Annealing Copper Wire

[Robert E Holt]

Guys, any blacksmith or knife forger will tell you, dipping hot metal into water or oil has the effect of hardening the wire. If you let it cool on its own it will be much softer and malleable.

I have always heard that copper is an exception to this. To harden copper you heat it to annealing temperature and cool is very slowly. To soften it you cool it quickly. I annealed some last night on my Lump Charcoal fired grill. Once it was red hot I dropped it into icewater. It appears to be very soft.

 

[justBonsai]

The point of annealing is to produce unstressed grains in the metal that are soft and workable. By quenching you "lock" in that grain structure and prevent any reverting to the previous state. In the case of knife makers it's the same thing. The reason why steel becomes harder after quenching is because the carbon and other precipitates in the steel get locked in the position they were set in by the heating without being given a chance to leave the steel's crystal structure. This causes deformation and stress in the steel which in turn makes it harder. At least for bonsai wire made up of copper or aluminum it's a homogeneous metal with no precipitates so quenching will not make it harder--rather that the wire can be ready to use in less time.

 

[0soyoung]

The point of annealing is to produce unstressed grains in the metal that are soft and workable. By quenching you "lock" in that grain structure and prevent any reverting to the previous state. In the case of knife makers it's the same thing. The reason why steel becomes harder after quenching is because the carbon and other precipitates in the steel get locked in the position they were set in by the heating without being given a chance to leave the steel's crystal structure. This causes deformation and stress in the steel which in turn makes it harder. At least for bonsai wire made up of copper or aluminum it's a homogeneous metal with no precipitates so quenching will not make it harder--rather that the wire can be ready to use in less time.

Right, even though copper has some impurities, their effects on mechanical properties are negligable. Copper work hardens because defects, dislocations, in the crystal structure of the copper grains that are induced by bending (or other distortions of the annealed shape). Brent of evergreengardenworks.com went over all of this years ago, in one of the Articles on his web site - nicely written and easily understandable, IMHO.

 

[PierreR]

Hi guys, I'm one of those knife makers your hinting about. Steel and copper are two different animals. Steel is taken to a higher temp, to allow carbon and other trace materials to more freely disperse, then is quenched, as mentioned, to trap the molecules into a more structured matrix. Then the steel is tempered to reduce stresses, and to lower the hardness into a range where the steel isn't brittle, but still hard/tough enough, to take and hold an edge, or to withstand abuse, as in an axe or camp knife.

This information I copied some time ago, not sure of the source.

Copper has a cubic crystal structure. It is the particular variation (face centered cubic) that gives it it's extreme ductility so that you can bend a wire into really sharp curves. Bending a copper wire work hardens it which introduces defects known as dislocations into the structure. These defects interfere with further deformation and make the copper hard and strong so it is not easily rebent. Aluminum work hardens less than copper while gold barely work hardens at all.

Annealing the copper eliminates the dislocations so that the copper is once again composed of nice perfect crystals. This allows the copper wire to be reused since it is now soft and easily bent. Generally annealing is done at greater than 1/2 of the melting point on the absolute temperature scale. Copper melts at 1083C = 1356K so the annealing is done at greater than 678K = 405C = 761F, it is more common to anneal at about 700 to 800C. The copper can be worked and annealled many, many times. The copper will maintain it's soft crystal structure after annealing at any realistic cooling rate (from very slow like letting fire die down to fast like throwing it in a bucket of water). Generally, I would suggest water cooling to prevent excessive oxidation of the surface.

EDIT: I believe Osoyoung refered to the source.

 

[justBonsai]

Hi guys, I'm one of those knife maker guys your hinting about. Steel and copper are two different animals. Steel is taken to a higher temp, to allow carbon and other trace materials to more freely disperse within the structure, then is quenched, as mentioned, to trap the molecules into a more structured matrix. Then the steel is tempered to reduce stresses in the steel, and to lower the herdness into a range where the steel isn't brittle, but still hard/tough enough, to take and old an edge, or to withstand abuse, as in an axe or camp knife.

