Method and device for forming composite casting mold with quick response function of aerospace vehicle

Abstract

The invention discloses an aerospace vehicle rapid response function composite casting mold forming method and device, and belongs to the crossing field of a sand mold 3D printing technology and an integrated die casting technology. According to the method, firstly, a numerical control machining center or sand mold 3D printing equipment is adopted for manufacturing a multi-material composite core mold, then a cut or printed sand mold / core is assembled on a core mold base in a ridge-closing mode, a servo cabin metal mold is driven to be matched with the sand mold core mold through a mold closing locking mechanism, and the whole set of die-casting mold is formed. Secondly, light alloy (magnesium, aluminum, titanium and the like) is smelted at a high temperature, the speed field and the pressure field of high-temperature molten metal mold filling are indirectly controlled by controlling the movement speed of a piston rod, and high-quality castings are obtained through crystallization and solidification under the pressure. The innovatively proposed'metal mold and sand mold 'combined die-casting die can quickly realize the dynamic heat balance of the temperature of the die. According to the aerospace vehicle rapid response function composite casting mold forming method and device, innovative and green development of a light high-strength alloy casting process is promoted.

Description

Technical Field

[0001] The present invention belongs to the intersection field of sand mold 3D printing and integrated die-casting technology, and specifically relates to a method and device for forming a composite mold with a rapid response function for an aerospace vehicle. Background Art

[0002] Integrated die-casting technology refers to the technology of directly obtaining complete parts and realizing the original functions by redesigning multiple independent parts that need to be assembled in the original design, using an ultra-large (generally ≥6,000T) die-casting machine to form them in one die-casting, but it is still pressure casting in essence, with additional ultra-high vacuum and ultra-large size. In 2020, Tesla used integrated die-casting technology in the production of the rear floor of Model Y, integrating its original 80 stamped and welded parts into one component, which reduced its weight by 10% and reduced costs by 40%, which attracted much attention. Integrated die-casting technology is widely used in the aerospace field, which can improve the overall strength and precision of spacecraft, reduce manufacturing costs, and improve product performance and reliability.

[0003] Among various casting methods, sand casting is the most widely used. It is suitable for casting castings of different alloys, structures and sizes, and has a fast response. Sand casting is based on sand particles, with binders and other additives added to form sand with a certain fluidity. The sand is filled around the shape of the casting, and a complex casting mold can be formed under the action of external forces such as impact and vibration. At present, in my country's aerospace, rail transit and other fields, there is also a situation of small product production batches, many varieties and short cycles. There are large-profile parts suitable for low-pressure casting, thin-walled parts suitable for pressure-regulating casting, and thick-walled parts with large wall thickness differences suitable for differential pressure casting. However, my country's existing low-pressure, differential pressure and pressure-regulating related anti-gravity casting equipment has a single function and low pressure difference control accuracy, which cannot meet the development and trial production tasks of different products.

[0004] The method and device for rapid response functional composite casting of aerospace vehicles can quickly respond to the iterative design needs of complex thin-walled structures of aerospace vehicles. The applicable scope of integrated die-casting technology can realize the integrated rapid forming of complex thin-walled aerospace vehicle servo cabins. Through the precise control of metal filling and solidification processes through multi-material combined core molds, excellent performance of aerospace vehicle cabins can be obtained, which will promote the rapid development of the aviation and aerospace industries. Summary of the invention

[0005] To solve the above problems, the present invention discloses a method and device for forming a composite mold with a rapid response function for aerospace vehicles. The method and device are suitable for integrated rapid forming of large thin-walled rotating body castings, which is beneficial to improving the forming efficiency, flexible manufacturing capability and mechanical properties of the servo cabin of the aerospace vehicle.

[0006] The rapid response function composite casting method for aerospace vehicles has the following specific implementation steps:

[0007] Step (1) selecting a suitable type of foundry sand according to the characteristics of the casting, and using a CNC machining center or a sand mold 3D printing device to manufacture a multi-material composite core mold.

[0008] Step (2) assembles the cut or printed sand mold / core on the core mold base, and drives the servo cabin metal mold to cooperate with the sand mold core mold through the mold locking mechanism to form a complete set of die-casting molds.

[0009] Step (3) turns on the refrigeration device or the heating device to achieve thermal equilibrium between the temperature of the external metal mold and the internal sand mold core mold.

