Jun 13 , 2025
Aluminum casting is a fundamental manufacturing process for producing complex aluminum components across various industries, including automotive, aerospace, and construction. It involves melting aluminum and pouring it into a mould cavity, where it solidifies into the desired shape. The quality of the final casting hinges on several factors, including the proper functioning of key equipment and the careful selection of refractory lining materials that directly contact the molten metal.
The primary equipment involved in aluminum casting includes melting furnaces, holding furnaces, and casting machines.
Melting Furnaces: These are crucial for transforming solid aluminum ingots and scrap into molten metal. The key factor for high-quality casting here is precise temperature control and efficient melting. Overheating can lead to excessive dross formation and gas pick-up, while insufficient melting can result in incomplete filling of the mould. Common types include reverberatory furnaces, crucible furnaces, and induction furnaces.
· Lining Materials: Due to direct contact with molten aluminium at high temperatures (typically 700-800°C), the lining materials must exhibit excellent refractoriness, chemical inertness, and resistance to thermal shock and wetting by aluminium.
o Alumina-based refractories (e.g., high-alumina bricks, castables, and ramming mixes): These are widely used due to their good refractoriness and resistance to aluminium attack. They often contain additives like chromium oxide or silicon carbide to further improve performance.
o Silicon carbide (SiC) refractories: Known for their excellent thermal conductivity and resistance to thermal shock, SiC is often used in areas subjected to rapid temperature changes.
o Mullite refractories: Offering a balance of refractoriness and thermal shock resistance, mullite is another common choice.
o Ceramic fiber blankets and modules: Used for insulation behind the working lining to reduce heat loss.
Holding Furnaces: Once melted, the aluminium is often transferred to holding furnaces, which maintain the molten metal at a specific casting temperature while allowing impurities to settle. The critical factor here is maintaining a consistent, stable temperature and preventing contamination or oxidation of the molten aluminium.
· Lining Materials: Similar to melting furnaces, the lining materials need to withstand molten aluminium contact and maintain temperature stability.
o Alumina-based refractories: High-alumina castables and bricks are commonly used for their resistance to wetting and corrosion.
o Phosphate-bonded alumina refractories: These offer good strength and resistance to molten aluminium.
o Silicon carbide refractories: Can be used in specific areas for their thermal properties.
o Insulating firebricks and ceramic fibre: Used for thermal insulation.
o High density calcium silicate boards carbon fiber reinforced：used as the lining part contacting with the molten aluminum with no pollutions of the metal, high strength, easy to install and light weight.
Casting Machines: These machines are responsible for accurately pouring the molten aluminium into the mould. The type of casting machine depends on the desired casting process (e.g., die casting, sand casting, permanent mould casting). The key factor for high-quality casting in this stage is precise control over pouring speed, pressure, and solidification rate to ensure complete mould filling, minimal porosity, and accurate dimensions.
· Lining Materials (for components in contact with molten aluminium):
o Launders/Transfer systems: Often lined with dense, non-wetting alumina or silicon carbide materials to ensure smooth flow and prevent metal pick-up. Also it can be made from high density low shrinkage technical calcium silicate boards by CNC materials machining to be special shapes.
o Dosing furnaces (if separate from holding furnaces): Lined with similar materials to holding furnaces.
o Shot sleeves (for die casting): Typically made of specialized steel alloys, but sometimes incorporate ceramic inserts or coatings for improved longevity and reduced sticking.
o Crucibles (if used for pouring): Made from silicon carbide-graphite or clay-graphite composites, offering good thermal conductivity and resistance to thermal shock.
In summary, achieving high-quality aluminium castings relies on a synergistic interplay between precisely controlled equipment parameters and the judicious selection of refractory lining materials that can withstand the aggressive environment of molten aluminium, ensuring both process efficiency and product integrity.
