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How many places make titanium? I assume only a few in the world? Is there such a thing as Ti with impurities any more? Is all Ti of top strength, durability, etc. or is there still low quality Ti, and if so where, who, and how do I stay away from it? Is there only one way to weld Ti that makes a strong durable product? Best way to shape Ti into bicycle tubes? I am in the market to buy a MTB for me 175 pounds and will give me a efficient yet comfortable ride if possible. Do I understand correctly that overtime Ti becomes brittle and stiff, or does that not apply to mountain bike frames due to shapes, size/diameter of tubes and then being welded into a frame/structure? What else should I know? Thank you
 

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ORA in Taiwan is the world's biggest and most advanced mfg of Ti bike frames. They make their own but mostly contract with other labels and bike brands. The quality is outstanding.

You are not correct about Ti getting brittle or stiff. Ti is Ti. The biggest risk with it is having contaminated welds or overheating it when welding. ORA and others heat treat after welding. Ti in and of itself has a fatigue life of zero, meaning if you had a thin piece of it you could bend it back and forth a zillion times and it would not fail. Pure Ti is not suitable for making bike frames, only alloyed Ti. Alloying changes properties of ductility, hardness, strength, and fatigue life. Ti frames can crack, but it is rare and usually the result of loading it in a manner outside of the design intentions.

Just stuff off the top of my head. Google-Fu for more.
 

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ORA in Taiwan is the world's biggest and most advanced mfg of Ti bike frames. They make their own but mostly contract with other labels and bike brands. The quality is outstanding.

You are not correct about Ti getting brittle or stiff. Ti is Ti. The biggest risk with it is having contaminated welds or overheating it when welding. ORA and others heat treat after welding. Ti in and of itself has a fatigue life of zero, meaning if you had a thin piece of it you could bend it back and forth a zillion times and it would not fail. Pure Ti is not suitable for making bike frames, only alloyed Ti. Alloying changes properties of ductility, hardness, strength, and fatigue life. Ti frames can crack, but it is rare and usually the result of loading it in a manner outside of the design intentions.

Just stuff off the top of my head. Google-Fu for more.
I'd disagree with some of that. Ti welds often are brittle and they crack, I'd wager at a much higher incidence than aluminum or steel ones. Just do a few searches for the cracks on the Ti frame-makers here and on the internet and you'll get many examples. The issue is it's difficult to weld Ti without O2 (displaced by inerert gasses). Any O2 contaminating makes the weld brittle. This is one of the biggest issues.

In general, bikes don't fail because they reach their fatigue life (which Ti doesn't have), they fail due to flaws or over-stress events beyond the intended fatigue limit. While aluminum does have a fatigue life-limit, it's not reasonable that you'll reach this in 20 years of riding. Flaws are things like bad welds, corrosion pits, one section of the bike under-designed as compared to the intended fatigue limit, and so on. These flaws and over-stress events are usually what do a bike in.
 
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