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!
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.
Mountaineering ice screws. Its a dream for pro alpinists, since you have to drag every gram up there in thin air, so focus on weight saving is extreme, ie drilling holes into aluminum spoons before 8000m expeditions was normal in 70s-80s in eastern Europe block. Normal stainless steel ones are much heavier.
Those must have been soft hammers. Titanium isn't magic. It's neither as hard, nor as strong, as steel. It's a lot lighter, which makes it a wonder material in certain applications that can take advantage of it's excellent strength-to-weight ratio. But if max hardness, or strength at a given size, is what you are after, without a weight constraint, steel wins.
I mean, I'm no materials scientist but one google tells me that Titanium is AS strong as steel but much less dense. I just browsed through the top 10 Google results and everyone states that titanium is roughly equal to steel in strength but with various other benefits. So your comment is definitely off-base somewhere, you make it seem like steel is much stronger, which clearly isn't the case.
The article mentions that the Soviet Union had lots of titanium ore, and also that it was heavily used in the A-12/SR-71 family of aircraft.
I remember reading elsewhere that the CIA set up a bunch of front operations across the world to buy titanium (or maybe titanium ore) from the USSR without them finding out what it was being used for. They didn't want the "Ship to:" part of the order form reading "Lockheed Skunkworks, Burbank Califoria". Heh.
If only we could find a cheap way to get the metal out of titanium dioxide. Like a Haber process-level breakthrough.
Then we could start replacing steel with titanium in many applications. Think entire freight trains, cargo ships, containers, cars, trucks, tractors -- all that heavy steel replaced by titanium alloys.
Enormous quantities of fuel and energy saved by lower density and higher strength. In many applications, it would likely make stainless steel obsolete.
Trillions of dollars of value may be locked up in such a breakthrough.
I think it could be one of those 'grass-is-greener' scenarios. Steel is really nice to work with. It's strong and elastic and you can do all sorts of things to alter its properties, like even in a home shop.
Titanium always looks really hard to work with, just from the few times I've seen youtube types get some into their lathe chucks.
Would the added (in some ways just different) performance make up the difference? No idea. I mean, would people use so much aluminium if it wasn't straightforward to extrude it into interesting shapes? I don't think I would.
The straight characteristics of a material are one thing: what you can actually do with it are another.
That's why I said titanium alloys specifically. With such a large-scale industrial transformation, definitely many alloys would be explored, to fit the needs of new industries. We don't use pure iron for any serious applications either.
You are correct in that steel is harder and stiffer than titanium. Steel is also more re-usable, smelt-able than titanium.
However, when it comes to fatigue (which I assume, you are referring to fracture strain) titanium has a significant edge. The fracture strain for steel is roughly 15%, but for titanium alloys, it often reaches and exceeds 50%.
I don't say this to contradict you, but to point out that as with most things in life, "it depends".
Like steel, titanium alloys have a distinct non-zero fatigue limit, and thus can be engineered to have infinite fatigue lives. Though the exact details differ and steel or titanium can be better depending on exactly what the conditions are.
> Then we could start replacing steel with titanium in many applications.
The world's production of stainless steel is growing almost exponentially and we are replacing many applications or ordinary steel with stainless. Every year millions of tons of steel are lost to rust.
Resting next to me is a titanium ring, it is extremely light, resistant to ambient temp change, and is usually cool to the touch. It cost $15 or so. It wears in a really beautiful way, aging like it's enjoying itself.
On my finger is a tungsten carbide ring, it's extremely dense (that of gold, slightly heavier than uranium), and has a lot of interesting properties. It's warmed quickly by my fingers, and rings the most beautiful tone when I strike it with some bar stock of AI.
Wolfram has been a very nice metal in my life, I wish it was more common, and would love to try to add some knurling to it.
I wear a titanium ring too and keep my real one safely locked away. It’s an incredible metal that I proudly wear around. Mine cost about the same.
I also have a titanium pocketknife (James Brand), carabiner, keyrings, pens, camera (fujifilm makes a few), and some beloved snow peak dishes. And the silly titanium iPhone. It’s such a great metal to make things to carry with.
