A method for simultaneously inhibiting the pre-crystalline structure and the fracture chill layer of a high-pressure casting AlSi10MnMg alloy material

Abstract

The application discloses a method for synchronously inhibiting pre-crystalline structure and fracture chill layer of a high-pressure casting AlSi10MnMg alloy material, and belongs to the technical field of non-ferrous metal new material preparation. The method comprises the following steps: refining by a transfer ladle, staticizing in a holding furnace, regulating and controlling alloy components to a narrow range, and re-measuring cleanliness; a high-pressure casting whole-process temperature drop control system is constructed, high-temperature staticizing of aluminum liquid in the holding furnace, material ladle heat radiation insulation, high-temperature hot oil circulation insulation of a split pressure chamber, and a three-stage pressure injection process with high slow speed and low fast speed are combined to control the residence time of the aluminum liquid in the pressure chamber, the material ladle soup taking single cycle time and the filling rate of the pressure chamber; and the die casting parameters are optimized to match the split pressure chamber to realize precise mold filling and temperature control. The method can eliminate coarse pre-crystalline structure, reduce the maximum size of the fracture chill layer, improve the microstructure uniformity of the castings, and make the cast body as-cast tensile strength, yield strength and elongation after fracture meet the demand of high-end precision parts on mechanical property stability.

Description

Technical Field

[0001] This invention belongs to the field of new non-ferrous metal material preparation technology, specifically relating to a method for simultaneously suppressing the pre-crystallization structure and fracture chilling layer in high-pressure cast AlSi10MnMg alloy materials. Background Technology

[0002] With the rapid development of automotive lightweighting and the new energy vehicle industry, as well as the increasing demands on the strength, toughness, and dimensional accuracy of components from high-end equipment such as drones and robots, high-pressure die-casting aluminum alloys are widely used in the manufacturing of integrated die-cast parts due to their advantages of high efficiency, low cost, and near-net-shape forming. AlSi10MnMg alloy, as a typical die-casting aluminum alloy, combines excellent casting performance with good mechanical properties, meeting the forming requirements of complex structural parts. It is suitable for the production of integrated die-cast aluminum alloy automotive parts, and the stability of its mechanical properties directly determines the safety and reliability of the final product.

[0003] However, in actual industrial production, the mechanical properties (especially elongation) of high-pressure cast AlSi10MnMg alloy products exhibit significant fluctuations in different parts of the product, and are generally lower than the theoretical mechanical properties of the material. This problem severely restricts the further application of this alloy in the field of high-end precision parts. The core reason for the fluctuation and decline in mechanical properties is the simultaneous generation of two harmful coarse phases in the pressure chamber during high-pressure casting: pre-crystallized structures (ESCs) and a fracture chilling layer, such as... Figure 1 As shown, these two coarse phases enter the mold cavity with the molten aluminum and remain in the casting, disrupting the continuity of the matrix microstructure, causing stress concentration, and consequently leading to large fluctuations in the alloy's elongation after fracture, strength, and other properties.

[0004] like Figure 2 , Figure 3 As shown, the formation of precrystallized structures (ESCs) in the pressure chamber originates from the residence process of molten aluminum in the pressure chamber. After the molten aluminum is injected into the pressure chamber, there is a certain residence time before the injection punch advances. During this period, due to heat exchange between the pressure chamber wall and the molten aluminum, the molten aluminum undergoes non-uniform cooling, forming coarse α-Al and α-Al(FeMn)Si crystal nuclei inside the molten aluminum. These nuclei continuously grow to form the precrystallized structure. The grain size of the precrystallized structure is much larger than that of the matrix grains, and its loose structure and poor bonding with the matrix significantly reduce the toughness and plasticity of the alloy, making the casting prone to fracture at the precrystallized structure under stress.

[0005] The formation of the fracture chilled layer is related to the contact between the molten aluminum and the inner wall of the pressure chamber. After the molten aluminum is injected into the pressure chamber, it comes into contact with the low-temperature inner wall of the pressure chamber and rapidly cools to form a dense chilled layer. When the injection punch pushes the molten aluminum to fill the mold at high speed, the high-speed flow of molten aluminum will exert a shearing and scouring effect on the chilled layer on the inner wall of the pressure chamber, breaking the chilled layer into fragments of varying sizes, i.e., the fracture chilled layer. These fragments enter the mold cavity with the molten aluminum and are distributed inside the casting. They not only disrupt the continuity of the matrix structure, but also form microcracks at the interface between the fragments and the matrix, further deteriorating the mechanical properties of the alloy.

[0006] To simultaneously reduce the fracture chilling layer and coarse pre-crystallized structure in aluminum alloy castings and improve the uniformity of the microstructure in high-pressure cast AlSi10MnMg alloy materials, the following technical solutions or suggestions have been proposed in relevant patent literature:

[0007] (1) Adjustment of high-pressure casting process parameters. By increasing the pouring temperature of the molten aluminum, accelerating the injection speed to shorten the residence time of the molten aluminum in the pressure chamber, increasing the pressure chamber filling rate (material cake thickness), and reducing the amount of lubricating oil used in the punch, the temperature drop of the molten aluminum in the pressure chamber can be reduced, thereby inhibiting the formation of pre-crystallized structure or fracture chilling layer. However, the process window of this scheme is relatively narrow and is easily affected by alloy composition, casting shape and die casting cycle, making it difficult to completely avoid the formation of fracture chilling layer and coarse pre-crystallized structure in the pressure chamber.

[0008] (2) Alloy composition optimization. By appropriately increasing the Si content in the alloy, or adding rare earth elements such as Ce and La, the formation temperature and quantity of pre-crystallized structure and fracture chilled layer can be reduced. However, while increasing the Si content can suppress the formation of harmful phases to a certain extent, it will lead to a decrease in the mechanical properties of the alloy, which cannot meet the high toughness requirements of high-end parts; while adding rare earth elements can refine the structure and reduce harmful phases to a certain extent, its improvement effect is relatively limited, and it will significantly increase the cost of raw materials, thus limiting its application in actual large-scale production.

[0009] (3) Temperature field control of the pressure chamber. Pressure chambers with oil circuit insulation design or pressure chambers made of ceramic materials are used to reduce thermal conductivity. By reducing heat dissipation from the pressure chamber wall, the temperature of the molten aluminum is kept stable, thereby inhibiting the formation of harmful phases. However, in the rapid cycle production process, the continuous heat dissipation of the mold will cause large fluctuations in the pressure chamber temperature, and the pressure chamber temperature will also be affected by the ambient temperature and production rhythm, resulting in poor temperature control stability.

[0010] (4) Shorten the die casting cycle time. By speeding up the rhythm of auxiliary operations such as spraying, part removal, and pouring, the residence time of aluminum liquid in the pressure chamber and the cooling time of the scoop are reduced, thereby reducing heat loss. However, this solution is greatly limited by the shape of the casting and the performance of the die casting equipment. For castings with complex structures, it is difficult to significantly shorten the part removal and spraying time; moreover, excessively speeding up the operation rhythm will increase the labor intensity of the operators and may also lead to new quality problems such as casting deformation and uneven spraying. The overall effect is unstable and cannot fundamentally solve the problem of harmful phase formation.

