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Seamless Titanium Tubing source?

Halcohead

Stainless
Joined
Apr 10, 2005
Location
Bay Area, Ca
Does anyone know where to find seamless 6al-4v titanium tubing or how to look for it? I googled it and didn't come up with anything of interest. MSC and ebay didn't come up with anything. So far none of the local metal dealers seem to have anything.

I need a wall thickness of around .065" and about 2.5' of it. I also need a 6-8" long tube that's 1.25" OD with ~.100 wall thickness. Also, I need 4 chunks of the stuff 0.625"x3"x1" and some 3/16" plate. One might wonder what I'm making... a unicycle frame. Due to the cost of the ti and my serious wish not to screw up, i'm going to be making two frames. A practice one on 304 stainless, and then the real thing with the Ti.

Might there be someone out there who happens to have this material on hand and would like to sell it?

My boss gave me the stainless, but does anyone have any idea how much the titanium I listed above will cost? I'm guessing around $200-$250. Yes, I'm aware of the fact that cutter costs can quickly exceed that of the material of I'm not careful.
 
One thing to remember when working with Ti is that has alot of memory. If you are bending it it will bend back straight, and your weld joints MUST be tight. Tring to fill a gap on it is very difficult.
 
Thanks for the info. I found a bike fabrication site that sells the tubing I need for around $40 per foot. They don't say if it's seamless, though. I saw the plate I needed on ebay for less than $100.

The only bending I'll be doing on the tube is to ovalize it in a large slip-roll with the third roller removed. Is the is a bad idea? I don't have access to a hydraulic press, so that's why I'm using the slip-roll. I guess there's a way around this if there happens to be someone out there who sells ovalized ti tubing, but somehow I doubt it.

I hear for welding this stuff I should purge the tubes with argon and use a large 1" dia. gas cup around the tungsten electrode. Those things alone are $85 and seem a bit excessive for 1 job. I can make my own purge caps, but then again, it'd be nice if I didn't have to go to the trouble.
 
To do the welding corectly you will have to use back up gas and a large cup. If you have a lathe you could make one out of phoalic. You can also put a piece steel wool in your large cup to smooth out the gas flow.
 
Well, i guess what i heard was correct. Dang. I think I'll just buy the cup, since I have no idea what phoalic is, let alone where I'd get it or how I'd cut it.

I assume a larger cup will need a higher rate of gas flow.
 
My guess is that jayhawkman meant "phenolic" for the cup. It's easily machinable, and is made from laminated layers of resin and cloth or paper. I didn't realize it would stand up the the heat involved, though - cups are generally ceramic or glass, right? And you'd have to thread it (internally) for your tig torch - and that's more like a garden hose thread than a standard 60 deg thread, isn't it? Also, why does the tube have to be seamless? Do you think there are going to be problems with ovalizing it if it isn't? I can't say for sure, because I've never bought any titanium, but I would expect that seamless tube would make this a very expensive project.

Andrew
 
find someone who is parting out old aircraft.Alot of the parts are only good for scrap and that may include some titanium tubing.
 
You may or may not be aware but one of the larger US based makers of Ti framed DF bikes (Litespeed), rolls/forms their 6Al4V frame tubing from sheet stock just outside of Chattanooga, Tn. Their 3Al2.5V frames are made from both tubing and from formed sheet, depending on the end product. They like to futz with oddball tube shapes and change the product almost annually.
Steve
 
Andrew: I need seamless because I will have to bore it out to fit a seatpost and I've had enough trouble boring seamless aluminum, I wouldn't want to deal with a weld in ti on an 8" boring job. Also, in the bike industry welded tube is known for having weak spots and creating inconsistencies in frame construction.

I hear litespeed does that with sheet ti because they don't have a source of double or triple butted ti tubing yet. From what I understand it's much more complicated than average welded ti tubing.

I have no idea where i would meet someone who scraps old aircraft. I'll look around.
 
Just my .02 on this, but unless you just want to do this as an experiment (and an expensive one), I'd go with 4130 steel tubing. It is a lot easier to work with and weld. For oddball shapes such as you are talking about, you really need an enclosed glove box to weld Ti. The trailer cup or oversize cup only provides limited protection of the weld. Curves and tubing will present some real problems for you as your shield may not be adequate.

Aircraft junk will not contain any Ti tubing unless it is in the form of hydraulic lines or other plumbing. All welded tubular aircraft frames are 4130. There are some exceptions to this, but very VERY few.
 
FWIW, the easiest (???) way to weld Ti is inside a positive-pressure glove box. If you prefer to weld in the open, a trailing shield can be fabricated or purchased http://www.timet.com/fabfig12.htm You'll also need backup shielding, in addition to a 1" cup and gas lens. Shielding gas must continue to flow until the weldment has cooled below 800*F, to avoid weld contamination.

The weldability of ASTM grades 9,18 and 28 is Excellent (Ti-3Al-2.5V alloy). For ASTM grades 5,23,24 and 29 it is only Fair - Good (Ti-6Al-4V alloy).

------------------------------------------------

Another reason to consider 4130 is that is available for purchase in oval form.

http://www.chassisshop.com/

Barry Milton
 
I'm thinking of titanium because of weight. When you are jumping 2' vertically 30 times on a 17 mile ride, you don't want to haul around any more weight than possible.

If I could get aermet in a thin eough wall thickness at the right diameter that's what I would use. I might get enough chromoly for a frame when i order the titanium, and then compare the rides of the titanium stainless, and chromoly. One nice thing about titanium is how flexible it is. Unicycles don't have shock absorbers, so a flex is a useful trait in the right places (yes, i could build a uni with shocks, but that's a heavily discussed topic that's not wortht he time in the end).

Is it possible to make a positive pressure glove box?
 
A positive pressure box is exactly what it sounds like. A box, large enough to hold whatever your welding, and maybe some gloves to get into it with. A regulated pressure gas is introduced into the box, so that outside air doesn't try to get in thru small holes and such. Plus the positive pressure vents some of the burnt gases and such. Make sure you have a small vent to allow pressure relief.
David from jax
 
Here's one shop-built version:

http://www.nmpproducts.com/tiweld.htm

It is similar in design and construction to the commercial models, but they use recirculation & filtering to reduce Oxygen levels to less than 1ppm. A positive pressure box should hold levels to about 10ppm which may be good enough for your needs.

welding_glovebox.jpg


All of this assumes that you have highly developed TIG welding skills on thin aluminum, as Ti and Al are similar to weld. You may want to practice welding .065 aluminum until your welds are technically perfect. Use the destructive testing that's outlined in any of the welding handbooks or find a facility to X-ray the welds. Welding .065 Ti is similar to welding .020 steel, just need to practice until it is easy.
 
You said you could get tube from a framebuilders' supply - it should already be properly sized for a standard seatpost diameter, and probably only needs reaming to clean up the seam and ensure roundness after welding, if it needs reaming at all.

Given the short length of the tube you're talking about, it's hard to imagine you'll have a lot of trouble with seamed tubing - the only load is going to be axial (compression), right? And unless you're putting a bend in there somewhere (fork rake on a unicycle?), there isn't going to be ANY detectable flex in the frame. Tire pressure will make far more difference than anything else. True, weight will affect handling, but flex won't be an issue on a structure like that - basically a straight-bladed bicycle fork with a seat on top, right?

If you have to go with seamless, could you turn the seatpost to fit the tube? Make sure you lube the seatpost good, as they want to get stuck in Ti frames. I struggled to remove one once (from a customer's bike), and bloodied my own nose with the saddle when it finally let go.

Andrew
 








 
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