In production practice, suitable production methods can be selected according to the specific conditions of alloy composition, variety, specification, use, quantity and quality requirements, market demand, equipment configuration and national conditions.
Aluminum alloy tubes can be divided into seamless aluminium tubes according to extrusion mode, and aluminium alloy tubes can be divided into ordinary aluminium tubes and Thin-walled Aluminium tubes according to thickness: corrosion resistance and light weight.
Aluminum alloy tubes are widely used in all walks of life, such as automobiles, ships, aerospace, aviation, electrical appliances, agriculture, electromechanical, household and so on. Aluminum tubes are everywhere in our life.
Aluminum alloy tubes are divided into square tubes, circular tubes, pattern tubes and special-shaped tubes according to their accuracy: ordinary aluminium tubes and precise aluminium tubes. Among them, precise aluminium tubes need to be reprocessed after extrusion, such as cold drawing, fine drawing and rolling.
The eight major elements affecting the properties of aluminium alloys are: vanadium, calcium, lead, tin, bismuth, antimony, beryllium and sodium. According to the different uses of finished products, the elements added in the process of processing are different because of the different melting points, different structures and the compounds formed by aluminium, so the effects on the properties of aluminium alloys are also different.
1. Metal Elements: The Effect of Copper Elements铜是重要的合金元素，有一定的固溶强化效果，此外时效析出的CuAl2有着显著的时效强化效果。铝板中铜含量通常在2.5%-5%，铜含量在4%-6.8%时强化效果最好，所以大部门硬铝合金的含铜量处于这范围。
Copper is an important alloy element, which has a certain solid solution strengthening effect. In addition, CuAl2 precipitated during aging has a significant aging strengthening effect. The copper content in aluminium sheet is usually 2.5% - 5%, and the copper content is 4% - 6.8%. Therefore, the copper content of most hard aluminium alloys is in this range.
2. Metal Elements: The Effect of Silicon ElementsAl-Mg2Si合金系合金平衡相图Mg2Si在铝中的最大溶解度为1.85%，且随温度的降低而减速小，变形铝合金中，硅单独加入铝板中只限于焊接材料，硅加入铝中亦有一定的强化作用。
The maximum solubility of Mg2Si in Al-Mg2Si alloy equilibrium phase diagram is 1.85%, and decreases with the decrease of temperature. In deformed aluminum alloy, the addition of silicon to aluminum plate is limited to welding materials, and the addition of silicon to aluminum also has a certain strengthening effect.
3. Metal Elements: The Effect of Magnesium镁对铝的强化是显著的，每增加1%镁，抗拉强度大约升高34MPa。假如加入1%以下的锰，可能增补强化作用。因此加锰后可降低镁含量，同时可降低热裂倾向，另外锰还可以使Mg5Al8化合物平均沉淀，改善抗蚀性和焊接机能。
Magnesium strengthens aluminium remarkably. The tensile strength increases by about 34 MPa for every 1% increase of magnesium. If less than 1% manganese is added, the strengthening effect may be added. Therefore, manganese can reduce magnesium content and hot cracking tendency. In addition, manganese can also make Mg5Al8 compound precipitate averagely, improve corrosion resistance and welding function.
4. Metal Elements: The Effect of Manganese锰在固溶体中的最大溶解度为1.82%。合金强度随溶解度增加不断增加，锰含量为0.8%时，延伸率达最大值。Al-Mn合金长短时效硬化合金，即不可热处理强化。
The maximum solubility of manganese in solid solution is 1.82%. The strength of the alloy increases with the increase of solubility. When the content of manganese is 0.8%, the elongation reaches the maximum. Al-Mn alloy can harden for long and short time, i.e. it can not be strengthened by heat treatment.
5. Metal Elements: The Effect of Zinc
The solubility of zinc in aluminium in equilibrium phase figure 275 of Al-Zn alloy system is 31.6%, while it decreases to 5.6% at 125. When zinc is added to aluminium alone, the progress of strength of aluminium alloy is limited under the condition of deformation. At the same time, stress corrosion cracking and tendency exist, which limits its application.
6. Metal Elements: Effects of Iron and Silicon铁在Al-Cu-Mg-Ni-Fe系锻铝合金中，硅在Al-Mg-Si系锻铝中和在Al-Si系焊条及铝硅锻造合金中，均作为合金元素加的，在其它铝合金中，硅和铁是常见的杂质元素，对合金机能有显著的影响。它们主要以FeCl3和游离硅存在。在硅大于铁时，形成β-FeSiAl3（或Fe2Si2Al9）相，而铁大于硅时，形成α-Fe2SiAl8（或Fe3Si2Al12）。当铁和硅比例不当时，会引起铸件产生裂纹，铸铝中铁含量过高时会使铸件产生脆性。
In Al-Cu-Mg-Ni-Fe forged aluminium alloys, silicon is added as alloying elements in Al-Mg-Si forged aluminium alloys, Al-Si welding rods and Al-Si forged alloys. Among other aluminium alloys, silicon and iron are common impurity elements, which have a significant effect on the function of the alloys. They mainly exist in FeCl3 and free silicon. When silicon is larger than iron, the phase of beta-FeSiAl3 (or Fe2Si2Al9) is formed, while when iron is larger than silicon, the phase of alpha-Fe2SiAl8 (or Fe3Si2Al12) is formed. When the ratio of iron to silicon is not appropriate, cracks will occur in the castings. When the iron content in the cast aluminum is too high, brittleness will occur in the castings.
7. Metal Elements: Effects of Titanium and Boron钛是铝合金中常用的添加元素，以Al-Ti或Al-Ti-B中间合金形式加入。钛与铝形成TiAl2相，成为结晶时的非自发核心，起细化锻造组织和焊缝组织的作用。Al-Ti系合金产生包反应时，钛的临界含量约为0.15%，假如有硼存在则减速小到0.01%。
Titanium is a common addition element in aluminium alloys, which is added in the form of Al-Ti or Al-Ti-B master alloys. TiAl2 phase is formed between titanium and aluminium, which becomes the non-spontaneous core during crystallization and refines the forging structure and weld structure. The critical content of titanium in Al-Ti alloy is about 0.15% when cladding reaction occurs. If boron exists, the reduction is less than 0.01%.
Chromium forms intermetallic compounds (CrFe) Al7 and (CrMn) Al12 in aluminium sheet, which hinder the recrystallization nucleation and growth process. It has a certain strengthening effect on the alloy, and can also improve the toughness and reduce the stress corrosion cracking sensitivity of the alloy. However, with the increase of quenching sensitivity, the anodic oxide film becomes yellow, and the addition of chromium in aluminium alloys generally does not exceed 0.35%, which decreases with the increase of transition elements in the alloys.
The addition of 0.015%-0.03% strontium to the aluminium alloy for extrusion can change the beta-AlFeSi phase in the ingot into Chinese alpha-AlFeSi phase, reduce the average time of the ingot by 60%-70%, improve the mechanical function and plastic workability of the material, and improve the roughness of the surface of the product. For high silicon (10%-13%) wrought aluminium alloy, adding 0.02%-0.07% strontium element can reduce the primary crystallization to the minimum, and improve the mechanical properties. Tensile strength B increases from 233 MPa to 236 MPa, yield strength 0.2 increases from 204 MPa to 210MPa, and elongation increases from 9% to 12%. The addition of Strontium in hypereutectic Al-Si alloy can reduce the size of primary silicon particles, improve the plastic processing function, and smooth hot and cold rolling.