Can A Very Cold Coin Be Broken?

itsnotjustme · October 25, 2003 2:35PM

I know I've read about steel tools breaking in the cold of northern Alaska. Could a Morgan dollar be placed in liquid Nitrogen or Oxygen and then broken, with a clean break? Would certain metals work better? Might we force a clad layer separation that way?

airplanenut · October 25, 2003 2:40PM

I don't think you'd get a clean break, if it happened... think of it like this:

When metal is frozen, it loses some/all of its original pliability. It's almost like wood... damp wood bends, dry wood is solid as solid can be. If you snap a board, it splinters- as with pretty much any other solid that I know of (barring very pliable materials like thin plastics). So I'd say it can break eventually, but not cleanly.

Jeremy

coinlieutenant · October 25, 2003 2:56PM

Intersting question.

I really dont know but i would think that it could break cleanly given the correct temperature and enough shear (dF/dx > 0) is applied.

It wouldnt break like we would think though. Breaking properties are related to molecular makeup. Metals dont have a crystalline structure, but....

Keep in mind this is stream of consciousness here. Probably has something to do with tinsile strength as well.

I think the answer is "yes" but since I am a scientist, you can only state as fact what you can prove...and I cant prove this one off the top of my head.

John

mgoodm3 · October 25, 2003 3:02PM

Metal does get brittle at low temps. I would presume that the structure is not necessarily weakened so it would take quite a bit of force to break, but would respond differently than normal.. wouldn't bend or flex as it would normally.

itsnotjustme · October 25, 2003 3:12PM

This requires an experiment. Who has access to liquified gas (or other means to chill coins)?

airplanenut · October 25, 2003 3:28PM

<< This requires an experiment. Who has access to liquified gas (or other means to chill coins)? >>

My dad does

... but I doubt he'd let me do it

I could have him gold plate a coin if you'd like

Geoman · October 25, 2003 3:48PM

Sure it can break if it is cold enough. I had one of those Kryptonite U-shaped bike locks, that somone snapped in half and stole my mountain bike. Talked to the detectives, and they said they you can buy these spray cans of a liquid nitrogen type material, that they spray on the metal kryptonite locks, that gets is so cold that they can just take a regular hammer and hit it, and it breaks. My lock showed a clean break. Never got the bike back either, as it is not a high priority for the police.

Heck, up here in northern Minnesota, we hit -60F (60 below zero) yes, that is a few years ago. And that was actualy air temp, and not wind chill. At -60F you can spit, and the spit explodes in the air, as it freezes before it hits the ground.

cladking · October 25, 2003 3:52PM

<< 

Heck, up here in northern Minnesota, we hit -60F (60 below zero) yes, that is a few years ago. And that was actualy air temp, and not wind chill. At -60F you can spit, and the spit explodes in the air, as it freezes before it hits the ground. >>

I've always wondered about this... did you see any carbon dioxide (dry ice) precipitate out of the air?

Was there any haze in the air?

tjkillian · October 25, 2003 6:25PM

Dry ice sublimes at -110F and does not melt unless it is under great pressure. I was playing with dry ice just last weekend with my little boy preparing for Halloween. I put a pure silver bar next to the dry ice and it got cold very quickly. I has a very high thermal conductivity, one of the highest. The next time I get some dry ice and have a pair of goggles, I shall try breaking the silver with a hammer.

Tom

ccr · October 25, 2003 7:02PM

<< Was there any haze in the air? >>

I was told that in Alaska that people that work on septic tanks or in the sewer departments in the winter are at a high risk of lung infections. It freezes ( " it ", well use your imagination on this

) floats in the air and you can see it as a " fog " or " haze ".

Senlathiel · October 25, 2003 11:07PM

I have access to liquid nitrogen--I work in a lab that does cell culture. However, I don't have the equipment that could break the coin. I don't think I could do it with a pair of plyers. Maybe I can just hit it with a hammer?

itsnotjustme · October 25, 2003 11:35PM

After getting it cold, I would put it down on a cloth with one rim propped on a cloth covered solid item about 1/4 inch hig. Then I would strike with an object that is as wide as the coin, but thin, and lightly padded.

MacCoin · October 25, 2003 11:44PM

I can't say anything about it breaking but I do know if its to cold not to put your tonge on it

Shamika · October 26, 2003 12:05AM

No experiment is necessary. Pull up a chair and I'll explain.

Metal is a crystalline solid. This means that its atomic structure is ordered.

The crystalline structure for most of the common metals are either BCC, FCC, or HCP. BCC stands for Body-Centered Cubic. FCC stands for Face-Centered Cubic. HCP stands for Hexagonal Close-Packed. Since this is not a crystallography forum, I won't get into the details of what these structures look like.

Anyway, most metals have a "ductile-to-brittle transition temperature" whereby their impact strength drops very quickly. This transition temperature is material specific. However, FCC metals DO NOT exhibit a ductile-to-brittle transition.

And guess what? Silver just so happens to have an FCC structure. Thus it will not fracture in a brittle fasion even at low temperatures.

