I had heard that high strength alloys of aluminum will lose some of the critical strength and machining properties if melted to many cycles. I understand this was from some of the additives burning off.
Rule of thumb was for best strength to use extrusion or known high strength alloys and avoid castings in successive re-melts. That included transmissions etc. Save the cheaper alloys for ornamental purposes only.
Good question and Great thread.
DC
Is melting aluminum illegal?
Moderator: Harold_V
Re: Is melting aluminum illegal?
Well its nice to see that the legality of melting aluminum is such a non-issue that my post has strayed into a discussion on dirty aluminum. Although he may be an unreliable source for legal advice, he sure can supply me with aluminum scrap. He makes the horseshoes out of 6061 T6 aluminum and every few months they take a few 50 gallon drums of chips to the local scrap yard. Is this a good aluminum for casting purposes? From what I know it should be an excellent source of a KNOWN alloy. However I'd like to hear more from those with more experience.
Been you to have any spliff man?
Re: Is melting aluminum illegal?
Melting down chips has it's own set of problems, but nothing particularly terrible.
The big issues are moisture and oil used in the cutting fluid. Either will add hydrogen to the melt which will need to be degassed out of it. Preheating the chips to about 750 degrees before adding them to the melt helps a lot.
BTW, 6061-T6 is a preciptation hardening grade. As-cast it's gummy to machine, but if you solution anneal and then harden it machines very nicely.
Back to the legality, nationally it's not an issue if you are not doing it commercially, although as I recall, most of the EPA regs for permits are triggered by a certain amount of pollutant generated. You need to find out if there are any local regulations that prohibit melting metal, similar to local regulations prohibiting backyard burning or using charcoal lighting fluid in California.
The big issues are moisture and oil used in the cutting fluid. Either will add hydrogen to the melt which will need to be degassed out of it. Preheating the chips to about 750 degrees before adding them to the melt helps a lot.
BTW, 6061-T6 is a preciptation hardening grade. As-cast it's gummy to machine, but if you solution anneal and then harden it machines very nicely.
Back to the legality, nationally it's not an issue if you are not doing it commercially, although as I recall, most of the EPA regs for permits are triggered by a certain amount of pollutant generated. You need to find out if there are any local regulations that prohibit melting metal, similar to local regulations prohibiting backyard burning or using charcoal lighting fluid in California.
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rmcdona413
Re:melting aluminum-
You would not want to use piston alloy as cylinder head material as piston is typically over 12% Si (Silicon) Cylinder alloys typically range from 6 to 8%