Do you mind sharing where you got the titanium keyrings and carabiners?
I've been searching forever for decent keyrings. There's a few carabiners (though the titanium ones are hard to find there too, and usually covered in obnoxious branding). But keyrings especially seem to be an under-served market. There's either (1) the usual mass-produced, flimsy, cheap garbage, or (2) something tougher and more expensive, but covered in branding.
I've settled with (2) for now (though it's not even titanium), but it'd be nice to not have to look at a giant billboard every time I pull out my keys.
I have one too. It’s not my favorite to wear because it has zero heft. It’s unsubstantial and has a strange plasticky somewhat sticky feel. I plan on replacing it with gold. I can’t complain about the price though - they came in a box of 3.
I have a nickel allergy so titanium is my first port of call for jewellery, though my wedding ring is zirconium and some of my old, pre-allergy stuff is now plated with rhodium.
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.
There was a blog called "Atomic Delights" that would explain the manufacturing processes featured in the videos. Found it super interesting, especially considering the challenge of shipping products at Apple level volumes.
A MBP with the natural titanium finish as seen in the iPhone 15 Pro would be fantastic.
Wasn't one of the major problems that Titanium doesn't play well with Wifi? The TiBook predated built-in wifi, and I thought one of the reason to shift to Aluminum was wifi performance.
Almost everything about the article is wrong, oversimplified, or misleading.
Take this paragraph, for instance:
> But despite its abundance, it's only recently that civilization has been able to use titanium as a metal (titanium dioxide has been in use somewhat longer as a paint pigment). Because titanium so readily bonds with oxygen and other elements, it doesn’t occur at all in metallic form in nature. One engineer described titanium as a “streetwalker," because it will pick up anything and everything. While copper has been used by civilization since 7000 BC, and iron since around 3000 BC, titanium wasn’t discovered until the late 1700s, and wasn’t produced in metallic form until the late 19th century.
As this is basically a bunch of bullet points in paragraph form, it'll be easier to handle if we break it down:
> But despite its abundance, it's only recently that civilization has been able to use titanium as a metal (titanium dioxide has been in use somewhat longer as a paint pigment).
The same also applies to aluminum, magnesium, nickel, etc.
> Because titanium so readily bonds with oxygen and other elements, it doesn’t occur at all in metallic form in nature.
The same also applies to aluminum, magnesium, and even iron. (I mean, there's some meteoric iron, but it's very rare.) Pure metals are very rare in nature. What distinguishes iron and copper from aluminum and titanium is the energy required to split the oxide into metal.
> One engineer described titanium as a “streetwalker," because it will pick up anything and everything.
Titanium is not more reactive than aluminum and it's far less reactive than magnesium. In fact, it's slightly less reactive than iron overall. (i.e., more chemically stable under normal conditions and in contact with common acids.)
> While copper has been used by civilization since 7000 BC, and iron since around 3000 BC, titanium wasn’t discovered until the late 1700s, and wasn’t produced in metallic form until the late 19th century.
This has everything to do with the temperature required to separate the metal from the oxygen atoms binding it, and nothing to do with anything else. What's more, it applies even more strongly to aluminum, which was discovered in 1825 -- three decades after the discovery of titanium. (1791.) So there's absolutely nothing unique about titanium in this regard.
I could go on. But basically this is an "I hecking love science" article that barely scratches the surface of the subject -- and still manages to be subtly misleading.
> The same also applies to aluminum, magnesium, nickel, etc.
the oxides of aluminum, magnesium, and nickel were not in use as paint pigments
> What distinguishes iron and copper from aluminum and titanium is the energy required to split the oxide into metal. (...) Titanium is not more reactive than aluminum
the particularly relevant issue here, as i understand it, is that titanium has a stable carbide, which prevents you from reducing it carbothermically; you end up with titanium carbide instead of titanium metal. aluminum's carbide is unstable even in water, while iron's carbide is mechanically strong but still easy to reduce to iron with air. copper's carbide is poorly characterized and even more unstable, and it even occurs native
there are other things that titanium reacts more strongly with than aluminum does. titanium tetrachloride, for example, which is mentioned in the article, isn't a mere salt like normal chlorides; it's a volatile fuming liquid, because titanium forms covalent bonds with the chlorine like a motherfucking nonmetal. you can argue about whether this makes it more or less reactive than aluminum in this context; the reaction produces more energy per metal atom but less energy per chlorine atom
this kind of dirty trick is why titanium wasn't isolated until decades after the creation of metallic calcium, sodium, potassium, aluminum, and even the isolation of some of the rare earths
so i think the characterization in the article is fair
> the oxides of aluminum, magnesium, and nickel were not in use as paint pigments
Aluminum oxides were used as a pigment, predominantly in blue (cobalt aluminum oxide) but also in white.