[0010] Step (4) adds the metal to be smelted from the feed hopper, passes through the high-temperature smelting device and the piston rod, and allows the molten metal to enter the die-casting mold to maintain a certain pressure and temperature.

[0011] Step (5) adjusts the temperature of the refrigeration device and the heating device so that the metal mold and the sand mold core mold have local differentiated temperatures; at the same time, the pressure difference of the flow channel inside the mold is controlled by the pressure regulating device to actively regulate the solidification process of the casting.

[0012] Step (6) After the metal filling is completed, the mold locking mechanism is driven to move to both sides to remove the sand mold and casting on the core mold base.

[0013] The frozen sand core mold in step (7) can be directly recycled (recycling rate ≥ 90%), and the resin sand core mold can be directly recycled and reused after vibration, crushing, magnetic separation and drying processes, thereby realizing green, low-carbon and environmentally friendly integrated die-casting process.

[0014] Furthermore, the molding sand material is quartz sand or non-quartz sand for casting, such as one or more of zircon sand, chromite sand and olivine sand, which have different thermal conductivity and specific heat, so as to manufacture a core mold with controllable shape.

[0015] Furthermore, the multi-material composite core mold can be one or more of a resin sand mold and a frozen sand mold. The mold temperature near the gate and runner is too high, and it is urgent to cool down and dissipate heat; while the mold temperature at the end of the mold is too low, and the melt fluidity decreases, resulting in defects such as cold shut and insufficient injection of the casting, and it is urgent to heat up. By combining the normal temperature resin sand core with the low temperature frozen sand core, the dynamic thermal balance of the integrated die casting mold can be achieved.

[0016] Furthermore, the sand mold 3D printing process adopts different resin contents (2wt.%~4wt.%) and curing agent contents (1wt.‰~5wt.‰), and the strength and hardness of the prepared sand mold meet different pressure casting conditions.

[0017] Furthermore, the frozen sand mold is coated with a uniform strengthening coating on its surface by a spraying process, so as to ensure that the frozen sand core can withstand the pressure of the high-temperature molten metal and play a sealing role. The coating can be epoxy resin, water-based or alcohol-based coating.

[0018] A composite casting device for aerospace vehicles with rapid response functions includes: an integrated die-casting frame, a core mold base, a smelting and pouring system, a mold assembly system, a temperature control system and a pressure regulating device. The core mold base is located on the integrated die-casting frame, and the smelting and pouring system includes a pouring platform bracket, a high-temperature smelting device, a feed hopper, a ball screw mechanism and a piston rod. The pouring platform bracket is connected to the integrated die-casting frame through the ball screw mechanism. The mold assembly system consists of a mold locking mechanism, a die-casting metal mold and a sand mold core mold. The hydraulic cylinder drives the die-casting metal molds on both sides to move toward each other and complete the assembly with the sand mold core mold. The temperature control system can realize a dual cycle of refrigeration and heating, and its installation position is located in the inner chamber of the die-casting metal mold. The refrigeration system consists of a refrigeration device, an air pump and a low-temperature gas delivery pipeline, and the heating system is realized by a thermal resistance wire.

[0019] Furthermore, the smelting and pouring system indirectly controls the velocity field and pressure field of the high-temperature molten metal filling the mold by controlling the movement speed of the piston rod, fills the mold cavity at an extremely high speed in an extremely short time, and crystallizes and solidifies under pressure to obtain a casting.

[0020] Furthermore, the filling speed of the high-temperature metal melt is 40-60 m / s, that of the thin-walled part is 80-100 m / s, and the holding time is set to 15-20 s.

[0021] Furthermore, the mold assembly system needs to be tested for sealing effect, with specific parameters: vacuuming time 1.5s, average vacuum degree 93kPa, and maximum 99.5kPa, indicating that the mold sealing structure has a good effect and can meet the authenticity required by high vacuum die-casting.

[0022] Furthermore, the refrigeration device can adjust the strength, hardness and air permeability of the frozen sand mold by accurately controlling the temperature of the cryogenic gas (-5°C to -40°C). The cryogenic gas can be one or more of cryogenic nitrogen, carbon dioxide and cold air.

