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Aluminum

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What is aluminum

Aluminum (symbol Al in the periodic table) is a lightweight, silvery-white metal with good electrical and thermal conductivity. It is the most abundant metal element in the earth’s crust, accounting for about 8.2% of the total mass of the earth’s crust. Aluminum has an atomic number of 13 and belongs to Group 13 (IIIA) in the periodic table. It is a typical amphoteric metal that can react under both acidic and alkaline conditions.

Discovery of aluminum

Aluminum was discovered later than other metals. In 1808, British chemist Sir Humphry Davy confirmed the existence of alum and called the aluminum in it (Alumium was later changed to Aluminum). In 1825, Danish chemist and physicist Hans Oss began to experiment with aluminum extraction. It was not until 1827 that Friedrich Wöhler used potassium metal to reduce molten anhydrous aluminum chloride to obtain a relatively pure metallic aluminum element.

Characteristics of aluminum and aluminum alloys

A. Low density

The density of aluminum is 2.7g/cm³ (one-third of the density of iron and copper), with good ductility and conductivity of two-thirds of copper wire, but only one-third of its mass. It is cheaper and is widely used in the manufacture of high-voltage wires, cables, and radio industries. The density of pure aluminum is relatively low, but the density and hardness of aluminum alloys have been greatly improved. At present, aluminum alloys have been widely used in manufacturing industries such as aircraft, automobiles, trains, and ships. In addition, space rockets, space shuttles, and artificial satellites also use a large amount of aluminum and its aluminum alloys.

B. Thermal conductor

Aluminum is a good conductor of heat (its thermal conductivity is 3 times greater than that of iron). Aluminum can be used in industry to manufacture various heat exchangers, heat dissipation materials, and cookware.

C. Ductility

In the air, a dense oxide protective film will form on the surface of aluminum, making it corrosion-resistant. Therefore, it is often used to manufacture medical equipment, chemical reactors, refrigeration equipment, petroleum refining equipment, oil and gas pipelines, etc.

D. Low temperature resistance

Low temperature resistance. When the temperature is low, the strength of aluminum increases instead of being brittle. Therefore, it is an ideal material for low temperature devices, such as cold storage, freezer, Antarctic snow vehicle, and hydrogen peroxide production equipment.

E. Reflectivity

Aluminum sheet also has good light reflection performance, and it reflects ultraviolet rays more strongly than silver. The purer the aluminum, the better its reflective ability. Therefore, it is often used to make high-quality reflectors, such as solar cooker reflectors.

Classification of aluminum alloys

By processing methods, aluminum alloys can be classified into:

Casting aluminum alloys

Casting aluminum alloys are a type of aluminum alloys designed specifically for casting processes. These alloys have a specific composition so that they can be poured into a mold in a molten state and formed into parts of the desired shape after cooling and solidification. Casting aluminum alloys are widely used in multiple industries due to their excellent characteristics.

Casting aluminum alloys are generally cast using lost film casting, which has high precision and smooth surface.

Casting aluminum alloy products are generally accompanied by a series of machining and surface treatment processes after casting, such as CNC Turning Process, CNC Milling Process, Anodized, polished, etc.

Characteristics of cast aluminum alloys:

Low density: Compared with other metals, cast aluminum alloys have a lower density, which means they are relatively light.

High specific strength: Despite the low density, these alloys still have high strength.

Good corrosion resistance: A dense oxide layer naturally forms on the surface of aluminum, providing good corrosion protection.

Good casting processability: The design of cast aluminum alloys allows them to flow well during the casting process, fill complex shaped molds, and are not prone to cracks or holes after cooling.

Design flexibility: Due to the flexibility of the casting process, complex geometries can be produced, which is very beneficial for part design.

