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  #1  
Old 12-10-2007, 09:54 AM
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suburbanartists suburbanartists is offline
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Hardening copper pipe? How to?

Hard Copper pipe 1/2 inch M copper (water pipe) cost me $10 for 10 feet.
Same size and weight costs $30 in Soft roll form.

I use these as backbones for some of my folk art weathervane style pieces.

I need to anneal the hard copper, make it flexible to get the bends into the "spine" without kinking it. But then when this is done i need to reharden the copper pipe to get it back to it's original stiffness, or at least a state much stiffer than soft copper.

I know to anneal copper do the opposite of steel (heat and water dunk to soften the copper).

BUT from what i can find you really can't reharden by heating and then slow cooling (air cool). They say it hardens by work hardening but this is no good for me as once i get the pipe into shape that's where it needs to stay.

Anyone have any info on the hardening of copper?

Thanks Sub
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  #2  
Old 12-10-2007, 11:29 AM
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Re: Hardening copper pipe? How to?

If you have a blast cabinet… that’ll work, if not buy one of those cheep (50 bucks) auto body type spot sand blasters. The sand or abrasive peen-ing will harden it, and the tiny blasted texture, well, you might like it.
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  #3  
Old 12-10-2007, 02:04 PM
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suburbanartists suburbanartists is offline
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Re: Hardening copper pipe? How to?

Duck Thanks, i did hear about that but not sure about the blast marks. I guess i could sand them out if not too deep. Anyone know about any other way. or if heating to specific temp and slow cool would harden at least somewhat?

How do they harden the pipes in the factory?
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  #4  
Old 12-10-2007, 02:42 PM
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suburbanartists suburbanartists is offline
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Re: Hardening copper pipe? How to?

Just did a search. Factory draws out the pipe into longer and thinner profiles. This work hardens the copper. Other than that, hard and soft copper are the same. They heat treat to anneal only. Pull and reshape to work harden it.
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Old 12-10-2007, 10:31 PM
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Mr. Malloy Mr. Malloy is offline
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Re: Hardening copper pipe? How to?

Hi, I am working with a simalure issue. Regarding hardening: I am weld-repairing some steel tools. I have been able to mig weld the cracked steel but I want to weld a support brace along side for support. this is on two metal shears, both broken in same place. I was told that tool steel is harder than my mig steel. And that they should be anealed after to make them hard again? Is this sounding like it makes any sense? I have never anealed anything. I am doing this for hire so I want to do it right. Any feedback would be appreciated.
Douglas
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  #6  
Old 12-11-2007, 09:43 AM
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suburbanartists suburbanartists is offline
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Re: Hardening copper pipe? How to?

Steel and copper have very different properties. You should make a new post for this. Many here should be able to help you. Tool steel is harder. Remember harder means more brittle. Heat and slow cool to anneal the steel, not sure how to do that if you've already welded it. You may also want to temper it after it's annealed. (Not sure of its use?)
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  #7  
Old 12-16-2007, 04:27 PM
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Re: Hardening copper pipe? How to?

Quote:
Originally Posted by suburbanartists View Post
not sure how to do that if you've already welded it.
welding it has already annealed the steel near the weld (making it softer, more ductile less brittle)
ideally the whole piece would be annealed and then retempered (making it harder again)
getting an even temper is tricky with a large piece
followed by an oil quench (typical for a tool steel)

http://www.anvilfire.com/FAQs/quenchants.htm
http://en.wikipedia.org/wiki/Annealing_(metallurgy)
http://en.wikipedia.org/wiki/Tempering

mig wire comes in various hardnesses, though they tend to all be far harder than mild steel
google "hard face" mig


Quote:
Originally Posted by suburbanartists View Post
I know to anneal copper do the opposite of steel (heat and water dunk to soften the copper).
http://www.steamengine.com.au/ic/faq...ng-copper.html
Quote:
In annealing of copper, the heating is the important part. The rate of
cooling is immaterial.

