Pressure die casting is a casting method that the liquid or semi-liquid metal under the effect of high pressure fill mold at high speed and solidification into casting. It uses a pressure of 4 to 500 MPa, the metal filling rate is 0.5 to 120 m / sec. In 1838, Americans Bruce G. first used pressuredie casting method to produce printed newspaper type, the following year appeared pressure die casting patents. After the 1860s, pressure die casting method has been greatly developed, not only enable to produce tin-lead alloy die casting and zinc alloy die casting, but also produce aluminum, copper alloy and magnesium alloy die castings.
Die casting machine of pressure die casting using is divided into hot chamber die casting machine and cold chamber die casting machine. Pressure chamber of hot chamber die casting machine is immersed in the liquid metal. Metal fill into the injection when the piston at the highest position of the pressure chamber , the piston under pressure, the pressure chamber through a gooseneck airway press metal into the closed casting mold cavity and quickly solidified shape. Cold chamber die casting machine and holding furnace pressure chamber are separated. When the first die-cast metal is poured into a quantitative liquid pressure chamber, and then pressed into the mold injection piston cavity and solidified forming. Hot chamber die -casting machine apply for low melting point of lead alloy and zinc alloy castings, andalso used to die-cast magnesium alloy castings. Cold chamber die casting machine suitable for casting aluminum, copper alloy or magnesium alloy castings.
Pressure die casting method can make complicated shape castings , the surface roughness of Ra5 ~ 0.32 microns, the size precision can reach 4 ~ 7, the minimum wall thickness of zinc alloy die castings was 0.4 mm, it can effectively save material, energy and processing time. Grams of casting weight small to dozens of kilograms. Pressure die casting method suitable for mass production of the casting, the production efficiency is high; the production process is easy to realize mechanization and automation, it widely used in automobile, agricultural machinery, electrical equipment, instrument, medical equipment and other manufacturing industries.