A die casting method for lightweight and high-toughness automobile aluminum castings

Abstract

The present application relates to the technical field of aluminum alloy material automobile parts processing, and particularly relates to a die casting method for lightweight high-toughness automobile aluminum castings, comprising the following steps: a, aluminum alloy melting; b, mold preparation; c, die casting forming; d, cooling and solidification; e, air cooling; and f, edge cutting. The air cooling step of the existing die casting forming process of automobile aluminum castings is improved. When the aluminum castings are air cooled, the outer side wall of the aluminum castings is air cooled by straight airflow, and the inner side wall of the aluminum castings is air cooled by circulating airflow formed by airflow guidance. The inner and outer side walls of the aluminum castings are synchronously cooled by the circulating airflow, which can well reduce energy consumption and improve the structural integrity, mechanical properties and subsequent processing adaptability of the aluminum castings.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy automotive parts processing technology, and in particular to a die-casting method for lightweight, high-toughness automotive aluminum castings. Background Technology

[0002] Die casting of automotive aluminum parts is an advanced manufacturing technology that involves pressing molten aluminum alloy into a metal mold cavity under high pressure and high speed, followed by rapid cooling and shaping to mass-produce automotive aluminum alloy structural and functional components. Its core advantages lie in high production efficiency, high dimensional accuracy, and the ability to form complex structures. Simultaneously, the lightweight nature of aluminum alloys (density only 1 / 3 that of steel) significantly reduces the curb weight of automobiles, contributing to fuel efficiency in gasoline vehicles and improving the range of new energy vehicles. Therefore, it has become an indispensable key process in modern automobile manufacturing, widely used in core systems such as engines, transmissions, chassis, and bodies.

[0003] The automotive aluminum die-casting part in this application refers to the automotive headlight drive aluminum disc. Since the drive aluminum disc in the automotive headlight is a key component integrating heat dissipation, circuit control and mechanical adjustment functions, its core function is to ensure the efficient and stable operation of the headlight under complex working conditions. In the die-casting production process of the automotive headlight drive aluminum disc, since the temperature of the die-cast part is still 200-250℃ after die-casting, the existing die-casting process includes an air cooling step to air cool the die-cast part. However, the existing air cooling steps only air cool one side of the die-cast part, which leads to uneven cooling of the die-cast part during air cooling. This can easily have an adverse effect on the three core dimensions of the die-cast part: structural integrity, mechanical properties and subsequent processing adaptability.

[0004] For example, Chinese invention patent application number CN201910007145.7 discloses an automatic die-casting production line and process for aluminum parts. The automatic die-casting process for aluminum parts discloses a cooling output step, which uses a cooling fan directly above the conveyor belt to simultaneously cool the aluminum workpiece. However, unilateral air cooling can easily cause uneven cooling of the aluminum workpiece. Summary of the Invention

[0005] To address the above problems, this invention provides a die-casting method for lightweight and high-toughness automotive aluminum castings. By improving the air-cooling step in the existing automotive aluminum casting die-casting process, the outer wall of the aluminum casting is directly cooled by the airflow during air cooling, while the inner wall of the aluminum casting is cooled by airflow guidance to form a circulating airflow. The circulating airflow is used to simultaneously cool the inner wall of the aluminum casting, so that the inner and outer walls of the aluminum casting are cooled synchronously.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A die-casting method for lightweight, high-toughness automotive aluminum castings includes the following steps:

[0008] Step a: Melting the aluminum alloy. Place the aluminum alloy ingot into a furnace and heat it until it reaches a molten state.

[0009] Step b: Mold preparation, cleaning and preheating the mold on the die-casting machine, and spraying the mold cavity with a release agent. After spraying, the mold is closed.

[0010] Step c, die casting: The molten aluminum from step a is injected into the pressure chamber of the die casting machine, and the aluminum is pressed into the mold cavity at high speed through the injection system;

[0011] Step d: Cooling and solidification, the molten aluminum in the mold cavity cools and solidifies into an aluminum casting;

[0012] Step e, air cooling: Open the mold and eject the aluminum casting from the mold cavity using the ejector rod. The ejected aluminum casting is then picked up by a robotic arm located next to the die-casting machine and transferred to the positioning slot of the air cooling equipment for air cooling. During air cooling, the inner and outer surfaces of the aluminum casting are cooled simultaneously.

[0013] Step f, trimming: After air cooling, the aluminum casting is transferred to the trimming equipment, which then trims the riser and polishes the burrs and flash of the aluminum casting.

[0014] As an improvement, in step a, the aluminum alloy ingot is one of the Al-Si series die-cast aluminum alloy grades: A380, ADC12, and AlSi8.

[0015] In step a, the melting temperature of the aluminum alloy ingot is usually controlled at 700-750℃.

[0016] The following are the melting and pouring temperatures for the above-mentioned die-cast aluminum alloy grades:

[0017]

[0018] As an improvement, in step b, the preheating temperature of the mold is 185-250℃, and the temperature difference inside the mold after preheating does not exceed ±10℃.

