Precision forging processes are diverse, and can be divided into hot forging, cold forging, warm forging, composite forging, isothermal forging, etc. according to different forming temperatures. Each process has its own characteristics and is applied to specific occasions according to different materials and parts requirements.
Hot forging process: Hot forging is a precision forging process that is performed above the recrystallization temperature. First of all, because it is forged at high temperature, the material has low deformation resistance and good plasticity, which means that it can be easily hammered into parts with complex geometric shapes, such as some parts with complex internal structures in automobile engines, which are best suitable for hot forging. However, because the metal will produce strong oxidation when it comes into contact with oxygen in the air under high temperature, the disadvantage is that the surface quality and dimensional accuracy of the workpiece are relatively low. The commonly used process method for hot forging is closed die forging, which helps to improve the utilization rate of materials and reduce waste such as flash, and to a certain extent strengthens the control of the forming size of parts.
Cold forging process: The cold forging process forges parts at room temperature. In this process, since it is operated at room temperature, the shape and size of the parts will not change due to temperature changes, so the shape and size of the workpiece can be easily and accurately controlled; and during the cold treatment process, the surface of the workpiece does not produce oxidation and burning, so a higher surface quality can be achieved. Because the material does not deform under high temperature softening conditions, the workpiece formed by cold forging also has higher strength and precision. However, due to the lack of high temperature assistance, the plasticity of the workpiece is relatively poor and the deformation resistance is large during the cold forging process. This state has relatively high requirements for molds and equipment, and it is difficult to use cold forging technology alone to achieve the forging of parts with complex structures, so there are limitations in the manufacture of parts with large size and complex structure.
Warm precision forging process: Warm precision forging is to heat the metal to a suitable temperature below the recrystallization temperature for forging. It seems to be an "intermediate technology" that balances cold forging and hot forging. Warm forging takes the advantages of both cold forging and hot forging and avoids their disadvantages: it not only breaks through the limitations of cold forging in forming, such as large deformation resistance, not too complex part shape, and the need for additional intermediate heat treatment and surface treatment steps; it also overcomes the problem of reduced surface quality and dimensional accuracy caused by strong oxidation during hot forging. Warm precision forging technology is suitable for the production of precision forged parts that want to improve the machinability of materials without sacrificing a lot of surface quality and dimensional accuracy. For example, some structural parts with medium precision and slightly special requirements for mechanical properties are very suitable for this process.
Composite precision forging process: The composite precision forging process is a process technology that combines cold, warm and hot forging processes to complete the forging of a workpiece. In the development of modern manufacturing industry, as the requirements for precision forging parts become more complex and precise, a single forging forming process is often difficult to meet the needs. The composite precision forging process rationally organizes the cold, warm and hot forging links, gives full play to the advantages of each link, abandons their respective shortcomings, and achieves an all-round improvement in the overall quality of parts. For example, the common composite processes currently include warm forging-cold finishing, hot forging-cold forging, etc. Among them, the warm forging-cold finishing combination can first use warm forging to initially shape the material to reduce some deformation resistance, and then use cold finishing to further improve the dimensional accuracy and surface quality of the workpiece; while the hot forging-cold forging composite process can first use the advantages of hot forging for forming complex shapes, and then use cold forging to strengthen the mechanical properties and surface conditions of the material.
Isothermal precision forging process: Isothermal precision forging is the process of die forging the blank at a constant temperature. In the aerospace industry, this process is often used for the precision forming of difficult-to-deform materials such as titanium alloys, aluminum alloys, and magnesium alloys. In recent years, it has gradually been applied to the precision forming of non-ferrous metals in the automotive and machinery industries. It is particularly suitable for the processing of metal materials with a narrow forging temperature and particularly sensitive to deformation temperature, such as some titanium alloy blades in aircraft engines. Since titanium alloys have good forgeability only within a very narrow temperature range, isothermal precision forging is suitable. This process can ensure that the material is deformed under relatively stable temperature conditions, effectively preventing forging defects caused by fluctuations in material properties due to temperature changes, and ensuring the quality and precision of parts.
