Forging is defined as the forming or deforming of metal in its solid state. Much forging is done by the upsetting process where a hammer or ram moves horizontally to press against the end of a rod or stem to widen and change the shape of the end. The part usually moves through successive stations before reaching its final shape. High strength bolts are “cold-headed” in this manner. Engine valves are also formed by upset forging.

In the automotive industry, forging is used to make suspension components such as idler arms and wheel spindles and powertrain components such as connecting rods and transmission gears. Forgings are often used for pipeline valve stems, bodies, and flanges, sometimes made of copper alloy for increased corrosion resistance. Hand tools such as wrenches are usually forged as are many wire rope fittings such as sockets and turnbuckles. Forgings are used extensively in shipbuilding, for aerospace components, in agricultural machinery, and on off-road equipment. Electrical transmission components such as suspension clamps and pedestal caps use copper alloy forgings for improved weather resistance.

Forging steels used for axles, connecting rods, pins, etc. are typically 0.30-0.40% carbon for increased formability. Heat treatment after forging allows the parts to develop better mechanical properties than would low-carbon steel. In heavy crankshafts and high-strength gears, carbon content is sometimes increased to 0.50% with other alloying elements added for improved hardenability.