The Shop > Metal Stuff
Aluminum Copper Alloy Experiment
Joules:
The slag is dross and impurities that precipitate out of the metal to the melt/crucible wall. I was thinking your aluminium bronze wouldn't be true, but as you created it in a steel crucible it will have pulled some iron out of the metal into the melt. Casting molten metal into moulds is almost a chill process as the temperature drops off quite rapidly. if you can slow the cooling to extended times you will form large or even single crystal components as in Rolls Royce turbine blades, though they have a little more trickery than just that. Watching the big forge hammers "beat the crap out" of metal is probably the simplest way of explaining whats happening. You are purifying the metal by squeezing out impurities that would remain in the metal and create weakness across the grain structure. The heat allows the impurities to migrate through the metal, as when it cools they are locked in.
NormanV:
Thank you Joules for taking the time to read my questions and to reply. What you say makes sense. Now I just have to translate that into action and make my metal machinable.
Joules:
Norman, as mentioned by others. It work hardens rapidy and is really abrasive on HSS tooling. You know when you have it wrong as the metal screams at you, and watch if you drill it, the metal is really grabby and will clamp down on a drill bit and shatter it. LOL those have been my experiences with Ally Bronze, does make great bearings though.
NormanV:
I've just been into the workshop and tried to drill it. After my heat treatment it seems to be harder than ever! :doh:
At the moment it feels very disappointing, I searched for a long time to find some scrap copper. It took a long time to melt it and the result is....... difficult!
This is the problem when you experiment to try to save money, it can turn out cheaper to buy the thing that seemed so expensive in the first place.
No worries, I have learned something new and I will remember it because I did it and did not just read it.
mattinker:
The answer to your question about why your alloy is not sof when cooling down after casting might be in this article.
http://mit.imt.si/Revija/izvodi/mit144/slama.pdf
The scale forming on the outside of you steel crucible looks like oxidisation.
Have fun with your traction engine on the beach!
Cheers, Matthew
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