Vacuum casting is a process that uses a vented mold. Molten metal relies on air pressure to flow into the mold and then purges the air to form a vacuum. This casting method is mainly used for small parts or jewelry with exquisite detail.
Vacuum modeling is a physical modeling method, which combines vacuum technology and sand casting, plastic film sand mold cavity surface and the back sealed up, with the vacuum pump to produce negative pressure, resulting in sand mold inside and outside The pressure difference makes the molding sand fastened and formed. After placing the sand center, clamping and casting, waiting for the solidification of the casting, releasing the negative pressure or stopping the pumping, the mold sand will be crushed to obtain the castings. According to the current field of application can be divided into vacuum seal modeling (V method) and real-time vacuum casting (FV method). Its advantages are:
(1) moderate degree of vacuum, high mold cavity, casting quality is also high.
(2) Vacuum casting can simulate mold flow analysis and simulation of the computer to predict the occurrence of casting defects. The design of the modeling program can save time and improve the production efficiency.
Vacuum differential pressure casting, the main is the resistance of the holding furnace and the mold all sealed in the sealed cap into the larger pressure 500kPa compressed air, then the mold and crucible internal pressure equal to the liquid metal will not rise , And then add 50kPa pressure on the metal surface, liquid metal will rise filling cavity. Particularly suitable for the production of complex thin-walled castings, but the equipment is large, troublesome operation, only when the special requirements apply. The advantages are as follows:
(1) Compared with the traditional gravity casting and vacuum suction casting, vacuum differential pressure casting shows good filling ability on 1mm thick sheet samples.
(2) The castings have a relatively dense crystalline structure and mechanical properties. In the castings, the strength properties are about 20% -25% higher than vacuum suction casting and gravity casting, while the elongation is increased by about 50%.
(3) Vacuum die-casting can effectively reduce the porosity of die casting, casting density increased by 1%.