Casthouse

A casthouse is a specialized facility within a primary aluminum smelter where molten aluminum metal, tapped from Hall-Héroult electrolytic reduction cells, is processed, alloyed if required, refined for cleanliness, and cast into solid commercial products for delivery to fabricators and end-users. While casthouse operations are specific to the aluminum smelting stage of the value chain — which begins with bauxite mining and alumina refining — they are a critical link in the transformation of raw mineral into tradeable commodity and are therefore important context for bauxite and alumina producers seeking to understand the downstream value chain. In a casthouse, molten aluminum (typically at approximately 850-900°C) from the reduction cells is transported in large crucibles by overhead cranes to holding furnaces, where the metal's temperature and composition are controlled. Alloying elements such as silicon, magnesium, copper, manganese, and zinc may be added to produce specific aluminum alloys (such as the 3xxx, 5xxx, and 6xxx series used in automotive, aerospace, packaging, and construction applications). Metal treatment processes — including degassing with inert gas (argon or nitrogen) to remove dissolved hydrogen, fluxing to remove non-metallic inclusions and alkali metals, and filtration through ceramic foam filters or deep bed filter boxes — ensure the required cleanliness standard is achieved before casting. Casting operations produce various product forms: large rolling ingots for hot rolling mills, extrusion billets for extrusion presses, wire rod for drawing, and foundry alloy ingots or T-bar. Casting machines include direct chill (DC) casting machines (the most common) for wrought alloy ingots and billets, and continuous casting machines for strip and rod. Safety in the casthouse is paramount due to the severe explosion risk created by any contact between molten aluminum and water or moisture.