[0019] As an improvement, in step b, a spraying robot is installed on the top of the die-casting machine to automatically spray the mold release agent onto the cavity, and the spraying robot is stored above the residual water tank after the spraying is completed.

[0020] The spraying robot evenly sprays release agent onto the mold cavity and core surface to reduce friction between the casting and the mold, facilitating demolding. The selection and amount of release agent should be appropriate; too much will lead to surface defects and porosity in the casting. After spraying, the spraying robot moves to the top of the residual water tank to collect the release agent dripping from the spraying robot.

[0021] As an improvement, in step b, after the mold is closed, the mold is locked around its perimeter by a mold-locking assembly.

[0022] The clamping assembly locks the mold around its perimeter, ensuring that the clamping force is greater than the expansion force on the mold when the molten aluminum is filled, thus preventing molten aluminum leakage (i.e., excessive "flash") at the mold parting surface.

[0023] As an improvement, in step c, the injection system is a two-stage injection system. The first stage injection speed is 0.2-0.5 m / s and the injection time is 0.1-0.5 s. The second stage injection speed is 2-6 m / s and the injection time is 0.01-0.2 s. The injection pressure in the first stage is 30-70 MPa, and the pressure in the pressurization stage is 50-100 MPa.

[0024] The first stage of injection is used to fill the pressure chamber and initially fill the cavity, avoiding excessive turbulence and air entrapment of the molten aluminum. The second stage of injection is used to quickly fill the cavity, ensuring that the molten aluminum fills the entire cavity before solidification. It is applied after the molten aluminum is filled. The pressurization stage is used to compact the casting and reduce shrinkage cavities and porosity defects.

[0025] As an improvement, in step d, the molten aluminum in the mold cavity is cooled by water, with a cooling water flow rate of 0.5-1.0 m / s and a cooling water temperature of 20-30℃.

[0026] The water-cooled cooling channels are optimized according to the wall thickness and heat distribution of the aluminum casting to ensure uniform mold temperature. The conformal cooling channels can better fit the shape of the aluminum casting, improve the cooling effect, and reduce shrinkage cavities and deformation. The distance between the cooling channel and the cavity surface is usually 1.5-2 times the diameter of the cooling channel, and the spacing is usually 3-5 times the diameter of the cooling channel.

[0027] As an improvement, in step e, the aluminum casting is centrally cooled by an air-cooling device, which consists of several groups of axial flow fans arranged in regular polygons, and each group of axial flow fans is provided with a positioning groove group for supporting the aluminum casting on the front side, and the positioning groove group is inclined.

[0028] In air cooling mode, the axial flow fan cools the outer wall of the aluminum casting, and simultaneously, the axial flow fan creates a circulating gas flow for cooling on the inner wall of the aluminum casting.

[0029] As an improvement, in step e, the positioning groove assembly carrying the aluminum casting forms an airflow channel on the inner wall of the aluminum casting through louvers.

[0030] The positioning groove assembly that does not support the aluminum casting guides the airflow by forming a flat plate with louvers.

[0031] Compared to existing air-cooling technologies, the air-cooling technology of this invention can directly cool the outer wall of the aluminum casting while simultaneously forming a circulating cooling airflow on the inner wall of the aluminum casting. By utilizing the simultaneous cooling of the gas inside and outside, the technology achieves the effect of uniform cooling of the aluminum casting.

[0032] As an improvement, in step e, a guide fan is provided at the middle position of the regular polygonal area surrounded by the axial flow fan, which guides the hot airflow accumulated in the regular polygonal area.

[0033] Since the circulating airflow on the inner wall of the aluminum casting is guided by the direct cooling airflow on the outer wall of the aluminum casting, the heat of the aluminum casting is ultimately concentrated in the middle area of ​​the regular polygonal region. It is necessary to use a guide fan to quickly remove the heat to avoid heat accumulation and continuous temperature rise in the middle area.

[0034] The beneficial effects of this invention are as follows:

[0035] (1) In the air cooling step of the present invention, while the outer wall of the aluminum casting is air-cooled by direct airflow, the direct airflow is guided by the angle between the aluminum casting and the direct airflow, so that the direct airflow is guided to the inner wall of the adjacent aluminum casting for air cooling, and the air-cooling airflow on the inner wall will flow on the surface of the polygonal aluminum casting, so that the aluminum casting is uniformly cooled, while energy consumption is reduced, and the structural integrity, mechanical properties and subsequent processing adaptability of the aluminum casting are improved.

[0036] (2) In the mold preparation step of the present invention, a spraying robot is used to spray the mold cavity with a release agent to reduce the friction between the casting and the mold, making it easier to demold. After the spraying robot finishes spraying, it will be stored above the residual water tank. During the entire release agent spraying process, the spraying agent will not drip and the degree of automation is high.

[0037] (3) In the die casting process of the present invention, a two-stage injection and pressurization stage is adopted, which avoids excessive turbulence and air entrapment of aluminum liquid in the early stage of filling, and ensures that the aluminum liquid fills the cavity during the solidification period. In addition, the pressurization stage applies pressure after the aluminum liquid is filled to compact the casting, reduce shrinkage cavities and porosity defects during die casting of aluminum casting, and further improve the die casting quality of aluminum casting.

