mold, a sprue is provided in the middle section of the core, which is connected to the main runner. The sprue has a Y-shaped forked structure, with the forked portion extending to the outer wall of the core and connecting to the mold cavity. The sprue replenishes the molten metal in the middle section of the mold cavity, reducing cold shut defects, and the Y-shaped forked structure reduces the erosion of the sand core by the molten metal.

[0011] Furthermore, in the aforementioned closed-cavity sand core venting casting mold, the middle box is located outside the core section, and the inner wall of the middle box has a groove. The groove is arranged around the inner wall of the middle box, and the support column is connected to the groove. The groove provides support and limitation for the sand core. The side wall of the groove has a venting chamber, which is arranged from top to bottom and connects to the first venting hole corresponding to the support column. The middle box has a venting nozzle, which connects the venting chamber to the outside of the casting mold and to the venting pipe. The groove enables precise positioning of the sand core, preventing sand core displacement. The venting chamber collects the gas discharged from the first venting hole, achieving centralized venting and reducing external piping. The venting nozzle is connected to a vacuum pump through an venting pipe. Before pouring, the vacuum pump is turned on in advance to create negative pressure in the closed cavity, and then pouring begins. After pouring is completed, the vacuum pump is turned off after the surface of the casting has formed a crust to ensure the quality of the casting.

[0012] Furthermore, in the aforementioned closed-cavity sand core venting casting mold, vent nozzles are arranged in an array around the outer periphery of the casting mold, and the vent nozzles are connected to air pipes. A three-way or five-way solenoid valve is used to connect multiple vent nozzles to a single air pipe, which is then connected to a vacuum pump. The vacuum pump extracts gas from the closed cavity through the multiple vent nozzles, preventing porosity or shrinkage cavities and ensuring casting quality.

[0013] Furthermore, in the aforementioned closed-cavity sand core venting casting mold, the upper box is provided with upper vent holes, which are arranged in an array around the mold cavity axis and are connected to the mold cavity. The upper vent holes include outer ring vent holes and inner ring vent holes, with the outer ring vent holes arranged vertically. The core part is provided with a venting channel, one end of which opens onto the side wall of the core part and communicates with the mold cavity. The end of the venting channel away from the communicating mold cavity is located at the top of the core part. When the mold is closed, the upper opening of the venting channel communicates with the inner ring vent holes.

[0014] Furthermore, in the aforementioned closed-cavity sand core venting casting mold, the middle box and the top surface of the sand core are located on the same plane. An upper venting groove is provided on the parting surface formed by the middle box and the sand core. A lower venting groove is provided on the bottom surface of the middle box, and the upper and lower venting grooves are arranged radially around the center of the casting mold. The upper and lower venting grooves provide supplementary venting paths, and the radial layout prevents gas from mixing within the grooves, further enhancing venting performance.

[0015] As can be seen from the above technical solution, this utility model has the following beneficial effects: The casting mold with a closed-cavity sand core for venting utilizes an upper, middle, and lower structure, simplifying complex cores and adapting to the casting of complex parts. The independently designed gating plate facilitates replacement and maintenance of the gating system, reducing maintenance costs and improving maintenance convenience. The spirally arranged inner core, with an inner copper tube containing vent holes, vents the gas within the closed cavity formed by the molten metal surrounding the inner core, preventing defects such as porosity, backfiring, and poor filling. This improves the quality of the castings. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the casting mold for the closed-cavity sand core venting of this utility model. Figure 2 This is an axial sectional view of the casting mold for the closed-cavity sand core venting of this utility model; Figure 3 This is a schematic diagram of the structure of the sand core; Figure 4 As shown Figure 2 A magnified view of a portion of the image; Figure 5 This is a structural schematic diagram of the lower box plate; Figure 6 This is a schematic diagram of the upper box structure; Figure 7 This is a top view of the structure of the middle box; Figure 8 As shown Figure 7 A magnified view of a portion of the image; Figure 9 This is a structural schematic diagram of the middle box viewed from below; Figure 10 The casting having a closed internal cavity structure; Figure 11 As shown Figure 10 Axial sectional view.

