Image Credit: Inductoheat
Forging machines use compressive force and a high workpiece temperature to shape metal by plastic deformation. This product area covers equipment for hot forging, a metallurgical process that forms metal parts by forcing hot metal into dies under pressure. A type of hot forming, hot forging involves the plastic deformation of a metal at a temperature and strain rate where recrystallization and deformation occur simultaneously. This prevents strain hardening, which can reduce ductility and contribute to brittle failure and structural fatigue.
Advantages and Disadvantages of Hot Forging
Hot forging machines are used to produce metal parts made out of aluminum, copper and steel. They are recommended for deforming metals with a high formability ratio, especially with low-to-medium accuracy. Advantages also include homogenized grain structure, increased ductility, the elimination of chemical impurities, and reduced scale formation. Disadvantages include possible warping of the metal during the cooling process, less precise tolerances, and possible chemical reactions between the metal and its surrounding atmosphere.
Types of Forging Machines
- Drop forging machines produce complex shapes by dropping heated metal into a punch and die that gradually compresses the part. The punch's ram causes this malleable metal to conform to the shape of the punch and die cavities. Power hammers or drop hammers, as drop forging equipment is known, may use pneumatic, hydraulic, or electrical power. The dies and punches may be flat or V-shaped, and the striking force can range from 11,000 to 425,000 pounds (lbs). Because only one ram is needed to form the part, flash is produced and needs to be trimmed.
- Open die forging machines are used with ingots, billets, bars or preforms. They deform the workpiece between flat or shaped dies without completely restricting metal flow. This results in the lengthening of the workpiece while reducing its cross-section. Using multiple impacts, lengthening and upsetting can be achieved. Metal parts can range from a few centimeters (cm) to 30 meters (m) in length, and weigh from several to several hundred thousand kilograms (kg). Open die forging machines can used to make fairly complex shapes, but are usually used to produce simple solids or hollows that considerable machining to achieve their final shape.
- Closed die forging machines do not require the formation of flash to ensure the complete filling of the die. The metal is deformed in a cavity that does not permit the escape of excess material, which places greater requirements on proper die design.
- Isothermal forging machines heats materials and dies to the same temperature. To prevent oxidation, it is usually performed on superalloys in a vacuum of highly-controlled atmosphere.
Equipment for hammer and press forging is available, but requires a skilled operator in place of a programmable hammer.