In any case, the dominant white dyes of the Early Modern period -- and prior periods -- were lead based. The presence of TiO2-based pigments is actually one good way to identify a modern forgery.
> the particularly relevant issue here, as i understand it, is that titanium has a stable carbide
This turned out to be solvable via calciothermic or magnesiothermic reduction -- which is now effectively the go-to method for just about everything that can't be reduced with carbon. All titanium dioxide reduction processes demand quite a lot of energy, though; more than aluminum and far more than iron.
The article may be an oversimplification, but your comment is an equal oversimplification. There are many environmental conditions that need to be assumed when comparing reactivity.
For instance, if you have pure Titanium, pure Magnesium, pure aluminum in a vacuum at room temperature and proceed to introduce oxygen, you get the following reactions (simplified elemental chemical reactions, the Enthalpy of formation is what is important here):
Ti + O2 -> TiO2
(Std. Enthalpy of formation is -945kJ/mol)
Mg + O -> MgO
(Std. Enthalpy of formation is -601kJ/mol)
4Al + 3O2 -> 2 Al2O3
(Std. Enthalpy of formation is -1675kJ/mol)
As a result, aluminum is most reactive, followed by titanium, then magnesium.
This is the reason why aluminum is used in solid rocket motors and various other explosive devices.
Under different conditions, these numbers may change: for instance a reaction with water instead of air may yield different enthalpies. At quick glance in water, titanium is actually least reactive when compared to aluminum and magnesium.
So from a high enough vantage point, Ti is very slightly less reactive than Al, less reactive than Mg, and not too far from Fe. A far cry from being "a streetwalker" of a metal.
to make a fair comparison here, you need to normalize per mole of metal. these enthalpies of formation are reported per mole of oxide, but there's twice as much Al per mole of Al2O3 than Ti in TiO2.
Great overview: Titanium production technology essentially “willed into existence” by the US government (mainly the military branches) but now critical in health care for implants that embed with bone and that do not induce rejection.
Love titanium, something so cool about it. It’s like steel with no downsides. I’ve got 5 ti bikes and a few ti watches, one of my favorite pieces though is my snow peak double wall titanium mug.
Finally a titanium stan thread! Due to skin allergies/sensitivities, the only material I can wear for watches seems to be titanium. Luckily the market for them are mostly all stylish and functional. And they're so light! It's like I'm wearing another piece of clothing on my wrist that's cold and tells me the time.
Do your bikes have carbon forks or TI? when I looked at TI bikes for fun in the past, the carbon forks surprised me, seemed like that should have been titanium too. How has your mug held up? Has it been compatibly durable compared to steel vacuum mugs? Snow peak makes great products but leans more lightweight than durable from my experience with their dishware
Titanium needs to be in a bigger tube with thinner walls to take advantage of the properties compared to steel - the very first titanium bicycles used the available surplus tubing from defense/aeronautics industry that was close to steel bicycle tubing size and were notably not great until they used slightly bigger tubing and better titanium alloys. Forks have a couple of design features that make it hard to work with titanium tubing, the height from bottom of headtube to where the top of the tire is has to have extra space for clearance or a tiny object or some mud will clog up the fork pretty quickly or cause an immediate stop in front wheel rotation, and that part of the fork has to be extremely stiff. Some of of the first carbon forks had a titanium steerer tube for a minimal weight saving and to make it easier to work with the stem attachment system. Several equipment changes to this part of the bicycle have come about in the last couple of decades to accommodate carbon fiber more easily. The market for titanium was just too niche by comparison to make those changes necessary.
