We supply the market with over three million metric tons of casthouse products annually.
The most common uses of primary aluminium are extruding, rolling and casting.
Aluminium can be extruded and shaped into a variety of tubes and profiles.
Aluminium logs are heated to 500 degrees Celsius and pressed through shaping tools (like toothpaste coming out of a tube), to make profiles for various products.
Aluminium is increasingly taking over from copper as the preferred metal for tubing in heat exchangers and air conditioners. There is no end to what shapes aluminium can take.
Emissions from the extrusion process
After extrusion, the sections are cooled and hardened, and then surface treated if required. Surface treatment can cause emissions. The electrolytic baths, where extrusions are given an extra protective coating, contain aluminium compounds. Effluents from the baths can be minimized by selecting the right type of coating and cleaning the emissions and discharges to air and water.
Aluminium can be processed in a cold and hot condition.
Aluminium is ductile. It can be rolled from 60 cm to 2-6 mm. Final foil products can be as thin as 0.006 mm and still be completely impermeable to light, aroma or taste.
The metal itself forms a protective oxide coating and is highly corrosion resistant. Various types of surface treatment can further improve these properties.
Emissions from the rolling process
The oil that is added during various rolling processes to ensure a good surface finish and to control temperatures gives rise to traces of oil in air emissions.
When coating rolled strip, solvents from the coatings are liberated in the drying furnace. Research and development programs have been initiated to reduce the amount of solvents in coatings and use of coatings with less environmental impact.
The properties of aluminium change when small quantities of other metals are added to produce aluminium alloys.
These can give greater strength, brilliance and ductility, all depending on what the metal is to be used for. And they can make aluminium easier to form into an endless variety of products.
The most common alloy materials added to aluminium are copper, magnesium and silicon. To increase quality, the grain refining substances strontium, sodium, or titanium/titanium boride, are added in small quantities.
The four main casting methods are:
- Sand casting
- Low pressure die casting
- Permanent mould casting
- High pressure die casting
The raw cast product generally requires machine finishing and is often coated.
Emissions from casting
Generally, melting and casting in permanent molds does not have negative effects on the environment. When sand casting and organic compounds are used, it is necessary to clean emissions and ensure that limits on emissions to air and water are not exceeded. When coating is involved, the emissions are the same as for rolled products.