This information I copied some time ago, not sure of the source.

EDIT: I believe Osoyoung refered to the source.

By chance are you on bladeforums? I'm hoping to become a knifemaker when I have more free time and money. Heat treating methods and cycles can vary a lot depending on the specific steel or alloy, but quenching and tempering is the gist of it. Unfortunately my time is consumed by school as I'm still working on my undergraduate degree. I plan to travel to Japan in a few years first as a study abroad program and hopefully again to study bonsai and knifemaking.

 

[PierreR]

No, I am on several other forums. Not as much as I used to be. Getting tired of the rhetoric some days...
Critical temps, beating the "nose" on the quench curve, sometimes thermal cycling, so much to learn. A big reason why some makers choose no more than 3-4 steels, and learn them well. Sometimes a maker specializes with one steel.

 

[wlambeth]

Normally I use copper wire as is. I frequently purchase from home depot off their wire racks.
But if I heat treat it I will certainly use water to quickly cool it down.
Great information thanks

 

[sorce]

31st

Normally I use copper wire as is. I frequently purchase from home depot off their wire racks.
But if I heat treat it I will certainly use water to quickly cool it down.
Great information thanks

Your world is about to change!

Sorce

 

[Paradox]

Bumping this old thread to relate my experience with doing this on my second attempt, this time in my fire place.

It worked great! I was able to get a uniform bright orange wire from doing it in the fire place.
I found that the key to getting a nice uniform heating on the wire was to build up a good coal base and make sure there as a nice bed of orange coals on the bottom of the fireplace and I put mostly charred, ember pieces of wood on top of the wire.

I found that the thickness of the wire determined the time it took to get a nice even orange color

Thin wire: 18-14 gauge could be heated in 15 min
Medium wire: 10-12 gauge could be heated well in 20 min
Heavy wire 6-8 gauge needed 25 minutes to get the nice even glow

 

[M. Frary]

worked great

It's cool isn't it?

 

[Paradox]

It's cool isn't it?

Yep. I knew it was working right when I saw the whole coil a nice even bright orange and when I pulled the coils out of the coals, they were soft.

 

[M. Frary]

Yep. I knew it was working right when I saw the whole coil a nice even bright orange and when I pulled the coils out of the coals, they were soft.

Have you used any yet? That's when the satisfaction sets in.
My only problem is finding the big fat wire and the thin,thin wire to anneal.

 

[Paradox]

Have you used any yet? That's when the satisfaction sets in.
My only problem is finding the big fat wire and the thin,thin wire to anneal.

No havent yet. I got most of mine from Home Depot and some I scrounged from some wire I found thrown away.
The 18 gauge/1 mm wire was found in the picture hanging section of Home Depot. They sell coils of it to hang pictures.
The rest was regular solid strand electrical wire.

 

[M. Frary]

The 18 gauge/1 mm wire was found in the picture hanging section of Home Depot.

I'll be scoping that out. Thanks!

 

[Random User]

Aluminum works the same as copper wire, but I find it much easier to find copper. Often times what works for thinner branch sizes is the ground cable (that has multiple strands (12-ish?)) for grounding the plumbing in the house. I'm sure that someone would have the "technical name" for it, but to me, it's just ground cable. I unwrap it, and heat the coils with an acetylene torch... toss it in a bucket of water when it's consistently red-hot all 'round, and presto...

Might be a good task to do when you're having a back yard BBQ next summer... toss it in the camp fire, then into a child's splash tub, or some such thing...

... I also clamp one end in a bench vice and then pull the wire once along it's length (between my fingers) with a heavy welding glove on... this straightens it for use.

Aluminum will "work harden" much faster than copper will, and eventually break, where copper will continue to flex... but on the other hand copper (if too soft for a given branch) might have to be worked a few times (flexed back and forth) to "stiffen" the spine, or you might have to select a larger size wire if you have it.

