a manufacturing process in which room temperature metal tubes or wires are pulled through dies to reduce their cross-sectional diameter.
How Cold Drawing Works
Drawing is a standard metalworking process that stretches and lengthens metal in whatever form it comes in, be it wires, tubes, or rods. The "cold" in the term "cold drawing" is a misnomer. The metal is not actually cold but rather room temperature. By not heating the metal, the final product remains strong under tension.
To start the cold draw process, a metalworker inserts the wire into a die with an opening larger than the wire's original diameter. A die is a machine tool that shapes and cuts materials. A die is usually customized to fit a particular task so a factory would theoretically already have a machine tailored for a specific diameter. The machine draws or pulls the wire through this die, which is angled to shape and stretch the wire into its desired size. The resulting drawn bar is smaller in diameter than the original undrawn bar.
Cold Drawing Example
Cold drawing is useful in making the steel wires workers use to prestress concrete. Prestressed concrete is important in construction as it makes concrete stronger under tension. Manufacturers lay steel wire into concrete beams, stretch the wires, anchor them, and release them. This creates compression stress in the beam and ultimately makes it stronger. The steel wires needed for this process must be high tensile (it must resist breaking under tension) and multi-stranded.
Our hypothetical building materials supply company, Strongarm Supplies, sells prestressed PC steel wire for concrete. PC grade steel wire is a twisted cable made up of 2, 3, 7, or 19 steel wire strands. Strongarm makes its PC steel wire through a cold drawing process. Wire diameters measure 4.0mm to 12.0 mm. To achieve this diameter, they gradually reduce a 20mm wire in 20% increments using a drawing machine. This makes the wire small enough to make strands for the larger PC Strand.
Significance of Cold Drawing
Introducing cold drawing to a manufacturing process can benefit factories that produce materials requiring high strength. Because cold drawing increases the amount of material you get and reduces waste, you have the potential to save money on materials. You'll also get a stronger product, a smoother surface, and a straighter product (if working with something like steel bars). A better product means better customer satisfaction.
Cold Drawing vs. Cold Rolled
In a cold draw, a die machine reduces the wire's diameter. In a cold roll, a metal sheet goes through rollers to reduce its thickness. These rollers apply intense pressure since the metal starts at room temperature. Like a cold draw, the metal sheet will need to go through several rollers to achieve the desired thickness. The result of a cold roll is a more polished and consistent product. If you ever find yourself confused about the two terms, just remember that you are flattening something out in a roll, as you would roll dough with a rolling pin.