[Jewelry making - Article 00216] - Re: [Orchid] Drawing 18K wire

[Jim]

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Hi Susan,

    You said you used clean 18kt scrap. I will bet that some of the
    scrape you used was from old castings. The alloys used for sheet and
    wire are different then the alloys used for casting grain. Casting
    grain usually contains some type of degasser, typically zinc. Its
    purpose in a casting grain alloy is to help control porosity and
    reduce oxidation. However, it is not good in sheet and wire because
    it tends to migrate to the grain boundaries which results in stress
    cracking. I suspect the "slivers" you describe are a result of using
    cast scrape in your melt. 

    The slivers could also be caused by not annealing often enough when
    rolling or drawing your wire. A good rule of thumb is to anneal after
    not more then a 10% reduction in thickness. You can not anneal too
    often. When in doubt anneal again. Also never quench any hot metal in
    pickle. Always quench in clean water first and then place the metal
    into hot pickle. It is complicated but quenching in hot pickle can
    lead to stress corrosion under certain conductions. So why take the
    chance when it is so simple to avoid? 

    All that said, it is possible to use casting scrape for sheet and
    wire if you anneal even more frequently. My own experience with using
    casting scrape for this purpose is mixed. It is rarely worth the
    extra effort required because I never seem to get enough usable
    material for the job at hand. 

Good Luck
Jim Miller

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