High-quality metal material gear box casting device and method

Abstract

The application discloses a high-quality metal material gear box casting device and method, which comprises a heat-insulating sand box, a female die sand mold is slidably arranged on the inner wall of the heat-insulating sand box, a male die sand mold is assembled in the female die sand mold, a heat-insulating cylinder is slidably connected at the gear box shaft hole forming position of the female die sand mold and the male die sand mold, a non-contact lower rotary pushing mechanism is fixedly installed in the heat-insulating cylinder, a plurality of heating material conveying pipes are fixedly embedded in the male die sand mold, the bottom end of the heating material conveying pipe is communicated with the inner wall of the gear box shaft hole forming position of the female die sand mold, and the top end of the heating material conveying pipe is communicated with the inner wall of the side part of the female die sand mold; and a heat-insulating cover is covered on the top port of the heat-insulating sand box. The application relates to the technical field of gear boxes. The application solves the problems of sufficient flow of casting liquid at the gear box shaft hole forming position, elimination of flow dead zones and air hole defects, and inhibition of the composition unevenness caused by segregation.

Description

Technical Field

[0001] This invention relates to the field of gearbox technology, and in particular to a high-quality metal gearbox casting apparatus and method. Background Technology

[0002] In the field of metal casting, gearboxes are the core components of transmission systems. Gearboxes have complex structures, and their shaft holes usually have a large thickness ratio and deep cavity structure, which puts extremely high requirements on the density, uniformity and mechanical properties of the castings.

[0003] Currently, gearbox casting equipment typically uses sand casting process for direct casting. The flow path of the casting liquid during filling is relatively long, and slow or stagnant flow is likely to occur in the end area. Dead corners of the gearbox and shaft hole areas are prone to air entrapment and air trapping, which eventually form surface bubbles or internal porosity defects. This not only reduces the density of the casting, but also directly affects the sealing performance and service life of the gearbox after subsequent machining. Meanwhile, the stagnation of the casting liquid inevitably leads to micro-segregation and macro-segregation. Studies show that point-like segregation often occurs in gearbox billets, with significant positive segregation of alloying elements such as C, Cr, and Mn within the segregation points. This as-cast segregation evolves into banded defects during subsequent hot working, and coarse segregations with a bandwidth exceeding 40 μm are difficult to eliminate through conventional heat treatment. Segregation defects can cause uneven deformation of the gearbox during heat treatment. How to achieve sufficient flow of the casting liquid at the shaft hole forming area, eliminate flow dead zones and porosity defects, and simultaneously suppress the compositional inhomogeneity caused by segregation is a technical challenge that urgently needs to be overcome in this field. Therefore, we propose a high-quality metal material gearbox casting device and method. Summary of the Invention

[0004] To address the issues of ensuring sufficient flow of casting liquid at the gearbox shaft hole forming area, eliminating flow dead zones and porosity defects, and suppressing compositional unevenness caused by segregation, the present invention aims to provide a high-quality metal gearbox casting apparatus and method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a high-quality metal material gearbox casting device, comprising a heat-insulating sand box, a concave sand mold slidably fitted on the inner wall of the heat-insulating sand box, a convex sand mold assembled in the concave sand mold, a heat-insulating cylinder slidably connected to the gearbox shaft hole forming parts of the concave sand mold and the convex sand mold, a non-contact downward rotary pushing mechanism fixedly installed in the heat-insulating cylinder, a plurality of heated material conveying pipes fixedly embedded in the convex sand mold, the bottom end of the heated material conveying pipes communicating with the inner wall of the gearbox shaft hole forming part of the concave sand mold, and the top end of the heated material conveying pipes communicating with the inner wall of the side part of the concave sand mold; a heat-insulating cover is closed at the top port of the heat-insulating sand box.

[0006] Preferably, the gap between the concave sand mold and the convex sand mold after assembly is the gearbox forming cavity. The bottom of the concave sand mold is provided with a gearbox shaft hole forming cavity. A circular hole is opened at the center of the bottom of the gearbox shaft hole forming cavity. The inner wall of the circular hole and the outer wall at the bottom port of the heat insulation cylinder are slidably connected.

