A partition temperature control and pulse pressurization coordinated vacuum high-pressure casting mold and forming process

Abstract

The application discloses a vacuum high-pressure casting mold with partition temperature control and pulse pressurization and a forming process, and belongs to the technical field of metal precision casting. The mold divides a cavity into a thin-wall fast cooling area, a thick-wall hot spot area and a gate heat preservation area, sets 3D printing conformal cooling runner and an electromagnetic heating module, and realizes that the temperature difference of the mold is controlled within the range of ±3 DEG C. The forming process constructs a vacuum filling type environment, applies 120-180 MPa pulse local pressurization to the thick-wall hot spot area in the semi-solid state of the metal liquid, and is supplemented by constant pressure delay feeding. The application establishes a three-in-one collaborative mechanism of vacuum pore inhibition, partition temperature control and pulse pressurization, effectively solves the densification forming problem of aluminum alloy castings with a wall thickness difference of greater than or equal to 5 mm, significantly improves the density and mechanical properties of the castings, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of precision metal casting technology, specifically relating to a vacuum high-pressure casting mold and forming process with zoned temperature control and coordinated pulse pressurization. Background Technology

[0002] Aluminum alloys, due to their high specific strength, good thermal conductivity, and excellent formability, are widely used in high-end manufacturing fields such as new energy vehicles, aerospace, and construction machinery. High-pressure die casting is the mainstream process for achieving efficient and high-precision mass production of aluminum alloy structural components. In recent years, the demand for integrated and lightweight structural components has been increasing, leading to the widespread application of aluminum alloy castings with large wall thickness differences. These castings have large differences in wall thickness and complex structures. During conventional die casting, problems such as uneven temperature field distribution, air entrapment during filling, and insufficient feeding at thick-walled hot spots are prone to occur. This results in defects such as porosity, shrinkage cavities, and shrinkage porosity inside the casting, severely reducing the density, mechanical properties, and service safety of the casting. This has become a key challenge limiting the high-quality manufacturing of aluminum alloy die castings with large wall thickness differences.

[0003] To improve the quality of aluminum alloy die casting, researchers both domestically and internationally have conducted extensive studies on mold cooling, vacuum degassing, zoned temperature control, and magnetic field-assisted solidification, and have disclosed relevant technical solutions. Chinese patent application CN121732755A discloses a die casting water jacket insert with integrated conformal cooling channels. This technology uses selective laser melting to prepare conformal cooling channels and dynamically adjusts the cooling flow rate through magnetic control to achieve differentiated cooling in different areas of the mold, thus improving the problem of uneven cooling in traditional direct-flow water channels to some extent. However, this technology only optimizes the cooling channels and only has single cooling control capabilities. It lacks local heating and insulation structures, cannot achieve bidirectional control of the mold temperature field, makes it difficult to achieve directional sequential solidification of the casting, and has limited ability to suppress hot spots in thick walls.

[0004] Chinese patent application CN121491303A discloses a vacuum die-casting method for high-reliability aluminum alloy motor end caps. This technology uses electromagnetic coil-assisted solidification control, combined with a vacuum environment to reduce porosity defects in the casting, and utilizes magnetic field induction to delay solidification in the hot spot zone, ensuring unobstructed feeding channels. It is suitable for forming complex aluminum alloy structural parts. However, this technology lacks a conformal cooling system and zoned temperature control closed loop, making precise zoned temperature control of the mold impossible. Furthermore, it lacks a mechanical pulse pressurization structure, and its feeding capability relies solely on pressure transmission and prolonged solidification time, resulting in limited feeding strength for castings with large wall thickness differences. This limits its process adaptability to complex structural parts with significant wall thickness variations.

[0005] Chinese patent CN117001012B discloses an additive manufacturing method for a multi-structure conformal cooling channel plate, which optimizes the forming process of 3D printed conformal cooling channels, achieves high-precision flow channel fabrication, and improves the forming quality and reliability of complex conformal cooling channel structures. However, this technology only focuses on the additive manufacturing process of the flow channels and does not include a complete die-casting forming control system. It lacks core functions such as zoned temperature control, vacuum degassing, and casting feeding, making it unable to coordinate with the die-casting process and difficult to comprehensively solve the problem of internal defects in castings.

[0006] Chinese patent application CN120480141A discloses a vacuum die-casting system, a high-vacuum die-casting method, and its application. This system optimizes the response characteristics of the vacuum valve, achieving a high vacuum level of 50 mbar in the mold cavity, effectively reducing porosity defects in the castings. However, this technology focuses solely on optimizing the vacuum system, representing a single-defect control technique. It does not incorporate temperature field control and localized feeding techniques, making it difficult to achieve coordinated control of porosity and shrinkage defects.

[0007] In summary, existing aluminum alloy die-casting technologies generally suffer from limited functionality and low system integration. They typically involve optimizing individual technologies within cooling, vacuum, temperature control, and feeding, lacking a synergistic solution that integrates multiple technologies. This makes it difficult to simultaneously achieve precise zoned temperature control of the mold, efficient conformal cooling, high-vacuum degassing, and directional feeding for thick-walled parts, thus failing to meet the high-quality forming requirements of aluminum alloy castings with large wall thickness variations. Therefore, the industry currently lacks a vacuum high-pressure casting mold and forming process capable of achieving zoned temperature control, conformal cooling, pulsed pressurization, and high-vacuum coordinated control, suitable for aluminum alloy castings with large wall thickness variations. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies, such as single function, low system integration, lack of multi-technology synergy and coupling, and difficulty in simultaneously solving the problems of porosity, shrinkage cavities, hot spot concentration, and uneven microstructure in aluminum alloy castings with large wall thickness differences. This invention provides a vacuum high-pressure casting mold and forming process with zoned temperature control and pulse pressurization. Through a three-in-one synergistic mechanism of vacuum suppressing porosity, zoned temperature control eliminating hot spots, and pulse pressurization solving shrinkage cavities, this invention achieves high density, high performance, high efficiency, and stable forming of complex aluminum alloy castings with large wall thickness differences.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0010] A vacuum high-pressure casting mold with zoned temperature control and coordinated pulse pressurization includes:

[0011] The mold cavity is divided into a thin-walled rapid cooling zone, a thick-walled hot spot zone, and a runner insulation zone according to the difference in casting wall thickness.

[0012] 3D printed conformal cooling channels, with built-in thin-walled rapid cooling zone and thick-walled hot spot zone, the distance between the conformal cooling channels and the cavity surface is 8~15mm, and the channel diameter is 6~12mm;

[0013] An electromagnetic heating module is embedded in the thick-walled hot spot area and the runner insulation area. The electromagnetic heating module includes an induction coil and a magnetic core, and is used to rapidly heat local areas of the mold.

[0014] The zoned temperature control system includes temperature sensors, a controller, and a medium circulation device. The temperature sensors are respectively arranged in the thin-walled rapid cooling zone, the thick-walled hot spot zone, and the runner insulation zone to monitor the mold temperature of each zone in real time. The controller adjusts the cooling medium flow rate and electromagnetic heating power according to the temperature feedback to keep the temperature difference of each zone within ±3℃.

[0015] The vacuum pumping system, including a vacuum pump, vacuum tank, filter and vacuum valve, is used to extract the gas in the mold cavity before filling, so that the vacuum degree of the mold cavity is 35~50mbar.

[0016] A pulse boosting mechanism is provided at the corresponding position of the thick-walled hot spot area, including a boosting cylinder, a boosting rod and a sealing assembly. The boosting rod can apply pulse local boosting of 120~180MPa to the thick-walled area during the semi-solid stage of the molten metal.

[0017] Furthermore, the 3D printed conformal cooling channel is formed using selective laser melting technology, and the material is H13 mold steel or 18Ni300 martensitic aging steel. The surface roughness Ra of the inner wall of the channel is ≤3.2μm, and the channel layout follows the principle of equal spacing, with the distance between adjacent channels being 20~45mm.

[0018] Furthermore, the induction coil of the electromagnetic heating module adopts medium-frequency electromagnetic induction heating, with a frequency range of 8~18kHz and a power density of 0.7~1.5W / cm². 2 The magnetic core is made of ferrite material, and the distance between the induction coil and the cavity surface is 10~20mm.

[0019] Furthermore, the partitioned temperature control system adopts a PID closed-loop control algorithm, the cooling medium is a mixture of water-soluble release agent and cooling water, the cooling medium temperature is 15~35℃, and the flow rate adjustment range is 5~50L / min.

[0020] Furthermore, the vacuum valve of the vacuum pumping system is a hydraulically driven fast-response valve with an opening time of 42~50ms and a closing time of 28~35ms, and the vacuum tank volume is 5~10 times the cavity volume.

[0021] Furthermore, the front end of the booster rod of the pulse booster mechanism is a tapered structure with a taper of 2~5°, a front chamfer of R3~R5, a booster rod stroke of 20~50mm, and a booster response time of 80~100ms.

[0022] This invention also provides a zoned temperature-controlled synergistic pulse pressurization vacuum high-pressure casting process, comprising the following steps:

[0023] S1. Mold preheating and zone temperature control: Before mold closing, the thin-walled fast cooling zone is preheated to 120~150℃ by the electromagnetic heating module, and the thick-walled hot spot zone and the runner insulation zone are preheated to 180~260℃. The zone temperature control system is activated to stabilize the temperature of each zone within the set value ±3℃.

