Aluminum Cavitation and identifying metals we melt...

Discussion in 'General foundry chat' started by Haus, Sep 22, 2021.

  1. Haus

    Haus Copper

    OK, odd story.

    I got ahold of an old exterior light fixture that was being tossed out. I immediately saw what looked like an aluminum shade around the bulb itself and it was a metal fixture so I grab it.

    Take it apart, there's a transformer inside (it was a big sodium bulb style old school exterior fixture for a small barn) Unfortunately transformer was all Aluminum wires for wrap , no copper. The body of the thing was a grayish metal, I figure it to be some style of Pot Metal. I bash it up with a hammer into small pieces (it breaks easily, doesn't bend).

    I'm doing a melt of some aluminum I picked up, and afterwards decided to test this mystery metal. Put in a small piece in a crucible I had just emptied and scraped of aluminum. It melts pretty fast, no white fumes/smoke (so no Zinc I guess). The metal was a dull medium gray, so I figured it wasn't aluminum. I then melt the rest of the housing and pour into an ingot mold.

    Now, I'm used to the fact that as Aluminum cools it will often form a depression on the top as the center cools and everything compacts. It's cavitation from what I've read and normal to expect Aluminum to do this, less so though on some other metals like copper. I pour the mystery metal and no cavitation at all, top of the ingot stayed nice and flat as it cooled. But it pours with a silvery brightness right there will the aluminum I poured a few seconds ago??

    Safe to just call it Monkey Metal and call it a day? Are there better methods you guys use for easily identifying the non-ferrous stuff we pick up and play with beyond "melt a little and find out!"??
  2. Sometimes you can get so much hydrogen dissolved into aluminium that there's no contraction as the hydrogen bubbles come out of solution on cooling and you end up with a casting you can blow air through like a sponge. Probably working out the density of the mystery metal by accurately weighing it and measuring water displaced by a sample for volume will let you make an educated guess as to the metal.
    dtsh likes this.
  3. dtsh

    dtsh Silver

    This is what I do. Before I had an analytical balance I used an inexpensive digital scale and it tended to work well enough. There are a number of methods of getting the specific gravity, try a few and go with the one that works best for you and the equipment you have at hand.
  4. Petee716

    Petee716 Gold Banner Member

    It's probably die cast zamack. It melts about 750f. You wouldnt get zinc fumes at aluminum temps I dont think.
  5. Peedee

    Peedee Silver

    What Petee said

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