Metal Forming

The term metal forming refers to a group of manufacturing methods by which the given material, usually shapeless or of a simple geometry is transformed into a useful part without change in the mass or composition of the material. This part usually has a complex geometry with well-defined (a) shape, (b) size, (c) accuracy and tolerances, (d) appearance and (e) properties. Metal forming processes such as cold and hot forging, extrusion, rolling, bending and deep drawing where metal is formed by plastic deformation. Desirable material properties for forming include low yield strength and high ductility. These properties are affected by temperature and rate of deformation (strain rate). When the work temperature is raised, ductility is increased and yield strength is decreased. The effect of temperature gives rise to distinctions between COLD FORMING i.e. billet initially at room temperature, WARM FORMING i.e. billet heated above room temperature, but below the recrystallization temperature of the billet material, and HOT FORMING i.e. billet heated above the recrystallization temperature. For example, the yield stress of a metal increases with deformation i.e. strain during cold forming. In hot forming, however, the yield stress, in general, increases with deformation strain rate. Forming processes are especially attractive in cases where:

•The part geometry is of moderate complexity and the production volumes are large, so that tooling costs per unit product can be kept low (e.g., automotive applications) or

•The part properties and metallurgical integrity are extremely important (e.g., load carrying aircraft, jet engine, and turbine components) The design, analysis and optimization of forming processes require: Engineering knowledge regarding metal flow, stresses and heat transfer.