[0007] Preferably, the bottom of the punch sand mold is provided with a gearbox shaft hole forming mold core, and a cylindrical hole is opened on the punch sand mold. The cylindrical hole passes through the axis of the gearbox shaft hole forming mold core. The inner wall of the cylindrical hole is slidably sleeved on the outer wall of the heat insulation cylinder, and the end face at the bottom port of the cylindrical hole is in contact with the bottom of the gearbox shaft hole forming cavity.

[0008] Preferably, the heating conveying pipe is made of ceramic material, and two spiral coils are fixedly sleeved on the outer wall of the heating conveying pipe. The two spiral coils have opposite spiral directions and are orthogonally arranged. The two spiral coils are coaxially nested, and each of the two spiral coils is electrically connected to an AC power source that can provide a phase difference of 90°, so as to generate an electromagnetic field with an axially propelling wave component inside the heating conveying pipe, thereby driving the molten metal inside the pipe to flow upward in a directional direction. The bottom port of the heating conveying pipe is connected to the inner wall of the gearbox shaft hole forming cavity near the bottom.

[0009] Preferably, the non-contact downward rotary push mechanism includes an electric push rod fixedly installed in the heat insulation cylinder, a motor fixedly installed at the bottom of the telescopic end of the electric push rod, a cylindrical block fixedly connected to the output shaft at the bottom of the motor, and a plurality of electromagnetic pole posts arranged in a ring array fixedly installed on the outer wall of the cylindrical block, with the magnetic poles of the electromagnetic pole posts arranged radially relative to the axis of the cylindrical block.

[0010] Preferably, the heat insulation cover has a casting hole and a vent hole, which are connected to the gearbox molding cavity, and the heat insulation cover is pressed onto the top surface of the concave mold and the convex mold.

[0011] A method for using a high-quality metal gearbox casting device includes the following steps: S1. Place the concave mold into the heat insulation sand box, insert the heat insulation cylinder into the concave mold, then insert the convex mold onto the heat insulation cylinder, cover with the heat insulation cover, and fix the heat insulation cover. S2, casting liquid, non-contact downward rotary push mechanism operates, pushing the casting liquid at the gearbox shaft hole forming area downward in a spiral posture; S3, the casting liquid at the gearbox shaft hole forming point enters the heating conveying pipe, which continuously heats the casting liquid in the heating conveying pipe and simultaneously conveys the casting liquid obliquely upwards back to the forming cavity at the side of the concave mold sand mold, and then returns from the forming cavity at the horizontal forming point to the forming cavity at the gearbox shaft hole forming point, so that the casting liquid circulates.

[0012] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: 1. In this invention, the molten metal drawn from the bottom of the shaft hole is heated in the heating conveying pipe and transported back to the side of the sand mold, and then returned to the shaft hole forming area. The casting liquid circulates, so that every dead corner of the gearbox can be fully formed by the casting liquid, avoiding cavitation and effectively eliminating the uneven composition caused by segregation.

[0013] 2. In this invention, the downward spiral flow helps to bring the crystallized dendrite fragments on the surface of the shaft hole into the interior of the melt, increasing the nucleation core and refining the grains; at the same time, the forced convection can effectively break up the growing dendrites, prevent the columnar crystals from becoming too developed, promote the formation of equiaxed crystals, and significantly improve the mechanical properties of the shaft hole.

[0014] 3. In this invention, after the gearbox is formed, the spiral coil is energized to heat and melt the solidified waste inside, thereby separating the waste from the gearbox and making it easier for the finished gearbox to be removed from the gearbox forming cavity of the concave mold sand mold. Attached Figure Description

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Figure 1 This is a schematic cross-sectional view of the entire structure of the present invention; Figure 2 This is a schematic diagram of the structure of the concave mold sand mold of the present invention; Figure 3 This is a schematic diagram of the punch sand mold structure of the present invention; Figure 4 This is a schematic diagram of the non-contact downward rotary push mechanism of the present invention; Figure 5 This is a schematic diagram of the structure of the heat insulation cover of the present invention.

