Direct chill casting

Direct Chill casting is a method for the fabrication of cylindrical or rectangular solid ingots from non-ferrous metals, especially Aluminum, Copper, Magnesium and their alloys. The original ingots are usually further processed by other methods (rolling, forging, etc.). More than a half of global aluminum production uses the Direct Chill casting process.[1]

Direct Chill casting operates by pouring liquid metal continuously into a short mold (7.5–15 cm deep) that is open at the bottom. Only an outer layer of metal solidifies within the water-cooled mold. After leaving the closed mold at its bottom (e.g. with 5–15 cm/min), water is directly sprayed on the new ingot, continuing the solidification until complete. Only about 20% of the heat of the molten metal is removed through the mold wall, the secondary cooling (Direct Chill) contributing the majority of cooling.[1] Typically the process is started with a starter-dummy block at the bottom of the mold, and runs until the maximum length possible in the machine is reached (up to 10 m).[1]

The casting method reduces the internal stress in the cooled material by allowing contractions on all side, as opposed to only on the top of the ingot in a traditional trough mold.

References
  1. Dr. Dmitri Kopeliovich, Direct Chill (DC) casting, http://www.substech.com/dokuwiki/doku.php?id=direct_chill_dc_casting
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