With the rapid development of aluminum processing technology, the quality requirements for aluminum products are getting higher and higher. How to better purify the aluminum liquid and eliminate the internal defects of aluminum products has received general attention from the aluminum processing industry in various countries. Industrial practice shows that the bubble floatation method is currently one of the most effective methods for purifying aluminum melt. It uses a rotating nozzle (graphite rotor) to spray inert gas into the aluminum liquid. The key equipment for the bubble floatation method to purify molten aluminum is the degassing unit, and the graphite rotor is the main consumable part of the aluminum degassing box.
When the molten aluminum degassing box is working, the graphite rotor rotates at a constant speed of 200~300r/min, and the gas of certain pressure and flow is introduced from the upper part of the rotor column, and injected from the pores around the rotor head through the gas channel inside the rotor column. In the aluminum liquid in the degassing tank, bubbles are continuously blown out. When the rotor head blades are rotating, they have the dual functions of stirring the molten aluminum and thinning the bubbles, causing a large number of small bubbles to rise in the molten aluminum along a spiral track until they escape the surface of the molten aluminum to complete the degassing and purification process. Obviously, this purification process places higher requirements on the graphite material used to manufacture the rotor.
The graphite rotor rotates at high temperatures and is in a state of red heat. At the same time, it is subject to the dual effects of high-temperature oxidation and molten aluminum erosion and erosion, and it will gradually be consumed, especially near the part that contacts the surface of the molten aluminum, where the loss is the most serious. In addition, due to normal and abnormal shutdowns, overhauls, and other reasons in the aluminum casting and rolling production, it is often necessary to lift the rotor in the red hot state from the molten aluminum and expose it to the air. Therefore, the graphite material of the rotor is required to have high mechanical strength and erosion resistance, as well as good oxidation resistance and corrosion resistance.