Structural Properties
The structural reliability achieved in a forging is unequalled by other production processes. There are no internal gas pockets or voids that could cause unexpected failure under stress or impact. The structural reliability of forgings means reduced inspection requirements, uniform response to heat treatment, and consistent machinability. These qualities contribute to faster production rates and lower costs.
Directional strength is a direct result of the forging process. In the forging process, controlled deformation results in improved mechanical properties of the material. Forging produces directional alignment (or "grain flow") for important directional properties in strength, ductility, and resistance to impact and fatigue. These properties are deliberately oriented in directions requiring maximum strength.
Properly developed grain flow in forgings follows the outline of the component. In contrast, bar stock and plate have unidirectional grain flow; any changes in contour will cut flow lines. As a result, the material is more susceptible to fatigue stress. To the designer, the structural integrity of forgings means safety factors based on material that will respond predictably to its environment without costly special processing to correct for internal defects.
The resulting higher strength-to-weight ratio can be used to reduce section thickness in part designs without jeopardizing performance characteristics of safety. Weight reduction, even in parts produced from less expensive materials, can amount to a considerable cost savings over the life of a product run.
Consistency
The consistency of material from one forging to the next, and between separate quantities of forgings is extremely high. Forged parts are made through a controlled sequence of production steps rather than random flow of material into the desired shape. Uniformity of composition and structure piece-to-piece, lot-to-lot, assure reproducible response to heat treatment, minimum variation in machinability, and consistent property levels of finished parts.
Dimensional characteristics are remarkably stable. Successive forgings are produced from the same die impression, and because die impressions exert control over all contours of the forged part, the possibility of transfer distortion is eliminated.
Economics
Economically, forged products are attractive because of their inherent superior reliability, improved tolerance capabilities, and the higher efficiency with which forgings can be machined and further processed by automated methods.
The near absence of internal discontinuities or surface inclusions in forgings provides a dependable machining base for metal-cutting processes such as turning, milling, drilling, boring, broaching, and shear spinning; and shaping processes such as electrochemical machining, chemical milling, electrical-discharge machining, and plasma jet techniques.
Forged parts are readily fabricated by assembling processes such as welding, bolting, or riveting. The selection of a forging can often eliminate the need for assemblies. In many cases, forgings are ready for use without surface conditioning or machining. The forged surface is suited to plating, polishing, painting, or treatment with decorative or protective coatings.
