6-4 titanium cracks



anerobic

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Sep 4, 2003
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so i just discovered 2 horizontal cracks (one on each side) across the seat tube/top tube weld on my ti frame. it's reynolds 6-4 titanium tubing. the cracks are an inch long and extend both backward and forward into the actual tubing. this bike is a year and half old. what gives? faulty welding? faulty design? (there is a about a 3 inch seat tube extension above the weld)
anyone heard of such a thing?
 
Sounds like you could have embrittlement of the tubing due to faulty welding. If so, this should be a defect covered under your warranty.
 
anerobic said:
so i just discovered 2 horizontal cracks (one on each side) across the seat tube/top tube weld on my ti frame. it's reynolds 6-4 titanium tubing. the cracks are an inch long and extend both backward and forward into the actual tubing. this bike is a year and half old. what gives? faulty welding? faulty design? (there is a about a 3 inch seat tube extension above the weld)
anyone heard of such a thing?

Are the tubes seemed? 6/4 ti is stronger in theory than the more common 3/2.5 - that is if the tubes are drawn. Chances are your 6/4 is seemed and annealed making it prone to defects such as what you experienced. Here is a detailed explanation...

http://www.spectrum-cycles.com/624.htm
 
No issues with the tubing quality, but the question is who built the frame and your warranty coverage. If it was a reputable brand name or framebuilder, I'll bet they'll want to see this failure and make it right.

I'm no expert, but have heard often that Ti is prone to embrittlement from contact with hydrogen/oxygen (air) or other contamination during the welding process. What this means is that any hydrogen hitting the tubes while they are above a certain temperature causes the metal to take on a brittle crystalline structure, like glass. To prevent this,a pure inert gas atmosphere has to be maintained during the welding and cool-down. The criticality of these steps is one reason Ti frames are costly.
 
Sorry to hear about your 6/4 Ti. issues :(

I was on Seven's web site a few months back, and thought I read something about 6/4 Ti. in that its typically seemed / drawn tubes = thus over time could find a weak link on the seemed edges of the tubing/welds. I cannot find that part on there web site now: http://www.sevencycles.com/building/materialstechnology.html

Litespeed Vortex's are 6/4 Ti. , but look at the down tube on that thing, its multi-shaped , and thus in multi-shaping the tubes its welded along 1- or more of the edges to create the tube.

It looks like Seven has done it right , with there Argen Ti tubing 3/2.5 oversized Butted , seemless , and the fact that each tube is drawn at super fine tolerences- very uniform - which mainly effects riding characteristics - and I believe overall durability.
 
dhk said:
I'm no expert, but have heard often that Ti is prone to embrittlement from contact with hydrogen/oxygen (air) or other contamination during the welding process. What this means is that any hydrogen hitting the tubes while they are above a certain temperature causes the metal to take on a brittle crystalline structure, like glass. To prevent this,a pure inert gas atmosphere has to be maintained during the welding and cool-down. The criticality of these steps is one reason Ti frames are costly.
It takes prolonged contact with a higher concentration of hydrogen in air to cause embrittlement. With welding the primary concern is oxidation. Preparation for welding titanium typically includes an ultrasonic cleaning to knock off any oxide on the surface. The shielding gas prevents oxidation from the air when the metal is heated. My guess is that the crack is caused by one of the following:
1) A contaminated weld.
2) A vent hole in the seat tube. If the tubes aren't pre-heated properly, the seat tube will try to contract upon cooling more than the top tube can. This would put the part of the tube with the hole in tension, leading to fatigue problems. Check to see if there's a vent hole drilled in the seat tube and if the crack goes into it.
 
i don't see a vent hole. in fact, i can't see the cracks from the inside of the seat tube because there is an [i'm guessing]aluminum sleeve at the top of the seat tube. the cracks go through the ti tubing but not through the aluminum sleeve. i guess the ti tubing is thinner at the top of the seat tube than elsewhere, to accomodate the sleeve, since i can't see a step off looking down inside. and just to re-iterate for the other post, this IS drawn and seemless reynolds tubing


and let me
artmichalek said:
It takes prolonged contact with a higher concentration of hydrogen in air to cause embrittlement. With welding the primary concern is oxidation. Preparation for welding titanium typically includes an ultrasonic cleaning to knock off any oxide on the surface. The shielding gas prevents oxidation from the air when the metal is heated. My guess is that the crack is caused by one of the following:
1) A contaminated weld.
2) A vent hole in the seat tube. If the tubes aren't pre-heated properly, the seat tube will try to contract upon cooling more than the top tube can. This would put the part of the tube with the hole in tension, leading to fatigue problems. Check to see if there's a vent hole drilled in the seat tube and if the crack goes into it.
 
I just found out from a Trialtir-USA represenitive , that ALL Colnago Ti. tubing(6/4) is seamless
 
dhk said:
No issues with the tubing quality, but the question is who built the frame and your warranty coverage. If it was a reputable brand name or framebuilder, I'll bet they'll want to see this failure and make it right.

I'm no expert, but have heard often that Ti is prone to embrittlement from contact with hydrogen/oxygen (air) or other contamination during the welding process. What this means is that any hydrogen hitting the tubes while they are above a certain temperature causes the metal to take on a brittle crystalline structure, like glass. To prevent this,a pure inert gas atmosphere has to be maintained during the welding and cool-down. The criticality of these steps is one reason Ti frames are costly.
Air O2 is the enemy of Ti and AL welding. This happens even with venerable Serotta frames. Happens with both 3/2.5 and 6/4 tubing. Check on your warranty. Demand a new Frame. If it is happening in one place it may be ready for other cracking to showup. Sounds like a Monday frame.
 

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