Forging is one of the two major components of forging (forging and stamping), which uses forging machinery to exert pressure on the metal billet to produce plastic deformation to obtain forgings with certain mechanical properties, shape and size.
According to the forming mechanism, forging can be divided into free forging, die forging, ring rolling and special forging.
1, free forging. It refers to a simple universal tool, or in forging equipment between the upper anvil and the lower anvil directly applied to the blank, so that the blank deformation to obtain the required geometry and internal quality of the forging method. Forgings produced by free forging are called free forgings. Free forging is mainly to produce small batches of forgings, forging hammer, hydraulic press and other forging equipment for blank forming processing, to obtain qualified forgings. The basic processes of free forging include upsetting, drawing, punching, cutting, bending, torsion, offset and forging. Free forging is done by hot forging.
2, die forging. Die forging is divided into open die forging and closed die forging. The metal blank is compressed and deformed in a certain shape of forging die chamber to obtain forgings. Die forging is generally used to produce parts with small weight and large batches. Die forging can be divided into hot die forging, warm forging and cold forging. Warm forging and cold forging are the future development direction of forging, and also represent the level of forging technology.
According to the material, die forging can also be divided into black metal forging, non-ferrous metal forging and powder forming. As the name implies, the material is carbon steel and other ferrous metals, copper and aluminum and other non-ferrous metals and powder metallurgy materials.
Extrusion should belong to die forging, which can be divided into heavy metal extrusion and light metal extrusion.
Closed die forging and closed upsetting are two advanced die forging processes, because there is no flash, the material utilization rate is high. The finish machining of complex forgings can be accomplished by one process or several processes. Because there is no flash, the area of forgings is reduced and the load required is reduced. However, it should be noted that the blank can not be completely restricted, so it is necessary to strictly control the volume of the blank, control the relative position of the forging die and measure the forgings, and strive to reduce the wear and tear of the forging die.
3, rolling ring. Rolling ring refers to the production of ring parts with different diameters by special equipment roller, which is also used to produce wheel parts such as automobile hub and train wheel.
4. Special forging. Special forging includes roll forging, cross wedge rolling, radial forging, liquid forging and other forging methods, which are more suitable for the production of some special shapes of parts. For example, roll forging can be used as an effective pre-forming process, greatly reducing the subsequent forming pressure; cross wedge rolling can produce steel balls, transmission shafts and other parts; radial forging can produce large barrels, step shafts and other forgings.
By forging, the defects such as as as as-cast porosity can be eliminated and the microstructure can be optimized. At the same time, the mechanical properties of forgings are generally better than those of castings with the same material because of the preservation of complete metal streamline. In the related machinery, the important parts with high load and severe working conditions are usually forged, except the rolled sheets, profiles or welded parts with simple shapes.
The initial recrystallization temperature of steel is about 727 C, but 800 C is generally used as the dividing line. Hot forging is used when the temperature is higher than 800 C. It is called warm forging or Semi-Hot forging between 300 800 C and cold forging at room temperature. The forgings used in most industries are hot forging, warm forging and cold forging are mainly used for automobile, general machinery and other parts of the forging, warm forging and cold forging can effectively save material.
As mentioned above, according to the forging temperature, it can be divided into hot forging, warm forging and cold forging.