# Titanium vs Chromoly?



## Wulf1971 (Dec 15, 2008)

I'm in an argument with a friend who insists that chromoly is stronger than titanium. Is it true that titanium has to be equal in weight to chromoly to be as strong? Can anyone provide a link to info either supporting or debunking this?


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## keith_mahoney (May 18, 2008)

Seriously guy?
Why would titanium be so expensive and used so extensively in military aircraft if it needed the same weight as steel to be as strong as steel?
In order for titanium to weigh as much as steel you need much more volume or size. If it was equal strength on a weight basis, it would be inferior to steel due to the large amounts needed.

I think your friend is just pulling your chain.


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## Wulf1971 (Dec 15, 2008)

That's exactly what I was thinking. It just does not make any sense, but it would be nice to have some proof.


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## Rykoh (Mar 26, 2009)

http://www.sheldonbrown.com/frame-materials.html


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## Wulf1971 (Dec 15, 2008)

Rykoh said:


> http://www.sheldonbrown.com/frame-materials.html


Thank you.


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## cheesy (Apr 15, 2009)

Depends on the alloys but he is almost right 350M can have a yeild of around 2400MPa.....


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## Thylacine (Feb 29, 2004)

Thermophilic micro-alloyed steels can be over twice as strong as 3-2.5 Titanium, which has a similar UTS to 4130 CroMo. However, a UTS is only one part of a much larger equation, so it's a bit of a pointless argument.

Ti makes a strong argument for it's use as a bike frame because of it's excellent strength-to-weight, good impact toughness and fatigue strength, corrosion resistance, and fantastic ride quality. It's not used because it's 'insanely strong' because it's not.


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## disease (Nov 27, 2007)

Wulf1971 said:


> I'm in an argument with a friend who insists that chromoly is stronger than titanium. Is it true that titanium has to be equal in weight to chromoly to be as strong? Can anyone provide a link to info either supporting or debunking this?


Your friend is right in one respect. 3AL-2.5V in its annealed condition is listed on Matweb as having an ultimate tensile strength of 89,900 psi. 4130 chromoly that has been normalized(heat treated and stress relieved) actually has a higher ultimate tensile strength(90,000 psi). These listings are based on tests of samples of a certain dimension, not a certain weight. For example, a comparison can be made by pulling until failure a 1/4" rod of annealed titanium and a 1/4" rod of normalized 4130. They will both break at about the same tension(89,900-90,000 psi). The important fact to keep in mind is that the 3AL-2.5V titanium sample will weigh much less than the 4130 sample.


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## rustola (Jan 15, 2008)

these articles by scot nicol on different materials for bike frames are outstanding:

Scot Nicols Metallurgy 101

It's not really as simple as "x is stronger than y"


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## disease (Nov 27, 2007)

rustola said:


> It's not really as simple as "x is stronger than y"


On that note, I wonder about all those titanium products out there, including frames and forks. I notice that very few of them claim to be CWSR(Cold Worked Stress Relieved). Should we assume that anything that does not claim to be CWSR is simply lower strength annealed titanium, being sold at a premium to uninformed buyers?

Any framebuilders care to enlighten us?


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## smudge (Jan 12, 2004)

disease said:


> On that note, I wonder about all those titanium products out there, including frames and forks. I notice that very few of them claim to be CWSR(Cold Worked Stress Relieved). Should we assume that anything that does not claim to be CWSR is simply lower strength annealed titanium, being sold at a premium to uninformed buyers?
> 
> Any framebuilders care to enlighten us?


Most American builders that I'm familiar with use CWSR tubing rather than annealed. That said, not too many of them make the claim that they use it on every tube. There may be builders who use annealed tubing on the seat and chain stays. It can be very difficult to cleanly bend CWSR tubing to "extreme angles". An example using some of my notes...I built a couple of 29ers concurrently a few months back. They both had roughly 440mm chain stays in 7/8" diameter with .035" wall. the tire clearance bend was bent to 42* and the springback took it back to 28* while the heel bend went from 15* back to 6*. Two of the four chainstays had slight rippling on the inside radius of the 28* bend while the other two bent cleanly. You can bend 30* angles all day on annealed tubing with no rippling.

I often wonder about the bikes with bends in the main tubes and if they're using annealed on them. FWIW, I'm not implying that it's bad or wrong, I just wonder.


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## disease (Nov 27, 2007)

smudge said:


> Most American builders that I'm familiar with use CWSR tubing rather than annealed. That said, not too many of them make the claim that they use it on every tube. There may be builders who use annealed tubing on the seat and chain stays. It can be very difficult to cleanly bend CWSR tubing to "extreme angles". An example using some of my notes...I built a couple of 29ers concurrently a few months back. They both had roughly 440mm chain stays in 7/8" diameter with .035" wall. the tire clearance bend was bent to 42* and the springback took it back to 28* while the heel bend went from 15* back to 6*. Two of the four chainstays had slight rippling on the inside radius of the 28* bend while the other two bent cleanly. You can bend 30* angles all day on annealed tubing with no rippling.
> 
> I often wonder about the bikes with bends in the main tubes and if they're using annealed on them. FWIW, I'm not implying that it's bad or wrong, I just wonder.


Your point about bending issues raises a question about components. Titanium riser bars and layback posts never claim to be CWSR, as far as I am aware. If springback issues are a problem in manufacturing, then they may be using annealed tubing. On the other hand, the springback problems may have been worked out if the part is mass produced rather than custom made.

I see so many titanium seatposts and handlebars for sale. They are always described as 3Al-2.5V, and use terms like "aerospace grade". They almost never claim whether the tubing is seamless or not. Few if any of them bother to define what condition that 3Al-2.5V tubing is in. Condition is very important. Unless the tubing is solution treated and aged up to 130,000 PSI ultimate strength, it is not much stronger than heat treated 4130 chromoly, at 89,000 PSI yield strength. It will have the exceptional properties of titanium, such as the ability to bend considerably, as well as be light weight, but it is ultimately no stronger than normailized 4130. I am strictly speaking about ultimate tensile strength and yield strength here.


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