The pressure die casting process is a method in which a liquid or semi-liquid alloy liquid is pressed into a mold cavity at a high speed under a high pressure, and a contoured and dimensionally accurate casting is obtained by coagulation under pressure. High pressure and high speed are the two characteristics of the pressure die casting process, and are also the basic characteristics that distinguish other casting methods. The pressure is usually in the range of a few megapascals to tens of megapascals, the filling speed is usually 0.5 to 70 m/s, and the filling time is very short, generally 0.01 to 0.03 s.
During the operation of the pressure die casting process, there are many factors affecting the filling of the molten metal, including the injection force, the injection speed, the filling time and the temperature of the die-casting mold. The choice of injection specific pressure should be determined according to the structural characteristics of different alloys and castings. For the selection of filling speed, generally for castings with high thick wall or internal quality requirements, lower filling speed and high supercharging pressure should be selected; for castings with high wall thickness or surface quality and complex castings, should be selected Higher ratio and higher filling speed.
The pouring temperature of the pressure die casting process should be considered simultaneously with the pressure, die casting temperature and filling speed. In continuous production, the temperature of die-casting tends to increase, especially for die-casting high-melting alloys, which rises rapidly. Excessively high temperatures, in addition to making the liquid metal sticky, the castings cool slowly, making the grains coarse. Therefore, when the temperature of the die-casting type is too high, the cooling measures should be taken. It is usually cooled with compressed air, water or a chemical medium.
In the pressure die casting process, the time required for the liquid metal to enter the cavity to fill the cavity is called the filling time, and its length depends on the size and complexity of the casting. The length of the holding time depends on the material and wall thickness of the casting. After holding the pressure, the casting should be taken out.
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