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Problem with heated aluminium. Answered

i make balls of aluminium rings from chainmail technics and in a test phase i filled those balls with kevlar, which is being used by the jugglers round here. So, aim was to make burning juggling balls from chainmail. I used aluminium cos it conducts heat very well, so that ppl hardly would get burned from juggling with these balls.
Problem is, that the aluminium became rough and prim and the rings started to split shortly after the ball was being set on fire.
I dunno bout forging, but is there a way that i can keep the aluminium rings away from this effect (tempering?)? Is there a way to light up such balls without damaging the rings?


thanx guys for all your posts. the description of the catalogue says, that it got an alloy. As i dunno which one, i just sent an email to my vendor a minute ago. i use aluminium rings 1. cos my vendor sells them as standard and 2. i started with chainmail in march, 2009 and that time i was lookin for aluminium as i intended to use them as adornment for a coat (one of my former projects) and wanted the stuff to be as lightweight as possible - that's how i came to my vendor. Prim is a word that i found in an online-dictionary as one of the translations for sum effect (i'm german). What i wanted to say is that after the burning the rings had become the opposite of shiny, hard and easy to break (so maybe stiff is a better word?). Well, dunno, never thought bout copper. Might be a good idea, sounds good (i was thinkin bout the conduction, too, when i gave a try on the burning version). Coincidental i met one the local jugglers when i came from the supermarket today and he also said that i might try steel rings. But anyways: if there's a way to use the aluminium instead of other materials, i'd be interested. Otherwise i would probably have to find a new seller for such rings as my vendor only sells aluminium, brass and titan rings.

You might be able to get some help from doing a "stress relief" - that is, pre-heating-&-cooling the completed balls to & from their juggling temperature, but slowly and evenly in a controlled temperature furnace. The rapid and uneven heating when the ball is ignited may be part of the problem.

Do you know what alloy of aluminum you are using? The tempering effect really depends on which other metals may have been added in small quantities in to give the aluminum more strength or improve other properties.

Is "prim" in "the aluminum became rough and prim" a typo? It's not a metal working term I'm familiar with.

Also, is the metal splitting at the joint where you closed the ring (as Seandogue suggested - I second his advice on welding vs. crimping), or somewhere else?
(Any chance you could post a picture of one of the split rings? That'd help a lot.)

I'd have thought of copper, which conducts heat even better than aluminunum and is easier to work, for this sort of application. Is the aluminumum for the lower weight, or lower cost, or because you had the Al rings on hand, or just to see if it would work? (Those are all good and valid reasons to choose the Al - I'm just curious. :)

Oxidation is going to be a problem with aluminum, as well as thermal expansion. If the rings are simply crimped, then you need to weld the rings to ensure that thermal expansion does not cause them to split. As for pitting and other surface effects on the aluminum balls, you *might benefit from having them anodized, although I suspect the protective effect would only be temporary

scrap that comment about having them anodized. I misread your post. I don't think you can successfully anodize the finished chain ball. You *might be able to, but I suspect they'll say no at a shop. You could always make the gizmo out of steel, since that would simply form a mild rust stain over time, but then it'd weigh a ton.