Techniques for Removing Sodium from Molten Aluminum
Martin B. Taylor, STAS Ltée
Track: BILLET PROCESS AND EQUIPMENT - Molten Metal Treatment
ABSTRACT --- Lithium, sodium, calcium and magnesium may all be reduced
efficiently from molten aluminum to very low levels of parts per million (ppm) in the
potroom crucible before transfer to the melter/holder furnace, within a few minutes;
no chlorine is required, only the use of aluminum fluoride salt. Some removal,
particularly of sodium, may also be obtained by simply transferring from one crucible
to another while transporting or delivering molten aluminum, without the introduction
of either gas or salt. On the other hand, these same elements may also be reduced
in the holder furnace in the casthouse, using either salts or gases by various means
including: manual additions of fluxes, or chlorine lances, or, more recently, rotary
gas/flux injectors. Degassers may also be used as in-line treatment for removing
alkalines with the use of argon and chlorine.
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