How Are Aluminum Alloys Rolled, Extruded, and Forged?

Aluminum processing is divided mainly into cast-alloy and wrought-alloy processes. Casting methods include sand casting, die casting, permanent-mold gravity casting, low-pressure casting, and vacuum suction casting. A wrought aluminum alloy is melted and cast into an ingot, then rolled, extruded, or forged to change its microstructure and shape. The following sections focus on wrought aluminum processing.

Rolling

Rolling is the most widely used pressure-working method. Friction between rotating rolls and the workpiece draws the metal into the roll gap, where compression produces plastic deformation. Aluminum rolling is one of the world’s fastest-growing and most widely used aluminum-processing methods. Products include sheet, strip, narrow strip, and foil in many grades, specifications, properties, functions, and applications. Rolling offers high production efficiency, high output, and a wide product range.

Rolled aluminum alloys are widely used in vehicles for wheels, body panels, body sheet, hoods, connecting rods, bearings, heat exchangers, and other components.

Extrusion

Extrusion applies external force to a metal billet in a container and causes it to flow through a die opening, producing a required cross-sectional shape and size. Industrial methods include direct, indirect, lateral, continuous, hydrostatic, and glass-lubricated extrusion.

Extrusion can produce hollow and solid aluminum profiles, tubes, bars, and wire with complex cross sections and offers high production flexibility. Compared with rolling, however, it has higher cost, lower output, and lower yield. Automotive demand for lightweight structures has driven rapid growth in extruded aluminum. Applications include passenger-car bumpers, truck side supports, bus luggage racks, windows, seat rails, front-trim pillar enclosures, and upper and lower trim sections.

Forging

Forging applies pressure to an aluminum-alloy billet with forging machinery, producing plastic deformation and a forging with specified mechanical properties, shape, and dimensions. Compared with other processes, forging provides stable shape and dimensions, excellent overall mechanical properties, and high production efficiency. Depending on tooling and production method, forging is classified as open-die, closed-die, or special forging. Open-die forging uses simple tools such as hammers, anvils, swages, shaped anvils, punches, and supports to upset, bend, pierce, enlarge holes, and otherwise form ingots or bars into blanks.