Wire drawing is cold working process which is carried out below the recrystallization temperature of metal.
It is the process of reducing the diameter (cross section area) of metal rod by passing it through the die blocks (conical hole having an included angle of 8-24). The diameter of rod decreases through plastic deformation while its volume remains the same.
The rods to be used are pickled in acid to remove any scale.
The end of the rod, which is to be passed through the hole, is tapered sufficiently, to pass through the conical hole. The rod (from tapered side) is then pulled with the help of power driven drives like pulleys or rotating drums to pass it through conical hole.
Due to cold working process, the wire losses its ductility so immediate annealing is required to restore the ductility.
For making a continuous wire, the wire is passed through a series of holes (decreasing size) in dies.
A lot of heat is generated during the process so water is circulated continuously during the process to cool the dies and drums.
A lubricant is used to decrease the friction between die and metal rod. Dry soap and synthetic lubricants are generally used as lubricants.
The dies used in wire drawing are generally made up of steel and tungsten carbide.
Defects in wire drawing:
Central cracking due to large die angle and high friction.