The 3000 series alloy aluminum plate is an alloy aluminum plate with Mn as the main alloying element, and belongs to a heat-treated non-reinforced alloy aluminum plate. It has high plasticity, good welding performance, high strength compared with 1000 series alloy aluminum plate, and corrosion resistance is similar to 1000 series alloy aluminum plate. It is a medium strength alloy aluminum plate with good corrosion resistance. It has wide application and large dosage.
The role of alloying elements and impurity elements in 3000 series alloy aluminum plates
Mn: Mn is the only main alloying element in the 3000 series alloy aluminum plate. Its content is generally in the range of 1.0% to 1.6%. The strength, plasticity and processability of the alloy are good. Mn and Al can form MnAl6 phase. The strength of the alloy increases with the increase of Mn content. When the Mn content is higher than 1.6%, the strength of the alloy increases, but due to the formation of a large amount of brittle compound MnAl6, the alloy is prone to cracking when deformed. As the Mn content increases, the recrystallization temperature of the alloy increases accordingly. Because of its large supercooling ability, the alloy produces large intragranular segregation during rapid cooling crystallization. The concentration of Mn is low in the center of the dendrite and high in the edge, when the cold processed product is obvious. When Mn is segregated, coarse crystal grains are easily formed after annealing.
Fe: Fe can be dissolved in MnAl6 to form a (FeMn)Al6 compound, thereby reducing the solubility of Mn in Al. 0.4%~0.7% Fe is added to the alloy, but Fe+Mn is guaranteed to be no more than 1.85%, which can effectively refine the grain after annealing of the sheet. Otherwise, a large amount of coarse FeMn Al6 compound will be formed. Significantly reduce the mechanical properties and process properties of the alloy.
Si: Si is a harmful impurity. Si and Mn form a complex ternary phase T (Al12Mn3Si2), which also dissolves Fe to form a (AlFeMnSi) quaternary phase. If Fe and Si exist in the alloy at the same time, the α(Al12Mn3Si2) or β(Al9Fe 2Si2) phase is formed first, which destroys the strong influence of Fe, so the Si in the alloy should be controlled below 0.6%. Si also reduces the solubility of Mn in Al and is more affected than Fe. Fe and Si can accelerate the decomposition process of Mn from supersaturated solid liquid during thermal deformation, and can also reduce some mechanical properties.
Mg: A small amount of Mg (≈0.33%) can refine the grain of the alloy after annealing and slightly increase the tensile strength, but also damage the surface gloss of the annealed material. Mg may also be an alloying element in an Al-Mg alloy, and 0.3% to 1.3% of Mg is added, the strength of the alloy is increased, and the elongation (annealing state) is lowered, so that an Al-Mg-Mn alloy is developed.
Cu: The alloy contains 0.05% to 0.5% of Cu, which can significantly increase its tensile strength. However, a small amount of Cu (0.1%) can reduce the corrosion resistance of the alloy, so the Cu content in the alloy should be controlled below 0.2%.
When the content of Zn:Zn is less than 0.5%, the mechanical properties and corrosion resistance of the alloy are not significantly affected. The weldability of the alloy is controlled to be less than 0.2%.