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:Who chose the images of metal grinding?

[Smidge204]

The article I clicked on - the only link in the summary as I write this - leads to a page that has both a huge photo on top showing the two side by side (titanium vs steel) but also a video where they grind various items. The difference is very noticeable.

=Smidge=

Titanium: not recommended for rings

[steveha]

I read a story about a couple who loved bicycling (and loved their titanium bicycle frames). They decided to have rings made from titanium.

One day the guy had some kind of accident, and his ring finger was mashed; it swelled up badly. They took him to the emergency room. In the ER, someone got out the cutters to cut the ring off the swollen finger. Whoops, titanium. The cutters (probably simple diagonal cutters) had no problem with the usual soft gold rings, but titanium was too hard! They wound up getting a Dremel tool or the equivalent and cutting the titanium ring off (very carefully, I imagine).

The moral of the story: if you get a titanium ring made, maybe you should wear it like a necklace.

P.S. Merry Christmas everyone.

steveha

Re:Titanium: not recommended for rings

[Anonymous Coward]

I suppose the anecdote could be imaginary, but I did read it in a bicycling magazine. I didn't make it up.

And I'm puzzled by your comments about the ring saving his finger. My understanding is that his finger got mashed, not that the ring got mashed hard enough to deform it. So he had a finger swelling up, and a non-deformed ring at the base of the finger.

steveha

Re:Safety first?

[smidget2k4]

Gloves + rotating grinder = BAD. You don't want a glove to get caught in that, your hand goes with it. Better to be burned by some sparks than to lose a few fingers (at best).

Re:a magnet?

[budgenator]

Steel is actually an alloy containing predominately iron, usually has a good amount of precipitated Ferric Carbide crystals , ferric-Carbide in solution with the iron and often trace elements and occasionally minute amounts of pure carbon which is detrimental. The amount of carbide in solution and precipitated greatly controls the physical properties of the metal and is controlled by the heat treatments the steel is exposed to during manufacture.

Re:Interesting!

[BlueParrot]

If you know of a more reliable way, I'd like to hear about it. No, seriously.

Physics to the rescue:
http://en.wikipedia.org/wiki/Elitzur-Vaidman_bomb-tester [wikipedia.org]

Re:a magnet?

[Ceriel Nosforit]

Well yes, but since the reply was nitpicking, I decided to respond with more nitpicking in a vain attempt to show how useless it was. My original reply was, I thought obviously, a useful thumb rule for a person who didn't know much about metals and metal alloys. It was was not a wikipedia entry; by experts for experts. I'd bore the OP to an early grave if I tried to tell him about the finer points of metallurgy.

And why the heck need I waste all this text explaining myself to you anyway? It's all evident... :\

Re:a magnet?

[necro81]

Most steels are magnetic to various degrees. However, when designing some stuff that would be used in an MRI suite, I did some research and found that some grades of stainless steel - specifically, 300-series [wikipedia.org] stainless steels (302, 304, 316, etc.) - are more or less nonmagnetic [physlink.com]. They can't be used inside the bore of the scanner, but that's mostly because it screws up the uniformity or the magnetic and RF fields necessary for imaging. This was a handy discovery for me, because sometimes aluminum and plastics aren't strong enough, and titanium is a lot harder to work with.

It reminded me of something that I had happen

[edwardpickman]

We were building a rig for a show and there were a lot of surplus aitcraft parts around. I found a large bracket that was perfect but it needed an extra hole drilled in it. The piece was light enough I assumed it was aluminum. I was using a hardened drill bit that should have cut through stainless. After five minutes I checked it and I barely scratched the surface. Aircraft Aluminum can be fairly hard but it seemed rediculous so I tried again but still nothing. I flipped over the part and there stamped/cast on the otherside was Titanium. Needless to say I gave up. All I managed to do was kill a good drill bit. If it seems really light for it's size and can't easily be scratched there's a good chance it's Titanium.

Re:is there a better way?

[arivanov]

A good test is with fuming Concentrated Nitric Acid or "royal water" - mix of Nitric Acid with Sulfuric, the one that dissolves gold. It will also dissolve nearly anything else on earth even group 8 noble metals.

Titanium is passivated in it and does not dissolve or show any signs of damage (except in extremely high saturation fuming nitric acid). At the same time it happily dissolves is hidrocloric, hidrofluoric acid. It will also dissolve in sulfuric acid even in low concentrations. IIRC it did not like the strong organic acids either, but I do not recall which dissolve it and which not at the moment (it is been a while since I gave in to the dark side of IT and left chemistry).

Note, that as most commercial titanium is actually various titanium alloys they may get coloured or change their appearance when passivated. Most importantly - if it is titanium it will smile at nitric acid and any strong oxidising agent and shrug it off.

This all is off the top of my head. Check with a good inorganic chemistry book before bringing a flask of something obnoxious to a shop.

Re:is there a better way?

[Mspangler]

x-ray fluorescence. There are portable "guns" that can do this now, for only about $30,000.

The old ones took up a room, had a radioactive source, and the spectrometer had to be cooled with liquid N2.

The modern PMIs are pretty nice. Point at a piece of metal, pull the trigger, and in 5 seconds it tells you if it is 304, 316, C-276, 800HT, or whatever. If the metal is not in the database, then it tells you the elemental makeup so you can look it up, and if it's a real alloy enter it into the database. If it's some odd corrosion product (C-276, but missing some chrome) that can help analyze corrosion problems.

I have one on next year's budget wish list. (And yes, I am a metallurgical engineer.)

 

Re:What kind of pansy want's Titanium?

[Khyber]

http://trewtungsten.com/ [trewtungsten.com]

Damn right real men use Tungsten.

No dremel?

[ed1park]

How bout a blow torch, chlorine gas or liquid oxygen? :)

Even bulk titanium metal is susceptible to fire, when it is heated to its melting point. A number of titanium fires occur during breaking down devices containing titanium parts with cutting torches.

When used in the production or handling of chlorine, care must be taken to use titanium only in locations where it will not be exposed to dry chlorine gas which can result in a titanium/chlorine fire. Care must be taken even when titanium is used in wet chlorine due to possible unexpected drying brought about by extreme weather conditions.

Titanium can catch fire when a fresh, non-oxidized surface gets in contact with liquid oxygen. Such surfaces can appear when the oxidized surface is struck with a hard object, or when a mechanical strain causes the emergence of a crack. This poses the possible limitation for its use in liquid oxygen systems, such as those found in the aerospace industry.

http://en.wikipedia.org/wiki/Titanium [wikipedia.org]

Call me paranoid, but I think I'll stick to gold if I ever wear jewelry. But interesting to know if you're ever in a McGuyver type situation. :)

Re:is there a better way?

[cshake]

An interesting discovery you will make with such a device is that nearly anything that is painted will show up as having titanium in it. That's because titanium is used to create the white base for most paint. Of course black won't have it.
I have seen this demonstrated by a professor who has one of the X-ray things, pointed it at a textbook and came up with 'mostly titanium' because the paint and ink on the cover was the only part that was metallic, and since titanium makes up most of the metal in paint, it shows up as that. The dangerous part about those is that it will tell you the composition of a metal, you just have to be careful which metal you're pointing it at, since it has very shallow penetration. On a solid block, it will give you the composition of the coating and not the inside.

Wow, a class in materials for a MechE degree will actually teach something?!?