Introduction of Graphite Rotors for Aluminum Industry

Graphite rotors are mainly used for the purification of liquid aluminum. Liquid aluminum alloy purification treatment process is the main means to improve the comprehensive performance of aluminum alloy. In the purification treatment process, the method of mixing the purification gas and solvent, and using the rotation of the graphite rotor to spray the aluminum melt for purification treatment is currently an advanced treatment method in the world.

Working principle of aluminum liquid degassing graphite rotor: The graphite rotor is composed of two parts: the rotor rod and the nozzle. The transmission system drives the graphite rotor to rotate, and argon or nitrogen is blown into the aluminum melt through the rotor rod and nozzle. The high-speed rotating graphite rotor breaks up the argon or nitrogen gas entering the aluminum melt to form many small bubbles, which are dispersed in the molten metal. At the same time, the rotating rotor also promotes the diffusion of hydrogen and inclusions in the aluminum melt, making them contact with the bubbles. The bubbles in the melt rely on the gas partial pressure difference and the principle of surface adsorption to absorb hydrogen in the melt, adsorb oxidation slag, and be taken out of the melt surface with the bubbles rising, so that the melt can be purified.

The anti-oxidation graphite rotor is made of high-purity graphite. The quality of graphite itself has a significant impact on the service life of the rotor. At the same time, an anti-oxidation protective coating is applied on the surface, and the service life can be extended to 50-60 days.

Graphite rotor use and maintenance:
1. The rotating nozzle is made of high-purity graphite. In addition to breaking up the bubbles, the structure of the nozzle also uses the centrifugal force generated by agitating the aluminum alloy melt to make the melt enter the nozzle and mix with the horizontally ejected gas to form a gas/liquid flow, increase the contact area and contact time between the bubbles and the aluminum alloy liquid, and improve the degassing and purification effect.
2. The high temperature and oxidation resistant graphite rotor treated with special process is 3-4 times more durable than the non-oxidation resistant rotor. It can last 55-65 days at about 700°C, and 25-35 days at temperatures above 1000°C. With an anti-oxidation protective coating on the surface, the service life can be extended to 50-60 days.
3. Before the graphite rotor for aluminum casting is immersed in the aluminum liquid, it should be preheated at about 100 mm above the liquid surface for 5 minutes to 10 minutes to avoid the impact of rapid cooling on the material; before the rotor is immersed in the liquid, the gas must be introduced; the rotor can stop the gas supply after it is raised from the liquid surface to prevent the air holes of the rotor nozzle from being blocked.
4. The main cause of graphite rotor damage is high-temperature oxidation: the main component of graphite is carbon, and graphite can be visibly oxidized under air conditions exceeding 600°C. The products of carbon oxidation reactions are CO and CO2 gases, which cannot protect the rotor; generally speaking, the degassing box cannot be completely sealed, and most of the inner chambers of the box are not filled with protective gas protection, so the oxidation of graphite rotors is inevitable. As a result of its oxidation, the shaft diameter of the rotor shaft gradually decreases until it breaks and is scrapped.