[0038] (4) In the die casting process, after the mold is closed, the mold locking assembly is used to lock the mold around the mold, so that when the mold is forming aluminum castings, the locking force is greater than the expansion force on the mold when the aluminum liquid is filled, preventing aluminum liquid leakage at the mold parting surface, improving the forming quality of aluminum castings and reducing flash forming.

[0039] In summary, this invention has the advantages of uniform cooling of aluminum castings, less flash in die casting, and high forming quality, and is especially suitable for the field of automotive aluminum casting forming and processing technology. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the die-casting process in Embodiment 1 of the present invention;

[0041] Figure 2 This is a schematic diagram of the aluminum casting structure of the present invention;

[0042] Figure 3 This is a three-dimensional structural diagram of the automotive aluminum casting die-casting system according to Embodiment 2 of the present invention;

[0043] Figure 4 This is a three-dimensional structural diagram of the die-casting machine according to Embodiment 2 of the present invention;

[0044] Figure 5 This is a side view of the die-casting machine according to Embodiment 2 of the present invention;

[0045] Figure 6 This is a side view of the mold structure in Embodiment 2 of the present invention;

[0046] Figure 7 This is a partial structural diagram of the mold-locking assembly in Embodiment 2 of the present invention;

[0047] Figure 8 This is a schematic diagram of the three-dimensional structure of the spraying robot in Embodiment 2 of the present invention;

[0048] Figure 9 This is a three-dimensional structural diagram of the material-grabbing robot of Embodiment 2 of the present invention;

[0049] Figure 10 This is a front view of the air-cooled device according to Embodiment 2 of the present invention;

[0050] Figure 11 This is a partial structural diagram of the air-cooled equipment in Embodiment 2 of the present invention;

[0051] Figure 12 This is a schematic diagram of the working airflow state of the air-cooled equipment in Embodiment 2 of the present invention;

[0052] Figure 13 This is a schematic diagram of the three-dimensional structure of the positioning groove group in Embodiment 2 of the present invention. Figure 1 ;

[0053] Figure 14 This is a schematic diagram of the three-dimensional structure of the positioning groove group in Embodiment 2 of the present invention. Figure 2 ;

[0054] Figure 15 This is a schematic diagram of the three-dimensional structure of the extrusion plate in Embodiment 2 of the present invention;

[0055] Figure 16 This is a schematic diagram of the three-dimensional structure of the positioning frame in Embodiment 2 of the present invention;

[0056] Figure 17 This is a three-dimensional structural diagram of the regulating valve in Embodiment 2 of the present invention;

[0057] Figure 18 This is a schematic diagram of the three-dimensional structure of an existing air-cooled equipment.

[0058] Figure reference numerals:

[0059] Aluminum casting 100, riser 101, flow channel 200;

[0060] Die casting machine 1, frame 11, injection mechanism 12, injection chamber 121, injection cylinder 122, sprue 123, mold closing mechanism 13, front plate 131, middle plate 132, rear plate 133, slide bar 134, pusher 135, mold 14, fixed mold 141, moving mold 142, mold locking assembly 15, locking frame 151, wedge block 152, locking block 153, locking pusher 154, locking groove 155;

[0061] 2. Spraying robot arm; 21. Residual water tank; 22. Robot arm; 23. Nozzle;

[0062] Material handling robot 3, material handling robot arm 31, gripper 32;

[0063] Air-cooled equipment 4, axial flow fan 41, positioning slot assembly 42, positioning frame 421, louver 422, hinged connecting rod 423, hook spring 424, notch 425, strip groove 426, extrusion plate 427, guide plate 428, housing 43, guide fan 44, regulating valve 45, valve plate 451, motor 452, connecting rod 453;

[0064] Conveyor line 5;

[0065] Edge trimming equipment 6. Detailed Implementation

[0066] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0067] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0068] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0069] Example 1:

[0070] like Figure 1 As shown, a die-casting method for lightweight, high-toughness automotive aluminum castings includes the following steps:

[0071] Step a: Melting the aluminum alloy. Place the aluminum alloy ingot into a furnace and heat it until it reaches a molten state.

[0072] Step b: Mold preparation, cleaning and preheating the mold on the die-casting machine, and spraying the mold cavity with a release agent. After spraying, the mold is closed.

[0073] Step c, die casting: The molten aluminum from step a is injected into the pressure chamber of the die casting machine, and the aluminum is pressed into the mold cavity at high speed through the injection system;

[0074] Step d: Cooling and solidification, the molten aluminum in the mold cavity cools and solidifies into an aluminum casting;

[0075] Step e, air cooling: Open the mold and eject the aluminum casting from the mold cavity using the ejector rod. The ejected aluminum casting is then picked up by a robotic arm located next to the die-casting machine and transferred to the positioning slot of the air cooling equipment for air cooling. During air cooling, the inner and outer surfaces of the aluminum casting are cooled simultaneously.

[0076] Step f, trimming: After air cooling, the aluminum casting is transferred to the trimming equipment, which then trims the riser and polishes the burrs and flash of the aluminum casting.