[0017] In the diagram: 1. Upper box, 11. Second upper runner groove, 12. Riser groove, 13. Upper vent, 131. Outer ring vent, 132. Inner ring vent, 2. Middle box, 21. Groove, 211. Venting chamber, 23. Venting nozzle, 24. Upper vent groove, 25. Lower vent groove, 3. Lower box, 31. Lower box plate, 311. Core part, 3111. First upper runner groove, 3112. Middle runner, 3113. Support runner, 3114. Air guide channel, 32. Casting plate, 321. Sprue, 322. Lower runner, 4. Mold cavity, 5. Sand core, 51. Inner core, 511. Outer sand part, 512. Inner copper tube, 52. Outer core, 521. Top ring, 522. Support column, 5221. First vent, 53. Connecting column. Detailed Implementation Example

[0018] like Figure 1-2 The mold shown is a closed-cavity sand core venting casting mold, comprising an upper mold 1, a middle mold 2, and a lower mold 3. The upper mold 1, middle mold 2, and lower mold 3 are sequentially connected to form a mold cavity 4, within which a sand core 5 is connected. The lower mold 3 includes a lower mold plate 31 and a casting plate 32. A core portion 311 is provided at the top of the lower mold plate 31, extending into the mold cavity 4. The casting plate 32 has a gate 321 and a runner 322 on the side of the casting plate 32 near the lower mold plate 31, which communicates with the mold cavity 4. The connecting surfaces of the upper mold 1 and middle mold 2, the middle mold 2 and lower mold 3, and the connecting surfaces of the lower mold plate 31 and casting plate 32 are respectively provided with positioning bosses and positioning holes. These positioning bosses and positioning holes are used for mold closing guidance to ensure mold closing accuracy; this is a standard feature and will not be elaborated further.

[0019] like Figure 3 The casting mold shown is for a closed-cavity sand core with venting. The sidewall of the sand core 5 is inclined inward from top to bottom and is shaped like an inverted cone. The sand core 5 includes an inner core 51 and an outer core 52. The outer core 52 is connected to the outside of the inner core 51 and is integrally formed with the inner core 51 via a connecting post 53. The outer core 52 includes a top ring 521 and a support post 522 integrally connected to the lower side of the top ring 521. The support post 522 has a first vent hole 5221 from top to bottom. The inner core 51 is a tube extending spirally from top to bottom. The connecting post 53 is located at each pitch position of the inner core 51. The connecting post 53 is a hollow cylinder and is aligned with the first vent hole 5221. The connecting post 53 and the first vent hole 5221 are connected. The spirally extending inner core 51 forms a spiral cavity inside the casting, forming a cooling channel for the casting.

[0020] like Figure 4The casting mold for a closed-cavity sand core with venting shown has an inner core 51 comprising an outer sand portion 511 and an inner copper tube 512. The outer sand portion 511 is arranged to wrap around the outside of the inner copper tube 512. The inner copper tube 512 is provided with vent holes, which are densely arranged along the outer circumference of the inner copper tube 512. The inner copper tube 512 extends into the first vent hole 5221 through a connecting post 53, forming a venting channel. The copper tube 512 serves as the skeleton of the inner core 51, improving the joint strength of the inner core 51. During the casting process, the molten metal surrounds the inner core 51 to form a closed inner cavity, and the inner copper tube 512 with vent holes vents the gas in the closed inner cavity out through the first vent hole 5221.

[0021] like Figure 5 The casting mold for closed-cavity sand core venting shown has a cylindrical core portion 311. The top of the core portion 311 has a first upper gating groove 3111, and the core portion 311 has a middle gating 3112 along its axis. After the mold is closed, the upper openings of the first upper gating groove 3111 and the middle gating 3112 are connected, and the lower opening of the middle gating 3112 is connected to the lower gating 322. The first upper gating groove 3111 is arranged radially on the top surface of the core portion 311.

[0022] In this embodiment, in the aforementioned closed-cavity sand core venting casting mold, the core portion 311 has a sprue 3113 in the middle section. The sprue 3113 is connected to the central runner 3112. The sprue 3113 is designed with a Y-shaped fork structure, and the fork of the sprue 3113 extends to the outer wall of the core portion 311 and is connected to the mold cavity 4. The sprue 3113 replenishes the molten metal in the middle section of the mold cavity, reducing cold shut defects. The Y-shaped fork structure reduces the scouring of the sand core by the molten metal.

