jcornell

Is it possible to fire-weld copper?

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TLMG is of course referring to fluxes that melt at high temps like borax and not the fluxes that are liquid at lower temps.  You would definitely look into lower temp fluxes like soldering uses. (Sal ammoniac for instance).

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Tristan: Have you tried either commercial paste/liquid flux OR the jewelers standby of dissolving borax in water?

Ron Reil was forge welding copper before he found out what Mokume is. Heck he went a little nuts playing with forge welded copper.

Regardless of what Ron was doing in the 80's what you say is undoubtedly true and heck cable is probably oxidized as it sits before going into the fire. Pickle it first, then flux, then into the fire? Maybe use copper pipe as a can?

On the other hand buying new stock holds even more true here than in the bladesmith's realm.

Just because a challenge triggers the tinker in me doesn't mean that's the way to go. :rolleyes:

Thanks for jumping in Tristan.

Frosty The Lucky.

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I have not tried a lower temp flux, but it would need to be liquid at a really low temp,  if I was going to try this I would weld a box to enclose my item and do all I could to keep air out of it or burn the air up before welding the copper. Like I said, probably more hassle  than buying a copper bar. But go ahead and try it, fortune favors the bold.

 

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I think you can control the melting together of wire stock. I have also combined/alloyed copper, nickle, tin, and zinc together in a forge to create a type of red-bronze and not had much of an oxidation problem. The impurities tend to float to the top when the metal gets molten and I just wire wheel them off. I make it into a brick, cut pieces off and cast them in a little 2x2x1/8 inch form for workable pieces. Here's a photo of the brick, the cast piece, and a couple of spacers for a knife handle I'm working on.

Red Bronze.JPG

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Melting it into one chunk is different than forge welding. You can melt it all into a block but the idea that all the scum floats is only partly true. What you can't see is the oxygen that copper LOVES. It readily dissolves into the Cu and makes it brittle. If you notice any cracking it is likely oxygen. When they melt copper commercially they have to protect it. That is one reason why the Japanese traditionally cast copper and its alloys underwater to protect it from the air.

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I'm not making the connection. If the copper absorbs the oxygen during heating, how does casting it in water protect it from that? Or does it absorb the O2 when in liquid state?

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You have me wondering how you cast underwater too. Prophylactic methods of preventing oxy contamination of molten copper, say a sprinkle of borax and deoxidizing is really easy. However underwater casting metals really piques my interest.

Frosty The Lucky.

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Sorry, I jumped ahead to far there. I was using the casting in water as an example of the steps humans have taken to avoid oxygen and copper from coming together. When heating it can be kept under a glass like borax or literally glass. Commercially it is kept in an oxy free environment  and the use of strong chemicals to rob oxy from the solution.

the method of casting copper into water is basically for ingots that will then be hammered and or rolled out.if the link works here is a video on the process https://m.youtube.com/watch?v=WUVUYH_vvZE

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Nice video thanks for sharing. I don't think the wife will be too keen on me trying it in the kitchen though! :blink:

Ian Ferguson has a short section on this method in his book "Mokume Gane" (I knew I'd read about it somewhere before), but he said "Whether the process is of any great advantage over contemporary procedures of casting in a closed mold, has never been sufficiently analyzed...However it would appear that casting copper and its alloys under water goes some way to excluding gasses from the ingot and provides a clean, dense surface." (p. 58).

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Nassau refining used to take a large tree and dump it in their vat of molten copper to deoxidize it.  They owned a mountain side in a forest just for this.  My father got to go see this when touring them as they were recycling their company's copper scrap at the time.  Me I stir with a DRY DRY DRY charcoal stick or melt it under a layer of powdered charcoal.

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I read an article with analysis of copper cast in water and it is better than just in the air for sure, but not as good as the commercial processes of today. But if you need to make your own alloys then it is a reasonable thing to do.

Thomas, I have a hard time imagining so much molten copper you could put a whole tree in it! That is awesome! Thanks for the tip on charcoal.

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I know this is an old post, but this may help someone who wants to try welding copper cable. I have welded electrical cable about 3/4" dia. in my propne forge no problem. I used plenty of borax and kept it fuel rich. At a certain point, it gets a greenish look to it and thats when I pulled it out and forged the many strands solid.  No issues with oxidation, at least for me.

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I never cast under water, but I tried a technique for making pellets and shot I found in a metallurgy book somewhere a few times. Basically, you dripped it into the water and they formed round droplets.  I worried about steam, but outside of a little spitting, it never turned out to be an issue.  I also found that with aluminum, I could get sometimes get little strands to form. Had trouble getting consistent shapes and sizes. Dunno, haven't tried it in about 13 or 14 years. Now I think I would worry about steam again.  So, four years late on this post. Whoops.

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 The pellet making process you found,   in the book that you read,   has been used since it was first invented and patented in 1782 in England.

The molten lead was run through holes in a perforated metal plate. That plate  was located at the top of a tower several stories up.

Sufficiently high that the descending lead droplets formed spheres and solidified before they landed in a water bath located at the bottom of the tower.

The larger desired shot, required much taller towers.

The process was resulted in more accurate spheres than the previous method of making shot that of casting and molding of molten lead.

The Manufacturing process was further improved by the Bliemeister method of 1962.

SLAG.

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