[0077] In step a, the aluminum alloy ingot is one of the Al-Si series die-cast aluminum alloy grades: A380, ADC12, and AlSi8.

[0078] In step a, the melting temperature of the aluminum alloy ingot is usually controlled at 700-750℃.

[0079] In this invention, the compositional characteristics, properties, and applications of Al-Si die-cast aluminum alloys are as follows:

[0080] The composition of aluminum alloy ingots with alloy grade ADC12 is as follows: Si content 9.6-12.0%, Cu content 1.5-3.5%, Mg content ≤0.3%, belonging to high silicon copper alloys; properties: tensile strength 220-240MPa, hardness 85-95HV, elongation 1.5-2.5%, high cost performance, suitable for mass production; applications: mostly used for structural parts (such as brackets, housings) and non-load-bearing parts (such as engine accessory housings, gearbox end covers).

[0081] The composition characteristics of aluminum alloy ingots with alloy grade A380 are as follows: Si content 7.5-9.5%, Cu content 3.0-4.0%, with a slightly lower silicon content than ADC12 and a higher copper content; performance: tensile strength 240-260MPa, hardness 90-100HV, mechanical properties superior to ADC12, and better wear resistance; applications: suitable for parts that bear certain loads (such as engine oil pans, clutch housings, steering gear housings).

[0082] The composition characteristics of aluminum alloy ingots with alloy grade A365 are: Si content 9.0-10.0%, Mg content 0.4-0.6%, Cu content ≤0.3%, belonging to high silicon magnesium alloy (copper-free or low copper); performance: tensile strength 260-280MPa, elongation 3.0-5.0%, toughness and impact resistance are better than the former two, and corrosion resistance is better; application: used for parts with high toughness requirements (such as chassis structural parts, battery housing support parts for new energy vehicles).

[0083] In addition, in step b, the preheating temperature of the mold is 185-250℃, and the temperature difference inside the mold after preheating does not exceed ±10℃.

[0084] It is worth noting that the functions of mold preheating include: 1. reducing the temperature difference between the molten aluminum and the mold, thus reducing thermal shock to the mold; 2. improving the fluidity of the molten aluminum, ensuring complete filling of the cavity; 3. controlling the cooling rate of the casting, reducing stress and deformation; 4. improving mold life and reducing the risk of thermal fatigue cracking.

[0085] Preferably, in step c, the injection system is a two-stage injection system. The first stage injection speed is 0.2-0.5 m / s and the injection time is 0.1-0.5 s. The second stage injection speed is 2-6 m / s and the injection time is 0.01-0.2 s. The injection pressure in the first stage is 30-70 MPa, and the pressure in the pressurization stage is 50-100 MPa.

[0086] It should be noted that the two-stage injection + pressurization setup of the aluminum casting die-casting device follows the core logic of the molten metal flow pattern within the mold cavity: "stable first, then fast; filling first, then pressurizing." By precisely matching the process requirements of different filling stages, it fundamentally resolves the core contradiction between "filling integrity" and "casting defect control." Its advantages can be broken down into the following six key dimensions based on specific parameters (speed, time, pressure):

[0087] Phase 1: Low-speed, low-pressure filling (0.2-0.5 m / s, 0.1-0.5 s, 30-70 MPa) – Solving the problem of “smooth filling and reducing initial defects”.

[0088] The core objective of the first stage is to ensure that the molten metal enters the mold cavity smoothly and orderly, avoiding "impact disturbances" in the early stages of filling, and reducing defects such as gas and oxide inclusions from the source.

[0089] Avoid air ingress and oxidation:

[0090] Molten aluminum has a low density (approximately 2.7 g / cm³) and is sensitive to fluidity. If the initial velocity is too high (e.g., 2-6 m / s directly), the molten metal will impact the cavity wall, gating system, or core like a "high-pressure water gun," forcibly drawing in air and paint volatiles from inside the cavity, forming subcutaneous pores and internal pinholes. At the same time, the high-speed impact will intensify the contact between the molten aluminum and air, generating more oxide inclusions (Al₂O₃). These defects will directly lead to a decrease in casting strength and failure of airtightness (such as hydraulic components and radiators).

[0091] At a low speed of 0.2-0.5 m / s, the molten aluminum can slowly rise along the cavity wall in a "laminar flow" state, and air can be discharged in an orderly manner through the exhaust channel. The amount of oxide inclusions generated is only 1 / 5 to 1 / 3 of that generated during high-speed filling.

[0092] Ensure that complex cavities are filled "without dead angles":

[0093] For complex castings with narrow slits, deep cavities, and multiple cores (such as automotive gearbox housings and motor end covers), low-speed filling allows the molten metal to have enough time (0.1-0.5s) to "penetrate" to every corner of the cavity, avoiding incomplete filling and cold shuts (gaps where the molten metal has not fused) caused by the liquid flow "rushing through" local areas.

[0094] Reduce mold impact and extend mold life:

[0095] Injection pressure of 30-70MPa is only used to propel the molten metal flow, not for "high-pressure impact". If the initial pressure is too high, the mold gate and cavity wall will be subjected to instantaneous impact loads, which will easily lead to mold cracking and gate wear in the long term. Low speed and low pressure can make the mold more evenly stressed, and the mold life can be extended by 20%-30%.