[0011] (5) Flow channel design and collection technology. A special collection bag is designed at the bottom of the flow divider cone or on the flow channel to capture and filter the pre-crystallized structure generated in the pressure chamber using the flow characteristics of the molten aluminum, preventing it from entering the mold cavity and affecting the casting body. However, the pre-crystallized structure and the fracture chilling layer are small in size and flow at high speed with the molten aluminum, resulting in poor filtration effect of the collection bag and failure to achieve effective capture. In practical applications, it is difficult to achieve the expected results and cannot solve the problem of harmful phases being entangled in the casting.

[0012] In summary, existing technical solutions are all single-process improvements targeting individual defects such as pre-crystallized structures or fracture chilling layers. No patent literature has yet proposed a systematic key process intervention method to simultaneously suppress both harmful phases. Furthermore, the specific process parameter ranges suitable for AlSi10MnMg alloys in existing solutions are unclear, and the improvement effect of single-process optimization measures is easily affected by various factors such as product shape and size, ambient temperature, and die-casting cycle. This results in the frequent occurrence of pre-crystallized structures and fracture chilling layers in high-pressure cast AlSi10MnMg alloy castings, and the problem of fluctuating mechanical properties remains unresolved. Therefore, developing a method that can simultaneously suppress pre-crystallized structures and fracture chilling layers in the pressure chamber, is suitable for industrial production, and has stable and reliable performance has become an urgent technical challenge to be solved in the field of high-pressure casting of AlSi10MnMg alloys. Summary of the Invention

[0013] To address the technical shortcomings of existing technologies that cannot simultaneously suppress the pre-crystallized structure and fracture chilling layer in the pressure chamber of high-pressure cast AlSi10MnMg alloys, resulting in large fluctuations and low performance of the castings, this invention provides a method for simultaneously suppressing the pre-crystallized structure and fracture chilling layer in high-pressure cast AlSi10MnMg alloy materials. This method clarifies the suitable alloy composition range and process window, and through the synergistic effect of multiple processes, achieves simultaneous suppression of the two harmful phases, improving the uniformity of the microstructure and the stability of the mechanical properties of the castings, thus meeting the production requirements of high-end precision parts.

[0014] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0015] A method for simultaneously suppressing pre-crystallized microstructure and fracture chilling layer in high-pressure cast AlSi10MnMg alloy materials includes the following steps:

[0016] (1) Refining of aluminum liquid in transfer package: The AlSi10MnMg alloy aluminum liquid in the transfer package is degassed and slag removed for refining. The density of the aluminum liquid is tested to be ≥2.6g / cm³. 3 If the K-modulus value, which characterizes the slag content, is ≤0.1, the material must be refined again.

[0017] (2) Cooling of aluminum liquid in holding furnace: The refined aluminum liquid is introduced into the holding furnace and cooled at 695±5℃ for 20~30 minutes;

[0018] (3) Aluminum liquid composition control and cleanliness re-inspection: The aluminum liquid composition in the holding furnace is tested to ensure that Si=10.3~11wt%, Mn=0.4~0.5wt%, Mg=0.1~0.6wt%, Fe≤0.2wt%, other single impurities≤0.05wt%, and other impurities total≤0.15wt%, with the remainder being Al. If the requirements are not met, the composition is adjusted and the aluminum liquid is refined again. After the aluminum liquid composition is qualified, the aluminum liquid density is tested again to be ≥2.6g / cm³. 3 If the K modulus value is ≤0.1, then refine it again;

[0019] (4) Die-casting parameter settings: A split-type pressure chamber is adopted, with a punch diameter of 50~80mm and a pressure chamber filling rate of ≥35%; the pressure chamber is heated by hot oil circulation, with a hot oil temperature of 190±5℃; the injection speed is 0.25~0.3m / s at low speed and 1.5~2m / s at high speed, the molten metal flow velocity at the inner gate is ≥45m / s, and the pressure is 800~1000kgf / cm 2 ;

[0020] (5) Scooping soup with a ladle: control the single cycle of scooping soup with a ladle to be ≤15 seconds. When the ladle is in standby mode, the bottom of the ladle is 10±3mm away from the aluminum liquid surface. The steps of scooping, transportation positioning, pouring, retraction and reset and standby are completed in sequence.

[0021] (6) Complete high pressure casting according to the above parameters, control the residence time of aluminum liquid in the pressure chamber, and simultaneously suppress the formation of pre-crystallized structure and fracture chilling layer in the pressure chamber and the entrainment of casting.

[0022] Furthermore, in steps (1) and (3), the density test of molten aluminum is performed in accordance with GB / T 43139-2023 "Density Test of Cast Aluminum Alloy Liquid Solidification Samples under Pressure", and the K modulus test is performed in accordance with GB / T 15115-2024 "Die Cast Aluminum Alloys".

[0023] Furthermore, in step (1), degassing is performed by rotary jetting of argon or nitrogen, and slag removal is performed by adding a slag remover and then scraping off the slag.

[0024] Furthermore, in step (4), the integrated oil circuit channel inside the split-type pressure chamber is controlled by a hot oil circulation system through an oil temperature controller, so that the outlet temperature is 3~10℃ lower than the inlet temperature.

[0025] Furthermore, in step (4), hot oil is introduced into the internal oil circuit of the pressure chamber through an oil temperature controller. The inlet temperature of the oil temperature controller is 180~210℃, and the outlet temperature is 3~10℃ lower than the inlet temperature.

[0026] Furthermore, in step (4), the flow rate of the molten metal at the ingate is determined by CAE simulation analysis, and the cross-sectional area of ​​the ingate is adjusted according to the casting size to match the flow rate requirements.

[0027] Furthermore, in step (5), the scoop is driven by a robotic arm and equipped with an infrared positioning device to ensure the accuracy of the distance between it and the aluminum liquid surface during standby. During the standby phase, the scoop is kept warm by the thermal radiation of the aluminum liquid.

[0028] Furthermore, in step (5), the time to complete the scooping action is ≤3 seconds, the time to complete the transport positioning action is ≤3 seconds, the time to complete the pouring action is ≤2 seconds, the time to complete the retraction and reset action is ≤2 seconds, and the standby time is ≤5 seconds.

[0029] Furthermore, in step (6), the residence time of the molten aluminum in the pressure chamber is ≤5 seconds.

[0030] Compared with the prior art, the technical advantages of the present invention are as follows:

[0031] 1. Overcome the limitations of improving single defects and achieve simultaneous suppression of two harmful phases.

[0032] Existing technologies can only address one type of defect—either the pre-crystallized structure or the fractured chilled layer—by proposing improvement measures for a single process. They cannot simultaneously suppress both types of defects, and the improvement effect is easily affected by factors such as product shape and ambient temperature, making it difficult to maintain a stable performance. This invention, through a multi-stage synergy involving narrow-range alloy composition design, full-process temperature drop control, and injection process optimization, simultaneously suppresses the generation and entrapment of two harmful phases from both thermodynamic and kinetic perspectives. By precisely controlling the content of elements such as Si, Mn, and Mg, the precipitation temperature of harmful phases is reduced. Combined with pressurized room temperature control and rapid injection processes, the nucleation and growth of harmful phases and the breakage of the chilled layer are reduced. Industrial verification shows that it can completely eliminate coarse pre-crystallized structures and reduce the maximum size of the fractured chilled layer from 1 mm to 300 μm, solving the industry problem of existing technologies' inability to simultaneously control both types of defects.

[0033] 2. Optimize alloy composition matching to meet multiple performance requirements without increasing additional costs.