[0023] Furthermore, the pressure of the pressure regulating device is set to -0.01MPa~-0.03MPa, and the directional flow and solidification of the molten metal are achieved through the local pressure difference, so that the solidification process of the casting with uneven wall thickness can be accurately controlled, the casting can be solidified layer by layer, and the overall mechanical properties of the casting can be improved.

[0024] Beneficial effects of the present invention:

[0025] 1. The present invention realizes the integrated die-casting of aerospace vehicle castings through a "metal mold + sand mold" combined mold; through the combined use of normal temperature resin sand core and low temperature frozen sand core, the temperature dynamic thermal balance of the integrated die-casting mold can be achieved. This method can accurately control the solidification process of the casting and improve the overall mechanical properties of the casting.

[0026] 2. The present invention integrates sand mold 3D printing technology into an integrated die-casting method, shortening the technical development cycle of light alloy cabins of aerospace vehicles, reducing cabin casting defects, and improving process yield and stability.

[0027] 3. The present invention reduces the mold cost of integrated die-casting technology and improves the manufacturing accuracy of complex molds, especially solving the problem of large-scale rapid and precise forming of high-performance, large-scale, extra-large, and complex aerospace vehicle castings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of a composite casting device with rapid response function for aerospace vehicles;

[0029] Figure 2 Schematic diagram of the internal assembly of the die-casting core mold and metal casting mold;

[0030] Figure 3 Schematic diagram of the piping arrangement of the heating and cooling devices;

[0031] Figure 4 Schematic diagram of the die-casting core mold and metal casting structure of the servo cabin;

[0032] List of reference numerals:

[0033] 1-integrated die-casting frame, 2-core mold base, 3-die-casting metal mold, 4-pouring platform bracket, 5-high-temperature melting device, 6-feed hopper, 7-ball screw mechanism, 8-piston rod, 9-mold locking mechanism, 10-pressure regulating device, 11-refrigeration device, 12-air pump, 13-thermal resistance wire, 14-low-temperature gas delivery pipeline; 15-servo cabin metal mold, 16-cold air channel; 17-servo cabin core mold. DETAILED DESCRIPTION

[0034] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to directions in the accompanying drawings, and the words "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0035] like Figure 1-4As shown, the composite casting forming device of the aerospace vehicle rapid response function of the present embodiment includes an integrated die-casting frame 1, a core mold base 2, a smelting and pouring system, a mold assembly system, a temperature control system and a pressure regulating device 10; the core mold base 2 is located on the integrated die-casting frame 1, and the smelting and pouring system is located above the mold assembly system, including a pouring platform bracket 4, a high-temperature smelting device 5, a feed hopper 6, a ball screw mechanism 7 and a piston rod 8; the high-temperature smelting device 5 is arranged on the pouring platform bracket 4, and a feed hopper 6 is provided on the top of the high-temperature smelting device 5; the rear side of the pouring platform bracket 4 is connected to the ball screw mechanism 7; the piston rod 8 is inside the chamber of the high-temperature smelting device 5, and pushes the melted high-temperature molten metal into the sand mold; The pouring platform bracket 4 is connected to the integrated die-casting machine frame 1 through the ball screw mechanism 7; the mold assembly system is composed of a mold locking mechanism 9, a die-casting metal mold 3 and a sand mold core mold; the hydraulic cylinder drives the die-casting metal molds 3 on both sides to move toward each other and complete the assembly with the sand mold core mold; the temperature control system can realize a dual cycle of refrigeration and heating, and its installation position is located in the inner chamber of the die-casting metal mold 3; the refrigeration system is composed of a refrigeration device 11, an air pump 12 and a low-temperature gas delivery pipeline 14, and the heating system is realized by a thermal resistance wire 13; a servo cabin metal mold 15 is provided in the die-casting metal mold 3; a servo cabin core mold 17 is provided in the servo cabin metal mold 15; a cold air channel 16 is provided on the servo cabin metal mold 15.

[0036] The smelting and pouring system indirectly controls the velocity field and pressure field of the high-temperature metal liquid filling the mold by controlling the movement speed of the piston rod, fills it into the mold cavity at a very high speed in a very short time, and crystallizes and solidifies under pressure to obtain a casting. The filling speed of the high-temperature metal melt is 40m / s, the thin-walled part is 80m / s, and the holding time is set to 15s. The mold assembly system needs to be tested for sealing effect, with specific parameters: vacuum time 1.5s, average vacuum degree 93kPa, which can meet the authenticity of high vacuum die-casting requirements. The refrigeration device achieves the strength, hardness and air permeability of the frozen sand mold by accurately controlling the temperature of the low-temperature gas (-40℃). The low-temperature gas can be one or more of low-temperature nitrogen, carbon dioxide and cold air. The pressure of the pressure regulating device is set to -0.01MPa, which realizes the precise control of the solidification process of the casting with uneven wall thickness, and the casting is solidified layer by layer, which improves the overall mechanical properties of the casting.

