US20250381595A1

US20250381595A1 - Low-Pressure Mold and Production Process for Aluminum Alloy Integrated Brake Calipers

Info

Publication number: US20250381595A1
Application number: US19/246,545
Authority: US
Inventors: Haijun Guo; Hongbiao Li; Xiaodi WANG; Hui Chi; Jiaze Xu; Qiang Liu; Longtao Kang; Qinghai Wang; Song SHENG; Xi Li; Yong Li; Yacong Zhang; Xiaoying Ma; Dengyao Li; Wei Cai; Zexin Wu; Bao Tan; Shenghui Tao; Shuai Liu
Original assignee: CITIC Dicastal Co Ltd
Current assignee: CITIC Dicastal Co Ltd
Priority date: 2024-07-08
Filing date: 2025-06-23
Publication date: 2025-12-18
Also published as: CN118455490A

Abstract

The present invention discloses a low-pressure mold and production process for aluminum alloy integrated brake calipers, relating to the technical field of casting. The mold comprises a bottom plate, a right mold core and a left mold core are provided on the bottom plate, and the right mold core and the left mold core have the same internal structure and are each provided with a sprue assembly. The low-pressure casting process has higher production efficiency and yield than gravity casting. Castings produced by low-pressure casting have higher structural compactness and more excellent mechanical properties than those produced by gravity casting.

Description

TECHNICAL FIELD

The present invention relates to the technical field of casting, specifically to a low-pressure mold and production process for aluminum alloy integrated brake calipers.

BACKGROUND

Brake calipers are an important component of automobile brake systems. Integrated brake calipers have better rigidity, deformation resistance, and more stable braking performance than split calipers. Meanwhile, aluminum alloy calipers are more advantageous than cast iron calipers in weight, heat dissipation, corrosion resistance, and visual effect. Therefore, as the automobile industry increasingly focuses on green environmental protection and appearance, the proportion of integrated aluminum alloy brake calipers in medium- and high-end passenger vehicles is increasing. Production processes for brake calipers are currently mainly based on gravity casting. Because the flow and feeding of molten metal rely on natural gravity during gravity casting, the filling and feeding capabilities of the molten metal are relatively poor, resulting in poor compactness and high porosity of casting structures and thus affecting the quality and performance of the calipers. In addition, relatively low dimensional accuracy and poor surface quality of gravity casting cannot meet the appearance requirements of medium- and high-end vehicles for attractive and fashionable calipers.

SUMMARY

In view of the above technical problems, the technical solution adopted by the present invention is as follows: A low-pressure mold for aluminum alloy integrated brake calipers includes a bottom plate, a right mold core and a left mold core are provided on the bottom plate, and the right mold core and the left mold core have the same internal structure and are each provided with a sprue assembly; the mold further includes an ejection rod pushing plate, an ejection rod is provided on the ejection rod pushing plate, the ejection rod pushing plate drives the ejection rod to rise and fall, and a casting is released from the mold through the ejection rod; the right mold core includes an upper mold core and a lower mold core, the upper mold core is fixedly mounted on a top plate, the lower mold core is fixedly mounted on the bottom plate, the top plate drives the upper mold core to move up and down to open and close the mold, a sand core is provided between the upper mold core and the lower mold core for forming a cavity structure of the casting, and the sand core is connected to a negative pressure exhaust device; the sprue assembly includes a sprue bush and a sprue cup fixed on the lower mold core through a pressure plate; the sprue assembly further includes a sprue spreader, the sprue spreader is fixedly mounted on the upper mold core, and the sprue bush, the sprue cup and the sprue spreader are arranged coaxially.
Further, a filter screen is placed on the sprue bush, and the filter screen is made of fibers.
Further, the sprue bush and the sprue cup are made of ceramic.
Further, a riser is further provided on the right mold core, an insulation insert is provided at an upper portion of the riser, and asbestos is placed inside the insulation insert.
Further, the insulation insert has a thickness of 3-5 mm.
Further, a novel cooling insert is further provided on the right mold core, and the novel cooling insert on the right mold core is located at a thick position of the casting; the novel cooling insert consists of an insert I and an insert II, which are tightly matched and welded together; the insert I has a cavity structure with a wall thickness of 15-20 mm; and the insert II has a water inlet pipeline and a water outlet pipeline, with diameters of 8 mm.
Further, an exhaust groove with a depth of 0.1-0.25 mm and a width of 20-35 mm is provided on a parting surface between the upper mold core and the lower mold core.
Further, an aluminum stopper with a height of 15-40 mm and a fit clearance of 2-4 mm is further provided between the upper mold core and the lower mold core.
Further, the ejection rod has a diameter of 8-16 mm and is used with an ejection rod sleeve, and the ejection rod sleeve is provided with an exhaust groove.
A production process for aluminum alloy integrated brake calipers includes the following steps:

