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7005 aluminum

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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7005 aluminum

Unread postAuthor: Moonbogg » Thu Jan 08, 2009 2:48 am

Making a cannon here, and 6061-T6 is what I am thinking of using, but the need to heat treat scares me. If the welds remain weak for some reason its NOT going to be good.
Anyway, I have read that a type of aluminum, 7005 can be welded without the need for heat treating and that it regains its strength substantially simply by sitting around for a few weeks.
I can't find the stuff anywhere!! Anyone know where to find this stuff at? I'm trying to see if it even comes in 4" diameter and similar sizes.
Both 6061 and 7005 are used for bike frames, for whatever that may be worth.
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Unread postAuthor: psycix » Thu Jan 08, 2009 5:37 am

Do you really NEED to weld?
Maybe you could tap threads and screw parts together.
Using less common alloys will indeed be hard to find and probably more expensive.
Or you could just look into heat treatment. Its not that hard.
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Unread postAuthor: Mateo » Thu Jan 08, 2009 10:29 pm

there are machine shops that make the things still made in the US all over this country. i have a close relationship with someone who owns a bike buisness and has his bikes welded together up in portland oregon. im sure this is the type of tubing your looking for or close to it as these are high quality bikes not target type.

anyways those machine shops have big trash cans full of scrap metal that they pay people to get hauled away. if you can find one of these places then theyll probably give you some piping.
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Unread postAuthor: SpudBlaster15 » Thu Jan 08, 2009 11:33 pm

You don't *NEED* to heat treat 6061-T6 after welding. The welded area will have the properties of 6061-0. Tensile strength drops by a factor of 2.5 or so, and the yield strength drops by a factor of 5. Significantly weaker, but the strength of 6061-0 may be usable, depending on how far you are going to be pushing the chamber. Also, It's not difficult to artificially age harden the 6061-0 and restore the T6 temper. You'll first need to anneal the entire structure, giving it a uniform 0 temper. The rest you can do it in a conventional oven. 18 - 20 hours at 300 - 320F to reach T6 from 0 IIRC.

It's true that 7005 naturally age hardens very quickly. However, if the material was artificially age hardened at the factory to give it additional strength (Which is likely the case), the naturally aged welded area will still be weaker than the rest of the structure. Natural age hardening will produce a maximum temper of T4 IIRC. 6061 also age hardens at room temperature. The process is however very slow.

I say forget the 7005. It's too rare to be found in the exact dimensions you want. 6061-T6 on the other hand is very common. Personally, I'd weld the 6061-T6, then anneal the entire structure, and artificially re-age it to a grade of T6
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