Copper-clad steel (CCS), also known as copper-covered steel or the trademarked name Copperweld is a bi-metallic product, mainly used in the wire industry that combines the high mechanical resistance of steel with the conductivity and resistance to corrosion of copper.
The first recorded attempt to make copper clad steel wire took place in the early 1860s, according to the Copper Clad Handbook, issued by the Duplex Metals Co., Chester, PA at the turn of the 20th century. Although for over 100 years people had been suggesting various ways of uniting copper and steel, it was not until the period mentioned that Farmer and Milliken tried wrapping a strip of copper about a steel wire. American engineers in 1883 and again in the 1890s made attempts to produce a copper-steel wire, in one instance at least, by electro-plating copper on steel.
The Duplex Metals Co. traces its beginning to John Ferreol Monnot between 1900 and 1905. He had been very much interested in the work of Mr. Martin in Paris, and, as the Handbook says: "After several years devoted to experimenting, organized the Duplex Metals Company. Prior to his discovery of the process under which this company operates in producing its copper clad, probably almost every other possible way of welding copper and steel together had been tried by Mr. Monnot, but found useless for the purpose."
The main properties of these conductors include:
- Good corrosion resistance of copper
- High tensile strength of steel
- Resistance against material fatigue
Since the outer conductor layer is low-impedance copper, and the center is higher impedance steel, the skin effect gives copper-clad RF transmission lines impedance at high AC frequencies similar to that of a solid copper conductor.
Tensile strength of copper-clad steel conductors is greater than that of ordinary copper conductors permitting greater span lengths than with copper.
Another advantage is that smaller diameter copper-clad steel conductors may be used in coaxial cables, permitting higher impedance and smaller cable diameter than with copper conductors of similar strength.
Due to the inseparable union of the two metals, it deters theft since copper recovery is impractical and thus has very little scrap value.
Installations with copper-clad steel conductors are generally recognized as fulfilling the required specifications for a good ground. For this reason it is used with preference by utilities and oil companies when cost is a concern.
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