What is a graphite rotor? How to do antioxidant treatment?


Graphite rotors are mainly used to purify molten aluminum. The purification treatment of liquid aluminum alloy is the main means to improve the comprehensive performance of aluminum alloy. In the purification process, the method of mixing the purified gas with the solvent and blowing the mixture into the aluminum melt through the rotation of the graphite rotor is currently the most advanced treatment method in the world.

First, the graphite rotor works continuously in an aluminum melt of about 750 rpm at a speed of 200 rpm ~ 400 rpm, and the service life is generally required to reach more than one month. Our graphite rotor is made of high-purity graphite, and the quality of the graphite itself has a significant impact on the service life of the rotor. At the same time, the surface is coated with an anti-oxidation protective coating, which can extend the service life to 50-60 days.

Second, the working principle of graphite rotor:

The graphite rotor consists of a rotor rod and a nozzle. The drive 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 that enters the aluminum melt, forming many small bubbles that 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, bringing it into contact with the bubbles. The bubble uses the principle of gas partial pressure difference and surface adsorption to absorb the hydrogen in the melt, absorb the oxidation slag, and be brought out of the melt surface as the bubble rises, so that the melt is purified.



Third, the use and maintenance of graphite rotor;

1. The rotary nozzle is made of high-purity graphite. The structure of the nozzle not only considers the bubbles to be dispersed, but also uses the centrifugal force generated by stirring the aluminum alloy melt to make the melt enter the nozzle and evenly mix with the horizontally sprayed gas to form a gas/liquid jet, increase the contact area and contact time between the bubble and the aluminum alloy liquid, and improve the degassing and purification effect.

2. The general service life should be more than one month. Durability is 3-4 times better than non-oxidation resistant rotors. About 700 55-65 days, above 1000 25-35 days, the surface has an anti-oxidation protective coating, the service life can be extended to 50-60 days.

3. Before immersion in molten aluminum, the graphite rotor should be preheated for about 100 mm above the liquid level for 5 to 10 minutes to avoid the influence of quenching on the material; Before the rotor is immersed in liquid, gas needs to be introduced; The air supply can only be stopped after the rotor has raised the liquid level to prevent the pores of the rotor nozzle from being blocked.

4. The main reason for the damage of the graphite rotor is high-temperature oxidation: the main component of graphite is carbon, and visible oxidation occurs in graphite in air above 600. The products of the carbon oxidation reaction are CO and CO2 gases, which do not protect the rotor. Generally speaking, the degassing box cannot be completely sealed, and most of the chamber cavity is not protected by protective gas, so the oxidation of the graphite rotor is inevitable. As a result of oxidation, the diameter of the rotor shaft gradually decreases until it breaks and is scrapped.