Ghosts

Discussion in 'General foundry chat' started by Miles Lowry, Sep 18, 2020.

  1. Miles Lowry

    Miles Lowry Copper

    hey guys, maybe y'all can answer something for me. Whenever I put extruded aluminum in the foundry it melts down but kinda leaves a ghost of itself behind. Can anyone explain this phenomenon?
     
  2. That's the thick anodized skin of aluminium oxide: melting point 5400 deg F.
     
  3. Miles Lowry

    Miles Lowry Copper

    Icy, so I basically just have to scrape it off?
     
  4. There'll always be oxides to skim off the surface of the molten metal before a pour, there's even a kind of slack tube of oxides hanging off the crucible that the molten metal exits from as you stop pouring and move to the next mould.
     
  5. Petee716

    Petee716 Gold Banner Member

    Just push it over to the side when you add more metal so it doesn't get pushed down into the melt and then skim it all when you're ready to pour. Unless you get a big thick mess on top, then skim it off mid-melt as necessary. But every time you skim, a brand new layer of oxide forms immediately that you have to skim off at the end anyway. Avoid stirring the melt so all of the crud stays on top.

    Pete
     
  6. Miles Lowry

    Miles Lowry Copper

    too late but thanks for the advice. I'll know for next time.
     

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