Aluminum is a versatile material within many different industries, especially for creating automotive castings. In fact, automotive transmission housings and pistons are made from aluminum castings. However, the aluminum casting form must be created with particular specifications for the overall assembly to work correctly. Aluminum pouring rates during manufacturing have a direct effect on the final casting form.
Aluminum Casting Features
Molten aluminum can be formed into almost any shape. Aluminum casting uses a mold assembly for holding molten metal. The mold's shape determines the final aluminum form. The molten aluminum lines the mold and cools until it has hardened. Workers remove the mold to reveal an aluminum part or item. Casting is an inexpensive manufacturing process for producing numerous aluminum items.
Rapid Pouring Rate
One of the simplest methods for pouring molten aluminum into a casting is using basic gravity. The aluminum travels downward from a holding container and into an open mold. However, workers must be careful during pouring for avoiding the addition of dross, or unwanted debris. One way to avoid dross additions is creating a rapid pour rate. Pouring the molten aluminum quickly prevents dross additions, but the aluminum encounters turbulence during the pour, which adds air into the mixture. Excess air mixed with the molten aluminum compromises the final aluminum product. The hardened aluminum's composition can have air pockets, rather than a solid form, making the item crack easily under stress.
Slow Pouring Rate
A slow pouring rate creates a quality aluminum casting. Molten aluminum has natural chemical reactions with moisture and air, compromising the final composition. Slow pours typically enter the mold through the bottom or the sides, as opposed to dropping downward with a gravity pour. The molten aluminum remains as one mass as it enters the mold, retaining a solid composition. The aluminum mass also keeps most of the metal's surface area protected from outside chemical reactions, such as oxidization.
Typically, slow aluminum pours are instigated by machines rather than workers. Aluminum movement can occur by using a vacuum for pulling the metal or pushing the material with air pressure. Pumps are also used for creating centrifugal forces for metal movement.
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