making small copper pipe more bendable

I'm trying to curl up some small copper pipe (or tube, if you prefer) to make a toy boat along this line:
https://en.wikipedia.org/wiki/File:Rew11d04-577_coil_type_pop_pop.JPG
I tried some 10 mm (or so) pipe that I found in the cellar, and it kinked too easily. I got some "5 mm X 0.45 mm" tubes from a hobby shop (aimed at model railways, I think), and that's even harder to bend & easier to kink.
Is it worth trying to anneal a piece with a blowtorch? If so, what's the best procedure?
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On Wednesday, November 14, 2012 1:45:03 PM UTC, Adam Funk wrote:

I just bropught some of this for a studetn project.
http://www.tradingdepot.co.uk/DEF/product /!!COP10/10/BARE!!/D013002/Plumbing%20Supplies%20&%20Heating%20Supplies/Copper%20Tube%20/%20Copper%20Pipe%20and%20Accessories/Coils%20of%20Copper%20Tube/Coil%20Plain%20Copper%20Tube%2010mm%20x%2010m
similar thing in be here & queue
http://www.diy.com/nav/fix/plumbing/plumbing-supplies/copper_pipes/-finish-Plain+Copper+Coil/Streamline-Blue-Label-EN-1057-Copper-Tube-Soft-Coil-W010C-10-10mm-x-10m-9264631
no ideas if it's suitable ....
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http://www.tradingdepot.co.uk/DEF/product /!!COP10/10/BARE!!/D013002/Plumbing%20Supplies%20&%20Heating%20Supplies/Copper%20Tube%20/%20Copper%20Pipe%20and%20Accessories/Coils%20of%20Copper%20Tube/Coil%20Plain%20Copper%20Tube%2010mm%20x%2010m
http://www.diy.com/nav/fix/plumbing/plumbing-supplies/copper_pipes/-finish-Plain+Copper+Coil/Streamline-Blue-Label-EN-1057-Copper-Tube-Soft-Coil-W010C-10-10mm-x-10m-9264631
Fill with fine dry sand, seal the ends and bend. The sand "should" stop the walls of the tube collapsing.
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On 14/11/2012 13:42, Adam Funk wrote:

Heat to cherry red, then plunge into cold water.
To be sure, fill the annealed tube with Wood's Metal, bend to shape, then melt the Wood's Metal out by placing the tube in boiling water.
Colin Bignell
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On 14/11/2012 14:22, Nightjar wrote:

Woods Metal not cheap
http://www.ebay.co.uk/sch/i.html?_odkw=%22woods+metal%22&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313&_nkw rrobend&_sacat=0
For this relatively small application you could always use plumbers' solder.
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On 14/11/2012 14:53, newshound wrote:

http://www.ebay.co.uk/sch/i.html?_odkw=%22woods+metal%22&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313&_nkw rrobend&_sacat=0
But it lasts forever. I inherited mine from my father.

That would leave a residue inside the tube, which Wood's metal usually does not. As the application seems to involve heating the coil, that may be important.
Colin Bignell
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On 14/11/2012 16:20, Nightjar wrote:

In principle, but would it be likely to matter for this low-tech application? In my experience, without flux the solder just won't wet the oxidised bore.
I think annealing might be enough with thick-wall tube, but I'd be nervous about modern tube kinking without internal support. The sand method is good, but is it easily removed from a relatively tight set of coils?
--
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and wrong.
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On 2012-11-14, newshound wrote:

I'll try it.

Let me put it this way: I spent less than £2 on the hull *and* I got to eat the kippers.
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On 14/11/2012 20:20, Adam Funk wrote:

OK but £13 for a kilo of Woods metal when you need less than 100 grams. An engineer is someone who can do for a shilling what any fool can do for a pound.
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On 14/11/2012 22:59, newshound wrote:

The cadmium puts me off a bit...
--
Rod

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On 14/11/2012 23:01, polygonum wrote:

Just wear an old asbestos face mask....
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Copper is very easy to anneal. Heat until the copper is a uniform dull red colour and then either quench in water or just leave to cool. Keep moving the flame around so as not to overheat or burn any particular area. A dimly lit room makes the colour easier to see. Unlike ferrous metals which harden with a fast quench and anneal with a slow cool, copper also anneals with a fast quench. Because copper work hardens so quickly if you bend or hammer it you may need to anneal it multiple times as you work it into the desired shape but you can do so as often as you like without harming the material.
--
Dave Baker



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How does that work? As I understand it, annealing happens while the metal is hot: the domains grow. A fast quench (of metals that go this way) causes rapid contraction which puts unconformities into the domains as they cool, so hardening (outer) parts. I suppose in copper this doesn’t happen as much for some reason?
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On Thursday, November 15, 2012 10:50:15 AM UTC, Jon Fairbairn wrote:

Oh god. [/me tries to recall Metallurgy from when we were both at Cambridge].
In both copper and ferrous metals, heating a work-hardened piece allows the dislocations to move around, untangle themselves, and dissipate. This removes the work hardening.
When you heat ferrous metals, they undergo a phase change to a different crystalline form (which happens to be hard). If you then cool them fast, they don't have time to change crystal layout, so they stay hard. If you cool them slowly, they /do/ have time to change crystal form, so end up soft.
Copper doesn't undergo this phase change, so can be annealed quickly.
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That’s essentially what I thought, but probably a more accurate description than my memory of it (I didn’t do much metallurgy, switching to compsci).

Thanks. That makes sense.
--
Jón Fairbairn snipped-for-privacy@cl.cam.ac.uk
http://www.chaos.org.uk/~jf/Stuff-I-dont-want.html (updated 2012-10-07)
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On 16/11/2012 11:11, Jon Fairbairn wrote:

The copper bit is OK, with iron and steel it is all a bit more complicated and depends on the carbon level. Plenty of stuff on the web!
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Most of the copper pipe you buy is in hard or "half hard " condition. Makes it stronger. You can anneal it by heating to red heat and letting cool. It will then bend better but will have reduced pressure rating.
Annealed pipe can be bought, it usually comes in a coil and is thicker guage hence more expensive.
One thing you might do if it is a project is consider automotive hydraulic copper brake pipe if you need a really high pressure.
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For a pop pop boat? I think that might be overkill. ;-)
Tim
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On 2012-11-14, Tim+ wrote:

To be powered by a candle or alcohol lamp, so as someone else has said, this is a low-tech application.
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To stop it from kinking, you can buy and external spring,fits over the pipe while you bend it.
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