Copper strip and wire may be produced with a combination of high elastic limit and good corrosion resistance, making them an ideal choice for springs. The main groups of alloys are:
- Phosphor bronze, typically CW451K (PB102) with a yield strength of about 500N/mm2.
- Nickel silver, typically CW409J (NS106). This is silver coloured and has excellent tarnish resistance.
- Copper beryllium CW100C (CB101). This alloy is used where very high yield strength is required (greater than 1000N/mm2). These alloys are expensive and phosphor bronze will be adequate for most engineering applications.
A useful Specification is BS EN 1654:1998 (Copper and copper alloys. Strip for springs and connectors).
The French scientist Millardet – while seeking a cure for downy mildew-diseased vines in the Bordeaux district of France – chanced to notice that those vines bordering the highways, which had been daubed with a paste of copper sulphate and lime in water in order to make the grapes unattractive to passers-by, appeared freer of downy mildew. This chance observation led to experiments with mixtures of copper sulphate, lime and water, and in 1885 Millardet announced to the world that he had found a cure for the dreaded mildew. This became known as Bordeaux mixture and saw the commencement of protective crop spraying.
Copper and copper-nickel tubes are used for vehicle brake pipes due to their good fatigue and corrosion resistance (especially against salt on the roads), where fluid loss could be disastrous. Because of their ductility, they are easy to fit; they are standard equipment for many cars, fire engines, military vehicles, JCBs and other heavy vehicles.
The same or better performance can be achieved with less tube and fin material. In other words, more heat can be dissipated with less material. Less tube, more heat! Technically speaking, a coil made with smaller diameter tubes can be designed with a higher ‘heat transfer coefficient’ compared to a coil made with larger diameter tubes.
The following brasses have sufficient strength, machinability and electrical conductivity:
CW508L (CZ108), CW509L (CZ109) and CW614N (CZ121).
Since ancient times copper has been used in coins; the Romans used copper widely in this application. The reasons for using copper are its excellent corrosion resistance, ease of stamping, good electrical conductivity for vending machines and ease of recycling.
Because the thermal conductivity is so high – it is 23 times better than stainless steel or titanium and 1.6 times better than aluminum.
Condenser coils with round copper tubes and aluminium fins have been a winning combination for ACR coils for many years. Manufacturers enjoy the assembly advantages provided by these components while technicians find it easy to join and repair copper tubing in the field. More importantly, this well established technology has a proven record of durability in the field resulting in a high level of customer satisfaction.
Smaller diameter tubes allow for more effective heat transfer.
1 degree, using batten rolls.