melting copper

[captain Jack]

I know this may be a little off the normal treasure topics here, but it's something I've been curious about. My friend and I work together installing hardwood floors and enter many a construction site. We, this year, decided to snath up all of the scrap copper we saw laying around to see how much we could gather as we have heard it is pretty valuable as far as recycling goes. (I think you can get somewhere between $1-$2 a pound)
We have probably 20 pounds of stripper copper wire and flashing pieces in a 5gal bucket on our work truck that we add to almost daily. We got to talkiing about how sweet it would be to have some copper bars like the silver bars we have invested in. But in researching the melting point of copper I found that not only do I have access to, or want to pay for a system to melt down the copper, but found that copper has to be melted in the absence of oxygen. If it oxidizes it is not worth anything.
I was wondering if anyone on here had the equipment to melt down the copper into ingots of some sort. I would be willing to pay a reasonable price or maybe let you keep a portion of the copper for yourself in return for the work. The price would have to be reasonable because I would have to pay to ship X amount of copper both ways.
Not sure if anyone has or would be willing to do this but I thought I'd put it out there. If anyone is interested or has any comments post 'em or PM me! Man I think those sparkling copper bars would look pretty! Thanks for any advice.

Jeff

 

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[BioProfessor]

If you plan to sell the ingots after you make them, you have the same problem as all the people who have mentioned making gold bars - alloy, alloy, alloy. What you have will not be pure copper. Just like gold is not pure gold. If you are going to sell it, you will have to determine the alloy. Since you are mixing copper from what might be different things, you are probably mixing different alloys in your bucket. When you melt all this down, if the assay doesn't come back as a standard copper alloy, it won't be worth that much (I don't think) because whomever buys it will have to re-alloy it to get it to a standard so it can be used to fabricate parts or whatever. It's not really like gold where they buy the gold content. Gold is fairly consistent in what is added to make the carat so adjusting up or down is much easier. If you still want to go this direction, I can give you more information about keeping the atmosphere oxygen free. I make a good bit of copper alloy.

If you are not going to sell them, you can make a mold out of 1/4" plate steel. Just make it in the shape of the ingot you want, tack weld it, put some refractory cement in the cracks, smoke it with acetylene soot and you are good to go. You can have your friendly local welder melt the copper with a torch and pour it into the molds. The metal won't stick to the soot and should release from the mold once it has been cooled. Shine em up, stack em up, and they'll look neat.

Daryl

 

[EDDE]

what about the molds divers use for lead weight belts
to make weight's out of melted lead shot etc

 

[BioProfessor]

Soot them and they should work. Try one first to make sure it can handle the heat.

Daryl

 

[Rob in KS]

Daryl,
You sure do some interesting stuff!! Does your garage look like a mad scientists laboratory?

 

[BioProfessor]

My whole house, office, and lab at the university all look that way.

Gotta love it.

Daryl

 

[BioProfessor]

But I do like the results from alloying my own copper.

Daryl

 

[Real de Tayopa Tropical Tramp]

HI YA Prof: I agree with you even IF yer a prof, heheh. I will add one thing, if you are getting any electrical contact materiel, separate it since many times it has a much more valuable metal added to it to form an alloy that will hold up to the intended service.

The old Spanish many times simply used the so called soap stone for their molds, I have even seen them made from charcoal. They used sifted local clay for the separating agent in the moulds.

One method used when banditry was getting too bad was to simply dump the molten silver into an excavation in the earth in say 500 # blocks to be transported in two wheel carts where possible, quite effective.

I am curious, if you intend to sell it, why do you have to smelt it in a no oxy condition, since it will have to be resmelted in any event? A no oxy state is fairly easy to attain.

There are many excellent inexpensive home made furnace plans on the internet, check with Google or SCIRUS.

Don Jose de La Mancha

p.s. Nice work Prof., makes a happy head of the household.

 

[BioProfessor]

Molds are easy to make. My favorite is just a fine clay powder (Delft). I was thinking that since he wanted to pour ingots, there would be a lot of very hot metal and you don't want an exploding or cracking mold from the intense heat (about 2000 degrees F for copper). I have made molds to cast fairly large ingots and using 1/4" cold rolled steel plate is just easy to get, easy to work with, and cheap. They also produce an ingot that has very smooth and straight sides and top. No sand marks or any imperfections. I was thinking this was what they wanted since they were going to shine them up. They will also hold up to the heat so they are my first choice for this kind of job.

The reason you have to keep the atmosphere during the melting and pouring is because of the annealing needed to work the copper. If the atmosphere around the copper has oxygen, there will be quite a bit of oxidation occurring in the melted copper. When it is poured, it will produce an ingot of copper that is usually too brittle to work. The metal just refuses to soften up enough to work when it is annealed. I use a standard Argon gas shield during the entire process and it has worked great so far. The alloy I make is about $1 a gram so I have to be careful not to screw it up.

You are right in saying it won't matter if your buyer is going to resmelt anyway. But if there is too much oxidation, the yield during the smelt will be significantly reduced. Most good metal buyer/smelters can tell this by hitting the ingot with a hammer. Price could go down.

My 2 cents.

Daryl

 

[Real de Tayopa Tropical Tramp]

HI Prof: No change for your two cents, accepted. snicker. Argon works nicely.

In essence, I can find no argument on your posts -- much as I would like to, simply because I am a onry Irishman heheheheh.

Don Jose de La Mancha

 

[captain Jack]

HI YA Prof: I agree with you even IF yer a prof, heheh. I will add one thing, if you are getting any electrical contact materiel, separate it since many times it has a much more valuable metal added to it to form an alloy that will hold up to the intended service.

Most of what I have is electrical wiring that is stripped, different gauges, but I would think they would primarily be the same make-up. A little copper piping, and flashing and that's about it. I'd say 95% wiring.

Prof, I actually heard a thing on the radio today about bringing in copper and gold etc in for recycling, I called 'em and they said they were offering $1.70 - $2.50 a pound. If I melted all the copper together, or at least all the wiring together, the quality of the sum should equal at least that of the lowest grade right? Meaning I should be able to expect at least the lowest offering price right? Or am I way wrong on that one?
BTW, how much are those torches and how do you keep the oxygen out? I know one way is to use coal because it burns most of the oxygen but I don't see myself building a 2000 degree fire.
Seems like buying the torches and casts and everything would cost more than the copper is worth. Of course, if I ever start finding a decent amount of gold and silver with my MDing I could then use it to melt those down as well I guess.

 

[BioProfessor]

When you take copper or other metal to a recycling dealer, they sort it into bins. It gets sorted again when buyer of the bin gets it. They have to be able to put different kinds of copper into different bins - again to keep the same alloys together. So if you melt it all together, they will look at you kind of funny and say "Next. Whose Next." A mixed copper alloy ingot is really a paperweight.

Torches are about $150 on the low end but then you don't want to buy one. Just find a welding shop. It will be much cheaper. Just drop by and tell them what you want to do. They may have a melting pot and molds. Never know. It will not keep the oxygen out. To melt the copper in an oxygen free environment, you need an electric melter/furnace placed in some sort of surrounding shield that can be filled with Argon. Argon is heavier than air and will tend to stay in the container and replace the oxygen. You need to keep a small amount of Argon going into the container to make sure the container is under "positive pressure" for Argon.

My suggestion. Melt the copper together with a torch and make ingots to shine up and keep. Take all the bits an pieces to a recycle dealer if you want to sell it.

Daryl

 

[captain Jack]

right on, thanks for the adivce. Much appreciated, and thanks for the patience with those of us who are less chemically inclined!