Wire is a long, thin, flexible metal rod that has a uniform cross section. Only ductile metals, or metals that can be easily drawn out, can be used for making wire. The chief ductile metals are copper, steel, brass, tungsten, gold, silver, and aluminum.
How wire is made.
Early people made wire by hammering metal into plates. They then cut these plates into strips and used hammers and files to round the strips. Ancient civilizations typically used wire for jewelry. In Pompeii, an ancient city of Italy, bronze wire rope was used at least as early as A.D. 79. By about A.D. 1000, wire was made by drawing metal through a tapered hole in a form called a die. Machine-drawn wire was first made in Germany in the mid-1300’s. Today, all wire is machine-made. The rest of this section discusses the production of steel wire.
The first step in making wire involves heating iron or steel billets, 2-inch (5-centimeter) square blocks of metal, and then running them through rollers that press them into thinner, longer shapes. They come out as long rods about 1/4 inch (6 millimeters) in diameter. The rods are cast into coils and cleansed with acid and water.
Pulling the rods through one or more tungsten carbide dies draws them out to form wire. A die has a funnel-like shape with a round opening smaller than the rod. The rod, which is pointed at one end by hammering, may be run into the die as thread runs through the eye of a needle. When the pointed end passes through the die, a pair of pincers, which are operated mechanically or by hand, seize it and draw it far enough to be attached to an upright drum. The drum rotates, pulling the wire through the die. The wire winds on the drum. Fine wire is drawn through a series of dies of continuously decreasing diameters. Drawn wire tends to harden, and so it is softened between drawing steps using a heat treatment called patenting. Most wire is round. However, wire may be drawn through specially shaped dies to make it square, oval, flat, or triangular.
Sizes of wire.
Round wire is measured according to its diameter, often expressed as a gauge. American Wire Gauge, or Brown and Sharpe, is the standard gauge used in the United States and Canada for copper and other nonferrous (containing no iron) wire. With this gauge, the higher the gauge number, the thinner the wire. The gauge commonly used in the United Kingdom is the imperial standard gauge. France and Germany use gauges based on the millimeter. Steel Wire Gauge, or Washburn and Moen, is the U.S. standard for steel wire.
Uses of wire.
Manufacturers make telephone and electric-power wires of copper and aluminum, which are highly ductile as well as good conductors of electric current. Platinum wire serves as electrodes (electric terminals) when high resistance to corrosion is required. Manufacturers use wire to make a wide variety of products, including automobile springs, bolts, fences, nails, paper clips, screens, screws, staples, strings for musical instruments, and watch springs. Electromagnets made from coils of insulated copper or aluiminum wire are used in generators and motors. Wire cables and ropes consist of wires twisted together. Thick steel-wire cables support large suspension bridges. Wire ropes are used in construction, mining, and oil-drilling equipment.
