WIRE DRAWING

Prepared BY :- DEVESH AGRAWAL

Wire drawing is primarily the same as the bar drawing except it involves smaller diameter material that can be coiled.

It is generally performed as a continuous operation on the draw bench.

In the forging operation the products are discrete in nature.it means we can produce one product then take it out as a single product but in this product is continuous in nature.

Small diameter wire is generally draw on tandem machines which consists of a series of dies ,each held in the water cooled die block. each die reduces the cross section by small amount so as to avoid the excessive stress in the wire.

Tandem machines are a series of machines in which the smaller diameter wire will be drawn. Diameter will be reduced in no. of stages.

Cooling arrangement is there for avoiding thermal failure in the wire.

PROCESS OF DRAWING

It is performed in no of steps .in order to avoid failure of wire.

First of all there will be a starting stock in coil form then it goes to the box containing lubricant where its lubrication has been done and then it goes inside the die. The opening of the die will decide how much reduction will be there. then after it goes to draw block. the roatating draw block will provide the a continuous pull on the incoming wire.

There are some treatment which have to be done before actual drawing process .for steel drawing these are .these are cleaning and neutralization

LUBRICATION

Proper lubrication is essential in order to improve die life, reduce drawing forces, reduce temperature, and to improve surface finish.

These can be of three types Wet drawing lubrication Dry drawing lubrication coating

DIE PROPERTIES Die material for drawing are usually

tool steel and carbides, & diamond dies are used for very fine wires.

The portion which is responsible for the wire drawing is made up of carbide and rest portion is of steel because carbide is much costlier.

The entrance angle and the approach angle will decide the die pull in order to facilitate easy entry of the wire in to the die and reduction in the die pull or pulling forces.

The shape of the bell causes hydrostatic pressure to increases and promote the flow of lubricant in to the die.

The back relief allows the metal to expand slightly as the wire leaves the die and also minimises abrasion if the drawing stops or the die is out of alignment.

DRAWING EQUIPMENT These are the equipments which provide

pulling force to pull the incoming wire.these can be of two types.

ROTATING DRUM:- Wires of very small cross section (less than 13mm) can be drawn up to many kilometres by this. tension in this setup provides the force required to drawing the wire.

DRAW BENCH:- this is used for drawing wires of diameter usually greater than 20mm.tension is given by grippers. and maximum pulling lenth can not exceed 30m.

LIMIT OF REDUCTION

Reduction in cross section area per pass may range from near zero to about 45%.

Reduction more than 45% may result in to lubrication break down. and surface finish can not achieved at a higher reduction.

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