Low-pressure forming device for light-weight aluminum alloy casting and operation process

Abstract

The invention discloses a light-weight aluminum alloy casting low-pressure forming device and an operation technology, and the light-weight aluminum alloy casting low-pressure forming device comprises a heat preservation furnace which is installed on a lifting base and is provided with a liquid rising pipe, an opening and closing cylinder installed on a support, and an upper mold installed at the lower end of the opening and closing cylinder, a connecting pipeline matched with the output end of the air compressor is arranged on the outer wall of the heat preservation furnace, a pressure relief pipeline is further arranged on the heat preservation furnace, and the heat preservation furnace further comprises a gas rapid filling unit. The low-pressure casting machine is provided with the quick gas filling unit, so that a large amount of nitrogen can be quickly filled into the furnace, the gas filling time is shortened, the working efficiency of the low-pressure casting machine is greatly improved, and the quick gas filling unit can be repeatedly used by releasing the nitrogen in the furnace into the hollow pipe for the first time; and meanwhile, the nitrogen is extruded by the gravity of the heavy object to maintain the air pressure in the furnace to reach a set constant pressure range, and the device is also suitable for different liquid levels of molten aluminum alloy in the furnace.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy low-pressure casting, and in particular to a low-pressure forming device for lightweight aluminum alloy castings and an operating process. Background Art

[0002] When casting lightweight aluminum alloy parts, a low-pressure casting machine is generally used for casting. The low-pressure casting machine includes an upper and lower mold, a holding furnace with a liquid riser, and an air compressor for adding inert gas (usually nitrogen) to the holding furnace. When the low-pressure casting machine is working, nitrogen is first filled into the holding furnace through the air compressor. When the air pressure in the furnace reaches a certain value, the molten aluminum alloy solution begins to rise and enter the mold. After the filling of the mold cavity is completed, it is pressurized (the liquid aluminum alloy can fill the mold cavity more fully, reduce defects such as pores and looseness inside the casting, thereby improving the density and overall quality of the casting. Pressurization helps the liquid metal to form a denser structure during the solidification process, which is particularly important for castings that require high strength and good mechanical properties). After the pressure is increased to the set value, the pressure is maintained. After the casting in the mold is cooled and solidified by the cooling system in the mold, the pressure is relieved (the pressure is relieved through the pressure relief pipe on the holding furnace), so that the aluminum alloy solution in the liquid riser flows back to the holding furnace.

[0003] For the existing low-pressure casting machines, affected by factors such as the exhaust volume of the air compressor, the size of the holding furnace and the amount of molten aluminum alloy inside the holding furnace, the process of filling nitrogen into the holding furnace through the air compressor and causing the molten aluminum alloy in the riser to begin to rise conventionally takes at least 3 minutes. For larger holding furnaces with less molten aluminum alloy, it may take more than ten minutes or even longer, seriously affecting the working efficiency of the entire low-pressure casting machine. Therefore, the present application provides a low-pressure forming device and operating process for lightweight aluminum alloy castings to meet the needs. Summary of the invention

[0004] The purpose of the present application is to provide a low-pressure forming device and operating process for lightweight aluminum alloy castings, so as to solve the technical problems raised in the above background.

[0005] To achieve the above-mentioned objectives, the present application provides the following technical solutions: a low-pressure forming device for lightweight aluminum alloy castings, comprising a heat-insulating furnace installed on a lifting base and having a liquid riser, an opening and closing cylinder installed on a bracket, an upper mold installed at the lower end of the opening and closing cylinder, a lower mold arranged below the upper mold, a connecting pipe adapted to an output end of an air compressor is arranged on the outer wall of the heat-insulating furnace, a pressure relief pipe is also arranged on the heat-insulating furnace, and also includes a gas rapid filling unit, which can quickly fill the heat-insulating furnace with inert gas before aluminum alloy casting, so that the gas pressure in the heat-insulating furnace is quickly maintained within a constant range, and within this range, the aluminum alloy solution in the liquid riser does not rise.