[0034] Existing composition optimization methods either increase the Si content to suppress harmful phases, leading to decreased alloy toughness and making it unsuitable for high-end component requirements; or add rare earth elements, which, while slightly improving defects, significantly increase material costs and may reduce casting fluidity. This invention employs a narrow-range composition design, controlling Si at 10.3~11wt%, Mn at 0.4~0.5wt%, Mg at 0.1~0.6wt%, and Fe ≤0.2wt%, eliminating the need for adding precious elements like rare earths. This lowers the precipitation temperature of harmful phases while avoiding toughness loss due to excessive Si content, balancing the alloy's strength, toughness, and casting fluidity. Implementation data shows that the as-cast tensile strength of the casting reaches 260~340MPa, the yield strength 140~180MPa, and the elongation after fracture is consistently 6~11%, demonstrating superior overall performance compared to comparative products.

[0035] 3. Establish a full-process temperature drop control system to improve process stability and controllability.

[0036] Existing temperature drop control technologies often focus on single stages, such as optimizing pressure chamber temperature control or shortening the die-casting cycle. These methods are easily affected by production rhythm and ambient temperature, resulting in large temperature fluctuations and an inability to stably prevent the aluminum liquid from dropping to the range where harmful phases precipitate in large quantities. This invention constructs a full-process temperature drop control system consisting of "high-temperature quenching in the holding furnace - thermal radiation insulation in the scoop - hot oil circulation insulation in the pressure chamber - rapid injection to shorten residence time." By using a 695±5℃ high-temperature quenching furnace to store enthalpy, precise positioning and preheating of the scoop to reduce contact temperature drop, and hot oil circulation in the pressure chamber to ensure uniform wall temperature, the rapid injection process shortens the residence time of the aluminum liquid in the pressure chamber, effectively reducing the overall temperature drop of the aluminum liquid, significantly reducing the fluctuation of mechanical properties between different batches of castings, and greatly improving process stability and controllability.

[0037] 4. It has strong process adaptability and can be compatible with large-scale industrial production without major equipment modifications.

[0038] Existing technologies often have narrow improvement schemes or process windows, are difficult to adjust parameters, or rely on specialized equipment such as ceramic pressure chambers, resulting in high costs, susceptibility to breakage, and short service life, making them unsuitable for industrial mass production. The process measures of this invention are all based on existing high-pressure casting equipment, requiring no large-scale modifications; only adjustments to process parameters and optimization of the scoop's movement procedure are needed for implementation. Furthermore, precise process windows are clearly defined for each stage, such as a pressure chamber filling rate ≥35%, hot oil temperature 190±5℃, and a single cycle of the scoop's scooping action ≤15 seconds. These parameters can be flexibly adjusted according to the casting size, adapting to the production of castings of different specifications, such as new energy vehicle electronic control boxes and front engine compartment crossbeams. The process cost is comparable to existing technologies, making it easy to promote and apply.

[0039] 5. Strengthen the whole-process control of cleanliness to reduce defective nucleation substrates from the source.

[0040] Existing technologies often neglect the impact of aluminum melt cleanliness on the pre-crystallized structure, performing only a single refining process during the transfer ladle stage. This easily leads to residual gases and oxide inclusions in the aluminum melt, which become heterogeneous nucleation substrates for the pre-crystallized structure, exacerbating defect formation. This invention establishes a three-tiered cleanliness control system: "transfer ladle refining - holding furnace quenching - cleanliness re-inspection." During the transfer ladle stage, degassing, slag removal, and refining are performed. Holding furnace quenching promotes the flotation of residual gases and inclusions. Two tests ensure that the aluminum melt density is ≥2.6 g / cm³. 3 With a K-modulus value ≤ 0.1, oxide inclusions and gas content are significantly reduced. This not only reduces the nucleation substrate of the pre-crystallized structure but also avoids microcracks caused by impurities, effectively reducing internal defects in castings and significantly improving product quality stability.

[0041] From the perspective of metallographic characterization, the simultaneous suppression effect of this invention on two harmful phases is directly verified. Figure 4 Comparison of metallographic structures of AlSi10MnMg alloy die-cast structural parts produced without and using the process of this invention (1 - without the method of this invention, 2 - using the full process method of this invention). In the AlSi10MnMg alloy casting body produced without the process of this invention, there are a large number of coarse α-Al phases and coarse coral-like α-Al(FeMn)Si phases, and the fracture chilling layer is widely distributed and large in size. In contrast, in the AlSi10MnMg alloy casting body produced using the full process of this invention, only fine α-Al phases and α-Al(FeMn)Si phases were detected, with no obvious coarse pre-crystallized structure, and the maximum size of the fracture chilling layer in the casting body was significantly reduced from 1 mm to 300 μm. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the quenching layer on the inner wall of the pressure chamber and the pre-crystallized structure inside the molten aluminum.

[0043] Figure 2 Diagrams showing the pre-crystallized structure and fracture chilling layer incorporated into the casting;

[0044] Figure 3 Elongation at fracture of AlSi10MnMg alloy castings not produced using the process of this invention;

[0045] Figure 4 Comparison of metallographic structures of AlSi10MnMg alloy die-cast structural parts produced without and with the process of this invention (1-not using the method of this invention, 2-using the full process method of this invention).

[0046] Figure 5 This is a schematic diagram of a cold chamber die casting machine (1-fixed mold, 2-mold, 3-material spoon, 4-molten aluminum, 5-injection punch, 6-pressure chamber, 7-moving mold, 8-mold cavity).

[0047] Figure 6 A schematic diagram of the oil circuit design within a split-chamber mold;

[0048] Figure 7 A flowchart illustrating the heat preservation process of the material spoon in the cold chamber high-pressure casting process.

[0049] Figure 8 Figures showing the formation temperatures of the α-Al phase pre-crystallization structure and fracture chilling layer in AlSi10MnMg alloy;

[0050] Figure 9 Figure showing the formation temperature of the α-Al(FeMn)Si phase pre-crystallization structure in AlSi10MnMg alloy;

[0051] Figure 10 A comparison chart of the tensile strength of AlSi10MnMg alloy die-cast structural parts produced by the original process and the process of this invention;

[0052] Figure 11 A comparison chart of the yield strength of AlSi10MnMg alloy die-cast structural parts produced by the original process and the process of this invention;

[0053] Figure 12 A comparison chart of the elongation after fracture of AlSi10MnMg alloy die-cast structural parts produced by the original process and the process of this invention.

[0054] Figure 13 A comparison chart showing the fracture chilling layer occurrence rate of AlSi10MnMg alloy die-cast structural parts produced by the original process and the process of this invention.

[0055] Figure 14 Toughness cross-section of tensile specimens for key components of the electronic control box of new energy vehicles.

[0056] Figure 15 Toughness cross-section of a tensile specimen for a key component of the power battery tray frame structure.

[0057] Figure 16 Toughness cross section of a tensile specimen for a key component of the front engine compartment crossbeam structure of a new energy vehicle.

[0058] Figure 17 This is a fracture chilling layer defect diagram of an AlSi10MnMg alloy tensile specimen when using a conventional wide composition range process.

[0059] Figure 18 This image shows the fracture chilling layer defect on the cross-section of an AlSi10MnMg alloy tensile specimen when using a traditional spoon to scoop soup. Detailed Implementation

[0060] 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.

