Process Specification for Low Pressure Casting

Low pressure casting is a method of filling a cavity with liquid metal under pressure to form a casting. Known for its lower pressure, what are the specifications for this casting process?

1, Filling and boosting of low pressure casting

Liquid pressure refers to the required pressure when the metal level rises to the gate. The rising speed of the metal liquid in the riser should be as slow as possible in order to facilitate the exhaustion of the gas in the cavity, and at the same time, it can prevent the metal liquid from splashing when entering the gate.

2, boost and boost speed of low pressure casting

后 After the metal liquid fills the cavity, it continues to pressurize, so that the crystal solidification of the casting is performed under a certain pressure. The pressure at this time is called the crystallization pressure. The larger the crystallization pressure, the better the shrinkage effect, and the denser the cast structure obtained. But increasing the quality of castings by increasing the pressure through crystallization is not always applicable.

3. Holding time of low pressure casting

After the pressure in the cavity is increased to the crystallization pressure, it is maintained under the crystallization pressure for a period of time until the casting is completely solidified. If the pressure holding time is not enough, the casting is released before the solidification of the casting is complete, and the metal liquid in the cavity will be totally or partially returned to the donation, causing the casting to be "emptied" and scrapped.

4. Mold temperature and pouring temperature for low pressure casting

Low-pressure casting can use various molds. The working temperature of non-metallic molds is generally room temperature, and the working temperature of metal molds has certain requirements. For example, when casting aluminum alloy at low pressure, the working temperature of metal mold is generally controlled at 200 ~ 250 ° C, and when casting thin-walled complex parts, it can reach 300 ~ 350 ° C.

If metal low pressure casting is used, in order to improve its life and casting quality, the paint must be applied, the paint should be uniform, and the thickness of the paint should be determined according to the surface finish of the casting and the structure of the casting.