Wire drawing is a metal forming process used to reduce the cross-section and increase the length of a workpiece. This process is associated with tensile force, which differs from other metal-forming processes like extrusion and forging.

In this process, a large cross-section workpiece is forced to pass through a die with a smaller opening compared to the workpiece’s cross-sectional area. This will plastically deform the workpiece by reducing its cross-sectional area and increasing its length. This process is used to manufacture wire, bars, and tubes.

WIRE DRAWING

Wire drawing is a cold working process. It is an operation to produce various sizes of wire within a specific tolerance range. The process involves reducing the diameter of the coarse wire by passing it through a series of drawing dies, where the consecutive die diameter is smaller than the previous one.

The dies are typically made of cold-hardened cast iron, tungsten carbide, diamond, or other tool materials. The maximum area reduction per pass is less than 45%.

ROD DRAWING

Rod drawing is similar to wire drawing, but the workpiece is rigid and has a larger diameter compared to wire. This process requires heavier equipment than wire drawing, as rods need to be kept straight, unlike coils.

The workpiece is first fed into the die and pulled by a carriage, which increases its length and reduces its cross-section. The rod is then cut into several segments.

TUBE DRAWING

Tube drawing is also similar to the other two processes, but it uses a mandrel to reduce the wall thickness and the cross-sectional diameter of the tube.

The mandrel is placed together with the die, and the workpiece is pulled by a carriage system, as in the case of rod drawing. The tubes can be circular or rectangular. It also requires multiple passes to complete the drawing operation.

Process Workflow:

1. Manufacture hot-rolled bars through other metal-forming processes like forging, extrusion, or centrifugal casting.
2. Straighten the bars to facilitate entry into the die.
3. Remove any dust or scale particles on the bars. This process is done through pickling.
4. Prepare the surface by applying a lubricant. This process uses degreasing, copper plating, phosphating, or black oxide coating. Degreasing uses a ferrous hydroxide coating. In phosphating, magnesium or iron phosphate is applied. Cu and Sn are used for lubricating high-strength materials. Oil and grease are used for wire drawing, and soap is used for dry drawing.
5. Now, pass the bars through various dies to convert them into the desired shape. The dies are made of high-strength alloy steels like tungsten carbide, subjected to various stresses.

Applications:

• This process manufactures copper, aluminum, and other wires for the electrical industry.
• Paperclips, spiral springs, and other small-diameter rods and tubes are drawn products.
• It is used to produce long lengths with small cross-sections.