Does copper age harden?

Copper tubing to be exact. I have a couple rolled lengths of soft copper tube. One length is about 20 years old and the other about 4
years old. Both are the soft copper tubing commonly used for refrigeration or water. It comes with a plastic cap on each end. Anyway, my old rolled length, which I discovered the other day when cleaning out some junk, is much stiffer than the new roll. So I am wondering if the copper got stiffer over time because the older stuff is quite a bit harder to bend than the newer stuff. Eric
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On 06/24/2015 12:27 PM, snipped-for-privacy@whidbey.com wrote:

You sure it isn't just K or L over M, maybe? I've no reason to think it will harden just with age; I've pieces around that are at least 50 or 60 yo that I use chunks off of periodically and never noticed any real difference.
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Maybe that's it, different types. I thought all the coiled copper tubing for refrigeration was the same. Thanks. Eric
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On 06/25/2015 11:45 AM, snipped-for-privacy@whidbey.com wrote:

I think the only difference re: the HVAC line-specific line is it is specially cleaned/produced to minimize any oil contaminants. AFAIK wall thicknesses are K and L (no M, the cheapie box store variant usually found) but that's still enough between the two to make a noticeable difference in stiffness. I suppose there could be some difference in an alloy between manufacturers, too, not sure how much variation there might be in that regard.
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On 06/25/2015 3:20 PM, dpb wrote:
...

OK, _now_ I see that you have measured wall thickness; I concur on likely treating differences is the difference...
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Except for certain alloys it doesn't age harden. But refer tube has a pretty wide tolerance in wall thickness. Typically +-10% of the thickness. My guess is that when copper was cheaper, they erred on the plus side, now they lean to the minus.
One could as much as 20% thicker than the other.
Paul K. Dickman

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On Wed, 24 Jun 2015 13:15:47 -0500, "Paul K. Dickman"

Greetings Paul, I can check that. I just checked, both coils have the same wall thickness and O.D. I think it must just be different types of copper tube. Eric
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On Thu, 25 Jun 2015 09:51:29 -0700, snipped-for-privacy@whidbey.com wrote:

More likely it's different degrees of annealing. Copper readily work hardens, and the soft type has to be thoroughly annealed so it will freely bend.
Heat treating isn't always consistent.
--
Ed Huntress

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http://www.g-w.com/pdf/sampchap/9781566379656_ch03.pdf "Soft copper tubing has a tendency to harden as a result of vibration, oxidation, and bending. This is called work-hardening."
-jsw
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