[0024] S2. Vacuum evacuation: After mold closing, start the vacuum evacuation system to extract the gas in the cavity, control the vacuum level of the cavity at 35~50mbar, and maintain this vacuum level until the filling is completed;

[0025] S3. Vacuum filling: The molten aluminum alloy is injected into the mold cavity at a low injection speed of 0.3~0.8m / s at a temperature of 680~720℃, and then the injection speed is switched to a high injection speed of 2.0~4.0m / s to complete the filling. The filling time is controlled at 0.1~0.3s.

[0026] S4. Pulse local pressurization: After the molten metal is filled, delay for 2-5 seconds until the molten metal in the thick-walled hot spot area solidifies to a semi-solid state, then start the pulse pressurization mechanism to apply a pulse local pressurization of 120-180MPa to the thick-walled hot spot area. The pulse frequency is 0.5-2.0Hz and the number of pulses is 3-8.

[0027] S5. Pressure holding and delayed feeding: After the pulse pressurization ends, maintain a pressure of 80~120MPa for 10~30s until the casting is completely solidified;

[0028] S6. Mold opening and part removal: Release the pressure holding, stop the temperature control system and vacuum system, and open the mold to remove the casting after the mold has cooled to 80~90℃.

[0029] Furthermore, the zoned temperature control described in step S1 adopts a dynamic thermal balance strategy. The temperature control system is started 5 to 10 minutes before filling and the electromagnetic heating power and cooling medium flow rate are adjusted in real time according to the feedback from the temperature sensor to ensure that the temperature difference between the thin-walled rapid cooling zone and the thick-walled hot spot zone is 60 to 100°C and the temperature difference between the thick-walled hot spot zone and the runner insulation zone is 15 to 25°C.

[0030] Furthermore, the triggering timing of the pulsed local pressurization in step S4 is determined by monitoring the temperature of the molten metal in the thick-walled hot spot region using a temperature sensor. Pressurization is initiated when the temperature drops to 20-40°C below the liquidus line.

[0031] Compared with the prior art, the technical advantages of the present invention are as follows:

[0032] 1. A three-pronged synergistic mechanism of "vacuum-temperature control-pressurization" achieves comprehensive defect suppression.

[0033] This invention constructs a synergistic mechanism of vacuum suppression of porosity, zoned temperature control to eliminate hot spots, and pulsed pressurization to solve shrinkage defects: The vacuum pumping system reduces the vacuum level of the mold cavity to 35-50 mbar before filling, which can suppress gas entrainment during the filling process of molten metal and reduce porosity defects from the source; The zoned temperature control system combines 3D printed conformal cooling channels and electromagnetic heating modules to achieve differentiated temperature control of the thin-walled rapid cooling zone, the thick-walled hot spot zone, and the runner insulation zone. Rapid cooling in the thin-walled area ensures the filling effect, delayed cooling in the thick-walled area optimizes the shrinkage compensation conditions, and insulation in the runner area maintains the smooth flow of the shrinkage compensation channel; The pulsed pressurization mechanism applies pulsed local pressurization of 120-180 MPa in the semi-solid stage of the molten metal, and breaks through the resistance of the solidification shell through pulsed pressure fluctuations, forcing the molten metal into the shrinkage region to complete the densification and shrinkage compensation. The three technologies rely on a zoned temperature control system to achieve sequential coordination. The vacuum stage lays the foundation for low-porosity forming, the temperature control stage constructs a reasonable solidification sequence, and the pressurization stage completes the final feeding, forming a complete defect suppression system. This can significantly reduce the porosity of castings, effectively eliminate shrinkage defects, and greatly reduce the scrap rate of casting production.

[0034] 2. Precise temperature control in zones regulates the solidification sequence, optimizing the forming effect of castings with varying wall thicknesses.

[0035] This invention achieves precise control of the solidification sequence of castings through a cavity partitioning design that integrates 3D-printed conformal cooling channels and electromagnetic heating modules. In the thin-walled rapid cooling zone, after filling, the casting is rapidly cooled below the solidus line, forming a self-compensating solidified shell. In the thick-walled hot spot zone, an electromagnetic heating module is installed, with the cooling medium flow rate controlled at 5-15 L / min, extending the solidification time in this area and ensuring the continuous unobstructed flow of the feeding channels. An electromagnetic heating module is also installed in the gating insulation zone to maintain the liquid state of the molten metal in the gating, forming a stable pressure transmission channel. This partitioned temperature control strategy can reduce the solidification time difference between different areas of the casting, balancing the filling quality of thin-walled castings with the feeding effect of thick-walled castings, and is suitable for the solidification control requirements of castings with large wall thickness differences.

[0036] 3. Dynamic compression with pulse boosting optimizes the compression effect.

[0037] This invention employs a pulsed pressure boosting mechanism, applying a pulsed pressure of 120-180 MPa during the semi-solid stage of the molten metal. The pulse frequency is 0.5-2 Hz, and the number of pulses is 3-8. A single pressure pulse creates instantaneous high pressure, breaking down the solidified skeleton and driving the molten metal to flow and fill shrinkage pores. Pressure is released during the pulse intervals, facilitating the escape and uniform distribution of gas inside the molten metal. The superposition of multiple pulses can increase the feeding depth. The pulsed pressure boosting triggering timing is monitored and controlled in real time by a temperature sensor. It is activated when the temperature of the molten metal in the thick-walled hot spot region drops to 20-40°C below the liquidus. At this stage, the molten metal possesses both fluidity and structural stability, making it a suitable range for pressure boosting and feeding. This can increase the density of the thick-walled areas of the casting and effectively improve the feeding efficiency.

[0038] 4. The integrated design of 3D printed conformal flow channels and electromagnetic heating optimizes mold structure and performance.

[0039] This invention integrates a 3D-printed conformal cooling channel and an electromagnetic heating module into the mold body, enabling flexible control of the mold's heating and cooling functions. The 3D-printed conformal cooling channel is formed using selective laser melting technology, allowing it to be flexibly bent along the cavity contour and maintain an equidistant distance of 8-15mm from the cavity surface, ensuring uniform cooling. The channel diameter can be adjusted as needed within the range of 6-12mm to adapt to the temperature control requirements of different areas. The surface roughness Ra of the channel's inner wall is ≤3.2μm, reducing fluid resistance and improving heat exchange efficiency. The electromagnetic heating module is embedded inside the mold, with the induction coil 10-20mm away from the cavity surface. It generates eddy current heat through electromagnetic induction, resulting in a heating rate superior to traditional heating methods. The heating power and heating area can be flexibly adjusted to achieve precise local temperature control. The integration of these two technologies endows the mold with rapid heating and cooling capabilities, shortens temperature control response time, and provides structural support for dynamic and precise temperature control.

[0040] 5. Zoned closed-loop temperature control system improves process stability and batch consistency.

[0041] This invention's zoned temperature control system employs a PID closed-loop control algorithm. Each temperature control zone is equipped with an independent temperature sensor, flow regulating valve, and electromagnetic heating controller, achieving independent temperature control and coordinated regulation. The temperature sensors are K-type thermocouples, positioned 3-5 mm from the mold cavity surface, to collect mold temperature data in real time. The controller, based on the deviation between the set temperature and the measured temperature, adjusts parameters through a PID algorithm to achieve stepless adjustment of the cooling medium flow rate from 5 to 50 L / min, stabilizing the temperature of each zone within the set value ±3℃. This system can be linked with the die-casting machine's production cycle, completing preheating before filling and automatically resetting the temperature control parameters after the casting is removed, maintaining dynamic temperature balance in the mold. Compared to traditional temperature control methods, this zoned closed-loop control significantly reduces temperature fluctuations, improves process repeatability, and reduces batch-to-batch casting quality variations.

[0042] 6. Vacuum high-pressure composite process, balancing the integrity of casting filling and the density of microstructure.

[0043] This invention integrates vacuum technology with high-pressure die casting, retaining the advantages of high-speed filling in high-pressure die casting while reducing gas entrapment by utilizing the vacuum environment. The vacuum pumping system activates after mold closing, reducing the cavity vacuum to 35-50 mbar. The vacuum valve employs a hydraulically driven, fast-response valve with a closing time of 28-35 ms, ensuring timely closure to prevent molten metal from entering the vacuum system. High-speed filling at 2.0-4.0 m / s in a vacuum environment optimizes the flow of molten metal, reducing turbulence and splashing, significantly decreasing gas entrapment, mitigating metal oxidation, reducing oxide inclusions, and improving the surface quality and internal purity of the casting. Compared to traditional die casting processes, this vacuum-high-pressure composite process significantly reduces porosity defects, enhances filling capacity in thin-walled areas, and adapts to the molding requirements of thinner-walled castings. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of this invention.

[0045] A vacuum high-pressure casting mold with zoned temperature control and coordinated pulse pressurization, the specific configurations of each structure are as follows:

[0046] Mold cavity: According to the difference in casting wall thickness, it is divided into thin-walled rapid cooling zone, thick-walled hot spot zone and runner insulation zone.

