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  1. #16
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by NedsHead View Post
    G'day Graham,

    I have a question, what are the common impurities found in scrap lead?

    Since you're looking to test for pure lead you may have two other options available, chemical testing for the common impurities or a melting point test,

    Regarding the melting point test,

    pure lead has a melting point of 327.5 °C, so anything above or below that would indicate impurities present and I imagine it wouldn't be too far fetched to build a small apparatus that can be powered from a vehicle 12v cigarette lighter socket, a 12v PID controller and a small insulated vessel with a sight glass to view the lead sample, you could even re-purpose an old car cigarette lighter for the heating element

    Might be a silly idea but it's something...
    In principle I like the idea but just a heads up that measuring an accurate melting point for something like lead is not as easy as it sounds.
    Because lead is relatively poor conductor, the usual way to melt lead quickly is to heat it at a higher temperature than its melting point.
    To accurately measure the melting point an apparatus has to be used that heats the lead evenly in a staged or ramped temperature sequence, and in such a way that the device measuring the temperature is not affected by the heating apparatus. This is tricky and takes time and I suspect that Graham is after something relatively quicker than this.

    A quickish comparative method might be to use a calibrated soldering iron.
    However, the soldering iron cannot be just poked at/into a piece of metal as this will drain heat from the tip and take some time to eventually melt the metal.
    Something like the following might be worth a try.
    Cut off a small (1c size) piece of lead from the material to be tested and removing the oxide.
    Cut a match head size off that, and place that into a narrow/tall heat proof container. This should not be metallic but something like a glass or ceramic as this will also reduce heat losses.
    Allow the soldering iron to reach equilibration temperature and then push that onto the chip and see if it melts.

    By calibrated I don't mean calibrated to a know temperature but just set to where it melts pure lead and then back it off a whisker
    Use of as larger soldering iron would be more accurate and quicker.
    The soldering iron tip will need to be cleaned between tests to avoid contaminating the next sample.
    Reshaping the copper tip to enable the iron to be applied to the workpiece vertically might be easier to handle.

    BTW melting point is not completely foolproof as there are some lead/silver mixtures that have melting points very close to the same temperature as pure lead, although chances of finding that in a scrap yard are going to be pretty small.

  2. #17
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    Hi Nedshead
    The impurities I have experienced have been lead oxide,paint, bituminous materials and the like.

    When I cast balls, the ingot generally has been cast twice to refine the metal to remove most of the dross. I started using the Lee ingot mould but found it way too small. I made a similar,but larger ingot mould out of 25mm angle iron

    I am trying to keep the lead hardness process at the scrappy very simple and cant see a reason to melt lead there.
    Found a simpler system today and it consists of a set of graded lead graphite which for my purpose 6B and 5B will suffice. It fairly cheap and is portable with a conversion chart-see below.

    Here are details I found on U tube. https://www.youtube.com/watch?v=21esd_H8VUU&t=61s.I I will try simple and cheap first.

    Grahame
    Last edited by Grahame Collins; 3rd Mar 2021 at 08:03 PM. Reason: karnt spel mi wurds

  3. #18
    BobL is offline Member: Blue and white apron brigade
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    Somewhat basic but effective

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