6. Combined Casting-Forging Process for Branch-Shaped Parts

Typical branch-shaped forgings such as aluminum alloy steering knuckles and control arms have complex structures. If the traditional die forging processes are employed to produce the forgings from the wrought aluminum alloy bar, although high strength and good quality of the forgings can be obtained, there will be problems such as multi-step billet-making and multiple heating, which will not only cause long production cycle and low efficiency, but also lead to low material utilization and high energy consumption. If the casting processes are employed to form the part, although it has the advantages of good fluidity and easy forming, there will be defects such as shrinkage cavities, porosities and coarse grains in the casting, causing the mechanical properties to fail to meet the requirements of use ^[1].

In recent years, the casting process and the forging process are combined to form a part to solve the above technical problems, that is, combined casting-forging process. Researchers have carried out the following two aspects of research on the combined casting-forging process: (1) the squeeze casting is used to obtain the pre-formed part, and then the semi-closed or closed precision forging is used for final forming; (2) the cast bar or cast block is taken as the billet of closed precision forging. The key to this process lies in the forging process which eliminates the shrinkage cavities and porosities that generate during the casting process and improves the mechanical properties of the part.