25 2月 Liquid aluminum purification and sustainable development in aluminum deep processing

Liquid aluminum purification

Q1: Why does liquid aluminum need to be degassed and filtered before deep processing?

A1: Liquid aluminum is easily mixed with hydrogen (mainly from water vapor decomposition) and non-metallic inclusions (such as oxides, slag, etc.) during smelting and transportation. These impurities will cause defects such as pores, looseness, and cracks in the final aluminum material, significantly reducing the mechanical properties (such as strength, and ductility) and corrosion resistance of the material.
Hydrogen hazards: 1 cubic meter of liquid aluminum can dissolve up to 20 mL of hydrogen, and hydrogen precipitates to form pores during solidification.
Inclusions: Inclusions will become stress concentration points and accelerate material failure.
Therefore, degassing and filtration of liquid aluminum are the core processes to improve the quality of aluminum and ensure the reliability of deep-processed products (such as automotive parts and aerospace components).

Q2: What are the key technologies for filtration of liquid aluminum? How does an alumina ceramic foam filter work?

A2: Liquid aluminum filtration removes inclusions by physical interception, among which alumina ceramic foam filters are the mainstream technology.

Functional principle:
1. High-purity alumina (Al₂O₃) is sintered at high temperatures to form a porous structure with a porosity of 30% to 50% and a customizable pore size (such as 10-30 PPI).
2. When the aluminum liquid flows through the ceramic foam filter, the inclusions are intercepted by the multi-layer channels, and the purification efficiency can reach more than 95%.
Advantages and characteristics:
High-temperature resistance (above 1600℃), strong thermal shock resistance, suitable for continuous casting environment.
High chemical stability, no reaction with aluminum liquid, avoiding secondary pollution.
Application scenario: widely used in the production of high-end aluminum products such as automotive aluminum wheels and electronic foils.Q3: What types of aluminum liquid degassing equipment are there? What is its technical principle?

A3: The mainstream degassing unit includes a rotary jet degassing machine and a vacuum degassing device. The core goal is to reduce the hydrogen content of aluminum liquid.

Rotary jet degasser:

Principle: Introduce inert gas (such as nitrogen, and argon) into the aluminum liquid, and break the gas into microbubbles through the high-speed rotating rotor.
Effect: The bubbles absorb hydrogen atoms and float up and carry them out, and the hydrogen content can be reduced to below 0.1 mL/100g.

Vacuum degassing device:

Principle: Under a vacuum environment, the hydrogen partial pressure in the aluminum liquid decreases, and hydrogen spontaneously precipitates and is extracted.
Effect: Suitable for high-end aerospace aluminum materials, with a hydrogen removal rate of over 90%.

Both technologies can significantly reduce pore defects and improve material density.

Q4: What contribution does the aluminum liquid purification process make to sustainable development?

A4: Aluminum liquid purification directly promotes the green transformation of the aluminum industry:

1. Reduce scrap rate: After purification, the qualified rate of aluminum materials increases by 20%-30%, and the energy consumption of remelting is reduced (the energy consumption per ton of recycled aluminum is only 5% of that of original aluminum).

2. Extend material life: High-purity aluminum is more corrosion-resistant, extending the product life cycle and reducing resource consumption.
3. Support circular economy: The purification process is compatible with the purification of recycled aluminum (waste aluminum), promoting closed-loop recycling of aluminum (75% of the world’s aluminum is still recycled).
4. Low-carbon emission reduction: High-efficiency degassing/filtration equipment can reduce smelting temperature and time and reduce carbon emissions.

Q5: How will aluminum deep processing technology develop in the future?

A5: The industry is moving towards **high efficiency, intelligence, and zero defects:

Composite purification technology: Combined with new processes such as electromagnetic purification and ultrasonic degassing, the impurity removal rate can reach ＞99%.
Digital control: Real-time monitoring of hydrogen content and inclusion concentration through sensors, and dynamic adjustment of process parameters.
Sustainable material innovation: Develop reusable ceramic filter plates and low-energy degassing units to reduce environmental footprint further.

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