[0061] A method for simultaneously suppressing pre-crystallized microstructure and fracture chilling layer in high-pressure cast AlSi10MnMg alloy materials includes the following steps:

[0062] 1. Refining of molten aluminum in transshipment packages

[0063] The AlSi10MnMg alloy molten aluminum prepared in the melting furnace was transferred to a transfer ladle. Degassing was performed using rotary jet argon or nitrogen to ensure the complete removal of gases such as hydrogen from the molten aluminum. Subsequently, a slag remover was added to the transfer ladle for slag removal, eliminating oxide inclusions and impurities from the molten aluminum. After refining, samples were taken from the transfer ladle to test the density and slag content of the molten aluminum: the density of the molten aluminum was tested according to GB / T 43139-2023 "Density Test of Cast Aluminum Alloy Molten Aluminum under Reduced Pressure Solidification Samples", requiring a density ≥ 2.6 g / cm³. 3 The slag content is characterized by the K-modulus value, and should be performed in accordance with GB / T 15115-2024 "Die Casting Aluminum Alloys", requiring a K-modulus value ≤ 0.1. If the test results do not meet the above requirements, degassing and slag removal refining must be carried out again until the test results are qualified.

[0064] 2. Calming of molten aluminum in the holding furnace

[0065] The refined molten aluminum from the transfer package is poured into the holding furnace next to the die-casting machine. The temperature of the holding furnace is set to 695±5℃, and the molten aluminum is kept at this temperature for 20~30 minutes for calming treatment.

[0066] 3. Aluminum liquid composition control and cleanliness re-inspection

[0067] After the aluminum liquid has settled, a direct-reading spectrometer is used to sample and analyze the chemical composition of the aluminum liquid in the holding furnace. The composition must meet the following requirements: Si = 10.3~11wt%, Mn = 0.4~0.5wt%, Mg = 0.1~0.6wt%, Fe ≤ 0.2wt%, other individual impurity elements ≤ 0.05wt%, total other impurity elements ≤ 0.15wt%, and the remaining content must be entirely Al. Once the aluminum liquid composition is deemed acceptable, the density and slag content of the aluminum liquid are sampled again, following the same testing standards as in step 1, requiring an aluminum liquid density ≥ 2.6 g / cm³. 3 The K-modulus value should be ≤0.1. If the re-inspection fails, degassing and slag removal refining must be carried out again.

[0068] 4. Die-casting parameter settings

[0069] Figure 5This is a schematic diagram of a cold chamber die casting machine, with the following parameter settings: punch diameter 50~80mm, effective chamber length 390mm, a split-type chamber with a chamber filling rate ≥35%; the chamber is heated by hot oil circulation, with the hot oil temperature controlled at 190±5℃; the injection punch uses three-stage injection control, with a low-speed setting of 0.25~0.3m / s and a high-speed setting of 1.5~2m / s; the molten metal flow velocity at the ingate is calculated to be ≥45m / s through CAE simulation analysis; and the pressurization pressure is set to 800~1000kgf / cm³. 2 .

[0070] Figure 6 This is a schematic diagram of the oil circuit design within a split-chamber mold. The chamber integrates a dedicated oil circuit channel, through which hot oil is introduced via an oil temperature controller for circulating temperature control, ensuring uniform temperature on the chamber walls. The inlet temperature of the oil temperature controller connected to the mold is controlled at 190±5℃. By adjusting the oil temperature and flow rate, the outlet temperature is kept 3~10℃ lower than the inlet temperature, ensuring continuous heat preservation of the chamber by the circulating hot oil, preventing localized low-temperature zones on the chamber walls, and reducing the formation of chilled layers and pre-crystallized structures.

[0071] 5. Use a ladle to scoop out the soup.

[0072] Figure 7 This is a flowchart illustrating the heat preservation process of the ladle in the cold chamber high-pressure casting process. The ladle's scooping action is controlled by the robotic arm of the high-pressure casting machine. An infrared positioning device is used to ensure the accuracy of the action, and the cycle of the ladle's scooping action is controlled to be ≤15 seconds. The specific action breakdown is as follows:

[0073] ① Scooping molten aluminum: When in standby mode, the bottom of the scoop is 10±3mm away from the surface of the molten aluminum. The heat radiation of the high-temperature molten aluminum is used to preheat the scoop, reducing the instantaneous temperature drop when the scoop comes into contact with the molten aluminum. The robotic arm starts from the standby position, drives the scoop to descend and tilt to scoop the molten aluminum. After the scoop scoops the molten aluminum, it rises to leave the liquid surface to complete the scooping process. The time of this process is controlled within ≤3 seconds.

[0074] ② Transportation and positioning: The material scoop rises to the dripping position, allowing excess molten aluminum to drip back into the holding furnace, preventing excessive molten aluminum from causing the pressure chamber filling rate to exceed the standard; then the robotic arm carries the molten aluminum forward quickly to the top of the pressure chamber of the die-casting machine, fine-tunes the positioning, pauses and waits until pouring begins. This process is controlled within ≤3 seconds to reduce heat loss of molten aluminum in the open environment.

[0075] ③ Pouring: Pouring begins after the pouring signal is triggered. At the same time, the die casting injection delay timer starts. When the timer ends, the pouring is completed and a die casting injection signal is sent to the die casting machine. The robotic arm begins to retreat. The time of this process is controlled within ≤2 seconds to reduce oxidation and temperature drop during the aluminum liquid pouring process.

[0076] ④ Retreat and reset: The robotic arm drives the scoop to quickly retreat to the standby position on the surface of the molten aluminum in the heat preservation furnace. The scoop returns to the baking state and is ready for the next soup scooping cycle. The time of this process is controlled within ≤2 seconds to reduce the temperature drop of the scoop.

[0077] ⑤ Standby: The scoop continuously receives heat radiation from the molten aluminum in the standby position. The infrared positioning device adjusts the position of the scoop in real time to keep the bottom of the scoop 10±3mm away from the molten aluminum surface at the feeding port of the holding furnace. At the same time, the standby time is shortened by optimizing the injection rhythm and controlling the process time to ≤5 seconds, further reducing the temperature drop of the scoop.

[0078] 6. Die casting and post-processing

[0079] Control the residence time of molten aluminum in the pressure chamber to ≤5 seconds (from the completion of pouring to the start of the punch), and open the mold and remove the part after die casting is completed.

[0080] Technical principle of the invention:

[0081] 1. The role of each raw material

[0082] As the main alloying element in AlSi10MnMg alloys, the core function of limiting its content to a narrow range is to lower the precipitation initiation temperature of the α-Al phase, the main phase in the pre-crystallized structure and fracture chilling layer. For example... Figure 8 As shown, when Si = 10.3~11wt% and Mn = 0.4~0.5wt%, the initial precipitation temperature of the α-Al phase in the pre-crystallized structure and the α-Al phase in the fracture chilling layer decreases to 589~592℃. Compared with the traditional wide composition range (Si = 9.5~11.5wt% and Mn = 0.4~0.8wt%), this composition design effectively reduces the initial precipitation temperature of harmful phases, reduces the nucleation driving force of the pre-crystallized structure from a thermodynamic perspective, and avoids excessive aggregation of the eutectic Si phase, thus balancing the alloy's casting fluidity and toughness. If the Si content is too low, the alloy solidification temperature increases, and the aluminum liquid is prone to premature nucleation of the α-Al phase in the pressure chamber due to a slight temperature drop, resulting in a coarse pre-crystallized structure; if the Si content is too high, it will lead to a large amount of eutectic Si phase precipitation and aggregation, significantly reducing the alloy's toughness and elongation after fracture, making it difficult to meet the requirements of high-end precision parts.

