7 Things You Didn’t Know About Titanium | GCN Tech Does Science

(collisions reverberating) – We’ve looked at the myths
surrounding carbon fiber. We’ve lifted the lid on aluminum. We’ve investigated whether
steel is in fact real; it was. But, there is still a big gap in the GCN Material Sciences Course. And that, is titanium. For a while, in the early ’90s, titanium was going to
be the next big thing. And to be fair, it briefly was, but little by little it became
eclipsed by carbon fiber. Nevertheless though, it still has a legion of super loyal
fans, and quite right too. So if you’re not onboard
the titanium train yet, or perhaps more accurately,
military aircraft or submarine, what do you need to know? (relaxed chill music) Despite having the reputation
that it’s the preserve of the Russian or American military, which to be fair, it kind of was, titanium is actually the
ninth most common element in the earth’s crust. And as well as using it to make bikes, you can also find it
in sun cream and paper, to make it whiter. Clearly though, what makes paper white doesn’t really help very much
when you’re making bikes, other than perhaps drawing
up your initial ideas, and that is because it’s titanium oxide that’s used in paper, whereas
when we’re making bikes we need a titanium alloy. The very first titanium
bikes were actually though made out of pure titanium,
but they were very flexible and they weren’t very much good. And it wasn’t until a
titanium alloy called 3AL/2.5V that that changed, having blended in 3% aluminum and 2.5% vanadium. The other common titanium
alloy for bikes is 6AL/4V. Both have a very high
Young’s modulus, which is a measure of the
stiffness of the material, so they have a gPA of about 110 as opposed to, let’s say 6061 aluminum, which has a GPa about about 69. And they also have a much
higher yield strength, so that is the point at which a material stops returning to its original position when a stress is removed. So six-four titanium has an MPa of 1000, whereas again 6061 aluminum
has an MPa of just 270. And what that means is that the material won’t deform or bend or buckle in a crash. Three two-five actually
has a lower yield strength than six-four titanium, but
then that’s one of the reasons why it is used almost
exclusively in bike-building, because six-four titanium is
incredibly hard to work with. It’s more brittle and less ductile, so forming it into simple shapes, like, I don’t know, tubes for a start, is incredibly hard. And actually most six-four titanium tubes are rolled from sheet
metal and then welded, whereas three-2.5 tends to be seamless. And so that actually gives a
more consistent overall tube, and therefore is better from
a quality control perspective. So in other words,
basically, although on paper the material properties
of six-four titanium might look better, it won’t
necessarily yield a better bike. Titanium is renowned as being
super light, but in fact, as a material, it’s actually
60% denser than aluminum. However, given what we’ve just heard about the other material properties, you can still see why titanium frames tend to come out slightly
lighter than aluminum ones. So, the best examples of each would be about 1000 grams for a titanium frame and about 1100 grams for aluminum. So, 100 grams in it. And the reason that difference
is actually still quite small is probably down to a measure
of just how much easier it is to work and manipulate aluminum, and we we’ll come on to
that a little bit later on. And we also have to bear in mind that super light titanium frames will also have exceedingly
thin-walled tubing as a result of that extra density. And then when we compare it to steel, titanium is as strong but 45% less dense. And so that explains why titanium frames are significantly lighter than steel. That toughness in terms
of material properties does make titanium very
difficult to work with, as we’ve already touched on. Fortunately though,
much of that difficulty is actually dealt with by the
tube manufacturers themselves. One of those things is that
internally butted tubes can’t be made safely from titanium. Basically the danger is that
titanium can be overworked, and then that would lead to
a weakness in the material. Now on the flip side, what you can do is externally butt the tubing, so instead of a mandrel
working away inside the tube, titanium is shaved off from the outside. However that does rely heavily on the straightness of the
tubing in the first place, because any imperfections in that would also then be reflected
in the wall thicknesses. So, that’s probably why this
bike behind me (taps frame) is made out of straight
gauge titanium tubing. Titanium is also a little
bit trickier to weld than steel or aluminum, and that’s because it’s reactive to oxygen
at higher temperatures, meaning that when it is welded, it needs to be done in
an absence of that gas. Now to be fair, all metals need to be welded in an inert gas environment, but titanium is particularly sensitive. So to put it in context,
if you’re welding steel an acceptable purge, so called, needs to be about 1000
parts of oxygen per million, whereas with titanium, it’s
just 10 parts per million. So that is a little bit
of challenge to a welder, and if any oxygen does get into the weld, then the titanium oxidizes. Which, if you remember
from earlier in the video, is a very white, almost
worthless white powder. The technique then is to weld
in an inert argon atmosphere, so basically you pipe
argon gas into the tubes, and then externally to the weld as well, but then that ensures that
it’s all nice and strong. The last thing that can
make titanium a bit tricky is working. So you see, we mentioned earlier that aluminum can be
engineered and manipulated into all sorts of complicated shapes, but with titanium, even bending a simple S-bend chainstay, for example, extreme care has to be taken
you don’t overwork the material which can then lead to it becoming brittle and therefore weak. In order to avoid that, the
titanium needs to be annealed, which is where you heat it up and then you allow it to cool
down slowly in between each incremental step of the process. It’s quite time consuming,
labor intensive, and it’s another reason why titanium bikes tend to be quite expensive. Is it expensive though? Well, yes compared to aluminum bikes. But it’s probably on a
part with custom steel, and significantly cheaper,
you’ve got to say, than top-end carbon fiber. It is a boutique material, and so yes, there is a boutique cost as well. So the raw material is
between $10 and $12 per kilo. Finished tubes are between
$100 to $120 per kilo. But that puts it a little
bit more than standard steel and on a par with stainless steel. But dare I say though, and because it’s not quite so
fashionable at the moment perhaps, in the cycling world, there are some relative
bargains to be had. And to be fair, we’ve given you an awful lot of information so far, but we’ve not quite got to the nub yet of why titanium has such a loyal following and can be, frankly, so great. You can get a custom titanium
frame really quite easily and it’s going to be considerably lighter than an equivalent custom steel frame, so about 400 grams lighter. I’d guess an average custom
steel frame is about 1600 grams; titanium could be about 1200 grams. Which is pretty important
if you are looking to build a super light road bike. Yes titanium is reactive, but your frame is not going to corrode, not like steel, not like aluminum; it is going to last. And so for many people,
the Ti bike is the keeper. Beauty is very much in
the eye of the beholder, but I think titanium has
undeniably a special something. I mean look at the raw finish on this; it’s like it’s glowing. Ah, the ride quality,
even harder to pin down than aesthetics. Now traditionally, titanium
has a ride feel like no other. But the boundaries between
materials are blurring; engineering is taking
things to new places. So steel can now be as stiff as aluminum; aluminum can now be as
forgiving as carbon fiber. But titanium traditionally
has always been about zing. I heard it described back in the day like a great titanium frame
was trying to spring forward and gain momentum off every
bump or ripple in the road. And that, to my mind,
sounds pretty amazing. Now unfortunately, I’ve
literally never spent any proper time on a titanium bike. So at some point soon
I hope to remedy that. Well there is your Titanium 101. Hopefully you can add it now as a material that you know as much about as steel, aluminum, and carbon fiber. Please give this video a big thumbs up; if nothing else you’ve been
looking at some bike porn for the last few minutes. And if you want to watch
one of those videos, refresh your knowledge
about the other materials, why not check out the one
about aluminum just down there.

Leave a Reply