Brass is the generic term for a range of copper-zinc alloys with differing combinations of properties, including strength, machinability, ductility, wear-resistance, hardness, colour, antimicrobial, electrical and thermal conductivity, and corrosion resistance.
Brasses set the standard by which the machinability of other materials is judged and are also available in a very wide variety of product forms and sizes to allow minimum machining to finished dimensions. Brass does not become brittle at low temperatures like mild steel.
Brass also has excellent thermal conductivity, making it a first choice for heat exchangers (radiators). Its electrical conductivity ranges from 23 to 44% that of pure copper.
These silver coloured copper-nickel-zinc alloys containing 10-20% nickel can be regarded as special brasses. In most respects they show similar corrosion characteristics to the brasses, but the higher nickel versions have superior tarnish resistance and resistance to stress corrosion cracking. They are available in all forms and are used for tableware (silver-plated to give EPNS), telecommunication components, food manufacturing equipment, jewellery, model making, tool brush anchor wire and pins, musical instruments, e.g. ‘silver bands’, flutes, test probes and contact springs. Read more.
Colours of Brass
Brasses have a range of attractive colours,red, yellow, gold, brown, bronze, silver. Brass with 1% manganese will weather to a chocolate brown colour. Nickel-silvers will polish to a brilliant silver colour. Brasses are easy to shape and, with all these colours available, it is not surprising that architects and designers have used brasses to enhance the appearance of new and refurbished buildings, both inside and out.
Brass and Hygiene
Copper and brass are playing a leading role in the fight against hospital-acquired infections such as MRSA and Clostridium difficile. It has been shown that these pathogens, which can be spread by touch, will die in a few hours on copper/brass surfaces. This does not happen on stainless steel or plastic.
The brass industry throughout the world is well organised and equipped to recycle products at the end of their long lives and process scrap (swarf and offcuts). Making brass from new (virgin) copper and zinc would be uneconomical and wasteful of raw materials so new brass products are made from recycled scrap, illustrating the sustainable nature of this material. In the UK brass manufacturers use almost 100% brass scrap.
After machining clean the components with hot detergent, rinse thoroughly in cold water then immerse in a tarnish inhibitor (a mixture of monoethylene glycol and benzotriazole) then dry in air.
A recent study found that the highly toxic E.coli 0157:H7 strain of bacteria survive for much shorter periods of time on copper and brass surfaces than stainless steel. This has wide-ranging implications for reducing outbreaks from cross contamination of E.coli in the food processing industry.
Use a corrosion resistant leaded naval brass, CW712R (CZ112).
Machining data for copper casting alloys are similar to those of their wrought counterparts. The most easily machinable are classified as Group 1 and include CC491K (LG2) with a rating of 90% (this rating is based on a 100% value for free machining brass CZ121,CW609N). The more difficult alloys to machine are classified as Group 3 and include the aluminium bronzes such as CC333G (AB2) with a rating of 20%. For further details see CDA publication 44 Machining Brass, Copper and its Alloys.
The brass selected is free machining with good ductility and is an excellent choice for this application. I suggest that the component is annealed in the range 400 to 600oC to give maximum ductility to ensure that the crimping will be successful. There is no need for tin plating; in this environment the brass will darken with time with no loss of properties.
It is important that the lead content (1.6 to 2.5%) of this brass is maintained at the specification level in all of the connectors since higher lead levels may lead to cracking on crimping. With this in mind I suggest that the source of the brass is from the UK or Europe where full certification will be available.
Brasses will slowly tarnish in the atmosphere; outdoors the process is more rapid due to the effect of moisture, salt (in marine environments) and pollutants such as sulphur dioxide (acid rain) in industrial areas. The tarnishing can be greatly delayed and the range of colours, which give copper alloys their aesthetic appeal, maintained by either lacquering or waxing (or both).
Lacquering: one of the most effective lacquers is Incralac. Lacquers must be applied in dry, factory conditions and are not suitable for protecting components which are handled by the public, such as handrails, since acid levels of moisture in the skin (pH 5.5) damage the lacquer.
Waxes: copper alloys may be more cheaply protected by waxing. It is important to use natural non-reactive waxes such as Carnauba or Beeswax, not synthetic waxes which will eventually granulate and absorb water. Natural waxes are not affected by UV light.
You require a high tensile brass with good machinability. Use CW721R (CZ114).
Yes, brass swarf is very valuable and should be recycled. The brass industry relies on recycling for its survival; they will be able to clean the oil from the swarf before remelting it.
This publication provides information on compositions and properties of standard brasses in wrought and cast condition, together with details of BS and European Standards, forms available, fabrication methods and examples of typical applications.
Publication 120 summarises the main compositions and the range of properties for the most commonly specified copper and copper alloys.
A collection of data sheets summarising physical and mechanical properties of the brasses – nickel brass and nickel silver– at low, ambient and elevated temperatures which is not available elsewhere.
For equivalents of copper alloys worldwide, their chemical compositions, material designation and national standards