What is a Graphite Rotor? How to Do Antioxidant Treatment?
The graphite rotor works continuously in the aluminum melt at about 750 ℃ at a speed of 200r/min~400r/min, and the graphite rotor generally has a service life of more than one month.
The graphite rotor is made of high-purity graphite blocks. 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.
Ⅰ. The working principle of graphite rotor
The graphite rotor consists of a rotor rod and a 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 entering the aluminum melt to form many small bubbles, which are dispersed in the molten metal.
At the same time, the rotating graphite rotor also promotes the diffusion of hydrogen and inclusions in the aluminum melt, making it contact with the bubbles. The bubbles in the melt rely on the gas partial pressure difference and the principle of surface adsorption to absorb the hydrogen in the melt and adsorb the oxidized slag inclusions, and is brought out of the melt surface as the bubbles rise, so that the melt can be purified.
Ⅱ. The use and maintenance of graphite rotor
1. The rotary nozzle is made of high-purity graphite. In addition to dispersing bubbles, the structure of the nozzle also uses the centrifugal force generated by stirring the aluminum alloy melt to make the melt enter the nozzle and mix with the horizontally ejected gas to form a gas. / The liquid flow is ejected to increase the contact area and contact time between the bubbles and the aluminum alloy liquid, and to improve the degassing and purification effect.
2. The general service life of graphite rotor is required to reach more than one month. 3-4 times more durable than its non-oxidative rotor.
About 700 ℃ up to 55-65 days, more than 1000 ℃ up to 25-35 days, with an anti-oxidation protective coating on the surface, the service life can be extended to 50-60 days.
3. Before the graphite rotor is immersed in the aluminum liquid, preheat for 5min~10min at about 100mm above the liquid level to avoid the effect of rapid cooling on the material; the graphite rotor must be filled with gas before being immersed in the liquid; the graphite rotor can only be used after the liquid level is raised. Stop the air supply to prevent the air holes 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, graphite has visible oxidation phenomenon under the air condition of over 600℃, and the products of carbon oxidation reaction are CO and CO2 gas, which cannot protect the graphite rotor;
Generally speaking, the degassing box cannot be completely sealed, and most of the boxes are not filled with protective gas, so the oxidation of the graphite rotor is inevitable. As a result of its oxidation, the shaft diameter of the graphite rotor shaft is gradually reduced until it is broken and scrapped.
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