There are many factors that affect the quality of aluminum and its alloys. Among them, the hydrogen content, inclusions and alkali metal concentration of molten aluminum have the most important impact on the quality of aluminum alloy. At present, major domestic and foreign manufacturers mostly use online refining and degassing systems for the refining and purification of aluminum melt. The online refining and degassing systems are mostly box-type rotary degassing units. The aluminum liquid flows into the degassing cabinet and is used in refractory materials. The inner lining stays, and the furnace cover of the box body is equipped with a heater to keep the molten aluminum in a molten state. At the same time, a degassing rotor is installed in the furnace cover. The inert gas is sprayed into the molten aluminum through the rotating rotor and passes through high speed The rotating rotor breaks into countless small bubbles, which diffuse and rise in the aluminum liquid, thereby removing hydrogen. During the ascending process of the small bubbles, due to the effect of surface tension, some impurities are brought out of the molten aluminum to the surface, forming scum to remove the impurities in the molten aluminum.
After the die-cast aluminum alloy is melted and refined, the aluminum water will take the position of the subcontracted water, the time before and after the refining agent is added, the nitrogen flow rate of the rotating degassing, the speed of the graphite rotor, the degassing time, the diameter of the graphite rotor during the subcontracting and degassing. The influence of height on the density of molten aluminum is measured and analyzed during the production process.
1. After degassing, the degassing effect of different positions of aluminum liquid in the subcontract is inconsistent, and the position near the turntable is the worst.
2. Nitrogen flow has a certain impact on the bubble generation location, large flow bubbles spread farther, but cause aluminum liquid toss more serious, which will cause production safety hazards.
3. Rotation speed has a great influence on the degassing effect of molten aluminum. High speed can ensure more gas diffusion and ensure that molten aluminum does not roll.
4. The putting time of the refining agent has little effect on the rotating degassing, and it cannot achieve the purpose of refining inside the molten aluminum. The surface scum on the molten aluminum can be treated. It is recommended to use a slag remover to treat the surface aluminum slag. According to the refining agent specification, the use temperature of the refining agent is 700 ~ 750 ℃, and the use temperature of the slag and degassing agent is ≥ 680 ℃. The use of the refining agent requires a higher temperature of the aluminum liquid. Not easy to control.
5. Rotation speed and nitrogen flow must be used in conjunction to ensure the degassing effect and the molten aluminum will not be oxidized due to tumbling. The flow rate of 15L/min at 400r/min can meet the requirements.
6. During the degassing process, the rolling condition of the molten aluminum and whether the molten aluminum splashes have an effect on the degassing and oxidation of the molten aluminum. After degassing, the aluminum slag on the surface of the molten aluminum and the sample density can reflect the degassing effect of the molten aluminum.