- By Matthew
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Copper and Copper Alloys
Pure copper is very ductile, which means it has a high elongation. Pure copper can be annealed at 12,000 to 15,000 PSI yield strength, and when reduced or cold worked substantially, can go to 45,000 PSI yield strength. Copper at elevated temperatures can be 6,000 to 15,000 PSI yield strength. Pure copper can be made into slab and further reduced into copper plate or hot rolled coils. Copper can also be continuous cast and usually milled (to remove the imperfect surface) and cold reduced all in line. It can be made into light gauge coils, sheet, rod, and wire.
Copper can also be extruded. A lot of air conditioning and refrigeration tubing is extruded into large diameter tubes and further reduced into small diameter tubes, ¼” or less. Pure copper is difficult to weld because it takes the heat away from the weld quickly. Some copper is made round, but is rolled into a flat shape. Copper is rolled into a flat wire for electric motors and transformers. This allows more windings on a transformer motor without increasing the diameter or size. Copper has good corrosion characteristics under certain acids and alkalis. One of the most important aspects of copper is that it has a high electrical conductivity. Certain copper alloys have high fatigue characteristics. Beryllium copper, as an example, is used to make ignition points and springs where continuous bending is necessary.
Another important characteristic of copper is that it has a very good heat transfer. That is why it is very common in condensers and heat exchangers as used in air conditioners and refrigerators. When copper is made into a tube, sometimes it has internal spiral grooves which doubles the surface area inside the tube and allows for better turbulence. This improves the heat exchanger affect for air conditioning and refrigeration and reduces the cost of the product.
The number one use for copper is copper wire. There are various copper alloys used for many other different products. Copper aluminum alloys have a special advantage in phosphoric acid, which is a very difficult acid to contain. As an example, copper alloys are used for making beer and sulfuric acid. It is also used in transporting sea water. One of the great uses for copper alloys is bearing applications. Copper nickel alloys have advantages in high load bearing material. Copper nickel magnesium alloys are used in radio resistors. In rolling mill applications, much of the copper is continuous cast and reduced on a rolling mill. Many square and rectangular bus bars are made from copper because of the high electrical conductivity used to transport high amps or continuous power throughout a building. All of these products are rolled on a rolling mill. This may be a tandem rolling mill where each rolling mill runs a little faster depending upon the reduction from one rolling mill to another.
Another use for copper, because of its heat transfer characteristics, is continuous casting of steel. By water cooling the copper mold, high temperature steel can be poured through a mold on a continuous cast basis and made into a slab or ingot. Also, copper foil is used in electronics and is sometime cladded to plastic for printed circuits. There are many copper rolling mill applications.