S1. Aluminum Melting

- aluminum alloy is composed of the following raw materials in percentage by weight: Si, 6.5-7.5%; Mg, 0.4-0.6%; Ti, 0.05-0.2%; Sr, 0.02-0.03%; Fe≤0.13%; Gu≤0.02%; other individual elements (excluding Al)≤0.03%; the total quantity of the other elements (excluding Al) is ≤0.10%, with the remaining Al;
- after aluminum is melted, the molten aluminum is refined with nitrogen for 15-25 minutes at a temperature of 700-720° C., and then the refined molten aluminum is kept warm and stood for 30-50 minutes before use;

S2. Preparation of a Sand Core

- organic resin sand is used, and the required gas generation rate is ≤13 ml/g; particle size index AFS: 53-63; during preparation, the temperature of a sand core mold is 200-230° C., and the curing time is 180-200 seconds;
- after the sand core is made, its surface is uniformly coated with a composite coating, and then the sand core is thoroughly dried at 100° C. for later use;
- where the composite coating is a uniformly mixed mixture of an alcohol-based coating and alcohol in a ratio of 1:1 for later use; the coating can prevent sand adhesion on the surface of the casting and improve the surface quality of the casting;

S3. Low Pressure Casting

- the prepared sand core is put into a mold cavity, the mold cavity is blown with an air gun, then a filter screen is placed at each sprue position, and the mold is closed;
- the temperature of the molten aluminum during the casting process is set at 700-720° C.;
- rising stage: 5-15 seconds, the pressure rises from 0 to 100-160 mbar, and the molten aluminum rises from a holding furnace to the lower end of the sprue cup under the action of pressure;
- pressure stabilizing stage: 1-5 seconds, the pressure remains unchanged from the rising stage, ensuring that the molten aluminum maintains a stable liquid level during filling;
- filling stage: 15-25 seconds, the pressure increases from 100-160 mbar to 200-280 mbar, and the molten aluminum slowly fills the entire mold cavity through the sprue bush and the sprue cup under continuous pressure;
- increasing stage: 5-10 seconds, the pressure continues to rapidly increase from 200-280 mbar to 600-900 mbar after the molten aluminum fills the mold cavity;
- pressure maintaining stage: 100-150 seconds, the pressure is maintained at 600-900 mbar, and the mold cavity is continuously fed and cooled;
- cooling stage: 80-110 seconds, the casting is continuously solidified and cooled inside the mold cavity after pressure relief;
- an air duct connected to the negative pressure exhaust device is open throughout;

S4. Sand Shaking

- after the casting is cooled to room temperature, the sand core in the casting is shaken to break it up and remove the sand;

S5. Rough Machining

- runners of the casting are removed according to drawing requirements; and

S6. Heat Treatment

- solid solution temperature 535-545° C., solid solution holding time 420-500minutes, quenching water temperature 30-50° C., aging temperature 160-175° C., and aging holding time 300-380 minutes.

Compared to the prior art, the beneficial effects of the present invention are as follows: (1) the low-pressure casting process has higher production efficiency and yield than gravity casting; (2) castings produced by low-pressure casting have higher structural compactness and more excellent mechanical properties than those produced by gravity casting; (3) aluminum alloy integrated brake calipers produced by the process of the present invention have a yield strength greater than 280 MPa, a tensile strength greater than 320 MPa, an elongation rate greater than 2%, a casting production efficiency up to two pieces in 300 seconds, and a yield rate greater than 95%; and (4) due to the similarity in the design of brake calipers, the present invention has strong universality for integrated brake calipers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a production process of the present invention.

FIG. 2 is a schematic diagram of an overall structure of the present invention.

FIG. 3 is a cross-sectional view of an overall structure of the present invention.

FIG. 4 is a schematic structural diagram of integrated brake calipers of the present invention.

FIG. 5 is a schematic diagram of a pouring system of the present invention.

FIG. 6 is a schematic diagram of a sand core of the present invention.

