Forging

Forging is a manufacturing process that shapes metal by plastic deformation under compressive forces. It is distinguished from casting and extrusion by forming with dies or tools without melting the workpiece. It can be performed at high temperatures (hot forging) or near ambient temperature (cold forging). Hot forging allows easier deformation and refinement of grain structure; cold forging yields higher strength and dimensional accuracy but requires ductile materials and strong tooling.

Common methods include open-die forging, where the workpiece is deformed between flat or rounded dies to produce rough shapes, and closed-die (impression-die) forging, which uses shaped dies to produce near-net shapes. Upset forging increases the material volume along the same axis, often forming bolt heads and similar features. Isothermal forging maintains a constant temperature to optimize grain flow during shaping. Swaging uses rotary hammering to reduce or shape material, and various hammering and pressing techniques deploy drop hammers, power hammers, mechanical presses, or hydraulic presses.

Materials and equipment typical of forging encompass a wide range of metals, including steel, aluminum, titanium, and copper alloys. Equipment includes power hammers and hydraulic, mechanical, or screw presses, along with dedicated dies. While tooling costs are high, forging can produce parts with superior mechanical properties and good surface finish, often near-net shapes, reducing downstream machining. Post-forging processes may include trimming, heat treatment, and finishing.

Forging has ancient roots in toolmaking and weapon production and remains essential in modern industry. It is widely used for automotive components such as crankshafts and gears, structural and aerospace parts, fasteners like bolts and rivets, and various machinery elements. Advantages include refined grain flow and improved toughness; potential defects include laps, cold shuts, or undesirable grain misalignment if badly executed. Safety and energy requirements are important considerations in production planning.