Rolling

Rolling is one of the most important primary working processes, practiced in highly specialized, high productivity, capital-intensive plants. The products of flat hot rolling are relatively thick plates, sheets, and strips, typically down to 1.6 mm (0.060 in.) in cold rolling processes, these are capable of producing the thinnest of all metal products (strip and foil, to a few micrometers or a fraction of a thousandth of an inch) to very tight tolerances and controlled surface finish. Most of these products are further processed during sheet metal working operations (Figure 6). Hot-rolled bars and wires serve as starting materials for other bulk deformation processes or machining.

Shapes are mostly hot rolled or hot extruded for structural applications, although cold-rolled precision shapes fill an important niche. All these processes yield products of two-dimensional configuration, in often very long lengths, and are capable of producing high-quality (close-tolerance) products at very high rates and low cost. Closer to final application are three dimensional products of hot and cold ring rolling (rotating rings of jet engines, ball-bearing races), forge rolling for complex shapes (cutlery), gear rolling, and cross (transverse) rolled shapes of axial symmetry (performed during forging of double ended wrenches).

Seamless tubes are made by hot piercing or hot extrusion and are further reduced by special rolling processes for immediate use (for example, in oil fields) and for further working, including cold reduction and drawing.