Large-scale forgings are used in key parts of large-scale machinery, so the quality requirements for large-scale forgings are very high in the production process. According to the forming mechanism, the forging of large forgings can be divided into free forging, die forging, ring rolling and special forging.
free forging. Refers to the processing method of using simple general-purpose tools or directly applying external force to the blank between the upper and lower anvils of the forging equipment to deform the blank to obtain forgings with the required geometric shape and internal quality. The forging produced by free forging method is called free forging.
Free forging mainly produces forgings with small batches. Forging equipment such as forging hammers and hydraulic presses are used to form blanks to obtain qualified forgings. The basic process of free forging includes upsetting, drawing, punching, cutting, bending, twisting, shifting and forging. Free forging adopts hot forging method.
Die forging. Die forging is divided into open die forging and closed die forging. Metal blanks are compressed and deformed in a forging die chamber with a certain shape to obtain forgings. Die forging is generally used to produce parts with small weight and large batches. Die forging can be divided into hot forging, warm forging and cold forging. Warm forging and cold forging are the future development direction of die forging, and also represent the level of forging technology. According to the material, die forging can also be divided into ferrous metal die forging, non-ferrous metal die forging and powder product forming. As the name suggests, the materials are ferrous metals such as carbon steel, non-ferrous metals such as copper and aluminum, and powder metallurgy materials. Extrusion should be attributed to die forging, which can be divided into heavy metal extrusion and light metal extrusion. Closed die forging and closed upsetting are two advanced technologies of die forging. Since there is no flash, the utilization rate of materials is high.
It is possible to complete the finishing of complex forgings with one process or several processes. Since there is no flash, the force-bearing area of the forging is reduced, and the required load is also reduced. However, it should be noted that the billet cannot be completely restricted. For this reason, the volume of the billet should be strictly controlled, the relative position of the forging die should be controlled, and the forging should be measured, so as to reduce the wear of the forging die.
Grind the ring. Ring rolling refers to the production of ring forgings of different diameters through special equipment ring rolling machines, and is also used to produce wheel-shaped parts such as automobile hubs and train wheels.
Special forging. Special forging includes roll forging, cross wedge rolling, radial forging, liquid die forging and other forging methods, which are more suitable for the production of parts with special shapes. For example, roll forging can be used as an effective preforming process to greatly reduce the subsequent forming pressure; cross wedge rolling can produce steel balls, drive shafts and other parts; radial forging can produce large forgings such as barrels and stepped shafts.