[0023] like Figure 6 The casting mold with a closed internal cavity and sand core venting shown has a second upper gating channel 11 and a riser channel 12 on the side of the upper box 1 near the middle box 2. The second upper gating channel 11 is radially arranged around the outer periphery of the riser channel 12. The second upper gating channel 11 and the first upper gating channel 3111 are correspondingly arranged. After the mold is closed, the second upper gating channel 11 and the first upper gating channel 3111 form the upper gating, and the riser channel 12 is connected to the upper end of the middle gating 3112. The upper gating and lower gating 322 are poured simultaneously to achieve uniform filling of the top of the mold cavity and reduce cold shut defects.

[0024] In this embodiment, the upper box 1 is provided with upper vent holes 13, which are arranged in an array around the axis of the mold cavity 4 and are connected to the mold cavity 4. The upper vent holes 13 include outer ring vent holes 131 and inner ring vent holes 132, with the outer ring vent holes 131 being vertically arranged. The core part 311 is provided with a venting channel 3114, one end of which is open on the side wall of the core part 311 and connected to the mold cavity 4. The end of the venting channel 3114 away from the connected mold cavity 4 is located at the top of the core part 311. When the box is closed, the upper opening of the venting channel 3114 is connected to the inner ring vent holes 132.

[0025] like Figure 7-8 The casting mold with a closed internal cavity for sand core venting shown has a middle box 2 located outside the core part 311. The inner wall of the middle box 2 has a groove 21, which surrounds the inner wall of the middle box 2. A support column 522 is connected to the groove 21, which provides support and positioning for the sand core 5. The side wall of the groove 21 has a venting chamber 211, arranged from top to bottom, which connects to the first vent hole 5221 on the corresponding support column 522. The middle box 2 has a vent nozzle 23, which connects the venting chamber 211 to the outside of the casting mold and to an venting pipe. The groove 21 enables precise positioning of the sand core 5, preventing displacement. The venting chamber 211 collects the gas discharged from the first vent hole 5221, achieving centralized venting and reducing external piping. The exhaust nozzle 23 is connected to the vacuum pump via an exhaust pipe. Before pouring, the vacuum pump is turned on in advance to create a negative pressure in the sealed inner cavity, and then pouring begins. After pouring is completed, the vacuum pump is turned off after the surface of the casting has formed a crust to ensure the quality of the casting.

[0026] In this embodiment, exhaust nozzles 23 are arranged in an array around the outer periphery of the casting mold, and the exhaust nozzles 23 are connected to air pipes. Multiple three-way valves or five-way valves are used to connect multiple exhaust nozzles 23 to a single air pipe, which is connected to a vacuum pump. The vacuum pump draws gas from the closed inner cavity through multiple exhaust nozzles 23, avoiding porosity or shrinkage cavities and ensuring the quality of the casting.

[0027] like Figure 9 The casting mold shown has a closed-cavity sand core venting design, with the top surfaces of the middle box 2 and the sand core 5 on the same plane. An upper venting groove 24 is provided on the parting surface formed by the middle box 2 and the sand core 5. A lower venting groove 25 is provided on the bottom surface of the middle box 2. The upper and lower venting grooves 24 and 25 are arranged radially around the center of the casting mold. The depth of the upper and lower venting grooves 24 and 25 is less than 0.5 mm. To prevent fire, the casting mold is buried during pouring. The upper and lower venting grooves 24 and 25 provide supplementary venting paths, and the radial layout prevents gas from mixing within the grooves, further enhancing venting performance.

[0028] This invention is used for casting castings with a closed internal cavity structure. First, a sand core 5 needs to be poured. An inner copper tube 512 is machined according to the inner cavity of the casting. Ventilation holes are machined on the surface of the inner copper tube 512, ensuring that the holes are densely distributed on the surface of the inner copper tube 512. The diameter of the vent holes is selected as 0.5 mm. The opening of the inner copper tube 512 is positioned externally according to the location of the first vent hole 5221, ensuring that the inner copper tube 5 extends beyond the sand core to the surface of the outer core 52. The inner copper tube 512 is placed in the sand core mold 5, so that the opening of the inner copper tube 512 extends to the outer wall of the sand mold. Then, the mold is closed, the core is injected, and dried. In the resulting sand core 5, the inner copper tube 512 is completely enclosed by the outer sand portion 511.

