How To Tell If It's Really Titanium

With the growing popularity of titanium, some disreputable merchandisers are passing off other materials as the more expensive metal. Popular Science looks at a surefire way to prove what that credit card/crowbar/ring is really made of. "Hold any genuine titanium metal object to a grinding wheel (even a little grindstone on a Dremel tool will do), and it gives off a shower of brilliant white sparks unlike any softer common metal. The sparks are tiny pieces of cut titanium--the friction of the grinder heats them till they burn white-hot. Hold a grindstone to the shackle of a "titanium" padlock from Master Lock, however, and you'll instead see the telltale fine, long, yellow sparks of high-carbon steel."

Re:color, texture, weight

[Alaria Phrozen]

Wtf is with these fake links? Do you get money or something for that stupid city?

Density test

[Ostsol]

If the object in question is constructed from a single material, then a density test should work. Use water displacement and a scale to determine the volume and mass, respectively. From that you can calculate the density and compare the value to the actual density of titanium. Of course, this won't work if the object merely has titanium components and it cannot be disassembled. . .

He also runs periodictable.com

[Ed Pegg]

The author of this Popular Science article, Theo Gray, also recently relaunched http://www.periodictable.com/ [periodictable.com] Thousands of elemental pictures and videos are available there, all linked in with his Popular Science series.

Mods smoke crack

[The Anarchist Avenge]

Parent is warning about fake link in the GP. How exactly is this offtopic?

A few simple ones

[BlueParrot]

a: Titanium is not ferromagnetic, and hence it is not attracted by magnets as strongly as iron is ( the difference in force should be orders of magnitude ).
b: Titanium's density is 4.5g/cm^3 , iron is 7.8g/cm^3
c: Titanium is corrosion resistant to dillute sulfuric and hydrochloric acid, iron is not.

Laser?

[Anonymous Coward]

What are they teaching kids in school these days? [wikipedia.org]

They can be cut off.

[raygundan]

I know an ER doc who thought the same thing, until somebody came into her ER with one, and it was as trivial to cut off as anything else. Even if they lack a proper cutting tool, you can just squeeze it until it shatters. Titanium is strong, but it's not like a ring made of the stuff is somehow immune to being cut or broken. Hospitals are full of interesting tools, and it sounds like even in your story, they improvised fairly well.

Re:a magnet?

[Ceriel Nosforit]

Useful trivia:
Steel is a blend of iron and carbon. Mostly iron, in all its incarnations, and iron is always magnetic.

High-carbon steel is very hard but a bit brittle, while steels with less carbon will usually deform before they crack. There is always a compromise between hardness and toughness.

Re:a magnet?

[Kazymyr]

...iron is always magnetic.

That is a big fallacy. There are some alloys in which iron is around 98-99% which are non-magnetic (think unusual alloying elements like niobium and rhenium).

Re:a magnet?

[LynnwoodRooster]

Nope. Get above 0.15% carbon or so and you lose almost all the magnetic properties of iron. It's one reason that loudspeakers are made with low carbon steel (usually 1006, 1008, or 1010 grade) since you get too much carbon and the flux no longer flows well, meaning you need a LOT more magnet and a higher grade magnet to get the same flux in the gap.

And yes, I am a loudspeaker engineer... ;)

MERRY CHRISTMAS!

Re:is there a better way?

[ByteSlicer]

A laser spectrometer [wikipedia.org] can do this for you. It will still create microscopic damage though.

Re:Titanium: not recommended for rings

[1729]

Actually, titanium rings can be cut off fairly easily, at least according to the guy who made my wedding band:

http://boonerings.com/faq.htm#4 [boonerings.com]

Tungsten carbide rings are difficult to cut, but they can safely be cracked with vise grips:

http://www.trewtungsten.com/remove.php [trewtungsten.com]

The power to the door was pneumatic though

[Dr_Barnowl]

.. not hydraulic

Re:wow

[techno-vampire]

You don't even need that much heat. Just warm it in your hands, and if you get a faint pine smell it's amber.

