Aluminum Temper information
What is an alloy?
An alloy is simply a mixture of metals melted together to form a new metal with characteristics distinct from those metals from which it is made.
What is an Aluminum Alloy?
An Aluminum alloy is an alloy primarily of pure aluminum, mixed with different alloying elements that give rise to an entire range of materials, each of which is designed to maximize a particular characteristic such as strength, ductility, formability, machinability, or electrical conductivity.
Do the different alloys have a different color or aspect?
No, they are aesthetically interchageable.
Is it necessary to specify the alloy?
Only if there is some physical characteristic of the alloy that will have some bearing on the success of the project (such as corrosion resistence) is it necessary to specify the actual alloy. Generally, the fabricator will purchase the material on the basis of shape or form, and it will arrive with the most commonly available and least expensive alloy present locally.
If there is any question of the integrity of the material in any way, the designs must be approved by an engineer, but you will be able to accept substitutions of alloys with confidence that the resulting product will be aesthetically acceptable.
What is Temper?
This is the quality of metal that describes it’s ability to spring back after it is flexed – in effect, the stiffness. It doesn’t have anything to do with how hard the metal is. Soft temper means that when it is bent, it stays bent, and it doesn’t take much force to do it. Hard temper means that when it is bent, it springs back flat, and it takes a lot of force to put a kink into it. There are several degrees of temper; Soft, 1/4 Hard, 1/2 Hard, 3/4 Hard, and Hard. All metals are subject to temper, and it is a quality of the product that is imparted at the mill. It has no impact on hardness, color, machinability or weldability. However, bending (kinking) and heating to a high temperature can remove the temper and soften the metal at that point. This is called annealing.
What about Finishing?
Finishing aluminum is a little more complex than it seems at first.
It can be polished, with an abrasive finish like #4 satin finish, or even a high polish, but the metal itself is comparatively soft, so these finishes mar easily and they are not recommended without applying a clear organic coating to protect them.
Aluminum is an extremely reactive metal. It combines instantly on contact with air to form a thin film of aluminum oxide which in turn is extremely un-reactive and protects the surface from further corrosion. This film is not really visible, but it if the metal is touched, it comes off on your hands as a black smudge. The metal does not stain or visibly corrode (except in extreme chemical envrionments like salt spray from winter street salt or exposure to seawater) but this smudging is undesirable in most environments. Having said that, there are many architectural environments in which bare aluminum extruded shapes are used with acceptable results.
The best way for a fabricator keep the silvery look of the parent metal is to abrade the surface with the abrasive finish you require, then lacquer the piece with a clear organic finish. Be sure to use an organic finish that is specifically designed for use with aluminum – conventional finishes will either react with the metal, or will not adhere correctly.
This was invented for aluminum (it also works with titanium). It is a process of dipping the aluminum into a liquid solution that contains chemicals that clear the metal surface of its coating of aluminum oxide whereupon a dye is introduced into the solution which can now penetrate the surface of the metal to some depth. The process requires a high current to pass through the metal during the process in order to fix the dye and seal the aluminum with a hard surface, so it must be done in anodizing shops and cannot be touched up on site. It produces an extremely durable tint to the metal, the color of which can be specified (and there are scores available). However, be aware that most of the anodizing colors available are meant to be used in interiors and will fade in the sunlight. There is a broad range of exterior colors available, but you must specify them as such.
This is the finish that is most common on natural-colored pre-finished aluminum sheet, available from many architectural metal suppliers. It is simply a non-dyed version of the anodizing process described above, and one of the most common methods to render large aluminum surfaces wear-resistant and corrosion resistant.
This is the extremely common method for producing the extremely durable dark “bronze” finish on architectural aluminum extrusions used in window frames. The process is identical to those above, and the color is light fast for exterior purposes. The shade of bronze can be specified from extremely light to almost black.
The same process, but not for color – it is a method for creating an extremely hard surface to any aluminum material. This is used for example for bolts, sheets that need abrasion resistance etc., or to minimize galvanic reaction between aluminum surfaces and other metals. It is not really architecturally interesting, and somewhat expensive, but has many uses in Industry. It is used in very expensive cookware to impart a hard non-stick surface to pots and pans.
Go To Aluminum Temper information
Many of the forms in which aluminum is regularly produced are available in not just a single alloy, but a number of alloys. It is not always necessary to specify the alloy in specifying the material – the fabricator will acquire the appropriate material by simply requesting from the supplier whatever form and dimensions are required and the supplier will ship the most common alloy in stock, unless directed to a particular alloy. But it is of interest that the stock finish (or “mill finish”, which is the surface finish of the material as it comes from the manufacturer) of different alloys is sometimes different between alloys (as seen in the difference in mill finish between tread plate, and brite tread plate), and the length in which the same product is available will be different for different alloys (for example, the forms of aluminum produced in the 6063 alloys are generally available in 16 to 24 foot lengths, whereas the same forms of aluminum produced in the 6061 alloys of generally in 12 foot lengths, and so on).