[0096] II. Second Stage: High-Speed ​​Injection (2-6 m / s, 0.01-0.2 s) – Solving the problem of “rapid shrinkage compensation and ensuring complete mold filling”

[0097] After the molten metal fills 80%-90% of the cavity through the first stage, the remaining space in the cavity (especially in thin-walled and far-end areas) will face the risk of being "unfilled" due to the rapid solidification of the molten aluminum (aluminum has a narrow crystallization temperature range and a fast solidification rate). The high-speed injection in the second stage is precisely to "fill the cavity before solidification".

[0098] Breaking the limits of thin-walled component filling:

[0099] For thin-walled castings with a wall thickness of ≤3mm (such as laptop casings and 5G base station heat sinks), the solidification time of molten aluminum in the mold cavity is only 0.05-0.1s. If the low speed of the first stage is used, the molten metal will solidify before reaching the end of the mold cavity, resulting in "insufficient filling"; while the high speed of 2-6m / s allows the molten aluminum to quickly "rush" to the end of the mold cavity within 0.01-0.2s, ensuring 100% filling of the thin-walled area.

[0100] Improve the surface quality and dimensional accuracy of castings:

[0101] High-speed liquid flow can more fully "fit" the mold cavity surface, accurately replicate the mold texture (such as patterns and markings), and reduce "surface depressions and pits"; at the same time, high-speed filling can reduce the temperature gradient difference of the molten metal in the cavity, avoid "dimensional deviation" caused by local solidification shrinkage, and the casting dimensional tolerance can be controlled within ±0.1mm (50% improvement in accuracy compared to low-speed filling).

[0102] III. Pressurization Stage: High-pressure compaction (50-100MPa) – Solving the problems of "densification and reducing internal shrinkage cavities and porosity".

[0103] During solidification, molten aluminum undergoes volume shrinkage (approximately 6.5%). If only injection pressure is used, the solidified area will experience insufficient molten metal to compensate for the shrinkage, resulting in internal shrinkage cavities and porosity (such as voids in the core of the casting), leading to a decrease in strength and airtightness (such as in engine cylinder blocks and hydraulic valve blocks). The core of the pressurization stage is to "apply high pressure in the early stages of solidification to forcibly replenish the molten metal."

[0104] Eliminate internal shrinkage cavities and porosity, and improve density:

[0105] When the molten metal begins to solidify (forming a "solidified shell" but the core remains liquid), a pressure of 50-100 MPa is applied through the injection punch to forcefully compress the molten metal, "replenishing" the solidification shrinkage area and "compacting" the shrinkage cavities. After pressurization, the density of the casting can be increased from 85%-90% to over 95%, the tensile strength increased by 15%-20%, and the airtightness (such as helium leak detection rate) can meet ≤1×10⁻⁶. -9 The stringent requirement of Pa·m³ / s.

[0106] Enhanced heat exchange between molten metal and mold:

[0107] High pressure allows molten metal to adhere more tightly to the mold cavity wall, accelerates heat conduction, shortens solidification time (by about 10%-15%), and indirectly improves die casting production efficiency (e.g., from 12 molds / minute to 14 molds / minute).

[0108] IV. Overall Synergistic Advantages: Balancing "quality" and "efficiency" to adapt to diverse scenario needs

[0109] The two-stage injection plus pressurization setup is not "stage-isolated," but rather achieves a synergistic effect of "1+1+1>3" through parameter matching:

[0110]

[0111] The essence of this parameter setting is to decompose "filling" and "compacting" into independent and controllable stages. Low speed solves "initial stability", high speed solves "later shrinkage compensation", and high pressure solves "solidification density" - ultimately achieving the production goal of "few defects, high precision, sufficient strength and durable molds" for aluminum castings. It is especially suitable for fields with stringent requirements for die casting quality, such as automobiles, 3C, and new energy.

[0112] In addition, in step d, the molten aluminum in the mold cavity is cooled by water, with a cooling water flow rate of 0.5-1.0 m / s and a cooling water temperature of 20-30℃.

[0113] It is worth noting that the cooling rate is a key factor affecting the microstructure and mechanical properties of aluminum castings; different cooling rates will lead to different microstructures and properties.

[0114] 1. The effect of cooling rate on tissue:

[0115] Rapid cooling (cooling rate > 50℃ / s): forms fine grains and a uniform microstructure, improving the strength and hardness of the casting.

[0116] Slow cooling (cooling rate <10℃ / s): leads to coarse grains, uneven microstructure, and reduced mechanical properties of castings.

[0117] 2. Factors affecting cooling rate:

[0118] Thermal conductivity of mold materials: Copper alloy molds have much higher thermal conductivity than steel molds, which can significantly improve the cooling rate.

[0119] Cooling system design: A well-designed cooling system can improve cooling efficiency and accelerate cooling speed.

[0120] Casting wall thickness: The thicker the wall, the slower the cooling rate, which makes it easier to form coarse structure and shrinkage defects.