[0047] 3D-printed conformal cooling channels: These are integrally formed using selective laser melting technology, with H13 mold steel or 18Ni300 maraging steel as the forming material. The surface roughness Ra of the channel's inner wall is ≤3.2μm. The channels incorporate thin-walled rapid cooling zones and thick-walled hot spots, arranged according to an equidistant principle. The channel diameter is 6~12mm, the spacing between adjacent channels is 20~45mm, and the distance between the channel and the cavity surface is 8~15mm.

[0048] Electromagnetic heating module: Embedded in the thick-walled hot spot area and the insulated area of ​​the gating system, the module consists of an induction coil and a ferrite core, employing medium-frequency electromagnetic induction heating with a heating frequency of 8~18kHz and a power density of 0.7~1.5W / cm³. 2 The induction coil is 10-20mm away from the cavity surface, and is used for local rapid heating and constant temperature preservation of the mold.

[0049] The zoned temperature control system consists of temperature sensors, a PID closed-loop controller, and a media circulation device. Temperature sensors are respectively placed in the thin-walled rapid cooling zone, the thick-walled hot spot zone, and the runner insulation zone to collect the mold temperature in each zone in real time. The controller dynamically adjusts the cooling medium flow rate and electromagnetic heating power based on the temperature feedback. The cooling medium is a mixture of PW-100C type water-soluble polyether modified silicone oil release agent and cooling water, with a volume ratio of 1:20, a temperature of 15~35℃, and a flow rate of 5~50L / min.

[0050] Vacuum pumping system: It consists of a vacuum pump, vacuum tank, filter and vacuum valve. The volume of the vacuum tank is 5 to 10 times the volume of the mold cavity. The vacuum valve opens for 42 to 50 ms and closes for 28 to 35 ms, so as to stably control the vacuum degree of the mold cavity at 35 to 50 mbar and eliminate the porosity defects of the casting.

[0051] Pulse boosting mechanism: Located at the center of the thick-walled hot spot area, it consists of a boosting cylinder, a boosting rod, and a sealing assembly; the front end of the boosting rod has a 2~5° tapered structure with a chamfer of R3~R5, the boosting rod stroke is 20~50mm, and the boosting response time is 80~100ms; it can apply pulsed local boosting of 120~180MPa to the thick-walled area during the semi-solid stage of the molten metal to meet the densification and feeding requirements of the casting.

[0052] A zoned temperature-controlled, pulsed-pressure vacuum high-pressure casting process is disclosed, wherein the casting material is AlSi10Mg, AlSi7Mg, or A356.2 aluminum alloy, the ratio of the maximum wall thickness to the minimum wall thickness is 3:1 to 8:1, and the wall thickness difference is ≥5mm. The process includes the following steps:

[0053] S1. Mold preheating and zone temperature control: The zone temperature control system is started 5-10 minutes before mold closing. The electromagnetic heating module preheats the thin-walled fast cooling zone to 120-150℃, the thick-walled hot spot zone and the runner insulation zone to 180-260℃. The controller adjusts the heating power and cooling medium flow rate in real time to keep the temperature of each zone stable within the set value ±3℃ error range.

[0054] S2. Vacuum Evacuation: After the mold is closed, start the vacuum evacuation system to quickly extract the air from the cavity, control the cavity vacuum at 35~50mbar, and maintain this vacuum level throughout the process until the molten metal filling is completed, preventing gas from being entrained.

[0055] S3. Vacuum filling: The qualified aluminum alloy melt is heated to 680~720℃. First, the melt is injected into the mold cavity at a low injection speed of 0.3~0.8m / s to smoothly fill the runner and thin-walled area. Then, the injection speed is switched to a high injection speed of 2.0~4.0m / s to complete the overall filling. The total filling time is controlled at 0.1~0.3s to ensure complete filling without air entrapment.

[0056] S4. Pulse local pressure boosting: After filling is completed, delay for 2-5 seconds, monitor the temperature of the molten metal in the thick-walled hot spot area through a temperature sensor. When the temperature drops to 20-40℃ below the liquidus line, start the pulse pressure boosting mechanism to apply a pulse local pressure of 120-180MPa to the thick-walled hot spot area. The pulse frequency is 0.5-2.0Hz and the number of pulses is 3-8.

[0057] S5. Pressure holding and delayed shrinkage compensation: After the pulse pressurization operation is completed, maintain a pressure of 80~120MPa for 10~30s until the casting is completely solidified, eliminating shrinkage cavities and porosity defects in thick-walled areas.

[0058] S6. Mold opening and part removal: After the casting has solidified, release the mold holding pressure and simultaneously stop the zone temperature control system and vacuum pumping system; after the mold has cooled naturally to 80~90℃, open the mold and remove the casting.

[0059] The preparation principle of this invention:

[0060] 1. Cavity zone temperature control mechanism and molding regulation function

[0061] This invention, based on the principle of solidification sequence control in castings, divides the mold cavity into zones, forming a thin-walled rapid cooling zone, a thick-walled hot spot zone, and a gating insulation zone. This is suitable for the solidification characteristics of complex aluminum alloy castings with wall thickness differences ≥ 5mm. The solidification time varies significantly across different wall thickness zones. The zoned structure can match the differentiated temperature control requirements of each zone. The thin-walled zone is cooled more intensely to ensure the strength of the formed shell; the thick-walled hot spot zone uses temperature compensation to regulate the solidification rate; and the gating zone maintains a stable temperature to ensure the continuous unobstructed flow of the feeding channels. This zoned approach coordinates the overall solidification process of the casting, reduces the difference in solidification time between zones, and balances the integrity of filling in the thin-walled zone with the feeding effect in the thick-walled zone, effectively mitigating molding defects such as cold shuts, flow marks, and shrinkage porosity.

[0062] 2. Conformal cooling channel structure design and heat transfer characteristics

[0063] This invention utilizes selective laser melting technology to fabricate 3D-printed conformal cooling channels. The molding material is selected from H13 mold steel or 18Ni300 maraging steel, balancing mold structural strength and heat transfer performance. The distance between the channels and the cavity surface is controlled at 8-15 mm, the channel diameter is set at 6-12 mm, and an equidistant arrangement is adopted, with adjacent channels spaced 20-45 mm apart. These structural parameters balance the mold's mechanical properties and cooling uniformity, ensuring a stable temperature field on the cavity surface. The 3D printing process allows for flexible channel arrangement following the cavity contour, maintaining a constant distance between the channels and the cavity surface, improving the uneven cooling problem of traditional straight channels, enhancing mold surface temperature uniformity, and extending the mold's service life.

[0064] 3. Zoned electromagnetic heating mechanism and temperature field control

[0065] This invention employs medium-frequency electromagnetic induction heating to achieve precise local temperature control of the mold. The heating frequency is set to 8~18kHz, and the power density is controlled at 0.7~1.5W / cm². 2 The distance between the induction coil and the cavity surface is 10-20mm, and a ferrite core is used to improve electromagnetic coupling efficiency. This parameter configuration is adapted to the surface heating requirements of the mold, and the heat penetration depth can be adjusted to ensure heating efficiency and temperature uniformity, avoiding abnormal local temperature rise in the mold that could affect material properties. The electromagnetic heating method allows for flexible division of heating zones, and compared with traditional heating methods, it has a faster heating rate and lower energy consumption, adapting to the zoned constant temperature control requirements of thick-walled hot spots and runner insulation zones, thus optimizing the solidification structure of the casting.

[0066] 4. Pulse-pressurization compensation mechanism and tissue densification effect

[0067] This invention implements pulsed localized pressurization during the semi-solid stage of molten metal. The pressurization pressure is set to 120-180 MPa, the pulse frequency to 0.5-2 Hz, and the number of pulses to 3-8. The pressurization is triggered when the molten metal temperature drops to 20-40°C below the liquidus. This operating condition matches the rheological characteristics of semi-solid molten metal, effectively transmitting the feeding force and meeting the solidification feeding requirements of thick-walled areas. The pulsed loading method can act on the solidification skeleton of the casting, extending the depth of the feeding effect. Simultaneously, during the pressure intermittent phase, it promotes the expulsion of internal gases, synergistically improving the density of the casting structure, reducing shrinkage cavities and porosity defects in thick-walled areas, and optimizing the mechanical properties of the casting.

[0068] 5. Vacuum filling process matching and flow molding control

[0069] This invention employs a vacuum environment combined with a two-stage filling process. The cavity vacuum level is controlled at 35~50 mbar, with a low-speed filling speed of 0.3~0.8 m / s and a high-speed filling speed of 2.0~4.0 m / s. The vacuum environment optimizes the flow properties of the molten metal and reduces the risk of gas entrapment during the filling process. The two-stage filling process balances the stability of the gating system with the integrity of the cavity filling, adapting to the molding requirements of complex thin-walled structures. This process combination allows for complete molding at a relatively low melt filling temperature, reducing molten metal oxidation and burn-off, minimizing mold heat load, simultaneously suppressing porosity defects, and improving casting quality and production stability.

[0070] The present invention will be further illustrated below through specific embodiments and comparative examples.

[0071] Example 1

[0072] A vacuum high-pressure casting mold with zoned temperature control and coordinated pulse pressurization, the specific configurations of each structure are as follows:

[0073] Mold cavity: According to the difference in casting wall thickness, it is divided into thin-walled rapid cooling zone, thick-walled hot spot zone and runner insulation zone.

