Aluminum-magnesium-manganese alloy plates are widely used in building curtain walls, roofing systems, and industrial manufacturing due to their excellent machinability, corrosion resistance, and lightweight properties. However, during bending processes, the material is prone to springback due to its elastic deformation recovery characteristics, leading to discrepancies between the forming angle and design requirements, affecting assembly accuracy and structural stability. To reduce springback while ensuring forming accuracy, a comprehensive approach is needed, addressing material properties, process parameters, mold design, and post-processing.
Material properties are the fundamental factor affecting springback. The yield strength, elastic modulus, and work hardening index of aluminum-magnesium-manganese alloys directly influence the amount of springback. Higher yield strength results in stronger elastic recovery after plastic deformation; lower elastic modulus leads to a larger proportion of elastic deformation and more significant springback. Therefore, when selecting materials, alloy grades with lower yield strength, moderate elastic modulus, and low work hardening index should be prioritized, such as some rust-resistant aluminum series. These materials undergo more complete plastic deformation during bending, with a smaller proportion of elastic recovery, effectively reducing springback. If the material has high hardness, annealing can be performed before bending to reduce yield strength and hardness, thereby decreasing the tendency for elastic deformation and reducing the forming force required for bending.
Optimizing process parameters is crucial for controlling springback. The ratio of bending radius to material thickness (r/t) significantly affects springback. A smaller r/t value results in more complete material deformation, a lower proportion of elastic recovery, and less springback. However, it's important to note that an excessively small bending radius may cause material fracture; therefore, it must be set appropriately based on material properties. Controlling bending speed and forming force is equally important. Appropriately increasing bending force can enhance plastic deformation and suppress elastic recovery; however, excessive force should be avoided to prevent damage to the mold or material. Conversely, reducing bending speed improves stress distribution, reduces internal stress accumulation caused by rapid deformation, and thus reduces springback. For complex bending parts, multiple bending or segmented bending processes can be used, gradually applying smaller bending forces to reduce springback caused by a single bend.
The rationality of mold design directly affects forming accuracy. The shape and dimensions of the mold's working parts need to be pre-corrected based on the material's springback characteristics. For example, in the design of punches or dies, a certain amount of compensation can be added in advance so that the part reaches the design dimensions exactly after springback. Furthermore, using arc-shaped punches or adjustable punches can optimize stress distribution, reduce stress concentration, and thus reduce elastic recovery. Zero-clearance die design, by better constraining the material, can reduce elastic recovery during forming, thereby reducing springback. For bending parts with high precision requirements, differential temperature dies can also be used to change the yield strength of different areas of the material through local heating or cooling, further suppressing springback.
The choice of bending method plays a crucial role in springback control. The tension bending process applies tangential tension during bending, placing the entire sheet metal cross-section in a tensile stress state. After unloading, the springback tendencies of the inner and outer fibers cancel each other out, significantly reducing springback. The correction method applies additional correction pressure to the sheet metal at the end of bending, forcing the inner metal at the bend to produce tangential tensile strain, suppressing elastic recovery. Both methods reduce springback at its source by changing the stress state and are suitable for bending parts with high precision requirements.
Post-processing is the final guarantee for ensuring forming accuracy. After bending, the parts can undergo stress-relief annealing. Low-temperature heating eliminates residual stress generated during bending, preventing deformation or cracking due to stress release during subsequent use. For parts requiring high surface quality, sandblasting or wire drawing processes can be used to further improve surface roughness and conceal minor springback marks. Post-processing correction is also a common method, using specialized tools or equipment to straighten the bent workpiece, adjusting it to the designed angle to ensure assembly accuracy.
Auxiliary measures during processing are equally important. Applying lubricant or a protective film to the bending area reduces surface damage caused by friction and compression, preventing stress concentration due to surface defects and thus reducing the risk of springback. Optimizing the mold surface quality to ensure it is smooth and defect-free reduces contact stress with the aluminum-magnesium-manganese alloy plate, further improving forming quality. Simultaneously, controlling the temperature and humidity of the processing environment to prevent changes in material properties due to environmental factors is also crucial for ensuring forming accuracy.
Springback control in the bending process of aluminum-magnesium-manganese alloy plates needs to be integrated throughout the entire process, including material selection, process design, mold manufacturing, and post-processing. By selecting appropriate materials, optimizing process parameters, improving mold design, adopting advanced bending methods, and implementing effective post-processing, springback can be significantly reduced, forming accuracy can be improved, and the demand for high-quality bent parts in the construction and industrial sectors can be met.
