Aluminum ingots supply the transportation, construction, and industrial sectors, where they are remelted to make cast‑engine parts, wheels, building profiles, and many other fabricated products. They are also widely used in smaller foundries and metal‑casting shops that need controlled chemistry and convenient handling sizes.
Types of aluminum ingots :
Primary ingots: Made from mined bauxite that is refined into alumina and then smelted; these are high‑purity (often 99.5–99.8% Al) and used where trace‑element control is important.
Secondary/remelting ingots: Produced by recycling scrap aluminum; usually cheaper but may have slightly more variable alloy content.
Foundry/Alloy ingots: Pre‑alloyed with elements such as silicon, magnesium, or copper for specific casting applications (for example, ADC12, 356, 383 grades).
Aluminum ingots are manufactured in a clear, step‑by‑step process that starts either from bauxite ore (primary production) or from scrap aluminum (recycling). Below is a simplified “how‑it‑is‑done” sequence, combining both routes.
1. Source the raw material
Primary route: Bauxite ore is mined and refined into alumina (aluminum oxide) via the Bayer process.
Secondary/recycled route: Clean aluminum scrap (old castings, sheets, extrusions, etc.) is sorted by alloy and grade before melting.
2. Melt the aluminum
The raw material (alumina in smelters or scrap in foundries) goes into a furnace (typically electric or gas‑fired) and is heated above about 660 °C until it becomes molten aluminum. Temperature and atmosphere are controlled to avoid oxidation and excessive dross formation.
3. Hold and homogenize the melt
Liquid aluminum is transferred to a holding furnace where it stays at a controlled temperature to ensure uniform composition and to allow any major slag or dross to float to the surface. Chemical analysis is often done at this stage to check alloy content.
4. Purify and degas the melt
Degassing: Rotary‑impeller or bubbling systems inject an inert gas (like argon or nitrogen), sometimes with a small flux, to remove dissolved hydrogen and reduce porosity.
Filtration: The melt may pass through ceramic‑foam filters or other media to remove solid inclusions and non‑metallic particles.
5. Pour into molds
Molten aluminum is poured (manually or by automated teeming ladles) into water‑ or air‑cooled steel or graphite molds shaped to the desired ingot form (rectangular, T‑shaped, etc.). For continuous or semi‑continuous lines, direct‑chill casting uses a water‑cooled mold and a continuous downward draw of the solidifying shell.
6. Cool and solidify
The metal in the mold rapidly loses heat, forming a solidified shell and then a fully solid ingot. Cooling‑water flow, mold design, and casting speed are tuned to minimize internal stresses, cracks, and segregation.
7. Strip and cut the ingots
Once solid, the cast blocks are removed from the molds and often cut to standard length using saws or shears. For direct‑chill or continuous casting, the semi‑solid bar is pulled out and automatically cut into discrete ingots.
8. Clean and inspect
Ingots are washed or brushed to remove surface oxides, mold residues, and superficial defects. They are then inspected for dimensions, surface quality, and sometimes subjected to hardness or chemical‑analysis checks.
9. Marking, stacking, and shipping
Each ingot is typically stamped or labeled with alloy grade, heat number, and batch information, then stacked and palletized for storage or shipment to extruders, rolling mills, or foundries.
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