Casting of aluminum alloys -Sand, precision casting and related processes

Cast aluminum alloys have the advantage of being suitable for all known casting processes. Given their moderate melting temperature and good casting properties, they are most widely used in metal molds (i.e., permanent molds), gravity die-casting, low-pressure or suction die-casting, pressure die-casting (and its vacuum and semi-solid metal injection variants), especially for large-scale production runs of automotive parts. In most cases, these processes offer an advantage over sand casting in terms of cost, mechanical properties and dimensional characteristics for medium to large-scale automotive production runs.

Today, however, sand casting covers the entire spectrum of parts and applications. For certain very large automotive series with medium to high mechanical characteristics (manifolds, suspension wishbones, engine blocks, etc.), this process is once again becoming the least expensive, thanks to the use of large automated worksites with productivity of up to 300 molds (often multi-cavity) per hour (case of automated vertical parting line sand molding (Disamatic) with coreless parts). On the other hand, for medium-to-small production runs (for aerospace, railways and various mechanical industries), the use of coolers enables very high mould characteristics to be achieved, combined with complex external and internal shapes. It is obviously the best choice for single parts or large components (e.g. street furniture).

Moulding with gas-forming models (Lost foam) now seems to have found a stable niche: cylinder heads and engine blocks, as well as some very complex core-moulded parts (which create internal cavities that cannot be geometrically demoulded).

Lost-wax and plaster casting are mainly used for small and medium-sized precision parts for the aerospace, electronics and automotive industries (compression wheels or impellers for turbochargers).

The V process, on the other hand, is designed for large parts, most often for their appearance (cash dispenser casings).

Sand ablation molding is still in its infancy, although some small-scale production is underway in the USA. If its promises are fulfilled, it could cover a wide spectrum of parts, thanks to its high potential mechanical properties and its apparent advantages in terms of sand recycling.

Given the diversity of processes available in aluminum casting, it is the judicious choice of the alloy/process pairing best suited to the specifications of the part and its production volume that enables castings to be produced under the best conditions of quality and profitability.

To complete this approach, the reader is invited to consult the following articles:

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