The vacuum pressure casting, as this name indicates, is casting method which the major processes including the melting, pouring, solidifying are performed inside the vacuum chamber. The vacuum is able to minimum the gas content of the product, and prevent further oxidation happening to the metal. This is a quite expansive technic, manufacturing the special alloy steel and oxidate-like titanium casting part can use this method to achieve a very high specification requirements.
Vacuum Die Casting Process
The vacuum die casting is further modified technic to the vacuum casting. It is vacuum assisted high pressure die casting method but the main process performs after a certain degree of vacuum building up. The degree of vacuum is about to be 50~80 kPa. In practice, there're 2 major kind of method for the vacuum die casting:
1. using a vacuum cover seal the mold. The cover take the whole mold closed, and pump out the air inside, then do the die casting works.
2. the vacuum is created by the help the mold parting surface. There is specific designed air vent groove in the mold which connected with the vacuum system. When the injection plunger close the pouring gate, the air pump works to create the vacuum to a certain degree, then the die casting works could be conducted.
Vacuum Die Casting VS Traditional Casting
Compared with traditional casting, the same thing is: both are made by pouring molten or semi-molten metal into the mold, and then the required part is obtained by cooling and solidifying the metal.
Differences from traditional casting.
1. The die-casting process, after pouring, before the metal liquid enters the mold, it enters the pressure chamber and then is pressurized and injected into the mold. This makes the filling speed of die casting faster than ordinary gravity casting.
2. In the process of die casting, there will be the process of pressurization and pressure-holding, by applying pressure, which makes the denseness of the metal inside after solidification better than the traditional casting parts.
Advantages of Vacuum Die Casting
Vacuum molding is a physical molding method, which combines vacuum technology with sand casting, relying on plastic film to seal the cavity surface and the back of the sand mold, with the help of vacuum pump pumping to generate negative pressure, resulting in the pressure difference inside and outside the sand mold so that the mold sand is tightly formed, after placing the sand core, closing the mold, casting, waiting for the casting to solidify, lifting the negative pressure or stop pumping, the mold sand will then collapse and get the casting. According to the current field of application, it can be mainly divided into vacuum sealed mold making (V method) and solid vacuum casting (FV method). The advantages are:
(1) Moderate vacuum, high die cavity tightness and high casting quality.
(2) Vacuum casting with computer simulation of mold flow analysis, can predict the generation of casting defects, for the design of the mold making scheme, can significantly save time and improve production efficiency.
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