Many precision forging processes have been put into production. According to forming temperature, they can be classified into hot precision forging, cold precision forging, warm precision forging, composite precision forging, isothermal precision forging, etc.

Hot Precision Forging

Hot precision forging refers to precision forging carried out above the recrystallization temperature. In this process, materials feature low deformation resistance and good plasticity, making it easy to form workpieces with relatively complex geometries. However, severe oxidation leads to poor surface quality and low dimensional accuracy of workpieces. Closed-die forging is the commonly adopted method for hot precision forging.

Cold Precision Forging

Cold precision forging is performed at room temperature. Its characteristics are as follows: the shape and dimension of workpieces are relatively easy to control, eliminating errors induced by high temperature; finished workpieces have high strength, high precision and good surface quality. During cold forging, workpieces show poor plasticity and high deformation resistance, which imposes stringent requirements on dies and equipment. Besides, it is difficult to form parts with complex structures.

Warm Precision Forging

Warm precision forging is conducted at a suitable temperature below the recrystallization temperature. This near-net forming technology breaks through the limitations of cold forging — high deformation resistance, restriction on part complexity, and mandatory intermediate heat treatment and surface treatment procedures. It also addresses the problem of degraded surface quality and dimensional accuracy caused by heavy oxidation in hot forging. Warm forging combines the merits of both cold and hot forging while overcoming their respective drawbacks.

Composite Precision Forging

As precision-forged workpieces grow increasingly complex and require higher accuracy, simple cold, warm or hot forging alone can no longer meet requirements. Composite precision forging integrates cold, warm and hot forging processes to complete the forging of a single workpiece. It leverages the advantages and avoids the disadvantages of the three individual processes.

Isothermal Precision Forging

Isothermal precision forging means die forging and forming of billets at an approximately constant temperature. It is widely used for precision forming of hard-to-deform materials such as titanium alloys, aluminum alloys and magnesium alloys in the aerospace industry. In recent years, it has also been applied to precision forming of non-ferrous metals in automotive and machinery industries. Isothermal forging is mainly used for metallic materials with a narrow forging temperature window, especially titanium alloys which are highly sensitive to forming temperature.