The use requirement of forging determines the shape characteristics of blank, various use requirements and shape characteristics, forming the corresponding blank forming process requirements. When forging the forgings, the forgings are mainly based on the requirements of the external quality, such as the shape, size, machining precision, surface roughness, and the internal quality of its chemical composition, metal structure, mechanical properties, physical and chemical properties, according to the requirements of the use of forgings. Forging factories must consider the forging process performance of forging materials to determine the blank forming method for different forgings.
In the selection of blank forming program, the forging factory also considers the adaptability principle. According to the structure, shape, size and working conditions of the forgings, a suitable blank scheme is selected. For example, when the diameter of the stepped shaft is small, the bar material can be used when the diameter of each step is small. If the difference is large, forging blanks should be adopted. In general, metal type casting should not be used for forgings with complex shape and thin wall. The larger size blank is usually not made of die forging, pressure casting and melt casting, and the free forging is used to make the blank.
Forging is a forming method for plastic deformation of solid metals under pressure, and is also seen in forging factories. It requires better plasticity and less resistance to deformation. The forging method is suitable for manufacturing forgings, such as shafts, gears, crankshafts and canister, which are of high force, compact structure and uniform quality. The free forging and forging is simple and short preparation period, but the product is simple in shape, and it is a forging method of single piece production and large forgings. Die forging is a method of forging with a membrane on free equipment. It can be forged more complex, medium and small forgings of medium and small billets, forging parts of die forging are more complex, material utilization and birth. The yield is higher than that of free forging, but it can only forge large volume small and medium-sized forgings.