Chances are the word wire conjures up visions of coiled springs and coat hangers in your mind. Though it's true that these familiar products are made of steel wire, there are literally hundreds of thousands of other uses for wire. To list a few: paper clips, nails, screws of all kinds, bed springs, machine nuts, fan grilles, wire baskets, wire rope, staples, chain link fencing, belt buckles, radial tire belts and refrigerator shelving.
Wire is manufactured by drawing hot rolled rod through one or more dies. Rod is made by a hot rolling process that's almost identical to the process used to manufacture hot rolled bars.
A major difference is its smaller size. Most rod is 7/32-inch in diameter. Another is the controlled cooling step (above). Hot rolled rod is allowed to cool slowly and evenly to give it properties that enhance its suitability for wire-making.
Incidentally, steel rod has few applications in its as-rolled state. Almost all the rod we make at our Aliquippa rod mill is eventually drawn into wire by us or by our customers.
Rod becomes wire the instant it is drawn through a die. Like other cold finishing operations, cold drawing reduces cross-section size, increases strength and imparts a good surface finish to the steel. Depending on the end use application, wire may be drawn through as many as eight dies. The great strength developed by repetitive drawing explains why wire is steel in its strongest form. A typical wire drawing machine at J&L's Aliquippa wire mill (above) uses motor-driven "blocks" or reels to pull the wire through the dies.
Along with strength, the wire-making process
increases the stiffness and hardness of the steel. Many wire applications,
though, require supple, flexible steel. Consequently, we heat-treat
much of the wire we make to soften the steel. We use several different
heat treatment processes, but all involve heating the steel to
a specific temperature and then cooling it at a carefully controlled
rate.