[0083] The core role of Mn is to lower the initial precipitation temperature of intermetallic compounds in the pre-crystallized α-Al(FeMn)Si structure, regulate the morphology of the Fe phase, and synergistically suppress the adhesion of the fracture chilling layer. For example... Figure 9As shown, when Mn = 0.4~0.5wt%, the initial precipitation temperature of the α-Al(FeMn)Si intermetallic compound in the pre-crystallized structure decreases to 590~605℃. Furthermore, trace amounts of Fe in the AlSi10MnMg alloy easily form acicular β-Al5FeSi phase. This phase not only reduces the alloy's mechanical properties but also enhances the adhesion strength between the fracture chilling layer and the inner wall of the pressure chamber, causing the chilling layer to easily break into small fragments and be drawn into the casting during high-speed punching. Mn can form a stable α-Al(FeMn)Si blocky phase with Fe, replacing the acicular β-Al5FeSi phase. Simultaneously, when the Mn content is limited to 0.4~0.5wt%, the precipitation pattern of Si can be precisely matched. This reduces the initial precipitation temperature and nucleation rate of the α-Al(FeMn)Si phase in the pre-crystallized structure while avoiding the problems of intermetallic compound aggregation due to excessively high Mn content and incomplete transformation of the acicular Fe phase due to excessively low Mn content.

[0084] The main role of magnesium (Mg) is to enhance the strength of the alloy matrix and simultaneously optimize the uniformity of the microstructure. Mg can form the Mg2Si reinforcing phase with Al and Si, which is dispersed in the matrix to improve tensile strength. However, excessive Mg content can lead to increased solidification shrinkage, making casting cracks more likely, and accelerating aluminum oxidation, increasing inclusion content and providing more heterogeneous nucleation substrates for pre-crystallized structures. Conversely, insufficient Mg content will fail to form enough reinforcing phases, making it difficult to meet the strength requirements of high-end components. The narrow range defined in this invention can achieve a cast tensile strength of 260~340MPa and a yield strength of 140~180MPa while avoiding excessive formation of oxide inclusions, thus balancing strength and microstructure cleanliness.

[0085] Limiting Fe content to ≤0.2wt%, other individual impurities to ≤0.05wt%, and total other impurities to ≤0.15wt% is crucial for reducing the formation of heterogeneous nucleation substrates and fracture-induced chilling layers in the pre-crystallized structure. Excessive Fe exacerbates acicular phase formation, while other impurities (such as Cu and Zn) disrupt alloy phase equilibrium, reduce solidification temperature stability, and lead to non-uniform cooling of molten aluminum in the pressure chamber. Simultaneously, impurity particles become core nucleation sites for the pre-crystallized structure, accelerating coarse grain growth. Strictly controlling impurity content avoids these problems and lays the microstructural foundation for simultaneously suppressing these two harmful phases.

[0086] 2. The role of each process step

[0087] The density of the refined aluminum liquid in the transfer package is controlled to be ≥2.6 g / cm³. 3 The core function of a K-modulus value ≤ 0.1 is to remove gases and oxide inclusions from molten aluminum, preventing these inclusions from becoming the nucleation substrate for pre-crystallized structures, while simultaneously reducing microporosity caused by gases and improving the fluidity of the molten aluminum. Density and K-modulus values ​​are critical for ensuring cleanliness: density ≥ 2.6 g / cm³. 3This indicates that the gas content in the molten aluminum meets the standard, and there is no porosity caused by a large number of bubbles; a K-modulus value ≤ 0.1 indicates that the slag content meets the requirements, which can prevent oxide inclusions from aggravating the growth of pre-crystallized structures and the breakage of the fracture chilled layer. Molten aluminum that does not meet the standards can be refined to ensure the consistency of the cleanliness of the molten aluminum and avoid performance fluctuations between batches.

[0088] The high-temperature quenching of molten aluminum in the holding furnace allows for sufficient enthalpy reserve to compensate for temperature drops during subsequent aluminum transfer and pouring, preventing the aluminum temperature from falling to a level where harmful phases precipitate in large quantities. The quenching time promotes the floating of residual gases and minute inclusions, further improving the cleanliness of the molten aluminum. Simultaneously, it homogenizes the composition and temperature of the molten aluminum, preventing localized aggregation of pre-crystallized structures caused by localized component segregation. Excessive temperature will exacerbate aluminum oxidation, while insufficient temperature will prevent adequate quenching and enthalpy reserve. Too short a quenching time will prevent inclusions from fully floating, while too long a time will lead to the burning away of alloying elements, affecting compositional stability.

[0089] The core function of cleanliness re-inspection is to provide double protection for the cleanliness of molten aluminum, avoid introducing new impurities or gases during the composition adjustment process, ensure that all molten aluminum entering the pressure chamber meets the cleanliness requirements, eliminate the material basis for the nucleation of pre-crystallized structures from the source, form a closed loop with the first two levels of control, and improve process stability.

[0090] The scooping cycle is controlled to be ≤15 seconds (scooping ≤3 seconds, transport positioning ≤3 seconds, pouring ≤2 seconds, retraction and reset ≤2 seconds, standby ≤5 seconds). This minimizes the exposure time of molten aluminum in an open environment, reduces heat loss, and prevents rapid temperature drops that could trigger pre-crystallization. When in standby mode, the scoop is 10±3mm above the molten aluminum surface, allowing for preheating through thermal radiation from the molten aluminum. This reduces the instantaneous temperature drop upon contact with the molten aluminum, preventing localized overcooling and the formation of fine pre-crystallized grains. Excessive operating time can lead to excessive temperature drops in the molten aluminum; too far a distance prevents effective preheating; and too close a distance can cause the scoop to stick to the molten aluminum, introducing impurities.

[0091] The pressure chamber temperature control uses hot oil circulation to insulate the split pressure chamber, maintaining the oil temperature at 190±5℃. This ensures a uniform and stable chamber wall temperature, preventing localized low temperatures that could lead to rapid cooling of the molten aluminum upon contact, forming a dense chilled layer. Simultaneously, the stable chamber temperature reduces the heat exchange rate between the molten aluminum and the wall surface, delaying the growth of pre-crystallized structures. Excessive oil temperature can cause overheating of the chamber wall, affecting the smoothness of the punch movement; conversely, insufficient oil temperature will fail to inhibit chilled layer formation. Maintaining the temperature difference between the oil inlet and outlet at 3~10℃ ensures consistently stable insulation performance.

[0092] Controlling the residence time of molten aluminum in the pressure chamber to ≤5 seconds shortens the nucleation and growth time of the pre-crystallized structure from a kinetic perspective, avoiding the formation of coarse grains. Controlling the injection speed parameters to low velocities of 0.25~0.3m / s and high velocities of 1.5~2m / s shortens the residence time of molten aluminum in the pressure chamber and reduces the shearing and scouring force of the high-speed molten aluminum on the chilled layer of the pressure chamber wall, reducing the risk of chilled layer breakage and entrapment into the casting. An ingate flow velocity ≥45m / s ensures rapid filling of the mold cavity, preventing secondary cooling of molten aluminum in the cavity and the formation of new harmful phases.

[0093] 3. Technical effects achieved

[0094] Existing technologies can only improve a single defect, either the pre-crystallized structure or the fracture chilled layer, and cannot simultaneously control both. However, this invention, through multi-system synergy, can completely eliminate coarse pre-crystallized structures and reduce the maximum size of the fracture chilled layer from 1 mm in existing technologies to 300 μm, solving the long-standing technical problem of the inability to simultaneously suppress the two harmful phases in the industry.