Snow Peak's titanium spork is awesome as well. I got two and use one for my regular meals and the other I EDC in a cargo pocket for use away from home.
Tea, especially green tea, in a titanium mug is, in my experience, utterly gross.
Maybe anodized titanium would work better? I don’t know what the chemistry behind the problem is, but even stainless steel kills green tea after a while.
It’s super light, about the same weight as single wall stainless cup. The mouthfeel is nice, hot coffee doesn’t make the titanium feel as hot as steel gets and the feel is more similar to ceramic than stainless steel. It cleans up really nice and truly doesn’t stain. I even used a dc transformer to do some custom anodizing on mine and it looks really cool.
I've got a Ti double-walled mug from Snow Peak that I use a lot around the house. The big strengths are light weight, near indestructability, and a cool Ti functional aesthetic. It's double-walled and holds heat well, but I prefer the "mouth feel" of ceramic or glass when drinking coffee, so I don't use it much for coffee.
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 on its own.
What's really interesting is the ringing sound it makes when you play with it or move around wearing it, it's a noticibly higher pitch than steel is.
I also have a necklace/spacepen lanyard, wallet chain, and coif made of titanium by Bim also. My keyrings and bottle opener are also titanium. It's such a cool metal. Kind of a pity it makes a very poor knife blade. Speaking of: I also replaced the screws and hinges of my bespoke Benchmade knife with titanium ones, because why not?
It's incredibly durable. This thing will probably be a family heirloom for generations.
Ti is 6.0 on Moh's similar to feldpspar. It'll scratch lots of things. I have to warn people to keep it away from jewelry it'll scratch most ordinary stuff including glass. I accidentally damaged my bathroom sink washing it after polishing (thrown in the dryer in a bag by itself). Little scratch marks around the drain just from washing. Not trying to grind it down into the sink or anything.
>Could it save you walking down a dark alley at night?
From a knife probably. Still hurt like fuck without a gambeson. I don't think it's even slightly bulletproof because the rings are just butted against each other not welded at all. In fact it might making being shot worse by adding titanium fragments. But I haven't tested that.
Readit News
They were awesome, unbelievably light, but very durable. They also made nice sparks when dragged across concrete pavement.
I've always wondered what a titanium one would be like.
I remember reading elsewhere that the CIA set up a bunch of front operations across the world to buy titanium (or maybe titanium ore) from the USSR without them finding out what it was being used for. They didn't want the "Ship to:" part of the order form reading "Lockheed Skunkworks, Burbank Califoria". Heh.
Highly reccomended and goes into further engineering and design challenges of the RS-71 Blackbird and its titanium construction.
I do not like a face of shard!
I like to whale upon a tool
A shattered hammer is not cool!
If only we could find a cheap way to get the metal out of titanium dioxide. Like a Haber process-level breakthrough.
Then we could start replacing steel with titanium in many applications. Think entire freight trains, cargo ships, containers, cars, trucks, tractors -- all that heavy steel replaced by titanium alloys.
Enormous quantities of fuel and energy saved by lower density and higher strength. In many applications, it would likely make stainless steel obsolete.
Trillions of dollars of value may be locked up in such a breakthrough.
Titanium always looks really hard to work with, just from the few times I've seen youtube types get some into their lathe chucks.
Would the added (in some ways just different) performance make up the difference? No idea. I mean, would people use so much aluminium if it wasn't straightforward to extrude it into interesting shapes? I don't think I would.
The straight characteristics of a material are one thing: what you can actually do with it are another.
Looks like alloys are much more mallable, while losing almost none of the qualities of pure titanium.
Also: Go nukkular, high-temperature to be specific.
However, when it comes to fatigue (which I assume, you are referring to fracture strain) titanium has a significant edge. The fracture strain for steel is roughly 15%, but for titanium alloys, it often reaches and exceeds 50%.
I don't say this to contradict you, but to point out that as with most things in life, "it depends".
Source: https://www.ulbrich.com/blog/titanium-versus-steel-a-battle-....
Based on this tech: https://en.m.wikipedia.org/wiki/FFC_Cambridge_process
Still waiting for my titanium girders though...
