Automotive Castings
Cars, trucks, semis, two wheelers, motorcycles, mopeds and industrial vehicles like pneumatic forklifts and bulldozers are composed of die cast parts. Engine, transmission and steering wheel parts are manufactured by die casting. They may be small, large, complex or simple, and are often highly stressed and thus need to be long-lasting and durable. Parts like steering wheels, engine blocks, cylinder heads, brake calipers and discs and suspension components are all die cast. They tend to have a complex design, and can be hollow, solid, flat, have projections and holes. These vehicle parts are mass produced in high volumes by automotive manufacturing companies.
Because of their intricate design, many automotive castings are made via the high pressure die casting process, in which the liquid zinc or aluminum alloy is injected at high speeds. Two vertical platens contain bolsters that hold the die halves - one that is fixed in place, and one that is able to open and close. The metal is poured in from the holding pot and shot into the mold by a hydraulic piston. After the metal solidifies, the mold opens and the metal part is ejected. During high pressure die casting, blistering caused by gas inclusions is a common concern. Since this process takes more energy, it is only cost effective for mass produced items. Zinc is considered the easiest alloy to cast. It has a low melting point of between 700º and 800º F and is therefore cast in a hot chamber, which has the holding pot inside the furnace and a continuous flow system. It is mostly used for smaller automotive parts and is considered long-lasting. Zinc is alloyed with copper for rigidity, aluminum for strength, and tin if more flexibility is desired. Since pure aluminum cracks and shrinks when die cast, it is alloyed with silicone to increase fluidity. It can sometimes also be alloyed with copper, which minimizes ductility and improves corrosion resistance. Like zinc, aluminum is also lightweight and easy to cast. It exhibits high strength and dimensional stability.
