Upsetting is a very important deformation process in the free forging of large forged special-shaped parts. Reasonable selection of parameters of upsetting process plays a decisive role in the quality of large forging. Repeated upsetting can not only increase the forging ratio of blank, but also break carbide in alloy steel, so as to achieve uniform distribution. It can also increase the transverse mechanical properties of forging parts and reduce the heterogeneity of mechanical properties.
Although the development of plasticity is rapid, and a relatively complete theoretical system has been established in many fields, there are still some deficiencies in the theory and technology of forging process. Some problems cannot be solved, some cannot be qualitatively analyzed, and some arguments are even wrong. The upsetting is the main deformation of the large cake forging shaped parts and the wide plate forging, and the upsetting deformation is large. However, the frequency of acoustic detection of this kind of forging is very high, mainly because of the defects of the transverse inner crack layer in the inner part, which can not be explained by the current process theory.
Therefore, from the beginning of the 1990s, Chinese scholars after a long time of careful research, from the main deformation zone and passive deformation zone theory, upsetting theory is further studied.
The forging of large forgings not only needs to reach the required parts shape and size, but also important is to break the cast yarn to refine the grain, uniform structure, forging shrinkage holes, pores and porosity and other defects to increase the internal quality of the forgings.
In this paper, the tensile stress theory of rigid plastic mechanical model and shear stress theory of hydrostatic mechanical model were put forward. At the same time, many qualitative physical simulation experiments were carried out, and the generalized slip line method and mechanical block method were used to interpret and analyze the stress state of the workpiece. A large number of data confirmed the rationality and correctness of the theory. In this paper, the distribution law of stress in the cylinder is revealed when ordinary plate is used to upset the cylinder. Then a new upsetting process of conical plate is put forward, and a mechanical model of rigid plasticity for the upsetting of square cylinder is established.