Wire drawing

Drawing is the reduction of cross section of usually round wires. The cross section of the wire will be reduced in one or several steps until reaching the required measurements.

According to the cross section reduction the wire is elongating.

Due to the cold deformation the wire is becoming harder.

A tensile strength is increasing and the strain to rupture is reduced. Before using the wire for other processes an annealing is required. When annealing the structure compacting caused by the cold forming of the wire will be recristalized.

Principle
Caused by the smaller drawing die diameters from one drawing step to the next the wire diameter is reduced by the diameter given through the drawing die. With a constant entrance speed of the wire the finished wire has a drawing speed after the last drawing die which is linear to the diameter reduction of the wire. This is equal for all individual drawing steps.

According to the cross section reduction in each drawing step the wire is stretched. The definition is wire elongation and this value is given in percent or the cross section reduction is given in percent.

Wire drawing is dividing into 3 different machine types which are:

  • Rod drawing machines
  • Medium wire drawing machines
  • Fine wire drawing machines

Material
In the wire industry the typical material is copper and copper alloys or aluminium and aluminium alloys.

The starting wires are usually hard or soft wires with oxygen free surface for the rod drawing machine. Typical diameters for copper are 8 mm, for aluminium usually
9,5 mm.

Annealing
Copper rod drawing machines are usually equipped with an annealer. The annealer is softening the wire after the last drawing die and before going onto the spooler. Current is heating up the hard drawn wire. The wire is going through contact rolls and an electrical voltage is applied. This results in a current which is heating up the wire to min. of 300°C. To avoid oxidation of the wire surface during the annealing, steam or nitrogen is injected into the annealing zone which is eliminating the oxygen containing air. After annealing the wire is cooled down using water to a normal temperature before going to the spoolers.

Wire drawing machines for cables are part of our delivery program.

Drawing of steel wires
The drawing of steel wires requires specially designed machines. These machines are as well part of our delivery program.