[0006] As a preferred implementation in this embodiment, the gas rapid filling unit includes a hollow tube with an opening at the upper end and a closed lower end, and a weight slidably installed in the inner cavity of the hollow tube; An elastic sealing sleeve is arranged on the outer wall of the weight, and the outer wall of the elastic sealing sleeve is in sliding contact with the inner wall of the hollow tube; A plurality of main pipes are arranged on the outer wall of the hollow pipe, and the plurality of main pipes are all provided with electric valves, the gas outlet ends of the plurality of main pipes are sealed and connected with the branch pipes corresponding to the upper end of the insulation furnace, and the plurality of branch pipes are communicated with the inner cavity of the insulation furnace; It also includes an air pressure sensor arranged in the inner cavity of the main air outlet, and the air pressure sensor and the electric valve are both electrically connected to the controller.

[0007] As a preferred implementation manner in this embodiment, it also includes a pressure relief unit to prevent the heavy object from being pushed out of the hollow tube by air pressure, and also to prevent the air pressure in the insulation furnace from being unable to be maintained within a constant range when gas is subsequently injected into the insulation furnace by the hollow tube.

[0008] As a preferred implementation in this embodiment, the pressure relief unit includes an exhaust pipe that passes through the weight and a mounting frame installed at the upper end of the hollow pipe and having a gear rod; A ball valve is installed on the exhaust pipe, and a driving gear ring is installed on the outer wall of the hand-cranked wheel of the ball valve, and the gear rod is arranged correspondingly to the driving gear ring; A limiting protrusion is arranged on the outer wall of the elastic sealing sleeve, and a limiting sliding groove matched with the limiting protrusion is arranged in the inner cavity of the hollow tube.

[0009] As a preferred implementation manner in this embodiment, it also includes a variable resistance unit, which can automatically change the resistance between the weight and the inner wall of the hollow tube according to the size of the air pressure, and the resistance is proportional to the air pressure.

[0010] As a preferred implementation manner in this embodiment, the variable resistance unit includes an extrusion chamber arranged inside the weight, and the air inlet end of the extrusion chamber is sealed by an elastic diaphragm.

[0011] As a preferred implementation in this embodiment, the extrusion cavity is provided with a plurality of arc-shaped extrusion rods in a circumferential manner, an extrusion plate installed on the upper end of the elastic diaphragm, and a plurality of movable rods arranged in the extrusion cavity by rotating a pin shaft; A plurality of mounting plates are slidably arranged on the extrusion plate through a slider, the lower end of the movable rod is rotatably connected with the corresponding mounting plate, the upper end of the movable rod is slidably contacted with the corresponding end of the resistance rod, and the resistance rod is fixedly mounted on the corresponding arc-shaped extrusion rod; The outer end of the arc-shaped extrusion rod is in contact with the inner wall of the elastic sealing sleeve; The pin shaft is located above the middle portion of the movable rod.

[0012] An operating process of a low-pressure forming device for lightweight aluminum alloy castings comprises the following steps: S1: Inflation, first open the electric valve 9, and use the gravity of the weight 11 to quickly squeeze the nitrogen in the hollow tube 10 into the insulation furnace 2, and maintain the gas pressure in the furnace within a set constant pressure range, and then the air compressor will accurately pressurize it; S2: Nitrogen refluxes. After the casting in the cavity is solidified and the insulation furnace 2 is depressurized for the first time, the electric valve 9 is opened to allow the nitrogen in the insulation furnace 2 to enter the hollow tube 10, and finally the pressure in the furnace is maintained within the set constant pressure range. S3: During the subsequent pressure relief, the pressure can be relieved directly through the pressure relief pipe on the insulation furnace 2.

