Forging is a kind of process method which exerts pressure to metal material with metal forming machine to make it plastic deformation to get the casting of specific mechanical performance, shape and dimension. It is one of the two parts of forging and pressing. Through forging, the defects of loose cast condition of metal generated during smelting process can be eliminated and the micro structure of the metal can be improved. Moreover, as it reserves the complete metal flow line, the forging piece is usually better than the ordinary casting in mechanical performance. Most of important parts which bear higher load and severe operation condition are made of forging pieces, except for those parts with simple shape which can be made of rolling metal plate, section materials or welding parts.

Deformation Temperature

Forging can be divided into heat forging (forging temperature is higher than the recrystallization temperature of metal material), warm forging (forging temperature is higher than the recrystallization temperature of metal material) and cold (temperature) forging by deformation temperature. The recrystallization temperature of steel is about 460°C. Generally, it is popular to take 800°C as the division, which means forging in the temperature higher than 800°C is heat forging, and that between 300~800°C is called warming forging or semi-heat forging.

Closed Die Forging and Closed Upsetting

Because there is no trimming for forging, the utilization rate of material is high, the complicated finishing can be completed in one or several processes, the stressed forging surface is reduced and the needed load is also reduced. However, please pay attention to not fully limit the blank material, so the volume of blank material shall be controlled strictly. Control the relative location of forging mold and measure the forging piece to reduce the abrasion to forging mold.

The Move Pattern of Blank Material

Forging can be divided into free forging, upsetting forging, extruding, die forging, closed die forging, closed upsetting forging by the move patterns of blank material.

1. Free forging: make metal deformed between two anvils with impact force or pressure to get the required forge pieces. It mainly includes manual forging and mechanical forging.

2. Die forging: die forging can be divided into open die forging and closed die forging. The blank metal material is deformed by extrusion in a special shaped die chamber to get the required forge pieces. It also can be divided into cold upsetting, rolling forging, radial forging, extruding, etc.

3. Because there is no trimming for closed die forging and closed upsetting forging, the utilization rate of material is high, the complicated finishing can be completed in one or several processes, the stressed forging surface is reduced and the needed load is also reduced. However, please pay attention to not fully limit the blank material, so the volume of blank material shall be controlled strictly. Control the relative location of forging mold and measure the forging piece to reduce the abrasion to forging mold.

The Move Pattern of Die Forging

The forging can be divided into rotary forging, rotary swaging, roll forging, transverse rolling, ring rolling, skew rolling, etc. by the move patterns of die forging. Rotary forging, rotary swaging and ring rolling also can be used in precision forging. To increase the utilization rate of material, we can adopt roll forging and cross rolling for the front-end-of-line processing to the long and thin material. Just as free forging, the rotary forging is also local forming with the advantages of the feasibility of forming even under less forge force compared to the forge piece size. This forging method, including free forging, makes material extending freely from the nearby of mold surface, so it is difficult to control the precision. Through controlling the move pattern of die mold and rotary forging processes with computer, we can easily get products of complex shapes and high precision with lower forging force, such as turbine blade of many varieties and big size.