Application features of die casting die:
1) The metal liquid enters the mold cavity under high pressure and high speed, which causes severe conflict and impact on the surface of the mold cavity, causing corrosion and wear on the surface of the mold.
2) Molten metal in the process of pouring is inevitably brought in by slag, which has complex chemical effect on the surface of forming parts. The compound of aluminum and iron is like a wedge, which accelerates the cause and development of die casting die cracks.
3) Thermal stress is the key reason for the surface cracks of die-casting parts. In the production process of each die-casting, apart from the high-speed and high-pressure erosion of metal liquid, the surface of the formed parts also absorbs the heat released by the metal in the solidification process, which results in heat exchange. Due to the heat conduction of the die material, the temperature of the surface layer of the formed part rises sharply, and there is a large temperature difference between the surface layer and the internal layer, thus the internal stress occurs. When the metal liquid fills the cavity, the surface of the cavity first reaches high temperature and expands, while the inner mold temperature is low and the relative expansion amount is small, which causes the surface pressure stress. After the mold is opened, the surface of the mold cavity contacts with the air, which causes tensile stress due to the cooling of shrinkage air and coating. This kind of alternating stress increases with the continuous production. When the fatigue limit of the die material is exceeded, the surface layer of the die will be plastic deformed and crack will occur.
Selection principle of working temperature of die casting die:
1) The mold temperature is insufficient, the internal structure of the casting is loose, the air is troublesome, and it is difficult to form.
2) The mold temperature is too high, the internal structure of the casting is compact, but the casting is easy to be “welded” and attached to the mold cavity
It is not easy to unload the casting. At the same time, too high temperature will make the mold expand and affect the dimensional accuracy of the casting.
3) The mold temperature should be selected within the appropriate boundary, usually after proper test, thermostatic control is better
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