[0013] In summary, the technical effects and advantages of the present invention are as follows: The invention has a reasonable structure and is provided with a gas rapid filling unit, which can allow a large amount of nitrogen to be quickly filled into the furnace, thereby reducing the filling time and greatly improving the working efficiency of the low-pressure casting machine. Furthermore, by releasing the nitrogen in the furnace into the hollow tube for the first time, the gas rapid filling unit can be reused, and the gravity of the heavy object is used to squeeze the nitrogen to maintain the gas pressure in the furnace within a set constant pressure range, which is also applicable even when the liquid level height of the aluminum alloy melt in the furnace is different. In the present invention, a pressure relief unit is provided to prevent the heavy object from being pushed out of the hollow tube by air pressure, and also to prevent the air pressure in the insulation furnace from being unable to be maintained within a constant range when the hollow tube subsequently injects gas into the insulation furnace. In the present invention, a variable resistance unit is provided to prevent the heavy object from moving too fast, thereby causing severe friction of the elastic sealing sleeve, causing tooth collapse, and requiring long-term stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0015] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 for Figure 1 Schematic diagram of the structure of the gas rapid filling unit; Figure 3 for Figure 2 Schematic diagram of the structure of medium and heavy objects; Figure 4 for Figure 3 Schematic diagram of the structure of a medium-heavy object viewed from above; Figure 5 for Figure 4 Schematic diagram of the cross-sectional structure of a medium-heavy object; Figure 6 for Figure 5 Enlarged structural diagram of point A in the middle Figure 7 for Figure 2 Schematic diagram of the partial cross-section structure of the middle main pipe.

[0016] In the figure: 1. lifting base; 2. insulation furnace; 3. lower mold; 4. upper mold; 5. bracket; 6. opening and closing cylinder; 7. branch pipe; 8. main pipe; 9. electric valve; 10. hollow pipe; 11. heavy object; 12. elastic sealing sleeve; 13. limiting protrusion; 14. exhaust pipe; 15. ball valve; 16. driving gear ring; 17. mounting frame; 18. gear rod; 19. elastic diaphragm; 20. extrusion chamber; 21. arc extrusion rod; 22. resistance rod; 23. movable rod; 24. extrusion plate; 25. mounting plate; 26. pin shaft; 27. slider; 28. air pressure sensor; 29. ​​limiting slider. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Example: Reference Figure 1A lightweight aluminum alloy casting low-pressure forming device shown in the figure includes a holding furnace 2 installed on a lifting base 1 and with a liquid riser, an opening and closing cylinder 6 installed on a bracket 5, an upper mold 4 installed at the lower end of the opening and closing cylinder 6, and a lower mold 3 is arranged below the upper mold 4. A connecting pipe adapted to the output end of an air compressor is arranged on the outer wall of the holding furnace 2. A pressure relief pipe is also arranged on the holding furnace 2, and also includes a gas rapid filling unit. Before aluminum alloy casting, inert gas can be quickly filled into the holding furnace 2, so that the gas pressure in the holding furnace 2 is quickly maintained in a constant range, and within this range, the aluminum alloy solution in the liquid riser does not rise.

[0019] As a preferred implementation in this embodiment, Figure 1-4 and Figure 7 As shown, the gas rapid filling unit includes a hollow tube 10 with an opening at the upper end and a closed lower end, and a weight 11 slidably installed in the inner cavity of the hollow tube 10; An elastic sealing sleeve 12 is disposed on the outer wall of the weight 11, and the outer wall of the elastic sealing sleeve 12 is in sliding contact with the inner wall of the hollow tube 10; A plurality of main pipes 8 are arranged on the outer wall of the hollow pipe 10, and electric valves 9 are arranged on the plurality of main pipes 8. The gas outlet ends of the plurality of main pipes 8 are sealedly connected with the branch pipes 7 corresponding to the upper end of the insulation furnace 2, and the plurality of branch pipes 7 are communicated with the inner cavity of the insulation furnace 2. It also includes an air pressure sensor 28 disposed in the inner cavity of the air outlet of the main pipe 8. The air pressure sensor 28 and the electric valve 9 are both electrically connected to the controller.