In the figures: 1—bottom plate; 2—top plate; 3—connecting plate; 4—ejection rod pushing plate; 5—right mold core; 6—left mold core; 7—reset rod; 8—positioning key; 9—negative pressure exhaust device; 10—ejection rod; 11—insulation insert; 12—upper mold core; 13—aluminum stopper; 14—ejection rod sleeve; 15—casting; 16—lower mold core; 17—point cooling joint; 18—sprue spreader; 19—exhaust plug; 20—sand core; 21—filter screen; 22—sprue bush; 23—sprue cup; 24—pressure plate; 25—ejection rod boss; 26—riser.

DETAILED DESCRIPTION

The technical solution of the present invention will be further illustrated in conjunction with the accompanying drawings and specific embodiments.
A low-pressure casting mold for aluminum alloy integrated brake calipers, as shown in FIGS. 1-6 , first requires a lean pouring system design. On the one hand, sufficient feeding capability is required to achieve sequential solidification of castings and ensure casting yield. On the other hand, the weight of the pouring system is minimized to improve material utilization and shorten a casting cycle. Based on the product structure characteristics of integrated calipers, two sprues are provided on two sides of a casting 15, the two sprues are connected to 2 inner runners and 3 inner runners respectively, and the inner runners are connected to the casting 15 for feeding. By simulation analysis and calculation, the weight of the casting 15 is 3-5 kg, the minimum diameter of the sprue is 50 mm, the thickness of the sprue is 25-40 mm, the width of the inner runner is 35-55 mm, and the thickness of the inner runner is greater than ⅔ of the thickness of the cross section of the casting 15 at a sprue entrance. Meanwhile, a riser 26 is provided at a distance of 10-15 mm from the casting on each inner runner to ensure the feeding capability of the runner, and the height of the riser 26 is greater than twice the thickness of the cross section of the casting 15 at the sprue entrance.
A low-pressure casting mold for aluminum alloy integrated brake calipers includes a bottom plate 1, a top plate 2, a connecting plate 3, an ejection rod pushing plate 4, a right mold core 5, a left mold core 6, a reset rod 7, positioning keys 8, and an ejection rod 10. The right mold core 5 and the left mold core 6 are provided on the bottom plate 1, the right mold core 5 and the left mold core 6 have the same structure and are mirror images of each other, and both the right mold core 5 and the left mold core 6 are provided with a sprue assembly. The ejection rod pushing plate 4 is connected to an ejection oil cylinder of the mold, the ejection rod 10 is arranged on the ejection rod pushing plate 4, and the ejection rod pushing plate 4 drives the ejection rod 10 to eject. The ejection rod 10 is in contact with an ejection rod boss 25 on the casting 15 to achieve mold release of the casting 15, which can, on the one hand, prevent the ejection rod 10 from leaving an ejection mark on the casting 15 to affect the appearance of the casting 15, and on the other hand, avoid the problem of empty ejection of the ejection rod 10 due to runner shrinkage. The ejection rod 10 has a diameter of 8-16 mm and is used with an ejection rod sleeve 14 to protect the mold. In addition, the ejection rod sleeve 14 is provided with an exhaust groove for exhausting. When the mold is closed, the reset rod 7 can completely reset the ejection rod pushing plate 4. The reset rod 7 is arranged on the bottom plate 1, a limit rod is arranged above the reset rod 7, the reset rod 7 is in contact with the limit rod, the limit rod is arranged on the ejection rod pushing plate 4, a spring is sleeved on the limit rod, a first end of the spring is fixedly mounted on the ejection rod pushing plate 4, and a second end of the spring is fixedly mounted on the top plate 2.
The right mold core 5 includes an upper mold core 12, a lower mold core 16, and a sand core 20. The lower mold core 16 is fixedly mounted on the bottom plate 1, and four groups of positioning keys 8 are provided on the lower mold core 16. When the mold is closed, the lower mold core 16 and the upper mold core 12 are accurately closed through the positioning keys 8.
The bottom plate 1 is fixedly connected to a low-pressure casting machine, the upper mold core 12 is fixedly mounted on the top plate 2, the top plate 2 is fixedly mounted to the connecting plate 3, the top plate 2 is connected to a moving platform plate through the connecting plate 3, and the moving platform plate drives the top plate 2 and the upper mold core 12 to move up and down through the connecting plate 3, achieving the opening and closing of the mold. The sand core 20 is provided between the upper mold core 12 and the lower mold core 16 for forming a cavity structure of the casting 15, and the sand core 20 is connected to a negative pressure exhaust device 9. A large amount of gas is generated by heating the sand core 20, resulting in the occurrence of pores and pin holes in the casting 15. Therefore, the negative pressure exhaust device 9 is provided at a thick position of the sand core 20. An exhaust plug 19 having a diameter of 8-12 mm is placed on the sand core 20, and then is connected to the negative pressure exhaust device 9 above through a straight hole of the mold. When air is introduced into the negative pressure exhaust device 9, negative pressure is generated in channels to suck out the gas generated by heating the sand core 20.
The sprue assembly includes a sprue bush 22, a sprue cup 23, a pressure plate 24, and a sprue spreader 18. The sprue bush 22 and the sprue cup 23 are fixed to the lower mold core 16 through the pressure plate 24, the sprue spreader 18 is fixed to the upper mold core 12, and axes of the sprue bush 22, the sprue cup 23, and the sprue spreader 18 are on a straight line. Both the sprue bush 22 and the sprue cup 23 are made of ceramic. The ceramic sprue bush 22 and sprue cup 23 can effectively improve the heat preservation capability of a sprue position, reduce the temperature loss of molten aluminum at the sprue, and improve the feeding capability of the sprue position. A point cooling joint 17 is provided on the sprue spreader 18. When molten aluminum is filled, the sprue spreader 18 can change the flow direction of the molten aluminum. During solidification, the sprue spreader 18 can cool the sprue and shorten the casting cycle.
A conical filter screen 21 is placed on the sprue bush 22. After the mold is closed, the sprue spreader 18 is used to press the filter screen 21 to prevent the molten aluminum from flushing away the filter screen 21. The filter screen 21 is made of fibers, so that the sprue with the filter screen 21 can be directly used for melting after being cut off, and the fiber screen will not pollute the molten aluminum, reducing raw material waste and improving economic efficiency.
The riser 26 is provided on the runner of the right mold core 5, an insulation insert 11 is provided at an upper portion of the riser 26, and asbestos is placed inside the insulation insert 11 to increase the feeding capability of the riser 26.
The insulation insert 11 has a thickness of 3-5 mm.
A novel cooling insert is further provided on the right mold core 5. The novel cooling insert on the right mold core 5 is located at a thick position of the casting 15 to improve the local cooling speed of the casting 15, achieve sequential solidification, and obtain finer grain structures. The novel cooling insert consists of an insert I and an insert II, which are tightly matched and welded together to prevent water leakage.
The insert I has a cavity with a wall thickness of 15-20 mm; and the insert II has a water inlet pipeline and a water outlet pipeline, with diameters of 8 mm. During working, cooling water enters the cavity of the insert I through the water inlet pipeline and can flow out through the water outlet pipeline after filling the cavity. A conventional cooling insert has only a cooling pipeline, while the novel cooling insert having the water cavity inside achieves more sufficient heat exchange and much greater cooling capacity than the conventional cooling insert.
An exhaust groove with a depth of 0.1-0.25 mm and a width of 20-35 mm is provided on a parting surface between the upper mold core 12 and the lower mold core 16.
An aluminum stopper 13 with a height of 15-40 mm and a fit clearance of 2-4 mm is further provided between the upper mold core 12 and the lower mold core 16. The aluminum stopper 13 can prevent molten aluminum leakage during production.
A production process for aluminum alloy integrated brake calipers includes the following steps:

