David Jenkins
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| posted on 21/7/09 at 12:05 PM |
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Annealling aluminium - what temperature?
I had one of those "Doh!" moments this morning...
Last weekend I had to bend some aluminium channel (windscreen frame) and had quite a bit of bovver getting it annealled correctly. Tried rubbing soap
on it - it disappeared before turning black. Tried rubbing the safe end of a match on it until the woodstarted to char and leave a black mark -
sort-of worked.
Now I remember that I have a Maplins remote IR thermometer... Doh! It's accurate to a few degrees and, apart from having to make an adjustment
for the metal's shiny surface (it's calibrated for a dark surface) very easy to use.
So, the question is, what's the annealing temperature for aluminium alloy? Oh - and what's the melting point, just in case?!
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matt_gsxr
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| posted on 21/7/09 at 12:10 PM |
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I don't know the answer to your question, but....
The shinny thing is one problem, and the fact that these IR things only go to 200deg C is another.
I had some issues with this on my exhaust headers/manifold.
To solve the shinny problem I painted with VHT paint first (just a little square).
Matt
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garage19
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| posted on 21/7/09 at 12:13 PM |
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The way i was tought to do it for 3mm sheet was to dust it over with just the acetalyne turned on which leaves a layer of soot. Then turn the oxy on
and when the soot burns off the plate has got hot enough. No idea what the actual temp was though.
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bonzoronnie
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| posted on 21/7/09 at 12:14 PM |
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Hi
A general rule of thumb is to cover the area being warmed with a block of soap.
When the soap turs brown & starts to blister. The alloy has reached the correct tem and is ready for bending.  
By that, i do mean, smear the area with a soap block 
Don't heat up the block of soap 
[Edited on 21/7/09 by bonzoronnie]
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miikae
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| posted on 21/7/09 at 12:20 PM |
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An extract from Azom.com.
Annealing is carried out in the range 300-410°C depending on the alloy. Heating times at temperature vary from 0.5 to 3 hours, conditional on the size
of the load and the alloy type. Generally, the time need not be longer than that required to stabilise the load at temperature. Rate of cooling after
annealing is not critical.
Mike
[Edited on 21-7-2009 by miikae]
If it can be done it i will be done .
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MikeCapon
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| posted on 21/7/09 at 12:20 PM |
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Hi David. This looks a good article.
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BATHO
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| posted on 21/7/09 at 12:35 PM |
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Hi,
Use a black marker pen on the panel, then warm it up until it disappears!
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britishtrident
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| posted on 21/7/09 at 12:51 PM |
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bonzoronnie method is the way I was taught, any hotter and the alloy melts.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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David Jenkins
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| posted on 21/7/09 at 01:08 PM |
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Hmm - as said above - I tried soap and it disappeared before turning black.
Good point about the IR thermometer's upper limit... 
The oxy-acetylene would be good - if I had it in my workshop! 
Ah well - another good idea flushed down the WC pan of life...
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907
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| posted on 21/7/09 at 01:17 PM |
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Hi David,
Anneal 350 - 400C
MP 659C (pure)
I use the soap method.
Always mark the underside so you don't play the flame onto the soap mark,
or mark either side of where you heat and let the heat creep along the bar to the marks.
In saying all that I've just done mine, no need to anneal, just bent it, but then again I am a big strong boy.
Cheers
Paul G
p.s. A useful book to have is A C Davies, The Science and Practice of Welding.
Look it up on Amazon
 
Rescued attachment windscreen-frame-s.jpg
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luke
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| posted on 21/7/09 at 03:16 PM |
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when back in school we used to put washing up liquid on it.
IIRC it went black when at the right temperature.
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907
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| posted on 22/7/09 at 06:44 AM |
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If you wanted to borrow my jigs David you are more than welcome.
Cheers
Paul G
 
Rescued attachment WS-jigs-s.jpg
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David Jenkins
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| posted on 22/7/09 at 07:45 AM |
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Thanks Paul, but mine are all done now.
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vinnievector
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| posted on 22/7/09 at 08:57 PM |
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your alu
Hi ,all the tips the guys gave will work however it will remain in the temper state you heated to ,
At work i have to make some complex shapes in alu there are different temper rates of alu and different alu mixes dependant on if you want sheer or
tensional .but for your screen frame you should go for some 2024T0 and the thinnest gauge you can get away with ,at temper rate of 0 the alu will be
soft to work with shape to your screen frame this will then have to be heat treated to your desired temper rate 6 would be fine for your frame these
treatment times are on the net .good luck vin
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cfv23844
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| posted on 23/7/09 at 11:25 PM |
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annealing aluminum
I used a red marking pen (Sharpie) and heated with a hand held propane torch till area marks disappeared and Voila! easy bend.
regards
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