[0095] AlSi10MnMg alloy high-pressure castings prepared by comparative process have tensile strengths below 250MPa and elongation after fracture that is low (3-5%). However, this invention, through synergistic regulation, enables the casting body to achieve a tensile strength of 260-340MPa, a yield strength of 140-180MPa, and an elongation after fracture that is stable at 6-11%, thereby improving mechanical properties and meeting the stringent requirements for mechanical property stability of high-end precision components.

[0096] Existing technologies for improving alloy microstructure and properties typically require the addition of rare earth elements and other precious elements, which increases raw material costs by more than 30%. However, this invention does not require the addition of precious elements or large-scale modification of existing equipment. It can be achieved simply through parameter optimization and process control, with process costs comparable to existing technologies. At the same time, it avoids the problem of reduced casting fluidity caused by the addition of precious elements, achieving a triple breakthrough of "performance improvement, cost control, and industrial adaptability".

[0097] Existing technologies have narrow process windows and are easily affected by ambient temperature, casting size, and production rhythm, resulting in unstable performance. In contrast, this invention, through closed-loop control of the entire process and narrow parameter range limitation, can be adapted to the production of AlSi10MnMg alloy castings of different specifications, such as electric control boxes for new energy vehicles, power battery tray frames, and front engine compartment crossbeams. Within an ambient temperature fluctuation range of ±10℃ and a production rhythm adjustment range of ±2 seconds, it can still stably suppress two harmful phases, and its process stability and adaptability are superior to existing technologies.

[0098] Comparison of the performance and defect control effects of the process of this invention with the original die-casting process:

[0099] To visually verify the improved technical solution of this invention, the entire process of this invention is compared with the original production process of AlSi10MnMg alloy high-pressure casting in terms of the mechanical properties of the casting body and the control effect of harmful phases.

[0100] Statistical analysis of the mechanical properties test results of the casting body, as follows: Figure 10 , Figure 11 Figure 12 , Figure 13 As shown in the figure, compared to the original process, the AlSi10MnMg alloy die-cast structural parts continuously produced using the process of this invention exhibit significantly improved as-cast tensile strength, yield strength, and elongation after fracture, as well as enhanced stability. Specifically, tensile strength increased from 165-300 MPa to 260-340 MPa, yield strength from 90-180 MPa to 140-180 MPa, and elongation after fracture from 1%-10% to 6-11%. Furthermore, due to the effective elimination of pre-crystallized structures in the pressure chamber and a significant reduction in the number and size of the fracture chilling layer, the fracture chilling layer incidence rate of the tested samples decreased from 64% to 8%. The elongation after fracture of key parts of the casting body consistently reached over 6%, with the average elongation after fracture exceeding 7%, fully meeting the high toughness requirements of automotive exterior structural parts.

[0101] The present invention will be further illustrated below through specific embodiments and comparative examples.

[0102] Example 1 (Electrical Control Box of New Energy Vehicle)

[0103] A method for simultaneously suppressing pre-crystallized microstructure and fracture chilling layer in high-pressure cast AlSi10MnMg alloy materials includes the following steps:

[0104] 1. Refining of molten aluminum in transshipment packages

[0105] The AlSi10MnMg alloy molten aluminum prepared in the melting furnace was transferred to a transfer ladle and degassed using rotary argon injection. Subsequently, a slag remover was added to the transfer ladle for slag removal. After refining, samples were taken from the transfer ladle to test the density and slag content of the molten aluminum. The density of the molten aluminum was tested according to GB / T 43139-2023 "Density Test of Cast Aluminum Alloy Molten Aluminum Solidification Samples under Reduced Pressure", and the measured density was 2.62 g / cm³. 3 The slag content was characterized by the K-modulus value, and the test was carried out in accordance with GB / T 15115-2024 "Die Casting Aluminum Alloys". The measured K-modulus value was 0.1, which meets the requirements.

[0106] 2. Calming of molten aluminum in the holding furnace

[0107] The refined molten aluminum from the transfer package is poured into the holding furnace next to the die-casting machine. The temperature of the holding furnace is set to 695±5℃, and the molten aluminum is kept at this temperature for 25 minutes to calm it down.

[0108] 3. Aluminum liquid composition control and cleanliness re-inspection

[0109] After the aluminum melt was cooled, a direct-reading spectrometer was used to sample and analyze the chemical composition of the aluminum melt in the holding furnace. The measured composition was: Si = 10.45 wt%, Mn = 0.48 wt%, Mg = 0.35 wt%, Fe = 0.18 wt%, and other impurity elements totaling 0.08 wt%. The remaining content was entirely Al. The composition meets the narrow-range design requirements and requires no adjustment.

[0110] 4. Die-casting parameter settings

[0111] A split-type injection chamber (70mm inner diameter, 390mm effective length) was selected, with the following parameters set: punch diameter 65mm, chamber filling rate 38%; the chamber is heated by hot oil circulation, with the hot oil temperature controlled at 190℃, introduced from the chamber oil inlet, and the measured outlet temperature was 183℃; the injection punch uses three-stage injection control, with a low speed set at 0.28m / s, a high speed set at 1.8m / s, and an ingate cross-sectional area of ​​320mm². 2 The flow velocity of the molten metal at the ingate was calculated to be 48 m / s using CAE simulation analysis, and the pressurization pressure was set to 900 kgf / cm². 2 .

[0112] 5. Use a ladle to scoop out the soup.

[0113] The high-pressure die-casting machine uses a robotic arm to control the scooping action of the molten aluminum. An infrared positioning device is used, and the program is set as follows: ① Scooping molten aluminum: The scoop is positioned 12mm above the molten aluminum surface. The robotic arm then descends and tilts the scoop at a 30° angle to scoop the molten aluminum. The scooping is complete when it rises above the surface. ② Transport and positioning: The scoop rises to the dripping position, and the robotic arm carries the molten aluminum forward to the pressure chamber of the die-casting machine. ③ Pouring: Pouring begins, and a die-casting delay timer (set to 1.5 seconds) is started. Pouring is complete when the timer expires. ④ Retreat and reset: The robotic arm drives the scoop to quickly retreat to the standby position above the molten aluminum surface in the holding furnace. ⑤ Standby: The scoop remains in the standby position, continuously receiving heat radiation from the molten aluminum. The infrared positioning device adjusts the scoop's position in real time, maintaining a 10mm distance between the bottom of the scoop and the molten aluminum surface at the holding furnace's scooping port. The standby period lasts for 5 seconds. The total time for a single die-casting cycle is less than 14 seconds.

[0114] 6. Die casting and post-processing

[0115] The aluminum liquid stays in the pressure chamber for 4 seconds (from the completion of pouring to the start of the punch). After die casting is completed, the mold is opened and the part is removed.

[0116] 7. Test Results

[0117] Cross-sectional inspection of the casting revealed no visible fractured fragments of the chilled layer. Relevant morphological features are shown in [reference needed]. Figure 14 Metallographic analysis of the sample (100x magnification) revealed no coarse α-Al or α-Al(FeMn)Si pre-crystallized structures. The α-Al grain size was uniform. Mechanical property testing showed a tensile strength R... m =283MPa, yield strength R p0.2 =173MPa, elongation after fracture A=10%, tensile fracture surface exhibits ductile fracture characteristics, no fracture chilling layer defects.

