Choosing the right metal alloys for casting work is vital. As we have discussed previously in this blog, aluminium alloys are used in most of our metal casting. However, copper alloys also have their place.
In this blog, we look in detail at the use of copper and explore its unique mechanical and physical properties. We also examine the reasons why this metal is sometimes used as an alternative to aluminium.
The history of copper
Copper is a soft, malleable and ductile material that is orange-red in colour. It is one of the few metals found in nature in its pure form.
Copper was known to some of the earliest civilisations on the planet and it has been in use for an estimated 11,000 years. A copper pendant found in Iraq can be dated to 8700 BC. For nearly 5,000 years, copper was the only known metal and it was used to make utensils, tools, weapons and ornaments in prehistoric times.
The Earth’s crust contains vast quantities of copper. However, only a small percentage of the total amount can be extracted cost effectively.
Copper is known for its strength and excellent electrical/thermal conductivity. In fact, copper has the best electrical conductivity of any metal, except silver. It is widely used in wiring – both in the residential and industrial sector.
Copper does not usually corrode – which explains its use in pipes, electrical cables, saucepans and radiators. For this reason, the metal is often used in jewellery (rings) and other decorative items. With these unique properties, it comes as no surprise that copper is the third most produced metal in the world after iron (steel) and aluminium.
The unique properties of copper
The raw metal is often mixed with other materials to produce alloys, such as brass (copper and zinc), bronze (usually copper, tin and other metals) and cupronickel (copper and nickel). This enhances the mechanical and physical properties. Cast copper alloys are used in many components for the transport sector – such as bearings, bushings and gears.
Copper is stronger than aluminium so it is the ideal choice of material where high tensile strength is a key requirement. For example, one customer uses our castings in lifting equipment.
However, copper is also heavier and more expensive than aluminium so the choice of metal is dependent on our customers’ needs and budget.
The casting process
The sand casting process works in a similar way for both copper and aluminium alloys. However, there are a few important differences.
Firstly, our foundry engineers use an induction furnace rather than a combination gas/electric oven to cast copper alloys. This is because copper has a higher melting temperature.
Secondly, the sand can be coated with a special material due to the high temperatures involved when casting certain copper alloys. The special coating on the sand prevents the heat of the metal burning into the mould. This ensures a good finish on the casting.
In the next few blogs, we will be looking in more detail at the individual copper alloys used in our metal casting work.