[0029] Begin casting. Select a suitable sand box and place the casting plate 31, lower box plate 31, and middle box 2 into the sand box in sequence. Insert vent plugs into the vent nozzles 23, then place the sand core 5. Connect the upper box 1 to the top of the middle box 2 to seal it, forming the mold cavity 4. The vent plug is selected as a hollow cylinder with a diameter of 12mm and a height of 8mm. Connect an air pipe to the outside of the vent nozzle 23. Heat-connect the air pipe and the vent plug to prevent the air pipe from falling off. The air pipe is centrally connected to a separate air pipe through a three-way valve or a five-way valve. Before casting, connect the separate air pipe to a compressed air pipe and blow air into the mold cavity 4 (control the air pressure to avoid sand core damage; <0.5Mpa is recommended) to avoid venting channel blockage.

[0030] Before pouring begins, the separate air pipe and compressed air pipe are separated and connected to the vacuum pump. The vacuum pump extracts the gas inside the inner copper tube 512 through the separate air pipe, creating a negative pressure inside the inner copper tube 512. The gas outside the inner core 51 enters the inner copper tube 512 through the gap of the outer sand part 511 and the vent holes on the surface of the inner copper tube 512. The vacuuming time should be maintained for 1 minute or more.

[0031] Then, pouring begins. The molten metal (aluminum) is poured from gate 321 into the lower sprue 322. Part of the molten metal in the lower sprue 322 flows into the bottom of the mold cavity 4, and part flows upward into the middle sprue 3112. Part of the molten metal in the middle sprue 3112 flows into the middle of the mold cavity 4 through the Y-shaped branch sprue 3113, and part flows into the top of the mold cavity 4 through the upper sprue formed by the second upper sprue groove 11 and the first upper sprue groove 3111. During the pouring process, the molten metal envelops the inner core 51, forming a closed inner cavity. The vacuum pump continuously evacuates the cavity, and the gas inside is extracted by the vacuum pump through the inner copper tube 512. The gas inside the mold cavity 4 is discharged through the upper vent 13, upper vent groove 24, and lower vent groove 25. After pouring, the vacuum pump must be kept running until a crust forms on the surface of the casting (the crusting time is determined according to the casting wall thickness, which can be inferred by those skilled in the art based on the actual situation), then the vacuum pump is turned off.

[0032] After pouring, the casting is separated into its own container and removed. The inner core 51 remains attached to the inner cavity of the casting, requiring separation. This can be achieved by simultaneously heating the casting and the inner core 51 to burn off the adhesive in the outer sand section 511, turning the sand into loose sand. High-pressure water is then injected into the inner cavity of the casting to clean away any remaining sand. The inner copper tube 512, being a thin-walled copper tube, is directly extracted from the inner cavity of the casting to obtain a complete casting.

[0033] The above embodiments are exemplary and are intended to illustrate the technical concept and features of this utility model, so that those skilled in the art can understand the content of this utility model and implement it accordingly. They should not be construed as limiting the scope of protection of this utility model. All equivalent changes or modifications made in accordance with the spirit and essence of this utility model should be covered within the scope of protection of this utility model.

Claims

1. A casting mold with a closed internal cavity for sand core venting, characterized in that: The mold includes an upper box (1), a middle box (2), and a lower box (3); the upper box (1), the middle box (2), and the lower box (3) are connected in sequence to form a mold cavity (4), and a sand core (5) is connected inside the mold cavity (4); the lower box (3) includes a lower box plate (31) and a casting plate (32); the lower box plate (31) has a core part (311) at the top, and the core part (311) extends into the mold cavity (4); the casting plate (32) has a gate (321), and the casting plate (32) has a runner (322) on the side near the lower box plate (31), and the runner (322) is connected to the mold cavity (4).

2. The casting mold for closed-cavity sand core venting according to claim 1, characterized in that: The sidewall of the sand core (5) is inclined inward from top to bottom and is set as an inverted cone shape; the sand core (5) includes an inner core (51) and an outer core (52), the outer core (52) is connected to the outside of the inner core (51), and the outer core (52) is integrally set with the inner core (51) through a connecting post (53); the outer core (52) includes a top ring (521), and a support post (522) integrally connected to the lower side of the top ring (521), the support post (522) is provided with a first exhaust hole (5221) from top to bottom; the inner core (51) is set as a tube extending spirally from top to bottom, the connecting post (53) is set at each pitch position of the inner core (51), the connecting post (53) is set as a hollow column, the connecting post (53) is aligned with the first exhaust hole (5221), and the connecting post (53) and the first exhaust hole (5221) are connected.

