Basic Knowledge of Forging And Forging - Forging Materials

Core Tip: The forging materials are mainly carbon steel and alloy steel with various compositions, followed by aluminum, magnesium, copper, titanium and their alloys. The original states of materials include bar, ingot, metal powder, and liquid metal

The forging materials mainly consist of carbon steel and alloy steel with various compositions, followed by aluminum, magnesium, copper, titanium and their alloys. The original states of materials include bar, ingot, metal powder, and liquid metal. The ratio of the cross-sectional area of a metal before deformation to the cross-sectional area after deformation is called the forging ratio. The correct selection of forging ratio, reasonable heating temperature and holding time, reasonable initial and final forging temperature, reasonable deformation amount and deformation speed are closely related to improving product quality and reducing costs.

Generally, circular or square bar materials are used as blanks for small and medium-sized forgings. The grain structure and mechanical properties of the bar material are uniform and good, with accurate shape and size, good surface quality, and easy to organize for mass production. As long as the heating temperature and deformation conditions are reasonably controlled, high-quality forgings can be forged without significant forging deformation. Ingots are only used for large forgings. Ingot is a cast structure with large columnar crystals and loose centers. Therefore, it is necessary to crush the columnar crystals into fine grains through large plastic deformation, and compact them loosely in order to obtain excellent metal structure and mechanical properties.

Powder metallurgy preforms formed by pressing and firing can be made into powder forgings by non flash forging in the hot state. The density of forging powder is close to that of general die forgings, with good mechanical properties and high precision, which can reduce subsequent cutting processing. The internal structure of powder forgings is uniform without segregation, and can be used to manufacture small gears and other workpieces. However, the price of powder is much higher than that of general bar materials, which limits its application in production. By applying static pressure to the liquid metal poured into the mold cavity, it can solidify, crystallize, flow, undergo plastic deformation, and form under pressure to obtain the desired shape and properties of the forging. Liquid metal forging is a forming method between die casting and die forging, especially suitable for complex thin-walled parts that are difficult to form by general die forging.

In addition to conventional materials such as carbon steel and alloy steel with various compositions, forging materials also include aluminum, magnesium, copper, titanium, and their alloys. Iron based high-temperature alloys, nickel based high-temperature alloys, and cobalt based high-temperature alloys are also forged or rolled as deformation alloys. However, these alloys have relatively narrow plastic zones, making forging relatively difficult. Different materials have strict requirements for heating temperature, forging temperature, and final forging temperature.