Forging of large forgings not only needs to meet the shape and size of the required parts, but also important factors such as crushing as-cast microstructure, refining grains, uniform structure, forging shrinkage, pores and shrinkage, and improving the internal quality of forgings. The larger the size of the ingot, the more serious the defects in the ingot, and the more difficult it is to forge the defect, which increases the difficulty of forging. In the forging process, upsetting and lengthening are the most basic processes and indispensable processes. For forgings with special shapes, tire die forging is also more common.
Both the forgings and the wide forgings are mainly made up of upsetting, and the amount of deformation of the upset is very large. However, the ultrasonic flaw detection rate of this type of forgings is very high, mainly due to the internal internal cracking defects. The current process theory cannot explain this.
To this end, since the 1990s, Chinese scholars have conducted in-depth research on the theory of upsetting from the main deformation zone and the theory of passive deformation zone after a long period of serious research. The tensile stress theory of the rigid plastic mechanics model and the shear stress theory of the hydrostatic stress mechanics model are proposed. At the same time, a large number of qualitative physical simulation experiments are carried out, and the generalized slip line method and the mechanical block method are used. Solving and analyzing the stress state inside the workpiece, a large amount of data proves the rationality and correctness of the theory, reveals the distribution law of internal stress when using ordinary flat plate upsetting cylinder, and then proposes a new process of thickening of tapered plate. The rigid plasticity model of the square cylinder upset.
In the free forging production of large forgings, upsetting is a very major deformation process. The reasonable selection of the upsetting process parameters plays a decisive role in the quality of the forgings. Repeated drawing can not only improve the forging ratio of the blank, but also break the carbide in the alloy steel to achieve uniform distribution; it can also improve the transverse mechanical properties of the forging and reduce the anisotropy of mechanical properties.