[0121] Aluminum liquid temperature: The higher the temperature, the longer the cooling time and the slower the cooling rate.

[0122] 3. Methods for controlling cooling rate:

[0123] For thin-walled parts and simple structural parts, conventional cooling systems can be used, with the cooling rate controlled at 20-50℃ / s.

[0124] For thick-walled parts and complex structural parts, measures such as quench blocks and spot cooling can be used to increase the local cooling rate and control the cooling rate at 50-100℃ / s.

[0125] For castings requiring specific microstructure and properties, microstructure can be controlled by precisely regulating the cooling rate.

[0126] Example 2:

[0127] like Figures 2-17 As shown in the figure, with reference to Embodiment 1, Embodiment 2 of the present invention is applied to one of Embodiment 1. The system includes: a die-casting machine 1, a spraying robot 2, a material-grabbing robot 3, an air-cooling device 4, a conveyor line 5, and an edge-cutting device 6.

[0128] Among them, such as Figures 4-5 As shown, the die casting machine 1 includes a frame 11, an injection mechanism 12, a mold closing mechanism 13, and a mold 14. The injection mechanism 12, the mold closing mechanism 13, and the mold 14 are mounted on the frame 11. The injection mechanism 12 includes an injection chamber 121, an injection cylinder 122, and a sprue 123. The injection chamber 121 stores molten aluminum. The injection cylinder 122 is connected to the sprue 123. An injection punch is provided in the injection cylinder 122. The injection punch is made of high-strength alloy and is the core component that directly pushes the molten metal. The injection cylinder 122 is a hydraulic actuator that provides injection force and boosting pressure. The sprue 123 is connected to the fixed mold 141 in the mold 14. After the molten aluminum in the injection chamber 121 enters the sprue 123, it is pushed by the injection cylinder 122 and the injection punch along the sprue 123 into the cavity of the mold 14.

[0129] The mold closing mechanism 13 comprises a front plate 131, a middle plate 132, a rear plate 133, a slide bar 134, and a pusher 135. The fixed mold 141 of the mold 14 is mounted on the front plate 131, and the moving mold 142 is mounted on the middle plate 132. The front plate 131, the middle plate 132, and the rear plate 133 are arranged in parallel, and the front plate 131 and the rear plate 133 are both fixedly mounted on the frame 11. A slide bar 134 is arranged in parallel between the front plate 131 and the rear plate 133. The middle plate 132 is driven by the pusher 135 to move along the slide bar 134 to the front plate 131, so that the moving mold 142 and the fixed mold 141 close. It should also be emphasized that an ejector pin unit is installed on the middle plate 132. The ejector pin unit is used to eject the aluminum casting 100 in the cavity of the moving mold 142. The ejector pin unit consists of a hydraulic ejector and an ejector pin. The hydraulic ejector drives the ejector pin to extend and eject the aluminum casting 100.

[0130] In addition, a vacuum device is connected and installed on the moving mold 142. The vacuum device is used to remove the air in the cavity, so that the molten aluminum can fill the cavity.

[0131] And, as Figure 8 As shown, the spraying robot 2 is installed on the top of the die-casting machine 1, specifically directly above the fixed mold 141. The spraying robot 2 automatically sprays the mold release agent onto the cavity of the mold 14. After spraying, the spraying robot 2 is stored above the residual water tank 21, which collects the mold release agent dripping from the spraying robot 2 to prevent it from flowing everywhere.

[0132] The spraying robot 2 consists of a telescopic robotic arm 22 and a nozzle 23 installed at the telescopic swing end of the robotic arm 22. The robotic arm 22 drives the nozzle 23 to extend between the fixed mold 141 and the moving mold 142, and the nozzle 23 sprays the mold release agent onto the cavities on the fixed mold 141 and the moving mold 142.

[0133] Furthermore, such as Figures 6-7 As shown, after the mold 14 is closed, the mold 14 is locked around its perimeter by the mold locking assembly 15. Specifically, the mold locking assembly 15 includes a locking frame 151, a wedge block 152, a locking block 153, and a locking pusher 154. The locking frame 151 is installed on the side wall of the moving mold 142. The locking pusher 154 is installed on the locking frame 151 and is perpendicular to the locking frame 151. The pushing end of the locking pusher 154 is equipped with a locking block 153. The locking block 153 is provided with a locking groove 155 that matches the wedge block 152. The wedge block 152 is installed on the side walls of the fixed mold 141 and the moving mold 142 respectively. The locking of the fixed mold 141 and the moving mold 142 is achieved through the cooperation of the locking groove 155 and the wedge block 152.

[0134] like Figures 10-17As shown, an air-cooling device 4 is provided next to the die-casting machine 1. The die-cast aluminum casting 100 is picked up and removed from the mold 14 by the material-grabbing robot 3. The material-grabbing robot 3 picks up the aluminum casting 100 and transfers it to the air-cooling device 4 for centralized cooling. The air-cooling device 4 is composed of several groups of axial flow fans 41 arranged in a regular polygon (the regular polygon can be an equilateral triangle, a square, a regular pentagon, etc., and is not limited to the square defined in this embodiment). Each group of axial flow fans 41 is provided with a positioning groove group 42 for supporting the aluminum casting 100 on the front side. The positioning groove group 42 is inclined.

