One of the techniques widely used in the world along with fluxes is the technique of degassing of liquid aluminium alloys by the rotary treatment of melt with inert gas purging.
The principle of operation (for aluminium alloys)
A special rotor is immersed in the aluminium melt. It starts rotating at a speed of 350 – 600 rpm, and at this, an inert gas (mostly nitrogen) is passed through the rotor. Duration of the treatment is from a few to 10 minutes. The rotor has a special shape with channels that ensures a uniform distribution of inert gas bubbles in the melt. The rotor material based on SiC/C is specially designed for long-term operation in the aluminium melt. On average, the flow rate of the inert gas (nitrogen) is 20 liters per minute for every 100 kg of the aluminium melt. Therefore, it is necessary to perform the treatment for 10 minutes at the flow rate of 20 nitrogen liters per minute to process 1000 kg of the aluminium melt.
This technique enables the following
- Effective degassing, notably, hydrogen removal from the aluminium melt. This technology permits to achieve the lowest possible level of hydrogen. The principle of operation is based on hydrogen diffusion from the melt into inert gas bubbles.
- Remove some non-metallic inclusions due to the effect of bubbling/flotation.
Compared with flux processing, it has the following advantages
- Higher degree of degassing (hydrogen removal) from the aluminium melt.
- Low operating costs.
- Compliance with environmental requirements.
- Possibility of degassing in furnaces during continuous metal casting.
Depending on the purpose, we can offer the customer stationary and mobile melt degassing units in various design.