Cable and rod production
Cables are manufactured from individual wires which themselves are made by drawing the end of a rolled rod through a tapered hole. Wire can be galvanised or sheathed to prevent corrosion. Stainless steel wire can also be produced.
The production of wire from wire rod involves a variety of processes such as patenting, heat treatment (annealing) and wire drawing. Wire drawing is a cold working process which increases the strength and hardness of wire but reduces its ductility. This can be countered by subsequent heat treatment (annealing).
In the drawing process the end of the rolled rod is passed through a tapered hole drawing die manufactured from hard tungsten carbide to resist wear. The wire is lubricated before entering the die. by passing it through a box containing soap. The rod is gripped and pulled through the tapered die thus elongating it and reducing its cross-section.
Cables are made up of a number of individual steel wires, which are spun together into a strand.
A number of strands, usually six, are woven around a central core to form a rope, and a number of ropes, again usually six, form a cable. The largest ropes normally produced are approximately 100mm in diameter and are made up into six strands each containing 52 wires.
Cables are widely used in tensile structures.
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The high strength of cables make them ideal for use in tension structures such as suspension bridges, as guys or stays to main structural members and for other purposes, such as supporting lifts.
Cables are often exposed and it is important that they are protected against corrosion.
Cables can be protected by zinc coating (galvanising) which provides sacrificial protection to underlying wires against corrosion. Alternatively synthetic sheathing can be used to provide a barrier between the rope and the environment. Sheathing can be nylon or PVC and can be coloured. Some cables are now manufactured using stainless steel wires which are particularly suitable for some corrosive environments.
Rods are also manufactured as solid extruded sections.
Rods are also used in tension structures and are usually in the form of round bars with threaded ends attached to various forms of couplers which allow the rods to be tightened to remove any slack. Bracing members may also be designed using solid rods, but hollow sections are more efficient where both tension and compression forces are to be resisted. In comparison with cables, rods and tubes can be painted and maintained conventionally, and are cheaper than cables.
