Aluminum casting

Aluminum casting is the production of parts by pouring molten aluminum alloy into a mold. Aluminum melts at approx. 660°C, and its casting alloys are usually poured at approx. 680–760°C – significantly lower than cast iron or steel. This makes it possible to cast aluminum in sand molds, permanent molds and under pressure.

How aluminum casting works

1. Charge preparation – alloy ingots of known composition, e.g. according to PN-EN 1676, and possibly carefully selected in-house scrap.
2. Melting – in a furnace with temperature control; overheating increases hydrogen absorption and oxidation of the metal.
3. Refining and modification – removal of gases and oxides and refinement of the structure, e.g. silicon modification.
4. Mold pouring – smooth and free of turbulence, which would draw oxides into the metal.
5. Solidification – directed so that the risers feed the casting and no shrinkage cavities form.
6. Finishing – shakeout, removal of the gating system, grinding, inspection and machining.

The most common defects in aluminum castings

• Gas porosity – hydrogen dissolved in the liquid metal is released during solidification; refining and the right temperature prevent it.
• Porosity and shrinkage cavities – thick sections are not fed with enough metal; risers and proper design help.
• Oxide inclusions – oxide films drawn into the casting during turbulent pouring.
• Misruns – the metal solidifies before it fills thin sections; metal and mold temperature are the deciding factors.
• Hot tears – the result of stresses during solidification, depending on the alloy and the shape.

We describe more practical examples in our article on the most common mistakes in aluminum sand casting.

Why you should not cast aluminum at home

Casting at home from cans or scrap produces castings of unknown composition, full of pores and oxides, and it is also dangerous: contact between liquid metal and moisture can cause a violent splash. Technical parts require an alloy of defined composition, controlled melting and a mold designed for the specific casting.

Aluminum casting in our foundry

We melt certified charge material in three furnaces with digital melt control, and we refine and modify the metal before pouring. We cast in permanent molds (0.1 to 50 kg), in sand molds (1 to 100 kg) and by high-pressure die casting, in series of up to 100,000 pieces per year. How to choose the right technology is described on the page aluminum castings – choosing the technology.

See also: aluminum casting alloys, permanent mold casting, sand casting i high-pressure die casting.