[0118] Example 2 (Power Battery Tray Frame Structure)

[0119] A method for simultaneously suppressing pre-crystallized microstructure and fracture chilling layer in high-pressure cast AlSi10MnMg alloy materials includes the following steps:

[0120] 1. Refining of molten aluminum in transshipment packages

[0121] The AlSi10MnMg alloy molten aluminum prepared in the melting furnace was transferred to a transfer ladle and degassed using rotary argon injection. Subsequently, a slag remover was added to the transfer ladle for slag removal. After refining, samples were taken from the transfer ladle to test the density and slag content of the molten aluminum. The density of the molten aluminum was tested according to GB / T 43139-2023 "Density Test of Cast Aluminum Alloy Molten Aluminum Solidification Samples under Reduced Pressure", and the measured density was 2.63 g / cm³. 3 The slag content was characterized by the K-modulus value, and the test was carried out in accordance with GB / T 15115-2024 "Die Casting Aluminum Alloys". The measured K-modulus value was 0.05, which met the requirements.

[0122] 2. Calming of molten aluminum in the holding furnace

[0123] The refined molten aluminum from the transfer package is poured into the holding furnace next to the die-casting machine. The holding furnace temperature is set to 692℃, and the molten aluminum is kept at this temperature for 22 minutes to calm it down.

[0124] 3. Aluminum liquid composition control and cleanliness re-inspection

[0125] After the aluminum melt was cooled, a direct-reading spectrometer was used to sample and analyze the chemical composition of the aluminum melt in the holding furnace. The measured composition was: Si = 10.65 wt%, Mn = 0.45 wt%, Mg = 0.22 wt%, Fe = 0.12 wt%, with other impurity elements totaling 0.08 wt%, and the remaining content being entirely Al. The composition meets the narrow-range design requirements and requires no adjustment.

[0126] 4. Die-casting parameter settings

[0127] A split-type injection chamber (60mm inner diameter, 390mm effective length) was selected, with the following parameters set: punch diameter 65mm, chamber filling rate 42%; the chamber is heated by hot oil circulation, with the hot oil temperature controlled at 188℃; the injection punch uses three-stage injection control, with a low speed set at 0.25m / s, a high speed set at 1.5m / s, and an ingate cross-sectional area of ​​320mm². 2 The flow velocity of molten metal at the ingate was calculated to be 46 m / s using CAE simulation analysis, and the pressurization pressure was set to 950 kgf / cm². 2 .

[0128] 5. Use a ladle to scoop out the soup.

[0129] The high-pressure die-casting machine uses a robotic arm to control the scooping action of the molten aluminum. An infrared positioning device is used, and the program is set as follows: ① Scooping molten aluminum: The scoop is positioned 8mm above the molten aluminum surface. The robotic arm then descends and tilts the scoop at a 30° angle to scoop the molten aluminum. The scooping is complete when it rises above the surface. ② Transport and positioning: The scoop rises to the dripping position, and the robotic arm carries the molten aluminum forward to the pressure chamber of the die-casting machine. ③ Pouring: Pouring begins, and a die-casting delay timer (set to 1.5 seconds) is started. Pouring is complete when the timer expires. ④ Retreat and reset: The robotic arm drives the scoop to quickly retreat to the standby position above the molten aluminum surface in the holding furnace. ⑤ Standby: The scoop remains in the standby position, continuously receiving heat radiation from the molten aluminum. The infrared positioning device adjusts the scoop's position in real time, maintaining the bottom of the scoop 8mm above the molten aluminum surface at the furnace's scooping port. The standby period lasts for 5 seconds. The total time for a single die-casting cycle is less than 12 seconds.

[0130] 6. Die casting and post-processing

[0131] The aluminum liquid stays in the pressure chamber for 4 seconds (from the completion of pouring to the start of the punch). After die casting is completed, the mold is opened and the part is removed.

[0132] 7. Test Results

[0133] Cross-sectional inspection of the casting revealed no fractured chilled layer fragments in the main body; relevant morphology is shown in [reference needed]. Figure 15 Metallographic analysis of the sample (100x magnification) revealed no coarse α-Al or α-Al(FeMn)Si pre-crystallized structures. The α-Al grain size was uniform. Mechanical property testing showed a tensile strength R... m =279MPa, yield strength R p0.2 =141MPa, elongation after fracture A=9.5%.

[0134] Example 3 (Front engine compartment crossbeam structural component of new energy vehicle)

[0135] A method for simultaneously suppressing pre-crystallized microstructure and fracture chilling layer in high-pressure cast AlSi10MnMg alloy materials includes the following steps:

[0136] 1. Refining of molten aluminum in transshipment packages

[0137] The AlSi10MnMg alloy molten aluminum prepared in the melting furnace was transferred to a transfer ladle and degassed using rotary argon injection. Subsequently, a slag remover was added to the transfer ladle for slag removal. After refining, samples were taken from the transfer ladle to test the density and slag content of the molten aluminum. The density of the molten aluminum was tested according to GB / T 43139-2023 "Density Test of Cast Aluminum Alloy Molten Aluminum Solidification Samples under Reduced Pressure", and the measured density was 2.64 g / cm³. 3 The slag content was characterized by the K-modulus value. The test was conducted in accordance with GB / T 15115-2024 "Die Casting Aluminum Alloys". The measured K-modulus value was 0, which met the requirements.

[0138] 2. Calming of molten aluminum in the holding furnace

[0139] The refined molten aluminum from the transfer package is poured into the holding furnace next to the die-casting machine. The holding furnace temperature is set to 695℃, and the molten aluminum is kept at this temperature for 30 minutes to calm it down.

[0140] 3. Aluminum liquid composition control and cleanliness re-inspection

[0141] After the aluminum melt was cooled, a direct-reading spectrometer was used to sample and analyze the chemical composition of the aluminum melt in the holding furnace. The measured composition was: Si = 10.85 wt%, Mn = 0.42 wt%, Mg = 0.55 wt%, Fe = 0.15 wt%, Cr = 0.05 wt%, with other impurity elements totaling 0.08 wt%, and the remaining content being entirely Al. The composition meets the narrow-range design requirements and requires no adjustment.

[0142] 4. Die-casting parameter settings

[0143] A split-type injection chamber (inner diameter 80mm, effective length 390mm) was selected, with the following parameters set: punch diameter 65mm, chamber filling rate 36%; the chamber is heated by hot oil circulation, with the hot oil temperature controlled at 195℃; the injection punch uses three-stage injection control, with a low speed set at 0.3m / s, a high speed set at 1.6m / s, and an ingate cross-sectional area of ​​320mm². 2 .

[0144] 5. Use a ladle to scoop out the soup.

[0145] The high-pressure die-casting machine uses a robotic arm to control the scooping action of the molten aluminum. An infrared positioning device is used, and the program is set as follows: ① Scooping molten aluminum: The scoop is positioned 10mm above the molten aluminum surface. The robotic arm then descends and tilts the scoop at a 30° angle to scoop the molten aluminum. The scooping is complete when it rises above the surface. ② Transport and positioning: The scoop rises to the dripping position, and the robotic arm carries the molten aluminum forward to the pressure chamber of the die-casting machine. ③ Pouring: Pouring begins, and a die-casting delay timer (set to 2 seconds) is started. Pouring is complete when the timer expires. ④ Retreat and reset: The robotic arm drives the scoop to quickly retreat to the standby position above the molten aluminum surface in the holding furnace. ⑤ Standby: The scoop continuously receives heat radiation from the molten aluminum in the standby position. The infrared positioning device adjusts the scoop's position in real time, maintaining the bottom of the scoop 10mm above the molten aluminum surface at the holding furnace's scooping port. The standby period lasts 4.2 seconds. The total time for a single die-casting cycle is less than 12 seconds.

