Forging is a processing method that uses forging machinery to exert pressure on metal blanks to produce plastic deformation to obtain forgings with certain mechanical properties, shapes and sizes. It is one of the two major components of forging (forging and stamping). Forging can eliminate the defects of as cast porosity and optimize the microstructure. At the same time, because the complete metal streamline is preserved, the mechanical properties of forgings are generally better than those of castings of the same material. For important parts with high load and severe working conditions in related machinery, forgings are mostly used, except for rolled plates, profiles or weldments with simple shape.

According to the movement mode of forging die, forging can be divided into rotary forging, rotary forging, roll forging, cross wedge rolling, ring rolling and cross rolling. Rotary forging, rotary forging and ring rolling can also be processed by precision forging. In order to improve the utilization rate of materials, roll forging and cross rolling can be used as the previous process processing of slender materials. Like free forging, rotary forging is also locally formed. Its advantage is that compared with the size of forgings, it can also be formed when the forging force is small. In this forging method, including free forging, the material expands from the vicinity of the die surface to the free surface during processing, so it is difficult to ensure the accuracy. Therefore, by controlling the movement direction of the forging die and the rotary forging process with computer, products with complex shape and high accuracy can be obtained with low forging force, such as the production of forgings such as steam turbine blades with many varieties and large sizes.