Whether you allow it to cool naturally or drop it into water makes no
difference to the final softness.
.
Traditionally, we drop it into water because that's what we were told, but
it is not necessary. It's only a matter of convenience
I agree sandblasting to work harden it seem the most practical solution

Last edited by Ice Czar : 12-16-2007 at 04:55 PM.
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  #8  
Old 12-18-2007, 04:47 PM
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Re: Hardening copper pipe? How to?

Thanks for the feedback. I did anneal the copper pipe in a coal forge and water dunk. They do say not necessary to dunk it but why waste time if it doesn't make a difference. The pipe was so long though that i could not get the middle of it into the fire. So to anneal the middle of the pipe i made an open wood fire outside and heated the pipe in the wood coals. This was a bit slower than the coal forge but worked fine. I heated to a dark red and poored some water onto it. Worked fine.

Then i hand bent the tube into shape and soldiered on my copper flashing pieces. The bending and soldiered pieces seems to have made it stiff enough for my purposes. I will try the sandblast method when the copper tubes don't get hard enough thru the bending alone. others have also said that sandblasting would harden it well. Thanks
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  #9  
Old 12-19-2007, 01:53 AM
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Re: Hardening copper pipe? How to?

one thing to keep in mind when sandblasting is that you can induce stress into the piece if you blast from just one direction.

I did a number of large patina sheet metal architectural panels (3'x9') this summer, sandblasting is an important step to increase the surface area for this particular patina process, but blasting only one side bows the hell out of the panels.

In larger dimensional members its not a real consideration but as the material thickness decreases and the length increases it has the same potential as warping via welding does.

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  #10  
Old 12-19-2007, 09:30 AM
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Aaron Schroeder Aaron Schroeder is offline
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Re: Hardening copper pipe? How to?

Not to long ago I saw a episode of "how it's made" about making a brass musical instrument. Before they bent a number of tubes they first filled them with water which they then froze in a fridge. I thought that was a simple and eligant way to prevent the tubes from kinking. Maybe filling your tubes with ice would work for you. At least you wouldn't have to worry about rehardening the work.
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  #11  
Old 12-19-2007, 11:58 AM
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suburbanartists suburbanartists is offline
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Re: Hardening copper pipe? How to?

Ice - Do you think a wire wheel would harden copper? Do you think the tiny impacts would be comparable to the sandblast impacts?
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  #12  
Old 12-19-2007, 02:48 PM
warren01 warren01 is offline
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Re: Hardening copper pipe? How to?

If you use a media like walnut shell instead of sand it will work harden the copper tubing. Wire brushing will also harden the copper along with buffing. Basically any type of vibration to slightly "move" the copper will work harden. I have heard and never tried, but it has suggested to place the copper piece in front of stereo speakers with the bass up and will work harden. Then there is the trick to drive around with the piece in the back of a pick-up going down a gravel road.
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  #13  
Old 12-19-2007, 06:37 PM
Harryman Harryman is offline
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Re: Hardening copper pipe? How to?

Blasting with plastic pellets or glass beads would work too.

Tumbling in steel shot is good, it would give you a nice burnished finish but would be tough if the pieces are large.
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  #14  
Old 12-19-2007, 07:17 PM
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suburbanartists suburbanartists is offline
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Re: Hardening copper pipe? How to?

So i need to turn down the funky cold madina tunes when shaping? Ha ..Ha
Warren you said buffing? ...What about hand sanding? This is what i already do to finish so if it will work harden i could save a step.

If the vibration thing is true i could hook up to palm sander with no paper in it. But i'm sure the pieces would prefer a harden off to some public enemy.

Warren you make those cool vessels. i remember them from an older post. Very cool. looks like they are made from sheet copper. Do you have to harden them?

Last edited by suburbanartists : 12-19-2007 at 07:28 PM.
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  #15  
Old 12-19-2007, 10:36 PM
John M John M is offline
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Re: Hardening copper pipe? How to?