- S1. Aluminum melting: Aluminum alloy is composed of the following raw materials in percentage by weight: Si, 6.5-7.5%; Mg, 0.4-0.6%; Ti, 0.05-0.2%; Sr, 0.02-0.03%; Fe≤0.13%; Gu≤0.02%; other individual elements (excluding Al)≤0.03%; the total quantity of the other elements (excluding Al) is ≤0.10%, with the remaining Al. After aluminum is melted, the molten aluminum is refined with nitrogen for 15-25 minutes at a temperature of 700-720° C., and then the refined molten aluminum is kept warm and stood for 30-50 minutes before use. The refining and standing can improve the purity of the molten aluminum and reduce the gas content and slag inclusion of the molten aluminum.
- S2. Preparation of a sand core: Organic resin sand is used, and the required gas generation rate is ≤13 ml/g; particle size index AFS: 53-63. During preparation, the temperature of a sand core mold is 200-230° C., and the curing time is 180-200 seconds. After the sand core 20 is made, its surface is uniformly coated with a composite coating, and then the sand core is thoroughly dried at 100° C. for later use. The composite coating is a uniformly mixed mixture of an alcohol-based coating and alcohol in a ratio of 1:1 for later use. The coating can prevent sand adhesion on the surface of the casting 15 and improve the surface quality of the casting 15.
- S3. Low pressure casting: The prepared sand core 20 is put into a mold cavity, the mold cavity is blown with an air gun, then a filter screen 21 is placed at each sprue position, and the mold is closed. The temperature of the molten aluminum during the casting process is set at 700-720° C. Rising stage: 5-15 seconds, the pressure rises from 0 to 100-160 mbar, and the molten aluminum rises from a holding furnace to the lower end of the sprue cup 23 under the action of pressure; pressure stabilizing stage: 1-5 seconds, the pressure remains unchanged from the rising stage, ensuring that the molten aluminum maintains a stable liquid level during filling; filling stage: 15-25 seconds, the pressure increases from 100-160 mbar to 200-280 mbar, and the molten aluminum slowly fills the entire mold cavity through the sprue bush 22 and the sprue cup 23 under continuous pressure; increasing stage: 5-10 seconds, the pressure continues to rapidly increase from 200-280 mbar to 600-900 mbar after the molten aluminum fills the mold cavity; pressure maintaining stage: 100-150 seconds, the pressure is maintained at 600-900 mbar, and the mold cavity is continuously fed and cooled; cooling stage: 80-110 seconds, the casting 15 is continuously solidified and cooled inside the mold cavity after pressure relief; an air duct connected to the negative pressure exhaust device 9 is open throughout.
- S4. Sand shaking: After the casting 15 is cooled to room temperature, the sand core 20 in the casting 15 is shaken to break it up and remove the sand.
- S5. Rough machining: Runners of the casting 15 are removed according to drawing requirements.
- S6. Heat treatment: solid solution temperature 535-545° C., solid solution holding time 420-500 minutes, quenching water temperature 30-50° C., aging temperature 160-175° C., and aging holding time 300-380 minutes.

