3XXX series aluminum
 

Anyone have any information on 3XXX series aluminum? Argon 18 uses this series alloy in their frames, but it seems like most frame manufacturers use 6XXX or 7XXX alloys.

In a bike frame application how significant is the alu series vs the overall quality of the build/welds?

Well since I'm no Al lover (for frame tubing) and not a metallurgist my comments can only be general. A frame material needs to have certain qualities. Metals usually need an amount of elongation capacity, a high fatigue level, enough strength and stiffness as well as an ability to be joined together in a manor that doesn't violate the mentioned qualities. Many of the AL alloys don't have all these qualities in a combination that works well for bike frame tubing. This is why the 6xxx and 7xxx series have been adapted so fully, they have working solutions that are not too expensive.

I don't know the 3xxx series qualities so I can't talk directly to their positive points or drawbacks. But that almost no one uses them makes me think some basic issues are at play.

BTW if steel was "discovered" tomorrow it would be heralded as a wonder metal. Plentiful, inexpensive, environmentally friendly (compared to AL and TI), able to be made very strong and stiffer then AL or TI, able to be joined with low skill and inexpensive methods, long fatigue life, "pleasant" failure mode, great elongation. I could go on. Andy.

I agree - it is very odd that no one else uses 3xxx series aluminum, so odd, that I wonder if when Argon18 describes their frames as "Triple-butted 3001 Aluminum Thermo-Tech tubing" I wonder if somehow they don't mean 3001 series aluminum, especially since 3xxx series aluminum can't be heat treated.

I always take whatever a catalog says, WRT engineering things, with a grain of salt. They are written by marketing people, not engineers. Andy.

One of their TT frames is described as made from "3005 T3 aluminum". T3 stands for solution heat treatment and cold hardening. Nobody else knows anything about this mysterious alloy, since, as you say, 3xxx is normally non-heat-treatable. Normal 3xxx would make no sense in a bike frame, because its benefits are workability at the expense of strength, and it can be used to make complex shapes (one common application is soda cans.) Common 3xxx alloys have about half the tensile strength of 6061-T6.

It is possible (though, I think, unlikely) that Argon 18 has specific expertise in materials science and they have figured out a way to make a variation of 3xxx aluminum heat-treatable, which would let them take advantage of good workability of the alloy during assembly and then heat-treat the finished frame. It is also possible that they simply make their bike frames out of soda-can 3005 because it's easy, and then apply heat treatment anyway, whether or not it has any effect on the tensile strength.

The numbers say what the alloy composition mix includes..

GENERAL ALUMINUM INFORMATION from Aircraft Spruce

Interestingly it looks like 3005 alu may have higher tensile and yield strength, based on what I've found here:
Aluminium / Aluminum 3005 Alloy (UNS A93005)
and
Aluminium / Aluminum 6061 Alloy (UNS A96061)
Obviously the heat treatment will have a big impact on these values.

Ultimately I think that tubing size and weld quality will be the biggest determinant in frame quality (don't most frames usually fail at the welds?).

It's still very odd that I can't find a single other frame manufacturer that uses 3xxx series aluminum...

Numbers in your links are messed up. The first link says "3005-T14" but it almost certainly means "3005-H14" (there's no such thing as T14, and numbers match what's reported for 3005-H14 by other sources.) The second link most likely reports strength figures for 6061-O (softened/annealed). So, you're comparing figures for cold-hardened 3005 versus fully softened 6061.

Apples to apples yield strengths as per matweb.com:
3005-O: 55 MPa
3005-H14: 165 MPa
3005-H18: 225 MPa

6061-O: 55 MPa
6061-T6: 276 MPa
7075-T6: 462 MPa

OK, I think I have the answer. Notations like "3001-T3" and "3005-T3" in Argon 18's lingo has absolutely nothing to do with standard alloys. It is their internal designation of the manufacturing process, used also for carbon frames (their current top-level carbon frames are "7003-HM" and "7050-HM"). I don't know the full meaning of all numbers, but T3 stands for triple-butted aluminum (T2 is double-butted).

For proof, look at frames here: http://www.argon18bike.com/documents..._2010_EN_l.pdf

As to what alloy they do use, that's hard to say, but looks like at least some of their older bikes were sold with "7005" stickers on the frame.

Nice sleuthing hamster! It looks like this is another case of marketing "clarifying" things :rolleyes:

The biggest question I have now is why invent an arbitrary naming scheme (when a known and accepted one already exists) and then not explain/define it anywhere?

Because the miss direction got you thinking and talking. That's the first job of marketing. Andy.