Copper Plate 0.5-200mm Copper Plate C1100 C10100 Chromium Zirconium Copper Plate

Copper Plate 0.5-200mm Copper Plate C1100 C10100 Chromium Zirconium Copper Plate

Electrolytic Tough Pitch (ETP) copper is the most widely used grade of copper in electrical applications all over the world and represents over half of global copper use. It is extensively used in electric power systems, electrical installations in homes, offices and industry and all kinds of electrical and electronic equipment.

ETP1 is the highest purity tough pitch copper with a maximum impurity content of 0.0065% (compared to ETP with a maximum of 0.0355). The very high purity means that ETP1 is used for the most demanding electrical applications such as the transmission of power and signals.

Cu-ETP1 and Cu-ETP are made from the highest purity copper cathodes Cu-CATH1 (CR001A) and Cu-CATH2 (CR002A), designated in EN1978:1998.

History

The term ‘tough pitch’ originates from the time when molten copper, after refining, was cast into ingot moulds. During refining the copper was oxidised to remove impurities then reduced by hydrogen to give the correct oxygen level. To monitor this process, a small sample was taken and the solidification surface observed. If the surface sunk there was too much oxygen; if it was raised there was too much hydrogen. If it was level (correct pitch), the oxygen was correct, and the properties good; in other words ‘tough’, hence tough pitch.

A level of 0.02% to 0.04% oxygen is maintained in ETP copper to oxidise the remaining impurities to oxides which would otherwise dissolve in the copper forming solid solutions thereby reducing conductivity. Oxides have little effect on conductivity.

Heat Treatment

It may be necessary to stress relieve ETP copper to reduce the possibility of distortion or cracking after machining or cold working. This may be done at 150 to 200oC but does not soften the copper. If this is required then a full anneal at 400 to 650oC is needed. Copper cannot be hardened by heat treatment and it does not become harder with time. It does not have a ‘shelf life’.

Properties

A summary of the properties from the annealed (soft) to the hard condition is shown.

• Tensile strength: 220-385 N/mm2
• Proof strength: 60-325 N/mm2
• % Elongation: 55-4
• Hardness (HV): 45-155
• Electrical conductivity: 100-101.5% IACS
• Thermal conductivity: 394 W/moC

Fabrication

This copper will suffer from steam (hydrogen) embrittlement when heated in a hydrogen (reducing) atmosphere.

Machining

While ETP copper like other pure coppers cannot be regarded as a free-machining material, it is not difficult to machine, especially in the work-hardened condition. The machinability rating is 20% (free-machining brass is 100%).

Resistance to Corrosion

All coppers corrode at negligible rates in unpolluted air and water due to the formation of a protective oxide surface layer. Copper artefacts have been found in nearly pristine condition after being in the earth and under the sea for thousands of years. However, copper is susceptible to more rapid attack in the presence of ammonia, sulphur, hydrogen sulphide and mercury. All coppers are virtually immune to stress corrosion cracking.

Resistance to Softening

Softening is time and temperature dependent and it is difficult to estimate precisely the time at which it starts and finishes. It is usual, therefore, to consider the time to ‘half-softening’, i.e. the time taken for the hardness to fall by 50% of the original increase in hardness caused by cold reduction. In the case of ETP copper, this softening occurs at temperatures above 150oC. It has been established experimentally that such copper would operate successfully at a temperature of 105oC for periods of 20-25 years, and that it could withstand short-circuit conditions as high as 250oC for a few seconds without any adverse effect.

Creep

Creep is slow deformation of a material with time at temperature and must be allowed for in the design of any component above room temperature.

ETP copper does not creep at room temperature (unlike high conductivity aluminium) under normal stresses. However, creep must be considered in the temperature range above 150oC though this temperature is well above the usual operating temperature of busbars.

Applications

Due to the combination of high conductivity, good corrosion resistance, workability and aesthetics, ETP copper is widely used for:

• Busbars
• Motor windings and components
• Transformer windings and components

ETP1, with its higher purity, is used for:

• Automotive cables
• Signal cable braid shielding

Available Forms

ETP copper is available in bar, plate, sheet, strip, tube and wire.

Specifications

• UK: C100 (ETP1) C101 (ETP) (British Standard BS designation). UK Standards are superseded by European Standards.
• Europe: CW004A (ETP) CW003A (ETP1) (European Standard EN designation).
• USA: C11000 (ETP) C11040 (ETP1) (American Society for Testing and Materials ASTM designation).
• Japan: C1100 (ETP) (Japanese Industrial Standards JIS designation).