[0020] Before the holding furnace 2 starts casting, the holding furnace 2 is at normal pressure. At this time, all the electric valves 9 can be opened by the controller. At this time, the nitrogen stored in the hollow tube 10 is transported to the holding furnace 2 by the gravity of the weight 11. The air pressure in the holding furnace 2 is squeezed and maintained within the set constant pressure range (when the air pressure in the furnace is within this constant pressure range, no molten metal flows in the riser pipe) by the gravity of the weight 11. The air pressure in the furnace is detected by the pressure sensor 28. When the furnace is stabilized in the set constant pressure range, the controller controls the electric valve 9 to close. Thereafter, the air compressor accurately pressurizes the furnace so that the molten metal in the riser pipe rises and enters the mold cavity for casting. Then, pressurization (after pressurization, the air pressure in the furnace is significantly higher than before) and pressure maintenance are performed. When the first pressure relief is performed, in order to ensure that the nitrogen can be repeatedly returned to the hollow tube 2 for subsequent use, the electric valve 9 can be controlled to open so that the nitrogen in the furnace enters the hollow 2, and the weight 11 is lifted up to a certain height. Keep stable, at this time, the hollow tube 10 is balanced with the air pressure in the furnace. When the air pressure sensor 28 detects that the air pressure in the furnace is stable within the set constant pressure range, the electric valve 9 is controlled to close. At this time, the aluminum alloy melt in the riser pipe flows back into the furnace. When the second pressure relief is performed later, the automatic pressure relief pipeline on the insulation furnace 2 can be directly used for pressure relief. After the pressure relief, the air pressure in the furnace is maintained within the set constant pressure range (there is no need to use the weight 11 to squeeze the nitrogen in the hollow tube 10 to inflate the furnace). That is, each insulation furnace 2 At the beginning, it is only necessary to use the gravity of the weight 11 to pressurize the nitrogen in the hollow tube 10 into the furnace, so that a large amount of nitrogen can be quickly filled into the furnace, reducing the filling time and greatly improving the working efficiency of the low-pressure casting machine. By releasing the nitrogen in the furnace into the hollow tube 10 for the first time, the gas rapid filling unit can be reused. At the same time, the gravity of the weight 11 is used to squeeze the nitrogen and maintain the gas pressure in the furnace to reach the set constant pressure range, which is also applicable even for different liquid levels of the aluminum alloy melt in the furnace.

[0021] It should be noted that: 1. An inflation tube with a one-way inflation head is provided on the hollow tube 10 to facilitate the injection of nitrogen into the hollow tube 10; 2. The gravity of the weight 11 can be increased or decreased as needed to adjust the constant pressure range in the furnace; 3. The set constant pressure range should be smaller than the furnace pressure when the molten metal in the riser rises, because the molten metal in the riser cannot flow at a constant speed at a certain speed due to the gravity of the weight 11, and the molten metal is injected into the cavity at a uniform speed, which is beneficial to improve the mechanical properties of the casting. Therefore, the furnace can only reach the set constant pressure range through the gravity of the weight 11, and the air compressor system is used to accurately adjust the air pressure subsequently; 4. An elastic sealing ring is provided at the upper end of the branch pipe 7, and the lifting base 1 drives the insulation furnace 2 to rise and fall so that the branch pipe 7 and the pipe mouth of the main pipe 8 collide with each other to form a seal.

[0022] As a preferred implementation scheme in this embodiment, it also includes a pressure relief unit to prevent the heavy object 11 from being pushed out of the hollow tube 10 by air pressure, and also to prevent the subsequent hollow tube 10 from injecting gas into the insulation furnace 2, causing the air pressure in the insulation furnace 2 to be unable to be maintained within a constant range.

[0023] At the beginning, when the furnace is depressurized for the first time and the liquid level of the melt in the furnace is very low, since there is a pressurization stage before the pressure relief, the gas pressure at this time is higher than the set range and the amount of nitrogen in the furnace is also large. After the pressure relief, it is easy to cause the heavy object 11 to be lifted to a very high height or even detach from the hollow tube 11. Therefore, a pressure relief unit is set to allow excess nitrogen in the hollow tube 10 to leak out.

[0024] As a preferred implementation in this embodiment, Figure 3 As shown, the pressure relief unit includes an exhaust pipe 14 that penetrates the weight 11 and a mounting frame 17 that is mounted on the upper end of the hollow tube 10 and has a gear rod 18; A ball valve 15 is installed on the exhaust pipe 14, and a driving gear ring 16 is installed on the outer wall of the hand-cranked wheel of the ball valve 15, and a gear rod 18 is arranged corresponding to the driving gear ring 16; A limiting protrusion 13 is provided on the outer wall of the elastic sealing sleeve 12 , and a limiting sliding groove adapted to the limiting protrusion 13 is provided in the inner cavity of the hollow tube 10 .