[0016] In the diagram: 1. Insulating sand box; 2. Cavity sand mold; 21. Gearbox shaft hole forming cavity; 22. Round hole; 3. Punch sand mold; 31. Gearbox shaft hole forming mold core; 32. Cylindrical hole; 4. Insulating cylinder; 5. Non-contact downward rotary push mechanism; 51. Electric push rod; 52. Motor; 53. Cylindrical block; 54. Electrode column; 6. Heated conveying pipe; 61. Spiral coil; 7. Insulating cover; 71. Casting hole; 72. Vent hole. Detailed Implementation

[0017] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0018] Please see Figures 1 to 5It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0019] This invention provides a technical solution: the core supporting component of a high-quality metal gearbox casting device is a heat-insulating sand box 1, which has a hollow cavity inside and a smooth sliding surface machined on the inner wall. The concave mold 2 is adapted to slide on the inner wall of the heat-insulating sand box 1, ensuring that the concave mold 2 can slide smoothly along the axial direction of the heat-insulating sand box 1. At the same time, the heat insulation characteristics of the heat-insulating sand box 1 are used to reduce the rapid loss of internal heat during the casting process and ensure that the casting liquid is in a stable temperature environment.

[0020] The concave sand mold 2 has an assembly groove that is adapted to the convex sand mold 3. The convex sand mold 3 is assembled in the assembly groove of the concave sand mold 2. After the two are assembled, the gap formed between the outer wall of the convex sand mold 3 and the inner wall of the concave sand mold 2 is the gearbox forming cavity. The shape of the forming cavity is completely matched with the outer contour of the gearbox to be cast, and is used to realize the forming of the main structure of the gearbox.

[0021] A heat insulation cylinder 4 is slidably connected to the gearbox shaft hole forming area of ​​the concave sand mold 2 and the convex sand mold 3. The bottom of the concave sand mold 2 is provided with a gearbox shaft hole forming cavity 21, which is used to form the shaft hole structure of the gearbox. A circular hole 22 is opened at the center of its bottom. The inner diameter of the circular hole 22 is adapted to the outer diameter of the bottom port of the heat insulation cylinder 4, so that the bottom port of the heat insulation cylinder 4 can be slidably sleeved on the inner wall of the circular hole 22, realizing the precise positioning and sliding fit between the heat insulation cylinder 4 and the concave sand mold 2.

[0022] The bottom of the punch sand mold 3 corresponds to the position of the gearbox shaft hole forming cavity 21, and a gearbox shaft hole forming mold core 31 is provided. The gearbox shaft hole forming mold core 31 is embedded in the gearbox shaft hole forming cavity 21 and cooperates with the gearbox shaft hole forming cavity 21 to form a complete gearbox shaft hole forming structure. A cylindrical hole 32 is opened on the punch sand mold 3. The cylindrical hole 32 passes through the axis of the gearbox shaft hole forming mold core 31. The inner wall of the cylindrical hole 32 is slidably sleeved with the outer wall of the heat insulation cylinder 4, and the end face at the bottom port of the cylindrical hole 32 is blocked with the bottom of the gearbox shaft hole forming cavity 21, which further improves the assembly stability of the punch sand mold 3, the heat insulation cylinder 4, and the concave sand mold 2.

[0023] A non-contact downward spiral pushing mechanism 5 is fixedly installed in the heat insulation cylinder 4. This non-contact downward spiral pushing mechanism 5 is used to achieve non-contact spiral pushing of the casting liquid at the gearbox shaft hole forming area, avoiding contamination caused by direct contact with the casting liquid, while ensuring uniform filling of the casting liquid. Specifically, the non-contact downward spiral pushing mechanism 5 includes an electric push rod 51 fixedly installed in the heat insulation cylinder 4. The fixed end of the electric push rod 51 is fixedly connected to the inner wall of the heat insulation cylinder 4 to ensure the stability of the electric push rod 51 during operation.

[0024] A motor 52 is fixedly installed at the bottom of the telescopic end of the electric push rod 51. The motor 52 is coaxially arranged with the telescopic end of the electric push rod 51. The electric push rod 51 can drive the motor 52 to move up and down along the axial direction of the heat insulation cylinder 4, thereby realizing the lifting and lowering adjustment of the motor 52. A cylindrical block 53 is fixedly connected to the output shaft at the bottom of the motor 52. The cylindrical block 53 is coaxial with the output shaft of the motor 52. The motor 52 can drive the cylindrical block 53 to rotate around its own axis.