In my mind, this is what real technology entrepreneurship looks like. As opposed to the latest crypto or social media thing.
The world's production of stainless steel is growing almost exponentially and we are replacing many applications or ordinary steel with stainless. Every year millions of tons of steel are lost to rust.
Its a gigsntic shift noone is noticing
On my finger is a tungsten carbide ring, it's extremely dense (that of gold, slightly heavier than uranium), and has a lot of interesting properties. It's warmed quickly by my fingers, and rings the most beautiful tone when I strike it with some bar stock of AI.
Wolfram has been a very nice metal in my life, I wish it was more common, and would love to try to add some knurling to it.
I also have a titanium pocketknife (James Brand), carabiner, keyrings, pens, camera (fujifilm makes a few), and some beloved snow peak dishes. And the silly titanium iPhone. It’s such a great metal to make things to carry with.
I've been searching forever for decent keyrings. There's a few carabiners (though the titanium ones are hard to find there too, and usually covered in obnoxious branding). But keyrings especially seem to be an under-served market. There's either (1) the usual mass-produced, flimsy, cheap garbage, or (2) something tougher and more expensive, but covered in branding.
I've settled with (2) for now (though it's not even titanium), but it'd be nice to not have to look at a giant billboard every time I pull out my keys.
Source - my wife breaks out from nickel in jean rivets but niobium is good enough for piercings
> "Titanium! It's made out of titanium! Like the spy planes! This is an incredible material, it's stronger than steel yet lighter than aluminium."
https://youtu.be/bNHkrnU77m0?t=92
There was a blog called "Atomic Delights" that would explain the manufacturing processes featured in the videos. Found it super interesting, especially considering the challenge of shipping products at Apple level volumes.
A MBP with the natural titanium finish as seen in the iPhone 15 Pro would be fantastic.
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?
Take this paragraph, for instance:
> But despite its abundance, it's only recently that civilization has been able to use titanium as a metal (titanium dioxide has been in use somewhat longer as a paint pigment). Because titanium so readily bonds with oxygen and other elements, it doesn’t occur at all in metallic form in nature. One engineer described titanium as a “streetwalker," because it will pick up anything and everything. While copper has been used by civilization since 7000 BC, and iron since around 3000 BC, titanium wasn’t discovered until the late 1700s, and wasn’t produced in metallic form until the late 19th century.
As this is basically a bunch of bullet points in paragraph form, it'll be easier to handle if we break it down:
> But despite its abundance, it's only recently that civilization has been able to use titanium as a metal (titanium dioxide has been in use somewhat longer as a paint pigment).
The same also applies to aluminum, magnesium, nickel, etc.
> Because titanium so readily bonds with oxygen and other elements, it doesn’t occur at all in metallic form in nature.
The same also applies to aluminum, magnesium, and even iron. (I mean, there's some meteoric iron, but it's very rare.) Pure metals are very rare in nature. What distinguishes iron and copper from aluminum and titanium is the energy required to split the oxide into metal.
> One engineer described titanium as a “streetwalker," because it will pick up anything and everything.
Titanium is not more reactive than aluminum and it's far less reactive than magnesium. In fact, it's slightly less reactive than iron overall. (i.e., more chemically stable under normal conditions and in contact with common acids.)
> While copper has been used by civilization since 7000 BC, and iron since around 3000 BC, titanium wasn’t discovered until the late 1700s, and wasn’t produced in metallic form until the late 19th century.
This has everything to do with the temperature required to separate the metal from the oxygen atoms binding it, and nothing to do with anything else. What's more, it applies even more strongly to aluminum, which was discovered in 1825 -- three decades after the discovery of titanium. (1791.) So there's absolutely nothing unique about titanium in this regard.