Efficient and stable production of aluminum alloy brake calipers is achieved through low-pressure casting. Aluminum alloy integrated brake calipers produced by this process have a yield strength greater than 280 MPa, a tensile strength greater than 320 MPa, an elongation rate greater than 2%, a casting production efficiency up to two pieces in 300 seconds, and a yield rate greater than 95%.

Claims

What is claimed is:

1. A low-pressure mold for aluminum alloy integrated brake calipers, comprising a bottom plate (1), wherein a right mold core (5) and a left mold core (6) are provided on the bottom plate (1), and the right mold core (5) and the left mold core (6) have the same structure and are each provided with a sprue assembly; and

further comprising an ejection rod pushing plate (4), wherein an ejection rod (10) is provided on the ejection rod pushing plate (4), the ejection rod pushing plate (4) drives the ejection rod (10) to rise and fall, and a casting (15) is released from the mold through the ejection rod (10);

wherein the right mold core (5) comprises an upper mold core (12) and a lower mold core (16), the upper mold core (12) is fixedly mounted on a top plate (2), the lower mold core (16) is fixedly mounted on the bottom plate (1), the top plate (2) drives the upper mold core (12) to move up and down to open and close the mold, a sand core (20) is provided between the upper mold core (12) and the lower mold core (16) for forming a cavity structure of the casting (15), and the sand core (20) is connected to a negative pressure exhaust device (9);

the sprue assembly comprises a sprue bush (22) and a sprue cup (23) fixed on the lower mold core (16) through a pressure plate (24); and

the sprue assembly further comprises a sprue spreader (18), the sprue spreader (18) is fixedly mounted on the upper mold core (12), and the sprue bush (22), the sprue cup (23) and the sprue spreader (18) are arranged coaxially.

2. The low-pressure mold for aluminum alloy integrated brake calipers according to claim 1, wherein a filter screen (21) is placed on the sprue bush (22), and the filter screen (21) is made of fibers.

3. The low-pressure mold for aluminum alloy integrated brake calipers according to claim 1, wherein a riser (26) is further provided on the right mold core (5), an insulation insert (11) is provided at an upper portion of the riser (26), and asbestos is placed inside the insulation insert (11).

4. The low-pressure mold for aluminum alloy integrated brake calipers according to claim 3, wherein the insulation insert (11) has a thickness of 3-5 mm.