[0135] During air cooling, the axial flow fan 41 cools the outer wall of the aluminum casting 100, and simultaneously, the axial flow fan 41 forms a circulating gas flow cooling on the inner wall of the aluminum casting 100.

[0136] Specifically, the axial flow fan 41 is installed on the outside of the polygonal housing 43, making the axial flow fan 41 also polygonal in arrangement. The positioning slot assembly 42 is installed obliquely inside the housing 43, corresponding one-to-one with the axial flow fan 41. The positioning slot assembly 42 includes a positioning frame 421, louvers 422, a hinged connecting rod 423, and a hook spring 424. The positioning frame 421 is hollow for loading the aluminum casting 100. The side plates of the positioning frame 421 corresponding to the inner and outer walls of the aluminum casting 100 are respectively provided with notches 425 and strip grooves 426. The notches 425 are set directly opposite the outer wall of the aluminum casting 100, and the strip grooves are... The 426 is positioned opposite the inner wall of the aluminum casting 100, and several groups of the strip grooves 426 are arranged at equal intervals. A louver 422 is rotatably installed at each group of strip grooves 426. Along the direction in which the positioning frame 421 is inserted into the aluminum casting 100, an extrusion plate 427 is provided on the innermost louver 422 of the positioning frame 421. The extrusion plate 427 is set at a right angle to the corresponding louver 422. The extrusion plate 427 is located inside the positioning frame 421. The louvers 422 are synchronously rotated through the hinged connecting rod 423. A hook spring 424 is provided between the end of the hinged connecting rod 423 and the positioning frame 421.

[0137] Furthermore, a guide plate 428 for guiding gas flow is provided at the end of the positioning frame 421 that forms an angle with the housing 43.

[0138] An regulating valve 45 is also provided between the axial flow fan 41 and the corresponding positioning slot group 42. The regulating valve 45 is electrically controlled and has a rotating and swinging valve plate 451. Driven by the motor 452 and the connecting rod 453, all valve plates 451 are rotated and swinged, thereby controlling the airflow direction of the axial flow fan 41 towards the outer wall of the aluminum casting 100, so that the airflow on the outer wall of the aluminum casting 100 is smoother.

[0139] When the air-cooling device 4 is performing air cooling, the aluminum casting 100 is first inserted into the positioning frame 421 of the corresponding positioning slot group 42. The axial flow fan 41 is started to directly blow air onto the outer wall of the aluminum casting 100. The airflow passes through the notch 425 and acts on the outer wall of the aluminum casting 100. The airflow flows along the inclined direction of the aluminum casting 100 and reaches the guide plate 428. Through the guidance of the guide plate 428, the airflow flows to the inner wall of the next adjacent aluminum casting 100 for cooling.

[0140] like Figures 12-14 As shown, it is worth emphasizing that the positioning groove group 42 carrying the aluminum casting 100, after the aluminum casting 100 is inserted into the positioning frame 421, causes the louvers 422 to flip due to the contact and extrusion between the aluminum casting 100 and the extrusion plate 427, so that the louvers 422 are set perpendicular to the aluminum casting 100, thereby opening the strip groove 426 and forming a parallel flow channel 200 on the inner wall of the aluminum casting 100. The flow channel 200 guides the airflow, so that the airflow quickly carries away the heat on the inner wall of the aluminum casting 100, and this part of the airflow will continuously circulate on the polygonal arrangement of the inner wall of the aluminum casting 100.

[0141] When the positioning slot group 42 is not inserted into the aluminum casting 100 or the aluminum casting 100 in the positioning slot group 42 is removed, in order to ensure that the gas circulation on the inner wall of other aluminum castings 100 is not affected, it is necessary to ensure that the strip groove 426 on the positioning frame 421 is closed when the positioning slot group 42 is not carrying an aluminum casting 100. Therefore, when the positioning slot group 42 is not carrying an aluminum casting 100, the louver 422 flips and closes the strip groove 426 to form a flat plate by the elastic tension of the hook spring 424, so that the airflow flows on the flat plate formed by the louver 422 and is guided to the next group of aluminum castings 100, so that the gas circulation always flows on the inner wall of the aluminum casting 100.

[0142] like Figure 18 As shown, conventional air-cooling equipment uses a fan to directly blow air onto the casting to cool it. However, this conventional method only cools one side of the casting, which, as mentioned above, easily leads to uneven cooling. If air is blown directly onto both sides of the casting, the airflow will collide at the casting, causing heat to accumulate and not dissipate. In contrast, the air-cooling method of this invention blows air directly onto the outer wall of the aluminum casting while circulating air around the inner wall, allowing the heat to be quickly carried away and ensuring rapid cooling. Therefore, the air-cooling method of this invention represents a creative improvement in both cooling uniformity and speed compared to existing methods.

[0143] In order to avoid heat accumulation in the regular polygonal area surrounded by the axial flow fan 41, a guide fan 44 is provided at the middle position of the regular polygonal area, which guides the hot airflow accumulated in the regular polygonal area.