[0074] 3D-printed conformal cooling channels: These are integrally formed using selective laser melting technology, with H13 mold steel as the forming material. The surface roughness Ra of the inner wall of the channel is ≤3.2μm. The channel incorporates a thin-walled rapid cooling zone and a thick-walled hot spot zone, arranged according to an equidistant principle. Specifically, the thin-walled rapid cooling zone has a channel diameter of 10mm, an adjacent channel spacing of 25mm, and a distance of 10mm between the channel and the cavity surface; the thick-walled hot spot zone has a channel diameter of 8mm, an adjacent channel spacing of 40mm, and a distance of 12mm between the channel and the cavity surface.

[0075] Electromagnetic heating module: Embedded in the thick-walled hot spot area and the gating insulation area, the module consists of an induction coil and a ferrite core, employing medium-frequency electromagnetic induction heating. The heating frequency for the thick-walled hot spot area is 10kHz, and the power density is 1.0W / cm². 2 The heating frequency of the insulated area of ​​the gating system is 10kHz, and the power density is 0.8W / cm³. 2 The induction coil is 15mm away from the cavity surface, which is used for local rapid heating and constant temperature preservation of the mold.

[0076] The zoned temperature control system consists of temperature sensors, a PID closed-loop controller, and a media circulation device. Temperature sensors are respectively placed in the thin-walled rapid cooling zone, the thick-walled hot spot zone, and the runner insulation zone to collect the mold temperature in each zone in real time. The controller dynamically adjusts the cooling medium flow rate and electromagnetic heating power based on the temperature feedback. The cooling medium is a mixture of PW-100C type water-soluble polyether modified silicone oil release agent and cooling water, with a volume ratio of 1:20, a temperature of 15℃, and a flow rate of 5L / min.

[0077] Vacuum pumping system: It consists of a vacuum pump, vacuum tank, filter and vacuum valve. The volume of the vacuum tank is 5 times the volume of the mold cavity. The vacuum valve opens in 50ms and closes in 35ms, so as to stably control the vacuum degree of the mold cavity at 50mbar and eliminate the porosity defects of the casting.

[0078] Pulse boosting mechanism: Located at the center of the thick-walled hot spot area, it consists of a boosting cylinder, a boosting rod, and a sealing assembly; the front end of the boosting rod has a 2° conical structure with a front chamfer of R3, the boosting rod stroke is 20mm, and the boosting response time is 100ms; it can apply a pulse local boosting pressure of 120MPa to the thick-walled area during the semi-solid stage of the molten metal to meet the densification and feeding requirements of the casting.

[0079] A zoned temperature-controlled, pulsed pressure-boosting vacuum high-pressure casting process is disclosed. The casting material is AlSi7Mg aluminum alloy, with a minimum wall thickness of 3mm, a maximum wall thickness of 9mm, a wall thickness difference of 5mm, and a maximum wall thickness to minimum wall thickness ratio of 3:1. The process includes the following steps:

[0080] S1. Mold preheating and zone temperature control: The zone temperature control system is started 5 minutes before mold closing. The electromagnetic heating module preheats the thin-walled fast cooling zone to 120°C, the thick-walled hot spot zone to 180°C, and the runner insulation zone to 195°C. The controller adjusts the heating power and cooling medium flow rate in real time to keep the temperature of each zone stable within the set value ±3°C error range.

[0081] S2. Vacuum Evacuation: After the mold is closed, start the vacuum evacuation system to quickly extract the air from the cavity, reduce the cavity vacuum to 50mbar, and maintain this vacuum level throughout the process until the molten metal filling is completed, preventing gas from being entrained.

[0082] S3. Vacuum filling: The qualified AlSi7Mg aluminum alloy melt is heated to 680℃. First, the melt is injected into the mold cavity at a low injection speed of 0.3m / s to smoothly fill the runner and thin-walled area. Then, the injection speed is switched to a high injection speed of 2.0m / s to complete the overall filling. The total filling time is controlled at 0.3s to ensure complete filling without air entrapment.

[0083] S4. Pulse local pressure boosting: After filling is completed, delay for 2 seconds, monitor the temperature of the molten metal in the thick-walled hot spot area through a temperature sensor. When the temperature drops to 20°C below the liquidus line, start the pulse pressure boosting mechanism to apply a pulse local pressure of 120MPa to the thick-walled hot spot area. The pulse frequency is 0.5Hz and the number of pulses is 3.

[0084] S5. Pressure Holding and Delay Compensation: After the pulse pressurization operation is completed, maintain a pressure of 80MPa for 10s until the casting is completely solidified, eliminating shrinkage cavities and porosity defects in thick-walled areas.

[0085] S6. Mold Opening and Part Removal: After the casting has solidified, release the mold holding pressure and simultaneously stop the zoned temperature control system and vacuum pumping system; after the mold has cooled naturally to 80°C, open the mold and remove the casting.

[0086] Example 2

[0087] A vacuum high-pressure casting mold with zoned temperature control and coordinated pulse pressurization, the specific configurations of each structure are as follows:

[0088] Mold cavity: According to the difference in casting wall thickness, it is divided into thin-walled rapid cooling zone, thick-walled hot spot zone and runner insulation zone.

[0089] 3D-printed conformal cooling channels: These are integrally formed using selective laser melting technology, with H13 mold steel as the forming material. The surface roughness of the inner wall of the channel is Ra≤3.2μm. The channel incorporates a thin-walled rapid cooling zone and a thick-walled hot spot zone, arranged according to an equidistant principle. Specifically, the thin-walled rapid cooling zone has a channel diameter of 12mm, an adjacent channel spacing of 30mm, and a distance of 8mm between the channel and the cavity surface; the thick-walled hot spot zone has a channel diameter of 6mm, an adjacent channel spacing of 35mm, and a distance of 15mm between the channel and the cavity surface.

[0090] Electromagnetic heating module: Embedded in the thick-walled hot spot area and the gating insulation area, the module consists of an induction coil and a ferrite core, employing medium-frequency electromagnetic induction heating. The heating frequency in the thick-walled hot spot area is 15kHz, and the power density is 1.2W / cm². 2 The heating frequency of the insulated area of ​​the gating system is 15kHz, and the power density is 1.0W / cm³. 2 The induction coil is 15mm away from the cavity surface, which is used for local rapid heating and constant temperature preservation of the mold.

[0091] The zoned temperature control system consists of temperature sensors, a PID closed-loop controller, and a media circulation device. Temperature sensors are respectively placed in the thin-walled rapid cooling zone, the thick-walled hot spot zone, and the runner insulation zone to collect the mold temperature in each zone in real time. The controller dynamically adjusts the cooling medium flow rate and electromagnetic heating power based on the temperature feedback. The cooling medium is a mixture of PW-100C type water-soluble polyether modified silicone oil release agent and cooling water, with a volume ratio of 1:20, a temperature of 35℃, and a flow rate of 50L / min.

[0092] Vacuum pumping system: It consists of a vacuum pump, vacuum tank, filter and vacuum valve. The volume of the vacuum tank is 10 times the volume of the mold cavity. The vacuum valve opens in 45ms and closes in 30ms, so as to stably control the vacuum degree of the mold cavity at 40mbar and eliminate the porosity defects of the casting.

[0093] Pulse boosting mechanism: Located at the center of the thick-walled hot spot area, it consists of a boosting cylinder, a boosting rod, and a sealing assembly; the front end of the boosting rod has a 5° conical structure with a front chamfer of R5, a boosting rod stroke of 50mm, and a boosting response time of 80ms; it can apply a pulsed local boosting pressure of 180MPa to the thick-walled area during the semi-solid stage of the molten metal to meet the requirements of densification and feeding of castings.

[0094] A zoned temperature-controlled, pulse-pressurized vacuum high-pressure casting process is disclosed. The casting material is A356.2 aluminum alloy. The minimum wall thickness of the casting is 4mm, the maximum wall thickness is 32mm, the wall thickness difference is 28mm, and the ratio of the maximum wall thickness to the minimum wall thickness is 8:1. The process includes the following steps:

[0095] S1. Mold preheating and zone temperature control: The zone temperature control system is started 10 minutes before mold closing. The electromagnetic heating module preheats the thin-walled fast cooling zone to 130℃, the thick-walled hot spot zone to 230℃, and the runner insulation zone to 250℃. The controller adjusts the heating power and cooling medium flow rate in real time to keep the temperature of each zone stable within the set value ±3℃ error range.

[0096] S2. Vacuum Evacuation: After the mold is closed, start the vacuum evacuation system to quickly extract the air from the cavity, reduce the cavity vacuum to 40mbar, and maintain this vacuum level throughout the process until the molten metal filling is completed, preventing gas from being entrained.

[0097] S3. Vacuum filling: The qualified A356.2 aluminum alloy melt is heated to 720℃. First, the melt is injected into the mold cavity at a low injection speed of 0.8m / s to smoothly fill the runner and thin-walled area. Then, the injection speed is switched to a high injection speed of 4.0m / s to complete the overall filling. The total filling time is controlled at 0.1s to ensure complete filling without air entrapment.

