1. Melting and Casting: This is the initial step in aluminum sheet processing. First, aluminum ingots and other alloying elements are placed in a furnace in a specific proportion for smelting. High temperatures allow for thorough melting and uniform mixing. During the smelting process, parameters such as temperature, time, and furnace atmosphere must be strictly controlled to ensure uniform distribution of alloy components and melt quality. After smelting, the melt is poured into specific molds for casting, forming ingots of various shapes, most commonly flat and round. These ingots serve as billets for subsequent processing.
2. Rolling: Rolling is a key step in aluminum sheet processing. The ingots are subjected to pressure processing in a rolling mill, gradually thinning them to the desired thickness and width. The rolling process consists of two stages: hot rolling and cold rolling. Hot rolling is performed at higher temperatures, generally between 400 and 500°C. Hot rolling breaks down coarse grains in the ingot, improves the metal's microstructure, and enhances the aluminum sheet's plasticity and workability. The thickness of the aluminum sheet after hot rolling typically ranges from a few millimeters to several dozen millimeters. Cold rolling is performed at room temperature. Its primary purpose is to further improve the dimensional accuracy and surface quality of aluminum sheet, reduce thickness tolerances, and achieve a smoother surface. Cold rolling can also adjust the sheet's mechanical properties, such as strength and hardness, by controlling rolling process parameters.
3. Extrusion: The extrusion process involves placing a billet into the die cavity of an extruder and applying strong pressure to force it through a specific die pattern, resulting in various profiles. Extrusion is suitable for producing aluminum sheet products with complex shapes and irregular cross-sections, such as architectural door and window frames and industrial special-shaped pipes. During the extrusion process, the metal is subjected to triaxial compressive stress within the die, which helps improve its plasticity and produce products with high dimensional accuracy and excellent surface quality.
4. Stretching: Stretching involves stretching aluminum sheet in a stretching machine. The tensile force causes plastic deformation, thereby changing the sheet's shape and size. Stretching can be used to manufacture pipes, bars, and some special-shaped components. During the stretching process, parameters such as the stretching speed and force must be properly controlled to ensure product quality and precision. Furthermore, the stretched aluminum sheet may experience work hardening, requiring appropriate heat treatment to eliminate internal stresses and restore its plasticity.
5. Forging: Forging is a processing method that applies pressure to the aluminum sheet, causing it to plastically deform to achieve the desired shape and properties. The forging process can further refine the aluminum sheet's grain structure, improving its strength, toughness, and fatigue resistance. Forged aluminum sheet is often used to manufacture components subject to high loads and complex stresses, such as aircraft engine blades and key automotive components. The forging process is divided into two methods: open-die forging and die forging. Open-die forging involves forging the blank between upper and lower anvils, offering flexibility but lower production efficiency. Die forging, in which the blank is placed in a die and forged, can produce products with complex shapes and high dimensional accuracy, offering relatively high production efficiency.
6. Surface Treatment: Surface treatment is often required to enhance the aluminum sheet's corrosion resistance, decorative properties, and other properties. Common surface treatment methods include anodizing, electrophoretic coating, and powder coating. Anodizing involves using an aluminum plate as the anode and performing electrolysis in a specific electrolyte to form a thin film of aluminum oxide on the surface. This film exhibits excellent corrosion resistance, wear resistance, and adsorption properties, and can be dyed to impart various colors to the aluminum plate. Electrophoretic coating involves immersing the aluminum plate in an electrophoretic tank containing paint particles. The electric field causes the paint particles to be evenly deposited on the surface of the aluminum plate, forming a dense coating. The electrophoretic coating exhibits excellent weather resistance, water resistance, and adhesion. Powder coating involves applying dry powder paint to the aluminum plate using a spray gun and then curing it through heat to form a solid coating. Powder coatings offer advantages such as rich colors, wear resistance, and stain resistance.
