FredSmith Posted July 11, 2011 Share Posted July 11, 2011 HI, I'm new to blacksmithing, and i recently decided to try melting down some wire from a jumpstart cable that was broken. I think it is copper. Can I put the metal into a thick casserole dish to melt down, or will that not work? thanks Quote Link to comment Share on other sites More sharing options...
MattBower Posted July 11, 2011 Share Posted July 11, 2011 HI, I'm new to blacksmithing, and i recently decided to try melting down some wire from a jumpstart cable that was broken. I think it is copper. Can I put the metal into a thick casserole dish to melt down, or will that not work? thanks That will not work, at least not safely. Household ceramics are not made to hold up to the temperatures and thermal shock that a crucible experiences, or to retain strength at extreme temperatures. (They may be fired at those temperatures, but they are ramped up and down very slowly -- many times slower than what a crucible experiences -- and they are not asked to do work at firing temperatures.) And molten metal is much more dangerous than solid metal at just about any temperature. If these are copper cables, the melting point is near 2000 F -- and you need to superheat by a few hundred degrees for casting. For these sorts of temperatures you really need a crucible made of some sort of refractory material. For lower melting metals you can get by with a welded steel crucible if you don't mind contaminating the melt, but that's not a good idea for something that melts as high as copper. Are you trying to cast something to near final shape, or do you just want to melt the stuff into ingot form, then work the solid ingot to shape? If all you want to do is melt it into an ingot, you can get some scrap graphite (e.g., from eBay), route/carve/mill a cavity in it, and melt your copper directly in that cavity. In that case the graphite serves as both crucible and mold. I know a guy who makes shibuichi ingots this way. Put some charcoal on top of the wire to help prevent the metal from absorbing contaminants from the forge atmosphere. Be aware that fine wire has a high ratio of surface area to mass. That's always a good recipe for losing a lot of metal in the dross. The thicker the wire, the better off you are. And if you can get a pool of molten metal, then submerge your wire in that pool while it melts, you'll waste much less. Anything that you add to a melt must be preheated above the boiling point of water before it touches molten metal. If there's any water trapped inside when it's submerged, you may have a very bad day. This goes for your tongs and other tools, too. If you're hoping to cast to shape, I should mention that pure copper has a reputation for casting poorly. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted July 11, 2011 Share Posted July 11, 2011 As mentioned copper loves to oxidize forming a bright copper coloured ceramic in your crucible that is absolutely useless. Unless you degas it too you end up with lots of bubbles in anything you cast from it. I heartily recommend taking a jewelry casting class before trying it your self---or find the local backyard metal casters. Also please try to be specific in your questions; I own casserole dishes made from at least 4 different materials all having different properties. Which of them is/are like yours???? Quote Link to comment Share on other sites More sharing options...
MattBower Posted July 11, 2011 Share Posted July 11, 2011 As mentioned copper loves to oxidize forming a bright copper coloured ceramic in your crucible that is absolutely useless. Unless you degas it too you end up with lots of bubbles in anything you cast from it. I almost mentioned deoxidizing with a modern (zinc) penny or two, but I figured somebody would draw and quarter me. Quote Link to comment Share on other sites More sharing options...
FredSmith Posted July 12, 2011 Author Share Posted July 12, 2011 Thanks, I guess that I will wait until I get some graphite, and try easier things first. The casserole dish is made from glass, and almost an inch thick. Quote Link to comment Share on other sites More sharing options...
MattBower Posted July 13, 2011 Share Posted July 13, 2011 Crushed glass is often used as a cover for molten metal charges. It melts and forms a protective, impermeable layer between the metal and the atmosphere. A good campfire will turn soda-lime glass into soft taffy. Borosilicate (old Pyrex) will last a bit longer, but it'll still be at least extremely soft (or worse, I've never played with it at those temperatures) well below the melting point of copper. And neither one of them is good for the amount of thermal shock you're looking at. Definitely try the graphite. You can find good deals on scraps on eBay. It will eventually burn away in the forge, but it should last a good number of uses. Tutorial here. The part about turning out the ingot before it cools completely (but after it's solid) is probably pretty important for mold longevity. Quote Link to comment Share on other sites More sharing options...
WmHorus Posted July 13, 2011 Share Posted July 13, 2011 Someone told me to toss in some borax to achieve the same effect as the same effect as the graphite. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted July 13, 2011 Share Posted July 13, 2011 Borax helps prevent the molten metal from absorbing gasses but I don't believe it de-gasses the melt. Nassau Recycling always added a tree to their copper melts to de-oxidize---but the results were rather spectacular in a "Better have the Fire Squad and EMTs on hand if you try this at home" way! Quote Link to comment Share on other sites More sharing options...
MattBower Posted July 13, 2011 Share Posted July 13, 2011 Borax helps prevent the molten metal from absorbing gasses but I don't believe it de-gasses the melt. Nassau Recycling always added a tree to their copper melts to de-oxidize---but the results were rather spectacular in a "Better have the Fire Squad and EMTs on hand if you try this at home" way! I don't think so either. The typical deoxidizers for copper seem to be pretty scary-sounding chemicals. Zinc is probably the most benign of them. It doesn't take much, either --I've read that a couple percent by weight is enough. Edit: Here's far more than I ever knew about degassing copper. Quote Link to comment Share on other sites More sharing options...
MattBower Posted July 13, 2011 Share Posted July 13, 2011 I notice that Budget Casting Supply sells expensive phosphor copper shot for degassing. (Phosphorous is mentioned as a degasser in the link in my previous post.) But you can buy copper phosphorus brazing rods quite cheaply. Hmm. Same alloy, or close enough? I don't know. But it's a thought. Quote Link to comment Share on other sites More sharing options...
Bentiron1946 Posted July 14, 2011 Share Posted July 14, 2011 There always seems to be a big fascination with casting copper but there are better and easier metals to cast than copper. Take a look at this guys web site, http://www.backyardmetalcasting.com/ , he has some good ideas, not all of them but some of them are good. I started out scrounging plumbing brass, you know valve bodies, PRV off of water heater, old hose bibs and the like. Not the best of materials but they will be easier than pure copper like you get from electrical products generally. I still scrounge all the copper, brass, aluminum and steel I come across that ain't nailed down. Then I take it over to the salvager's and get cash for it, that way you can buy some real fine casting metal, silicon bronze. That stuff will pour like water and you don't need to degas it ever. Wonderful stuff that silicon bronze. You can get it from Budget Casting Supply http://www.budgetcastingsupply.com/ Quote Link to comment Share on other sites More sharing options...
Kurr Posted September 4, 2011 Share Posted September 4, 2011 Degassing phospor shot is 15% I believe. I think brazing rod is 6%. Copper is a beast to work with. Quote Link to comment Share on other sites More sharing options...
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