[0025] A plurality of electromagnetic poles 54 arranged in a ring array are fixedly installed on the outer wall of the cylindrical block 53, with the magnetic poles of the electromagnetic poles 54 arranged radially relative to the axis of the cylindrical block 53. When it is necessary to push the casting liquid, the electric push rod 51 drives the motor 52 to descend, bringing the cylindrical block 53 and the electromagnetic poles 54 closer to the casting liquid in the gearbox shaft hole forming cavity 21. Then, the motor 52 drives the cylindrical block 53 to rotate, and at the same time, the electromagnetic poles 54 are energized to generate magnetism. Under the action of magnetism, the casting liquid at the gearbox shaft hole forming area is pushed downward in a spiral posture. After the pushing is completed, the electric push rod 51 raises the motor 52 and the cylindrical block 53, and at the same time, the electromagnetic poles 54 are de-energized to prevent the casting liquid from flowing back when it is pulled up.

[0026] Several heating conveying pipes 6 are fixedly embedded in the punch sand mold 3. The number of heating conveying pipes 6 can be reasonably set according to the size of the gearbox forming cavity and the circulation requirements of the casting liquid, preferably 4-8, and they are distributed in a ring array in the punch sand mold 3 to ensure uniform circulation of the casting liquid. The bottom end of the heating conveying pipe 6 is connected to the inner wall of the gearbox shaft hole forming area of ​​the concave sand mold 2, specifically to the inner wall of the gearbox shaft hole forming cavity 21 near the bottom, so that the casting liquid in the gearbox shaft hole forming cavity 21 can enter the heating conveying pipe 6; the top end of the heating conveying pipe 6 is connected to the inner wall of the side of the concave sand mold 2, so that the heated casting liquid can flow back to the side area of ​​the gearbox forming cavity to form a complete circulation loop.

[0027] Two spiral coils 61 are fixedly sleeved on the outer wall of the heating conveying pipe 6. The two spiral coils 61 have opposite spiral directions and are orthogonally arranged, and are coaxially nested. Each of the two spiral coils 61 is electrically connected to an AC power source providing a 90° phase difference. When the AC power is turned on, the two spiral coils 61 generate an alternating magnetic field. Due to the 90° phase difference and opposite spiral directions, their superposition generates an electromagnetic field with an axially propelling wave component inside the heating conveying pipe 6. This electromagnetic field not only continuously heats the casting liquid inside the heating conveying pipe 6, preventing solidification during transport, but also drives the molten metal to flow upwards in a directional direction, achieving automatic conveying of the casting liquid without the need for additional conveying power components, thus simplifying the device structure.

[0028] A heat-insulating cover 7 is fitted over the top port of the heat-insulating sand box 1. The heat-insulating cover 7 adopts the same heat-insulating design as the heat-insulating sand box 1, and is used to seal the top port of the heat-insulating sand box 1 to reduce internal heat loss and prevent external impurities from entering the gearbox molding cavity, thus ensuring casting quality. The heat-insulating cover 7 has a casting hole 71 and a vent hole 72. The casting hole 71 is used to inject casting liquid into the gearbox molding cavity, and its position corresponds to the top feeding area of ​​the gearbox molding cavity, which facilitates the rapid and uniform filling of casting liquid. The vent hole 72 is used to expel air in the gearbox molding cavity and gas generated during the heating process of the casting liquid, so as to avoid gas residue in the casting liquid forming pores and affecting the molding quality of the gearbox. Both the casting hole 71 and the vent hole 72 are connected to the gearbox molding cavity, and after the heat-insulating cover 7 is closed, its bottom end face presses against the top surface of the concave mold 2 and the convex mold 3, further fixing the concave mold 2 and the convex mold 3.

[0029] Both the concave sand mold 2 and the convex sand mold 3 are embedded with heating pipes and cooling pipes for heat preservation during casting and cooling during solidification. Their structures will not be described in detail.