I could go on. But basically this is an "I hecking love science" article that barely scratches the surface of the subject -- and still manages to be subtly misleading.
the oxides of aluminum, magnesium, and nickel were not in use as paint pigments
> What distinguishes iron and copper from aluminum and titanium is the energy required to split the oxide into metal. (...) Titanium is not more reactive than aluminum
the particularly relevant issue here, as i understand it, is that titanium has a stable carbide, which prevents you from reducing it carbothermically; you end up with titanium carbide instead of titanium metal. aluminum's carbide is unstable even in water, while iron's carbide is mechanically strong but still easy to reduce to iron with air. copper's carbide is poorly characterized and even more unstable, and it even occurs native
there are other things that titanium reacts more strongly with than aluminum does. titanium tetrachloride, for example, which is mentioned in the article, isn't a mere salt like normal chlorides; it's a volatile fuming liquid, because titanium forms covalent bonds with the chlorine like a motherfucking nonmetal. you can argue about whether this makes it more or less reactive than aluminum in this context; the reaction produces more energy per metal atom but less energy per chlorine atom
this kind of dirty trick is why titanium wasn't isolated until decades after the creation of metallic calcium, sodium, potassium, aluminum, and even the isolation of some of the rare earths
so i think the characterization in the article is fair
Aluminum oxides were used as a pigment, predominantly in blue (cobalt aluminum oxide) but also in white.
In any case, the dominant white dyes of the Early Modern period -- and prior periods -- were lead based. The presence of TiO2-based pigments is actually one good way to identify a modern forgery.
> the particularly relevant issue here, as i understand it, is that titanium has a stable carbide
This turned out to be solvable via calciothermic or magnesiothermic reduction -- which is now effectively the go-to method for just about everything that can't be reduced with carbon. All titanium dioxide reduction processes demand quite a lot of energy, though; more than aluminum and far more than iron.
For instance, if you have pure Titanium, pure Magnesium, pure aluminum in a vacuum at room temperature and proceed to introduce oxygen, you get the following reactions (simplified elemental chemical reactions, the Enthalpy of formation is what is important here):
Ti + O2 -> TiO2 (Std. Enthalpy of formation is -945kJ/mol)
Mg + O -> MgO (Std. Enthalpy of formation is -601kJ/mol)
4Al + 3O2 -> 2 Al2O3 (Std. Enthalpy of formation is -1675kJ/mol)
As a result, aluminum is most reactive, followed by titanium, then magnesium.
This is the reason why aluminum is used in solid rocket motors and various other explosive devices.
Under different conditions, these numbers may change: for instance a reaction with water instead of air may yield different enthalpies. At quick glance in water, titanium is actually least reactive when compared to aluminum and magnesium.
https://en.wikipedia.org/wiki/Reactivity_series
So from a high enough vantage point, Ti is very slightly less reactive than Al, less reactive than Mg, and not too far from Fe. A far cry from being "a streetwalker" of a metal.
Maybe anodized titanium would work better? I don’t know what the chemistry behind the problem is, but even stainless steel kills green tea after a while.
Though it's heavier than an insulated plastic mug, and _way_ more expensive.
Fun fact: if you try to microwave coffee in it, it mostly just slightly heats the metal lol
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 on its own.
What's really interesting is the ringing sound it makes when you play with it or move around wearing it, it's a noticibly higher pitch than steel is.
I also have a necklace/spacepen lanyard, wallet chain, and coif made of titanium by Bim also. My keyrings and bottle opener are also titanium. It's such a cool metal. Kind of a pity it makes a very poor knife blade. Speaking of: I also replaced the screws and hinges of my bespoke Benchmade knife with titanium ones, because why not?
A bit obsessed as you can tell.
tl;dr I have a mithril shirt
It's incredibly durable. This thing will probably be a family heirloom for generations.
Ti is 6.0 on Moh's similar to feldpspar. It'll scratch lots of things. I have to warn people to keep it away from jewelry it'll scratch most ordinary stuff including glass. I accidentally damaged my bathroom sink washing it after polishing (thrown in the dryer in a bag by itself). Little scratch marks around the drain just from washing. Not trying to grind it down into the sink or anything.
>Could it save you walking down a dark alley at night?
From a knife probably. Still hurt like fuck without a gambeson. I don't think it's even slightly bulletproof because the rings are just butted against each other not welded at all. In fact it might making being shot worse by adding titanium fragments. But I haven't tested that.
Welded or rivited rings would be much more robust. Especially vs piercing weapons, like arrows or fighting knives.
But much more expensive.