In aluminum series processing back plate production, flatness control must be implemented throughout the entire process, including raw material selection, rolling technology, straightening, stress relief, structural reinforcement design, installation, and storage and transportation. Each step requires strict control to achieve high-precision flatness.
The quality of raw materials is the primary prerequisite for controlling flatness. The aluminum alloy grade and condition must be scientifically selected based on the mechanical performance requirements of the final product, the processing method, and the usage environment. For example, 3-series aluminum-manganese alloys (such as 3003) are commonly used for building exterior walls due to their excellent rust resistance; 5-series aluminum-magnesium alloys (such as 5052) have strong corrosion resistance and are suitable for coastal environments; 6-series aluminum-magnesium-silicon alloys (such as 6061) balance strength and processing performance and are widely used in the aerospace field. Simultaneously, the thickness accuracy and uniformity during the hot and cold rolling processes of ingot casting must be strictly monitored to avoid uneven stress distribution during subsequent processing due to thickness deviations.
The rolling process is the core element in controlling plate shape and flatness. During cold rolling, it is crucial to ensure that the surface finish and cylindricity of the work rolls and support rolls meet extremely high precision requirements. Rolling force and tension must be precisely set using AGC (Automatic Thickness Control) and AFC (Automatic Shape Control) systems. Stable tension is key to flattening the aluminum sheet; tension fluctuations can lead to localized yielding or uneven elongation, creating potentially uneven areas. Furthermore, rolling speed and lubrication conditions must be kept stable to prevent localized deformation caused by speed variations or insufficient lubrication.
The straightening process is a critical step in eliminating internal stress in the rolled sheet. For aluminum series processing-back plates of varying thicknesses and widths, a tension straightener, a precision roll straightener, or a combination of both must be selected. Tension straightening eliminates internal stress and deformation by applying tensile force close to the material's yield strength; roll straightening corrects deformation through repeated bending using staggered straightening rolls. Straightening process parameters, such as tension value, straightening speed, and roll gap, must be precisely set according to the sheet characteristics to avoid secondary deformation due to improper parameters.
Stress relief processes are crucial for hard or semi-hard aluminum series processing back plates. Annealing after precision straightening requires a forced hot air circulation or protective atmosphere furnace to strictly ensure uniform temperature distribution within the furnace, preventing uneven stress release due to temperature differences. Holding time and cooling rate must also be precisely controlled according to the alloy grade and thickness to ensure complete stress release while avoiding grain coarsening.
Strengthening structural design is an effective means of improving the flatness of large-size aluminum series processing back plates. For ultra-large and ultra-long aluminum plates, structural strength needs to be improved by increasing the flange width, thickening the plate, increasing the size of reinforcing ribs, and densifying their distribution. Reinforcing ribs must be effectively and securely connected to the aluminum plate flanges and panels, and their cross-sectional dimensions and distribution distances must meet structural calculation and specification requirements. Furthermore, the aluminum plate's own shape and structure (such as hyperboloid shapes) can also improve flatness by optimizing stress distribution.
The installation process significantly affects the final flatness of the aluminum series processing back plate. The installation of the keel must ensure horizontal and vertical alignment. Longer keels must be corrected for deformation before installation, and rubber gaskets should be used to level the flat surface. Sufficient space must be allowed between the aluminum plate and the keel for thermal expansion and contraction to prevent dents at nail points due to temperature changes. A trial installation should be conducted beforehand; if uneven surfaces are found on the keel, leveling should be done immediately using shims.
Proper handling during storage and transportation is the last line of defense for ensuring the flatness of the aluminum series processing-back plate. Finished aluminum series processing-back plates must be stacked flat in a temperature- and humidity-controlled warehouse, away from heat sources, strong airflows, and vibration environments to prevent deformation due to gravity or uneven ground. During transportation, sturdy and reliable packaging racks should be custom-made, filled with moisture-proof and cushioning materials, and secured with high-strength straps to prevent damage from movement during transport.