If you see the truck bed on a newer Ford pickup with large cracks in it, that is what happens to aluminum when flexed heavily over time... I've heard of the entire side of the box falling off, but have not seen more than 8-12" cracks in the corners.

I don't know of bonsai wire availability in the U.S., but the only place I've found it is at LeeValley Tools... but it's really expensive, so I'd only use it on a tree that is more "refined".

 

[Paradox]

Aluminum works the same as copper wire, but I find it much easier to find copper. Often times what works for thinner branch sizes is the ground cable (that has multiple strands (12-ish?)) for grounding the plumbing in the house. I'm sure that someone would have the "technical name" for it, but to me, it's just ground cable. I unwrap it, and heat the coils with an acetylene torch... toss it in a bucket of water when it's consistently red-hot all 'round, and presto...

Might be a good task to do when you're having a back yard BBQ next summer... toss it in the camp fire, then into a child's splash tub, or some such thing...

... I also clamp one end in a bench vice and then pull the wire once along it's length (between my fingers) with a heavy welding glove on... this straightens it for use.

Aluminum will "work harden" much faster than copper will, and eventually break, where copper will continue to flex... but on the other hand copper (if too soft for a given branch) might have to be worked a few times (flexed back and forth) to "stiffen" the spine, or you might have to select a larger size wire if you have it.

If you see the truck bed on a newer Ford pickup with large cracks in it, that is what happens to aluminum when flexed heavily over time... I've heard of the entire side of the box falling off, but have not seen more than 8-12" cracks in the corners.

I don't know of bonsai wire availability in the U.S., but the only place I've found it is at LeeValley Tools... but it's really expensive, so I'd only use it on a tree that is more "refined".

Julian Adams (Adams Bonsai) and Jim Gremel both sell annealed copper wire in the U.S. at very reasonable prices.
I annealed my own because I wanted to try it out and see if I could do it in case I ever need to.

I stripped the wire on my deck by wrapping it around a railing and pulling the plastic coating off. I didnt want to put it in my fireplace in my house with the plastic on.
I pulled it straight while it was still tied onto my deck railing. I then wrapped it on a coffee can or plastic bucket to make the even coils. Worked fine.

I took mine out of the fire and let it cool a bit on the stone side of the fireplace and just go back to a black color then dropped it into a bucket of water.

It has been my experience so far working with both aluminum and copper that copper work hardens faster and much better than aluminum. I have a hard time removing some larger gauge copper wire from a tree by uncoiling it than I do aluminum.

Copper has much better holding power than aluminum. You need much bigger aluminum wire than you do copper wire and Ive found aluminum does not hold as well on flexible branches such as pine and juniper.

 

[Random User]

"I have a hard time removing some larger gauge copper wire from a tree by uncoiling it than I do aluminum. "

Being a deciduous tree guy, I mostly use it as guy wires, so it's easily re-purposed.

I just cut it off if I have put it on a branch in the traditional manner... but am lucky enough to have different sizes available to me from "Industrial" wiring... although, I don't have an abundance of different sizes. The guy wire technique on deciduous trees is pretty much a "one-size-fits-all" application, so most anything will do... and it doesn't even "have" to be wire necessarily... but thats a conversation that leads way off topic.

 

[sorce]

finding the big fat wire and the thin,thin wire

I may have another swell return package for you!

@Paradox ....Awesome!

Sorce

 

[Canaima]

Great chain...question for all: what is the best place to buy copper wire so I can do my own annealing? Any good online sources?

 

[Srt8madness]

Great chain...question for all: what is the best place to buy copper wire so I can do my own annealing? Any good online sources?

Idk but it's probably just as cheap to get it already done. I just ordered from here, a really good guy.

Copper Bonsai Wire | Black River Bonsai

www.blackriverbonsai.com