During the production process of die-cast aluminum accessories, residual stress is often generated due to factors such as rapid solidification of molten metal and mold constraints. These residual stresses may cause deformation and cracking of accessories during subsequent processing and use, seriously affecting their quality and performance.
First of all, the generation of residual stress is mainly due to the uneven thermal expansion and contraction during the die-casting process. When the high-temperature aluminum liquid is injected into the mold cavity, it quickly cools and solidifies, while the temperature of the mold itself is relatively low. This large temperature gradient causes the aluminum parts to be hindered by the mold during solidification and contraction, thereby generating thermal stress. At the same time, during the die-casting filling process, the uneven flow of aluminum liquid will also cause uneven internal stress distribution, further increasing the complexity of residual stress.
For the analysis of residual stress, commonly used methods include X-ray diffraction and finite element simulation analysis. X-ray diffraction can accurately measure the size and direction of residual stress on the surface of aluminum accessories. By measuring different parts, a stress distribution map can be drawn to provide a basis for subsequent stress relief measures. Finite element simulation analysis can simulate the die-casting process in the product design stage, predict the generation of residual stress, optimize the die-casting process parameters in advance, and reduce the formation of residual stress.
In terms of eliminating residual stress, the commonly used method is heat treatment process. By heating the die-cast aluminum accessories to a certain temperature and then slowly cooling them, the atoms inside the metal can be rearranged, thereby reducing the residual stress. For example, artificial aging treatment, keeping the temperature at an appropriate temperature for a period of time, can effectively eliminate some residual stress, and at the same time improve the mechanical properties of aluminum parts, and increase their strength and hardness.
Mechanical processing methods can also be used to eliminate residual stress. For example, appropriate cutting of aluminum accessories to remove a layer of metal on the surface can release some residual stress. In addition, shot peening is used to hit the surface of aluminum parts with high-speed projectiles, causing plastic deformation on the surface, introducing a certain compressive stress, offsetting the internal residual tensile stress, and improving the fatigue strength and stress corrosion resistance of aluminum parts.
Vibration aging treatment is also an effective method for eliminating residual stress. By applying vibrations of a certain frequency and amplitude to aluminum accessories, the residual stress inside the metal can be relaxed and homogenized. This method has the advantages of high efficiency, energy saving, and no pollution, and has been widely used in industrial production.
In addition, optimizing die-casting process parameters, such as adjusting die-casting temperature, pressure, speed, and preheating temperature of the mold, can reduce the generation of residual stress from the source. For example, appropriately increasing the preheating temperature of the mold can reduce the temperature difference between the aluminum liquid and the mold and reduce the formation of thermal stress; reasonably controlling the die-casting speed can make the aluminum liquid filling more stable and uniform, and avoid excessive stress caused by high-speed impact.
The residual stress problem of die-cast aluminum accessories needs to start from two aspects: analysis and elimination. A variety of methods should be used in combination to ensure that the quality and performance of aluminum accessories meet the actual use requirements, improve the reliability and stability of the product, and promote the wide application and development of die-cast aluminum accessories in various fields.
