Do I need to anneal these Lowes aluminum rods before bending?

[pacocap]

Hello everyone. I've been lurkin' for awhile. This is my first post. I bought some aluminum rod stock from Lowes:

Steelworks Aluminum Round 1/4" x 3' (Hillman Group Item # 11270, Aluminum Round)

Steelworks Aluminum Round 3/8 x 3' (Hillman Group Item # 11273, Aluminum Round)

I have read a number of posts here about the need to anneal aluminum rod before bending if it has been tempered. First of all, does anyone know the specs of the above materials? Are they tempered and in need of annealing before bending a 3/4" radius 45 and 90 degrees? Also there is some disagreement about the annealing procedure. Should I heat just the bend areas or the whole thing? In either case, at what sustained temperature? Should I quench or cool slowly at room temp? Ductile and tensile strength are not important, rather, aesthetics are more important, plus I'd rather not break the material.

I forgot to add:

Has anyone tried this Harbor Freight Tubing Bender to bend solid aluminum rod up to 3/8"?

[HuFlungDung]

With very limited experience in forming aluminum, I would say that you have to bend it while it is cold. Bending it when hot will typically crack it (try it!). I don't know about intermediate annealing, whether that helps or not, sorry, not much help.

[pacocap]

Originally Posted by HuFlungDung I would say that you have to bend it while it is cold.

Yes, that much is clear but first there are other questions to be answered.

[diecutter]

I know even less about bending aluminum than HoFlungDung, but you might try this. Take a test piece of rod and bend it slightly, then heat up the bend area and quench it in water. Bend and quench in steps till you reach your angle.

This may help prevent cracking since most nonferrous metals have work hardening stress removed by quenching which is the exact opposite of how stress is relieved in ferrous metals. Worth a try.

[cncnitro]

I am not fabbie,but a machinist. My boss is a fabricator by trade and he swear by this: heat your part with acetylene gas only and when the soot begin to stick to the aluminum, remove heat, and bend. Be careful not to overheat and melt your part.
We mainly use 6061 t6 aluminum. Experiment, good luck!

part-><-fabbie

[pacocap]

Originally Posted by diecutter Take a test piece of rod and bend it slightly, then heat up the bend area and quench it in water. Bend and quench in steps till you reach your angle. This may help prevent cracking since most nonferrous metals have work hardening stress removed by quenching which is the exact opposite of how stress is relieved in ferrous metals. Worth a try.

OK, assuming that your last assertion is correct, I don't see how bending it cold at first could be a good thing. It would probably be better to heat before even attempting to bend. But if you do, then it is already annealed according to multiple posts and no need to reheat:

http://www.cnczone.com/forums/showpo...66&postcount=8
http://www.cnczone.com/forums/showpo...88&postcount=2
http://www.cnczone.com/forums/showpo...0&postcount=11

Note the differences of opinion about temperatures and whether or not to quench.

[pacocap]

Originally Posted by cncnitro My boss is a fabricator by trade and he swear by this: heat your part with acetylene gas only and when the soot begin to stick to the aluminum, remove heat, and bend. Be careful not to overheat and melt your part.

Yeah well I think you skipped a couple of steps. After you deposit soot you're supposed to heat the piece until the soot is consumed and then cool it before bending:

Aluminum Bending Tip
Annealing Aluminum [PDF]

In any case I tried this and it would not budge in the HF bender so my next attempt will be to bend it between two pieces of iron pipe in a vise.

[HuFlungDung]

http://www.weldingtipsandtricks.com/...allurgy-4.html

[pacocap]

OK, here's the conclusion to this thread.

As I already mentioned, I tried the soot deposit/burn-off annealing method as described in the two sources above. The PDF seems most authoritative. I then tried bending the 3/8" rod between two short pieces of 3/4" galvanized pipe held tight in a vise (I had to use a hammer to tighten the vise). First I annealed the 45 deg angle section and then bent it after air cooling. I then repeated this with the 90 deg section. Pic below:



I then re-annealed the bends for good measure in an attempt to relieve strain which, from what I have read, can cause the bends to become distorted later on.

Some notes here. Although this method shows up frequently on the net, and is probably standard procedure in weld shops, this is not by any stretch true annealing. Annealing requires heating the material to the proper temperature and holding it there for hours, then slowly cooling it by degrees in an oven or heated solutions. Often a cold quench is done when a certain safe temperature is reached. Then all stress and strain is removed. This simplified annealing method will soften tempered aluminum enough to bend it without cracking but it is not good enough for critical uses where the probably weakened material could break under stress or distort at a later date. For my purposes this doesn't matter but for some uses this would be a safety concern. Caution is advised.

Finally, I did get a response from The Hillman Group, which supplies this rod stock to Lowes: "This is made from 6063 aluminum with a T5 temper."

"6063-T5 has an ultimate tensile strength of at least 22,000 psi (152 MPa) in thicknesses up to 0.5-inch (13 mm), and 21,000 psi (145 MPa) from 0.5 to 1.0-inch (25 mm) thick, and yield strength of at least 16,000 psi (110 MPa) up to 0.5-inch (13 mm) and 15,000 psi (103 MPa) (from 0.5 to 1.0-inch (25 mm). It has elongation of 8%."

I hope someone else finds this information useful.