[0144] It should also be noted that, such as Figure 2 , Figure 9 As shown, the material handling robot 3 consists of a material handling robot arm 31 and a gripper 32. The gripper 32 transfers the aluminum casting 100 by gripping the riser 101 on the aluminum casting 100.

[0145] like Figure 3 As shown, the conveyor line 5 is set between the air-cooling equipment 4 and the edge-cutting equipment 6. The material-grabbing robot 3 picks up the air-cooled aluminum casting 100 from the air-cooling equipment 4 and places it on the conveyor line 5 for conveying. The conveyor line 5 is a conventional crawler conveyor line. After the aluminum casting 100 is conveyed by the conveyor line 5 to the edge-cutting equipment 6, it is moved by manpower or a robot arm into the edge-cutting equipment 6 for the removal of risers and flash at the edges.

[0146] Among them, the edge trimming device 6 is a hydraulic edge trimming device. The aluminum casting 100 is placed on the loading platform of the edge trimming device 6. The loading platform is provided with a positioning groove that conforms to the shape of the aluminum casting 100. Then, the hydraulic lifter located above the loading platform drives the cutter to descend and trim the aluminum casting 100 on the loading platform to remove the riser and flash on the edge of the aluminum casting 100. The shape of the cutter is consistent with the edge shape of the aluminum casting 100.

[0147] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A die-casting method for lightweight, high-toughness automotive aluminum castings, characterized in that, Includes the following steps: Step a: Melting the aluminum alloy. Place the aluminum alloy ingot into a furnace and heat it until it reaches a molten state. Step b: Mold preparation, cleaning and preheating the mold on the die-casting machine, and spraying the mold cavity with a release agent. After spraying, the mold is closed. Step c, die casting: The molten aluminum from step a is injected into the pressure chamber of the die casting machine, and the aluminum is pressed into the mold cavity at high speed through the injection system; Step d: Cooling and solidification, the molten aluminum in the mold cavity cools and solidifies into an aluminum casting; Step e, air cooling: Open the mold and eject the aluminum casting from the mold cavity using the ejector rod. The ejected aluminum casting is then picked up by a robotic arm located next to the die-casting machine and transferred to the positioning slot of the air cooling equipment for air cooling. During air cooling, the inner and outer surfaces of the aluminum casting are cooled simultaneously. Step f, trimming: After air cooling, the aluminum castings are transferred to the trimming equipment, which then trims the risers and polishes the burrs and flash of the aluminum castings. In step e, the aluminum casting is centrally cooled by an air-cooling device, which consists of several groups of axial flow fans arranged in regular polygons. Each group of axial flow fans has a positioning groove group for supporting the aluminum casting on its front side, and the positioning groove group is inclined. When air-cooled, the axial flow fan cools the outer wall of the aluminum casting, and simultaneously, the axial flow fan creates a circulating gas flow for cooling on the inner wall of the aluminum casting. The positioning groove assembly that supports the aluminum casting forms an airflow channel on the inner wall of the aluminum casting through louvers; the positioning groove assembly that does not support the aluminum casting forms a flat plate through louvers to guide the airflow.

2. The die-casting method for lightweight, high-toughness automotive aluminum castings according to claim 1, characterized in that: In step a, the aluminum alloy ingot is one of the Al-Si series die-cast aluminum alloy grades: A380, ADC12, and AlSi8. In step a, the melting temperature of the aluminum alloy ingot is usually controlled at 700-750℃.

3. The die-casting method for lightweight, high-toughness automotive aluminum castings according to claim 1, characterized in that: In step b, the preheating temperature of the mold is 185-250℃, and the temperature difference inside the mold after preheating does not exceed ±10℃.

4. The die-casting method for lightweight, high-toughness automotive aluminum castings according to claim 1, characterized in that: In step b, a spraying robot is installed on the top of the die-casting machine to automatically spray the mold release agent onto the cavity. After spraying, the spraying robot is stored above the residual water tank.

5. The die-casting method for lightweight, high-toughness automotive aluminum castings according to claim 1, characterized in that: In step b, after the mold is closed, the mold is locked around its perimeter by a mold-locking assembly.

6. The die-casting method for a lightweight, high-toughness automotive aluminum casting according to claim 1, characterized in that: In step c, the injection system is in two stages. The first stage injection speed is 0.2-0.5 m / s and the injection time is 0.1-0.5 s. The second stage injection speed is 2-6 m / s and the injection time is 0.01-0.2 s. The injection pressure in the first stage is 30-70 MPa and the pressure in the pressurization stage is 50-100 MPa.

7. The die-casting method for a lightweight, high-toughness automotive aluminum casting according to claim 1, characterized in that: In step d, the molten aluminum in the mold cavity is cooled by water with a flow rate of 0.5-1.0 m / s and a water temperature of 20-30℃.

8. The die-casting method for a lightweight, high-toughness automotive aluminum casting according to claim 1, characterized in that: In step e, a guide fan is installed at the middle position of the regular polygonal area surrounded by the axial flow fan, and the guide fan exhausts the hot airflow accumulated in the regular polygonal area.

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