What are the distribution patterns of deformation in forgings?

2024-08-14 15:28:19

The deformation distribution law inside the forgings of block type, cylinder type, and shaft type was systematically studied using physical simulation methods. The experiment found that during the deformation process, due to the effect of boundary friction, there is no obvious transition zone between the large deformation zone and the rigid zone, and a severe shear deformation zone is formed between the two zones; As the deformation increases, the stress situation inside the material will change after the deformation zone undergoes significant deformation. When the deformation continues to increase, it is manifested as the shear band starting to move and causing the rigid zone to enter the plastic state layer by layer.

Under the above conditions, coupled with the presence of inclusions and coarse grain boundaries, cracks are easily generated at the inclusions and grain boundaries. During the upsetting process, the deformation is very severe in the shear band between the rigid zone in contact with the anvil surface and the large deformation zone in the middle. When the deformation reaches a certain value, the original rigid zone begins to deform, causing a sharp increase in load and often leading to defect propagation. Similar phenomena also occur during the deformation process of module, cylinder, and shaft forgings.

The micro deformation distribution of defects such as inclusions and voids was studied using the cloud pattern method, which proved that the morphology of defects directly affects the degree of stress concentration. The combined effect of shear deformation and local stress of defects leads to the fracture of the metal matrix between defects. Micro inclusions are connected by cracks, and then the inclusions are squeezed into the cracks until larger inclusion cracks are formed, which is one of the important reasons for exceeding the detection limit. This can satisfactorily explain the cause of the formation of the center clamping layer defect in block type forgings, and lay a theoretical foundation for eliminating such defects.

The morphology of inclusions and the condition of grain boundaries directly affect the performance of large forgings, and unreasonable defect distribution is highly likely to become a major hidden danger for sudden failure of large forgings during use. Although the current inspection standards cannot scientifically evaluate it, the deformation characteristics should be fully utilized in the forging process to ensure the reasonable distribution of defects. Studying the distribution law of deformation can effectively solve the problem of cavity compaction and provide process parameters for deformation control of grain size and even production of composite performance forgings.