Chemical composition of cast aluminum alloys

Designation Si,% Cu,% Mn,% Mg,% Zn,% Ti,% Others,%
201.0 0.1 max. 4.0-5.2 0.2-0.5 0.15-0.55 0.15-0.35 Ag 0.4-1.0
208.0 2.5-3.5 3.5-4.5 0.5 max. 0.1 max. 1.0 max. 0.25 max.
222.0 2.0 max. 9.2-10.7 0.5 max. 0.15-0.35 0.8 max. 0.25 max.
333.0 8.0-10.0 3.0-4.0 0.5 max. 0.05-0.5 1.0 max. 0.25 max.
356.0 6.5-7.5 0.25 max. 0.35 max. 0.2-0.45 0.35 max. 0.25 max.
413.0 11.0-13.0 1.0 max. 0.35 max. 0.1 max. 0.5 max.
443.0 4.5-6.0 0.6 max. 0.5 max. 0.05 max. 0.5 max. 0.25 max.
514.0 0.35 max. 0.15 max. 0.35 max. 3.5-4.5 0.15 max. 0.25 max.
518.0 0.35 max. 0.25 max. 0.35 max. 7.5-8.5 0.15 max.
705.0 0.2 max. 0.20 max. 0.4-0.6 1.4-1.8 2.7-3.3 0.25 max. Cr 0.2-0.4
713.0 0.25 max. 0.4-1.0 0.6 max. 0.2-0.5 7.0-8.0 0.25 max.
852.0 0.4 max. 1.7-2.3 0.1 max. 0.6-0.9 0.25 max. Sn5.5-7.0, Ni0.9-1.5

Application of cast aluminum alloys

Cast aluminum alloys are widely used in many industries due to their good casting properties, low density, high specific strength and good corrosion resistance. The following are some of the main application areas of cast aluminum alloys:

Automotive industry

  • Engine parts: cylinder block, cylinder head, piston, etc.
  • Transmission system: gearbox housing, clutch housing, differential housing, etc.
  • Suspension system: steering housing, shock absorber housing, etc.
  • Body parts: wheels, frames, brake system components (such as brake calipers, cylinders and brake discs), etc.

Aviation industry

  • Structural parts: beams, frames, stringers, etc.
  • Engine parts: casing, turbine blades, etc.
  • Auxiliary systems: pump body, bracket, wheel hub, etc.

Machinery and instrumentation

  • Casing: used to protect internal components from external factors.
  • Supercharger pump body: pump body manufacturing for supercharging system.

Other industrial applications

  • Gas turbine: blades and other high-temperature parts.
  • Pump body: the outer shell of a pump used for liquid transportation.
  • Pendant: a bracket used to fix or hang various devices.
  • Inlet lip: The component used to guide air into the engine.

Rolled aluminum alloys

Rolled aluminum alloys refer to aluminum alloy products that are processed by the rolling process. Rolling is a metal forming process in which the metal is compressed between a pair of rotating rollers to change its shape. For aluminum alloys, this process can turn it into sheets, strips, foils, tubes, bars or wires. Rolled aluminum alloys are widely used in many industries, including aerospace, automotive, construction, packaging and electrical.

Classification of rolled aluminum alloys

  • Plate, strip, foil: These are the most common rolled aluminum alloy products, accounting for more than 80% of the total output of rolled aluminum. Plates and strips have a large width-to-thickness ratio and can be further processed into various components.
  • Tubes, bars, wires: These products are also produced by rolling methods. Although they are not as common as plates and strips, they are very important in specific applications.

Rolling process:

  • Hot rolling: It is carried out at a higher temperature to reduce the hardness of the material and increase its plasticity for easy forming. Hot rolling is generally used to process aluminum alloys from thicker billets into thinner plates or strips.
  • Cold rolling: It is carried out at room temperature or below the recrystallization temperature. The thickness can be reduced and the hardness and strength of the material can be increased through multiple rolling. Cold rolling can improve the surface finish and dimensional accuracy of the product.

Applications of rolled aluminum alloys

  • Aerospace: used to manufacture aircraft structural parts, skins, wing beams, etc.
  • Automotive industry: used to manufacture body panels, engine hoods, trunk lids, etc.
  • Construction industry: used for door and window frames, roofing materials, decorative materials, etc.
  • Packaging materials: used for beverage cans, food packaging foils, etc.
  • Electrical industry: used to manufacture the outer skin of wires and cables, etc.

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