[0025] During the first pressure relief, the weight 11 rises under the action of the gas pressure in the furnace. As the weight 11 rises, the driving gear ring 16 on the ball valve 15 arranged thereon engages with the gear rod 18, and the passage of the exhaust pipe 14 is opened, and the nitrogen in the hollow tube 10 is discharged from the exhaust pipe 14 until the hollow tube 10 and the gas pressure in the furnace reach a balance within the set constant pressure range.

[0026] It should be noted that the function of the limiting protrusion 13 is to prevent the weight 11 from rotating when it moves upward or downward, and to prevent the driving gear ring 16 and the gear rod 18 from changing their positions and failing to engage with the gears.

[0027] As a preferred implementation mode of this embodiment, it also includes a variable resistance unit, which can automatically change the resistance between the weight 11 and the inner wall of the hollow tube 10 according to the size of the air pressure, and the resistance is proportional to the air pressure.

[0028] When the furnace begins to be filled with nitrogen, the weight 11 moves downward in the hollow tube 10, first performing an acceleration motion with a decreasing acceleration, and when the speed reaches the maximum, performing a deceleration motion until it reaches zero. At this time, due to the excessive air pressure below, that is, the air pressure is greater than the sum of the weight of the weight 11 and the friction resistance, the weight 11 will move upward for a distance, and this process will be repeated until the weight 11 is stable and the air pressure in the furnace is stable. When the pressure is released, the weight 11 moves upward in the hollow tube 10, first performing an acceleration motion with a decreasing acceleration, and when the speed reaches the maximum, performing a deceleration motion. After the speed reaches zero, the weight will move downward for a distance and then recover. When the weight 11 moves upward or downward, it is easy to cause the movement speed to be too fast. Too fast movement speed will cause more intense friction between the elastic sealing sleeve 12 and the hollow tube 10, affecting the service life of the sealing elastic sealing sleeve 12. Too fast movement speed will easily cause a violent collision between the driving gear 16 and the gear rod 18, which is easy to cause tooth breakage. At the same time, it also makes the weight 11 take a long time to achieve stability (at this time, the air pressure in the tube and the furnace is within the set constant pressure range).

[0029] As a preferred implementation in this embodiment, Figure 4 and Figure 5 As shown, the variable resistance unit includes an extrusion chamber 20 arranged inside the weight 11 , and the air inlet end of the extrusion chamber 20 is sealed by an elastic diaphragm 19 .

[0030] During inflation, when the electric valve 9 is suddenly opened, the air pressure in the hollow tube 10 decreases rapidly, and when the weight 11 starts to move downward, the extrusion force acting on the elastic diaphragm 9 suddenly decreases, that is, the resistance of the weight 11 to descend decreases. As the weight moves downward, the air pressure in the hollow tube 10 becomes greater and greater, and the extrusion force acting on the elastic diaphragm 9 becomes greater and greater, making the elastic diaphragm 19 more concave, and the extrusion cavity 20 is squeezed, so that part of the elastic sealing sleeve 12 (the part of its inner wall directly located in the extrusion cavity 20) expands outward and forms an extrusion with the inner wall of the hollow tube 10, so that The resistance to the heavy object gradually increases, and finally the movement speed of the heavy object 11 is reduced, so as to prevent the heavy object 11 from moving too fast. When the pressure is released, when the electric valve 9 is suddenly opened, the air pressure in the furnace quickly enters the hollow tube 10, and the air pressure in the hollow tube 10 increases rapidly. At this time, the extrusion pressure acting on the elastic diaphragm 9 becomes larger, and the resistance to the upward movement of the heavy object 11 becomes larger. As the heavy object 11 moves upward, the air pressure in the hollow tube 10 becomes lower and lower, and the extrusion pressure acting on the elastic diaphragm 9 becomes smaller and smaller, and the resistance to the heavy object 11 becomes smaller and smaller, so as to effectively prevent the heavy object 11 from moving too fast.

