Brass is an alloy composed of copper and zinc. Different varieties of this metal can be created depending on the proportion of its composition, as well as different properties. Brass is produced when copper is fused with calamine, a zinc ore. In the melting process, the zinc is extracted from the calamine and mixed with the copper. Other materials may also be added. It has a colour similar to gold.
Properties of brass
- It has a density of between 8.4 and 8.7gr /cm3 and melts at between 900 and 940 °C.
- The composition of brass influences its mechanical properties, which is why industrial brasses must contain less than 50% zinc.
- Brass is very resistant to oxidation and corrosion even in high salinity conditions, which is why it is used for shipbuilding.
- It does not produce sparks on mechanical impact.
- It is a wear resistant metal and is also a good conductor of electricity.
- It is easy to deform plastically without breaking (ductility) and is also machinable in both hot and cold conditions.
- It can be exposed to extreme temperatures or light without altering the material.
Types of brass
Depending on the percentage of zinc it contains, there are three main groups of brass:
- First titre: zinc 34%.
- Second grade: zinc between 33%-44%.
- Third grade: more than 42%. Not recommended for industrial use.
As far as ordinary brass is concerned, three groups can be distinguished:
- Red brasses (between 10%-20% Zinc): One of these brasses is the one used in jewellery as it resembles gold.
- Yellow brasses (between 25%-35% Zinc): these are brasses for springs, cartridges, ammunition...
- Alpha + beta brass (between 36%-42% Zinc): it is less ductile than the two previous ones and is not cold rolled, but hot worked.
Special brasses are those to which another type of material is also added, the most common are the following:
- Aluminium brass.
- Iron brass: better hardness and tensile strength.
- Lead brass: mechanical strength and machinability.
- Manganese brass: has higher tensile strength and is less ductile.
- Tin-plated brass: it is more resistant to traction and corrosion. The best known alloys are admiralty metal and naval brass (zinc 40%).
- Silicon brass: e.g. bronsil is very resistant to corrosion.
- Complex brass: highly resistant to corrosion and cavitation.
The manufacture of primary brass has a high economic value as it is an alloy of copper and zinc. Moreover, if it could be recycled, it would be an unnecessary waste of raw materials. Brass manufacturers use scrap brass to manufacture their products. The recycling of this material is simple as it does not need the electro-refining process like other materials. To obtain recycled brass with the same properties as the original, you only need to melt the brass scrap as long as it is clean of other waste.
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