How steel wire is made

Roll the rod

Billets of steel are hot-rolled in a rod mill into a coiled rod. This is the raw material for every wire drawer.

Clean and lubricate

Wire rod is cleaned of scale and coated with a lubricant. Without it the die would rub the surface raw and wear out fast. Some wire is dipped in copper sulfate solution so a copper film forms, and in dry drawing the rod passes through a container of lubricant that coats it.

Point the end and thread it

The tip of the rod is shrunk by hammering, filing or rolling so that it will fit through the first die. A worker threads it through, and the machine's drum grips the end.

Pull it through the dies

A rotating drum winds up the wire and drags it through the die. Steel wire uses dies of tungsten carbide. Each pull reduces the area by 15 to 25 percent for small wires and 20 to 45 percent for larger ones.

15 to 45% reduction per pull

Anneal between pulls

Drawing hardens the wire. When the total reduction goes past about 50 percent, the wire is annealed to make it soft again so it can be drawn further.

Draw in a continuous train

Production machines run several dies in a row, each with its own drum. Because the wire speeds up after every die, each drum turns faster than the one before. Telephone wire is drawn 20 to 30 times from rod stock.

Final anneal and coil

A last anneal can be given to the finished wire to maximize its ductility. It is then wound into coils or onto spools.