Causes and Solutions of Common Defects (Blowholes, Shrinkage Cavities) in Aluminum Die Casting

Causes and Solutions of Common Defects (Blowholes, Shrinkage Cavities) in Aluminum Die Casting

Aluminum die casting is widely used in automotive, new energy, electronics and other industries due to its advantages of high efficiency, light weight and high forming accuracy. However, defects such as blowholes and shrinkage cavities are prone to occur during the production process, which directly affect the strength, tightness and service life of die castings. Clarifying the causes of these two types of defects and adopting scientific and effective solutions are the key to improving the quality of aluminum die castings and reducing production costs.

Blowhole defects are mainly manifested as small holes inside or on the surface of castings, and there are three main causes: first, the aluminum alloy liquid contains excessive gas, insufficient degassing during smelting, or the raw materials themselves are mixed with moisture and oil; second, the exhaust of the die casting mold is not smooth, and the gas in the cavity cannot be discharged in time and is wrapped inside the casting; third, the die casting process parameters are unreasonable, such as too fast injection speed and insufficient pressure, leading to gas failing to escape in time.

Shrinkage cavity defects mostly appear in the thick and large parts of castings, showing irregular cavities. The core cause is the volume shrinkage of the aluminum alloy liquid during the solidification process and insufficient feeding. Specifically, it comes from the unreasonable design of the mold gate and riser, which cannot provide sufficient feeding metal liquid for the solidified part; the die casting temperature is too high, which increases the solidification shrinkage of the metal liquid, and the cooling speed is uneven, so the thick-walled part cools slowly and the shrinkage cannot be supplemented; the alloy composition ratio is improper, resulting in poor fluidity and affecting the feeding effect.

Corresponding solutions can be taken for the two types of defects: blowholes can be improved by optimizing the smelting process, using refining agents for degassing, drying raw materials, reasonably designing the mold exhaust system, and adjusting the injection parameters; shrinkage cavities need to optimize the gate and riser structure to ensure sufficient feeding, control the die casting temperature and cooling speed, and optimize the alloy composition to improve fluidity. At the same time, strengthening the production process control and standardizing the operation process can effectively reduce the two types of defects and improve the quality stability of aluminum die castings.