Steel, on the other hand, has a BCC structure and will exhibit brittle fracture at low temperatures. There are some famous case studies of this happening involving ships during WWII whereby the ship literally cracked in half. The hulls were made from a steel allow that had a unusually high ductile-to-brittle transition temperature at 40F.

I hope this helps.

mgoodm3 · October 26, 2003 12:32AM

Thankyou, I think that will be adequate.

fcloud · October 26, 2003 12:33AM

I would think if cold metal could be broken easily, NASA sure would have problems in space.

tjkillian · October 26, 2003 12:40AM

<< Anyway, most metals have a "ductile-to-brittle transition temperature" whereby their impact strength drops very quickly. This transition temperature is material specific. However, FCC metals DO NOT exhibit a ductile-to-brittle transition. And guess what? Silver just so happens to have an FCC structure. Thus it will not fracture in a brittle fasion even at low temperatures. Steel, on the other hand, has a BCC structure and will exhibit brittle fracture at low temperatures. There are some famous case studies of this happening involving ships during WWII whereby the ship literally cracked in half. The hulls were made from a steel allow that had a unusually high ductile-to-brittle transition temperature at 40F. I hope this helps. >>

Now this makes me angry: I hold a degree in Mechanical Engineering and have take several courses in metallurgy and they never taught this is class. Of course everyone knows about FCC, BCC, etc and maybe even austenite, pearlite, ferradite, etc and grain growth, but why did they not talk about "ductile-to-brittle transition"? A whole course in steel design and never once did they talk about it or write about it.

Tom

MrEureka · October 26, 2003 12:41AM

Shamika - Thank you. Now, what about a 90% silver alloy?

Shamika · October 26, 2003 12:57AM

tjkillian,

Ductile-to-brittle transitions are taught in the sophmore level "Intro to Material Science" class that most, if not all, ABET accredited 4 year engineering degrees require.

As a mechanical engineering student, you should have had this demonstrated to you in a material science lab via an Izod or Charpy pendulum impact test. You may have just forgotten about it since it was a sophmore class. I know I don't remember everything I learned.

If not, you have every right to be upset.

coinlieutenant · October 26, 2003 1:03AM

Shamika,

Great explanation. That was interesting. My post was way off. I will stick to oceanography/meteorology effects on coins from now on...

John

Shamika · October 26, 2003 1:05AM

MrEureka,

Copper is also FCC. So is nickel, copper, gold, and platinum. So it appears, either by luck or design, that the mint chose wisely with regards to coinage metals.

On the other hand, zinc is HCP. So not only are todays copper plated coins cheap, but they are brittle at low temperatures.

Oh for the days of large cents...

itsnotjustme · October 26, 2003 2:47AM

What is the temp for Zinc?

I had a material science class in an accredited engineering program, but don't remember any talk of this. I knew certain metals became brittle, but not based on structure.

Shamika · October 26, 2003 4:08AM

The ductile-to-brittle transition temperature for zinc is around room temperature. Keep in mind, however, that this transition occurs over a short temperature range as opposed to a precise temperature.

Also, "brittle fracture" is the mode of failure and one should not think that you can simply "snap" a coin in half. The impact strength of a metal is weakened relative to what it would be at ductile temperatures, but would still be difficult to break.

itsnotjustme · October 26, 2003 2:13PM

I used a can of dust off to cool a zinc Lincoln, then hit it with my stapler. It did not break. Staples did fly though. Need a more controlled experiment.

coindaughter · October 26, 2003 2:43PM

Now this is a thread! Cool!

Thanks!

foodude · October 26, 2003 2:45PM

Heck, up here in northern Minnesota, we hit -60F (60 below zero) yes, that is a few years ago. And that was actualy air temp, and not wind chill. At -60F you can spit, and the spit explodes in the air, as it freezes before it hits the ground. Yeah it even gts old here in the more southern part of MN- the Twin Cities ... I figure that is why airplanes and Southern California were invented ...

wallstreetman · October 26, 2003 3:06PM

If it doesnt freeze with a can of Freon, forget about it, this is how the thieves do it! Freezes up lug nuts real quick, they break right off with a hammer!

jjroll · October 27, 2003 12:56AM

Back in high school we placed a quarter in liquied nitrogen then dropped it on the floor. It shattered into many small pieces. Not even close to a clean break.

jjroll

mgoodm3 · October 27, 2003 1:14AM

I remember the the -60 in Northern MN. I was in the twin cities at the time. I remember the farce in I think it was Embarass or Tower where the newsmen were all gathered and they started screwing with the official thermometer bringing it down into a nearby swamp and it got to -69. Then the weather service invalidated all readings past the time they started screwing with the thermometer and MN was denied an all-time state record cold reading. It was a balmy -33F at my house in the twin cities.

Pistareen · October 27, 2003 4:11AM

I sold a woman an Athenian owl tetradrachm once upon a time. It was a gift for her father and she couldn't afford much, so I found her one with a bankers mark that still had good detail. I got a horrified email two weeks after she received it that reported her dad loved it, but while showing it off to his grandchildren, one of the kids dropped it in his martini glass and the thing broke in two right along the bankers mark. No more Athenian owl.

