Complete Guide to different kinds of Aluminum alloys scrap
Updated: Dec 2, 2019
In scrap industry, I realized early that there are different kinds of alloys for aluminum scrap metal and for me to understand the business properly, I would need to understand the following:
1. What are different kinds of alloys commonly used in aluminum manufacturing, hence, different kind of aluminum alloy scraps?
2. What are the differences in these alloys?
3. Why does these differences matter and where does it originate from?
4. Which purpose are these different alloys used for (hence, the final customer)?
5. What does different series numbers signify (they are not random numbers)?
I wanted to share my inputs on all the above questions in hope that others would find useful. If you like it, please feel free to share or send me your feedback.
There are 7 different alloys commonly used in aluminum manufacturing. Each series starts with a number 1-7 (1xxx, 2xxx, 3xxx, 4xxx, 5xxx, 6xxx & 7xxx). That number basically determines what alloying element has been added to the aluminum.
A very brief description of the different series is listed below:
· 1000 Series is the purest of aluminum—required to have 99% minimum aluminum. It is weldable but under narrow guidelines. Because of its superior corrosion resistance, it is mainly used in specialized chemical tanks or conductive bus bars.
· 2000 Series aluminum is mixed with copper alloys and is often used for aircraft and aerospace industries.
· 3000 Series is mixed with manganese and is very “formable” and heat treatable. This aluminum alloy is often used for cookware and heat exchangers in power plants and vehicles.
· 4000 Series mixes aluminum with silicon, allowing for a lower melting point which improves fluidity when molten (sort of a fancy way of saying it melts well). The 4000 Series aluminum is often used as filler material for welding and brazing.
· 5000 Series aluminum is mixed with magnesium (different than manganese) and has both a high tensile strength and formability; hence it is widely used in fabrication such as transportation, tanks, vessels and bridges.
· 6000 Series is mixed with magnesium and silicone and used predominately in the form of extrusions and structural components like angles, beams and tubes.
· 7000 Series is mixed with zinc alloys. It comprises very high strength aluminum and is often used in high performance applications like aircraft, aerospace and competitive sporting equipment.
The most common aluminum used in the general fabrication industry is 3000, 5000 or 6000 series alloys.
In pure form, aluminum is so soft that it cannot be used as a structural part. To increase its strength and other mechanical properties, it is normal to add various alloying elements and apply sequential heat treatments. Aluminum alloy 6061 and alloys of the 7000 series are most commonly used in the production of strong and sturdy goods. The 6061-aluminum alloy (Al-Mg-Si) contains 0.8–1.2 Mg, 0.4–0.8Si and 0.15–0.4Cu (wt%). It shows good corrosion resistance, strength and weldability. The 7000 series alloys (Al-Zn-Mg-(Cu)) have the highest strength of all aluminum alloys. The 7005 Al-4.0-5.0Zn-1.0-1.8 Mg) and 7075 (Al-5.1-6.1Zn-2.1-2.9 Mg-(1.2-2.0Cu)) alloys are used to produce frames. 7075 aluminum alloy is also widely used in the aero industry.
2000 series alloys
These were the first age-hardenable aluminum alloys; the development of their compositions, transformation schedules and heat treatments started in the 1920s.
The corrosion resistance of these alloys depends to a large extent on the heat treatment conditions: the quenching rate must be as high as possible and ageing conditions should tend towards over ageing. Otherwise, these alloys will be sensitized to intracrystalline corrosion and stress corrosion.
It has long been known that even when delivered in appropriate tempers, their susceptibility to corrosion is, in general, too high to allow their use without protection in most environments: atmosphere, water, etc. Protections commonly used are paint, cladding with 1050A, and anodizing. They are, however, not enough to compensate these alloys’ intrinsically low corrosion resistance due to their high copper content.
Selecting an alloy series
One of the first selection criteria must be regarding the alloy series, because performance and workability are quite different for strain-hardenable and age-hardenable alloys.
Alloying elements are added to wrought alloys in quantities ranging from 1 to 7% (in mass per cent), and in higher quantities, up to 20% silicon, to casting alloys. These elements are copper, magnesium, manganese, silicon, and zinc.
Some of these elements may be added simultaneously: silicon and magnesium for casting alloys of the series 40000, magnesium and silicon for wrought alloys of the 6000 series, and zinc and copper for those of the 7000 series. Alloying elements determine the common basic properties of alloys belonging to the same series.
The metallurgy of industrial aluminum alloys is, therefore, based on six systems:
aluminum–silicon (with or without magnesium),
aluminum–zinc (with or without copper).
The influence of the main alloying elements is explained in below table:
International alloy designation system
There are over 500 different aluminum alloys, and for convenience these are separated into categories called alloy series. The International Alloy Designation System (IADS) is a classification scheme that is used in most countries to categorize aluminum alloys according to their chemical composition. This system is used by the aerospace industry to classify the alloys used in aircraft. All aluminum alloys are allocated into one of eight series that are given in below table. The main alloying element(s) is used to determine into which one of the eight series an alloy is allocated. The main alloying element(s) for the different series are given in below table. The 8000 series is used for those alloys that cannot be allocated to the other series, although the principal alloying element is usually lithium.
Numbering of aluminum alloys
Each alloy within a series has a four-digit number: XXXX. The first digit indicates the series number. For example, 1XXX indicates it is in the 1000 series, 2XXX is a 2000 series alloy, and so forth. The second digit indicates the number of modifications to the alloy type. For example, with the alloy 5352 Al the second digit (3) indicates that the alloy has been modified three times, but has a similar composition to earlier versions 5052 Al, 5152 Al and 5252 Al. The last two numbers in the four-digit system only have meaning for the 1000 series alloys. In this series, the last two digits specify the minimum purity level of the aluminum. As examples, 1200 Al has a minimum purity of 99.00% and 1145 Al is at least 99.45% pure. The last two digits in the 2000 to 8000 series has no meaningful relationship to the alloy content and serves no purpose other than to identify the different alloys in a series.
When an alloy is being developed it is prefixed with an X to signify it has not yet been fully evaluated and classified by the IADS. For example, the alloy X6785 indicates it is a new 6000 series alloy that is being tested and evaluated. When the evaluation process is complete, the prefix is dropped, and the alloy is known as 6785 Al.
Most countries use the IADS to classify aluminum alloys. However, some nations use a different classification system or use the IADS together with their own system. For example, in the UK the IADS is used by the aerospace industry, although sometimes the British Standards (BS) system is also used to classify aluminum alloys. There are three principal types of specifications used in the UK: (i) BS specifications for general engineering use, (ii) BS specifications for aeronautical use (designated as the L series), and (iii) DTD (Directorate of Technical Development) specifications for specialist aeronautical applications.
Composition of aluminum alloys
1. 1000 series
2. 2000 series
3. 3000 series
4. 4000 series
5. 5000 series
6. 6000 series
7. 7000 series
8. 8000 series
**Blog Source: Wikipedia, Google, AG UNIVERSAL USA LLC.
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