Rolling edges on aluminum armor: types of AL

[Caspian]

I've never got the annealing right on aluminum. i'll try the propane torch idea that was in another thread. i think however that it depends on the type of aluminum. just the other day i rolled a perfect edge on a breastplate, made from aluminum roadsign, no heat treatment whatsoever. i then carefully tried to roll the edges on the backplate, which was made from a completely different roadsign. cracking started to appear. I can produce flawless rolled edges on "soft" aluminum roadsigns, but sometimes even this is not an indicator. I did try to anneal some hard, brittle aluminum one time, but i still did not have much success. I think that people who say alumimum cracks when you try to roll it are being too general. Ive rolled the edges on "good" aluminum without heat treatment and i used a steel hammer on a steel anvil edges or ball stake, no problem and no cracking, i just had to take my time, like all rolled edges. I just wish there was some way to tell if the roadsign i buy from the scrapyard is capable of being rolled, before i buy it. Oh well, i guess this is impossible. anybody got any ideas??

[Frederich Von Teufel]

Caspian, aluminum street signs are made from a variety of different aluminum alloys (as you have found through your experimentation.) Usually the local government gets them through the normal governmental bid process (i.e. the lowest bidder for the job), but sometimes they'll have a special batch run for themselves. In the end, the sign can be made out of almost anything.

Usually (in probably 80%+ situation) the sign will be made from either 3000 series aluminum, or 6000 series aluminum. The 3000 series is almost pure aluminum, and is very easy to work, and work hardens the slowest. If you've bought any aluminum kitchenware or pans, it's made out of 3000 series.

6000 series, however, can have some funky alloys and hardnesses. The T6061 that is used to make shields is a good demonstration of this. Some people have run their car over a shield made of T6061 with no discernable effect to the shield. T6061 can also work harden at the drop of a hat.

Some of the things that are added to aluminum can drastically effect how you anneal it too. There are a couple of alloys that must be taken up to very high temps, then _very_ slowly cooled (on the order of 100 degrees per hour maximum) to anneal them. This is usually done in a kiln, something that a normal shop doesn't have.

There are also some aluminum alloys that should be avoided completely since they have no "hard" stage at all. They seem to go from being soft, to being brittle, with no inbetween stage (5164? I think it is, is a perfect example of that. It's a magnesium-aluminum alloy. Beautiful stuff, doesn't tarnish stays, nice and shiny, very light-weight. Also refuses to harden at all. Simply breaks and cracks when you are working it. Useless stuff for armouring.)

The 3000 series alloys are best for complex curves in armouring and will make you happiest in the end. Most of the other alloys can be so difficult to work with that they should be left for simple bend and curves only.

Of course, until you work it, you can't really tell the difference between the alloys on an unknown street sign. Sucks when you've spent time cutting out peices only to find that you can't use it for what you want. My advise is to test a little peice of each sign before anything else, then mark the sign with a "good" or a "bad", then use the appropriate sign for what you need.


Frederich

[Caspian]

Thanks for the advise. Very helpful explanation.

Caspian.

[Jeff]

I agree with Frederik.

I don't know much about all the kinds of aluminium, but what I use is 3003, and I don't have any problem of crack when dishing or roling. You must be carefull when you flute alu however. The flute line might tear if the chisel pass have been to deep.

[Guy Dawkins]

The important thing to remember about aluminum is that there are two basic divisions.
Non-heat treatable and Heat treatable.
the non-heat treatable grades will be easier to form, Although, if done properly the heat treatable grades can also be formed. But, its harder to do and if done wrong, will crack.
The non-heat treatable grades are:
1100
3000 series, like 3003
5000 series, like 5005,5052, 5083,5083,5454.
The heat treatable grades are:
2000, like 2024
6000, like 6061
7000, like 7050,7075

All aluminum grades have a temper designation after the series number, like: H32 or T651
The H means it is non-heat treatble. The T means is is heat treatable.

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Guy

[This message has been edited by Guy Dawkins (edited 03-12-2001).]