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The graphite rotor works continuously at a speed of 200r/min~400r/min in the aluminum melt at about 750°C. The service life is generally required to reach more than one month. Our 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 antioxidant protective coating is done on the surface, the service life can be extended to 50-60 days.
Graphite rotor working principle.
Graphite rotor consists of two parts: rotor bar and nozzle. The transmission system drives the graphite rotor to rotate, and the argon or nitrogen is blown into the aluminum melt through the rotor bar and nozzle. High-speed rotating graphite rotor to enter the molten aluminum argon or nitrogen gas to break up the formation of many small bubbles, so that they are dispersed in the metal liquid, while the rotating rotor also prompted the molten aluminum hydrogen, inclusions diffusion, so that they are in contact with the bubbles, bubbles in the melt by gas partial pressure difference and surface adsorption principle, absorbing hydrogen in the melt, adsorption of oxidation slag, and with the bubbles rise and be taken out of the surface of the melt, so that the melt can be purified.
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 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 flow to eject, increasing the contact area and contact time between the bubbles and the aluminum alloy liquid, and improving the degassing and purification effect.
2. The general service life is required to reach more than one month. Compared with its non-oxidation rotor durability is 3-4 times better. About 700 ℃ up to 55-65 days, more than 1000 ℃ up to 25-35 days, in the surface made antioxidant protective coating, service life can be extended to 50-60 days.
3, graphite rotor before dipping into the aluminum liquid, about 100mm above the liquid level preheat 5min~10min, to avoid the impact of rapid cooling on the material; the rotor must be passed into the gas before dipping into the liquid; the rotor can only stop supplying gas after the liquid level is raised, 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.