At school we once tried melting down a significant amount of aluminium turnings and it was a complete waste of time - lots of slag and not much else.

Quote Originally Posted by Ricardoco View Post
Again i agree but im not sure that a max of 5nm of oxide per surface is the problem if your chips are cut correctly rather the burn off.
I heard that it's the oxide layer formed when the swarf heats up in the furnace that's the problem, as it's significantly thicker than what is formed from the lower temperatures during machining. If the however the swarf was plunged into a molten pool of aluminium, then it does not make (much) contact with oxygen whilst hot, so cannot oxidise further. This does present a safety hazard though if the swarf is wet or has oil on it which is pretty likely...