Ghyslain Dube

Aluminium Cleanliness Monitoring: Methods and Applications in Process Development and Quality Control

The control of metal cleanliness is an essential part of the production of critical alloys. The measurement of metal cleanliness is complicated by the nonuniformity of the distribution of nonmetallic inclusions and by the extremely low concentrations encountered in most wrought aluminium alloys.

A salt-free treatment of aluminum dross using plasma heating

The plasma dross treatment process is similar in operation and equipment to the conventional RSF process, but its elimination of salt fluxes solves the problem of corrosive gas evolution, and also results in salt-free by-products (NMP), which are recyclable and are a marketable raw material for other industries. Labor and equipment demands are about the same for both processes, but the new process dispenses with the costs of salt purchase and landfilling or recycling of salt cake.The new process is the first industrial application of plasma heating technology in the aluminum industry, and greatly reduces environmental risks, while providing a closed-loop, pollution-and waste-free dross treatment method.

The TAC Process: A Proven Technology

The Treatment of Aluminum in Crucibles (TAC) process U.S. Patent No. 4,470,846 has been introduced into Alcan casting plants since 1982. Production experience combined with process demonstrations in other plants permitted a full evaluation of metallurgical variables, treatment conditions, and process and equipment performances. The effect of variables such as metal temperature and presence and type of electrolyte was studied. A new type of treatment (TAC II) involving metal transfer in a treatment crucible was demonstrated and led to improved alkali removal. Recycling of spent AlF3 through potlines was established. The effect of the treatment on metal cleanliness was substantiated specially for the removal of Al4C3 inclusions.

Removal of Lithium in Commercial Metal

An effective process to remove trace levels of lithium and other alkaline impurities contained in aluminum tapped from electrolytic reduction cells has been developed by Alcan Smelters and Chemicals Limited.