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Copper in the USA: Bright Future Glorious Past
The four classes of copper fabricators together account for about 97% of the total copper (including alloying metal) consumed each year in the United States. Other industries, such as steel, aluminum, and chemical, consume the remaining 3%.
The wire rod mills’ share of metal consumed has grown sharply over the last 20 years, to about 49% today, while brass mills have dropped to 40%. Foundries account for about 7% of fabricated products, and powder plants use only about 1% of the US supply of copper.
Copper wire mill products are destined for use as electrical conductors. Starting with wire rod, these mills cold draw the wire (with necessary anneals) to final dimensions through a series of dies. The individual wires may be stranded and normally are insulated before being gathered into cable assemblies.
Brass mills melt and alloy feedstock to make strip, sheet, plate, tube, rod, bar, mechanical wire, forgings, and extrusions. Somewhat less than half the copper input is refined and the rest is scrap. Fabricating processes, such as hot rolling, cold rolling, extrusion, and drawing are employed to convert the melted and cast feedstock into mill products.
About 45% of the output of US brass mills is unalloyed copper and high-copper alloys, chiefly in such forms as plumbing and air conditioning tube, busbar and other heavy-gage, flat products for electrical use, strip for auto radiator and other heat-exchanger fins, and roofing sheet. Copper alloys comprise the remaining 55%. Free-cutting brass rod, which exhibits outstanding machinability and good corrosion resistance, and brass strip, which has high strength, corrosion resistance, excellent formability, and good electrical properties, together constitute about 80% of the total tonnage of copper alloys shipped from US brass mills. Other alloy types of major commercial significance include copper-nickels, which are strong and particularly resistant to seawater and used for coinage; tin bronzes (phosphor bronzes), which are noted for their excellent cold forming behavior and strength; tin brasses, known for outstanding corrosion resistance; nickel silvers, which combine a silvery appearance with good formability and corrosion resistance; beryllium coppers, which provide outstanding strength when hardened; and aluminum bronzes, which have high strength along with good resistance to oxidation, chemical attack, and mechanical abrasion.
Foundries use pre-alloyed ingot, scrap, and virgin metal as raw materials. Their chief products are shaped castings for many different industrial and consumer goods, the most important of which are plumbing products and industrial valves. Centrifugal and continuous cast copper alloy products find major application as bearings, cylinders, and other symmetrical components.
Powder plants produce powder and flake for further fabrication into powder metallurgy parts, chiefly small sintered 4 bronze bushings, and other uses.