Die casting is a metal forming process in which molten metal is put under pressure and injected into a die. The molten metal enters the die cavity through sprue holes in the fixed die half. The melt is directed to the cavity by runners (passageways) and gates (inlets) in the ejector half. Locking pins on the die secure the two halves together. The metal, kept just above its melting temperature, quickly solidifies into the shape of the die casting. Ejector pins remove the die cast part. Die castings are made from alloy tool steels. They have at least two sections to permit the removal of castings, the fixed die, or cover, half and the ejector die half. Some dies also have parts, such as removable slides and cores, to produce holes, threads and other desired shapes in the casting. Openings in the die allow the addition of coolant and lubricant. Dies are either air- or water-cooled. The cooling of the die provides for quick cycling and is one of the factors in the high rate of production. It also gives a fine grain structure and superior strength and finish to the metal castings. The molds used by die casting manufacturers will perform up to 5 million shots in its lifetime. The services provided by die casting manufacturers have many advantages over other processes. Die casting is efficient and economical, offering a wide range of durable shapes and components. Little or no machining is required after die castings are made because the process provides very close tolerances for even complex part shapes. Metal castings can be easily plated or finished. Die castings are dimensionally stable and heat resistant. These lightweight parts, even while having thin walls, retain the strength of an alloy because they do not consist of separate parts welded together. Die casting manufacturers utilize a number of materials, including zinc, aluminum, magnesium, copper, lead and tin. Zinc is the easiest alloy to cast, has a low melting point and is economical and easily palatable. Zinc also has high impact strength, offers high ductability and promotes long die life. Aluminum alloys possess high dimensional stability for complex shapes and thin walls. Aluminum die casts are of a lightweight alloy that has good corrosion resistance, mechanical properties, high thermal and electrical conductivity and strength at high temperatures. Along with being the easiest alloy to machine, magnesium is also the lightest typically die cast. Magnesium die casting also has excellent strength-to-weight ratio. Copper is one of the hardest alloys and offers the highest mechanical properties of any other alloy that is cast. A dimensionally stable alloy, copper has high corrosion and wear resistance and strength approaching that of steel parts. Lead and tin are used for special forms of corrosion resistance. Although they have high density, parts with extremely close dimensions are able to be formed from lead castings and tin castings.