Re:a magnet?

[the eric conspiracy]

Depends on the type of stainless. Austentitic is not ferromagnetic, while martensitic is.

Re:A few simple ones

[florescent_beige]

It's hard to determine the density of something like a ring because even if you weight it you don't know its volume. But there is a way around that, weigh the item in air then in water and take the ratio of the weights. A jewelry store would be more open to that idea than coming at the thing with a power tool. Here's the arithmetic: volume of item = v density titanium = d_t density water = d_w weight in air w_a = v*d*g weight in water w_w = w_a - v*d_w*g w_w/w_a = (w_a - v*d_w*g)/w_a = 1 - d_w/d_t plugging in d_w = 1 g/cc d_t = 4.5 g/cc w_w/w_a = 1 - 1/4.5 = .78 If it's steel: w_w/w_a = 1 - 1/7.8 = .87 Most jewellers would have a setup that can weigh something immersed in water, it's how they tell themselves what the material is. If they say they don't then you are probably being had.

Re:Titanium: not recommended for rings

[Anonymous Coward]

Put the ring in a vice and slowly compress it until it cracks, that's the recommended way to get a tungsten ring off anyways.

Re:A few simple ones

[florescent_beige]

It's effectively the same thing but the weight ratio is more practical. The volume of jewellery is so small that reading the change in water level in a graduated cylinder is really hard. It's generally smaller than the meniscus.

Plus most jewellers are already set up to do the water-weighing.

Re:is there a better way?

[necro81]

How much are you paying for that service? For $30,000-40,000, you can buy a handheld x-ray fluorescence analyzer [niton.com]. These things got started in testing for lead paint, and now get used to test and check for lots of things - including alloy composition verification. An XRF shines x-rays of a known energy at the test sample, then detects and analyzes the spectrum that is reflected back. Each element has a characteristic x-ray emission spectrum based on the energy of electrons dropping into lower shells. In 10-20 seconds, you can get a really good breakdown of the elements in the test sample.

Re:Why titanium anyway?

[YrWrstNtmr]

After having steel framed glasses for many years, and started getting a skin reaction exactly where the frames touch my skin...I asked the optometrist about it. She said "oh...you have nickel allergy. You need something else besides steel frames."

Bought the (too expensive) Ti frames, and the condition went away almost immediately. Within days. Couple years later, tried another pair of steel ones. It started coming back. All Ti from then on.

And the Ti frames are significantly stronger/more flexible.

Re:a magnet?

[Gordonjcp]

And in fact, some soldering iron thermostats use this property. When the iron is cold, a magnet pulls the contact closed. Once it heats above the Curie point, the magnet lets go and the contact breaks.

Re:Titanium: not recommended for rings

[ghideon]

Ed Harris' character from the Abyss.
http://imdb.com/title/tt0096754/ [imdb.com]

Theodore Gray is clueless.

[SvnLyrBrto]

Titanium and steel may very well spark in the manner he describes. But this little gem, so far as I'm concerned, renders everything he says suspect:

it was just aluminum, which doesn't burn.

Aluminum most certianly *DOES* burn. Though fairly difficult to ignite, aluminum burns ferociously and spectacularly and is notoriously difficult to extinguish, as the crew of the HMS Sheffield learned much to their dismay. The fuel of the Space Shuttle's solid rocket boosters is aluminum. And aluminum is the fuel component of thermite.

I think that the "scientific" opinion of anyone so clueless as to try to claim that aluminum won't burn should be discarded with the lowest grain of salt

cya
john

Re:a magnet?

[Anonymous Coward]

You've never tried to stick a magnet to a stainless steel fridge, have you?

To be fair, maybe he has. When I went fridge shopping, most "stainless steel" fridges the salesmen were trying to pawn off were magnetic.