[0030] Method of using high-quality metal gearbox casting equipment This embodiment provides a method for using a high-quality metal gearbox casting device, which employs the high-quality metal gearbox casting device described in Embodiment 1 above, and specifically includes the following steps: S1, Assembly of the device: Insert the concave sand mold 2 into the heat insulation sand box 1, so that the outer wall of the concave sand mold 2 slides and fits against the inner wall of the heat insulation sand box 1, ensuring that the concave sand mold 2 is installed in place; then insert the heat insulation cylinder 4 into the concave sand mold 2, so that the bottom end of the heat insulation cylinder 4 slides and fits against the inner wall of the round hole 22 of the concave sand mold 2, realizing the positioning and installation of the heat insulation cylinder 4; then insert the convex sand mold 3 into the heat insulation cylinder 4 through the cylindrical hole 32, so that the convex sand mold 3 is assembled in the assembly groove of the concave sand mold 2, and the end face at the bottom end of the cylindrical hole 32 is in contact with the bottom of the gearbox shaft hole forming cavity 21; finally, cover the heat insulation cover 7, so that the heat insulation cover 7 presses against the top surface of the concave sand mold 2 and the convex sand mold 3, and fix the heat insulation cover 7 with bolts and other fasteners to complete the assembly of the entire device.

[0031] S2, Casting liquid delivery: Casting liquid is poured into the gearbox forming cavity through the casting hole 71 on the heat insulation cover 7. During the casting process, the non-contact downward rotating push mechanism 5 is started simultaneously. The electric push rod 51 drives the motor 52 to descend, so that the cylindrical block 53 and the electromagnetic pole 54 approach the casting liquid in the gearbox shaft hole forming cavity 21. The motor 52 drives the cylindrical block 53 to rotate, and at the same time, the electromagnetic pole 54 is energized to generate magnetism. Under the action of magnetism, the casting liquid at the gearbox shaft hole forming area is pushed downward in a spiral posture.

[0032] S3, Circulating Heating of Casting Fluid: As the non-contact downward pushing mechanism 5 pushes, the casting fluid in the gearbox shaft hole forming cavity 21 enters the bottom end of the heating conveying pipe 6 under pressure; at the same time, the AC power supply connected to the two spiral coils 61 is turned on, and the two spiral coils 61 generate an alternating magnetic field with a phase difference of 90°, forming an electromagnetic field with an axial pushing wave component inside the heating conveying pipe 6; this electromagnetic field continuously heats the casting fluid in the heating conveying pipe 6 to prevent the casting fluid from solidifying, and drives the casting fluid in the pipe to flow upward in a directional direction, so that the casting fluid flows out from the top of the heating conveying pipe 6 and returns to the gearbox forming cavity at the side of the concave sand mold 2; subsequently, the casting fluid flows slowly from the side forming cavity and returns to the forming cavity at the gearbox shaft hole forming location, forming a circulating flow of casting fluid; during the circulation process, the pores in the casting fluid will rise with the flow process and be discharged through the vent 72 on the heat insulation cover 7, while the casting fluid temperature remains uniform, effectively reducing defects such as shrinkage porosity and pores.

[0033] S4, Molding and Demolding: After the casting liquid circulates for a period of time, the non-contact lower rotary push mechanism 5 and AC power supply are turned off to stop the casting liquid circulation. The device is kept sealed, allowing the casting liquid to cool and solidify in the gearbox molding cavity. After the casting liquid has completely solidified to form the finished gearbox, the fixing parts of the heat insulation cover 7 are removed, the heat insulation cover 7 is opened, and then the punch sand mold 3 and the heat insulation cylinder 4 are taken out. The spiral coil 61 is then energized to heat and melt the solidified waste inside, separating the waste from the gearbox. The finished gearbox is then taken out from the gearbox molding cavity of the concave sand mold 2. Finally, the concave sand mold 2 is taken out from the heat insulation sand box 1, completing the entire casting process.

