Copper Melting for School's Science Dept.

[Archie Zietman]

Hello.
So, basically the science department at my school is gathering scrap everything copper and melting down two copper ingots for looking at eddy currents and magnetism in the physics dept. The head knows I'm a blacksmith and I've been enlisted to help with the planning.

So here's the setup Does this seem like a good plan?

We're not pouring. The art dept is building molds the right size out of the hottest firing clay we can buy. It's just two ingot shaped molds we'll melt everything into, so we don't have to deal with the xxxxxx casting properties of pure copper.

We're using the electric kiln of a parent at the school. Not a reducing atmosphere in there, so we have a problem.

How shall we minimize oxidation? I'm thinking cut everything up as dang small as we possibly can, pile it in the molds, and, during the melt, keep a few pieces of charcoal in the kiln to use up any O2 there is. Then, when we get a-melting put on some kind of flux.
It's crude but seems like a good method to me.
Hot air in between the pieces will rise up right? So we shouldn't have to worry about gassy casts, we're not pouring it out, which helps.

Thanks eversomuch,
Merry Being,
Archie

[saintjohnbarleycorn]

thats an interesting project. Since they were melting copper some thousand (s) of years ago, I would guess you could get away with a primitive system. But I don't know about the problems of oxidation I would think the heat and weight of the liquid would drive the oxygen out, but that is above my level of education. Does the art dept. do anything special with silver? It oxidizes also doesn't it? I know its not much help. let me know how it all turns out I am interested in the electrical part of the experiment. thanks.

[Phil Dwyer]

I used to cast a lot of silver and gold, some brass and occasionally copper and aluminum. We just used borax flux, which floats to the top, and in our case adhered to the crucibles as we poured, flung or sucked it into our molds. Copper, of course, was the "hardest" to work with only because it took so much darn heat to melt it.

[Hillbillysmith]

It should be simple to do. The setup sounds good. Just cut it up in small pieces and put some borax in it and fire it up. As long as your not pouring it, I highly doubt that you'll have a problem with the borax sticking to anything. It'll just grab all of the oxides and float them to the top and leave a protective layer to keep the oxygen out of the casting Once it hits and holds to a bright yellow color, shut the heat down slowly and just let sit. Once it's cool, you should be able to just pop it out of the mold and take a wire brush to it and get the dried borax off.

[acoop101]

copper can be melted easily using a coating of charcoal ontop as a flux, scrape the slag back before you pour so that you don't get inclusions.

[eggwelder]

had melted copper dissolve a cast iron ladle i melted it in.. will post a pic of it if i can find it. also had bronze go thru 1/4 in thick steel crucible on second use. 

[the iron dwarf]

eddy currents are a lot easier to generate in something less conductive,

it takes a lot more power to heat copper than steel in an induction forge and the heat there is generated by inducing an eddy current in the work.

some threads here on induction in the forges section

[Glenn]

 Those directly involved (as few as possible) should have FULL protective gear, including hard hats, eye protection, full face shields, Welding jacket and additional welding sleeves, welding blankets around the body to ankles, aprons, leather steel toes shoes, welding gloves, and anything else you can imagine. More than one fire extinguisher and additional fire suppression equipment should be close by and fully charges and at the ready. Everyone should also be trained in their use.

 

I would first put everyone, (read EVERYONE) except those directly involved behind a glass wall, like in the hallway looking in.

 

You MUST have a (parental) signed release for everyone involved. Plan for the worse that could happen and hope for the best. Try to find someone from the industry that does such things and have them come in and explain how to do this safely and ask them to be present during the project so they can say STOP is they see anything out of place.

 

All this safety stuff sounds like overkill until you have something go wrong and have no plan B. Do you have a plan where you can safely stop a hole that may develop in the mold? What about a hole in the ladle pouring hot metal out onto the floor and splashing about?  Is the mold as close as safely possible to the heater? Did you practice the dance and know each step you must take and how to immediately go to plan B? Did you practice with water in the container? Fill it to the brim and add weights to match 2x the amount of hot metal weight you plan to use, and then practice the dance. Spill any of the water? 

 

Yes a long post. But then I have had a procedure using hot liquid metal that was done many times, go bad. I had to be actively involved with the use of plan B, instead of going into duck and cover mode. A review showed I did nothing wrong, things just happened sometimes.  

 

Safety always comes first. If it can not be done safely, then do not do it. Having a plan B is just as important. Practice is the reason everyone knows what to do, how to do it, when to do it, and how it feels when you do it right, and what to do when it goes wrong.