I. Material parameters
1. Basic Properties of Aluminum
Aluminum is silvery white and can form a protective oxide film in moist air to prevent corrosion of the metal. It has a relative density of 2.7g/cm 3 , a melting point of 660°C, a boiling point of 2327°C and is light. It also has good electrical and thermal conductivity, high reflectivity and resistance to oxidation.
2. Related Properties of Aluminum
① Density
Aluminum has a small density, only 2.7g/cm, although it is relatively soft, it can be made into various aluminum alloys, such as hard aluminum, super-hard aluminum, rust-proof aluminum, cast aluminum, etc. Widely used in the manufacturing industries of airplanes, cars, trains, ships, etc.
② Thermal Conductivity
Aluminum is a good conductor of heat, its thermal conductivity is three times greater than that of iron. In industry, aluminum can be used to manufacture various heat exchangers, heat dissipation materials and kitchen utensils, etc.
③ Ductility
It has good ductility (its ductility is second only to gold and silver) and can be made into aluminum foil thinner than 0.01mm at 100℃~150℃. These aluminum foils are widely used for packaging cigarettes, candy, etc., and can also be made into aluminum wires, aluminum bars, and can be rolled into various aluminum products.
④ Electrical Conductivity
It is second only to silver and copper. Although its conductivity is only 2/3 of that of copper, its density is only 1/3 of that of copper. Therefore, to transmit the same amount of electricity, the mass of aluminum wire is only half that of copper wire. The oxide film on the surface of aluminum not only has the ability to resist corrosion, but also has a certain insulating property. Therefore, aluminum has a wide range of uses in the electrical manufacturing industry, the wire and cable industry, and the radio industry.
3 . Chemical composition
Aluminum alloy shells generally use 6 series alloys, with the aluminum content generally above 80% and the vast majority between 85%-90%.
| Common aluminum alloy chemical composition table | |
| AL1 Series/Pure Aluminum | Pure Series 1 aluminum has an aluminum content greater than 99%. The series with the lowest aluminum content, such as 1050, has an aluminum content of 99.5%. The production process is relatively simple and the price is relatively cheap. It is the most commonly used series in conventional industries. |
| AL-Cu2 series/aluminum-copper alloy | Series 2 aluminum alloy represents 2024, 2A12 (i.e. LY12). Series 2 aluminum plate is characterized by high hardness, very high strength and good cutting processability, but low corrosion resistance. Among them, the copper element content is the highest, about 3-5%. Series 2 aluminum material belongs to aviation aluminum material and the price is relatively high. |
| AL-Mn3 series/aluminum-manganese alloy | 3 series aluminum alloy mainly represents 3003 and 3A21. Series 3 is mainly composed of manganese, with a content between 1.0-1.5. It is a series with good rust prevention ability, used to process parts that require good formability, high corrosion resistance and good weldability. |
| AL-Mg5/ Aluminum-Magnesium Alloy | 5 series aluminum alloy represents 5052, 5083 and 5A06. 5 series aluminum is one of the most commonly used aluminum alloy plate series, with magnesium as the main element and a magnesium content between 3-5%. It may also be referred to as an aluminum-magnesium alloy. Its main characteristics are low density, high tensile strength, high elongation, good fatigue resistance, but it cannot be heat treated for strengthening. In the same area, the weight of aluminum-magnesium alloy is smaller than other series and is widely used in conventional industries. |
| AL-Mg-Si6/ Aluminum-magnesium-silicon alloy | Series 6 aluminum alloy represents 6061, 6063 and 6082, mainly containing magnesium and silicon elements. Series 6 is a heat treatable reinforcing alloy with good formability, weldability and machinability, and also has medium strength. After annealing, it can still maintain good operability, suitable for applications with high corrosion resistance and oxidation requirements. It has good usability, is easy to coat and has good processability. |
| AL-Zn7/aluminum-zinc alloy | Series 7 aluminum alloy represents 7075, mainly containing zinc elements. It also belongs to the aviation series, is an aluminum-magnesium-zinc-copper alloy, is a heat treatable alloy, belongs to the super-hard aluminum alloy, and has good wear resistance. It also has good weldability, but low corrosion resistance. Among this series, 7075-T651 aluminum alloy is particularly superior, known as the best aluminum alloy product, with high strength, far superior to any carbon steel. This alloy also has good mechanical properties and anodic reactions. |
In terms of industrial aluminum profiles, the most commonly used materials at present are materials 6063 and 6061. These two aluminum alloy materials are the most widely used in industrial aluminum materials. 6063 is softer, has better cutting and processing performance, especially in surface treatment, it is better than 6061, so this material should be chosen for making aluminum shells.
01 Chemical Composition of Aluminum Alloy 6063
- Al: remaining
- Si: 0.20~0.60
- Cu: 0.10
- Mg: 0.45~0.9
- Zn:0.10
- Mn:0.10
- Ti:0.10
- Cr:0.10
- Fe:0.35
Single: 0.05 Total: 0.15
02 Hardness of 6063 aluminum alloy
Between 8-12HW, tensile strength ≥205mpa, yield stress ≥170mpa, elongation rate ≥7%.
03 Features of 6063 aluminum alloy profile
Accurate dimensions, high strength, after oxidation coloring and spray surface treatment, the appearance is smooth, beautiful, elegant in color, comfortable to the touch, and has good corrosion resistance.
