What is pure aluminum?
Pure aluminum is generally defined as aluminum with a purity of 99.0% to 99.9%, and China is defined as aluminum with a purity of 98.8% to 99.7%. Chinese processing industry pure aluminum grades are 1080, 1080A, 1070, 1070A(L1), 1370, 1060(L2), 1050, 1050A(L3), 1A50(LB2), 1350, 1145, 1035(L4), 1A30(L4- 1), 1100 (L5-1), 1200 (L-5), 1235, etc. Iron and silicon are its main impurities and increase according to the number of grades.
The structure of pure aluminum
Industrial pure aluminum can be regarded as an aluminum-iron-silicon alloy with very low content of iron and silicon. In the impurity phase, in addition to acicular hard and brittle FeAl3 and massive hard and brittle silicon particles, two ternary phases can also be formed. When Fe>Si, α(Fe2SiAl8) phase is formed; when Si>Fe, The β(FeSiAl5) phase is formed. Both phases are brittle compounds, the latter being more harmful to plasticity. Therefore, Fe>Si is generally used in industrial pure aluminum. When Fe>Si, it can also narrow the crystallization temperature range and reduce the tendency of casting cracks. When Fe/Si ≥ 2~3, industrial pure aluminum sheets with fine grains and good stamping properties can be produced. It should be pointed out that iron and silicon mostly exist in the form of ternary compounds in industrial pure aluminum, and there are few opportunities for FeAl3 and free silicon to appear.
Industrial pure aluminum has the general characteristics of aluminum, low density, good electrical and thermal conductivity, good corrosion resistance, good plastic processing performance, can be processed into plates, strips, foils and extruded products, etc. spot welding.
Industrial pure aluminum cannot be strengthened by heat treatment, and its strength can be improved by cold deformation. The only form of heat treatment is annealing. The starting temperature of recrystallization is related to the impurity content and degree of deformation, generally around 200 °C. σb=80～100MPa of annealed sheet, σ0.2=30～50MPa, ζ=35%～40%, HB=25～30. After 60%~80% cold deformation, although it can be increased to 150~180MPa, the ζ value has dropped to 1%~1.5%. Increasing the content of iron and silicon impurities can improve the strength, but reduce the plasticity, electrical conductivity and corrosion resistance. The mechanical properties of different cold work hardening states can be obtained by adjusting the annealing temperature after cold deformation or by controlling the amount of cold deformation after annealing.
Types of Pure aluminum
(1) 1A50 industrial pure aluminum
Features and scope of application: It is industrial pure aluminum, with high plasticity, corrosion resistance, electrical conductivity and thermal conductivity, but low strength, heat treatment can not strengthen the machinability; gas welding, hydrogen atom welding and contact welding, not easy to braze Welding; easy to withstand various pressure processing and extension, bending.
Aluminum Al: 99.50
Silicon Si: ≤0.25
Copper Cu: ≤0.05
Magnesium Mg: ≤0.05
Manganese Mn: ≤0.05
Titanium Ti: ≤0.05
Iron Fe: 0.000-0.400
Note: Single: ≤0.03
Tensile strength σb (MPa): ≤137
Elongation δ10 (%): ≤3
(2) 1A99 industrial pure aluminum
Silicon Si: 0.003
Iron Fe: 0.003
Copper Cu: 0.003
Aluminum Al: 99.99
Tensile strength σb/(MPa): 35-100
Elongation (δ10/%): ≥0.5