To effectively manage oxidized slag, we cannot rely solely on "final filtration", but must implement a three-level defense system of "source reduction, process stabilization, and end interception".

1. Source: Reduce the formation of oxide film (melting section)

1. Low temperature rapid melting Control the melting temperature at 730-750 ℃ to avoid overheating above 780 ℃. The higher the temperature, the exponential increase in the growth rate of the oxide film. Optimization of melting feeding sequence: first add low melting point waste to the bottom, and then increase the block material to avoid direct burning of the aluminum liquid by the flame.
2. Violent feeding is prohibited, and the use of a feeding machine to smoothly feed into the furnace is strictly prohibited. "High altitude throwing of materials" is strictly prohibited. When smashing into the molten pool, the surface facial mask will be directly pressed into the deep, forming permanent internal oxidation groups.
3. During the melting stage, a covering agent (KCl NaCl based) is used to isolate the air. The covering agent can not only prevent oxidation, but also adsorb the generated floating slag.

2. Refining: Remove the slag (purification section)

1. Precise gas refining - argon chlorine synergistic pure argon bubbles are carried away by flotation to remove impurities, but the efficiency is limited. Introducing trace amounts of chlorine gas (2%~5%) for argon chlorine mixed refining is a key process: Cl ₂ reacts with aluminum to form AlCl ₂, which is gaseous and can "stretch" the oxide film cluster, causing it to break; At the same time, AlCl3 can wet oxide inclusions, forming larger aggregates that are easier to float up; Chlorine gas can also remove sodium and calcium, reduce the surface tension of the melt, and facilitate slag separation.
2. Standardization of rotor parameters: rotor speed: 350~500 rpm (too high generates microbubbles but causes air entrainment, too low results in uneven stirring); Depth of immersion of rotor: 150-200mm below the liquid surface to avoid inhaling air; Refining time: ≥ 20 minutes. After refining, let it stand for ≥ 30 minutes to allow sufficient time for the inclusion to float up.
3. After refining the slag removal operation, the surface floating slag must be removed. When scraping slag, the slag rake should be flat to prevent pushing the slag into the deep. Many factories' slag inclusion is due to not paying attention when removing the slag, which pushes the oxide scale back.

3. Transfer note: Preventing secondary entanglement (flow field control) is the most critical and easily overlooked aspect of controlling oxidized leather slag.

1. The drop control of all flow channel interfaces should not exceed 50mm. The connection between the static furnace and the degassing box, and between the degassing box and the filtration box, must use a "subsurface flow" connection, which means that the aluminum liquid flows out from below the liquid surface and does not pass through the air.
2. Seal and cover the flow channel with a cover plate to reduce air convection.
3. The distribution bag (Bag Filter/Distribution Bag) must be made of ceramic fiber cloth or high-temperature resistant cloth above the crystallizer. Function: Transform the aluminum liquid from a "waterfall style" to a "permeation style", eliminate liquid column impact, and maintain a calm liquid level. Requirement: The bag must not be torn or leave residue, and should be replaced regularly. The bag broke and the debris immediately surged.

4. Filtration: the last physical interception

1. Common grade of ceramic foam filter (CFF): 40ppi (coarse filtration) → 50ppi (fine filtration) → 60ppi (high-end foil). Installation location: filter box, the last checkpoint before casting. Management points: preheating to prevent aluminum liquid from encountering cold crust; Record the pressure drop. If the pressure drop is too large, it indicates blockage and the medium needs to be replaced; Prohibit "crossover" (bypass filter box, which is a lazy operation in many factories).
2. For aviation grade and high-purity flat ingots, deep bed filtration (deep bed) or tubular filters using alumina balls can intercept micron sized oxide film fragments.

5. Casting: The "gatekeeper" of the solidification interface

1. Automatic liquid level control (LHC) controls the liquid level fluctuation in the crystallizer within ± 1mm. The liquid level fluctuates, which can swallow the surface oxide film into the solidified shell. High end casting machines must be equipped with electromagnetic/laser liquid level control systems.
2. The casting speed should be matched with a slow starting stage, and then increased after establishing a stable solidification shell to prevent gas and slag entrapment.