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.
Types of Die Castings
Aluminum castings are die castings made from aluminum materials.
Aluminum die castings are commonly used in the production of hardware and tools because of the great resistance of aluminum castings to corrosion and high temperatures, as well as their conductivity. In addition, aluminum castings are used in applications requiring the production of intricate part features and components.
Automotive castings , which include engine blocks, cylinder heads, brake calipers and discs and suspension components, are increasingly being manufactured out of lightweight material, such as aluminum, to economize fuel consumption by decreasing the overall weight of the vehicle.
Brass castings are used in the architectural and construction industries and in decorative applications, such as doorknobs.
Bronze castings are used in applications requiring high strength, making them ideal for use in the architectural and construction industries.
Copper die castings are used in applications requiring exceptional strength and resistance to corrosion. Copper castings consist of brass and bronze castings.
Die casters shape metal by putting pressure on molten metal in a die.
Gravity die castings are produced by pouring molten aluminum into a metallic tool at a casting temperature of 750¼. Gravity die castings have good tolerances and surface finishing.
High pressure die castings have very thin walls. The metal enters the die cavity at high speeds and under great pressure, which increases the chance of porosity.
Lead die castings offer great corrosion resistance and are used in the production of parts in the plumbing industry. Lead castings, particularly tin castings, also provide close production tolerances but are generally not as strong as other diecast metals.
Low pressure die castings are formed when metal from an airtight furnace is transferred into a metallic tool through a rising tube. Low pressure die casting is suitable for relatively small lot sizes and for applications in which heat treatment is needed to improve the mechanical properties.
Magnesium die castings are particularly useful in applications where weight is a factor. Magnesium die castings are very lightweight and cost-effective, especially in comparison to other diecast metals.
Metal castings are metal impressions made with molds.
Zinc die castings are often used in the production of small parts for the electronics and automotive industries. Zinc castings lend themselves well to secondary operations such as painting and plating.
本文转自：China Industry News