The comprehensive purification of refining agent and CFF filtration is the aluminum melt purification technology commonly used by the majority of aluminum processing enterprises. This process comprehensively integrates the degassing and slag removal advantages of FILD, MINT, SNIF, and other purification methods, with low purification costs and convenient production operation has resulted in excellent casting quality.
Purification of refining agent is to blow the auxiliary refining agent into the aluminum melt with gas as the carrier, and achieve the purpose of degassing and slag removal through adsorption, dissolution and chemical reaction. In this purification process, the gas is the carrier for transporting the refining agent, and it also has the function of removing slag.
On the surface of the aluminum melt, there is generally a dense oxide film on the inner surface, which severely hinders the escape of hydrogen from the aluminum melt. Because the refining agent can break the oxide film on the surface of the melt into fine particles and adsorb and dissolve them, the hydrogen in the aluminum melt can easily escape into the atmosphere. At the same time, the refining agent adsorbs and dissolves the Al2O3 inclusions in the aluminum melt, and removes the moisture adsorbed in the Al2O3. In addition, the refining agent chemically reacts in the aluminum melt, generating a gas that is insoluble in the aluminum melt. The inert bubbles bring hydrogen and non-metallic inclusions out of the surface of the aluminum melt together to achieve the purpose of purifying the aluminum melt. This is the principle of purifying the refining agent.
The purification process and control points of the refining agent are: using 99.99% pure nitrogen, the high-quality refining agent is blown into the bottom of the melt bath evenly and steadily through the refining tank (the blowing depth is not less than 300mm), and the blowing time is 20~30min. The amount of refining agent is 1.5~2kg per ton of melt, and the height of aluminum melt tumbling and splashing during refining is generally 30~50mm, not exceeding 180mm. The temperature of the lead melt during refining is 710-740℃, and the scum on the surface of the aluminum melt is removed after refining.