[0037] The specific implementation steps of the aerospace vehicle rapid response function composite casting method of this embodiment are as follows:

[0038] Step (1) selecting a suitable type of foundry sand according to the characteristics of the casting, and using a CNC machining center or a sand mold 3D printing device to manufacture a multi-material composite core mold.

[0039] Step (2) assembles the cut or printed sand mold / core on the core mold base, and drives the servo cabin metal mold to cooperate with the sand mold core mold through the mold locking mechanism to form a complete set of die-casting molds.

[0040] Step (3) turns on the refrigeration device or the heating device to achieve thermal equilibrium between the temperature of the external metal mold and the internal sand mold core mold.

[0041] Step (4) adds the metal to be smelted from the feed hopper, passes through the high-temperature smelting device and the piston rod, and allows the molten metal to enter the die-casting mold to maintain a certain pressure and temperature.

[0042] Step (5) adjusts the temperature of the refrigeration device and the heating device so that the metal mold and the sand mold core mold have local differentiated temperatures; at the same time, the pressure difference of the flow channel inside the mold is controlled by the pressure regulating device to actively regulate the solidification process of the casting.

[0043] Step (6) After the metal filling is completed, the mold locking mechanism is driven to move to both sides to remove the sand mold and casting on the core mold base.

[0044] The frozen sand core mold in step (7) can be directly recycled (recycling rate ≥ 90%), and the resin sand core mold can be directly recycled and reused after vibration, crushing, magnetic separation and drying processes, thereby realizing green, low-carbon and environmentally friendly integrated die-casting process.

[0045] The molding sand materials are quartz sand, zircon sand and chromite sand, and a core mold with controllable shape is manufactured. The mold temperature is too high near the gate and the runner, and it is urgently needed to cool down and dissipate heat; while the mold temperature at the end of the mold is too low, and the fluidity of the melt decreases, resulting in defects such as cold shut and dissatisfaction of the casting, and it is urgently needed to heat up. The dynamic thermal balance of the integrated die-casting mold can be achieved by combining the use of normal temperature resin sand cores and low-temperature frozen sand cores. The sand mold 3D printing process adopts different resin contents (2wt.%) and curing agent contents (2.5wt.‰), and the strength and hardness of the prepared sand mold meet different pressure casting conditions. The frozen sand mold adopts a spraying process to cover its surface with a uniform strengthening coating to ensure that the frozen sand core can withstand the pressure of high-temperature molten metal while playing a sealing role.

[0046] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above-mentioned implementation mode, but also include technical schemes composed of any combination of the above technical features.

Claims

1. A composite casting method for aerospace vehicle with rapid response function, characterized in that: The steps include: Step (1) selecting a suitable type of foundry sand according to the characteristics of the casting, and using a CNC machining center or sand mold 3D printing equipment to manufacture a multi-material composite core mold; Step (2) assembling the cut or printed sand mold / core on the core mold base, and driving the servo cabin metal mold to cooperate with the sand mold core mold through the mold locking mechanism to form a complete set of die-casting molds; Step (3) turning on the refrigeration device or the heating device to achieve thermal equilibrium between the temperature of the external metal mold and the internal sand mold core mold; Step (4) adding the metal to be smelted from the feed hopper, passing through the high-temperature smelting device and the piston rod so that the molten metal enters the die-casting mold to maintain a certain pressure and temperature; Step (5) adjusting the temperature of the refrigeration device and the heating device so that the metal mold and the sand mold core mold have different temperatures; at the same time, the pressure difference of the flow channel inside the mold is controlled by the pressure regulating device to actively regulate the solidification process of the casting; Step (6) After the metal filling is completed, the mold locking mechanism is driven to move to both sides to remove the sand mold and casting on the core mold base; Step (7) The frozen sand core mold is directly recycled, and the resin sand core mold is directly recycled and reused after the vibration, crushing, magnetic separation and drying processes, thereby realizing the green, low-carbon and environmentally friendly integrated die-casting process.

