Casting can be divided into gravity casting and pressure casting according to the casting process of metal liquid. Gravity casting refers to the process of pouring the metal liquid into the mold under the earth's gravity, also called casting.
The generalized gravity casting include sand casting, metal mold casting, investment casting, die casting, mud casting; metal type casting refers to narrow gravity casting. Pressure casting refers to the process of pouring metal liquid into the mold under the action of other external forces (without gravity). Generalized pressure die casting includes die casting and pressure casting, vacuum casting, low pressure casting, centrifugal casting, etc. the narrow pressure casting for special pressure casting machine is called metal die casting, or die casting. The precision casting factory has long been engaged in gravity casting of sand and metal types. These foundry processes are the most commonly used and lowest relative prices in the present nonferrous metal casting.
The die casting is a metal type pressure casting on the die-casting machine. It is the most productive casting process at present. The die casting machine is divided into two types, the hot chamber die-casting machine and the cold chamber die casting machine. The hot chamber die casting machine is highly automated, with less material loss and higher production efficiency than the cold chamber die casting machine. But it is restricted by the heat resistance of the machine parts, and it can only be used for the casting of low melting point materials such as zinc alloys and magnesium alloys. Because of the high melting point, the widely used aluminum alloy castings can only be produced on the cold chamber die casting machine. The main characteristics of die casting is the molten metal in the cavity filling under high pressure and high speed, and under high pressure forming, solidification, deficiency of die casting is: because the liquid metal in the process of high pressure, high speed filling cavity, inevitably the cavity in the air wrapped in the castings, the formation of blowhole so Aluminum Alloy die casting for heat treatment, zinc alloy die casting surface spray (but not painting). Otherwise, the inner hole in the castings will be heated by heat and cause the casting to be deformed or bubbling when heating the above treatment. In addition, the allowance for mechanical machining of die castings should also get a little smaller. Generally around 0.5mm, it can reduce the weight of the casting, reduce the cutting volume, reduce the cost, and avoid penetrating the surface dense layer, revealing the subsurface porosity, causing the workpiece to be scrapped.
