Upsetting Technology of Large Aluminum Forgings

The forging of large aluminum forgings not only needs to meet the required part shape and size, but also is important to break the as cast structure, refine the grain, uniform structure, forging shrinkage cavity, air hole, shrinkage porosity and other defects, so as to improve the internal quality of forgings. The larger the aluminum ingot size is, the more serious the defects in the aluminum ingot are, and the more difficult it is to improve the defects by forging, thus increasing the forging difficulty. In the forging process, upsetting and elongation are the most basic and indispensable processes. Die forging is also commonly used for forgings with special shapes.

The main deformation of cake forgings and wide plate forgings is upsetting, and the amount of upsetting deformation is large. However, at present, the scrap rate of ultrasonic flaw detection of this kind of forgings is very high, mainly because there is a transverse internal crack layer defect inside. However, the current process theory cannot explain this.

For this reason, since the 1990s, Chinese scholars have conducted in-depth research on upsetting theory based on the main deformation zone and passive deformation zone theory after a long time of careful research. The tensile stress theory of the rigid plastic mechanical model and the shear stress theory of the hydrostatic stress mechanical model during plate upsetting were proposed. At the same time, a large number of qualitative physical simulation experiments were carried out, and the stress state inside the workpiece was analyzed by using the generalized slip line method and the mechanical block method. A large number of data proved the rationality and correctness of the theory, and revealed the distribution law of the internal stress when the cylinder was upset by using a common plate, Furthermore, a new upsetting process of conical plate is put forward, and a rigid plastic mechanical model of square cylinder upsetting is established.

Upsetting is a very important deformation process in the free forging production of large forgings. The reasonable selection of upsetting process parameters plays a decisive role in the quality of forgings. Repeated upsetting and drawing can not only improve the forging ratio of the billet, but also break the carbides in the alloy steel to achieve the goal of uniform distribution; It can also improve the transverse mechanical properties of forgings and reduce the anisotropy of mechanical properties.