[0098] S4. Pulse local pressure boosting: After filling is completed, delay for 5 seconds, monitor the temperature of the molten metal in the thick-walled hot spot area through a temperature sensor. When the temperature drops to 40°C below the liquidus line, start the pulse pressure boosting mechanism to apply a pulse local pressure of 180MPa to the thick-walled hot spot area. The pulse frequency is 2.0Hz and the number of pulses is 8.

[0099] S5. Pressure Holding and Delay Compensation: After the pulse pressurization operation is completed, maintain a pressure of 120MPa for 30s until the casting is completely solidified, eliminating shrinkage cavities and porosity defects in thick-walled areas.

[0100] S6. Mold Opening and Part Removal: After the casting has solidified, release the mold holding pressure and simultaneously stop the zoned temperature control system and vacuum pumping system; after the mold has cooled naturally to 90°C, open the mold and remove the casting.

[0101] Example 3

[0102] A vacuum high-pressure casting mold with zoned temperature control and coordinated pulse pressurization, the specific configurations of each structure are as follows:

[0103] Mold cavity: According to the difference in casting wall thickness, it is divided into thin-walled rapid cooling zone, thick-walled hot spot zone and runner insulation zone.

[0104] 3D-printed conformal cooling channels: These are integrally formed using selective laser melting technology, with H13 mold steel as the forming material. The surface roughness of the channel's inner wall is Ra≤3.2μm. The channels incorporate a thin-walled rapid cooling zone and a thick-walled hot spot zone, arranged according to an equidistant principle. Specifically, the thin-walled rapid cooling zone has a channel diameter of 8mm, an adjacent channel spacing of 20mm, and a distance of 8mm between the channel and the cavity surface; the thick-walled hot spot zone has a channel diameter of 10mm, an adjacent channel spacing of 45mm, and a distance of 12mm between the channel and the cavity surface.

[0105] Electromagnetic heating module: Embedded in the thick-walled hot spot area and the gating insulation area, the module consists of an induction coil and a ferrite core, employing medium-frequency electromagnetic induction heating. The heating frequency in the thick-walled hot spot area is 8kHz, and the power density is 0.9W / cm². 2 The heating frequency of the insulated area of ​​the gating system is 8kHz, and the power density is 0.7W / cm³. 2 The induction coil is 15mm away from the cavity surface, which is used for local rapid heating and constant temperature preservation of the mold.

[0106] The zoned temperature control system consists of temperature sensors, a PID closed-loop controller, and a media circulation device. Temperature sensors are respectively placed in the thin-walled rapid cooling zone, the thick-walled hot spot zone, and the runner insulation zone to collect the mold temperature in each zone in real time. The controller dynamically adjusts the cooling medium flow rate and electromagnetic heating power based on the temperature feedback. The cooling medium is a mixture of PW-100C type water-soluble polyether modified silicone oil release agent and cooling water, with a volume ratio of 1:20, a temperature of 25℃, and a flow rate of 25L / min.

[0107] Vacuum pumping system: It consists of a vacuum pump, vacuum tank, filter and vacuum valve. The volume of the vacuum tank is 7 times the volume of the mold cavity. The vacuum valve opens in 48ms and closes in 32ms, which stabilizes the vacuum level of the mold cavity at 45mbar and eliminates the porosity defects of the casting.

[0108] Pulse booster mechanism: Located at the center of the thick-walled hot spot area, it consists of a booster cylinder, a booster rod, and a sealing assembly; the front end of the booster rod has a 3.5° conical structure with a front chamfer of R4, a booster rod stroke of 35mm, and a booster response time of 90ms; it can apply a pulse local booster of 150MPa to the thick-walled area during the semi-solid stage of the molten metal to meet the requirements of densification and feeding of castings.

[0109] A zoned temperature-controlled, pulsed-pressure vacuum high-pressure casting process is disclosed. The casting material is AlSi10Mg aluminum alloy. The minimum wall thickness is 3.5 mm, the maximum wall thickness is 17.5 mm, the wall thickness difference is 14 mm, and the ratio of the maximum wall thickness to the minimum wall thickness is 5:1. The process includes the following steps:

[0110] S1. Mold preheating and zone temperature control: The zone temperature control system is started 7 minutes before mold closing. The electromagnetic heating module preheats the thin-walled fast cooling zone to 140℃, the thick-walled hot spot zone to 220℃, and the runner insulation zone to 240℃. The controller adjusts the heating power and cooling medium flow rate in real time to keep the temperature of each zone stable within the set value ±3℃ error range.

[0111] S2. Vacuum Evacuation: After the mold is closed, start the vacuum evacuation system to quickly extract the air from the cavity, reduce the cavity vacuum to 45mbar, and maintain this vacuum level throughout the process until the molten metal filling is completed, preventing gas from being entrained.

[0112] S3. Vacuum filling: The qualified AlSi10Mg aluminum alloy melt is heated to 700℃. First, the melt is injected into the mold cavity at a low injection speed of 0.5m / s to smoothly fill the runner and thin-walled area. Then, the injection speed is switched to a high injection speed of 3.0m / s to complete the overall filling. The total filling time is controlled at 0.2s to ensure complete filling without air entrapment.

[0113] S4. Pulse local pressure boosting: After a 3.5s delay following the completion of the filling process, the temperature of the molten metal in the thick-walled hot spot area is monitored by a temperature sensor. When the temperature drops to 30°C below the liquidus line, the pulse pressure boosting mechanism is activated to apply a pulse local pressure of 150MPa to the thick-walled hot spot area. The pulse frequency is 1.2Hz and the number of pulses is 5.

[0114] S5. Pressure holding and delayed shrinkage compensation: After the pulse pressurization operation is completed, maintain a pressure of 100MPa for 20s until the casting is completely solidified, eliminating shrinkage cavities and porosity defects in thick-walled areas.

[0115] S6. Mold Opening and Part Removal: After the casting has solidified, release the mold holding pressure and simultaneously stop the zoned temperature control system and vacuum pumping system; after the mold has cooled naturally to 85°C, open the mold and remove the casting.

[0116] Example 4

[0117] A vacuum high-pressure casting mold with zoned temperature control and coordinated pulse pressurization, the specific configurations of each structure are as follows:

[0118] Mold cavity: According to the difference in casting wall thickness, it is divided into thin-walled rapid cooling zone, thick-walled hot spot zone and runner insulation zone.

[0119] 3D-printed conformal cooling channels: These are integrally formed using selective laser melting technology, with the forming material being 18Ni300 maraging steel. The surface roughness of the channel's inner wall is Ra≤3.2μm. The channels incorporate a thin-walled rapid cooling zone and a thick-walled hot spot zone, arranged according to an equidistant principle. Specifically, the thin-walled rapid cooling zone has a channel diameter of 11mm, an adjacent channel spacing of 28mm, and a distance of 9mm between the channel and the cavity surface; the thick-walled hot spot zone has a channel diameter of 7mm, an adjacent channel spacing of 38mm, and a distance of 14mm between the channel and the cavity surface.

[0120] Electromagnetic heating module: Embedded in the thick-walled hot spot area and the gating insulation area, the module consists of an induction coil and a ferrite core, employing medium-frequency electromagnetic induction heating. The heating frequency in the thick-walled hot spot area is 12kHz, and the power density is 1.5W / cm². 2 The heating frequency of the insulated area of ​​the gating system is 12kHz, and the power density is 1.2W / cm³. 2 The induction coil is 15mm away from the cavity surface, which is used for local rapid heating and constant temperature preservation of the mold.

[0121] The zoned temperature control system consists of temperature sensors, a PID closed-loop controller, and a media circulation device. Temperature sensors are respectively placed in the thin-walled rapid cooling zone, the thick-walled hot spot zone, and the runner insulation zone to collect the mold temperature in each zone in real time. The controller dynamically adjusts the cooling medium flow rate and electromagnetic heating power based on the temperature feedback. The cooling medium is a mixture of PW-100C type water-soluble polyether modified silicone oil release agent and cooling water, with a volume ratio of 1:20, a temperature of 20℃, and a flow rate of 15L / min.

[0122] Vacuum pumping system: It consists of a vacuum pump, vacuum tank, filter and vacuum valve. The volume of the vacuum tank is 8 times the volume of the mold cavity. The vacuum valve opens in 46ms and closes in 31ms, which stabilizes the vacuum level of the mold cavity at 42mbar and eliminates the porosity defects of the casting.

[0123] Pulse booster mechanism: Located at the center of the thick-walled hot spot area, it consists of a booster cylinder, a booster rod, and a sealing assembly; the front end of the booster rod has a 3° conical structure with a front chamfer of R3.5, a booster rod stroke of 25mm, and a booster response time of 95ms; it can apply a pulse local booster of 140MPa to the thick-walled area during the semi-solid stage of the molten metal to meet the requirements of densification and feeding of castings.

[0124] A zoned temperature-controlled, pulsed pressure-boosting vacuum high-pressure casting process is disclosed. The casting material is AlSi7Mg aluminum alloy. The minimum wall thickness of the casting is 3mm, the maximum wall thickness is 24mm, the wall thickness difference is 21mm, and the ratio of the maximum wall thickness to the minimum wall thickness is 8:1. The process includes the following steps:

[0125] S1. Mold preheating and zone temperature control: The zone temperature control system is started 8 minutes before mold closing. The electromagnetic heating module preheats the thin-walled fast cooling zone to 130℃, the thick-walled hot spot zone to 230℃, and the runner insulation zone to 250℃. The controller adjusts the heating power and cooling medium flow rate in real time to keep the temperature of each zone stable within the set value ±3℃ error range.

