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Topic: Changing the comp of an alloy with a chemical reaction  (Read 3952 times)

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Offline mantrid

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Changing the comp of an alloy with a chemical reaction
« on: February 07, 2010, 07:54:37 PM »
Hello everyone
This is my first post.
I have a hobby of casting bronze sculptures. I use silicon bronze for this which is ideal for this use. Recently I have got hold of some manganese bronze which has a high zinc content (possibly 30 to 40%) which burns gently when I melt the alloy producing huge amounts of oxide that makes pouring and creating a nice cast very difficult.
My question is if I add silicon dioxide in the form of sand to the molten bronze will some kind of displacement reaction happen between the zinc and silicon dioxide leaving silicon in the alloy and removing the zinc as zinc oxide.

If not is there something else I could add to remove the zinc fairly rapidly (thats fairly safe) as I do not want to keep the metal molten for extended periods of time due to the fuel cost.

One other question. Is there a method that can be carried at home without expensive equipment for finding the ratios of various metals in an alloy. I am particularly interested in bronze so the metals I would be interested in are copper, tin, silicon, zinc.
Thank you
M

Offline BluRay

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Re: Changing the comp of an alloy with a chemical reaction
« Reply #1 on: February 09, 2010, 06:22:28 PM »
Hello everyone
This is my first post.
I have a hobby of casting bronze sculptures. I use silicon bronze for this which is ideal for this use. Recently I have got hold of some manganese bronze which has a high zinc content (possibly 30 to 40%) which burns gently when I melt the alloy producing huge amounts of oxide that makes pouring and creating a nice cast very difficult.
My question is if I add silicon dioxide in the form of sand to the molten bronze will some kind of displacement reaction happen between the zinc and silicon dioxide leaving silicon in the alloy and removing the zinc as zinc oxide.
No.

Quote
If not is there something else I could add to remove the zinc fairly rapidly (thats fairly safe) as I do not want to keep the metal molten for extended periods of time due to the fuel cost.
I sincerely don't see a simple way to remove zinc from the molten metal. However I don't have clear the fact you have to keep the metal molten for extended periods of time: it has to do with the low ability of that alloy to fill perfectly the cast?

Quote
One other question. Is there a method that can be carried at home without expensive equipment for finding the ratios of various metals in an alloy. I am particularly interested in bronze so the metals I would be interested in are copper, tin, silicon, zinc.
You are talking about chemical analysis; what do you think those chemists are payd for? :)

Offline mantrid

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Re: Changing the comp of an alloy with a chemical reaction
« Reply #2 on: February 10, 2010, 06:12:57 PM »
Thanks Blu ray

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I sincerely don't see a simple way to remove zinc from the molten metal. However I don't have clear the fact you have to keep the metal molten for extended periods of time: it has to do with the low ability of that alloy to fill perfectly the cast?

I mean that I dont want to keep the metal molten for a long time while the zinc is being removed/oxidised. I was hoping there was something I could add to rapidly remove the zinc as a slag in maybe 20 mins or so. The zinc is burning at melting temperature anyway but it is very slow. Just a gently flame on the surface.

Quote
You are talking about chemical analysis; what do you think those chemists are payd for? :)
I dont like paying for anything. Anyone in a lab willing to be sent a sample to test in their lunch break? :)

Offline BluRay

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Re: Changing the comp of an alloy with a chemical reaction
« Reply #3 on: February 13, 2010, 03:21:32 PM »
I mean that I dont want to keep the metal molten for a long time while the zinc is being removed/oxidised. I was hoping there was something I could add to rapidly remove the zinc as a slag in maybe 20 mins or so. The zinc is burning at melting temperature anyway but it is very slow. Just a gently flame on the surface.
If you try to remove it with some oxidant, you will certainly remove, at least, manganese as well and I don't even know which other metal is present in the alloy, apart from copper and tin.

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