Aluminium shaping - Wire drawing and stretching

Drawing and stretching are comparable processes. They consist in deforming a blank through a die. Drawing is more specific to wires, drawing to tubes and bars.

Both drawing and stretching can serve several purposes:

• reduce a spun or rolled blank to smaller dimensions; spinning or the CLC process cannot directly produce small wires, bars or thin-walled tubes;

• calibrate extruded products to achieve tighter dimensional tolerances than those possible with extrusion (see standards in the Documentation section);

• increase the mechanical properties of hot-worked blanks.

• Semi-finished products obtained by wire drawing are intended for electrical and mechanical applications. The French market for electrical conductors was 75,000 t in 1984, 79,000 t in 1985 and 77,000 t in 1986. These include bare cables for power transmission, insulated cables for power distribution, as well as flexible cables and household wiring. Mechanical applications include products as varied as civil and aeronautical rivets, knitting needles and welding wire. The product range is extremely broad. In 1986, the European market for mechanical applications was around 18,000 t in 1983; in the United States, it reached 60,000 t.

  In terms of specifications, wires for mechanical applications often require good ductility combined with a high level of mechanical characteristics or good deformation isotropy. Electrical conductors require a compromise between mechanical characteristics and electrical resistivity.

• Drawn bars are mainly used for mechanical applications requiring machining (bar turning, impact extrusion) or are intended for forging or closed-die forging.

  Drawn tubes have a wide variety of applications, such as automotive heat exchangers, hydraulic lines (aircraft, rolling stock) and leisure equipment (bicycles, flying wings, arrows, etc.). They require a meticulous surface finish.

  The European bar-turning market stood at 64,000 t in 1983 and 65,000 t in 1984.

  The European market for heat exchanger tubes (heating and cooling) for the automotive industry was 3,000 t and 3,200 t respectively for the same two years.

  The market for flying wings and ultralight motorized vehicles represented 200 t in Europe in 1984.

  In 1986, the U.S. market for bow arrows was worth over 20 million units a year ("500 t).

  For general information on drawing and wire-drawing, please refer to the articles entitled "Cold calibration of steel bars"....