Maybe they were this stuff,

Martensitic stainless steels are not as corrosion resistant as the other two classes, but are extremely strong and tough as well as highly machineable, and can be hardened by heat treatment. Martensitic stainless steel contains chromium (1214%), molybdenum (0.21%), zero to less than 2% nickel, and about 0.11% carbon (giving it more hardness but making the material a bit more brittle). It is quenched and magnetic. It is also known as "series-00" steel.
http://en.wikipedia.org/wiki/Stainless_steel [wikipedia.org]

Re:a magnet?

[DougF]

Actually, titanium holds an edge very well. I've used my diver's knife with a titanium blade for 7 years and have not had to sharpen it once. It's still just as sharp as the day I bought it. I dive several times a year and use it to dig for shark's teeth, as a tool, and for protection. Not a scratch, a mar to the edge, nor any rust to the blade.

Re:It reminded me of something that I had happen

[greyhueofdoubt]

You were either using a really dull bit, or you were using a bit that was too large and needed to be pilot drilled.

I work with titanium all the time, and we use the same cobalt steel bits for Ti work that we use for anything else. It is rough on end mills, but at that point you should be using specialized coolants and cutting speeds.

The best way to test for Ti? Heft. The stuff can look like steel to a layperson (I personally think it's easy to tell Ti vs CRES vs Fe) but the feel of it is very different. If you pick up a metal piece that feels like it should be hollow because it's so light, it might be titanium. Or it could be hollow, I suppose.

If the piece is large enough, you can ring it with another piece of metal and listen for the sustain. Titanium parts, e.g., guide vanes, will ring considerably longer and at a higher pitch than softer, heavier metals (steel) or softer, lighter metals (aluminum, except the harder allows like 7075).

Or send the parts to me, I'll take a look. If they're fakes, I'll just toss them on the scrap heap. Promise.

-b

Re:a magnet?

[Grishnakh]

Sorry, that's not my understanding of the metal's properties. I guess for digging around in the sand, you don't really need a fine edge, but nothing to my knowledge compares to the ability of steel (esp. high-carbon steel) to hold an edge. High-carbon steel is very brittle, which helps it to hold an extremely sharp edge; this is why Japanese samurai swords were forged to have one side harder than the other side, so the sharp side would be extremely hard, but the other side would be less hard and more strong (done by using clay on one side during quenching) so that the blade as a whole wouldn't break easily.

There's a reason no other knives are made of titanium, or anything besides steel for that matter.

Titanium is known to be a very strong metal. If you know anything about metallurgy and its terminology, strong and hard are different properties, and usually work against each other: a metal is usually strong, but not hard, or vice versa, not both. Steel can be made to be hard, but brittle, or strong (which is more flexible) but not very hard.

Anyone with a titanium ring knows that it's not a hard metal at all: it's easily scratched unless it has a protective coating (usually diamond). Sure, it might prevent a automatic pressure door on an undersea rig from locking you in, but it doesn't hold a sharp edge at all.

Re:Density test

[Anonymous Coward]

The density test is easy to do, and only has one difficulty. First get a container bigger than the titanium thing you want to test. The difficult thing is to ensure you are testing ONLY a piece of titanium. For example, some frames for eyeglasses are titanium, but you only want to test the frame, or part of the frame, and not the lenses.
After you have the container, get a second and even larger container. Put the first container inside the second, and Fill the first container with water to the brim. Then dunk the titanium thing. The water that overflows will equal the volume of the object, and will be caught in the second container. You may now measure that volume, by measuring the quantity of overflowed water.
Next, take the titanium thing and weigh it.
Next divide the weight by the volume. some common materials are: Lead, ~11 grams/milliliter (1 milliliter is also 1 cubic centimter); copper, ~9 gm/ml; iron/steel, ~8 gm/ml; titanium, ~4.5 gm/ml; aluminum, You can see that titanium has a different enough value from the others, that it should be accurately identifiable.
Of course, to be really really sure, testing the thing nondestructively, use an X-ray spectrometer. :)