I couldn't explain why once-buried ancient coins crystallize and become fragile, but some will break clean in half when dropped.

Shamika · October 27, 2003 4:25AM

Pistareen,

Several issues may explain why the coin broke. First of all, the bankers mark could very well have cracked the coin. Such an indentation made after minting would qualify as a "stress raiser". Sharp notches or indentations are frowned upon when designing parts to be manufactured as they act as points of concentration when the part is put under stress (or dropped).

A small fissure can also be an ideal environment for corrosion. Moisture during burial would set up shop in the fissure and slowly weeken the coin.

Finally, ancient coins were heated just prior to stamping (minting) since the metal is softer at elevated temperatures. However, this preheating encourages the growth of crystalline domains (grains) which also encourages brittle behaviour.

mgoodm3 · October 27, 2003 4:53AM

Shamika, thanks for providing all of the interesting info for this thread. I have learned a lot. I don't mean to be picky but the term is "Stress riser".

Placid · October 27, 2003 4:56AM

Mint damage

mgoodm3 · October 27, 2003 4:58AM

Looks like stress raiser or riser can be used. I've only seen riser in my experience. Sorry.

Shamika · October 27, 2003 5:04AM

mgoodm3,

Although "raiser" and "riser" are both used in the "literature", I too prefer "riser". I've always thought that "raiser" sounds to much like razor, so I shouldn't encouage it's use.

Shamika · October 27, 2003 5:07AM

Placid,

Your coin split due to a planchet defect. Pretty cool!

Placid · October 27, 2003 5:11AM

Not my coin. So pcgs could tell a coin that was split using cold from a actual mint error?

Shamika · October 27, 2003 5:21AM

Any person with a little knowledge in fracture mechanics or failure analysis could easily ascertain whether or not the coin broke due to cold.

I'm still willing to bet that your morgan dollar had a flaw from lamination or had a piece of slag in the original ingot that was then rolled out just prior to having planchets stamped out of it. I've seen coins that split right along their rims due to this. The result was two coins; one with only an obverse and one with only a reverse.

Still, I'd love to see your Morgan in person.

Keyrock · October 27, 2003 5:38AM

Well if anyone wants to donate some circulated pieces I have plenty of liquid nitrogen here at work and I'd give it a shot, send a PM.......

Conder101 · October 27, 2003 8:59PM

I wouldn't really expect liquid nitrogen to work too well. Not cold enough. As far as liquid gases go, it's downright warm.

tjkillian · October 27, 2003 9:22PM

<< I wouldn't really expect liquid nitrogen to work too well. Not cold enough. As far as liquid gases go, it's downright warm. >>

Well if you take all gases in to account, maybe, but nitrogen is 78% of the atmosphere and boils a -320F and 21% of the atmosphere is oxygen which boils at -297F, which is warmer still.

Tom

Shamika · October 27, 2003 11:09PM

Actually, I think liquid nitrogen would work fine. However, when the question was originally posed by Brian, I don't think he had -320F in mind as opposed to, say, -10F.

Shamika · October 27, 2003 11:19PM

"Could a Morgan dollar be placed in liquid Nitrogen or Oxygen and then broken, with a clean break?"

After further review, I stand corrected. It appears Brian DID have these super low temperatures in mind.

At these temperatures, all bets are off. Compressive strengths would not change significantly, but tensile and flexural strengths would be reduced substantially.

Although FCC metals do not show a tight ductile-to-brittle transition temperature range, they would slowly shift from a ductile to a ductile/brittle to a brittle fracture.

I still believe that a silver coin would be impossible to break with gloved hands, but a hammer would probably do the job.

tjkillian · October 27, 2003 11:46PM

For Halloween my little boy want to have some dry ice, which sublimes at -110F at 14.7psig (sublimation is the state change from a solid to a gas without going through a liquid stage). Silver is one of the best thermal conductors so it will approach the sublimation temperature at which time I shall hit my silver bar (.999 silver) with a hammer and let everyone know if I can break it.

Tom

Shamika · October 28, 2003 12:09AM

Tom,

One subject that I didn't touch on is strain rate.

High strain rates will favor brittle fracture. Think of silly putty. If you pull it apart very quickly it will snap in half (brittle), but if you pull it apart slowly it will be drawn out into a fine thread (ductile).

Although I mentioned using a hammer, two pairs of pliers or a large vise would make for a better experiment.

Mikey · October 28, 2003 12:28AM

I remember hot dogs dipped in liquid nitrogen and then shattered with a hammer. Makes one think about frozen extremities.

tjkillian · October 28, 2003 1:18AM

Shamika, ok, I will use two channel lock pliers. I will need to do it fast as silver will warm to its surroundings much faster than you'd think. I guess I'll do it for several different coins as well. Anyone have any early gold they'd like broken in half?

Tom

Can A Very Cold Coin Be Broken?

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