Smelting Brass
Smelting Brass
(OP)
My question is this...
I have a small foundry at home powered by propane. I know for a fact that it can melt copper, zinc, lead, tin, bismuth, and anything else within a 2500 degree range. I have been trying to make brass, but i have yet to get a nice "nugget" of brass from the furnace. I put a measured amount of copper into the crucible, heat it up to about 2300 degrees, then add the zinc. when i do this it produces a cloud, (I'm guessing of zinc, or zinc oxides) and sparks a little. when all is said and done, i end up with a piece of mostly copper, some zinc, and very little specks of brass. even more frustrating yet, for some reason, I cannot remelt the nugget because it simply wont melt no matter how high i turn the temperature! I have also tried to use map gas, (which supposedly burns about 800 degrees hotter,) and still get nothing. so, i guess my question is...what exactly is the smelting process for brass? what goes in first, copper or zinc, and at what temperature does brass melt? I would really like to know because I want to try my hand and making brass coins. The crucible I'm using is made of some sort of steel alloy, but doesn't melt, under the intense heat. The crucible is surrounded by a ceramic "cup" of sorts, to insulate it. and all of this is inside a big steel wok to protect the work surface beneath. The torch is basically turned on, and aimed directly into the crucible. the metals are then added, then they melt. What am I doing wrong? do I need a more professional setup?
I have a small foundry at home powered by propane. I know for a fact that it can melt copper, zinc, lead, tin, bismuth, and anything else within a 2500 degree range. I have been trying to make brass, but i have yet to get a nice "nugget" of brass from the furnace. I put a measured amount of copper into the crucible, heat it up to about 2300 degrees, then add the zinc. when i do this it produces a cloud, (I'm guessing of zinc, or zinc oxides) and sparks a little. when all is said and done, i end up with a piece of mostly copper, some zinc, and very little specks of brass. even more frustrating yet, for some reason, I cannot remelt the nugget because it simply wont melt no matter how high i turn the temperature! I have also tried to use map gas, (which supposedly burns about 800 degrees hotter,) and still get nothing. so, i guess my question is...what exactly is the smelting process for brass? what goes in first, copper or zinc, and at what temperature does brass melt? I would really like to know because I want to try my hand and making brass coins. The crucible I'm using is made of some sort of steel alloy, but doesn't melt, under the intense heat. The crucible is surrounded by a ceramic "cup" of sorts, to insulate it. and all of this is inside a big steel wok to protect the work surface beneath. The torch is basically turned on, and aimed directly into the crucible. the metals are then added, then they melt. What am I doing wrong? do I need a more professional setup?





RE: Smelting Brass
Why not just buy some brass at the composition you want and melt that?
rp
RE: Smelting Brass
RE: Smelting Brass
Hope it helps,it is more from memory rather than any reference.
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RE: Smelting Brass
RE: Smelting Brass
Very tough to dissolve.
Also tried some salts... hazardous for health though.
I think that you are creating Oxides and these are the ones that have very high melting points.
RE: Smelting Brass
Yes, starting with a brass or bronze is best, and #1 copper scrap is so valuable these days that you can trade it 2 to 3 for one with brass scrap- especially if you don't mind a little lead, tin and antimony in the mix.
But if you insist on doing your own alloying, here's another thought: start with zinc, cover with charcoal or borax or both (to flux the oxides and to keep away oxygen). Melt the zinc, then add the required quantity of solid copper and slowly raise the temperature, keeping covered with the molten borax the whole time. The borax forms a skin which, if left unbroken, reduces the oxidation and volatilization of the zinc. All the copper-zinc sub-alloys are going to be lower melting than pure copper if I remember the diagram correctly, so you should be able to slowly dissolve the copper into the zinc to form a puddle of the desired composition. Cast an ingot, then mechanically remove the borax and charcoal from the surface prior to re-melting.
Any time you melt brasses you're going to need borax there to reduce oxidation (at my scale that's certainly true, so I suspect it'll be true at yours as well). It's tough to keep the molten borax out of your castings. By the way, the molten borax is hard on the refractories as well- it fluxes their oxides too over time.
Popping zinc into molten copper is a recipie for rapid zinc loss by fire, with the nasty toxic fume to be concerned with. I wouldn't recommend it.
From experience, the dissolution of solid copper into a brass puddle below the melting point of pure copper is relatively slow, so this will take some time.
RE: Smelting Brass
Posts concerning the boil of Zinc is quite common and is used in several metallurgical processes, like recovery of Zinc from galvanizing dross where the Zinc is vaporized and condensed and the recovery of Silver from Lead.
Be real careful when working around molten Zinc as the fumes are very detrimental to one's health. It call zinc fume poisoning and can make one feel very bad.
I concur with getting the proper scrap or ingot metal for you project.
RE: Smelting Brass
The first link is to a lot of metal suppliers. The second is to a hobbyist with a lot links to others.
http:/
http://www.backyardmetalcasting.com/links.html
RE: Smelting Brass
RE: Smelting Brass
Typical flux has soda ash , silica ,and borax. Avoid fluorspar, it can make "spinels".
The brass will melt a few hundred degrees lower than Cu, your temps should be well below Zn boiling (if you start with brass).
Brass founders ague,= zinc chills, = oxide shakes; not all that terrible; Avoid FRESH ZnO, no problem after it is a few hours old.