2. The method for forming a composite mold with a rapid response function for an aerospace vehicle according to claim 1, characterized in that: The molding sand material is quartz sand or non-quartz sand for casting, such as one or more of zircon sand, chromite sand and olivine sand, and its thermal conductivity and specific heat are different, so as to manufacture a sand mold core mold with controllable shape. The multi-material composite core mold is one or more of a resin sand mold and a frozen sand mold; by combining the normal temperature resin sand core with the low temperature frozen sand core, the dynamic thermal balance of the integrated die-casting mold is achieved.

3. The method for forming a composite mold with a rapid response function for an aerospace vehicle according to claim 1, characterized in that: The sand mold 3D printing process adopts a resin content of 2wt.% to 4wt.% and a curing agent content of 1wt.‰ to 5wt.‰, and the strength and hardness of the prepared sand mold meet different pressure casting conditions.

4. The method for forming a composite mold with a rapid response function for an aerospace vehicle according to claim 3, characterized in that: The frozen sand mold is coated with a uniform strengthening coating on its surface by a spraying process; the strengthening coating is epoxy resin, water-based or alcohol-based coating.

5. A composite casting device with a rapid response function for aerospace vehicles, characterized in that: The invention comprises an integrated die-casting frame (1), a core mold base (2), a smelting and pouring system, a mold assembly system, a temperature control system and a pressure regulating device (10); the core mold base (2) is located on the integrated die-casting frame (1), the smelting and pouring system is located above the mold assembly system, and comprises a pouring platform bracket (4), a high-temperature smelting device (5), a feed hopper (6), a ball screw mechanism (7) and a piston rod (8); the high-temperature smelting device (5) is arranged on the pouring platform bracket (4), and the top of the high-temperature smelting device (5) is provided with a feed hopper (6); the rear side of the pouring platform bracket (4) is connected to the ball screw mechanism (7); the piston rod (8) is inside the chamber of the high-temperature smelting device (5) to push the molten high-temperature metal liquid into the sand mold; the pouring platform bracket (4) is connected to the ball screw mechanism (7) by a pressure regulating device (8); the high-temperature smelting device (5 ... The ball screw mechanism (7) is connected to the integrated die-casting frame (1); the mold assembly system is composed of a mold locking mechanism (9), a die-casting metal mold (3) and a sand mold core mold; the hydraulic cylinder drives the die-casting metal molds (3) on both sides to move towards each other and complete the assembly with the sand mold core mold; the temperature control system can realize a dual cycle of refrigeration and heating, and its installation position is located in the inner chamber of the die-casting metal mold (3); the refrigeration system is composed of a refrigeration device (11), an air pump (12) and a low-temperature gas transmission pipeline (14), and the heating system is realized by a thermal resistance wire (13); a servo cabin metal mold (15) is provided in the die-casting metal mold (3); a servo cabin core mold (17) is provided in the servo cabin metal mold (15); and a cold air channel (16) is provided on the servo cabin metal mold (15).

6. The composite casting device for aerospace vehicle with rapid response function according to claim 5, characterized in that: The high-temperature metal melt filling speed is 40-60 m / s, 80-100 m / s for thin-walled parts, and the holding time is set to 15-20s.

7. The composite casting device for aerospace vehicle rapid response function according to claim 5, characterized in that: The mold assembly system needs to be tested for sealing effect, with specific parameters: vacuum time 1.5 s, average vacuum degree 93 kPa, and maximum 99.5 kPa, indicating that the mold sealing structure has a good effect and can meet the authenticity required by high vacuum die-casting.

8. The composite casting device for aerospace vehicle rapid response function according to claim 5, characterized in that: The refrigeration device precisely controls the temperature of the cryogenic gas to -5°C to -40°C; the cryogenic gas used is one or more of cryogenic nitrogen, carbon dioxide and cold air.

9. The composite casting device for aerospace vehicle with rapid response function according to claim 5, characterized in that: The pressure of the pressure regulating device (4) is set to -0.01 MPa to -0.03 MPa, so as to achieve precise control of the solidification process of the casting with uneven wall thickness, so that the casting can be solidified layer by layer, thereby improving the overall mechanical properties of the casting.

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