[0146] 6. Die casting and post-processing

[0147] The aluminum liquid stays in the pressure chamber for 5 seconds (from the completion of pouring to the start of the punch). After die casting is completed, the mold is opened and the part is removed.

[0148] 7. Test Results

[0149] Cross-sectional inspection of the casting revealed no fractured chilled layer fragments exceeding 300 μm in size on the main body cross-section. (See relevant morphology figures.) Figure 16 Metallographic analysis of the sample (100x magnification) showed that the pre-crystallization structure in the compression chamber was almost completely suppressed, and no coarse α-Al phase or α-Al(FeMn)Si phase pre-crystallization structure was detected; Mechanical property testing: tensile strength R m =271MPa, yield strength R p0.2 =145MPa, elongation after fracture A=10%, meeting the requirements of heat-free die casting process.

[0150] Comparative Example 1 (using a traditional broad component range)

[0151] The process is basically the same as in Example 1, except that the alloy composition is adjusted to Si=9.8wt%, Mn=0.65wt%, Mg=0.45wt%, and Fe=0.25wt% (which is within the broad range of the conventional Silafont-36 standard, but exceeds the narrow range of this invention).

[0152] Test results: The precipitation temperature of the α-Al precrystallized structure rose to approximately 625℃, resulting in the formation of a large number of coarse dendrites during the residence in the pressure chamber; metallographic analysis showed that the area fraction of the precrystallized structure in the casting body was 4.5%, and there was obvious aggregation of coarse α-Al(FeMn)Si phase; mechanical property test: tensile strength R m =249MPa, yield strength R p0.2=130MPa, elongation after fracture A=3.73%, the fracture surface has a fracture chilling layer defect, and exhibits obvious crystalline brittle fracture characteristics. Relevant morphology is shown in [reference needed]. Figure 17 .

[0153] Comparative Example 2 (using conventional injection parameters)

[0154] The procedure is basically the same as in Example 1, except that the injection parameters are changed as follows: the low speed is set to 0.15 m / s, the high speed is set to 3.0 m / s, the filling rate of the pressure chamber is 30%, and the pressure chamber is kept warm without hot oil circulation (room temperature 45°C).

[0155] Test results: Due to the long residence time (approximately 8 seconds) and low pressure chamber temperature during the low-speed stage, a large amount of chilled layer was generated; the excessively high speed caused severe breakage of the chilled layer, with fragments being drawn into the casting. The cross-section of the sample showed that there were >2mm fractured chilled layer fragments inside the casting; Mechanical property test: Tensile strength R m =237MPa, yield strength R p0.2 =123MPa, elongation after fracture A=3.37%.

[0156] Comparative Example 3 (using the traditional spoon-based soup-scooping procedure)

[0157] The process is basically the same as in Example 1, except that the scoop's action program is changed to a conventional setting: it is kept away from the liquid surface during standby, with no heat radiation for heat preservation, and a single cycle time of 20 seconds.

[0158] Test results: The total temperature drop of the molten aluminum in the ladle and pressure chamber exceeded 75℃, causing the temperature of the molten aluminum to drop to the pre-crystallization range (580~620℃). Large-sized pre-crystallized structures were found in the casting body, and the low temperature led to an increase in the fracture chilling layer defect rate. The cross-section of the sample showed that there were fracture chilling layer fragments >1mm inside the casting. The relevant morphology is shown in [reference needed]. Figure 18 Mechanical property testing: tensile strength R m =248MPa, yield strength R p0.2 =129MPa, elongation after fracture A=4.03%.

[0159] 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 method for simultaneously suppressing pre-crystallized microstructure and fracture chilling layer in high-pressure cast AlSi10MnMg alloy materials, characterized in that, Includes the following steps: (1) Refining of aluminum liquid in transfer package: The AlSi10MnMg alloy aluminum liquid in the transfer package is degassed and slag removed for refining. The density of the aluminum liquid is tested to be ≥2.6g / cm³. 3 If the K-modulus value, which characterizes the slag content, is ≤0.1, the material must be refined again. (2) Cooling of aluminum liquid in holding furnace: The refined aluminum liquid is introduced into the holding furnace and cooled at 695±5℃ for 20~30 minutes; (3) Aluminum liquid composition control and cleanliness re-inspection: The aluminum liquid composition in the holding furnace is tested to ensure that Si=10.3~11wt%, Mn=0.4~0.5wt%, Mg=0.1~0.6wt%, Fe≤0.2wt%, other single impurities≤0.05wt%, and other impurities total≤0.15wt%, with the remainder being Al. If the requirements are not met, the composition is adjusted and the aluminum liquid is refined again. After the aluminum liquid composition is qualified, the aluminum liquid density is tested again to be ≥2.6g / cm³. 3 If the K modulus value is ≤0.1, then refine it again; (4) Die-casting parameter settings: A split-type pressure chamber is adopted, with a punch diameter of 50~80mm and a pressure chamber filling rate of ≥35%; the pressure chamber is heated by hot oil circulation, with a hot oil temperature of 190±5℃; the injection speed is 0.25~0.3m / s at low speed and 1.5~2m / s at high speed, the molten metal flow velocity at the inner gate is ≥45m / s, and the pressure is 800~1000kgf / cm 2 ; (5) Scooping soup with a ladle: control the single cycle of scooping soup with a ladle to be ≤15 seconds. When the ladle is in standby mode, the bottom of the ladle is 10±3mm away from the aluminum liquid surface. The steps of scooping, transportation positioning, pouring, retraction and reset and standby are completed in sequence. (6) Complete high pressure casting according to the above parameters, control the residence time of aluminum liquid in the pressure chamber, and simultaneously suppress the formation of pre-crystallized structure and fracture chilling layer in the pressure chamber and the entrainment of castings; In step (1), degassing is performed by rotary jetting of argon or nitrogen, and slag removal is performed by adding a slag remover and then scraping off the slag. In step (4), the integrated oil circuit channel inside the split-type pressure chamber is controlled by a hot oil circulation system through an oil temperature controller, so that the outlet temperature is 3~10℃ lower than the inlet temperature. In step (4), hot oil is introduced into the internal oil circuit of the pressure chamber through the oil temperature controller. The inlet temperature of the oil temperature controller is 180~210℃, and the outlet temperature is 3~10℃ lower than the inlet temperature. In step (4), the flow rate of the molten metal in the ingate is determined by CAE simulation analysis and the cross-sectional area of ​​the ingate is adjusted according to the casting size to match the flow rate requirements; In step (5), the time to complete the scooping action is ≤3 seconds, the time to complete the transport and positioning action is ≤3 seconds, the time to complete the pouring action is ≤2 seconds, the time to complete the retraction and reset action is ≤2 seconds, and the standby time is ≤5 seconds; In step (5), the scoop is driven by a robotic arm and equipped with an infrared positioning device to ensure the accuracy of the distance between it and the aluminum liquid surface during standby. During the standby phase, the scoop is kept warm by the thermal radiation of the aluminum liquid. In step (6), the residence time of the molten aluminum in the pressure chamber is ≤5 seconds.

2. The method for simultaneously suppressing the pre-crystallization structure and fracture chilling layer in the high-pressure casting AlSi10MnMg alloy material according to claim 1, characterized in that, The method is used for the production of AlSi10MnMg alloy die-cast structural parts for new energy vehicle electronic control boxes, power battery tray frames, or front engine compartment crossbeams.

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