3. The casting mold for closed-cavity sand core venting according to claim 2, characterized in that: The inner core (51) includes an outer sand part (511) and an inner copper tube (512). The outer sand part (511) is wrapped around the outside of the inner copper tube (512). The inner copper tube (512) is provided with vent holes. The vent holes are densely arranged along the outer periphery of the inner copper tube (512). The inner copper tube (512) extends into the first exhaust hole (5221) through the connecting post (53) to form an exhaust channel.

4. The casting mold for closed-cavity sand core venting according to claim 1, characterized in that: The core part (311) is cylindrical, and the top of the core part (311) is provided with a first upper gating groove (3111). The core part (311) is provided with a middle gating (3112) along the axis. After the mold is closed, the upper openings of the first upper gating groove (3111) and the middle gating (3112) are connected, and the lower opening of the middle gating (3112) is connected with the lower gating (322). The first upper gating groove (3111) is radially arranged on the top surface of the core part (311).

5. The casting mold for closed-cavity sand core venting according to claim 1, characterized in that: The upper box (1) is provided with a second upper gating channel (11) and a riser channel (12) on the side near the middle box (2). The second upper gating channel (11) is radially arranged on the outer periphery of the riser channel (12). The second upper gating channel (11) and the first upper gating channel (3111) are arranged correspondingly. After the boxes are closed, the second upper gating channel (11) and the first upper gating channel (3111) form an upper gating channel. The riser channel (12) is connected to the upper end of the middle gating channel (3112).

6. The casting mold for closed-cavity sand core venting according to claim 4, characterized in that: The core part (311) is provided with a sprue (3113) in the middle section. The sprue (3113) is connected to the middle sprue (3112). The sprue (3113) is provided with a Y-shaped forked structure. The forked part of the sprue (3113) extends to the outer wall of the core part (311) and is connected to the mold cavity (4).

7. The casting mold for closed-cavity sand core venting according to claim 2, characterized in that: The middle box (2) is located outside the core part (311). The inner wall of the middle box (2) is provided with a groove (21). The groove (21) is arranged around the inner wall of the middle box (2). The support column (522) is connected in the groove (21). The groove (21) provides support and limit for the sand core (5). The side wall of the groove (21) is provided with an exhaust chamber (211). The exhaust chamber (211) is arranged from top to bottom. The exhaust chamber (211) connects to the first exhaust hole (5221) provided on the corresponding support column (522). The middle box (2) is provided with an exhaust nozzle (23). The exhaust nozzle (23) connects the exhaust chamber (211) and the outside of the casting mold. The exhaust nozzle (23) is connected to the air pipe.

8. The casting mold for closed-cavity sand core venting according to claim 7, characterized in that: The exhaust nozzles (23) are arranged in an array around the outer periphery of the casting mold, and the multiple exhaust nozzles (23) are connected to the air pipe.

9. The casting mold for closed-cavity sand core venting according to claim 8, characterized in that: The upper box (1) is provided with an upper vent hole (13), the upper vent hole (13) is arranged in an array around the axis of the mold cavity (4), and the upper vent hole (13) and the mold cavity (4) are connected; The upper vent (13) includes an outer vent (131) and an inner vent (132), with the outer vent (131) being vertically arranged; the core (311) is provided with an air guide channel (3114), one end of which is open on the side wall of the core (311) and connected to the mold cavity (4); the end of the air guide channel (3114) away from the connected mold cavity (4) is located at the top of the core (311); when the mold is closed, the upper opening of the air guide channel (3114) is connected to the inner vent (132).

10. The casting mold for closed-cavity sand core venting according to claim 1, characterized in that: The top surfaces of the middle box (2) and the sand core (5) are on the same plane; the parting surface formed by the middle box (2) and the sand core (5) is provided with an upper venting groove (24); the bottom surface of the middle box (2) is provided with a lower venting groove (25), and the upper venting groove (24) and the lower venting groove (25) are respectively arranged radially around the center of the casting mold.

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