The essence of die casting is a method of filling the die casting mold cavity with liquid or semi-liquid metal at a high speed under the action of high pressure and forming and solidifying under pressure to obtain castings.

High-pressure and high-speed filling of die casting molds are the two major characteristics of die casting.

Its commonly used injection pressure is from thousands to tens of thousands of kPa, or even as high as 2 × 105kPa.

The filling speed is about 10~50m/s, and sometimes even more than 100m/s.

The filling time is very short, generally in the range of 0.01~0.2s. Compared with other casting methods, die casting has the following three advantages:

Good Castings Quality

Castings have high dimensional accuracy, generally equivalent to grade 6~7, or even up to grade 4; good surface finish, generally equivalent to grade 5~8; high strength and hardness, the strength is generally 25~30% higher than that of sand casting, but the extension the rate is reduced by about 70%; the size is stable, and the interchangeability is good; it can die casting thin-walled and complex castings.

For example, the current minimum wall thickness of zinc alloy die castings can reach 0.3mm; aluminum alloy castings can reach 0.5mm; the minimum casting hole diameter is 0.7mm; the minimum pitch is 0.75mm.

High Production Efficiency

The machine has high productivity. For example, the domestic JIII3 horizontal cold air die casting machine can die-cast 600-700 times in an average of eight hours, and the small hot-chamber die casting machine can die-cast 3,000-7,000 times in an average of eight hours; die casting bell alloys have a lifespan of hundreds of thousands or even millions of times; easy to realize mechanization and automation.

Excellent Economic Effect

Due to the precise size of the die casting parts, the surface is smooth and clean.

Generally, it is not used directly without mechanical processing, or the processing volume is very small, so it not only improves the metal utilization rate but also reduces a lot of processing equipment and man-hours; the price of castings is easy; combination die-casting can be used to make other metal or non-metallic materials, saves both assembly man-hours and metal.

Although die casting has many advantages, it also has some disadvantages that need to be solved, such as:

•  During die casting, due to the high speed of liquid metal filling the cavity and the unstable flow state, the general die casting method is used, and the casting is prone to pores and cannot be heat treated.
• Die casting is more difficult for complex concave castings.
• With high melting point alloys (such as copper, and ferrous metals), the die casting mold life is low.
• It is not suitable for small-batch production. The main reason is that the manufacturing cost of the die casting mold is high, the production efficiency of the die casting machine is high, and the small batch production is uneconomical.