Profile wall thickness: Conforms to GB5237.1~5237.6-2004, GB/T6892 standards
Performance indicators: complies with GB5237.1~5237.6-2004, GB/T6892 standards
II. Aluminum Alloy Shell Classification Parameters
01 Aluminum Shell Adapter
It has played a notable role in reducing consumer costs, saving social resources and reducing electronic waste. However, some issues arose during the implementation of this standard, such as some adapter casings not supporting USB charging. Applying this pattern may cause damage to the voltage regulator and a decrease in connection rate during charging.
02 Aluminum power supply
Generally, the shell is made of plastic rubber, which can provide insulation. The quality of the shell is also related to consumer safety. A high-quality housing can provide good insulation and waterproofing, while a low-quality housing can not only affect the normal use of the machine, but also endanger consumer safety. So which power supply is safest? The answer is, without a doubt, a shell made from guaranteed, high-quality materials.
03 Waterproof power supply casing
Mainly, aluminum casing is produced by injection molding of plastic materials. It has a high degree of waterproofing, is resistant, is not prone to water infiltration and can meet customer needs well.
III. Common parameters for surface treatment processes
01 Blasting
The process of cleaning and roughening the metal surface by the impact of high-speed sand flow. This aluminum part surface treatment method can give the surface of the part a certain degree of cleanliness and different roughness, improve the mechanical properties of the surface of the part, thereby increasing the fatigue resistance of the part, increasing the adhesion between it and the coating, extending the durability of the coating and facilitating the leveling and decoration of the painting.
02 Brushing
The manufacturing process of repeated scraping of lines on the aluminum plate with sandpaper. Brushing can be divided into straight line brushing, random line brushing, spiral line brushing and line brushing. The metal brushing process can clearly show every fine stroke, making the metal matte with a fine luster, giving the product a sense of fashion and technology.
03 Anodizing
This refers to the electrochemical oxidation of metals or alloys. Under specific process conditions and in the corresponding electrolyte, aluminum and its alloys form an oxide film on the aluminum product (anode) due to the effect of the applied current.
Anodizing not only solves the defects of aluminum's surface hardness and wear resistance, but also extends the service life of aluminum and improves its aesthetics. It has become an indispensable part of aluminum surface treatment and is currently the most widely used and successful process.
Anodizing is a common process used for aluminum alloy housings, where parameters related to resistance to high temperatures, ultraviolet light and oxide film are important.
1) High temperature resistance
The anodizing film has excellent insulation and heat resistance. This is because the thermal conductivity of the anodized film is much lower than that of pure aluminum. Anodized film can withstand temperatures around 1,500℃, while pure aluminum can only withstand 660℃.
The difference between anodized and non-anodized aluminum alloy lies in the chemical dissolution of the outer oxide film in contact with the electrolyte. When the rate of oxide formation on the aluminum surface gradually balances with the rate of chemical dissolution, the oxide film can reach its maximum thickness under these electrolytic parameters.
In sulfuric acid electrolyte, the higher the oxidation temperature, the greater the thermal stability of the film layer obtained. When boric acid or boric acid and glycerin are added to the sulfuric acid electrolyte, the oxidation temperature can be increased to 40°C (preferably not exceeding 39°C).
For this formula, the obtained oxide film layer will not crack at 130°C when the temperature is 29°C, and the heat resistance can reach 150°C or even higher (the test thickness of the film layer is of about 7 microns) when the temperature is 35°C. If a weak alkaline oxidation process is used, the heat resistance of its film layer is higher than that of sulfuric acid anodized film.
2) Ultraviolet Light
In international standard classifications, ultraviolet light anodizing involves surface treatment and colored metal coating. The following are the international standards organization standards for ultraviolet light anodizing:
ISO 6581:2018
Anodizing of Aluminum and its Alloys – Determination of Light and Heat Resistance of Colored Anodized Coatings
ISO 6581:2010
Anodizing of Aluminum and its Alloys – Determination of Ultraviolet and Heat Fastness of Colored Anodized Coatings
ISO 6581:1980
Anodizing of Aluminum and its Alloys – Determination of Ultraviolet Solidity of Colored Anodized Coatings
Aluminum alloys have high strength, low density, strong electrical and thermal conductivity, excellent mechanical properties and good machinability. After anodizing treatment, the surface of aluminum and its alloys can obtain a dense film layer, much thicker than the natural oxide film, which improves the corrosion resistance of the metal surface. It gives the metal a natural shine, smooth texture and beauty while producing a tough coating. Anodized aluminum surface treatment can provide any color and prevent damage from harsh weather conditions and harmful ultraviolet rays.
3) Oxide Film
The. Anodic oxide film is a two-layer structure. The inner layer is a dense and thin glass-like film of high purity alumina (Al2O3), with a thickness of about 0.01~0.05mm and high hardness. The outer layer is a hydrated alumina film (Al2O3·H2O).
B. The oxide film has many pores, which have a conical capillary shape, and the size of the pores increases from the inside to the outside. Therefore, it has excellent adsorption capacity, is easy to dye in different colors, enhancing its decorative function; It has strong adhesion to paint, making it suitable as a base coat for painting. To improve corrosion resistance, pore sealing treatment must be carried out.
w. The oxide film is an insulator. When the film thickness is 1μm, the breakdown voltage is 25V. The resistivity of pure aluminum oxide film is 109Ω/cm 2 .
d. The oxide film has excellent heat resistance and can withstand temperatures of up to 1500°C. Its thermal conductivity is lower than that of metal.
