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Making Zamak ZA-12 from Zinc

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vtsteam:
Hi Kjelle, thanks! what are you up to these days?  :beer:

Yes, the more I think about it the more it makes sense that dissolving a metal in another metal could be inhibited by too fast a heat. Zinc has to be poured when it is not too hot, or it flares up. Aluminum and copper take time to dissolve in it, so it seems logical that you should keep zinc just above its melting temperature, and not hotter, while waiting for the others to be absorbed. That will take time. Too fast a heat will force you to pour before the others have a chance to begin to dissolve.

I'm re-lining my oil fired furnace to do some iron casting, next.

mattinker:
Hi Steve,

My personal experience has been, melt the Al, just above 640C dissolve in the Cu (I use very fine electrical wire) stop the heat source, and feed in the Zn. As the Zn content rises, the melting point will drop. If it "flares up" you are way to hot, remember the boiling point of Zn is 700C so, if you start adding the Zn at just above the melting point of the Al, it won't get above 700C. Pyrometers with a K type thermocouples are very cheap now, the IR pyrometers don't always work on molten metal!         Cheers, Matthew

vtsteam:
Interesting Matthew. Sounds like an excellent and precise way to go about it.  :beer:

I'm doing my whole melt at about 450C, and using ordinary soft copper tubing. No problem with zinc flare, and I seem to get good results, too.

Zinc is pretty forgiving stuff, until you get up to dealing with it when brass melting. Then it can be tricky. I think a pyrometer would be useful there for me. Think I'd want a type R, however, because of the iron furnace. But so far, have managed pretty well without any of them.

vtsteam:
Speaking of pyrometers. Matthew, the type R are very expensive, using rare metals. As you say, the new digital IR pyrometers may not work well with molten metal.

There is one other type, not expensive, which I've been meaning to build. That's an incandescent filament comparative pyrometer. About 5 years ago I found this DIY version here. Glad the site hasn't disappeared yet:

https://www.metallab.net/pyrometer.php

mattinker:
Steve,

I have both a Ktype and an IR pyrometer, the Ktype is rated up to 1260C, so, it should be useful for cast iron as well!

Cheers, Matthew

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