A low strength but very workable alloy with excellent corrosion resistance. It is not heat treatable. It is easily welded, however it is soft, and spalls when machined.
1100-O: Annealed (or “soft”, bendable condition)
1100-H14: Strain hardened
A free machining, heat treatable alloy, with fair corrosion resistance, but not very easily welded.
2011-T3: Heat treated, cold worked and naturally aged
Heat treatable with high strength, good machinability and fair corrosion resistance. It welds very poorly.
2024-O: Annealed (or “soft”, bendable condition)
2024-T3: Heat treated, cold worked and naturally aged
2024-T351: Heat treated, cold worked and naturally aged
This alloy is not heat treatable but welds very well and has very good workability. Like alloy 1100 it is somewhat soft and difficult to machine.
3003-H14: Strain hardened
3003-H22: Strain hardened, partially annealed
Poor machinability, good workability and welds very well. It finishes very well, and offers excellent corrosion resistance.
5005-H34: Strain-hardened and stabilized
Strong, not heat treatable, easily welded, with excellent corrosion characteristics.
5052-O: Annealed (or “soft”, bendable condition)
5052-H32: Strain-hardened and stabilized
Very strong, not heat treatable, with excellent corrosion resistance and good weldability.
5086-H116: Strain-hardened only
5086-H32: Strain-hardened and stabilized
5086-H34: Strain-hardened and stabilized
Heat treatable, easily welded, with very good corrosion resistance and finishing characteristics. Very commonly used for architectural products
6061-O: Annealed (or “soft”, bendable condition)
6061-T4: Heat treated and naturally aged
6061-T6: Heat treated and artificially aged
6061-T65: Heat treated and artificially aged
6061-T6511: Heat treated and artificially aged
This heat treatable is specifically designed for extrusions, very popular for architectural shapes.
6063-T52: Cooled from an elevated temperature shaping process and artificially aged
High strength, excellent corrosion resistence, heat treatable, and weldable, but has poor workability.
7050-T7451: Heat treated, overaged and strengthened
Heat treatable, this alloy is the strongest and hardest aluminum alloy. It has good machining characteristics but is not very easliy welded nor is it very workable.
7075-O: Annealed (or “soft”, bendable condition)
7075-T6: Heat treated and artificially aged
7075-T651: Heat treated and artificially aged
Go To Aluminum Alloys information
Temper is a measure of a metal’s resistence to bending or kinking. It does not refer to how hard the metal is. Low temper, such as H-1 (also referred to as “1/8 Hard”), indicates a tendency to bend or kink permanently when subjected to very little force. High temper,such as H-8 or “Full Hard”, indicates a tendency to spring back upon bending.
The letters that appear after each alloy number refer to the “temper” of the alloy itself and are independent of the alloy. This means that a single alloy can be available in a variety of tempers and a variety of alloys can be available in the same temper.
F temper (as fabricated tempers)
This letter indicates that there has been no effort to control the temper of the material – you receive it “as is”.
O temper (annealed temper)
Annealing is a process of heating up metal past a critical tempurature whereby the material is relieved of the internal stresses from production or fabrication. It is the lowest temper available (the most easily bent).
W temper (solution heat treated temper)
This letter refers to metal that has undergone a specific procedure to produce a temper for a particular batch of metal in order to comply with some specific need of the customer.
H tempers (strain-hardened tempers)
This letter designates a process of stretching or compressing in order to impart a particular temper.
H_1 1/8 hard
H_2 1/4 hard
H_3 3/8 hard
H_4 1/2 hard
H_5 5/8 hard
H_6 3/4 hard
H_7 7/8 hard
H_8 Full hard
T tempers (thermally treated tempers)
These tempers are imparted by heating, quenching, or cooling in a controlled way.
T1 Cooled after being shaped to its final dimensions during a process involving a lot of heat (such as extrusion), then naturally aged to a stable condition.
T2 Cooled after being shaped to its final dimensions during a process involving a lot of heat (such as extrusion), then cold worked.
T3 Solution heat treated, cold worked and naturally aged to a stable condition.
T4 Solution heat treated and naturally aged to a stable condition
T5 Cooled after being shaped to its final dimensions during a process involving a lot of heat (such as extrusion), then artificially aged. T5 is T1 that has been artificially aged.
T6 Solution heat treated and artificially aged to a stable condition. T6 is T4 that has been artificially aged.
T7 Solution heat treated and naturally aged past the point of a stable condition. This process provides control of some special characteristics.
T8 Solution heat treated, cold worked and artificially aged. T8 is T3 that has been artificially aged.
T9 Solution heat treated, artificially aged and cold worked A stable temper T9 is T6 that has been cold worked.
T10 Cooled after being shaped to its final dimensions during a process involving a lot of heat (such as extrusion), then cold worked and artificially aged. T10 is T2 that has been artificially aged.