Bronze is an alloy composed of copper (the base alloy) and tin (which makes up 3 to 20%). It can also include other metals, achieving different properties in the material. The differences between copper and bronze, although seemingly very similar, are significant and it is necessary to be able to distinguish between the two.
Current applications include its use in mechanical parts resistant to friction and corrosion, in good quality musical instruments such as bells, gongs, cymbals, saxophones, and in the manufacture of harp strings, guitars and pianos.
Characteristics of bronze
- It has a matt golden colour, although it varies according to the metals.
- It has a density of 8.90 g/cm3 and its melting point is between 830°C and 1020°C.
- It is a good conductor of electricity.
- As it accumulates less heat than other metals, it is used in the manufacture of industrial products.
- It has a lower rigidity, making it an easy material to handle.
- Bronze extends the life of products made from it, as it is resistant to corrosion.
- It is a safe material in the presence of materials that can ignite, as it does not generate sparks when it strikes a rigid surface.
Types of bronze alloys
The composition of bronze can vary according to the metals used, creating various types of alloys. The most common are as follows:
- Basic bronze: Copper 89% + Tin 11%. There is also the so-called alpha bronze alloy which is a solid mixture of copper + 4-5% tin.
- Sol bronze: Copper + up to 60% cobalt. Used in jewellery.
- Cuproaluminium or aluminium bronze: Copper + up to 11% Aluminium.
- Bell bronze: Copper 78% + Tin 22%.
- Kane-Kane: Copper 60% + Tin 24% + Zinc 9% + Iron/Lead + may add a small amount of antimony or arsenic. It is a traditional bronze in Japan.
- Arsenical bronze: Copper 70% + Arsenic 30%. It is the first bronze used by humans.
Bronze recycling
It is an alloy composed of copper and tin, two metals that are extracted from the earth's crust through mining. It is therefore very important to recycle this metal, as it is a non-renewable resource. In addition, this extraction involves a high consumption of water and energy, which contributes to the pollution of rivers. Recycling helps to reduce the extraction of its components as much as possible in order to ensure that reserves are available for the future. On the other hand, copper is a harmful metal as it contains toxins.
Like all other metals, it is melted down and then the pure bronze is separated so that it can be reused. By melting copper and tin ingot, a bronze ingot is produced, which can also be melted and cast into moulds. In the furnace, the piece is melted and then analysed. If the required properties are not what you need, you can add the necessary amount of metal to obtain what you want.
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