Copper is a reddish metal, that is very ductile and malleable, and has high electrical and heat conductivity. It is used as a major element in hundreds of alloys. Commercially pure copper is not suitable for welding. Though it is very soft, it is very difficult to machine due to its high ductility. Beryllium copper contains from 1.50 to 2.75 percent beryllium. It is ductile when soft, but loses ductility and gains tensile strength when hardened. Nickel copper contains either 10, 20, or 30 percent nickel. Nickel alloys have moderately high to high tensile strength, which increases with the nickel content. They are moderately hard, quite tough, and ductile. They are very resistant to the erosive and corrosive effects of high velocity sea water, stress corrosion, and corrosion fatigue. Nickel is added to copper zinc alloys (brasses) to lighten their color; the resultant alloys are called nickel silver. These alloys are of two general types, one type containing 65 percent or more copper and nickel combined, the other containing 55 to 60 percent copper and nickel combined. The first type can be cold worked by such operations as deep drawing, stamping, and spinning. The second type is much harder end is not processed by any of the cold working methods. Gas welding is the preferred process for joining copper and copper alloys
Uses. The principal use of commercially pure copper is in the electrical industry where it is made into wire or other such conductors. It is also used in the manufacture of nonferrous alloys such as brass, bronze, and Monel metal. Typical copper products are sheet roofing, cartridge cases, bushings, wire, bearings, and statues.
Capababilities. Copper can be forged, cast, and cold worked. It can also be welded, but its machinability is only fair. Copper alloys can be welded.
Limitations. Electrolytic tough pitch copper cannot be welded satisfactorily. Pure copper is not suitable for welding and is difficult to machine due to its ductility.
Properties. Pure copper is nonmagnetic; has a Brinell hardness number of 60 to 110; a tensile strength of 32,000 to 60,000 psi (220,640 to 413,700 kPa); specific gravity of 8.9; melting point of 1980°F (1082°C); and is corrosion resistant. Copper alloys have a tensile strength of 50,000 to 90,000 psi (344,750 to 620,550 kPa) and a Brinell hardness number of 100 to 185.
Appearance test. Copper is red in color when polished, and oxidizes to various shades of green.
Fracture test. Copper presents a smooth surface when fractured, which is free from crystalline appearance.
Spark test. Copper gives off no sparks.
Torch test. Because copper conducts heat rapidly, a larger flame is required to produce fusion of copper than is needed for the same size piece of steel. Copper melts suddenly and solidifies instantly. Copper alloy, containing small amounts of other metals, melts more easily and solidifies more slowly than pure copper.
Brass and bronze.
Brass, an alloy of copper and zinc (60 to 68 percent copper and 32 to 40 percent zinc), has a low melting point and high heat conductivity. There are several types of brass, such as naval, red, admiralty, yellow, and commercial. All differ in copper and zinc content; may be alloyed with other elements such as lead, tin, manganese, or iron; have good machinability; and can be welded. Bronze is an alloy of copper and tin and may contain lead, zinc, nickel, manganese, or phosphorus. It has high strength, is rust or corrosion resistant, has good machinability, and can be welded.
Appearance test. The color of polished brass and bronze varies with the composition from red, almost like copper, to yellow brass. They oxidize to various shades of green, brown, or yellow.
Fracture test. The surface of fractured brass or bronze ranges from smooth to crystalline, depending upon composition and method of preparation; i. e., cast, rolled, or forged.
Spark test. Brass and bronze give off no sparks.
Torch test. Brass contains zinc, which gives off white fumes when it is melted. Bronze contains tin. Even a slight amount of tin makes the alloy flow very freely, like water. Due to the small amount of zinc or tin that is usually present, bronze may fume slightly, but never as much as brass.
Appearance test. When polished, aluminum bronze appears a darker yellow than brass.
Fracture test. Aluminum bronze presents a smooth surface when fractured .
Spark test. Aluminum bronze gives off no sparks.
Torch test. Welding aluminum bronze is very difficult. The surface is quickly covered with a heavy scum that tends to mix with the metal and is difficult to remove.
Subscribe via RSS