2017-05-15 11:18:00

Aluminum Foundry Products

Production of aluminum products (all types of castings exclusive of ingots) has increased over the past 30 years at a fairly steady rate.

Aluminum casting alloys must contain, in addition to strengthening elements, sufficient amounts of eutectic-forming elements (usually silicon) in order to have adequate fluidity to feed the shrinkage that occurs in all but the simplest castings. Required amounts of eutectic formers depend in part on casting process. Alloys for sand casting generally are lower in eutectics than those for casting in metal molds, because sand molds can tolerate a degree of hot shortness that would lead to extensive cracking in non-yielding metal molds.

The range of cooling rates characteristic of the casting process being used controls to some extent the distribution of alloying and impurity elements. For example, the extremely high cooling rates inherent in die casting result in fine dispersion of strengthening and eutectic-forming constituents, and reasonably good castings can be obtained in spite of impurity contents that would render sand or plaster-mold castings unacceptable. However, with these minor exceptions, most aluminum foundry alloys can be cast by all processes, and choice of casting technique usually is controlled by factors other than alloy composition.

A large number of aluminum alloys has been developed for casting, but most of them are varieties of six basic types: aluminum-copper, aluminum-copper-silicon, aluminum-silicon, aluminum-magnesium, aluminum-zinc-magnesium and aluminum-tin alloys.

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Aluminum gravity casting process
Process : Aluminium gravity castingMaterial : aluminiumMachine :  die-machine ranging from 250T to 1600TUsed for :  Engine blocks and manifolds, machine bases, gears, pulleys

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Aluminium gravity casting parts
Process: Aluminium gravity castingMaterial: aluminiumMachine: die-machine with 1200TUsed for: Engine blocks and manifolds, machine bases, gears, pulleys, agriculture parts,marine parts, medical parts

Aluminum-copper alloys that contain 4 to 5% Cu, with the usual impurities iron and silicon and sometimes with small amounts of magnesium, are heat-treatable and can reach quite high strength and ductility, especially if prepared from ingot containing less than 0.15% iron.

Manganese in small amounts also may be added, mainly to combine with the iron and silicon and reduce their embrittling effect. However, these alloys have poor castability and require very careful gating if sound castings are to be obtained. Such alloys are used mainly in sand casting; when they are cast in metal molds, silicon must be added to increase fluidity and curtail hot shortness, and this addition of silicon substantially reduces ductility.

AI-Cu alloys with somewhat higher copper contents (7 to 8%), formerly the most commonly used aluminum casting alloys, have steadily been replaced by AI-Cu-Si alloys and today are used to a very limited extent. The best attribute of these higher-copper Al-Cu alloys is their insensitivity to impurities, but they have very low strength and only fair castability. Also in limited use are AI-Cu alloys that contain 9 to 11 % Cu, whose high-temperature strength and wear resistance make them suitable for automotive pistons and cylinder blocks. These alloys usually contain manganese as an impurity because wrought metal scrap is used in preparing them. The manganese has little effect.

Very good high-temperature strength is an attribute of alloys containing copper, nickel and magnesium, sometimes with iron in place of part of the nickel.

Investment Casting, Sand Casting, Die Casting, Green Sand Casting

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