Annealing Copper Wire Finally and Need a Little Advice Pls

[August44]

I have been collecting copper wire remnants for a year or so and want to get it annealed. I have been told that I can use an electric kiln locally but would like to get input on:

The highest temp that I should go and should I set the firing up with a hold. If so, how long should the hold be? The wire you see in the picture is what I will be annealing. There is some 14 gauge, some 13 gauge, some 12 gauge, some 11 gauge, and some 6 gauge. Also wanted to know why some copper wire I bought from one source starts to work harden when you start installing it, which can make it tough to say the least, and the second group bought from another source takes an hour or two to get hard. Is one over heated and one under heated? I don't want mine to work hard almost immediately, and don't think I want it to take two hours either. Any advice to keep me from screwing this up after all the work would really be appreciated. Thanks, August

 

[leatherback]

Typical temperature to use is 400C / ~700F for annealing.

Also wanted to know why some copper wire I bought from one source starts to work harden when you start installing it, which can make it tough to say the least, and the second group bought from another source takes an hour or two to get hard.

Sounds odd. Copper that has been annealed gets harder as you bend it, immediatly. It is a physics process, not a chemical process.

which can make it tough to say the least

One of the reasons why in general people are adviced to only use copper when you need to and/or make sure you wire correctly the first go.

 

[Shibui]

As far as I know there's no need to hold coper at a temp to get good annealing. I've only ever heated it to red then straight out of the fire and let it air cool.

Agree that copper should harden as it is bent. Hardening slowly afterwards makes no sense to me but if you can find some metalurgy that supports the process I'm willing to learn.

I don't find it difficult to apply copper wire because it hardens AS you bend it, not before you bend it. Provided you are careful to only bend where you want the bends, it goes on relatively easy.
I did have one batch that was harder and difficult to apply but that was not annealed - or not annealed properly. Maybe that's what is causing your difficulty with the wire that hardens when you start?

 

[SeanS]

Remember to (try to) not bend or straighten it too much before you apply it. Cut the desired length and try not to handle it too much before and during application. Only bend it as you’re applying it, bending only the part of the length of wire that is behind wound on (if that makes sense?).
Unlike aluminum you should avoid straightening or pre-bending copper to fit it into tight spots as much as possible.

 

[JeffS73]

There are two good reasons for a hold. One is ensuring all of the copper reaches the desired temperature, partly dependent on how you pack the kiln and wire diameter.
The other is that if you hold above the recrystallisation temp, crystals will grow larger. Dislocation of crystals increases hardness. Larger crystals mostly correlate with softer wire, but there are limits.
Making the best, most useful copper wire would take some careful testing, there are no empirical numbers that cover every situation.

FYI, I'm just another amateur who read some stuff, not a metallurgist!

Perhaps the most important thing is how to get rid of the scale (copper oxide) that forms on the surface. Some people quench, others pickle. Whatever you do, dispose of it in a responsible way as its extremely toxic to soil and aquatic life.

 

[Brian Van Fleet]

Annealing is achieved at a little over half the melting point. Melting point of copper is 1357k or 1983f, so if you set your kiln to around 1000f-1200f and give the wire a few minutes to achieve that temp throughout, you’re probably good.

When I used to anneal my own in fire, I went more by color, and there was a point when the wire turned a certain shade of purple, just before becoming red-hot, that I would pull it and quench it.

If it gets hot spots, the wire gets brittle there and breaks. Since you’re talking about relatively thin wire, it’s ok if you under-anneal just a little. 6 gauge will take longer, and I’d do that wire in a separate batch.