[0031] As a preferred implementation in this embodiment, Figure 4-6As shown, a plurality of arc-shaped extrusion rods 21, an extrusion plate 24 mounted on the upper end of the elastic diaphragm 19, and a plurality of movable rods 23 rotatably arranged in the extrusion chamber 20 via a pin shaft 26 are arranged in a circumferential manner in the extrusion chamber 20; A plurality of mounting plates 25 are slidably provided on the extrusion plate 24 through a slider 27, the lower end of the movable rod 23 is rotatably connected with the corresponding mounting plate 25, the upper end of the movable rod 23 is slidably contacted with the end of the corresponding abutment rod 22, and the abutment rod 22 is fixedly mounted on the corresponding arc-shaped extrusion rod 21; The outer end of the arc-shaped extrusion rod 21 contacts the inner wall of the elastic sealing sleeve 12; The pin shaft 25 is located above the middle portion of the movable rod 23 .

[0032] When the elastic diaphragm 9 is squeezed, the lower ends of the multiple movable rods 23 will rotate counterclockwise, thereby forming an extrusion resistance on the resistance rod 22, and finally causing the arc-shaped extrusion rod 21 to squeeze the elastic sealing sleeve 12. During the whole process, the mounting plate 25 always slides on the extrusion plate 24. Since the pin shaft 26 and the movable rod 23 cooperate to form a labor-saving lever, the variable resistance unit can achieve a good variable resistance effect and can effectively prevent the problem of the heavy object 11 moving too fast.

[0033] It should be noted that, first, both ends of the extrusion plate 24 are provided with limit slide bars 29, and the two limit slide bars 29 are slidably arranged in the slide grooves provided on the inner wall of the extrusion chamber 20 away from the ends of the extrusion plate 24, so that the extrusion plate 24 can move along the vertical direction, so that the forces on each movable rod 23 can be balanced, which is conducive to smooth deceleration and also prevents a certain part of the elastic sealing sleeve from being seriously worn and affecting its service life; second, the extrusion chamber 20 is respectively provided with limit cavities adapted to the arc-shaped extrusion rod 21 and the resistance rod 22.

[0034] An operating process of a low-pressure forming device for lightweight aluminum alloy castings comprises the following steps: S1: Inflation, first open the electric valve 9, and use the gravity of the weight 11 to quickly squeeze the nitrogen in the hollow tube 10 into the insulation furnace 2, and maintain the gas pressure in the furnace within the set constant pressure range, and then use the air compressor to accurately pressurize; S2: Nitrogen reflux. After the casting in the cavity is solidified and the holding furnace 2 is depressurized for the first time, the electric valve 9 is opened to allow the nitrogen in the holding furnace 2 to enter the hollow tube 10, and finally the pressure in the furnace is maintained within the set constant pressure range. S3: When the pressure is subsequently released, the pressure can be released directly through the pressure release pipe on the holding furnace 2.

[0035] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-pressure forming device for lightweight aluminum alloy castings, comprising a heat preservation furnace (2) mounted on a lifting base (1) and having a liquid riser, an opening and closing cylinder (6) mounted on a bracket (5), an upper mold (4) mounted at the lower end of the opening and closing cylinder (6), a lower mold (3) being arranged below the upper mold (4), a connecting pipe adapted to the output end of an air compressor being arranged on the outer wall of the heat preservation furnace (2), and a pressure relief pipe being also arranged on the heat preservation furnace (2), characterized in that: It also comprises a gas rapid filling unit, which can rapidly fill the insulation furnace (2) with inert gas before the aluminum alloy casting is performed, so that the gas pressure in the insulation furnace (2) is rapidly maintained within a constant range, and within this range, the aluminum alloy solution in the riser does not rise.