[0126] S2. Vacuum Evacuation: After the mold is closed, start the vacuum evacuation system to quickly extract the air from the cavity, reduce the cavity vacuum to 42mbar, and maintain this vacuum level throughout the process until the molten metal filling is completed, preventing gas from being entrained.

[0127] S3. Vacuum filling: The qualified AlSi7Mg aluminum alloy melt is heated to 690℃. First, the melt is injected into the mold cavity at a low injection speed of 0.4m / s to smoothly fill the runner and thin-walled area. Then, the injection speed is switched to a high injection speed of 2.5m / s to complete the overall filling. The total filling time is controlled at 0.25s to ensure complete filling without air entrapment.

[0128] S4. Pulse local pressure boosting: After a 4-second delay following the completion of the filling process, the temperature of the molten metal in the thick-walled hot spot area is monitored by a temperature sensor. When the temperature drops to 25°C below the liquidus line, the pulse pressure boosting mechanism is activated to apply a pulse local pressure of 140MPa to the thick-walled hot spot area. The pulse frequency is 1.0Hz and the number of pulses is 6.

[0129] S5. Pressure Holding and Delay Compensation: After the pulse pressurization operation is completed, maintain a pressure of 90MPa for 25s until the casting is completely solidified, eliminating shrinkage cavities and porosity defects in thick-walled areas.

[0130] S6. Mold Opening and Part Removal: After the casting has solidified, release the mold holding pressure and simultaneously stop the zoned temperature control system and vacuum pumping system; after the mold has cooled naturally to 80°C, open the mold and remove the casting.

[0131] Example 5

[0132] A vacuum high-pressure casting mold with zoned temperature control and coordinated pulse pressurization, the specific configurations of each structure are as follows:

[0133] Mold cavity: According to the difference in casting wall thickness, it is divided into thin-walled rapid cooling zone, thick-walled hot spot zone and runner insulation zone.

[0134] 3D-printed conformal cooling channels: These are integrally formed using selective laser melting technology, with the forming material being 18Ni300 maraging steel. The surface roughness of the channel's inner wall is Ra≤3.2μm. The channels incorporate a thin-walled rapid cooling zone and a thick-walled hot spot zone, arranged according to an equidistant principle. Specifically, the thin-walled rapid cooling zone has a channel diameter of 9mm, an adjacent channel spacing of 22mm, and a distance of 11mm between the channel and the cavity surface; the thick-walled hot spot zone has a channel diameter of 8mm, an adjacent channel spacing of 42mm, and a distance of 13mm between the channel and the cavity surface.

[0135] Electromagnetic heating module: Embedded in the thick-walled hot spot area and the gating insulation area, the module consists of an induction coil and a ferrite core, employing medium-frequency electromagnetic induction heating. The heating frequency in the thick-walled hot spot area is 18kHz, and the power density is 1.3W / cm². 2 The heating frequency of the insulated area of ​​the gating system is 18kHz, and the power density is 1.1W / cm³. 2 The induction coil is 15mm away from the cavity surface, which is used for local rapid heating and constant temperature preservation of the mold.

[0136] The zoned temperature control system consists of temperature sensors, a PID closed-loop controller, and a media circulation device. Temperature sensors are respectively placed in the thin-walled rapid cooling zone, the thick-walled hot spot zone, and the runner insulation zone to collect the mold temperature in each zone in real time. The controller dynamically adjusts the cooling medium flow rate and electromagnetic heating power based on the temperature feedback. The cooling medium is a mixture of PW-100C type water-soluble polyether modified silicone oil release agent and cooling water, with a volume ratio of 1:20, a temperature of 30℃, and a flow rate of 40L / min.

[0137] Vacuum pumping system: It consists of a vacuum pump, vacuum tank, filter and vacuum valve. The volume of the vacuum tank is 9 times the volume of the mold cavity. The vacuum valve opens in 42ms and closes in 28ms, which stabilizes the vacuum level of the mold cavity at 35mbar and eliminates the porosity defects of the casting.

[0138] Pulse booster mechanism: Located at the center of the thick-walled hot spot area, it consists of a booster cylinder, a booster rod, and a sealing assembly; the front end of the booster rod has a 4° conical structure with a front chamfer of R4.5, a booster rod stroke of 40mm, and a booster response time of 85ms; it can apply a pulse local booster of 160MPa to the thick-walled area during the semi-solid stage of the molten metal to meet the requirements of densification and feeding of castings.

[0139] A zoned temperature-controlled, pulse-pressurized vacuum high-pressure casting process is disclosed. The casting material is A356.2 aluminum alloy. The minimum wall thickness of the casting is 4mm, the maximum wall thickness is 20mm, the wall thickness difference is 16mm, and the ratio of the maximum wall thickness to the minimum wall thickness is 5:1. The process includes the following steps:

[0140] S1. Mold preheating and zone temperature control: The zone temperature control system is started 9 minutes before mold closing. The electromagnetic heating module preheats the thin-walled fast cooling zone to 150°C, the thick-walled hot spot zone to 240°C, and the runner insulation zone to 260°C. The controller adjusts the heating power and cooling medium flow rate in real time to keep the temperature of each zone stable within the set value ±3°C error range.

[0141] S2. Vacuum Evacuation: After the mold is closed, start the vacuum evacuation system to quickly extract the air from the cavity, reduce the cavity vacuum to 35mbar, and maintain this vacuum level throughout the process until the molten metal filling is completed, preventing gas from being entrained.

[0142] S3. Vacuum filling: The qualified A356.2 aluminum alloy melt is heated to 710℃. First, the melt is injected into the mold cavity at a low injection speed of 0.6m / s to smoothly fill the runner and thin-walled area. Then, the injection speed is switched to a high injection speed of 3.5m / s to complete the overall filling. The total filling time is controlled at 0.15s to ensure complete filling without air entrapment.

[0143] S4. Pulse local pressure boosting: After a 3-second delay following the completion of the filling process, the temperature of the molten metal in the thick-walled hot spot area is monitored by a temperature sensor. When the temperature drops to 35°C below the liquidus line, the pulse pressure boosting mechanism is activated to apply a pulse local pressure of 160MPa to the thick-walled hot spot area. The pulse frequency is 1.5Hz and the number of pulses is 7.

[0144] S5. Pressure holding and delayed shrinkage compensation: After the pulse pressurization operation is completed, maintain a pressure of 110MPa for 15s until the casting is completely solidified, eliminating shrinkage cavities and porosity defects in thick-walled areas.

[0145] S6. Mold Opening and Part Removal: After the casting has solidified, release the mold holding pressure and simultaneously stop the zoned temperature control system and vacuum pumping system; after the mold has cooled naturally to 85°C, open the mold and remove the casting.

[0146] Example 6

[0147] A vacuum high-pressure casting mold with zoned temperature control and coordinated pulse pressurization, the specific configurations of each structure are as follows:

[0148] Mold cavity: According to the difference in casting wall thickness, it is divided into thin-walled rapid cooling zone, thick-walled hot spot zone and runner insulation zone.

[0149] 3D-printed conformal cooling channels: These are integrally formed using selective laser melting technology, with H13 mold steel as the forming material. The surface roughness of the channel's inner wall is Ra≤3.2μm. The channels incorporate a thin-walled rapid cooling zone and a thick-walled hot spot zone, arranged according to an equidistant principle. Specifically, the thin-walled rapid cooling zone has a channel diameter of 8mm, an adjacent channel spacing of 20mm, and a distance of 8mm between the channel and the cavity surface; the thick-walled hot spot zone has a channel diameter of 10mm, an adjacent channel spacing of 45mm, and a distance of 12mm between the channel and the cavity surface.

[0150] Electromagnetic heating module: Embedded in the thick-walled hot spot area and the runner insulation area, the module consists of an induction coil and a ferrite core, employing medium-frequency electromagnetic induction heating. The heating frequency for the thick-walled hot spot area and the runner insulation area is 8kHz, with a power density of 1.1W / cm². 2 The induction coil is 15mm away from the cavity surface, and is used for local rapid heating and constant temperature preservation of the mold.

[0151] The zoned temperature control system consists of temperature sensors, a PID closed-loop controller, and a media circulation device. Temperature sensors are respectively placed in the thin-walled rapid cooling zone, the thick-walled hot spot zone, and the runner insulation zone to collect the mold temperature in each zone in real time. The controller dynamically adjusts the cooling medium flow rate and electromagnetic heating power based on the temperature feedback. The cooling medium is a mixture of PW-100C type water-soluble polyether modified silicone oil release agent and cooling water, with a volume ratio of 1:20, a temperature of 25℃, and a flow rate of 25L / min.

[0152] Vacuum pumping system: It consists of a vacuum pump, vacuum tank, filter and vacuum valve. The volume of the vacuum tank is 7 times the volume of the mold cavity. The vacuum valve opens in 48ms and closes in 32ms, which stabilizes the vacuum level of the mold cavity at 42.5mbar and eliminates the porosity defects of the casting.

