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The story of titanium

construction-physics.com

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Re: The story of titanium

#171

Post by justinator »

johnwalkr wrote: post #101
petertodd wrote: post #50

Earlier quoted context omitted.

Also fatigue resistance. Bicycle design is a good example of where this matters: steel has a significant fatigue limit, and can endure cyclic stresses below that limit indefinitely. Aluminum has no fatigue limit, so any flexing is inevitably eating away at fatigue life. Thus aluminum bike frames have to be made much stronger and stiffer than otherwise necessary, to avoid bikes breaking unexpectedly due to fatigue. An…

For a rigid road bike aluminum can definitely be made stronger and lighter, even though what you wrote about fatigue limit is technically true. People like steel because they feel it’s more comfortable to ride. For mountain bikes, you will find almost zero steel bikes. Here the stiffness and lightness of aluminum (and carbon fiber at the high end) is almost universally preferred. One advantage that adds to the potent…

> For mountain bikes, you will find almost zero steel bikes

Surly makes (only) steel mountain bikes, and I think there are approx. a... there's a lot of them out there. One reason is that they are inexpensive (relatively) and take a lot of abuse.

https://surlybikes.com/bikes/trail

Re: The story of titanium

#172

Post by justinator »

scythe wrote: post #154
AlotOfReading wrote: post #20

Earlier quoted context omitted.

Steel's strength varies by orders of magnitude depending on the alloy and heat treatment. It's an incredibly flexible family of materials. Some members of that family are far stronger than anything in the titanium family, e.g. 4340 steel has a nominal yield strength of >1800 MPa, compared to <1300 MPa for Ti 10-2-3.

Wikipedia: >4340 steel is an ultra-high strength steel https://en.wikipedia.org/wiki/4340_steel The alloy composition calls for 0.2-0.3% molybdenum and expects accuracy to within a few per mille for ten elements. Moly is considered so important that there are entire towns in the United States established to mine it to secure the military supply chain.

Is this true? From the Wikipedia article, the two mines that produce molybdenum as the main product are the two in CO, Henderson and Climax. They have no towns associated with them. Climax is near Leadville, but Leadville existed as a mining town before molybdenum was being mined at any scale. The other mine isn't close to any town that has more than a trailer park of people.

The others mine molybdenum as a byproduct of copper. I guess you could say the Bagdad mine has a company town, but it wasn't made to secure the military supply chain 140 year ago.

Re: The story of titanium

#173

Post by lenkite »

thaumasiotes wrote: post #138
kylehotchkiss wrote: post #30

Earlier quoted context omitted.

I could see a day when titanium laptops return. Apple has invested in the some of the best mass machining in the world. I wonder what it’d look like sandblasted like their laptops and with their new coatings.

> I could see a day when titanium laptops return. I don't get it. I was issued a metal macbook once. I had to buy a plastic case for it, because the bare metal scratched my fingernails. Why would we want a hard metal case instead of a soft plastic one?

> because the bare metal scratched my fingernails.

Nice multi-purpose titanium laptop. You can even trim your fingernails on the same!

Re: The story of titanium

#174

Post by peter_d_sherman »

Great article!

>"The earth contains a lot of titanium - it’s the ninth most abundant element in the earth’s crust. By mass, there’s more titanium in the earth’s crust than carbon by a factor of nearly 30, and more titanium than copper by a factor of nearly 100."

>"Titanium was nearly as strong as stainless steel, but weighed 40% less."

Consider Steel I-Beams, used in construction:

https://en.wikipedia.org/wiki/I-beam

Observation: If the workability difficulties of Titanium could be solved, at scale -- then not Steel, but Titanium I-Beams -- could be produced, en masse...

If this could be done cheaply enough, then, in the future, Titanium I-Beams -- produced in the U.S.A. -- could retake the worldwide market for construction I-Beams that was historically lost when other countries started producing Steel I-Beams cheaper than the U.S. did...

Anyway, an excellent article!

Re: The story of titanium

#175

Post by thaumasiotes »

lenkite wrote: post #173
thaumasiotes wrote: post #138

Earlier quoted context omitted.

> I could see a day when titanium laptops return. I don't get it. I was issued a metal macbook once. I had to buy a plastic case for it, because the bare metal scratched my fingernails. Why would we want a hard metal case instead of a soft plastic one?

> because the bare metal scratched my fingernails. Nice multi-purpose titanium laptop. You can even trim your fingernails on the same!