[0034] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A high-quality metal gearbox casting device, comprising a heat-insulating sand box (1), characterized in that: The inner wall of the heat-insulating sand box (1) is slidably fitted with a concave sand mold (2), and a convex sand mold (3) is assembled in the concave sand mold (2). The gearbox shaft hole forming parts of the concave sand mold (2) and the convex sand mold (3) are slidably connected to a heat-insulating cylinder (4). A non-contact downward rotary push mechanism (5) is fixedly installed in the heat-insulating cylinder (4). Several heating conveying pipes (6) are fixedly embedded in the convex sand mold (3). The bottom end of the heating conveying pipe (6) is connected to the inner wall of the gearbox shaft hole forming part of the concave sand mold (2), and the top end of the heating conveying pipe (6) is connected to the inner wall of the side of the concave sand mold (2). A heat-insulating cover (7) is closed at the top port of the heat-insulating sand box (1).

2. The high-quality metal gearbox casting device according to claim 1, characterized in that: The gap between the concave sand mold (2) and the convex sand mold (3) after assembly is the gearbox forming cavity. The bottom of the concave sand mold (2) is provided with a gearbox shaft hole forming cavity (21). A round hole (22) is opened at the center of the bottom of the gearbox shaft hole forming cavity (21). The inner wall of the round hole (22) and the outer wall at the bottom port of the heat insulation cylinder (4) are slidably connected.

3. The high-quality metal material gearbox casting device according to claim 2, characterized in that: The bottom of the punch sand mold (3) is provided with a gearbox shaft hole forming mold core (31). A cylindrical hole (32) is opened on the punch sand mold (3). The cylindrical hole (32) passes through the axis of the gearbox shaft hole forming mold core (31). The inner wall of the cylindrical hole (32) is slidably sleeved on the outer wall of the heat insulation cylinder (4). The end face at the bottom port of the cylindrical hole (32) is blocked by the bottom of the gearbox shaft hole forming cavity (21).

4. The high-quality metal gearbox casting device according to claim 1, characterized in that: The heating conveying pipe (6) is made of ceramic material. Two spiral coils (61) are fixedly sleeved on the outer wall of the heating conveying pipe (6). The two spiral coils (61) have opposite spiral directions and are orthogonally arranged. The two spiral coils (61) are coaxially nested. The two spiral coils (61) are electrically connected to an AC power supply that can provide a phase difference of 90° to generate an electromagnetic field with an axially propelling wave component inside the heating conveying pipe (6), thereby driving the molten metal in the pipe to flow upward in a directional direction. The bottom port of the heating conveying pipe (6) is connected to the inner wall of the gearbox shaft hole forming cavity (21) near the bottom.

5. The high-quality metal gearbox casting device according to claim 1, characterized in that: The non-contact downward rotating push mechanism (5) includes an electric push rod (51) fixedly installed in the heat insulation cylinder (4). A motor (52) is fixedly installed at the bottom of the telescopic end of the electric push rod (51). A cylindrical block (53) is fixedly connected to the output shaft at the bottom of the motor (52). Several electromagnetic poles (54) arranged in a ring array are fixedly installed on the outer wall of the cylindrical block (53). The magnetic poles of the electromagnetic poles (54) are arranged radially relative to the axis of the cylindrical block (53).

6. The high-quality metal gearbox casting device according to claim 1, characterized in that: The heat insulation cover (7) is provided with a casting hole (71) and an exhaust hole (72), which are connected to the gearbox molding cavity. The heat insulation cover (7) is pressed against the top surface of the concave mold (2) and the convex mold (3).

7. A method of using a high-quality metal gearbox casting device, characterized in that, The high-quality metal gearbox casting apparatus according to any one of claims 1-6 includes the following steps: S1, put the concave mold (2) into the heat insulation sand box (1), insert the heat insulation cylinder (4) into the concave mold (2), then insert the convex mold (3) onto the heat insulation cylinder (4), cover the heat insulation cover (7), and fix the heat insulation cover (7). S2, casting liquid, non-contact downward pushing mechanism (5) runs, pushing the casting liquid at the gearbox shaft hole forming point downward in a spiral posture; S3, the casting liquid at the gearbox shaft hole forming point enters the heating conveying pipe (6), the heating conveying pipe (6) continuously heats the casting liquid in the heating conveying pipe (6), and simultaneously conveys the casting liquid obliquely upwards, returning to the forming cavity at the side of the concave sand mold (2), and then returning from the forming cavity at the horizontal position to the forming cavity at the gearbox shaft hole forming point, and the casting liquid circulates.

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