[0153] Pulse booster mechanism: Located at the center of the thick-walled hot spot area, it consists of a booster cylinder, a booster rod, and a sealing assembly; the front end of the booster rod has a 3.5° conical structure with a front chamfer of R4, a booster rod stroke of 35mm, and a booster response time of 90ms; it can apply a pulse local booster of 150MPa to the thick-walled area during the semi-solid stage of the molten metal to meet the requirements of densification and feeding of castings.

[0154] A zoned temperature-controlled, pulsed-pressure vacuum high-pressure casting process is disclosed. The casting material is AlSi10Mg aluminum alloy. The minimum wall thickness is 3.5 mm, the maximum wall thickness is 17.5 mm, the wall thickness difference is 14 mm, and the ratio of the maximum wall thickness to the minimum wall thickness is 5:1. The process includes the following steps:

[0155] S1. Mold preheating and zone temperature control: The zone temperature control system is started 7 minutes before mold closing. The electromagnetic heating module preheats the thin-walled fast cooling zone to 140℃, the thick-walled hot spot zone to 220℃, and the runner insulation zone to 240℃. The controller adjusts the heating power and cooling medium flow rate in real time to keep the temperature of each zone stable within the set value ±3℃ error range.

[0156] S2. Vacuum Evacuation: After the mold is closed, start the vacuum evacuation system to quickly extract the air from the cavity, reduce the cavity vacuum to 42.5 mbar, and maintain this vacuum level throughout the process until the molten metal filling is completed, preventing gas from being entrained.

[0157] S3. Vacuum filling: The qualified AlSi10Mg aluminum alloy melt is heated to 700℃. First, the melt is injected into the mold cavity at a low injection speed of 0.5m / s to smoothly fill the runner and thin-walled area. Then, the injection speed is switched to a high injection speed of 3.0m / s to complete the overall filling. The total filling time is controlled at 0.2s to ensure complete filling without air entrapment.

[0158] S4. Pulse local pressure boosting: After filling is completed, delay for 3.5s, monitor the temperature of the molten metal in the thick-walled hot spot area through a temperature sensor. When the temperature drops to 30°C below the liquidus line, start the pulse pressure boosting mechanism to apply a pulse local pressure of 150MPa to the thick-walled hot spot area. The pulse frequency is 1.25Hz and the number of pulses is 5.

[0159] S5. Pressure holding and delayed shrinkage compensation: After the pulse pressurization operation is completed, maintain a pressure of 100MPa for 20s until the casting is completely solidified, eliminating shrinkage cavities and porosity defects in thick-walled areas.

[0160] S6. Mold Opening and Part Removal: After the casting has solidified, release the mold holding pressure and simultaneously stop the zoned temperature control system and vacuum pumping system; after the mold has cooled naturally to 85°C, open the mold and remove the casting.

[0161] Comparative Example 1 (cavity vacuum degree exceeds 50 mbar)

[0162] Compared with Example 6, the vacuum pumping system stably controls the cavity vacuum at 80 mbar, while the rest of the mold structure, process steps and parameters are the same as in Example 6.

[0163] Comparative Example 2 (the electromagnetic heating power density in the thick-walled hot spot area and the insulated area of ​​the gating system is less than 0.7 W / cm³) 2 )

[0164] Compared with Example 6, the power density of the thick-walled hot spot area and the insulated area of ​​the gating system in the electromagnetic heating module was adjusted to 0.5 W / cm². 2 The remaining mold structure, process steps and parameters are the same as in Example 6.

[0165] Comparative Example 3 (3D printing conformal cooling channels removed)

[0166] Compared with Example 6, the 3D-printed conformal cooling channel is eliminated, and a conventional drilled cooling channel is used. The rest of the mold structure, process steps and parameters are the same as in Example 6.

[0167] Comparative Example 4 (Pulse booster mechanism removed)

[0168] Compared with Example 6, the pulse boosting mechanism is omitted, and the pulse local boosting operation is not performed. The rest of the mold structure, process steps and parameters are the same as those in Example 6.

[0169] Comparative Example 5 (without zoned temperature control system)

[0170] Compared with Example 6, the zoned temperature control system is eliminated, and all areas of the mold are preheated at a uniform temperature of 150°C. The flow rate of the cooling medium and the electromagnetic heating power are not dynamically adjusted. The rest of the mold structure, process steps and parameters are the same as those in Example 6.

[0171] Single-factor experiments on key process parameters

[0172] To determine the optimal range of key process parameters for this invention, the following single-factor experiments were designed. Each experiment was based on the scheme described in Example 3, with only the single parameter to be screened changed, while the remaining parameters remained unchanged. The tensile strength, yield strength, elongation after fracture, density, and porosity of the casting were used as comprehensive performance evaluation indicators.

[0173] 1. Single-factor experiment on cavity vacuum degree

[0174] Horizontal settings: 27.5, 35.0, 42.5, 50.0, 57.5 mbar. Other process parameters are the same as in Example 3. The test results are shown in Table 1.

[0175]

[0176] Results analysis: When the cavity vacuum degree is in the range of 27.5~42.5 mbar, the mechanical properties and density of the casting are significantly optimized with the increase of vacuum degree, and the porosity continues to decrease; when it exceeds 42.5 mbar, the increased vacuum pumping load can easily cause slight entrapment of molten metal, and the performance will decline. The optimal parameter is determined to be 42.5 mbar.

[0177] 2. Single-factor experiment on electromagnetic heating power density

[0178] Horizontal settings: 0.3, 0.7, 1.1, 1.5, 1.9 W / cm 2 The vacuum degree of the fixed cavity was 42.5 mbar, and the other parameters were the same as in Example 3. The test results are shown in Table 2.

[0179]

[0180] Results analysis: Increasing the heating power density can effectively eliminate thick-walled hot spots and improve filling fluidity (0.3~1.1 W / cm). 2 Performance steadily improved across the range; exceeding 1.1W / cm². 2 Subsequent localized overheating led to grain coarsening and a decrease in mechanical properties. The optimal parameter was determined to be 1.1 W / cm². 2 .

[0181] 3. Single-factor experiment on pulsed pressure boosting

[0182] Horizontal settings: 90, 120, 150, 180, 210 MPa; fixed cavity vacuum degree: 42.5 mbar; electromagnetic heating power density: 1.1 W / cm³. 2 The remaining parameters are the same as in Example 3, and the test results are shown in Table 3.

[0183]

[0184] Results analysis: Pulse pressurization can compact semi-solid molten metal and eliminate shrinkage cavities, with a steady improvement in densification effect in the 90~150MPa range; pressure exceeding 150MPa can easily lead to micro-deformation of the mold, stress concentration on the surface of the casting, and a slight decrease in performance. The optimal parameter was determined to be 150MPa.

[0185] 4. Single-factor experiment on pulse frequency

[0186] Horizontal settings: 0.25, 0.50, 0.75, 1.00, 1.25, 1.50, 1.75, 2.00, 2.25 Hz; fixed cavity vacuum degree: 42.5 mbar; electromagnetic heating power density: 1.1 W / cm³. 2 The pulse boosting pressure was 150 MPa, and the other parameters were the same as in Example 3. The test results are shown in Table 4.

[0187]

[0188] Results analysis: The feeding effect is best when the pulse frequency matches the solidification rate of the molten metal, and the performance continues to improve in the 0.25~1.25Hz range; frequencies exceeding 1.25Hz are prone to causing pressure fluctuations and disrupting the continuity of the solidification structure, resulting in a gradual decrease in performance. The optimal parameter was determined to be 1.25Hz.

[0189] 5. Single-factor experiment on holding pressure

[0190] Horizontal settings: 60, 80, 100, 120, 140 MPa; fixed cavity vacuum degree: 42.5 mbar; electromagnetic heating power density: 1.1 W / cm³. 2The pulse boosting pressure was 150 MPa, the pulse frequency was 1.25 Hz, and the other parameters were the same as in Example 3. The test results are shown in Table 5.

[0191]

[0192] Results analysis: Holding pressure can maintain the density of the microstructure during the solidification stage of the casting, and the performance gradually reaches its peak in the range of 60~100MPa; pressure exceeding 100MPa tends to prolong the solidification period and increase residual stress, resulting in a slight decline in overall performance. The optimal parameter was determined to be 100MPa.

[0193] Material performance index testing

[0194] The castings prepared in Examples 1-6 and Comparative Examples 1-5 were subjected to comprehensive performance testing. The test indicators included mechanical properties (tensile strength, yield strength, elongation after fracture), density, and porosity. The test methods followed national standards or industry-standard methods.

[0195] Test method description:

[0196] 1. Mechanical property testing: Room temperature tensile tests were conducted using a universal testing machine, in accordance with GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Room temperature test method". The specimens were taken from the thick-walled area of ​​the casting and processed into standard tensile specimens (10 mm in diameter and 50 mm in gauge length).

[0197] 2. Density test: The Archimedes displacement method was adopted, and the ratio of the actual density of the casting to the theoretical density was measured according to GB / T 43139-2023 "Density test of cast aluminum alloy liquid solidification specimen under reduced pressure".

[0198] 3. Porosity test: X-ray non-destructive testing combined with metallographic section analysis was adopted, and the porosity area ratio was statistically analyzed according to GB / T 5677-2018 "Radiographic Inspection of Castings".

