Annealing Aluminium to assist bending

[UK-Corlett]

Hi

I am starting to clad my TD in Aluminium and wanted to share my annealing oven.

Here in the UK extruded Aluminium is supplied in 2014 Grade, I can't find the US equivalent but essentially its a 3.9-5.0% copper alloy.
But its too strong to do anything with in the as extruded state. So I have annealed mine with great results.

The Idea is to put the copper in solution and to do this you need a high temperature approx 430C (800F) for 20mins.
Well 430C is quite hot, so I went for an oven supplied this heat from charcoal.
You have to let the charcoal calm down and stop smoking also my small tube only lasted half of the run so I have to re-fill and continue.

I got hold of an old K-Type thermocouple to measure the temp reading it off my old volt meter, 17.5mVolts is ideal. I pushed an extra 6" in every 5 min.
As you can see it all went well .




Once the annealing is over these kinds of bends are possible. This is a 1"/1" U Section 3/64" thick.
This is my wheel arch trim. No buckling or stretch marks.


Clive

[KCStudly]

Nicely done!

[edgeau]

Cool. How do you do the bend?

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[flyguide]

Very nice I did mine with a torch and soap method. Then let the screws do the bending work.

[TimC]

Very impressive. I did the soap and torch method as well with good results. This looks to be a more controlled heat treatment.

[UK-Corlett]

Hi Edgeau

I have a roller stand the type of thing that supports long lengths of wood for a table saw.
I rolled it back and forth like using an "English Wheel" using a cardboard pattern for shape.

Hi Soap lovers.
The use of the oven allowed me to pull 7 lengths through at once. so Although it took a couple of hours all were done at once.
As the material is slowly removed from the oven it cools down slowly which looks to be very important.
One bag of charcoal cost £5 and a bail of rockwool £20. I guess that could have bought a lot of gas.
The issue I had with flame annealing was also the inconsistency of the anneal along the length of the strip.

Dislocation Theory - In a normalised regular aluminium crystal lattice the atoms can move over them selves easily because of small faults in the lattice. Working the material resolves those faults and it becomes harder to work "work hardening". You can introduce single crystals of copper into the lattice it too prevents the aluminium lattice from moving. However the copper can be put into solid solution and effectively removed from the lattice. Further heat treatment and or time can precipitate out the copper returning it to the lattice, "Age hardening".

Classic use of this is aircraft rivets, solution treated to be soft, pulled into the air frame where they rapidly age harden and gain back their strength.

In all the data I looked at there is "time" required to put the copper into solution. Say 20min at 800F. The time is reduced the hotter you get. But under a temp and the copper is un-effected and over a temp you get re-crystallization grain growth of the aluminium. So increasing the temp to reduce the time and you could remodel the alloy too much. Also it looks like the cooling rate is important too, so much so that hardening is done by heating to 500C and water quenching.

From "Aluminium Federation - The Properties of Aluminium and its Alloys" BS-2014 UNS-A92014
Annealing of work hardened alloys - Over 360C ideally 400 to 425 for 20 min.
Annealing of Non worked alloys -360C +/- 10C for 1 hour.
Complete annealing 400C-425C for 1 hour cooling rate 15C/hour
Temper T4 water quench from 502C

The above is for full annealing and I am not sure we want this for our application as we are not going to heavily deform it and we want it strong after.

SO! Soap method works but you will not get a full annealing, however its cheap quick and does not require a thermocouple.

Clive

[alaska teardrop]

Clive,

Very clever. Good work. Thanks for sharing.

Coincidentally, I was just talking with the production manager at the local aluminum extrusion company two days ago. I asked him if I could get extrusions right out of the machine before the hardening process in the oven. He said, yes and that they often do that for customers who then form the extrusion. The customer will then bring it back to be hardened in the oven if necessary. Maybe you could do that also.

Fred

[Aguyfromohio]

Very nice, thanks for posting.
Have you tried bending it the other way, like a cap for a curved teardrop wall?
Just curious if that 1 inch leg can bend tightly around the inside diameter without buckling or wrinkling.

[UK-Corlett]

Aguyfromohio

No but I have some aluminium section to bend soon which is a Z section. I have been told to use a stepped wheel. I don't know how this will work out or what my stepped wheel will look like. But a wheel which is a fully supporting negative of your aluminium, which guides and steadies the Web could work.

Give me a week or two and I will post.

Clive

[KCStudly]

Maybe stepped wheel is another term for progressive dies (like how the form rain gutters from flat stock in the back of a truck)? That sounds more like something that would be used in a mass production environment, or at least a well equipped machine shop, not your average home builder.

[Aguyfromohio]

Maybe stepped wheel is another term for progressive dies (like how the form rain gutters from flat stock in the back of a truck)? That sounds more like something that would be used in a mass production environment, or at least a well equipped machine shop, not your average home builder.

Progressive dies usually means a few dies, one after the other that the material moves through, each die making one more change to the material shape. Like rolling over the dutch hem on the edge of a gutter.

I believe the stepped wheel is just a single die, of sorts, to keep the material from rolling over while being bent. I've seen three-wheel benders with stepped wheels like this. Just a single stepped wheel on a handle would sure help control the bend.

[KCStudly]

Ah. I guess I would have thought those would be called profile dies, or contour dies, but stepped dies works, too.