In the production of die-cast aluminum alloy communication products, the formation of internal porosity during the aluminum housing process can severely affect its structural strength and sealing performance, thereby impacting the stability and lifespan of the communication equipment. Porosity formation mainly stems from factors such as gas dissolution during aluminum alloy smelting, poor mold venting, unreasonable die-casting parameters, and product design defects. Therefore, comprehensive control from multiple dimensions, including raw material processing, mold design, process parameter optimization, and product structure design, is necessary to effectively avoid porosity defects.
Aluminum alloy smelting is the primary step in porosity control. Molten aluminum readily absorbs hydrogen from the air at high temperatures. If refining and degassing are incomplete, hydrogen will precipitate during solidification, forming porosity. Therefore, highly efficient refining agents and degassing equipment must be selected to remove hydrogen and oxide inclusions from the molten aluminum through physical adsorption and chemical reactions. For example, using a rotary degassing device in conjunction with nitrogen or argon purging can significantly reduce the hydrogen content in the molten aluminum. Simultaneously, strict control of smelting temperature and time is essential to prevent prolonged exposure of the molten aluminum to air and reduce gas absorption. Furthermore, the selection and pretreatment of the furnace charge are equally crucial. It is essential to ensure the aluminum ingot surface is clean and free of oil, and that the proportion of recycled materials is appropriate to avoid introducing impurities that could lead to gas generation.
Mold design plays a decisive role in porosity control. The mold's venting system must ensure that all gas within the cavity is completely expelled during die casting, preventing gas from being trapped in the molten aluminum and forming porosity. The layout of venting channels should cover the last area filled by the molten aluminum, especially in thick-walled or structurally complex areas, where overflow channels should be added to guide gas out. Simultaneously, the mold cavity surface must be kept smooth to prevent excessive roughness from obstructing the flow of molten aluminum and causing gas entrapment. In addition, the mold's cooling system design must be reasonable, controlling the solidification sequence of the molten aluminum through directional cooling to avoid localized overheating and gas retention. For example, adding cooling channels in thick-walled areas can accelerate solidification in those areas and reduce the risk of porosity formation.
Optimizing die casting process parameters is the core of porosity control. Injection speed, injection pressure, and mold temperature must be adjusted in tandem to ensure smooth filling of the cavity by the molten aluminum and sufficient venting. Excessive injection speed can lead to air entrapment in the molten aluminum, while insufficient speed may cause the aluminum to cool and lose fluidity, resulting in cold shuts or porosity. Therefore, a reasonable injection speed curve must be set based on the product structure and the characteristics of the molten aluminum. Staged injection is typically used to balance filling and venting requirements. The injection pressure must be sufficient to ensure tight filling of the cavity with molten aluminum, but excessive pressure may cause mold core deformation or flash, hindering gas venting. Mold temperature control is equally crucial. Excessive temperature prolongs the solidification time of the molten aluminum, increasing the risk of gas release; excessively low temperature may result in insufficient fluidity of the molten aluminum, leading to cold shuts. Therefore, the mold temperature must be stabilized within a reasonable range using a mold temperature controller, typically 180-220℃, with adjustments made based on the aluminum alloy grade and product structure.
Product structural design must balance strength and venting requirements. Uneven wall thickness is a common cause of porosity; thick-walled areas are prone to shrinkage cavities or porosity due to prolonged solidification time. Therefore, the design should minimize wall thickness differences or optimize the structure by adding reinforcing ribs, rounded corners, etc. For unavoidable thick-walled sections, core-pulling or cooling systems can be added to accelerate solidification and reduce porosity. Furthermore, the design of internal holes or grooves must consider venting paths to avoid gas stagnation areas. For example, the design of antenna slots or heat dissipation holes must ensure smooth gas escape, preventing pore buildup due to structural enclosure.
Detailed management during production is equally crucial. The selection and use of release agents must be cautious; water-based release agents with low volatility and low gas generation should be used, and uniform spraying should be ensured to avoid localized accumulation that leads to gas generation. Simultaneously, mold venting channels and overflow channels must be cleaned regularly to prevent aluminum shavings or release agent residue from clogging venting passages. In addition, humidity control of the production environment is also important; high humidity increases the risk of hydrogen absorption by molten aluminum housing. Therefore, the workshop must be kept dry, and preheating and drying of aluminum ingots and molds should be performed when necessary.
Porosity control in die-cast aluminum alloy communication products requires a comprehensive approach encompassing raw material processing, mold design, process parameter optimization, product structure design, and production management. By meticulously controlling every step, the porosity defect rate can be significantly reduced, product quality and reliability can be improved, thereby meeting the stringent requirements of communication equipment for high-performance housings.
