On completion of the smelting process, aluminium is casted into the various products such as ingots and wire rods. Casting is carried out in a casthouse, which has electrically heated furnaces and ingots casting machines. Aluminium casting processes can be subdivided into ingot casting and mould casting.
Under the ingot casting technique, molten aluminium metal is poured into separate moulds until the metal solidifies into ingots. This technique consists of uphill and downhill casting. Uphill casting leads to better surface quality due to the usage of casting powder. The quality of products in this process is higher with simultaneous casting of many ingots. Downhill casting, on the other hand, is cheaper but results in lower quality of products and casting rate.
Mould casting can be chiefly subdivided into die and sand casting. Under die casting process, molten aluminium metal is poured into mould cavities under high pressure; the cavities are subsequently machined into dies. The die casting method is especially suited for applications where many small to medium sized parts are needed with a fine surface quality and dimensional consistency.
Sand casting allows smaller batches of products to be made at a reasonable cost. Through this technique, manufacturers benefit from the small size of operations and can create products at a low cost. Sand casting also allows most metals to be cast depending on the type of sand used for the moulds. In addition to this, sand can be recycled many times and requires little maintenance