Fumeless In-Line Degassing and Cleaning of Liquid Aluminum

Abstract

Arising from a basic study of the generation and behavior of non-metallic inclusions in liquid aluminum, a process has been developed for fumeless degassing and cleaning of aluminum on an in-line basis. No prior fluxing or degassing is needed in melting and holding furnaces, the metal being treated continuously in a unit placed between holding furnace and casting point. The metal first enters a degassing chamber where it is treated with nitrogen under a liquid flux cover; it then passes through a bed of flux-coated coarse refractory granules to complete the cleaning operation, and finally through a bed of uncoated coarse granules to remove entrapped flux. Over 15 million lb. of various alloys have been processed in this way. Gas contents have been lower than with conventional chlorine degassing and metal cleanliness similar to that achieved with the flake alumina filter described by Brondyke and Hess (Transactions of AIME, 1964, Vol. 230, pp 1553–56.) The process is suitable for treating primary metal and can be used to control sodium content at low levels. In addition to eliminating the need for fume treatment plant in casting shops, the process offers savings in operating cost, processing time, and metal loss through dross formation.