Manufacturing process of aluminum alloy die castings is a systematic project, encompassing multiple stages from raw material preparation to finished product forming. Correctness of process and precision of controlling processing considerations directly determine mechanical properties, dimensional accuracy, surface quality, and production stability of castings. In mass production in civilian industries such as automobiles, electronics, and home appliances, standardized manufacturing processes can improve production speed and reduce manufacturing costs, while neglecting key processing considerations can easily lead to defects such as porosity, cracks, and dimensional deviations, affecting product qualification rates.

 

Manufacturing process for aluminum alloy die castings should revolve around core objective of "accurate forming speed and guaranteed quality," be planned in conjunction with factors such as complexity of casting structure and performance requirements. Core process includes three main stages: raw material melting, die casting, and subsequent processing. Process characteristics of each stage are interrelated and jointly determine final product quality.
Raw material melting is fundamental stage of manufacturing, its core objective is to obtain aluminum alloy liquid with uniform composition and high purity. Initially, aluminum alloy raw materials need to be selected according to performance requirements of casting. Common aluminum alloys include ADC12 and A380. Raw materials must undergo visual screening to remove severely oxidized ingots and those with many inclusions. Melting process is usually carried out in a resistance furnace or gas furnace. Aluminum ingots and alloy additives are added to furnace and heated to 700-720℃ to melt them. During this process, mixture must be stirred evenly with a stirring device to ensure uniform alloy composition. To improve purity of molten aluminum, degassing and impurity removal treatments are required. Common degassing methods include argon or nitrogen refining, which uses inert gas bubbles to adsorb hydrogen and impurities from molten aluminum. Impurity removal can be achieved by using a filtration device to filter solid inclusions from molten aluminum. After melting, chemical composition and temperature of molten aluminum need to be tested to ensure it meets process requirements before proceeding to die casting stage.
Die casting is core step in forming aluminum alloy die castings. Molten aluminum is rapidly forced into mold cavity under high pressure, and after cooling and solidification, a casting blank is obtained. Based on production needs, mainstream die casting processes are divided into cold chamber die casting and hot chamber die casting. Aluminum alloys, due to their relatively good melting point, are mostly used in cold chamber die casting. Die casting process requires precise control of key parameters: injection speed is typically divided into three stages: slow pressure building, fast filling, and final deceleration. Slow pressure building avoids aluminum liquid impacting runner; fast filling ensures aluminum liquid promptly covers cavity; and final deceleration reduces air entrapment. Injection pressure needs to be adjusted according to casting wall thickness, ensuring sufficient aluminum liquid filling and achieving required casting density. Mold temperature is controlled between 180-250℃ to avoid excessively low temperatures causing rapid solidification of aluminum liquid and resulting in cold shuts, while excessively high temperatures can easily cause sticking. After aluminum liquid fills cavity, a certain holding time is required to compensate for solidification shrinkage of aluminum liquid. Blank is removed from mold after casting has completely solidified.

 

Subsequent processing is a supplementary step to improve precision and surface quality of casting. It is selectively carried out according to product requirements. Core processes include cleaning, shaping, machining, and surface pretreatment. Cleaning process primarily removes burrs, scale, gating gates from casting surface. This can be done manually by filing, mechanically grinding, or using automated cleaning equipment. Care must be taken to avoid damaging casting surface during cleaning. Shaping process addresses minor deformations in casting by using tooling fixtures to correct them and ensure dimensional accuracy meets requirements. Machining is suitable for critical areas requiring high dimensional accuracy, such as threaded holes and locating holes. It utilizes CNC lathes and milling machines, ensuring machining allowances are controlled within correct range to avoid over-machining and affecting casting's mechanical properties. Surface pretreatment includes degreasing and oil removal, laying foundation for subsequent surface treatment processes.
During production and processing of aluminum alloy die castings, it is crucial to control key aspects at each stage, mitigate defect risks, and ensure a stable production rate. Core processing considerations include process parameter control, mold maintenance, quality monitoring, and adherence to stable standards.
Accurate control of process parameters is core factor in determining quality of finished product.
During smelting stage, temperature of molten aluminum must be monitored in real time to prevent excessively high temperatures from accelerating oxidation or excessively low temperatures from affecting fluidity. Strict control of degassing, impurity removal time and process parameters is essential to ensure purity of molten aluminum meets standards. In die-casting stage, an automated control system must monitor parameters such as injection speed, pressure, and mold temperature in real time, establishing a parameter fluctuation early warning mechanism for timely adjustments in case of deviations. Regular calibration of testing instruments is necessary to ensure parameter detection accuracy. In subsequent processing stages, appropriate machining tools and cutting parameters must be selected based on characteristics of casting material to prevent excessively high temperatures during processing that could cause casting deformation. Proper positioning and clamping are also crucial during machining to prevent processing deviations.
Mold maintenance is critical for ensuring production continuity.
Die-casting molds operate under high temperature and high pressure environments for extended periods, making them prone to problems such as cavity wear, guide mechanism jamming, and cooling water blockage. Therefore, a regular maintenance mechanism is necessary. Before daily use, mold cavity, gating system, and cooling system must be inspected. Residual impurities and oxide scale must be removed, release agent and lubricant applied. During production, mold temperature distribution should be regularly checked to ensure uniform cooling. After production, mold should be thoroughly cleaned, worn parts repaired, and vulnerable components replaced. When mold is not in use for extended periods, rust and moisture prevention treatments should be implemented. Furthermore, during mold installation, coaxiality and fitting accuracy must be ensured to avoid casting defects caused by mold closing deviations.
Full-process quality monitoring is crucial for controlling product quality.
Upon raw materials arrive at factory, their chemical composition and appearance quality must be tested to prevent unqualified materials from being used in production. After smelting, aluminum liquid composition and purity must be tested to prevent impurities from affecting casting performance. After die casting, casting blanks undergo appearance inspection and dimensional sampling to screen for surface defects and dimensional deviations. After subsequent processing, finished product inspection is conducted, including appearance quality, dimensional accuracy, and mechanical properties, ensuring product meets delivery requirements. Simultaneously, a quality traceability system should be established to record production and processing data for each batch, facilitating subsequent defect tracing and process optimization.
Standardization and environmental control are fundamental aspects of production and processing. During smelting stage, it is essential to ensure stable operation and protection of furnace to prevent burns from splashing hot molten aluminum. During die-casting stage, it is crucial to ensure die-casting machine's stability and safety devices are in good working order, and operators must wear protective equipment as required to prevent mechanical injuries. Proper ventilation is necessary at production site, smelting slag and casting waste must be disposed of promptly.