There's a couple other options you could try...Maybe use brass or bronze tubing and try to bend it hot. It will be much stronger when it cools, and will patina in very similar fashion. You can buy a tubing bender like a used lite weight Hossfeld or cheaper imported knock off and bend your copper tubing cold.

You can anneal the copper pipe, and bend it back and forth very close to your finished shape. The more you bend and shape the annealed pipe, the more you will work harden it. I doubt you will obtain any significant work hardening from grinding or wire wheeling type M pipe, or any other fully annealed copper for that matter, sheet or otherwise. Maybe a little from media blasting, but nothing that will give you the structure that you need.

If weight is not an issue you could fill your finished form with pourable epoxy for strength also...but there are lots and lots of tubing benders out there that would probably help with bending cold stuff...

Best of luck with the project,

JM
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  #16  
Old 12-19-2007, 11:08 PM
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Re: Hardening copper pipe? How to?

seems to me that while there would be some impact energy transfered from a wire wheel, it would be substantially less than an impact at a right angle to the surface. In other words many times more work to get similar work hardening.

The ice idea, or any incompressible fluid or material will not only allow you to bend without kinking, but also hammer the copper directly. You can fill it up with water and cap it. some side support would still be a good idea at least for hammering, maybe a sandbag
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  #17  
Old 12-20-2007, 09:20 AM
John M John M is offline
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Re: Hardening copper pipe? How to?

you can fill the pipe with table salt also, and solder or braxe caps on the end to reduce wall collapse during bending. This is a usful old world application...
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  #18  
Old 12-20-2007, 09:56 AM
warren01 warren01 is offline
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Re: Hardening copper pipe? How to?

Quote:
Originally Posted by suburbanartists View Post
So i need to turn down the funky cold madina tunes when shaping? Ha ..Ha
Warren you said buffing? ...What about hand sanding? This is what i already do to finish so if it will work harden i could save a step.

If the vibration thing is true i could hook up to palm sander with no paper in it. But i'm sure the pieces would prefer a harden off to some public enemy.

Warren you make those cool vessels. i remember them from an older post. Very cool. looks like they are made from sheet copper. Do you have to harden them?
What I think that you have to remember is that once the copper has been moved once from bending or whatever it has started to lose the plastic state. So by further bending ,,,,,,,,,, back and forth, shaking, beating it with a plastic or wooden hammer, the vibration from a wire wheel, the vibration from a buffing wheel, will all harden the copper some. I do not think hand sanding will make the copper stiffer.
As far as the vessels I make the raised vessels get quite hard because you hammer plannish the surface to smooth as the last steps. On the welded vessels those are wire brushed and get harden (I use a braided style wire brush at 22,000 rpm) some but not lets say extra stiff. Copper will still dent and bend easy, it is just its nature. If you try to make the copper too hard it will get brittle and crack. If the issue you have that because of the weight you have bending than sometimes you can re-inforce the tubing with a steel rod.
I have many pieces from copper tubing and copper wire and all though a little fragile during the build process once completed they hold up fine.
For example here is a horse made from 3/8in copper tubing. It has been outside for over five years in Michigan winters with sometimes a foot of snow on it or an inch of frozen rain.
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  #19  
Old 12-20-2007, 10:10 AM
John M John M is offline
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Re: Hardening copper pipe? How to?

Beautiful work Warren...
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  #20  
Old 06-15-2008, 08:51 PM
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Re: Hardening copper pipe? How to?

Hi, have you considered bending the pipe as you would when plumbing, no heat involved? It is not difficult, for gentle bends ,say up to 60 deg over about 8", a bending spring will be more than adequate, youcan work them down the pipeto bend anywhere but they can stick and kink pipe. Better to buy or even hire a pipe bender, easy to use and bend anyway you want. THEN do your brazing/solder etc.
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