Forging is one of the two major components of forging (forging and stamping) by using a forging machine to apply pressure to a metal blank to plastically deform it to obtain a forging with certain mechanical properties, a certain shape and size. Forging can eliminate defects such as as-cast looseness caused by metal in the smelting process, optimize the microstructure, and at the same time, the mechanical properties of the forgings are generally superior to those of the same materials due to the preservation of the complete metal flow lines. For important parts of the relevant machinery with high load and severe working conditions, forgings are often used except for the available rolled sheets, profiles or welded parts.
Deformation temperature
According to the deformation temperature, the forging can be further divided into hot forging (the forging temperature is higher than the recrystallization temperature of the billet metal), warm forging (the forging temperature is lower than the recrystallization temperature of the metal), and cold (normal temperature). The recrystallization temperature of steel is about 460 ° C, but 800 ° C is generally used as the dividing line, and higher than 800 ° C is hot forging; between 300 and 800 ° C is called warm forging or semi-hot forging.
Closed die forging and closed boring
Because of the absence of flash, the material utilization rate is high. Finishing of complex forgings is possible with one or several processes. Since there is no flash, the area of force applied to the forging is reduced and the required load is also reduced. However, care should be taken not to completely limit the blank. To this end, the volume of the blank is strictly controlled, the relative position of the forging die is controlled, and the forging is measured to reduce the wear of the forging die.
How the blank moves
According to the movement mode of the blank, the forging can be divided into free forging, upsetting, extrusion, die forging, closed die forging, and closed upsetting.
1. Free forging. The impact force or pressure is used to deform the metal between the upper and lower two irons (anvil) to obtain the required forgings, mainly hand forging and mechanical forging.
2, die forging. Die forging is divided into open die forging and closed die forging. The metal blank is pressed and deformed in a forging die having a certain shape to obtain a forged piece, which can be further divided into cold heading, roll forging, radial forging and extrusion, and the like.
3. Closed die forging and closed upsetting Because there is no flash, the material utilization rate is high. Finishing of complex forgings is possible with one or several processes. Since there is no flash, the area of force applied to the forging is reduced and the required load is also reduced. However, care should be taken not to completely limit the blank. To this end, the volume of the blank is strictly controlled, the relative position of the forging die is controlled, and the forging is measured to reduce the wear of the forging die.
Forging die movement
According to the movement mode of the forging die, forging can be divided into pendulum, pendulum swivel, roll forging, cross wedge rolling, boring ring and cross rolling. Swing, swivel and shackle can also be used for precision forging. In order to improve the utilization of materials, roll forging and cross rolling can be used as a front-end process for slender materials. The same rotary forging as free forging is also partially formed, which has the advantage that it can be formed in the case of a smaller forging force than the forging size. This type of forging, including free forging, expands from the vicinity of the mold surface to the free surface during processing. Therefore, it is difficult to ensure accuracy. Therefore, the movement direction of the forging die and the swaging process can be controlled by computer. The forging force obtains products with complex shapes and high precision, such as forgings such as steam turbine blades with large variety and large size.