[0199] The key performance indicators of the embodiments of the present invention are compared with those of the comparative examples, and the performance test results are shown in Table 6.

[0200]

[0201] Test Result Analysis:

[0202] In terms of overall performance, the castings of Examples 1-6 all exhibited excellent and stable properties, with tensile strength ranging from 331.4 to 399.8 MPa, yield strength from 241.2 to 291.6 MPa, elongation after fracture from 4.83 to 8.17%, density from 98.96 to 99.82%, and porosity from 0.06 to 0.56%. Among them, the casting of Example 6 achieved peak comprehensive performance, with a tensile strength of 399.8 MPa, a yield strength of 291.6 MPa, an elongation after fracture of 8.17%, a density as high as 99.82%, and an internal porosity of only 0.06%, realizing low-defect, high-density, and high-performance forming of aluminum alloy castings with large wall thickness differences.

[0203] Comparative Examples 1-5, due to the absence of the core structure of this invention or the exceeding of reasonable parameters, resulted in frequent internal defects in the castings, a comprehensive decline in overall performance, and all indicators significantly lower than those of all embodiments. In Comparative Example 1, the cavity vacuum exceeded the upper limit of this invention, leading to insufficient vacuum degassing and ineffective removal of residual gas from the cavity. This caused the casting porosity to surge to 1.00%, with porosity defects disrupting the continuity of the metal matrix, resulting in a significant decrease in tensile strength and yield strength, and severe deterioration of plasticity. In Comparative Example 2, the electromagnetic heating power density was lower than the lower limit of this invention, making precise temperature control between the thick-walled hot spot area and the gating insulation area impossible. This resulted in disordered solidification sequence, localized shrinkage porosity at the hot spots, a decrease in density to 97.68%, and a simultaneous decline in mechanical properties. In Comparative Example 3, the 3D-printed conformal cooling channel of this invention was omitted, and conventional drilled channels were used. This failed to achieve differentiated gradient cooling between thin-walled and thick-walled areas, resulting in extremely poor cooling uniformity and numerous shrinkage cavities inside the casting. The first example has poor overall performance due to its high porosity (1.47%) and density (96.51%). The second example, Comparative Example 4, lacks the pulse booster mechanism, thus missing the local densification and feeding effect during the semi-solid stage. After solidification and shrinkage in the thick-walled area, the molten metal cannot replenish the area, leading to a concentrated outbreak of shrinkage defects such as shrinkage porosity (1.83%) and elongation after fracture (2.95%). This significantly increases the brittleness of the casting, failing to meet the requirements for structural components. The third example, Comparative Example 5, eliminates the zoned temperature control system and adopts uniform preheating across the entire area, breaking the solidification gradient of rapid cooling for thin walls and slow cooling for thick walls. This results in coarse grains, uneven microstructure, increased residual stress, and a significant decrease in density and mechanical properties, further demonstrating that zoned temperature control is the core key to eliminating hot spots and optimizing the microstructure in this invention.

[0204] The above content should not be construed as limiting the specific implementation of this invention to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of this invention, and all such deductions or substitutions should be considered as falling within the patent protection scope defined by the submitted claims.

Claims

1. A vacuum high-pressure casting mold with zoned temperature control and coordinated pulse pressurization, characterized in that, include: The mold cavity is divided into a thin-walled rapid cooling zone, a thick-walled hot spot zone, and a runner insulation zone according to the difference in casting wall thickness. 3D printed conformal cooling channels, with built-in thin-walled rapid cooling zone and thick-walled hot spot zone, the distance between the conformal cooling channels and the cavity surface is 8~15mm, and the channel diameter is 6~12mm; An electromagnetic heating module is embedded in the thick-walled hot spot area and the runner insulation area. The electromagnetic heating module includes an induction coil and a magnetic core, and is used to rapidly heat local areas of the mold. The zoned temperature control system includes temperature sensors, a controller, and a medium circulation device. The temperature sensors are respectively arranged in the thin-walled rapid cooling zone, the thick-walled hot spot zone, and the runner insulation zone to monitor the mold temperature of each zone in real time. The controller adjusts the cooling medium flow rate and electromagnetic heating power according to the temperature feedback to keep the temperature difference of each zone within ±3℃. The vacuum pumping system, including a vacuum pump, vacuum tank, filter and vacuum valve, is used to extract the gas in the mold cavity before filling, so that the vacuum degree of the mold cavity is 35~50mbar. A pulse boosting mechanism is provided at the corresponding position of the thick-walled hot spot area, including a boosting cylinder, a boosting rod and a sealing assembly. The boosting rod can apply pulse local boosting of 120~180MPa to the thick-walled area during the semi-solid stage of the molten metal.

2. The vacuum high-pressure casting mold with zoned temperature control and coordinated pulse pressurization according to claim 1, characterized in that, The 3D printed conformal cooling channels are formed using selective laser melting technology. The materials are H13 mold steel or 18Ni300 martensitic aging steel. The surface roughness Ra of the inner wall of the channel is ≤3.2μm. The channel layout follows the principle of equal spacing, and the distance between adjacent channels is 20~45mm.

3. The vacuum high-pressure casting mold with zoned temperature control and coordinated pulse pressurization according to claim 1, characterized in that, The induction coil of the electromagnetic heating module uses medium-frequency electromagnetic induction heating, with a frequency range of 8~18kHz and a power density of 0.7~1.5W / cm². 2 The magnetic core is made of ferrite material, and the distance between the induction coil and the cavity surface is 10~20mm.

4. The vacuum high-pressure casting mold with zoned temperature control and coordinated pulse pressurization according to claim 1, characterized in that, The zoned temperature control system adopts a PID closed-loop control algorithm. The cooling medium is a mixture of water-soluble release agent and cooling water. The temperature of the cooling medium is 15~35℃, and the flow rate adjustment range is 5~50L / min.

5. The vacuum high-pressure casting mold with zoned temperature control and synergistic pulse pressurization according to claim 1, characterized in that, The vacuum valve of the vacuum pumping system is a hydraulically driven fast-response valve with an opening time of 42~50ms and a closing time of 28~35ms. The volume of the vacuum tank is 5~10 times the volume of the cavity.

6. The vacuum high-pressure casting mold with zoned temperature control and coordinated pulse pressurization according to claim 1, characterized in that, The pulse boosting mechanism has a tapered front end with a taper of 2-5°, a chamfer of R3-R5, a stroke of 20-50mm, and a boosting response time of 80-100ms.

7. A zoned temperature control and pulse-pressurized vacuum high-pressure casting process for a mold according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Mold preheating and zone temperature control: Before mold closing, the thin-walled fast cooling zone is preheated to 120~150℃ by the electromagnetic heating module, and the thick-walled hot spot zone and the runner insulation zone are preheated to 180~260℃. The zone temperature control system is activated to stabilize the temperature of each zone within the set value ±3℃. S2. Vacuum evacuation: After mold closing, start the vacuum evacuation system to extract the gas in the cavity, control the vacuum level of the cavity at 35~50mbar, and maintain this vacuum level until the filling is completed; S3. Vacuum filling: The molten aluminum alloy is injected into the mold cavity at a low injection speed of 0.3~0.8m / s at a temperature of 680~720℃, and then the injection speed is switched to a high injection speed of 2.0~4.0m / s to complete the filling. The filling time is controlled at 0.1~0.3s. S4. Pulse local pressurization: After the molten metal is filled, delay for 2-5 seconds until the molten metal in the thick-walled hot spot area solidifies to a semi-solid state, then start the pulse pressurization mechanism to apply a pulse local pressurization of 120-180MPa to the thick-walled hot spot area. The pulse frequency is 0.5-2.0Hz and the number of pulses is 3-8. S5. Pressure holding and delayed feeding: After the pulse pressurization ends, maintain a pressure of 80~120MPa for 10~30s until the casting is completely solidified; S6. Mold opening and part removal: Release the pressure holding, stop the temperature control system and vacuum system, and open the mold to remove the casting after the mold has cooled to 80~90℃.

8. The zoned temperature control and pulsed pressure boosting vacuum high-pressure casting process according to claim 7, characterized in that, The zoned temperature control described in step S1 adopts a dynamic thermal balance strategy. The temperature control system is started 5 to 10 minutes before filling. The electromagnetic heating power and cooling medium flow rate are adjusted in real time according to the feedback from the temperature sensor to ensure that the temperature difference between the thin-walled rapid cooling zone and the thick-walled hot spot zone is 60 to 100°C, and the temperature difference between the thick-walled hot spot zone and the runner insulation zone is 15 to 25°C.

9. The zoned temperature control and pulsed pressure boosting vacuum high-pressure casting process according to claim 7, characterized in that, The timing of triggering the pulsed local pressurization in step S4 is determined by monitoring the temperature of the molten metal in the thick-walled hot spot region using a temperature sensor. Pressurization is initiated when the temperature drops to 20-40°C below the liquidus line.

10. The zoned temperature control and pulsed pressure boosting vacuum high-pressure casting process according to claim 7, characterized in that, The process is applicable to complex aluminum alloy castings with a wall thickness difference ≥ 5 mm, where the ratio of the maximum wall thickness to the minimum wall thickness is 3:1 to 8:1, and the casting material is AlSi10Mg, AlSi7Mg, or A356.2 aluminum alloy.

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