2. A lightweight aluminum alloy casting low-pressure forming device according to claim 1, characterized in that: The gas rapid filling unit comprises a hollow tube (10) with an opening at the upper end and a closed lower end, and a weight (11) slidably mounted in the inner cavity of the hollow tube (10); An elastic sealing sleeve (12) is provided on the outer wall of the weight (11), and the outer wall of the elastic sealing sleeve (12) is in sliding contact with the inner wall of the hollow tube (10); A plurality of main pipes (8) are arranged on the outer wall of the hollow pipe (10), and each of the plurality of main pipes (8) is provided with an electric valve (9), the gas outlet ends of the plurality of main pipes (8) are sealedly connected to the branch pipes (7) corresponding to the upper end of the insulation furnace (2), and the plurality of branch pipes (7) are in communication with the inner cavity of the insulation furnace (2); It also includes an air pressure sensor (28) arranged in the inner cavity of the air outlet of the main pipe (8), and the air pressure sensor (28) and the electric valve (9) are both electrically connected to the controller.

3. A lightweight aluminum alloy casting low-pressure forming device according to claim 2, characterized in that: It also includes a pressure relief unit to prevent the weight (11) from being pushed out of the hollow tube (10) by air pressure, and also to prevent the air pressure in the insulation furnace (2) from being unable to be maintained within a constant range when the hollow tube (10) subsequently injects gas into the insulation furnace (2).

4. A lightweight aluminum alloy casting low-pressure forming device according to claim 3, characterized in that: The pressure relief unit comprises an exhaust pipe (14) disposed through the weight (11) and a mounting frame (17) mounted on the upper end of the hollow tube (10) and having a gear rod (18); A ball valve (15) is installed on the exhaust pipe (14), and a driving gear ring (16) is installed on the outer wall of the hand-cranked wheel of the ball valve (15), and the gear rod (18) is arranged corresponding to the driving gear ring (16); A limiting protrusion (13) is provided on the outer wall of the elastic sealing sleeve (12), and a limiting sliding groove adapted to the limiting protrusion (13) is provided in the inner cavity of the hollow tube (10).

5. A lightweight aluminum alloy casting low-pressure forming device according to claim 4, characterized in that: It also includes a variable resistance unit, which can automatically change the resistance between the weight (11) and the inner wall of the hollow tube (10) according to the size of the air pressure, and the resistance is proportional to the air pressure.

6. A lightweight aluminum alloy casting low-pressure forming device according to claim 5, characterized in that: The variable resistance unit comprises an extrusion chamber (20) arranged inside the weight (11), and an air inlet end of the extrusion chamber (20) is sealed by an elastic diaphragm (19).

7. A lightweight aluminum alloy casting low-pressure forming device according to claim 6, characterized in that: The extrusion cavity (20) is provided with a plurality of arc-shaped extrusion rods (21) in a circular shape, an extrusion plate (24) mounted on the upper end of the elastic diaphragm (19), and a plurality of movable rods (23) rotatably arranged in the extrusion cavity (20) via a pin shaft (26); A plurality of mounting plates (25) are slidably arranged on the extrusion plate (24) via a slider (27); the lower end of the movable rod (23) is rotatably connected to the corresponding mounting plate (25); the upper end of the movable rod (23) is slidably contacted with the end of the corresponding abutment rod (22); and the abutment rod (22) is fixedly mounted on the corresponding arc-shaped extrusion rod (21); The outer end of the arc-shaped extrusion rod (21) contacts the inner wall of the elastic sealing sleeve (12); The pin shaft (25) is located above the middle portion of the movable rod (23).

8. An operating process of a low-pressure forming device for lightweight aluminum alloy castings, characterized in that: The following steps are included: S1: Inflation, first opening the electric valve (9), and using the gravity of the weight (11) to quickly squeeze the nitrogen in the hollow tube (10) into the insulation furnace (2), and maintaining the gas pressure in the furnace within a set constant pressure range, and subsequently precisely pressurizing by the air compressor; S2: nitrogen refluxes, and after the casting in the cavity is solidified and the insulation furnace (2) is depressurized for the first time, the electric valve (9) is opened to allow the nitrogen in the insulation furnace (2) to enter the hollow tube (10), and finally the gas pressure in the furnace is maintained within a set constant pressure range; S3: When the pressure is subsequently released, the pressure can be released directly through the pressure release pipe on the insulation furnace (2).

Images