I am looking to buy some Aluminum bar from Grainger because I can get local pickup. They have bars with T6511 and some with “extruded” temper. I can’t find what “extruded” temper is, but I am guessing it means there is nothing done, and that kind of aluminum should be avoided. Then again, the tensile strength is higher on the extruded one, so I am kind of confused. Anyone have guidance?
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T6511 apparently applies to extrusions only which gives a hint as to ‘extruded temper’.
The aluminium is formed typically by casting, rolling or extrusion. Rolled and extruded Aluminium contain significant internal stresses due to the large forces applied to deform it into the target shape. When you machine this it can banana like a piece of wet wood as you change the balance of internal stresses and the metal finds a new shape.
To overcome some of this problem it is common to heat treat and in some cases also stretch a few % the rolled or extruded material to reduce these internal stresses and help it find a more permanent shape.
The last 1 on the T6511 appears to state that the extrusion may have been straightened after extruding to reach tolerance.
Tempered Aluminium alloys tend to clog up cutters less if you are not using a lubricant, retain their shape better etc. Cast and tempered is the go to for ‘tooling plate’ for optimium dimensional stability.
On the downside, many of these tempered 6 series alloys are less strong than a 7 series or other alloy, are unsuitable for some types of welding and a bunch of other characteristics.
It’s worth a skim through the data sheets from the manufacturers to compare what alloys are suited to.
Here’s a quick guide to the various ‘series’ of alloys.
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Thanks, I found that kind of info on the T6511. I know that stuff is good to machine, but the “extruded” temper version of 6061 is what leaves me baffled. Here are the two products for comparison.
Not very clear is it?
Some further reading, this gives an overview of the various suffixes which apply based on what has been done since extrusion.
It may be that this ‘extruded’ temper is referring to quenching straight out of the extruder as described here.
“To be considered T4, the aluminum plate (or extrusion, etc.) must be produced, allowed to cool, and then solution treated and quenched. However, aluminum producers quench extrusions right out of the extrusion press while they are still hot. Technically, this produces T3 material, not T4. If you age T3 material, you get T5 material, not T6.”
There is further description of the heating and ageing processes here.
Without asking the vendor, perhaps their stock system has a required field for “Temper” for an alloy which has to have a value selected and ‘extruded’ is what is selected to indicate an alloy without a specific temper?
I think you hit the nail on the head there. I am 90% sure it won’t be a fun time machining, but at 2 dollars a foot, I’ll order some next time I make a grainger order and find out. If it works, they have some dirt cheap aluminum available for free pickup. I’ll report back whenever I get some and find out if it works, or is a nightmare.
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