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Aluminium and light alloy treatment > Purification, slagging, and covering

PURIFICATION, SLAGGING, AND COVERING

Fluxes and systems for the purification, slagging and covering of the molten alloy

degassing tablets

To achieve a perfect treatment of alloys, FONDERMAT offers the following solutions:


Aluminium based alloys oxidise easily, in both the liquid and solid phase, creating a thin, compact film that protects it from further oxidation. However, at the foundry, the turbulence induced by pouring and mechanical cup pick-up cause this film to break, corrupting its protective function and causing the oxide particles to be entrapped.

PURIFICATION AND SLAGGING
The purpose of the de-oxidation (purification) treatment is to eliminate the oxides, specifically alumina, reducing the amounts or transforming them into complex compounds that can easily be separated from the molten metal. To facilitate this operation, suitable blends of granules/fluxes are added to the bath. To remove the oxides, the granules/fluxes must be well distributed in the fluid mass, and this is achieved through vigorous mechanical agitation or through the injection of inert gasses. In the slagging phase that follows, all of the slag and with it the oxides brought to the surface through de-oxidation, are eliminated.

COVERING
Covering treatments are used to prevent metal oxidation during melting and time in the furnace by forming a barrier that hinders the contact between the air and the bath, thus preventing contamination by external agents. Traditional covering treatments are obtained with specific fluxes. These fluxes have a low specific gravity and therefore cover the surface of the liquid alloy, protecting it from air contact. They are sufficiently fluid so as to ensure their uniform distribution on the surface of the bath.