At the beginning of industrial fan production, after ch […]
At the beginning of industrial fan production, after chemical milling and roll-bending leveling, occasional severe agitation and warping deformation occur in the chemical milling area. After correction by manual hammering, there are a lot of hammer marks on the surface of the hammered parts, which fails to meet the technical requirements, affects the quality of industrial fans, and leveling by manual hammering. It requires high technical level of sheet metal workers, labor and The problem of high labor intensity, for a long time, the problem of fan blade aluminum milling has become a technical point for industrial fan manufacturers.
In order to solve the problem of fan blade aluminum plate milling, we can carry out pre-stretching test on aluminum plate according to process requirements.
There are residual internal stresses in the rolled industrial fan aluminum plate. During the rolling process of the plate, the surface temperature is lower than the center temperature, and the surface temperature is lower than the center temperature, and the surface layer is blocked by the roller friction, so that the plate has residual internal stress after the rolling process is completed. After the heat treatment process is completed, the surface is colder than the center. The surface cools and shrinks first. The surface generates compressive stress on the center. The center resists surface shrinkage and generates tensile stress on the surface. Therefore, rolled and quenched plates After removing a part of the material through mechanical processing or chemical milling, the original internal stress balance state of the plate is destroyed, and the plate is deformed. The way to solve this problem is to pre-stretch the aluminum plate.
The so-called pre-stretched plate is to apply a single-direction external force to both ends of the quenched plate and pull it to cause a small amount of plastic deformation of the plate to eliminate or reduce the original residual stress of the plate and make it uniform. .
During the fan blade aluminum sheet stretching process, the stress and strain at each point on the sheet are changed according to the stress-strain curve of the secondary deformation. When the stress is less than the yield limit, the stress and strain are linear. When the stress is greater than a fixed value, the stress and strain no longer change in a linear relationship, and the stress increment foot decreases as the strain increases. Therefore, under the action of tensile force, part of the original residual stress first enters the yield zone. With the increase of the strain, the internal stress (tensile stress) distribution at each point in the sheet is gradually uniformed, the tensile deformation continues to increase, and the points of the original residual stress in the sheet become the tensile stress. When they are all larger than a fixed value, the tensile stress distribution of the plate is basically uniform. With the quenched plate inverted, the residual stress can be eliminated after the plate elastically shrinks when the external load is removed.
From the above analysis, it can be seen that during the manufacturing process of industrial fan blades, the deformation is caused by the residual stress in the quenched sheet. After chemical milling, the original stress equilibrium state of the sheet is destroyed, causing the aluminum sheet to deform. Secondly, when rolling and leveling, the residual stress in the plate can cause warping deformation of the part. Therefore, the deeper the chemical milling, the more severe the bending deformation after chemical milling.