5. The low-pressure mold for aluminum alloy integrated brake calipers according to claim 1, wherein a novel cooling insert is further provided on the right mold core (5), and the novel cooling insert on the right mold core (5) is located at a thick position of the casting (15); and

the novel cooling insert consists of an insert I and an insert II, which are tightly matched and welded together; the insert I has a cavity structure with a wall thickness of 15-20 mm; the insert II has a water inlet pipeline and a water outlet pipeline, with diameters of 8 mm.

6. The low-pressure mold for aluminum alloy integrated brake calipers according to claim 1, wherein an exhaust groove with a depth of 0.1-0.25 mm and a width of 20-35 mm is provided on a parting surface between the upper mold core (12) and the lower mold core (16).

7. The low-pressure mold for aluminum alloy integrated brake calipers according to claim 1, wherein an aluminum stopper (13) with a height of 15-40 mm and a fit clearance of 2-4 mm is further provided between the upper mold core (12) and the lower mold core (16).

8. The low-pressure mold for aluminum alloy integrated brake calipers according to claim 1, wherein the ejection rod (10) has a diameter of 8-16 mm and is used with an ejection rod sleeve (14), and the ejection rod sleeve (14) is provided with an exhaust groove.

9. The low-pressure mold for aluminum alloy integrated brake calipers according to claim 1, wherein the sprue bush (22) and the sprue cup (23) are made of ceramic.

10. A production process for aluminum alloy integrated brake calipers, comprising the following steps:

S1. aluminum melting:

aluminum alloy is composed of the following raw materials in percentage by weight: Si, 6.5-7.5%; Mg, 0.4-0.6%; Ti, 0.05-0.2%; Sr, 0.02-0.03%; Fe≤0.13%; Gu≤0.02%; other individual elements (excluding Al)≤0.03%; the total quantity of the other elements (excluding Al) is ≤0.10%, with the remaining Al;

after aluminum is melted, the molten aluminum is refined with nitrogen for 15-25 minutes at a temperature of 700-720° C., and then the refined molten aluminum is kept warm and stood for 30-50 minutes before use; the refining and standing can improve the purity of the molten aluminum and reduce the gas content and slag inclusion of the molten aluminum;

S2. preparation of a sand core:

organic resin sand is used, and the required gas generation rate is ≤13 ml/g; particle size index AFS: 53-63; during preparation, the temperature of a sand core mold is 200-230° C., and the curing time is 180-200 seconds;

after the sand core (20) is made, its surface is uniformly coated with a composite coating, and then the sand core is thoroughly dried at 100° C. for later use;

wherein the composite coating is a uniformly mixed mixture of an alcohol-based coating and alcohol in a ratio of 1:1 for later use; the coating can prevent sand adhesion on the surface of the casting (15) and improve the surface quality of the casting (15);

S3. low pressure casting:

the prepared sand core (20) is put into a mold cavity, the mold cavity is blown with an air gun, then a filter screen (21) is placed at each sprue position, and the mold is closed;

the temperature of the molten aluminum during the casting process is set at 700-720° C.;

rising stage: 5-15 seconds, the pressure rises from 0 to 100-160 mbar, and the molten aluminum rises from a holding furnace to the lower end of the sprue cup (23) under the action of pressure;

pressure stabilizing stage: 1-5 seconds, the pressure remains unchanged from the rising stage, ensuring that the molten aluminum maintains a stable liquid level during filling;

filling stage: 15-25 seconds, the pressure increases from 100-160 mbar to 200-280 mbar, and the molten aluminum slowly fills the entire mold cavity through the sprue bush (22) and the sprue cup (23) under continuous pressure;

increasing stage: 5-10 seconds, the pressure continues to rapidly increase from 200-280 mbar to 600-900 mbar after the molten aluminum fills the mold cavity;

pressure maintaining stage: 100-150 seconds, the pressure is maintained at 600-900 mbar, and the mold cavity is continuously fed and cooled;

cooling stage: 80-110 seconds, the casting (15) is continuously solidified and cooled inside the mold cavity after pressure relief;

an air duct connected to the negative pressure exhaust device (9) is open throughout;

S4. sand shaking:

after the casting (15) is cooled to room temperature, the sand core (20) in the casting (15) is shaken to break it up and remove the sand;

S5. rough machining:

runners of the casting (15) are removed according to drawing requirements; and

S6. heat treatment:

solid solution temperature 535-545° C., solid solution holding time 420-500 minutes, quenching water temperature 30-50° C., aging temperature 160-175° C., and aging holding time 300-380 minutes.