Generally, forged components are shaped either by a hammer or press. Forging on the hammer is carried out in a succession of die impressions using repeated blows. The quality of the forging, and the economy and productivity of the hammer process depend upon the tooling and the skill of the operator. The advent of programmable hammers has resulted on less operator dependency and improved process consistency. In a press, the stock is usually hit only once in each die impression, and the design of each impression becomes more important while operator skill is less critical. Press forging use a slow squeezing action of a press, to transfer a great amount of compressive force to the work piece. Unlike an open-die forging where multiple blows transfer the compressive energy to the outside of the product, press forging transfers the force uniformly to the bulk of the material. This results in uniform material properties and is necessary for large weight forgings. Parts made with this process can be quite large as much as 125 kg (260 lb) and 3m (10 feet) long.

Upset Forgings:

Upset forging increases cross-section by compressing the length, this is used in making heads on bolts and fasteners, valves and other similar parts.

Cold

Cold forging involves either impression die forging or true closed die forging with lubricant and circular dies at or near room temperature. Carbon and standard alloy steels are most commonly cold-forged. Parts are generally symmetrical and rarely exceed 25 lb. The primary advantage is the material savings achieved through precision shapes that require little finishing. Completely contained impressions and extrusion-type metal flow yield draft less, close-tolerance components. Production rates are very high with exceptional die life. While cold forging usually improves mechanical properties, the improvement is not useful in many common applications and economic advantages remain the primary interest. Tool design and manufacture are critical.

Warm

Warm forging has a number of cost-saving advantages which underscore its increasing use as a manufacturing method. The temperature range for the warm forging of steel runs from above room temperature to below the re-crystallization temperature, or from about 800 to 1,800°F. However, the narrower range of from 1,000 to 1,330°F is emerging as the range of perhaps the greatest commercial potential for warm forging. Compared with cold forging, warm forging has the potential advantages of: Reduced tooling loads, reduced press loads, increased steel ductility, elimination of need to anneal prior to forging, and favorable as-forged properties that can eliminate heat treatment.

Hot

Hot forging is the plastic deformation of metal at a temperature and strain rate such that re-crystallization occurs simultaneously with deformation, thus avoiding strain hardening. For this to occur, high work piece temperature (matching the metal's re-crystallization temperature) must be attained throughout the process. A form of hot forging is isothermal forging, where materials and dies are heated to the same temperature. In nearly all cases, isothermal forging is conducted on super alloys in a vacuum or highly controlled atmosphere to prevent oxidation