Forging is a processing method that uses forging machinery to exert pressure on metal blank to produce plastic deformation and obtain forgings with certain mechanical properties, shape and size. It is one of two parts of the forging pressure (forging and stamping). Forging can eliminate defects such as loose metal casting in smelting process and optimize microstructure. At the same time, the mechanical properties of forgings are generally better than those of castings made of the same material, because it preserves a complete metal streamline. Except for rolling plates, profiles or weldments, forgings are mainly used for important components with high mechanical load and severe working conditions.
Forging is generally divided into free forging, mould forging and die forging. Each forging method has its own characteristics and scope of application. When selecting the forging method, the most reasonable method must be adopted based on the requirements for product components (quantity, processing requirements, size and shape, etc.) in the drawings and the actual conditions of existing production conditions (areas, units). For example, single, small, complex and large forgings are mostly free forgings; Die forging or die forging shall be adopted for mass production or small batch forging; For mass production, die forging or other special die forging (such as extrusion, rolling, roll forging, etc.) shall be adopted. In short, according to the results of process and economic analysis, select a reasonable, feasible, energy saving, energy saving and efficient forging process plan.
1. Strength requirements: strength, complexity, surface roughness, quality and other factors of parts shall be considered. Low strength requirement, complex shape, casting; Simple shape, high strength requirements, forged. However, when the shape of the part is complex and the casting cannot guarantee the strength, the forging method is still used. The combination of forging and machining can obtain parts with small surface roughness and high precision.
2. Annual output: What forging method depends on the annual output of forgings. The annual production test is very small and can be forged freely; Small annual wing production, die forging; Large output, die forging; The annual output is large, and the special die forging production line is available.
3. Shape and size: The shape and size of die forgings will determine the type of equipment used for die forging, that is, each type of die forging equipment is applicable to typical forgings:
① Die forging hammer is suitable for forging gears, shafts, connecting rods, bending parts and forks with complex shapes;
② The hot die forging press is suitable for forging gears and long shafts with little change in section. If the roll forging machine blank is used, the long shaft with large section change can also be forged;
③ Flat forging machine is suitable for forging local rolling parts with rods and forgings with holes.
4. Workpiece material: it will determine the blanking process, heating temperature, cold trimming or hot trimming, and heat treatment process.
5. Precision: machining allowance and forging tolerance will be determined.
6. Hardness: it will determine the heat treatment process.
7. Surface roughness: decide whether to use machining.
8. Cleaning method: The cleaning method is determined by the shape, size, material, hardness and other comprehensive factors of the parts.
9. Equipment conditions: Although a certain plastic equipment has its suitable typical forgings, it also depends on the specific situation. If the forging on the flat forging machine is more suitable, but there is no flat forging machine in the workshop and the output is not large, the die forging can be replaced on other equipment.