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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 purification gas and solvent and using the graphite rotor to rotate and blow to the aluminum melt for purification treatment is the advanced treatment method in the world at present.
The working principle of graphite rotor for aluminum melt degassing: Graphite rotor consists of two parts: rotor bar and nozzle. The drive system drives the graphite rotor to rotate, and the argon or nitrogen gas is blown into the aluminum melt through the rotor bar and nozzle. The high-speed graphite rotor breaks up the argon or nitrogen gas into the aluminum melt to form many small bubbles, which are scattered in the metal liquid, while the rotating rotor also promotes the diffusion of hydrogen and inclusions in the aluminum melt to make contact with the bubbles, which absorb the hydrogen in the melt by the gas partial pressure difference and the surface adsorption principle, adsorb oxidation inclusions, and are taken out of the surface of the melt with the rising of the bubbles to purify the melt.
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, while the anti-oxidation protective coating is done on the surface, 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, and the structure of the nozzle, in addition to considering that the air bubbles should be broken up, also uses the centrifugal force generated by stirring the aluminum alloy melt, so that the melt enters the nozzle and mixes evenly with the gas ejected horizontally, forming a gas/liquid stream to eject, increasing the contact area and contact time between the air bubbles and the aluminum alloy liquid, and improving the degassing and purification effect.
2, after a special process of high-temperature anti-oxidation graphite rotor compared with the non-oxidation rotor durability 3-4 times better. About 700 ℃ up to 55-65 days, more than 1000 ℃ up to 25-35 days, in the surface made of antioxidant protective coating, the service life can be extended to 50-60 days.
3, aluminum casting with graphite rotor in the aluminum liquid before immersion, in the liquid level above about 100mm preheat 5min ~ 10min, to avoid the impact of rapid cooling on the material; rotor immersion in the liquid before the gas must be passed into; rotor in the liquid level before stopping the gas supply, to prevent the rotor nozzle pore blockage.
4, graphite rotor damage is the main reason for high temperature oxidation: graphite composition is mainly carbon, graphite in more than 600 ℃ air conditions visible oxidation phenomenon, carbon oxidation reaction products are CO and CO2 gas, the rotor can not play a protective role; generally speaking, in addition to the gas box can not be completely sealed, and most of the box cavity is not filled with protective gas protection, graphite rotor oxidation is inevitable. As a result of oxidation, the diameter of the rotor shaft becomes smaller and smaller until it breaks and is scrapped.