Process and Production of Aluminium Sand Casting
Aluminium sand casting is most commonly used to make metal castings. The technology uses one-shot sand molds to cast complex parts of nearly any metal alloy, including cast aluminum alloys. Sand castings are generally less productive because the sand must be broken to remove the finished casting.
1. Aluminium sand casting process
Aluminium sand casting techniques include the use of: melting (holding) furnaces, foundry molds and sand molds. Cast aluminum alloys are first melted in an oven and then poured through a ladle, usually by hand, into the cavity of a sand mold. This cavity in the mold is formed using a mold casting model (usually wood). After the metal is fully solidified, the sand mold is separated along the parting plane and the solidified casting is taken out.
Sand casting is used to produce various metal parts with complex geometries. These castings vary widely in size and weight, ranging from hundreds of grams to tons. Aluminium sand casting produces many automotive aluminium castings and components: cylinder blocks and cylinder heads, transmissions, housing unit chassis and many more.
2. The production of aluminium sand casting
The first step in the aluminum sand casting process is to create a mold for casting. Sand molds are disposable, so each casting has to be remade. Sand molds are formed by compacting sand in each of the two mold halves. Sand stuffing around the model is an imprint of the casting shape. When the model is withdrawn, it is in the form of a cavity that will form the casting. To generate any internal cavity of the casting, the model cannot be generated, using the form of a single component, the so-called rod. These rods are also made of sand before forming the mold.
The sand casting mold making process includes: installing the model; compacting the sand; removing the model. The duration of making the sand mold depends on: the size of the casting; the number of rods; the sand mold. If the type of sand mold requires heating or baking, the duration of its production is greatly increased. Also, the mold surfaces are often lubricated to make removal of the finished casting easier. The application of lubrication also promotes the flow of metal and improves the quality of the casting surface. Lubricants are selected based on the type of sand used and the melt temperature.
Once the aluminum sand casting has been molded, it is ready to pour molten metal. The surface of the mold is first smeared to ensure the free removal of the casting. The core is then set, the upper die is mounted on the lower die and they are firmly connected. It is very important to keep the two halves of the mold firmly closed to prevent any metal flow.