# 7000 series



## modifier (May 11, 2007)

Since I found out that 7000 series aluminum didn't need to be heated and quenched after welding to regain it's integrity I've been wondering why people still build with 6061?

I haven't checked into availability of 7000 series frame parts and tubing lately. I assume that in the old days there wasn't much available other than 6061 but I would think that builders would rather use 7000 to avoid the heat treating process and suppliers would supply what was called for.

I know in certain applications like offroad motorcycle triple clamps a softer series like 5000 or I think maybe even 3000 is used but for bike tubing where almost everyone is so into everything being as stiff as possible 7000 would once again fit the bill.

My Canfield Bros Jedi is full 7000.

So what is the scoop on 6000 vs 7000?


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## j-ro (Feb 21, 2009)

7000 series still needs to be 'artificially aged' after welding. 
A typical Columbus Zonal tubeset needs 5 hours at190f and 4hours at 350f if I remember right.
Thats what I'm cooking mine at anyway.
Fancier 7000 tubesets require similar treatment but usually higher heat and longer times.

The heat cycle allows the tubing to normalize after being superheated at the joints to weld, You could probabally realize the same effect if you just put the frame on the shelf for a few years before you rode it.

The 6000 series requires heat cycles of around 900*f which most smaller shops and home builders cant easily achieve. Some also call for a quenching in special solution which is another barrier to small production.

I think that 6000 was used to make the absolutely lightest, stiffest frame possible. That niche has been filled by carbon fiber now.


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## modifier (May 11, 2007)

j-ro said:


> 7000 series still needs to be 'artificially aged' after welding.
> A typical Columbus Zonal tubeset needs 5 hours at190f and 4hours at 350f if I remember right.
> Thats what I'm cooking mine at anyway.
> Fancier 7000 tubesets require similar treatment but usually higher heat and longer times.
> ...


I'm aware that 7000 needs to be artificially aged but I think the natural aging process is only a few weeks if someone wanted to go that route. I'm not sure about special types of 7000 series special requirements.

So 6000 is lighter than 7000?


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## j-ro (Feb 21, 2009)

I think 6000 series frames can be made lighter due to the same strength being achieved by thinner ( and thereby lighter) material

Somewhere I have a columbus catalog that lists the temps and times needed to age a frame.
nowhere in it does it say to go without it or that a rest period of several weeks is sufficient.

It must be a 2010 catalog, the newest one only lists airplane under aluminum, in years past it was the top of the line, now it seems to be the only one? ; http://www.ceeway.com/acrobat files/CATALOGO-COLUMBUS-2011tubing.pdf


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## Feldybikes (Feb 17, 2004)

I thought 7000 is more expensive than 6000. Heat treating (+quenching) makes 6000 more expensive for a small builder, but the cost/frame when doing 100 at a time isn't all that much.

At least, that what I thought. I seem to recall reading that 7000 is better (stronger?) overall, too.

The above information mar or may not be true.


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## mtbikedroid (Jul 1, 2007)

From the website: The alloy 7000, used by Columbus for the tube sets Metal Altec2 Plus, Zonal and Airplane, is defined as self-tempering: it is air-hardened. This means that in the areas overheated by the welding the supersaturated structure is restored, which, owing to the natural ageing (which takes place at ambient temperature), allows for a 75% recovery of the initial properties after a lapse of time of about 3 weeks. Nevertheless, Columbus advises to carry out a precipitation hardening treatment in the oven in order to give the structure a bigger homogeneity of the precipitates, with consequent improvement of the fatigue behaviour of the frame.


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## modifier (May 11, 2007)

•
7005 tubing comes pre-heat treated; thus no solution heat treatment is required (only artificial aging after welding)
•
Residual stress remains in the frame after the welding process; it’s important to relieve the majority of these stresses through a controlled heat treating process
•
Proper heat treating creates precipitates within the grain structure at desired locations; ultimately improving hardness
•
Precipitates serve to strengthen the material by minimizing the movement of dislocations between adjacent grain boundaries
•
Artificial aging process for 7005 frames:
6 hours @ 200°F
4 hours @ 320°F

I don't know if that's 6 [email protected] then 4 [email protected] or either [email protected] or [email protected]?


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## modifier (May 11, 2007)

And here is something from 2008. http://forums.mtbr.com/frame-building/designing-building-aluminum-409862.html


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## modifier (May 11, 2007)

One more thing then I'm done.

1. The heat from welding anneals aluminum joints (and the surrounding areas) making them very soft.

2. To restore the temper of the material after welding some sort of post-weld treatment must be performed.

3. 6000 and 7000 series alloys require very different post-weld treatments. 6061 for example requires solution heat treating (a complex series of heating and quenching in special solutions), whereas 7005 only requires artificial aging (baking at specific temperatures for certain times).

4. Easton's Scandium is a 7000 series alloy.

You could physically weld almost any aluminum alloy to Scandium, but you'd have problems when you went to heat treat the finished product. So, to have it actually work you need to stick with 7005 tubes. That way you can artificially age the entire frame and restore it's strength.


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## marco529 (Jul 11, 2011)

modifier said:


> I modified a 6061 rear triangle on a bike recently and had it heat treated after welding then aged it in my oven. This worked but the quenching bent everything up pretty bad even though I had it braced with a steel structure.


I feel like i remember reading a story about a bike mfg doing frame alignment as soon as their frames came out of heat treat, while the metal was still relatively soft. they had to bring a jig setup or something to their heat treaters as timing was pretty critical. Kind of takes 6061 out of the realm of small builders.


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## modifier (May 11, 2007)

1st stage treated 6061 stays pretty mailable for a few days at least and even though it took some force to straighten things after they had been tortured out of shape by quenching I was able to straighten it. Then after artificial aging it was very strong.

The aging process for 7005 is a 2 stage process. 6 hrs at 200 then 4 hrs at 320 and over aging can be a problem so temps and pulling should be pretty closely monitored.

I had a long talk with a builder today who has used a lot of 7005 and it was pretty eye opening. There are certainly a lot of benefits to using it but the rub is getting the material and the frame components.

Easton is no longer making 7005 tubing and neither is anyone else in the US. It's all coming out of Taiwan I guess and quality can vary a lot plus it can be expensive. There aren't very many off the shelf component that are available unless you are doing a simple double triangle frame that looks like every other simple double triangle frame. Not much at all for full suspension according to him. And things don't seem to be getting any better at this point. 

So in the end it's a choice between two evils. A pain in the ass heat treating process or a very small and possibly expensive choice of what to work with with quality control issues.

Maybe that's why a lot of small builders work with steel or titanium.

I might have to rethink things.


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