It would be less effective than a file, since there's just the one point on the sharp edge of the laptop.

Most people are not looking to scuff up the face of their fingernails, which is what happens when you handle such a laptop naturally.

Re: The story of titanium

#176

Post by psd1 »

muz754 wrote: post #92
danielodievich wrote: post #3

As a kid in my father's workshop we had several 4mm thick titanium plates, scavenged from some industrial stuff in USSR research facility nearby. I had a lot of fun getting my visiting friends tey to dent it with hammers. No matter how hard you struck it just didn't care. Only the oxidation patina would show some trace of impact. It was absolute magic to me. And so incredibly light!

Some hammers might not be that hard - you don’t want it to blow up in your face if you’re hitting a hardened steel tool.

I do not like my hammer hard!

I do not like a face of shard!

I like to whale upon a tool

A shattered hammer is not cool!

Re: The story of titanium

#177

Post by nullc »

saberience wrote: post #23
petertodd wrote: post #21

Earlier quoted context omitted.

Read this for starters: https://www.thomasnet.com/articles/metals-metal-products/ste... "When comparing the tensile yield strengths of titanium and steel, an interesting fact occurs; steel is by-and-large stronger than titanium." Many people confuse this issue, because they're actually talking about measures of strength/weight ratios, on which titanium does really well. But if you are size limited rather than weight…

Every source says that titanium is as strong as the most commonly used steel. Sure if you're going for lesser used alloys of steel you may as well compare to lesser used alloys of titanium. Or just compare iron with titanium, as that's really comparing one element with another, and is the "fair" comparison. And anyway, your original comment suggested someone was totally in the wrong for thinking a 4mm titanium plate…

Titanium is quite expensive. I don't know if it makes sense to compare it to mild steel and not compare it to fancier steel selections which are still much less expensive than titanium and also much easier to work.

AR500 has a HRC of 47, modulus of 220 GPa, and tensile strength of 1740 MPa. Ti-6Al-4V is 37, 113.8 GPa, and 880 MPa respectively. The AR500 costs less than half as much as the Ti, and is much easier to work (though obviously working will degrade the properties).

The titanium is super really light, however... so the choice of material will depend on how relatively important weight is vs size and how simple your geometry is such that the added difficulty in working with Ti doesn't add problems.

Obviously there are also other grades of Ti too, but I think the comparison generally holds: If you don't care about weight/mass there is a steel selection which will be stronger, cheaper, and easier to form.

If you do care a lot about weight, an aluminum alloy often comes out the winner unless you just don't care much about costs or have fatigue concerns.

Re: The story of titanium

#178

Post by [deleted] »

petertodd wrote: post #15
myself248 wrote: post #9

Earlier quoted context omitted.

Decades ago, Sears sold magnesium stepladders. I've used one, and it's freakishly light, a 6-foot step ladder that you can walk around with balanced on one finger. I've always wondered what a titanium one would be like.

A lot heavier actually. In an application like a stepladder, you have to work with certain minimum dimensions for the stepladder to be practical (eg rungs and sides have to fit in the hands nicely). You also have to have certain minimum thicknesses on the parts to have sufficient resistance to local deformation (eg dropping a hammer on the rungs). That forces the parts to be significantly larger and stronger than the…

[deleted]

Re: The story of titanium

#179

Post by Vicinity9635 »

redman25 wrote: post #103
Vicinity9635 wrote: post #87

I have a titanium chainmail shirt: https://www.etsy.com/listing/505806057/titanium-chainmaille-... (me in 2nd pic) It weighs just 6.6 lbs. (the page says 6.5 but I had to have him add a bit cause I got too swole in the lats a couple of years ago.) It's fun to have someone try it on then watch them struggle as they can't figure out how to get it off lol If you bend over and stick your arms down it basically slide off…

Curious how durable a Ti shirt would be. Could it save you walking down a dark alley at night?

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Re: The story of titanium

#180

Post by Vicinity9635 »

NickNameNick wrote: post #110
redman25 wrote: post #103

Earlier quoted context omitted.

Curious how durable a Ti shirt would be. Could it save you walking down a dark alley at night?

Looks like they're just butted rings, so you're relying on the rididity of each ring to resist opening up. Welded or rivited rings would be much more robust. Especially vs piercing weapons, like arrows or fighting knives. But much more expensive.

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