Brass is the name used to describe a copper alloy, which has a certain zinc content. Copper is one of the metals that were first able to be worked by humans, as it melts at a temperature of around 1,080°C and is very easy to work due to its low hardness. Zinc has an even lower melting point (420°C) and is able to form mixed crystals with copper. By combining copper with zinc, an alloy is formed, which is harder than copper, but still has very good working properties.
Humans have been using brass for around 5,000 years. This materials therefore one of the oldest alloys there is. The only exception is bronze, which has been used for more than 6,000 years. Bronze is also a copper alloy; however, it contains the heavy metal tin instead of zinc. It was always a popular material as this alloy produces very attractive colour nuances if the zinc fraction is varied.
At this point it is noted that it is not possible to estimate the zinc fraction by interpreting the colour, as modern brass alloys contain other alloying elements, which on the one hand affect its hardness and corrosion resistance, but on the other hand also affect its colour. Aluminium, iron, manganese, nickel and silicon are most frequently added as alloys, as that brass can be adapted to the present day needs of industry.
Properties of brass
Despite its high copper content, it is not harmful. Quite the opposite, copper-zinc alloys have a bactericidal effect and prevent the colonisation of bacteria. For this reason, brass door handles are useful fittings, for example, in public buildings and in public transport.
Unlike steel alloys, brass cannot be hardened by heating. Brass can only be strain or work-hardened. The hardening occurs when the material is worked mechanically, e.g. by cold working. The action of force does not harden brass. Modern alloys contain virtually no air or slag and for this reason cannot be hardened. The hardness is produced instead by straining (stretching) the metal microstructure. The stresses produced during working affect the hardness of the material.
If cold-worked brass is heated to 450 – 600°C, the hardening achieved can be removed again, depending on its composition. At this temperature, the crystals in the metal microstructure can rearrange. If the heating remains within a range of 300 – 450°, depending on the temperature, different degrees of hardness can be achieved. If the alloy is heated to 250 – 300° it can be relaxed to such an extent that at least no more stress corrosion cracking can occur.
If special hardness or machinability requirements are set for a copper-zinc alloy in Saxony, a suitable alloy composition should be chosen, because of the material properties named above. If lead is added to the alloy, the properties for machining improve increasingly. Aluminium on the other hand reduces susceptibility to corrosion and increases the strength of brass.
Machining at Rime
Brass can only be cut using Co2 laser cutting machines to a very limited extent, as the material is far too reflective. However, cutting is possible with solid-state lasers. At Rime we cut this material purely mechanically using our metal guillotine. Further working by milling, punching, roll bending and bending is also no problem at all. In this way, diverse products can be produced by Rime.