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Aluminium Degassing

Aluminium Degassing

Degassing is a technological intermediate step in the production of aluminium between the melting and casting of the metal. Mainly hydrogen has been dissolved in liquid aluminium because of reaction with water vapor. To prevent the formation of pores during casting, hydrogen is removed – the liquid metal is degassed. Typically, degasification is achieved by injecting an inert gas in the metal, usually argon, which binds to hydrogen bubbles. For the industrial process to be more efficient, the size of the argon bubbles must be as small as possible. At present, the most widely used method is online degassing system.

When melting aluminum scrap, the process of removing excess hydrogen is essential to producing quality aluminum castings.

Hydrogen is introduced by moisture. Excess hydrogen has a negative effect on the mechanical properties of finished aluminum by creating porosity and overall shrinkage. It is important to remove excess hydrogen during the melting and pouring process.

Introducing inert gases such as argon or nitrogen into the molten metal can be used to remove hydrogen. As inert gas bubbles move up through the molten aluminum, hydrogen diffuses into the inert gas bubbles and essentially disappears. Traditional degassing systems limit mixing, especially at the bottom, where higher speeds are required which results in more surface turbulence. Bubbles are larger and degassing takes longer to achieve desired results. Melters desire superior bubble shearing and dispersion, longer bubble retention time in the metal, complete molten metal circulation, a non-clogging rotor, and to be more thermal shock resistant. Plus they would prefer to use less inert gas in the process.

Online Degassing System

AdTech online degassing systems achieve better degassing aluminium results in less time and with less overall cost.

The rotor head offers increased metal movement by throwing metal outward and drawing metal from bottom for improved circulation. The unique rotational movement of the rotor head shears bubbles to prevent gas from rising. The cleverly designed rotor pushes metal outward and pulls from the bottom to improve flow, thus increasing reaction surface area. It operates at a lower rpm and eliminates “dead zones” in the melt.

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