Resource Library

What values of electrical conductivity can be obtained in high purity copper castings? Are they comparable to the values available for wrought alloys?

Generally the values of International Annealed Copper Standard for conductivity (IACS) values are lower than those of the wrought alloys due to the presence of a small % of gas porosity and a small % of impurities such as iron. A value of 93% IACS is guaranteed but with a very low porosity % and very pure copper, values up to 102% IACS may be obtained. Reputable foundries carry out careful conductivity checks on the copper raw material used for casting, such as offcuts of busbars or cathode copper, to ensure that as high a conductivity as possible is obtained.

What alternatives are there to the leaded free-machining brasses such as CW614N (CZ121)?

Brasses have been developed where the lead is replaced by silicon. These are marketed under names such as Envirobrass and Eco Brass. They are slightly more expensive than the leaded brasses and not quite as machinable, but have excellent mechanical properties.

I am producing electrical connectors with a requirement for good springyness and fatigue resistance. I am also concerned about the effects of corrosion. What should I use?

A good choice would be tin-plated (2-6 microns) phosphor bronze strip, (CW 450K) CuSn4.

What are the benefits of flame-free jointing techniques?

Copper flame-free jointing can be done by press fittings and push-fit fittings. The benefits of these types of fittings are:

  • Work can be undertaken with occupants in the building
  • No flux fumes
  • No additional ventilation required
  • No need for hot work permits/certificates
  • Quick to install
I am trying to identify the brass Hpb59-1. It is proposed to use this brass in the cast condition for valves used in fire protection systems in buildings.

This is a Chinese Specification composition 57-60 copper, 0.8-1.9% lead, balance zinc. It is a leaded Muntz Metal. A more suitable alloy for this application would be the gunmetal LG2 (CC491K) 85%copper, 5% tin, 5% zinc, 5% lead. It has better corrosion resistance and is easily cast.

When a car is scrapped, can the copper be recovered?

Yes, copper is easily separated from other materials such as steel and plastic.  It is recovered, remelted and reused.

I am using a leaded gunmetal casting which is machined and then crimped onto a copper pipe. I have had a number of failures due to leakage. Can you explain this?

Leaded Gunmetal is a cast alloy which is not designed to be cold worked. Crimping involves extreme deformation which will not usually be tolerated by the gunmetal without cracking. However, castings do not have a uniform structure and in the areas free from lead and possibly a smaller grain size some ductility is present. This will account for some of the castings surviving the crimping without cracking.

When a sprinkler system operates, do all of the sprinkler heads open?

No, only the sprinkler heads that are affected by the heat of the fire.

What are the benefits of using cast copper rotors in high efficiency motors?

Induction motor rotors were traditionally made by die casting aluminium around a stack of steel laminations, so forming the rotor bars and end rings. Copper has much better conductivity, which would result in better efficiency, but was not used because it was difficult to die-cast due to its higher melting point.  The casting issues have now been solved by improvements in die materials and process control.

Using copper offers a range of options to the motor designer.  If the rotor size is unchanged, efficiency can be improved. On the other hand, the rotor size can be reduced while maintaining the original efficiency, so reducing the cost.

I am using CW614N (CZ121) to make machined components for a major motor manufacturer. The process results in about 3 tonnes per week of brass swarf which is contaminated with machining oil. Could this still be recycled?

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.

I understand that welding may have an effect on the corrosion resistance of the nickel aluminium bronzes. If so what treatment may be carried out to reduce this effect?

Yes, the heating effect of welding has the effect of producing a phase change in the alloy which on cooling leads to the formation of the corrodable martensitic beta phase. Annealing at 675oC for 2 to 6 hours after welding restores the pre weld structure and relieves stress. It is very effective in resisting subsequent corrosion.

What finishes are available for copper?

Bright copper, pre-oxidised copper, pre-patinated copper or post-patinated copper.