Framebuilders - 6061 vs. 7005 Aluminum tubing

For those in the know, is there any significant difference between 6061 and 7005 aluminum alloy tubing that might create a superior frame for say cyclocross ? Are there many inherent differences ? Thank you for your insights.

OK, never mind, found a lot of info on other sites.

http://www.matweb.com

7005 has much better (I believe twice) fatigue strength.

OK, never mind, found a lot of info on other sites.
Could you let us know the sites where you got the best info from? Thanks!

My books say that 7xxx AL is not suitable for arc or gas welding where as 6xxx series AL is.

Having said that, 7005 is not specifically mentioned. Since some bikes are made out of it, welding properties must not be too bad.

Like ElJam says, it's quite a bit stronger, so you could theoretically build a lighter frame. By playing with tubing sizes, the frame could end up more or less stiff, the 2 do not necessarily go hand in hand.

There are bunches more out there

http://www.matukas.pri.ee/KB/alumiinium/AL6061vs7005frames.pdf
http://www.bikeforums.net/archive/index.php/t-6981.html
http://www.bikeforums.net/archive/index.php/t-15193.html

My books say that 7xxx AL is not suitable for arc or gas welding where as 6xxx series AL is.

The chart I have, which I think I grabbed from either Miller or Lincoln, says that you can weld 7005 to 7005 using 5556, 5183, or 5356 filler wire. You can join it to most other weldable aluminum alloys using 5356 filler, though there are some exceptions.

For those in the know, is there any significant difference between 6061 and 7005 aluminum alloy tubing that might create a superior frame for say cyclocross ? Are there many inherent differences ? Thank you for your insights.

In layman's terms 7005 is stronger than 6061 (for bicycle frame building applications almost a parallel between chromoly and high tensile steel). The extra strength of 7005 allows for thinner wall thicknesses and therefore a lighter frame. Butted and double butted aluminium tubes are usually 7005 for this reason. Building a 7005 frame with the same tubular wall thicknesses as those utilized for a 6061 frame defeats the purpose as the frame would weigh the same and the advantage is lost. During heat treatment, 7005 is tempered with a sudden blast of cool air, whereas 6061 is dunked in water (I hope I got that one right and not the other way around!) :p

Now here's what's interesting... in one of my factory visits in China, I asked the very same question. Somewhere along the conversation of heat treatment (and various sushi and beer type comparisons between the west and east), I asked "does the heat treatment or temper (T6) in aluminium last forever?" The answer was a rather casual, no!

Now I'm kicking myself here, because I wasn't really listening (maybe I got distracted by the prospect of eating the turtle soup :twitchy:)... but the temper apparently diminishes in time, like it self-anneals or something. Don't ask me how many years, but just in case you want to bequeath the frame to your grandson or something, it might pay to check this aspect in your research. One of them lasts a heck of lot longer than the other, I'm just not sure which one it is.

Please bear in mind that this is what I've been told and I have not had the time or the need to verify the information. So if you find out, please kindly post back and let us know.

Funny that, suddenly I feel like having some sushi... :rolleyes:

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